JPH0549031B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a recording material, and more particularly to a recording material with improved stability of colored images. (Prior Art) Recording materials using an electron-donating colorless dye and an electron-accepting compound are already well known as pressure-sensitive paper, heat-sensitive paper, light-sensitive pressure-sensitive paper, electrically conductive heat-sensitive recording paper, and the like. For example, US Patent 2140449, US Patent
4480052, 4436920, Special Publication No. 60-3922, No. 57 No.
-179836, 60-123556, 60-123557, etc. are detailed. The performance that a recording material should have is (1) sufficient color density, (2) no fogging, (3) sufficient fastness of the color material after color development, and (4) color development. The color must be appropriate and suitable for copying machines, (5) the S/N ratio must be high, (6) the coloring material must have sufficient chemical resistance, and (7) it must be easily soluble in organic solvents. However, we have not yet obtained anything that completely satisfies these requirements. Especially in recent years, with the diversification of requirements for recording systems,
Research is being carried out to improve these characteristics. Among these, requirements regarding (3) are especially strong for blue color recording materials. Conventionally, diphenylmethane compounds, triphenylmethane compounds, phthalide compounds, leucomethylene blue compounds, and the like have been known as compounds that develop a blue to blue-purple color. However, each of these compounds has drawbacks. For example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e., crystal violet lactone) develops quickly and exhibits a deep blue color, but the light resistance of the colored image is extremely poor. 3,7-bis(dimethylamino)-10-benzoylphenothiazine (i.e., benzoylleucomethylene blue), which is a leucomethylene blue-based compound, has extremely excellent light resistance in its color image, but the color development is very slow and cannot be easily observed under organic microscope. It has the disadvantage of very poor color development with coloring agents. In addition, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-
2-methylindol-3-yl)-4 or 7
-Azaphthalide has the drawbacks of poor solubility in the solvent used for encapsulation and strong self-coloring property. The present inventors investigated the oil solubility, water solubility, partition coefficient, pKa, polarity of substituents, position of substituents, and crystalline dissolution when mixed with each of electron-donating colorless dyes and electron-accepting compounds. We have pursued the development of good materials for recording materials and recording materials, focusing on characteristics such as changes in sex. (Object of the Invention) Therefore, an object of the present invention is to provide a recording material which has good stability of a colored image and also satisfies other requirements. (Structure of the Invention) An object of the present invention is to provide a recording material that utilizes color development through contact between an electron-donating colorless dye and an electron-accepting compound, using crystal violet lactone as the colorless dye and the following general colors (): (In the formula, R and R' may be the same or different and represent an alkyl group having 1 to 10 carbon atoms,
R ₁ may have an alkoxy group or phenyloxy group as a substituent, and R 1 represents an alkyl group or phenyl group having 1 to 12 carbon atoms, and R ₂ represents an alkyl group or phenyl group having 1 to 8 carbon atoms. , Y represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms). This was achieved by a recording material characterized by using a mono- or di-substituted salicylic acid derivative or a metal salt thereof having a total carbon number of 13 or more. Some examples of these include 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3-(4-diethylamino-2-ethoxy phenyl)-3-(1-isoamyl-2-methylindol-3-yl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl-3-(1-β)
-ethoxyethyl-2-methylindole-3-
yl) phthalide, 3-(4-diethylamino-2
-ethoxyphenyl)-3-(1-β-phenoxyethyl-2-methylindol-3-yl)phthalide, 3-(4-dibutylamino-2-ethoxyphenyl)-3-(1-ethyl-2- Methylindol-3-yl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-phenylindol-3-yl)phthalide, 3-(4-N-cyclohexyl) -N-ethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3-(4-N-ethyl-N-isoamylamino-2-isoamyloxyphenyl) enyl)-3-(1-
Ethyl-2-methylindol-3-yl)phthalide, 3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3-(4-N- cyclohexyl-N-ethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3-(4-N-butyl-
N-ethylamino-2-methylphenyl)-3-
(1-ethyl-2-methylindol-3-yl)
Phthalide, 3-(4-diethylaminophenyl)-
3-(1-ethyl-2-methylindole-3-
yl) phthalide, 3-(4-diethylamino 2-
ethoxyphenyl)-3-(1-hexyl-2-methylindol-3-yl)phthalide, 3-(4
-diethylamino-2-ethoxyphenyl)-3
-(1-octyl-2-phenylindole-3
-yl)phthalide, 3-(4-diethylamino-
2-ethoxyphenyl)-3-(1-octyl-2
-methylindol-3-yl)phthalide, and the like. The usage ratio of crystal violet lactone and p-substituted aminophenylindolphthalide is:
Although it is determined by performance, color development phase, and economical efficiency, it is preferable that the p-substituted aminophenylindolphthalide derivative accounts for 10% or more, especially 30% or more.
% or more. Among the p-substituted aminophenyl indolyl phthalide derivatives according to the present invention, 4-substituted amino-2-alkoxyphenylindolphthalide is preferred from the viewpoint of its various color development properties. The electron-accepting compound used in the recording material according to the present invention is a mono- or di-substituted salicylic acid derivative or a metal salt thereof having a total carbon number of 13 or more. Examples of the substituent of the salicylic acid derivative include an alkyl group having 1 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an alkoxy group which may have a substituent having 1 to 20 carbon atoms, and a halogen atom. To give some examples,
3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-dithyabutylsalicylic acid, 3,5-di-dodecylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3-phenyl-
5-(α,α-dimethylbenzyl)salicylic acid,
3,5-di-(α-methylbenzyl)salicylic acid,
3,5-dicyclohexylsalicylic acid, 4-dodecyloxysalicylic acid, 4-octadecyloxysalicylic acid, 4-benzyloxysalicylic acid, 4
-β-phenethyloxysalicylic acid, 4-β-phenoxyethoxysalicylic acid, 4-(4-phenoxybutoxy)salicylic acid, 5-(p'-α'-methylbenzyl-p-α-methylbenzyl) Salicylic acid, 4-β-p-trioxyethoxysalicylic acid, 4-β-p-methoxyphenoxyethoxysalicylic acid, 4-β-p-butylphenoxyethoxysalicylic acid, 5-α-(α-methylbenzyl)
Examples include phenethylsalicylic acid and the like and metal salts thereof (eg, zinc salts, aluminum salts, calcium salts, etc.). These may be used alone or in combination. The recording material according to the present invention is made of a combination of a specific electron-donating colorless dye and an electron-accepting compound. It is particularly advantageous in terms of long-term preservation of records, since it hardly changes color or fades even when exposed to light, heating, or humidification. In the recording material according to the present invention, crystal violet lactone and p-substituted aminophenyl indolylphthalide are substituted with well-known triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, and indolyl azaphthalide. compound, leucoauramine compound,
It is also possible to assemble recording materials by using it in combination with various compounds such as rhodamine lactam compounds, triphenylmethane compounds, triazene compounds, and spiropyran compounds. In this case, it is preferable to use the colorless dye of the present invention in an amount of 60% or more from the viewpoint of improving properties. When these colorless dyes and electron-accepting compounds are applied to recording materials, they are used in the form of fine dispersions or fine droplets. For use with pressure sensitive paper, U.S. Patent No. 2505470
No. 2505471, No. 2505489, No. 2548366, No. 2505471, No. 2505489, No. 2548366, No.
No. 2712507, No. 2730456, No. 2730457, No.
It can take various forms as described in prior patents such as No. 31034040, No. 3418250, and No. 4010038. Most commonly they consist of at least one pair of sheets containing separately an electron-donating colorless dye and an electron-accepting compound. U.S. patent for method of manufacturing capsules
A method using coacervation of a hydrophilic colloid sol described in No. 2800457 and No. 2800458,
U.S. Patent No. 867797, U.S. Patent No. 950443, U.S. Patent No. 989264, U.S. Patent No.
Examples include the interfacial polymerization method described in US Pat. No. 1,091,076, and the method described in US Pat. No. 3,103,404.
The capsule wall material is preferably a synthetic resin wall material, for example a polyurethane and/or polyurea capsule. In general, electron-donating colorless dyes are used alone or in combination with solvents (synthetic oils such as alkylated naphthalene, alkylated diphenyl, alkylated diphenylmethane, alkylated terphenyl, chlorinated paraffin; vegetable oils such as cotton oil and castor oil; Animal oil:
A coloring agent sheet is obtained by dissolving the coloring agent in mineral oil, a mixture thereof, etc.) and incorporating it into microcapsules, and then coating it on a support such as paper, high-quality paper, plastic sheet, resin-coated paper, etc. Neutral paper is particularly preferred as the support. The combination of colorless electricity-donating dyes of the present invention has good solubility in synthetic oils such as alkylated naphthalenes, alkylated diphenyls, and alkylated diphenylalkanes, so it can be used in combination with paraffinic oils that have low solubility. There are advantages. In addition to the electron-donating colorless dye, ultraviolet absorbers, antioxidants, and the like may be added as additives to the microcapsules. In particular, from the viewpoint of improving the stability of the electron-donating colorless dye in the capsule before use and the coloring of the capsule, benzotriazole-based ultraviolet absorbers, hindered amine-based antioxidants, hindered phenol-based antioxidants, aniline It is preferable to add a quinoline-based antioxidant, a quinoline-based antioxidant, and the like. The electron-accepting compound, alone or in combination, or together with other electron-accepting compounds, is dispersed in a binder such as styrene-butadiene latex or polyvinyl alcohol, and is used as a support for paper, plastic sheets, resin-coated paper, etc. together with the pigments described below. A developer sheet is obtained by applying it to the body. The amounts of the electron-donating colorless dye and the electron-accepting compound to be used depend on the desired coating thickness, the form of the pressure-sensitive copying paper, the capsule manufacturing method, and other conditions, and may be appropriately selected depending on the conditions. It is easy for one skilled in the art to determine this amount to use. When used in thermal paper, the electron-donating colorless dye and electron-accepting compound should be 10μ or less in the dispersion medium.
It is preferably used after being pulverized and dispersed to a particle size of 3μ or less. A water-soluble polymer aqueous solution having a concentration of about 0.5 to 10% is generally used as the dispersion medium, and dispersion is carried out using a ball mill, sand mill, horizontal sand mill, attritor, colloid mill, etc. The ratio of the electron-donating colorless dye to the electron-accepting compound used is preferably between 1:10 and 1:1 in terms of polymerization ratio, and particularly preferably between 1:5 and 2:3. At that time, nitrogen-containing organic compounds such as fatty acid amide, acetoacetanilide, diphenylamine, benzamide, carbazole, etc. or 2,
3-di-m-tolylbutane, o-fluorobenzoyldurene, chlorobenzoylmesitylene,
4,4'-dimethylbiphenyl, or carboxylic acid esters such as dimethyl isophthalate, diphenyl phthalate, dimethyl terephthalate, methacryloxybiphenyl, etc., or polyether compounds such as di-m-tolyloxyethane, β-phenoxylene, etc. Siethoxyanisole, 1-phenoxy-2-p-ethylphenoxyethane, bis-β-(p-methoxyphenoxy)ethoxymethane, 1-2'-methylphenoxy-2-''-ethylphenoxyethane, 1-tolyloxy-2-p
-Methylphenoxyethane, 1,2-diphenoxyethane, 1,4-diehnoxybutane, bis-
β-(p-ethoxyphenoxy)ethyl ether,
1-phenoxy-2-p-chlorophenoxyethane, 1-2'-methylphenoxy-2-4''-ethyloxyphenoxyethane, 1-4'-methylphenoxy-2-4''-fluorophenoxyethane, etc. It is preferable to use a compound with a melting point of 75°C to 130°C. These are used in finely dispersed form at the same time as a colorless dye or at the same time as an electron-accepting compound. In particular, it is preferable to disperse the colorless dye at the same time from the viewpoint of preventing fogging. The amount of these used is added at a weight ratio of 20% or more and 300% or less, particularly preferably 40% or more and 150% or less, based on the electron-accepting compound. The coating liquid obtained in this way further contains:
Additives are added to meet various requirements. Examples of additives include dispersing oil-absorbing substances such as inorganic pigments and polyurea fillers in the binder to prevent staining of the recording head during recording, and also to improve releasability from the head. For this purpose, fatty acids, metal soaps, etc. are added. Therefore, in addition to colorless dyes and electron-accepting compounds that directly contribute to color development, pigments, waxes,
Additives such as antistatic agents, ultraviolet absorbers, antifoaming agents, conductive agents, fluorescent dyes, and surfactants are coated on the support to form a recording material. Specifically, pigments such as kaolin, calcined kaolin, talc, waxite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, calcined gypsum, silica, magnesium carbonate, titanium oxide, alumina, barium carbon, and sulfuric acid are used as pigments. It is selected from barium, mica, microballoon, urea-formalin filler, polyethylene particles, cellulose filler, etc. with a particle size of 0.1 to 15μ. Examples of waxes include paraffin wax, carboxy-modified paraffin wax, cownabar wax, microcrystalline wax, polyethylene wax, and higher fatty acid esters. Examples of the metal soap include polyvalent metal salts of higher fatty acids, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. It is applied dispersed in a binder.
Water-soluble binders are generally used, such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride. Examples include copolymers, polyacrylic acid, polyacrylic acid amide, methylol-modified polyacrylamide, starch derivatives, casein, and gelatin. In addition, in order to impart water resistance to these binders, water-resisting agents (gelling agents, cross-linking agents) may be added, or emulsions of hydrophobic polymers, specifically styrene-
Butadiene rubber latex, acrylic resin emulsion, etc. can also be added. The coating liquid is base paper,
It is applied to high-quality paper, synthetic paper, plastic sheet, or neutral paper at a rate of about 2 to 10 g/m ² . Furthermore, a protective layer of approximately 0.2 to 2 μm consisting of a water-soluble or water-dispersible polymer compound such as polyvinyl alcohol, hydroxyethyl starch, or epoxy-modified polyacrylamide and a crosslinking agent is provided on the surface of the coating layer to improve resistance. You can also do it. When used for thermal paper, also OLS2228581
No. 2110854, Japanese Patent Publication No. 52-20142, and the like. Alternatively, operations such as preheating, humidity control, or stretching of coated paper may be added prior to recording. Electric thermal paper is disclosed in, for example, JP-A-49-11344 and JP-A-50.
-Manufactured by the method described in No. 48930.
Generally, a conductive substance, a basic dye mainly containing the fluoran derivative of the present invention, and an electron-accepting compound are dispersed together with a binder and a solution is applied to a support such as paper, or a conductive substance is applied to the support to form a conductive layer. The electrically conductive thermal paper of the present invention is produced by forming a coating composition and applying thereon a coating liquid in which a colorless dye, an electron-accepting substance, and a binder are dispersed. Note that the sensitivity can also be improved by using the thermoplastic substance described above in combination. The photosensitive pressure sensitive paper is manufactured by the method described in, for example, Japanese Patent Application Laid-Open No. 179836/1983. Generally silver iodobromide,
Photoinitiators such as silver bromide, silver behenate, Michler's ketone, benzoin derivatives, benzophenone derivatives and polyfunctional monomers such as crosslinkers such as polyallylates, poly(meth)acrylates, poly(meth)acrylamides, colorless dyes and optionally It is encapsulated together with a solvent in a capsule walled with a synthetic resin such as polyether urethane or polyurea. After imagewise exposure, the colorless dye in the unexposed area is brought into contact with a color developer to be colored. The electron-donating colorless dye according to the present invention is synthesized by a known method. For example, the corresponding benzoylbenzoic acid and indole, or the corresponding carboxybenzoylindole and aniline derivative are combined in the presence of a condensing agent such as acetic anhydride or phosphorus oxychloride, and if necessary, evaporated with chloroform, toluene, benzene chloride, etc. After reacting for 1 to 10 hours at a reaction temperature of 50 to 130°C using a volatile organic inert solvent, the reaction product is placed in ice water or cold dilute hydrochloric acid to hydrolyze the condensing agent, and then the above volatile organic inert solvent is added. is added, and further made alkaline with an aqueous sodium hydroxide solution to transfer the generated pigment into the solvent.
It is obtained by distilling off the solvent under reduced pressure. (Examples of the Invention) Examples are shown below, but the present invention is not limited only to these examples. Examples 1-4 Preparation of color former sheet The electron-donating colorless dye shown in Table 1 was dissolved in 30 g of alkylated naphthalene. Add this solution to water with 6g of gelatin and 4g of gum arabic dissolved in it.
It was added to 50g of the oil while stirring vigorously to emulsify it to form oil droplets with a diameter of 1 to 10μ, and then 250g of water was added.
Acetic acid was added little by little to bring the pH to about 4 to cause coacervation, creating a wall of gelatin and gum arabic around the oil droplets, and formalin was added and the pH was raised to 9 to harden the wall. The thus obtained microcapsule dispersion was applied to paper and dried to obtain a color former sheet. Preparation of color developer sheet: 5% of 20g of the electron-accepting biocompound shown in Table 1.
It was dispersed in 200 g of water-soluble SBR latex, and further 20 g of kaolin (diyodia kaolin) was added and well dispersed to prepare a coating liquid. The obtained coating liquid was applied to paper and dried to obtain a color developer sheet. When the thus prepared color forming agent sheet and color developing agent sheet were brought into contact with each other and pressure or impact was applied, a blue printed image was instantaneously obtained. The results of the light fastness test and hue test of this image are shown in Table 1. Comparative Examples 1 to 3 A color former sheet and a color developer sheet were obtained in the same manner as in Example 1 except that the electron-donating colorless dye and electron-accepting compound in Example 1 were changed to the compounds shown in Table 1. Color was developed in the same manner as in Example 1, and a light fastness test was conducted. The results are shown in Table 1. [Light resistance test of colored material] The colored material was irradiated with 32,000 lux light for 10 hours, and the color density before and after irradiation was compared to determine the survival rate. Chromogen residual rate = Color density after test / Color density before test x 10
0 (%) [Hue test] The microcapsule layer of the color former sheet was layered on the developer sheet, and a load of 300 kg/cm ² was applied to develop color. After leaving this in a dark place for 24 hours, the wavelength
The spectral absorption curve of the color former between 380 and 780 nm was measured, the absorption maximum (λ _nax ) was measured, and the hue was observed.

【table】

[Table] From the results in Table 1, it can be seen that the recording material of the present invention clearly has excellent light resistance and has a preferable blue hue. Example 5 Preparation of coloring agent sheet Partial sodium salt of polyvinylbenzenesulfonic acid (manufactured by National Starch Co., Ltd., VERSA,
TL500, average molecular weight 500,000) was added to 95 parts of hot water at about 80°C with stirring and dissolved. Dissolve in approximately 30 minutes and then cool. The pH of the aqueous solution is 2-3
A 20% by weight aqueous sodium hydroxide solution was added to this to adjust the pH to 4.0. while 1.0% crystal violet lactone and 2.5% 3-(4-
diethylamino-2-ethoxyphenyl)-3
-(1-octyl-2-methylindole-3
100 parts of diisopropylnaphthalene in which -yl)phthalide was dissolved was emulsified and dispersed in 100 parts of a 5% aqueous solution of the partial sodium salt of the polyvinylbenzenesulfonic acid to obtain an emulsion having a particle size of 4.5 μm in average diameter. Separately, add 6 parts of melamine, 11 parts of 37% by weight formaldehyde aqueous solution, and 30 parts of water at 60°C.
After heating and stirring for 30 minutes, a transparent mixed aqueous solution of melamine, formaldehyde and melamine-formaldehyde initial condensate was obtained. The pH of this mixed aqueous solution was 6-8. Hereinafter, this mixed aqueous solution of melamine, formaldehyde, and melamine-formaldehyde initial condensate will be referred to as an initial condensate solution. Add and mix the initial condensate solution obtained by the above method to the above emulsion, and while stirring,
The pH was adjusted to 6.0 with a wt% hydrochloric acid solution, the liquid temperature was raised to 65°C, and stirring was continued for 360 minutes. This capsule liquid was cooled to room temperature and adjusted to pH 9.0 with 20% by weight sodium hydroxide. 200 parts of a 10% by weight polyvinyl alcohol aqueous solution and starch particles for this capsule dispersion.
A microcapsule coating solution containing a coloring agent was prepared by adding 50 parts and adjusting the solid content concentration to 20% by adding water. This coating solution was applied to a 50 g/m ² base paper using an air knife coater so that the solid content was 5 g/m ² and dried to obtain a color former-containing microcapsule sheet. Preparation of color developer sheet 10 parts of zinc 3,5-di-α-methylbenzylsalicylate was added to 20 parts of 1-isopropylphenyl-2-phenylethane and dissolved by heating at 90°C.
Add this to 2% polyvinyl alcohol (PVA-205).
(manufactured by Kuraray) and further added 0.1 part of 10% sodium sulfosuccinate aqueous solution as a surfactant to prepare an emulsion using a homogenizer so that the average particle size of the emulsion was 3μ. Next, 80 parts of calcium carbonate, 20 parts of zinc oxide,
A dispersion of 1 part of sodium hexametaphosphate and 200 parts of water was prepared using a Keddy Mill, and after mixing the above emulsion, 10% of sodium hexametaphosphate was added as a binder.
Add 100 parts of water-soluble PVA-110 (manufactured by Kuraray) and 10 parts (as solid content) of carboxy-modified SBR latex (SN-304, manufactured by Sumitomo Nogatux), and adjust by adding water so that the solid content concentration is 20%.
A coating liquid (A) was obtained. Next, 10 parts of zinc 3,5-di-α-methylbenzylsalcylate, 80 parts of calcium carbonate, and zinc oxide.
20 parts, 1 part sodium hexametaphosphate and water
Using 200 parts, it was uniformly dispersed using a sand grinder so that the average particle size was 3 μm. Add 10% PVA-110 (manufactured by Kuraray) to the resulting dispersion.
100 parts of an aqueous solution and 10 parts (as solid content) of carboxy-modified SBR latex (SN-304 manufactured by Sumitomo Naugatux) were added, and water was added to adjust the solid content concentration to 20% to obtain a coating liquid (B). Coating liquid (A) and coating liquid (B) were mixed at A/B = 50/50 in terms of zinc 3,5-di-α-methylbenzylsalicylate, and 5.0 g/cm ² was applied to 50 g/m ² base paper. The color developer sheet was coated using an air knife coater and dried to obtain a color developer sheet. When the color was developed in the same manner as in Example 1, a blue printed image was obtained. This image had high density and excellent light resistance and heat resistance. Example 6 10 parts of crystal violet lactone and 3-
(4-diethylamino-2-ethoxyphenyl)-
3-(1-ethyl-2-methylindole-3-
A dispersion was prepared by mixing and pulverizing 20 parts of phthalide with 150 parts of a 10% polyvinyl alcohol aqueous solution and 70 parts of water using a ball mill for 12 hours. The particle size after grinding was approximately 1.5 microns. (Component A) the other 30 parts of 4-β-(p-methoxyphenoxy)
Zinc ethoxysalicylate, 30 parts of a 10% polyvinyl alcohol aqueous solution of 150 parts of 2-benzyloxynaphthalene, and 55 parts of water were mixed and ground using a sand mill to prepare a dispersion. The particle size of the insoluble material after pulverization was about 2 microns. (Component B) Next, 5 parts of component A and 40 parts of component B were mixed, coated on paper, and dried to obtain thermal paper. When this thermal paper was heated with a thermal pen, it turned blue. The color image obtained was very stable against light, and even when the image was irradiated with an ultraviolet lamp for one hour, there was almost no change in either hue or density.

Claims (1)

[Claims] 1. In a recording material that utilizes color development due to contact between an electron-donating colorless dye and an electron-accepting compound, the colorless dye includes crystal violet lactone and the following general colors (): (In the formula, R and R' may be the same or different and represent an alkyl group having 1 to 10 carbon atoms,
R ₁ represents an alkyl group having 1 to 12 carbon atoms or a phenyl group, which may have an alkoxy group or a phenyloxy group as a substituent, and R ₂ represents an alkyl group having 1 to 8 carbon atoms or a phenyl group. , Y represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms). A recording material characterized by using a mono- or di-substituted salicylic acid derivative or a metal salt thereof having a total carbon number of 13 or more.