JPH04299178A - Thermally reversible recording material and recording medium - Google Patents

Abstract

PURPOSE:To provide a thermally reversible recording material and recording medium by employing a recording layer in which organic crystal particles composed of oxycarboxylic acid having melting point in the range of 60-120 deg.C or a derivative thereof are dispersed into a matrix polymer. CONSTITUTION:Oxycarboxylic acid or derivative thereof includes gallic acid, mandelic acid, tropic acid, malic acid, alpha-oxysubstituent, carboxylated alkylphenol, ester of oxybenzoic acid and oxyalkylcarboxylic acid, ester of hydroquinone and alkylenediol, oxybenzoic acid alkylester, and the like, whereas matrix polymer includes polyester, polyacrylic acid ester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, cellulose acetate, and the like. A reflection layer 2, a recording layer 3 and a surface coat layer 4 are applied on a polymer sheet 1 to provide a recording medium.

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, it relates to 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 recording media using the same. .

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. There are ways to use it to change transparency.

Phase change thermosensitive recording materials utilize the melting and solidification behavior of organic crystal particles in a matrix polymer, and utilize the fact that the transparency of the particles changes depending on the solidification conditions. It solidifies and records the difference in transparency of the solidified form (polycrystalline state, single crystalline state, amorphous state, etc.) depending on the conditions. This heat-sensitive recording material is composed of a combination of a matrix polymer and the following meltable organic molecules, as disclosed in Japanese Unexamined Patent Publication No. 54-119377, 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. In addition, a recording material made by improving this and further adding carbon black and antioxidants was developed in JP-A-57-
It is disclosed in Japanese Patent No. 82087 and Japanese Patent No. 57-82088.

0004

[Problems to be Solved by the Invention] However, although many organic crystal particles are disclosed herein, no efforts have been made to improve their compatibility and dispersibility with matrix polymers. However, there was a problem in that it was difficult to obtain a high-quality dispersion, making it impossible to obtain records with excellent recording resolution and high density. Another problem was that the transparentization temperature range was as narrow as several degrees centigrade, and there was no margin for recording conditions.

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 a special organic crystalline molecule and a matrix polymer. .

A second object is to provide a recording medium that can be widely used for cards with a display function, facsimile paper, etc. by using this heat-sensitive recording material.

[0007]

[Means for Solving the Problems] In order to achieve the first object, the reversible thermosensitive recording material of the present invention comprises 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. In a recording material whose transparency changes reversibly by melting and solidifying the particles, the organic crystal particles are
It is characterized by being composed of an oxycarboxylic acid or a derivative thereof having a melting point of 60 to 120°C.

[0008] Furthermore, in the configuration of the present invention, the oxycarboxylic acid or its derivative is preferably at least one selected from the following formulas a to e.

a. H(CH2)n(OH)COOH
(However, n=7 to 25, n: an integer) b. HO(C4 H4)(CH2)n COOH(
However, n=0 to 18, n: integer) c. HO(C4H4)COO(CH2)nCOO
H (where n=1 to 18, n: integer) d. HO(C4H4)OCO(CH2)nCOO
H (where n=1 to 18, n: integer) e. HO(C4H4)COO(CH2)nH (where n=1 to 18 (n: integer) where (C4H4) is an o, m, or p phenylene group, and (CH2)n is an alkylene group .

[0010] Furthermore, in the configuration of the present invention, the oxycarboxylic acid or its derivative is preferably an α-oxyalkylcarboxylic acid.

[0011] Furthermore, in the configuration of the present invention, it is preferable that the matrix polymer is made of a thermoplastic transparent polymer having hydrogen bonding groups.

[0012] Furthermore, in the structure of the present invention, the organic crystal particles include higher alcohols, fatty acids, alkylamines,
6 of oxycarboxylic acid and one selected from dicarboxylic acids, diamines, alkylene glycols, benzoic acid derivatives, carboxyalkylphenols, aminoalkylphenols, aminoalkyl alcohols, and alkylamides;
Preferably, it is a eutectic or a complex having a melting point of 0 to 120°C.

[0013] Furthermore, in the configuration of the present invention, it is preferable that the polymer composition contains a crystal nucleating agent having a hydrogen bonding surface.

[0014] Furthermore, in the configuration of the present invention, it is preferable that the polymer composition contains an antioxidant having active hydrogen.

In order to achieve the second object, the reversible heat-sensitive recording material of the present invention is formed on a polymer sheet on which a light-reflecting film is formed, and an abrasion-resistant surface coating layer is further formed on the heat-sensitive recording material. It is characterized by being recorded and erased by the head.

[0016]

[Function] The reversible thermosensitive recording material of the present invention has a structure in which the above-mentioned oxycarboxylic acid or its derivative is contained as organic crystal particles in a matrix polymer, and two hydrogen bonds between a hydroxyl group and a carboxyl group in the molecule are melted. -Plays a major role in crystallization behavior. Since it has two hydrogen-bonding functional groups in one molecule, it has high crystallinity and crystal strength. Most have a moderate melting point of 60 to 120°C, and their melting and crystallization behavior is highly reliable. Although oxycarboxylic acid is a molecule that has two hydrogen-bonding functional groups in its molecule,
Unlike alkylene diamines, alkylene dicarboxylic acids, alkylene glycols, etc., it has a moderate melting point of 60 to 120°C, and the melting point does not differ much depending on the odd or even number of carbon atoms in the alkyl chain, making it extremely suitable for the present invention. It is the material. The recording properties of the reversible thermosensitive recording material of the present invention vary greatly in melting and crystallization behavior not only due to the properties of the organic crystal particles but also due to their interaction with the matrix polymer. As the matrix polymer, one having appropriate compatibility is suitable, and a combination in which the compatibility is too large and dissolves a large amount of organic crystal particles is not suitable for the present invention. The crystallization behavior of an oxycarboxylic acid 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.

The recording layer made of the reversible thermosensitive recording material of the present invention has a structure containing the above-mentioned oxycarboxylic acid or its derivative as organic crystal particles in a matrix polymer,
Through the heating and cooling process, the organic crystal particles in the matrix polymer change into a transparent single crystal state and an opaque polycrystal state (
It takes two states (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 the physical changes of melting and solidification of organic crystal particles, if a wear-resistant surface coating layer is applied, it will not deteriorate over time even when contacted by a thermal head. A recording sheet that is small and has high repeat durability can be constructed.

[0019]

EXAMPLES Next, the present invention will be explained based on examples. 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 wear-resistant surface coating layer 4 is further formed on the recording layer 3. In FIG. 2(a), the organic crystal particles 6A are in a transparent state and are single crystal particles. On the other hand, in FIG. 2(b), the organic crystal particles 6B are in an opaque state and are polycrystalline particles. In FIG. 2, the recording layer 3 is composed of a matrix polymer 5 and organic crystal particles 6, and the organic crystal particles 6 in the matrix polymer 5 are separated into a transparent single crystal state 6A and an opaque polycrystal state 6 by heating and cooling processes.
It takes two states: B (light scattering state). This corresponds to erasing and recording, respectively.

The organic crystal particles of the present invention have a particle size of 60 to 1
An oxycarboxylic acid or a derivative thereof having a melting point at 20°C is used. Oxycarboxylic acid is a molecule that has a hydroxyl group and a carboxyl group in one molecule, and is also called an oxyacid, and has two or more of these hydrogen-bonding groups in one molecule. Gallic acid, mandelic acid, tropic acid, malic acid, tartaric acid, citric acid, etc. also belong to this category. As the oxycarboxylic acid or its derivative in the present invention, at least one selected from the above formulas a to e is suitable. The molecule of the formula a is an oxyalkylcarboxylic acid, and an α-oxy substituted one where n=7 to 25 (n: an integer) is particularly suitable. The molecule of formula b is a carboxylated alkylphenol, and the position of the carboxyl group is arbitrary, and n=0 to 18 (n: integer) is suitable. The molecule of formula c is an ester of oxybenzoic acid and oxyalkylcarboxylic acid, and n=1 to 18 (n: integer) is suitable. The molecule of formula d is an ester of hydroquinone and alkylene diol, and is suitably an alkylene group where n=1 to 18 (n: integer). The molecule of the formula e is an oxybenzoic acid alkyl ester, and n = 1 to 18 (n: an integer) is suitable.This is a material that is industrially used as a preservative, food additive, plasticizer, etc., and has low toxicity. , suitable for recording materials used in direct contact with consumers.

These oxycarboxylic acids include distinct higher alcohols, fatty acids, alkylamines, oxycarboxylic acids, dicarboxylic acids, diamines, alkylene glycols,
Organic molecular crystal particles having a melting point of 60 to 120° C. can also be formed by forming a eutectic or a complex with the like.

On the other hand, matrix polymers generally include polyester, polyacrylic ester, polyvinyl chloride,
Examples include vinyl chloride-vinyl acetate copolymer, cellulose acetate, polyvinyl butyral, polystyrene, and styrene-butadiene copolymer, but the behavior of matrix polymers differs greatly depending on the combination with organic crystal particles, and in the present invention, matrix polymers containing hydrogen bonding groups A transparent matrix polymer is suitable. 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, etc. are 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.

[0023] The amount of organic crystal particles constituting the reversible thermosensitive recording layer added to the matrix polymer can range from 5 to 50% by weight, but is preferably 15 to 30% by weight.
It is desirable to add 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.

Furthermore, supercooling phenomenon often occurs in the melting and crystallization behavior of the present invention, but this causes instability of recording, so a recording material system having a composition that does not cause supercooling is useful. 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 the melting and crystallization characteristics. It is also effective to include an antioxidant having active hydrogen, and phenolic antioxidants are suitable.

When a recording medium using the reversible thermosensitive recording material of the present invention is provided with an abrasion-resistant surface coating layer, the recording medium exhibits little deterioration over time even when contacted by a thermosensitive head and has high repeat durability. be able to. This recording medium can be written and erased in heat mode not only with a thermal head but also with a laser. A heated roller may also be used for erasing. Next, the present invention will be explained using specific examples.

Example 1 As a recording material, 2 g of α-oxystearic 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. 1 as a recording layer 3 on a 0.2 mm polyester (polyethylene terephthalate) sheet 1 on which an aluminum vapor-deposited layer 2 is formed as shown in FIG.
It was formed with a thickness of 3 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 thus obtained reversible thermosensitive recording sheet using a thermosensitive head. The transparent temperature range of this sheet is approximately 90-110℃
Met. From this condition, energy is given by a thermal head 12
Writing was performed at 0°C and erasing was performed at 100°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. Also,
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 α-oxybehenic acid, 0.1 g of a phenolic antioxidant, and an OH group-containing polyester (
3 g of "Vylon" manufactured by Toyobo Co., Ltd. and 4 g of vinyl chloride-vinyl acetate copolymer were mixed in 100 ml of tetrahydrofuran.
0.2 to form the aluminum vapor deposited layer 2 shown in FIG.
2 mm as the recording layer 3 on the polyester sheet 1
It was formed with a thickness of 5 μm. On the recording layer 3, a prepolymer of ultraviolet curable acrylic resin was coated to a thickness of 15 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 obtained reversible thermosensitive recording sheet using a thermosensitive head. The transparent temperature range of this sheet is approximately 90-110℃
Met. From this condition, energy is given by a thermal head 12
When writing was performed at 0°C and erasing was performed at 100°C, clear recording characteristics were obtained. When the life characteristics were further repeated and the life characteristics were measured, it withstood 500 repetitions.

Example 3 As a recording material, 2.5 g of butyl oxybenzoate, 0.1 g of a hindered phenolic antioxidant, and 7.5 g of vinyl chloride-vinyl acetate-acrylamide copolymer were used.
A 20 μm thick recording layer was formed on a 1 mm thick sheet of 0.2 mm hard polyvinyl chloride which had been dissolved in 100 ml of tetrahydrofuran to form a layer colored blue on the surface. On top of the recording layer 3, a 15 μm thick UV-curable acrylic resin prepolymer is further applied as an abrasion-resistant surface coating layer 4.
After coating, it was cured by UV irradiation. Writing and erasing was performed on the thus obtained reversible thermosensitive recording sheet using a thermosensitive head. The clearing temperature range of this sheet was approximately 70-90°C. The recording characteristics measured with a Macbeth densitometer are shown in (Figure 3). Approximately 70-90
It can be seen that the clearing temperature range in °C is wide and records with high contrast can be obtained. Under these conditions, energy was applied using a thermal head to write at 100°C and erase at 80°C.

[0029]

Effects of the Invention As described above, the present invention provides the following effects by using oxycarboxylic acid or its derivatives having a melting point of 60 to 120°C as organic crystal particles of a reversible thermosensitive recording material comprising organic crystal particles and a matrix polymer. A heat-sensitive recording material having high reliability and excellent recording properties can be obtained.

Further, a recording sheet in which the reversible thermosensitive recording material of the present invention is formed on a polymer sheet can be widely used as a reversible thermosensitive recording sheet that can be written and erased using a thermosensitive recording head or a laser. As described above, the present invention has great industrial value.

[Brief explanation of the drawing]

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 shows recording characteristics of a reversible thermosensitive recording material in Example 3 of 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)

Claims (8)

[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 are A reversible thermosensitive recording material comprising an oxycarboxylic acid or a derivative thereof having a melting point of ~120°C. 2. The reversible thermosensitive recording material according to claim 1, wherein the oxycarboxylic acid or its derivative is at least one selected from the following formulas a to e. a. H(CH2)n (OH)COOH (where n
=7-25, n: integer) b. HO(C4 H4)(CH2)n COOH(
However, n=0 to 18, n: integer) c. HO(C4H4)COO(CH2)nCOO
H (where n=1 to 18, n: integer) d. HO(C4H4)OCO(CH2)nCOO
H (where n=1 to 18, n: integer) e. HO(C4 H4)COO(CH2)nH (where n=1 to 18 (n: integer) where (C4 H4) is a phenylene group, (CH2)
n is an alkylene group. 3. The reversible thermosensitive recording material according to claim 2, wherein the oxycarboxylic acid or its derivative is an α-oxyalkylcarboxylic acid. 4. The reversible thermosensitive recording material according to claim 1, wherein the matrix polymer is a thermoplastic transparent polymer having hydrogen bonding groups. 5. The organic crystal particles contain one selected from higher alcohols, fatty acids, alkyl amines, dicarboxylic acids, diamines, alkylene glycols, benzoic acid derivatives, carboxyalkylphenols, aminoalkylphenols, aminoalkyl alcohols, and alkylamides. The reversible thermosensitive recording material according to claim 1, which is a eutectic or a complex with a carboxylic acid having a melting point of 60 to 120°C. 6. The reversible thermosensitive recording material according to claim 1, wherein the polymer composition contains a crystal nucleating agent having a hydrogen bonding surface. 7. The reversible heat-sensitive recording material according to claim 1, wherein the polymer composition contains an antioxidant having active hydrogen. 8. 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.