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Title:
SOLID PIGMENT DISPERSION, PROCESS FOR PREPARING THE SAME AND PROCESS FOR PREPARING AQUEOUS OR ORGANIC SOLVENT-BASED INKJET INK
Document Type and Number:
WIPO Patent Application WO/2019/007922
Kind Code:
A1
Abstract:
Object: To provide a highly-dispersible solid pigment composition as an intermediate product, and a process for automatically and continuously preparing the composition. Means to Solve the Object: A solid pigment dispersion as an intermediate product, wherein the dispersion is redispersible with an aqueous or organic dispersion medium and the dispersion contains 20 to 80% by weight of one or more pigments and 20 to 80% by weight of one or more dispersing aids, in each case based on the total weight of the one or more pigments and the one or more dispersing aids, and has a 50% cumulative volume particle diameter distribution D50 of 150nm or less, as determined for the redispersed pigment particles by laser light scattering.

Inventors:
HARADA DAISUKE (JP)
Application Number:
PCT/EP2018/067871
Publication Date:
January 10, 2019
Filing Date:
July 03, 2018
Export Citation:
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Assignee:
CLARIANT INT LTD (CH)
International Classes:
C09D11/322; C09B67/00
Domestic Patent References:
WO2009145284A12009-12-03
Foreign References:
EP2471875A12012-07-04
EP2048206A12009-04-15
US20080139706A12008-06-12
JP2004217916A2004-08-05
JP2007099918A2007-04-19
JP2002322396A2002-11-08
JP2014177532A2014-09-25
JP2016027078A2016-02-18
JP5553509B22014-07-16
Attorney, Agent or Firm:
JACOBI, Carola (Industriepark Höchst / G 860, Frankfurt, DE)
Download PDF:
Claims:
CLAIMS

1 . A solid pigment dispersion as an intermediate product, wherein the dispersion is redispersible with an aqueous or organic dispersion medium and the dispersion contains 20 to 80% by weight of one or more pigments and 20 to 80% by weight of one or more dispersing aids, in each case based on the total weight of the one or more pigments and the one or more dispersing aids, and has a 50% cumulative volume particle diameter distribution D50 of 1 50nm or less, as determined for the redispersed pigment particles by laser light scattering.

2. A solid pigment dispersion as claimed in claim 1 , wherein the 90% cumulative volume particle diameter distribution D90 is 300nm or less, as determined for the redispersed pigment particles by laser light scattering. 3. A solid pigment dispersion as claimed in claim 1 , wherein the 90% cumulative volume particle diameter distribution D90 is 200nm or less, as determined for the redispersed pigment particles by laser light scattering.

4. A solid pigment dispersion as claimed in any one of claims 1 to 3, wherein the 50% cumulative volume particle diameter distribution D50 is

100nm or less, as determined for the redispersed pigment particles by laser light scattering.

5. A solid pigment dispersion as claimed in any one of claims 1 to 4, wherein said one or more dispersing aids comprise two or more dispersing aids.

6. A solid pigment dispersion as claimed in any one of claims 1 to 5, wherein said dispersion is redispersible with an aqueous dispersion medium and said one or more dispersing aids comprise a dispersing aid having a molecular weight of 1 0000g/mol or less.

7. A solid pigment dispersion as claimed in claim 6, wherein said dispersing aid having a molecular weight of 1 0000g/mol or less comprises one or more dispersing aids selected from the group consisting of a wax, a macromolecule and a glycol.

8. A solid pigment dispersion as claimed in claim 6, wherein said dispersing aid having a molecular weight of 1 0000 g/mol or less comprises two or more dispersing aids selected from the group consisting of a wax, a macromolecule and a glycol.

9. A solid pigment dispersion as claimed in claim 7 or 8, wherein said dispersing aid having a molecular weight of 1 0000g/mol or less comprises a combination of a wax and/or a glycol with a macromolecule in a weight ratio of 90: 10 to 40:60.

10. A solid pigment dispersion as claimed in any one of claims 7 to 9, wherein said wax comprises a wax having a melting point of 30 to 150°C.

1 1 . A solid pigment dispersion as claimed in claim 1 0, wherein said wax having a melting point of 30 to 1 50°C comprises a water-soluble wax.

12. A solid pigment dispersion as claimed in claim 1 1 , wherein said water-soluble wax comprises a montan acid derivative wax.

13. A solid pigment dispersion as claimed in any one of claims 7 to 12, wherein said macromolecule comprises a polyester. 14. A solid pigment dispersion as claimed in claim 13, wherein said polyester comprises a water-soluble polyester having a softening point or melting point of 50 to 200°C.

15. A solid pigment dispersion as claimed in claim 14, wherein said water-soluble polyester has a 5-sulfoisophthalic acid group.

16. A solid pigment dispersion as claimed in any one of claims 1 to 1 5, wherein said dispersion is redispersible with an aqueous dispersion medium and the amount of the residual liquid dispersion medium is 5% by weight or less based on the entire dispersion .

17. A solid pigment dispersion as claimed in any one of claims 1 to 5, wherein said dispersion is redispersi ble with an organic dispersion medium and said one or more dispersing aids are selected from the group consisting of polyvinyl resins.

18. A solid pigment dispersion as claimed in claim 17, wherein said polyvinyl resin is a polyvinylbutyral resin having a degree of acetalization of 60% or more and/or a vinyl chloride-vinyl acetate copolymer having a vinylacetate content of at least 1 % by weight and at most 30% by weight.

19. A solid pigment dispersion as claimed in claim 17 or 1 8, wherein said polyvinyl resin has a melting point of 30 to 150°C.

20. A solid pigment dispersion as claimed in any one of claims 17 to 1 9, wherein said dispersion contains a further dispersing aid selected from the group consisting of urethane resins, polyethyleneimine resins, amino acid derivative resins, and (meth)acrylic resins in an amount of more than 0% by weight to 40% by weight relative to the mixture of said one or more pigments and said one or more of dispersing aids.

21 . A solid pigment dispersion as claimed in claim 20, wherein the sum (mg KOH/g) of the acid number and amine number of said resin is at least

10 and at most 1 50.

22. A solid pigment dispersion as claimed in any one of claims 1 to 5 and 17 to 21 , wherein the dispersion is redispersible with an organic dispersion medium and the amount of the residual liquid dispersion medium is 1 0% by weight or less based on the entire dispersion .

23. A solid pigment dispersion as claimed in any one of claims 1 to 22, as an intermediate product for preparing inkjet inks, toners or developers for printers, pigment compositions for color filters, or pigments compositions for writing materials.

24. A process for preparing a solid pigment dispersion redispersible with an aqueous dispersion medium, as claimed in any one of claims 1 to 1 6 and 23, using a continuous automatic apparatus capable of continuously carrying out, at least, the following steps (1 )-(4) in the same single apparatus: (1 ) a step of introducing the one or more pigments and one or more solid dispersing aids (A) in a dispersing unit;

(2) a step of mixing one or more aqueous liquid dispersion media

comprising one or more wetting dispersing aids (B) with the one or more pigments;

(3) a step of applying a shearing force to the mixture comprising the one or more pigments, the one or more dispersing aids (A+B) and the one or more liquid dispersion media to knead the mixture; and

(4) a step of drying the mixture by removing the one or more dispersion media.

25. A process as claimed in claim 24, wherein, in step (2), relative to the total amount of 100 parts by weight of the one or more pigments and the one or more solid dispersing aids (A), 5 to 150 parts by weight of the one or more aqueous liquid dispersion media comprising 0.05% by weight or more of the one or more wetting dispersing aids (B) are supplied, and the pigments and the dispersion media are mixed.

26. A process as claimed in claim 24 or 25, wherein said one or more aqueous liquid dispersion media consist of water or contain water and a water-miscible organic medium in a weight ratio of 90: 1 0 to 10:90.

27. A process for preparing a solid pigment dispersion redispersible with an organic dispersion medium, as claimed in claims 1 to 5 and 1 7 to 23, using a continuous automatic apparatus capable of continuously carrying out, at least, the following steps (1 ')-(4') in the same single apparatus:

(1 ') a step of introducing the one or more pigments, along with or without one or more dispersing aids (Α'), in a dispersing unit; (2') a step of mixing one or more organic liquid dispersion medium comprising or not comprising one or more dispersion media (Α') and/or

(Β') with the one or more pigments;

(3') a step of applying a shearing force to the mixture comprising the one or more pigments, the one or more dispersing aids (A' or A'+B') and the one or more liquid dispersion media to knead the mixture; and (4') a step of drying the mixture by removing the one or more liquid

dispersion media,

wherein said one or more dispersing aids (Α') are used in at least one of steps (1 ') and (2'), and said one or more dispersing aids (Α') are selected from the group consisting of polyvinyl resins and said one or more dispersing aids (Β') are selected from the group consisting of urethane resins, polyethyleneimine resins, amino acid derivative resins and

(meth)acrylic resins.

28. A process as claimed in claim 27, wherein, in step (2'), relative to the amount of 1 00 parts by weight of the one or more pigments or to the total amount of 1 00 parts by weight of the one or more pigments and the one or more solid dispersing aids (Α'), 5 to 1 60 parts by weight of the one or more organic liquid dispersion media, or 5 to 1 50 parts by weight of the one or more organic liquid dispersion media comprising 5% by weight or more of the one or more dispersing aids (Β'), are supplied, and the pigments and the dispersion media are mixed . 29. A process as claimed in claim 27 or 28, wherein said organic liquid dispersion media contain an alkyleneglycol ether.

30. A process as claimed in claim 27 or 28, wherein said organic liquid dispersion media contain an alkyleneglycol ether and another organic medium . 31 . A process as claimed in claim 29 or 30, wherein said alkyleneglycol ether is one or more selected from the group consisting of diethyleneglycol dimethylether, diethyleneglycol diethylether, diethyleneglycol dibutylether, dipropyleneglycol dimethylether, dipropyleneglycol diethylether, and dipropyleneglycol dibutylether.

32. A process as claimed in any one of claims 24 to 31 , wherein, in the continuous automatic apparatus, step (4) or (4') is followed by continuously carrying out the following further steps:

(5) or (5') a step of extruding the kneaded and dried pigments;

(6) or (6') a step of obtaining a solid pigment dispersion in the form of a shaped article.

33. A process as claimed in any one of claims 24 to 32, wherein the continuous automatic apparatus is a continuous automatic kneader.

34. A process as claimed in any one of claims 24 to 32, wherein the continuous automatic apparatus is a continuous automatic twin-screw extruder. 35. A process as claimed in any one of claims 24-34, wherein the one or more pigments and the one or more dispersing aids (A) or (Α') are previously mixed, followed by the introduction of the mixture into the dispersing unit in the step (1 ).

36. A process as claimed in any one of claims 24 to 35, wherein the proportion of the oversize particles having a particle size of more than 5 μηη in the redispersible solid pigment dispersion, which do not pass a filter having a pore side of 5 μηι, is 1 0% by weight or less of the total weight of the redispersible solid pigment dispersion, calculated based on the difference in the dry weight of the filter before and after the filtration .

37. A process for preparing an inkjet ink, comprising redispersing a solid pigment dispersion obtained by a process as claimed in any one of claims 24 to 36 in a dispersion medium .

Description:
[Document Name] Description

[Title of I nvention] SOLI D PI GMENT DISPERSION, PROCESS FOR

PREPARI NG TH E SAME AN D PROCESS FOR PREPARI NG AQU EOUS OR ORGAN I C SOLVENT-BASED I N KJ ET I N K

[Technical Field]

[0001 ]

The present invention relates to a solid pigment dispersion as an intermediate product having excellent various properties such as pigment dispersibility and storageablity and imparting excellent performance to final products, and a process for preparing the same.

[Background Art]

[0002]

Organic pigments, which have vivid coloration and excellent durability, are used in many image forming systems such as inkjet recording, toners for laser color printers, and color filters for displays.

When pigments are used in these image formation applications, such pigments themselves are not frequently used directly in a part of a step of preparing final products. I n many cases, common methods include mixing a pigment with a dispersing aid and the like, finally dividing the mixture to prepare a dispersion as an intermediate product, mixing and processing the product with other components to provide final products. I n the case of an inkjet ink, for example, a pigment dispersion as an intermediate product is prepared in advance, the dispersion is processed into an ink liquid by redispersion in a solvent for ink, and the ink liquid is provided for end uses. Pigment dispersions as such intermediate products should have several common basic properties, including properties shown in Table 1 , for example.

[0003]

[Table 1 ]

(1 ) I mproving performance of (A) High degree of pigment dispersion

final product

(B) Good quality of final product

(2) Easy to handle and

' (C) Being solid and not causing agglomeration or the like having stable performance

during transportation, storage and the like

Performance

required for (D) Containing no additive that induces aggregation or the pigment like on redispersion

composition as

intermediate

product (3) Producible at lower cost ' (E) Dispersible in closed system having little volatilization with good reproducibility of solvent

(F) Adaptable to continuous automatic operation (4) Usable for preparation of (G) Dispersion medium having no or little hazardousness organic solvent-based ink and offensive odor problems can be used

having no environmental

burdens and being harmless

to human body

Table 1 : Basic properties of pigment dispersion required as intermediate product

[0004]

To allow pigment dispersions as intermediate products to be used in many applications, it is necessary to obtain both formulation and production techniques of pigment compositions that can achieve the properties shown in Table 1 . For simplicity hereinafter, description will be made below regarding basic properties to be possessed by pigment dispersions, and formulations for achieving such properties, while focusing it on inkjet applications. Next, production techniques to obtain solid pigment dispersions as such intermediate products will be reviewed, and objects of the present invention will be described.

[0005]

For a pigment dispersion as an intermediate product, first, it is necessary to improve the performance and quality of final products. For this purpose, (A) it is desirable that the pigment dispersion have a high degree of dispersion, specifically, for example, a 50% cumulative volume particle diameter distribution (D 5 o, also referred to as median diameter) of 200 nm or less, preferably 1 50 nm or less, more preferably 1 00 nm or less. A large particle diameter of a pigment in an ink is likely to cause clogging of nozzles and precipitation of the pigment in the ink. Next, (B) it is desirable that components contained in the pigment dispersion do not damage the quality of final products, for example, do not decrease the gloss of images, or do not contain a low-melting-point compound, such as a compound having a melting point of 20°C or less, particularly 15°C or less, or 10°C or less, in an amount that causes adhesion or the like between image surfaces when the surfaces come in contact with each other.

[0006] A second property of the pigment dispersion as an intermediate product is that the dispersion is easy to handle and has stable performance. For this purpose, it is necessary that (C) the dispersion do not alter in quality during storage or the like until the next step and be easy to handle and that (D) the dispersion do not cause pigment aggregation and the like during redispersion in the next step. The pigment dispersion as an intermediate product may be often processed into a final product as an inkjet ink after transported to another plant following the production . I n such a case, if the pigment dispersion is in a liquid form, its weight and volume are larger, and its handling is troublesome. A larger storage space is also required, which is uneconomical. For these reasons, the

dispersion, as an intermediate product, is desirably in a solid form .

Additionally, the solid is required to have stable quality even after storage, without causing agglomeration or the like.

[0007]

For easier handleability as an intermediate product, it is necessary that the pigment dispersion can be easily redispersed in a dispersion medium. When a solid pigment dispersion for inkjet printing is dispersed in water as an inkjet ink medium to prepare an ink, a humectant such as ethylene glycol may be often dissolved in water in advance for the protection of printed images. I n such a case, the dispersing aid has to have the nature of being capable of maintaining its adsorption on the pigment after redispersion to maintain high dispersibility (D), so as not to desorb the dispersing aid from the surface of the redispersed pigment into water and thus make the dispersion unstable.

[0008] A third property necessary for the solid pigment dispersion as an intermediate product is that the dispersion can be provided with good reproducibility at a lower cost. For this purpose, it is preferred that (E) the dispersion be dispersible in a closed system having little volatilization of the solvent and (F) be prepared by an automatically-operatable apparatus.

Furthermore, such a preparation process using an automatically-operatable apparatus should be usable for both aqueous and organic medium-based dispersions. With respect to such production techniques, conventional techniques are reviewed with a focus on inkjet inks, as follows.

[0009]

Conventional pigment inks are prepared by, for example, passing a pigment and a polymer solution through a zirconia bead medium-packed dispersing unit so that the pigment is dispersed in a circulating manner (see Patent Literature 1 ). I n dispersion methods using such a medium, the medium is physically broken to cause contamination, and the medium is likely to cause clogging of inkjet nozzles.

[001 0]

As a method not including use of a grinding medium such as beads, there is disclosed a method including, for example, mixing a pigment with a dispersion medium such as water and dispersing the mixture by a two-roll mill or three-roll mill (Patent Literature 2). I n the case of a roll mill system, however, individual differences are likely to occur because the pressure between the rolls is manually adjusted. The dispersion medium is likely to evaporate because the dispersion is carried out in an

environment open to the air, and moreover, there is also a problem of low working efficiency.

[001 1 ] I n contrast to the conventional batch manner described above, an example is known in which pigment dispersion is attempted using a single- screw continuous kneader or twin-screw continuous kneading extruder that has high production efficiency and can be continuously automatically operated. For example, Example 1 of Patent Literature 3 describes an example in which a carbon black pigment is melt and dispersed using a twin-screw continuous kneader. Since only the kneader is insufficient to obtain a necessary degree of dispersion, an additional off-line rotary dispersing unit is provided in the next step. Thus, it cannot be said that the productivity is high . Use of a twin-screw extruder for carrying out salt milling of a pigment is known (e.g., Patent Literature 4), but washing off of the inorganic salt such as common salt is required after the use. Thus, this cannot be said to be a suitable method for obtaining a solid pigment dispersion .

[0012]

Patent Literature 5 discloses an example using a twin-screw continuous extruder, which is an instance where the introduction of starting materials, dispersion and discharging are automatically and continuously carried out in a continuous automatic apparatus. According to this method, an organic pigment is automatically dispersed in a polyester resin, and thus, a solid pigment dispersion can be obtained. However, in the

Examples, most of the median particle diameters D50 is as large as 200 nm or more. Generally, in inkjet printing applications, it is preferred that D 50 be 1 50 nm or less and D 90 be 200 nm or less. More preferably, it is required that D50 be 1 00 nm or less. The method of Patent Literature 5 does not achieve such a high level.

[001 3] Additionally, a fourth property is that dispersion media having no or little hazardousness and offensive odor problems can be used. The image forming methods employed in inkjet printing are widely used, including computer image outputs. As the application extends to commercial applications such as printing methods in the place of planographic printing , or print board production, the waterfastness, intensity and the like of images become required, and applications using organic solvents for such ink liquids are expanding. For this case, solvent-based ink compositions having no environmental burdens and being harmless to human body are required . From the viewpoint of pigment dispersion, dispersions using an aromatic-based medium or ketone-based medium have been used, and inks prepared from such a dispersion by means of the same aromatic-based medium or ketone-based medium have been used. However, these media have problems such as hazardousness and offensive odor. When considering such environmental pollution, glycol ethers and alcohols are preferable, but these media, which generally have a low solubility for resins, are disadvantageous for finely divided pigments. When inkjet recording is used in the commercial applications described above, the recording area is generally large, and its cost restriction is large. Thus, how to enhance the efficiency of the step of preparing a pigment dispersion and to reduce its preparation cost will be a large challenge.

[0014]

As mentioned above, materials and compositions for obtaining easily redispersible solid pigment dispersions, which do not cause troubles such as aggregation during transportation and storage, and additionally can achieve excellent image quality, are not known in the conventional art.

Even if these were obtained, the conventional dispersion technology could not simultaneously achieve dispersibility and productivity at the same time, or lacks safety. In fact, no solutions thereto have been found.

[0015]

In the description above, pigment dispersion has been principally discussed in connection with inkjet recording. Simultaneous achievement of high dispersibility and productivity is in the same situation not only in the case of inkjet, but also in the case of toners for printers, pigment compositions for color filters, pigments for writing tools such as ballpoint pens and the like.

[Citation List]

[Patent Literature]

[0016]

[Patent Literature 1]

JP2004217916A

[Patent Literature 2]

JP2007099918A

[Patent Literature 3]

JP2002322396A

[Patent Literature 4]

JP2014177532A

[Patent Literature 5]

JP2016027078A [Summary of Invention]

[Technical Problem]

[0017] l n view of the situations described above, a first object of the present invention is to provide a solid pigment dispersion (1 ) of which final product has good performance and (2) that is easy to handle as an intermediate product and redispersible, and furthermore, a second object of the present invention is to provide (3) a process for preparing the

composition at a low cost easily.

[Solution to Problem]

[001 8]

As a results of intensive studies in order to solve the

disadvantages of the conventional art, thereby achieving the objects, the present inventors have found the following findings and guidelines as an idea to achieve the objects of the present invention .

[001 9]

1 ) A solid pigment dispersion as an intermediate product should contain a pigment and a dispersing aid as main components. The primary function of the dispersing aid is to (a) impart a high degree of dispersion to the pigment, and secondary functions thereof include (b) the prevention of the dispersed pigment from fusing and agglomerating during storage etc., (c) the maintenance of the degree of dispersion required for redispersion, and (d) particularly in the case of an organic medium-based composition, being free of problems such as environmental burdens, hazardousness to human body, or offensive odor.

[0020]

2) As a pigment dispersing aid to achieve the high degree of dispersion under the requirement (a) described above, at least one dispersing aid is preferably selected from low-molecular dispersing aids, macromolecular dispersing aids, and inorganic dispersing aids.

[0021 ]

3) Next, as a dispersion condition to satisfy the requirement (b), it is desirable that the softening or melting point of the dispersing aid be sufficiently higher than room temperature. I n addition, although it does not relate to dispersing aids, the dispersion medium remaining in the

composition may cause agglomeration, and thus, a sufficiently small amount of the residual medium is advantageous.

[0022]

4) Additionally, as a third requirement (c), it is necessary for the pigment dispersion not to aggregate by the interaction with ink additives contained in the redispersion liquid. For example, in the case of aqueous inkjet inks, a polyhydric alcohol, for example, is often added to impart wetting properties, but when adsorption and desorption of the dispersing aid on and from the pigment are caused by the polyhydric alcohol, the adsorption and desorption may lead to aggregation . For this reason, a dispersing aid having adsorptivity strong enough to prevent such

aggregation is advantageous.

[0023]

5) Furthermore, as a fourth requirement (d), it is envisaged to use glycol ethers and alcohols instead of aromatic or ketone-based media that have been conventionally used as a dispersion medium. However, these media have generally a low solubility for resins and thus, may be

disadvantageous for finely divided pigments. Therefore, dispersing aids are desired which enable fine dispersion by use of a highly safe, label-free medium particularly in the GHS classification (Globally Harmonized System of Classification and Labelling of Chemicals), and also preparation of inks using such a medium.

[0024]

6) I n diverse search for materials that satisfy the requirements (a) to (d) described above, it has been found that wettable waxes and glycols having a softening point or melting point higher than room temperature and, among these, water-soluble waxes and polyvinyl-based resins are preferable.

[0025]

7) I n a further search for dispersing aids other than the above- mentioned materials satisfying the requirements (a) to (d) described above, it has been found that macromolecular materials having a softening point or melting point higher than room temperature, having a moderate

hydrophobic-hydrophilic balance, and having a weight average molecular weight of 1 0000 g/mol or less are preferable, among these, polyesters are preferable, and furthermore among these, water-soluble oligomers are preferable.

[0026]

8) Subsequent to the above material search, an examination was then made on a preparation method to obtain a solid pigment dispersion with high productivity. Further searches and examinations were made with attention paid on an automatic dispersing machine combining screw conveying and kneading mechanisms as an apparatus for continuously carrying out mixing, grinding, kneading, and drying in a closed system . As a result, it has been found that there exists a method of kneading and dispersion without use of a liquid dispersion medium in a mixed system of a pigment and a resin by a twin-screw extruder, as is shown in Patent Literature 5. However, the D50 achieved therein is about 200 nm or more, and instances achieving higher dispersion which provides D 5 o of 1 50 nm or less have not been found so far.

[0027]

9) The present inventors have reviewed the reason why said higher dispersion cannot be achieved in said Patent Literature 5 and, as a result, have considered that a major reason is that, since the dispersion is carried out in the melt state using a high molecular weight resin as a dispersion medium, the shearing force is absorbed by the resin during dispersion and thus, is not sufficiently transmitted to the pigment.

[0028]

10) It was expected that, instead of the above method using a resin as a dispersion medium, if a pigment mixture is prepared in the form of a slurry using a low-molecular liquid such as a solvent, the shearing force is then efficiently applied on the pigment, thus enabling dispersion . Thus, a liquid dispersion medium and a wetting dispersing aid were added through a liquid injection port provided in the extruder to prepare a mixture in a slurry form, followed by kneading the mixture, and it was then found that D50 was 150 nm or less.

[0029]

However, even in this case, particularly for an aqueous

composition, it has been found that a good degree of dispersion may not be achieved without addition of a dispersing aid to water. I n discussion of such a phenomenon, the pigment composition mixed with water exhibits dilatant flow properties, and the flowability thereof drastically decreases when a pressure is applied thereto. Thus, water, which has a large surface tension, cannot sufficiently penetrate into the pigment composition . l n contrast, it is believed that, when water, which has been previously mixed with a wetting dispersing aid, is injected, the water then assumes a lowered surface tension and sufficiently diffuses even into a highly-flowable dispersion, thus imparting a slurry flowability and dispersion stability suitable for pigment dispersion .

[0030]

1 1 ) A solid pigment dispersion having a high degree of dispersion was able to be obtained by further drying, extruding and shaping a pigment uniformly mixed with a liquid dispersion medium.

[0031 ]

12) The pigment dispersion obtained via the course described above was stable on storage, and an ink obtained by redispersing the pigment dispersion in an ink medium had good performance such as filterability, nozzle dischargeability, and image intensity.

[0032]

13) The above can be summarized as follows. That is, it was difficult to achieve D50 of 1 50 nm or less by means of melt dispersion of a mixture only comprising a pigment and a resin using a twin-screw extruder. I n contrast, if a solid dispersing aid was mixed with a pigment, the mixture was loaded in an extruder and optionally mixed with a dispersion medium containing a further dispersing aid to disperse the pigment to give a slurry, then as surprisingly high dispersibility as D 50 of 150 nm or less was achieved by one passage through the extruder (1 pass). D 90 of 300 nm or less was also simultaneously achieved . Selecting a pigment dispersing aid so as to obtain an optimal melting or softening point value and controlling the amount of the pigment dispersing aid prevented agglomeration on storage, provided excellent ink dischargeability, and improved the intensity of images recorded. Furthermore, it has been found that using a plurality of dispersing aids having different properties in combination with a pigment in an appropriate composition ratio makes the pigment dispersible in a slurry form with a high degree of dispersion by a continuous kneading apparatus, and inks using such a dispersion exhibit high performance.

[0033]

That is, the present invention relates to the following:

[0034]

1 . A solid pigment dispersion as an intermediate product, wherein the dispersion is redispersible with an aqueous or organic dispersion medium and the dispersion contains 20 to 80% by weight of one or more pigments and 20 to 80% by weight of one or more dispersing aids, in each case based on the total weight of the one or more pigments and the one or more dispersing aids, and has a 50% cumulative volume particle diameter distribution D 5 o of 1 50 nm or less, as determined for the redispersed pigment particles by laser light scattering.

[0035]

2. A solid pigment dispersion according to 1 described above, wherein the 90% cumulative volume particle diameter distribution D90 is 300 nm or less, as determined for the redispersed pigment particles by laser light scattering.

[0036]

3. A solid pigment dispersion according to 1 described above, wherein the 90% cumulative volume particle diameter distribution Dgo is 200 nm or less, as determined for the redispersed pigment particles by laser light scattering.

[0037] 4. A solid pigment dispersion according to any one of 1 to 3 described above, wherein the 50% cumulative volume particle diameter distribution D 5 o is 1 00 nm or less, as determined for the redispersed pigment particles by laser light scattering.

[0038]

5. A solid pigment dispersion according to any one of 1 to 4 described above, wherein the one or more dispersing aids comprise two or more dispersing aids.

[0039]

6. A solid pigment dispersion according to any one of 1 to 5 described above, wherein the dispersion is redispersible with an aqueous dispersion medium and comprises a dispersing aid having a molecular weight of 1 0000 g/mol or less.

[0040]

7. A solid pigment dispersion according to 6 described above, wherein the dispersing aid having a molecular weight of 1 0000g/mol or less comprises one or more dispersing aids selected from the group consisting of a wax, a macromolecule and a glycol .

[0041 ]

8. A solid pigment dispersion according to 6 described above, wherein the dispersing aid having a molecular weight of 1 0000 g/mol or less comprises two or more dispersing aids selected from the group consisting of a wax, a macromolecule and a glycol .

[0042]

9. A solid pigment dispersion according to 7 or 8 described above, wherein the dispersing aid having a molecular weight of 1 0000g/mol or less comprises a combination of a wax and/or a glycol with a macromolecule in a weight ratio of 90: 1 0 to 40:60.

[0043]

10. The solid pigment dispersion according to any one of 7 to 9 described above, wherein the wax comprises a wax or a glycol having a melting point of 30 to 150°C.

[0044]

1 1 . A solid pigment dispersion according to 10 described above, wherein the wax having a melting point of 30 to 1 50°C comprises a water- soluble wax.

[0045]

12. A solid pigment dispersion according to 1 1 described above, wherein the water-soluble wax comprises a montan acid derivative wax.

[0046]

13. A solid pigment dispersion according to any one of 7 to 12 described above, wherein the macromolecule comprises a polyester.

[0047]

14. A solid pigment dispersion according to 13 described above, wherein the polyester comprises a water-soluble polyester having a softening point or melting point of 50 to 200°C.

[0048]

15. A solid pigment dispersion according to 14 described above, wherein the water-soluble polyester has a 5-sulfoisophthalic acid group.

[0049]

16. A solid pigment dispersion according to any one of 1 to 1 5 described above, wherein the dispersion is redispersible with an aqueous dispersion medium and the amount of the residual liquid dispersion medium is 5% by weight or less based on the entire dispersion .

[0050]

17. A solid pigment dispersion according to any one of 1 to 5 described above, wherein the dispersion is redispersible with an organic dispersion medium and the one or more dispersing aids are selected from the group consisting of polyvinyl resins.

[0051 ]

18. A solid pigment dispersion according to 17 described above, wherein the polyvinyl resin is a polyvinylbutyral resin having a degree of acetalization of 60% or more and/or a vinyl chloride-vinyl acetate copolymer having a vinylacetate content of at least 1 % by weight and at most 30% by weight.

[0052]

19. A solid pigment dispersion according to 17 or 18 described above, wherein the polyvinyl resin has a melting point of 30 to 1 50°C.

[0053]

20. A solid pigment dispersion according to any one of 1 7 to 19 described above, wherein the dispersion contains a further dispersing aid selected from the group consisting of urethane resins, polyethyleneimine resins, amino acid derivative resins, and (meth)acrylic resins in an amount of more than 0% by weight to 40% by weight relative to the mixture of the one or more pigments and the one or more of dispersing aids.

[0054]

21 . A solid pigment dispersion according to 20 described above, wherein the sum (mg KOH/g) of the acid number and amine number of the resin is at least 10 and at most 1 50. [0055]

22. A solid pigment dispersion according to any one of 1 to 5 and 1 7 to 21 described above, wherein the dispersion is redispersible with an organic dispersion medium and the amount of the residual liquid dispersion medium is 1 0% by weight or less based on the entire dispersion.

[0056]

23. A solid pigment dispersion according to any one of 1 to 22 described above, as an intermediate product for preparing inkjet inks, toners or developers for printers, pigment compositions for color filters, or pigments compositions for writing materials.

[0057]

24. A process for preparing a solid pigment dispersion redispersible with an aqueous dispersion medium, according to any one of 1 to 1 6 and 23 described above, using a continuous automatic apparatus capable of continuously carrying out, at least, the following steps (1 )-(4) in the same single apparatus:

(1 ) a step of introducing the one or more pigments and one or more solid dispersing aids (A) in a dispersing unit;

(2) a step of mixing one or more aqueous liquid dispersion media comprising one or more wetting dispersing aids (B) with the one or more pigments;

(3) a step of applying a shearing force to the mixture comprising the one or more pigments, the one or more dispersing aids (A+B) and the one or more liquid dispersion media to knead the mixture; and

(4) a step of drying the mixture by removing the one or more dispersion media.

[0058] 25. A process according to 24 described above, wherein, in step (2), relative to the total amount of 1 00 parts by weight of the one or more pigments and the one or more solid dispersing aids (A), 5 to 1 50 parts by weight of the one or more aqueous liquid dispersion media comprising 0.05% by weight or more of the one or more wetting dispersing aids (B) are supplied, and the pigments and the dispersion media are mixed.

[0059]

26. A process according to 24 or 25 described above, wherein the one or more aqueous liquid dispersion media consist of water or contain water and a water-miscible organic medium in a weight ratio of 90: 10 to 1 0:90.

[0060]

27. A process for preparing a solid pigment dispersion redispersible with an organic dispersion medium, according to any one of 1 to 5 and 1 7 to 23 described above, using a continuous automatic apparatus capable of continuously carrying out, at least, the following steps (1 ') - (4') in the same single apparatus:

(1 ') a step of introducing the one or more pigments, along with or without one or more dispersing aids (Α'), in a dispersing unit;

(2') a step of mixing one or more organic liquid dispersion medium comprising or not comprising one or more dispersion media (Α') and/or (Β') with the one or more pigments;

(3') a step of applying a shearing force to the mixture comprising the one or more pigments, the one or more dispersing aids (A' or A'+B') and the one or more liquid dispersion media to knead the mixture; and

(4') a step of drying the mixture by removing the one or more liquid dispersion media, wherein the dispersing aids (Α') are used in at least one of steps (1 ') and (2'), and the one or more dispersing aids (Β') are selected from the group consisting of urethane-based resins, polyethyleneimine resins, amino acid derivative resins and (meth)acrylic resins.

[0061 ]

28. A process according to 27 described above, wherein, in step (2'), relative to the amount of 1 00 parts by weight of the one or more pigments or to the total amount of 1 00 parts by weight of the one or more pigments and the one or more solid dispersing aids (Α'), 5 to 1 50 parts by weight of the one or more organic liquid dispersion media, or 5 to 1 50 parts by weight of the one or more organic liquid dispersion media comprising 5% by weight or more of the one or more dispersing aids (Β'), are supplied, and the pigments and the dispersion media are mixed.

[0062]

29. A process according to 27 or 28 described above, wherein the organic liquid dispersion media contain an alkyleneglycol ether.

[0063]

30. A process according to 27 or 28 described above, wherein the organic liquid dispersion media contain an alkyleneglycol ether and another organic medium.

[0064]

31 . A process according to 29 or 30 described above, wherein the alkyleneglycol ether is one or more selected from the group consisting of diethyleneglycol dimethylether, diethyleneglycol diethylether,

diethyleneglycol dibutylether, dipropyleneglycol dimethylether,

dipropyleneglycol diethylether, and dipropyleneglycol dibutylether.

[0065] 32. A process according to any one of 24 to 31 described above, wherein, in the continuous automatic apparatus, step (4) or (4') is followed by continuously carrying out the following further steps:

(5) or (5') a step of extruding the kneaded and dried pigments;

(6) or (6') a step of obtaining a solid pigment dispersion in the form of a shaped article.

[0066]

33. A process according to any one of 24 to 32 described above, wherein the continuous automatic apparatus is a continuous automatic kneader.

[0067]

34. A process according to any one of 24 to 32 described above, wherein the continuous automatic apparatus is a continuous automatic twin- screw extruder.

[0068]

35. A process according to any one of 24-34 described above, wherein the one or more pigments and the one or more dispersing aids (A) or (Α') are previously mixed, followed by the introduction of the mixture into the dispersing unit in the step (1 ).

[0069]

36. A process according to any one of 24 to 35 described above, wherein the proportion of the oversize particles having a particle size of more than 5 μηη in the redispersible solid pigment dispersion, which do not pass a filter having a pore side of 5 μηι, is 1 0% by weight or less of the total weight of the redispersible solid pigment dispersion, calculated based on the difference in the dry weight of the filter before and after the filtration .

[0070] 37. A process for preparing an inkjet ink, comprising redispersing a solid pigment dispersion obtained by a process according to any one of 24 to 36 described above in a dispersion medium. [Advantageous Effects of I nvention]

[0071 ]

According to the present invention, a formulation of a solid pigment dispersion adaptable for high quality image formation applications, for example, a solid pigment dispersion that has a median diameter D50 value of 1 50 nm or less, particularly 1 00 nm or less and can achieve excellent dispersion performance, and a process for preparing the same can be provided. The "solid", as used herein, means a substance having a softening or melting point higher than room temperature (23°C) and being in a solid form at room temperature, preferably a substance having a softening or melting point sufficiently higher than room temperature. Whether a substance is a solid or not is easily determined from the appearance of the substance at room temperature.

[0072]

The pigment composition obtained in the present invention is a solid material in which pigment surface is protected with a dispersing aid . For this reason, the pigment is unlikely to aggregate, and it is possible to obtain a high quality ink by introduction into an ink vehicle, simple

dispersion, and filtration.

[0073]

Additionally, since the pigment composition is a dry solid, the pigment does not precipitate even after transportation, storage, and the like. Thus, it is possible to provide a process for preparing a pigment dispersion that can easily be metered during ink production in the next step.

[0074]

Furthermore, since, according to the present invention, a continuous kneading apparatus such as an extruder is used, an economical pigment dispersion process can be provided, which can continuously disperse a pigment in a large scale, has less variations between batches, and is preferable also from the viewpoint of working environment safety.

[0075]

Furthermore, since automation by means of a machine is enabled according to the present invention, it is possible to provide a method of obtaining a pigment composition having smaller differences between individuals such as operators and smaller variations in the performance.

[0076]

The pigment dispersion is a solid material that contains no dispersion medium or a minimum amount of a dispersion medium, and contains a pigment and the minimum necessary types of additives. Thus, for the respective applications and required performance, additives suitable for the respective applications can be added in the next step to the pigment dispersion . Even a solid pigment dispersion dispersed for use in inkjet, for example, can be used as an ink for color filter production through

appropriate choice and addition of a binder, a medium and the like, and thus, it is possible to establish a highly-flexible production system that can prepare various products from the same intermediate products. The pigment dispersion can be also used for the preparation of, for example, toners for printers, pigment compositions for color filters, pigment compositions for writing tools such as ballpoint pens, paints, and printing inks, in addition to inkjet inks.

[0077]

Furthermore, since highly safe (re)dispersing solvents can be used, it is possible to provide a solvent-based colorant composition that having no environmental burdens and being harmless to human body.

[0078]

Other effects of the present invention will be apparent from the description below.

[Brief Description of Drawings]

[0079]

[Figure 1 ] Figure 1 is an exemplary conceptual diagram of an apparatus used in the present invention for preparing a solid pigment dispersion .

[Figure 2] Figure 2 shows a relation between the weight proportion of the pigment in the solid pigment dispersion and the D 5 o-

[Figure 3] Figure 3 shows a relation between the proportion of a dispersing aid B in the pigment dispersion and the particle diameters D50 and D90. [Figure 4] Figure 4 shows a relation between the amount of water injected as a dispersion medium and the pigment particle diameters D50 and D90.

[Description of Embodiments]

[0080]

I n the sense of the present invention, a solid pigment dispersion as an intermediate product redispersible by using an aqueous dispersion medium refers to a solid pigment dispersion designed for redispersion using water or a water-based dispersion medium . I n this case, the water-based dispersion medium is a medium consist of water and a water-miscible organic medium. The weight ratio between water and the organic medium can be 90: 1 0 to 1 0:90 in one embodiment, 20:80 to 80:20 in one

embodiment, 30:70 to 70:30 in one embodiment, 40:60 to 60:40 in one embodiment, for example, about 50:50 of water : organic medium.

Examples of such water-miscible organic media include acetylene derivatives, alcohols, glycol ethers, and ketones. It is possible to use media of the same type as liquid dispersion media listed below for use in the preparation of the solid pigment dispersion

[0081 ]

I n the sense of the present invention, a solid pigment dispersion as an intermediate product redispersible by using an organic dispersion medium refers to a solid pigment dispersion designed for redispersion using an organic medium. I n this case, the organic medium may consist only of an organic medium or may contain water in an amount of less than 10% by weight, less than 5% by weight in another embodiment, less than 1 % by weight in still further embodiment. Examples of such organic media include ketones, esters, alcohols, glycol ethers, UV monomers such as H DDA (1 ,6-hexanediol diacrylate), TPGDA (tripropylene glycol diacrylate), and I BOA-B (isobornyl acrylate), and mixed media thereof. Also in this case, it is possible to use organic media of the same type as organic dispersion media listed below for use in preparation of the solid pigment dispersion .

[0082]

" D50" as used in the present invention, with respect to particles in a powder or a dispersion liquid, refers to a diameter at which the cumulative proportion of the particles reaches 50% by volume, determined by laser light scattering. " D90" refers to a diameter at which the cumulative proportion of the particles reaches 90% by volume, determined in the same manner.

[0083]

The solid pigment dispersion of the present invention is a solid pigment dispersion as an intermediate product containing 20 to 80% by weight of a pigment, 30 to 80% by weight of the pigment in another embodiment, 35 to 70% by weight of the pigment in a yet further

embodiment, and 20 to 80% by weight of a dispersing aid, 20 to 70% by weight of the dispersing aid in another embodiment, 30 to 65% by weight of the dispersing aid in a yet further embodiment, based on the total weight of the pigment and the dispersing aid .

[0084]

The solid pigment dispersion of the present invention contains a pigment(s) as an essential component(s). As the pigments, any of organic pigments, carbon black pigments, and inorganic pigments composed of metal compounds etc. can be used . However, since the specific gravity of these pigments is generally larger than that of water, a dispersing aid is essential in order to prevent pigment precipitation . As the pigments, organic pigments are preferable because such pigments have a high chroma, can be easily finely divided, and have a small difference in the specific gravity compared to the dispersion medium . Carbon black pigments can also be used for black coloring.

[0085]

As the organic pigment, a pigment suitable for the intended application is used. For example, in the case of inkjet image formation on plain paper, yellow, magenta, and cyan coloring pigments, which are the three primary colors of the subtractive color mixture method, can be used . For additive color mixture such as color filters, red, green, and blue pigments are used . I n addition to these primary colors, characteristic color pigments such as orange may be used as appropriate, in order to enhance the image gradation .

[0086]

Examples of organic pigments that can be used in the applications described above include azo pigments, lake pigments, thioindigo pigments, anthraquinone pigments (e.g., anthanthrone pigments,

diaminoanthraquinonyl pigments, indanthrone pigments, flavanthrone pigments, and anthrapyrimidine pigments), perylene pigments, perinone pigments, diketo-pyrrolo-pyrrole pigments, dioxazine pigments,

phthalocyanine pigments, quinophthalone pigments, quinacridone pigments, isoindoline pigments, and isoindolinone pigments, and among these, pigments having a red, blue, or yellow hue may be selected as appropriate.

[0087]

I n the present invention, the black pigment includes carbon black, and examples thereof include, but are not particularly limited to, furnace black, lamp black, acetylene black, and channel black (C. I . Pigment Black 7). Examples of commercially available carbon black products include

No.2300, 900, MCF88, No. 20B, No.33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B (all trade names, manufactured by Mitsubishi Chemical Corporation), COLOU R BLACK FW1 , FW2, FW2V, FW18, FW200, S 1 50, S1 60, S 1 70, PRI NTEX 35, U, V, 140U , N I Pex 150, SPECIAL BLACK 6, 5, 4A, 4, 250 (all trade names, manufactured by Orion Engineered Carbons), Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, and 700 (all trade names, manufactured by Columbian Carbon Japan Ltd ., and Columbian Chemicals), and REGAL 400R, 330R, 660R, MOGUL L,

MONARCH 700, 800, 880, 900, 1000, 1100, 1300, 1400, and ELFTEX 12 (all trade names, manufactured by Cabot Corporation).

[0088]

Examples of water-soluble dyes include C.I. Acid Black 1, 2, 24, and 94; C.I. Food Black 1 and 2; C.I. Direct Black 19, 38, 51, 71, 154, 168, 171, and 195; and C.I. Reactive Black 3, 4, and 35. Among these, one or combinations of two or more may be used.

[0089]

Examples of pigments used as a cyan or blue pigment in the present invention include phthalocyanine pigments such as C.I. Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Blue 15:5, Pigment Blue 15:6, and Pigment Blue 16; Pigment Blue 56, Pigment Blue 60 or 61, and Pigment Blue 80. Among these, one or combinations of two or more may be used.

[0090]

A red or magenta pigment used in the present invention is suitably selected from monoazo, disazo, β-naphthol, naphthol AS, azo lake, metal complex, benzimidazolone, anthanthrone, anthraquinone, quinacridone, dioxazine, perylene, thioindigo, triaryl carbonium, or diketo-pyrrolo-pyrrole pigments. Specific examples thereof include particularly C.I. Pigment Red 2, Pigment Red 3, Pigment Red 4, Pigment Red 5, Pigment Red 9, Pigment Red 12, Pigment Red 14, Pigment Red 31, Pigment Red 32, Pigment Red 38, Pigment Red 48:2, Pigment Red 48:3, Pigment Red 48:4, Pigment Red 53:1, Pigment Red 57:1, Pigment Red 112, Pigment Red 122, Pigment Red 144, Pigment Red 146, Pigment Red 147, Pigment Red 149, Pigment Red 150, Pigment Red 168, Pigment Red 169, Pigment Red 170, Pigment Red 175, Pigment Red 176, Pigment Red 177, Pigment Red 179, Pigment Red 181, Pigment Red 184, Pigment Red 185, Pigment Red 186, Pigment Red 187, Pigment Red 188, Pigment Red 202, Pigment Red 207, Pigment Red 208, Pigment Red 209, Pigment Red 210, Pigment Red 214, Pigment Red 238, Pigment Red 242, Pigment Red 247, Pigment Red 253, Pigment Red 254, Pigment Red 256, Pigment Red 257, Pigment Red 262, Pigment Red 263, Pigment Red 266, Pigment Red 269, Pigment Red 274, Pigment Red 293, and Pigment Violet 19. Among these, one or combinations of two or more may be used.

[0091]

In order to improve the shading, chroma and strength, dyes may be added. As a water-soluble dye, any dye appropriately selected from C.I. Direct Red 4, 17, 28, 37, 63, 75, 79, 80, 81, 83, and 254; C.I. Acid Red 1, 6, 8, 18, 32, 35, 37, 42, 52, 85, 88, 115, 133, 134, 154, 186, 249, 289, and 407; C.I. Basic Red 9, 12, and 13; C.I. Reactive Red 4, 23, 24, 31, and 56 and the like may be used. As an oil-soluble dye, any dye selected from C.I. Solvent Red 8, 24, 49, 52, 89, 91, 92, 111, 122, 124, 125, 127, 130, 135, 149, 179, 195, 214, 225, 233, Solvent Violet 13, 26, 31, 36, 46, 49, 59, 60, Vat Red 41 and the like may be used. Preferable are Solvent Red 52, Solvent Red 195, Solvent Violet 59, and Vat Red 41.

[0092]

A yellow pigment used in the present invention can be selected from, for example, monoazo, disazo, benzimidazoline, isoindolinone, isoindoline, and perinone pigments. Specific examples thereof include C.I. Pigment Yellow 1, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 81, Pigment Yellow 83, Pigment Yellow 87, Pigment Yellow 97, Pigment Yellow 111, Pigment Yellow 120, Pigment Yellow 126, Pigment Yellow 127, Pigment Yellow 128, Pigment Yellow 139, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 155, Pigment Yellow 173, Pigment Yellow 174, Pigment Yellow 175, Pigment Yellow 176, Pigment Yellow 180, Pigment Yellow 181, Pigment Yellow 185, Pigment Yellow 191, Pigment Yellow 192, Pigment Yellow 194, Pigment Yellow 196 or Pigment Yellow 213, Pigment Yellow 214, and Pigment Yellow 217. Among these, one or combinations of two or more may be used.

[0093]

In order to improve the shading, chroma and strength, dyes may be added. Such a dye can be suitably selected from oil-soluble dyes such as C.I. Solvent Yellow 33, C.I. Solvent Yellow 43, C.I. Solvent Yellow 104, C.I. Solvent Yellow 116, C.I. Solvent Yellow 135, C.I. Solvent Yellow 160, and C.I. Solvent Yellow 179, disperse dyes such as C.I. Direct Yellow 81, and water-soluble dyes such as C.I. Basic Yellow 40. Among these, C.I. Solvent Yellow 33, C.I. Solvent Yellow 135, C.I. Solvent Yellow 160:1, C.I. Solvent Yellow 179 and the like are particularly suitably used.

[0094]

As pigments for three primary colors of the subtractive color mixture, according to the present invention, at least one pigment for each color is preferably selected from magenta pigments Pigment Red 31, 32, 122, 146, 147, 150, 185, 186, 202, 238, and 269 and Pigment Violet 19, cyan pigments Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:5, and 15:6, and yellow pigments Pigment Yellow 74, 120, 151, 154, 155, 180, 185, 192,

213, and 214. More preferably, selecting at least one for each color from Pigment Red 122, 202 and Pigment Violet 19; Pigment Blue 15:3 and 15:4; and Pigment Yellow 74, 155, and 1 85, or combining two or more of these, is particularly preferable from the viewpoint from the hue, chroma and light fastness.

[0095]

As a green pigment for additive color mixture, green pigments such as Pigment Green 7 and Pigment Green 36 can also be used .

[0096]

Besides the aforementioned three primary color pigments, the pigments of the present invention may include pigments suitably used as characteristic colors. For example, as a violet pigment, C. I . Pigment Violet 19 and Pigment Violet 23 or Pigment Violet 32, Pigment Blue 60, and Pigment Blue 80 may be particularly used . Particular examples of orange pigments include C. I . Pigment Orange 5, Pigment Orange 1 3, Pigment Orange 34, Pigment Orange 36, Pigment Orange 38, Pigment Orange 43, Pigment Orange 62, Pigment Orange 68, Pigment Orange 70, Pigment Orange 72, or Pigment Orange 74. One of or two or more of these in combination may be suitably used .

[0097]

As a second material constituting the solid pigment dispersion of the present invention, a dispersing aid is included as an essential component, in addition to the pigments described above. This is because the pigment dispersing step includes three steps of (i) adsorption of a wetting dispersing aid and the like on the pigment surface, (ii) mechanical grinding in a dispersion medium, and (iii) dispersion stabilization, and the pigment dispersing aid plays an important role in any of the steps.

Pigment dispersing aids include wetting dispersing aids which can be adsorbed mainly onto the surface of pigments (many pigments have hydrophobic surface) to enhance the affinity between the dispersion medium such as water and the pigment and stabilize the dispersion;

dispersing aids which can prevent aggregation by means of a steric repulsion effect of long molecular chains (macromolecular dispersing aids); and inorganic dispersing aids which can be adsorbed onto pigment particles and can prevent aggregation by means of electrostatic repulsion based on their chargeability. I n the preparation process of the present invention, it is necessary to introduce a dispersing aid having at least one of these functions before, simultaneously with, or after the introduction of the pigment into the pigment dispersing/shaping unit.

[0098]

With respect to the chemical structure of wetting dispersing aids that can be used in the present invention, dispersing aids each having a common structure of surfactants, in other words, hydrophilic and lipophilic groups, in the molecule can be used . Such surfactants are mainly classified into anionic surfactants, cationic surfactants, nonionic

surfactants, zwitterionic surfactants and the like, any of which can be used .

[0099]

When an aqueous medium is used as a dispersion medium for dispersing the pigment, a dispersing aid suited for aqueous systems is preferably used . I n the case of dispersion in an organic medium, a nonaqueous dispersing aid is preferably used .

[01 00]

First, dispersing aids used when such an aqueous medium is employed will be described below.

[01 01 ] Any of anionic surfactants such as sodium alkyl sulfonates, cationic surfactants such as quaternary ammonium compounds and polyalkylamine group-containing compounds, and nonionic surfactants such as higher alcoholic alkylene oxide compounds and polyhydric alcoholic ester compounds, for example, can be used as an aqueous dispersing aid .

[01 02]

Other appropriate examples of the anionic surfactants that can be used include sulfates and sulfonates, sodium dodecyl sulfate (SDS), sodium dodecyl benzenesulfonate, sodium dodecyl naphthalene sulfate, and dialkylbenzene alkyl sulfates and sulfonates.

[01 03]

Examples of the nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, acetylene alcohols, acetylene glycols, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene octyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether, and dialkylphenoxy

poly(ethyleneoxy)ethanol.

[01 04]

I n the present invention, particularly preferable are acetylene alcohols and acetylene glycols, for example, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4,7- diol, and alkylene oxide adducts of 2,4-dimethyl-5-decyn-4-ol and 2,4- dimethyl-5-decyn-4-ol. Commercially available products thereof include OLFI N E E 1 01 0 and SU RFYNOL 61 (Nissin Chemical Co., Ltd .).

[01 05] Examples of the cationic surfactants suitable for the present invention include alkylbenzyldimethylammonium chloride,

dialkylbenzenealkylammonium chloride, lauryltrimethylammonium chloride, alkylbenzenemethylammonium chloride, alkylbenzyldimethylammonium bromide, benzalkonium chloride, cetylpyridinium bromide, C 12, C 15, and C1 7 trimethylammonium bromides, halogen salts of quaternarized polyoxyethyl alkylamine, and dodecylbenzyltriethylammonium chloride.

[01 06]

As the wetting dispersing aid of the present invention, primary, secondary, and tertiary amine salt compounds, for example, hydrochlorides and acetates of lauryl amine, coconut amine, stearyl amine, and rosin amine can also be used . Ionic compounds, for example, pyridinium salt compounds such as cetylpyridinium chloride and cetylpyridinium bromide can also be used .

[01 07]

Examples of the macromolecular surfactants in the present invention include anionic, cationic, and nonionic surfactants as in the case of low molecular surfactants. Examples of the anionic surfactants include polycarboxylic acid surfactants and naphthalene sulfonic acid-formalin condensation polymer surfactants. Examples of the nonionic surfactants include polyalkylene glycol surfactants and polyether surfactants, and examples of the cationic surfactants include polyalkylene polyamine polymers. At least one or more surfactants selected from each type can be used .

[01 08]

I n the present invention, as a dispersing aid to be mixed with the pigment in advance before dispersion (hereinafter, referred to as dispersing aid A), any of wetting dispersing aids, macromolecular dispersing aids, and inorganic dispersing aids can be used . The dispersing aid A is preferably mixed in a dried state with the pigment and conveyed in the unit. For this purpose, the dispersing aid (A) is solid, and is more preferably a dispersing aid, such as a waxy compound and a macromolecular compound, having a molecular weight (weight average molecular weight, if applicable) of generally 1 0000 g/mol or less, particularly 8000 g/mol or less and more than 800 g/mol, particularly 900 g/mol or more.

[01 09]

Alternatively, a dispersing aid, which is injected along with water as a dispersion medium (hereinafter, referred to as dispersing aid B), is not necessarily solid for exerting its effect. Any of liquid and solid dispersing aids can be used provided that the dispersing aid improves the affinity between water and the pigment. Particularly preferable are wetting active agents having high penetrability, and, among these, low molecular weight compounds are preferable.

[01 1 0]

Particularly preferable examples of the dispersing aid (A) used in the preparation process according to the present invention include polyalkylene glycols and waxes. Polyalkylene glycols preferably have a weight average molecular weight of 800 to 1 0000 g/mol, and particularly, polyethylene glycols having a weight average molecular weight of 1 000 g/mol (melting point: 30 to 40°C) to 8000 g/mol (melting point: 55 to 63°C) are preferable. Waxes are, in a narrow sense, oily and fatty substances comprising a higher fatty acid and a monovalent or divalent higher alcohol (wax ester), and practically include, in a broad sense, neutral fats, higher fatty acids, and hydrocarbons that show properties similar to those of said substance. I n many cases, waxes, which are soft and smooth solid at room temperature, has an amphipathic nature because of a long-chain hydrocarbon group as a hydrophobic group and a hydrophilic ester structure in the molecule. Particularly, when a water-soluble wax is used, the wax can be adsorbed onto and stabilize the pigment without raising the viscosity of water as a dispersion medium.

[01 1 1 ]

Waxes have a lubricant function in the solid state. Thus, when a wax is contained in the solid pigment dispersion of the present invention, the pigment particles are unlikely to aggregate and agglomerate during storage. From this viewpoint, waxes are preferable.

[01 12]

Many waxes have a specific gravity of 1 or less, which is smaller than that of pigments. For example, when a pigment is dispersed in water, such a wax has also an effect of preventing precipitation and aggregation by the buoyancy of the wax covering the pigment surface. Waxes are also preferable because waxes are present on the pigment surface after image formation and protect the pigment by their lubricant action, resulting in an improvement in the image intensity.

[01 1 3]

Examples of the waxes that can be used according to the present invention include natural waxes such as carnauba wax, candelilla wax, rice wax, and Japan wax, modified natural waxes, semi-synthetic waxes, fully- synthetic waxes, amide waxes, synthetic polyolefins such as polyethylene and polypropylene, chlorinated or fluorinated polyolefin waxes,

thermoplastic polyester resins, epoxy resins, styrene-acrylate copolymer resins, styrene-butadiene copolymer resins, and cycloolefin copolymer resins. With respect to the melting point of the waxes, waxes that melt on kneading of the pigment are preferable. For transporting or storing the solid pigment dispersion or for using the dispersion in a final product, such as an inkjet image, the wax preferably has a high melting point. For this reason, the melting point of the wax is 30 to 150°C, preferably 35 to 120°C, more preferably 40 to 1 1 0°C, still more preferably 45 to 1 00°C, particularly preferably 50 to 80°C.

[01 14]

Although any of the waxes described above can be used in the present invention, particular preference is given to esters of higher fatty acids and monovalent or divalent higher alcohols, which are oily substances (wax esters) and correspond to the narrow definition of waxes. Among these, water-soluble waxes are suitably used in aqueous dispersions for inkjet and the like. Among water-soluble waxes, montanic ester waxes, for example, Licowax® KST manufactured by Clariant (a polyhydric alcohol ester of montanic acid, melting point (DSC): 56°C, dropping point: 56 to 63°C), are particularly preferable.

[01 1 5]

Other particularly preferable examples of the dispersing aid (A) used in the loading stage in the preparation process of the present invention include amphipathic polymers, and among these, preferable are polyester polymers having an anionic group and an alcohol ester group in the molecule. As such compounds, polymers as described in, for example, Japanese Patent No. 5553509B and among these, polymers having a weight average molecular weight of 1 0000 g/mol or less are preferable.

Such polymers can contain a polyester comprising structural units 1 to 3 or 1 to 4 below: [01 1 6]

[Formula 1 ]

(3)

in which, R 1 s each independently represent H or represent a (C i to C i s)n- or iso-alkyl group, preferably a methyl,

R 2 represents a linear or branched (Ci to C3o)alkyl group or represents a linear or branched (C2 to C3o)alkenyl group, cycloalkyi group having 5 to 9 carbon atoms, (C6 to C3o)aryl group, or (C6 to Cso)arylalkyl group, m, n, and o each independently represent a number of 1 to 200,

x, y, and z each independently represent a number of 1 to 50, provided that x + y > 2, and z has to be more than 0,

u represents a number of 0 to 5, preferably 0 to 0.5, particularly preferably a number of 0 to 0.25, and

Me represents Li + , Na + , K + , Mg ++ /2, Ca ++ /2, AI +++ /3, N H 4 + , a monoalkyl ammonium ion, dialkyl ammonium ion, trialkyl ammonium ion and/or tetraalkyl ammonium ion, where the alkyl substituents of the ammonium ions are each independently, a (Ci to C22)alkyl group or (C2 to

Cio)hydroxyalkyl group.

Particular preference is given to polyesters obtained by

polycondesating a terephthalic dialkyl ester, a 5-sulfoisophthalic dialkyl ester or a salt of 5-sulfoisophthalic acid, ethylene glycol, propylene glycol, and a polyaklylene glycol monoalkyl ether; or polyesters obtained by polycondensating a terephthalic dialkyl ester, a 5-sulfoisophthalic dialkyl ester or a salt of 5-sulfoisophthalic acid, ethylene glycol, propylene glycol, a polyaklylene glycol monoalkyl ether and even another polycondensatable monomers having 3 to 6 functional groups.

[01 1 7]

As specific compounds, for example, surfactants as sold by

Clariant under trade names TexCare® SRN240, 300, and SRA300F are suitably used .

[01 1 8]

I n one advantageous aspect, as the dispersing aid (A), a wax dispersing aid and/or a glycol is used in combination with a polyester dispersing aid . The weight ratio of wax ester dispersing aid and/or glycol : polyester dispersing aid in this case is preferably 90: 1 0 to 40:60, more preferably 85:15 to 50:50, particularly 80:20 to 60:40, above all, 80:20 to

70:30.

[0119]

In the preparation process of the present invention, as the dispersing aid (B) to be used as a mixture with a dispersion medium such as water, the various dispersing aids mentioned above are suitably used. Among these, low molecular-weight surfactants, and among these, acetylene glycol-based surfactants, have high wetting properties, and thus are preferable. Examples thereof include SURFYNOL 104E, SURFYNOL 104H, SURFYNOL 104A, SURFYNOL 104BC, SURFYNOL 104DPM, SURFYNOL 104PA, SURFYNOL 104PG-50, SURFYNOL 420, and

SURFYNOL 440 manufactured by Air Products and Chemicals, Inc., and OLFINE E1004, OLFINE E1010, OLFINE E1020, OLFINE PD-001, OLFINE PD-002W, OLFINE PD-004, OLFINE PD-005, OLFINE EXP.4001, OLFINE EXP.4200, OLFINE EXP.4123, and OLFINE EXP.4300 manufactured by Nissin Chemical Co., Ltd. One of these may be used singly, or two or more of these may be used in combination. Among these, OLFINE® E1010 and SURFYNOL® 465 are suitably used.

[0120]

In addition to the acetylene diol-based surfactants, surfactants known as silicone-based surfactants and other surfactants also can be used. Silicone-based surfactants are compounds having a polysiloxane skeleton, and specific examples of the silicone-based surfactants include BYK-347, BYK-377, and BYK-3455 manufactured by BYK Japan KK. One of these may be used singly, or two or more of these may be used in combination.

[0121] As mentioned above, according to the present invention, it is also possible to disperse a pigment in an organic medium. I n this case, one or more solid dispersing aids selected from polyvinyl resins are used .

[0122]

Examples of polyvinyl resins include, for example, polyvinylbutyral resins and vinyl chloride-vinyl acetate copolymers. As the polyvinylbutyral resin, a polyvinylbutyral resin having a degree of acetalization of preferably 60% or more, particularly preferably 65% or more is used . Preferable vinyl chloride-vinyl acetate copolymers are those having a vinyl acetate content of 1 % by weight or more, preferably 5% by weight or more and 30% by weight or less, preferably 20% by weight or less.

[0123]

Examples of commercially available products of such dispersing aids include Vinnol® E grade such as Vinnol® E 1 8/38 and 1 5/45 (Wacker Chemie AG), SOLBI N CN, CN L, and C5R (N issin Chemical Co., Ltd .), and S-LEC BL grade such as S-LEC BL-1 , BL-1 0, BL-S, and BM-1 (SEKISU I CH EMI CAL CO., LTD.).

[0124]

Additionally, in this case, the solid pigment dispersion may further contain still another dispersing aid, preferably selected from polyethylene imine resins, (meta)acrylic resins, urethane resins, and amino acid derivative resins. Such even another aid may be contained in an amount of more than 0% by weight to 40% by weight, preferably 2 to 30% by weight, more preferably 4 to 27% by weight, relative to a mixture of at least one pigment and at least one dispersing aid selected from polyvinyl resins.

[0125] As these polyethylene imine resins, (meta)acrylic resins, urethane resins, polyamino acid derivative resins, preferable are those having a total of the acid number and the amine number (mgKOH/g) of 1 0 or more, particularly preferably 1 5 or more, particularly preferably 20 or more, particularly 25 or more, and 1 50 or less, preferably 130 or less, particularly preferably 1 00 or less, particularly 80 or less. It should be noted that the acid number and the amine number can be measured in accordance with J IS K0070 and J IS K7237, respectively.

[0126]

I n the range of the total of acid number and amine number thus defined, the pigment well interacts with the dispersing aid to achieve a high dispersibility.

[0127]

Commercially available examples of such urethane resins, polyethylene imine resins, amino acid derivative resins, and (meta)acrylic resins include Solsperse® grade such as Solsperse® 31000, 32000, 39000, 54000, 71 000, and 74500 (Lubrizol Corporation), BYKJ ET grade such as BYKJ ET® 91 50, 91 51 , and 91 52 (BYK Chemie GmbH), Efka grade such as Efka® 4046, 4047, 4080, and 7701 (BASF SE), and AJ ISPER PB® grade such as AJ ISPER® PB821 , 822, and 824.

[0128]

The weight average molecular weight of the dispersing aid described above is generally 5000 to 200000 g/mol, preferably 1 0000 to 100000 g/mol, particularly preferably 1 0000 to 50000 g/mol . Also in this case, dispersing aids that melt on the kneading of the pigment are preferable. During the transportation and storage of the solid pigment dispersion or when used in final products such as an inkjet image, a higher melting point is preferable. Thus, the melting point of dispersing aid used is 30 to 1 50°C, preferably 35 to 120°C, more preferably 40 to 1 1 0°C, still more preferably 45 to 100°C, particularly preferably 50 to 80°C.

[0129]

The solid pigment dispersion of the present invention contains a pigment and a dispersing aid as its essential components. I n one embodiment, the solid pigment dispersion of the present invention consists of a pigment and a dispersing aid, except for a residual dispersion medium . However, depending on the applications for which the solid pigment dispersion is used, various additives, such as vehicle polymers, a curing agent such as a photopolymerization initiator, a moisturizing agent, a dissolving aid, a penetration regulator, a viscosity modifier, a pH adjusting agent, a dissolving aid, an antioxidant, a preservative, an anti-mold agent, a corrosion inhibitor, a chelate to capture metal ions that affect dispersion may be added in addition to the pigment and the dispersing aid .

[01 30]

The present invention also relates to a process for preparing the solid pigment dispersion described above. I n systems using an aqueous dispersion medium for redispersion, the process as a first embodiment uses a continuous automatic apparatus capable of continuously carrying out, at least, the following steps (1 )-(4) in the same single apparatus:

(1 ) a step of introducing one or more pigments and one or more dispersing aids (A) in a dispersing unit;

(2) a step of mixing one or more aqueous liquid dispersion media

comprising one or more wetting dispersing aids (B) with the one or more pigments; (3) a step of applying a shearing force to the mixture comprising the one or more pigments, the one or more dispersing aids (A + B) and the one or more liquid dispersion media to knead the mixture; and

(4) a step of drying the mixture by removing the one or more liquid

dispersion media.

[01 31 ]

Meanwhile, in systems using an organic dispersion medium for redispersion, the process as a second embodiment comprises:

(1 ') a step of introducing one or more pigments, along with or without a dispersing aid (Α') in a dispersing unit;

(2') a step of mixing one or more organic liquid dispersion media comprising or not comprising one or more dispersing aids (Α') and/or (Β') with the one or more pigments;

(3') a step of applying a shearing force to the mixture comprising the one or more pigments, the one or more dispersing aids (A' or A'+ B') and the one or more liquid dispersion media to knead the mixture; and

(4') a step of drying the mixture by removing the one or more liquid

dispersion media,

wherein the dispersing aid (Α') is used in at least one of the steps (1 ') and (2').

[01 32]

Here, the dispersing aid (Α') is selected from the group consisting of polyvinyl resins, and the dispersing aid B' is selected from urethane resins, polyethylene imine, amino acid derivative resins, and (meta)acrylic resins.

[01 33] An essential material for preparing the solid pigment dispersion of the present invention is a liquid dispersion medium. The liquid dispersion medium is not necessarily required for end uses of the solid pigment dispersion of the present invention, but such a medium may contribute to the prevention of aggregation by stabilizing finely divided pigment particles by its solvation effect and the like when the pigment is dispersed.

Examples of such a liquid dispersion medium include, in the case of an aqueous dispersion medium, in addition to water, organic media including alcohols, various esters, and ketones, such as methanol, ethanol, isopropanol, glycols such as ethylene glycol, ethyl acetate, ethyl lactate, acetone, and butanone. From the viewpoint of environmental safety and the like, water or a mixed medium of water and an organic medium such as alcohol is preferable. When a mixed medium of water and an organic medium is used, the weight ratio between water and the organic medium can be 90: 1 0 to 1 0:90 in one embodiment, 20:80 to 80:20 in one

embodiment, 30:70 to 70:30 in one embodiment, 40:60 to 60:40 in one embodiment, for example, about 50:50 of water : organic medium.

[01 34]

I n systems using an organic dispersion medium for redispersion, as the liquid dispersion medium, organic media having light burdens and low risks on the environment and on human body, for example, alkylene glycol ethers, alcohols, and cyclic ethers can be used, and alkylene glycol ethers are preferable. Examples of the alkylene glycols include, for example, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and dipropylene glycol dibutyl ether.

Mixtures of two or more organic media can also be used, and for example, mixtures of an alkylene glycol ether with another organic medium, for example, an alcohol such as isopropanol and isobutanol, a divalent alcohol such as propanediol, hexanediol, a trivalent alcohol such as glycerin, a cyclic ether such as γ-butyrolactone, and a ketone such as acetone may be used . I n this case, the weight ratio between the alkylene glycol ether and the other organic medium can be, for example, 90: 10 to 1 0:90 in one embodiment, 20:80 to 80:20 in one embodiment, 30:70 to 70:30 in one embodiment, 40:60 to 60:40 in one embodiment, for example, about 50:50 of alkylene glycol ether : another organic medium . The organic dispersion medium may consist only of an organic medium or may contain water in an amount of less than 10% by weight, less than 5% by weight in one embodiment, less than 1 % by weight in one embodiment.

[01 35]

I n the process of the present invention according to the first embodiment described above, in step (2), relative to the total amount of 1 00 parts by weight of the pigment(s) and the solid dispersing aid(s) (A), the liquid dispersion medium (media) comprising, based on the active component, preferably 0.01 % by weight or more, 0.05% by weight or more in one embodiment, 0.1 % by weight or more in one embodiment, preferably 10% by weight or less, 5% by weight or less in one embodiment, 3% by weight or less in one embodiment, of the one or more wetting dispersing aids (B) is/are supplied in an amount of preferably 5 to 1 50 parts by weight, 8 to 120 parts by weight in one embodiment, 10 to 1 00 parts by weight in one embodiment, 30 to 60 parts by weight in one embodiment via a liquid injection port and the pigment(s) and the liquid dispersion medium (media) are mixed, in step (3), the mixture is kneaded, and then, in step (4), the mixture is dried, by means of a continuous automatic machine. When the pigment(s), dispersing aid(s), and liquid dispersion medium (media) are brought in the compositional range as above, the rheological nature of the mixture becomes dilatant, and a large shearing force caused by screw driving efficiently concentrates on the pigment particles, and as a result, fine division is made possible.

[01 36]

The process of the present invention according to the second embodiment described above also comprises (1 ') a step of introducing starting materials in a dispersing unit, (2') a step of mixing a liquid dispersion medium (media) with the pigment(s), (3') a step of kneading the mixture under the action of a shearing force, and (4') a step of drying the mixture. I n this case,

a first variant in which the dispersing aid(s) (Α') is/are added in step (1 '), and none of the dispersing aid(s) (Α') and (Β') is used in step (2'), - a second variant in which the dispersing aid(s) (Α') is/are added in both steps (1 ') and (2'), and no dispersing aid (Β') is used in step (2'), a third variant in which the dispersing aid(s) (Α') is/are added in step (1 '), and the dispersing aid(s) (Β') is/are only used in step (2'), a fourth variant in which the dispersing aid(s) (Α') is/are added in step (1 '), and both the dispersing aid(s) (Α') and dispersing aid(s) (Β') are used in step (2'),

a fifth variant in which no dispersing aid (Α') is added in step (1 '), and the dispersing aid(s) (Α') is/are only used in step (2'), and

a sixth variant in which no dispersing aid (Α') is added in step (1 '), and both the dispersing aid(s) (Α') and dispersing aid(s) (Β') are used in step (2'), are possible. Variants employing both (Α') and (Β'), with which smaller pigment particle diameter is easily obtained, may be preferable.

[01 37]

I n step (2'), relative to the amount of 1 00 parts by weight of the pigment(s) or to the total amount of 1 00 parts by weight of the pigment(s) and the solid dispersing aid(s) (Α'), the organic liquid dispersion medium (media) is/are supplied in an amount of 5 to 1 50 parts by weight in one embodiment, 8 to 120 parts by weight in one embodiment, 1 0 to 100 parts by weight in one embodiment, 30 to 60 parts by weight in one embodiment via a liquid injection port and the pigment(s) and the liquid dispersion medium (media) are mixed, in step (3), the mixture is kneaded, and then, in step (4), the mixture is dried, by means of a continuous automatic machine. I n this case, the organic liquid dispersion medium (media) may comprise (Β') in an amount of preferably 5% by weight or more, 1 0% by weight or more in one embodiment, 20% by weight or more in one embodiment and preferably 60% by weight or less, 55% by weight or less in one

embodiment, 50% by weight or less in one embodiment, relative to the weight of the organic liquid dispersion medium (media). The dispersing aid(s) (Α') may be used only in step (1 ') or only in step (2') or in both steps (1 ') and (2'). The amounts are only required to finally be in the range of 20 to 80% by weight of the pigment(s) and 20 to 80% by weight of the dispersing aid(s) (Α'). Thereby, the rheological nature of the mixture becomes dilatant, and a large shearing force caused by screw driving efficiently concentrates on the pigment particles, and as a result, finer division is enabled .

[01 38] The present invention is still more preferably a process for preparing a solid pigment dispersion using a dispersing unit capable of continuously carrying out, following the step (4) or (4') described above, the following further steps:

(5) or (5') a step of extruding the dispersed pigment(s);

(6) or (6') a step of obtaining a solid pigment dispersion in the form of a shaped product.

[01 39]

One step (1 pass) of the extruder used in the present invention takes a shorter time than the three-roll method and the like. Thus, for sufficient dispersion of the pigment(s), the pigment(s) is/are desirably subjected to surface treatment therefor so that the pigment(s) is/are well wettable by the dispersion medium . For this purpose, the solid dispersing aid(s) (A) or (Α') is/are preferably mixed with the pigment(s) before, simultaneously with and/or after the introduction of the pigment(s) into the extruder. The surface of the pigment(s) has/have fine hydrophobic irregularities. When the wetting dispersing aid(s) (A) or (Α'), for example, are adsorbed onto the unevenness, wetting by the dispersion medium is promoted . As a result, the liquid dispersion medium is homogeneously mixed with the pigment(s) sufficiently, and residual coarse pigment particles and clogging of inkjet nozzles can be reduced.

[0140]

I n step (1 ) or (1 '), mixing the pigment(s) and the solid dispersing aid(s) (A) or (Α') in advance improves the wetting with the liquid dispersion medium in step (2) or (2'). Addition of a dispersion medium (media) to the mixture of the pigment(s) as flowable powder and the solid dispersing aid(s) (A) or (Α') in step (2) or (2') can provide dilatant flow properties suitable to fine dispersion, and a shearing force from the kneading mechanism is transmitted to the pigment particles efficiently. I n subsequent step (3) or (3'), the pigment(s) is/are ground, and the dispersing aid(s) A or A' and B or B' can stabilize the pigment(s) in the form of finely divided particles. The kneaded pigment(s) obtained in step (3) or (3') is/are then subjected to the steps (4) or (4') of volatilizing the liquid dispersion medium (media) and drying, and thus can be withdrawn as a solid pigment dispersion . I n the case of a twin-screw extruder having a shaping function, after step (4) or (4'), the solid dispersion can be further shaped into the form of pellets.

This is more preferable in respect of improvement in the handleability during ink production .

[0141 ]

I n order to carry out steps (1 ) to (4) or (1 ') to (4') described above in the present invention, at least the process from the addition of the liquid dispersion medium (media) to the kneading, and also the subsequent step of drying, have to be automated. The reason is as follows: the mixture of the pigment(s) and the solid dispersing aid(s) (A) or (Α') is flowable and easy to handle, but when a dispersion medium (media) is/are added to the powdery mixture, the flowability of the mixture drastically decreases, that is, so-called dilatant behavior appears. This state transforms the mixture to a hard mass, and thus, it is difficult to homogeneously mix the pigment(s) and the solid dispersing aid(s) (A) or (Α') by a batch operation such as a manual operation . As a result, it is difficult to achieve a high dispersibility intended. Examples of the apparatus capable of carrying out this automatic continuous operation include twin-screw continuous kneader

(kneading) apparatuses, and KRC kneader manufactured by Kurimoto, Ltd . can be used, for example. [0142]

An example of the method including continuously carrying out steps (5) and (6) in addition to (1 ) to (4) or (1 ') to (4') described above includes a method using a multi-screw extruder. Particularly, a method using a twin-screw extruder is preferable. An example of such an apparatus includes a twin-screw kneading extruder, model TEM-58SX, commercially available from TOSH I BA MACH I N E CO., LTD. I n the present invention, either of a twin-screw continuous kneader or a twin-screw extruder can be used. For achieving a particle diameter of nano-order for inkjet pigments and the like, a higher shearing force and a longer shearing time are desirable. For this purpose, a twin-screw extruder, which allows a relatively long kneading time, is preferable. Hereinafter, the process according to the present invention will be described in detail, but, for simplicity, the description relates to a process using a twin-screw extruder and, regarding a system using an organic dispersion medium for

redispersion, to a process in which a dispersing aid (Α') is added in step

(1 ').

[0143]

The conceptual diagram of the twin-screw extruder used in the present invention is shown in Figure 1 . A pigment previously mixed with a solid dispersing aid (A) or (Α') is introduced via the starting material introduction port into the apparatus (step (1 ) or (1 ')), and conveyed by rotating screws while a liquid dispersion medium such as water is injected thereto via a liquid injection port (step (2) or (2')). The pigment including the liquid dispersion medium injected thereto is transferred by the screws to a barrel (kneading section), and is ground and dispersed while subjected to heat and a large shearing force during passage through the intermeshing section of a plurality of screws (step (3) or (3')). From the finely divided pigment composition, the dispersion medium is vaporized under

evacuation(step (4) or (4')). Then, the composition is extruded from the screws into a shaping section (die) (step (5)) and shaped into a form of, e.g., cylindrical pellets by passing through the die (step (6)).

[0144]

With respect to twin-screw extruders that can be used in the present invention, any one comprising a kneading section and two screw shafts capable of controlling the temperature of the output die can be used without any particular limitation. Models having screw elements called kneading elements (also referred to as kneading discs or paddles) arranged alongside on a portion of the two screw shafts are preferable, and completely intermeshing co-rotating twin-screw kneading extruders having said screw elements are particularly preferable.

[0145]

When a mixture of the pigment and the solid dispersing aid (A) or (Α') is introduced in a twin-screw kneading extruder, the mixing can be carried out in a conventional method using a machine such as a kneader- mixer, V type mixer, double cone-type mixer, cubic mixer, and ribbon mixer or manually. I ntroduction can be carried out using any apparatus capable of supplying the starting material at a constant rate without particular limitation . Examples of such an apparatus can include screw feeders, table feeders, belt conveyor-type metering feeders, and electromagnetic feeders.

[0146]

The pigment mixed with the solid dispersing aid (A) or (Α') and introduced is conveyed in accordance with the rotation of the screws. At the liquid injection port, a liquid dispersion medium is introduced . The liquid dispersion medium contains principally water in the case of an aqueous ink, and additionally a dispersing aid (B). This dispersing aid (B) may be the same as the dispersing aid (A) mixed in the first step, but dispersing aids that can improve the penetrability of water into the pigment are even more preferable. Among these, low molecular surfactants, for example, low molecular surfactants having a (weight average) molecular weight of preferably 800 g/mol or less, particularly 600 g/mol or less are suitably used . If necessary, the dispersion medium may contain an organic medium and the like. The introduction of a liquid dispersion medium into pigment is carried out by, for example, via a liquid injection port by means of a metering pump.

[0147]

The pigment mixed with the liquid dispersion medium such as water is transferred to the kneading section, provided with a shearing force at a moderate setting temperature by the kneader function of the apparatus, and then dispersed .

[0148]

The setting temperatures of the kneading section, drying section, and die of the extruder are not particularly limited, if, at such temperatures, a solid dispersion is formed and the processed product may be extruded . The appropriate temperature of the kneading section is specifically in the range of 20 to 200°C, preferably in the range of 30 to 1 50°C, more preferably in the range of 40 to 120°C, still more preferably in the range of 50 to 90°C. When the kneading temperature is lower than said range, the dispersibility tends to decrease. I n contrast, when the temperature is higher than said range, the starting materials such as the pigment may be thermally decomposed, and troubles are likely to occur. Particularly preferably, the temperature of the kneading section is set to a temperature less than the boiling point of the liquid dispersion medium such that the liquid dispersion medium is not brought to boiling.

[0149]

The temperature of the drying section after kneading varies depending on the medium used and the degree of vacuum. If the kneading section zone is extended in order to improve the degree of dispersion, the length of the drying zone has to be correspondingly reduced .

Nevertheless, in order to obtain a higher degree of drying, the drying temperature is preferably set higher than the kneading temperature. The appropriate drying temperature is specifically in the range of 30 to 250°C, preferably in the range of 50 to 200°C, more preferably in the range of 60 to 120°C, still more preferably in the range of 70 to 1 00°C. When the temperature is lower than said range, drying will be insufficient, and the shaped pellets are likely to aggregate. At a temperature higher than said range, the starting materials such as the pigment may be thermally decomposed. Particularly preferably, in order to avoid troubles such as cracking inside the pellets occurring when the liquid dispersion medium boils, the temperature of the drying section is also set to a temperature lower than the boiling point of the liquid dispersion medium.

[01 50]

The number of revolutions (processing speed) of the screws can be set as appropriate depending on the model and type of the extruder, the starting materials, the shape of the screws, and the like, within the acceptable range of the extruder used . An extruder having a longer total length of screws can achieve a larger number of revolutions. This is because such an extruder has higher processing performance for mixing, shearing, and the like. Specifically, the number of revolutions is

appropriately 50 rpm or more, preferably 80 to 300 rpm.

[01 51 ]

Any shape and combination of screw elements that may be used in the present invention can be selected without particular limitation .

However, it is preferable to use a pair or more of kneading elements (kneading disks, paddles) having higher kneading action and shearing action.

[01 52]

The output dies can be changed as appropriate depending on the desired solid dispersion. Specific examples thereof include round dies having various bore diameters to obtain cylindrical processed products, and flat dies to obtain plate processed products. A processed product having subjected to processing such as kneading in the barrel of the twin-screw kneading extruder is continuously extruded through the small bores of the die. The extrudate can be cut to a desired length by an appropriate cutter, for example, a roller crusher, cutter mill, pin mill or the like. The cut extrudate pieces, as such or after further drying, can be used as a finely divided solid pigment dispersion. Alternatively, the extrudate extruded through the small bores of the die may be cut to a desired length by, for example, a rotary cutter equipped on the tip of the die (e.g., a rotary cutter for KEXN-30, manufactured by Kurimoto, Ltd .) to obtain a finely divided solid pigment dispersion directly or after drying without any special particle size regulating operation . The particulates described above can be pressed to obtain tablets.

[01 53] The solid pigment dispersion, which has been transferred from the extruding section to the shaping section and then shaped into a required form, for example, granules, pellets, cylinders, or the like, contains, in addition to the pigment, the dispersing aid, etc. The dispersing aid etc. provide the pigment with suitable viscoelasticity and serve as an adhesive among particles, and thus, the shape of the dispersion can be retained . The components such as the dispersing aid etc. have to be easily dispersed when redispersed in water or the like in the later step. For the pigment dispersibility, the shape retention and redispersibility of the shaped pigment, the total amount of the dispersing aids A and B (for a system using an aqueous dispersion medium for redispersion), or the amount of the dispersing aid A' or the total amount of the dispersing aid A' and B' (for a system using an organic dispersion medium for redispersion) is 15 to 80% by weight, 20 to 70% by weight in one embodiment, 30 to 65% by weight in one embodiment, based on the total weight of the solid pigment dispersion . When the amount is smaller than said range, the degree of dispersion decreases as well as the adhesive function for shape retention becomes insufficient, and thus, the dispersion is likely to be crushed during transportation and storage. When the amount is larger than said range, the pigment particles become tacky and the pellets are likely to aggregate and agglomerate.

[01 54]

When the dispersing aid B used after being dissolved in a liquid dispersion medium is liquid, it reduces the softening or melting point of the solid dispersing aid in the solid pigment dispersion . For this reason, an extremely high concentration of the liquid dispersing aid B is likely to induce agglomeration etc. of the solid pigment dispersion during storage. Moreover, in addition to the agglomeration of the solid pigment dispersion, the concentration of the liquid dispersing aid in the ink increases and the adhesiveness of the image increases, causing image defects. Thus, the proportion of the liquid dispersing aid B is, based on the content of active component of in liquid dispersing aid, preferably 0.07% by weight or more, 0.1 % by weight or more in one embodiment and preferably 1 0% by weight or less, 5% by weight or less in one embodiment, 3% by weight or less in one embodiment, relative to the weight of the solid pigment dispersion . When the concentration of the liquid dispersing aid (B) is lower than said range, the dispersed particle diameter increases, resulting in reduced filterability.

[01 55]

I n the solid pigment dispersion after dispersion and drying, a small amount of the residual liquid dispersion medium may remain . One reason for this is that elevating the drying temperature may induce the thermal decomposition etc. of the pigment and additives. When the amount of the residual dispersion medium is large, the softening or melting point of the solid dispersing aid in the composition decreases, and thus, agglomeration etc. of the solid pigment dispersion during storage may be induced .

Accordingly, the proportion of the residual dispersion medium in the composition after drying is, in a system using an aqueous dispersion medium for redispersion, preferably 1 0% by weight or less, more preferably 5% by weight or less, still preferably 3% by weight or less, particularly 1 % by weight or less, and in a system in which an organic dispersion medium is used for redispersion, may be preferably 20% by weight or less, more preferably 1 5% by weight or less because of the relative easiness of redispersion in an organic dispersion medium, but is still more preferably 10% by weight or less, particularly preferably 5% by weight or less, for example, 3% by weight or less or 1 % by weight or less, based on the weight of the solid pigment dispersion. I n a system using an aqueous dispersion medium for redispersion, in order to achieve good redispersibility, the proportion of the residual dispersion medium in the composition after drying is advantageously more than 0.3% by weight, preferably 0.5% by weight or more, based on the weight of the solid pigment dispersion.

[01 56]

The proportion described above can be applied to non-aqueous inkjet inks such as mono-functional and multi-functional UV monomer-based UV inks.

[01 57]

The solid pigment dispersion prepared by the present invention is used in applications requiring high tinting strength, chroma and high dispersibility, such as paints, printing inks, inkjet inks, color filters, toners or developers for electrostatic recording, and writing tools. When the dispersion is used in an inkjet ink, for example, the inkjet ink can be prepared by redispersing the pigment composition obtained by the present process at a desired concentration in an aqueous medium or organic medium, and adding necessary additives such as an ultraviolet absorber thereto, and then, filtering the mixture, for example.

[01 58]

As described above, the solid pigment dispersion obtained by the process of the present invention contains no medium or only a small amount of a medium used as the dispersion medium, or, may not contain additives varying depending on applications. For this reason, only using the solid pigment dispersion and adding substances suitable for each application makes the dispersion usable in many applications. Since the process of the present invention utilizes an automatic continuous production apparatus such as an extruder, it can prepare a large amount of the pigment composition with good reproducibility and thus can achieve a great cost reduction in preparing and supplying a highly dispersible pigment.

[Examples]

[01 59]

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[01 60]

(Dispersed particle diameter test: aqueous)

2.4 g of a solid pigment dispersion after dispersion and drying and 17.6 g of ion exchange water were weighed and stirred in a juicer-mixer for 3 minutes. The dispersion liquid was 1 00-fold diluted with ion exchange water, and D50 and D90 were determined by a particle size distribution analyzer (ELS-Z manufactured by Otsuka Electronics Co., Ltd .).

[01 61 ]

(Dispersed particle diameter test: organic)

2.4 g of a solid pigment dispersion after dispersion and drying and 17.6 g of diethylene glycol diethylether were weighed and stirred in a juicer- mixer for 3 minutes. The dispersion liquid was 100-fold diluted with dipropylene glycol dimethyl ether, and D50 and D90 were determined by a particle size distribution analyzer (ELS-Z manufactured by Otsuka

Electronics Co., Ltd .).

[01 62] (Method for measuring the residual amount of dispersion medium : aqueous) The moisture content in a solid pigment dispersion was determined after heating at 1 05°C from the weight difference before and after the heating using a Basic moisture analyzer MA1 50 manufactured by Sartorius Japan K. K.

[01 63]

(Method for measuring the residual amount of dispersion medium : organic)

The content of the dispersion medium in a solid pigment dispersion was determined after heating at 200°C from the weight difference before and after the heating using a Basic moisture analyzer MA1 50 manufactured by Sartorius Japan K. K.

[01 64]

(Filterability test: aqueous)

2.4 g of a solid pigment dispersion and 1 7.6 g of ion exchange water were weighed and stirred in a juicer-mixer for 3 minutes. To the pigment dispersion liquid, 20 g of a mixed medium comprising 1 5% by weight of glycerin, 20% by weight of diethylene glycol, and 65% by weight of ion exchanged water was added to prepare an ink having a pigment concentration of 4%. Then, 20 ml. of the ink was passed through a disc filter SH D-005-M PKC (pore diameter: 5 microns) manufactured by ROKI TECH NO CO., LTD. The filter was dried, and the dry weight difference before and after filtration was determined with an electronic balance to determine the weight of the residue based on 1 00% of the active component of the pigment.

[01 65]

I nks caused clogging of the filter and inks having a residue weight of more than 1 0% by weight relative to the solid pigment dispersion were rated as NG, and inks having a residue weight of 1 0% by weight or less were rated as OK.

[01 66]

(Filterability test: organic)

2.4 g of a solid pigment dispersion and 1 7.6 g of diethylene glycol diethylether were weighed and stirred in a juicer-mixer for 3 minutes. To this pigment dispersion liquid, 20 g of diethylene glycol dimethyl ether was added to prepare an ink having a pigment concentration of 4%. Then, 20 ml. of the ink was passed through a disc filter SH D-005-MPKC (pore diameter: 5 micrometers) manufactured by ROKI TECH NO CO., LTD. The filter was dried, and the dry weight difference before and after filtration was determined with an electronic balance to determine the amount of the residue based on 1 00% of the active component of the pigment.

[01 67]

I nks caused clogging of the filter and inks having a residue weight of more than 1 0% by weight relative to the solid pigment dispersion were rated as NG, and inks having a residue weight of 1 0% by weight or less were rated as OK.

[01 68]

(Agglomeration evaluation by means of storage test: aqueous)

10 g of each sample was taken and sealed in a glass container, and the sample was stored in a constant temperature and humidity chamber at 40°C and 80% RH for 10 days. Thereafter, the lid was opened, and the pigment composition was stirred with a spatula while visually observing the pigment dispersion . Samples in which no change in the appearance and no agglomeration were observed were scored as A, samples in which aggregation and agglomeration were partially observed were scored B, and samples in which obvious agglomeration was visually observed were scored as C.

[01 69]

(I nk stability evaluation by means of storage test: organic)

20 ml. of each filtered ink obtained in said filterability test was stored at 60°C for four weeks. I nks having no precipitation were scored as A, inks having partial precipitation were scored as B, and inks having precipitation on the entire bottom were scored as C.

[01 70]

(Dischargeability evaluation by means of print test: aqueous)

An ink cartridge of a commercially available inkjet printer: model PX-1 05 (manufactured by SEI KO EPSO N CORPORATION) was filled with 20 ml. of each filtered ink obtained in said filterability test. Solid printing was carried out while checking whether printing was achieved without clogging of the heads. I nks that enabled printing on 1 5 sheets or more of A4-sized wood-free paper without clogging were scored as A, inks that enabled printing on 1 0 to 14 sheets were scored as B, and inks that enabled printing on less than 1 0 sheets were scored as C.

[01 71 ]

(Dischargeability evaluation by means of print test: organic)

An ink cartridge of a commercially available inkjet printer: model BN-20 (manufactured by Roland DG Corporation) was filled with 20 ml. of each filtered ink obtained in said filterability test. Solid printing was carried out while checking whether printing was achieved without clogging of the heads. I nks that enabled printing on 15 sheets or more of A4-sized wood-free paper without clogging were scored as A, inks that enabled printing on 1 0 to 14 sheets were scored as B, and inks that enabled printing on less than 10 sheets were scored as C.

[01 72]

(Waterfastness test)

Two sheets of A4-sized printed matter obtained in the print test were superposed with their printed surfaces opposed to each other, and thereon, a 1 kg metal plate having a 1 0 cm χ 1 0 cm size was placed .

Then, the sheets were left to stand in the same constant temperature and humidity chamber at 40°C and 80% RH as in the storage test mentioned above. The metal plate was removed 1 0 days after and the images were observed . Printed matter having no change observed visually was scored as A, printed matter in which exfoliation was observed partially on the images was scored as B, and printed matter in which damage was observed on the entire images was scored as C.

[01 73]

Example 1

2 kg of a pigment (Pigment Red 122, Clariant Chemicals Ltd ., trade name: I nk Jet Magenta E02, hereinafter, abbreviated as PR122) (about 66.6% by weight based on the total weight of the pigment and a dispersing aid A) and 1 kg of a wax as a dispersing aid A (Clariant

Chemicals Ltd ., trade name: Licowax KST, weight average molecular weight: 1 500, acid number: 5 mgKOH/g, saponification number: 1 5 mgKOH/g, melting point (DSC): 56°C, hereinafter, abbreviated as WAX) (about 33.3% by weight) were mixed together in a Henschel mixer at 2000 rpm for three minutes. Then, the total amount of 3 kg of the mixture was fed into a twin-screw kneading extruder (manufactured by TOSH I BA

MACH I N E CO., LTD., model : TEM SS26) over one hour. The setting of the twin-screw kneading extruder included a number of revolutions of the screws: 100 rpm, a die bore diameter: 2 mm, a temperature of all the barrels and dies: 50°C, and a twisting angle of the kneading element: 60°. The pigment loaded was transferred to the liquid injection port, and water as a dispersion medium was injected by a metering pump over an hour. This water is 300g of ion exchanged water (1 0% by weight relative to the total weight of the pigment and the dispersing aid A) plus an aqueous solution of 3 g of an acetylene glycol nonionic surfactant (dispersing aid B; N issin Chemical Co., Ltd., trade name: OLFI N E E 1 01 0, active component content: 100%, weight average molecular weight: 500 or less) (1 % concentration relative to the water, 0.1 % relative to the total amount of the pigment and the dispersing aid A). The pigment composition into which the water containing the dispersing aid B was injected was transferred to the kneading section, and kneaded by the kneader at 1 00 rpm and 50°C. Then, the pigment composition was dried by heating to 80°C while the pressure inside the kneader was reduced by a vacuum pump. When the dispersed particle diameter of the pigment composition taken out were measured, D50 was 148 nm and D90 was 1 68 nm. The amount of the residual dispersion medium (water) in the solid pigment dispersion measured in accordance with the method of J IS «0068:2001 was 0.5% by weight based on the total amount of the pigment composition.

[01 74]

Example 2

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in

Example 1 except that the amount of water injected as a dispersion medium was 1500 g (50% based on the total of the pigment and the dispersing aid A).

[01 75]

Example 3

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the concentration of the dispersing aid B dissolved in the water was 0.5% by weight relative to the weight of the water.

[01 76]

Example 4

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the concentration of the dispersing aid B dissolved in the water was 3% by weight relative to the weight of the water.

[01 77]

Example 5

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the concentration of the dispersing aid B dissolved in the water was 5% by weight relative to the weight of the water.

[01 78]

Example 6

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the amount of water injected was 3 kg (1 00% by weight relative to the total amount of the pigment and the dispersing aid A).

[01 79] Example 7

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the amount of the pigment was 1 .5 kg and the amount of the dispersing aid A was 1 .5 kg.

[01 80]

Example 8

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the amount of the pigment was 1 .2 kg and the amount of the dispersing aid A was 1 .8 kg.

[01 81 ]

Example 9

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the amount of the pigment was 0.6 kg and the amount of the dispersing aid A was 2.4 kg.

[01 82]

Example 1 0

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the amount of the pigment was 2.4 kg and the amount of the dispersing aid A was 0.6 kg.

[01 83]

Example 1 1

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that 750 g of the wax of Example 1 and 250 g of a polyester-based surfactant having a 5-sulfoisophthalic acid group in the molecule (Clariant Japan K. K., Texcare SRA 300F, weight average molecular weight: 6250, melting point (DSC): 1 35°C, hereinafter,

abbreviated as polyester A) were used as a dispersing aid A.

[01 84]

Example 12

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that 500 g of the wax of Example 9, 250 g of polyester A, and 250 g of polyethylene glycol (Clariant Japan K. K., PEG 1 500, weight average molecular weight: 1 000, melting point: 45°C, hereinafter, abbreviated as PEG) were mixed as a dispersing aid A.

[01 85]

Example 1 3

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 1 1 except that the amount of the pigment was 1 .5 kg, the amount of the dispersing aid was 1 .5 kg, including 1 .125 kg of the wax and 0.375 kg of polyester A.

[01 86]

Example 14

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 1 1 except that the amount of the pigment was 1 .2 kg, and the amount of the dispersing aid was 1 .8 kg, including 1 .35 kg of the wax and 0.45 kg of polyester A. [01 87]

Example 1 5

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 1 1 except that the amount of the pigment was 2.4 kg, and the amount of the dispersing aid was 0.6 kg, including 0.45kg of the wax and 0.1 5kg of polyester A.

[01 88]

Example 1 6

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 1 1 except that the pigment used was Pigment Yellow 74 (Clariant Chemicals Ltd ., trade name: I nk Jet Yellow 5GXW, hereinafter, abbreviated as PY74).

[01 89]

Example 1 7

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 1 1 except that the pigment used was Pigment Blue 15:3 (Clariant Chemicals Ltd ., trade name: PV Fast Blue BG, hereinafter, abbreviated as PB 1 5:3).

[01 90]

Example 1 8

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in

Example 1 1 except that the pigment used was Pigment Black 7 (N I PEX 1 50, Orion Engineered Carbons) and the pigment concentration and the dispersing aid A concentration were each 50%.

[01 91 ]

Example 1 9

Example 1 was repeated except that the amount of the pigment of

Example 1 was 0.8 kg, the amount of polyester A of Example 1 1 as a dispersing aid A was 3.2 kg, and the amount of water injected was 2 kg (50% by weight relative to the total amount of the pigment and the dispersing aid A).

[01 92]

Example 20

Example 2 was repeated except that 50% of the water injected was replaced by isopropanol (99.5% purity, manufactured by KANTO

CH EMI CAL CO., I NC.).

[01 93]

Example 21

Example 2 was repeated except that 50% of the water injected was replaced by ethylene glycol (99% purity, manufactured by KANTO

CH EMI CAL CO., I NC.).

[01 94]

Example 22

Example 2 was repeated except that 50% of the water injected was replaced by acetone (99.5% purity, manufactured by KANTO CH EM I CAL CO., I NC.).

[01 95]

Comparative Example 1 Example 1 1 was repeated in the same manner under the same conditions except that no water was injected via the liquid injection port.

[01 96]

Comparative Example 2

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that, as a dispersing aid A, an acrylic polymer (BASF SE, Joncryl 690, weight average molecular weight: 1 6,500, acid number: 240 mgKOH/g, hereinafter, abbreviated as acrylic polymer A) was used instead of the wax.

[01 97]

Comparative Example 3

100 g of the pigment of Example 1 , 3 g of the dispersing aid B, and 400 g of a 25% by weight aqueous solution of acrylic polymer A used in Comparative Example 2 were mixed together to form a slurry. The slurry was dispersed by two passes (one pass time: 1 .5 minutes) through a three- roll mill (Buhler, model SDY-200). The pigment paste was dried in an oven at 1 00°C for five hours to obtain a solid pigment dispersion .

[01 98]

Comparative Example 4

100 g of the pigment of Example 1 1 , 50 g of the wax, 50 g of polyester A were mixed together, and, to the mixture, 200 g of ion exchange water containing 2 g of the dispersing aid B was added . The mixture was dispersed by two passes (one pass time: 1 .5 minutes) through the three-roll mill of Comparative Example 3. The pigment paste was dried in an oven at 100°C for five hours to obtain a solid pigment dispersion .

[01 99] Comparative Example 5

100 g of the pigment of Example 1 , 3 g of the dispersing aid B, and 400 g of a 25% by weight aqueous solution of acrylic polymer A used in Comparative Example 2 were mixed together to form a slurry. The slurry was heated to 1 00°C and dispersed for five minutes by a two-roll mill

(Nishimura Koki Co., LTD., model: NS-250), and then, dried in an oven at

100°C for five hours to obtain a solid pigment dispersion .

[0200]

Comparative Example 6

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Comparative Example 5 except that 1 00g of a mixture of the same amounts of the wax and polyester A used in Example 1 1 , instead of acrylic polymer A, and 200 g of ion exchanged water containing 2 g of the dispersing aid B were used and dispersion was carried out by the same two-roll mill as in Comparative Example 5 under the same conditions.

[0201 ]

Comparative Example 7

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Comparative Example 5 except that the pigment used was Pigment Yellow 74 (I nk Jet Yellow 5GXW, Clariant Chemicals Ltd .).

[0202]

Comparative Example 8

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Comparative Example 5 except that the pigment used was Pigment Blue

15:3 (PV Fast Cyan BG, Clariant Chemicals Ltd .).

[0203]

Comparative Example 9

Comparative Example 5 was repeated in the same manner under the same conditions except that the pigment used was Pigment Black 7 (N I PEX 1 50, Orion Engineered Carbons).

[0204]

Comparative Example 1 0

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 1 1 except that the amount of the pigment of Example 1 1 was 2.7 kg and the amount of the dispersing aid A having the same composition as that in Example 1 1 was 0.3 kg.

[0205]

Comparative Example 1 1

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that no dispersing aid B was added to the injected water in Example 2.

[0206]

Comparative Example 12

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 2 except that the amount of the injected water was 6 kg (200% relative to the total amount of the pigment and the dispersing aid) in Example 2. [0207]

Comparative Example 1 3

A solid pigment dispersion was obtained in the same manner under the same conditions as in Comparative Example 1 0 except that the amount of the pigment was 0.3 kg and the amount of the dispersing aid A was 2.7 kg.

[0208]

With respect to the solid pigment dispersions of Examples 1 to 22 and Comparative Examples 1 to 1 3, the particle diameter values of D50 and D90, filterability, dischargeability from nozzles, image waterfastness, and the amount of the residual dispersion medium were measured by each of the test methods mentioned above, and the results are listed in Table 2.

[0209]

Additionally, in accordance with the agglomeration evaluation method described above, 1 0 g of each sample of Examples 1 to 22 and

Comparative Examples 1 to 1 3 was taken, sealed in a glass container, and stored in a constant temperature and humidity chamber at 40°C. Then, the lid was opened, the state of the pigment composition was visually observed, and the results are listed as storage stability in Table 2.

[021 0]

[Table 2]

Acryl Insufficient

C.E.2 PR122 67 33 Extruder Yes 50 0.2 (0.1) 0.1 - - - polymer A torque

Unmeasurabl

e because

Acryl

C.E.3 PR122 50 50 Three roll - 150 1 (1.5) polymer did 0.4 NG c c A polymer A

not dissolve

again

WAX,

C.E.4 PR122 50 50 Three roll - 100 1 (1.0) 176 310 0.2 NG c B A

Polyester A

Acryl

C.E.5 PR122 50 50 Two roll - 150 1 (1.5) 400 713 0.1 NG c C A polymer A

WAX,

C.E.6 PR122 50 50 Two roll - 200 1 (2.0) 195 323 0.2 NG c B A

Polyester A

Acryl

C.E.7 PY74 50 50 Two roll - 150 1 (1.5) 211 296 0.2 NG c B A polymer A

Acryl

C.E.8 PBI15:3 50 50 Two roll - 150 1 (1.5) 159 273 0.2 NG c B A polymer A

Acryl

C.E.9 PBk7 50 50 Two roll - 150 1 (1.5) 189 308 0.3 NG c B A polymer A

WAX,

C.E.10 PR122 90 10 Extruder Yes 50 0.2 (0.1) 326 565 1.1 NG c C A

Polyester A

C.E.11 PR122 67 WAX 33 Extruder Yes 50 0 (0) 256 389 0.2 NG B B A

C.E.12 PR122 67 WAX 33 Extruder Yes 200 ° 5 ° (0.1) 155 255 6.3 NG B C A

WAX,

C.E.13 PR122 10 90 Extruder Yes 50 0.2 (0.1) 179 254 3.3 OK B B C

Polyester A

* ' Isopropyl alcohol 50% of water injected

"> Ethylene glycol 50% of water injected

Acetone 50% of water injected

[021 1 ]

The following can be said from Table 2.

[0212]

(1 ) As can be seen from the relation between the filterability and the pigment particle diameter, except for Comparative Example 1 3, in which the proportion of the pigment was a very low level (1 0% by weight), the filterability is satisfactory at D50 of 1 50 nm or less. When D50 exceeds 170 nm, the filterability decreases, accompanied by a decrease in the

dischargeability from the nozzle. The ink dischargeability from the nozzle is also satisfactory at D50 of 1 50 nm or less, but when D50 exceeds 1 50 nm, the dischargeability decreases. From these results, D50 is preferably 1 50 nm or less for satisfying the properties of inkjet inks.

[021 3]

The same can be said for D 9 o- It can be seen that satisfactory results can be obtained at 300 nm or less and D90 of 200 nm or less is particularly desirable.

[0214]

(2) The relation between the proportion of the pigment calculated based on the total weight of the pigment and the dispersing aid (% by weight), and D50 is shown in Figure 2. From Examples 1 1 , 1 3, 14, and 15 and Comparative Examples 10 and 1 3 using a PR122 + (WAX + polyester A) system (the amount of injected dispersion medium: 50%, 0.1 % of the dispersing aid B in the dispersion), it can be seen that D50 tends to exceed 150 nm when the proportion of the pigment is less than about 20% and more than 80%. I n the case of Examples 2, 7, 8, 9, and 1 0 using a PR122 + WAX system (the amount of injected dispersion medium : 50%, 0.1 % of the dispersing aid B in the dispersion), a D 5 o value of 1 50 nm or less is obtained in the range of the pigment proportion of 20% by weight to 80% by weight. Thus, the lower limit of the amount of the pigment was determined to be 20% by weight and the upper limit to be 80% by weight.

[021 5]

(3) When the particle diameter D50 is plotted as a function of the amount of the dispersing aid B added that is supplied as a mixture with water (the weight proportion of the dispersing aid B in the solid pigment dispersion) (Examples 2 to 5 and Comparative Example 1 1 ) (Figure 3), it is expected that D50 is likely to rapidly increase at 0.1 % or less and to exhibit no large variation at 0.1 % or more. The acetylene glycol-based surfactant (Nissin Chemical Co., Ltd ., OLFI N E E1 01 0) used as a dispersing aid B is a water-soluble liquid . Therefore, when the amount thereof added exceeds 10%, the pigment particles aggregate together into agglomerates during storage, and the printed matter under a high humidity environment absorbs moisture. Thus, the image intensity is likely to decrease, and the practical performance decreases.

(4) The amount of water injected is plotted as a function of the particle diameter to provide Figure 4 (Examples 1 , 2, and 6, and

Comparative Example 12). From this figure, D90 exceeds 200 nm when the amount of water as a dispersion medium is approximately 1 50 based on 1 00 of the weight of the solid pigment composition. When the amount of water exceeds that value, coarse particles increase, and the filterability

decreases.

[021 6]

Example 23

0.7 kg of a pigment (Pigment Red 122, Clariant Chemicals Ltd., trade name: I nk Jet Magenta E02, hereinafter, abbreviated as PR122) (70% by weight based on the total weight of the pigment and dispersing aid A') and 0.3 kg of a vinyl chloride - vinyl acetate copolymer as a dispersing aid A' (Wacker Chemie AG, trade name: Vinnol E 1 8/38, weight average molecular weight: 33000 - 43000, softening point: 70°C, hereinafter, abbreviated as PVC/PVAc) (30% by weight) were mixed in a Henschel mixer at 2000 rpm for three minutes. Then, 1 kg of the mixture was fed into a twin-screw kneading extruder (manufactured by TOSH I BA MACH I N E CO., LTD., model TEM SS26) over one hour. The setting of the twin-screw kneading extruder included a number of revolutions of the screws: 1 00 rpm, a die bore diameter: 2 mm, a temperature of all the barrels and dies: 50°C, and a twisting angle of the kneading elements: 60°. The pigment loaded was transferred to the liquid injection port and dipropylene glycol dimethyl ether as a dispersion medium was injected by a metering pump over an hour. The pigment composition into which 100 g of dipropylene glycol dimethyl ether (10% by weight relative to the total weight of the pigment and the dispersing aid A') was injected was transferred to the kneading section and kneaded by the kneader at 100 rpm and 50°C. Then, the pigment composition was dried by heating to 50°C while the pressure inside the kneader was reduced by a vacuum pump. When the dispersed particle diameter of the pigment composition taken out was measured, D50 was 1 1 0 nm and D90 was 1 87 nm . The amount of the residual dispersion medium in the solid pigment dispersion measured in accordance with the method of J IS «0068:2001 was 3.7% by weight based on the total amount of the pigment composition .

[021 7]

Example 24 The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 23 except that the amount of dipropylene glycol dimethyl ether injected as a dispersion medium was 500 g (50% based on the total of the pigment and the dispersing aid A') and 50 g of a polyethylene imine dispersant (dispersing aid B'; Lubrizol Corporation, trade name: Solsperse 32000, active component content: 100%, melting point/softening point (DSC): 30 to 35°C, acid number (mgKOH/g): 1 5.5±2.5, amine number (mgKOH/g): 35.1 ±4.5) was dissolved in the medium.

[021 8]

Example 25

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 24 except that the concentration of the dispersing aid B' dissolved in the dispersion medium was 20% by weight relative to the weight of the dispersion medium.

[021 9]

Example 26

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 24 except that the concentration of the dispersing aid B' to be dissolved in the dispersion medium was 30% by weight relative to the weight of the dispersion medium .

[0220]

Example 27

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 24 except that the concentration of the dispersing aid B' dissolved in the dispersion medium was 50% by weight relative to the weight of the dispersion medium.

[0221 ]

Example 28

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 23 except that the amount of dipropylene glycol dimethyl ether injected was 1 kg (1 00% by weight based on the total amount of the pigment and the dispersing aid A').

[0222]

Example 29

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 28 except that a polyvinylbutyral resin, S-LEC BL-1 0 (SEKISU I MATERIAL SOLUTIONS CO., LTD ., weight average molecular weight:

15000, softening point: 67°C, hereinafter, abbreviated as PVB) was used as a dispersant A'.

[0223]

Example 30

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 29 except that 0.7 kg of the pigment was singly fed and 1 kg of dipropylene glycol dimethyl ether in which 30% by weight of the dispersant A' was dissolved was injected .

[0224]

Example 31 The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 23 except that the amount of dipropylene glycol dimethyl ether injected was 250 g.

[0225]

Example 32

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 31 except that the amount of the pigment was 400 g and the amount of the dispersing aid A' was 600 g.

[0226]

Example 33

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 31 except that the amount of the pigment was 200 g and the amount of the dispersing aid A' was 800 g.

[0227]

Example 34

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 31 except that the amount of the pigment was 800 g and the amount of the dispersing aid A' was 200 g.

[0228]

Example 35

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 24 except that the amount of dipropylene glycol dimethyl ether injected was 250 g and the concentration of the dispersing aid B' dissolved in the dispersion medium was 30% by weight relative to the weight of the dispersion medium.

[0229]

Example 36

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that Lubrizol Corporation, trade name: Solsperse 71 000, active component content: 1 00%, acid number (mgKOH/g): 0, amine number (mgKOH/g): 78 was used as a dispersing aid B'.

[0230]

Example 37

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the pigment used was Pigment Yellow 155 (Clariant Chemicals Ltd ., trade name: I nk Jet Yellow 4GC, hereinafter, abbreviated as PY1 55).

[0231 ]

Example 38

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the pigment used was Pigment Yellow 150

(Lanxess, trade name: Levascreen Yellow G01 , hereinafter, abbreviated as PY1 50).

[0232]

Example 39 The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the pigment used was Pigment Blue 15:4 (Clariant Chemicals Ltd ., trade name: Hostaperm Blue BT-61 7D, hereinafter, abbreviated as PB1 5:4).

[0233]

Example 40

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the pigment used was Pigment Black 7 (N I PEX 1 50, Orion Engineered Carbons).

[0234]

Example 41

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in

Example 35 except that the dispersing aid B' was Bykjet 91 51 (BYK-Chemie GmbH : active component content: 1 00%, acid number (mgKOH/g): 8, amine number (mgKOH/g): 1 8).

[0235]

Example 42

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the dispersing aid B' was EFKA4047 (BASF SE: active component content: 35%, acid number (mgKOH/g): 14, amine number (mgKOH/g): 24).

[0236]

Example 43 The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the dispersing aid B' was PB822 (Ajinomoto Fine- Techno Co., I nc. : active component content: 1 00%, acid number

(mgKOH/g): 14, amine number (mgKOH/g): 1 7).

[0237]

Example 44

Example 30 was repeated except that 50% of the medium injected was replaced by isopropanol (99.5% purity, manufactured by KANTO

CH EMI CAL CO., I NC.).

[0238]

Example 45

Example 30 was repeated except that 50% of the medium injected was replaced by isobutanol (99% purity, manufactured by KANTO

CH EMI CAL CO., I NC.).

[0239]

Example 46

Example 30 was repeated except that 50% of the medium injected was replaced by acetone (99.5% purity, manufactured by KANTO

CH EMI CAL CO., I NC.).

[0240]

Comparative Example 14

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 23 except that no medium was injected via the liquid injection port.

[0241 ]

Comparative Example 1 5 7 g of the same pigment and 3 g of the same dispersing aid A' as those used in Example 23, and 1 g of a dispersing aid B', and 1 0 g of dipropylene glycol dimethyl ether were mixed together to give a slurry. The slurry was heated to 100°C and dispersed for five minutes by a three- roll mill (Nishimura Koki Co., LTD., model: NS-250), and then, dried in an oven at 100°C for five hours to obtain a solid pigment dispersion.

[0242]

Comparative Example 1 6

7 g of the same pigment and 3 g of the same dispersing aid A' as those used in Example 23, and 1 0 g of dipropylene glycol dimethyl ether were mixed together to give a slurry. The slurry was heated to 1 00°C and dispersed for five minutes by a three-roll mill (Nishimura Koki Co., LTD., model : NS-250), and then, dried in an oven at 100°C for five hours to obtain a solid pigment dispersion .

[0243]

Comparative Example 1 7

7 g of the same pigment and 3 g of the same dispersing aid A' as those used in Example 23, 1 g of a dispersing aid B', and 1 0 g of

dipropylene glycol dimethyl ether were mixed together to give a slurry. The slurry was dispersed by two passes (one pass time: 1 .5 minutes) through a two-roll mill (Buhler, model: SDY-200), and then, dried in an oven at 1 00°C for five hours to obtain a solid pigment dispersion .

[0244]

Comparative Example 1 8

7 g of the same pigment and 3 g of the same dispersing aid A' as those used in Example 23, 1 g of a dispersing aid B', and 1 0 g of

dipropylene glycol dimethyl ether were mixed together to form a slurry. The slurry was dispersed by two passes (one pass time: 1 .5 minutes) through a two-roll mill (Buhler, model: SDY-200), and then, dried in an oven at 1 00°C for five hours to obtain a solid pigment dispersion .

[0245]

Comparative Example 1 9

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Comparative Example 1 7 except that the pigment used was Pigment Yellow 150 (Lanxess, trade name: Levascreen Yellow G01 , hereinafter,

abbreviated as PY1 50).

[0246]

Comparative Example 20

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Comparative Example 1 7 except that the pigment used was Pigment Blue 15:4 (Clariant Chemicals Ltd ., trade name: Hostaperm Blue BT-61 7D).

[0247]

Comparative Example 21

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Comparative Example 1 7 except that the pigment used was Pigment Black 7 (N I PEX 150, Orion Engineered Carbons).

[0248]

Comparative Example 22

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the amount of the pigment was 1 800 g and the amount of the dispersing aid A' was 200 g.

[0249]

Comparative Example 23

The pigment was dispersed followed by drying to obtain a solid pigment dispersion in the same manner under the same conditions as in Example 35 except that the amount of the pigment was 200 g and the amount of the dispersing aid A' was 1 800 g.

[0250]

[Table 3]

C.E.14 PR122 70 PVC/PVAc 30 Extruder No 0 No 0 289 449 0 NG B B

C.E.15 PR122 70 PVC/PVAc 30 Three roll Yes 100 S32000 10 (10) 219 323 2.7 NG C B

C.E.16 PR122 70 PVC/PVAc 30 Three roll Yes 100 No 0 254 355 2.5 NG C C

C.E.17 PR122 70 PVC/PVAc 30 Two roll Yes 100 S32000 10 (10) 221 334 1.9 NG C C

C.E.18 PR122 70 PVC/PVAc 30 Two roll Yes 100 S32000 10 (10) 316 360 1.5 NG C C

C.E.19 PY150 70 PVC/PVAc 30 Two roll Yes 100 S32000 10 (10) 197 355 2.2 NG C C

C.E.20 PBI15:4 70 PVC/PVAc 30 Two roll Yes 100 S32000 10 (10) 172 266 1.5 NG C C

C.E.21 PBk7 70 PVC/PVAc 30 Two roll Yes 100 S32000 10 (10) 191 392 2.5 NG C C

C.E.22 PR122 90 PVC/PVAc 10 Extruder Yes 25 S32000 30 (7.5) 313 551 5.5 NG C C

C.E.23 PR122 10 PVC/PVAc 90 Extruder Yes 25 S32000 30 (7.5) 256 389 8.3 NG B B

[0251 ]

The following can be said from Table 3.

[0252]

(1 ) As can be seen from the relation between the filterability and the pigment particle diameter, also in the case of the organic systems, the filterability is satisfactory at D50 of 1 50 nm or less. When D50 exceeds 170 nm, the filterability decreases, accompanied by a decrease in the

dischargeability from the nozzle. The ink dischargeability from the nozzle is also satisfactory at D 5 o of 1 50 nm or less, but when D 5 o exceeds 1 50 nm, the dischargeability decreases. From these results, also in the organic systems, D 5 o is preferably 1 50 nm or less for satisfying the properties of inkjet inks.

[0253]

The same can be said for D90. It can be seen that satisfactory results can be obtained at 300 nm or less and D90 of 200 nm or less is particularly desirable.

[0254]

(2) I n can be seen that, from Examples 33 and 34 and

Comparative Examples 22 and 23 (PR122 + PVC/PVAc in all), D50 exceeds 150 nm when the proportion of the pigment is less than approximately 20% and more than 80%. Accordingly, it can be determined that also in the organic systems, from the viewpoint of a D 5 o value of 1 50 nm or less, the lower limit and the upper limit of the amount of the pigment are suitably 20% by weight and 80% by weight, respectively.

[0255]

(3) Comparative Example 14, in which no dispersion medium such as dipropylene glycol dimethyl ether was used, has a D50 value of 289 and a D90 value of 449, being inferior in dispersibility. I n comparison with Example 23, in which a dispersion medium was added, the shearing force on dispersion is absorbed by the resin and thus insufficiently transmitted to the pigment, leading to a reduced dispersibility in Comparative Example 14. I n contrast, in Example 23, in which a dispersion medium was added, it is appreciated that the dispersing aid is dissolved in the dispersion medium to make the flowing property dilatant, the shearing force from the machine is efficiently transmitted to the pigment particles, thus leading to an enhanced dispersibility. This is also the case in Example 1 1 (with dispersion medium) and Comparative Example 1 (without dispersion medium) shown in Table 2, which are aqueous dispersion systems.