JPH058535A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material provided with a thermal recording layer on a support body having as main components reactant and co-reactant which generate coloring reaction with heat, wherein recording density is high and coloring density is uniform and mechanical strength is excellent using low printing energy. CONSTITUTION:A thermal recording material is provided with a thermal recording layer having as main components reactant and co-reactant which generate coloring reaction with heat. For a support body of the material, a sheet base material obtained by forming fibered substance obtained by ejection of synthetic resin, having Bekk smoothness of 60sec. or above is used. Thus, by using the sheet base material with high smoothness obtained by forming the fibered substance by the ejection of the synthetic resin as a support body, a thermal recording material having high recording density, uniform coloring density, and excellent mechanical strength can be obtained by using low printing energy.

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 material, and more particularly to a heat-sensitive recording material which has a high recording density with a low printing energy and a uniform color density and is excellent in mechanical strength.

[0002]

2. Description of the Related Art A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a reaction product and a co-reactant as a main component capable of causing a color reaction by heat is formed by a heat head, a heat pen, a laser beam or the like. By heating, a recorded image can be obtained instantly. In addition, because it can be recorded with a relatively simple device, maintenance is easy, noise is not generated, etc., measurement recorder, facsimile, printer, computer terminal, label, ticket vending machine It is used in a wide range of fields. In particular, in the field of facsimile, the demand for the heat-sensitive method has greatly increased, and it has become the mainstream of the recording method. Further, along with the spread of facsimiles, the price of the facsimile has been reduced, the energy consumption and the size thereof have been reduced, and the quality requirement for the heat-sensitive recording material has become strict. That is, there has been a demand for a heat-sensitive recording material capable of obtaining high sensitivity corresponding to low energy and stable printing, in other words, capable of obtaining a sufficient color density even with a small heat energy.

Further, since the heat-sensitive recording material is used in a wide range of fields as described above, not only energy saving but also various quality characteristics suitable for each application are required. For example, a heat-sensitive recording material for labels is used for price display of foods, etc., but it is required to have excellent image storability and mechanical strength even in an environment such as freezing or water wetting.

As a method for improving the mechanical strength and water resistance of paper generally used as a support, a method of coating or impregnating a sheet with a water-soluble resin, an aqueous emulsion or the like is generally used. In order to obtain such high mechanical strength and water resistance, it is necessary to increase the coating amount and the impregnation amount, resulting in high cost.

There is also a method of using a film having high mechanical strength and high water resistance as a support, but it is difficult to improve the adhesiveness between the support and the coating layer and the cost becomes high, so that it is not very practical. Not the right way.

Further, there is a method of providing mechanical strength and water resistance by using a support obtained by laminating a film and paper, but even if the film is thickened, mechanical strength such as high tear strength as desired is obtained. There is a drawback that strength cannot be obtained.

[0007]

DISCLOSURE OF THE INVENTION The present invention is an inexpensive heat-sensitive material which is excellent in mechanical strength, which can not be achieved by the above-mentioned prior art, and which has a low printing energy, a high recording density and a uniform color density. It is intended to provide recording material.

[0008]

Means for Solving the Problems When the present inventors prepared a heat-sensitive recording material using a sheet-like substrate formed by molding a fibrous substance obtained by injecting a synthetic resin, paper was prepared. Mechanical strength and water resistance are dramatically improved compared to those used as a support, and compared to those using a film as a support, the fibers have fine pores and the sheet contains air. Therefore, the mechanical strength per unit weight is high, the cushioning property is good, and the heat insulating property is excellent. Therefore, it has been revealed that a high recording density can be obtained with a low printing energy. In addition, as a result of studying the relationship between the surface smoothness of such a sheet-like substrate and the uniformity of the color density, it became possible to apply the heat-sensitive recording layer more uniformly to a sheet having a higher surface smoothness, which was heat-printed. It was revealed that a uniform color density was obtained. Therefore, when a fibrous substance obtained by injecting a synthetic resin is used as a base material for a sheet having high surface smoothness obtained by molding, it has excellent mechanical strength and water resistance, and recording density at low printing energy is low. It was found that an inexpensive thermal recording material having a high color development density and a uniform color density can be obtained, and the present invention has been completed.

Examples of the material for the injection-molded sheet-like base material used in the present invention include resins such as polyethylene, polypropylene, polyester, nylon, rayon, polyacrylic acid ester and polyurethane, and mixtures thereof. Moreover, you may add a wettability improving agent, an antistatic agent, an antioxidant, a fluorescent whitening agent, etc. to a sheet-shaped base material as needed.

In the present invention, as a method for obtaining a sheet-shaped substrate, pellet-shaped or chip-shaped resin is melted by heating, extruded into a fibrous form from a die head having pores at the tip, and then air is blown to form the fibers. After randomly orienting and re-orienting on the forming belt, the sheet is melt-blown by heat-sealing with a heat roll, the resin is melted by heating and extruded from the die head, and then the fibers are blown by high-speed air flow. Use the spunbond method to obtain a sheet by stretching the fiber diameter to reduce the fiber diameter and heat-sealing the fibers, and the flash spin method to obtain a sheet in the same manner as the spunbond method by adding a solvent to the resin and extruding from the die head. be able to.

In the present invention, the heat-sensitive recording layer is uniformly applied by setting the Bekk smoothness of the sheet-like base material obtained by molding a fibrous substance obtained by injecting a synthetic resin to 60 seconds or more. This makes it possible to obtain a uniform color density when printed by heating. However, when the Bekk smoothness of the sheet-shaped substrate is lower than 60 seconds, it becomes impossible to uniformly apply the heat-sensitive recording layer due to the unevenness of the sheet surface,
When printed with heat, color density unevenness occurs. In such a case, a method is generally used in which an undercoat layer is provided on the support so that the heat-sensitive recording layer can be uniformly applied. However, when the Bekk smoothness of the sheet-shaped substrate is lower than 60 seconds, the heat-sensitive recording layer is formed. In order to apply it uniformly, the undercoat layer must be applied in a considerably thick thickness, which is costly and impractical.

In the present invention, an undercoat layer is preferably provided on the sheet-shaped substrate in order to obtain uniform color development and high printing density.

Examples of the pigment used in the undercoat layer of the present invention include kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, calcium oxide, magnesium oxide, titanium oxide, zinc oxide, natural silica, synthetic silica and aluminum hydroxide. Pigments such as, and synthetic or natural fillers such as urea-formalin resin particles and cellulose fibers can be used alone or in combination.

As the adhesive for the undercoat layer of the present invention, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylic acid soda, acrylic acid amide / acrylic acid ester Water-soluble adhesive such as polymer / acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, poly Latex such as vinyl acetate, polyurethane, polyacrylic acid ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer may be used alone or in combination. It can be.

Further, various additives such as a surfactant and a thermoplastic material may be added to the undercoat layer.

[0016] In the present invention, the coating amount of the undercoat layer is preferably in the range of 0.5 to 15 g / ^{m 2} on a dry coating amount, more preferably in the range of 2 to 6 g / ^{m 2.} If the coating amount is too small, the unevenness on the surface of the substrate cannot be covered, and the effect of providing the undercoat layer cannot be obtained. On the other hand, if the coating amount is too large, the production cost increases and it is not practical.

In the present invention, the coating method for applying the undercoat layer coating solution onto the support is not particularly limited, and may be an air knife coater, a rod coater, a curtain coater, a die coater, a roll coater, Various coating devices such as a blade coater can be used.

In the heat-sensitive recording material used in the heat-sensitive recording layer of the present invention, two or more kinds of components are brought into contact with each other by heat,
Any combination of a reactant and a co-reactant that causes a color-forming reaction may be used, and examples thereof include a combination of an electron-donating colorless dye precursor and an electron-accepting compound.

Specific examples of the electron-donating colorless dye precursor include (1) triarylmethane compound 3,3-bis (P-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone) ), 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- (p-dimethylaminophenyl) -3- (2-phenylindole-
3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-)
Yl) -6-Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5 -Dimethylaminophthalide, 3-p
-Dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

(2) Diphenylmethane compound 4,4'-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-2,4,5-trichlorophenyl leuco auramine and the like.

(3) Xanthene compound Rhodamine B anilinolactam, Rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3- Diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3 -Diethylamino-7
-(2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N
-Ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6- Methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitroanilinofluorane,
3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propyl) amino-6-
Methyl-7-anilinofluorane, 3- (N-ethyl-
N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N
-Ethyl-N-tetrahydrofuryl) amino-6-methyl-7-anilinofluorane and the like.

(4) Thiazine type compounds benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and the like.

(5) Spiro compound 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3 -Methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like can be mentioned, and these can be used alone or in combination of two or more kinds.

As the electron-accepting compound, a phenol derivative, an aromatic carboxylic acid derivative or a metal compound thereof, an N, N'-diarylthiourea derivative and the like are used. Of these, particularly preferred are phenol derivatives, specifically, p-phenylphenol, p-hydroxyacetophenone, 4-hydroxy-4′-methyldiphenyl sulfone, 4-hydroxy-4′-isopropoxydiphenyl sulfone, 4-hydroxy-4′-benzenesulfonyloxydiphenyl sulfone, 1,1-
Bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 2, 2-
Bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) butane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethyl Hexane,
2,2-bis (3-chloro-4-hydroxyphenyl)
Propane, 1,1-bis (p-hydroxyphenyl)-
1-phenylethane, 1,3-di [2- (p-hydroxyphenyl) -2-propyl] benzene, 1,3-di [2- (3,4-dihydroxyphenyl) -2-propyl] benzene, 1 , 4-di [2- (p-hydroxyphenyl) -2-propyl] benzene, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 3,3'-dichloro-4,4'-dihydroxy Diphenyl sulfone, 3,3'-diallyl-
4,4'-dihydroxydiphenyl sulfone, 3,3 '
-Dichloro-4,4'-dihydroxydiphenyl sulfide, methyl 2,2-bis (4-hydroxyphenyl) acetate, butyl 2,2-bis (4-hydroxyphenyl) acetate, 4,4'-thiobis (2-t -Butyl-5-methylphenol), bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-isopropyloxydiphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, p-hydroxy. Benzyl benzoate, chlorobenzyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, benzyl gallate, stearyl gallate, salicylanilide, 5-chlorosalicylanilide, etc. Is mentioned.

Further, as the heat-sensitive recording material, a coloring system comprising a combination of an imino compound and an aromatic isocyanate compound and a combination of a higher fatty acid metal salt such as ferric stearate and a phenol such as gallic acid is used. can do. Furthermore, there is no particular limitation as long as it is used as a heat-sensitive recording material, such as a coloring system in which a diazonium compound, a coupler and a basic substance are combined, and any of them can be used.

The adhesive used for the heat-sensitive recording layer is
For example, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch derivative, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylic acid, acrylic acid amide /
Acrylic ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer, ethylene / maleic anhydride copolymer, isobutylene / maleic anhydride copolymer, etc. Latex of water-soluble adhesive, polyvinyl acetate, polyurethane, polyacrylic acid ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, etc. Is mentioned. In addition to these adhesives, a water resistance agent (gelling agent, cross-linking agent) may be added for the purpose of imparting water resistance.

As a pigment in the heat-sensitive recording layer, diatomaceous earth,
Talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, calcium oxide, magnesium oxide,
Examples thereof include titanium oxide, zinc oxide, natural silica, synthetic silica, aluminum hydroxide, urea-formalin filler, and cellulose filler. Further, the heat-sensitive recording material according to the present invention may contain a heat-fusible substance in order to further improve its thermal response. As the heat-fusible substance, a substance having a melting point of 60 ° C. to 180 ° C. is preferable, and a substance having a melting point of 80 ° C. to 140 ° C. is particularly preferable. For example, waxes such as N-hydroxymethylstearic acid amide, stearic acid amide and palmitic acid amide, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2. -Bis (3-methylphenoxy) ethane, 2,2'-bis (4
-Methoxyphenoxy) diethyl ether, bis (4-
Polyether compounds such as methoxyphenyl) ether,
Diphenyl carbonate, dibenzyl oxalate, dioxalate (p
Carbonic acid such as -chlorobenzyl) ester or oxalic acid diester derivative can be used alone or in combination.

In addition, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide and castor wax. , A dispersant such as dioctyl sodium sulfosuccinate,
A benzophenone-based or benzotriazole-based ultraviolet absorber, a surfactant, a fluorescent dye, or the like can be added as necessary.

In the present invention, the coating amount of the heat-sensitive recording layer is
The dry coating amount is preferably in the range of 1 to 15 g / m ² , and more preferably 3 to 10 g / m ² . If the coating amount is too small, uniform color development cannot be obtained due to the exposure of the base fibers, and if the coating amount is too large, the production cost will be high, which is not practical.

In the present invention, the coating method for coating the heat-sensitive recording layer coating liquid on the support is not particularly limited, and may be an air knife coater, rod coater, curtain coater, die coater, roll coater, Various coating devices such as a blade coater can be used.

If desired, an overcoat layer may be provided on the heat-sensitive recording layer in order to improve the storability of printed images.

[0032]

EXAMPLES Next, the present invention will be described in more detail by way of examples. All parts and% shown below are based on weight. The value indicating the coating amount is the coating amount after drying unless otherwise specified.

Example 1 (1) Preparation of injection-molded sheet-like base material After pellets of high-density polyethylene resin were melted by heating and extruded into a fibrous shape from a die head having pores at the tips,
Fiber is stretched by high-speed air flow to make fiber diameter about 1 to 200
μm, the fibers are oriented and heat-sealed, and the basis weight is 56 g /
An injection-molded sheet-shaped substrate having m ² and a Beck smoothness of 23 seconds was obtained (spunbond method).

(2) Preparation of coating liquid for undercoat layer A mixture having the following composition was dispersed to prepare a coating liquid for undercoat layer. Calcined kaolin (trade name: Ansilex, Engelhard, oil absorption 110 ml / 100 g): 100 parts Styrene-butadiene copolymer latex (50% water dispersion product): 24 parts Phosphate esterified starch (trade name: MS- 4600,
Made by Japan Food Processing Co., Ltd., 10% aqueous solution): 60 parts Water: 52 parts

(3) Preparation of heat-sensitive coating liquid Mixtures having the following compositions were pulverized and dispersed by a sand mill until the average particle size became about 1 μm, and the liquids A and B were mixed.
Liquid] was prepared.

[0036]   [Liquid A] 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinof Luo Lan: 40 copies 10% polyvinyl alcohol aqueous solution: 20 parts Water: 40 copies

[B liquid] Bisphenol A: 50 parts 2-benzyloxynaphthalene: 50 parts 10% polyvinyl alcohol aqueous solution: 50 parts Water: 100 copies

Next, a heat-sensitive coating liquid was prepared with the following composition by using the prepared [solution A] and [solution B]. [Liquid A]: 50 parts [Liquid B]: 250 parts Zinc stearate (40% dispersion liquid): 25 parts 10% aqueous polyvinyl alcohol solution: 216 parts Calcium carbonate: 50 parts Water: 417 parts

Each coating solution thus prepared was used as a super liquid.
-Smoothed with a calendar to obtain Beck smoothness of 85
Seconds with the wire bar on the injection molded sheet
A heat-sensitive recording material was produced by obtaining such a coating amount. Undercoat layer 4.0 g / m^Two Thermal recording layer 5.5 g / m^Two

Example 2 The same as Example 1, except that the undercoat layer was not coated and only the heat-sensitive recording layer was coated on the support having Beck smoothness of 85 seconds. A thermosensitive recording material was prepared.

Example 3 When a pellet of a high-density polyethylene resin was heated and melted, di-chloro-di-fluoromethane was added thereto and extruded into a fibrous form from a die head having pores at the tip, and then the fiber was extruded by a high-speed air stream. Extend the fiber diameter to about 1 ~ 200μm
Then, the fibers were oriented and heat-sealed to obtain an injection-molded sheet-shaped substrate having a basis weight of 56 g / m ² and a Beck smoothness of 30 seconds (flash spin method). The support thus obtained was subjected to a smoothing treatment with a super calender, the Beck smoothness was set to 93 seconds, the undercoat layer was not coated on the support, and only the thermal recording layer was coated. A thermal recording material was prepared in the same manner as in Example 1.

Comparative Example 1 A thermosensitive recording material was prepared in the same manner as in Example 1 except that the support of Example 1 was made of high-quality paper having a basis weight of 60.0 g / m ² and a Bekk smoothness of 72 seconds.

Comparative Example 2 Example 1 except that the support of Example 1 was emulsion impregnated paper having a basis weight of 62.0 g / m ² and a Bekk smoothness of 65 seconds.
A thermal recording material was prepared in the same manner as in.

Comparative Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1 except that the support of Example 1 was supercalendered and the Bekk smoothness was changed to 52 seconds.

Comparative Example 4 The same as Example 1 except that the support of Example 1 was supercalendered to have Beck smoothness of 52 seconds, the undercoat layer was not coated, and only the heat-sensitive recording layer was coated. Then, a thermosensitive recording material was prepared.

The evaluation results are collectively shown in Table 1. The Beck's smoothness of the sheet-shaped substrate before coating the undercoat layer was measured with a Beck's smoothness tester (manufactured by Kumagai Riki Kogyo Co., Ltd.), and the dry tensile strength and wet tensile strength were measured with a Tensilon CR7000 tester (manufactured by Orientec Co., Ltd.) Each was measured. In addition, the color uniformity was developed with a stamp color machine HG-100 (manufactured by Toyo Seiki Co., Ltd.), and the uniformity of the color image area was visually evaluated. What was observed was evaluated as Δ, and when uneven coloring was remarkable was evaluated as x. The printing density is Okura Denki (TH-PMD) and the dot density is 8 dots / m.
m, head resistance is 1299Ω, thermal head is used, head voltage is 20V, energization time is 0.6ms and 1.2m
It was printed with s and measured with a Macbeth RD-918 type reflection densitometer.

[0047]

[Table 1] * Indicates the Beck's smoothness of the sheet-shaped substrate before coating the undercoat layer.

As is clear from Table 1, the heat-sensitive recording material using the injection-molded sheet as the support has high dry and wet tensile strength, and good print density and uniform color developability. In Comparative Examples 1 and 2 in which high-quality paper and emulsion-impregnated paper were used as the support, the color development uniformity was good, but the dry and wet tensile strength was weak and the print density was low. Further, in Comparative Example 3, if the Beck smoothness of the injection-molded sheet is set to 60 seconds or less, even if an undercoat layer is provided, the effect is not exhibited, and in Comparative Example 4, there is no undercoat layer. The unevenness of the surface of the sheet deteriorates, the heat-sensitive recording layer cannot be uniformly applied, and the print density and uniform color developability deteriorate.

[0049]

EFFECT OF THE INVENTION The heat-sensitive recording material of the present invention uses a fibrous substance obtained by injecting a synthetic resin to form a sheet-like base material, which is used as a support. It has a high color density and a uniform color density, has excellent mechanical strength, and has an extremely high practical value.

Claims (2)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer provided on a support, wherein the support is a sheet-like substrate formed by molding a fibrous substance obtained by injecting a synthetic resin. Heat sensitive recording material 2. The heat-sensitive recording material according to claim 1, wherein the support has a Bekk smoothness of 60 seconds or more.