JPH04338585A - Thermal recording material for laser recording and image recording method using the same - Google Patents

Abstract

PURPOSE:To record an image of high quality at a high speed by a laser beam in a thermal recording material for laser recording having a high sensitivity, reduced in the coloration of a background after thermal recording and capable of performing recording of high quality. CONSTITUTION:In a thermal recording material for laser recording wherein a thermal layer containing a substantially colorless color former and a developer is provided on a support, the thermal layer contains a dye capable of converting laser beam light energy to heat energy and becoming colorless by the absorption of light of a specific wavelength range.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a non-contact heat-sensitive recording material for recording using laser light and an image recording method using the same.

0002

[Prior Art] A thermal recording method in which a thermal head is closely scanned on the surface of a thermosensitive recording material having a thermosensitive coloring layer provided on a support, and a colored image is recorded by transmitting thermal energy directly to the thermosensitive coloring layer or through a protective layer. is widely known and is used in facsimiles, printers, etc. However, in such a thermal recording method, since the thermal head is placed in close contact with the thermal recording material for scanning, the thermal head may wear out or components of the thermal recording material may adhere as residue to the surface of the thermal head. The recorded image may not be obtained correctly due to
Furthermore, the problem of the thermal head being destroyed is likely to occur.

[0003] Furthermore, in the thermal recording method using such a thermal head, there are limitations in controlling the heating and cooling of the heating element at high speed and increasing the density of the heating element due to the structural characteristics of the thermal head. The drawback was that there were limits to high-speed recording, high-density, and high-quality recording.

In order to solve the above-mentioned problems of the thermal recording method using a thermal head, a laser beam is used,
It has been proposed to perform non-contact, high-speed, and high-density thermal recording on heat-sensitive recording materials (for example,
No. 23617, JP-A-54-121140, JP-A-5
7-11090, JP 58-56890, JP 58-94494, JP 58-134791, JP 58-145493, JP 59-89192, JP 60- No. 205182, JP-A-62-5619
Publication No. 5).

However, in such a recording method using laser light, the heat-sensitive layer generally has difficulty absorbing light in the visible and near-infrared regions, so the laser output necessary for color development must be increased considerably. The drawback was that thermal energy could not be obtained, making it extremely difficult to create a small and inexpensive device.

[0006] Furthermore, in Japanese Patent Publication No. 50-774, microcapsules containing ink are applied to base paper, and the ink in the capsules is ejected by irradiating it with strong light.
A recording method has been proposed, but the sensitivity is very low and it has not yet been realized.

[0007] Therefore, many proposals have been made to make the heat-sensitive layer efficiently absorb laser light, and generally, it is done to add a light-absorbing substance that matches the wavelength of the laser light into the heat-sensitive layer. It is being said.

[0008] The mechanism of image recording using laser light is that a light absorbing material absorbs the laser light that is imagewise irradiated onto the heat-sensitive layer and converts the energy of the laser light into thermal energy.
An image is recorded on a heat-sensitive recording material by heating the heat-sensitive layer to cause the color forming components (color former and color developer) contained in the heat-sensitive layer to react. Furthermore, when microcapsules are used, a light-absorbing substance that absorbs laser light is generally added within the microcapsules containing the color former, or added to the heat-sensitive layer outside the microcapsules, or both. Ru.

In this case, the microcapsule wall is heated with laser light to make the microcapsule wall permeable to substances, thereby bringing the color-forming components inside and outside the microcapsule into contact with each other, causing color development and recording an image on the heat-sensitive recording material. do. Therefore, it is possible to improve the sensitivity of the heat-sensitive recording material by using a light-absorbing substance with good light-absorbing efficiency or by increasing the amount of the light-absorbing substance contained in the heat-sensitive layer.

0010

[Problem to be Solved by the Invention] In this case, if the light-absorbing substance added is not colorless, the heat-sensitive layer will be colored by the light-absorbing substance, and the background of the recording material will be colored, resulting in low contrast and poor quality recording. In addition, when producing a multicolor recording material by overlapping heat-sensitive layers with different color hues, not only the background is colored, but also the color developed by heat recording becomes cloudy due to the color of the heat-sensitive layer itself, making it difficult to obtain a clear and vivid image. This is not preferable because the hue cannot be changed.

Generally, colorless light-absorbing substances are mostly inorganic compounds, but since most of them have low light-absorbing efficiency, it has been desired to develop organic compounds with high light-absorbing efficiency and less coloring. .

[0012]Although increasing the amount of light-absorbing substance added can improve the thermal sensitivity of the recording material, it is difficult to obtain good recorded images because the recording material itself becomes darker in proportion to the amount added. It is.

However, even if the organic compound has good laser light absorption efficiency and is colored, if the color of the organic compound can be made colorless after being recorded with laser light, After recording the image, the heat-sensitive layer of the recording material can be made colorless to make the background white or colorless, so the content of the organic compound can be increased to improve the heat sensitivity and improve the quality of the image. It is also possible.

[0014] Accordingly, a first object of the present invention is to provide a heat-sensitive recording material for laser recording which is highly sensitive and capable of high-quality recording with less coloring of the background after heat recording. A second object of the present invention is to provide an image recording method for recording high-quality images using a laser.

[0015]

[Means for Solving the Problems] The above-mentioned objects of the present invention are to provide a heat-sensitive recording material for laser recording, which comprises a support and a heat-sensitive layer containing a substantially colorless color former and color developer. The heat-sensitive recording material for laser recording is characterized in that the heat-sensitive layer contains a dye that can convert laser light into thermal energy and becomes colorless by absorbing light in a specific wavelength range, and After irradiating the laser beam imagewise from the heat-sensitive layer side or the support side of the heat-sensitive recording material for laser, the dye contained in the heat-sensitive layer can then be made colorless on the entire surface of the heat-sensitive layer side and/or the support side. This was achieved using an image recording method characterized by irradiating light with a certain wavelength.

[0016] The substantially colorless color forming agent and color developer used in the present invention are components that are substantially colorless before the reaction, but cause a coloring reaction when they come into contact with each other.
Specifically, a combination of an electron-donating dye precursor (color former) and an acidic substance (color developer) or a combination of a diazo compound (color former) and a coupling compound (color developer) is preferred.

The electron-donating dye precursor used in the present invention is not particularly limited as long as it is substantially colorless, but it develops color by donating electrons or accepting protons such as acids. A compound having a partial skeleton such as a lactone, a lactam, a sultone, a spiropyran, an ester, an amide, etc., and whose partial skeleton opens or cleaves upon contact with a color developer is used. Specifically, crystal violet lactone, benzoylleucomethylene blue, malachite green lactone, rhodamine B lactam, 1,3,3-trimethyl-6
'-Ethyl-8'-butoxyindolinobenzospiropyran and the like.

In the present invention, a yellow precursor, a cyan precursor and a magenta precursor are used, particularly when a multicolor thermosensitive recording material is produced by laminating heat-sensitive layers having different color hues. For specific examples of these substances,
It is described in detail in JP-A-61-24495.

Color developers for these color formers include:
Acidic substances such as phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters are used. A specific example thereof is described in, for example, Japanese Patent Laid-Open No. 61-291183.

The diazo compound used in the present invention reacts with a color developer called a coupling component to be described later to develop a desired hue, and decomposes when exposed to light of a specific wavelength before the reaction. , is a photodegradable diazo compound that no longer has color-forming ability even when a coupling component acts on it. The hue in this coloring system is mainly determined by the diazo dye produced by the reaction between the diazo compound and the coupling component. Therefore, as is well known, the color hue can be easily changed by changing the chemical structure of the diazo compound or the chemical structure of the coupling component, and almost any color hue can be obtained depending on the combination. can.

The photodegradable diazo compound in the present invention mainly refers to aromatic diazo compounds, and more specifically refers to compounds such as aromatic diazonium salts, diazosulfonate compounds, and diazoamino compounds.

The diazonium salt has the general formula ArN2 +
It is a compound represented by X- (wherein Ar represents a substituted or unsubstituted aromatic moiety, N2 + represents a diazonium group, and X- represents an acid anion).
.

It is generally said that the photodecomposition wavelength of a diazonium salt is its maximum absorption wavelength. It is also known that the maximum absorption wavelength of diazonium salts varies from about 200 nm to about 700 nm depending on its chemical structure ("Photodegradation and chemical structure of photosensitive diazonium salts" by Takahiro Tsunoda and Ao Yamaoka, Nippon Photo) Academic Journal 29(4) 197-2
05 page (1965)). That is, if a diazonium salt is used as a photodegradable compound, it will be decomposed by light of a specific wavelength depending on its chemical structure, and if the chemical structure of the diazonium salt is changed, it will be decomposed by light of a specific wavelength depending on its chemical structure. The hue of the pigment also changes.

A large number of diazosulfonates that can be used in the present invention are known, and can be obtained by treating each diazonium salt with a sulfite. Further, other diazo compounds that can be used in the present invention include diazoamino compounds. The diazoamino compound is a compound in which a diazo group is coupled with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulfonic acid, monoethanolamine, diethanolamine, guanidine, or the like.

Details of these diazo compounds are described in, for example, JP-A-2-136286. As a light source for photolysis, various light sources that emit light of a desired wavelength can be used, such as various fluorescent lamps, xenon lamps, xenon flash lamps, mercury lamps of various pressures, photographic flashes, strobes, etc. A light source can be used. Further, in order to make the optical fixing zone compact, the light source section and the exposure section may be separated using an optical fiber.

Coupling components that form a dye by coupling with the diazo compound (diazonium salt) used in the present invention include, for example, 2-hydroxy-3-naphthoic acid anilide, as well as resorcinol and other compounds disclosed in JP-A-62 -14
Examples include those described in No. 6678.

Furthermore, by using two or more of these coupling components in combination, an image of any color tone can be obtained. Since the coupling reaction between these diazo compounds and the coupling component is likely to occur in a basic atmosphere, a basic substance may be added to the layer.

As the basic substance, a poorly water-soluble or water-insoluble basic substance or a substance that generates an alkali when heated is used. Examples include inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines,
Piperazines, guanidines, indoles, imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, formazines,
Examples include nitrogen-containing compounds such as pyridines. Specific examples of these are described, for example, in JP-A-61-291183. Two or more basic substances may be used in combination.

In the present invention, light in a specific wavelength range is a region that includes not only wavelengths in the visible light region but also infrared rays, ultraviolet rays, X-rays, and electron beams, and is absorbed by the light absorbing and decomposing dye described later. A wavelength range in which the dye is colorless is selected.

Colored dyes that become colorless by absorbing light in a specific wavelength range (hereinafter referred to as light-absorbing and decomposing dyes) used in the present invention are not particularly limited, and may be selected from among known light-absorbing and decomposing substances. , can absorb laser light of a specific wavelength well and convert it into thermal energy,
It is selected from those that become colorless when irradiated with light in a specific wavelength range.

As the light-absorbing and decomposing dye that can be used in the present invention, an ionic dye-counterion compound (Japanese Patent Application Laid-Open No. 62-15
0242, JP-A-1-152450), cationic dye-borate anion complex (JP-A-62-143044)
, 3-substituted coumarin compound (JP-A-61-114234
), bis(diiminosuccinonitrilo) metal complex (Japanese Patent Publication No. 3-10087), and the like. Among these, ionic dye-counterion compounds are preferred, and cationic dye-borate anion complexes are particularly preferred.

The above ionic dye-counterion compound is:
It is a compound consisting of an ionic dye that is ionically bonded to a reactive counterion, and is colored because it has the ability to absorb light, but when it is irradiated with light of a specific wavelength, it absorbs that light. When the ionic dye is excited, the counter ion donates electrons to the excited ionic dye or accepts electrons from the excited ionic dye to generate free radicals, making it colorless. When such a compound is added to the heat-sensitive layer, the background of the recording material is colored, but by irradiating it with light in a specific wavelength range, the background of the recording material can be made colorless or white.

In the present invention, among such ionic dye-counter ion compounds, the following general formula (Chemical formula 1), which is a cationic dye-counter ion compound, is used.

[Formula 1] (However, D+ is a cationic dye such as cyanine, carbocyanine, hemicyanine, rhodamine, azomethane, etc., and R1, R2, R3 and R4 are alkyl groups,
An aryl group, an alkaryl group, an allyl group, an aralkyl group, an alkenyl group, an alkenylalkynyl group, an alicyclic group, or a saturated or unsaturated heterocyclic group, which may be the same or different. ) A cationic dye-borate anion complex compound is preferred.

[0034] Specific examples of such compounds are disclosed in JP-A-62-
150242 in detail. In the present invention, the following (chemical formula 2) having a maximum absorption wavelength of 740 nm is used.

A cationic dye-borate anion complex compound represented by the following formula is particularly preferred.

As the anionic dye-counterion compound, the following general formula (Chemical formula 3) is used.

[Formula 3] (However, D- is an anionic dye, R5, R6
are groups consisting of an aromatic nucleus such as a phenyl group or a naphthyl group, and may be the same or different. n is 1 or 2
It is. ) Anionic dye-iodonium ion compounds can be mentioned. Specific examples of such compounds are also described in detail in JP-A-62-150242.

In the present invention, the maximum absorption wavelength is 570n.
The following (Chemical formula 4) with m

Particularly preferred are those represented by the following formula. The 3-substituted coumarin compound that can be used in the present invention has a wavelength of 390 nm.
It has light absorption ability at ~500 nm. Eel like this 3
For specific examples of position-substituted coumarin compounds, see JP-A-61
It is described in detail in No.-114234.

[0037] Furthermore, the bis(diiminosuccinonitrilo) metal complex has the following general formula (Chemical formula 5):

embedded image (where M represents, for example, nickel, palladium, platinum or cobalt). The above bis(diiminosuccinonitrilo) metal complex has a wavelength of 650
It has maximum absorption ability at ~1150 nm. Specific examples and synthesis methods of such bis(diiminosuccinonitrilo) metal complexes are described in detail in Japanese Patent Publication No. 3-1008.

The color forming agent or color developer used in the present invention can be used as a solid dispersion in the heat-sensitive layer by a known method. It is preferable to use it in encapsulation from the viewpoint of shelf life (preventing fogging), such as preventing contact with colorants, and from the viewpoint of controlling color development sensitivity, such as developing color with a desired laser energy. Particularly from the viewpoint of storage stability of the recording material, it is preferable to use the color former in microcapsule form.

[0039] Any of the interfacial polymerization method, internal polymerization method, and external polymerization method can be adopted as a method for producing the microcapsules that can be used in the present invention, but in particular, the core material containing the coloring agent is dissolved in water. It is preferable to employ an emulsion polymerization method in which a polymer substance is emulsified in an aqueous solution in which a polymer is dissolved, and then a wall of polymer material is formed around the oil droplets.

[0040] A reactant forming a polymeric substance is added to the interior of the oil droplet and/or to the exterior of the oil droplet. Specific examples of the polymeric material include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene-methacrylate copolymer, styrene-acrylate copolymer, and the like. Preferred polymeric materials are polyurethanes, polyureas, polyamides, polyesters, polycarbonates, particularly preferred are polyurethanes and polyureas. Two or more types of polymeric substances can also be used in combination.

Specific examples of the water-soluble polymer include gelatin, polyvinylpyrrolidone, polyvinyl alcohol, and the like. For example, when polyurea is used as a capsule wall material, polyisocyanates such as diisocyanates, triisocyanates, tetraisocyanates, and polyisocyanate prepolymers, polyamines such as diamines, triamines, and tetraamines, and two amino groups are used. A microcapsule wall can be easily formed by reacting the prepolymer, piperazine or its derivative, polyol, etc. contained above in an aqueous solvent by an interfacial polymerization method.

[0042] Furthermore, for example, a composite wall made of polyurea and polyamide or a composite wall made of polyurethane and polyamide can be produced by adjusting the pH of the emulsifying medium serving as the reaction liquid using, for example, polyisocyanate and acid chloride, or polyamine and polyol. It can be prepared by heating. For details on the manufacturing method of these composite walls made of polyurea and polyamide, please refer to JP-A-58-6
It is described in Japanese Patent No. 6948.

The light-absorbing and decomposing dye used in the present invention can be added inside or outside the microcapsules, or both inside and outside the microcapsules. Furthermore, metal-containing dyes, charge control agents such as nigrosine, or other arbitrary additives can be added to the microcapsule walls used in the present invention, if necessary.

These additive substances can be incorporated into the walls of the capsule during wall formation or at any other time. In addition, in order to adjust the chargeability of the capsule wall surface as necessary,
Monomers such as vinyl monomers may be graft-polymerized, or these polymers may be attached.

Furthermore, a solid sensitizer may be added in order to swell the microcapsule walls during heating with laser light. As the solid sensitizer, those having a melting point of 50° C. or more, preferably 120° C. or less, and solid at room temperature can be selected from among those called plasticizers for the polymer used as the microcapsule wall. For example, when the wall material is made of polyurea or polyurethane, hydroxy compounds, carbamate ester compounds, aromatic alkoxy compounds, organic sulfonamide compounds, aliphatic amide compounds, aryl amide compounds, etc. are preferably used.

[0046] When a diazo compound is used as a coloring agent in the present invention, it is also possible to use a coloring aid. The coloring aid that can be used in the present invention is a substance that increases the coloring density during laser heating printing or lowers the minimum coloring temperature, lowers the melting point of coupling components or diazo compounds, etc. This is to create a situation where the diazo compound and the coupling component are likely to react by lowering the softening point of the diazo compound.

Coloring aids include phenolic compounds, alcoholic compounds, amide compounds, sulfonamide compounds, etc. Specific examples include p-tert-octylphenol, p-benzyloxyphenol, phenyl p-oxybenzoate, Benzyl carbanylate, phenethyl carbanylate, hydroquinone dihydroxyethyl ether, xylylene diol, N-hydroxyethyl-
Compounds such as methanesulfonic acid amide and N-phenyl-methanesulfonic acid amide can be mentioned. These may be contained in the core material or may be added outside the microcapsules as an emulsified dispersion.

In the present invention, the heat-sensitive layer is transparent, and the OH
When used in P or when the heat-sensitive layer is layered to produce a multicolor recording material, the color forming agent, color developer, and light-absorbing decomposition dye that are not microencapsulated are mixed with an organic solvent that is sparingly soluble or insoluble in water. After dissolving, it is preferable to mix this with an aqueous phase having a water-soluble polymer containing a surfactant as a protective colloid and use it in the form of an emulsified dispersion.

[0049] In particular, from the viewpoint of improving the storage stability of the recording material, it is preferable to encapsulate the color forming agent into microcapsules and to form the color developer into an emulsified dispersion. The light-absorbing and decomposing dye is emulsified and dispersed together with a color former or developer.

The above organic solvent used in this case is:
It can be appropriately selected from high boiling point oils. In addition to esters, preferred oils include dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, diisobutylbiphenyl, 1
-Methyl-1-dimethylphenyl-1-phenylmethane, 1-ethyl-1-dimethylphenyl-1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane, triallylmethane (e.g. tritolylmethane) , tolyldiphenylmethane), terphenyl compounds (e.g. terphenyl), alkyl compounds (e.g. terphenyl), alkylated diphenyl ethers (
Examples include propyl diphenyl ether), hydrogenated terphenyl (eg, hexahydro terphenyl), diphenyl ether, and the like.

Among these, it is particularly preferable to use esters from the viewpoint of emulsion stability of the emulsified dispersion. Examples of esters include phosphate esters (for example, triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, cresyl diphenyl phosphate), phthalate esters (
dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, octyl phthalate, butylbenzyl phthalate), dioctyl tetrahydrophthalate, benzoate ester (ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate, benzyl benzoate),
Abietate ester (ethyl abietate, benzyl abietate), dioctyl adipate, isodecyl succinate, dioctyl azelaate, oxalate ester (
dibutyl oxalate, dipentyl oxalate), diethyl malonate, maleate esters (dimethyl maleate, diethyl maleate, dibutyl maleate), tributyl citrate, sorbate esters (methyl sorbate, ethyl sorbate, butyl sorbate) , sebacate ester (dibutyl sebacate, dioctyl sebacate),
Ethylene glycol esters (formic acid monoesters and diesters, butyric acid monoesters and diesters, lauric acid monoesters and diesters, palmitic acid monoesters and diesters, stearic acid monoesters and diesters, oleic acid monoesters and diesters)
, triacetin, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, boric acid esters (tributyl borate, tripentyl borate), and the like.

Among these, it is preferable to use tricresyl phosphate alone or in combination because the emulsion dispersion stability of the color developer is particularly good. It is also possible to use the above oils together or with other oils.

In the present invention, an auxiliary solvent may be added to the above-mentioned organic solvent as a low-boiling solubilizing agent. Particularly preferred examples of such co-solvents include ethyl acetate, isopropyl acetate, butyl acetate and methylene chloride.

The water-soluble polymer to be contained as a protective colloid in the aqueous phase to be mixed with the oil phase containing these components is appropriately selected from known anionic polymers, nonionic polymers, and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives, etc. are preferred.

[0055] The surfactant to be contained in the aqueous phase may be appropriately selected from anionic or nonionic surfactants that do not interact with the protective colloid to cause precipitation or aggregation. can. Preferred surfactants include sodium alkylbenzene sulfonate, sodium alkyl sulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonylphenyl ether), and the like.

[0056] The emulsified dispersion in the present invention is produced by combining an oil phase containing the above components and an aqueous phase containing a protective colloid and a surfactant using means commonly used for fine particle emulsification, such as high-speed stirring and ultrasonic dispersion. It can be mixed and dispersed easily.

[0057] The ratio of the oil phase to the aqueous phase (oil phase weight/aqueous phase weight) is preferably from 0.02 to 0.6, particularly from 0.02 to 0.6.
．． It is preferable that it is 1-0.4. If it is less than 0.02, the aqueous phase is too large and diluted, and sufficient color development cannot be obtained;
．． On the contrary, if it is 6 or more, the viscosity of the liquid increases, resulting in inconvenience in handling and decreased stability of the coating liquid.

When coating the capsule liquid and emulsion dispersion liquid (hereinafter referred to as heat-sensitive layer liquid) prepared as described above on a support, a known coating method using a water-based or organic solvent-based coating liquid is used. It will be done.

In this case, in order to safely and uniformly apply the heat-sensitive layer liquid and maintain the strength of the coating film, in the present invention, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, polyvinyl alcohol, carboxy-modified Combined use of polyvinyl alcohol, polyacrylamide, polystyrene and its copolymers, polyester and its copolymers, polyethylene and its copolymers, epoxy resins, acrylate and methacrylate resins and their copolymers, polyurethane resins, polyamide resins, etc. You can also.

[0060] The support used in the present invention may be transparent or opaque. When a transparent support is used that does not exhibit absorption at the wavelength of the laser beam to be irradiated and has dimensional stability without being deformed by the heat generated during laser irradiation, the transparent support It is also possible to record by irradiating laser light through it. The thickness of the support used is 10 μm to 200 μm.

Examples of such transparent supports include:
Polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate films, polyolefin films such as polystyrene films, polypropylene films, and polyethylene films, polyimide films, polyvinyl chloride films, polyvinylidene chloride films,
Examples include polyacrylic film and polycarbonate film, and these can be used alone or in combination.

On the other hand, examples of the opaque support for the recording material include paper, synthetic paper, an aluminum vapor-deposited base, and the transparent support coated with a pigment or the like. In this case,
In order for laser light to be irradiated from the heat-sensitive layer side and efficiently absorbed by the heat-sensitive layer, it is preferable to use a material that is highly reflective to laser light as the opaque support for the recording material.

The support used in the present invention is particularly preferably a polyester film subjected to heat-resistant treatment and antistatic treatment. In the present invention, in order to prevent the whole heat-sensitive layer from peeling off from the support, it is desirable to provide an undercoat layer on the support before coating the heat-sensitive layer containing microcapsules or the like on the support.

[0064] As the undercoat layer, acrylic ester copolymer, polyvinylidene chloride, SBR, water-based polyester, etc. can be used, and the film thickness is 0.1-0.
5 μm is desirable. The undercoat layer made of these compositions is
Blade coating method, air knife coating method, gravure coating method,
The coating is performed by a known coating method such as a roll coating method, a spray coating method, a dip coating method, or a bar coating method. The coating amount is preferably 1 to 20 g/m2, particularly 3 to 20 g/m2.
It is preferable to set it as 10g/m2.

Further, pigments, waxes, hardeners, etc. may be added to the heat-sensitive layer, if necessary. The heat-sensitive layer is a coloring agent,
The total amount of color developer and light absorption decomposition dye is 0.1 to 10 g/m
2 and the thickness of the layer is 1
It is desirable that the coating be applied to a thickness of ~10 μm.

In the present invention, it is preferable to provide a protective layer on the heat-sensitive layer by a known method in order to prevent deterioration of apparent transparency due to light scattering on the surface of the heat-sensitive layer. Details of the protective layer are described, for example, in "Paper and Pulp Technology Times" (September issue, 1985), pages 2 to 4, and in Japanese Patent Application Laid-open No. 318546/1983.

In order to improve the transparency of the protective layer, a combination of silica-modified polyvinyl alcohol and colloidal silica is particularly preferred. In the present invention, a protective layer containing silicone resin as a main component can be provided together with or in place of the conventionally used protective layers described above. This provides good water resistance without impairing the transparency of the heat-sensitive layer.

[0068] Waxes, metal soaps, etc. may be added to the protective layer for the purpose of improving thermal head suitability during thermal printing and improving the water resistance of the protective layer. The amount of these used is preferably 0.2 to 7 g/m2.

The laser used in the present invention is not particularly limited, but a laser that emits a laser beam with a wavelength that is efficiently absorbed by the light-absorbing and decomposing dye is selected from known lasers. . Specific examples include helium-neon laser, argon laser, carbon dioxide laser, YAG laser, semiconductor laser (G
aAs bonding laser), etc.

When the support of the heat-sensitive recording material is transparent, image recording using the recording material of the present invention is carried out by irradiating a laser beam from the heat-sensitive layer side or the support side in an imagewise manner, and then recording an image using a laser beam of a specific wavelength. This can be carried out by a method of exposing the entire surface of the heat-sensitive layer side and/or the support side to light of a certain range. By this entire surface exposure, the light-absorbing and decomposing dye contained in the heat-sensitive layer becomes colorless, so that a clear image can be obtained.

When the support of the heat-sensitive recording material is opaque, the image is recorded by irradiating laser light from the heat-sensitive layer side in an imagewise manner, and then the entire surface of the heat-sensitive layer side is exposed to light to make the recording material A high-quality reflection image with a white background can be obtained.

[0072] When a diazo compound is used as a coloring agent, in the light of a specific wavelength range for full-surface exposure,
By including light that can decompose the diazo compound, or by simultaneously irradiating each with the necessary light, it is possible to make the dye colorless and fix the image at the same time. Moreover, a multicolor image can be easily obtained by overlaying a heat-sensitive layer containing a combination of a color forming agent and a color developer that develop colors of different hues and a light-absorbing and decomposing dye that absorbs laser beams of different wavelengths.

[0073]

Effects of the Invention: The heat-sensitive layer of the recording material of the present invention has a high light absorption efficiency for laser light and contains a light-absorbing decomposing dye that becomes colorless by absorbing light in a specific wavelength range. Even if the thermal sensitivity is significantly improved by increasing the content of decomposable dye, clear images can be obtained. Therefore, if the recording material of the present invention is used, laser recording can be performed at high speed, and the quality of the obtained image is good.

[0074]

[Examples] The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited thereby. Note that "parts" indicating the amount added indicate "parts by weight."

Example 1. Preparation of capsule liquid 14 g of 2-anilino-3-methyl-6-N-ethyl-N-butylaminofluorane (leuco dye), Takenate D-110N
(Product name of capsule wall material manufactured by Takeda Pharmaceutical Co., Ltd.) 6
0g, 2g of Sumithorp 200 (trade name of ultraviolet absorber manufactured by Sumitomo Chemical Co., Ltd.) and 3g of the light-absorbing decomposition substance shown below (chemical formula 6) (maximum absorption wavelength 740nm)

[C6]

1-phenyl-1-xylylethane 55
g and 55 g of methylene chloride and dissolved therein. The obtained solution was mixed with 100 g of 8% by weight polyvinyl alcohol aqueous solution, 40 g of water, and 1.4 g of 2% by weight sodium salt of dioctyl sulfosuccinate (dispersing agent).
The mixture was mixed with an aqueous solution of 1, and then emulsified for 5 minutes at 10,000 rpm using an Ace homogenizer (manufactured by Nippon Seiki Co., Ltd.). After adding 150 g of water to the obtained emulsion, an encapsulation reaction was carried out at 40°C for 3 hours to reduce the average particle size to 0.
．． A 7 μm capsule solution was prepared.

Preparation of color developer emulsion dispersion 8 g of color developer (a) represented by the following (Chemical formula 7),

[C7] 4 g of color developer (b) represented by the following (Chemical formula 8),

[Chemical formula 8] and 30 g of a color developer (c) represented by the following (Chemical formula 9),

[Chemical formula 9]

1-phenyl-1-xylylethane 8.
It was dissolved in a mixture of 0g and 30g of ethyl acetate. The obtained solution was added to 100 g of an 8% by weight polyvinyl alcohol aqueous solution.
and 150g of water and 0 of sodium dodecylbenzenesulfonate.
．． After mixing with 5 g of aqueous solution, use an Ace homogenizer (
(manufactured by Nippon Seiki Co., Ltd.) at 10,000 rpm for 5 minutes at room temperature so that the average particle size was 0.5 μm to obtain an emulsified dispersion.

Preparation of heat-sensitive recording material: 5.0 g of the above capsule liquid, 10 g of the above color developer emulsified dispersion.
Stir and mix 0g of water and 5.0g of water to a thickness of 70μ.
After coating on a transparent polyethylene terephthalate (PET) support with a solid content of 15 g/m2 and drying, a layer as shown in Table 1 below was applied on the heat-sensitive layer formed as described above. The protective layer liquid of the composition has a thickness of 2 after drying.
A transparent heat-sensitive recording material according to the present invention was prepared by coating and drying to a thickness of μm.

[0080]

[Table 1] Composition of protective layer liquid────────────────────────
──────────10% by weight polyvinyl alcohol
20g water

30g 2% by weight sodium salt of sulfosuccisandioctyl
0.3g polyvinyl alcohol 3g, water 100%
Kaolin dispersion obtained by dispersing g and 35 g of kaolin using a ball mill.
3g Hydrin Z-7 (manufactured by Chukyo Yushi Co., Ltd.)
0.5g────────
──────────────────────────
──

[0081] Semiconductor laser light (G
After image-wise irradiation with an aAs bonding laser), infrared rays were irradiated with an infrared lamp to obtain a black recorded image. The laser output is 35 mJ/m for 1 millisecond at the surface of the heat-sensitive layer.
The energy was adjusted to be m2. The reflection density of the colored portion of the obtained image was measured using a Macbeth densitometer and found to be 1.45. Further, no coloring of the background portion of the recording material was observed after recording.

Example 2. Heat-sensitive samples were prepared in the same manner as in Example 1, except that 100 g of 10 wt% gelatin was used instead of 100 g of 8 wt% polyvinyl alcohol used in the preparation of the capsule liquid and developer emulsion dispersion in Example 1. A recording material was prepared and an image was recorded to obtain a black image. The reflection density of the colored portion of the obtained image was measured using a Macbeth densitometer and was found to be 1.45, and no coloring of the background was observed.

Example 3. Preparation of capsule liquid A:
0)

[Chemical formula 10]

To 50 parts of the compound, methylene chloride 1
50 g, 50 parts of tricresyl phosphate, 150 parts of trimethylolpropane trimethacrylate and 3 parts of trimethylolpropane m-xylylene diisocyanate:
1 adduct in 75% ethyl acetate solution (Takenate D1
10N (trade name manufactured by Takeda Pharmaceutical Co., Ltd.) were uniformly mixed to form an oil phase solution.

On the other hand, 7% by weight of polyvinyl alcohol (
PVA217E: degree of fight 88-89%, degree of polymerization 1.7
00: trade name manufactured by Kuraray Co., Ltd.) 600 parts were prepared to form a water-soluble polymer aqueous solution.

Next, a dissolver was attached to a 5 liter stainless steel pot equipped with a warm bath, and after the aqueous polymer solution was added, the oil phase solution was added while stirring the dissolver, and the emulsion was observed under a microscope. Emulsification and dispersion was performed so that the average particle size of the particles was approximately 1.5 μm. After the dispersion was completed, the stirring was loosened and 42°C hot water was passed into the hot bath, and the temperature inside the pot was maintained at 40°C to complete the encapsulation reaction in 3 hours. Ion exchange resin MB- is added to the obtained liquid.
After adding 25 ml of No. 3 (trade name manufactured by Organo Co., Ltd.) and stirring, the mixture was filtered to obtain a capsule liquid.

Preparation of Dispersion A: The substances shown in Table 3 below were mixed, predispersed using a dissolver, and then dispersed using Dynomil (WILLY A. BACHOFEN A).
．． A dispersion liquid A was obtained by emulsifying and dispersing the dispersion liquid to an average particle size of 2 μm.

[0088]

[Table 2] ──────────────────────────
────────── 15% by weight polyvinyl alcohol aqueous solution
33 parts (PVA-205 manufactured by Kuraray Co., Ltd., trade name) Coupler of the compound shown below (Chemical formula 11)
4. Part 3

[Chemical Formula 11] Couplers of the following compounds (Chemical Formula 12)
0.6 parts

[Chemical formula 12] Organic basic compound of the following (Chemical formula 13)
5.0 copies

[Chemical Formula 13] Color development improver shown below (Chemical Formula 14)
3.0 copies

[Chemical Formula 14] The following (Chemical Formula 15) light-absorbing and decomposing dye (maximum absorption wavelength 570
nm) 0.5 part

[Chemical formula 15] Water

70 copies──────────
──────────────────────────
─

Preparation of dispersion B Dispersion B was obtained by mixing and stirring the materials shown in Table 3 below.

[Table 3] ──────────────────────────
────────── Univer 70 (manufactured by Shiraishi Kogyo Co., Ltd., product name)
Part 20 Chaobrite

───(Schiele Kaolin Co., Ltd. (Th
Product name) 40% by weight sodium hexametaphosphate aqueous solution manufactured by Kaolin Company
0.5 part water


Part 30──────────────────
──────────────────

Preparation of heat-sensitive recording material 20 parts of the capsule liquid A, 20 parts of dispersion liquid A, and dispersion liquid B7
1 part and 1.5 parts of a 2% by weight aqueous solution of Nissan Rapizol 13-90 (trade name, manufactured by NOF Corporation) were stirred and mixed to form a polyethylene terephthalate (PE) solution with a thickness of 70 μm.
A heat-sensitive layer was provided on the support of T) by coating and drying so that the solid content was 15 g/m2. Furthermore, a protective layer was provided by applying a mixture having the composition shown in Table 4 below to a thickness of 2 μm on the heat-sensitive layer, thereby producing a recording material.

[0091]

[Table 4] Composition of protective layer ────────────────────────
──────────10% by weight polyvinyl alcohol
20g water

30g2
Weight% Dioctyl Sulfosuccinate Sodium Salt
Kaolin dispersion made by dispersing 0.3g polyvinyl alcohol 3g, water 100g and kaolin 35g using a ball mill.

3g Hydrin Z-7 (product name manufactured by Chukyo Yushi Co., Ltd.) 0.5g
──────────────────────────
──────────

The obtained recording material was imagewise irradiated with argon (Ar+) laser light with a wavelength of 560 nm from the heat-sensitive layer side, and then the entire surface was exposed to light using a fluorescent lamp to make the light-absorbing and decomposing dye colorless. The remaining diazo compound was decomposed and fixed using Dry 100 (manufactured by Ricoh Co., Ltd.) to obtain a blue image. The output of the laser beam was adjusted so that the energy was 40 mJ/mm 2 in 1 millisecond at the surface of the heat-sensitive layer of the recording material. The reflection density of the obtained blue recorded image was measured using a Macbeth reflection densitometer and was found to be 1.12. No coloring of the background of the recording material was observed after recording.

Example 4 Preparation solution of emulsified dispersion B of coupler/base/light-absorbing decomposition dye 1. Polyvinyl alcohol 4% by weight aqueous solution
170 parts solution2. Solution 2. was prepared by mixing the compositions shown in Table 5 below. adjusted.

[0094]

[Table 5] ──────────────────────────
────────Coupler of the following (Chemical formula 15)

1.4 parts

[Chemical Formula 15] The following coupler (Chemical Formula 16)

1.4 parts

[Chemical formula 16] Triphenylguanidine (organic basic compound)
6 parts Color development improver shown below (Chemical formula 17)
14 parts

[Chemical Formula 17] The following (Chemical Formula 18) light absorption decomposition agent (maximum absorption wavelength 658n
m) 1 copy

[Chemical formula 18] Tricresyl phosphate
10 parts ethyl acetate
Part 20────────────────────────
────────

Solution 1. Solution 2.
was added, mixed, and emulsified at 20°C to obtain an emulsified dispersion B having an average particle size of 3 μm. Preparation of Coating Liquid The compositions shown in Table 6 below were mixed to prepare a coating liquid.

[0096]

[Table 6] ──────────────────────────
────────Capsule liquid A

4.9 parts Hydroquinone 5% by weight aqueous solution
0
．． Two-part coupler/base dispersion B
Part 3.7──────────────────────────
───────

Preparation of protective layer solution A protective layer solution was prepared by mixing the compositions shown in Table 7 below.

[Table 7] ──────────────────────────
───────Silica-modified polyvinyl alcohol
1 part solids (P
VAR2105 (Product name manufactured by Kuraray Co., Ltd.) Colloidal silica
Solid content: 1.5 parts (Snowtex 30, trade name manufactured by Nissan Chemical Co., Ltd.) Stearin Sun Zinc
0.02 part solid content (Hydrin Z-7, trade name manufactured by Chukyo Yushi Co., Ltd.) Paraffin wax
Solid content: 0.02 parts (Hydrin P-Z, trade name manufactured by Chukyo Yushi Co., Ltd.)──────────────────
──────────────

Preparation of heat-sensitive recording material The coating solution was coated on a polyethylene terephthalate (PET) transparent support with a thickness of 70 μm at a solid content of 15 g/m2.
A heat-sensitive layer was provided by coating and drying to obtain the following. Further, the protective layer liquid was coated on the heat-sensitive layer at a dry weight of 2 g/m 2 and dried to provide a protective layer, thereby producing a recording material.

[0099] The obtained recording material was exposed to H with a wavelength of 630 nm.
After e-Ne laser light is irradiated imagewise from the heat-sensitive layer side to obtain a black image, the entire surface is exposed to a fluorescent lamp to make the light-absorbing and decomposing dye in the heat-sensitive layer of the recording material colorless, and then Recopy Super Dry is applied. 100 (manufactured by Ricoh Co., Ltd.) to fix the image. The output of the laser beam was adjusted so that the energy was 40 mJ/mm 2 in 1 millisecond at the surface of the heat-sensitive layer of the recording material.

The reflection density of the obtained black image was measured using a Macbeth reflection densitometer and was found to be 1.22. Next, when the obtained recorded image was projected by an overhead projector, the projected image was clear, with no stains even on the background area where no image was recorded.

Comparative Example 1. A recording material was prepared in exactly the same manner as in Example 1, except that the light-absorbing and decomposing dye used in Example 1 was not used, and an image was recorded in the same manner. No image was formed at all.

Comparative Example 2. The following absorption dye (Chemical formula 20) was used instead of the light absorption and decomposition dye used in Example 1.

[Chemical Formula 20] A recording material was produced in the same manner as in Example 1 except for the materials used, and an image was recorded in the same manner. A clear black image was obtained, but the background part was colored slightly green. was.

[Chemical formula 19]

Claims (2)

[Claims] 1. A heat-sensitive recording material for laser recording, comprising a heat-sensitive layer containing a substantially colorless color forming agent and a color developer provided on a support, the heat-sensitive layer converting laser light into thermal energy. 1. A heat-sensitive recording material for laser recording, characterized in that it contains a dye that can be converted and becomes colorless by absorbing light in a specific wavelength range. 2. After the laser heat-sensitive recording material according to claim 1 is irradiated with laser light from the heat-sensitive layer side or the support side in an imagewise manner, the heat-sensitive layer is then applied to the entire surface of the heat-sensitive layer side and/or the support side. An image recording method characterized by irradiating light having a wavelength capable of rendering colorless the colored dye contained in the image recording method.