JP5658109B2 - Reversible thermosensitive recording material - Google Patents

Description

  The present invention relates to a reversible thermosensitive recording material capable of rewriting a recording, which makes it possible to repeatedly record and erase an image by utilizing a reversible change in transparency depending on the temperature of a thermosensitive recording layer.

  Magnetic cards and IC cards that can record and store various kinds of information are used in commuter pass tickets for transportation, admission permits to event venues and buildings, and various prepaid cards. However, with these cards, it is not possible to directly check the contents of the stored records, so it is not possible to easily check the payment amount or balance, and to clarify the content guarantee of the stored information to the user. There was a problem from the point of view. Conventionally, in order to solve such problems, these cards are used as recording media, and visual recording is performed on the cards, the recording is erased, and the recording is rewritten as the stored information is changed. Has been proposed (see Patent Documents 1 to 3). For example, in a heat-sensitive recording material, the heat-sensitive recording layer is made of a reversible heat-sensitive recording paint so that the heat-sensitive recording layer is transparent according to the temperature when heat is applied from the outside such as a thermal head. There is a technique for changing the light transmittance in a range from a state to a cloudy state, while maintaining the state after cooling. If this technology is used, it is possible to display the changed contents so as to be visible at any time in the cards as described above on the assumption that the stored information contents are changed. Therefore, it is extremely useful.

  However, the reversible thermosensitive recording material constituting such a thermosensitive recording layer has scratches or abrasion on the surface of the reversible thermosensitive recording material caused by repeated pressure or heating by a thermal head or the like when image formation and erasing are repeated. This causes a problem that image formation cannot be performed. In view of this, studies have been made to provide a heat-resistant protective layer for the purpose of improving the durability of the thermosensitive recording layer. For example, it has been proposed to provide a protective layer made of a thermoplastic resin or a thermosetting resin or a protective layer made of an ultraviolet curable resin or an electron beam curable resin on the thermosensitive recording layer (Patent Documents 4 to 4). 6). However, even if the protective layer is formed, there is a problem that wrinkles scraped by the thermal head adhere to the thermal head and image formation and erasure become insufficient. Therefore, in order to prevent the generation of head wrinkles by imparting lubricity to the protective layer, silicone oil is added to the curable resin, or a curable silicone resin or a silicone-modified resin is used as the protective layer forming material. (See Patent Documents 7 to 9).

  Furthermore, recently, due to increasing environmental problems, many manufacturers are actively working on this environmental measure, and there is a movement to construct products using materials with excellent environmental conservation. The above-mentioned reversible thermosensitive recording material is no exception, and it is possible to rewrite a disposable object as many times as possible, especially against the backdrop of garbage problems and forest destruction problems. As a result, it has been noticed that it helps to solve environmental problems (eco), and has been actively studied and partly put into practical use. However, most of the raw materials for conventional reversible thermosensitive recording materials are derived from petroleum, and from the original point of view, the current environmental preservation on a global scale is still insufficient.

  As can be seen in Non-Patent Documents 1 and 2, polyhydroxy polyurethane resin using carbon dioxide as a raw material has been known for a long time, but its application development has not progressed. This is because the above-mentioned resins that have been conventionally known are clearly inferior in terms of characteristics as compared with the conventional polyurethane-based resins that are the same type of high-molecular compound (fossilized plastic) (see Patent Documents 10 and 11). .

  On the other hand, the global warming phenomenon, which is thought to be caused by the ever-increasing carbon dioxide emissions, has become a global problem in recent years, and the reduction of carbon dioxide emissions is an important issue worldwide. Therefore, there is a long-awaited technology that can use carbon dioxide as a raw material for production. Furthermore, from the viewpoint of the exhaustible petrochemical resource (oil) problem, the shift to renewable resources such as biomass and methane has become a global trend.

  Against the background as described above, the polyhydroxy polyurethane resin has been reviewed again. In other words, carbon dioxide, which is the raw material for this resin, is an easily available and sustainable carbon resource, and plastics that use carbon dioxide as a raw material solve problems such as global warming and resource depletion. It is because it can be said that it is an effective means.

JP-A 63-139784 Japanese Patent Publication No. 01-30638 JP 05-85047 A Japanese Patent Laid-Open No. 06-8626 Japanese Patent Application Laid-Open No. 06-344672 Japanese Patent Laid-Open No. 08-11433 JP-A-2005-212362 JP 2005-53124 A JP 05-38881 A U.S. Pat. No. 3,072,613 JP 2000-319504 A

N. Kihara, T. Endo, J. Org. Chem., 1993, 58, 6198 N. Kihara, T. Endo, J. Polymer Sci., Part A Polmer Chem., 1993, 31 (11), 2765

  Under such circumstances, the surface of the reversible thermosensitive recording material having the thermosensitive recording layer can be provided with good heat resistance and lubricity, and the image forming and erasing can be repeated by a heating element such as a thermal head. Even if the thermal head heat and pressure are high, there is no flaws on the surface and no head wrinkles. Furthermore, it has good printability when printing on the surface, and is environmentally friendly with environmental protection on a global scale. Development of a reversible thermosensitive recording material is demanded.

  Therefore, the object of the present invention is excellent in heat resistance and slipperiness, and even if image formation and erasing are repeated many times by a heating element such as a thermal head, and even if heat and pressure are high, surface scratches and head wrinkles adhere. The object of the present invention is to develop a technology capable of providing an environmentally-friendly product that can use carbon dioxide as a raw material and is also useful from the viewpoint of protecting the global environment, even though it is a reversible thermosensitive recording material having a slippery protective layer.

  The above object is achieved by the present invention described below. That is, the present invention relates to a heat-sensitive recording material having a base material and a heat-sensitive recording layer provided on at least one surface of the base material, an intermediate layer provided as necessary, and a slippery protective layer in this order. The thermosensitive recording layer is a reversible thermosensitive recording layer comprising, as a main component, a polymer resin and an organic low molecular weight substance dispersed in the polymer resin, and the transparency can reversibly change with temperature, and Self-crosslinked polysiloxane modified with a slippery protective layer having an isocyanate group masked in its structure, derived from a reaction between a 5-membered cyclic carbonate polysiloxane compound represented by the following general formula (1) and an amine compound A reversible thermosensitive recording material characterized in that it is formed of a resin composition containing a polyhydroxy polyurethane resin as a main component.

該式中のＲ₁は、炭素数１〜１２のアルキレン基（該基中にＯ、Ｓ、又はＮの各元素による連結及び／又は−(Ｃ₂Ｈ₄Ｏ)_b−による連結を有していてもよい）を表す。上記式（１）中のＲ₂は、ないか、又は、炭素数２〜２０のアルキレン基を表し、Ｒ₂は、脂環族基又は芳香族基に連結していてもよい。ｂは１〜３００の数を表わし、ａは１〜３００の数を表す。］

R ₁ in the formula has an alkylene group having 1 to 12 carbon atoms (linkage by each element of O, S, or N and / or linkage by — (C ₂ H ₄ O) _b — in the group). May be present). R ₂ in the above formula (1) is absent or represents an alkylene group having 2 to 20 carbon atoms, and R ₂ may be linked to an alicyclic group or an aromatic group. b represents a number from 1 to 300, and a represents a number from 1 to 300. ]

  Preferred embodiments of the reversible thermosensitive recording material of the present invention include the following. The 5-membered cyclic carbonate polysiloxane compound is a reaction product of an epoxy-modified polysiloxane compound and carbon dioxide, and the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin contains 1 carbon dioxide in its structure. A reversible thermosensitive recording material comprising in the range of ˜25% by mass. A reversible thermosensitive recording material in which the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin has a polysiloxane segment content in the molecule of 1 to 75% by mass. The masked isocyanate group is a reaction product of an organic polyisocyanate group and a masking agent, and the masked portion is dissociated by heat treatment to form an isocyanate group, and a self-crosslinking polysiloxane modified polyhydroxy A reversible thermosensitive recording material which reacts with a hydroxyl group in the structure of a polyurethane resin and self-crosslinks. The self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin is a reversible product obtained by modifying a polysiloxane-modified polyhydroxypolyurethane resin derived from the reaction between a 5-membered cyclic carbonate polysiloxane compound and an amine compound with a modifier. Sensitive thermal recording material. A reversible thermosensitive recording material in which the intermediate layer comprises a single layer or a combination of multiple layers comprising a printed layer, a colored layer, and a heat-resistant protective layer.

  According to the present invention, the slipping protective layer is formed using the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin, so that it is excellent in slipping and heat resistance, and can be heated and pressured by a thermal head or a heat roll. A reversible thermosensitive recording material is provided that is strong, further prevents surface flaws and head wrinkles due to a thermal head, and has good printability. The above resin can provide such an excellent reversible thermosensitive recording material. At the same time, carbon dioxide can be used as a raw material, and carbon dioxide can be incorporated into the resin, contributing to the reduction of global warming gas. It is possible to provide a reversible thermosensitive recording material as an environmentally friendly product.

Next, the present invention will be described in more detail with reference to preferred embodiments.
The reversible heat-sensitive recording material of the present invention comprises a heat-sensitive recording layer whose transparency can be reversibly changed depending on temperature on at least one surface of a substrate, and an intermediate layer formed thereon if necessary. A slipping protective layer is provided, and the slipping protective layer has the following structure. That is, the polymer compound constituting the slippery protective layer contains an isocyanate group masked in the molecule, and is a self-crosslinked polysiloxane derived from the reaction of a 5-membered cyclic carbonate polysiloxane compound and an amine compound. It is characterized by comprising a modified polyhydroxy polyurethane resin as a main component.

  The masked isocyanate group of the resin is a reaction product of an organic polyisocyanate group and a masking agent, and the masked portion is dissociated by heat treatment to form an isocyanate group. It reacts with the hydroxyl group in the structure of the hydroxy polyurethane resin and self-crosslinks. For this reason, by using this resin, it is possible to obtain a slipping protective layer which is excellent in slipping and heat resistance, and further has excellent surface scratches and head wrinkle prevention by a thermal head and printing suitability. Furthermore, the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin characterizing the present invention is a resin derived from the reaction of a specific 5-membered cyclic carbonate polysiloxane compound and an amine compound, Since a siloxane compound can be obtained as a reaction product of an epoxy-modified polysiloxane compound and carbon dioxide, it can be a material that contributes to environmental conservation.

[Self-crosslinking polysiloxane modified polyhydroxy polyurethane resin]
The self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin used in the present invention uses a modifier having at least one free isocyanate group and a masked isocyanate group. It can be easily obtained by reacting with a hydroxyl group in a polysiloxane-modified polyhydroxypolyurethane resin derived from a reaction between a membered cyclic carbonate polysiloxane compound and an amine compound. As a modifier used at this time, a reaction product of an organic polyisocyanate compound and a masking agent may be used. Below, each component is demonstrated.

(Modifier)
<Organic polyisocyanate compound>
Below, the component of the modifier used when producing the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin characterizing the present invention will be described. As the modifier, a reaction product of an organic polyisocyanate compound and a masking agent is used. The organic polyisocyanate compound is an organic compound having at least two isocyanate groups in an aliphatic or aromatic compound, and has been widely used as a raw material for synthesizing polyurethane resins. Any of these known organic polyisocyanate compounds are useful in the present invention. Particularly preferred organic polyisocyanate compounds are as follows.

  For example, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), 4,4′- Examples include dicyclohexylmethane diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, and xylylene diisocyanate. Furthermore, adducts of these organic polyisocyanate compounds and other compounds, for example, those having the following structural formulas are exemplified, but the present invention is not limited thereto.

<Masking agent>
The modifier used in the present invention is a reaction product of the above-described organic polyisocyanate compound and masking agent, and the following can be used as the masking agent. For example, there are masking agents such as alcohols, phenols, active methylenes, acid amides, imidazoles, ureas, oximes, and pyridines, and these may be used alone or in combination. Specific masking agents include those listed below.

  Examples of alcohols include methanol, ethanol, propanol, butanol, 2-ethylhexanol, methyl cellosolve, and cyclohexanol. Examples of phenol-based compounds include phenol, cresol, ethylphenol, and nonylphenol. Examples of the active methylene type include dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone. Examples of acid amides include acetanilide, acetic acid amide, caprolactam, and γ-butyrolactam. Examples of imidazole compounds include imidazole and 2-methylimidazole. Examples of urea-based materials include urea, thiourea, and ethylene urea. Examples of oxime-based compounds include formamide oxime, acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime. Examples of pyridine-based compounds include 2-hydroxypyridine and 2-hydroxyquinoline.

<Method of synthesizing denaturant>
A modifier having at least one free isocyanate group and a masked isocyanate group used in the present invention by reacting an organic polyisocyanate compound as listed above with a masking agent as listed above. Synthesize. Although the synthesis method is not particularly limited, the masking agent as described above and the organic polyisocyanate compound are functional groups in which one or more isocyanate groups are excessive in one molecule, in the presence or absence of an organic solvent and a catalyst. It can be easily obtained by reacting at a temperature of 0 to 150 ° C., preferably 20 to 80 ° C. for 30 minutes to 3 hours.

(Polysiloxane-modified polyhydroxypolyurethane resin)
The polysiloxane-modified polyhydroxypolyurethane resin modified with the specific modifier as described above of the present invention is obtained by a reaction between a specific 5-membered cyclic carbonate polysiloxane compound and an amine compound. Below, each component used in this case is demonstrated.

<5-membered cyclic carbonate polysiloxane compound>
The 5-membered cyclic carbonate polysiloxane compound represented by the general formula (1) used in the present invention is produced by reacting an epoxy-modified polysiloxane compound and carbon dioxide as shown in the following [Formula-A]. can do. More specifically, the epoxy-modified polysiloxane compound is prepared in the presence or absence of an organic solvent and in the presence of a catalyst at a temperature of 40 ° C. to 150 ° C. under a normal pressure or a slightly increased pressure. Obtained by reacting with carbon dioxide for hours.

  Examples of the epoxy-modified polysiloxane compound used in the present invention include the following compounds.

  The epoxy-modified polysiloxane compounds listed above are preferable compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Accordingly, not only the compounds exemplified above, but also any other compounds that are currently commercially available and can be easily obtained from the market can be used in the present invention.

  Examples of the catalyst that can be used in the reaction of the above-described epoxy-modified polysiloxane compound and carbon dioxide include a base catalyst and a Lewis acid catalyst.

  Base catalysts include tertiary amines such as triethylamine and tributylamine, cyclic amines such as diazabicycloundecene, diazabicyclooctane and pyridine, alkali metal salts such as lithium chloride, lithium bromide, lithium fluoride and sodium chloride , Alkaline earth metal salts such as calcium chloride, quaternary ammonium salts such as tetrabutylammonium chloride, tetraethylammonium bromide, benzyltrimethylammonium chloride, carbonates such as potassium carbonate and sodium carbonate, zinc acetate, lead acetate, copper acetate And metal acetates such as iron acetate, metal oxides such as calcium oxide, magnesium oxide and zinc oxide, and phosphonium salts such as tetrabutylphosphonium chloride.

  Examples of the Lewis acid catalyst include tin compounds such as tetrabutyltin, dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin octoate.

  The amount of the catalyst is 0.1 to 100 parts by mass, preferably 0.3 to 20 parts by mass, per 50 parts by mass of the epoxy-modified polysiloxane compound. If the amount used is less than 0.1 parts by mass, the effect as a catalyst is small, and if it exceeds 100 parts by mass, various performances of the final resin may be deteriorated. Therefore, in the case where the residual catalyst causes a significant decrease in performance, it may be configured to be removed by washing with pure water.

  Examples of the organic solvent that can be used in the reaction between the epoxy-modified polysiloxane compound and carbon dioxide include dimethylformamide, dimethylsulfoxide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, and tetrahydrofuran. These organic solvents and other poor solvents such as methyl ethyl ketone, xylene, toluene, tetrahydrofuran, diethyl ether, and cyclohexanone may be used in a mixed system.

<Amine compound>
As shown in the following [Formula-B], the resin used in the present invention is obtained by, for example, combining a 5-membered cyclic carbonate polysiloxane compound and an amine compound obtained by the above reaction in the presence of an organic solvent at 20 ° C to It can be obtained by reacting at a temperature of 150 ° C.

  As an amine compound used for the said reaction, diamine is preferable, for example, What was conventionally used for manufacture of a polyurethane resin can be used, and it is not specifically limited. For example, aliphatic diamines such as methylenediamine, ethylenediamine, trimethylenediamine, 1,3-diaminopropane, hexamethylenediamine, octamethylenediamine; phenylenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 4 , 4′-methylenebis (phenylamine), 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, metaxylylenediamine, paraxylylenediamine, and the like; 1,4-cyclohexanediamine, 4 , 4'-diaminocyclohexylmethane, 1,4'-diaminomethylcyclohexane, isophoronediamine and other alicyclic diamines; monoethanoldiamine, ethylaminoethanolamine, hydroxyethylaminopropylamine Like alkanol diamine is. Furthermore, any other compounds that are currently commercially available and can be easily obtained from the market can be used in the present invention.

(Synthesis of self-crosslinking polysiloxane modified polyhydroxy polyurethane resin)
The self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin characterizing the present invention can be obtained by reacting the modifier obtained as described above with the polysiloxane-modified polyhydroxypolyurethane resin. Specifically, it is obtained by reacting a hydroxyl group in the polysiloxane-modified polyhydroxypolyurethane resin with at least one free isocyanate group in the modifier.

The modification rate of the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin characterizing the present invention with a modifier is preferably 2 to 60%. If the modification rate is less than 2%, sufficient crosslinking will not occur, and when used as a slippery protective layer of a reversible thermosensitive recording material, the slipperiness and heat resistance may be insufficient. On the other hand, if the modification rate exceeds 60%, there is a possibility that the dissociated isocyanate group may remain without reacting, which is not preferable. The modification rate is calculated as follows.
Modification rate (%) = {1− (hydroxyl group of resin after modification ÷ hydroxyl group of resin before modification)} × 100

  The reaction between the modifier and the polysiloxane-modified polyhydroxypolyurethane resin is carried out in the presence or absence of an organic solvent and a catalyst at a temperature of 0 to 150 ° C., preferably 20 to 80 ° C., for 30 minutes to 3 hours. It is preferable. By setting it as such reaction conditions, the target resin can be obtained easily. However, it should be noted that the reaction is performed at a temperature lower than the dissociation temperature of the masking agent during the reaction, so that the synthesized self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin has a masked isocyanate group in its structure. It is necessary to.

  The self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin characterizing the present invention is such that the proportion of the polysiloxane segment in the resin is 1 to 75% by mass in the content of the segment in the resin molecule. Is preferred. That is, if it is less than 1% by mass, the expression of the function accompanying the surface energy based on the polysiloxane segment becomes insufficient, which is not preferable. On the other hand, if it exceeds 75% by mass, the performance of the polyhydroxyurethane resin such as mechanical strength and abrasion resistance becomes insufficient, such being undesirable. Preferably it is 2-65 mass%, and it is more preferable that it is 5-30 mass%.

  Moreover, it is preferable that the number average molecular weight (standard polystyrene conversion value measured by GPC) of the self-crosslinking type polysiloxane modified polyhydroxypolyurethane resin characterizing the present invention is about 2,000 to 100,000. Furthermore, it is more preferable that it is about 5,000-70,000.

  Furthermore, the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin that characterizes the present invention preferably has a hydroxyl value of 20 to 300 mgKOH / g. If the hydroxyl value is less than the above range, it is difficult to obtain a carbon dioxide reduction effect. On the other hand, if the hydroxyl value exceeds the above range, various physical properties as a polymer compound may not be obtained.

(Sliding protective layer)
In addition, when forming a slippery protective layer with the above-mentioned resin characterizing the present invention, for the purpose of adjusting coating properties for various intermediate layers described later, improving film formability, and adjusting the content of polysiloxane segments. In addition to the above-mentioned self-crosslinking type polysiloxane-modified polyhydroxypolyurethane resin, various conventionally known binder resins can be mixed and used. As the binder resin used in this case, for example, those capable of chemically reacting with the polyisocyanate group generated by dissociation of the masking agent in the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin are preferable. Even a resin which does not have can be used in the present invention.

  As these binder resins, conventionally used binder resins can be used and are not particularly limited. For example, acrylic resin, polyurethane resin, polyester resin, polybutadiene resin, silicone resin, melamine resin, phenol resin, polyvinyl chloride resin, cellulose resin, alkyd resin, modified cellulose resin, fluorine resin, polyvinyl butyral resin, epoxy resin, polyamide resin Etc. can be used. Also, resins obtained by modifying various resins with silicone or fluorine can be used. When these binder resins are used in combination, the amount used is 5 to 90 parts by mass, more preferably about 10 to 60 parts by mass with respect to 100 parts by mass of the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin characterizing the present invention. It is good to use in the range.

  Furthermore, in order to improve the heat resistance and lubricity of the slippery protective layer, fine particles such as conventionally known organic lubricants, silica, calcium carbonate, precipitated barium sulfate, and various resin crosslinked particles can be contained.

  The method for forming the slippery protective layer (film) characterizing the present invention is not particularly limited. For example, the above-mentioned self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin is dissolved or dispersed in a suitable organic solvent, and this is, for example, a wire bar method, gravure printing method, screen printing method, reverse roll coating using a gravure plate It can be formed as a crosslinked film by coating with a forming means such as a method and then drying. The drying temperature at this time is preferably in the range of 50 to 140 ° C, more preferably 50 to 100 ° C. For example, a sufficient crosslinked film is formed by treating at a temperature of 50 to 100 ° C. for several hours to several days. Moreover, 0.01-3.00 micrometers is preferable, for example, and, as for the thickness of the slipperiness protective layer formed by the above methods, 0.1-2.0 micrometers is preferable.

〔Base material〕
The reversible thermosensitive recording material of the present invention comprises a slipping protective layer that characterizes the present invention having the above-described configuration, on at least one surface of a substrate, and a thermosensitive recording layer described later and an intermediate provided as necessary. It is obtained by forming through layers. As a base material used in this case, for example, a plastic film, a glass plate, a metal plate, or a plate or sheet like paper can be used, and various thicknesses are possible. In addition, those provided with a colored coating layer on the front surface or the back surface thereof, plastic films kneaded with colored pigments, and the like can also be used as a substrate. Further, a plastic film provided with a reflective layer such as metal vapor deposition can also be used as a substrate.

(Thermosensitive recording layer)
The thermosensitive recording layer constituting the reversible thermosensitive recording material of the present invention comprises a polymer resin and an organic low molecular weight substance dispersed in the polymer resin as a main component, and the reversible feeling that the transparency can reversibly change with temperature. It is a thermal recording layer. Since the reversible thermosensitive recording material of the present invention has such a reversible thermosensitive recording layer, it can be repeatedly recorded and erased by heating. Hereinafter, each component for forming a reversible thermosensitive recording layer will be described.

(Polymer resin)
The polymer resin constituting the reversible thermosensitive recording layer is capable of forming a layer in which an organic low-molecular substance described later is uniformly dispersed and held, and is preferably a highly transparent and mechanically stable resin. . Examples of such resins include polyvinyl chloride, polyvinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride- Vinyl chloride copolymers such as acrylate copolymers, polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride copolymers such as vinylidene chloride-acrylonitrile copolymers, polyesters, polyamides, polyacrylates or polyacrylates Examples thereof include methacrylates and acrylate-methacrylate copolymers. These may be used alone or in combination of two or more.

(Organic low molecular weight substance)
The organic low molecular weight substance constituting the reversible thermosensitive recording layer is preferably present in a state of being dispersed in the above polymer resin in the form of particles and having a particle size distributed in the range of about 0.1 to 2 μm. . Generally called wax or wax, it is a solid at room temperature and contains a long-chain alkyl group having about 10 to 60 carbon atoms, fatty acids, alcohols, esters, amides, and ketones composed of long-chain alkyl groups. , Ethers, thioethers or amines are preferred.

  Specific examples include the following. Lauric acid, dodecanoic acid, myristic acid, palmitic acid, pentadecanoic acid, stearic acid, arachidic acid, behenic acid, heneicosanoic acid, tricosanoic acid, glinoselic acid, pentacosanoic acid, cerotic acid, heptacosanoic acid, montanic acid, mellicic acid, nonadecanoic acid Higher fatty acid compounds such as oleic acid; higher alcohol compounds such as stearyl alcohol, behenyl alcohol, C30 alcohol; octadecyl laurate, tetradecyl palmitate, dodecyl behenate, methyl stearate, tetradecyl stearate, octadecyl stearate, stearic acid High such as stearyl, behenyl stearate, behenyl behenate, behenyl montanate, stearic acid C30 alcohol ester, behenic acid C30 alcohol ester Fatty acid ester compounds; such as palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, N-stearyl stearic acid amide, N-oleyl palmitic acid amide, N-stearyl erucic acid amide, N-stearyl oleic acid amide Amide compounds; ketone compounds such as distearyl ketone and dibehenyl ketone.

Furthermore, the following higher aliphatic ethers, higher aliphatic thioethers, higher aliphatic amines, and the like are exemplified, but the present invention is not limited thereto. For example, C ₁₆ H ₃₃ —O—C ₁₆ H ₃₃ , C ₁₆ H ₃₃ —S—C ₁₆ H ₃₃ , C ₁₈ H ₃₇ —S—C ₁₈ H ₃₇ , C ₁₂ H ₂₅ —S—C ₁₂ H ₂₅ , _{C 19 H 39 -S-C 19} H 39, C 12 H 25 -S-S-C 12 H 25, C 11 H 23 -OCO-CH 2 CH 2 -O-CH 2 CH 2 -OCO-C 11 H ₂₃ , C ₁₇ H ₃₅ —OCO—CH ₂ CH ₂ —O—CH ₂ CH ₂ —OCO— C ₁₇ H ₃₅ , C ₁₂ H ₂₅ —OCO—CH ₂ CH ₂ —S—CH ₂ CH ₂ —OCO—C ₁₂ H ₂₅ , C ₁₈ H ₃₇ —OCO—CH ₂ CH ₂ —S—CH ₂ CH ₂ —OCO—C ₁₈ H ₃₇ , C ₁₈ H ₃₇ —OCO—CH ₂ CH ₂ —NH—CH ₂ CH ₂ —OCO etc. -C ₁₈ H ₃₇ and the like. These long-chain alkyl group-containing compounds may be used singly or in combination of two or more.

  The reversible thermosensitive recording layer comprises an organic low molecular weight substance (hereinafter referred to as “low melting point organic low molecular weight substance” in addition to the above organic low molecular weight substance). By adding a high melting point organic low molecular weight substance), it is possible to widen the temperature range for transparency. As the high melting point organic low molecular weight substance, a substance having a melting point of 80 ° C. to 180 ° C. is preferable, and saturated aliphatic bisamide and saturated aliphatic dicarboxylic acid having a melting point in the range of 90 ° C. to 160 ° C. are particularly preferable.

  Specific high melting point organic low molecular weight substances that can be used in the present invention include the following. For example, saturated aliphatic bisamides include ethylene bis stearamide, ethylene bis behenamide, hexamethylene bis behenamide, hexamethylene bis behenamide, N, N-distearyl adipate amide, N, N-diamide. Examples include stearyl eicosane diamide, N, N-distearyl sebacic diamide, N, N-dilauryl decanedioic acid amide, N, N-distearyl dodecanedioic acid amide, and the like. Examples of saturated aliphatic dicarboxylic acids include adipic acid, pyrophosphoric acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, tridecanediic acid, tetradecanediic acid, pentadecanediic acid, hexadecanediic acid, peptadecanediic acid, octadecane Examples include diacid, nonadecanedioic acid, and eicosandioic acid.

  However, it is not limited to these, and other high-melting-point organic low-molecular substances such as bisamides, dicarboxylic acids, saturated fatty acid monoamides, methylolamides, unsaturated fatty acid bisamides, and aromatic bisamides other than those described above can be used. These high melting point organic low molecular weight substances can be used alone or in combination.

  When the low melting point organic low molecular weight substance and the high melting point organic low molecular weight substance are used as the organic low molecular weight substance, the blending ratio is preferably in the range of 99: 1 to 45:55 by mass ratio. Outside this range, not only the effect of increasing the clearing temperature range is not obtained, but also the contrast between the transparent state and the white turbid state becomes insufficient, which is not preferable.

  Furthermore, the forming material for the reversible thermosensitive recording layer may contain a lubricant, an antistatic agent, a plasticizer, a dispersant, a stabilizer, a surfactant, an inorganic or organic filler, if necessary. .

  The film thickness of the reversible thermosensitive recording layer is usually 1 to 40 μm, preferably 2 to 20 μm. If the heat-sensitive recording layer is too thick, heat distribution in the layer occurs, which is not preferable. On the other hand, if the thermosensitive recording layer is thinner than this, the white turbidity is lowered and the contrast is lowered, which is not preferable.

[Middle layer]
The reversible thermosensitive recording material of the present invention can be provided with various intermediate layers as required. The intermediate layer may be a single layer or a combination of multiple layers, and can be appropriately provided as necessary within the scope of the effect of the present invention. Specifically, for example, a printed layer or a colored layer for the purpose of designability, and a heat-resistant protective layer can be provided. Conventionally known materials can be used for the printing layer and the colored layer, and examples of materials used for the heat-resistant protective layer include silicone resins, acrylic resins, alkyd resins, UV curable resins, and EB curable resins.

[Other layers]
Furthermore, if it is within the range of the effect of the present invention, the magnetic recording layer for recording information between the substrate and the thermosensitive recording layer, and the contrast between the transparent state and the clouding state of the thermosensitive recording layer are improved. A reflective layer such as metal vapor deposition can be provided on the substrate. Furthermore, an adhesive layer that enhances the adhesion of the substrate, the heat-sensitive recording layer, and various intermediate layers can be provided.

  The reversible thermosensitive recording material of the present invention comprises a unique self-crosslinking polysiloxane-modified polyhydroxy compound in a resin composition for forming a top protective layer provided on at least one surface of a substrate. Since the polyurethane resin is used, the polysiloxane segment of the resin is oriented on the surface of the protective layer. For this reason, the heat resistance, slipperiness, and non-adhesiveness to the thermal head of the polysiloxane segment are imparted to the formed slippery protective layer. Moreover, the 5-membered cyclic carbonate polysiloxane compound forming the resin used in the present invention can incorporate carbon dioxide into the resin by using carbon dioxide as a production raw material. For this reason, the present invention makes it possible to provide a reversible thermosensitive recording material that is useful from the viewpoint of reducing carbon dioxide, which is a cause of global warming, as an environmentally friendly material product that could not be achieved with conventional products. Become.

  Next, the present invention will be described in more detail with reference to specific production examples, polymerization examples, examples and comparative examples, but the present invention is not limited to these examples. In the following examples, “part” and “%” are based on mass unless otherwise specified.

<Production Example 1> (Production of modifier)
Trimethylolpropane and hexamethylene diisocyanate trimer adduct [Coronate HL (trade name), manufactured by Nippon Polyurethane Co., Ltd., NCO = 12.9%, solid content 75%] 100 parts, ethyl acetate 24.5 parts at 100 ° C. Then, 25.5 parts of ε-caprolactam was added and allowed to react for 5 hours. According to the infrared absorption spectrum of the obtained modifier (measurement apparatus is FT-720 manufactured by HORIBA, Ltd., the same applies hereinafter), the absorption due to the free isocyanate group remains at 2,270 cm ⁻¹ . Quantified, the theoretical value was 2.1% at a solid content of 50%, whereas the measured value was 1.8%. The main structure of the above modifier is presumed to be the following formula.

<Production Example 2> (Production of modifier)
While admixing 100 parts of hexamethylene diisocyanate and water [Duranate 24A-100 (trade name), manufactured by Asahi Kasei Corporation, NCO = 23.0%] and ethyl acetate at 80 ° C., 32 parts of methyl ethyl ketoxime was added. Added and allowed to react for 5 hours. According to the infrared absorption spectrum of the obtained modifier, absorption due to free isocyanate groups remains at 2,270 cm ⁻¹ , and when this free isocyanate group is determined, the theoretical value is 2.9% at a solid content of 50%. On the other hand, the measured value was 2.6%. The main structure of the above modifier is presumed to be the following formula.

<Production Example 3> (Production of modifier)
Trimethylolpropane and tolylene diisocyanate trimer adduct [Coronate L (trade name), manufactured by Nippon Polyurethane Co., Ltd., NCO = 12.5%, solid content 75%] 100 parts, ethyl acetate 67.3 parts at 80 ° C. While stirring well, 17.3 parts of methyl ethyl ketoxime was added and allowed to react for 5 hours. According to the infrared absorption spectrum of the resulting modifier, absorption due to free isocyanate groups remains at 2,270 cm ⁻¹ , and when the free isocyanate groups are quantified, the theoretical value is 2.3% at a solid content of 50%. On the other hand, the measured value was 2.0%. The main structure of the above modifier is presumed to be the following formula.

<Production Example 4> (Production of 5-membered cyclic carbonate polysiloxane compound)
In a reaction vessel equipped with a stirrer, a thermometer, a gas introduction tube and a reflux condenser, a divalent epoxy-modified polysiloxane represented by the following formula A [Shin-Etsu Chemical Co., Ltd., X-22-163; epoxy equivalent 198 g / Mol] After 100 parts, 100 parts of N-methylpyrrolidone and 1.2 parts of sodium iodide were added and dissolved uniformly, carbon dioxide was bubbled at a rate of 0.5 liters / minute for 30 hours at 80 ° C. The mixture was heated and stirred.

  After completion of the reaction, the resulting solution was diluted by adding 100 parts of n-hexane, and then washed 3 times with 80 parts of pure water in a separatory funnel to remove N-methylpyrrolidone and sodium iodide. Thereafter, the n-hexane solution was dehydrated with magnesium sulfate and concentrated to obtain 92 parts (yield: 89.7%) of a colorless and transparent liquid 5-membered cyclic carbonate polysiloxane compound (1-A).

In the infrared absorption spectrum of the obtained product (1-A), absorption of a carbonyl group of a cyclic carbonate group not present in the raw material was confirmed near 1,800 cm ⁻¹ . Moreover, the number average molecular weight of the product was 2,450 (polystyrene conversion, Tosoh; GPC-8220). In the obtained 5-membered cyclic carbonate polysiloxane compound (1-A), 18.1% of carbon dioxide was immobilized.

<Production Example 5> (Production of 5-membered cyclic carbonate polysiloxane compound)
Instead of the divalent epoxy-modified polysiloxane A used in Production Example 4, a divalent epoxy-modified polysiloxane B represented by the following formula B (Shin-Etsu Chemical Co., Ltd., KF-105; epoxy equivalent 485 g / mol) was used. Other than this, the reaction was carried out in the same manner as in Production Example 4 to obtain 99 parts (yield 91%) of a colorless and transparent liquid 5-membered cyclic carbonate polysiloxane compound (1-B). The obtained product was confirmed by infrared absorption spectrum, GPC and NMR.
In the obtained 5-membered cyclic carbonate polysiloxane compound (1-B), 8.3% of carbon dioxide was immobilized.

<Polymerization Example 1> (Production of self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin)
A reaction vessel equipped with a stirrer, a thermometer, a gas introduction tube and a reflux condenser was replaced with nitrogen, and 100 parts of the 5-membered cyclic carbonate polysiloxane compound obtained in Production Example 4 was added to this with a solid content of 35%. Thus, N-methylpyrrolidone was added and dissolved uniformly. Next, 23.9 parts of hexamethylene diamine was added and stirred for 10 hours at a temperature of 90 ° C. until the hexamethylene diamine could not be confirmed. Next, 20 parts (solid content 50%) of the modifier obtained in Production Example 1 was added and reacted at 90 ° C. for 3 hours. After confirming that the absorption of the isocyanate group by the infrared absorption spectrum disappeared, a self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin solution used in the examples of the present invention was obtained.

<Polymerization Examples 2 to 4> (Production of self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin)
Hereinafter, in the same manner as in Polymerization Example 1, a 5-membered cyclic carbonate polysiloxane compound, a polyamine compound, and a modifier were combined and reacted in the same manner as in Polymerization Example 1, and the polymerization examples 2 to 4 shown in Table 1 were performed. A self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin solution used in the examples of the present invention was obtained.

<Comparative polymerization example 1> (Production of polysiloxane-modified polyhydroxypolyurethane resin)
A polysiloxane-modified polyhydroxypolyurethane resin solution used in Comparative Example was obtained in the same manner as in Polymerization Example 1 except that the modifier obtained in Production Example 1 was not used.

<Comparative polymerization example 2> (Polyester polyurethane resin)
The polyurethane resin used in the comparative example was synthesized as follows. A reaction vessel equipped with a stirrer, a thermometer, a gas introduction pipe and a reflux condenser was replaced with nitrogen, and 150 parts of polybutylene adipate having an average molecular weight of about 2,000 and 15 parts of 1,4-butanediol were mixed with 200 parts of methyl ethyl ketone. And 50 parts of dimethylformamide were dissolved in a mixed organic solvent. Thereafter, 62 parts of water-added MDI (methylenebis (1,4-cyclohexane) -diisocyanate) dissolved in 171 parts of dimethylformamide was gradually added dropwise while stirring well at 60 ° C. Reacted for hours. This solution had a viscosity of 3.2 MPa · s (25 ° C.) at a solid content of 35%. The film obtained from this solution had a breaking strength of 45 MPa, a breaking elongation of 480%, and a thermal softening temperature of 110 ° C.

<Comparative Polymerization Example 3> (Polysiloxane-modified polyurethane resin)
The polysiloxane-modified polyurethane resin used in the comparative example was synthesized from diol and amine as follows. 150 parts of polydimethylsiloxanediol represented by the following formula (C) and having an average molecular weight of about 3,200 and 10 parts of 1,4-butanediol are mixed organics consisting of 200 parts of methyl ethyl ketone and 50 parts of dimethylformamide. A solvent was added, and 40 parts of water-added MDI dissolved in 120 parts of dimethylformamide was gradually added dropwise. After completion of the addition, the mixture was reacted at 80 ° C. for 6 hours. This solution has a solid content of 35% and a viscosity of 1.6 MPa · s (25 ° C.). A film obtained from this solution has a breaking strength of 21 MPa and a breaking elongation of 250%, and the heat softening temperature is 135. ° C.

<Examples 1-4 and Comparative Examples 1-3>
Using each of the resin solutions (solid content 35%) obtained in the above polymerization examples and comparative polymerization examples, a heat-sensitive recording layer, a heat-resistant protective layer (intermediate layer), and a slippery protective layer were formed on the substrate by the following method. By forming in this order, reversible thermosensitive recording materials of Examples and Comparative Examples were prepared. As a base material, a metal reflective base material in which an aluminum layer having a thickness of 0.1 μm was formed on a 188 μm polyethylene terephthalate film by a vacuum deposition method was used.

(Formation of thermal recording layer)
After preparing a solution with the following composition and applying it on the above-mentioned base material using a wire bar, it was dried by heating at 140 ° C. for 4 minutes, and the thickness was 12 μm, and the transparency could reversibly change with temperature. A heat-sensitive recording layer was formed.
(Thermosensitive recording layer coating composition; clearing temperature range = 75 to 108 ° C)
Vinyl chloride-vinyl acetate copolymer (manufactured by Nissin Chemical) 30 parts Behenic acid 7 parts Sebacic acid 6 parts Di-2-ethylhexyl phthalate 3 parts Polyisocyanate (Nippon Polyurethane, Coronate HL) 2 parts Tetrahydrofuran 100 parts Ethylene glycol monoethyl 70 parts of ether

(Formation of heat-resistant protective layer)
On the heat-sensitive recording layer formed above, a heat-resistant protective layer as an intermediate layer was formed as follows. Specifically, an acrylic ultraviolet curable resin (manufactured by Dainichi Seika Kogyo Co., Ltd.) was applied on the heat-sensitive recording layer so that the thickness after drying was 5 μm, and then irradiated with ultraviolet rays at 500 mJ / cm ² . A heat-resistant protective layer was formed.

(Formation of slippery protective layer)
Using the resin solutions (solid content 35%) prepared in Polymerization Examples 1 to 4 and Comparative Polymerization Examples 1 to 3, respectively, the metal reflective substrate on which the heat-sensitive recording layer and the heat-resistant protective layer were formed as described above was used. A slipping protective layer was formed as an upper layer. Specifically, first, each resin solution was diluted with a solvent (tetrahydrofuran) so that a film having a desired thickness could be formed, thereby obtaining a resin composition. As shown in Table 2, a crosslinking agent was externally added to the resin solution of the comparative polymerization example. Using the resin composition prepared as described above, it was applied with a wire bar so that the thickness after drying was 1.0 μm, dried in a drier and cross-linked, and the top layer of the substrate was lubricated A protective layer was formed, and reversible thermosensitive recording materials of Examples 1 to 4 and Comparative Examples 1 to 3 were obtained.

<Evaluation>
For each of the reversible thermosensitive recording materials of Examples 1 to 4 and Comparative Examples 1 to 3 obtained above, image formation was performed using a line-type thermal head (8 dots / mm), and a hot plate pressure bonding method (hot plate) The operation for erasing the image at a temperature of 100 to 105 ° C. was repeated 100 times to perform a mounting test. And each characteristic was evaluated as follows and the result was shown in Table 3, respectively.

(Sticking)
The releasability of the reversible thermosensitive recording material from the thermal head during a pressing operation with the thermal head when the printing test was performed under the above conditions was visually observed and evaluated. The evaluation criteria were 5 for the one with the best release and 1 for the worst with a relative evaluation in 5 stages.

(Head contamination)
The state of contamination of the thermal head subjected to the mounting test under the above conditions was observed with an optical microscope and evaluated. At that time, 5 was assigned with the least contamination, 1 was assigned with the least contamination, and a relative evaluation was performed in five stages.

(Surface scratches)
The presence or absence of scratches on the surface of each reversible thermosensitive recording material after the test was visually observed and judged according to the following criteria.
○: No scratch △; Slightly scratch ×: Scratch

(Static friction coefficient)
The static coefficient of friction on the surface of each of the reversible thermosensitive recording materials of Examples and Comparative Examples was measured and evaluated with a surface property tester (manufactured by Shinto Kagaku).

(Image degradation)
The difference between the cloudiness density of the reversible thermosensitive recording material in the initial stage and the cloudiness density of the reversible thermosensitive recording material when the image was erased after the 100-times repeated mounting test as described above was calculated using a Macbeth reflection densitometer (RD-914). ) And the difference is shown in Table 3. The larger this difference, the greater the degradation.

(Environmental compatibility)
The presence or absence of carbon dioxide immobilization in each resin of the forming material of the “sliding protective layer” of the reversible thermosensitive recording materials of Examples and Comparative Examples was evaluated by ○ ×.

  According to the present invention, a slippery protective layer mainly composed of a self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin is formed on the uppermost layer on one side of the substrate, thereby imparting slipperiness and heat resistance, A reversible thermosensitive recording material that is resistant to heating and pressure of a thermal head or a thermal roll, and further prevents surface flaws and head wrinkles due to the thermal head and has good printability. Thus, rewriting of characters and images can be satisfactorily performed over a long period of time. By applying the material to IC cards, etc., where stored information is changed as needed, it is possible to repeatedly display information for ensuring contents in good condition, so that the problem of disposable items is suppressed. Therefore, its use is expected. Further, since the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin used in the present invention can use carbon dioxide as a raw material for production, according to the present invention, carbon dioxide can be reduced as a global warming gas. It is possible to provide reversible thermosensitive recording materials as products that can contribute to the global environment, and this is also expected as a technology that contributes to environmental conservation.

Claims (6)

Provided on at least one side of the substrate and the substrate, and the heat-sensitive recording layer, the heat-sensitive recording material which have a a top layer of lubricous protective layer,
The thermosensitive recording layer is a reversible thermosensitive recording layer comprising, as a main component, a polymer resin and an organic low molecular weight substance dispersed in the polymer resin, and the transparency can reversibly change with temperature, and
Self-crosslinking type polysiloxane having an isocyanate group masked in its structure, wherein the slippery protective layer is derived from a reaction between a 5-membered cyclic carbonate polysiloxane compound represented by the following general formula (1) and an amine compound reversible thermosensitive recording material characterized in that the modified polyhydroxy polyurethane resin is formed by including the resin composition.

R ₁ in the formula has an alkylene group having 1 to 12 carbon atoms (linkage by each element of O, S, or N and / or linkage by — (C ₂ H ₄ O) _b — in the group). May be present). R ₂ in the above formula (1) is absent or represents an alkylene group having 2 to 20 carbon atoms, and R ₂ may be linked to an alicyclic group or an aromatic group. b represents a number from 1 to 300, and a represents a number from 1 to 300. ]   The 5-membered cyclic carbonate polysiloxane compound is a reaction product of an epoxy-modified polysiloxane compound and carbon dioxide, and the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin contains 1 carbon dioxide in its structure. The reversible thermosensitive recording material according to claim 1, comprising in the range of -25% by mass.   The reversible thermosensitive recording material according to claim 1 or 2, wherein the self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin has a polysiloxane segment content in the molecule of 1 to 75% by mass.   The masked isocyanate group is a reaction product of an organic polyisocyanate group and a masking agent, and the masked portion is dissociated by heat treatment to form an isocyanate group, and a self-crosslinking polysiloxane modified polyhydroxy The reversible thermosensitive recording material according to any one of claims 1 to 3, which reacts with a hydroxyl group in the structure of the polyurethane resin and self-crosslinks.   The self-crosslinking polysiloxane-modified polyhydroxypolyurethane resin is obtained by modifying a polysiloxane-modified polyhydroxypolyurethane resin derived from a reaction between a 5-membered cyclic carbonate polysiloxane compound and an amine compound with a modifier. Item 5. The reversible thermosensitive recording material according to any one of Items 1 to 4. And the thermosensitive recording layer, between the uppermost lubricous protective layer, further comprising an intermediate layer, said intermediate layer, printed layer, colored layer, comprising a single layer or multilayer combination comprising a heat protective layer according Item 6. The reversible thermosensitive recording material according to any one of Items 1 to 5.