JPH06278362A - Rewritable heat sensitive recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To provide a heat sensitive recording medium and its manufacture which can contrive an improvement in contrast between an image part and nonimage part and also an improvement in workability is contrived at the time of manufacture. CONSTITUTION:In a heat sensitive recording medium 1, a principal part is constituted of a filmy recording layer 11 obtained by scattering behenic acid within polyester resin and a black layer 12 which is provided on one side of the filmy recording layer 11 and has scattered carbon black within the same. Then in the heat sensitive recording medium 1, since a member corresponding to a body of heat sensitive recording medium as in the past is not in existence, in the case where the same is applied to ID cards, a film thickness of the filmy recording layer 11 can be set up thicker by amount wherein a substrate is not in existence and an improvement in contrast between the image part and nonimage part is contrived. Then since the recording layer 11 is formed after the behenic acid is added, melted and agitated within hot-melted polyester resin by coating by an extruding machine and an improvement in workability can be contrived by amount not using a solvent such as tetrahydrofuran.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable heat-sensitive recording medium having a recording layer whose transparency reversibly changes depending on temperature, and more particularly to a rewritable thermal recording medium having a contrast between an image portion and a non-image portion. The present invention relates to an improvement in a heat-sensitive recording medium that can be improved, and at the same time, can be improved in workability during manufacturing, and an improved manufacturing method thereof.

[0002]

2. Description of the Related Art As a thermal recording medium of this type, Japanese Patent Laid-Open No. 55-154198 and US Pat.
As described in Japanese Patent Publication No. 3, a recording layer containing a thermoplastic resin such as polyvinyl chloride and an organic low molecular weight substance such as a higher fatty acid dispersed in the resin as a main component is provided on a support. The structure is known.

This heat-sensitive recording medium is constructed by skillfully utilizing the property that the light absorption characteristic (light scattering property) of the recording layer reversibly changes depending on temperature. That is, this recording layer has a specific temperature T near room temperature.
_It has two state transition temperatures T ₁ and T ₂ (provided that T ₁ <T ₂ ) at a temperature higher than ₀ , and becomes cloudy when the recording layer is heated to T ₂ or higher and held and then cooled to T ₀ or lower. When the recording layer in the cloudy state is heated to T ₁ or more and less than T ₂ and then cooled to T ₀ or less, the light scattering property is decreased while the light scattering property increases to the maximum light shielding state. It becomes transparent. Moreover, the maximum light-shielding state and the transparent state of the recording layer can be stably maintained under a temperature condition of T ₀ or less, and these states can be reversibly changed. When set to, the recording medium can be used as a rewritable recording medium that can be differentiated from the other state.

[0004]

By the way, this thermosensitive recording medium is used as an ID for a cash card, a credit card, or the like.
When applied to cards, the thickness of the card base material that constitutes the support is usually set to a large value, and the total thickness of the card is also subject to certain restrictions, so the thickness of the recording layer formed on top of this is inevitable. I had to set it thin.

Therefore, since the thickness of the recording layer is reduced,
There is a problem that the contrast between the image part and the non-image part cannot be increased.

Further, in the case of producing this kind of thermal recording medium including the above-mentioned applications, the resin material constituting the resin base material and the organic low molecular weight substance are dissolved in an organic solvent such as tetrahydrofuran and the solution is placed on a support. A method of forming a recording layer by coating and drying the composition on the surface is adopted (JP-A-62-25788).
(See Japanese Patent Publication No. 3).

However, the above-mentioned tetrahydrofuran has a problem that the workability is poor because it gives off an offensive odor and easily reacts with oxygen in the air to form explosive peroxides.

Furthermore, the dispersion state of the organic low molecular weight substance dispersed in the resin base material is easily influenced by the volatilization state of the solvent in the solution in which the resin material and the organic low molecular weight substance are dissolved, and the drying conditions of the above solution are There is a problem in that it is difficult to form a recording layer having uniform characteristics because the characteristics of the recording layer change due to the difference.

The present invention has been made by paying attention to such a problem, and its object is to improve the contrast between the image part and the non-image part even when applied to ID cards and the like. It is an object of the present invention to provide a thermal recording medium and a method for producing the same, which can improve workability during production.

[0010]

That is, the invention according to claim 1 is based on a resin base material and an organic low molecular weight substance dispersed in the resin base material as main components, and its transparency is reversible depending on temperature. It is characterized in that it is composed of a film-like recording layer that changes into a color, and a coloring layer provided on one surface of the recording layer and containing a dye or a pigment mixed therein. A film-like recording layer whose main component is an organic low-molecular substance dispersed in this resin matrix and whose transparency reversibly changes depending on temperature; and a metal reflection layer laminated on one side of this recording layer. And consists of
Further, the invention according to claim 3 is a film-shaped recording layer comprising a resin base material and an organic low molecular weight substance dispersed in the resin base material as main components, and the transparency thereof reversibly changes depending on temperature. And a magnetic recording layer laminated on one side of this recording layer.

The heat-sensitive recording medium according to the present invention comprises a film-shaped recording layer and a coloring layer, a metal reflection layer or a magnetic recording layer provided on one side of the recording layer. Since there is no member corresponding to the support of the thermal recording medium described in the prior art, when the thermal recording medium according to claims 1 to 3 is applied to ID cards, no support is present. Since it is possible to set the film thickness of the film-shaped recording layer to a corresponding extent, there is an advantage that the contrast between the image portion and the non-image portion can be improved.

In the heat-sensitive recording medium according to the first and second aspects of the present invention, an adhesive layer is formed on the colored layer or the metal reflective layer, and the adhesive layer is releasably attached to a release paper or the like. By constructing the label by using such a label, there is also an advantage that the range of application of this type of thermal recording medium can be expanded.

In the inventions according to claims 1 to 3, the resin material forming a part of the film-like recording layer has a refractive index close to that of an organic low molecular weight substance described below and is incompatible. A thermoplastic resin having excellent mechanical strength and having film forming ability and good transparency can be mentioned, and specific examples thereof include polyester resins such as saturated copolyester; polyvinyl chloride resin; vinyl chloride-vinyl acetate copolymer, Vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer, and other vinyl chloride copolymers; polyvinylidene chloride resin; vinylidene chloride-vinyl chloride copolymer Polymers, vinylidene chloride-acrylonitrile copolymers and other vinylidene chloride copolymers; polyamide resins; silicone Fats; there are polyacrylate or polymethacrylate resin, or this copolymer and the like, etc. can be applied as a mixture which like alone, or two or more kinds.

On the other hand, as the organic low molecular weight substance dispersed in the above resin material, a fatty acid or a fatty acid derivative, or
Examples thereof include alicyclic organic acids, and more specifically, those containing saturated or unsaturated mono- or dicarboxylic acids, or their esters and amides.

Specific examples of the saturated fatty acids include undecanoic acid, lauric acid, myristic acid, pentadecanoic acid, barmitic acid, heptadecanoic acid, stearic acid, nanodecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, Examples thereof include montanic acid and melissic acid, and specific examples of unsaturated fatty acids include oleic acid, elaidic acid, linoleic acid, sorbic acid and stearolic acid.

The fatty acid or fatty acid derivative or alicyclic organic acid is not limited to these, and it is possible to apply one kind or a mixture of two or more kinds of these. Is.

In the invention according to claim 1, the colored layer provided on one side of the film-like recording layer includes a transparent portion (a portion in a transparent state where light scattering property is reduced) and a white turbid portion (light). It has the effect of making a difference in the reflection density from the area where the scattering property is increased and the maximum light shielding state).
That is, in a recording layer on which a recorded image including a transparent portion and a white turbid portion is formed, when light is incident on the transparent portion, the light is absorbed by the colored layer, whereas the light is incident on the white turbid portion. Since the reflected light is reflected by the cloudy part, a difference in reflection density occurs between the transparent part and the cloudy part, so that the image part and the non-image part can be differentiated.

Such a colored layer can be arbitrarily set according to the type of dye or pigment to be applied.
A black pigment (such as carbon black) is applied to set it to black.

On the other hand, in the second aspect of the invention, the metal reflective layer provided on one side of the film-like recording layer also has an effect of making a difference in reflection density between the transparent portion and the cloudy portion of the recording layer. . That is, when light is incident on the transparent portion, the light is strongly reflected by the action of the metal reflection layer, whereas the light incident on the cloudy portion is only weakly reflected on the cloudy portion. A difference in reflection density occurs between the transparent portion and the cloudy portion, so that the image portion and the non-image portion can be differentiated as in the invention according to claim 1.

As the metal material applicable to the metal reflection layer, aluminum which can be formed into a film by means such as vacuum deposition,
Examples include tin, silver, magnesium, chromium, nickel and the like.

Further, in the invention according to claim 3, the magnetic recording layer provided on one side of the film-like recording layer functions in the same manner as the colored layer of the invention according to claim 1 in terms of light reflectivity, but in addition to this function The magnetic recording information can also be written. As the magnetic recording layer, a magnetic recording material applied to a conventional magnetic card or the like can be applied.

Next, the invention according to claim 4 is the above-mentioned claim 1.
3 to 3 relate to a method for manufacturing a thermal recording medium according to the invention.

That is, the invention according to claim 4 is as follows.
On the premise of the method for producing a heat-sensitive recording medium according to any one of 3 to 3, an organic low molecular weight substance that is also heat-melted is dispersed in a heat-melted thermoplastic resin, and the melt dispersion is formed into a film by an extrusion molding method to form the recording layer. It is characterized by forming.

Further, in the method for producing a heat-sensitive recording medium according to the present invention, the organic low molecular weight substance is contained in the thermoplastic resin which is heat-melted without using a solvent such as tetrahydrofuran when forming the recording layer. Since it has been dispersed, it has the advantages that the problems in working due to tetrahydrofuran are ameliorated and that a film-like recording layer having uniform characteristics can be formed regardless of the difference in drying conditions.

The advantages of this manufacturing method are not limited to the thermosensitive recording medium according to claims 1 to 3 and are similarly present in the conventional method of manufacturing a thermal recording medium having a support. The invention according to claim 5 is created for such a technical reason.

That is, the invention according to claim 5 provides a recording layer which comprises a resin base material and an organic low molecular weight substance dispersed in the resin base material as main components and whose transparency reversibly changes depending on temperature. Assuming a method for manufacturing a rewritable heat-sensitive recording medium provided on a support, the same low-melting organic low-molecular substance is dispersed in a heat-melting thermoplastic resin, and the melt dispersion is formed into a film by an extrusion molding method. To form the recording layer.

In the invention according to claim 5, the support is composed of a plastic film or sheet in which a coloring agent such as a dye or a pigment is blended, a paint or an ink containing the dye or the pigment, as in the conventional case. Examples include a plastic film or sheet on which a colored layer is laminated, and a plastic film, sheet or paper on which a metal reflective layer of aluminum, tin, silver, magnesium, chromium, nickel or the like is further provided. Then, specific examples of the plastic film or sheet include polyethylene terephthalate,
Examples thereof include a material group having excellent heat resistance, transparency, and mechanical strength such as polyethylene naphthalate, polycarbonate, and polyparabanic acid.

[0028]

According to the heat-sensitive recording medium of the present invention, the film-shaped recording layer and the coloring layer, the metal reflection layer, or the magnetic recording layer provided on one surface of the recording layer. Since there is no member corresponding to the support of the conventional thermal recording medium, the thermal recording medium is
When applied to a D card, the film thickness of the film-like recording layer can be set to a large amount because there is no support, and the contrast between the image portion and the non-image portion can be improved.

On the other hand, according to the method for producing a heat-sensitive recording medium according to the inventions of claims 4 to 5, when the recording layer is formed, an organic solvent is added to the thermoplastic resin which is heat-melted without using a solvent such as tetrahydrofuran. Since the molecular substance is dispersed, the adverse effects on the work due to tetrahydrofuran are improved, and a recording layer having uniform characteristics can be formed regardless of the difference in drying conditions.

[0030]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 A thermosensitive recording medium 1 according to this example has a film-like recording layer 11 in which behenic acid is dispersed in a polyester resin as shown in FIG. 1, and one side of the film-like recording layer 11. And a black layer 12 made of vinyl chloride-vinyl acetate copolymer resin in which carbon black is dispersed. In this heat-sensitive recording medium 1, when the recording layer 11 in a cloudy state is heated to a temperature of 76 ° C. or higher and lower than 104 ° C. and held by a means such as a thermal head, and then cooled to a proper temperature near room temperature or lower, its light scattering property is obtained. Decreases and becomes transparent, while
When the recording layer in the transparent state is heated to 104 ° C. or higher by the above means and held and then cooled to an appropriate temperature near room temperature or lower, its light scattering property is increased to the maximum light shielding state, and these It was a medium capable of reversibly changing its state.

Then, in the recording layer 11 having a character pattern formed of a transparent portion (a transparent portion) and a white turbid portion (a maximum light shielding portion), when light is incident on the transparent portion, this Since the light is absorbed by the black layer 12 and the light incident on the white turbid portion is reflected by the white turbid portion, a difference in reflection density occurs between the transparent portion and the white turbid portion, and the character pattern is visually observed. It was a thing.

{Manufacture of Thermal Recording Medium} The thermal recording medium according to this example is manufactured by the following steps.

First, a polyester resin (2 parts by weight) having the following characteristics was heated to 130 ° C. and melted, and then behenic acid (1 part by weight) was added to the melted resin. Melt and stir. The melt dispersion thus obtained is coated on a slide glass by an extruder (extruder) to form a film-shaped recording layer 11
Was formed.

(Characteristics of Polyester Resin) Glass Transition Point: 45 ° C. Softening Point: 121 ° C. Melt Viscosity: 150 poise And vinyl chloride-vinyl acetate in which carbon black is dispersed on one surface of the film-like recording layer 11. The thermosensitive recording medium 1 was manufactured by coating a coating material containing a copolymer resin as a main component and drying it to form a black layer 12.

Comparative Example The polyester resin (2 parts by weight) applied in Example 1 was dissolved in tetrahydrofuran (8 parts by weight), and behenic acid (1 part by weight) was added and dissolved, and then dispersed. A thermosensitive recording medium prepared by coating the above coating solution on a 180 μm-thick polyester sheet on which a black layer made of carbon black and vinyl chloride-vinyl acetate copolymer resin has been formed, and drying at 100 ° C. for 2 minutes. Was manufactured.

Recording operation was performed on this thermosensitive recording medium by the same means as in Example 1. As a result, reversible thermosensitive recording characteristics were not exhibited.

Example 2 The thermal recording medium 2 according to this example is formed in a label shape, and has a film-like recording layer 21 in which behenic acid is dispersed in a polyester resin, as shown in FIG. A metal reflection layer 22 made of aluminum vacuum-deposited on one surface of the film-like recording layer 21, a pressure-sensitive adhesive layer 23 made of polyacrylic acid ester laminated on the metal reflection layer 22, and a pressure-sensitive adhesive layer 23 formed on the pressure-sensitive adhesive layer 23. The release sheet 24 made of laminated kraft paper constitutes the main part.

The film-like recording layer 21 according to this example is formed into a film by the same method as in Example 1, and its recording characteristics are the same as those of the recording layer according to Example 1. It was similar.

Then, the release sheet 24 is peeled off from the label-like heat-sensitive recording medium 2 to expose the pressure-sensitive adhesive layer 23, which is attached to a card substrate 30 made of polyvinyl chloride and heat-sensitive as shown in FIG. The recording card 3 was manufactured.

[0041]

According to the heat-sensitive recording medium according to the present invention, a film-shaped recording layer and a coloring layer, a metal reflection layer, or a magnetic recording layer provided on one surface of the recording layer. Since there is no member corresponding to the support of the conventional heat-sensitive recording medium, when these heat-sensitive recording media are applied to ID cards and the like, the film-shaped recording layer is formed in the amount corresponding to the absence of the support. It is possible to set a large film thickness, and there is an effect that the contrast between the image portion and the non-image portion is improved and the recording image quality is improved.

On the other hand, according to the method for producing a heat-sensitive recording medium according to the inventions of claims 4 to 5, when the recording layer is formed, an organic solvent is added to the thermoplastic resin which is heat-melted without using a solvent such as tetrahydrofuran. Since the molecular substance is dispersed, the adverse effects on the work due to tetrahydrofuran are improved, and a recording layer having uniform characteristics can be formed regardless of the difference in drying conditions.

Therefore, the thermosensitive recording medium having uniform recording characteristics can be manufactured easily and safely.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of a thermal recording medium according to a first embodiment.

FIG. 2 is a structural cross-sectional view of a label-shaped thermal recording medium according to a second embodiment.

FIG. 3 is a structural cross-sectional view of a thermal recording card obtained from the label-shaped thermal recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal recording medium 2 Thermal recording medium 11 Film recording layer 12 Black layer 21 Film recording layer 22 Metal reflective layer 23 Adhesive layer 24 Release sheet

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Susumu Watanabe 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.

Claims (5)

[Claims] 1. A film-shaped recording layer comprising a resin base material and an organic low-molecular substance dispersed in the resin base material as main components, the transparency of which changes reversibly depending on temperature, and the recording layer. A rewritable heat-sensitive recording medium comprising a colored layer provided on one surface of which a dye or pigment is mixed. 2. A film-shaped recording layer comprising a resin base material and an organic low-molecular substance dispersed in the resin base material as main components, the transparency of which changes reversibly depending on temperature, and the recording layer. A rewritable heat-sensitive recording medium comprising a metal reflection layer laminated on one side of the above. 3. A film-shaped recording layer comprising a resin base material and an organic low-molecular substance dispersed in the resin base material as main components, the transparency of which changes reversibly depending on temperature, and the recording layer. A rewritable heat-sensitive recording medium comprising a magnetic recording layer laminated on one side thereof. 4. A method for producing a heat-sensitive recording medium according to claim 1, wherein a heat-melted thermoplastic resin is dispersed in the same low-melting organic low molecular weight substance, and the melt dispersion is extruded. A method for producing a heat-sensitive recording medium, which comprises forming the recording layer into a film. 5. A rewritable recording medium comprising, as a main component, a resin base material and an organic low molecular weight substance dispersed in the resin base material, and a recording layer whose transparency reversibly changes depending on temperature. In the method for producing a heat-sensitive recording medium, the same low-melting organic low-molecular substance is dispersed in a heat-melting thermoplastic resin, and the melt dispersion is formed into a film by an extrusion molding method to form the recording layer. A method for manufacturing a heat-sensitive recording medium, comprising: