JPH0411396B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fixable heat-sensitive recording material with improved storage stability, and more particularly, to a fixable heat-sensitive recording material that develops color with high density during heat-sensitive recording. In recent years, high-speed printers, facsimile machines, etc. have made remarkable progress in response to society's demand for outputting large amounts of information as hard copies as quickly as possible. Electrophotography, electrostatic recording, discharge recording, inkjet recording, thermosensitive recording, and the like are known as methods for forming images on recording media according to electrical information, such as high-speed printers and facsimiles. Among these methods, the thermal recording method has been rapidly becoming popular in recent years because the apparatus is relatively simple and the recording paper is also relatively inexpensive. As one method of the heat-sensitive recording method, a heat-sensitive recording sheet made by combining a color-forming substance such as crystal violet lactone and a phenolic compound such as bisphenol A is described in, for example, Japanese Patent Publication No. 14039/1983. and is already known. These thermosensitive recording sheets are currently widely used as office copy paper, recording paper for various recorders, electrocardiographs, calculators, computer terminals, facsimiles, and the like. However, with the above conventional method, if the background is heated incorrectly after printing, the background may become colored and the print may become unreadable, or there is a possibility that it may be tampered with after printing.
Improvements are strongly desired. Conventionally, a heat-sensitive photosensitive material that has a component that generates an alkali by thermal decomposition on a support, a diazonium salt and a coupler compound that develop color with an alkali, and has a binder agent, an acid stabilizer, etc. added as necessary, is a diazo type photosensitive material. It is well known as a heat-developable photosensitive material. Therefore, development is carried out only by heat, without using ammonia gas, which is used in the conventional dry diazo method, which is convenient because no irritating gases are generated. Many color developers have already been announced, and representative compounds include inorganic or organic ammonium salts, urea or its derivatives, basic substances such as triethanolamine, and thermally decomposable compounds such as trichloroacetic acid. Salts obtained by neutralization with acids are known. However, in recent years, particularly high recording speeds have been required in the thermal recording method, and it is also required to produce sufficient color density with less thermal energy and to have good storage stability. However, in methods using substances that generate alkali through thermal decomposition, such as the above substances,
In order to improve recording sensitivity, it is necessary to use substances with a low thermal decomposition temperature, and as a result, thermal decomposition of these substances gradually progresses even at room temperature.
Pre-coupling development occurs due to natural decomposition of the color developer before development, causing fog and deterioration of storage stability. On the other hand, if a substance with a high thermal decomposition temperature is used to improve storage stability, this will cause a significant decrease in color density as the thermal recording speed increases.
In order to overcome this drawback, in the field of copying paper using diazo-type photothermographic materials, it is known to use fusible base particles as a color developer that is melted by heat to create an alkaline atmosphere. For example, in Japanese Patent Publication No. 39-1874, various mono- and polyamines of aliphatic and alicyclic amines are listed as examples, but if the above color developer is coated on a support together with a diazonium salt and a coupler compound, it will be preserved. Significant deterioration in sex is observed. Furthermore, when an acidic substance is added to a particulate dispersion of a heat-melting color developer and coated on a support together with a diazonium salt and a coupler compound in order to improve storage stability, a significant decrease in color density is observed. In addition, for the same purpose of improving shelf life, a three-layer coating method in which a heat-melting color developer is separated from a layer containing a diazonium compound via an intermediate layer, as described in Japanese Patent Publication No. 40-377, reduces manufacturing costs. Not only does this have disadvantages, but also the coloring density is low and cannot be put to practical use, especially when used in high-speed thermal recording as in the present invention. The object of the present invention is to overcome the above-mentioned drawbacks and to provide a heat-sensitive recording medium that has excellent storage stability, high color density, and is fixable. A photosensitive and thermosensitive layer comprising an acid-stabilized diazonium salt that can be formed and a binder material, a water-soluble binder comprising a natural or synthetic polymer compound on the layer, and a hydrophobic coupler dispersed in the form of particles in the water-soluble binder. A color developer layer containing as a main component a particulate dispersion of a hydrophobic guanidine derivative having the following general formula capable of supplying the necessary amount of base to enable the compound and the acid-stabilized diazonium salt to sufficiently react with the coupler compound. By providing this, it is an object of the present invention to provide a fixing type heat-sensitive recording medium with improved storage stability. Further, the present invention provides a fixing type heat-sensitive recording material particularly excellent in storage stability when the hydrophobic coupler compound is a compound having a diffusion-resistant group such as a long-chain aliphatic alkyl group or a long-chain aliphatic alkoxyl group. general formula [In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent hydrogen, alkyl, cyclic alkyl, aryl, aralkyl, amino, alkylamino, acylamino, carbamoylamino, heterocyclic residue having 18 or less carbon atoms, and R ₅ 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, alkoxy, nitro, acylamino, alkylamino Also includes those having a substituent selected from groups and halogens] Furthermore, typical examples thereof are shown in Table 1,
This does not limit the invention. In the table

[Formula] represents a cyclohexyl group.

【formula】 【formula】

【formula】 These guanidine derivatives shown in Table 1 can be easily synthesized by known methods or methods similar thereto. Examples of the diazonium salt used in the present invention include 1-diazo-4-N,N-dimethylaminobenzene borofluoride salt, 1-diazo-4-morpholinobenzene diazonium salt, which is used in conventionally known diazo type copying materials. borofluoride salt, 4-diazo-diphenylamino borofluoride salt, 1-diazo-
2.5-Dimethoxy-4-morpholinobenzenediazonium borofluoride salt, 1-diazo-2.5-
Dibutoxy-4-morpholinobenzene borofluoride salt and the like can be arbitrarily selected and used. Further, as the binder material for forming the photosensitive and thermosensitive layer of the present invention, an aqueous solvent such as starch,
It is also possible to use a water-soluble polymer binder such as methylcellulose, polyvinyl alcohol, polyacrylamide, gum arabic, or a synthetic resin emulsion, but this is because diazonium compounds tend to cause a coloring reaction in the presence of a small amount of water. For the purpose of the present invention, for example, vinyl acetate, cellulose acetate, vinyl chloride, acrylic resin, vinyl chloride-vinyl acetate copolymer solution, etc. are used as a resin binder in an organic solvent such as methanol, acetone, methyl ethyl ketone, ethyl acetate, methyl acetate, or toluene. It is more preferably used to improve the storage stability of certain fixing type thermosensitive recording materials. Furthermore, as the acid stabilizer for stabilizing the diazonium salt and preventing precoupling with the coupler compound, any of the organic acids and inorganic acids commonly used in conventionally known diazo type copying materials can be used.
Specific examples include tartaric acid, citric acid, boric acid, phosphoric acid, etc., but in particular, by using a thermally decomposable acid as an acid stabilizer for diazonium salt, the storage stability, which is the object of the present invention, can be improved by thermal recording. It is possible to obtain a fixing type heat-sensitive recording material with improved and high sensitivity. As the thermally decomposable acid, halogenated acetic acids such as trichloroacetic acid, dichloroacetic acid, and monochloroacetic acid, cyanoacetic acid, oxalic acid, malonic acid, maleic acid, and curconic acid are preferably used. In addition, an antioxidant, an image intensifier, and the like may be appropriately added to form a photosensitive and thermosensitive layer. Further, as the coupler compound used in the color developer layer of the present invention, the following compounds having a hydrophobic aromatic hydroxy compound and a hydrophobic active hydrogen are used by dispersing them in the form of fine particles in a water-soluble binder. I can do it. Specifically, it is shown in Table 2, but this does not limit the present invention. Table-2 In addition, the coupler compound can be contained in the photosensitive and thermosensitive layer if necessary, and when the binder material of the photosensitive and thermosensitive layer is a water-soluble polymer, for example, sodium 2,3-dihydroxynaphthalene-6-sulfonate, 2-hydroxynaphthalene. -3.6-Sodium disulfonate, 1-(3-aminobenzamide)
-4-naphthol, 1-(3-aminobenzamide)-7-naphthol, 1,4-bisacetoaceto-
A water-soluble coupler compound such as ethylenediamine can be used, and when the binder material of the photosensitive and thermosensitive layer is a resin binder soluble in an organic solvent, the above Table-2
The hydrophobic coupler compounds specifically described in can be used. Thus, by adding two or more coupler compounds to the light and heat sensitive layers and developer layers of the present invention, dyes exhibiting desired spectral absorption properties may be produced. For example, when forming a black image, when two or more coupler compounds are all contained together with a diazonium salt in a light- and heat-sensitive layer, some of the coupler compounds may have high coupling activity due to the difference in coupling activity between the respective coupler compounds and the diazonium salt. Pre-coupling by the coupler compound is likely to occur and cause a decline in storage stability, but as in the present invention, for example, in a preferred example, pivaloylacetanilide is dispersed in the form of fine particles in a water-soluble polymer binder of the color developer layer. Sodium 1,8-dihydroxynaphthalene-6-sulfonate and phloroglucin were prepared as 1-diazo-2,5-diethoxy-
When added to a light-sensitive heat-sensitive layer together with 4-morpholinobenzene and a borofluoride salt, the dyes obtained from the respective coupler compounds and the diazonium salt are yellow, cyan, and reddish-purple, respectively, and form a substantially black image. I can do it. In addition, the water-soluble binder made of a natural or synthetic polymer compound used in the color developer layer of the present invention includes generally known polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, gum arabic, gelatin, casein, and styrene. Water-soluble binders such as maleic anhydride copolymer and polyacrylic acid amide can be used. From the viewpoint of storage stability of the fixable heat-sensitive recording material, as in the present invention, both the coupler compound and the guanidine derivative contained in the color developer layer are hydrophobic, and they physically interact with each other as a fine particle dispersion in the water-soluble binder. For example, in a method in which the coupler compound and the guanidine derivative are both dissolved in a polar organic solvent and a resin binder is used, the contact area between the coupler compound and the basic guanidine derivative becomes large. Coloring of the compound occurs over time, causing deterioration in storage stability. In addition, in order to prevent such deterioration, when using the coupler compound and guanidine derivative in a finely dispersed state in an organic solvent system, for example, cyclohexane,
It is limited to non-polar solvents such as n-hexane, and resin binders that are compatible with the solvent are limited to resin binders that do not have polar groups, mainly petroleum resins such as terpene resins and cyclized rubber. ,
Such a resin binder generally has a low softening point and tends to generate so-called staking, which is an adhesion sound with a thermal head during thermal recording, which is undesirable. In addition, the color developer layer of the present invention also contains formalin, which is commonly used to make water-soluble binders water resistant.
Water resistance agents such as glyoxal, glutaraldehyde, epoxy compounds and other appropriate melting point depressants include animal waxes, vegetable waxes, petroleum waxes, polyhydric alcohol esters of higher resin acids, higher ketones, higher amines, Examples include higher fatty acid amides, condensates of higher fatty acids and amines, synthetic paraffins and chlorinated paraffins, and these may be used alone or in combination of two or more in the form of fine powders or emulsions. As the support, in addition to paper, synthetic resin films, laminated paper, woven fabric sheets, etc. can also be used. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 Solution A: 1-diazo-2.5-dibutoxy-4-morpholinobenzene borofluoride salt 1 g Maleic acid 0.4 g Vinyl acetate 3 g Methyl ethyl ketone 80 ml Methanol 20 ml Solution B: 1.3-diphenyl-2-P-tolyl-guanidine (Compounds in Table 1) 7 g Stearamide 3 g 10% aqueous gum arabic solution 7 g Water 20 g A composition was ground and dispersed in a ball mill for 24 hours to prepare Solution B. C liquid: A composition containing 10 g of 10% aqueous gum arabic solution, 7 g of water, and 20 g of water is prepared under the same conditions as Solution B. Solution D: Solution B 10g Solution C 5g 10% polyvinyl alcohol aqueous solution 20g Glyoxal 0.2g Water 10g The above Solution A was applied onto a polyester film so that the coating amount after drying was 4.0g/m ³ to form a photosensitive and thermosensitive layer. Then, a color developer layer was formed by coating Liquid D on the layer so that the coating amount after drying was 7.0 g/m ³ to obtain a fixable heat-sensitive recording material. This thermosensitive recording material developed a yellow color when heated for 0.5 seconds on a hot plate at 120°C. Further, the color was developed by heating and then fixed by exposure to ultraviolet light. When the color density after fixing was measured using a densitometer manufactured by Tokyo Kohden Co., Ltd., it was 1.21.
It was hot. In addition, the heat-sensitive recording material created in this way was heated to 40℃.
It was left to stand for 24 hours under 90% conditions and fixed by ultraviolet exposure, but there was almost no background fog in the moisture resistance test and the background density was 0.11. Example 2 In Example 1, except that the same amount of 2-hydroxynaphthalene-3-carboxylic acid-α-morpholino-propylamide (compound (4) in Table 2) as the diazonium salt was added to the composition of Solution A. Totally Example 1
A fixing type thermosensitive recording material was prepared in the same manner as described above. This heat-sensitive recording material was heated for 0.5 seconds on a hot plate at 120° C. and then fixed with ultraviolet light to obtain a black color with a color density of 1.16. Further, even in a moisture resistance test under the same conditions as in Example 1, there was almost no background fog, and the background density after fixing was 0.10. Comparative example 1 In Example 1, 1,3-diphenyl-2 of liquid B
A fixable heat-sensitive recording material was obtained in the same manner as in Example 1 except that stearylamine was used instead of -P-tolyl-guanidine. When heated for 0.5 seconds on a hot plate at 120°C, a yellow color developed, but the color density was weak, and the color density after fixing with ultraviolet light was 0.36, and the color developed with lower thermal energy than the guanidine derivative according to the present invention. The concentration is quite low. Comparative Example 2 A fixable heat-sensitive recording material was prepared in the same manner as in Example 1 except that a water-soluble coupler compound was used in liquid C in the following composition. Solution C: Sodium 1.8-dihydroxy-naphthalene-6-sulfonate 10 g Water 25 g This thermosensitive recording material developed a blue color with a color density of 1.02 when heated for 0.5 seconds on a hot plate at 120°C. However, when this heat-sensitive recording material was subjected to a moisture resistance test under the same conditions as in Example 1, the background color developed almost over the entire surface, and the background density after ultraviolet light fixation was 0.75. As explained above, by containing the hydrophobic guanidine derivative and the hydrophobic coupler compound according to the present invention in the developer layer, it is possible to obtain a fixable heat-sensitive recording material that has particularly good moisture resistance and storage stability, and also has high color density. I can do it.

Claims (1)

[Scope of Claims] 1. A light-sensitive and heat-sensitive layer on a support, comprising an acid-stabilized diazonium salt capable of reacting with a coupler compound to form a dye, and a binder material; further on the layer, a water-soluble layer comprising a natural or synthetic polymer compound; a hydrophobic coupler compound dispersed in particulate form in the water-soluble binder and the acid-stabilized diazonium salt of the following general formula capable of supplying the necessary amount of base to sufficiently react with the coupler compound. A fixable heat-sensitive recording material having improved storage stability and comprising a color developer layer containing a particulate dispersion of a hydrophobic guanidine derivative as a main component. general formula [In the formula, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen, alkyl having 18 or less carbon atoms, cyclic alkyl, aryl, aralkyl, amino, alkylamino, acylamino,
Carbamoylamino, represents a heterocyclic residue, R ₅ is lower alkylene, phenylene, naphthylene or [Formula] (wherein X represents lower alkylene, SO ₂ , S ₂ , S, O, -NH- or a single bond) The aryl group in the formula includes those having a substituent selected from lower alkyl, alkoxy, nitro, acylamino, alkylamino groups and halogen. 2. The fixable heat-sensitive recording material with improved storage stability according to claim 1, wherein the hydrophobic coupler compound is a compound having a diffusion-resistant group.