JPH10287055A - Thermal recording material or heat development photosensitive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material having satisfactory preservation stability of an image and high film quality or a heat development photosensitive material having an antihalation layer including high thermal color erasability and excellent preservation stability or filter layer. SOLUTION: This thermal recording material comprises a thermal recording layer containing acid precursor represented by a general formula (1) and thermal color erasable substance represented by a general formula (2), and the heat development photosensitive material comprises a layer containing the precursor represented by the formula (1) and the substance represented by the formula (2). The general formula (1); P-A1 , where P indicates a protecting group to be decomposed by heating or aging under acid or neutral condition, A indicates residue of acid HA decomposed or volatilized by heating to vanish its acidic. The general formula (2); LD.HA2 , where LD indicates colorless or light leuco dye, and HA2 indicate acid selected from the same range of definition as the HA1 .

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 or a heat-developable light-sensitive material having an improved preservability using an acid precursor and a heat-decolorable substance in combination.

[0002]

2. Description of the Related Art A thermosensitive recording material expresses an image area and a non-image area as a temperature difference distribution. The color transfer reaction and the sublimation transfer of a colorant, the color development reaction between two components by heat melting and capsule destruction, and the phase transition. Many methods have been devised, such as those using changes in optical characteristics and ablation by laser light, and have been put to practical use as output materials for printers, word processors, facsimile machines, etc. I have. However, the thermosensitive recording material in a narrow sense currently used is a so-called positive type recording material in which a white or transparent thermosensitive layer provided on a support such as paper or plastic develops a color by heating.

On the other hand, on the other hand, there has been almost no practical use of a so-called negative-type heat-sensitive recording material in which a colored heat-sensitive layer loses its color or changes to a light color by heating. There have been few proposals so far. For example, JP-A-59-229385 discloses a method of decolorizing a basic dye precursor formed with an acid with an ethyleneoxy derivative of a bisphenol, and JP-A-Hei. No. 235,692, these methods have problems that the thermal sensitivity is low and the storage stability of the color forming composition is poor. Japanese Patent Application Laid-Open No. 1-272,487 describes a decolorizable thermosensitive recording material in which the color forming composition and a strongly basic substance are separated by a barrier layer to improve storage stability. Heat sensitivity and image contrast are low, and the manufacturing process is complicated. Further, JP-A-3-189,189
No. 4,985,867, a decolorization type heat-sensitive recording material of a type in which diaryl isobenzofuran is used as a colorant and the color is erased by utilizing the Diels-Alder reaction is described, but this method has the essential feature that the colorant is extremely weak to light. Problems. On the other hand, US Pat. No. 4,5,559 discloses a method in which a dye is decolorized by a reaction between a polymethine dye and a nucleophile, which is applied to an antihalation layer of a photothermographic material.
48,896 and 5,135,842;
No. 5,182,436, and the like, furthermore, U.S. Pat.
No. 4,759, 5,395,747, EP 605,285 A1 and the like disclose a thermal decoloring composition comprising a polymethine dye and an α-sulfonyl acetate salt which generates a carbanion by heating as a decolorizing agent. However, in either method, the coloring agent itself is unstable to light or heat or the stability of the coloring composition is poor,
There is a problem that it can be used only for extremely limited applications. As a method for improving these problems, Japanese Patent Application No. Hei.
No. 167,416 describes a decolorizable thermosensitive recording material and a photothermographic material using a thermodecolorable substance.
In this method, the storage stability can be increased to some extent by increasing the ratio of the thermally decomposable acid to the leuco dye, but the amount of acid added is limited from the viewpoint of coatability and film quality, and further improvement is required. Was desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having high thermal sensitivity and high image contrast, good storage stability of an image and good film quality. Another object of the present invention is to provide a photothermographic material having a film quality, which has an antihalation layer or a filter layer having high heat decoloring property and good storage stability.

[0005]

The object of the present invention is to provide: 1) an acid precursor represented by the following general formula (1) and a thermal decoloring property represented by the following general formula (2) on a support. A heat-sensitive recording material having a heat-sensitive recording layer containing a substance, or 2) on a support, an acid precursor represented by the general formula (1) and a acid precursor represented by the general formula (2) This has been achieved by a photothermographic material characterized by having a layer containing a thermal decolorable substance. Formula (1) P-A _{1 In the} formula, P represents a protecting group which decomposes on heating or under aging under acidic or neutral conditions, and A ₁ is an acid HA ₁ which decomposes or volatilizes upon heating to eliminate the acidity. Represents a residue,
A ₁ represents an acid precursor in which the acidic group of HA ₁ is protected by P. In the general formula ₍₂₎ LD · HA 2 expression, LD represents a colorless or light-colored leuco dye, HA
₂ represents an acid selected from the same definition range as HA _1. LD
· HA ₂ represents the color body of LD was developed by HA _2.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the general formula (1), A ₁ represents a residue of the acid HA ₁ which decomposes or volatilizes by heating to lose the acidity. Acids having such properties include those in which volatile acids volatilize upon heating, such as trifluoroacetic acid and difluoroacetic acid, those in which acidic groups disappear by thermal decomposition, such as picric acid and tetrazoles, and those in which trichloroacetic acid and trichloroacetic acid are used. Examples include acetic acid and acetoacetic acid that decarboxylate with heat,
In the present invention, carboxylic acids which decarboxylate by heat are particularly useful. Examples of carboxylic acids that can be decarboxylated by heat include acetic acids substituted with an electron-withdrawing group, malonic acids, oxamidic acids, propiolic acids, β-halocinnamic acids, α, β-epoxycarboxylic acids, benzoic acids substituted with an electron-withdrawing group, and polyhydroxy. Benzoic acids, aminobenzoic acids and the like can be mentioned. In the present invention, a carboxylic acid that decarboxylates at 50 ° C. or higher is useful. Further, from the viewpoint of storage stability and heat sensitivity, 8
Those that decarboxylate at 0 to 200 ° C. are particularly preferred. Hereinafter, typical examples of the carboxylic acid (HA ₁ ) useful for the present invention, which is decarboxylated by heating, are shown, but the present invention is not limited thereto. The following examples also serve as examples of HA _{2 in} the general formula (2).

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In the general formula (1), P represents a protecting group for an acidic group which decomposes on heating or aging under acidic or neutral conditions. It is preferably a protecting group which gradually decomposes in the range of pH 1 to 7 and 25 ° C. to 80 ° C., and more preferably p
It is a protecting group that gradually decomposes in the range of H2 to 5, and 25 ° C to 60 ° C. Degradation rate is preferably close to a degradation rate of the HA _1. Such protecting groups for acidic groups are described in R. Taylor, "In Chemistry of Carboxilic acids and derivative.
s, (S. Patai Editor) ", Chapter 15, p. 859 (Wiley, New Y
ork, 1979); Protective Gr by Theodra W. Green
Various examples are described in "oupes in Organic Synthesis" and the like. For example, protective groups for carboxyl groups include t
-Butyl group, 2-haloethyl group, methoxymethyl group, benzyloxymethyl group, cinnamyl group, benzyl group,
1,1-diphenylethyl group, diphenylmethyl group, triphenylmethyl group, 9-anthrylmethyl group, alkyl group such as piperonyl group, t-butyldimethylsilyl group,
and silyl groups such as t-butyldiphenylsilyl group. It is preferably an alkyl group having a hydrogen atom at the β-position, more preferably a tertiary alkyl group having a hydrogen atom at the β-position, and a tertiary alkyl group having an aryl or vinyl group at the α-position and having a hydrogen atom at the β-position. It is a primary or tertiary alkyl group. Examples of the protecting group for the acidic alcoholic hydroxyl group such as phenols include ethers such as t-butyl group, methoxymethyl group, methylthiomethyl group and t-butyldimethylsilyl group, and esters such as acetate, benzoate and carbonate. Are preferred examples.

The acid precursor (P-A ₁ ) of the present invention is obtained by protecting the above-mentioned acidic group of HA ₁ with P. Representative examples are shown below, but the present invention is not limited to these.

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In the general formula (2), LD represents a colorless or pale leuco dye. For known leuco dyes, see Moriga and Yoshida, "Dyes and Chemicals", page 9, 84 (Chemical Products Industry Association, 1964); "New Edition Dye Handbook", page 242 (Maruzen, 1970); R. Garner, "Reports on the Progres"
s of Appl. Chem. ", 56, 199 (Maruzen, 197).
4); "Memory / Recording / Photosensitive Material", page 144 (Academic Publishing Center, 1985) and the like. The leuco dye useful in the present invention is a compound that forms a color by reacting with an acidic developer and has been widely used in pressure-sensitive paper and heat-sensitive paper, and thus far yellow-orange-red-violet-blue-green-black. To near infrared and almost all hues are known. Also, structurally, diaryl phthalide type, fluoran type, bisindolyl phthalide type, aryl indolyl phthalide type, aryl endyl phthalide type, acyl leucodine type, leuco auramine type, spiropyran type, rhodamine Various skeletons such as lactams, leukotriarylmethanes, diarylchromenes, and styryls are known. Among them, those particularly useful in the present invention are of the type in which the leuco dye is opened to form a color by the action of an acid.
Hereinafter, representative leuco dyes useful in the present invention will be exemplified, but the present invention is not limited thereto.
All those known in the literature, patents and the like can be used in principle in the present invention.

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[0050] HA ₂ in the general formula (2) has the same meaning as HA ₁ in the general formula (1), HA ₁ and HA ₂ may but be different even in the same, it is the same as preferable.

The thermal decolorizable substance represented by the general formula (2) is
It is formed by any combination of the aforementioned LD component (leuco dye) and HA ₂ component. The combination is illustrated below, but the present invention is not limited to this. LD · HA ₂ LD · HA ₂ (1) · (1) (33) · (1) (3) · (1) (33) · (9) (3) · (10) (33) · (9) (3) ・ (12) (34) ・ (10) (3) ・ (22) (38) ・ (1) (3) ・ (28) (47) ・ (10) (3) ・ (29) ( 53) ・ (10) (3) ・ (47) (55) ・ (1) (24) ・ (1) (55) ・ (10)

The heat-decolorable substance of the general formula (2) is an LD
Component (leuco dye) and HA ₂ component is reacted with (acid) in a suitable reaction solvent, a mixture of both in a solid state can be obtained by coloring the leuco dye is finely mixed and dispersed. At this time, a binder used for the thermosensitive recording material or the photothermographic material may be coexisted. The molar ratio of the leuco dye (P) to the acid (HA ₂ ) is 1: 1 to 1:10
And more preferably 1: 1 to 1: 5. When using leuco dyes with low coloring properties or when raw preservability is extremely important, increase the acid ratio to such an extent that coating properties and film quality are not deteriorated, and high heat sensitivity (high color erasing speed) is required Use a lower acid ratio.

When the acid precursor of the present invention is used for a heat-sensitive recording material or a photothermographic material, it is used together with the above-mentioned heat-decolorable substance in a binder. At this time, the molar ratio between the acid precursor and the acid in the heat-decolorable substance is 1: 1 to 1:
10 is preferable, and 1: 1 to 1: 5 is more preferable. When high thermal sensitivity (high color erasing rate) is required, the ratio of the acid precursor is reduced, and when high storage stability is required, the ratio of the acid precursor is increased to provide properties according to the purpose. be able to.

From the viewpoint of raw storage stability of the heat-sensitive recording material or the photothermographic material, the glass transition temperature of the binder is preferably 50 or less.
C. or higher is desirable. Examples of the binder include gelatin, casein, starches, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol, polyacrylamide, a water-soluble binder such as ethylene-maleic anhydride copolymer, and polyvinyl butyral, triacetyl cellulose, methyl acrylate-
Any water-insoluble binder such as butadiene copolymer and acrylonitrile-butadiene copolymer can be used.

Other additives can be used together with the acid precursor of the present invention in order to adjust the thermal sensitivity and raw storage stability of the heat-sensitive recording material or the photothermographic material. Additives used in combination to adjust the thermal sensitivity include stearamide, N-methylol stearamide, ethylenebisstearamide, 2-benzyloxynaphthalene,
Phenyl-hydroxy-2-naphthoate, 1,2-diphenoxyethane, 4,4′-dimethoxydiphenyl ether, 4-benzylbiphenyl, diphenyl carbonate, dibenzyl oxalate, benzyl 4-hydroxybenzoate, etc. Those used as sensitizers are useful. In particular, in the present invention, the addition of an aprotic, highly polar compound is effective for improving the thermal sensitivity.
The amount of the additive used is 10 to 500 with respect to the heat-decolorable substance.
%, Preferably 20 to 200% by weight.

Examples of additives that can be used in combination for adjusting the raw preservability include alcohols, amides, sulfonamides, ureas, urethanes, and other hydrogen bonding compounds.

As the support used in the heat-sensitive recording material or the photothermographic material of the present invention, high-quality paper, baryta paper,
Papers such as coated paper, cast coated paper, synthetic paper, etc., polymer films such as polyethylene, polypropylene, polyethylene terephthalate, polyethylene-2,6-naphthylene dicarboxylate, polyarylene, polyimide, polycarbonate, triacetyl cellulose, glass, metal Examples include foil and nonwoven fabric. The transmission type image, for example, OHP using the thermal recording material of the present invention
When it is used for a film for medical use, a medical X-ray film, a film for ultrasonic diagnosis, a film for plate making, or the like, a transparent support is used. For plate making films, the thermal expansion coefficient is small, the dimensional stability is good, and the P
A support having no absorption in the photosensitive area of the S plate is selected.

In the heat-sensitive recording material of the present invention, as a heating method as a means for forming an image, a method of contacting with a heated block or plate, a method of contacting with a heat roller or a heat drum, a halogen lamp, an infrared or infrared ray There are a method of irradiating an infrared lamp heater, a method of imagewise heating with a thermal head of a thermal printer, and a method of irradiating a laser beam. In order to form an image with less heat energy, the heat-sensitive recording material of the present invention can be heated to an appropriate temperature in advance.

When an image is formed by irradiating a laser beam, a dye that absorbs light having the wavelength of the laser beam must be present in order to convert the laser beam into heat energy. Excimer laser, argon laser, helium neon laser, semiconductor laser, glass (YAG) laser, carbon dioxide laser,
Although there is a dye laser and the like, a helium neon laser, a semiconductor laser and a glass laser are laser light sources useful in the present invention. Among them, a semiconductor laser is particularly useful because the device is small and inexpensive. The oscillation wavelength of a semiconductor laser is usually 670 to 830 nm, and a dye having absorption in the near infrared is used. As the near-infrared absorbing dye, a cyanine dye, a squarylium dye, a merocyanine dye, an oxonol dye, a phthalocyanine dye, and the like are used.

The acid precursor of the present invention is added for improving storage stability when the heat-decolorable substance represented by the general formula (2) is used for the purpose of preventing halation of a photothermographic material or imparting a filter effect. It can be used as an agent. The photothermographic material to which the present invention can be applied is a black-and-white or color photothermographic material using an organic silver salt as a silver source such as so-called dry silver, or a black-and-white photothermographic material using a silver salt diffusion transfer method under heating. And any heat-developed color diffusion transfer type photosensitive material utilizing dye diffusion transfer.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

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【Example】

Example 1 The following compounds were dissolved in methyl ethyl ketone to prepare a coloring composition solution, applied to a 100 μm-thick polyethylene terephthalate film, and dried to produce a transparent coloring sheet. Polyvinyl butyral is manufactured by Monsanto Butva
r ^TM B76 was used. Samples -1 polyvinyl butyral 0.85 g / m ² leuco dye (3) 1mmol / m ² acid (10) 3mmol / m ² acid precursor (3) 3mmol / m ² Sample -2 polyvinyl butyral 0.85 g / m ² Leuco Dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² acid precursor (3) 9 mmol / m ² Sample-3 polyvinyl butyral 0.85 g / m ² Leuco dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² acid precursor (13) 3 mmol / m ² sample-4 polyvinyl butyral 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² acid precursor (14) 3 mmol / m ² sample-5 polyvinyl butyral 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (4) 3 mmol / m ² acid precursor (4) 3 mmol / m ² sample-6 polyvinyl butyral 0.85 g / m ² Leuco dye (3) 1 mmol / m ² acid (1) 3 mmol / m ² acid precursor (1) 3 mmol / m ² Sample-7 polyvinyl butyrate Lal 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (22) 3 mmol / m ² acid precursor (6) 3 mmol / m ² sample-8 Polyvinyl butyral 0.85 g / m ² leuco dye (55) 1 mmol / m ² acid (31) 3 mmol / m ² acid precursor (9) 3 mmol / m ² Sample-9 polyvinyl butyral 0.85 g / m ² leuco dye (55) 1 mmol / m ² acid (10) 3 mmol / m ² Acid precursor (3) 3 mmol / m ² sample-10 Polyvinyl butyral 0.85 g / m ² Leuco dye (3) 1 mmol / m ² acid (31) 3 mmol / m ² Acid precursor (9) 3 mmol / m ² Reference sample -1 Polyvinyl butyral 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² Reference sample-2 polyvinyl butyral 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid ( 1) 3 mmol / m ^{2 The} above thermal recording material was applied to Fuji Thermal Imager, FTI
When an image was recorded by -210, clear negative images were obtained in all cases. Further, the recording material is previously prepared at 60 ° C. for 7 hours.
After storage for days, images were recorded in the same manner using a thermal imager. Table 1 shows the results of measuring the minimum density and the maximum density of the image portion and the non-image portion for both.

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Table 1 shows that the heat-sensitive recording material of the present invention has excellent storage stability. Further, the coated surface of the heat-sensitive recording material of the present invention was all good, but in Reference Sample 1, when the amount of acid was increased to 6 mmol / m ² , the acid precipitated and a transparent sheet could not be produced.

Example 2 (Preparation of silver halide particles A) 7.5 g of inert gelatin and 10 mg of potassium bromide were dissolved in 900 ml of water, the temperature was adjusted to 35 ° C. and the pH was adjusted to 3.0, and 74 g of silver nitrate was added. The aqueous solution containing 370 ml of the aqueous solution containing potassium bromide and potassium iodide in a molar ratio of (96/4) was added over 10 minutes by the control double jet method while maintaining the pAg at 7.7. At this time, 1 × 10 ⁻⁵ mol / Ag mol of hexacyanoferrate (III) and hexachloroiridium (III) complex salt were added simultaneously with the start of silver nitrate addition. Then, 4-
0.3 g of hydroxy-6-methyl-1,3,3a, 7-tetrazaindene was added, the pH was adjusted to 5 with sodium hydroxide, the average particle size was 0.06 μm, and the variation coefficient of the projected diameter area was 8 %, And a [100] face ratio of 87% were obtained. This emulsion was coagulated and precipitated using a gelatin coagulant and desalted.
1 g was added to adjust the pH to 5.9 and the pAg to 7.5.

(Preparation of Organic Fatty Acid Silver Emulsion A) 300 ml of water
Put 10.6 g of behenic acid in it, dissolve by heating at 90 ° C,
With sufficient stirring, 31.1 ml of 1N sodium hydroxide
Was added and left as it was for 1 hour. afterwards,
After cooling to 30 ° C., 7.0 ml of 1N phosphoric acid was added and, with sufficient stirring, 0.13 g of N-bromosuccinimide was added.
Was added. Thereafter, silver halide grains A prepared in advance were added while stirring at 40 ° C. so that the silver amount was 10 mol% with respect to behenic acid.
Further, 25 ml of a 1N aqueous solution of silver nitrate was continuously added over 2 minutes, and the mixture was left as it was for 1 hour with stirring. While stirring this aqueous mixture, 37 g of a 1.2 wt% solution of polyvinyl acetate in n-butyl acetate was gradually added to form a floc of the dispersion, water was removed, and water was washed twice and water was removed. After performing, polyvinyl butyral (average molecular weight 3
2,000) of a 1: 2 mixed solution of butyl acetate and isopropyl alcohol (2.5 wt%) was added with stirring, and then the mixture of gel-like silver behenate and silver halide thus obtained was mixed with polyvinyl butyral (average molecular weight). 40
00) 12.5 g and isopropyl alcohol 57 g were added and dispersed to obtain an organic fatty acid silver emulsion A.

The following layers were sequentially coated on the heat-treated polyethylene terephthalate support to prepare Samples 1 and 2 in which only the back surface was changed. In addition, each drying is 75
C. for 5 minutes.

(Back surface side coating) The following coloring composition was applied to the opposite surface of the surface on which the photosensitive layer was to be provided so as to have a predetermined coating amount, thereby forming a back surface for preventing halation. Sample-1 (Invention) Polyvinyl butyral (Butvar ^™ B76 manufactured by Monsant) 0.85 g / m ² Leuco dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² Acid precursor (3) 3 mmol / m ² Sample-2 (reference sample) Polyvinyl butyral (Butvar ^™ B76 manufactured by Monsant) 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² (coating on photosensitive layer side) Photosensitive layer: Was applied to the opposite surface of the back layer so that the coated silver amount was 1.5 g / m ² to form a photosensitive layer. Organic fatty acid silver salt emulsion A 73 g Sensitizing dye D-1 (0.05% methanol solution) 4 ml Phthalazine (5% methanol solution) 2.5 ml Hydrazine derivative H-1 (1% methanol solution) 2 ml Antifoggant-1 ( 2.5 ml Developer-1 (10% acetone solution) 13 ml 2-mercapto-5-methylbenzotriazole (0.5% DMF solution) 5 ml CaBr ₂ (0.3% methanol solution) 6 .5ml

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Surface protective layer: A solution having the following composition was wetted to a thickness of 1
It was applied on the photosensitive layer so as to be 00 microns. Acetone 175 ml Methanol 15 ml Cellulose acetate 8.0 g 4-methylphthalic acid 0.72 g Tetrachlorophthalic acid 0.22 g Tetrachlorophthalic anhydride 0.5 g

(Evaluation of Storage Stability and Decoloring Property of Dye Layer on Back Side) For each of Samples 1 and 2 differing only in the back side coating composition prepared above, at 60 ° C. under light shielding conditions.
The residual ratio of the dye of the sample aged for 7 days was determined to be 90.8% and 37.5%, respectively. Thus, it was found that the sample 1 of the present invention had significantly improved storability compared to the reference sample 1. Next, the sample 1 of the present invention was exposed at 80 ° C. and 100 ° C. without exposure.
Thermal development was performed at 120 ° C., 120 ° C., and 140 ° C., and the time required for decoloring the dye layer on the back surface side at each temperature was determined. 50 seconds at 100 ° C, 10 seconds at 120 ° C, 14
At 0 ° C., it was found that the color was erased in 10 seconds. Note that 80
At 300C, the color was not completely erased even after the treatment for 300 seconds. As described above, it was found that the system of the present invention can erase the color at about 100 ° C. or more even in thermal development using a heat drum.

Claims (4)

[Claims] 1. A heat-sensitive recording layer containing an acid precursor represented by the following general formula (1) and a thermo-decolorable substance represented by the following general formula (2) on a support. Thermosensitive recording material. Formula (1) P-A _{1 In the} formula, P represents a protecting group which decomposes on heating or under aging under acidic or neutral conditions, and A ₁ is an acid HA ₁ which decomposes or volatilizes upon heating to eliminate the acidity. Represents a residue,
A ₁ represents an acid precursor in which the acidic group of HA ₁ is protected by P. In the general formula ₍₂₎ LD · HA 2 expression, LD represents a colorless or light-colored leuco dye, HA
₂ represents an acid selected from the same definition range as HA _1. LD
· HA ₂ represents the color body of LD was developed by HA _2. 2. A support comprising a layer containing an acid precursor represented by the general formula (1) and a thermo-decolorable substance represented by the general formula (2) on a support. Photothermographic material. 3. The heat-sensitive recording material according to claim 1, wherein HA ₁ is a carboxylic acid which is decarboxylated by heating. 4. A method according to claim 1, wherein P in the general formula (1) is a protecting group for protecting the hydroxyl group of the carboxylic acid by an ester bond, and the protecting group is an alkyl group having a hydrogen atom at the β-position. The heat-sensitive recording material according to claim 1 or the photothermographic material according to claim 2.