JPH1016410A - Heat decoloring substance and heat recording material and heat development photosensitive material using the substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat sensitivity and shelf stability by using a heat decoloring substance represented by the specified formula in a heat decoloring substance to be decomposed by heat and turned into colorless or light color. SOLUTION: A heat decoloring substance used suitably for a heat-sensitive recording material of high heat sensitivity and high image contrast and of good image shelf stability or a heat development photosensitive material having a halation preventing layer or a filter layer of high heat decoloring properties is represented by the formula LD. HA. In the formula, ID represents a colorless or light-color leuco dye, HA represents acid to be decomposed or evaporated by heat to lose its acidity, and LD. HA represents an LD coloring body colored by HA. As HA, carboxylic acid decarbonized by heat is used, and as LD, the leuco dye to be ring opened and colored by acid is used. As a leuco dye, diaryl phthalide fluoran and the like provided with various kinds of skeletons are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel heat-decolorable substance which is decomposed by heating to become colorless or light-colored, and to a heat-sensitive recording material or a photothermographic material using the same.

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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. Japanese Unexamined Patent Publication No. 3-189,189 discloses a color erasing type recording material in which these drawbacks are improved, in which a diaryl isobenzofuran is used as a colorant and a color is erased by utilizing the Diels-Alder reaction.
The system had the inherent problem that the colorant was very sensitive to light. On the other hand, U.S. Pat. Nos. 4,548,896 and 5,135,842 disclose a method of decolorizing a dye by a reaction between a polymethine dye and a nucleophile as applied to an antihalation layer of a photothermographic material.
No. 5,314,795 and U.S. Pat. No. 5,395,747.
And EP-A-605,285 A1, etc., describe a thermal decoloring composition in which a polymethine dye and an α-sulfonyl acetate salt which generates a carbanion by heating as a decoloring agent are combined. There is a problem that the agent can be used only for extremely limited applications because the agent itself is unstable to light or heat and the stability of the coloring composition is poor.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to firstly provide a heat-decolorable substance having high heat sensitivity and high storage stability, and secondly heat sensitivity and image contrast. Another object of the present invention is to provide a heat-developable photosensitive material having a high anti-halation layer or a filter layer having a high thermal decoloring property.

[0005]

The object of the present invention has been attained by the present invention of the following 1) to 5). 1) A thermal decolorable substance represented by the following general formula. In the formula, LD represents a colorless or pale-colored leuco dye;
Represents an acid which is decomposed or volatilized by heating to lose the acidity, and LD / HA represents an LD color-form formed by HA. 2) The heat-decolorable substance according to 1), wherein HA in the general formula is a carboxylic acid that decarboxylates by heating. 3) The heat-decolorable substance according to 1), wherein in the general formula, LD is a leuco dye that forms a color by ring opening with an acid. 4) A heat-sensitive recording material having a heat-sensitive recording layer containing the heat-decolorable substance described in 1), 2) or 3) on a support. 5) A photothermographic material having a layer containing the thermodecolorable substance according to 1), 2) or 3) on a support.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the above general formula, LD represents a colorless to pale leuco dye. For well-known leuco dyes, see Moriga and Yoshida, “Dyes and Chemicals,” p.
4); "New Edition Dye Handbook", p. 242 (Maruzen, 1970);
R. Garner "Reports on the Progress of Appl. Che
m. "56, 199 (1971);" Dyes and chemicals "1
9, p. 230 (Chemical Products Industry Association, 1974);
Recording and Photosensitive Materials ", 144 pages (JSPS, 198
See 5) for details. The leuco dye useful in the present invention is a compound that develops a color by reacting with an acidic developer and has been widely used in pressure-sensitive paper and heat-sensitive paper.
It is known that the color develops in almost any hue from purple to blue to green to black to near infrared. Also, structurally, diaryl phthalide type, fluoran type, bisindolyl phthalide type, aryl indolyl phthalide type, aryl indolyl azaphthalide type, acyl leukoaazine type, leuco auramine type, spiropyran type, Various skeletons such as rhodamine 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. The following are representative examples of leuco dyes useful in the present invention,
The present invention is not limited to them, and all those known in the literature and patents can be used in principle in the present invention.

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In the above general formula, HA represents an acid which decomposes or volatilizes upon heating to lose its 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. Although those which decarboxylate by heat, such as acetic acid and acetoacetic acid, are known, carboxylic acids which are decarboxylated by heat are particularly useful in the present invention. 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 polyhydroxybenzoic acid. Acids, aminobenzoic acids and the like. In the present invention, a carboxylic acid that decarboxylates at 50 ° C. or more is useful, and further, from the viewpoint of storage stability and heat sensitivity, from 80 to 2%.
Those which decarbonate at 00 ° C. are particularly desirable. Hereinafter, typical examples of the carboxylic acid which is useful for the present invention and which is decarboxylated by heating are shown, but the present invention is not limited thereto.

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

Next, a method for producing the thermo-decolorable substance of the present invention will be described. The thermo-decolorizable substance of the present invention can be prepared by reacting an LD component (leuco dye) and an HA component (acid) in an appropriate reaction solvent, or by mixing and dispersing the mixture of both components in a fine state to form a leuco dye. It can be obtained by coloring. At this time, a binder used for the thermosensitive recording material or the photothermographic material may be coexisted. The molar ratio between the leuco dye and the acid in the heat-decolorable substance of the present invention is 1: 1. However, when used in a thermosensitive recording material or a photothermographic material, an extra acid may be added according to the purpose. Is also good. At this time, the molar ratio of the leuco dye to the acid is preferably from 1: 1 to 1:10, and more preferably from 1: 1 to 1: 5. When high thermal sensitivity (high color erasing speed) is required, lower the ratio of acid, and when raw storability is important, increase the ratio of acid to provide properties according to the purpose. Can be. The thermal sensitivity and storage stability can be adjusted by the kind of the binder used in combination and other additives.

From the viewpoint of the raw storage stability of the heat-sensitive recording material or the photothermographic material, the binder has a glass transition temperature of 50.
It is desirable that the melting point of the additive be 100 ° C. or higher. As the binder, gelatin, casein, starches, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyacrylamide, a water-soluble binder such as ethylene-maleic anhydride copolymer, and polyvinyl butyral, triacetyl cellulose, methyl acrylate-butadiene copolymer, Any of the water-insoluble binders such as acrylonitrile-butadiene copolymer can be used.

The additives for adjusting the thermal sensitivity include:
Stearamide, N-methylol stearamide, ethylenebisstearamide, 2-benzyloxynaphthalene, phenyl 1-hydroxy-2-naphthoate, 1,2-diphenoxyethane, 4,4'-dimethoxydiphenyl ether, 4 Those usually used as sensitizers in thermal paper, such as -benzylbiphenyl, diphenyl carbonate, dibenzyl oxalate, and benzyl 4-hydroxybenzoate, are useful. In particular, in the present invention, the addition of an aprotic, highly polar compound is effective for improving the thermal sensitivity. The additive is used in an amount of 10 to 500% by weight, preferably 20 to 200% by weight, based on the heat-decolorable substance.

Examples of the additives for improving the storage stability of the heat-decolorable substance include hydrogen bonding compounds such as alcohols, amides, sulfonamides, ureas and urethanes. In addition, since the main factor of deterioration of storage stability is decomposition of decarboxylated carboxylic acid with time, it is effective to add a precursor that gradually releases decarboxylated carboxylic acid over time.

As the support used for 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 or an infrared or infrared 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 the semiconductor laser is usually 670 to 830 nm, and a dye having absorption in the near infrared region 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 thermo-decolorable substance of the present invention can be used for the purpose of preventing halation of a photothermographic material or imparting a filter effect. The heat-decolorable substance of the present invention has high storage stability, and easily becomes colorless or light-colored in the process of heat development of the photothermographic material. 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.

[0043]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 1.5 g of polyvinyl butyral, 2 g of leuco dye (1)
Then, 3.2 g of acid (1) was dissolved by heating in 20 ml of toluene. This colored liquid is applied to a thickness of 1 such that the coating amount is 2 g / m ^2.
It was applied on a 00 μm polyethylene terephthalate film and dried. Furthermore, a silicone liquid (Shin-Etsu Silicone FL-100, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied thereon at a thickness of 0.1 μm to prepare a colored transparent sheet. When the above-mentioned heat-sensitive recording material was image-recorded with a Fuji Thermal Imager, FTI-210, a clear negative image was obtained. The recording material was stored in advance at 50 ° C. for 3 days, and then image-recorded by a thermal imager in the same manner. 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 cases.

[0045]

[Table 1]

From Table 1, it can be seen that the heat-sensitive recording material of the present invention has high heat sensitivity and gives a negative image with high contrast by a normal thermal imager. Further, it can be seen that the heat-sensitive recording material of the present invention has excellent storage properties.

Example 2 The following compounds were dissolved in methyl ethyl ketone to prepare a colored composition solution, applied to a 100 μm-thick polyethylene terephthalate film, and dried to produce a colored transparent sheet. Polyvinyl butyral is manufactured by Monsanto Butva
r ^TM B76 was used. Sample-1 Polyvinyl butyral 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (1) 3 mmol / m ² IR dye-1 0.13 mg / m ² Sample-2 Polyvinyl butyral 0.85 g / m ² leuco Dye (3) 1 mmol / m ² acid (1) 5 mmol / m ² IR dye-1 0.13 mg / m ² Sample-3 polyvinyl butyral 0.85 g / m ² Leuco dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² IR dye-1 0.13 mg / m ² sample-4 polyvinyl butyral 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (1) 3 mmol / m ² IR dye-2 0.13 mg / m ² sample-5 polyvinyl butyral 0.85 g / m ² leuco dye (3) 1 mmol / m ² acid (10) 3 mmol / m ² IR dye-2 0.13 mg / m ² sample-6 polyvinyl butyral 0.85 g / m ² leuco dye (3) 1mmol / m ² acid (1) 3mmol / m ² IR dye -3 0. 3 mg / m ² sample -7 polyvinylbutyral 0.85g / m ² leuco dye (3) 1mmol / m ² acid (10) 3mmol / m ² IR dye -3 0.13 mg / m ² sample -8 polyvinylbutyral 0.85g / M ² leuco dye (55) 1 mmol / m ² acid (1) 3 mmol / m ² IR dye-3 0.13 mg / m ² sample-9 polyvinyl butyral 0.85 g / m ² leuco dye (55) 1 mmol / m ² Acid (10) 3 mmol / m ² IR dye-3 0.13 mg / m ² Sample-10 Polyvinyl butyral 0.85 g / m ² Leuco dye (33) 1 mmol / m ² Acid (1) 3 mmol / m ² IR dye-3 0.13 mg / m ² reference sample -1 nitrocellulose (viscosity 1000 seconds, manufactured by Daicel Industries, Ltd.) 0.85 g / m ² reference dye -1 0.35 g / m ² reference dye -2 0.55g / m ² IR dye -1 0.13 g / m ² reference sample -2 polyvinyl butyral 0.85 g / m ² Remark Dye -1 0.35 g / m ² Reference dye -2 0.55g / m ² IR dye -1 0.13 g / m ²

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<Exposure conditions for image formation> Spectra Di
ode Labs No. SDL-2430 (wavelength range: 800-8)
30 nm) to obtain an output of 800 mW.
An image writing laser was used. Using this laser, the beam diameter was 160 μm, and the laser scanning speed was 0.1 μm.
5m / sec (center of scanning), sample feed speed 15mm /
Exposure was performed on the above-mentioned sample so that an image of 22 mm × 9 mm was formed with the scanning pitch set to 8 lines / mm in seconds.
At this time, the laser energy density on the sample was 10 mJ /
It was mm ^2. The energy density was changed as shown in Table 2 by changing the laser scanning speed and the laser output. <Evaluation of Dye Residual Rate at Laser Scanning Center (Image Area)>
Minimum density (Dmin) at the center of laser scanning (image area)
Was determined by Macbeth blue light or green light density measurement, and the dye remaining ratio was evaluated from the ratio to the non-image area. Table 2 shows the obtained results.

[0051]

[Table 2]

Table 2 shows that in the present invention, the sample using the dye absorbing the wavelength of the laser beam is superior to the sample using the ablation by the laser beam.

Example 3 (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 a heat-treated polyethylene terephthalate support to prepare a sample. In addition, each drying was performed at 75 ° C. for 5 minutes.

(Back surface side coating) The following coloring composition was applied to the surface opposite to the surface on which the photosensitive layer was provided so as to have a predetermined coating amount, to give a back surface for preventing halation. Polyvinyl butyral 0.85 g / m ² (Butvar ^™ B76 manufactured by Monsant) Leuco dye (3) 1 mmol / m ² Acid (1) 3 mmol / m ² (coating on photosensitive layer side) Photosensitive layer: coated with a liquid having the following composition Coating was carried out on the opposite side of the back layer so that the 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 4 ml (0.05% methanol solution) 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 applied on the photosensitive layer to a wet thickness of 100 μm. 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 Decoloring Property of Dye Layer on Back Side) The photothermographic material prepared above was exposed at 80 ° C., 100 ° C., 120 ° C., 140
The time required for the dye layer on the back surface side to be decolored at each temperature was determined by using thermal development at ℃. 20 at 100 ° C
It was found that the color was erased in 10 seconds at 120 ° C. and 5 seconds at 140 ° C. At 80 ° C., 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 was capable of decoloring at about 100 ° C. or more even in thermal development using a heat drum.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Ito 210 Nakanakanuma, Minamiashigara-shi, Kanagawa Prefecture Fuji Photo Film Co., Ltd.

Claims (5)

[Claims] 1. A heat-decolorable substance represented by the following general formula. In the formula, LD represents a colorless or pale-colored leuco dye;
Represents an acid which is decomposed or volatilized by heating to lose the acidity, and LD / HA represents an LD color-form formed by HA. 2. The method according to claim 1, wherein HA in the general formula is a carboxylic acid which is decarboxylated by heating.
The heat-decolorable substance described. 3. The thermo-decolorizable substance according to claim 1, wherein in the general formula, LD is a leuco dye which forms a color by opening a ring with an acid. 4. A heat-sensitive recording material comprising a heat-sensitive recording layer containing the heat-decolorable substance according to claim 1, on a support. 5. A photothermographic material comprising, on a support, a layer containing the thermodecolorable substance according to claim 1, 2 or 3.