JPH0336034B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a heat-sensitive recording material, particularly a heat-sensitive recording material that has excellent color development and less background fog. ``Prior art'' Heat-sensitive recording materials, such as thermal paper, are produced by dispersing leuco dyes (color formers) and acids (color developers) such as organic acids and phenolic substances into fine particles, and then mixing the two. Auxiliary agents such as binders, sensitizers, fillers, and lubricants are added to the liquid and applied as a coating liquid to a support such as paper, film, or synthetic paper. Alternatively, color recording is obtained by a chemical reaction that occurs when both are melted and brought into contact. A thermal printer or the like equipped with a built-in thermal head is used to heat such a heat-sensitive recording material to develop color. Compared to other recording methods, thermal recording has the following advantages: (1) it makes no noise during recording, (2) it does not require development, fixing, etc., (3) it is maintenance-free, and (4) there is no machinery required for recording. Due to its relatively low cost, it is widely used in facsimile machines, computer output paper, calculator printers, recorders for medical measurements, automatic ticket vending machines, thermal recording labels, etc. Specific examples of heat-sensitive recording materials include, for example, Japanese Patent Publication No. 43-4160.
No. 45-14039, etc.,
Such conventional heat-sensitive recording materials have low thermal responsiveness and, when used for high-speed recording, do not provide sufficient color density and cannot be used satisfactorily for the recent wide range of uses mentioned above. Therefore, several attempts to improve such thermal responsiveness have been proposed, for example,
No. 27599, JP-A No. 48-19231, etc. disclose a method of improving thermal responsiveness by adding a thermofusible substance. However, even with these techniques, fully satisfactory results have not yet been obtained. In addition, the inventors have the following formula He discovered a method of using the compound as a color developer and filed patent applications as Japanese Patent Application No. 59-24311 and Japanese Patent Application No. 59-63277. It should be noted that improving the thermal responsiveness of a thermosensitive recording material often results in other drawbacks such as background fogging. ``Problems to be Solved by the Invention'' There is a desire for a heat-sensitive recording material that does not cause background fog and has high heat responsiveness. "Means for Solving the Problem" In order to solve the above-mentioned problems, the present inventors have conducted intensive research and found that a phenolic compound represented by the following formula (1) and a phenolic compound represented by the following formula (2) are used in the heat-sensitive coloring layer. The present invention was completed by discovering that the above-mentioned problems could be solved by incorporating a phthalimide compound represented by the following formula. [In the formula, R ₁ , R ₂ , R ₃ , and R ₄ are each independently hydrogen,
C _1-4 alkyl, halogen or allyl, X is

[Formula] (R ₅ and R ₆ represent hydrogen or C _1-4 alkyl), S or SO ₂ ] (In the formula, R ₇ is substituted with C _1-4 alkyl; alkoxy (C _1-4 ) alkyl (C _1-4 ); cyclohexyl; substituted aminoalkyl (C _1-4 ); C _1-4 alkyl; Benzyl or phenethyl which may be substituted with methyl, ethyl, or phenyl which may be substituted with halogen) The heat-sensitive recording material of the present invention can be prepared by combining the phenolic compound of formula (1) and the phthalimide compound of formula (2) as follows. It can be obtained by incorporating color-forming substances as shown in the following, a binder, and other necessary fillers, lubricants, sensitizers, etc. into the heat-sensitive color-forming layer. The compounds of formulas (1) and (2) are each used in an amount of 0.5 to 5 times the weight of the color-forming substance. Specific examples of compounds of formula (1) include:

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etc. can be mentioned. Further, as specific examples of the compound of formula (2),

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[Formula] etc. Common examples of color-forming substances include xanthene compounds, triarylmeth compounds, spiropyran compounds, diphenylmethane compounds, and thiazine compounds. -anilino-3-methyl-6-diethylaminofluorane,
2-anilino-3-methyl-6-(methylcyclohexylamino)-fluorane, 2-anilino-
3-Methyl-6-(ethylisopentylamino)-
Fluoran, 2-anilino-3-methyl-6-dibutylaminofluorane, 2-(p-chloroanilino)-3-methyl-6-diethylaminofluorane, 2-(p-fluoroanilino)-3-methyl-6 -dibutylaminofluoran, 2-anilino-3-methyl-6-(p-toluidinoethylamino)-fluoran, 2-(o-chloroanilino)-
6-dibutylaminofluorane, 2-(o-fluoroanilino)-6-diethylaminofluorane,
2-(o-fluoroanilino)-6-dibutylaminofluorane, 2-anilino-3-methyl-6-
Piperidinofluorane, 2-(m-trifluoromethylanilino)-6-diethylaminofluorane, 2-ethoxyethylamino-3-chloro-6
-diethylaminofluorane, 2-anilino-3
-Chloro-6-diethylaminofluorane, 2-
Chloro-3-methyl-6-diethylaminofluorane and the like are triarylmethane compounds such as 3,3'-bis-(p-dimethylaminophenyl)-
6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis-(p-dimethylaminophenyl) phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethyl aminoindol-3-yl) phthalide, etc., as spiropyran compounds such as 3-methyl-3-spirodinaphthopyran, 3-methyl-naphtho-
(3-methoxy-benzo)spiropyran, 1,3,
3-trimethyl-6'-nitro-8'-methoxyspiro (indoline-2,2'-benzopyran), 1,
3,3-trimethyl-6'-nitrospiro (indoline-2,2'-benzopyran), etc., 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halofhenyl-leucoolamine as a diphenylmethane compound Examples of thiazine compounds include benzoylleucomethylene blue and P-nitrobenzylleucomethyllene blue. These leuco dyes may be used alone or in combination. As a binder, methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol,
Carboxy-modified polyvinyl alcohol, polyacrylamide, polyacrylic acid, starch and its derivatives, casein, gelatin, styrene, alkali salts of maleic anhydride copolymers, alkali salts of iso(or diiso)butylene-maleic anhydride copolymers or polyvinyl acetate,
Water-insoluble emulsions such as vinyl chloride/vinyl acetate copolymers, polystyrene, polyacrylic esters, polyurethanes, and styrene/butadiene/acrylic acid copolymers are used. Examples of fillers include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay alumina, magnesium hydroxide, aluminum hydroxide, barium sulfate,
Examples include polystyrene resin, urea-formalin resin, and the like. As other additives, lubricants such as zinc stearate, calcium stearate, and aluminum stearate, various surfactants, antifoaming agents, and the like may be added as necessary. The heat-sensitive recording material of the present invention is prepared by separately pulverizing the above-mentioned color-forming substance and the compounds of formulas (1) and (2) with the addition of a binder, etc., so that the average particle size is 0.5 to 3μ. , and can be obtained by mixing these before use, applying the mixture as a coating liquid to a support, and drying it. The compounds of formula (1) and formula (2) may be ground together or may be ground separately. As the support, any material such as paper, synthetic paper, synthetic resin, or film can be used, but paper is generally used. ``Example'' The present invention will be explained in more detail with reference to Examples. In the examples, parts indicate parts by weight. Example 1 Liquids [A] to [C] were prepared by separately grinding and dispersing mixtures having the following compositions using a sand grinder so that the average particle size was 1 to 3 μm. [A] Liquid 2-(2-fluoroanilino)-6-dibutylaminofluorane 25 parts 25% PVA aqueous solution 20〃 Water 50〃 [B] Liquid Bis-(3-allyl-4-hydroxyphenyl)-sulfone 12.7 parts 25% PVA aqueous solution 16〃 Water 71.3〃 [C] Solution N-methylphthalimide 12.7 parts Calcium carbonate 21.3〃 25% PVA aqueous solution 16〃 Water 50〃 Then [A] solution: [B] solution: [C] solution 6:47:
A heat-sensitive coloring layer forming liquid (coating liquid) is prepared by mixing the liquid in a ratio of 47 to 47, and it is applied to the surface of high-quality paper having a basis weight of approximately 50 g/m ² to a dry solid content of 10 g/m ² and dried. Thermal recording material (thermal recording paper) was obtained. Example 2 2-(2) in the composition of solution [A] used in Example 1
-fluoroanilino)-2-anilino-3-methyl-6- instead of -6-dibutylaminofluorane
This was carried out in the same manner as in Example 1, except that methylcyclohexylaminofluorane was used and N-(2,3-dimethylphenyl)phthalimide was used instead of N-methylphthalimide in the composition of liquid [C]. A thermosensitive recording material of the invention was obtained. Example 3 Bis- in the composition of liquid [B] used in Example 1
Bis-(2-methyl-4-hydroxy-5-tertbutylphenyl) sulfide is used instead of (3-allyl-4-hydroxyphenyl)-sulfone, and N-methylphthalimide is used in the composition of liquid [C]. A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that N-(2-chlorophenyl)phthalimide was used instead of. Example 4 Bis- in the composition of liquid [B] used in Example 1
2,2-bis-(4-hydroxyphenyl)-propane was used in place of (3-allyl-4-hydroxyphenyl)-sulfone, and in place of N-methylphthalimide in the composition of liquid [C]. A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that N-methoxyethyl phthalimide was used. Examples 5 to 7 The heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the following compound was used in place of N-methylphthalimide in the composition of liquid [C] used in Example 1. I got it. Example 5 N-benzyl phthalimide Example 6 N-cyclohexyl phthalimide Example 7 N-(β-dimethylaminoethyl) phthalimide comparative example 1 Substitute for N-methyl phthalimide in the composition of liquid [C] used in Example 1 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that stearamide was used. Comparative Example 2 Bis(3) in the composition of liquid [B] used in Example 1
-2,2-bis-(p-hydroxyphenyl) instead of -allyl-4-hydroxyphenyl)sulfone
- Using propane and N- in the composition of liquid [C]
A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that ethylene bisstearamide was used instead of methyl phthalimide. The test results of the heat-sensitive recording materials (thermal recording paper) obtained in the above Examples and Comparative Examples are shown in the following table.

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[Table] "Effects of the Invention" According to the present invention, a heat-sensitive recording material excellent in both background fog and thermal response can be obtained.

Claims (1)

[Claims] 1 Formula (1) in the thermosensitive coloring layer [In formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represent hydrogen, C _1-4 alkyl, halogen or allyl,
is a compound of [formula] (R ₅ and R ₆ represent hydrogen or C _1-4 alkyl), S or SO ₂ ) and formula (2) [In formula (2), R ₇ is C _1-4 alkyl; alkoxy (C _1-4 ) alkyl (C _1-4 ); cyclohexyl; substituted aminoalkyl (C _1-4 ); C _1-4 alkyl represents benzyl or phenethyl which may be substituted with , or phenyl which may be substituted with methyl, ethyl, or halogen.