JPH07117352A - Reversible thermal recording medium - Google Patents

Abstract

PURPOSE:To prevent the lowering of the contrast of an image and to enhance repeated durability even when the formation-erasure of an image is repeatedly performed by a heating means applying heat and pressure at the same time in a reversible thermal recording medium performing the formation/erasure of an image by utilizing a transparency change or color forming reaction. CONSTITUTION:In a reversible thermal recording medium wherein a thermal layer reversibly generating a transparency-opacity change or a color forming- erasing change by changing heating temp. is provided on a support and a protective layer is further provided on the thermal layer, the protective layer has recessed and projected parts and the thermal layer is provided in the recessed parts.

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 medium, and more particularly, it is a reversible thermosensitive recording medium capable of repeatedly forming and erasing an image by utilizing a change in transparency or a coloring reaction with temperature. The present invention relates to a thermal recording medium.

[0002]

2. Description of the Related Art In recent years, reversible thermosensitive recording media have attracted attention because they can temporarily form images and can erase the images when they are no longer needed. As a typical example, the glass transition temperature (Tg) is from 50 to 60 ° C. to 8
A reversible thermosensitive recording medium in which an organic low molecular weight substance such as a higher fatty acid is dispersed in a resin base material such as a vinyl chloride-vinyl acetate copolymer having a low glass transition temperature of less than 0 ° C. is known (special feature: JP-A-54-119377, JP-A-55-1
54198 and the like).

When a heat roller, a hot pen or the like is used as a heating method for image formation and erasing, and only heat is applied without applying much pressure, repeated image formation-
Even if it is erased, there is no problem in durability. However, when pressure is applied using a thermal head, etc., and heating is performed simultaneously, the resin base material around the organic low molecular weight substance particles changes during repeated image formation and deletion, and the finely dispersed organic low molecular weight substance There is a drawback that the particles gradually become larger in size, the effect of scattering light is lessened, the opacity is lowered, and finally the image and the contrast are lowered.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks and is transparent-opaque and color-dependent depending on temperature.
In a reversible thermosensitive recording medium whose decoloring changes reversibly,
It is an object of the present invention to provide a reversible thermosensitive recording medium in which the contrast of an image is less deteriorated even when image formation and erasing are carried out by using a heating means for applying heat and pressure at the same time, and moreover, the repeating durability is improved. is there.

[0005]

According to the present invention, a heat-sensitive layer which reversibly causes a transparent-opaque change or a color-decoloring change depending on temperature on a support, and further a heat-sensitive layer thereon. In a reversible thermosensitive recording medium provided with a protective layer for protecting the thermosensitive layer, a reversible thermosensitive recording medium characterized in that a surface of the protective layer on the support side is provided with irregularities and a thermosensitive layer is provided in the concave portion. Provided. Also provided is the reversible thermosensitive recording medium, wherein the protective layer is a heat-resistant sheet,
In particular, the reversible thermosensitive recording medium is characterized in that a non-adhesive portion is provided between the thermosensitive layer provided on the heat resistant sheet and the support. Further, there is provided the reversible thermosensitive recording medium characterized in that an adhesive layer is provided between the support and the thermosensitive layer.

That is, the inventors of the present invention provided a reversible thermosensitive recording medium having a thermosensitive layer on which a transparent-opaque change or a color-erasing change reversibly occurs depending on temperature. As a result of diligent studies, by providing the heat-sensitive layer having the above-described structure, a reversible heat-sensitive recording medium having improved durability against repeated image formation-erasing by heating means for simultaneously applying pressure from a thermal head and the like is obtained. The present invention has been completed and the present invention has been completed.

The present invention will be described in more detail below with reference to the accompanying drawings. First, the reversible thermosensitive recording layer of the present invention and a conventional reversible thermosensitive recording medium are shown in the drawings. Figure 3
(A) is a conventional reversible thermosensitive recording medium. Figure 4
The reversible thermosensitive recording medium of the present invention comprises a support, a protective layer provided with irregularities, and a thermosensitive layer provided in the depressions. Figure 5
(B) is a reversible thermosensitive recording medium of the present invention in which a heat-sensitive layer is provided on the uneven surface of a heat-resistant sheet, and the surface having the heat-sensitive layer and a support are bonded together. FIG. 6 shows a reversible thermosensitive recording medium of the present invention which is laminated in the same manner as in FIG. 5B and has a non-adhesive portion containing air between the thermosensitive layer and the support.

The present invention will be described more specifically. Figure 3
The conventional reversible thermosensitive recording medium shown in FIG.
As shown in (b), the resin base material of the heat-sensitive layer is deformed by the heat and pressure by the heating means such as a thermal head, the organic low-molecular substance dispersed in the heat-sensitive layer is expanded, and the repeated durability is lowered. Resulting in.

In the reversible thermosensitive recording medium of the present invention shown in FIG. 4, a thermosensitive layer is provided in a grid pattern on a support, and a protective layer is provided in a space between the grids. Is absorbed by the lattice of the protective layer and the pressure applied to the heat-sensitive layer can be reduced, so that the deformation of the resin is small, the organic low molecular weight substance is maintained as fine particles, and the heat and pressure of the thermal head etc. are applied at the same time. It is possible to improve the durability against repeated image formation and erasing by the heating means.

The reversible thermosensitive recording medium of the present invention shown in FIG. 5 (b) is provided with a thermosensitive layer in the concave portions of the grid-shaped irregular surface of the heat-resistant sheet, and is supported as shown in FIGS. 5 (a) and 5 (b). It is a laminate of the body and the heat-resistant sheet surface with the heat-sensitive layer, and the protrusion of the heat-resistant sheet absorbs the pressure of the heating body to prevent the particles of the organic low-molecular substance in the heat-sensitive layer from expanding, so that the durability is repeated. Is improved. Further, the reversible thermosensitive recording medium shown in FIGS. 4 and 5 (b) has an adhesive layer provided between the support and the thermosensitive layer, so that the adhesiveness between the support and the thermosensitive layer can be improved. .

Further, the thermosensitive recording medium shown in FIG. 6 has a non-adhesive portion provided between the thermosensitive layer and the support. Since the non-adhesive portion has air inside, the non-adhesive portion serves as a heat insulating layer. , Thermal sensitivity is improved. In addition, the non-adhesive area also serves as a cushion, and even if the thermal head is pressed and pressed, the pressure actually applied to the heat-sensitive material will be low. Repeated durability can be improved without expansion of the particles of the molecular substance.

The size of the space of the protective layer such as the heat-resistant sheet is
1 μm or more and 10 mm or less are preferable, and 2 μm or more, 1
mm or less is more preferable. If the space is too large, the role of protecting the heat-sensitive layer becomes difficult and the repeated durability becomes poor. If the space is too small, the contrast will be low. The space ratio of the protective layer such as the heat-resistant sheet is preferably 10 to 90%, more preferably 20 to 70%. If the proportion of the space is too large, the role of protecting the heat-sensitive layer becomes difficult, and the repeated durability becomes poor. If the space ratio is too small, the contrast becomes low.

A protective layer (thickness 0.1 to 0.1) laminated on the heat-sensitive layer.
10 μm), silicone rubber, silicone resin (described in JP-A-63-221087),
Polysiloxane graft polymer (JP-A-63-317)
No. 385), an ultraviolet curable resin or an electron beam curable resin (described in JP-A-2-566), or a phosphazene resin (Japanese Patent Publication No. 5-92658).

In the present invention, when a heat-resistant sheet is used as the protective layer, it may have any shape, but a shape that disturbs light (for example, a material having a large number of irregularities or an irregular shape) is provided on the heat-sensitive layer. Then, the background becomes cloudy and the transparency decreases, so that the less uneven the object, the better the transparency, and the better the transparency, the better. The material of the heat resistant sheet is preferably at least one kind of sheet selected from polyethylene terephthalate, fluorine-containing polymer, polysulfone, polyethylene naphthalate, polyphenylene sulfide, polyarylate, polyimide and polyamide. In addition to the above, a heat resistant sheet having a softening point of 100 ° C. or higher is preferable. Furthermore, the transparent sheet is more preferable than the colored sheet, because the transparent sheet has a higher contrast when it changes from transparent to cloudy.

In the present invention, the protective layer may be provided by providing a convex heat-sensitive layer on a support and then applying and drying a protective layer-forming coating solution from the heat-sensitive layer, or Another method is to provide a heat-sensitive layer in the concave portion of the heat-resistant sheet on the side of the support and to bond the support and the surface of the heat-resistant sheet provided with the heat-sensitive layer. When a protective layer is formed by coating, a solvent is used, but it is desirable that the solvent is difficult to dissolve the resin of the heat sensitive layer and the organic low molecular weight substance. As a solvent in which the resin of the heat sensitive layer and the organic low molecular weight substance are difficult to dissolve, n-hexane, methyl alcohol,
Examples thereof include ethyl alcohol and isoproyl alcohol, and alcohol-based solvents are particularly preferable in terms of cost.
Further, silicone oil, fluororesin, and filler such as calcium carbonate and talc may be added in consideration of transportability and blocking. Further, a fluorescent whitening agent (described in JP-A-3-253388) may be contained in the protective layer.

Furthermore, an intermediate layer may be provided between the protective layer and the heat-sensitive layer in order to protect the heat-sensitive layer from the solvent, monomer components, etc. of the coating solution for forming the protective layer (Japanese Patent Laid-Open No. 1-1999).
No. 133781). As the material for the intermediate layer, the following thermosetting resins and thermoplastic resins can be used in addition to those listed as the resin base material in the heat sensitive layer. That is,
Examples thereof include polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate and polyamide. The thickness of the intermediate layer is. It is preferably about 1 to 2 μm.

The heat-sensitive layer is of a type in which the light-shielding property (transparency) is reversibly changed by changing the heating temperature,
It may be either of two types, that is, a type that reversibly develops and erases color by changing the heating temperature.

The heat-sensitive layer of the type that causes a change in transparency is mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material. The reversible thermosensitive recording material here has a temperature range in which it becomes transparent, as described later. Further, the reversible thermosensitive recording material herein utilizes the transparency change (transparent state, cloudy opaque state) as described above, and the difference between the transparent state and the cloudy opaque state is presumed as follows. That is, in the case of (I) transparent, the particles of the organic low molecular weight substance dispersed in the resin base material are composed of large particles of the organic low molecular weight substance, and the light incident from one side is not scattered. It looks transparent because it penetrates to the other side, and in the case of (II) white turbidity,
Particles of organic low-molecular weight substances are composed of polycrystals of fine crystals of organic low-molecular weight substances, and the crystal axes of the individual crystals point in various directions, so the light incident from one side is the organic low-molecular weight substance particles. It is derived from the fact that it appears white because it is refracted many times at the crystal interface and is scattered.

In FIG. 1 (which shows the change in transparency due to heat), a heat-sensitive layer containing a resin base material and an organic low-molecular substance dispersed in the resin base material as main components is, for example, T ₀ or less. It is cloudy and opaque at room temperature. When it is heated to a temperature T ₂ , it becomes transparent, and even if it is returned to room temperature below T _{0 in} this state, it remains transparent. It is considered that this is because the organic low-molecular-weight substance undergoes a semi-molten state from the temperature T ₂ to T ₀ or lower and the crystal grows from a polycrystal to a single crystal. Further heating to a temperature of T ₃ or higher results in a semi-transparent state intermediate between maximum transparency and maximum opacity. Next, when this temperature is lowered, the first cloudy opaque state is restored without taking the transparent state again. This is after the organic low molecular weight substance melts at temperature T ₃ or higher,
It is considered that this is because a polycrystal is precipitated by cooling. It should be noted that when this opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature of T ₀ or lower, an intermediate state between transparent and opaque can be obtained.
In addition, even if the material becomes transparent at room temperature, it is returned to the cloudy opaque state again when heated to a temperature of T ₃ or higher and then returned to room temperature. That is, both opaque and transparent forms at room temperature and intermediate forms thereof can be obtained.

Therefore, the heat-sensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent background and a transparent image on a cloudy background, and the change can be repeated many times. It is possible. By arranging a coloring sheet on the back surface of such a heat-sensitive layer, it is possible to form an image of the color of the coloring sheet on a white background or a white image on the background of the color of the coloring sheet. Also, when projected with an OHP (overhead projector) or the like, the cloudy part becomes a dark part, and the transparent part transmits light and becomes a bright part on the screen.

In order to prepare a reversible thermosensitive recording medium according to this type of the present invention, generally, (a) a resin matrix and an organic low molecular weight substance are used.
Dispersion of fine particles of organic low molecular weight substance in a solution of two components or (b) a resin base material solution (a solvent that does not dissolve at least one organic low molecular weight substance is used) Is coated on a flexible support 1 such as a plastic film and dried to form the heat sensitive layer 2.

The solvent for forming the heat-sensitive layer can be variously selected depending on the type of the resin base material and the organic low molecular weight substance, and examples thereof include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene and benzene. To be The organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state in the heat-sensitive layer obtained not only when the dispersion liquid is used but also when the solution is used.

The resin base material used for the heat-sensitive layer is a material that forms a layer in which an organic low molecular weight substance is uniformly dispersed and held, and has an effect on the transparency at maximum transparency. Therefore, the resin base material is preferably a resin having good transparency, mechanical stability, and good film forming property.

Examples of such resins include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride- Vinyl chloride-based copolymers such as acrylate copolymers; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-based copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; styrene-butadiene copolymers Polymers; polyacrylates or polymethacrylates or acrylate-methacrylate copolymers; silicone resins and the like. These may be used alone or in combination of two or more.

On the other hand, as the organic low molecular weight substance, any substance which changes from polycrystal to single crystal due to heat in the recording layer may be used, and generally, one having a melting point of 30 to 200 ° C., preferably 50 to 150 ° C. is used. . Such organic low-molecular substances include alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkylamines; alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes; cycloalkenes; cycloalkynes; saturated or Unsaturated mono- or dicarboxylic acids or their esters, amides or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts; arylcarboxylic acids or their esters, amides or ammonium salts; halogenallylcarboxylic acids or Thioalcohols; esters, amides or ammonium salts thereof; thiocarboxylic acids or their esters, amines or ammonium salts; thioalcohols Carboxylic acid esters, and the like. These may be used alone or in combination of two or more. The carbon number of these compounds is preferably 10 to 60, preferably 10 to 38, and particularly preferably 10 to 30. The alcohol group moiety in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance is at least one of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH-, -COO.
_{R, -NH -, - NH 2} , -S -, - SS -, - O-, is preferably a compound containing a halogen and the like.

More specifically, as these compounds,
Uric acid, dodecanoic acid, myristic acid, pentadecane
Acid, palmitic acid, stearic acid, behenic acid, nonadeca
Higher fatty acids such as acid, araginic acid and oleic acid; steer
Methyl phosphate, tetradecyl stearate, stearin
Acid octadecyl, octadecyl laurate, palmitin
Of higher fatty acids such as tetradecyl acid acid and dodecyl behenate
Steal; Etc., such as ether or thioether. Above all, the present invention
Higher fatty acids, especially palmitic acid, stearic acid,
Higher fatty acids having 16 or more carbon atoms such as henic acid and lignoceric acid
Is preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.
Yes.

In order to widen the range of temperature at which the material can be made transparent, the organic low molecular weight substance may be appropriately combined, or such an organic low molecular weight substance may be combined with another material having a different melting point. These are disclosed, for example, in JP-A-63-39378 and JP-A-63-13038.
No. 0, JP-A No. 2-1363, JP-A No. 3-2089 and the like are disclosed, but not limited thereto. The ratio of the organic low molecular weight substance and the resin base material in the heat sensitive layer is
The weight ratio is preferably about 2: 1 to 1:16, more preferably 1: 2 to 1: 8. When the ratio of the resin base material is less than this, it becomes difficult to form a film in which the organic low molecular weight material is retained in the resin base material. Becomes difficult.

In addition to the above components, additives such as a surfactant and a high boiling point solvent may be added to the heat sensitive layer in order to facilitate the formation of a transparent image. Specific examples of these additives are as follows. Examples of high boiling point solvents: tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, diphthalate. -n-octyl, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-adipate
2-ethylhexyl, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetylricinoleate, butyl acetylricinoleate, butyl Phthalyl butyl glycolate, tributyl acetyl citrate.

Examples of surfactants and other additives; polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide , Lower olefin oxide adduct of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salt of higher alkylbenzene sulfonic acid; higher fatty acid, aromatic carboxylic acid, higher fatty acid sulfonic acid, aromatic sulfonic acid, sulfuric acid monoester Or phosphoric acid mono- or di-ester Ca,
Ba or Mg salt; low-sulfated oil; poly long-chain alkyl acrylate; acrylic oligomer; poly long-chain alkyl methacrylate; long-chain alkyl methacrylate-amine-containing monomer copolymer; styrene-maleic anhydride copolymer;
Olefin-maleic anhydride copolymer.

When the image of this recording medium is used as a reflection image, the contrast can be increased by providing a light reflecting layer on the back surface of the recording layer even if the thickness of the recording layer is reduced. Specifically, vapor deposition of Al, Ni, Sn and the like can be mentioned (described in JP-A-64-14079).

Next, a description will be given of a case where the heat-sensitive layer is formed by a reversible thermochromic composition utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound. A thermochromic composition utilizing a color-forming reaction between an electron-donating color-developing compound and an electron-accepting compound has a non-coloring property when the electron-donating color-developing compound and the electron-accepting compound are heated and melt-mixed. When a crystalline chromophore is generated, on the other hand, when the amorphous chromophore is heated at a temperature lower than the melting temperature, the phenomenon that the electron-accepting compound causes crystallization and the chromophore disappears. It was used.

The thermochromic composition instantly develops color upon heating, and the color-developed state thereof is stable even at room temperature. On the other hand, the composition in the color-developed state is instantly heated by heating at a temperature not higher than the color development temperature. The color is erased, and the erased state is stable even at room temperature. The color-changing composition is amorphous when the electron-donating color-forming compound and the electron-accepting compound are heated and melt-mixed. On the other hand, the phenomenon that the electron-accepting compound is crystallized to decolor the color-forming material when the amorphous color-forming material is heated at a temperature lower than the melting temperature is used. It is a thing.

The thermochromic composition instantly develops color upon heating, and the color-developed state thereof is stable even at room temperature. On the other hand, the composition in the color-developed state is instantly heated by heating at a temperature not higher than the color development temperature. The color is erased and the erased state is stable even at room temperature, and such a reversible peculiar coloring / decoloring behavior is a novel and surprising phenomenon that has never been seen before.

The principle of coloring and erasing, that is, image formation and image erasing when this composition is used as a heat-sensitive layer will be described with reference to the graph shown in FIG. In FIG. 2, the vertical axis of the graph represents the color density, the horizontal axis represents the temperature, the solid line represents the image forming process by heating, and the broken line represents the image erasing process by heating. A is the density in the completely erased state, B is the density in the completely colored state when heated to a temperature of T ₅ or higher, C is the density at a temperature of T ₄ or lower in the completely colored state, and D is T ₄ ~ T ₅
It shows the concentration when erased by heating at a temperature between.

This composition according to the invention is in the colorless state (A) at temperatures below T ₄ . To perform recording (image formation), a color image (B) is formed by heating to a temperature of T ₅ or higher with a thermal head or the like to form a recorded image. Even if the recorded image is returned to the temperature of T ₄ or lower according to the solid line, the state (C) is maintained as it is and the recording memory property is not lost.

Next, in order to erase the recorded image, the formed recorded image is heated to a temperature between T _{4 and} T _{5 which} is lower than the coloring temperature, so that a colorless state (D) is obtained. In this state, even if the temperature is returned to T ₄ or lower, the colorless state (A) is maintained as it is. That is, the process of forming the recorded image reaches C by the path of the solid line ABC and the recording is held. Next, in the process of erasing the recorded image, the erased state is maintained by reaching A through the path of the broken line CDA. The behavior characteristics of forming and erasing the recorded image are reversible and can be repeated many times.

The reversible thermochromic composition contains a color former and a color developer as essential components. Then, the coloring state is formed by heating and melting the color-developing agent and the color-developing agent, while the coloring state is erased by heating at a temperature lower than the coloring temperature, and the coloring state and the erasing state exist stably at room temperature. Is. As described above, the mechanism of coloring and decoloring in the composition is such that when the coloring agent and the color developer are heated and melt mixed at the coloring temperature, the composition is amorphized to form a color. This is based on the property that when the developer is heated to a temperature lower than the coloring temperature, the developer of the colored composition causes crystallization to form an erased state of coloring.

A composition comprising an ordinary color-developing agent and a color-developing agent, for example, a leuco compound having a lactone ring, which is a dye precursor widely used in conventional thermal recording paper, and a phenolic compound exhibiting a color-developing action. When this is melt-mixed by heating, it becomes a coloring state based on the ring opening of the lactone ring of the leuco compound. This colored state is an amorphous state in which both are compatible. Although this colored amorphous state is stable at room temperature, it does not crystallize even when heated again, and because the phenolic compound is not separated from the leuco compound, there is no ring closure of the lactone ring and decolorization. I don't.

On the other hand, when the composition of the color former and the developer according to the present invention is melt-mixed by heating, it becomes a color-developed state, exhibits an amorphous state as in the conventional case, and is stable at room temperature. Exist. However, in the case of the present invention, when the composition in the colored amorphous state is heated at a temperature not higher than the coloring temperature, that is, a temperature at which the molten state is not reached, crystallization of the developer occurs and a compatibility state with the color developing agent occurs. The bond due to can not be retained, and the color developer separates from the color developer. It is considered that due to the crystallization of the color developer from the color developer, the color developer cannot accept electrons from the color developer and the color developer is decolorized.

The above-mentioned peculiar coloring and decoloring behaviors observed in this thermochromic composition are the mutual solubility of the color former and the color developer by heating and melting, the strength of both actions in the color developing state, and the Although the solubility of the colorant in the color former and the crystallinity of the color developer are related, in principle, it causes amorphization due to heating and melting, while on the other hand, it is crystallized by heating at a temperature lower than the coloring temperature. Any color-developing agent / developing agent system that causes the change can be used as the composition component in the present invention. Further, those having such characteristics show endothermic change due to melting and exothermic change due to crystallization in thermal analysis, so that the color former / developer system applicable to the present invention can be easily analyzed by thermal analysis. You can check. Further, the reversible thermochromic composition system according to the present invention may include a third substance,
For example, it has been found that the reversible coloring / decoloring behavior is retained even when a polymer substance is present.

In the thermochromic composition of the present invention, the decoloring is caused by the separation from the color former due to the crystallization of the color developer, and therefore, in order to obtain a composition having an excellent decolorizing effect, The choice of is important.

Examples of the color developer preferably used in the present invention are as follows. As described above, the color developer applicable to the present invention can be easily found by thermal analysis.
It is not limited to them. (1) Organic phosphoric acid compound represented by the following general formula (1) R ¹ —PO (OH) ₂ (1) (wherein R ¹ is a linear or branched alkyl group or alkenyl having 8 to 30 carbon atoms) Represents a group.) Specific examples of the organic phosphoric acid compound include the following. Octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid. (2) Organic acid having a hydroxyl group at the α-position carbon represented by the following general formula (2) R ² —CH (OH) COOH (2) (wherein R ² is a linear or branched chain having 6 to 28 carbon atoms). It represents a branched alkyl group or an alkenyl group.) Specific examples of the organic acid having a hydroxyl group at the α-position carbon include the following. α-Hydroxyoctanoic acid, α
-Hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid , Α-hydroxydocosanoic acid and the like.

The color former used in the present invention is a compound exhibiting an electron-accepting property, and is a colorless or light-colored dye precursor itself, and is not particularly limited, and conventionally known ones, for example, triphenylmethanephthalide-based compounds. There are compounds, fluoran compounds, phenothiazine compounds, leuco auramine compounds, rhodamine lactam compounds, spiropyran compounds, indolinophtalide compounds, and the like. Specific examples include the following. 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-
Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl)-
6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-
Bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7- Methylfluorane, 3-diethylamino-7,8
-Benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-
Ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylamino Fluoran, 2-
{3,6-bis (diethylamino) -6- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- ( o-
Chloranilino) fluorane, 3-dibutylamino-7
-(O-Chloranilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6
-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N,
N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluorane, benzoleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-2'- Methoxy-benzoindolino-spiropyran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'methoxy-5'-chlorophenyl) phthalide, 3- (2'-
Hydroxy-4'-dimethylaminophenyl) -3-
(2'-methoxy-5'-nitrophenyl) phthalide,
3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methoxyphenyl) phthalide, 3-morpholino-7- (N-propyl-). Trifluoromethylaniline)
Fluoran, 3-diethylamino-5-chloro-7-
(N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5
-Chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-
Phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α
-Phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-
(N-methoxytoluidino) -7- (pn-butylanilino) fluorane, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane,
3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorenspiro (9,3 ')-6'-dimethylaminophthalide, 3-
(N-benzyl-N-cyclohexylamino) -5,6
-Benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N- (2-ethoxypropyl) amino-6- Methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'. −
Benzofluorane, 3-N-methyl-N-isobutyl-
6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ',
4'-dimethylanilino) fluorane and the like.

Particularly preferred color formers used in the present invention are those containing halogen as a substituent. Examples of such a thing include the following. 3,3-bis (p-dimethylaminophenyl) -6
-Chlorophthalide, 3-cyclohexylamino-6-chlorofluorane, 3-cyclohexylamino-6-bromofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluorane, 3
-Dipropylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-phenylamino-fluorane, 3-pyrrolidino-6-chloro-7-phenylamino-fluorane, 3-diethylamino-6-chloro-7
-(M-trifluoromethylphenyl) amino-fluorane, 3-cyclohexylamino-6-chloro-7- (o
-Chlorophenyl) amino-fluorane, 3-diethylamino-6-chloro-7- (2 ', 3'-dichlorophenyl) amino-fluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-dibutylamino-
6-chloro-7-ethoxyethylamino-fluorane,
3-diethylamino-7- (o-chlorophenyl) amino-fluorane, 3-diethylamino-7- (o-bromophenyl) amino-fluorane, 3-diethylamino-7- (o-chlorophenyl) amino-fluorane, 3
-Dibutylamino-7- (o-fluorophenyl) amino-fluorane, 6'-bromo-3'-methoxybenzoindolino-pyrrolospirane, 3- (2'-methoxy-
4'-Dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2 '-Methoxy-5'-chlorophenyl) phthalide, 2- {3,6-bis (diethylamino)}-9- (o-chlorophenyl) amino-xanthyl lactam benzoate and the like.

A more preferable color former used in the present invention is a compound represented by the following general formula (3).

[Chemical 1] (However, R ³ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁴ is a hydrogen atom or an optionally substituted amino group, X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenylamino group. , Y represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 2 carbon atoms, and m and n each represent an integer of 1 or 2.)

Specific examples of the compound represented by the general formula (3) include the following. 3- (N-
Methyl-N-phenylamino) -7-amino-fluorane, 3- (N-ethyl-N-phenylamino) -7-amino-fluorane, 3- (N-propyl-N-phenylamino) -7-amino- Fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -7-amino-
Fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-amino-fluorane, 3- {N-
Propyl-N- (p-methylphenyl) amino} -7-
Amino-fluorane, 3- {N-methyl-N- (p-ethylphenyl) amino} -7-amino-fluorane, 3
-{N-ethyl-N- (p-ethylphenyl) amino}
-7-amino-fluorane, 3- {N-propyl-N-
(P-Ethylphenyl) amino} -7-amino-fluorane, 3- {N-methyl-N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluorane, 3- {N
-Ethyl-N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluorane, 3- {N-propyl-
N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluorane, 3- {N-methyl-N- (p-chlorophenyl) amino} -7-amino-fluorane, 3-
{N-ethyl-N- (p-chlorophenyl) amino}-
7-amino-fluorane, 3- {N-propyl-N-
(P-Chlorophenyl) amino} -7-amino-fluorane, 3- (N-methyl-N-phenylamino) -7-
Methylamino-fluorane, 3- (N-ethyl-N-phenylamino) -7-methylamino-fluorane, 3-
(N-propyl-N-phenylamino) -7-methylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7-ethylamino-fluorane,
3- {N-ethyl-N- (p-methylphenyl) amino} -7-benzylamino-fluorane, 3- {N-methyl-N- (2 ', 4'-dimethylphenyl) amino}-
7-methylamino-fluorane, 3- {N-ethyl-N
-(2 ', 4'-Dimethylphenyl) amino} -7-ethylamino-fluorane, 3- {N-methyl-N-
(2 ', 4'-Dimethylphenyl) amino} -7-benzylamino-fluorane, 3- {N-ethyl-N-
(2 ', 4'-Dimethylphenyl) amino} -7-benzylamino-fluorane, 3- (N-methyl-N-phenylamino) -7-dimethylamino-fluorane, 3- (N
-Ethyl-N-phenylamino) -7-dimethylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7-diethylamino-fluorane,
3- {N-ethyl-N- (p-methylphenyl) amino} -7-diethylamino-fluorane, 3- (N-methyl-N-phenylamino) -7-dipropylaminofluorane, 3- (N- Ethyl-N-phenylamino) -7
-Dipropylaminofluorane, 3- {N-methyl-N
-(P-Methylphenyl) amino} -7-dibenzylamino-fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-dibenzylamino-fluorane, 3- {N-ethyl -N- (p-methylphenyl)
Amino} -7-di (p-methylbenzyl) amino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7-acetylamino-fluorane, 3-
{N-ethyl-N- (p-methylphenyl) amino}-
7-benzoylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7- (o-methoxybenzoyl) amino-fluorane, 3- {N-ethyl-N- (p-methyl) Phenyl) amino} -6-methyl-7-phenylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -6-methyl-7-phenylamino-fluorane, 3- {N- Methyl-N- (p-methylphenyl) amino} -6-tert
-Butyl-7- (p-methylphenyl) amino-fluorane, 3- (N-ethyl-N-phenylamino) -6-
Methyl-7- (N-ethyl-N- (p-methylphenyl) amino-fluorane, 3- {N-propyl-N-
(P-Methylphenyl) amino} -6-methyl-7-
{N-methyl-N- (p-methylphenyl) amino}-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -5-methyl-7-benzylamino-fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -5 -Chloro-7-dibenzylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -5-methoxy-7-dibenzylamino-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -6-methyl-fluorane, 3- {N-
Ethyl-N- (p-methylphenyl) amino} -5-methoxy-fluorane and the like.

The color developer is applied alone or as a mixture of two or more kinds. Similarly, the color-developing agent can be applied alone or in a mixture of two or more kinds. The thermochromic composition can be used as a reversible thermosensitive recording medium by forming the recording layer 3 on the substrate 1. In this case, the color-developing agent and the color-developing agent can be used as they are or by being encapsulated in microcapsules. Such a reversible thermosensitive recording medium can be obtained by uniformly dispersing or dissolving a color former and a developer together with a binder in water or an organic solvent according to a conventionally known method, and coating the substrate on a substrate.

As the binder, various conventional binders can be appropriately used. Examples thereof include polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methoxy cellulose, carboxymethyl cellulose, methyl cellulose, cellulose acetate, gelatin, casein, starch, polyacrylic acid. Soda, polyvinylpyrrolidone, polyacrylamide, maleic acid copolymer, acrylic acid copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polyacrylic acid esters, polymethacrylic acid esters, vinyl chloride-vinyl acetate copolymer Coalesce, styrene copolymer, polyester,
There is polyurethane etc.

Microencapsulation of the color former and / or the developer can be carried out by a known method such as a coacervation method, an interfacial polymerization method or an in situ polymerization method. In the present invention, various additives used in ordinary thermal recording paper, such as dispersants, surfactants, fillers, color image stabilizers, and oxidants, are used with the intention of improving coating properties or recording properties as necessary. It is also possible to add an inhibitor, a light stabilizer, a lubricant and the like.

The support may be paper, synthetic paper, plastic film or a composite thereof depending on the purpose of use, and is not particularly limited as long as it has flexibility.

The formation of a recorded image is not particularly limited by a hot pen, a thermal head, laser heating, etc. depending on the purpose of use. Similarly, the erasing of the recorded image is not particularly limited as long as the erasing temperature conditions such as the heating roller, the sheet heating element, the constant temperature bath, the warm air, and the thermal head are given. In addition, so-called overwriting is possible in which the recorded image is erased by the thermal head set to the erasing temperature and at the same time the recorded image is formed by another thermal head set to the recording temperature.

[0051]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. Parts herein are by weight.

Example 1 A PET film having a thickness of 250 μm was used as a support, an A1 layer was provided on the support, and a space distance was about 1 on the A1 layer.
A stainless steel having a mesh of 400 μm is placed, and on this, vinyl chloride-vinyl acetate-phosphate ester copolymer 39 parts (Denka Vinyl # 1000P manufactured by Denki Kagaku Kogyo Co., Ltd.) Palmitic acid 2 parts Stearic acid 3 parts Eicosan diacid 5 parts A coating solution for forming a heat-sensitive layer consisting of 3 parts of diisodecyl phthalate, 80 parts of tetrahydrofuran and 45 parts of toluene was applied, and dried by heating to form a heat-sensitive layer having a thickness of about 5 μm and a width of about 1400 μm. Then, the stainless steel mesh on the support was removed, and further, 10 parts of a 75% urethane acrylate UV curable resin butyl acetate solution (Dainippon Ink and Chemicals Co., Ltd .: Unidic C7-157) Isopropyl alcohol (IP. A) A coating solution for forming a protective layer consisting of 10 parts was applied, and after heating and drying, 80
Cured with a w / cm UV lamp, approximately 2μ on the heat-sensitive layer
A reversible thermosensitive recording medium was prepared by providing a protective layer having a thickness of m.

Example 2 A heat-sensitive layer-forming coating solution similar to that used in Example 1 was applied onto a polyimide film of a heat-resistant sheet having a depression on one side, and the depression of the polyimide film had a thickness of about 5 μm.
A heat-sensitive layer having a thickness of about 1400 μm in length and about 1400 μm in width was provided, and a vinyl chloride-vinyl acetate-phosphate ester copolymer (Denka Vinyl # 1000P manufactured by Denki Kagaku Kogyo Co., Ltd.) was formed on the Al surface of the same support as in Example 1. ) T. H. An adhesive layer made of F (tetrahydrofuran) was applied, and the polyimide film surface provided with the thermosensitive layer was placed on the surface of the adhesive layer, dried, and laminated to prepare a reversible thermosensitive recording medium.

Example 3 The thickness of the heat-sensitive layer was set to 4 μm, and the length between the support and the heat-sensitive layer was 1 mm.
A reversible thermosensitive recording medium was prepared in the same manner as in Example 2 except that a non-adhesive portion having a width of 400 μm, a width of 1400 μm and a height of 1 μm was provided.

Comparative Example 1 A PET film having a thickness of 250 μm was used as a support, an A1 layer was provided on this support, and 39 parts of a vinyl chloride-vinyl acetate-phosphate ester copolymer (manufactured by Denki Kagaku Kogyo Co., Ltd.) : Denka vinyl # 1000P) Palmitic acid 2 parts Stearic acid 3 parts Eicosane diacid 5 parts Diisodecyl phthalate 3 parts Tetrahydrofuran 80 parts Toluene 45 parts Apply a heat-sensitive layer forming coating solution, heat dry to a thickness of about 5 μm. A heat sensitive layer was provided. Furthermore, a coating solution for forming a protective layer, comprising 10 parts of a 75% butyl acetate solution of a urethane acrylate-based UV curable resin (manufactured by Dainippon Ink and Chemicals: Unidick C7-157) isopropyl alcohol (IPA) Is applied and after heating and drying 80
Cured with a w / cm UV lamp, approximately 2μ on the heat-sensitive layer
A reversible thermosensitive recording medium was prepared by providing a protective layer having a thickness of m.

Using the reversible thermosensitive recording medium prepared as described above, a cloudy image was formed with a thermal head and erased with a heat roller. The graph of FIG. 7 shows the result of the degree of white turbidity deterioration when this formation-erasure was repeated 10 times.

[0057]

As is clear from the description of Examples and Comparative Examples, the reversible thermosensitive recording medium of the present invention is provided with a thermosensitive layer in the concave portion of the surface of the protective layer on the side of the support, so that a thermal head or the like is provided. It is a reversible thermosensitive recording medium in which even if a heating means for simultaneously applying heat and pressure by the heating element is used, deterioration of white turbidity due to repetition is small, image contrast is high, and repetition durability is improved.

[Brief description of drawings]

FIG. 1 is an illustration showing that an image is formed and erased on a heat sensitive layer according to the present invention.

FIG. 2 is an explanatory diagram showing that an image is formed / erased in another heat-sensitive layer according to the present invention.

FIG. 3A is a diagram showing a conventional reversible thermosensitive recording medium. FIG. 6B is a diagram showing a state in which a hot stamp is brought into contact with a conventional reversible thermosensitive recording medium.

FIG. 4 is a diagram showing a reversible thermosensitive recording medium of the present invention.

FIG. 5A is a diagram in which a heat-sensitive sheet is provided with a heat-sensitive layer. (B) is a diagram showing a reversible thermosensitive recording medium using a heat-resistant sheet as a protective layer of the present invention.

FIG. 6 is a diagram showing a reversible thermosensitive recording medium of the present invention in which a non-adhesive portion is provided between a support and a thermosensitive layer.

FIG. 7 is a graph showing the density difference between the reversible thermosensitive recording media obtained in Examples 1 to 3 and Comparative Example 1 and the initial cloudy density when image formation-erasing was repeated 10 times.

[Explanation of symbols]

 1 ... Support 2 ... Thermosensitive layer (recording layer) 3 ... Protective layer 4 ... Heat-resistant sheet 5 ... Non-adhesive part 6 ... Hot stamp

Claims (4)

[Claims] 1. A heat-sensitive layer which reversibly causes a transparent-opaque change or a color-decoloring change depending on temperature, and a protective layer for protecting the heat-sensitive layer are provided on the support. A reversible thermosensitive recording medium, characterized in that irregularities are provided on the surface of the protective layer on the side of the support, and a thermosensitive layer is provided in the concave portions. 2. The reversible thermosensitive recording medium according to claim 1, wherein the protective layer is a heat resistant sheet. 3. A non-adhesive portion is provided between the heat-sensitive layer provided on the heat-resistant sheet and the support.
The reversible thermosensitive recording medium described. 4. The reversible thermosensitive recording medium according to claim 1, further comprising an adhesive layer provided between the support and the thermosensitive layer.