JPH0920084A - Reversible thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermal record medium with which image density is not lowered at the time of formation of images even when image formation and deletion are repeated, change of contrast is only a little, repetition durability is improved, and a clear image having high contrast can be obtained. SOLUTION: In a reversible thermal record medium having, on a support body, a heat sensitive layer which contains at least a resin and is temperature- dependent and its transparency changes reversibly, an ultraviolet rays or electron rays curing resin is used as a resin matrix in the heat sensitive layer. An elastic modulus of the heat sensitive layer cured by irradiation of ultraviolet rays or electron rays at a rubber-like area whose temperature exceeds a glass transition temperature is within a range not less than 6×10<6> and less than 10<7> dyn/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium, and more specifically, repetitive writing and erasing of information mainly utilizing reversible change in transparency depending on the temperature of a recording layer (thermosensitive layer). The present invention relates to a reversible thermosensitive recording medium that can be used.

[0002]

2. Description of the Related Art In recent years, reversible thermosensitive recording media have attracted attention because they allow temporary image formation (writing of information) and can erase the image (erasing of information) when it is no longer needed. Typical examples thereof include higher fatty acids in a resin matrix such as a vinyl chloride-vinyl acetate copolymer having a glass transition temperature (Tg) of 50 to 60 ° C. to less than 80 ° C. and having a low glass transition temperature. A reversible thermosensitive recording medium in which various organic low-molecular substances are dispersed is known (JP-A-54).
-119377, JP-A-55-154198, etc.). However, in this reversible thermosensitive recording medium, distortion is generated in the recording layer during repeated image formation and erasure by a heating element such as a thermal head, and the image density during image formation is lowered and the contrast is lowered. There is a drawback that it will end up.

As a solution to the above-mentioned drawbacks, the present inventors first define the average degree of polymerization and the vinyl chloride unit content of the resin matrix used in the reversible thermosensitive recording layer (particularly the average polymerization). By increasing the temperature), a reversible thermosensitive recording medium has been proposed in which the heat resistance of the resin base material is improved and the durability is improved (JP-A-92-154547). The use of this reversible thermosensitive recording medium alleviates the abovementioned drawbacks considerably. However, if the energy applied to the heating element such as the thermal head is high, there is a drawback that the image density during image formation deteriorates while writing and erasing information is repeated a plurality of times.

Further, in JP-A-5-085045, a thermosetting resin comprising a hydroxyl-modified vinyl chloride-vinyl acetate copolymer and an isocyanate compound is used as a resin matrix used in a reversible thermosensitive recording layer, and heat resistance is used. A thermal recording medium has been proposed which has improved mechanical strength and improved repeated durability such as a thermal head. By the way, in a reversible thermosensitive recording medium of a type in which an organic low molecular weight substance is dispersed in a resin, it usually becomes transparent in a certain temperature range and becomes cloudy at a higher temperature, and an image is recorded by utilizing this state change. Although it is erased, in order to reversibly change to transparent and cloudy by heat, it is necessary that the temperature range at which the material becomes transparent is maintained to some extent wide and stable. However, the thermosetting resin of this kind has a change in the degree of curing with time, and specifically, the degree of curing at the time of forming the recording layer changes with the passage of time. As the degree of hardness of the resin changes with time, the clearing temperature range also shrinks with time, making it impossible to erase in the initial image erasing temperature setting, and this erasing temperature setting becomes very complicated. is there. This problem is a new problem, and no solution has been proposed so far.

A reversible thermosensitive recording medium in which the resin base material used in the reversible thermosensitive recording layer is an ultraviolet curable resin is described in JP-A-6-106847. However, all of the resin base materials were ultraviolet curable resins, and there was almost no contrast between transparency and cloudiness, and images were unreadable.

A reversible thermosensitive recording medium using a resin obtained by curing and polymerizing an ultraviolet curable resin or an electron beam curable resin as a resin base material used for the reversible thermosensitive recording layer, in whole or in part, It is described in JP-A-7-32734. However, when the ultraviolet curable resin or the electron beam curable resin is used for the entire resin base material, the one described in this publication has almost no contrast and the image cannot be read, as in the above case. Also,
In this publication, when an ultraviolet curable resin or an electron beam curable resin is used as a part of the resin base material, the optimum compounding ratio of the ultraviolet curable resin or the electron beam curable resin to another resin is specified. In the examples, the compounding ratio of the ultraviolet curable resin and the vinyl chloride-vinyl acetate copolymer is 55.7: 44.
No. 3, although the contrast is still low at this blending ratio, there is a drawback that the image cannot be read. Further, in the above-mentioned embodiment, there is a drawback in that the white turbidity occurs immediately after printing, but the whiteness disappears within a few minutes. Further, the gel fraction value of the resin base material in the heat sensitive layer is 30.
% Or more, and a reversible heat-sensitive recording material having a heat-pressure step difference of 40% or less and a heat-pressure step change rate of 70% or less is disclosed in JP-A-7-172072.
It is described in. However, the one described in this publication has a defect that the contrast after initial or repeated printing / erasing is low when the gel fraction is too high or the thermal pressure step and the thermal pressure step change rate are too low. Further, there is a defect that the contrast becomes low even when the temperature of the heat-sensitive layer when the heat-sensitive layer is cured by irradiation of ultraviolet rays or electron beams is too high.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned inconvenience, and to obtain a good image density and contrast even if image formation and erasing with high energy by a thermal head are repeatedly performed. Another object is to provide a reversible thermosensitive recording medium that can obtain

[0008]

According to the present invention, at least a resin and an organic low-molecular substance dispersed in the resin material are contained as a main component on a support, and transparency is reversibly dependent on temperature. In a reversible thermosensitive recording medium provided with a variable thermosensitive layer, an ultraviolet or electron beam curable resin is used as a resin matrix in the thermosensitive layer, and the glass transition temperature of the thermosensitive layer after being cured by irradiation with ultraviolet rays or electron beams. Provided is a reversible thermosensitive recording material characterized by having an elastic modulus in a rubber-like region exceeding 6 × 10 ⁶ or more and less than 10 ⁷ dyn / cm ² . Further, according to the present invention, there is provided the reversible thermosensitive recording material, wherein the gel fraction of the thermosensitive layer is 30% to 65%. According to the present invention,
A reversible thermosensitive recording medium comprising a support and a thermosensitive layer containing at least a low-molecular substance contained in a resin and a resin base material as a main component, and the transparency of which reversibly changes depending on temperature. Is at least one selected from the group selected from polyvinyl chloride, polyester, polyethylene, polypropylene, polystyrene, polyacrylate, polyacrylamide, polyamide, polyvinylpyrrolidone, natural rubber, polysiloxane, polyvinyl alcohol, and polyacrolein, or a copolymer of these. It is composed of at least two kinds of a combination (resin A) and an ultraviolet curable resin (resin B), and the weight ratio of the resin A and the resin B is 95: 5 to 65:
A reversible thermosensitive recording medium is provided, which is a resin obtained by curing a resin mixture within the range of 35 with ultraviolet rays. Further, according to the present invention, there is provided the reversible thermosensitive recording medium, wherein the ultraviolet curable resin (resin B) is a polyester acrylate resin. Furthermore, according to the present invention, there is provided the reversible thermosensitive recording medium, wherein the weight ratio of the resin A to the resin B is in the range of 95: 5 to 77:23. Also, according to the present invention, there is provided the reversible thermosensitive recording medium, wherein the ultraviolet curable resin (resin B) is a (poly) urethane acrylate resin. Furthermore, according to the present invention, the resin A and the resin B are
The reversible thermosensitive recording medium is characterized in that the weight ratio thereof is within the range of 90:10 to 72:28. Further, according to the present invention, there is provided the reversible thermosensitive recording material, wherein at least one kind of ultraviolet ray or electron beam curable resin contains an ε-caprolactone adduct.
Further, according to the present invention, two or more kinds of the organic low molecular weight substances are mixed, and the melting point of the organic low molecular weight substance having the lowest melting point is 60 ° C. or higher, and the organic low molecular weight substance having the lowest melting point is used. There is provided the reversible thermosensitive recording material, characterized in that the content is 20% by weight or less of the whole organic low molecular weight substance mixed with two or more kinds.

The present inventors analyzed and examined the mechanism of why the decrease in image density and contrast caused by repeated use of forming and erasing an image on a reversible thermosensitive recording medium occurs. As a result, when an image was formed by pressing a heating element such as a thermal head or a thermal destruction type thermal recording medium printer onto the surface of the recording medium, the following phenomenon was observed. In a reversible thermosensitive recording medium having a recording layer in which particles of an organic low-molecular substance are dispersed in a resin base material, the recording layer is used before the application of energy or when the number of repetitions is small when forming and erasing an image with a heating element. There is no distortion that changes the existing state of the material that constitutes the material, and the organic low-molecular-weight substance particles are uniformly dispersed in the resin base material as shown in FIG. 1 (a). As described above, in the recording layer of the present invention, the uniform dispersion state of the organic low molecular weight substance particles is maintained even by repeated recording / erasing). However, during image formation, when the image forming means such as a heating element is pressed against the recording medium and moved relatively, stress is applied to the inside of the recording layer. While the application of energy in the same direction is repeated, the stress is a main cause of distortion inside the recording layer in the direction of application of energy as shown in FIG. Is in a deformed state. As energy application is further repeated in the same direction, distortion progresses, and FIG.
Aggregation of the low-molecular organic material particles deformed as shown in (c) starts, and finally, the aggregated particles re-aggregate as shown in FIG. It will be in a state of becoming. In such a state, it becomes almost impossible to form an image, which is a so-called deteriorated state. It is considered that these phenomena are related to the cause of decrease in image density after repeated formation and deletion of an image on a reversible thermosensitive recording medium. Usually, in order to form the heat-sensitive layer on the support, the heat-sensitive layer-forming coating liquid is applied on the support, heated and dried, and then immediately irradiated with ultraviolet rays or electron beams to cure the heat-sensitive layer. However, if the medium temperature at the time of irradiation with ultraviolet rays or electron beams is too high, the curing degree of the heat-sensitive layer will be high, and conversely, if the medium temperature is too low, irradiation with ultraviolet rays or electron beams will reduce the curing degree of the heat-sensitive layer. Such a difference in the curing degree causes not only a difference in the repeated durability of printing and erasing but also a difference in the image contrast, which makes it impossible to manufacture a reversible thermosensitive recording material of stable quality. Further, even if the heat-sensitive layer is cured by irradiation with ultraviolet rays or electron beams, there is a drawback that the repeated durability of printing and erasing is poor depending on the type of the organic low molecular weight substance.

The inventors of the present invention have conducted studies to improve the above-mentioned drawbacks. As a result, the glass transition temperature of the heat-sensitive layer after curing the resin base material in the heat-sensitive layer by irradiation of ultraviolet rays or electron beams Elastic modulus in rubber-like region beyond 6 × 10
^When it is in the range of ⁶ or more and less than 10 ⁷ dyn / cm ² , aggregation or maximization of the organic low-molecular-weight substance particles in the recording layer as described above is unlikely to occur, and after the formation and deletion of the image is repeated. It was confirmed that the image density did not deteriorate and high contrast could be maintained. Further, these actions and effects are due to the fact that the gel fraction of the heat sensitive layer is 30 to 65%, and that the resin of the recording layer in the reversible heat sensitive recording medium (usually the "resin base material") is an organic low molecular weight substance. (Other resin except particles may be used), polyvinyl chloride, polyester, polyethylene, polypropylene, polystyrene, polyacrylate, polyacrylamide, polyamide, polyvinylpyrrolidone, natural rubber, polysiloxane, polyvinyl alcohol, polyacrolein At least one selected from the group selected or a copolymer thereof (resin A) and an ultraviolet curable resin (resin B),
Weight ratio of the resin A to the resin B 95: 5 to 65:35
By using a resin composition obtained by curing the above resin composition, the organic low-molecular-weight substance in the heat-sensitive layer is a mixture of two or more kinds and has the lowest melting point. It was found that a certain organic low molecular weight substance is 20% or less (weight ratio) of the whole organic low molecular weight substance, and at least one kind of ultraviolet ray or electron beam curing resin contains ε-caprolactone adduct, and it can be further enhanced. did.

As the resin B, various UV-curable resins described below can be used, but polyvalent acrylate resins such as (poly) ester acrylate resin and (poly) urethane acrylate resin are preferable, and particularly preferable are
It is a (poly) urethane acrylate resin, more preferably an acrylate resin to which ε-caprolactone is added. Further, the preferable use ratio of the resin B is slightly different depending on the kind of the resin B, but will be described later in detail. The present invention has been made based on these findings.

The reversible thermosensitive recording medium of the present invention will be described in more detail below. The reversible thermosensitive recording medium of the present invention utilizes the transparency change (transparent state, cloudy opaque state) depending on the temperature as described above, and the difference between the transparent state and the cloudy opaque state is presumed as follows. That is, in the case of (I) transparency, the particles of the organic low molecular weight substance dispersed in the resin base material are in close contact with each other with no gap between the organic low molecular weight substance and the resin base material, and voids are also formed inside the particles. Light that is incident from one side does not scatter and is transmitted to the other side without being scattered. (II) In the case of white turbidity, the particles of the organic low molecular weight substance are fine crystals of the organic low molecular weight substance. It has a gap at the interface of crystals or at the interface of particles and resin base material, and light incident from one side is refracted at the interface between voids and crystals, and between voids and resin, and appears white because it is scattered. Is derived.

In FIG. 2 (representing the change in transparency due to heat), a thermosensitive layer mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material is, for example, T _0.
At the following room temperature, it is cloudy and opaque. When this is heated, it gradually becomes transparent from the temperature T ₁ and starts at the temperature T _{2 to} T
_When it is heated to ₃ , it becomes transparent, and in this state, it remains transparent even if it is returned to room temperature below T ₀ again. This is because the resin begins to soften near the temperature T ₁ , and as the softening progresses, the resin shrinks to reduce the interface between the resin and the organic low-molecular substance particles or the voids in the particles, so that the transparency gradually increases and the temperature T increases. ₂
At ~ T ₃ , the organic low-molecular weight substance becomes semi-molten and becomes transparent by filling the remaining voids with the melted organic low-molecular weight substance, and crystallizes at a relatively high temperature where the seed crystal is cooled while remaining in the resin. However, because the resin is still in a softened state, the resin follows the volume change of the particles due to crystallization, and voids cannot be created,
This is probably because the transparent state is maintained. The crystallization temperature at this time is referred to as a high temperature crystallization temperature (TB ₁ ).

Further heating to a temperature of T ₄ or higher results in a semitransparent state between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the state returns to the original cloudy and opaque state without taking the transparent state again. After this the organic low molecular weight substance at a temperature T ₄ or more completely melted, crystallized little higher temperature than T ₀ becomes supercooled state, this time, can not follow the volume change of the resin is caused by the crystallization, voids It seems to happen. The crystallization temperature at this time is referred to as a low temperature crystallization temperature (TB ₂ ).

However, the temperature-transparency change curve shown in FIG. 2 is only a representative example, and the transparency of each state may change depending on the material by changing the material. The transparency-white turbidity change of the reversible thermosensitive recording medium is caused by the high temperature crystallization temperature (TB ₁ ) and the low temperature crystallization temperature (T
Since it is determined by the balance between B ₂ ) and the softening temperature (TA) of the resin, it is possible to improve the contrast when the difference between the high temperature crystallization temperature (TB ₁ ) and the low temperature crystallization temperature (TB ₂ ) is large. . Further, in the transparent-white turbidity change of the reversible thermosensitive recording medium, there is a softening start temperature (TA) of the thermosensitive layer between the high temperature crystallization temperature (TB ₁ ) and the low temperature crystallization temperature (TB ₂ ) of the organic low molecular weight substance. However, if the high temperature crystallization temperature (TB ₁ ) and the softening start temperature (TA) are too close to each other, the softening degree of the resin decreases at the high temperature crystallization temperature, and the volume of the organic low molecular weight substance particles accompanying the crystallization increases. There is a drawback that the resin becomes a little hard to follow the change, the transparency is lowered and the contrast is lowered.

In the reversible thermosensitive recording medium of the present invention,
Elasticity in the rubber-like region above the glass transition temperature of the thermal layer.
Rate is 10⁷dyn / cm^TwoWhen it is above, softening of the heat sensitive layer starts
Since the temperature (TA) shifts to the high temperature side, the contrast drops.
And the elastic modulus is 6 × 10 ⁶Repeated if less than
This causes a problem that the subsequent image deterioration becomes large. Also, the heat sensitive layer
When the gel fraction value of the sol exceeds 65%, the softening start temperature of the heat-sensitive layer
Since (TA) shifts to the high temperature side, the contrast drops and
If the percentage value is less than 30%, image deterioration after repeated
It causes the problem of becoming large. In addition, the entire resin base material
The ratio of UV curable resin to 35% by weight
And the softening start temperature of the resin becomes high, and for the above reason
The transparency decreases and the contrast deteriorates. Also, resin mother
The ratio of UV curable resin to the whole material is 5% by weight lower
And the degree of cross-linking of the resin base material is low and image formation and deletion are repeated.
There is a drawback that the deterioration after returning becomes large. Also feeling
The lowest melting point of organic low-molecular substances mixed with two or more in the thermal layer
The melting point of the organic low molecular weight substance, which is the point, was less than 60 ° C.
The content of organic low-molecular-weight substances with the lowest melting point is low.
If the ratio exceeds 20% by weight of the total molecular substance, heat sensitivity
Organic low-molecular substance with low melting point even if the resin in the layer is cured
Is completely melted by applying energy from the thermal head
Distortion is likely to occur inside the heat-sensitive layer.
The state where the organic low-molecular substance as shown in 1 (d) is maximized
It becomes impossible to form an image after repeated durability
There is a drawback that UV or electron beam curing irradiation
If it is not an ε-caprolactone adduct,
The degree of curing of the heat-sensitive layer changes depending on the medium temperature during irradiation
And a stable quality reversible thermosensitive recording material can be obtained.
Disadvantages.

The preferred use ratio of the ultraviolet curable resin is
It depends on the compatibility with the ultraviolet curable resin and the other resin (resin A), but in the case of the (poly) ester acrylate resin, 5 to 23% by weight, particularly preferably 12
Is in the range of up to 20% by weight. In the case of a (poly) urethane acrylate-based resin, it is in the range of 10 to 28% by weight, particularly preferably 17 to 23% by weight. In the present invention, the method for measuring the gel fraction of the heat-sensitive layer is to form a heat-sensitive layer on a support in an arbitrary film thickness, and after irradiating an electron beam or an ultraviolet ray, peel the film by the support to remove the film. The initial weight was measured, after which the membrane was sandwiched between 400 mesh wire nets, immersed in a solvent in which the resin before crosslinking was soluble for 24 hours, and then vacuum dried, and the weight after drying was measured. The gel fraction is calculated by the following equation. Gel fraction (%) = [weight after drying (g) / initial weight (g)] × 100

The ultraviolet curable resin used in the present invention undergoes a polymerization reaction upon irradiation with ultraviolet rays and is cured to be a cured resin. As the ultraviolet curable resin, any monomer, oligomer, or prepolymer can be used, but it has good transparency, good film formability, good compatibility with other resin (resin A), and starts softening. It is good if the temperature does not become too high. Preferred are (poly) urethane acrylate-based resins and (poly) ester acrylate-based resins, and more preferred are (poly) urethane acrylate-based resins. Particularly preferred is an acrylate resin added to ε-caprolactone.

The thickness of the recording layer is preferably 1 to 30 μm,
It is more preferably 4 to 18 μm. If the recording layer is too thick, heat distribution will occur in the layer, making it difficult to achieve uniform transparency. On the other hand, if the recording layer is too thin, the turbidity decreases and the contrast decreases. The turbidity can be increased by increasing the amount of the fatty acid in the recording layer.

To prepare the reversible thermosensitive recording medium of the present invention, a recording layer is formed on a support by the following method, for example. In some cases, the sheet may be formed without using the support. 1) Dissolve a resin base material and an organic low molecular weight substance in a solvent, apply this on a support member, evaporate the solvent to form a film or sheet and cure, or cure after forming into a sheet form Method. 2) The resin base material is dissolved in a solvent that dissolves only the resin base material, and the organic low molecular weight substance is pulverized or dispersed therein by various methods, and this is applied onto a support member, and the solvent is evaporated to form a film or A method in which a sheet is formed and crosslinked, or a sheet is formed and then cured. 3) A method in which a resin base material and an organic low molecular weight substance are heated and melt-mixed without using a solvent, and this is molded into a film or sheet, cooled, and then cured. As the recording layer or the solvent for preparing a thermosensitive recording medium, various types can be selected depending on the types of the resin base material and the organic low-molecular substance.
Examples include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, benzene and the like. It is to be noted that the organic low-molecular substance is precipitated as fine particles in the recording layer obtained when the solution is used, as well as when the dispersion is used, and exists in a dispersed state.

In the present invention, the resin used as the resin base material of the recording layer of the reversible thermosensitive recording medium is as described above.
It is preferable to use a mixture of the resin A and the resin B, or a mixture of the mixture with another resin capable of forming a film or sheet, having good transparency and being mechanically stable. Examples of such resin A include polyvinyl chloride, polyester,
Examples thereof include one or a mixture of two or more selected from polyethylene, polypropylene, polystyrene, polyacrylate, polyacrylamide, polyamide, polyvinylpyrrolidone, natural rubber, polysiloxane, polyvinyl alcohol, poiacrolein or copolymers thereof. The UV curable resin (resin B) includes monofunctional monomers and polyfunctional monomers, and specific examples include the following. These may be used alone or in combination of two or more.

Examples of monofunctional monomers: (1) methyl methacrylate (MMA) (2) ethyl methacrylate (EMA) (3) n-butyl methacrylate (BMA) (4) i-butyl methacrylate (IBMA) (5) t-Butyl Methacrylate (TBMA) (6) 2-Ethylhexyl Methacrylate (EHMA) (7) Lauryl Methacrylate (LMA) (8) Alkyl Methacrylate (SLMA) (9) Tridecyl Methacrylate (TDMA) ( 10) Stearyl Methacrylate (SMA) (11) Cyclohexyl Methacrylate (CHMA) (12) Benzyl Methacrylate (BZMA) (13) Methacrylic Acid (MMA) (14) 2-Hydroxyethyl Methacrylate (HEMA) (15) Methacryl 2-hydroxypropyl acid (HPM
A) (16) Dimethylaminoethyl Methacrylate (DMMA) (17) Dimethylaminoethyl Methyl Methacrylate Methacrylate (DMCMA) (18) Diethylaminoethyl Methacrylate (DEMA) (19) Glycidyl Methacrylate (GMA) (20) Methacryl Tetrahydrofurfuryl acid (THFM
A) (21) 2-Ethoxyethyl methacrylate (ETMA) (22) 2-Ethylhexyl acrylate (23) Phenoxyethyl acrylate (24) 2-Ethoxyethyl acrylate (25) 2-Ethoxyethoxyethyl acrylate (26) 2-Hydroxy Ethyl acrylate (27) 2-Hydroxypropyl acrylate (28) Dicyclopentenyloxyethyl acrylate (29) N-vinylpyrrolidone (30) Vinyl acetate

Examples of bifunctional monomers: (31) allyl methacrylate (AMA) (32) ethylene glycol dimethacrylate (EDMA) (33) triethylene glycol dimethacrylate (3ED
MA) (34) Tetraethylene glycol dimethacrylate (4E
DMA) (35) 1,3-butylene glycol dimethacrylate (B
DMA) (36) 1,6-hexanediol dimethacrylate (HX
MA) (37) 1,4-butanediol acrylate CH_Two= CHCOO (CH_Two)_FourOOCCH = CH_Two (38) 1,6-hexanediol diacrylate CH_Two= CHCOO (CH_Two)₆OCOCH = CH_Two (39) 1,9-Nonanediol diacrylate CH_Two= CHCOO (CH_Two)₉OCOCH = CH_Two (40) Neopentyl glycol diacrylate CH_Two= CHCOOCH_Two-C (CH_Three)_TwoCH_TwoOOCC
H = CH_Two (41) Tetraethylene glycol diacrylate CH_Two= CHCOO (CH_TwoCH_TwoO)_FourOCCH = CH_Two (42) Tripropylene glycol diacrylate(43) Tripropylene glycol diacrylate (44) Polypropylene glycol diacrylate(45) Bisphenol A. EO adduct diacrylate

Embedded image (46) Glycerin methacrylate acrylate

Embedded image (47) Diacrylate of neopentyl glycol with 2 mol of propylene oxide added (48) Diethylene glycol diacrylate (49) Polyethylene glycol (400) Diacrylate (50) Diacrylate of ester of hydroxypivalic acid and neopentyl glycol (51) 2 , 2-Bis (4-acryloxy-diethoxyphenyl) propane (52) Dipentacrylate of neopentyl glycol adipate

Embedded image (53) Diacrylate of ε-caprolactone adduct of neopentyl glycol hydroxypivalate

Embedded image (54) Diacrylate of ε-caprolactone adduct of neopentyl glycol hydroxypivalate

Embedded image (55) 2- (2-hydroxy-1,1-dimethylethyl) -5-hydroxymethyl-5-ethyl-1,3-dioxane diacrylate

[Chemical 6] (56) Tricyclodecane dimethylol diacrylate

Embedded image (57) ε-caprolactone adduct of tricyclodecane dimethylol diacrylate

Embedded image (58) Diacrylate of diglycidyl ether of 1,6-hexanediol

Embedded image (59) Addition product of phenylene diisocyanate (1 mol) and 2-hydroxyethyl acrylate (2 mol) (60) Addition of 1,6-hexamethylene diisocyanate (1 mol) and 2-hydroxyethyl acrylate (2 mol) Stuff

Examples of trifunctional or higher polyfunctional monomers: (61) trimethylolpropane trimethacrylate (T
MPMA) (62) Trimethylolpropane triacrylate (63) Pentaerythritol triacrylate (64) Glycerin PO-added triacrylate

Embedded image(65) Tris acryloyloxyethyl phosphate (CH_Two= CHCOOCH_TwoCH_TwoO)_ThreePO (66) pentaerythritol tetraacrylate (67) Propylene oxide of trimethylolpropane
3-Mole adduct triacrylate (68) Glyceryl propoxy triacrylate (69) Dipentaerythritol polyacrylate (70) Dipentaerythritol caprolactone adduct
Polyacrylate (71) Propionic Acid / Dipentaerythritol Triac
Related (72) Hydroxypivalaldehyde modified dimethylol
Ropin triacrylate (73) Tetra of propionic acid dipentaerythritol
Acrylate(74) Ditrimethylolpropane tetraacrylate (75) Pentaa of dipentaerythritol propionate
Crelate(76) Dipentaerythritol hexaacrylate (D
PHA)(77) ε-caprolactone adduct of DPHA

Embedded image (78) Trimethylolpropane-4,4'-diphenylmethane diisocyanate 3 mol Additive (1 mol) and 2-hydroxyethyl acrylate (3 mol) Additive (79) 1,3,6-hexamethylenetriisocyanate ( (1 mol) and 2-hydroxyethyl acrylate (3 mol) (80) Addition product of isocyanurate-modified polyisocyanate and 2-hydroxyethyl acrylate

Examples of oligomers: (81) Bisphenol A-diepoxy acrylic acid adduct

Embedded image (82) Poly (ethylene adipate) diacrylate (83) Poly (neopenthylene adipate) diacrylate (84) Ethylene glycol / poly-ε-caprolactone adduct diacrylate (85) Polyisocyanate reacted with polyester polyol Urethane acrylate oligomer obtained by reacting the isocyanate adduct with hydroxyacrylate (86) Urethane acrylate oligomer obtained by reacting the terminal isocyanate adduct obtained by reacting polyether polyol with polyisocyanate (87) ) Urethane acrylate oligomer obtained by reacting a terminal isocyanate addition product obtained by reacting polybutadiene polyol with polyisocyanate with hydroxy acrylate

Further, UV irradiation is used as a means for curing the mixture of the resin A and the resin B in the heat-sensitive layer in the present invention, but the following photopolymerization initiator and photopolymerization accelerator may be used. . Specific examples thereof include, but are not limited to, the following. The photopolymerization initiator can be roughly classified into a radical reaction type and an ion reaction type, and the radical reaction type is further divided into a photocleavage type and a hydrogen abstraction type. Specific examples include those shown in Table 1 below.

[0027]

[Table 1- (1)]

[0028]

[Table 1- (2)]

These photopolymerization initiators may be used alone or in admixture of two or more. As the addition amount, the resin B1
0.005 to 1.0 part by weight is preferable with respect to parts by weight,
More preferably, it is 0.01 to 0.5 part by weight.

Next, as a photopolymerization accelerator, hydrogen-abstraction type photopolymerization initiators such as benzophenone type and thioxanthone type have the effect of improving the curing rate, and are aromatic tertiary amines or aliphatic type. There are amines. Specifically, the following are mentioned.

Embedded image

Embedded image These photopolymerization accelerators are used alone or in combination of two or more. The amount added is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 1 part by weight with respect to 1 part by weight of the photopolymerization initiator.
3 parts by weight.

The ultraviolet irradiation device used in the present invention comprises a light source, a lamp, a power source, a cooling device, and a carrying device. The light source includes a mercury lamp, a metal halide lamp, a gallium lamp, a mercury xenon lamp, and a flash lamp, and a light source having an emission spectrum corresponding to the ultraviolet absorption wavelength of the above-mentioned photopolymerization initiator and photopolymerization accelerator may be used. .

Regarding ultraviolet irradiation conditions, the lamp output and the conveying speed may be determined according to the irradiation energy required for curing the resin. Further, when the reversible thermosensitive recording medium is turbid and is irradiated with ultraviolet rays, the surface portion of the medium is not cured. Therefore, it is better to irradiate ultraviolet rays when the medium is in a transparent state.

On the other hand, as the organic low molecular weight substance, any substance that changes from polycrystal to single crystal due to heat in the recording layer (any substance that changes within the temperature range of T _{1 to} T ₃ shown in FIG. 2 may be used. A substance having a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. is used as such an organic low molecular weight substance: alkanol; alkanediol; halogenalkanol or halogenalkanediol; alkylamine; alkane; alkene; alkyne; Alkanes; Halogen alkenes; Halogen alkynes; Cycloalkanes; Cycloalkenes; Cycloalkynes; Saturated or unsaturated mono- or dicarboxylic acids or their esters, amides or ammonium salts; Saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts Allyl carvone Or their esters, amides or ammonium salts; halogenallylcarboxylic acids or their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; carboxylic acid esters of thioalcohols and the like. These are used alone or in combination of two or more.The carbon number of these compounds is 10 to 10.
60, preferably 10 to 38, particularly preferably 10 to 30. The alcohol group in the ester may be saturated, may not be saturated, and may be halogen-substituted. In any case, the organic low molecular weight substance contains at least one kind of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH, -COOR, -N
_{H, -NH 2, -S -,} - S-S -, - O-, is preferably a compound containing a halogen and the like.

More specifically, these compounds include higher fatty acids such as lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, alginic acid and oleic acid; methyl stearate. , tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, esters of higher fatty acids dodecyl behenate _{like; C 16 H 33 -O-C} 16 H 33, C 16 H 33 -S-C 16 H 33 _{, C 18 H 37 -S-C} 18 H 37, C 12 H 25 -S-C 12 H 25, C 19 H 39 -S-C 19 H 39, C 12 H 25 -S-S-C 12 H 25 ， And ether or thioether. Among them, in the present invention, higher fatty acids, particularly palmitic acid, pentadecanoic acid,
Nonadecanoic acid, arachidic acid, stearic acid, behenic acid,
Higher fatty acids having 16 or more carbon atoms such as lignoceric acid are preferable, and higher fatty acids having 16 to 24 carbon atoms are more preferable.

The weight ratio of the organic low molecular weight substance to the resin in the recording layer is preferably about 2: 1 to 1:16.
It is more preferably 1: 2 to 1: 8. If the ratio of the resin is less than this, it becomes difficult to form the organic low-molecular substance in the film held in the resin, and if it is more than this, it becomes difficult to make the film opaque because the amount of the organic low-molecular substance is small. .

In addition to the above components, additives such as a surfactant, a high boiling point solvent and a plasticizer can be added to the recording layer in order to facilitate the formation of a transparent image. These additives are particularly effective in curing the resin base material because they lower the softening start temperature of the resin base material and facilitate transparency.
Specific examples of these additives are as follows. Examples of high boiling point solvents; tributyl phosphate, tri-2-phosphate
Ethylhexyl, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate , Dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate,
Dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-2 azelate
-Ethylhexyl, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetylricinoleate, butyl acetylricinoleate, butylphthalylbutyl glycolate, acetylcitric acid Tributyl etc.

Examples of plasticizers: fatty acid ester, polyester plasticizer, epoxy plasticizer and the like.

Examples of surfactants and other additives: polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide , Lower olefin oxide adducts of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salt of higher alkylbenzene sulfonic acid; higher fatty acid, aromatic carboxylic acid, higher fatty acid sulfonic acid, aromatic sulfonic acid, sulfuric acid monoester Or Ca, Ba or Mg salt of phosphoric acid mono- or di-ester; low degree of sulfated oil; poly long chain alkyl acrylate; acrylic orgomer; poly long chain alkyl methacrylate; long chain alkyl methacrylate-amine containing mono Over copolymer; a styrene - maleic anhydride copolymer; olefin - maleic anhydride copolymers and the like.

A protective layer may be provided on the recording layer to protect the recording layer. Protective layer (thickness 0.1-1
0 μm) include silicone rubber, silicone resin (described in JP-A-63-221087), polysiloxane graft polymer (Japanese Patent Application No. 62-1525).
No. 50) or an ultraviolet curable resin or an electron beam curable resin (described in Japanese Patent Application No. 63-310600). In any case, a solvent is used at the time of coating, and it is preferable that the solvent does not easily dissolve the resin of the recording layer and the organic low-molecular substance. Examples of the solvent that hardly dissolves the resin and the organic low molecular weight substance in the recording layer include n-hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like, and an alcohol solvent is particularly preferable from the viewpoint of cost.

Further, an intermediate layer may be provided between the protective layer and the recording layer in order to protect the recording layer from the solvent, the monomer component and the like of the protective layer forming liquid (JP-A-1-13378).
1). As the material of the intermediate layer, the following thermosetting resins and thermoplastic resins can be used in addition to those listed as the material of the resin base material in the recording layer. That is, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin,
Phenol resin, polycarbonate, polyamide and the like can be mentioned. The thickness of the intermediate layer is preferably about 0.1 to 2 μm.

The reversible thermosensitive recording medium of the present invention can also be used as a card by providing a magnetic recording layer (Japanese Utility Model Laid-Open No. 2-3876). In this case, the magnetic recording layer may be provided on the back surface of the support or between the support and the heat-sensitive layer.

As mentioned above, in the present invention, a colored layer may be provided between the support and the recording layer in order to improve the visibility. The coloring layer is formed by applying a solution or dispersion containing a coloring agent and a resin binder as main components to the target surface and drying, or simply by laminating a coloring sheet.
Here, as the colorant, any change in transparency and white turbidity of the upper recording layer can be recognized as a reflection image, and red, yellow, blue,
Dyes and pigments having colors such as navy blue, purple, black, brown, grey, orange and green are used. As the resin binder, various thermoplastic, thermosetting or ultraviolet curable resins are used.

When the present invention is used as a heat-sensitive recording image display device for displaying an image, there are various types, but a typical one is to perform image formation / erasure on a reversible recording medium. The image forming means and the image erasing means are the same heating element, for example, a thermal head, and a thermal recording image display device capable of performing image processing by changing the energy applied to the thermal head, or the image forming means is a thermal The head, the image erasing means is a thermal head, hot stamp,
There is a heat-sensitive recording image display device selected from one of a contact pressure type means for adhering a heating element such as a heat roller and a heat block, or a non-contact type means using warm air or infrared rays. Specifically, for example, in FIG.
The heat-sensitive recording / erasing device as shown in (b), (c) and (d) can be mentioned.

FIG. 3 (a) is a schematic view of a contact pressure type heating device for making a reversible thermosensitive recording medium 1 stationary by pressing a hot stamp 2 to make it transparent. In the figure, reference numeral 3 denotes a balance table. FIG. 3B is a schematic view of a contact-type heating device which makes the heat roller 4 transparent. In the figure, reference numeral 5 denotes an idle roller. In this apparatus, the heat roller 4 and the idle roller 5 rotate at the same peripheral speed, and the reversible thermosensitive recording medium 1 is moved while being held therebetween. FIG. 3 (c)
1 is a schematic diagram of a non-contact type heat-sensitive device that performs transparency by hot air from a dryer 6, and in the drawing, 7 denotes a feed roller. FIG. 3D is a schematic view of a contact-pressing type heating device that makes the heat block 8 transparent. In the figure, reference numeral 7 denotes a feed roller. Although not shown in FIG. 3, it goes without saying that a thermal head can be used as the image erasing device as shown in FIG.

A specific example of using the heat-sensitive recording image display device for displaying an image in the present invention will be described below. First, FIG. 4A shows an example in which the image forming means and the image erasing means for forming and erasing an image on the reversible recording medium are thermal heads. FIG.
In (a), the image-formed reversible thermosensitive recording medium 1-1 in the figure is sent out to the right by the platen roll 11 in the figure, and at that time, the energy is removed by the image erasing thermal head 9 in the figure. The applied image erases the image (at the same time, a displacement stress is generated between the recording medium and the contact surface of the thermal head, but the degree is extremely small because the resin of the recording layer is cross-linked. No energy is applied to the thermal head for driving, and only the platen roll 11 in the figure is driven, and thereafter it is conveyed to the stopper 13 in the figure by the guide rolls 12 and 12 in the figure.

In FIG. 4B, the image-erased reversible thermosensitive recording medium 1-2 in the drawing is fed leftward by the guide roll 12 in the drawing, and then further fed by the platen roll 11 in the drawing. It is sent to the left. At that time 1 in the figure
A new image is formed by applying energy with the image forming thermal head of 0 (at the same time, a displacement stress is generated between the recording medium and the contact surface of the thermal head.
The degree is extremely small). At this time, energy is not applied to the image erasing thermal head 9 in the drawing, and only the platen roll 11 in the drawing is driven and further conveyed to the left.

It is clear that image display using a reversible thermosensitive recording medium can be carried out by using the thermosensitive recording image forming apparatus as described above. In the thermal recording image forming apparatus described above, the thermal heads 9 and 10 in the figure can be the same thermal head, and from the image erasing thermal head 9 in the figure to the hot stamp, heat roller, heat block, etc. It is also possible to change to a contact pressing type erasing device or a non-contact type erasing device using warm air or infrared rays. Further, in this apparatus, it is defined that an image erasing thermal head is provided in FIG. 9 and an image forming thermal head is provided in 10 in the figure. However, even if the reverse apparatus is used, there is no problem.

Secondly, the image forming means and the image erasing means for forming and erasing an image on the reversible thermosensitive recording medium are the same thermal head, and a guide roll is provided behind the thermal head as a pressing means as a pressing means. An example using is shown in FIG. In FIG. 5, the image-formed reversible thermosensitive recording medium 1-1 in the figure is sent out to the right by the platen roll 11 in the figure, and at that time, in the image forming-erasing thermal head 14 in the figure. , The old image is erased and a new image is formed. Next, the reversible recording medium 1-3 on which a new image is formed in the figure is further fed to the right by the platen roll 11 in the figure, and 12, 1 in FIG.
It moves between the two guide rolls and moves to the right. As described above, it is obvious that the image display can be performed even in such a thermosensitive recording image forming apparatus. The image formation and erasure can be performed without contact. Further, between the image formation and the erasing, it is possible to employ means such as non-contact heating above the image forming temperature or heating while applying pressure above the image forming temperature.

In the reversible thermosensitive recording medium of (a) of the present invention, since the recording layer as a whole has a crosslinked network structure, the recording layer does not cause distortion including the organic low molecular weight substance particles and is always good. Clear records can be erased.

[0050]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. All parts and percentages here are on a weight basis.

Example 1 A transparent PET film having a thickness of 188 μm was used as a support, an Al layer was provided thereon, and 5 parts of vinyl chloride-vinyl acetate-phosphate ester copolymer (Denka vinyl # manufactured by Denki Kagaku Kogyo Co., Ltd.) was used. 1000P) A coating liquid for forming an adhesive layer consisting of 95 parts of THF was applied and dried by heating to form an adhesive layer having a thickness of about 0.8 μm. Further thereon, vinyl chloride-vinyl acetate copolymer 31.2 parts (Denka Vinyl # 1000MT manufactured by Denki Kagaku Kogyo Co., Ltd.) ester acrylate UV curable resin 7.8 parts (Dainippon Ink and Chemicals Co., Ltd .: Unidick C4 -782) Behenic acid (NOF: NAA-22S) 2 parts Eicosane diacid (Okamura Oil Co., Ltd .: SL-20 / 93) 5 parts Lignoceric acid (Miyoshi oil / fat: L-88) 3 parts THF 120 parts Toluene 12 parts 80W after applying a recording layer forming solution consisting of
It was cured with a UV lamp of 1 cm / cm to provide a recording layer having a thickness of about 10 μm (medium temperature at the time of UV irradiation: 65 ° C.). Further, a protective layer solution consisting of a UV-curable resin 75% butyl acetate solution 10 parts (manufactured by Dainippon Ink and Chemicals Co., Ltd .: Unidic C7-157) isopropyl alcohol 10 parts toluene 1 part was applied on it, and after heating and drying 80 W / c
and a protective layer having a thickness of about 3.5 μm was provided to prepare a reversible thermosensitive recording medium.

Example 2 Denka vinyl # 1000MT of Example 1 was added to 37.05.
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that 1.95 parts of Unidic C4-782 was used.

Example 3 Denka vinyl # 1000MT of Example 1 was added to 35.88.
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that 3.12 parts of Unidick C4-782 was used.

Example 4 The Denka vinyl # 1000MT of Example 1 was added to 33.15.
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the amount of unidic C4-782 was 5.85 parts.

Example 5 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that Denka vinyl # 1000MT was 30.13 parts and Unidick C4-782 was 8.97 parts.

Example 6 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that Denka vinyl # 1000MT was 29.25 parts and Unidick C4-782 was 9.75 parts.

Example 7 25.35 parts of Denka vinyl # 1000MT was used, and Unidick C4-782 was treated with Takelac UV-6030.
(Urethane acrylate-based 90% ethyl acetate solution: Takeda Yakuhin Kogyo Co., Ltd.) was used in an amount of 14.41 parts, and IRUGACURE 184 (CIBA) as a polymerization initiator.
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that 0.68 part of GEIGY) and 2 parts of diisodecyl phthalate were added.

Example 8 Denka vinyl # 1000MT was added to 31.2 parts, and UV was used.
-6030 is 8.23 parts, IRUGACURE18
A reversible thermosensitive recording medium was prepared in the same manner as in Example 7 except that 4 was 0.39 part and diisodecyl phthalate was not added.

Example 9 Unidic C4-782 was converted to NK ester A-NPG
(Neopentyl glycol diacrylate: manufactured by Shin-Nakamura Chemical Co., Ltd.), the amount used was 7.41 parts, and the polymerization initiator IRUGACURE184 was added in an amount of 0.39 parts. A thermal recording medium was created.

Example 10 Example 1 except that Denka vinyl # 1000MT was 25.35 parts, Unidic C4-782 was 13.65 parts, and 2.5 parts of diisodecyl phthalate was added.
A reversible thermosensitive recording medium was prepared in the same manner as in.

Example 11 36.05 parts of Denka vinyl # 1000MT, 2.1 parts of Takelac UV6030, polymerization initiator IRUGAC
A reversible thermosensitive recording medium was prepared in the same manner as in Example 7 except that 0.01 part of URE184 was used.

Example 12 Denka vinyl # 1000MT was 33.15 parts, Unidic C4-782 was 2.54 parts, and ε-caprolactone adduct of dipentaerythritol hexaacrylate (DPCA120 manufactured by Nippon Kayaku Co., Ltd.) was added. 2.
Example 1 was repeated except that 54 parts of the recording layer-forming solution was applied, dried by heating at 120 ° C., and then cured by an 80 W / cm ultraviolet lamp at a high temperature of 80 ° C. or higher. A reversible thermosensitive recording medium was prepared in the same manner.

Example 13 5.5 parts of eicosane diacid and 3.5 parts of lignoceric acid
Reversible thermosensitive recording material was prepared in the same manner as in Example 12 except that 1.0 part of behenic acid and 1.0 part of stearyl stearate (manufactured by NOF CORPORATION) were added.

Example 14 A reversible thermosensitive recording material was prepared in the same manner as in Example 12 except that 2.5 parts of lignoceric acid and 2.0 parts of stearyl stearate were used.

Example 15 A reversible thermosensitive recording material was prepared in the same manner as in Example 12 except that 2.0 parts of lignoceric acid and 3.0 parts of stearyl stearate were used.

EXAMPLE 16 5.08 parts of Unidic C4-782 and DPCA
A reversible heat-sensitive recording material was prepared in the same manner as in Example 12 except that 120 was 0 part.

Example 17 Stearyl stearate was mixed with palmityl stearate (S
A reversible thermosensitive recording material was prepared in the same manner as in Example 14, except that the melting point was changed to 57.5 ° C. manufactured by IGMA.

COMPARATIVE EXAMPLE 1 Denka Vinyl # without adding Unidic C4-782
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the amount of 1000 MT was changed to 39 parts.

Comparative Example 2 Denka vinyl # 1000MT was replaced with 19.5 parts, and Unidick C4-782 was replaced with NK ester A-400 (polyethylene glycol diacrylate: Shin Nakamura Chemical Co., Ltd.), and the amount used was 19.5 parts. , Polymerization initiator IRUG
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that 5 parts of ACURE184 (1-hydroxycyclohexyl phenyl ketone) was added.

Comparative Example 3 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that Denka Vinyl # 1000MT was 37.83 parts and Unidick C4-782 was 1.17 parts.

Comparative Example 4 Example 1 was repeated except that Denka Vinyl # 1000MT was 23.4 parts and Unidic C4-782 was 15.6 parts.
A reversible thermosensitive recording medium was prepared in the same manner as in.

Comparative Example 5 23.4 parts of Denka vinyl # 1000MT, 16.47 parts of Takelac UV6030, polymerization initiator IRUGA
A reversible thermosensitive recording medium was prepared in the same manner as in Example 7 except that CURE184 was changed to 0.78 part.

Comparative Example 6 Denka vinyl # 1000MT 37.83 parts, Takelac UV6030 1.11 parts, polymerization initiator IRUGA
A reversible thermosensitive recording medium was prepared in the same manner as in Example 7 except that CURE184 was changed to 0.06 part.

Comparative Example 7 A support and an adhesive layer were prepared in the same manner as in Example 1, and further 100 parts of Denka vinyl # 1000 MT 100 parts NK ester A-400 (polyethylene glycol diacrylate: Shin-Nakamura Chemical Co., Ltd.) were prepared. 12-tricosanone 40 parts 1,12-tetradecanedioic acid 10 parts IRUGACURE 184 5 parts THF 1000 parts toluene 300 parts A recording layer forming solution consisting of 300 parts is applied, and after heating and drying 80 W
The film was cured with a UV lamp of 1 cm / cm to form a recording layer having a thickness of about 10 μm. Further, a protective layer was provided thereon in the same manner as in Example 1 to prepare a reversible thermosensitive recording medium.

Next, the reversible thermosensitive recording media of Examples 1 to 17 and Comparative Examples 1 to 7 were subjected to repeated durability tests of image formation and erasing. 0.30m using Oki Electric thermal head printer as image forming printer
An image was formed with an applied energy of J / dot. The image was erased by the heat of warm water. The results of 70 times of image formation and erasing under the above conditions are shown in Table 2. The density values in Table 1 were measured 10 minutes after printing with a Macbeth RD914 reflection densitometer. The image visibility was visually evaluated. Also, TMA / ss150c manufactured by Seiko Denshi Kogyo Co., Ltd.
Table 2 shows the results of the dynamic viscoelasticity measurement at 150 ° C. The results of measuring the gel fraction values are shown in Table 2.
It was shown to.

[0076]

[Table 2]

[0077]

As is clear from the description of Examples and Comparative Examples, according to the thermoreversible thermosensitive recording medium of the present invention, there is little deterioration of a cloudy image even when image formation and erasing are repeated, and there is no change in contrast. Less, repeated durability is improved.

[Brief description of the drawings]

FIG. 1A, FIG. 1B, FIG. 1C and FIG. 1D are diagrams showing the influence of a heat sensitive layer of a reversible thermosensitive recording medium by a heating element in a conventional image display.

FIG. 2 is a diagram showing changes in transparency of a reversible thermosensitive recording medium according to the present invention due to heat.

FIG. 3 shows various specific examples of image erasing means in a thermosensitive recording image display device.

4A and 4B are examples in which an image is formed and erased on a reversible thermosensitive recording medium using a thermal head by the method of the present invention.

FIG. 5 shows an example in which an image is formed on and erased from a reversible thermosensitive recording medium using a thermal head and a guide roll as a pressing unit provided after the thermal head.

[Explanation of symbols]

 1 ... Reversible thermosensitive recording medium 1-1 ... Reversible thermosensitive recording medium with image formed 1-2 ... Reversible thermosensitive recording medium with image erased 1-3 ... Reversible thermosensitive recording medium with newly formed image 2 ... Hot stamp 3 ... Stamp stand 4 ... Heat roller 5 ... Idle roller 6 ... Dryer 7 ... Feed roller 8 ... Heat block 9 ... Image erasing head 10 ... Image forming head 11 ... Platen roll 12 ... Guide roll 13 ... Stopper 14 ... Image forming / erasing head

Front Page Continuation (72) Inventor Nobuyoshi Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Fumito Masuchibuchi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Akihide Ito 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Company (72) Inventor Kunichika Moroboshi 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Company (72) ) Inventor Tetsuya Amano 1-3-6 Nakamagome, Ota-ku, Tokyo, within Ricoh Co., Ltd. (72) Yoshihiko Hotta 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh, Inc.

Claims (9)

[Claims] 1. A reversible sensation comprising a support and a heat-sensitive layer whose main component is at least a resin and an organic low-molecular substance dispersed in the resin base material and whose transparency reversibly changes depending on temperature. In a thermal recording medium, an ultraviolet or electron beam curable resin is used as a resin base material in the thermosensitive layer, and the elastic modulus in a rubber-like region exceeding the glass transition temperature of the thermosensitive layer after being cured by irradiation with ultraviolet rays or electron beams. In the range of 6 × 10 ⁶ or more and less than 10 ⁷ dyn / cm ² is a reversible thermosensitive recording material. 2. The gel fraction of the heat sensitive layer is 30% to 65%.
The reversible thermosensitive recording material according to claim 1, wherein 3. A reversible heat-sensitive material comprising a support and a heat-sensitive layer which comprises at least a resin and an organic low-molecular substance dispersed in a resin base material as a main component and whose transparency reversibly changes depending on temperature. In the recording medium, the resin is polyvinyl chloride,
At least one selected from the group selected from polyester, polyethylene, polypropylene, polystyrene, polyacrylate, polyacrylamide, polyamide, polyvinylpyrrolidone, natural rubber, polysiloxane, polyvinyl alcohol, and polyacrolein, or a copolymer thereof (resin A). A resin mixture comprising at least two kinds of ultraviolet curable resin (resin B), and the weight ratio of the resin A and the resin B is within the range of 95: 5 to 65:35,
The reversible thermosensitive recording medium according to claim 1 or 2, which is a resin cured by ultraviolet rays. 4. The reversible thermosensitive recording medium according to claim 3, wherein the ultraviolet curable resin (resin B) is a polyester acrylate resin. 5. The weight ratio of the resin A and the resin B is
The reversible thermosensitive recording medium according to claim 4, wherein the reversible thermosensitive recording medium is in the range of 95: 5 to 77:23. 6. The ultraviolet curable resin (resin B) comprises:
The reversible thermosensitive recording medium according to claim 3, which is a (poly) urethane acrylate resin. 7. The weight ratio of the resin A and the resin B is
The reversible thermosensitive recording medium according to claim 4, wherein the reversible thermosensitive recording medium is in the range of 90:10 to 72:28. 8. The reversible thermosensitive recording material according to claim 1, wherein at least one of the ultraviolet ray and electron beam curable resins contains an ε-caprolactone adduct. 9. A mixture of two or more kinds of the organic low molecular weight substances, and the melting point of the organic low molecular weight substance having the lowest melting point is 60.
20% of the total of the organic low-molecular weight substances in which the content of the organic low-molecular weight substances having a melting point of ℃ or more and the lowest melting point is mixed in two or more kinds.
The reversible thermosensitive recording material according to claim 1 or 2, characterized in that the content is not more than weight%.