JPH0228479B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fixable multicolor thermosensitive recording material which has improved storage stability and which develops color at high density during high-speed thermosensitive 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. Furthermore, recently, attempts have been made to obtain multicolor recording by utilizing differences in heating temperature and thermal energy, and various multicolor thermosensitive recording materials have been proposed accordingly. For example, if two heat-sensitive layers that develop different colors depending on the change in color temperature are applied, the heat-sensitive layer that develops color at low temperatures will develop a single color, and at high temperatures, the heat-sensitive layers that develop color at low temperatures and You can obtain a two-layer mixed color that develops in color. In this case, if color-forming substances with completely different hues, such as red-blue or red-green, are used, it is possible to differentiate between monochromatic colors and mixed colors, and a two-color product can be obtained. Similarly, three colors can be obtained by applying three layers. However, the color formers commonly used in conventional multicolor thermosensitive recording materials include (a) leuco dyes such as triphenylmethane, fluoran, and phenothiazine, and pt-butylphenol, 4.4' - Combinations of organic acidic substances such as isopropylidene diphenol and p-phenylphenol (b) Combinations of long chain aliphatic iron salts such as ferric stearate and phenols such as tannic acid and gallic acid. However, with these conventional methods, if the printed material is accidentally heated after printing, the background may become colored and the printed text may become unreadable, or there is a possibility that the printed material may be tampered with after printing.Therefore, improvements are strongly desired. There is. 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, in the development process, the ammonia gum used in the conventional dry diazo method is not used, and development is performed only by heat, which is convenient because no irritating gas is 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 thermal recording systems, and it has been 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, these substances gradually undergo thermal decomposition 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. An object of the present invention is to overcome the above-mentioned drawbacks of conventional diazo-type photothermographic materials and provide a heat-sensitive recording medium that is highly sensitive, has excellent storage stability, and can be fixed. The object of the present invention is to provide a multicolor heat-sensitive recording material that can be fixed by utilizing the difference in thermal energy. In other words, in a heat-sensitive recording material formed by coating on the same support multiple layers of two or more heat-sensitive layers having different coloring temperatures, each containing a coupler compound that reacts with an acid-stabilized diazonium salt to form a dye, The object of the present invention is to provide a fixable multicolor heat-sensitive recording material, which contains in its layer a fine particulate dispersion of the acid-stabilized diazonium salt and a hydrophobic guanidine derivative represented by the following general formula. In particular, at least one of the coupler compounds used in the heat-sensitive recording medium is a compound having a diffusion-resistant group such as a long-chain aliphatic alkyl group or a long-chain aliphatic alkoxyl group, and the coupler compound is formed into fine particles. Provided is a fixable multicolor thermosensitive recording material which has particularly excellent storage stability when contained in a thermosensitive recording layer as a dispersion. The general formula is or [In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are hydrogen, alkyl having 18 or less carbon atoms, cyclic alkyl, aryl,
Represents aralkyl, amino, alkylamino, acylamino, carbamoylamino, heterocyclic residue,
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, alkoxy, nitro, acylamino, alkylamino Also included are those having substituents selected from groups and halogens. ] 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-
Diptoxy-4-morpholinobenzene borofluoride salts and the like can be arbitrarily selected and used. Further, as the binder material for forming the heat-sensitive layer of the present invention, a binder material made of a natural or synthetic polymer compound can be used, but it is necessary to stabilize the diazonium salt contained in the heat-sensitive layer and prevent pre-coupling. Therefore, the coating liquid for forming the heat-sensitive layer is acidic with a pH of 5 or less, and in order to stably exist the guanidine derivative of the present invention, which is a basic compound, as a fine particle dispersion in such an acidic coating liquid, generally It is preferable to use a nonionic polymer compound with excellent protective colloidal properties as the binder material.
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, the heat-sensitive layer can also be formed by appropriately adding an antioxidant, an image intensifying agent, and the like. Further, as the coupler compound used in the present invention, the following compounds having a water-soluble aromatic hydroxy compound or a hydrophobic aromatic hydroxy compound and a hydrophobic active hydrogen are dispersed in fine particles in a binder material. It can be used. Specifically, it is shown in Table 2, but this does not limit the present invention. If necessary, two or more coupler compounds may be combined to form a dye exhibiting desired spectral absorption characteristics. In addition, the 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, as well as other appropriate melting point depressants such as animal waxes, These include vegetable 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 and chlorinated paraffins, etc. These may be used alone or in combination of two or more in the form of fine powder or emulsion. As the support, in addition to paper, synthetic resin films, laminated paper, woven fabric sheets, etc. can also be used. In the present invention, multilayer coating is performed, and the difference in coloring temperature between the respective heat-sensitive layers is preferably 10 to 100°C. That is, when the temperature difference is less than 10° C., the low-temperature coloring layer and the high-temperature coloring layer develop color at the same time, so that almost no single color can be obtained by low-temperature coloring. It is preferable to maintain a temperature difference as much as possible in this way,
If the temperature exceeds 100℃, bleeding may occur and it is not practical. In addition, in the present invention, the coloring temperature of each heat-sensitive layer is determined by the melting point of the hydrophobic guanidine derivative used as a color developer, the type of melting point depressant used together if necessary, and the amount ratio with the hydrophobic guanidine derivative. Not only can it be changed, but if the coupler compound is contained in the heat-sensitive layer as a fine particle dispersion of a hydrophobic coupler compound, it can also be changed depending on the melting point of the coupler compound, so the coloring temperature of each heat-sensitive layer can be changed quite freely. It has the advantage of being controllable. Preferred combinations of color-forming substances include red-blue, red-green, red-black, magenta-cyan-yellow, and red-green-blue. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1

【table】

[Table] The amount of the above F solution applied after drying on plain paper is 10.0
g/m ² and dried at 60°C for 3 minutes to form a high-temperature coloring layer. Liquid C was applied onto the layer so that the coating amount after drying was 7.0 g/m ² and dried at 60° C. for 3 minutes to form a low-temperature coloring layer. Comparative example 1 In Example 1, 1,3-diphenyl-2 of liquid A
A fixable heat-sensitive recording material was obtained in the same manner as in Example 1 except that stearylamine was used in place of -P-tolylguanidine and 1,3-dicyclohexyl-2-phenylguanidine in Solution D. Comparative Example 2 A fixable thermosensitive recording material was obtained in the same manner as in Comparative Example 1 except that 2-phenylimidazoline was used instead of stearylamine. The low-temperature coloring part of the fixable multicolor heat-sensitive recording material prepared in this manner was heated for 0.5 seconds on a 90°C hot plate, and then heated on a 130°C hot plate to develop color.
By heating for 0.5 seconds, both the low-temperature coloring area and the high-temperature coloring area were colored, and after heating and coloring, they were fixed by exposure to ultraviolet light. The low-temperature coloring area was colored red, and the high-temperature coloring area was black. After fixing, color density and background fog due to heating during drying were measured using a densitometer manufactured by Tokyo Kohden Co., Ltd.

[Table] As explained above, by incorporating the hydrophobic guanidine derivative according to the present invention in the form of a fine particle dispersion in the heat-sensitive layer, a multicolor coloring thermosensitive layer with excellent preservability and high sensitivity fixation can be obtained. You can get records.

Claims (1)

[Scope of Claims] 1. A heat-sensitive material comprising two or more heat-sensitive layers having different coloring temperatures, each containing a coupler compound that reacts with an acid-stabilized diazonium salt to form a dye, coated on the same support in multiple layers. A fixable multicolor heat-sensitive recording medium, wherein at least one of the heat-sensitive layers contains a fine particle dispersion of the acid-stabilized diazonium salt and a hydrophobic guanidine derivative represented by the following general formula. body. general formula or [In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are hydrogen and the number of carbon atoms
represents an alkyl, cyclic alkyl, aryl, aralkyl, amino, alkylamino, acylamino, carbamoylamino, heterocyclic residue of 18 or less,
R ₆ represents 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 Also included are those having substituents selected from alkyl, alkoxy, nitro, acylamino, alkylamino groups and halogen. 2. The fixable multicolor thermosensitive recording material according to claim 1, wherein at least one of the coupler compounds is a hydrophobic compound having a diffusion-resistant group.