JP4098189B2 - Thermal recording material - Google Patents

Description

The present invention relates to a novel long-chain side-chain-containing polyurea having units introduced from a hydrophilic group-containing compound, a long-chain alkyl group-containing compound and a polysiloxane compound, or from them, a low molecular weight polymer, a polyol and / or a polyamine. The present invention relates to a heat-sensitive recording material formed using an adhesive.

  Conventionally, an ink ribbon used in a thermal printer or the like has a thin polyester film as a base material, a melt-type thermal transfer ink layer on the surface of the base material, and a back layer (heat-resistant protection) on the surface that contacts the thermal head on the back surface of the base material. (Also referred to as a layer). As this back layer forming material, use of a cross-linked cured product composed of a silicone-modified polyurethane resin and polyisocyanate (see Patent Document 1) and use of an acrylic silicone graft copolymer (see Patent Documents 2 to 4) have been proposed. Yes. The back layer is required to have appropriate slipperiness, heat resistance, adhesion to the substrate film, printing performance, and that no powder is lost due to contact friction with the thermal head and that it does not burn onto the head. However, few conventional thermosensitive recording materials have a back layer satisfying these required performances, and improvements are desired.

Japanese Patent Laid-Open No. 61-227087 JP-A-62-30082 JP-A-1-214475 JP-A-2-274596

The purpose of the present invention, adhesion to the substrate, the heat resistance is good, no printing failure or ink migration problems, back layer having excellent performance such as image sticking of the thermal head does not occur is formed It is to provide a thermal recording material.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that “the relationship between the phase structure and the interface structure of the segmented urethane resin having a functional group introduced” (Katsuhiko Nakamae, Seiji Asaoka, Sudaryanto, Japan Adhesive Society). , Vol. 31 (No. 3), pages 70 to 75 (1955)), the sulfone group-introduced polyurethane exhibits a phase separation structure when a dry coating film is formed, and is polar at the interface with the substrate. The present invention has been achieved by further developing a phenomenon in which a coating film having excellent adhesion can be obtained because the groups are oriented.

The above object is achieved by the present invention described below. That is , the present invention relates to a thermosensitive recording material comprising a base sheet, a thermosensitive recording layer provided on one side of the base sheet, and a back layer provided on the other side of the base sheet. The layer is a polyisocyanate, (A) a compound having both a hydrophilic group other than at least one hydroxyl group and at least one active hydrogen-containing group, and (B) a straight chain having 8 to 64 carbon atoms in the molecule. Two carbon atoms having an alkyl group having a shape or a branch (the group becomes a side chain in the resulting polyurethane resin) and two adjacent carbon atoms or 1 to 3 carbon atoms existing therebetween A bifunctional organic compound (hereinafter sometimes referred to as “compound (B)”) having a group having active hydrogen in each of them (the group is incorporated into the main chain in the resulting polyurethane resin), and (C) at least 1 With active hydrogen-containing groups The thermosensitive recording material and a manufacturing method thereof, characterized in that it comprises a layer comprising a hydrophilic polyurethane resin having a long-chain branches obtained by reacting a that polysiloxane compound.

According to the above present invention, formed using the polyurethane down with long side chains, adhesion to only substrate for coating and drying, heat resistance and sliding property is good, poor printing or ink migration Thus, there is provided a heat-sensitive recording material having an excellent back surface layer that does not have the above-mentioned problems and having excellent performance in terms of maintenance properties such as no generation of head wrinkles.

The present invention is described in further detail below.
The polyurethane resin constituting the polyurethane aqueous dispersion having a long side chain used in the present invention comprises a unit having a hydrophilic group other than a hydroxyl group in the polyurethane molecular chain, a unit of the compound (B) , a polysiloxane segment (poly A long-chain side-chain-containing hydrophilic polyurethane resin having units introduced from a siloxane compound and having these units linked by urethane bonds and / or urea bonds. Further, in addition to the above units, a long-chain side chain-containing hydrophilic polyurethane resin having a unit having a low molecular weight polymer chain in the side chain or main chain and a unit from polyol and / or polyamine. In the present invention, the long-chain side chain-containing polyurethane resin includes polyurethane, polyurea and polyurethane-polyurea having a urethane bond and / or a urea bond.
The long-chain side chain-containing polyurethane aqueous dispersion used in the present invention is obtained by dispersing or emulsifying the long-chain side chain-containing hydrophilic polyurethane resin in an aqueous medium.

The polyurethane aqueous dispersion having a long side chain used in the present invention has a polyisocyanate and (A) at least one hydrophilic group other than the hydroxyl group, preferably one and at least one active hydrogen-containing group, preferably and two compounds both having a compound (B), at least one (C) an active hydrogen-containing group, preferably a polysiloxane compound having two or one of these components and (D) molecular chains A long chain obtained by reacting a low molecular weight polymer having at least one, preferably two, active hydrogen-containing groups at the end with (E) a polyol and / or a polyamine in the absence or presence of a chain extender. It is obtained by dispersing or emulsifying a hydrophilic polyurethane resin having a side chain in water. The active hydrogen-containing group in the present invention refers to a functional group having active hydrogen such as a hydroxyl group, a mercapto group, a carboxyl group, and an amino group reactive with an isocyanate group.

In the hydrophilic polyurethane resin having a long side chain forming the aqueous dispersion used in the present invention , as a side chain, (i) in a unit introduced from the above compound (B), a carbon atom of the main chain A straight-chain or branched long-chain alkyl group having 8 to 64 carbon atoms bonded directly or through another atomic group, or (i) a long-chain alkyl group, and (ii) the above compound (D ) In the unit introduced from the above compound (A), a hydrophilic group other than a hydroxyl group in the unit introduced from the above compound (A), and a unit introduced from the above compound (C) (poly In addition to the side chains of (i) and (ii) above, the siloxane segment) is a trunk portion (in the main chain) if the raw material component is, for example, a double-end reactive type, and a branch if it is a single-end reactive type. Units introduced into the part (side chain) and further introduced from the above compound (E) Present in the main chain.

The long-chain side-chain-containing polyurethane aqueous dispersion used in the present invention is prepared by a known synthesis method using a reaction catalyst under no solvent or in an organic solvent (recovered after production of the aqueous dispersion) as necessary. Is reacted to synthesize a long-chain side-chain-containing hydrophilic polyurethane resin, and after the reaction, the obtained long-chain side-chain-containing hydrophilic polyurethane resin is mixed with water or a mixed solvent of water and a hydrophilic solvent using a neutralizing agent. (Hereinafter referred to as an aqueous medium) is dispersed or emulsified into a polyurethane aqueous dispersion. This is because the neutralizing agent partially or completely neutralizes the hydrophilic groups other than hydroxyl groups in the long-chain side chain-containing hydrophilic polyurethane resin so that the resin can be dispersed or self-emulsified in an aqueous medium. As a result, a very stable self-dispersing or self-emulsifying polyurethane aqueous dispersion is produced, and a heat-sensitive recording material characterized by being environmentally friendly is provided.

(Function)
When a dry coating film is formed on the surface of a plastic substrate from the long-chain side chain-containing polyurethane aqueous dispersion used in the present invention, the surface energy is low due to the difference in surface energy between segments constituting the polyurethane molecular chain. The polysiloxane segment and the long-chain alkyl group portion of the branch portion, as well as the low molecular weight polymer chain, are oriented on the surface layer, the portion having a trunk urethane bond and / or urea bond, the hydrophilic functional group portion, and the substrate side. .

  In a polyurethane having a polysiloxane segment used for forming a back layer (heat-resistant protective layer) of a conventional thermosensitive recording material, heat resistance was obtained by the presence of the polysiloxane segment. Polyurethane resin can be used as an environmentally friendly aqueous dispersion, and low molecular weight polymer chains with low surface energy are oriented on the surface of the base material, thereby exhibiting sufficiently high heat resistance even if the polysiloxane segment content is small. be able to. Furthermore, by increasing the polysiloxane segment content, it is possible to further improve the slipperiness as well as the heat resistance.

  Therefore, a long-chain side chain-containing hydrophilic polyurethane resin having a low polysiloxane segment content can be used for thermal transfer applications for fax machines that do not require slipperiness. For thermal transfer applications other than the above, long-chain side-chain-containing hydrophilic polyurethane resins with increased polysiloxane segment content can be used to provide not only moderate slip properties but also heat resistance, adhesion, and wear resistance. It is possible to form a coating film having excellent properties and non-contamination of the head, and a heat-sensitive recording material having various characteristics can be provided.

The raw material components used for production of the long-chain side chain-containing polyurethane resin used in the present invention are described below.
(A) As a compound having both at least one active hydrogen-containing group and a hydrophilic group other than a hydroxyl group in the same molecule, compounds such as sulfonic acid, carboxylic acid, phosphoric acid, and amine are used. be able to. Those containing two active hydrogen-containing groups are preferred. This component has an effect of imparting adhesion to the base material of the long-chain side-chain-containing polyurethane resin, dispersion in the aqueous medium, and the polyurethane resin becomes a self-emulsifying type and takes a stable form in the aqueous medium.
For example, if it is a sulfonic acid-type compound, the following compound, its derivative, etc. will be mentioned.

In addition, if it is a carboxylic acid compound, dimethylolpropanoic acid, dimethylolbutanoic acid and their alkylene oxide low-mole adducts (number-average molecular weight less than 500) or γ-caprolactone low-mole adducts (number-average molecular weight less than 500). And half esters derived from an acid anhydride and glycerin, and compounds derived from a monomer containing a hydroxyl group and an unsaturated group and a monomer containing a carboxyl group and an unsaturated group by a free radical reaction.
The above are examples of preferred compounds used in the present invention, and the present invention is not limited to these exemplified compounds.
Accordingly, not only the exemplified compounds described 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.

The (B) compound to introduce a long-chain alkyl groups in Polyurethane molecule (B), in the molecule may contain a linear or an alkyl group (unsaturated group having a branched 8 to 64 carbon atoms (The same applies to R below) (the group is a side chain in the resulting polyurethane resin) and two adjacent carbon atoms or two to three carbon atoms present between them each group having an active hydrogen to carbon atoms (the group may incorporated in the main chain in the resulting polyurethane resin) bifunctional organic compound having may be mentioned as representative compounds. Examples of such compounds include 1,2- or 1,3-alkanediols (HOCH ₂ CH (OH) R, HOCH ₂ CH ₂ CH (OH) R) and dehydrated dimers thereof (HOCH (R ) CH ₂ OCH ₂ (R) CHOH etc.) (R is the above alkyl group); 1,2- or 1,3-alkanediamines; 1- or 2-monoglycerides and monoglycerin ethers are preferred. . Particularly preferred is 1,2-alkanediol.

  Examples of 1,2- or 1,3-alkanediols include octane 1,2 (or 1,3) -diol, decane 1,2 (or 1,3) -diol, dodecane 1,2 (or 1). , 3) -diol, tetradecane 1,2 (or 1,3) -diol, octadecane 1,2 (or 1,3) -diol, tetracosane 1,2 (or 1,3) -diol, and the like. Examples of the 1- or 2-monoglyceride include, for example, 1- (or 2-) monocaprin glyceride, 1- (or 2-) monolauring glyceride, 1- (or 2-) monomyristating glyceride, 1- (or 2-). Examples of monopalmiting glyceride, 1- (or 2-) monoaraking glyceride, and 1- or 2-monoglycerol ether include batyl alcohol, seraalkyl alcohol, and chimyl alcohol.

In addition to the above, hydroxy fatty acids, 1,2- or 1,3-alkanediamines, symmetric α-glycols (RCH (OH) CH (OH) R: R is the above alkyl group) and alkylene oxides thereof Low molar adducts (number average molecular weight less than 500), higher alcohols and polyester diols of the above 1,2- or 1,3-alkanediols and dibasic acids (OHCH (R) CH ₂ OC (O) R ′ CO (O) CH ₂ CH (R) OH, etc.) (R is the above alkyl group, R ′ is a divalent organic group that is a residue of a dibasic acid), and the like.
These are examples of preferred compounds used in the present invention. The present invention is not limited to these exemplified compounds, and any other compounds that are readily available from the currently marketed market are Can be used for invention.

(C) As a polysiloxane compound having at least one active hydrogen-containing group, for example, the following compounds can be used.

(1) Amino-modified polysiloxane compound

(2) Epoxy-modified polysiloxane compound

(3) Alcohol-modified polysiloxane compound

(4) Mercapto-modified polysiloxane compound

  The polysiloxane compounds having active hydrogen-containing groups 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. Particularly preferred compounds in the present invention are polysiloxane compounds having two hydroxyl groups or amino groups.

(D) The low molecular weight polymer having at least one active hydrogen-containing group at one molecular end is any low molecular weight polymer having at least one, preferably two active hydrogen-containing groups at one molecular end. Although it can be used and is not particularly limited, those having a glass transition temperature of 80 ° C. or lower are preferred, and those having a glass transition temperature of −100 to 20 ° C. are more preferred. Any of these low molecular weight polymers can be used regardless of the kind of monomers constituting them. The weight average molecular weight in terms of standard polystyrene by the GPC method is usually about 1,000 to 20,000.

The production method of such a low molecular weight polymer is not particularly limited. For example, radical polymerizable monomers such as (meth) acrylic monomers are publicly known using thioglycol as a chain transfer agent as shown in the following formula: method (e.g., JP-bulk polymerization method using the bulk polymerization catalyst according to 2000-128911 publication) by polymerizing, the low molecular weight polymer having at least one active hydrogen-containing group at the molecular end (the following formula The polymer chain is bonded to the S atom.

(E) As polyol, conventionally known ones such as short-chain diols and polymer polyols conventionally used in the production of polyurethane, and as polyamines, short-chain diamines conventionally used in the production of polyurethanes. Etc. can be used, but these are not particularly limited.

Examples of the short-chain diol include aliphatic glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentyl glycol, and the like. Alkylene oxide low molar adduct (number average molecular weight less than 500); 1,4-bishydroxymethylcyclohexane, alicyclic glycols such as 2-methyl-1,1-cyclohexanedimethanol, and alkylene oxide low molar adducts thereof (Number average molecular weight less than 500); Aromatic glycols such as xylylene glycol and their alkylene oxide low molar adducts (number average molecular weight less than 500); Bisphenols such as bisphenol A, thiobisphenol, sulfone bisphenol and their alkylenes Kishido low molar adduct (number average molecular weight of less than 500); Compound alkyl dialkanolamines such as alkyl diethanolamine C ₁ -C ₁₈ and the like. Examples of the polyhydric alcohol compound include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, tris- (2-hydroxyethyl) isocyanurate, 1,1,1-trimethylolethane, 1,1, Examples include 1-trimethylolpropane. These can be used alone or in combination of two or more.

Examples of the polymer polyol include the following.
(1) Polyether polyols such as those obtained by polymerizing or copolymerizing alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) and / or heterocyclic ethers (tetrahydrofuran, etc.), specifically polyethylene glycol , Polypropylene glycol, polyethylene glycol-polytetramethylene glycol (block or random), polytetramethylene ether glycol, polyhexamethylene glycol, etc.

(2) Polyester polyol, for example, aliphatic dicarboxylic acids (for example, succinic acid, adipic acid, sebacic acid, glutaric acid, azelaic acid, etc.) and / or aromatic dicarboxylic acids (for example, isophthalic acid, terephthalic acid, etc.) And low molecular weight glycols (for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentyl glycol, 1,4-bishydroxy Methyl polycyclohexane etc.), specifically polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene-butylene adipate diol, polyneope Chill - hexyl adipate diol, poly-3-methylpentane adipate diol, polybutylene isophthalate diol,

(3) Polylactone polyol, such as polycaprolactone diol or triol, poly-3-methylvalerolactone diol,
(4) Polycarbonate diol, such as polyhexamethylene carbonate,
(5) Polyolefin polyol, such as polybutadiene glycol, polyisoprene glycol or hydride thereof,
(6) Polymethacrylate diols, for example, α, ω-polymethyl methacrylate diol, α, ω-polybutyl methacrylate diol, and the like.
The molecular weight of these polyols is not particularly limited, but the number average molecular weight is usually about 500 to 2,000. Moreover, these polyols can be used individually or in combination of 2 or more types.

  Examples of polyamines include short chain diamines, aliphatic, aromatic diamines and hydrazines. Examples of the short-chain diamine include aliphatic diamine compounds such as methylene diamine, ethylene diamine, trimethylene diamine, hexamethylene diamine, and octamethylene diamine; phenylene diamine, 3,3′-dichloro-4,4′-diaminodiphenyl methane, 4, Aromatic diamine compounds such as 4'-methylenebis (phenylamine), 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone; cyclopentadiamine, cyclohexyldiamine, 4,4'-diaminodicyclohexylmethane, 1, Examples include alicyclic diamine compounds such as 4-diaminocyclohexane and isophoronediamine. Further, hydrazines such as hydrazine, carbodihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, phthalic acid dihydrazide and the like can be mentioned. These can be used alone or in combination of two or more. As a polyol and a polyamine, a diol compound and a diamine compound are preferable.

  As the polyisocyanate compound used in the present invention, any of those conventionally used for producing polyurethane can be used and is not particularly limited. For example, preferred are toluene-2,4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy- 1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, 4,4'-methylenebis (phenylene isocyanate) (MDI), jurylene diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate, benzidine Aromatic diisocyanates such as diisocyanate, o-nitrobenzidine diisocyanate, 4,4'-diisocyanate dibenzyl;

  Aliphatic diisocyanates such as methylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate; 1,4-cyclohexylene diisocyanate, 4,4-methylenebis (cyclohexyl isocyanate), Obtained by reacting 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, alicyclic diisocyanates such as hydrogenated MDI, hydrogenated XDI, etc., or these diisocyanate compounds with low molecular weight polyols and polyamines so that the terminal is isocyanate. Naturally, polyurethane prepolymers and the like can also be used.

When producing the long-chain side-chain-containing polyurethane aqueous dispersion used in the present invention, first, 1 to 30 compounds each having both the above-mentioned compound and (A) a hydrophilic group other than a hydroxyl group and an active hydrogen-containing group are used. (B) 1 to 95% by weight of a compound having a long chain alkyl group and an active hydrogen-containing group in the side chain, (C) 1 to 90% by weight of a polysiloxane compound having an active hydrogen-containing group, (D ) 0 to 80% by weight of a low molecular weight polymer having an active hydrogen-containing group at one molecular end, 0 to 80% by weight of (E) polyol and / or polyamine (however, the total of A to E is 100% by weight) The long-chain side-chain-containing hydrophilic polyurethane resin is synthesized using the above-mentioned ratio. If necessary, an appropriate amount of a chain extender (the desired amount of chain extender) is added so that the equivalent ratio of all active hydrogen-containing groups to isocyanate groups in these reaction components is approximately 1.0. A hydrophilic polyurethane resin is synthesized by reacting in the presence of the molecular weight and the desired physical properties until there is no isocyanate group. The reaction may be a one-shot method or a multistage method, and is usually carried out at 20 to 150 ° C, preferably 60 to 110 ° C. Thereafter, the obtained polyurethane resin is dispersed or emulsified in an aqueous medium using a neutralizing agent to obtain a self-dispersing or emulsifying stable polyurethane aqueous dispersion. In addition, (D) and (E) in the above reaction components are components that are not necessary, and are used to adjust the solution viscosity, adhesive strength, film strength, and film hardness of the resulting hydrophilic polyurethane resin. .
As for the molecular weight of these obtained long-chain side chain-containing hydrophilic polyurethane resins, the weight average molecular weight (measured by GPC, standard polystyrene conversion) is preferably in the range of 2,000 to 500,000.

  In the present invention, a catalyst can be used as necessary during the synthesis of polyurethane. Examples of the catalyst include dibutyltin laurate, dioctyltin laurate, stannous octoate, lead octylate, salts of organic and inorganic acids such as tetra-n-butyl titanate, and organic metal derivatives such as triethylamine. Examples include amines and diazabicycloundecene catalysts.

In the present invention, the polyurethane synthesis reaction may be performed without a solvent or in an organic solvent. In the case of using an organic solvent, after the polyurethane aqueous dispersion is prepared, the organic solvent is removed by an appropriate means such as vacuum drying (degassing).
Preferable examples of the organic solvent include those that are inert to isocyanate groups or that are less active than the reaction components. Examples of such solvents include ketone solvents (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), aromatic hydrocarbon solvents (toluene, xylene, swazol (aromatic hydrocarbon solvent manufactured by Cosmo Oil Co., Ltd.). ), Solvesso (aromatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.), aliphatic hydrocarbon solvents (n-hexane, etc.), alcohol solvents (methanol, ethanol, isopropanol, etc.), ether solvents (dioxane, Tetrahydrofuran, etc.), ester solvents (ethyl acetate, butyl acetate, isobutyl acetate, etc.), glycol ether ester solvents (ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybutyl acetate, Til-3-ethoxypropionate), amide solvents (dimethylformamide, dimethylacetamide, etc.), lactam solvents (n-methyl-2-pyrrolidone, etc.) Among these, solvent recovery, urethane synthesis Considering the solubility, reactivity, boiling point, and emulsifying dispersibility in water, methyl ethyl ketone, ethyl acetate, acetone, tetrahydrofuran and the like are particularly preferable.

  In the present invention, an isocyanate-terminated reaction terminator may be added when an isocyanate group remains at the polymer terminal during polyurethane synthesis. As the reaction terminator, for example, not only monofunctional compounds such as monoalcohols and monoamines, but also compounds having two functional groups having different reactivities with respect to isocyanate can be used. For example, monoalcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol; monoethylamine, n-propylamine, diethylamine, di-n-propylamine, Examples include monoamines such as di-n-butylamine; alkanolamines such as monoethanolamine and diethanolamine. Among them, alkanolamines are preferable in that the reaction can be easily controlled.

  As a neutralizing agent used when producing an aqueous dispersion of a long-chain side chain-containing polyurethane resin, for example, for anionic components (sulfonic acid type, carboxylic acid type, etc.), organic amines (ammonia, ethylamine) are used. , Trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-phenyldiethanolamine, monoethanolamine, dimethylethanolamine, diethylethanolamine, morpholine, N-methylmorpholine, 2-amino-2 -Ethyl-1-propanol etc.), alkali metals (lithium, potassium, sodium etc.), inorganic alkalis (lithium hydroxide, sodium hydroxide, potassium hydroxide etc.). On the other hand, for the cationic component (tertiary amine type), for example, formic acid, lactic acid, acetic acid and the like can be mentioned, and these can be used alone or in combination of two or more.

The long-chain side-chain-containing hydrophilic polyurethane resin forming the long-chain side-chain-containing polyurethane aqueous dispersion used in the present invention is (1) when the above compounds (A) to (C) are used, The unit introduced from the compound (A) is 1 to 30% by weight, preferably 2 to 20% by weight, the unit introduced from the compound (B) is 1 to 95% by weight, preferably 5 to 70% by weight, the compound Long chain side containing 1 to 90% by weight, preferably 1 to 80% by weight of units introduced from (C) (total of units introduced from compounds (A) to (C) is 100% by weight). A chain-containing hydrophilic polyurethane resin is preferred.
(2) When the above compounds (A) to (E) are used, the unit introduced from the compound (A) is 1 to 30% by weight, preferably 2 to 20% by weight, as the structural unit. 1 to 95% by weight of units introduced from the compound (B), preferably 5 to 70% by weight, 1 to 90% by weight of units introduced from the compound (C), preferably 1 to 80% by weight, 1) to 80% by weight of units introduced from D), preferably 1 to 60% by weight and 1 to 80% by weight of units introduced from compound (E), preferably 1 to 60% by weight (compound (A) The total of units introduced from (E) is 100% by weight.) The long-chain side-chain-containing hydrophilic polyurethane resin contained is preferable.

  In the present invention, the units introduced from the respective compounds (A) to (E) constituting the long-chain side-chain-containing hydrophilic polyurethane resin are such that each of these compounds has two active hydrogen-containing groups such as a hydroxyl group. Taking the case where the polyisocyanate is a diisocyanate (OCN-R-NCO) as an example, the OH group of each compound (HO-X-OH) reacts with the isocyanate group of the diisocyanate to give each compound A urethane bond is formed as described below and incorporated into the main chain of the polyurethane molecular chain. If a high molecular weight diamine is used as the compound (E), a unit to be introduced from this unit is linked to another unit by a urea bond. Further, when a chain extender is used, when a low molecular diol or diamine is used as the chain extender, a structure in which molecular chains including units connected by the above bonds are connected by urethane bonds or urea bonds is obtained. Therefore, in the present invention, the hydrophilic polyurethane resin includes a polyurethane resin having a urethane bond in a molecular chain and a polyurethane-polyurea resin having a urethane bond and a urea bond. Further, when a compound having an amino group as an active hydrogen-containing group is used, when a short chain diamine is further used as a chain extender, a polyurea resin in which each unit is connected by a urea bond is produced. Therefore, in the present invention, the hydrophilic polyurethane resin includes a polyurea resin.

Various additives can be added to the long-chain side-chain-containing hydrophilic polyurethane aqueous dispersion used in the present invention , if necessary, depending on the purpose of use. Additives include, for example, antioxidants (hindered phenols, phosphites, thioethers, etc.), light stabilizers (hindered amines, etc.), ultraviolet absorbers (benzophenones, benzotriazoles, etc.), gas discoloration stability An agent (hydrazine type, etc.) , a metal deactivator, etc., or a combination of two or more of these may be mentioned.

Next, a heat-sensitive recording material having a back layer formed using the polyurethane aqueous dispersion having the above-mentioned long chain side chain will be described.
The back layer of the heat-sensitive recording material can be composed only of the long-chain side chain-containing hydrophilic polyurethane resin, but a crosslinking agent, other binder resin, and a wax compound can be added as necessary.
As the wax compound, any conventionally known wax having a molecular weight in the range of 250 to 10,000 can be used, and is not particularly limited. For example, natural waxes such as candelilla wax, carnauba wax, rice wax, wood wax, beeswax, lanolin, whale wax, montan wax, ozokerite, ceresin; petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam and the like Modified waxes of derivatives; hydrogenated waxes such as hydrogenated castor oil and its derivatives; synthetic hydrocarbons such as Fischer-Tropsch wax, polyester wax, chlorinated hydrocarbons; 12-hydroxystearic acid, stearamide, phthalic anhydride Examples include synthetic fatty acid derivatives such as imide. These can be used alone or in combination of two or more. By adding the above-mentioned wax to the long-chain side-chain-containing hydrophilic polyurethane resin used in the present invention, further heat resistance, blocking resistance, slipperiness, and the like can be imparted. The solid content concentration in which the wax is contained in the long-chain side-chain-containing hydrophilic polyurethane aqueous dispersion is not particularly limited, but is 95% by weight or less, preferably 1 to 20% by weight with respect to the polyurethane resin.

In the present invention, the back layer can be crosslinked. The crosslinking method is not particularly limited as long as it is a crosslinking method utilizing the reactivity of a hydrophilic group such as a urethane group or a urea group and / or a carboxyl group.
Examples of the crosslinking method utilizing a urethane group include crosslinking with a polyisocyanate crosslinking agent. As the polyisocyanate crosslinking agent, known ones that have been conventionally used can be used and are not particularly limited. For example, dimer of 2,4-toluylene diisocyanate, triphenylmethane triisocyanate, tris- (p-isocyanatephenyl) thiophosphite, polyfunctional aromatic isocyanate, polyfunctional aromatic aliphatic isocyanate, polyfunctional aliphatic Examples thereof include blocked polyisocyanates such as isocyanate, fatty acid-modified polyfunctional aliphatic isocyanate, and blocked polyfunctional aliphatic isocyanate, and polyisocyanate prepolymers. These polyisocyanate cross-linking agents are particularly effective in improving heat resistance and ink transferability if they are in an appropriate amount. However, if the amount used is too large, unreacted isocyanate will remain, resulting in problems such as reduced heat resistance and ink transfer. In order to cause this, it is preferable to use 120 parts by weight or less, preferably 1 to 50 parts by weight with respect to 100 parts by weight of the polyurethane resin.

  As a crosslinking method using a hydrophilic group, for example, a carboxyl group, for example, known methods conventionally used such as an epoxy-based crosslinking agent, a carbodiimide-based crosslinking agent, an oxazoline-based crosslinking agent, or a metal complex-based crosslinking agent are used. It can be used and is not particularly limited. For example, as the epoxy-based crosslinking agent, a conventionally known commercially available epoxy resin such as “Epicoat” (manufactured by Yuka Shell Epoxy Co., Ltd.) can be added and used. As the carbodiimide-based cross-linking agent, a commercial product of “Carbodilite” trade name (manufactured by Nisshinbo Co., Ltd.) can be obtained and used. Moreover, as an oxazoline type crosslinking agent, the commercial item of the brand name (made by Nippon Shokubai Co., Ltd.) of "Epocross" can be obtained and used. As the metal complex-based crosslinking agent, titanium organic compound-based, zirconium organic compound-based commercially available under the trade name of “Orgatyx” (manufactured by Matsumoto Pharmaceutical Co., Ltd.) are available, and aluminum, chromium, cobalt, copper, Iron, nickel, vanadium, zinc, indium, calcium, magnesium, manganese, yttrium, cerium, strontium, palladium, barium, molybdenium, lanthanum, tin sold under the trade name "Narsem" (manufactured by Nippon Kagaku Sangyo Co., Ltd.) An acetylacetone complex can be obtained and used. These cross-linking agents are particularly effective for improving heat resistance and ink transferability if they are in an appropriate amount, but if the amount used is too large, the pot life is shortened and the film becomes brittle. The use is preferably 40 parts by weight or less, preferably 0.5 to 20 parts by weight per 100 parts by weight.

  As the binder resin other than the hydrophilic polyurethane resin having a long chain side chain used in the present invention, any of the resins conventionally used for forming the back layer can be used and is not particularly limited. For example, conventionally known silicone resins, polyester resins, polyamide resins, polyimide resins, polystyrene resins, polyurethane resins, polycarbonate resins, norbornene resins, cellulose resins, polyvinyl alcohol resins, polyvinyl formal resins , Polyvinyl butyral resins, polyvinyl pyrrolidone resins, polyvinyl acetate resins, polyvinyl acetal resins, and the like. Although the usage-amount of these resin is not specifically limited, Usually, it is 900 weight part or less with respect to 100 weight part of this polyurethane resin, Preferably it is the range of 5-400 weight part.

If necessary, known antistatic agents, organic fine particles, inorganic fine particles and other additives can be used as appropriate. Examples of the organic fine particles and inorganic fine particles include silicone resin fine particles, fluororesin fine particles, acrylic resin fine particles, urethane resin fine particles, polyethylene resin fine particles, and reactive siloxane.
Examples of the antistatic agent include metal oxides such as carbon black, tin oxide, and titanium oxide, various metal alkoxides, conductive fillers such as ITO powder, organic conductive materials such as polyaniline, polythiophene, and polypyrrole, and modified ethylene oxide. And the like.

In the present invention, when the back layer of the heat-sensitive recording material is formed, it is used in the present invention which uses one liquid or contains the long-chain side chain-containing hydrophilic polyurethane resin as a film-forming component using the above-mentioned crosslinking agent. An aqueous dispersion is used as the back layer forming paint. The paint may be prepared without a solvent. The solid content of the prepared paint is not particularly limited, but is usually about 1 to 95% by weight.

The heat-sensitive recording material of the present invention can be produced by a conventionally known method using the above-mentioned coating material for forming the back layer, and the production method itself is not particularly limited. In addition, the materials other than the back layer forming material such as the base material sheet and the heat sensitive recording layer (ink layer) forming material can be known materials and are not particularly limited.
In forming the back layer of the heat-sensitive recording material of the present invention, the water-based back layer forming paint containing the long-chain side chain-containing hydrophilic polyurethane resin of the present invention is applied to the back surface (surface) of the base sheet by a conventionally known method. Is applied to the heat-sensitive recording layer) so as to have a dry thickness of about 0.01 to 1 μm to form a film.

  Hereinafter, the present invention will be described more specifically with reference to production examples, examples and comparative examples, but the present invention is not limited thereto. In the following text, “parts” represents parts by weight, and “%” represents weight percent.

[Examples 1-4 and Comparative Examples 1-3]
After replacing the reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen blowing tube, and a manhole with nitrogen gas, (A) a hydrophilic group-containing compound component of the types and amounts shown in Tables 1 and 2, (B ) A long-chain alkyl group-containing diol component, (C) a polysiloxane component having a hydroxyl group at both ends or one end, and a chain extender (short-chain diol component), or (D) a hydroxyl group at one end The low molecular weight polymer component and the (E) polymer diol component were added, a predetermined amount of tetrahydrofuran was added, and the solution was uniformly dissolved to adjust the solution concentration. Subsequently, a predetermined amount of hexamethylene diisocyanate was added and reacted at 80 ° C. After confirming that there was no absorption due to a free isocyanate group of 2,270 cm ^{−1 in} the infrared absorption spectrum, the mixture was cooled to 50 ° C., and 45% in Examples 1 to 4 and 25 in Comparative Examples 1 to 3 based on the solid content. A predetermined amount of ion-exchanged water and a neutralizing agent were added, and the system was uniformly emulsified. Finally, the tetrahydrofuran in the system was recovered by vacuum degassing to obtain a polyurethane aqueous dispersion. Tables 1 and 2 show the raw material composition of polyurethane, the properties of the paint and polyurethane (PU).
The molecular weight of polyurethane is measured by GPC and is a weight average molecular weight in terms of standard polystyrene. For the polysiloxane content, the siloxane content measured by the infrared spectroscopic analysis method of JIS K0117 was displayed as the polysiloxane content.

(note)
(A)
A-1: dimethylolbutanoic acid A-2: dimethylolpropanoic acid (B)
B-1: AOG-X68 (1,2-hydroxyalkane (manufactured by Daicel Chemical Industries))
_{CH 2 (OH) -CH (OH} ) - (CH 2) n CH 3
(N is an integer, average molecular weight 360)
B-2: AOG-Y08 (1,2-hydroxyalkane (manufactured by Daicel Chemical Industries))
_{CH 2 (OH) -CH (OH} ) - (CH 2) n CH 3
(N is an integer, average molecular weight 550)

・Ｃ−２：（Ｘ−２２−１７６ＤＸ、片末端ポリシロキサンジオール（信越化学社製）（ｎは整数、平均分子量３，２０５）

(C)
C-1: (KF-6001, both-end polysiloxane diol (manufactured by Shin-Etsu Chemical)

C-2: (X-22-176DX, one-end polysiloxane diol (manufactured by Shin-Etsu Chemical Co., Ltd.) (n is an integer, average molecular weight 3,205)

（Ｒ₁＝Ｈ又はＣＨ₃、Ｒ₂＝エチル基、平均分子量２，０００、Ｔｇ＝−２４℃）
（Ｅ）
・ＰＣＤ：プラクセルＣＤ２２０（ポリカーボネートジオール（ダイセル化学工業社製、ｎは整数、平均分子量２，０００）

ＴＥＡ：トリエチルアミン
架橋剤：カルボジライトＶ−０２（日清紡社製、カルボジイミド系架橋剤） (D)
・ D-1:

(R ₁ = H or CH ₃ , R ₂ = ethyl group, average molecular weight 2,000, Tg = −24 ° C.)
(E)
PCD: Plaxel CD220 (polycarbonate diol (manufactured by Daicel Chemical Industries, n is an integer, average molecular weight 2,000)

TEA: Triethylamine crosslinking agent: Carbodilite V-02 (Nisshinbo Co., Ltd., carbodiimide crosslinking agent)

[Examples 5-8, Comparative Examples 4-6]
Using each paint obtained in Examples 1 to 4 and Comparative Examples 1 to 3, the thickness after drying is 0.1 μm on the surface of a 6 μm thick polyethylene terephthalate film (manufactured by Toray) by gravure printing. After coating, the solvent was dried in a dryer. When the coating materials of Example 4 and Comparative Example 3 were used, the back layer was formed by applying and drying with a gravure coater.

Next, a transfer ink composition was prepared with the following formulation. This ink composition is heated to 100 ° C., and applied to the back surface of each PET film on which the above heat-resistant protective layer is formed by a hot melt roll coating method so that the coating thickness is 5 μm, thereby forming a transfer ink layer. Thermal transfer materials of Examples and Comparative Examples were obtained.
[Ink composition]
・ 10 parts of paraffin wax ・ 10 parts of carnauba wax ・ 1 part of polybutene (manufactured by Nippon Oil Corporation) ・ 2 parts of carbon black

Using each of the thermal transfer materials obtained above, printing was performed with a thin film thermal head under the condition of printing energy of 1 mJ / dot (4 × 10 ⁻⁴ / cm ² ). At this time, the sticking property, head inertia, adhesion property, and migration property were observed and measured, and evaluated. The evaluation method is as follows. The evaluation results are shown in Table 3.

(1) Sticking property When a thermal transfer material is subjected to a mounting test, evaluation of wrinkling and sticking of the thermal transfer material during the pressing operation between the thermal head and the thermal transfer material and thermal fusion with the image receiving sheet are performed. The case where there was no sticking was rated as “◯”, the case where a slight heat burn occurred was evaluated as “Δ”, and the case where running was not possible due to breakage was marked as “X”.
(2) Head durability When the thermal transfer material was subjected to a mounting test, the presence or absence of dirt on the head thermal element portion was observed.
(3) Adhesiveness A cross-cut cellophane tape peeling test (cross-cut method) was performed on the adhesiveness between the heat-resistant protective layer and the substrate PET film.
(4) Transferability The degree of transfer to an ink layer such as low molecular weight polysiloxane or polyethylene wax after leaving the rolled thermal transfer material in an oven at 40 ° C. for 3 days is evaluated by touch and visual observation. Those with no transition were marked with ◯, and those with transition were marked with ×.

Claims (6)

In a thermosensitive recording material comprising a base sheet, a thermosensitive recording layer provided on one side of the base sheet, and a back layer provided on the other side of the base sheet, the back layer comprises polyisocyanate and (A) a compound having both a hydrophilic group other than at least one hydroxyl group and at least one active hydrogen-containing group; and (B) a linear or branched alkyl having 8 to 64 carbon atoms in the molecule. Each of the two carbon atoms having a group (which is a side chain in the resulting polyurethane resin) and having two adjacent carbon atoms or 1 to 3 carbon atoms between them. A length obtained by reacting a bifunctional organic compound having a group having the group (which is incorporated into the main chain in the resulting polyurethane resin) with a polysiloxane compound having at least one active hydrogen-containing group (C) Chain side chain Heat-sensitive recording material characterized by comprising a layer containing a hydrophilic polyurethane resin. The polyurethane resin further comprises (D) a low molecular weight polymer having at least one active hydrogen-containing group at one end of the molecular chain, and (E) a polyol and / or a polyamine, which are reacted by adding to the long chain side. The heat-sensitive recording material according to claim 1, which is a polyurethane resin having a chain. The polyurethane resin is 1 to 30% by weight of units introduced from the compound (A) and 1 to 95% by weight of units introduced from the compound (B), each linked by a urethane bond and / or a urea bond. The thermosensitive recording according to claim 1, comprising 1 to 90% by weight of units introduced from the compound (C) (the total of units introduced from the compounds (A) to (C) is 100% by weight). Material . The polyurethane resin is 1 to 30% by weight of units introduced from the compound (A) and 1 to 95% by weight of units introduced from the compound (B), each linked by a urethane bond and / or a urea bond. 1 to 90% by weight of units introduced from the compound (C), 1 to 80% by weight of units introduced from the compound (D), and 1 to 80% by weight of units introduced from the compound (E) ( The heat-sensitive recording material according to claim 2, comprising a total of 100% by weight of units introduced from the compounds (A) to (E). The heat-sensitive recording material according to claim 1 or 2, wherein the hydrophilic group other than the hydroxyl group is a carboxyl group, a sulfonic acid group or an amino group. In a method for producing a thermosensitive recording material comprising a base sheet, a thermosensitive recording layer provided on one side of the base sheet, and a back layer provided on the other side of the base sheet, , Polyisocyanate, (A) a compound having both a hydrophilic group other than at least one hydroxyl group and at least one active hydrogen-containing group, and (B) a straight chain having 8 to 64 carbon atoms in the molecule or Each of two carbon atoms having an alkyl group having a branch (the group becomes a side chain in the resulting polyurethane resin) and two adjacent carbon atoms or 1 to 3 carbon atoms existing therebetween A bifunctional organic compound having a group having active hydrogen in (the group is incorporated into the main chain in the resulting polyurethane resin) and (C) a polysiloxane compound having at least one active hydrogen-containing group. Obtained Method for producing a heat-sensitive recording material hydrophilic polyurethane resin having a long-chain side-chain that is characterized by forming with a polyurethane aqueous dispersion that is dispersed or emulsified in an aqueous medium.