GB2196354A - Sheet recording material containing an azaphthalide dye former - Google Patents

Abstract

A recording sheet, especially for pressure-sensitive recording, consists of a support coated with a binder layer in which are microcapsules containing a solution in an oily solvent of a p-substituted aminophenylindolylazaphthalide derivative as a dye precursor and, in amount of 5-200% by wt of the precursor, an ultraviolet absorbent, especially a benzotriazole substituted at the 2 position with a hydroxy alkylphenyl moiety, preferably absorbing in the range of 380-780 nm. The sheet is used with a developer sheet consisting of an electron acceptor, such as clay, metal salt of an aromatic carboxylic acid or phenolic resin, coated in a binder on a support. The coated surfaces are placed together and local pressure is applied to cause color formation. The u.v.-absorbent protects the dye precursor from loss of color forming ability if the microcapsules are subjected to light before color forming.

Description

SPECIFICATION Sheet recording material containing an azaphthalide dye former The present invention relates to recording sheets and, more particularly, to recording sheets utilizing the color formation reaction between a substantially colorless electron-donating dye and an electron-accepting compound.

Recording sheets using substantially colorless electron-donating dye precursors (hereinafter referred to as "color formers") and electron-accepting compounds (hereinafter referred to as "color developers") are well known and used as pressure-sensitive paper, heat-sensitive paper, light-sensitive and pressure-sensitive paper, electric heat-sensitive recording paper, etc. These recording sheets are described in detail in, for example, British Patent 2,140,449, U.S. Patents 4,480,052, 4,436,920, Japanese Patent Publication No. 23992/85 (corresponding to U.S. Patent 4,181,328 and British Patent 1,552,517) and Japanese Patent Applications (OPI) Nos.

179836/82, 123556/85 and 123557/85 (the term "OPI" as used herein refers to a published unexamined Japanese patent application.

The minimum properties which recording sheets must possess include, for example, (1) suffici- ently high color formation density and color formation sensitivity, (2) absence of fog, (3) fastness to light, heat, and humidity of the colored substances formed from the color formers, and (4) sufficiently high light fastness of a microcapsule layer containing the color formers.

As color formers able to provide colored substances having excellent fastness in these recording sheets, p-substituted aminophenylindolylazaphthalide derivatives have been proposed, for example, in Japanese Patent Publications Nos. 16807/76 (corresponding to U.S. Patents 3,775, 424 and 3,853,869), 38243/76, 20798/83 (corresponding to U.S. Patents 4,275,905 and 4,299,411), and 4856/86 (corresponding to U.S. Patent 4,668,790).

Recording sheets with microcapsules containing the above p-substituted aminophenylindolylazaphthalide derivatives have a disadvantage in that the light fastness of the microcapsule layer is not sufficiently high; that is, the color-forming properties of the microcapsule layer are reduced following irradiation with light.

The present invention is intended to overcome the aforesaid'problems, and the object of the present invention is to provide a recording sheet containing a p-substituted aminophenylindolylazaphthalide derivative in microcapsules wherein the light fastness of the microcapsule layer is improved.

To achieve the foregoing objects, the present invention provides a recording sheet comprised of, on a support, an electron-accepting compound and microcapsules containing a solution of, as a substantially colorless electron-donating dye, a psubstituted aminophenylindolylazaphthalide derivative together with an ultraviolet absorbing agent.

Preferred as ultraviolet absorbing agents are those having spectral absorption in the range of 270 to 380 m,u. Examples of such preferred ultraviolet absorbing agents include salicylic acidbased ultraviolet absorbing agents such as phenyl salicylate, p-tert-butylphenyl salicylate and poctylphenyl salicylate; benzophenone-based ultraviolet absorbing agents such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2, 2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and 2-hydroxy-4-methoxy-5-sulfobenzophenone; benzotriazole-based ultra violent absorbing agents such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tertbutylphenyl)benzotriazole, 2-(2'-hydroxy-3', 5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tertbutyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzo- triazole, 2-(2'-hydroxy-3', 5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole and 2-[2'-hydroxy-3',5'-bis(ex,ex-dimethylbenzyl)phenyl]benzotriazole; and cyanoacrylatebased ultraviolet absorbing agents such as 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate and ethyl2-cyano-3,3'-diphenyl acrylate. Of these compounds, benzotriazole-based ulraviolet absorbing agents are preferred.

The amount of the ultraviolet absorbing agent used is preferably 5 to 200% by weight, more preferably 10 to 100% by weight, of the weight of the p-substituted aminophenylindolylazaphthalide derivatives.

Preferred as the psubstituted aminophenylindolylazaphthalide derivative to be used as the color former in the present invention is at least one compound represented by the following general formula (I):

wherein one of X and Y is -N= and the other is -CH=; Z is a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 18 carbon atoms or an aralkyloxy group having 7 to 13 carbon atoms; W is a hydrogen atom or a halogen atom; R1 is a hydrogen atom or an alkyl group having not more than 12 carbon atoms which is unsubstituted or substituted by a halogen atom, a hydroxyl group, a cyano group or a lower alkoxy group (preferably having 1 to 5 carbon atoms);R2 is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms; and R3 and R4 are independently from each other a hydrogen atom, an alkyl group having not more than 12 carbon atoms which is unsubstituted or substituted by a halogen atom, a hydroxyl group, a cyano group or a lower alkoxy group (preferably having 1 to 5 carbon atoms), a cycloalkyl group having 5 to 7 carbon atoms, a benzyl group, or a phenyl group, and further may form a pyrrolidinyl group composed of -NR3R4.

Synthesis of these compounds is known and can be found, for example, in the abovementioned Japanese Patent Publications Nos. 16807/76, 38243/76, 20798/83 and 4856/86.

Preferred examples of the p-substituted aminophenylindolylazaphthalide compounds represented by the above general formula (I) are shown in Table 1.

TABLE 1 Compound No. R1 R2 R3 R4 z w 1 n-C8H17 CH3 -C2E5 C -C2H5 -OC2H5 H 2 -C2H5 -CH3 -C2H5 -C2H5 -OC6H13 H 3 -C2-H5 -CH3 -C2H5 -C2H5 -OC2H5 H 4 -C2H5 -CH3 -C2H5 -C2H5 -OC5H11 H 5 iso-C5H11 11 -C2H5 -C2115 O 3 H 6 n-C5H11 -CH3 -C2H5 -C2H5 -OC3H7 H

7 n-C8H17 -CH3 z -CH3 - C2R5 H 8 17 -CH3 -N C - C2E5 H 9 -C 2115 -C2H5 -C2H5 Or2 5 H 10 2 5 e 4 9 4 9 -OC2H5 H 11 -CH3 -C2H5 -C2R5 -0C2R5 H 12 H R -C2H5 -C2H5 -OisoCgH11 H 13 -C2H5 -CH3 -C2H5 C2H5 CH2cH2 H Note One of X and Y is -N= and the other is -CH=.

The p-substituted aminophenylindolylazaphthalide derivatives of formula (I) may be used in admixture with other color formers, such as triphenylmethanephalide compounds, fluoran compounds, phenothiazine compounds, indolylphthalide compounds (e.g., 3-[4-(diethylamino)-2-ethoxyphenyl]-3-(2-methyl-1-octyl-3-indolyl)phthalide, 3-[4-(diethylamino)-2-ethoxyphenyl]-3-(2-methyl-1ethyl-3-indolyl)phthalide, 3-[4-(diethylamino)-2-methoxyphenyl]-3-(2-methyl-1-ethyl-3-indolyl)phthalide, etc.), leucoauramine compounds, rhodaminelactam compounds, triphenylmethane compounds, triazine compounds or spiropyran compounds, as described, for example, in U.S. Patent 4,601,920.

In the above case, it is desirable from the viewpoint of fastness of the colored substance that the p-substituted aminophenylindolylazaphthalide derivative of formula (I) employed in the recording sheet of the present invention be used in such an amount as to constitute at least 30% by weight of the total weight of the color formers. Further, the p-substituted aminophenylindolylazaphthalide derivative is preferably used in an amount of from 0.01 to 0.15 g/m2.

The total coating amount of these color formers is preferably 0.03 to 0.15 g/m2.

The color former and electron-acceptor are normally, as in the Examples, in separate layers on separate supports, but they may be on respective layers on opposite sides of the same support, or the microcapsules could be in a layer with the electron acceptor.

The color formers to be used in the present invention are dissolved in a solvent or mixture of solvents together with the ultraviolet absorbing agents, encapsulated and coated on a support.

For example, pressure-sensitive paper is prepared according to the method as described in U.S.

Patents 2,712,507, 2,730,456, 4,601,920, heat-sensitive paper is prepared according to the method as described in U.S. Patent 4,480,052, light-sensitive and pressure-sensitive paper is prepared according to the method as described in Japanese Patent Application (OPI) No.

179836/82, and electric heat-sensitive recording paper is prepared according to the method as described in U.S. Patent 4,173,677.

As the solvents to be used, natural or synthetic oils can be used alone or in combination with each other. Examples of these solvents include cotton seed oil, kerosene, paraffin, naphthene oil, alkylated biphenyl, alkylated terphenyl, chlorinated paraffin, alkylated naphthalene, and diphenylalkane.

Color former-containing microcapsules can be prepared by techniques such as the interfacial polymerization method as described, for example, in U.S. Patents 3,429,827, 3,577,515, 3,886,085, 4,021,595, etc., the inter-polymerization method as described, for example, in U.S.

Patents 3,726,804, 3,796,669, etc., the layer-separation method, the outer-polymerization method and the coacervation method as described, for example, in U.S. Patents 2,800,457, 2,800,458, 3,687,865, etc.

In preparing a coating solution containing color former-containing microcapsules, water-soluble binders and latex-based binders are generally used.

In addition, a capsule-protecting agent such as cellulose powder, starch granules and talc may be added to obtain a color former-containing microcapsule coating solution.

Examples of color developers which react with the color formers used in the recording sheet of the present invention include clay substances such as acid clay, activated clay, attapulgite, zeolite, bentonite, kaolin and the like as described, for example, in U.S. Patents 3,845,383 and 3,856,553, the metal salts of aromatic carboxylic acids as described, for example, in U.S.

Patents 4,559,242 and 4,601,920, and phenolic resin as described, for example, in U.S. Patents 3,970,769 and 4,076,887.

These color developers are preferably used in an amount of from 0.1 to 3.0 g/m2.

The above color developer can be coated on a support such as paper together with a binder such as styrene-butadiene latex to form a color developer sheet.

The performance of the recording sheet of the present invention was tested using a color developer sheet prepared by the method described below.

Preparation of Color Developer Sheet 2 parts by weight (all parts hereafter being by weight) of zinc oxide, 18 parts of calcium carbonate and 4 parts of zinc 3,5-di-ar-methylbenzylsalicylate were added to and mixed with 70 parts of water. The resultant mixture was dispersed for 30 minutes by the use of an attritor. To the dispersion, 2.5 parts (as solids) of carboxy-modified styrene-butadiene rubber (SBR) latex and 12 parts of a 10 wt% aqueous polyvinyl alcohol (PVA) (degree of saponification: 99%; degree of polymerization: 1,000) were added and uniformly stirred to form a coating solution. This coating solution was coated on a paper of 50 g/m2 by the use of an air knife coater so that the solids coated was 4 g/m2 and then dried to obtain a color developer sheet.

The present invention is described in greater detail with reference to the following examples, although it is not intended to be limited thereto.

EXAMPLES 1 TO ii AND COMPARATIVE EXAMPLES 1 TO 4 A color former and an ultraviolet absorbing agent as shown in Table 2 were dissolved in 100 parts of diisopropylnaphthalene and emulsified or dispersed in 100 parts of a 4.4% aqueous solution of the partial sodium salt of polyvinylbenzenesulfonic acid (average molecular weight: 500,000) which had been adjusted to pH 4, to form an emulsion having an average particle diameter of 4.5 jtm. Separately, 6 parts of melamine, 11 parts of a 37 wt% aqueous formaldehyde solution and 30 parts of water were heated to 60"C while stirring. After 30 minutes, a transparent aqueous solution of the mixture of melamine, formaldehyde and melamine-formaldehyde initial condensates was obtained. The pH of the aqueous solution of the mixture was 6.0 to 8.0.The aqueous solution of the mixture of melamine, formaldehyde and melamine-formaldehyde initial condensates is hereinafter referred to as "initial condensate solution". The initial condensate solution thus obtained was added to and mixed with the emulsion as obtained above. The resultant mixture was adjusted to pH 6.0 by adding a 3.6 wt% hydrochloric acid p-Substituted Aminophenylindolylaza- Light Fastphthalide Compound Other Color Forming ness of and Addition Amount Agent and Addition Ultraviolet Absorbing Agent Microcapsule Example No.Thereof* Amount Thereof* and Addition Amount Thereof* Layer Example 7 Compound 3 6.0 - 2-(2'-Hydroxy-3',5'-di-tert- 2.0 0.82 of Table 1 butylphenyl)-5-chlorobenzotriazole Comparative " 6.0 - None 0.59 Example 2 Example 8 Compound 1 4.0 Crystal Violet 2.0 2-(2'-Hydroxy-5'-methylphenyl)- 3.0 0.88 of Table 1 lactone benzotriazole Example 9 " 4.0 " 2.0 2-(2'-Hydroxy-3'-tert-butyl-5'- 3.0 0.86 methylphenyl)-5-chlorobenzotriazole Example 10 " 4.0 " 2.0 2-(2'-Hydroxy-3',5'-di-tert- 3.0 0.86 butylphenyl)-5-chlorobenzotriazole Comparative " 4.0 " 2.0 None 0.51 Example 3 Example 11 " 3.0 Crystal Violet 2.0 2-(2'-Hydroxy-5'-methylphenyl)- 3.0 0.90 lactone benzotriazole Rhodamine B-p- 1.0 nitroanilinolactam (cont'd) p-Substituted Aminophenylindolylaza- Light Fastphthalide Compound Other Color Forming ness of and Addition Amount Agent and Addition Ultraviolet Absorbing Agent Microcapsule Example No. Thereof* Amount Thereof* and Addition Amount Thereof* Layer Comparative Compound 1 3.0 Crystal Violet 2.0 None 0.53 Example 4 of Table 1 lactone Rhodamine B-p- 1.0 nitroanilinolactam *: Parts by weight based on 100 parts of diisopropylnaphthalene

Claims (13)

1. A recording sheet comprising a support having thereon (i) an electron accepting compound and (ii) microcapsules containing (a) as a substantially colorless electron-donating dye precursor, a psubstituted aminophenylindolylazaphthalide derivative and (b) an ultraviolet absorbing agent.

2. A recording sheet as claimed in Claim 1, wherein the spectral absorption of the ultraviolet absorbing agent is in the range of 270 to 380 mu.

3. A recording sheet as claimed in Claim 1, wherein the ultraviolet absorbing agent is selected from a salicylic acid-based ultraviolet absorbing agent selected from phenyl salicylate, ptert-butylphenyl salicylate and p-octylphenyl salicylate; a benzophenone-based ultraviolet absorbing agent selected from 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and 2-hydroxy-4-methoxy-5-sulfobenzophenone; a benzotriazole-based ultraviolet absorbing agent selected from 2-(2'-hydroxy-5'-me thyiphenyi)benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tertbutylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2' hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole and 2-[2hydroxy-3',5'-bis(a, cr-dimethyl- benzyl)phenyl]-benzotriazole; or a cyanoacrylate-based ultraviolet absorbing agent selected from 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate.

4. A recording sheet as claimed in Claim 3, wherein the ulraviolet absorbing agent is a benzotriazole-based ultraviolet absorbing agent.

5. A recording sheet as claimed in any of Claims 1 to 4, wherein the amount of the ulraviolet absorbing agent is 5 to 200% by weight of the p-substituted aminophenylindolylazaphthalide derivatives.

6. A recording sheet as claimed in any of Claims 1 to 5, wherein the p-substituted aminophenylindolylazaphthalide derivative is represented by the following general formula (I):

wherein one of X and' Y is -N= and the other is -CH=; Z is a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 18 carbon atoms or an aralkyloxy group having 7 to 13 carbon atoms; W is a hydrogen atom or a halogen atom; R, is a hydrogen atom or an alkyl group having not more than 12 carbon atoms which is unsubstituted or substituted by a halogen atom, a hydroxyl group, a cyano group, or a lower alkoxy group;R2 is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms; and R3 and R4 are independently from each other a hydrogen atom, an alkyl group having not more than 12 carbon atoms which is unsubstituted or substituted by a halogen atom, a hydroxyl group, a cyano group or a lower alkoxy group, a cycloalkyl group having 5 to 7 carbon atoms, a benzyl group, or a phenyl group, and further may form a pyrrolidinyl group as -NR3R4.

7. A recording sheet as claimed in any preceding claim, wherein the p-substituted aminophenylindolylazaphthalide derivative is used in combination with one or more other color former selected from triphenylmethanephthalide compounds, fluoran compounds, phenothiazine compounds, indolylphthalide compounds, leucoauramine compounds, rhodaminelactam compounds, triphenylmethane compounds, triazine compounds and spiropyran compounds.

8. A recording sheet as claimed in Claim 7, wherein the p-substituted aminophenylindolylazaphthalide derivative constitutes at least 30% by weight of the total weight of the color former.

9. A recording sheet as claimed in any preceding claim, having thereon a layer of said electron-accepting compound and microcapsules containing said precursor and absorbing dye.

10. A recording sheet as claimed in any preceding claim, which is pressure-sensitive.

11. A recording sheet as claimed in Claim 1, substantially as hereinbefore described with reference to any of Examples 1 to 10.

12. An assembly of a pressure-sensitive recording sheet bearing a layer in a binder of microcapsules containing a solution of a substantially colorless electron-donating dye precursor and an ultraviolet absorbing agent as defined in any of Claims 1 to 9 or 11, and a color developer sheet comprising a support bearing a layer of an electron-accepting compound.

13. A colored image formed by local imagewise treatment of a recording sheet as claimed in any of Claims 1 to 10 or an assembly as claimed in Claim 11.