JP2009126072A - Reversible thermosensitive recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reversible thermosensitive recording medium capable of coloring even with a low energy, excellent in erasability, and having storage stability which copes with a practical use. <P>SOLUTION: The reversible thermosensitive recording medium having a reversible thermosensitive recording layer containing a reversible thermosensitive composition capable of forming a relatively colored state and a discolored state by the difference of a heating temperature and/or of a cooling rate after heating using a leuco dye as an electron-donating coloring compound and a developer as an electron-accepting compound on a substrate is characterized in that the developer is a phenol compound having a saturated straight chain alkyl group whose carbon number is not less than 23 bonded to the P position with a divalent hydrogen bonding group, the developer has a melt viscosity of not greater than 10 sec when the developer alone by the capillary phenomenon at a 15°C higher temperature than its melting point, and is used by a ratio (weight ratio) of such that the difference between a melt viscosity when the leuco dye is combined with the developer and a melt viscosity when the developer alone is not less than 10 sec. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound, and can control the formation of a color image and erase it by controlling thermal energy. The present invention relates to a reversible thermosensitive recording medium.

  2. Description of the Related Art Conventionally, thermal recording media using a color development reaction between an electron donating color developing compound (hereinafter also referred to as a color former or a leuco dye) and an electron accepting compound (hereinafter also referred to as a developer) are widely known. With the progress of OA, it has been widely used as output paper for facsimiles, word processors, scientific measuring instruments, etc., and recently as magnetic thermal cards such as prepaid cards and point cards. From the above viewpoint, it is desired to develop a reversible thermosensitive recording medium that can be rewritten any number of times. The present inventors have disclosed a long-chain aliphatic hydrocarbon group as a developer in Patent Document 1 (Japanese Patent No. 2981558). An organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenolic compound having a colorant and combining these with a leuco dye as a color former Therefore, color development and color erasing can be easily performed under heating and cooling conditions, and the color development state and color erasure state can be stably maintained at room temperature, and color development and color erasure can be repeated. A reversible thermosensitive coloring composition and a reversible thermosensitive recording medium using the composition for a recording layer have been proposed. Thereafter, use of a phenolic compound having a long-chain aliphatic hydrocarbon group having a specific structure (for example, Patent Documents 2 and 3: Patent No. 3380277 and Patent No. 3557076) has been proposed. Structural developers have been developed.

  In recent years, as seen in the ratification of the Kyoto Protocol and the movement of team minus 6%, activities to prevent global warming have become active, and in order to achieve reduction of carbon dioxide emissions in electrical appliances, etc. Various efforts have been made. Although the field of reversible thermal recording is recognized as being superior to the past in that it can be used repeatedly, the movement is similar in this field as well, and it is possible to write and erase images with lower energy than before. I've been looking for ways to do it. On the other hand, with the evolution of the times, the applications are expanding and the demand for quality is also increasing. For example, this means that the image does not disappear even under severe storage conditions such as high temperature, and the printing speed is improved.

  However, none of them achieved these simultaneously. In terms of energy saving, attempts have been made to improve thermal efficiency. For example, Patent Document 4 (Japanese Patent Application Laid-Open No. 5-124346) proposes a method in which a cushion member obtained by applying polyurethane foam or a foamable plastic filler and then heating and foaming is used as an under layer. In this method, in order to improve thermal efficiency, it is possible to reduce energy consumption for both erasing and printing in areas close to static color development such as low-speed printing. Because it is necessary to apply heat, the thermal response becomes important. In the case of color development, it can be solved by setting the energy high, but since there is an appropriate energy range in erasing, erasing defects and background fogging are likely to occur, and this technology alone cannot provide a quality that can withstand practical use.

  On the other hand, in terms of image storage, various attempts have been made in the above publications and the like, but at present, sufficient quality has not been obtained.

Japanese Patent No. 2981558 Japanese Patent No. 3380277 Japanese Patent No. 3557076 JP-A-5-124346

  Therefore, in view of the above prior art, an object of the present invention is to propose a reversible thermosensitive recording material that can develop color even with low energy, has excellent erasing characteristics, and has storability that can withstand practical use.

  As a result of various studies by the present inventors, it has been found that the high-speed erasing performance is enhanced if there is a large difference between the melt viscosity in the vicinity of the melting point of the developer involved in color development and the melt viscosity of the mixture of the developer and leuco dye. It was. That is, the ratio is preferably such that the melt viscosity when the developer alone is 10 seconds or less, and the difference between the melt viscosity when the developer and the leuco dye are combined is 10 seconds or more.

  The relationship between the difference in melt viscosity and image erasability is unknown, but color development is related to the phenomenon of melt mixing of leuco dye and developer, and erasure is related to the phenomenon of developer reassembly. I think that it is the following mechanism. When the developer is once mixed with the leuco dye and has a low viscosity, the color former is delocalized in the color developing layer, so that re-assembly of the developer molecules at the time of erasure hardly occurs. On the other hand, when the melt viscosity of the mixture is high, it is suggested that the color developing component stays on the surface of the developer dispersion, and it is considered that the developer is reassembled at the time of erasure. At that time, it is considered that the lower the melt viscosity of the developer itself, the higher the mobility. Therefore, reaggregation is likely to occur, and those having a high melt viscosity are difficult to reverse. A conventional developer of this type of structure has a long chain alkyl group bonded to a heteroatom-containing divalent group capable of generating a hydrogen bond, and the chain sites are constricted due to temperature changes. Although it may be because the relaxation is not sufficient, it is difficult to achieve a significant decrease in viscosity due to an increase in temperature, and it is difficult to achieve a significant decrease in viscosity due to eutectic fusion with a leuco dye during melting. In fact, it has been found in the present invention that the unerased residue becomes remarkable both when the developer has a melt viscosity of more than 10 seconds and when the difference in melt viscosity is less than 10 seconds.

  On the other hand, it is considered that heat-resistant image storage stability can be obtained by the combination and ratio of the developer and the leuco dye having a large difference in melt viscosity of the color former, based on the same idea as described above.

  The melt viscosity in the present invention is evaluated by the following method. The powder to be used is ground in advance in a mortar. Next, an appropriate amount of the powder is placed on a thin glass (cover glass or the like), and melted by heating to a temperature 15 ° C. higher than the melting point of the developer using a hot plate or the like. At the same time, a glass capillary tube (Drummond 1-000-0020) previously marked at a position 15 mm from the end is heated at the same temperature. After confirming the uniform melting of the powder, if the tip of the glass capillary is immediately immersed in the melt, the melt surface rises to the marking position by capillary action. The time required for the liquid level to reach the marking position after soaking was adopted as the melt viscosity. This method can easily evaluate the viscosity of the melt and has good reproducibility.

  The temperature for measuring the melt viscosity should originally be aimed at the vicinity of the melting point, but under these conditions, the state of the system is influenced by the ambient atmosphere. Conversely, measurement at a temperature far exceeding the melting point does not reproduce the actual printing environment, and is not preferable because it induces deterioration due to air oxidation of the material. .

  That is, the above-mentioned problems are solved by (1) “cooling after heating temperature and / or heating using a leuco dye as an electron donating color developing compound and a developer as an electron accepting compound on a support. In a reversible thermosensitive recording medium having a reversible thermosensitive recording layer containing a reversible thermosensitive composition capable of forming a relatively colored state and a decolored state due to a difference in speed, the developer has the following general formula ( 1), and the developer has a melt viscosity by capillary action in a region 15 ° C. higher than the melting point of 10 seconds or less when the developer alone, and the developer and the above A reversible thermosensitive recording, wherein the difference between the melt viscosity when combined with a leuco dye and the melt viscosity when the developer alone is 10 seconds or more (weight ratio) is used with the leuco dye. Medium;

（式中、Ｘは少なくとも１つのヘテロ原子を有する２価の基を示し、Ｒ_１は（ＣＨ_２）ｌで示されるメチレン基（ｌは０以上の整数）を示し、ｍは０以上の整数を示し、Ｙは水素結合性の２価の基を示し、Ｒ_２は（ＣＨ_２）ｎＣＨ_３で示されるアルキル基（ｎは２３以上の整数）を表す）」、
（２）「一般式（１）のｎが２６乃至３５であることを特徴とする、前記第（１）項に記載の可逆性感熱記録媒体」
（３）「該顕色剤が下記一般式（２）で表される尿素化合物であることを特徴とする、前記第（１）項に記載の可逆性感熱記録媒体；

(In the formula, X represents a divalent group having at least one hetero atom, R ₁ represents a methylene group represented by (CH ₂ ) l (l is an integer of 0 or more), and m is an integer of 0 or more. Y represents a hydrogen-bonded divalent group, R ₂ represents an alkyl group represented by (CH ₂ ) nCH ₃ (n represents an integer of 23 or more) ”
(2) “Reversible thermosensitive recording medium according to item (1), wherein n in the general formula (1) is 26 to 35”
(3) “The reversible thermosensitive recording medium according to (1) above, wherein the developer is a urea compound represented by the following general formula (2);

（式中ｎは２３以上の整数を表す）」、
（４）「可逆表示部が設けられた情報記憶部を有する部材であって、該可逆表示部が前記第（１）項乃至第（３）項のいずれかに記載の可逆性感熱記録媒体で形成されたものであり、該情報記憶部を有する部材が、カード、ディスク、ディスクカートリッジ又はテープカセットのいずれかであることを特徴とする情報記憶部を有する部材」、
（５）「前記第（１）項乃至第（３）項のいずれかに記載の可逆性感熱記録媒体を支持体上に有する可逆性感熱記録ラベルであって、該支持体の可逆性感熱記録層を有する面とは反対の面に、接着剤層又は粘着剤層を設けたことを特徴とする可逆性感熱記録ラベル」、
（６）「可逆表示部が設けられた情報記憶部を有する部材であって、該可逆表示部が前記第（５）項に記載の可逆性感熱記録ラベルを用いて形成されたものであり、該情報記憶部を有する部材が、カード、ディスク、ディスクカートリッジ又はテープカセットのいずれかであることを特徴とする情報記憶部を有する部材」、
（７）「前記第（１）項に記載の可逆性感熱記録媒体、前記第（５）項に記載の可逆性感熱記録ラベル、又は前記第（４）項、第（６）項のいずれかに記載の情報記憶部を有する部材の可逆性感熱記録媒体を用いる画像処理方法において、前記可逆性感熱記録層を加熱することにより画像の形成及び／又は消去を行なうことを特徴とする画像処理方法」、
（８）「サーマルヘッドを用いて画像を形成することを特徴とする前記第（７）項に記載の画像処理方法」、
（９）「サーマルヘッド又はセラミックヒータを用いて画像を消去することを特徴とする前記第（８）項に記載の画像処理方法」により達成される。

(Where n represents an integer of 23 or more) ",
(4) “A member having an information storage unit provided with a reversible display unit, wherein the reversible display unit is the reversible thermosensitive recording medium according to any one of the items (1) to (3). A member having an information storage unit, wherein the member having the information storage unit is a card, a disk, a disk cartridge, or a tape cassette,
(5) “Reversible thermosensitive recording label having the reversible thermosensitive recording medium according to any one of items (1) to (3) on a support, wherein the support is reversible thermosensitive recording. A reversible thermosensitive recording label characterized in that an adhesive layer or a pressure-sensitive adhesive layer is provided on the surface opposite to the surface having the layer ",
(6) “A member having an information storage unit provided with a reversible display unit, wherein the reversible display unit is formed using the reversible thermosensitive recording label according to the item (5), A member having an information storage unit, wherein the member having the information storage unit is a card, a disk, a disk cartridge, or a tape cassette.
(7) “The reversible thermosensitive recording medium according to (1), the reversible thermosensitive recording label according to (5), or any of (4) and (6)” above. An image processing method using a reversible thermosensitive recording medium having a member having an information storage section according to claim 1, wherein the image is formed and / or erased by heating the reversible thermosensitive recording layer. "
(8) “Image processing method according to item (7), wherein an image is formed using a thermal head”,
(9) This is achieved by “the image processing method according to item (8), wherein the image is erased using a thermal head or a ceramic heater”.

  As will be apparent from the following detailed and specific description, the reversible thermosensitive recording medium of the present invention has low energy consumption during printing, and is excellent in high-speed printing suitability and storage stability.

The present invention is described in detail below.
In the present invention, a reversible thermosensitive recording medium using a phenol compound can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating.
This basic coloring / decoloring phenomenon will be described.
FIG. 1 shows the relationship between the color density of this recording medium and the temperature. When the temperature of the recording medium initially in the decolored state (A) is raised, the leuco dye and the developer are melted and mixed at a temperature T1 at which the recording medium starts to melt, and color development occurs and a molten color state (B) is obtained. When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature and a fixed color state (C) is obtained. Whether or not this color development state is obtained depends on the rate of temperature decrease from the molten state. In slow cooling, the color disappears during the temperature decrease, and the same color erasing state (A) as the initial state or the rapid color development state (C ) A relatively low concentration state is formed. On the other hand, when the rapid cooling coloring state (C) is heated again, decoloring occurs at a temperature T2 lower than the coloring temperature (D to E), and when the temperature is lowered from here, the same decoloring state (A) as the initial state is restored. The actual color developing temperature and color erasing temperature vary depending on the combination of the developer and color former used, and can be selected according to the purpose. Further, the density of the melt coloring state and the coloring density when rapidly cooled are not necessarily the same and may be different.

  In the recording medium of the present invention, the colored state (C) obtained by quenching from the molten state is a state in which the developer and the color former are mixed in a state in which they can contact each other, and this forms a solid state. Often doing. This state is a state where the developer and the color former are aggregated to maintain the color development, and it is considered that the color development is stabilized by the formation of this aggregated structure. On the other hand, the decolored state is a state in which both phases are separated. This state is a state in which molecules of at least one compound aggregate to form a domain or crystallize, and the color former and developer are separated and stabilized by aggregation or crystallization. It is done. In many cases, in the present invention, more complete color erasure occurs due to phase separation of the two and crystallization of the developer. In both the decoloring by slow cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG. 1, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

  In order to perform erasing in an extremely short heating time such as thermal head heating, the inventors of the present invention have a crystallization speed of the developer when heated from the color developing state (C) to the erasing temperature (T2). Therefore, various studies were conducted.

  The basic structure of the developer used in the reversible thermosensitive recording medium is controlled by the structure having the ability to develop leuco dyes in the molecule, such as phenolic hydroxyl groups and carboxylic acid groups, and the cohesion between molecules. It has been said that a known developer such as a compound having one or more structures having a structure in which long-chain hydrocarbon groups are linked, for example, can be used. As the characteristics of the compound having a melt viscosity in the present invention, among them, the compound has a melting point around 140 ° C., and further has a hydrogen bonding association group and a super long chain alkyl group in the structure. It is mentioned that it is a phenolic compound shown by these. The ultra long chain alkyl group mentioned here is a linear alkyl group having two or more carbon atoms longer than a behenyl group which is generally present at a low price as an industrial chemical and longer than a tetracosyl group. It can be obtained by a carbon increase reaction.

（式中、Ｘは少なくとも１つのヘテロ原子を有する２価の基を示し、Ｒ_１は（ＣＨ_２）ｌで示されるメチレン基（ｌは０以上の整数）を示し、ｍは０以上の整数を示し、Ｙは水素結合性の２価の基を示し、Ｒ_２は（ＣＨ_２）ｎＣＨ_３で示されるアルキル基（ｎは２３以上の整数）を表す）

(In the formula, X represents a divalent group having at least one hetero atom, R ₁ represents a methylene group represented by (CH ₂ ) l (l is an integer of 0 or more), and m is an integer of 0 or more. Y represents a hydrogen-bonded divalent group, R ₂ represents an alkyl group represented by (CH ₂ ) nCH ₃ (n represents an integer of 23 or more)

The structure of the general formula (1) has been proposed in Japanese Patent No. 3380277 of Patent Document 2, and it is preferable that n is larger, but it is described that n is 22 or more, which is not preferable in terms of manufacturing cost. Yes. As a result of intensive synthesis and evaluation of compounds having n of 22 or more, the present inventors have found that the storage stability is remarkably improved when n is 23 or more, particularly n is 27 or more. Furthermore, it was found that n is 26 to 35 as a more preferable range, and 27 to 34 as a particularly preferable range.
Among them, the urea compound represented by the following general formula (2) is particularly excellent.

（式中ｎは２３以上の整数を表す）

(Where n represents an integer of 23 or more)

Such a phenolic compound can be obtained, for example, by the following synthesis method.
[Synthesis example]

To the reaction vessel, 50 mL of toluene and 2.0 g of mellic acid were added, 1.1 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 3 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 10 mL of acetone was added and stirred with ice cooling. Thereto was gradually added an aqueous solution in which 0.43 g of sodium azide was dissolved so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 1.5 hours. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 0.48 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 2.35 g, and the yield was 95%.
Other phenolic compounds can be obtained in the same manner.

In addition, the leuco dyes used in the present invention can be used alone or in combination, and are known dye precursors such as phthalide compounds, azaphthalide compounds and fluoran compounds.
Specific examples of the leuco dye used in the present invention include the following.
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) Luolan, 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) fluorane, 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-6-diethylaminofluorane, -(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-xylidino-3-methyl-6-dibutylaminofluorane, 2- (o-chloroanilino) -6-diethylaminofluor Oran, 2- (o-chloroanilino) -6-dibutylaminofluorane, 2- (m-trifluoromethylanilino) -6-diethylaminofluorane, 2,3-dimethyl-6-dimethylaminofluorane, 3- Methyl-6- (N-ethyl-p-toluidino) fluorane, 2-chloro-6-diethylaminofluorane, 2-bromo-6-diethylamino Nofluorane, 2-chloro-6-dipropylaminofluorane, 3-chloro-6-cyclohexylaminofluorane, 3-bromo-6-cyclohexylaminofluorane, 2-chloro-6- (N-ethyl-N-isoamyl) Amino) 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) fluor Lan, 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-methylindole- 3-yl) -3- (2-methyl-4-diethylaminophenyl) -7-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4 Diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (4-Nn-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- And azaphthalide and 3,3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide.

A leuco dye having a melting point (decomposition point) higher than the melting point of the developer by 10 ° C. or more, preferably 15 ° C. or more is preferably used. Among them, 2-anilino-3-methyl-6-diethylaminofur is particularly preferable as the leuco dye. Oran, 2-anilino-3-methyl-6-di (n-butylamino) fluorane, 2- (3-toluidino) -3-methyl-6-diethylaminofluorane and 2-xylidino-3-methyl-6-dibutyl By using at least one of aminofluoranes, it is possible to obtain a clear printed image with good color density, erasability and storage stability of the image area, pure color tone and pure black.
Here, the color former and the developer can be used by being encapsulated in a microcapsule.

  In the present invention, examples of the binder resin used for forming the reversible thermosensitive recording layer together with the leuco dye and the developer include polyvinyl chloride, polyvinyl acetate, vinyl chloride vinyl acetate copolymer, ethyl cellulose, polystyrene, and styrene copolymer. Polymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid copolymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, Examples include carboxymethyl cellulose and starches. The role of these binder resins is to keep the materials of the composition uniformly dispersed without being displaced by the application of heat for recording and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. For example, the binder resin may be crosslinked with heat, ultraviolet light, electron beam, or the like.

  Specific examples of the crosslinked resin used in the present invention include acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, phenoxy resin, polyvinyl butyral resin, cellulose acetate propionate, and cellulose acetate butyrate. A resin having a reactive group, or a resin obtained by copolymerization of a monomer having a group reactive with a crosslinking agent and another monomer may be used, but the present invention is not limited to these compounds.

  Further, in the present invention, a resin having a hydroxyl value of 70 (KOHmg / g) or more is preferably contained (initially used). Examples of the resin having a hydroxyl value of 70 (KOHmg / g) or more include acrylic polyol resins and polyester polyols. Resins, polyurethane polyol resins, and the like are used, and acrylic polyol resins are preferably used because they have particularly good color stability and good decoloring properties. The hydroxyl value is 70 (KOHmg / g) or more, particularly preferably 90 (KOHmg / g) or more. The magnitude of the hydroxyl value affects the crosslink density and thus affects the chemical resistance and physical properties of the coating film. The present inventors have found that durability, coating film surface hardness, and crack resistance are improved when the hydroxyl value is 70 (KOHmg / g) or more. Whether or not the resin is a reversible thermosensitive recording material using a resin having a hydroxyl value of 70 (KOHmg / g) or more can be confirmed by analyzing the amount of residual hydroxyl groups and the amount of ether bonds.

  In addition, acrylic polyol resins have different characteristics depending on the structure. Hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate ( HPMA), 2-hydroxybutyl monoacrylate (2-HBA), 1,4-hydroxybutyl monoacrylate (1-HBA), etc. are used, but it is particularly preferable to use a monomer having a primary hydroxyl group. Since the crack resistance and durability are good, 2-hydroxyethyl methacrylate is preferably used.

  As the crosslinking agent (curing agent) used in the present invention, a conventionally known crosslinking agent capable of reacting with an active hydrogen group of a polyol, for example, isocyanates, epoxy compounds, hydroxy group-containing siloxane capable of dehydration condensation with a polyol, methylol group-containing Examples include urea derivatives, methylol group-containing guanamine derivatives, and methylol group-containing phenols. Of these, isocyanate curing agents are preferably used. The isocyanate compound used here is selected from known modified urethane monomers, allophanate-modified, isocyanurate-modified, burette-modified, carbodiimide-modified, blocked isocyanate and the like. The isocyanate monomer that forms the modified product includes tolylene diisocyanate (TDI), 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 (LDI), isopropylidenebis (4-cyclohexylisocyanate) (IPC) ), Cyclohexyl diisocyanate (CHDI), tolidine diisocyanate (TODI), and the like. It is not limited to the compounds.

  Furthermore, you may use the catalyst used for this kind of reaction 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 total amount of the curing agent may or may not undergo a crosslinking reaction. That is, an 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 progressed at all, but an unreacted curing agent is detected. However, this does not mean that there is no resin in a crosslinked state. Further, as a method for distinguishing whether the polymer in the present invention is in a crosslinked state or in a non-crosslinked state, it can be distinguished by immersing the coating film in a highly soluble solvent. That is, since the polymer in the non-crosslinked state dissolves in the solvent and does not remain in the solute, the presence or absence of the polymer structure of the solute may be analyzed.

As a drying / curing method for the reversible thermosensitive recording layer, a curing treatment is performed as necessary after coating and drying. A constant temperature bath or the like may be used for a relatively short time at a relatively high temperature, or a heat treatment may be performed at a relatively low temperature for a long time. As specific conditions for the crosslinking reaction, it is preferable to heat from about 1 minute to 150 hours under a temperature condition of about 30 ° C. to 130 ° C. from the viewpoint of reactivity. More preferably, heating is performed for about 2 minutes to 120 hours under a temperature condition of 40 ° C to 100 ° C. In addition, since productivity is emphasized in production, it is difficult to take time until the crosslinking is sufficiently completed. Therefore, a crosslinking step may be provided separately from the drying step. As a condition for the crosslinking step, it is preferable to heat at a temperature of 40 ° C. to 100 ° C. for about 2 minutes to 120 hours.
The film thickness of the reversible thermosensitive recording layer is preferably in the range of 1 to 20 μm, more preferably 3 to 15 μm.

  In the reversible thermosensitive recording layer of the present invention, conventionally known additives can be used in order to improve the coating characteristics of the reversible thermosensitive recording layer as required. These additives include, for example, surfactants, conductive agents, fillers, antioxidants, light stabilizers, and color stabilizers.

  In the present invention, the ratio of the color forming component to the resin in the reversible thermosensitive recording layer is preferably 0.1 to 10 with respect to the color developing component 1, and if it is less than this, the heat intensity of the reversible thermosensitive recording layer is insufficient. If the amount is larger than this, the color density is lowered, which causes a problem.

  Further, an erased state is formed by using together the developer having the above-described characteristics and a compound having a divalent group containing at least one N atom or O atom in the molecule as a decoloring accelerator. In the process, it was found that an intermolecular interaction was induced between the color erasing accelerator and the developer, and the erasing speed was remarkably increased.

As the decoloring accelerator used in the present invention, an amide group (—NHCO—), a secondary amide group (> NCO—), a urethane group (—NHCOO—), a urea group (—NHCONH—), a ketone group ( -CO-), diacyl hydrazide groups (-CONHNHCO-), sulfone groups (-SO _2- ) and the like are preferred, and compounds having amide groups, secondary amide groups, and urethane groups are particularly preferred. Examples of the compound having a group or a urethane group include compounds represented by the following general formulas (3) to (10).

（式中、Ｒ^３，Ｒ^４，Ｒ^６，Ｒ⁸，Ｒ⁹は炭素数１以上２２以下の直鎖アルキル基、分枝アルキル基、不飽和アルキル基を示し、Ｒ⁸，Ｒ⁹は環を形成していてもよく、形成される環はＮ原子、Ｏ原子またはＳ原子を介していてもよく、芳香族環、脂肪族環を有していてもよい。またアルキル基は水酸基、ハロゲン原子、アルコキシ基等の置換基を有していてもよい。Ｒ^５は炭素数１〜１８の２価の官能基、Ｒ^７は炭素数４〜１８の３価の官能基を示す。またＹはＮ原子またはＯ原子を含む２価の基を示し、ｓは０または１の整数を示す。）
Ｒ^３、Ｒ^４、Ｒ^６、Ｒ⁸、Ｒ⁹の好ましい例としては、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ウンデシル基、ドデシル基、ステアリル基、ベヘニル基、オレイル基および末端に水酸基を有する炭素数１〜１０のヒドロキシアルキル基等が挙げられる。またＲ⁸、Ｒ⁹の他の好ましい例としてはメチル基、エチル基、ベンジル基、フェニルエチル基、シクロヘキシルメチル基、ヒドロキシエチル基等が挙げられ、環状の構造を形成する場合にはブチレン基、ペンタメチレン基、ヘキサメチレン基、−Ｃ₂Ｈ₄ＯＣ₂Ｈ₄−基、−Ｃ_２Ｈ_４ＮＣ_２Ｈ_４−基、−Ｃ_２Ｈ_４ＯＣ_２Ｈ_４ＯＣ_２Ｈ_４−基等が挙げられる。Ｒ^５の好ましい例としてはメチレン基、エチレン基、プロピレン基、ブチレン基、ペンタメチレン基、ヘキサメチレン基、ヘプタメチレン基、オクタメチレン基、−Ｃ_３Ｈ_６ＯＣ_３Ｈ_６−基、−Ｃ_２Ｈ_４ＯＣ_２Ｈ_４−基、−Ｃ_２Ｈ_４ＯＣ_２Ｈ_４ＯＣ_２Ｈ_４−基等が挙げられる。またＲ^７の好ましい例として、

(In the formula, R ³ , R ⁴ , R ⁶ , R ⁸ , and R ⁹ represent a linear alkyl group having 1 to 22 carbon atoms, a branched alkyl group, and an unsaturated alkyl group, and R ⁸ and R ⁹ represent a ring. The ring formed may be via an N atom, an O atom or an S atom, and may have an aromatic ring or an aliphatic ring. It may have a substituent such as an atom or an alkoxy group, R ⁵ represents a divalent functional group having 1 to 18 carbon atoms, R ⁷ represents a trivalent functional group having 4 to 18 carbon atoms, and Y. Represents a divalent group containing an N atom or an O atom, and s represents an integer of 0 or 1.)
Preferred examples of R ³ , R ⁴ , R ⁶ , R ⁸ and R ⁹ include hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, stearyl, behenyl, oleyl and Examples thereof include a hydroxyalkyl group having 1 to 10 carbon atoms having a hydroxyl group at the terminal. Other preferred examples of R ⁸ and R ⁹ include a methyl group, an ethyl group, a benzyl group, a phenylethyl group, a cyclohexylmethyl group, a hydroxyethyl group, and the like. When forming a cyclic structure, a butylene group, A pentamethylene group, a hexamethylene group, a —C ₂ H ₄ OC ₂ H ₄ — group, a —C ₂ H ₄ NC ₂ H ₄ — group, a —C ₂ H ₄ OC ₂ H ₄ OC ₂ H ₄ — group, and the like. It is done. Preferred examples of R ⁵ include methylene group, ethylene group, propylene group, butylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, —C ₃ H ₆ OC ₃ H ₆ — group, —C _2. H ₄ OC ₂ H ₄ - _{group, -C 2 H 4 OC 2 H} 4 OC 2 H 4 - group, and the like. As a preferred example of R ⁷ ,

等が挙げられる。Ｙの好ましい例としてはアミド基、ウレタン基、尿素基、ケトン基、ジアシルヒドラジド基等が挙げられる。ただし、本発明はこれらに限定されるものではない。

Etc. Preferable examples of Y include amide group, urethane group, urea group, ketone group, diacyl hydrazide group and the like. However, the present invention is not limited to these.

Specific examples of the compounds represented by the general formulas (3) to (10) include the following.
_{C 11 H 23 CONHC 12 H 25} , C 15 H 31 CONHC 16 H 33, C 17 H 35 CONHC 18 H 37, C 17 H 35 CONHC 18 H 35, C 21 H 41 CONHC 18 H 37, C 15 H 31 CONHC _{18 H 37, C 17 H 35} CONHCH 2 NHCOC 17 H 35, C 11 H 23 CONHCH 2 NHCOC 11 H 23, C 7 H 15 CONHC 2 H 4 NHCOC 17 H 35, C 9 H 19 CONHC 2 H 4 NHCOC 9 H _{19, C 11 H 23 CONHC 2} H 4 NHCOC 11 H 23, C 17 H 35 CONHC 2 H 4 NHCOC 17 H 35, (CH 3) 2 CHC 14 H 35 CONHC 2 H 4 NHCOC 14 H 35 (CH 3) 2 , C _{1 H 43 CONHC 2 H 4 NHCOC} 21 H 43, C 17 H 35 CONHC 6 H 12 NHCOC 17 H 35, C 21 H 43 CONHC 6 H 12 NHCOC 21 H 43, C 17 H 33 CONHCH 2 NHCOC 17 H 33, C _{17 H 33 CONHC 2 H 4 NHCOC} 17 H 33, C 21 H 41 CONHC 2 H 4 NHCOC 21 H 41, C 17 H 33 CONHC 6 H 12 NHCOC 17 H 33, C 8 H 17 NHCOC 2 H 4 CONHC 18 H 37 _{, C 10 H 21 NHCOC 2 H} 4 CONHC 10 H 21, C 12 H 25 NHCOC 2 H 4 CONHC 12 H 25, C 18 H 37 NHCOC 2 H 4 CONHC 18 H 37, C 21 H 43 NHCOC 2 H 4 _{CONHC 21 H 43, C 18 H} 37 NHCOC 6 H 12 CONHC 18 H 37, C 18 H 35 NHCOC 4 H 8 CONHC 18 H 35, C 18 H 35 NHCOC 8 H 16 CONHC 18 H 35, C 12 H 25 OCONHC 18 H ₃₇ , C ₁₃ H ₂₇ OCONHC ₁₈ H ₃₇ , C ₁₆ H ₃₃ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ OCONHC ₁₈ H ₃₇ , C ₂₁ H ₄₃ OCONHC ₁₈ H _37, C ₁₂ H ₂₅ OCONHC ₁₆ H ₃₃ , C ₁₃ H ₂₇ OCONHC ₁₆ H ₃₃ , C ₁₆ H ₃₃ OCONHC ₁₆ H ₃₃ , C ₁₈ H ₃₇ OCONHC ₁₆ H ₃₃ , C ₂₁ H ₄₃ OCONHC ₁₆ H ₃₃ , C ₁₂ H ₂₅ OCONHC ₁₄ H ₂₉ , C ₁₃ H ₂₇ O CONHC ₁₄ H ₂₉ , C ₁₆ H ₃₃ OCONHC ₁₄ H ₂₉ , C ₁₈ H ₃₇ OCONHC ₁₄ H ₂₉ , C ₂₂ H ₄₅ OCONHC ₁₄ H ₂₉ , C ₁₂ H ₂₅ OCONHC ₁₂ H ₃₇ , C ₁₃ H ₂₇ OCONHC ₁₂ H ₃₇ C ₁₆ H ₃₃ OCONHC ₁₂ H ₃₇ , C ₁₈ H ₃₇ OCONHC ₁₂ H ₃₇ , C ₂₁ H ₄₃ OCONHC ₁₂ H ₃₇ , C ₂₂ H ₄₅ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ NHCOOC ₂ H ₄ OCONC ₁₈ H _{37 18} H ₃₇ NHCOOC ₃ H ₆ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ NHCOOC ₄ H ₈ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ NHCOOC ₆ H ₁₂ OCONHC ₁₈ H ₃₇ , C ₁₈ H ₃₇ NHCOOC _{8 16 OCONHC 18 H 37, C 18} H 37 NHCOOC 2 H 4 OC 2 H 4 OCONHC 18 H 37, C 18 H 37 NHCOOC 3 H 6 OC 3 H 6 OCONHC 18 H 37, C 18 H 37 NHCOOC 12 H 24 OCONHC 18 H ₃₇ C ₁₈ H ₃₇ NHCOOC ₂ H ₄ OC ₂ H ₄ OC ₂ H ₄ OCONHC ₁₈ H ₃₇ , C ₁₆ H ₃₃ NHCOOC ₂ H ₄ OCONHC ₁₆ H ₃₃ , C ₁₆ H ₃₃ NHCOOC ₃ H ₆ OCONHC ₁₆ H _{33 16} H ₃₃ NHCOOC ₄ H ₈ OCONHC ₁₆ H ₃₃ , C ₁₆ H ₃₃ NHCOOC ₆ H ₁₂ OCONHC ₁₆ H ₃₃ , C ₁₆ H ₃₃ NHCOOC ₈ H ₁₆ OCONHC ₁₆ H ₃₃ , C ₁₈ H ₃₇ OCOHNC _{6 H 12 NHCOOC 18 H 37,} C 16 H 33 OCOHNC 6 H 12 NHCOOC 16 H 33, C 14 H 29 OCOHNC 6 H 12 NHCOOC 14 H 29, C 12 H 25 OCOHNC 6 H 12 NHCOOC 12 H 25, C 10 H ₂₁ OCOHNC ₆ H ₁₂ NHCOOC ₁₀ H ₂₁ , C ₈ H ₁₇ OCOHNC ₆ H ₁₂ NHCOOC ₈ H ₁₇ ,

表中、ｎ，ｎ’，ｎ''，ｎ'''，ｎ''''は０〜２１の整数を示す。ただし全てが５以下であることはない。

In the table, n, n ′, n ″, n ′ ″, and n ″ ″ represent integers from 0 to 21. However, all are not 5 or less.

  Further, according to the present invention, a protective layer containing a resin in a crosslinked state can be provided on the reversible thermosensitive recording layer. As the resin used for the protective layer, the same thermosetting resin as the above-mentioned reversible thermosensitive recording layer and / or a conventionally known ultraviolet curable resin or electron beam curable resin can be used. Furthermore, in the present invention, the protective layer may contain a conventionally known inorganic / organic filler, lubricant, ultraviolet absorbing material and the like. In the formation of 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 of the protective layer, the dispersion apparatus of the coating liquid, the binder, the coating method, the drying / curing method, and the like can be known methods used for the recording layer.

  Furthermore, the adhesion between the reversible thermosensitive recording layer and the protective layer is improved, the alteration of the reversible thermosensitive recording layer is prevented by coating the protective layer, the additives contained in the protective layer are transferred to the reversible thermosensitive recording layer, or the reversible In order to prevent the additive contained in the thermal recording layer from moving to the protective layer, an intermediate layer (first protective layer) may be provided therebetween. The thickness of the intermediate layer is preferably in the range of 0.1 to 20 μm, more preferably 0.3 to 10 μm. As the solvent used in the intermediate layer coating solution, the dispersion device of the coating solution, the binder, the coating method, the drying / curing method, etc., known methods used in the recording layer can be used. Furthermore, in the present invention, the intermediate layer may contain a conventionally known inorganic / organic filler, lubricant, ultraviolet absorbing material and the like.

  The support of the reversible thermosensitive recording medium of the present invention is paper, resin film, PET film, synthetic paper, metal foil, glass or a composite thereof, and the like, as long as it can hold the reversible thermosensitive recording layer. Good. Moreover, the thing of the thickness as needed can be used individually or by bonding. That is, it is preferably 60 to 150 μm, and a support having an arbitrary thickness from about several μm to about several mm is used.

  In the present invention, an undercoat layer is preferably provided between the support and the reversible thermosensitive recording layer in order to improve the color development sensitivity by effectively utilizing the heat applied to the medium during recording. The undercoat layer can be formed by a method of foaming after applying a foamable plastic filler, a method of providing a polyurethane foam, a method of applying and drying a coating liquid containing hollow particles, etc., among which organic or inorganic micro hollow body particles are formed. A method of coating and providing using the contained binder resin is particularly preferable. For the undercoat layer, the same resin as the resin for the reversible thermosensitive recording layer and the protective layer can be used. The undercoat layer can contain inorganic fillers such as calcium carbonate, magnesium carbonate, titanium oxide, silicon oxide, aluminum hydroxide, kaolin, and talc and / or various organic fillers. In addition, a surfactant, a dispersant, and the like can be contained. Furthermore, when providing the said undercoat layer, crack generation | occurrence | production prevention and generation | occurrence | production of a burr | flash are improved by providing through an adhesive layer. The adhesive layer can be formed by the same coating method as that for each of the above layers. Further, as the fine hollow particles, the maximum particle size (D100) is 5.0 to 10.0 μm, and at the same time, the ratio D100 / D50 to the 50% frequency particle size (D50) is 2.0 to 3.0. It is more preferable to use a material that meets the above conditions. Instead of providing the undercoat layer, a plastic sheet including voids such as foamable PET may be used.

The reversible thermosensitive recording label of the present invention comprises an adhesive layer or a pressure-sensitive adhesive layer on the surface opposite to the surface on which the reversible thermosensitive recording layer of the support constituting the above-described reversible thermosensitive recording medium is formed. is there.
This reversible thermosensitive recording label includes an adhesive layer or a pressure-sensitive adhesive layer (non-peeling paper type), and a release paper attached under the adhesive layer or pressure-sensitive adhesive layer (peeling paper type). As a material constituting the adhesive layer, a hot melt type material is usually used.

Commonly used materials can be used for the adhesive layer or the pressure-sensitive adhesive layer.
For example, urea resin, melamine resin, phenol resin, epoxy resin, vinyl acetate resin, vinyl acetate-acrylic copolymer, ethylene-vinyl acetate copolymer, acrylic resin, polyvinyl ether resin, vinyl chloride-vinyl acetate Copolymer, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, chlorinated polyolefin resin, polyvinyl butyral resin, acrylic ester copolymer, methacrylic ester copolymer, natural rubber , Cyanoacrylate resins, silicon resins, and the like, but are not limited thereto.

  The reversible thermosensitive recording medium of the present invention is produced by combining at least a reversible thermosensitive layer constituting the reversible thermosensitive recording medium as a reversible display unit and a member having an information storage function (information storage unit). It can be used as an information display storage member.

Next, the information display storage member will be described.
The members having the information storage unit and the reversible display unit can be roughly classified into the following three items.
(1) A member having an information storage function is used as a support for a reversible thermosensitive recording medium, and a reversible thermosensitive layer is directly formed thereon.
(2) The support surface of a reversible thermosensitive recording medium which has a reversible thermosensitive layer formed on a support and is separately bonded to a member having an information storage function.
(3) The reversible thermosensitive recording label bonded to a member having an information storage function via an adhesive layer or an adhesive layer.
In these cases (1), (2), and (3), it is necessary to set the functions of the information storage unit and the reversible display unit so that the functions of the information storage unit are set. The position can be arbitrarily selected according to the purpose, and it can be provided on the surface of the reversible thermosensitive recording medium opposite to the surface on which the reversible thermosensitive layer is provided, between the support and the thermosensitive layer, or heat sensitive. It can also be provided on a part of the layer.
The member having the information storage function is not particularly limited, and a general card, disk, disk cartridge, or tape cassette can be used.

Examples of these include thick cards such as IC cards and optical cards, flexible disks, magneto-optical recording disks (MD), disk cartridges with built-in disks that can rewrite storage information such as DVD-RAM, and CD-RWs. Examples thereof include a disc that does not use a disc cartridge, a write-once disc such as a CD-R, an optical information recording medium (CD-RW) that uses a phase-change storage material, and a video tape cassette.
The information display storage member having both the reversible display function and the information storage function will be described in the case of a card, for example, by displaying a part of the information stored in the information storage unit on the reversible thermosensitive recording layer. The owner or the like can confirm information by looking at the card without a special device, and the convenience is greatly improved compared to a card to which the reversible thermosensitive recording medium is not applied.

The information storage unit is not particularly limited as long as it can store necessary information. For example, magnetic recording, contact IC, non-contact IC, or optical memory is useful.
The magnetic recording layer is formed by coating the support using a commonly used metal compound such as iron oxide or barium ferrite and a resin such as vinyl chloride, urethane or nylon, or without using a resin. It forms by methods, such as vapor deposition and sputtering, using the said metal compound. Further, the reversible thermosensitive recording layer in the reversible thermosensitive recording medium used for display can also be used as a storage unit in a manner such as a barcode or a two-dimensional code.

In addition, as an example of using the reversible thermosensitive recording label of (3) above, when the reversible thermosensitive recording layer is difficult to apply as a support, such as a vinyl chloride card with a magnetic stripe, An adhesive layer or a pressure-sensitive adhesive layer can be provided on the entire surface or a part thereof.
By doing so, the convenience of this medium can be improved, such as being able to display a part of the information stored in the magnetism.
The reversible thermosensitive recording label provided with the adhesive layer or the pressure-sensitive adhesive layer is applicable not only to the above-described magnetic PVC card but also to a thick card such as an IC card or an optical card.

Further, the reversible thermosensitive recording label can be used in place of a display label on a disk cartridge having a built-in disk capable of rewriting storage information such as a flexible disk, MD, DVD-RAM and the like.
Further, in the case of a disc that does not use a disc cartridge such as a CD-RW, a reversible thermosensitive recording label can be directly attached to the disc, or a reversible thermosensitive recording layer can be provided directly on the disc. By doing so, it is possible to apply to applications such as automatically changing display contents in accordance with changes in the stored contents.

The reversible thermosensitive recording label of the present invention can also be displayed by rewriting a part of the stored information added to the CD-R by sticking the reversible thermosensitive recording label on a write-once disc such as a CD-R.
Further, it may be used as a display label for a video tape cassette.
As a method of providing a thermoreversible recording function on a thick card, a disc cartridge, and a disc, in addition to the method of applying the reversible thermosensitive recording label, a method of directly applying a reversible thermosensitive recording layer on them, There is a method of forming a reversible thermosensitive recording layer on the support and transferring the thermosensitive recording layer onto a thick card, a disc cartridge, or a disc.
When transferring, an adhesive layer such as a hot melt type or an adhesive layer may be provided on the reversible thermosensitive recording layer.
When attaching a reversible thermosensitive recording label or providing a reversible thermosensitive recording layer on a rigid object such as a thick card, disk, disk cartridge, tape cassette, etc., improve the contact with the thermal head. In order to form an image uniformly, it is preferable to provide a cushioning layer or sheet between the rigid substrate and the label or the reversible thermosensitive recording layer.

  The present invention further provides an image processing method, wherein the reversible thermosensitive recording medium, the member having the information storage unit or the label is used to form and / or erase an image by heating.

For image formation, an image recording means such as a thermal head or a laser that can partially heat the medium on the image is used. For erasing the image, an image erasing means such as a hot stamp, a ceramic heater, a heat roller, hot air, a thermal head, a laser or the like is used.
Among these, a ceramic heater is preferably used. By using a ceramic heater, the apparatus can be miniaturized, a stable erased state can be obtained, and an image with good contrast can be obtained.
The set temperature of the ceramic heater is preferably 90 ° C. or higher, and more preferably 100 ° C. or higher.
Further, by using a thermal head as the image erasing means, it is possible to further reduce the size of the entire apparatus, to reduce power consumption, and to realize a battery-driven handy type apparatus. If a single thermal head is used for both forming and erasing, the size can be further reduced.
When forming and erasing with a single thermal head, once the previous image has been erased, a new image may be formed again. The energy is changed for each image, and the previous image is erased at one time. It is also possible to use an overwrite method that forms the film.
In the overwrite method, the time required for forming and erasing is reduced, and the recording speed is increased. In the case of using a card having a reversible thermosensitive recording layer and an information storage unit, the above device includes means for reading and rewriting the memory of the information storage unit.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the text, “part” or “%” is based on weight unless otherwise specified.

[Example 1]
<Preparation of hollow particles>
Dissolve 55 g of sodium chloride in 160 g of ion-exchanged water, add 1.0 g of adipic acid-diethanolamine condensate and 25 g of colloidal silica 20% aqueous solution, adjust the pH from 3.8 to 4.2 with sulfuric acid, and uniformly Mix to make the aqueous phase. 45 g acrylonitrile, 16 g methacrylonitrile, 5 g N-methylolacrylamide, 23 g isobornyl methacrylate, 0.1 g ethylene glycol dimethacrylate, 0.3 g azobisisobutyronitrile, 1,1-azobis (cyclohexane-1-carbonitrile (V-40) 0.1 g and isobutane 15 g are mixed, stirred and dissolved to obtain an oil phase, which is mixed with an aqueous phase and an oil phase, and stirred at 3500 rpm for 1 minute with a homomixer. This was transferred to a separable flask and purged with nitrogen, and then reacted with stirring at 70 ° C. for 6 hours and then at 90 ° C. After the reaction, the mixture was cooled and filtered to obtain capsule particles. The hollow particles were formed by heating to form a hollow particle having a Tg of 105 ° C., a hollow ratio of 91%, and a particle size of D10. Is 9.0μm, D100 / D50 was 2.0.

<Preparation of undercoat layer>
Aqueous dispersion of hollow particles (solid content concentration 30%) 30 parts Polyurethane resin emulsion (solid content concentration 35%, Dai-ichi Kogyo Seiyaku Superflex 150) 28 parts Fully saponified polyvinyl alcohol aqueous solution (solid content concentration 16%) 9 Part Water 50 parts The above mixture was stirred and dispersed to prepare an undercoat layer coating solution. The undercoat layer coating solution having the above composition was applied on a white PET film (manufactured by Teijin) with a thickness of about 250 μm using a wire bar and dried at 80 ° C. for 2 minutes to provide an undercoat layer with a thickness of about 14 μm.

<Preparation of reversible thermosensitive recording layer>
3 parts developer with the following structure (Mp142 ° C)

アクリルポリオール樹脂の５０％メチルエチルケトン（ＭＥＫ）溶液 ９部
（水酸基価：７０、分子量：２８０００、Ｔｇ８０℃）
ジオクタデシルウレタン １部
メチルエチルケトン（ＭＥＫ） ７０部
上記組成物をボールミルを用いて平均粒径約１μｍまで粉砕分散した。得られた分散液に２−アニリノ−３−メチル−６−ジブチルアミノフルオラン１部、日本ポリウレタン社製コロネートＨＬ（アダクト型ヘキサメチレンジイソシアネート７５％酢酸エチル溶液）２部を加え、良く攪拌し感熱記録層塗布液を調製した。上記組成の可逆性感熱記録層塗布液を、上記中間層塗布済みＰＥＴフィルム上にワイヤーバーを用い塗布し、１１０℃３分で乾燥した後、６０℃で２４時間加熱して、膜厚約１０μｍの可逆性感熱記録層を設けた。
さらにこの記録層上に下記組成よりなる中間層液をワイヤーバーを用い塗布し、９０℃１分で乾燥した後、６０℃２時間加熱して、膜厚約１μｍの中間層を設けた。更にこの中間層上に、下記組成よりなる保護層液をワイヤーバーを用いて塗工した後、照射エネルギー８０Ｗ／ｃｍの紫外線ランプ下を１２ｍ／分の搬送速度で通して硬化して膜厚４μｍの保護層を設け、本発明の可逆性感熱記録媒体を作製した。

9 parts of 50% methyl ethyl ketone (MEK) solution of acrylic polyol resin (hydroxyl value: 70, molecular weight: 28000, Tg 80 ° C.)
Dioctadecyl urethane 1 part Methyl ethyl ketone (MEK) 70 parts The above composition was pulverized and dispersed to a mean particle size of about 1 µm using a ball mill. To the obtained dispersion, 1 part of 2-anilino-3-methyl-6-dibutylaminofluorane and 2 parts of Coronate HL (Adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. were added and stirred well. A recording layer coating solution was prepared. The reversible thermosensitive recording layer coating liquid having the above composition is applied onto the intermediate layer-coated PET film using a wire bar, dried at 110 ° C. for 3 minutes, and then heated at 60 ° C. for 24 hours to obtain a film thickness of about 10 μm. The reversible thermosensitive recording layer was provided.
Further, an intermediate layer solution having the following composition was applied onto the recording layer using a wire bar, dried at 90 ° C. for 1 minute, and then heated at 60 ° C. for 2 hours to provide an intermediate layer having a thickness of about 1 μm. Further, a protective layer solution having the following composition was coated on the intermediate layer using a wire bar, and then cured by passing under a UV lamp with an irradiation energy of 80 W / cm at a conveyance speed of 12 m / min, to a film thickness of 4 μm. A reversible thermosensitive recording medium of the present invention was prepared.

[Intermediate layer liquid]
10% MEK solution of polyester polyol resin (Takelac U-21, Takeda Pharmaceutical Co., Ltd.) 100 parts Zinc oxide (Sumitomo Osaka Cement Co., Ltd.) 10 parts Coronate HL (Nippon Polyurethane Co., Ltd.) 15 parts

[Protective layer solution]
7 parts of urethane acrylate UV curable resin (C7-157 manufactured by Dainippon Ink Co., Ltd.)
Dipentaerythritol caprolactone-modified acrylic acid ester 3 parts (KAYARAD DPCA-120 manufactured by Nippon Kayaku Co., Ltd.)
Silica (P-527 manufactured by Mizusawa Chemical Co., Ltd.) 1.5 parts 90 parts ethyl acetate

[Example 2]
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compound (Mp137 ° C.) was used as the developer in Example 1.

[Example 3]
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the following compound (Mp 140 ° C.) was used as the developer in Example 1.

[Example 4]
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compound (Mp 142 ° C.) was used as the developer in Example 1.

[Example 5]
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the following compound (Mp 141 ° C.) was used as the developer in Example 1.

[Example 6]
Except for changing 2-anilino-3-methyl-6-dibutylaminofluorane used in Example 4 to 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluorane, A reversible thermosensitive recording medium was produced in the same manner as in Example 1.

[Example 7]
Except that 2-anilino-3-methyl-6-dibutylaminofluorane used in Example 5 was changed to 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluorane, A reversible thermosensitive recording medium was produced in the same manner as in Example 1.

[Comparative Example 1]
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the following compound (Mp 140 ° C.) was used as the developer in Example 1.

[Comparative Example 2]
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compound (Mp123 ° C.) was used as the developer in Example 1.

[Comparative Example 3]
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compound (Mp125 ° C.) was used as the developer in Example 1.

[Comparative Example 4]
A reversible thermosensitive recording medium was prepared in the same manner as in Example 1 except that the following compound (Mp 120 ° C.) was used as the developer in Example 1.

[Comparative Example 5]
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the amount of the compound as a developer in Example 1 was changed from 1 part to 2 parts.

[Comparative Example 6]
A reversible thermosensitive recording medium was produced in the same manner as in Example 1 except that the amount of the compound (Mp 142 ° C.) as a developer in Example 1 was changed from 1 part to 0.3 part.

(Evaluation methods)
1. Melt viscosity The target powder was finely ground in advance in a mortar, and the mixed powder of the developer and leuco dye was thoroughly mixed in the mortar. Next, the hot plate was heated to 15 ° C. higher than the melting point of the developer, monitored using a thermocouple, and waited until the target temperature was reached. An appropriate amount of powder was placed on a cover glass (made of borosilicate glass) manufactured by Matsunami Glass Co., Ltd., and a glass capillary tube (1-000-0020 manufactured by Drummond Co.) marked in advance at a position 15 mm from the end was prepared, and the target temperature was reached. At the time, both were placed on a hot plate, and after confirming the uniform melting of the powder by visual observation, the tip of the glass capillary was quickly immersed in the melt. The glass tube was left on the hot plate while leaving the tip immersed in the melt. The time required for the liquid level to reach the marking position after soaking was measured three times and averaged and adopted as the melt viscosity.

2. Printing energy Print the gradation image while changing the set voltage in 0.5V increments in the range of 10-22V with thermal printing erasure simulator (conveyance speed 30mm / s) and measure the image density with Macbeth densitometer RD-914. did. The printing energy (mJ / dot) at which the image density is 1.0 was obtained by extrapolation.

3. High-speed erasing suitability Solid images are printed with the energy of the saturation concentration described above, and then in the thermal printing erasing simulator (conveyance speed 120mm / s) equipped with ceramic heater (heater width 4mm) in the range of 80-140 ° C. The image was erased while changing the set temperature in increments of 5 ° C. The density of the portion where the image disappeared most and the non-printed portion at that time was measured with a Macbeth densitometer RD-914.

4). Image storability A solid image was printed in the same manner as in 3, and the image density before and after storage at 60 ° C. for 24 hours was measured with a Macbeth densitometer RD-914.
The above evaluation results are shown in Table 4.

It is a figure which shows the color development and decoloring characteristic of the reversible thermosensitive coloring composition of this invention. It is a figure which shows the example which stuck the reversible thermosensitive recording label on the disk cartridge of MD. It is a figure which shows the example which stuck the reversible thermosensitive recording label on CD-RW. It is a figure which shows the example used as a display label of a videotape cassette. It is a figure which shows the example of the image processing apparatus of this invention.

Explanation of symbols

34 Magnetic head 38 Ceramic heater 40 Transport roller 47 Transport roller 53 Thermal head

Claims (9)

Using a leuco dye as an electron-donating color-forming compound and a developer as an electron-accepting compound on a support, a relatively colored state and decoloration due to differences in heating temperature and / or cooling rate after heating In the reversible thermosensitive recording medium having a reversible thermosensitive recording layer containing a reversible thermosensitive composition capable of forming a developed state, the developer is a phenolic compound represented by the following general formula (1), The developer has a melt viscosity due to capillary action in a region 15 ° C. higher than the melting point of 10 seconds or less when the developer is used alone, and the melt viscosity and the developer when the developer and the leuco dye are combined. A reversible thermosensitive recording medium, characterized in that it is used with the leuco dye at a ratio (weight ratio) such that the difference from the melt viscosity when the agent is used alone is 10 seconds or more.

(In the formula, X represents a divalent group having at least one hetero atom, R ₁ represents a methylene group represented by (CH ₂ ) l (l is an integer of 0 or more), and m is an integer of 0 or more. Y represents a hydrogen-bonded divalent group, R ₂ represents an alkyl group represented by (CH ₂ ) nCH ₃ (n represents an integer of 23 or more) The reversible thermosensitive recording medium according to claim 1, wherein n in the general formula (1) is 26 to 35. The reversible thermosensitive recording medium according to claim 1, wherein the developer is a urea compound represented by the following general formula (2).

(Where n represents an integer of 23 or more) A member having an information storage unit provided with a reversible display unit, wherein the reversible display unit is formed of the reversible thermosensitive recording medium according to any one of claims 1 to 3, and the information storage unit A member having an information storage unit, wherein the member having any of the above is a card, a disk, a disk cartridge, or a tape cassette. A reversible thermosensitive recording label comprising the reversible thermosensitive recording medium according to any one of claims 1 to 3 on a support, on the surface opposite to the surface having the reversible thermosensitive recording layer of the support, A reversible thermosensitive recording label provided with an adhesive layer or a pressure-sensitive adhesive layer. A member having an information storage unit provided with a reversible display unit, wherein the reversible display unit is formed using the reversible thermosensitive recording label according to claim 5, and has the information storage unit Is a card, a disk, a disk cartridge, or a tape cassette. The reversible thermosensitive recording medium according to claim 1, the reversible thermosensitive recording label according to claim 5, or the reversible thermosensitive recording medium having a member having an information storage unit according to claim 4 or 6 is used. In the image processing method, an image is formed and / or erased by heating the reversible thermosensitive recording layer. The image processing method according to claim 7, wherein an image is formed using a thermal head. The image processing method according to claim 8, wherein the image is erased using a thermal head or a ceramic heater.

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