JP2002006280A - Thermally reversible multicolor image recording medium which uses heat sensitive shape memory material and method for image formation in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a full-color reversible recording medium in which holding and rewriting of information is possible for many times in the process of thermally reversible recording which uses a cholesteric liquid crystal compound in such a manner that the image information given by adding thermal energy is maintained as a visible image after the energy is removed and that the information can be erased under specified conditions. SOLUTION: A heat sensitive shape memory material layer consisting of a thermally expanding organic material layer and a shape memory resin layer is deposited on a supporting body. The period of the helical structure of a cholesteric liquid crystal layer is varied by changes in the pressure due to deformation of the shape memory material layer transmitted to the adjacent cholesteric liquid crystal layer so as to control interferential color light. Further, by using the hardware techniques such as a conventional thermal head, images with various colors such as multicolor-full-color display and iridescent display can be held at normal temperature and repeatedly rewritten.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a recording medium for forming a multicolor image using a thermally reversible recording medium and a method for forming the image. More specifically, the present invention relates to a thermoreversible multicolor image recording medium for displaying multicolor images used in the fields of magnetic cards, IC cards, boarding passes, labels, etc. for the purpose of decoration, security, and the like, and an image forming method thereof.

[0002]

2. Description of the Related Art In recent years, the information environment has changed drastically due to the rapid spread of computers and the development and expansion of information networks, and the increase in the amount of information and the accompanying increase in information output have accelerated.

[0003] As information output means, print output on paper and display output by a printer are generally used. However, print output uses a large amount of paper as a recording medium. It leads to serious global environmental problems such as global warming. In addition, display output requires a writing / erasing mechanism, electrodes, a circuit board, and the like on a recording medium, and thus has problems in terms of robustness and cost.

[0004] As a new recording medium having the potential to solve these problems, a reversible (rewritable) recording medium is currently in the spotlight.

[0005] Reversible recording media include heat, light, pressure, electricity,
A visible image is formed by applying energy such as magnetism, the image can be retained even if energy is removed, the image can be erased by applying energy again, and the visible image is rewritten many times by repetition Means recording material.

[0006] Among reversible recording media, thermoreversible recording media are the most rapidly developed and practically used in the market. An advantage of the thermal recording method is that a high-precision hardware technology that has been widely used can be used as it is, and a printer that is small and maintenance-free can be easily manufactured.

[0007] The reversible thermal recording technology which has been practically used from the viewpoint of materials is roughly divided into a transparent / opaque type using a reversible change in physical light scattering and a color-forming compound. It is divided into two types: color-developing and decoloring using reversible chemical reactions. In particular, the latter uses a reversible recording medium capable of forming a monochromatic color image such as black or blue on a white background. Currently, research institutes and companies are actively conducting research and development to achieve functionalization and high quality.

On the other hand, cholesteric liquid crystalline compounds that exhibit interference colors based on physical light diffraction are nowadays attracting much attention as new thermoreversible multicolor recording materials because of the possibility of multicolor full color display and iridescent color display. Is taking a bath. This interference color is based on the reflected light due to the molecular arrangement of the cholesteric liquid crystal having a helical periodic structure. When the interference color has a molecular arrangement of helical period = P, the wavelength λ = nPsin θ (here, n Is the average refractive index of the liquid crystal, and θ is only light having a wavelength width dλ = dnPsin θ (dn = anisotropy of the refractive index) centered on the angle formed between the reflected light and the molecular plane, and other wavelengths are selectively reflected. The light in the area is transmitted. Since the helical period P of the cholesteric liquid crystal changes due to heat, pressure, electricity, the presence of impurities, and the like, the wavelength λ of the reflected light can also be changed over the entire visible wavelength range. Therefore, the spiral period P drawn by the molecule
If is controlled by heat and can be fixed reversibly, it is expected to develop as a thermo-reversible recording material for multi-color and full-color display. In addition, the interference color based on the molecular arrangement changes depending on the reading angle, and a so-called iridescent color display can be obtained.

However, the cholesteric liquid crystal compound generally has a problem that a written visible image obtained by heating is erased by removing thermal energy and the image cannot be retained.

[0010]

The problem to be solved by the present invention is to maintain a visible image based on a cholesteric liquid crystal compound after removing heat energy, and more specifically, to provide a multi-color full-color display. In a thermoreversible recording using a cholesteric liquid crystal compound capable of color display of a beetle and a beetle, image information given by applying heat energy is retained as a visible image after energy removal, and heat energy is added again. Accordingly, it is possible to provide a thermally reversible recording method in which the visible image can be erased by repeating the process, and the visible image can be rewritten many times by repetition.

[0011]

Means for Solving the Problems As a result of intensive studies by the present inventors to solve the above-mentioned problems, the present inventors have found out that a pressure change caused by a thermally reversible shape memory material is used.
Reflects light in any visible wavelength range according to a heat-sensitive shape memory material layer composed of at least a thermally expandable organic material layer and a shape memory resin layer, and a pressure generated based on a shape change due to heating of the shape memory material. The object is achieved by providing a thermoreversible multicolor image recording medium comprising a layer made of a cholesteric liquid crystal material and a thermal mode image forming method using the thermoreversible multicolor image recording medium. Was successful.

Hereinafter, the present invention will be described in detail.

According to the present invention, multicolor image recording is performed by changing the interference color of a cholesteric liquid crystal by using a pressure change caused by a heat-sensitive shape memory material, and the image is stored semi-permanently and is rewritable. An object of the present invention is to provide a novel thermosensitive recording medium and an image forming method thereof.

According to the present invention, a heat-sensitive shape memory material composed of a thermally expandable organic material and a shape memory resin is heated based on a shape change caused by heating to an arbitrary temperature Tn (T1 ≦ Tn ≦ T2). By changing the helical period P of the cholesteric liquid crystal according to the pressure and appropriately generating interference colors such as red, green, and blue, a multicolor image can be formed.

In the thermoreversible multicolor image recording medium used in the present invention, a pressure is generated by heating to an arbitrary temperature Tn between T1 and T2, and an interference color change based on the pressure at room temperature is generated. (Image) is stably present, while the image is erased after cooling (normal temperature) by heating to a temperature T3 (T2 <T3) at which the shape memory resin returns to the shape before deformation,
A recording medium having a memory property in which the erased state exists stably is used.

As shown in FIGS. 1, 2 and 3, the thermoreversible multicolor image recording medium has a heat-sensitive shape memory material comprising a heat-expandable organic material and a shape memory resin. Layer comprising a layer containing a light-absorbing substance on a support as necessary, or a reversible layer containing a color-forming compound and a color developer at a minimum. Typical examples include a layer provided with a thermal recording material, but the present invention is not limited thereto. In the image forming method of the present invention, there is no particular limitation as long as temperature conditions for image writing and erasing are given, and thermal heads, laser heating, hot pens, heating rollers, and sheet heating elements that have been widely used so far have been used. Hard technologies such as heating and heating lamps are commonly used. The cholesteric liquid crystal material layer is preferably provided adjacent to the heat-sensitive shape memory material layer so that a pressure change based on a shape change of the heat-sensitive shape memory material layer is easily transmitted.

[Thermosensitive Shape Memory Material Layer] The thermosensitive shape memory material has a layered structure as a thermosensitive shape memory material layer.
It is effective to have a laminated structure of a thermally expandable organic material layer and a shape memory resin layer. Specific examples of the heat-expandable organic material include, for example, paraffin wax, higher fatty acids,
Examples thereof include butyl rubber, silicon rubber, and natural rubber, but are not limited to those listed here, and any material having a large coefficient of thermal expansion can be used as appropriate. These materials can be used alone or in combination of two or more.

These materials are mainly formed by hot melt coating, and the film thickness is 0.01 to 100 μm.
The degree is preferred.

The shape memory resin is a resin which stores the shape of a material at a certain temperature, and shows a phenomenon that when deformed, the material returns to its original shape at a certain temperature. Specific examples include, for example, cross-linked polyolefin, cross-linked fluororesin, trans polyisoprene, polynorbornene, syndiotactic-1, 2-polybutadiene and the like, but are not limited to those listed here. One or more of these materials can be used. Among them, trans polyisoprene and polynorbornene are particularly preferably used.

The shape memory resin is mainly formed by a coating pressure bonding method, and its thickness is preferably about 0.01 to 50 μm.

[Liquid Crystal Recording Layer] As the cholesteric liquid crystal material used in the liquid crystal recording layer, it is necessary to select a cholesteric liquid crystal material compound that reflects light in the visible wavelength range at room temperature. There is no particular limitation as long as it is satisfied, and any known cholesteric liquid crystal compound can be used regardless of low-molecular liquid crystal or high-molecular liquid crystal. Illustrative examples of cholesteric liquid crystalline compounds include halides of cholesterol, cholesterol monocarboxylate, sitosterol monocarboxylate, cholestanol ester of benzoic acid derivative, dicholesteryl dibasic ester, main chain type liquid crystal polymer Compounds, side chain type liquid crystal polymer compounds, rigid main chain type liquid crystal polymer compounds, and the like.

More specifically, for example, cholesteryl chloride, cholesteryl acetate, cholesteryl nonanoate, methyl cholesterol carbonate, ethyl cholesterol carbonate, cholesteryl p-methoxybenzoate, cytosteryl benzoate, cytosteryl p-methyl benzoate, cholesteryl benzoate, 10 , 12
-Docosadiyne dicarboxylic acid cholesteryl ester,
8,12-eicosadiene diacid cholesteryl ester, 4- (7-cholesteryloxycarbonylheptyloxy) phenoxyoctanoic acid cholesteryl ester,
L-glutamic acid-γ-benzyl / L-glutamic acid-
γ-dodecyl copolymer and the like. The compounds are not limited to those shown here, and these cholesteric liquid crystal compounds can be used alone or in combination of two or more. Further, other liquid crystal compounds such as nematic liquid crystal and smectic liquid crystal having no chiral component may be added to these cholesteric liquid crystal compounds. In particular, it is preferable to use a liquid crystal having an excellent response to a pressure change of the heat-sensitive shape memory material layer. For example, it is desirable to use a low-molecular liquid crystal such as cholesteryl chloride, cholesteryl acetate, and cholesteryl nonanoate.

In the present invention, the cholesteric liquid crystalline compound may be used as a molecule dispersed in a binder resin.
The compounding ratio of the liquid crystal compound is preferably set to 15 parts by weight or more with respect to 10 parts by weight of the binder resin. If the compounding ratio is less than 15 parts by weight, the reflected light intensity in the visible region based on the helical period of the cholesteric liquid crystal tends to decrease. As the resin that can be used, the same resin as the resin used for the reversible thermosensitive recording material layer described later can be used, and as the organic solvent that can be used, an organic solvent used for forming the protective layer and the intermediate layer described later is used. Can be done.

[0024] When having a binder resin, the thickness is 1 to 5
0 μm, preferably 5 to 25 μm. In addition, when having no binder resin, 3 to 50 μm,
Preferably, it is 5 to 20 μm. If the film thickness is too small, the intensity of reflected light may be insufficient. Conversely, if the film thickness is too large, it is difficult to change the helical period of the cholesteric liquid crystal.

If necessary, in order to obtain a cholesteric liquid crystal having a uniform alignment state, an alignment film may be provided usually in contact with the liquid crystal. The alignment film can be formed of an organic polymer material such as polyimide, polyvinyl alcohol, polyamide, or polyvinylidene fluoride, a silane coupling agent, or the like. The liquid crystal recording layer is preferably provided adjacent to the heat-sensitive shape memory material layer so that a pressure change based on the shape change of the heat-sensitive shape memory material layer is easily transmitted.

[Support] As the support, paper, synthetic paper, plastic film such as acrylic resin, polycarbonate, polyester, etc., glass plate and the like are used depending on the purpose of use.

[Light Absorbing Material] In the recording medium of the present invention, in order to improve the light absorptivity to laser light and to increase the light-to-heat conversion efficiency, the light absorbing material is disposed adjacent to the heat-sensitive shape memory material layer. It is preferable to include a layer to which one or more kinds are added. The light absorbing material is used, for example, when writing is controlled by light such as a laser, and in some cases, a polychromatic dye is also used. These light-absorbing substances are selected according to the wavelength of the laser light used. When performing the recording process using various laser light wavelengths, corresponding to the wavelength range of the laser light used in the recording process, it is preferable to use a mixture of light absorbing substances so as to exhibit high absorption . Known light-absorbing substances can be used, and specifically, carbon black, azo compounds, azulene compounds, perylene compounds, anthraquinone compounds, phthalocyanine compounds, naphthalocyanine compounds, metal complexes And the like, but are not limited to those listed here.
These materials can be used alone or in combination of two or more.

The light absorbing substance may be added to the heat-sensitive shape memory material layer or may be added to another layer. In the addition of the heat-sensitive shape memory material layer, for example, it is used by dissolving or dispersing in the heat-sensitive shape memory material layer. As another layer, for example, a layer containing a light absorbing substance may be provided in contact with the support. When the light-absorbing substance is provided as an independent layer, the light-absorbing substance is dissolved or dispersed in a resin solution such as an epoxy resin, a silicone resin, an acrylic resin, or a urethane resin, and applied or vapor-deposited. Layers can be made.

[Coloring / Decoloring Type Thermosensitive Recording Layer] When a cholesteric liquid crystalline compound is used for a thermoreversible recording material,
Although it has great potential for multi-color / full-color display and iridescent coloring display, it was selected to improve contrast and improve visibility because the color display is based on the reflected light due to interference of the selected wavelength. Materials that absorb incident light other than the wavelength of the interference color
It is necessary to separately provide the cholesteric liquid crystal on the back surface of the coloring region. In particular, in order to extend the wavelength of the interference color based on the molecular arrangement of the cholesteric liquid crystal over the entire visible wavelength range, it is desirable to provide a black material for improving visibility.

As such an absorbing material, a light absorbing substance such as the above-mentioned carbon black can be used.
In this case, since the absorbing material is also unnecessarily present in the non-image area, the background has a black color or the like, and an image display with low contrast is obtained.

In order to eliminate incident light absorption in a non-image area and obtain a high-contrast image display, a color-developing / decoloring type heat-sensitive recording material containing at least a color former and a color developer must be used. It is effective to apply. Preferably, in order to cope with interference colors in the entire visible wavelength range based on the helical period of the cholesteric liquid crystal, it is useful to use a coloring / erasing type thermosensitive recording material that develops black. That is,
Temperature range where the thermosensitive shape memory material shows a shape change (T1-
A reversible thermosensitive recording material is used in which a monocolor (preferably black) color is formed by heating to T2) and the color is erased by heat treatment to a temperature (T3 or higher) at which the thermosensitive shape memory material returns to its original shape. It is desirable. The coloring / erasing type thermosensitive recording material may also have a function as a light absorbing substance for improving the efficiency of converting light to heat with respect to laser light.

Examples of the color-forming compound that can be used in the reversible thermosensitive recording material layer of the present invention include electron-donating organic compounds such as leuco auramines, diaryl phthalides, polyaryl carbinols, and acyl auramines. , Aryl auramines, rhodamine B lactams,
Examples include indolines, spiropyrans, fluorans, cyanine dyes, crystal violet, and electron-accepting organic compounds such as phenolphthalein.

Further, specific examples of the electron donating organic compound include crystal violet lactone, malachite green lactone, crystal violet carbinol, malachite green carbinol, N- (2,3-
Dichlorophenyl) leuco auramine, N-benzoyl auramine, rhodamine B lactam, N-acetyl auramine, N-phenyl auramine, 2- (phenyliminoethanedylidene) -3,3-dimethylindoline, N
-3,3-trimethylindolinobenzospiropyran,
8'-methoxy-N-3, 3-trimethylindolinobenzospiropyran, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-6-benzyloxyfluoran, 1,2-benz-6-diethylaminofluoran, 3,6-di-p-toluidino-4, 5-dimethylfluoran-phenylhydrazide-γ-lactam, 3-amino-5-methylfluoran, 2-anilino-6- (N-cyclohexyl-N-methylamino) -3
-Methylfluoran, 2-anilino-3-methyl-6-
(N-methyl-N-propylamino) fluoran, 3-
[4- (4-phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluoran, 2-
Anilino-6- (N-methyl-N-isobutylamino)
-3-methylfluoran, 2-anilino-6- (dibutylamino) -3-methylfluoran, 3-chloro-6-
(Cyclohexylamino) fluoran, 2-chloro-6
-(Dibutylamino) fluoran, 7- (N, N-dibenzylamino) -3- (N, N-diethylamino) fluoran, 3,6-bis (diethylamino) fluoran-
γ- (4′-nitroanilino) lactam, 3-diethylaminobenzo [a] -fluoran, and the like. Specific examples of the electron-accepting organic substance include phenolphthalein, tetrabromophenolphthalein, and phenonolphthaleinethyl. Examples thereof include esters and tetrabromophenolphthalein ethyl ester, but are not limited thereto. These can be used alone or in combination of two or more. Among them, a fluoran-based compound which can obtain a black color is particularly preferably used.

In the present invention, a color-developing compound and a color developing agent which become decolored when the interaction increases and become colored when the interaction decreases may be used. For example, among the above-mentioned compounds, cyanine dyes and crystal violet may be in a decolored state when the interaction with the developer is increased, and may be in a colored state when the interaction is decreased.

In the present invention, when the color-forming compound is an electron donating organic substance, phenols, phenol metal salts, carboxylic acid metal salts, sulfonic acid, sulfonate, phosphorus Acids, metal phosphates, acid phosphates, acid phosphates metal salts, phosphorous acids, acid compounds such as metal phosphites, and acid compounds having long-chain aliphatic groups, and color-forming compounds Is an electron-accepting organic substance, examples thereof include basic compounds such as amines. Of these, phenols and phenol metal salts are particularly preferable because they have high color density and stability in a color-developing state and can easily repeat color development and decoloration. Further, a color developer used in combination with a cyanine dye or crystal violet, which forms a decolored state by increasing the interaction with the color-forming compound and a color developing state by decreasing the interaction, includes sulfone. Examples include acids, sulfonates, phosphoric acids, metal phosphates, acid phosphates, metal acid phosphates, phosphorous acid, metal phosphites, and the like. The materials for the color developer are not limited to those listed here, and these materials can be used alone or in combination of two or more.

In the present invention, the compounding ratio of the color developing compound to the color developing agent is such that the color developing compound is added in an amount of 0.1 part by weight to the color developing compound.
It is preferably set to 1 to 100 parts by weight, more preferably 1 to 10 parts by weight. If the developer is less than 0.1 parts by weight, it is difficult to sufficiently increase the interaction between the color former and the developer during recording or erasing. Conversely, if the amount of the developer exceeds 100 parts by weight, the color density in the color-developed state tends to decrease.

In the present invention, a decoloring agent can be contained in the reversible thermosensitive recording medium. The effects of the decoloring agent include effects such as lowering the decoloring density for improving the contrast, improving the decoloring speed, and expanding the decoloring temperature range. The effect of the decoloring agent is particularly effective when the heating means for recording / erasing is such as a thermal head which applies energy in a short time in a pulsed manner. Specific examples of the decoloring agent used in the present invention are shown below, but the present invention is not limited to these, and these decoloring agents can be used alone or in combination of two or more.

The following are specific examples of the decoloring agent. The fatty acid, fatty acid derivative or fatty acid metal salt fatty acid used as the decoloring agent includes a polybasic acid such as a saturated or unsaturated monobasic acid or dibasic acid. Fatty acid derivatives include esters of these fatty acids with monohydric or polyhydric alcohols, as well as amides, anilides, hydrazides, ureides or anhydrides. Metal salts include, for example, sodium, potassium, calcium, magnesium, zinc, iron, nickel, copper salts of these fatty acids. Specific examples of fatty acids include, for example, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, nonadecanoic acid, eicosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, octacosanoic acid, and the like. And dibasic acids such as oleic acid, elaidic acid, linoleic acid, sorbic acid, hexadecandioic acid and octadecanoic acid. Examples of the fatty acid esters include, for example, methyl ester, ethyl ester, propyl ester, butyl ester, hexyl ester,
There are octyl ester, decyl ester, dodecyl ester, tetradecyl ester, hexadecyl ester, octadecyl ester, eicosyl ester, cholesterol ester, and the like. Examples of polyhydric alcohol esters include, for example, monoglyceride, diglyceride, triglyceride of the above-mentioned fatty acid and the like. .

Steroid alcohols (sterols) are also used as decolorizing agents. Specific examples thereof include cholesterol, stegmasterol, pregnenolone, methylandrostenediol, estradiol benzoate, epiandrostene, stenolone, β-sitosterol, and pregnenolone acetate. , Β-cholestanol, 5,16-pregnadien-3β-ol-20
-One, 5-α-pregnen-3β-ol-20-one, 5-pregnene-3β, 17-diol-20-one 21-acetate, 5-pregnene-3β, 17-
Diol-20-one 17-acetate, 5-pregnene-3β, 21-diol-20-one 21-acetate, 5-pregnen-3β, 17-diol diacetate, locogenin, tigogenin, esmilagenin,
Hecogenin, diosgenin and derivatives thereof are exemplified.

Waxes and resin waxes are also used as a decolorizing agent. Specific examples thereof include vegetable waxes such as cadylin wax, carnauba wax, rice wax, wood wax, and animal waxes such as beeswax and whale wax. , Paraffin wax, montan wax, ozokerite, ceresin and other mineral waxes, paraffin wax, microcrystalline wax, petroleum wax such as petroladom, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, modified wax, stearamide, phthalic anhydride There are synthetic waxes such as imides. Examples of paraffins include n-alkanes such as tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonancosane, triacontane, dotriacontane, tetratriacontane, hexatriacontane, octatriacontane, tetracontane, and the like, There is paraffin to do. As fats and oils, for example, soybean oil, coconut oil, linseed oil, lanolin, cottonseed oil, rapeseed oil,
There are castor oil, whale oil, beef tallow, hydrogenated oil and the like.

[0041] Higher alcohols are also used as decolorizers. Specific examples thereof include, for example, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, nanodecyl alcohol,
Examples include eicosyl alcohol, phytol, seryl alcohol, and melisyl alcohol.

Phosphates, benzoates,
Tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, and the like can also be used as phthalic acid esters, oxyacid esters, and phosphoric acid esters. Benzoic acid esters include methyl benzoate, ethyl benzoate, butyl benzoate and the like. Examples of phthalates include dimethyl phthalate, diethyl phthalate, diheptyl phthalate, di-n-octyl phthalate, 2-ethylhexyl phthalate, diisononyl phthalate, octyl decyl phthalate, diisodecyl phthalate, butyl phthalate Benzyl and the like. Examples of the oxyacid esters include methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycole, and tributyl acetyl citrate.

When silicone oil is used as the decoloring agent, a conventionally known one may be used. That is, dimethyl silicone oil, methylphenyl silicone oil, alkyl-modified silicone oil, polyether-modified silicone oil, alcohol-modified silicone oil, fluoro-modified silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil,
Terminal reactive silicone oil and the like.

As the surfactant used as the decoloring agent, any of various conventionally known commercial products can be used.
For example, one or a mixture of two or more commercially available anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, and the like can be used. The surfactants preferably used in the present invention are specifically exemplified by trade names, such as Spamin (manufactured by Miyoshi Oil & Fats), Neoperex (manufactured by Kao), Penest Roll (manufactured by Tokai Sekiyu Kogyo), and Rifnon (manufactured by Tokai Sekiyu Kogyo) , Softamine (Chukyo Yushi), Softex KV (Kao), Light Fix (Kyoeisha Yushi Kagaku Kogyo), Emalox (Yoshimura Oil Chemical), Sopanol (Lion Yushi), Lipomin SA (Lion Yushi), etc. is there.

Further, amines hexylamine, heptylamine, octylamine, decylamine, dipropylamine, N, N-dimethylpropylamine, N-ethyl-N-methylbutylamine, propylenediamine, trimethylenediamine, diphenylamine, N-phenylamine Methyldiphenylamine, N-ethylphenylamine, triphenylamine, phenylenediamine, toluenediamine,
N, N-dimethylphenylenediamine, aminophenylamine, benzylamine, dibenzylamine, tribenzylamine, benzidine, 2,2-dimethylbenzidine, diphenylmethane-4,4′diamine, naphthylamine, N-phenylnaphthylamine, phenyl-β -Naphthylamine, N, N'-sec-butyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, octyldiphenylamine and the like are also used as the decoloring agent.

As the decoloring agent used in the present invention, a liquid crystal compound may be used. As the liquid crystal compound, a conventionally known one, for example, a nematic liquid crystal or a smectic liquid crystal can be used. More specifically, Schiff base type, azo and azoxy type, benzoate ester type, biphenyl type, phenylcyclohexane type, pyrimidine type,
Dioxane, cholesteryl and terphanyl compounds. Therefore, in the temperature range in which the reversible thermosensitive recording material layer comprising at least the color former and the color developer develops, the above-mentioned cholesteric liquid crystal compound that reflects light in the visible wavelength range according to the temperature is decolorized. It may have functions.

Further, the decoloring agent used in the present invention is not limited to the above exemplified compounds, and many compounds can be used. For example, a compound generally used as a plasticizer for a polymer material or a nucleating agent for crystallization can be used. Compounds and the like can be used. Examples thereof include dibenzylidene sorbitols such as p-methyldibenzyldensorbitol, dimethyldibenzylidenesorbitol, p-ethyldibenzylidenesorbitol, condensates of D-sorbitol and benzaldehyde, and higher fatty acid amides.

The amount of the decoloring agent to be added is preferably 1 to 200 parts by weight, more preferably 10 to 100 parts by weight, per 1 part by weight of the coloring compound. If the amount is less than 1 part by weight, a sufficient decoloring effect cannot be obtained. Further, as the compound added as the decoloring agent of the present invention, a compound having a long-chain structure in the molecule may be used. The long-chain structure preferably contains, for example, a saturated hydrocarbon chain having 10 or more carbon atoms.

In the reversible thermosensitive recording material layer of the thermoreversible multicolor image recording medium of the present invention, if necessary, various types of general thermosensitive recording paper used for the purpose of improving coating properties or recording properties can be used. Additives, for example, dispersants, surfactants, polymeric cationic conductive agents, fillers, color image stabilizers, antioxidants, light stabilizers such as ultraviolet absorbers, lubricants, coloring dyes,
A fluorescent dye, a heat insulating agent, a heat storage agent and the like can be added to the recording layer.

The reversible thermosensitive recording material layer of the thermoreversible multicolor image recording medium of the present invention comprises the above-mentioned color former, developer,
As long as a decoloring agent or the like is present, any embodiment may be used. In the present invention, the above-described composition may be carried in a binder resin. The main role of the binder resin in the thermal recording medium is to improve the strength of the recording medium,
The purpose of the present invention is to prevent the reversible thermochromic composition from aggregating due to repetition of coloring and decoloring, and to maintain a state in which the composition is uniformly dispersed. Since the composition is often aggregated by applying heat during color development, it is preferable to use a binder resin having high heat resistance. Examples of such a binder resin include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene-based copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, and polyacryl. Acid esters, polymethacrylic acid esters, acrylic acid copolymers, maleic acid copolymers, polyvinyl alcohol, chlorinated vinyl chloride resins, and mixtures of these binder resins, but are not particularly limited and are known in the art. Any binder resin can be used. These binder resins can be used alone or in combination of two or more.

In the present invention, the compounding ratio of the binder resin is preferably set to 0.01 to 100 parts by weight, more preferably 0.05 to 20 parts by weight, per part by weight of the decoloring agent. This is because when the amount of the binder resin is less than 0.01 part by weight, the strength improvement of the thermosensitive recording medium is small, and when the amount of the binder resin exceeds 100 parts by weight, the color density in a color-developing state tends to decrease.

The thickness of the reversible thermosensitive recording material layer having a binder resin is 1 to 50 μm, preferably 5 to 25 μm. Further, in the case of a thermosensitive recording medium having no binder resin, the thickness is preferably 0.5 to 50 μm. If the film thickness is too small, the resulting reversible thermosensitive recording material layer may have insufficient color density in the color-developed state. Conversely, if the film thickness is too large, a large amount of heat energy is used during recording / erasing. It becomes necessary to perform high-speed recording / erasing.

When the above-mentioned heat-sensitive composition is uniformly dispersed, mixed or dissolved in a binder resin, a melt of the composition or a solution of water or an organic solvent is prepared, and if necessary, other components are added. And dispersing, mixing or dissolving with a binder resin by various dispersion methods. Then, the obtained product is coated on a suitable support to form a thermosensitive recording medium.

The dispersion method used in the present invention includes a mixer method, a sand mill method, a ball mill method, an impeller mill method,
Colloid mill method, three-roll mill method, kneader method, two-roll method, Banbury mixer method, homogenizer method,
A nanomizer method can be used. These dispersion methods are used for the viscosity of a melt or a solution, the use of a heat-sensitive recording medium,
What is necessary is just to select suitably according to a form etc.

Further, the coating method includes spin coating, pull-up coating, air doctor coating, blade coating, rod coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, and transfer coating. It is possible to use a gravure coating method, a kiss roll coating method, a cast coating method, a spray coating method, a curtain coating method, a calendar coating method, an extrusion coating method, an electrostatic coating method, a bar coating method, and the like. These coating methods can be appropriately selected according to the use, form, and the like of the thermosensitive recording medium.

If necessary, a protective layer is formed on the upper surface of the liquid crystal recording layer, an undercoat layer is formed on the upper surface of the support, the liquid crystal recording layer is separated from the protective layer, and the reversible thermosensitive recording material layer is separated from the liquid crystal recording layer. An intermediate layer may be provided between both layers. Furthermore,
A cholesteric liquid crystal material as a reversible thermosensitive recording material may be contained in the protective layer or an intermediate layer provided on the lower surface of the protective layer.

[Protective Layer] In order to prevent the surface from being deformed or discolored by heat and pressure when heat is applied, the protective layer is preferably provided when used many times. It is also effective in transmitting a pressure change due to deformation of the shape memory resin layer to the cholesteric liquid crystal layer without escape. The protective layer has chemical resistance,
It can also have a role of improving weather resistance, water resistance, friction resistance, head matching, and the like. In the protective layer,
Conventionally known resins such as polyvinyl alcohol, styrene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin and urea-formaldehyde resin are used. These may be used alone or as a mixture of two or more kinds. However, it is also possible to add a curing agent to the resin for forming the protective layer, form a layer, and cure the layer after the layer is formed. Further, a film having necessary characteristics for the protective layer may be laminated and used.

In addition, conventionally known ultraviolet curable resins are also preferably used. In addition, as a solvent when using the ultraviolet curable resin, organic solvents such as tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, toluene, and benzene are used. . Note that a photopolymerizable monomer effective as a reactive diluent may be used instead of these organic solvents.

As the ultraviolet-curable resin used for forming the protective layer, all monomers or oligomers (or prepolymers) which are polymerized and cured by irradiation with ultraviolet rays can be used. Examples of such low-molecular compounds include ester acrylate, urethane acrylate, epoxy acrylate, butadiene acrylate, silicon acrylate, and melamine acrylate. The ester acrylate is obtained by reacting a polyhydric alcohol such as 1,6-hexanediol, propylene glycol or diethylene glycol with a polybasic acid such as adipic acid, maleic anhydride or trimellitic acid, and acrylic acid. . The coating method and the coating amount of the protective layer are not particularly limited, but the coating amount is in the range where the coating thickness on the liquid crystal recording layer is 0.1 to 20 μm, preferably 0, from the performance and economy of the protective layer. It is good to set it in the range of 0.5 to 10 μm.

[Undercoat Layer] The undercoat layer is provided for the purpose of improving heat insulation, improving adhesion to the support, improving the resistance of the support to a solvent, and the like. One of the important roles of the undercoat layer is to improve the heat insulation to make the applied heat energy useful for recording and erasure of recording, and to sharpen the color development and erasure by installing the undercoat layer for heat insulation. Can be. The layer of the layer may be formed by coating fine hollow particles of an organic or inorganic material on a support,
Specifically, a fine hollow body having a particle size of about 10 to 50 μm formed of glass, ceramics, or plastic is sufficiently dispersed and mixed in a solvent together with a binder resin, and uniformly coated and dried on a support. good. In addition, the undercoat layer prevents, for example, the developer in the reversible thermosensitive recording material layer from penetrating into the support. Decoloring failure due to the above is prevented, and the provision of the undercoat layer has many advantages in terms of improving the decoloring ability and the degree of freedom in selecting a support. The coating thickness of the undercoat layer is 0.5 to 10 μm, preferably 1 to 5 μm.

[Intermediate Layer] The intermediate layer is provided for various purposes such as improving the adhesion between the liquid crystal recording layer and the protective layer, and preventing the color-forming composition of the reversible thermosensitive recording material layer from migrating to the protective layer. However, since a hardening resin having high heat resistance and high friction resistance is often used for the protective layer in particular, the formation of an intermediate layer for improving the adhesiveness has many advantages. In many cases. As described above, since the intermediate layer is often used for the purpose of improving the adhesiveness, the coating thickness is desirably small, and the general thickness is 0.1 to 5 μm, preferably 0.5 to 5 μm.
３3 μm. The binder resin for forming the undercoat layer and the intermediate layer, in addition to the binder resin described above,
Methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, cellulose acetate, nitrocellulose, polyvinylpyrrolidone,
Gelatin, casein, starch and the like are used.

Specific examples of the organic solvent used for the protective layer, undercoat layer, intermediate layer and other functional layers of the thermoreversible multicolor image recording medium of the present invention include methanol, methanol, and the like.
Alcohols such as ethanol, 1-propanol and 1-butanol, methylene chloride, chloroform, carbon tetrachloride, halogenated aliphatic hydrocarbons such as 1,1,2-trichloroethane, benzene, toluene, o-xylene, p-
Aromatic hydrocarbons such as xylene, m-xylene, monochlorobenzene and dichlorobenzene, tetrahydrofuran,
Ethers such as dioxane and methyl cellosolve; further, ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylformamide, N, N-dimethylacetamide; esters such as methyl acetate and ethyl acetate; Sulfoxide, sulfoxides such as sulfolane and sulfones and the like,
It is not limited to these. These solvents are:
Types or two or more types are used.

When the protective layer, the intermediate layer and the like are formed by coating, it is preferable to select from those which do not dissolve the lower layer.

Next, a method of writing and erasing a multicolor image on the thermoreversible multicolor image recording medium of the present invention will be described, but the present invention is not limited thereto.

(1) To write an image on a thermoreversible multicolor image recording medium, the thermally expandable organic material layer is thermally expanded by heating a thermal head from the front side or irradiating a laser beam from the support side. Due to this expansion force, pressure is applied to the liquid crystal recording layer through the shape memory resin layer, and after cooling (at room temperature), the helical period of the cholesteric liquid crystal of the liquid crystal recording layer is locally changed, and the interference color changes to change the image. Is formed. The heat Tn at the time of writing (T1 ≦
(Tn ≦ T2) is adjusted to be lower than the temperature T3 (T2 <T3) at which the resin of the shape memory resin layer causes shape memory.

(2) The erasure of the image recorded on the thermoreversible multicolor image recording medium is performed by reheating the resin of the shape memory resin layer to a temperature T3 or higher at which the shape memory occurs. At this time, the shape memory resin layer, which once became convex and pressurized the liquid crystal recording layer, returned to the original flat surface by the reheating, and at the same time, the helical cycle of the cholesteric liquid crystal returned to the original state. Information is erased. After erasing,
The image can be written again. As a heat source for erasing, a heater, an infrared lamp, and the like can be used in addition to a thermal head and a laser beam.

[0067]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes the following inventions and embodiments. 1. A heat-sensitive shape memory material layer comprising a thermally expandable organic material layer and a shape memory resin layer on a support, and light in an arbitrary visible wavelength range according to a pressure generated based on a shape change of the heat-sensitive shape memory material layer. And a cholesteric liquid crystal layer that reflects light. 2. 2. An image forming method, wherein a thermal head is used for writing and recording on the recording medium according to 1. 3. 2. The thermoreversible multicolor image recording medium according to the above item 1, wherein a light-absorbing substance is contained in the heat-sensitive shape memory material layer or in a layer adjacent to the heat-sensitive shape memory material layer. 4. 3. In the writing record on the recording medium described,
An image forming method using a laser beam. 5. Adjacent to the heat-sensitive shape memory material layer, the heat-sensitive shape memory material layer develops a color in a temperature region showing a shape change,
2. The thermoreversible multicolor image recording medium according to the above item 1, comprising a reversible thermosensitive recording material layer comprising at least a color former and a color developer. 6. 6. An image forming method, wherein a thermal head or a laser beam is used for writing and recording on the recording medium according to the above item 5.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples. In the examples, “parts” means “parts by weight”.

Example 1 On a glass plate, 10 parts of polyethylene oxide was dissolved in 100 parts of tetrahydrofuran, 5 parts of carbon black was dispersed therein, spin-coated, and formed into a film having a thickness of about 0.1 μm. Hot melt coated saturated fatty acid to a thickness of about 2 μm, and trans-polyisoprene of a thickness of about 0.5 μm is coated thereon and pressed.
A heat-sensitive shape memory material layer was formed. Then 1.98 parts of cholesteryl chloride and 4.02 parts of cholesteryl nonanoate were added to 12 parts of methyl ethyl ketone and 12 parts of toluene.
The solution obtained by dissolving in a mixed solvent was applied to form a film having a thickness of about 3 μm after drying, and a 3.5 μm-thick polyetheretherketone film was further laminated thereon as a protective layer. At 150 ° C. to obtain a thermoreversible multicolor image recording medium sample.

Next, writing and recording of the sample with a semiconductor laser beam were performed at a laser output of 10 mW for 50 nanoseconds. As a result, at normal temperature (24 ° C.), the image area was observed from directly above the sample. It was confirmed that a multicolor display was formed in which the interference color was green and the non-image area was red. When the viewing angle with respect to the sample was set to be oblique from directly above, the interference color was shifted to blue in both the image area and the non-image area, and so-called iridescent coloring was obtained.

Further, when this sample was heat-treated at 150 ° C., the image information was erased, and it was confirmed that the sample could be used repeatedly. This method was excellent as an image forming method for beetle color display using a thermoreversible multicolor image recording medium. Was confirmed.

Example 2 In Example 2, the following compounds were used.

Embedded image Compound 1

Embedded image Compound 2

[Solution I] Compound 1 10 parts Vinyl chloride / vinyl acetate copolymer 5 parts (Slek A manufactured by Sekisui Chemical Co., Ltd.) Toluene 30 parts Methyl ethyl ketone 10 parts [Solution II] Compound 2 10 parts Saturated polyester resin 10 parts (Toyobo Co., Ltd.) Byron 200) Toluene 30 parts Methyl ethyl ketone 10 parts [Solution III] methacrylic resin 10 parts (BR-60 manufactured by Mitsubishi Rayon Co., Ltd.) Calcium carbonate 10 parts Toluene 40 parts

The components I, II and III were dispersed in a sand mill for 2 hours to obtain a uniform dispersion. 3 parts of the dispersion liquid I and 20 parts of the liquid II were uniformly mixed to prepare a coating liquid.

The coating solution was applied onto a 200-μm-thick white PET sheet so that the film thickness after drying was about 6 μm, and dried to obtain a color-developing / decoloring type thermosensitive recording layer. Subsequently, the dispersion III was dried to a thickness of about 2 μm after drying.
m and dried to form an intermediate layer.

Further, a C24 n-paraffin wax was hot-melt-coated to a thickness of about 3 μm on the film, and after forming a film, a polynorbornene film having a thickness of about 0.5 μm was applied and pressed to form a heat-sensitive shape memory material layer. .

Next, cholesteryl chloride 1.98
Of cholesteryl nonanoate, 4.02 parts of cholesteryl nonanoate, was dissolved in a mixed solvent of 12 parts of methyl ethyl ketone and 12 parts of toluene, and this was applied on the intermediate layer and dried to a thickness of 3 μm.
m of a liquid crystal recording layer, and a protective layer on top of the liquid crystal recording layer.
By laminating a 5 μm thick polyetheretherketone film, a thermoreversible multicolor image recording medium sample was obtained. After heating this sample to 140 ° C.,
(° C.), a sample having a white surface over the entire surface was obtained.

The sample in this state has a tip of about 85 ° C.
When printing was performed using a thermal head of normal temperature (23
(° C.), the printed portion shows a bluish-green color when observed from directly above the sample, and printing was continued using a thermal head with the tip at about 95 ° C., and at normal temperature (23 ° C.) It was confirmed by observation from directly above the sample that the printed portion exhibited a blue color. As a result, since the non-printed portion remained white, a high-contrast multicolor display was obtained. When stored at room temperature (23 ° C.) for three months, the change in the multicolor display was not observed at all and was stable. Next, when the printed sample was passed between hot rolls having a roll temperature of 140 ° C., the multicolor display was erased, and the original entire white state was restored. When the same printing and erasing were repeated again, it was confirmed that there was reproducibility, and it was an excellent multicolor image forming method using a thermoreversible recording medium to which hardware technology such as a conventional thermal head can be applied. It was confirmed that it was.

From the above results, it has been widely used in multicolor image formation recording using a thermally reversible pressure variable material and a cholesteric liquid crystal compound capable of multicolor / full color display and iridescent color display. It can be seen that a high-quality image can be held at room temperature and a thermally reversible recording method can be provided by using the thermal head or semiconductor laser as it is.

[0079]

According to the present invention, it is possible to hold a multicolor image such as a multi-color full-color display or an iridescent color display at room temperature by using a conventional hardware technology such as a thermal head. And a reversible recording medium and an image forming method thereof can be provided.

[Brief description of the drawings]

FIG. 1 shows the configuration of a typical thermoreversible multicolor image recording medium according to the present invention.

FIG. 2 shows a configuration of a typical thermoreversible multicolor image recording medium according to the present invention.

FIG. 3 shows a configuration of a typical thermoreversible multicolor image recording medium according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 support 2 light-absorbing substance layer 3 thermally expandable organic material layer 4 shape memory resin layer 5 liquid crystal recording layer 6 protective layer 7 cholesteric liquid crystal compound 8 thermoreversible multicolor image recording medium 9: heat-expandable organic material layer containing a light-absorbing substance 10: shape memory resin layer containing a light-absorbing substance 11 ... binder resin 12 ... undercoat layer 13 ... color-developing / decoloring type thermosensitive recording layer 14 ... intermediate layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B41M 5/26 102

Claims (6)

[Claims] 1. A heat-sensitive shape memory material layer comprising a heat-expandable organic material layer and a shape-memory resin layer on a support, and an arbitrary pressure depending on a pressure generated based on a change in shape of the heat-sensitive shape memory material layer. A thermoreversible multicolor image recording medium comprising a cholesteric liquid crystal layer that reflects light in the visible wavelength range. 2. An image forming method, wherein a thermal head is used for writing and recording on the recording medium according to claim 1. 3. The thermoreversible multicolored color according to claim 1, wherein a light-absorbing substance is contained in the heat-sensitive shape memory material layer or in a layer adjacent to the heat-sensitive shape memory material layer. Image recording medium. 4. An image forming method according to claim 3, wherein a laser beam is used for writing and recording on the recording medium. 5. A reversible heat-sensitive material comprising at least a color-forming compound and a color developer, which is adjacent to the heat-sensitive shape memory material layer and develops a color in a temperature region where the heat-sensitive shape memory material layer changes its shape. A thermoreversible multicolor image recording medium comprising a recording material layer. 6. An image forming method using a thermal head or a laser beam for writing and recording on a recording medium according to claim 5.