JP3106599B2 - Reversible thermosensitive recording material - 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 material which can be reversibly recorded and erased by heating. The present invention is most effective when used in 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, and a facsimile recording paper.

[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 mainly the liquid crystal polymer such as cholesteric liquid crystal to control the thermal behavior of its molecular arrangement. 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, for example, JP-A-54-11.
9377, comprising a combination of a matrix polymer and a fusible organic molecule such as:
Extremely diverse recording materials can be constructed. 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, general polymers such as polyester, polyamide, polyacrylic acid, styrene, silicone, polyvinyl chloride, polyvinylidene chloride, and polyacrylonitrile are disclosed. Further, a recording material obtained by improving this and further adding carbon black and an antioxidant is disclosed in JP-A-57-82087 and JP-A-57-82088.

However, these compounds, which have been widely studied, have a relatively low transparency temperature in the range of several tens of degrees Celsius, resulting in inferior storage stability of recording, and a narrow width of several degrees Celsius. There is a problem that there is no margin. For example, behenic acid having 22 carbon atoms (melting point: 80, which is a typical linear saturated fatty acid capable of obtaining high resolution and contrast).
° C), the reversible thermosensitive recording material in combination with vinyl chloride / vinyl acetate copolymer has a transparent temperature range of about 68 ° C to 74 ° C, and its width is as narrow as about 6 ° C for stable recording. Was difficult.

As a method of improving such a low clarifying temperature and a narrow temperature range, a method of forming organic crystal particles by mixing an aliphatic dicarboxylic acid with a higher fatty acid having 16 or more carbon atoms is disclosed in JP-A-2-1363. And JP-A-3-2089. In JP-A-2-1363, a dicarboxylic acid having a higher fatty acid as a main component and having 4 to 16 carbon atoms or a derivative thereof is added at a weight of 95: 5 to 20:80,
The temperature range is expanded by eutecticizing both molecules. In JP-A-3-2089, an aliphatic dicarboxylic acid containing a higher fatty acid as a main component and having 20 or more carbon atoms is added at a weight ratio of 95: 5 to 50:50, and the temperature range is expanded by eutecticizing both. These are intended to solve the problem by eutecticization of crystalline organic molecules, and as characteristics thereof, the transparency temperature is 100 ° C. or less, and the temperature range is at most about 20 ° C.

[0006]

However, when a recording medium made of a reversible thermosensitive recording material is used, it is necessary to perform recording stably and maintain the recorded information in a stable manner by controlling the temperature control stability of the recording heat source. Considering the margin and the normal use environment temperature, it is necessary to increase the transparency temperature to a higher temperature range and increase the transparency temperature range.

Accordingly, an object of the present invention is to consider mainly the characteristics of aliphatic dicarboxylic acids as organic crystal particles, and to provide a reversible thermosensitive recording material having a high transparency temperature, a wide temperature range, excellent recording resolution and high contrast. Is to provide.

[0008]

SUMMARY OF THE INVENTION The present invention has a melting point of 120.degree.
The above aliphatic dicarboxylic acid and a hydrogen bonding acid amide group
Having a melting point of 50 to 100 ° C and a carbon number of 12 or more.
Organic crystal particles mixed with a saturated fatty acid amide are dispersed in a matrix polymer composed of a thermoplastic transparent polymer having a hydrogen bonding group such that the mixing ratio is in the range of 3: 7 to 8: 2 by weight. Composed of organic crystal particles
The reversible thermosensitive recording material having a transparency temperature range of 20 ° C. or more due to solidification and reversibly changing the transparency has solved the conventional problems and achieved the above object.

[0009]

The reversible thermosensitive recording material of the present invention is characterized in that organic crystal particles obtained by mixing an aliphatic dicarboxylic acid having two hydrogen-bonding groups and a linear aliphatic compound having one hydrogen-bonding group are converted into a hydrogen-bonding group. And dispersed in a matrix polymer made of a thermoplastic transparent polymer having Aliphatic dicarboxylic acids have a high clearing temperature and a wide clearing temperature range, but are inferior in turbidity and are difficult to obtain good contrast. The present invention takes advantage of the characteristics of the aliphatic dicarboxylic acid having a high clarifying temperature and a wide clarifying temperature range, and mixes a linear aliphatic compound having a high turbidity and a good contrast with the aliphatic dicarboxylic acid. In addition to forming the organic crystal particles by eutecticizing the molecules constituting the organic crystal particles by combining them, this is further combined with a thermoplastic transparent polymer having a hydrogen bonding group to form hydrogen bonding existing in the matrix polymer. An object of the present invention is to provide a reversible thermosensitive recording material having extremely good recording characteristics by interaction with a group.

In arriving at the present invention, as a result of intensive studies on many organic compounds as organic crystal particles of the reversible thermosensitive recording material, the recording sensitivity and recording characteristics were determined with respect to the melting point of the organic crystal particles and the organic compound having a hydrogen bonding group. It turns out that the number and type of hydrogen-bonding groups in the molecule are important, especially the strength of the interaction with the organic crystal particles that occurs when using a thermoplastic polymer with hydrogen-bonding groups as a matrix polymer. It has been found.

As a result of examining the effect of the interaction between the organic crystal particles and the matrix polymer due to the hydrogen bonding property, a linear aliphatic compound having one hydrogen-bonding group, which has been often studied so far, is considered to be incompatible with the matrix polymer. Although the interaction and compatibility are improved and the transparency temperature range is widened while maintaining good contrast, the range is about 10 ° C. due to the small number of hydrogen bonds, and no significant improvement was obtained.

As a result of further study of the materials, it was found that, by improving the film forming method and the constitution of the recording medium, even if the aliphatic dicarboxylic acid was used alone, the clearing temperature was high and the range was wide and effective. However, with aliphatic dicarboxylic acid alone, sufficient opacity (white turbidity) was not obtained in terms of contrast, and the contrast of recorded images was insufficient. In other words, aliphatic dicarboxylic acids are thought to have high crystallinity and crystal strength and a high melting point because of a strong bond called a hydrogen bond, which tends to increase the transparency temperature range. It is thought that the compatibility becomes too high due to the large interaction between the particles and the dispersibility itself as a crystal particle state in the polymer is improved, but the crystal particle size becomes finer, it is hard to be cloudy, and the change in transmittance is small. Can be

In the present invention, as a result of intensive studies on the improvement of the properties of the aliphatic dicarboxylic acid, a straight-chain aliphatic compound having one hydrogen-bonding group in addition to the aliphatic dicarboxylic acid having a melting point of 120 ° C. or higher. Is mixed in a matrix polymer containing a hydrogen bonding group to realize high contrast and a clearing temperature range of 20 ° C. or higher. As described above, the recording characteristics were greatly improved by the configuration of the present invention. This is the effect of forming a complex such as a mixed crystal or eutectic by association or complex formation due to hydrogen bonding interaction between components in the organic crystal particles and between the organic crystal particles and the matrix polymer having a hydrogen bonding group. Seems to have greatly contributed. Although it is not yet precisely understood, the phenomenon of widening the clearing temperature range with high contrast has many complex crystal forms due to the interaction between the polymer and the organic crystal particles composed of a plurality of components. As a result, it is considered that the thermal characteristics of each form are different, and the degree of white turbidity is increased by a fine crystalline state.

[0014]

FIG. 1 is a conceptual cross-sectional view of one constitution of the reversible thermosensitive recording material of the present invention. The recording layer 3 of the present invention is formed on the polymer sheet substrate 1 on which the reflection layer 2 is formed by aluminum evaporation. An abrasion-resistant surface coat layer 4 is further formed on the recording layer 3. As shown in FIG. 2, the recording layer 3 includes a matrix polymer 5 of a thermoplastic transparent polymer having a hydrogen bonding group and organic crystal particles 6, and the organic crystal particles 6 in the matrix polymer 5 are heated and cooled. And a transparent state 6A and an opaque white turbid state 6B (light scattering state). This corresponds to erasure / recording, respectively.

The organic crystal particles 6 of the present invention have an aliphatic dicarboxylic acid, a hydrogen-bonding acid amide group and a melting point.
Unsaturated fatty acids having 12 or more carbon atoms having a temperature of 50 to 100 ° C.
And mid . Aliphatic dicarboxylic acid has a melting point of 120 ° C.
Any of the above may be used, but in particular, the general formula HOOC
The compound of (CH2) nCOOH (where n is an integer of 6 to 24) has a carboxyl group at both ends of a hydrocarbon chain, and has good crystallinity because an intermolecular hydrogen bond is generated at both ends of the molecule. Since the melting point is as high as 120 ° C. or more, a relatively high transparency temperature can be obtained, which is preferable. Note that n (the length of the hydrocarbon chain) in the formula is the melting point of the organic crystal particles 6,
An appropriate length is selected from the balance between the interaction of hydrogen bonds in the polymer and the solubility of the organic crystal particles 6 in the matrix polymer 5 and the dispersibility of the organic crystal particles 6 in the matrix polymer 5.

[0016]

Further, as the linear aliphatic compound, hydrogen bond
Charcoal having compatible acid amide group and melting point of 50-100 ° C
Preferred are unsaturated fatty acid amides having a prime number of 12 or more,
The complex is about as long as the aliphatic dicarboxylic acid
Must be easy to make and meet the melting point requirements.
Are met. For example, oleic acid amide, elka
Acid amide, etc., which is industrially used as a lubricant for resin, a sensitizer for thermal recording paper, an anti-blocking agent for toner, etc.It has low toxicity and is suitable for recording materials for direct contact with consumers It is a thing.

In order to obtain excellent recording performance, an aliphatic dicarboxylic acid and a hydrogen bonding acid amide group having a melting point of 50
The mixing ratio of unsaturated fatty acid amide having 12 or more carbon atoms, which is １００100 ° C., is important. The mixing ratio is such that an aliphatic dicarboxylic acid and a hydrogen-bonding acid amide group are mixed in a weight ratio.
Unsaturated with 12 or more carbon atoms having a melting point of 50-100 ° C
Excellent recording performance is obtained when the ratio with the sum fatty acid amide is 3: 7 to 8: 2. When the proportion of the aliphatic dicarboxylic acid is higher than the composition ratio , the compound has a hydrogen-bonding acid amide group.
Unsaturated fat having 12 or more carbon atoms having a melting point of 50-100 ° C
Since there is little eutecticity with the fatty amide and the complex portion does not act, the characteristics are close to those of the aliphatic dicarboxylic acid alone and high contrast cannot be obtained. Conversely, hydrogen-bonding acid amides
Having at least 12 carbon atoms having a group and a melting point of 50 to 100 ° C.
When the proportion of the unsaturated fatty acid amide is larger than the above-mentioned range of the composition ratio, the effect of the aliphatic dicarboxylic acid is reduced, so that a value of the clearing temperature range of 20 ° C. or more cannot be obtained.

On the other hand, generally, the matrix polymer 5 includes polyester, polyacrylate, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, cellulose acetate, polyvinyl butyral, polystyrene, styrene.
There are butadiene copolymers and the like.
The behavior greatly differs depending on the combination with organic crystal particles, and a transparent matrix polymer containing a hydrogen bonding group is particularly suitable as the matrix polymer 5 used in the present invention.
The reason is that, due to the interaction between the hydrogen bonding group present near the interface of the organic crystal particles 6 that have become the composite and the hydrogen bonding group contained in the matrix polymer 5, the melting and solidification behavior is made of a single compound. This is because the characteristics are different from those of the organic crystal particles 6 and the behavior of the change in transparency also changes. The recording performance obtained by the configuration using the matrix polymer 5 of the thermoplastic resin having the hydrogen bonding group and the organic crystal particles 6 is the same for both the aliphatic dicarboxylic acid and the linear aliphatic compound having one hydrogen bonding group. It is preferable because the excellent characteristics of (1) are utilized, the transparency temperature range is high and the range is wide, and the contrast is excellent. Specific examples include adhesive (OH group-containing) polyester and partially saponified vinyl acetate.
Suitable are vinyl chloride copolymer, polyamide, polyurethane, thermoplastic phenolic resin, vinyl alcohol copolymer, acrylic acid copolymer, acrylamide copolymer, maleic acid copolymer and the like. 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 addition amount of the organic crystal particles 6 constituting the reversible thermosensitive recording layer 3 to the matrix polymer 5 is 5 to 5.
Although it can be added in the range of 60%, addition of 15 to 30% is desirable. If the ratio of the organic crystal particles 6 is higher than this, the binding force is weakened and it is difficult to form a uniform coating as the recording layer 3. Conversely, when the ratio of the matrix polymer 5 increases, the amount of the organic crystal particles 6 decreases, so that it becomes difficult to make it opaque and the recording contrast deteriorates.

When a recording medium using the reversible thermosensitive recording material of the present invention is provided with a wear-resistant surface coat layer 4, for example, a recording medium that has little deterioration over time even with contact with a thermal head and has high repetitive durability. Can be configured. This recording medium can be written / erased in a heat mode not only by a thermal head but also by a laser. In some cases, a heat roller is used for erasing.

Next, the present invention will be described with reference to examples.

[0023]

[0024]

[0025]

[0026]

(Comparative Example 1) As a comparison, a single aliphatic dicarboxylic acid was mixed with organic crystal particles 6
When a reversible thermosensitive recording material is used for
Icosandicarboxylic acid (melting point 127 ° C) with organic crystal particles
Used as 6 and partially saponified vinyl chloride / vinyl acetate
Using the copolymer (hydroxyl group ratio about 12%) in the configuration of FIG.
When the thickness of the recording layer 3 is about 10 μm, the clearing temperature region is
It shows good properties of about 80-120 ° C and width of about 40 ° C,
As a measure of contrast, the Macbeth optical density during cloudiness is
Approximately 0.8.
Was not expensive. Further, as the organic crystal particles 6, docosano
(Melting point 70 ° C) alone,
Beth optical density is 0.6 or less, high turbidity and high cost
But the transparency temperature range is about 61-6
At 9 ° C., the width was narrow at 9 ° C., and there was no margin for recording.

[0028]

(Example 1 ) As the organic crystal particles 6 of the reversible thermosensitive recording material, 0.8 g of eicosandicarboxylic acid of HOOC (CH ₂ ) ₁₈ COOH (melting point 127 ° C.) was used as an aliphatic dicarboxylic acid, and a hydrogen bonding group was used. Erucamide with acid amide group (melting point 81 ° C)
Was mixed with 0.2 g. Further, 3 g of a partially saponified vinyl chloride / vinyl acetate copolymer resin (hydroxyl ratio: about 5%) was used as the matrix polymer 5 and mixed and dissolved in 15 g of tetrahydrofuran to prepare a stock solution of a recording material. As the thermoplastic transparent polymer of the intermediate layer 8 as an anchor effect, a vinyl chloride / vinyl acetate copolymer resin is used, and 0.3 g of a vinyl chloride / vinyl acetate copolymer resin is used.
Was dissolved in 12 g of tetrahydrofuran, and as shown in FIG. 3 , a 5 μm-thick intermediate layer 8 was formed on a 0.2 mm polyester substrate 1 on which an aluminum vapor-deposited reflection layer 2 was formed. Further, after drying, a stock solution of a recording material was applied onto the intermediate layer 8 and dried in a thermostat at 100 ° C. to obtain a recording layer 3 having a thickness of 10 μm. The recording layer 3 was further coated with a UV-curable acrylic resin prepolymer of 15 μm as a wear-resistant surface coat layer 4 and then cured by irradiating ultraviolet rays to produce a reversible thermosensitive recording sheet.

The reversible thermosensitive recording sheet was written / erased by a thermosensitive head. The clearing temperature range of this sheet was about 67 to 110 ° C, and the clearing temperature range was about 44 ° C. Under these conditions, energy was applied by a thermal head to write at 120 ° C. and erase at 100 ° C., and clear recording was performed. When the life characteristics were further measured repeatedly, they withstood 500 or more repetitions.

(Example 2 ) As the organic crystal particles 6 of the reversible thermosensitive recording material, 0.3 g of HOOC (CH ₂ ) ₈ COOH sebacic acid (melting point 134 ° C.) was used as the aliphatic dicarboxylic acid, and the acid of the hydrogen bonding group was used. 0.3 g of oleamide having an amide group (melting point: 70 ° C.)
Behenic acid having a carboxyl group of a hydrogen bonding group (melting point: 8
1 ° C.) and 0.4 g. Further, 3 g of an adhesive (hydroxyl-containing) polyester resin was used as the matrix polymer 5 and mixed and dissolved in 15 g of tetrahydrofuran to prepare a stock solution of a recording material. A vinyl chloride / vinyl acetate copolymer resin was used as the thermoplastic transparent polymer of the intermediate layer 8, and a reversible thermosensitive recording sheet was produced in the same manner as in Example 1 .

The reversible thermosensitive recording sheet was written / erased by a thermosensitive head. The clearing temperature range of this sheet is about 65 to 98 ° C., and the clearing temperature range is about 3
4 ° C. Under this condition, when energy was applied by a thermal head and writing was performed at 110 ° C. and erased at 90 ° C., clear recording was performed, and the repetition life characteristics were measured. It was done.

[0033]

As described above, the present invention comprises a polymer composition in which organic crystal particles are dispersed in a matrix polymer,
The organic crystal particles have an aliphatic dicarboxylic acid having a melting point of 120 ° C. or higher, a hydrogen-bonding acid amide group, and a melting point of 50 to 100.
And a matrix polymer is a thermoplastic transparent polymer having a hydrogen bonding group, the transparency of which changes reversibly depending on the heating temperature, and the transparency temperature range is 20 ° C. Since it is a reversible thermosensitive recording material as described above, it has a wide and high transparency temperature range, so that it has a high recording margin, a high contrast, and a highly reliable excellent recording characteristic. .

The recording sheet obtained by forming the reversible thermosensitive recording material of the present invention on a polymer sheet can be widely used as a reversible thermosensitive recording sheet which can be written / erased by a thermosensitive recording head or laser. Thus, the present invention is of great industrial value.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view showing the configuration of an embodiment of a recording medium in a reversible thermosensitive recording material according to the present invention.

FIG. 2 (A) is a view showing a state of organic crystal particles in a transparent state in a reversible thermosensitive recording material according to one embodiment of the present invention. FIG. 2 (B) is opaque in a reversible thermosensitive recording material according to one embodiment of the present invention. Diagram showing the state of organic crystal particles in the state

FIG. 3 is a configuration diagram of a reversible thermosensitive recording medium according to an embodiment of the present invention.

Continuation of the front page (56) References JP-A-5-24348 (JP, A) JP-A-5-85041 (JP, A) JP-A-5-85046 (JP, A) JP-A-4-129793 (JP) , A) JP-A-62-225392 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/36

Claims (2)

(57) [Claims] 1. A recording material comprising a polymer composition in which organic crystal particles are dispersed in a matrix polymer, wherein the organic crystal particles have an aliphatic dicarboxylic acid having a melting point of 120 ° C. or higher;
A mixture containing an unsaturated fatty acid amide having 12 or more carbon atoms having a hydrogen bonding acid amide group and a melting point of 50 to 100 ° C., in a mixing ratio of 3: 7 to 8: 2 by weight. there are, the matrix polymer is a thermoplastic transparent polymer having a hydrogen bond group, reversibly transparency varies with the heating temperature, the reversible thermosensitive recording material comprising a permeable brightening temperature width is 20 ° C. or higher . 2. An aliphatic dicarboxylic acid having the general formula HOOC
The reversible thermosensitive recording material according to claim 1, wherein (CH2) nCOOH (where n is an integer of 6 to 24).