JP2003039835A - Reversible heat sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible heat sensitive recording medium in which a breakdown of a release between layers or a deformation does not occur in a laminated structure when an image is rewritten by irradiating with a laser beam or when the image is secondarily processed by heating. SOLUTION: The reversible heat sensitive recording medium comprises a laminate having a recording layer 2 capable of displaying or erasing a visible image by reversibly changing a transparency or a color developability according to a temperature. The medium further comprises a photothermal conversion layer 3 containing an infrared absorption pigment and an ultraviolet absorption layer 7 superposed in this order on the layer 2 in such a manner that these layers 2, 3 and 7 are made of a resin having a crosslinking structure. The layer 7 has a polymeric copolymer of a monomer having an ultraviolet absorptive molecular structure and a polymerizable monomer. The ultraviolet absorption layer has a mean permeability of 10% or less of a range 300 to 360 nm of a wavelength and is an ultraviolet absorption layer having a visible light transmittance.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a reversible thermosensitive recording medium capable of displaying and erasing a visible image by heat or light.

[0002]

2. Description of the Related Art As a reversible thermosensitive recording medium capable of displaying or erasing a visible image and rewriting the image, an organic low molecular compound which reversibly changes transparency by adjusting heating temperature and cooling rate after heating. It is known to use a reversible thermosensitive recording material dispersed in a resin matrix.

In the reversible thermosensitive recording material described in JP-A-63-41186, a predetermined organic low molecular weight compound is mixed in a suitable resin base material such as vinyl chloride-vinyl acetate copolymer in a dispersed state. However, a transparent / white turbid contrast is generated in a large number of dots or divided areas depending on the processing temperature, and this is reflected by a light reflection layer such as an aluminum vapor deposition layer to display an image that is easy to see with good contrast.

In addition, the color tone is reversibly changed by adjusting the heating temperature and the cooling rate after heating.
A reversible thermosensitive recording material using an electron-donating color-forming compound (so-called leuco dye), which has a lactone ring in its molecular structure and changes color by opening the lactone ring by electron emission, is known. There is.

For example, a reversible thermosensitive recording medium containing a resin base material, a leuco dye, and an acid / base compound as a color-developing agent is disclosed in JP-A-2-188293 and JP-A2-1.
As described in JP-A-88294, these are ones in which coloring and decoloring are repeated by utilizing the difference in reaction rate between acid and base.

Further, JP-A-5-124360 and JP-A-6-210954 disclose that a resin base material, a leuco dye, and an electron-accepting compound having a long-chain alkyl group as a developer are used as components. A reversible thermosensitive recording medium is disclosed. This is because the developer itself has a cohesive force due to its long-chain alkyl structure, and by repeating contact and separation with the leuco dye, coloring and erasing are repeated.

Reversible thermosensitive recording media such as cards, labels and films using these reversible thermosensitive recording materials may record images such as characters and pictures with a thermal head capable of heating control in dot units. In many cases, when a thermal head is directly contacted with the surface of a reversible thermosensitive recording medium to repeatedly rewrite a visible image, not only the deterioration of the material constituting the recording medium due to heat progresses but also pressure, shearing force, scratches, etc. The durability is impaired by the addition of physical deterioration effects such as force.

In order to prevent physical deterioration due to contact of the thermal head, a non-contact visible image forming method using a laser beam is effective, and among them, a visible image rewritable by a semiconductor laser is downsized. And cost reduction is possible.

In addition, since an expensive information rewriting card equipped with an IC chip can usually rewrite a visible image less than the number of times the IC chip can be repeatedly rewritten, the life of the card is extended as much as possible. For this purpose, a non-contact visible image forming method using a laser beam is effective.

When an image is rewritten by using a semiconductor laser, it is necessary to efficiently perform photothermal conversion in order to realize downsizing and low output of the device. An infrared absorbing dye such as a cyanine dye having an absorption peak is used, and this is added to the reversible thermosensitive recording layer or a layer adjacent thereto.

[0011]

However, when a layer to which an infrared absorbing dye is added is provided in the reversible thermosensitive recording layer or in a layer adjacent to the reversible thermosensitive recording layer and rewriting is performed with a semiconductor laser, rewriting can be repeated without contact. , The durability is good, but the infrared absorbing dye is deteriorated by the ultraviolet rays exposed during use,
There are problems that the durability period of actual use as a card or label is shortened, and that it cannot withstand outdoor use for a long time.

The cause of this problem is that the infrared absorbing dye has a weaker weather resistance than the recording layer, so that even if the deterioration of the recording layer is not particularly remarkable, the infrared absorbing dye may be added earlier than that. The inventors of the present application have considered that the cause may be that the function is deteriorated under the influence of ultraviolet rays.

Further, although inorganic pigments such as carbon black have good weather resistance, the contrast of the image is lowered due to the opacity, and the color tone of the infrared absorber causes restrictions on the design of cards and the like.

Therefore, an object of the invention according to each claim of the present application is to solve the above-mentioned problems and to provide a reversible thermosensitive recording medium using a material containing an infrared absorbing dye, such as a reversible recording card or a label. Design constraints (color balance imbalance)
Or the contrast is not reduced, the color selection of the infrared absorbing dye is not restricted, the transparency is high, the printing sensitivity is sufficient with a semiconductor laser, and it is exposed to ultraviolet rays outdoors. The reversible recording medium has weather resistance and storage stability that can sufficiently withstand the above.

In addition, as another problem in the invention according to each claim of the present application, in the case of irradiating a laser beam to rewrite an image or in the case of heating for secondary processing,
It is to provide a reversible thermosensitive recording medium in which destruction or deformation such as delamination does not occur in the laminated structure.

[0016]

In order to solve the above problems, according to the present invention, a laminate having a recording layer capable of displaying and erasing a visible image by reversibly changing the transparency or the color developability according to temperature. In the reversible thermosensitive recording medium consisting of, the recording layer, a photothermal conversion layer containing an infrared absorbing dye and an ultraviolet absorbing layer are provided in this order, and these recording layer, the photothermal converting layer and the ultraviolet absorbing layer are crosslinked. The reversible thermosensitive recording medium is characterized by comprising a resin having a structure.

In the reversible recording medium of the present invention having the above-described structure, by irradiating a laser beam or the like from the outermost layer direction, the photothermal conversion layer is caused to generate heat so that a required amount of heat is conducted to the recording layer. This allows the image record to be printed and erased.

In the reversible thermosensitive recording medium, since the ultraviolet absorbing layer is provided on the photothermal converting layer containing the infrared absorbing dye, the ultraviolet rays of the natural light entering the recording medium are converted into the photothermal converting layer. UV light does not reach the layer containing the infrared-absorbing dye before it is reached.

In the reversible thermosensitive recording medium described above, the reversible thermosensitive recording layer is an ultraviolet absorbing layer having an average transmittance of 10% or less in the wavelength range of 300 nm to 360 nm and having visible light transmittance. It may be a recording medium.

Due to the property of absorbing the ultraviolet rays of the ultraviolet absorbing layer as described above, the infrared absorbing dye is surely prevented from being deteriorated by the ultraviolet rays and becomes a reversible thermosensitive recording medium having further excellent weather resistance.

The reversible thermosensitive recording medium is preferably the above-mentioned reversible thermosensitive recording medium in which the ultraviolet absorbing layer is an ultraviolet absorbing layer made of a polymer copolymer of a monomer having an ultraviolet absorbing molecular structure and a polymerizable monomer. Compared to the one containing a low-molecular type UV absorber, the high-molecular-weight copolymer containing a monomer having an UV-absorbing molecular structure as the polymerization component has better thermal stability and UV-absorption performance stability. Bleed of the ultraviolet absorber can be suppressed, and a reversible recording medium free from delamination or change with time can be obtained as compared with the above, and thus more excellent effects can be obtained. Further, since it has a higher ultraviolet absorbing function than the low molecular type, the layer can be formed thin.

The reversible recording medium of the present invention constructed as described above can be applied as an infrared laser reversible recording medium for displaying and erasing a visible image by an infrared laser.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the invention relating to the reversible recording medium of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the reversible recording medium of the embodiment has a recording layer 2 provided on one surface of a substrate 1 made of a synthetic resin film, and a visible light transmitting material made of a material containing an infrared absorbing dye. Is a film-like reversible recording medium in which a light-to-heat conversion layer 3, a visible light-transmitting ultraviolet absorbing layer 7, and a visible light-transmitting protective layer 4 are sequentially laminated toward the outermost layer.

The resin base material used for the recording layer 2 is preferably a synthetic resin which is transparent and has a good film-forming property, such as polyvinyl chloride, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-
Vinyl acetate-acrylic acid copolymer, vinyl chloride-vinyl acetate-alcohol copolymer, other vinyl acetate compounds, vinyl chloride-based copolymer, polyvinylidene chloride, vinylidene chloride copolymer, polyester resin, polyurethane resin, acrylic Examples of the resin include resins, which can be used alone or in combination of two or more.

When a radiation-curable resin such as an electron beam or an ultraviolet ray is mixed with the above resin base material, the elastic modulus in the high temperature region is increased, and the durability against repeated use can be improved. As such a resin, for example, a polyfunctional acrylate monomer having excellent curability such as tetraethylene glycol diacrylate and trimethylolpropane triacrylate can be favorably used. In the case of ultraviolet curing, an appropriate amount of a photopolymerization initiator such as a benzoin-based, acetophenone-based, thioxanthone-based or peroxide-based photopolymerization initiator is added to effect curing polymerization.

The organic low molecular weight compound used when the recording layer is made of a recording material of a type whose transparency is changed is an aggregate having a diameter of about 0.1 to 2.0 μm in a high molecular resin base material. It is dispersed and melted or crystallized by heat treatment, and well-known organic low-molecular compounds such as fatty acid alkyl esters having 12 or more carbon atoms such as methyl stearate and ethyl stearate and other higher fatty acids can be adopted.

Such an organic low molecular weight compound may be a compound consisting of carboxylic acid, dicarboxylic acid, ketone, ether, alcohol, ester and its derivative, and one kind or a mixture of two or more kinds thereof may be used. Can also be used.

Well-known leuco dyes having a lactone ring portion in the molecular structure can be favorably used as the dye precursor used in the recording material of the type in which the color developability changes. For example, phthalide compounds such as crystal violet lactone, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3-diethylamino-6- Methyl-7-anilinofluorane, 3-diethylamino-
Fluoran compounds such as 6-methyl-7-xylidinofluorane can be mentioned.

Examples of the electron-accepting compound used in the leuco dye include the following compounds. Carbon number 6
Organic phosphoric acid compounds, aliphatic carboxylic acid compounds or phenol compounds having the above aliphatic groups. Preferred is a phenolic compound having one aliphatic group having 12 or more carbon atoms.

The thickness of the recording layer 2 varies depending on the type and color tone of the recording material used, the composition mixture ratio and the like, but it is 3 to 30 μm.
m is preferable, and more preferably 5 to 20 μm.
This is because if the thickness is thin, the contrast of the visible image cannot be obtained, and if it is thick, the temperature distribution of heat transfer in the layer thickness direction becomes large, which affects the printing and erasing speed of the image.

When the photothermal conversion layer 3 is provided as an adjacent layer in the recording layer 2, a resin base material used for the photothermal conversion layer 3 is preferably a transparent and good film-forming material, and is also excellent in heat resistance. It is more preferable that there is no degradability or yellowing. Examples thereof include polyester resin, polyurethane resin, acrylic resin and the like.

As the infrared absorbing dye to be added to the photothermal conversion layer 3, one having an absorption peak near the oscillation wavelength of the semiconductor laser light used is selected and adopted. Generally 70
Since a semiconductor laser of 0 to 900 nm is general-purpose,
Examples of infrared absorbing dyes include cyanine dyes, polymethine dyes, anthraquinone dyes, phthalocyanine dyes, and naphthalocyanine dyes having an absorption peak in the wavelength range.

In order to sufficiently obtain the effects of the present invention, it is preferable to selectively employ an infrared absorbing dye having good chemical stability such as weather resistance and heat resistance.

The thickness of the photothermal conversion layer 3 may be changed according to the type of resin base material used and the addition amount of the dye, but it is usually preferably 0.1 to 10 μm, and 0.5 to 5 μm.
Is more preferable. If the thickness is thin, a sufficient amount of heat generation cannot be obtained, and if it is thick, the contrast of the recording layer is lowered.

The following materials are suitable for the ultraviolet absorbing layer 7 used in the present invention.

That is, a material obtained by dissolving or dispersing a low molecular weight type ultraviolet absorber in a polymer resin to form a layer or coating a high molecular type ultraviolet absorber is a material for the ultraviolet absorbing layer.

Examples of the low molecular weight ultraviolet absorber include organic ultraviolet absorbers and inorganic ultraviolet absorbers.

The organic ultraviolet absorber is a compound having an ultraviolet absorbing ability in its molecular structure, specifically, 2, 4
-Dihydroxybenzophenone, 2-hydroxy-4-
Methoxybenzophenone, 2,2'-dihydroxy-4
-Benzophenone-based, such as methoxybenzophenone, 2
-(2'-hydroxy-5-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) benzotriazole and other benzotriazoles, hindered amines, triazines, Examples thereof include benzoate compounds. These ultraviolet absorbers may be used alone or in combination of two or more.

Examples of the inorganic ultraviolet absorber include pigments having absorption in the ultraviolet region such as titanium oxide, zinc oxide, tin oxide, silica and alumina. Among these, those having no absorption in the visible light region are more preferable. These ultraviolet absorbers may be used alone or in combination of two or more.

Further, as the polymer resin forming the ultraviolet absorbing layer, those which are transparent and have a good film forming property are preferable, and those which are excellent in heat resistance and have no decomposability or yellowing are preferable. Examples thereof include polyester resin, polyurethane resin, acrylic resin and the like.

The content of the ultraviolet absorber in the polymer resin is
UV absorber 5 to 50 per 100 parts by weight of polymer resin
Parts by weight are preferred. This is because if the amount is too small, it is difficult to obtain sufficient weather resistance, and if the amount is too large, bleeding or brittleness occurs and the adhesiveness, durability, etc. are affected.

As the polymer type ultraviolet absorber, a polymer copolymer having a structure showing an ultraviolet absorbing function in the polymer structure can be used.

Specifically, a monomer having an ultraviolet absorbing molecular structure such as benzotriazole or benzophenone having a reactive unsaturated ethylene group in the molecular structure is co-polymerized with a polymerizable monomer such as methyl methacrylate, styrene or ethylene. Polymerized high molecular weight copolymers can be applied, and monomers having an ultraviolet absorbing molecular structure such as benzotriazole and benzophenone having a hydroxyethyl group in the molecular structure can be used together with monomers such as isocyanate, carboxylic acid and carboxylic acid ester. Examples thereof include high-molecular copolymers that have been added and polycondensed.

The following compounds may be mentioned as specific examples of the above-mentioned monomer having an ultraviolet absorbing molecular structure. Benzophenones such as 2-hydroxy-4-methacryloxybenzophenone, 2-hydroxy-4-acryloxybenzophenone, 2-hydroxy-4- (2-methacryloxy) ethoxybenzophenone, 2-hydroxy-4- (2-acryloxy) ethoxybenzophenone Compounds, 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole, 2-
(2'-Hydroxy-5'-acryloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methacryloxypropylphenyl) -2H
-Benzotriazole, 2- (2'-hydroxy-5 '
Examples thereof include benzotriazole-based compounds such as -acryloxypropylphenyl) -2H-benzotriazole.

These monomers may be a single component or a plurality of components, and may be a copolymer with a reactive monomer having other functionality such as reactive HALS (hindered amine light stabilizer).

Further, these polymer type ultraviolet absorbers are
They may be used alone or as a mixture of two or more kinds, or may be used as a mixture with a low molecular weight ultraviolet absorber.

The polymer type ultraviolet absorber is characterized in that it is superior in thermal stability and ultraviolet ray absorption performance stability as compared with the low molecular type ultraviolet absorber, and further has a characteristic that the bleed of the ultraviolet absorber is higher than that of the low molecular type ultraviolet absorber. Since a reversible recording medium can be obtained and the reversible recording medium can be obtained without delamination or change over time, the present invention has more excellent effects. Moreover, since the ultraviolet absorbing function is higher than that of the low molecular type, the layer can be formed thin.

The proportion of the structure having an ultraviolet absorbing function in the polymer structure is preferably about 5 to 60% by weight. With a small amount less than such a range, sufficient weather resistance cannot be obtained,
If a large amount is blended beyond the above range, the polymer film-forming property and strength will be insufficient.

The thickness of the ultraviolet absorbing layer is about 1 to 30 μm, preferably 2 to 20 μm. This is because if the thickness is thin, the effect of absorbing ultraviolet rays cannot be sufficiently obtained, and if it is thick, problems such as delamination of layers and deterioration of contrast of recording material are likely to occur.

In the ultraviolet absorbing layer, a wavelength of 300 is used.
The average transmittance in the range of nm to 360 nm is preferably 10% or less. This makes it possible to sufficiently prevent the infrared absorbing dye itself from deteriorating and decomposing, and avoiding the sensitivity deterioration and disappearance of the printing and erasability by the infrared laser at the practical use level.

The above-mentioned recording layer, photothermal conversion layer and ultraviolet absorbing layer are formed of a resin having a crosslinked structure.

The resin having a crosslinked structure in the present invention is not limited to a thermosetting resin, but a thermoplastic resin may be blended with a suitable crosslinking agent to react, and a part of the thermoplastic resin or This is a concept including a cross-linked one as a whole.

For example, when utilizing a thermal crosslinking reaction using an isocyanate compound as a crosslinking agent, it is necessary that the molecular structure of the resin has a functional group such as a hydroxyl group or a carboxyl group. By crosslinking, the elastic modulus of the resin at high temperature is improved, and thermal deformation of the layer is suppressed.

By the way, in the case of uncrosslinked, the recording layer, the photothermal conversion layer and the ultraviolet absorbing layer are softened or melted by the instantaneous heating during laser printing, and at that time, each layer of the reversible recording medium is distorted. , As a result, cracks occur,
Destruction and deformation occur.

Therefore, when the photothermal conversion layer 3 is heated by the irradiation of the infrared laser and the heat is conducted to the recording layer 2 and the ultraviolet absorbing layer 7 which are vertically adjacent to each other, both layers are heated at a high temperature. It is considered that if the elastic moduli are too different, deterioration or distortion is likely to occur and physical deterioration such as peeling or crushing is likely to occur when a thermal history is repeatedly given.

Further, it is considered that the photothermal conversion layer 3 itself also plays a role of firmly connecting the recording layer 2 and the ultraviolet absorbing layer 7, and the difference in elastic modulus at a high temperature causes distortion to easily cause a problem such as peeling.

However, when the resin is three-dimensionally cured by thermal crosslinking or the like, the elastic modulus in a high temperature state is improved and the thermal deformation of the adjacent recording layer 2, photothermal conversion layer 3 and ultraviolet absorbing layer 7 is suppressed. , Destruction and deformation of each layer are reduced even by instantaneous heating during laser printing without causing delamination, and excellent repetitive durability for rewriting. Also, reversible heat-sensitive recording in secondary processing by heating press. Problems such as delamination of the medium itself are eliminated.

Further, by mixing the resin having no functional group with the resin having a functional group, flexibility, laminating property, adhesiveness and the like can be adjusted.

In the case of utilizing a thermal crosslinking reaction using an isocyanate compound as a crosslinking agent, specific examples of the isocyanate compound include polyisocyanate compounds having a large number of isocyanate groups, such as hexamethylene diisocyanate, toluene diisocyanate, xylylene diisocyanate and these. Examples thereof include an adduct type, a burette type or a trimer type of a polyisocyanate compound using trimethylolpropane.

Further, a visible light transmitting protective layer 4 can be provided on the ultraviolet absorbing layer 7. As a material for forming the protective layer 4, a material excellent in scratch resistance, stain resistance and the like is preferable in consideration of contact with the outside. Specific examples include polyethylene terephthalate, polyether imide, polyether ketone, polyether ether ketone, polysulfone, polyphenylene sulfide, polyacrylate, polyether sulfone, polycarbonate, polyethylene naphthalate, polyimide, acrylic resin, but ultraviolet light. The use of curable resins or electron beam curable resins is preferred.

The ultraviolet curable resin or electron beam curable resin is
It is possible to use a mixture in which various acrylate monomers, other additives, etc. are appropriately mixed with a main component composed of an oligomer such as urethane acrylate and epoxy acrylate, and handling property, workability, curability and the like are adjusted. The ultraviolet curable resin is polymerized and cured by adding an appropriate amount of a photopolymerization initiator such as a benzoin-based, acetophenone-based, thioxanthone-based or peroxide-based photopolymerization initiator.

The thickness of the protective layer 4 varies depending on the type of resin material used and the like, but is preferably 0.5 to 20 μm,
More preferably, it is 2 to 10 μm. If the thickness is thin, a sufficient protective effect cannot be obtained, and if it is thick, the contrast of the recording layer is lowered.

In the case of a recording material of a type whose transparency changes, as shown in FIG.
Is preferably provided between the recording layer 2 and the recording layer 2, or a light reflection layer is provided on the surface of the substrate 1 opposite to the recording layer 2 to improve the visibility of the image.

The light-reflecting layer is composed of, for example, an adhesive layer of a vapor-deposited foil such as aluminum or tin, or a coating layer or vapor-deposited film of a light-reflecting paint mixed with aluminum powder. From the viewpoints of color, gloss, cost, and versatility, it is particularly preferable to use an aluminum vapor deposition film. As a method for forming the metal vapor deposition layer, a well-known method such as a vacuum vapor deposition method, sputtering, ion plating, or electron beam vapor deposition method can be selectively adopted.

As the base material 1, a film made of a known synthetic resin can be used. The reversible recording medium can be appropriately selected in consideration of handleability in finishing the card, label, etc. by secondary processing, heat resistance, heat shrinkability, deformation resistance, versatility, cost, and the like.

When the above-mentioned five-light reflecting layer is provided on the surface opposite to the recording layer, visible light transmittance is also required. Specifically, polyester films such as polyethylene terephthalate can be used because of their superior performance.

An adhesive layer or an adhesive layer is provided on the outermost surface of the base material 1 in order to facilitate the secondary processing of the recording medium, that is, the workability of attaching it to another support such as a card or a label. be able to. These are laminated with a known adhesive or pressure-sensitive adhesive depending on the type of adherend, the means of adhesion, the use, the purpose and the like.

For example, a vinyl chloride-vinyl acetate-acrylic acid copolymer, acrylic resin, polyester resin, urethane resin, or other adhesive or pressure-sensitive adhesive is coated,
Alternatively, a double-sided tape or the like may be attached. In the case of a double-sided tape, one having a support such as a non-woven fabric in the adhesive layer can be used. In the case of an adhesive material, a separator can be further laminated to maintain the product form up to secondary processing.

As shown in FIG. 2, the reversible recording medium of the second embodiment is a reversible recording medium (transfer film) capable of transferring.
However, it does not have a base material.

In the transfer film, a protective layer 4 corresponding to the outermost layer after transfer is provided on a peeling base material 5, and an ultraviolet absorbing layer 7 is provided thereon. Further, a photothermal conversion layer 3 is provided thereon, a recording layer 2 made of a recording material is provided thereon, and an adhesive layer 6 is formed as the outermost layer.

The peeling substrate 5 is in the form of a sheet such as a peelable film or paper, and is made of a material that is required to have physical properties such that it is bendable, tough and not easily broken so that it can be easily peeled off and peeled. To use a plastic film material, the base material is mixed with an appropriate amount of a plasticizer or a reinforcing agent so that the required mechanical properties can be obtained. Further, a releasable resin such as a silicone resin or a fluororesin may be further provided at the interface with the protective layer 4 to improve the releasability.

The adhesive layer 6 is made of a thermoplastic resin having a good thermal adhesive property, and it is preferable to adopt, for example, a polyester resin. Further, in order to improve the thermal adhesiveness, it is also preferable to employ a thermal adhesive resin in which an isocyanate compound or a derivative thereof is blended as a crosslinking agent or a resin having a carboxyl group.

Further, in the reversible recording medium of the second embodiment, a light reflecting layer may be provided between the recording layer 2 and the adhesive layer 6 in order to improve the visibility of the image.

Using the transfer film described above, a card,
In order to form a recording display portion by laminating and integrating a main portion on an arbitrary base material such as a label, the adhesive layer 6 is thermocompression-bonded to the base material surface, and then the peeling base material 5 is peeled off. Thereby, at least the adhesive layer 6, the recording layer 2, the photothermal conversion layer 3, the ultraviolet absorbing layer 7, and the protective layer 4 (main part of the reversible recording medium) can be easily adhered and fixed to the surface of an arbitrary substrate. it can.

3 to 5 show an example of the structure of a card, a label or the like when secondary processing is performed using a reversible recording medium or a transfer sheet. Reference numeral 10 in FIG. 3 is a transferred reversible recording medium, reference numeral 20 is a base material of a card or label, and reference numeral 30 is a magnetic tape.

Reference numeral 40 in FIG. 4 is a contact type IC chip, reference numeral 50 in FIG. 5 is a non-contact type IC chip, and reference numeral 60 is an antenna coil.

[0078]

Examples and Comparative Examples [Example 1] Polyethylene terephthalate resin (PET) film substrate (25 μm thick)
Aluminum was vapor-deposited on the surface of the above through an adhesive, and the following reversible recording material was dissolved in tetrahydrofuran and applied thereon, and dried by heating at 110 ° C. for 5 minutes.
/ Cm × 10m / min, UV irradiation, layer thickness 10μm
Then, a recording layer was formed with the following composition.

<Recording Layer> Vinyl Chloride-Vinyl Acetate-Acrylic Acid Copolymer 100 parts by weight (Nissin Chemical Co., Ltd .: Solvain MF) tetraethylene glycol diacrylate 50 parts by weight Photopolymerization initiator (Ciba Geigy: Irgacure 184) ) 2 parts by weight polyester plasticizer (P-29 manufactured by DIC) 25 parts by weight stearyl behenate 40 parts by weight dodecane diacid 8 parts by weight Next, a coating composition for the light-heat conversion layer having the following composition on the formed recording layer. And heat-dry at 130 ° C for 5 minutes to obtain a layer thickness of 1
A μm photothermal conversion layer was formed.

<Photothermal conversion layer> Polyester urethane 257 parts by weight (Toyobo: Byron UR-8200: solid content 30 wt%) Isocyanate compound 21 parts by weight (Nippon Polyurethane Co .: Coronate L: solid content 75% by weight) Phthalocyanine dye ( Yamamoto Kasei Co., Ltd .: D99-038) 7 parts by weight Methyl isobutyl ketone 170 parts by weight Toluene 170 parts by weight Next, a coating material for the ultraviolet absorbing layer having the following composition is applied on the photothermal conversion layer and heated and dried at 130 ° C. for 5 minutes. And thickness 5 μm
The ultraviolet absorption layer of was prepared.

[0081]   <Ultraviolet absorption layer> Acrylic resin 100 parts by weight (Mitsubishi Rayon: LR-1503: solid content 50% by weight) Benzotriazole UV absorber 20 parts by weight (Ciba Geigy: Chinubin 234) Isocyanate compound 9 parts by weight (Nippon Polyurethane Co .: Coronate L: Solid content 75% by weight) Toluene 200 parts by weight

<Protective Layer> Next, the formed photothermal conversion layer is coated with a protective layer made of an epoxy acrylate type ultraviolet curing resin, and 160 W / cm × 10 m / mi.
The film was irradiated with ultraviolet rays at n to obtain a film having a protective layer with a layer thickness of 5 μm.

Further, up to the protective layer, a transparent polyethylene terephthalate resin (PET) film substrate (10
(0 μm thickness) was similarly applied in sequence to obtain a sample for transmittance measurement.

Further, the following coating material was applied to the opposite side of the polyethylene terephthalate resin (PET) film substrate (thickness of 25 μm) from the above treatment, and dried by heating at 130 ° C. for 5 minutes to form an adhesive layer having a thickness of 4 μm. Formed.

<Adhesive Layer> Vinyl Chloride-Vinyl Acetate-Acrylic Acid Copolymer 100 parts by weight (Nisshin Chemical Co., Ltd .: Solvain MF) methyl isobutyl ketone 250 parts by weight Toluene 250 parts by weight Obtained as above. A film made of a reversible recording material is overlaid on a sheet substrate made of polyvinyl chloride, a press temperature of 140 ° C., a press time of 20 minutes, and a press pressure of 20 k.
The card type reversible recording medium was prepared by adhering with a heat and pressure treatment of g / cm 2 and punching on a card.

The card-type reversible recording medium thus obtained was evaluated as follows, and the results are shown in Table 1.

(1) Printing / erasing characteristics: 800 n from the upper surface of the protective layer of the card type reversible recording medium
The laser output is gradually increased every 0% to 2% by irradiating a semiconductor laser with an oscillation wavelength of m, and the initial setting condition is 100%. The printing characteristics and erasing characteristics of the card are investigated, and the laser sensitivity is evaluated. did.

Evaluation was carried out using a Macbeth reflection densitometer (RD-918).
In step S), the density is measured, and the output value at which 110% or less of the minimum density of the recording medium in the present embodiment, which is measured in advance, starts to be the print output (%), and the maximum density is 95% or more. The output value at which the start of the output appears was evaluated as the erase output (%).

(2) 160 W / cm × 10 m / m of weather resistant card type reversible recording medium
After 30 passes of UV irradiation in in and leave for a long time,
A laser writing test was performed with the print output and the erase output obtained in (1). The results are shown in Table 1 together with the result of ∘ when printing and erasing were possible as in the case of blank, and as x when printing and erasing were impossible.

Separately, an ultraviolet ray fade meter (manufactured by Gas Testing Machine Co., Ltd.) was used to irradiate the ultraviolet rays for 8 hours and 24 hours, and after leaving it for a while, a laser writing test was performed with the print output and erase output obtained in (1). went. The results are shown in Table 1 together with the result of ∘ when printing and erasing were possible as in the case of blank, and as x when printing and erasing were impossible.

(3) Transmittance measurement Separately, an ultraviolet absorbing layer was coated on transparent PET, the transmittance at each wavelength of 10 nm between 300 nm and 360 nm was measured by a spectrophotometer, and the average value was averaged. And rate.

(4) Durability Under the conditions of printing output and erasing output obtained in (1), printing and erasing were repeated alternately at intervals of 1 minute, and laser repeating durability was evaluated. After repeating 1000 times,
The physical deterioration such as scratches and cracks was visually confirmed, and if the degree was good, it was marked with a circle, and if it was poor, it was marked with a mark.

(5) Peelability A peeling test was conducted on the card-type reversible recording medium, which had been adhered by the heat and pressure treatment by the above-mentioned press, by the cross-cut tape peeling method from above the visible image forming portion. When there was no peeling in each layer and there was no problem, the circles were marked, and when peeling was seen in any of the layers, the mark was marked.
It was also written inside.

Further, based on the above evaluations (1) to (5), a comprehensive evaluation (three-step evaluation of yes / no / good) is carried out,
The results are also shown in Table 1.

Example 2 The same procedure as in Example 1 was carried out except that the composition of the ultraviolet absorbing layer was changed as follows, and the results of the same evaluations are also shown in Table 1.

[0096]   <Ultraviolet absorption layer> Polymeric benzotriazole type UV absorber 100 parts by weight (Nippon Shokubai: UV-G714) Isocyanate compound 3 parts by weight (Sumitomo Bayer Urethane Co., Ltd .: Sumijour N3200) Methyl ethyl ketone 300 parts by weight

[Example 3] The same procedure as in Example 2 was carried out except that the composition and forming method of the recording layer 2 were changed as follows.

The following reversible recording material compositions were dispersed for 2 hours using a paint shaker.

<Dispersion> Dye precursor: Crystal violet lactone 10 parts by weight Electron-accepting compound: Hydroxyphenylpropiono-behenyl hydrazide 20 parts by weight Resin base material: Acrylic polyol (Mitsubishi Rayon: LR-1503) 50 parts by weight Solvent: Toluene: 150 parts by weight of the recording material composition was dispersed in the recording material composition, and the following curing agents were added and well stirred to prepare a coating liquid.

<Curing Agent> Isocyanate compound (manufactured by Nippon Polyurethane Company: Coronate L: solid content 75 wt%) 5 parts by weight Prepared on the surface of a transparent polyethylene terephthalate resin (PET) film substrate (25 μm thick) as described above After applying the above coating liquid and drying at 130 ° C. for 5 minutes, 60
Aging was performed at 16 ° C. for 16 hours to form a recording layer having a layer thickness of 10 μm.

Comparative Example 1 The recording layer was made to have the following composition and U
The same procedure as in Example 2 was performed except that V irradiation was not performed.

[0102]   <Recording layer> Vinyl chloride-vinyl acetate-acrylic acid copolymer 100 parts by weight (Nissin Chemical Co., Ltd .: Solvain MF) Polyester plasticizer (DIC: P-29) 25 parts by weight Stearyl behenate 40 parts by weight Dodecane diacid 8 parts by weight

[Comparative Example 2] The same procedure as in Example 2 was carried out except that the photothermal conversion layer had the following composition.

[0104]   <Photothermal conversion layer> Polyester urethane 257 parts by weight (Toyobo: Byron UR-8200: Solid content 30 wt%) Phthalocyanine dye (Yamamoto Kasei: D99-038) 7 parts by weight Methyl isobutyl ketone 170 parts by weight 170 parts by weight of toluene

[Comparative Example 3]

The same procedure as in Example 2 was carried out except that the ultraviolet absorbing layer had the following composition. <Ultraviolet Absorbing Layer> Polymeric benzotriazole ultraviolet absorber 100 parts by weight (Nippon Shokubai: UV-G714) methyl ethyl ketone 300 parts by weight

[Comparative Example 4] The same procedure as in Example 1 was carried out except that the ultraviolet absorbing layer was omitted from Example 1 and the protective layer was coated on the photothermal conversion layer. In addition, the transparent PE
The measured value of T is shown.

[0108]

[Table 1]

In Comparative Examples 1 to 4, physical deterioration was confirmed in repeated durability, and peeling was observed in the secondary processing by hot pressing.

On the other hand, in Examples 1 to 3, there was no physical deterioration in durability, and the visually printed images were good.
Further, it was confirmed that each layer was not peeled off even in the secondary processing by the hot press, and the secondary processing suitability was excellent. It is considered that this is because the strain was reduced by reducing the difference in elastic modulus between the three layers of the recording layer, the photothermal conversion layer, and the ultraviolet absorbing layer at high temperature.

In Comparative Example 4, when irradiation with ultraviolet rays was performed in the light resistance test, printing and erasing could not be performed under the initial laser output conditions, and visual observation revealed that the color tone peculiar to the infrared absorbing dye was lost. It was being appreciated. Further, when the reversible recording medium after the test and the reversible recording medium before the test were evaluated for static temperature characteristics by contact with a heating stamp controlled at each temperature, no difference was found in the static recording characteristics between the two. It was Further, it was confirmed from the transmittance measurement data of the sample having the same composition formed on the transparent film that the absorption peak peculiar to the infrared absorbing dye was lowered by the irradiation of ultraviolet rays.

From these facts, by irradiation of ultraviolet rays,
It could be assumed that the cause was that the infrared absorbing dye itself deteriorated and decomposed, and the photothermal conversion function of the infrared laser deteriorated.

On the other hand, in the examples, it was found that the print could be erased even after the irradiation of the ultraviolet rays, and the deterioration and decomposition of the infrared absorbing dye by the ultraviolet rays could be prevented. Further, there was no difference in contrast, resolution, etc. of the printed image as compared with the comparative example having no ultraviolet absorbing layer, and there was no problem of visibility.

Compared with Example 1 in which a low molecular type ultraviolet absorber was contained in the resin base material, Example 2 using a high molecular type ultraviolet absorber was able to endure a longer-term weather resistance test. Therefore, it can be used predominantly in the present invention.

[0115]

As described above, the present invention is a reversible thermosensitive recording medium in which an ultraviolet absorbing layer is provided on a layer containing an infrared absorbing dye, so that the contrast decreases even when used for a long period of time. In addition, there is no restriction on color selection of the infrared absorbing dye, and there is no restriction on the design of a reversible recording card or label using a reversible thermosensitive recording medium.

The reversible thermosensitive recording medium of the present invention comprises
When a semiconductor laser is used for erasing a print, there is an advantage that it is applied to a semiconductor laser having good transparency, sufficient printing sensitivity, and weather resistance enough to withstand outdoor use.

Further, the reversible thermosensitive recording medium of the present invention comprises
Since the recording layer, the photothermal conversion layer and the ultraviolet absorbing layer are made of a resin having a crosslinked structure, when the laser beam is applied to rewrite the image or when the secondary processing is performed by heating, the laminated structure may be damaged such as delamination or the like. There is an advantage that the deformation does not occur.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment showing a reversible thermosensitive recording medium.

FIG. 2 is a sectional view of a second embodiment showing a transfer film.

FIG. 3 is a sectional view showing an embodiment of a card or label using a reversible thermosensitive recording medium.

FIG. 4 is a sectional view showing an embodiment of a card or label using a reversible thermosensitive recording medium.

FIG. 5 is a sectional view showing an embodiment of a card or label using a reversible thermosensitive recording medium.

[Explanation of symbols]

1 base material 2 recording layers 3 Photothermal conversion layer 4 protective layer 5 Peeling substrate 6 Adhesive layer 7 UV absorbing layer 10 Reversible recording medium 20 Base material 30 magnetic tape 40 Contact IC chip 50 Non-contact type IC chip 60 antenna coil

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme coat (reference) B41M 5/18 QF term (reference) 2C005 HA05 HA10 JC02 KA23 LB07 2H026 AA07 AA09 AA24 BB01 CC10 DD05 DD42 DD46 FF01 FF11 FF22 2H111 HA07 HA14 HA23 HA34

Claims (4)

[Claims] 1. A reversible thermosensitive recording medium comprising a laminated body having a recording layer capable of displaying and erasing a visible image by reversibly changing transparency or color developability according to temperature. A reversible thermosensitive recording medium characterized in that a photothermal conversion layer containing an absorbing dye and an ultraviolet absorbing layer are provided in this order, and the recording layer, the photothermal converting layer and the ultraviolet absorbing layer are made of a resin having a crosslinked structure. 2. The ultraviolet absorbing layer has a wavelength of 300 nm to 36 nm.
The reversible thermosensitive recording medium according to claim 1, which is an ultraviolet absorbing layer having an average transmittance of 10% or less in a range of 0 nm and having visible light transmittance. 3. The reversible thermosensitive recording medium according to claim 1, wherein the ultraviolet absorbing layer is an ultraviolet absorbing layer made of a polymer copolymer of a monomer having an ultraviolet absorbing molecular structure and a polymerizable monomer. 4. The reversible thermosensitive recording medium according to claim 1, wherein the reversible recording medium is a reversible recording medium for an infrared laser that displays and erases a visible image with an infrared laser.