JPH0536238B2 - - 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] The thermal recording method has recently come into widespread use in facsimile machines, printers, etc. due to its advantages such as the ability to reduce the size and weight of devices and to perform noiseless recording. 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 under high humidity, and has the drawback that even after fixing, the background tends to discolor in bright places. Also β−
A method is also 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, since the rate of coupling with the diazonium salt differs depending on each coupler, it is very difficult to always show a black color under any coloring conditions. 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. [Object of the Invention] The present invention has been made in order to solve the above-mentioned drawbacks, and its purpose is to provide a black coloring light-fixing type thermal recording medium that always shows good pure black coloring under any heating conditions. It is about providing. [Structure of the Invention] To summarize the present invention, the present invention relates to a black coloring light-fixing type heat-sensitive recording medium, and the present invention relates to a light-fixing type heat-sensitive recording medium containing a diazonium salt and a coupler as main components. : (However, in the formula, R ₁ to _{R 3} each have a carbon number of 1 to
4 alkyl group, X represents a counter anion component), a blue-coloring β-naphthol coupler, and the following formula and: At least one of the yellow-colored couplers represented by
It is characterized by containing seeds. Specific examples of diazonium salts used in the present invention include the following. In order to improve the storage stability under high humidity of the photofixable heat-sensitive recording medium of the present invention, it is desirable to select a water-insoluble or slightly water-soluble diazonium salt. For this purpose, preferred anion components of the diazonium salt include BF ₄ ^- , PF ₆ ^- , and organic boron ions represented by the following general formula. However, R ₄ to _{R 7} each represent an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, a heterocyclic group, or a cyano group. A specific example is shown below. The blue color-forming coupler used in the present invention is a β-naphthol coupler, and is preferably a poorly water-soluble material, particularly from the viewpoint of storage stability. Examples of such couplers include: Naphthol AS, Naphthol AS-D, Naphthol AS-OL, Naphthol AS-E, Naphthol AS-BG, Naphthol ASITR, Naphthol AS
−BS, naphthol AS−LC, naphthol AS−
BO, naphthol AS−MX, naphthol AS−
SW, β-naphthol, 2-hydroxy-3-naphthoic acid methyl ester, 2-hydroxy-3-
naphthoic acid hydroxyethylamide, 2-hydroxy-3-naphthoic acid amide, 2-hydroxy-
3-naphthoic acid-γ-morpholinopropylamide, 2-hydroxy-3-naphthoic acid-β-N,
N-dimethylamino-ethylamide, 2-hydroxy-3-naphthoic acid-γ-N,N-dimethylamino-propylamide, 2-hydroxy-3-naphthoic acid-β-N,N-dimethylamino-ethylamide, 2- Hydroxy-3-naphthoic acid-β-
Morpholino-ethylamide, 2-hydroxy-3
-Naphthoic acid-γ-2'-methyl-morpholino-propylamide. The yellow color coupler of the present invention is preferably selected from the following. The mixing ratio of the blue coupler and the yellow coupler is usually 10:1 to 1:10, preferably 5:1 to 1:2 in terms of molar ratio. Also, the molar ratio of diazonium salt and coupler mixture is 1:1.
~1:5 is appropriate. In the medium of the present invention, a basic substance is also preferably used 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 poorly water-soluble basic substance in order to improve raw storage stability under high humidity conditions. Examples include distearylamine, 2-phenylimidazole, 1,3-di-o-tolylguanidine, and 1,2,3-triphenylguanidine. 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 rendering diazonium salt water insolubilizing or water hardly solubilizing, can be used. However, R ₄ to _{R 7} each represent an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, a heterocyclic group, or a cyano group. M ⁺ is L _i or
Represents Na ⁺ . A specific example of this is shown below. These organic boron salts are added to the paint as a solution, and the amount used is 0.1 to 1000% by weight, more preferably 10 to 300% by weight of the diazonium salt in solid form. 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 and styrene-butadiene latexes, and various solvent-soluble binders such as polyester, polyvinyl, cellulose, and rubber binders. In addition, in the present invention, pigments such as silica, aluminum hydroxide, and calcium carbonate, antioxidants such as thiourea and ascorbic acid, various waxes as coloring sensitivity and coloring density improvers, and tripolyline for improving storage stability are used. Aluminum acid 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. [Example] Next, the specific production of the photofixable heat-sensitive 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 with a basis weight of 64 g/m ² using a wire bar, and dried at 55°C. The dry coating amount was 5.0 g/m ² .

20% aqueous dispersion of [formula] 3g 20% aqueous dispersion of naphthol AS 4.5g 20% aqueous dispersion of naphthol AS-G 2.5g 20% aqueous dispersion of 1,3-di-o-tolylguanidine 5g carbonic acid 40% aqueous dispersion of calcium 10g 20% aqueous dispersion of stearamide 5g 20% aqueous solution of sodium tetraphenylboronate
3 g 10% aqueous solution of PVA 14 g This photofixable thermosensitive recording medium was pressed against a hot plate at a predetermined temperature for 5 seconds under a pressure of 100 g/cm ² to develop color, and a black image was formed. The maximum density at this time was 1.32, and the color development temperature was 78°C, which was the temperature that gave half the maximum 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 has extremely excellent fixing properties, with fixing completed in about 10 seconds when left for about an hour under room light or exposed at a distance of 2 cm using two 85W ultraviolet fluorescent lamps. 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 humidity 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 coated with a wire bar on a high-quality paper having a basis weight of 34 g/m ² and dried at 120° C. to prepare pre-coated 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 paint having the following formulation was applied onto the precoated paper using a wire bar and dried at 60°C. The dry coating weight was 2.8 g/m ² .

〔Effect of the invention〕

As explained above, the black coloring light-fixing thermosensitive recording medium of the present invention was able to achieve very good black coloring by combining a specific diazonium salt and a coupler.

Claims (1)

[Scope of Claims] 1. A photofixable heat-sensitive recording medium containing a diazonium salt and a coupler as main components, which has the following general formula: (However, in the formula, R ₁ to _{R 3} each have a carbon number of 1 to
4 alkyl group, X represents a counter anion component), a blue-coloring β-naphthol coupler, and the following formula and: At least one of the yellow-colored couplers represented by
A black colored light-fixing heat-sensitive recording medium characterized by containing seeds.