JP7129174B2 - Photosensitive resin composition, method for producing the same, and use thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photosensitive resin composition containing a specific modified polyvinyl alcohol, a photopolymerization initiator and a specific compound, a method for producing the same, and a powder comprising the photosensitive resin composition. The present invention also relates to a coating agent, a coated product and a heat-sensitive recording material using the photosensitive resin composition.

Polyvinyl alcohol is known as a water-soluble synthetic polymer, and is used as a raw material for synthetic fiber vinylon, paper processing agents, printing plate materials, fiber processing agents, adhesives, stabilizers for emulsion polymerization and suspension polymerization, and inorganic substances. It is widely used for binders, films, etc. On the other hand, efforts are being made to control the crystallinity or introduce functional groups to improve specific performance, and various so-called modified polyvinyl alcohols have been developed.

A modified polyvinyl alcohol containing a photosensitive functional group can form a crosslinked product by irradiation with ultraviolet rays alone or after adding a photopolymerizable compound or the like. Applications using such a cross-linking system include the formation of a printing plate material that utilizes the formation of a solvent-soluble portion and a solvent-insoluble portion in polyvinyl alcohol, or the formation of a film with excellent water resistance. Used coating agent and the like.

Several proposals have been made so far as photosensitive modified polyvinyl alcohol. For example, Patent Document 1 exemplifies a photosensitive modified polyvinyl alcohol in which a styrylpyridinium residue or a styrylquinolinium residue is introduced as a photosensitive functional group using acetalization. However, acetalization requires a large amount of an acid catalyst. For example, when the modified polyvinyl alcohol is used as a coating agent, there is a problem of corrosion of coating machines due to the acid catalyst remaining in the modified polyvinyl alcohol. is concerned.

On the other hand, as a photosensitive modified polyvinyl alcohol that does not use acetalization, Patent Document 2 describes modified polyvinyl alcohol in which methacryloyl groups are introduced into side chains by reacting polyvinyl alcohol having carboxyl groups in side chains with glycidyl methacrylate. Alcohol is exemplified. However, in order to obtain the modified polyvinyl alcohol, it is necessary to undergo multi-step reactions, which complicates the process.

Japanese Patent Publication No. 8-9262 JP-A-3-274558

An object of the present invention is to provide a photosensitive resin composition containing photosensitive modified polyvinyl alcohol and having excellent film water resistance after ultraviolet irradiation. Another object of the present invention is to provide a simple method for producing a photosensitive resin composition without acetalization.

As a result of extensive studies by the present inventors, a photosensitive resin composition containing a modified polyvinyl alcohol having a double bond derived from an unsaturated carboxylic acid or a derivative thereof in a side chain, a photopolymerization initiator and a specific compound The inventors have found that the above problems can be solved by the method, and have completed the present invention.

Specifically, the present invention relates to the following inventions.
[1] A photosensitive resin composition (D ) and;
A compound (C) having a conjugated double bond and two or more hydroxyl groups bonded to carbon atoms constituting the conjugated double bond, or a salt or oxide thereof (C1); Cyclic nitroxyl radical (C2); and alkoxyphenol (C3); at least one selected from the group consisting of
The modified polyvinyl alcohol (A) has a viscosity average polymerization degree of 200 or more and 4500 or less, a saponification degree of 65 mol% or more and 99.9 mol% or less, and a 1,2-glycol bond amount of 1.4 mol% or more. .The photosensitive resin composition (D), which is less than 9 mol %.
[2] A compound having a conjugated double bond and having two or more hydroxyl groups bonded to a carbon atom constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1) is a carbon constituting an aromatic ring The photosensitive resin composition (D) of [1] above, which is a compound having two or more hydroxyl groups bonded to an atom, a salt thereof, or an oxide thereof.
[3] A compound having a conjugated double bond and having two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1) is α,β-unsaturated The photosensitive resin composition (D) of [1] above, which is a compound in which two or more hydroxyl groups are bonded to the α- and β-positions of a carbonyl compound, a salt thereof, or an oxide thereof.
[4] The photosensitive resin composition (D) of any one of the above [1] to [3], wherein the modified polyvinyl alcohol (A) has 0.01 mol% or more and less than 5 mol% of double bonds in the side chain. .
[5] Any one of the above [1] to [4], wherein the modified polyvinyl alcohol (A) further has an ethylene unit in the main chain, and the content of the ethylene unit is 1 mol% or more and less than 20 mol%. Photosensitive resin composition (D).
[6] A powder composed of the photosensitive resin composition (D) according to any one of [1] to [5], which has a yellow index of less than 40.
[7] A coating agent containing the photosensitive resin composition (D) according to any one of [1] to [5] and water.
[8] A coated product obtained by applying the coating agent of [7] above to the surface of a substrate.
[9] A heat-sensitive recording material comprising the coated product of [8] above.
[10] A step of reacting polyvinyl alcohol (E) with an unsaturated carboxylic acid or a derivative thereof in the presence of compound (C) to obtain a composition containing modified polyvinyl alcohol (A) and compound (C). , and a method for producing a photosensitive resin composition (D) according to any one of the above [1] to [5], comprising the step of mixing the composition and a photopolymerization initiator (B).

The film obtained by irradiating the photosensitive resin composition of the present invention with ultraviolet rays has a low swelling rate and a low elution rate in water, and is excellent in water resistance. Moreover, according to the production method of the present invention, the photosensitive resin composition can be obtained by a simple method that does not use acetalization.

[Photosensitive resin composition (D)]
The photosensitive resin composition (D) of the present invention is a modified polyvinyl alcohol (A) (hereinafter abbreviated as "modified PVA (A)") having a double bond derived from an unsaturated carboxylic acid or a derivative thereof in the side chain. may be), a photoinitiator (B) and a compound (C). The photosensitive resin composition (D) of the present invention can form a crosslinked product by irradiating with ultraviolet rays to form a film having excellent water resistance.

The method for producing the photosensitive resin composition (D) of the present invention is not particularly limited. to obtain a composition containing modified polyvinyl alcohol (A) and compound (C), and mixing the composition with a photopolymerization initiator (B). Here, polyvinyl alcohol (E) is PVA having no double bond in the side chain (hereinafter sometimes referred to as "PVA (E)").

(Modified PVA (A))
The PVA (E) is a polyvinyl ester monomer obtained by polymerizing a vinyl ester monomer using a conventionally known method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, and a dispersion polymerization method. It can be produced by subjecting an ester to a saponification reaction. Preferred polymerization methods from an industrial point of view are solution polymerization, emulsion polymerization and dispersion polymerization. In the polymerization operation, it is possible to employ any of a batch method, a semi-batch method and a continuous method.

Examples of vinyl ester monomers that can be used for polymerization include vinyl acetate, vinyl formate, vinyl propionate, vinyl caprylate, and vinyl versatate. preferred from

When polymerizing the vinyl ester-based monomer, the vinyl ester-based monomer may be copolymerized with other monomers as long as the gist of the present invention is not impaired. Monomers that can be used include, for example, ethylene, propylene, n-butene, α-olefins such as isobutylene; acrylic acid and its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-acrylate, Acrylic acid esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and octadecyl acrylate; methacrylic acid and its salts; methyl methacrylate, Methacrylates such as ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate and octadecyl methacrylate Acid esters; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts or quaternary salts thereof, N- acrylamide derivatives such as methylolacrylamide and derivatives thereof; methacrylamide derivatives such as methylol methacrylamide and its derivatives; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether Vinyl ethers; Nitriles such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl chloride and vinyl fluoride; Vinylidene halides such as vinylidene chloride and vinylidene fluoride; Allyl compounds such as allyl acetate and allyl chloride; acids, unsaturated dicarboxylic acids such as itaconic acid and fumaric acid, and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; and isopropenyl acetate. The copolymerization amount of such other monomers is usually 20 mol % or less.

In addition, when the vinyl ester monomer is polymerized, a chain transfer agent may coexist for the purpose of adjusting the degree of polymerization of the resulting polyvinyl ester. Examples of chain transfer agents include aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde and benzaldehyde; ketones such as acetone, methyl ethyl ketone, hexanone and cyclohexanone; mercaptans such as 2-hydroxyethanethiol and dodecylmercaptan; trichlorethylene and perchlorethylene. Among them, aldehydes and ketones are preferably used. The amount of the chain transfer agent to be added is determined according to the chain transfer constant of the chain transfer agent to be added and the desired degree of polymerization of the polyvinyl ester. % is desirable.

For the saponification reaction of polyvinyl ester, an alcoholysis or hydrolysis 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 is carried out. Applicable. Solvents used in the saponification reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; and aromatic hydrocarbons such as benzene and toluene. can be used alone or in combination of two or more. Among them, it is convenient and preferable to use methanol or a mixed solution of methanol and methyl acetate as a solvent and perform the saponification reaction in the presence of sodium hydroxide as a basic catalyst.

Modified PVA (A) can be obtained by esterifying PVA (E) obtained through the above saponification reaction with an unsaturated carboxylic acid or derivative thereof in the presence of compound (C). At this time, by performing the reaction in the presence of the compound (C), the hue of the powder composed of the obtained modified PVA (A) and the photosensitive resin composition (D) containing the modified PVA (A) is further improved. It can be improved further. Moreover, when reacting PVA (E) with an unsaturated carboxylic acid or a derivative thereof, heating is preferred in order to promote the reaction. The heating temperature is preferably 80 to 180°C. The heating time is appropriately set in relation to the heating temperature, but is usually 10 minutes to 24 hours.

The method of reacting PVA (E) with unsaturated carboxylic acid or derivative thereof in the presence of compound (C) is not particularly limited, but (i) unsaturated carboxylic acid or derivative thereof, PVA (E) and compound (C) is dissolved in a solvent, and the unsaturated carboxylic acid or its derivative is reacted with PVA (E) in the presence of the compound (C) in the solution; (ii) powdery unsaturated carboxylic acid or (iii) a method of reacting a derivative thereof, powdery PVA (E) and powdery compound (C) without a solvent; A method of adding a powder of PVA (E) to swell the mixture, then removing the solvent to obtain a mixed powder, and heating the obtained mixed powder.

The solvent used in method (i) is not particularly limited as long as it can dissolve PVA (E), unsaturated carboxylic acid or its derivative and compound (C). Examples include water and dimethylsulfoxide. The solid content concentration of the solution is preferably 1 to 40% by mass.

In the method (iii), the solvent for dissolving the unsaturated carboxylic acid or derivative thereof and the compound (C) includes alcohols such as methanol, ethanol and propanol, esters such as methyl acetate, and water. Removal of the solvent can be performed by heating or reducing pressure.

In method (ii) or (iii), the amount of unsaturated carboxylic acid or derivative thereof in the mixed powder before heating is preferably 0.01 parts by mass or more based on 100 parts by mass of PVA (E), and 0.01 part by mass or more. 1 part by mass or more is more preferable, and 0.5 parts by mass or more is even more preferable. On the other hand, the amount of unsaturated carboxylic acid or derivative thereof in the mixed powder before heating is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and 15 parts by mass or less with respect to 100 parts by mass of PVA (E). is more preferred.

In order to obtain modified PVA (A) by method (i), many steps such as a dissolution step of PVA (E), a reaction step with unsaturated carboxylic acid or its derivative, a washing step, and a solvent removal step are required. From the standpoint of quality and production cost, method (ii) or (iii) above is preferably adopted. The above method (ii) is preferable when importance is placed on productivity and production cost, and the above method (iii) is preferable when importance is placed on the homogeneity of the modified PVA (A).

(Unsaturated carboxylic acid or derivative thereof)
The unsaturated carboxylic acid or derivative thereof used in the present invention includes acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, propynoic acid, 2-pentenoic acid, 4-pentenoic acid, 2-heptenoic acid, 2-octenoic acid, cinnamic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, eleostearic acid, stearidonic acid, arachidonic acid, eicosapentaenoic acid, Unsaturated monocarboxylic acids such as sardine acid, docosahexaenoic acid, sorbic acid and salts thereof; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, methacrylic acid 2 - unsaturated monocarboxylic acid hydroxy esters such as hydroxyethyl, 2-hydroxypropyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate and their derivatives; maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid. Acids, unsaturated dicarboxylic acids such as muconic acid, phenylmaleic acid and chloromaleic acid and salts thereof; unsaturated tricarboxylic acids such as aconitic acid; unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride and citraconic anhydride. ; unsaturated carboxylic acid alkyl esters such as acrylic acid alkyl esters, methacrylic acid alkyl esters, crotonic acid alkyl esters; maleic acid monoalkyl esters such as maleic acid monomethyl ester (monomethyl maleate), fumaric acid monoalkyl esters, itaconic acid mono Unsaturated dicarboxylic acid monoesters such as alkyl esters; and unsaturated dicarboxylic acid diesters such as dialkyl maleates, dialkyl fumarate and dialkyl itaconates. These can be used alone or in combination of two or more.

Among these, unsaturated carboxylic acids or derivatives thereof are unsaturated carboxylic acids, unsaturated carboxylic acid monoesters, unsaturated dicarboxylic acids, unsaturated carboxylic acid anhydrides or An unsaturated dicarboxylic acid monoester is preferred. In addition, from the viewpoint of having a relatively high boiling point and being easy to handle, unsaturated carboxylic acids or derivatives thereof include methyl methacrylate, methyl 3,3-dimethyl-4-pentenoate, maleic anhydride, citraconic acid, itaconic acid, fumaric acid, and anhydride. More preferred are maleic acid, aconitic acid, phenylmaleic acid, chloromaleic acid, muconic acid or maleic acid monoalkyl esters, and even more preferred are methyl methacrylate, citraconic acid and itaconic acid.

The modified PVA (A) preferably has 0.01 mol % or more and less than 5 mol % of double bonds derived from unsaturated carboxylic acids or derivatives thereof in side chains. Here, the modified PVA (A) has 0.01 mol% or more and less than 5 mol% of double bonds derived from an unsaturated carboxylic acid or a derivative thereof in the side chain means that the modified PVA (A) has an unsaturated carboxylic acid or a derivative thereof. It means that the side chain has a double bond derived from an acid or a derivative thereof, and the amount of the double bond is 0.01 mol % or more and less than 5 mol % with respect to all monomer units.

When the amount of the double bond is less than 0.01 mol %, the film after being irradiated with ultraviolet rays tends to have a high swelling rate and elution rate in water, resulting in insufficient water resistance. The amount of the double bond is more preferably 0.03 mol % or more, still more preferably 0.05 mol % or more. On the other hand, the modified PVA (A) having a double bond content of 5 mol % or more is difficult to produce, and even if it can be produced, the productivity tends to be low. The amount of the double bond is more preferably 4.5 mol % or less, still more preferably 4 mol % or less, and particularly preferably 3.5 mol % or less. The above double bond means a carbon-carbon double bond.

The amount of double bonds derived from unsaturated carboxylic acid or its derivative in modified PVA (A) can be measured by a known method. Specifically, measurement by ¹ H-NMR is convenient. When measuring the amount of the double bond, it is preferable to remove the unreacted unsaturated carboxylic acid or derivative thereof in advance and perform purification. The purification method is not particularly limited, and a method of washing with a solution in which the modified PVA (A) does not dissolve and the unreacted unsaturated carboxylic acid or its derivative can dissolve is also possible. , After making an aqueous solution with a concentration of about 1 to 20% by mass, the modified PVA (A ) is simple and preferable for refining by precipitating.

It is important that the modified PVA (A) has a viscosity average degree of polymerization of 200 or more, preferably 250 or more, and more preferably 300 or more. If the viscosity-average degree of polymerization is less than 200, the solubility in water is high, and the swelling rate and elution rate in water of the film after irradiation with ultraviolet rays are high, resulting in insufficient water resistance. On the other hand, it is important that the modified PVA (A) has a viscosity average degree of polymerization of 4,500 or less, preferably 4,000 or less, and more preferably 3,000 or less. If the viscosity-average degree of polymerization exceeds 4500, production is difficult, and even if production is possible, the productivity tends to be low. The viscosity average degree of polymerization is a value obtained by measuring according to JIS-K6726 (1994). Specifically, when the degree of saponification is less than 99.5 mol%, the intrinsic viscosity [η] (liter/ g) was used to determine the viscosity-average degree of polymerization (P) according to the following formula.
P=([η]×10 ⁴ /8.29) ^(1/0.62)

From the viewpoint of water solubility of the modified PVA (A), it is important that the degree of saponification of the modified PVA (A) is 65 mol% or more, preferably 68 mol% or more, more preferably 70 mol% or more. If the degree of saponification is less than 65 mol%, the solubility in water will be insufficient. On the other hand, it is important that the degree of saponification of the modified PVA (A) is 99.9 mol% or less, preferably 99.5 mol% or less. If the degree of saponification exceeds 99.9 mol%, production is difficult, and even if production is possible, the productivity tends to be low. The degree of saponification is a value obtained by measuring according to JIS-K6726 (1994).

It is important that the modified PVA (A) has a 1,2-glycol bond content of 1.4 mol % or more, preferably 1.5 mol % or more, and more preferably 1.6 mol % or more. Modified PVA (A) having a 1,2-glycol bond content of less than 1.4 mol % has high crystallinity and insufficient solubility in water. On the other hand, it is important that the modified PVA (A) has a 1,2-glycol bond content of less than 1.9 mol %, preferably 1.8 mol % or less, more preferably 1.7 mol % or less. Modified PVA (A) having a 1,2-glycol bond content of 1.9 mol % or more has low crystallinity, and the obtained film has insufficient water resistance. Incidentally, the amount of 1,2-glycol bond can be obtained from the analysis of ¹ H-NMR spectrum as described in Examples below.

The method for adjusting the amount of 1,2-glycol bonds in modified PVA (A) is not particularly limited, but for example, vinylene carbonate is copolymerized so that the amount of 1,2-glycol bonds in PVA (E) is within the above range. and a method in which the polymerization temperature is set to a temperature higher than normal conditions, specifically, for example, 75 to 200° C., and polymerization is performed under pressure. In the latter method, the polymerization temperature is preferably 190°C or lower, more preferably 180°C or lower.

It is preferable that the modified PVA (A) further has ethylene units in its main chain and the content of the ethylene units is 1 mol % or more and less than 20 mol %. Here, having an ethylene unit in the main chain means that the modified PVA (A) has a structural unit (--(CH ₂ --CH ₂ )--) derived from an ethylene monomer in the main chain. The content of ethylene units means the number of moles of structural units derived from ethylene with respect to the number of moles of monomer units constituting the main chain of the modified PVA (A).

By setting the content of the ethylene unit to 1 mol % or more, the water resistance of the resulting film can be further improved. The ethylene unit content is more preferably 1.5 mol % or more, more preferably 2.5 mol % or more. On the other hand, when the content of ethylene units is 20 mol % or more, insoluble matter tends to occur when the modified PVA (A) is dissolved in water. The ethylene unit content is more preferably 10 mol % or less, and even more preferably 8 mol % or less. Modified PVA (A) having ethylene units in the main chain can be obtained by using PVA (ethylene-vinyl alcohol copolymer) having ethylene units in the main chain as PVA (E). Thus, the PVA (E) having an ethylene unit is obtained by copolymerizing a vinyl ester monomer and ethylene to obtain an ethylene-vinyl ester copolymer, and then saponifying the ethylene-vinyl ester copolymer. can be obtained by

The modified PVA (A) is preferably water-soluble. In the present specification, the modified PVA (A) being water-soluble means that an aqueous solution with a concentration of 4% by mass in which the modified PVA (A) is dissolved is obtained at a temperature of 98°C.

(Photoinitiator (B))
Although the photopolymerization initiator (B) used in the present invention is not particularly limited, benzophenones, thioxanthones, acetophenones, acylphosphines, benzoin alkyl ethers, anthraquinones, benzils, diacetyls, ketals, and metallocenes. initiators such as Among them, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[ 4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methylpropane is preferred, and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methylpropane is more preferred.

The content of the photopolymerization initiator (B) is preferably 0.001 parts by mass or more and less than 10 parts by mass relative to the modified PVA (A). If the content of the photopolymerization initiator (B) is less than 0.001 parts by mass, the water resistance of the film tends to be insufficient after being irradiated with ultraviolet rays. The content of the photopolymerization initiator (B) is preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, and even more preferably 0.05 parts by mass or more. On the other hand, when the content of the photopolymerization initiator (B) is 10 parts by mass or more, the photopolymerization initiator (B) tends to bleed out during film formation. The content of the photopolymerization initiator (B) is preferably 8 parts by mass or less, more preferably 5 parts by mass or less.

(Compound (C))
The photosensitive resin composition (D) of the present invention further contains a compound (C), and the compound (C) has a conjugated double bond and is bonded to a carbon atom constituting the conjugated double bond. It is important that it is at least one selected from the group consisting of a compound having two or more hydroxyl groups or a salt thereof or an oxide thereof (C1); a cyclic nitroxyl radical (C2); and alkoxyphenol (C3); .

The content of the compound (C) is not particularly limited, and is preferably 0.001 parts by mass or more and less than 5 parts by mass relative to the modified PVA (A). If the content of compound (C) is less than 0.001 parts by mass, insoluble matter tends to form when the resulting modified PVA (A) is dissolved in water. The content of compound (C) is more preferably 0.005 parts by mass or more, still more preferably 0.01 parts by mass or more, and particularly preferably 0.05 parts by mass or more. On the other hand, when the content of the compound (C) is 5 parts by mass or more, the film tends to have insufficient water resistance after being irradiated with ultraviolet rays. The content of compound (C) is more preferably 3 parts by mass or less, still more preferably 2 parts by mass or less, and particularly preferably 1 part by mass or less.

The compound having a conjugated double bond and having two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1) used in the present invention includes carbon-carbon two Examples include conjugated polyenes having a structure in which heavy bonds and carbon-carbon single bonds are alternately connected. Compounds with conjugated double bonds include not only conjugated polyenes, but also aromatic hydrocarbons such as benzene, and α,β-unsaturated compounds having a carbon-carbon double bond conjugated with a carbonyl group in the molecule. Carbonyl compounds are also included. Among these, the compound (C1) is a compound in which two or more hydroxyl groups are bonded to the carbon atoms constituting the aromatic ring, or a salt thereof, or An oxide is preferable, and a compound in which two or more hydroxyl groups are bonded to the α- and β-positions of an α,β-unsaturated carbonyl compound, a salt thereof, or an oxide thereof is also preferable. Examples of compounds in which two or more hydroxyl groups are bonded to carbon atoms constituting an aromatic ring include polyphenols. Examples of the polyphenol include pyrogallol, phloroglucinol, hydroxyquinol, hydroxybenzene such as hexahydroxybenzene; phenol carboxylic acid such as gallic acid; phenol carboxylic acid ester such as gallic acid alkyl ester; Examples include catechins such as catechin-3-gallate. Gallic acid alkyl esters include methyl gallate, ethyl gallate, propyl gallate, octyl gallate, and dodecyl gallate. Among these, compound (C1) is preferably phenolcarboxylic acid or phenolcarboxylic acid ester, more preferably gallic acid or gallic acid alkyl ester, and still more preferably gallic acid alkyl ester.

The cyclic nitroxyl radical (C2) used in the present invention has a heterocyclic ring formed from carbon atoms and heteroatoms, and the nitrogen atom of the nitroxyl radical (=N-O) forms part of the ring. Refers to the compound that forms. Examples of the heteroatom constituting the ring include nitrogen atom, oxygen atom, phosphorus atom, sulfur atom and the like. The number of atoms forming the ring is usually 5 or 6. A substituent such as an alkyl group, a hydroxyl group, a carboxyl group, a sulfo group, or a halogen group may be bonded to the atoms forming the ring. The number of substituents and the bonding positions of the substituents are not particularly limited, and a plurality of substituents may be bonded to the same or different atoms. The cyclic nitroxyl radical is 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) or its Derivatives are preferred. As the TEMPO derivative, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl is preferably used.

Alkoxyphenol (C3) used in the present invention is preferably a compound in which one hydrogen atom in the benzene ring is substituted with an alkoxy group and one hydrogen atom is substituted with a hydroxyl group. At this time, the bonding position of the alkoxy group is not particularly limited, but it is preferably at the ortho or para position from the viewpoint of further reducing the insoluble content in water in the modified PVA (A) obtained, and is preferably at the para position. It is more preferable to have Preferred alkoxyphenols include methoxyphenol, ethoxyphenol, propoxyphenol, butoxyphenol and the like. Among them, methoxyphenol and ethoxyphenol are preferable, and methoxyphenol is more preferable, from the viewpoint that the resulting modified PVA (A) has a good hue and is excellent in water solubility.

The powder composed of the photosensitive resin composition (D) of the present invention preferably has a yellow index (hereinafter sometimes abbreviated as “YI”) of less than 40. When YI is 40 or more, insoluble matter tends to be generated when dissolved in water. YI is more preferably 30 or less, more preferably 25 or less, and particularly preferably 20 or less. YI in this specification is a value measured and calculated according to JIS-Z8722 (2009) and JIS-K7373 (2006).

[Method for producing photosensitive resin composition (D)]
The method for producing the photosensitive resin composition (D) of the present invention is not particularly limited. to obtain a composition containing the modified PVA (A) and the compound (C), and mixing the composition with the photopolymerization initiator (B).

The method for mixing the composition containing the modified PVA (A) and the compound (C) with the photopolymerization initiator (B) is not particularly limited, but (i) the modified PVA (A) and the compound (C) A method of mixing the containing powder and a powdery photopolymerization initiator (B); (ii) a solution of a composition containing the modified PVA (A) and the compound (C) and a powdery photopolymerization initiator (B); (iii) a method of mixing a powdery composition containing modified PVA (A) and compound (C) with a solution of photopolymerization initiator (B); (iv) A method of mixing a solution of a composition containing the modified PVA (A) and the compound (C) and a solution of the photopolymerization initiator (B) can be mentioned. Among them, the above method (i) is preferable because the manufacturing method is simple.

The main component of the composition containing the modified PVA (A) and the compound (C) or the solvent for dissolving the photopolymerization initiator (B) is preferably water, and may contain other components other than water. Other ingredients include hydrophilic solvents. Examples of hydrophilic solvents include alcohols such as methanol, ethanol and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; cellosolves; carbitols;

[Coating agent]
A coating agent containing the photosensitive resin composition (D) of the present invention and water is also a preferred embodiment of the present invention. Specific examples of the coating agent include coating agents for forming overcoat layers and thermosensitive coloring layers in thermal recording materials, clear coating agents, white or colored coating agents containing pigments, etc., and inkjet recording materials. Coating agents for forming ink-receiving layers, coating agents for forming filler layers in base paper for release paper, and the like.

The photosensitive resin composition (D) of the present invention can also be used for applications other than coating agents, such as printing plate materials, adhesives, thickeners, film materials, and the like.

[Coating]
A coated product obtained by applying the above coating agent to the surface of a substrate is also a preferred embodiment of the present invention. Examples of coated materials include heat-sensitive recording materials, inkjet recording materials, base paper for release paper, and other coated papers. Moreover, the manufacturing method of the said coated material has the process of coating the said coating agent on a base-material surface. The above-described coated product can be easily obtained by such a manufacturing method.

The base material is not particularly limited, but includes paper (including synthetic paper), cloth, wood board, metal plate, film, and the like. Among them, paper is preferable from the viewpoint of allowing the coating agent to permeate into the inside of the base material and suitably increasing the water resistance and the like.

The coating method is not particularly limited, and known methods such as size press, air knife coater, roll coater, bar coater, blade coater, curtain coater and cast coater can be employed.

The coated article usually has a base material and a coating layer (film) obtained by applying the coating agent to at least one surface of the base material, but between the base material and the coating layer Alternatively, another layer may be formed on the surface of the coating layer. However, it is preferable that the coating layer is formed on the outermost surface in order to suitably exhibit the excellent water resistance and the like of the coated product.

[Thermal recording material]
A heat-sensitive recording material comprising the above coated material is also a preferred embodiment of the present invention. A heat-sensitive recording material has a layer structure in which, for example, a substrate, a heat-sensitive coloring layer and an overcoat layer are laminated in this order. At least one of the thermosensitive coloring layer and the overcoat layer is preferably formed as a coating layer by applying the coating agent.

As the base material for the heat-sensitive recording material, both 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 films, sheets, highly transparent paper, and the like. Examples of the opaque supporting substrate include ordinary paper, pigment-coated paper, cloth, wood, metal plate, synthetic paper, opacified synthetic resin film and sheet. Among these, paper is preferable from the viewpoint of allowing the coating agent to permeate into the inside of the base paper and suitably enhancing the water resistance and the like.

When the above coating agent is used as an overcoat layer or a thermosensitive coloring layer of a thermosensitive recording material, other components than the photosensitive resin composition (D) of the invention and water are added to the extent that the effects of the invention are not impaired. may contain. Other components include cross-linking agents, water-soluble resins, water-dispersible resins, lubricants and fillers when forming an overcoat layer, and thermal dyes and color developers when forming a thermosensitive coloring layer. agents, cross-linking agents, water-soluble resins, water-dispersible resins, lubricants and fillers.

Examples of the cross-linking agent include aldehyde compounds such as glyoxal and glutaraldehyde, and polyoxazoline. When the composition for forming the thermosensitive coloring layer, the overcoat layer, and the like further contains the above-described crosslinking agent, the obtained thermosensitive recording material can be further improved in water resistance, blocking resistance, and the like.

Examples of the water-soluble resin include starch and derivatives thereof, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose, gum arabic, polyvinyl alcohol, alkali metal salts of polyacrylic acid (sodium salts, etc.), polyvinyl Pyrrolidone, (meth)acrylamide-(meth)acrylic acid ester copolymer, (meth)acrylamide-(meth)acrylic acid ester-(meth)acrylic acid terpolymer, styrene-maleic anhydride copolymer alkali Metal salts (sodium salts, etc.), alkali metal salts (sodium salts, etc.) of isobutylene-maleic anhydride copolymers, polyacrylamides, sodium alginate, gelatin, casein and the like.

Examples of the water-dispersible resin include polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer. coalescence, styrene-butadiene-acrylic acid copolymer, and the like.

Examples of the lubricant include higher fatty acid, higher fatty acid amide, higher fatty acid metal salt, paraffin wax, microcrystalline wax and the like.

Examples of the filler include calcium carbonate, zinc oxide, aluminum oxide, colloidal alumina, aluminum hydroxide, pseudoboehmite, satin white, organic pigments, polystyrene fine particles, polyvinyl acetate fine particles, urea-formalin resin fine particles, and the like. .

Examples of the heat-sensitive dyes 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-ethylcarbazol-3-yl) -triarylmethane compounds such as 5-dimethylaminophthalide; 4,4'-bisdimethylaminobenzhydrin benzyl ether, diphenylmethane compounds such as N-halophenyl leuco auramine; 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, xanthene compounds such as 3-dibutylamino-6-methyl-7-anilinofluorane; thiazine compounds such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue; 3-methyl -spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methylnaphtho-(3-methoxy-benzo)-spiro-based compounds, and the like. These heat-sensitive dyes are appropriately selected depending on the use of the heat-sensitive recording material, etc., and may be used alone or in combination of two or more.

As the developer, phenol derivatives and aromatic carboxylic acid derivatives are preferred, and bisphenols are particularly preferred. Examples of phenol derivatives 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)-2- ethyl-hexane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, dihydroxydiphenyl ether and the like. Examples of aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzyl Examples include salicylic acid and polyvalent metal salts of the above carboxylic acids.

The content of these other components in the coating agent is usually 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 parts by mass or less, with respect to 100 parts by mass of the modified PVA (A). It is more preferably not more than 10 parts by mass, and particularly preferably not more than 10 parts by mass.

The coating amount of the coating agent, for example, in the case of an overcoat layer, is appropriately selected to the extent that heat conduction from the thermal head of the thermal recording device to the thermal coloring layer of the thermal recording material is not hindered. The conversion is 1 to 10 g/m ² , preferably 2 to 7 g/m ² .

The heat-sensitive recording material may have other layers in addition to the base material, the heat-sensitive coloring layer and the overcoat layer. The other layer may include an undercoat layer between the substrate and the thermosensitive coloring layer. Even in such a case, the heat-sensitive recording material can exhibit high water resistance and blocking resistance.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples. In the examples, "%" and "parts" mean "% by mass" and "parts by mass", respectively, unless otherwise specified.

[Viscosity average degree of polymerization of PVA]
The viscosity average degree of polymerization of PVA was measured according to JIS-K6726 (1994). Specifically, when the saponification degree is less than 99.5 mol%, the intrinsic viscosity [η] (liter/g ) was used to determine the viscosity-average degree of polymerization (P) according to the following formula.
P=([η]×10 ⁴ /8.29) ^(1/0.62)

[Saponification degree of PVA]
The degree of saponification of PVA was measured according to JIS-K6726 (1994).

[Amount of double bonds introduced into modified PVA (A)]
For modified PVA (A), the amount of double bonds introduced into modified PVA (A) was measured using ¹ H-NMR. The amount of double bonds is the amount of double bonds with respect to all monomer units of the modified PVA (A).

[1,2-glycol bond amount of modified PVA (A)]
A methanol solution of sodium hydroxide was added to each of PVA (E) used in the following examples and modified PVA (A) obtained, and the mixture was kept at 60° C. for 5 hours to resaponify PVA. At this time, the amount of sodium hydroxide was adjusted to 0.1 mol per 1 mol of the vinyl alcohol unit of PVA. The obtained PVA was subjected to Soxhlet extraction with methanol for 1 week to obtain purified PVA having a degree of saponification of 99.9 mol % or more.

The purified PVA obtained by the above method was dried under reduced pressure at 90° C. for 2 days to completely remove methanol. Then, the purified PVA was dissolved in dimethylsulfoxide-d ₆ to form a 0.1% by mass solution, several drops (about 0.1 ml) of trifluoroacetic acid were added to the solution, and ¹ H-NMR was measured. The amount of 1,2-glycol bonds contained in purified PVA (the content of monomer units bonded by 1,2-glycol bonds) is a peak of 3.2 to 4.0 ppm derived from methine protons of vinyl alcohol units. It is calculated according to the following formula (I) from (integral value α) and the peak at 3.25 ppm (integral value β) derived from one methine proton of the 1,2-glycol bond unit. Here, since the 1,2-glycol bond amount of PVA does not change before and after resaponification, the value obtained by the following formula (I) is the 1,2-glycol bond amount of each PVA.
Content of 1,2-glycol bond units in PVA (mol%) = 100 × β/α (I)

[Evaluation of water solubility of modified PVA (A)]
The resulting modified PVA (A) was dissolved in water at 98° C. to prepare a 4% by mass aqueous solution. The aqueous solution was visually confirmed and evaluated according to the following evaluation criteria.
None: dissolved at 98°C.
Yes: Insoluble matter was generated in the liquid at 98°C.

[Yellow index (YI) of powder composed of photosensitive resin composition (D)]
The yellow index (YI) of the powder made of the photosensitive resin composition (D) is less than 100 μm and After removing powder exceeding 1000 μm, measurement was performed using a color meter (SM-T-H1 manufactured by Suga Test Instruments Co., Ltd.). The yellow index is a value measured and calculated according to JIS-Z8722 (2009) and JIS-K7373 (2006).

[Swelling rate, elution rate and water resistance of film made of photosensitive resin composition (D)]
A 4% by mass aqueous solution of the photosensitive resin composition (D) was prepared, 62 g of the solution was poured onto a 20 cm×20 cm PET film, and air-dried at 20° C. and 65% humidity for 7 days. The film made of the prepared photosensitive resin composition (D) was peeled off from the PET film and cut into a size of 5 cm×8 cm. This film was irradiated with ultraviolet rays for 90 seconds at an intensity of 20 μW/cm ² using a Handy Cure Rub (HLR100T-2, Sen Special Light Source Co., Ltd.).

A film made of the photosensitive resin composition (D) after irradiation with ultraviolet rays was immersed in 100 g of distilled water and left at 20° C. overnight. After removing excess moisture from the film, the film was dried in a hot air dryer at 105°C for 3 hours. The elution rate of the film in water was calculated from the film mass before immersion and the film mass after drying, and the swelling rate of the film in water from the film mass after immersion and after drying was calculated from the following equations.
Elution rate (%) = 100 × {(film weight before immersion) - (film weight after drying)} / (film weight before immersion)
Swelling rate (times) = (film weight after immersion) / (film weight after drying)

Also, based on the results of the elution rate and swelling rate, comprehensive water resistance was evaluated according to the following evaluation criteria.
A: Swelling rate 0-3 times, elution rate 0-10 mass% B: Swelling rate 3-20 times, elution rate 10-60 mass% C: Swelling rate is 20 times or more, and the elution rate is 60% by mass or more

[Example 1]
(Production of modified PVA (A))
100 parts by mass of powdery PVA having a viscosity average polymerization degree of 1700, a saponification degree of 98.0 mol%, an ethylene modification amount of 4 mol%, and a 1,2-glycol bond amount of 1.6 mol% as PVA (E) in the flask. , 2.95 parts by mass of itaconic acid as an unsaturated carboxylic acid or derivative thereof, and 0.1 part by mass of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a compound (C) are added and mixed. After that, the solid was heat-treated under stirring for 1 hour at 85°C, 1 hour at 90°C, and 4 hours at 120°C to carry out a reaction to obtain a composition containing the modified PVA (A) and the compound (C). Obtained.

The obtained composition containing modified PVA (A) was purified by reprecipitation, and ¹ H-NMR measurement was performed. was 98.0 mol %, the viscosity average degree of polymerization was 1700, the amount of ethylene modification was 4 mol %, and the amount of 1,2-glycol bond was 1.6 mol %. Table 2 shows the results.

(Preparation of photosensitive resin composition (D))
1-[4-(2-hydroxy ethoxy)-phenyl]-2-hydroxy-2-methylpropane) was added in powder form to prepare a photosensitive resin composition (D). YI of the obtained powder composed of the photosensitive resin composition (D) was 13. Furthermore, the swelling rate, elution rate and water resistance of the resulting film composed of the photosensitive resin composition (D) were evaluated according to the methods described above. Table 2 shows the results.

[Examples 2 to 5, 7 to 9, Comparative Examples 2 and 4]
The procedure was the same as in Example 1 except that the type of PVA (E), the type and amount of unsaturated carboxylic acid or derivative thereof, the type and amount of compound (C), and the heat treatment conditions were changed as shown in Table 1. to obtain a photosensitive resin composition (D). The YI of the powder composed of the obtained photosensitive resin composition (D), and the swelling rate, elution rate and water resistance of the film composed of the obtained photosensitive resin composition (D) were evaluated according to the methods described above. . Table 2 shows the results.

[Example 6]
A separable flask was charged with 500 parts by mass of dimethyl sulfoxide (DMSO), PVA (E) having a viscosity average polymerization degree of 1000, a saponification degree of 99.5 mol%, an ethylene modification amount of 6 mol%, and a 1,2-glycol bond amount of 1.5%. 100 parts by mass of 6 mol % PVA was added, and the temperature was raised to 105° C. while stirring to obtain a homogeneous solution. 23 parts by mass of methyl methacrylate as unsaturated carboxylic acid or derivative thereof, 0.2 parts by mass of propyl gallate as compound (C), and 0.2 parts by mass of phenothiazine are added to the uniform solution and stirred until uniform. did. After the mixture became homogeneous, 1.9 parts by mass of sodium acetate was added as a transesterification catalyst, reacted at 105°C for 5 hours, and then allowed to cool to room temperature. After diluting the reaction solution by adding 100 parts by mass of DMSO, the solution was added dropwise to 1000 parts by mass of methanol to precipitate modified PVA. The precipitated modified PVA was washed twice with 1000 parts by mass of methanol, and then vacuum dried to obtain modified PVA (A). Table 2 shows the analytical results of the obtained modified PVA (A). Furthermore, a photosensitive resin composition (D) was obtained in the same manner as in Example 1, except that the type of modified PVA (A) was changed. The YI of the powder composed of the obtained photosensitive resin composition (D), and the swelling rate, elution rate and water resistance of the film composed of the obtained photosensitive resin composition (D) were evaluated according to the methods described above. . Table 2 shows the results.

[Comparative Example 1]
1-[ 1 part by mass of 4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methylpropane was added in powder form to prepare a photosensitive resin composition (D). The YI of the powder composed of the obtained photosensitive resin composition (D), and the swelling rate, elution rate and water resistance of the film composed of the obtained photosensitive resin composition (D) were evaluated according to the methods described above. . Table 2 shows the results.

[Comparative Example 3]
1-[4-(2-hydroxy 1 part by mass of ethoxy)-phenyl]-2-hydroxy-2-methylpropane was added in powder form to prepare a photosensitive resin composition (D). The YI of the powder composed of the obtained photosensitive resin composition (D), and the swelling rate, elution rate and water resistance of the film composed of the obtained photosensitive resin composition (D) were evaluated according to the methods described above. . Table 2 shows the results.

Claims (9)

A photosensitive resin composition (D) containing a modified polyvinyl alcohol (A) having a double bond derived from an unsaturated carboxylic acid or a derivative thereof in a side chain, a photopolymerization initiator (B) and a compound (C). hand;
A compound (C) having a conjugated double bond and two or more hydroxyl groups bonded to carbon atoms constituting the conjugated double bond, or a salt or oxide thereof (C1); Cyclic nitroxyl radical (C2); and alkoxyphenol (C3); at least one selected from the group consisting of
The modified polyvinyl alcohol (A) has a viscosity average polymerization degree of 200 or more and 4500 or less, a saponification degree of 65 mol% or more and 99.9 mol% or less, and a 1,2-glycol bond amount of 1.4 mol% or more. less than .9 mol % ;
Modified polyvinyl alcohol (A) has 0.01 mol% or more and less than 5 mol% of a double bond derived from an unsaturated carboxylic acid or a derivative thereof in the side chain,
A photosensitive resin composition (D) in which the content of the compound (C) is 0.05 parts by mass or more and less than 5 parts by mass with respect to 100 parts by mass of the modified polyvinyl alcohol (A ). A compound having a conjugated double bond and having two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, a salt thereof, or an oxide thereof (C1) has a hydroxyl group at the carbon atom constituting the aromatic ring. The photosensitive resin composition (D) according to claim 1, which is a compound in which two or more are bonded or a salt thereof or an oxide thereof. A compound having a conjugated double bond and having two or more hydroxyl groups bonded to carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1) is an α,β-unsaturated carbonyl compound. 2. The photosensitive resin composition (D) according to claim 1, which is a compound having two or more hydroxyl groups bonded to the α-position and β-position, or a salt thereof or an oxide thereof. The photosensitive resin composition according to any one of claims 1 to 3 , wherein the modified polyvinyl alcohol (A) further has ethylene units in its main chain, and the content of the ethylene units is 1 mol% or more and less than 20 mol%. Thing (D). A powder comprising the photosensitive resin composition (D) according to any one of claims 1 to 4 , which has a yellow index of less than 40. A coating agent comprising the photosensitive resin composition (D) according to any one of claims 1 to 4 and water. A coated product obtained by applying the coating agent according to claim 6 to the surface of a substrate. A heat-sensitive recording material comprising the coated material according to claim 7 . a step of reacting polyvinyl alcohol (E) with an unsaturated carboxylic acid or a derivative thereof in the presence of compound (C) to obtain a composition containing modified polyvinyl alcohol (A) and compound (C); 5. The method for producing the photosensitive resin composition (D) according to any one of claims 1 to 4 , comprising the step of mixing the composition and the photopolymerization initiator (B).