JPH0664329A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a high transparency and a suitability for high-speed copying without lowering a coloring density by a method wherein in a thermal recording material provided with a thermal recording layer on a top surface of a translucent substrate, a binder is used by a specific ratio (wt.%) to the other components. CONSTITUTION:In a thermal recording material, a thermal recording layer is provided on a top surface of a translucent substrate. In this invention, a binder is used by 20-150wt.% to the other components. In this manner, the binder inhibits that the material becomes opaque, which is caused by a light confusion occurring at an interface of fine particles of the thermal recording layer with the air, without reducing the heat sensitivity of the thermal recording layer. Therefore, this translucent recording material has a high transparency and a suitability for high-speed diazo copying without generating a coloring density reduction caused by the addition of the binder.

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 having excellent recording suitability and transparency and having excellent stability.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording material has an electron-donating compound and an electron-accepting compound (hereinafter referred to as a color developer).
It is known to use a recording material containing a diazonium salt and a coupler (and a base if necessary), and is widely used as a recording material for facsimiles and printers.

The performance that these thermal recording materials should have is as follows:
Sufficient color density and color sensitivity, excellent image quality of the color image, no fog, sufficient storage of the color material after color development, good runnability in facsimile and printer That is.

Further, in addition to the performance which a thermal recording material using a semitransparent support should have as a normal thermal recording material, high speed printing is also carried out by a contact transmission latent image forming method (for example, diazo copy) using this recording medium as an original. It is required that the background part be transparent and the printed part be opaque.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material having high transparency in an unprinted portion and excellent suitability for high speed copying in a contact transmission latent image forming method (for example, diazo copy).

[0006]

As the translucent support used in the present invention, a plastic film, tracing paper made by beating, or impregnated tracing paper or glassine paper obtained by impregnating high-quality paper with resin is used. To be Although a plastic film has high smoothness and sufficient transparency, it has a problem in foldability and coating suitability. Further, the tracing paper produced by beating has sufficient transparency, but has a problem in smoothness after coating the heat-sensitive recording layer. The semitransparent support used in the present invention is preferably impregnated tracing paper or glassine paper obtained by impregnating high-quality paper with resin. Further, when a diazo copy or the like is taken after being printed with a pencil and rubbed with an eraser after printing, it is preferable that the change in transparency due to these is small, so that an opacity of 30 to 70% (JISP813
A semi-transparent support having a measurement method of 8) is preferred. Further, in order to maintain high smoothness after coating the thermosensitive recording layer, the Bekk smoothness of the semitransparent support is preferably 150 seconds or more, and particularly preferably 300 seconds or more.

In the present invention, at least two kinds of components undergo a chemical reaction during recording to develop color. In this case, generally, two or more kinds of heat-reactive compounds are dispersed in the form of fine particles, and a binder or the like is mixed therewith, and each heat-reactive compound is coated on a support so as to be separated by the binder or the like. One or both are melted and brought into contact with each other by heating to cause a color reaction. In this case, the heat-reactive compound may be either a combination of an electron-donating compound and a color developer or a combination of a diazo compound and a coupler (and a base if necessary). The most widely used combination among these is a combination of an electron-donating compound and a color developing agent, and although there are a great many kinds of combinations, they are roughly classified to form an image of a metal compound. It is divided into those forming a dye image.

To form an image of a metal compound, phenols and other organic reducing agents, chelating agents, sulfur compounds, amino compounds and the like are used as electron donating compounds, and organometallic salts are used as electron accepting compounds. There is something I did. Both of these react with each other by heating to produce a metal, a metal complex compound, a metal sulfide, and the like, thereby forming a colored image. Specifically, a combination of thiourea and a heavy metal salt (US Pat. No. 2,740,895), a combination of gallic acid and the like and a stearic acid metal salt (US Pat. No. 2,663,363).
654-7), a combination of hydroquinone and silver behenate (US Pat. No. 3,031,329), a combination of hexamethylenetetramine and a tin compound (US Pat. No. 2,8).
13, 043) etc.

In the case of forming a dye image, there is one in which an electron-donating dye precursor is used as an electron-donating compound and a phenol or other acidic substance is used as a developer (Japanese Patent Publication No. 43-4,160). Issue, Japanese Patent Publication No. 44-3,680
issue). The electron-donating dye precursor is not particularly limited, but is usually colorless, having a property of developing electrons by donating electrons or by accepting protons such as acids, lactone, lactam, sultone, A compound having a partial skeleton such as spiropyran, ester, amide, etc., which is opened or cleaved by a partial contact with a developer is used. Specifically, crystal violet lactone, benzoyl leuco methylene blue, malachite green lactone, rhodamine B lactam, 1,3,3-
Trimethyl-6-ethyl-8-butoxyindolinobenzospiropyran, 3-propyl-3-methylamino-6
-Methyl-7-anilinofluorane and the like.

The color developer for these color-developing agents can be appropriately selected and used from known ones. For example, as a developer for a leuco dye, a phenol compound, a sulfur-containing phenol compound, a carboxylic acid compound,
Examples thereof include sulfone-based compounds, urea-based or thiourea-based compounds, and the details thereof are described in, for example, Paper Pulp Technology Times (1985), pages 49-54 and 65-70. In the present invention, among these, those having a melting point of 50 ° C. to 250 ° C. are preferable, and among them, 60 ° C. to 2
Phenols and organic acids that are sparingly soluble in water at 00 ° C are desirable. When two or more developers are used in combination, the solubility increases, which is preferable. Particularly preferable developers among the developers used in the present invention are represented by the following general formulas (1) to (4).

[0011]

[Chemical 1]

M is an integer of 0 to 2, and n is an integer of 2 to 11.

[0013]

[Chemical 2]

R ₁ represents an alkyl group, an aryl group, an aryloxyalkyl group or an aralkyl group, and a methyl group and a butyl group are particularly preferable.

[0015]

[Chemical 3]

R ₂ represents an alkyl group. Especially the butyl group,
Pentyl, heptyl and octyl groups are preferred. R
₃ represents a hydrogen atom or a methyl group, and n is 0-2.

[0017]

[Chemical 4]

R ₄ represents an alkyl group, an aralkyl group or an aryloxyalkyl group.

On the other hand, the diazo compound reacts with a coupler called a coupling component described later to develop a desired hue. In addition, it decomposes when it receives light of a specific wavelength before the reaction, and after that, it no longer has the ability to develop color even if the coupling component acts.Therefore, the diazo compound in the non-image area is photolyzed to fix the recorded image. You can

The hue in this coloring system is mainly determined by the diazo dye produced by the reaction of the diazo compound and the coupling component. Therefore, as is widely known, the coloring hue can be easily changed by changing the chemical structure of the diazo compound or the chemical structure of the coupling component, and almost any coloring hue can be obtained depending on the combination. You can

The photodecomposable diazo compound as used herein mainly refers to an aromatic diazo compound, and more specifically, a compound such as an aromatic diazonium salt, a diazosulfonate compound or a diazoamino compound.

The coupler for the diazo compound used in the present invention is a coupling component which forms a dye by coupling with a diazo compound (diazonium salt). Specific examples thereof include 2-hydroxy-3-naphthoic acid anilide and resorcin.
The thing described in -146678 can be mentioned. Further, by using two or more of these coupling components in combination, an image with any color tone can be obtained.

Since the coupling reaction between the diazo compound and the coupling component easily occurs in a basic atmosphere, a basic substance may be added in the layer. As the basic substance, a hardly water-soluble or water-insoluble basic substance or a substance which generates an alkali by heating is used. Examples thereof are inorganic and organic ammonium salts, organic amines, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines. And nitrogen-containing compounds such as piperidines, amidines, formazines and pyridines. Specific examples of these are described in, for example, JP-A-61-2911.
No. 83. Two or more basic substances may be used in combination.

These two-component color-developing heat-sensitive recording materials are
It is usually used as a heat-sensitive recording sheet from the viewpoints of (1) primary color development and no need for development, and (2) easy handling. In particular, the one using the dye precursor as the electron-donating compound has a higher (3) color density.
(4) The thermosensitive recording materials of the respective coloring hues are easy to obtain and have great utility.

Since the present heat-sensitive recording medium is used as an original image in a contact transmission latent image forming method (for example, diazo copy), a combination in which the transparency of the background portion is high and the transparency of the printing portion is low is appropriately selected at the wavelength of printing light. it can. In the present invention, the electron donating compound or the diazo compound may be encapsulated in microcapsules in order to improve the raw storage stability and the record storage stability of the heat-sensitive recording material.
Details of preferable microcapsules and microencapsulation in this case are described in, for example, JP-A-63-63.
60787 and 63-92489.

Further, the coating liquid may contain a heat-fusible substance. The inclusion of this heat-fusible substance is preferable because it increases the color development rate and enables recording at a lower temperature. The heat-fusible substance is the temperature at which the heat-sensitive recording sheet is used (usually 100 to 300 ° C.), for example, waxes such as paraffin wax, carnauba wax, microcrystalline wax, stearamide, lower polyethylene, phenanthrene, acetanilide,
Examples thereof include biphenyl, benzyl, N, N-dimethyl-p-toluenesulfonamide, p-toluenesulfonamide and the like. These can be used alone or in combination. When both the color former and the developer have a high melting point for the desired color development temperature, it is desirable that the heat-fusible substance to be used is compatible with both the color former and the developer. . Further, when at least one of the color former and the developer is heat fusible, it is not always necessary to include the heat fusible substance.

The coating solution further contains kaolin, calcium carbonate, silica, zinc oxide, talc, urea-formalin resin, etc. as a retainer for the heat-fusible substance (heat-melted substance) or as an anti-sticking agent for the thermal head. Can be made. The amount of the holding agent added is 0 to 3 of the heat fusible substance.
It is 00% by weight.

In the present invention, it was found that the binder has the effect of improving transparency in addition to the isolation of the heat-reactive substance. The binder can be selected from the following viewpoints. (1) The absorbance at 1 mol / l at the printing light wavelength is 0.1 or less, and (2) the film after drying alone is transparent. Examples of binders that can be used as a main component of 90% or more in the present invention include styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, sodium polyacrylate, polyvinyl alcohol, styrene-butadiene rubber latex, vinyl acetate latex, acrylonitrile- Examples of the film-forming substance include synthetic polymer substances such as butadiene rubber latex and methyl acrylate-butadiene rubber latex. These binders can be used alone or in combination. Further, in the case of a water-soluble polymer, a lower molecular weight allows a higher concentration to be used, which is advantageous from the viewpoint of productivity. Further, it is preferable that the latex has a minimum film forming temperature of 25 ° C. or lower in view of transparency during film formation.

The amount of the binder added in the present invention is preferably small in order to improve the thermal sensitivity at the time of heat-sensitive recording, but is preferably large in order to improve the transparency. In order to achieve both, the binder in the thermosensitive recording layer
It is preferable to add 20 to 150% by weight, and particularly preferably 30 to 80% by weight, to components other than the above.

It is important that none of the binder, the heat-fusible substance and the holding agent as described above substantially causes a color-forming reaction with the color-forming agent and the color-developing agent. Specifically, one of a color former or a developer and a binder, a heat-fusible substance or a holding agent are mixed at an arbitrary ratio and dried at 120 ° C. or below,
It is preferable that the reflection density (V.D. visual density) is 0.20 or less.

The coating solution is used in an amount of 50 to 2,000 parts by weight, preferably 100 to 1,50 parts by weight of the developer or coupling component, based on 100 parts by weight of the electron-donating compound or diazo compound.
0 parts by weight and 50-4,000 parts by weight of filler are prepared. Further, a trace amount of coating aid can be contained as necessary. The filler may be the same as the retention agent.

The coating amount of the heat-sensitive recording layer is not particularly limited, but it is usually in the range of ^{2 to} 15 g / m ² , preferably 3 to 12 g / m ^{2 in} dry weight. Incidentally, in order to further enhance the stability of the recorded image and to improve the scratch resistance and the running property, it is possible to add various conventionally known techniques such as providing an overcoat layer. As a coating method, all conventionally known methods can be used.

[0033]

In the present invention, it is considered that the added binder has a function of suppressing opacity due to light scattering generated at the interface between the fine particles in the thermal recording layer and the air without reducing the thermal sensitivity of the thermal recording layer.

[0034]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. In the examples, "part" means "part by weight" and "%" means "% by weight".

Example 1 20 parts of 3-propyl-3-methylamino-6-methyl-7-anilinofluorane was added to 1 part.
It was dispersed in a ball mill for 24 to 48 hours together with 00 parts of a 3% PVA205 (manufactured by Kuraray Co., Ltd.) aqueous solution to give an average particle size of 0.
A 9 μm dispersion was obtained. Furthermore, together with 40 parts of bisphenol A and 200 parts of a 3% PVA205 aqueous solution, 24-48.
The mixture was dispersed by a ball mill for an hour to obtain a dispersion liquid having an average particle size of 0.9 μm. In addition, 30 parts of calcium carbonate (manufactured by Shiraishi Calcium Co .; Univer 70) was added with sodium hexametaphosphate
A pigment dispersion was obtained by dispersing with a homogenizer together with 100 parts of a 5% aqueous solution. The dispersions thus obtained were mixed, and 50 parts of 21% zinc stearate emulsion and 15% PVA103 (manufactured by Kuraray Co., Ltd.) aqueous solution were added as shown in Table 1 to give an opacity of 60% and smoothness. The amount of the coloring agent applied was 0.7 g / m ² on the base paper at a speed of 500 seconds, and the surface smoothness was raised to about 700 seconds through a gross calender with a linear pressure of 100 kg / cm. 1 to
Got 5. Comparative Example 1 Compared to Example 1, 15% PVA103
Comparative Example 1 was obtained in exactly the same manner except that was not added. <Examples 6 to 9> Compared with Example 1, 15% PVA1
Example 6 was carried out in the same manner as in Example 6 except that an aqueous solution of 40% polyacrylic acid Na-maleic acid Na copolymer (Poise 520; Kao Corporation) was added instead of 03 as shown in Table 1.
~ 9 was obtained.

[Quality Evaluation Test Method] (1) Opacity Measured according to the JISP8138 method. The lower the number, the higher the transparency. (2) Color density The semitransparent heat-sensitive recording material was pressed against a hot plate at 120 ° C. for 5 seconds at a pressure of ² kg / m ² to develop color, and the color density was measured with a Macbeth densitometer (Macbeth RD-914R type). The higher the value, the higher the color density. (3) Background density The background part of the semitransparent thermal recording material was measured with a Macbeth densitometer. The lower the number, the less the stains and the better. (4) High speed suitability of diazo A semitransparent recording material was used as an original, and diazo copy was performed using Recopy SD-480 type, and the speed at which the background of the diazo copy reached a density of 0.20 was examined by a Macbeth densitometer. The lower the number, the higher the speed suitability.

[0037]

[Table 1]

[0038]

As is clear from the results of Table 1, the semitransparent recording material of the present invention has high transparency and suitability for high-speed copying of diazo copy without causing a decrease in color density due to addition of a binder. .

Claims (1)

[Claims] 1. A recording material having a thermosensitive recording layer provided on a semitransparent support, wherein a binder is added to the other components in an amount of 2%.
A heat-sensitive recording material characterized by being used in an amount of 0 to 150% by weight.