JPH04347684A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To provide a reversible thermal recording material improved in the adhesiveness at the interface of a support and a thermal layer and generating no release of the thermal layer even when the formation and erasure of an image are repeated many times. CONSTITUTION:In a reversible thermal recording material wherein a thermal layer based on a resin matrix material and the org. low molecular substance dispersed in the resin matrix material and reversibly changed in its transparency in dependence on heat is provided on a support, the support is formed by laminating an adhesive layer composed of polyether sulfone or polyether ether ketone to the surface of a film composed of polyether sulfone or polyether ether ketone or the surface of a polyester film.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible heat-sensitive recording material in which images can be repeatedly formed and erased by utilizing the reversible change in transparency of a heat-sensitive layer depending on the temperature.

0002

BACKGROUND OF THE INVENTION In recent years, reversible thermosensitive recording materials have attracted attention in which temporary images can be formed and the images can be erased when no longer needed. Typical examples include glass transition temperatures (Tg) ranging from 50 to 60°C to 80°C.
Reversible thermosensitive recording materials are known in which low-molecular-weight organic substances such as higher fatty acids are dispersed in a resin matrix such as vinyl chloride-vinyl acetate copolymer with a low glass transition temperature of less than 0°C. 1987-119377, JP-A-55-1
Publications such as No. 54198).

[0003] In these reversible thermosensitive recording materials,
Polyester films, glass plates, metal plates, etc. are used as supports, but these supports have insufficient adhesion at the interface between the support and the heat-sensitive layer, and require repeated image formation and erasing. There was a drawback that the heat-sensitive layer peeled off during repeated use, making it impossible to use it repeatedly.

0004

[Problems to be Solved by the Invention] The present invention provides a reversible heat-sensitive recording material that improves the adhesion at the interface between the support and the heat-sensitive layer, and in which the heat-sensitive layer does not peel off no matter how many times image formation and erasing are repeated. The purpose is to provide

[0005]

[Means for Solving the Problems] According to the present invention, the main component is a resin base material on a support and an organic low-molecular substance dispersed in the resin base material, and the transparent state and the cloudy state depend on heat. In a reversible heat-sensitive recording material provided with a heat-sensitive layer in which the A reversible thermosensitive recording material characterized in that it has an adhesive layer laminated on its surface made of polyether sulfone or polyether ether ketone, and in particular, the thickness of the adhesive layer is 0.1 to 3.0 μm. is provided.

[0006] The inventors of the present invention have conducted intensive studies on supports with improved adhesion between the support and the heat-sensitive layer in reversible heat-sensitive recording materials.
Alternatively, it has been found that the conventional drawbacks can be overcome by constructing it with polyetheretherketone.

According to the present invention, when polyether sulfone or polyether ether ketone is used as the support, when the heat-sensitive layer is coated, the organic solvent in the heat-sensitive layer, such as tetrahydrofuran (THF), is mixed with the polyether. Dissolve the surface of sulfone or polyetheretherketone,
It is presumed that this is because the heat-sensitive layer partially impregnates the support, thereby improving the adhesion at the interface between the support and the heat-sensitive layer. Furthermore, when a polyester film is used as a support and an adhesive layer containing the above-mentioned polyether sulfone or polyether ether ketone as a main component is provided on the surface of the polyester film, the adhesiveness is improved for the same reason as above. This has been confirmed. In this case, the thickness of the adhesive layer is 0
．． 1 to 3.0 μm is preferable, more preferably 0.5 to 3.0 μm.
2.0 μm is good. If the thickness is 0.1 μm or less, the heat-sensitive layer will impregnate all the way to the support side, so there will be no effect on adhesion;
In the above case, the adhesion at the interface between the support and the adhesive layer deteriorates, resulting in the problem of layer peeling.

The reversible thermosensitive recording material of the present invention utilizes the above-mentioned change in transparency (transparent state, cloudy opaque state), and the difference between the transparent state and the cloudy opaque state is presumed as follows. . In other words, (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 light incident from one side is not scattered and is scattered in the opposite direction. (ii) In the case of cloudiness, the particles of the organic low-molecular-weight substance are composed of polycrystals, which are aggregates of fine crystals of the organic low-molecular-weight substance, and the crystal axes of the individual crystals are The reason for this is that because the particles face in various directions, light incident from one side is refracted and scattered many times at the interface of the crystals of the organic low-molecular substance particles, resulting in the appearance of white.

In FIG. 1 (which shows the change in transparency due to heat), the heat-sensitive layer whose main components are a resin base material and an organic low-molecular substance dispersed in the resin base material is, for example, T
At room temperature below 0, it is cloudy and opaque. This temperature is T
When heated to 2, it becomes transparent, and even if it is returned to room temperature below T0 in this state, it remains transparent. This is considered to be because the organic low-molecular substance passes through a semi-molten state and crystals grow from polycrystal to single crystal from temperature T2 to below T0. Further heating to a temperature of T3 or higher results in a translucent state intermediate between maximum transparency and maximum opacity. Next, when this temperature is lowered, the liquid returns to its initial cloudy and opaque state without becoming transparent again. This is considered to be because polycrystals precipitate when the organic low-molecular substance is melted at a temperature of T3 or higher and then cooled. Note that when this opaque state is heated to a temperature between T1 and T2 and then cooled to room temperature, that is, a temperature below T0, it can take an intermediate state between transparent and opaque. Moreover, if the material that becomes transparent at room temperature is heated again to a temperature of T3 or higher and then returned to room temperature, it will return to a cloudy, opaque state. That is, it can take both opaque and transparent forms, as well as an intermediate state between them, at room temperature. Therefore, by selectively applying heat to the heat-sensitive layer, it is possible to form a cloudy image on a transparent background and a transparent image on a cloudy background, and this change can be repeated many times. . If a colored sheet is placed on the back side of such a thermosensitive member, it is possible to form an image in the color of the colored sheet on a white background or a white image on the background of the color of the colored sheet. Furthermore, if the image is projected using an OHP (overhead projector) or the like, the cloudy areas become dark areas, and the transparent areas allow light to pass through and become bright areas on the screen.

In order to form and erase images 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 single thermal head for forming and erasing images. In the former case, the cost of the device increases because two thermal heads are required, but if the energy application conditions for each thermal head are set separately and the reversible thermosensitive recording material is passed through once, image formation and erasing can be performed. You can do it by doing. In the latter case, since the image is formed and erased using one thermal head, the conditions for applying energy to the thermal head each time the heat-sensitive recording material passes are adjusted depending on the area where the image is to be formed and the area where the image is to be erased. The operation is complicated, as the image on the thermal recording material must be changed in detail, or the image on the thermal recording material must be erased and then run in the opposite direction again to form an image under different energy conditions. Therefore, the equipment cost is low.

[0011] To make the reversible thermosensitive recording material of the present invention,
For example, a solution of polyether sulfone or polyether ether ketone dissolved in an organic solvent is coated on a support made of polyether sulfone or polyether ether ketone or on the surface of a polyester film by the following method, and then dried. It can be manufactured by forming a heat-sensitive layer as a film on the adhesive layer laminated as a film or by molding it into a sheet. 1) A method in which a resin base material and an organic low-molecular substance are dissolved in a solvent, this is applied onto a support member, and the solvent is evaporated to form a film or sheet. 2) Dissolve the resin base material in a solvent that dissolves only the resin base material, crush or disperse organic low-molecular substances therein using various methods, apply this onto a support member, and evaporate the solvent to form a film. Or make it into a sheet. Various solvents can be selected as the solvent for preparing the heat-sensitive layer or heat-sensitive recording material depending on the resin base material and the type of organic low-molecular substance, such as tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone,
Examples include chloroform, carbon tetrachloride, ethanol, toluene, and benzene. It should be noted that in the heat-sensitive layer obtained not only when a dispersion is used but also when a solution is used, the organic low-molecular substance precipitates as fine particles and exists in a dispersed state.

In the present invention, the resin used for the resin matrix of the heat-sensitive layer of the reversible heat-sensitive recording material is preferably a resin that can form a film or sheet, has good transparency, and is mechanically stable. Such resins 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. Vinyl chloride copolymers such as polymers; vinylidene chloride copolymers such as polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylates -Methacrylate copolymer; silicone resin, etc. are mentioned. These may be used alone or in combination of two or more.

On the other hand, the organic low-molecular substance may be one that changes from polycrystal to single crystal due to heat in the recording layer (changes within the temperature range T1 to T3 shown in FIG. 1), and generally has a melting point. 30-200℃ preferably 50-150℃
A certain degree is used. Such organic low-molecular substances include alkanols; alkanediols; halogenalkanols or halogenalkanediols; alkylamines; alkanes; alkenes; alkynes; halogenalkanes; halogenalkenes; halogenalkynes; cycloalkanes; cycloalkenes; cycloalkynes; saturated or Unsaturated mono- or dicarboxylic acids or their esters, amides or ammonium salts; Saturated or unsaturated halogenated fatty acids or their esters, amides or ammonium salts; Allylcarboxylic acids or their esters, amides or ammonium salts; Halogenated allylcarboxylic acids or their esters, amides or ammonium salts; Examples include esters, amides or ammonium salts thereof; thioalcohols; thiocarboxylic acids or esters, amines or ammonium salts thereof; carboxylic acid esters of thioalcohols. These may be used alone or in a mixture of two or more. The carbon number of these compounds is 10~
60, preferably 10-38, especially 10-30. The alcohol group moiety in the ester may be saturated or unsaturated, or may be substituted with halogen. In any case, the organic low-molecular substance contains at least one of oxygen, nitrogen, sulfur, and halogen in the molecule, such as -OH, -COOH, -CONH, -COOR, -NH.
, -NH2, -S-, -S-S-, -O-, halogen, etc. are preferred.

More specifically, these compounds include lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, alagic acid, henicosanoic acid, tricosanoic acid, lignoceric acid, and pentacosanoic acid. esters of higher fatty acids such as methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, dodecyl behenate, etc. ; C16H33-O-C16H33, C16
H33-S-C16H33, C18H37-S
-C18H37, C12H25-S-C12H
25, C19H39-S-C19H39,
Examples include ethers or thioethers such as C12H25-S-S-C12H25. Among these, in the present invention, higher fatty acids, particularly palmitic acid, pentadecanoic acid, nonadecanoic acid, arachidic acid, henicosanoic acid, tricosanoic acid,
1 carbon number such as lignoceric acid, stearic acid, behenic acid, etc.
Higher fatty acids having 6 or more carbon atoms are preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.

In addition, in order to widen the range of temperatures at which transparency can be achieved, the organic low-molecular substances described in this specification may be appropriately combined, or such organic low-molecular substances and other materials having different melting points may be combined. All you have to do is combine them. These include, for example, JP-A-63-39378 and JP-A-63-13038.
Although it is disclosed in publications such as No. 0 and specifications such as Japanese Patent Application No. 14754/1983 and Japanese Patent Application No. 140109/1999,
It is not limited to these.

The weight ratio of the organic low-molecular substance to the resin base material in the heat-sensitive layer is preferably about 2:1 to 1:16, more preferably 1:1 to 1:3. If the ratio of the resin base material is less than this, it will be difficult to form a film that holds the organic low molecular weight substance in the resin base material, and if it is higher than this, the amount of the organic low molecular weight substance will be small and the film will become opaque. becomes difficult.

[0017] The thickness of the heat-sensitive layer is preferably 1 to 3 μm, and 2 to 3 μm.
-20 micrometers is more preferable. If the heat-sensitive layer is too thick, heat distribution will occur within the layer, making it difficult to achieve uniform transparency. Furthermore, if the heat-sensitive layer is too thin, the white turbidity will decrease and the contrast will decrease. Furthermore, white turbidity can be increased by increasing the amount of organic low-molecular substances in the heat-sensitive layer.

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

Examples of surfactants and other additives; polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkyl amine, 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, sulfuric acid monoesters 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; long-chain alkyl methacrylate-amine-containing monomer copolymers ; Styrene-maleic anhydride copolymer; Olefin-maleic anhydride copolymer.

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 a heating means using a writing method such as a thermal head and reducing the transparency of the transparent portion. good. A protective layer laminated on the heat-sensitive layer (thickness 0.
1 to 10 μm), silicone rubber, silicone resin (described in JP-A No. 63-221087)
, polysiloxane graft polymer (JP-A-63-31
7385), ultraviolet curable resin, or electron beam curable resin (described in JP-A-2-566). In either case, a solvent is used during coating, but it is desirable that the solvent is difficult to dissolve the resin and organic low-molecular substance of the heat-sensitive layer. Solvents that do not easily dissolve the resin and organic low-molecular substances of the heat-sensitive layer include n-hexane, methyl alcohol,
Examples include ethyl alcohol and isopropyl alcohol, and alcohol-based solvents are particularly desirable from the viewpoint of cost.

Furthermore, in order to protect the reversible recording material from the solvent, monomer components, etc. of the protective layer forming liquid, an intermediate layer can be provided between the protective layer and the reversible recording material (see Japanese Patent Laid-Open No. 1-133781). (described in the issue). 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 base material in the heat-sensitive layer. That is, specific examples thereof 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. If it is less than this, the protective effect will decrease, and if it is more than this, the thermal sensitivity will decrease.

[0022]

EXAMPLES All parts and percentages herein are based on weight. Example 1 Behenic acid on a 50 μm thick transparent polyethersulfone film

6 parts eicosane 2 acid

Part 4 Diallyl phthalate
2 parts Vinyl chloride-vinyl acetate copolymer
20 parts Tetrahydrofuran (THF)
180 parts toluene

A solution consisting of 20 parts was applied with a wire bar and dried by heating to form a heat-sensitive layer with a thickness of 15 μm. Furthermore, polyamide resin (CM-8000 manufactured by Toray Industries) 10
part ethyl alcohol

A solution consisting of 90 parts was applied with a wire bar and dried by heating to form an intermediate layer with a thickness of approximately 1.5 μm.
Urethane acrylate ultraviolet curing resin
10 parts (Dainippon Ink, Unidic, 17-824-9) Toluene
1
A reversible thermosensitive recording material was prepared by applying a solution consisting of 0 parts with a wire bar, heating and drying, and then irradiating it with a UV lamp of 80 W/cm to form a protective layer with a thickness of about 5 μm.

Example 2 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that the polyether sulfone film in Example 1 was replaced with a polyether ether ketone film.

Example 3 Instead of the polyether sulfone film in Example 1, a polyester film (50 μm thick) was used on top of it.
polyether sulfone
Part 5 THF

A solution consisting of 95 parts was applied using a wire bar and dried by heating to form an adhesive layer having a thickness of about 0.8 μm, and a reversible thermosensitive recording material was prepared thereon in the same manner as in Example 1.

Example 4 A reversible thermosensitive recording material was prepared in the same manner as in Example 3 except that polyether ether ketone was used instead of polyether sulfone.

Example 5 A reversible thermosensitive recording material was prepared in the same manner as in Example 3 except that the thickness of the adhesive layer in Example 3 was changed to 0.1 μm.

Example 6 A reversible thermosensitive recording material was prepared in the same manner as in Example 3 except that the thickness of the adhesive layer in Example 3 was changed to 3.0 μm.

Comparative Example 1 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that a polyester film was used instead of the polyether sulfone film in Example 1.

[0029] Using the reversible thermosensitive recording material prepared as described above, knit-polyester adhesive tape No. 31B of "8th, 5th, 2nd base tape method" in JIS-K5400 was used.
Adhesion was evaluated by In addition, using a thermal head of 8 dotS/mm, the strength test conditions (applied voltage 1.0 W.
After forming an image with an applied pulse width of 0.7 msec), it was made transparent and erased using a heat roller (80 to 85°C, 10 mm/min), and the peeling of the layer after repeating the same conditions 100 times was evaluated. The results are shown in Table 1 below.

[0030]

[Table 1] *1 Peeling score of 10 points to 10 points peeling

[0031]

Effects of the Invention As is clear from the description of the examples, the reversible heat-sensitive recording material of the present invention uses a polyether sulfone film or a polyether ether ketone film as a support, or uses a polyester film surface as a support. By using an adhesive layer laminated with polyether sulfone or polyether ether ketone as the main component, the organic solvent in the heat-sensitive layer, such as THF, dissolves the surface and partially impregnates the support. It is possible to provide a reversible heat-sensitive recording material in which the adhesion at the interface between the heat-sensitive layer and the heat-sensitive layer is improved and the layer does not peel off even after image formation and erasing are repeated many times.

[Brief explanation of drawings]

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

Claims (3)

[Claims] Claim 1: A heat-sensitive layer comprising a resin base material and an organic low-molecular substance dispersed in the resin base material as main components on a support, and which changes reversibly between a transparent state and a cloudy state depending on heat. 1. A reversible thermosensitive recording material, characterized in that the support is composed of polyether sulfone or polyether ether ketone. 2. The reversible heat-sensitive recording material according to claim 1, wherein the support is a polyester film surface with an adhesive layer made of polyether sulfone or polyether ether ketone laminated thereon. [Claim 3] The thickness of the adhesive layer made of polyether sulfone or polyether ether ketone is 0.1.
3. The reversible thermosensitive recording material according to claim 2, wherein the thickness is 3.0 .mu.m.