JPH0585047A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To enhance durability and to form a high contrast screen by forming a reversible thermal recording material by providing a thermal layer wherein an org. low-molecular substance is dispersed in a phenol resin as a main component and a support. CONSTITUTION:A reversible thermal recording material is obtained by forming a thermal layer wherein an org. low-molecular substance is dispersed in a matrix composed of a phenol resin on a support such as a plastic film. The thermal layer is in a turbid opaque state, for example, at temp. To or lower and, when said layer is heated to temp. T2, it becomes transparent and, even when the thermal layer is again returned to room temp. To or lower, the transparent state is held. When the thermal layer is further heated to temp. T3 or less, it becomes an opaque state between the max. transparency and the max.opacity and, when this temp. is lowered, the thermal layer returns to the first turbid opaque state without again taking a transparent state. As mentioned above, by selectively applying heat to the thermal layer to selectively heat said layer, a turbid image can be formed to a transparent part and a transparent image can be formed to a turbid part.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, reversible thermosensitive recording materials have been attracting attention because they enable temporary image formation and can erase the image when it is 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 during image formation and erasing, and only heat is applied without applying much pressure, repeated image formation-
Even if 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 deforms as the image is repeatedly formed and erased, resulting in finely dispersed organic low molecular weight material. There is a drawback that the particles gradually become larger in diameter, the effect of scattering light is reduced, the opacity is reduced, and finally the image and the contrast are reduced.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks, and in a reversible thermosensitive recording material in which the transparent state and the cloudy state reversibly change depending on the temperature, it is The present invention provides a reversible thermosensitive recording material in which the white turbidity is not significantly reduced even when image forming and erasing are performed by using a heating means which applies pressure at the same time, and further, the durability is improved repeatedly.

[0005]

SUMMARY OF THE INVENTION The present invention comprises:
A reversible thermosensitive recording material comprising a resin base material and an organic low-molecular substance dispersed in the resin base material as a main component, and a heat-sensitive layer in which transparency reversibly changes depending on temperature is provided as the resin base material. , Using a phenol resin, in particular, using an alkylphenol resin as a resin base material, and further providing an adhesive layer between the support and the heat-sensitive layer in these recording materials. .

That is, a reversible heat-sensitive material comprising a support and a heat-sensitive layer whose main component is a resin base material and an organic low-molecular substance dispersed in the resin base material, and whose transparency reversibly changes depending on temperature. As a result of diligent examination of the resin base material in the recording material,
By using a phenol resin, durability is improved against repeated image formation-erasing by heating means such as applying pressure from a thermal head and heating at the same time, and a high white turbidity and high contrast image are formed. It has been found that a reversible thermosensitive recording material can be obtained.

In the present invention, it is not clear why the use of a phenol resin as the resin base material improves the durability against repeated image formation and erasing by a heating means such as a thermal head, but the phenol resin is a mechanical resin. Since the mechanical strength and hardness are extremely large, even if recording and erasing are repeated using a heating means such as a thermal head that applies heat and pressure at the same time, there is little deformation of the resin base material existing around the organic low molecular weight substance fine particles. It is assumed that the organic low molecular weight substance is maintained as fine particles and thus the durability is improved.

The reversible thermosensitive recording material of the present invention utilizes the transparency change (transparent state, cloudy opaque state) as described above, and the difference between the transparent state and the cloudy opaque state is presumed as follows. . That is, in the case of (i) transparent, the particles of the organic low-molecular 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. It looks transparent because it is transmitted to the side, and (ii) in the case of cloudiness, 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 crystals of the organic low molecular weight substance particles, and the light appears white because it is scattered.

In FIG. 1 (representing the change in transparency due to heat), a heat-sensitive 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 conceivable that the organic low-molecular-weight substance undergoes a semi-molten state until the following and the crystal grows from a polycrystal to a single crystal.
Further heating to a temperature of T ₃ or higher results in a semitransparent state between the maximum transparency and the maximum opacity. Next, when this temperature is lowered, the initial cloudy opaque state is restored without taking the transparent state again. It is considered that this is because the organic low molecular weight substance is melted at a temperature of T ₃ or higher and is then cooled to precipitate polycrystals. It should be noted that when this opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature of T ₀ or lower, an intermediate state between transparent and opaque can be obtained. Also, the transparent material that has become transparent at room temperature returns to the cloudy and opaque state when heated again to a temperature of T ₃ or higher and then returned to room temperature. That is, it can take both opaque and transparent forms at room temperature and intermediate forms thereof. Therefore,
The heat-sensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent background or a transparent image on a cloudy background, and the change can be repeated many times.

In order to produce the reversible thermosensitive recording material used in the present invention, generally, (1) a resin matrix and an organic low molecular weight substance are used.
A plastic in which a dispersion liquid in which components are dissolved or (2) a solution of a resin base material (a solvent that does not dissolve at least one of organic low molecular weight substances is used) is dispersed in the form of fine particles It may be applied on a support such as a film, a glass plate or a metal plate and dried to form a laminated heat sensitive layer. 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. Of course, when using the dispersion,
Even when a solution is used, the organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state in the obtained heat-sensitive layer.

In the present invention, the phenol resin used as the resin base material is phenolic-OH such as phenol, cresol, xylenol, p-alkylphenol, p-phenylphenol, chlorophenol, bisphenol A, phenolsulfonic acid and resorcin.
It is a polymer compound in which aldehydes such as formalin and furfural are added to and condensed with those having, and can be classified as follows. Phenol / formalin resin Cresol / formalin resin Modified phenolic resin Phenol / furfural resin Resorcin resin Among them, modified phenolic resin is preferable, and alkylphenol resin is particularly preferably used. Further, when the base material is a material such as an Al vapor deposition layer that does not easily have an adhesive force with a resin, an adhesive layer must be provided between the support and the thermosensitive recording layer.

On the other hand, as the organic low molecular weight substance, 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) may be used.
Generally, those having a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. are used. Such organic low molecular weight substances include alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkylamines; alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes; cycloalkenes; cycloalkynes; 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 combination of two or more. The carbon number of these compounds is 10
60, preferably 10-38, particularly 10-30 are preferred. The alcohol group portion 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, these compounds include lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, araginic acid, henicosanoic acid, tricosanoic acid, lignoceric acid, pentacosan. Higher fatty acids such as acids, cerotic acid, heptacosanoic acid, montanic acid, melissic acid, oleic acid; esters of higher fatty acids such as methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate and dodecyl behenate. _{; 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, Etc., such as ether or thioether. Among them, in the present invention, higher fatty acids, particularly palmitic acid, pentadecanoic acid,
Higher fatty acids having 16 or more carbon atoms such as nonadecanoic acid, arachidic acid, heicosanoic acid, tricosanoic acid, stearic acid, behenic acid, and lignoceric acid are preferable, and the carbon number is 16 to 24.
Of higher fatty acids are more preferred.

The weight ratio of the organic low molecular weight substance to the resin base material in the heat sensitive layer is preferably from 2: 1 to 1:16, and more preferably from 1: 1 to 1: 3. When the ratio of the resin base material is less than this, it becomes difficult to form a film in which the organic low molecular weight substance is retained in the resin base material, and when it exceeds the ratio, the amount of the organic low molecular weight substance is small, so that it becomes opaque. Becomes difficult.

In addition to the above components, additives such as a surfactant and a high boiling point solvent may be added to the heat sensitive layer in order to facilitate the formation of a transparent image. Specific examples of these additives are as follows. Examples of high boiling point solvents: tributyl phosphate, tri-2-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.

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.

Further, 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 a heating means such as a thermal head by a writing method. 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.

Further, in order to protect the reversible recording material from the solvent and the monomer component of the protective layer forming liquid, an intermediate layer such as polyamide can be provided between the protective layer and the reversible recording material. The thickness of the intermediate layer varies depending on the use, but is 1 to 20.
About μm is preferable. If it is less than this, the protective effect is lowered, and if it is more than this, the thermal sensitivity is lowered.

[0020]

EXAMPLES All parts and percentages herein are by weight. Example 1 Behenic acid 9 parts Eicosane diacid 1 part Alkylphenol resin (Gunei Chemical Industry Co., Ltd. PS2880) 30 parts on a film in which an Al layer having a thickness of about 40 nm is provided on a polyester film having a thickness of about 50 μm 30 parts Di-phthalate 2 Ethylhexyl 3 parts Tetrahydrofuran 150 parts Toluene 15 parts A solution consisting of 15 parts was applied with a wire bar and dried by heating to about 5 μm.
An m-thick heat sensitive layer was provided.

Example 2 Behenic acid 9 parts Eicosane diacid 1 part Alkylphenol resin (Gunei Chemical Industry Co., Ltd. PS2851) 30 parts phthalate on a film in which an Al layer having a thickness of about 40 nm is provided on a polyester film having a thickness of about 50 μm. Di-2 ethylhexyl acid 3 parts Tetrahydrofuran 150 parts Toluene 15 parts A solution consisting of 15 parts is applied with a wire bar and dried by heating to give about 5 μm.
An m-thick heat sensitive layer was provided.

Comparative Example Behenic acid 9 parts Eicosane 2 acid 1 part Vinyl chloride-vinyl acetate copolymer VYHH 30 parts Diphthalic acid di-2 on a film having an Al layer of about 40 nm thickness on a polyester film of about 50 μm thickness Ethylhexyl 3 parts Tetrahydrofuran 150 parts Toluene 15 parts A solution consisting of 15 parts was applied with a wire bar and dried by heating to give about 5 μm.
An m-thick heat sensitive layer was provided.

A solution of polyamide resin (CM8000, manufactured by Toray Industries, Inc. CM8000) 10 parts ethyl alcohol 90 parts was applied on each heat-sensitive layer prepared as described above with a wire bar and dried to give about 0.5 μm.
A m-thick intermediate layer is provided, and a 75% butyl acetate solution of urethane acrylate-based UV curable resin (Unidik C7-157, Dainippon Ink and Chemicals, Inc.) 10 parts Toluene 10 parts solution is applied with a wire bar. And after heating and drying, 8
A reversible thermosensitive recording medium was prepared by curing with a 0 W / cm ultraviolet lamp to form a protective layer having a thickness of about 2 μm.

Using the reversible thermosensitive recording material prepared as described above, a thermal head of 8 dots / mm was used, and the applied energy was increased from the normal printing conditions under the forced test conditions (applied power 1.0 W applied pulse width). 0.7 mse
After printing with c) and making it cloudy, heat roller (80
Magbeth reflection densitometer RD for image part (white cloudy part) density and transparent part (background part) density as a result of 10 times of clearing and erasing at ~ 85 ° C, 10 mm / min, and repeating printing-erasing 10 times under the same conditions. = 514, the measured values are shown in FIGS. 2, 3, and 4. In the comparative example, the density of the image portion (white turbid portion) is high, and almost no white turbidity occurs after 10 times of printing, but in Examples 1 and 2, the density of the image portion (white turbid portion) is low and the transparency is high and the printing number is high up to 10 times. Maintains contrast.

Example 3 Vinyl chloride-vinyl acetate-phosphate ester copolymer (Denka Vinyl 1000P, Denki Kagaku Kogyo Co., Ltd.) 20 on a film in which an Al layer having a thickness of about 40 nm was provided on a polyester film having a thickness of about 50 μm 20 Solution of 80 parts by weight of methyl ethyl ketone was coated with a wire bar and dried by heating to about 0.
An adhesive layer having a thickness of 5 μm was provided, and the same solution as in Example 2 was applied and dried by heating with a wire bar to provide a heat sensitive layer having a thickness of about 5 μm. A 75% butyl acetate solution of urethane acrylate UV curable resin (Unidick C7-157 manufactured by Dainippon Ink and Chemicals, Inc.) 10 parts A solution consisting of 10 parts toluene was applied with a wire bar, and after heating and drying, 8
A reversible thermosensitive recording medium was prepared by curing with a 0 W / cm ultraviolet lamp to form a protective layer having a thickness of about 2 μm.

Lattice-like cuts were made on the surfaces of the recording medium of Example 3 and the recording medium of Example 2 prepared as described above with a cutter knife, and cellophane tape (manufactured by Nichiban) was attached to the surface. As a result of peeling off and testing the adhesiveness of the thermal recording layer, the recording layer of Example 2 was Al.
Although peeled from the interface with the layer, the recording layer of Example 3 was not peeled.

[0027]

As is apparent from this example, in the resin base material using the reversible heat-sensitive recording material, the use of the phenol resin as the resin base material improves the durability due to its heat resistance and improves the white turbidity. Is high, and there is an effect that a high-contrast image can be formed.

[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 graph showing the image density when recording and erasing are repeated using the reversible thermosensitive recording material of Example 1 of the present invention.

FIG. 3 is a graph showing the image density when recording and erasing are repeated using the reversible thermosensitive recording material of Example 2 of the present invention.

FIG. 4 is a diagram showing the case of using the reversible thermosensitive recording material of Comparative Example of the present invention,
6 is a graph showing the image density when recording and erasing are repeated.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Makoto Kawaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Fumito Masuchibuchi 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Inside Ricoh Company (72) Inventor Nogichi Dori 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (3)

[Claims] 1. A reversible sensation comprising, on a support, a thermosensitive layer comprising a resin matrix and an organic low molecular weight substance dispersed in the resin matrix as a main component, and the transparency reversibly changing depending on temperature. A reversible heat-sensitive recording material, wherein a phenol resin is used as the resin base material in the heat recording material. 2. The phenol resin as a resin base material is an alkylphenol resin.
The reversible thermosensitive recording material described. 3. The reversible thermosensitive recording material according to claim 1, wherein an adhesive layer is provided between the support and the thermosensitive layer.