JPH0220434B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fixable heat-sensitive recording material that has improved storage stability when coated in a single layer, and moreover, relates to a fixable heat-sensitive recording material that develops color with high density even during high-speed 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. It 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, heat-sensitive photosensitive materials that have on a support a component that generates alkali through thermal decomposition, a diazonium salt that develops color with alkali, and a coupler compound, and where necessary binders, acid stabilizers, etc. are added, are called diazo-type photosensitive materials. 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, even in the thermal recording method, there is a demand for particularly high recording speed, 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 provide a heat-sensitive recording material that has excellent storage stability when coated in a single layer, has a high color density, and can be fixed. A binder consisting of an acid-stabilized diazonium salt that can react to form a dye, a natural or synthetic polymer compound, a hydrophobic coupler compound dispersed in the form of fine particles in the binder, and the acid-stabilized diazonium salt as a coupler compound. A fixing type characterized by forming a single-layer photosensitive/thermosensitive layer by containing a fine particulate dispersion of a hydrophobic guanidine derivative having the following general formula capable of supplying the necessary amount of base for sufficient reaction. An object of the present invention is to provide a thermosensitive recording medium. 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. The general formula is [In the formula, R ₁ and R ₂ represent hydrogen, an alkyl having 18 or less carbon atoms, a cyclic alkyl, a substituted or unsubstituted aromatic group, amino, alkylamino, acylamino, carbamoylamino, or a heterocyclic residue. R ₃ represents an alkyl having 18 or less carbon atoms, a cyclic alkyl, a substituted or unsubstituted aromatic group, amino, alkylamino, acylamino, carbamoylamino, or a heterocyclic residue. ] Furthermore, typical examples are shown in Table 1.
This does not limit the invention. In the table

[Formula] represents a cyclohexyl group. 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. Furthermore, as the binder material for forming the photosensitive/thermosensitive layer of the present invention, a binder material made of a natural or synthetic polymer compound may be used, but stabilization and precoupling of the diazonium salt contained in the photosensitive/thermosensitive layer may be used. In order to prevent this, the coating liquid for forming a photosensitive and heat-sensitive layer is acidic with a pH of 5 or less, and the guanidine derivative of the present invention, which is a basic compound, is stably present in the form of a fine particle dispersion in the acidic coating liquid. In general, it is preferable to use a nonionic polymer compound with excellent protective colloidal properties as the binder material, and for example, methylcellulose, hydroxymethylcellulose, polyvinyl alcohol, polyacrylamide, etc. can be suitably used. Furthermore, for applications requiring water resistance, it is a matter of course that the water resistance can be improved by using a synthetic resin emulsion in which a nonionic polymer compound is the main component of the binder material. 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, gluconic acid, and the like 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 present invention, the following compounds having a hydrophobic aromatic hydroxy compound and a hydrophobic active hydrogen can be used by dispersing them in the form of fine particles in a binder material. Specifically, it is shown in Table 2, but this does not limit the present invention. If necessary, two or more hydrophobic coupler compounds may be combined to form a dye exhibiting desired spectral absorption characteristics. From the viewpoint of storage stability of the fixing type heat-sensitive recording material, it is preferable that the coupler compound and the guanidine derivative are both hydrophobic and physically separated from each other as a fine particle dispersion in a water-soluble binder as in the present invention. For example, in a method in which the coupler compound and the guanidine derivative are both dissolved in a polar organic solvent and a synthetic resin binder is used, the contact area between the coupler compound and the basic guanidine derivative increases, which may cause coloring of the coupler compound over time. This will cause deterioration in storage stability. In addition, the photosensitive and heat-sensitive layer of the present invention may contain other water-resistant agents such as formalin, glyoxal, glutaraldehyde, and epoxy compounds, which are commonly used to make water-soluble binders water-resistant, and animal waxes as appropriate melting point depressants. , plant waxes,
Petroleum waxes, polyhydric alcohol esters of higher fatty acids, higher ketones, higher amines, higher fatty acid amides, condensates of higher fatty acids and amines, synthetic paraffins, chlorinated paraffins, etc. These may be used in combination as fine powder or emulsion. 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: A solution containing 70 g of the compound shown in Table 1, 30 g of stearamide, 70 g of 10% aqueous methylcellulose solution, and 200 g of water was ground and dispersed in a ball mill for 72 hours to prepare Solution A. B liquid:

A composition with the formulation shown in [Table] is prepared under the same conditions as Solution A. Solution C: Water 100g Citric acid 2g Sulfosalicylic acid 3g 1-diazo-2,5-diethoxy-4-morpholinobenzene borofluoride salt 2g Solution A 6g Solution B 120g 10% hydroxyethyl cellulose aqueous solution 30g 20% polyacrylamide aqueous solution 35g The coating amount of liquid C on plain paper after drying is 11.0
g/m ² to form a photosensitive and heat sensitive layer, and dried at 60° C. for 3 minutes to obtain a fixable heat sensitive recording material. Example 2 Solution D: A composition containing 70 g of the compound shown in Table 1, 30 g of stearamide, 70 g of 10% aqueous methylcellulose solution, and 200 g of water is prepared under the same conditions as Solution A. E liquid:

A composition with the formulation shown in [Table] is prepared under the same conditions as Solution A. Solution F: Water 100g Malonic acid 2g Sulfosalicylic acid 3g 1-diazo-2,5-diethoxy-4-morpholinobenzene borofluoride salt 2g Solution D 7g Solution E 100g 10% methylcellulose aqueous solution 30g 20% polyacrylamide aqueous solution 35g Above F Apply the solution onto a polyester film so that the coating amount after drying is 10.0 g/m ² and heat at 60°C.
The mixture was dried for 3 minutes to obtain a fixable heat-sensitive recording material. Comparative Example 1 A fixable heat-sensitive recording material was obtained in the same manner as in Example 2 except that stearylamine was used instead of the compound shown in Table 1. Comparative Example 2 In Example 2, 2 was used instead of the compound in Table 1.
A fixable heat-sensitive recording material was obtained in the same manner as in Example 2 except that -phenylimidazoline was used. Comparative Example 3 Solution G: Water 100g Malonic acid 2g Sulfosalicylic acid 3g 1-Diazo-2,5-diethoxy-4-morpholinobenzene borofluoride salt 2g Sodium 2,3-dihydroxy-6-sulfonate 1.5g Example 2 D liquid 100g 10% methyl cellulose aqueous solution 30g 20% polyacrylamide aqueous solution 35g More than G liquid applied on plain paper after drying, the coating amount is 11.0
g/m ² and dried at 60° C. for 3 minutes to obtain a fixable heat-sensitive recording material. Comparative Examples 4, 5 and 6 In Example 2, 1,3-di-O-tolylguanidine 1,2,
A fixing type thermal paper was obtained in the same manner as in Example 2 except for 3-triphenylguanidine and 1,3-diphenyl-2-cyclohexylguanidine. The fixing type heat-sensitive recording material created in this way is
Develop color by heating for 0.5 seconds on a hot plate at 140℃,
After the color was developed by heating, it was fixed by exposure to ultraviolet light. After establishment,
Color density and background fog due to heating during drying were measured using a densitometer manufactured by Tokyo Kohden Co., Ltd.
In addition, this fixing type heat-sensitive recording material was heated at 35℃ and 80% for 24 hours.
Table 3 shows the results of leaving it for a while, fixing it by UV exposure, and measuring the background fog in a moisture resistance test.

[Table] As explained above, by incorporating the hydrophobic guanidine derivative and the hydrophobic coupler compound according to the present invention in the form of fine particle dispersion in the light and heat sensitive layer, a fixing type with particularly good moisture resistance and storage stability and high color density can be obtained. A thermosensitive recording material can be obtained by coating in a single layer.

Claims (1)

[Scope of Claims] 1. A binder material consisting of an acid-stabilized diazonium salt, a natural or synthetic polymer compound capable of reacting with a coupler compound to form a dye on a support, and a binder material dispersed in the binder material in the form of fine particles. A photosensitive material containing a fine particulate dispersion of a hydrophobic guanidine derivative having the following general formula capable of supplying the necessary amount of base to enable the hydrophobic coupler compound and the acid-stabilized diazonium salt to sufficiently react with the coupler compound. A fixable heat-sensitive recording material characterized by forming a heat-sensitive layer. general formula [In the formula, R ₁ and R ₂ represent hydrogen, an alkyl having 18 or less carbon atoms, a cyclic alkyl, a substituted or unsubstituted aromatic group, amino, alkylamino, acylamino, carbamoylamino, or a heterocyclic residue. R ₃ represents an alkyl having 18 or less carbon atoms, a cyclic alkyl, a substituted or unsubstituted aromatic group, amino, alkylamino, acylamino, carbamoylamino, or a heterocyclic residue. 2. The fixing type heat-sensitive recording material according to claim 1, wherein the binder material is a nonionic polymer compound. 3. The fixable heat-sensitive recording material according to claim 1, wherein the hydrophobic coupler compound is a compound having a diffusion-resistant group.