JPS592888A - Diazo-based heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain a diazo-based heat-sensitive recording material having a high chromogenic property and good storage stability by a method in which a diazo layer and a coupler layer are laminated on a supporter, a heat-meltable substance and a binder are added to the lower layer, and ester of imidazol carboxylic acid is added to the other layer. CONSTITUTION:A coating liquid composed of a diazo compound, a heat-meltable substance (e.g., N-stearylbenzamide), and a water-insoluble binder(e.g., vinyl chloride-vinyl acetate copolymer) and a coating liquid composed of a coupler (e.g., naphthol AS) and 0.5-10pts.wt. (based on diazo compound) ester of imidazole carboxylic acid (e.g., diethyl 2-ethyl-4,5-imidazole dicarboxylate) are orderly coated on a supporter and dried to obtain an objective recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, particularly a heat-sensitive recording material that can be photofixed. That is, the present invention provides a diazo-based thermosensitive recording material that develops color when recorded with a thermal head at a certain temperature, loses its ability to develop color in non-printed areas when further irradiated with light, and does not recolor when heated again. It is related to.

In addition to being used as copy paper for books and documents, thermosensitive recording materials are also used as output recording paper for computers, facsimile machines, medical measuring machines, etc., as well as thermal recording magnetic ticket paper and thermal recording label paper. be done. In addition, heat-sensitive recording materials are also being considered for use as paper for creating securities, gift certificates, admission tickets, certificates, slips, etc. by taking advantage of their ease of automatic recording. In order to obtain high recording reliability, the heat-sensitive recording material must be able to be fixed.

Conventionally, as fixable heat-sensitive recording materials, diazo-based materials that utilize a color-forming reaction between a diazo compound and a coupler are known. However, from the standpoint of practicality, conventional products have not yet been satisfactory in terms of thermal response to thermal heads and long-term storage stability. In particular, in fields such as facsimile, there is a strong demand for high-speed recording performance (high-speed color development) in order to reduce information transmission costs, but conventional diazo-based products still cannot adequately meet these requirements. It didn't satisfy me.

With conventional diazo photosensitive paper, when a color reaction is to be carried out, it is possible to use aqueous ammonia or alkaline aqueous solution as a developer, and to adopt conditions that allow a sufficient color reaction to occur. Even when performing a color reaction, a sufficient amount of heat could be supplied. Therefore, in the case of diazo photosensitive paper, no special measures were required to allow the color reaction to occur at high speed. However, in the case of a heat-sensitive recording material that performs a coloring reaction with a small amount of heat energy, such as a thermal head or a thermal pen, which is the object of the present invention,
Since the image forming means used in the case of diazo photosensitive paper cannot be used, various measures are required to efficiently cause a coloring reaction by using less thermal energy and energy.

The present inventors have conducted extensive research to develop a diazo-based heat-sensitive recording material that has high color development and excellent long-term storage properties, unlike the diazo-based heat-sensitive recording materials that have been proposed in the past.As a result, the present invention was developed. It has been completed.

That is, according to the present invention, a diazo layer containing a diazo compound as a main component and a coupler layer containing a coupler as a main component are laminated on a support, and a layer forming the lower layer of the diazo layer and the coupler layer is laminated on a support. A diazo-based heat-sensitive recording material is provided, which contains a thermofusible substance together with a water-insoluble binder, and further contains an imidazole carboxylic acid ester in at least one of the diazo layer and the coupler layer.

In the heat-sensitive recording material of the present invention, the order of the diazo layer and the coupler layer is arbitrary, but the layer forming the lower layer contains a thermofusible substance together with a water-insoluble binder. This structure makes the lower layer hydrophobic and provides a product with no pre-coupling and excellent long-term shelf life. First, in the present invention, by incorporating imidazole carboxylic acid esters into one or both of the diazo layer and the coupler layer, the actual concentration can be significantly increased without reducing the storage stability. That is, the imidazole carboxylic acid esters decompose upon heating, creating an alkaline atmosphere in the coloring system, promoting the coloring reaction, and increasing the concentration.

Conventionally, it has been known to add an inorganic or organic ammonium salt, urea, guanidine, or imidazole to a coloring system in order to make it alkaline. However, these additives exhibit alkalinity even before heat development, causing fog, which impairs the long-term shelf life of the product. In order to overcome these drawbacks, it is necessary to use a substance that hardly promotes the color reaction (development) at room temperature but rapidly raises the pH of the reaction system when heated. Imidazole carboxylic acids have been known as such unique substances (Japanese Patent Application Laid-Open No. 138821/1982), and when heated to their melting point, this compound causes a CO2 removal reaction.
, converts into imidazole and significantly accelerates development. However, these imidazole carboxylic acids have a high melting point and require a large amount of energy to reach the temperature necessary to decompose them, and decomposition does not proceed sufficiently, especially when heated using a thermal head. , pT-■ of the coloring system did not increase, and the image density could not be said to be sufficient. The present invention was made to solve these drawbacks, and is characterized by the use of imidazole carboxylic acid esters. These imidazole carboxylic acid esters have a lower melting point than imidazole carboxylic acid, and can remove CO2 sufficiently during heating without impairing the long-term shelf life of the product.
It causes a reaction and decomposes, and even heating with a thermal head can sufficiently improve image density.

The imidazole carboxylic acid esters used in the present invention are:
It can be produced by esterifying imidazole carboxylic acids having one or more carboxyl groups with various aliphatic or aromatic alcohols. The imidazole carboxylic acid esters used in the present invention can have an inert substituted group such as an alkyl group, an alkoxy group, a nitro group, an amine group, an aryl group, or an aralkyl group in the imidazole core. The imidazole carboxylic acid esters used in the present invention generally have a melting point of 250°C or lower, but in the case of the present invention, it is particularly advantageous to use those having a melting point of 200°C or lower, preferably 150°C or lower. . Specific examples of imidazole carboxylic acid esters are shown below, but the invention is not limited to these.

Methyl 4-imidazolecarboxylate, ethyl 4-imidazolecarboxylate, diethyl 2-methyl-4,5-imidazoledicarboxylate, diethyl 2-ethyl-4,5-imidazoledicarboxylate, ethyl 2-methyl-4-imidazolecarboxylate , 1-Mef Roux 4-= )
o -methyl 5-imidazolecarboxylate, ethyl 1-methyl-4-nitro-5-imidazolecarboxylate,
Ethyl 4-amino-5-imidazolecarboxylate, 2-
Benzimidazole carboxylate, ethyl phosphate, phenyl 4-imidazole carboxylate, benzyl 4-imidazole carboxylate, and the like.

In the heat-sensitive recording material of the present invention, the stacking order of the diazo layer and the coupler layer is arbitrary, but the layer forming the lower layer contains a thermofusible substance together with a water-insoluble binder. With this configuration, the lower layer becomes hydrophobic. Further, in the present invention, one or both of the diazo layer and the coupler layer contain the imidazole carboxylic acid ester. The amount used is 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, per 1 part by weight of the diazo compound. Note that the thermofusible substance can be contained in the upper layer as well as the lower layer,
Can be stacked as independent layers.

The diazo compound and coupler used in the present invention are those commonly used in diazo photosensitive paper, and include, for example, those shown below.

Diazo Compound: As the diazo compound used in the present invention, a commonly used diazo compound, for example, one represented by the following general formula is used.

1g However, in general formulas [1], [revised] and ([11), R1゜R6, R8 is hydrogen, halogen, 01-C6 alkyl group R1, is hydrogen, halogen, C6-C5 alkyl group or alkoxyl group, R, is the same or different C6 to C6 alkyl group, hydroquine alkyl group, or group or alkoxyl group, or halogen)
, R7 hydrogen, halogen, trifluoromethyl group, C1
~C3 alkyl group or alkoxyl group, or (
Dirt. , Ayu, R,6: Same as R,,3), M+,
M2 and M3 are acid residues or acid residues forming a double salt with a metal salt.

In this case, the acid residues include norogen ion and BF;
Preferably, it is a fluorine-containing inorganic acid ion such as PFJ,
On the other hand, metal salts that form double salts with acid residues include:
For example, there are Zn012.0d01□, 5nc12, etc.

Specific examples of those corresponding to general formula (1) include the following.

Specific examples of those corresponding to general formula (n) include the following.

Specific examples of those corresponding to the general formula Cl1l] include the following.

00H8 In the present invention, in order to obtain a product with further improved long-term shelf life, HBF is used as the diazo compound.

Advantageously, it is used in the form of a water-insoluble salt, such as a fluorine-containing salt such as HPF6.

Coupler: Couplers used in the present invention include phenol, resorcin, methylresorcin, 4,4-bisresorcin,
Phloroglucin, resorcinic acid, phloroglucinic acid, 2
-Methyl-5-methoxy-1,3-dihydroxybenzene, 5-methoxy-1,3-dihydroxybenzene, 4
Phenols such as -N,N-dimethylphenol, 2,6-dimethyl-1,3.5-trihydroxybenzene, 2,6-dihydroxybenzoic acid, 2,6-cyhydroxy-3,5-dibromo-4-methoxybenzoic acid Derivatives, α-naphthol, β-naphthol, 4-methoxy-1
-naphthol, 2,3-dihydroxynaphthalene, 2,
Sodium 3-dihydroxynaphthalene-6-sulfonate,
2-hydroxy-3-propylmorpholinonaphthoic acid,
2-hydroxy-3-naphtho-0-)luidide, 2-hydroxy-3-naphthoic acid morpholinopropylamide,
Naphthol derivatives such as naphthol derivatives, acetoacetanilide, 4-benzoylamino-2,5-jethoxyacetoacetanilide, N-acetoacetooctadecylamine, N,N'-bis(acetoaceto)decane-1,
Examples include active methylene compounds such as 10-diamine and 2,4.6-tribromoacetoacetanilide,
Of course, the present invention is not limited to these, and any one that can act as a coupler for the diazo compound can be applied.

In the present invention, a thermofusible substance is used to enhance high-speed color development, and specific examples of such substances include the following.

Alcohol derivatives such as 2-tribromoethanol, 2,2-dimethyltrimethylene glycol, 1,2-cyclohexanediol, acid derivatives such as malonic acid, glutaric acid, maleic acid, methylmaleic acid, beeswax, shellac wax, etc. Animal waxes, vegetable waxes such as carnauba wax, mineral waxes such as montan wax,
Petroleum waxes such as paraffin wax and microcrystalline wax, other synthetic waxes such as polycompounds of higher fatty acids,
Synthetic paraffin, chlorinated paraffin, metal salts of higher fatty acids, higher straight chain glycols, dialkyl 3,4-evogyshihexahydrophthalate, etc.

The thermofusible substance used in the present invention preferably has a melting point or softening point in the range of 50 to 250°C.

If the melting point or softening point is less than 50°C, the shelf life of the product tends to decrease, and if it exceeds 250°C,
The thermal response of the product to the thermal head becomes unsatisfactory. In addition, from the viewpoint of obtaining a product with high-speed coloring property (high-speed recording property), these thermofusible substances used in the present invention should be used in an amount of 1 to 30 parts by weight, preferably 2 to 30 parts by weight, per 1 part by weight of the diazo compound.
If this amount is less than the above range, the color development will be insufficient, and the resulting product will be
This makes it unsuitable as a recording material for high-speed recording. In the case of the present invention, it is particularly preferable to use 2 parts by weight or more for high-speed output recording such as facsimile. On the other hand, if the amount added is too large, blurring of the image may occur during color development by heating, which is not desirable. Therefore, in the case of the present invention, the amount of the thermofusible substance added is preferably kept within the above range.゛In addition, in the present invention, the heat-sensitive coloring layer further contains an auxiliary component as required, including an acidic substance,
Basic substances, fillers and others may be included.

Acidic substance: An acidic substance is added as necessary to prevent a coupling reaction and for storage stability, and examples thereof include the following.

Tartaric acid, citric acid, boric acid, lactic acid, gluconic acid, sulfuric acid, etc.

Filler: A filler is added to improve the matching property to a thermal head when heating is performed by a thermal head, and examples of such fillers include the following.

Organic and inorganic solid particles such as rum, calcium carbonate, titanium, talc, kaolin, silica, alumina, etc.

As other auxiliary ingredients, zinc chloride, zinc sulfate, sodium citrate, guanidine sulfate, calcium gluconate, sorbitol, saccharose, etc. are used to suppress or assist color development.

In the present invention, water-insoluble binders used to make the diazo layer or coupler layer forming the lower layer a hydrophobic layer include polyester, polystyrene, chlorinated rubber, polyvinyl acetate, polyvinyl chloride, and polycitadiene. , polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutadiene, styrene/butadiene/
Organic solvent-soluble or Water-dispersed resins can be used.

In addition to organic solvent-soluble or water-dispersible resins, binders used in other layers include polyvinyl alcohol, polyacrylamide, casein, gelatin,
Starch and its derivatives, polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, ethylcellulose, styrene-maleic anhydride copolymer, in(
Alternatively, water-soluble resins such as diiso)butylene-maleic anhydride copolymers can also be used.

The supports used in the present invention include paper bases, plastic films, and bases prepared by precoating paper with synthetic resins, fillers, and the like.

Next, the present invention will be explained in detail using examples.

Example! After applying an aqueous dispersion containing 1.5 parts of polyvinyl alcohol and 0.5 parts of calcium carbonate to the surface of a high-quality paper weighing 50 f/m2 and drying it, an undercoat layer with a coating weight of 2 f/m2 was provided. On top of that, a methyl cellosolve dispersion consisting of the following components was applied and dried to obtain a coating weight of 3.35 f/
A diazo layer of m2 was provided.

4-Mercaptotolyl-xybenzenediazonium borofluoride salt 0°3
5-part N-stearylbenzamide
1.0 part vinyl chloride-vinyl acetate copolymer
2.0 parts Next, on the diazo layer, an aqueous dispersion consisting of the following components was applied and dried to give an adhesion of 2.4 y/
After providing one layer of m20 coupler, the surface was calendered to obtain a Bekk smoothness of 400 seconds to obtain a heat-sensitive recording material.

Naphthol A, S O
, 5 parts 4-benzoylamino-2,5-jethoxy
0.5
Diethyl carbonate (melting point: 9.4°C) Silica: 0.5 parts Methyl cellulose: 0.5 parts Next, this heat-sensitive recording material was transferred to a commercially available high-speed recording facsimile machine for 1.5 parts. After printing and recording, a clear black image was obtained when the image was fixed by irradiation with ultraviolet rays using a commercially available diazo copying machine. The image density of this item was 1.1 with a Macbeth densitometer.
It was 02. In addition, this thermal paper before printing was heated at 40℃-90℃.
Although the sample was left in a □ environment of %R,H for 24 hours, the skin concentration increased by only 0.03. Also, 60℃-dry
The increase in skin area after being left in an RH environment for 24 hours is 0.0
It was 7.

Examples 2 to 5 Diethyl 2-ethyl-4,5-imidazoledicarboxylate in Example 1 was replaced with the compound shown below, and the rest was as in Example 1.
In the same manner as above, actual concentration and storage stability were investigated. The results are shown in Table-1.

Table-1 Comparative Examples 1 to 4 Diethyl 2-ethyl-4,5-imidazoledicarboxylate in Example 1 was replaced with the compound shown below, and the rest were as in Example 1.
The actual concentration and storage stability were investigated in the same manner as above. Table the results.
Shown in 2.

Table-2 Patent applicant Ricoh Co., Ltd. Agent: Patent Attorney Toshiaki Ikeura

Claims (1)

[Claims] (1) A diazo layer containing a diazo compound as a main component and a coupler layer containing a coupler as a main component are laminated on a support, and the layer forming the lower layer of the diazo layer and the coupler layer is a thermofusible layer. A diazo thermal recording material characterized in that it contains a substance together with a water-insoluble binder, and further contains an imidazole carboxylic acid ester in at least one of the diazo layer and the coupler layer.