JPH0767863B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material excellent in heat response, light resistance, weather resistance, oil resistance and optical readability in the near infrared region.

(Prior Art) Generally, in a thermal recording paper, a colorless or light-colored basic colorless dye and an organic developer such as a phenolic substance are ground and dispersed into fine particles, respectively, and then the both are mixed to form a binder,
A coating solution obtained by adding fillers, sensitivity improvers, lubricants and other auxiliaries to a support such as paper, synthetic paper, film, plastic, etc., such as hot pens, thermal heads, hot stamps, lasers. Color recording is obtained by an instantaneous chemical reaction caused by heating with light or the like.

These thermal recording papers have been applied to a wide range of fields such as measuring recorders, computer terminal printers, facsimiles, automatic ticket vending machines, and bar code labels, but recently these recording devices have been diversified and improved in performance. Accordingly, the required quality of the thermal recording paper has become higher. For example, with the increase in recording speed, it is required to obtain a clear color image with high density even with a small amount of heat energy, and on the other hand, a heat-sensitive recording paper having excellent storage stability such as light resistance, weather resistance and oil resistance is required. Is required.

These thermosensitive recording papers are also used as thermosensitive labels, but since the color development is in the visible region, it is not suitable for reading with semiconductor lasers in the near infrared region, which is widely used as bar code scanners for POS systems and the like. Could not fit.

On the other hand, JP-A-62-243652 and JP-A-62-24
3653, JP 62-257970, and JP 62-28
In Japanese Patent No. 8078, there is proposed a heat-sensitive recording paper using a divinyl compound excellent in coloring in the near infrared region and a known developer.

(Problems to be Solved by the Invention) However, in these thermal recording papers, since the storage stability (light resistance, weather resistance, oil resistance) of the recorded image is remarkably poor, the recorded image portion is exposed to light and heat. When left for a long time under environmental conditions affected by humidity, etc., the color fades and the image density decreases, and sometimes the color disappears completely, which significantly reduces the optical reading rate in the near infrared region. Will end up.

Also, sebum components may adhere to the colored image, or plasticizers (DOP, DOA) contained in wrap films such as PVC films.
Etc.), the image density remarkably decreases and the color disappears, so that the optical reading rate in the near infrared region remarkably decreases. Due to the above difficulties, there is a problem in putting these thermal recording papers to practical use.

An object of the present invention is to provide a heat-sensitive recording material having excellent thermal responsiveness, light resistance, weather resistance, oil resistance, and optical readability in the near infrared region such as a barcode.

(Means for Solving the Problems) In the present invention, as the basic colorless dye in the thermosensitive color developing layer, a fluoran-based leuco dye represented by the following general formula (I), a divinyl compound represented by the general formula (II) and a general formula (II) III)
By incorporating three kinds of fluorene-based leuco dyes represented by the above, the above problems are solved at once.

[In the formula, R ₁ represents a hydrogen atom or an alkyl group, and R ₂ represents a halogen atom or an alkyl group. T ₁ and T ₂ represent a hydrogen atom, an alkyl group or a phenyl group, but T ₁ and T ₂ do not simultaneously become a phenyl group. ] [Wherein R ₁₀ is an alkyl group having 8 or less carbon atoms, R ₁₁ is an alkyl group having 8 or less carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, a chlorine atom, a bromine atom, or a carbon atom having 4 or less carbon atoms as a substituent] A benzyl group or a phenyl group which may have an alkyl group is shown. X ¹ and X ² represent an alkyl group having 8 or less carbon atoms, an alkoxy group having 8 or less carbon atoms, a fluorine atom, a chlorine atom or a bromine atom, and m and n represent 0, 1, 2 or 3, and (X ¹ ) _m
X ¹ comrades, (X ²⁾ _n X ² comrades may also say be the same. X ³ represents a chlorine atom or a bromine atom, and both of the four atoms may be present at the same time. ] [In the formula, R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ are each a hydrogen atom; C ₁ to
Alkyl C _8; tetrahydrofurfuryl group; unsaturated alkyl group of C ₃ -C _9; alkoxyalkyl group of C ₃ -C _8; cycloalkyl group C ₅ -C ₈ tetrahydropyran-2-methyl group; Halogen atom, alkyl group optionally substituted by C ₁ -C ₄ alkoxyl group; halogen atom, aryl group optionally substituted by C ₁ -C ₄ alkyl group, C ₁ -C ₄ alkoxyl group a halogen atom, an alkyl group of C ₁ -C _4, C
₁ represents an alkyl group having C ₂ -C ₈ having -C ₄ good phenoxy group optionally substituted with an alkoxyl group. Also, R ₁₂ and R ₁₃ , R
₁₄ and R ₁₅ and R ₁₆ and R ₁₇ may form a heterocycle with each other or the adjacent benzene ring. Examples of the fluoran-based leuco dye used in the present invention include the following, but the invention is not limited thereto.

2-methyl-6-p- (p-dimethylaminophenyl)
Aminoanilinofluorane, 3-methyl-6-p- (p
-Dimethylaminophenyl) aminoanilinofluorane, 2-chloro-3-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 2-chloro-3-methyl-6-p- (p -Phenylaminophenyl) aminoanilinofluorane Among the fluorane-based leuco dyes represented by the general formula (I), the most preferable ones are those represented by the following structural formulas (IV) and (V) in view of productivity, cost and performance. 2-methyl-6 shown
-P- (p-dimethylaminophenyl) aminoanilinofluorane (mp.197-203 ° C), 2-chloro-3-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane (mp .191.5-196 ° C).

Examples of the divinyl compound used in the present invention include the following, but are not limited to these.

Of the divinyl compounds represented by the general formula (II), 3,3 is most preferable in view of productivity, cost and performance.
-Bis- [2- (p-dimethylaminophenyl) -2-
(P-Methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide (mp. 133-135 ° C and 3,3-bis- [2
-(P-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide (mp. 133-135 ° C).

Among the fluorene-based leuco dyes represented by the general formula (III), 3,6-bis (dimethylamino) fluorene-9-spiro-3 ′-(6 ′) is most preferable in consideration of productivity, cost and performance. -Dimethylamino) phthalide.

The mixing ratio of the divinyl compound, the fluorene-based leuco dye and the fluoran-based leuco dye in the present invention is 0.1 to 25 parts by weight of fluorene-based leuco dye and 0.05 to 3 parts by weight of fluoran-based leuco dye to 1 part by weight of the divinyl compound. Most preferred.

Further, as the organic developer used in the present invention, bisphenol A, 4-hydroxybenzoic acid ester, 4-
Hydroxyphthalic acid diesters, phthalic acid monoesters, bis- (hydroxyphenyl) sulfides, 4
-Hydroxyphenyl aryl sulfones, 4-hydroxyphenyl aryl sulfonates, 1,3-di [2-
(Hydroxyphenyl) -2-propyl] -benzenes, 4-hydroxybenzoyloxybenzoic acid esters, bisphenol sulfones and other color developers are preferable, and specific examples thereof are shown below.

Bisphenol A 4,4'-isopropylidene diphenol (also known as bisphenol A) 4,4'-cyclohexylidene diphenol p, p '-(1-methyl-normalhexylidene) diphenol 1,7-di ( 4-Hydroxyphenylthio) -3,5-dioxaheptane 4-hydroxybenzoic acid esters 4-benzyl benzyl 4-hydroxybenzoate 4-hydroxybenzoic acid ethyl 4-hydroxybenzoate propyl 4-hydroxybenzoate isopropyl 4-hydroxybenzoic acid Butyl 4-hydroxybenzoic acid Isobutyl 4-hydroxybenzoic acid methylbenzyl 4-hydroxyphthalic acid diesters 4-hydroxyphthalic acid dimethyl 4-hydroxyphthalic acid diisopropyl 4-hydroxyphthalic acid dibenzyl 4-hydroxyphthalic acid dihexyl phthalic acid monoester Phthalic acid monobenzyl ester Phthalic acid monocyclohexyl ester Phthalic acid monophenyl ester Phthalic acid monomethylphenyl ester Phthalic acid monoethylphenyl ester Phthalic acid monoalkylbenzyl ester Phthalic acid monohalogen benzyl ester Phthalic acid monoalkoxybenzyl ester Bis- (hydroxy Phenyl) sulfides Bis- (4-hydroxy-3-tert-butyl-6-methylphenyl) sulfide Bis- (4-hydroxy-2,5-dimethylphenyl) sulfide Bis- (4-hydroxy-2-methyl-5) -Ethylphenyl) sulfide bis- (4-hydroxy-2-methyl-5-isopropylphenyl) sulfide bis- (4-hydroxy-2,3-dimethylphenyl) sulfide bis- (4-hydroxy 2,5-Diethylphenyl) sulfide Bis- (4-hydroxy-2,5-diisopropylphenyl) sulfide Bis- (4-hydroxy-2,3,6-trimethylphenyl) sulfide Bis- (2,4,5-tri Hydroxyphenyl) sulfide Bis- (4-hydroxy-2-cyclohexyl-5-methylphenyl) sulfide Bis- (2,3,4-trihydroxyphenyl) sulfide Bis- (4,5-dihydroxy-2-tert-butyl- Phenyl) sulfide bis- (4-hydroxy-2,5-diphenylphenyl)
Sulfide Bis- (4-hydroxy-2-tert-octyl 5-methylphenyl) sulfide 4-hydroxyphenyl aryl sulfones 4-hydroxy-4'-isopropoxydiphenyl sulfone 4-hydroxy-4'-methyldiphenyl sulfone 4-hydroxy -4'-n-Butyloxydiphenylsulfone 4-hydroxyphenylarylsulfonates 4-hydroxyphenylbenzenesulfonate 4-hydroxyphenyl-p-trisulfonate 4-hydroxyphenylmethylenesulfonate 4-hydroxyphenyl-p-chloro Benzenesulfonate 4-hydroxyphenyl-p-tert-butylbenzenesulfonate 4-hydroxyphenyl-p-isopropoxybenzenesulfonate 4-hydroxyphenyl-1'-naphth Phosphorus sulfonate 4-hydroxyphenyl-2'-naphthalene sulfonate 1,3-di [2- (hydroxyphenyl) -2-propyl] benzenes 1,3-di [2- (4-hydroxyphenyl) -2- Propyl] benzene 1,3-di [2- (4-hydroxy-3-alkylphenyl) -2-propyl] benzene 1,3-di [2- (2,4-dihydroxyphenyl) -2-propyl] benzene 1 , 3-Di [2- (2-hydroxy-5-methylphenyl) -2-propyl] benzene resorcinols 1,3-dihydroxy-6 (α, α-dimethylbenzyl)
-Benzene 4-hydroxybenzoyloxybenzoate benzyl 4-hydroxybenzoyloxybenzoate methyl 4-hydroxybenzoyloxybenzoate ethyl 4-hydroxybenzoyloxybenzoate propyl 4-hydroxybenzoyloxybenzoate butyl 4-hydroxybenzoyloxybenzoate Isopropyl 4-hydroxybenzoyloxybenzoate tert-butyl 4-hydroxybenzoyloxybenzoate Hexyl 4-hydroxybenzoyloxybenzoate Octyl 4-hydroxybenzoyloxybenzoate Nonyl 4-hydroxybenzoyloxybenzoate Cyclohexyl 4-hydroxybenzoyloxybenzoate 4-hydroxybenzoyloxybenzoic acid β-phenethyl 4-hydroxybenzoyloxybenzoic acid Phenyl 4-hydroxybenzoyloxybenzoic acid α-naphthyl 4-hydroxybenzoyloxybenzoic acid β-naphthyl 4-hydroxybenzoyloxybenzoic acid sec-butyl bisphenol sulfone (I) bis- (3-1-butyl-4-hydroxy-) 6-Methylphenyl) sulfone Bis- (3-ethyl-4-hydroxyphenyl) sulfone Bis- (3-propyl-4-hydroxyphenyl) sulfone Bis- (3-methyl-4-hydroxyphenyl) sulfone Bis- (2- Isopropyl-4-hydroxyphenyl)
Sulfone Bis- (2-ethyl-4-hydroxyphenyl) sulfone Bis- (3-chloro-4-hydroxyphenyl) sulfone Bis- (2,3-dimethyl-4-hydroxyphenyl) sulfone Bis- (2,5-dimethyl -4-hydroxyphenyl) sulfone bis- (3-methoxy-4-hydroxyphenyl) sulfone 4-hydroxyphenyl-2'-ethyl-4'-hydroxyphenylsulfone 4-hydroxyphenyl-2'-isopropyl-4'-
Hydroxyphenyl sulfone 4-hydroxyphenyl-3'-isopropyl-4'-
Hydroxyphenyl sulfone 4-hydroxyphenyl-3'-sec butyl-4'-hydroxyphenyl sulfone 3-chloro-4-hydroxyphenyl-3'-isopropyl-4'-hydroxyphenyl sulfone 2-hydroxy-5-t-butylphenyl -4'-hydroxyphenyl sulfone 2-hydroxy-5-t-aminophenyl-4'-hydroxyphenyl sulfone 2-hydroxy-5-isopropylphenyl-4'-hydroxyphenyl sulfone 2-hydroxy-5-t-octylphenyl- 4'-hydroxyphenyl sulfone 2-hydroxy-5-t-butylphenyl-3'-chloro-4'-hydroxyphenyl sulfone 2-hydroxy-5-t-butylphenyl-3'-methyl-4'-hydroxyphenyl sulfone 2-hydro Ci-5-t-butylphenyl-3'-isopropyl-4'-hydroxyphenyl sulfone 2-hydroxy-5-t-butylphenyl-3'-chloro-4'-hydroxyphenyl sulfone 2-hydroxy-5-t- Butylphenyl-3'-methyl-4'-hydroxyphenyl sulfone 2-hydroxy-5-t-butylphenyl-3'-isopropyl-4'-hydroxyphenyl sulfone 2-hydroxy-5-t-butylphenyl-2'- Methyl-4'-hydroxyphenyl sulfone Bisphenol sulfone (II) 4,4'-sulfonyldiphenol 2,4'-sulfonyldiphenol 3,3'-dichloro-4,4'-sulfonyldiphenol 3,3'- Dibromo-4,4'-sulfonyldiphenol 3,3 ', 5,5'-tetrabromo-4,4'-sulfonyldiphenol 3,3 ′ -Diamino-4,4′-sulfonyldiphenol and others p-tert-butylmephenol 2,4-dihydroxybenzophenone novolac type phenol resin 4-hydroxyacetophenone p-phenylphenol benzyl-4-hydroxyphenylacetate p-benzylphenol These color developers can be used alone or in admixture of two or more.

Further, in the present invention, a polyvalent metal salt of an organic acid may be contained as a stabilizer for the purpose of further enhancing storage stability such as light resistance, weather resistance and oil resistance.

Among these stabilizers, the most preferable one is the following general formula (V
It is a halogen-substituted zinc benzoate derivative represented by I).

[In the formula, X represents a halogen atom, A is a hydrogen atom, a nitro group, a C _{1 to} C ₁₂ alkyl group, a C _{1 to} C ₁₂ alkoxy group,
It represents a C ₃ -C ₁₀ cycloalkyl group, a cyano group or a hydroxyl group, 1 represents an integer of 1 to 2, and m represents an integer of 0 to 5. ] In the description of the general formula (VI), a C ₁ -C ₁₂ alkyl group and C ₁ -C
_{The 12} alkoxy groups may be linear or branched, and include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, hexyl group, Examples thereof include an octyl group, a nonyl group, a dothesyl group, a methoxy group, an ethoxy group and a tert-butoxy group. Examples of the C _{3 to} C ₁₀ cycloalkyl group include cyclohexyl group, 2-ethylcyclohexyl group, p-tert-
A butylcyclohexyl group is exemplified.

The above-mentioned stabilizer is a compound having a specific molecular structure selected from many organic carboxylic acid metal salts. Zinc benzoate having 1 to 2 halogen atoms in the benzene nucleus as substituents has properties not found in organic carboxylic acids of the same kind and polyvalent metal salts thereof in light resistance, weather resistance and oil resistance.

Examples of typical halogen-substituted zinc benzoate-chlorine derivative used in the present invention include the followings, but not limited thereto.

Further, as sensitizers, fatty acid amides such as stearic acid amide and barmitic acid amide, ethylene bisamide,
Montan wax, polyethylene wax, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, p-benzyl biphenyl, phenyl α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2 It is also possible to add naphthoic acid phenyl ester, 1,2-di (3-methylphenoxy) ethylene and the like.

The binder used in the present invention has a polymerization degree of 200 to 1
900 fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, amide modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, butyral modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene Maleic anhydride copolymers, styrene-butadiene copolymers and cellulose derivatives such as ethyl cellulose, acetyl cellulose,
Examples thereof include polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid ester, polyvinyl butyral polystyrol and copolymers thereof, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin and coumarone resin. . These polymeric substances are used by dissolving them in solvents such as water, alcohols, ketones, esters, hydrocarbons, etc., or in the state of being emulsified or pasty dispersed in water or other medium, depending on the required quality. It can also be used together.

The amount of organic developer and basic colorless dye used in the present invention,
The types and amounts of other various components are determined according to the required performance and recording suitability, and are not particularly limited, but usually 1 to 8 parts of the organic developer to 1 part of the basic colorless dye. 1 to 20 parts of filler is used, and 10 to 25% of the total solid content of the binder is suitable.

The desired thermosensitive recording medium can be obtained by applying a coating solution having the above composition to an arbitrary support such as paper, synthetic paper, film, or plastic.

The above-mentioned organic developer, basic colorless dye and materials to be added as necessary are atomized by a ball mill, attritor, sand grinder or the like to a particle size of several microns or less by a grinder or an appropriate emulsifying device, and a binder and Various kinds of additive materials are added according to the purpose to prepare a coating liquid.

In this coating liquid, a filler, a release agent for preventing sticking of fatty acid metal salts, a fatty acid amide, an ethylene bisamide, a montan wax, a lubricant for preventing pressure coloration of polyethylene wax, sodium dioctylsulfosuccinate, Add dispersants such as sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate / sodium salt, alginate, benzophenone-based or triazole-based UV absorbers, other defoaming agents, optical brighteners, and water resistance agents You can

As the filler used in the present invention, all inorganic organic fillers used in the field of ordinary paper processing can be used, and examples thereof include clay, talc, silica, magnesium carbonate, alumina, aluminum hydroxide, and hydroxide. Magnesium, barium sulfate, kaolin, titanium oxide, zinc oxide,
Examples of the fine particles include calcium carbonate, aluminum oxide, urea, formalin resin, polystyrene, and phenol resin.

Further, an overcoat layer of a polymer substance or the like can be provided on the heat-sensitive layer for the purpose of enhancing the storage stability.

(Operation) The reason why the thermal recording paper of the present invention is excellent in optical readability in the near infrared region is explained as follows. A recorded image using a conventional recording material using an electron-donating color former such as a fluoran leuco dye does not absorb light in the near infrared region at all. However, the specific divinyl compound, the specific fluorane-based leuco dye, and the specific fluorene-based leuco dye used in the present invention, in the near-infrared region when a color is generated by a heat melting reaction with an electron accepting substance (developing agent). It absorbs light in the near infrared region (especially in the 700-1500 nm range) very efficiently.

Further, the recorded image of the thermal recording paper of the present invention has light resistance, weather resistance,
The extremely high stability in terms of oil resistance is explained as follows. Generally, a thermal recording paper is composed of a basic colorless dye as an electron donor and an organic acidic substance such as a phenol compound, an aromatic carboxylic acid or an organic sulfonic acid as an electron acceptor. The heat-melting reaction between these basic colorless dyes and the color developer is an acid-base reaction based on electron donation / acceptance, whereby a metastable "charge transfer complex" is formed and a color image is obtained. .

On the other hand, when the divinyl compound, the fluorane-based leuco dye or the fluorene-based leuco dye of the present invention and the organic developer cause the above-mentioned chemical reaction, the chemical bonding force is extremely weak. However, when three kinds of the divinyl compound, the fluoran-based leuco dye and the fluorene-based leuco dye are used in combination, a synergistic action occurs between the divinyl compound, the fluoran-based leuco dye and the fluorene-based leuco dye during the hot melt reaction. As a result, the organic developer and the divinyl compound,
The chemical bond strength between the organic developer and the fluoran-based leuco dye and between the organic developer and the fluorene-based leuco dye is dramatically increased. Therefore, even if exposed to environmental conditions affected by light, heat, humidity, etc. for a long time, even if a hairdressing composition or oils and fats adhere, their chemical bonds are not broken, and the color image is stable, It is considered that the optical readability in the near infrared region of the recorded image does not deteriorate.

Furthermore, the reason why it is excellent in thermal responsiveness is that when the divinyl compound, the fluoran-based leuco dye and the fluorene-based leuco dye of the present invention undergo a hot melt color reaction, the melting point is lowered and the color density is increased.

(Example) Hereinafter, the present invention will be described with reference to an example.

In the description, parts indicate parts by weight.

[Examples (Test Nos. 1 to 3)] Liquid A (developer dispersion liquid) Liquid B (dye dispersion 1) Liquid C (dye dispersion 2) Liquid D (dye dispersion 3) Each liquid of the above composition was ground with an attritor to an average particle size of 1 micron. Next, the dispersion liquids are mixed at the following ratios to prepare a coating liquid.

Each coating solution is applied to one side of 50 g / m ² base paper to a coating amount of 6.0 g / m ² and dried, and this sheet is treated with a super calender so that the smoothness is 200 to 600 seconds and heat-sensitive. I made a chart paper.

[Comparative Example (Test Nos. 4 to 6)] Liquid A (developer dispersion liquid) Liquid D (dye dispersion) Each liquid of the above composition was ground with an attritor to an average particle size of 1 micron. Next, the dispersion liquids are mixed at the following ratios to prepare a coating liquid.

Each coating solution is applied to one side of 50 g / m ² base paper to a coating amount of 6.0 g / m ² and dried, and this sheet is treated with a super calender so that the smoothness is 200 to 600 seconds and heat-sensitive. I made a chart paper.

[Comparative Example (Test Nos. 7 to 9)] Liquid A (developer dispersion liquid) Liquid E (dye dispersion 1) Liquid F (dye dispersion 2) Each liquid of the above composition was ground with an attritor to an average particle size of 1 micron. Next, the dispersion liquids are mixed at the following ratios to prepare a coating liquid.

Each coating solution is applied to one side of 50 g / m ² base paper to a coating amount of 6.0 g / m ² and dried, and this sheet is treated with a super calender so that the smoothness is 200 to 600 seconds and heat-sensitive. I made a chart paper.

Quality performance tests were conducted on all the thermal recording papers of Examples and Comparative Examples, and the results are shown in Tables 1 and 2.

Note (1) Static color density; 10g / cm ^{2 on} hot plate heated to 135 ℃
Measured with a Macbeth densitometer (RD-914, amber filter used; the same applies hereafter) after pressing for 5 seconds under the pressure of.

Note (2) Dynamic color density: Tokyo Shibaura Denki-Thermal Facsimile KB-4800, applied voltage 16.00V, pulse width 3.0
Measure the image density recorded in milliseconds with a Macbeth densitometer.

Note (3) Infrared reflectance (%); Measure the infrared reflectance of the image portion recorded by the method of Note (2) with a spectrophotometer (wavelength 1000 nm).

Note (4) Light resistance: The image density dynamically recorded by the method of Note (2) was taken as the untreated density, and the density after the color-developed portion was irradiated with light for 6 hours by the fade meter was taken as the processed density. The residual rate is calculated from the following formula.

The infrared reflectance is a measured value of the image portion after the light processing.

Note (5) Oil resistance: With the image density dynamically recorded by the method of Note (2) as the unprocessed density, castor oil was dropped on the color-developed part, 10 seconds later, lightly wiped with filter paper, and left at room temperature for 72 hours. The concentration when left to stand was defined as the concentration after the treatment. The residual rate is calculated from the following formula.

The infrared reflectance is a measured value of the image portion after the oil treatment.

Note (6) Weather resistance: The thermosensitive recording paper sample dynamically recorded by the method of Note (2) was left under the conditions of 40 ° C and 90% RH, and the density of the recorded portion for 48 hours was measured with a Macbeth densitometer. The residual rate is calculated from the following formula.

The spectrophotometer (wavelength 1000
nm).

(Effects of the Invention) The effects of the present invention are as follows.

(1) Excellent thermal response.

(2) Excellent optical readability in the near infrared region.

(3) It is excellent in stability such as light resistance, oil resistance, and weather resistance, and as a result, long-term storage stability and near-infrared readability after long-term storage.

(4) Due to the effect of (3) above, it can withstand use under severe conditions such as a bar code label.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Fujimura 5-21-1 Oji, Kita-ku, Tokyo Inside the Central Research Laboratory, Tojo Paper Manufacturing Co., Ltd. (56) Reference JP-A-62-148287 (JP, A)

Claims (2)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or pale-colored basic colorless dye and an organic developer as main components, wherein the thermosensitive coloring layer is a basic colorless dye. A heat-sensitive recording containing three kinds of a fluorane-based leuco dye represented by the following general formula (I), a divinyl compound represented by the general formula (II) and a fluorene-based leuco dye represented by the general formula (III) as material. [In the formula, R ₁ represents a hydrogen atom or an alkyl group, and R ₂ represents a halogen atom or an alkyl group. T ₁ and T ₂ represent a hydrogen atom, an alkyl group or a phenyl group, but T ₁ and T ₂ do not simultaneously become a phenyl group. ] [Wherein R ₁₀ is an alkyl group having 8 or less carbon atoms, R ₁₁ is an alkyl group having 8 or less carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, a chlorine atom, a bromine atom, or a carbon atom having 4 or less carbon atoms as a substituent] A benzyl group or a phenyl group which may have an alkyl group is shown. X ¹ and X ² represent an alkyl group having 8 or less carbon atoms, an alkoxy group having 8 or less carbon atoms, a fluorine atom, a carbon atom or a bromine atom, and m and n represent 0, 1, 2 or 3, and (X ¹ ) m
X ¹ comrades, (X ²⁾ n X ² comrades may be be the same or different. X ³ represents a chlorine atom or a bromine atom, and (X ³ )
_At least one of X ³ 's in ₄ is a bromine atom. ] [Wherein, R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ are each a hydrogen atom; a C _{1 to} C ₈ alkyl group; a C _{5 to} C ₈ cycloalkyl group; C ₃
To C ₈ alkoxyalkyl group; C _{3 to} C ₉ unsaturated alkyl group, tetrahydrofurfuryl group, tetrahydropyran-
2-methyl group; a halogen atom, C ₁ -C ₄ of which may be substituted alkyl group alkoxyl group, C ₁ -C ₄ in the aryl group which may be substituted with an alkoxyl group; a halogen atom, C ₁ ~ C ₄ alkyl group: a C ₂ -C ₈ alkyl group having a phenoxy group which may be substituted with a C ₁ -C ₄ alkoxyl group. In addition, R ₁₂ and R ₁₃ , R ₁₄ and R ₁₅ , and R ₁₆ and R ₁₇ may form a hetero ring with each other or an adjacent benzene ring. ] 2. A fluorane-based leuco dye represented by the general formula (I) is 2-chloro-3-methyl-6-p- (p-
Phenylaminophenyl) aminoanilinofluorane or 2-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane and the divinyl compound represented by the general formula (II) is 3,3- Screw [2-
(P-Dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide or 3,3-bis [2- (p-dimethylaminophenyl) -2- (P-Methoxyphenyl) ethenyl] -4,5,
6,7-tetrachlorophthalide, and the above general formula (I
II) the fluorene-based leuco dye is 3,6-bis (dimethylamino) fluorene-9-spiro-3'-
The heat-sensitive recording material according to claim 1, which is (6'-dimethylamino) phthalide.