JP2613776B2 - Thermal recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more particularly, to a heat-sensitive recording material in which various properties are improved by providing an undercoat layer between a support and a heat-sensitive coloring layer.

[Prior art] In recent years, various recording materials have been researched and developed in the information recording field in accordance with the demands of society such as diversification and increase of information, resource saving, non-pollution, etc. The heat-sensitive recording material is (1) a color image is recorded simply by heating, and a complicated developing step is not required. (2) The heat-sensitive recording material can be manufactured using a relatively simple and compact apparatus. (3) In many cases, paper is used as a support. In this case, not only the support cost is low, but also
Because of the advantages of the obtained recording material being close to plain paper, it has advantages such as computer output, printers such as calculators, recorders for medical measurement, low and high-speed facsimile, ticket vending machines, and thermal copying. , POS
Widely used in the field of system labels.

The thermosensitive recording material is usually manufactured by coating and drying a thermosensitive coloring layer liquid containing a coloring component capable of causing a coloring reaction by heating on a support such as paper, synthetic paper or a synthetic resin film. The thus-obtained thermosensitive recording material is heated by a hot pen or a hot head to record a color image. Conventional examples of such a heat-sensitive recording material include, for example, JP-B-43-4160 and JP-B-45-14.
There is a heat-sensitive recording material disclosed in Japanese Patent Publication No. 039, but such a conventional heat-sensitive recording material has, for example, a low thermal response, and a sufficient color density cannot be obtained during high-speed recording. And
As a method for improving such a defect, for example, Japanese Patent Laid-Open No.
No. 424 discloses nitrogen-containing compounds such as acetamido, stearoamide, m-nitroaniline, and dinitrile phthalate, JP 52-106746 discloses acetoacetic anilide, and JP 53-11036 discloses N. , N-diphenylamine derivative, benzamide derivative, carbazole derivative,
JP-A-53-39139 discloses alkylated biphenyl,
Biphenylalkane is disclosed in Japanese Patent Application Laid-Open No. Sho 56-144193.
-A method of increasing the speed and increasing the sensitivity by adding a hydroxybenzoate derivative respectively has been disclosed, but at present, no satisfactory results have been obtained by any of the methods. Was. As another method, a method of increasing the sensitivity by lowering the melting point by amorphizing a leuco dye having a high melting point is disclosed in
-164890 and the like. However, since the surface of an amorphous dye is activated and has high reactivity,
There is a problem that liquid fogging or background fogging of the heat-sensitive coloring liquid or the heat-sensitive recording material is large and the whiteness is inferior.

To suppress background fog and increase dynamic color sensitivity,
Reduce the thermal conductivity of the support to 0.04 Kcal / mh ° C or less.
Or a layer having fine hollow sphere particles as a main component is provided on a support (JP-A-59-5093 and JP-A-59-5093).
No. 225987), but these have insufficient foaming properties and inflexibility of the wall material, insufficient heat insulating properties, or the adhesion between the thermal head and the thermosensitive recording material. May not be sufficient, and it cannot be said that satisfactory results have been obtained. Further, a method using non-foamable fine hollow particles of 5 μm or less made of a thermoplastic resin for the intermediate layer ( Japanese Patent Application Laid-Open No. Sho 62-5886) has also been proposed, but simply using such hollow particles does not provide satisfactory results.

〔Purpose〕

An object of the present invention is to provide a high-sensitivity thermosensitive recording material.

〔Constitution〕

According to the present invention, an undercoat layer containing plastic spherical hollow particles and a thermosensitive coloring layer mainly containing a leuco dye and a developer capable of causing the leuco dye to develop color when heated are sequentially laminated on a support. In the heat-sensitive recording material, the plastic spherical hollow particles are made of plastic having a glass transition temperature of 40 to 90 ° C., and have an average particle size of 0.20 to 1.5 μm.
m and a hollowness of 40 to 90%.

The undercoat layer containing the fine hollow particles of the present invention functions as a heat insulating layer, and improves the coloring sensitivity by efficiently utilizing the heat energy from a thermal head or the like.

The plastic spherical hollow particles used in the present invention have a thermoplastic polymer as a shell, contain air or other gas inside, are minute hollow particles already in a foamed state, and have a glass transition temperature of 40 to The shell is made of a thermoplastic polymer at 90 ° C. When the glass transition temperature is lower than 40 ° C., the material is plasticized when heated in a drying step or the like in the production of a heat-sensitive recording material, and cannot exist as spherical hollow particles. Conversely, those with a glass transition temperature higher than 90 ° C lack the elasticity, which reduces touchability with the thermal head and reduces the effect of improving sensitivity.At the same time, it also causes background coloring in the super calendering process after coating and drying. Become.

The average particle diameter of the plastic hollow spherical particles is 0.20.
However, those having an average particle diameter (particle diameter) smaller than 0.2 μm are difficult in terms of cost due to production problems such as difficulty in making the hollowness arbitrary. Conversely, when the thickness is larger than 1.5 μm, the smoothness of the surface after coating and drying is reduced, so that the touch property with the thermal head is reduced and the sensitivity improving effect is reduced. Therefore, it is desirable that such a particle distribution is such that the particle diameter is within the above-mentioned range and the distribution peak with little variation is uniform.

Further, the plastic spherical hollow particles used in the present invention have a hollowness of 40 to 90%.
%, The thermal insulation from the thermal head is released through the support to the outside of the heat-sensitive recording material, and the effect of improving sensitivity is insufficient. Conversely, hollowness is 90
%, The mechanical strength is reduced, so that the spherical hollow state is destroyed by mechanical energy in the dispersion step or the like, and the sensitivity improving effect is reduced and the productivity is significantly reduced. Here, the hollowness is a ratio of the outer diameter to the inner diameter of the hollow particles, and is represented by the following equation.

The plastic spherical hollow particles used in the present invention can be easily and inexpensively produced from an acrylic resin such as an acrylate or acrylonitrile, a styrene resin such as styrene, or a copolymer resin thereof.

To provide the undercoat layer on a support, the plastic spherical hollow particles are dispersed in water together with a binder such as a known water-soluble polymer or aqueous polymer emulsion, and the resultant is applied to the support surface and dried. It is obtained by doing. In this case, the coating amount of the plastic spherical hollow particles is at least 1 g, preferably about ^{2 to} 15 g per 1 m2 of the support, and the coating amount of the binder resin is an amount that strongly bonds the undercoat layer to the support. Usually, it is 2 to 50% by weight based on the synthesis amount of the plastic spherical hollow particles and the binder resin.

In the present invention, the binder used when forming the undercoat layer is appropriately selected from conventionally known water-soluble polymers and / or aqueous polymer emulsions. Specific examples thereof include, as water-soluble polymers, polyvinyl alcohol, starch and derivatives thereof, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, sodium polyacrylate,
Polyvinyl pyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkaline salt, isobutylene / maleic anhydride copolymer alkaline salt, polyacrylamide , Sodium alginate, gelatin, casein and the like. Examples of the aqueous polymer emulsion include latexes such as styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, vinyl acetate resin, vinyl acetate / acrylic acid copolymer, styrene / acrylic ester copolymer,
Emulsions such as acrylic ester resins and polyurethane resins are exemplified.

In the undercoat layer of the present invention, together with the plastic spherical hollow particles and the binder, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, heat-fusible substances, surfactants Agents and the like can be used in combination. In this case, specific examples of the filler and the heat-fusible substance include various substances described below in relation to the thermosensitive coloring layer component.

Since the surface of the undercoat layer formed on the support as described above has considerable irregularities, it is preferable to smooth the plane by calendering after forming the undercoat layer.

The leuco dye used in the present invention is applied alone or as a mixture of two or more kinds. As such a leuco dye, those applied to this kind of heat-sensitive material are arbitrarily applied, for example, triphenylmethane And leuco compounds of dyes such as fluoran compounds, phenothiazine compounds, auramine compounds, spiropyran compounds and indolinophthalide compounds are preferably used. Specific examples of such leuco dyes include, for example, those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethyl Aminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofurf Oran, 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzfluoran, 3-diethylamino -6-methyl-7-chlorofluoran, 3- (Np-tolyl-N-ethylamino) -6-methyl- -Anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3.6 -Bis (diethylamino) -9- (o-chloroanilino) xanthyl lactam benzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) Fluoran, 3-dibutylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N-amylamino-6-methyl-7
-Anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N, N- Diethylamino) -5-methyl-7-
(N, N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-
Pyrirospiran, 6'-bromo-3'-methoxy-benzoindolino-
Pyrirospiran, 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'-dimethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl) phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-
Methylphenyl) phthalide, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl -7-anilinofluoran, 3- (N-methyl-N-isopropyl) amino-6
Methyl-7-anilinofluoran 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7 -(N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (α-phenylethylamino) Fluoran, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7 -(Α-phenylethylamino) fluoran, 3-diethylamino-7-pipe Jinofuruoran, 2-chloro-3-(N-Mechirutoruijino) -7-
(Pn-butylanilino) fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenespiro (9,
3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4'-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluoran, 3-N-methyl-N-isopropyl-6-methyl-7
-Anilinofluoran, 3-N-ethyl-N-amyl-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (2 ', 4'-
Dimethylanilino) fluoran and the like.

Further, as the color developer used in the present invention, various compounds having an electron accepting property which causes the leuco dye to develop color upon contact, or an oxidizing agent are used. Such materials are conventionally known, and specific examples thereof include the following.

4,4'-isopropylidenebisphenol, 4,4'-isopropylidenebis (o-methylphenol), 4,4'-secondarybutylidenebisphenol 4,4'-isopropylidenebis (2-tert-butylphenol), 4 4,4'-cyclohexylidenediphenol, 4,4'-isopropylidenebis (2-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4 -Ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-
2-methyl) phenol, 1,1,3-tris (2-methyl-4-hydroxy-5-
Tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-
Cyclohexylphenyl) butane, 4,4'-thiobis (6-tert-butyl-2-methyl) phenol, 4,4'-diphenolsulfone, 4-isopropoxy-4'-hydroxydiphenylsulfone, 4-benzyloxy-4 '-Hydroxydiphenylsulfone, 4,4'-diphenolsulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -propane, 1 , 3-Bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N ' -Diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro-salicylanilide, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy -2-Naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis ( 4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4'-diphenolsulfone, 2,2'-diallyl-4,4'-diphenolsulfone, 3,4 -Dihydroxyphenyl-4'-methylphenylsulfone, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, thiocyan Antipyrine complex of zinc acid, tetrabromobisphenol A, tetrabromobisphenol S and the like.

In the thermosensitive coloring layer of the present invention, in order to apply the leuco dye and the developer on the undercoat layer, various conventional binders can be appropriately used. The same ones as exemplified in the coating of the coating layer can be used.

Further, in the present invention, together with the leuco dye and the developer, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, heat-fusible substances, surfactants, etc. Can be used in combination. in this case,
As the filler, for example, calcium carbonate, silica,
Inorganic fine powders such as zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated calcium and silica, urea-formalin resin, styrene / methacrylic acid copolymer, Organic fine powders such as polystyrene resin can be given. Examples of the heat-fusible substance include higher fatty acids or their esters, amides and metal salts, and various waxes.
50-200 such as condensates of aromatic carboxylic acids and amines, phenyl benzoate, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalate, higher ketones, and other heat-fusible organic compounds. Those having a melting point on the order of ° C. are mentioned.

In the present invention, a layer containing a filler, a binder, a heat-fusible substance or the like may be provided as an intermediate layer between the undercoat layer and the thermosensitive coloring layer, if necessary. In this case, specific examples of the filler, the binder, and the heat-fusible substance include those similar to those exemplified in relation to the thermosensitive coloring layer or the undercoat layer.

Further, the heat-sensitive recording material of the present invention may be provided with a protective layer on the heat-sensitive coloring layer for the purpose of improving the matching property of a thermal head or the like, and further improving the storage stability of a recorded image. As the components constituting the protective layer, the above-mentioned fillers, binders, surfactants, and heat-fusible substances can also be used.

The heat-sensitive recording material of the present invention is produced, for example, by applying the above-described coating liquid for forming each layer on a suitable support such as paper, synthetic paper, or plastic film, and then drying it. Applied.

〔effect〕

The heat-sensitive recording material of the present invention was formed by sequentially laminating an undercoat layer containing plastic spherical hollow particles and a heat-sensitive coloring layer mainly composed of a leuco dye and a developer that causes the leuco dye to develop color when heated. Due to the configuration, the color developing sensitivity is excellent.

〔Example〕

Next, the present invention will be described in more detail with reference to examples.
The parts and percentages shown below are based on weight.

Example [Solution A] 3- (N-methyl-3-N-cyclohexyl) amino-
6-methyl-7-anilinofluorane 20 parts Polyvinyl alcohol 10% aqueous solution 20 parts Water 60 parts [Solution B] benzyl p-hydroxybenzoate 10 parts Polyvinyl alcohol 10% aqueous solution 25 parts Calcium carbonate 15 parts Water 50 parts The above composition The mixture consisting of the materials has an average particle size of 2μ.
m using a sand mill to disperse [Liquid A]
And [B solution] were adjusted.

[Liquid C]

Plastic spherical hollow particle dispersion (solids concentration 47%) 40
Part (glass transition temperature 60 ° C,) (average particle size 0.4 μm,) (hollowness 75%) 10% aqueous solution of polyvinyl alcohol 10 parts water 50 parts The mixture having the above composition was stirred and dispersed with a disper to disperse the undercoat liquid. It was adjusted and applied to the surface of a commercially available high-quality paper (basis weight: 52 g / m ² ) so that the weight was 6 g / m ² after drying to obtain an undercoated paper.

Next, the above [Solution A] and [Solution B] were mixed and stirred at a weight ratio of 1: 8 to prepare a thermosensitive coloring layer forming solution, which was dried on the surface of the undercoated paper and weighed. After coating and drying at 7 g / m ² to provide a heat-sensitive coloring layer, it was further subjected to a super calender treatment so as to have a Beck smoothness of 500 to 600 seconds to obtain a heat-sensitive recording material of the present invention.

Comparative Example 1 In Examples, plastic spherical non-hollow particles [SPMM-Mitsui Toatsu Co., Ltd.] were used instead of plastic spherical hollow particles.
HS, solid content concentration 40%], and a heat-sensitive recording material for comparison was obtained in the same manner as in Example.

Comparative Example 2 A comparative thermosensitive recording material was obtained in the same manner as in the example, except that plastic spherical hollow particles having an average particle size of 3 μm and a glass transition temperature of 110 ° C. were used as the plastic spherical hollow particles.

For each thermosensitive recording material obtained as described above,
Thermal Facsimile Rifax 120 manufactured by Ricoh Co., Ltd.
And the image density was measured with a Macbeth densitometer. Table 1 shows the results.

From Table 1, it was confirmed that the heat-sensitive recording material of the present invention had high sensitivity.

Claims (1)

(57) [Claims] 1. A heat-sensitive layer formed by sequentially laminating, on a support, an undercoat layer containing plastic hollow spherical particles and a heat-sensitive coloring layer mainly composed of a leuco dye and a developer capable of causing the leuco dye to develop color when heated. In a recording material, the plastic spherical hollow particles are made of plastic having a glass transition temperature of 40 to 90 ° C., and have an average particle size of 0.20 to 1.5 μm and a hollowness of 40 to 90%. material.