JPH08197844A - Reversible thermal recording material and reversible thermal recording method - Google Patents

Abstract

PURPOSE: To prevent erasing performance from being deteriorated without generating a fog even by repetitive use. CONSTITUTION: A reversible thermal recording material is provided wherein a recording layer containing a pigment precursor becoming a pigment by emitting an electron and a benzoic compound having at least one phenolic functional group, is provided. The recording layer contains preferably a compound having a 12 or more C alkyl group. Thereby, a repeatedly usable reversible thermal recording material and a reversible thermal recording method can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording material and a reversible thermosensitive recording method capable of repeatedly displaying and erasing a visible image.

[0002]

2. Description of the Related Art Magnetic cards and IC cards are used as various types of prepaid cards, but the recorded contents cannot be directly visually inspected, so the payment amount and the remaining amount cannot be easily checked, and the contents are guaranteed to the user. Was difficult. Therefore, a recording material or a recording method capable of visually recording and erasing the recording is being studied.
Above all, a method capable of forming a dye image from the viewpoint of easy viewing is expected.

As a reversible recording material capable of forming a dye image, a recording material in which a leuco dye having a lactone ring portion releases an electron to open the lactone ring to develop a color is known. The reversible recording material has a recording layer with a temperature T
Coloring occurs when heated to 1 and is rapidly cooled to fix the colored state. After heating again to the temperature T2 (T2 <T1),
The color disappears when slowly cooled.

Japanese Unexamined Patent Publication (Kokai) No. 2-188293 discloses a reversible thermosensitive recording medium provided with a recording layer containing a leuco dye, a color-developing / reducing agent that develops or reduces color by thermal reaction, and a binder. Has been done. This publication repeats coloring and erasing by utilizing the difference in reaction rate between acid and base.

Japanese Unexamined Patent Publication (Kokai) No. 4-247985 discloses a reversible thermosensitive recording material provided with a recording layer containing a leuco dye, a developer which is a phosphonic acid having a long chain alkyl group, and a binder as main components. ing. This publication discloses that the color developer has a cohesive force due to its structure, and the color development and the color erasing are repeated by contacting and separating the color developer and the leuco dye.

[0006]

However, since the reversible thermosensitive recording medium disclosed in Japanese Patent Laid-Open No. 2-188293, which is the former, has low print storage performance, recorded prints are erased. Further, when printing and erasing are repeated, the erasing performance deteriorates and the afterimage of the written printing occurs.

In the latter reversible thermosensitive recording material disclosed in JP-A-4-247985, when printing and erasing are repeated, fog occurs and the display surface is colored. Then, the erasing performance is deteriorated and the afterimage of the written print is generated.

As described above, there are problems to be solved in a recording medium capable of repeatedly recording and erasing while forming a dye image.

It is an object of the present invention to provide a reversible heat-sensitive recording material and a reversible heat-sensitive recording method which do not cause fog even after repeated use and do not deteriorate the erasing performance.

[0010]

SUMMARY OF THE INVENTION The gist of the present invention comprises a dye precursor that emits electrons to form a dye, a benzoic acid compound having at least one phenolic functional group, and an aliphatic saturated dicarboxylic acid. A reversible heat-sensitive recording material having a recording layer that The recording layer preferably contains a compound having an alkyl group having 12 or more carbon atoms. The different gist of the present invention is to provide a dye precursor that becomes a dye by emitting electrons, a benzoic acid compound having one or more phenolic functional groups, an aliphatic saturated dicarboxylic acid, and a carbon number of 1
A composition containing a compound having two or more alkyl groups is heated and rapidly cooled to develop a color, and then the colored composition is heated to a temperature lower than the temperature at the time of color development and gradually cooled to erase the color. It is a reversible thermosensitive recording method.

The dye precursor used in the present invention includes:
A leuco dye having a lactone ring in its molecular structure can be used. The leuco dye has a property of emitting an electron and developing a color by opening the lactone ring portion. Further, when electrons are supplied, the lactone ring portion is closed again and the color disappears. The color developed depends on the molecular structure of the leuco dye.

Specifically, crystal violet lactone, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3-
Yl) -4-azaphthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, and 3-diethylamino-6-methyl-
7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 2- (2-chloroanilino) -6-diethylaminofluorane, 2- (2-chloroanilino) -6-dibutylaminofluor Oran, 2-
Anilino-3-methyl-6- (N-ethylisopentylamino) fluorane, 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane, 3-benzylethylamino-6-methyl-7-anilinoflu Oran,
Examples thereof include fluorane compounds such as 3-diethylamino-6-chloro-7-anilinoflurane and 3-methylpropylamino-6-methyl-7-anilinofluorane.

The benzoic acid compound having one or more phenolic functional groups is a color-developing and color-reducing agent that thermally reacts with the dye precursor to develop or reduce color. Specifically, for example, 4- (4
-Hydroxyphenyl) benzoic acid, 4- (4-hydroxyphenoxy) benzoic acid, 2- (4-hydroxybenzoyl) benzoic acid, 2- (4-hydroxy-3-phenylbenzoyl) benzoic acid, 3- (4-hydroxy) Phenyl) benzoic acid, 2- (4-hydroxyphenyl) benzoic acid, 4- (3,4-dihydroxyphenyl) benzoic acid,
4- (2,3-dihydroxyphenyl) benzoic acid, 4-
(2,4-dihydroxyphenyl) benzoic acid, 3-
(3,4-dihydroxyphenyl) benzoic acid, 2-
(3,4-dihydroxyphenyl) benzoic acid, 4- (4
Examples include -hydroxybenzyl) benzoic acid and 4- (4-hydroxybiphenyl) benzoic acid.

Examples of the aliphatic saturated dicarboxylic acid used in the present invention include sebacic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid. , Heneicosanedioic acid, docosanedioic acid, tricosanedioic acid, tetracosanedioic acid, hexacosanedioic acid, triacontanedioic acid, tetratriacontanedioic acid and the like are used.

Examples of the compound having a long chain alkyl group having 12 or more carbon atoms used in the present invention include aliphatic carboxylic acids, aliphatic amides, alcohols, ketones and their derivatives. These are hydroxyl groups as functional groups,
It may have a halogen group or a phenol group. In particular,
For example, lauric acid, hydroxylauric acid, palmitic acid, hydroxypalmitic acid, stearic acid, hydroxystearic acid, dihydroxystearic acid, behenic acid, lauric acid amide, hexadecanoic acid amide, stearyl acid amide, behenic acid amide, lauryl alcohol,
Cetyl alcohol, stearyl alcohol, lauron,
Examples include stearone.

A dye precursor, a benzoic acid compound having at least one phenolic functional group, an aliphatic saturated dicarboxylic acid, and a compound having a long-chain alkyl group having 12 or more carbon atoms are dispersed in a polymer binder. It is applied as a recording layer to a support such as paper, synthetic paper or plastic film.

As the polymer binder, a resin having good transparency and film-forming property and high heat resistance is used. In particular,
For example, polymethacrylic acid ester, polyacrylic acid ester or copolymers thereof, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-alcohol. Copolymer, other vinyl acetate compound, vinyl chloride copolymer, polyvinylidene chloride, vinylidene chloride copolymer, polyvinyl alcohol, polyester, polyamide, polyurethane, polystyrene, acrylonitrile-
Examples thereof include styrene copolymers and acrylonitrile-butadiene-styrene copolymers.

The compounding ratio is 1 for a benzoic acid compound having at least one phenolic functional group per 10 parts by weight of the dye precursor.
0 to 100 parts by weight, preferably 20 to 50 parts by weight, the aliphatic saturated dicarboxylic acid is 10 to 80 parts by weight, preferably 1
0 to 40 parts by weight, 5 to 50 parts by weight, preferably 5 to 30 parts by weight, for compounds having a long-chain alkyl group having 12 or more carbon atoms, and 10 to 200 parts by weight, preferably 20 for binder.
~ 100 parts by weight.

A protective layer may be provided on the recording layer in order to improve durability and matching with the thermal head. Examples of the protective layer include polyethylene terephthalate, polyetherimide, polyetheretherketone, polysulfone, polyphenylene sulfide,
A resin having high heat resistance such as polyacrylate, polyether sulfone, polycarbonate, polyethylene naphthalate, polyimide, acrylic resin, ultraviolet curable resin or electron beam curable resin is preferable.

A stabilizer, a sensitizer, an ultraviolet absorber, a dispersant, etc. are contained in the recording layer in order to improve the heat-resistant storage stability and heat stability of the color-developed state, prevent discoloration / fading by light, and improve sensitivity. Can be made.

The constitution of the reversible thermosensitive recording material of the present invention is shown in FIG.
Shown in On a synthetic resin substrate sheet 1 such as polyethylene terephthalate, a dye precursor, a benzoic acid compound having one or more phenolic functional groups, an aliphatic saturated dicarboxylic acid, and a long-chain alkyl group having 12 or more carbon atoms are contained. A recording layer 2 containing a composition in which the compound described above is dispersed in a polymer binder, and a protective layer 3 are laminated.

The reversible thermosensitive recording material has a temperature T1 under a heating condition of a few msec, such as a thermal head.
When heated up to high temperature, coloration occurs, and when rapidly cooled, the coloration is fixed. In addition, a low temperature T2 for a relatively long time of about 1 to several seconds such as hot stamping and heating rolls.
Decoloration occurs by heating (T2 <T1). That is, reversible image formation is possible by controlling the heating temperature and the heating time.

[0023]

EXAMPLES Examples will be described below, but the present invention is not limited thereto. (Example 1) Liquids A and B shown below were dispersed in a paint shaker for about 2 hours, and then liquid A: liquid B = 1:
The coating liquid was prepared by mixing well in the ratio of 3.

Liquid A Dye precursor: 3-methylisobutylamino-6-methyl-7-anilinofluorane 30 parts by weight Binder: Polymethylmethacrylate 10 parts by weight Solvent: Toluene 150 parts by weight Liquid B One or more phenolic functional groups Benzoic acid compound having: 4- (4-hydroxyphenyl) benzoic acid 30 parts by weight Aliphatic saturated dicarboxylic acid: eicosane diacid 24 parts by weight Binder: polymethylmethacrylate 25 parts by weight Solvent: toluene 200 parts by weight Coating solution thickness 188 μm The surface of the white polyethylene terephthalate resin film was coated with a bar coater and dried to prepare a recording layer having a thickness of 10 μm.
A reversible thermosensitive recording material of the present invention was obtained by applying an ultraviolet curable resin on this to a thickness of 2 μm and curing it with ultraviolet rays to form a protective layer.

(Example 2) Liquids A and B shown below were dispersed in a paint shaker for about 2 hours, respectively, and then A
The coating liquid was prepared by mixing well at the ratio of liquid: liquid B = 1: 3.

Liquid A Dye precursor: 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane 30 parts by weight Binder: polymethylmethacrylate 10 parts by weight Solvent: toluene 150 parts by weight Solution B: 1 phenolic functional group Benzoic acid compound having three or more: 4- (4-hydroxyphenyl) benzoic acid 30 parts by weight Aliphatic saturated dicarboxylic acid: eicosanedioic acid 20 parts by weight Compound having an alkyl group having 12 or more carbon atoms: stearic acid amide 5 parts by weight Binder : Polymethylmethacrylate 25 parts by weight Solvent: Toluene 200 parts by weight A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that the above composition was used.

Example 3 Liquids A and B shown below were dispersed in a paint shaker for about 2 hours, and then A
The coating liquid was prepared by mixing well at the ratio of liquid: liquid B = 1: 3.

Solution A Dye precursor: 2- (2-chloroanilino) -6-diethylaminofluorane 30 parts by weight Binder: polymethylmethacrylate 10 parts by weight Solvent: toluene 150 parts by weight Solution B having one or more phenolic functional groups Benzoic acid compound: 4- (4-hydroxyphenyl) benzoic acid 30 parts by weight Aliphatic saturated dicarboxylic acid: tetradecanedioic acid 18 parts by weight Binder: Polymethylmethacrylate 25 parts by weight Solvent: Toluene 200 parts by weight In addition to using the above composition A reversible thermosensitive recording material was prepared in the same manner as in Example 1.

(Example 4) Liquids A and B shown below were dispersed in a paint shaker for about 3 hours, respectively.
The coating liquid was prepared by mixing well at the ratio of liquid: liquid B = 1: 3.

Solution A Dye precursor: 3-diethylamino-6-methyl-7-anilinofluorane 30 parts by weight Binder: Polyvinyl alcohol 20 parts by weight Solvent: Water 250 parts by weight Solution B Liquid benzoic acid having one or more phenolic functional groups Compound: 4- (4-hydroxyphenyl) benzoic acid 30 parts by weight Aliphatic saturated dicarboxylic acid: dodecanedioic acid 24 parts by weight Binder: polyvinyl alcohol 20 parts by weight Solvent: water 250 parts by weight Examples other than using the above composition A reversible thermosensitive recording material was prepared in the same manner as in 1.

Comparative Example 1 Liquid A Dye precursor: 3-methylisobutylamino-6-methyl-7-anilinofluorane 30 parts by weight Binder: Polymethylmethacrylate 10 parts by weight Solvent: Toluene 150 parts by weight Liquid B Developer : 4-hydroxybenzoic acid 30 parts by weight Aliphatic saturated dicarboxylic acid: eicosanedioic acid 20 parts by weight Binder: polymethylmethacrylate 25 parts by weight Solvent: toluene 200 parts by weight In the same manner as in Example 1 except that the above composition is used. A reversible thermosensitive recording material was prepared.

(Rewrite test) 5 prepared as described above
The reflection density of each type of reversible thermosensitive recording material was measured with a Macbeth reflection densitometer RD-914 to obtain the background density. In addition,
The reflection density of the white polyethylene terephthalate resin film used is 0.06.

After printing on the reversible thermosensitive recording material with a thermal head (0.35 mJ / dot), the reflection density of the printed portion was measured to obtain the printing density. Further, the printed portion was heated with a hot printing plate at 130 ° C. for 10 seconds to erase the print, and the reflection density of the portion where the print was erased was measured to obtain the erase density. Table 1 shows the background density, print density and erase density.

[0034]

[Table 1] As is clear from Table 1, Examples 1 to 4 which are reversible thermosensitive recording materials having a recording layer containing a dye precursor, a benzoic acid compound having one or more phenolic functional groups, and an aliphatic saturated dicarboxylic acid. Has a low background density and can be printed and erased. Among them, carbon number 12
Example 2 containing the compound having the above alkyl group
Shows excellent performance with high print density and low erase density.

Durability was evaluated using the recording materials of Examples 1 to 4. When printing and erasing were repeated about 50 times, there was no particular change in the printing density and the erasing density.

However, Comparative Example 1 has a high background density, and
Printing is possible, but it is not deleted. That is, it does not have reversibility.

[0037]

As described above, according to the present invention, a reversible thermosensitive recording material and a reversible thermosensitive recording method that can be repeatedly used can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a reversible thermosensitive recording material used in the present invention.

[Explanation of symbols]

 1 base material 2 recording layer 3 protective layer

Claims (3)

[Claims] 1. A recording layer containing a dye precursor that emits electrons to become a dye, a benzoic acid compound having at least one phenolic functional group, and an aliphatic saturated dicarboxylic acid. Reversible thermosensitive recording material. 2. The reversible thermosensitive recording material according to claim 1, wherein the recording layer contains a compound having an alkyl group having 12 or more carbon atoms. 3. A dye precursor that emits electrons to become a dye, a benzoic acid compound having one or more phenolic functional groups, an aliphatic saturated dicarboxylic acid, and a compound having an alkyl group having 12 or more carbon atoms. A reversible thermosensitive recording method, which comprises heating and rapidly cooling a contained composition to develop a color, and then heating the colored composition to a temperature lower than a temperature at the time of color development and gradually cooling to erase the color.