JPH02206586A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance the sensitivity of a thermal recording material by successively laminating an undercoat layer containing spherical porous inorganic particles having a total pore capacity of 0.4ml/g or more and a surface pore average diameter of 0.005mum or more and a thermal color-forming layer on a substrate. CONSTITUTION:An undercoat layer containing spherical porous inorganic particles having a total pore capacity of 0.4ml/g or more and a surface pore average diameter of 0.005mum or more is formed on a substrate. Furthermore, a thermal color-forming layer is laminated on the undercoat layer to form a thermal recording material. The spherical porous inorganic particles are preferably incorporated in the aforesaid undercoat layer in the amount of 5-80wt.%. As the material of the spherical porous inorganic particles, carbonates of alkaline earth metal, silicates of alkaline earth metal, metallic oxides, and the like are concretely exemplified. The thermal color-forming layer is mainly composed of a color former and a color developer, and waxes and the like are contained thereto, as necessary.

Description

Detailed Description of the Invention (A) Industrial Application Field The present invention relates to a heat-sensitive recording material, and more specifically, it utilizes a color reaction between a colorless or light-colored electron-donating dye precursor and an electron-accepting compound at room temperature. This invention relates to improvements in heat-sensitive recording materials.

(B) Prior Art A two-component color-forming thermosensitive recording material consisting of a colorless or light-colored electron-donating dye precursor (hereinafter referred to as a color former) and an electron-accepting compound (hereinafter referred to as a color developer) is a primary color-developing material, and is developed by developing. It has many advantages such as no post-processing is required and it is easy to handle, and it occupies the mainstream of heat-sensitive recording materials.

It is widely used for facsimiles, recording of measuring instruments, labels, etc. Particularly in the field of facsimile, the growth is remarkable and the quality requirements are becoming stricter.

In other words, as facsimile machines become faster, it is required to record with short pulse widths, that is, to obtain sufficient density even with small thermal energy, and to avoid coloring due to preheating of the thermal head after printing. Adhesion of molten material (residue) must also be suppressed as much as possible.

As a response to the above conflicting demands, for example, the intermediate layer containing an inorganic powder with an oil absorption of 50 d/100 F or more as disclosed in JP-A No. 54-23545, and the foamable plastic filler as described in JP-A-59-225987. It has been proposed to provide a foamed layer or the like.

However, with such heat-sensitive recording materials that develop color with low thermal energy, there is a tendency for thermal energy to increase the adhesion of thermal melt to the thermal head, and when printing for a long period of time,
Printing may become unclear due to head residue, or in severe cases, may not be printed at all. Even if the residue is good, if printing is performed with high energy, the density may decrease significantly due to the penetration of the hot melt into the lower layer.

(C) Problems to be Solved by the Invention An object of the present invention is to provide a heat-sensitive recording material comprising a heat-sensitive recording layer containing a color forming agent and a color developer as main components on a support, and to provide a high It is an object of the present invention to provide a heat-sensitive recording material which has less residue adhering to the recording material and less decrease in density when printed with high h energy.

(D) Means for solving the 8 problems: As a result of intensive research, the present inventors have found that the undercoat layer between the support and the heat-sensitive recording layer contains specific spherical porous inorganic particles. As a result, it was possible to obtain a heat-sensitive recording material that has high sensitivity even with low thermal energy, does not generate residue even with high thermal energy, and exhibits little decrease in color density.

The specific spherical porous inorganic particles of the present invention have a total pore volume of 0.4 td/f or more and an average diameter of surface pores of o, o o sμ or more, more preferably In addition to these characteristics, it has an average particle diameter of 3μ or less and a specific surface area of 400W? /f or higher.

Hollow pigments satisfying the above properties are also preferred.

The spherical porous inorganic pigment of the present invention is produced by mixing one of the aqueous solutions of compounds A and B with an organic solvent and emulsifying it into a water-in-oil emulsion, for example, in the inorganic chemical reaction A + B - + C + D that proceeds in a normal aqueous solution. It is obtained as a suspension by a method of proceeding with a precipitation reaction with A or B on the surface of droplets of an aqueous solution in this emulsion. This also includes cases where it becomes porous during drying. Examples include the method of JP-A No. 63-229140 and JP-A No. 63-258642, and non-hollow spherical porous inorganic pigments can also be obtained by the same method.

The spherical shape produced by the above reaction is almost spherical, but in particular, the eccentricity as seen in electron micrographs is 0.
9 or less is considered almost spherical.

Porous means that pores are distributed on the surface and inside of the spherical pigment.

Inorganic materials constituting such spherical porous inorganic particles include alkaline earth metal carbonates, alkaline earth metal silicates, and metal oxides. Specific examples include calcium carbonate, barium carbonate, calcium silicate, magnesium silicate, silica (silicic anhydride), alumina, and zirconia.

The spherical porous inorganic particles of the present invention may be used in combination of two or more types, and the amount used is not necessarily limited, but the ratio of the spherical porous inorganic particles of the present invention to Undercoat Jl is 3. It is generally from 1% by weight to 80% by weight, preferably from 5% by weight to 50% by weight.

In addition to the spherical porous inorganic particles contained in the undercoat layer of the present invention, white pigments such as calcined kaolin, kaolin, natural silica, synthetic silica, aluminum hydroxide, calcium carbonate, calcium oxide, magnesium carbonate, magnesium oxide, Urea-formalin filler, cellulose filler, etc. are used.

Examples of the binder include styrene-butadiene rubber latex, acrylic resin emulsion resin, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, styrene-maleic anhydride copolymer,
Examples include starch, starch derivatives, casein, gelatin, and the like. As other dispersants, antifoaming agents, lubricants, etc., those used for general coated paper can be used.

The heat-sensitive coloring layer provided on the intermediate layer mainly contains a color former and a color developer, but waxes, sensitivity improvers, metal soaps, ultraviolet absorbers, etc. are added as necessary, and the above-mentioned An oil-absorbing pigment may also be mixed.

The color forming agent used in the present invention is not particularly limited as long as it is used in general pressure-sensitive recording paper, heat-sensitive recording paper, etc. To give a specific example, (1) 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone), 3 as a triarylmethane compound;
．． 3-bis(p-dimethylaminophenyl)phthalide,
a-(p-dimethylaminophenyl)-3-(1,2
-dimethylindol-3-yl]phthalide, 3-(p
-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl)phthalide, 3.3-bis- (1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3.
3-bis-(1,2-dimethylindol-3-yl)
-6-dimethylaminophthalide, 3.3-bis-(9-
Ethylcarbazol-3-yl)-5-dimethylaminophthalide, 3,3-bis-(2-phenylindole-
3-yl)-5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrole-2
-yl]-6-dimethyl-amino7talide, etc.: (2) As a diphenylmethane compound, 4.4'-
His-dimethylamine benzhydrin pencil ether, N-halophenylleukoolamine, N-2,4,5
-Trichlorophenylleucoauramine, etc.: (3) As a xanthine compound, rhodamine B-
7-nilinolactam, Rhodamine B-p-nitroanilinolactam, Rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino -7-phenylfluorane, 3
-diethylamino-7-3,4-dichloroanilinofluorane, 3-diethylamino-7-(2-chloroani!
J/) Fluoran, 3-diethyl°amino-6-methyl-7-anilinofluorane, 3-piperidi7-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7- 7 Nylinofluorane, 3-ethyl-tolylamino-6-meth? -7-phenylfluorane, 3-diethylamino-7-(4-nitroanilino]fluoran, etc.: (4) As a thiazine compound, benzoylleucomethylene blue, p-nitrobenzoyl icomethylene blue, etc.: (53 As a spiro compound, 3-methyl-spiro-dinaphthopyran, 3-ether-spiro-dinaphthopyran,
3.3'-Cyclolosebirodinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methylna7)-(
Examples include 3-methoxy-benzo)-spiropyran, 3-7' lobi-spirogipenzopyran, and mixtures thereof. These are determined by the application and desired properties.

As the color developer used in the present invention, phenol derivatives and aromatic carboxylic acid derivatives are preferable, and bisphenols are particularly preferable. Specifically, as phenols,
p-octylphenol, p-tert-butylphenol, p-phenylphenol, 1.1-bis(p-
hydroxyphenyl)propane, 2.2-bis(p-hydroxyphenyl)propane, 1.1-bis(p-hydroxyphenyl)pentane, 1.1-bis(p-hydroxyphenyl)hexane, 2.2-bis( p-hydroxyphenyl)hexane, 1゜1-bis(p-hydroxyphenyl)-2-dithylhexane, 2.2-bis(4
-hydroxy-3,5-dichlorophenyl)propane and the like.

Examples of aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3.5-di-tart-butylsalicylic acid, and 3.5-di-α-methylbenzylsalicylic acid. and polyvalent metal salts of these carboxylic acids.

Examples of waxes include paraffin wax, cowboy wax, microcrystalline wax, and polyethylene wax, as well as higher fatty acid amides such as stearic acid amide, ethylene bisstearamide, and higher fatty acid esters.

Examples of metalstones include polyvalent metal salts of higher fatty acids, ie, zinc stearate, aluminum stearate, calcium stearate, zinc oleate, and the like.

Sensitivity improvers include those with a sharp melting point of 80 to 140°C and good thermal responsiveness, such as benzoic acid and terephthalic acid esters, naphthalene sulfonic acid esters, and naphthyl. Ether derivatives, anthryl ether derivatives, aliphatic ether sensitizers, phenanthrene, fluorene, and other sensitizers can be used.

The waxes mentioned above can also be used as sensitizers.

These are dispersed and applied in a binder.

Binders are generally water-soluble, such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and imbutylene-maleic anhydride copolymer. , polyacrylic acid, starch derivatives, casein, gelatin, and the like. In addition, in order to impart water resistance to these binders, water-resisting agents (gelling agents, cross-linking agents) are added, and emulsion of hydrophobic polymers, specifically styrene-butadiene rubber latex, acrylic resins, etc. Emulsion paste etc. can also be added.

As the apparatus used for coating the intermediate layer and the heat-sensitive layer, a coater head such as a blade coater, an air knife coater, a roll coater, a roll coater, a curtain coater, etc. can be used.

Furthermore, in order to improve the surface smoothness of the coated product, machine calender, super calender cross calender,
Devices such as brushing can be used.

The coating amount of the heat-sensitive recording layer on the support is not limited, but is usually 3 to 15 t/r on dry weight. , preferably 4 to 10 f/r? is within the range of

Note that it is also possible to provide a protective layer on the heat-sensitive layer for solvent resistance and the like.

(E) By incorporating specific spherical porous inorganic particles between the working support and the heat-sensitive recording 1, the sensitivity is high even at low energy, there is little adhesion of residue to the head, and printing is possible with high energy. Even in such cases, it is possible to obtain a heat-sensitive recording material with little decrease in density.

The reason for this effect is that the energy from the thermal head can be used effectively due to the heat insulating properties of specific spherical porous inorganic particles, which improves color development sensitivity, and also because the shape is spherical. It is thought that when particles with a particle size of 3 μm or less are used, smoothness becomes better, sensitivity is improved, and uniform images can be obtained. In addition, since it is porous, it quickly absorbs the heat-sensitive recording layer composition that melts when heated, which has the effect of suppressing the generation of head scum and preventing excessive penetration of melted material, thereby reducing the color density. It is thought that there are few.

(F) Examples Examples of the present invention are shown below, but the present invention is not limited thereto.

In addition, "parts" and "chi" in the examples indicate "parts by weight" and "parts by weight," respectively.

Examples 1-2 Calcined kaolin (manufactured by Diakaolin, Astra Bake) and spherical porous silica (manufactured by Meiki Yushi Kogyo, E-20)
were dispersed in an aqueous sodium hexametaphosphate solution, changing the ratio as shown in Table 1, to obtain a 45% slurry. In addition, 20% phosphate ester starch solution (Japan Food Processing Bag, M
15 parts of S4600), latex (manufactured by Japan Synthetic Rubber,
JSB, 0692) and mix thoroughly.

Basis weight 50 fAr? The undercoated paper was coated on a high-quality paper with a solid content of 8 and dried to obtain an undercoated paper.

As a coloring agent, 5t of 3-N,N-diethylamino-6-methyl-7-7-7-ethylaminofluorane was added to 25F of Tivolivinyl alcohol (manufactured by Kuraray, PVA-105) and soaked in water for a day and a night. The mixture was dispersed to obtain a color former dispersion.

10F of bisphenol A as a color developer and 10F of stearic acid amide as a sensitizer were mixed and dispersed overnight in a ball mill with 100 tons of 5% polyvinyl alcohol.
A dispersion of a color developer and a sensitizer was obtained.

Calcium carbonate (Shiraishi Kogyo Bag, Brt-15) as a pigment
) 25 t was dispersed in 40 f of a 0.5 t sodium hexametaphosphate aqueous solution using a homogenizer to obtain a pigment dispersion.

Mix the above color forming agent, color developer, sensitizer, and pigment dispersion,
Further, 52 hours of a 30% solution of zinc stearate was added to obtain a heat-sensitive coating liquid. This liquid was coated on the above-mentioned undercoated paper so that the solid content coating amount was 5 t/lri, and after drying, super calendering was performed so that the Peck smoothness was between 300 sec and 500 sec to obtain a sample. Ta.

The sample is a thermal printing test device (THPMD) made by Daii Denki.
) at 18 m5ec/11ne, pa/lz width 0.8
Solid printing was performed under conditions of m5ec and 1.0 msec, and the density was measured using a Macbeth reflection densitometer.

At the same time, the dirt on the thermal head after printing was observed, and the dirt was evaluated in four stages: O1, ■, Δ, and ×. The results are shown in Table 1.

Example 3 A thermosensitive sample was obtained in the same manner as in Examples 1 and 2, except that spherical porous calcium carbonate (Tankarjin) having a specific surface area of 300 nVt was used instead of the spherical porous silica E-20. The blending ratio and evaluation results are shown in Table 1.

Example 4 In Examples 1 and 2, instead of spherical porous silica E-20, K and spherical porous hollow silica (manufactured by Meiki Yushi Kogyo, B-
A thermosensitive sample was obtained in the same manner except that 60) was used.

The blending ratio and evaluation results are shown in Table 1.

Comparative Example 1 A thermosensitive sample was obtained in the same manner as in Examples 1 and 2 except that the entire amount of spherical porous silica E-20 was replaced with Astrapaque. The blending ratio and evaluation results are shown in Table 1.

Comparative Example 2 In Examples 1 and 2, borosilicate glass hollow spherical particles (manufactured by Nippon Silkani Industry Co., Ltd., K
A heat-sensitive sample was obtained in the same manner except that -330) was used. The blending ratio and evaluation results are shown in Table 1.

(The following is a blank space) (G) Effects of the Invention From the results in Table 1, it is clear that the heat-sensitive recording material of the present invention has high color development sensitivity and less generation of dregs.

Claims (3)

[Claims] (1) In a heat-sensitive recording material comprising an undercoat layer and a heat-sensitive coloring layer laminated in this order on a support, the undercoat layer has a total pore volume of 0.4 ml/g or more, and has surface pores. A heat-sensitive recording material characterized by containing spherical porous inorganic particles having an average diameter of 0.005μ or more. (2) Claim 1 wherein the spherical porous inorganic particles have an average particle diameter of 3 μ or less and a specific surface area of 400 m^2/g or more.
The heat-sensitive recording material described. (3) The heat-sensitive recording material according to claim 1 or 2, wherein the spherical porous inorganic particles are hollow bodies.