JPH0576919B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a light-fixing type thermosensitive recording medium that performs recording by heating and fixing non-recorded areas by light irradiation, and more specifically, it is capable of thermal recording with high sensitivity,
The present invention also relates to a black coloring light-fixing type heat-sensitive recording medium that has excellent storage stability. <Prior Art> Recently, thermal recording methods have come into widespread use in facsimile machines, printers, etc. because the devices can be made smaller and lighter and recording can be performed without noise. However, the currently widely used dye-colored thermal recording paper that utilizes the reaction between an electron-donating substance and an electron-accepting substance cannot be colored by reheating or organic solvents, or can be colored by using adhesives or cellophane tape. There was a problem with the color fading. There is a fixable heat-sensitive recording paper that solves these drawbacks and utilizes a heat-developable diazo method. When this heat-developable diazo paper is used as a heat-sensitive recording paper, recording is first performed using heat, and then fixing is performed using light. Various color tones can be obtained by selecting a coupler, but pure black color tone is particularly desired. Conventionally, phloroglucin has been widely used to obtain a black color tone. However, recording paper containing phloroglucin as a coupler tends to cause pre-coupling at high temperatures, and even after fixing, the background tends to discolor in bright places. Also β−
A method has also been used in which a naphthol-based blue coupler and a phenol-based or active methylene-based yellow to red coupler are mixed. However, in this case, the coupling speed differs depending on the combination of diazonium salt and coupler, so it is extremely difficult to find a combination of a mixture of diazonium salt and coupler that can always produce a black color under any coloring conditions. be.
Furthermore, many proposals have been made regarding the heat development diazo method. However, nothing has yet been produced that can satisfy both the high thermal sensitivity recordable by a thermal head and sufficient storage stability. <Problems to be Solved by the Invention> The present invention has been made in order to solve the above-mentioned drawbacks, and its purpose is to provide a light-fixing type thermosensitive material that always shows a good pure black tone under any heating conditions. The goal is to provide recording media. <Means for Solving the Problems> The present invention has found a specific combination of a blue color-forming coupler and a yellow to red color-forming coupler in order to produce a light-fixing heat-sensitive recording medium that exhibits a pure black color. It is something. That is, the present invention provides a light-fixing heat-sensitive recording medium in which a light-fixing heat-sensitive recording layer containing a diazonium salt and a coupler as main components is provided on a substrate, in which a blue color-forming coupler is provided in the light-fixing heat-sensitive recording layer. General formula below ()
and at least one compound selected from the following general formula () as a yellow to red color-forming coupler.

embedded image [wherein R ₁ represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkyl group]. ]

[In the formula, R ₂ represents hydrogen, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group. ] Next, the heat-sensitive recording material used in the present invention will be explained in detail. As the diazonium salt of the present invention, a conventionally known diazonium salt having an absorption wavelength peak in the region of 350 to 430 nm is used. That is, the diazonium salt can be photodecomposed by irradiating light in the above wavelength range. Specific examples of diazonium salts include 4-N,N-dimethylaminobenzenediazonium salt, 4-N,N-diethylaminobenzenediazonium salt, 4-N,N-diethylamino-3-(4'-chlorophenoxy)- 6-chlorobenzenediazonium salt, 4-morpholino-2,5-
Diethoxybenzenediazonium salt, 4-morpholino-2,5-n-dibutoxybenzenediazonium salt, diphenylamine-4-diazonium salt, 4-(p-tolylmercapto)-2,5-diethoxybenzenediazonium salt, 4- Examples include pyrrolidino-3-methylbenzenediazonium salt and 4-benzamide-2,5-diethoxybenzenediazonium salt. The anion components of these diazonium salts include Cl ^-・1/2ZnCl ₂ ,
BF ^- ₄ , TiF ₆ ^2- , SnF ₆ ^2- , ZnF ₄ ^2- , PF ₆ ^- ,
Examples include SCN ^- , phosphotungstate ion, phosphomolybdate ion, arylsulfonate ion, organic boron ion, and the like. Here, specific examples of arylsulfonic acid ions are shown below.

【formula】

【formula】

【formula】

【formula】

[Formula] In the above specific examples, the 2,3-dihydroxynaphthalene-6-sulfonic acid ion also functions as a coupler. Further, the organic boron ion is represented by the following general formula.

[Formula] However, R ₁ to _{R 4} each represent an alkyl group, an alkenyl group, a cycloalkyl group, an allyl group, an aryl group, a heterocyclic group, or a cyano group. A specific example is shown below.

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] Specific examples of the blue color-forming coupler represented by the general formula () used in the present invention are shown below.

[ka]

[ka]

[ka]

[ka]

[ka]

[ka]

【formula】

【formula】

【formula】

[ka]

【formula】

【formula】

[Formula] Yellow ~ of the general formula () used in the present invention
Specific examples of red coloring couplers include the following.

【formula】

[ka]

[ka]

[ka]

[C] The molar ratio of the above blue color coupler and yellow to red color coupler is usually 10:1 to 1:
5, preferably 8:1 to 1:2. The molar ratio of the diazonium salt to the coupler mixture is suitably 1:1 to 1:5. In the medium of the present invention, it is preferable to also use a basic substance to create a basic atmosphere suitable for the coupling reaction between the diazonium salt and the coupler during heating. Conventionally, water-soluble basic substances such as urea and its derivatives, inorganic and organic ammonium salts, and organic amines have been used. However, it is preferable to use a water-insoluble or sparingly water-soluble basic substance in order to improve raw storage stability under high humidity conditions.
Examples of this include distearylamine, 2-phenylimidazole, 2,4-diamine-6{2'-methylimidazolyl-(1'){ethyl-s-triazine, 1,3-di-o-tolylguanidine and 1 , 2,3-tolylphenylguanidine and the like. In the present invention, in order to further improve the storage stability at high humidity, an organic boron salt having the following general formula, which is an agent for making the diazonium salt water insoluble or hardly water soluble, can be used.

[Formula] [However, R ₁₂ to _{R 14} each represent an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, a heterocyclic group, or a cyano group. M represents Li or Na. ] A specific example of this is shown below.

[ka]

[ka]

[C] These organic boron salts are added to the paint as a solution, and the amount used is 0.1 to 1000% by weight of the diazonium salt in solid form, more preferably 10 to 300% by weight. be. The binders used in the present invention include conventionally known water-soluble binders such as polyvinyl alcohol (hereinafter abbreviated as PVA), starch, isobutylene-maleic anhydride copolymer salt, polyvinyl acetate, polyacrylic Examples include various emulsions such as acid esters, polyurethanes, styrene-butadiene latexes, polyesters, polyvinyls, polyurethanes, celluloses, rubbers, and various solvent-soluble binders. In addition, in the present invention, inorganic pigments such as silica, aluminum hydroxide, and calcium carbonate, organic pigments such as crosslinked styrene fine particles, urea-formalin resin fine particles, benzoguanamine resin fine particles, oxalic acid,
Acid stabilizers such as tartaric acid and trichloroacetic acid, antioxidants such as thiourea ascorbic acid, various waxes as coloring sensitivity and coloring density improvers, and aluminum tripolyphosphate for improving storage stability can be used. Substrates used in the present invention include wood-free paper, coated paper, art paper, synthetic resin film, woven fabric sheet,
Metal, glass, etc. can be used. The photo-fixable heat-sensitive recording medium of the present invention is prepared by dissolving or dispersing the diazonium salt, coupler mixture and other necessary components in water or a solvent, and coating the solution together with a binder on the above substrate to form a photo-fixable heat-sensitive recording layer. be done. The photofixable heat-sensitive recording layer referred to in the present invention contains a diazonium salt, two or more couplers, and if necessary a basic substance, all in one layer, or contains two or more diazonium salts and couplers.
It can also be constructed by having it exist in two or more layers. <Example> Next, the specific production of the photofixable thermosensitive recording medium of the present invention will be described with reference to Examples, but the present invention is not limited thereto. Example 1 A paint having the following formulation was prepared, applied onto high-quality paper weighing 64 g/m ² using a wire bar, and dried at 55°C. The dry coating weight was 6.2 g/m ² . 20% aqueous dispersion of 4-(p-tolylmercapto)-2,5-diethoxybenzenediazonium PF ₆ salt 3 g

【formula】 4g of 20% aqueous dispersion of

20% aqueous dispersion of [chemical] 1g 20% aqueous dispersion of 1,3-di-o-tolylguanidine 5g 40% aqueous dispersion of calcium carbonate 11g 20% aqueous dispersion of stearamide 5g Tetraphenylboron 20% aqueous solution of sodium
3g 10% aqueous solution of PVA 14g When this photofixable thermosensitive recording medium was pressed against a hot plate at a predetermined temperature for 5 seconds under a pressure of 100g/m ² to develop color, the maximum density of black was 1.29; The temperature at which the coloring started was 78°C, which was the temperature that gave half the density. Furthermore, the color tone did not change depending on the temperature of the hot plate and always showed a pure black tone. A density of 1.10 was obtained when recording with a thermal head under printing conditions of an applied voltage of 16 V and a pulse width of 3.0 msec. Even when recording was performed by varying the applied voltage and pulse width, the color tone produced was always pure black. This light-fixing heat-sensitive recording medium can be left in room light for about an hour, or if exposed to light using two 85W ultraviolet fluorescent lamps at a distance of 2cm, it will complete fixing in about 10 seconds and has extremely excellent fixing properties. was. It was confirmed that the background color after fixing was also white, giving it excellent naturalness as a recording paper, and that no color developed even when heated after fixing. On the other hand, regarding storage stability, unrecorded media
℃, 60% relative humidity, shielded from light for 6 months or 40℃,
After being left in the dark for 24 hours at a relative temperature of 90%, the ground concentrations were measured to be 0.20 and 0.23, respectively. After light fixation, the ground color was only slightly gray. All concentrations were measured using the visual filter of Macbeth Densitometer (RD514). Example 2 A paint having the following formulation was applied to a high-quality paper with a basis weight of 64 g/m ² using a wire bar, and dried at 120° C. to produce prerecorded paper. The dry coating weight was 3.5 g/m ² . 30 g of 10% aqueous solution of PVA 5 g of 20% aqueous solution of glyoxal 15 g of 40% aqueous dispersion of calcium carbonate A diazo dye having the following formulation was applied onto the precoated paper using a wire bar and dried at 60°C. The dry coating weight was 3.2 g/m ² . 4-N,N-diethylamino-3-(4'-chlorophenoxy)-6-chlorobenzenediazonium PF ₆ salt 0.6g Stearamide 3g Finely powdered silica 2g Sodium tetraphenylboronate 0.4g Vinyl chloride-vinyl acetate co 2.5 g of polymer (PVC/PVC = 86/14) 50 g of methyl ethyl ketone Further, a coupler paint having the following formulation was applied onto the diazo layer using a wire bar and dried at 55°C. The dry coating weight was 3.5 g/m ² .

【formula】 6.5g of 20% aqueous dispersion of

20% aqueous dispersion of [formula] 2g 20% aqueous dispersion of 1,2,3-triphenylguanidine 9g 40% aqueous dispersion of calcium carbonate 11g 20% aqueous solution of sodium tetraphenylboronate
6 g 10% aqueous solution of PVA 15 g When this photofixable thermosensitive recording medium was examined in the same manner as in Example 1, it exhibited pure black color development with a color development start temperature of 81° C. and a thermal head recording density of 1.02. A 24-hour storage test at 40°C and a relative humidity of 90% or less resulted in a soil concentration of 0.18. Further, the photofixing time was shortened to about 1/5 of that in Example 1, and the background color after fixing was sufficiently white and natural. Example 3 4-(p-tolylmercapto)-2 of Example 1,
5-diethoxybenzenediazonium PF ₆ salt
3 g of 20% aqueous dispersion was added to 4-morpholino-2,5-n
- Dibutoxybenzenediazonium PF ₆ salt 20
A photofixable thermosensitive recording medium of the present invention was prepared in the same manner as in Example 1 except that 3 g of the aqueous dispersion was used instead. When this photofixable thermosensitive recording medium was examined in the same manner as in Example 1, the color density on the hot plate was 1.18, the temperature at which color development started was 82°C, and the recording density on the thermal head was 1.05. Further, the developed color tone was a good pure black tone as in Example 1. Comparative Example 1 In Example 3, an aqueous dispersion of a yellow to red color-forming coupler was

A light-fixing thermosensitive recording medium for comparison was prepared in the same manner as in Example 3, except that 1 g of the 20% aqueous dispersion of the formula was used instead. When this light-fixing type thermosensitive recording medium was examined in the same manner as in Example 3, the color density on the hot plate was 1.10, the temperature at which color development started was 84°C, and the recording density on the thermal head was 1.06, which were about the same as in Example 3. However, the developed color tone was deep blue and not pure black. <Effects of the Invention> As explained above, in the light-fixing heat-sensitive recording medium of the present invention, by combining a specific blue color-forming coupler and a yellow to red color-forming coupler with respect to diazonium salt, very good We were able to achieve a black color.

Claims (1)

[Scope of Claims] 1. A light-fixable heat-sensitive recording medium comprising a light-fixable heat-sensitive recording layer containing a diazonium salt and a coupler as main components on a substrate, wherein the light-fixable heat-sensitive recording layer has a blue color. A light characterized by containing at least one compound selected from the following general formula () as a color coupler and at least one compound selected from the following general formula () as a yellow to red color coupler. Fixed heat-sensitive recording medium. [Formula] [In the formula, R ₁ represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkyl group. ] [In the formula, R ₂ represents hydrogen, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group. ]