JP3368384B2 - Reversible thermosensitive recording material, production method thereof and image display method using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is clarified by changing the heating temperature, by using a heat-sensitive layer reversibly produce Opaque, reversible formation of images and the erasure can be performed repeatedly The present invention relates to a thermosensitive recording material, a method for producing the same, and an image display method using the recording material.

[0002]

2. Description of the Related Art In recent years, reversible heat-sensitive recording materials have been attracting attention because they can form images temporarily 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 material is known in which an organic low molecular weight substance such as a higher fatty acid is dispersed in a resin matrix such as a vinyl chloride-vinyl acetate copolymer having a low glass transition temperature of less than 0 ° C. 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 at the same time, the resin base material around the organic low-molecular-weight material particles is deformed during repeated image formation and deletion, and the organic low-molecular-weight material dispersed finely 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. Furthermore, there is a defect that scratches and the like are generated on the surface due to friction, and the contrast is lowered.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks and changes the transparency by changing the heating temperature.
In a reversible heat-sensitive recording material utilizing aging, even if image formation-erasing is performed using a heating means such as a thermal head that applies heat and pressure at the same time, the white turbidity does not decrease much, the durability is excellent and the printing is repeated. Provided are a reversible thermosensitive recording material excellent in density and contrast, a method for producing the same, and an image display method using the same.

[0005]

According to Means for Solving the Problems] The present invention, on a support, transparent by changing the heating temperature, the reversible heat-sensitive recording material having a thermosensitive layer reversibly produce Opaque, thermosensitive Spacer particles in the layer (however, the thickness of the heat-sensitive layer
A reversible thermosensitive recording material, which is transparent or non-transparent by changing the heating temperature on the support. /> in the reversible thermosensitive recording material having a thermosensitive layer reversibly produce bright translucent, reversible, characterized in that the spacer particles is provided an anchor layer obtained by dispersing contained between the support and the heat-sensitive layer A heat-sensitive recording material is provided, and on the support,
Transparent by changing the heating temperature, the reversible heat-sensitive recording material having a thermosensitive layer reversibly produce Opaque, based on the support the spacer adjustment layer obtained by dispersing spacer particles around the heat-sensitive layer reversible thermosensitive recording material characterized by comprising is provided. And, in particular, the spacer particles are spherical, and the spacer particles are dispersed and contained in a state of protruding from the heat-sensitive layer, and the spacer particles are plate-shaped, needle-shaped, column-shaped, scale-shaped, or irregular-shaped. The reversible thermosensitive recording material is provided, which is characterized by the following. Further, a heat-sensitive layer is provided by coating a support with a dispersion liquid in which spacer particles are dispersed in a heat-sensitive layer liquid containing a resin base material and an organic low-molecular substance as a main component, and drying. A method for producing the reversible heat-sensitive recording material is provided, and further, a dispersion in which spacer particles are dispersed in an anchor layer liquid is applied on a support and dried to provide an anchor layer, and further thereon. A method for producing the reversible thermosensitive recording material is provided, which comprises coating a thermosensitive layer liquid containing a resin base material and an organic low-molecular substance as a main component, and drying the liquid to form a thermosensitive layer. There is provided an image display method characterized by using a thermosensitive recording material and performing image formation and / or erasing using a thermal head.

[0006] The present inventors have on the support, a transparent by changing the heating temperature, in the reversible thermosensitive recording material having a reversibly resulting thermosensitive layer Opaque, heat-sensitive layer, or the support As a result of diligent examination of the anchor layer or the like provided between the body and the heat-sensitive layer, by providing a heat-sensitive layer or anchor layer containing spacer particles dispersed, or by providing a spacer adjustment layer around the heat-sensitive layer, It has been found that a reversible thermosensitive recording material can be obtained which has improved durability against repeated image formation-erasing by a heating means such as applying pressure from a thermal head or the like and heating at the same time.

In the present invention, the spacer particles are dispersed and contained in the heat-sensitive layer or the anchor layer,
Alternatively, it is not clear why providing a spacer adjustment layer around the heat-sensitive layer improves the durability against repeated image formation and erasing by a heating means such as a thermal head, but heating with heat and pressure applied simultaneously by the thermal head, etc. When the image formation-erasure is repeatedly performed by using the means shown in FIG.
As shown in FIG. 3A, when the spacer particles are absent, the resin of the heat sensitive layer is deformed by the heat and pressure of the thermal head.
As in the case of (b), spacer particles are used, and particularly those using spacer particles having good heat resistance do not apply pressure from the thermal head or the like to the heat sensitive layer, and therefore the resin in the heat sensitive layer is less likely to be deformed by pressure. It is presumed that the durability is improved because the organic low molecular weight substance is maintained as fine particles.

The spacer particles used in the present invention may have any shape, and may be spherical, plate-like, needle-like, scallop-like, scale-like, or indefinite shape, and preferably transparent. When the spacer particles have a spherical shape, since the effect of scattering light is small, it is possible to suppress undesired side effects such as clouding of the background and deterioration of transparency. When the spacer particles have a shape other than the spherical shape, distortion of the heat-sensitive layer in the flow direction is less likely to occur as compared with the spherical shape, and the reduction in contrast between printing and erasing can be suppressed. This is because when the thermal head is brought into contact with the thermal recording material, spherical spacer particles move in the layer softened by the thermal head (FIG. 7),
Needle-shaped, katsura-shaped, scale-shaped, or irregular-shaped spacer particles may be present across the softened layer and the unsoftened layer, and these particles may be present in the softened layer. It does not move (FIG. 8), distortion of the heat-sensitive layer is less likely to occur, and deterioration can be suppressed.

The material constituting the spacer particles is spherical, plate-like such as metal, metal oxide, metal sulfide, metal carbide, graphite, carbon black, silicon carbide, mineral, inorganic salt, organic pigment or polymer compound. , Needle-like, columnar, scale-like, or indefinite shape. Examples of highly effective ones are listed below. Metals: aluminum, silicic acid, germanium, tin,
Copper, zinc, silver, iron, cobalt, nickel, chromium, and alloys based on these. Metal oxides: alumina, beryllium oxide, magnesium oxide, cuprous oxide, zinc oxide, indium oxide, tin oxide, titanium oxide, silicon oxide, iron oxide, cobalt oxide,
Nickel oxide, manganese oxide, tantalum oxide, vanadium oxide, tungsten oxide, molybdenum oxide and these compounds doped with impurities. Metal sulfides: copper sulfide, zinc sulfide, tin sulfide, molybdenum sulfide. Minerals: earth minerals, lime minerals, strontium minerals, barium minerals, zirconium minerals, titanium minerals, tin minerals, phosphorus minerals, aluminum minerals (wax, kaolin,
Clay), silicon minerals (quartz, mica, talc, zeolite, diatomaceous earth, acid clay). Inorganic salt: Carbon salt or sulfate of alkaline earth metal element (magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, magnesium sulfate, calcium sulfate, strontium sulfate, barium sulfate), metal silicate such as magnesium silicate, boro Mainly composed of aluminum oxide and potassium titanate. Polymer compounds: phenol resin, melamine resin, urethane resin, epoxy resin, silicone resin, urea resin, diallyl phthalate resin, alkyd resin, acetal resin, acrylic resin, methacrylic resin, polyester resin, cellulose resin, starch and its derivatives, Polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, fluororesin,
Polyethylene, polypropylene, polystyrene, polydivinylbenzene, polyvinyl acetal, polyamide,
Polyvinyl alcohol, polycarbonate, polysulfone, polyether sulfone, polyphenylene oxide,
Polyphenylene sulfide, polyether erkelate, polyamino bismaleimide, polyarylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyimide, polyamide imide, polyacrylonitrile, benzoguanamine resin, and compositions containing these as the main components. In addition to the above polymer compounds, those having a melting point or softening point of 200 ° C. or higher are particularly effective. These may be used alone or in admixture of two or more. Fibrous materials: carbon fiber, alumina fiber, silicon carbide fiber, metal fiber, glass fiber, boron fiber, ceramic fiber, whiskers, aramid fiber, polyester fiber and other synthetic resin fibers. These may be used alone or in admixture of two or more.

Further, in order to prevent the pressure of a heating element such as a thermal head from being applied to the heat-sensitive layer, the size of the spacer particles is the thickness of the heat-sensitive layer, or, if an alker layer is provided, the size of the heat-sensitive layer and the anchor layer. 1-2 times the thickness is good, 1.1-
1.5 times is more preferable. However, the spacer particles are heat-sensitive
When contained in the layer, 1.2 times or less of the thickness of the heat-sensitive layer
Excluding those of size. If the size of the spacer particles is smaller than this, heat and pressure of a heating element such as a thermal head are applied to the heat-sensitive layer, and repeated durability deteriorates.
If the size of the spacer particles is larger than this, it is difficult for the heat of the heating element such as the thermal head to be transferred to the heat sensitive layer, so that the white turbidity cannot be made uniform.

Further, in order to fully exhibit the function of the spacer particles, it is necessary that at least 3 or more spacer particles are provided for each heat-generating layer of the thermal head, and 2 or less. If it only exists, it becomes impossible to prevent the pressure of the thermal head, which is the function of the spacer particles, from being applied to the heat-sensitive layer, and the durability against repeated use deteriorates.

As a method of providing the spacer particles on the support, a method of dispersing the spacer particles in the heat-sensitive layer to make the spacer particles protrude from the heat-sensitive layer, and providing an anchor layer, the spacer particles are provided in the anchor layer. There is a method in which it is dispersed and contained so that it protrudes from the anchor layer. Spacer particles can be dispersed and contained in the heat-sensitive layer as shown in FIG. 4 by dispersing the spacer particles in the heat-sensitive layer forming coating solution and applying the coating solution onto the support. Further, spacer particles are dispersed in the anchor layer-forming coating solution and coated on the support to make the spacer particles project as shown in FIG. 5 , and then the thermosensitive layer-forming coating solution is coated. As shown in FIG. 6 , spacer particles can be dispersed and contained in the heat sensitive layer. After the spacer particles are dispersed and contained in this anchor layer, it is easier to uniformly disperse the spacer particles by applying the heat sensitive layer, but the method of dispersing and containing the spacer particles in the heat sensitive layer is difficult to disperse uniformly. The number of spacer particles for one heating element of the thermal head may be too large, and the transparency may be slightly lowered. The heat-sensitive layer is of a type in which the light-shielding property (transparency) is reversibly changed by changing the heating temperature, and the type of which is reversibly colored / erased by changing the heating temperature.
However, the reversible thermosensitive recording material of the present invention is
And a heat-sensitive layer of this type. 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 weight 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.

The difference between the transparent state and the cloudy opaque state is presumed as follows for the heat-sensitive layer utilizing the transparency change (transparent state, cloudy opaque state) as described above. That is, (i) in the case of transparency, the particles of the organic low-molecular substance dispersed in the resin matrix are composed of large particles of the organic low-molecular substance, and the light incident from one side is not scattered and is opposite. It appears to be transparent because it is transmitted to the side, and (ii) in the case of turbidity, the particles of the organic low-molecular substance are composed of polycrystals of fine crystals of the organic low-molecular substance, and the crystal axis of each crystal Since the light is directed in various directions, the light incident from one side is refracted many times at the interface of the crystal of the organic low molecular weight substance particles, and is scattered and thus appears white.

In FIG. 1 (representing the change in transparency due to heat), a thermosensitive layer mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material is, for example, T
It is cloudy and opaque at room temperature below ₀ . This is the temperature T ₂
When it is heated to ₀ , it becomes transparent, and even if it is returned to room temperature below T _{0 in} this state, it remains transparent. This is the temperature T ₂ to T ₀
It is considered that the organic low molecular weight substance is in a semi-molten state until the following and the crystal grows from a polycrystal to a single crystal.
Upon further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when this temperature is lowered, the first cloudy opaque state is restored without taking the transparent state again. It is considered that this is because when the organic low molecular weight substance is melted at a temperature of T ₃ or higher, the polycrystal is deposited by being cooled. 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. Also, the transparent material that has become transparent at room temperature returns to the cloudy and 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. By arranging a coloring sheet on the back surface of such a heat-sensitive body, it is possible to form a color image of the coloring sheet on a white background or a white image on the background of the coloring sheet. Also, O
When projected with an HP (overhead projector) or the like, the cloudy portion becomes a dark portion, the transparent portion transmits light, and becomes a bright portion on the screen.

In order to form and erase an image using such a reversible thermosensitive recording material, it is necessary to have two thermal heads for image formation and image erasure, or to change the applied energy conditions. Therefore, it is effective to use a thermal head having a single thermal head for image formation and image deletion. In the former case, the cost of the apparatus increases because two thermal heads are required, but if the reversible heat-sensitive recording material is passed once with different energy application conditions for each thermal head, image formation and erasure can be performed. You can do it. In the latter case, since the image is formed and erased by one thermal head, the conditions for applying energy to the thermal head at one time when the thermal recording material passes should be adjusted according to the image forming portion and the erasing portion. The operation is complicated, but the operation is complicated, such as changing finely, or erasing the image on the thermal recording material once and then running the thermal recording material again in the opposite direction to form an image under different energy conditions. Therefore, the equipment cost is reduced.

In the present invention, a reversible thermosensitive recording material is prepared by dissolving a resin base material and an organic low molecular weight substance or a solution of a resin base material (at least one of the organic low molecular weight substances is dissolved as a solvent). If not necessary, disperse spacer particles in a dispersion liquid in which organic low-molecular substances are dispersed in the form of fine particles, and then coat and dry on a support such as a plastic film, glass plate, metal plate, etc. The heat sensitive layer may be formed. The solvent for forming the heat-sensitive layer or the heat-sensitive recording material can be variously selected depending on the type of the resin base material and the organic low molecular weight substance, for example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, benzene and the like. Can be mentioned. 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.

In the present invention, the resin used as the resin base material of the heat-sensitive layer of the reversible heat-sensitive recording material is preferably a resin which can form a film or a sheet, has good transparency and is mechanically stable. 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-acrylate copolymer. Vinyl chloride-based copolymers such as polymers; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-based copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylates -Methacrylate copolymer; silicone resin and the like can be mentioned. Of course, these may be used alone or in combination with two or more kinds.

On the other hand, the organic low molecular weight substance may be any substance that changes from polycrystal to single crystal in the recording layer due to heat (changes within the temperature range of T _{1 to} T ₃ shown in FIG. 1).
Generally, those having a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. are 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; allylcarboxylic acids or their esters, amides or ammonium salts; halogenallylcarboxylic acids or Of their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; of thioalcohols Carboxylic acid esters, and the like. These may be used alone or in admixture of two or more. The carbon number of these compounds is 10
60, preferably 10-38, particularly 10-30 are preferred. 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, -COOR, -N.
_{H, -NH 2, -S -,} - S-S -, - 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
Acid, araginic acid, henicosanoic acid, tricosanoic acid,
Gnoceric acid, pentacosanoic acid, cerotic acid, heptaco
Higher grades such as sanic acid, montanic acid, melissic acid, oleic acid
Fatty acid; methyl stearate, tetradecyl stearate
, Octadecyl stearate, octadecyl laurate
Such as tetradecyl palmitate and dodecyl behenate
Esters of higher fatty acids; C₁₆H₃₃-OC₁₆H₃₃  , C₁₆H₃₃-SC₁₆H₃₃
  , C₁₈H₃₇-SC₁₈H₃₇  , C₁₂H_{twenty five}-SC₁₂
H_{twenty five}  , C₁₉H₃₉-SC₁₉H₃₉  , C₁₂H_{twenty five}-S-
S-C₁₂H_{twenty five}  ， Etc., such as ether or thioether. Above all, the present invention
Higher fatty acids, especially palmitic acid, pentadecanoic acid,
Nonadecanoic acid, arachidic acid, heicosanoic acid, tricosane
Carbon such as acid, stearic acid, behenic acid, lignoceric acid
A higher fatty acid having a number of 16 or more is preferable, and has 16 to 24 carbon atoms
And higher fatty acids are more preferable. Also, the temperature at which it can be transparent
To increase the breadth of the organic
Appropriate combination of molecular substances or such organic compounds
The child substance and another material having a different melting point may be combined. This
These are disclosed, for example, in JP-A-63-39378 and JP-A-63-
Publications such as 130380 and Japanese Patent Application No. 63-14754.
And Japanese Patent Application No. 1-140109.
However, the present invention is not limited to these.

The weight ratio of the organic low molecular weight substance to the resin base material in the heat sensitive layer is preferably about 2: 1 to 1:16, and more preferably 1: 2 to 1: 6. If the ratio of the resin base material is below this range, it will be difficult to form a film in which the organic low molecular weight material is retained in the resin base material. Becomes difficult.

The thickness of the heat sensitive layer is preferably 1 to 30 μm,
2 to 20 μm is more preferable. If the heat-sensitive layer is too thick, heat distribution will occur in the layer and it will be difficult to achieve uniform transparency. On the other hand, if the heat-sensitive layer is too thin, the white turbidity is lowered and the contrast is lowered. Further, the white turbidity can be increased by increasing the amount of the organic low molecular weight substance in the heat sensitive layer.

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-phosphate
Ethylhexyl, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate , Dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate,
Dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-2 azelaate
-Ethylhexyl, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetylricinoleate, butyl acetylricinoleate, butylphthalylbutyl glycolate, acetylcitric acid Tributyl.

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 adducts 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 Ca, Ba or Mg salt of phosphoric acid mono- or di-ester; low degree of sulfated oil; poly long chain alkyl acrylate; acrylic orgomer; poly long chain alkyl methacrylate; long chain alkyl methacrylate to amine-containing mono Chromatography copolymers; styrene-maleic anhydride copolymer; olefin-maleic anhydride copolymer.

In the present invention, as the support of the reversible thermosensitive recording material, as described above, a plastic film,
A glass plate, a metal plate or the like is used. When the support is made of a material such as Al vapor-deposited layer that has poor adhesion to the resin, an adhesive layer may be provided between the support and the heat sensitive layer.

In addition, a protective layer may be provided on the heat-sensitive layer of the present invention in order to prevent the transparency of the transparent portion from being lowered due to the deformation of the surface due to the heat and pressure of the heating means such as a thermal head. good. A protective layer (thickness: 0.
(1 to 10 μm), silicone rubber, silicone resin (described in JP-A-63-221087), polysiloxane graft polymer (JP-A-63-210).
No. 317385), an ultraviolet curable resin, an electron beam curable resin (described in JP-A-2-566), and the like.
In any case, a solvent is used at the time of coating, 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. Examples of the solvent that hardly dissolves the resin of the heat-sensitive layer and the organic low molecular weight substance include n-hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol, and the like, and the alcohol solvent is particularly preferable from the viewpoint of cost. As an application, spacer particles can also be applied to the protective layer.

Further, an intermediate layer may be provided between the protective layer and the reversible recording material in order to protect the reversible recording material from the solvent and the monomer component of the protective layer forming liquid (JP-A-1-133781). No. publication). As the material for the intermediate layer, the following thermosetting resins and thermoreversible resins can be used in addition to those listed as the resin matrix in the heat-sensitive layer. That is, specifically, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like can be mentioned. Although the thickness of the intermediate layer varies depending on the use, it is preferably about 0.1 to 2 μm. If it is less than this, the protective effect is lowered, and if it is more than this, the thermal sensitivity is lowered.

Subsequently, in the reversible thermosensitive recording material of the present invention, the thermosensitive layer is formed by a reversible thermochromic composition utilizing a color reaction between an electron-donating color-forming compound and an electron-accepting compound. I will describe what is done.
A thermochromic composition utilizing a color-forming reaction between an electron-donating color-developing compound and an electron-accepting compound is prepared by heating and melting the electron-donating color-developing compound and the electron-accepting compound. Amorphous chromophores are formed, while when the amorphous chromophore is heated at a temperature lower than the melting temperature, the electron-accepting compound causes crystallization and the chromophore disappears. It utilizes the phenomenon of.

The thermochromic composition instantly develops color upon heating, and the color development state thereof is stable even at room temperature. On the other hand, the composition in the color development state is instantaneously 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 color developing and erasing behavior is a novel and surprising phenomenon that has never been seen before.

The principle of coloring and erasing, that is, image forming and image erasing when this composition is used as a thermal recording medium is shown in FIG.
This will be explained with reference to the graph shown in. 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 It shows the concentration when heat erasing is performed at a temperature between T _{5 and} T ₅ .

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 51, 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 the state becomes colorless (D). 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 formation and erasure of 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 causes an amorphization and a coloring state. On the other hand, it is based on the property that, when heated at a temperature lower than the coloring temperature, the developer of the colored composition causes crystallization to form an erased state of coloring. However, even in this case, since the heat-sensitive layer is heated to a temperature of T ₅ or higher and then decolored, the particles of the color-developing agent and the color-developing agent are restored to form a new color-developed state. Is advantageous to.

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 effect. 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 also 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, at a temperature at which the molten state is not reached, crystallization of the developer occurs and the composition is compatible with the color former. The bond due to the state cannot be maintained, 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 behavior observed in the thermochromic composition is the mutual solubility of the coloring agent and the color developing agent by heating and melting, the strength of both actions in the color developing state, and the color developing agent. Is related to the solubility of the color developing agent, the crystallinity of the developer, etc.
In principle, it causes amorphization by heating and melting, while
Any color former / developer system that causes crystallization by heating at a temperature lower than the color development temperature can be used as a 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 contain a third substance, for example, the reversible decoloring behavior thereof is retained even if a polymer substance is present. Was confirmed.

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

Next, 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 ones. (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) Representing a group) Specific examples of this 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 straight chain having 6 to 28 carbon atoms) Representing a linear or branched alkyl group or 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 per se, 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-Diethylaminofluorane, 2- {3,6-bis (diethylamino) -6- (o
-Chloranilino) xanthyl benzoate lactam}, 3
-Diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7
-(O-chloranilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N
-Methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- Anilino Fluoran, 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) fluorane, 3-diethylamino-5-
Chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α-phenyl Ethylamino) 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) fluorene spiro (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.

The color former preferably used in the present invention is a compound represented by the following general formula (3).

(Wherein 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, m is an integer of 1 or 2, Y is a carbon number 1
To an alkyl group having 4 to 4 or an alkoxy group having 1 to 2 carbon atoms, n
Represents an integer of 1 or 2. )

Specific examples of the compound represented by the general formula (3) include the followings. 3- (N-methyl-N-phenylamino) -7-amino-fluorane, 3- (N-ethyl-N-phenylamino) -7-amino-fluorane, 3- (N-propyl-)
N-phenylamino) -7-amino-fluorane, 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-
Fluoran, 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-methylphenyl) 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-ter
t-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 developing agents are applied alone or in admixture of two or more. Similarly, the color-developing agent can be applied alone or in a mixture of two or more kinds. The thermochromic composition can be formed as the thermosensitive layer 2 on the support 1 and used as a reversible thermosensitive recording material. In this case, the reversible thermosensitive recording material can be obtained by uniformly dispersing or dissolving a color former and a developer together with a binder resin in water or an organic solvent according to a conventionally known method, and coating this on a substrate. To be

As the binder resin, various conventional binder resins can be appropriately used, and examples thereof include polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methoxy cellulose, carboxymethyl cellulose, methyl cellulose, cellulose acetate, gelatin, casein, starch and poly. Sodium acrylate, polyvinyl pyrrolidone, polyacrylamide, maleic acid copolymer, acrylic acid copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polyacrylic acid esters, polymethacrylic acid esters, vinyl chloride / vinyl acetate There are copolymers, styrene copolymers, polyesters, polyurethanes and the like.

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. Inhibitors, light stabilizers, lubricants and the like can also be added.

The support 1 is made of paper, synthetic paper,
It may be a plastic film or a composite thereof, and is not particularly limited as long as it is flexible. Also,
Similar to the above, formation of a protective layer for protecting the heat-sensitive layer and the like can be appropriately performed as necessary, and spacer particles can also be applied to the protective layer.

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.

[0048]

EXAMPLES The present invention will now be described in more detail with reference to the following examples, which should not be construed as limiting the invention thereto. In addition, both parts and% are based on weight.

Example 1(Reference example) On white PET with a thickness of about 188 μm     γ-Fe₂O₃                                                  10 copies     Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 parts       (VACH manufactured by UCC)     Isocyanate (2 parts of Coronate L manufactured by Nippon Polyurethane Company)       50% toluene solution)     Methyl ethyl ketone 40 parts     40 parts of toluene Apply the solution consisting of
A magnetic recording layer having a thickness of 0 μm was provided. in addition   Special acrylic UV curing resin (Dainippon Ink and Chemicals Co., Ltd. 10 parts   Unidic C7-164, 49% butyl acetate solution)   Toluene 4 parts After applying the solution consisting of
Approximately irradiate UV light for 5 seconds with a W / cm UV lamp
A smooth layer having a thickness of 1.5 μm was provided. Al about 40 on it
It was vacuum-deposited so as to have a thickness of 0Å, and a light reflection layer was provided. It
On it   Stearic acid 5 parts   Eico diacid 5 parts   Diisodecyl phthalate 3 parts   Vinyl chloride-vinyl acetate-phosphate ester copolymer 40 parts     (# 1000p, manufactured by Denki Kagaku Kogyo)   Spacer particles     (Sekisui Fine Chemical Co., Ltd., Micropearl       SP-206 particle size 6 μm) 3 parts   T. H. F (tetrahydrofuran) 120 parts   80 parts of toluene Of the spacer particles and then heat-drying
A thermosensitive layer (reversible thermosensitive recording layer) with an outer thickness of about 5 μm
Provided. On top of that   Polyamide resin (Toray, CM8000) 10 parts   90 parts of methanol Solution of about 0.5 μm thick
An intermediate layer was provided. On top of that   75% butyl acetate solution of urethane acrylate UV curable resin     (Dainippon Ink and Chemicals, Unidic C7-157) 10 parts   Toluene 10 parts The solution is applied and dried by heating, then 80w / cm purple
Can be cured with an outside line lamp and provided with a protective layer of about 2 μm thickness
An inverse thermosensitive recording material was prepared (Fig. 4).

Example 2 (Reference Example) A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that spacer particles (manufactured by Sumitomo Chemical Co., Ltd., Fine Pearl 3000F 3 parts, particle diameter 6 μm) were used.

Example 3 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that 3 parts of spacer particles (Nippon Shokubai Kagaku Kogyo KK, Eposter GP-90, particle size 9 μm) were used.

Example 4 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that an anchor layer having spacer particles dispersed therein was provided between the AL layer and the thermosensitive layer (FIG. 6). As the anchor layer, urethane acrylate UV curable resin (Dainippon Ink and Chemicals, Unidick C7-164, 49% butyl acetate solution) 10 parts Toluene 10 parts Spacer particles (Sekisui Fine Chemical Co., Micropearl SP) -206, particle diameter 6 μm) A solution of 3 parts was applied, heated and dried, and then cured by an 80 w / cm ultraviolet lamp to provide an anchor layer having a thickness of about 1 μm other than the spacer particles.

Comparative Example 1 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that spacer particles were not used in the thermosensitive layer.

The reversible thermosensitive recording material prepared as described above was used to form a printed image using a thermal head of 8 dots / mm, and the image was erased using the thermal head to make it transparent. The image (white turbidity) 50 times repeatedly was measured with a Macbeth reflection densitometer RD-514. The results are shown in Table 1.

[0055]

[Table 1]

Example 5 (Reference Example) 10 parts of γ-Fe ₂ O ₃ vinyl chloride-vinyl acetate-vinyl alcohol copolymer on white PET having a thickness of about 188 μm 10 parts (VAGH manufactured by UCC) Isocyanate (Japan Polyurethane Company) Manufactured by Coronate L 2 parts 50% toluene solution) Methyl ethyl ketone 40 parts A liquid consisting of 40 parts toluene is applied with a wire bar and dried by heating to about 1
A magnetic recording layer having a thickness of 0 μm was provided. A special acrylic UV-curable resin (manufactured by Dainippon Ink and Chemicals, Inc., 10 parts Unidic C7-164, 49% butyl acetate solution) and a solution of 4 parts of toluene were applied thereto with a wire bar, followed by heating and drying.
Ultraviolet rays were irradiated for 5 seconds with a W / cm ultraviolet lamp to provide a smooth layer having a thickness of about 1.5 μm. Al about 40 on it
It was vacuum-deposited so as to have a thickness of 0Å, and a light reflection layer was provided. Furthermore, stearic acid 5 parts, eico 2 acid 5 parts, phthalic acid diisodecy 3 parts vinyl chloride-vinyl acetate-phosphoric acid ester copolymer (Denka 1000P) 40 parts aluminum borate whiskers (Arborex (diameter 0.5 .About.1.0, length 10-30 .mu.m) (manufactured by the company) 5 parts THF 120 parts A solution consisting of 80 parts toluene 80 parts was applied and dried by heating at 120.degree. To provide a thermosensitive layer having a thickness of about 5 .mu.m other than spacer particles. . Furthermore, a 75% butyl acetate solution of urethane acrylate-based UV-curable resin (Unidick (7-157) manufactured by Dainippon Ink and Chemicals, Inc.) 10 parts Silicone oil (KF-50 manufactured by Shin-Etsu Silicone Co., Ltd.) 0.01 part IPA A solution consisting of 10 parts was applied, heated to 80 ° C. and dried, then 80 w /
A reversible thermosensitive recording material was prepared by curing with a cm 2 ultraviolet lamp and providing a protective layer having a thickness of about 2.5 μm (FIG. 8).

Example 6 0.5 part of potassium titanate (manufactured by Otsuka Chemical Co., Ltd., DENTOL BK.200 (diameter 0.2 to 0.5, length 10 to 20 μm)) based on the same base material as in Example 5 A solution of 5 parts of vinyl chloride-vinyl acetate copolymer and 95 parts of THF was applied, and the solution was dried by heating at 120 ° C.
An anchor layer with a thickness of 5 μm was provided. A reversible thermosensitive recording material was prepared by applying the same solution for forming a thermosensitive layer as in Example 5 except that the spacer particles were not added thereto, and further applying a protective layer (FIG. 9).

Example 7 The same substrate as in Example 5 was used, and a urethane acrylate UV-curable resin (Dainippon Nippon Kabushiki Kaisha) was applied to the outer peripheral portion of the heat-sensitive layer-using portion (where the thermal head of the non-printing portion always hits during printing). Indick Unidick (7-157) 10 parts Potassium titanate (Otsuka Chemical BK-100 (diameter 0.2 to 0.5, length 10 to 20 μm)) 0.1 part solution is gravure coated. After heating and drying at 80 ℃,
It was cured with an 80 w / cm ultraviolet lamp to provide a spacer adjusting layer having a thickness of about 4 μm. Outside the spacer adjustment layer,
The same heat-sensitive layer-forming solution as in Example 6 was applied, and the protective layer-forming solution was applied on the entire surface thereof to prepare a reversible heat-sensitive recording material (FIG. 10).

Comparative Example 2 A reversible thermosensitive recording material was prepared by using the same substrate as in Example 5 and providing the same thermosensitive layer and protective layer as in Example 6 thereon.

The reversible thermosensitive recording material prepared as described above was used to form a printed image using a thermal head of 8 dots / mm, and the image was erased using the thermal head to make it transparent (voltage 16V / 23V, Thermal resistance 30
00Ω). The image (white) 100 times repeatedly was measured with the Macbeth reflection densitometer RD-514. The results are shown in Table 2.

[0060]

[Table 2]

[0061]

In the reversible thermosensitive recording material of the present invention, spacer particles are dispersed and contained in the thermosensitive layer, or an anchor layer is provided below the thermosensitive layer and the spacer particles are dispersed and contained in the anchor layer. As a result, even if image formation and erasing are repeatedly performed using a heating means such as a thermal head that applies heat and pressure at the same time, the organic low molecular weight substance is maintained in fine particles, and therefore durability is improved. Further, when the spacer particles having a plate shape, a needle shape, a column shape, a scale shape, or an indefinite shape are used, distortion of the heat-sensitive layer due to a thermal head or the like can be suppressed and the contrast is improved. Furthermore, when a spacer adjusting layer is provided around the heat sensitive layer, the durability is improved and the contrast is further improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in transparency of a reversible thermosensitive recording material according to the present invention due to heat.

FIG. 2 is a diagram showing a change in a coloring state of a reversible thermosensitive recording material according to the present invention due to heat.

FIG. 3 (a) is a schematic view in the case where a thermal head is brought into contact with a reversible thermosensitive recording material containing no spacer particles in the thermosensitive layer. (B) is a schematic diagram in the case of contacting a thermal head with a reversible thermosensitive recording material in which spacer particles are dispersedly contained in the thermosensitive layer of the present invention.

FIG. 4 is a reversible thermosensitive recording material provided with a thermosensitive layer containing spherical spacer particles dispersed therein according to the present invention.

FIG. 5 is a reversible thermosensitive recording material of the present invention provided with an anchor layer containing spherical spacer particles dispersed therein.

FIG. 6 is a reversible thermosensitive recording material according to the present invention, which further comprises a thermosensitive layer on the anchor layer of FIG.

FIG. 7 is a schematic view of a reversible thermosensitive recording material provided with a thermosensitive layer containing spherical spacer particles dispersed therein, in which a thermal head is brought into contact.

FIG. 8 shows a reversible thermosensitive recording material provided with a thermosensitive layer in which spacer particles having a shape other than spherical are dispersed and contained.
The schematic diagram at the time of contacting a thermal head.

FIG. 9 is a reversible thermosensitive recording material of the present invention provided with an anchor layer in which spacer particles having a shape other than spherical are dispersed and contained.

FIG. 10A is a perspective view of a reversible thermosensitive recording material of the present invention in which a spacer adjusting layer is provided around a thermosensitive layer. (B)
Is a sectional view taken along line AA.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Amano 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Kunichika Moroboshi 1-3-6 Nakamagome, Ota-ku, Tokyo In stock company Ricoh (72) Inventor Fumito Masuchibuchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside company Ricoh (56) Reference JP 5-58034 (JP, A) JP 5 -77548 (JP, A) JP-A-63-280684 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/36

Claims (9)

(57) [Claims] To 1. A on a support, transparent by changing the heating temperature, the reversible heat-sensitive recording material having a thermosensitive layer reversibly produce Opaque, spacer particles the heat-sensitive layer
(However, if the size of the heat-sensitive layer is 1.2 times or less,
Reversible thermosensitive recording material characterized by not excluding) dispersedly contained. On 2. A support transparent by changing the heating temperature, the reversible heat-sensitive recording material having a thermosensitive layer reversibly produce Opaque, spacers between the support and the heat-sensitive layer A reversible thermosensitive recording material comprising an anchor layer containing dispersed particles. To 3. A on a support, transparent by changing the heating temperature, the reversible heat-sensitive recording material having a thermosensitive layer reversibly produce Opaque, around the heat-sensitive layer based on the support A reversible thermosensitive recording material comprising a spacer adjusting layer in which spacer particles are dispersed. 4. The reversible thermosensitive recording material according to claim 1, 2 or 3, wherein the spacer particles are spherical. 5. The reversible thermosensitive recording material according to claim 4, wherein the spacer particles are dispersed and contained in a state of protruding from the thermosensitive layer. 6. The spacer particles are plate-shaped, needle-shaped, column-shaped,
The reversible thermosensitive recording material according to claim 1, 2 or 3, which has a scale-like or irregular shape. 7. A heat-sensitive layer is provided by coating a support with a dispersion liquid in which spacer particles are dispersed in a heat-sensitive layer liquid containing a resin base material and an organic low-molecular substance as a main component, and drying. The method for producing a reversible heat-sensitive recording material according to claim 1. 8. A dispersion liquid in which spacer particles are dispersed in an anchor layer liquid is applied on a support and dried to form an anchor layer, and a resin base material and an organic low molecular weight substance are mainly formed on the anchor layer. The method for producing a reversible thermosensitive recording material according to claim 2, wherein a thermosensitive layer liquid as a component is applied and dried to form a thermosensitive layer. 9. An image display method, wherein the reversible thermosensitive recording material according to claim 1, 2 or 3 is used, and an image is formed and / or erased by using a thermal head.