JPH04119878A - Support body for thermosensitive recording - Google Patents

Abstract

PURPOSE:To obtain clear and densified images by specifying terms of physical properties for a support body. CONSTITUTION:A support body 1 is composed of a porous film base 3 made of biaxially oriented film which is made of thermoplastic resin containing inorganic pulverized powder and a reverse layer 4 made of thermoplastic resin film having coefficient of dynamic friction of 0.3-1.2, preferably of 0.5-1.1, which is laminated to the reverse side of the base 3. The reverse layer 4 is made in thickness of 0.3-2.0mum, preferably of 0.5-1.5mum, and the support body 1 is made in physical properties that the opacity is 70% or more, preferably 80% or more, with density of 0.91g/cm<2> or below, preferably of 0.86g/cm<2> or below, and compressibility to stress of 32kg/cm<2> is 15-35%, preferably 20-30%. Thereby clear and densified images can be obtained.

Description

[Detailed description of the invention] [Background of the invention] The present invention relates to a heat-sensitive recording support that is capable of high-speed printing, has excellent resolution, is clear at high density, and does not curl due to heat even after printing.

<Prior art> In general, the thermal recording method heats a thermal recording head (hereinafter simply referred to as head) in response to an input signal, and brings the coloring agent and coloring agent on the recording image receiving sheet in contact with the head into melt contact. , is a recording method that produces a colored image, has a recording speed commensurate with the amount of information carried over the telephone line, is a primary color system that does not require development and fixing processes, and has extremely low wear on the head. It is rapidly being applied to information devices such as printers and facsimiles.

In particular, with the remarkable increase in the amount of information in recent years, there has been a shift from the early so-called low-speed machines (recording time of one A4 page in about 3 minutes) to high-speed machines (about 10 seconds) and even higher speeds. There is a need for a heat-sensitive recording material that can handle the increased speed of recording devices and provide clear images, and synthetic resin films are being used in place of conventional natural paper in some cases. It is increasing.

For example, as an example of using a resin film containing inorganic fine powder, JP-A-2-70479 discloses that the resin film has fine cavities and the content of the fine cavities is 40 to 100 cc/100 g.
A heat-sensitive recording material characterized in that a biaxially stretched resin film layer is used as a component of the support of the heat-sensitive recording layer, and the biaxially stretched resin film layer is made of the same or different material as the film. A heat-sensitive recording material further laminated with a film layer is disclosed.

<Problem to be solved by the invention> However, in recent years, with the advancement of technology, high-speed printing has become required, and resin films containing inorganic fine powder are coated on the back side in order to provide back-side slipperiness. Attempts have been made to increase the amount of inorganic fine powder blended in order to roughen the film, or by doing so, the amount of voids generated in the film due to stretching increases, the smoothness of the surface decreases, and as a result, the density of the image decreases. As a result, it was not possible to obtain clear images at high speed, with excellent resolution, and with high density.

[Summary of the invention]

Summary> In view of the above-mentioned problems, the present inventor has conducted intensive research, and as a result, has developed a material that has cushioning properties and has a reduced shrinkage rate against heat.
The coefficient of dynamic friction is 0 on the back side of the axially stretched porous film base material.
．． 3 to 1.2 laminated thermoplastic resin thin film as the back layer has good slipperiness on the back surface, enables high-speed printing, and has excellent resolution, with high density and clarity even with minute printing energy. Furthermore, the present invention was completed based on the knowledge that it is possible to obtain a heat-sensitive recording support that does not curl due to heat even after printing.

That is, in the heat-sensitive recording support of the present invention, the back surface of a porous film base material made of a biaxially stretched film of a thermoplastic resin containing fine inorganic powder has a dynamic friction coefficient of 0. 3-1
．． 2. A heat-sensitive recording support having a structure in which a back layer made of a thermoplastic resin film is laminated, characterized in that the physical properties of the support satisfy the following conditions (a) to (b). That is.

(a) The back layer has a thickness of 0.3 to 2. Must be 0 μm.

(b) The opacity of the support is 70% or more and the density is 0.
．． 91 g/cJIi or less, the compression ratio under stress of 32 kg/cm2 is 15 to 35%.

Effects> A thermal recording material using the thermal recording support of the present invention is capable of high-speed printing, has excellent surface smoothness, and has excellent cushioning properties due to the large number of microvoids contained in the support. This improves the adhesion between the print head and the heat-sensitive recording material, resulting in a transferred image with rich gradation.

Furthermore, since the heat shrinkage rate of the support is low, it is possible to obtain a heat-sensitive recording material that does not curl even after printing.

[Detailed description of the invention]

[1] Heat-sensitive recording support (1) Structure The heat-sensitive recording support of the present invention has a kinetic friction coefficient on the back side of a porous film base made of a biaxially stretched film of a thermoplastic resin containing fine inorganic powder. 0.3-1.2, preferably 0. It has a structure in which a back layer made of a thermoplastic resin film of 5 to 1.1 is laminated, and its physical properties are (a) the thickness of the back layer is 0. 3-2. 0μm
1 Preferably 0.5 to 1.5 μm.

(b) The opacity of the support is 70% or more, preferably 80% or more, the density is 0.91 g/cm or less, preferably 0.86 g/ci or less, and the compression ratio under a stress of 32 kg/c♂ is 15 to 15. 359o, preferably 20-30%.

This shows that.

Specifically, such a support uses a polyolefin biaxially stretched film containing 15 to 45% by weight of inorganic fine powder in the base layer, and has a dynamic friction coefficient (J) on the outermost back side of the base layer. - TAPPI Paper Pulp Test Method - Value measured by o30 It is a thermoplastic resin film with a multilayer structure that has a transparency of 70% or more, a whiteness of 85% or more according to JIS-P8123, and a density of 0.91g/cut or less.
Center line average roughness (Ra) of 3 to 2.0 μm is JISB-
The value measured with 0 [iol is 0.6 μm or less, and JI
Bekk smoothness measured with SP-8119 is 1,000 ~
It is preferable to have a surface layer of 8.000 seconds, and the compressibility of the support (the amount of compression when a load of 32 cg/c is applied) is 15 to 35%.

In order to make the dynamic friction coefficient of the back layer 0.3 to 1.2, either increase the content of inorganic fine powder or increase the thickness of the back layer by 2.0 μm.
If it is too thick than m, the front and back balance will be lost and curling will occur. Conversely, if the thickness of the back layer is less than 0.3 μm, the coefficient of dynamic friction cannot be made sufficiently small, so it is important that the thickness of the back layer is 0.3 to 2.0 μm. . For example, in the case of heavy calcium carbonate having an average particle size of 1.5 μm, the content of the inorganic fine powder must be 25% by weight or more.

If the dynamic friction coefficient is smaller than the above range, the slipperiness increases, and if it is larger, the slipperiness decreases, both of which cause the problem that high-speed printing is not possible.

Furthermore, if the compression ratio is smaller than the above range, the cushioning properties will be lost and the color density as a thermosensitive recording paper will be lowered, and if it is larger, the density will be too low and the paper will not have stiffness.

(2) Constituent Materials Polyolefin is usually used as the thermoplastic resin for the base layer, back layer, and surface layer. Such polyolefins include polyethylene, polypropylene, ethylene/propylene copolymer, and ethylene/propylene copolymer.
Vinyl acetate copolymer, propylene/butene-1 copolymer, poly(4-methylpentene-1), polystyrene, etc. can be used. Of course, other thermoplastic resins such as polyamide, polyethylene terephthalate, and polybutylene phthalate can also be used, but polypropylene resins are preferred from the cost standpoint.

The inorganic fine powder used for the base layer and back layer includes calcium carbonate, calcined clay, diatomaceous earth, talc, titanium oxide, barium sulfate, aluminum sulfate, silica, etc. with an average particle size of 10 μm or less. Illustrated. In particular, it is preferable to have an average particle diameter of 4 μm or less, or to set the centerline average roughness (Ra) of the surface layer to a range of 0.6 μm or less.

(3) Structure A cross-sectional view of an example of the structure of a heat-sensitive recording material using the above-mentioned support for heat-sensitive recording is shown in FIG.

The support 1 shown in FIG. 1 includes an outermost surface layer 2 made of a biaxially oriented polypropylene film, a base layer 3 made of a biaxially oriented porous film of polypropylene containing fine inorganic powder, and a back surface made of a biaxially oriented polypropylene film. It consists of a laminated biaxially stretched film with a three-layer structure consisting of layer 4, and a heat-sensitive recording layer 5 can be provided on the surface layer 2 to form a heat-sensitive recording body 6.

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

If the thickness of the outermost surface layer 2 is too thick, the Beck smoothness will improve, but the amount of voids in the support 1 will be small, and the compressibility will decrease.
Color density decreases. Conversely, the thickness of the outermost surface layer 2 is set to 0.
If it is less than 3 μm, the Bekk smoothness of the outermost surface layer 2 will decrease due to the influence of the inorganic fine powder protruding from the surface of the base material layer 3, and the density will be low when the pulse width is narrow during high-speed printing. The Bekk smoothness is 1,000 seconds or more, preferably 2,000 seconds or more, and the higher the Bekk smoothness, the higher the color density and the higher the printing speed. However, if the Bekk smoothness is too high, sticking may occur and the color density may decrease, so the upper limit is set to 8,000 seconds. The opacity of support 1 is 70
% or higher, the higher the opacity, the more the contrast of the image stands out and the more visually appealing it becomes. There is a correlation between the density and compressibility of the support 1; 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 of the film before stretching (ρO) and the density of the film after stretching (ρ) using the following formula.

ρ0 The smaller the density (JIS P8118) of the support 1 and the higher the compression ratio, the better the contact between the heat-sensitive recording sheet and the head, and the higher the color density.

[II) Production of heat-sensitive recording support Such a heat-sensitive recording support 1 is made of, for example, a thermoplastic resin containing 0 to 5 weight 29.5 weight of inorganic fine powder, and a thermoplastic resin containing 15 to 45 weight 9 (weight 9.5 weight) of inorganic fine powder. The thermoplastic resins containing l are each melt-kneaded in separate extruders, then supplied to one die, and melt-laminated within the die.The laminate is coextruded from the die, and the laminate is made into a thermoplastic resin. After cooling to a temperature 30 to 100 °C lower than the melting point of the resin, it is reheated again to a temperature near the melting point, and is heated sequentially or simultaneously in the longitudinal direction (3 to 8 times in the MD force direction) and in the transverse direction (in the TD force direction). 3
Obtained by biaxial stretching up to 12 times.

Furthermore, it is possible to suppress the thermal shrinkage rate of the film by increasing the annealing treatment temperature conditions.

The heat shrinkage rate of the support is preferably 2.5% or less in the MD force direction and 2.0% or less in the TD force direction, and preferably 2.5% or less in the MD force direction.
More preferably, it is 0% or less, and 1.5% in the TD force direction. If the heat shrinkage rate exceeds this range, curling tends to occur after printing.

[III] Production of thermosensitive recording material (1) Ingredients A thermosensitive recording layer 5 containing a coloring agent and a coloring agent is provided on the support 1 obtained as described above to form a thermosensitive recording material 6. Regarding the combination of the coloring agent and the coloring agent contained in the heat-sensitive recording layer 5, any combination that causes a coloring reaction when the two come into contact can be used. For example, a colorless or pale basic dye and a coloring agent can be used. Examples include combinations with inorganic or organic acidic substances, higher fatty acid metal salts such as ferric stearate and phenols such as gallic acid, and combinations of diazonium compounds with couplers and basic substances. Applicable.

Color former Various types of colorless or light-colored basic dyes are known to be blended as a color former in the heat-sensitive recording layer 5, such as 3,3-bis(p-dimethylaminophenyl)-6-
Dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)3-(1,2-dimethylindole-
3-yl)phthalide, 3-(p-dimethylaminophenyl)3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylinto-3-
yl)-5-dimethylaminophthalide, 3,3-bis(
1,2-dimethylindol-3yl)-6-dimethylaminophthalide, 3. B-bis(9-ethylcarbazol-3-yl)6-dimethylaminophthalide, 3,3-
Bis(2phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-
Triallylmethane dyes such as 3-(1-methylpyrrol-3-yl)6-dimethylaminophthalide, 4,4'
-Bis-dimethylaminohenzhydrylbenzyl ether, N-halophenylleucoolamine, N-2,4,
Diphenylmethane dyes such as 5-trichlorophenylleucoauramine, hendiylleucomethylene blue, p
Thiazine dyes such as nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-bennruthpirone naphthopyran, 3-methyl-naphtho-(6 '-Methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, and other spiro-based dyes;
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-cynotylfluorane, 3-(N-ethyl-p-toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane ,3
-diethylamino-7-N methylaminofluorane, 3
-diethylamino 7-cyhenruaminofluorane, 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)fluoran, 3-diethylamino-6
Methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-(N-ethyl-Nisoamylamino)-6
-Methyl-7-phenylaminofluorane, 3-(N-
Cyclohexyl N-methylamino)-6-methyl-7-
Phenylaminofluorane, 3-piperisino-6-methyl-7-phenylaminofluorane, 3-piperidino-
6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-quinricinofluorane,
3-diethylamino-7 (0-chlorophenylamino)
Fluoran, 3-butylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl 7-p-butylphenylaminofluorane, 3N-methyl-N-tetrahydrofurfurylamino 6-methyl-
Examples include fluoran dyes such as 7-anilinofluorane and 3-N ethyl-N-tetrahydrofurfurylamino 6-methyl-7-anilinofluorane.

Various inorganic or organic acidic substances that develop color upon contact with the basic dye are known. Examples of inorganic acidic substances include activated clay, acid clay, attapulgite, bentonite, colloidal arunica, Examples include aluminum silicate, and 4-tert- as an organic acidic substance.
Butylphenol, 4-hydroxydiphenoxide, α
-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tart-octylcatechol, 2
, 2'-dihydroxydiphenol, 2,2'-methylenebis(4-methyl-6-tert-isobutylphenol), 4,4'-isopropylidenebis(2-
tert-butylphenol), 4.4'-5e
e-butylidene diphenol, 4-phenylphenol, 4,4'-isopropylidene diphenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone, 4,4' cyclohexylidene diphenol, Hensyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin,
Phenolic compounds such as phenol polymers, benzoic acid, p-tertbutylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-see-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-methylhensyl)salicylic acid, 3,5-di-te
rt-butylsalicylic acid, 3phenyl-5-(α, α-
Aromatic carboxylic acids such as dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and the above phenolic compounds and aromatic carboxylic acids, such as zinc, magnesium, aluminum, calcium, titanium, manganese, soot, and nickel. Examples include salts with polyvalent metals such as .

Amount Ratio Note that two or more of the basic dyes (color formers) and color formers may be used in combination, if necessary. The ratio of the basic dye and coloring agent to be used is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited.In general, 1 part by weight of the basic dye is used. The coloring agent is used in an amount of 1 to 20 parts by weight, preferably 2 to 10 parts by weight.

(2> Coating liquid Coating liquids containing these substances generally use water as a dispersion medium,
It is prepared by dispersing the dye (coloring agent) and coloring agent uniformly or separately using a stirring/pulverizing machine such as a whole mill, attritor, or Santo mill.

The coating liquid contains starches, hydroquine ethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride. Binders such as acid copolymer salts, ethylene/acrylic acid copolymer salts, styrene/butadiene copolymer emulsions, urea resins, melamine resins, amide resins, amino resins, etc. are added in an amount of 2 to 40% by weight of the total solid content, preferably 5～
The content should be about 25% by weight.

Other compounding agents Furthermore, various auxiliary agents can be added to the coating liquid as necessary, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate ester. , a dispersant such as a fatty acid metal salt, an ultraviolet absorber such as hensifenone, an antifoaming agent, a fluorescent dye, a colored dye, a conductive substance, etc. are added as appropriate.

In addition, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, stearic acid amide, stearic acid methylene bisamide, oleic acid amide, balmitic acid amide, coconut fatty acid amide, etc. Fatty acid amides, 2,2'-methylenebis(
4-methyl 6-tert-butylphenol), 1,
1,3 Tris(2-methyl-4-hydroxy-5-te
Hindered phenols such as rtbutylphenyl)butane, UV absorbers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-hydroxy4-benzyloxybenzophenone, 1,2-di(3 -methylphenoxy)ethane, 1,2-diphenoxyethane, 1-phenoxy-2-(4-methylphenoxy)ethane, dimethyl terephthalate, butyl terephthalate, dibenzyl terephthalate, p-hensyl-biphenyl , 1,4-jethoxynaphthalene, 1,4-jethoxynaphthalene, esters such as 1-hydroxynaphthoic acid phenyl ester, and various known thermoplastic substances, kaolin, clay, talc, calcium carbonate, calcined resin. , titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay may also be added.

(3) Coating In the heat-sensitive recording material 6 using the support 1 of the present invention, the method of forming the heat-sensitive recording layer 5 is not particularly limited. It is formed by a method such as drying. Furthermore, the amount of coating liquid to be applied is not particularly limited, and is usually 2 to 12 g/rr in terms of dry weight. ,
Preferably, it is prepared in a range of about 3 to 10 g/rd.

Note that an overcoat layer may be provided on the heat-sensitive recording layer 5 of the heat-sensitive recording body 6 for the purpose of protecting the recording layer.
Various known techniques in the field of manufacturing the thermosensitive recording material 6 can be added as needed, such as applying an adhesive treatment to the back surface of the thermosensitive recording material 6 and processing it into an adhesive label.

[Example of practical experience]

EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

Note that various physical properties in Examples and Comparative Examples were measured by the following methods.

Compression rate> The amount of compression when a load of 32 kg/c♂ was applied, and was determined by the following formula.

Thickness of test piece (μm) <Center line average roughness> Measured using Koita Institute three-dimensional roughness measuring machine (SE-3AK) and analyzer Model SP^-11 (trade name). The value (Ra) was calculated.

Heat Shrinkage Rate> It was determined by the following formula from the dimensions before and after heating in an oven at 120°C for 30 minutes.

Production of heat-sensitive recording material (application example)> On the outermost surface layer (A) side [(B) in the case of a single-layer stretched film] of the synthetic paper (support) obtained in each example and comparative example,
An anchor coat layer was provided by applying a water-based coating solution containing a mixture of polyethylene anchor material and silica for blocking prevention, and the coating amount after drying of the coating solution for the heat-sensitive recording layer prepared as described above was 5 g/ rr? After coating and drying, a heat-sensitive recording material was prepared by applying a super calender.

High-speed printing performance> The surface of this heat-sensitive recording medium was coated with a printing device manufactured by Daikin Electric Co., Ltd. (dot density - 8 dat/mm, applied voltage - 0, 19 W).
/dat), 100 seconds each for 5 seconds, 30 seconds, and 60 seconds.
The paper was printed and evaluated based on the number of misprints.

<Printing performance> A printing device manufactured by Daikane Electric Co., Ltd. (dot density 8 dots/mm, printing power 0.19w/
Macbeth density was examined by printing with different printing pulse widths (see Figure 2).

Table 1 shows the Macbeth density (highlighted part) when the pulse width is 0.8 milliseconds.

In addition, the gradation of the obtained print was visually evaluated in the following five grades.

5: Very good 4, Good 3: No practical problem 2, Practical problem 1: Bad print curl 8 dat/mm, applied voltage -0.19 w/d
at) with a printing pulse width of -1.7 m5ec,
Punch out to 5cm x 5cm, about the cull height of the four corners,
Evaluation was made on the following five levels.

5: Very good. (without curl) 4. Good. (hardly curled) 3. There may be some curling, but there is no practical problem.

2: The curl is large and there is a problem in practical use.

1: Defective. (No problem at all) Example 1 97% by weight of polypropylene (melting point 164-167°C) with a melt index (MI) of 4 g/10 minutes was blended with 3% by weight of heavy calcium carbonate with an average particle size of 1.5 μm. Composition (A), a composition (B) in which 10% by weight of calcium carbonate with an average particle size of 1.5 μm was blended with a mixture of 85% by weight of polypropylene with an MI of 0.8 g/10 min and 5% by weight of high-density polyethylene; ), Ml is 4 g/l 0
55% by weight of polypropylene with an average particle size of 1.5μm
A composition (C) containing 45% by weight of calcium carbonate was melt-kneaded in separate extruders at a temperature of 260°C, and then supplied to a co-extrusion die, and melt-laminated within the die. This was extruded at a temperature of 250°C and cooled to a temperature of about 60°C using a cooling roll.

After heating this laminate to a temperature of 145°C,
Vertical direction (MD direction) by utilizing the difference in circumferential speed of a large number of roll groups
After stretching the film 5 times in the transverse direction (TD force direction) using a tenter and heating it again to a temperature of about 162°C, the film was stretched 8.5 times in the transverse direction (TD force direction) at a temperature of 162°C using a tenter, and annealed at a temperature of 165°C. , cooled to a temperature of 60°C, and slit the ears to form 3 layers (A/B/C-1.0 μm/78 μm/1.0
A synthetic paper (support) having a structure of .mu.m) was obtained.

The density of this thing is 0.67g/ci and the opacity is 92%
The porosity was 30%, the compressibility was 27%, and the physical properties of the back surface were that the coefficient of dynamic friction was 0.80.

Examples 2 to 6, Comparative Examples 1 and 2 A support having the physical properties shown in Table 1 was obtained in the same manner as in Example 1 except that the composition of each layer of the support and the degree of aperture of the die were changed.

Comparative Example 3 Ml: 0.8 g/l, 0 minute polypropylene 45 weight ff
19ci, 10% by weight of high-density polyethylene, and 45% by weight of heavy calcium carbonate with an average particle size of 1.5 μm (B) was extruded into a sheet at a temperature of 250°C using an extruder, and then extruded with a cooling roll. Cooled to a temperature of approximately 60°C.

After heating this sheet to a temperature of 150°C, it was stretched 5 times in the machine direction (M Stretched 7.5 times in the transverse direction (TD) at a temperature of 162°C, annealed at a temperature of 165°C, and then stretched at 60°C.
The film was cooled to a temperature of , and the edges were slit to obtain a biaxially stretched film with a thickness of 80 μm.

Comparative Example 4 A biaxially stretched film was obtained in the same manner as in Comparative Example 3 except that composition (B) containing 85% by weight of polypropylene, 5% by weight of high-density polyethylene and 10% by weight of heavy calcium carbonate was used. Ta.

Example 7 A three-layer synthetic paper was obtained in the same manner as in Example 1, except that talc with an average particle size of 2.0 μm was used instead of heavy calcium carbonate.

Example 8 A synthetic paper with a three-layer structure was obtained in the same manner as in Example 1, except that baked clay having an average particle size of 0.8 μm was used instead of heavy calcium carbonate.

Example 9 The support obtained in Example 1 was placed on the front and back sides of a high-quality paper with a wall thickness of 40 μm, and the printing surface was A55. /A/B/C1 density -0,
A heat-sensitive recording support having a structure of 85 g/cIj was obtained.

A heat-sensitive recording material was prepared by providing a heat-sensitive recording layer on the A-layer side, and evaluated.
There were no problems with printing performance (rating 5), and no curling after printing (rating 5).

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a heat-sensitive recording material using the heat-sensitive recording support of the present invention, and FIG. It is a correlation diagram of concentration. DESCRIPTION OF SYMBOLS 1... Support body, 2... Surface layer, 3... Base material layer, 4
... Back layer, 5... Heat-sensitive recording layer, 6... Heat-sensitive recording body.

Claims (1)

[Claims] 1. A thermoplastic resin film having a dynamic friction coefficient of 0.3 to 1.2 is placed on the back side of a porous film base material made of a biaxially stretched film of a thermoplastic resin containing fine inorganic powder. 1. A heat-sensitive recording support having a structure in which a back layer is laminated, characterized in that the physical properties of the support satisfy the following conditions (a) to (b). (a) The thickness of the back layer is 0.3 to 2.0 μm. (b) The opacity of the support is 70% or more and the density is 0.9.
The compression ratio under stress of 1 g/cm^2 or less and 32 kg/cm^2 is 15 to 35%. 2. Wall thickness is 0.3 to 2.0 μm and center line average roughness is 0.
．． 2. The thermal recording support according to claim 1, further comprising a thermoplastic resin film having a diameter of 6 μm or less and a Bekk smoothness of 1,000 to 8,000 seconds laminated on the surface of the support. 3. The heat-sensitive recording support according to claim 1 or 2, wherein the heat shrinkage rate at 120°C of the support is 2.5% or less in the MD direction and 2.0% or less in the TD direction.