JPH0444888A - Thermal recording material - Google Patents

Abstract

PURPOSE:To ensure that the subject material has high water-proofness, high chemical resistance and excellent shelf life and image preservation by microcapsulating at least, one of coloring components and adding at least, one kind of p-hydroxy bezoate alkylester to a thermally sensitive layer. CONSTITUTION:From a viewpoint of enhancing image density, it is recommended that a coupler or a color developer not be capsulated but only a diazo compound or an electron-donative dye precursor be microcapsulated. To control the intrin sic glass transition point of a capsule wall, it is necessary to replace the type of a capsule wall forming agent. The preferable capsule wall material is polyure thane and polyurea. Alkyl p-hydroxy benzoate is a material which enhances color density or decreases a minimum coloring temperature during thermal printing process and acts as a thermal sensitivity sensitizer. The preferable type of the alkyl p-hydroxy benzoate is alkyl p-hydroxy benzoate with a total sum of 2 to 12 carbon atoms excepting a p-hydroxy benzoate skeleton.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material having a heat-sensitive layer having good storage stability and heat sensitivity.

(Prior art) The thermal recording method has three advantages: (1) no development is required; (2) when the support is paper, the quality of the paper is similar to that of ordinary paper; (3) it is easy to handle; and (4) color density is high. (5) The recording device is simple and inexpensive; and (6) There is no noise during recording. Therefore, it has rapidly become popular in the fields of black and white facsimiles and printers in recent years. These heat-sensitive recording materials are made by coating a support such as paper or synthetic paper with a color former or developer, and are recorded using a heating process using a thermal head based on electrical signals corresponding to the original. . With the rapid development of the information industry, heat-sensitive recording materials used in such heat-sensitive recording methods have recently been developed to have good water resistance and chemical resistance, as well as good shelf life and image preservation properties. is desired.

In response to such demands, the present inventors have developed and already proposed a heat-sensitive recording material in which at least one of the color-forming components is microencapsulated to improve chemical resistance, water resistance, raw storage stability, and image storage stability (for example, JP-A No. 63-92489, No. 6
No. 3-45084, No. 63-134282).

(Problems to be Solved by the Invention) However, in these heat-sensitive recording materials, a part of the coloring component is microencapsulated, so while the raw storage stability and image storage stability are good, the image density is low. It was difficult to increase the temperature, and the heat sensitivity was low.

As a result of intensive study by the present inventors to solve the above-mentioned drawbacks,
The inventors have discovered that by incorporating p-hydroxybenzoic acid alkyl ester into the heat-sensitive layer, the image density of the heat-sensitive recording material can be increased and the heat sensitivity can be significantly improved, and the present invention has been achieved.

Therefore, the first object of the present invention is to provide a heat-sensitive recording material that not only has good water resistance, chemical resistance, raw storage stability, and image storage stability, but also can realize high image density.

A second object of the present invention is to provide a heat-sensitive recording material that not only has good water resistance, chemical resistance, raw storage stability, and image storage stability, but also has high thermal sensitivity.

(Means for Solving the Problems) The above aspects of the present invention are to provide a substantially colorless coloring component A on a support, and a substantially colorless coloring component that reacts with the coloring component A to form a color. In the heat-sensitive recording material provided with a heat-sensitive layer containing B, at least one of the coloring components is microencapsulated, and at least one p-hydroxybenzoic acid alkyl ester is contained in the heat-sensitive layer. This was achieved using a heat-sensitive recording material that has the following characteristics.

The heat-sensitive recording material of the present invention includes an embodiment in which coloring component A is a diazo compound and coloring component B is a coupler, as well as an embodiment in which coloring component A is an electron-donating dye precursor and coloring component B is a color developer. .

In the present invention, the diazo compound used as the color-forming component A is a compound that reacts with the cambling component described below to develop a desired hue, but it decomposes especially when exposed to light of a specific wavelength before the reaction. It is preferable to use 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.

The photodegradable diazo compound referred to 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.

For example, it is said that the photodecomposition wavelength of a diazonium salt is its maximum absorption wavelength. Also, the maximum absorption wavelength of diazonium salts varies from about 200 nm to 700 nm, depending on their chemical structure.
It is known that the change occurs down to about nanometers ("Photodecomposition and chemical structure of photosensitive diazonium salts" by Takahiro Tsunoda and Ao Yamaoka, Journal of the Photographic Society of Japan 29 (4), pp. 197-205 (
1965)).

That is, when a diazonium salt is used as a photodegradable compound, it is decomposed by light of a specific wavelength depending on its chemical structure, and
If the chemical structure of the diazonium salt is changed, the hue of the dye will also change when the coupling reaction occurs, even if the same coupling component is used.

Details of these diazo compounds are described, for example, in JP-A-63-134282.

The color developer for the diazo compound used in the present invention is a coupling component that forms a dye by coupling with the diazo compound (diazonium salt), and specific examples include 2-hydroxy-3-naphthoic acid. In addition to anilide, patent application No. 60-287485 includes resorcinol.
Examples include those listed in the No.

Since the coupling reaction between these diazo compounds and the coupling component is likely to occur under 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, virols, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidacillins, triazoles. Examples include nitrogen-containing compounds such as morpholines, piperidines, amidines, formazines, and pyridines. Specific examples of these are:
For example, it is described in Japanese Patent Application Laid-Open No. 61-291183.

Two or more basic substances may be used in combination.

On the other hand, the electron-donating dye precursor used in the color-forming unit consisting of a combination of an electron-donating dye precursor and a color developer according to the present invention may be one that supplies electrons or accepts protons such as acids. There are no particular limitations as long as it has the property of coloring, but it is usually almost colorless and includes lactones, lactams, sultones, spiropyrans, esters,
A compound having a moiety such as an amide and whose partial skeleton is ring-opened or cleaved upon contact with a color developer is used.

Specifically, crystal violet lactone, benzoylleucomethylene blue, malachite green lactone, rhodamine B lactam, 1.2゜3-trimethyl-
Examples include 6°-ethyl-8′-butoxyindolinobenzospiropyran.

Examples of the color developer used with these electron-donating dye precursors include phenol compounds, organic acids or metal salts thereof, and oxybenzoic acid esters. The preferred melting point of the color developer is 50"C to 250C, especially 60C
~200°C, poorly soluble phenols and organic acids in water are desirable.

Specific examples of these color developers are disclosed in, for example, Japanese Patent Application Laid-Open No. 61-291.
It is described in No. 183.

In the present invention, regardless of whether a combination of a diazo compound and a coupler or a combination of an electron-donating dye precursor and a color developer is used, heat-sensitive To improve the storage stability and image storage stability of recording materials, especially from the viewpoint of increasing image density, couplers or color developers are not microencapsulated, and only diazo compounds or electron-donating dye precursors are used. It is preferable to microencapsulate.

The type of microcapsules that can be used in the present invention is not particularly limited, but as mentioned above, microcapsules containing a diazo compound or an electron-donating dye precursor have a substance isolation effect on the microcapsule wall at room temperature. Preferably, the material prevents contact between the inside and outside of the capsule, and the permeability of the material increases only while it is heated above a certain temperature. Such microcapsules are
By appropriately selecting the capsule wall material, capsule core material, additives, etc., the permeation start temperature can be freely controlled. The transmission start temperature in this case corresponds to the glass transition temperature of the capsule wall (e.g., JP-A No. 5
9-91438, Japanese Patent Application No. 59-190886, Japanese Patent Application No. 59-99490, etc.).

In order to control the glass transition point specific to the capsule wall, it is necessary to change the type of capsule wall forming agent. Capsule wall materials include polyurea, polyurethane, polyurea/urethane mixed capsules, urea-formalin capsules,
Polyurea/other synthetic resin mixed capsules in which other synthetic resins are encapsulated in the core material, polyesters, polyamides, etc. are preferred, and polyurethane and polyurea are particularly preferred.

Specific examples of microencapsulation techniques, materials, and compounds used can be found in U.S. Pat. Nos. 3.726804 and 3.
, 796,696.

When making microcapsules, they can be made from an emulsion containing 0.2% by weight or more of the component to be microencapsulated.

Here, when forming a coloring unit layer having a combination of a diazo compound and a coupling compound as a coloring unit, the amount of the coupling component is 0.1 to 1 part by weight of the diazo compound.
It is preferable to use the basic substance in an amount of 10 parts by weight and 0.1 to 20 parts by weight. In addition, when forming a color forming unit layer in which the color forming unit is a combination of an electron donating dye precursor and a color developer, the amount of the color developing agent is 0.3 to 160 parts by weight per 1 part by weight of the electron donating dye precursor. Parts by weight, preferably 0°3-8
Preferably, 0 part by weight is used.

Next, the p-hydroxybenzoic acid alkyl ester used in the present invention will be explained in detail.

The above p-hydroxybenzoic acid alkyl ester is a substance that increases the color density or lowers the minimum color temperature during thermal printing, and is a substance that increases the color density during heating printing or lowers the minimum color temperature.
Diazo compounds, basic substances, coupling components, electron-donating dye precursors, It can create a situation in which color developers etc. react easily, and acts as a heat sensitivity sensitizer.

Among the above p-hydroxybenzoic acid alkyl esters, p-hydroxybenzoic acid alkyl esters having a total number of carbon atoms excluding the p-hydroxybenzoic acid skeleton of 2 to 12 are particularly preferred in the present invention, examples of which include: For example, p-hydroxybenzoic acid ethyl ester, p-hydroxybenzoic acid-n-propyl ester, p-hydroxybenzoic acid isopropyl ester, p-hydroxybenzoic acid butyl ester, p-hydroxybenzoic acid isobutyl ester, p-hydroxybenzoic acid pentyl ester ester, p-hydroxybenzoic acid hexyl ester, p-hydroxybenzoic acid heptyl ester, p-hydroxybenzoic acid octyl ester, p-hyroxybenzoic acid ester, p-hyroxybenzoic acid hexyl ester, p-hydroxybenzoic acid octyl ester, p-hyroxybenzoate! acid nonyl ester, p-hydroxybenzoic acid undecyl ester, p-hydroxybenzoic acid undecyl ester,
Examples include P-hydroxybenzoic acid dodecyl ester.

The benzene core of benzoic acid may have a substituent such as halogen or alkyl. Examples include isopropyl 2-methyl-4-hydroxybenzoate, n-7'' lobil 3-chloro-4-hydroxybenzoate, and the like.

Although these may be used alone, it is particularly preferable to use a mixture of two or more from the viewpoint of color development, fogging, and solubility. In any case, it can be added to the outside of the microcapsule as an emulsified dispersion together with a coupler or a color developer, or it can be added as a solid dispersion.

In order to further increase the effect of the alkylphenol mentioned above, a coloring aid can also be used in combination. Such color development aids include phenolic compounds, alcoholic compounds, amide compounds, sulfonamide compounds, etc. Specific examples include p-tert-octylphenol, p-benzyloxyphenol, and phenyl p-oxybenzoate. ,
Compounds such as hensyl carbanylate, phenethyl carbanylate, hydroquinone dihydroxyethyl ether, xylylene diol, N-hydroxyethyl-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 a dispersion.

The heat-sensitive recording layer contains silica, barium sulfate,
Pigments such as titanium oxide, aluminum hydroxide, zinc oxide, and calcium carbonate, and fine powders such as styrene beads and urea-melamine resin can be used.

Similarly, metal soaps can also be used to prevent sticking. Assuming that these usage amounts are 0.2
~7 g/m is suitable.

The heat-sensitive recording material of the present invention can be coated using a suitable binder.

Binders include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, gum arabic, gelatin, polyvinylpyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic acid ester, ethylene-vinyl acetate, etc. Various emulsions such as polymers can be used. The amount used is 0.5 to 5 g/nf in terms of solid content.

In the present invention, in addition to the above materials, citric acid, alcohol soap, oxalic acid, boric acid, phosphoric acid, birophosphoric acid, etc. can be added as acid stabilizers.

The coupling components, basic substances, alkylphenols, color developers, etc. used in the present invention can be simply dispersed and used, or can be used in an oil phase in which they are dissolved in a solvent that is sparingly soluble or insoluble in water, together with protective colloids and surfactants. the aqueous phase containing the side,
It can also be used as an emulsified dispersion by mixing and dispersing it using means commonly used for emulsifying fine particles, such as high-speed stirring and ultrasonic dispersion. When the emulsified dispersion obtained in the latter manner is used in a coating solution and coated and dried on a support,
The resulting heat-sensitive layer can have surprisingly good transparency.

The above support may be a transparent support, depending on the purpose and use.
Both opaque supports such as paper are used.

The paper used for the support is heat-extracted pH 6 sized paper using a neutral size material such as alkyl ketene dimer.
~9 Neutral paper (described in JP-A-55-14281)
The use of is advantageous in terms of storage stability over time.

In order to prevent the coating liquid from penetrating into the paper and improve the contact between the thermal recording head and the thermal recording layer, Japanese Patent Application Laid-Open No. 57-116687
The paper described in the above-mentioned issue and having a Bekk smoothness of 90 seconds or more is advantageous.

In addition, paper having an optical surface roughness of 8μ or less and a thickness of 40 to 75μ described in JP-A-58-136492, JP-A-58-136492,
Paper with a density of 0°9 g/cm3 or less and an optical contact ratio of 15% or more, described in JP-A No. 8-69097, JP-A-58-690
Canadian standard freeness described in No. 97 (JIS P812
Paper made from pulp beaten to 400 cc or more in 1) to prevent penetration of coating liquid, JP-A-58-656
No. 95, the glossy side of base paper made by a Yankee machine is used as the coating surface to improve color density and resolution, and JP-A No. 59-35985 describes a method in which the base paper is subjected to corona discharge treatment. Papers with improved coating suitability may also be used in the present invention with good results. In addition to these, any support commonly used in the field of heat-sensitive recording paper can be used as the support of the present invention.

When a transparent support is used as the support, the recorded matter can be used as an OHP sheet or the like.

Examples of transparent supports include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate films, polystyrene films, polypropylene films, and polyolefin films such as polyethylene. It can be used by pasting them together.

The thickness of the transparent support used is 20 to 200μ,
Particularly preferred is one of 50 to 100 μm.

The support may be provided with perforations so that the support can be conveyed with high precision during printing.

When a transparent support is used as a support, it can be seen as a transmitted image or a reflected image from one side of the transparent support, but especially in the latter case, if the back side of the background part is visible, the image Since the color is dull, a layer containing a white pigment may be additionally coated on the outermost layer on the reflective side from the side where the recorded image is viewed. Examples of preferable white pigments include talc, calcium carbonate, Calcium sulfate, magnesium carbonate, magnesium hydroxide, alumina, synthetic silica, titanium oxide, barium sulfate, kaolin,
Examples include calcium silicate and urea resin.

In the present invention, an undercoat layer can be provided on the transparent support to enhance adhesion between the transparent support and the heat-sensitive layer.

Gelatin, synthetic polymer latex, nitrile cellulose, etc. are used as the material for the undercoat layer. The coating amount of the undercoat layer is 0.1g/rd to 2.0g/rd. It is preferably in the range of Og/rd, particularly 0.2g/n (~1.Og/rrr
A range of is preferred.

If it is less than 0.1 g/n, the adhesion between the support and the heat-sensitive layer will not be sufficient, and even if it is increased to 2.0 g/n or more, the adhesive force between the support and the heat-sensitive layer will reach saturation, resulting in a cost increase. be at a disadvantage.

The undercoat layer is desirably cured using a hardening agent, since the image quality of the heat-sensitive layer may deteriorate if it swells with water contained in the heat-sensitive layer when the heat-sensitive layer is coated thereon.

As hardeners that can be used in the present invention, the following can be mentioned.

■Divinylsulfone N,N“-ethylenebis(vinylsulfonylacetamide), l,3-bis(vinylsulfonyl)-2-propatol, methylenebismaleimide,
5-acetyl-1,3-diacryloyl-hexahydro-s-triazine, 1.3.5-)lyacryloyl-hexahydro-8-triazine, 1,3.5-1-rivinylsulfonyl-hexahydro-3 -Activated vinyl compounds such as triazines.

■2.4-dichloro-6-hydroxy-3-triazine sodium salt, 2,4-dichloro-6-medoxys
-h lyazine, 2,4-dichloro-6-(4-sulfoanilino)-s-triazine sodium salt, 2,4-dichloro-6-(2-sulfoethylamino)-s-triazine, N-N”- Bis(2-chloroethylcarbamyl)
Active halogen compounds such as piperazine.

■Bis(2,3-epoxypropyl)methylpropylammonium I)-toluenesulfonate, 1,4-bis(2',3'-epoxypropyloxy)butane, 1,3,5-triglycidyl Isocyanurate, 1.
Epoxy compounds such as 3-diglycidyl-5-(racetoxy-β-oxypropyl)isocyanurate.

■2.4.6-1-lyethylene-8-triazine, 1.
6-hexamethylene-N,N'-bisethyleneurea,
Ethylenimino compounds such as bis-β-ethyleneiminoethylthioether.

■1.2-di(methanesulfonoxy)ethane, ■, 4
- Methanesulfonic acid ester compounds such as di(methanesulfonoxy)butane and 1°5-di(methanesulfonoxy)pentane.

■Dicyclohexylcarbodiimide, 1-cyclohexyl-3-(3-trimethylaminopropyl)carbodiimide-p-trienesulfonate, 1-ethyl-3-(
3-dimethylaminopropyl) carbodiimide hydrochloride.

■2,5-dimethylisoxadur/perchlorate, 2
Isoxazole compounds such as -ethyl-5-phenylisoxazole-3'-sulfonate and 5.5"-(paraphenylene)bisisooxadur.

■Inorganic compounds such as chromium alum and chromium acetate.

■N-carboethoxy 2-isopropoxy 1,2-dihydroquinoline, N-(1-morpholinocarboxy)-
Dehydrated condensation type peptide reagents such as 4-methylpyridinium chloride, active ester compounds such as N,N-aziboyldioxydisuccinimide, and N,N'terephthaloyldioxydisuccinimide.

[Phase] Isocyanates such as toluene-2,4-diisocyanate and 16-hexamethylene diisocyanate.

■Dialdehydes such as glutaraldehyde, glyoxal, dimethoxyurea, and 2,3-dihydroxy-1,4-dioxane.

Among these, dialdehydes such as glutaraldehyde and 2°3-dihydroxy-1,4-dioxane, and boric acid are particularly preferred.

The amount of these hardeners added is based on the weight of the base coat material.
An appropriate addition amount can be selected in the range of 0.20% by weight to 3.0% by weight depending on the coating method and desired degree of curing.

If the amount added is less than 0.20% by weight, the degree of curing will be insufficient no matter how long it is left, and the undercoat layer will swell when the heat-sensitive layer is applied. If the amount is too high, the degree of curing will proceed too much, and the adhesion between the undercoat layer and the support will deteriorate, resulting in the disadvantage that the undercoat layer will become film-like and peel off from the support.

Depending on the curing agent used, if necessary, the pH of the solution can be made alkaline by adding caustic soda or the like, or the pH of the solution can be made acidic by adding citric acid or the like.

Moreover, it is also possible to add an antistatic agent if necessary.

Furthermore, before applying the undercoat layer, it is desirable to activate the surface of the support by a known method.

Activation treatment methods include acid etching treatment,
Flame treatment using a gas burner, corona treatment, glow discharge treatment, etc. are used, but from the point of view of cost or simplicity, U.S. Pat.
, No. 846.727, No. 3,549.406, No. 3,590,107, etc. are most preferably used.

In the present invention, an overcoat layer may be provided on the heat-sensitive layer in order to impart water resistance and scratch resistance.

As the material for the overcoat layer, polyvinyl alcohol, silicon-modified polyvinyl alcohol, gelatin, styrene-maleic anhydride copolymer, starch, etc. may be used alone or in combination as a binder, and further, in order to harden these binders. It is desirable to use the same hardening agent as that used for the above-mentioned undercoat layer, or to use borax, boric acid, colloidal silica, or the like.

In particular, when the main components are silicon-modified polyvinyl alcohol and colloidal silica, it can be scratched to form an overcoat layer with good transparency.

The coating amount of the overcoat layer is from 0.3g/rrf to 5
g/rrf range, particularly 0.5 g/rrf.
It is preferably in the range of rrt to 4g/rrf.

If the coating amount is less than 0.3 g/rrf, sufficient water resistance and scratch resistance cannot be achieved, and if it is greater than 4 g/rrf, extra energy is required during printing, which is not preferable.

The coating liquid according to the present invention can be applied by a generally well-known coating method,
For example, dip coating method, air knife coating method, curtain coating method, roller coating method, doctor coating method,
Coating can be performed by a wire barcode method, a slide coating method, a gravure coating method, or an extrusion coating method using a hopper as described in US Pat. No. 2,681.294. U.S. Pat. No. 2,761.791 and U.S. Pat. No. 3,508.947, as appropriate.
No. 2,941,898, and No. 3゜526.
Specification No. 528, Yuji Harasaki, "Coating Engineering" 25
It is also possible to apply the product simultaneously in two or more layers using the method described on page 3 (published by Asakura Shoten in 1973), and an appropriate method can be selected depending on the amount of application, application speed, etc. .

Adding pigment dispersants, thickeners, flow modifying agents, antifoaming agents, foam inhibitors, mold release agents, colorants, etc. to the coating liquid used in the present invention as necessary will not impair the properties. I have no qualms as far as it goes.

The coating amount of the heat sensitive layer is 3g/rrf to 20g/po, especially 5g
/n (preferably between ~15 g/rrf.

If it is less than 3 g/%, sufficient sensitivity cannot be obtained, and if it is applied more than 20 g/%, no improvement in quality is observed, which is disadvantageous in terms of cost.

In the present invention, the transparent heat-sensitive layer as described above can be easily formed by combining a plurality of heat-sensitive layers, such as stacking them, laminating them on a conventional opaque heat-sensitive layer, or providing heat-sensitive layers on both sides of a transparent support. It can also be made into a multicolor heat-sensitive recording material.

The heat-sensitive recording material of the present invention can be used as a printer sheet for facsimiles and electronic computers that require high-speed recording.

In this case, when a diazo compound is used as a color-forming component, it is especially advantageous for image storage stability to have an exposure zone for photolysis.

Further, as a light source for photolysis, various light sources that emit light of a desired wavelength can be used, and these light sources include, for example, various fluorescent lamps, xenon lamps, xenon flash lamps, mercury lamps of various pressures, photographic flash,
Examples include strobes and the like. 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.

(Effects of the Invention) The heat-sensitive recording material of the present invention uses at least one of the color-forming components encapsulated in microcapsules, so it has good shelf life and record keeping properties. - Since the hydroxybenzoic acid alkyl ester is used, the resulting image density is significantly increased compared to conventional ones, and the thermal sensitivity is extremely good.

(Examples) The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1 The following diazo compound: 3.4 parts Tricresyl phosphate: 6 parts Methylene chloride 12 parts Trimethylolpropane trimethacrylate: 18 parts D-11ON (75% by weight ethyl acetate solution) (Takeda Pharmaceutical Co., Ltd.) ■Made by (product name): Mix 24 parts and add 8 parts of polyvinyl alcohol (Kuraray PVA-217E).
After adding it to an aqueous solution consisting of 63 parts of a wt% aqueous solution and 100 parts of distilled water, it was emulsified and dispersed at 20°C, and the average particle size was 2μ.
After obtaining the emulsion of m, the obtained emulsion was heated at 40°C for 3
Stirring was continued for hours.

After cooling this liquid to 20°C, Amberlite IR-
120B (manufactured by Rohm and Haas (product name))
00 cc was added, stirred for 1 hour, and then filtered to obtain capsule liquid A.

1.1 part of a coupler base H2CH3 represented by the following structure of Kaboo A, a sensitizer, and 0.5 part of tricresyl phosphate were dissolved by heating in 10 parts of ethyl acetate.

The obtained oily liquid was mixed with 8% polyvinyl alcohol (PVA2
17E: Made by Kuraray ■) and mixed with an aqueous solution of 0.5 g of sodium dodecylbenzenesulfonate, manufactured by Nippon Seiki ■
At room temperature and at 10.0
Emulsification was carried out at 0 rpm for 5 minutes to obtain an emulsified dispersion with a particle size of 0.5 μm.

Kulit Gen A and Kuuri Silica-modified polyvinyl alcohol (PVA made by Kuraray ■)
R2105) 10% by weight Liquid: 10 parts Colloidal silica (Snowtex 30 manufactured by Nichichi Kagaku ■) 30% by weight
Liquid: 5 parts Zinc stearate (Hydrin Z7 manufactured by Middle East Oil Co., Ltd.) 30% by weight liquid
: 0.42 parts paraffin wax (Hydrin P-7 manufactured by Middle East Oil Co., Ltd.) 30% by weight liquid 20. 42
A protective layer solution A was obtained by mixing the two parts.

After applying corona discharge treatment to a biaxially stretched polyethylene terephthalate film with a thickness of 75 μm, capsule liquid A was prepared.
A coating solution containing 5.0 parts and 7.0 parts of coupler/base dispersion was applied so that the dry coating amount was 6 g/rd.

Next, protective layer liquid A was applied in a dry coating amount of 2 g/rd to obtain a recording sheet.

The coating was done using a wire bar and then dried in an oven at 50'C.

G mode (High Fuck 7!) was applied to the obtained heat-sensitive recording material.
, 700) (manufactured by Hitachi, Ltd.), and then a Recopy Super Dry 100 (
■The entire surface was exposed and fixed using a RICOH camera (manufactured by Ricoh). The resulting yellow recorded image density was measured using a Macbeth transmission densitometer.

Next, in order to examine raw storage stability, we measured the background density (fog) of the heat-sensitive recording material and the fog after performing a forced deterioration test by storing it in a dark place for 24 hours under the condition of 40"C1 relative humidity of 90%. Macbeth was measured at different transmission densities to examine changes in fog.The results are shown in Table 1.

Table 1 Example 2 A heat-sensitive recording sheet was obtained in exactly the same manner as in Example 1 except that a sensitizer was used. Table 1 shows the results of various measurements carried out in the same manner as in Example 1. Ta.

Example 3 Leuco dye Takene[)-LION represented by the following structural formula (capsule wall agent manufactured by Takeda Pharmaceutical ■)
60 g and 2 g of Sumisorb 200 (ultraviolet absorber manufactured by Sumitomo Chemical ■) were added and dissolved in a mixed solvent of 55 g of 1-phenyl-1-xylylethane and 55 g of methylene chloride. This leuco dye solution was mixed with an aqueous solution of 100 g of 8% polyvinyl alcohol aqueous solution, 40 g of water, and 1.4 g of 2% sodium salt of dioctyl sulfosuccinate (dispersing agent). Emulsify at .00 rpm for 5 minutes, then add 150 g of water.
was added and reacted at 40°C for 3 hours to produce a capsule liquid with a capsule size of 0.7 μm.

i Color developer represented by the following structural formula (a) 8 g, (b) 4
g and (C) 30 g, sensitizer (d) 5 g, (e) 5 and 5 g), 1 phenyl-1-xylylethane 8.0 g
was dissolved in 30 g of ethyl acetate. The obtained developer solution was mixed with 8% polyvinyl alcohol aqueous solution (long) and water (1 1/2).
50 g, and 0.5 g of sodium dodecylhenzenesulfonate.
The mixture was mixed with 5 g of an aqueous solution and emulsified for 5 minutes at room temperature and 10,000 rpm using an Ace homogenizer manufactured by Nippon Seiki ■ to obtain an emulsified dispersion with a particle size of 0.5 μm.

Color developer (a) Zinc salt Color developer (b) Color developer 7FI CC) C,H,-CH C4H1 Sensitizer (d) Sensitizer (e) Sensitization scrape) Above capsule liquid B5. Og, developer emulsion dispersion 10.0
g and 5.0 g of water were stirred and mixed, and one side of a transparent polyethylene terephthalate (PET) support with a thickness of 75 μm was subjected to corona discharge treatment, and then coated so that the solid content was log/nf, and dried. Then, the same protective layer solution A used in Example 1 was applied onto the heat-sensitive recording layer so that the solid content was 2.5 g/rrr.
It was dried in an oven at 0"C.

The facsimile machine used in Example 1 was used to perform thermal recording on the obtained thermosensitive recording material. The obtained black recorded image, fog and transparency before and after the forced deterioration test were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 A thermosensitive recording sheet was obtained in exactly the same manner as in Example 1, except that no aggravating agent was used, and the results of various measurements carried out in the same manner as in Example 1 are shown in Table 1.

Comparative Example 2 A heat-sensitive recording sheet was obtained in exactly the same manner as in Example 1, except that 2° was used as the sensitizer. Table 1 shows the results of various measurements carried out in exactly the same manner as in Example 1.

Furthermore, when the coupler/base emulsion was observed under a microscope,
Needle-shaped sensitizer precipitates were observed.

Comparative Example 3 A heat-sensitive recording sheet was obtained in exactly the same manner as in Example 3, except that no sensitizer was used. Table 1 shows the results of various measurements carried out in the same manner as in Example 3.

From the results shown in Table 1, the heat-sensitive recording material according to the present invention can be used in both cases, when a combination of a photodegradable diazo compound and a coupler is employed, and when a combination of an electron-donating dye precursor and a color developer is employed. It was also demonstrated that the sensitivity (image density) and shelf life (fogging) were improved.

Claims (1)

[Claims] 1) A heat-sensitive layer containing a substantially colorless color forming component A and a substantially colorless color forming component B that reacts with the color forming component A to form a color is provided on a support. In heat-sensitive recording materials,
At least one of the coloring components is microencapsulated, and at least one p-
A heat-sensitive recording material characterized by containing a hydroxybenzoic acid alkyl ester. 2) The heat-sensitive recording material according to claim 1, wherein the color-forming component A is a photodegradable diazo compound and the color-forming component B is a coupler. 3) The heat-sensitive recording material according to claim 1, wherein the color-forming component A is an electron-donating dye precursor and the color-forming component B is a color developer.