JPH09142018A - Thermal recording material - Google Patents

Abstract

(57) Abstract: A thermal recording material excellent in offset printing suitability is provided. SOLUTION: The initial contact angle between the surface of the thermosensitive recording layer and water is 6
A thermal recording material having a contact angle change rate of 0 ° or more and 3 ° / sec or less.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermal recording material,
In particular, it relates to a heat-sensitive recording material excellent in offset printing suitability.

[0002]

2. Description of the Related Art A thermosensitive recording material generally comprises a support having thereon a thermosensitive recording layer mainly composed of an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting developer. The dye precursor and the color developer react instantaneously by heating with a thermal head, a hot pen, a laser beam or the like, and a recorded image is obtained.
It is disclosed in -14039 and the like. Such a heat-sensitive recording material has advantages such that recording can be obtained with a relatively simple device, maintenance is easy, and no noise is generated.
It is widely used not only for facsimile and computer terminals. In particular, in the case of heat-sensitive recording materials used as chart paper for various equipment, cashier receipts, CD / ATM specifications, receipts of gas and water charges issued by handy terminals, etc., the heat-sensitive recording layer Therefore, there is an increasing demand for a heat-sensitive recording material having excellent suitability for offset printing.

Here, the offset printing suitability means piling when printing is performed on the surface of the thermosensitive recording layer,
Piling is a problem that peeling and gradual deposition of the thermal recording layer on the blanket causes chipping or blurring of the printed image area and scumming of the non-printed area, which is very troublesome in printing. It is an obstacle.

Conventionally, as a method for improving the printability (piling) of a heat-sensitive recording material, for example, an increase in the amount of binder in the heat-sensitive recording layer has been proposed, but deterioration such as a decrease in color developing sensitivity has occurred. . In addition, JP-A 1-1507
7 publication, 2-50844 publication, 5-28623 publication.
No. 7, for example, proposes a method of improving printability at the same time as water resistance by containing polyvinyl alcohol or modified polyvinyl alcohol and zircolammonium carbonate in the heat-sensitive recording layer. The improvement in water resistance was not consistent with the improvement in printability.

[0005] Japanese Patent Application Laid-Open No. 4-1481 / 1991 proposes improvement of printability of a thermosensitive recording material having a protective layer provided on a thermosensitive recording layer. However, when a protective layer is provided, water blocking is likely to occur due to dissolution of the protective layer film with water, and in applications such as handy terminals, thermosensitive recording materials provided with a protective layer are currently avoided. is there.

By the way, the dampening water in the offset printing optimizes the printing conditions by adjusting the supply amount thereof. However, in the case of a heat-sensitive recording material that does not have printability, for example, when the dampening water supply amount is increased, a so-called emulsified ink is formed, the tack is lowered, and blanket piling in the image area is suppressed, but the non-image area is Excessive water permeates the surface of the thermosensitive recording layer after transfer, and the coating strength of the thermosensitive recording layer is reduced, and blanket piling is likely to occur in the non-image area. Although the blanket piling in the image area is improved, the blanket piling in the image area is easily deteriorated. As described above, the influence of the dampening water is very important for the offset printing suitability, but in JP-A-2-169291, the contact angle between the surface of the heat-sensitive recording layer and water is [TAPPI T-45.
8 os-40] above 60 ° has been proposed as a method for improving background fog and stickiness when touched by wet hands, but the effect of improving offset printability is still insufficient. Is.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to provide a heat-sensitive recording material excellent in offset printing suitability (piling).

[0008]

The present inventors have intensively studied a method for obtaining a thermosensitive recording material excellent in offset printing suitability, particularly excellent in piling. As a result, they have found that it is important that the fountain solution used for offset printing does not excessively penetrate into the heat-sensitive recording layer in order to obtain desired results.

That is, the heat-sensitive recording material of the present invention is usually a colorless or light-colored dye precursor and a heat-sensitive recording material containing an electron-accepting compound which reacts with the dye precursor to form a color upon heating. The initial contact angle between water and water is 60 ° or more, and the rate of change of the contact angle is 3 ° / sec or less.

Further, preferably, by containing the fluororesin in the heat-sensitive recording layer, it is possible to easily satisfy the two specific requirements of the initial contact angle and the change rate of the contact angle.

Here, the "contact angle" means 20 ° C. and 65%.
This is the contact angle formed by dropping distilled water droplets on the surface of the thermosensitive recording layer in an RH atmosphere, and the "initial contact angle" is the contact angle measured 1 second after water is dropped on the surface of the thermosensitive recording layer (゜)
Say. The “contact angle change speed” is the value (° / sec) obtained by dividing the difference in contact angle between 1 second after dropping and 6 seconds after dropping by time, that is, 5 seconds (° / sec). Indicates the degree of change. For the contact angle measurement in the present invention, a FACE automatic contact angle meter CA-Z type manufactured by Kyowa Interface Science Co., Ltd. was used.

Further, as a method for evaluating the permeability of water to paper or the like, the Steckigt sizing degree test, the Cobb sizing degree test and the like have been generally used from the past, but in comparison with these test methods, in the present invention. The contact angle measurement can accurately grasp the wettability of water on the surface of the thermosensitive recording layer as well as the permeability, and know the behavior when the dampening water during offset printing actually transfers to the surface of the thermosensitive recording layer. We have found that it can be an effective indicator.

When the initial contact angle is less than 60 °, the affinity between the surface of the heat-sensitive recording layer and water increases, and the strength of the surface of the heat-sensitive recording layer decreases, so that the heat-sensitive recording layer is easily removed from the blanket. Easy to generate piling. Further, if the initial contact angle is less than 60 °, the replacement of ink with water is hindered, the ink adhesion is deteriorated, and density unevenness or density reduction in the image area tends to occur.

On the other hand, if the rate of change of the contact angle is larger than 3 ° / sec, water excessively penetrates into the thermosensitive recording layer, and the strength decreases not only on the surface of the thermosensitive recording layer but also on the entire thermosensitive recording layer. Piling is likely to occur.

Further, even if only one of the two specific requirements of the initial contact angle and the change rate of the contact angle in the present invention is satisfied, the excellent printability desired by the present invention cannot be obtained. For example, even if the initial contact angle is 60 ° or more, if the contact angle changing speed is higher than 3 ° / sec.
Piling may occur after the eyes. this is,
The contact between the damp blanket and the surface of the heat-sensitive recording layer occurs twice or more continuously, the time during which the surface of the heat-sensitive recording layer is in contact with water is extended, and the strength of the heat-sensitive recording layer decreases after the second cylinder. This is because the state becomes easy.

The method of adjusting the initial contact angle and the rate of change of the contact angle in the present invention may be adjusted according to the kind and blending ratio of the materials constituting the heat-sensitive recording layer, and in particular, the absorption of water in the heat-sensitive recording layer. It is important to appropriately select materials such as pigments, binders and dispersants so that the properties and the affinity are not improved. It is also effective to add a lubricant such as wax for improving water repellency.

The pigment used in the present invention includes diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, amorphous silica, amorphous calcium silicate, and amorphous silica. Aluminum acid, aluminum hydroxide, barium sulfate, zinc sulfate, aqueous colloidal silica, urea-formalin resin, melamine resin, silicone resin, polyethylene resin, nylon resin, wheat starch particles and the like can be appropriately added, but as a main pigment Oil absorption 120ml / 100g
It is preferable to use the following calcium carbonate, magnesium carbonate, amorphous silica, amorphous calcium silicate, amorphous aluminum silicate, aluminum hydroxide and the like.
Further, when a pigment having an oil absorption of more than 120 ml / 100 g is used for preventing dust adhesion to the heating head and improving sticking property, the oil absorption is 120 ml / 10.
Oil absorption of 120 ml / 10
It is preferable that the content is 20% by weight or less with respect to 0 g or less of the pigment so that the water absorption of the thermal recording layer itself is not increased as much as possible.

As the binder used in the present invention,
It is preferable to use one having excellent film-forming property, one having low hygroscopicity, and one having improved water resistance by the combined use of a crosslinking agent and the like. For example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer,
Water-soluble adhesives such as alkali salts of styrene / maleic anhydride copolymer, alkali salts of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic acid ester, styrene / butadiene copolymer, acrylonitrile / Examples of the latex include butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer and the like. Examples of the crosslinking agent used in combination with the binder include melamine, epoxy, dimethylol urea, polyaldehyde, and zirconium salt.

The dispersant used in the present invention is added when the dye precursor or the electron-accepting compound is finely pulverized in water or when the pigment is dispersed, and it may be added depending on the kind and amount of the dispersant used. The affinity or permeability of the thermosensitive recording layer for water is likely to change. For example, starch, hydroxyethyl cellulose, rather than low molecular type surfactants such as di-2-ethylhexyl sulfosuccinate, dodecylbenzene sulfonate, alkyl diphenyl ether disulphonate, alkyl naphthalene sulfonate, hexametaphosphate, etc. , Methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, modified polyvinyl alcohol, polycarboxylic acid salts such as ammonium salts of styrene-maleic acid monoalkyl ester copolymers do not increase the affinity for water, or , Acetylene alcohol, acetylene glycol, silicone oil compounds and other dispersion aids for the purpose of defoaming effect tend to increase water permeability when added in excess. The type and amount of dispersant is desirable to select and use appropriate.

Furthermore, the present inventor can easily meet the two specific requirements of the initial contact angle and the change rate of the contact angle in the present invention by including the fluororesin in the heat-sensitive recording layer. It was found that excellent printability of This is because the fluororesin extremely lowers the surface free energy of the thermosensitive recording layer and improves the effect of blocking contact with water, that is, the water repellency of the thermosensitive recording layer surface.

The fluororesin used in the present invention includes:
It can be appropriately selected and used from conventionally known materials. For example, a homopolymer of an acrylic acid ester derivative or a methacrylic acid ester derivative containing a perfluoroalkyl group having 3 to 20 carbon atoms or a copolymer thereof is preferable. As the copolymerization component, ethylene, vinyl acetate,
Vinyl chloride, vinyl fluoride, vinylidene halide, acrylonitrile, methacrylonitrile, styrene, α-
Methyl styrene, p-methyl styrene, acrylic acid and its alkyl ester, methacrylic acid and its alkyl ester, acrylamide, methacrylamide, diacetone acrylamide, methylol diacetone acrylamide, N-methylol acrylamide, vinyl alkyl ether, halogenated alkyl vinyl ether. , Vinyl alkyl ketone, butadiene, isoprene, chloroprene, glycidyl acrylate, maleic anhydride, and the like, which may be used alone or in combination of two or more compounds containing no fluoroalkyl group.

Commercially available aqueous emulsion type products of these fluororesins include Asahi Guard AG-550.
(All are product names made by Asahi Glass), Sumiflu oil, EM
-201 (all are trade names manufactured by Sumitomo Chemical Co., Ltd.), Scotch van, FC-808 (all are trade names manufactured by 3M Company),
F-60 (trade name manufactured by Dainippon Ink), polyflon, neoflon, and die-free ME413 (all trade names manufactured by Daikin Industries) can be used.

As the fluororesin in the present invention, phosphoric acid esters containing a perfluoroalkyl group having 3 to 20 carbon atoms are also preferable, and they can be used as they are or in the form of ammonium salts. Commercially available phosphoric acid esters include Asahi Guard, AG-53.
0 (all are product names made by Asahi Glass), Sumireze resin,
FP-110 (both are trade names made by Sumitomo Chemical Co., Ltd.), Z
onyl, RP (all are trade names of du Pont), Scotchban, FC-807 (all 3
Product name manufactured by M Co., etc. can be used.

The amount of the fluororesin added is not particularly limited,
Usually, it is added in the range of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the components of the heat-sensitive recording layer.
If the addition amount of the fluororesin is less than 0.01% by weight, the water-repellent effect may be insufficient, and if it is more than 10% by weight, the heat-sensitive recording layer coating liquid may be applied to the support. May cause repellency, decrease in ink receptivity during offset printing, decrease in coloring sensitivity, and decrease in storability of image area.

Regarding the constitution of the heat-sensitive recording material in the present invention, any conventional constitution may be used. The electron-donating, usually colorless or light-colored dye precursor and the electron-accepting compound of the present invention, alone or in combination, are usually finely pulverized in a water-soluble binder to form an aqueous dispersion, and then the dispersion is prepared. To prepare a heat-sensitive recording layer coating solution. For coating liquid,
In addition, a plurality of components such as a sensitizer, an antioxidant and an anti-sticking agent are added as needed.

The dye precursor used in the heat-sensitive recording material of the present invention is not particularly limited as long as it is generally used for pressure-sensitive recording paper or heat-sensitive recording paper.

A specific example is as follows. (1) Triarylmethane compound: 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-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-ethylcarbazol-3-yl) -5-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6
-Dimethylaminophthalide, etc.

(2) Diphenylmethane compound: 4,
4′-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenylleuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc.

(3) Xanthene compound: Rhodamine B
Anilinolactam, Rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino -7-Chlorofluorane, 3
-Diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-
Methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Anilinofluoran, 3-piperidino-6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluoran,
3-diethylamino-7- (4-nitroanilino) fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilino Fluoran, 3- (N-
Ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran,
3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran and the like,

(4) Thiazine-based compounds: benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue, etc.

(5) Spiro compounds: 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran,
Examples thereof include 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, and 3-propylspirobenzopyran; Two or more can be used in combination.

The electron-accepting compound used in the present invention is not particularly limited as long as it is one generally used in heat-sensitive recording materials, and examples thereof include 4-phenylphenol, 4-t-butylphenol and 4-phenylphenol. Hydroxyacetophenone, 2,2'-dihydroxydiphenyl, 2,
2′-methylenebis (4-chlorophenol), 2,
2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-ethylenebis (2-methylphenol), 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4 '-Hydroxyphenyl) propane, 4,4'-cyclohexylidenebis (2
-Isopropylphenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, bis (4-hydroxyphenyl) acetic esters, gallic acid Alkyl esters,
Phenolic compounds such as novolak type phenolic resins,
Phthalic acid monoanilide paraethoxybenzoic acid, parabenzyloxybenzoic acid, 3-5-di-t-butylsalicylic acid, 3-5-di-α-methylbenzylsalicylic acid, 3-
Aromatic carboxylic acids such as methyl-5-t-butylsalicylic acid, 4-n-octyloxycarbonylaminosalicylic acid, 4-n-decyloxycarbonylaminosalicylic acid, and these phenolic compounds and zinc, calcium, barium, nickel, A polyvalent metal salt such as manganese, cobalt, and aluminum can be appropriately added.

A sensitizer is added to the heat-sensitive recording material of the present invention in order to obtain good heat response. Examples of the sensitizer include stearic acid amide, N-hydroxymethylstearic acid amide, behenic acid amide, N
Fatty acid amides such as -hydroxymethylbehenic acid amide, N-stearylstearic acid amide, ethylenebisstearic acid amide; urea derivatives such as N-stearylurea; naphthol derivatives such as 2-benzyloxynaphthalene; m-terphenyl; -Benzylbiphenyl, 4-
Biphenyl derivatives such as allyloxybiphenyl, 2,
Polyether compounds such as 2'-bis (4-methoxyphenoxy) diethyl ether and bis (4-methoxyphenyl) ether, diphenyl adipate, dibenzyl oxalate, di (4-chlorobenzyl) oxalate, dimethyl terephthalate, terephthalic acid Carboxylic esters such as dibenzyl, sulfonic esters such as phenylbenzenesulfonate, diphenylsulfones such as bis (4-allyloxyphenyl) sulfone, diketones such as 4-acetylacetophenone, acetoacetic anilides, fatty acids Thermally fusible substances such as anilides and 1,2-bis (3,4-dimethylphenyl) ethane can be used as long as the desired effects of the present invention are not impaired. These compounds may be used alone or in combination of two or more. You may use together.

In addition, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, stearic acid amide,
Lubricants such as higher fatty acid amides such as methylol stearic acid amide and oleic acid amide, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, and castor wax can be added. Further, a benzophenone-based or benzotriazole-based ultraviolet absorber, a fluorescent dye, or the like can be added as necessary.

As the support used in the present invention, paper is mainly used, but a non-woven fabric, a plastic film, a synthetic paper, a metal foil, or a composite sheet in which these are combined can be optionally used. Further, an undercoat layer composed of a single layer or a plurality of layers of pigment or resin can be provided between the heat-sensitive recording layer and the support.
Further, various known techniques in the production of heat-sensitive recording materials such as machine calender, super calender, gloss calender and brushing can be used to improve the surface smoothness.

The amount of smearing of the heat-sensitive recording layer is usually 0.1 to 1.0 g / m ^{2 in} terms of the amount of dye precursor smeared. 0.1g
When the amount is less than / m ² , sufficient color development characteristics cannot be obtained, and when the amount is more than 1.0 g / m ² , the color development sensitivity is not improved, which is economically disadvantageous. .

[0037]

The present invention relates to a heat-sensitive recording material containing a normally colorless to light-colored dye precursor and an electron-accepting compound which reacts upon heating to develop the color of the dye precursor. The contact angle is 60 ° or more and the change rate of the contact angle is 3 ° / sec or less. Conventional thermal recording materials are liable to cause piling during offset printing, that is, the thermal recording layer is peeled off and gradually deposited on the blanket, resulting in chipping or scratching of the printed image area and scumming of the non-printed image area. However, this can be solved by setting the initial contact angle between the surface of the heat-sensitive recording layer and water to be 60 ° or more and the change rate of the contact angle to be 3 ° / sec or less.

The reason for this is that by making the initial contact angle and the rate of change of the contact angle the above-mentioned specific requirements, it is possible to suppress excessive wetting of the dampening water on the surface of the heat-sensitive recording layer and permeation into the heat-sensitive recording layer. The surface strength is retained and excellent offset printability without piling can be obtained.
Further, by containing a fluororesin in the heat-sensitive recording layer, it is possible to easily meet two specific requirements of the initial contact angle and the change rate of the contact angle, and to obtain even more excellent offset printing suitability. To do.

[0039]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
All parts and percentages shown below are based on weight.

Example 1 <Preparation of coating liquid for thermosensitive recording layer> A mixed liquid of the following (A) and (B) was pulverized in a Dynomill (sand mill manufactured by WEB) so that the volume average particle diameter was 2 μm or less. , Each dispersion was prepared. Further, the mixed solution of (C) was stirred with a homomixer for 5 minutes to obtain a pigment dispersion.

(A) Dye dispersion liquid 3-dibutylamino-6-methyl-7-anilinofluorane 30 parts 2.5% polyvinyl alcohol aqueous solution 70 parts

(B) Electron-accepting compound dispersion liquid 4-n-octyloxycarbonylaminosalicylate zinc 40 parts 2.5% aqueous solution of polyvinyl alcohol 60 parts 2.5% aqueous solution of ammonium salt of styrene maleic acid monoester copolymer 60 Department

(C) Pigment Dispersion Calcium carbonate having an oil absorption of 80 ml / 100 g (Shiraishi Central Research Institute: Callite SA) 50 parts 2.5% polyvinyl alcohol aqueous solution 200 parts

Next, in addition to the dispersions (A), (B) and (C), the following were mixed and stirred to prepare a coating solution for the heat sensitive recording layer. (A) Dye dispersion 100 parts (B) Electron-accepting compound dispersion 160 parts (C) Pigment dispersion 250 parts 40% Zinc stearate aqueous dispersion 25 parts 40% Methylol stearamide amide aqueous dispersion 25 parts 10% Polyvinyl alcohol aqueous solution 200 parts 10% dimethylol urea aqueous solution 10 parts Water 125 parts

<Preparation of heat-sensitive coated paper> A coating solution having the following composition was applied to a base paper having a basis weight of 40 g / m ^{2 so} that the solid content was 9 g / m ² , dried, and heat-sensitive coated. Paper was made. Calcined kaolin 100 parts 50% styrene butadiene latex aqueous dispersion 24 parts Water 200 parts

<Preparation of heat-sensitive recording material> The prepared heat-sensitive recording layer coating solution was applied onto the surface of the heat-sensitive coated paper so that the solid content was 5 g / m ^2, and dried. After forming the thermosensitive recording layer, the Bekk smoothness of the surface of the thermosensitive recording layer is 400.
A supercalendering treatment was performed for about 500 seconds to prepare a heat-sensitive recording material.

Example 2 Calcium carbonate 5 of the (C) pigment dispersion in Example 1
Example 1 except that 45 parts of calcium carbonate and 5 parts of amorphous calcium silicate having an oil absorption of 135 ml / 100 g (manufactured by Mizusawa Chemical Co., Ltd .: P-832) were used instead of 0 part.
A thermal recording material was prepared in the same manner as in.

Example 3 2. of (B) electron-accepting compound dispersion liquid in Example 1.
Instead of 60 parts of an aqueous ammonium salt solution of a 5% styrene-maleic acid monoester copolymer, 58 parts of an aqueous ammonium salt solution of a 2.5% styrene-maleic acid monoester copolymer, and acetylene glycol (manufactured by Nisshin Chemical Industry: Surfy A thermal recording material was prepared in the same manner as in Example 1 except that 2 parts of Nole 104E) was used.

Example 4 10% dimethylolurea aqueous solution 10 in Example 1
A thermosensitive recording material was prepared in the same manner as in Example 1 except that 10 parts of 10% zircolammonium carbonate was used instead of parts.

Example 5 A thermosensitive recording material was prepared in the same manner as in Example 1 except that 25 parts of 20% paraffin wax dispersion was added to the thermosensitive recording layer coating solution in Example 1.

Example 6 10 parts of 18% fluororesin emulsion (Sumitomo Chemical: Sumifuru Oil E was added to the coating solution for the thermosensitive recording layer in Example 1).
A thermal recording material was prepared in the same manner as in Example 1 except that M201) was added.

Example 7 10 parts of an 18% fluororesin solution (Asahi Glass: Asahi Guard AG530) was added to the thermosensitive recording layer coating solution of Example 1.
A thermal recording material was prepared in the same manner as in Example 1 except that was added.

Comparative Example 1 Calcium carbonate 5 of the pigment dispersion (C) in Example 1
A thermosensitive recording material was prepared in the same manner as in Example 1 except that 50 parts of amorphous calcium silicate was used instead of 0 part.

Comparative Example 2 (B) Electron-accepting compound dispersion of Example 1
Thermosensitive recording was carried out in the same manner as in Example 1 except that 60 parts of a 2.5% sodium di-2-ethylhexyl sulfosuccinate aqueous solution was used instead of 60 parts of an aqueous ammonium salt solution of a 5% styrene-maleic acid monoester copolymer. The material was made.

Comparative Example 3 (B) Electron-accepting compound dispersion of Example 1
Instead of using 60 parts of an aqueous ammonium salt solution of 5% styrene maleic acid monoester copolymer, 50 parts of an aqueous ammonium salt solution of 2.5% styrene maleic acid monoester copolymer, and 10 parts of acetylene glycol were used. A thermal recording material was prepared in the same manner as in Example 1.

Comparative Example 4 Except that the number of parts of the 40% zinc stearate aqueous dispersion in Example 1 was changed from 25 parts to 5 parts, and the number of the 40% methylol stearic acid amide aqueous dispersion was changed from 25 parts to 5 parts. A thermal recording material was prepared in the same manner as in Example 1.

Comparative Example 5 10% polyvinyl alcohol aqueous solution 2 in Example 1
Instead of 00 parts, 10% polyacrylamide aqueous solution 2
A thermosensitive recording material was prepared in the same manner as in Example 1 except that 100 parts was used.

The thermal recording materials prepared in Examples 1 to 7 and Comparative Examples 1 to 5 were subjected to the following tests, and the results are shown in Table 1.

<Measurement of initial contact angle and rate of change of contact angle> F manufactured by Kyowa Interface Science at 20 ° C. and 65% RH atmosphere
The measurement was performed using an ACE automatic contact angle meter CA-Z type.
Distilled water droplets were dropped on the surface of the heat-sensitive recording layer, and the contact angles after 1 second and 6 seconds were measured. The contact angle after 1 second from the dropping was taken as the initial contact angle, and 1 second after dropping and 6 seconds after dropping. Change in contact angle (° / sec) by dividing the difference in contact angle by time (5 sec)
And

<Offset Printing Suitability> The offset printing suitability was evaluated using an RI tester manufactured by Meisei Seisakusho. Trans G indigo normal (manufactured by Dainippon Ink and Chemicals) 0.4
Using cc, printing was performed after passing through a water roll, and the peeled state of the heat-sensitive recording layer was visually evaluated. The peeling state was visually evaluated according to the following indexes. ⊚: There was almost no peeling of the heat-sensitive recording layer. ◯: The thermal recording layer was slightly peeled off, but there was no practical problem. Δ: Peeling of the heat-sensitive recording layer is rather large, which is a problem in practical use. X: Peeling of the heat-sensitive recording layer was so large that it was not practical.

[0061]

[Table 1]

As is clear from Table 1, the thermal recording materials of Examples 1 to 7 show excellent printability, while
The thermal recording materials of Comparative Examples 1 to 5 have low printability.

[0063]

As is apparent from the examples, the offset printing suitability is improved by setting the initial contact angle between the surface of the heat-sensitive recording layer and water to be 60 ° or more and the contact angle change rate to be 3 ° / sec or less. An excellent thermal recording material can be obtained. Further, by containing a fluororesin in the heat-sensitive recording layer, a heat-sensitive recording material having further excellent offset printing suitability can be obtained.

Claims (2)

[Claims] 1. A heat-sensitive recording material containing a usually colorless to light-colored dye precursor and an electron-accepting compound that reacts with the dye precursor to form a color when heated, and the initial contact angle between the surface of the heat-sensitive recording layer and water. A thermal recording material having a contact angle change rate of not less than 60 ° and not more than 3 ° / sec. 2. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer contains a fluororesin.