JPH0585048A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To provide a reversible thermal recording material capable of holding the particle size of an org. low-molecular substance to an initial state even when the formation and erasure of an image are repeated using the heating means simultaneously applying heat and pressure of a thermal head, capable of forming and erasing an image by low energy and enhanced in durability. CONSTITUTION:In a reversible thermal recording material wherein a thermal layer based on a resin matrix and the org. low-molecular substance dispersed in the resin matrix and reversibly changed in its transparency in dependence on temp. is provided on a support, a metal salt of trimellitic acid/lanoline alcohol ester is added to the thermal layer so that the content thereof becomes 10-50 pts.wt. per 100 pts.wt. of the org. low-molecular substance.

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]

According to the present invention, a resin base material and an organic low molecular weight substance dispersed in the resin base material are main components on a support, and the transparency is reversible depending on the temperature. In a reversible thermosensitive recording material provided with a thermosensitive layer that changes to, a metal salt of trimellitic acid lanolin alcohol ester is contained in the thermosensitive layer, and particularly, the trimellitic acid lanolin alcohol ester in the thermosensitive layer The content of the metal salt is 10 to 100 parts by weight of the organic low molecular weight substance.
There is provided a reversible thermosensitive recording material characterized by being 50 parts by weight.

In the present invention, the reason why the metal salt of trimellitic acid lanolin alcohol ester in the heat-sensitive layer achieves the initial purpose is not clear, but the metal salt is not compatible with the resin base material in the heat-sensitive layer. Due to poor solubility, good dispersion stability between the organic low molecular weight substance and the resin base material, and excellent wettability of the organic low molecular weight substance, when repeatedly performing image formation and erasing with a thermal head, etc. , The particle size of the organic low molecular weight substance uniformly dispersed in the resin base material can be maintained in the initial state, and since the organic low molecular weight substance has excellent wettability, image formation and erasing can be performed with low energy. It is considered possible to improve the durability by reducing the stress of the heat sensitive layer.

The metal salt of trimellitic acid lanolin alcohol ester in the present invention is an ester of trimellitic acid and lanolin alcohol, which is obtained by neutralizing unreacted carboxylic acid of trimellitic acid with a metal base. Lanolin alcohols are higher alcohols having 13 to 33 carbon atoms, most of which are branched and in particular have a sterol nucleus. Examples of metal salts include sodium, potassium, calcium, magnesium, barium, zinc, lead,
Examples thereof include metal salts such as manganese, iron, nickel, cobalt and aluminum.

The content of the trimellitic acid lanolin alcohol ester in the present invention is preferably 10 to 50 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the organic low molecular weight substance.
40 parts by weight is excellent. When the content is less than 10 parts by weight, the particle size of the organic low molecular weight substance in the resin matrix becomes large when the thermal head repeats image formation and erasing many times, and the cloudiness to transparency becomes insufficient and the final Has a problem of deterioration of durability. On the other hand, when the amount is more than 50 parts by weight, the matrix composed of the organic low molecular weight substance and the resin base material cannot function sufficiently and there is a drawback that the initial cloudiness to transparency is poor.

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 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 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 and a transparent image on a cloudy background, and the change can be repeated many times. Is. By arranging a coloring sheet on the back surface of such a heat sensitive member, an image of the color of the coloring sheet or a white image of the background of the coloring sheet can be formed on a white background. 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. 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 is increased because two thermal heads are required, but if the reversible thermosensitive 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, an image is formed and erased by one thermal head. Therefore, the conditions for applying energy to the thermal head at one time when the thermal recording material passes are 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 once erasing the image on the thermosensitive recording material and then running the thermosensitive recording material in the reverse direction again to form an image under different energy conditions. Therefore, the equipment cost is reduced.

In order to prepare 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.

The resin base material used for the heat-sensitive recording layer is a material that forms a layer in which an organic low molecular weight substance is uniformly dispersed and held, and has an effect on the transparency at maximum transparency. Therefore, the resin base material is preferably a resin having good transparency, mechanical stability, and good film forming property. Examples of such resins include polyvinyl chloride; vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-
Vinyl chloride-based copolymers such as acrylate copolymers; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-based copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides;
Examples thereof include polyacrylate or polymethacrylate or acrylate-methacrylate copolymer; silicone resin and the like. These resins may be used alone or in combination with two or more.

On the other hand, as the organic low molecular weight substance, any substance that changes from polycrystal to single crystal due to heat in the recording layer (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 higher fatty acids such as lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, alginic acid and oleic acid; methyl stearate. , Esters of higher fatty acids such as 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 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.

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: 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.

Further, in order to widen the temperature range in which the material can be made transparent, the organic low molecular weight substances described in this specification may be appropriately combined, or such organic low molecular weight substances may be combined with other materials having different melting points. .. These are, for example, JP-A-6
3-39378, Japanese Patent Application Laid-Open No. 63-130380, etc., Japanese Patent Application No. 63-14754, Japanese Patent Application No. 1-140.
However, the present invention is not limited thereto.

In addition to the above components, additives such as a surfactant and a high boiling point solvent can 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.

When an image of this recording material is used as a reflection image, if a layer that reflects light is provided on the back surface of the recording layer, the contrast can be increased even if the thickness of the recording layer is reduced. Specifically, vapor deposition of Al, Ni, Sn and the like can be mentioned (as 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 transparency of the transparent portion from being lowered by the deformation of the surface due to the heat and pressure of the heating means such as a thermal head by the writing method. good. A protective layer (thickness: 0.
(1 to 5 μm), silicone rubber, silicone resin (described in JP-A-63-221087),
Polysiloxane graft polymer (JP-A-63-317)
No. 385), 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-based solvent is particularly preferable in terms of cost.

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 monomer components of the protective layer forming liquid (JP-A-1-133781). No. publication). As the material for the intermediate layer, the following thermosetting resins and thermoplastic resins can be used in addition to those listed as the resin base material in the heat sensitive layer.
That is, 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. The thickness of the intermediate layer varies depending on the use, but 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.

[0025]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. All parts and percentages herein are by weight.

Example 1 On a transparent polyester film with a thickness of about 100 μm: 6 parts of stearic acid 4 parts of eicosane diacid 2 parts of di-2 ethylhexyl phthalate 2 parts of calcium salt of trimellitic acid lanolin alcohol ester 0.8 parts -Vinyl chloride-vinyl acetate copolymer (VYHH manufactured by UCC Co., Ltd.) 30 parts-THF 180 parts-Toluene 20 parts
A reversible thermosensitive recording layer having a thickness of 5 μm was provided. Furthermore, a solution comprising 10 parts of polyamide resin (CM8000 manufactured by Toray Industries, Inc.) and 90 parts of ethyl alcohol was applied with a wire bar and dried by heating to about 1
A μm thick intermediate layer was provided. Furthermore, 75% butyl acetate solution of urethane acrylate UV curable resin (Unidick 17-824-9 manufactured by Dainippon Ink and Chemicals Co., Ltd.) 10 parts ・ Toluene / MEK (1/1 solution) solution uniformly After the solution was dissolved, it was coated with a wire bar, heated and dried, and then cured with an 80 W / cm ultraviolet lamp to provide a protective layer having a thickness of about 5 μm to prepare a reversible thermosensitive recording material for a card film.

Example 2 A reversible thermosensitive recording material for a card film was prepared in the same manner as in Example 1, except that the calcium salt of trimellitic acid lanolin alcohol ester of Example 1 was replaced with zinc of trimellitic acid lanolin alcohol ester. Created.

Example 3 A reversible heat-sensitive film for a card was prepared in the same manner as in Example 1 except that the content of the calcium salt of trimellitic acid lanolin alcohol ester in Example 1 was changed from 8% by weight to 55% by weight. The recording material was created.

Example 4 Except that the content of the calcium salt of trimellitic acid lanolin alcohol ester in Example 1 was changed to 30% by weight,
A reversible thermosensitive recording material for a card film was prepared in the same manner as in Example 1.

Comparative Example 1 A reversible thermosensitive recording material for a card film was prepared in the same manner as in Example 1 except that the calcium salt of trimellitic acid lanolin alcohol ester of Example 1 was omitted.

Using the reversible thermosensitive recording material prepared as described above, a thermal head of 8 dots / mm was used, and a strong test condition (applied voltage 1.0 W, applied pulse) in which applied energy was increased under normal printing conditions. Width 10mse
After printing with c) and making it cloudy, heat roller (80-
Using the Macbeth reflection densitometer RD-514, the density of the image part (white turbid part) and the density of the transparent part (background part) as a result of repeating the printing to the erasing 10 times under the same conditions after clearing and erasing at 85 ° C 10 mm / mim) It was measured. The results are shown in Table 1.

[0032]

[Table 1]

[0033]

As is clear from the description of the examples, the reversible thermosensitive recording material of the present invention contains a metal salt of trimellitic acid lanolin alcohol ester in the reversible thermosensitive recording layer, so that The particle size of the organic low molecular weight substance can be maintained in the initial state even if the image formation to erasure is repeated many times using the heating means that applies heat and pressure simultaneously, and the image formation and erasure can be performed with low energy. Since this is possible, stress in the heat-sensitive layer can be reduced, which is effective in improving durability.

[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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Togori, 1-3-3 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor, Kunichika Moroboshi 1-3-6, Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Fumito Masuchibuchi 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd.

Claims (2)

[Claims] 1. A reversible sensation comprising a support and a thermosensitive layer comprising a resin base material and an organic low-molecular substance dispersed in the resin base material as a main component, and the transparency of which reversibly changes depending on temperature. A reversible heat-sensitive recording material comprising a heat-sensitive layer containing a metal salt of trimellitic acid lanolin alcohol ester in the heat-sensitive layer. 2. The content of the metal salt of trimellitic acid lanolin alcohol ester in the heat-sensitive layer is 10 to 50 parts by weight with respect to 100 parts by weight of the organic low molecular weight substance. The reversible thermosensitive recording material described.