JPH05169806A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To improve the heat shrink balance of each layer and to suppress the generation of a curl by forming a surface layer and a base material layer from a crystalline resin having high crystrallinity and a high m.p. and forming a backing layer from a thermoplastic resin having specific melting peak temp. and providing a thermal recording layer on the surface layer. CONSTITUTION:In the support of thermal recording paper, a surface layer A composed of a uniaxially stretched film of a crystalline propylene resin containing 8-65wt.% of an inorg powder and having melting peak temp. of a DSC curve of 160 deg.C or higher, a base material layer B composed of a biaxially stretched film of a crystalline propylene resin containing 30wt.% or more of an inorg. powder and having melting peak temp. of a DSC curve of 160 deg.C or higher and a backing layer C composed of 85-20 pts.wt. of the above-mentioned crystalline propylene resin and at least one kind of a thermoplastic resin having melting peak temp. of a DSC curve of 160 deg.C or lower are provided. A thermal recording layer D is provided on the surface layer A of the support to enable thermal recording reduced in the generation of a curl.

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 paper, and more particularly to a heat-sensitive recording paper which has a small curl even when heat is applied during heat-sensitive recording and does not pose a practical problem.

[0002]

2. Description of the Related Art A thermal recording method generally heats a thermal recording head (hereinafter simply referred to as "head") according to an input signal,
It is a recording method in which a color developing agent and a color developing agent on a recording image receiving sheet in contact with this are melted and contacted to obtain a colored image, having a recording speed commensurate with the amount of information in a band put on a telephone line,
Since it is a primary color developing system that does not require development and fixing steps, and the head is consumed very little, it is rapidly applied to information equipment such as printers and facsimiles. However, the development of various types of office equipment and the diversification of applications are rapidly progressing, and there is a demand for the development of a thermal recording material that can meet the respective requirements. For example, a thermosensitive recording material that can obtain a high density and clear image even with a minute printing energy is desired as a material that can respond to the high speed of recording equipment. To meet this demand, not only the thermal recording layer is examined. It has come to be recognized that it is necessary to study the support in various ways, and the number of cases where a synthetic resin film is used instead of the conventional natural paper is increasing.

As a recent support, paper or synthetic paper made of stretched film of propylene resin containing inorganic fine powder (Japanese Patent Publication No. 46-40794), or transparent polyethylene terephthalate film or silica on the surface of transparent film is used. BACKGROUND ART Coated synthetic paper and the like in which an inorganic compound such as calcium carbonate or the like is applied together with a binder to improve whiteness and dyeing property are used. However, considering the after-use of thermal recording paper (copying, pencil writing, storability, etc.), the support should have micro voids inside because of its strength, dimensional stability, and adhesion with the print head. It is said that a synthetic paper obtained by stretching a polyolefin resin film containing a large number of inorganic fine powders is preferable (Japanese Patent Laid-Open Nos. 59-148693, 61-279589, and Sho-61-279589).
62-282970, JP-A-63-99984, JP-A-63-299976,
JP-A-2-70479, etc.). The synthetic paper obtained by stretching such a polyolefin resin film has opacity and softness, and in order to improve the adhesion with the print head and the paper feeding / discharging property, the melting point of the polyolefin resin of the material is The film is stretched at a lower temperature to form microvoids inside the film.

[0004]

However, at the time of printing, the surface temperature of the thermosensitive recording paper is 190 although it is for a short time.
However, since the melting point of the polyolefin resin film is 167 ° C. or lower, which is considerably lower than that of polyethylene terephthalate (240 to 255 ° C.) or polyamide, the synthetic paper shrinks due to heat during printing. ,
There is a defect that the printed thermal recording paper curls toward the inner surface on which it is printed. On the other hand, in order to prevent such curl, the stretching temperature may be set to be close to the melting point of the base resin, but in this case, the opacity and softness of the base resin are deteriorated. There are drawbacks. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide a heat-sensitive recording paper which has a small curl even when heat is applied during transfer recording, and which poses no practical problem.

[0005]

As a result of earnest studies, the present inventors were able to solve the above problems. That is, the present invention contains 8 to 65% by weight of inorganic fine powder,
And, the melting peak temperature of the DSC curve is composed of a uniaxially stretched film of a crystalline propylene resin having a temperature of 160 ° C. or higher, and contains a surface layer (A) on which a heat-sensitive recording layer is to be provided, and 30% by weight or less of inorganic fine powder, Base layer (B) made of a biaxially stretched film of a crystalline propylene-based resin having a melting peak temperature of 160 ° C. or higher on the DSC curve, and a crystalline propylene-based resin 8 having a melting peak temperature of 160 ° C. or higher on the DSC curve
5 to 20 parts by weight and the melting peak temperature of the DSC curve is 16
At least one thermoplastic resin having a temperature of 0 ° C. or lower (however, the melting peak temperature difference of the DSC curve is 4 ° C. or more lower than that of the crystalline propylene resin) 15 to 15
A heat-sensitive recording paper having a heat-sensitive recording support comprising a backside layer (C) consisting of 80 parts by weight, wherein a heat-sensitive recording layer is provided on the surface layer (A). , Thermal recording paper is provided.

The present invention will be described in more detail below.
A schematic view of the thermal recording paper of the present invention is shown in FIG. The heat-sensitive recording support used in the present invention is constituted by providing the surface layer A on the upper surface of the base material layer B and the back surface layer C on the lower surface, and further, the surface layer A
A heat-sensitive recording layer D is provided on the upper surface of 1. Each layer will be described in detail below.

Surface layer (A) The melting peak temperature of the DSC curve for forming the surface layer is 160
The crystalline propylene-based resin having a temperature of ℃ or more is not particularly limited as long as this condition is satisfied. For example, a propylene homopolymer having a crystallinity of 40% or more by the DSC method, a propylene-hexene copolymer, propylene-pentene, -1
Examples thereof include propylene-based resins such as copolymers.
Here, the melting peak temperature of the DSC curve refers to sample resin 6 to
It is the temperature of the peak appearing in the DSC curve when the temperature of a 10 mg sample was raised from room temperature to 280 ° C. at a heating rate of 10 ° C./min. The inorganic fine powder contained in the surface layer may be any inorganic fine powder, for example, calcium carbonate, calcined clay, diatomaceous earth, talc, titanium oxide,
Examples thereof include barium sulfate, aluminum sulfate and silica. It is preferable that these inorganic fine powders do not form a large convex portion on the surface layer, and the 325 mesh sieve residue is 10
It is preferably ppm or less. The particle size is preferably 3 μm or less. The content is preferably such that the surface smoothness (Beck index) measured by JIS P8119 is about 200 to 3000 seconds. In practice, it is 8 to 65% by weight, preferably 8 to 55% by weight, based on the total surface layer. The film having the above composition is uniaxially stretched at a temperature lower than the melting peak end temperature of the DSC curve of the crystalline propylene-based resin (the high temperature side skirt of the DSC peak) to form a surface layer. The uniaxially stretched film may have either a single layer structure or a multilayer structure. Further, the surface layer may optionally have a melting peak temperature of a DSC curve of 160 ° C. or less and a crystallinity of 30% or more, for example, a thermoplastic resin such as ethylene-propylene copolymer, high density polyethylene, or medium density. Polyethylene, low density polyethylene and the like can be contained in an amount of 10% by weight or less. The thickness of the surface layer is preferably 3 to 50 μm.

Substrate Layer (B) The melting peak temperature of the DSC curve for forming the substrate layer is 16
The crystalline propylene-based resin having a temperature of 0 ° C. or higher may be the same as or similar to the resin forming the surface layer.
This base material layer contains 0 to 30% by weight, preferably 8 to 25% by weight, of the same inorganic fine powder as that contained in the surface layer.
It is contained. A material having the above composition is biaxially stretched to form a film to form a base material layer. By this biaxial stretching, when an inorganic fine powder is contained, a large number of microvoids are generated with this powder as a core. This base material layer is a thermoplastic resin having a temperature peak of a DSC curve of 160 ° C. or less, for example, an ethylene-propylene copolymer, for example, in order to facilitate the stretchability, if necessary.
High density polyethylene, medium density polyethylene, low density polyethylene and the like can be contained in an amount of 0 to 10% by weight. The thickness of the base material layer is 20 to 80% of the total thickness of the support. 20
If it is less than%, the rigidity (waist) of the thermosensitive recording paper is lowered and it is not practical. On the other hand, when the thickness exceeds 80%, the thickness of the surface layer becomes thin, so that the temperature of the base material layer rises due to the heating of the thermal head and the like, and the amount of shrinkage of the thermal recording paper increases to prevent curling. The effect decreases.

Backside layer (C) The backside layer has a melting peak temperature of DSC curve of 85 to 20 parts by weight, preferably 60 to 25 parts by weight, of a crystalline propylene resin having a melting peak temperature of 160 ° C. or higher. A thermoplastic resin having a melting point of 160 ° C. or less, which has a melting peak temperature of a DSC curve that is lower than the melting peak temperature of the DSC curve of the crystalline propylene resin by 4 ° C. or more, that is, an ethylene-propylene copolymer, a high-density polyethylene. 15-80 parts by weight, preferably 20-70 parts by weight of a resin selected from medium density polyethylene, low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer and ethylene-methyl acrylate copolymer. It is composed of parts. In order to give the back layer a slip property with a roll at the time of printing and a writing property to the back layer after printing, an inorganic fine powder similar to that used for the surface layer or the base material layer is used as the resin component 100. 5 to 1 relative to parts by weight
It is preferable to contain 10 parts by weight, preferably 8 to 90 parts by weight, and it is preferable that the surface smoothness (Beck index) measured according to JIS P8119 is about 50 to 2000 seconds. The backing layer is formed into a film by uniaxially stretching the one having the above composition.

As a method for producing the heat-sensitive recording support used in the present invention by using the above surface layer, base material layer and back surface layer, a uniaxially stretched film-shaped base material layer is uniaxially coated on one side. The front surface layer before stretching is melt-laminated, and the back surface layer before uniaxial stretching is melt-laminated on the opposite surface, and after this multilayer sheet is once cooled, it is heated again and orthogonal to the uniaxial stretching direction of the base material layer. It can be obtained by stretching again in the desired direction and then heat treating. The total thickness of the heat-sensitive recording support of the present invention is usually 50 to 500 μm, preferably 55.
〜120 μm, Young's modulus (JIS P813
2) is preferably 9,000 to 26,000 kg / cm ² .

Next, the heat-sensitive recording layer formed on the surface layer (A) of the heat-sensitive recording support will be described. (1) Compounding agent A thermosensitive recording layer of the present invention is obtained by providing a thermosensitive recording layer containing a color former and a color former on the thermosensitive recording substrate obtained as described above. With respect to the combination of the color former and the color former contained in the heat-sensitive recording layer, any combination can be used as long as they are brought into contact with each other to cause a color reaction, for example, a colorless or pale basic dye and an inorganic or inorganic dye. Examples include combinations with organic acidic substances, or combinations of higher fatty acid metal salts such as ferric stearate with phenols such as gallic acid, and further combinations of diazonium compounds with couplers and basic substances. Is applicable.

Coloring Agent As the colorless or light-colored basic dye that can be used as the coloring agent in the heat-sensitive recording layer, various types can be used. For example, 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-methylindole-
3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide,
3,3-bis (1,2-dimethylindol-3-yl)
-5-Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindole-3-
) -6-Dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide and other triallylmethane dyes, 4,4'- Diphenylmethane dyes such as bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leucolamin, and thiazines such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue. Dyes, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-
Phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-
Spiro dyes such as methoxybenzo) spiropyran and 3-propyl-spiro-dibenzopyran, lactam dyes such as rhodamine-β anilinolactam, rhodamine (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-dimendylaminofluorane, 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-cyclopentyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7 -(P-toluidino) fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxyphenylamino) fluorane, 3- (N-ethyl-N-isoamylamino) ) -6-Methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-
7-phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-
Phenylaminofluorane, 3-piperidino-6-methyl-7-phenylcyminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-dibutylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7
-P-butylphenylaminofluorane, 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-
Examples thereof include fluoran dyes such as 7-anilinofluorane and 3-N-ethyl-N-tetrahydroflufurinoamino-6-methyl-7-anilinofluorane.

[0013] The inorganic or organic acidic substance coloration in contact with color developer the basic dye, can be used various known. Examples of inorganic acidic substances include activated clay, acid clay, attapulgite, bentonite, colloidal silica, and aluminum silicate.
tert-Butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-dihydroxydiphenol, 2,2′-methylenebis (4-methyl) -6-tert-isobutylphenol), 4,4'-isopropylidenebis (2-te
rt-butylphenol), 4,4'-sec-butylidene diphenol, 4-phenylphenol, 4,4'-isopropylidene bis (2-tert-butylphenol), 4-phenylphenol, 4,4'-isopropylidenedi Phenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone,
4,4'-Cyclohexylidenediphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenol 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-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5
-Di-tert-butylsalicylic acid, 3-phenyl-5
Aromatic carboxylic acids such as-(α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and the phenolic compounds and aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium Examples thereof include salts with polyvalent metals such as manganese, tin, and nickel.

Quantitative ratio The basic dyes (color formers) and color formers may be used in combination of two or more, if necessary. Further, the ratio of the basic dye and the color developing agent to be used is appropriately selected according to the type of the basic dye or the color developing agent to be used and is not particularly limited, but generally 1 part by weight of the basic dye is used. On the other hand, 1 to 20 parts by weight, preferably 2 to 10 parts by weight, of the color former is used.

(2) Coating liquid A coating liquid containing these substances generally uses water as a dispersion medium,
It can be prepared by uniformly or separately dispersing the dye (color former) and the color former with a stirring / crushing machine such as a ball mill, an attritor or a sand mill. In the coating liquid,
Starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diisobutylene
Binders such as maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin, melamine resin, amide resin, amino resin, etc. It is preferable to contain 2 to 40% by weight, preferably 5 to 25% by weight of the total solid content.

Other Compounding Agents Further, various auxiliary agents can be added to the coating liquid as required. For example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, lauryl alcohol sulfate / sodium salt, fatty acid. A dispersant such as a metal salt, an ultraviolet absorber such as a benzophenone type, an antifoaming agent, a fluorescent paint, a coloring dye, a conductive substance and the like can be appropriately added.

If necessary, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide and palm fatty acid. Fatty acid amides such as amides, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 1,3,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, etc. Hindered phenols, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4
-UV absorbers such as benzyloxybenzophenone,
1,2-di (3-methylphenoxy) ethane, 1,2-
Diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, p-benzyl-biphenyl, 1,4-
Esters such as dimethoxynaphthalene, 1,4-diethoxynaphthalene, and 1-hydroxynaphthoic acid phenyl ester, and various known thermoplastics, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particles It is also possible to add inorganic pigments such as anhydrous silica and activated clay.

(3) Coating The method for forming the heat-sensitive recording layer on the surface layer (A) is not particularly limited, and for example, a method for coating / drying the coating liquid by air knife coating, blade coating, etc. Formed by. The present invention is not limited particularly also the coating amount of the coating liquid, usually dry weight 2~12g / m ^2, are preferably prepared in a range of about 3 to 10 g / m ^2. An overcoat layer may be provided on the heat-sensitive recording layer of the heat-sensitive recording paper for the purpose of protecting the heat-sensitive recording layer, and the back surface of the heat-sensitive recording paper is treated with an adhesive to form an adhesive label. If necessary, various known techniques in the field of manufacturing thermal recording paper can also be carried out.

[0019]

As a support for heat-sensitive recording, a crystalline resin having high crystallinity and a high melting point is used as a surface layer and a base material layer, and a thermoplastic resin having a melting peak temperature of a DSC curve of 160 ° C. or less is used as a back layer. By forming a thermosensitive recording layer on this support by using the one provided, the difference in temperature distribution due to the time factor of the heat conduction between the front surface layer and the back surface layer caused by the heat during printing (temperature of the front surface layer> According to (temperature of base material layer> temperature of back surface layer), the heat shrinkage of each layer is balanced, and the degree of curling of the entire thermosensitive recording paper becomes low.

[0020]

EXAMPLES The present invention will be described below with reference to examples. Example 1 (1) Polypropylene having a melt index (MI) of 0.8 g / 10 min (melting peak temperature of DSC curve = 166 ° C.)
75 parts by weight of calcium carbonate having an average particle size of 1.5 μm 25
Parts by weight were blended, melt-kneaded by an extruder set at 270 ° C., extruded in a sheet form from a die, and cooled by a cooling device to obtain an unstretched sheet. After heating this sheet to 150 ° C., it is stretched 5 times in the longitudinal direction to form a uniaxially stretched base material layer (B).
Was prepared. (2) Polypropylene 55 of polypropylene with MI 4.0 g / 10 min (melting peak temperature of DSC curve = 167 ° C.)
45 parts by weight of calcium carbonate having an average particle size of 1.5 μm was mixed with parts by weight, melt-kneaded with an extruder set at 220 ° C.,
Surface layer extruded into a sheet from the die and before uniaxial stretching
(A) was prepared, and this was laminated on one side of the substrate layer of (1) only uniaxially stretched. On the opposite side, polypropylene with MI 4.0 g / 10 min (melting peak temperature of DSC curve = 125
35 ° C.) and high-density polyethylene of MI 10.0 / 10 min (melting peak temperature of DSC curve = 125 ° C.)
45 parts by weight of calcium carbonate having an average particle size of 1.5 μm was mixed with 20.0 parts by weight, melt-kneaded with another extruder set at 220 ° C., extruded into a sheet from a die, and the back surface before uniaxially stretching. Prepare layer (C), laminate it and then 60
After cooling to ℃, heated to 162 ℃, stretched 7.5 times in the transverse direction with a tenter, then annealed at 167 ℃, cooled to 60 ℃, slit the ears, 3 layers
A support for thermal recording having a structure (A / B / C: thickness 10 μm / 45 μm / 25 μm) was obtained. The opacity of this support is 9
It was 0%. (3) Further, the surface layer of the obtained heat-sensitive recording support.
An aqueous coating liquid containing a polyethylene-based anchor material and silica for preventing blocking is applied onto (A) to form an anchor coating layer, and the coating liquid for the thermosensitive recording layer prepared as follows is dried. Was coated to a coating amount of 5 g / m ² and dried, and then supercalendered to obtain a thermosensitive recording paper. A coating liquid for coating on a support to obtain a heat-sensitive recording layer was prepared as follows. Solution A Preparation 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane 10 parts Dibenzyl terephthalate 20 parts Methylcellulose 5% aqueous solution 20 parts Water 40 parts It was crushed to 3 μm. Preparation of Solution B 4,4′-isopropylidenediphenol 30 parts Methylcellulose 5% aqueous solution 40 parts Water 20 parts This composition was ground with a sand mill until the average particle size became 3 μm. Preparation of coating liquid A liquid 90 parts, B liquid 90 parts, silicon oxide pigment (trade name: Mizukasil P-527, average particle diameter: 1.8 μm, oil absorption: 1
80 cc / 100 g, manufactured by Mizusawa Chemical Co., Ltd.) 30 parts, 10 parts polyvinyl alcohol aqueous solution 300 parts, and water 28 parts were mixed and stirred to obtain a coating liquid. The curl height, opacity and writability of the obtained thermal recording paper were measured. The measuring method is shown below. The writability was such that it could be put to practical use. Curl height: The thermal recording paper to be measured is solidly printed and printed on a Sony Multiscan Video Printer UP-930 (product name), and MD (machine direction)
Direction and TD (traverse direction) directions were cut into squares of 50 mm square, and the floating height (mm) was measured when this was placed on a flat surface for 24 hours under the conditions of temperature of 23 ° C. and humidity of 50%. Opacity: Measured according to JIS P8138. Writability It was measured using a writing tester manufactured by Toyo Seiki.

The compositions of the back surface layers (C) of the supports in Examples 2 to 10 and Comparative Examples 1 to 3 are shown in Table 1.
A thermal recording paper was produced in the same manner as in Example 1 except that the composition described in Example 1 was used, and the curl height, opacity and writability were measured. The results are shown in Table 1. In addition, the writability was such that it could be put to practical use in both Examples and Comparative Examples.

Example 11 The thickness of A / B / C of the three layers of the support is 17.5 μm / 45.
A thermosensitive recording paper was produced in the same manner as in Example 1 except that the slit width of the die was changed to be μm / 17.5 μm, and the curl height, opacity and writability were measured as described above. did. The results are shown in Table 1. The writability was such that it could be put to practical use.

[0023]

[Table 1]

[0024]

[Table 2]

Example 12 (1) Polypropylene having a melt index (MI) of 0.8 g / 10 min (melting peak temperature of DSC curve = 166
(° C) 80 parts by weight, 20 parts by weight of calcium carbonate having an average particle size of 1.5 μm are blended, melt-kneaded by an extruder set at 270 ° C., extruded into a sheet from a die, and cooled by a cooling device. A stretched sheet was obtained. This sheet was heated to 150 ° C. and then stretched 5 times in the machine direction to prepare a uniaxially stretched base material layer (B). (2) MI 4.0 g / 10 min polypropylene (DSC
(Melting peak temperature of curve = 167 ° C.) 85 parts by weight and 15 parts by weight of calcium carbonate having an average particle size of 1.5 μm were compounded for the outer layer of the surface layer (A), and MI 4.0 / 1.
0 minute polypropylene (melting peak temperature of DSC curve =
167 ° C.) 55 parts by weight and 45 parts by weight of calcium carbonate having an average particle size of 1.5 μm were mixed and melted and kneaded with the composition for the inner layer of the surface layer (A) at the same time. Adjust the porosity of the dies so that the outer layer has a thickness of 3 μm and the inner layer has a thickness of 12 μm, and each is extruded into a sheet from the die to prepare a surface layer (A) consisting of two layers before uniaxially stretching. This was laminated on one surface of the substrate layer (1) which was uniaxially stretched only. MI 4.0g / 10 on the opposite side
Min polypropylene (melting peak temperature of DSC curve = 1
25 ° C.) 20.0 parts by weight were mixed with 45 parts by weight of calcium carbonate having an average particle size of 1.5 μm, melt-kneaded with another extruder set at 220 ° C., extruded into a sheet form from a die, and uniaxially stretched. Prepare the back surface layer (C) before, stack this,
Then, after cooling to 60 ° C., it was heated to 162 ° C., stretched to 7.5 times in the transverse direction with a tenter, annealed at 167 ° C., cooled to 60 ° C., and the ears were slit to form three layers (A / B / C: Thickness 15μm / 45μm / 20μ
A m-structured support for heat-sensitive recording was obtained. The opacity of this support was 90%. (3) Further, using the thus obtained support for thermal recording,
A thermosensitive recording layer was formed in the same manner as in Example 1 to obtain a thermosensitive recording paper. When the obtained thermal recording paper was measured in the same manner as in Example 1, the curl height and the opacity were
9 mm and 89% respectively. The writability was such that it could withstand practical use.

[0026]

According to the present invention, it is possible to obtain a heat-sensitive recording paper which has a small curl even when heat is applied during transfer recording, and which poses no practical problem.

[Brief description of drawings]

FIG. 1 is a schematic view of a thermosensitive recording paper of the present invention.

[Explanation of symbols]

 A front surface layer B base material layer C back surface layer D thermal recording layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B32B 27/32 E 8115-4F

Claims (1)

[Claims] 1. A uniaxially stretched film of a crystalline propylene resin containing 8 to 65% by weight of an inorganic fine powder and having a melting peak temperature of a DSC curve of 160 ° C. or higher,
A surface layer (A) on which a heat-sensitive recording layer should be provided, and a biaxially stretched film of a crystalline propylene resin containing 30% by weight or less of inorganic fine powder and having a melting peak temperature of a DSC curve of 160 ° C. or higher. Material layer (B), 85 to 20 parts by weight of a crystalline propylene resin having a melting peak temperature of 160 ° C. or higher on the DSC curve, and a melting peak temperature of 160 ° C. or lower on the DSC curve (however, compared with the above crystalline propylene resin. And the melting peak temperature difference of the DSC curve is 4 ° C.
A lower surface layer (C) which comprises 15 to 80 parts by weight of at least one thermoplastic resin
A heat-sensitive recording paper having a support for heat-sensitive recording, comprising: a heat-sensitive recording layer provided on the surface layer (A).