JPH1081071A - Thermal recording material - Google Patents

Abstract

(57) [Problem] To provide a heat-sensitive recording material excellent in white streaking, sticking and head abrasion while having high image quality. SOLUTION: A thermosensitive recording layer mainly comprising a leuco dye on a support, a developer for coloring the leuco dye by heating and a binder resin as a binder, and a protective layer further provided thereon with a protective layer. In the material, an organic pigment having an average particle diameter of 1.2 to 3.0 times the protective layer thickness and an organic pigment having an average particle diameter of 0.05 to 0.7 μm are mixed in the protective layer. Used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Various recording materials have been proposed which utilize a color development reaction between a colorless or light-colored leuco dye and a color developer which develops color when contacted by heat and pressure. One such heat-sensitive recording material does not require frequent processing such as development and fixing, and can be recorded in a short time with a relatively simple device, has less noise, and has further advantages such as lower cost. Thus, it is useful as various recording materials for electronic computers, facsimile machines, ticket vending machines, label printers, recorders and the like.

As a color-forming dye used for a heat-sensitive recording material, for example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring is used, and as a developer, an organic acid, a phenolic substance or the like is conventionally used. ing. The heat-sensitive recording material using this leuco dye and a developer,
It is widely used because of its high image density and high whiteness of the background.

[0004] These heat-sensitive recording materials are generally produced by coating the above-described color-forming dye and color developer on paper. In recent years, there has been an increasing number of cases where the smoothness of the surface is increased by an under layer or the like due to a demand for higher image quality. In addition, with the diversification of uses, not only paper but also plastic films having high smoothness are often used as supports. Examples of using such a plastic film as a support include recording materials for video printers, OHP films, and the like.

Particularly, in order to form a transparent and high-quality thermosensitive recording medium such as OHP, a support having high smoothness such as a plastic film is used, and a layer coated on the support has high smoothness. Is required. However, the configuration of the recording medium itself does not differ greatly from a normal paper-based thermal recording medium. Such a thermosensitive recording material has good adhesion between the recording material and the thermal head and good color uniformity, but is added for the purpose of generating sticking due to the good adhesion and improving matching. The surface of the recording material is liable to get dirt and dust due to the problem of head abrasion due to inorganic pigments, etc., and the film base has high chargeability. When the printing is in progress, the component in the coating layer is melted) and the thermal head material is caught between the thermal recording material and the thermal head. There is a problem that it easily occurs.

Conventionally, a protective layer containing an inorganic pigment (inorganic filler) (Japanese Patent Laid-Open No. 61-225095) and an organic pigment (organic filler) have been added in a protective layer to improve sticking and white stripes. JP-A-58-025988
And Japanese Patent Application Laid-Open No. 05-278334), however, the inorganic filler is insufficient in terms of head wear, and the configuration described also with respect to the organic filler has a disadvantage against white streaks and sticks. Insufficient.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce head abrasion and to eliminate the phenomenon (hereinafter referred to as stick or sticking) of a phenomenon in which white streaks or components in a coating layer are melted and adhered to a thermal head during heating and coloring. It is to provide a recording material.

[0008]

According to the present invention, first, there is provided a heat-sensitive material comprising a leuco dye on a support, a developer for causing the leuco dye to heat and form a color, and a binder resin as a binder. In a thermosensitive recording material comprising a recording layer and a protective layer provided thereon, an organic pigment having an average particle diameter of 1.2 to 3.0 times the thickness of the protective layer and an average particle diameter of 0 in the protective layer. The present invention provides a heat-sensitive recording material characterized by using a mixture with an organic pigment having a thickness of 0.05 to 0.7 µm. Second, in the above first, the protective layer thickness of 1.2 to
A heat-sensitive composition wherein the mixing ratio of the organic pigment having an average particle diameter of 3.0 times to the organic pigment having an average particle diameter of 0.05 to 0.7 μm is in the range of 1: 100 to 1:20. A recording material is provided. Thirdly, there is provided a heat-sensitive recording material according to the first aspect, wherein the content ratio of the resin and the two kinds of organic pigments in the protective layer is resin: organic pigment = 1: 0.5 to 1: 6. Is done. Fourthly, in the first aspect, there is provided a heat-sensitive recording material, wherein the organic pigment in the protective layer is a guanamine-formaldehyde copolymer represented by the following structural formula (I).

Embedded image (Where R is H, CH ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ ,
NH ₂ , NO ₂ , an acetyl group, C ₆ H ₁₁ , C ₆ H ₅ , a benzyl group or a methylphenyl group. Fifth, in the first aspect, there is provided a heat-sensitive recording material characterized by using a polyvinyl acetal resin having a polymerization degree of 2,000 or more as a resin in a protective layer and an isocyanate compound as a crosslinking agent. Sixth, in the first aspect, there is provided a heat-sensitive recording material characterized in that the surface on which the protective layer is coated has a smoothness of 5000 seconds or more.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the heat-sensitive recording material of the present invention will be described below. In the present invention, the use of a soft organic pigment is effective against head wear. As described above, as described above, dust on the recording material surface or head scum generated during printing is caught between the thermal recording material and the thermal head during printing, and an image is formed in a streak shape at that portion and in the vicinity thereof. It is a phenomenon that comes out. Sticking is a phenomenon in which the components in the coating layer are melted at the time of color development by heating and adhere to the thermal head. The present inventors have conducted studies to improve this phenomenon, and as a result, it has been found that the surface state of the protective layer and the friction coefficient of the surface are significantly involved. As a method for obtaining a protective layer surface and a friction coefficient compatible with white streaks and sticks, the present inventors have proposed an organic pigment having an average particle diameter of 1.2 to 3.0 times the protective layer thickness (large) in the protective layer. Filler) and average particle size 0.05 ~
It has been found that this can be achieved by using an organic pigment (small filler) having 0.7 μm mixed in an appropriate ratio. This effect can improve white stickiness by finely roughening the surface with an organic filler smaller than the protective layer film thickness, and prevent sticking to the thermal head by improving the stick of the large organic filler from the protective layer surface. Further, since the large organic filler prevents the head from sticking to each other, it is possible to suppress the deformation of the surface of the protective layer at the time of heating. Therefore, even at the time of heating, the effect of preventing white stripes by the surface formed by the small organic filler can be maintained.

[0010] Furthermore, in order to improve sticking, waxes are added to the protective layer, a resin modified with silicone is used alone or in combination as a binder resin, the ratio of resin to filler is adjusted, The dynamic friction coefficient can be adjusted up or down by changing the type. 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.

Examples of the organic pigment in the present invention include organic fillers such as crosslinked polystyrene resin, urea-formalin resin, silicone resin, crosslinked polymethylmethacrylate resin, and guanamine-formaldehyde resin, or those obtained by embedding them. These can be used alone or as a mixture. Of these, a guanamine-formaldehyde resin is preferred because of the heat resistance of the pigment itself, the state of surface formation, and the ease of adjusting the friction coefficient of the surface. In addition, the particle shape of the organic pigment in the present invention may be irregular or spherical.

The average particle size of the organic pigment in the present invention is:
Although it depends on the thickness of the protective layer from the viewpoint of controlling the surface shape, it is preferably about 1.2 to 3.0 times the thickness of the protective layer for a large organic pigment that prevents adhesion to the head. From the point of view, 1.2 to 2.0 times is more preferable. If the ratio is less than 1.2 times, the effect of preventing head adhesion will be reduced. Conversely, if it exceeds 3.0 times, the dot reproducibility is reduced, and the image quality is reduced. For small organic pigments whose surface is finely roughened to prevent white streaks, the average particle size is preferably between 0.05 and 0.7 μm. 0.05μm
If it is less than 0.7, the effect of roughening the surface is small, and 0.7
If it exceeds μm, the surface roughness becomes large, and the image quality deteriorates, which is not preferable.

Similarly, regarding the mixing ratio between the large pigment and the small pigment, large pigment: small pigment = 1: 20 to 1: 1.
00 is preferable, and when the content of the large pigment is large, the dot reproducibility lowers, and the image quality deteriorates, which is not preferable. Also, if the amount is too small, the effect of preventing sticking is reduced.

In the present invention, the content ratio of the resin and the pigment is preferably in the range of resin: pigment = 1: 0.5 to 1: 6, more preferably 1: 1 to 1: 4. When the resin: pigment ratio is less than 1: 0.5, the effect on white streaks and sticking is low. When the ratio is more than 1: 6, the effect of the resin as a binder is small, and the protective layer is easily peeled off. I will.

In the present invention, large irregularities on the surface of the protective layer,
From the viewpoint of controlling small irregularities, the smoothness of the surface on which the protective layer is applied is preferably as high as possible, and the smoothness of the protective layer-coated surface is preferably 5000 seconds or more (by Oken formula). In the present invention, a state in which large organic pigments are scattered on a surface finely roughened by small organic pigments is ideal.

The support used in the present invention may be paper and 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 laminate of these. Film, synthetic paper and the like.

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, and is not particularly limited. Known ones, for example, triphenylmethanephthalide, triallylmethane, fluoran, phenothidiane, thiofluoran, xanthene, indophthalyl, spiropyran, azaphthalide, chromenopyrazole, methine, rhodamine anilino Leuco compounds such as lactams, rhodamine lactams, quinazolines, diazaxanthenes and bislactones are preferably used. Examples of such compounds include, for example, those shown below.

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-methyl-2,
4-dimethylanilino) fluoran, 2-benzylamino-6- (N-ethyl2,4-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, 2-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-anilino-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 others.

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 a long-chain alkyl group in the molecule disclosed in Japanese Unexamined Patent Publication No. 5-124360. For example, an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having an aliphatic group having 12 or more carbon atoms, a metal salt of mercaptoacetic acid having an aliphatic group having 10 to 18 carbon atoms, or a metal salt of 5 to 8 carbon atoms And alkyl phosphates of caffeic acid having an alkyl group, and acidic phosphate esters 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.

Embedded image (In the formula, R ₁ represents a linear alkyl group having 12 to 24 carbon atoms.)

The following are specific examples of the organic phosphoric acid compound represented by the general formula (1). 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.

Embedded image (In the formula, R ₂ represents an aliphatic group having 11 to 29 carbon atoms.)

Specific examples of the α-hydroxyalkylphosphonic acid represented by the general formula (2) include α-hydroxydodecylphosphonic acid, α-hydroxytetradecylphosphonic acid, α-hydroxyhexadecylphosphonic acid, and α-hydroxyhexadecylphosphonic acid. Examples include hydroxyoctadecylphosphonic acid, α-hydroxyeicosylphosphonic acid, α-hydroxydocosylphosphonic acid, and α-hydroxytetracosylphosphonic acid.

As the organic phosphoric acid compound, an acidic organic phosphoric acid ester represented by the following general formula (3) is also used.

Embedded image (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.)

Specific examples of the acidic organic phosphate represented by the general formula (3) include dihexadecyl phosphate, dioctadecyl phosphate, dieicosyl phosphate, didocosyl phosphate, monohexadecyl phosphate, and monooctadecyl. Phosphate, monoeicosyl phosphate, monodocosyl phosphate, methyl hexadecyl phosphate, methyl octadecyl phosphate, methyl eicosyl phosphate, methyl docosyl phosphate, amyl hexadecyl phosphate,
Octyl hexadecyl phosphate, lauryl hexadecyl phosphate and the like can be mentioned.

(B) Aliphatic carboxylic acid compounds α-hydroxy fatty acids represented by the following general formula (4) are preferably used.

Embedded image R ₅ —CH (OH) —COOH (4) (In the formula, 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. α-hydroxydecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid , Α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid and the like.

As the aliphatic carboxylic acid compound, an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms and substituted by a halogen atom and having a halogen atom at least in the α-position or β-position carbon is also used. It is 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-bromoeicosanoic 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, perfluorooctadecanoic acid and the like.

The aliphatic carboxylic acid is an aliphatic carboxylic acid compound having an oxo group in the carbon and having an aliphatic group having 12 or more carbon atoms, wherein 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-oxotetradecanoic 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.

Embedded image (In the formula, 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.)

Specific examples of the dibasic acid represented by the general formula (5) include the following. Dodecylmalic acid, tetradecylmalic acid, hexadecylmalic acid, octadecylmalic acid, eicosylmalic acid, docosylmalic acid, tetracosylmalic acid, dodecylthiomalic acid, tetradecylthiomalic acid, hexadecylthiomalic acid, octadecyl Thiomalic acid, eicosylthiomalic acid, docosylthiomalic acid, tetracosylthiomalic acid, dodecyldithiomalic acid, tetradecyldithiomalic acid, eicosyldithiomalic acid, docosyldithiomalic acid, tetracosyldithiomalic acid Acids and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (6) is also preferably used.

Embedded image (In the formula, R ₇ , R ₈ , and R ₉ represent a hydrogen atom or an aliphatic group, and at least one of them is an aliphatic group having 12 or more carbon atoms.)

Specific examples of the dibasic acid represented by the general formula (6) include 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-Dioctadecylbutanedioic acid, 2-methyl-3-dodecylbutanedioic acid, 2-methyl-3-tetradecylbutanedioic acid, 2
-Methyl-3-hexadecylbutanedioic acid, 2-ethyl-
3-dodecyl butane diacid, 2-propyl-3-dodecyl butane diacid, 2-octyl-3-hexadecyl butane diacid, 2-tetradecyl-3-octadecyl butane diacid, and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (7) is also preferably used.

Embedded image (In the formula, R ₁₀ and R ₁₁ represent a hydrogen atom as an aliphatic group, at least one of which is an aliphatic group having 12 or more carbon atoms.)

Specific examples of the dibasic acid represented by the general formula (7) 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, Didocosylmalonic acid, Methyloctadecylmalonic acid, Methyldocosylmalonic acid, Methyl Tetracosylmalonic acid, ethyloctadecylmalonic acid, ethyleicosylmalonic acid, ethyldocosylmalonic acid, ethyltetracosylmalonic acid and the like.

As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (8) is also preferably used.

Embedded image (Wherein, R ₁₂ represents an aliphatic group having 12 or more carbon atoms, n represents 0 or 1, m represents 1, 2 or 3, and when n is 0, m is 2 or 3; When n is 1, m is 1 or 2
It is. )

The following are specific examples of the dibasic acid represented by the general formula (8). 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-hexanedioic acid, 2-eicosyl-hexanedioic acid, 2-docosyl-hexanedioic acid 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.

Embedded image

Embedded image

Embedded image

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

Embedded image (Wherein Y is -S, -O-, -CONH- or -COO
R ₁₃ represents an aliphatic group having 12 or more carbon atoms;
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, 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, an alkyl caffeic acid ester represented by the following general formula (10) can also be used.

Embedded image (In the formula, R ₁₄ represents 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, caffeic acid-n-hexyl, caffeic acid-n-octyl and the like.

(C) Metal salt of mercaptoacetic acid A metal salt of alkyl or alkenyl mercaptoacetic acid represented by the general formula (11) can be preferably used.

Embedded image (R ₁₅ —S—CH ₂ —COO) ₂ M (11) (wherein, R ₁₅ represents an aliphatic group having 10 to 18 carbon atoms;
Represents tin, magnesium, zinc or copper. )

Specific examples of the metal mercaptoacetate represented by the general formula (11) include the following. Tin decyl mercapto acetate, tin dodecyl mercapto acetate, tin tetradecyl mercapto acetate, tin hexadecyl mercapto acetate, octadecyl mercapto acetate, magnesium decyl mercapto acetate, magnesium dodecyl mercapto acetate, magnesium tetradecyl mercapto acetate , Magnesium hexadecylmercaptoacetate, magnesium octadecylmercaptoacetate, zinc decylmercaptoacetate, zinc dodecylmercaptoacetate, zinc tetradecylmercaptoacetate, zinc hexadecylmercaptoacetate, zinc octadecylmercaptoacetate, copper decylmercaptoacetate Salts, copper dodecylmercaptoacetate, copper tetradecylmercaptoacetate,
Copper hexadecyl mercaptoacetate, copper octadecyl mercaptoacetate, 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 color 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 in combination of two or more, and the color former can also be applied alone or in combination of two or more.

Next, various known resins can be used as the binder resin in the thermosensitive coloring layer used in the present invention.
For example, polyacrylamide, maleic acid copolymer, polyacrylate, polymethacrylate,
Vinyl chloride / vinyl acetate copolymer, styrene copolymer,
Polyester, polyurethane, polyvinyl butyral,
Ethyl cellulose, polyvinyl acetal, polyvinyl acetoacetal, polycarbonate, epoxy resin,
Polyamide and the like.

The specific examples of the leuco dye, the color developer, and the binder resin, which are the main components in the heat-sensitive coloring layer of the heat-sensitive recording material of the present invention, are not limited to these. Also,
If necessary, known fillers, pigments, surfactants, and heat-fusible substances can be added.

The resin used for the protective layer of the present invention is often used after being dissolved in an organic solvent (toluene, methyl ethyl ketone, alcohols, etc.). Dissolve and come into contact with each other, causing color development immediately after application. To prevent this coloring,
Selective use of a leuco dye and / or a developer which is insoluble or slightly soluble in a solvent to be used. The leuco dye and / or the developer is coated with microcapsules so that the dye and the developer are less likely to come into contact with each other. A resin layer is provided on the coloring layer,
It is desirable to take a method of making the dye and the developer hardly contact with each other. Among them, as the color developer, the above-mentioned general formula (1)
It is preferable to use an organic phosphoric acid compound represented by the following formulas in terms of fogging due to a solvent, color sensitivity, color density, and head matching.

The heat-sensitive recording layer of the present invention is prepared by uniformly dispersing or dissolving a color former and a developer together with a binder resin in water or an organic solvent, applying the resultant on a support, and drying. The construction method is not particularly limited. In the case of using a dispersion in which a developer is dispersed in the coating liquid for the recording layer, the particle size of the developer is 0.1% because the particle size of the developer greatly affects the surface roughness of the protective layer and, consequently, the dot reproducibility during printing. 5 μm or less is preferable. The thickness of the recording layer depends on the composition of the recording layer and the use of the thermosensitive recording medium, but is about 1 to 50 μm, preferably 3 to 20 μm.
It is about μm. 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.

In the present invention, a layer containing a pigment, a binder, a heat-fusible substance or the like is provided as an intermediate layer between the support and the thermosensitive coloring layer, if necessary, for example, to improve smoothness. I can do it.

In the present invention, a protective layer is provided on the heat-sensitive coloring layer in order to improve chemical resistance, water resistance, friction resistance, light resistance, and head matching with a thermal head. The resin used here is poly (meth)
Acrylic acid ester resin, polyvinyl butyral resin,
Polyvinyl acetoacetal resin, ethyl cellulose,
Methyl cellulose, cellulose acetate, hydroxyethyl cellulose, cellulose acetate propionate, polyurethane resin, polyester grease, polyvinyl acetate resin, styrene acrylate resin, polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyether Thermoplastic resins such as resin, polyamide resin, polycarbonate resin, polyethylene resin, polypropylene resin, and polyacrylamide resin are used. Further, these silicone-modified resins are used alone or in combination to adjust the coefficient of friction. A silicone-modified resin is a resin having a siloxane bond and an alkyl group such as a methyl group bonded to a silicon atom, and having a reactive functional group such as a hydroxyl group, a carboxyl group, an epoxy group, an amino group, or a mercapto group at the molecular terminal or in the molecule. An organopolysiloxane having a group is copolymerized with a base resin. 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. From the viewpoint of the dispersibility of the pigment and the heat resistance of the resin, as the preferable combination of the resin and the crosslinking agent in the present invention, a polyvinyl acetal resin having a polymerization degree of 2000 or more as the resin and an isocyanate compound as the crosslinking agent are preferable. Specific examples of the isocyanate compound include toluylene diisocyanate, a dimer thereof, diphenylmethane diisocyanate,
Compounds having two or more isocyanate groups in the molecule, such as polymethylene polyphenyl isocyanate, hexamethylene diisocyanate, polyisocyanate, and derivatives thereof, may be mentioned.

The coating method of the protective layer is not particularly limited, and it can be applied by a conventionally known method. The preferred protective layer thickness is 0.1-20 μm, more preferably 0.5-10 μm
m. If the thickness of the protective layer is too thin, the storage layer of the recording medium and the function as a protective layer such as head matching are insufficient, and if it is too thick, the thermal sensitivity of the recording medium decreases and the cost is disadvantageous.

The recording method of the thermosensitive recording medium of the present invention is not particularly limited, such as a hot pen, a thermal head, and laser heating, depending on the purpose of the specification. Further, the present invention is not limited to the transparent and opaque thermosensitive recording media. Further, the present invention provides a reversible,
It is not limited to an irreversible thermosensitive recording medium.

[0056]

The present invention will be described below with reference to examples. In the following, all parts and percentages are based on weight.

Example 1 The following composition was pulverized and dispersed in a ball mill to a particle size of 0.3 μm to prepare a recording layer coating solution. [Solution A] 3-diethylamino-6-methyl-7-anilinofluoran 4 parts Octadecylphosphonic acid 12 parts Polyvinyl butyral 6 parts (Denka Butyral # 3000-2, manufactured by Denki Kagaku Kogyo Co., Ltd.) Toluene 57 parts Methyl ethyl ketone 57 parts

The coating solution prepared as described above was
[Liquid A] was applied on a 5 μm polyester film and dried to form a 10 μm thick thermosensitive recording layer. The smoothness of the surface of the heat-sensitive recording layer was 7,000 seconds.

Next, the following composition was dispersed in a ball mill,
A dispersion [liquid B] for a protective layer coating liquid was prepared. [Liquid B] Melamine-formaldehyde copolymer particles 30 parts (Nippon Shokubai, Eposta-S, average particle size 0.3 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK dissolved) Liquid) methyl ethyl ketone 140 parts

Next, the following composition was dispersed in a ball mill,
A protective layer coating liquid dispersion [liquid C] was prepared. [Liquid C] Guanamine-formaldehyde copolymer particles 30 parts (Nippon Shokubai, Eposta-M30, average particle size 3.0 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK dissolved) Liquid) methyl ethyl ketone 140 parts

Further, the following composition was sufficiently stirred to prepare a protective layer coating solution [D solution]. [Solution D] [Solution B] 150 parts [Solution C] 5 parts Silicone modified polyvinyl butyral resin 20 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 53 parts ( Sekisui Chemical, KS-5, degree of polymerization 2400, 5% MEK solution) Methylene diisocyanate derivative compound 1 part (Nippon Polyurethane, Coronate HX) methyl ethyl ketone 110 parts Toluene 77 parts

The coating solution for protective layer prepared as described above [D
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 1.5 μm was provided to prepare a thermosensitive recording medium of the present invention. At this time, the magnification of the large particle size filler with respect to the protective layer is 2.0 times.

Example 2 A heat-sensitive recording layer was formed on a polyester film in the same manner as in Example 1.

Next, the following composition was dispersed in a ball mill,
A protective layer coating liquid dispersion [E liquid] was prepared. [E Solution] Melamine-formaldehyde copolymer particles 30 parts (Nippon Shokubai, Eposta-S6, average particle diameter 0.6 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK dissolved) Liquid) methyl ethyl ketone 140 parts

Next, the following composition was dispersed in a ball mill,
A dispersion [solution F] for a protective layer coating liquid was prepared. [Solution F] Crosslinked poly (methyl methacrylate) particles 30 parts (Nippon Shokubai, Eposta-MA1004, average particle size 4.0 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK solution) 140 parts of methyl ethyl ketone

Further, the following composition was sufficiently stirred to prepare a protective layer coating solution [solution G]. [Solution G] [Solution E] 100 parts [Solution F] 2.5 parts Silicone-modified polyvinyl butyral resin 20 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 69 Parts (manufactured by Sekisui Chemical, KS-1, degree of polymerization 500, 5% MEK solution) 92 parts of methyl ethyl ketone 65 parts of toluene

The protective layer coating solution [G
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 3 μm was provided to prepare a thermosensitive recording medium of the present invention. At this time, the magnification of the large particle size filler with respect to the protective layer is 1.3 times.

Example 3 Inorganic pigment (average particle size: 6 μm) on a polyester film
And an intermediate layer containing a resin, and the same heat-sensitive recording layer as in Example 1 was formed thereon. The smoothness of the surface of the heat-sensitive recording layer was 500 seconds. A protective layer similar to that of Example 2 was provided on this heat-sensitive recording layer, and a heat-sensitive recording medium of the present invention was produced.
At this time, the magnification of the large particle size filler with respect to the protective layer is 1.3.
It is twice.

Example 4 A heat-sensitive recording layer was formed on a polyester film in the same manner as in Example 1.

Next, the following composition was dispersed in a ball mill,
A protective layer coating liquid dispersion (H liquid) was prepared. [H Solution] Crosslinked polymethyl methacrylate particles 30 parts (Nippon Shokubai, Eposter MA1006, average particle diameter 6.0 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK solution) 140 parts of methyl ethyl ketone

Further, the following composition was sufficiently stirred to prepare a protective layer coating solution [solution I]. [Solution I] [Solution B] 150 parts [Solution H] 5 parts Silicone modified polyvinyl butyral resin 20 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 53 parts ( Sekisui Chemical, KS-1, polymerization degree 500, 5% MEK solution) methyl ethyl ketone 110 parts toluene 77 parts

The protective layer coating solution [I
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 2 μm was provided to prepare a thermosensitive recording medium of the present invention. At this time, the magnification of the large particle size filler with respect to the protective layer is 3.0 times.

Example 5 A heat-sensitive recording layer was formed on a polyester film in the same manner as in Example 1.

Next, the following composition was dispersed in a ball mill,
A dispersion [solution J] for a protective layer coating solution was prepared. [Liquid J] Crosslinked polymethyl methacrylate particles 30 parts (Nippon Shokubai, Eposter MA08W, average particle size 0.08 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK solution) 140 parts of methyl ethyl ketone

Further, the following composition was sufficiently stirred to prepare a protective layer coating solution [K solution]. [Solution K] [Solution J] 100 parts [Solution C] 5 parts Silicone modified polyvinyl butyral resin 20 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 73 parts ( Sekisui Chemical, KS-1, degree of polymerization 500, 5% MEK solution) methyl ethyl ketone 70 parts toluene 37 parts

The protective layer coating solution [K
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 2 μm was provided to prepare a thermosensitive recording medium of the present invention. At this time, the magnification of the large particle size filler with respect to the protective layer is 1.5 times.

Comparative Example 1 A heat-sensitive recording layer was formed on a polyester film in the same manner as in Example 1.

Next, the following composition was pulverized and dispersed in a ball mill to a volume average particle size of 0.3 μm to prepare a dispersion (L liquid) for a protective layer coating liquid. [Liquid L] Silica powder (Mizukasil P-832, manufactured by Mizusawa Chemical) 30 parts Silicone modified polyvinyl butyral resin 24 parts (manufactured by Dainippon Seika, SP-712, solid content, 12.5%) Methyl ethyl ketone 146 parts

Further, the following composition was sufficiently stirred to prepare a protective layer coating solution [M solution]. [Liquid M] [Liquid C] 2.4 parts [Liquid L] 24 parts Silicone modified polyvinyl butyral resin 70 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Methyl ethyl ketone 88 parts

The protective layer coating solution [M
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 1.5 μm was provided to prepare a comparative thermosensitive recording medium. At this time, the magnification of the large particle size filler with respect to the protective layer is 2.0 times.

Comparative Example 2 A heat-sensitive recording layer was formed on a polyester film in the same manner as in Example 1.

Next, the following composition was dispersed in a ball mill,
A dispersion [N liquid] for a protective layer coating liquid was prepared. [N Liquid] Crosslinked polymethyl methacrylate particles 30 parts (Nippon Shokubai, Eposter MA1010, average particle diameter 10 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK solution) Methyl ethyl ketone 140 Department

Further, the following composition was sufficiently stirred to prepare a protective layer coating solution [O solution]. [Liquid O] [Liquid E] 100 parts [Liquid N] 10 parts Silicone modified polyvinyl butyral resin 25 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 53 parts ( Sekisui Chemical, KS-1, degree of polymerization 500, 5% MEK solution) methyl ethyl ketone 40 parts toluene 10 parts

The protective layer coating solution [O prepared above
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 3 μm was provided to prepare a comparative thermosensitive recording medium. At this time, the magnification of the large particle size filler with respect to the protective layer is 3.3 times.

Comparative Example 3 In the same manner as in Example 1, a heat-sensitive recording layer was formed on a polyester film.

Next, the following composition was dispersed in a ball mill,
A dispersion liquid [P liquid] for a protective layer coating liquid was prepared. [P liquid] Crosslinked polymethyl methacrylate particles 30 parts (Nippon Shokubai, Eposter MA1001, average particle diameter 1 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK solution) Methyl ethyl ketone 140 Department

Next, the following composition was dispersed in a ball mill to prepare a protective layer coating liquid [Q liquid]. [Solution Q] [Solution P] 150 parts [Solution C] 5 parts Silicone modified polyvinyl butyral resin 20 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 53 parts ( Sekisui Chemical, KS-1, polymerization degree 500, 5% MEK solution) methyl ethyl ketone 110 parts toluene 77 parts

The coating solution for protective layer [Q
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 2 μm was provided to prepare a comparative thermosensitive recording medium. At this time, the magnification of the large particle size filler with respect to the protective layer is 1.5 times.

Comparative Example 4 A heat-sensitive recording layer was formed on a polyester film in the same manner as in Example 1.

Next, the following composition was dispersed in a ball mill,
A protective layer coating solution [R solution] was prepared. [Solution R] [Solution E] 150 parts [Solution C] 5 parts Silicone modified polyvinyl butyral resin 20 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 53 parts ( Sekisui Chemical, KS-1, polymerization degree 500, 5% MEK solution) methyl ethyl ketone 110 parts toluene 77 parts

The coating solution for protective layer [R
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 3 μm was provided to prepare a comparative thermosensitive recording medium. At this time, the magnification of the large particle size filler with respect to the protective layer is 1.0 times.

Comparative Example 5 A heat-sensitive recording layer was formed on a polyester film in the same manner as in Example 1.

Next, the following composition was dispersed in a ball mill,
A protective layer coating liquid dispersion [S liquid] was prepared. [S Liquid] Crosslinked polymethyl methacrylate particles 30 parts (Nippon Shokubai, Eposter MA03W, average particle size 0.035 μm) Polyvinyl acetoacetal resin solution 30 parts (Sekisui Chemical, KS-1, 10% MEK solution) 140 parts of methyl ethyl ketone

Next, the following composition was dispersed in a ball mill to prepare a protective layer coating liquid [T liquid]. [Liquid T] [Liquid S] 100 parts [Liquid C] 10 parts Silicone modified polyvinyl butyral resin 60 parts (manufactured by Dainichi Seika, SP-712, solid content, 12.5%) Polyvinyl acetoacetal resin solution 162 parts ( Sekisui Chemical, KS-1, polymerization degree 500, 5% MEK solution)

The coating solution for protective layer [T
Liquid] on the heat-sensitive recording layer obtained above, and dried.
A protective layer having a thickness of 2 μm was provided to prepare a comparative thermosensitive recording medium. At this time, the magnification of the large particle size filler with respect to the protective layer is 1.5 times.

<Evaluation> The thermosensitive recording medium produced as described above was evaluated as follows.

(1) White Streaks A black solid was printed under the following printing conditions using a thermal printing simulator manufactured by Okura Electric. (Printing conditions) Thermal head dot density: 8 dots / mm Applied power: 0.68 W / dot Pulse width: 0.30 msec Line cycle: 10 msec / line Printing length: 30 cm Printing width: 20 cm For each example, n = 3 And print n = 1
The average number of white stripes per unit was calculated.

(2) Sticking Printing was performed under the same conditions as in the evaluation of the white stripe except that the pulse width was set to 0.50 msec, and the sound of sticking between the thermal recording medium and the thermal head during printing was evaluated according to the following criteria. (Standard) ○: almost no sticking sound △: a little sticking sound ×: there is sticking sound

(3) Peeling of protective layer Using a thermal printing simulator manufactured by Okura Electric Co., printing was performed under the following printing conditions. (Printing conditions) Thermal head dot density: 8 dots / mm Applied power: 0.68 W / dot Pulse width: From 0.20 to 1.2 msec in steps of 0.1 ms Line cycle: 10 msec / line Protect from any pulse width under these printing conditions It was evaluated whether the layer peeled off.

(4) Dot uniformity Printing was performed under the same conditions as those for the evaluation of white stripes, and the surface was observed with an optical microscope to evaluate the dot reproducibility visually. (Standard) ○: Good dot reproducibility (reproduces dot shape,
In addition, all dots are uniformly colored. Δ: Slightly poor dot reproducibility (dot shape and color uniformity are slightly reduced) ×: Poor dot reproducibility (no dot shape and color development) (Some of them are not dots)

(5) Head Wear Using a thermal printing simulator manufactured by Okura Electric Co., black solid was printed under the following printing conditions. (Printing conditions) Thermal head dot density: 8 dots / mm Applied power: 0.68 W / dot Pulse width: 0.30 msec Line cycle: 10 msec / line Printing length: 5 cm Printing width: 3 cm These conditions are cycled to print 1 km length. The head wear was measured.

Table 1 shows the particle size of the filler used, and Table 2 shows the evaluation results.

[0103]

[Table 1]

[0104]

[Table 2]

Table 2 shows that the heat-sensitive recording material of the present invention is excellent in white streaks, sticking and head wear.

[0106]

According to the heat-sensitive recording material of the present invention, the protective layer contains
Since a mixture of an organic pigment having an average particle diameter of 1.2 to 3.0 times the protective layer thickness and an organic pigment having an average particle diameter of 0.05 to 0.7 μm was used, white stripes, sticking, Excellent head wear.

Claims (6)

[Claims] 1. A heat-sensitive recording layer comprising a leuco dye on a support, a heat-sensitive recording layer mainly composed of a developer for coloring the leuco dye by heating and a binder resin as a binder, and a protective layer provided thereon. In the recording material, an organic pigment having an average particle diameter of 1.2 to 3.0 times the protective layer thickness and an organic pigment having an average particle diameter of 0.05 to 0.7 μm are mixed in the protective layer. A heat-sensitive recording material characterized by being used. 2. The method according to claim 1, wherein the protective layer has a thickness of 1.2.
The mixing ratio of the organic pigment having an average particle diameter of up to 3.0 times and the organic pigment having an average particle diameter of 0.05 to 0.7 μm is in the range of 1: 100 to 1:20. Thermal recording material. 3. The method according to claim 1, wherein the resin in the protective layer and
The content ratio of various organic pigments is resin: organic pigment = 1: 0.5
To 1: 6. 4. The heat-sensitive recording material according to claim 1, wherein the organic pigment in the protective layer is a guanamine-formaldehyde copolymer represented by the following structural formula (I). Embedded image (Where R is H, CH ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ ,
NH ₂ , NO ₂ , an acetyl group, C ₆ H ₁₁ , C ₆ H ₅ , a benzyl group or a methylphenyl group. ) 5. The method according to claim 1, wherein a polyvinyl acetal resin having a polymerization degree of 2,000 or more is used as the resin in the protective layer.
A heat-sensitive recording material characterized by using an isocyanate compound as a crosslinking agent. 6. The heat-sensitive recording material according to claim 1, wherein the smoothness of the surface on which the protective layer is applied is 5000 seconds or more.