JP2003118235A - Reversible heat-sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible heat-sensitive recording medium which has excellent light resistance, coating liquid dispersibility, and excellent durability without occurrence of a dent on the medium even by repeatedly using. SOLUTION: The reversible heat-sensitive recording medium comprises a reversible heat-sensitive recording layer containing at least an electron donative colorational compound and an electron acceptive compound, color developed by heating to a color generating temperature, and achromatized by heating to an achromatizing temperature or heating to a color developing temperature or higher and gradually cooling in such a manner that at least one layer on the recording layer contains metal oxide composite particles obtained by complexing a metal oxide having an ultraviolet absorbing performance or an ultraviolet shielding performance with another metal oxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a reversible thermosensitive color-forming composition utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound and controlling a thermal energy to form a color image. The present invention relates to a reversible thermosensitive recording medium capable of forming and erasing data.

[0002]

2. Description of the Related Art Conventionally, electron-donating color-forming compounds (hereinafter referred to as
A heat-sensitive recording medium utilizing a color-forming reaction between a color former or a leuco dye) and an electron-accepting compound (hereinafter also referred to as a developer) is widely known, and with the progress of OA, a facsimile, a word processor, It has been widely used as an output paper for scientific measuring instruments, and recently as a magnetic heat sensitive card such as a prepaid card or a point card. However, due to environmental issues, these conventional recording media that have been put to practical use have been urged to be reviewed such as recycling and reduction of the usage amount. It cannot be used repeatedly, and new information is added to a portion where no image is recorded, and the area of the recordable portion is limited. Therefore, in reality, the amount of information to be recorded is reduced or the card is remade when the recording area is exhausted. Therefore, against the background of the problems of dust and deforestation, which have been actively discussed in recent years, it has been desired to develop a reversible thermosensitive recording medium that can be rewritten many times.

Due to these requirements, various reversible thermosensitive recording media have been proposed. For example, polymer type reversible thermosensitive recording media utilizing physical changes such as transparency and cloudiness are disclosed in JP-A-63-107584 and JP-A-4-7857.
It is disclosed in Japanese Patent Publication No. 3 and the like. Further, a dye type reversible thermosensitive recording medium utilizing a chemical change has also been newly proposed. Specifically, a combination of gallic acid and phloroglucinol is used as a color developer. JP-A-60-1936
No. 91, JP-A-61-2376 using compounds such as phenolphthalein and thymolphthalein as color developers.
No. 84, JP-A-62-138556, in which the recording layer contains a homogenous solution of a color former, a developer and a carboxylic acid ester.
JP-A-62-138568 and JP-A-62-140881, JP-A-63-173684 using an ascorbic acid derivative as a developer, and bis (hydroxyphenyl) acetic acid as a developer. Alternatively, a salt of gallic acid and a higher aliphatic amine is used.
Japanese Unexamined Patent Application Publication No. Hei 2-188294 and the like are disclosed.

Furthermore, the present inventors have previously proposed that Japanese Patent Laid-Open No. 5-12.
No. 4360, an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having a long-chain aliphatic hydrocarbon group is used as a color developing agent, and by combining this with a leuco dye which is a color developing agent, color development and decolorization. Can be easily carried out under heating and cooling conditions, the colored and decolored states can be stably maintained at room temperature, and the reversible thermosensitive coloring composition capable of repeating coloring and decoloring. And a reversible thermosensitive recording medium using the same as a recording layer. Further, thereafter, it has been proposed to use a phenol compound having a long chain aliphatic hydrocarbon group having a specific structure (described in JP-A-6-210954).

However, no matter how much such a reversible thermosensitive recording medium is proposed, if it is irradiated with light for a long period of time,
A tendency is observed to give a dark brown coloration which does not fade. It is considered that this is because the molecular structure of the leuco dye is changed by the irradiation of light to produce a non-reversible colored product. Therefore, in a heat-sensitive recording medium using a leuco dye, it is common to use an ultraviolet absorber so that ultraviolet rays, which are particularly problematic, do not reach the leuco dye directly.

For example, Japanese Patent Application Laid-Open No. 62-48585 discloses a method of providing an intermediate layer between a recording layer and a protective layer and adding an ultraviolet absorber therein. But,
The ultraviolet absorber used here has a molecular weight of about 20.
It is a low molecular weight UV absorber in the range of 0 to 400.
These cause problems such that the main component of the ultraviolet absorber migrates to the underlying recording layer with the passage of time or by repeating erasing and printing, thereby changing the coloring and decoloring characteristics of the recording layer. Further, it may be deposited on the surface of the protective layer to reduce the effect of absorbing ultraviolet rays, or may adhere to the thermal head to disturb the printed image, which may cause a serious problem. Further, the addition of the ultraviolet absorber lowers the film strength of the protective layer, which causes punching due to repeated erasing and printing, thus causing a serious problem in practical use.

Therefore, Japanese Patent Application Laid-Open No. 7-68937 discloses a method of adding microcapsules containing an ultraviolet absorber which is liquid at room temperature to the protective layer. This is done for the purpose of preventing the bleed-out of the ultraviolet absorber. However, in this case, since the liquid phase is mixed in the protective layer, the film strength is lowered, which causes serious problems in practical use such as punching due to repeated erasing and printing. At this time, if the microcapsules are damaged, the UV absorber diffuses inside or on the surface of the reversible thermosensitive recording medium, resulting in deterioration of coloring / decoloring characteristics or contamination of card users, thermal heads, etc. Will cause problems.

Therefore, Japanese Patent Laid-Open No. 8-224960,
JP-A-9-207437 discloses a method of adding a polymer having an ultraviolet absorbing structure to the protective layer. However, the heat resistance and durability required for the surface of the protective layer are strong, and a polymer that is not in a crosslinked state is not sufficient as compared with a resin that is in a crosslinked state such as an ultraviolet curable resin or a thermosetting resin. Even if the polymer is solidified with a resin in a crosslinked state, the layer has a sea-island structure, and after being used many times, it begins to collapse from the part of the polymer which is not crosslinked, and dents occur on the surface of the recording medium. I will end up. Then, there is a problem that the number of repetitions is practically limited to a small number due to defective erasing or defective printing.

Next, in JP-A-10-100541, etc., the intermediate layer or the protective layer has an ultraviolet shielding effect.
A method of adding a particular inorganic pigment is shown. The inorganic pigment protects against UV rays by its own UV absorption ability and UV scattering ability due to the controlled particle size. However, in order to exert the ultraviolet shielding effect with the inorganic pigment, it is necessary to add a large amount of very fine particles.
When the blending amount is large, the transparency is impaired, the surface activity due to microparticulation becomes extremely strong, which causes the catalytic action to change the properties of other blending components, and reacts with the dye to cause background fogging, and further secondary Dispersibility is extremely poor because aggregation easily occurs, pigment unevenness occurs in the coating film, and problems such as punching on the surface of the recording medium from the portion with few pigments when used many times Had.
From the above, it is the current situation that a reversible thermosensitive recording medium sufficient to satisfy both light resistance and durability at the same time has not been provided.

[0010]

SUMMARY OF THE INVENTION Therefore, in view of the above-mentioned prior art, an object of the present invention is excellent in light resistance, coating liquid dispersibility, and durability without causing hammering to a recording medium even after repeated use. An object is to provide a reversible thermosensitive recording medium having excellent properties.

[0011]

Means for Solving the Problems The above-mentioned problems can be solved by (1) "a support comprising at least an electron-donating color-forming compound and an electron-accepting compound, which is colored by heating to a coloring temperature and erased. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer that is erased by heating to a color temperature or heating to a coloring temperature or higher and then gradually cooling, at least one layer on the reversible thermosensitive recording layer is exposed to ultraviolet rays. (2) "Reversible thermosensitive recording medium containing metal oxide composite particles obtained by compounding a metal oxide having an absorbing property or an ultraviolet shielding property with another metal oxide", (2) Reversible according to the above (1), wherein the content of the metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance in the oxide composite particles is in the range of 5% or more and 60% or less. Sensitive recording medium ", 3) “The metal oxide having the ultraviolet absorbing ability or the ultraviolet shielding ability in the metal oxide composite particles is selected from the group consisting of cerium oxide, titanium oxide and zinc oxide. In the reversible thermosensitive recording medium according to the above (1) or (2), the average particle diameter of the metal oxide composite particles is 0.1 μm or more and 6.0 μm or less. The reversible thermosensitive recording medium according to any one of items (1) to (3) above, (5) "the metal oxide composite particles are on the thermosensitive recording layer. In at least one layer of at least 10% by weight based on the binder resin for said layer 200
The first (1), characterized in that it contains less than or equal to wt%
The reversible thermosensitive recording medium according to any one of the items 1 to 4 above, (6) "wherein the reversible thermosensitive recording layer contains a resin in a crosslinked state with an isocyanate compound. (1) The reversible thermosensitive recording medium according to any one of (1) to (5), (7) "A phenol compound having an alkyl chain having 8 or more carbon atoms is used as an electron-accepting compound. The reversible thermosensitive recording medium according to any one of the above items (1) to (6),
(8) "A reversible thermosensitive material according to any one of items (1) to (7), characterized in that a compound having an alkyl chain having 8 or more carbon atoms is used as a color-decoloration controlling agent. Recording medium ", (9)" At least one on the thermosensitive recording layer
The layer is a protective layer, and the protective layer contains an ultraviolet curable resin or a resin in a cross-linked state with an isocyanate compound, in any one of the above items (1) to (8). Reversible thermosensitive recording medium ", (10)
"The reversible thermosensitive recording medium has a thermoreversible recording unit and an information storage unit, and the reversible thermosensitive recording medium according to any one of the above items (1) to (9). ",
(11) "The reversible thermosensitive recording medium according to item (10), characterized in that the information storage section is a magnetic recording layer or an IC", (12) "the reversible thermosensitive recording medium is in the form of a card. Alternatively, the reversible thermosensitive recording medium according to any one of (1) to (11) above, which is processed into a sheet shape, and (13) "used in a roll shape. The reversible thermosensitive recording medium according to any one of the items (1) to (11) above, (14) "the reversible thermosensitive recording medium has a printed portion. The reversible thermosensitive recording medium according to any one of the items (1) to (13).

Further, the above-mentioned problem is to heat the reversible thermosensitive recording medium according to any one of (15) "(1) to (14) of the present invention to a temperature lower than the color formation start temperature. And (16) "A reversible recording medium processing apparatus characterized by erasing the color." (16) "Has an erasing apparatus provided on the reversible recording medium for erasing a colored image by heating. The heating portion is a heater selected from a thermal head, a ceramic heater, a planar heater, and a heat roller, which is achieved by the reversible recording medium processing apparatus described in the above item (15).

As a result of studies to solve the above-mentioned problems, the inventors of the present invention selected metal oxides having an ultraviolet absorbing property or an ultraviolet shielding property from other metal oxides having a low surface activity and good dispersion stability. It has been found that such an object can be achieved by compounding with, and the present invention has been completed. That is, the present invention is composed of at least an electron-donating color-forming compound and an electron-accepting compound on a support, and is colored by heating to a color-forming temperature, and is heated to a color-erasing temperature or is heated to a color-forming temperature or higher and gradually cooled. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer that is erased by applying a metal oxide having an ultraviolet absorbing property or an ultraviolet shielding property to at least one layer on the reversible thermosensitive recording layer, another metal is used. By containing metal oxide composite particles that are compounded with an oxide, it has excellent light resistance and coating liquid dispersibility, and has excellent durability that does not cause punching on the recording medium even after repeated use. It has been found that a reversible thermosensitive recording medium can be obtained. Further, the content of the metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance is in the range of 5% or more and 60% or less, and the metal oxide is composed of cerium oxide, titanium oxide and zinc oxide, thereby improving the light resistance. It was found that the purpose of was surely achieved. Further, the reversible thermosensitive recording layer contains a resin in a crosslinked state with an isocyanate compound, and the protective layer further contains an ultraviolet curable resin or a resin in a crosslinked state with an isocyanate compound, thereby ensuring the purpose of improving durability. I have found that it will be achieved.

The reversible thermosensitive recording medium of the present invention will be described in detail below. The present inventor has already found that the addition of the filler to the recording medium is effective in terms of repeated durability. So, if you use a filler that is effective in ultraviolet absorption performance or ultraviolet shielding performance,
We thought that it was effective not only in durability but also in light resistance. However, the filler is not effective in light resistance unless it is made into ultrafine particles. The ultrafine particle filler causes problems such as impairing transparency, causing deterioration of other compounding ingredients, and further causing punching and burrs due to secondary aggregation. Therefore, the present inventors have solved the problems so far by confining a metal oxide having an ultraviolet absorbing performance or an ultraviolet shielding performance into a metal oxide having no ultraviolet absorbing performance or an ultraviolet shielding performance to form a composite, It has been found that a reversible thermosensitive recording medium which is excellent in light resistance and coating liquid dispersibility and which is excellent in durability without being struck on the recording medium even when repeatedly used is obtained. The composite form of the metal oxide composite particles may be a metal oxide having an ultraviolet absorbing performance or an ultraviolet shielding performance deposited in the inner voids of a porous metal oxide having no ultraviolet absorbing performance or an ultraviolet shielding performance, Further, a metal oxide having no ultraviolet absorbing performance or ultraviolet shielding performance may be coated with a metal oxide having an ultraviolet absorbing performance or an ultraviolet shielding performance. That is, by impregnating a metal oxide having an ultraviolet absorbing ability or an ultraviolet shielding ability into a metal oxide having no ultraviolet absorbing ability or an ultraviolet shielding ability to form a composite, the transparency is impaired, or the deterioration of other compounding components is prevented. Invited,
Furthermore, it is possible to solve problems such as punching due to secondary aggregation. Cerium oxide, titanium oxide, zinc oxide and the like are preferably used as the metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance. In addition, the content ratio of the metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance is 5
% Or more and 60% or less, and more preferably 10% or more and 55% or less. If the content of the metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance is less than 5%, the effect on the ultraviolet rays is small, and if the content exceeds 60%, the metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance is converted into the ultraviolet absorbing performance or the ultraviolet radiation. The same problem as described above occurs that it becomes difficult to trap the metal oxide in the metal oxide having no shielding performance, the other components are deteriorated, and secondary agglomeration easily occurs. Further, as the metal oxide having no ultraviolet absorbing property or ultraviolet shielding property, silica, talc, mica and the like are preferably used. The content of the metal oxide composite particles in the layer is preferably 10% by weight or more and 200% by weight or less, more preferably 15% by weight, based on the binder resin of the layer to be included.
The above is 180% by weight. This is because if the content is less than 10% by weight, the effect on ultraviolet rays is small, and if it exceeds 200% by weight, the strength of the layer becomes brittle and burrs are easily generated. The average particle size of the metal oxide composite particles is 0.1 μm.
m or more and 6.0 μm or less, and more preferably 0.
It is 5 μm or more and 5.5 μm or less. Average particle size is 0.1μ
If it is less than m, problems such as impairing transparency, inducing alteration of other compounding components, and punching and burrs due to secondary aggregation occur. Further, if it exceeds 6.0 μm, there arises a problem that the coating film strength cannot be obtained. As the polymer of the recording layer used in the present invention, a polymer in a crosslinked state by an isocyanate compound is used. The polymer is
It has a group that reacts with a crosslinking agent, and contains, for example, a hydroxyl group, an amino group, a carboxyl group, and the like. Among them, a polymer having a hydroxyl group is preferably used, and the hydroxyl group having 10 or more is particularly preferably used. Hydroxyl value is 1
If it is less than 0, sufficient coating film strength cannot be obtained. Further, as the curing agent, those which cross-link with the resin are widely used, but isocyanate type curing agents are particularly preferably used. The amount of the curing agent added may be such that the durability of the recording medium is satisfied, and the number of active groups of the curing agent is 0.3 to 2.0 in molar ratio with respect to the number of hydroxyl groups of the polymer.
And the range of 0.8 to 1.5 is particularly preferably used. If the amount of the curing agent added is less than 0.3, the thermal strength will be insufficient and the durability will decrease. Further, if the addition amount of the curing agent exceeds 2.0, the influence on the coloring / decoloring characteristics becomes large, which is a problem.

The reversible thermosensitive recording medium of the present invention will be described in more detail below. As the resin in the cross-linked state used in the present invention, specifically, a cross-linking agent such as acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, phenoxy resin, polyvinyl butyral resin, cellulose acetate propionate, and cellulose acetate butyrate. Examples of the resin include a resin having a reactive group or a resin obtained by copolymerizing a monomer having a group reactive with a crosslinking agent and another monomer, but the present invention is not limited to these compounds. Further, a resin in which a benzotriazole-based ultraviolet absorbing skeleton or a siloxane bond skeleton is block-copolymerized or graft-copolymerized with the above-mentioned resins can be given.

An isocyanate type curing agent is preferably used as the curing agent used in the present invention. The isocyanate compound used here is selected from urethane modified products, allophanate modified products, isocyanurate modified products, burette modified products, carbodiimide modified products, and blocked isocyanate modified products of known isocyanate monomers. Further, as the isocyanate monomer forming the modified product, tolylene diisocyanate (TD
I), 4,4′-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI),
Naphthylene diisocyanate (NDI), paraphenylene diisocyanate (PPDI), tetramethylxylylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), lysine diisocyanate (LD)
I), isopropylidene bis (4-cyclohexyl isocyanate) (IPC), cyclohexyl diisocyanate (CHDI), tolidine diisocyanate (TOD
I) and the like, but the present invention is not limited to these compounds.

Further, a catalyst used in this type of reaction may be used as a crosslinking accelerator. Examples of the crosslinking accelerator include tertiary amines such as 1,4-diaza-bicyclo [2,2,2] octane and metal compounds such as organic tin compounds. Further, the whole amount of the curing agent added may or may not undergo a crosslinking reaction. That is, the unreacted curing agent may be present. Since this type of crosslinking reaction proceeds over time, the presence of an unreacted curing agent does not indicate that the crosslinking reaction has not progressed at all, but an unreacted curing agent is detected. This suggests that a resin in a crosslinked state is present. Further, as a method for distinguishing whether the polymer in the present invention is in a crosslinked state or a non-crosslinked state, it can be distinguished by immersing the coating film in a solvent having high solubility. That is, since the polymer in the non-crosslinked state is dissolved in the solvent and does not remain in the solute, the presence or absence of the polymer structure of the solute may be analyzed. Therefore, if the presence of the polymer structure in the solute cannot be confirmed, it can be said that the polymer is in a non-crosslinked state and can be distinguished from the polymer in the crosslinked state. When other layers are laminated, TEM (transmission electron microscope) or SEM
Confirm the layer structure and film thickness from cross-sectional photographs such as (scanning electron microscope). Then, remove all unrelated layers,
Expose the desired layer. The layer is then scraped off and measured according to the method described above.

Examples of leuco dyes used in the present invention are shown below, but the present invention is not limited thereto. Further, leuco dyes may be used alone or in combination. 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-di (n-butylamino) fluorane, 2-anilino-3-
Methyl-6- (Nn-propyl-N-methylamino)
Fluorane, 2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluorane, 2-anilino- 3-methyl-6-
(Nn-amyl-N-methylamino) fluorane, 2
-Anilino-3-methyl-6- (N-sec-butyl-
N-methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N-iso
-Amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-N -Methylamino) fluorane, 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluoran, 2- (M-Trichloromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trichloromethylanilino) ) -3-Methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2- (2,4-dimethylanilino) -3-methyl- - diethylaminofluoran,
2- (N-ethyl-p-toluidino) -3-methyl-6
-(N-ethylanilino) fluorane, 2- (N-ethyl-p-toluidino) -3-methyl-6- (N-propyl-p-toluidino) fluorane, 2-anilino-6-
(Nn-hexyl-N-ethylamino) fluorane,
2- (o-chloroanilino) -6-diethylaminofluorane, 2- (o-chloroanilino) -6-dibutylaminofluorane, 2- (m-trifluoromethylanilino) -6-diethylaminofluorane, 2,3 -Dimethyl-6-dimethoraminofluorane, 3-methyl-6-
(N-ethyl-p-toluidino) fluorane, 2-chloro-6-diethylaminofluorane, 2-bromo-6-
Diethylaminofluorane, 2-chloro-6-dipropylaminofluorane, 3-chloro-6-cyclohexylaminofluorane, 3-bromo-6-cyclohexylaminofluorane, 2-chloro-6- (N-ethyl-N −
Isoamylamino) fluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2-anilino-3
-Chloro-6-diethylaminofluorane, 2- (o-
Chloroanilino) -3-chloro-6-cyclohexylaminofluorane, 2- (m-trifluoromethylanilino) -3-chloro-6-diethylaminofluorane, 2
-(2,3-Dichloroanilino) -3-chloro-6-diethylaminofluorane, 1,2-benzo-6-diethylaminofluorane, 3-diethylamino-6- (m-
Trifluoromethylanilino) fluorane, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-
Ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindole-3)
-Yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, 3- (1-octyl-2)
-Methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl)
-3- (2-methyl-4-diethylaminophenyl)-
4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -7-azaphthalide, 3- (1-ethyl-2-methylindole- 3-yl) -3- (4-diethylaminophenyl) -4-azaphthalide, 3- (1
-Ethyl-2-methylindol-3-yl) -3-
(4-N-n-amyl-N-methylaminophenyl)-
4-azaphthalide, 3- (1-methyl-2-methylindol-3-yl) -3- (2-hexyloxy-4-
Diethylaminophenyl) -4-azaphthalide, 3,3
-Bis (2-ethoxy-4-diethylaminophenyl)
-4-azaphthalide, 3,3-bis (2-ethoxy-4)
-Diethylaminophenyl) -7-azaphthalide.

As the color former used in the present invention, conventionally known leuco dyes may be used alone or in combination in addition to the above-mentioned fluoran compound and azaphthalide compound. The color former is shown below. 2- (p-acetylanilino)
-6- (Nn-amyl-Nn-butylamino) fluorane, 2-benzylamino-6- (N-ethyl-p-
Toluidino) fluorane, 2-benzylamino-6-
(N-methyl-2,4-dimethylanilino) fluorane, 2-benzylamino-6- (N-ethyl-2,4-
Dimethylanilino) fluorane, 2-benzylamino-
6- (N-methyl-p-toluidino) fluorane, 2-
Benzylamino-6- (N-ethyl-p-toluidino)
Fluorane, 2- (di-p-methylbenzylamino)-
6- (N-ethyl-p-toluidino) fluorane, 2-
(Α-Phenylethylamino) -6- (N-ethyl-p
-Toluidino) fluorane, 2-methylamino-6-
(N-methylanilino) fluorane, 2-methylamino-6- (N-ethylanilino) fluorane, 2-methylamino-6- (N-propylanilino) fluorane, 2
-Ethylamino-6- (N-methyl-p-toluidino)
Fluoran, 2-methylamino-6- (N-methyl-
2,4-dimethylanilino) fluorane, 2-ethylamino-6- (N-ethyl-2,4-dimethylanilino)
Fluorane, 2-dimethylamino-6- (N-methylanilino) fluorane, 2-dimethylamino-6- (N-
Ethylanilino) fluorane, 2-diethylamino-6
-(N-methyl-p-toluidino) fluorane, 2-diethylamino-6- (N-ethyl-p-toluidino) fluorane, 2-dipropylamino-6- (N-methylanilino) fluorane, 2-dipropylamino- 6- (N
-Ethylanilino) fluorane, 2-amino-6- (N
-Methylanilino) fluorane, 2-amino-6- (N
-Ethylanilino) fluorane, 2-amino-6- (N
-Propylanilino) fluorane, 2-amino-6-
(N-methyl-p-toluidino) fluorane, 2-amino-6- (N-ethyl-p-toluidino) fluorane,
2-amino-6- (N-propyl-p-toluidino) fluorane, 2-amino-6- (N-methyl-p-ethylanilino) fluorane, 2-amino-6- (N-ethyl-p-ethylanilino) fluorane , 2-amino-6-
(N-propyl-p-ethylanilino) fluorane, 2
-Amino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-ethyl-2,
4-dimethylanilino) fluorane, 2-amino-6-
(N-propyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-methyl-p-chloroanilino) fluorane, 2-amino-6- (N-ethyl-p-
Chloroanilino) fluorane, 2-amino-6- (N-
Propyl-p-chloroanilino) fluorane, 1,2-
Benzo-6- (N-ethyl-N-isoamylamino) fluorane, 1,2-benzo-6-dibutylaminofluorane, 1,2-benzo-6- (N-methyl-N-cyclohexylamino) fluorane, 1 , 2-benzo-6-
(N-ethyl-N-toluidino) fluorane, etc.

Specific examples of other color formers preferably used in the present invention are as follows. 2-anilino-3-methyl-6- (N-2-ethoxypropyl-N-
Ethylamino) fluorane, 2- (p-chloroanilino) -6- (Nn-octylamino) fluorane, 2
-(P-chloroanilino) -6- (Nn-palmitylamino) fluorane, 2- (p-chloroanilino) -6
-(Di-n-octylamino) fluorane, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (o-methoxybenzoylamino) -6-
(N-methyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6-diethylaminofluorane, 2-dibenzylamino-4-methoxy-6- (N
-Methyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6- (N-ethyl-p-toluidino) fluorane, 2- (α-phenylethylamino)
-4-Methyl-6-diethylaminofluorane, 2-
(P-Toluidino) -3- (t-butyl) -6- (N-
Methyl-p-toluidino) fluorane, 2- (o-methoxycarbonylamino) -6-diethylaminofluorane, 2-acetylamino-6- (N-methyl-p-toluidino) fluorane, 4-methoxy-6- (N -Ethyl-p-toluidino) fluorane, 2-ethoxyethylamino-3-chloro-6-dibutylaminofluorane, 2
-Dibenzylamino-4-chloro-6- (N-ethyl-
p-toluidino) fluorane, 2- (α-phenylethylamino) -4-chloro-6-diethylaminofluorane, 2- (N-benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluor Oran, 2
-Anilino-3-methyl-6-pyrrolidinofluorane,
2-anilino-3-chloro-6-pyrrolidinofluorane, 2-anilino-3-methyl-6- (N-ethyl-N
-Tetrahydrofurfurylamino) fluorane, 2-mesidino-4 ', 5'-benzo-6-diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-
Methyl-6-pyrrolidinofluorane, 2- (α-naphthylamino) -3,4benzo-4′-bromo-6- (N-
Benzyl-N-cyclohexylamino) fluorane, 2
-Piperidino-6-diethylaminofluorane, 2-
(Nn-propyl-p-trifluoromethylanilino)
-6-morpholinofluorane, 2- (di-Np-chlorophenyl-methylamino) -6-pyrrolidinofluorane, 2- (Nn-propyl-m-trifluoromethylanilino) -6- Morpholinofluorane, 1,2-benzo-6- (N-ethyl-Nn-octylamino) fluorane, 1,2-benzo-6-diallylaminofluorane, 1,2-benzo-6- (N -Ethoxyethyl-N
-Ethylamino) fluorane, benzoleucomethylene blue, 2- [3,6-bis (diethylamino) -7-
(O-Chloroanilino) xanthyl] benzoate lactam, 2- [3,6-diethylamino) -9- (o-chloroanilino) xanthyl] benzoate lactam, 3,3-
Bis (p-dimethylaminophenyl) -phthalide, 3,
3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis- (p-dimethylaminophenyl)
-6-diethylaminophthalide, 3,3-bis- (p-
Dimethylaminophenyl) -6-chlorophthalide, 3,
3-bis- (p-dibutylaminophenyl) phthalide,
3- (2-methoxy-4-dimethylaminophenyl)-
3- (2-hydroxy-4,5-dichlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-methoxy-5-chlorophenyl)
Phthalide, 3- (2-hydroxy-4-dimethoxyaminophenyl) -3- (2-methoxy-5-chlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-methoxy- 5-nitrophenyl) phthalide, 3- (2-hydroxy-4-diethylaminophenyl) -3- (2-methoxy-5-methylphenyl) phthalide, 3- (2-methoxy-4-dimethylaminophenyl) -3- (2-Hydroxy-4-chloro-5-methoxyphenyl) phthalide, 3,6-bis (dimethylamino) fluorenspiro (9,3 ′)-6′-
Dimethylaminophthalide, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-
2'-methoxy-benzoindolino-spiropyran, etc.

Next, the color developer used in combination with the color former will be described. The color developer was previously described in JP-A-5-124.
As disclosed in Japanese Unexamined Patent Application Publication No. 360-36042 together with a representative example of an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having a long-chain aliphatic hydrocarbon group, a color developer capable of developing a color former in the molecule. A compound having both a functional structure and a structure for controlling the cohesive force between molecules is used. As a structure having a color developing ability, an acidic group such as a phenolic hydroxyl group, a carboxyl group or a phosphoric acid group is used, but not limited to these, a group capable of developing a color forming agent such as a thiourea group or a metal carboxylate group is used. You can bring it. A typical example of a structure that controls the cohesive force between molecules is a hydrocarbon group such as a long-chain alkyl group. It is preferable that the number of carbon atoms in the hydrocarbon group is 8 or more in order to obtain good color development / decolorization characteristics. Further, this hydrocarbon group may contain an unsaturated bond, and a branched hydrocarbon group is also included. Also in this case, the main chain portion preferably has 8 or more carbon atoms. As described above, the color developer has a structure in which a structure having a color developing ability and a structure such as a hydrocarbon group that controls the cohesive force between molecules are connected. A divalent group containing a hetero atom or a group in which a plurality of these groups are combined may be sandwiched and bonded to this connecting portion. Hereinafter, the color developer used in the present invention will be specifically exemplified. The color developers may be used alone or in combination of two or more.

[0022]

[Chemical 1] In the formula, X ₁ represents a divalent group containing a hetero atom or a direct bond, and X ₂ represents a divalent group containing a hetero atom. R
₁ represents a divalent hydrocarbon group, and R ₂ has 1 to 22 carbon atoms.
Represents a hydrocarbon group of. Further, p represents an integer of 0 to 4, and R ₁ and X _{2 which} are repeated when p is 2 to 4 may be the same or different. Further, q represents 1 to 3. Specifically, R ₁ and R ₂ represent a hydrocarbon group which may have a substituent, and these may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and are composed of both of them. It may be a hydrocarbon group. Further, the aliphatic hydrocarbon group may be linear or branched, and may have an unsaturated bond. Examples of the substituent attached to the hydrocarbon group include a hydroxyl group, a halogen, and an alkoxy group. Note that R ₁ may be a direct bond. Also, the sum of carbon numbers of R ₁ and R ₂ is 7
The number of carbon atoms is preferably 8 or more, more preferably 11 or more, since the stability of color development and the decoloring property are deteriorated below. X ₁ and X ₂ represent a divalent group containing a hetero atom,

[0023]

[Table 1] Preferably, it represents a divalent group having at least one group shown in Table 1. Specific examples thereof include those shown in Table 2.

[0024]

[Table 2] Specific examples of the phenol compound in the present invention are shown in Table 3, but the present invention is not limited thereto.
Moreover, the phenol compounds may be used alone or in combination.

[0025]

[Table 3]

Examples of the organic phosphoric acid-based color developer include the following compounds. Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, phosphoric acid ditetradecyl ester, phosphoric acid dihexadecyl ester, phosphoric acid Dioctadecyl ester, phosphoric acid dieicosyl ester, phosphoric acid dibehenyl ester, etc.

The following compounds can be exemplified as the aliphatic carboxylic compound. 2-hydroxytetradecanoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecanoic acid, 2-hydroxyeicosanoic acid, 2-hydroxydocosanoic acid, 2-bromohexadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid , 2-bromodocosanoic acid, 3-bromooctadecanoic acid, 3-bromodocosanoic acid, 2,3-dibromooctadecanoic acid, 2-
Fluorododecanoic acid, 2-fluorotetradecanoic acid, 2
-Fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2-fluoroeicosanoic acid, 2-fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, per Fluorooctadecanoic acid etc.

Examples of the aliphatic dicarboxylic acid and tricarboxylic acid compounds include the following compounds. 2-
Dodecyloxysuccinic acid, 2-tetradecyloxysuccinic acid, 2-hexadecyloxysuccinic acid, 2-octadecyloxysuccinic acid, 2-eicosyloxysuccinic acid,
2-dodecyloxysuccinic acid, 2-dodecylthiosuccinic acid, 2-tetradecylthiosuccinic acid, 2-hexadecylthiosuccinic acid, 2-octadecylthiosuccinic acid, 2-eicosylthiosuccinic acid, 2-docosylthiosuccinic acid, 2
-Tetracosylthiosuccinic acid, 2-hexadecyldithiosuccinic acid, 2-octadecyldithiosuccinic acid, 2-eicosyldithiosuccinic acid, dodecylsuccinic acid, tetradecylsuccinic acid, pentadecylsuccinic acid, hexadecylsuccinic acid, octadecylsuccinic acid, eicosylsuccinic acid Acid, docosyl succinic acid, 2,3-dihexadecyl succinic acid,
2,3-Dioctadecyl succinic acid, 2-methyl-3-hexadecyl succinic acid, 2-methyl-3-octadecyl succinic acid, 2-octadecyl-3-hexadecyl succinic acid, hexadecyl malonic acid, octadecyl malonic acid, eicosyl Malonic acid, docosylmalonic acid, dihexadecylmalonic acid, dioctadecylmalonic acid, didocylmalonic acid, methyloctadecylmalonic acid, 2-hexadecylglutaric acid, 2-octadecylglutaric acid, 2-eicosylglutaric acid, docosylglutaric acid, 2-pentadecyl adipic acid, 2-octadecyl adipic acid, 2-eicosyl adipic acid, 2-docosyl adipic acid, 2-hexadecanoyloxypropane-1,2,3-tricarboxylic acid, 2-octadecanoyloxy Propane-1,2,3
-Tricarboxylic acids and the like.

In the reversible thermosensitive recording medium of the present invention, if necessary, an additive for improving or controlling the coating characteristics and the coloring and decoloring characteristics of the recording layer can be used. These additives include, for example, surfactants, conductive agents, fillers, antioxidants, light stabilizers, color development stabilizers, decolorization accelerators and the like. The decolorization accelerator is preferably a compound having a divalent group containing a hetero atom and an alkyl chain having 8 or more carbon atoms, or a compound having an N, N′-2 substituent. Is not limited to these compounds.

The reversible thermosensitive recording medium of the present invention can form a relatively colored state and a relatively decolored state depending on the heating temperature and / or the cooling rate after heating. The basic coloring / decoloring phenomenon of the composition composed of the color former and the developer used in the present invention will be described. FIG. 1 shows the relationship between the color density and the temperature of this recording medium. When the temperature of the recording medium initially in the color erasing state (A) is raised, color is developed at the temperature T ₁ at which melting starts, and the state becomes the melt color developing state (B). When the melted color development state (B) is rapidly cooled, the color development state can be lowered to room temperature, and the solid color development state (C) is obtained. Whether or not this color-developed state is obtained depends on the rate of temperature decrease from the molten state, and in slow cooling, decoloring occurs in the process of temperature decrease, and the same decolorized state (A) or rapid-cooled colored state (C) as in the beginning is obtained. ) A relatively less concentrated state is formed. On the other hand, when the temperature of the rapidly cooled color development state (C) is increased again, the color disappears at a temperature T ₂ lower than the color development temperature (D to E).
Return to. The actual color-developing temperature and decoloring temperature vary depending on the combination of the color-developing agent and the color-developing agent used, and can be selected according to the purpose. Further, the density in the molten color state and the color density in the case of rapid cooling do not always coincide with each other and may differ from each other.

In the recording medium of the present invention, the color-developed state (C) obtained by quenching from the molten state is a state in which the color-developing agent and the color-developing agent are mixed in such a state that the molecules can contact with each other, and this is a solid. Often forms a state. This state is a state in which the color developer and the color former are aggregated and the color is maintained, and it is considered that the color formation is stabilized by the formation of this aggregate structure.
On the other hand, the decolored state is a state in which both are phase-separated. This state is a state in which molecules of at least one compound are aggregated to form a domain or crystallized, and it is considered that the color former and the developer are separated and stabilized by aggregation or crystallization. To be In the present invention, in many cases, more complete decoloring occurs due to phase separation of the two and crystallization of the developer. In both the decolored state from the molten state by slow cooling and the decolored state by heating from the colored state shown in FIG. 1, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

The color image of the present invention may be formed by heating with a thermal head or the like to a temperature at which it is melt-mixed and then rapidly cooled. Decoloring is performed by two methods, namely, a method of gradually cooling from a heated state and a method of heating to a temperature slightly lower than the coloring temperature. However, these are the same in the sense that both are phase-separated, or at least one is temporarily kept at a temperature at which crystallization occurs. The reason why the material is rapidly cooled in the formation of the colored state is to prevent the phase separation temperature or the crystallization temperature from being maintained. The quenching and gradual cooling here are relative to one composition, and the boundary changes depending on the combination of the color former and the developer.

The ratio of the color-developing agent to the color-developing agent varies in an appropriate range depending on the combination of the compounds used, but the molar ratio is generally in the range of 0.1 to 20 for the color-developing agent per color-developing agent 1. It is preferably in the range of 0.2 to 10. If the amount of the developer is smaller or larger than this range, the density of the color-developed state is lowered, which is a problem. The proportion of the decolorization accelerator is preferably 0.1% by weight to 300% by weight, more preferably 3% by weight to 100% by weight, based on the color developing agent. Further, the color former and the color developer can also be used by being encapsulated in microcapsules. The ratio of the color-forming component to the resin in the recording layer is preferably 0.1 to 10 with respect to the color-forming component 1, and if it is less than this, the thermal strength of the recording layer is insufficient, and if it is more than this, the color density is lowered. Becomes a problem.

To form the recording layer, a coating liquid prepared by uniformly mixing and dispersing a mixture of the above-mentioned developer, color former, various additives, curing agent, resin in crosslinked state and coating liquid solvent. To use. Specific examples of the solvent used for preparing the coating liquid include water; alcohols such as methanol, ethanol, isopropanol, n-butanol, and methylisocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, cyclohexanone. Such as ketones; amides such as N, N-dimethylformamide, N, N-dimethylacetamide; diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H
-Ethers such as pyran; 2-methoxyethanol,
Glycol ethers such as 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate; methyl acetate, ethyl acetate, acetic acid Isobutyl, amyl acetate, ethyl lactate,
Esters such as ethylene carbonate; aromatic hydrocarbons such as benzene, toluene, xylene; hexane,
Aliphatic hydrocarbons such as heptane, iso-octane and cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane and chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2- Pyrrolidone, N-octyl-2
Examples thereof include pyrrolidones such as pyrrolidone.

The coating liquid can be prepared using a known coating liquid dispersing device such as a paint shaker, a ball mill, an attritor, a three-roll mill, a Keddy mill, a sand mill, a dyno mill and a colloid mill. Further, each material may be dispersed in a solvent by using the above coating liquid dispersion device, or each material may be individually dispersed in a solvent and mixed. Further, it may be melted by heating and then precipitated by quenching or cooling.

The coating method for providing the recording layer is not particularly limited, and blade coating, wire bar coating, spray coating, air knife coating, bead coating, curtain coating, gravure coating, kiss coating, Known methods such as reverse roll coating, dip coating, and die coating can be used.

The method of drying and curing the recording layer is as follows:
Curing treatment is performed if necessary. The heat treatment may be carried out at a relatively high temperature for a short time using a high temperature tank or at a relatively low temperature for a long time. From the viewpoint of reactivity, it is preferable to heat the cross-linking reaction at a temperature of about 30 ° C. to 130 ° C. for about 1 minute to 150 hours. More preferably, it is preferable to heat at a temperature condition of 40 ° C. to 100 ° C. for about 2 minutes to 120 hours. In addition, since productivity is important in manufacturing, it is difficult to take time until crosslinking is sufficiently completed. Therefore, a crosslinking process may be provided separately from the drying process. The conditions for the crosslinking step are 40 ° C to 1
It is preferable to heat at a temperature of 00 ° C. for about 2 minutes to 120 hours.

The thickness of the recording layer is preferably in the range of 1 to 20 μm, more preferably 3 to 15 μm. Adhesion between the recording layer and the protective layer is improved, alteration of the recording layer by coating the protective layer is prevented, additives contained in the protective layer are transferred to the recording layer, or additives contained in the recording layer are transferred to the protective layer. In order to prevent this, an intermediate layer may be provided between the two.
The thickness of the intermediate layer is preferably in the range of 0.1 to 20 μm, more preferably 0.3 to 10 μm. The solvent used for the coating liquid for the intermediate layer, the dispersion device for the coating liquid, the binder, the coating method, the drying / curing method and the like may be the known methods used for the recording layer. Further, the metal oxide composite particles obtained by compositing the metal oxide having the ultraviolet absorbing ability or the ultraviolet shielding ability described in claim 1 with another metal oxide can be added to this layer.

In forming the protective layer, the thickness of the protective layer is preferably in the range of 0.1 to 20 μm, more preferably 0.3 to 10 μm. The solvent used for the coating liquid for the protective layer, the dispersion device for the coating liquid, the binder, the coating method, the drying / curing method and the like may be the known methods used for the recording layer. Further, the metal oxide composite particles obtained by compositing the metal oxide having the ultraviolet absorbing ability or the ultraviolet shielding ability described in claim 1 with another metal oxide can be added to this layer as well. That is, it may be added to either the intermediate layer or the protective layer, or may be added to both. Further, even when another functional layer comes in between, it can be added to that layer.

The recording layer, the intermediate layer, and the protective layer may be added with other fillers having no ultraviolet absorbing property or ultraviolet shielding property, and the fillers can be divided into inorganic fillers and organic fillers. As the inorganic filler, calcium carbonate, magnesium carbonate, anhydrous silicic acid, hydrous silicic acid, hydrous aluminum silicate, hydrous calcium silicate, alumina, iron oxide, calcium oxide, magnesium oxide, chromium oxide, manganese oxide, silica, Examples include talc, mica, and the like. As the organic filler, silicone resin, cellulose resin, epoxy resin, nylon resin, phenol resin, polyurethane resin, urea resin,
Melamine resin, polyester resin, polycarbonate resin, styrene resin such as styrene, polystyrene, polystyrene / isoprene, styrene vinylbenzene, acrylic resin such as vinylidene chloride acryl, acrylic urethane, ethylene acryl, polyethylene resin, benzoguanamine formaldehyde, melamine formaldehyde, etc. Formaldehyde resin, polymethylmethacrylate resin, vinyl chloride resin and the like. In the present invention, the filler may be used alone, but may be contained in two or more kinds. In the case of plural fillers, the method of combining the inorganic filler and the organic filler is not particularly limited. The shape may be spherical, granular, plate-like, needle-like, or the like. The content of the filler in the protective layer is 5 to 50 in terms of volume fraction.
% By volume.

A lubricant may be added to the recording layer, the intermediate layer and the protective layer. Specific examples of the lubricant include synthetic waxes such as ester wax, paraffin wax and polyethylene wax: vegetable waxes such as hardened castor oil: Animal waxes such as beef tallow oil: Higher alcohols such as stearyl alcohol and behenyl alcohol: margaric acid,
Higher fatty acids such as lauric acid, mystyric acid, palmitic acid, stearic acid, behenic acid, and flomenic acid: higher fatty acid esters such as fatty acid esters of sorbitan: stearic acid amide, oleic acid amide, lauric acid amide, ethylenebisstearic acid Examples thereof include amides, amides such as methylenebisstearic acid amide, and methylolstearic acid amide. The content of the lubricant in the layer is 0.1 to 95% by volume, and more preferably 1 to 75%.

In order to form a color image using the reversible thermosensitive recording medium of the present invention, it is sufficient that the color image is heated once above the color development temperature and then rapidly cooled. In particular,
For example, when the recording layer is heated for a short time with a thermal head or a laser beam, the recording layer is locally heated, so that the heat is immediately diffused and abrupt cooling occurs to fix the coloring state. On the other hand, in order to erase the color, it may be heated and cooled for a relatively long time using an appropriate heat source, or may be temporarily heated to a temperature slightly lower than the coloring temperature. When heated for a long time, the temperature of a wide range of the recording medium rises and the subsequent cooling slows down, so that decoloring occurs in the process. In this case, as a heating method, a heat roller, a heat stamp, hot air, or the like may be used, or a thermal head may be used to heat for a long time. In order to heat the recording layer to the decoloring temperature range, the applied energy may be slightly lowered from that at the time of recording by adjusting the voltage applied to the thermal head or the pulse width. With this method,
Recording and erasing can be done only with the thermal head, and so-called overwriting becomes possible. As the recording device, an inkjet printer, a thermal transfer printer, a sublimation printer, or the like may be used in addition to a commonly used printer. Further, it can be erased by heating in a decoloring temperature range with a heat roller or a heat stamp.

Further, a coloring layer having an arbitrary pattern or the like is formed on a part or the entire surface of the reversible thermosensitive recording medium of the present invention by printing such as offset printing or gravure printing, or by an ink jet printer, a thermal transfer printer, a sublimation printer or the like. Alternatively, an OP varnish layer containing a curable resin as a main component may be provided on a part or the entire surface of the colored layer. These supports may have a magnetic recording layer on the same surface as the reversible thermosensitive recording layer and / or on the opposite surface. The reversible thermosensitive recording medium of the present invention may be attached to another medium via an adhesive layer or the like. The reversible thermosensitive recording medium of the present invention may be processed into a sheet shape or a card shape, and its shape can be processed into any shape, and printing processing can be performed on the surface of the medium. In addition, the reversible thermosensitive recording medium of the present invention may use an irreversible thermosensitive recording layer in combination, and the color tone of each recording layer may be the same or different.

[0044]

The present invention will be described in more detail with reference to the following examples. In the examples, "parts" and "%" are based on weight.

[0045] (Example 1) Preparation of recording layer liquid 1) Developer 4 parts

[0046]

[Chemical 2] 2) Dialkyl urea (manufactured by Nippon Kasei Co., Ltd., Haclean SB) 1 part 3) Acrylic polyol 50% solution (Mitsubishi Rayon Co., LR503) 9 parts 4) Methyl ethyl ketone 70 parts It was pulverized and dispersed so as to have a size of 1 μm. 5) 2-anilino-3-methyl-6 dibutylaminofluorane 1 part 6) Isocyanate (Nippon Polyurethane Company, Coronate HL) 2 parts The above composition was added to a dispersion liquid in which a color developer was pulverized and dispersed, and well stirred. A recording layer coating solution was prepared.

[0047] Preparation of protective layer liquid 1) Acrylic polyol 40% solution (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Isocyanate curing agent 3.4 parts     (Coronate HX made by Nippon Polyurethane Company)           NCO / OH = 1.0 3) Metal oxide composite particles (ST-3 manufactured by Asahi Glass Co., Ltd.) 4 parts     ・ Metal oxide with UV absorption or UV shielding performance: Titanium oxide     ・ Metal oxide content with UV absorption or UV shielding performance: 35%     ・ Average particle size: 3 μm 4) Methyl ethyl ketone 10 parts The above composition was well stirred to prepare a protective layer coating liquid.

Preparation of Reversible Thermosensitive Recording Medium The recording layer coating solution having the above composition was coated on a polyester film having a thickness of 188 μm using a wire bar, and 100
After drying at 2 ° C. for 2 minutes, curing was performed at 60 ° C. for 24 hours to form a recording layer having a film thickness of about 10 g / m ² . Further, a protective layer coating solution having the above composition is applied onto the recording layer using a wire bar, dried at 100 ° C. for 2 minutes, and then cured at 60 ° C. for 24 hours to protect the film having a thickness of about 3 g / m ² . Layers were provided to prepare a reversible thermosensitive recording medium of the present invention.

(Example 2) A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the metal oxide composite particles (ST-3 manufactured by Asahi Glass Co., Ltd.) used in the protective layer of Example 1 were changed as follows. Was produced. Metal oxide composite particles (SZ-3 manufactured by Asahi Glass Co., Ltd.) 2 parts-Metal oxide having ultraviolet absorption performance or ultraviolet shielding performance: zinc oxide-Metal oxide content having ultraviolet absorption performance or ultraviolet shielding performance: 50%・ Average particle size: 3 μm

[0050] (Example 3) Preparation of recording layer liquid 1) Developer 3 parts

[0051]

[Chemical 3] 2) Dialkyl urea (manufactured by Nippon Kasei Co., Ltd., Haclean SB) 1 part 3) 70% saturated polyester solution 6 parts (manufactured by Dainippon Ink and Chemicals, DE-140-70) 4) Tetrahydrofuran 60 parts Using a ball mill, the above composition. And pulverized and dispersed so that the average particle size was about 1 μm. 5) 2-anilino-3-methyl-6dibutylaminofluorane 1 part 6) Isocyanate (Nippon Polyurethane Company, Coronate HX) 2 parts The above composition was added to a dispersion liquid in which a color developer was pulverized and dispersed, and well stirred. A recording layer coating solution was prepared.

[0052] Preparation of intermediate layer liquid 1) Acrylic polyol 40% solution (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Isocyanate curing agent 3.4 parts     (Coronate HL made by Nippon Polyurethane Company)           NCO / OH = 1.0 3) Metal oxide composite particles (SQE10T manufactured by Suzuki Yushi Kogyo Co., Ltd.) 6 parts     ・ Metal oxide with UV absorption or UV shielding performance: Titanium oxide     ・ Metal oxide content with UV absorption or UV shielding performance: 11%     ・ Average particle size: 1.0 to 1.5 μm 4) Methyl ethyl ketone 10 parts The above composition was well stirred to prepare a protective layer coating liquid.

Preparation of protective layer liquid 1) 40% acrylic polyol solution (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Isocyanate (Coronate HX manufactured by Nippon Polyurethane Co., Ltd.) 1.5 parts 3) Silicone oil 2 parts 4) Methyl ethyl ketone 7 parts The above composition was thoroughly dissolved and stirred to prepare a protective layer coating liquid.

Preparation of reversible thermosensitive recording medium The recording layer coating solution having the above composition was coated on a polyester film having a thickness of 188 μm using a wire bar, and 100
After drying at 2 ° C. for 2 minutes, curing was performed at 60 ° C. for 24 hours to form a recording layer having a film thickness of about 10 g / m ² . Further, an intermediate layer coating solution having the above composition was applied onto the recording layer using a wire bar and dried at 100 ° C. for 2 minutes to form an intermediate layer having a film thickness of about 3 g / m ² . The coating solution for protective layer having the above composition was applied onto the intermediate layer using a wire bar, dried at 100 ° C. for 2 minutes, and then cured at 60 ° C. for 24 hours to give a film thickness of about 2 g /
A protective layer of m ² was provided to prepare a reversible thermosensitive recording medium of the present invention.

[0055] (Example 4) Preparation of recording layer liquid 1) Developer 3 parts

[0056]

[Chemical 4] 2) Dialkyl urea (manufactured by Nippon Kasei Co., Ltd., Haclean SB) 1 part 3) 70% saturated polyester solution 6 parts (manufactured by Dainippon Ink and Chemicals, DE-140-70) 4) Tetrahydrofuran 60 parts Using a ball mill, the above composition. And pulverized and dispersed so that the average particle size was about 1 μm. 5) 2-anilino-3-methyl-6dibutylaminofluorane 1 part 6) Isocyanate (Nippon Polyurethane Company, Coronate HX) 2 parts The above composition was added to a dispersion liquid in which a color developer was pulverized and dispersed, and well stirred. A recording layer coating solution was prepared.

[0057] Preparation of intermediate layer liquid 1) Acrylic polyol 40% solution (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Isocyanate curing agent 3.4 parts     (Coronate HL made by Nippon Polyurethane Company)           NCO / OH = 1.0 3) Metal oxide composite particles (SQF30C manufactured by Suzuki Yushi Kogyo Co., Ltd.) 5 parts     ・ Metal oxide with UV absorption or UV shielding performance: Cerium oxide     ・ Metal oxide content with ultraviolet absorption or ultraviolet shielding performance: 29%     ・ Average particle size: 3 to 4 μm 4) Methyl ethyl ketone 10 parts The above composition was well stirred to prepare a protective layer coating liquid.

[0058] Preparation of protective layer liquid 1) Acrylic polyol 40% solution (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Isocyanate curing agent 3.4 parts     (Coronate HX made by Nippon Polyurethane Company)           NCO / OH = 1.0 3) Metal oxide composite particles (SQE10Z, manufactured by Suzuki Yushi Kogyo Co., Ltd.) 4 parts     ・ Metal oxide with UV absorption or UV shielding performance: Zinc oxide     ・ Metal oxide content with UV absorption or UV shielding performance: 41%     ・ Average particle size: 1.0 to 1.5 μm 4) Methyl ethyl ketone 10 parts The above composition was well stirred to prepare a protective layer coating liquid.

Preparation of reversible thermosensitive recording medium A recording layer coating solution having the above composition was coated on a polyester film having a thickness of 188 μm using a wire bar, and 100
After drying at 2 ° C. for 2 minutes, curing was performed at 60 ° C. for 24 hours to form a recording layer having a film thickness of about 10 g / m ² . Further, an intermediate layer coating solution having the above composition was applied onto the recording layer using a wire bar and dried at 100 ° C. for 2 minutes to form an intermediate layer having a film thickness of about 3 g / m ² . The coating solution for protective layer having the above composition was applied onto the intermediate layer using a wire bar, dried at 100 ° C. for 2 minutes, and then cured at 60 ° C. for 24 hours to give a film thickness of about 2 g /
A protective layer of m ² was provided to prepare a reversible thermosensitive recording medium of the present invention.

(Example 5) Metal oxide composite particles used in the intermediate layer of Example 4 (SQF30C manufactured by Suzuki Yushi Kogyo Co., Ltd.)
A reversible thermosensitive recording medium was produced in the same manner as in Example 4 except that the protective layer was changed to the following. Metal oxide composite particles (S-3018-02, manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) 3 parts Metal oxide having ultraviolet absorbing performance or ultraviolet shielding performance: Cerium oxide Contains metal oxide having ultraviolet absorbing performance or ultraviolet shielding performance Amount: 23-24% ・ Average particle size: 1.0 to 3.0 μm

Preparation of protective layer liquid 1) Urethane acrylate UV curable resin 15 parts (Dainippon Ink and Chemicals, C7-157) 2) Filler (Mizusawa Chemical Co., P527) 5 parts 3) Ethyl acetate 85 parts The composition was well dissolved and stirred to prepare a protective layer coating liquid.

Preparation of Reversible Thermosensitive Recording Medium The recording layer coating solution having the above composition was coated on a polyester film having a thickness of 188 μm using a wire bar, and 100
After drying at 2 ° C. for 2 minutes, curing was performed at 60 ° C. for 24 hours to form a recording layer having a film thickness of about 10 g / m ² . Further, the intermediate layer coating solution having the above composition was applied onto the recording layer using a wire bar, dried at 100 ° C. for 2 minutes, and then cured at 60 ° C. for 24 hours to obtain an intermediate layer having a film thickness of about 3 g / m ² . Layers were provided. The coating solution for protective layer having the above composition was applied onto the intermediate layer using a wire bar and dried at 90 ° C. for 1 minute, and then passed under a UV lamp with irradiation energy of 80 W / cm at a conveying speed of 9 m / min. A reversible thermosensitive recording medium of the present invention was prepared by curing and providing a protective layer having a film thickness of 2 μm.

Comparative Example 1 A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the protective layer liquid of Example 1 was adjusted as follows.

[0064] Preparation of protective layer liquid 1) 10 parts of ultraviolet absorbing polymer solution (PUVA-30S, manufactured by Otsuka Chemical Co., Ltd.)           Weight average molecular weight: 10,000           UV absorption structure: Benzotriazole structure 2) Silicon oil 1 part 3) Tetrahydrofuran 7 parts The above composition was well stirred to prepare a protective layer coating liquid.

(Comparative Example 2) A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the protective layer solution of Example 1 was adjusted as follows.

[0066] Preparation of protective layer liquid 1) 10% acrylic polyol 40% solution (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 2) Isocyanate (Nippon Polyurethane Co., Coronate HX) 1.5 parts 3) Low molecular weight UV absorber (Sumisorb 310 manufactured by Sumitomo Chemical Co., Ltd.) 1 part           UV absorption structure: Benzotriazole structure 4) Silicone oil 2 parts 5) Methyl ethyl ketone 7 parts The above composition was thoroughly stirred to prepare a protective layer coating liquid.

(Comparative Example 3) A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the protective layer liquid of Example 1 was adjusted as follows.

[0068] Preparation of protective layer liquid 1) 10% acrylic polyol 40% solution (LR327 manufactured by Mitsubishi Rayon Co., Ltd.) 2) Isocyanate (Nippon Polyurethane Co., Coronate HX) 1.5 parts 3) UV shielding inorganic filler 6 parts     (Titanium oxide MT100S manufactured by TAYCA) 4) Methyl ethyl ketone 7 parts The above composition was well stirred to prepare a protective layer coating liquid.

(Comparative Example 4) A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the protective layer liquid of Example 1 was adjusted as follows.

[0070] Preparation of protective layer liquid 1) Acrylic polyol 40% solution (LR327, manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts 2) Isocyanate (Nippon Polyurethane Co., Coronate HX) 1.5 parts 3) UV shielding inorganic filler 3 parts     (Titanium oxide MT100S manufactured by TAYCA) 4) 3 parts of inorganic filler (talc, high filler # 5000PJ) 5) Methyl ethyl ketone 7 parts The above composition was well stirred to prepare a protective layer coating liquid.

The above Examples 1 to 4 and Comparative Examples 1 to 5
The reversible thermosensitive recording medium prepared in 1. was evaluated by the following evaluation methods, and the results are shown in Table 1 below. Test 1 Erasing and printing were repeated 50 times using a recording medium surface card printer R3000 (manufactured by Kyushu Matsushita Co., Ltd.) after repetition, and the state of the recording medium surface was visually observed and evaluated in the following ranks. Rank 1: No scratch was generated on the surface of the recording medium. Rank 2: No hit was generated on the surface of the recording medium,
A scratch has occurred. Rank 3: A scratch was generated on the surface of the recording medium. Rank 4: The recording medium surface was severely struck and scratched. Test 2 Change in color density after repetition 50 erase and print using card printer R3000.
Repeated times, the change in color density was visually observed and evaluated according to the following ranks. Rank 1: The image area was in a good color-developed state and no change in density was observed. Rank 2: Coloring in the image area was non-uniform, and a decrease in density was also observed. Rank 3: The color development of the image area was extremely poor, and the density was drastically reduced. Test 3 Using the light-resistant card printer R3000, the printed part after the first and 50th repetitions is left for 100 hours under irradiation of 5500lux. After that, the printing section is changed to the card printer R300.
0 erases the entire surface. The erasure residue at that time was measured with a Macbeth densitometer RD914, and the light resistance was expressed by the difference in the change.

[0072]

[Equation 1] Change in residual erase concentration after light irradiation = erase concentration after light resistance test-background density test after light resistance test 4 Dispersibility The dispersibility of the filler was confirmed from a cross-sectional photograph. ◯: Evenly dispersed Δ: Secondary aggregation is partially observed ×: Aggregated lumps are seen and not uniformly dispersed

[0073]

[Table 1] In Examples 1 to 5, there were no dents and changes in color density after repeated, and there was no coloring due to light irradiation.
In Comparative Examples 1 to 4, although the initial light resistance was good, the dents upon repeated, the decrease in color density, the light resistance, and the dispersibility were poor.

[0074]

As is clear from the detailed and specific description above, the reversible thermosensitive recording medium of the present invention is excellent in light resistance and coating liquid dispersibility, and can be struck on a recording medium even after repeated use. It does not occur and has excellent durability.

[Brief description of drawings]

FIG. 1 is a diagram showing color developing / decoloring characteristics of a reversible thermosensitive recording medium of the present invention.

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Claims (16)

[Claims] 1. A support comprising at least an electron-donating color-forming compound and an electron-accepting compound, which develops color upon heating to a color-forming temperature and is heated to a color-erasing temperature or heated to a temperature not lower than the color-forming temperature and gradually cooled. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer that is erased by applying a metal oxide having an ultraviolet absorbing property or an ultraviolet shielding property to at least one layer on the reversible thermosensitive recording layer, another metal is used. A reversible thermosensitive recording medium containing metal oxide composite particles which are composited with an oxide. 2. The content of the metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance in the metal oxide composite particles is in the range of 5% or more and 60% or less. The reversible thermosensitive recording medium according to 1. 3. The metal oxide having the ultraviolet absorbing performance or the ultraviolet shielding performance in the metal oxide composite particles,
The reversible thermosensitive recording medium according to claim 1 or 2, which is selected from the group consisting of cerium oxide, titanium oxide and zinc oxide. 4. The reversible thermosensitive recording according to claim 1, wherein the metal oxide composite particles have an average particle size of 0.1 μm or more and 6.0 μm or less. Medium. 5. The metal oxide composite particles are contained in at least one layer on the thermosensitive recording layer in an amount of 10% by weight or more and 200% by weight or less based on a binder resin for the layer. The reversible thermosensitive recording medium according to any one of claims 1 to 4, which is characterized in that. 6. The reversible thermosensitive recording medium according to claim 1, wherein the reversible thermosensitive recording layer contains a resin in a crosslinked state with an isocyanate compound. 7. The reversible thermosensitive recording medium according to claim 1, wherein a phenol compound having an alkyl chain having 8 or more carbon atoms is used as the electron accepting compound. 8. The reversible thermosensitive recording medium according to claim 1, wherein a compound having an alkyl chain having 8 or more carbon atoms is used as the color-decoloration controlling agent. 9. The heat-sensitive recording layer, wherein at least one layer is a protective layer, and the protective layer contains an ultraviolet curable resin or a resin in a crosslinked state with an isocyanate compound. The reversible thermosensitive recording medium according to any one of 1. 10. The reversible thermosensitive recording medium comprises a thermoreversible recording section and an information storage section.
10. The reversible thermosensitive recording medium according to any one of 1 to 9. 11. The information storage unit is a magnetic recording layer or an IC.
The reversible thermosensitive recording medium according to claim 10, wherein 12. The reversible thermosensitive recording medium is processed into a card shape or a sheet shape.
12. The reversible thermosensitive recording medium according to any one of 1 to 11. 13. The reversible thermosensitive recording medium according to claim 1, which is used in a roll form. 14. The reversible thermosensitive recording medium according to claim 1, wherein the reversible thermosensitive recording medium has a printed portion. 15. A reversible recording medium processing apparatus, comprising: heating the reversible thermosensitive recording medium according to claim 1 to a temperature lower than a color development start temperature to erase the color. . 16. A heater provided with an erasing device for erasing a colored image provided on a reversible recording medium by heating, and a heating portion of the erasing device is a heater selected from a thermal head, a ceramic heater, a planar heater and a heat roller. The reversible recording medium processing apparatus according to claim 15, wherein