JP4253867B2 - Reversible thermosensitive recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reversible thermosensitive recording medium used for a membership card, an ID card, a credit card, a cash card, an IC card, and the like. More specifically, recording and erasing can be performed reversibly by heat, and high contrast and The present invention relates to a highly resistant reversible thermosensitive recording medium.
[0002]
[Prior art]
Conventionally, there has been a very high demand for a medium capable of reversibly recording and erasing information such as characters, symbols, and graphics for member cards, ID cards, credit cards, cash cards, IC cards, and the like. A reversible thermosensitive recording medium capable of reversibly recording and erasing information by heating is disclosed in, for example, Japanese Patent Laid-Open Nos. 54-119377, 55-154198, and 5-85045. Has been. Such a reversible thermosensitive recording medium is provided with a thermosensitive recording layer made of a mixture of a resin matrix material and an organic low molecular weight compound dispersed in the resin matrix material on a support. The heat-sensitive recording layer reversibly changes between two states, a transparent state and a cloudy state, depending on the heating temperature, and records, displays, and erases information. Each state is maintained at room temperature. Is done.
[0003]
Such a reversible thermosensitive recording medium is produced by providing a thermosensitive recording material directly on a card substrate by a printing method, a coating method, etc., and a point card using a polyethylene terephthalate (PET) substrate is put into practical use. Has been. On the other hand, plastic cards such as membership cards, ID cards, and IC cards with a thickness of 0.76 mm are provided with a heat-sensitive recording layer on another plastic support, processed into a tape, film, etc., and then used as an adhesive. It is produced by providing on a plastic card via.
[0004]
Such a reversible thermosensitive recording medium utilizing a phase change by heat is strongly demanded to improve the contrast between the recorded state and the erased state and to improve the chemical resistance. As a method for improving the contrast between the transparent state and the opaque state, for example, in Japanese Patent Application Laid-Open No. 64-14079, a light reflecting layer made of a metal such as aluminum is provided on the thermosensitive recording layer outside the support. A method for improving the contrast is disclosed. For example, Japanese Patent Application Laid-Open No. 4-220400 discloses a method for improving the contrast by providing an air layer in an adhesive layer for adhering the thermosensitive recording layer to the card substrate. It is disclosed.
[0005]
[Problems to be solved by the invention]
However, as in the above prior art, when a heat-sensitive recording material is provided on the light reflecting layer, the light reflecting layer is mainly a vapor-deposited film such as metal aluminum, and the resin matrix material of the heat-sensitive recording material that adheres to the vapor-deposited film. When the material is limited and the intended reversible characteristics cannot be obtained or the reversible characteristics are obtained, the adhesion to the light reflecting layer and the chemical resistance are poor. Even when an air layer is provided on the back side of the heat-sensitive recording layer, the heat-sensitive recording layer may change or peel off due to point pressure or rubbing. That is, in any of these methods, there was a problem in the adhesion between layers and chemical resistance, and sufficient resistance could not be obtained.
[0006]
The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a reversible thermosensitive recording medium having high contrast, which can improve the resistance of the reversible thermosensitive recording medium.
[0007]
[Means for Solving the Problems]
As a result of earnest research to solve the above problems, the present inventors can improve the contrast by providing a predetermined contrast improving means inside the plastic support that supports the reversible thermosensitive recording layer, Since the heat-sensitive recording layer can be directly formed on the plastic support via an adhesive, it has been found that the adhesion between the two is improved, and consequently the chemical resistance is improved, and the present invention has been completed.
[0008]
That is, according to the present invention, a thermosensitive recording layer containing a resin matrix and a low molecular weight organic substance dispersed in the resin matrix and having a reversible change in transparency depending on temperature is supported on the plastic via the adhesive layer. In the heat-sensitive recording medium provided on the body, the plastic support includes a first plastic support layer and a second plastic support layer constituting the uppermost layer of the plastic support, and the first plastic A means for improving the contrast of the heat-sensitive recording layer, comprising a light reflecting layer that totally reflects incident light, is provided on the lower surface portion of the support layer or the upper surface portion of the second plastic support layer, The contrast improving means is formed in a region corresponding to the display part on the surface of the reversible thermosensitive recording medium, The reversible thermosensitive recording medium is provided in which the first plastic support layer and the second plastic layer are integrated by thermal lamination.
[0010]
The contrast improving means is preferably formed in the inner region of the support corresponding to the display portion on the surface of the reversible thermosensitive recording medium.
[0011]
In the present invention, a colored layer can be provided adjacent to the contrast improving means.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. Throughout the drawings, the same reference numerals are assigned to the same members and portions.
FIG. 1 is a cross-sectional view of the reversible thermosensitive recording medium of the present invention and shows the basic structure of the present invention.
[0013]
A reversible thermosensitive recording medium 10 shown in FIG. 1 includes a plastic support 11 having a contrast enhancing means 12 described later in detail. A reversible thermosensitive recording layer 14 is provided on the plastic support 11 via an adhesive layer 13, and a protective layer 15 is provided thereon.
[0014]
In the present invention, it is preferable that the plastic support 11 has a total thickness of 500 μm or more. ,Up A first support layer on which the adhesive layer 13 is directly formed and a second support layer provided in contact with the first support layer. preferable. The first support layer is light transmissive Rate is It is preferably 0.5 to 1.0, and the second support layer preferably has a light transmittance of 0 to 1.0.
[0015]
In the present invention, the thermosensitive recording layer 14 is reversibly changed in white turbidity / transparency due to a change in the crystal form of a low molecular weight organic substance dispersed in a resin matrix material. Can be controlled. For example, the thermosensitive recording layer 14 is transparent at a temperature of about 70 to 100 ° C., and can become cloudy at 120 ° C., for example. At normal temperature, both the transparent state and the cloudy state are maintained.
[0016]
The organic low molecular weight substance dispersed in the heat-sensitive recording layer 14 is known in the art, and examples thereof include fatty acids, fatty acid derivatives, and alicyclic carboxylic acids. More specifically, saturated or unsaturated acids or dicarboxylic acids can be used as these acids, and examples of derivatives thereof include esters and amides. Specific examples of saturated fatty acids include undecanoic acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nanodecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, montanic acid, melicic acid Etc. Specific examples of the unsaturated fatty acid include oleic acid, elaidic acid, linoleic acid, sorbic acid, stearic acid and the like. These organic low molecular weight substances can be used alone, but it is preferable to use a mixture of two or more kinds.
[0017]
Examples of the resin matrix material for dispersing the organic low molecular weight substance include acrylic resins, urethane resins, polyester resins, cellulose acetate resins, nitrocellulose resins, vinyl chloride resins, vinyl acetate resins or copolymers thereof. Or mixtures thereof.
[0018]
Further, in order to control the clearing temperature range of the reversible thermosensitive recording part, a resin plasticizer, a high boiling point solvent or the like can be added at a ratio of 0.1% to 20% by weight with respect to the resin matrix material. Furthermore, in order to improve the repetitive print erasure resistance of the reversible thermosensitive recording part, 0.5% to 10% by weight of the resin matrix material with a three-dimensional crosslinkable curing agent and a crosslinking agent suitable for the resin matrix material to be used. Can be added at a ratio of
[0019]
The organic low molecular weight substance is preferably blended in the range of 15 to 70% by weight with respect to the weight of the resin matrix. If the organic low molecular weight material is less than 15% by weight, the whiteness at the time of cloudiness is insufficient, and if the organic low molecular weight material exceeds 70% by weight, the film strength of the thermosensitive recording layer may not be sufficient. .
[0020]
Usually, the thermosensitive recording layer 14 can be formed to 4 μm to 40 μm.
The adhesive layer 13 for adhering the thermosensitive recording layer 14 on the plastic support 11 is provided by applying a polymer material having a softening point of 150 ° C. or less to a film thickness of 0.5 μm to 10 μm by a printing method or a coating method. Is preferred. Examples of such a polymer material include polyvinyl chloride, polyvinyl acetate, polyester resin, polyethylene resin, polyurethane resin, acrylic resin alone, mixed or copolymer, and elastomer. Preferably, polyvinyl chloride, polyurethane resin, or polyester resin is used.
[0021]
The protective layer 15 provided on the heat-sensitive recording layer 15 is transparent and plays a role of protecting the heat-sensitive recording layer 14 from physical rubbing such as a thermal head, irritation by sweat, chemicals, and the like. The film thickness can be set to about 0.2 to 10 μm by a printing method, a coating method, or the like. The protective layer 15 is usually formed of a resin. Examples of such a resin include (meth) acrylate resins, urethane (meth) acrylate resins, epoxy (meth) acrylate resins, acrylic resins, and urethane resins. Conventionally known ultraviolet or electron beam curable resins such as resin, vinyl chloride resin-vinyl acetate copolymer resin, polyester resin, melamine resin, epoxy resin, polystyrene resin, polyimide resin, etc. may be used alone or in combination. it can. In addition, waxes such as polyethylene wax, carnauba wax, and silicon wax, or extender pigments such as calcium carbonate, zinc stearate, silica, alumina, talc, silicone oils, etc. are used to improve resistance and prevent sticking during recording. The fats and oils can be added as long as the transparency of the protective layer 15 is not impaired. Further, when recording / erasing with a thermal head, in order to control the thermal conductivity, hollow fillers, beads and the like can be added within a range that does not impair the transparency.
[0022]
In the present invention, the adhesive layer 13, the heat-sensitive recording layer 14, and the protective layer 15 can be separately formed on the plastic support 11 separately, but these three-layer structures are formed on the plastic film 16 in advance. A protective layer, a heat-sensitive recording layer, and an adhesive layer are formed in this order by a printing method, a coating method, and the like, and this plastic film 16 is brought into contact with the surface of the plastic support 11 in the adhesive layer 13 to allow those skilled in the art. It is preferable to transfer the three-layer structure onto the plastic support 11 by a known method such as a thermal transfer method, a hot roll transfer method, a thermal laminating method, an extrusion molding method, an injection molding method, or a calendar molding method. In this case, the protective layer 15 is preferably one that can be easily peeled off from the plastic film 16, but any of the resins exemplified above has such peelability.
[0023]
The plastic film 16 used in the transfer method is preferably a tough plastic film excellent in heat resistance, tensile strength and the like. As such a plastic film, for example, a film such as a polyethylene terephthalate film (PET film), a polyethylene naphthalate film (PEN film), a polyimide film, or a polyphenylene sulfide film (PPS film) can be used. These films are selected from a range of 4 μm to 100 μm in thickness with excellent physical properties in consideration of processability and operability, and preferably a thickness of about 16 μm to 50 μm is used.
[0024]
In the present invention, the heat-sensitive recording layer 14 and therefore the adhesive layer 13 and the protective layer 15 are also formed on the display portion on the surface of the reversible heat-sensitive recording medium as shown in FIG. 1 (and FIGS. 2 to 6). Can be formed only over the entire surface of the support 11. Moreover, it is preferable that the contrast improvement means 12 is provided in the internal area | region of the support body 11 corresponding to the said display part.
[0025]
As will be described in more detail below, the contrast improving means 12 includes one that improves contrast by the difference in refractive index with respect to incident light, and one that improves contrast by substantially totally reflecting incident light. The former contrast improving means can be provided inside the support 11, and the latter contrast improving means can be constituted by a light reflecting layer provided inside the support 11, by the cavity where air usually exists.
[0026]
Hereinafter, the contrast enhancing means 12 (see FIG. 1) according to the present invention will be described in more detail with reference to FIGS.
FIG. 2 is a schematic cross-sectional view of a reversible thermosensitive recording medium having contrast enhancing means according to the first aspect of the present invention.
[0027]
As shown in FIG. 2, the plastic support 11 is formed by laminating two plastic support layers 111 and 112 as shown in a preferred embodiment with respect to FIG. As described above, the first support layer 111 on which the adhesive layer 13 is directly formed is a transparent one having a light transmittance of 0.5 to 1.0. The second support layer provided in contact with the body layer 111 preferably has a light transmittance of 0 to 1.0. As the plastic constituting the support layers 111 and 112, for example, a plastic material such as a polyvinyl chloride resin, a polyester resin such as polyethylene terephthalate, a polyolefin resin such as polyethylene or polypropylene, a polycarbonate resin, or an ABS resin may be used. it can. A white pigment, a black pigment or other colorant can be added to these plastic materials according to the light transmittance.
[0028]
The thickness of each of the support layers 111 and 112 is selected from a range of about 50 μm to 1000 μm. As described above, the thickness of the plastic support 11 that is preferably bonded is preferably 500 μm or more. is there.
[0029]
Now, as shown in FIG. 2, the first support layer 111 has grooves or recesses 21 extending from the back surface thereof to a region corresponding to the display portion on the surface of the thermal recording medium. The depth of the groove 21 is 0.05 μm to a depth corresponding to 50% of the thickness of the first support layer 111 in order to ensure the strength of the first support layer 111. Is preferred.
[0030]
As described above, the cavity 121 defined by the groove 121 and the upper surface of the second support layer 11b (in which air exists) exists in the internal region of the plastic support 11 corresponding to the display unit. Thus, the first support layer 111 is in a non-contact state with the second support layer 112 at the site, the refractive index of the incident light is changed, and the thermal recording layer 14 is in a transparent state and a cloudy state. The contrast can be improved. Thus, in the first aspect, the cavity 121 in which air exists constitutes a contrast improving means.
[0031]
In the first aspect, the groove 21 is provided from the back surface of the first support layer 111. However, the groove 21 is not the first support layer 111 but the second support layer 112. It goes without saying that the same effect of improving contrast can be obtained even if it is provided from the upper surface.
[0032]
FIG. 3 is a schematic cross-sectional view of a reversible thermosensitive recording medium having contrast enhancing means according to the second aspect of the present invention.
As shown in FIG. 3, the plastic support 11 is composed of two plastic support layers 111 and 112, as in the thermal recording medium of FIG. However, in the second mode in FIG. 3, the spacer 31 is interposed between the support layers 111 and 112. The spacer 31 has an opening 31a in a region corresponding to the display portion of the heat-sensitive recording medium. In the opening 31a, the first support layer 111 and the second support layer 112 are in a non-contact state. As a result of the cavity 121 ′ being formed inside the support 11 at that portion, the same contrast enhancement effect as the contrast enhancement means shown in FIG. 2 is achieved.
[0033]
Such a spacer 31 is, for example, a polyvinyl chloride resin having good adhesion to the plastic support 11 or workability, a polyester resin such as polyethylene terephthalate, a polyolefin resin such as polyethylene or polypropylene, a polycarbonate resin, an ABS resin, etc. It is preferable to form the plastic material. Moreover, it is preferable that the thickness of the spacer 31 exists in the range of 10 micrometers-500 micrometers. In addition, it is preferable that the total thickness of the whole support body 11 including the spacer 31 is 500 μm or more as described above.
[0034]
FIG. 4 is a schematic cross-sectional view of a reversible thermosensitive recording medium having contrast enhancing means according to the third aspect of the present invention.
As shown in FIG. 4, the plastic support 11 is composed of two plastic support layers 111 and 112 as in the thermal recording medium of FIG. 2, and the first support is similar to the plastic support 11 shown in FIG. Grooves or recesses 21 are formed in the body layer 111 from the back surface to a region corresponding to the display portion on the surface of the thermal recording medium. However, in this third aspect, the grooves 21 are filled with a plurality of beads 41 or spherical particles. The bead 41 supports the first support layer 111 in the cavity 121 and also causes a void to exist in the cavity 121. Therefore, it is preferable that the spherical diameter of the beads 41 is substantially equal to the groove 21, and mechanical strength for supporting the first support layer 111 is required. Such beads can be formed of glass or polymeric material. As the polymer material, for example, melamine resin, acrylic resin, polyester resin, urethane resin, nylon resin, polycarbonate resin and the like can be used. These beads 41 can be fixed in the cavity 121 by the adhesive 42. Needless to say, since the adhesive 42 must not be embedded in the beads 41, the beads 41 are adhesives for fixing the beads. It is preferable to have a particle size 1.3 to 3 times the thickness of 42. The bead 41 can usually have a diameter of 1 to 100 μm.
[0035]
Thus, even if the beads 41 are filled in the cavity 121, the first support layer 111 and the second support layer 112 have many contact portions with the beads but do not contact each other. Therefore, the same contrast enhancement effect as that of the contrast enhancement means constituted by the cavity 121 as in the first embodiment can be obtained. As shown in FIG. 4, the adhesive 42 can be provided so as to fix the beads on the first support layer 111 side, but the groove 21 can be provided in the second support layer. Similarly, beads can be provided so as to be fixed on the second support layer 112 side.
[0036]
In the third aspect, the bead 41 is filled in the cavity 121 defined by the groove 21, but the bead 41 is placed in the cavity 121 'defined by the spacer 31 described with reference to FIG. Needless to say, the same effect can be obtained by filling. Also,
FIG. 5 is a schematic cross-sectional view of a reversible thermosensitive recording medium having contrast enhancing means according to the fourth aspect of the present invention.
[0037]
As shown in FIG. 5, the plastic support 11 is composed of two plastic support layers 111 and 112 as in the heat-sensitive recording medium of FIG. However, in the fourth aspect, the contrast improving means comprising the light reflecting layer 51 is formed on the upper surface of the second support layer 112. Such a light reflecting layer 51 is a layer having metallic luster, and can be provided by metallic luster paint, transfer of metal foil, adhesion and laminating method, metal vapor deposition method or the like. The light reflecting layer 51 totally reflects incident light and improves the contrast of the heat-sensitive recording layer 14 in a transparent state and a white turbid state.
[0038]
The light reflecting layer 51 may be provided not on the upper surface of the second support layer 111 but on the back surface of the first support layer 111.
FIG. 6 is a cross-sectional view of the thermal recording medium according to the fifth aspect of the present invention.
[0039]
The thermal recording medium shown in FIG. 6 is used as a contrast improving means for changing the color tone of the thermal recording layer 14 in the support 11 provided with any one of the contrast improving means 12 shown in FIGS. A colored layer 61 is further provided adjacent to the colored layer 61. The colored layer 61 can be provided on the bottom surface of the cavity, that is, on the upper surface of the second support layer 112 or on the back surface of the first support layer 111. Such a colored layer 61 can usually be formed by dispersing and dissolving a color pigment, a dye or the like in ink and printing it.
[0040]
As can be seen from the above description, in the present invention, since the contrast improving means 12 is provided inside the plastic support 11, the heat-sensitive recording layer 14 can be directly bonded with the adhesive 13. Of the reversible thermosensitive recording medium is greatly improved.
[0041]
【Example】
Examples of the present invention will be described in detail below.
Example 1
In this example, a thermal recording medium having the structure shown in FIG. 2 was produced.
[0042]
That is, a protective layer paint having the following composition is applied to a transparent polyethylene terephthalate (PET) film 16 (see FIG. 1) having a thickness of 25 μm using a gravure method with a high-pressure mercury lamp at 500 mJ / cm. ² Curing was performed with an energy of (205 nm) to form a protective layer having a coating thickness of 4 μm. On the upper surface of this protective layer, a heat-sensitive recording paint having the following composition consisting of an organic low molecular weight substance dispersed in a resin matrix material was applied using a gravure method at a drying temperature of 130 ° C. and a coating thickness of 9 μm. Further, a reversible thermosensitive recording sheet was obtained by applying an adhesive paint having the following composition on the upper surface of the thermosensitive recording layer by a gravure printing method at a drying temperature of 100 ° C. and a coating thickness of 3 μm.
[0043]
On the other hand, as the first support layer 111, a portion of the transparent polyvinyl chloride resin sheet having a light transmittance of 0.7 and a thickness of 100 μm, which substantially corresponds to the heat-sensitive recording layer forming portion, is scraped off to a depth of about 30 μm. Was provided. The grooved sheet 111 was integrated with a black polyvinyl chloride resin sheet having a thickness of 660 μm as the second support layer 112 by using a thermal laminating method to produce a plastic support 11.
[0044]
Subsequently, the reversible thermosensitive recording sheet was transferred onto the first support layer 111 of the plastic support 11 under the conditions of a transfer temperature of 230 ° C. and 0.5 seconds by a thermal transfer method to obtain a reversible thermosensitive recording medium.
[0045]
The obtained reversible thermosensitive recording medium could be printed with an applied energy of 0.4 mJ / dot using a thermal head, and the print data could be erased with an applied energy of 0.2 mJ / dot using a thermal head. . The contrast at this time was ΔOD = 0.5 or more, the number of repeated printings was also realized 100 times or more, and a reversible thermosensitive recording medium having high interlayer adhesion and practicality was obtained.
[0046]
(Composition of protective coating)
50 parts by weight of acrylic oligomer
50 parts by weight of urethane acrylate
1 part by weight of benzophenone photoinitiator
Teflon filler 1.5 parts by weight
Calcium carbonate 1.5 parts by weight
70 parts by weight of toluene
70 parts by weight of methyl ethyl ketone
[0047]
(Composition of thermal recording layer paint)
16 parts by weight of behenic acid
4 parts by weight of sebacic acid
50 parts by weight of vinyl chloride / vinyl acetate copolymer resin
120 parts by weight of tetrahydrofuran
40 parts by weight of toluene
[0048]
(Composition of adhesive paint)
40 parts by weight of polyester resin
40 parts by weight of toluene
40 parts by weight of methyl ethyl ketone
[0049]
Example 2
In this example, a thermal recording medium having the structure shown in FIG. 3 was produced.
That is, first, a portion substantially corresponding to the heat-sensitive recording layer forming region was cut out from a transparent polyvinyl chloride resin sheet having a light transmittance of 0.7 and a thickness of 100 μm to form an opening 31a, thereby producing a spacer 31. Next, a transparent polyvinyl chloride resin sheet having a light transmittance of 0.7 and a thickness of 100 μm as the first support layer 111 and a black polyvinyl chloride resin sheet 112 having a thickness of 560 μm as the second support layer. The plastic support 11 was obtained by interposing the spacer 31 between them and integrating them using a thermal laminating method.
[0050]
Thereafter, the reversible thermosensitive recording sheet prepared in the same manner as in Example 1 was transferred onto the first support layer 111 of the plastic support 11 under the conditions of a transfer temperature of 230 ° C. and 0.5 seconds by a thermal transfer method to be reversible. A heat-sensitive recording medium was obtained.
[0051]
The obtained reversible thermosensitive recording medium could be printed with an applied energy of 0.4 mJ / dot using a thermal head, and the print data could be erased with an applied energy of 0.2 mJ / dot using a thermal head. The contrast at this time was ΔOD = 0.5 or more, the number of repeated printings was 100 times or more, and a reversible thermosensitive recording medium with high adhesion between layers and practicality was obtained.
[0052]
Example 3
In this example, a reversible thermosensitive recording medium having the structure shown in FIG. 3 was produced.
That is, grooves 21 having a depth of 10 μm are formed in a transparent PET sheet having a light transmittance of 0.8 and a thickness of 200 μm as the first support layer 111, and polymer beads having an average particle diameter of 10 μm are formed in the grooves 21. A polymer bead-dispersed paint having the following composition dispersed was applied at a drying temperature of 60 ° C. and a coating thickness of 5 μm using a screen printing method so that the protruding portion of the polymer beads was present about 10% of the bead sphere diameter. A black PET sheet having a thickness of 560 μm was integrated with this beaded sheet 111 using a thermal laminating method to obtain a plastic support 111.
[0053]
Subsequently, the reversible thermosensitive recording sheet produced in the same manner as in Example 1 was transferred onto the first support layer 111 of the plastic support 11 by the thermal transfer method under the conditions of a transfer temperature of 230 ° C. and 0.5 seconds to be reversible. A heat-sensitive recording medium was obtained.
[0054]
The obtained reversible thermosensitive recording medium could be printed with an applied energy of 0.4 mJ / dot using a thermal head, and the print data could be erased with an applied energy of 0.2 mJ / dot using a thermal head. . The contrast at this time was ΔOD = 0.5 or more, the number of repeated printings was also realized 100 times or more, and a reversible thermosensitive recording medium having high interlayer adhesion and practicality was obtained.
[0055]
(Composition of polymer bead paint)
5 parts by weight of polyester resin beads
50 parts by weight of urethane resin
70 parts by weight of toluene
70 parts by weight of methyl ethyl ketone
[0056]
Example 4
In this example, a thermal recording medium having the structure shown in FIG. 6 was produced.
That is, a portion substantially corresponding to the heat-sensitive recording layer forming region of the transparent polyvinyl chloride resin sheet having a light transmittance of 0.7 and a thickness of 100 μm of the first support layer 111 is scraped to a depth of about 30 μm to form a groove 21. did. On the other hand, a colored paint having the following composition is applied to a portion corresponding to the groove 21 of a white polyvinyl chloride resin sheet having a thickness of 660 μm as the second support layer 112 by using a screen printing method, a drying temperature of 60 ° C., and a coating thickness of 2 μm. Was applied to form a colored layer 61. The first support layer 111 and the second support layer 112 were integrated using a heat laminating method to obtain a plastic support 11.
[0057]
Next, the reversible thermosensitive recording sheet produced in the same manner as in Example 1 was transferred onto the first support layer 111 of the plastic support 11 under the conditions of a transfer temperature of 230 ° C. and 0.5 seconds by a thermal transfer method to be reversible. A heat-sensitive recording medium was obtained.
[0058]
The obtained reversible thermosensitive recording medium could be printed with an applied energy of 0.4 mJ / dot using a thermal head, and the print data could be erased with an applied energy of 0.2 mJ / dot using a thermal head. . The contrast at this time was ΔOD = 0.5 or more, the number of repeated printings was also realized 100 times or more, and a reversible thermosensitive recording medium having high interlayer adhesion and practicality was obtained.
[0059]
(Composition of colored paint)
5 parts by weight of red dye
50 parts by weight of urethane resin
70 parts by weight of toluene
70 parts by weight of methyl ethyl ketone
[0060]
Example 5
In this example, a reversible thermosensitive recording medium having the structure shown in FIG. 5 was produced.
First, a metallic gloss paint having the following composition in which aluminum powder is dispersed in a portion corresponding to a heat-sensitive recording layer forming region of a transparent PET sheet having a light transmittance of 0.8 and a thickness of 200 μm as the first support layer 111 is screen-printed. The coating method was applied at a drying temperature of 60 ° C. and a coating thickness of 3 μm. Further, this and a white PET sheet having a thickness of 560 μm were integrated using a heat laminating method to obtain a plastic support 11.
[0061]
Subsequently, the reversible thermosensitive recording sheet produced in the same manner as in Example 1 was transferred onto the first support 111 of the plastic support 11 by a thermal transfer method under the conditions of a transfer temperature of 230 ° C. and 0.5 seconds, thereby reversible. A thermal recording medium was obtained.
[0062]
The obtained reversible thermosensitive recording medium could be printed with an applied energy of 0.4 mJ / dot using a thermal head, and the print data could be erased with an applied energy of 0.2 mJ / dot using a thermal head. . The contrast at this time was ΔOD = 0.5 or more, the number of repeated printings was also realized 100 times or more, and a reversible thermosensitive recording medium having high interlayer adhesion and practicality was obtained.
[0063]
(Composition of metallic luster paint)
15 parts by weight of aluminum powder
50 parts by weight of urethane resin
70 parts by weight of toluene
70 parts by weight of methyl ethyl ketone
[0064]
Comparative Example 1
A transparent PET sheet having a light transmittance of 0.8 and a thickness of 200 μm as a first support layer and a black PET sheet having a thickness of 560 μm as a second support layer are subjected to a heat laminating method through an adhesive for PET. And integrated to obtain a plastic support. Subsequently, the reversible thermosensitive recording sheet produced in the same manner as in Example 1 was transferred onto the first support layer of the plastic support by the thermal transfer method under the conditions of a transfer temperature of 230 ° C. and 0.5 seconds, and the reversible thermosensitive recording sheet. A recording medium was obtained.
[0065]
The obtained reversible thermosensitive recording medium could be printed with an applied energy of 0.4 mJ / dot using a thermal head, and the print data could be erased with an applied energy of 0.2 mJ / dot using a thermal head. . The contrast at this time is ΔOD = 0.3 or less, and the number of repeated printings is 100 times or more, but the contrast is too low to be practically unsuitable.
[0066]
【The invention's effect】
As described above, according to the present invention, a reversible thermosensitive recording medium is provided on the back surface or the back surface of a plastic card or plastic sheet by providing a configuration for improving the contrast inside the plastic support. The heat-sensitive recording layer can be repeatedly printed and erased, the adhesion between the layers is remarkably improved, and a highly durable and high-contrast reversible thermosensitive recording medium is provided.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a basic structure of a reversible thermosensitive recording medium according to the present invention.
FIG. 2 is a schematic cross-sectional view of a reversible thermosensitive recording medium according to an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of a reversible thermosensitive recording medium according to another embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view of a reversible thermosensitive recording medium according to still another embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view of a reversible thermosensitive recording medium according to still another embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view of a reversible thermosensitive recording medium according to still another embodiment of the present invention.
[Explanation of symbols]
11 ... Plastic support
12 ... Contrast improvement means
13 ... Adhesive layer
14 ... thermal recording layer
15 ... Protective layer
16 ... plastic film
21 ... Groove
31 ... Spacer
41 ... Bead
42. Adhesive
51. Light reflection layer
61 ... colored layer
111 ... 1st support body layer
112 ... Second support layer

Claims (3)

A heat-sensitive recording medium comprising a resin matrix and a low-molecular-weight organic substance dispersed in the resin matrix, the heat-sensitive recording layer having a reversible change in transparency depending on temperature provided on a plastic support via an adhesive layer The plastic support is composed of a first plastic support layer and a second plastic support layer constituting the uppermost layer of the plastic support, and the lower surface portion of the first plastic support layer or the second plastic support layer. the upper surface portion of the second plastic support layer, made of a light reflecting layer which totally reflects the incident light, means are provided to improve the contrast of the heat-sensitive recording layer, the contrast improvement unit, the display of the reversible thermosensitive recording medium surface parts are formed in a region corresponding to the first and the plastic support layer and the second plastic layer, it is integrated by heat lamination Reversible thermosensitive recording medium comprising a. Claim 1 Symbol mounting of the reversible thermosensitive recording medium, characterized in that a colored layer adjacent to said contrast enhancing means. The reversible thermosensitive recording medium according to claim 1 or 2 , wherein the adhesive layer is made of a polymer material having a softening point of 150 ° C or lower.

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