JPH11208113A - Manufacture of reversible thermal recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a reversible thermal recording body wherein a developed color image is formed on a white ground and color can be developed and vanished by different heating conditions alone, which has high recording sensitivity and of which the developed color density does not change, nor the color vanishing property lowers, even when color is developed and vanished repeatedly, by using a small-sized apparatus. SOLUTION: In regard to a thermal recording layer containing a colorless or light-colored dye precursor and a developer and a color vanishing accelerator which develop and vanish the color of the precursor reversibly, a coating solution prepared by mixing and dispersing the dye precursor, the developer and the color vanishing accelerator simultaneously is applied at least on one surface of a sheetlike support and dried and thereby the thermal recording layer is formed. The dye precursor, the developer and the color vanishing accelerator are mixed and dispersed in water or an organic solvent. In the case of dispersing them in water, a water solution of a water-soluble macromolecular compound may be used so as to keep the dispersed materials stable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a reversible thermosensitive recording medium capable of performing coloring and decoloring by controlling heating conditions, and maintaining the colored and decolored states at room temperature. It is. More specifically, the present invention relates to a method for producing a reversible thermosensitive recording medium which forms a color image on a white background, has high recording sensitivity, and has excellent image storability.

[0002]

2. Description of the Related Art Conventionally, heat-sensitive recording media have a compact recording device, are inexpensive, and are easy to maintain. Therefore, computers, measuring instruments, registers, CD / ATMs, facsimile machines, automatic ticket vending machines, handy terminals, etc. However, recently, it has been used as a magnetic heat-sensitive card such as a prepaid card or a point card due to its combination with magnetic recording. In these magnetic cards, the magnetic information is rewritten each time it is used, but the thermal recording image is not rewritten. Therefore, new information such as the residual number is added to the portion where no image is recorded. However, since the area of the recordable portion is limited, the actual situation is that the amount of information to be thermally recorded is unavoidably reduced, or the card is recreated when the recording area is exhausted. As means for solving such a problem, development of a reversible thermosensitive recording medium which can be rewritten any number of times is strongly desired.

[0003] Against the background of garbage problems and deforestation problems that have been actively discussed in recent years, there is a demand for the recycling of thermal recording paper. There are various methods for regenerating thermosensitive recording paper. Among them, as a versatile method that does not require a large device such as a deinking device, the development of a reversible thermosensitive recording material that can be rewritten many times has been developed. Is desired. Further, the reversible thermosensitive recording medium has attracted attention as a recording material for a simple display as disclosed in JP-A-3-233490 and JP-A-5-42762, and is suitable for these apparatuses. The development of a reversible thermosensitive recording medium is also strongly desired.

[0004] Against this background, various reversible thermosensitive recording media have been proposed. For example, JP-A-63-107
584, JP-A-4-78573 and 4-
Japanese Patent No. 358878 and the like disclose a polymer type reversible thermosensitive recording medium utilizing a change in transparency due to heating conditions. However, since the recording method uses transparency-white turbidity due to the phase change of the polymer, sufficient transparency or sufficient opacity cannot be easily obtained, and the contrast between the color-developed portion and the decolored portion becomes low, resulting in darkness. There is a problem that visibility in a place is poor. In addition, in general, a white image is recorded on a colored background, and it is difficult to obtain a so-called paper-like recording medium on which a colored image is recorded on a white background.

As a method for solving these problems, there has been proposed a dye-type reversible thermosensitive recording medium which enables reversible recording while using a dye used in a conventional thermosensitive recording medium. The dye-type reversible thermosensitive recording medium is easy to record a color image on a white background, and is a recording method using a change in absorption wavelength due to heating conditions.
A relatively high contrast is obtained. For example, the following system is known as a dye type reversible thermosensitive recording medium.

JP-A-58-191190 and JP-A-60-193691 disclose methods using gallic acid and phloroglucinol as a color developer. However, since water or water vapor is required for erasure,
There is a disadvantage that the decoloring device becomes large. JP-A-60-264285 and JP-A-62-1408.
No. 81 discloses a thermochromic material having hysteresis. However, the image holding temperature range is
Since it is limited at both the upper and lower limits, it has the drawback that the device becomes complicated and the temperature of the use environment is limited. JP-A-63-173684 discloses a method using an ascorbic acid derivative as a color developer. However, there is a disadvantage that the color is not sufficiently erased during erasing.

JP-A-2-188293 and JP-A-2-188294 disclose a method using a salt of a specific organic acid such as gallic acid and a higher aliphatic amine as a color developer. . However, since the coloring reaction and the decoloring reaction are competing reactions, it is difficult to control so that either reaction proceeds selectively, and there is a disadvantage that it is difficult to obtain high contrast. JP-A-5-1243
No. 60 and JP-A-6-210954,
A method using an organic phosphoric acid compound having a long-chain alkyl group or a phenolic compound as a color developer is disclosed. However, when erasing, there are drawbacks that the color may not be sufficiently erased, and the storability of the color image may be insufficient. As described above, a number of techniques have been disclosed for reversible thermosensitive recording media, but each of them has various drawbacks, and a practically satisfactory one has not yet been obtained.

As a reversible thermosensitive recording medium overcoming these problems, the present inventors have previously developed a reversible thermosensitive recording medium using a compound having a long-chain alkyl group and a sulfonyl (thio) urea group as a color developer. Proposed (Japanese Patent Laid-Open No. 9-272261)
No.). This reversible thermosensitive recording material uses a small device, forms a color image on a white background, can develop and decolor only by differences in heating conditions, has high contrast, and has excellent image storability. It is a recording medium. But,
This reversible thermosensitive recording medium also, like other reversible thermosensitive recording media, repeatedly performs color development and decoloration at the same location,
There has been a problem that the coloring density is increased and a constant density cannot be obtained, and the decoloring property is reduced.

According to the present invention, a color image can be formed on a white background using a small apparatus, and color development and decoloration can be carried out only by a difference in heating conditions. It is another object of the present invention to provide a method for producing a reversible thermosensitive recording medium in which the color density does not change and the decoloring property does not decrease even when color formation and decoloration are repeatedly performed.

[0009]

The inventors of the present invention can perform color development and color erasing only by heating, and have a high reversible thermal color development and a color erasable reversible color with a high contrast between the color development area and the color erasure area. In order to obtain a thermal recording material, we focused on a dye-type reversible thermosensitive recording system using the reaction between a dye and a developer, and as a result of diligent research, we mixed and dispersed a dye precursor, a developer, and a decolorization accelerator simultaneously. It has been found that a desired reversible thermosensitive recording medium can be obtained by producing a coating solution, and the present invention has been completed.

That is, the present invention relates to a heat-sensitive recording layer containing a colorless or light-colored dye precursor, and a developer and a decolorization accelerator for reversibly coloring and decoloring the dye precursor. A reversible heat-sensitive recording material characterized in that a coating solution obtained by simultaneously mixing and dispersing a color developer and a decolorizing accelerator is coated on at least one surface of a sheet-like support, and dried to form a heat-sensitive recording layer. Manufacturing method ”. In the present invention, a developer containing at least one compound represented by any of the following general formulas (I), (II) and (III) is used as a developer. And a reversible thermosensitive recording medium manufactured by the above-described manufacturing method.

The reversible thermo-coloring method for a reversible thermo-sensitive recording medium according to the present invention is characterized in that the thermo-sensitive coloring layer of the recording medium is heated by a normal thermo-sensitive recording head, a heat roll, a heat stamp or the like to color-record an image. And save. The erasing method is to erase the color image by heating the heat-sensitive coloring layer at a temperature lower than the coloring heating temperature after the recording has been used or at the time of rewriting.

In the reversible thermosensitive recording material obtained by the method for producing a reversible thermosensitive recording material of the present invention, a dye precursor,
The heat-sensitive recording layer containing the developer and the color developer rapidly develops color by heating, and the color development state is maintained at room temperature by rapid cooling. On the other hand, the color image portion held at room temperature can be erased by heating to a color development temperature or lower, and the decolored state is maintained even when cooled to room temperature.
Although the mechanism of this decolorization is not clear, when the color former is heated below the color development temperature, the long-chain alkyl groups in the color developer are oriented to induce crystallization of the color developer, and the dye and the color developer are heated. It is considered that the colorant separates and decolorizes. Generally, the heating temperature for color development is 80 to 180 ° C.
0 ° C. to 120 ° C., and lower than the coloring heating temperature.
Generally, coloring is performed by a thermal head or the like, which is easy to rapidly cool after heating. Decoloring is performed by maintaining the temperature in a temperature range equal to or lower than the coloring heating temperature, and controls the heating / cooling speed. No need. The temperature holding time at the time of decoloring is preferably 0.1 second or more. The process of recording and erasing the color image will be described with reference to FIG.

In FIG. 1, when the unrecorded recording material in the state A is heated, the color density rapidly increases at a temperature T2 or higher via the state B, and further increases via the state C.
When the coloring reaction is completed, the state reaches the state D, which indicates the highest coloring density. When the state D is rapidly cooled to room temperature, the state F is reached via the state E. State F is a state in which coloring is maintained at room temperature, and the recording of the image is completed. When the recorded image is heated and held in the temperature range T1, the color density gradually decreases, and the state changes to the state A 'via the state G, and the color is completely erased. When this is cooled to room temperature, it reaches state A.
State A is a state where the decolored state is maintained at room temperature,
This completes the erasure of the image. The above color-decoloring reversible cycle can be repeatedly performed.

It is not clear what mechanism the color erasure accelerator acts on the color development and color erasure reaction between the dye and the color developer. It is considered that this affects the mobility of the long-chain alkyl group of the colorant molecule. That is, when the color developing system in the amorphous state is heated to the color erasing temperature range, it is considered that the color developing system exhibits fluidity and orients the long-chain alkyl group of the developer molecule. Is considered to decrease the viscosity of the color-developing system, thereby increasing the mobility of the long-chain alkyl group of the color-developing molecule, thereby promoting the crystallization of the color-developing agent and increasing the color erasing speed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, mixing and dispersion of a dye precursor, a color developer and a decolorizing accelerator are carried out with water or an organic solvent. When dispersing in water, an aqueous solution of a water-soluble polymer compound may be used to stably maintain the dispersion. As the water-soluble polymer compound, generally, water-soluble synthetic polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide and styrene-maleic anhydride copolymer salt, and methyl cellulose, hydroxyethyl cellulose, starch derivatives, gelatin and casein, etc. An aqueous solution of a water-soluble natural polymer compound or a derivative thereof as described above can be used.

The amount of the water-soluble polymer compound is preferably from 5 to 20% by weight based on the solid content of the dispersion, and if it is less than 5% by weight, the dispersion time becomes longer, and
Above, the color density is reduced. In the present invention,
For the purpose of improving dispersion efficiency and whiteness, a surfactant may be added. As the surfactant to be added, various nonionic and anionic surfactants can be used. Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene fatty acid ester, and acetylene. Examples of anionic surfactants such as glycol surfactants and acetylene alcohol surfactants include naphthalenesulfonic acid formalin condensates and polycarboxylic acid type polymer surfactants. The amount of the surfactant added is preferably 0.05 to 5% by weight based on the solid content of the dispersion.

In the present invention, usable organic solvents are not particularly limited, but include, for example, hydrocarbons, halogenated hydrocarbons, alcohols, and ethers.
Acetals, ketones, and esters are used alone or as a mixed organic solvent. Specific examples of hydrocarbons include, for example, benzene, toluene, xylene, cyclohexane, cyclopentane, petroleum ether, ethylene,
Naphthalene and the like, as specific examples of halogenated hydrocarbons, for example, chloroform, methyl chloride, carbon tetrachloride, chlorobenzene, dichlorobenzene and the like, as specific examples of alcohols, for example, methanol, ethanol, propanol, isopropanol, Butanol and the like, as specific examples of ether-acetals, for example, ethyl ether, isopropyl ether, diethyl acetal and the like, as specific examples of ketones, for example, acetone, methyl ethyl ketone, diethyl ketone, and the like, as specific examples of esters Examples include, but are not limited to, ethyl acetate, methyl acetate, methyl propionate, and the like. Regardless of whether water or an organic solvent is used, a conventionally known disperser can be used, and specific examples thereof include a sand mill, a dyno mill, an attritor, and a ball mill, but are particularly limited. Not something.

Further, it is possible to emulsify and disperse a mixture of a dye precursor, a color developer and a decolorization accelerator. As the emulsification dispersion method in the present invention, a mixture obtained by heating and melting a mixture of a dye precursor, a color developer and a decolorization accelerator is emulsified with an aqueous solution containing an emulsifier or the like by a high-speed stirrer or the like, if necessary. A method in which a mixture of a color developer and a decolorizing accelerator is heated and melted, and the resulting mixture is emulsified and dispersed in an aqueous solution containing an emulsifier or the like by high-pressure injection using a fine nozzle to form an oil in water droplet.

Examples of the emulsifiers used in the emulsification dispersion include, for example, alkali soaps, organic amine soaps, sulfates of higher alcohols, synthetic surfactants including nonionic surfactants, proteins, vegetable gums, alginates, carboxymethylcellulose, saponin. And polyvinyl alcohol. The amount of the emulsifier added is preferably 0.05 to 20% by weight based on the solid content of the dispersion.

The compound used as a dye precursor in the present invention includes triphenylmethane, fluoran and diphenylmethane compounds, and can be selected from conventionally known compounds. For example, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2
-Methylindol-3-yl) -4-azaphthalide,
Crystal violet lactone, 3,3'-bis (4
-Diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilino Fluoran, 3
-Diethylamino-6-methyl-7- (o, p-dimethylanilino) fluoran, 3- (N-ethyl-Np-
Toluidino) -6-methyl-7-anilinofluoran,
3-pyrrolidino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7- Anilinofluoran, 3-diethylamino-7- (o-chloroanilino) fluoran,
3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6-methylfluoran, 3-cyclohexylamino-6-chlorofluor Oran.

Further, 3- (N-ethyl-N-cyclohexyl) -6-methyl-7- (p-chloroanilino)
Fluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, 3- [N- (3-ethoxypropyl) -N-ethylamino] -6-methyl-7-
Anilinofluoran, 3- (Nn-hexyl-N-ethylamino) -7- (o-chloroanilino) fluoran, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl- 7-anilinofluoran, 3
-(N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran, 2,2-bis {4-
[6 ′-(N-cyclohexyl-N-methylamino)-
3′-Methylspiro [phthalide-3,9′-xanthen] -2′-ylamino] phenyl} propane and 3
One or more selected from -dibutylamino-7- (o-chloroanilino) fluoran and the like can be used. From the viewpoint of image preservation, 2,2-bis {4- [6 ′-(N-
Cyclohexyl-N-methylamino) -3′-methylspiro [phthalide-3,9′-xanthen] -2′-ylamino] phenyl} propane is particularly preferred.

The developer used in the present invention is not limited to this, but at least one of the following general formulas (I), (II) and (III) It is preferable to contain the compound of formula (I).

The substance of the general formula (I):

Embedded image(However, R₁Is naphthyl group or hydrogen atom, halogen
Atom, lower alkyl group or lower alkoxy group
Y represents a member selected from the substituted phenyl group; ₁Is
The following chemical formula:

Embedded image Represents one member selected from a divalent group represented by the following formula, and n represents an integer of 11 to 30. )

The substance of the general formula (II):

Embedded image (However, Y ₂ is the same as Y _1, m represents an integer of 11-30.)

The substance of the general formula (III):

Embedded image (However, p represents the integer of 14-30.)

Specific examples of compounds used as a color developer in the reversible thermosensitive recording medium according to the present invention are shown below.
These compounds may be used alone or
Mixtures of more than one species may be used.

[0027]

Embedded image

[0028]

Embedded image

[0029]

Embedded image

The length of the long-chain alkyl group of the color developer according to the present invention must be 11 or more, and is 30 or more.
The following is preferred. In that area, 14-21
Is more preferable. If the number of carbon atoms is less than 11, the decoloring ability does not reach a practical level, and if it exceeds 30, the color developing ability may be reduced.

Specific examples of the compound used as a decolorization accelerator in the present invention include oxalic acid diesters (Japanese Patent Application Laid-Open No.
JP-A-4-1583), di (4-methylbenzyl) oxalate (Japanese Patent Publication No. 5-62597), 1,2-bis (m-tolyloxy) ethane (JP-A-60-56588)
JP), diphenyl sulfone (JP-A-60-1566)
No. 7), p-benzylbiphenyl (Japanese Unexamined Patent Publication No.
2382), 1-hydroxy-2-naphthoic acid phenyl ester (JP-A-57-19089),
Dibenzyl terephthalate (JP-A-58-98285), benzyl p-benzyloxybenzoate (JP-A-57-201691), diphenyl carbonate, ditolyl carbonate (JP-A-58-136489), m- Terphenyl (JP-A-57-89994), 1,5-
Bis (p-methoxyphenoxy) -3-oxapentane (JP-A-62-181183), 1,4-bis (p-tolyloxy) benzene (JP-A-2-15378)
No. 3), benzenesulfoanilide (JP-A-58-2).
No. 11493), 2-chloroacetoacetanilide, 4-ethoxymethylsulfonylbenzene, 4-methoxyacetoacetanilide, o-methylacetoanilide, 4-methoxybenzenesulfanilide, 3,4-dimethylacetoanilide, 2-methoxybenzenesulfanilide, [1,4-bis {2- (4-methylbenzyloxy) ethoxy]] benzene. [1,4-bis {2- (4-methylbenzyloxy) ethoxy]] benzene is particularly preferable among the above-mentioned decolorization accelerators.

In the present invention, a conventionally known color developer comprising a phenol or an organic acid and a sulfonyl (thio) urea aromatic compound having no long-chain alkyl group as long as the desired effect is not impaired. Can be used in combination with the developer having a long-chain alkyl group according to the present invention.

These conventional developers are, for example, 2,2-
Bis (4-hydroxyphenyl) propane (bisphenol A), 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,4-bis (1-methyl-1-
(4′-hydroxyphenyl) ethyl) benzene, 1,
3-bis (1-methyl-1- (4'-hydroxyphenyl) ethyl) benzene, dihydroxydiphenyl ether (JP-A-1-180382), benzyl p-hydroxybenzoate (JP-A-52-140483), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (JP-A-60-13)
852), 1,1-di (4-hydroxyphenyl) cyclohexane, 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane (Japanese Unexamined Patent Publication No.
52694), 3,3'-diallyl-4,4'-
Dihydroxydiphenyl sulfone (JP-A-60-208)
286).

Further, N- (p-toluenesulfonyl) -N'-phenylurea, N- (p-toluenesulfonyl) -N '-(p-methoxyphenyl) urea,
-(P-toluenesulfonyl) -N '-(o-tolyl)
Urea, N- (p-toluenesulfonyl) -N '-(m
-Tolyl) urea, N- (p-toluenesulfonyl)-
N '-(p-tolyl) urea, N- (p-toluenesulfonyl) -N'-benzylurea
No. 2061), 4,4′-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane,
4,4'-bis (o-toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (benzenesulfonylaminocarbonylamino) -diphenylmethane, 1,2-bis [4 '-(p-toluenesulfonylaminocarbonyl) Amino) phenyloxy] ethane, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether and 3,3′-
Bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone (as described in JP-A-5-14735)
No. 7).

The heat-sensitive recording layer according to the present invention may further contain waxes and pigments within a range not to impair the effects of the present invention, and usually contains a binder. Known waxes such as paraffin, amide wax, bisimide wax, and metal salts of higher fatty acids can be used. However, the addition of the zinc salt increases the decoloring density as the color is repeatedly formed and decolored, and the erasing of the color image may be incomplete. Therefore, the content of the zinc salt is determined by the dry weight of the heat-sensitive recording layer. Is preferably 1% by weight or less.

Examples of the pigment include inorganic fine particles such as silica, clay, calcined clay, talc, calcium carbonate, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, and surface-treated calcium carbonate and silica. In addition to powder, organic fine powder such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be used.

Examples of the binder include polyvinyl alcohols having various molecular weights, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose and ethylcellulose;
Sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, alginic acid Water-soluble polymer materials such as soda, gelatin, and casein, and polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, and polybutyl methacrylate , Ethylene / vinyl acetate copolymer, and styrene /
Latexes such as butadiene / acrylic copolymers can be used.

In the thermosensitive recording layer of the reversible thermosensitive recording medium obtained by the method for producing a reversible thermosensitive recording medium of the present invention,
Generally, the content of the dye precursor is preferably 5 to 40% by weight of the dry weight of the heat-sensitive recording layer, and the content of the color developer is generally 5 to 50% by weight of the dry weight of the heat-sensitive recording layer. Is preferred. When the content of the color developer is less than 5% by weight, the color developing ability becomes insufficient, and even when it is used in a large amount exceeding 50% by weight, the color developing ability is saturated, and the color forming density and the color erasing density are reduced. There is no particular improvement in the contrast of the image, which may be economically disadvantageous. The content of the decoloring accelerator of the present invention is generally 5 to 50% of the dry weight of the heat-sensitive recording layer.
% By weight. 5 content of decolorization accelerator
If the amount is less than 5% by weight, the effect of promoting decoloration is insufficient.
When used in a large amount exceeding 0% by weight, the color density may be insufficient. Further, within the above range, the weight ratio of (dye precursor / color developing agent of the present invention) can be used at 1/10 to 10/1, preferably 1/4 to 4/1. Further, (decoloring accelerator / developing agent) can be used in a weight ratio of 1/10 to 10/1, but preferably 1/2 to 2/1. In this range, the effect of mixing and dispersing the three components is particularly enhanced.

Further, the heat-sensitive recording layer is formed of a phenol, an organic acid, or a sulfonyl (thio) having no long-chain alkyl group.
When a conventionally known color developer comprising a urea-based aromatic compound is contained, its content is preferably 10% by weight or less of the weight of the heat-sensitive recording layer. Phenols, organic acids,
Alternatively, if the content of a conventionally known color developer comprising a sulfonyl (thio) urea-based aromatic compound having no long-chain alkyl group is more than 10% by weight, the decoloring reaction is inhibited, and the color-developing portion and the decoloring portion May decrease in contrast.

When waxes and pigments are contained in the heat-sensitive recording layer, their contents are 5 to 20% by weight, respectively.
It is preferably from 0 to 50% by weight, and the content of the binder is generally from 5 to 20% by weight.

The support used in the reversible thermosensitive recording medium according to the present invention may be a paper (including acidic paper and neutral paper) which has been used for a conventional thermosensitive recording medium, and a surface coated with a pigment, latex or the like. In addition to coated paper, laminated paper, synthetic paper made of polyolefin resin, plastic films such as polyolefin, polyester, and polyimide, glass plates and conductive rubber sheets can be selected. On at least one surface of such a support, a coating solution containing a mixture of the above-mentioned required components is applied and dried to produce a reversible thermosensitive recording medium. The coating amount is preferably from 1 to 15 g / m ² in a state where the coating liquid layer has dried, 2 to 10 g / m ² is particularly preferred.

In the present invention, an undercoat layer may be provided below the reversible thermosensitive coloring layer. Further, a back layer can be provided on the back surface of the reversible thermosensitive recording medium to prevent blocking at the time of contact between the surfaces, suppress permeation of water or oil from the back surface, and control curl. Further, a coating layer such as a protective layer or a printing layer can be formed on the reversible thermosensitive coloring layer in order to improve heat resistance, printing suitability, and repeated durability of coloring and decoloring.

In the present invention, the reversible thermosensitive recording medium can be further processed in order to increase the added value of the reversible thermosensitive recording medium to give a higher function. For example, adhesive paper, re-wet adhesive paper, delayed-tack paper by applying processing with adhesive, re-wet adhesive, delayed-tack adhesive on the back surface, or reversible heat-sensitive that can be magnetically recorded by magnetic processing It can be a recording medium. In addition, a recording paper capable of recording on both sides can be provided by using the back surface to have a function as thermal transfer paper, inkjet paper, carbonless paper, electrostatic recording paper, and xerographic paper. Of course, a double-sided reversible thermosensitive recording medium can also be used. The device for recording (coloring) and erasing (erasing) images can be selected from thermal heads, thermostats, heating rollers, hot pens, sheet heating elements, laser light, infrared light, etc., depending on the purpose of use. It is not particularly limited to these.

[0044]

The present invention will be specifically described below with reference to examples. Unless otherwise specified, “parts” and “%” represent “parts by weight” and “% by weight”, respectively. <Example 1> A reversible thermosensitive recording medium was prepared by the following operation. (1) Preparation of mixed dispersion A: Ingredients Amount (parts) 2,2-bis {4- [6 '- (N- cyclohexyl--N- methylamino) -3'-methylspiro [phthalide -3,9' -Xanthen] -2'-ylamino] phenyl} propane 20 N- (2-naphthylbenzenesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 3) 20 [1, 4-bis {2- (4-methylbenzyloxy) ethoxy}] benzene 20 polyvinyl alcohol 10% aqueous solution 30 water 10 The above composition was ground using a sand grinder until the average particle size became 1.1 μm.

(2) Formation of a reversible thermosensitive recording layer: 75 parts of the above mixed dispersion A, 30 parts of calcined clay, 2 parts of a 25% paraffin wax emulsion, and 100 parts of a 10% aqueous solution of polyvinyl alcohol were mixed, stirred, and coated. Liquid. This coating solution was applied onto one surface of a support so that the coating amount after drying was 5.0 g / m ^2, and dried to form a reversible thermosensitive recording layer.

(3) Formation of an intermediate layer: 5 parts of a kaolinite clay dispersion (solid content: 60%) and 200 parts of a carboxylic acid-modified polyvinyl alcohol aqueous solution (solid content: 10%) are mixed and mixed, and the mixture is stirred and mixed. A coating solution was prepared. This coating solution was applied on the heat-sensitive recording layer described in the above item (2) so that the coating amount after drying was 1.5 g / m ^2, and dried to form an overcoat layer. (4) Super calendar processing: The thermal recording medium obtained as described above is processed by a super calendar,
The surface smoothness of the thermosensitive recording layer was adjusted to 3000 to 5000 seconds to obtain a reversible thermosensitive recording medium. (5) Formation of overcoat layer: polyester acrylate (Aronics M-8030, manufactured by Toagosei Co., Ltd.) 40
Parts, 40 parts of polyester acrylate (manufactured by Toa Gosei Co., Aronics M-6200) and 20 parts of calcium carbonate (manufactured by Bihoku Powder Chemical Industry, Ryton A) were mixed and stirred, and the mixture was stirred on the intermediate layer described in the above item (3). The coating amount was 2.5 g / m ² . The obtained coating layer was irradiated with an electron beam under the conditions of an oxygen concentration of 300 ppm or less in an electron beam irradiation chamber, an acceleration voltage of 175 kV, and an absorbed dose of 3 Mrad to form an overcoat layer and obtain a reversible thermosensitive recording medium.

(6) Color development and color erasure test: The reversible thermosensitive recording medium thus obtained was subjected to a printing voltage of 21.7 V and a printing pulse of 1.1.7 using a thermal color development tester THPMD manufactured by Okura Electric. Printing was performed under the condition of 0 ms. The print color density was measured with a Macbeth reflection densitometer RD-914. further,
The colored sample was heated using a thermal gradient tester manufactured by Toyo Seiki Co., Ltd. under the conditions of a heating temperature of 100 ° C., a pressure of 1 kg / cm ² , and a heating time of 1 second.
914. Table 1 shows the test results. (7) Storage test: After measuring the print color density in the same manner as in the color test of the above item (6), the obtained color sample was subjected to 50 tests.
The color density after standing for 2 days under a temperature of ° C. was measured in the same manner. At this time, the preservability of the image portion was evaluated by an image preservation ratio: (color density after standing at 50 ° C. for 2 days) / (color density immediately after printing). Table 1 shows the test results. (8) Repeat durability test: The print color density and the color erasing density after repeating the color developing property and the color erasing test of the above item (6) 50 times were measured with a Macbeth reflection densitometer RD-914.
Table 1 shows the test results.

Example 2 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 1. However, when preparing the dispersion A, N- (2-naphthylbenzenesulfonyl) -N'-
Instead of [4- (n-octadecanoylamino) phenyl] urea (Compound No. 3), N- (p-methoxybenzenesulfonyl) -N ′-[4- (n-octadecanoylamino)
Phenyl] urea (Compound No. 2) was used. Table 1 shows the test results. Example 3 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 1. However, when preparing the dispersion A, N
-(2-Naphthylbenzenesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No.
N- (4-hydroxyphenyl) -N'-n-octadecylurea (Compound No. 11) was used in place of 3). Table 1 shows the test results.

Example 4 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 1. However, when preparing the dispersion A, N- (2-naphthylbenzenesulfonyl) -N'-
Octadecylphosphonic acid (Compound No. 17) was used instead of [4- (n-octadecanoylamino) phenyl] urea (Compound No. 3). Table 1 shows the test results. <Example 5> A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 1. However, in preparing the dispersion A,
2,2-bis {4- [6 ′-(N-cyclohexyl-N
-Methylamino) -3'-methylspiro [phthalide-
3,9′-Xanthen] -2′-ylamino] phenyl} propane was replaced by 3-dibutylamino-6-methyl-7-anilinofluoran. Show test results
Shown in 1. Example 6 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 1. However, in preparing dispersion B,
Oxalic acid-di-p-methylbenzyl ester was used instead of [1,4-bis {2- (4-methylbenzyloxy) ethoxy]] benzene. Table 1 shows the test results.

Example 7 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 1. However, over-
The layer was formed as follows. UV-curable vehicle (manufactured by Dainichi Seika Kogyo Co., Ltd., trademark: Seikabeam PPC-
D-9 (revised)｝ with an offset printing machine at 2 g / m ²
After applying with a dry coating amount of 1.2 KW
Using an ultraviolet curing device having one mercury lamp, an overcoat layer was formed by irradiating ultraviolet rays at a distance of 10 cm from the lamp and a transport speed of 15 m / min.
Table 1 shows the test results.

Comparative Example 1 A reversible thermosensitive recording medium was prepared by the following operation. (1) Preparation of Dispersion A: Ingredients Amount (parts) 2,2-bis {4- [6 '- (N- cyclohexyl--N- methylamino) -3'-methylspiro [phthalide -3,9'- Xanthene] -2′-ylamino] phenyl} propane 20 Polyvinyl alcohol 10% aqueous solution 10 Water 70 The above composition was ground using a sand grinder until the average particle size became 1.1 μm.

[0052] (2) Preparation of Dispersion B: Ingredients Amount (parts) N-(2-naphthylsulfonyl benzenesulfonyl) -N '- [4- (n- octadecanoylamino) phenyl] urea (Compound No.3 20) Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was pulverized using a sand grinder until the average particle size became 1.1 μm. (3) Dispersion C Preparation: Ingredients Amount (parts) [1,4-bis {2- (4-methyl-benzyloxycarbonyl) ethoxy}] sand grinder benzene 20 polyvinyl alcohol 10% aqueous solution of 10 water 70 the composition And pulverized until the average particle size becomes 1.1 μm.

(4) Formation of reversible thermosensitive recording layer: 75 parts of solution A, 75 parts of solution B, 75 parts of solution C, 30 parts of calcined clay,
2 parts 25% paraffin wax emulsion and 1
100 parts of a 0% aqueous polyvinyl alcohol solution was mixed and stirred to obtain a coating solution. This coating solution is applied on one side of the support,
The coating was performed so that the coating amount after drying was 5.0 g / m ^2, and the coating was dried to form a reversible thermosensitive recording layer. (5) Formation of a reversible thermosensitive recording medium: In the same manner as in Example 1, an intermediate layer was formed, a super calendering treatment was performed, and an overcoat layer was formed to prepare a reversible thermosensitive recording medium. Table 1 shows the test results. Comparative Example 2 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Comparative Example 1. However, in preparing dispersion B,
N- (2-Naphthylbenzenesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No.
Instead of 3), N- (p-methoxybenzenesulfonyl)-
N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 2) was used. Table 1 shows the test results.

Comparative Example 3 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Comparative Example 1. However, when preparing the dispersion B, N- (2-naphthylbenzenesulfonyl) -N'-
Instead of [4- (n-octadecanoylamino) phenyl] urea (Compound No. 3), N- (4-hydroxyphenyl) -N′-n-octadecylurea (Compound No. 1)
1) was used. Table 1 shows the test results. Comparative Example 4 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Comparative Example 1. However, in preparing dispersion B,
N- (2-Naphthylbenzenesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No.
Instead of 3), octadecylphosphonic acid (compound N
o. 17) was used. Table 1 shows the test results.

Comparative Example 5 A reversible thermosensitive recording medium was prepared by the following operation. (1) Preparation of Dispersion A: Ingredients Amount (parts) 2,2-bis {4- [6 '- (N- cyclohexyl--N- methylamino) -3'-methylspiro [phthalide -3,9'- Xanthene] -2'-ylamino] phenyl} propane 20 N- (2-naphthylbenzenesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 3) 20 Polyvinyl alcohol 10% liquid 20 water 40 The above composition was pulverized using a sand grinder until the average particle size became 1.1 μm.

[0056] (2) Preparation of Dispersion B: Ingredients Amount (parts) [1,4-bis {2- (4-methyl-benzyloxycarbonyl) ethoxy}] benzene 20 polyvinyl alcohol 10% aqueous solution of 10 water 70 the composition Was ground using a sand grinder until the average particle size became 1.1 μm.

(3) Formation of a reversible thermosensitive recording layer: 75 parts of solution A, 75 parts of solution B, 30 parts of calcined clay, 2 parts of 25% paraffin wax emulsion, and 100 parts of a 10% polyvinyl alcohol aqueous solution were mixed. The mixture was stirred to obtain a coating solution. This coating solution was applied onto one surface of a support so that the coating amount after drying was 5.0 g / m ^2, and dried to form a reversible thermosensitive recording layer. (4) Formation of a reversible thermosensitive recording medium: In the same manner as in Example 1, an intermediate layer was formed, a super calender treatment was performed, and an overcoat layer was formed. Table 1 shows the test results.

Comparative Example 6 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Comparative Example 5. However, when preparing the dispersion B, N- (2-naphthylbenzenesulfonyl) -N'-
Instead of [4- (n-octadecanoylamino) phenyl] urea (Compound No. 3), N- (4-hydroxyphenyl) -N′-n-octadecylurea (Compound No. 1)
1) was used. Table 1 shows the test results.

[0059]

[Table 1]

As is clear from Table 1, the reversible thermosensitive recording medium in which the dyes, developers and decolorizing accelerators of Comparative Examples 1 to 4 were each dispersed alone, and the dyes and developers of Comparative Example 5 In the reversible thermosensitive recording medium obtained by mixing and dispersing the two components and using only the decolorization accelerator, after repeated color development and color erasure tests, an increase in color density and a decrease in color erasure were observed. In contrast to the reversible thermosensitive recording media of these comparative examples, the reversible thermosensitive recording media of Examples 1 to 7 using the coating solution in which the dye, the developer and the decolorizing accelerator of the present invention were mixed and dispersed were colored. There is no change in density and it has excellent decoloring properties.

[0061]

The reversible thermosensitive recording medium according to the present invention forms a color image on a white background, has high contrast, and is excellent in image storability. Therefore, the reversible thermosensitive recording medium of the present invention has extremely high practical value.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a temperature and a color density in a cycle of color development and color erasure of a reversible thermosensitive recording medium according to the present invention.

Claims (4)

[Claims] 1. A thermosensitive recording layer containing a colorless or pale color dye precursor and a color developing agent and a color erasing accelerator for reversibly coloring and decoloring the dye precursor, wherein the dye precursor, the color developing agent and A method for producing a reversible thermosensitive recording material, comprising applying a coating solution in which a color accelerator is simultaneously mixed and dispersed onto at least one surface of a sheet-like support, and drying the coating solution to form a thermosensitive recording layer. 2. The developer according to claim 1, wherein the developer has the following general formula (I): (However, R ₁ represents a member selected from a naphthyl group or a phenyl group substituted by a hydrogen atom, a halogen atom, a lower alkyl group and a lower alkoxy group;
₁ is the following chemical formula: Represents one member selected from the divalent group represented by
Represents an integer of 10 to 29. 2. A reversible thermosensitive recording material obtained by the method for producing a reversible thermosensitive recording material according to claim 1, which comprises at least one compound represented by the formula: 3. The developer according to claim 1, wherein the developer has the following general formula (II) in one molecule: (Where Y ₂ is the same as Y ₁ and m represents an integer of 11 to 30). The reversible thermosensitive recording material according to claim 1, comprising at least one compound represented by the following formula: A reversible thermosensitive recording medium obtained by a production method. 4. The developer according to claim 1, wherein the developer has the following general formula (III): The reversible thermosensitive recording medium according to claim 1, wherein p contains at least one compound represented by the following formula (p is an integer of 14 to 30). Record body.