JP3044590B2 - Method for producing reversible thermosensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a reversible thermosensitive recording material capable of repeatedly forming and erasing an image by utilizing a reversible change in transparency of a thermosensitive layer depending on the temperature. .

[0002]

2. Description of the Related Art In recent years, a reversible thermosensitive recording material which can form a temporary image and erase the image when it becomes unnecessary has been attracting attention. A typical example is a glass transition temperature (Tg) of 50 to 60 ° C to 8 ° C.
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 base material 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
No. 54198).

When manufacturing these reversible thermosensitive materials,
Tetrahydrofuran is used as a basic solvent capable of dissolving or dispersing both a resin base material and an organic low-molecular substance. Since this type of organic solvent has a very low boiling point and a high evaporation rate, the solvent on the surface evaporates before coating and drying, forming a film of the resin base material on the surface and evaporating the solvent inside the layer. Not only does it hinder volatilization, but the particle size of the organic low-molecular substance dispersed in the resin base material increases and precipitates on the surface of the layer over time. Further, there is a defect that the contact property is deteriorated at the interface between the support and the layer due to the residual solvent in the layer. Therefore, there is a coating problem that another layer cannot be smoothly laminated on this surface, and while applying pressure using a thermal head or the like and simultaneously heating and image forming-erasing a number of times, The organic low-molecular-weight substance particles gradually become larger in diameter, and the effect of scattering light is lost, so that the white turbidity is reduced and the image contrast is eventually reduced. In addition, since particles of the organic low-molecular substance are deposited on the surface, even if a protective layer is laminated thereon, the particles of the organic low-molecular substance gradually migrate into the protective layer and adhere to head scum due to contact with the thermal head. And there was a disadvantage that it could not be repeated many times.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks, and achieves uniform image formation and erasure by using a heating means such as a thermal head for simultaneously applying heat and pressure, which is repeated many times. Another object of the present invention is to provide a method for producing a reversible thermosensitive recording material that can form a stable image and that has no head residue.

[0005]

According to the present invention, a solution in which a resin base material and an organic low-molecular substance are dissolved in a solvent, or a dispersion liquid in which a resin base material and a low-molecular organic substance are dissolved in a solvent is applied on a support, dried, and dried. In the method for producing a reversible thermosensitive recording material for forming a thermosensitive layer in which a transparent state and a cloudy state are reversibly changed depending on the temperature of the surface of the support on the side on which the solution or dispersion is applied, was a T _1, when the temperature of the rear surface of the support was T _2, and dried by heating such that T ₁ ≦ T _2, specifically, at the same time as the coating of the solution or the dispersion To heat the back surface of the support, or to after-heat dry the back surface of the support immediately after coating, especially as these heating equipment,
The method for producing a reversible thermosensitive recording material is characterized by using a hot roll drying facility, a hot air drying facility, and a hot plate drying facility, and using a hot back roll drying facility as a heating facility in the case of simultaneous heating with coating. Provided.

In a reversible thermosensitive recording material provided with a thermosensitive layer in which a transparent state and a cloudy state change reversibly depending on heat, the particle size of the organic low-molecular substance is closer to the support than to the surface. It is important to make the particle diameter of the organic low-molecular substance have a gradient in the depth direction of the heat-sensitive layer so that the particle size becomes large.

That is, in such a reversible thermosensitive recording material, the portion of the thermosensitive layer in the vicinity of the support is hardly affected by the heat and pressure of the thermal head. Even if pressure is applied, the particle size does not change, and the same image formation as in the initial stage can be obtained. Further, the heat and pressure of the thermal head greatly affect the vicinity of the surface of the heat-sensitive layer, but the particle diameter of the organic low-molecular substance is small, so that the periphery of the particle is thickly covered with a resin base material. Therefore, even if the heat and pressure of the thermal head are repeated many times, the organic low-molecular substance dispersed in the resin base material is maintained as fine particles, and there is no reduction in image contrast. Further, since the particles of the organic low-molecular substance on the surface of the heat-sensitive layer are covered with the resin base material, there is no migration, and therefore even when repeated with a thermal head, no residue adheres to the thermal head and uniform image formation can be obtained.

The average particle size of the organic low-molecular substance in the heat-sensitive layer is preferably from 0.1 to 5.0 μm, and more preferably from 0.3 to 3.0 μm, in the vicinity of the support in the heat-sensitive layer. The portion near the surface of the heat-sensitive layer is 0.05 to 1.0 μm, preferably 0.1 to 1.0 μm.
A particle size of 1 to 0.8 μm is good. When the particle diameter in the vicinity of the support is 0.1 μm or less, it is sufficiently covered with the resin base material, and the change in the white turbid state and the transparent state is insufficient at low energy, and the contrast of the image is reduced. On the other hand, when the thickness is 5.0 μm or more, the scattering effect is reduced and the turbidity is reduced. When the particle size of the heat-sensitive layer near the surface is 0.05 μm or less, it becomes difficult to form a polycrystalline state in a matrix dispersed in crystal growth, and the turbidity decreases.
When the thickness is 1.0 μm or more, the coating of the base metal material is insufficient, and the growth of the particle diameter is promoted and the particles are deposited on the surface. As a result, a defect of adhesion of head residue occurs.

The present inventors have conducted intensive studies on a production method for obtaining a reversible thermosensitive recording material having a gradient in the particle size of the organic low molecular substance in the depth direction of the thermosensitive layer. Simultaneously with the application of the solution or dispersion for layer formation,
Alternatively, immediately after the coating, the temperature of the coated surface of the support is increased by heating the support with at least one facility such as a hot roll drying facility, a hot air drying facility, a hot plate drying facility, or a hot back roll drying facility. Heated below the temperature of the back of
Since the evaporation rate and diffusion rate of the solvent before coating and drying are appropriately adjusted, the growth of the particle size of the organic low-molecular substance is suppressed without forming a film of the heat-sensitive layer, and particles from the vicinity of the support are suppressed. It has been found that a heat-sensitive layer having a gradient of the particle diameter is formed due to the formation.

According to the production method of the present invention, the particle size of the organic low-molecular substance is 0.1 to 5.0 μm near the support and 0.05 to 1.0 μm near the surface of the heat-sensitive layer.
A particle size of μm is obtained. The heating temperature of the support at this time is preferably from 50 ° C. to 140 ° C. while maintaining the temperature of the coating surface of the support below the temperature of the back surface of the support.
C. is particularly preferred. When the heating temperature is 50 ° C. or lower, the particle diameter grows and becomes large, and furthermore, precipitates on the surface of the heat-sensitive layer. Conversely, when the temperature is 140 ° C. or higher, there is a problem that the support expands and contracts due to heat and is deformed.

The reason for simultaneous heating drying or after heat drying and particle formation of the present invention is not clear, but the estimated melanism is as shown in FIG. In the case of the method, the temperature of the coating surface of the support becomes higher than the temperature of the back surface of the support because hot air is blown to the coating surface side. Since a film containing the resin base material and the organic low-molecular substance is formed on the surface, the solvent remains from the surface of the heat-sensitive layer to the inside of the layer, and particles grow due to the influence of the residual solvent between the drying step and the drying step. As a result, a large layer of particles is formed on the entire heat-sensitive layer. However, as shown in FIG. 2A, when the support is heated at the same time as or immediately after the coating of the present invention, and the temperature of the coated surface of the support is kept at or below the temperature of the support, Drying of the solvent and the resin matrix starts near the support, and then evaporation of the solvent during the drying process with the organic low-molecular substance fixed by the resin matrix by evaporation of the solvent on the surface and drying of the resin matrix. Further, it is presumed that the drying of the resin base material is completed and completely fixed, so that the particle growth is suppressed and a layer having a small particle is formed.

FIG. 3 shows the temperature profile at this time.
FIG. 3A shows a temperature profile of the support when dried by the production method of the present invention, and FIG. 3B shows a temperature profile of the support when dried by the conventional production method. This profile was obtained by measuring the temperature with a thermocouple attached to both sides of the support, and calculating by the finite element method on the basis of this data. The temperature profile in the coating film is estimated.

The heating and drying equipment of the present invention includes a hot roll drying equipment, a hot air drying equipment, a hot plate drying equipment and a hot back roll drying equipment. This is effective in a contact drying system, that is, a hot roll drying facility and a hot plate drying facility. In the hot-air drying equipment, the effect of heat on the support is improved by making the gap between the support and the hot-air outlet as narrow as possible. Examples of the hot roll drying equipment system of the present invention include steam heating, infrared heating, electromagnetic heating, and dielectric heating. Examples of the hot air drying equipment include steam heating and infrared heating. Furthermore, steam heating, infrared heating, electromagnetic heating, dielectric heating and the like can be mentioned as a hot plate drying equipment system.

The heating and drying method of the present invention will be described with reference to FIGS. 4 and 5 show a hot roll drying method, in which a coating solution is applied to a support sent from an unwinder by a coating equipment 3. At this time, simultaneous heating can be performed by disposing a hot roll drying facility 2 on the back surface as shown in FIG. FIG. 5 shows an after heat drying method in which a hot roll drying equipment 2 is installed immediately after coating. FIG. 6 shows a case where a hot plate drying facility 7 is installed in place of the hot roll drying facility of FIG. 5, and FIG. 7 shows an after heat drying method in which a hot air drying facility 8 is similarly arranged. After these drying operations, it is passed through an annealing box 5 and wound up by a winder 6.

The reversible thermosensitive recording material of the present invention utilizes the change in transparency (transparent state, cloudy opaque state) as described above. The difference between this transparent state and cloudy opaque state is presumed as follows. . That is, (i) in the case of transparency, the particles of the organic low-molecular substance dispersed in the resin base material are composed of large particles of the organic low-molecular substance, and the light incident from one side is not scattered and is opposite. (Ii) In the case of cloudiness, the particles of the organic low-molecular substance are composed of polycrystals composed of fine crystals of the organic low-molecular substance, and the crystal axes of the individual crystals Is oriented in various directions, so that light incident from one side is refracted many times at the interface between the crystals of the organic low-molecular substance particles, and is scattered, so that it appears white.

In FIG. 1 (representing a change in transparency due to heat), a heat-sensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material is, for example, T
_At a room temperature of ₀ or less, it is cloudy and opaque. This is called temperature T ₂
When the temperature is returned to room temperature below T ₀ , the film remains transparent. This is from temperature T ₂ to T ₀
It is considered that the crystal grows from a polycrystal to a single crystal through the semi-molten state of the organic low-molecular substance until the following.
Upon further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the state returns to the original cloudy and opaque state without taking the transparent state again. This after low-molecular organic material is melted at a temperature T ₃ or more, presumably because the polycrystals precipitated by being cooled. When the opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature lower than T ₀ , an intermediate state between transparent and opaque can be obtained. Also, by returning to room temperature After heating to be again T ₃ or more temperature which became clear at the normal temperature, the flow returns to cloudy opaque state again. That is, both opaque and transparent forms at room temperature and intermediate states thereof can be taken. Therefore,
By selectively applying heat, the heat-sensitive layer can be selectively heated 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. If a colored sheet is arranged on the back of such a heat-sensitive layer, a color image of the colored sheet on a white background or a white image on a colored background of the colored sheet can be formed. Further, when projected by an OHP (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. It is effective to use a device having a single thermal head for forming an image and erasing an image. In the former case, the cost of the apparatus increases because two thermal heads are required, but if the energy application conditions for each thermal head are different and the reversible thermosensitive recording material is passed once, the image formation and erasing can be performed. You can do it. In the latter case, in order to form and erase an image with one thermal head, the condition for applying energy to the thermal head at one time when the thermal recording material passes is adjusted according to the part where the image is formed and the part to be erased. Although the operation is complicated, the operation is complicated, for example, the image is formed under different energy conditions by changing the thermal recording material in a small direction or by erasing the image on the thermal recording material once and then running the thermal recording material in the opposite direction again. Therefore, the equipment cost is reduced.

The reversible thermosensitive recording material used in the present invention can be formed as a film on a support member or formed into a sheet by the following method, for example. 1) A method of dissolving a resin base material and an organic low-molecular substance in a solvent, applying this on a support member, and evaporating the solvent to form a film or sheet. 2) The resin base material is dissolved in a solvent in which only the resin base material is dissolved, and the organic low-molecular substance is pulverized or dispersed therein by various methods, applied to a support member, and the solvent is evaporated to form a film. Or a method of forming a sheet. The solvent for 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 substance.
Examples include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, benzene and the like. In addition, not only when a dispersion is used, but also when a solution is used, in a heat-sensitive layer obtained, organic low-molecular substances are precipitated as fine particles and exist in a dispersed state.

In the present invention, the resin used as the resin base material of the heat-sensitive layer of the reversible thermosensitive recording material is preferably a resin which can form a film or sheet, has good transparency, and is mechanically stable. Examples of such a resin include polyvinyl chloride; vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. Vinylidene chloride copolymers such as polyvinylidene chloride, polyvinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-acrylate copolymer; polyesters; polyamides Polyacrylate or polymethacrylate or acrylate-methacrylate copolymers; silicone resins and the like. These may be used alone or as a mixture of two or more.

On the other hand, any organic low-molecular substance may be used as long as it changes from polycrystal to single crystal by heat in the recording layer (changes in the temperature range of T _{1 to} T ₃ shown in FIG. 1).
Generally, those having a melting point of about 30 to 200 ° C, preferably about 50 to 150 ° C are used. Such organic low molecular weight substances include alkanol; alkane diol; halogen alkanol or halogen alkane diol; alkylamine; alkane; alkene; alkyne; halogen alkane; halogen alkene; halogen alkyne; cycloalkane; cycloalkene; cycloalkyne; 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; Esters, amides or ammonium salts thereof; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; Carboxylic acid esters, and the like. These may be used alone or in combination of two or more. These compounds have 10 to 10 carbon atoms.
60, preferably 10 to 38, particularly preferably 10 to 30. The alcohol group in the ester may be saturated, may not be saturated, and may be halogen-substituted. In any case, the organic low-molecular-weight substance contains 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, these compounds include higher fatty acids such as lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, araginic acid and oleic acid; methyl stearate , tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, esters of higher fatty acids dodecyl behenate _{like; C 16 H 33 -O-C} 16 H 33, C 16 H 33 -S-C 16 H 33
_{, C 18 H 37 -S-C} 18 H 37, C 12 H 25 -S-C 12 H 25
_{, C 19 H 39 -S-C} 19 H 39, C 12 H 25 -S-S-C 12
H ₂₅ , And ether or thioether. Among them, in the present invention, higher fatty acids, particularly higher fatty acids having 16 or more carbon atoms, such as palmitic acid, stearic acid, behenic acid, and lignoceric acid, are preferable, and higher fatty acids having 16 to 24 carbon atoms are more preferable.

In order to widen the range of temperatures at which transparency can be obtained, the organic low-molecular substance described in this specification may be appropriately combined, or such an organic low-molecular substance may be combined with another material having a different melting point. . These are disclosed, for example, in JP-A-63
JP-A-39378, JP-A-63-130380, and Japanese Patent Application Nos. 63-14754 and 1-14011.
No. 09, but not limited thereto.

The thickness of the heat-sensitive layer is preferably 1 to 3 μm,
-20 μm is more preferable. If the heat-sensitive layer is too thick, heat distribution within the layer will occur, making it difficult to achieve uniform transparency. On the other hand, if the heat-sensitive layer is too thin, the turbidity decreases and the contrast decreases. Further, the turbidity can be increased by increasing the amount of the organic low-molecular substance in the heat-sensitive layer. The ratio between the organic low-molecular substance and the resin base material in the heat-sensitive layer is preferably about 2: 1 to 1:16, more preferably 1: 1 to 1: 3 by weight. When the ratio of the resin base material is less than this, it becomes difficult to form an organic low-molecular substance in a film held in the resin base material. Becomes difficult.

In addition to the above components, additives such as a surfactant and a high-boiling solvent can be added to the heat-sensitive layer in order to facilitate 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 azelate
-Ethylhexyl, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, acetyl citric 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 salts of higher alkylbenzene sulfonic acids; higher fatty acids, aromatic carboxylic acids, higher fatty acid sulfonic acids, aromatic sulfonic acids, monoesters of sulfuric acid Or Ca, Ba or Mg salts of phosphoric acid mono- or di-esters; low sulfated oils; poly long chain alkyl acrylates; acrylic oligomers; poly long chain alkyl methacrylates; Chromatography copolymers; styrene-maleic anhydride copolymer; olefin-maleic anhydride copolymer.

When an image of this recording material is used as a reflection surface image, providing a light-reflecting layer on the back surface of the recording layer can increase the contrast even if the thickness of the recording layer is reduced. Specific examples include vapor deposition of Al, Ni, Sn and the like (described in JP-A-64-14079).

Further, a protective layer may be provided on the heat-sensitive layer of the present invention in order to prevent the surface from being deformed by the heat and pressure of the heating means by a writing method such as a thermal head and the transparency of the transparent portion being reduced. good. A protective layer (having a thickness of 0.1 mm) laminated on the heat-sensitive layer.
1-5 μm) as silicone rubber, silicone resin (described in JP-A-63-221087),
Polysiloxane graft polymer (JP-A-63-317)
385), an ultraviolet curable resin or an electron beam curable resin (described in JP-A-2-566). In any case, a solvent is used at the time of coating, and it is preferable that the solvent does not easily dissolve the resin of the thermosensitive layer and the organic low-molecular substance. Examples of the solvent that hardly dissolves the resin and the organic low-molecular substance in the heat-sensitive layer include n-hexane, methyl alcohol, ethyl alcohol, and isopropyl alcohol, and an alcohol-based solvent is particularly desirable in terms of cost.

Further, an intermediate layer can be provided between the protective layer and the reversible recording material in order to protect the reversible recording material from a solvent, a monomer component and the like of the protective layer forming solution (JP-A-1-1337981). No. gazette). As the material of the intermediate layer, the following thermosetting resins and thermoreversible resins can be used in addition to those listed as the resin base material in the thermosensitive layer.
That is, specific examples include polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide, and the like. The thickness of the intermediate layer varies depending on the application, but is preferably about 0.1 to 2 μm. Below this, the protection effect decreases, and above this, the thermal sensitivity decreases.

[0029]

EXAMPLES All parts and percentages herein are by weight. Example 1 Behenic acid 7 parts Eicosane diacid 3 parts Vinyl chloride-vinyl acetate copolymer 28 parts (VYHH manufactured by Union Carbide) di-2 ethylhexyl phthalate 3 parts Tetrahydrofuran 128 parts on a transparent polyester film having a thickness of about 100 μm A reversible thermosensitive recording layer was coated on a support by a simultaneous heating method using a hot roll drying method with a solution consisting of 14 parts of toluene under the following coating conditions. Line speed 6m / min Drying box temperature 120 ° C Surface temperature of hot roll drying equipment 90 ° C Contact time between support and hot roll drying equipment 5 seconds Coating method 1 nozzle coating method Drying time 1 minute Thickness of thermal recording layer About 5 μm

Example 2 A reversible thermosensitive recording layer was coated on a support in the same solution as in Example 1 by an after-heating method using a hot roll drying method under the following coating conditions. Run speed 6m / min Drying box temperature 120 ° C Surface temperature of hot roll drying equipment 90 ° C Contact time between support and hot back roll drying equipment 5 seconds Coating method Nozzle coating method Drying time 1 minute Thickness of thermal recording layer About 5 μm

Example 3 A reversible thermosensitive recording layer was formed on a support by preparing the same solution as in Example 1, and applying the following coating conditions by an after-heating method using a hot plate drying method. Run speed 6m / min Temperature in drying box 120 ° C Surface temperature of hot plate drying equipment 90 ° C Contact time between support and hot plate drying equipment 5 seconds Coating method Nozzle coating method Drying time 1 minute Thermal recording layer thickness 5 μm

Example 4 The same solution as in Example 1 was prepared, and a reversible thermosensitive recording layer was coated on a support by the after-heating method using a hot air drying method under the following coating conditions. Run speed 6m / min Drying box temperature 120 ° C Hot air drying equipment temperature 90 ° C Contact time between support and hot air drying equipment 5 seconds Coating method Nozzle coating method Drying time 1 minute Thermal recording layer thickness 5 μm

Comparative Example A solution was prepared in the same manner as in Example 1, and none of the hot roll drying equipment, hot plate drying equipment and hot air drying equipment was used.
Coating was performed in the same manner as in Example 1 to form a reversible thermosensitive recording layer.

Each of the five types of reversible thermosensitive recording layers prepared as described above was cut into A4 size, and a solution consisting of 5 parts of polyamide (CM8000, manufactured by Toray) and 95 parts of methanol was applied with a wire bar. It is dried in a thermostat to form an intermediate layer having a thickness of about 1 μm. Further, a solution consisting of 10 parts of an ultraviolet-curable resin (Unidic C7-157 manufactured by Dainippon Ink) and 10 parts of IPA is applied as a protective layer on the intermediate layer with a wire bar, and after drying by heating, the protective layer is cured by irradiation with ultraviolet rays. A 4 μm protective layer was provided. With respect to the five types of reversible thermosensitive recording materials, a printing durability test, a scum adhesion test to a thermal head, and a particle size of a fatty acid in a thermosensitive recording layer and deformation of a support were evaluated. Table 1 shows the results.

The printing durability test was performed using a thermal head printing tester manufactured by Yashiro Electric Co., Ltd. The thermal head was a Ricoh thin film full-surface type, the platen roll pressure on the thermal head was 3 kg / head, the pulse width was 1 ms, and the voltage was 25 V. Printing was performed under the conditions to form an image. Next, the image was erased by passing through a heat roller set at 80 ° C. Printing and erasing were repeated 30 times, and the initial image density and the image density after 30 times printing were measured with a Macbeth reflection densitometer (RD514), and the difference between the initial image density and the image density after 30 times was examined. Regarding the adhesion of the residue to the thermal head, the adhesion of the residue to the thermal head after printing 30 times was observed. The deformation of the support was determined by visually observing the deformation of the support due to heat. The particle size of the fatty acid in the thermosensitive recording layer was measured from a cross-sectional photograph of the reversible thermosensitive recording material.

[0036]

[Table 1]

The reversible thermosensitive recording material of the present invention can be applied to the formation of a heat-sensitive recording layer on a support by using a simultaneous heating method or an after-heat drying method on the support to form a coating on the support. Since the temperature can be kept below the temperature of the back surface of the support, the particle diameter of the organic low-molecular substance in the heat-sensitive recording layer has a gradient, and the particles of the organic low-molecular substance on the surface of the heat-sensitive recording layer are further coated with a resin base material. be able to. As a result, even if image formation and erasure are repeated by the thermal head, there is an effect that the image density hardly decreases and no residue adheres to the thermal head.

[Brief description of the 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 (a) shows the case where the temperature of the coated surface of the support is maintained at or below the temperature of the back surface of the support in the formation of the heat-sensitive layer by applying and drying the solution or dispersion for forming a heat-sensitive layer on the support. The figure which showed the change of the particle diameter of the organic low molecular weight substance in this layer.
(B) shows the case where the temperature of the coated surface of the support is higher than the temperature of the back surface of the support in the formation of the heat-sensitive layer by applying and drying the solution or dispersion for forming the heat-sensitive layer on the support. The figure which showed the change of the particle diameter of an organic low molecular substance.

FIG. 3 (a) is a temperature profile of a support during drying by the operation of the present invention. (B) Temperature profile of the support during drying by conventional operation.

FIG. 4 is a schematic view showing a hot roll drying method which is an example of a simultaneous heating and drying method in forming a heat-sensitive layer by applying and drying a solution or dispersion for forming a heat-sensitive layer on a support.

FIG. 5 is a schematic diagram showing a hot roll drying method which is an example of an after heat drying method in forming a heat-sensitive layer by applying and drying a solution or dispersion for forming a heat-sensitive layer on a support.

FIG. 6 is a schematic diagram showing a hot plate drying method which is an example of an after heat drying method in forming a heat sensitive layer by applying and drying a solution or dispersion for forming a heat sensitive layer on a support.

FIG. 7 is a schematic diagram showing a hot air drying method as an example of an after heat drying method in forming a heat-sensitive layer by applying and drying a solution or dispersion for forming a heat-sensitive layer on a support.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unwander 2 Hot roll drying equipment 3 Coating equipment 4 Back roll 5 Drying box 6 Winder 7 Hot plate drying equipment 8 Hot air drying equipment

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihiko Hotta 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kunichika Moroboshi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Makoto Kawaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Co., Ltd. (72) Akira Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Inside Ricoh Company (72) Inventor Fumito Masuchi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (56) References JP-A-62-225392 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41M 5/36

Claims (5)

(57) [Claims] 1. A solution in which a resin base material and an organic low-molecular substance are dissolved in a solvent, or a dispersion in which a low-molecular organic substance is dispersed in a solvent is applied on a support and dried to form a transparent state or a cloudy state depending on temperature. Wherein the temperature of the surface of the support on which the solution or dispersion is applied is T _1, and the back surface of the support is A method for producing a reversible thermosensitive recording material, comprising heating and drying such that T ₁ ≦ T _2, where T ₂ is the temperature of T ₂ . 2. A solution in which a resin base material and an organic low-molecular substance are dissolved in a solvent or a dispersion liquid in which a resin base material and a low-molecular organic substance are dissolved is coated and dried on a support, and a transparent state and a cloudy state are obtained depending on the temperature. In the method for producing a reversible thermosensitive recording material, which forms a thermosensitive layer in which the reversible change occurs, the reversible thermosensitive recording material is characterized in that the backside of the support is heated simultaneously with the application of the solution or the dispersion. Production method. 3. A solution in which a resin base material and an organic low-molecular substance are dissolved in a solvent, or a dispersion in which a low-molecular organic substance is dispersed in a solvent is applied and dried on a support to form a transparent state and a cloudy state depending on the temperature. A method for producing a reversible thermosensitive recording material, wherein a reversible thermosensitive recording material is formed, wherein the back surface of the support is after-heat-dried immediately after the application of the solution or the dispersion. Material manufacturing method. 4. The reversible thermosensitive recording material according to claim 1, wherein at least one of a hot roll drying facility, a hot air drying facility, and a hot plate drying facility is used as the heat drying facility. Method. 5. The method for producing a reversible thermosensitive recording material according to claim 2, wherein a thermal back roll drying facility in which a back roll is thermally rolled is used as the heating facility.