JP5956888B2 - THERMAL RECORDING MATERIAL, ITS MANUFACTURING METHOD, AND PRINTED MATERIAL MANUFACTURING METHOD USING THIS THERMAL RECORDING MATERIAL - Google Patents

Description

  The present invention relates to a heat-sensitive recording material containing a vinyl alcohol polymer, a method for producing the same, and a method for producing a printed material using the heat-sensitive recording material.

  A vinyl alcohol polymer represented by polyvinyl alcohol (hereinafter sometimes abbreviated as “PVA”) is known as a water-soluble synthetic polymer, and is a raw material for vinylon which is a synthetic fiber, a paper processing agent. It is widely used for fiber processing agents, adhesives, stabilizers for emulsion polymerization and suspension polymerization, inorganic binders, films and the like. In particular, PVA is superior in strength properties and film-forming properties compared to other water-soluble synthetic polymers, and by utilizing these properties, a coating layer such as a heat-sensitive color forming layer or an overcoat layer is formed in a heat-sensitive recording material. It is heavily used as a material.

  In order to further enhance the properties of such PVA, PVA with various modifications has been developed. As one of the modified PVA, silyl group-containing PVA can be mentioned. This silyl group-containing PVA has high water resistance and high binder strength against inorganic substances. However, the silyl group-containing PVA is (a) difficult to dissolve unless an alkali or acid such as sodium hydroxide is added when preparing an aqueous solution, and (b) the viscosity stability of the prepared aqueous solution is low. When the film containing the inorganic substance is formed, it is difficult to satisfy both the water resistance of the obtained film and the binder strength against the inorganic substance at the same time. Therefore, a heat-sensitive recording material produced using such a PVA as a coating layer does not have water resistance or the like that can sufficiently meet the recent high demand for heat-sensitive recording materials. In addition to water resistance, the coating layer of the heat-sensitive recording material is also required to have plasticizer resistance such that performance is not deteriorated even when stored in contact with a film containing a plasticizer.

  Therefore, water solubility and the like are improved by setting the product (P × S) of the viscosity average degree of polymerization (P) and the content of the monomer unit having a silyl group (S: mol%) within a certain range. The proposed silyl group-containing PVA (see JP-A-2004-43644) and a heat-sensitive recording material (see JP-A-2005-194437) obtained using a coating agent containing such a silyl group-containing PVA are proposed. Has been. However, in these silyl group-containing PVA, the upper limit of the product (P × S) is 370, and the content of the monomer unit having a silyl group is increased to enhance the characteristics as the silyl group-containing PVA. And the trade-off relationship between improving water solubility and the like has not been resolved. That is, as described in paragraph 0009 of JP 2004-43644 A, when the product (P × S) is 370 or more, an alkali or an acid is added when preparing an aqueous solution of silyl group-containing PVA. Otherwise, there is a disadvantage in handling that it may not be dissolved. That is, it cannot be said that the silyl group-containing PVA sufficiently corresponds to the above requirement for the heat-sensitive recording material.

JP 2004-43644 A JP 2005-194437 A

  The present invention has been made based on the above-described circumstances, and an object thereof is to provide a heat-sensitive recording material excellent in water resistance and plasticizer resistance, a method for producing the same, and a method for producing printed matter using the same. And

The invention made to solve the above problems is
It is a heat-sensitive recording material containing a PVA containing a monomer unit having a group represented by the following formula (1) and satisfying the following formula (I).

The formula (1), ^{R 1} is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ² is a group represented by an alkoxyl group, an acyloxyl group, or OM. M is a hydrogen atom, an alkali metal or an ammonium group. R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group. The hydrogen atom which the alkyl group, alkoxyl group, and acyloxyl group represented by R ^{1 to} R ⁴ have may be substituted with a substituent containing an oxygen atom or a nitrogen atom. m is an integer of 0-2. n is an integer of 3 or more. When a plurality of R ^{1 to} R ⁴ are present, each of the plurality of R ^{1 to} R ⁴ independently satisfies the above definition.
370 ≦ P × S ≦ 6,000 (I)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

  The PVA contained in the heat-sensitive recording material includes a monomer unit having a group represented by the above formula (1), and a structure in which a silyl group is connected to a main chain via an alkylene group having 3 or more carbon atoms. have. Therefore, for example, when a coating layer (such as a thermosensitive coloring layer or an overcoat layer) of the thermosensitive recording material is produced using the coating agent containing PVA, the amount of modification of the silyl group of PVA contained in the coating agent Even if it raises, since the water solubility in the neutral area | region of this PVA is high, the handleability of a coating agent is good and the fall of viscosity stability is also suppressed. Therefore, according to the thermosensitive recording material, the amount of silyl group modification of PVA contained can be increased, and water resistance, plasticizer resistance and the like can be improved.

It is preferable that the PVA further satisfies the following formulas (II) and (III).
200 ≦ P ≦ 4,000 (II)
0.1 ≦ S ≦ 10 (III)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

  Thus, by setting the viscosity average degree of polymerization (P) of the PVA and the content (S) of the monomer unit within the above ranges, the water solubility and viscosity stability of the PVA are increased, and the water-resistant recording material has water resistance. And plasticizer resistance can be improved.

  N in the above formula (1) is preferably an integer of 6 or more and 20 or less. By setting n in the above range, the content of the crosslinking agent used in combination with the PVA can be reduced, and even when no crosslinking agent is used, the water resistance and plasticizer resistance of the resulting heat-sensitive recording material. Etc. can be fully exhibited.

  The monomer unit is preferably represented by the following formula (2).

In said formula (2), the definition of R < ¹ > -R < ⁴ >, m, and n is the same as that of said formula (1). X is a direct bond, a divalent hydrocarbon group, or a divalent organic group containing an oxygen atom or a nitrogen atom. R ⁵ is a hydrogen atom or a methyl group.

  When the monomer unit has the structure represented by the formula (2), various performances of the heat-sensitive recording material can be further enhanced.

X in the above formula (2) represents —CO—NR ⁶ — * (R ⁶ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. * Represents a group represented by the above formula (1) and It is preferable that it is represented by the following. Thus, while maintaining the performance derived from the silyl group of the PVA by having the amide structure in the position where the monomer unit is separated from the silyl group, water solubility and viscosity stability can be further improved. As a result, various functions of the thermosensitive recording material can be further enhanced.

  X in the above formula (2) is represented by —CO—NH— * (* represents a bonding site with the group represented by the above formula (1)), and n is an integer of 12 or less. Good. By setting the monomer unit to such a structure, the water solubility and viscosity stability of the PVA can be increased, and various functions of the thermosensitive recording material can be further enhanced, and the production of the PVA can be facilitated. Can be done.

  The PVA including a monomer unit having a group represented by the above formula (2) saponifies a copolymer of an unsaturated monomer represented by the following formula (3) and a vinyl ester monomer. It is good that it is obtained by doing. By using the PVA obtained by such a method, various characteristics of the heat-sensitive recording material can be more suitably exhibited.

In the above formula (3), the definitions of R ^{1 to} R ⁵ , X, m and n are the same as those in the above formula (2).

  The thermosensitive recording material comprises a substrate, a thermosensitive coloring layer formed on the surface of the substrate, and an overcoat layer formed on the surface of the thermosensitive coloring layer, and at least one of the thermosensitive coloring layer and the overcoat layer. However, it may be formed by applying a coating agent containing the PVA. By doing in this way, the said layer of the said thermosensitive recording material can be formed from said PVA, etc., and water resistance and plasticizer resistance can be improved more effectively.

  The production method of the present invention for producing the heat-sensitive recording material has a step of coating the base material with the coating agent containing the PVA. According to the manufacturing method, the thermosensitive recording material can be easily obtained.

  Furthermore, this invention includes the manufacturing method of printed matter which has the process printed on the said thermosensitive recording material. According to the production method, since the above-mentioned heat-sensitive recording material is used, a printed matter having excellent water resistance and plasticizer resistance can be obtained.

  As described above, the heat-sensitive recording material of the present invention can exhibit high water resistance and plasticizer resistance by including the specific PVA. Moreover, according to the manufacturing method, the heat-sensitive recording material can be easily obtained. Furthermore, according to the method for producing a printed matter of the present invention, since the heat-sensitive recording material is used, a printed matter having excellent water resistance and plasticizer resistance can be obtained.

  Hereinafter, embodiments of the heat-sensitive recording material, the method for producing the same, and the method for producing printed matter using the same will be described in detail.

  The heat-sensitive recording material of the present invention contains PVA containing specific monomer units described in detail below. The heat-sensitive recording material has a layer structure in which, for example, a base material, a heat-sensitive coloring layer and an overcoat layer are laminated in this order, and at least one of the heat-sensitive coloring layer and the overcoat layer includes the PVA. It is formed as a coating layer by coating. Here, it is preferable that the overcoat layer is formed by applying a coating agent containing the PVA. By doing in this way, the said layer of the said thermosensitive recording material can be formed from said PVA, etc., and water resistance and plasticizer resistance can be improved more effectively.

<Base material>
As the base material of the heat-sensitive recording material, conventionally known transparent and opaque support bases can be used. Examples of the transparent support substrate include polyester, polystyrene, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polycarbonate, polyimide, cellophane, celluloid and other films, sheets, highly transparent paper, and the like. Examples of the opaque support substrate include ordinary paper, pigment-coated paper, cloth, wood, metal plate, synthetic paper, opaque synthetic resin film, and sheet. Among these, paper is preferable from the viewpoint of allowing the coating agent to penetrate into the base paper and improving water resistance and the like.

<Coating agent>
The coating agent is usually an aqueous solution of the PVA and may contain other components. As the other components, when forming an overcoat layer, a crosslinking agent, a water-soluble polymer, a polymer dispersion, a lubricant and a filler, etc. Agents, crosslinking agents, water-soluble polymers, polymer dispersions, lubricants and fillers.

<PVA>
The PVA includes a monomer unit having a group represented by the formula (1). That is, the PVA is a copolymer containing a monomer unit having a group represented by the formula (1) and a vinyl alcohol unit (—CH ₂ —CHOH—), and further another monomer unit. You may have.

The formula (1), ^{R 1} is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group.

R ² is a group represented by an alkoxyl group, an acyloxyl group, or OM. M is a hydrogen atom, an alkali metal, or an ammonium group ( ⁺ NH ₄ ). Examples of the alkoxyl group include a methoxy group and an ethoxy group. Examples of the acyloxyl group include an acetoxy group and a propionyloxy group. Examples of the alkali metal include sodium and potassium. Among these groups represented by R ² , an alkoxyl group or a group represented by OM is preferable, and an alkoxyl group having 1 to 5 carbon atoms and a group represented by OM in which M is hydrogen or an alkali metal are more preferable. A methoxy group, an ethoxy group, and a group represented by OM in which M is sodium or potassium are more preferable.

R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include the above-described alkyl groups having 1 to 5 carbon atoms. R ³ and R ⁴ are preferably a hydrogen atom or a methyl group.

The hydrogen atom which the alkyl group, alkoxyl group, and acyloxyl group represented by R ^{1 to} R ⁴ have may be substituted with a substituent containing an oxygen atom or a nitrogen atom. Examples of the substituent containing an oxygen atom include an alkoxyl group and an acyloxyl group. In addition, examples of the substituent containing a nitrogen atom include an amino group and a cyano group.

In ^the case where R 1 to R ⁴ is present in plural, each ^R 1 to R ⁴ that there are two or more, independently meets the above definition.

m is an integer of 0 to 2, and 0 is preferable. When m is 0, that is, the monomer unit has three R ² groups, the effect of modification can be further enhanced.

n is an integer of 3 or more. The upper limit of n is not particularly limited, but is, for example, 20 and is preferably 12. The PVA has a structure in which n in the formula (1) is 3 or more, that is, the silyl group is connected to the main chain via an alkylene group having 3 or more carbon atoms, so that the amount of modification of the silyl group Even if it raises, the fall of water solubility and viscosity stability is suppressed. The reason why such an effect appears is not sufficiently elucidated. For example, a hydrophobic alkylene group having 3 or more carbon atoms reduces the hydrolysis rate of Si—R ² in an aqueous solution, thereby causing a reaction. This is presumed to inhibit Further, n is more preferably an integer of 6 or more. By setting n in such a range, the content of the crosslinking agent usually used in combination with the above PVA can be reduced, and even when no crosslinking agent is used, The plasticizer resistance and the like can be sufficiently exhibited.

  The specific structure of the monomer unit is not particularly limited as long as it has a group represented by the above formula (1), but is preferably represented by the above formula (2).

In said formula (2), the definition of R < ¹ > -R < ⁴ >, m, and n is the same as that of said formula (1). The same applies to these preferred groups or numerical ranges.

  X is a direct bond, a divalent hydrocarbon group, or a divalent organic group containing an oxygen atom or a nitrogen atom. By having the structure represented by the above formula (2), the monomer unit can improve various performances such as water solubility and viscosity stability, water resistance and plasticizer resistance of the resulting heat-sensitive recording material. it can.

  Examples of the divalent hydrocarbon group include a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms and a divalent aromatic hydrocarbon group having 6 to 10 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include a methylene group, an ethylene group, and a propylene group. Examples of the divalent aromatic hydrocarbon group having 6 to 10 carbon atoms include a phenylene group. Examples of the divalent organic group containing an oxygen atom include an ether group, an ester group, a carbonyl group, an amide group, and a group in which these groups are connected to a divalent hydrocarbon group. Examples of the divalent organic group containing a nitrogen atom include an imino group, an amide group, and a group in which these groups are connected to a divalent hydrocarbon group.

Among the groups represented by X, a divalent organic group containing an oxygen atom or a nitrogen atom is preferable, a group containing an amide group is more preferable, and —CO—NR ⁶ — * (R ⁶ is a hydrogen atom or a carbon atom) It is an alkyl group having 1 to 5 atoms. * Is more preferably a group represented by the bonding site with the group represented by the above formula (1). In this way, the monomer unit has a polar structure, preferably an amide structure, at a position away from the silyl group, so that the performance derived from the silyl group is maintained and the water solubility and viscosity stability are further improved. Can do. As the above R ^6, or more increase the above functions, in that it enables to easily perform production of the PVA, a hydrogen atom is preferable.

R ⁵ is a hydrogen atom or a methyl group.

  As said monomer unit, what is represented by following formula (4) is still more preferable.

In the above formula (4), the definitions of R ¹ , R ² , R ⁵ , X and m are the same as in the above formula (2). The same applies to these preferred groups or numerical ranges.

In the above formula (4), R ³ ′ and R ⁴ ′ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include the above-described alkyl groups having 1 to 5 carbon atoms. R ³ ′ and R ⁴ ′ are preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom. The hydrogen atom contained in the alkyl group represented by R ³ ′ and R ⁴ ′ may be substituted with a substituent containing an oxygen atom or a nitrogen atom. Examples of the substituent containing an oxygen atom include an alkoxyl group and an acyloxyl group. In addition, examples of the substituent containing a nitrogen atom include an amino group and a cyano group. When there are a plurality of R ³ ′ and R ⁴ ′, a plurality of R ³ ′ and R ⁴ ′ satisfy the above definition independently.

  In the above formula (4), n ′ is an integer of 1 or more. The upper limit of n is not particularly limited, but is 18 for example and 10 is preferable.

When the monomer unit is represented by the above formula (4), various functions of the thermosensitive recording material can be expressed more effectively. The reason for this is not clear, but it is assumed that the above-described function of reducing the hydrolysis rate of Si—R ² and inhibiting the reaction in the coating agent (aqueous solution) containing the PVA is more effectively exhibited. Is done.

The PVA satisfies the following formula (I).
370 ≦ P × S ≦ 6,000 (I)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

The viscosity average degree of polymerization (P) is measured according to JIS-K6726. That is, when the saponification degree of the PVA is less than 99.5 mol%, the saponification degree is re-saponified to 99.5 mol% or more, and after purification, the intrinsic viscosity [η] measured in water at 30 ° C. (unit: (Deciliter / g) can be obtained by the following equation.
P = ([η] × 1000 / 8.29) ^{(1 / 0.62)}

The content of the monomer unit (S: mol%) can be obtained from proton NMR of the vinyl ester polymer before saponification. Here, when the proton NMR of the vinyl ester polymer before saponification is measured, the vinyl ester polymer is purified by reprecipitation with hexane-acetone, and the monomer having an unreacted silyl group is contained in the polymer. The body is sufficiently removed and then dried at 90 ° C. under reduced pressure for 2 days, and then dissolved in CDCl ₃ solvent for analysis.

The product (P × S) of the viscosity average degree of polymerization (P) and the content (S) of the monomer units corresponds to the number (average value) of the monomer units per 100 molecules. When this product (P × S) is less than the above lower limit, various properties derived from silyl groups such as film strength and water resistance of the heat-sensitive recording material cannot be sufficiently exhibited. On the other hand, when the product (P × S) exceeds the upper limit, the water solubility of PVA and the viscosity stability of the aqueous solution are lowered, and various performances of the resulting heat-sensitive recording material are liable to be lowered. The product (P × S) preferably satisfies the following formula (I ′), and more preferably satisfies the following formula (I ″).
400 ≦ P × S ≦ 3,000 (I ′)
500 ≦ P × S ≦ 2,000 (I ″)

The PVA preferably further satisfies the following formulas (II) and (III).
200 ≦ P ≦ 4,000 (II)
0.1 ≦ S ≦ 10 (III)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

  Thus, by setting the viscosity average degree of polymerization (P) and the content rate (S) of the monomer units in the above ranges, water solubility and viscosity stability are improved, and the water resistance and resistance of the resulting heat-sensitive recording material are improved. Plasticizer properties and the like can be improved.

Furthermore, in the viscosity average polymerization degree (P), it is more preferable to satisfy the following formula (II ′), and it is more preferable to satisfy the following formula (II ″).
500 ≦ P ≦ 3,000 (II ′)
1,000 ≦ P ≦ 2,400 (II ″)

  When the viscosity average degree of polymerization (P) is less than the above lower limit, the water resistance and plasticizer resistance of the resulting heat-sensitive recording material may be lowered. Conversely, when the viscosity average degree of polymerization (P) exceeds the above upper limit, water solubility, viscosity stability, etc. may be reduced.

Moreover, in the content rate of the said monomer unit, it is more preferable to satisfy | fill following formula (III '), and it is still more preferable to satisfy | fill following formula (III'').
0.25 ≦ S ≦ 6 (III ′)
0.5 ≦ S ≦ 5 (III ″)

  When the content (S) of the monomer unit is less than the lower limit, water resistance, plasticizer resistance, and the like of the resulting heat-sensitive recording material may be deteriorated. Conversely, when the monomer unit content (S) exceeds the above upper limit, water solubility, viscosity stability, and the like may decrease.

  Although there is no restriction | limiting in particular as the saponification degree of the said PVA, 80 mol% or more is preferable, 90 mol% or more is more preferable, 95 mol% or more is more preferable, 97 mol% or more is especially preferable. When the saponification degree of the PVA is less than the above lower limit, the water resistance, plasticizer resistance and the like of the resulting heat-sensitive recording material may be lowered. The upper limit of the saponification degree of the PVA is not particularly limited, but is 99.9 mol%, for example, in consideration of productivity. Here, the saponification degree of PVA says the value measured according to the method of JIS-K6726.

<Method for producing PVA>
Although it does not specifically limit as a manufacturing method of the said PVA, For example, a copolymer obtained by copolymerizing a vinyl ester monomer and the monomer which has group represented by the said Formula (1) ( It can be obtained by saponifying a vinyl ester polymer).

  Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Among these, vinyl acetate is preferable.

  In addition, for the purpose of adjusting the degree of polymerization (P) of the obtained PVA in the copolymerization of the monomer having a group represented by the above formula (1) and a vinyl ester monomer, the present invention The polymerization may be carried out in the presence of a chain transfer agent as long as the gist of the present invention is not impaired. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-hydroxyethanethiol, n-dodecanethiol, Mercaptans such as mercaptoacetic acid and 3-mercaptopropionic acid; and halogens such as tetrachloromethane, bromotrichloromethane, trichloroethylene and perchloroethylene.

  As a monomer which has group represented by the said Formula (1), the compound represented by the said Formula (3) can be mentioned, for example. By using the compound represented by the formula (3), finally, a PVA containing a monomer unit having a group represented by the formula (2) can be easily obtained.

In the above formula (3), the definitions of R ^{1 to} R ⁵ , X, m and n are the same as those in the above formula (2). The same applies to these preferred groups or numerical ranges.

  Examples of the compound represented by the above formula (3) include 3- (meth) acrylamidopropyltrimethoxysilane, 4- (meth) acrylamidobutyltrimethoxysilane, 8- (meth) acrylamideoctyltrimethoxysilane, and 6- (meta ) Acrylamide hexyltrimethoxysilane, 12- (meth) acrylamide dodecyltrimethoxysilane, 18- (meth) acrylamide octadecyltrimethoxysilane, 3- (meth) acrylamidepropyltriethoxysilane, 3- (meth) acrylamidopropyltributoxysilane , 3- (meth) acrylamidopropylmethyldimethoxysilane, 3- (meth) acrylamidopropyldimethylmethoxysilane, 3- (meth) acrylamide-3-methylbutyltrimethoxysilane, 4- (meth) Acrylamide-4-methylbutyltrimethoxysilane, 4- (meth) acrylamide-3-methylbutyltrimethoxysilane, 5- (meth) acrylamide-5-methylhexyltrimethoxysilane, 4-pentenyltrimethoxysilane, 5-to Examples include xenyl trimethoxysilane.

  Examples of the method for copolymerizing the vinyl ester monomer and the monomer having the group represented by the formula (1) include a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. A well-known method is mentioned. In particular, when the polymerization temperature is lower than 30 ° C., an emulsion polymerization method is preferable, and when the polymerization temperature is 30 ° C. or higher, a bulk polymerization method performed without solvent or a solution polymerization method performed using a solvent such as alcohol is used. Usually adopted.

  In the case of the emulsion polymerization method, examples of the solvent include water, and lower alcohols such as methanol and ethanol may be used in combination. Moreover, a well-known emulsifier can be used as an emulsifier. As an initiator for copolymerization, a redox initiator using iron ions, an oxidizing agent and a reducing agent in combination is preferably used for controlling the polymerization. In the case of the bulk polymerization method or the solution polymerization method, the reaction can be carried out by either a batch method or a continuous method in carrying out the copolymerization reaction. When the copolymerization reaction is carried out using the solution polymerization method, examples of the alcohol used as the solvent include lower alcohols such as methanol, ethanol, and propanol. Examples of the initiator used for the copolymerization reaction in this case include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 1,1′-azobis ( Azo initiators such as cyclohexane-1-carbonitrile) and 2,2′-azobis (N-butyl-2-methylpropionamide); peroxide initiators such as benzoyl peroxide and n-propyl peroxycarbonate And known initiators such as Although there is no restriction | limiting in particular about the polymerization temperature at the time of performing a copolymerization reaction, The range of 5 to 50 degreeC is suitable.

  In the case of this copolymerization reaction, a copolymerizable monomer can be copolymerized as necessary as long as the gist of the present invention is not impaired. Examples of such monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; carboxylic acids such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, or the like Derivatives; (meth) acrylic acid or salts thereof or esters; acrylamide derivatives such as acrylamide, N-methylacrylamide, N-ethylacrylamide; methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether; ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1, -Hydroxy group-containing vinyl ethers such as butanediol vinyl ether; allyl acetate; allyl ethers such as propyl allyl ether, butyl allyl ether, hexyl allyl ether; monomers having an oxyalkylene group; isopropenyl acetate; 3-butene-1 Hydroxy groups such as -ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3-buten-1-ol Containing α-olefins; Monomers having sulfonic acid groups such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyl Trimethylammonium chloride Vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine, etc. And a monomer having a cationic group. The amount of these monomers used varies depending on the purpose and application of use, but is usually 20 mol% or less, preferably 10 mol, based on all monomers used for copolymerization. % Or less.

  The vinyl ester polymer obtained by the copolymerization is then saponified in a solvent according to a known method and led to PVA.

  As the catalyst for the saponification reaction, an alkaline substance is usually used, and examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. The amount of the alkaline substance used is preferably in the range of 0.004 to 0.5 in terms of a molar ratio based on the vinyl ester monomer unit in the vinyl ester polymer. More preferably, it is in the range of 0.05. Further, this catalyst may be added all at once in the early stage of the saponification reaction, or a part thereof may be added in the early stage of the saponification reaction, and the rest may be added in the middle of the saponification reaction.

  Examples of the solvent that can be used for the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, diethyl sulfoxide, dimethylformamide, and the like. Of these solvents, methanol is preferred. Further, in the use of methanol, the water content in methanol is preferably adjusted to 0.001 to 1% by mass, more preferably 0.003 to 0.9% by mass, and particularly preferably 0.005 to 0.8% by mass. It is good to be.

  The saponification reaction is preferably performed at a temperature of 5 to 80 ° C, more preferably 20 to 70 ° C. The time required for the saponification reaction is preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours. The saponification reaction can be carried out by either a batch method or a continuous method. If necessary, the remaining saponification catalyst may be neutralized after completion of the saponification reaction. Examples of usable neutralizing agents include organic acids such as acetic acid and lactic acid, and ester compounds such as methyl acetate. Can do.

  The PVA obtained by the saponification reaction can be washed as necessary. Examples of the cleaning liquid used in this cleaning include lower alcohols such as methanol, lower fatty acid esters such as methyl acetate, and mixtures thereof. A small amount of water, alkali, acid, or the like may be added to these cleaning liquids.

  Although it does not specifically limit as a content rate of the said PVA in the said coating agent, 4 mass% or more and 20 mass% or less are preferable. Thus, by setting the content ratio of the PVA in the coating agent to a relatively high concentration, it is possible to effectively improve the water resistance, plasticizer resistance, and the like of the obtained thermal recording material.

<Other ingredients>
Examples of the crosslinking agent include aldehyde compounds such as glyoxal and glutaraldehyde, zirconium compounds such as ammonium zirconium carbonate, titanium compounds such as titanium lactate, epoxy compounds such as polyamidoamine epichlorohydrin, and polyoxazoline. When the coating agent for forming the thermosensitive coloring layer, the overcoat layer and the like contains a crosslinking agent together with PVA, the water resistance and plasticizer resistance of the resulting thermosensitive recording material can be further enhanced.

  Examples of the water-soluble polymer or polymer dispersion include starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, gum arabic, polyvinyl alcohol, and alkali salts of polyacrylic acid (sodium Salt), polyvinylpyrrolidone, (meth) acrylamide- (meth) acrylic acid ester copolymer, (meth) acrylamide- (meth) acrylic acid ester- (meth) acrylic acid terpolymer, styrene-maleic anhydride Water-soluble polymers such as copolymer alkali salts (sodium salts, etc.), isobutylene-maleic anhydride copolymer alkali salts (sodium salts, etc.), polyacrylamide, sodium alginate, gelatin, casein, etc. Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer emulsion, styrene-butadiene copolymer, styrene-butadiene- Examples thereof include latex such as acrylic acid copolymer.

  Examples of the filler include kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, precipitated silica, gel silica, colloidal silica, aluminum oxide, aluminum hydroxide, synthetic aluminum silicate, and synthetic silica. Examples thereof include magnesium oxide, polystyrene fine particles, polyvinyl acetate-based fine particles, urea-formalin resin fine particles, and the like.

  Examples of the lubricant include higher fatty acid, higher fatty acid amide, higher fatty acid metal salts such as zinc stearate, paraffin wax, microcrystalline wax, and the like.

  The thermal dye is not particularly limited, and examples thereof include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3- (p-dimethylaminophenyl)- 3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis- (9-ethyl) Triarylmethane compounds such as carbazol-3-yl) -5-dimethylaminophthalide; Diphenylmethane compounds such as 4,4′-bisdimethylaminobenzhydrin benzyl ether and N-halophenylleucooramine; Rhodamine B -Anilinolactam, 3-diethylamino-7-benzylaminofluorane, 3-diethylamino -7-butylaminofluorane, 3-diethylamino-7- (chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3 -Ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-cyclohexyl-methylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7- (β-ethoxyethyl) Aminofluorane, 3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluorane, 3- (N-ethyl-N-isoamyl) -6-methyl-7-phenylaminofluorane, 3-dibutyl Xanthene compounds such as amino-6-methyl-7-anilinofluorane; benzoylleucomethylene blue, p Thiazine compounds such as nitrobenzoylleucomethylene blue; spiro compounds such as 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methylnaphtho- (3-methoxy-benzo) -spiropyran A compound etc. can be mentioned. These thermal dyes are appropriately selected depending on the application of the thermal recording material, and are used alone or as a mixture of two or more.

  The developer is not particularly limited, but a phenol derivative and an aromatic carboxylic acid derivative are preferable, and bisphenols are particularly preferable. Specific examples of the phenol derivative include p-octylphenol, p-tert-butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) propane, 1 , 1-bis (p-hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl)- Examples thereof include 2-ethyl-hexane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, dihydroxydiphenyl ether, and the like. Specific examples of the aromatic carboxylic acid derivative include p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-di-α- Examples thereof include methylbenzyl salicylic acid and polyvalent metal salts of the above carboxylic acids.

  Although it does not specifically limit as solid content concentration of the said coating agent, From points, such as coating property, 5 mass% or more and 20 mass% or less are preferable.

  Although it does not specifically limit as pH of the said coating agent, It is preferable to set it as 4-8. Since the PVA used in the coating agent is excellent in solubility in water, a uniform aqueous solution can be obtained without particularly adding an alkali or acid such as sodium hydroxide to water, and the handling property is excellent. Moreover, according to the said coating agent, sufficient viscosity stability can be exhibited also in a neutral area | region. Accordingly, various performances of the heat-sensitive recording material can be effectively exhibited.

  The method for producing the heat-sensitive recording material by applying the coating agent to a substrate is not particularly limited and can be performed by a known method. Specifically, in the case of forming the thermosensitive coloring layer by coating the coating agent, a method of coating the coating agent on the surface of the substrate can be mentioned. In the case of forming the film, there may be mentioned a method of applying the coating agent on the surface of the thermosensitive coloring layer formed on the surface of the substrate. As the coating method, methods such as an air knife method, a plate method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, and an extrusion method can be used.

As the coating amount of the coating agent, for example, when an overcoat layer is formed, it is appropriately selected to such an extent that thermal conduction from the thermal head of the thermal recording apparatus to the thermal coloring layer of the thermal recording material is not hindered. 1 to 10 g / ^{m 2} in terms of solid content, preferably 2~7g / ^{m 2.} For example, when forming a thermosensitive coloring layer, it is usually 3 to 10 g / m ² , preferably 4 to 8 g / m ² in terms of solid content.

  The thermosensitive recording material may have other layers in addition to the base material, thermosensitive coloring layer and overcoat layer. As said other layer, the undercoat layer etc. which are arrange | positioned between a base material and a thermosensitive coloring layer can be mentioned. The thermosensitive recording material may contain the PVA in a base material. Even in such a case, the heat-sensitive recording material can exhibit high water resistance and plasticizer resistance.

<Method for producing printed matter>
By printing on the heat-sensitive recording material, a printed matter having excellent water resistance and plasticizer resistance can be obtained. The printing apparatus used for printing is not particularly limited, and a conventionally known thermal recording apparatus equipped with a thermal head can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. Moreover, in the following Examples and Comparative Examples, unless otherwise specified, parts and% represent parts by mass and% by mass, respectively.

In addition, the monomer (monomer A) which has the silyl group used by the Example and the comparative example is as follows.
MAmPTMS: 3-methacrylamideamidopropyltrimethoxysilane MAmPTES: 3-methacrylamideamidopropyltriethoxysilane MAmBTMS: 4-methacrylamidobutyltrimethoxysilane MAmOTMS: 8-methacrylamidooctyltrimethoxysilane MAmDDTMS: 12-methacrylamidododecyltrimethoxysilane MAmODTMS: 18-methacrylamidooctadecyltrimethoxysilane AMBTMS: 3-acrylamido-3-methylbutyltrimethoxysilane 4-PTMS: 4-pentenyltrimethoxysilane VMS: vinyltrimethoxysilane MAMTMTS: methacrylamidomethyltrimethoxysilane AMPTMS: 2 -Acrylamide-2-methylpropyltrimethoxysilane

[Synthesis of silyl group-containing PVA]
PVA is produced by the following method, the degree of saponification, the content of monomer units having a group represented by the above formula (1) (S) (in some examples, monomer units having a silyl group) Content) and viscosity average degree of polymerization (P). Further, the performance of the thermal recording material was evaluated according to the following evaluation method.

[Analysis method of PVA]
Analysis of PVA was performed according to the method described in JIS-K6726 unless otherwise specified.

[Synthesis Example 1] Production of PVA1 Into a 6 L separable flask equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, a comonomer dropping port and an initiator addition port, 1,500 g of vinyl acetate, 500 g of methanol, the above formula (1 ) MAmPTMS 1.87 g as a monomer (monomer A) having a group represented by) was charged, and the inside of the system was purged with nitrogen for 30 minutes while carrying out nitrogen bubbling. Further, a comonomer solution having a concentration of 8% was prepared by dissolving MAmPTMS in methanol as a delay solution, and nitrogen substitution was performed by bubbling nitrogen gas. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.8 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate polymerization. The delay solution was added dropwise to polymerize the monomer composition (ratio of vinyl acetate and monomer A (MAmPTMS)) in the polymerization solution at a constant rate for 2.7 hours at 60 ° C. and then cooled to stop the polymerization. . The total amount of comonomer solution (sequentially added solution) added until the polymerization was stopped was 99 g. Further, the solid content concentration when the polymerization was stopped was 29.0%. Subsequently, an unreacted vinyl acetate monomer is removed while sometimes adding methanol under reduced pressure at 30 ° C., and a methanol solution containing 40% of polyvinyl acetate (PVAc) having a group represented by the above formula (1) Got. Furthermore, a methanol solution containing 10% by mass of methanol and sodium hydroxide was added so that the molar ratio of sodium hydroxide to the vinyl acetate unit in PVAc was 0.04 and the solid content concentration of PVAc was 30% by mass. In this order, with stirring, the saponification reaction was started at 40 ° C. A gel was formed in about 5 minutes after the addition of the alkaline solution. This gel-like material was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to allow saponification to proceed. Then, methyl acetate was added to neutralize the remaining alkali. After confirming the completion of neutralization using a phenolphthalein indicator, the mixture was filtered to obtain a white solid. Methanol was added thereto, and the mixture was allowed to wash at room temperature for 3 hours. After repeating the above washing operation three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain PVA1 having a group represented by the above formula (1). The polymerization degree (P) of PVA1 was 1,700, and the saponification degree was 98.6 mol%.

The content of the monomer unit having the group represented by the above formula (1) of the obtained PVA1 (content of the monomer unit having a silyl group) is the proton NMR of PVAc which is a precursor of this PVA. I asked for it. Specifically, after reprecipitation purification of the obtained PVAc was sufficiently performed three times or more with n-hexane / acetone, drying was performed under reduced pressure at 50 ° C. for 2 days to prepare a PVAc for analysis. This PVAc was dissolved in CDCl ₃ and measured at room temperature using 500 MHz proton NMR (JEOL GX-500). From the peak α (4.7 to 5.2 ppm) derived from the main chain methine of the vinyl acetate unit and the peak β (3.4 to 3.8 ppm) derived from the methyl of the methoxy group of the monomer A unit, the following formula is obtained. The content (S) of the monomer unit having a group represented by the above formula (1) was calculated. In PVA1, the content (S) was 0.5 mol%. The results of analyzing the obtained PVA are shown in Table 1.
Content S (mol%) of the monomer unit having a group represented by the formula (1)
= {(Peak area of β / 9) / (peak area of α + (peak area of β / 9))} × 100

[Synthesis Examples 2 to 21 and Comparative Synthesis Examples 1 to 15] Manufacture of PVA2 to PVA36 Polymerization conditions such as the amount of vinyl acetate and methanol, the type and addition amount of monomer A, the concentration of PVAc during saponification, and the vinyl acetate unit PVA2 to PVA36 were obtained in the same manner as in Synthesis Example 1 except that the saponification conditions such as the molar ratio of sodium hydroxide were changed as shown in Tables 1 and 2. Tables 1 and 2 show the results of analysis for each obtained PVA.

[Example 1] Production of heat-sensitive recording material A heat-sensitive recording paper (heat-sensitive recording material) was produced by the following method, and its water resistance and plasticizer resistance were evaluated.

(1) Preparation of aqueous dispersions of thermal dye, developer and pigment [composition of aqueous dispersion A of thermal dye]
Leuco dye (manufactured by Yamamoto Kasei Co., Ltd., trade name: OBD-2) 20%
10% PVA (made by Kuraray Co., Ltd .: PVA203) aqueous solution 20%
60% water
[Composition of aqueous dispersion B of developer]
Developer (Nippon Soda Co., Ltd .: D-8) 20%
10% PVA (made by Kuraray Co., Ltd .: PVA203) aqueous solution 20%
60% water
[Composition of aqueous pigment dispersion C]
Stearic acid amide 10%
Baked kaolin 20%
30% PVA (made by Kuraray: PVA205) aqueous solution with a concentration of 5%
40% water

  An aqueous dispersion A, an aqueous dispersion B and an aqueous dispersion C having the above composition were prepared separately, and pre-stirred for 15 minutes in a beaker.

  Next, the aqueous dispersion A was transferred to a sand grinder (manufactured by Kansai Paint Co., Ltd .: batch type tabletop sand grinder), 300 mL of glass beads (soda quartz glass having a diameter of 0.5 mm) were added, and a high rotation speed (2,170 rpm), The dispersoid was dispersed over 6 hours under the condition of cooling. As a result of measurement with a laser diffraction particle size analyzer (manufactured by Shimadzu Corporation: SALD-1000), the dispersed particle size of the aqueous dispersion A of the obtained thermal dye was 0.46 μm. Moreover, as a result of measuring with the color difference meter (Nippon Denshoku Industries Co., Ltd. product: Z-1001DP), the whiteness of the aqueous dispersion A was -8.1. The whiteness indicates that 0 is completely white, and the greater the negative value is, the more colored it is.

  Similarly, transfer the aqueous dispersion B to a sand grinder, add 300 mL of glass beads (soda quartz glass having a diameter of 0.5 mm), dispersoid over 6 hours under conditions of high rotation speed (2,170 rpm) and cooling. Was dispersed.

  Further, the aqueous dispersion C was transferred to a homogenizer, and the dispersoid was dispersed for 2 minutes under the condition of a rotational speed of 10,000 rpm.

(2) Preparation of coating agent for thermosensitive coloring layer 2 parts of aqueous dispersion A, 4 parts of aqueous dispersion B, 2 parts of aqueous dispersion C, and 2% of 10% aqueous solution of PVA117 (manufactured by Kuraray Co., Ltd.) After partially mixing and stirring, a necessary amount of water was added to prepare a coating agent for a thermosensitive coloring layer having a solid content concentration of 21%.

(3) Preparation of coating agent for overcoat layer 0.2 parts of ethylene glycol-propylene glycol copolymer (Nippon Yushi Co., Ltd .: Pronon 104) and silica (Shionogi Pharmaceutical Co., Ltd .: Carplex CS-5) While adding 2.8 parts of 10% aqueous solution of PVA1 slowly at room temperature while adding 72.5 parts of water to 50 parts, it is further added with zinc stearate dispersion (manufactured by Chukyo Yushi Co., Ltd., Hydrin Z730; solid content). 7.5 parts of 30% concentration was added to prepare a silica-dispersed aqueous solution of PVA1. A necessary amount of water was added to the obtained silica-dispersed aqueous solution of PVA1 to prepare a coating agent for an overcoat layer having a solid content concentration of 12%.

(4) Production of heat-sensitive recording paper On the surface of the base paper (basis weight: 52 g / m ² high-quality paper), the thermal coloring layer coating agent prepared in (2) above is converted into a solid content using a wire bar coater. 6 g / m ^{2 was} applied and dried at 50 ° C. for 5 minutes. The obtained coated paper is surface-treated with a super calender (linear pressure: 30 kg / cm), and the coating agent for the overcoat layer prepared in (3) above is applied to the coated paper surface using a wire bar coater. After coating 3 g / m ^{2 in} terms of solid content, it was dried at 50 ° C. for 10 minutes. Further, the coated paper was surface-treated with a super calendar (linear pressure: 30 kg / cm) to produce a heat-sensitive recording paper.

  Immediately after the thermal recording paper is manufactured, a thermal facsimile printer (Ricoh Co., Ltd .: Rifax 300) is used to print on the thermal recording paper to obtain a printed matter. The drug properties were evaluated. The results are shown in Table 3.

[water resistant]
The printed thermal recording paper (printed material) was immersed in distilled water at 30 ° C. for 24 hours, and the recording density and wet lab were evaluated by the following methods.

Recording density Before and after immersion in distilled water, the color density of the printed part was measured using a Macbeth densitometer (Macbeth Co., model: RD-514). When the color density of the printed part before immersion in distilled water is less than the color density of the printed part after immersion in distilled water, the water resistance of the thermal recording paper is excellent. A five-step evaluation was performed with E being the worst water resistance.

-Wet rub test After immersion in distilled water, the surface of the printed part was rubbed with a fingertip, and the elution state of the overcoat layer of the thermal recording paper was observed. As the less water elution of the overcoat layer of the thermal recording paper is, the better the water resistance of the thermal recording paper is, and a five-step evaluation is performed with S being the most excellent in water resistance and E being the worst in water resistance. .

[Plasticizer resistance]
A soft polyvinyl chloride film (including a plasticizer) was superimposed on the printed thermal recording paper (printed material), and both were brought into contact with each other at 30 ° C. under a load of 300 g / m ² for 24 hours. Before and after the contact, the color density of each printed portion was measured using a Macbeth densitometer (manufactured by Macbeth, model: RD-514). When the plasticizer resistance of the thermal recording paper is excellent as the color density of the printed part before contact with the two decreases less as the color density of the printed part decreases after contact. Was evaluated on a five-level scale, with A representing the worst plasticizer resistance.

[Examples 2 to 21 and Comparative Examples 1 to 15]
In Example 1, a thermal recording paper was produced in the same manner as in Example 1 except that PVA shown in Table 3 was used instead of PVA1 used in the overcoat layer, and its water resistance and plasticizer were used. Sex was evaluated. The results are also shown in Table 3.

  As shown in Table 3, when a thermal recording paper was produced by forming an overcoat layer with the coating agents of Examples 1 to 21, even in a PVA single system that does not use a crosslinking agent, the water resistance and resistance of the thermal recording paper were as follows. It can be seen that the plasticizer properties are good. Here, it is assumed that each evaluation item is C or higher, and that two or more of the three items are B or higher. Furthermore, PVA viscosity average polymerization degree (P), saponification degree, monomer unit structure, content rate (S), and product of viscosity average polymerization degree (P) and content rate (S) (P × S) are specified. The thermal recording papers of Examples 1, 2, 4 to 6, 9, 10, 13, 15 to 20 are particularly excellent in water resistance and plasticizer resistance (wet rub test, evaluation of plasticizer resistance). Is B or more, and one of them is A or more). For example, the heat-sensitive recording papers of Examples 3, 7, 8, 11, 12, 14, and 21 have a slight decrease in water resistance and plasticizer resistance. This is because the viscosity average degree of polymerization (P) or saponification degree is decreased, the product (P × S) of the viscosity average degree of polymerization (P) and the content (S) is small or large, the monomer unit This is due to the difference in the structure. In particular, the details of Examples 3, 7, and 8 are not clear, but the viscosity of the coating agent increases due to the large product (P × S) of the viscosity average degree of polymerization (P) and the content (S), It is considered that the wet rub performance is lowered due to the difficulty of penetrating into paper (base material).

  On the other hand, when PVA does not satisfy the prescribed requirements (Comparative Examples 1 to 15), it can be seen that the water resistance and plasticizer resistance of the thermal recording paper are deteriorated or the water solubility of PVA itself is lowered. This is due to the difference in the structure of the monomer units, the decrease in water resistance due to the decrease in the product (P × S) of the viscosity average polymerization degree (P) and the content rate (S), and the increase in (P × S). This is thought to be due to a decrease in the handling of the coating agent.

  As described above, the heat-sensitive recording material of the present invention is excellent in water resistance and plasticizer resistance, and can be suitably used as a heat-sensitive recording paper.

Claims (9)

A heat-sensitive recording material comprising a vinyl alcohol polymer containing a monomer unit having a group represented by the following formula (1) and satisfying the following formulas (I) , (II) and (II) .

(In Formula (1), R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ² is an alkoxyl group, an acyloxyl group, or a group represented by OM. M is a hydrogen atom. R ³ and R ⁴ each independently represents a hydrogen atom or an alkyl group, and a hydrogen atom possessed by an alkyl group, an alkoxyl group, or an acyloxyl group represented by R ^{1 to} R ^4. May be substituted with a substituent containing an oxygen atom or a nitrogen atom, m is an integer of 0 to 2, n is an integer of 3 or more, and multiple R ^{1 to} R ⁴ are present. When it does, each R < ¹ > -R < ⁴ > which exists plurally satisfy | fills the said definition independently.)
370 ≦ P × S ≦ 6,000 (I)
200 ≦ P ≦ 4,000 (II)
0.1 ≦ S ≦ 10 (III)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%) 2. The heat-sensitive recording material according to claim 1 , wherein n in the formula (1) is an integer of 6 or more and 20 or less. The heat-sensitive recording material according to claim 1, wherein the monomer unit is represented by the following formula (2).

(In formula (2), the definitions of R ^{1 to} R ⁴ , m and n are the same as those in formula (1). X represents a direct bond, a divalent hydrocarbon group, an oxygen atom or a nitrogen atom 2. R ⁵ is a hydrogen atom or a methyl group.) X in the above formula (2) is —CO—NR ⁶ — * (R ⁶ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. * Is a group represented by the above formula (1); The heat-sensitive recording material according to claim 3 , which is represented by : X is -CO-NH in the formula (2) - * (. * Is showing the bonding site to the group represented by the formula (1)) represented by, n is 12 or less integer claims Item 4. The heat-sensitive recording material according to Item 3 . The vinyl alcohol polymer is either one of claims 1 is copolymerised Noken product of an unsaturated monomer and a vinyl ester monomer represented by the following formula (3) according to claim 5 1 The heat-sensitive recording material according to Item.

(In formula (3), definitions of R ^{1 to} R ⁵ , X, m and n are the same as in formula (2).) A substrate, a thermosensitive coloring layer formed on the surface of the substrate, and an overcoat layer formed on the surface of the thermosensitive coloring layer;
At least one of the heat-sensitive coloring layer and overcoat layer, the heat-sensitive recording according to any one of claims 1 to 6 Ru coating layer der derived from a coating agent comprising the vinyl alcohol polymer Wood. The method for producing a thermosensitive recording material according to any one of claims 1 to 7 , further comprising a step of applying a coating agent containing the vinyl alcohol polymer to a substrate. Method for producing a printed matter, comprising the step of printing on the heat-sensitive recording material as claimed in any one of claims 7.