JPH0225355B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermosensitive recording medium that develops color when heated, and which can also fix non-recorded areas by irradiation with light if necessary. With the development of information and communications, demand for hard copy technology has increased, and various recording methods have been developed. Among these, the thermal recording method, which records electrical information by converting it into heat using a thermal head, has the advantages of being able to make the device smaller and lighter, and can record noise with less noise. It is becoming more and more used. Traditionally, thermal recording paper has been produced using the so-called "3M type," which uses a reaction between an organic acid metal salt and a reducing agent, and the so-called "NCR type," which uses a reaction between a leuco dye and a color developer. It is used. However, these materials have the problem that the recording cannot be fixed and the color develops when reheated, or the color develops or disappears due to the solvent of the adhesive, cellophane tape, or vermilion. One possible way to solve these problems is to use heat-developable diazo photosensitive paper. That is, a recording is obtained by reacting a diazonium salt and a coupler by heating to form an azo dye, and furthermore, the diazonium salt in the non-recording area is photolyzed by light irradiation and fixed. Heat-developable diazo photosensitive paper is a well-known technology in the field of diazo copying, and has the advantage of eliminating ammonia odor during wet processing and development, which is a disadvantage of wet diazo photography and dry diazo photography. In the thermal development diazo method, the original written on transparent paper and the thermal development diazo paper are placed on top of each other, and the diazonium salt in the non-document areas is decomposed by exposing the original side to light. using
By heating at 100-200℃ for several seconds to tens of seconds,
A positive azo dye recorded image corresponding to the original is obtained by reacting the coupler with the diazonium salt in the written area of the original. When such a heat-developable diazo paper is used as a heat-sensitive recording paper, a heat-writing process is first carried out, followed by a fixing operation, and the order of heating and exposure is reversed from that of heat-developable diazo photography. Here, heating is done for several milliseconds by a thermal head.
Since this process is carried out in an extremely short period of time, it is required to have better thermal sensitivity than the diazo heat development method. The object of the present invention is to realize a heat-sensitive recording medium with high heat sensitivity and good storage stability using a diazo compound. In other words, in the conventional heat development diazo method, all three components, the diazonium salt, the coupler, and the basic substance, are water-soluble and are affected by the humidity in the air, which poses problems in terms of storage stability and color development sensitivity. . As a result of repeated research in order to prevent the above-mentioned drawbacks of the heat development diazo method, the present inventors have discovered that a diazonium salt, a coupler and a basic substance are included on a support in a layer in which at least the basic substance is close to the support. Excellent thermal sensitivity and long-term storage when a water-insoluble or poorly water-soluble guanidine derivative is used as the basic substance and a water-insoluble or poorly water-soluble substance as the coupler. It was discovered that it has stability. Figure 1 shows the conventional diazonium salt, Kuplar,
1 is a cross-sectional view showing a thermosensitive recording medium having a thermosensitive coloring layer in which a basic substance coexists; 1 is a support; 2 is a thermosensitive coloring layer; FIG. 2 is a cross-sectional view of an embodiment of the present invention, in which the thermosensitive coloring layer consists of two layers, a lower layer 3 and an upper layer 4, each containing at least a basic substance. FIG. 3 shows another embodiment, in which an isolation layer 5 is formed between the two heat-sensitive coloring layers shown in FIG.
Next, the constituent components of the thermosensitive coloring layer will be explained. Diazonium salts used in the present invention include, for example, P-diazo-N-ethyl, N-hydroxyethylaniline chloride zinc chloride, p-diazo-N, N-diethylaniline chloride zinc chloride, P-diazo-N,N- Dimethylaniline chloride zinc chloride, P-diazo-N-benzyl-
N-ethylaniline chloride zinc chloride, 4-diazo-N,N-diethylaniline fluoroborate, 4-benzamide-2,5-diethoxybenzenediazonium chloride zinc chloride, 4-methoxy-6-benzamide-m-toluidine-diazonium Zinc chloride, 4-diazo-diphenylamine sulfate, sodium 1-diazo-3-naphthol-4-sulfonate, sodium 1-diazo-2-naphthol-4-sulfonate, 2-methoxy-4-morpholinobenzenediazonium chloride Zinc chloride, 4-morpholino-2,5-dibutoxybenzenediazonium chloride zinc chloride, 4
-P-methoxybenzamide-2,5-diethoxybenzenediazonium chloride zinc chloride, 2
-N,N-diethyl-m-toluidinediazonium fluoroborate, 6-morpholino-m-toluidine-diazonium fluoroborate, sodium 2-diazo-1-naphthol-4-sulfonate, 2-diazo-1-naphthol-5- Examples include sodium sulfonate and 4-diazo-4'-methoxy-diphenylamine chloride. The guanidine derivative selected as the basic substance is solid at room temperature, preferably has a melting point of 60°C or higher,
It is insoluble or poorly soluble in water and has the following general formula:

[expression] or

[Formula] [In the formula, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ represent hydrogen, alkyl having 18 or less carbon atoms, cyclic alkyl, aryl, acyl, acylamino, amino group, R ₁ , R ₂ ,
At least one of R ₃ and R ₄ is an aryl group, and R ₆ is lower alkylene, phenylene, naphthylene, or

[Formula] (In the formula, X is lower alkylene, SO ₂ , S ₂ , S, O, -NH-
or a single bond), and the aryl group in the formula includes those having a substituent selected from lower alkyl, alkoxy, nitro, acylamino, alkylamino, and halogen. ] It is a compound represented by Specific examples are given below, but these do not limit the present invention. Guanidine derivatives (1) Phenylguanidine (2) 1.3-diphenylguanidine (3) 1.3-di-0-tolylguanidine (4) 1.3-di-P-methoxyphenylguanidine (5) 1-dimethyl-3-phenylguanidine Enylguanidine (6) 1-benzoyl-3-phenylguanidine (7) 1-benzyl-3-phenylguanidine (8) 1.2.3-triphenylguanidine (9) 1.1.3-triphenylguanidine (10) 1.2 -dibenzoyl-3-phenylguanidine (11) 1,3-diphenyl-2-cyclohexylguanidine (12) 0-tolylbiguanide (13) p-di(1,3-diphenylguanidino) diphenyl (14) Di-(phenylguanidino) Ethane(15) Di-(triphenylguanidino)methane Since these guanidine derivatives are basic substances, they form a basic atmosphere particularly effectively at temperatures near their melting points, and couple the diazonium salt and coupler. Azo dyes can be formed. All of these guanidine derivatives are stable at room temperature, and require much longer time for decomposition during storage than conventionally known urea, imidazole derivatives, and the like. Furthermore, most of the conventionally known basic substances have very high water solubility, which has the disadvantage that the heat-sensitive layer develops color during storage under the influence of moisture in the air. However, since the guanidine derivative used in the present invention is poorly soluble, preferably insoluble, in water, it has excellent storage stability. The guanidine derivatives in the present invention may be used alone or in combination of two or more. Further, in order to adjust the color development temperature and color tone, it is also possible to use a conventionally used basic substance in combination. However, it is necessary that the proportion of the guanidine derivative in the total basic substances contained in the system is at least 60% by weight or more, preferably 80% by weight or more. As the coupler, a substance that is solid at room temperature, preferably has a melting point of 60° C. or higher, and is sparingly soluble in water, preferably insoluble in water, is used as in the case of the guanidine derivative. Examples of substances that meet this condition include 2,3-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, and 2,3-dihydroxynaphthalene.
6-sulfanyl-naphthalene, 2,3-dihydroxy-6-di(β-hydroxyethyl)sulfanyl-naphthalene, 1-carboxy-2,3-
Dihydroxynaphthalene, 1,4-dichloro-
2,3-dihydroxynaphthalene, 0-hydroxybiphenyl, naphthionic acid, 2,4-2',
4'-Tetrahydroxydiphenyl sulfide, a coupling component of naphthol dyes (naphthol
AS, AS-BO, AS-BS, AS-D, AS-E,
AS-G, AS-LB, AS-OL, AS-SW, AS-
TR, etc.) etc. A suitable anti-coupling agent is added to prevent coupling between the diazonium salt and the coupler at room temperature. Examples of this include tartaric acid, citric acid, oxalic acid,
Boric acid and phosphoric acid are suitable. Other additives that can be added include reducing agents such as thiourea, ascorbic acid, allyl isothiocyanate, etc., which prevent coloration due to oxidation after the diazonium salt is photodecomposed. Zinc chloride is also added as a stabilizer for the diazonium salt. Furthermore, guanidine sulfate, pentaerythritol, and the like, which contribute to promoting thermal color development, can also be added. Each layer of the recording medium is coated using a suitable binder. Examples of the binder include generally known water-soluble polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, polyvinylpyrrolidone, gum arabic, gelatin, casein, starch, styrene-maleic anhydride copolymer, and polyacrylate. Water-soluble binders such as styrene
There are various latexes such as butadiene latex and acrylonitrile-butadiene latex, and various emulsions such as polyvinyl acetate, polyacrylic acid ester, and ethylene-vinyl acetate copolymer. The material constituting the isolation layer 5 used in the embodiment of FIG. 3 has a melting point or softening point of 60 to 150.
℃ range is used. Examples of substances suitable for this purpose include waxes such as microcrystalline wax, montanic acid wax, montanic acid ester, oleic acid amide, stearic acid amide, lauric acid amide, ethylene bisstearic acid amide, paraffin wax, etc. Examples include vinyl acetate, vinyl chloride-vinyl acetate copolymer, linear saturated polyester, methacrylic acid ester, ethylene-vinyl acetate graft polymer, ethylene-vinyl acetate copolymer, polystyrene, epoxy resin, and 1,2-polybutadiene. The production of coating liquid consists of three types of basic liquids:
The second is an aqueous solution of a diazonium salt, an anti-coupling agent, a reducing agent, a diazonium stabilizer, etc., the second is an aqueous dispersion of a basic substance, and the third is an aqueous dispersion of a coupler. A water-soluble resin is added to these base liquids as necessary, and when dispersing the basic substance and coupler, a suitable surfactant is added as a dispersion accelerator. From these base liquids, the first
When constructing a conventional one-layer heat-sensitive coloring layer as shown in the figure, three types of base liquids are mixed immediately before coating, and the mixture is coated on a support. When constituting the two-layer thermosensitive coloring layer shown in Figure 2, an aqueous dispersion of a basic substance, or an aqueous dispersion of a basic substance and a diazonium salt is included among the three basic liquids. A lower layer 3 is provided by coating an aqueous solution or a mixture of a coupler with an aqueous dispersion, and then an upper layer 4 is provided by coating the remaining one or two solutions. In the case of a heat-sensitive coloring layer provided with the isolation layer 5 shown in FIG. 3, the same coating solution as that shown in FIG.
and a lower layer 3, and the lower layer 3, the isolation layer 5, and the upper layer 4 are coated in this order to constitute a thermosensitive coloring layer. Next, an example will be described. Example 1 Solutions A, B, and C were each prepared as follows. (Liquid A) P-diazo-N-ethyl-N-hydroxyethylaniline chloride An aqueous solution consisting of 2 parts by weight of zinc chloride, 1 part by weight of tartaric acid, and 97 parts by weight of water. (Liquid B) A dispersion obtained by kneading a mixture of 7 parts by weight of 1-carboxy-2,3-dihydroxynaphthalene and 93 parts by weight of a 0.1 PVA aqueous solution at room temperature for 8 hours using a ball mill. (Liquid C) A dispersion obtained by kneading a mixture of 3 parts by weight of 1,3-di-0-tolylguanidine, 3 parts by weight of fine powder silica, and 94 parts by weight of a 0.5% PVA aqueous solution at room temperature for 8 hours in a ball mill. 3 parts by weight of 50% SBR latex was added to 30 parts by weight of liquid C, and the mixture was coated on high-quality paper with a basis weight of 65 g/m ² to a dry coating weight of 3 g/m ² and dried with hot air. . Next, 30 parts by weight of liquid A, 30 parts by weight of liquid B, 10%
Mix 10 parts by weight of PVA aqueous solution, apply on liquid C coating layer, dry with hot air at 50℃, dry coating amount 2g/m ²
A thermosensitive recording medium was produced. This thermosensitive recording medium is placed on a heating plate at a predetermined temperature for 5 seconds.
When pressed under a pressure of 100 g/cm ² to develop color, a blue image was formed. The maximum density at this time was 1.2, and the color development temperature was 98°C, which was the temperature that gave half the maximum density. Further, it was fixed by being left under room light for about 1 hour or exposed under an ultraviolet lamp for about 10 seconds, and no color developed even when heated again. Meanwhile, 20~25℃, relative humidity 30~
The unrecorded paper was left for half a year under 60% light shielding. The recording paper that was initially exposed and fixed has a density of 0.15,
The recording paper that was exposed and fixed after six months had a density of 0.17. Furthermore, the maximum color density after six months was 1.2 and the color temperature was 98°C, indicating good storage stability. Example 2 On the liquid C coating layer prepared in Example 1, 10
% vinyl chloride-vinyl acetate copolymer (Denkabinyl #1000AS)
A thermosensitive recording medium was produced in the same manner as in Example 1, except that a 2 μm isolation layer was provided by coating the MEK solution and drying with hot air. When recorded in the same manner, it showed excellent color development properties and had even better storage stability than Example 1. Comparative Example 1 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that nitroguanidine, which is soluble in water, was used instead of 1.3 di-0-tolylguanidine in liquid C in Example 1. This thermosensitive recording medium developed a purple color and the maximum color density was 0.9. On the other hand, when this recording paper was stored in the same manner as in the example, the entire paper developed a purple color after one week, making it unsuitable for use as a recording paper. When this heat-sensitive recording medium was exposed to ultraviolet light and fixed, the density was 0.5, which is 0.35 higher than the density of 0.15 of the similarly fixed recording medium immediately after production, and the heat-sensitive recording medium of the present invention is clearly superior. I understand that. As explained above, a diazonium salt type heat-sensitive recording medium formed using a water-insoluble or sparingly soluble basic substance and a coupler has the advantage of being able to form a recording medium with high heat sensitivity and excellent storage stability. Further, the present invention has the advantage that good head matching properties can be obtained by incorporating a basic substance in the lower layer, and that it has excellent durability. In the layer structure of the present invention, it is more preferable to contain the diazonium salt and the coupler in the upper layer as in the example in order to avoid the adverse effect of basic substances on the diazonium salt from the viewpoint of storage stability.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional thermosensitive recording medium, FIG. 2 is a sectional view of Example 1, and FIG. 3 is a sectional view of Example 2. DESCRIPTION OF SYMBOLS 1...Support, 2...Thermosensitive coloring layer, 3...Lower layer of the heatsensitive coloring layer, 4...Upper layer, 5...Isolation layer.

Claims (1)

[Claims] 1. A heat-sensitive recording comprising a diazonium salt, a coupler, and a basic substance distributed on a support in separate layers such that at least the basic substance is contained in a layer close to the support. 1. A heat-sensitive recording medium characterized in that a water-insoluble or slightly water-soluble guanidine derivative represented by the general formula (1) or the general formula (2) is used as the basic substance. [Formula] [Formula] [In the formula, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ are hydrogen, carbon number 18
Represents the following alkyl, cyclic alkyl, aryl, acyl, acylamino, or amino group,
At least one of R ₁ , R ₂ , R ₃ , and R ₄ is an aryl group, and R ₆ is lower alkylene, phenylene,
Naphthylene, or [Formula] (wherein X represents lower alkylene, SO ₂ , S ₂ , S, O, -NH, or a single bond), and the aryl group in the formula is lower alkyl, nitro, acyl, amino , alkyl, amino group, or halogen. ]