HEAT SENSITIVE RECORDING MATERIAL

Title:

HEAT SENSITIVE RECORDING MATERIAL

Document Type and Number:

WIPO Patent Application WO/2002/078970

Kind Code:

Abstract:

Heat sensitive recording material, comprising at least one colour forming compound, at least one colour developing compound and at least one stabiliser, a composition consisting essentially of the inventive selection of compounds, and its use.

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Inventors:

AMIN MOHAMMED ASAD (GB)
BOARDMAN KENNETH ALFRED (GB)
O'NEIL ROBERT MONTGOMERY (GB)

Application Number:

PCT/EP2002/003309

Publication Date:

October 10, 2002

Filing Date:

March 25, 2002

Export Citation:

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Assignee:

CIBA SC HOLDING AG (CH)
AMIN MOHAMMED ASAD (GB)
BOARDMAN KENNETH ALFRED (GB)
O'NEIL ROBERT MONTGOMERY (GB)

International Classes:

B41M5/337; B41M5/30; B41M5/333; (IPC1-7): B41M5/30

Domestic Patent References:

WO2001016095A1	2001-03-08
WO2000053426A1	2000-09-14

Foreign References:

EP0104353A2	1984-04-04
EP0503856A1	1992-09-16
EP0252691A2	1988-01-13
EP0104353A2	1984-04-04
JP2000345067A	2000-12-12

Attorney, Agent or Firm:

CIBA SPECIALTY CHEMICALS HOLDING INC. (Patentabteilung Klybeckstrasse 141 Basel, CH)

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Claims:

Claims

A heat sensitive recording material comprising a support and a record layer formed on the support, the record layer comprising at least one colour forming compound of formula where R'is hydrogen or a C1 C6 alkyl group, R2 is a CiCe alkyl or alkoxyalkyl group, a cyclohexyl or phenyl group which may be substituted by C1C4alkyl, CiC4alkoxy or di (C1 C4alkyl) amino or R'and R2 may be joined together to form with the nitrogen to which they are bound a heterocyclic ring, R3 is hydrogen, a CiC4 alkyl or alkoxy group, R4 is hydrogen, a halogen, a trifluoromethyl group or a CiC4 alkyl group, at least one colour developing compound of formula R5 is hydrogen, a C1C5 alkyl group, an acetylamino group or a halogen atom, R6 is a hydrogen atom, a ClC5 alkyl group, a cycloalkyl group or a phenyl group which may be substituted by C1C4alkyl, C1C4alkoxy, hydroxy or a halogen atom and R 7is a C1C5 alkyl group, a cycloalkyl group or a phenyl group which may be substituted by C1C4alkyl, C1C4 alkoxy, hydroxy or a halogen atom, or R6 and R7 may be linked together to form with the nitrogen to which they are bound a saturated ring, and at least one stabiliser of formula (3A) or (3B) where, R8, R9, R10 and R11 are independently, a C1C12 alkyl, C5C8 cycloalkyl group, a phenyl group which may be substituted by CtC4alkyl, CtC4alkoxy, hydroxy or a halogen atom, an unsubstituted benzyl group or a benzyl group which is substituted by CC4alkyl, or a a, a dimethyl benzyl group, X is an oxygen atom, a sulfur atom, a SO2 group, a CH2 group or a group CHY in which Y is C1C12 alkyl ; Rt2 is a C1C12 alkyl or C5C8 cycloalkyl and R13 is C1 C12 alkyl or a phenyl group which may be substituted by CiC4aiky), Ci04aikoxy, or a halogen atom.

A heat sensitive recording material according to claim 1, wherein the colour forming compound is 3dibutylamino6methyl7anilinofluoran, 3diethylamino6methyl7 anilinofluoran, 3 (NethylNisoamylamino)6methyl7anilinofluoran, 3dipentylamino6 methyl7anilinofluoran, 3diethylamino6methyl7 (3methylanilino) fluoran or mixtures thereof.

3.	A heat sensitive recording material according to claim 1, wherein the colour developing compound is N (4hydroxyphenyl)4methylbenzenesulfonamide.

A heat sensitive recording material according to claim 1, wherein the stabiliser is 4,4' butylidenebis (2tertbutyl5methylphenol), 4,4'thiobis (2tertbutyl5methylphenol), 2,2' thiobis (4tertoctylphenol), 1,1,3tris (2methyl4hydroxy5tertbutylphenyl) butane, 1,1,3 tris (2methyl4hydroxy5cyclohexylphenyl) butane or mixtures thereof.

5.	A heat sensitive recording material according to claim 1, wherein the record layer also contains a sensitiser.

6.	A heat sensitive recording material according to claim 5, wherein the sensitiser is p benzylbiphenyl, 2benzyloxynaphthalene, ethylene glycol bis (mtolyl ether), 1,2 diphenoxyethane, dibenzyl oxalate and di (4methylbenzyl) oxalate.

Composition, consiting essentially of a colour forming compound of formula where R'is hydrogen or a CtC6 alkyl group, R2 is a CiC6 alkyl or alkoxyalkyl group, a cyclohexyl or phenyl group which may be substituted by CiC4alkyl, CiC4alkoxy or di (C1 C4alkyl) amino or R'and R2 may be joined together to form with the nitrogen a heterocyclic ring, R3 is hydrogen, a CtC4 alkyl or ålkoxy group, R4 is hydrogen, a halogen, a trifluoromethyl group or a C1C4 alkyl group, at least one colour developing compound of formula R5 is hydrogen, a CrC5 alkyl group, an acetylamino group or a halogen atom, R6 is a hydrogen atom, a CiC5 alkyl group, a cycloalkyl group or a phenyl group which may be substituted by C1C4alkyl, C1C4alkoxy, hydroxy or a halogen atom and R7 is a CiCe alkyl group, a cycloalkyl group or a phenyl group which may be substituted by C1C4alkyl, C1C4 alkoxy, hydroxy or a halogen atom, or R6 and R7 may be linked together to form with N a saturated ring, and at least one stabiliser of formula (3A) or (3B) where, R8, R9, R'° and R"are independently, a C1C12 alkyl, C5C8 cycloalkyl group, a phenyl group which may be substituted by C1C4alkyl, C1C4alkoxy, hydroxy or a halogen atom, an unsubstituted benzyl group or a benzyl group which is substituted by C1C4alkyl, or a a, α dimethyl benzyl group, X is an oxygen atom, a sulfur atom, a SO2 group, a CH2 group or a group CHY in which Y is C1C12 alkyl ; R12 is a CiCi2 alkyl or C5C8 cycloalkyl and R13 is Cl C12 alkyl or a phenyl group which may be substituted CiC4alkyl, CiC4alkoxy, or a halogen atom.

8.	Use of the composition according to claim 7 for the manufacture of a heatsensitive colored imageforming layer for the manufacture of heatsensitive recording material.

Description:

Heat Sensitive Recording Material This invention relates to a heat-sensitive recording material, typically in the form of sheets coated with chromogenic material (colour formers) and colour developer materials. In particular, the present invention relates to a heat-sensitive recording material with excellent thermal sensitivity and image stability characteristics.

Heat-sensitive recording materials are produced by applying to a support a colourless or light-coloured chromogenic substance and a colour developer, which reacts with the chromogenic substance upon heating to produce an image. Examples of such supports include paper, synthetic paper, plastic film or sheet. When a heating element such as a thermal print head is brought into contact with the recording material, reaction occurs between the colour former and colour developer to produce an image, thereby forming a record. These recording materials are widely used in facsimiles, ticket machines, label printers and instrument recorders etc.

Particularly desirable characteristics of the record layer of the heat sensitive recording material include good thermal sensitivity, low tendency for premature image development, and good resistance to the effects of light, heat, humidity, oils, plasticisers and water.

As a method for imparting these desirable characteristics to the record layer, EP-A 104,353 discloses a composition comprising a colour forming fluoran compound, an acidic substance, for example, a phenolic compound such as 4,4'-isopropylidene diphenol (bis phenol A) and a benzenesulfonamide compound.

The use of 4,4'-isopropylidene diphenol as a highly effective colour developer in heat sensitive recording materials is well established and requires no further explanation herein.

However, in recent times, its use in such applications has been the subject of some considerable debate due to concerns over certain aspects of its toxicity. Such concerns have naturally led to research into alternative colour developers and/or compositions having similar performance characteristics to 4,4'-isopropylidene diphenol in heat sensitive recording materials.

JP-A 2000-345067 discloses mixtures of a colour former, a mixture of at least two colour developers and 2-benzyloxy naphthalene. Though in the comparitive examples not more than one colour developer is used, the use of stabilizers is not described.

Accordingly, a heat sensitive recording material composition satisfying these performance characteristics have been found. This composition comprises as colour former, at least one compound of formula (1), as colour developer, at least one benzene sulfonamide compound of formula (2) and as stabiliser, at least one compound of formula (3A) or (3B) where R'is hydrogen or a Ci-C6 alkyl group, R2 is a C1-C6 alkyl or alkoxyalkyl group, a cyclohexyl or phenyl group which may be substituted by C1-C4alkyl, C1-C4-alkoxy or di (C1- C4alkyl) amino or R'and R2 may be joined together to form with the nitrogen to which they are bound a heterocyclic ring, R3 is hydrogen, a Ci-C4 alkyl or alkoxy group, R4 is hydrogen, a halogen, a trifluoromethyl group or a Ci-C4 alkyl group, R5 is hydrogen, a C1-C5 alkyl group, an acetylamino group or a halogen atom, R6 is a hydrogen atom, a C1-C5 alkyl group, a cycloalkyl group or a phenyl group which may be substituted by Ci-C4alkyl, Ci-C4-alkoxy, hydroxy or a halogen atom and R 7is a Ci-Cs alkyl group, a cycloalkyl group or a phenyl group which may be substituted by C1-C4alkyl, C1-C4-alkoxy, hydroxy or a halogen atom, or R6 and R7 may be linked together to form with the nitrogen to which they are bound a saturated ring, R8, R9, R'° and R"are independently, a Ci-C12 alkyl, C5-C8 cycloalkyl group, a phenyl group which may be substituted by Ci-C4alkyl, Ci-C4-alkoxy, hydroxy or a halogen atom, an unsubstituted benzyl group or a benzyl group which is substituted by Ci-C4alkyl, or a a, a-dimethyl benzyl group, X is an oxygen atom, a sulfur atom, a -SO2- group, a CH2 group or a group CH-Y in which Y is Ci-Cis alkyl ; R12 is a Ci-Cis alkyl or C5-C8 cycloalkyl and R13 is C1-C12 alkyl or a phenyl group which may be substituted by C1-C4alkyl, Ci-C4-alkoxy, or a halogen atom.

C1-C12 alkyl stands for methyl, ethyl, n-, i-propyl, n-, i-, sec,-or tert.-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, preferably Ci-Ce alkyl such as methyl, ethyl, n-, i-propyl, n-, i-, sec,-or tert.-butyl, n-pentyl, n-hexyl, more preferably Cl- C5alkyl such as methyl, ethyl, n-, i-propyl, n-, i-, sec,-or tert.-butyl, n-pentyl, and most preferred C1-C4 alkyl such as methyl, ethyl, n-, i-propyl, n-, i-, sec,-or tert.-butyl.

Ci-C4 alkoxy stands for methoxy, ethoxy, n-, i-propoxy, n-butoxy.

Cycloalkyl group stands for cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, cyclododecyl, preferably for C5-C8cycloalkyl such as cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl.

Halogen is to be understood as meaning fluorine, chlorine, bromine, iodine, in particular chlorine.

When R'and R2 or R6 and R7 together with the nitrogen atom to which they are bonded form a heterocyclic ring, this can be a 5-, 6-or 7-membered ring, especially a pyrrolidine, piperidine, morpholine or piperazine ring. The piperazine ring may be substituted, for example by alkyl, at the nitrogen atom that is not bonded to the phenyl or alkyl radical.

R'is preferably a Ci-C6alkyl group, especially C1-C4-alkyl.

R2 is preferably a Ci-C6alkyl group, C1-C4alkoxy-C1-C4alkyl group, a cyclohexyl group or a phenyl group or a 4-methylphenyl group.

Preferred meanings of R3 are hydrogen or methyl.

R4 is preferably hydrogen, trifluoromethyl or Ci-C4alkyl.

R5 is preferably hydrogen or methyl.

R6 is preferably hydrogen and R7 is preferably a phenyl group which is unsubstituted or substituted by methyl, methoxy or especially by hydroxy.

R3 and R10 are preferably identical and are each hydrogen or C1-C4alkyl and R9 and R"are also preferably identical and are preferably each tert.-butyl, cyclohexyl or tert.-octyl.

The preferred meaning of X is sulfur, a SO2 group or a CH2 group.

R13 is preferably Ci-Cis alkyl and R12 is preferably tert.-butyl, cyclohexyl or tert.-octyl.

Preferred colour formers of formula (1) include but are not limited to: 3-dimethylamino-6- methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl- 7-(3-trifluoromethylanilino) fluoran, 3-diethylamino-6-methyl-7-(2-chloroanilino) fluoran, 3- diethylamino-6-methyl-7- (4-chloroanilino) fluoran, 3-diethylamino-6-methyl-7- (2- fluoroanilino) fluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3-methylanilino) fluoran, 3-diethylamino-6-methyl-7- (4-methylanilino) fluoran, 3- diethylamino-6-ethoxyethyl-7-anilinofluoran, 3-diethylamino-7- (3-trifluoromethylanilino) fluoran, 3-diethylamino-7-(2-chloroanilino) fluoran, 3-diethylamino-7-(2-fluoroanilino) fluoran, 3-dibutylamino-7-anilinofluoran, 3-diethylamino-7-anilinofluoran, 3-dibutylamino-6-methyl-7- anilinofluoran, 3-dibutylamino-6-methyl-7-(2-chloroanilino) fluoran, 3-dibutylamino-6-methyl- 7- (4-chloroanilino) fluoran, 3-dibutylamino-6-methyl-7- (2-fluoroanilino) fluoran, 3- dibutylamino-6-methyl-7- (3-trifluoromethylanilino) fluoran, 3-dibutylamino-6-ethoxyethyl-7- anilinofluoran, 3-dibutylamino-6-chloro-anilinofluoran, 3-dibutylamino-6-methyl-7- (4- methylanilino) fluoran, 3-dibutylamino-7-(2-chloroanilino) fluoran, 3-dibutylamino-7-(2- fluoroanilino) fluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl- 7- (2-chloroanilino) fluoran, 3-dipentylamino-7- (3-trifluoromethylanilino) fluoran, 3- dipentylamino-6-chloro-7-anilinofluoran, 3-dipentylamino-7- (4-chloroanilino) fluoran, 3- pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-(N-methyl-N- propylamino)-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7- anilinofluoran, 3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-p- toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran,<BR& gt; 3- (N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluoran, 3- (N-ethyl-N-isobutylamino)-6-methyl- 7-anilinofluoran, 3-(N-butyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-(N-isopropyl-N-3- pentylamino)-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-ethoxypropylamino)-6-methyl-7- anilinofluorari.

Particularly preferred colour formers of formula (1) are 3-diethylamino-6-methyl-7- anilinofluoran, 3-diethylamino-6-methyl-7- (3-trifluoromethylanilino) fluoran, 3-diethylamino-6- methyl-7-(3-methylanilino) fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- dipentylamino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7- anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-p- toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran and 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran.

Examples of colour developers of formula (2) include but are not limited to: N- (2- chlorophenyl)-4-methylbenzenesulfonamide, N- (4-chlorophenyl)- 4- methylbenzenesulfonamide, N- (4-methylphenyl)- 4-methylbenzenesulfonamide, N- (4- hydroxyphenyl)-2-methylbenzenesulfonamide, N- (3-hydroxyphenyl)-4- methylbenzenesulfonamide, N- (3-hydroxyphenyl) benzenesulfonamide, N- (4- hydroxyphenyl)-4-methylbenzenesulfonamide, N- (4-hydroxyphenyl) benzenesulfonamide, N- (2-hydroxyphenyl)-4- methylbenzenesulfonamide, N- (2-hydroxyphenyl) benzenesulfonamide, N- (4-sulfamoylphenyl)- 4-methylbenzenesulfonamide, N- (4- methoxyphenyl)-4-methylbenzenesulfonamide, 4- (piperidinosulfonyl) acetanailide, N, N- dimethyl-4- (acetylamino)-benzenesulfonamide, 4- (morpholinosulfonyl)-acetanilide, N, N,- dimethyl-4-methylbenzenesulfonamide, 4- (morpholinosulfonyl) toluene, N-methyl- (4- methylbenzenesulfonamide), 4- (4-N-methylbenzenesulfonamide), 4- (4-N- methylpiperazinosulfonyl) toluene), 4- (4-N-methylpiperazinosulfonyl)- acetanilide, N- (2- chlorophenyl)-benzenesulfonamide, N- (4-chlorophenyl)-benzenesulfonamide, N- (3- chlorophenyl)-benzenesulfonamide, N- (2-methylphenyl)-benzenesulfonamide, N- (2- methoxyphenyl)-benzenesulfonamide, N- (2, 3-dichlorophenyl)-benzenesulfonamide, N- (3, 4- dichlorophenyl)-benzenesulfonamide, N- (2-nitrophenyl)-benzenesulfonamide, morpholinosulfonylbenzene, N-phenylbenzenesulfonamide, N-cyclohexyl- benzenesulfonamide, N- (2-chlorophenyl)-4-chlorobenzenesulfonamide, N- (4-chlorophenyl)- 4-chlorobenzenesulfonamide, N- (2-methylphenyl)-4-chlorobenzenesulfonamide, N- (4- methylphenyl)-4-chlorobenzenesulfonamide, N-(2-methoxylphenyl)-4- chlorobenzenesulfonamide, N- (2, 3-dichlorophenyl)-4-chlorobenzenesulfonamide, N- (3, 4- dichlorophenyl)-4-chlorobenzenesulfonamide, 4- (morpholinosulfonyl)-chlorobenzene, N- phenyl-4-chlorobenzenesulfonamide, N-cyclohexyl-4-chlorobenzenesulfonamide, and N, N- dimethyl-4-chlorobenenesulfonamide.

Preferred colour developers of formula (2) are N- (4-hydroxyphenyl)-4- methylbenzenesulfonamide, N- (4-hydroxyphenyl) benzenesulfonamide, N- (3- hydroxyphenyl)-4-methylbenzenesulfonamide, N- (3-hydroxyphenyl) benzenesulfonamide, N- (2-hydroxyphenyl)-4- methylbenzenesulfonamide, N- (2-hydroxyphenyl) benzenesulfonamide, N- (4-hydroxyphenyl)-2- methylbenzenesulfonamide, N- (4- methylphenyl)-4-methylbenzenesulfonamide, N- (4-methoxyphenyl)- 4- methylbenzenesulfonamide, N-(2-methylphenyl)-benzenesulfonamide, N-(2- methoxyphenyl)-benzenesulfonamide and N-phenylbenzenesulfonamide.

Examples of stabilisers of formulas (3A) or (3B) include but are not limited to: 2,2'- methylene-bis (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis (4-ethyl-6-tert-butylphenol), 4,4'-butylidene-bis (2-tert-butyl-5-methylphenol), 4,4'-thio-bis (2-tert-butyl-5-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5- cyclohexylphenyl) butane, bis (3-tert-butyl-4-hydroxy-6-methylphenyl) sulfone, 2,2'-thiobis (4- tert-octylphenol), 2,2'-thiobis (4-methylphenol), 2,2'-thiobis (4-ethylphenol), 2,2'-thiobis (4-isopropylphenol), 2,2'-thiobis (4-tert-butylphenol), 2,2'-thiobis (4-cumylphenol), 2,2'-thiobis (4-dodecylphenol), 2,2'-thiobis (4-benzylylphenol), 2,2'-thiobis (4-phenylphenol) and 2, 2'-thiobis (4-cyclohexylphenol).

Preferred stabilisers of formulas (3A) or (3B) are 2,2'-methylene-bis (4-methyl-6-tert- butylphenol), 4,4'-butylidene-bis (2-tert-butyl-5-methylphenol), 4,4'-thio-bis (2-tert-butyl-5- methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl- 4-hydroxy-5-cyclohexylphenyl) butane and 2,2'-thiobis (4-tert-octylphenol).

Preferably 0,5 to 5, especially 1 to 3 parts of colour developer and 0,05 to 2,0, especially 0,1 to 1,0 parts of stabiliser are used per 1 part of colour former.

Additional stabilisers may also be used in the heat sensitive recording materials of the invention. These include but are not limited to: bis (3,5-dibromo-4-hydroxyphenyl) sulfone, 2,2'-methylene bis (4,6-di-tert-butylphenyl) phosphate and alkali metal, ammonium and polyvalent metal salts thereof, 4-benzyloxy-4- (2-methylglycidyloxy) diphenyl sulfone, 4,4'- diglycidyloxydiphenyl sulfone, 1,4-diglycidyloxybenzene, 4- [a- (hydroxymethyl) benzyloxy]-4- hydroxydiphenyl sulfone, metal salts of p-nitrobenzoic acid, metal salts of phthalic acid mono benzyl ester, metal salts of cinnamic acid and mixtures thereof.

In addition, the heat sensitive recording material of the invention can contain a sensitiser.

Representative examples of sensitisers are stearamide, methylol stearamide, methylene bis (stearamide), p-benzylbiphenyl, m-terphenyl"4-methoxybiphenyl, dibenzyl oxalate, di (4- methylbenzyl) oxalate, di (4-chloro-benzyl) oxalate, dimethyl phthalate, dibenzyl terephthalate, dibenzyl isophthalate, 1,2-diphenoxyethane, 1,2-bis (4-methylphenoxy) ethane, ethylene glycol bis (m-tolyl ether), 1,2- (diphenoxymethyl) benzene, diphenyl sulphone, 4,4'-dimethylbiphenyl, phenyl-1-hydroxy-2-naphthoate, 4-methylphenyl biphenyl ether, 1,2-bis (3,4-dimethylphenyl) ethane, 1,4-di-ethoxynaphthalene, 1,4- diacetoxybenzene, 1,4-diproprionoxybenzene, o-xylylene-bis (phenyl ether), 4- (m- methylphenoxymethyl) biphenyl, p-hydroxyacetanilide, p-hydroxybutyranilide, p- hydroxynonananilide, p-hydroxylauranilide, and p-hydroxyoctadecananilide.

Preferred sensitisers are p-benzylbiphenyl, 2-benzyloxynaphthalene, m-terphenyl, dibenzyl oxalate, di (4-methylbenzyl) oxalate, dibenzyl terephthalate, 1,2-diphenoxyethane, 1,2-bis (4- methylphenoxy) ethane, ethylene glycol bis (m-tolyl ether), 1,2-(diphenoxymethyl) benzene, 4-methylphenyl biphenyl ether and 1,2-bis(3,4-dimethylphenyl) ethane.

The heat sensitive recording material of the invention can be prepared according to conventional methods. For example, the colour forming compound, colour developer, stabiliser and, if desired, the sensitiser are ground separately in water or a suitable dispersing medium, such as aqueous polyvinyl alcohol, to form an aqueous or other dispersion. The fine particle dispersions thus obtained are combined and then mixed with conventional amounts of binder, filler and lubricant.

Representative binders used for the heat sensitive recording material include polyvinyl alcohol (fully and partially hydrolysed), carboxy, amide, sulfonic and butyral modified polyvinyl alcohols, derivatives of cellulose such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose and acetyl cellulose, copolymer of styrene-maleic anhydride, copolymer of styrene-butadiene, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyamide resin and mixtures thereof.

Exemplary fillers, which can be used include calcium carbonate, precipitated calcium carbonate, clay, calcined clay, aluminium hydroxide, talc, titanium dioxide, zinc oxide, silica, polystyrene resin, urea-formaldehyde resin, hollow plastic pigment and mixtures thereof.

Representative lubricants for use in heat sensitive recording materials include stearamide, methylene bis stearamide, polyethylene, carnauba wax, paraffin wax, zinc stearate or calcium stearate and mixtures thereof.

Other additives can also be employed, if necessary. Such additives are for example fluorescent whitening agents and ultraviolet absorbers. The ultraviolet absorbers may be employed in either the thermosensitive colouring layer or in a protective layer, and if desired, may be used in microencapsulated form in the protective layer.

Representative examples of ultraviolet absorbers that may be used in the invention include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate and like salicylic acid type ultraviolet absorbers ; 2,4-Dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4- octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4- methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4- methoxy-5-sulfobenzophenone and like benzophenone type ultraviolet absorbers; 2-Ethylhexyl-2-cyano-3, 3-diphenylacrylate, ethyl-2-cyano-3, 3-diphenylacrylate and like cyanoacrylate type ultraviolet absorbers; Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, bis (1,2,2,6,6-pentamethyl-4-piperidyl)-2- (3, 5-di-tert-butyl-4-hydroxybenzyl)-2-n-butyl malonate and like hindered amine type ultraviolet absorbers; 2-(2'-Hydroxyphenyl) benzotriazole, 2-(2'-hydroxy-5'-methylphenyl) benzotriazole, 2-(2'- hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3,5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotria zole, 2- (2'- hydroxy-3,5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2- (2'-hydroxy-3,5'-di-tert- butylphenyl)-5-tert-butylbenzotriazole, 2- (2'-hydroxy-3, 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-3, 5'-di-tert-amylphenyl)-5-tert-amylbenzotriazole, 2- (2'-hydroxy-3, 5'-di-tert- amylphenyl)-5-methoxybenzotriazole, 2- [2'-hydroxy-3'- (3", 4", 5", 6"-tetrahydrophthalimido- methyl)-5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole, 2- (2'-hydroxy-3'-sec-butyl-5'-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-3'-tert-amyl-5- phenoxyphenyl)-5-methylbenzotriazole, 2- (2'-hydroxy-5'-n-dodecylphenyl) benzotriazole, 2- (2'-hydroxy-5'-sec-octyloxyphenyl)-5-phenylbenzotriazole, 2- (2'-hydroxy-3'-tert-amyl-5'- phenylphenyl)-5-methoxybenzotriazole, 2- [2'-hydroxy-3', 5'-bis (a, a-dimethylbenzyl)-phenyl] benzotriazole and like benzotriazole ultraviolet absorbers; 2- (2'-Hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-undecyl-5- methylphenyl) benzotriazole, 2-(2'-hydroxy-3'-tridecyl-5'-methylphenyl) benzotriazole, 2-(2'- hydroxy-3'-tetradecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-pentadecyl-5'- methylphenyl) benzotriazole, 2- (2-hydroxy-3-hexaadecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-4'-(2"-ethylhexyl) oxyphenyl] benzotriazole, 2-[2'-hydroxy-4'-(2"- ethylheptyl) oxyphenyl] benzotriazole, 2-[2'-hydroxy-4'-(2"-ethyloctyl) oxyphenyl] benzotriazole, 2-[2'-hydroxy-4'-(2"-propyloctyl) oxyphenyl] benzotriazole, 2-[2'-hydroxy-4'- (2"-propylheptyl) oxyphenyl] benzotriazole, 2-[2'-hydroxy-4'-(2"-propylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'- (1"-ethylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'- (1"- ethylheptyl) oxyphenyl] benzotriazole, 2-[2'-hydroxy-4'-(1"-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'- (1"-propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'- (1"-propylheptyl) oxyphenyl] benzotriazole,, 2- [2'-hydroxy-4'- (1"-propylhexyl) oxyphenyl] benzotriazole, 2- (2'-hydroxy-3'-sec-butyl-5'-tert-butylphenyl)-5-n-butylbenzo triazole, 2- (2'- hydroxy-3'-sec-butyl-5'-tert-butylphenyl)-5'-tert-pentylbenz otriazole, 2- (2'-hydroxy-3'-sec- butyl-5'-tert-butylphenyl)-5-n-pentylbenzotriazole, 2- (2'-hydroxy-3'-sec-butyl-5'-tert- pentylphenyl)-5'-tert-butylbenzotriazole, 2-(2'-hydroxy-3'-sec-butyl-5'-tert-pentylphenyl)-5'-n- butylbenzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-butylphenyl)-5-sec-butylbenzotriazole, 2- (2'- hydroxy-3', 5'-di-tert-pentylphenyl)-5-sec-butylbenzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'- tert-pentylphenyl)-5-sec-butylbenzotriazole, 2-(2'-hydroxy-3, 5'-di-sec-butylphenyl)-5- chlorobenzotriazole, 2-(2'-hydroxy-3, 5'-di-sec-butylphenyl)-5-methoxybenzotriazole, 2-(2'- hydroxy-3,5'-di-sec-butylphenyl)-5-tert-butylbenzotriazole, 2- (2'-hydroxy-3,5'-di-sec- butylphenyl)-5-n-butylbenzotriazole, octyl-5-tert-butyl-3- (5-chloro-2H-benzotriazole-2-yl)-4- hydroxybenzene propionate, condensate of methyl-3- [tert-butyl-5- (2H-benzotriazole-2-yl)-4- hydroxyphenyl] propionate and polyethylene glycol (molecular weight: about 300) and like benzotriazole ultraviolet absorbers.

The coating composition so obtained can be applied to a suitable substrate such as paper, plastic sheet and resin coated paper, and used as the heat sensitive recording material.

The system of the invention can be employed for other end use applications using colour forming materials, for example, a temperature indicating material.

The quantity of the coating is usually in the range of 2 to 10 g/m2, most often in the range 4 to 8g/m2.

The recording material containing such a thermosensitive colouring layer can in addition contain a protective layer and, if desired, an undercoat layer. The undercoat layer may be interposed between the substrate and the thermosensitive colouring layer.

The protective layer usually comprises a water-soluble resin in order to protect the thermosensitive colouring layer. If desired, the protective layer may contain water-soluble resins in combination with water-insoluble resins.

As such resins conventional resins can be employed. Specific examples are: polyvinyl alcohol ; starch and starch derivatives; cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose ; sodium polyacrylate ; polyvinyl pyrrolidone ; polyacrylamide/acrylic acid ester copolymers ; acrylamide/acrylic acid ester/methacrylic acid copolymers ; alkali metal salts of styrene/maleic anhydride copolymers ; alkali metal salts of isobutylene/maleic anhydride copolymers ; polyacrylamide ; sodium alginate ; gelatin ; casein; water-soluble polyesters and carboxyl modified polyvinyl alcohols.

The protective layer may also contain a water-resisting agent such as a polyamide resin, polyamide-epichlorohydrin resin, melamine-formaldehyde resin, polyfunctional aziridine, formaldehyde, glyoxal, or chromium alum.

Furthermore, the protective layer may contain fillers, such as finely-divided inorganic powders, e. g. calcium carbonate, silica, zinc oxide, titanium oxide, aluminium hydroxide, zinc hydroxide, barium sulphate, clay, talc, surface-treated calcium or silica, or a finely- divided organic powder, e. g., a urea-formaldehyde resin, a styrene/methacrylic acid copolymer or polystyrene.

The undercoat layer usually contains as its main components a binder resin and a filler.

Specific examples of binder resins for use in the undercoat layer are: polyvinyl alcohol ; starch and starch derivatives; cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose ; sodium polyacrylate ; polyvinyl pyrrolidone ; polyacrylamide/acrylic acid ester copolymers ; acrylamide/acrylic acid ester/methacrylic acid copolymers ; alkali metal salts of styrene/maleic anhydride copolymers ; alkali metal salts of isobutylene/maleic anhydride copolymers ; polyacrylamide ; sodium alginate ; gelatin ; casein; water-soluble polymers such as water-soluble polyesters and carboxyl-group-modified polyvinyl alcohols ; polyvinyl acetate; polyurethanes ; styrene/butadiene copolymers ; polyacrylic acid ; polyacrylic acid esters; vinyl chloride/vinyl acetate copolymers ; polybutylmethacrylate ; ethylene/vinylacetate copolymers and styrene/butadiene acrylic derivative copolymers.

Specific examples of fillers for use in the undercoat layer are: finely-divided inorganic powders, e. g. calcium carbonate, silica, zinc oxide, titanium oxide, aluminium hydroxide, zinc hydroxide, barium sulphate, clay, talc, surface-treated calcium, silica or calcined clay (eg Ansilex, Engelhard Corp.), and finely-divided organic powders of, e. g., urea-formaldehyde resins, styrene/methacrylic acid copolymers and polystyrene.

In addition, the undercoat layer may contain a water-resisting agent. Examples of such agents are given above.

Another embodiment of the present invention relates to a composition, consiting essentially of a colour forming compound of formula where Ri is hydrogen or a Ci-Ce alkyl group, R2 is a Ci-Ce alkyl or alkoxyalkyl group, a cyclohexyl or phenyl group which may be substituted by Ci-C4alkyl, Ci-C4-alkoxy or di (Ci- C4alkyl) amino or R'and R2 may be joined together to form with the nitrogen a heterocyclic ring, R3 is hydrogen, a Ci-C4 alkyl or alkoxy group, R4 is hydrogen, a halogen, a trifluoromethyl group or a C1-C4 alkyl group, at least one colour developing compound of formula R5 is hydrogen, a C :-C5 alkyl group, an acetylamino group or a halogen atom, R6 is a hydrogen atom, a Ct-C5 alkyl group, a cycloalkyl group or a phenyl group which may be substituted by Ci-C4alkyi, Ci-C4-alkoxy, hydroxy or a halogen atom and R 7is a C1-C5 alkyl group, a cycloalkyl group or a phenyl group which may be substituted by Ci-C4alkyl, Ci-C4- alkoxy, hydroxy or a halogen atom, or R6 and R7 may be linked together to form with N a saturated ring, and at least one stabiliser of formula (3A) or (3B) where, R8, R9, R10 and R11 are independently, a C1-C12 alky, C5-C8 cycloalkyl group, a phenyl group which may be substituted by C-C4alkyl, Ci-C4-alkoxy, hydroxy or a halogen atom, an unsubstituted benzyl group or a benzyl group which is substituted by Ci-C4alkyl, or a a, a- dimethyl benzyl group, X is an oxygen atom, a sulfur atom, a -SO2- group, a CH2 group or a group CH-Y in which Y is Ci-Cis alkyl ; Rt2 is a Cl-Cl2 alkyl or C5-C8 cycloalkyl and Rt3 is Ci- Ci2 alkyl or a phenyl group which may be substituted C :-C4alkyl, Ct-C4-alkoxy, or a halogen atom.

A further embodiment relates to the use of this inventive composition for the manufacture of a heat-sensitive colored image-forming layer for the manufacture of heat-sensitive recording material.

The invention will now be illustrated by the following examples, in which all parts or percentages are by weight.

Examples Example 1: This illustrates the preparation of a typical commercial heat-sensitive recording material comprising 3-dibutylamino-6-methyl-7-anilinofluoran as colour former, bis phenol A as colour developer and 2-benzyloxynaphthalene as sensitiser.

Dispersions A1, B1 and C1 are prepared by grinding the compositions shown below in an attritor until average particle sizes of about 1u are attained.

Dispersion A1 (Colour Former) 3-dibutylamino-6-methyl-7-anilinofluoran 10 parts Polyvinyl alcohol (10% aqueous solution) 35 parts Water 21.5 parts Dispersion B1 (Colour Developed bis phenol A 20 parts Polyvinyl alcohol (10% aqueous solution) 30 parts Water 75 parts Dispersion C1 (Sensitiser) 2-benzyloxynaphthalene 20 parts Polyvinyl alcohol (10% aqueous solution) 15 parts Water 25 parts A thermal coating mixture is then prepared by combining together the following components: parts Dispersion A1 66.5 Dispersion B1 125.0 Dispersion C1 60.0 Calcium Carbonate 33.0 Zinc stearate (33% aqueous dispersion) 15.0 Polyvinyl alcohol (20% aqueous solution) 65.0 Ciba@T ! NOPAL@ ABP-X (fluorescent whitening agent) 1.2- Water 200.8 This coating mixture is applied at a coatweight of about 5.0 g/m2 to a base paper weighing 50 g/m2 and then dried. The resulting sheet is calendered by means of a laboratory calender to produce the recording sheet.

Example 2: This illustrates the preparation of a heat-sensitive recording material comprising 3-dibutylamino-6-methyl-7-anilinofluoran as colour former, bis phenol A as colour developer and N- (4-hdroxyphenyl)-4-methylbenzenesulfonamide as co-developer.

Dispersion B2 is prepared by grinding the composition shown below in an attritor until an average particle size of about 1 p is attained.

Dispersion B2 (Color Developer) N- (4-hdroxyphenyl)-4-methylbenzenesulfonamide 20 parts Polyvinyl alcohol (10% aqueous solution) 15 parts Water 25 parts A thermal coating mixture is then prepared by combining together the following components: parts Dispersion A1 66.5 Dispersion B1 125.0 Dispersion B2 60.0 Calcium Carbonate 33.0 Zinc stearate (33% aqueous dispersion) 15.0 Polyvinyl alcohol (20% aqueous solution) 65.0 CibaTINOPALIC ABP-X (fluorescent whitening agent) 1.2 Water 200.8 This coating mixture is applied at a coatweight of about 5.0 g/m2 to a base paper weighing 50 g/m2 and then dried. The resulting sheet is calendered by means of a laboratory calender to produce the recording sheet.

Example 3: This illustrates the preparation of a heat-sensitive recording material according to the present invention comprising 3-dibutylamino-6-methyl-7-anilinofluoran as colour former, N- (4-hydroxyphenyl)-4-methylbenzenesulfonamide as colour developer, 4,4'- thiobis (2-tert-butyl-5-methylphenol) as stabiliser and 2-benzyloxynaphthalene as sensitiser.

Dispersion D1 is prepared by grinding the composition shown below in an attritor until an average particle size of about 11u is attained.

Dispersion D1 (Stabiliser) 4,4'-thiobis (2-tert-butyl-5-methylphenol) 5 parts Polyvinyl alcohol (10% aqueous solution) 5 parts Water 15 parts A thermal coating mixture is then prepared by combining together the following components: parts Dispersion A1 66.5 Dispersion B2 125.0 Dispersion C1 60.0 Dispersion D1 25.0 Calcium Carbonate 33.0 Zinc stearate (33% aqueous dispersion) 15.0 Polyvinyl alcohol (20% aqueous solution) 65.0 Ciba@T ! NOPAL@ ABP-X (fluorescent whitening agent) 1.2 Water 200.8 This coating mixture is applied at a coatweight of about 5.0 g/m2 to a base paper weighing 50 g/m2 and then dried. The resulting sheet is calendered by means of a laboratory calender to produce the recording sheet.

Example 4: A heat sensitive recording material is prepared in the same manner as in Example 3 except that in the preparation of dispersion D1, 1,1,3-tris (2-methyl-4-hydroxy-5- cyclohexylphenyl) butane is substituted for 4,4'-thiobis (2-tert-butyl-5-methylphenol).

Example 5: A heat sensitive recording material is prepared in the same manner as in Example 1 except that in the preparation of dispersion A1, 3-diethylamino-6-methyl-7- anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran.

Example 6: A heat sensitive recording material is prepared in the same manner as in Example 2 except that in the preparation of dispersion A1, 3-diethylamino-6-methyl-7- anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran.

Example 7: A heat sensitive recording material is prepared in the same manner as in Example 3 except that in the preparation of dispersion A1, 3-diethylamino-6-methyl-7- anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran.

Example 8: A heat sensitive recording material is prepared in the same manner as in Example 4 except that in the preparation of dispersion A1, 3-diethylamino-6-methyl-7- anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran.

Example 9: A heat sensitive recording material is prepared in the same manner as in Example 1, except that in the preparation of dispersion A1, 3- (N-ethyl-N-isoamylamino)-6- methyl-7-anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran and in the preparation of dispersion C1, p-benzylbiphenyl is substituted for 2-benzyloxynaphthalene.

Example 10: A heat sensitive recording material is prepared in the same manner as in Example 3 except that in the preparation of dispersion A1, 3- (N-ethyl-N-isoamylamino)-6- methyl-7-anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran and in the preparation of dispersion C1, p-benzylbiphenyl is substituted for 2-benzyloxynaphthalene.

Example 11: A heat sensitive recording material is prepared in the same manner as in Example 1 except that in the preparation of dispersion A1, 3-dipentylamino-6-methyl-7- anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran and in the preparation of dispersion C1, p-benzylbiphenyl is substituted for 2-benzyloxynaphthalene.

Example 12: A heat sensitive recording material is prepared in the same manner as in Example 3 except that in the preparation of dispersion A1, 3-dipentylamino-6-methyl-7- anilinofluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran and in the preparation of dispersion C1, p-benzylbiphenyl is substituted for 2-benzyloxynaphthalene.

Example 13: A heat sensitive recording material is prepared in the same manner as in Example 1 except that in the preparation of dispersion A1, 3-diethylamino-6-methyl-7- (3- methylanilino) fluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran and in the preparation of dispersion C1, p-benzylbiphenyl is substituted for 2-benzyloxynaphthalene.

Example 14: A heat sensitive recording material is prepared in the same manner as in Example 3 except that in the preparation of dispersion A1, 3-diethylamino-6-methyl-7- (3- methylanilino) fluoran is substituted for 3-dibutylamino-6-methyl-7-anilinofluoran and in the preparation of dispersion C1, p-benzylbiphenyl is substituted for 2-benzyloxynaphthalene.

Example 15: A heat sensitive recording material is prepared in the same manner as in Example 1 except that in the preparation of dispersion C1, ethylene glycol bis (m-tolyl ether) is substituted for 2-benzyloxynaphthalene.

Example 16: A heat sensitive recording material is prepared in the same manner as in Example 3 except that in the preparation of dispersion C1, ethylene glycol bis (m-tolyl ether) is substituted for 2-benzyloxynaphthalene.

Example 17: A heat sensitive recording material is prepared in the same manner as in Example 3 except that in the preparation of dispersion C1, ethylene glycol bis (m-tolyl ether) is substituted for 2-benzyloxynaphthalene and in the preparation of dispersion D1 4, 4'- butyliden bis (2-tert-butyl-5-methylphenol) is substituted for 4,4'-thio bis (2-tert-butyl-5- methylphenol).

Evaluation Initial Image Intensity and Background Whiteness Images are produced on the heat sensitive recording materials thus obtained by means of an Atlante Thermal Response Tester (Model 200). The colour densities of the recorded images and the background densities of the blank areas are measured with a Macbeth densitometer (Model 1200).

Background Whiteness after Ageing The background whiteness of the un-imaged recording material is measured with a Gretag SP 50 spectrophotometer before and after ageing (1 hr at 60°C/50% relative humidity).

Dynamic Sensitivity The dynamic thermal sensitivity of each heat sensitive recording material is measured using an Atlante Thermal Response Tester (Model 200).

Hydrothermal Resistance The imaged recording material is stored for 24 hr at 60°C/70% relative humidity. The colour densities of the imaged and un-imaged section of the recording material are measured using a MacBeth densitometer before and after the test.

Plasticiser Resistance The imaged recording material is contacted with a strip of PVC (phthalate ester plasticiser content 20-25%) under 100g cm' pressure for 24 hours/50° C. The colour density of the imaged section of the recording material is measured using a MacBeth densitometer before and after the test.

Oil Resistance The imaged recording material is coated with a thin layer of cottonseed oil using a gravure printer and stored for 24 hours/40° C. The colour density of the imaged section of the recording material is measured using a MacBeth densitometer before and after the test.

Light Fastness The recording material, comprising of an imaged and un-imaged section, is exposed to fluorescent tubes emitting artificial sunlight (approximately 1200 Lux) for 120 hours. The colour densities of the imaged and un-imaged sections of the recording material are measured using a MacBeth densitometer before and after the test.

Water Fastness The imaged recording material is immersed in de-ionised water for 3 hours at 20 C. The colour density of the imaged section of the recording material is measured using a MacBeth densitometer before and after the test.

The results of the above evaluations are illustrated in Table 1 and are rated in the following way: Initial intensity (Scale 1-10) 1 = poor intensity 10 = excellent intensity Background Whiteness (Scale 1-10) = poor whiteness (strong discoloration) 10 = excellent whiteness (no discoloration) Hydrothermal. Plasticiser and Oil Resistance (Scale 1-10) 1 = poor image stability 10 = excellent image stability Light and Water Fastness (Scale 1-10) 1 = poor image fastness 10 = excellent image fastness Table 1 Example Example Example Example Example Example Example Example 1 2(1) 3 4 5 6(1) 7 8 InitialIntensity 9 9 9 9 9 8 9 9 Background Whiteness 9 9 9 10 8 8 9 9 Background Whiteness after 8 7 8 9 6 4 7 8 ageing Dynamic Sensitivity 9 5 9 8 9 5 9 8 Hydrothermal Resistance Image 7 9 7 7 9 10 9 9 Background 7 5 7 9 5 2 5 8 Plasticiser Resistance 4 10 7 6 8 10 9 8 Oil Resistance 4 10 8 7 8 10 9 9 Light Fastness Image 8 10 9 9 8 10 9 9 Background 5 4 4 6 3 3 3 4 Water Fastness 4 5 5 5 5 4 6 5 (1) The recording material exhibited a strong tendency to adhere to thermal print head during recording Table 1 (continued) Example Example Example Example Example Example Example Example Example 9 10 11 12 13 14 15 16 17 InitialIntensity 9 9 9 9 9 8 9 9 Background Whiteness 9 9 9 9 9 9 9 9 10 Background Whiteness after 7 7 8 8 7 7 8 8 10 ageing Dynamic Sensitivity 9 9 9 9 8 8 9 9 8 Hydrothermal Resistance Image 8 8 6 6 8 8 7 7 6 Background 6 6 8 7 6 6 8 8 10 Plasticiser Resistance 7 8 4 7 8 9 5 7 5 Oil Resistance 7 8 3 7 8 9 4 8 7 Light Fastness Image 9 9 8 9 8 9 8 9 9 Background 4 3 4 3 3 2 6 4 6 Water Fastness 4 5 2 5 5 6 5 6 6 From the above results, it can be seen that Example 3 (composition according to the invention) performs similarly to a standard thermal paper composition (Example 1) containing 3-dibutylamino-6-methyl-7-anilinofluoran as colour former, bis phenol A as colour developer and 2-benzyloxynaphthalene as sensitiser with respect to initial intensity, background whiteness, background whiteness after ageing, dynamic sensitivity and hydrothermal resistance. In addition, it exhibits superior plasticiser, oil, light and water fastness properties. It is only slightly inferior with respect to background stability to light.

Example 4 (composition according to the invention) performs similarly to Example 1 with respect to initial intensity and hydrothermal resistance. It exhibits superior background whiteness, background whiteness after ageing, background hydrothermal stability, plasticiser, oil, light and water fastness properties. It is only slightly inferior with respect to dynamic sensitivity.

Example 2 contains 3-dibutylamino-6-methyl-7-anilinofluoran as colour former, bis phenol A as colour developer and N- (4-hdroxyphenyl)-4-methylbenzenesulfonamide as co-developer and exhibits superior performance in certain resistance tests compared with either Examples 3 or 4. However, this composition is unsuitable for use as a heat sensitive recording material due to its markedly inferior dynamic sensitivity and its highly undesirable tendency to adhere to the thermal print head during recording.

Example 7 (composition according to the invention) performs similarly to a standard thermal paper composition (Example 5) containing 3-diethylamino-6-methyl-7-anilinofluoran as colour former, bis phenol A as colour developer and 2-benzyloxynaphthalene as sensitiser with respect to initial intensity, dynamic sensitivity, hydrothermal resistance and light fastness background stability. It exhibits superior background whiteness, background whiteness after ageing, plasticiser, oil, light and water fastness properties.

Example 8 (composition according to the invention) performs similarly to Example 5 with respect to initial intensity, hydrothermal resistance, plasticiser and water resistance. It exhibits superior background whiteness, background whiteness after ageing, background hydrothermal resistance, oil and light fastness resistance. It is only slightly inferior with respect to dynamic sensitivity.

Example 6 contains 3-diethylamino-6-methyl-7-anilinofluoran as colour former, bis phenol A as colour developer and N- (4-hydroxyphenyl)-4-methylbenzenesulfonamide as co- developer and exhibits superior performance in certain resistance tests compared with either Examples 7 or 8. However, this composition is unsuitable for use as a heat sensitive recording material due to its markedly inferior dynamic sensitivity, its inferior background whiteness after ageing, its poor background hydrothermal stability and its highly undesirable tendency to adhere to the thermal print head during recording.

Example 10 (composition according to the invention) performs similarly to a standard thermal paper composition (Example 9) containing 3- (N-ethyl-N-isoamylamino)-6-methyl-7- anilinofluoran as colour former, bis phenol A as colour developer and p-benzylbiphenyl as sensitiser with respect to initial intensity, background whiteness, background whiteness after ageing, dynamic sensitivity, hydrothermal resistance and water fastness. It exhibits superior plasticiser, oil and light fastness properties. It is only slightly inferior in background light properties.

Example 12 (composition according to the invention) performs similarly to a standard thermal paper composition (Example 11) containing 3-dipentylamino-6-methyl-7- anilinofluoran as colour former, bis phenol A as colour developer and p-benzylbiphenyl as sensitiser with respect to initial intensity, background whiteness, background whiteness after ageing, dynamic sensitivity and hydrothermal resistance. It exhibits superior plasticiser, oil, light and water fastness properties. It is only slightly inferior in background hydrothermal stability and background light stability.

Example 14 (composition according to the invention) performs similarly to a standard thermal paper composition (Example 13) containing 3-diethylamino-6-methyl-7- (3- methylanilino) fluoran as colour former, bis phenol A as colour developer and p- benzylbiphenyl as sensitiser with respect to initial intensity, background whiteness, background whiteness after ageing, dynamic sensitivity and hydrothermal resistance. It exhibits superior plasticiser, oil, light and water fastness. It is only slightly inferior in background light stability.

Example 16 (composition according to the invention) performs similarly to a standard thermal paper composition (Example 15) containing 3-dibutylamino-6-methyl-7- anilinofluoran as colour former, bis phenol A as colour developer and ethylene glycol bis (m- tolyl ether) as sensitiser with respect to initial intensity, background whiteness, background whiteness after ageing, dynamic sensitivity and hydrothermal resistance. It exhibits superior plasticiser, oil, light and water fastness properties. It is only slightly inferior in background light stability.

Example 17 performs similarly to a standard thermal paper composition (Example 15) with respect to initial intensity, plasticiser resistance and background light stability. It exhibits superior background whiteness, background whiteness after ageing, background hydrothermal stability, oil, light and water fastness. It is only slightly inferior in dynamic sensitivity and hydrothermal resistance.

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