JP2701613B2 - Reversible thermosensitive recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium capable of recording and erasing reversibly by heating. The present invention is most effective when used for a rewritable memory card with a display function used as a prepaid card such as a commuter pass, a ticket, a coupon, an IC card, a facsimile recording paper, and an optical disk.

[0002]

2. Description of the Related Art Conventional reversible thermosensitive recording materials include a thermosensitive dye-based recording material which reversibly develops and decolors with a combination of a leuco dye, a developer and a decolorant, and an organic crystal in a matrix polymer. Using the melting and solidification behavior of particles, the phase change type reversible thermosensitive recording material that uses the change of particle transparency according to the coagulation conditions, and the thermal behavior of its molecular arrangement by liquid crystal polymer (mainly cholesteric liquid crystal). There is a method of changing transparency by utilizing the method.

[0003] The present invention relates to a phase-change type thermosensitive recording material utilizing the melting / solidification behavior of organic crystal particles in a matrix polymer and utilizing the fact that the transparency of the particles changes depending on the coagulation conditions. The fine particles are melted and solidified again by the method, and the transparency of the solidified form (polycrystalline state, single crystal state, amorphous state, etc.) is changed depending on the conditions and recorded. This heat-sensitive recording material is disclosed in JP-A-54-11937.
As disclosed in No. 7, it is composed of a combination of a matrix polymer and the following fusible organic molecules, so that extremely various recording materials can be composed. The fusible organic molecules disclosed herein include aliphatic and aromatic alcohols, carboxylic acids, amines, amides, and halides and sulfides thereof. On the other hand, as the matrix polymer, polyester, polyamide, polyacrylic acid,
Common polymers such as styrene, silicone, polyvinyl chloride, polyvinylidene chloride, and polyacrylonitrile are disclosed. A recording material obtained by improving this and further adding carbon black and an antioxidant is disclosed in
-82087 and JP-A-57-82088.

[0004]

However, in the case of a phase-change type thermosensitive recording material utilizing change in transparency by utilizing the melting and solidifying behavior of the organic crystal particles in the matrix polymer, recording / erasing is not possible. Since the organic crystal particles are sometimes repeatedly melted and solidified, the recording layer is deformed at the time of melting due to the pressure of the thermal recording head, and there is a major problem that the durability is not improved. This was a major problem that could not be avoided due to the principle of this recording.

Therefore, an object of the present invention is to provide a novel reversible heat-sensitive medium having excellent durability by using a recording material having a novel structure.

[0006]

According to the reversible thermosensitive recording medium of the present invention, a recording layer containing a crystalline organic molecule, a transparent matrix polymer and transparent particles is formed on a substrate, and the transparent particles are close to the thickness of the recording layer. This problem has been solved by a reversible thermosensitive recording medium containing high-strength particles having a size of 10% or less in a recording layer.

[0007]

According to the reversible thermosensitive recording medium of the present invention, 10% of transparent particles of high strength having a size close to the thickness of the recording layer are contained in the recording layer.
The transparent particles are mainly composed of hard spherical particles. Therefore, even if the recording material is easily deformed due to heat and changes the transparency by utilizing the melting and solidifying behavior of the organic crystal particles in the matrix polymer, the particles of the present invention serve as the pillars of the recording layer and provide a thermal recording. Resists head pressure. Therefore, even when the recording is melted, the recording layer is not deformed, and the durability is greatly improved. The present invention solves the major problem of deformation due to melting of the recording layer, which is inevitable on the principle of recording, by a simple method.

[0008]

FIG. 1 shows a typical embodiment of the present invention. FIG.
Is a polymer sheet substrate 1 on which an aluminum deposited reflective layer 2 is formed.
The recording layer 3 of the present invention is formed thereon. The recording layer 3
Is further formed with a surface coat layer 5. The recording layer 3 contains hard transparent particles 4 having a size almost close to the thickness of the recording layer. When the portion of the organic crystal particles in the recording layer 3 is enlarged, the organic crystal particles 6 are dispersed in the matrix polymer as shown in FIG. 2, and the organic crystal particles in the matrix polymer are heated and cooled. Numeral 6 indicates two states: a transparent single crystal particle 6A state and an opaque polycrystalline particle 6B state (light scattering state). This corresponds to erasure / recording, respectively.

The recording layer of the present invention is characterized in that the recording layer contains 10% or less of high-strength transparent particles having a size close to the thickness of the recording layer. More than 10% of the particles are not necessary to prevent thermal deformation. The particle size and the amount added need to be contrived so as not to affect the image quality of recording / display. These transparent particles are made of glass or polymer in terms of strength, and vary in size depending on the thickness of the recording layer.
A range of 0 μm is preferred, and a narrower particle size distribution is desirable. The relationship between the size of the particles and the thickness of the recording layer is desirably the same, but the average size of the particles is ± 20% of the recording layer.
%, The effect of the present invention is sufficiently exhibited, and is preferably within ± 10%. Therefore, it is desirable to use particles having a particle size distribution within the above range. As polymer particles,
Many materials such as melamine resin, acrylic resin, nylon resin and polycarbonate can be used. As the transparent particle shape of the present invention, spherical particles are preferable from the viewpoint of production,
The basic idea of the present invention is not limited to spherical particles because it is a high hardness particle having a size close to that of the recording layer.

The organic crystal particles and the matrix polymer in the present invention may be made of any material as in the prior art. In particular, the organic polymer particles and the matrix polymer are composed of molecules having a hydrogen bonding group.
Desirable in terms of crystallinity. As the organic crystal particles, molecules having a melting point at 60 to 120 ° C. having at least one of a carboxyl group and a hydroxyxyl group as a hydrogen bonding group are suitable. These molecules are further separated into higher alcohols, fatty acids, alkylamines, oxycarboxylic acids, dicarboxylic acids, diamines, alkylene glycols,
Form a eutectic or complex with
Alternatively, organic molecular crystal particles having a melting point can be formed.

On the other hand, matrix polymers generally include polyester, polyacrylate, polyvinyl chloride,
There are vinyl chloride-vinyl acetate copolymer, cellulose acetate, polyvinyl butyral, polystyrene, styrene-butadiene copolymer and the like, but in the present invention, when a hydrogen-bonding group-containing transparent matrix polymer is used, the cloudiness accompanying a change in crystal form is increased. -It is preferable because the change in transparency is large and the contrast is easily obtained. Specific examples include adhesive (OH group-containing) polyester, partially saponified vinyl acetate / vinyl chloride copolymer, polyamide, polyurethane, thermoplastic phenolic resin, vinyl alcohol copolymer, acrylic acid copolymer, and acrylamide copolymer. Polymers, maleic acid copolymers and the like are suitable. Since the recording material of the present invention is a thin film, considerable transparency can be obtained. In addition, it is natural that a plasticizer is used in combination therewith as appropriate.

The amount of the organic crystal particles constituting the recording layer relative to the matrix polymer can be in the range of 5 to 50%, but preferably 15 to 40%. If the ratio of the organic crystal particles is more than this, the binding force is weakened and it is difficult to form a uniform coating as a recording layer. Conversely, when the ratio of the matrix polymer is high, the amount of the organic crystalline particles is small, so that it is difficult to make opaque, and the recording contrast is poor.

The inclusion of a crystal nucleating agent having a hydrogen bonding surface in the recording layer of the present invention is very effective in improving the reliability of crystallization characteristics. It is also effective to include an antioxidant having active hydrogen. Therefore, it is preferable that the transparent particles have at least a hydrogen bonding group on the surface because the crystallization characteristics of the crystalline organic molecule can be improved.

The reversible thermosensitive recording medium of the present invention is used for a method of recording and erasing using not only a thermosensitive head but also a direct heating means such as a heat roller.

In the reversible thermosensitive recording medium of the present invention, since recording / erasing is performed by directly heating the recording medium, a wear-resistant surface coat layer greatly improves durability. The configuration of the reversible thermosensitive recording medium of the present invention, which has a surface coat layer having excellent wear resistance and avoids thermal deformation of the recording layer, has little deterioration over time even with contact with a heating means, and has high repetitive durability. A recording medium can be configured.

The reversible thermosensitive recording medium of the present invention is configured as a memory card with a display function having a magnetic recording section 8 as shown in FIG. 3, and is widely used for cashless use. The application as an IC card can be greatly expected.

Next, the present invention will be described with reference to examples. (Example 1) As a recording material, 2 g of hydroxystearic acid, 0.1 g of a phenolic antioxidant, and 8 g of a partially saponified hydroxyl-containing vinyl chloride / vinyl acetate copolymer
Are dissolved in 100 ml of tetrahydrofuran, and the glass beads having an average particle diameter of 15 μm as transparent particles 4 are added.
8 g was dispersed, and a recording layer 3 having a thickness of 13 μm was formed on a 0.2 mm polyester polymer sheet substrate 1 on which an aluminum vapor-deposited layer 2 shown in FIG. 1 was formed. The recording layer 3
Was further coated with a UV-curable acrylic resin prepolymer of 20 μm as an abrasion-resistant surface coat layer 5 and then cured by irradiation with ultraviolet light. Writing and erasing were performed on the reversible thermosensitive recording sheet thus formed by a thermosensitive head. The clearing temperature range of this sheet is about 70 ~
90 ° C. Under these conditions, energy was applied by a thermal head to write at 100 ° C. and erase at 80 ° C. When the written opaque region and the erased transparent region were analyzed by X-ray diffraction, diffraction peaks were observed in both regions, and it was found that the region was microcrystalline. These are shown in FIG.
As shown in FIG. 7, the organic crystal particles 6 correspond to an opaque polycrystalline particle 6B state (light scattering state) and a transparent single crystal particle 6A state, respectively. Further, the deterioration of the recorded image quality due to the glass beads was not visually observed. When a durability test was performed, 1200 repetitions became possible, and a life that was about seven times as long as that when no glass beads were added was obtained.

Example 2 As a recording material, behenic acid 2
g, phenolic antioxidant 0.1 g, adhesive polyester (Toyobo Co., Ltd. Byron) 2 g, and polyurethane 5 g are dissolved in tetrahydrofuran 100 ml, and transparent particles 4 are made of melamine resin having an average particle diameter of 20 μm. 0.3 g of spherical particles were dispersed, and a recording layer 3 having a thickness of 20 μm was formed on a 0.2-mm polyester polymer sheet substrate 1 on which an aluminum deposition layer 2 shown in FIG. 1 was formed.
A UV-curable acrylic resin prepolymer of 25 μm is further provided on the recording layer 3 as a wear-resistant surface coat layer 5.
After coating, the coating was cured by irradiation with ultraviolet rays. Writing and erasing were performed on the reversible thermosensitive recording sheet thus formed by a thermosensitive head. The clearing temperature range of this sheet was about 90 to 110 ° C. From this condition, energy was given by the thermal head and writing was performed at 120 ° C and 100 ° C
As a result, clear recording characteristics were obtained. When the life characteristics were further measured repeatedly, they withstood 1860 repetitions.

Example 3 As a recording material, 2 g of stearyl alcohol, 0.1 g of a hindered phenolic antioxidant, and 8 g of a vinyl chloride / vinyl acetate / acrylamide copolymer were dissolved in 100 ml of tetrahydrofuran. As transparent particles, 0.3 g of melamine resin spherical particles having an average particle diameter of 20 μm were dispersed, and the surface was colored gold to form a reflective layer of 0.2 mm as shown in FIG.
The recording layer 3 was formed with a thickness of 25 μm on a 1 mm thick polymer sheet 1 of hard polyvinyl chloride. The recording layer was further coated with a UV-curable acrylic resin prepolymer of 20 μm as a wear-resistant surface coat layer 4 and then cured by irradiation with ultraviolet light. Writing and erasing were performed on the reversible thermosensitive recording sheet thus formed by a thermosensitive head. The clearing temperature range of this sheet is about 70
９０90 ° C. Under these conditions, energy was applied by a thermal head to write at 100 ° C. and erase at 80 ° C.

The recording sheet is cut and the reversible thermosensitive recording section 7 is cut.
Further, a magnetic recording layer 8 was formed to obtain a recording card with a display function as shown in FIG. The reversible thermosensitive recording section 7 of the recording card with a display function also allows recording and erasing with a thermal head, and together with the magnetic recording layer 8, showed the function of a rewritable memory card.

[0021]

As described above, the present invention relates to a reversible thermosensitive recording medium having a recording layer composed of a polymer composition in which organic crystal particles are dispersed in a matrix polymer, and a high strength medium having a size close to the thickness of the recording layer. 10% of transparent particles in the recording layer
Since it is a reversible thermosensitive recording medium configured to include the following, it has an effect of providing a reversible thermosensitive recording medium having extremely excellent durability against writing / erasing with a thermosensitive recording head, and has a great industrial value. is there.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view showing one embodiment of a reversible thermosensitive recording medium of the present invention.

FIG. 2 is a conceptual cross-sectional view showing two states of organic crystal particles in a recording layer of a reversible thermosensitive recording medium of the present invention. (A) is a transparent state of organic crystal particles (b) is an opaque state of organic crystal particles

FIG. 3 is a conceptual sectional view showing another embodiment of the reversible thermosensitive recording medium of the present invention.

FIG. 4 is a conceptual cross-sectional view showing a magnetic card with a display function as one embodiment of the reversible thermosensitive recording medium of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 polymer sheet substrate 2 reflection layer 3 recording layer 4 transparent particle 5 surface coating layer 6 organic crystal particle 6A transparent single crystal particle 6B opaque polycrystalline particle 7 reversible thermosensitive recording section 8 magnetic recording section

Claims (4)

(57) [Claims] 1. A recording layer comprising a crystalline organic molecule, a transparent matrix polymer and transparent particles is formed on a substrate, wherein said transparent particles are high-strength particles having a size close to the thickness of said recording layer. A reversible thermosensitive recording medium, wherein the layer contains the transparent particles in an amount of 10% or less. 2. The reversible thermosensitive recording medium according to claim 1, wherein the transparent particles comprise spherical particles of glass or a polymer having an average particle size of 1 to 100 μm and a particle size distribution. 3. The reversible thermosensitive recording medium according to claim 1, wherein the crystalline organic molecule has a hydrogen bonding group, and the transparent particles have at least a hydrogen bonding group on the surface. 4. The reversible thermosensitive recording medium according to claim 1, wherein a light reflecting film is formed between the substrate and the recording layer.