JP2925156B2 - Thermal recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a heat-sensitive recording material, and more particularly, to the use of a color reaction between a colorless or pale-color electron-donating dye precursor and an electron-accepting compound at room temperature. The present invention relates to improvement of a heat-sensitive recording material.

(B) Prior Art A two-component color-forming heat-sensitive recording material comprising a colorless or pale-colored electron-donating dye precursor (hereinafter, referred to as a color former) and an electron-accepting compound (hereinafter, referred to as a developer) has a primary color development and Post-processing is not required, and it has many advantages such as being close to plain paper and being easy to handle, and occupies the mainstream of heat-sensitive recording materials.

Applications include facsimile, measurement instrument records,
Widely used for labels and the like. Particularly in the facsimile field, the growth is remarkable, and the required quality is becoming severer accordingly.

That is, as the facsimile speed increases, it is required that recording with a short pulse width, that is, sufficient density can be obtained even with small thermal energy, and that the color does not develop due to the heat of the thermal head after printing. The adherence (waste) of the hot melt must be minimized.

As a response to the above conflicting demands, for example, an intermediate layer containing an inorganic powder having an oil absorption of 50 ml / 100 g or more disclosed in JP-A-54-23545, and a foamable plastic filler disclosed in JP-A-59-225987 are used. It has been proposed to provide a foamed layer or the like.

However, such a heat-sensitive recording material that develops a color with low heat energy tends to increase the adhesion of a hot melt to a heat head due to heat energy, and if printing is performed for a long time, the print becomes unclear due to head debris. In the worst case, printing may not be performed. Further, even when the residue is good, when printing is performed with high energy, the decrease in density may be increased due to the penetration of the hot melt.

(C) Problems to be Solved by the Invention An object of the present invention is to provide a heat-sensitive recording material having a heat-sensitive recording layer containing a color former and a color developer as main components on a support, which has high sensitivity and a high sensitivity. An object of the present invention is to provide a heat-sensitive recording material which causes little adhesion of scum to printing and has a low density reduction even in high energy printing.

(D) Means for Solving the Problems That is, as a result of intensive studies, the present inventors have found that at least one or more coating layers (intermediate layers) mainly composed of a pigment and an adhesive are formed on a support. By providing a specific spherical porous inorganic particle in the heat-sensitive recording layer, high sensitivity even when printing with low energy, and less scum even when printing with high energy, lowering of color density As a result, it was possible to obtain a heat-sensitive recording material having a small amount.

As the specific spherical porous inorganic particles of the present invention, the total pore volume is 0.4 ml / g or more, and the average diameter of the surface pores is 0.0
More than 05μ, more preferably, in addition to such properties, the average particle size is 3μ or less, and the specific surface area is 200m
² / g or more. Hollow pigments satisfying the above properties are also preferred.

The spherical porous inorganic pigment of the present invention is obtained, for example, by mixing and emulsifying either an aqueous solution of the compound of A or B with an organic solvent in an inorganic chemical reaction A + B → C + D which proceeds in a normal aqueous solution to form a water-in-oil type. The emulsion is obtained by a method in which the precipitation reaction with A or B proceeds on the surface of the aqueous solution droplet in the emulsion. The case where it becomes porous by heating during drying is also included. The methods described in JP-A-63-229140 and JP-A-63-258642 are mentioned as examples, and solid spherical inorganic particles which are not hollow can be obtained in the same manner.

Although the shape of the particles is substantially spherical when formed by the above reaction, it is determined in particular by the shape obtained from an electron micrograph, and when considered as elliptical, the major axis a,
As the short axis b, An eccentricity of 0.9 or less represented by is regarded as substantially spherical. Porous means that pores are distributed on the surface and inside of the spherical particles.

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.

Two or more kinds of the spherical porous inorganic particles of the present invention may be used in combination, and the use amount is not particularly limited, but is most preferably contained in the thermosensitive coloring layer in an amount of 5 to 60% by weight. Further, a pigment other than the present invention may be used in combination.

The thermosensitive coloring layer containing the spherical porous inorganic particles of the present invention may be directly applied to paper, synthetic paper, film, etc., but it is preferable to provide one or more intermediate layers between them and the thermosensitive coloring layer. However, sensitivity, scum, etc. are good. As the pigment contained in the intermediate layer,
Spherical porous inorganic particles are good but calcined kaolin, kaolin, natural silica, synthetic silica, aluminum hydroxide,
Calcium carbonate, calcium oxide, magnesium carbonate,
Magnesium oxide, urea-formalin filler, cellulose filler and the like are used.

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

The heat-sensitive color-forming layer provided on the support mainly contains a color former and a developer other than the spherical porous inorganic particles of the present invention, but if necessary, waxes, a sensitivity improver, metal soap,
An ultraviolet absorber or the like may be added, and another pigment may be further mixed.

The color former used in the present invention is not particularly limited as long as it is used for general pressure-sensitive recording paper, heat-sensitive recording paper and the like. Specific examples include: (1) 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3
3-bis (p-dimethylaminophenyl) phthalide, 3
-(P-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-
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-ethylcarbazole-
3-yl) -5-dimethylaminophthalide, 3,3-bis- (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-
3- (1-methylpyrrol-2-yl) -6-dimethyl-aminophthalide and the like: (2) As a diphenylmethane-based compound, 4,4′-bis-dimethylaminobenzhydrin benzyl ether;
N-halophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like: (3) As xanthene compounds, rhodamine B-anilinolactam, rhodamine Bp-nitroanilinolactam, rhodamine B -P-chloroanilinolactam,
3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3
-Diethylamino-7-3,4-dichloroanilinofluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7
-Anilinofluoran, 3-piperidino-6-methyl-
7-anilinofluoran, 3-ethyl-tolylamino-
6-methyl-7-anilinofluoran, 3-ethyl-tolylamino-6-methyl-7-phenyltylfluoran,
3-diethylamino-7- (4-nitroanilino) fluoran and the like: (4) benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like as thiazine compounds: (5) 3-methyl-spiro- and spiro-based compound
Dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-
Benzylspiro-dinaphthopyran, 3-methylnaphtho-
Examples thereof include (3-methoxy-benzo) -spiropyran, 3-propyl-spiro-dibenzopyran and the like, or a mixture thereof. These are determined by the application and desired properties.

As the color developer used in the present invention, a phenol derivative and an aromatic carboxylic acid derivative 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
-Ethyl-hexane, 2,2-bis (4-hydroxy-3,5
-Dichlorophenyl) propane and the like.

Examples of the aromatic carboxylic acid derivative include p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid And carboxylic acids, such as their polyvalent metal salts.

Examples of the wax include paraffin wax, kauna wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylenebisstearamide, and higher fatty acid ester.

Examples of the metal soap include higher fatty acid polyvalent metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like.

Sensitizers having a sharp melting point of 80 to 140 ° C. and good thermal responsiveness include, specifically, benzoic acid and terephthalic acid esters, naphthalenesulfonic acid esters, and naphthyl. Sensitizers such as ether derivatives, anthryl ether derivatives, aliphatic ethers, phenanthrene, and fluorene can be used. The above-mentioned waxes can also be used as a sensitizer.

 These are dispersed and applied in a binder.

Water-soluble binders are generally used, and polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, Polyacrylic acid,
Examples include starch derivatives, casein, gelatin and the like.
For the purpose of imparting water resistance to these binders, a water-resistant agent (gelling agent, cross-linking agent) may be added, or an emulsion of a hydrophobic polymer, specifically, a styrene-butadiene rubber latex, an acrylic resin emulsion or the like may be used. Can be added.

As an 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 rod coater, and a curtain coater can be used.

Further, in order to improve the surface smoothness of the coated product, an apparatus such as a machine calender, a super calender, a gloss calender, and 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 g / m ² , preferably 4 to 15 g in dry weight.
It is in the range of 10 g / m ² .

Note that a protective layer may be provided on the heat-sensitive layer for solvent resistance and the like.

(E) Action By containing specific spherical porous inorganic particles in the heat-sensitive coloring layer, the heat-sensitive recording material has high sensitivity even at low energy, little adhesion of head residue, and little decrease in density even when printing at high energy. Can be obtained.

As a cause of the effect, in addition to the color development sensitivity being improved because the energy from the thermal head can be effectively used due to the heat insulating properties of the specific spherical porous inorganic particles, the shape is spherical, and especially It is considered that when the particles having a particle diameter of 3 μm or less are used, the smoothness is improved, the sensitivity is improved, and a uniform image can be obtained. In addition, because it is porous, it quickly absorbs the heat-sensitive recording composition that has melted when heated, suppresses the generation of head scum, and has the effect of preventing excessive penetration of the melt. Conceivable.

(F) Examples Examples of the present invention will be shown below, but the present invention is not limited to these examples.

In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

Examples 1 and 2. Calcined kaolin (George Akao phosphoric acid, Astrapaque) alone or spherical porous silica (Suzuki Yushi Kogyo, E-
2C) and dispersed in an aqueous solution of sodium hexametaphosphate in the ratio shown in Table 1 to obtain a 45% slurry. And 20
% Phosphated starch aqueous solution (manufactured by Japan Food Processing Co., Ltd., MS46
00) 15 parts, SB latex (Nippon Synthetic Rubber, JSR069)
Add 15 parts of 2) and mix well.

Coating was performed on a high-quality paper having a basis weight of 50 g / m ^{2 so that} the coating amount of the solid content was 8 g / m ² , followed by drying to obtain an intermediate layer coated paper.

5 g of 3-N, N-diethylamino-6-methyl-7-anilinofluoran as a color former was dispersed with 25 g of 5% polyvinyl alcohol (manufactured by Kuraray, PVA-105) in a ball mill for 24 hours to obtain a color former dispersion. .

10 g of bisphenol A as a color developer and 10 g of stearic acid amide as a sensitizer were mixed and dispersed with 100 g of 5% polyvinyl alcohol in a ball mill for 24 hours to obtain a dispersion of the color developer and the sensitizer.

Spherical porous silica (Suzuki Yushi Kogyo, E-
2C) 10 g of sodium hexametaphosphate 0.5% aqueous solution 40 g
The resulting mixture was dispersed in a homogenizer to obtain a pigment dispersion.

The above color former, developer, sensitizer and pigment dispersion were mixed, and 5 g of a 30% solution of zinc stearate was added to obtain a heat-sensitive coating liquid. The solution to the above intermediate layer coated paper, after coating and dried so as to the coating amount as the solid content is 5 g / m ^2, Bekk smoothness is 300sec
A super calendar was applied so that it could enter from 500 seconds to obtain a sample.

Sample is made by Okura Electric Co., Ltd., thermal printing test equipment (THPMD)
, A solid black print was made under the conditions of 18 msec / 1ine, pulse width 0.8 msec, 1.0 msec, and the density was measured with a Macbeth reflection densitometer. At the same time, the dirt on the thermal head after printing was checked, and The test was performed in four stages of Δ and ×. The results are shown in Table 1.

Example 3 In Examples 1 and 2, the pigment used for the intermediate layer was only calcined kaolin (Astrapek), and spherical porous hollow silica (Suzuki) was used instead of the spherical porous silica (E-2C) used for the heat-sensitive coating solution. A heat-sensitive sample was obtained in the same manner except that B-6C) was used. The mixing ratio and evaluation result are the first
It is shown in the table.

Example 4 In Examples 1 and 2, the pigment used for the intermediate layer was only calcined kaolin (Astrapek), and the specific surface area was changed in place of the spherical porous silica (E-2C) used for the heat-sensitive coating solution.
A heat-sensitive sample was obtained in the same manner except that 150 m ² / g of spherical porous calcium carbonate (char A) was used. Table 1 shows the evaluation results.

Comparative Examples 1 and 2 In Example 3, spherical porous hollow silica (B-6C)
Instead of light calcium carbonate (Shiraishi Kogyo, Brt-1
5) Alternatively, a heat-sensitive sample was obtained in the same manner except that calcined kaolin (Engelhard, Ansilex) was used.

 Table 1 shows the formulation and evaluation results.

Comparative Example 3 A heat-sensitive sample was obtained in the same manner as in Examples 1 and 2, except that the heat-sensitive coating liquid was applied directly to high quality paper instead of the intermediate layer coated paper. Table 1 shows the evaluation results.

Comparative Example 4 A heat-sensitive sample was obtained in the same manner as in Comparative Example 3 except that light calcium carbonate (Brt-15, manufactured by Shiraishi Kogyo) was used instead of the spherical porous silica (E-2C).

 Table 1 shows the evaluation results.

(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-forming sensitivity and little generation of scum.

Continuation of the front page (56) References JP-A-62-222887 (JP, A) JP-A-62-176878 (JP, A) JP-A-57-189884 (JP, A) JP-A-62-149475 (JP) JP-A-63-60103 (JP, A) JP-A-62-240580 (JP, A) JP-B-61-56118 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB Name) B41M 5/28-5/34

Claims (3)

(57) [Claims] An at least one coating layer comprising a pigment and an adhesive as a main component is provided on at least one surface of a support, and a color former and a color developer which comes into contact with the color former are provided thereon. And a heat-sensitive recording material provided with a coloring layer containing spherical porous inorganic particles having a total pore volume of 0.4 ml / g or more and an average diameter of surface pores of 0.005 μ or more. 2. The heat-sensitive recording material according to claim 1, wherein the spherical porous inorganic particles have an average particle size of 3 μm or less and a specific surface area of 200 m ² / g or more. 3. The heat-sensitive recording material according to claim 1, wherein the spherical porous inorganic particles are hollow.