GB2257993A

GB2257993A - Colour formers for pressure sensitive recording material

Info

Publication number: GB2257993A
Application number: GB9215626A
Authority: GB
Inventors: Hideaki Fujisaki; Fukushige Kiriyama; Hajime Kawai; Katsuhiko Tsunemitsu
Original assignee: Yamada Chemical Co Ltd
Current assignee: Yamada Chemical Co Ltd
Priority date: 1991-07-26
Filing date: 1992-07-23
Publication date: 1993-01-27
Also published as: JPH05212957A; GB9215626D0

Abstract

A pressure sensitive recording material comprising as a colour former (a) at least one phthalide compound represented by the Formula (1): <IMAGE> wherein R<1>, R<2> and R<3> are specified in the description and n is 0 to 4 and (b) at least one fluoran compound represented by the formula (II): <IMAGE> wherein R<4> to R<9> are specified in the description. The material may also contain further colour formers of formulae IV to VII <IMAGE> wherein R<10>to R<29> are as specified in the description and X and Y are either a C atom or a N atom.

Description

TITLE OF THE INVENTION A PRESSURE SENSITIVE RECORDING MATERIAL BACKGROUND OF THE INVENTION The present invention relates to a pressure sensitive recording material, the image developed thereon being readable by an optical character reader (OCR).

As a color former, the developed image on which has absorption in both the visible region and the near infrared region, there have been proposed various compounds in Japanese Patent Application Laid-Open Nos.

59-1997S7 (1984), 62-243653 (1987) and 63-37158 (1988).

These compounds have been proposed for OCR with using a light source in a near-infrared region, such as a semi-conductor laser. Previously reported semi-conductor lasers can be divided into two classes, i.e., Ga-As laser having an emission wavelength of 750 to 850 nm and In-P laser having an emission wavelength of 1200 to 1600 nm.

Both of the emission wavelengthes have been limited in a near infrared region.

Recently, a semi-conductor laser having a shorter emission wavelength has been developed for increasing a recording density of an optical disc and therefore it has been needed to provide a leuco pigment having an absorption in from visible to near infrared region.

However, the above-mentioned compounds have the absorptions in long wave length regions, which are inclined to near infrared region. And there are some drawback such as weakness of their color densities in visible region, unstability of the image, and high cost for production.

The present inventors have found that the phthalide compound disclosed in Japanese Patent Application Laid Open (KOKAI) No. 61-87758 (1986) can provide a blue image which has an intense absorption in from visible to infrared region of not less than 650 nm, and is suitable as a color former for optical character reader and that the use of the phthalide compound in combination with a particular fluoran compound provides excellent hue of formed color and image stability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pressure sensitive recording material comprising as a color former at least one phthalide compound represented by the formula (I):

wherein R1 and R2 represent independently an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkoxyalkyl group having 3 to 7 carbon atoms, an aralkyl group, or an aryl group which may be substituted, or R1 and R2 form a heterocyclic ring together with a nitrogen atom to which R1 and R2 connect; R3 represents a halogen atom, an alkyl group, an alkoxy group or an amino group which may be substituted; and n is 0 to 4, and at least one fluoran compound represented by the formula (Il)

wherein R4 and R5 represent independently an alkyl group, a cycloalkyl group, an alkoxyalkyl group, a tetrahydrofurfuryl group, an alkenyl group, an aralkyl group, or an aryl group which may be substituted, or R4 and R5 form a heterocyclic group together with a nitrogen atom to which R4 and R5 connect; and R6, R7 and R9 represent independently a hydrogen atom, an alkyl group or a halogen atom, R8 represents a hydrogen atom, an alkyl group, a halogen atom, an alkylamino group, an aralkylamino group, or an arylamino group which may be substituted, or R6 and R7, or R8 and R9 form a naphthalene ring together with a benzene ring to which R6 and R7 or R8 and R9 connect.

DETAILED DESCRIPTION OF THE INVENTION The present invention particularily relates to a pressure sensetive recording material in which a color former which is colorless or light-colored is subjected to a contact with an electron-acceptable developer so as to develop the color former.

As examples of the phthalide compound represented by the formula (I), the followings are shown: 3-[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]- 6-dimethylaminophthal ide, 3-[1,1-bis(4-diethylaminophenyl)ethylene-2-yl]- 6-dimethylaminophthalide, 3-[1,1-bis(4-dibutylaminophenyl)ethylene-2-yl]- 6-dimethylaminophthal ide, 3-[1,1-bis(4-dipropylaminophenyl)ethylene-2-yl]- 6-dimethylaminophthalide, 3-[1,1-bis (4-dihexylaminophenyl) ethylene-2-yl]6-dimethylaminophthalide, 3-[1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] 6-dimethylaminophthal ide, 3-[1,1-bis(4-piperidinophenyl)ethylene-2-yl]- 6-dimethylaminophthal ide, 3-[1,1-bis(4-dibenzylaminophenyl)ethylene-2-yl]- 6-dimethylaminophthalide, 3-[1,1-bis (4-dimethylaminophenyl) ethylene-2-yl]6-diethylaminophthalide, 3-[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]- 6-dipropylaminophthalide, 3-[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]- 6-dibutylaminophthalide, 3-[1,1-bis (4-dimethylaminophenyl) ethylene-2-yl]6-dihexylaminophthalide, 3-[l,1-bis(4-dimethylaminophenyl)ethylene-2-yl]- 6-diamylaminophthalide, 3-[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]- 6-dioctylaminophthalide, 3-[1,1-bis (4-dimethylaminophenyl) ethylene-2-yl]6-methylphthalide, 3-[1,1-bis(4-diethylaminophenyl)ethylene-2-yl]- 6-ethylphthalide, 3-[1,1-bis(4-dibutylaminophenyl)ethylene-2-yl]- 6-propylphthalide, 3-[1,1-bis(4-dipropylaminophenyl)ethylene-2-yl]- 6-chlorophthalide, 3-[1,1-bis (4-dihexylaminophenyl) ethylene-2-yl]6-bromophthalide, 3-[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]- 6-methoxyphthalide, 3-[1,1-bis (4-piperidinophenyl) ethylene-2-yl]6-ethoxyphthalide, 3-[1,1-bis(4-dibenzylaminophenyl)ethylene-2-yl]- 6-benzyloxyphthalide, 3-[1,1-bis (4-dimethylaminophenyl) ethylene-2-yl]6-phthalide, 3-[l,1-bis(4-diethylaminophenyl)ethylene-2-yl]phthalide, 3-[1,1-bis(4-dipropylaminophenyl)ethylene-2-yl]phthalide, 3-[1,1-bis (4-dibutylaminophenyl) ethylene-2-yl] phthalide, 3-[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]phthalide, 3-[1,1-bis(4-piperidinophenyl)ethylene-2-yl]phthalide, 3-[1,1-bis (4-durolidinophenyl) ethylene-2-yl]6-dimethylaminophthalide, and 3-[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]- 6-durolidinophthalide.

As examples of the fluoran compound represented by the formula (II) and used in combination with the abovementioned phthalide compounds, the followings are shown: 3-chloro-6-cyclohexylaminofluoran, 2-methyl- 6-diethylaminofluoran, 2-methyl- 6- (N-ethyl-N-p-tolyl) aminofluoran, 2-tert-butyl-6-diethylaminofluoran, 8-diethylaminobenzo [a] fluoran, 8-(N-ethyl-N-iso-pentylamino)benzo[a]fluoran, 2-anilino-6-diethylaminofluoran, 2-anilino-6- (N-ethyl-N-n-hexylamino) fluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-di-n-butylaminofluoran, 2-anilino-3-methyl-6-di-n-pentylaminofluoran, 2-anilino-3-methyl-6-(N-methyl-N-n-propylamino)fluoran, 2-anilino-3-methyl-6-(N-ethyl-N-iso-pentylamino)fluoran, 2-anilino-3-methyl-6-(N-ethyl-N-n-hexylamino)fluoran, 2-anilino-3-methyl-6-(N-ethyl-N-p-tolylamino)fluoran, 2-anilino-3-methyl-6- (N-ethyl-N-ethoxypropylamino) - fluoran, 2-anilino-3-methyl-6-(N-methyl-N-cyclohexylamino)fluoran, 2-anilino-3-methyl-6- (N-ethyl-N-tetrahydrofurfurylamino) - fluoran, 2-anilino-3-methyl-6-pyrrolidinylfluoran, 2-anilino-3-chloro-6-diethylaminofluoran, 2-m-trifluoromethylanilino-6-diethylaminofluoran, and 2-o-chloroanilino-6-di-n-butylaminofluoran.

Among these compounds, it is preferred a fluoran compound represented by the formula (III):

wherein R4 and R5 have the same meanings as above.

Preferably, an additional color-producing agent is used in combination with the compounds represented by the formulae (I) and (II) to make the image more blackcolored and to improve the durability and visual impression of the image.

The preferred compounds which can be used with the compounds represented by the formulae (I) and (II) include compounds represented by the following formulae (IV) to (VII):

wherein R10 and R11 represent independently an alkyl group or alkoxyalkyl group, and R12 and R13 represent independently an alkyl group or an aryl group,

wherein R14, R15 and R18 represent independently an alkyl group, a cycloalkyl group, an alkoxyalkyl group, an aralkyl group or an aryl group, R17 represents an alkyl group or an aryl group, R16 represents a hydrogen atom, an alkyl group or an alkoxy group, and X and Y represent independently a carbon atom or a nitrogen atom,

wherein R19, R20, R21, R22, R23 and R24 represent independently an alkyl group, and R25 and R26 represent independently a hydrogen atom, an alkyl group or alkoxy group, and

wherein R27, R28 and R29 represent independently an alkyl group, an aralkyl group, an alkoxyalkyl group, or a phenyl group which may be substituted.

Examples of the compounds represented by these formulae are shown below, but not limited to them.

Examples of the compound represented by the formula (IV) include: 3, 3-bis (l-ethyl-2-methylindole-3-yl)phthalide, 3,3-bis(l-butyl-2-methylindole-3-yl)phthalide, 3,3-bis(l-pentyl-2-methylindole-3-yl)phthalide, 3,3-bis(1-iso-pentyl-2-methylindole-3-yl)phthalide, 3,3-bis(l-hexyl-2-methylindole-3-yl)phthalide, and 3,3-bis(1-octyl-2-methylindole-3-yl)phthalide.

Examples of the compound represented by the formula (V) include: 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl2-methylindole-3-yl)phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (l-butyl- 2-methylindole-3-yl)phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl2-methylindole-3-yl)-4-azaphthalide, 3- (4-diethylamino-2-pentyloxyphenyl) -3- (1-ethyl- 2-methylindole-3-yl)-4-azaphthalide, 3- (4-diethylamino-2-hexyloxyphenyl) -3- (1-ethyl2-methylindole-3-yl)-4-azaphthalide, 3-(4-cyclohexylmethylamino-2-ethoxyphenyl)-3-(1-ethyl2-methylindole-3-yl)-4-azaphthalide, and 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-octyl2-methylindole-3-yl)-4-azaphthalide.

Examples of the compound represented by the formula (VI) include: 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (4-diethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide, and 3,3-bis (4-diethylaminophenyl) -6-dimethylaminophthalide.

Examples of the compound represented by the formula (VII) include: 1,2-dihydro-l-ethyl-8-[N-(4-methylphenyl)-N-ethylamino] 2,2,4-trimethylspiro[llH-chromeno(2,3-g)quinoline- 11,3'-phthalide], 1,2-dihydro-1-ethyl-8-[N,N-di-n-butylamino]- 2,2,4-trimethylspiro[11H-chromeno(2,3-g)quinoline- 11,3'-phthalide], 1.2-dihydro-1-ethyl-8- (N,N-di-n-pentylamino]-2,2,4 trimethylspiro[llH-chromeno(2,3-g)quinoline-11,31- phthalide], l,2-dihydro-l-n-butyl-8-[N-ethyl-N-(4-methylphenyl)- amino]-2,2,4-trimethylspiro[11H-chromeno (2,3-g) quinoline11,3'-phthalide], 1,2-dihydro-1-n-butyl-8-[N-ethyl-N-iso-pentylamino]- 2,2,4-trimethylspiro[llH-chromeno(2,3-g)quinoline- 11,3'-phthalide], and 1,2-dihydro-1-amyl-8- [N,N-dibutylamino]2,2,4-trimethylspiro [11H-chromeno (2,3-g) quinoline11,3'-phthalide].

Furthermore, a near infrared-absorbing compound can be used within limits not to impair performance of the compound represented by the formula (I).

Examples of the near infrared-absorbing compound include: 3,3-bis[2-(4-dimethylaminophenyl)-2-(4-methoxyphenyl) vinyl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[2-(4-pyrrolidinophenyl)-2-(4-methoxyphenyl)- vinyl]-4, 5,6, 7-tetrachlorophthalide, 2-chloro-3-methyl-6-[p-(pl-phenylaminophenylamino)- phenylamino) fluoran, 3,6,6'-tris (dimethylamino) spiro [fluorene-9,3'-phthalide], 3- (4-diethylamino-2-methoxyphenyl) -3- [1-(4-chlorophenyl)1,3-butadienyl]phthalide, 3,3-bis (4-dimethylaminophenyl) -4-azaphthalide, 3, 3-bis (4-diethylaminophenyl) -4-azaphthalide, 3, 3-bis (4-dibutylaminophenyl) -4-azaphthalide, 3, 3-bis (4-diamylaminophenyl) -4-azaphthalide, 3,3-bis (4-dibenzylaminophenyl) -4-azaphthalide, and 3,3-bis(4-ethylbenzylaminophenyl) -4-azaphthalide.

The pressure sensitive recording material can be produced by using known methods. For example, methods as described in U.S. Patent Nos. 2,800,458 and 2,800,457 can be employed.

The pressure sensitive recording material (e.g.

pressure sensitive copying paper) is produced, for example, as described below.

A phthalide compound represented by the formula (I) is dissolved in a solvent, dispersed together with a binder in water and then formed into microcapsule. The microcapsule solution is applied to a substrate such as a sheet of paper and dried to form an upper sheet.

Further, a developer is applied to another substrate such as a sheet of paper to form a lower sheet. They are overlaid to each other to use. The ratio for the phthalide compound, the solvent and the binder in the production of the microcapsules can be chosen in accordance with the known method.

As the developer, clay materials such as clay, bentonite, activated clay and acid clay, metal salts of salicylic acid and their derivatives, p-phenylphenol formalin resin, p-octylphenol formalin resin and their metal salts are used. Among these, metal salts of salicylic acid derivatives are preferred for improving further coloring density and image stability. Examples of the salicylic acid derivatives are: salicylic acid, 3-methyl-5-tert-butylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-cyclohexylsalicylic acid, 5-cyclohexylsalicylic acid, cresotinic acid, 5-nonylsalicylic acid, 5-cumylsalicylic acid, 3-phenylsalicylic acid, 2, 5-dihydroxysalicylic acid, naphthoic acid, hydroxynaphthoic acid, 3-tert-butyl-5-a- methylbenzylsalicylic acid, and 3,5-di(a-methylbenzyl)- salicylic acid.

Polyvalent metals that form salts with such acids may be zinc, magnesium, calcium, aluminum, nickel and copper. Among them, zinc, magnesium and calcium are preferred, zinc being particularly preferred.

As the binder in case of producing the pressure sensitive recording material, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, gum arabic, gelatin, casein, starch, polyvinyl pyrrolidone or styrene-maleic acid anhydride copolymer may be used.

As the solvent for dissolving the color former, various kinds of solvents such as alkyl benzene, alkyl naphthalene, alkyl biphenyl, diallylethane, hydrogenated terphenyl or chlorinated paraffin series solvent can be used alone or in admixture. The microcapsulation can be carried out by means of a coacervation method, an interface polymerization method, an in-situ method or the like.

In addition, it is also possible to use, for example, various antioxidants, UV-absorbers and surface active agents together as required.

The compound represented by the formula (I) is usually applied to the substrate in an amount of 0.05 to 0.5 g/m2, preferably 0.1 to 0.3 g/m2.

The ratio of an amount of the compound represented by the formula (II) to that of the compound represented by the formula (I) in the material is usually 20 to 200% by weight, preferably 30 to 100% by weight.

The compound represented by the formula (I) in the present invention can be synthesized by condensing an aldehyde derivative and a diphenylethylene derivative as shown in Scheme 1 or a diphenylacrolein derivative and a benzoic acid derivative as shown in Scheme 2 in an organic solvent such as methanol, ethanol, i-propylalcohol, ethylcellosolve, chloroform, tetrachloroethylene, benzene, toluene, chlorobenzene and o-dichlorobenzene at a temperature of from room temperature to 1500C for a period of from several ten minutes to several ten hours in the presence of, if necessary, an acid catalyst such as formic acid, acetic acid, acetic anhydride, p-toluenesulfonic acid, phosphorus oxychloride, sulfuric acid, hydrochloric acid and nitric acid.

Scheme 1

Scheme 2

The compound represented by the formula (II) is disclosed in U.S. Patent Nos. 3,669,711 and 4,444,591.

The developed image on the pressure sensitive recording material of the present invention has an intense absorption in a region of not less than 650 nm, which is necessary for reading by OCR, and is excellent in light fastness. Accordingly, the pressure sensitive recording material is highly valuable in industry.

[Examples] The present invention will now be described more specifically referring to examples but the invention is not restricted only to the following examples unless it goes beyond the scope of the invention.

Svnthesis Example 1 Synthesis of 3-[1, 1-bis (4-dimethylaminophenyl)ethylene-2- yl] -6-dimethylaminophthalide

To 200 ml of toluene, 26.6 g of l,l-bis(4dimethylaminophenyl)ethylene and 20.0 g of 2-formyl-5dimethylaminobenzoic acid were added and reaction was carried out under reflux with heating for 3 hours. After the reaction, 200 ml of an aqueous 5% sodium hydroxide solution was added and stirred for 30 min. Then, a toluene layer was removed. The toluene layer was concentrated and the product was crystallized from methanol to obtain 40.5 g of white crystals. A toluene solution of the crystals rapidly formed a clear greenblue color with silica gel.

m.p. 130 - 1440C, Xmax 673 nm (with acetic acid).

Svnthesis Example 2 Synthesis of 3-[1,1-bis(4-diethylaminophenyl)ethylene-2- yl]-6-dimethylaminophthalide

To 200 ml of toluene, 32.4 g of 1,1-bis(4diethylaminophenyl)ethylene and 20.0 g of 2-formyl-5dimethylaminobenzoic acid were added and reaction was carried out under reflux with heating for 3 hours. After the reaction, 200 ml of an aqueous 5% sodium hydroxide solution was added and stirred for 30 min. Then, a toluene layer was removed. The toluene layer was concentrated and the product was crystallized from methanol to obtain 45.8 g of white crystals. (Further, the product crystallized from diethylene glycol monomethylether instead of methenol had a m.p. of 149 1510C, which is different from the m.p. described below.) A toluene solution of the crystals rapidly formed a clear green-blue color with silica gel.

m.p. 94 - 1190C, Xmax 660 nm (with acetic acid).

Svnthesis Example 3 Synthesis of 3-[1,1-bis(4-pyrrolidinophenyl)ethylene-2- yl] -6-dimethylaminophthalide

To 100 ml of toluene, 14.0 g of l,l-bis(4pyrrolidinophenyl)ethylene and 10.0 g of 2-formyl-5dimethylaminobenzoic acid were added and reaction was carried out under reflux with heating for 3 hours. Then, the same procedure as Synthesis Example 1 was repeated to obtain 10.0 g of white crystals. A toluene solution of the crystals rapidly formed a clear green-blue color with silica gel.

m.p. 131 - 1460C, Xmax 665 nm (with acetic acid).

Synthesis Example 4 Synthesis of 3-[1,1-bis (4-dimethylaminophenyl) ethylene-2 yl]phthalide

To 100 ml of toluene, 13.2 g of 1,1-bis(4 dimethylaminophenyl)ethylene and 7.5 g of 2-formylbenzoic acid were added and reaction was carried out under reflux with heating for 3 hours. Then, the same procedure as Synthesis Example 1 was repeated to obtain 18.5 g of white crystals. A toluene solution of the crystals rapidly formed a clear green color with silica gel.

m.p. 187 - 1890C, #max 633 nm (with acetic acid).

Svnthesis Example 5 Synthesis of 3-[1,1-bis (4-dimethylaminophenyl)ethylene-2- yl] -6-diethylaminophthalide

To 100 ml of toluene, 13.2 g of l,1-bis(4- dimethylaminophenyl)ethylene and 12.5 g of 2-formyl-5diethylaminobenzoic acid were added and reaction was carried out under reflux with heating for 3 hours. Then, the same procedure as Synthesis Example 1 was repeated to obtain 16.5 g of white crystals. A toluene solution of the crystals rapidly formed a clear green-blue color with silica gel.

m.p. 123 - 1250C, Xmax 675 nm (with acetic acid).

According to the above-mentioned Synthesis Examples, the following compounds were also synthesized. Their developed colors and #max's are shown together with their structures.

Blue #max 680 nm Blue #max 650 nm Blue #max 640 nm

Blue Xmax 660 nm Blue #max 650 nm Blue Xmax 630 nm

R2C N < N CH2 H3C 1C CR3 II CH I hmax CR0 O 630 nm C= O OCH3

Blue Xmax 670 nm Example 1 Three point three (3.3) parts (by weight, here and hereinafter) of the compound obtained in Synthesis Example 1 and 6.7 parts of 2-anilino-3-methyl-6-(N-ethyl N-iso-pentylamino)fluoran were dissolved in 90 parts of KMC-113 (an alkylnaphthalene solvent for a pressure sensitive copying paper, ex.Kureha Chemical Industries Co., Ltd.), to which a solution containing 24 parts of gelatin and 24 parts of gum arabic dissolved in 400 parts of water and adjusted to pH 7 was added. The mixture was emulsified by using a homogenizer. After adding 1000 parts of warm water to the emulsion and stirring at 500C for 30 min, about one part of an aqueous 10% sodium hydroxide solution was added and then further stirred at 500C for 30 min. After was adjusting pH to 4.5 by gradually adding a diluted acetic acid and stirring at 500C for about one hour, it was cooled to 0 to 50C and further stirred for 30 min.Then, 35 parts of an aqueous 4% glutaraldehyde solution was gradually added to harden capsules. pH was adjusted to 6 with an aqueous diluted sodium hydroxide solution and then stirring was applied at room temperature for several hours to complete capsulation. The capsule solution was uniformly applied to a paper by a wire bar so that the amount after drying was 7 g/m2 in terms of nonvolatile matter and then dried to obtain a capsule-coated paper (upper paper).

When the paper was laid on a paper coated with zinc 3,5-di(a-methylbenzyl)salicylate (lower paper) and manuscripted by a ball-point pen or struck by a typewriter, dense blue images rapidly appeared on the lower paper.

The image had an intense absorption at 650 to 750 nm and was readable by OCR. The image was excellent in the light fastness.

Example 2 A black image was obtained in the same way as in Example 1 except that 3.5 parts of the compound obtained in Synthesis Example 2, 3.5 parts of 2-anilino-3-methyl6-(N-ethyl-N-n-hexylamino)fluoran, 2.5 parts of 3-chloro 6-cyclohexylaminofluoran, -and 0.5 part of 2-methyl-6-(Nethyl-N-p-tolylamino)fluoran were used instead of 3.3 parts of the compound obtained in Synthesis Example 1 and 6.7 parts of 2-anilino-3-methyl-6-(N-ethyl-N-iso pentylamino) fluoran.

Examole 3 A black-blue image was obtained in the same way as in Example 1 except that 5.7 parts of the compound obtained in Synthesis Example 1, 2.8 parts of 2-anilino3-methyl-6-N,N-diethylaminofluoran and 1.5 parts of 8 N,N-diethylamino-benzo[a]fluoran were used instead of 3.3 parts of the compound obtained in Synthesis Example 1 and 6.7 parts of 2-anilino-3-methyl-6-(N-ethyl-N-isopentylamino)fluoran.

The image was had an intense absorption at 650 to 750 nm and was readable by. OCR. The image was excellent in the light fastness.

Comparative Example 1 A pressure sensitive copying paper was obtained by the same way as in Example 1 except that the compound obtained in Synthesis Example 1 was not used and 10 parts of 2-anilino-3-methyl-6-(N-ethyl-N-iso-pentylamino)fluoran was solely used. The pressure sensitive copying paper formed a black color but had no absorption in a region o not less than 650 nm and, accordingly, was not readable by OCR.

Comoarative Example 2 A black image was obtained by the same way as in Example 3 except that 3, 3-bis (4-dimethylaminophenyl) -6- dimethylaminophthalide was used instead of the compound obtained in Synthesis Example 1. The image had no absorption in a region of not less than 650 nm and, accordingly, was not readable by OCR.

Claims

WRAT IS CAlMED IS:

1. A pressure sensitive recording material comprising as a color former at least one phthalide compound represented by the formula (I):

wherein K1 and R2 represent independently an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkoxyalkyl group having 3 to 7 carbon atoms, an aralkyl group, or an aryl group which may be substituted, or R1 and R2 form a heterocyclic ring together with a nitrogen atom to which R1 and R2 connect; R3 represents a halogen atom, an alkyl group, an alkoxy group or an amino group which may be substituted; and n is 0 to 4, and at least one fluoran compound represented by the formula (Il)

2. A pressure sensitive recording material according to Claim 1, wherein the fluoran compound is represented by the formula (III):

wherein R4 and R5 have the meanings as defined in Claim 1.

3. A pressure sensitive recording material according to Claim wherein the ratio of an amount of the compound represented by the formula (II) to that of the compound represented by the formula (I) in the material is 20 to 200% by weight.

4. A pressure sensitive recording material according to Claim 1,2 or 3 which further comprises at least one compound represented by the following formulae (IV) to (VII):

A @ pressure sensitive recording material as claimed in claim 1 substantially as hereinbefore described