JP2655839B2 - Reversible thermosensitive recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reversible thermosensitive recording material for recording and erasing by utilizing a reversible change in transparency of a thermosensitive layer depending on temperature.

2. Description of the Related Art As a heat-sensitive recording material capable of reversible recording and erasing, a heat-sensitive recording material in which a low-molecular organic material such as a higher fatty acid is dispersed in a resin such as polyester or polyamide on a support is disclosed in Nos. -119377 and 55-154198. Recording with this type of recording material, that is, image formation and erasing, utilizes a change in transparency due to the temperature of the heat-sensitive layer. In particular, when such a reversible thermosensitive recording material is made by a coating method, that is, by applying a heat-sensitive layer forming solution on a support and drying to provide a heat-sensitive layer, unevenness commonly called citron skin occurs on the surface of the heat-sensitive layer. The transparency of the transparent portion is apt to decrease, and therefore, when a recording having such a low-transparency image portion or non-image portion is projected by an overhead projector as an original drawing for projection, an image in which the brightness of the non-image portion is reduced is obtained. However, when a colored sheet is arranged on the back surface of the recorded matter and viewed as a reflection image, there is a disadvantage that an image with reduced contrast is obtained.

Purpose The purpose of the present invention is to make the surface of the heat-sensitive layer uniform,
An object of the present invention is to provide a reversible thermosensitive recording material capable of forming a high-contrast clear image.

The reversible thermosensitive recording material of the present invention has a thermosensitive layer whose main component is a resin base material and an organic low-molecular substance dispersed in the resin base material, and has a heat-sensitive layer whose transparency reversibly changes depending on temperature. The heat-sensitive recording material is characterized in that the heat-sensitive layer further contains a silicone oil.

The recording (and erasing) principle of the recording material of the present invention utilizes a change in transparency of the heat-sensitive layer (or sheet) depending on the temperature.
This will be described with reference to the drawings. In FIG. 1, and the resin base material, the heat-sensitive layer mainly composed of a resin matrix organic low-molecular material dispersed in is in the cloudy opaque state at room temperature, for example T ₀ or less. When this is heated to a temperature between T _{1 and} T ₂ , it becomes transparent, and in this state, it remains transparent even when it is returned to room temperature of T ₀ or lower. Upon further heating to T ₃ below temperature, the semi-transparent state in the middle between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the film returns to the original cloudy and opaque state without taking the transparent state again. In addition, this thing of this opaque state
After heating to a temperature between T ₀ through T _1, it may take the state between the normal temperature, i.e. when cooled to T ₀ temperature below the transparent and opaque. Also, the one that became transparent at room temperature again
Heated to T ₃ or more temperature, by returning to room temperature, return to the cloudy opaque state again. That is, both opaque and transparent forms at room temperature and intermediate states thereof can be taken.

Thus after heating the entire heat-sensitive layer to a temperature between T ₁ through T ₂ by heat roll or the like, and transparent to cool to room temperature T ₀ or less, then it is heated to T ₃ or more image-wise to a thermal head or the like If that part is made opaque, a white image is formed in this layer. If a colored sheet is arranged under the heat-sensitive layer having such a white image, this image can be recognized as a white image with the color of the colored sheet as a background. Meanwhile, T ₁ through T such the entire part opaque thermosensitive layer after heating to T ₃ or more temperature, after cloudy opacify the whole has cooled to T ₀ or less, imagewise a thermal head or the like _By heating to a temperature between the _two to make the portion transparent, a transparent image is formed with a white background as a background. If a colored sheet is arranged under the heat-sensitive layer having such a transparent image, this image can be recognized as an image of the color of the colored sheet against a white background.

Above-mentioned recording and erasing operation to the heat-sensitive layer can be repeated more than 10 ⁴ times.

In order to prepare the heat-sensitive recording material of the present invention, generally, (1) a solution in which three components of a resin base material, an organic low-molecular substance and silicone oil are dissolved, or a solution of a resin base material (the organic low-molecular substance is not dissolved as a solvent) The organic low-molecular substance is dispersed in fine particles, and a dispersion obtained by dissolving or dispersing the same in a silicone oil is coated on a support such as paper, a plastic film, a glass plate, or a metal plate ( Or impregnation)
Drying to form a heat-sensitive layer, or (2) kneading the three components in the presence of a solvent, if necessary, while heating,
This is formed by forming this into a sheet shape and making itself a heat-sensitive sheet. Examples of the solvent include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, benzene and the like. The organic low-molecular substance is precipitated as fine particles in the heat-sensitive layer or heat-sensitive sheet obtained not only when a dispersion is used but also when a solution or kneaded material is used, and exists in a dispersed state.

The resin base material used for the heat-sensitive layer is a material which forms a layer in which an organic low-molecular substance is uniformly dispersed and held, and which has an effect when transparent with maximum transparency. For this reason, the base material is preferably a resin which has good transparency, is mechanically stable, and has good film-forming properties. 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. Polyvinylidene chloride, such as polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer; polyester; polyamide; polyacrylate or polymethacrylate or acrylate; Examples include methacrylate copolymers and silicone resins. These may be used alone or as a mixture of two or more.

On the other hand, the organic low-molecular substance may be appropriately selected in accordance with the selection of the temperatures T _{0 to} T ₃ in FIG.
° C, particularly preferably about 50 to 150 ° C. Such organic low molecular weight substances include alkanol; alkane diol; halogen alkanol or halogen alkane diol; alkylamine; alkane; alkene; alkyne; halogen alkane; halogen alkane; 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; Acids or their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts Carboxylic acid esters of thio alcohol. These may be used alone or in combination of two or more. The carbon number of these compounds is 10 to 60, preferably 10 to 38, particularly preferably 10 to 30. The alcohol group in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance contains at least one kind of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH,-
_{COOR, -NH, -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, arachiic acid,
Higher fatty acids such as oleic acid; esters of higher fatty acids such as methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, docosyl 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 , 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.

Next, when the heat-sensitive layer is formed by the method described above, the silicone oil used for the heat-sensitive layer is effective in forming a uniform coating film of the heat-sensitive layer after the solvent is evaporated. Here, as silicone oil, dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane,
Examples include alkyl-modified polysiloxane, amino-modified polysiloxane, carboxyl-modified polysiloxane, and alcohol-modified polysiloxane.

The ratio between the organic low-molecular substance and the resin base material in the heat-sensitive layer is preferably about 1: 0.5 to 1:16 by weight. 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 substance is retained in the resin base material. Becomes difficult.

On the other hand, the amount of silicone oil used is 10
This amount is about 0.001 to 1 part by weight based on 0 part by weight.
If the amount is less than 001 parts by weight, it is difficult to make the surface of the heat-sensitive layer uniform.

Hereinafter, the present invention will be described in more detail with reference to Examples.
All parts and percentages are based on weight.

Example 1 Behenic acid 10 parts Vinyl chloride-vinyl acetate copolymer (VYHH manufactured by UCC) 28 parts Methylphenyl silicone oil (1% tetrahydrofuran solution) (KF50 manufactured by Shin-Etsu Silicone) 0.5 part on a 75 μm-thick polyester film Apply a solution consisting of 150 parts of tetrahydrofuran with a wire bar, dry and
By providing a thick thermosensitive layer, a white opaque reversible thermosensitive recording material was prepared.

Example 2 A reversible heat-sensitive recording material was prepared in the same manner as in Example 1, except that methylphenyl silicone oil was changed to methyl silicone oil (KF-69 manufactured by Shin-Etsu Silicone Co., Ltd.).

Example 3 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that the methylphenyl silicone oil was changed to an alcohol-modified silicone oil (SF8428 manufactured by Toray Silicone Co., Ltd.).

Example 4 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that the methylphenyl silicone oil was changed to an amino-modified silicone oil (SF8417 manufactured by Toray Silicone Co., Ltd.).

Comparative Example 1 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that methylphenyl silicone oil was omitted.

Comparative Example 2 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that methylphenyl silicone oil was used as a silicone resin (KR-266, 1% THF solution, manufactured by Shin-Etsu Chemical Co., Ltd.).

Next, each recording material was heated at 70 ° C. and 90 ° C. for 1 minute, allowed to cool to room temperature, placed on black paper, and the reflection density was measured with a Macbeth densitometer RD514. In addition, the recording material was heated at 70 ° C. and clarified by applying the recording material to an overhead projector, and the brightness was visually evaluated for uniformity. The results are shown in the table below.

Effect Since the reversible thermosensitive recording material of the present invention contains silicone oil, there is no unevenness in the thermosensitive layer such as citron skin, and therefore, a clear image with higher contrast than before can be formed.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle of recording and erasing in the thermosensitive layer of the reversible thermosensitive recording material of the present invention.

Claims (1)

(57) [Claims] 1. A reversible thermosensitive recording material comprising, as main components, a resin base material and an organic low-molecular substance dispersed in the resin base material, and having a heat-sensitive layer whose transparency reversibly changes depending on temperature. And a reversible thermosensitive recording material further comprising a silicone oil in the thermosensitive layer.