JPH082112A - Thermal recording material - Google Patents

Abstract

PURPOSE:To stabilize a background color by using 1,3-diphenylurea as a coupler without together using a phenol compd. CONSTITUTION:A thermal recording material has a thermal color forming layer containing a colorless or light-colored dye precursor and a coupler reacting with the dye precursor at the time of heating to develop a color. The coupler is 1,3-diphenylurea represented by formula and not used together with a phenol compd. The thermal color forming layer contains no sensitizer but contains a light absorber absorbing light to convert the same to heat. After recording is applied to the thermal recording material, heat is applied thereto to erase a recording image to again perform thermal recording. Or, after recording is applied to the thermal recording material, an alcoholic solvent is brought into contact with the recorded part to erase a recording image to again perform thermal recording.

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 having excellent stability of a background color portion and a heat-sensitive recording material having a vivid color tone and reversible recording property.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording material is prepared by grinding and dispersing a colorless or light-colored electron-donating colorless dye and a color developing agent such as a phenolic compound into fine particles, respectively, and then mixing the two with a binder, A coating solution obtained by adding a filler, a sensitivity improver, a lubricant, and other auxiliaries is applied to a support such as paper, synthetic paper, film and plastic.
A visible record is obtained by developing a color by an instantaneous chemical reaction by heating with a Maruhead, a hot stamp, a laser beam or the like.

The thermosensitive recording medium is applied to a wide range of fields such as a measuring recorder, a computer terminal printer, a facsimile, an automatic ticket vending machine and a bar code label. However, recently, the diversification of recording devices for thermal recording media,
Higher performance has been advanced, and therefore, the quality required for the thermal recording material has also become higher. For example, from the viewpoint of speeding up recording, there is a demand for a heat-sensitive recording material that can obtain a clear color image with high density even with smaller heat energy. On the other hand, from the viewpoint of storage stability of the recording medium, there is a demand for a thermal recording medium excellent in light resistance, oil resistance, water resistance, solvent resistance and the like.

On the other hand, as plain paper recording systems such as electrophotographic systems and ink jet systems have become widespread, thermal recording systems are often compared with these plain paper recording systems. For example, the stability of the recording portion (image) of the thermal recording material or the stability of the unrecorded portion (background color portion) of the thermal recording material before and after recording (hereinafter referred to as background color stability) is recorded on plain paper. It is required to approach the same quality as the system. In particular, thermal recording materials are required to have background color stability against heat (hereinafter referred to as background color heat resistance) and background color stability against solvents. In other words, the recording medium is, so to speak, “heat-sensitive” only when recording,
It is desired to be "insensitive" except when recording.

Regarding the background color stability of the thermal recording material, for example,
Japanese Patent Laid-Open No. 4-353490 discloses a thermosensitive recording medium in which the whiteness of the background color portion is stable even under high temperature conditions of about 90 ° C. This heat-sensitive recording material is characterized by containing a 4-hydroxydiphenylsulfone compound and a metal salt of phosphate.

Further, the rapid increase in the amount of recording materials consumed with the construction of various networks and the widespread use of facsimiles and copying machines has caused social problems such as the problem of dust disposal. As one idea for dealing with this problem, a recording medium having a property that recording and erasing can be repeatedly performed, that is, reversible recording property has been attracting attention.

Regarding the recording material having reversible recording property, it is detailed in the review article of Paper and Paper Co., Ltd. 47 11 (1993) p1309-1322, for example, JP-A-3-230993 and JP-A-4-366682. Discloses a recording material that utilizes the reversible change of a recording material between a transparent state and a cloudy state depending on a given temperature, and a recording material that utilizes the reversibility of a thermochromic material and a reversible leuco dye. A recording body and the like using a change in color tone have been proposed.

[0008]

The background color stability of the thermosensitive recording medium disclosed in Japanese Patent Laid-Open No. 4-353490 is 95% in a dryer.
When processed at 5 ℃ for 5 hours, the Macbeth density of the background color is about 0.11 and shows a considerable stability, but it is still insufficient in terms of the stability of the background color at a temperature higher than that, for example, 120 ℃. there were.

Regarding a reversible recording material, a recording material utilizing the reversible change of the recording material between a transparent state and a cloudy state (in other words, a recording material utilizing a change in transparency of the recording material) is (1) Poor image clarity,
(2) There were drawbacks such as slow white turbidity (erasing) speed and (3) temperature control required for erasing. In addition, since this white turbid recording medium provides contrast between transparent and opaque, there is no problem when it is used as a transparent recording medium such as OHP.
In the case of being used as an opaque recording material such as a word processor paper, it is necessary to provide a colored layer below a layer that reversibly changes to a transparent / white turbid state (reversible change layer). Therefore, the reversible change layer is preferably a thin layer in order to provide contrast, that is, in order to bring out the color of the colored layer (background color) clearly, while a thick layer is preferable in order to make it appear white. Thus, it is necessary to strictly control the thickness of the coating layer.

In a reversible recording medium using a thermochromic material, most of the thermochromic material is
There is a problem that the memory property is poor and continuous heat supply is required to maintain the color-developed state.

On the other hand, reversible recording materials using a leuco dye as a color-forming source are disclosed in JP-A-60-193691 and JP-A-60.
-255482, JP-A-60-257289, etc. The recording materials of these publications are recording materials using a specific fluoran dye as a color former and phloroglucinol or gallic acid as a color developer. However, this recording material has a problem in practical use because the erasing operation is performed with water or steam. In addition, JP-A-2-188293 and JP-A-2-188293
2-188294 discloses a material having a simple layer structure and having both a color-developing (color-developing) which gives a reversible color change to a leuco dye only by controlling thermal energy (color development) and a color-reducing action (a color-developing and color-reducing agent). ) Is disclosed. However, this color-developing / reducing agent has a problem that the color density is low because the decoloring action already contributes in the color-developing process. Also recently, Japan Hard
In copy '93, Yokota et al. published a reversible recording medium using an amidophenol derivative having a long-chain alkyl. However, this recording medium also has a temperature control during erasing.
However, there was a drawback such as the need to gradually reduce the temperature.

Therefore, the present invention provides a heat-sensitive recording material having excellent ground color stability against heat and solvent, and recording-
An object of the present invention is to provide a heat-sensitive recording material having reversible recording property that can be erased and re-recorded.

[0013]

[Means for Solving the Problems] The above problems were solved by a thermosensitive recording medium using 1,3-diphenylurea as a developer.

Patents using urea compounds in heat-sensitive recording materials are disclosed in JP-A-58-211496, JP-A-59-184694, JP-A-61-211085 and the like. The urea compound used in these publications is a urea compound (1-phenylurea derivative) in which only one amino group portion of urea is substituted, and with this, heat resistance of sufficient background color or reversible recording property is obtained. Couldn't get In Japanese Patent Application Laid-Open No. 58-211496, 1,3-diphenylurea is mentioned as an example, but in this case, 1,3-diphenylurea is a compound which has been conventionally known such as bisphenol A. In this combination, satisfactory heat resistance against background color or reversible recording property could not be obtained. Further, JP-A-57-87993, JP-A-58-82787, and JP-A-59-6.
Japanese Patent No. 7083 also discloses a thermosensitive recording medium in which a urea compound and a phenol compound are used in combination. In these publications, the urea compound is used as a melting point adjusting agent for the phenol compound only because it has a limited number of carbon atoms. However, as long as it is used in combination with a phenolic compound, sufficient background color heat resistance or reversible recording property could not be obtained.

Further, a heat-sensitive recording material using a bisurea compound is disclosed in JP-A Nos. 5-1317152 and 5-147357. This bisurea compound has a structure having a sulfonyl group adjacent to the urea group (Ar—SO ₂
It is characterized by having two -NH- (C = O) -NH-). However, this bisurea compound also has a problem in heat resistance of the background color, and no reversible recording property was observed.

The present inventors have found that certain specific urea compounds,
That is, by using 1,3-diphenylurea alone as a color developer, a thermal recording material having excellent background color heat resistance can be obtained.
Alternatively, they have found that a heat-sensitive recording material having reversible recording properties can be obtained, and completed the present invention.

That is, the present invention provides a thermosensitive recording material having a thermosensitive coloring layer containing a colorless or light-colored dye precursor and a developer which reacts when heated to develop the dye precursor. Is a 1,3-diphenylurea represented by the following general formula (1), which is not used in combination with a phenol compound.

[0018]

Embedded image

In the heat-sensitive recording material of the present invention, the phenol compound conventionally known as a color developer is not used in combination with 1,3-diphenylurea. Such a phenol compound has a strong color-developing function, and when the phenol compound is used, the performance of the heat-sensitive recording material (recordability, heat resistance, solvent resistance, etc.) is mainly determined by the phenol compound. Depends on the compound. Therefore, the heat-sensitive recording material using the phenol compound in combination cannot obtain sufficient background color stability or reversible recording property. As the phenol compound, bisphenol A, bisphenol S, 4-hydroxy-4'-iso-propoxydiphenyl sulfone, 4-hydroxy-4'-n-butyroxydiphenyl sulfone, benzyl 4-hydroxybenzoate, etc. Is an unfavorable compound.

In the heat-sensitive recording material of the present invention, in particular, in order to obtain a heat-sensitive recording material having excellent background color heat resistance, it is generally preferable not to use a sensitizer. Since the sensitizer generally has a function of melting the dye precursor and the color developer at a temperature equal to or higher than its melting point to develop a color, if the sensitizer is used, the heat resistance of the thermal recording material is This is because it mainly depends on the melting point of the agent. As the sensitizer, 2-di (3-methylphenoxy) ethane, p-benzylbiphenyl, β-
Benzyloxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, diphenyl carbonate, ditolyl carbonate, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, 1,2-bis (m-tolyloxy) ethane, 1,5-bis (p-methoxyphenoxy) -3
-Oxapentane, dibenzyl oxalate, di (p-methylbenzyl) oxalate, di (p-chlorobenzyl oxalate) and the like.

That is, the present invention provides a thermosensitive recording material having a thermosensitive coloring layer containing a colorless or light-colored dye precursor and a developer which reacts when heated to develop the dye precursor. Is 1,3-diphenylurea (1),
Further, the present invention relates to a thermosensitive recording material having excellent heat resistance in an unrecorded portion (ground color portion), characterized in that the thermosensitive coloring layer does not contain a sensitizer.

The heat-sensitive recording material of the present invention, which has excellent heat resistance, has very good ground color stability against heat and solvent. That is, even if this recording medium is placed in a high temperature environment of 120 ° C or higher, the recording surface of the thermal recording medium (the surface on which the thermosensitive coloring layer is provided)
The ground color of is substantially unchanged (does not develop color). However, when the high energy of the thermal head, which is usually 200 ° C. to 300 ° C., is instantaneously applied to this recording medium, the recording medium develops a dark color. Regarding the heat-sensitive recording materials known from the past, in terms of heat resistance against background color, on the other hand, even if a heat block of 120 ° C. or more is applied to the surface of the heat-sensitive recording layer, no color is developed, but on the other hand, It was unthinkable that a thermal head could record practically sufficient density. Moreover, the material which can do such a thing was not known at all.

Since the heat-sensitive recording material of the present invention has high heat resistance, for example, (a) a heat-lamination in which after the heat-sensitive recording of the heat-sensitive recording material, the recording surface of the heat-sensitive recording material is heat-bonded with a plastic film or the like. (B) As a transfer sheet for electrophotography, toner is attached to the surface of the thermosensitive recording layer of the thermosensitive recording medium to thermally fix it, or (c) Toner is recorded on the recording surface of the thermosensitive recording medium. It is also possible to attach and heat fix.

Further, the thermosensitive recording medium of the present invention has an advantage that the manufacturing process is very easy to control. That is, conventionally, in the production of a thermosensitive recording medium, the drying step after coating the thermosensitive coloring layer requires very strict temperature control so that the background coloring of the coated surface does not occur, and therefore, there is a limit to high-speed coating. there were. However, the thermosensitive recording material of the present invention does not cause coloration of the ground color portion even when hot air of 120 ° C. is applied, so high temperature drying in the drying step is possible, and the control range of the drying temperature can be greatly expanded. is there. Therefore, it is possible to expect a dramatic improvement in productivity.

Further, the thermosensitive recording medium of the present invention hardly loses the recording portion or changes the background color portion even when it is brought into contact with a solvent other than the alcohol type, and is stable to the solvent. Is also high. Therefore, it is also possible to write with an oil-based ink on the surface of the heat-sensitive recording layer of the heat-sensitive recording material.

The reversible recording property is another important property of the thermosensitive recording medium using the 1,3-diphenylurea of the present invention. That is, in the heat-sensitive recording material of the present invention, after heat-sensitive recording on the heat-sensitive recording material, a certain amount of heat is applied to the heat-sensitive recording material by a heat roll, a thermal head, a hot stamp, a dryer, a warm air dryer or the like. Alternatively, the recorded image can be erased by irradiating light with a laser, a halogen lamp, a strobe or the like, or by bringing it into contact with an alcohol solvent such as methanol or ethanol. Then, by applying a thermal head or a laser to the erasing surface of the thermosensitive recording medium from which the recording portion has been erased, re-recording can be performed.

In the heat-sensitive recording material of the present invention, a sensitizer may be used when reversible recording property is important. This is because the sensitizer may have a function of enhancing decoloring property. Examples of the sensitizer include 2-di (3-methylphenoxy) ethane, p-benzylbiphenyl, β-benzyloxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, dibenzyl terephthalate, p- Benzyl benzyloxybenzoate, diphenyl carbonate, ditolyl carbonate, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, 1,2-bis (m-tolyloxy) ethane, 1,5- Examples thereof include bis (p-methoxyphenoxy) -3-oxapentane, dibenzyl oxalate, di (p-methylbenzyl) oxalate, and di (p-chlorobenzyl oxalate).

The heat-sensitive recording material of the present invention is useful as a reversible recording material (rewrite recording material or rewritable recording material). Further, in recent years, a liquid crystal screen (liquid crystal display) or the like has been used as an information display body (medium for temporarily displaying information).
Utilizing the reversible recording property, it can be considered to be used as a very simple information display body. However, in the latter case, it is necessary to record and erase at almost the same speed.

There are two methods for erasing the recording portion of the thermosensitive recording medium of the present invention. One method is a method of erasing a recorded image by heat using a heat roll, a thermal head, a hot stamp, a carbon dioxide gas laser, a semiconductor laser, sunlight, a halogen lamp, a dryer, a hot air dryer, or the like. . The temperature condition at the time of erasing depends on the temperature range that can be supplied by each heat source, and therefore cannot be necessarily specified. High temperature conditions (100 ° C to 250 ° C) require a short time, and low temperature conditions (less than 100 ° C) require a longer time. For example, when the recording portion of the heat-sensitive recording material of the present invention is erased by a heat roll, it is appropriate that the decoloring temperature is 100 ° C to 200 ° C and the feeding speed is 8 mm to 45 mm / sec. Another method is methanol, ethanol, n-propyl alcohol.
This is a method of erasing the recorded portion by bringing into contact with an alcohol solvent such as vinyl alcohol or iso-propyl alcohol.

The 1,3-diphenylurea used in the present invention (a) itself has a high color developing ability as a color developing agent in a thermosensitive recording medium. (b) A thermal recording material prepared by coating this support together with an electron-donating dye precursor on a support,
Excellent ground color heat resistance (120 ° C or higher). (c) A thermosensitive recording medium using this compound has a function of reversible recording property (coloring / decoloring property). It has characteristics such as. Thus, 1,3-diphenylurea is an interesting material that has both a color developing property and a color erasing property while being a single color developing agent.

A general method for producing the thermosensitive recording medium of the present invention is to disperse (a) a dye precursor and (b) 1,3-diphenylurea together with a binder having a dispersing function, According to this method, an auxiliary agent such as a filler or a lubricant is added to prepare a coating solution, which is applied on a support by a usual method and dried.

In the heat-sensitive recording material of the present invention, 1,3-diphenylurea may be used alone when background heat resistance is required,
Japanese Patent Application No. 5-231105, Japanese Patent Application No. 5-311502, Japanese Patent Application
It may be used in combination with the biurea compound described in the specification of 5-315023 or Japanese Patent Application No. 5-317211, the monourea compound described in the specification of Japanese Patent Application No. 5-250328, or the specification of Japanese Patent Application No. 5-250329. On the other hand, when reversible recording is required, Japanese Patent Application No. 5-
231105, Japanese Patent Application No. 5-311502, Japanese Patent Application No. 5-315023
Description, or Japanese Patent Application No. 5-317211, Japanese Patent Application No. 5-2503
Among the urea compounds described in 28 specification or Japanese Patent Application No. 5-250329 specification, a urea compound having reversible recording property can be used in combination.

As the dye precursor used in the heat-sensitive recording material of the present invention, those known in the field of heat-sensitive recording can be used, and although not particularly limited, triphenylmethane leuco dyes, Fluoran-based leuco dyes and fluorene-based leuco dyes are preferred. Hereinafter, typical dye precursors will be exemplified.

3,3-bis (4'-dimethylaminophenyl)
-6-Dimethylaminophthalide (also known as crystal violet lactone (CVL)) 3,3-bis (4'-dimethylaminophenyl) -6-pyrrolidylphthalide 3,3-bis (4'-dimethylamino) Phenyl) phthalide (also known as malachite green lactone (MGL)) tris [4- (dimethylamino) phenyl] methane (also known as leuco crystal violet (LCV)) 3-dimethylamino-6-methyl-7- (m -Trifluoromethylanilino) fluorane 3-diethylamino-6-methyl-fluorane 3-diethylamino-7-methyl-fluorane 3-diethylamino-7-chloro-fluorane 3-diethylamino-6-methyl-7-chlorofluorane 3- Diethylamino-6-methyl-7-anilinofluorane 3-diethylamino-6-methyl-7-p-methylanilinofluorane 3-diethylamino-6-methyl-7- ( o, p-Dimethylanilino) fluorane 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane 3-diethylamino-6-methyl-7- (o-chloroanilino) fluorane 3-diethylamino-6 -Methyl-7- (p-chloroanilino) fluorane 3-diethylamino-6-methyl-7- (o-fluoroloanilino) fluorane 3-diethylamino-6-methyl-7- (pn-butylanilino)
Fluorane 3-diethylamino-6-methyl-7-n-octylaminofluorane 3-diethylamino-6-chloro-7-anilinofluorane 3-diethylamino-6-ethoxyethyl-7-anilinofluorane 3-diethylamino- Benzo [a] fluorane 3-diethylamino-benzo [c] fluorane 3-diethylamino-6-methyl-7-benzylaminofluorane 3-diethylamino-6-methyl-7-dibenzylaminofluorane 3-diethylamino-7-di (P-Methylbenzyl) aminofluorane 3-diethylamino-6-methyl-7-diphenylmethylaminofluorane 3-diethylamino-7-dinaphthylmethylaminofluorane 10-diethylamino-4-dimethylaminobenzo [a] fluorane 3 -Dibutylamino-6-methyl-fluorane 3-dibutylamino-6-methyl-7-chlorofluorane 3-dibutylamino-6- Methyl-7-anilinofluorane 3-dibutylamino-6-methyl-7-p-methylanilinofluorane 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluorane 3-dibutyl Amino-6-methyl-7- (m-trifluoromethylanilino) fluorane 3-dibutylamino-6-methyl-7- (o-chloroanilino) fluorane 3-dibutylamino-6-methyl-7- (p-chloroanilino ) Fluoran 3-dibuethylamino-6-methyl-7- (o-fluoroloanilino) fluorane 3-dibuethylamino-6-methyl-7- (pn-butylanilino) fluoran 3-dibutylamino-6-methyl- 7-n-octylaminofluorane 3-dibutylamino-6-chloro-7-anilinofluorane 3-dibutylamino-6-ethoxyethyl-7-anilinofluorane 3-din-pentylamino-6-methyl -7- Anilinofluorane 3-di n-pentylamino-6-methyl-7- (o, p-di Methylanilino) fluorane 3-di n-pentylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane 3-di n-pentylamino-6-methyl-7- (o-chloroanilino) fluorane 3-di n-Pentylamino-6-methyl-7- (p-chloroanilino) fluorane 3-di n-pentylamino-6-methyl-7- (o-fluoroloanilino) fluorane 3-pyrrolidino-6-methyl-7- Anilinofluorane 3-piperidino-6-methyl-7-anilinofluorane 3- (N-methyl-Nn-propylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-Nn- Propylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-iso-propylamino) -6-methyl-7-
Anilinofluorane 3- (N-ethyl-Nn-butylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-iso-butylamino) -6-methyl-7-anilino Fluoran 3- (N-ethyl-Nn-hexylamino) -6-methyl-7-p-
Methylanilinofluorane 3- (N-ethyl-Nn-hexylamino) -6-methyl-7- (o,
p-Dimethylanilino) fluorane 3- (N-ethyl-Nn-hexylamino) -6-methyl-7- (m-
Trifluoromethylanilino) fluorane 3- (N-ethyl-Nn-hexylamino) -6-methyl-7- (o-
Chloroanilino) fluorane 3- (N-ethyl-N-iso-amylamino) -6-methyl-7-anilinofluorane 3- (N-ethyl-N-iso-amylamino) -6-chloro-7-anilinoflu Oran 3- (N-ethyl-N-3-methylbutylamino) -6-methyl-7
-Anilinofluoran 3- (N-ethyl-Np-toluidino) -6-methyl-7-anilinofluoran 3- (N-ethyl-Np-toluidino) -6-methyl-7- (p-methylanilino) Fluoran 3- (N-ethyl-Np-toluidino) -6-methyl-7- (o, p-dimethylanilino) fluoran 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-
Methyl-7-anilinofluorane 3- (N-cyclohexyl-N-methylamino) -6-methyl-7
-Anilinofluorane 3- (N-cyclohexyl-N-methylamino) -7-anilinofluorane 3- (N-ethyl-N-3-methoxypropylamino) -6-methyl-7-anilinofluorane 3- (N-Ethyl-N-3-ethoxypropylamino) -6-methyl-7-anilinofluorane 2- (4-oxahexyl) -3-dimethylamino-6-methyl
-7- Anilinofluorane 2- (4-oxahexyl) -3-diethylamino-6-methyl
-7- Anilinofluorane 2- (4-oxahexyl) -3-dipropylamino-6-methyl-7-anilinofluorane 3- (4``-aminostilbrudil-4'-amino)- 7,8-Benzofuran 3,6,6'- Tris (dimethylamino) spiro [fluorene
-9,3'-phthalide] 3,6,6'-tris (diethylamino) spiro [fluorene
-9,3'-phthalide] 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-diethylamino- 2-Ethoxyphenyl) -3- (1-octyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-diethylamino-2-n-hexylphenyl) -3- (1-
Ethyl-2-methylindol-3-yl) -4-azaphthalide 3- (4-cyclohexylmethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -Four-
Azaphthalide 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-
Azaphthalide 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide 3,3-bis (2-methyl-1-octylindol-3-yl)
Phthalide 3- (1-Ethyl-2-methylindol-3-yl) -3- (1-
n-Butyl-2-methylindol-3-yl) phthalide 3,7-bis (dimethylamino) -10-benzoylphenothiazine 3,7-bis (dimethylamino) -N- [pN-bis (4,4 '-Dimethylaminophenyl) methylamino] benzoylphenothiazine 3,7-bis (dimethylamino) -N- [pN-bis (4,4'-diethylaminophenyl) methyl] benzoylphenothiazine 3,6-bis (diethylamino) fluorane- γ- (2'-nitro) anilinolactam 3,6-bis (diethylamino) fluorane-γ- (3'-nitro) anilinolactam 3,6-bis (diethylamino) fluorane-γ- (4'-nitro) Anilinolactam 3,6-bis (diethylamino) fluorane-γ-anilinolactam

These dye precursors may be used alone or in admixture of two or more. The fluoran dye precursor can be preferably used in the present invention, particularly from the viewpoint of heat resistance of the heat-sensitive recording material. When importance is attached to the ground color heat resistance, naturally, a dye precursor having a high melting point and a high decomposition temperature is preferable. When reversible recording is important, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, triphenylmethane dyes, etc. are not stable and have a structure that can withstand repeated use. Higher temperature dye precursors are preferred.

As the binder which can be used in the heat-sensitive recording material of the present invention, fully saponified polyvinyl alcohol having a polymerization degree of 200 to 1900, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol and sulfonic acid are used. Polyvinyl alcohols such as modified polyvinyl alcohol, butyral modified polyvinyl alcohol and other modified polyvinyl alcohols; cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, ethyl cellulose and acetyl cellulose;
Styrene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid ester, polyacrylamide, polyacrylic acid ester, polyvinyl butyral, polystyrol, and combinations thereof. Examples thereof include synthetic polymers such as copolymers consisting of; and resins such as polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, and coumarone resin. Among these examples, the polyvinyl alcohol-based binder is desirable in terms of dispersibility, binder property, and thermal stability of background color. Further, in the case of reversible recording, a binder with little deterioration that can withstand repeated use is preferable.
These binders are used in a state of being dissolved in a solvent such as water, alcohol, ketone, ester, or hydrocarbon, or in a state of being emulsified in a medium such as water, or dispersed in a paste form, depending on required quality. It is also possible to use together.

As the filler used in the thermosensitive recording medium of the present invention, inorganic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, zinc oxide, titanium oxide, zinc hydroxide and aluminum hydroxide, Alternatively, polystyrene-based organic filler, styrene / butadiene-based organic filler, styrene / acrylic-based organic filler, hollow organic filler, etc. may be mentioned.

In the heat-sensitive recording material of the present invention, in addition to the above, a releasing agent such as a fatty acid metal salt, a lubricant such as waxes, a benzophenone- or benzotriazole-based ultraviolet absorber, a waterproofing agent such as glyoxal, a dispersant, A defoaming agent or the like can also be used.

In the thermosensitive recording medium of the present invention, the amount of (a) the dye precursor and (b) 1,3-diphenylurea, and (c) the types and amounts of other various components are required. It is determined by performance and suitability for recording, and is not particularly limited. However, usually, for 1 part of dye precursor, 1,
3-diphenylurea is 1 to 8 parts, the filler is 1 to 20 parts, and the binder is about 10 to 25% by weight in the total solid content.
When a heat-sensitive recording material is repeatedly used, such as a reversible recording material, it is desirable that the composition be as simple as possible. These materials are pulverized by a pulverizer such as a ball mill, attritor, or sand grinder, or a suitable emulsifying device to a particle size of several microns or less, and a coating liquid is prepared by adding various additives according to the binder and purpose. And
A desired thermosensitive recording medium can be obtained by applying the coating liquid to a support.

The support used in the present invention is paper,
Examples thereof include synthetic paper, non-woven fabric, metal foil, plastic film, plastic sheet, and composite sheet combining these.

Further, in the heat-sensitive recording material of the present invention, an overcoat layer made of a polymeric substance is provided on the heat-sensitive color developing layer for the purpose of improving the storage stability of the recording material, or a filler is added for the purpose of increasing the color developing sensitivity of the recording material. An undercoat layer such as a polymer substance containing a may be provided below the thermosensitive color developing layer.

In the case of the heat-sensitive recording material of the present invention having a high ground color stability, a plastic film may be heat laminated to provide a transparent and strong protective coating.
For example, even after heat-sensitive recording on the heat-sensitive recording material of the present invention, a heat-resistant card can be easily prepared using a commercially available simple laminating machine.

Further, in the heat-sensitive recording material of the present invention, by utilizing high ground color stability, a plastic film can be heat laminated to provide a transparent and strong protective coating. For example, even after heat-sensitive recording on the heat-sensitive recording material of the present invention, a card having excellent stability such as heat resistance can be easily prepared by using a commercially available simple laminating machine. Examples of the plastic film used in the heat-sensitive recording material of the present invention include low density polyethylene, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer,
Ethylene / methyl methacrylate copolymer, ethylene /
There may be mentioned thermoplastic resins such as methacrylic acid copolymers.

The heat-sensitive recording material of the present invention may contain a light absorber which absorbs light and converts it into heat in the heat-sensitive recording layer. The light absorber is not particularly limited as long as it is a substance that absorbs the emission wavelength of various light sources.

When a light source having a continuous wavelength, such as a strobe flash, is used as a light source for recording, the light absorber is used as a light absorber.
The heated reaction product of the thiourea derivative / copper compound described in 30954, graphite, copper sulfide, lead sulfide, molybdenum trisulfide, black titanium, etc. described in JP-A-3-86580, carbon black, etc. Can be mentioned.

On the other hand, when a light source having a single wavelength, for example, a semiconductor laser is used as a recording light source, it is used as a light absorbing agent in JP-A-54-4142 and JP-A-58-94494.
JP-A-58-209594, JP-A-2-217287, JP-A-3-73814, etc., polymethine dyes (cyanine dyes), azolenium dyes, pyrylium dyes, thiopyrylium. Dyes, squarylium dyes, croconium dyes, dithiol complexes, mercaptophenol metal complex dyes, mercaptonaphtho-
It is desirable to use a leuco metal complex dye, a phthalocyanine dye, a naphthalocyanine dye, a triarylmethane dye, an immonium dye, a diimmonium dye, a naphthoquinone dye, an anthraquinone dye, a metal complex dye. Further, the light absorbing agents mentioned in the case of the light source having a continuous wavelength can be similarly used or can be used together.

Specifically, for example, the Color-Chemique encyclopedia (edited by the Society of Organic Synthesis, CMC Publishing (1988) p196-2)
00) Table 1, chemical industry (vol. 5, 1986, p379-389) Table 3 near-infrared absorbing dyes, JP-A-61-69991, JP-A-61-246391, US- PATENT: 35570122, US-PATENT:
3575871, US-PATENT: 3637769, and other near-infrared absorbing dyes, 1,1,5,5-tetrakis (p-dimethylaminophenyl) -3-methoxy-1,4-pentadiene (or its cation), 1,1,5,5-Tetrakis (p-diethylaminophenyl) -3-methoxy-1,4-pentadiene (or its cation), toluenedithiol nickel complex, 4-
tert-butyl-1,2-benzenedithiol nickel complex,
Examples thereof include a bisdithiobenzyl nickel complex, a bis (4-ethyldithiobenzyl) nickel complex, and a bis (4-n-propyldithiobenzyl) nickel complex. You may use these light absorbers individually or in mixture of 2 or more types.

These light absorbers are used (a) by simply mixing them in various materials required for an optical recording material, and (b) JP-A-2-
As described in Japanese Patent No. 217287, a method in which a light absorber is melt-mixed in advance and dissolved or dispersed in various materials required for the optical recording medium, or (c) necessary for the optical recording medium The light absorbing agent may be dissolved or dispersed in a solvent in advance in a variety of materials, and the dissolved or dispersed mixture may be used according to the method of use after removing the solvent. Further, the light absorber is a color developer, a dye precursor sensitizer,
It may be co-dispersed (simultaneous mixture dispersion) with a mixture of a developer and a sensitizer, or a mixture of a dye precursor and a sensitizer.

The heat-sensitive recording material of the present invention, even if it contains a light absorber, has, for example, background stability such as heat resistance and solvent resistance,
Alternatively, performance such as reversible recording hardly changes. However, when a sensitizer was used, the background color heat resistance tended to decrease. Even with a heat-sensitive recording material containing a light absorbing agent, it is possible to carry out toner recording, thermal lamination or the like as in the case of not containing it.

A heat-sensitive recording material containing a light-absorbing agent was heat-laminated with a plastic film before or after heat-sensitive recording to prepare a heat-sensitive card. Can also be recorded.

[0051]

[Function] 1,3-diphenylurea used in the present invention is
Basically, it is a developer that is excellent in color development and is also excellent in stability of background color against heat and solvent, and on the other hand, it is a developer that also has reversible recording property. The detailed reasons for the background color stability and the reversible recording property have not yet been clarified. However, it is estimated as follows.

The structure of 1,3-diphenylurea used in the present invention changes depending on the conditions as shown in the following formula. Since this change is a phenomenon similar to keto / enol tautomerism, it is referred to as keto or enolization here for convenience.

Embedded image

It is considered that the enolization is necessary for 1,3-diphenylurea to function as a color developing agent. The enolization requires high temperature conditions. Since the thermal head momentarily reaches a high temperature of 200 to 300 ° C, the urea compound that contacts the thermal head undergoes enolization and develops a color development function to cleave the lactone ring of the dye precursor to develop color. I think that the. Therefore, the urea compound does not change until the temperature at which enolization occurs, and the background color is stable because it does not react with the dye precursor, which seems to be the reason for the high heat resistance.

On the other hand, if the formed enol compound is dissolved for some reason and turned into a keto, it is considered that decoloring may occur. Ketone formation may occur by contacting with an appropriate temperature and heat amount or an alcohol solvent. It is thought that the color will disappear and the color will disappear. Since enolization and ketoization occur under completely different conditions, enolization and ketoization can be repeated under each condition,
It seems that reversible recording will be possible.

Further, the reason why it is possible to write on the recording surface of the heat-sensitive recording material with the oil-based ink (in other words, the background color portion of the heat-sensitive recording material does not change with the oil-based ink) is 1,3-diphenyl. It is considered that urea has extremely low solubility in the solvent used in the oil-based ink, and even if the urea is contacted with these solvents, the dye precursor and the developer are not substantially mixed.

[0056]

EXAMPLES In the following description, parts and% indicate parts by weight and% by weight, respectively.

[Examples 1 to 5] 1,3-diphenylurea was used as a color developer, and the following five kinds of dye precursors were used as dye precursors to prepare thermosensitive recording materials. ODB: 3-N, N-diethylamino-6-methyl-7-anilinofluorane ODB-2: 3-N, N-dibutylamino-6-methyl-7-anilinofluorane CVL: 3,3-bis (P-Dimethylaminophenyl) -6-
Dimethylaminophthalide NEW-Blue: 3- (4-Diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-
Azaphthalide I-red: 3,3-bis (1-ethyl-2-methylindole)
That is, first, the developer dispersion (liquid A) and the dye precursor dispersion (solution B) having the following formulations were ground to an average particle diameter of 1 micron with a sand grinder. (Liquid A: Developer dispersion liquid) 1,3-diphenylurea 6.0 parts 10% polyvinyl alcohol aqueous solution 18.8 parts Water 11.2 parts (liquid B: dye precursor dispersion liquid) Each dye precursor 2.0 parts 10% polyvinyl alcohol aqueous solution 4.6 Part Water 2.6 parts Next, the liquid A (developing agent dispersion), the liquid B (dye precursor dispersion), and the kaolin clay dispersion were mixed at the following ratio to prepare a coating liquid. Solution A: Developer dispersion 36.0 parts Solution B: Dye precursor dispersion 9.2 parts Kaolin clay (50% dispersion) 12.0 parts Coating solution 6.0 g / m ² on one side of 50 g / m ² base paper
It is coated and dried so that it has a surface area of m ² , and this sheet is treated with a super calendar so that the smoothness is 500 to 600 seconds.
A thermosensitive recording medium was prepared.

Comparative Examples 1 to 8 Examples 1 to 5 were prepared by using the following eight kinds of compounds as color developers.
A thermal recording material for a comparative example was prepared in the same manner as in. Bisphenol A (A-1) Bisphenol S (A-2) 4-Hydroxy-4'-iso-propoxydiphenyl sulfone
(A-3) 4-Hydroxy-4'-n-butyroxydiphenyl sulfone
(A-4) Phenylurea (A-5) JP-A-58-211496 JP Bisurea compound (A-6) JP-A-5-147357 JP Amidophenol derivative (A-7) 1-phenyl 3- (p-toluyl) urea (A-8)

[Chemical 4] That is, a dispersion liquid of each compound shown above having the following formulation was ground to an average particle diameter of 1 micron with a sand grinder. (C liquid: developer dispersion) 6.0 parts of the above-mentioned developer compounds (A-1 to A-8) 10% aqueous polyvinyl alcohol solution 18.8 parts water 11.2 parts Next, at the following ratio, liquid C (developing agent) Dispersion liquid), a dispersion liquid (B liquid) of the dye precursor (ODB) used in Example 1,
And the dispersion liquid of kaolin clay was mixed to prepare a coating liquid. Liquid C: Developer dispersion 36.0 parts Liquid B: Dye precursor dispersion (ODB dispersion) 9.2 parts Kaolin clay (50% dispersion) 12.0 parts This coating liquid on one side of 50 g / m ² base paper Coating amount 6.0g /
It is coated and dried so that it has a surface area of m ² , and this sheet is treated with a super calendar so that the smoothness is 500 to 600 seconds.
A thermal recording material for a comparative example was produced.

[Comparative Example 9] The developer dispersions (D and E solutions) and the dye precursor dispersions (F solutions) having the following formulations were ground to an average particle diameter of 1 micron with a sand grinder. (Solution D: Developer dispersion) 1,3-diphenylurea 6.0 parts 10% Hydroxyethyl cellulose aqueous solution 18.8 parts Water 11.2 parts (Solution E: developer dispersion) Bisphenol A (BPA) 6.0 parts 10% Hydroxyethyl cellulose aqueous solution 18.8 parts Water 11.2 parts (F liquid: Dye precursor dispersion liquid) ODB 2.0 parts 10% Hydroxyethyl cellulose aqueous solution 4.6 parts Water 2.6 parts Next, at the following ratio, liquid D, E Liquid (developer dispersion),
Liquid F (dye precursor dispersion liquid) and a dispersion liquid of calcium carbonate were mixed to prepare a coating liquid. D liquid: Developer dispersion 24.0 parts E liquid Developer dispersion 12.0 parts F liquid: Dye precursor dispersion 9.2 parts Calcium carbonate (50% dispersion) 12.0 parts This coating liquid is 50 g / m ² base paper Coating amount on one side of 6.0g /
It is coated and dried so that it has a surface area of m ² , and this sheet is treated with a super calendar so that the smoothness is 500 to 600 seconds.
A thermal recording material for a comparative example was produced.

* Evaluation of thermal recording material The obtained thermal recording material was subjected to a recording property test with a thermal printer, a thermal stability test of the background color, and an oil ink suitability test. Examples 1-5 and Comparative Examples 1-9
The evaluation results of are shown in Tables 1-2.

[Recordability test]: In order to check the recording aptitude, a word processor (RUPO-90F (manufactured by Toshiba)) was used to record on the prepared thermal recording medium with the maximum applied energy, and the recording portion was recorded. It was measured with a Macbeth densitometer (RD-914, an amber filter was used. Hereinafter, the density was measured under these conditions). In this case, the larger the Macbeth value, the higher the recording density and the better the recording suitability.

[Ground color thermal stability test]: In order to check the thermal stability of the ground color of the recording sheet, a hot plate heated to 120 ° C. and 150 ° C. was pressed at a pressure of 10 g / cm ² respectively. The prepared thermal recording material was pressed for 5 seconds, and the recording material was measured with a Macbeth densitometer. In this case, the smaller the Macbeth value, the lower the degree of coloring of the ground color and the higher the thermal stability of the ground color.

[Oil-based ink suitability test (ground-color discoloration test with oil-based ink)]: Oil-based red magic ink No. 500
(Manufactured by Teranishi Chemical Co., Ltd.) was used to write on the prepared thermosensitive recording medium, and the degree of discoloration with respect to the original red color was visually measured. ◎ ... No discoloration ○ ... Almost no discoloration △ ... Slightly discolored × ... Remarkably discolored

[0064]

[Table 1]

[Table 2]

Next, a thermal lamination test and a reversible recording property test were conducted on the obtained thermosensitive recording medium. The evaluation results are shown in Table 3.

[Thermal laminate test (preparation of laminate recording material)]: Simple laminator (MS Pouch H-140)
The thermosensitive recording material thus obtained was sandwiched between pouch films using Meiko Shokai Co., Ltd. to prepare a laminated thermosensitive recording material, and its ground color part was measured by a Macbeth densitometer. In this case, the smaller the Macbeth value is, the more stable the ground color is. In other words, it is shown that the lamination can be performed without causing the color development. The thermosensitive recording medium using 1,3-diphenylurea (however, with no additive) was capable of laminating while the ground color remained stable.

[Reversible recording test]: Similar to the recording test, the obtained thermal recording medium was recorded by a word processor, and the recorded thermal recording medium was transferred between 180 ° C. heat rolls. It was passed at a speed of 30 mm / sec, and the recorded part and the ground color part were measured with a Macbeth densitometer. In this case, it is shown that the smaller the Macbeth density of the recording portion, the higher the decoloring property.
After that, the recording was performed again by the above-mentioned word processor and the Macbeth density of the recording portion was measured.

[0068]

[Table 3]

[Example 6] In the thermosensitive recording medium of Example 1, a reversible recording property test by a heat roll was repeated to obtain 10
I went 0 times. The Macbeth densities at the 100th recording and the background color were 1.09 and 0.08.

[Example 7] In the thermosensitive recording medium of Example 3, after recording with a word processor, the recording surface was wiped with ethanol, and the Macbeth density of the recording portion was measured.
It was 0.22.

[Embodiment 8] In the thermosensitive recording material of Embodiment 2, a toner is produced by a copying machine (NP6060 / manufactured by Canon Inc.).
When recording was performed, no change was observed in the background color, and toner recording was possible.

[Examples 9 to 14] As described below, 3-N, N-diethylamino-6-methyl-7-anilinofluorane (alias: ODB) was used as a dye precursor as a color developer. 1,3-
A heat-sensitive recording material containing a light absorber was prepared by using diphenylurea and a heat melt of the following absorbing dye and sensitizer as a light absorber. Cyanine dye (trade name: NK-2014 / manufactured by Japan Photosensitive Dye Research Institute) naphthalocyanine dye (trade name: NIR-14 / Yamamoto Kasei Co., Ltd.) immonium dye (trade name: IRG- 002 / Nippon Kayaku Co., Ltd. Anthraquinone dye (trade name: IR-750 / Nippon Kayaku Co., Ltd.) Bisdithiobenzyl nickel complex (BDBNi) 4-tert-butyl-1,2-benzenedithiol nickel complex
(BDNi) That is, first, to 94 parts of 4-biphenyl-p-tolyl ether, 6 parts of each absorption dye was added, and heated to 100 to 150 ° C.,
After melt-mixing, it was pulverized to obtain a light absorber. Then, the light absorbent dispersion having the following composition was ground to an average particle size of 1 micron with a sand grinder. (G Liquid: Light Absorber Dispersion) Light Absorber 4.0 parts 10% Polyvinyl alcohol aqueous solution 10.0 parts Water 6.0 parts Then, the developer dispersions (liquid A) used in Examples 1 to 5 at the following ratios. ), The dye precursor used in Example 1 (OD
The dispersion liquid of B) (liquid B), the liquid G (light absorbent dispersion liquid), and the dispersion liquid of kaolin clay were mixed to prepare a coating liquid. Liquid A (developer dispersion liquid) 36.0 parts Liquid B (dye precursor dispersion liquid) 9.2 parts Liquid G (light absorber dispersion liquid) 20.0 parts Kaolin clay (50% dispersion liquid) 12.0 parts This coating liquid 50 g / m Coating amount 6.0g / on one side of base paper ²
It is coated and dried so that it has a surface area of m ² , and this sheet is treated with a super calendar so that the smoothness is 500 to 600 seconds.
A thermosensitive recording medium was prepared.

[Examples 15 to 16] A heat-sensitive recording material was prepared by using an absorbing dye alone as a light absorbing agent instead of a thermal melt of each absorbing dye and a sensitizer. Toluenedithiol nickel complex (TDNi) 1,1,5,5-tetrakis (p-diethylaminophenyl) -3-
Methoxy-1,4-pentadiene (TDEPMP) The following light absorbing developer dispersion (solution H) was ground with a sand grinder to an average particle size of 1 micron. (Liquid H: Light-absorbing developer dispersion) 1,3-diphenylurea 6.0 parts TDNi or TDEPMP 1.0 part 10% polyvinyl alcohol aqueous solution 18.8 parts Water 10.2 parts Colorant dispersion (H
Liquid), the dispersion liquid of the dye precursor (ODB) used in Example 1 (liquid B), and the dispersion liquid of kaolin clay were mixed to prepare a coating liquid. Solution H (light-absorbing developer dispersion) 36.0 parts Solution B (dye precursor dispersion) 9.2 parts Kaolin clay (50% dispersion) 12.0 parts This coating solution is applied to one side of a 50 g / m ² base paper. Quantity 6.0g /
It is coated and dried so that it has a surface area of m ² , and this sheet is treated with a super calendar so that the smoothness is 500 to 600 seconds.
A thermosensitive recording medium was prepared.

Evaluation of Thermal Recording Material Containing Light Absorber The obtained thermal recording material was subjected to a recording property test and a background color thermal stability test (120 ° C., 150 ° C.). Table 4 shows the evaluation results.

[Optical recording test]: An optical recording medium was irradiated with laser light by using a laser plotter apparatus described in Japanese Patent Laid-Open No. 3-239598, and the recording portion was subjected to Macbeth density. It was measured with a meter. As the light irradiation conditions, a semiconductor laser LT015M with an oscillation wavelength of 830 nm and an output of 30 mW was used as a recording light source.
An aspherical plastic lens with a numerical aperture of 0.45 and a focal length of 4.5 mm using D (Sharp Co., Ltd.) as a light collecting lens.
Recording speed of 50mm / s using AP4545 (Konica Corp.)
ec, recording interval was 50 microns, and solid recording of 1 cm in length and width was obtained.

[0076]

[Table 4]

[Embodiment 17] The heat-sensitive recording material of Example 10 was passed through a heat-recording material optically recorded at a speed of 30 mm / sec between heat rolls of 180 ° C to obtain a recording portion and a ground-color portion. When measured with a Macbeth densitometer, the recording area was 0.17 and the background color area was 0.
It was 09. When optical recording is performed again on this recording medium, the recording section
It was 1.29.

[0078]

As described above, the 1,3-diphenylurea used in the present invention has a stable ground color portion under the environmental temperature condition of 120 to 150 ° C. It is an epoch-making developer capable of obtaining a sufficient image density recording with a thermal head or the like. Further, 1,3-diphenylurea is a phenylurea-based compound,
It is an inexpensive material and is advantageous in terms of cost.

Further, the following points can be mentioned as effects of the present invention. (1) By using 1,3-diphenylurea as a color developer, a thermal recording material having excellent background color stability (heat resistance, solvent resistance, etc.) can be obtained as compared with a conventional thermal recording material. (2) The obtained thermosensitive recording medium having excellent ground color stability can be used under severe conditions (for example, 120 ° C.
It can be used under temperature conditions in the range of 150 ° C). (3) The obtained thermosensitive recording medium has the recording surface of the thermosensitive recording medium,
It is possible to write freely with the oil-based ink. (4) The obtained thermosensitive recording medium can be easily heat-laminated by a simple laminator or the like, and, for example, a card or the like can be easily made. (5) Since the obtained thermal recording material has high ground color stability, toner recording can be performed on the thermal recording material.

Further, regarding the heat-sensitive recording material having the erasing function, (6) using the obtained heat-sensitive recording material, recording with color tone
It is possible to create a new recording system that can be repeatedly erased. (7) The obtained thermosensitive recording medium can be repeatedly used many times, which saves resources. (8) Some of the obtained thermal recording media can be erased only by passing them through a heat roll, and unlike the conventionally known reversible recording thermal recording media, a strict temperature control is performed at the time of erasing. Does not need (9) Unlike liquid crystal displays, thermal energy
It can be used as a simple display using.

Similar effects can be expected by incorporating a light absorbing agent in the heat-sensitive recording material of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisami Satake 5-21-1 Oji, Kita-ku, Tokyo Inside Nippon Paper Industries Co., Ltd.

Claims (7)

[Claims] 1. A thermosensitive recording medium having a thermosensitive color developing layer comprising a colorless or light-colored dye precursor and a developer which reacts when heated to develop the dye precursor, wherein the developer has a general formula: A thermosensitive recording medium which is 1,3-diphenylurea represented by (1) and which is not used in combination with a phenol compound. Embedded image 2. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive color-developing layer does not contain a sensitizer, and the heat-sensitive recording material is excellent in heat resistance of the background color portion. 3. The heat-sensitive recording material according to claim 1 or 2, wherein the heat-sensitive color forming layer contains a light absorbing agent that absorbs light and converts it into heat. 4. The claim 1, claim 2, or claim 3.
A heat-sensitive recording card obtained by laminating the heat-sensitive recording material described above with a plastic film. 5. The claim 1, claim 2, or claim 3.
An electrophotographic transfer sheet using the thermal recording medium described. 6. The method according to claim 1, claim 2, or claim 3.
A reversible recording method comprising recording on the thermosensitive recording medium described above, applying heat to the recording portion to erase the recorded image, and recording again by heat. 7. The method according to claim 1, claim 2, or claim 3.
After recording on the thermosensitive recording medium described above, the reversible recording method is characterized in that the recording portion is brought into contact with an alcohol solvent to erase the recorded image, and the thermosensitive recording is carried out again.