JP2013244702A - Dispersant for thermal recording material, and the thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersant for a thermal recording material with excellent dispersibility and the thermal recording material with excellent color developing sensitivity.SOLUTION: A dispersant for a thermal recording material contains a polyoxyalkylene modified vinyl alcohol polymer which has a specific polyoxyalkylene group structured of a polyoxypropylene block and (poly)oxyethylene block as a side chain, of which a viscosity average polymerization degree is 150-1,000, and a saponification degree is 40-99.99 mol%, and a polyoxyalkylene group modification rate is 0.1-5 mol%. The thermal recording material contains the polyoxyalkylene modified vinyl alcohol polymer.

Description

  The present invention relates to a dispersant for heat-sensitive recording material having excellent dispersibility. Furthermore, a dispersion liquid containing the dispersant for the heat-sensitive recording material, having a small particle diameter of the dispersed particles, little liquid fog, and excellent storage stability, a coating liquid that can be produced using this dispersion liquid, The present invention relates to a heat-sensitive recording material excellent in color development sensitivity, a method for producing the same, and a method for producing a printed matter using the heat-sensitive recording material.

  In recent years, with the diversification of information and the expansion of needs, various recording materials have been researched and developed and put into practical use in the information recording field. Among them, the heat-sensitive recording material is (1) simple image recording is possible only by the heating process, (2) the required device mechanism is simple and easy to make compact, and the recording material is easy to handle and inexpensive. The information processing field (desktop computer, computer output, etc.), medical measurement recorder field, low / high-speed facsimile field, automatic ticket machine field (passage ticket, admission ticket, etc.), thermal copying It is used in the machine field, the POS system label field, and the like.

  Such a heat-sensitive recording material generally comprises a base material provided with a heat-sensitive coloring layer mainly composed of a colorless or light-colored electron-donating dye (such as a leuco dye) and an electron-accepting developer. By heating with a thermal head, a thermal pen, laser light or the like, the dye and the developer react instantaneously to obtain a recorded image.

  In the production process of the thermal recording material, a coating liquid containing a dye and a developer is prepared, but as a means for increasing the sensitivity of the thermal recording material, the dye particles in the coating liquid are uniformly dispersed, Methods for making finer particles are known. For example, a method using a vinyl alcohol polymer having a sulfonic acid group (see Patent Document 1), a dispersant having excellent dispersibility in dyes and developers, and also having a function as a dispersant and a binder for dyes and the like A method using a vinyl alcohol polymer having a carboxyl group (see Patent Document 2), a method using a resin composition containing a vinyl alcohol polymer having a carboxyl group and a water-soluble salt of an olefin-maleic acid copolymer (See Patent Document 3) and the like.

  However, some problems remain in these conventional techniques. For example, in a dispersion containing a dye, the liquid fog of the dispersion becomes more intense as the dye particles become smaller (liquid fog refers to a phenomenon in which the dispersion becomes darker as the dye particles become smaller). If the dispersion is heated for the purpose of improving the whiteness and anti-wet skin fog, the dispersion state becomes unstable, re-aggregation, viscosity increase and gel. This may occur. That is, in the prior art, a dispersion having a small dispersed particle size, little liquid fog, and excellent storage stability has not been obtained.

Japanese Patent Laid-Open No. 58-179691 JP-A-8-48076 JP 11-321103 A

  The present invention relates to a dispersion for a heat-sensitive recording material having excellent dispersibility, a dispersion containing the dispersion for the heat-sensitive recording material, having a small particle size, small liquid fog, and excellent storage stability, and this dispersion It is an object of the present invention to provide a coating liquid that can be produced using a thermosensitive recording material, a thermosensitive recording material excellent in color development sensitivity, a method for producing the same, and a method for producing a printed material using the thermosensitive recording material.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a specific polyoxyalkylene-modified vinyl alcohol polymer, and based on this finding Further studies were made to complete the present invention.

（一般式（Ｉ）中、Ｒ^１は水素原子または炭素数１〜８のアルキル基を表す。Ｒ^２およびＲ^３は、いずれか一方がメチル基であり、他方が水素原子である。１０≦ｍ≦４０であり、１≦ｎ≦５０である。）
［２］上記［１］の感熱記録材料用分散剤および液体媒体を含有し、染料、顕色剤および増感剤からなる群より選ばれる少なくとも１種が分散している分散液；
［３］前記液体媒体が水である、上記［２］の分散液；
［４］ロータ回転数が６０ｒｐｍの条件でＢＬ型粘度計により２０℃で測定される粘度が３０ｍＰａ・ｓ以上１０００ｍＰａ・ｓ以下である、上記［２］または［３］の分散液；
［５］上記［１］の感熱記録材料用分散剤、染料、顕色剤および液体媒体を含有する塗工液；
［６］前記液体媒体が水である、上記［５］の塗工液；
［７］増感剤をさらに含有する、上記［６］の塗工液；
［８］基材、およびこの基材の表面に上記［５］〜［７］のいずれかの塗工液から形成される感熱発色層を有する感熱記録材料；
［９］ＰＯＡ変性ＰＶＡを含有する感熱記録材料であって、
該ＰＯＡ変性ＰＶＡは、ポリオキシプロピレンブロックと（ポリ）オキシエチレンブロックとから構成され、下記一般式（Ｉ）で示されるＰＯＡ基を側鎖に有し、粘度平均重合度が１５０以上１０００以下であり、けん化度が４０モル％以上９９．９９モル％以下であり、ポリオキシアルキレン基変性率が０．１モル％以上５モル％以下である感熱記録材料；

（一般式（Ｉ）中、Ｒ^１は水素原子または炭素数１〜８のアルキル基を表す。Ｒ^２およびＲ^３は、いずれか一方がメチル基であり、他方が水素原子である。１０≦ｍ≦４０であり、１≦ｎ≦５０である。）
［１０］基材、およびこの基材の表面に感熱発色層を有し、
該感熱発色層が、前記ＰＯＡ変性ＰＶＡ、染料および顕色剤を含有する、上記［６］の感熱記録材料；
［１１］前記感熱発色層が増感剤をさらに含有する、上記［１０］の感熱記録材料；
［１２］上記［１０］または［１１］の感熱記録材料の製造方法であって、
前記ＰＯＡ変性ＰＶＡ、染料、顕色剤および液体媒体を含有する塗工液を基材に塗工する工程を有する製造方法；
［１３］前記塗工液が増感剤をさらに含有する、上記［１２］の製造方法；
［１４］上記［８］〜［１１］のいずれかの感熱記録材料を加熱する工程を有する印刷物の製造方法；
に関する。 That is, the present invention
[1] A polyoxyalkylene group composed of a polyoxypropylene block and a (poly) oxyethylene block and represented by the following general formula (I) (hereinafter, “polyoxyalkylene group” is abbreviated as “POA group”) In the side chain, the viscosity average polymerization degree is 150 or more and 1000 or less, the saponification degree is 40 mol% or more and 99.99 mol% or less, and the POA group modification rate is 0.1 mol% or more and 5 or less. Dispersant for heat-sensitive recording material containing a polyoxyalkylene-modified vinyl alcohol polymer (hereinafter, “polyoxyalkylene-modified vinyl alcohol polymer” may be abbreviated as “POA-modified PVA”) which is less than or equal to mol%. ;

(In General Formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ^One of R ² and R ³ is a methyl group, and the other is a hydrogen atom. 10 ≦ m ≦ 40, and 1 ≦ n ≦ 50.)
[2] A dispersion containing the dispersant for heat-sensitive recording material according to [1] and a liquid medium, wherein at least one selected from the group consisting of a dye, a developer and a sensitizer is dispersed;
[3] The dispersion according to [2], wherein the liquid medium is water;
[4] The dispersion according to [2] or [3] above, wherein the viscosity measured at 20 ° C. with a BL-type viscometer at a rotor rotational speed of 60 rpm is 30 mPa · s or more and 1000 mPa · s or less;
[5] A coating solution containing the dispersant for heat-sensitive recording material, the dye, the developer and the liquid medium according to [1] above;
[6] The coating liquid according to [5], wherein the liquid medium is water;
[7] The coating solution according to [6], further including a sensitizer;
[8] A heat-sensitive recording material having a base material and a thermosensitive coloring layer formed on the surface of the base material from the coating liquid according to any one of the above [5] to [7];
[9] A heat-sensitive recording material containing POA-modified PVA,
The POA-modified PVA is composed of a polyoxypropylene block and a (poly) oxyethylene block, has a POA group represented by the following general formula (I) in the side chain, and has a viscosity average polymerization degree of 150 to 1,000. A thermosensitive recording material having a saponification degree of 40 mol% or more and 99.99 mol% or less and a polyoxyalkylene group modification rate of 0.1 mol% or more and 5 mol% or less;

(In General Formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ^One of R ² and R ³ is a methyl group, and the other is a hydrogen atom. 10 ≦ m ≦ 40, and 1 ≦ n ≦ 50.)
[10] A substrate and a thermosensitive coloring layer on the surface of the substrate;
The heat-sensitive recording material according to the above [6], wherein the heat-sensitive color developing layer contains the POA-modified PVA, a dye and a developer.
[11] The heat-sensitive recording material according to [10], wherein the heat-sensitive coloring layer further contains a sensitizer;
[12] The method for producing a heat-sensitive recording material according to [10] or [11],
A production method comprising a step of coating a substrate with a coating solution containing the POA-modified PVA, a dye, a developer and a liquid medium;
[13] The production method of the above [12], wherein the coating solution further contains a sensitizer;
[14] A method for producing a printed matter comprising a step of heating the heat-sensitive recording material according to any one of [8] to [11] above;
About.

  Since the dispersant for heat-sensitive recording material of the present invention contains a specific POA-modified PVA, it is possible to efficiently disperse dispersoids such as dyes, developers, and sensitizers. The particle size of the dispersed particles is small, the liquid fog is small, and the storage stability is excellent. Furthermore, the heat-sensitive recording material of the present invention is excellent in color development sensitivity.

  The present invention will be described in detail below.

[Dispersant for thermal recording materials]
The dispersant for the heat-sensitive recording material of the present invention is a coating liquid for forming the heat-sensitive color forming layer of the heat-sensitive recording material or a dispersant for dispersing the dispersoid in various dispersion liquids for preparing the coating liquid. And a dispersant used for producing a thermosensitive recording material, which contains the following POA-modified PVA.

(POA-modified PVA)
The POA-modified PVA in the present invention has a POA group represented by the above general formula (I) in the side chain. The POA-modified PVA includes, for example, a monomer unit having a POA group represented by the general formula (I) composed of a polyoxypropylene block and a (poly) oxyethylene block in the side chain, and a vinyl alcohol unit (- CH ₂ —CHOH—), and may further have other monomer units.

  The POA group represented by the general formula (I) in the side chain of the POA-modified PVA has a polyoxypropylene block in which the number of repeating units of oxypropylene units is m and the number of repeating units of oxyethylene units is n (poly ) An oxyethylene block, and the (poly) oxyethylene block is arranged on the terminal side of the POA group. Here, when n is 1, the POA group is composed of a polyoxypropylene block and an oxyethylene block. When n is 2 or more, the POA group is a polyoxypropylene block and a polyoxypropylene block. It is comprised from an ethylene block. When the POA group has such a structure, excellent dispersibility of the thermal recording dispersant and storage stability of the dispersion liquid due to the interaction between the POA groups are exhibited. Although details of the mechanism at this time have not been clarified, as described later, the relatively hydrophilic (poly) oxyethylene block is located on the terminal side of the POA group. This is considered to be because the hydrophobic group interaction between the groups or the interaction between the POA group and the dispersoid is promoted. Therefore, the dispersant of the present invention containing such specific POA-modified PVA is suitably used for the production of a heat-sensitive recording material.

  The number m of repeating units of the oxypropylene unit in the POA group represented by the general formula (I) needs to satisfy 10 ≦ m ≦ 40, preferably 15 ≦ m ≦ 38, and more preferably 20 ≦ m ≦ 35. When m is less than 10, the interaction between POA groups is not sufficiently exhibited, and the dispersion stability of the dispersion is lowered. Further, the number n of repeating units of the oxyethylene unit needs to satisfy 1 ≦ n ≦ 50, preferably 3 ≦ n ≦ 40, and more preferably 5 ≦ n ≦ 10. When n is 0, the interaction between the POA groups is not sufficiently exhibited, and the dispersion stability of the dispersion is lowered. On the other hand, even when n exceeds 50, the interaction between POA groups is not sufficiently exhibited.

R ¹ in the POA group represented by the general formula (I) is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ¹ is preferably a hydrogen atom, a methyl group or a butyl group, more preferably a hydrogen atom or a methyl group.

One of R ² and R ³ in the POA group represented by the general formula (I) is a methyl group, and the other is a hydrogen atom. At this time, it is preferable that R ² is a methyl group and R ³ is a hydrogen atom because it is easy to produce POA-modified PVA.

  The method for producing POA-modified PVA in the present invention is not particularly limited, and is composed of a polyoxypropylene block and a (poly) oxyethylene block, and an unsaturated monomer having a POA group represented by the above general formula (I) A method of saponifying the resulting POA-modified vinyl ester polymer by copolymerizing with a vinyl ester monomer is preferred.

  Here, the unsaturated monomer is preferably an unsaturated monomer represented by the following general formula (II). Therefore, as a method for producing POA-modified PVA, a polyoxypropylene block and a (poly) oxyethylene block are used, and the POA group having a POA group represented by the general formula (I) is represented by the following general formula (II). A method of saponifying the resulting POA-modified vinyl ester polymer by copolymerizing a saturated monomer and a vinyl ester monomer is more preferable.

In the general formula (II), R ¹ , R ² , R ³ , m, and n are the same as those in the general formula (I). R ⁴ represents a hydrogen atom or a —COOM group, where M represents a hydrogen atom, an alkali metal or an ammonium group. R ⁵ represents a hydrogen atom, a methyl group or a —CH ₂ —COOM group, where M is as defined above. Note that M in R ⁴ and M in R ⁵ may be the same or different. X represents —O—, —CH ₂ —O—, —CO—, — (CH ₂ ) _k —, —CO—O— or —CO—NR ⁶ —. When X is asymmetric, the direction is not limited. Here, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and 1 ≦ k ≦ 15.

The X is preferably —CO—NH— * or —CH ₂ —O—, more preferably —CO—NH— *, when the POA group side is “*”.

In the unsaturated monomer represented by the general formula (II), preferred examples and numerical ranges of R ¹ , R ² , R ³ , m, and n are the same as those described above in the description of the general formula (I). In particular, from the viewpoint of easy synthesis of the unsaturated monomer represented by the general formula (II), it is preferable that R ² is a methyl group and R ³ is a hydrogen atom.

In the unsaturated monomer represented by the general formula (II), R ¹ is preferably a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom, and R ⁵ is preferably a hydrogen atom or a methyl group. .

When R ^{1 in the} general formula (II) is a hydrogen atom, R ⁴ is a hydrogen atom, and R ⁵ is a hydrogen atom or a methyl group, the unsaturated monomer represented by the general formula (II) is a polyoxyalkylene mono (Meth) acrylamide, polyoxyalkylene mono (meth) allyl ether, polyoxyalkylene monovinyl ether, polyoxyalkylene mono (meth) acrylate, and the like, specifically, polyoxypropylene (poly) oxyethylene monoacrylamide, Polyoxypropylene (poly) oxyethylene monomethacrylamide, polyoxypropylene (poly) oxyethylene monoallyl ether, polyoxypropylene (poly) oxyethylene monomethallyl ether, polyoxypropylene (poly) oxyethylene monovinyl ether, polyoxypropylene Examples include len (poly) oxyethylene monoacrylate and polyoxypropylene (poly) oxyethylene monomethacrylate. Among them, polyoxypropylene (poly) oxyethylene monoacrylamide, polyoxypropylene (poly) oxyethylene monomethacrylamide, polyoxypropylene (poly) oxyethylene monoallyl ether are preferably used, and polyoxypropylene (poly) oxyethylene Monomethacrylamide and polyoxypropylene (poly) oxyethylene monoallyl ether are particularly preferably used.

When R ^{1 in the} above general formula (II) is an alkyl group having 1 to 8 carbon atoms, specifically, as the unsaturated monomer represented by the general formula (II), R ^{1 in the} general formula (II) is hydrogen. Examples include those in which the hydroxyl group at the terminal of the unsaturated monomer exemplified in the case of atoms is substituted with an alkoxy group having 1 to 8 carbon atoms. Among them, an unsaturated monomer in which a hydroxyl group at the terminal of polyoxypropylene (poly) oxyethylene monomethacrylamide or polyoxypropylene (poly) oxyethylene monoallyl ether is substituted with a methoxy group is preferably used. An unsaturated monomer in which the terminal hydroxyl group of (poly) oxyethylene monomethacrylamide is substituted with a methoxy group is particularly preferably used.

  The temperature when copolymerizing the unsaturated monomer represented by the general formula (II) and the vinyl ester monomer is not particularly limited, but is preferably 0 ° C. or higher and 200 ° C. or lower, and 30 ° C. or higher and 140 ° C. The following is more preferable. When the copolymerization temperature is lower than 0 ° C., it is difficult to obtain a sufficient polymerization rate. Moreover, when the temperature which superposes | polymerizes is higher than 200 degreeC, it is difficult to obtain POA modified PVA which has the POA group modification rate prescribed | regulated by this invention. As a method for controlling the temperature employed in the copolymerization to 0 ° C. or more and 200 ° C. or less, for example, by controlling the polymerization rate, the heat generated by the polymerization is balanced with the heat released from the surface of the reactor. Examples thereof include a method and a method of controlling by an external jacket using an appropriate heat medium, but the latter method is preferable from the viewpoint of safety.

  The polymerization method employed for the copolymerization of the unsaturated monomer represented by the general formula (II) and the vinyl ester monomer is batch polymerization, semi-batch polymerization, continuous polymerization, or semi-continuous polymerization. Either of these may be used. As a polymerization method, an arbitrary method can be adopted from known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these, a bulk polymerization method or a solution polymerization method in which polymerization is performed in the absence of a solvent or in the presence of an alcohol solvent is preferably employed. When the purpose is to produce a copolymer having a relatively high degree of polymerization, an emulsion polymerization method is employed. As the alcohol solvent used in the bulk polymerization method or the solution polymerization method, methanol, ethanol, n-propanol or the like can be used, but is not limited thereto. Two or more of these solvents can be used in combination.

  As the initiator used for copolymerization, conventionally known azo initiators, peroxide initiators, redox initiators and the like may be appropriately selected according to the polymerization method. As the azo initiator, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethyl valeronitrile) and the like, and peroxide initiators include perisopropyl compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; t-butyl Perester compounds such as peroxyneodecanate, α-cumylperoxyneodecanate, and t-butylperoxydecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, etc. Is mentioned. Furthermore, the initiator can be combined with potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like to form an initiator. Moreover, as a redox-type initiator, what combined said peroxide and reducing agents, such as sodium hydrogen sulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid, Rongalite, is mentioned.

  In addition, when copolymerization of the unsaturated monomer represented by the general formula (II) and the vinyl ester monomer is performed at a high temperature, the POA-modified PVA caused by the decomposition of the vinyl ester monomer Coloring may be seen. In that case, an antioxidant such as tartaric acid may be added to the polymerization system in an amount of 1 ppm to 100 ppm (relative to the mass of the vinyl ester monomer) for the purpose of preventing coloring.

  Vinyl ester monomers used for copolymerization include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, and lauric acid. Examples thereof include vinyl, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate and the like. Of these, vinyl acetate is most preferred.

  In the copolymerization of the unsaturated monomer represented by the general formula (II) and the vinyl ester monomer, another monomer may be copolymerized within a range not impairing the gist of the present invention. Examples of monomers that can be used include α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid and salts thereof; acrylic acid esters; methacrylic acid and salts thereof; methacrylic acid esters; acrylamide; -Methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt or quaternary salt thereof, N-methylolacrylamide and its derivative, etc. Acrylamide derivatives; methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and Methacrylamide derivatives such as salts thereof or quaternary salts thereof, N-methylol methacrylamide and derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t- Vinyl ethers such as butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene chloride , Vinylidene halides such as vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, allyl chloride; maleic acid, itaconic acid, Examples thereof include unsaturated dicarboxylic acids such as fumaric acid and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like.

  In addition, for the purpose of adjusting the degree of polymerization of the resulting POA-modified vinyl ester polymer in the copolymerization of the unsaturated monomer represented by the general formula (II) and the vinyl ester monomer, Copolymerization may be carried out in the presence of a chain transfer agent as long as the gist of the present invention is not impaired. Chain transfer agents include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; halogenated hydrocarbons such as trichloroethylene and perchloroethylene; sodium phosphinate 1 Examples thereof include phosphinic acid salts such as hydrates, among which aldehydes and ketones are preferably used. The addition amount of the chain transfer agent can be determined according to the chain transfer constant of the chain transfer agent to be added and the degree of polymerization of the target POA-modified vinyl ester polymer. 0.1 mass% or more and 10 mass% or less are desirable.

  For the saponification reaction of the POA-modified vinyl ester polymer, an alcohololysis reaction using a conventionally known basic catalyst such as sodium hydroxide, potassium hydroxide or sodium methoxide or an acidic catalyst such as p-toluenesulfonic acid or the like. Hydrolysis reactions can be applied. Examples of the solvent that can be used in this reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene; These can be used alone or in combination of two or more. Among them, it is convenient and preferable to perform the saponification reaction using methanol or a methanol / methyl acetate mixed solution as a solvent and sodium hydroxide as a catalyst.

  The POA group modification rate (S) of the POA-modified PVA needs to be 0.1 mol% or more and 5 mol% or less, preferably 0.2 mol% or more and 3 mol% or less, 0.5 mol% or more and 2 mol% or less. % Or less is more preferable. When the POA group modification rate exceeds 5 mol%, the water solubility of the POA-modified PVA decreases due to an increase in the proportion of POA groups contained in one molecule of the POA-modified PVA. Handling properties are deteriorated, and physical properties due to interaction between POA groups in a high concentration aqueous solution are not sufficiently exhibited. On the other hand, when the POA group modification rate is less than 0.1 mol%, the water solubility of the POA-modified PVA is excellent, but the proportion of POA groups contained in one molecule in the POA-modified PVA is low. The physical properties due to the interaction of are not fully expressed. The POA group modification rate is calculated from the polyoxypropylene block and the (poly) oxyethylene block that the POA-modified PVA has in the side chain in the number of moles of all monomer units constituting the POA-modified PVA. It is the ratio (mol%) of the number of moles of the POA group that is constituted and represented by the general formula (I). The POA group modification rate may be determined either from POA-modified PVA or from the precursor POA-modified vinyl ester polymer, and both can be determined by proton NMR.

For example, when the POA-modified PVA consists of only a vinyl alcohol unit, a vinyl acetate unit and a polyoxypropylene (poly) oxyethylene monomethacrylamide unit as the unsaturated monomer unit represented by the general formula (II), The POA group modification rate can be calculated by this method. That is, for example, when obtaining from a precursor POA-modified vinyl ester polymer (POA-modified polyvinyl acetate), specifically, first, a POA-modified vinyl ester polymer using a mixed solvent of n-hexane / acetone. After the reprecipitation purification is sufficiently performed three times or more, drying is performed under reduced pressure at 50 ° C. for 2 days to prepare a sample of POA-modified vinyl ester polymer for analysis. The sample is then dissolved in CDCl ₃ and measured at room temperature using proton NMR. And the area of the peak α (4.7 to 5.2 ppm) derived from the proton of the main chain methine of the vinyl ester monomer and the peak β (0.8 to 0.8 derived from the proton of the terminal methyl group of the oxypropylene unit) From the area of 1.0 ppm), the POA group modification rate can be calculated using the following formula. In the formula, m represents the number of repeating units of the oxypropylene unit.

POA group modification rate (S) (mol%) = [(Area of peak β / 3 m) / {Area of peak α + (Area of peak β / 3 m)}] × 100

  Even when the POA-modified PVA has a structure other than the above structure, the POA group modification rate can be easily determined by appropriately changing the calculation target peak or calculation formula.

  The viscosity average polymerization degree of the POA-modified PVA needs to be 150 or more and 1000 or less, preferably 180 or more and 700 or less, and more preferably 200 or more and 500 or less. When the viscosity average degree of polymerization of the POA-modified PVA is less than 150, it is difficult to be a dispersant that sufficiently exhibits the target performance, and the performance of the resulting heat-sensitive recording material is not sufficiently exhibited. On the other hand, when the viscosity average degree of polymerization of the POA-modified PVA exceeds 1000, the viscosity of the dispersion containing the dispersant for the heat-sensitive recording material of the present invention becomes too high and handling becomes difficult. It is difficult to prepare a high coating liquid, and as a result, a uniform thermosensitive coloring layer cannot be obtained.

The viscosity average degree of polymerization of the POA-modified PVA is measured according to JIS K6726. That is, after the POA-modified PVA is re-saponified and purified, it is obtained by the following equation from the intrinsic viscosity [η] (unit: deciliter / g) measured in water at 30 ° C.

Viscosity average polymerization degree = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

  The saponification degree of the POA-modified PVA needs to be 40 mol% or more and 99.99 mol% or less, preferably 60 mol% or more and 99 mol% or less, and more preferably 75 mol% or more and 96 mol% or less. When the degree of saponification is less than 60 mol%, the dispersion stability of the resulting dispersion decreases. On the other hand, if the degree of saponification exceeds 99.99 mol%, production of POA-modified PVA becomes difficult, which is not practical. The saponification degree of the POA-modified PVA is a value that can be measured according to JIS K6726.

(Other ingredients)
The dispersant for the heat-sensitive recording material may be composed only of the POA-modified PVA, but the POA such as a general pressure-sensitive recording material or other dispersant used for the heat-sensitive recording material together with the POA-modified PVA. You may further contain other components other than modified PVA as needed. Examples of the other components include PVA other than the POA-modified PVA such as carboxylic acid-modified PVA and sulfonic acid-modified PVA, sulfonated celluloses, sulfonated starches, carboxyethyl cellulose, hydroxyethyl cellulose, and polyacrylic acids. , Ethylene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, higher alcohol Sulfate esters, alkyl polyether sulfates, alkyl sulfonic acids, aryl sulfonates, phosphate esters, aliphatic phosphate esters, aromatic phosphate esters, polyoxyethylene alkyl sulfate esters, poly Xylethylene aryl sulfates, polyoxyethylene alkyl aryl sulfates, dialkyl sulfosuccinates, alkyl benzene sulfonates, polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkyl aryl ether phosphates, etc. It is done.
The content of the POA-modified PVA in the heat-sensitive recording material dispersant of the present invention is not particularly limited, but is preferably 50% by mass or more, more preferably 80% by mass or more, and 90% by mass or more. More preferably.

[Dispersion]
The dispersion of the present invention contains a dispersant for a heat-sensitive recording material containing the POA-modified PVA and a liquid medium, and at least one selected from the group consisting of a dye, a developer and a sensitizer is used as a dispersoid. It is dispersed and may contain other components as required. The liquid medium that can serve as a dispersion medium is preferably water, and specifically includes water alone or a mixed solvent of water and an organic solvent. Hereinafter, the dispersion of the present invention will be described.

(dye)
As the dye, any known dyes in the field of conventional pressure-sensitive recording materials or heat-sensitive recording materials can be used and are not particularly limited. Specific examples of the dye include electron donating dyes (such as leuco dyes). For example, 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) Triarylmethane compounds such as phthalide and 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide; 4,4′-bisdimethylaminobenzhydrin benzyl ether, N-halophenyl Diphenylmethane compounds such as leucooramine; rhodamine B-anilinolactam, 3-diethylamino-7-benzylamino Fluorane, 3-diethylamino-7-butylaminofluorane, 3-diethylamino-7- (chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-ani Linofluorane, 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-phenylaminofluor Xanthene compounds such as orane and 3-dibutylamino-6-methyl-7-anilinofluorane; Thiazine compounds such as illeucomethylene blue and p-nitrobenzoyl leucomethylene blue; 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho (3-methoxy-benzo ) -Spiro-pyran compounds such as spiropyran. These dyes may be used alone or in combination of two or more.

(Developer)
Any known developer in the field of conventional pressure-sensitive recording materials or heat-sensitive recording materials can be used as the developer, and is not particularly limited. Specific examples of the color developer include electron-accepting agents such as phenol derivatives, aromatic carboxylic acid derivatives, N, N′-diallylthiourea derivatives, allylsulfonylurea derivatives, and zinc salts of organic compounds. And polyvalent metal salts such as benzenesulfonamide derivatives and urea urethane compounds. Among these, phenol derivatives and aromatic carboxylic acid derivatives are preferable, and bisphenols are particularly preferable.

  Specific examples of the phenol derivative include phenols such as p-octylphenol, pt-butylphenol, and 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 Bisphenols such as (p-hydroxyphenyl) -2-ethylhexane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, bis (p-hydroxyphenyl) sulfone (bisphenol S); And diphenyl ether. Examples of the aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-t-butylsalicylic acid, 3,5-di-α- Examples include methylbenzyl salicylic acid and polyvalent metal salts of the above carboxylic acids. These developers may be used alone or in combination of two or more.

(Sensitizer)
As the sensitizer, those used in conventional pressure-sensitive recording materials or heat-sensitive recording materials can be used, and there is no particular limitation. Specific examples of the sensitizer include benzyl-2-naphthyl ether, stearic acid amide, methylenebisstearic acid amide, benzyl p-benzyloxybenzoate, 1,2-di (3-methylphenoxy) ethane, 1 , 2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4 -Methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-benzylbiphenyl, p-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ) Ether, m-terphenyl, benzyl-4-methylthiophenyl ether, 1-hydroxy- -Naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid-di-p-methylbenzyl ester, oxalic acid-di-p-chlorobenzyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, Examples thereof include p-acetoluidide, p-acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene and the like. These sensitizers may be used alone or in combination of two or more.

  The content of the heat-sensitive recording material dispersant in the dispersion containing the dye as a dispersoid (dye dispersion) is preferably 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the dye, and 7 parts by mass. The amount is more preferably 30 parts by mass or less, and further preferably 8 parts by mass or more and 20 parts by mass or less. By setting the content in the above range, the dispersion state of the dye is further improved, and the sensitivity and image storage stability of the resulting heat-sensitive recording material are further improved.

  The content of the heat-sensitive recording material dispersant in the dispersion liquid (developer dispersion liquid) containing the developer as a dispersoid is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the developer. Is preferably 7 parts by mass or more and 30 parts by mass or less, and more preferably 8 parts by mass or more and 20 parts by mass or less. By setting the content in the above range, the dispersion state of the developer is further improved, and the sensitivity and image storability of the resulting thermal recording material are further improved.

  The content of the heat-sensitive recording material dispersant in the dispersion containing the sensitizer as a dispersoid (sensitizer dispersion) is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the sensitizer. Is preferably 7 parts by mass or more and 30 parts by mass or less, and more preferably 8 parts by mass or more and 20 parts by mass or less. By setting the content in the above range, the dispersion state of the sensitizer is further improved, and the sensitivity and image storability of the resulting thermosensitive recording material are further improved.

  For the dispersion of the dispersoid, a ball mill, attritor, sand mill, SC mill, ring mill, spike mill, coball mill, dyno mill or the like can be usually used. A dispersion containing a dispersoid having a particle size of 0.1 to 1 μm (preferably 0.2 to 0.7 μm, more preferably 0.3 to 0.5 μm) is obtained using the above-described dispersant for heat-sensitive recording material. It is done.

  The dispersion preferably has a viscosity (η) of 30 mPa · s or more and 1000 mPa · s or less, and 40 mPa · s or more and 900 mPa · s or less, measured at 20 ° C. with a BL type viscometer at a rotor rotation speed of 60 rpm. Or less, more preferably 50 mPa · s or more and 800 mPa · s or less. When the viscosity of the dispersion is in the above range, a coating liquid having excellent coating properties can be more easily prepared.

[Coating fluid]
The coating liquid of the present invention contains a dispersant for a heat-sensitive recording material containing the POA-modified PVA, a dye, a developer, and a liquid medium, and preferably further contains a sensitizer. After the coating liquid is applied to the surface of the base material, it is dried to form a heat-sensitive recording layer, whereby a heat-sensitive recording material excellent in color development sensitivity and background whiteness can be produced smoothly.
The coating liquid may be produced by any method. For example, at least one selected from the group consisting of the above-described dye dispersion, developer dispersion, and sensitizer dispersion is used. It is preferable that the above-mentioned dye dispersion and developer dispersion are used at least to mix them, and the above-described dye dispersion, developer dispersion and sensitization are used. It is more preferable to produce by mixing these using at least an agent dispersion.

  The liquid medium contained in the coating liquid is preferably water, and specifically includes water alone or a mixed solvent of water and an organic solvent. In particular, when the coating liquid is produced using at least one selected from the group consisting of the above-described dye dispersion, developer dispersion, and sensitizer dispersion, the liquid contained in each of these dispersions The medium can be at least a part of the liquid medium contained in the coating liquid.

(binder)
The coating solution preferably further contains a binder as necessary. As the binder, all known binders in the field of conventional pressure-sensitive recording materials or heat-sensitive recording materials can be used, and are not particularly limited. Among them, preferred is a binder that, when mixed with the above dispersion, does not cause the liquid to develop color, aggregate, or excessively increase in viscosity. Examples of such binders include starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose; PVA other than the above-mentioned POA-modified PVA, polyacrylic acid soda, polyvinylpyrrolidone, acrylamide- Acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic acid terpolymer, alkali metal salt of styrene-maleic anhydride copolymer, alkali metal salt of isobutylene-maleic anhydride copolymer, polyacrylamide, Water-soluble polymers such as sodium alginate, gelatin, and casein; polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride-vinyl acetate copolymer Polybutyl methacrylate, ethylene - vinyl acetate copolymer, styrene - butadiene copolymer, styrene - butadiene - like acrylic acid copolymer.
It is preferable that the content rate of the said binder in a coating liquid is 1-20 mass parts with respect to 100 mass parts of total amounts of dye, a color developer, and a sensitizer.

(Other ingredients)
In addition to the thermal recording dispersant, dye, developer, sensitizer, and binder containing the POA-modified PVA, the coating liquid improves coating suitability, and the whiteness of the resulting thermal recording material. In order to further improve color development sensitivity, dispersibility, etc., it contains other components such as fillers, surfactants, heat-soluble substances, lubricants, antifoaming agents, dispersants, wetting agents, pressure coloring inhibitors. Also good.

  As the filler, diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, zinc sulfate, Examples thereof include inorganic fillers such as amorphous silica, amorphous calcium silicate, colloidal silica; and organic fillers such as melamine resin filler, urea-formalin resin filler, polyethylene powder, and nylon powder.

  Examples of the lubricant include higher fatty acid metal salts such as zinc stearate and calcium stearate, higher fatty acid amides such as stearamide, paraffin, polyethylene wax, polyethylene oxide, and caster wax.

[Thermal recording material]
A thermal recording material having the thermal coloring layer on the surface of the substrate is obtained by coating the coating liquid of the present invention on the surface of the substrate and then drying to form the thermal recording layer. Such a heat-sensitive recording material can contain the above-mentioned POA-modified PVA. Therefore, the present invention includes a heat-sensitive recording material containing the above POA-modified PVA. This thermosensitive recording material typically has a substrate and a thermosensitive coloring layer on the surface of the substrate, and the thermosensitive coloring layer contains the above-mentioned POA-modified PVA, dye and developer. The thermosensitive coloring layer preferably further contains a sensitizer.

  As the base material, usually paper is mainly used, but in addition to paper, various woven fabrics, nonwoven fabrics, synthetic resin films, synthetic resin laminated papers, synthetic papers, metal foils, vapor deposition sheets, or these are bonded together. The obtained composite sheet or the like can be arbitrarily used depending on the purpose.

The base material may have an undercoat layer containing a filler and a resin on the thermosensitive coloring layer side as required. As the filler contained in the undercoat layer, those exemplified as the filler that can be contained in the coating solution can be used. The coating amount of the undercoat layer is preferably from 1 g / ^{m 2} or more 30 g / ^{m 2} or less in terms of solid content, 3 g / ^{m 2} or more 20 g / ^{m 2} or less is more preferable.

In the case of forming the heat-sensitive recording layer by drying or the like after coating the coating liquid of the present invention on the surface of the substrate, examples of the coating liquid coating method include air knife method, plate method, Examples include a gravure method, a roll coater method, a spray method, a dip method, a bar method, and an extrusion method. The coating amount of the coating solution is preferably 1 g / ^{m 2} or more 12 g / ^{m 2} or less in terms of solid content, more preferably 2 g / ^{m 2} or more 10 g / ^{m 2} or less.

In the heat-sensitive recording material of the present invention, a protective layer containing a filler and a resin may be provided on the heat-sensitive coloring layer as necessary. The protective layer may further contain a crosslinking agent for the purpose of further improving the water resistance and the like. As a filler contained in a protective layer, what was illustrated as a filler which can be contained in the said coating liquid can be used. The coating amount of the protective layer is preferably 0.3 g / ^{m 2} or more 10 g / ^{m 2} or less in terms of solid content, 0.5 g / ^{m 2} or more 8 g / ^{m 2} or less is more preferable.

[Printed matter]
When the above heat-sensitive recording material is partially heated, the heated portion develops color and a printed matter is obtained. There is no particular limitation on the printing apparatus used for printing by heating, and a conventionally known thermal recording apparatus equipped with a thermal head can be used.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples. In the following Examples and Comparative Examples, “part” and “%” mean mass basis unless otherwise specified.

  About each PVA obtained by the following manufacture example, each measurement was performed in accordance with the following method.

[Viscosity average degree of polymerization and degree of saponification]
The viscosity average polymerization degree and saponification degree of PVA were determined by the method described in JIS K6726.

[POA group modification rate]
The POA group modification rate of PVA was determined according to the method using proton NMR described above. For proton NMR, JEOL GX-500 (500 MHz) was used.

[Production Example 1]
Production of PVA1 An unsaturated monomer having 250 g of vinyl acetate, 750 g of methanol, and POA group in a 3 L reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet, a monomer dropping port and an initiator addition port Monomer A (monomer A is represented by the general formula (II), and R ^{1 to} R ⁵ , X, m and n are as shown in Table 2. Arrangement of Oxypropylene Unit and Oxyethylene Unit Is a block, and the block of the oxypropylene unit is located on the X side with respect to the block of the oxyethylene unit.) 0.95 g was charged, and the inside of the system was purged with nitrogen for 30 minutes while bubbling nitrogen. Moreover, the solution which made the density | concentration 20% by melt | dissolving the monomer A in methanol as a delay solution was prepared, and nitrogen substitution was carried out by bubbling of nitrogen gas. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 1.2 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate polymerization. While the delay solution was added dropwise so that the monomer composition (ratio of vinyl acetate and monomer A) in the polymerization solution was constant, polymerization was performed at 60 ° C. for 5 hours, and then the polymerization was stopped by cooling. The total amount of monomer A used until the polymerization was stopped was 47 g. Further, the solid content concentration when the polymerization was stopped was 17.9%. Subsequently, unreacted vinyl acetate was removed while occasionally adding methanol under reduced pressure at 30 ° C. to obtain a methanol solution (concentration 50%) of POA-modified vinyl ester polymer (POA-modified PVAc). Furthermore, 3.5 g of an alkaline solution (sodium hydroxide in 10% methanol) was added to 244.8 g of a POA-modified PVAc methanol solution prepared by adding methanol thereto (100.0 g of POA-modified PVAc in the solution). Saponification was carried out (POA modified PVAc concentration of saponified solution 40%, molar ratio of sodium hydroxide to vinyl acetate units in POA modified PVAc 0.0075). After adding the alkaline solution, a gel was formed in about 30 minutes. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to allow saponification to proceed, and then 500 g of methyl acetate was added to remain. The alkali was neutralized. After confirming that neutralization was completed using a phenolphthalein indicator, a white solid was obtained by filtration, and a washing operation was performed by adding 2000 g of methanol thereto and allowing to stand at room temperature for 3 hours. After this washing operation was repeated three times, the white solid obtained by centrifugal drainage was left to dry in a dryer at 65 ° C. for 2 days to obtain POA-modified PVA (PVA1).
Table 3 shows the measurement results of the viscosity average polymerization degree, saponification degree, and POA group modification rate of PVA1.

[Production Examples 2-29, 32, 33]
Production of PVA 2 to 29, i to x, xiii and xiv Amounts of vinyl acetate and methanol (before the start of polymerization), types of unsaturated monomers having POA groups used during polymerization (Table 2) and amounts thereof used, Various PVA (PVA2-19, iVA) were prepared in the same manner as in Production Example 1 except that the polymerization rate, the concentration of PVAc during saponification, and the molar ratio of sodium hydroxide to vinyl acetate units were changed as shown in Table 1. ~ X, xiii and xiv) were obtained.
Table 3 shows the measurement results of the viscosity average polymerization degree, saponification degree, and POA group modification rate of these PVA. PVAxiv was used as a binder in the following Examples or Comparative Examples, and had a viscosity average polymerization degree of 1700, a saponification degree of 98.5 mol%, and a POA group modification rate of 0 mol%.

[Production Examples 30 and 31]
Production of PVAxi and xii Unsaturated monomers (compounds III and IV) having the following structures were used as unsaturated monomers having POA groups used during polymerization, respectively, and the amounts used, vinyl acetate and methanol (polymerization) Various POA-modified PVAs (PVAxi and xii) were obtained in the same manner as in Production Example 1 except that the amount charged before start) was changed as shown in Table 1.
Table 3 shows the measurement results of the viscosity-average polymerization degree, saponification degree, and POA group modification rate of these POA-modified PVA.

(In compound III, the oxypropylene unit and the oxyethylene unit are each arranged in a block form, and the positions of the polyoxyethylene block and the polyoxypropylene block are as described in the above formula.)

(The oxypropylene units and oxyethylene units in Compound IV are randomly arranged.)

[Example 1]
Using PVA1, each dispersion, coating solution, and heat-sensitive recording material were prepared as follows.

(1) Preparation of dye dispersion leuco dye (manufactured by Yamamoto Kasei Co., Ltd .: ODB-2) 100 parts PVA1 10 parts 2,4,7,9-tetramethyl-5-decyne-4,7-diol (Air Products and Chemicals Co., Ltd .: Surfynol 104E) 0.2 parts distilled water 204 parts

The leuco dye, PVA1,2,4,7,9-tetramethyl-5-decyne-4,7-diol and distilled water were mixed, preliminarily stirred in a beaker for 60 minutes, and then a bead mill (manufactured by AIMEX: Transfer to Ready-mill type NVM-03), add glass beads (soda quartz glass with a diameter of 0.5 mm) (filling rate 82%), discharge rate 55 mL / min, high rotation speed (3400 rpm), under cooling For 30 minutes (8 passes) to prepare a dye dispersion having a solid concentration of 35%.

(2) Preparation of developer dispersion bisphenol S (manufactured by Nippon Soda Co., Ltd .: D-8) 100 parts PVA1 10 parts 2,4,7,9-tetramethyl-5-decyne-4,7-diol (air Products & Chemicals Co., Ltd .: Surfynol 104E) 0.2 parts Distilled water 110 parts

A developer dispersion having a solid concentration of 50% was prepared in the same manner as the dye dispersion. As a result of measuring the particle diameter with a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation: SALD-2200), the average particle diameter of the developer was 0.6 μm.

(3) Preparation of sensitizer dispersion benzyl-2-naphthyl ether 100 parts PVA1 10 parts 2,4,7,9-tetramethyl-5-decyne-4,7-diol (manufactured by Air Products and Chemicals Co., Ltd .: Surfinol 104E) 0.2 parts distilled water 165 parts

A sensitizer dispersion having a solid concentration of 40% was prepared in the same manner as the dye dispersion. As a result of measuring the particle diameter with a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation: SALD-2200), the average particle diameter of the sensitizer was 0.5 μm.

(4) Preparation of thermal recording paper 25 parts of dye dispersion (converted to solid content), 60 parts of developer dispersion (converted to solid content), 40 parts of sensitizer dispersion (converted to solid content), silica (Mizusawa Chemical Industries) Co., Ltd .: Mizusilica P-603) 100 parts, 10% PVAxiv aqueous solution 20 parts (in terms of solid content) and distilled water 27 parts were mixed and stirred to prepare a coating solution. After coating the coating liquid on the surface of the base paper (basis weight: 60 g / m ² fine paper) using a Mayer bar at a coating amount of 3 g / m ² (in terms of solid content), A thermal recording paper was prepared by drying the film and subjecting it to a surface treatment with a super calender (linear pressure: 30 kg / cm).

  The following items were evaluated for the dye dispersion and the thermal recording paper obtained above.

(I) Dispersibility of PVA As an index of dispersibility of PVA, the particle diameter of the dye in the dye dispersion was measured. Specifically, when the particle diameter of the dye immediately after preparation of the dye dispersion was measured with a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation: SALD-2200), the average particle diameter was 0.36 μm. Rank 5 was determined using the following criteria.
5: Less than 0.4 μm 4: 0.4 μm or more and less than 0.5 μm 3: 0.5 μm or more and less than 0.7 μm 2: 0.7 μm or more and less than 1.0 μm 1: 1.0 μm or more

(Ii) Solution viscosity of the dye dispersion The viscosity η ₁ immediately after the preparation of the dye dispersion is determined according to TOKIMEC INC. When measured at a rotor rotation speed of 60 rpm and a temperature of 20 ° C. using a manufactured BL type viscometer, it was 47 mPa · s.
5: Less than 50 mPa · s 4: 50 mPa · s or more and less than 150 mPa · s 3: 150 mPa · s or more and less than 400 mPa · s 2: 400 mPa · s or more and less than 1000 mPa · s 1: 1000 mPa · s or more

(Iii) Storage stability of the dye dispersion The viscosity η ₂ of the dye dispersion stored at 20 ° C. for 3 days immediately after the preparation was measured by the same method as in the above (ii), and the viscosity η ₁ immediately after the preparation was When the viscosity ratio η ₂ / η ₁ was determined to be 1.03, it was determined as Rank 5 using the following criteria.
5: 1.00 or more and less than 1.10 4: 1.10 or more and less than 1.20 3: 1.20 or more and less than 1.50 2: 1.50 or more and less than 1.80 1: 1.80 or more

(Iv) Whiteness of the dye dispersion (liquid fog)
The dye dispersion liquid that had passed 1 hour immediately after preparation was hand-coated on a commercially available thermal paper (manufactured by KOKUYO Co., Ltd .: Thailand-2010) (the coating amount was about 5 g / m ² ). When ISO whiteness of this coated paper was measured with PF-10 (manufactured by Nippon Denshoku Industries Co., Ltd.), the whiteness was 84. Therefore, it was determined as Rank 5 using the following criteria.
5:82 or more 4:79 or more and less than 82 3:75 or more and less than 79 2:72 or more and less than 75 1:72

(V) Color development sensitivity of thermal recording paper Color development test using a thermal gradient tester (manufactured by Toyo Seiki Seisakusho: TYPE HG-100, press pressure 0.6 kg / cm ² , press time 5 seconds, press temperature 120 ° C.) Then, the color density of the thermal recording paper was measured (GretagMacbeth reflection densitometer: RD-19) and found to be 1.27.
5: 1.25 or more 4: 1.20 or more and less than 1.25 3: 1.10 or more and less than 1.20 2: 1.00 or more and less than 1.10 1: less than 1.00

(Vi) Comprehensive evaluation of thermal recording paper For the above five evaluation items, an inclined score was given as shown below for the physical properties that greatly affect the performance of the thermal recording paper, and a comprehensive evaluation as a thermal recording paper was performed. The thermal recording paper using PVA1 was 44 points. A score of 30 or more points was determined to be acceptable, and a score of less than 30 was determined to be unacceptable.

Overall Evaluation = Dispersibility score x 2 + Solution viscosity score + Storage stability score x 2 + Whiteness score x 2 + Color development sensitivity score x 3

[Examples 2 to 19 and Comparative Examples 1 to 13]
Each dispersion, coating solution, and thermal recording paper were prepared in the same manner as in Example 1 except that PVA2-19 and i to xiii listed in Table 3 were used instead of PVA1. The obtained dye dispersion and thermal recording paper were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3.

  Since the dispersant for heat-sensitive recording material of the present invention contains the above-mentioned specific POA-modified PVA, it has excellent dispersibility, and the dispersion containing the dispersant has a small particle size of the dispersed particles and little liquid fog. Excellent storage stability. Moreover, according to the coating liquid which can be manufactured using the said dispersion liquid, the thermosensitive recording material which is excellent in color development sensitivity can be manufactured smoothly. Such a heat-sensitive recording material is useful in fields requiring high-speed printing such as facsimiles by taking advantage of its characteristics.

Claims (14)

It is composed of a polyoxypropylene block and a (poly) oxyethylene block, has a polyoxyalkylene group represented by the following general formula (I) in the side chain, has a viscosity average polymerization degree of 150 to 1,000, and a saponification degree Is a polyoxyalkylene-modified vinyl alcohol polymer having a polyoxyalkylene group modification rate of 0.1 mol% or more and 5 mol% or less. Agent.

(In General Formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ^One of R ² and R ³ is a methyl group, and the other is a hydrogen atom. 10 ≦ m ≦ 40, and 1 ≦ n ≦ 50.)   A dispersion comprising the dispersant for heat-sensitive recording material according to claim 1 and a liquid medium, wherein at least one selected from the group consisting of a dye, a developer and a sensitizer is dispersed.   The dispersion according to claim 2, wherein the liquid medium is water.   4. The dispersion according to claim 2, wherein the viscosity measured at 20 ° C. with a BL-type viscometer at a rotor rotational speed of 60 rpm is 30 mPa · s or more and 1000 mPa · s or less.   A coating solution containing the dispersant for heat-sensitive recording materials according to claim 1, a dye, a developer, and a liquid medium.   The coating liquid according to claim 5, wherein the liquid medium is water.   The coating solution according to claim 5 or 6, further comprising a sensitizer.   A thermosensitive recording material comprising a substrate and a thermosensitive coloring layer formed on the surface of the substrate from the coating liquid according to claim 5. A heat-sensitive recording material containing a polyoxyalkylene-modified vinyl alcohol polymer,
The polyoxyalkylene-modified vinyl alcohol polymer is composed of a polyoxypropylene block and a (poly) oxyethylene block, has a polyoxyalkylene group represented by the following general formula (I) in the side chain, and has a viscosity average A heat-sensitive recording material having a polymerization degree of 150 to 1,000, a saponification degree of 40 mol% to 99.99 mol%, and a polyoxyalkylene group modification rate of 0.1 mol% to 5 mol%.

(In General Formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ^One of R ² and R ³ is a methyl group, and the other is a hydrogen atom. 10 ≦ m ≦ 40, and 1 ≦ n ≦ 50.) A substrate, and a thermosensitive coloring layer on the surface of the substrate;
The thermosensitive recording material according to claim 9, wherein the thermosensitive coloring layer contains the polyoxyalkylene-modified vinyl alcohol polymer, a dye, and a developer.   The thermosensitive recording material according to claim 10, wherein the thermosensitive coloring layer further contains a sensitizer. A method for producing a heat-sensitive recording material according to claim 10 or 11,
The manufacturing method which has the process of applying to the base material the coating liquid containing the said polyoxyalkylene modified vinyl alcohol polymer, dye, a color developer, and a liquid medium.   The manufacturing method of Claim 12 with which the said coating liquid further contains a sensitizer.   The manufacturing method of printed matter which has the process of heating the thermosensitive recording material in any one of Claims 8-11.