JPS61215087A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having high sensitivity, by containing a coupler being at least one compound selected from compounds represented by formulae (I), (II) and a sensitizer being an 1, 4- dihydroxynaphthalene derivative represented by formula (III) in a thermal color forming layer. CONSTITUTION:In a thermal recording material provided with a thermal color forming layer based on a leuco dye and a coupler capable of allowing said leuco dye to develop a color under heating, an 1, 4-dihydroxynaphthalene derivative represented by formula (III) is a compound with m.p. of 70-120 deg.C and melted sharply at this temp. and excellent in the solubility and compatibility with the coupler or the leuco dye and, therefore, the color forming sensitivity thereof becomes high. The couplers represented by formulae (I), (II) can be together used along with an electron acceptive substance reacting with the leuco dye under heating to allow the same to develop a color and, for example, a phenolic substance, an org. or inorg. acidic substance or esters or salts thereof are used. Further, as an auxiliary additive component, a filler, a surfactant, a heat-meltable substance (or lubricant) or the like can be together used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer.

[Prior art]

Recently, various recording sheets have been researched and developed and put into practical use in the information recording field in response to social demands such as the diversification and increase of information, resource conservation, and pollution-free technology.Among them, thermal recording sheets are , (]) Colored images are recorded simply by heating to R1, and no complicated development process is required; (2)
(3) paper is often used as a support; Because the support Cos. I- is not only inexpensive, but also has the advantages that the resulting recording sheet has a feel similar to that of plain paper, it is suitable for use in computer output 1, in the field of printers such as calculators, in the field of recorders for medical measurement, etc. It is widely used in the fields of low and high speed facsimiles, automatic ticket vending machines, thermal copying, etc.

The above-mentioned heat-sensitive recording sheet is usually manufactured by coating a support such as paper, synthetic paper, or synthetic resin film with a heat-sensitive coloring layer solution containing a coloring component that can cause a coloring reaction when heated, and drying it. A colored image is recorded on the heat-sensitive recording sheet thus obtained by heating it with a thermal pen or a thermal head. Conventional examples of such heat-sensitive recording sheets include, for example, the heat-sensitive recording sheet disclosed in Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-14039; Responsiveness was low, and sufficient color density could not be obtained during high-speed recording.

As a method for improving such drawbacks, for example, Japanese Patent Application Laid-Open No. 49-3
No. 4842 discloses acetamide, stearamide, m
Nitrogen-containing compounds such as -21-roaniline and dinitrile phthalate, acetoacetanilide in JP-A-52-106746, and N-containing compounds in JP-A-53-11036.
, N-diphenylamine derivative, benzamide derivative,
The speed can be increased by incorporating carbazole derivatives, alkylated biphenyls and biphenylalkanes in JP-A No. 53-39139, and p-oxybenzoic acid ester derivatives in JP-A-56-144193. , methods for increasing sensitivity have been disclosed, but among these, a method using a P-oxybenzoic acid ester derivative as a color developer is said to be the most effective.

However, recently, the speed of thermal facsimile has become even faster.
As miniaturization is being considered, there is a growing demand for higher sensitivity of heat-sensitive recording sheets, and the above-mentioned methods for increasing sensitivity do not provide sufficiently satisfactory results.

〔the purpose〕

An object of the present invention is to provide a heat-sensitive recording material that has higher sensitivity than conventional products.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive color-forming layer is provided on a support, the heat-sensitive color-forming layer mainly contains a leuco dye and a color developer capable of coloring the leuco dye when heated, in the heat-sensitive color-forming layer, the formula: (1) A color developer using at least one compound represented by the formula (U) and the general formula (m) (wherein R1 and R2 are hydrogen, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a benzyl group, and R3 represents hydrogen or a benzyl group.

In the present invention, the general formula (II) used as a sensitizer
Specific examples of the 1,4-dihydroxynaphthalene derivative represented by T) include the following.

The 1,4-dihydroxynaphthalene derivative represented by the above general formula (III) is a compound with M and P of 70 to 120°C, and it melts sharply at this temperature, and has high solubility with color developers and leuco dyes. Because of the excellent compatibility, the sensitivity (dynamic color development sensitivity) of the heat-sensitive recording material is thought to be increased.

The leuco dyes used in the present invention may be applied singly or in a mixture of two or more types. As such leuco dyes, those applied to this type of heat-sensitive material can be arbitrarily applied. Phenylmethane type, fluorane type,
Leuco compounds of dyes such as phenothiazine, auramine, spiropyran, and indolinophthalide are preferably used.

Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dibutylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet 1-heractone), 3.3-bis (p-dimethylaminophenyl)-6-dibutylaminophenyl, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, -only-3,3-bis(p-dibutylaminophenyl)phthalide, 3- Cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- (N-(3'-trifluoromethylphenyl)
amino)-6-dinithylaminofluorane, 2-(3
, 6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, Q- 3-diethylamino-7-( 0-chloroanilino)fluoran, 3-dibutylamino-7-(0-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N- diethylamino)-5-methyl-7-(
N.

N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2'- 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy- 5'-21-phenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy- 4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N -benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluorane, 3 -(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α -phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-47-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

Further, the color developer represented by the formulas (1) and (n) used in the present invention may be one of various commonly used conventional color developers that react with the leuco dye when heated to develop color. Electron-accepting substances can be used in combination, and specific examples include phenolic substances such as those shown below,
Examples include organic or inorganic acidic substances, esters and salts thereof, and the like.

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di t,e
rt-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis (2,6
-dibromophenol), 4,4'-isopropylidene bis(2,6-dichlorophenol), 4,4'-isopropylidene bis(2-methylphenol), 4,4'
-isopropylidene bis(2,6-dimethylphenol), 4,4'-isopropylidene bis(2-tert-
butylphenol), 4.4'-5ec-butylidenediphenol, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis(2-methylphenol, 4-phenylphenol, 4-hydroxydiphenoxide) , α-naphthol, β-naphthol, 3.5
-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone, pyrogallol, phloroglycin, fluorocrystalline Zinecarboxylic acid, 4jet-octylcatechol,
2,2'-methylenebis(4-chlorophenol), 2
．． 2'-methylenebis(4-methyl-6-tert
-butylphenol), 2,2'-dihydroxydiphenyl, ethyl ρ-hydroxybenzoate, propyl P-hydroxybenzoate, butyl P-hydroxybenzoate, P
-benzyl hydroxybenzoate, p-hydroxybenzoate-P-chlorobenzyl, P-hydroxybenzoate-〇=thalolbenzyl, P-hydroxybenzoate-ρ-methylbenzyl, p-hydroxybenzoate-〇-octyl,
Benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenylsulfone, 4-hydroxy-4'- Chlorodiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 2-hydroxy-p-toluic acid, 3,5-di-ta
Zinc rt-butylsalicylate, 3,5-di-tert-
tin butylsalicylate, tartaric acid, oxalic acid, maleic acid,
Citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, etc.

In the present invention, in order to bind and support the leuco dye, developer and sensitizer on the support, various conventional binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxycellulose,
Cellulose derivatives such as hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/acrylic acid ester/methacrylic acid ternary copolymer, styrene Water-soluble polymers such as / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer Latexes such as polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, and the like are used.

Furthermore, in the present invention, in addition to the leuco dye, color developer, and sensitizer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, heat-sensitive recording materials, etc. A fusible substance (or lubricant), etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. ,
Organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin can be mentioned, and examples of the thermofusible substance include higher fatty acids or their esters, amides, or metal salts. , various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, and other thermoplastics. Examples include melting organic compounds having a melting point of about 50 to 200°C.

The heat-sensitive recording material of the present invention can have various structures, including all conventionally known structures that utilize a color-forming reaction between a leuco dye and a color developer.

〔effect〕

The recording material of the present invention includes a color developer using at least one of the formulas (I) and (II) in the thermosensitive coloring layer, and a general formula (m) in which R, , R2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a benzyl group, and R3 represents hydrogen or a benzyl group), so the dissolution energy during thermal recording is low (conventional It has a high sensitivity not found in other countries.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

Example 1 [Liquid A] 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anirite fluorane 300 parts 10% polyvinyl alcohol aqueous solution 300II water
4001
1 [Liquid B] 1.4-dimethoxynaphthalene 50I!
Zinc stearate 251! Calcium carbonate 100 parts 10% polyvinyl alcohol aqueous solution 250n water
475+7
The mixtures having the above compositions were ground and dispersed using a sand grinder for 2 to 4 hours to prepare liquids A and B.

Next, liquid A and liquid 8 were mixed and stirred so that the weight ratio was A:B= ], :8 to prepare a heat-sensitive coating liquid.

[Liquid C]

Polystyrene 40% dispersion 750 parts 10
% polyvinyl alcohol aqueous solution 20071 water
50
/1 The above mixture was dispersed in a sand grinder for 30 minutes to obtain an undercoat coating liquid.

Next, this undercoat coating liquid was prepared and dried to form an undercoat layer on a 52 g/m high-quality paper so that the coating amount after drying was 4 g/m, and then the heat-sensitive coating liquid was applied to The leuco dye was coated and dried so that the amount of leuco dye coated after drying was 0.5 g/rn'. These coated papers were calendered to a Beck smoothness of 700 to 1,500 seconds to prepare a heat-sensitive recording material of the present invention.

Example 2 A heat-sensitive recording material of Example 2 was prepared in the same manner as in Example 1 except that formula (1) in the above-mentioned [Liquid B] was used.

Comparative Example 1 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that stearic acid amide was used instead of 4-dume-1-xinaphthalene.

Examples 3 and 4 1,4-jethoxynaphthalene (Example 3) instead of 1,/l-zume 1-xinaphthalene in Example 1,
Thermal recording materials of Examples 3 and 4 were prepared in the same manner except that 1,4-dibenzyloxinaphthalene (Example 4) was used.

Comparative Example 2 Instead of [R liquid] in Example 1, [D
liquid] was prepared.

(11) Liquid] Benzyl P-hydroxybenzoate 100 parts Zinc stearate 50! ! Calcium carbonate 100++ Polycarboxylic acid type surfactant 5H2O% polyvinyl alcohol aqueous solution 250# water
495#Next, the weight ratio of the A liquid shown in Example 1 and the above liquid is A:D=I:
A heat-sensitive coating liquid was prepared by mixing and stirring so that the basis weight was 5.
Coating amount after drying is 5 g / rrr on high quality paper of 2 g / i
It was applied with a wire bar so that A heat-sensitive recording material of Comparative Example 2 was prepared using this coated paper in the same manner as in Example 1.

The above thermosensitive recording sheet was tested for its dynamic color development sensitivity, and the results are shown in Table 1. The test method in this case is as follows. The head power was 0.45W using a printing experiment device with a thin film head made by Kenshu Electronics Co., Ltd.
/dot, 1 line recording time 20m5/Q, scanning line density gX 3.85 dots 1ml1, pulse width 0.4.0.6.0.8.1.0.1.2 (msec)
Macbeth Densitometer RD-514
(filter-enratten-106).

As can be seen from Table 1, the heat-sensitive recording material of the present invention is a system using a known sensitizer such as stearamide, or a conventionally known system using a p-hydroxybenzoate ester developer. It is clear that its dynamic color development sensitivity is higher than that of the system.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer is provided on a support, the heat-sensitive color forming layer is mainly composed of a leuco dye and a color developer capable of coloring the leuco dye when heated, and the heat-sensitive color forming layer contains the formula (I). ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ A color developer using at least one of the compounds represented by general formula (III) ▲ Mathematical formulas, chemical formulas , tables, etc. ▼ (In the formula, R_1 and R_2 represent hydrogen or an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a benzyl group, and R_3
1,4-dihydroxynaphthalene derivative represented by: hydrogen or benzyl group.