JP2010175650A - Polarizing plate and method for producing same - Google Patents

Abstract

（式中、Ｒ¹は水素原子又は炭素数１〜４のアルキル基を示し、Ａ¹、Ａ²は、同一又は異なって、２価の有機基を示し、Ｘ¹、Ｘ²は、同一又は異なって、酸素原子、硫黄原子、又は−ＮＲ²−基を示す。Ｒ²は水素原子又は炭素数１〜６のアルキル基を示す。ｎは０又は１を示す）で表される基が挙げられる。
【選択図】 なしPROBLEM TO BE SOLVED: To provide a polarizing plate in which a protective film is transparent and birefringence hardly changes even when stress is applied.
A polarizing plate of the present invention is a polarizing plate having a structure in which at least one surface of a polarizer is protected by a protective film made of a resin, wherein the resin has a part of a hydroxyl group of a glucose skeleton with an unsaturated carboxylic acid. It is a cured product of an active energy ray-curable resin composition containing a cellulose derivative substituted with a group containing an acid acyl group. As a group containing an unsaturated carboxylic acyl group, the following formula (1)
[Chemical 1]

(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, A ¹ and A ² are the same or different and represent a divalent organic group, and X ¹ and X ² are the same or Differently, it represents an oxygen atom, a sulfur atom, or a —NR ² — group, R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents 0 or 1). It is done.
[Selection figure] None

Description

  The present invention relates to a polarizing plate used for a liquid crystal display device and the like and a method for producing the same.

  The polarizing plate is used as a polarized light supplying element and a polarized light detecting element in a liquid crystal display device. Conventionally, as a polarizing plate, a film in which a protective film made of triacetyl cellulose (TAC) is bonded to at least one surface of a polarizer made of a stretched polyvinyl alcohol (PVA) film doped with iodine or the like has been used. . In this case, if birefringence is present in the protective film itself, the function as a polarizing plate is greatly reduced. To prevent this, a TAC film without optical anisotropy prepared by a solvent casting method is used. .

  In such a conventional polarizing plate, since the PVA film is stretched at a high magnification, a large stress is generated in a relaxing direction. The protective film needs to be rigid enough to withstand this stress, but when TAC is used as a protective film, the shrinkage stress of the polarizer at the periphery of the film is superior to that of TAC in large screen applications such as liquid crystal TVs. As a result, deformation occurs, and color loss may occur due to the birefringence of the TAC protective film.

  JP-A-2005-92112 proposes a cured product of an active energy ray-curable resin composition as an alternative to a TAC protective film. According to this technique, a polarizing plate having small birefringence and excellent heat and moisture resistance can be obtained. However, if the birefringence is small, the birefringence changes at the location where the contraction stress of the polarizer is large, and the function as a polarizing plate is impaired.

JP 2005-92112 A

  An object of the present invention is to provide a polarizing plate in which a protective film is transparent and birefringence hardly changes even when stress is applied, and a method for producing the same.

  As a result of intensive studies to achieve the above object, the present inventors have at least one surface of a polarizer protected by a protective film made of a cured product of an active energy ray-curable resin composition containing a specific resin. The present inventors have found that the protective film is transparent and birefringence hardly changes even when stress is applied.

  That is, the present invention provides a polarizing plate having a structure in which at least one surface of a polarizer is protected by a protective film made of a resin, wherein the resin includes a part of hydroxyl groups of a glucose skeleton containing an unsaturated carboxylic acyl group. A polarizing plate characterized by being a cured product of an active energy ray-curable resin composition containing a cellulose derivative substituted with a group.

（式中、Ｒ¹は水素原子又は炭素数１〜４のアルキル基を示し、Ａ¹、Ａ²は、同一又は異なって、２価の有機基を示し、Ｘ¹、Ｘ²は、同一又は異なって、酸素原子、硫黄原子、又は−ＮＲ²−基を示す。Ｒ²は水素原子又は炭素数１〜６のアルキル基を示す。ｎは０又は１を示す）
で表される基が含まれる。 The group containing the unsaturated carboxylic acyl group includes the following formula (1):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, A ¹ and A ² are the same or different and represent a divalent organic group, and X ¹ and X ² are the same or Differently, it represents an oxygen atom, a sulfur atom, or a —NR ² — group, R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents 0 or 1.
The group represented by these is included.

  The cellulose derivative is preferably at least one selected from methyl cellulose derivatives, ethyl cellulose derivatives, and cellulose acetate derivatives.

  The present invention also provides an active energy ray-curable resin composition containing a cellulose derivative in which a hydroxyl group of a glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group on at least one surface of a polarizer. After manufacturing, the active energy ray-curable resin composition is cured to form a protective film, and a method for producing a polarizing plate is provided.

  According to the polarizing plate of the present invention, since a cured product of an active energy ray-curable resin composition containing a specific resin is used as a protective film for a polarizer, the protective film is transparent and birefringence changes even when stress is applied. Hard to do. Moreover, birefringence is also small. According to the production method of the present invention, a polarizing plate having such excellent characteristics can be produced easily.

  The polarizing plate of the present invention has a structure in which at least one surface of the polarizer is protected by a protective film made of resin. The polarizer is not particularly limited, and a film obtained by doping and stretching iodine, a dichroic dye on a substrate such as polyvinyl alcohol (PVA), an acetalized product thereof, an ethylene-vinyl acetate copolymer, a saponified product thereof, or the like, or A film obtained by cross-linking them can be used. Among these, an iodine-containing polyvinyl alcohol film obtained by doping polyvinyl alcohol with iodine and crosslinked with boric acid or the like is particularly preferable.

  In the present invention, a cured product of an active energy ray-curable resin composition containing a cellulose derivative in which a hydroxyl group of a glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group as a resin constituting the protective film Is used. Cellulose derivatives in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group can be used alone or in combination of two or more. In the present specification, the active energy ray-curable resin composition means a composition capable of forming a resin cured by irradiation with active energy rays.

  As a cellulose derivative in which a part of hydroxyl groups of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group, a part of hydroxyl groups at the 2nd, 3rd and 6th positions of the glucose skeleton in the molecule are unsaturated carboxylic acids. Any radically curable cellulose derivative substituted with a group containing an acid acyl group is not particularly limited. Examples of the unsaturated carboxylic acid acyl group include unsaturated carboxylic acids having about 3 to 10 carbon atoms such as acryloyl group, methacryloyl group, α-ethylacryloyl group, α-propylacryloyl group, α-butylacryloyl group, and crotonic acid acyl group. An acyl group etc. are mentioned.

As a typical example of a group containing an unsaturated carboxylic acyl group, a group represented by the above formula (1) can be mentioned. In Formula (1), R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, A ¹ and A ² are the same or different and represent a divalent organic group, and X ¹ and X ² are It is the same or different and represents an oxygen atom, a sulfur atom, or a —NR ² — group. R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. n represents 0 or 1.

Examples of the alkyl group having 1 to 4 carbon atoms in R ¹ include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl group and the like. R ¹ is particularly preferably a hydrogen atom or a methyl group.

As the divalent organic group for A ¹ and A ² , a divalent hydrocarbon group, a divalent heterocyclic group, or two or more of these groups are bonded directly or via one or two or more linking groups. A divalent group.

  Examples of the divalent hydrocarbon group include linear or branched C 1-20 carbon atoms such as methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octamethylene, decamethylene, and dodecamethylene groups. Alkylene group; 3- to 15-membered divalent alicyclic hydrocarbon group such as cyclopentylene, cyclohexylene, cyclooctylene, pentylidene, hexylidene, adamantanediyl group (cycloalkylene group, divalent bridged alicyclic ring) Formula groups and the like); arylene groups such as phenylene and naphthylene groups; and divalent groups in which two or more of these are bonded.

  The divalent heterocyclic group was selected from oxygen atoms, sulfur atoms and nitrogen atoms such as oxirane ring, oxetane ring, oxolane ring, pyrrolidine ring, piperidine ring, furan ring, thiophene ring, pyridine ring and quinoline ring. And a group obtained by removing two hydrogen atoms from an aromatic or non-aromatic ring containing at least one heteroatom.

  The divalent hydrocarbon group and divalent heterocyclic group may have a substituent. Examples of the substituent include a halogen atom such as a fluorine atom and a chlorine atom; an alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl and butyl groups; and 1 to 6 carbon atoms such as trifluoromethyl group. A haloalkyl group of 1 to 6 carbon atoms such as methoxy, ethoxy, propoxy, isopropyloxy and butoxy groups; an acyl group having 1 to 10 carbon atoms such as acetyl, propionyl and benzoyl groups; acetoxy, propionyloxy and benzoyloxy And an acyloxy group having 1 to 10 carbon atoms such as (meth) acryloyloxy group; an alkoxycarbonyl group having 2 to 6 carbon atoms such as methoxycarbonyl and ethoxycarbonyl group; a nitro group; and a cyano group.

Examples of the linking group include —O—, —S—, —NR ³ —, —CO—, and the like. R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

Examples of the alkyl group having 1 to 6 carbon atoms in R ² and R ³ include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl groups.

  Examples of the cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group include a cellulose ether derivative in which a part or all of the remaining hydroxyl group of the glucose skeleton is etherified, glucose Cellulose organic acid ester derivatives in which some or all of the remaining hydroxyl groups of the skeleton are organic acid ester, cellulose inorganic acid ester derivatives in which some or all of the remaining hydroxyl groups of the glucose skeleton are inorganic acid ester, glucose Examples thereof include a cellulose carbamate derivative in which part or all of the remaining hydroxyl groups of the skeleton are carbamated, and a cellulose acetal derivative in which part or all of the remaining hydroxyl groups of the glucose skeleton are acetalized.

  Cellulose ether derivatives include methyl cellulose derivatives, ethyl cellulose derivatives, carboxymethyl cellulose derivatives, cyanoethyl cellulose derivatives, hydroxyethyl cellulose derivatives, hydroxypropyl cellulose derivatives, ethyl hydroxyethyl cellulose derivatives, and the like. Cellulose organic acid ester derivatives include cellulose acetate derivatives, cellulose acetate propionate derivatives, cellulose acetate butyrate derivatives, cellulose acetate benzoate derivatives, and the like. Cellulose inorganic acid ester derivatives include cellulose nitrate derivatives, cellulose sulfate derivatives and the like. Cellulose carbamate derivatives include cellulose phenyl carbamate derivatives.

  Among these, cellulose ether derivatives and cellulose organic acid ester derivatives are preferable, and methyl cellulose derivatives, ethyl cellulose derivatives, and cellulose acetate derivatives are particularly preferable.

  In the cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group, the degree of substitution of the group containing an unsaturated carboxylic acyl group is, for example, 0.1 to 1.0, Preferably it is 0.2-0.6. In the cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group, the degree of substitution of substituents other than the group containing an unsaturated carboxylic acyl group is, for example, 2. It is 0-2.9, Preferably it is 2.4-2.8. These substitution degrees are appropriately selected in consideration of solvent solubility, handleability, optical characteristics, and the like.

  The cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group can be produced by using a known cellulose derivative as a raw material and utilizing a known reaction.

（式中、Ａ¹は前記に同じ）
で表されるポリイソシアネート化合物と、下記式（３）

（式中、Ｒ¹、Ａ²、Ｘ¹、Ｘ²は前記に同じ）
で表される不飽和カルボン酸誘導体とを反応させることにより製造できる。 For example, a cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group represented by the above formula (1) (where n = 1) is, for example, free A cellulose derivative having a hydroxyl group of the following formula (2)

(Wherein A ¹ is the same as above)
And a polyisocyanate compound represented by the following formula (3):

(Wherein R ¹ , A ² , X ¹ and X ² are the same as above)
It can manufacture by making the unsaturated carboxylic acid derivative represented by these react.

  Examples of cellulose derivatives having a free hydroxyl group include various cellulose derivatives having a substitution degree of less than 3, for example, cellulose ethers such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, cyanoethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose; cellulose acetate, Cellulose organic acid esters such as cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate benzoate; cellulose inorganic acid esters such as cellulose nitrate and cellulose sulfate; cellulose carbamates such as cellulose phenyl carbamate; cellulose acetals and the like. Among these, cellulose ether and cellulose organic acid ester are preferable, and methyl cellulose, ethyl cellulose, and cellulose acetate are particularly preferable.

  The polyisocyanate compound represented by the formula (2) is not particularly limited as long as it is a compound having at least two isocyanate groups in the molecule. Examples of the polyisocyanate compound include aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic polyisocyanate, and araliphatic polyisocyanate. A polyisocyanate compound can be used individually or in combination of 2 or more types.

  Examples of the aliphatic polyisocyanate include 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, and 3-methyl-1,5-penta. Methylene diisocyanate, 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 2,6-diisocyanate methylcaproate, lysine diisocyanate And aliphatic diisocyanates such as

  Examples of the alicyclic polyisocyanate include 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4′-methylenebis (cyclohexyl isocyanate). , Such as methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3-bis (isocyanate methyl) cyclohexane, 1,4-bis (isocyanate methyl) cyclohexane, isophorone diisocyanate, norbornane diisocyanate And formula diisocyanates.

  Examples of aromatic polyisocyanates include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and naphthylene. 1,4-diisocyanate, naphthylene-1,5-diisocyanate, 4,4'-diphenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane And aromatic diisocyanates such as isocyanate and 4,4'-diphenyl ether diisocyanate.

  Examples of the araliphatic polyisocyanate include 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, ω, ω′-diisocyanate-1,4-diethylbenzene, 1,3-bis. Aroaliphatic diisocyanates such as (1-isocyanate-1-methylethyl) benzene, 1,4-bis (1-isocyanate-1-methylethyl) benzene, 1,3-bis (α, α-dimethylisocyanatomethyl) benzene Etc.

  When an aliphatic polyisocyanate, an alicyclic polyisocyanate, or an araliphatic polyisocyanate is used as the polyisocyanate compound, a resin with little discoloration can be obtained. In the present invention, as the polyisocyanate compound, the above-exemplified aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic polyisocyanate, dimer or trimer by araliphatic polyisocyanate, reaction Products or polymers (eg, diphenylmethane diisocyanate dimers and trimers, reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate , Polyether polyisocyanate, polyester polyisocyanate, etc.) can also be used. As the polyisocyanate compound, alicyclic diisocyanates such as isophorone diisocyanate are particularly preferable.

  Moreover, as the polyisocyanate compound represented by the formula (2), a both-end isocyanate urethane prepolymer obtained by reacting polyols and polyisocyanate can also be used. Polyols include general polyols, polyether polyols, polyester polyols, polycarbonate polyols, and the like.

  Examples of the unsaturated carboxylic acid derivative represented by the formula (3) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl ( (Meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate and other terminal (meth) acrylic acid ester having a hydroxyl group; 2-aminoethyl (meth) acrylate and the like having an amino group (meth) Examples include acrylic acid esters or (meth) acrylic acid amides; (meth) acrylic acid esters having a mercapto group at the terminal, such as 2-mercaptoethyl (meth) acrylate. Among these, (meth) acrylic acid ester having a hydroxyl group at the terminal, such as 2-hydroxyethyl (meth) acrylate, is preferable.

  As a reaction sequence of the cellulose derivative having a free hydroxyl group, the polyisocyanate compound represented by the formula (2), and the unsaturated carboxylic acid derivative represented by the formula (3), (i) cellulose having a free hydroxyl group After reacting the derivative and the polyisocyanate compound represented by the formula (2) to produce a cellulose derivative having an isocyanate group at the terminal, an unsaturated carboxylic acid represented by the formula (3) is added to the reaction product. A method of reacting a derivative, (ii) an unsaturated carboxylic acid having an isocyanate group at a terminal by reacting a polyisocyanate compound represented by formula (2) with an unsaturated carboxylic acid derivative represented by formula (3) The method (i) may be any method such as a method in which a cellulose derivative having a free hydroxyl group is reacted with this reaction product after the derivative is formed. Because gelation is liable to proceed during the initial reaction, and more preferably the method of (ii).

  The cellulose derivative having a free hydroxyl group is preferably subjected to a dehydration treatment before use in the reaction in order to prevent deactivation of the polyisocyanate compound and system turbidity.

  For each of the above reactions, a method usually used for the reaction between a polyisocyanate compound and a compound having active hydrogen can be used. The reaction is carried out in an appropriate organic solvent such as butyl acetate. A catalyst such as a tin compound can also be used for the reaction. The reaction temperature is, for example, about 0 to 180 ° C, preferably about 20 to 150 ° C.

（式中、Ｒ¹、Ａ²、Ｘ²は前記に同じ）
で表される不飽和カルボン酸アシル基とイソシアネート基を有する化合物とを反応させることにより製造できる。 In addition, a cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group represented by the above formula (1) (where n = 0) is, for example, free A cellulose derivative having a hydroxyl group of the following formula (4)

(Wherein R ¹ , A ² and X ² are the same as above)
It can manufacture by making the compound which has the unsaturated carboxylic acyl group represented by and an isocyanate group react.

  As the cellulose derivative having a free hydroxyl group, those described above can be used.

  Representative examples of the compound represented by the formula (4) include 2- (meth) acryloyloxyethyl isocyanate, 2- [2- (meth) acryloyloxyethyloxy] ethyl isocyanate, and the like.

  In the present invention, in the active energy ray-curable resin composition, as an active energy ray-curable compound, a cellulose derivative in which a part of the hydroxyl groups of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acyl group However, it may further contain other active energy ray-curable compounds. Examples of such other active energy ray curable compounds include radical curable compounds and cationic curable compounds.

  The radical curable compound has at least one ethylenic double bond in the molecule and is irradiated with active energy rays (for example, ultraviolet rays, visible light, electron beams, X-rays, etc.) in the presence of a polymerization initiator. And a polymerizable compound. Examples of such compounds include (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and t-butyl (meth) acrylate. , 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, dicyclopentenyl (meth) acrylate, glycidyl (meth) acrylate, methoxyethyl (meth) ) Acrylate, ethoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, phenoxyethyl (meth) acrylate, norbornyl (meth) acrylate, isovol Monofunctional (meth) acrylic acid ester monomers such as ru (meth) acrylate, (meth) acryloylmorpholine, γ- (meth) acryloyloxypropyltrimethoxysilane; styrene, α-methylstyrene, vinyltoluene, vinyl acetate, Vinyl monomers such as allyl acetate, vinyl propionate, vinyl benzoate, N-vinyl pyrrolidone, N-vinyl imidazole, N-vinyl caprolactam; 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (Meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, bisphenol A-diglycid Bifunctional (meth) acrylic acid esters such as ether di (meth) acrylate, ethylene oxide modified bisphenol A-di (meth) acrylate; trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol penta (Meth) acrylate, pentaerythritol hexa (meth) acrylate, tri (meth) acrylate of ethylene oxide-added trimethylolpropane, dipentaerythritol penta (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, 1,3,5 -A trifunctional or more polyfunctional monomer such as triacryloylhexahydro-s-hydrazine can be mentioned. Among these, polyfunctional monomers having two or more functions are preferable. These radically curable compounds can be used alone or in combination of two or more.

  Moreover, (meth) acrylate oligomers, such as ester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, and acrylic (meth) acrylate, can also be used as the radical curable compound.

  Examples of the cationic curable compound include vinyl ether compounds, epoxy compounds, oxetane compounds, and the like.

  Examples of vinyl ether compounds include ethylene oxide modified bisphenol A-divinyl ether, ethylene oxide modified hydroquinone divinyl ether, and the like.

  Examples of the epoxy compound include 1,2-epoxycyclohexane, limonene diepoxide, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, 1,4-butanediol diglycidyl ether, Methylolpropane diglycidyl ether, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, bisphenyl A-diglycidyl ether, bisphenyl F-diglycidyl ether, bisphenyl S-diglycidyl ether, hydrogenated bisphenol A -Diglycidyl ether etc. are mentioned.

  Examples of the oxetane compound include 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, and di [(3-ethyl-3-oxetanyl) methyl] ether.

  In the present invention, the active energy ray-curable resin composition may contain a thermosetting compound in addition to the active energy ray-curable compound.

  The proportion of the cellulose derivative in which a part of the hydroxyl groups of the glucose skeleton in the total curable compound in the active energy ray-curable resin composition is substituted with a group containing an unsaturated carboxylic acyl group is, for example, 30% by weight or more. It is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more.

  In addition to the above curable compound, the active energy ray-curable resin composition includes a photopolymerization initiator, and, if necessary, a photosensitizer, a photocationic polymerization initiator, a thermal cationic polymerization initiator, a thermal radical. You may mix | blend a polymerization initiator, a photo accelerator, a light stabilizer, a ultraviolet absorber, a leveling agent, an antifoamer, etc.

  As a photoinitiator, it can select suitably according to the kind of active energy ray which is a hardening means. Examples of photopolymerization initiators include acetophenone, 3-methylacetophenone, benzophenone, 4-chlorobenzophenone, 4,4-diaminobenzophenone, 1-hydroxy-cyclohexyl-phenyl-ketone, 2,2-dimethoxy-2-phenylacetone , Xanthofluorenone, benzaldehyde, anthraquinone, benzoin ethyl ether, benzoin propyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 4-oxanthone, camphorquinone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one and the like can be mentioned.

  The content in the active energy ray-curable resin composition of the cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylic acid acyl group is the content in the active energy ray-curable resin composition. For example, 30 to 99.9% by weight, preferably 50 to 99.5% by weight, more preferably 70 to 99% by weight, particularly preferably 90 to 90% by weight based on the entire solid content (including components that solidify upon curing). 99% by weight.

  The content of the photopolymerization initiator in the active energy ray-curable resin composition is, for example, 0.1% with respect to the entire solid content (including components that are solidified by curing) in the active energy ray-curable resin composition. It is about 10 to 10% by weight, preferably about 1 to 8% by weight.

  The polarizing plate of the present invention is formed by coating the active energy ray-curable resin composition on at least one surface of a polarizer and then curing the active energy ray-curable resin composition to form a protective film. Manufactured.

  The coating method of the active energy ray-curable resin composition is not particularly limited, and various coating methods such as a doctor blade, a wire bar, a die coater, and a gravure coater can be used. When coating, the viscosity of the curable resin composition may be adjusted using a solvent.

  The coating film made of the active energy ray-curable resin composition is cured by irradiating active energy rays to form a protective film. Examples of active energy rays include ultraviolet rays, visible rays, electron beams, and X-rays. Among these, it is preferable to use ultraviolet rays. Examples of ultraviolet ray generation sources include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultrahigh-pressure mercury lamps, chemical lamps, xenon lamps, black light lamps, metal halide lamps, and the like.

  The thickness of the protective film is, for example, 10 to 200 μm, preferably 30 to 100 μm, from the viewpoints of thin and lightweight properties, protective properties, handleability and the like.

  The polarizing plate of the present invention uses a cured product of an active energy ray-curable resin composition containing an unsaturated carboxylic acid acyl group and a compound having an alicyclic skeleton and a cellulose derivative as a protective film for the polarizer. Has a great advantage that the birefringence hardly changes even when stress is applied.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The photoelastic coefficient and retardation of the cured film (cured film) and the glass transition temperature were measured by the following methods.

[Measurement of photoelastic coefficient and phase difference]
A cured film having a thickness of 100 μm was prepared and measured using a three-dimensional birefringence meter (“KOBRA-WR”) manufactured by Oji Scientific Instruments.

[Measurement of glass transition temperature]
An active energy ray-curable resin composition is applied to a cold-rolled steel sheet (thickness 0.3 mm × width 20 mm × length 50 mm) (thickness 40 μm), and a small UV irradiator (produced by Eyegraphic Co., Ltd., “ECS”). -401GX ", rated voltage 200V, high-pressure mercury lamp) was irradiated with ultraviolet rays with an integrated light amount of 350 mJ / cm ² from a distance of 11 cm to obtain a cured film of the active energy ray-curable resin composition. This was heated from 25 ° C. to 200 ° C. using a rigid pendulum type viscoelasticity measuring apparatus (manufactured by A & D Co., Ltd., “RPT-3000W”), and the glass transition temperature (Tg) was measured.

Synthesis example 1
Ethylcellulose (80.4 parts by weight) having a hydroxyl value of 32.9 mgKOH / g was dissolved in 723.6 parts by weight of butyl acetate, and ethylcellulose was dehydrated while distilling butyl acetate at 128 ° C. After distilling a mixed solution of 124.8 parts by weight of butyl acetate and water, the moisture in the butyl acetate solution of ethyl cellulose was measured with a Karl Fischer moisture meter, and the moisture was 0.025% by weight. After dehydration, butyl acetate distilled in ethylbutyl butyl acetate was added to adjust the concentration of ethylcellulose to 10% by weight.

  In an atmosphere containing 5% oxygen and a mixture of oxygen and nitrogen, 38.06 parts by weight of butyl acetate, 100 parts by weight of isophorone diisocyanate (IPDI), 0.046 parts by weight of dibutyltin dilaurate (the concentration of IPDI and HEA in the reaction product is The amount of 300 ppm by weight) was charged into a flask and mixed, and the temperature was raised to 40 ° C. Here, 52.25 parts by weight of 2-hydroxyethyl acrylate (HEA) was added dropwise over 1 hour. When the isocyanate concentration (NCO concentration in the solution) reaches 9.94% by weight, the mixture is cooled to room temperature and has an isocyanate group at the terminal where 1 mol of isophorone diisocyanate and 1 mol of 2-hydroxyethyl acrylate have reacted (meth) A solution containing an acrylic ester was obtained.

  679 parts by weight of a butyl acetate solution (10% by weight solution) of ethyl cellulose having a hydroxyl value of 32.9 mgKOH / g previously dehydrated under an atmosphere of oxygen concentration of 5% in which oxygen and nitrogen are mixed, 0.0282% by weight of dibutyltin dilaurate The portion was charged into a flask and stirred, and the temperature was raised to 100 ° C. 19.42 parts by weight of a solution containing a (meth) acrylic acid ester having an isocyanate group at the terminal prepared earlier was dropped over 1 hour. Thereafter, aging was performed, and when the isocyanate concentration became 0.1% by weight or less, the solution was cooled to room temperature, and a solution containing a cellulose derivative in which the hydroxyl group of ethylcellulose was substituted with a group containing an acryloyl group (solid content 16.4). % By weight).

Synthesis example 2
Cellulose acetate (manufactured by Daicel Chemical Industries, L-20) was dried at 150 ° C. for 24 hours to adjust the water content in the cellulose acetate to 0.86% by weight. The hydroxyl value at this time was 97.13 mgKOH / g. After mixing 35 parts by weight of the dried cellulose acetate, 316 parts by weight of cyclohexanone and 65 parts by weight of toluene, and distilling a mixture of cyclohexanone, toluene and water at 155 ° C., the moisture in the cyclohexanone solution of cellulose acetate was Karl Fischer moisture. When measured with a measuring instrument, the water content was 0.015% by weight. After dehydration, the concentration of cellulose acetate was adjusted with cyclohexanone so as to be 10.9% by weight.
In a mixed oxygen and nitrogen atmosphere with an oxygen concentration of 5%, 211 parts by weight of a cyclohexanone solution (10.9 wt% solution) of cellulose acetate having a hydroxyl value of 97.13 mgKOH / g previously dehydrated was placed in a flask and stirred. The temperature was raised to 70 ° C. After reaching 70 ° C., 4.6 parts by weight of isocyanate acrylate (2-acryloyloxyethyl isocyanate; Showa Denko, AOI-VM) was added. Two hours after the addition of AOI-VM, 0.08 part by weight of dibutyltin dilaurate was charged into the flask and stirred to continue the reaction. Thereafter, aging was performed, and when the isocyanate concentration became 0.1% by weight or less, the solution was cooled to room temperature, and a solution containing a cellulose derivative in which the hydroxyl group of cellulose acetate was substituted with a group containing an acryloyl group (solid content 12. 8% by weight) was obtained.

Example 1
To 100 parts by weight of a solution containing a cellulose derivative in which the hydroxyl group of ethyl cellulose obtained in Synthesis Example 1 is substituted with a group containing an acryloyl group, 0.82 part by weight of 1-hydroxy-cyclohexyl-phenyl-ketone is mixed to obtain an active energy. A linear curable resin composition 1 was obtained. The active energy ray-curable resin composition 1 was applied to a glass plate with a film thickness of 600 μm using an applicator, dried at 80 ° C. for 1 hour, and then a small UV irradiator (“ECS-401GX” manufactured by Eye Graphic Co., Ltd.). The ultraviolet ray with an integrated light quantity of 500 mJ / cm ² was irradiated three times from a distance of 11 cm with a rated voltage of 200 V and a high-pressure mercury lamp) to obtain a single cured film (thickness of 98 μm) of the active energy ray-curable resin composition 1. While visually observing the appearance of the obtained cured film, the photoelastic coefficient and the phase difference were measured.

Example 2
To 100 parts by weight of a solution containing a cellulose derivative in which the hydroxyl group of the cellulose acetate obtained in Synthesis Example 2 is substituted with a group containing an acryloyl group, 0.82 part by weight of 1-hydroxy-cyclohexyl-phenyl-ketone is mixed and activated. The energy beam curable resin composition 2 was obtained. The active energy ray-curable resin composition 2 was applied to a glass plate with a film thickness of 600 μm using an applicator and dried at 80 ° C. for 1 hour, and then a small UV irradiator (“ECS-401GX” manufactured by Eye Graphic Co., Ltd.). The ultraviolet ray with an integrated light quantity of 500 mJ / cm ² was irradiated three times from a distance of 11 cm with a rated voltage of 200 V and a high-pressure mercury lamp) to obtain a single cured film (thickness 77 μm) of the active energy ray-curable resin composition 2. While visually observing the appearance of the obtained cured film, the photoelastic coefficient and the phase difference were measured.

Comparative Example 1
Mixing 500 parts by weight of an ethyl acetate solution of ethyl cellulose having a hydroxyl value of 32.9 mg KOH / g of 10% by weight, 50 parts by weight of pentaerythritol triacrylate, and 5 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone, and active energy ray-curing property. A resin composition 3 was obtained. The active energy ray-curable resin composition 3 was applied on a glass plate with a film thickness of 550 μm using an applicator, dried at 80 ° C. for 1 hour, and then irradiated with ultraviolet rays in the same manner as in Example 1 to obtain active energy rays. A single cured film (thickness: 100 μm) of the curable resin composition 3 was obtained. While visually observing the appearance of the obtained cured film, the photoelastic coefficient and the phase difference were measured.

Comparative Example 2
500 parts by weight of an ethyl acetate solution of ethyl cellulose having a hydroxyl value of 32.9 mg KOH / g of 10% by weight, 50 parts by weight of dipentaerythritol hexaacrylate, and 5 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone are mixed, and active energy ray curing is performed. Resin composition 4 was obtained. The active energy ray-curable resin composition 4 was applied on a glass plate with a film thickness of 550 μm using an applicator, dried at 80 ° C. for 1 hour, and then irradiated with ultraviolet rays in the same manner as in Example 1 to obtain active energy rays. A single cured film (thickness: 100 μm) of the curable resin composition 4 was obtained. While visually observing the appearance of the obtained cured film, the photoelastic coefficient and the phase difference were measured.

Comparative Example 3
500 parts by weight of an ethyl acetate solution of ethyl cellulose having a hydroxyl value of 32.9 mg KOH / g of 10% by weight, 50 parts by weight of pentaerythritol ethoxytetraacrylate, and 5 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone are mixed, and active energy ray curing is performed. Resin composition 5 was obtained. The active energy ray-curable resin composition 5 was applied to a glass plate with a film thickness of 550 μm using an applicator, dried at 80 ° C. for 1 hour, and then irradiated with ultraviolet rays in the same manner as in Example 1 to obtain active energy rays. A single cured film (thickness: 100 μm) of the curable resin composition 5 was obtained. While visually observing the appearance of the obtained cured film, the photoelastic coefficient and the phase difference were measured.

  Table 1 shows the measurement results of the appearance, glass transition temperature, photoelastic coefficient, and retardation of the cured films obtained in Examples and Comparative Examples. In the table, “-” indicates that measurement is not possible.

Claims (4)

  A polarizing plate having a structure in which at least one surface of a polarizer is protected by a protective film made of a resin, wherein the resin has a hydroxyl group of a glucose skeleton partially substituted with a group containing an unsaturated carboxylic acid acyl group A polarizing plate, which is a cured product of an active energy ray-curable resin composition containing a cellulose derivative. The group containing an unsaturated carboxylic acyl group is represented by the following formula (1):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, A ¹ and A ² are the same or different and represent a divalent organic group, and X ¹ and X ² are the same or Differently, it represents an oxygen atom, a sulfur atom, or a —NR ² — group, R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents 0 or 1.
The polarizing plate according to claim 1, which is a group represented by:   The polarizing plate according to claim 1 or 2, wherein the cellulose derivative is at least one selected from methyl cellulose derivatives, ethyl cellulose derivatives, and cellulose acetate derivatives.   After applying an active energy ray-curable resin composition containing a cellulose derivative in which a part of the hydroxyl group of the glucose skeleton is substituted with a group containing an unsaturated carboxylate acyl group on at least one surface of the polarizer, A method for producing a polarizing plate, comprising: curing an energy ray-curable resin composition to form a protective film.