JPH0374637B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a light-fixing thermosensitive recording medium that performs recording by heating and fixes non-recorded areas by irradiation with light, and more specifically relates to a heat-sensitive recording medium that performs thermal recording with high sensitivity. It is possible and
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 make the device smaller and lighter and to perform recording 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 using this heat-developable diazo paper as a heat-sensitive recording paper,
First, recording is performed using heat, and then fixing is performed using light. Various color tones can be obtained at this time depending on the selection of the coupler, but
In particular, there is a strong demand for pure black color tone.

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 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, because the coupling speed differs depending on the combination of diazonium salt and coupler, 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. It is. Furthermore, many proposals have been made regarding the thermal phenomenon 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 good pure black coloring under any heating conditions. The goal is to provide recording media.

<Means for Solving the Problems> In order to produce a light-fixing type heat-sensitive recording medium exhibiting good pure black tone color development, the present invention uses a diazonium salt, a blue color-forming layer as a composition of a heat-sensitive color forming layer provided on a substrate. A specific combination of three components, a coupler and a yellow to red color-forming coupler, has been discovered.
That is, at least one compound selected from the following general formula () and/or () as the diazonium salt, at least one compound selected from the following general formula () as the blue coloring coupler, and a yellow to red compound. The object of the present invention is achieved by using at least one compound selected from the following general formula () as a color-forming coupler.

[In the formula, R ₁ and R ₂ represent hydrogen or a substituted or unsubstituted alkyl group. However, R ₁ and R ₂ are not hydrogen atoms at the same time. Y represents hydrogen or halogen. ] [In the formula, R ₃ represents a C ₁ to C ₁₈ alkyl group or an alkoxyl group, and R ₄ represents a C ₁ to C ₁₈ alkyl group. X represents a counter anion component. ] [In the formula, R ₅ represents a substituted or unsubstituted aromatic ring or a substituted or unsubstituted alkyl group. ] [In the formula, R ₆ represents a substituted or unsubstituted alkyl group or alkoxyl group, and R ₇ represents a substituted or unsubstituted alkyl group. ] Specific examples of the diazonium salt represented by the general formula () used in the present invention are shown below.

Specific examples of the diazonium salt represented by the general formula () used in the present invention include the following.

In order to improve the shelf life of the photofixable thermosensitive recording medium of the present invention at high temperatures, it is desirable to select a diazonium salt that is insoluble or poorly soluble in water. For this purpose, preferable anion components of the diazonium salt include BF ₄ , PF ₄ and organic boron ions represented by the following general formula.

[However, R ₁₁ to _{R 14} 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.

Specific examples of the blue coloring coupler represented by the general formula () used in the present invention are shown below.

(naphthol AS) (Naphthol AS-D) (Naphthol AS-OL) (Naphthol AS-E) (Naphthol AS-ITR) (Naphthol AS-BO) Yellow ~ of the general formula () used in the present invention
Specific examples of red coloring couplers include the following.

The molar ratio of the blue coupler and the yellow to red coupler is usually 10:1 to 1:
10 The ratio is preferably 5:1 to 1:2. The molar ratio of the diazonium salt to the coupler mixture is suitably 1:1 to 1:5.

In the photofixable thermosensitive recording 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 distearylmine, 2-phenylimidazole, 1,3-di-o
-Tolylguanidine, 1,2,3-triphenylguanidine, 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 insolubilizing or hardly water soluble, can be used.

[However, R ₁₁ 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 _L1 or Na. ] A specific example of this is shown below.

These organic boron salts are added to the paint as a solution, but the amount used is preferably 0.1 to 1000% by weight of the diazonium salt in solid form.
10-300% parts by weight.

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, and styrene-butadiene latexes, and various solvent-soluble binders such as polyester-based, polyvinyl-based, polyurethane-based, cellulose-based, and rubber-based binders.

In addition, in the present invention, inorganic materials 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 triclochloric acid, antioxidants such as thiourea ascorbic acid, various waxes as color sensitivity and color 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 photofixable heat-sensitive recording medium of the present invention is produced by dissolving or dispersing the diazonium salt, the coupler mixture and other necessary components in water or a solvent, and coating the solution together with a binder on the above-mentioned substrate. Here, the diazonium salt, the coupler mixture and, if necessary, the basic substance are all contained in one heat-sensitive coloring layer or are separated into two or more heat-sensitive coloring layers, and in the latter case, many combinations are possible. can be taken.

<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 with a basis weight of 64 g/m ² using a wire bar, and dried at 55°C. The dry coating weight was 4.5 g/m ² .

3g of 20% aqueous dispersion of 4g of 20% aqueous dispersion of 20% aqueous dispersion of 1 g 20% aqueous dispersion of 1,3-di-o-tolylguanidine 5 g 40% aqueous dispersion of calcium carbonate 11 g 20% aqueous dispersion of stearic acid amide 5 g Sodium tetraphenylboronate 20 % aqueous solution 3 g 10% aqueous solution of PVA 14 g When 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, the maximum density of black was 1.32. The color density was 78°C, which was defined as the temperature that gave half the maximum density. Moreover, the color tone did not change depending on the temperature of the hot plate and always showed pure black.

When recording with a thermal head under printing conditions of an applied voltage of 16 V and a pulse width of 3.0 msec, a density of 1.10 was obtained. Even when recording was performed by varying the applied voltage and pulse width, the developed color tone 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 after fixing was also white and had 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 applied onto a high-quality paper with a basis weight of 65 g/m ² using a wire bar, and dried at 120° C. to prepare a 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 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 2.8 g/m ² .

0.6g Stearamide 3g Finely powdered silica 2g Sodium tetraphenylborate 0.4g Vinyl chloride-vinyl acetate copolymer (PVC/vinyl acetate = 86/14) 2.5g Methyl ethyletone 50g Furthermore, the following formulation was applied on this diazo layer. Coupler paint was applied with a wire bar and dried at 55℃. The dry coating weight was 3.5 g/m ² .

6.5g of 20% aqueous dispersion of 2g of 20% aqueous dispersion of 20% of 1,2,3-triphenylguanidine
9 g of aqueous dispersion 11 g of 40% aqueous dispersion of calcium carbonate 6 g of 20% aqueous solution of sodium tetraphenylboronate 15 g of 10% aqueous solution of PVA When this photofixable thermosensitive recording medium was examined in the same manner as in Example 1, color development started. The temperature was 81°C, and the thermal head recorded a pure black color with a recording density of 1.07. 40
℃, 24-hour storage test under 90% relative humidity
It was 0.18. Also, the light fixing time is about 1/1 of that of Example 1.
2, and the skin after fixing was sufficiently white and natural.

Example 3 A product was prepared in the same manner as in Example 2 except that the diazonium salt in Example 2 was changed to the following one.

This photofixable thermosensitive recording medium exhibited almost the same good characteristics as Example 2.

<Effects of the Invention> As explained above, the photofixable thermosensitive recording medium of the present invention was able to achieve very good black coloring by combining the diazonium salt of the present invention and the coupler.

Claims (1)

[Scope of Claims] 1. A photofixable heat-sensitive recording medium containing a diazonium salt and a coupler as main components, in which at least one compound selected from the following general formulas () and/or () is added as a diazonium salt to the recording medium. and,
It is characterized by containing at least one compound selected from the following general formula () as a blue coloring coupler and at least one compound selected from the following general formula () as a yellow to red coloring coupler. Light-fixed heat-sensitive recording medium. [In the formula, R ₁ and R ₂ represent hydrogen or a substituted or unsubstituted alkyl group. However, R ₁ and R ₂ are not hydrogen atoms at the same time. Y represents hydrogen or halogen. ] [In the formula, R ₃ represents a C ₁ to C ₁₈ alkyl group or an alkoxyl group, and R ₄ represents a C ₁ to C ₁₈ alkyl group. X represents a counter anion component. ] [In the formula, R ₅ represents a substituted or unsubstituted aromatic ring or a substituted or unsubstituted alkyl group. ] [In the formula, R ₆ represents a substituted or unsubstituted alkyl group or alkoxy group, and R ₇ represents a substituted or unsubstituted alkyl group. ]