JP2002240438A - Reversible heat-sensitive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermal recording material enabling formation and erasure of an image in a clear contrast and being capable of holding the image stable with time in the environment of daily life. SOLUTION: The reversible thermal recording material contains, on a substrate, a reversible heat-sensitive composition composed of a dye precursor, and a reversible developer causing a reversible change of color tone in the dye precursor according to a difference in a cooling speed after heating. The reversible developer has a spacer group not containing a hydrogen bond association group between a phenol group and the hydrogen bond association group, and a peak of heating is not observed in the process of a temperature rise in DSC measurement of a colored mixture which is obtained by rapidly cooling the composition after it is melted by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive composition capable of forming and erasing images by controlling thermal energy.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording material comprises a support having thereon a heat-sensitive recording layer mainly composed of an electron-donating usually colorless or pale-color dye precursor and an electron-accepting developer. By heating with a thermal head, a hot pen, a laser beam, or the like, the dye precursor and the developer react instantaneously to obtain a recorded image. Japanese Patent Publication No. 43-4160, Japanese Patent Publication No. Sho 4
It is disclosed in JP-A-5-14039.

In general, it is impossible for such a heat-sensitive recording material to form an image once and erase that portion and return to the state before image formation. There was no choice but to add to the formation. For this reason, when the area of the heat-sensitive recording portion is limited, there has been a problem that the recordable information is limited and all necessary information cannot be recorded.

In recent years, reversible thermosensitive recording materials capable of repeatedly forming and erasing images have been devised to address such problems. For example, JP-A-54-119377 and JP-A-63-119377 disclose a reversible thermosensitive recording material. 39377, JP-A-63-4
Japanese Patent No. 1186 describes a heat-sensitive recording material composed of a resin base material and an organic low-molecular compound dispersed in the resin base material. However, in this method, the transparency of the heat-sensitive recording material is reversibly changed by heat energy, so that the contrast between the image forming portion and the non-image forming portion is insufficient.

In the methods described in Japanese Patent Application Laid-Open Nos. 50-81157 and 50-105555, since the image to be formed changes according to the environmental temperature, the image forming state and the erasing state are changed. Are different from each other, and these two states cannot be stably maintained for an arbitrary period at room temperature.

Further, Japanese Patent Application Laid-Open No. Sho 59-120492 discloses that an image forming state is controlled by keeping a recording material in a hysteresis temperature range by utilizing a hysteresis characteristic of a coloring component.
Although a method for maintaining the erased state is described, this method requires a heating source and a cooling source for image formation and erasure, and the temperature range in which the image formation state and the erased state can be maintained is limited to the hysteresis temperature range. However, it is still insufficient for use in the temperature environment of daily life.

On the other hand, JP-A-2-188293, JP-A-2-188294, and International Publication No.
No. 11898 describes a reversible thermosensitive recording medium comprising a leuco dye and a color-reducing agent which causes the leuco dye to develop and decolor the color by heating. The color-developing agent is an amphoteric compound having an acidic group for coloring the leuco dye and a basic group for decolorizing the colored leuco dye, and has a coloring effect by an acidic group or a decolorizing effect by a basic group by controlling thermal energy. One is preferentially generated to perform color development and decoloration. However, in this method, it is impossible to completely switch between the coloring reaction and the decoloring reaction only by controlling the heat energy, and since both reactions occur at a certain ratio at the same time, a sufficient coloring density cannot be obtained. Can't do it perfectly. Therefore, sufficient image contrast cannot be obtained. Also,
Since the decolorizing action of the basic group also acts on the colored portion at room temperature,
The phenomenon that the density of the color-developed portion decreases over time is inevitable.
Further, JP-A-5-124360 describes a reversible thermosensitive recording medium that develops and decolorizes a leuco dye by heating, and as an electron accepting compound, an organic phosphonic acid compound, an α-hydroxy aliphatic carboxylic acid, Specific phenolic compounds such as fatty acid dicarboxylic acids and alkylthiophenols having an aliphatic group having 12 or more carbon atoms, alkyloxyphenols, alkylcarbamoylphenols, and alkyl gallates are exemplified. However, even with this recording medium, the two problems of low color density or incomplete erasing cannot be solved at the same time, and the stability of the image over time is satisfactory for practical use. Absent. Further, Japanese Patent Application Laid-Open
No. 2,294,063, as a decolorizing accelerator for improving the erasability of the reversible thermosensitive recording medium, fatty acids, waxes, higher alcohols, various esters of phosphoric acid / benzoic acid / phthalic acid or oxyacid, silicone oil There are disclosed liquid crystal compounds, surfactants, and saturated hydrocarbons of fatty acids having 10 or more carbon atoms, but the effects are small, and the image density at the time of erasing is still high and cannot be said to be practical.

As described above, according to the conventional technology, a practical reversible image having a clear image contrast, capable of forming and completely erasing a high-density image, and capable of maintaining a stable image over time in an environment of daily life. It was difficult to produce a thermosensitive recording material. On the other hand, as already described in Japanese Patent Application Laid-Open No. Hei 7-179043 or Japanese Patent Application No. 10-93313,
Although it has been found that a colorless or pale-colored electron-donating dye precursor has a reversible color developer that causes reversible color change upon heating, that is, color development and decoloration, a better image for practical use has been found. In order to obtain a quality and easy-to-use recording medium, there is room for improvement in the image density at the time of erasing, the erasing start temperature, the erasing temperature range, and the like.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermosensitive composition capable of forming and erasing an image with good contrast and maintaining a stable image over time in an environment of daily life. To provide. More specifically, the present invention provides a reversible thermosensitive composition having a lower image density at the time of erasing, less erasure, and an erasing temperature capable of performing uniform erasing at a lower temperature and a wide temperature range. That is the task.

[0010]

Means for Solving the Problems The present inventors have developed a dye precursor on a support and a reversible developer which causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. Wherein the reversible developer is a compound having at least a phenol group, a hydrogen bond associative group, and a monovalent hydrocarbon group having 6 or more carbon atoms in the molecule. Further, between the phenol group and the hydrogen bond associative group, a spacer group having no hydrogen bond associative group is provided, and the dye precursor and the reversible developer are heated and melted, and then rapidly cooled. Erasing an image over a wide temperature range by using a reversible thermosensitive composition characterized by using a combination that does not observe an exothermic peak in a heating process in a differential scanning calorimetry (DSC) or a differential thermal analysis of the color mixture obtained by the above method. Is completely and evenly This has led to the completion of the present invention found that it can be implemented in.

In the reversible developer used in the present invention, the monovalent hydrocarbon group having 6 or more carbon atoms is preferably an aliphatic hydrocarbon group, and an oxygen atom, a sulfur atom, or an unsaturated bond in the chain. May be included. The reason for the spacer group is that the phenol group interacts with the dye precursor but has a certain degree of freedom, or that the compound itself has a relatively low melting point to provide sufficient color sensitivity. Therefore, it is necessary to use a group not containing a hydrogen bond associative group, and specifically, an aliphatic hydrocarbon group which may contain an oxygen atom or a sulfur atom is preferable. Specific examples of the hydrogen bond associative group include a functional group having a —SO ₂ NH— bond or a —CONH— bond as a minimum constituent unit, and among them, a —CONH— bond having no alkylene chain at both terminals. Is preferably a hydrogen-bond associative group having a minimum structural unit of As a specific example, an amide (—CON
H-, -NHCO-), urea (-NHCONH-), urethane (-NHCOO-, -OCONH-), diacylamine (-CONHCO-), diacylhydrazide (-
CONHNHCO-), carbohydrazone (-CONH
N = CH-, -CH = NNHCO-), oxalic acid diamide (-NHCOCONH-), acylurea (-CONH
CONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-), semicarbazide (-NHCONHNH-, -NHNHCONH)
-), Acyl semicarbazide (-CONHNHCONH
-, - NHCONHNHCO-), diacyl aminomethane (-CONHCH ₂ NHCO -), 1- acylamino-1- Ureidometan (-CONHCH ₂ NHCONH
-, - NHCONHCH ₂ NHCO-), include groups such as malonamide (-NHCOCH ₂ CONH-).

Specific examples of the reversible color developer used in the present invention include, for example, JP-A-7-164746 and JP-A-7-164746.
No. 2,570,34, Japanese Patent Application Laid-Open No. 2000-263946, and Japanese Patent No. 311479, but the present invention is not limited to these.

The reversible color developer according to the present invention may be used alone or as a mixture of two or more types. Usually, the amount of the electron accepting compound according to the present invention to the colorless or pale color dye precursor is as follows. 5 to 5000% by weight, preferably 1
0 to 3000% by weight.

The dye precursor used in the present invention is typified by known compounds generally used in pressure-sensitive recording paper and heat-sensitive recording paper, but is not particularly limited. Specific examples include, for example, the following, but the present invention is not limited thereto.

(1) Triarylmethane compounds 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindole-
3-yl) phthalide, 3- (4-diethylamino-2-
Ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2)
-Methylindol-3-yl) -4-azaphthalide,
3- (4-diethylamino-2-ethoxyphenyl)-
3- (1-ethyl-2-methylindol-3-yl)
-4,7-diazaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -7-azaphthalide, 3-
(P-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,
2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,
3-bis (9-ethylcarbazol-3-yl) -5
Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6 -Dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -4
-Azaphthalide and the like.

(2) Diphenylmethane compounds 4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenylleucouramine, N-2,4,5-trichlorophenylleucouramine and the like.

(3) Xanthene compounds rhodamine B anilinolactam, rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3- Diethylamino-7-phenylfluoran, 3-diethylamino-7-phenoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7- (3 , 4-Dichloroanilino) fluorane, 3-diethylamino-7-
(2-chloroanilino) fluoran,

3-Diethylamino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl- 7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Phenethylfluoran, 3-diethylamino-7- (4
-Nitroanilino) fluoran, 3-dibutylamino-
6-methyl-7-anilinofluoran, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamyl) amino-6 Methyl-7-anilinofluoran, 3- (N-
Methyl-N-cyclohexyl) amino-6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-tetrahydrofuryl) amino-6-methyl-7-anilinofluoran and the like.

(4) Thiazine compounds Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like.

(5) Spiro compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3 -Methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like.

The above dye precursors may be used alone or in combination of two or more.

A specific example of a method for producing a reversible thermosensitive recording material using the reversible thermosensitive composition of the present invention includes a method of forming a reversible thermosensitive recording layer by coating on a support.

As a method for preparing a coating liquid for incorporating the composition of the present invention into the reversible thermosensitive recording layer, a method in which each compound is dissolved alone in a solvent or dispersed in a dispersion medium and then mixed, and a method in which each compound is mixed Are mixed and then dissolved in a solvent or dispersed in a dispersion medium, each compound is heated and dissolved, homogenized, cooled, and then dissolved in a solvent or dispersed in a dispersion medium. Not something. At the time of dispersion, a dispersant may be used if necessary. When water is used as the dispersion medium, a water-soluble polymer such as polyvinyl alcohol and various surfactants can be used as the dispersant. In the case of aqueous dispersion, a water-soluble organic solvent such as ethanol may be mixed. In addition, when an organic solvent typified by hydrocarbons is a dispersion medium, lecithin, phosphates, and the like may be used as a dispersant.

A binder can be added to the reversible thermosensitive recording layer for the purpose of improving the strength of the reversible thermosensitive recording layer. Specific examples of the binder include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acryl. Water-soluble polymers such as acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic acid Ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl chloride copolymer, polyvinyl chloride, ethylene Vinylidene chloride copolymers, latexes such as polyvinylidene chloride. The role of these binders is to keep the materials of the composition uniformly dispersed without unevenness due to the application of heat for printing and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. Recently, high value-added reversible thermosensitive recording materials such as prepaid cards and stored cards are increasingly used, and with this, high durability products such as heat resistance, water resistance and adhesiveness are required. It is becoming. Curable resins are particularly preferred for such requirements.

Examples of the curable resin include a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin.
Examples of the thermosetting resin include resins that are cured by reacting a hydroxyl group and a carboxyl group with a crosslinking agent such as a phenoxy resin, a polyvinyl butyral resin, and a cellulose acetate propionate resin. Examples of the crosslinking agent at this time include isocyanates, amines, phenols, epoxies and the like.

Monomers used in the electron beam and curing beam resins include monofunctional monomers represented by acrylics, difunctional monomers, polyfunctional monomers and the like. And a photopolymerization accelerator.

Further, a heat-fusible substance can be contained in the reversible thermosensitive recording layer as an additive for adjusting the color development sensitivity of the reversible thermosensitive recording layer. Those having a melting point of 60 ° C to 200 ° C are preferred, and those having a melting point of 80 ° C to 180 ° C are particularly preferred. A sensitizer used in general thermosensitive recording paper can also be used. Examples of these compounds include waxes such as N-hydroxymethyl stearamide, behenamide, stearamide, palmitamide, naphthol derivatives such as 2-benzyloxynaphthalene, p-benzylbiphenyl,
Biphenyl derivatives such as 4-allyloxybiphenyl,
1,2-bis (3-methylphenoxy) ethane, 2,
Polyether compounds such as 2'-bis (4-methoxyphenoxy) diethyl ether and bis (4-methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate,
Examples thereof include carbonic acid or oxalic acid diester derivatives such as bis (p-methylbenzyl) oxalate and the like, and two or more kinds thereof can be added in combination.

Examples of the support used for the reversible thermosensitive recording material containing the reversible thermosensitive composition of the present invention include paper, various nonwoven fabrics, woven fabrics, synthetic resin films such as polyethylene terephthalate and polypropylene, and polyethylene and polypropylene. Paper laminated with synthetic resin, synthetic paper, metal foil, glass, etc., or a composite sheet combining these can be used arbitrarily according to the purpose, but is not limited thereto, and these are opaque, semi-transparent. It may be transparent or transparent. In order to make the background appear white or another specific color, a white pigment, a colored dye or a bubble may be contained in or on the support. In particular, in the case of aqueous coating of films, etc., when the hydrophilicity of the support is small and it is difficult to apply the reversible thermosensitive recording layer, the same water-soluble polymer as used for the hydrophilic treatment of the surface by corona discharge etc. or the binder May be subjected to an easy adhesion treatment such as coating on the surface of a support.

The layer structure of the reversible thermosensitive recording material containing the reversible thermosensitive composition of the present invention may be only the reversible thermosensitive recording layer. If necessary, a protective layer may be provided on the reversible thermosensitive recording layer, and at least one of a water-soluble polymer, a white or colored dye or hollow particles between the reversible thermosensitive recording layer and the support. May be provided. In this case, the protective layer and / or the intermediate layer may be composed of two or three or more layers. The reversible thermosensitive recording layer may also be formed as a multilayer of two or more layers by containing each component in one layer or changing the mixing ratio for each layer. Further, in the reversible thermosensitive recording layer and / or other layers and / or
Alternatively, a material on which information can be recorded electrically, optically, and magnetically may be included on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided. In addition, anti-blocking, anti-curl on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided,
A back coat layer can be provided for the purpose of preventing static charge.

The method for forming a reversible thermosensitive recording material by laminating a functional layer containing the reversible thermosensitive composition of the present invention on a support is not particularly limited, and is formed by a conventional method. be able to. For example, a smearing device such as an air knife coater, a blade coater, a bar coater, and a curtain coater, and various printing machines using a method such as lithographic, letterpress, intaglio, flexo, gravure, screen, and hot melt can be used. Further, each layer can be held by UV irradiation and EB irradiation in addition to the usual drying step.

The reversible thermosensitive recording layer is prepared by mixing each dispersion obtained by pulverizing each component, coating the mixture on a support and drying, and dissolving each solution obtained by dissolving each component in a solvent. It can be obtained by, for example, a method of mixing and coating and drying on a support. Drying conditions vary depending on a dispersion medium or solvent such as water. In addition, there is a method in which the components are mixed and heated to melt a fusible component, and the mixture is heated and applied.

The reversible thermosensitive recording layer and / or the protective layer and / or the intermediate layer include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, and hydroxide. Aluminum, pigments such as urea-formalin resin, etc., as well as metal salts of higher fatty acids such as zinc stearate and calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearamide, etc. Waxes such as caster wax, and a dispersant such as dioctyl sodium sulfosuccinate, a surfactant, a fluorescent dye, and an ultraviolet absorber can also be contained.

Next, the method of coloring and decoloring the reversible thermosensitive composition of the present invention will be described. In order to perform color development, rapid cooling may be performed following heating, and for example, heating by a thermal head, laser light, or the like is possible. In addition, the color can be erased by cooling slowly after heating, for example, by using radiant heat from a light source such as a thermal head, a hot roll, a hot stamp, high-frequency heating, hot air, an electric heater and a tungsten lamp, a halogen lamp, or the like. it can.

[0034]

The present invention will be described in more detail with reference to the following examples. Parts and percentages in the examples are on a weight basis.

DSC of Examples 1 to 5 and Comparative Examples 1 to 4
Measurement A composition comprising the dye precursor of the present invention and a reversible developer was prepared as follows. First, the dye precursor and the reversible developer were weighed so as to have a mixing ratio (weight ratio) of 1: 5, and were mixed and pulverized in a mortar. 1 g of this mixture was placed in an aluminum cup and quickly melted on a hot plate at 180 ° C. Subsequently, the molten mixture was put into the ice water bath prepared in advance together with the aluminum cup at once, and rapidly cooled. After cooling down,
The coloring mixture was dried under reduced pressure at room temperature to obtain the composition of the present invention. Table 1 shows the compositions of the present invention used in the examples and comparative examples.

[0036]

[Table 1]

The DSC measurement of each composition in the color-developing state shown in Table 1 shows that among these compositions, the composition of the present invention did not have a definite exothermic peak in the process of raising the temperature. In each of the compositions of Comparative Examples, an exothermic peak was confirmed. D
Among the measurement results of SC, Examples 1 to 5 are shown in FIGS.
Comparative Examples 1 to 4 are shown in FIGS.

Preparation of reversible thermosensitive recording materials of Examples 1 to 5 and Comparative Examples 1 to 4 (A) Preparation of reversible thermosensitive dispersion 2 parts of a dye precursor and 8 parts of a reversible developer were subjected to LR-2528.
Using PSZ beads having a diameter of 1 mm as a dispersion medium together with 40 parts of a thermosetting acrylic polyol (manufactured by Mitsubishi Rayon Co., effective solid content of 50%) and 150 parts of tetrahydrofuran (THF), paint conditioner was used.
The mixture was pulverized and dispersed for 4 hours to prepare a dispersion.

(B) Coating of the reversible thermosensitive dispersion prepared in the coating of the reversible thermosensitive recording layer (A)
10 parts of an adduct type hexamethylene diisocyanate (effective solid content: 75%) was added and stirred to prepare a recording layer coating liquid. This coating solution was smeared on a polyester film sheet having a thickness of 100 μm so that the solid content was 8.5 g / m ² , followed by drying at 60 ° C. for 24 hours and hardening.

(C) Coating of ultraviolet absorbing layer On the recording layer prepared in (B), ZS-303 (supplied by Sumitomo Chemical Co., ultrafine zinc oxide, effective solid content 30%) 100
Parts, 45 parts of LR-503 (manufactured by Mitsubishi Rayon Co., Ltd., thermosetting acrylic polyol, effective solid content: 50%), 10 parts of Coronate HL, and 75 parts of 2-butanone were coated with a UV-absorbing layer coating solution having a composition of solids The solution was smeared so as to have an amount of 2.0 g / m ² and dried at 60 ° C. for 24 hours to perform hardening.

(D) Coating of protective layer On the ultraviolet absorbing layer prepared in (C), a urethane acrylate UV curable resin (manufactured by Dainippon Ink) was diluted with ethyl acetate to form a coating liquid for the protective layer. 3.0g solid smear
/ M ^2, and cured by an ultraviolet irradiation device to obtain a reversible thermosensitive recording material having a protective layer.

Test 1 (Coloring density = thermal responsiveness) The reversible thermosensitive recording materials obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were applied to a Kyocera print head KJT-256-8MGF.
1 with Okura Electric Thermal Facsimile Printing Tester TH-P
Printing was performed using an MD with an applied pulse of 1.1 millisecond and an applied voltage of 19 volts, and the density of the obtained color image was measured using a densitometer Macbeth RD918.

Test 2 (Erasability of Image) The reversible thermosensitive recording materials obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were applied to a Kyocera print head KJT-256-8MGF.
1 with Okura Electric Thermal Facsimile Printing Tester TH-P
Printing was performed using an MD with an applied pulse of 1.1 milliseconds and an applied voltage of 19 volts.
After heating at 1 ° C. for 1 second, the concentration was measured in the same manner as in Test 1.

Test 3 (Decoloring start temperature) The reversible thermosensitive recording materials obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were used with a Kyocera print head KJT-256-8MGF.
1 with Okura Electric Thermal Facsimile Printing Tester TH-P
Printing was performed using an MD with an applied pulse of 1.1 milliseconds and an applied voltage of 19 volts.
After heating for 10 seconds in total at 10 ° C. intervals from 10 ° C. to 170 ° C., each concentration was measured in the same manner as in Test 1. The heating temperature at which the optical density of the printed image was lower than 0.10 was defined as the decolorization start temperature.

Test 4 (Change over time in color density = image stability) The reversible thermosensitive recording materials obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were used as print heads KJT-256-8MGF manufactured by Kyocera.
1 with Okura Electric Thermal Facsimile Printing Tester TH-P
Using an MD, an applied voltage of 1.1 milliseconds and an applied voltage of 19
After printing under the condition of bolts and storing for 24 hours in an atmosphere of a temperature of 50 ° C. and a relative humidity of 20%, in the same manner as in Test 1,
The density of the color-developed portion was measured, and the image remaining ratio was calculated by the following equation (1).

[0046]

A = (C / B) × 100 A: Image residual ratio (%) B: Image density before test C: Image density after test

Test 1 of Examples 1 to 5 and Comparative Examples 1 to 4
Table 2 shows the results of.

[0048]

[Table 2]

[0049]

As shown in Tables 1 and 2, a reversible thermosensitive composition comprising a dye precursor and a reversible color developer which causes a reversible color change in the dye precursor upon heating. In the contained reversible thermosensitive recording material, the combination having no exothermic peak in the DSC measurement of the composition in the color-developed state during the temperature rise process can form and erase images with clear contrast, and can be used in the environment of everyday life. With time, a reversible thermosensitive recording material capable of maintaining a stable image could be obtained.

[Brief description of the drawings]

FIG. 1 is a DSC measurement diagram of the reversible thermosensitive composition of Example 1 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 2 is a DSC measurement diagram of the reversible thermosensitive composition of Example 2 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 3 is a DSC measurement diagram of the reversible thermosensitive composition of Example 3 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 4 is a DSC measurement diagram of the reversible thermosensitive composition of Example 4 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 5 is a DSC measurement diagram of the reversible thermosensitive composition of Example 5 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 6 is a DSC measurement diagram of the reversible thermosensitive composition of Comparative Example 1 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 7 is a DSC measurement diagram of the reversible thermosensitive composition of Comparative Example 2 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 8 is a DSC measurement diagram of the reversible thermosensitive composition of Comparative Example 3 used in the present invention. Measure the heating rate at 4 ° C / min.

FIG. 9 is a DSC measurement diagram of the reversible thermosensitive composition of Comparative Example 4 used in the present invention. Measure the heating rate at 4 ° C / min.

[Explanation of symbols]

 1 DSC measurement line 2 Exothermic peak

Claims (3)

[Claims] 1. A reversible thermosensitive composition containing a dye precursor on a support and a reversible developer which causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. Wherein the reversible developer is a compound having at least a phenol group, a hydrogen bond associative group, and a monovalent hydrocarbon group having 6 or more carbon atoms in a molecule, and further comprising the phenol group and the hydrogen bond associative. Differential scanning calorimetric analysis of a color mixture obtained by heating and melting the dye precursor and the reversible developer and then rapidly cooling after having a spacer group not containing a hydrogen bond associative group between the functional groups. Alternatively, a reversible thermosensitive composition using a combination that does not observe an exothermic peak during a temperature rise process in differential thermal analysis. 2. The reversible thermosensitive composition according to claim 1, wherein the hydrogen bond associative group has a minimum constitutional unit of a —CONH— bond having no alkylene chain at both terminals. 3. The method according to claim 1, wherein the spacer group is an oxygen atom, a sulfur atom,
Or an aliphatic hydrocarbon group which may contain at least one kind of unsaturated bond.
Or the reversible thermosensitive composition according to 2.