JPH11109549A - Heat developable copying material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat developable copying material having a higher fixation rate and more satisfactory preservability in comparison with a conventional method and capable of obtaining a high image density. SOLUTION: When a recording layer contg. a diazo compd., a coupling component which develops color by reaction with the diazo compd. and a basic material as a color developing auxiliary agent is disposed on a substrate to obtain a heat developable type copying material, the diazo compd. is encapsulated in heat responsiveness microcapsules and at least one kind of the coupling component and the color developing auxiliary agent is encapsulated in the microcapsules making a polymer contg. at least one kind selected from styrene and acrylic acid units and soluble in an aq. alkali soln. as a wall material. The basic material is preferably encapsulated from the viewpoint of preservability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-developable copying material using a diazo compound, and more particularly to a heat-developable copying material having a high fixing speed and excellent raw storability.

[0002]

2. Description of the Related Art Copying materials utilizing the photosensitivity of diazo compounds are widely used because they are inexpensive, and the following three types are known when roughly classified.

The first is a type known as a wet development type. In this method, a photosensitive layer containing a diazo compound and a coupling component as main components is provided on a support, this material is superposed on a document, exposed, and then developed using an alkaline solution.

[0004] The second type is a type known as a dry development type. Unlike the wet development type, development is performed with ammonia gas.

A third type is known as a heat development type, and includes a photosensitive layer containing an ammonia gas generating agent such as urea capable of generating an ammonia gas by heating. Activated diazo compounds and coupling components by heating and melting using a higher fatty acid amide as a color development aid, containing alkali salts of compounds that lose properties as an acid when heated, such as trichloroacetic acid in the layer There is a type that uses it.

[0006] The wet type has drawbacks in maintenance and management, such as the need for replenishment and disposal of the developer due to the use of the developer, the large size of the apparatus, and the like. In addition, it has drawbacks such as not being able to be retouched and the copy image not being able to withstand long-term storage.

Also, in the case of the dry type, as in the case of the wet type, it is necessary to replenish the developing solution and, in addition, it is necessary to provide a gas suction facility so as to prevent the generated ammonia gas from leaking outside. However, it has disadvantages such as an increase in size and a strong ammonia smell immediately after copying.

On the other hand, the heat developing type has a maintenance advantage that a developing solution is unnecessary unlike the wet type and the dry type, but the developing temperature is as high as 150 ° C. to 200 ° C. In addition, if the temperature control is not performed within the range of about ± 10 ° C., the development will be insufficient or the color tone will be changed. Therefore, in order to obtain a good image, the cost of the apparatus must be increased. was there.

In order to withstand such high-temperature development, the diazo compound used must also have high heat resistance. However, such a compound may be disadvantageous in obtaining a high image density. Many.

Therefore, conventionally, low-temperature development (90 ° C. to 1
(30 ° C.), but there is a drawback that the shelf life of the material itself is reduced.

Therefore, the heat development type has not yet reached the mainstream of the diazo copying system, although the maintenance advantages are expected to be sufficiently higher than those of the wet type and the dry type. It is.

By heating a material provided with a single recording layer containing a diazo compound, a coupling component and a color-forming auxiliary on a support to quickly obtain a desired color-forming density, it is necessary to heat the material. Each component must instantaneously melt, diffuse, and react to form a coloring dye.

In this case, if a copying material is designed so that a high-density image can be obtained by sufficiently developing a color even at a low heating temperature, it is a matter of course that the recording layer is stored even at room temperature before copying. The color development reaction progresses little by little, and the background portion, which must be white, becomes colored and causes background contamination.

The above-mentioned problem that is seemingly incompatible is that a diazo compound, a coupling component and a color-forming auxiliary, provided on a support and provided with a heat-developable photosensitive layer, contain the diazo compound in a microcapsule. The problem was substantially solved by including the compound in the compound (JP-A-59-91438). However, also in this case, when the image density is sufficiently increased, there is a disadvantage that the preservability of the recording material before use, that is, the raw preservability becomes insufficient.

In general, plain paper is used as a support for a copying material. However, when a plain paper is used as a support and a recording layer having the above-mentioned structure is provided thereon, There is also a problem that the sensitivity is reduced due to the influence of a weakly acidic support on the components, especially the basic substance used as a color development aid. As a countermeasure, it is conceivable to use neutral paper for the support, but from the viewpoint of cost, glossiness, etc., it has not come into general use.

[0016]

That is, it has a single recording layer, is excellent in both storability and fixing speed, and has a practical level of cost without using a special support. There has been a need for heat developable copy materials.

Accordingly, an object of the present invention is to provide a fixing speed which is higher than that of the conventional art, and which has better preservability than before.
An object of the present invention is to provide a heat-developable copying material capable of obtaining a high image density.

[0018]

The above object has been achieved by microencapsulating a diazo compound and microencapsulating a color-forming component or an auxiliary which reacts with the diazo compound using a specific wall material.

That is, the heat-developable copying material of the present invention is a heat-developable copying material comprising a support having thereon a recording layer containing a diazo compound, a coupling component which reacts with the diazo compound to form a color, and a coloring aid. In a copying material, the diazo compound is encapsulated in a thermoresponsive microcapsule, and the coupling component and / or the coloring aid include at least one of a styrene unit and an acrylic acid unit; Characterized by being encapsulated in a capsule using a polymer soluble in water as a wall material.

In the heat-developable copying material of the present invention, the diazo compound is encapsulated in a thermoresponsive capsule, and the coupling component which reacts with the diazo compound to form a color and / or the basic substance which is a color-forming auxiliary is an alkali. It is encapsulated in a capsule having a soluble polymer as a wall material, and the components relating to color development are encapsulated in microcapsules having different characteristics. The deterioration of the copy material such as yellowing of the background due to the undesired reaction can be significantly reduced as compared with the related art.

Further, the capsule wall of the thermoresponsive capsule in which the diazo compound is encapsulated is made thinner than when a coupling component or a color-forming auxiliary which reacts with the diazo compound to form a color is dispersed in the system. It is useful for improving the photo-fixing speed of a diazo compound because the ultraviolet light shielding property is reduced.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, each component of the present invention will be described in detail.

The diazo compounds used in the present invention are known diazo compounds such as photodegradable diazonium salts, diazosulfonates and diazoamino compounds, which form a color by undergoing a coupling reaction with a coupling component and which decompose by light when decomposed by light. Can be appropriately selected and used.

In the present invention, among these diazo compounds, it is preferable to use a diazonium salt represented by the following general formula, particularly from the viewpoint of photosensitivity and image density.

The ArN ₂ ⁺ X ^- (wherein, Ar represents an aromatic moiety substituted or unsubstituted, N ₂ ⁺ represents a diazonium group, X ^-. Represents an acid anion) Specific examples of the diazonium salt 4-diazo-1-dimethylaminobenzene, 4-diazo-1-diethylaminobenzene, 4-diazo-1-dipropylaminobenzene, 4-diazo-1-methylbenzylaminobenzene,
4-diazo-1-dibenzylaminobenzene, 4-diazo-1-ethylhydroxyethylaminobenzene, 4-
Diazo-1-diethylamino-3-methoxybenzene,
4-diazo-1-dimethylamino 2-methylbenzene,
4-diazo-1-benzoylamino-2,5-diethoxybenzene, 4-diazo-1-morpholinobenzene,
-Diazo-1-morpholino-2,5-diethoxybenzene, 4-diazo-1-morpholino-2,5-dibutoxybenzene, 4-diazo-1-toluylmercapto-2,
5-diethoxybenzene, 4-diazo-1,4-methoxybenzoylamino-2,5-diethoxybenzene and the like.

Specific examples of the acid forming the diazonium salt include C _n F _{2n + 1} COOH (n is an integer of 1 to 9) and C _m F _{2m + 1} SO ₃ H (m is 1 to 9). , Boron tetrafluoride, tetraphenylboron, hexafluorophosphoric acid, aromatic carboxylic acid, and metal halides such as zinc chloride and tin chloride.

The diazo compound used in the present invention is preferably used after being microencapsulated.

The coupling component used in the present invention is a component which forms a dye by coupling with a diazo compound under heating, and specific examples thereof include resorcin, phloroglucin, and 2,3-dihydroxynaphthalene-6-sulfone. Acid, 1-hydroxy-2-naphthoic acid morphopropylamide, 1,5-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid Morpholinopropylamide, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-
3-naphthoic acid 2'-methylanilide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-
3-naphthoic acid octylamide, 2-hydroxy-3-
Naphthoic acid N-dodecyloxypropylamide, 2-hydroxy-3-naphthoic acid tetradecylamide, acetanilide, acetoacetanilide, benzoylacetanilide, 1-phenyl-3-methyl-5-pyrazolone,
1- (2 ', 4', 6'-trichlorophenyl) -3-
Benzamide-5-pyrazolone, 1 (2 ', 4', 6 '
-Trichlorophenyl) -3-anilino-5-pyrazolone, 1-phenyl-3-phenylacetamido-5-pyrazolone and the like.

An image of any color tone can be obtained by using two or more of these coupling components in combination.

In the present invention, a basic substance acting as a color-forming aid is added for the purpose of making the system basic during thermal development to promote the coupling reaction. As such a basic substance, a water-insoluble or water-insoluble basic substance or a substance that generates an alkaline substance by heating is used.

Specific examples of the basic substance include inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and derivatives thereof, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles,
Examples include nitrogen-containing compounds such as imidazoles, imidazolines, triazoles, morpholines, piperidines, amidines, formamidines, and pyridines. These basic substances can be used in combination of two or more.

In the present invention, particularly from the viewpoint of enhancing the thermal sensitivity, the recording layer contains a fatty acid amide, an N-substituted aliphatic amide, a phenol derivative, a naphthol derivative, an alkoxy-substituted benzene, an alkoxy-substituted naphthalene, a hydroxy compound, an acid compound. Compounds such as compounds, sulfonamide compounds, ketone compounds, urea compounds, and esters can be added.

These compounds reduce the melting point of the coupling component or the basic substance, or improve the heat permeability of the microcapsule wall. As a result, these compounds function as a thermal sensitizer, and Melting substances are also included. Here, the heat-fusible substance is a substance which is solid at normal temperature and melts by heating and has a melting point of 50 ° C. to 150 ° C., and is a substance which dissolves a diazo compound, a coupling component or a basic substance.

In the present invention, the coupling component is preferably used in an amount of 0.1 to 10 parts by weight, and the color-forming aid is preferably used in an amount of 0.1 to 20 parts by weight based on 1 part by weight of the diazo compound. The application amount of the diazo compound is 0.05 to 5.0.
It is desirably about g / m ² .

In the present invention, the thermoresponsive microcapsules containing the diazo compound are prepared by emulsifying a core substance and then forming a wall of a polymer substance around the oil droplets.
The reactant forming the polymer substance is located inside the oil droplet and / or
Or it is added outside the oil droplets. Specific examples of the polymer substance include polyurethane, polyurea, polyamide, polyester, polycarbonate, urea-formaldehyde resin, and melamine resin.

Two or more polymer substances can be used in combination as the capsule wall material. Preferred polymeric substances are polyurethanes, polyureas, polyamides, polyesters, polycarbonates, more preferably polyurethanes and polyureas. In the case of polyurethane and polyurea, tolylene diisocyanate trimethanol propane adduct, tolylene diisocyanate isocyanurate, xylylene diisocyanate trimethanol propane adduct, xylylene diisocyanate isocyanurate, hydrogenated xylylene diisocyanate isocyanate It is preferred to use a nullate form.

As the physical properties of these high-molecular substances, high-molecular substances that do not melt at the temperature during thermal recording and have a melting point of 150 ° C. or higher are preferable.

Microcapsules can be prepared from emulsions containing 0.2% by weight or more of the components to be microencapsulated.

The heat-responsive microcapsules containing the diazo compound used in the present invention are prepared by dissolving the diazo compound in a non-aqueous solvent having a low boiling point together with a monomer for forming the capsule wall, and then distilling off the solvent during the polymerization reaction. It is preferable that the microcapsules contain substantially no solvent as obtained by

The polymer forming the microcapsule wall can be obtained by polymerizing the corresponding monomer by the method described above. The amount of the monomer used is such that the average particle size of the obtained microcapsule is 0.3 to 12 μm. It is determined to be.

By enclosing the diazo compound in the microcapsules thus produced, the contact between the diazo compound and the coupling component at room temperature can be prevented more than ever.

In the present invention, the coupling component and / or the basic substance which are not contained in the thermoresponsive microcapsules are encapsulated in a capsule having a wall material made of a polymer soluble in an aqueous alkali solution as described later. .

The microcapsules having an alkali-soluble polymer as a wall material used in the present invention are emulsified and dispersed in a W / O type, and a coupling component or a basic substance and an organic acid coexist in oil, and an acidic component is contained. It elutes from the inside and acts to make the alkali-soluble resin hydrophobic so as to form a partition wall. The particle size distribution of the microcapsules used in the present invention is 1
μm to 10 μm, and D50 is 3 μm to 8 μm.
The range of μm has good thermal response sensitivity and does not break down due to pressure.

The alkali-soluble polymer used for the wall material of the microcapsules is melted by heating and is not directly involved in the coupling reaction. However, after heating with a basic substance, it eutectically melts, and the molten coupling component becomes a diazo compound. It is considered that the coupling reaction proceeds due to the contact.

Since the eutectic point of the coupling component and the basic substance in the present invention can be inferred to be a site of the coupling reaction, in the present invention, the viewpoint of accelerating the generation of the naphtholate anion which controls the coupling reaction. Therefore, it is preferable to use, for example, higher fatty acid amides having 10 to 22 carbon atoms and N-substituted higher fatty acid amides among the basic substances exemplified above. Specific examples of the higher fatty acid amide include, for example, lauric amide, myristyl amide, palmitic amide, stearic amide, arachidic amide, behenic amide, eicoic amide, elaidic amide and the like. Specific examples of the fatty acid amide include N-methylol stearamide, N-methylolcaproamide, N-methylollauric amide, N-methylolbehenamide and the like. In connection with the higher fatty acid amide and the N-substituted higher fatty acid amide, it is known that naphthol-based, phenol-based, and active methylene-based coupling components rapidly eutectic. Specifically, it is preferable to select a specific coupling component whose eutectic point is adjusted to a range of 80 ° C. to 150 ° C. by the DSC method. Here, the eutectic point can be measured using a highly versatile DSC method in thermal analysis and can be confirmed by the appearance of an endothermic peak.

Next, the alkali-soluble polymer used as the microcapsule wall material will be described.

The polymer soluble in an aqueous alkali solution (hereinafter, appropriately referred to as an alkali-soluble polymer) used in the present invention contains a styrene unit and / or an acrylic acid unit, is water-insoluble, and is soluble in an aqueous alkali solution. Polymers include, for example, polyacrylic acid, polymethacrylic acid, isobutylene-maleic anhydride copolymer, diisobutene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, ethylene-acrylic acid copolymer, One or more selected from a styrene-acrylic acid copolymer and a styrene-methacrylic acid copolymer having the above-mentioned dissolving property can be used. The alkali solubility of these polymers can be appropriately adjusted by a known method depending on the monomer ratio of the copolymer and the use of a crosslinking agent. In the present invention, being soluble in an alkaline aqueous solution means being uniformly and transparently dissolved in an aqueous solution having a pH of 10 or more. Among these alkali-soluble polymers, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers alone or mixtures thereof with isobutylene-maleic anhydride copolymers or styrene-maleic anhydride copolymers And from the viewpoint of solubility. Also, to control the properties of the capsule, other alkali-soluble polymers, for example,
Casein, modified PVA, CMC, gum arabic and the like can be used in combination.

In the present invention, it is preferable that the method for producing capsules using the alkali-soluble polymer as a wall material is carried out by a phase separation method. Therefore, the glass transition temperature (Tg) of the polymer used as the wall material is in the range of 95 ° C. to 105 ° C., and the molecular weight is preferably in the range of several thousand to tens of thousands in terms of weight average molecular weight. That is, Tg is 10
If the temperature exceeds 5 ° C., or if the molecular weight exceeds the order of tens of thousands, the coverage of the capsule wall is reduced and phase separation cannot be performed well, and the Tg is lower than 95 ° C. or the molecular weight is lower than several thousands. However, there is a possibility that coarse particles may progress due to agglomeration due to blocking between capsule walls, and both are not preferred.

The water-insoluble organic solvent used for preparing the capsule solution using the alkali-soluble polymer of the present invention includes:
Tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilauryl phthalate,
Examples include dicyclohexyl phthalate, butyl oleate, dioctyl sebacate, dibutyl sebacate, dioctyl adipate, trioctyl trimellitate, acetyl triethyl citrate, octyl maleate, and dibutyl maleate.

In the present invention, it is preferable to use a heating phase separation method in preparing capsules using an alkali-soluble polymer. In a specific method for producing capsules by this heating phase separation method, an amount of aqueous ammonia that can be dissolved in an alkali-soluble resin is added, and the mixture is stirred and dissolved while being heated to about 50 ° C to 60 ° C. Next, the coupling component and / or the color-forming aid and acetic acid are both dissolved in an organic solvent such as a phthalic ester solvent. The amount of acetic acid added at this time is adjusted according to the oxidation number of a polymer used as a wall material such as a styrene-acrylic acid copolymer. Next, an organic solvent in which components contained in a capsule such as a coupler are dissolved is mixed with twice the amount of an alkali-soluble resin solution, and the mixture is stirred with a commercially available homomixer to obtain an emulsion. After the solution was stirred at a liquid temperature of 60 ° C. for 30 minutes, it was confirmed that the pH became 7, and this was regarded as the end point. The capsule particle size at this time is also affected by the stirring speed, but is substantially determined by the particle size of the core agent. The capsule dispersion thus prepared was measured with a commercially available laser scattering diffraction particle size distribution analyzer (LA-910: manufactured by Horiba, Ltd.), and D50 was calculated. It was found that the capsule dispersion was prepared in the range of 5 μm to 10 μm. Was. The capsule was placed on a glass plate, and the shape was observed with an electron microscope. As a result, the core substance was in a continuous particle state encapsulated in a styrene-acrylic acid copolymer. The encapsulation method by this heating phase separation has an advantage that it can be manufactured at lower cost than the conventional interfacial polymerization method and the like.

The stability of the coupling component or the basic substance itself is improved by enclosing the coupling component or the basic substance which reacts with the diazo compound to form a color in a capsule using the alkali-soluble polymer as a wall material, further,
According to the configuration of the present invention, the wall thickness of the thermo-responsive capsule containing the diazo compound can be reduced by about 50% as compared with the conventional one, in other words, the heat can be prevented. The particle size of the responsive capsule can be reduced to about half. As a result, the light fixing speed is remarkably increased, and quick fixing is enabled.

The capsule containing an alkali-soluble polymer as a wall material may be either a coupling component or a basic substance, or both may be encapsulated in a capsule. In consideration of the stability when using plain paper, it is preferable that a basic substance as a color development aid is included.

The components not encapsulated in the two types of microcapsules, for example, the heat sensitizer and other color-forming auxiliaries, stabilizers, and the like may be used as a solid dispersion with a water-soluble polymer using a sand mill or the like. Preferred water-soluble polymers include water-soluble polymers used when preparing microcapsules (for example, see JP-A-59-190886). In this case, the solid dispersion components with respect to the water-soluble polymer solution are added so as to be 10 to 40% by weight, respectively. The size of the dispersed particles is preferably 10 μm or less.

In the case of forming a substantially transparent recording layer, the above components are dissolved in an organic solvent which is hardly soluble or insoluble in water, and then a water containing a surfactant and a water-soluble polymer as a protective colloid. It is mixed with the phase and used in the form of an emulsified dispersion.

The heat-developable copying material of the present invention preferably contains an ascorbic acid derivative represented by the following general formula from the viewpoint of improving the preservability of the background.

General formula

[0057]

Embedded image

In the formula, R represents a hydrogen atom, an alkyl group or an alkylcarbonyl group, and M represents a hydrogen atom or an alkali metal atom.

The carbon number of the alkyl group is preferably from 1 to 20, and particularly preferably from 1 to 10. The carbon number of the alkylcarbonyl group is preferably from 2 to 20. These alkyl group and alkylcarbonyl group may further have a substituent, and the substituent includes -OH, a lower alkoxy group, -CO-R '(R' is -OH, a lower alkoxy group,
Or an amino group) or -OCO-R "(R" is a lower alkoxy group or an amino group), and among them, -OH and a lower alkoxy group are particularly preferable.

As specific examples of the ascorbic acid derivative represented by the general formula of the present invention, the following specific examples (1) to (3)
Among them, the compound of the specific example (1) is particularly preferable.

[0061]

Embedded image

The amount of the ascorbic acid derivative used is as follows:
It is preferably 0.001 to 0.1 g / m ² .
If it is less than 0.001 g / m ² , there is no effect on improving the preservability of the background, and if it exceeds 0.1 g / m ² , the heat sensitivity is undesirably lowered.

The coating solution of the present invention can be prepared by known coating methods such as bar coating, blade coating, air knife coating, gravure coating, doctor coating, slide coating, roll coating, spray coating, dip coating, curtain coating and the like. It is applied by applying a method described in Yuji “Coating Engineering”, page 253 (published by Asakura Shoten in 1973) according to the purpose.

The recording layer (also referred to as a photosensitive layer) of the present invention is set so that the solid content after coating and drying is 1.5 to 15 g / m ² .

In the copying material of the present invention, it is preferable that the diazo compound, the coupling component, the base, and the like are contained in the same layer as described above in view of the simplicity of production and the like. It is also possible to adopt a laminated type configuration that is included.

In the copying material of the present invention, it is necessary to have the recording layer and the support as described above. However, other known layer configurations may be applied as long as the effects of the present invention are not impaired. Can be. For example, Japanese Patent Application Laid-Open No. 61-5 / 1986
After providing an intermediate layer as described in No. 4980, etc.,
A photosensitive layer can be applied. Further, a protective layer can be further provided on the photosensitive layer.

When an image is formed on the copy material of the present invention, the image-wise exposure corresponding to the original is performed to decompose the diazo compound in the exposed portion, and then the entire copy material is heated to obtain the unexposed portion of the diazo compound. And a coupler to obtain a color image. Here, since the wall of the thermoresponsive microcapsule is made thin, it is possible to reduce the shielding property of ultraviolet rays.

For imagewise exposure corresponding to a document, it is easy to perform close contact exposure if it is a transparent document, but other methods, for example, exposure with a laser beam may be adopted.

As a light source for exposure, various fluorescent lamps, xenon lamps, mercury lamps and the like are used. In this case, it is preferable that the emission spectrum of the light source substantially coincides with the absorption spectrum of the diazo compound used.

As the heating means in the step of heating and developing the entire surface of the photosensitive layer of the copying material, known heating means such as infrared rays, a high frequency wave, a heat block and a heat roller can be appropriately used according to the purpose. .

[0071]

EXAMPLES Examples will be shown below, but the present invention is not limited by these examples. “Parts” indicating the amount of addition represents “parts by weight”.

Example 1 Preparation of Microcapsule Solution Encapsulating a Diazo Compound 2 parts of a diazonium salt represented by the following formula (4), 1 part of a compound represented by the following formula (5) and a compound represented by the following formula (6) One part of the resulting compound was added to and dissolved in 5 parts of ethyl acetate.

[0073]

Embedded image

In the solution of the diazo compound or the like, 3 parts of an isocyanurate having a structure of TDI isocyanurate (Sumidur FL-2: trade name manufactured by Sumitomo Bayer Urethane Co., Ltd.) and the structure of a trimethylol lopan adduct of XDI (Takenate D-1)
10N: 3 parts of trade name (manufactured by Takeda Pharmaceutical Co., Ltd.) was added and mixed with stirring.

The diazonium salt thus obtained,
An ethyl acetate solution of the isocyanate and the compounds represented by the formulas (5) and (6) is mixed with an aqueous solution in which 1 part of polyvinyl alcohol (PVA217E, manufactured by Kuraray Co., Ltd.) is dissolved in 10 parts of water, and emulsified. By dispersing, an emulsion having an average particle size of 1.0 μm was obtained. Water 10 was added to the obtained emulsion.
The mixture was heated to 40 ° C. with stirring to react isocyanate as a wall-forming substance for 3 hours.
With m, microcapsules containing the diazo compound and the compounds of formulas (5) and (6) as core material were obtained.

The above encapsulation reaction was performed under a reduced pressure of 400 mmHg to 500 mmHg using a water jet pump.

Preparation of Coupler-Encapsulated Microcapsule Solution 3.45 parts of 2-hydroxy-3-naphthoic acid anilide and 0.85 part of acetic acid were sufficiently dissolved in 24 parts of tricresyl phosphate. Next, styrene, which is an alkali-soluble resin,
The above coupler solution was mixed with 50 parts of 5% ammonium aqueous solution of an acrylic acid copolymer (Tg: 102 ° C., weight average molecular weight: 8000), and the mixture was stirred with a homomixer (manufactured by Mitsui Electric Seiki Co., Ltd.) at 12,000 to 10,000 rpm for 3 minutes to emulsify. A liquid was obtained. The obtained emulsion is heated to 60 ° C., and while the temperature is maintained at that temperature, the mixture is slightly agitated for 30 minutes to adjust the pH of the dispersion to 7
The end point was defined as the end point, and a coupler-encapsulated microcapsule dispersion having an average particle size of 5 μm was obtained.

Preparation of Basic Substance Dispersion Triphenylguanidine (basic substance) dispersion having an average particle size of 2 μm was added by adding 10 parts of triphenylguanidine to 100 parts of a 5% by weight aqueous solution of polyvinyl alcohol and dispersing for 24 hours by a sand mill. I got

Preparation of Coating Solution Capsule solution 1 of the diazo compound obtained as described above
In 0 parts, 20 parts of a capsule solution of the above coupler, 12.5 parts of a triphenylguanidine dispersion, 10 parts of a 40% by weight calcium carbonate (Univar 70, manufactured by Shiroishi Kogyo), and 5 parts of a 20% by weight stearamide dispersion , 3,5-di-α
-Dispersion 2 of 40% by weight of zinc methylbenzylsalicylate 2
And 1 part of a 5% by weight solution of L-ascorbic acid (Vitamin C, manufactured by Takeda Pharmaceutical Co., Ltd.) represented by the specific example (1) was added to obtain a coating solution.

Preparation of Copy Material The above coating solution was coated on a smooth high-quality paper (76 g / m ² ) using a coating bar and dried at 5 g / m ² (0.2 g / m ² as a diazo compound). A bar was applied so that the LA ascorbic acid was 0.02 g / m ² ) and dried at 50 ° C. for 3 minutes to obtain a copy material of the present invention.

Evaluation of Chromogenicity After imagewise exposure, a heat block heated to 100 ° C. was pressed against a copy material for 2.5 seconds and developed, and the density of the image area was measured with a Macbeth densitometer. The larger the value, the better the color development. The results are as shown in Table 1.

Evaluation of Storage Property In order to evaluate the storage property (raw storage property) of the obtained recording material, the recording material was stored in a dark place atmosphere at 40 ° C. and a relative humidity of 90% (90% RH) and at a relative humidity of 60 ° C. The recording material was subjected to a forced deterioration test in which the recording material was allowed to stand in a dark place atmosphere of 30% (30% RH) for one day. The background density before and after each test was measured with a Macbeth densitometer, and the difference was defined as background fog. It is evaluated that the smaller these values are, the better the preservability is. Table 1 shows the results
As shown in FIG.

Evaluation of light fixability Copiart 100 (scale 1) manufactured by Fuji Photo Film Co., Ltd.
Using 0), the density of the background portion after exposure to development was measured by a Macbeth densitometer. The smaller the value, the faster the fixing speed. The results are as shown in Table 1.

(Example 2) Instead of the alkali-soluble microcapsule solution containing the coupler, 12.5 parts of the coupler dispersion solution prepared as described below was used, and instead of the triphenylguanidine dispersion solution added to the coating solution, A coating material was prepared by preparing a coating solution in exactly the same manner as in Example 1, except that 20 parts of a basic substance-encapsulated alkali-soluble microcapsule solution prepared as described below was added, and evaluated in the same manner as in Example 1. went. The results are as shown in Table 1.

Preparation of Coupler Dispersion 10 parts of 2-hydroxy-3-naphthoic acid anilide was added to 100 parts of a 5% by weight aqueous solution of polyvinyl alcohol, and dispersed by a sand mill for 24 hours to obtain a dispersion having an average particle diameter of 2 μm. .

Preparation of Alkali-Soluble Microcapsule Solution Encapsulating Basic Substance 3.45 parts of triphenylguanidine and 0.85 of acetic acid
Parts were sufficiently dissolved in 24 parts of tricresyl phosphate. Next, the coupler solution was mixed with 50 parts of a 5% aqueous ammonium solution of a styrene-acrylic acid copolymer (Tg: 102 ° C., weight average molecular weight: 8,000), which was an alkali-soluble resin, and mixed with a homomixer (manufactured by Mitsui Electric Seiki Co., Ltd.) at 12,000. ~
The mixture was stirred at 10,000 rpm for 3 minutes to obtain an emulsion. The obtained emulsion is heated to 60 ° C. and kept at that temperature for 3 hours.
The microcapsule dispersion containing the basic substance and having an average particle diameter of 5 μm was obtained when the pH of the dispersion reached 7 as a result of slight stirring for 0 minutes.

(Example 3) Coupler / basic substance-encapsulated microcapsules prepared as follows, instead of the coupler-encapsulated alkali-soluble microcapsule liquid and triphenylguanidine (basic substance) dispersion liquid added to the coating solution A coating material was prepared by preparing a coating solution in exactly the same manner as in Example 1 except that 40 parts of the dispersion was added, and evaluation was performed in the same manner as in Example 1. The results are as shown in Table 1.

Preparation of Coupler / Basic Substance-Encapsulated Alkali-Soluble Microcapsule Solution 2 parts of 2-hydroxy-3-naphthoic acid anilide, 2 parts of triphenylguanidine and 0.85 part of acetic acid were sufficiently added to 24 parts of tricresyl phosphate. Dissolved. Next, a styrene-acrylic acid copolymer (T
g: 102 ° C., weight average molecular weight: 8000) 5% of an aqueous ammonium solution was mixed with the above coupler solution, and mixed with a homomixer (manufactured by Mitsui Electric Seiki Co., Ltd.) at 12000 to 1000.
The mixture was stirred at 0 rpm for 3 minutes to obtain an emulsion. The obtained emulsion is heated to 60 ° C., and the temperature is maintained at that temperature, and the mixture is weakly stirred for 30 minutes. The end point is when the pH of the dispersion reaches 7, and the average particle diameter is 5 μm. An encapsulated microcapsule dispersion was obtained.

(Comparative Example 1) 25 parts of a coupler dispersion prepared in the same manner as in Example 2 was added instead of the alkali-soluble microcapsule solution containing the coupler, and the stirring conditions in the preparation of the diazo compound-containing microcapsule solution were changed. A diazo compound-encapsulated thermoresponsive microcapsule having an average particle size of 1.0 μm was obtained by control, and a coating material was prepared in exactly the same manner as in Example 1 except that the microcapsule was used. Evaluation was performed in the same manner as in Example 1. Table 1 shows the results
As shown in FIG.

Comparative Example 2 A coating solution was prepared and copied in exactly the same manner as in Comparative Example 1, except that a diazo compound-encapsulated thermoresponsive microcapsule having an average particle diameter of 0.5 μm was used. Materials were prepared and evaluated in the same manner as in Example 1. The results are as shown in Table 1.

[0091]

[Table 1]

As is clear from the results shown in Table 1, Comparative Example 1 in which only the diazo compound was microencapsulated, Comparative Example 2 in which the particle size of the diazo compound-containing microcapsules was reduced, that is, the capsule wall was made thinner. Although the coloring property and the fixing speed were improved, the storage stability was remarkably reduced.
In comparison with these, it was found that the heat-developable copying material of the present invention did not decrease the storage stability even when the capsule wall was made thin, and achieved excellent color development and fixing speed.
This effect was not affected when either one of the coupling component and the basic substance was microencapsulated, or when both were microencapsulated.

[0093]

As described in detail above, the heat-developable copying material of the present invention has a higher fixing speed than the conventional one, has better storage stability than before, and can obtain a high image density. It showed excellent properties.

Claims (1)

[Claims] 1. A heat-developable copying material comprising a support provided with a recording layer containing a diazo compound, a coupling component which reacts with the diazo compound to form a color, and a color-forming auxiliary, wherein the diazo compound is thermally responsive. Encapsulated in a hydrophobic microcapsule, wherein at least one of the coupling component and the color-forming auxiliary contains at least one selected from styrene units and acrylic acid units, and has a wall material made of a polymer soluble in an aqueous alkaline solution. A heat-developable copying material characterized in that it is included in a heat-developable copying material.