JPH07102740B2 - Thermal recording material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a recording material having high sensitivity; that is, high printing density with low printing energy and high image quality.

(Prior Art) Recording materials using an electron-donating dye precursor and an electron-accepting compound are pressure-sensitive recording paper, heat-sensitive recording paper, photosensitive pressure-sensitive recording paper,
It is well known as an electrically conductive recording paper.

For example, British Patent 2140449, U.S. Patent 4480052, U.S. Pat. No. 4,436,920, JP-B-60-23922, JP-A-57-179836, 60-123556, 60-.
Detailed in 123557 etc.

The recording material should have (1) sufficient color density and color sensitivity, (2) good dot reproducibility, excellent graininess and gradation, and (3) no fog. , (4) Sufficient fastness of the coloring material after coloring, (5) Appropriate coloring hue and suitability for copiers (6) High S / N ratio, (7) Resistance of coloring material Although it has sufficient chemical properties, there is currently no product that completely satisfies these requirements.

Various recording methods have been studied in order to solve these problems, but among them, the development of thermal recording materials is remarkable. For thermal recording materials, higher sensitivity,
That is, there is a demand for a recording material that can obtain a sufficient density with low printing energy. Further, in recent years, since a thermal paper is used for outputting a high-quality image comparable to a silver halide photograph, a high-quality thermal paper having improved dot reproducibility of a print head has been demanded.

In order to meet such demands for high sensitivity and high image quality, methods such as improving the thermal responsiveness of the thermosensitive coloring layer material and improving the smoothness of the recording paper surface to increase the adhesion between the thermal head and the recording paper are being investigated. However, there is a limit to each method, and no satisfactory method has been obtained.

(Object of the Invention) An object of the present invention is to obtain a thermal recording material which can obtain a high printing density with a low printing energy, has good dot reproducibility of a print head, and is free from problems such as head stain.

(Structure of the Invention) As a result of intensive studies to solve the above problems, the present inventors have found that in a heat-sensitive recording material in which a heat-sensitive recording layer is provided on a support, it is provided between the support and the heat-sensitive recording layer. The object of the present invention has been achieved by providing a microporous layer containing a synthetic resin and / or a cellulose derivative as a main component as an intermediate layer.

If the intermediate layer used in the present invention is a microporous layer containing a synthetic resin and / or a cellulose derivative as a main component,
Any object can achieve the object of the present invention.
Such an intermediate layer can be prepared by casting a solution of a synthetic resin and / or a cellulose derivative in a thin layer on a support, and then removing or exchanging the solvent under appropriate controlled conditions. The thickness of the microporous intermediate layer is 1-10.
0 μm is preferable, and 5 to 50 μm is more preferable. The pore size of the microporous intermediate layer is preferably 0.05 to 1000 μm, more preferably 0.1 to 200 μm.

In this case, as the support on which the solution of the synthetic resin and / or the cellulose derivative is cast, any paper that is commonly used in the field of heat-sensitive recording materials, or any common material such as synthetic resin film can be used. be able to. As specific examples, JP-A-61-297760, 62-41082 and 62-51.
No. 478, No. 62-53879, No. 62-73991, etc.

Also, microporous membranes have been known for a long time, and the book written by R. Kesting is “Synthetic Polymer Membrane”.
For details, see s "McGraw-Hill, Inc. (1971).

For the material of the microporous layer, for example, U.S. Patent No. 1,421,
No. 341, No. 3,133,132, No. 2,944,017, Japanese Patent Publication 43-156
No. 98, No. 45-33313, No. 48-39586, those containing cellulose ester as a main component as described in No. 48-40050, etc., U.S. Patent Nos. 2,783,894, 3,408,315,
No. 4,340,479, No. 4,340,480, No. 4,450,126, German Patent DE 3,138,525, those containing an aliphatic polyamide as a main component as described in JP-A-58-37842,
U.S. Pat.Nos. 4,196,070 and 4,340,482, JP-A-55-99
No. 934, JP-A No. 58-91732, etc. containing polyfluorocarbon as a main component, JP-A No. 56-
154051, 56-86941, 56-12640, etc. containing polysulfone as a main component, German patent
Those containing polypropylene as the main component described in OLS 3,003,400, those containing nylon as described in Japanese Examined Patent Publication No. 49-8707, and polyvinylidene chloride, polyvinyl alcohol, etc. as the main components The following are known, and the effects of the present invention can be obtained by using any of them, but those containing a cellulose acetate derivative as a main component are particularly preferable.

Next, the thermosensitive color developing layer coating liquid used in the present invention will be described.

The thermosensitive color developing layer coating liquid is prepared by dispersing an electron-donating dye precursor (color former) and an electron-accepting compound (developing agent) separately in water together with a water-soluble polymer to obtain the resulting color former and developer. The dispersions of the agents are mixed and further prepared by adding inorganic and / or organic pigments, waxes, metal soaps and the like as required.
Generally, the coating amount of the color former is 0.2 to 2.0.
It is coated on the support provided with the porous layer so as to be g / m ² .

In addition, the surface of the support provided with the porous layer is subjected to corona discharge treatment, glow discharge treatment, ultraviolet irradiation, acid etching treatment with a mixed solution of chromium nitrate, flame treatment with a gas flame, etc. before applying the heat-sensitive layer coating liquid. It is preferable to do so in order to strengthen wetting and adhesion with the thermosensitive coloring layer. Further, in order to obtain high smoothness of the surface, an intermediate layer containing a pigment, a binder or the like as a main component may be provided between the surface of the microporous layer and the thermosensitive coloring layer.

Examples of the color former used in the present invention include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds and the like. Specific examples include those described in JP-A-55-227253. If some of these are shown, the triarylmethane compound is 3,3-
Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl)-
3- (1,3 dimethylindol-3-yl) phthalide,
There are 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide and the like, and as diphenylmethane compounds, 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N- There are halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, and the like, and xanthene-based compounds include rhodamine-B-anilinolactam, rhodamine- (p-nitrino) lactam, 2- (di- Benzylamino) fluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6
-Dibutylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-
Cyclohexylaminofluorane, 2-anilino-3-
Chlor-6-diethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-isobutylaminofluorane, 2-anilino-6-dibutylaminofluorane, 2-anilino-3-methyl-6- N-methyl-N
-Tetrahydrofurfurylaminofluorane, 2-anilino-3-methyl-6-piperidinoaminofluorane,
There are 2- (o-chloroanilino) -6-diethylaminofluorane, 2- (3,4-dichloroanilino) -6-diethylaminofluorane, and the like, and as the thiazine-based compound, benzoyl leucon methylene blue, p-nitrobenzyl leuco There are methylene blue and the like, and spiro compounds include 3-methyl-spiro-dinaphthopyran and 3-
Ethyl-spiro-dinaphthopyran 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho- (3-methoxy-benzo) -spiropyran, 3-propyl-spiro-dibenzopyran, etc. .

Phenolic compounds or salicylic acid derivatives and polyvalent metal salts thereof are preferable as the color developer used in the present invention.
Some examples of these are, as phenolic compounds, 2,2'-bis (4-hydroxyphenyl) propane, 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, 1,1 '. -Bis (3
-Chloro-4-hydroxyphenyl) cyclohexane,
1,1′-bis (4-hydroxyphenyl) cyclohexane, 1,1′-bis (3-chloro-4-hydroxyphenyl) -2-ethylbutane, 4,4′-sec-isooctylidenediphenol, 4, 4'-sec-butylidene diphenol, 4-tert-octylphenol, 4-p-methylphenylphenol, 4,4'-methylcyclohexylidenephenol, 4,4'-isopentylidenephenol, p
-Benzyl hydroxybenzoate and the like. Examples of salicylic acid derivatives include 4-pentadecylsalicylic acid, 3,5-di (α-methylbenzyl) salicylic acid, 3,5-di (ter-octyl) salicylic acid, 5-octadecylsalicylic acid, and
-Α- (p-α-methylbenzylphenyl) ethylsalicylic acid, 3-α-methylbenzyl-5-ter-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyl Oxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4
-Octadecyloxysalicylic acid, etc., and their zinc, aluminum, calcium, copper and lead salts. These color developers are preferably used in an amount of 50 to 800% by weight, more preferably 100 to 500% by weight of the color former. 50
If the content is less than 100% by weight, the color development is not sufficient, and if more than 800% by weight is added, no further effect can be expected, which is not preferable.

The heat-sensitive recording material of the present invention may contain a heat-fusible substance in the heat-sensitive color forming layer in order to improve its thermal response. Examples of preferable heat-fusible substances include benzyl p-benzyloxybenzoate, β-naphthyl-benzyl ether, stearamide, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane,
Di (2-methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α-naphthylbenzylether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropyl Phenyl ether, 1,4-butanediol-p-tert-
Octyl phenyl ether, 1-phenoxy-2- (4
-Ethylphenoxy) ethane, 1-phenoxy-2-
(4-chlorophenoxy) ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis (4
-Methoxyphenyl) ether and the like. The heat-fusible substance may be used alone or as a mixture, and in order to obtain sufficient thermal response, it is preferable to use 10 to 300% by weight with respect to the developer, and more preferably 20 to 20.
It is 0% by weight.

In the present invention, the color-developing agent, the color-developing agent and the heat-fusible substance are dispersed in a water-soluble binder. The binder used in the present invention is 5% by weight or more soluble in water at 25 ° C. Compounds are preferable, and specifically, polyvinyl alcohol (including modified polyvinyl alcohol such as carboxy-modified, itaconic acid-modified, maleic acid-modified, silica-modified and the like), methyl cellulose, carboxymethyl cellulose, starches (including modified starch), gelatin, Examples thereof include gum arabic, casein, hydrolyzate of styrene-maleic anhydride copolymer, polyacrylamide, and saponified product of vinyl acetate-polyacrylic acid copolymer. These binders are used not only for dispersion but also for the purpose of improving the coating strength.
A latex binder of a synthetic polymer such as a butadiene copolymer, a vinyl acetate copolymer, an acrylonitrile / butadiene copolymer, a methyl acrylate / butadiene copolymer, or polyvinylidene chloride can be used together. Further, if necessary, a crosslinking agent for a suitable binder may be added depending on the kind of the binder.

As the pigment, calcium carbonate, barium sulfate, lithopone, wax, kaolin, silica, amorphous silica and the like are used.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, and aluminum stearate. As the wax, paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene wax, fatty acid amide wax, etc. may be used alone or in combination.

Further, if necessary, a surfactant, an antistatic agent, an ultraviolet absorber, an antioxidant, an antifoaming agent, a conductive agent, a fluorescent dye, a coloring dye, etc. may be added.

Further, it is preferable to add an anti-color erasing agent in the heat-sensitive color developing layer in order to prevent decoloring of the image printed portion and to make the generated image fast. Phenol compounds, particularly hindered phenol compounds, are effective as anti-decoloring agents.
1,3-Tris (2-methyl-4-hydroxy-tert-butylphenyl) butane, 1,1,3-Tris (2-ethyl-
4-hydroxy-5-tert-butylphenyl) butane,
1,1,3-Tris (3,5-di-tert-butyl-4-hydroxyphenyl) butane, 1,1,3-Tris (2-methyl-4)
-Hydroxy-5-tert-butylphenyl) propane,
2,2'-methylene-bis (6-tert-butyl-4-methylphenol), 2,2'-methylene-bis- (6-tert
-Butyl-4-ethylphenol), 4,4'-butylidene-bis (6-tert-butyl-3-methylphenol), 4,4'-thio-bis- (3-methyl-6-tert-)
Butylphenol), and the like. The amount of such a phenolic compound used is preferably 1 to 200% by weight, more preferably 5 to 50% by weight, based on the electron-accepting compound.

The applied heat-sensitive recording material is dried and treated with a calender or the like before use.

Further, a protective layer may be provided on the heat-sensitive recording layer, if necessary. Any known protective layer can be used as the protective layer for the heat-sensitive recording material.

Further, if necessary, a back coat layer may be provided on the surface of the support of the heat-sensitive recording material opposite to the heat-sensitive recording layer. As the back coat layer, any one known as a back coat layer of a heat-sensitive recording material can be used.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.

(Example 1) A homogeneous mixed solution having the following composition was prepared and cast on a high quality paper using a doctor blade, and then at room temperature for 2 hours, followed by 80
After drying at 30 ° C. for 30 minutes, a microporous layer having a coating layer thickness of about 20 μm was formed.

Next, 2-anilino-3-methyl-6-Nethyl-Nisoamylaminofluorane, benzyl parahydroxybenzoate, β-naphthyl-benzyl ether, 20 g each to 100 g
With a 5% aqueous solution of polyvinyl alcohol (Kuraray PVA105) in a ball mill all day and night to give an average particle size of 1.5 μm.
Below, each dispersion was obtained. Also calcium carbonate
80 g was dispersed together with 160 g of 0.5% sodium hexametaphosphate solution with a homogenizer to obtain a pigment dispersion.

These dispersions were mixed with the following composition to obtain a thermosensitive coloring layer coating solution.

This thermosensitive color developing layer coating liquid was applied to the porous layer provided on the high-quality paper using a coating bar so that the dry weight of the coating layer was 5 g.
It was coated so as to be / m ² and dried at 50 ° C. for 1 minute to obtain a heat-sensitive recording sheet.

(Example 2) A homogeneous mixed solution having the following composition was prepared, cast on a high-quality paper, covered with an upper part for 2 seconds, and then allowed to stand in air at room temperature for several seconds, and then water at 20 ° C was removed. Dip it into the coagulation bath
The solvent was removed and dried to form a microporous layer having a coating layer thickness of about 20 μm.

The thermosensitive color developing layer coating solution obtained in Example 1 was coated on the porous layer provided on the high-quality paper using a coating bar so that the dry weight of the coating layer was 5 g / m ² , and at 50 ° C. It was dried for 1 minute to obtain a heat-sensitive recording sheet.

(Example 3) On the microporous layer obtained in Example 1, a coating solution having the following composition was further applied using a coating bar so that the dry coating amount was 5 g / m ² , and 50 It dried at 1 degreeC for 1 minute, and provided the 2nd intermediate | middle layer.

The thermochromic layer coating solution obtained in Example 1 was applied onto the second intermediate layer using a coating bar so that the dry weight of the applied layer was 5 g / m ^2, and dried at 50 ° C. for 1 minute. A thermosensitive recording sheet was obtained.

(Example 4) A thermosensitive recording sheet was obtained in the same manner as in Example 1 except that the support was replaced with synthetic paper (Yupo, manufactured by Oji Yuka).

Example 5 A thermal recording sheet was obtained in the same manner as in Example 1 except that the support was replaced by a polyester film instead of the high-quality paper.

(Comparative Example 1) The thermosensitive color developing layer coating solution obtained in Example 1 was directly applied to a fine paper without a microporous layer using a coating bar so that the dry weight of the coating layer was 5 g / m ^2. And then dried at 50 ° C. for 1 minute to obtain a heat-sensitive recording sheet.

(Comparative Example 2) The coating liquid having the composition obtained in Example 3 was applied on a high-quality paper using a coating bar so that the dry weight of the coating layer was 5 g / m ² , and dried at 50 ° C for 1 minute. Further, the thermosensitive color developing layer coating solution obtained in Example 1 was applied thereon by using a coating bar so that the dry weight of the coating layer was 5 g / m ² , and the temperature was 50 ° C. for 1 hour.
After drying for a minute, a heat sensitive recording sheet was obtained.

(Comparative Example 3) A thermosensitive recording sheet was obtained in the same manner as in Comparative Example 1, except that synthetic paper (Yupo, manufactured by Oji Yuka) was used as the support instead of the high-quality paper.

The thermal recording sheet obtained as described above is surface-treated with a calender, and the thermal head (KL
T-216-8MPD1) thermal printing experimental device, the pulse width was set under the conditions of head voltage 24V and pulse cycle 10ms.
Printing was carried out at 0.8, 1.0 and 1.2, and the printing density was measured by a Macbeth reflection densitometer RD-918.

In addition, the amount of dust on the head after printing (head contamination)
Was also measured at the same time.

The results are shown in Table 1 on the next page.

As shown in Table 1, the thermal recording sheet according to the present invention showed good color density even at low energy, good dot reproducibility, and good performance without head stain.

Claims (2)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer provided on a support, wherein the intermediate layer between the support and the heat-sensitive recording layer is a microporous material containing a synthetic resin and / or a cellulose derivative as a main component. A heat-sensitive recording material having a layer. 2. A heat-sensitive recording material characterized in that the intermediate layer according to claim 1 is a microporous layer made of a cellulose acetate derivative.