GB2196353A - Sheet recording material containing a phthalide 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 aminophenylindolylphthalide 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 270-380 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 a phthalide 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 precursor (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 following are minimum attributes for recording sheets: (1) color formation density and color formation sensitivity must be sufficiently high; (2) fog should not be formed; (3) the colored substances formed from the color formers should have sufficiently high fastness; and (4) a microcapsule layer containing the color formers should have sufficiently high light fastness.

As color formers able to provide colored substances having excellent fastness in these recording sheets, psubstituted aminophenylindolylphthalide derivatives have been proposed, for example, in Japanese Patent Publications Nos. 21329/73,:16726/74 and 8302/84.

Recording sheets with microcapsules containing the above psubstituted aminophenylindolylphthalide 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 psubstituted aminophenylindolylphthalide 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 p-substituted aminophenylindolylphthalide 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. Examples of such preferred ulraviolet absorbing agentsinclude 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 ultraviolet 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-3r,5'-bis(a,a-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 aminophenylindolylphthalide derivatives.

Preferred as the p-substituted aminophenylindolylphthalide 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 X, Y and Z are independently from each other 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 18 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 (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 may form a pyrrolidinyl group composed of -NR3R4. Synthesis of these compounds is known and can be found, for example, in the above-mentioned Japanese Patent Publications Nos. 21329/73, 16726/74, and 8302/84.

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

T A B L E 1

x l n c m No. R1 R2 R3 ~~~~~~~~ z w x y 3 1 tc -CH3 -C2H5 -C2H5 -OCH3 H H H < > > 3 u U u u u U u H H H o o o o o -CH3 -C2H5 cm -OC2H5 H H H U 01 &num; -CH3 -C2H5 -C2H5 -OC5H11 H H H u cJ U u u u u u' u u u I I I L 1 I I I I 1 I 8 b1 b1 m -C2H5 -C2H5 -ocn2cH H b1 H H 9 U C\1 C N U H5 CJ H H H UUUUUUUUU UU N -C2H5 -CH3 -C4H9 -C4H9 3: H H H UUUUUUU u -C2I{5 u u S H H H l l l l l l l l NK ~t : N = cS N N N N N N U A; u u U u u U U U u U I I I I I I I I I I o uz H c o H aZ H H o U (cont'd)

x X l X rf No ~~~~~~~~~ m Ln ~~~~~~~~~ ~~~~~~~~~~~~~~ C LnX 12 n-C12H25 - uN, -C2H5 -C2H5 -OC2H5 U H H OmO O I ri I I I 14 -C2H5 -CH3 iso-C5H11 -C2H5 -OC2H5 H H H 15 NUN ut U urS I O U1 kZy < H Un N U U U I O O U] UX ,l d rn n n n P: u u u U l l l ur N U) I.S') In 1 ~ N N N N 9 H U U U U ri O O N n et E Z < H < H o U The p-substituted aminophenylindolylphthalide derivatives of formula (I) may be used in admixture with other color formers, such as triphenylmethanephthalide compounds, fluoran compounds, phenothiazine compounds, indolylazaphthalide compounds (e.g., 3-[4-(diethylamino)-2 ethoxyphenyl]-3-(2-methyl-1-octyl-3-indolyl)-4-azaphthalide, 3-[4-(diethylamino)-2-ethoxyphenyl]-3 (2-methyl-i -ethyl-3-indolyl)-4-azaphthalide, 3-[4-(diethylamino)-2-hexyloxyphenylj-3-(2-methyl- 1 - ethyl-3-indolyl)-4-azaphthalide), leucoauramine compounds, rhodaminelactam compounds, triphenylmethane compounds, triazine compounds and 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 aminophenylindolylphthalide 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 aminophenylindolylphthalide 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 agent, encapsulated and coated on a support.

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

Patent 2,712,507, 2,730,456 or 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, 3,856,553, etc., the metal salts of aromatic carboxylic acids as described, for example, in U.S.

Patents 4,559,242, 4,601,920, etc., and phenol resins as described, for example, in U.S.

Patents 3,970,769, 4,076,887, etc.

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-a-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 I TO 10 AND COMPARATIVE EXAMPLES 1 TO 3 A color former and an ulraviolet 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 ,um. 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 solution while stirring. The reaction mixture was raised in temperature to 65"C, and further stirred for 360 minutes.

The capsule dispersion thus obtained was cooled to room temperature and adjusted to pH 9.0 with 20 wt% sodium hydroxide.

To the capsule dispersion thus obtained, 100 parts of a 10 wt% aqueous polyvinyl alcohol solution, 10 parts (as solids) of carboxy-modified styrene-butadiene rubber (SBR) latex, 50 parts of starch granules and 10 parts of calcium carbonate were added. The resultant mixture was adjusted to a solids concentration of 20% by adding water to prepare a color former-containing microcapsule coating solution.

The coating solution was coated on a paper of weight 50 g/m2 with an air knife coater so that the amount of solids coated was 5 g/m2 and then dried to obtain a microcapsule sheet for pressure-sensitive copying.

In the Comparative Examples, the same procedure as above was employed, except that no ultraviolet absorbing agent was employed.

Comparative Test (1) Light Fastness of Microcapsule Layer Two recording sheets were prepared corresponding to each of the Examples and Comparative Examples shown on Table 2. The microcapsule layer of one of each of the microcapsule sheets according to the Examples and Comparative Examples was irradiated with light for 8 hours by the use of a fluorescent light color fading tester (33,000 lux) and then placed on the color developer sheet Upon application of a load of 300 kg/cm2, color was formed. After allowing to stand for 24 hours in a dark place, the spectral absorption curve of the colored substance in the wavelength range of 380 to 780 nm was measured, and the density D at the maximum absorption was determined.

Each of the microcapsule sheets of the Examples and Comparative Examples which had not been irradiated with light was superposed on the color developer sheet and was made to form color by application of a load of 300 kg/cm2. After standing for 24 hours in a dark place, the spectral absorption curve of the colored substance in the wavelength range of 380 to 780 nm was measured, and the density (initial density (Do)) at the maximum absorption was measured.

Measurement of the spectral absorption curve was performed by the use of a Model 307 Hitachi Color Analyzer, and the light fastness value was calculated from the following equation: Density at Maximum Absorption after Light Irradiation with Fluorescent Lamp (D) Fastness = Value Initial Density at Maximum Absorption (Do) The results are shown in Table 2.

A greater light fastness value indicates a greater light fastness of the microcapsule layer.

As can be seen from the results of Table 2, the microcapsule sheet of the present invention is superior in the light fastness of the microcapsule layer as compared to the light fastness of the Comparative Examples.

"Hitachi" is a registered Trade Mark.

T A B L E 2 p-Substituted Aminophenyl- Other Color indolylphthalide Forming Agent Light Fast Compound and and Addition ness of Addition Amount Amount Ultraviolet Abosrbing Agent Microcapsule Example No. Thereof* Thereof* and Addition Amount Thereof* Layer Example 1 Compound 4 6.0 -- 2-(2'-Hydroxy-5'-methylphenyl)- 2.0 0.77 of Table 1 benzotriazole Example 2 " 6.0 -- 2-(2'-Hydroxy-3',5'-di-tert- 2.0 0.74 butylphenyl)-5-chlorobenzotriazole Example 3 " 6.0 -- 2-(2'-Hydroxy-3,5'-di-tert- 2.0 0.73 amylphenyl)benzotriazole Example 4 " 6.0 -- 2-Hydroxy-4-octoxybenzophenone 2.0 0.64 Example 5 " 6.0 -- 2-(2'-Hydroxy-5'-methylphenyl)- 1.0 0.77 benzotriazole 2-(2'-Hydroxy-3'-tert-butyl-5'- 1.0 methylphenyl)-5-chlorobenzotriazole Comparative " 6.0 -- None 0.50 Example 1 Example 6 Compound 3 6.0 -- 2-(2'-Hydroxy-5'-methylphenyl)- 2.0 0.76 of Table 1 benzotriazole (cont'd) p-Substituted Aminophenyl- Other Color indolylphthalide Forming Agent Light Fast Compound and and Addition ness of Addition Amount Amount Ultraviolet Absorbing Agent Microcapsule Example No. Thereof* Thereof* and Addition Amount Thereof* Layer Example 7 Compound 3 6.0 -- 2-(2'-Hydroxy-3',5'-di-tert- 2.0 0.74 of Table 1 butylphenyl)-5-chlorobenzotriazole Comparative " 6.0 -- None 0.48 Example 2 Example 8 Compound 4 4.0 Crystal 2.0 2-(2'-Hydroxy-5'-methylphenyl)- 3.0 0.80 of Table 1 Violet benzotriazole Lactone Example 9 " 4.0 " 2.0 2-(2'-Hydroxy-3'-tert-butyl-5'- 3.0 0.78 methylphenyl)-5-chlorobenzotriazole Exampel 10 " 4.0 " 2.0 2-(2'-Hydroxy-3',5'-di-tert- 3.0 0.78 butylphenyl)-5-chlorobenzotriazole Comparative " 4.0 " 2.0 None 0.45 Example 3 *: 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 aminophenylindolylphthalide 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 m,u.

3. A recording sheet as claimed in Claim 1 or 2, wherein the ultraviolet absorbing agent is a salicylic acid-based ultraviolet absorbing agent selected from phenyl salicylate, p-tert-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'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotri- azole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tertbutylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hy droxy-4'-octoxyphenyl)benzotriazole and 2-[2'-hydroxy-3',5'-bis(ot,xx-dimethylbenzyl)phenyl]benzotri- azole; or a cyanoacrylate-based ultraviolet absorbing agent selected from 2-ethylhexyl-2-cyano3,3'-diphenyl-acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate.

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

5. A recording sheet as claimed in any of Claims 1 to A, wherein the amount of the ultraviolet absorbing agent is 5 to 200% by weight of the tsubstituted aminophenylindolylphthalide derivatives.

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

wherein X, Y and Z are independently from each other 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 18 carbon atoms; W is a hydrogen atom or a halogen atom; Ri 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 may form a pyrrolidinyl group as -NR3R4.

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

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

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

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.