JP2922275B2 - Support for heat-sensitive recording medium provided with heat-sensitive recording layer containing color former and color former - Google Patents

Description

BACKGROUND OF THE INVENTION <Industrial Application Field> The present invention relates to a support used for a thermosensitive recording medium provided with a thermosensitive recording layer containing a color former and a color former. Particularly, the present invention relates to a support used for a thermosensitive recording medium provided with a thermosensitive recording layer including a color former and a color former which are excellent in resolution, clear at high density, and do not cause curling by heat even after printing. Things.

<Prior Art> In the thermal recording method, a thermal recording head (hereinafter, simply referred to as a head) is generally heated in accordance with an input signal, and a coloring agent and a coloring agent on a recording image receiving sheet in contact with the recording head are melt-contacted. It is a recording method for obtaining a color image, has a recording speed commensurate with the amount of information in the band that can be carried on the telephone line, is a primary color developing system that does not require development and fixing, and has very little head wear. It is rapidly applied to information devices such as printers and facsimile machines.

However, the development of various office equipment and the diversification of uses are rapidly developing, and the development of a heat-sensitive recording medium that can respond to each demand is demanded. For example, a thermosensitive recording medium that can obtain a clear image at a high density even with a small printing energy is desired as a device capable of responding to a higher speed of a recording device. It has been recognized that it is necessary to consider variously about the support, and a case in which a synthetic resin film case is used instead of conventional natural paper is increasing.

For example, JP-A-2-70479 discloses a biaxially stretched resin film layer having fine cavities and having a content of the fine cavities of 40 to 100 cc / 100 g. Is used as one component of the support of the heat-sensitive recording layer, or a heat-sensitive recording material characterized by further laminating a film layer made of the same or different material to the film on the biaxially stretched resin film layer. A recording is disclosed.

<Problems to be Solved by the Invention> However, if only such porosity is satisfied, the support for thermosensitive recording is not necessarily excellent in resolution, clear at high density, and does not generate curl due to heat even after printing. Can not get. Therefore, in order to obtain a clear image with a high density, it is necessary to improve the surface smoothness, which is a physical property other than the porosity.

Therefore, the present inventor reduces the amount of the inorganic fine powder to improve the surface smoothness, the amount of voids in the film due to stretching decreases, the cushioning property deteriorates, and the image density decreases. However, such a method cannot be a means for solving the problem.

[Summary of the Invention]

<Summary> The present inventor has conducted intensive research in view of the above problems, and as a result,
Laminating a biaxially stretched thin film film with improved smoothness as a surface layer on the surface of a biaxially stretched porous film substrate having cushioning properties and a reduced heat shrinkage rate, The inventors have found that a heat-sensitive recording support having excellent image properties, high density even at a small printing energy, high sharpness, and no curling due to heat even after printing can be obtained. Was.

That is, the heat-sensitive recording medium support provided with a heat-sensitive recording layer containing the color former and the color former of the present invention is a porous film substrate of a biaxially stretched film of a thermoplastic resin containing inorganic fine powder. A support for a thermosensitive recording medium having a thermosensitive recording layer containing a color former and a color former having a structure in which a surface layer made of a thermoplastic resin biaxially stretched film having a center line average roughness of 0.6 μm or less is laminated on the surface. Wherein the physical properties of the support satisfy the following conditions (a) to (c).

(A) The thickness of the surface layer is 0.3 to 2.0 μm, and the Beck smoothness is 1,000 to 8,000 seconds.

(B) The opacity of the support is 70% or more and the density is 0.91 g /
cm ^3, compressive ratio stress of 32 kg / cm ³ is 15% to 35%
That.

(C) The heat shrinkage at 120 ° C. in the MD direction is 2.5% or less,
The TD direction must be 2.0% or less.

<Effect> The thermosensitive recording medium using the heat-sensitive recording support of the present invention has excellent surface smoothness and excellent cushioning properties due to a large number of microvoids contained in the support. The adhesion to the body is improved, and a transferred image rich in gradation is obtained.

Further, since the heat shrinkage of the support is low, a thermosensitive recording medium free from curling even after printing can be obtained.

[Specific description of the invention]

[I] Thermal Recording Support (1) Configuration The thermal recording support of the present invention has a center line on the surface of a porous film substrate made of a biaxially stretched thermoplastic resin film containing inorganic fine powder. It has a structure in which a surface layer made of a thermoplastic resin film having an average roughness of 0.6 μm or less, preferably 0.5 μm or less is laminated, and its physical properties are (a) the thickness of the surface layer is 0.3 to 2.0 μm, preferably Is 0.5 to 1.5 μm and Beck smoothness is 1,000 to 8,000
Seconds, preferably 2,000 to 7,000 seconds.

(B) The opacity of the support is 70% or more, preferably 80
% Or more, a density of 0.91 g / cm ³ or less, preferably 0.86 g / cm ³
Hereinafter, the compressibility for a stress of 32 kg / cm ³ is 15 to 35%, preferably 20 to 30%.

(C) The heat shrinkage at 120 ° C. in the MD direction is 2.5% or less, preferably 2.0% or more, and the TD direction is 2.0% or less, preferably 1.5% or less.

It shows.

Specifically, a polyolefin biaxially stretched film containing 15 to 45% by weight of an inorganic fine powder is used for a base material layer, and a polyolefin substantially containing an amount of the inorganic fine powder suitable for a target quality is provided on the surface of the base material layer. JIS-P8138 formed by laminating a biaxially stretched film with a thickness of 0.3 to 2.0 μm as the outermost surface layer
Opacity is 70% or more, whiteness according to JIS-P8123
A thermoplastic resin film with a multilayer structure with a density of not less than 85% and a density of not more than 0.91 g / cm ³ , and the center line average roughness (Ra) of the surface layer is not more than 0.6 μm as measured by JIS B-0601. The Beck smoothness measured by JIS P-8119 is 1,000 to 8,
000 seconds and a compression rate of the support (a compression amount when a load of 32 kg / cm ² is applied) of 15 to 35%.

(2) Constituent Material Polyolefin is usually used as the thermoplastic resin used for the base layer and the surface layer. As such a polyolefin, polyethylene, polypropylene, ethylene / propylene copolymer, ethylene / vinyl acetate copolymer, propylene / butene-1 copolymer, poly (4-methylpentene-1), polystyrene and the like can be used. . Of course, other thermoplastic resins such as polyamide, polyethylene terephthalate, and polybutylene phthalate can be used, but a polypropylene resin is preferred from the viewpoint of cost.

Examples of the inorganic fine powder used for the base layer include calcium carbonate, calcined clay, diatomaceous earth, talc, titanium oxide, barium sulfate, aluminum sulfate, and silica having an average particle size of 10 μm or less. In particular, those having an average particle diameter of 4 μm or less have a center line average roughness (Ra) of the surface layer of 0.4.
It is suitable for setting the thickness to 6 μm or less.

(3) Structure FIG. 1 shows a cross-sectional view of an example of the structure of the thermosensitive recording medium using the above thermosensitive recording support.

The support 1 shown in FIG. 1 comprises an outermost surface layer 2 made of a biaxially oriented polypropylene film, a base layer 3 made of a biaxially oriented film of polypropylene containing inorganic fine powder, and a back layer 4 made of a biaxially oriented polypropylene film. A thermosensitive recording medium 6 can be obtained by providing a thermosensitive recording layer 5 on the surface layer 2 and comprising a laminated biaxially stretched porous film having a three-layer structure.

In addition, the heat-sensitive recording support 1 of the present invention comprises, besides the base layer 3, the front and back layers 2 and 4, other layers such as a pulp paper or a packing layer made of polyethylene terephthalate, and a uniaxially stretched film containing polypropylene containing inorganic fine powder. A paper-like layer or a back layer made of such a material may be provided.

If the outermost surface layer 2 is too thick, the Beck smoothness is improved, but the amount of voids in the support 1 is small, the compressibility is reduced, and the color density is reduced. Conversely, the thickness of the outermost surface layer 2
When the thickness is less than 0.3 μm, the Beck smoothness of the outermost surface layer 2 is reduced due to the influence of the inorganic fine powder protruding from the surface of the base material layer 3, and the density when the pulse width during high-speed printing is narrow is low. Beck smoothness is 1,000 seconds or more, preferably 2,000 seconds or more,
The higher the Beck smoothness, the higher the color density and the higher the speed of printing. However, if the Beck smoothness is too high, sticking occurs, and conversely, the color density may decrease, so the upper limit is 8,
000 seconds. The opacity of the support 1 is 70% or more. As the opacity is higher, the contrast of the image is more noticeable, and the image is more easily recognized. There is a correlation between the density of the support 1 and the compressibility. The more microvoids, the lower the density, but the higher the compressibility. The void ratio (porosity) of the support 1 is equivalent to 18 to 55%. Here, the void ratio (v) is calculated from the density (ρo) of the film before stretching and the density (ρ) of the film after stretching by the following equation.

The smaller the density of the support 1 (JIS P8118) and the higher the compression ratio, the more excellent the contact property between the heat-sensitive recording sheet and the head, the higher the coloring density, but the compression ratio is too high. In this case, the density becomes too low, and the rigidity as the thermal recording paper is lost. On the other hand, when the compression ratio is too low, the cushioning property is lost and the color density is reduced.

[II] Production of Support for Thermosensitive Recording Such a support 1 for thermosensitive recording is, for example, a thermoplastic resin containing 0 to 5% by weight of inorganic fine powder and a thermo-resin containing 15 to 45% by weight of inorganic fine powder. Melt and knead the plastic resins with separate extruders, and then supply them to one die,
After melt lamination in a die, the laminate is co-extruded from the die, cooled to a temperature 30 to 100 ° C. lower than the melting point of the thermoplastic resin, and then reheated to a temperature close to the melting point, and gradually Or at the same time vertically (MD direction)
It is obtained by biaxial stretching 3 to 8 times in the transverse direction (TD direction) 3 to 12 times.

In addition, it is possible to suppress the heat shrinkage of the film by increasing the annealing temperature condition. If the thermal grade yield exceeds the above range, there is a disadvantage that the curl after printing is large.

[III] Production of thermosensitive recording medium (1) Compounding agent A thermosensitive recording layer 5 containing a color former and a color former is provided on the support 1 obtained as described above, and a thermosensitive recording body 6 is obtained. As the combination of the color former and the color former contained in the heat-sensitive recording layer 5, any combination may be used as long as they come into contact with each other to cause a color reaction. For example, a colorless or pale white basic dye can be used. And a combination of an inorganic or organic acidic substance, or a higher fatty metal salt such as ferric stearate and a phenol such as gallic acid.
Further, a combination of a diazonium compound with a coupler and a basic substance is applicable.

Coloring Agent Various types of colorless or light-colored basic dyes known as colorants in the heat-sensitive recording layer 5 are known. 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-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- (1-methylpyrrol-3-yl)- Triallylmethane dyes such as 6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine Thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue; 3-methyl-spiro-dinaphthopyran; 3-phenyl-spiro-dinaphthopyran; 3-phenyl-spiro-dinaphthopyran; 3-benzyl- Spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxy Benzo) spiropyran,
Spiro dyes such as 3-propyl-spiro-dibenzopyran, rhodamine-B anilinolactam, rhodamine (p
Lactam dyes such as -nitroanilino) lactam and rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-
Methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluoran, 3- (N-ethyl-p-toluidino ) -7
-Methylfluoran, 3-diethylamino-7-N-acetyl-N-methylaminofluoran, 3-diethylamino-7-N-methylaminofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino -7-N-methyl-N-benzylaminofluoran, 3-diethylamino-7-N-chloroethyl-N
-Methylaminofluoran, 3-diethylamino-7-
N-diethylaminofluoran, 3- (N-ethyl-p
-Toluidino) -6-methyl-7-phenylaminofluoran, 3- (N-cyclopentyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-diethylamino-7- (2-carbomethoxyphenylamino) fluoran, 3- (N-ethyl-N-isoamylamino)-
6-methyl-7-phenylaminofluoran, 3- (N
-Cyclohexyl-N-methylamino) -6-methyl-
7-phenylaminofluoran, 3-piperidino-6
Methyl-7-phenylaminofluoran, 3-piperidino-6-methyl-7-phenylsiminofluoran, 3-
Diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3-dibutylamino-7- (o-chlorophenylamino) fluoran, 3-pyrrolidino-6
-Methyl-7-p-butylphenylaminofluoran,
3-N-methyl-N-tetrahydrofurfurylamino-
6-methyl-7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7
And fluoran dyes such as anilinofluoran.

Coloring agents As the inorganic or organic acidic substance that forms a color upon contact with the basic dye, various substances are known.For example, activated clay, acidic clay, attapulgite, bentonite, colloidal silica, and silicic acid as inorganic acidic substances Aluminum and the like are exemplified, and organic acid substances such as 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyaminophenol, 4-tert-octylcatechol, and 2,2′-dihydroxydiamine Phenol, 2,2'-methylenebis (4-methyl-6-tert-isobutylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol),
4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone, 4,4'- Cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak 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-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butyl Salicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl)
Aromatic carboxylic acids such as salicylic acid and 3,5-di-α-methylbenzyl salicylic acid, and the above-mentioned phenolic compounds and aromatic carboxylic acids and various compounds such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel. Examples thereof include salts with valent metals.

Amount ratio The basic dye (color former) and the color former may be used in combination of two or more, if necessary. The use ratio of the basic dye and the colorant is appropriately selected according to the type of the basic dye and the colorant used, and is not particularly limited, but is generally 1 part by weight of the basic dye. On the other hand, the color former is used in an amount of 1 to 20 parts by weight, preferably about 2 to 10 parts by weight.

(2) Coating liquid A coating liquid containing these substances is generally mixed with water using a dispersion medium such as a ball mill, attritor, or sand mill.
It is prepared by uniformly or separately dispersing a dye (color former) and a color former by a pulverizer.

In the coating liquid, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion,
A binder such as a urea resin, a melamine resin, an amide resin, or an amino resin is used in an amount of 2 to 40% by weight of the total solids, preferably 5 to 40% by weight.
About 25% by weight is contained.

Other compounding agents Furthermore, various auxiliaries can be added to the coating liquid as needed, for example, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate,
Dispersants such as sodium lauryl alcohol sulfate and fatty acid metal salts, ultraviolet absorbers such as benzophenones, other defoamers, fluorescent dyes, coloring dyes, and conductive substances are appropriately added.

If necessary, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, waxes such as ester wax, stearic acid amide, methylene bisamide stearate,
Fatty acid amides such as oleic acid amide, palmitic acid amide and palm fatty acid amide; 2,2'-methylenebis (4-
Hindered phenols such as methyl-6-tert-butyphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 2- (2 ′
Ultraviolet absorbers such as -hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxybenzophenone, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1- Phenoxy-2- (4-methylphenoxy) ethane, dimethyl terephthalate, dibutyl terephthalate,
Esters such as terephthalic acid dibenzyl ester, p-benzyl-binifel, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, further various known thermoplastic substances and kaolin, Inorganic pigments such as clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, finely divided anhydrous silica, activated clay and the like can also be added.

(3) Coating In the thermosensitive recording medium 6 using the support 1 of the present invention, the method of forming the thermosensitive recording layer 5 is not particularly limited. For example, a coating liquid is applied by air knife coating, blade coating, or the like. -It is formed by a drying method or the like. The present invention is not particular limitation on 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.

In addition, an overcoat layer can be provided on the heat-sensitive recording layer 5 of the heat-sensitive recording medium 6 for the purpose of protecting the recording layer and the like. Various known techniques in the field of manufacturing the thermal recording medium 6 can be added as necessary.

[Experimental example]

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

The measurement of various physical properties in Examples and Comparative Examples is based on the following methods.

<Compression rate> The compression rate when a load of 32 kg / cm ² was applied, and was determined by the following equation.

<Centerline average roughness> Kosaka Laboratory 3D roughness measuring instrument (SE-3AK) and analyzer M
odel SPA-11 (trade name), measured with center line average roughness (R
a) was asked.

<Thermal shrinkage> It was determined from the dimensions before and after heating in an oven at 120 ° C. for 30 minutes according to the following equation.

<Manufacture of heat-sensitive recording medium (application example)> Outermost surface layer (A) side of synthetic paper (support) obtained in each of Examples and Comparative Examples (for single-layer stretched film, (B))
In addition, a water-based coating solution in which a polyethylene-based anchor material and silica for blocking prevention are mixed is applied to form an anchor coating layer, and the coating amount after drying the coating solution for the heat-sensitive recording layer prepared as described above is reduced. It was applied at 5 g / m ² and dried, and then subjected to a super calendar to obtain a thermosensitive recording medium.

<Printing performance> Using a printing device (dot density: 8 dots / mm, printing power: 0.19 w / dot), printing was performed on the surface of the heat-sensitive recording material by changing the printing pulse width, and the Macbeth density was examined. (See FIG. 2).

Table 1 shows the Macbeth density (highlight portion) when the pulse width is 0.8 millisecond.

In addition, regarding the gradation of the obtained print, the following 5 was visually observed.
It was evaluated on a scale.

5: Very good 4: Good 3: No problem in practical use 2: There is a problem in practical use 1: Bad <Print curl> A printing device (dot density = Printing was performed with a print pulse width of 1.7 msec using 8 dot / mm and an applied voltage of 0.19 w / dot), punched out into 5 cm × 5 cm, and the curl height at the four corners was evaluated in the following five steps.

 5: Very good. (No curl) 4: Good. (Almost no curl) 3: Curls slightly but does not hinder practical use.

 2: Curl is large and has practical problems.

1: Bad. Example 1 A composition in which 3% by weight of heavy calcium carbonate having an average particle size of 1.5 μm is blended with 97% by weight of polypropylene having a melt index (MI) of 4 g / 10 min (melting point: 164 to 167 ° C.) (A),
Composition (B) comprising a mixture of 85% by weight of polypropylene of 0.8 g / 10 min and 5% by weight of high-density polyethylene mixed with 10% by weight of calcium carbonate having an average particle size of 1.5 μm, MI of 4 g
And a composition (C) in which 3% by weight of calcium carbonate having an average particle size of 1.5 μm is mixed with 97% by weight of polypropylene of 10 minutes,
After melt-kneading at a temperature of 260 ° C with separate extruders, they are supplied to one co-extrusion die, melt-laminated in the die, extruded at a temperature of 250 ° C, and cooled with a cooling roll to about 6 ° C.
Cooled to a temperature of 0 ° C.

After heating this laminate to a temperature of 145 ° C,
Vertical direction (MD direction) using the peripheral speed difference of many roll groups
Stretched 5 times and heated again to a temperature of about 162 ° C.
8.5 in the transverse direction (TD direction) at a temperature of 162 ° C using a tenter
After stretching twice and annealing at a temperature of 165 ° C, 60
℃ temperature, slit ears, 3 layers (A / B /
C = 1.0 μm / 78 μm / 1.0 μm) to obtain a synthetic paper (support).

It has a density of 0.67 g / cm ³ , opacity of 82%, porosity of 30%, compressibility of 27%, whiteness of 97% and heat shrinkage of MD
2.3% in the direction and 1.5% in the TD direction.
For 500 seconds, the center line roughness (Ra) was 0.39 μm.

Example 2 A support having the physical properties shown in Table 1 was obtained in the same manner as in Example 1 except that the annealing treatment conditions were changed to 170 ° C.

Examples 3 to 7, Comparative Examples 1 and 3 A support was obtained in the same manner as in Example 1, except that the composition of each layer of the support and the porosity of the die were obtained.

Comparative Example 2 A support having the physical properties shown in Table 1 was obtained in the same manner as in Example 1 except that the annealing treatment conditions were changed to 160 ° C.

Comparative Example 4 A composition (B) containing 65% by weight of polypropylene having an MI of 0.8 g / 10 minutes, 10% by weight of high-density polyethylene, and 25% by weight of heavy calcium carbonate having an average particle size of 1.5 μm was extruded using an extruder.
Extruded into a sheet at a temperature of 250 ° C and cooled with a cooling roll for about 60
Cooled to a temperature of ° C.

After heating this sheet to a temperature of 150 ° C., it is stretched 5 times in the longitudinal direction by utilizing the peripheral speed difference between a number of roll groups, and is again stretched to about 16 ° C.
After heating to a temperature of 2 ° C, stretched 7.5 times in the transverse direction at a temperature of 162 ° C using a tenter, annealing at a temperature of 165 ° C, cooled to a temperature of 60 ° C, and slit the ears Thus, a biaxially stretched film having a thickness of 80 μm was obtained.

Comparative Example 5 A biaxially stretched film was obtained in the same manner as in Comparative Example 4, except that the composition (B) was 92% by weight of polypropylene, 5% by weight of high-density polyethylene, and 3% by weight of heavy calcium carbonate. Was.

Example 8 A synthetic paper having a three-layer structure was obtained in the same manner as in Example 1, except that talc having an average particle size of 2.0 μm was used instead of heavy calcium carbonate to obtain the composition shown in Table 1.

Example 9 A synthetic paper having a three-layer structure was obtained in the same manner as in Example 1, except that calcined clay having an average particle size of 0.8 μm was used instead of heavy calcium carbonate.

Example 10 A / B / C / fine paper / A / B / C, density = 0.85 on the front and back surfaces of a high-quality paper having a thickness of 40 μm, using an adhesive.
A support for thermal transfer recording having a structure of g / cm ³ was obtained.

A heat-sensitive transfer recording medium was prepared by providing a heat-sensitive recording layer on the layer A side, and evaluated. A print with good gradation (Macbeth density = 0.24, evaluation 5) and no curl after printing (evaluation 5) Met.

Comparative Example 6 Outermost surface layer (A ′), surface layer (A), substrate layer (B) obtained in the same manner as in Production Example 1 described in JP-A-63-222891 (Cited Document 1). And the physical properties of the support having a four-layer structure of the back layer (C) were measured and evaluated.

The support is a synthetic paper having a four-layer structure, and the number of stretching axes of each layer is A '/ A / B / A = uniaxial stretching / uniaxial stretching / biaxial stretching / uniaxial stretching.

 Table 2 shows the results.

Comparative Example 7 "Yupo FPG # 60" described in JP-A-63-193836 (Cited Document 3) (surface layer (A) / core layer (B) / back layer (C) = uniaxial stretching / two layers) In the same manner as in Example 1 of the present invention, "a support for a heat-sensitive recording medium provided with a heat-sensitive recording layer containing a color former and a color former" was prepared.
The physical properties of the obtained support were measured and evaluated in the same manner as in the case of using.

 Table 2 shows the results.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a thermal recording medium using the thermal recording support of the present invention, and FIG. 2 is a graph showing the pulse width of a head and the Macbeth density of a print printed on the heated recording medium. It is a correlation diagram. 1 ... support, 2 ... obtained surface layer, 3 ... base material layer, 4 ...
Back layer, 5... Thermosensitive recording layer, 6.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B41M 5/40

Claims (1)

(57) [Claims] 1. A surface of a porous film substrate made of a biaxially stretched film of a thermoplastic resin containing an inorganic fine powder,
A support for a thermosensitive recording medium provided with a thermosensitive recording layer containing a color former and a color former having a structure in which a surface layer comprising a thermoplastic resin biaxially stretched film having a center line average roughness of 0.6 μm or less is laminated. A support for a heat-sensitive recording medium provided with a heat-sensitive recording layer containing a color former and a color former, wherein the physical properties of the support satisfy the following conditions (a) to (c): body. (A) The thickness of the surface layer is 0.3 to 2.0 μm, and the Beck smoothness is 1,000 to 8,000 seconds. (B) The opacity of the support is 70% or more and the density is 0.91 g /
cm ^3, compressive ratio stress of 32 kg / cm ³ is 15% to 35%
That. (C) The heat shrinkage at 120 ° C. in the MD direction is 2.5% or less,
The TD direction must be 2.0% or less.