JPH07205555A - Rewriting type thermal recording medium - Google Patents

Abstract

PURPOSE:To enhance printing characteristics by providing a transparent protective layer based on SiO on a thermal recording layer. CONSTITUTION:An metal reflection layer 2 composed of aluminum is formed on a substrate composed of polyethylene terephthalate and a thermal recording layer 3 wherein an org. monomeric substance such as higher saturated fatty acid is dispersed in a resin such as a vinyl chloride resin is laminated to the reflection layer 2. Further, a transparent protective layer 4 mainly constituted of SiO2 is provided on the thermal recording layer 3. The transparent protective layer has high hardness, high heat resistance and high abrasion resistance and can enhance heat conductivity as compared with an org. resin because it is composed of inorg. matter. When TiO2 is added to the protective layer 4, environment resistance can be enhanced and the toughness of the protective layer can be enhanced by the addition of ZrO2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable thermosensitive recording medium for recording / erasing information by using a thermosensitive recording material whose transparency changes reversibly depending on temperature.

[0002]

2. Description of the Related Art As a heat-sensitive recording material capable of reversible recording and erasing, a heat-sensitive recording layer in which an organic low molecular weight substance such as higher saturated fatty acid or higher ketone is dispersed in a resin such as vinyl chloride or vinyl acetate on a substrate. The one provided with No. 3 is disclosed in JP-A-54-11.
It is disclosed in Japanese Patent No. 9377 and Japanese Patent Laid-Open No. 55-154108. However, when information is recorded by directly heating the thermal recording layer 3 with a thermal head or the like, unevenness is created on the surface of the thermal recording layer 3 due to the heating temperature and pressure of the thermal head, and this becomes unerased when erased, After rewriting several times, clear recording cannot be performed.

Therefore, there is one in which a transparent protective layer 4 is further provided on the thermosensitive recording layer 3. For example, Japanese Patent Laid-Open No. 2-556, which is provided with an ultraviolet curable resin or an electron beam curable resin,
Japanese Patent Application Laid-Open No. 4-80080 provided with a polyurethane resin and Japanese Patent Application Laid-Open No. 4-2991 provided with a polyimide resin.
No. 80, etc. Further, it has been proposed to use a thermal printer under the conditions (such as the pressing of the thermal head is set low) exclusively for the rewritable thermal recording medium.

[0004]

However, when a commercially available thermal printer is used instead of the rewritable thermal recording medium dedicated printer, since the thermal head is pressed with high pressure, the transparent protective layer made of the resin shown in the above-mentioned prior art is used. When the film thickness of 4 is 5 μm or less, which is a practical film thickness, the hardness and heat resistance are insufficient even when the rewriting is performed several hundred times. Further, at a film thickness of several tens of μm or more, which shows sufficient hardness and heat resistance, the heat from the thermal head is not sufficiently transmitted to the heat-sensitive recording layer 3 due to the low thermal conductivity of these resins. There was a problem that it was not possible to record.

Further, when the transparent protective layer 4 is formed, in order to protect the thermosensitive recording layer 3 from the monomer components of the resin solution dissolved in the organic solvent and the solvent, the transparent protective layer 4 and the thermosensitive recording layer 4 are formed as shown in FIG. A resin solution dissolved in an alcoholic solvent or the like is applied between the recording layers 3 to form the intermediate layer 5, or a special solvent that does not dissolve the heat-sensitive recording layer is used as the solvent for the resin solution for forming the transparent protective layer 4. There was a problem that it had to be used.

[0006]

Therefore, in the present invention, a transparent protective layer whose main component is SiO ₂ is provided on a thermosensitive recording layer laminated on a substrate, and the transparent protective layer contains SiO ₂ as a main component. It is characterized in that the component is dissolved or dispersed in a lower alcohol such as methanol or ethanol or water, and is applied and dried.

[0007]

Therefore, the main component according to the present invention is Si.
The transparent protective layer of O ₂ has excellent heat resistance, mechanical strength, and thermal conductivity as compared with the transparent protective layer made of a conventional organic resin. It is possible to obtain a rewritable thermosensitive recording medium having no printing residue and good printing characteristics. Further, the transparent protective layer according to the present invention is made of Si.
Providing an intermediate layer on the heat-sensitive recording layer, since a component containing O ₂ as a main component dissolved or dispersed in a lower alcohol such as methanol or ethanol or water is applied and dried. Without, a transparent protective layer can be formed directly on the heat-sensitive recording layer.

[0008]

EXAMPLE FIG. 1 shows a cross-sectional structure of a rewritable thermosensitive recording medium according to the present invention. Polyethylene terephthalate (PE
T) Substrate 1 made of film, polyester film, etc.
A metal reflective layer 2 made of aluminum, gold or the like is laminated thereon, and a heat-sensitive recording layer 3 in which an organic low molecular weight substance such as higher saturated fatty acid or higher ketone is dispersed in a resin such as vinyl chloride or vinyl acetate is laminated in this order. Further thereon, a transparent protective layer 4 whose main component is SiO ₂ according to the present invention is provided. Here, the metal reflective layer 2 is provided to enhance the visibility of recorded information,
It may not be provided when the visibility is secured by another method, and may be provided on the surface opposite to the heat-sensitive recording layer 3 when the substrate 1 is transparent.

A transparent protective layer 4 whose main component is SiO _2.
Has high hardness, excellent heat resistance and abrasion resistance, and has high thermal conductivity as compared with organic resins because it is inorganic. Generally, the heat resistance of SiO ₂ ceramic coating film is 6
It has a large margin with respect to the recording temperature (about 150 ° C.) of the thermal head, which is 00 ° C. or higher. It also has a pencil hardness of 6H to 9H and is also excellent in environmental resistance.

If a transparent protective layer 4 containing SiO _{2 as the} main component and having TiO ₂ added is used,
Further, the environment resistance is improved, and the toughness is further improved by using a material to which ZrO ₂ is added.

Si forming the transparent protective layer 4 according to the present invention
Since the solvent of the ceramic coating material containing O ₂ as a main component is water or a lower alcohol such as ethanol or methanol, there is no fear of dissolving the thermosensitive recording layer 3 when coating on the underlying thermosensitive recording layer 3. The film can be directly formed on the thermosensitive recording layer 3, and the manufacturing process becomes easy. Hereinafter, the present invention will be described in detail with reference to Examples.
The parts here are based on weight.

Example 1 A PET film having a thickness of about 180 μm was used as the substrate 1, aluminum was formed as the metal reflective layer 2 to a film thickness of 40 nm, and stearic acid 1 part vinyl chloride / vinyl acetate copolymer was formed thereon. 2 parts (Denkalac TF-200 manufactured by Denki Kagaku Kogyo Co., Ltd.) N, N-dimethylformamide 5 parts A solution of 5 parts toluene was applied with a wire bar and dried by heating to provide a thermosensitive recording layer 3 having a thickness of about 7 μm. . Thermal recording layer 3
A solution consisting of 5 parts of a SiO ₂ ceramic coating material (Silvie coat manufactured by Nagae Sangyo Co., Ltd.) was directly applied onto the above with a wire bar and dried by heating to form a transparent protective layer 4 having a thickness of about 3 μm. At this time, the thermal recording layer 3 did not dissolve.

Example 2 A 100 μm-thick polyester film was used as the substrate 1, and aluminum was formed as the metal reflection layer 2 to a film thickness of 40 nm. A solution of stearic acid 1 part vinyl chloride / vinyl acetate copolymer 2 parts (Denkalac TF-200 manufactured by Denki Kagaku Kogyo Co., Ltd.) N, N-dimethylformamide 5 parts toluene 5 parts was applied thereto with a wire bar. It was dried by heating to provide a thermal recording layer 3 having a thickness of about 7 μm. Thermal recording layer 3
Directly on top of SiO ₂ · TiO ₂ ceramic coating material 5 parts (Nippa Institute, Glasca G95) Ethanol 1 part A solution consisting of 1 part is applied with a wire bar and dried by heating to about 3
A transparent protective layer 4 having a thickness of μm was provided. At this time, the thermal recording layer 3 did not dissolve.

Example 3 A PET film having a thickness of 100 μm was used as the substrate 1, and aluminum was formed as the metal reflection layer 2 with a thickness of 40 nm. A solution of stearic acid 1 part vinyl chloride / vinyl acetate copolymer 2 parts (Denkalac TF-200 manufactured by Denki Kagaku Kogyo Co., Ltd.) N, N-dimethylformamide 5 parts toluene 5 parts was applied thereto with a wire bar. It was dried by heating to provide a thermal recording layer 3 having a thickness of about 7 μm. Thermal recording layer 3
Directly on top of the SiO ₂ · ZrO ₂ ceramic coating material 5 parts (Nippa Institute, Glasca G401) Methanol 1 part A solution consisting of 1 part is applied with a wire bar and dried by heating to about 3
A transparent protective layer 4 having a thickness of μm was provided. At this time, the thermal recording layer 3 did not dissolve.

(Comparative Example 1) Soluble nylon (CM4000 manufactured by Toray Industries, Inc.) 1 part Ethanol 3 to prevent dissolution of the thermosensitive recording layer 3 on the thermosensitive recording layer 3 of Example 1 when the transparent protective layer resin solution is applied. Part of the solution is applied with a wire bar and dried by heating to about 2
A μm intermediate layer 5 was provided, and a solution consisting of polyurethane resin (Nipporan 179 manufactured by Nippon Polyurethane Industry Co., Ltd.) 1 part Curing agent (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) 1 part Methyl ethyl ketone 5 parts Toluene 5 parts was prepared with a wire bar. Approximately 3 after coating and heat drying
A transparent protective layer 4 having a thickness of μm was provided.

Comparative Example 2 A solution of soluble nylon (CM4000 manufactured by Toray Industries, Inc.) 1 part ethanol 3 parts was applied on the thermosensitive recording layer 3 of Example 1 with a wire bar and dried by heating to about 2 parts.
A μm intermediate layer 5 is provided, and a solution comprising polyurethane resin (Nipporan 179 manufactured by Nippon Polyurethane Industry Co., Ltd.) 1 part, curing agent (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) 1 part, methyl ethyl ketone 3 parts, toluene 3 parts by a wire bar. Approximately 1 after coating and heat drying
A transparent protective layer 4 having a thickness of 5 μm was provided.

(Comparative Example 3) A solution of soluble nylon (CM4000 manufactured by Toray Industries, Inc.) 1 part ethanol 3 parts was applied on the thermosensitive recording layer 3 of Example 2 with a wire bar and dried by heating to about 2 parts.
An intermediate layer 5 having a thickness of μm is provided, and a solution composed of 1 part of ultraviolet curable resin (DEFENSA manufactured by Dainippon Ink and Chemicals, Inc.) and 3 parts of butyl acetate is applied on the intermediate layer 5 with a wire bar, and the transparent protective layer 4 having a thickness of about 3 μm is irradiated with ultraviolet rays. Was set up.

Comparative Example 4 A solution of soluble nylon (CM4000 manufactured by Toray Industries, Inc.) 1 part ethanol 3 parts was applied on the heat-sensitive recording layer 3 of Example 2 with a wire bar and dried by heating to about 2 parts.
An intermediate layer 5 having a thickness of 10 μm is provided on the transparent protective layer 4 having a thickness of about 10 μm by applying a solution containing 1 part of butyl acetate and 1 part of a UV curable resin (DEFENSA manufactured by Dainippon Ink & Chemicals, Inc.) on the wire bar. Was set up.

The rewritable heat-sensitive recording medium produced as described above is heated at 70 ° C. for 5 minutes to make the heat-sensitive recording layer 3 transparent,
Commercial thermal printer (PC-PR201TL manufactured by NEC Corporation)
The results after printing with 3) are shown in Table-1. Here, scratches ⊚ indicate no scratches, scratches x indicate scratches, print ⊚ indicates good print visibility, and print × indicates poor print visibility.

[0020]

From this table, when the polyurethane resin of Comparative Example 1 and Comparative Example 2 and the ultraviolet curable resin of Comparative Example 3 and Comparative Example 4 were used as the material of the transparent protective layer 4, the transparent protective layer was recorded in the first recording. When the film thickness of 4 is thin, the printing characteristics are good, but scratches occur on the surface of the transparent protective layer 4,
When the thickness of the transparent protective layer 4 was large, the surface of the transparent protective layer 4 was not scratched, but the printing characteristics were poor. On the other hand, a transparent protective layer 4 composed mainly of SiO _{2 according} to the present invention is used.
When used for 200 times recording /
No scratch was generated even after erasing, and the printing characteristics were good.

[0022]

As described above, since the rewritable thermal recording medium according to the present invention is excellent in heat resistance and mechanical strength, it can be erased even if it is rewritten several hundred times or more using a commercially available thermal printer. Good printing characteristics can be obtained without any residue. Further, since the intermediate layer 5 is unnecessary, simplification of the manufacturing process and cost reduction can be achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a cross-sectional structure of a rewritable heat-sensitive material according to the present invention.

FIG. 2 is a configuration diagram showing a cross-sectional structure of a rewritable heat-sensitive material shown in the prior art.

[Explanation of symbols]

 1 Substrate 2 Metallic Reflective Layer 3 Thermal Recording Layer 4 Transparent Protective Layer 5 Intermediate Layer

Claims (6)

[Claims] 1. A heat-sensitive recording layer 3 comprising a polymer resin and an organic low-molecular substance dispersed in the polymer resin as a main component, the transparency of which reversibly changes depending on temperature. In the rewritable heat-sensitive recording medium, the rewritable heat-sensitive recording medium is characterized in that a transparent protective layer 4 containing SiO ₂ as a main component is provided on at least the heat-sensitive recording layer 3. 2. The rewritable heat-sensitive recording medium according to claim 1, wherein TiO ₂ is contained as another component of the transparent protective layer 4 of the rewritable heat-sensitive recording medium. recoding media. 3. The rewritable thermosensitive recording medium according to claim 1, wherein ZrO ₂ is contained as another component of the transparent protective layer 4 of the rewritable thermosensitive recording medium. recoding media. 4. The rewritable thermosensitive recording medium according to claim 1, 2, or 3, wherein the transparent protective layer 4 of the rewritable thermal recording medium is directly on the thermosensitive recording layer 3. A rewritable heat-sensitive recording medium characterized by being provided in. 5. The rewritable heat-sensitive recording medium according to claim 1, wherein the heat-sensitive recording layer 3 of the rewritable heat-sensitive recording medium is methanol. A rewritable heat-sensitive recording medium which is insoluble in lower alcohol such as ethanol or water. 6. Claim 1, claim 2, claim 3, claim 4
The rewritable thermosensitive recording medium according to claim 5, wherein the transparent protective layer 4 of the rewritable thermal recording medium is a solution in which a solute is dissolved or dispersed in a lower alcohol such as methanol or ethanol, or water. A rewritable thermosensitive recording medium characterized by being formed by coating and drying.