JPH0577549A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a reversible thermal recording material having a high transparentizing temperature range by incorporating a high molecular composition dispersed into a matrix polymer in an organic crystal grain comprising either of a fatty amide compound or a fatty urea compound and having a specific melting point. CONSTITUTION:The tetrahydrofuran solution of 17C stearic acid amide and a vinyl chloride-vinyl acetate copolymer is formed onto a high molecular sheet 1 with an aluminum deposit layer 2 in 10mum thickness to form a recording layer 3, and a surface coating layer 4 is shaped. The transparentizing temperature range of the recording medium extends over approximately 80-105 deg.C and has width of approximately 25 deg.C. The recording medium is heated at 120 deg.C by a thermal head and written, and can be erased at 95 deg.C. X-ray diffraction peaks are viewed in an opaque-made region and a transparent-made region respectively, and the opaquing region is brought to a light-scattering state because it is composed of a crystallite.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a reversible thermosensitive recording material capable of reversibly recording and erasing by heating. INDUSTRIAL APPLICABILITY 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 ticket, ticket, and coupon ticket, an IC card, and a recording sheet for facsimile.

[0002]

2. Description of the Related Art Conventional reversible thermosensitive recording materials include thermosensitive dye recording materials that reversibly develop and decolor by a combination of a leuco dye and a color developer and a decolorizer, and organic crystals in a matrix polymer. Utilizing the melting and solidification behavior of particles, the reversible thermosensitive recording material that utilizes the change in transparency of the recording material depending on the solidification conditions, and mainly the thermal behavior of its molecular arrangement by liquid crystal polymer such as cholesteric liquid crystal There is a method of changing transparency.

The present invention relates to a reversible thermosensitive recording material which utilizes the melting and solidification behavior of organic crystal particles in a matrix polymer and the fact that the transparency of the recording material changes depending on the solidification conditions. Fine particles are melted and solidified again, and the transparency of the solidified form (polycrystalline state, single crystalline state, amorphous state, amorphous state, etc.) is changed depending on the conditions, and recorded. This heat-sensitive recording material is composed of a combination of a matrix polymer and the following organic molecules, as disclosed in, for example, JP-A-54-119377, and can constitute an extremely wide variety of recording materials. Organic molecules disclosed herein include aliphatic and aromatic alcohols, carboxylic acids, amines, amides and their halides, sulfides, and the like. 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. A recording material obtained by improving this and further adding carbon black and an antioxidant is disclosed in JP-A-57-82087 and 57-82088.

[0004]

Many organic crystal particles have been disclosed so far, but the relationship between the crystallinity of the organic crystal particles and the compatibility / dispersibility with the matrix polymer, and the recording characteristics associated therewith, have been disclosed. The relationship was not clear, and there was the problem that recording with excellent contrast could not be obtained.
Further, since the transparency temperature is several tens of degrees Celsius, the storage stability of recording is inferior, and the range is as narrow as several degrees Celsius, so there is a problem that there is no margin in recording conditions. For example, in a conventional reversible thermosensitive recording material using a combination of typical behenic acid (melting point 80 ° C.) and a vinyl chloride / vinyl acetate copolymer, the clearing temperature range is about 68 ° C. to 74 ° C., and the width thereof is about It was as narrow as 6 ° C and it was difficult to perform stable recording.

Therefore, the present invention has a high contrast,
It is an object of the present invention to provide a novel reversible thermosensitive recording material system having a wide transparentization temperature range.

[0006]

The present invention contains at least one compound selected from an aliphatic amide compound and an aliphatic urea compound having at least one linear hydrocarbon group having 10 or more carbon atoms and having a melting point. The above-mentioned problems have been overcome by a reversible thermosensitive recording material containing a polymer composition in which organic crystal particles at 70 to 150 ° C are dispersed in a matrix polymer.

[0007]

The function required for the reversible thermosensitive recording material is as follows.
The presence / absence of reversible thermosensitive recording property and recording property is mentioned, and the reversible thermosensitive recording medium to which this material is applied includes storage stability, repetitive property and contrast.
Therefore, it is necessary for a reversible thermosensitive recording material to satisfy all of these factors. As a result of examining many organic compounds as organic crystal particles of a reversible thermosensitive recording material in order to solve conventional problems, the presence or absence of reversible recording properties and recording characteristics,
It has been found that the melting point of the organic crystal particles and the strength of the interaction between the constituent compound of the organic crystal particles and the matrix polymer are important for the performance or contrast.

In particular, the type of hydrogen-bonding group was important for obtaining good recording characteristics and contrast.
That is, the organic crystal particles provided for the reversible thermosensitive recording material of the present invention have hydrogen bonding groups (amide groups or urea groups).
And a compound in which this hydrogen-bonding group comprises a long-chain hydrocarbon chain portion. The balance between the hydrogen-bonding group and the long-chain hydrocarbon chain is necessary to satisfy the above-mentioned requirements. Specifically, since the amide group has a structure of -NHCO-, it has two moieties that contribute to hydrogen bonding, and exhibits strong association between molecules. The strength of this association influences the melting point of the molecule (that is, the organic crystal particles), the crystallinity (that is, the recording property and contrast due to cloudiness), and the dispersibility with the matrix polymer. That is, the melting point of the organic crystal particles is 70 to 150.
As high as ℃, good crystallinity can be obtained. Also, the urea group is
Since it has the structure of NHCONH-, it is a group having more one part that contributes to a hydrogen bond than an amide group, and exhibits stronger association between molecules. These hydrogen-bonding groups have a strong interaction with the matrix polymer and improve the reversible thermosensitive recording property. Further, the aliphatic hydrocarbon moiety bonded to these hydrogen-bonding groups affects the compatibility of the molecule with the matrix polymer and the melting point of the molecule. In particular, when the aliphatic hydrocarbon portion is a straight chain hydrocarbon group having 10 or more carbon atoms, the compatibility with the matrix polymer is high, and therefore it is preferable because it can be dispersed in fine particles in the matrix polymer of the organic crystal particles.

[0009]

EXAMPLE Organic crystal particles used in the present invention contain an aliphatic amide or an aliphatic urea compound, and have an amount of 70 to 150.
It has a melting point between ° C. These compounds are materials industrially used as, for example, lubricants for resins, sensitizers for thermal recording papers, antiblocking agents for toners, etc., have low toxicity, and are also suitable for recording materials for direct contact with consumers. It is a thing. The aliphatic amide compound in the present invention is a stable compound having a structure of (Chemical formula 1), (Chemical formula 2) or (Chemical formula 3), and a strong amide group having two hydrogen bonds causes a strong intermolecular structure. It has high crystallinity and high crystal strength because it causes association, and has a particularly high melting point among aliphatics. In particular, in the case where the amide compound has the structure of (Chemical Formula 2) or (Chemical Formula 3), the number of parts involved in hydrogen bonding is twice that of (Chemical Formula 1), so that stronger association is exhibited. Also, the aliphatic urea compound in the present invention is a stable compound having a structure of the formula (4), and a strong polar intermolecular group due to three hydrogen bonds causes strong association between molecules, resulting in crystallinity. It has a high melting point, a high crystal strength, and a high melting point like an aliphatic amide compound. These compounds are highly suitable for the present invention because their melting and crystallization behavior is high in the high temperature range of 70 ° C. or higher.

The organic crystal particles used in the present invention are
These aliphatic amide compounds or aliphatic urea compounds and higher alcohols, fatty acids, alkylamines, dicarboxylic acids, alkylenediols, alkylenediamines, alkylene glycols, hydroxycarboxylic acids, alkyl benzoates, carboxyalkylphenols, aminoalkylphenols, aminoalkyl alcohols. By forming a mixture with at least one selected from the above, a eutectic or complex is formed, and physical properties such as melting point in the range of 70 to 150 ° C. and dispersibility in a matrix polymer can be adjusted, and particularly reversible. It is useful when a reversible thermosensitive recording material is applied to the thermosensitive recording medium.

Furthermore, when an unsaturated group is present in the linear hydrocarbon chain in the molecule of the organic crystal particles, the solubility in an organic solvent during dispersion with the matrix polymer is particularly good, and the unsaturated group Is also suitable, the melting / crystallization behavior is clear, and good recording contrast can be obtained.

The matrix polymer used in the present invention is a thermoplastic resin that undergoes a structural change due to heat applied in order to carry out reversible thermosensitive recording, and is preferably transparent to light, and is preferably colorless. Examples of these matrix polymers include polyester, polyacrylic acid ester, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, cellulose acetate, polyvinyl butyral, polystyrene, and styrene / butadiene copolymer. The recording characteristics of the reversible thermosensitive recording material of the present invention largely differ in melting / crystallization behavior not only by the characteristics of the organic crystal particles but also by the interaction of the organic crystal particles with the matrix polymer. As the matrix polymer, one having a proper compatibility with the organic crystal particles is suitable, and a combination in which a large amount of the organic crystal particles are dissolved due to the large compatibility reduces the contrast and is not suitable for the present invention. The aliphatic amide compound or aliphatic urea compound in the present invention has a strong balance of hydrogen bonds with long-chain hydrocarbons in the portion of the straight-chain hydrocarbon group and thus exhibits strong interfacial activity, and crystallization behavior in the matrix polymer. Progress through the interface with the matrix polymer. Therefore, it is preferable that the interface between the organic crystal particle having the hydrogen bonding group and the matrix polymer also has the hydrogen bonding property. Therefore, as the matrix polymer, a thermoplastic resin having a hydrogen bonding group is suitable.
In particular, in the case of a copolymer resin containing a vinyl chloride repeating unit and a vinyl acetate repeating unit, it is possible to control the temperature range in which transparency is caused by the difference in the copolymerization ratio, and to partially saponify the vinyl acetate component to vinyl alcohol. It is particularly suitable because a three-component copolymer is used as a unit and the proportion of hydrogen-bonding groups of the matrix polymer can be controlled.
Further, the recording material of the present invention includes a plasticizer, a leveling agent,
Needless to say, additives such as a dispersant may be mixed if necessary.

The amount of organic crystal particles constituting the reversible thermosensitive recording layer added to the matrix polymer is 5 to 50%.
However, the addition of 15 to 30% is desirable. When the ratio of the organic crystal particles is higher than this, the binding force is weakened and it becomes difficult to uniformly coat the recording layer. On the other hand, when the ratio of the matrix polymer is high, the amount of organic crystalline particles is small, which makes opacity difficult and deteriorates the contrast of recording.

FIG. 1 is a conceptual sectional view showing the construction of an embodiment of a reversible thermosensitive recording medium using the reversible thermosensitive recording material of the present invention as a recording layer 3. The recording layer 3 is formed on the polymer sheet 1 on which the aluminum vapor-deposited reflective layer 2 is formed. A wear-resistant surface coating layer 4 is further formed on the recording layer 3. The recording layer 3 is contained in the matrix polymer as organic crystal particles containing an aliphatic amide compound or an aliphatic urea compound, and the organic crystal particles in the matrix polymer are transparent at room temperature according to two heating / cooling processes. There are two states, a state and an opaque state (light scattering state), which correspond to erasing and recording, respectively. The wider the clearing temperature range, the easier the control of the recording system. In the present invention,
Even when it is composed of a combination of organic crystal particles made of one compound and a matrix polymer, a transparent temperature region exists at a high temperature, and excellent recording / erasing characteristics having a width of 10 ° C. or more can be obtained.

The recording layer 3 can be prepared by a conventional coating method such as a gravure coating method, a bar coating method, a screen coating method, etc., in which a solution of the recording layer material is dissolved.

The wear-resistant surface coating layer 4 shown in FIG. 1 is not essential for application as a recording medium, but is generally formed in order to prevent damage such as scratches on the recording layer 3. It A transparent resin is used as the material of the surface coat layer 4, but a thermosetting or photocurable resin is preferable for the purpose of protecting the recording layer 3.

Next, the present invention will be described with reference to examples. Example 1 As a recording material, 1 g of stearic acid amide having a saturated hydrocarbon chain having 17 carbon atoms (melting point: 101 ° C.)
And 3 g of vinyl chloride / vinyl acetate copolymer (copolymerization ratio is vinyl chloride / vinyl acetate = 97/13) were dissolved in 15 g of tetrahydrofuran to form the aluminum vapor deposition layer 2 shown in FIG. A recording layer 3 having a thickness of 10 μm was formed on the polymer sheet 1 made of polyethylene terephthalate. On the recording layer 3, a prepolymer of an ultraviolet curable acrylic resin was further coated as a wear-resistant surface coat layer 4 to a thickness of 20 μm, and then ultraviolet irradiation was performed to cure the same. The transparentization temperature range of this recording medium is about 80 to 105 ° C.
The width was about 25 ° C.

Writing and erasing were performed on the reversible thermosensitive recording sheet thus formed by a thermosensitive head. That is, energy was applied by a thermal head to write at 120 ° C. and erase at 95 ° C. When the written opaque region and the erased transparent region were analyzed by X-ray diffraction, diffraction peaks were observed in the opaque region and the transparent region, respectively, and it was found that the opaque region was microcrystalline. It was It was found that these correspond to the opaque crystal state (light scattering state) and the transparent crystal state of the organic crystal particles, respectively.

(Example 2) As a recording material, carbon number 21
An erucic acid amide having one unsaturated moiety at a melting point of 81
2 g) and 4 g of vinyl chloride / vinyl acetate copolymer (copolymerization ratio is vinyl chloride / vinyl acetate = 97/13) were dissolved in 15 g of tetrahydrofuran to form the aluminum vapor deposition layer 2 shown in FIG. 15 as a recording layer 3 on a 2 mm polyethylene terephthalate polymer sheet 1.
It was formed with a thickness of μm. A 15 μm-thick prepolymer of an ultraviolet-curable acrylic resin was coated on the recording layer 3 as a wear-resistant surface coating layer 4 and then irradiated with ultraviolet rays to be cured. The transparency temperature range of the reversible thermosensitive recording sheet thus prepared was about 68 to 81 ° C, and its width was 13 ° C. The recording medium thus obtained was recorded / erased with the thermal head in the same manner as in Example 1, and the obtained recording characteristics were measured with a Macbeth densitometer. The results are shown in FIG. About 68-8
It can be seen that recording with a wide transparent temperature range of 1 ° C. and high contrast can be obtained.

2 g of erucic acid amide and vinyl chloride
4 g of vinyl acetate copolymer (copolymerization ratio is vinyl chloride / vinyl acetate = 50/50) and tetrahydrofuran 15
When a reversible thermosensitive recording sheet having the same constitution was dissolved in g, the clearing temperature region was about 57 to 81 ° C.,
The temperature range widened to 24 ° C due to the interaction of the fatty acid amide and the vinyl acetate component with hydrogen bonding. By widening the transparentization temperature region, it is possible to set recording conditions with more margin.

Under these conditions, when energy was applied by a thermal head and writing was performed at 90 ° C. and erasing was performed at 70 ° C., clear display was possible in both cases. Further, the life characteristics were measured repeatedly, and it was able to endure the repetition of 500 times.

(Example 3) As a recording material, carbon number 18 was used.
2 g of N-butyl-N-stearyl urea (melting point 98 ° C.) having one hydrocarbon chain of 4 and vinyl chloride / vinyl acetate copolymer (copolymerization ratio 97/13) 4 g were dissolved in tetrahydrofuran 15 g. , The aluminum vapor deposition layer 2 shown in FIG.
A recording layer 3 having a thickness of 15 μm was formed on the 0.2 mm polyethylene terephthalate sheet 1 on which the recording layer was formed. On the recording layer 3, as a wear-resistant surface coating layer 4, a prepolymer of an ultraviolet curable acrylic resin is further applied.
After the μm coating, it was irradiated with ultraviolet rays to be cured. The reversible thermosensitive recording sheet thus prepared has a transparency temperature range of about 7
It was 8 to 98 ° C. From this condition, the cloudiness temperature 105
As a result of writing and erasing on a reversible thermosensitive recording sheet with a thermosensitive head at a clearing temperature of 90 ° C and a clearing temperature of 90 ° C, good recording characteristics were obtained.

Example 4 As recording materials, 1.5 g of ethylenebisoleic acid amide (melting point 118 ° C.), 0.5 g of stearic acid amide (melting point 101 ° C.), vinyl chloride / vinyl acetate / acrylamide copolymer resin 7.5 g was dissolved in 20 g of tetrahydrofuran to form a recording layer having a thickness of 20 μm on a 1 mm-thick sheet of hard polyvinyl chloride having a layer whose surface was colored blue.
On the recording layer 3, as a wear-resistant surface coating layer 4, a prepolymer of an ultraviolet curable acrylic resin is further formed in a thickness of 15 μm.
After coating, it was irradiated with ultraviolet rays and cured. The clearing temperature range of this sheet was about 85 to 110 ° C. The reversible thermosensitive recording sheet created in this way has a thermal head
Writing / erasing was performed. Under the above conditions, energy is applied by the thermal head to write at 120 ° C and write at 100 ° C.
Erased with.

Example 5 As recording materials, 2 g of erucic acid amide (melting point 81 ° C.) and docosanol (melting point 69)
1 g) and 8 g of vinyl chloride / vinyl acetate copolymer resin are dissolved in 20 g of tetrahydrofuran, and as shown in FIG. 3, a recording layer 8 having a thickness of 20 μm is formed on a glass substrate 7 having a thickness of 1.2 mm. Formed by. A carbon film having a thickness of 0.1 μm was formed thereon as a light absorbing and heat generating layer 9, and then 0.2 μm of aluminum was vapor-deposited as a reflecting layer 8 to obtain an optical recording medium. The transparentization temperature range of this recording medium is about 6
It was 0 to 80 ° C. Writing and erasing were performed by irradiating the semiconductor laser 10 having an oscillation wavelength of 780 nm from the glass substrate 5 side of the optical recording medium having the recording layer 6 thus formed through the actuator lens 9. Under the above conditions, the laser power was controlled to control the heat generation in the carbon layer, and the recording layer 6 was written at 100 ° C. and erased at 70 ° C. When this light irradiation spot was observed with a microscope, it was found that good bit recording was performed without blurring of the spot edge.

[0025]

As described above, the present invention uses an aliphatic amide compound or an aliphatic urea compound having a melting point of 70 to 150 ° C. as an organic crystal particle of a reversible thermosensitive recording material comprising organic crystal particles and a matrix polymer. This has the effect of obtaining a heat-sensitive recording material having a wide and wide transparent temperature range and excellent recording characteristics with high reliability.

The recording medium in which the reversible thermosensitive recording material of the present invention is formed on a substrate such as a polymer sheet or glass can be widely used as a reversible thermosensitive recording material for writing / erasing with a thermosensitive recording head or a laser. is there. As described above, the present invention has great industrial value.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view showing the configuration of an embodiment using a reversible thermosensitive recording material of the present invention as a recording medium.

FIG. 2 is a recording characteristic diagram of the reversible thermosensitive recording material of the present invention.

FIG. 3 is a conceptual cross-sectional view showing the configuration of another embodiment in which the reversible thermosensitive recording medium of the present invention is used as a recording medium.

[Explanation of symbols]

 1 Polymer Sheet 2 Reflective Layer 3 Recording Layer 4 Surface Coat Layer 5 Glass Substrate 6 Recording Layer 7 Light Absorption and Heat Generation Layer 8 Reflective Layer 9 Lens 10 Laser Light

Claims (6)

[Claims] 1. A recording material comprising a polymer composition in which organic crystal particles having a melting point of 70 to 150 ° C. are dispersed in a matrix polymer, wherein the organic crystal particles are linear hydrocarbons having 10 or more carbon atoms. A reversible thermosensitive recording material comprising at least one compound selected from aliphatic amide compounds having at least one group and aliphatic urea compounds. 2. The reversible compound according to claim 1, wherein the aliphatic amide compound is a compound represented by the general formula of (Chemical formula 1), (Chemical formula 2) or (Chemical formula 3). Thermosensitive recording material. [Chemical 1] Here, R ¹ is a linear hydrocarbon chain having 1 to 25 carbon atoms, R ² is hydrogen, a linear hydrocarbon chain having 1 to 26 carbon atoms, or a methylol group, and at least ^one of R ¹ and R ² One is a linear hydrocarbon chain having 10 or more carbon atoms. [Chemical 2] Here, R ³ is a linear hydrocarbon chain having 10 to 25 carbon atoms, n
Is 1-8. [Chemical 3] Here, R ⁴ is a linear hydrocarbon chain having 10 to 25 carbon atoms, n
Is 1-8. 3. The reversible thermosensitive recording material according to claim 1, wherein the aliphatic urea compound is a compound represented by the formula (4). [Chemical 4] Here, R ⁵ and R ⁶ are hydrogen or a linear hydrocarbon chain having 1 to 26 carbon atoms, and at least one of them has 10 carbon atoms.
The above is a straight chain hydrocarbon chain. 4. Organic crystal particles are selected from higher alcohols, fatty acids, alkylamines, dicarboxylic acids, alkylenediols, alkylenediamines, alkylene glycols, hydroxycarboxylic acids, alkyl benzoates, carboxyalkylphenols, aminoalkylphenols and aminoalkyl alcohols. The reversible thermosensitive recording material according to claim 1, which is a mixture of at least one selected from the group consisting of aliphatic amide compounds and aliphatic urea compounds. 5. The matrix polymer is a thermoplastic transparent polymer having hydrogen-bonding groups.
The reversible thermosensitive recording material described in 1. 6. The reversible thermosensitive recording material according to claim 1, wherein the matrix polymer is a copolymer resin containing a vinyl chloride repeating unit and a vinyl acetate repeating unit.