JPH0225352B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material, and more particularly to a fixable diazo-based heat-sensitive recording material. Conventionally, as heat-sensitive recording materials, there are those that produce heat-sensitive coloring by utilizing the reaction between organic metal salts and reducing agents, and those that produce heat-sensitive coloring by using the reaction between leuco dyes and acidic substances. ing. However, such heat-sensitive recording materials have the disadvantage that recorded images cannot be fixed because they are non-fixable. That is, in the case of such a non-fixable heat-sensitive recording material, it is possible to perform recording again by performing another thermal printing after once recording by thermal printing. Therefore, the above-mentioned heat-sensitive recording materials have the risk of falsifying the information recorded thereon.
Confidence in records is low, and it cannot be applied to fields where reliability is required, such as recording or creating necessary items for securities, gift certificates, admission tickets, certificates, slips, etc. Furthermore, in the case of such recording materials, when exposed to an environment of 70° C. or higher, the entire surface develops color, which causes the problem that the recording becomes illegible. In particular, heat-sensitive recording materials that utilize the reaction between leuco dyes and acidic substances have the disadvantage that recorded information is erased when they come into contact with organic solvents or plasticizers in plastics. These drawbacks are due to the fact that these heat-sensitive recording materials are non-fixable. On the other hand, so-called diazo photosensitive paper, which utilizes the reaction between a diazo compound and a coupler, is widely known as a fixable recording material.
In this diazo photosensitive paper, by irradiating the unreacted diazo compound with light after image formation, it can be photodecomposed and fixed. Conventionally, heat-sensitive recording materials have been known in which the reaction between a diazo compound and a coupler is carried out by heating. This diazo-based heat-sensitive recording material has a heat-sensitive recording layer containing a diazo compound and its coupler as the main reaction components on a support, and one of the components in the heat-sensitive recording layer is formed as discontinuous particles. It is isolated from other components to prevent the color reaction from proceeding. However, all of the conventional ones are still insufficient in terms of storage stability and thermal coloring properties when viewed from a practical standpoint. for example,
In order to obtain a product with a high shelf life, it has been previously proposed to laminate a diazo compound and a coupler as separate layers, but in this case, the shelf life is relatively good, but it is still not sufficient. Also, the color development is still not satisfactory.
A highly colored image cannot be obtained by instantaneous heating. Recently, there has been a strong demand for heat-sensitive recording materials to have high-speed recording properties so that they can be used as output recording materials for facsimile, telex, electronic computers, medical measuring instruments, and the like. In particular, in the field of facsimile, heat-sensitive recording properties that are compatible with high-speed printing are required in order to reduce the cost of information transmission. Diazo-based heat-sensitive recording materials have the advantage of being fixable, but when applied to such uses, conventional ones have the disadvantage of insufficient thermal responsiveness to a thermal head. . The present inventors have overcome the above-mentioned drawbacks of conventionally proposed diazo-based heat-sensitive recording materials, and have provided a diazo-based heat-sensitive recording material having a laminated heat-sensitive recording layer.
As a result of intensive research to develop a product that has sufficient thermal response to heat heads and has excellent long-term storage stability, the present invention has been completed. That is, according to the present invention, at least one diazo compound selected from diazo compounds represented by the following general formulas () and () and phloroglucin as a coupler thereof are laminated as separate layers on a support. A diazo-based heat-sensitive recording material is provided. In the above formula, R ₁ , R ₂ , R ₃ , R ₅ , R ₆ and R ₇ are hydrogen, lower alkyl group, lower alkoxy group or halogen; R ₄ is hydrogen, lower alkyl group or lower alkoxy group; S; Y ₁ and Y ₂ are water-insoluble salt-forming acid residues. In this case, the acid residue is
Fluoric acid anions such as BF ₄ ^- and PF ₆ ^- are preferably used. Specific examples of those corresponding to general formula () include the following. Specific examples of those corresponding to general formula () include the following. In the present invention, in order to achieve the intended purpose, as the diazo compound to be contained in the layer, those represented by the general formulas () and () are selected, and as the coupler thereof, phloroglucin is selected, and All of these reactive components need to be laminated as separate layers on a support to form a thermosensitive coloring layer. With such a configuration, it is possible to obtain a heat-sensitive recording material that has significantly higher color development than conventional diazo-based heat-sensitive recording materials, can be colored by instantaneous heating, and has excellent long-term storage stability. can. In the present invention, a thermofusible substance is further added to the diazo compound layer and/or the phloroglucin layer in order to make the coloring reaction proceed more smoothly (instantaneously) during heating and to enable high-speed coloring. It is better. Specific examples of such things include, for example, the following: In the present invention, those having a melting point or softening point in the range of 50 to 250°C are used. Alcohol derivatives such as 2-tribromoethanol, 2,2-dimethyltrimethylene glycol, and 1,2-cyclohexanediol, acid derivatives such as malonic acid, glutaric acid, maleic acid, and methylmaleic acid, and animals such as beeswax and Serratus wax. plant waxes such as carnauba wax,
Mineral waxes such as Montan wax, petroleum waxes such as paraffin wax and microcrystalline wax, and other synthetic waxes such as polyhydric alcohol esters of higher fatty acids, higher amines, higher amides, condensates of fatty acids and amines, and fragrances. condensates of group and amines, synthetic paraffin, chlorinated paraffin, metal salts of higher fatty acids, etc. In the present invention, these thermofusible substances are used in an amount of 2 to 30 parts by weight, preferably 5 to 10 parts by weight, per 1 part by weight of the diazo compound. If this amount is less than the above range, the effect of improving color development will be reduced. In the case of the present invention, it is particularly preferable to use 5 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 undesirable. In the present invention, a binder is used to bind each component in the layers to each other and to stably support each layer on a support. Regarding this binder, in the case of the present invention, it is preferable to use one that melts or softens at a temperature of 50 to 250°C. When such a heat-fusible or heat-softening substance is used as a binder, this binder is also used together with the heat-fusible or heat-softening substance used as an added component in the layer during color development by heating. Since it melts or softens at the same time, it is possible to obtain a product with even higher thermochromic properties. Such thermofusible or thermosoftening binders include:
For example, the following can be mentioned: Polyvinyl acetate, polyvinyl chloride, vinyl chloride/vinyl acetate copolymer, polystyrene, polyester, styrene/butadiene/acrylic copolymer, polyacrylic ester, polyacrylamide, polymethacrylic ester, polybutadiene, etc. Further, in the case of the present invention, such a thermofusible or thermosoftening binder does not necessarily need to be used alone, and is usually used in order to more firmly bind each component in the layer to the support. A heat-retardant binder may also be used in a proportion not exceeding 30% by weight.
Examples of such binders include those shown below. Of course, in the present invention, such a heat-retardant substance can also be used alone. polyvinyl alcohol, polyacrylamide,
casein, gelatin, starch and its derivatives,
Polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, ethylcellulose, chlorinated rubber, polystyrene (MW: 100,000 or more), polyurethane, urea-formalin resin, phenolic resin, etc. Water-soluble, organic solvent-soluble, water-based dispersion resin, etc. Furthermore, in the present invention, the diazo compound layer and/or the phloroglucin layer may contain acidic substances, basic substances, fillers, and other substances as auxiliary components, if necessary. Acidic substance: Acidic substances are added as necessary to prevent coupling reactions and to maintain storage stability, and include, for example, the following. Tartaric acid, citric acid, boric acid, lactic acid, gluconic acid, sulfuric acid, etc. Basic substance: A basic substance is added as necessary to further promote the coupling reaction during heating, and examples thereof include the following. Caustic alkalis and alkali carbonates such as sodium hydroxide, calcium hydroxide, potassium carbonate, etc. As a substance that generates basicity when heated,
Urea, thiourea and their derivatives, alkali salts of trichloroacetic acid, ammonium chloride, ammonium sulfate, ammonium citrate, etc. Filler: A filler is added to improve the matching property to a thermal head when heating with a thermal head, etc. Fillers include, for example, the following. Organic and inorganic solid particles such as styrene resin particles, urea-formalin condensate resin particles, aluminum hydroxide, magnesium hydroxide, calcium carbonate, titanium, talc, kaolin, silica, and alumina. Other auxiliary ingredients used include zinc chloride, zinc sulfate, sodium citrate, guanidine sulfate, calcium gluconate, sorbitol, and sugar rose to suppress or assist color development. In order to obtain the heat-sensitive recording material according to the present invention, each layer-forming coating solution is prepared by dissolving or dispersing the above-mentioned layer-forming components in an appropriate solvent, and each of the coating solutions is coated on a support and dried. The product has a laminated structure including a diazo compound layer and a phloroglucin layer. In this case, the solvent for dissolving or dispersing the layer-forming components is appropriately selected depending on the properties of the layer to be formed and the purpose of formation. Such solvents include water or an aqueous medium in which an organic solvent is dissolved in water;
Benzene, toluene, xylene, n-hexane,
Examples include nonpolar or polar organic solvents such as n-heptane, cyclohexane, kerosene, methyl isobutyl ketone, methyl cellosolve, acetone, methyl ethyl ketone, dimethyl ether, and siloxane. In the present invention, when the diazo compound layer and the phloroglucin layer are laminated in direct contact with each other, the solvent for forming the upper layer coating solution is appropriately selected in relation to the components contained in the lower layer in order to prevent color development due to the reaction between the two. It is necessary to. That is, the solvent for forming the upper layer coating liquid must not dissolve the coupling reaction component contained in the formed lower layer. For example, when a phloroglucin layer-forming coating solution is first applied and dried on the support, and then a diazo compound layer-forming coating solution for forming an upper layer is applied and dried, the solvent in the diazo compound layer-forming coating solution is contained in the lower layer. It must be insoluble in phloroglucin. When the diazo compound layer-forming coating solution is applied, if phloroglucin in the lower layer is eluted into the coating solution, a coloring reaction will occur during the coating process. In the diazo compound layer and phloroglucin layer formed in the present invention, each of the reactive components may be present in the layer in the form of either discontinuous particles or continuous particles. In this case, "discontinuous particles" means that during layer formation,
When forming a layer using a dispersion in which a diazo compound or phloroglucin is dispersed as insoluble solid particles in a solvent, it refers to the state of existence of these reaction components in the layer, and is referred to as "continuous particles". refers to the state of presence of the reactive components in the layer, which is obtained when the layer is formed using a solution in which a diazo compound or phloroglucin is dissolved in a solvent. In the present invention, in order to obtain a product with balanced thermochromic properties and preservability, it is preferable that one of the diazo compound layer and the phloroglucin layer is a discontinuous particle layer, and the other is a continuous particle layer. If both of them are discontinuous particle layers, thermal coloring properties tend to decrease, while if both of them are continuous particle layers, thermal coloring properties tend to become too large and storage stability tends to decrease. In the present invention, the stacking order of the diazo compound layer and the phloroglucin layer on the support (e.g., paper, synthetic paper, plastic film, etc.) is arbitrary, and the diazo compound layer and the phloroglucin layer can be stacked on the support in that order or on the support. They can be stacked in the reverse order. Moreover, both layers do not necessarily have to be continuous, and an auxiliary component layer can be interposed between the two layers. Additionally, auxiliary component layers can be used as top and/or bottom layers. Next, examples of laminating various component layers used in the present invention on a support will be shown. In addition, each code shown below means the following. D... Diazo compound C... Phloroglucin X... Heat-fusible or heat-softening substance Moreover, Katsuko [ ] indicates that a layer is formed. An example of this is as follows. [D]...Diazo compound layer [D+X]...Layer containing a diazo compound and a heat-melting or heat-softening substance [D+Y]...Layer containing a diazo compound and a filler or other auxiliary component (1) [C]/[D+X] ], (2) [D+X]/[C] (3) [D]/[C+X], (4) [C+X]/[D] (5) [C+X]/[D+X], (6) [D+X] / [C
+X] (7) [C+X]/[D+X+Y], (8) [D+X]/[C+X+Y] (9) [C+X+Y]/[D+X+Y], (10) [D+X+Y]/[C+X+Y] (11) [C] /[Y]/[D+X], (12)[D+X]/[Y]/[C] (13)[D]/[Y]/[C+X], (14)[C+X]/[Y]/[ D] (15) [C+X]/[Y]/[D+X], (16) [C+X]/[Y]/[D+X] (17) [Y]/[C+X]/[D]/[X+Y], (18) [Y] / [C+X] / [D+X] / [X+
Y], (19) [C+X]/[D+X]/[C]/[X+
Y], (20) [Y]/[C+X]/[D+X]/
[X]/[Y], (21) [Y]/[C+X]/[D+X]/[C+
X]/[Y], (22) [X+Y]/[C+X]/[D+X], (23) [D+X]/[Y]/[C+X], (24) [X+Y]/[C]/[D+X] ]/[X+
[Y]/[Y] The diazo-based heat-sensitive recording material of the present invention can be usefully applied in various heat-sensitive recording fields, particularly as output recording paper for facsimile machines and electronic computers that require high-speed recording, Moreover, in the case of the present invention, characters and images recorded on the surface can be fixed by forming the image by heating and then decomposing the unreacted diazo compound with light. Furthermore, the heat-sensitive recording material of the present invention can be applied to recording necessary information on securities, gift certificates, admission tickets, certificates, slips, etc., and for creating them, by taking advantage of its fixing properties. Furthermore, the heat-sensitive recording material of the present invention can of course be applied as a heat-developable copying paper. Next, the present invention will be explained in more detail with reference to Examples. Example [C-1] Solution Phloroglucin 3 parts by weight Sodium citrate 0.5 Polyvinyl alcohol (10% aqueous solution) 10 Water 86.5 The above composition was dissolved to prepare [C-1] Solution. [C-2] Liquid Chloroglucine 5 parts by weight Stearamide 5 Polystyrene resin (:800) 2 Benzene 88 The above composition was dispersed for 24 hours using a ball mill to obtain a dispersion liquid [C-2]. Prepared.

[Table] The above composition was dispersed for 24 hours using a ball mill to prepare a dispersion liquid [D-1].

[Table] The above composition was dispersed for 24 hours using a ball mill to prepare a dispersion liquid [D-2]. [Y-1] Liquid Silica 5 parts by weight Parafine wax 3 Polyvinyl alcohol (10% aqueous solution) 10 Water 82 The above composition was dispersed for 1 hour using a homomixer to form a dispersion liquid [Y-1] A liquid was prepared. [Y-2] Liquid Calcium carbonate 5 parts by weight Polyvinyl acetate emulsion (solid content 50%)
4〃Water 91〃 Among the above compositions, calcium carbonate was dispersed in water using a homomixer for 1 hour, and then polyvinyl acetate emulsion was added and stirred until uniform.
A dispersion liquid [Y-2] was prepared. [D-10] Solution For comparison, [D-10] solution was prepared in the same manner as in [D-2] solution except that the following was used as the diazo compound. [C-10] Solution For comparison, in the same manner as in [C-1] except that phloroglucin was replaced with the following,
[C-10] Solution was prepared. Each of the above liquids was applied in the combination shown in Table 1 below on the surface of high-quality paper (approximately 50 g/m ² ) and dried to form each layer with an adhesion amount of 2 to 3 g/m ² (solid content). Laminated and further calendered to improve Beck's smoothness.
A heat-sensitive recording material with a temperature of 400 seconds was obtained.

【table】

[Table] * Comparative example Using the heat-sensitive recording material obtained as above as a sample, G
After printing in - mode, it was completely exposed and fixed using Ricopy High Start Type 4 (manufactured by Ricoh Co., Ltd.). These materials did not develop color even when heated, and the images did not disappear when exposed to organic solvents. Next, the heat-sensitive recording material obtained above was tested for color density and storage stability. The results are shown in Table-2. In addition, the color density is the solid print density in the G-mode of Refax 303 using a Macbeth densitometer (RD-
514). In addition, the shelf life of the sample is 40
A forced deterioration test was conducted in which the sample was left in a dark place at a temperature of 90% RH for 24 hours, and the skin concentration before and after the test was measured.
In this case, a Macbeth densitometer was used for concentration measurement. If the background density value is 0.15 or less, it is confirmed that the heat-sensitive recording material has a shelf life of 3 years or more when stored in dark color at room temperature and humidity.

[Table] * Comparative Example ** Color develops immediately after application From the above results, it can be confirmed that the product of the present invention clearly has improved storage stability and thermal response than the Comparative Example.

Claims (1)

[Scope of Claims] 1 At least one diazo compound selected from diazo compounds represented by the following general formulas () and () and phloroglucin as a coupler thereof are laminated as separate layers on a support. A diazo-based heat-sensitive recording material characterized by: (In the above formula, R ₁ , R ₂ , R ₃ , R ₅ , R ₆ and R ₇ are hydrogen, lower alkyl group, lower alkoxy group or halogen; R ₄ is hydrogen, lower alkyl group or lower alkoxy group; is S; Y ₁ and Y ₂ are water-insoluble salt-forming residues)