DESCRIPTION

PIGMENT DISPERSION, RECORDING INK, INK CARTRIDGE,

INK- JET RECORDING METHOD AND INK- JET RECORDING

APPARATUS

Technical Field

The present invention relates to pigment dispersions that

exhibit superior pigment-dispersion stability under long-term

storage, recording inks suited to ink-jet recording, and also ink

cartridges, ink-jet recording methods and ink-jet recording

apparatuses.

Background Art

Recently, ink-jet printers have become widely used by

virtue of lower noise and relatively less running cost, and also

color printers printable on regular paper have been actively put

into the market. However, it is very difficult for ink-jet

printers to satisfy all of common properties such as color

reproducibility, endurance, lightfastness, image-drying property,

non-feathering or non-bleeding of images, double-face printing

and discharge stability, thus inks are selectively employed

considering important properties for respective applications.

The inks for ink-jet printers are typically based on water

and contain colorants like dyes or pigments and humectants

such as glycerin to prevent clogging. The colorants are usually

dyes in view of superior color-producing property and stability.

However, lightfastness and water resistance of images formed

from inks containing dyes are relatively inferior. Specifically,

the water resistance of images is unsatisfactory on regular

paper, although it may be somewhat improved on dedicated

ink-jet recording paper having an ink-absorbing layer.

In order to solve these problems, recently, alternative

recording inks have been investigated ¹ in which pigments, in

place of the dyes, such as organic pigments and carbon black

are micronized with surfactants or dispersants and dispersed

into media such as water. Patent Literatures 1 and 2, for

example, disclose methods for improving ejection stability by

way of micronizing organic pigments into a particle diameter of

50nm or less using specific dispersants. Patent Literature 3

discloses an ink-jet ink using a specific organic pigment and an

anionic dispersant.

However, it is impossible to micronize organic pigments

into below their primary sizes regardless of any dispersants.

Furthermore, it is very difficult to reduce the particle size of

organic pigments into 50 nm or less without degrading color

tone. Furthermore, in cases where pigment dispersants of

lower-molecular weights are employed, there exists a problem

that dispersion stability of pigments is inferior, pigments are

likely to coagulate with aqueous solvents in inks! in cases

where pigment dispersants of lower-molecular weights are

employed, the dispersibility is likely to be poor due to higher

velocities of pigment dispersions. There exist also a problem

that printed matters from these inks are insufficient for scratch

resistance and water resistance.

Since ink-jet recording requires stable discharge of ink

droplets from a minute nozzle of ink-jet recording heads, it is

necessary that the ink is far from solidification due to drying at

orifices of the ink-jet recording heads. In cases where inks of

dispersed organic pigments are utilized for ink-jet recording,

however, dispersion stability of pigments may be degraded

under long-term storage in particular, thus the resulting

coagulation of pigments may lead to clogging of ejection nozzles

of ink-jet recording heads or non-ejection of inks. Especially

when the printing is suspended for a long period, nozzle

clogging is likely to occur, and the thickened inks may deposit

within maintenance devices such as nozzle caps or suction tubes,

which possibly hindering the function of maintenance devices.

Furthermore, when printing is temporarily suspended or

nozzles are stopped for a short period due to blanks or a single

blank in printing documents, there often occur problems such as

printing failures or intermittent discharge-failures due to

distorted-injection direction of ink droplets.

As for the other dispersing methods of organic pigments,

so-called surface -modified recording inks are proposed in which

pigments are stably dispersed, with no dispersant, by way of

modifying the pigment-particle surface into hydrophilic with

carboxyl group, carbonyl group, sulfone group, hydroxyl group,

and the like. As for black recording inks, for example,

so-called surface-modified carbon blacks have been developed in

which carbon blacks are stably dispersed, with no dispersant,

by way of introducing hydrophilic groups on the carbon surface.

In addition, as for inks of color pigments, so-called

surface-modified color pigments have been developed in which

the color pigments are stably dispersed with no dispersant.

However, these surface-modified recording inks typically lack

scratch resistance on regular paper or dedicated gloss paper,

and represent poor water resistance.

In order solve the problems described above, there is

proposed an ink-jet ink containing microcapsules or emulsion

where pigment particles are coated with a resin. In accordance

with such a proposal, since the pigment particles are coated

solidly by the resin, dispersion may be stable for a long period

and the ejection stability may be improved, ^" however, it is

expensive and difficult to make the dispersion particle diameter

into 150nm or less even pigments with a primary particle

diameter 50nm to lOOnm are coated with the resin.

Patent Literatures 4 and 5 describe a proposal in which a

colorant may be provided with a nanometer-particle diameter

and a uniform particle size distribution by way of depositing a

dye onto the surface of metal oxides and then coating it with an

organic compound having an ionic group, and the resulting

colorant can be utilized for ink-jet inks. In accordance with

this proposal, water resistance may be improved compared to

inks utilizing dyesJ however, lightfastness tends to be inferior

to the inks utilizing dyes, thus the resulting inks are

inappropriate for actual use.

As such, in cases where dispersants are utilized for

dispersing pigments or pigment surfaces are treated to be

hydrophilic, a resin may be added to inks in order to

complement the lack of water resistance and scratch resistance, ^'

however, it is typically impossible to obtain sufficient water

resistance when water-soluble polymers are utilized. For this

reason, methods using water-dispersible resins are proposed;

however, the water resistance is still insufficient since the

printed resin particles on recorded matters may easily disperse

into water again.

Recently, composite pigments are proposed in which an

organic pigment is coated over inorganic pigment particles.

When inorganic pigment particles of about 5 to 50 nm are

utilized as a core material, it is possible to obtain a colorant

pigment of less than lOOnm even when being coated with an

organic pigment (see Patent Literatures 6 and 7).

Complex-pigment colorants of 10 to 20 nm are commercially

available already. Application of these composite pigment

particles to paints or ink-jet inks are also proposed as disclosed

in Patent Literatures 8 and 9. However, these composite

pigment particles also suffer from the inferior dispersion

stability in particular under long-term storage and insufficient

water resistance and scratch resistance of printed matters

because of containing no fixing resin.

Ink compositions containing resins are also proposed, for

example, an ink containing a pigment and a water-dispersible

resin dispersed in water as disclosed in Patent Literature 10;

an ink containing a pigment dispersed in polymer emulsion

dispersion of a water-insoluble resin as disclosed in Patent

Literature 11; and an ink using an emulsion having a specific

film-forming temperature as disclosed in Patent Literature 12.

In addition, there exist many proposals with respect to

addition of polymer dispersants in order to improve fixing

ability of the complex pigment particles as disclosed in Patent

Literatures 9, 13, 14, 15, 16, 17, 18 and 19. In these proposals,

polymer dispersants are expected to enhance the fixing ability.

However, these polymer dispersants typically suffer from

insufficient water resistance due to their water solubility even

though the scratch resistance may be sufficiently improved.

Accordingly, such materials are demanded currently as a pigment dispersion that can exhibit superior pigment-dispersion

stability under long-term storage; a recording ink, containing

the pigment dispersion, that can represent superior ejection

stability without head clogging at printing, that can bring about

superior image durability such as water resistance and

lightfastness, that can provide high-quality images with

superior color tone on not only dedicated recording paper but

also regular paper, and that is suited to ink-jet recording, ^' and

the related technologies.

As for inks for the ink-jet recording at homes and offices,

aqueous inks are typically utilized that are based on water and

contain colorants, humectants such as glycerin, wetting agents

to control permeability into recording paper, surfactants and

other optional additives.

The ink-jet recording of aqueous inks is fixed typically

through permeation of the aqueous inks into recording media,

therefore, dedicated ink-jet recording paper has been developed

that is provided with enhanced absorbability, fixing ability for

coloring components on paper surface, and protection ability for

the coloring components. However, the dedicated ink-jet

recording paper is relatively expensive since its production

process involves multiple coating processes after paper making

and is inferior to the regular paper in terms of recycle ability

because of containing many processing chemicals; as such,

sufficient image quality on regular paper is desired currently.

The regular paper represents inferior ink-absorbability

and less assistance in ink performances compared to dedicated

ink-jet recording paper, therefore, there exist such problems in

recording on regular paper as (l) occurrence of feathering, (2)

occurrence of bleeding, (3) reduction of density, (4) reduction of

color developing property, (5) reduction of water resistance, (6)

reduction of light resistance, (7) reduction of gas resistance, (8)

reduction of fixing property, (9) show through of ink, and the

like. It is important to solve these problems in order to carry

out the ink-jet recording on the regular paper.

In recent years, pigments have been often used for

ink-jet inks through improvement of pigment-dispersibility

and/or micronization of particle diameter. The

pigment-dispersibility has been improved through improving

self dispersion stability i.e. imparting hydrophilicity by way of

surface modification such as oxidation, sulfonation, or graft

polymerization on pigment surface in addition of conventional

pigment dispersion using surfactants and/or water-soluble

resins. These pigments may improve the above-described (5),

(6) and (7); the concentration and coloring property of the

modified pigments are inferior to those of dyes, and also the

ejection stability, long-term preservability and re-dispersibility

of the pigment inks are inferior to those of dye inks. Thus, in

cases where pigments are used as colorants, it is important to

enhance ink density, color development, and reliability. In

order to address these problems, for example, a number of

ink-jet recording inks _. are proposed that contain colored polymer

particles, in particular emulsion of polyester or vinyl based

polymer particles (see Patent Literature 20, non-Patent

Literature 1). These proposals encompass inks containing a

colorant-including resin dispersion, in which the colorant is

included in a water-insoluble, aqueous dispersible resin. When

color organic pigments are used as the colorant, the image

density and the color reproducibility under conventional ink

formulations on regular paper are superior to those of pigment

inks with water-soluble dispersants.

Heretofore, control of ink permeability into the paper has

been investigated in order to reduce feathering and bleeding, to

enhance printing density and color development and to suppress

show through. A super-permeable ink-jet ink is commercially

available of which the surface tension is adjusted to below 35

mN/m to enhance permeability into paper. Such inks

effectively reduce the bleeding and are easily dried on regular

paper, meanwhile there exist such deficiencies as feathering,

lower print density and lower print quality. On the other hand,

a slow-permeation ink is also commercially available of which

the surface tension is adjusted to above 35 mN/m thereby to

slow permeation into paper and to hold the ink on surface area

of the paper, which may effectively lower feathering, increase

print density and color development, and to reduce show

through.

However, the lower permeability degrades remarkably

the drying ability after printing on the regular paper, thus

resulting in deterioration of fixing ability and/or bleeding

between colors in cases of multiple-color print. In view of

these problems, a complex ink set has been developed and

utilized in which a slowpermeation ink and a super-permeable

ink are combined to suppress the bleeding between colors

thereby to assure image quality. However, in cases of

double-sided printing using slow-permeation inks, a period is

required to wait ink-drying after printing, which deteriorate

productivity of the double-sided printing. A printing

apparatus is also commercially available which is equipped with

a device to heat paper before and after the printing in order to

enhance ink-drying ability (see Patent Literature 21).

However, such apparatuses suffer from enlarged and

complicated systems and wasteful heating energy due to

additional heating devices, which diminish advantages the

advantages of ink-jet recording.

Beside these proposals, ink-jet inks have been

investigated variously with respect to reliability as well as

image quality. Prevention of ink-viscosity increase is

demanded to suppress clogging of nozzle heads. For example,

Patent Literature 22 discloses that ink-voids can be prevented

by way of controlling viscosity-change into below 10 times and

diameter-change into below three times comparing after to

before condensing concentration of inks two times thereby

making pigments suppress the ink-spreading. Such inks,

however, hardly produce high quality images on regular paper.

Patent Literature 23 discloses an ink in which residual

after evaporating volatile contents in the ink is a liquid and the

viscosity of the residual is below 10 times of the initial viscosity.

However, the ink is one containing a dye thus also likely to

provide poor image-quality regardless of higher reliability.

Patent Literature 24 discloses an ink in which the

viscosity-increase is below 600 times comparing after to before

water-evaporation at 60°C. However, the ink is also one

containing a dye thus the water resistance is still insufficient in

spite that reliability as well as durability are intended to

increase by addition of water-soluble polymer.

Patent Literature 25 discloses that an ink with a

viscosity of 5 to 15 mPa-s is appropriate in order to assure

higher quality. This literature disclose that a certain

compound may be favorably added to adjust initial-vaporization

velocity and to arrange viscosity for reliability) which may

suggest a solution to solve items (3) and (4) in terms of those

containing pigments. However, this literature includes no

description in terms of particle-size stability of pigments, that

is, the ink may lack reliability under long-term preservation

depending on ejection heads and/or nozzle sizes although it may

be reliable after preservation for 24 hours.

As described above, it is necessary to use high-viscosity

inks in order to assure high-quality printing under higher

velocities, meanwhile it is difficult to assure reliability of

high-viscosity inks.

Patent Literatures 10 and 11 disclose addition of

water-insoluble resins into pigment inks for improving image

quality. Patent Literature 26 discloses that images on regular

paper can be improved using an ink in which the ratio of

pigments to resin emulsions is 1 ^: 0.1 to 1 : 1 and the average

particle diameter of coloring ingredients is 0.3 to 1.2 μm. Such

inks containing resin emulsions may suppress feathering

through lowering the bleeding, however, are likely to lack

reliability as ink-jet inks due to insufficient image density. As

for improvement in reliability, Patent Literature 27 discloses

an ink in which a water-insoluble is added to the ink and the

lowest temperature to form films is 40 ⁰ C or more, ^' Patent

Literature 28 discloses an ink in which the particle diameter of

additional emulsions is no more than 50 nm. However, the

reliability of these inks is likely to be still unsatisfactory and

the image quality is insufficient still. Patent Literature 29

discloses improvement in printing nonuniformity by use of inks

containing a pigment, saccharide or derivatives thereof, polyols

containing five or more hydroxyl groups and a resin emulsion.

Suck inks tend to exhibit lower permeability into regular paper

and are problematic in terms of feathering and/or bleeding,

fixing ability and drying period. Patent Literature 30 discloses

an ink consisting of a water-dispersible resin and a

self-dispersible pigment in which the solid content is 1.0 to 16%

by mass and image quality is improved on regular paper. This

proposal may lead to higher water resistance compared to those

containing dyes, ^" however, image supporting property may be

insufficient with respect to marker pens often utilized for

regular paper.

Furthermore, many investigations have been made

regarding to viscosity increase along with solid-content increase

when pigment dispersions and resin emulsions are added to

inks. For example, Patent Literatures 29 and 31 disclose ink

formulations in which viscosity-increase is not so significant in

spite of solid-content increase by way of adding a resin capable

of forming micelle aggregates. However, these proposals suffer

from lower image quality due to insufficient permeability onto

regular paper. The permeability onto paper can be explained

through capillary absorption represented by Lucas-Washburn

formula; and the higher is the viscosity, the lower surface

tension and/or the less contact angle between paper and inks is

required to achieve sufficient permeability. Patent Literatures

32 and 33 propose addition of polyvalent alcohol alkylethers

into inks of higher solid-contents in order to improve

permeability; however, these proposals suffer from lower image

quality due to insufficient permeability in cases where the

viscosity increases while the solid content increases.

It is publicly known that silicone surfactants and

fluorine-containing surfactants can enhance permeability even

in a minute amount and their employment has been

investigated in the art. For example, Patent Literatures 34

and 35 propose ink-jet inks with fluorine-containing

surfactants; Patent Literatures 36 and 37 propose inks with

pigment dispersions and fluorine-containing surfactants.

Patent Literature 38 also proposes an ink, with a viscosity of no

less than 5 mPa-s, including a fluorine-containing surfactant

and a polymer emulsion formed from polymer fine particles and

water-insoluble or hardly soluble coloring materials. However,

these proposals suffer from hue change along with increase of

pigment content in inks, thus it is difficult to attain favorable

hue at higher pigment contents, and also the water resistance

and fixing ability a ^r re likely to be insufficient in cases of self-dispersion pigments.

Patent Literature Y- Japanese Patent Application Laid-Open (JP A) No. 09 263720 Patent Literature 2 - JP-A No. 09-263722

Patent Literature 3: JP-A No. 2002-88286 Patent Literature 4: JP-A No. 11 166127

Patent Literature 5: JP-A No. 2001- 192582 Patent Literature 6: JP A No. 2002- 146231 Patent Literature T- JP-A No. 2002- 161221

Patent Literature 8: JP-A No. 2003-49096 Patent Literature 9: JP-A No. 2003 55591 Patent Literature 10: Japanese Patent Application Publication (JP B) No. 62- 1426

Patent Literature 11: JP-A No. 55 157668

Patent Literature 12: jp-A No. 01-217088 Patent Literature 13: JP A No. 2003-49096 Patent Literature 14: JP-A No. 2003- 105229

Patent Literature 15: JP-A No. 2003- 171594 Patent Literature 16: JP-A No. 2003- 192938

Patent Literature 17: jp-A No. 2003 327866 Patent Literature 18: jp-A No. 2003-268278 Patent Literature 19: JP-A No. 2003-327880

Patent Literature 20: JP-A No. 2000- 191972

Patent Literature 2V JP A No. 55-69464 Patent Literature 22: JP A No. 2002- 337449 Patent Literature 23: JP-A No. 2000-095983 Patent Literature 24: Jp-A No. 09- 111166 Patent Literature 25: JP A No. 2001-262025

Patent Literature 26: JP-A No. 04-332774

Patent Literature 27: Japanese Patent (JP B) No. 2867491

Patent Literature 28: JP-A No. 04- 18462 Patent Literature 29: JP-B No. 3088588

Patent Literature 30: JP-A No. 2004-35718 Patent Literature 31 : Jp-A No. 2004-99800 Patent Literature 32: Jp-A No. 2004- 155867 Patent Literature 33 : JP-A No. 2004-203903 Patent Literature 34: JP B No. 2675001

Patent Literature 35 : jp-β No. 2667401 Patent Literature 36: JP-A No. 04-211478 Patent Literature 37: JP-A No. 2003 277658 Patent Literature 38: JP-A No. 2003-226827 Non-Patent Literature 1 : Applied Expansion of

Functional Pigment Technology, by CMC Co., Ltd.

Disclosure of Invention

The present invention aims primarily to provide a

pigment dispersion' that exhibits superior dispersion stability

under long-term storage; a recording ink, using the pigment

dispersion and suited to ink-jet recording, that exhibits

excellent ejection stability without head clogging, provides

images with superior durability such as water resistance and

lightfastness, and forms high-quality images with proper color

tone on not only dedicated recording paper but also on regular

paper! an ink cartridge using the recording ink, an ink-jet

recording method and an ink-jet recording apparatus.

The present invention aims secondarily to provide a

recording ink that affords superior image quality on regular

paper with no inkless void and with higher image density, color

saturation, durability such as water resistance and

lightfastness, and represents excellent drying property and

beading on gloss paper, superior drying velocity and high-speed

printing, and appropriate ejection stability from nozzles; and

also an ink cartridge using the recording ink, an ink-jet

recording method and ink-jet recording apparatus.

These objects can be attained by the present invention

described below.

In a first aspect, the present invention provides a

pigment dispersion, comprising a pigment, a pigment dispersant,

a polymer dispersion stabilizer and water,

wherein the polymer dispersion stabilizer is an

alpha-olefin/maleic anhydride copolymer expressed by the

formula (l) below:

Formula (l)

in the formula (l), R represents an alkyl group and n is

an integer of 30 to 100.

Preferably, the acid value of the alpha-olefin/maleic

anhydride copolymer is 100 to 400 mgKOH/g.

Preferably, the alpha-olefin/maleic anhydride copolymer

is used as a solution in an alkaline solution or in an alkaline

aqueous solution, and the alkali amount in the alkaline solution

or in the alkaline aqueous solution is no less than that

corresponding to the acid value of the alpha-olefin/maleic -

anhydride copolymer.

Preferably, the pigment is an organic pigment, or a

complex pigment of an inorganic pigment coated with an organic

pigment.

Preferably, the organic pigment is one selected from

phthalocyanine pigments, quinacridone pigments and monoazo

yellow pigments.

Preferably, the inorganic pigment particles are at least

one selected from titanium dioxide particles, silica particles,

alumina particles, iron oxide particles, iron hydroxide particles

and tin oxide particles.

Preferably, the pigment dispersant is one of anionic

surfactants and nonionic surfactants having an HLB value of 10

to 20.

Preferably, the average particle diameter D50 of the

pigment dispersion is no larger than 150 nm.

In another aspect, the present invention provides a

recording ink, comprising a pigment dispersion described above,

a surfactant, a water-dispersible resin, a humectant and water.

Preferably, the surfactant is one of silicone surfactants

and fluorine-containing surfactants.

Preferably, the water-dispersible resin exhibits a

film-forming ability after printing on a recording media, and

has a minimum film-forming temperature of no higher than

30 ⁰ C.

Preferably, the humectant is at least one selected from

glycerin, diethylene glycol, triethylene glycol, 1,3-butanediol

and 3-methyl- l,3-butanediol.

Preferably, the recording ink further comprises a pH

adjuster of at least one selected from alcohol amines, alkali

metal hydroxides, ammonium hydroxides, phosphonium

hydroxides and alkali metal carbonates, and pH of the recording

ink is 7 to 11.

In still another aspect, the present invention provides a

recording ink, comprising at least a water-dispersible colorant,

a water-dispersible resin, a humectant and water,

wherein the water-dispersible colorant is a pigment

dispersion that comprises a pigment, a pigment dispersant and

a polymer dispersion stabilizer,

the polymer dispersion stabilizer is an

alpha-olefin/maleic anhydride copolymer expressed by the

formula (l) below, or a mixture of the alpha-olefin/maleic

anhydride copolymer and at least one of styrene/acrylic

copolymers, water-soluble polyurethane resins and

water-soluble polyester resins,

the content of the humectant is 20 to 35% by mass in the

recording ink, the solid content of the water-dispersible resin in

the ink (A) and the solid content of the pigment in the

water-dispersible colorant (B) satisfy a relation with respect to

their ratio (A/B) of 2 to 8,

Formula (l)

in the formula (l), R represents an alkyl group, n is an

integer of 30 to 100.

In still another aspect, the present invention provides a

recording ink, comprising at least a water-dispersible colorant,

a water-dispersible resin, a humectant and water,

wherein the water-dispersible colorant is a pigment

dispersion that comprises a pigment and a polymer dispersion

stabilizer,

the pigment bears at least a hydrophilic group on the

surface and behaves as a self-dispersible pigment of

water-dispersibility or water-solubility in the absence of

dispersant,

the polymer dispersion stabilizer is an

alpha-olefin/maleic anhydride copolymer expressed by the

formula (l) below, or a mixture of the alpha-olefin/maleic

anhydride copolymer and at least one of styrene/acrylic

copolymers, water-soluble polyurethane resins and

water-soluble polyester resins,

the content of the humectant is 20 to 35% by mass in the

recording ink, the solid content of the water-dispersible resin in

the ink (A) and the solid content of the pigment in the

water-dispersible colorant (B) satisfy a relation with respect to

their ratio (A/B) of 2 to 8,

Formula (l)

in the formula (l), R represents an alkyl group, n is an

integer of 30 to 100.

Preferably, the entire content of the water-dispersible

colorant and the water-dispersible resin is 12 to 40% by mass

based on the entire recording ink.

Preferably, the mass average molecular weight of the

alpha-olefin/maleic anhydride copolymer is no higher than

20000.

Preferably, the alpha-olefin/maleic anhydride copolymer

has an acid value of 100 to 400 mgKOH/g, and is used as a

solution in an alkaline solution or an alkaline aqueous solution

containing an alkali amount of no less than that corresponding

to its acid value.

Preferably, the pigment dispersant is one of anionic

surfactants and nonionic surfactants having an HLB value of 10

to 20.

Preferably, the nonionic surfactant having an HLB value

of 10 to 20 is one of polyoxyethylene beta-naphthylether,

polyoxyethylene laurylether and polyoxyethylene

styrenephenylether.

Preferably, the water-dispersible resin is one of polyester

resins, polyurethane resins, acrylic resins and acrylic silicone

resins, and the minimum film-forming temperature of the

water-dispersible resin is no higher than 30°C.

Preferably, the humectant is at least one selected from

glycerin, diethylene glycol, triethylene glycol, 1,3-butanediol

and 3-methyl- l, 3-butanediol.

Preferably, the recording ink further comprises a

surfactant, and the surfactant comprises at least one selected

from silicone surfactants and fluorine-containing surfactants.

Preferably, the recording ink has a viscosity of 5 to 20

mPa-s at 25°C and a surface tension of no higher than 35 mN/m

at 25°C.

In still another aspect, the present invention provides an

ink cartridge, comprising a recording ink described above in a

container.

In still another aspect, the present invention provides an

ink-jet recording method, comprising at least an ink ejecting

step, wherein a recording ink described above is, in the ink

ejecting step, applied a stimulus to record an image through

being ejected.

Preferably, the stimulus is at least one selected from

heat, pressure, vibration and light.

In still another aspect, the present invention provides an

ink-jet recording apparatus, comprising at least an ink ejecting

unit, wherein a recording ink described above is, by the ink

ejecting unit, applied a stimulus to record an image through

being ejected.

Preferably, the stimulus is at least one selected from

heat, pressure, vibration and light.

In still another aspect, the present invention provides an

ink recorded matter, comprising an image formed from a

recording ink described above on a recording medium.

The pigment dispersion according to the present

invention comprises a pigment, a pigment dispersant, a polymer

dispersion stabilizer and water, in which the polymer dispersion

stabilizer is an alpha-olefin/maleic anhydride copolymer

expressed by the formula (l) described above. The combination

of these ingredients may improve dispersion stability of the

pigment under long-term storage, thus the pigment dispersion

may be utilized as a colorant for ink-jet recording inks in

particular.

The recording ink according to the present invention, in

the first embodiment, comprises the pigment dispersant

according to the present invention, a surfactant, a

water-dispersible resin, a humectant and water. The recording

ink according to the present invention may bring about, by

virtue of the pigment dispersion according to the present

invention, excellent ejection stability without head clogging at

printing, highly durable images with superior water resistance

and lightfastness, and high quality images with favorable color

tone on not only dedicated recording paper but also regular

paper.

The ink cartridge according to the present invention

contains the inventive recording ink of the first embodiment in

a container. The ink cartridge may be appropriately utilized

for printers etc. of ink-jet recording processes. The recording

by use of the ink in the ink cartridge may bring about excellent

ejection stability without head clogging at printing, highly

durable images with superior water resistance and lightfastness,

and high quality images with favorable color tone on not only

dedicated recording paper but also regular paper.

The inventive ink-jet recording apparatus comprises at

least an ink electing unit that applies energy to the inventive

recording ink of the first embodiment to record images through

ejecting the recording ink. In the ink-jet recording apparatus,

the inventive recording ink is applied energy and ejected from

nozzles thereby to record images. Consequently, printing may

be carried out with excellent ejection stability without head

clogging, images may be formed with high durability such as

water resistance and lightfastness, and high quality images

with favorable color tone may be formed on not only dedicated recording paper but also regular paper.

The inventive ink-jet recording method comprises at

least an ink electing step that applies energy to the inventive

recording ink of the first embodiment to record images through

ejecting the recording ink. In the ink-jet recording method, the

inventive recording ink is applied energy and ejected from

nozzles thereby to record images. Consequently, printing may

be carried out with excellent ejection stability without head

clogging, images may be formed with high durability such as

water resistance and lightfastness, and high quality images

with favorable color tone may be formed on not only dedicated

recording paper but also regular paper.

The ink recorded matter according to the present

invention comprises an image formed from the inventive

recording ink of the first embodiment on a recording medium.

The image may be formed on the ink recorded matter with

excellent ejection stability without head clogging at printing,

highly durable with superior water resistance and lightfastness,

and of high quality with favorable color tone on not only

dedicated recording paper but also regular paper.

The inventive recording ink comprises at least, in the

second embodiment, a water-dispersible colorant, a

water-dispersible resin, a humectant and water, in which the

water-dispersible colorant is a pigment dispersion that

comprises a pigment, a pigment dispersant and a polymer

dispersion stabilizer, the polymer dispersion stabilizer is an

alpha-olefin/maleic anhydride copolymer expressed by the

formula (l) described above, or a mixture of the

alpha-olefin/maleic anhydride copolymer and at least one of

styrene/acrylic copolymers, water-soluble polyurethane resins

and water-soluble polyester resins, the content of the

humectant is 20 to 35% by mass in the recording ink, the solid

content of the water-dispersible resin in the ink (A) and the

solid content of the pigment in the water-dispersible colorant

(B) satisfy a relation with respect to their ratio (A/B) of 2 to 8.

The inventive recording ink comprises at least, in the

third embodiment, a water-dispersible colorant, a

water-dispersible resin, a humectant and water, in which the

water-dispersible colorant is a pigment dispersion that

comprises a pigment and a polymer dispersion stabilizer, the

pigment bears at least a hydrophilic group on the surface and

behaves as a self-dispersible pigment of water-dispersibility or

water-solubility in the absence of dispersant, the polymer

dispersion stabilizer is an alpha-olefin/maleic anhydride

copolymer expressed by the formula (l) described above, or a

mixture of the alpha-olefin/maleic anhydride copolymer and at

least one of styrene/acrylic copolymers, water-soluble

polyurethane resins and water-soluble polyester resins, the

content of the humectant is 20 to 35% by mass in the recording

ink, the solid content of the water-dispersible resin in the ink

(A) and the solid content of the pigment in the water-dispersible

colorant (B) satisfy a relation with respect to their ratio (A/B) of

2 to 8.

The recording ink of the second or third embodiment may

afford superior image quality on regular paper particularly with

no inkless void and with higher image density, color saturation,

durability such as water resistance and lightfastness, and

represents excellent drying property and beading on gloss paper,

superior drying velocity and high-speed printing, and

appropriate ejection stability from nozzles.

The inventive ink cartridge contains the inventive

recording ink of the second or third embodiment in a container.

The ink cartridge may be appropriately utilized for printers etc.

of ink-jet recording processes. The recording by use of the ink

in the ink cartridge may bring about superior image quality on

regular paper particularly with no inkless void and with higher

image density, color saturation, durability such as water

resistance and lightfastness, and may represent excellent

drying property and beading on gloss paper, superior drying

velocity and high-speed printing, and appropriate ejection

stability from nozzles, thus images may be recorded with high

clearness like printed matters.

The inventive ink-jet recording apparatus comprises at

least an ink electing unit that applies energy to the inventive

recording ink of the second or third embodiment to record

images through ejecting the recording ink. In the ink-jet

recording apparatus, the inventive recording ink is applied

energy and ejected from nozzles thereby to record images.

Consequently, the recording may bring about superior image

quality on regular paper particularly with no inkless void and

with higher image density, color saturation, durability such as

water resistance and lightfastness, and may represent excellent

drying property and beading on gloss paper, superior drying

velocity and high-speed printing, and appropriate ejection

stability from nozzles, thus images may be recorded with high

clearness like printed matters.

The inventive ink-jet recording method comprises at

least an ink electing step that applies energy to the inventive

recording ink of the second or third embodiment to record

images through ejecting the recording ink. In the ink-jet

recording method, the inventive recording ink is applied energy

and ejected from nozzles thereby to record images.

Consequently, the recording may bring about superior image

quality on regular paper particularly with no inkless void and

with higher image density, color saturation, durability such as

water resistance and lightfastness, and may represent excellent

drying property and beading on gloss paper, superior drying

velocity and high-speed printing, and appropriate ejection

stability from nozzles, thus images may be recorded with high

clearness like printed matters.

The inventive ink recorded matter comprises on a

recording medium an image formed by the inventive recording

ink of the second or third embodiment. The ink recorded

matter on regular paper may be with no inkless void and with

higher image density, color saturation, durability such as water

resistance and lightfastness, and may represent excellent

drying property and beading on gloss paper, superior drying

velocity and high-speed printing, and appropriate ejection

stability from nozzles, thus images may be recorded on the

recording medium with high clearness like printed matters.

Brief Description of Drawings

FIG. 1 is a schematic exemplary view of an ink cartridge

according to the present invention.

FIG. 2 is a schematic view of the ink cartridge of FIG. 1

and its case.

FIG. 3 is a schematic perspective view of an ink

cartridge-mounting portion of an ink-jet recording apparatus

with its cover being opened.

FIG. 4 is a schematic view that shows an entire

configuration of an ink-jet recording apparatus.

FIG. 5 is a schematic enlarged view that exemplarily

shows an ink-jet head according to the present invention.

Best Mode for Carrying Out the Invention

Pigment Dispersion

The pigment dispersion according to the present

invention comprises a pigment, a pigment dispersant, a polymer

dispersion stabilizer, and water, and also other optional

ingredients as required.

Polymer Dispersion Stabilizer

The polymer dispersion stabilizer may be

alpha-olefin/maleic anhydride copolymers expressed by the

structural formula (l) shown below.

Formula (l)

In the structural formula (l), R represents an alkyl group

of which the carbon-atom number is preferably 6 to 25, more

preferably 6 to 22, and the alkyl group may be of linear chain,

branched chain or cyclic; n is an integer of 30 to 100.

The alpha olefin/maleic' anhydride copolymers expressed

by the structural formula (l) are typically, at room temperature,

a solid and can hardly dissolve into water at all. The

alpha-olefin/maleic anhydride copolymers are effective to

stabilize pigment dispersions in which pigments are uniformly

finely dispersed into water. The effect for stabilizing the

dispersions is significant when the alpha-olefin/maleic

anhydride copolymers are dissolved in an alkaline or alkaline

aqueous solution in a condition that the alkaline quantity of the

alkaline or alkaline aqueous solution is no less than the

alkaline quantity corresponding to the acid value of the

alpha-olefin/maleic anhydride copolymer.

The alpha-olefin/maleic anhydride copolymers can be

easily dissolved into alkaline or alkaline aqueous solutions

under heating and stirring. In some cases where the olefin

chain of the copolymers is relatively long, it may be difficult to

dissolve the copolymers and thus insoluble matters may remain

in the solutions! in such cases, the copolymers may be

effectively utilized through merely removing the insoluble

matters using a filter etc.

Examples of the bases in the alkaline or alkaline aqueous

solutions include alkaline metal hydroxides such as sodium

hydroxide, potassium hydroxide and lithium hydroxide, ^' basic

substances such as ammonia, triethylamine and morpholineJ

alcohol amines such as triethanolamine, diethanolamine, N-methyl diethanolamine, 2-amino-2-ethyl l,3-propanediol and

choline.

The acid value of the alpha olefin/maleic anhydride

copolymers is preferably 100 to 400 mgKOH/g, more preferably

100 to 350 mgKOH/g. When the acid value is below 100

mgKOH/g, the solubility may be insufficient in the alkaline

solutions, and when the acid value is above 400 mgKOH/g,

ink-ejection may be disturbed due to higher viscosities of

dispersions or dispersion stability may be degraded.

The mass average molecular weight of the

alpha-olefin/maleic anhydride copolymers is preferably 5000 to

20000. When the mass average molecular weight is less than

5000, the dispersion stability of pigment dispersions may be

lowered, and when the mass average molecular weight is more

than 20000, the solubility may be insufficient in alkaline

solutions or the viscosity may be inappropriately higher.

The polymer dispersion stabilizer may be properly

synthesized or commercially available! examples of those

include T YPI lO, T-YP l I l, T-YP112 and T-YP113 (by Seico

PMC Co.).

The amount of the polymer dispersion stabilizers is

preferably 1 to 100 parts by mass based on 100 parts by mass of

pigments on the basis of solid content, more preferably 5 to 50

parts by mass. When the amount is less than 1 part by mass,

the effect of dispersion stabilization may be negligible, and

when the amount is more than 100 parts by mass, ink-ejection

may be blocked due to higher viscosities, or the cost may be

higher.

Pigment

The pigment is preferably a complex pigment which is

formed of organic or inorganic pigment particles coated with an

organic pigment or carbon black. The complex pigment may be

produced by depositing an organic pigment or carbon black on

inorganic pigment particles, or by mechanochemically mixing

and abrading an inorganic pigment and an inorganic pigment or

a carbon black. The adhesion between the organic pigment and

the inorganic pigment may be enhanced by disposing a layer of

polysiloxanes or organosilane compounds formed from

alkylsilanes therebetween as required.

Examples of organic pigment include aniline black as a

black pigment; anthraquinone, phthalocyanine blue,

phthalocyanine green, diazo- or monoazo yellow pigment, disazo

yellow pigment, pyranthoron, perylene, heterocyclic yellow,

quinacridone, (thio)indigo as color pigments, and the like.

Among these, phthalocyanine pigments, quinacridone pigments,

monoazo yellow pigments, disazo yellow pigments and

heterocyclic yellow pigments are especially preferable in terms

of color developing ability.

Examples of phthalocyanine pigments include copper

phthalocyanine blue and derivatives thereof (CI. pigment blue

15 ^: 3, 15 ^: 4), aluminum phthalocyanine, and the like.

Examples of quinacridone pigments include C.I. pigment

orange 48, C.I. pigment orange 49, C.I. pigment red 122, C.I.

pigment red 192, C.I. pigment red 202, C.I. pigment red 206, C.I.

pigment red 207, C.I. pigment red 209, C.I. pigment violet 19,

C.I. pigment violet 42, and the like.

Examples of monoazo yellow pigments include C.I.

pigment yellow 74, C.I. pigment yellow 109, C.I. pigment yellow

128, C.I. pigment yellow 151, and the like.

Examples of disazo yellow pigments include C.I. pigment

yellow 14, C.I. pigment yellow 16, C.I. pigment yellow 17, and

the like.

Examples of heterocyclic yellow pigments include C.I.

pigment yellow 117, C.I. pigment yellow 138, and the like.

Other coloring pigments may be found in "The Color

Index, third edition, by Society of Dyers and Colorists (1982)".

Examples of the inorganic particles include those of

titanium dioxide, silica, alumina, iron oxide, iron hydroxide, tin

oxide etc. These may be used alone or in combination.

It is preferred that the organic pigment particles have a

particle shape of lower aspect ratios, most preferably are

spherical. The color of the inorganic pigment particles is

preferably transparent or white in cases where the pigment is

to be colored, and black inorganic pigments are allowable in

cases where a black colorant is to be deposited. The primary

particle size of the inorganic pigment particles is preferably no

more than 100 nm, more preferably 5 to 50 nm.

The mass ratio of the inorganic pigment particles to the

organic pigment or carbon black as a color material, i.e.

inorganic pigment particles : color material, is preferably 3^ 1 to

1 -3 and more preferably 3:2 to 1 ^: 2. When the mass ratio of the

color material is small, color developing ability or coloring

power may be deteriorated, and when the amount of the color

material excessively higher, transparency or color tones may be deteriorated.

Examples of color particles, in which inorganic pigment

particles being coated with an organic pigment or carbon black,

include composite materials such as silica/carbon black

composite materials, silica/phthalocyanine C. I. PB 15^3

composite material, silica/disazo yellow composite material and

silica/quinacridone C.I. PR122 composite material (by Toda

Kogyo Co.). The primary particle diameters of these materials

are sufficiently small for favorable use.

When inorganic pigment particles with a primary

particle diameter of 20 nm are coated with an equivalent

amount of organic pigment, the primary particle diameter of

this pigment should become about 25 nm. When these

pigments can be dispersed into their primary particles using an

appropriate dispersant, an extremely fine pigment-dispersed

ink can be produced with a dispersing particle diameter of 25

nm. In these complex pigments, not only the organic pigment

on the surface affects the dispersion but also the properties of

the central inorganic pigment appear through the thin layer 2.5

nm thick, the selection of the pigment dispersant should be

based on both the organic and inorganic pigments.

The colorant pigment particles, in the present invention,

may be surface-treated with carboxyl, carbonyl, sulfonic,

hydroxyl group, or the like to turn into hydrophilic, then

aqueous dispersion thereof may be utilized. The process of

surface treatment may be conventional ones such as oxidization

treatment, azo reaction and plasma treatment.

Pigment Dispersant

The pigment dispersants for dispersing the organic

pigments or complex pigments are preferably anionic

surfactants or nonionic surfactants with an HLB value of 10 to

20.

Examples of anionic surfactants include polyoxyethylene

alkylether acetates, alkylbenzene sulfonates (e.g. NH ₄ , Na, Ca),

alkyldiphenylether disulfonates (e.g. NH ₄ , Na, Ca),

dialkylsuccinate sodium sulfonates, naphthalenesulfonic acid

formalin condensate sodium salts, polyoxyethylene polycyclic

phenylether sulfonate salts (e.g. NH4, Na), lauric acid salts,

polyoxyethylene alkylether sulfonate salts and oleate salts.

Among these, dioctylsulfosuccinate Na salt and polyoxyethylene

styrenephenylether sulfonate NH ₄ salt are preferable in

particular.

Examples of the nonionic surfactants with an HLB value

of 10 to 20 include polyoxyethylene alkylether, polyoxyalkylene

alkylether, polyoxyethylene polycyclic phenylether, sorbitan

fatty ester, polyoxyethylene sorbitan fatty ester,

polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine,

polyoxyethylene alkylamide, and acetylene glycol. Among

these, polyoxyethylene laurylether, polyoxyethylene

beta-naphthylether, polyoxyethylene sorbitan monooleate, and

polyoxyethylene styrenephenylether are preferable in

particular.

The pigment dispersion in the present invention may be

produced by the processes using apparatuses such as

homogenizers for high-speed stirring, ball-dispersion kneaders

such as a bead mill and ball mill, shear-dispersion kneaders

such as a roll mill, and an ultrasonic disperser, after a

dispersant is dissolved in an aqueous medium to prepare a

solution to which the organic or complex pigment is then added

and moistened sufficiently followed by adding the polymer

dispersant. After the mixing and dispersing processes, there

often exist coarse particles in the resulting dispersion, thus it is

typically required to remove the coarse particles of above 1 μm

diameter using a filter or centrifugal separator in order to

prevent blockings of production lines.

The amount of the dispersant is preferably 1 to 100 parts

by mass based on 100 parts by mass of the pigment, more

preferably 10 to 50 parts by mass. When the amount of the

dispersant is insufficient, the pigment may not be sufficiently

micronized, and when the amount is excessive, the excessive

dispersant non-adsorbed onto pigments tends to affect ink

properties, resulting in image bleeding or deterioration of water

and/or scratch resistance.

The pigment dispersions according to the present

invention may exhibit superior pigment-dispersion stability

under long-term storage, and thus may be favorably utilized as

colorants etc. in various applications, in particular colorants of

ink-jet recording inks explained below.

Recording Ink

Recording Ink of First Embodiment

The recording ink in the first embodiment according to

the present invention comprises the pigment dispersion

according to the present invention, a surfactant, a

water-dispersible resin, a humectant, and water, and also other

optional ingredients such as a wetting agent, a pH-adjuster and

the like as required.

The average particle diameter D50 of the inventive

pigment dispersion of colorant is preferably no more than 150

nm in the recording inks, more preferably no more than 100 nm.

When the average particle diameter D50 is above 150 nm, the

ejection stability may be degraded remarkably, resulting

possibly in nozzle clogging or ink-ejection deviation. When the

average particle diameter D50 is no more than 100 nm, the

ejection stability may be promoted and also color saturation

may be improved.

The amount of the pigment dispersion is preferably 2 to

15% by mass in the recording ink on the basis of solid content,

more preferably 3 to 10% by mass. When the amount is below

2% by mass, color development and image density of the ink

may be significantly lowered, and when the amount is above

15% by mass, the ink viscosity may rise excessively to

deteriorate the ejection condition, and also the production cost

may rise.

Recording Ink of Second and Third Embodiments

The recording inks in the second or third embodiment

according to the present invention comprise at least a

water-dispersible colorant, a water-dispersible resin, a

humectant, and water, and also other optional ingredients such

as a surfactant, a wetting agent and the like as required.

In the second embodiment of the recording ink, the

water-dispersible colorant is a pigment dispersion that contains

a pigment, a pigment dispersant, and a polymer dispersion

stabilizer,' in the third embodiment of the recording ink, the

water-dispersible colorant is a pigment dispersion that contains

a self-dispersible pigment and a polymer dispersion stabilizer.

In the recording ink according to the present invention,

the ratio of A/B in a range of 2 to 8 may increase the fixing

ability and improve the color development, in which A is a solid

content of the water-dispersible resin in the recording ink and

B is a solid content of the pigment in the water-dispersible

colorant in the recording ink. The fixing ability and the color

development may be improved along with raising the solid

content of water-dispersible resins to e.g. three or four times of

the solid content of pigments, and the effect to enhance image

density tends to saturate at around more than eight times,

therefore the ratio of A/B in the range of 2 to 8 is preferable in

view of production cost still. The total content of the

water-dispersible colorant and the water-dispersible resin is

preferably 12 to 40% by mass based on the entire weight of the

recording ink, more preferably 15 to 35% by mass. When the

content is below 12% by mass, the drying ability may be poor on

paper surface, possibly resulting in degradation of letter-image

quality on regular paper, and when the content is above 40% by

mass, the ink may easily dry at nozzle face, possibly resulting

in inferior ejection.

The solid contents of the colorant and the

water-dispersible resin may be measured through separating

exclusively the colorant or the water-dispersible resin from the

ink. In cases where pigments are employed as the colorant,

the ratio of the colorant to the water-dispersible resin can be

determined through measuring weight loss by

thermogravimetric analysis. In cases where molecular

structure of the colorant is definite, the solid content of the

colorant can be determined by NMR, fluorescent X-ray analysis

or the like.

Water-Dispersible Colorant

The water-dispersible colorant in the second embodiment

is a pigment dispersion that contains a pigment, a pigment

dispersant and a polymer dispersion stabilizer.

The water-dispersible colorant in the third embodiment

is a pigment dispersion that contains a pigment and a polymer

dispersion stabilizer, in which the pigment has at least a

hydrophilic group on the surface and is a self-dispersible

pigment that is water-dispersible and/or water-soluble in the

absence of dispersant.

The polymer dispersion stabilizer may be one of

alpha-olefin/maleic anhydride copolymers expressed by the

formula (l) below or a mixture of at least one of the

alpha-olefin/maleic anhydride copolymers and at least one of

styrene/acrylic copolymers, water-soluble polyurethane resins

and water-soluble polyester resins.

Formula (l)

In the formula (l), R represents an alkyl group of which

the carbon-atom number is preferably 6 to 25, more preferably 6

to 22; n is an integer of 30 to 100.

The alpha-olefin/maleic anhydride copolymers expressed

by the formula (l) may be properly synthesized or commercially

available; examples thereof include T YP112, T YP114, T-YP115

and T YP116 (by Seico PMC Co.).

The water-soluble polyurethane resins may be

commercially available ones! examples thereof include Takelac

W-5025, Takelac W-6010, Takelac W-5661, etc. (by Mitsui

Takeda Chemical Co.).

The water-soluble polyester resins may be commercially

available ones, ^' examples thereof include Nichigo Polyester

W-0030, Nichigo Polyester W-0005S30WO, Nichigo Polyester

WR-961 (by Nippon Synthetic Chemical Industries, Co.),

Pesresin A-210, Pesresin A 520 (by Takamatsu Yusi Co.), etc.

In cases where at least one of alpha-olefin/maleic

anhydride copolymers (A) and at least one of styrene/acrylic

copolymers, water-soluble polyurethane resins and

water-soluble polyester resins (B) are mixed, the mixing ratio

(A : B) is preferably 10 : 90 to 90 : 10.

The solid content of the polymer dispersion stabilizers is

preferably 1 to 100 parts by mass based on 100 parts by mass of

the pigments, more preferably 5 to 50 parts by mass. When the

solid content is below 1 part by mass, the effect to stabilize

dispersion may be negligible, and when more than 100 parts by

mass, ink-ejection may be blocked due to higher viscosities

and/or the cost may be higher.

Pigment

The pigment may be organic or inorganic. The pigment

may contain a dye in order to arrange the color tone as long as

the durability being maintained.

Examples of the inorganic pigments include titanium

oxide, iron oxide, calcium carbonate, barium sulfate, aluminum

hydroxide, barium yellow, cadmium red, chromium yellow, and

carbon black; among these, carbon black etc. is preferable. The

carbon black may be those produced by the publicly known

methods such as a contact method, furnace method and thermal

method.

The organic pigments include azo pigments, polycyclic

pigments, dye chelates, nitro pigments, nitroso pigments, and

aniline black. Among these, azo pigments and polycyclic

pigments are preferable. Examples of the azo pigments include

azo lakes, insoluble azo pigments, condensed azo pigments, and

chelate azo pigments. The polycyclic pigments include

phthalocyanine pigments, perylene pigments, perinone

pigments, anthraquinone pigments, quinacridone pigments,

dioxadine pigments, indigo pigments, thioindigo pigments,

isoindolinone pigments and quinophtalone pigments.

Examples of the dye chelates include basic dye chelates and

acidic dye chelates.

The color of the colorants may be properly selected

depending on the purpose; for example, the color may be

achromatic or chromatic. The colorant may be used alone or in

combination of two or more.

Examples of achromatic colorants include carbon black

(CI. pigment black 7) such as furnace black, lamp black,

acetylene black and channel black, ^" metal oxides such as copper

oxide, iron oxide (CI. pigment black 11) and titanium oxide, ^"

organic pigments such as aniline black (CI. pigment black l).

Examples of chromatic colorants include C.I. pigment

yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide),

53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 408, 109, 110, 117,

120, 128, 138, 150, 151, 153, 183; C.I. pigment orange 5, 13, 16,

17, 36, 43, 51; C.I. pigment red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2,

48:2 (permanent red 2B (Ca)), 48:3, 48:4, 49: 1, 52:2, 53: 1, 57: 1

(brilliant carmine 6B), 60: 1, 63: 1, 63:2, 64:1, 81, 83, 88, 101

(colcothar), 104, 105, 106, 108 (cadmium red), 112, 114, 122

(quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177,

178, 179, 185, 190, 193, 209, 219, ^" C.I. pigment violet

(rhodamine lake), 3, 5:1, 16, 19, 23, 38; C.I. pigment blue 1, 2,

15 (phthalocyanine blue) 15:1, 15:2, 15 ^: 3 (phthalocyanine blue),

16, 17: 1, 56, 60, 63; C.I. pigment green 1, 4, 7, 8, 10, 17, 18, 36.

The self-dispersible pigments, utilized for the recording

ink of the third embodiment, are surface-modified ones such

that at least a hydrophilic group bonds directly or through

another atomic group to the surface of the pigments. The ,

surface-treatment may be carried out by way of chemically

bonding a certain functional group such as sulfonic group and

carboxyl group to the surface of pigments or wet-oxidizing

pigments with hypohalous acids or their salts. Particularly

preferable are water-dispersible pigments to which surface the

carboxyl group bonds. Such surface-treatment with carboxyl

group may improve dispersion stability, provide high-quality

printing and increase water resistance of recorded matters after

printing.

In addition, such inks may exhibit superior

re-dispersibility even once dried, therefore there occurs

substantially no clogging of nozzles even after a long-term rest

and thus moisture of the ink around ink-jet head nozzles has

evaporated, and then proper printing may regenerate after

simple cleaning.

Preferably, the self-dispersible pigments have a volume

average particle diameter of 0.01 to 0.16 μm in inks.

Preferably, the self-dispersible carbon blacks exhibit

ionic properties, more preferably, have an anionic or cationic

charge.

Examples of the anionic hydrophilic groups include

-COOM, SO ₃ M, PO ₃ HM, PO ₃ M ₂ , SO ₂ NH ₂ , and -SO ₂ NHCOR,

in which M represents one of hydrogen atom, alkaline metals,

ammonium, and organic ammoniums, R represents one of alkyl

groups having a carbon-atom number of 1 to 12, phenyl groups

which may be substituted by a substituent, and naphthyl groups

which may be substituted by a substituent. Among these,

preferable are color pigments to which surface -COOM or

-SO ₃ M bonds.

M of alkaline metals in the hydrophilic group includes,

for example, lithium, sodium and potassium. Examples of the

organic ammoniums include mono- or tri-methyl ammonium,

mono- or tri-ethyl ammonium, mono or tri-methanol ammonium, and the like. As for the methods for producing the anionically charged color pigments, -COONa may be introduced on the surface of color pigments by way of, for example, oxidization-treating color pigments using sodium hypochlorite, sulfonating, or reacting with a diazonium salt.

The cationic hydrophilic groups are preferably quaternary ammonium groups, more preferably the quaternary ammonium groups shown below. Carbon blacks, to which at least one of these groups attaches, are preferable colorant in the present invention.

- NH ₃ „ - NR _{3 ^}

The cationic self-dispersible carbon blacks, to which

hydrophilic groups bond, may be properly produced depending

on the application; for example, N-ethylpyridyl group shown

below can be attached to carbon black through treating with

3-amino-N-ethylpyridinium bromide.

The hydrophilic groups may be attached to the surface of

carbon black through another atomic group. The another

atomic group may be alkyl groups having a carbon-atom number

of 1 to 12, phenyl groups which may be substituted by a

substituent, and naphthyl groups which may be substituted by a

substituent. Specific examples of the hydrophilic groups and

another atomic groups attached to the surface of carbon black

are - C2H4COOM (M: one of alkaline metals and quaternary

ammoniums), -PI1SO3M (Ph: phenyl group, M: one of alkaline

metals and quaternary ammoniums), and -CsH ₁ ONHs ⁺ .

Conventional organic pigments or inorganic pigment

particles may be coated with organic pigments or carbon blacks

to prepare complex pigments, and may be appropriately utilized

in the present invention. The methods for producing these

complex pigments may be, for example, deposition of organic

pigments on inorganic pigment particles or mechanochemical

processes by mechanically mixing and milling organic and

inorganic pigments. A layer of organosilane compounds, synthesized from polysiloxanes and alkylsilanes, may be

disposed between the organic and inorganic pigments to

strengthen the adhesion therebetween as required.

Examples of organic pigment include aniline black as

black pigment! anthraquinone, phthalocyanine blue,

phthalocyanine green, diaso, monoazo, pyranthoron, perylene,

heterocyclic yellow, quinacridone, (thio)indigo as color pigment.

Among these, carbon blacks, phthalocyanine pigments,

quinacridone pigments, monoazo yellow pigments, disazo yellow

pigments and heterocyclic yellow pigments are especially

preferable in terms of color developing ability.

Examples of phthalocyanine blue include copper

phthalocyanine blue and derivatives thereof (CI. pigment blue

15^3, 15:4), aluminum phthalocyanine, and the like. Examples

of quinacridone pigments include C.I. pigment orange 48, CI.

pigment orange 49, C.I. pigment red 122, C.I. pigment red 192,

C.I. pigment red 202, C.I. pigment red 206, C.I. pigment red 207,

C.I. pigment red 209, C.I. pigment violet 19, C.I. pigment violet

42, and the like. Examples of monoazo yellow pigments

include C.I. pigment yellow 74, C.I. pigment yellow 109, C.I.

pigment yellow 128, C.I. pigment yellow 151, and the like.

Examples of disazo yellow pigments include C.I. pigment yellow

14, C.I. pigment yellow 16, C.I. pigment yellow 17, and the like.

Examples of heterocyclic yellow pigments include C.I. pigment

yellow 117, C.I. pigment yellow 138, and the like. Other

coloring pigments may be found in "The Color Index, third

edition, by The Society of Dyers and Colorists (1982)".

The inorganic pigments may be exemplified by titanium

dioxide, silica, alumina, iron oxide, iron hydroxide, and tin

oxide; the particle shape is preferably of lower aspect ratios,

most preferably spherical. The color of the inorganic pigments

is preferably transparent or white in cases where chromatic

colorants are to be adsorbed, and may be black in cases where

black colorants are to be adsorbed. The primary particle

diameter of the organic pigment particles is preferably no more

than 100 nm, more preferably 5 to 50 nm.

The mass ratio of the inorganic pigment particles to the

organic pigments or carbon blacks as a -color material, i.e.

inorganic pigment particles ^' ■ colorants, is preferably 3^ 1 to- 1 ^3

and more preferably 3 ^: 2 to 1-2. In cases where the mass ratio

of colorants is relatively low, color developing ability or tinting

strength may be poor, and in cases where the mass ratio of

colorants is relatively high, transparency or color tones may be

deteriorated.

Examples of colorant particles in which inorganic

pigment particles being coated with organic pigments or carbon

blacks include composite materials by Toda Kogyo Corporation

such as silica/carbon black composite material,

silica/phthalocyanine C.I. PB15:3 composite material,

silica/disazo yellow composite material, silica/quinacridone C.I.

PR122 composite material, and the like, ^' the primary particle

diameters of these products are sufficiently small to be

employed.

When inorganic pigment particles with a primary

particle diameter of 20 nm are coated with an equivalent

amount of organic pigment, the primary particle diameter of

this pigment should become about 25 nm. When these

pigments can be dispersed into their primary particles using an

appropriate dispersant, an extremely fine pigment-dispersed

ink can be produced with a dispersing particle diameter of 25

nm. In these complex pigments, not only the organic pigment

on the surface affects the dispersion but also the properties of

the central inorganic pigment appear through the thin layer 2.5

nm thick, the selection of the pigment dispersant should be

based on both the organic and inorganic pigments.

Pigment Dispersant

The colorants in the second embodiment contain a

pigment dispersant. The pigment dispersant is preferably one

of anionic surfactants and nonionic surfactants having an HLB

value of 10 to 20.

Specific examples of the anionic surfactants include

polyoxyethylenealkylether acetate, alkylbenzene sulfonate (e.g.

NH ₄ , Na, Ca), alkyldiphenylether disulfonate (e.g. NH4, Na, Ca),

dialkylsuccinate sodium sulfonates, naphthalenesulfonic acid

formalin condensate sodium salts, polyoxyethylene polycyclic

phenylether sulfonate salts (e.g. NH4, Na), lauric acid salts,

polyoxyethylene alkylether sulfonate salts and oleate salts.

Among these, dioctylsulfosuccinate Na salt and polyoxyethylene

styrenephenylether sulfonate NH4 salts are preferable in

particular.

Examples of the nonionic surfactants with an HLB value

of 10 to 20 include polyoxyethylene alkylether, polyoxyalkylene

alkylether, polyoxyethylene polycyclic phenylether, sorbitan

fatty ester, polyoxyethylene sorbitan fatty ester,

polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine,

polyoxyethylene alkylamide, and acetylene glycol. Among

these, polyoxyethylene laurylether, polyoxyethylene

beta-naphthylether, polyoxyethylene sorbitan monooleate, and

polyoxyethylene styrenephenylether are preferable in

particular.

The amount of the dispersants is preferably 1 to 100

parts by mass based on 100 parts by mass of the pigments, more

preferably 10 to 50 parts by mass. When the amount of the

dispersant is insufficient, the pigment may not be sufficiently

micronized, and when the amount is excessively high, the

excessive dispersant non-adsorbed onto pigments tends to affect

ink properties, resulting in image bleeding or deterioration of

water and scratch resistance.

The pigment dispersion may be produced by the process

using apparatuses such as homogenizers for high-speed stirring,

ball-dispersion kneaders such as a bead mill and ball mill,

shear-dispersion kneaders such as a roll mill, and ultrasonic

dispersers, after the organic dispersant is dissolved in an

aqueous medium to prepare a solution to which the pigment is

then added and moistened sufficiently followed by adding the

polymer dispersant. After the mixing and dispersing processes,

there often exist coarse particles in the resulting dispersion,

thus it is typically required to remove the coarse particles of

above 1 μm diameter using a filter or centrifugal separator in

order to prevent blockings of production lines.

The average particle diameter D50 of pigment dispersions

is preferably no more than 150 nm in the recording inks, more

preferably no more than 100 nm. When the average particle

diameter D50 is above 150 nm, the ejection stability may worsen

remarkably, resulting possibly in nozzle clogging or ink-ejection

deviation. When the average particle diameter D50 is no more

than 100 nm, the ejection stability may be promoted and color

saturation may be improved.

The amount of the pigment dispersions is preferably 2 to

15% by mass in the entire recording inks on the basis of solid content, more preferably 3 to 12% by mass. When the amount is below 2% by mass, color development and image density may be significantly lowered, and when the amount is above 15% by mass, the ink viscosity may rise excessively to deteriorate the ejection condition, and also the production cost may rise. Common Ingredients of Recording Inks of First to Third

Embodiments Surfactant It is preferred that the surfactant is one of silicone surfactants and fluorine-containing surfactants, provided that the surfactant preferably leads to lower surface tension and higher leveling ability, and does not diminish dispersion stability in combination with other colorants or humectantsJ in particular, fluorine-containing surfactants are preferable.

It is preferred that the fluorine-containing surfactants

contain 2 to 16 carbon atoms, to which fluorine atoms being bonded, per molecule, more preferably 4 to 16 carbon atoms. In cases where the carbon atoms to which fluorine atoms being bonded is less than 2, the effect of fluorine atom may be negligible, and in cases where more than 16, the ink-storage

stability may be lower.

Examples of the fluorine-containing surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl

carboxylic acid compounds, perfluoroalkyl phosphate ester

compounds, perfluoroalkyl ethyleneoxide adducts, and

polyoxyalkylene ether polymer compounds having a

perfluoroalkylether group in their side chains. Among these,

the polyoxyalkylene ether polymer compounds having a

perfluoroalkylether group in their side chains are particularly

preferable in view of lower foaming property.

Examples of the perfluoroalkyl sulfonic acid compounds

include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonate

salts! examples of the perfluoroalkyl carboxylic compounds

include perfluoroalkyl carboxylic acid and perfluoroalkyl

carboxylate salts.

The perfluoroalkyl phosphate ester compounds include,

for example perfluoroalkyl phosphate ester and perfluoroalkyl

phosphate ester salts.

Examples of the polyoxyalkylene ether polymer

compounds having a perfluoroalkyl ether group in their side

chains include polyoxyalkylene ether polymer having a

perfluoroalkyl ether group in the side chains, sulfate ester salts

of polyoxyalkylene ether polymer having a perfluoroalkyl ester

group in the side chains and salts of polyoxyalkylene ether

polymer having a perfluoroalkyl ether group in the side chains.

Counter ions of the salts in these fluorine-containing

surfactants include Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH,

NH ₂ (CH ₂ CH ₂ OH) ₂ and NH(CH ₂ CH ₂ OH) ₃ .

The fluorine-containing surfactants may be appropriately

synthesized or commercially available. >

Examples of the commercially available ones include

Surflon S- H l, S 112, S- 113, S 121, S- 131, S 132, S- 141, S- 145

(by Asahi Glass Co., Ltd.), Fullard FC-93, FC-95, FC-98, FC 129,

FC- 135, FC- 170C, FC-430, FC-431 (by Sumitomo 3M Ltd.),

Megafac F-470, F1405, F-474 (by Dainippon Ink And Chemicals,

Inc.), Zonyl TBS, FSP, FSA, FSN lOO, FSN, FSO- IOO, FSO,

FS-300, UR (by DuPont), FT- I lO, FT-250, FT-251, FT-400S,

FT- 150, FT-400SW (by Neos Co.) and PF- 151N (by Omnova Inc.).

Among these, FT I lO, FT-250, FT-251, FT 400S, FT- 150,

FT-400SW (by Neos Co.) and PF- 151N (by Omnova Inc.) are

particularly preferable in view of proper printing quality, in

particular color development and uniform-coloring property on

paper.

Specific examples of the fluorine-containing surfactants

are those represented by the following formulas,

(l) Anionic Fluorine-Containing Surfactant

In the above formula, Rf represents a mixture of

fluorine-containing hydrophobic groups represented by the

following formulas; A represents SO3X, COOX or -PO3X (X is a

counter anion, specifically hydrogen atom, Li, Na, K, NH4, NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , or NH(CH ₂ CH ₂ OH) ₃ ).

CF,

In the above formula, Rf is a fluorine-containing group represented by the following formula, ^' X is substantially the

same as above, n represents an integer of 1 or 2, and m represents 2-n.

F-(-CF ₂ CF ₂ -) _Tγ CH ₂ CH—

In the above formula, n represents an integer of 3 to 10.

Rf ' — S— C ^CH ₂ -COO ¹ X

In the above formula, Rf and X are substantially the same as defined above.

Rf -SO ₃ -X

In the above formula, Rf and X are substantially the same as defined above.

(2) Nonionic Fluorine-Containing Surfactant

Rf-O- -CH ₂ CH ₂ O- -H

In the above formula, Rf is substantially the same as defined above, and n represents an integer of 5 to 20.

Rf -O H ₂ CH ₂ O -H

In the above formula, Rf is the same as defined above, and n represents an integer of 1 to 40. (3) Ampholytic Fluorine-Containing Surfactant

CH 3,

In the above formula, Rf is substantially the same as defined above. (4) Oligomer-Type Fluorine-Containing Surfactant

O -Rf"

-SO ₃ -X

In the above formula, Rf represents a fluorine-containing group represented by the following formula, in which 1 represents an integer of 0 to 10 and X is substantially the same as defined above.

In the above formulas, n is an integer of 1 to 4.

In the above formula, Rf is substantially the same as

defined above; 1, m, and n represent each an integer of 0 to 10.

The silicone surfactants may be appropriately selected

depending on the purpose, preferably are those far from

degradation at higher pH; examples thereof include

polydimethylsiloxanes with modified side chains,

polydimethylsiloxanes with modified both ends,

polydimethylsiloxane with modified one end, and

polydimethylsiloxane with modified side chains and both ends.

The modifying group is preferably polyoxyethylene groups,

polyoxyethylene polyoxypropylene groups or the like in view of

appropriate properties as aqueous surfactants.

These surfactants may be appropriately synthesized or

commercially available; examples thereof are those available

from BYK Chemie GmbH, Shin-Etsu Silicones Co. Ltd., Dow

Corning Tray Co. Ltd, or the like.

The polyether-modified silicone surfactants may be

properly selected depending on the application, for example,

may be the compounds expressed by the formula below in which

polyalkyleneoxide units are introduced into Si-side chains of

dimethylpolysiloxanes.

C H C H C H C H

C H , -S i— O S i- O- S i- O — S i- C H

C H C H m n C H

In the formula above, m, n, a and b represent each an

integer; R and R' represent each an alkyl group or an alkylene

group.

The polyether-modified silicone surfactants may be

commercially available; examples thereof include KF-618,

KF-642 and KF 643 (by Shin-Etsu Chemical Co.).

In addition to the fluorine-containing surfactants and

silicone surfactants described above, anionic surfactants,

nonionic surfactants, and ampholytic surfactants are

employable as required.

Examples of the anionic surfactants include

polyoxyethylene alkylether acetate salts, dodecylbenzene

sulfonate salts, succinate ester sulfonate salts, lauryl acid salts,

and salts of polyoxyethylene alkylether sulfate.

Examples of the nonionic surfactants include acetylene

glycol surfactants, ^f ρolyoxyethylene alkylethers,

polyoxyethylene alkylphenylethers, polyoxyethylene alkylesters

and polyoxyethylene sorbitan fatty acid esters.

Specific examples of acetylene glycol surfactants

described above includes 2,4, 7,9-tetramethyl-5 decine-4, 7'diol, 3,6-dimethyl-4-octine-3,6-diol and 3, 5 dimethyl- l-hexine-3 ol.

The acetylene glycol surfactants may be commercially available,

for example, Surfynol 104, 82, 465, 485, and TG supplied (by Air

Products Co., USA).

Specific examples of the ampholytic surfactants described

above include lauryl aminopropionate salts, lauryl

dimethylbetaine, stearyl dimethylbetaine, lauryl

dihydroxyethylbetaine, lauryl dimethylamine oxide, myristyl

dimethylamine oxide, stearyl dimethylamine oxide,

dihydroxyethyllaurylamine oxide, polyoxyethylene palm oil

alkyl dimethylamine oxide, dimethylalkyl(palm)betaine and

dimethyllauryl betaine.

These surfactants may be commercially available

products by, for example, Nikko Chemicals Co. Ltd., Nippon

Emulsion Co. Ltd., Nippon Shokubai Co. Ltd., Toho Chemical

Industry Co. Ltd. , Kao Corporation, Adeka Co. Ltd., Lion

Corporation, Aoki Oil Industrial Co. Ltd., and Sanyo Chemical

Industries Ltd.

The surfactants described above may be used alone or in

combination. There exist some instances where a surfactant

hardly dissolves into an ink but dissolves easily with another

ink and the resulting solution is stable with time.

The content of the surfactants is preferably 0.01 to 3.0%

by mass, more preferably 0.5 to 2.0% by mass. When the

content is less than 0.01% by mass, the effect to add the

surfactants may be negligible, and when the content is more

than 3.0% by mass, image density may be lower and/or show

through may appear due to excessively high permeability into

recording media.

Water-Dispersible Resin

The water-dispersible resin may be appropriately

selected depending on the purpose from, for example, condensed

synthetic resins, addition synthetic resins and natural polymer

compounds.

Examples of the condensed synthetic resins include -

polyester resins, polyurethane resins, polyepoxy resins,

polyamide resins, polyether resins and silicone resins.

Examples of the addition synthetic resins include polyolefin

resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl

ester resins, polyacrylic resins and unsaturated carboxylic acid

resins. Examples of the natural polymer compounds include

celluloses, rosins and natural rubbers.

The water-dispersible resin may be used in a form of

homopolymers or copolymers, and be selected from single-phase

type, core shell type, or power feed-type emulsions.

The water-dispersible resins may be those where the

resin itself has a hydrophilic group and is self-dispersible or

those where the resin itself has no dispersibility whereas the

dispersibility is imparted by a surfactant or a resin with a

hydrophilic group. Among these, ionomers of the polyester

resin and polyurethane resin, and emulsions of resin particles

obtained by emulsification/suspension polymerization of

unsaturated monomers are preferable. In cases of

emulsification polymerization of unsaturated monomers, the

water-dispersible resin can be easily obtained because the resin

emulsion is obtained by reacting in the water into which the

unsaturated monomer, a polymerization initiator, and a

surfactant, a chain transfer agent, a chelator and a pH adjuster

have been added, and objective natures are easily made because

the resin constitution is easily changed.

Examples of the unsaturated monomers include

unsaturated carboxylic acids, (meth)acrylate ester monomers,

(meth)acrylate amide monomers, aromatic vinyl monomers,

vinyl cyan compound monomers, vinyl monomers, allyl

compound monomers, olefin monomers, diene monomers,

oligomers having unsaturated carbons. These may be used

alone or in combination of two or more. Combination of these

monomers may make possible to flexibly modify various

properties, for example, polymerization reaction or graft

reaction using an oligomer polymerization initiator may lead to

modification of resin properties.

Examples of the unsaturated carboxylic acids include

acrylic acid, methacrylic acid, itaconic acid, fumaric acid and

maleic acid.

Examples of the monofunctional (meth)acrylate esters

include methyl methacrylate, ethyl methacrylate, isopropyl

methacrylate, n butyl methacrylate, isobutyl methacrylate,

n-amyl methacrylate, isoamyl methacrylate, n-hexyl

methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate,

decyl methacrylate, dodecyl methacrylate, octadecyl

methacrylate, cyclohexyl methacrylate, phenyl methacrylate,

benzyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl

methacrylate, 2-hydroxypropyl methacrylate,

dimethylaminoethyl methacrylate, methacryloxyethyltrimethyl

ammonium salts, 3-methacryloxypropyl trimethoxysilane,

methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl

acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate,

n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl

acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl

acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate,

2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,

dimethylaminoethyl acrylate and acryloxyethyltrimethyl

ammonium salts.

Examples of the multifunctional (meth)acrylate esters

include ethylene glycol dimethacrylate, diethylene glycol

dimethacrylate, triethylene glycol dimethacrylate, polyethylene

glycol dimethacrylate, l,3 butylene glycol dimethacrylate,

1,4-butylene glycol dimethacrylate, 1,6-hexanediol

dimethacrylate, neopentyl glycol dimethacrylate, dipropylene

glycol dimethacrylate, polypropylene glycol dimethacrylate,

polybutylene glycol dimethacrylate,

2,2'-bis(4-methacryloxydiethoxyphenyl)propane, trimethylol

propane trimethacrylate, trimethylol ethane trimethacrylate,

polyethylene glycol diacrylate, triethylene glycol diacrylate,

1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate,

1,6-hexanediol diacrylate, neopentyl glycol diacrylate,

1,9-nonanediol diacrylate, polypropylene glycol diacrylate, --

2,2'-bis(4-acryloxypropyloxyphenyl)propane,

2,2'-bis(4-acryloxydieth'oxyphenyl)propane trimethylol propane

triacrylate, trimethylol ethane triacrylate, tetramethylol

methane triacrylate, ditrimethylol tetraacrylate, tetramethylol

methane tetraacrylate, pentaerythritol tetraacrylate and

dipentaerythritol hexaacrylate.

Examples of the (meth)acrylate amide monomers include

acrylamide, methacrylamide, N,N-dimethylacrylamide,

methylenebisacrylamide and 2-acrylamide-2-methylpropane

sulfonate.

Examples of the aromatic vinyl monomers include

styrene, alpha-methylstyrene, vinyltoluene, 4-t butylstyrene,

chlorostyrene, vinyl anisole, vinyl naphthalene and divinyl

benzene.

Examples of the vinylcyan monomers include

acrylonitrile and methacrylonitrile.

Examples of the allyl monomers include allyl sulfonic

acid and salts thereof, allylamine, allyl chloride, diallylamine

and diallyldimethyl ammonium salts; examples of the olefin

monomers include ethylene and propylene! examples of the

diene monomers include butadiene and chloroprene.

Examples of the vinyl monomers include vinyl acetate,

vinylidene chloride, vinyl chloride, vinyl ether, vinyl ketone,

vinyl pyrrolidone, vinyl sulfonic acid and salts thereof, vinyl

trimethoxysilane and vinyl triethoxysilane.

Examples of the oligomers having an unsaturated carbon

include styrene oligomers having methacryloyl group,

styrene-acrylonitrile oligomers having methacryloyl group,

methyl methacrylate oligomers having methacryloyl group,

dimethylsiloxane oligomers having methacryloyl group and

polyester oligomers having acryloyl group.

As for the water-dispersible resins, molecular chains are

likely to be disrupted by dispersion destruction or hydrolysis

under strongly alkaline or acidic conditions. Thus pH thereof

is preferably 4 to 12, preferably 6 to H, ¹ and more preferably 7

to 9, particularly in view of miscibility with the

water-dispersible coloring agent.

The average particle diameter D50 of the

water-dispersible resins is associated with the viscosity of

dispersion liquids; that is, when compositions and solid

contents are the same, the smaller is the particle diameter, the

larger is the viscosity. As such, in order to prevent ink

viscosity to become excessively higher, the average particle

diameter D50 of water-dispersible resins is preferably 50 nm or

more. On the other hand, in cases where the particle diameter

is as large as a few tens microns, the particle size larger than

nozzle orifices of the ink-jet heads hiders the usage, or large

particles even with a diameter smaller than nozzle orifices tend

to impair ejection stability. Accordingly, the average particle

diameter D50 is preferably no larger than 200 nm, more

preferably no larger thanlδO nm.

The water-dispersible resins perform to fix the

water-dispersible colorants onto paper surface, and preferably

come to a film at ambient temperature so as to enhance the

fixing property of the colorants. Thus, the minimum

film-forming temperature (MFT) of the water-dispersible resins

is 30 ⁰ C or below, more preferably 20 ⁰ C or below

In addition, in cases where the glass transfer

temperature of the water-dispersible resins is -4O ⁰ C or below,

the resin films tend to be sticky and printed matters are

possibly tacky, thus, the water-dispersible resins preferably

have a glass transfer temperature of - 30 ⁰ C or above.

The content of the water-dispersible resins in the

recording inks is preferably 4 to 30% by mass in terms of solid

content, more preferably 6 to 24% by mass. Humectant

The recording ink according to the present invention

involves water as a liquid medium and thus also a humectant in

order to prevent drying of the ink and to improve dispersion

stability. The humectant may provide favorable effects to

improve solubility and to prevent inferior injection due to water

evaporation.

The humectant may be properly selected depending on

the application; examples thereof include polyvalent alcohols,

polyvalent alcohol alkylethers, polyvalent alcohol arylethers,

nitrogen-containing heterocyclic compounds, amides, amines,

sulfur-containing compounds, propylene carbonate, ethylene

carbonate and the like. These may be used alone or in

combination.

Examples of the polyvalent alcohols include glycerin,

diethylene glycol, 1,3-butanediol, 3 methyl- l,3 butanediol,

triethylene glycol, propylene glycol, dipropylene glycol,

trimethylol propane, trimethylol ethane, ethylene glycol,

tripropylene glycol, tetraethylene glycol, hexylene glycol,

polyethylene glycol, polypropylene glycol, 1,5-pentanediol,

1,6-hexanediol, glycerol, l,2,6 hexanetriol, l,2,4 butanetriol,

1,2,3-butanetriol, petriol, and the like.

Examples of the polyvalent alcohol alkyl ethers include

ethylene glycol monoethyl ether, ethylene glycol monobutyl

ether, diethylene glycol monomethyl ether, diethylene glycol

monoethyl ether, diethylene glycol monobutyl ether,

tetraethylene glycol monomethyl ether, propylene glycol

monoethyl ether, and the like. Examples of the polyvalent

alcohol arylethers include ethylene glycol monophenyl ether,

ethylene glycol monobenzyl ether, and the like.

Examples of the nitrogen-containing heterocyclic

compounds include 2-pyrrolidone, Nτnethyl-2-pyrrolidone,

N-hydroxyethyl-2-pyrrolidone, 1, 3-dimethyl imidazoledione,

epsilon-caprolactam, gamma-butyrolactone, and the like.

Examples of the amides include formamide, N-methyl

formamide, N,N-dimethyl formamide, and the like.

Examples of the amines include monoethanol amine,

diethanol amine, triethanol amine, monoethyl amine, diethyl

amine, triethyl amine, and the like. Examples of the

sulfur-containing compounds include dimethyl sulfoxide,

sulfolane, thiodiethanol, and the like.

Other humectants are preferably those containing

sugars, ^" examples of the sugars include monomeric sugars, two

sugars, oligosaccharides (including trisaccharide and

tetrasaccharide) and polysaccharides. Specific examples

include glucose, mannose, fructose, ribose, xylose, arabinose,

galactose, maltose, cellobiose, lactose, sucrose, trehalose, malt

triose, and the like. The polysaccharides are broadly defined

herein as sugars, which encompass the substances broadly

existing in natural world, such as alpha-cyclodextrin and

cellulose. Derivatives of these sugars include reducing sugars

of the above sugars such as sugar alcohols expressed by General

Formula: HOCH ₂ (CHOH) nCH ₂ OH where "n" represents an

integer of 2 to 5ϊ saccharides such as aldonic acid and uronic

acid, ^' amino acid, thio acid, and the like. Among these, sugar

alcohols are preferable, and specific examples thereof include

maltitol and sorbitol.

Among these humectants, glycerin, diethylene glycol,

1,3-butanediol, 3-methyl- l,3-butanediol, triethylene glycol,

1,6-hexanediol, propylene glycol, 1,5-pentanediol, dipropylene

glycol and trimethylol propane are particularly preferable in

view of storage and discharge stability.

The mass ratio of the pigments to the humectants

significantly affects the ink discharge stability from ink heads.

When the amount of humectants is insufficient compared to

solid content of pigments, water evaporation near the ink

meniscus of nozzles may result in discharge failure.

The content of humectants is preferably 10 to 50% by

mass and in the recording inks, more preferably 15 to 35% by

mass, still more preferably 22.5 to 32.5% by mass. The

recording inks within this range may advantageously afford

drying, storage, and reliability items. When the content is less

than 10% by mass, the inks tend to rapidly dry at nozzle faces

possibly to cause inferior ejection, meanwhile when the content

is more than 50% by mass, the drying velocity is lower on paper

surface, which may also impair printing quality of characters on

regular paper.

Wetting Agent

The wetting agents preferably contain at least a polyol

compound whose solubility is 0.2 to 5.0% by mass in water at

20 ⁰ C. Examples of the polyol compounds include aliphatic

diols such as 2-ethyl-2 methyl- l,3-peopanediol,

3, 3 dimethyl l,2-butanediol, 2,2 diethyl l, 3-propanediol,

2 -methyl- 2 -propyl- 1, 3 -propanediol, 2,4-dimethyl-2,4-pentanediol,

2,5-dimethyl-2, 5-hexanediol, 5"hexene- l,2-diol and

2-ethyl- l, 3-hexanediol. Among these, 2-ethyl- l,3-hexanediol

and 2,2,4-trimethyl- l, 3-pentanediol are particularly preferable.

The other wetting agents suited to simultaneous use may be properly selected as long as capable of adjusting desirable

physical properties; examples thereof include alkyl or allyl

ethers of polyhydric alcohols such as diethyleneglycol

monophenylether, ethyleneglycol monophenylether,

ethyleneglycol monoallylether, diethyleneglycol

monophenylether, diethyleneglycol monobutylether,

propyleneglycol monobutylether and tetraethyleneglycol

chlorophenylether> ^" and lower alcohols such as ethanol.

The content of the wetting agents in the inks is

preferably 0.1% by mass to 4.0% by mass. When the content is

less than 0.1% by mass, drying speed may be lower, thus

possibly resulting in bleeding of images, and when the content

is more than 4.0% by mass, dispersion stability of the colorants

may degrade, nozzle clogging tends to easily occurs, and image

density tends to decrease or show through tends to occur due to

excessively higher permeability into recording media.

pH Adjuster

The pH adjusters may be properly selected as long as

giving no adverse effect on recording inks and able to adjust pH

within 7 to 11; examples thereof include alcohol amines, alkali

metal hydroxides, ammonium hydroxides, phosphonium

hydroxides and alkali metal carbonates. In cases where the pH

exceeds 11, the materials of ink-jet heads and/or ink-supply

units may be dissolved, and such troubles may occur as

degradation or leakage of inks, inferior ink-ejection, or the like.

Examples of the alcohol amines include diethanolamine,

triethanolamine and 2-amino-2-ethyl- l,3-propanediol; examples

of the hydroxides of alkali metal include lithium hydroxide,

sodium hydroxide and potassium hydroxide.

Examples of the ammonium hydroxides include

ammonium hydroxide, quaternary ammonium hydroxide and

quaternary phosphonium hydroxide! examples of the alkali

metal carbonates of include lithium carbonate, sodium

carbonate and potassium carbonate.

The other ingredients may be appropriately selected

depending on the purpose, and include, for example,

antiseptic/antifungal agents, chelating reagents, antirust

agents, antioxidants, UV ray absorbers, oxygen absorbers and

light stabilizers.

Examples of the antiseptic/antifungal agents include

sodium dehydroacetate,' sodium sorbate, sodium

2-pyridinethiol- l-oxide, sodium benzoate and sodium

pentachlorophenol.

Examples of the chelating reagents include sodium

ethylenediamine tetraacetate, sodium nitrilotriacetate, sodium

hydroxyethyl ethylenediamine triacetate, sodium

diethylenetriamine pentaacetate and sodium uramil diacetate.

Examples of ^r the antirust agents include, acidic sulfite

salts, sodium thiosulfate, thiodiglycolic acid ammonium,

diisopropylammonium nitrate, pentaerythritol tetranitrate,

dicyclohexylammonium nitrate and benzotriazole.

Examples of the antioxidants include phenol antioxidants

(including hindered phenol antioxidants), amine antioxidants,

sulfur antioxidants and phosphorus antioxidants.

Examples of the phenol antioxidants (including hindered

phenol antioxidants) include butylated hydroxyanisole,

2,6-di-tert butyl-4-ethylphenol,

stearyl-beta-(3,5-di-tert butyl-hydroxyphenyl)propionate,

2,2'-methylene bis(4-methyl-6-tert-butylphenol),

2,2'-methylene-bis(4-ethyl-6-tert-butylphenol),

4,4'-butylidene-bis(3-methyl-6-tert-butylphenol),

3,9-bis[l, l-dimethyl-2- [beta-(3-tert-butyl-4-hydroxy-5-

methyphenyl)propionyloxy]ethyl] -2,4,8, 10-tetraixaspiro-

[5.5]undecane, 1, 1, 3- tris(2- methyl- 4-hydroxy 5 -tert-

butylphenyl)butane, l,3, 5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-

4-hydroxybenzyl)benzene and tetraxis[methylene-3-(3', 5'-di-

tert- butyl-4'-hydroxyphenyl)propionate]methane.

Examples of the amine antioxidants include

phenyl-beta-naphthylamine, alpha- naphthylamine,

N,N'-di-sec-butyl-p -phenylenediamine, phenothiazine,

N,N'-diphenyl-p-phenylenediamine, 2,6-di-tert-butyl-p-cresol,

2,6-di tert-butylphenol, 2, 4- dimethyl- 5 -tert butyl-phenol, butyl

hydroxyanisole, 2, 2' -methylene bis(4- methyl- 6-tert-butylphenol),

4,4'-butylidene bis(3 -methyl- 6-tert-butylphenol),

4,4'-thiobis(3-methyl-6-tert-butylphenol),

tetraxis [methylene- 3-(3, 5-di-tert butyl-4-dihydroxypheny I)-

propionatelmethane and l, l,3-tris(2 methyl-4-hydroxy-5-

tert"butylphenyl)butane.

Examples of the sulfur antioxidants include dilauryl

3,3'-thiodipropionate, distearyl thiodipropionate, lauryl stearyl

thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl

beta,beta'-thiodipropionate, 2-mercaptobenzimidazole and

dilauryl sulfide.

Examples of the phosphorous antioxidants include

triphenyl phosphite, octadecyl phosphite, triisodecyl phosphite,

trilauryl trithiophosphite, and trinonylphenyl phosphite.

Examples of the UV-ray absorbers include benzophenone

UV-ray absorbers, benzotriazole UV-ray absorbers, salicylate

UV-ray absorbers, cyanoacrylate UV-ray absorbers, and nickel

complex salt UV-ray absorbers.

Examples of the benzophenone UV-ray absorbers include

2 -hydroxy- 4-n-octoxybenzophenone,

2-hydroxy-4 n dodecyloxybenzophenone,

2,4-dihydroxybenzophenone, 2 -hydroxy- 4-methoxybenzophenone,

and 2,2',4,4'-tetrahydroxybenzophenone.

Examples of the benzotriazole UV-ray absorbers include

2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole,

2-(2'-hydroxy- 5'-methylphenyl)benzotriazole,

2-(2' hydroxy-4' octoxyphenyl)benzotriazole, and 2-(2'-hydroxy- 3'-tert butyl-5'-methylphenyl)-5-chlorobenzotriazole.

Examples of the salicylate UV-ray absorbers include

phenyl salicylate, p-tert-butylphenyl salicylate, and

p-octylphenyl salicylate.

Examples of the cyanoacrylate UV-ray absorbers include

ethyl-2-cyano-3,3'-diphenyl acrylate,

methyl-2-cyano-3-methyl-3-(p-methoxyphenyl) acrylate, and

butyl-2-cyano-3-methyl-3-(p methoxyphenyl) acrylate,

Examples of the nickel complex salt UV-ray absorbers

include nickel bis(octylphenyl) sulfide,

2,2'-thiobis(4-tert-octylphelate)-n-butylamine nickel (II),

2,2'-thiobis(4-tert-octylphelate)-2-ethylhexylamine nickel (II)

and 2,2'-thiobis(4-tert-octylphelate) triethanolamine nickel (II).

The recording inks according to the present invention

may be produced by dispersing or dissolving a pigment

dispersion according to the present invention, at least a silicone

surfactant or a fluorine-containing surfactant, a

water-dispersible resin, a humectant, and optional other

ingredients into an aqueous medium, and further stirring and

mixing them as required. The dispersing step may be carried

out using a sand mill, homogenizer, ball mill, paint shaker, or

ultrasonic dispersant, and the stirring and mixing step may be

carried out using a conventional stirring device equipped with

stirring blades, a magnetic stirrer, or high speed dispersing

device.

The physical properties of the inventive recording inks

may be properly selected depending on the application;

preferably the viscosity and the surface tension are within the

ranges described below. The viscosity of the inventive recording inks is preferably

no more than 20 mPa-s at 25°C, more preferably no more than

15 mPa-s. When the viscosity is above 20 mPa-s, the ejection

stability may be difficult to be maintained depending on head

configuration.

The surface tension of the inventive recording inks is

preferably no more than 35 mN/m at 25°C, more preferably no

more than 30 mM/m. When the surface tension is above 35

mN/m, ink leveling may hardly occur on recording media and

the drying period may be prolonged.

The color of recording inks according to the present

invention may be appropriately selected depending on the

purpose, and may be yellow, magenta, cyan or black.

Recording using an ink set combining two or more of these

colors may make possible to form multicolor images! recording

using all-color ink set may make possible to form full color

images.

The recording inks according to the present invention

may be suitably applied to substantially any printers equipped

various ink-jet heads, for example, so-called piezoelectric-type

ink-jet heads where a volume in an ink flow path is changed to

eject ink drops through deforming a vibration plate, which

forms a wall of the ink flow path, by action of a piezoelectric

element as a pressure-generating means to press to the ink in

the ink flow path (see JP-A No. 02-51734); so-called thermal

ink-jet heads where bubbles generate by heating an ink in an

ink flow path using an exothermic resistive element (see JP-A

No. 61-59911); electrostatic ink-jet heads where an electrode

and a vibration plate, which form a wall of an ink flow path, are

disposed in an opposed position, and a volume in an ink flow

path is changed to eject an ink by electrostatic power generated

between the electrode and the vibration plate (see JP-A No.

06-71882).

The recording inks according to the present invention can

be utilized for a variety of articles such as fountain pens, ball

pens, magic pens, and sign pens, in particular applied as ink-jet

recording inks to image forming apparatuses such printers in

ink-jet recording, more specifically, printers having a function

to facilitate printing fixation by heating paper or inks at 50°C

to 200°C during, before or after the printing. In addition, the

recording inks according to the present invention can applied

suitably for ink cartridges, ink recorded matters, ink-jet

recording apparatuses, and ink-jet recording methods according

to the present invention.

Ink Cartridge

The inventive ink cartridges have an inventive recording

ink in a container and other optional members as required.

The container may be, without limitation, appropriately

selected in terms of shape, structure, size, and material,

depending on the purpose; preferable examples thereof are ink

bags formed of aluminum-laminate films or resin films.

The ink cartridge will be explained with reference to

FIGs. 1 and 2. FIG. 1 is an exemplary inventive ink cartridge,

and FIG. 2 shows the ink cartridge packed within a casing or

outer packing.

An ink is introduced from an ink inlet 242 into an ink

bag 241 of the ink cartridge 200, then the ink bag 241 is

degassed and the ink inlet 242 is sealed by fusion bond, as

shown in FIG. 1. In use, the ink is supplied to the apparatus

through piercing an ink outlet 243 of a rubber member.

The ink bag 241 is typically formed from a packing

material such as aluminum-laminate film having no

air-permeability. As shown in FIG. 2, the ink bag 241 is

typically housed in a plastic cartridge case 244 and detachably mounted to various ink-jet recording apparatuses.

The inventive ink cartridges have the inventive recording

inks and are used by detachably amounting to various ink-jet

recording apparatuses, and particularly preferably to the

inventive ink-jet recording apparatuses described later.

Ink-jet Recording Apparatus and Ink Jet Recording Method

The inventive ink-jet recording apparatuses have at least

an ink ejecting unit and other optional units such as a stimulus

generation unit and a control unit.

The inventive ink-jet recording method contains at least

an ink ejecting step and also other optional steps such as a

stimulus generation step and a control step . The inventive

ink-jet recording method may be suitably carried out by the

inventive ink-jet recording apparatus; the ink ejecting step may

be suitably carried out by the ink ejecting unit.

Ink Ejecting Step and Ink Ejecting Unit

The ink ejecting step is one to eject the inventive

recording ink by applying a stimulus to the recording ink

thereby to form images.

The ink ejecting unit is one to eject the inventive

recording ink by applying a stimulus to the recording ink

thereby to form images. The ink ejecting may be properly

selected depending on the application; examples thereof include

various nozzles for ^f ink-jet printing.

The stimulus may be properly selected depending on the

application! examples thereof include heat, pressure, vibration,

and light. These may be used alone or in combination of two or

more. Among these, the heat and the pressure are preferable.

Examples of the stimulus generation unit include heating

devices, pressurizing devices, piezoelectric elements, vibration

generating devices, ultrasonic oscillators, and lights, more

specifically, piezoelectric actuators such as piezoelectric

elements, thermal actuators which utilize a phase change by

membrane boiling of the liquid using an electric thermal

conversion element such as an exothermal resistive element,

shape memory alloy actuators using a metallic phase change by

thermal change, and electrostatic actuators using an

electrostatic power.

The way to eject the recording ink may be properly ^■■

selected depending on the stimulus! in cases where the stimulus

is derived by "heat", such a method is available as heat energy

corresponding to recording signals is imparted using a thermal

head to the recording ink in a recording head to generate

bubbles in the recording ink by the heat energy and the

recording ink is jetted and ejected as liquid drops from a nozzle

pore of the recording head by pressure of the bubbles. In cases

where the stimulus is derived by "pressure", such a method is

available that a piezoelectric element is bended and a volume in

a pressure room is reduced to eject the recording ink as droplets

from the nozzle pore of the recording head by applying voltage

to the piezoelectric element adhered at a position called the

pressure room in the ink flow path in the recording head.

The droplet size of ejected recording inks is preferably 3

to 40 pi, the speed of ejected drops is preferably 5 to 20 m/s, the

driving frequency is preferably 1 kHz or more, and the

resolution is preferably 300 dpi or more.

The control unit may be properly selected depending on

the purpose! examples thereof include instruments such as

sequencers and computers.

An embodiment to carry out the inventive ink-jet

recording method by the inventive ink-jet recording apparatus

will be described with reference to drawings. The ink-jet

recording apparatus shown in FIG. 3 has a main body 101, -a

paper supply tray 102 mounted to the main body 101, a paper

discharge tray 103 for stocking the paper on which images being

recorded, and an ink cartridge section 104. An operation

section 105 of operation keys and displays etc. is disposed on

the ink cartridge loading section 104. The ink cartridge

section 104 has an openable/closable front cover 115 for

detaching the ink cartridge 201.

As shown in FIGs. 4 and 5, a carriage 133 is retained

with freely sliding in a main scanning direction by a guide rod 131 which is a guide member bridged laterally to right and left

side plates (not shown) and a stay 132, and is moved and

scanned by a main scanning motor (not shown) in an arrow

direction in FIG. 5.

In the carriage 133, a recording head 134 formed of four

heads to eject jet-ink drops of respective colors, i.e. yellow (Y),

cyan (C), magenta (M) and black (B), is loaded such that

multiple ink ejecting openings are arranged in a direction that

intersects with the main scanning direction with the ink

ejecting direction being directed downward.

The ink-jet recording head of the recording head 134

may be those containing a piezoelectric actuator such as a

piezoelectric element, thermal actuator utilizing phase change

by membrane boiling of the liquid using the electric thermal

conversion element such as an exothermal resistive element, a

shape memory alloy actuator using a metallic phase change by

thermal change, and an electrostatic actuator using the

electrostatic power, as the energy generation unit to jet the

recording ink.

The carriage 133 has a subtank 135 for each color to

supply each color ink. The inventive recording ink is supplied

from an inventive ink cartridge 201 mounted in the ink

cartridge loading section 105 to the subtank 135 through the

supplying tube for the recording ink (not shown).

Meanwhile, a paper supply section which supplies the

paper 142 taken on a paper stacking section 141 of the paper

supply tray 102 comprises a half moon type roller or paper

supply roller 143 which separates and feeds the paper one by

one from the paper stacking section 141 and a separation pad

144 opposed to the paper supply roller 143 and composed of the

material with large friction coefficient, and this separation pad

144 is urged toward the paper supply roller 143 side.

A feeding section for feeding the paper supplied from the

paper supply section beneath the recording head 134 has a

feeing belt 151 for feeding the paper 142 by absorbing

electrostatically, a counter roller 152 for feeding the paper 142

sent through a guide 145 from the paper supply section by

sandwiching with the feeding belt 151, a feeding guide 153 for

feeding the paper sent in a nearly vertical upward direction on

the feeding belt 151 by changing the direction of the paper at

about 90°, and a tip pressurizing roller 156 biased to the

feeding belt 151 side with a pushing member 154. An

electrical charging roller 156 which is an electrical charge mean

to charge the surface of the feeding belt 151 is also comprised.

The feeding belt 151 is an endless belt, is disposed

between a feeding roller 157 and a tension roller 158, and is

capable of going around in a belt feeding direction. This

feeding belt 151 has a surface layer which is a paper absorbing

surface formed from, for example, a resin material with a

thickness of about 40 μm to which resistance control has not

been given, for example, a copolymer of tetrafluoroethylene and

ethylene, and a back layer (medium resistant layer, an earth

layer) to which the resistance control by carbon has been given

with the same material as this surface layer. A guide member

161 corresponding to the printing region by the recording head

134 is disposed on the back side of the feeding belt 151. A

paper discharging section for discharging the paper 142

recorded at the recording head 134 comprises a separation nail

171 for separating the paper 142 from the feeding belt 151, a

paper discharging roller 172 and a discharging half moon type

roller 173. A paper discharge tray 103 is disposed beneath the

paper discharging roller 172.

A both side paper supply unit 181 is detachably loaded

on the backside section of the main body 101. The both side

paper supply unit 181 takes in the paper 142 returned in a

reverse direction rotation of the feeding belt 151, reverses the

paper 142 and supplies it again between the counter roller 152

and the feeding belt 151. A manual paper supply section 182 is

provided on the upper surface of the both side paper supply unit

181.

In this ink-jet recording apparatus, the paper 142 is

separated and supplied one by one from the paper supply

section, the paper 142 supplied in the nearly vertical upward

direction is guided by the guide 145, and fed by being

sandwiched with the feeding belt 151 and the counter roller 152.

The tip of the paper is further guided by the feeding guide 153,

mounted on the feeding belt 151 at the tip pressurizing half

moon type roller 155, and changed in about 90° in its feeding

direction.

At that time, the feeding belt 157 is charged by the

electrical charging roller 156, and the paper 142 is fed by being

absorbed electrostatically. The ink drop is jetted onto the

stopping paper 142 to record one line by driving the recording

head 134 depending on the image signals with moving the

carriage 133 there, and next line is recorded after feeding the

paper 142 to a given amount. A recording operation is

terminated by receiving a recording termination signal or a

signal that a back end of the paper 142 has reached the

recording region, then the paper 142 is discharged to the paper

discharge tray 103.

When a remaining amount near end of the recording ink

in the subtank 135 is detected, the recording ink in a given

amount is supplied from the ink cartridge 201 to the subtank

135.

In this ink-jet recording apparatus, when the recording

ink in the inventive ink cartridge 201 is finished out, a housing

in the ink cartridge 201 can be decomposed and only the ink bag

inside can be changed. Even when the ink cartridge is

constituted in vertical mounted front loading, it is possible to

stably supply the recording ink. Therefore, even when

disposed by occupying upwards of the main body 101, for

example, even when housed in a rack or an object has been

placed on the main body 101, it is possible to easily change the

ink cartridge 201.

Here, the present invention is described with respect to

the serial type (shuttle type) where the carriage being scanned,

the inventive recording inks can also be likewise applied to line

type ink-jet recording apparatuses having a line-type head.

The inventive ink-jet recording apparatuses and the

ink-jet recording methods can be applied to various recordings

based on ink-jet recording systems, for example, to printers for

ink-jet recording, facsimile apparatuses, copying apparatuses,

printer/facsimile/copier composite machines, and the like

Ink Recorded Matter

The inventive ink recorded matters are those recorded by

means of inventive ink-jet recording apparatuses and inventive

ink-jet recording methods. The inventive ink recorded matters

have images formed on recording media using the inventive

recording inks.

The recording media may be properly selected depending

on the purpose; examples thereof include regular paper, glossy

paper, special paper, fabrics, films, OHP sheets, or the like.

These may be used alone or in combination.

The inventive ink recorded matters are of high image

quality, with no bleeding, and excellently stable with time,

therefore can be suitably utilized for various printing,

literatures or documents with a variety of images and/or letters.

Examples

The present invention will be explained with reference to

examples, but it should be understood that the present

invention is not limited thereto at all. In the following

descriptions, all parts and percent are based on "mass" unless

indicated otherwise.

Preparation Example A- I

Preparation of Solution A- I of Polymer Dispersion Stabilizer

A mixture of ingredients shown below were mixed under

heating by a mechanical stirrer to dissolve alpha-olefin/maleic

anhydride copolymer (I), then a minute amount of insoluble

matters were filtered off using a filter having an average pore

size of 5 μm, thereby to prepare the solution A- I of polymer

dispersion stabilizer.

Alpha-olefin/maleic anhydride copolymer (I) ^{* x)} 10.0 parts

IN KOH aqueous solution ^*2) 68.62 parts

Deionized water 21.38 parts

1) T-YPI lO by Seico PMC Co., carbon-atom number of

olefin chain: 12 to 14, acid value: 385 mgKOH/g, mass average

molecular weight: 9000

2) 1.0 time amount of alkali on the basis of acid value

Preparation Example A-2

Preparation of Solution B of Polymer Dispersion Stabilizer

A mixture of ingredients shown below were mixed under

heating by a mechanical stirrer to dissolve alpha-olefin/maleic

anhydride copolymer (II), then a minute amount of insoluble

matters were filtered off using a filter having an average pore

size of 5 μm, thereby to prepare the solution B of polymer

dispersion stabilizer.

Alpha-olefin/maleic anhydride copolymer (II) ^{* x)} 10.0 parts

IN NaOH aqueous solution ^*2 > 28.08 parts

Deionized water 61.92 parts

1) T-YPl I l by Seico PMC Co., carbon-atom number of

olefin chain: 16 to 18, acid value : 221 mgKOH/g, mass average

molecular weight: 11000

2) 1.0 time amount of alkali on the basis of acid value

Preparation Example A-3

Preparation of Solution C of Polymer Dispersion Stabilizer

A mixture of ingredients shown below were mixed under

heating by a mechanical stirrer to dissolve alpha olefin/maleic

anhydride copolymer (III), then a minute amount of insoluble

matters were filtered off using a filter having an average pore

size of 5 μm, thereby to prepare the solution C of polymer

dispersion stabilizer.

Alpha-olefin/maleic anhydride copolymer (III) ^{* x)} 10.0 parts

IN LiOH aqueous solution ^*2) 17.34 parts

Deionized water 72.66 parts

1) T-YP112 by Seico PMC Co., carbon-atom number of

olefin chain: 20 to 24, acid valued 190 mgKOH/g, mass average

molecular weight: 10000

2) 1.2 times amount of alkali on the basis of acid value

Preparation Example A 4

Preparation of Solution D of Polymer Dispersion Stabilizer

A mixture of ingredients shown below were mixed under

heating by a mechanical stirrer to dissolve alpha-olefin/maleic

anhydride copolymer (IV), then a minute amount of insoluble

matters were filtered off using a filter having an average pore

size of 5 μm, thereby to prepare the solution D of polymer

dispersion stabilizer.

Alpha-olefin/maleic anhydride copolymer (IV) ^{* x)} 10.0 parts

IN ammonia aqueous solution ^*2 > 25.15 parts

Deionized water 64.85 parts

1) T-YP113 by Seico PMC Co., carbon-atom number of olefin

chain: 16 to 18, acid value : 310 mgKOH/g, mass average

molecular weight: 11400

2) 1.5 times amount of alkali on the ¹ basis of acid value

Example A- I

Preparation of Pigment Dispersion I

Monoazo yellow pigment ^* * ⁾ 20.0 parts

Polyoxyethylene beta-naphthylether (RT- 100) ^*2 > 6.6 parts

Deionized water 73.4 parts

1) C.I. pigment yellow 74, by Dainichiseika Color &

Chemicals Mfg. Co.

2) nonionic surfactant, HLB value: 18.5, by Takemoto Oil

& Fat Co.

Initially, the nonionic surfactant described above was

dissolved into deionized water to prepare a solution, then the

solution was mixed with to wet the pigment described above

sufficiently. The mixture was then dispersed at 2000 rpm for 4

hours by use of KDLA Model Dyno-Mill wet-type disperser (by

WAB Machinery Co.) filled with zirconia beads of 0.5 mm

diameter thereby to prepare a primary pigment dispersion.

The solution A- I of polymer dispersion stabilizer described

above was add in an amount of 20.0 parts to the primary

pigment dispersion to stir the mixture sufficiently thereby to

prepare pigment dispersion I. The average particle diameter

D50 of the pigment dispersion I was 49 nm in accordance with

the measurement using UPA-EX150 (by Micro Track Co.).

Example A-2

Preparation of Pigment Dispersion II

Quinacridone pigment (CI. pigment red 122) ^M) 20.0 parts

Polyoxyethylene laurylether (DKS NL-450) ^*2 > 6.6 parts

Deionized water 73.4 parts

1) by Dainichiseika Color & Chemicals Mfg. Co.

2) nonionic surfactant, HLB value : 18.3, by Dai-ichi Kogyo

Seiyaku Co.

Initially, the nonionic surfactant described above was

dissolved into deionized water to prepare a solution, then the

solution was mixed with to wet the pigment described above

sufficiently. The mixture was then dispersed at 2000 rpm for 2

hours by use of KDLA Model Dyno-Mill wet-type disperser (by

WAB Machinery Co.) filled with zirconia beads of 0.5 mm

diameter thereby to prepare a primary pigment dispersion-.

The solution B of polymer dispersion stabilizer described above

was add in an amount of 20.0 parts to the primary pigment

dispersion to stir the mixture sufficiently thereby to prepare

pigment dispersion II. The average particle diameter D50 of

the pigment dispersion II was 81 nm in accordance with the

measurement using UPA-EX150 (by Micro Track Co.).

Example A-3

Preparation of Pigment Dispersion III

Phthalocyanine pigment ^{* 1}} 20.0 parts

Polyoxyethylene styrenephenylether ^*2) 6.6 parts

Deionized water » 73.4 parts

1) C.I. pigment blue 15 ^: 3, by Dainichiseika Color &

Chemicals Mfg. Co.

2) Noigen EA- 197, nonionic surfactant, HLB value: 17.5,

by Dai-ichi Kogyo Seiyaku Co.

Initially, the nonionic surfactant described above was

dissolved into deionized water to prepare a solution, then the

solution was mixed with to wet the pigment described above

sufficiently. The mixture was then dispersed at 2000 rpm for 2

hours by use of KDLA Model Dyno-Mill wet-type disperser (by

WAB Machinery Co.) filled with zirconia beads of 0.5 mm

diameter thereby to prepare a primary pigment dispersion.

The solution C of polymer dispersion stabilizer described above

was add in an amount of 20.0 parts to the primary pigment

dispersion to stir the mixture sufficiently thereby to prepare

pigment dispersion III. The average particle diameter D50 of

the pigment dispersion III was 83 nm in accordance with the

measurement using UPA-EX150 (by Micro Track Co.).

Example A-4

Preparation of Pigment Dispersion IV

Silica/disazo yellow complex pigment ⁿ⁾ 24 parts

Sodium dioctylsulfosuccinate (Newcol 291M) ^*2) 8 parts

Deionized water 68 parts

1) inorganic/organic ratio ^: 1/1, primary particle size : 17

nm, by Toda Kogyo Co.

2) anionic surfactant, by Nippon Nyukazai Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion. The solution

C of polymer dispersion stabilizer described above was add in

an amount of 20.0 parts to the primary pigment dispersion to

stir the mixture sufficiently thereby to prepare pigment

dispersion IV. The average particle diameter D50 of the

pigment dispersion IV was 39 nm in accordance with the -

measurement using UPA EX150 (by Micro Track Co.).

Example A-5

Preparation of Pigment Dispersion V

Silica/quinacridone PR122 complex pigment ^M) 28 parts

Anionic surfactant High Tehnol NF- 17 ^*2) 9.2 parts

Deionized water 62.8 parts

l) inorganic/organic ratio: 1/1, primary particle size: 16 nm,

by Toda Kogyo Co.

2) polyoxyethylene styrenephenylether ammonium sulfonate

by Dai ichi Kogyo Seiyaku Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno-Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion. The solution

B of polymer dispersion stabilizer described above was add in

an amount of 21.0 parts to the primary pigment dispersion to

stir the mixture sufficiently thereby to prepare pigment

dispersion V. The average particle diameter D50 of the pigment

dispersion V was 75 nm in accordance with the measurement

using UPA EX150 (by Micro Track Co.).

Example A-6

Preparation of Pigment Dispersion VI

Silica/Phthalocyanine PB15:3 complex pigment ⁿ⁾ 24 parts

Polyoxyethylene laurylether (DKS NL- 180) ^*2 > 8 parts

Deionized water 68 parts

1) inorganic/organic ratio ^: 1/1, primary particle size ^: 16 nm,

by Toda Kogyo Co.

2) nonionic surfactant, HLB value : 16.2, by Dai ichi Kogyo

Seiyaku Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno-Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion. The solution

C of polymer dispersion stabilizer described above was add in

an amount of 20.0 parts to the primary pigment dispersion to

stir the mixture sufficiently thereby to prepare pigment

dispersion VI. The average particle diameter D50 of the

pigment dispersion VI was 78 nm in accordance with the

measurement using UPA-EX150 (by Micro Track Co.).

Example A"7

Preparation of Pigment Dispersion VII

Silica/disazo yellow complex pigment ^{* x)} 24 parts

Polyoxyethylene laurylether (DKS NL-450) ^*2) 8 parts

Solution C of polymer dispersion stabilizer 20 parts

Deionized water 68 parts

l) inorganic/organic ratio: l/l _; primary particle size: 17 nm,

by Toda Kogyo Co.

2) nonionic surfactant, HLB value : 18.3, by Dai-ichi Kogyo

Seiyaku Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

and the solution C of polymer dispersion stabilizer were mixed

with to wet the pigment described above ¹ sufficiently. The

mixture was then dispersed at 2000 rpm for 1.5 hours by use of

KDLA Model Dyno Mill wet-type disperser (by WAB Machinery

Co.) filled with zirconia beads of 0.5 mm diameter thereby to

prepare a pigment dispersion VII. The average particle

diameter D ₅₀ of the pigment dispersion VII was 39 nm in

accordance with the measurement using UPA-EX150 (by Micro

Track Co.).

Example A-8

Preparation of Pigment Dispersion VIII

Silica/Phthalocyanine PB15-3 complex pigment ^{* lj} 24 parts

Polyoxyethylene polycyclic phenylether ^*2) 8 parts

Deionized water 68 parts

1) inorganic/organic ratio: 1/I ₁ primary particle size: 16 nm,

by Toda Kogyo Co.

2) nonionic surfactant, Newcol 780, HLB value: 18.9,

by Nippon Nyukazai Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno-Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion. The solution

B of polymer dispersion stabilizer described above was add in

an amount of 20.0 parts to the primary pigment dispersion to

stir the mixture sufficiently thereby to prepare pigment

dispersion VIII. The average particle diameter D50 of the

pigment dispersion VII was 125 nm in accordance with the

measurement using UPAεX150 (by Micro Track Co.).

Comparative Example A- I

Preparation of Pigment Dispersion IX

Pigment dispersion IX was prepared in the same manner

as Example A-3 to prepare pigment the dispersion III except

that the solution C of polymer dispersion stabilizer was not

added. The average particle diameter D50 of the pigment

dispersion IX was 81 nm in accordance with the measurement

using UPA EX150 (by Micro Track Co.).

Comparative Example A-2

Preparation of Pigment Dispersion X

Pigment dispersion X was prepared in the same manner

as Example A-3 to prepare the pigment dispersion III except

that the solution C of polymer dispersion stabilizer was

exchanged into solution E of the styrene/maleic acid copolymer

shown below. The average particle diameter D50 of the

pigment dispersion X was 85 nm in accordance with the

measurement using UPA-EX150 (by Micro Track Co.). Solution E of the styrene/maleic acid copolymer:

Polymaron 351S, acid value : 560 mgKOH/g, average molecular

weight: 100000 to 110000, solid content: 10.2%, by Arakawa

Chemical Industries

Example A-9

Preparation of Recording Ink

Pigment Dispersion I 36 parts

Boncoat 4001 (aqueous acrylic emulsion) ^M > 6 parts

Glycerin 10 parts

Triethylene glycol 25 parts

2,2,4-Trimethyl- l,3 ^* pentanediol 4 parts

Polyfox PF- 151N (active ingredient: 50%) ^*2 > 2 parts

Proxel LV (antiseptic/antifungal agent) ^{* 3)} 0.2 part

Triethanolamine 0.1 part

Deionized water 16.7 pats

1) solid content: 50%, MFT: 5 ⁰ C, average particle

diameter: 100 nm, by Dainippon Ink & Chemicals, Inc.

2) oligomer-type nonionic fluorine-containing surfactant,

by Omnova Co.

3) l,2-benzisothiazolin- 3-one, active ingredient: 20%,

with dipropylene glycol, by Avecia Co.

The above-noted Boncoat 4001, glycerin, triethylene

glycol, 2,2,4-trimethyl- l,3-pentanediol, Polyfox PF- 151N, Proxel

LV, and triethanolamine were dissolved into deionized water to

prepare a vehicle, which was mixed with the pigment dispersion

I to prepare a mixture, then the mixture was press-filtered

through a cellulose acetate membrane filter of 0.8 μm average

pore size to prepare the recording ink of Example A 9.

Example A- 10

Preparation of Recording Ink

Pigment Dispersion II 42 parts

Hydran HW-940 (solid content: 50%) ^* D 7 parts

Glycerin 6 parts

3 Methyl l,3 butanediol 19 parts

2-Ethyl l,3-hexanediol 2 parts

Zoneal FS-300 (active ingredient: 40%) ^*2 > 2.5 parts

Proxel LV (antiseptic/antifungal agent) ^{* 3)} 0.2 part

2-Amino-2-ethyl- l,3-propanediol 0.1 part

Deionized water 18.2 pats

l) polyester/urethane aqueous ionomer, MFT: 0 ⁰ C,

average particle diameter: 20 nm, by Dainippon Ink &

Chemicals, Inc.

2) polyoxyethylene perfluoroalkylether, by DuPont Co.

3) l,2-benzisothiazolin-3-one, active ingredient: 20%,

with dipropylene glycol, by Avecia Co.

The above-noted Hydran HW-940, glycerin,

3-methyl- l, 3-butanediol, 2-ethyM, 3-hexanediol, Zoneal FS-300,

Proxel LV, and 2-amino-2-ethyl- l, 3-propanediol were dissolved

into deionized water to prepare a vehicle, which was mixed with

the pigment dispersion II to prepare a mixture, then the

mixture was press-filtered through a cellulose acetate

membrane filter of 0.8 μm average pore size to prepare the

recording ink of Example A- 10.

Example A- I l

Preparation of Recording Ink

Pigment Dispersion III 36 parts

Acrit WEM-321U (solid content: 38%) ^* D 7.9 parts

Glycerin 7.5 parts

1,3-Butanediol 22.5 parts

2-EthyM,3-hexanediol 4.0 parts

Polyfox PF- 156A (active ingredient: 30%) ^*2 > 3.3 parts

Proxel LV (antiseptic/antifungal agent) ^*3) 0.2 part

2-Amino-2-ethyl- l,3-propanediol 0.1 part

Deionized water 18.5 pats

1) acrylic/urethane aqueous emulsion, MFT: 10°C,

average particle diameter: 100 nm, by Taisei Kako Co.

2) anionic fluorine-containing surfactant, by Omnova Co.

3) l,2-benzisothiazolin-3-one, active ingredient: 20%,

with dipropylene glycol, by Avecia Co.

The above-noted Acrit WEM-321U, glycerin,

1, 3-butanediol, 2-ethyM, 3-hexanediol, Polyfox PF- 156A, Proxel

LV, and 2-amino-2 ^r ethyl- l,3-propanediol were dissolved into

deionized water to prepare a vehicle, which was mixed with the

pigment dispersion III to prepare a mixture, then the mixture

was press-filtered through a cellulose acetate membrane filter

of 0.8 μm average pore size to prepare the recording ink of

Example A- I l.

Example A 12

Preparation of Recording Ink

Pigment Dispersion IV 35 parts

Boncoat 4001 (aqueous acrylic emulsion) ⁿ⁾ 7.0 parts

Glycerin 7.5 parts

Diethylene glycol 22.5 parts

2,2,4-Trimethyl l,3 pentanediol 4.0 parts

Polyfox PF- 151N (active ingredient: 50%) ^*2 > 2.0 parts

Proxel LV (antiseptic/antifungal agent) ^*3 ^ 0.2 part

2 Amino-2-ethyl- l, 3 propanediol 0.1 part

Deionized water 21.7 pats

1) solid content: 50%, MFT: 5°C, average particle

diameter: 100 nm, by Dainippon Ink & Chemicals, Inc.

2) oligomer-type nonionic fluorine-containing surfactant,

by Omnova Co.

3) l,2-benzisothiazolin-3-one, active ingredient: 20%,

with dipropylene glycol, by Avecia Co.

The above-noted Boncoat 4001, glycerin, diethylene

glycol, 2,2,4 trimethyl- l, 3-pentanediol, Polyfox PF 151N, Proxel

LV, and 2-amino-2-ethyl- l,3-propanediol were dissolved into

deionized water to prepare a vehicle, which was mixed with the

pigment dispersion IV to prepare a mixture, then the mixture

was press-filtered through a cellulose acetate membrane filter

of 0.8 μm average pore size to prepare the recording ink of

Example A- 12.

Example A- 13

Preparation of Recording Ink

Pigment Dispersion V 38.9 parts

Hydran HW-940 (solid content: 50%) ^* *> 9.0 parts

Glycerin 6.0 parts

3-Methyl- l,3 butanediol 19 parts

2-Ethyl l, 3-hexanediol 2.0 parts

Zoneal FS-300 (active ingredient: 40%) ^*2) 2.5 parts

Proxel LV (antiseptic/antifungal agent) ^{* 3)} 0.2 part

Triethanolanine 0.1 part

Deionized water 18.2 pats

1) polyester/urethane aqueous ionomer, MFT: 0°C,

average particle diameter: 20 nm, by Dainippon Ink &

Chemicals, Inc.

2) polyoxyethylene perfluoroalkylether, by DuPont Co.

3) l,2-benzisothiazolin- 3-one, active ingredient: 20%,

with dipropylene glycol, by Avecia Co.

The above-noted Hydra ^ή HW-940, glycerin,

3-methyl l,3-butanediol, 2-ethyM, 3-hexanediol, Zoneal FS-300,

Proxel LV, and triethanolamine were dissolved into deionized

water to prepare a vehicle, which was mixed with the pigment

dispersion V to prepare a mixture, then the mixture was

press-filtered through a cellulose acetate membrane filter of 0.8

μm average pore size to prepare the recording ink of Example

A- 13.

Example A- 14 Preparation of Recording Ink

Pigment Dispersion VI 35 parts

Acrit WEM- 321U (solid content: 38%) ^{* i} > 7 parts

Glycerin 7.5 parts

1,3-Butanediol ' 22.5 parts

2-Ethyl- l,3-hexanediol 4 parts

Polyfox PF- 156A (active ingredient: 30%) ^*2) 3.3 parts

Proxel LV (antiseptic/antifungal agent) ^{* 3)} 0.2 part

2 Amino-2-ethyl l, 3 propanediol 0.1 part

Deionized water 20.4 pats

l) acrylic/urethane aqueous emulsion, MFT: 10°C,

average particle diameter: ioo nm, by Taisei Kako Co.

2) anionic fluorine-containing surfactant, by Omnova Co.

3) l,2-benzisothiazolin-3-one, active ingredient: 20%,

with dipropylene glycol, by Avecia Co.

The above-noted Acrit WEM-321U, glycerin,

1,3-butanediol, 2-ethyM,3-hexanediol, Polyfox PF- 156A, Proxel

LV, and 2-amino-2-ethyl" l, 3-propanediol were dissolved into

deionized water to prepare a vehicle, which was mixed with the

pigment dispersion VI to prepare a mixture, then the mixture

was press-filtered through a cellulose acetate membrane filter

of 0.8 μm average pore size to prepare the recording ink of

Example A- 14.

Example A 15

Preparation of Recording Ink

Pigment Dispersion VII 35 parts

Boncoat 4001 (aqueous acrylic emulsion) ⁿ⁾ 7 parts

Glycerin 7.5 parts

3-Methyl- l, 3-butanediol 22.5 parts

2,2,4-Trimethyl- l,3-pentanediol 4 parts

Polyfox PF- 151N (active ingredient: 50%) ^*2) 2 parts

Proxel LV (antiseptic/antifungal agent) ^{* 3)} 0.2 part

2 Amino-2-ethyl l,3-propanediol 0.1 part

Deionized water 21.7 pats

1) solid content: 50%, MFT: 5°C, average particle

diameter: 100 nm, by Dainippon Ink & Chemicals, Inc.

2) oligomer-type nonionic fluorine-containing surfactant,

by Omnova Co.

3) l,2-benzisothiazolin-3-one, active ingredient: 20%,

with dipropylene glycol, by Avecia Co.

The above-noted, Boncoat 4001, glycerin, 3-methyM,3-

butanediol, 2,2,4-trimethyl- l,3 pentanediol, Polyfox PF 151N,

Proxel LV, and 2 amino-2-ethyl- l,3-propanediol were dissolved

into deionized water to prepare a vehicle, which was mixed with

the pigment dispersion VII to prepare a mixture, then the

mixture was press-filtered through a cellulose acetate

membrane filter of 0.8 μm average pore size to prepare the

recording ink of Example A- 15.

Example A- 16

Preparation of Recording Ink

The recording ink of Example A- 16 was prepared in the

same manner as Example A- 14 except that the pigment

dispersion VI was exchanged into the pigment dispersion VIII.

Comparative Example A"3

Preparation of Recording Ink

The recording ink of Comparative Example A-3 was

prepared in the same manner as Example A 14 except that

Softanol EP- 5035 (polyoxyethylene polyoxypropylene branched

alkylether, active ingredient- 100%, by Nippon Shokubai Co.)

was used in place of the Polyfox PF- 156A such that the amounts

of both active ingredients being equivalent while adjusting the

additive amounts and additional deionized water.

Comparative Example A-4

Preparation of Recording Ink

The recording ink of Comparative Example A 4 was

prepared in the same manner as Example A-9 except the

Boncoat 4001 was not used.

Comparative Example A-5

Preparation of Recording Ink

The recording ink of Comparative Example A 5 was

prepared in the same manner as Example A- 10 except the

Zoneal FS 300 was not used.

Comparative Example A-6

Preparation of Recording Ink

The recording ink of Comparative Example A 6 was

prepared in the same manner as Example A- I l except the

pigment dispersion III was exchanged into the pigment

dispersion IX of Comparative Example 1.

Comparative Example A-7

Preparation of Recording Ink

The recording ink of Comparative Example A-7 was

prepared in the same manner as Example A- I l except the

pigment dispersion III was exchanged into the pigment

dispersion X of Comparative Example 2.

Comparative Example A-8

Preparation of Recording Ink

Ink Composition

C.I. Acid Red 52 (water-soluble dye) 3 parts

Glycerin 5 parts

Diethylene glycol ' 15 parts

2-Ethyl- l,3-hexanediol 2 parts

Polyoxyethylene (n=18) lauryl ether ^* D 1 part

Sodium dehydroacetate O. .2 part

Deionized water 8 parts

l) nonionic surfactant, HLB ^: 16.2, by Dai-ichi Kogyo

Seiyaku Co.

The composition of the ingredients described above was

stirred to produce a solution, then pH of the solution was

adjusted to approximately 10 by use of a 10% by mass aqueous

solution of lithium hydroxide thereby to prepare a coarse ink,

which was then press-filtered through a cellulose acetate

membrane filter of 0.8 μm average pore size to prepare the

dye-containing ink of Comparative Example A"8.

Ink properties were evaluated as follows with respect to

the resulting recording inks of Examples A"9 to A- 16 and

Comparative Examples of A"3 to A-8; and also the ejection

performance and images of these recording inks were evaluated

using an ink-jet printer (IPSIO G707, by Ricoh Co.) after filling

these recording inks into cartridges as shown in FIGs. 1 and 2.

The results are shown in Table 1.

Evaluation of Stability (Change Rate)

Stability of the recording inks was evaluated on the basis

of change rate of average particle diameters D50 after storage at

50 ⁰ C for one week in dry condition. The change rate was

calculated from the following equation; the average particle

diameter D50 was measured in accordance with the

measurement using UPA-EX150 (by Micro Track Co.).

Change Rate = D50 after storage/Dso before storage x 100

Measurement of Surface Tension

Surface tension of the recording inks is a static surface

tension measured on a platinum plate at 25°C using a surface

tension meter (CBVP-Z, Kyowa Interface Science Co.).

Measurement of pH

The pH was measured at 23°C using ISFET pH meter

KS701 (by Shindengen Electric Manufacturing Co.).

Evaluation of Ejection Stability

Ejection stability of respective inks was evaluated with

respect to allowable dormant or resting period in a condition

that an ink was filled within an ink cartridge and printing was

carried out after a pre-determined period without capping or

cleaning during the printing, ^' then the dormant or resting

period, till which no ejection-direction deviation appears or no

change causes for the mass-flow, was measured. The ink

cartridge filled with the inks was mounted to an ink-jet printer

(IPSIO G707, by Ricoh Company); and the ejection stability was

evaluated in accordance with the following criteria.

Evaluation Criteria

A: 600 seconds or more

B: 60 seconds or more and less than 600 seconds

C: less than 60 seconds

Evaluation of Color Saturation and Color Density

Each recording ink, filled in an ink cartridge, was loaded

to the ink-jet printer (IPSIO G707 by Ricoh Co.) in the same

manner as described above, and a solid image was printed by

one pass. Regular paper was used for printing test. After the

print was dried, brightness was measured using a reflective

spectroscopic densitometer (by X-Rite Co.). The ratio of

resulting saturation color to the standard saturation color

(Japan Color Version 2, yellow ^: 91.34, inagenta: 74.55, cyan ^:

62.82) was calculated and evaluated in accordance with the

following criteria. Inks that did not satisfy the following - ^■

criteria for the respective color densities were determined as C

in accordance with measurement by X-Rite densitometer.

Evaluation Criteria for Respective Colors: yellow: 0.7 or more,

magenta^ 0.9 or more, cyan: 0.9 or more

Paper for Printing Test

Regular paper: My Paper SA (by NBS Ricoh Co.),

XEROX 4024 (by Fuji Xerox Office Supply), PB Paper (by

Canon Inc.)

Ill

Evaluation Criteria A: 0.8 or more

B: 0.7 or more and less than 0.8 *

C: less than 0.7 Evaluation of Scratch Resistance

Each printed part of the image sample produced on the gloss paper by a method similar to saturation measurement was rubbed back and forth for 5 times using a white cotton cloth with a load of 90Og by a clock meter CM- I (by Toyo Seiki Seisaku-sho, Ltd). Each sample was then visually observed and evaluated in accordance with the following criteria. Paper for Printing Test

Gloss paper: PM Photo Print Paper (gloss) (by Seiko Epson Co.), Professional Photo paper PR- 101 (by Canon Inc.) Evaluation Criteria

A ^: little or no image dropouts or blur around images B: a little image dropouts, some blur around images C ^: notable image dropouts and blur around images Evaluation of Water Resistance Water droplets were dropped on each printed part of

image samples on regular paper formed by a similar method as the color saturation measurement, then conditions of printed matters were visually observed and evaluated in accordance with the following criteria.

Evaluation Criteria

A: substantially no change

B- marks appear around printed parts where water

droplets being dropped

C: bleeding appear around printed parts where water

droplets being dropped

Lightfastness

Image samples formed by a method similar to the

saturation measurement were radiated with 0.35 W/m ² (340 nm)

of xenon irradiance comparable to outdoor sunlight at 70 ⁰ C and

50% RH, and 89°C at black panel temperature for 24 hours

using Atlas Weatherometer Ci35AW. The resulting color

deterioration/alteration before and after the irradiation was

evaluated in accordance with the following criteria shown

below.

Evaluation Criteria

A^ substantially no change

B ^: recognizable change but acceptable

C: significant color deterioration/alteration

Table 1

The results of Table 1 demonstrate that the recording

inks of Examples A-9 to A- 16 containing the inventive pigment dispersions represent superior storage stability compared to those of Comparative Examples A-3 to A-8, and also the

recorded matters from the recording inks display clearness similar to that of dye-inks and afford higher reliability with superior water resistance and excellent lightfastness. Preparation Example B- I

Preparation of Solution B- I of Water-Soluble Polymer

Alpha-olefin/maleic anhydride copolymer (I) ^{* x)} 10.0 parts

IN LiOH aqueous solution ^*2) 17.34 parts

Deionized water ' 72.66 parts

1) expressed by the formula (l) described above, T-YP112

by Seico PMC Co., carbon-atom number of olefin chain: 20 to 24,

acid value: 190 mgKOH/g, mass average molecular weight:

10000

2) 1.2 times amount of alkali on the basis of acid value

A mixture of ingredients described above were mixed

under heating by a mechanical stirrer to dissolve

alpha-olefin/maleic anhydride copolymer (I) expressed by the

formula (l) described above, then a minute amount of insoluble

matters were filtered off using a filter having an average pore

size of 5 μm, thereby to prepare the solution B l of

water-soluble polymer.

Preparation Example B"2

Preparation of Surface-Treated Black Pigment Dispersion

A carbon black (CTAB specific surface area: 150 m ² /g,

DBP absorption number: 100 ml/100g) was added in an amount

of 90 g to 3000 ml of 2.5 N sodium sulfonate solution, then the

mixture was stirred at 300 rpm, 60°C to react for 10 hours

thereby to oxidize the carbon black. The reaction liquid was

filtered, the separated carbon black was neutralized using a

sodium hydroxide solution, which was then subjected to

extracorporeal ultrafiltration. The resulting carbon black was

rinsed with water, dried and dispersed into pure water in a

solid content of 30%.

Thereafter, 6.52 parts of aqueous solution B of

water-soluble polymer (expressed by the formula (l) described

above, T-YP115 by Seico PMC Co., carbon-atom number of olefin

chain: 16 to 18, acid value: 221 mgKOH/g, mass average

molecular weight: 11000, counter ion: ammonium ion, active

ingredient: 23%) was added to 100 parts of the carbon black

dispersion described above to prepare a black pigment

dispersion. The average particle diameter D50 of the black

pigment dispersion was 106 nm in accordance with the

measurement using UPA-EX150 (by Micro Track Co.).

Preparation Example B 3

Preparation of Yellow Pigment Surfactant Dispersion

Monoazo yellow pigment ⁿ⁾ 30.0 parts

Polyoxyethylene styrenephenylether ^*2 ^ 10.0 parts

Deionized water 60.0 parts

1) C.I. pigment yellow 74, by Dainichiseika Color &

Chemicals Mfg. Co.

2) Noigen EA- 177, nonionic surfactant, HLB value : 15.7,

by Dai-ichi Kogyo Seiyaku Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 4 hours by use

of KDLA Model Dyno Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion.

Then, 2.13 parts of a water-soluble polyurethane

(Takelack W-5661, by Mitsui Takeda Chemicals, Inc., active

ingredient- 35.2%) of a water-soluble polymer aqueous solution

and 2.93 parts of aqueous solution C of water-soluble polymer

(expressed by the formula (l) described above, T-YP114 by Seico

PMC Co., carbon-atom number of olefin chain: 12 to 14, acid

value : 385 mgKOH/g, molecular weight: 9000, counter ion:

ammonium ion, active ingredient: 25.6%) were added to the

primary pigment dispersion and the mixture was stirred

sufficiently to prepare a yellow pigment surfactant dispersion.

The average particle diameter D50 of the pigment surfactant

dispersion was 49 nm in accordance with the measurement

using UPA-EX150 (by Micro Track Co.).

Preparation Example B"4

Preparation of Magenta Pigment Surfactant Dispersion

Quinacridone pigment (CI. pigment red 122) ⁿ⁾ 30.0 parts

Polyoxyethylene beta-naphthylether (RT- 100) ^*2 > 10.0 parts

Deionized water 60.0 parts

l) by Dainichiseika Color & Chemicals Mfg. Co.

2) nonionic surfactant, HLB value : 18.5, by Takemoto Oil

& Fat Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno-Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion.

Then, 3.57 parts of a water-soluble styrene/acrylic

copolymer (JC 05 by Seico PMC Co., active ingredient: 21%) and

2.97 parts of aqueous solution D of water-soluble polymer

(expressed by the formula (l) described above, T-YP116 by Seico

PMC Co., carbon-atom number of olefin chain: 16 to 18, acid

value: 280 to 310 mgKOH/g, mass average molecular weight:

11400, counter ion: ammonium ion, active ingredient: 25.3%)

were added to the primary pigment dispersion and the mixture

was stirred sufficiently to prepare a magenta pigment

surfactant dispersion. The average particle diameter D50 of

the pigment surfactant dispersion was 81 nm in accordance

with the measurement using UPAεX150 (by Micro Track Co.).

Preparation Example B 5

Preparation of Cyan Pigment Surfactant Dispersion A

Phthalocyanine pigment ⁿ⁾ 30.0 parts

Polyoxyethylene laurylether (DKS NL-450) ^*2 > 10.0 parts

Deionized water 60.0 parts

l) C.I. pigment blue 15:3, by Dainichiseika Color &

Chemicals Mfg. Co.

2) nonionic surfactant, HLB value ^: 18.3, by Dai-ichi Kogyo

Seiyaku Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno-Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion.

Then, 2.51 parts of a water-soluble polyester (Nichigo

Polyester W-0030 by Nippon Synthetic Chemical Industry Co.,

active ingredient ^: 29.9%) of a water-soluble polymer aqueous

solution and 3.26 parts of aqueous solution B of water-soluble

polymer (expressed by the formula (l) described above, T-YP115

by Seico PMC Co., carbon-atom number of olefin chain: 16 to 18,

acid value ^: 221 mgKOH/g, mass average molecular weight:

11000, counter ion: ammonium ion, active ingredient: 23%) were

added to the primary pigment dispersion and the mixture was

stirred sufficiently to prepare a magenta pigment surfactant

dispersion. The average particle diameter D50 of the pigment

surfactant dispersion was 75 nm in accordance with the

measurement using UPA-EX150 (by Micro Track Co.).

Preparation Example B-6

Preparation of Cyan Pigment Surfactant Dispersion B

Phthalocyanine pigment ^{* :)} 30.0 parts

Polyoxyethylene styrenephenylether ^*2) 10.0 parts

Deionized water 60.0 parts

l) C.I. pigment blue 15^3, by Dainichiseika Color &

Chemicals Mfg. Co.

2) Noigen EA 177, nonionic surfactant, HLB value: 15.7,

by Dai-ichi Kogyo Seiyaku Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno-Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a primary pigment dispersion.

Then, 15.0 parts of the aqueous solution B- I of the

water-soluble polymer of the Preparation Example B- I was

added to the primary pigment dispersion and the mixture was

stirred sufficiently to prepare a cyan pigment surfactant

dispersion B. The average particle diameter D50 of the pigment

surfactant dispersion was 83 nm in accordance with the

measurement using UPA-EX150 (by Micro Track Co.).

Preparation Example B"7

Preparation of Cyan Pigment Surfactant' Dispersion C

Phthalocyanine pigment ^* ^ 30.0 parts

Polyoxyethylene laurylether (DKS NL"450) ^*2 > 10.0 parts

Deionized water 60.0 parts

1) C.I. pigment blue 15^3, by Dainichiseika Color &

Chemicals Mfg. Co.

2) nonionic surfactant, HLB value: 18.3, by Dai-ichi Kogyo

Seiyaku Co.

Initially, the surfactant described above was dissolved

into deionized water to prepare a solution, then the solution

was mixed with to wet the pigment described above sufficiently.

The mixture was then dispersed at 2000 rpm for 2 hours by use

of KDLA Model Dyno-Mill wet-type disperser (by WAB

Machinery Co.) filled with zirconia beads of 0.5 mm diameter

thereby to prepare a cyan pigment surfactant dispersion C.

The average particle diameter D50 of the pigment surfactant

dispersion was 75 nm in accordance with the measurement

using UPA-EX150 (by Micro Track Co.).

Examples B l to B I l and Comparative Example B- I to B-6

Preparation of Recording Ink

Inks were prepared in the following manner. The

humectants, wetting agents, surfactants and water were mixed

in the amounts and' ingredients shown in Tables 2, 3 and 4, and

stirred for one hour to form uniform mixtures. To the

respective mixtures, resin dispersions were added and stirred

for one hour, then pigment dispersions, antiseptic/antifungal

agents and a defoamer were added and mixed further one hour.

The resulting respective dispersions were then press-filtered

through a cellulose acetate membrane filter of 0.8 μm average

pore size to remove coarse particles and impurities to prepare

recording inks for evaluation.

Table 2

Table 3

Table 4

The ingredients in Tables 2 to 4 indicate the following

materials.

Acrylic Silicone Emulsion: solid content: 40%, average

particle diameter: 130 nm, MFT: o°C or lower, by Toyo Ink Mfg.

Co.

Acrylic Emulsion: John Clear 7600, solid content: 47%,

average particle diameter: 90 nm, MFT: 10 ⁰ C or lower, by

Johnson Polymer Co.

Polyurethane Emulsion: Hydran HW-930, solid content:

50%, average particle diameter: 200 nm or less, MFT: 0 ⁰ C or

lower, by DIC Co.

Polyester Emulsion: Pesresin A-520, solid content: 30%,

average particle diameter: 100 nm or less, MFT: 30 ⁰ C or lower,

by Takamatsu Oil & Fat Co.

Polyfox PF- 151N: oligomer-type nonionic

fluorine-containing surfactant, active ingredient: 50%, by

Omnova Co.

Zoneal FS-300: polyoxyethylene perfluoroalkylether,

active ingredient: 40%, by DuPont Co.

Softanol EP-5035: polyoxyethylene polyoxypropylene

branched alkylether, active ingredient: 100%, by Nippon

Shokubai Co.

Proxel GXL: key' ingredient: l,2-benzisothiazolin-3-one,

antifungal agent, active ingredient: 20%, with dipropylene

glycol, by Avecia Co.

KM-72F: self-emulsifying silicone defoamer, active

ingredient: 100%, by Shin-Etsu Chemical Co.

The recording inks of Examples B- I to B I l and

Comparative Examples B- I to B-6 were evaluated in accordance

with the evaluation methods shown below. The results are

shown in Tables 5 and 6.

Resin Amount versus Pigment

The ratio of amounts of resin dispersions to solid

contents of pigments in the inks was calculated by ^: ratio = solid

content of resin/solid content of pigment.

Solid Content of Ink

The total content of pigments and resins (emulsion plus

water-soluble resin) in inks was obtained.

Measurement of Ink Viscosity

Viscosity of inks was measured at 25°C using a

viscometer (RL-500, by Toki Sangyo Co.).

Measurement of Surface Tension of Ink

Surface tension of inks was measured at 25°C using an

automatic surface tension meter (CBVP-Z, by Kyowa Interface

Science Co.).

Arrangement of Printing Evaluation

A ink jet printer' (IPSIO G707, by Ricoh Co.) was set up

so as to apply an equivalent amount of inks onto recording

media by adjusting driving voltage on a piezoelectric element

under a condition of temperature 23°C and relative humidity

50%.

Ejection Stability

A chart, formed using Microsoft Word 2000 (by Microsoft

Co.), to paint 5% area of A4 paper with a solid image per one

color was printed consequently on 200 sheets of Type 6200

paper (by NBS Ricoh Co.), then ejection disturbance was

evaluated. The printing mode was selected as "no color

correction" modified from "regular plain paper & standard fast"

in accordance with user setup attached to the printer.

Evaluation criteria

A: no ejection disturbance

B ^: some ejection disturbance

D : significant disturbance or no ejection

Image Density

A chart, formed using Microsoft Word 2000 (by Microsoft

Co.), with a 64 point symbol "Jj" was printed on Xerox 4024

paper (Fuji Xerox Co.), the color of the symbol "B" part on the

print surface was measured using X-Rite 938 and evaluated by

the following evaluation criteria. The printing mode was

selected as "no color correction" modified from "regular plain

paper & standard fast" in accordance with user setup attached

to the printer.

Evaluation criteria

A: black > 1.3, yellow > 0.85, magenta > 0.95, cyan >

1.1

B: 1.3 > black > 1.2, 0.85> yellow > 0.80, 0.95 > magenta

> 0.90, 1.1 > cyan > 1.0

C: 1.2 > black > 1.1, 0.80 > yellow > 0.70, 0.90 > magenta > 0.80, 1.0 > cyan > 0.9

D: 1.1 > black, 0.70 > yellow, 0.80 > magenta, 0.9 > cyan Color Development

A chart, formed using Microsoft Word 2000 (by Microsoft Co.), similar with that of the image density described above was printed on Xerox 4024 paper (Fuji Xerox Co.), the symbol "|" part on the print surface was measured using X-Rite 938. The printing mode was selected as "no color correction" modified from "regular plain paper & standard fast" in accordance with user setup attached to the printer. The ratio of measured color saturation to that of the standard color (Japan color ver.2, yellow: 91.34, magenta ^: 74.55, cyan: 62.82) was calculated to evaluate by the following evaluation criteria. Evaluation criteria

A: 0.8 or more B: less than 0.8 Water Resistance

A chart was printed on Xerox Type 6200 paper (by NBS

Ricoh Co.) in a similar manner as the image density, then the symbol "(" part on the print surface was dried at temperature

23°C and 50% RH for 24 hours. The dried chart was then immersed in water at 30 ⁰ C for one minutes, slowly lifted up,

and dried mildly, then evaluated by the following evaluation

criteria.

Evaluation Criteria

A: no bleeding of color

B: some bleeding of color

Scratch Resistance

A chart, formed using Microsoft Word 2000 (by Microsoft

Co.), with a monocolor solid image of 3 cm by 3 cm was printed

on matte glossy paper dedicated for Ricoh Gel Jet Printer (by

NBS Ricoh Co.), and the resulting recorded matter was dried at

23°C and 50% RH for 24 hours. Then JIS L 0803 cotton No. 3,

attached to CM- I type clock meter by use of a double stick tape,

was reciprocated on the recorded matter 5 times so as to rub its

printed part, then ink stain on the cotton fabric was measured

using X-Rite 938 while subtracting the background density, and

the scratch resistance was evaluated by the following

evaluation criteria.

Evaluation criteria

A: less than 0.1 of stain density

B: 0.1 or more of stain density

Lightfastness

A chart was printed on Type 6200 paper (by NBS Ricoh

Co.), in a similar manner with that of the image density

described above, then the symbol "J" part on the print surface

was dried at temperature 23°C and 50% RH for 24 hours. This image portion was irradiated with 0.35 WVm ² (340 nm) of xenon

irradiance comparable to outdoor sunlight at 70 ⁰ C and 50% RH, and 89°C at black panel temperature for 24 hours using Atlas Weatherometer Ci35AW. The resulting color deterioration and alteration before and after the irradiation was evaluated in accordance with the following criteria shown below. Evaluation Criteria

A ^: substantially no change B- recognizable change but acceptable

C: significant color deterioration/alteration Drying Property

A chart was printed on Type 6200 paper (by NBS Ricoh Co.), in a similar manner with that of the image density described above, then the symbol "(" part on the print surface was contacted and pushed to a filter paper immediately after the printing, and the occurrence of transfer was evaluated.

A: no transfer and staining

B: slight transfer and staining

C: significant transfer and staining

Table 5

Table 6

In comparative Example B-2, excessively high viscosity

disturbed normal printing.

In comparative Example B-3, the excessively small

amount of the humectant prevented normal printing.

The mark "-" in Table 6 indicates that no data was

obtained.

Industrial Applicability

The inks according to the present invention, which

including the pigment dispersions according to the present

invention, may certainly provide excellent color development,

superior image quality and higher reliability, and may form

high-quality images with higher color saturation and proper

color tone on not only dedicated recording paper but also on

regular paper, thus may be favorably utilized for ink cartridges,

ink recorded matters, ink-jet recording apparatuses and ink-jet

recording methods.

The ink-jet recording apparatuses and ink-jet recording

methods according to the present invention may be applied to

various recordings of ink-jet recording processes, and also

favorably utilized for ink-jet recording printers, facsimiles,

copiers, and printer/facsimile/copier complex apparatuses in

particular.