JPH05169804A - 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 crystallinity 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 at least one kind of a crystalline thermoplastic resin (ethylene/propylene copolymer with crystallinity of 30%) 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 heat-sensitive 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 an inorganic fine powder, and A 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 a DSC curve, and at least one crystalline thermoplastic resin having a melting peak temperature of 160 ° C. or lower on a DSC curve (However, compared with the crystalline propylene-based resin of the above (A) and (B), the melting peak temperature difference of the DSC curve shows a temperature lower by 4 ° C. or more), and a back layer (C), A heat-sensitive recording paper having a heat-sensitive recording support having the above, wherein a heat-sensitive recording layer is provided on the surface layer (A).

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
The thermal recording layer D is provided on the upper surface of the. 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.

Back surface layer (C) The back surface layer contains a crystalline thermoplastic resin having a melting peak temperature of 160 ° C. or less of the DSC curve as a matrix component of the film. Examples of such resin include ethylene-propylene copolymer, high density polyethylene, medium density polyethylene, low density polyethylene and the like. In order to provide the back surface layer with slipperiness with a roll at the time of transfer and writing on the back surface layer after transfer, the same inorganic fine powder as that used for the surface layer or the base material layer is used as the resin component 100. Parts by weight,
5 to 110 parts by weight, preferably 8 to 90 parts by weight, and the surface smoothness measured according to JIS P8119.
The (Beck index) is preferably 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)
-6-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-
Phenylsiminofluorane, 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-
Examples thereof include fluoran dyes such as tetrahydrofurfurylamino-6-methyl-7-anilinofluorane and 3-N-ethyl-N-tetrahydrofurfurinoamino-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 thermal recording layer on this support by using the one provided, the temperature distribution of each layer along the difference in temperature distribution due to the time factor of the heat conduction to the front surface layer and the back surface layer caused by heat during printing The heat shrinkage is balanced, and the degree of curling of the entire thermal recording paper is reduced.

[0020]

EXAMPLES The present invention will be described below with reference to examples. Example 1 (1) Melt index (MI) 0.8 g / 10 minutes, DS
25 parts by weight of calcium carbonate having an average particle size of 1.5 μm was added to 75 parts by weight of polypropylene having a crystallinity of 50% by the method C and a melting peak temperature of a DSC curve of 166 ° C.
After melt-kneading with an extruder set to 70 ° C., it was extruded into a sheet form from a die and cooled with a cooling device to obtain an unstretched sheet. This sheet was heated to 150 ° C. and then stretched 5 times in the longitudinal direction to prepare a base layer (B) which was uniaxially stretched only. (2) MI 4.0 g / 10 minutes, crystallinity 4 by DSC method
8% and 55 parts by weight of polypropylene having a melting peak temperature of 167 ° C. on the DSC curve were mixed with 45 parts by weight of calcium carbonate having an average particle size of 1.5 μm, and the mixture was melt-kneaded by an extruder set at 220 ° C. and then sheeted from a die. A surface layer (A) before being extruded into a uniform shape and uniaxially stretched was prepared, and the surface layer (A) was laminated on one side of the uniaxially stretched base layer. On the other side, MI
55 parts by weight of high density polyethylene having a crystallinity of 40% by a DSC method and a melting peak temperature of a DSC curve of 125 ° C. were blended with 45 parts by weight of calcium carbonate having an average particle diameter of 1.5 μm. After melt-kneading with another extruder set to 220 ° C., extruded into a sheet form from a die to prepare a back surface layer (C) before uniaxially stretching, laminating this, then cooling to 60 ° C., then 162 ° C. After heating up to 7.5 times in the transverse direction with a tenter, annealing treatment at 167 ° C, cooling to 60 ° C, slitting the ears, 3 layers (A / B / C: thickness 10 μm / A support for thermal recording having a structure of 45 μm / 25 μm) was obtained. The opacity of this support was 90%. (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.

Examples 2 to 7 and Comparative Example 1 The composition of the back surface layer (C) of the support in Example 1 is 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 8 The thickness of A / B / C of 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 9 (1) Melt index (MI) 0.8 g / 10 minutes,
80 parts by weight of polypropylene having a crystallinity of 50% by the DSC method and a melting peak temperature of the DSC curve of 166 ° C.,
20 parts by weight of calcium carbonate having an average particle diameter of 1.5 μm was blended, melt-kneaded by an extruder set at 270 ° C., extruded into a sheet form from a die, and cooled by a cooling device to obtain an unstretched sheet. 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 minutes, crystallinity 48% by DSC method, and 85 parts by weight of polypropylene having a DSC curve melting peak temperature of 167 ° C. were mixed with 15 parts by weight of calcium carbonate having an average particle size of 1.5 μm. The composition for the outer layer of the surface layer (A), and MI 4.0 / 10 minutes, crystallinity 48% by DSC method, and 55 parts by weight of polypropylene having a melting peak temperature of 167 ° C. on the DSC curve had an average particle size of 1 .
The composition for the inner layer of the surface layer (A) containing 45 parts by weight of calcium carbonate of 5 μm was melt-kneaded in each extruder, and at the same time, the final thickness was 3 μm for the outer layer.
The porosity of the die is adjusted so that the inner layer and the inner layer are 12 μm, and each is extruded into a sheet from the die to prepare a surface layer (A) consisting of two layers before being uniaxially stretched. Was laminated on one side of the base layer which was uniaxially stretched only. On the opposite side, MI 10.0 g / 10 min, crystallinity 40% by DSC method and melting peak temperature of DSC curve of 125
55% by weight of high density polyethylene at ℃, average particle size of 1.5
After blending 45% by weight of calcium carbonate of μm, melt-kneading with another extruder set at 220 ° C., extruded into a sheet form from a die, prepare a back surface layer (C) before uniaxially stretching, and laminate this. Then, after cooling to 60 ° C., annealing treatment is performed at 167 ° C., cooling to 60 ° C., and the ears are slit to form three layers (A / B / C: thickness 15 μm / 45 μm / 20
A support for thermal recording having a (μm) structure was obtained. The opacity of this support was 90%. (3) Further, the surface layer of the obtained heat-sensitive recording support.
A thermal recording layer was provided on (A) in the same manner as in Example 1,
A thermosensitive recording paper was obtained. When the obtained thermal recording paper was measured in the same manner as in Example 1, the curl height and the opacity were 6 mm and 83%, 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

Claims (2)

[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) and at least one crystalline thermoplastic resin having a melting peak temperature of a DSC curve of 160 ° C. or lower (provided that (A) and
(B) a back surface layer (C) having a melting peak temperature difference of DSC curve of 4 ° C. or more lower than that of the crystalline propylene resin (B)) A heat-sensitive recording paper having: a heat-sensitive recording sheet, wherein a heat-sensitive recording layer is provided on the surface layer (A). 2. The melting peak temperature of the DSC curve is 160.
The thermosensitive recording paper according to claim 1, wherein the crystalline thermoplastic resin having a temperature of not higher than 0 ° C. is selected from the group consisting of an ethylene / propylene copolymer having a crystallinity of 30%, high density polyethylene, medium density polyethylene and low density polyethylene. ..