JP5501942B2 - Thermal recording material - Google Patents

Description

  The present invention relates to a heat-sensitive recording material, and more particularly, the heat-sensitive thermal protection layer is composed of a resin composition having at least a polysiloxane-modified polyhydroxypolyurethane resin. It relates to recording materials.

  In recent years, a dye or pigment is supported on one surface of a base material sheet such as a polyester film with a binder resin to form a heat-sensitive recording layer (ink layer), and the back surface is heated in a pattern to cover the ink layer. A heat-melting type heat-sensitive recording material that is transferred to a transfer material, and further a sublimation transfer recording material that uses a heat-sublimable dye as a dye and similarly sublimates and transfers only the dye to a transfer material are known.

  All of these methods are systems in which thermal energy is applied by the thermal head from the back side of the base sheet, so that the back side of the base sheet of the thermal recording material to be used is sufficiently slippery and peelable with respect to the thermal head. In addition, the thermal head is required not to stick to the back surface (sticking phenomenon). Therefore, for example, a technique has been proposed in which a back layer made of a silicone resin, a melamine resin, a phenol resin, a polyimide resin, a modified cellulose resin, or a mixture thereof is formed on the back surface of a base sheet of a heat-sensitive recording material (for example, , See Patent Document 1).

  In the above-mentioned heat-sensitive recording material, for the purpose of forming a heat-resistant protective layer on the back surface having heat resistance, the above resins are thermally cross-linked using various cross-linking agents, or inorganic fillers or fluororesin powders are used for these resins Attempts have been made to add, for example. However, although heat resistance can be obtained by these methods, it is insufficient as a measure for improving the slipperiness and non-adhesiveness with respect to the thermal head. The only silicone resin in the resins listed above is slippery and non-sticky, but it is usually a thin film with a thickness of about 2 to 5 μm in the heating step performed to completely crosslink the resin. There is another problem of damaging the base sheet. On the other hand, when incomplete crosslinking is performed so as not to damage the base sheet, when the heat-sensitive recording material is rolled up, unreacted in the heat-resistant protective layer formed on the back surface of the base sheet. The low molecular weight silicone moves to the ink layer in contact with the heat-resistant protective layer surface. As a result, there arises a problem that an image formed using such a heat-sensitive recording material becomes unclear.

  It is also known to use a silicone graft or a block acrylic copolymer for the heat-resistant protective layer. However, when a heat-sensitive recording material is produced by this method, the heat resistance is somewhat improved, but the film forming property of the acrylic component is insufficient, and the heat-resistant protective layer may be peeled off from the substrate. In addition, the heat-resistant protective layer is easily worn, and the worn protective layer is deposited on the thermal head, which causes new problems such as poor running of the thermal recording medium, poor printing, and a decrease in the life of the thermal head. .

  The present inventors have studied a method for solving these problems, and by using various silicone polyurethane copolymer resins, an excellent heat-resistant protective layer having heat resistance, slipperiness, non-adhesiveness, etc. It has been proposed that a heat-sensitive recording material can be obtained (see Patent Documents 2 to 4). However, these have not been studied from the viewpoint of global environmental conservation, which has become a global problem in recent years, and a review of technology from such a new viewpoint is demanded. In particular, carbon dioxide, which is considered to cause global warming in recent years, has become a major problem.

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 known so far are clearly inferior in characteristics compared to polyurethane resins which are conventional petrochemical polymers (petroplastics) (Patent Documents). 5-6).
On the other hand, the global warming phenomenon, which is thought to result from 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 production raw material. 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 above-mentioned polyhydroxy polyurethane resin is 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 58-13359 A Japanese Patent Laid-Open No. 61-227087 JP-A-62-202786 Japanese Patent Laid-Open No. 2-102096 US 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

  However, on the other hand, with the recent increase in the temperature of the thermal head and the reduction in the thickness of the base sheet accompanying the increase in printing speed, the heat-resistant protective layer on the back surface has further heat resistance, slipperiness and non-adhesiveness, Countermeasures against static electricity generated when the film is peeled off are required. At the same time, conventional heat-sensitive recording media (materials) are difficult to recycle products after use, and it is necessary to improve the point that they have become a large amount of waste.

  Accordingly, the object of the present invention is to provide a thermal recording material having a heat-resistant protective layer excellent in heat resistance, slipperiness and non-adhesiveness, but can be made from carbon dioxide as a raw material, which is useful from the viewpoint of the global environment, and is environmentally friendly. The purpose is to develop technology that can provide products.

式中のＲ₁は炭素数１〜１２のアルキレン基（該基中にＯ、Ｓ、または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。式中のＲ₂は、ないか、または、炭素数２〜２０のアルキレン基を表し、Ｒ₂は、脂環族基また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。］ The above object is achieved by the present invention described below. That is, the present invention is a thermosensitive recording material having a base sheet, a thermosensitive recording layer provided on at least one side of the base sheet, and a heat-resistant protective layer provided on the back surface in contact with the thermal head on the other side. The heat-resistant protective layer is formed of a resin composition containing at least a polysiloxane-modified polyhydroxypolyurethane resin derived from a reaction between a 5-membered cyclic carbonate polysiloxane compound represented by the following general formula (1) and an amine compound. A heat-sensitive recording material is provided.

R ₁ in the formula has an alkylene group having 1 to 12 carbon atoms (in which the group is linked by each element of O, S, or N and / or is linked by — (C ₂ H ₄ O) _b —). May be). R ₂ in the formula 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. ]

  According to the present invention, by forming a heat-resistant protective layer on the back using a polysiloxane-modified polyhydroxypolyurethane resin, heat resistance, slipperiness, non-adhesiveness, adhesion to a substrate sheet, and further antistatic effect A heat-sensitive recording material excellent in the above is provided. The above resins can provide such excellent thermal recording materials, and 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 greenhouse gases. It is possible to provide a thermal recording material as a product.

Infrared absorption spectrum of epoxy-modified polysiloxane. Infrared absorption spectrum of 5-membered cyclic carbonate polysiloxane. GPC elution curve of 5-membered cyclic carbonate polysiloxane (mobile phase: THF, column: TSK-Gel GMHXL + G2000HXL + G3000HXL, detector: IR).

Next, the present invention will be described in more detail with reference to preferred embodiments.
In the heat-sensitive recording material of the present invention, a heat-sensitive recording layer is provided on one surface of a base sheet, and a heat-resistant protective layer is formed on the other back surface. It is characterized by being a resin. That is, the heat-sensitive recording material of the present invention comprises a polysiloxane-modified polyhydroxypolyurethane whose heat-resistant 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. It is characterized by comprising a resin (hereinafter, also simply referred to as “resin used in the present invention” or “resin of the present invention”) or a resin composition containing the resin.

式中のＲ₁は炭素数１〜１２のアルキレン基（該基中にＯ、Ｓ、または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。式中のＲ₂は、ないか、または、炭素数２〜２０のアルキレン基を表し、Ｒ₂は、脂環族基また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 (in which the group is linked by each element of O, S, or N and / or is linked by — (C ₂ H ₄ O) _b —). May be). R ₂ in the formula 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 represented by the general formula (1) used in the present invention is obtained by reacting an epoxy-modified polysiloxane compound and carbon dioxide as shown by the following [Formula-A]. Can be manufactured. More specifically, the epoxy-modified polysiloxane compound is allowed to remain 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. at normal pressure or slightly increased pressure for 10 to 20 hours. Obtained by reacting with carbon dioxide.

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

  The epoxy-modified polysiloxane compounds listed above are preferred compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Accordingly, not only the above-exemplified compounds 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.

  As described above, the 5-membered cyclic carbonate polysiloxane compound used in the present invention is obtained by the reaction of an epoxy-modified polysiloxane compound and carbon dioxide. Examples of the catalyst used in this reaction include the following base catalysts and Lewis acid catalysts. Base catalysts include tertiary amines such as triethylamine and tributylamine, cyclic amines such as diazabicycloundecene, diazabicyclooctane and pyridine, alkalis such as lithium chloride, lithium bromide, lithium fluoride and sodium chloride. Metal salts, 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, Examples thereof include metal acetates such as copper acetate and 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 these catalysts used may be 0.1 to 100 parts by weight, preferably 0.3 to 20 parts by weight, per 50 parts by weight 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 is too much, various performances of the final resin may be deteriorated. Therefore, when the residual catalyst causes a serious performance deterioration, the residual catalyst may be removed by washing with pure water.

  Examples of organic solvents that can be used in the reaction of 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.

  As shown in the following [Formula-B], the resin used in the present invention is, for example, a 5-membered cyclic carbonate polysiloxane compound obtained by the above reaction and an amine compound at 20 ° C. in the presence of an organic solvent. 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.

  The polysiloxane-modified polyhydroxypolyurethane resin obtained as described above is such that the proportion of the polysiloxane segment in the resin is 1 to 75% by mass in terms of the content of the segment with respect to the resin molecule. preferable. 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, when it exceeds 75% by mass, the performance of the polyhydroxyurethane resin such as mechanical strength and abrasion resistance becomes insufficient, which is not preferable. More preferably, it is 2-60 mass%, and it is more preferable that it is 5-30 mass%.

  In addition, the resin used in the present invention preferably has a number average molecular weight (standard polystyrene conversion value measured by GPC) of about 2,000 to 100,000. Furthermore, it is more preferable that it is a thing of about 5,000-70,000.

  The polysiloxane-modified polyhydroxypolyurethane resin used in the present invention is derived from a reaction between an amine compound and a 5-membered cyclic carbonate polysiloxane compound represented by the general formula (1). For this reason, the hydroxyl group produced when the 5-membered cyclic carbonate group in the structure of the resin reacts with the amine compound brings about further improvement in the performance of the heat-sensitive recording material of the present invention. That is, since the hydroxyl group has hydrophilicity, the adhesion to the base sheet of the heat-resistant protective layer formed using the resin is remarkably improved, and furthermore, it cannot be achieved with the conventional product. An antistatic effect can be obtained. Further, by utilizing the reaction between a hydroxyl group in the resin structure and a crosslinking agent added to the resin, the heat resistance can be further improved, and a more excellent heat-resistant protective layer can be formed. .

  The resin used in the present invention preferably has a hydroxyl value of 20 to 300 mgKOH / g. When the hydroxyl group content is less than the above range, it is difficult to say that the carbon dioxide reduction effect is sufficiently obtained. On the other hand, when the hydroxyl group content exceeds the above range, it is not preferable because various physical properties such as a polymer compound are insufficient. .

  The heat-resistant protective layer constituting the heat-sensitive recording material of the present invention can be formed as a film made of the above-described polysiloxane-modified polyhydroxypolyurethane resin, but can also be formed into a crosslinked film using a crosslinking agent. As the crosslinking agent that can be used at this time, any crosslinking agent that reacts with a hydroxyl group in the resin structure can be used. Examples include alkyl titanate compounds and polyisocyanate compounds. Any known polyisocyanate compound conventionally used for crosslinking polyurethane resins is not particularly limited. Examples include adducts of polyisocyanates having the following structural formula and other compounds.

  In addition, when forming the heat-resistant protective layer on the back surface of the base material sheet constituting the heat-sensitive recording material of the present invention, for the purpose of coating appropriateness to the base material sheet, improving film formability, and adjusting the content of the polysiloxane segment In addition to the above-mentioned resins, various conventionally known binder resins can be mixed and used. As the binder resin used at this time, those capable of chemically reacting with a crosslinking agent such as the above-mentioned polyisocyanate adduct are preferable, but those having no reactivity can also be used in the present invention.

  As these binder resins, binder resins conventionally used for forming a heat-resistant protective layer on the back surface constituting the heat-sensitive recording material 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 these resins with silicone or fluorine can be used. When the binder resin is 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 polysiloxane-modified polyhydroxypolyurethane resin.

  The method for forming the heat-resistant protective layer constituting the heat-sensitive recording material of the present invention is not particularly limited. For example, the above-described polysiloxane-modified polyhydroxypolyurethane resin is dissolved or dispersed in an appropriate organic solvent, and this is, for example, a wire bar method, a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, or the like. It can be formed by coating with a forming means and drying. The drying temperature at this time is preferably in the range of 50 to 100 ° C. Further, the thickness of the heat-resistant protective layer is preferably 0.001 to 2.00 μm, particularly preferably 0.05 to 0.7 μm.

  The base sheet used in the heat-sensitive recording material of the present invention includes polycarbonate, polyarylate, polyetherimide, polysulfone, polyphenyl ether, polyamideimide, polyimide, polyethylene naphthalate, polyphenyl sulfide, polyether ketone, and fluororesin. In addition to films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyamide, etc. can be used. A film having biaxial orientation is preferred. Further, the thickness of the substrate is preferably 6 μm or less, more preferably in the range of 2.5 μm to 4.5 μm from the viewpoint of sensitivity in thermal recording.

  As the ink layer in the heat-sensitive recording material of the present invention, a conventionally known ink layer is used as it is, and is not particularly limited. That is, the ink layer used in the present invention is composed of colorants, waxes, resins and lubricants, additives such as surfactants, and the like. Examples of the colorant include pigments and dyes such as carbon black, petal, lake red C, benzidine yellow, phthalocyanine green, phthalocyanine blue, direct dyes, oil dyes, and basic dyes. The present invention is not limited to these exemplary compounds. Therefore, not only the compounds exemplified above, but also any compounds that are currently used in the hot melt thermal transfer system or the sublimation thermal transfer system and can be easily obtained from the market can be used in the present invention.

  Since the heat-sensitive recording material of the present invention uses a specific polysiloxane-modified polyhydroxypolyurethane resin in the resin composition forming the heat-resistant protective layer provided on the back surface of the base sheet, the polysiloxane segment of the resin is It will be oriented on the surface of the protective layer. For this reason, the formed heat-resistant protective layer is given heat resistance, slipperiness and non-adhesiveness to the thermal head of the polysiloxane segment. Further, together with this, the hydroxyl group in the structure of the polysiloxane-modified polyhydroxypolyurethane resin forming the heat-resistant protective layer strongly interacts with the substrate sheet at the interface, so that excellent adhesion to the substrate and flexibility are achieved. And antistatic effects are imparted. For this reason, the heat-sensitive recording material can have a better performance. The 5-membered cyclic carbonate polysiloxane compound constituting the resin used in the present invention can incorporate carbon dioxide into the resin by using carbon dioxide as a production raw material. Therefore, according to the present invention, it is possible to provide a heat-sensitive recording material as an environmentally-friendly material product that is useful from the viewpoint of reducing carbon dioxide, which is a cause of global warming, and which cannot be achieved by conventional products.

  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 5-membered cyclic carbonate polysiloxane compound)
In a reaction vessel equipped with a stirrer, a thermometer, a gas introduction tube and a reflux condenser, 100 parts of a divalent epoxy-modified polysiloxane represented by the following formula A, 100 parts of N-methylpyrrolidone, 1.2 parts of sodium iodide Was added and dissolved uniformly. Then, carbon dioxide gas was heated and stirred at 80 ° C. for 30 hours while bubbling carbon dioxide gas at a rate of 0.5 liter / min. The divalent epoxy-modified polysiloxane used above is X-22-163 (epoxy equivalent 198 g / mol) manufactured by Shin-Etsu Chemical Co., Ltd., and its infrared absorption spectrum is shown in FIG.

  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 (Horiba FT-720) of the obtained product (1-A), as shown in FIG. 2, a carbonyl group of a cyclic carbonate group not present in the raw material in the vicinity of 1,800 cm ^−1. Absorption was confirmed. Moreover, the number average molecular weight of the product was 2,450 (polystyrene conversion, Tosoh; GPC-8220) as shown in FIG. In the obtained 5-membered cyclic carbonate polysiloxane compound (1-A), 18.1% of carbon dioxide was immobilized.

<Production Example 2> (Production of 5-membered cyclic carbonate polysiloxane compound)
In this production example, instead of the bivalent epoxy-modified polysiloxane A used in the previous production example 1, a bivalent epoxy-modified polysiloxane B represented by the following formula B (manufactured by Shin-Etsu Chemical Co., Ltd., KF-105; Epoxy equivalent 485 g / mol) was used. And it was made to react like manufacture example 1 except this, and 99 parts (yield 91%) of the colorless and transparent liquid 5-membered cyclic carbonate polysiloxane compound (1-B) were obtained. The obtained product (1-B) was confirmed by infrared absorption spectrum, GPC and NMR in the same manner as in Production Example 1. In the obtained 5-membered cyclic carbonate polysiloxane compound (1-B), 8.3% of carbon dioxide was immobilized.

<Production Example 3> (Production of 5-membered cyclic carbonate polysiloxane compound)
In this production example, instead of the bivalent epoxy-modified polysiloxane A used in the previous production example 1, a bivalent epoxy-modified polysiloxane C represented by the following formula C (manufactured by Shin-Etsu Chemical Co., Ltd., X-22- 169AS; epoxy equivalent of 533 g / mol). And it was made to react like manufacture example 1 except this, and 71 parts (yield 68%) of colorless and transparent liquid 5-membered cyclic carbonate polysiloxane compound (1-C) were obtained. The obtained product was confirmed by infrared absorption spectrum, GPC, and NMR as in the case of Production Example 1. In the obtained 5-membered cyclic carbonate polysiloxane compound (1-C), 7.6% of carbon dioxide was immobilized.

<Comparative Production Example 1> (Production of 5-membered cyclic carbonate compound)
In this comparative production example, instead of the bivalent epoxy-modified polysiloxane A used in the previous production example 1, a divalent epoxy compound D represented by the following formula D (produced by Japan Epoxy Resin Co., Ltd., Epicoat 828; epoxy) Equivalent 187 g / mol) was used. And it was made to react like manufacture example 1 except this, and 118 parts (yield 95%) of white powder 5-membered cyclic carbonate compound (1-D) were obtained. The product was confirmed by infrared absorption spectrum, GPC and NMR. 19% of carbon dioxide was fixed in the obtained 5-membered cyclic carbonate compound (1-D).

<Polymerization Examples 1-3> (Production of polysiloxane-modified polyhydroxypolyurethane resin)
Using the 5-membered cyclic carbonate polysiloxane compounds obtained in the previous Production Examples 1 to 3, polysiloxane-modified polyhydroxypolyurethane resins used in the examples were synthesized in the following procedure. A reaction vessel equipped with a stirrer, thermometer, gas introduction pipe and reflux condenser was replaced with nitrogen, and the 5-membered cyclic carbonate polysiloxane compound obtained in Production Examples 1 to 3 was added thereto, and the solid content was 35%. N-methylpyrrolidone was added and dissolved uniformly. Next, a predetermined equivalent amount of the amine compound shown in Table 1 was added, and the mixture was stirred at a temperature of 90 ° C. for 10 hours until the amine compound could not be confirmed. Properties of the obtained three types of polysiloxane-modified polyhydroxypolyurethane resins are as shown in Table 1.

<Comparative polymerization example 1> (Production of polyhydroxypolyurethane resin)
The polyhydroxy 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 is replaced with nitrogen, and the 5-membered cyclic carbonate compound obtained in Comparative Production Example 1 is added thereto so that the solid content becomes 35%. N-methylpyrrolidone was added to and uniformly dissolved. Next, a predetermined equivalent of hexamethylene diamine was added and stirred for 10 hours at a temperature of 90 ° C. until the amine compound could not be confirmed. Properties of the obtained polyhydroxypolyurethane resin are as shown in Table 1.

<Comparative polymerization example 2> (Production of polyurethane resin)
A conventional polyurethane resin was synthesized from polyester, diol and diamine as Comparative Polymerization Example 2 as follows. First, a reaction vessel equipped with a stirrer, a thermometer, a gas introduction tube and a reflux condenser was replaced with nitrogen, and in this vessel, 150 parts of polybutylene adipate having an average molecular weight of about 2,000, 1,4-butanediol 15 Were dissolved in a mixed organic solvent consisting of 200 parts of methyl ethyl ketone and 50 parts of dimethylformamide. Thereafter, 62 parts of water-added MDI dissolved in 171 parts of dimethylformamide was gradually added dropwise with stirring at 60 ° C., and reacted at 80 ° C. for 6 hours after the completion of the addition.
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> (Production of polysiloxane-modified polyurethane resin)
The polysiloxane modified polyurethane resin used in the comparative example was synthesized from diol and diamine as follows. Specifically, 150 parts of polydimethylsiloxanediol represented by the following formula (E) and having an average molecular weight of about 3,200 and 10 parts of 1,4-butanediol are mixed with 200 parts of methyl ethyl ketone and 50 parts of dimethyl. A mixed organic solvent composed of formamide 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 1-6 and Comparative Examples 1-6>
(Formation of heat-resistant protective layer)
Using each polyurethane resin (solid content 35%) of Polymerization Examples 1 to 3 and Comparative Polymerization Examples 1 to 3 prepared earlier, a heat-resistant protective layer was formed on the substrate sheet surface. Specifically, the resin solution is diluted with a solvent so that the thickness after drying becomes 0.2 μm, and a crosslinking agent is added as necessary as shown in Table 2 to add a coating composition (resin composition And the composition was applied to the surface of a polyethylene terephthalate film (manufactured by Toray) having a thickness of 3.5 μm by gravure printing and dried in a dryer to form a heat-resistant protective layer on the surface of the base sheet. . Further, a heat-sensitive recording layer (transfer ink layer) is formed on the surface of the base film (sheet) opposite to the formed heat-resistant protective layer to produce each heat-sensitive recording material of Examples 1 to 6 and Comparative Examples 1 to 6. did. The formation of the transfer ink layer will be described later.

<Comparative Example 7>
As a comparison for evaluating the heat-sensitive recording material of the present invention, a heat-resistant protective layer was produced using a conventional silicone resin. Specifically, 100 parts of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., KS-841) and 1 part of catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., PL-7) are dissolved in 1,000 parts of toluene. Thus, a silicone resin coating composition was prepared. And it apply | coated on the base material sheet similarly to the Example, and formed the heat-resistant protective layer on one surface. Further, a thermosensitive recording layer (transfer ink layer) was formed on the surface of the base film (sheet) opposite to the formed heat-resistant protective layer as described below to obtain a thermosensitive recording material of Comparative Example 10.

(Formation of transfer ink layer)
On the surface of the base film (sheet) opposite to the heat-resistant protective layer formed on one side (back side) of the base sheet as described above, an ink composition having the following composition is heated to 100 ° C., A heat-sensitive recording layer (transfer ink layer) was formed by applying a hot melt roll coating method so that the coating thickness was 5 μm. These were used as the heat-sensitive recording materials of Examples 1 to 6 and Comparative Examples 1 to 7.

[Ink composition]
・ 10 parts of paraffin wax ・ 10 parts of carnauba wax ・ 1 part of polybutene (manufactured by Nippon Oil) ・ 2 parts of carbon black

(Evaluation)
Using the heat-sensitive recording materials of Examples and Comparative Examples obtained as described above, printing was performed under the following conditions, and a heat-sensitive recording mounting test was performed. Furthermore, in particular, with respect to the heat-resistant protective layer, the sticking property, thermal head contamination property, adhesion to the substrate, static friction coefficient, charging property, environmental friendliness, etc. are measured by the following methods, respectively. evaluated. The results are summarized in Table 3.

[Printing conditions for thermal recording mounting test]
Printer: Zebra 100XiIIIPlus
Thermal head: Kyocera KPA-106-12TA (flat)
Printing energy: 25 mJ / mm ²
Printing speed: 100mm / sec
Platen pressing: 350 gf / cm
Receiving paper; cast coated paper (manufactured by Lintec)
Printing pattern: CODE39 vertical bar code under printing conditions of 30mm wide and 40mm long

[Sticking]
The sticking property was evaluated by visually observing the detachability of the “heat-resistant protective layer” from the thermal head during the pressing operation with the thermal head when each heat-sensitive recording material was subjected to the mounting test. The evaluation criteria were 5 for the one with the best removal and 1 for the one with the lowest removal, and relatively evaluated on a five-point scale.

[Thermal head contamination]
The contamination of the thermal head was evaluated by visually observing the contamination state of the thermal head after each thermal recording material was used for the thermal recording mounting test. The evaluation standard was 5 with the least contamination and 1 with the least contamination, with a relative 5-level evaluation.

[Adhesiveness]
In the adhesion test, 10 × 10 grid cellophane tape peeling test was performed on the heat-resistant protective layer of each heat-sensitive recording material, and the remaining number after peeling was evaluated.

[Static friction coefficient]
The coefficient of static friction was measured and evaluated using a surface property tester (manufactured by Shinto Kagaku) for the heat-resistant protective layer of each thermosensitive recording material.

[Blocking properties, environmental friendliness]
Furthermore, the chargeability is determined by visually observing the blocking property between the films due to static electricity generated when the thermal recording material in the form of a film (sheet) is abruptly peeled off from the state of the roll. The case where it did not occur was evaluated as ○. The degree of environmental friendliness was judged as xx based on whether carbon dioxide was immobilized in each resin of the forming material of the “heat-resistant protective layer”.

  According to the present invention described above, the heat-resistant protective layer constituting the heat-sensitive recording material is formed using a specific polysiloxane-modified polyhydroxypolyurethane resin, so that the polysiloxane segments in the resin are oriented on the surface. Thus, the heat resistance, slipperiness and non-adhesiveness to the thermal head of the polysiloxane segment can be imparted. At the same time, the hydroxyl group of the polysiloxane-modified polyhydroxypolyurethane resin interacts strongly with the substrate sheet at the interface, thereby providing excellent adhesion and flexibility to the substrate of the heat-resistant protective layer and antistatic effect. Thus, a heat-sensitive recording material having a heat-resistant protective layer exhibiting excellent performance can be obtained. In addition, since the resin used in the present invention can use carbon dioxide as a production raw material, according to the present invention, it is possible to provide a heat-sensitive recording material as a global environment compatible product that can contribute to the reduction of carbon dioxide, which is a greenhouse gas. become.

Claims (8)

A heat-sensitive recording material comprising a base material sheet, a heat-sensitive recording layer provided on at least one surface of the base material sheet, and a heat-resistant protective layer provided on the back surface in contact with the thermal head on the other surface, It is formed of a resin composition containing at least a polysiloxane-modified polyhydroxypolyurethane resin derived from a reaction between a 5-membered cyclic carbonate polysiloxane compound represented by the following general formula (1) and an amine compound. Thermal recording material.

R ₁ in the formula has an alkylene group having 1 to 12 carbon atoms (in which the group is linked by each element of O, S, or N and / or is linked by — (C ₂ H ₄ O) _b —). May be). R ₂ in the formula 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 heat-sensitive recording material according to claim 1, wherein the 5-membered cyclic carbonate polysiloxane compound constituting the polysiloxane-modified polyhydroxypolyurethane resin is obtained by reacting an epoxy-modified polysiloxane compound and carbon dioxide.   The heat-sensitive recording material according to claim 2, wherein the polysiloxane-modified polyhydroxypolyurethane resin constituting the heat-resistant protective layer contains 1 to 25% by mass of carbon dioxide derived from a raw material.   The heat-sensitive recording material according to any one of claims 1 to 3, wherein a content of the polysiloxane segment in the molecule of the polysiloxane-modified polyhydroxypolyurethane resin constituting the heat-resistant protective layer is 1 to 75 mass%. .   The heat-sensitive recording material according to any one of claims 1 to 4, wherein the resin composition further contains another resin.   The heat-resistant protective layer is a film formed by crosslinking by a reaction between a hydroxyl group present in the structure of the polysiloxane-modified polyhydroxypolyurethane resin and a crosslinking agent that reacts with the hydroxyl group. The heat-sensitive recording material described in 1.   The heat-sensitive recording material according to any one of claims 1 to 6, wherein the thickness of the base sheet is in a range that can be expressed by 2.5 µm to 4.5 µm.   The heat-sensitive recording material according to claim 1, wherein the heat-resistant protective layer has a thickness in the range of 0.001 to 2.00 μm.

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