JPH04299177A - Thermally reversible recording material and recording medium - Google Patents

Abstract

PURPOSE:To obtain a thermally reversible recording material and recording medium by composing the thermally reversible recording material of a polymer composition composed of organic crystal particles and matrix polymer having hydrogen bond group. CONSTITUTION:A molecule having at least one of carboxyl group or hydroxyxyl group and melting point in the range of 60-120 deg.C is employed as an organic crystal particle having hydrogen bond group whereas adhesive (containing OH group) polyester, partially sponificated vinyl acetate-vinyl chloride copolymer or the like is employed as a matrix polymer containing hydrogen bond group. A thermally reversible recording material layer (recording layer 3) is formed on a substrate 1 having a metal reflection layer 2, and a surface coat layer 4 is further formed thereon to produce a thermally reversible recording medium which is used in a card having indicating function or an optical disc.

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 material that can be reversibly recorded and erased by heating, and a recording medium using the same. More specifically, we will introduce reversible thermosensitive recording materials useful for rewritable memory cards with display functions used as prepaid cards such as commuter passes, tickets, and coupons, IC cards, facsimile recording paper, and optical discs, and records using the same. Regarding the medium.

0002

[Prior Art] Conventional reversible heat-sensitive recording materials include heat-sensitive dye-based recording materials that reversibly develop and decolor using a combination of leuco dye, developer, and decolorizer, and organic crystals in a matrix polymer. Phase-change reversible thermosensitive recording materials that utilize the melting and solidification behavior of particles to change their transparency depending on the solidification conditions, and liquid crystal polymers (mainly cholesteric liquid crystals) to control the thermal behavior of their molecular arrangement. Methods have been proposed to utilize this to change transparency.

[0003] Furthermore, by utilizing the melting and solidifying behavior of organic crystal particles in a matrix polymer, a phase change thermosensitive recording material is used, which takes advantage of the fact that the transparency of the particles changes depending on the solidification conditions. is melted and solidified again, and depending on the conditions, the solidified form (polycrystalline state, single crystalline state,
There is a method proposed in Japanese Patent Application Laid-Open No. 119377/1983 as a method for creating and recording differences in transparency (such as amorphous state). This heat-sensitive recording material is composed of a combination of a matrix polymer and the following meltable organic molecules, and can be composed of a wide variety of recording materials. The meltable organic molecules disclosed herein include aliphatic and aromatic alcohols, carboxylic acids, amines, amides, and their halides and sulfides. On the other hand, as the matrix polymer, general polymers such as polyester, polyamide, polyacrylic acid, styrene, silicone, polyvinyl chloride, polyvinylidene chloride, and polyacrylonitrile are disclosed. Further, recording materials in which carbon black and antioxidants are further added by improving this are disclosed in Japanese Patent Application Laid-Open No. 57-82087 and Japanese Patent Application Laid-open No. 57-82088.
It is disclosed in the publication No.

0004

[Problem to be Solved by the Invention] However, although the above-mentioned known examples disclose meltable organic molecules and matrix polymers, no efforts have been made to improve their mutual compatibility, dispersibility, etc. However, there was a problem in that it was difficult to properly disperse the organic crystal particles, and recording with excellent recording resolution and high density could not be obtained.

[0005] Therefore, in order to solve the problems of the prior art, the first object of the present invention is to provide an excellent reversible thermosensitive recording material system by using organic crystalline molecules with a special structure and a matrix polymer. It is said that

[0006] The second purpose is to use this heat-sensitive recording material to
The objective is to provide a recording medium that can be widely used for cards with display functions, facsimile paper, optical memory, etc.

[0007]

[Means for Solving the Problems] In order to achieve the first object, the reversible thermosensitive recording material of the present invention is composed of a polymer composition in which organic crystal particles are dispersed in a matrix polymer, and the organic crystal particles are dispersed in a matrix polymer. It is characterized in that both the particles and the matrix polymer are composed of molecules having hydrogen bonding groups. This heat-sensitive recording material changes its transparency reversibly by melting and solidifying organic crystal particles, and records and erases information.

The reversible thermosensitive recording material of the present invention is also formed by coating a homogeneous solution consisting of a crystalline organic molecule having a hydrogen bonding group, a transparent matrix polymer having a hydrogen bonding group, and a proton-based organic solvent, and drying the coating. When the crystalline organic molecules are included in the matrix polymer as organic microcrystalline particles having an average diameter of 0.1 μm or less, a recording material exhibiting the most characteristics can be obtained.

[0009] As the organic crystal particles having hydrogen bonding groups of the present invention, molecules having at least one of a carboxyl group or a hydroxyl group and having a melting point of 60 to 120°C are used, and as the transparent matrix polymer containing hydrogen bonding groups, , adhesive (OH group-containing) polyester, partially saponified vinyl acetate-vinyl chloride copolymer, polyamide, polyurethane, thermoplastic phenolic resin, vinyl alcohol copolymer, acrylic acid copolymer, acrylamide copolymer,
It is preferable to use one selected from maleic acid copolymers.

Furthermore, in order to achieve the second object, the reversible thermosensitive recording material of the present invention is formed on a polymer sheet on which a reflective layer is formed, and a wear-resistant surface coating layer is further formed on the reversible thermosensitive recording material. There are two types of configurations: one is a recording sheet, and the other is a configuration in which it is formed on a substrate on which a reflective film is formed, a surface coat layer is further formed, and used as an optical recording medium that is recorded and erased by a laser.

[0011]

[Function] In the reversible thermosensitive recording material of the present invention, since both the organic crystal particles and the matrix polymer are made of molecules having hydrogen bonding groups, they have good compatibility and their melting and solidification characteristics are determined by mutual interaction. Combinations in which the compatibility is too high and a large amount of organic crystal particles are dissolved are not suitable for the present invention. The crystallization behavior of a molecule having a melting point of 60 to 120° C. and having a hydroxyl group or a carboxyl group as a hydrogen bonding group within a matrix polymer proceeds through a hydrogen bonding interface with the matrix polymer. Therefore, the number and nature of hydrogen bonding groups at the interface between the crystal particles and the polymer determine this behavior. In the structure of the present invention, since the organic crystal particles and the matrix polymer are composed of materials having appropriate compatibility and hydrogen bonding, microcrystal particles with an average diameter of 0.1 μm or less are precipitated, resulting in highly reliable and excellent It exhibits crystallization behavior, and the organic crystal particles and matrix polymer do not separate significantly, nor do giant crystal particles or cracks occur.

In producing the reversible thermosensitive recording material of the present invention, a homogeneous solution is prepared from the above organic crystal particles having hydrogen bonding groups, a transparent matrix polymer containing hydrogen bonding groups, and a proton-based organic solvent, and when a film is formed from this, the matrix It is possible to obtain an excellent recording material in which organic microcrystalline particles having an average diameter of 0.1 μm or less are dispersed in a polymer. Because this recording material has appropriate compatibility between the matrix polymer and organic crystal particles, the size of the microcrystal particles does not change even after repeated heating and cooling (recording/erasing) processes, resulting in high resolution, clarity, and longevity characteristics. It becomes an excellent recording material.

The organic crystal particles in the matrix polymer have two states at room temperature: a transparent single crystal state and an opaque polycrystalline state (light scattering state), which correspond to erasing and recording, respectively. The wider the clearing temperature range, the easier it is to control the recording system. In general, supercooling phenomenon often occurs in the melting/crystal behavior used in the present invention, and this causes recording instability. Since the recording material of the present invention does not cause supercooling, excellent recording characteristics can be obtained. Crystal nucleating agents and antioxidants also have the effect of preventing supercooling.

Furthermore, since the present invention is a reversible recording method that utilizes physical changes such as melting and solidification of organic crystal particles, if a wear-resistant surface coating layer is applied, deterioration over time will be prevented even when a thermal head is contacted. A recording sheet that is small and has high repeat durability can be constructed. Furthermore, when the reversible thermosensitive recording material of the present invention in which organic microcrystalline particles having an average diameter of 0.1 μm or less are dispersed is formed on a polymer substrate on which a reflective film is formed, and a surface coating layer is further formed, Since clear recording with very high resolution can be easily performed, an excellent high-density optical recording medium that can be recorded and erased using a laser can be obtained.

[0015]

EXAMPLES Next, the present invention will be explained based on examples. A typical embodiment of the invention is shown in FIG. In FIG. 1, a recording layer 3 of the present invention is formed on a polymer sheet 1 on which an aluminum vapor-deposited reflective layer 2 is formed. A surface coat layer 4 is further formed on the recording layer 3. The recording layer 3 is composed of a matrix polymer 5 and organic crystal particles 6, as shown in FIG.
It takes two states: B (light scattering state). This corresponds to erasing and recording, respectively.

Both the organic crystal particles and the matrix polymer of the present invention are composed of molecules having hydrogen bonding groups. The organic crystal particles include carboxyl groups as hydrogen bonding groups,
60 having at least one hydroxyl group
Molecules with melting points between ~120°C are used. These molecules are further formed into eutectics or complexes with separate higher alcohols, fatty acids, alkylamines, oxycarboxylic acids, dicarboxylic acids, diamines, alkylene glycols, etc. to form organic molecular crystals with a melting point of 60 to 120°C. It is also possible to configure particles.

On the other hand, matrix polymers generally include polyester, polyacrylate, polyvinyl chloride,
Examples include vinyl chloride-vinyl acetate copolymer, cellulose acetate, polyvinyl butyral, polystyrene, and styrene-butadiene copolymer, but in the present invention, a transparent matrix polymer containing hydrogen bonding groups is used. As a specific example,
Adhesive (OH group-containing) polyester, partially saponified vinyl acetate-vinyl chloride copolymer, polyamide, polyurethane, thermoplastic phenolic resin, vinyl alcohol copolymer, acrylic acid copolymer, acrylamide copolymer, maleic acid copolymer Combination etc. is suitable. Since the recording material of the present invention is a thin film, considerable transparency can be obtained. It is also natural to use a plasticizer in combination with this as appropriate.

[0018] The amount of organic crystal particles constituting the reversible thermosensitive recording layer added to the matrix polymer is 5 to 50%.
It can be added in a range of 15% to 30%. If the proportion of organic crystal particles exceeds this range, the binding force will be weakened and it will be difficult to achieve a uniform coating as a recording layer. Conversely, when the ratio of the matrix polymer increases, the amount of organic crystalline particles decreases, making it difficult to make the image opaque, resulting in poor recording contrast.

Incorporating a crystal nucleating agent having a hydrogen-bonding surface into the polymer composition of the present invention is very effective in improving the reliability of crystallization characteristics. Furthermore, it is similarly effective to include an antioxidant having active hydrogen.

A recording medium using the reversible thermosensitive recording material of the present invention can be written and erased in heat mode not only with a thermosensitive head but also with a laser. A heated roller may also be used for erasing. That is, by forming the reversible thermosensitive recording material of the present invention on a polymer substrate on which a reflective film is formed and further forming a surface coating layer, clear recording with extremely high resolution can be easily achieved. A high-density optical recording medium with excellent erasability is obtained. This can be used as a rewritable, low-cost optical disc.

In addition, when recording and erasing is performed with a thermal head, if a wear-resistant surface coating layer is applied, a recording medium with low deterioration over time and high durability against repeated contact with the thermal head can be constructed. be able to. Next, the present invention will be explained using examples.

Example 1 As a recording material, 2 g of stearic acid, 0.1 g of a phenolic antioxidant, and 8 g of partially saponified vinyl chloride-vinyl acetate copolymer having hydroxyl groups were dissolved in 100 ml of tetrahydrofuran. A recording layer 3 of 13 μm is placed on a 0.2 mm polyester (polyethylene terephthalate) sheet 1 on which an aluminum vapor-deposited layer 2 shown in FIG. 1 is formed.
It was formed with a thickness of . On the recording layer 3, a prepolymer of ultraviolet curable acrylic resin was coated to a thickness of 20 μm as a wear-resistant surface coating layer 4, and then cured by irradiation with ultraviolet rays.

Writing and erasing was performed on the thus prepared reversible thermosensitive recording sheet using a thermosensitive head. The clearing temperature range of this sheet was approximately 70-90°C. From this condition, the thermal head gives energy to 100
Writing was performed at 80°C and erasing was performed at 80°C. When the written opaque area and erased transparent area were analyzed by X-ray diffraction, diffraction peaks were observed in both, indicating that they were microcrystals. It was found that these correspond to the opaque polycrystalline state 6B (light scattering state) and the transparent single crystalline state 6A of the organic crystal particles 6, respectively. Furthermore, when observed with a scanning electron microscope, the interface between the crystal grains and the matrix polymer was not very clear and no undesirable cracks were observed.

Example 2 As a recording material, 2 g of behenic acid, 0.1 g of a phenolic antioxidant, 2 g of adhesive (OH group-containing) polyester (Vylon manufactured by Toyobo Co., Ltd.), and 5 g of polyurethane were dissolved in 100 ml of tetrahydrofuran. A recording layer 3 was formed to a thickness of 20 μm on a 0.2 mm polyester sheet 1 on which an aluminum vapor-deposited layer 2 shown in 1 was formed. On the recording layer 3, a prepolymer of ultraviolet curable acrylic resin was further coated to a thickness of 25 μm as a wear-resistant surface coating layer 4, and then cured by irradiation with ultraviolet rays. Writing and erasing was performed on the reversible thermosensitive recording sheet thus prepared using a thermosensitive head. The transparent temperature range of this sheet is approximately 90
The temperature was ~110°C. Under these conditions, when energy was applied using a thermal head to write at 120°C and erase at 100°C, clear recording characteristics were obtained. When the life characteristics were further repeated and the life characteristics were measured, it withstood 620 repetitions.

Example 3 As a recording material, 2 g of stearyl alcohol, 0.1 g of a hindered phenolic antioxidant, 6 g of vinyl chloride-vinyl acetate-acrylamide copolymer, and 2 g of polyamide were used.
g was dissolved in 100 ml of tetrahydrofuran, and a 1 mm thick sheet of 0.2 mm hard polyvinyl chloride on which a gold-colored layer was formed was coated as a recording layer.
It was formed with a thickness of μm. On the recording layer 3, a prepolymer of ultraviolet curable acrylic resin was further coated to a thickness of 20 μm as a wear-resistant surface coating layer 4, and then cured by irradiation with ultraviolet rays. Writing and erasing was performed on the reversible thermosensitive recording sheet thus prepared using a thermosensitive head. The clearing temperature range of this sheet was approximately 70-90°C. From this condition, energy is applied using a thermal head and writing is performed at 100℃8.
It was erased at 0°C. This recording sheet was cut and a magnetic recording layer 8 was further formed thereon to obtain a recording card with a display function.

Example 4 A homogeneous solution consisting of the reversible thermosensitive recording material of Example 1 was prepared as shown in FIG.
A recording layer having a thickness of 15 μm was formed on a polycarbonate disk substrate on which an aluminum vapor-deposited reflective layer shown in FIG. On the recording layer, a prepolymer of ultraviolet curable acrylic resin was further coated to a thickness of 20 μm as a surface coating layer 4, and then cured by irradiation with ultraviolet rays. Writing and erasing was performed on the optical disc thus produced using a semiconductor laser. As with Example 1, the basic recording characteristics of this sheet were that the transparent temperature range was approximately 70 to 90°C, the opaque temperature range was 90°C or higher, and writing and erasing were possible by adjusting the laser intensity. When the written opaque region and the erased transparent region were analyzed by X-ray diffraction, it was found that the organic crystal particles were in an opaque polycrystalline state (light scattering state) and a transparent single crystal state, respectively, as in Example 1. It was found that it is equivalent to

Example 5 A homogeneous solution of the reversible thermosensitive recording material of Example 2 was formed to a thickness of 20 μm as a recording layer 3 on a polymer disk substrate on which an aluminum vapor-deposited reflective layer was formed. On top of the recording layer 3, a prepolymer of ultraviolet curable acrylic resin was further coated to a thickness of 25 μm as a surface coating layer 4, and then cured by irradiation with ultraviolet rays. Writing and erasing was performed on the optical disc thus produced using a semiconductor laser. The basic recording characteristics of this optical disc are that the transparent temperature region is as shown in Example 2.
Similarly, it is about 90 to 110℃, and the transparent temperature range is 110℃.
It was above ℃. By adjusting the intensity of the semiconductor laser for writing and erasing, clear recording characteristics were repeatedly obtained. When the life characteristics were further repeatedly measured, the result was 1500.
It withstood many repetitions.

Example 6 A homogeneous solution consisting of the reversible thermosensitive recording material of Example 3 was prepared as shown in FIG.
0 with a black layer formed on the surface with the magnetic recording part 8 as shown in FIG.
．． The recording layer 7 was formed to a thickness of 23 μm on a 1 mm thick sheet of 2 mm hard polyvinyl chloride. After coating the recording layer 3 with a 20 μm thick UV-curable acrylic resin prepolymer as a surface coating layer 4,
It was cured by UV irradiation. Writing and erasing was performed on the magnetic and optical cards thus created using a semiconductor laser. The transparent temperature range of this recording sheet was about 70 to 90°C as in Example 3, and the opaque temperature range was 90°C or higher. This recording sheet was cut into a recording card with a display function.

[0029]

As described above, the present invention provides a reversible thermosensitive recording material comprising a polymer composition in which organic crystal particles are dispersed in a matrix polymer, in which both the organic crystal particles and the matrix polymer have hydrogen bonding groups. Since they are composed of molecules, organic crystal particles and matrix polymers are
They have good compatibility and their melting and solidification properties are determined by their interaction. This crystallization behavior progresses through the hydrogen-bonding interface with the matrix polymer, and the number and nature of the hydrogen-bonding groups at the interface determine this behavior, resulting in highly reliable and stable crystallization properties. Therefore, an excellent heat-sensitive recording material without separation or cracks between the organic crystal particles and the matrix polymer can be obtained.

Furthermore, in the above structure in which organic microcrystalline particles with an average diameter of 0.1 μm or less are stably dispersed, melting and
Even if the solidification process is repeated, the size of the microcrystalline particles does not change, making it possible to obtain a recording material with high resolution, clarity, and excellent longevity characteristics.

Furthermore, the reversible thermosensitive recording material of the present invention can be widely used as a reversible thermosensitive recording sheet that is written and erased using a thermosensitive recording head, and as a rewritable low-cost optical disc. As described above, the present invention has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a recording medium using a reversible thermosensitive recording material according to the present invention.

FIG. 2 is a diagram showing the state of organic crystal particles in the reversible thermosensitive recording material of the present invention. (a) shows a transparent state, and the organic crystal particles 6A are single crystal particles. On the other hand, in (b), the organic crystal particles 6B are in an opaque state and are polycrystalline particles.

FIG. 3 is a diagram showing a magnetic & optical card which is an embodiment of a recording medium using a reversible thermosensitive recording material according to the present invention.

[Explanation of symbols]

1 Polymer sheet 2 Reflective layer 3 Recording layer 4 Surface coat layer 5 Matrix polymer 6 Organic crystal particles (A: transparent single crystal particles, B: opaque polycrystal particles) 7 Magnetic recording section 8 Recording layer

Claims (7)

[Claims] 1. A recording material comprising a polymer composition in which organic crystal particles are dispersed in a matrix polymer, the transparency of which changes reversibly by melting and solidification of the organic crystal particles, wherein the organic crystal particles and the matrix A reversible thermosensitive recording material characterized in that both polymers are molecules having hydrogen bonding groups. 2. A film is formed by coating a homogeneous solution of a crystalline organic molecule having a hydrogen bonding group, a transparent matrix polymer containing a hydrogen bonding group, and a proton-based organic solvent, and drying the coating. The reversible thermosensitive recording material according to claim 1, which is a composition containing organic microcrystalline particles having an average diameter of 0.1 μm or less in a polymer. 3. The crystalline organic molecule having a hydrogen bonding group is composed of a molecule having a melting point of 60 to 120° C. and having at least one of a carboxyl group or a hydroxyl group, and the hydrogen bonding group-containing transparent matrix polymer is an OH selected from group-containing polyesters, partially saponified vinyl acetate-vinyl chloride copolymers, polyamides, polyurethanes, thermoplastic phenolic resins, vinyl alcohol copolymers, acrylic acid copolymers, acrylamide copolymers, and maleic acid copolymers. The reversible thermosensitive recording material according to claim 2, which is one type of reversible thermosensitive recording material. 4. The reversible thermosensitive recording material according to claim 1, wherein the polymer composition contains a crystal nucleating agent having a hydrogen bonding surface. 5. The reversible heat-sensitive recording material according to claim 1, wherein the polymer composition contains an antioxidant having active hydrogen. 6. The reversible thermosensitive recording material according to claim 1 is formed on a polymer sheet on which a light reflecting film is formed, and further has an abrasion-resistant surface coating layer formed thereon so that it can be recorded and recorded by a thermal head.
A recording medium characterized by being erased. 7. A recording medium characterized in that the reversible thermosensitive recording material according to claim 2 is formed on a substrate on which a reflective film is formed, further a surface coating layer is formed, and recording and erasing is performed using laser light.