JPH02188294A - Reversible thermosensitive recording medium - Google Patents

Abstract

PURPOSE:To chemically carry out a color development and discharging only under thermal energy control by using a color developer/subtracter consisting of salts of gallic acid and higher aliphatic amine expressed by a special formula. CONSTITUTION:A recording medium consists of a recording layer based on a leuco compound and a color developer/subtracter which develops or substracts colors by thermal reaction with the leuco compound, and a binder. The color developer/subtracter is salts of gallic acid and aliphatic amine expressed by formula (R is an alkyl group with eight or more carbons). More clearly, the binder is allowed to be dissolved in a coating liquid dispersed uniformly in water or an organic solvent. In addition, thickener or white pigment as liquid quality improver is added to this solution to prepare a recording layer coating liquid. This liquid is applied to a support such as paper, plastic film or sheet, and then dried to provide a recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image forming material. More specifically, the present invention relates to a reversible thermosensitive recording medium that performs image formation and erasing using differences in thermal energy.

<Prior art and problems to be solved by the invention> Conventionally,
For reversible image materials, see JP-A-58-191190.
No. 60-193691, U.S. Patent Specification 36
66525, "Japanese Patent Publication No. 119377/1983, 39377/1986, 41186/1986", U.S. Patent No. 4,028,118, 1986, 8115/1986
No. 7, and JP-A-50-105555.

However, U.S. Patent Specification No. 4028118,
81157 and Japanese Patent Application Laid-Open No. 50-105555, the image formed changes depending on the temperature, so there is no memorability of the image;
JP 60-193691, U.S. Patent Specification No. 3665
The recording layer described in No. 25 is provided with a recording layer consisting of a color former, a color developer, and a binder, and in some cases, a low vapor pressure solvent or a heat-melting substance is added.
The color is developed using thermal energy, and the color is erased with water, steam, or some type of press solvent. Coloring and decoloring are not repeated only by controlling thermal energy.

JP-A-54-119377, JP-A-63-39377
JP-A No. 63-41186 has a heat-sensitive layer whose main components are a resin matrix and an organic low-molecular substance dispersed in the resin matrix. In the recording method, the transparency of the heat-sensitive layer is reversibly changed by controlling thermal energy to form and erase images. That is, image formation and erasing are not performed by chemically developing and erasing colors.

As described above, conventional techniques do not provide systems that chemically develop and decolorize only by controlling thermal energy.

An object of the present invention is to provide a reversible fever recording medium with memory properties that chemically develops and decolors only by controlling thermal energy, which is not available in the prior art.

<! ml! Means for Solving the Problem> The reversible thermosensitive recording medium of the present invention mainly comprises a leuco compound, a color developer/reducer that thermally reacts with the leuco compound to develop or reduce color, and a binder. A recording medium provided with a recording layer as a component, the color developer and subtractor having the general formula (
1) (However, R represents an alkyl group of C1 or more.) Characterized by being a salt of gallic acid and an aliphatic amine, it can be chemically colored and discolored by controlling thermal energy. The purpose of the present invention is to provide a reversible thermosensitive recording medium.

<Operation> The principles of recording, ie, image formation and erasing, of the recording medium of the present invention are as follows. Colorless leuco dyes and phenolic compounds change color from colorless to colored when the lactone ring of the colorless leuco dye is opened by heat energy. but,
When a colored compound with an open lactone ring contacts a basic substance, the ring closes and returns to the original colorless compound with a lactone ring. A compound formed into a salt by a combination of gallic acid as a phenolic compound and a certain specific compound of an alkyl amine as a basic compound, that is, a color developer and subtractor, can open the lactone ring of a colorless leuco dye by simply controlling thermal energy. It can be ringed to form a colored compound, or it can be ring-closed to return to a colorless leuco form. This phenomenon is due to the structure of the color developer and the reversibility of the leuco dye. That is, as mentioned above, the color developing agent is an amine salt having a phenolic hydroxyl group, and in order to exhibit acidic properties or basic properties by the action of heat, it is used for leuco dyes.
This is because it acts as a color developer or a color reducing agent.

The recording medium of the present invention, which is provided with a recording layer made of a colorless leuco dye and a salt of gallic acid and an alkylamine as a developer and subtractor, forms a colored image using thermal energy (hl). This image can be erased by another thermal energy (h2), and when thermal energy (hl) is applied to the image forming body from which the image has been erased, an image is formed again. Formation and erasure of this image can be repeated any number of times. This image forming body maintains an image forming state or an image erasing state unless thermal energy is applied to it. After the formed image is erased, the background does not retain any traces of the formed image (it is a plain white reversible recording medium).

The color developing and reducing agent of the present invention is a salt of gallic acid and an aliphatic amine represented by the general formula (wherein R represents an alkyl group of C1 or more), and specific examples of the aliphatic amine include hexylamine , heptylamine, octylamine, nonylamine, decylamine, undecylamine, laurylamine, tridecylamine, tetradecylamine, pentadecylamine, cetylamine, heptadecylamine, stearylamine, and the like.

Specific examples of the color forming agent of the present invention, that is, leuco dye, include crystal violet lactone, 3-
Indolino-3-P-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 2-(2-fluorophenylamino)-
6-Dinithylaminofluorane, 2-(2-fluorophenylamino)-6-d-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5-methyl-7-t -butylfluorane, 3-diethylamino-6-methyl-7
-anilinofluorane, 3-diethylamino-6-methyl-7-P-butylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-anilino-
3-Methyl-6-(N-ethyl-P-toluidino)-fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3- Pyrrolidino-7-cyclohexylaminofluorane, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluorane, 3-N-ethylpentylamino-6-methyl-7-anilinofluorane, etc. Can be done.

Further, in the present invention, a commonly used polymeric material that dissolves in water or an organic solvent can be used as the binder. Please give specific examples: haorivinyl alcohol, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl chloride, linear saturated polyester, mono or copolymers of meccrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyurethane, polybutyral. , thermoplastic resins such as nitrocellulose can be used.

Next, in the method of coating the recording layer on the support in the present invention, specifically, the binder is dissolved in a coating liquid uniformly dispersed or dissolved in water or a Wi solvent, and if necessary, A recording layer coating solution containing a thickener, white pigment, etc. as a liquid property improver is applied onto a support such as paper, plastic film or sheet by bar coating, blade coating, air knife coating, gravure coating, or roll coating. A recording layer is provided by coating and drying by a coating method such as coating.

Furthermore, on the recording layer of the present invention, which is composed of a leuco dye, a developer, and a binder, it is possible to improve the thermal head matching property (resistance adhesion to the thermal head, sticking) or to improve the durability of the recording layer. Even if a protective layer is provided for the purpose of imparting properties, the characteristics of the recording medium of the present invention will not be impaired.

For example, as a component of the protective layer, a combination of a filler such as a colorless inorganic pigment or wax and a thermoplastic resin, a thermosetting resin, or an ultraviolet curing resin used for the binder of the recording layer is used.

The image forming or image erasing method according to the present invention is based on heat, and uses a thermal printer, a heat reflection copying device,
This can be carried out using a device such as a hot stamper or a hot roll.

Hereinafter, the present invention will be specifically explained with reference to Examples.

In addition, "1 part" in the examples indicates parts by weight.

Example I Solution A Solution B The above components A solution and B solution were separately ground and dispersed in a sand mill for 1 hour, and then these dispersions were added to 1 part of solution A.
The recording layer coating solution was prepared by thoroughly mixing 4 parts of liquid B on a subtable. This coating solution was applied onto 608/rrl high-quality paper using a Mayer bar so that the dry weight was 6 g/rrf, and dried to produce a reversible thermosensitive recording paper free from background fog.

The recording paper produced in this way was printed using a Toshiba thermal simulator (printing conditions: applied power 0.40 w/dat,
A clear and high-density blue print image was obtained by printing using a 2.5ms ON/0FF pulse.Next, the entire surface was pressed for 1 second with a thermal printing board heated to 120°C. After that, the printed image was erased and the recording layer returned to its original white state. When similar printing and erasing were carried out again, it was confirmed that there was reproducibility and that the medium was extremely excellent as a reversible thermosensitive recording medium.

Example 2 Solution A The above components A and B were separately ground and dispersed in a ball mill for 20 hours. Thereafter, these dispersions were sufficiently mixed in a ratio of 2 parts of Liquid A to 5 parts of Liquid B to prepare a recording layer coating liquid. This coating solution was applied to 60 g/n (high quality paper) using a Mayer bar so that the dry weight was 7 g/rrl, and dried to produce a reversible thermosensitive recording paper free from background fog.

The thus produced reversible thermosensitive recording paper was repeatedly printed and erased in the same manner as in Example 1, and its effects were confirmed.

However, the hue of the print is clear and highly concentrated black.

Example 3 Liquid A, B, and C were uniformly dispersed in advance in a sand mill for 2 hours. 3 parts of liquid A and 20 parts of liquid B were uniformly mixed and recorded. A layer coating solution was prepared.

This coating solution was coated on a 188 .mu.m white polyester sheet using a bar coater so as to have a dry film thickness of 6 .mu.m, and dried to form a recording layer. A reversible thermosensitive recording sheet was prepared by coating the recording layer with pre-dispersed liquid C using a bar coater so as to have a dry film thickness of 3 μm, and drying to form a protective layer.

This recording sheet had high whiteness with no background fog.

The recording sheet produced in this way is manufactured by Toshiba - Marchemirator (printing conditions: applied power 0.45W/dot).
, 2.5 ms 0N10FF) during the pulse, a clear and high-density (reflection density: 1.5) black print image was obtained. The printed image was erased when it was passed through a hot roll machine, and the recording sheet returned to its original white state.

When the same printing and erasing operations were repeated, it was confirmed that there was good reproducibility and that the medium was extremely excellent as a reversible thermosensitive recording medium.

<Effects of the Invention> The reversible fever recording medium of the present invention easily forms and erases images only by controlling thermal energy, and is a system that chemically develops and erases color.

Therefore, it is possible to form high contrast and clear images,
Various hues can be created by changing the leuco compound.

Image formation and erasing can be repeated many times. Therefore, it can be used not only for displays and electronic blackboards, but also as a balance display medium for cards that require counterfeit prevention, prepaid cards, and the like.

Patent applicant Toppan Printing Co., Ltd. Representative: Kazuo Suzuki

Claims (1)

[Scope of Claims] A recording medium provided with a recording layer on a support, the main components of which are a leuco compound, a developer and a binder that develop or reduce color by thermally reacting with the leuco compound, , the color developing and reducing agent is gallic acid represented by the general formula (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(1) (However, R represents an alkyl group of C_■ or more.) A reversible thermosensitive recording medium that can be colored or erased by the difference in thermal energy, which is characterized by being a salt of and a higher aliphatic amine.