JPH0995056A - Thermal sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal sheet with excellent dynamic and static thermal sensitivity and appropriate rigidity, pliability and strength and further, high handling efficiency, free from the formation of a color in the texture under pressure by making a support of a synthetic resin sheet with specific density. SOLUTION: This thermal sheet is composed of a thermally color forming layer formed on a support. The support is formed of a synthetic resin sheet with, for example, a density containing a cavity of 0.2-0.5g/cm<3> in the support itself. If the density is higher than 0.5g/cm<3> , the thermal sensitivity is lowered, and the tendency of color formation in the texture under pressure is increased. On the other hand, if the density is not higher than 0.2g/cm<3> , the strength of the support is low and it is difficult to form the thermally color forming layer by coating. The synthetic resin sheet containing a cavity in the support is obtained by a method for mixing a synthetic resin with a foaming material generating a gas by heat and generating foam by extrusion, or mixing the synthetic resin with a non-compatible material against this resin and stretch the synthetic resin sheet obtained by fusion and extrusion into a lengthwise and a crosswise direction.

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 sheet, and more particularly to a heat-sensitive recording sheet excellent in heat sensitivity and background color development due to pressure.

[0002]

2. Description of the Related Art Conventionally, a thermosensitive recording sheet utilizing a thermochromic reaction between an electron-donating color-forming compound called a color former and an electron-accepting compound called a color developer is widely known, and a computer and a word processor are known. Printers, facsimiles, printers for scientific measuring instruments, printers for CRT medical measuring instruments, etc., and recently are used for automatic ticket vending machines and also widely for label production.

Means for improving the thermal sensitivity of such a heat-sensitive sheet include improving the smoothness of the surface of the heat-sensitive layer,
Alternatively, there is a method of increasing the density of the color-forming component by reducing the content of a component that does not participate in the color-forming reaction, such as a filler or a binder, in the color-forming layer. However, although this method improves the efficiency of color development, that is, the heat sensitivity, it causes a problem of color development of the background due to pressure.

Further, as an attempt to effectively utilize the heat from the thermal head in order to improve the apparent thermal sensitivity of the heat-sensitive sheet, for example, Japanese Patent Application Laid-Open No. Sho 6-1994, which is related to our application.
In JP-A-3-299976, a density of 0.9 g / cm ³ or less, for example, 0.77 /
It has been disclosed that a synthetic paper of cm ^{3 is used} as a support, and it is disclosed in JP-A-5-58028 and JP-A-5-58.
In order to obtain a high-sensitivity heat-sensitive recording material, Japanese Patent Publication No. 029 discloses that a polypropylene support having a density of 0.6 to 0.8 g / cm ³ and a recording layer provided with a Beck smoothness of 800 seconds or more is used. Also, it is disclosed that a white polyester film containing microvoids is used as a support. Further, in Japanese Patent Laid-Open No. 2-302887,
0.5 to 0.8 g on the base paper layer in the thermal recording sheet
It is disclosed that a plastic film having a thickness of / cm ³ is laminated to improve head adhesion and prevent curling.

However, these methods do not provide sufficiently satisfactory thermal sensitivity, and the color development of the background due to pressure is not sufficiently reduced, and the rigidity, flexibility, strength, and tactile feel are different from those of the paper textured heat sheet. , At least our satisfying heat sensitive sheet has never been offered.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to improve the above problems in the prior art, to have both excellent dynamic and static thermal sensitivities as thermal sensitivities, and to develop the background color by pressure. The present invention provides a heat-sensitive sheet which has a low level of rigidity, moderate rigidity, flexibility and strength and is excellent in handleability.

[0007]

[Means for Solving the Problems] As a result of continuing intensive studies to improve the above problems, as a result of using a synthetic resin sheet having a specific density, the heat from the thermal head can be more effectively utilized, In addition, the support absorbs the applied pressure, which makes it possible to reduce the color development of the background, and also has excellent thermal sensitivity, and the background color is less developed due to pressure, and it has moderate strength, etc. When applying layers,
It was found that a heat-sensitive sheet excellent in handleability at the time of printing the heat-sensitive sheet can be obtained, and the present invention has been accomplished. Therefore, the object of the present invention is (1) "a thermosensitive sheet having a thermosensitive coloring layer provided on a support, wherein the support is a synthetic resin sheet having a density of 0.2 to 0.5 g / cm ^3. "Heat-sensitive sheet", (2) "The heat-sensitive sheet according to (1) above, characterized in that the support is a cavity-containing material", and (3) "The material of the support made of synthetic resin is polystyrene. The above (1) is characterized in that
Or the heat-sensitive sheet described in (2) above.

Hereinafter, the present invention will be described in detail. As mentioned above, the support used in the present invention has a density of 0.2 to 0.5 g /
is a synthetic resin sheet cm ^3, density of 0.5 g / c
It was found that when it exceeds m ³ , the thermal sensitivity is lowered and the color development of the background due to the pressure is deteriorated. Density is 0.2g / cm ³
If it is less than the above range, the strength of the support becomes weak and it becomes difficult to apply the heat-sensitive layer.

The heat-sensitive sheet of the present invention can be obtained, for example, by using a synthetic resin sheet having a cavity in the support. For example, a synthetic resin and a substance incompatible with the resin, such as calcium carbonate or silica,
Mixing an inorganic substance, melting, a synthetic resin sheet obtained by extrusion, a method of obtaining by stretching in the longitudinal and transverse directions, or synthetic resin, by heating, nitrogen, carbon dioxide, ammonia, oxygen, water vapor, or hydrocarbons And the like, and a method of obtaining by foaming by extruding can be mentioned. The latter method is more preferable for obtaining the heat-sensitive sheet support of the present invention, but it is needless to say that the support obtained by the latter method is not particularly limited thereto. Further, it is possible to use a sheet in which a synthetic resin sheet having these cavities and a synthetic resin sheet having no cavities are bonded together.

The thickness of the support of the present invention is not particularly limited, but is 50 to 1000 μm, preferably 80.
Approximately 500 μm is desirable. Examples of the synthetic resin material of the support used in the present invention include polyethylene, polypropylene, polystyrene, polyester, and the like, and polystyrene is preferable from the viewpoint of good processability of cavitation processing and cost. As polystyrene, in addition to styrene homopolymer, styrene copolymer containing styrene as a main component, for example, impact-resistant polystyrene, acrylonitrile-
Examples thereof include styrene (AS) resin and acrylonitrile-butadiene-styrene (ABS) resin.

The thermosensitive sheet of the present invention can be obtained by providing a thermosensitive coloring layer on these supports. The heat-coloring composition used as such a heat-sensitive color-developing layer is composed of a general color-developing agent and a color-developing agent that causes the color-developing agent to develop a color when heated. A colorless or light-colored leuco dye has been conventionally used as a developer, and an organic acid or a phenolic substance has been used. The heat-sensitive layer material obtained by combining the color-developing agent and the color-developing agent is particularly clear in the color tone of the obtained image, and
It has the advantages that the whiteness of the background is high and the durability of the image is excellent.

The heat-sensitive coloring layer in the heat-sensitive sheet of the present invention contains a leuco dye and a developer as main components, and the leuco dye may be used alone or in combination of two or more. What is applied to this type of heat-sensitive sheet is arbitrarily applied, for example, triphenylmethane-based, triallylmethane-based, fluorane-based, phenothiazine-based, thioferolane-based, xanthene-based, indolylphthalyl-based, spiropyran , Leuco compounds such as azaphthalide type, chromenopyrazole type, methine type, rhodamine anilinolactam type, rhodamine lactam type, quinazoline type, diazaxanthene type and bislactone type are preferably used. Examples of such compounds include those shown below. 3,3-bis (p
-Dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3-bis (p-dimethylaminophenyl)-
6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-
Bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3- (N-
Methyl-N-isoamylamino) -6-methyl-7-anilinofluorane, 3- (N-methyl-N-isobutylamino) -6-methyl-7-anilinofluorane, 3-
(Np-tolyl-N-ethylamino) -6-methyl-
7-anilinofluorane, 3- (N-methyl-N-amylamino) -6-methyl-7-anilinofluorane, 3
-(N, N-di-n-amylamino) -6-methyl-7
-Anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3- (N-methyl-N-isopropylamino) -6
-Methyl-7-anilinofluorane, 3- (N-methyl-N-tetrahydrofurfurylamino) -6-methyl-
7-anilinofluorane, 3-diethylamino-7,8
-Benzfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-pyrrolidino-6-methyl-7-ani Rinofluorane, 3-diethylamino-6-methyl-7- (m
-Trichloroanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane,
3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-
(2 ', 4'-dimethylanilino) fluorane, 3-
(N, N-diethylamino) -5-methyl-7- (N,
N-dibenzylamino) fluorane, benzoylleuco methylene bull-, 6'-chloro-8'-methoxybenzoindolinospiropyran, 6'-bromo-8'-methoxybenzoindolinospiropyran, 3- (2'-hydroxy- 4'-dimethylaminophenyl) -3- (2'-
Methoxy-5'-chlorophenyl) phthalide, 3- (2
′ -Hydroxy-4′-dimethylaminophenyl) -3
-(2'-methoxy-5'-nitrophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl) phthalide, 3- (2 ′ -Methoxy-4′-dimethylaminophenyl) -3- (2′-hydroxy-4′-chloro-5′-methylphenyl) phthalide, 3-morpholino-7- (N-propyltrifluoromethylanilino)
Fluorane, 3-pyrrodino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-
7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyridino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5
-Chloro-7- (α-phenylethylamino) fluoran, 3- (N-ethyl-Np-toluidino) -7-
(Α-phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylethyl) fluoran, 3-diethylamino-5-methyl-7
-(Α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinoaminofluoran, 2-chloro-3- (N-methyltoluidino) -7- (p-N-
Butylanilino) fluorane, 3,6-bis (dimethylamino) fluorene spiro (9,3 ′)-6′-dimethylaminophthalide, 3- (N-ethyl-N-cyclohexylamino) -5,6-benzo-7 -Α-naphthylamino-4'-bromofluorane, 3-diethylamino-6
-Chloro-7-anilinofluorane, 3- (N-ethyl-N-2-ethoxypropylamino) -6-methyl-7
-Anilinofluorane, 3- (N-ethyl-N-tetrafurfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'- Benzofluorane, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide, 3
-(P-Dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-phenylethylene-2-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (1-p-
Dimethylaminophenyl-1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3-
(4'-Dimethylamino-2'-methoxy) -3-
(1 "-p-dimethylaminophenyl-1" -p-chlorophenyl-1 ", 3" -butadiene-4 "-yl) benzophthalide, 3- (4'-dimethylamino-2'-benzyloxy) -3- (1 "-p-dimethylaminophenyl-1" -phenyl-1 ", 3" -butadiene-4 "
-Yl) benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3 '(6'-
Dimethylamino) phthalide, 3,3-bis {2- (p-
Dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl} -4,5,6,7-tetrachlorophthalide, 3-bis {1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl } -5,6-Dichloro-4,7
-Dibromophthalide, bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane, bis (p-dimethylaminostyryl) -1-p-tolylsulfonylmethane and the like.

In the present invention, various electron-accepting compounds, such as phenolic compounds, are used as color developers.
A thiophenol compound, a thiourea derivative, an organic acid and a metal salt thereof can be used, and specific examples thereof include those shown below, but the invention is not limited thereto. 4,4'-isopropylidenedipheno-
4,4'-isopropylidenebis-o-methylphenol, 4,4'-sec-butylidenebisphenol
4,4'-isopropylidene bis (2-tert-
Butylphenol), zinc p-nitrobenzoate, 1,
3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,
2- (3,4′-dihydroxyphenyl) propane, bis (4-hydroxy-3-methylphenyl) sulfide, 4- (β- (p-methoxyphenoxy) ethoxy)
Salicylic acid, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-
Hydroxyphenylthio) -3-oxapentane, phthalic acid monobenzyl ester monocalcium salt, 4,4 '
-Cyclohexylidene diphenol, 4,4'-isopropylidene bis (2-chlorophenol), 2,2'-
Methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-
Butyl-2-methylphenol) 1,1,3-tris (2-methyl-4-hydroxy-5)
-Cyclohexylphenyl) butane, 4,4'-thiobis (6-tert-butyl-2-methylphenol),
4,4'-diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4 '
-Diphenol sulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) propane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, saltylanilide, methyl bis (4-hydroxyphenyl) acetate, benzyl bis (4-hydroxyphenyl) acetate, 1,3- Bis (4-hydroxyphenyl) benzene, 1,4-bis (4-hydroxyphenyl) benzene, 2,4′-diphenol sulfone, 2,2′-diallyl-4,4′-hydroxyphenyl sulfone, 3,
4-dihydroxy-4'-methyldiphenyl sulfone,
1-Acetyloxy-2-naphthoate zinc, 2-acetyloxy-3-naphthoate zinc, 2-acetyloxy-
Zinc 1-naphthoate, α, α-bis (4-hydroxyphenyl) α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, 4,4′- Thiobis (2-methylphenol), 4,4'-thiobis (2-chlorophenol) and the like.

Further, in the heat-sensitive color forming layer of the heat-sensitive sheet of the present invention, various thermoplastic substances can be used in combination as a sensitivity improver, and specific examples thereof include the followings. It's not limited. Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, p -Benzylbiphenyl, ta-phenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, phenyl 1-hydroxy-2-naphthoate, 1
-Methyl hydroxy-2-naphthoate, diphenyl carbonate
Bonate, gray-collar carbonate, dibenzyl terephthalate, dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-
Dibenzyloxynaphthalene, 1,2-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane,
1,2-bis (4-methylphenoxy) ethane, 1,4
-Diphenoxybutane, 1,4-diphenoxy-2-butene, 1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4-diphenylthiobutane, 1,4-diphenylthio-2 -Butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-
Vinyloxyethoxy) biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane,
Dibenzyl disulfide, 1,1-diphenylethano-
, 1,1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis (4-methoxyphenoxy)
Propane, 1,5-bis (4-methoxyphenoxy)-
3-oxapentane, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) oxalate and the like.

In the case of obtaining the heat-sensitive sheet of the present invention, as a heat-sensitive color developing layer component, a leuco dye, a developer and, if necessary, additional components commonly used in this type of heat-sensitive sheet, such as fillers, surfactants and lubricants. , A color development inhibitor and the like can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, kaolin, talc, other inorganic fine powder such as surface-treated calcium or silica, Urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin, vinylidene chloride resin, and other organic fine powders can be mentioned. As the lubricant, higher fatty acid and its metal salt, higher fatty acid amide,
Examples include higher fatty acid esters, various types of animal, vegetable, mineral or petroleum waxes.

In the heat-sensitive color-developing layer of the heat-sensitive sheet of the present invention, polyvinyl alcohol, starch and its derivatives, methoxycellulose, and hydroxyethylcellulose are used as binders such as leuco dyes and developers. -, Carboxymethylcellulose, methylcellulose, ethylcellulose derivatives such as ethylcellulose, polyacrylic acid
Da, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymerization, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, poly Acrylamide, sodium alginate, gelatin, casein and the like are used.

By providing an intermediate layer containing a binder of a synthetic resin such as styrene or a copolymer of styrene between the support and the thermosensitive color forming layer, the thermosensitive color developing layer can be fixed to the support with good heat sensitivity. A sheet is obtained. The amount used is 20% or more, preferably 30% to 70% by weight of the intermediate layer. An emulsion of a styrene polymer, a styrene-acrylic acid ester copolymer, a styrene-methacrylic acid ester copolymer, a styrene-butadiene copolymer or the like is preferable. In addition, these polymers and / or copolymers include, as an aqueous emulsion resin, for example, polyvinyl acetate, polyurethane, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, acrylic acid ester / vinyl acetate copolymer, Those selected from ethylene / vinyl acetate copolymers and the like can be used in combination.

In the intermediate layer between the support and the thermosensitive color developing layer in the present invention, the filler, the surfactant, the lubricant, and the pressure developing agent used in the thermosensitive color developing layer are provided within a range that does not impair the desired effect. Etc. can be added to the intermediate layer.

If necessary, polyvinyl alcohol, starch and its derivatives, polyacrylic acid soda, polybi, rupyrrolidone, acrylamide / acrylic acid ester copolymer may be added to the intermediate layer as long as the desired effect is not impaired. Polymerization, acrylamide diacrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride / polymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polycocrylamido, soda alginate, gelatin, casein It is also possible to add a water-soluble resin such as.

In the present invention, a protective layer may be provided on the thermosensitive color developing layer, if desired. The protective layer includes polyvinyl alcohol, starch and its derivatives, polyacryloic acid soda, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, and double-layer copolymer. / Maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride heavy salt alkali salt, polyacrylamide, soda alginate, gelatin, casein as a main component, and a cross-linking agent or the above-mentioned as necessary. Fillers, surfactants, lubricants and the like can also be added.

In the present invention, a back coat layer may be provided on the back surface of the support sheet, if desired. For the back coat layer, the material used for forming the intermediate layer, the binder used for forming the thermosensitive coloring layer and / or the protective layer, and the material for forming can be used.

[0022]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but these examples are for illustrating the present invention and not for limiting the present invention. In addition,
All “parts” and% shown below are based on weight. Example 1 [Solution A] 3-dibutylamino-6-methyl-7-anilinofluorane 10 parts 10% aqueous polyvinyl alcohol solution 10 parts water 20 parts [Solution B] 4-hydroxy-4′-isopropoxyphenyl Sulfone 10 parts Paramethylbenzyl oxalate 15 parts Silicon dioxide 5 parts 10% Polyvinyl alcohol aqueous solution 20 parts Water 50 parts [C liquid] Calcium carbonate 15 parts Styrene-butadiene copolymer emulsion 15 parts (solid content 4.75% Mitsui Toatsusha Polylac 750) Water 65 parts A mixture of [A liquid], [B liquid], and [C liquid] are sufficiently stirred, and A liquid and B liquid are dispersed by a ball mill for 24 hours [A liquid]. And [B liquid] were adjusted. Next, [solution A] and [solution B] were mixed at a weight ratio of 1: 4 to obtain a thermosensitive coloring layer coating solution. As a support, the thickness is 180 μm and the density is 0.
Styrofoam sheet of 43 g / cm ³ (Eupearl L
PS (180 μm type) Pearl Package Co., Ltd.
Manufactured), and the amount of adhesion is 2.0 after the liquid C is dried on the support.
The coating is in g / m ^2, dried after coating on to become more the thermosensitive color developing coating solution to a dry coating weight 4.0 g / m ² thereof, to obtain a heat-sensitive recording sheet of dry invention. This heat-sensitive recording sheet had appropriate rigidity, flexibility and strength and was excellent in handleability at the time of coating the heat-sensitive layer and at the time of printing on the heat-sensitive sheet.

Example 2 As a support, a polystyrene foam sheet having a density of 0.22 g / cm ^{3 and a} thickness of 250 μm (Upearl LPS (250 μm
m type) A thermal recording sheet of the present invention was obtained in the same manner as in Example 1 except that Pearl Package Co., Ltd. was used. This heat-sensitive recording sheet had appropriate rigidity, flexibility and strength and was excellent in handleability at the time of coating the heat-sensitive layer and at the time of printing on the heat-sensitive sheet.

Comparative Example 1 A support having a thickness of 96 μm and a density of 0.75 g / cm
A heat-sensitive sheet for comparison was obtained in the same manner as in Example except that ³ (Yupo FPG # 95 manufactured by Oji Oka Kasei Synthetic Paper Co., Ltd.) was used. This heat-sensitive recording sheet had appropriate rigidity, flexibility and strength and was excellent in handleability at the time of coating the heat-sensitive layer and at the time of printing on the heat-sensitive sheet.

Comparative Example 2 A thermal recording sheet for comparison was obtained in the same manner as in Example except that a polystyrene film having a thickness of 70 μm and a density of 0.98 g / cm ³ was used as the support. The following evaluation was performed on each heat-sensitive sheet obtained as described above.
1. Dynamic thermal sensitivity: Using a simulator printing device manufactured by Okura Electric Co., head power 0.45 W / dot, scanning line density 8
× 7.7 dot / mm, pulse width 0.5 ms, and 1.0
Printed in ms, and the density is measured with a Macbeth densitometer (RD-914 filter # 106). 2. Static thermal sensitivity: Using a thermal gradient tester manufactured by Toyo Seisakusho, pressure 2 kg / cm ² , contact time 1 second, temperature 90 ° C. and 110
Color was developed at ℃, and the density was measured with a Macbeth densitometer (RD-914 filter # 106). 3. Color development: Rubbing the surface of the heat-sensitive coloring layer of the heat-sensitive recording sheet 6 times with a metal edge (width 5 mm, weight 150 g) and measuring the density with a Macbeth densitometer (RD-914 filter # 106).
Measured at

[0026]

[Table 1]

[0027]

As described above in detail and concretely,
The heat-sensitive sheet of the present invention is excellent in both dynamic heat sensitivity and static heat sensitivity as heat sensitivity, and has less color development of the background due to pressure, has appropriate rigidity and flexibility and strength, and is handled. It is also excellent in sex.

Front Page Continuation (72) Inventor Nao Yamamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. A heat-sensitive sheet having a heat-sensitive color forming layer provided on a support, wherein the support has a density of 0.2 to 0.5 g / cm.sup.2.
A heat-sensitive sheet characterized by being a synthetic resin sheet of ³ . 2. The heat-sensitive sheet according to claim 1, wherein the support is a void-containing material. 3. The heat-sensitive sheet according to claim 1, wherein the material of the support made of synthetic resin is polystyrene.