JPH0761128A - Thermal recording - Google Patents

Abstract

(57) [Abstract] [Purpose] Thermal recording with excellent print pixel reproducibility, high recording density, and excellent cutting suitability for recording materials in all areas from low density to high density, with no head residue attached. Provide the body. [Structure] A thermosensitive recording medium having a thermosensitive recording layer provided on a support, wherein an oil absorption of 80 ml is provided between the support and the thermosensitive recording layer.
/ 100 g or more pigment, and polyvinyl alcohol as an adhesive (acrylamido vinylpyrrolidone
A thermosensitive recording medium provided with an intermediate layer containing a graft copolymer with an acrylonitrile) copolymer as a main component.

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 material, and more particularly to a heat-sensitive recording material having excellent print pixel reproducibility, high recording density and excellent surface strength.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording which utilizes a color reaction between a color-forming agent and a color-forming agent which develops color by contacting with the color-forming agent, by contacting both color-forming substances with heat to obtain a color-developed image. The body is well known. Since such a thermal recording medium is relatively inexpensive and the recording device is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

With the diversification of uses, heat sensitivity is excellent in reproducibility of print pixels in any area from low density to high density, and a high quality recorded image comparable to silver halide photography can be obtained. The demand for recording media is increasing. Further, with the increase in speed of recording equipment, there is an increasing demand for a thermal recording material having excellent dynamic recording sensitivity.

In order to obtain such a high-sensitivity and high-quality heat-sensitive recording material, an intermediate layer composed of an oil-absorbing pigment may be provided (Japanese Patent Laid-Open Nos. 59-155097 and 61-44683).
Furthermore, a method of improving smoothness and heat insulation by combining these layers in multiple layers (JP-A-61-112886, JP-A-6-11286).
1-193880) and the like have been proposed. However, when an inorganic pigment having a high oil absorption property such as amorphous silica or calcined clay is used as the oil-absorption material, there is a drawback that the surface area becomes large and the paper surface strength decreases. Increasing the rate is accompanied by the drawback that the recording density is significantly reduced. Therefore, there is still room for improvement in order to obtain an overall balanced quality.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a high-quality recorded image with excellent reproducibility of print pixels in any area from low density to high density without the drawbacks described above. The object is to provide a heat-sensitive recording material.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have found that in a thermosensitive recording medium having a thermosensitive recording layer provided on a support, the oil absorption is 80 ml / 100 g or more between the support and the thermosensitive recording layer. Polyvinyl alcohol as a pigment and adhesive (acrylamide, vinylpyrrolidone, acrylonitrile)
It has been found that the above object can be achieved by providing an intermediate layer whose main component is a graft copolymer with a copolymer, and the present invention has been completed.

[0007]

As described above, the heat-sensitive recording material of the present invention comprises a pigment having an oil absorption of 80 ml / 100 g or more, polyvinyl alcohol and a (acrylamide-vinylpyrrolidone-acrylonitrile) copolymer between the support and the heat-sensitive recording layer. Although having an important feature in providing an intermediate layer containing a graft copolymer as a main component, the specific graft copolymer is excellent in adhesiveness to various inorganic pigments,
In particular, it is clear that an intermediate layer having excellent surface strength is formed because it exhibits outstandingly excellent adhesiveness to pigments having an oil absorption of 80 ml / 100 g or more, such as amorphous silica, aluminum silicate, and calcined clay. became. Even with the above-mentioned specific graft copolymer, if the blending amount is too large, the oil absorbency and heat retention of the intermediate layer are lowered, and the head meal and the recording density tend to be lowered. In order to obtain the desired effect of the present invention while maintaining a good quality balance, the blending amount is 1 to 50% by weight with respect to the pigment.
It is desirable to adjust the content in the range of about 2 to 30% by weight.

The ratio of the polyvinyl alcohol portion and the acrylamide / vinylpyrrolidone / acrylonitrile) copolymer portion of the specific graft copolymer is not particularly limited,
The polyvinyl alcohol part is 5 to 10 relative to the acrylamide / vinylpyrrolidone / acrylonitrile copolymer part.
A range of 0% by weight is preferred. The ratio of acrylamide, vinylpyrrolidone, and acrylonitrile is 60 to 90% by weight of acrylamide, 3 to 25% by weight of vinylpyrrolidone, and 1 to 20% of acrylonitrile with respect to the acrylamide / vinylpyrrolidone / acrylonitrile copolymer part. A weight% range is preferred. Further, within a range that does not impair the effects of the present invention, acrylamide
It is also possible to copolymerize a lower alkyl (meth) acrylate, (meth) acrylic acid or the like in the vinylpyrrolidone / acrylonitrile copolymer.

Further, in the intermediate layer, in addition to the oil-absorbing pigments as described above, various inorganic pigments such as talc and light calcium carbonate which are usually used, amino resins, phenol resins and styrene resins are also used. It is also possible to use an organic pigment together. Further, the specific graft copolymer, it is also possible to use an ordinary binder in combination, for example, starch, casein, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, water-soluble polymers such as polyvinylpyrrolidone and styrene. Various synthetic resin emulsions such as butadiene copolymer, styrene-vinylpyrrolidone copolymer, acrylonitrile-butadiene copolymer, colloidal silica particle composite styrene-vinylpyrrolidone ester copolymer, vinylpyrrolidone copolymer, etc. Etc. may be used together. The coating amount of the intermediate layer on the support was 5
It is desirable to adjust the thickness to be about 40 μm. 2
A multi-layer structure of more than one layer may be used.

The support is not particularly limited, and high-quality paper, base paper made by Yankee machine, single-sided gloss base paper,
Papers such as double-sided glossy base paper, cast coated paper, art paper, coated paper, medium coated paper, synthetic fiber paper, synthetic resin film and the like are appropriately used. The method for applying the intermediate layer is not particularly limited, and may be applied and dried by an appropriate application device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater, a short dwell coater.

The thermosensitive recording layer is applied onto the intermediate layer thus formed and dried to produce the thermosensitive recording material of the present invention. A combination of a color former and a color former contained in the thermosensitive recording layer is used. Is not particularly limited, and any combination can be used as long as they are brought into contact with each other by heat to cause a color reaction, for example, a colorless or pale basic dye and an inorganic or organic acidic substance. And a combination of a higher fatty acid metal salt such as ferric stearate and a phenol such as gallic acid. Further, it can be applied to various heat-sensitive recording materials such as a heat-sensitive recording material in which a diazonium compound, a coupler and a basic substance are combined, so that a recorded image can be obtained by heat.

However, the particular intermediate layer of the present invention provided on the support exerts an excellent effect particularly in the combination of the basic dye and the acidic substance, and is therefore preferably applied particularly to such a combination.

In the heat-sensitive recording material of the present invention, various types of known basic dyes of a colorless to light color which form a heat-sensitive recording layer together with a specific color former and a heat-fusible substance are known. The following is exemplified. 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide, 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, 3,3-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) -6-dimethylaminophthalide, 3,3 -Bis (2
-Phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-
Triarylmethane dyes such as (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-
Bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leuco auramine, N-2,
Diphenylmethane dyes such as 4,5-trichlorophenylleuco auramine, benzoyl leuco methylene blue, thiazine dyes such as p-nitrobenzoyl leuco methylene blue, 3-methyl-spiro-dinaphthopyran,
3-ethyl-spiro-dinaphthopyran, 3-phenyl-
Spiro dyes such as spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine ( Lactam dyes such as p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3
-Diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N- Ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-di Benzylaminofluorane, 3-diethylamino-7-N-methyl-
N-benzylaminofluorane, 3-diethylamino-
7-N-chloroethyl-N-methylaminofluorane,
3-diethylamino-7-N-diethylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluorane, 3- (N-ethyl-
p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3-dimethylamino-6-methyl-7
-Phenylaminofluorane, 3-diethylamino-6
-Methyl-7-phenylaminofluorane, 3-di-n
-Butylamino-6-methyl-7-phenylaminofluorane, 3-di-n-pentylamino-6-methyl-7
-Phenylaminofluorane, 3-diethylamino-7
-(2-carbomethoxy-phenylamino) fluorane, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane,
3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-di-n- Butylamino-7- (o-chlorophenylamino) fluorane,
3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3- (N-methyl-Nn-amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl) -N-n-amyl) amino-6-
Methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-methyl-Nn-hexyl) amino-6- Methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluorane, 3-
(N-ethyl-N-β-ethylhexyl) amino-6-
Methyl-7-phenylaminofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-cyclopentyl) amino-6- Methyl-7-phenylaminofluorane, 2,2-bis {4- [6'-
(N-Cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2 '
Fluorane dyes such as -ylamino] phenyl} propane. Of course, it is not limited to these dyes,
A combination of two or more dyes is also possible.

Various compounds are known as colorants used in combination with the above basic dyes, and examples thereof include the following. 4-tert-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol,
4-tert-octylphenol, 4,4'-sec-butylidene diphenol, 4-phenylphenol, 4,
4'-dihydroxy-diphenylmethane, 4,4'-isopropylidenediphenol, hydroquinone, 4,
4'-cyclohexylidene diphenol, 4,4'-
(1,3-dimethylbutylidene) bisphenol, 2,
2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenyl Sulfone, 2,4'-dihydroxydiphenyl sulfone,
4-hydroxy-4'-methyldiphenyl sulfone, 4
-Hydroxy-4'-methoxydiphenyl sulfone, 4
-Hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-3 ', 4'-trimethylene diphenyl sulfone, 4-hydroxy-3', 4'-tetramethylene diphenyl sulfone, 3,4-dihydroxy-
4'-methyldiphenyl sulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, 1,3-di [2-
(4-hydroxyphenyl) -2-propyl] benzene, hydroquinone monobenzyl ether, bis (4-hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxy Benzophenone,
2,2 ', 4,4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, 4-
Propyl hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, 4
-Phenyl hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p- Chlorobenzyl, 4
-Hydroxybenzoic acid-p-methoxybenzyl, novolac type phenolic resin, phenolic compounds such as phenolic polymers, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-
4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid,
3-tert-butylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3-phenyl −5- (α,
α-Dimethylbenzyl) salicylic acid, 3,5-di-α-
Aromatic carboxylic acids such as methylbenzyl salicylic acid, and organic acidic substances such as phenolic compounds, salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel etc. Of course, the above-mentioned coloring agents can also be used as needed.
One or more species can be used in combination.

The use ratio of the basic dye and the color developing agent should be appropriately selected according to the types of the basic dye and the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used.
About 100 to 700 parts by weight, preferably about 150 to 400 parts by weight, of the coloring agent is used with respect to 00 parts by weight. The coating liquid containing these is generally prepared by dispersing water with a dispersion medium, a basic dye, a colorant together or separately by a stirring / grinding machine such as a ball mill, attritor, or sand mill. However, in such a coating liquid, starches, hydroxyethyl cellulose, and
Methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene /
Vinylpyrrolidone copolymer salt, styrene-butadiene copolymer emulsion, etc.
Preferably about 15 to 30% by weight is blended.

Various auxiliaries can be further added to the coating liquid, for example, dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Examples thereof include dispersants such as lauryl alcohol sulfate / sodium salt and fatty acid metal salt, defoaming agents, fluorescent dyes, and coloring dyes. Further, in order to improve the adhesion of dust to the recording head, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, inorganic pigments such as activated clay, styrene microballs, nylon powder, polyethylene Powder, urea
Organic pigments such as formalin resin filler and raw starch particles can also be added. Further, a dispersion liquid or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax or the like may be added so that sticking does not occur due to contact with a recording device or recording head.

Further, in the heat-sensitive recording material of the present invention, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide are used as long as the desired effects of the present invention are not impaired. , 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl) -4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-
Hindered phenols such as tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, p
-Benzylbiphenyl, p- (4-tolyloxy) biphenyl, 1,5-bis (4-methoxyphenoxy) -3
-Oxa-pentane, 1,2-bis (phenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane,
1,2-bis (3-methylphenoxy) ethane, 1-
Ethers such as (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, 2-naphtholbenzyl ether, dibenzyl terephthalate, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid Esters such as di (4-methylbenzyl) ester and oxalic acid di (4-chlorobenzyl) ester, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxybenzophenone It is also possible to use an ultraviolet absorber such as the above and various known heat-fusible substances together as a sensitizer. Among these heat-fusible substances, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (phenoxy) ethane, 1- (2-methylphenoxy) -2-
(4-methoxyphenoxy) ethane, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, oxalic acid di (4-chlorobenzyl) ester, p-
Benzylbiphenyl, p- (4-tolyloxy) biphenyl, and 1,5-bis (4-methoxyphenoxy)-
3-Oxa-pentane is more preferable because it exhibits a particularly excellent sensitizing effect in relation to a specific storage stability improver.
The amount of the heat-fusible substance used is not particularly limited, but is generally 50 to 1000 parts by weight, preferably 100 to 500 parts by weight with respect to 100 parts by weight of the basic dye.
It is desirable to use it in the range of parts by weight.

The method for forming the heat-sensitive recording layer is not particularly limited, and the coating liquid for the heat-sensitive recording layer may be applied onto a support having an intermediate layer formed thereon, for example, an air knife coater, a blade coater, a bar coater, a gravure coater, or a curtain. It is formed by a method such as coating and drying with a suitable coating device such as a coater or a short dwell coater. Further, there is no particular limitation on the coating amount of the coating liquid, generally dry weight 2~12g / m ² approximately, is preferably adjusted in the range of about 2 to 8 g / m ^2.

After coating and drying the intermediate layer and the heat-sensitive recording layer, a smoothing treatment such as super calendering can be applied if necessary. Furthermore, it is possible to provide an overcoat layer on the heat-sensitive recording layer for the purpose of protecting the heat-sensitive recording layer, and to provide a backing layer on the support or to perform an adhesive treatment in the field of production of the heat-sensitive recording material. Various known techniques can be added.

The thermal recording material of the present invention thus obtained is
Since an intermediate layer containing a graft copolymer of a specific oil-absorbing pigment, polyvinyl alcohol and a (acrylamide-vinylpyrrolidone-acrylonitrile) copolymer as a main component is provided between the support and the heat-sensitive recording layer. Excellent pixel reproducibility in all areas from low density to high density, high recording density, and excellent surface strength of the recording material, so head dust and paper dust generation during cutting are effective. It is a thermal recording material that is effectively suppressed and has an excellent quality balance.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in the examples represent parts by weight and% by weight, respectively.

Example 1 [Preparation of coating liquid for intermediate layer] Amorphous silica (oil absorption: 150 ml)
/ 100 g) 100 parts, 20 parts of a 15% aqueous solution of a graft copolymer of polyvinyl alcohol and a (acrylamide-vinylpyrrolidone-acrylonitrile) copolymer and S
BR latex (solid content: 50%) 10 parts solid content 30
% To prepare an intermediate layer coating liquid. [Formation of Intermediate Layer] The obtained intermediate layer coating liquid was used to weigh 50 g / m 2.
^{The high-} quality paper of No. ² was coated and dried with an air knife coater so that the coating amount after drying was 8 g / m ² (thickness: 13 μm).

[Preparation of Coating Solution for Thermal Recording Layer] Preparation of Solution A 3- (N-cyclohexyl-N-methylamino) -6-
Methyl-7-phenylaminofluorane 10 parts, 1,2
A composition consisting of 20 parts of bis (4-methylphenoxy) ethane, 15 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water was pulverized with a sand mill until the average particle size became 0.8 μm.

Preparation of Solution B A composition comprising 30 parts of 4,4′-isopropylidenediphenol, 30 parts of a 5% aqueous solution of methylcellulose, and 70 parts of water was pulverized by a sand mill until the average particle diameter became 0.8 μm.

125 parts of solution A, 130 parts of solution B, 30 parts of silicon oxide pigment (oil absorption 180 ml / 100 g), 150 parts of 20% aqueous solution of oxidized starch, and 55 parts of water are stirred and mixed to prepare a coating liquid for the heat-sensitive recording layer. Prepared.

[Formation of heat-sensitive recording layer] The above-mentioned heat-sensitive recording layer coating solution is applied onto the above-mentioned intermediate layer with a pure blade coater so that the coating amount after drying is 5 g / m ^2, and dried, and then a super calender is used. A thermal recording paper was obtained by processing.

Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that calcined clay (oil absorption 85 ml / 100 g) was used in place of the amorphous silica in the preparation of the coating liquid for the intermediate layer.

Example 3 Except that the amount of a 15% aqueous solution of a graft copolymer of polyvinyl alcohol and a (acrylamide-vinylpyrrolidone-acrylonitrile) copolymer was 130 parts,
A thermal recording paper was obtained in the same manner as in Example 1.

Example 4 In the preparation of solution A of the heat-sensitive recording layer coating solution, 3-di (N- instead of 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane was used. A thermal recording paper was obtained in the same manner as in Example 1 except that (butyl) amino-6-methyl-7-phenylaminofluorane was used.

Comparative Example 1 Instead of amorphous silica, clay (oil absorption 20 ml / 1
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 100 g) was used.

Comparative Example 2 Instead of the graft copolymer of polyvinyl alcohol and (acrylamide / vinylpyrrolidone / acrylonitrile) copolymer, polyvinyl alcohol (polymerization degree: 100) was used.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 0, saponification degree of 98%) was used.

The five kinds of thermal recording papers thus obtained were
A thermal printer (SONY, UP-701 type video printer) was used to record with a print pulse time of 3 ms and 8 ms, and the recorded density was recorded with a Macbeth densitometer (RD-100
R type, using an amber filter) and the results are shown in Table 1. In addition, the reproducibility of the print pixels, the suitability for cutting, and the state of head residue adhesion were evaluated, and the results are also shown in Table 1.

[0033]

[Table 1]

The reproducibility of the printed pixels was evaluated by the ratio of the area of the printed dots to the area of one dot of the thermal head (dot reproducibility), and the evaluation criteria were as follows. ◎ ・ ・ ・ ・ 86% or more ○ ・ ・ ・ ・ 76-85% △ ・ ・ ・ ・ 70-75% × ・ ・ ・ 69% or less

The cutting suitability was evaluated based on the generation of paper dust when the recording portion and the blank portion of the recording paper were cut with a cutter, and the evaluation criteria were as follows. ◎ ・ ・ ・ ・ No generation of paper dust or peeling of the thermosensitive recording layer. ○: No paper dust was generated, but the thermal recording layer was slightly peeled off. × ・ ・ ・ ・ Paper powder is remarkably generated, and the thermal recording layer is often peeled off.

Further, regarding the head residue, a printing rate of 1 was obtained by using a heat-sensitive fax machine (NEFAX-27).
The occurrence of head shavings after copying 10 sheets at 00% was evaluated, and the evaluation criteria were as follows. ◎ ・ ・ ・ ・ Heads are not seen at all. × ・ ・ ・ ・ Heads are remarkably generated.

[0037]

As is clear from the results of Table 1, the thermosensitive recording medium of the present invention is excellent in reproducibility of print pixels in any area from low density to high density, and has high recording density. The recording material was excellent in cutting suitability and also excellent in head scrap.

Claims (3)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer, wherein an oil absorption is 8 between the support and the heat-sensitive recording layer.
A thermosensitive recording medium comprising an intermediate layer containing a pigment and a graft copolymer of polyvinyl alcohol and (acrylamide-vinylpyrrolidone-acrylonitrile) of 0 ml / 100 g or more as a main component. 2. The heat-sensitive recording material according to claim 1, wherein the pigment having an oil absorption of 80 ml / 100 g or more is one kind selected from amorphous silica, aluminum silicate and calcined clay. 3. A graft copolymer of polyvinyl alcohol and (acrylamido / vinylpyrrolidone / acrylonitrile) is added to 2 to 3 parts by weight of 100 parts by weight of a pigment.
The thermosensitive recording medium according to claim 1, which is used in an amount of 0 part by weight.