JPH10175373A - Transparent thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent thermal recording material having excellent transparency, and small adherence of refuse or dust. SOLUTION: This recording material comprises a thermal recording layer containing a colorless or pale color leuco dye, a developer for thermally color developing the dye and a binder resin as a binding agent as main components on a transparent support, and a protective layer containing resin and further on the recording layer. In this case, a back layer of a non-water soluble polyester resin having Tg of 55 deg.C or higher dissolved in an organic solvent is provided on a rear surface of the support.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent heat-sensitive recording medium utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound. It relates to a heat-sensitive recording material.

[0002]

2. Description of the Related Art Various recording materials have been proposed which utilize a color-forming reaction between a colorless or pale-colored leuco dye and a color developing agent upon contact with color by heat and pressure. One such heat-sensitive recording material does not require complicated processing such as development and fixing, and can be recorded in a short time with a relatively simple device, has less noise, and has advantages such as low cost. It is useful as various recording materials for electronic calculators, facsimile machines, ticket vending machines, label printers, recorders and the like.

[0003] These heat-sensitive recording materials are generally produced by coating the above-described color-forming dye and color developer on paper. In recent years, mainly in the medical field, a transparent dry film system that can be easily output has been demanded due to a waste liquid treatment problem caused by a wet process of a silver halide X-ray film and a flow of digitization of images. In such a flow, a transparent heat-sensitive recording film is also demanded in the heat-sensitive process because of the simplicity of the process.

However, a transparent thermosensitive recording material adds transparency, density gradation (γ characteristic), binding property and barrier function to the surface thermosensitive recording layer and the protective layer, and thus is used for general thermosensitive recording materials. Since the resin in the layer after coating and drying contains a large amount of resin, curling toward the surface side occurs due to distortion due to the increase in internal stress of the coating film due to shrinkage of the resin in the layer, and therefore, such as mounting to a shakasten There is a drawback that the handleability is poor and running defects occur during printing. In addition, when the water-soluble resin is applied to the back layer, expansion and contraction occur due to a change in humidity due to the high hygroscopicity of the resin, and the effect on curling tends to depend on the environment, and the effect is not constant. And when applying an organic solvent-based coating liquid, there was a problem that after drying, the skin was uneven and the uniformity of the coating was poor, and the transparency was reduced due to irregular reflection of light from the non-uniformity of the layer. . Further, the plastic film used for the transparent support is electrically insulating and has a high surface resistance, so that dust and dust easily adhere to the surface. The thermal head often used in the heat-sensitive process is a direct contact process between the recording sheet and the head, so if a highly smooth support such as a plastic film is used, the coated surface is likely to be smooth. A phenomenon in which such dust or dust is caught between the thermal recording material and the thermal head during printing, and the image is striped at that portion and in the vicinity thereof (hereinafter referred to as white stripes).
There is a problem that is easy to occur.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a transparent heat-sensitive recording material which is transparent, has little curl, has excellent transparency, and has little adhesion of dust and dust.

[0006]

According to the present invention, a colorless or light-colored leuco dye, a developer for heating the leuco dye to form a color, and a binder resin as a binder are mainly contained on a transparent support. In a heat-sensitive recording material comprising a heat-sensitive recording layer and a protective layer containing a resin thereon, a back layer of a water-insoluble polyester resin having a Tg of 55 ° C. or more dissolved in an organic solvent is provided on the back surface of the support. A transparent thermosensitive recording material characterized by being provided is provided. The details of the transparent thermosensitive recording material of the present invention will be described.

As described above, the curl is caused by the resin in the surface coating layer of the heat-sensitive recording layer and the protective layer shrinking after drying, which causes distortion due to an increase in internal stress of the coating film. Is what happens. Therefore, it is important to apply a back layer to one side of the support so as to curl the same amount as the front surface, and to balance the curl between the front surface and the back surface. The Tg (glass transition point) of a resin is the temperature at which it solidifies into a glassy state, and its physical properties such as specific volume, specific heat, and coefficient of thermal expansion rapidly change, micro-Brownian motion of molecules occurs, and the rigidity decreases. It increases but becomes brittle, and is also called the brittle point.

[0008] Therefore, Tg is a measure of the hardness and softness of the resin. A high Tg resin is indicated as a hard and brittle resin, and a low Tg resin is indicated as a soft and flexible resin. Therefore, Tg is 60
It has been found that by providing a back layer of a polyester resin at a temperature of not less than ° C., the resin can be curled toward the back side due to shrinkage due to hardness, thereby achieving a curl balance. At this time, if the polyester resin is 60 ° C. or less, curling does not occur due to high flexibility, and stickiness occurs after drying, causing blocking between the front surface and the back surface. Since the polyester resin used is insoluble in water, it is applied by dissolving in an organic solvent.However, since it is insoluble in water, it has no hygroscopic property and its effect on curling is not affected by environmental changes due to humidity changes. . And it was discovered that the use of cyclohexanone, which is a solvent that easily dissolves the polyester resin, suppresses the occurrence of yuzu skin, can form a uniform and clear coating film, and can be applied without impairing the transparency. With respect to the effect of cyclohexanone, the present inventors consider that the evaporation rate is low due to the high boiling point, so that the evaporation of the solvent is prevented from abruptly and the swirling convection generated during drying is suppressed.

In the case where a transparent support is used, the conductivity is increased by incorporating a large amount of conductive ions such as sodium in the back layer on the back surface in order to solve these problems because of the high electrical insulation. It has been proposed to reduce the surface resistance. However, if a large amount of conductive ionic substance is present, damage to the thermal head may occur. Is not practical.

[0010] Further, since electric conductivity is provided through moisture in the environment, the effect of preventing static electricity is reduced under low humidity conditions, and the system is easily affected by environmental fluctuations. Therefore, since two antistatic layers made of a conductive metal oxide dispersed with a polyester resin are provided on the back layer described above, the effect of the conductive metal oxide is large, and the surface resistance is reduced even by a low adhesion amount. Therefore, there is no adhesion of dust and dust, so that there is no generation of white stripes, and it is possible to improve the blocking when finished in a roll shape. In addition, since the conductive metal oxide is dispersed in the polyester resin, the back layer and the same resin do not cause a problem of poor compatibility and do not cause color separation, unevenness, cissing, or the like after application. The conductive metal oxide is finely pulverized and has a particle size of 0.1.
2 μm or less is effective, and the coating amount is 0.05 g / m ^2.
１1 g / m ² is preferred.

The transparent support used in the present invention is a polyester film such as polyethylene terephthalate or polybutylene terephthalate, a cellulose derivative film such as cellulose triacetate, a polyolefin film such as polypropylene or polyethylene, a polystyrene film or a film obtained by laminating these. It is. Since the transparency of the support also affects the transparency of the entire sheet, the haze degree of the support is 10% or less in the present invention.
Preferably, no more than 5% of the support is used.

The leuco dye used in the present invention is a compound having an electron donating property, and may be used alone or as a mixture of two or more kinds. However, it is a colorless or light-colored dye precursor itself, and is not particularly limited. Known ones, for example, triphenylmethanephthalide, triallylmethane, fluoran, phenothidiane, thiofluorane, xanthene, indophthalyl, spiropyran, azaphthalide, chromenopyrazole, methine, rhodamine anilinolactam , A rhoamine lactam type, a quinazoline type, a diazaxanthene type, a bislactone type or the like leuco compound is preferably used. Representative examples of such compounds include the following.

2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-
(Di-n-butylamino) fluoran, 2-anilino-
3-methyl-6- (Nn-propyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N
-Isopropyl-N-methylamino) fluoran, 2-
Anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluoran, 2-anilino-3-methyl-
6- (Nn-amyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-sec-butyl-N-ethylamino) fluoran, 2-anilino-
3-methyl-6- (Nn-amyl-N-ethylamino) fluoran, 2-anilino-3-methyl-6- (N
-Iso-amyl-N-ethylamino) fluoran, 2
-Anilino-3-methyl-6- (Nn-propyl-N
-Isopropylamino) fluoran, 2-anilino-3
-Methyl-6- (N-cyclohexyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N
-Ethyl-p-toluidino) fluoran, 2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluoran, 2- (m-trichloromethylanilino) -3
-Methyl-6-diethylaminofluoran, 2- (m-
Trifluoromethylanilino) -3-methyl-6-diethylaminofluoran, 2- (m-trifluoromethylanilino) -3-methyl-6- (N-cyclohexyl-N-
Methylamino) fluoran, 2- (2,4-dimethylanilino) -3-methyl-6-diethylaminofluoran, 2- (N-ethyl-p-toluidino) -3-methyl-6- (N-ethylanilino) Fluoran, 2- (N-
Methyl-p-toluidino) -3-methyl-6- (N-propyl-p-toluidino) fluoran, 2-anilino-
6- (Nn-hexyl-N-ethylamino) fluoran, 2- (o-chloroanilino) -6-diethylaminofluoran, 2- (o-bromoanilino) -6-diethylaminofluoran, 2- (o-chloroanilino ) -6
-Dibutylaminofluoran, 2- (o-fluoroanilino) -6-dibutylaminofluoran, 2- (m-trifluoromethylanilino) -6-diethylaminofluoran, 2- (p-acetylanilino) -6 − (N−n−
Amyl-Nn-butylamino) fluoran, 2-benzylamino-6- (N-ethyl-p-toluidino) fluoran, 2-benzylamino-6- (N-ethyl-2,
4-dimethylanilino) fluoran, 2-benzylamino-6- (N-ethyl-2,4-dimethylanilino) fluoran, 2-dibenzylamino-6- (N-methyl-
p-Toluidino) fluoran, 2-dibenzylamino-
6- (N-ethyl-p-toluidino) fluoran, 2-
(Di-p-methylbenzylamino) -6- (N-ethyl-p-toluidino) fluoran, 2- (α-phenylethylamino) -6- (N-ethyl-p-toluidino) fluoran, 2-methylamino -6- (N-methylanilino) fluoran, 2-methylamino-6- (N-ethylanilino) fluoran, 2-methylamino-6- (N-
Propylanilino) fluoran, 2-ethylamino-6
-(N-methyl-p-toluidino) fluoran, 2-methylamino-6- (N-methyl-2,4-dimethylanilino) fluoran, 2-ethylamino-6- (N-methyl-2,4- Dimethylanilino) fluoran, 2-dimethylamino-6- (N-methylanilino) fluoran,
2-dimethylamino-6- (N-ethylanilino) fluoran, 2-diethylamino-6- (N-methyl-p-
Toluidino) fluoran, di-diethylamino-6-
(N-ethyl-p-toluidino) fluoran, 2-dipropylamino-6- (N-methylanilino) fluoran, 2-dipropylamino-6- (N-ethylanilino) fluoran, 2-amino-6- (N- Methylanilino) fluoran, 2-amino-6- (N-ethylanilino) fluoran, 2-amino-6- (N-propylanilino) fluoran, 2-amino-6- (N-methyl-p
-Toluidino) fluoran, 2-amino-6- (N-ethyl-p-toluidino) fluoran, 2-amino-6
(N-propyl-p-toluidino) fluoran, 2-amino-6- (N-methyl-p-ethylanilino) fluoran, 2-amino-6- (N-ethyl-p-ethylanilino) fluoran, 2-amino-6 -(N-propyl-
p-ethylanilino) fluoran, 2-amino-6-
(N-methyl-2,4-dimethylanilino) fluoran, 2-amino-6- (N-ethyl-2,4-dimethylanilino) fluoran, 2-amino-6- (N-propyl-2,4 -Dimethylanilino) fluoran, 2-amino-6- (N-methyl-p-chloroanilino) fluoran, 2-amino-6- (N-ethyl-p-chloroanilino) fluoran, 2-amino-6- (N- Propyl-p
-Chloroanilino) fluorane, 2,3-dimethyl-6
-Dimethylaminofluoran, 3-methyl-6- (N-
Ethyl-p-toluidino) fluoran, 2-chloro-6
-Diethylaminofluoran, 2-bromo-6-diethylaminofluoran, 2-chloro-6-dipropylaminofluoran, 3-chloro-6-cyclohexylaminofluoran, 3-bromo-6-cyclohexylaminofluoran, 2 -Chloro-6- (N-ethyl-N-isoamylamino) fluoran, 2-chloro-3-methyl-6
-Diethylaminofluoran, 2-anilyl-3-chloro-6-diethylaminofluoran, 2- (o-chloroanilino) -3-chloro-6-cyclohexylaminofluoran, 2- (m-trifluoromethylanilino)- 3
-Chloro-6-diethylaminofluoran, 2- (2,2
3-dichloroanilino) -3-chloro-6-diethylaminofluoran, 1,2-benzo-6-diethylaminofluoran, 1,2-benzo-6- (N-ethyl-N-
Isoamylamino) fluoran, 1,2-benzo-6-
Dibutylaminofluoran, 1,2-benzo-6- (N
-Ethyl-N-cyclohexylamino) fluoran,
1,2-benzo-6- (N-ethyl-toluidino) fluoran and the like.

Next, the developer used in the present invention is an electron-accepting compound, and various conventionally known electron-accepting developers can be used.
It is an electron-accepting developer containing in its molecule a long-chain alkyl group shown in Japanese Patent Application No. 3-355078. For example, carbon number 12
Organic phosphoric acid compounds, aliphatic carboxylic acid compounds and phenol compounds having the above aliphatic groups, or C10 to C18
Or a metal salt of mercaptoacetic acid having an aliphatic group, or an alkyl ester of caffeic acid having an alkyl group having 5 to 8 carbon atoms, or an acidic phosphoric acid ester having an aliphatic group having 16 or more carbon atoms. The aliphatic group includes a linear or branched alkyl group and alkenyl group, and may have a substituent such as a halogen, an alkoxy group, and an ester. Hereinafter, specific examples of the developer will be described.

(A) Organic phosphoric acid compound A compound represented by the following general formula (1) is preferably used.

[0016]

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(R ₁ represents a straight-chain alkyl group having 12 to 24 carbon atoms) Specific examples of the organic phosphoric acid compound represented by the general formula (1) include the following.

Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, hexacosylphosphonic acid, octacosylphosphonic acid and the like.

As the organic phosphoric acid compound, α-hydroxyalkylphosphonic acid represented by the following general formula (2) is also preferably used.

[0020]

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(However, R ₂ is an aliphatic group having 11 to 29 carbon atoms.) When the α-hydroxyalkylphosphonic acid represented by the general formula (2) is specifically shown, α-hydroxydodecylphosphonic acid Α-hydroxytetradecylphosphonic acid, α-hydroxyhexadecylphosphonic acid, α-hydroxyoctadecylphosphonic acid, α-hydroxyeicosylphosphonic acid, α-hydroxydocosylphosphonic acid, α-hydroxytetracosylphosphonic acid, etc. No. As the organic phosphoric acid compound, an acidic organic phosphoric acid ester represented by the following general formula (3) is also used.

[0022]

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(In the formula, R ₃ represents an aliphatic group having 16 or more carbon atoms, and R ₄ represents a hydrogen atom or an aliphatic group having 1 or more carbon atoms.) The acid represented by the general formula (3) Specific examples of the organic phosphoric acid ester include dihexadecyl phosphate, dioctadecyl phosphate, dieicosyl phosphate, didocosyl phosphate, monohexadecyl phosphate, monooctadecyl phosphate, monoeicosyl phosphate, monodocosyl phosphate, and methyl. Examples include hexadecyl phosphate, methyl octadecyl phosphate, methyl eicosyl phosphate, methyl docosyl phosphate, amyl hexadecyl phosphate, octyl hexadecyl phosphate, lauryl hexadecyl phosphate, and the like.

(B) Aliphatic carboxylic acid compounds α-hydroxy fatty acids represented by the following general formula (4) are preferably used. R ₅ —CH (OH) —COOH (4) (where R ₅ represents an aliphatic group having 12 or more carbon atoms) Examples of the α-hydroxy aliphatic carboxylic acid compound represented by the general formula (4) include: The following are mentioned.

Α-hydroxydecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxydecanoic acid
Hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid, and the like.

The aliphatic carboxylic acid compound is an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms and substituted with a halogen element, at least in the α-position or β-position.
Those having a halogen element at the carbon at the position are also preferably used. Specific examples of such compounds include, for example, the following.

2-bromohexadecanoic acid, 2-bromoheptadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid, 2-bromodocosanoic acid, 2-bromotetracosanoic acid, 3-bromooctadecanoic acid, 3-bromo Eicosanoic acid, 2,3-dibromooctadecanoic acid, 2-fluorododecanoic acid, 2-fluorotetradecanoic acid, 2-
Fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2-fluoroeicosanoic acid, 2-fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, perfluoro Octadecanoic acid and the like. As the aliphatic carboxylic acid, an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms having an oxo group in the carbon, at least the carbon at the α-position, the β-position or the γ-position is an oxo group Are preferably used. Specific examples of such compounds include, for example, the following.

2-oxododecanoic acid, 2-oxotetradecanoic acid, 2-oxohexadecanoic acid, 2-oxooctadecanoic acid, 2-oxoeicosanoic acid, 2-oxotetracosanoic acid, 3-oxododecanoic acid, 3-oxo Tetradecanoic acid, 3-oxohexadecanoic acid, 3-oxooctadecanoic acid, 3-oxoeicosanoic acid, 3-oxotetracosanoic acid, 4-oxohexadecanoic acid, 4-oxooctadecanoic acid, 4-oxodokosanoic acid and the like. As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (5) is also preferably used.

[0029]

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(Where R ₆ represents an aliphatic group having 12 or more carbon atoms, X represents an oxygen atom or a sulfur atom, and n represents 1
Or 2 is represented. The following are specific examples of the dibasic acid represented by the general formula (5).

Dodecyl malate, tetradecyl malate, hexadecyl malate, octadecyl malate, eicosyl malate, docosyl malate, tetracosyl malate, dodecyl thiomalate, tetradecyl thiomalate, hexadecyl thiomalate Acid, octadecylthiomalic acid, eicosylthiomalic acid, docosylthiomalic acid, tetracosylthiomalic acid, dodecyldithiomalic acid, tetradecyldithiomalic acid, eicosyldithiomalic acid, docosyldithiomalic acid, tetracosyl Rudithiomalic acid and the like. As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (6) is also preferably used.

[0032]

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(However, R ₇ , R ₈ , and R ₉ represent hydrogen or an aliphatic group, at least one of which is an aliphatic group having 12 or more carbon atoms.) Formula (6) Specific examples of the dibasic acid include, for example, the following.

Dodecyl butane diacid, tridecyl butane diacid, tetradecyl butane diacid, pentadecyl butane diacid, octadecyl butane diacid, eicosyl butane diacid,
Docosyl butane diacid, 2,3-dihexadecyl butane diacid, 2,3-dioctadecyl butane diacid, 2-methyl-
3-dodecyl butane diacid, 2-methyl-3-tetradecyl butane diacid, 2-methyl-3-hexadecyl butane diacid, 2-ethyl-3-dodecyl butane diacid, 2-propyl-3-dodecyl butane Examples of aliphatic carboxylic acid compounds such as diacid, 2-octyl-3-hexadecylbutanedioic acid, 2-tetradecyl-3-octadecylbutanedioic acid, etc.
A dibasic acid represented by the following general formula (7) is also preferably used.

[0035]

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(However, R ₁₀ and R ₁₁ represent hydrogen or an aliphatic group, at least one of which is an aliphatic group having 12 or more carbon atoms.) A dibasic acid represented by the general formula (7) Specific examples include the following.

Dodecylmalonic acid, tetradecylmalonic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid, tetracosylmalonic acid, didotecilmalonic acid, ditetradecylmalonic acid, dihexadecylmalonic acid, Dioctadecylmalonic acid, dieicosylmalonic acid, didcosylmalonic acid, methyloctadecylmalonic acid, methyldocosylmalonic acid, methyltetracosylmalonic acid, ethyloctadecylmalonic acid, ethyleicosylmalonic acid, ethyldocosylmalonic acid, ethyl Tetracosylmalonic acid and the like. As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (8) is also preferably used.

[0038]

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(Where R ₁₂ represents an aliphatic group having 12 or more carbon atoms, n represents 0 or 1, and m represents 1, 2 or 3
And when n is 0, m is 2 or 3, and when n is 1, m represents 1 or 2.) Specific examples of the dibasic acid represented by the general formula (8) include, for example, The following are mentioned.

2-dodecyl-pentanedioic acid, 2-hexadecyl-pentanedioic acid, 2-octadecylpentanedioic acid, 2-eicosyl-pentanedioic acid, 2-docosyl-pentanedioic acid, 2-dodecyl-hexanedioic acid, 2-pentadecyl-hexane diacid, 2-octadecyl-hexane diacid, 2-eicosyl-hexane diacid, 2-docosyl-hexane diacid, and the like. As the aliphatic carboxylic acid compound, a tribasic acid such as citric acid acylated with a long-chain fatty acid is also preferably used. Specific examples include the following.

[0041]

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(C) Phenol compound A compound represented by the following general formula (9) is preferably used.

[0043]

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(Where Y is -S-, -O-, -CON
H- or an -COO-, R ₁₃ represents a number of 12 or more aliphatic group having a carbon, n is an integer of 1, 2 or 3. Specific examples of the phenol compound represented by the general formula (9) include the following.

P- (dodecylthio) phenol, p-
(Tetradecylthio) phenol, p- (hexadecylthio) phenol, p- (octadecylthio) phenol, p- (eicosylthio) phenol, p- (docosylthio) phenol, p- (tetracosylthio) phenol, p- (dodecyloxy) ) Phenol, p- (tetradecyloxy) phenol, p- (hexadecyloxy) phenol, p- (octadecyloxy) phenol, p- (eicosyloxy) phenol, p- (docosyloxy) phenol, p- (tetracosyloxy) phenol Ruoxy)
Phenol, p-dodecylcarbamoylphenol, p
-Tetradecylcarbamoylphenol, p-hexadecylcarbamoylphenol, p-octadecylcarbamoylphenol, p-eicosylcarbamoylphenol, p-docosylcarbamoylphenol, p-tetracosylcarbamoylphenol, hexadecyl gallate, octadecyl gallate , Eicosyl gallate, docosyl gallate, tetracosyl gallate and the like. As the phenol compound, caffeic acid alkyl esters represented by the following general formula (10) can also be used.

[0046]

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(However, R ₁₄ is an alkyl group having 5 to 8 carbon atoms.) Specific examples of the caffeic acid alkyl ester represented by the general formula (10) include caffeic acid-n-pentyl and caffeic acid. -N-hexyl, caffeic acid-n-octyl and the like.

(D) Metal salt of mercaptoacetic acid A metal salt of alkyl or alkenyl mercaptoacetic acid represented by the general formula (11) can be preferably used. (R ₁₅ -S-CH ₂ -COO) ₂ M (11) (where R ₁₅ represents an aliphatic group having 10 to 18 carbon atoms,
M represents tin, magnesium, zinc or copper. Specific examples of the metal mercaptoacetate represented by the general formula (11) include the following.

Tin decyl mercaptoacetate, tin dodecyl mercapto acetate, tin tetradecyl mercapto acetate, tin hexadecyl mercapto acetate, tin octadecyl mercapto acetate, magnesium decyl mercapto acetate, magnesium dodecyl mercapto acetate, magnesium tetradecyl mercapto Magnesium acetate, magnesium hexadecylmercaptoacetate, magnesium octadecylmercaptoacetate, zinc decylmercaptoacetate,
Dodecyl mercapto acetate zinc salt, tetradecyl mercapto acetate zinc salt, hexadecyl mercapto acetate zinc salt, octadecyl mercapto acetate zinc salt, decyl mercapto acetate copper salt, dodecyl mercapto acetate copper salt, tetradecyl mercapto acetate copper salt, hexadecyl mercapto acetate copper salt,
Octadecyl mercapto acetate copper salt and the like.

In the present invention, the color developer is not limited to the compounds described above, and various other electron-accepting compounds can be used. In the heat-sensitive recording medium of the present invention, the developer is used in an amount of 1 to 20 parts, preferably 2 to 10 parts, per part of the color former. The color developer can be applied alone or as a mixture of two or more types, and the color former can also be applied alone or as a mixture of two or more types.

As the binder resin in the heat-sensitive coloring layer used in the present invention, various known resins can be used, for example, polyacrylamide, maleic acid copolymer, polyacrylate, polymethacrylate, chloride, etc. There are vinyl / vinyl acetate copolymer, styrene copolymer, polyester, polyurethane, polyvinyl butyral, ethyl cellulose, polyvinyl acetal, polyvinyl acetoacetal, polycarbonate, epoxy resin, polyamide and the like. It is preferable from the viewpoint of transparency to use a resin having a ratio of the refractive index of the resin to the refractive index of the support between 0.8 and 1.2.

The resin used for the protective layer in the present invention includes, in addition to a water-soluble resin, an aqueous emulsion, a hydrophobic resin, an ultraviolet ray and an electron beam curable resin. Specific examples of the resin include poly (meth) acrylate resin,
Polyvinyl butyral resin, polyvinyl acetoacetal resin, ethyl cellulose, methyl cellulose, cellulose acetate, hydroxyethyl cellulose, cellulose acetate propionate, polyurethane resin, polyester resin, polyvinyl acetate resin, styrene acrylate resin, polyolefin resin, polystyrene resin Resin, polyvinyl chloride resin, polyether resin, polyamide resin, polycarbonate resin, polyethylene resin, polypropylene resin, polyacrylamide resin and the like. Further, a crosslinking agent can be added as needed. As the crosslinking agent used together with such a resin, a conventionally known compound can be used. Further, from the viewpoint of transparency, it is preferable to use a resin having a refractive index ratio of 0.8 to 1.2 with respect to the transparent support as the protective layer resin in the present invention.

In the present invention, as the filler for the protective layer, the smaller the particle size, the easier it is to form a finer surface and the better the transparency. At this time, it is preferable to use one having an average particle size of 1.0 μm or less. However, it is necessary not only to use a filler having a small particle size, but also to appropriately adjust the mixing ratio of the resin and the filler and the dispersibility in the layer, and to apply ultrasonic treatment to the coating liquid. In the present invention, a small amount of a filler having a particle size larger than the above-mentioned particle size can be added as long as the transparency is not reduced and the surface of the protective layer of the present invention can be formed. Examples of fillers include phosphate fiber, potassium titanate,
Acicular magnesium hydroxide, whisker, talc, mica, glass flake, calcium carbonate, plate charcoal, aluminum hydroxide, plate aluminum hydroxide, silica,
Clay, kaolin, talc, calcined clay, inorganic fillers such as hydrotalcite, crosslinked polystyrene resin, urea-formalin resin, silicone resin, crosslinked polymethacrylate methyl acrylate resin, melamine-formaldehyde resin, and organic fillers such as, The present invention is not limited to this.

In order to further improve the head matching, wax or oil is added to the protective layer, or a resin modified with silicon is used alone or as a mixture as a binder resin. The ratio of resin to filler is adjusted. The dynamic friction coefficient can be adjusted by changing the type of the organic pigment. Examples of the waxes that can be used here include stearic acid amide, palmitic acid amide, oleic acid amide, lauric acid amide, ethylenebisstearamide, methylenebisstearamide, methylol stearoamide, paraffin wax, polyethylene, and carnauba Wax, paraffin oxide, zinc stearate and the like. As the oil, a general silicone oil or the like can be used.

Organic resins (toluene, methyl ethyl ketone, alcohols, etc.) among the resins used for the protective layer of the present invention.
When used on a thermosensitive coloring layer, the leuco dye and the developer generally dissolve and come into contact with each other to form a color immediately after coating. In order to prevent this color formation, a leuco dye and / or a developer which is insoluble or slightly soluble in the solvent to be used is selected and used, and the leuco dye and / or the developer are coated with microcapsules, and the dye and the developer come into contact with each other. It is desirable to take a method of making the resin layer difficult to perform, providing a resin layer on the heat-sensitive coloring layer, and making it difficult for the dye and the developer to come into contact with each other. Among them, it is preferable to use the organic phosphoric acid compound represented by the general formula (1) as a color developer in terms of fog due to a solvent, color sensitivity, and color density. When this compound is used as a color developer, those having a hydroxyl group among the resins used in the above-mentioned heat-sensitive recording layer are preferable from the viewpoint of color development and storage. Specific examples include polyvinyl butyral and polyvinyl acetoacetal.

In the heat-sensitive recording layer of the present invention, the color-forming layer is formed by uniformly dispersing or dissolving the color former and the developer together with a binder resin in water or an organic solvent, or by microencapsulation, coating this on a support and drying. The coating method is not particularly limited. When a developer is dispersed in the coating liquid for the recording layer or a microencapsulated liquid is used,
Since the particle size of the developer or the microcapsules greatly affects the surface roughness and transparency of the protective layer and, consequently, the dot reproducibility at the time of printing, the particle size is preferably 1.0 μm or less. The thickness of the recording layer is about 1 to 50 μm, preferably about 3 to 20 μm, although it depends on the composition of the recording layer and the use of the thermosensitive recording medium. In addition, various additives such as a surfactant can be added to the recording layer coating liquid, if necessary, for the purpose of improving coatability or recording characteristics.

The polyester resin used in the back layer of the present invention is not particularly limited as long as it is obtained by polycondensation of a general polybasic acid and a polyhydric alcohol, except that Tg is 60 ° C. or higher. Representative examples of these include phthalic anhydride, maleic anhydride, fumaric acid, adipic acid as polybasic acids, and ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol as polyhydric alcohols, each of which is saturated. There are polyesters and unsaturated polyesters, and modified types such as polyester urethane and epoxy urethane.

As the organic solvent, those used for ordinary solvent coating for solubilizing polyester, specifically, methyl ethyl ketone, ethyl acetate, cellosolve acetate, dioxane, tetrahydrofuran, benzene, toluene, xylene, styrene monomer , Cyclohexanone, etc., which may be appropriately mixed for solubilization.

The conductive metal oxide used for the antistatic layer is ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In.
_At least one selected from the group consisting of ₂ O ₃ , SiO ₂ , MgO, BaO, MoO _3, and composite oxide fine particles thereof.
It is a species, and it is particularly preferable to use SnO ₂ . The main components in each layer of the transparent thermosensitive recording material of the present invention,
Specific examples of the leuco dye, the developer, the binder resin, and the antistatic agent have been described, but the present invention is not limited thereto. If necessary, known fillers, pigments, surfactants, and heat-fusible substances can be added.

[0060]

Next, the present invention will be described in more detail by way of examples. In the following, all parts and percentages are based on weight.

[0061]

【Example】

Example 1 The following composition was pulverized and dispersed in a ball mill to an average particle diameter of 0.3 μm to prepare a recording layer coating liquid.

[Solution A] 2-anilino-3-methyl-6-diethylaminofluoran 4 parts Octadecylphosphonic acid 12 parts Polyvinyl butyral (Denka Butyral # 3000-2, manufactured by Denki Kagaku Kogyo Co., Ltd.) 6 parts Toluene 57 parts Methyl ethyl ketone 57 A 75 μm-thick polyester film (Unitika T-75 Haze 3)
%) And dried to form a heat-sensitive recording layer having a thickness of 11 μm. Next, a filler dispersion (solution B) was prepared by dispersing the following composition in a ball mill to an average particle size of 0.3 μm.

[Solution B] Guanamine-formaldehyde copolymer particles (Nippon Shokubai, Epostar S, average particle diameter 0.3 μm) 30 parts Polyvinyl acetoacetal resin solution (KS-1, 10% MEK, Sekisui Chemical) Dissolved solution) 30 parts Methyl ethyl ketone 140 parts Further, the following composition was sufficiently stirred, and a protective layer coating solution (Solution C)
Was prepared.

[Solution C] Solution B 150 parts Silicon modified polyvinyl butyral resin (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) 45 parts Polyvinyl acetoacetal resin solution (manufactured by Sekisui Chemical, KS-1) , 10% MEK solution) 34 parts Methyl ethyl ketone 109 parts The protective layer coating solution [solution C] prepared as described above was subjected to ultrasonic treatment for 15 minutes, and then applied onto the previously obtained thermosensitive recording layer. After drying, a protective layer having a thickness of 1.5 μm was provided.

[Liquid D, back layer] Polyester resin (manufactured by Toyobo, CR-245, Tg = 60 ° C) 20 parts Methyl ethyl ketone 40 parts Cyclohexanone 40 parts [Liquid E antistatic layer] Tin oxide / polyester resin dispersion (Colcoat) , SP-2002, average particle size 0.2 μm) 8 parts Water 30 parts Methanol 30 parts The above [solution D] was coated on the back surface of the obtained support with a thickness of 8 μm.
After coating and drying the back layer so as to obtain, and further applying and drying an antistatic layer on the back layer so as to have a thickness of 0.4 μm, the obtained sample was cut into A6 size, After aging overnight in a constant temperature bath at 40 ° C., a transparent thermosensitive recording material of the present invention was obtained.

Example 2 The polyester resin [solution D] of Example 1 was replaced with Vylon 29
A transparent thermosensitive recording material of Example 2 was obtained in the same manner except that the temperature was changed to 0 (manufactured by Toyobo, Tg = 72 ° C.). Example 3 The polyester resin [D solution] of Example 1 was used in UE-369.
A transparent thermosensitive recording material of Example 3 was obtained in the same manner except that the temperature was changed to 0 (manufactured by Unitika, Tg = 90 ° C.).

Example 4 A transparent heat-sensitive recording material of Example 4 was obtained in the same manner except that the polyester resin of Example 1 was changed to UR-1400 (Toyobo, Tg = 83 ° C.) which is a polyester urethane resin. . Example 5 A transparent heat-sensitive recording material of Example 5 was obtained in the same manner as in Example 1 except that cyclohexanone in [solution D] was changed to toluene.

Comparative Example 1 The polyester resin [solution D] of Example 1 was replaced with GK-600.
(Manufactured by Toyobo, Tg = 45 ° C.), and a transparent thermosensitive recording material of Comparative Example 1 was obtained in the same manner. Comparative Example 2 The polyester resin of [Solution D] of Example 1 was replaced with Viron 30.
A transparent thermosensitive recording material of Comparative Example 2 was obtained in the same manner except that the temperature was changed to 0 (manufactured by Toyobo, Tg = 10 ° C.). Comparative Example 3 The polyester resin in the back layer of Example 1 was applied by diluting water-dispersed high molecular weight polyester polyester Vironal MD-1250 (manufactured by Toyobo, Tg = 62 ° C., solid content 40%) to 20% with water. Except for the above, a transparent thermosensitive recording material of Comparative Example 3 was obtained.

Example 6 The same procedure as in Example 1 was repeated except that the tin oxide / polyester resin of [Solution E] was changed to sodium polystyrene sulfonate (30% solution, manufactured by Sanyo Chemical Co., Ltd.). The material was obtained. The transparent thermosensitive recording materials of Examples and Comparative Examples obtained as described above were evaluated according to the following test methods.

Curl After the aged sample was left in an environment of 20 ° C. and 65% RH for 3 hours, the amount of curl was measured using a gold scale, and the values of the four pieces were averaged to obtain the curl value. -Coating uniformity The coating uniformity of the back layer of the sample was visually judged.

Surface resistance A sample was cut into a size of 10 × 10 cm.
% RH for 3 hours, and a HIGH RESISTANCE METER manufactured by Hewlett-Packard Company.
Set to type 4329A and set DISCHARGE
The resistance value was measured after 1 minute, CHARGE 1 minute, and MEASURE 1 minute.

Blocking The front and back surfaces of the sample are each superposed three by three.
Under a DRY environment at 40 ° C., a load of 5 kg was applied, and the degree of blocking after storage for one week was visually determined. Table 1 shows the results of evaluation by the above test methods.

[0073]

[Table 1]

From this table, it is clear that the transparent thermosensitive recording material of the present invention has good curlability and good handling properties and print runnability, has no problem in coating uniformity, has excellent transparency, and has low surface resistance, and therefore has good dust. Less adhesion of dust, etc.
Further, it was confirmed that there were no side effects such as blocking.

[0075]

The transparent thermosensitive recording material of the present invention is provided with a back layer of a water-insoluble polyester resin having a Tg of 60 ° C. or higher dissolved in an organic solvent on the back surface of the support, so that curling is reduced and dust, dust, etc. And a practical transparent heat-sensitive recording material free from adhesion.

[Procedure amendment]

[Submission date] February 7, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008] Therefore, Tg is a measure of the hardness and softness of the resin. A high Tg resin is indicated as a hard and brittle resin, and a low Tg resin is indicated as a soft and flexible resin. Therefore, Tg is 55
It has been found that by providing a back layer of a polyester resin at a temperature of not less than ° C., the resin can be curled toward the back side due to shrinkage due to hardness, thereby achieving a curl balance. At this time, if the polyester resin is 55 ° C. or less, curling does not occur because of high flexibility, and stickiness occurs after drying, causing blocking between the front surface and the back surface. Since the polyester resin used is insoluble in water, it is applied by dissolving in an organic solvent.However, since it is insoluble in water, it has no hygroscopic property and its effect on curling is not affected by environmental changes due to humidity changes. . And it was discovered that the use of cyclohexanone, which is a solvent that easily dissolves the polyester resin, suppresses the occurrence of yuzu skin, can form a uniform and clear coating film, and can be applied without impairing the transparency. With respect to the effect of cyclohexanone, the present inventors consider that the evaporation rate is low due to the high boiling point, so that the evaporation of the solvent is prevented from abruptly and the swirling convection generated during drying is suppressed.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0057

[Correction method] Change

[Correction contents]

The polyester resin used in the back layer of the present invention is not particularly limited as long as it is obtained by polycondensation of a general polybasic acid and a polyhydric alcohol, except that the Tg is 55 ° C. or higher. Representative examples of these include phthalic anhydride, maleic anhydride, fumaric acid, adipic acid as polybasic acids, and ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol as polyhydric alcohols, each of which is saturated. There are polyesters and unsaturated polyesters, and modified types such as polyester urethane and epoxy urethane.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Change

[Correction contents]

Example 6 The transparent heat-sensitive recording of Example 6 was carried out in the same manner as in Example 1 except that the tin oxide / polyester resin of [solution E] was changed to sodium polystyrene sulfonate (30% solution, manufactured by Sanyo Chemical Industries, Ltd.). The material was obtained. The transparent thermosensitive recording materials of Examples and Comparative Examples obtained as described above were evaluated according to the following test methods.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B41M 5/18 101D

Claims (3)

[Claims] 1. A heat-sensitive recording layer comprising, as a main component, a colorless or light-colored leuco dye, a developer for causing the leuco dye to develop a color and a binder resin as a binder, on a transparent support.
Further, in a heat-sensitive recording material comprising a protective layer containing a resin provided thereon, the Tg dissolved in an organic solvent is provided on the back surface of the support.
A transparent heat-sensitive recording material provided with a back layer of a water-insoluble polyester resin having a temperature of 55 ° C. or higher. 2. The transparent thermosensitive recording material according to claim 1, wherein cyclohexanone is used as at least one of the organic solvents in the transparent thermosensitive recording material. 3. The transparent thermosensitive recording material according to claim 1, wherein the back layer has a particle size of 0.2 μm dispersed with a polyester resin.
3. The transparent heat-sensitive recording material according to claim 1, further comprising an antistatic layer made of a conductive metal oxide of m or less.