JPH01306281A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain a heat-sensitive recording material which produces less scums, by setting the thermal deformation ratio of a mixture of a dispersant and a binder not higher than a predetermined value when a specified load is added thereto. CONSTITUTION:In a heat-sensitive recording material having a heat-sensitive color generating layer provided on a support body, the heat-sensitive color generating layer contains generally colorless or dim dye precursor in fine particles, a color developing agent which reacts to allow the dye to generate color when heat is added, a sensitizer and a binder. The thermal deformation ratio (c) of a mixture of a dispersant and the binder of the recording material measured by a thermal mechanical analysis using TMA module No. 943 of the thermal analysing system model 990 by Du Pont is obtained c=(a-b)X100/a(%) wherein (a) represents the thickness of a sample at a room temperature and (b) represents the thickness of the sample at 70 deg.C. When the mixture having the thermal deformation ratio not higher than 4% is employed, the adhering amount of scums can be reduced without lowering the sensitivity. The scums are generated more as the thermal deformation ratio becomes larger, and if the ratio exceeds 6%, the generation of scums becomes enormous.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Field of Application The present invention relates to a heat-sensitive recording material, and more specifically, the present invention relates to a heat-sensitive recording material. A heat-sensitive recording material manufactured by dispersing a color developer and a sensitizer for color development into fine particles in water together with a dispersant, mixing each dispersion liquid with a binder, applying the mixture to a support, and drying it. It is related to.

(B) Prior art and problems A thermosensitive recording material is basically manufactured by the following procedure.

That is, first, a dye precursor, a color developer, and a sensitizer are dispersed alone or in combination in water containing a dispersant, and the mixture is milled using a sand mill or a ball mill to form a dispersion of fine particles.

Next, the dye precursor fine dispersion, color developer fine dispersion, sensitizer fine dispersion, binder, etc. are thoroughly stirred and mixed to obtain a heat-sensitive coating liquid, which is then uniformly applied onto a substrate such as paper and dried. to form a thermosensitive coloring layer. Thereafter, the surface is smoothed using a supercalender to obtain a heat-sensitive recording material.

The following properties are required of the dispersant and binder used in the above heat-sensitive coating liquid.

(1) The dispersant and the binder should have good compatibility and be uniformly mixed when the dispersion of the dye precursor, developer, and sensitizer is mixed with the binder.

(2) The viscosity of the dispersant is not excessively high, which will not reduce the crushing efficiency of a sand mill or the like. Also, the foaming property is low and defoaming is quick.

(3) There is no unfavorable interaction with the dye precursor, color developer, or sensitizer that would cause a reaction.

(4) The binder must have high adhesion and exhibit sufficient picking strength when used as a heat-sensitive recording material.

Such dispersants and binders are very limited, and polyvinyl alcohol is often used as the main dispersant and binder (for example, JP-A-59-227
92), in order to further increase the crushing efficiency, a fine dispersion of a dye precursor, a fine color developer, and a fine sensitizer was prepared using a dispersant which is a water-soluble polymer such as a styrene-maleic anhydride copolymer. After obtaining the dispersion, polyvinyl alcohol is mixed and used.

However, with the above configuration, a thermofusible substance may adhere to the vicinity of the heat generating part of the thermal head installed in the printer, which generates color in the heat-sensitive coloring layer by heating, damaging the thermal head or degrading print quality. In many cases, pigments such as silicic acid, urea resin pigments, or light calcium carbonate, which exhibit high oil absorption, are used alone or in combination in order to suppress the amount of dregs generated. However, when the amount of pigment added increases, the heat source required to raise the temperature to the same temperature increases, causing adverse effects such as a so-called decrease in sensitivity, in which the color density decreases with the same applied energy. Moreover, the scum suppression effect was also at an unsatisfactory level.

(C) Purpose of the Invention The purpose of the present invention is to obtain a heat-sensitive recording material in which the amount of residue generated is small.

(D> Means for Solving the Problems The present inventors mainly used a normally colorless to light-colored dye precursor that has been made into fine particles, and a color developer and a sensitizer that react with the dye precursor when heated to develop a color. , and a heat-sensitive recording material in which a heat-sensitive coloring layer containing a binder is provided on a support, a thermomechanical analysis of a mixture of a dispersant and a binder is performed using a DuPont thermal analysis system 990 model TMA module 0943. The thermal deformation coefficient C obtained is calculated as c = (a-b) x 100/a (%), where a is the thickness of the sample at room temperature and b is the thickness of the sample at 70 ° C.
It has been found that by using a combination with a thermal deformation rate of 4% or less, the amount of deposits can be reduced without reducing sensitivity.

Any combination of dispersant and binder may be used as long as it has the characteristics described in the prior art section and satisfies the above conditions, but the selection is not easy. However, even if a combination is selected in which one or both of them has a small thermal deformation rate at 70°C, the thermal deformation rate of the mixture at 70°C will often increase on the contrary. For example, the above heat distortion rate at 70'C of methylcellulose as a dispersant and polyvinyl alcohol as a binder is 3.2, respectively.
%, 4.0%, but the heat distortion rate of the mixture with a weight ratio of 1:3 was 18%.

Further, the amount of deformation of hydroxyethyl cellulose at 70°Ck was 4%, but the amount of deformation of the mixture of hydroxyethyl cellulose and polyvinyl alcohol at a weight ratio of 1:3 was 5.3%.

Among these, a combination in which the dispersant is polyvinyl alcohol containing sulfone Ml and a binder is guar gum or a guar gum derivative, a combination in which each is methyl cellulose and guar gum or a guar gum derivative, and a combination in which each is hydroxyethyl cellulose and guar gum or a guar gum derivative. The combination, and the combination of hydroxyethyl cellulose and polyacrylamide, respectively, satisfy the conditions.

The addition ratio of the dispersant to the dye precursor, color developer and sensitizer is 1 to 7%, which is appropriate. If it is less than 1%, the crushing efficiency in a whole mill or sand mill will be reduced, and if it is 7% or more, the sensitivity will be reduced.

A more preferable addition rate is 1 to 3%.

The appropriate binder addition rate is 7 to 20%.

As it becomes less than 7%, the picking strength of the heat-sensitive coloring layer decreases, and eventually a part of the coating layer stains the roll during the calendering process.

Also, as the number increases, the sensitivity decreases, but 20
%, this becomes noticeable.

A more preferable addition rate is 7 to 10%.

In addition to the combination of dispersant and binder according to the present invention, other water-soluble polymers may be added for the purpose of improving the water retention of the heat-sensitive coating liquid or preventing fogging.

In the above case, the same effect can be obtained if the thermal deformation rate of all these mixtures at 70° C. is 4% or less.

The heat-sensitive recording material of the present invention usually uses paper, synthetic paper,
Alternatively, a film is used, and an air knife, blade,
1q is obtained by coating the heat-sensitive coloring layer on the support using IT equipment having a coater head such as a roll.

Furthermore, in order to improve scum, sensitivity, and print quality, one or two intermediate layers consisting mainly of a white or light-colored pigment and a binder are often provided between the support and the thermosensitive coloring layer.

The oil-absorbing pigment used in the intermediate layer has an oil absorption JIS
60d/100g according to the measurement method specified in K-5101
Although the above is desirable, a pigment of 60 m1/1003 or less may be used in combination. The particle size of the pigment is preferably 5.0 microns or less, preferably 1 μm or less in terms of volume average particle size, from the viewpoint of smoothness. Specifically, silicic acid, calcium carbonate-coated silicic acid, kaolin, calcined kaolin, talc, waxite, diatomaceous earth, calcicarbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, barium carbonate, urea. - Selected from formalin pigments, balloon-shaped plastic pigments, etc.

When coating on a support, these pigments are dispersed together with a dispersant, and a hydrophobic adhesive such as starch derivatives, polyvinyl alcohol, water-soluble polymer adhesives such as styrene-maleic anhydride, styrene-butadiene latex, or acrylic resin emulsicone is used. It is common to add emulsions of polymers.

In FIG. 1, one or more of a dye precursor, a color developer, and a sensitizer can be added at the same time.

The heat-sensitive color forming layer provided on the intermediate layer mainly contains a dye precursor, a color developer, a sensitizer, a binder, and a dispersant added when the above components are made fine. Waxes, metal soaps, etc. may be added for the purpose of preventing sticking, and the above-mentioned oil-absorbing pigments may also be mixed.

The dye precursor used in the present invention is not particularly limited as long as it is used in general pressure-sensitive recording paper, heat-sensitive recording paper, etc. Specific examples include (1) 3 as a triarylmethane compound; , 3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone) 1.3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl) -3-(1,2-dimethylindol-3-yl>phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)
Phthalide, 3-(p-dimethylaminophenyl)-3
-(2-phenylindol-3-yl)phthalide, 3
, 3-bis-(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3.3-bis-(1
, 2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis-(9-ethylcarbazole- -dimethylaminophthalide, 3,3-bis-(2-phenylindol-3-yl) )-5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)-6-dimethylaminophthalide, etc.: (2) As a diphenylmethane compound, 4,4
'-Bis-dimethylaminobenzhydrylbenzyl ether, N-halophenylleucoolamine, N-2.4
．． 5-Trichlorophenylleucoauramine etc.: (3)
As xanthine compounds, rhodamine B-anilinolactam, rhodamine B-p-chloroanilinolactam,
3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamine-7-phenylfluorane, 3-
Diethylamino-7-(3,4-dichloroanilino)fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-ethyl-
Tolylamino-6-methyl-7-7enylfluorane, 3-diethylamino-7-(4-nitroanilino)fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-(N-methyl- N-propyl)amino-6-methyl-7-7nilinofluorane, 3-(
N-ethyl-N-isopropyl)amino-6-medy-7-anilinofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluorane, etc.: (4) As a deazine compound, benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.: (5) As a spiro compound,
3-Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-cyclospirodinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methylnaphtho-(3-methoxy-benzo)spiropyran, 3 -propyl-spiro-dibenzopyran, etc.
Alternatively, a mixture thereof can be mentioned.

These are determined by the application and desired properties.

As the color developer, acidic substances generally used in thermosensitive recording paper, ie, electron-accepting compounds, are used, and in particular, phenol derivatives and aromatic carboxylic acid derivatives are used.

For example, phenol, p-t-butylphenol, p-
Phenylphenol, 1-naphthol, 2-naphthol, p-hydroxyacetophenone, 2,2'-dividroxybiphenyl, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-t-butylphenol) ), 4,4'-isopropylidene bis(2
-chlorophenol), 4.

4'-cyclohexylidene diphenol, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4
-hydroxyphenyl)pentane, 2,2-bis(4-
hydroxyphenyl)hexane, diphenol acetic acid methyl ester, bis(4-hydroxyphenyl)sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4' -isopropyloxydiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 4,4'-thiobis(2-t-butyl-5-methyl)phenol, 7-bis(4-hydroxyphenyldio)-3,5-dioxy Examples of aromatic carboxylic acid derivatives include benzoic acid, p-t-butylbenzoic acid, p-hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid isopropyl ester, and p-hydroxybenzoic acid isopropyl ester. Hydroxybenzoic acid benzyl ester, gallic acid lauryl ester, gallic acid stearyl ester, salicylanilide, 5-chlorosalicylanilide, metal salts such as zinc of 5-t-butylsalicylic acid, metal salts such as zinc of hydroxynaphthoic acid, etc. Can be mentioned.

Examples of waxes include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylene bisstearamide, and higher fatty acid esters.

Examples of metal soaps include polyvalent metal salts of higher fatty acids, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

The sensitizer has a sharp melting point of 80 to 140°C and has good thermal responsiveness. Specifically,
Sensitizers such as benzoic acid and terephthalic acid esters, naphthalene sulfonic acid esters, naphthyl ether derivatives, anthryl ether derivatives, aliphatic ethers, phenanthrene, fluorene, etc. can be used. The waxes mentioned above can also be used as sensitizers.

(E) Function The heat-sensitive recording material is pressed against a thermal head installed in a thermal printer or the like, and the heat-generating portion is energized and heated to develop color. At this time, a thermofusible compound such as a dye precursor adheres to the vicinity of the heat generating part, producing so-called scum. However, by specifying the thermal deformation rate at 70'C of the mixture of dispersant and binder, the amount of debris can be significantly reduced.

This difference becomes noticeable when the amount of pigment added to the heat-sensitive coloring layer is low, and when the thermal deformation rate at 70'C is 4% or less, Even if it is not added, hardly any scum is generated, or it increases as the thermal deformation rate increases, and when it is 6% or more, it increases significantly.

Although the mechanism behind the above difference in scum suspension is not entirely clear, the main mechanism is that the binder and dispersant mixture acts as a support that prevents the thermal head from coming into contact with the molten thermofusible compound. It is thought that then. Figures 1 and 2 have an intermediate layer, and the heat-sensitive coloring layer does not contain any pigment, and uses sulfonic acid group-containing polyvinyl alcohol with a heat deformation rate of 8.5% at 70'C as a dye precursor as a dispersant. 5% each for body, developer, and sensitizer, and 70' as binder.
10% polyvinyl alcohol with a thermal deformation rate of 4% in C was used (the thermal deformation rate at 70°C of a mixture with a vertical side ratio of 1:2 was 7.1%. ) This is a scanning electron micrograph of a colored area when printed on a heat-sensitive recording material. (
Printing is made by Okura Electric Co., Ltd. (Osaka), printing device TH-P
MD, thermal head resistance 185Ω, dot density 8
Dots/m, applied voltage 1'lv, energizing time 1.3 m
I did it with s. ) Figures 3 and 4 show that the binder has a thermal deformation rate of 0.4 at 70'C compared to polyvinyl alcohol.
% (the thermal deformation rate at 70'C of the mixture with a weight ratio of 1:2 was 0.5%). This is a scanning electron micrograph of the color-developing area.

In FIGS. 3 and 4, the structure, which is thought to be formed by the binder and looks like a platform with a flat top, or supports is more noticeable, and there appears to be a space between them. In other words, the organic fusible materials such as dye precursors that existed between the layers are absorbed into the intermediate layer.

This pillar-like structure has the function of preventing the molten dye precursor, developer, and sensitizer from coming into contact with the thermal head, and also prevents the molten dye precursor from migrating to the intermediate layer and from mixing. It is thought that this makes it easier.

On the other hand, in FIGS. 1 and 2, an organic fusible material containing a melted or softened binder covers the surface of the intermediate layer. It is thought that such a structure facilitates contact between the molten dye precursor and the like and prevents it from transferring to the intermediate layer, which is disadvantageous for dregs.

(")Example Next, the present invention will be explained in more detail with reference to Examples.

All parts and percentages are by weight.

Example 1 Preparation of intermediate layer coating A11 paper.

Calcined kaolin (Ansilex manufactured by Englehard) 100 parts Sodium hexametaphosphate 0.8 parts 48% styrene-butadiene latex (Nippon Gosei'!! JSRO692)
130 parts water
130 parts or more were made into a dispersion liquid using a homogenizer, and 20% phosphoric acid ester starch (Nihon Shokuhin Co., Ltd., MS-4) was added to this.
600) After adding 25 parts of the aqueous solution and mixing well, 40 g
/rd high quality paper with a solid content of 6 g/m and dried.

■Preparation of dye precursor dispersion...Liquid A 3-diethylamino-6-methyl-7-anilinofluorane 1 part 10% sulfone M group-containing polyvinyl alcohol aqueous solution 0.5 part water
3.5 parts of this mixture was ground in a bead mill until the average particle size was 2 μm.

■Preparation of developer dispersion liquid...B liquid 2.2-bis(
4-hydroxyphenyl)propane
1 part 10% polyvinyl alcohol aqueous solution containing sulfonic acid groups 0.5 part water
3.5 parts of this mixture was ground in a bead mill until the average particle size was 2 μm.

■Preparation of sensitizer dispersion...Liquid C 2-benzyloxynaphthalene 1 part 10% aqueous polyvinyl alcohol solution containing sulfonic acid groups
0.5 part water
3.5 parts This mixture was milled with a bead mill to an average particle size of 2μ.
It was crushed until it became

■Thermosensitive coloring layer forming liquid A 15 parts liquid B
20 parts C liquid
25 parts 10% polyvinyl alcohol aqueous solution 12
Department water
8 parts were mixed and stirred to prepare a coating liquid. This was applied to paper with an intermediate layer in an amount of dye precursor of 0.5 g/m, dried, and then the BEKK smoothness of the surface of the thermosensitive coloring layer was 4.
A heat-sensitive recording material was obtained by supercalendering to obtain a heat-sensitive recording material of 0.00 to 500 sec.

This is designated as sample Nα1 (comparative example).

(Sample Nα2 (Example), N(13 (Example), Nα4
(Preparation of Example)] In sample Nα1 (comparative example), 60 parts of a 2% guar gum A aqueous solution was used instead of the 10% polyvinyl alcohol aqueous solution that was the binder aqueous solution in the formation of the thermosensitive coloring layer, and additionally. Sample Nα2 (Example) was obtained in exactly the same manner as Sample Nα1 (Comparative Example) except that 8 parts of water was changed to zero.

Furthermore, in sample Nα2 (Example), 2% guar gum A aqueous solution was added in place of 60 parts of the 2% guar gum A aqueous solution in forming the heat-sensitive coloring layer.
Sample Nα3 (Example) was obtained in exactly the same manner except that 60 parts of guar gum C aqueous solution was used, and sample N04 (Example) was obtained in exactly the same manner except that 80 parts of 1.5% guar gum C aqueous solution was used.

[Preparation of samples Nα5 (comparative example), Nα6 (example) and Nα (example)] In sample Nα1 (comparative example), each dispersion of ■dye precursor, ■color developer, and ■sensitizer was prepared. Nα5 (comparative example) was obtained in exactly the same manner as in the preparation except that a 10% aqueous methyl cellulose solution was used in place of the aqueous 10% sulfonic acid group-containing polyvinyl alcohol solution as the dispersant aqueous solution.

Furthermore, in sample Nα5 (comparative example), 60 parts of a 2% guar gum A aqueous solution was used instead of 12 parts of a 10% polyvinyl alcohol aqueous solution in the formation of the heat-sensitive coloring layer, and 8 parts of additional water was set to zero. Sample N06 (Example) and Sample Nα6 (Example) were prepared in exactly the same manner, except that (1) 60 parts of a 2% guar gum C aqueous solution was added in place of 60 parts of a 2% guar gum A aqueous solution in forming the heat-sensitive coloring layer. Sample Nα7 (Example) was prepared in exactly the same manner except that it was used.

[Preparation of sample N08 (comparative example), Nα9 (example)] In sample Nα1 (comparative example), 10 in the preparation of each dispersion of ■dye precursor, ■color developer, and ■sensitizer. Sample No. 8 (comparative example) was obtained in exactly the same manner except that a 10% and droxyethyl cellulose aqueous solution was used instead of the sulfonic acid group-containing polyvinyl alcohol aqueous solution.

Furthermore, in sample Nα8 (comparative example), 60 parts of a 2% guar gum A aqueous solution was used instead of 12 parts of a 10% polyvinyl alcohol aqueous solution in the formation of the heat-sensitive coloring layer, and 8 parts of additional water was set to zero. Sample Nα9 (Example) was obtained in exactly the same manner.

In addition, in sample Nα8 (comparative example), sample N (110( Example) was obtained.

A list of all the above samples is shown in Table 1.

The above sample was printed using a printing device TH-PMD, the reflection density of the printed portion was measured using a Macbeth densitometer, and the amount of debris adhering to the normal head was evaluated using a WA microscope. The results are shown in Table 1.

Further, the dispersant and the binder were mixed at the actual addition amount of ff1ffl ratio, and the thermal deformation rate at 70'C was measured using a film equivalent to 0.0247'j/ctri (air-dried).

The test methods will be summarized later. The results are also shown in Table 1.

Test method [Measurement of thermal deformation rate] - Take a predetermined amount of an aqueous solution of a dispersant and a binder, mix well, take an amount that will become 0.0247'j/ci when air-dried, and place it in a constant temperature dryer at 40'C. Dry for 8 hours or more to obtain a sample for measurement.

The softening point was measured using a DuPont thermal analysis system 99 in a room at 25°C.
The measurements were carried out by thermomechanical analysis using a Model 0 TMA module N (1943).

The thermomechanical analysis was performed by raising the temperature from room temperature at a heating rate of 10° C./min and applying pressure with a 2.5 M diameter needle carrying a load of 110 g. The thermal deformation rate C is 70, where the thickness of the sample at room temperature is a.
If the thickness of the sample at °C is b, then c= (a-b)x
It was calculated as 100/a (%).

[Printing] Printing device TH-PMD manufactured by Jinyu Denki Co., Ltd. (Osaka), thermal head resistance 185Ω, dot density 8 dots/M
, the applied voltage was 11 V, and the current application time was 1.3 ms.

[Color density]

Reflection density was measured with a Macbeth densitometer.

[Cass]

After printing, the vicinity of the heat generating part of the thermal head was observed with the naked eye and with a microscope, and evaluated on a five-point scale.

The evaluation criteria are as follows.

1: Items with almost no residue observed even when observed under a microscope. Practically possible.

2: Items with extremely small amount of residue attached.

Practically acceptable limit.

3: The amount of deposits is between the evaluations of 1 and 5. Practically impossible.

4: The amount of deposits is the second highest after evaluation 5, and it can be clearly seen with the naked eye. Practically impossible.

5...Group with the largest amount of deposits.

Example 2 Liquid A in the formation of the heat-sensitive coloring layer in Example 1
15 parts B liquid
20 parts Solution C 25 parts Calcined kaolin (Engelhard 7Ncilex) 2 parts Light calcium carbonate (Shiraishi Calcium Co., Ltd. Unibuff 0) 3 parts 10% polyvinyl alcohol aqueous solution 17 parts Water
50.3 parts were mixed and stirred to prepare a coating liquid. 40g of this coating liquid was changed to paper with an intermediate layer.
The dye precursor was coated on high-quality paper in an amount of 0.55 g/m, dried, and then supercalendered so that the BEKK smoothness of the surface of the heat-sensitive coloring layer was 400 to 500 sec. Obtained recording materials.

This is designated as sample Nα11 (comparative example).

Next, in the above example sample No. 11 (comparative example), 1
1 q of sample Nα12 (Example) was prepared in exactly the same manner except that 85 parts of a 2% guar gum A aqueous solution was used instead of 17 parts of a 0% polyvinyl alcohol aqueous solution.

After printing, the color density of the sample was measured and residue was evaluated. The results are shown in Table 2.

Table 2 (Left below)
If the combination has a thermal deformation rate of 4% or less at 0'C, scum will not be generated to a practical level even if the pigment that is normally added to the heat-sensitive coloring layer for the purpose of reducing the amount of scum is omitted. Skewers decrease.

Further, as shown in Table 2, it can be seen that the present invention is more effective even when a pigment is added.

[Brief explanation of the drawing]

1 and 2 show electron micrographs of the surface of a heat-sensitive recording material after coloring prints other than the present invention, and FIGS. 3 and 4 show electron micrographs of the surface of a heat-sensitive recording material after coloring prints according to the present invention. Show photos.

Claims (1)

[Scope of Claims] 1) Supports a heat-sensitive color forming layer mainly consisting of a finely divided dye precursor that is usually colorless to light-colored, a color developer and a sensitizer that react with the dye precursor to develop color when heated, and a binder. In a heat-sensitive recording material provided on a body, the thermal deformation rate of a mixture of a dispersant and a binder at 70°C and a load of 160 g/cm^3 (thermal deformation rate = thickness before thermal deformation - after thermal deformation) 1. A heat-sensitive recording material having a thickness x 100/thickness before thermal deformation) of 4% or less. 2) The addition rate of the dispersant to the dye precursor, developer, and sensitizer is 1 to 7%, and the addition rate of the binder is 7 to 7%.
20%. The heat-sensitive recording material according to claim 1. 3) The heat-sensitive recording material according to claim 2, wherein the dispersant is a sulfonic acid group-containing polyvinyl alcohol, and the binder is guar gum or a guar gum derivative. 4) The heat-sensitive recording material according to claim 2, wherein the dispersant is methylcellulose and the binder is guar gum or a guar gum derivative. 5) The heat-sensitive recording material according to claim 2, wherein the dispersant is hydroxyethylcellulose and the binder is guar gum or a guar gum derivative. 6) The heat-sensitive recording material according to claim 2, wherein the dispersant is hydroxyethylcellulose and the binder is polyacrylamide.