JP7230449B2 - optical film - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical film, and more particularly, to an optical film for use as a retardation film, which exhibits a large retardation, a low haze, excellent light resistance, and reduced breakage during film production.

Since a polymer containing an alicyclic hydrocarbon monomer has excellent optical properties and durability, a retardation film in which the retardation is adjusted using the polymer is used, for example, in a VA liquid crystal display device. have been considered for use.

In the production of a retardation film for a VA-type liquid crystal display device (hereinafter referred to as VA), it is necessary to stretch in order to develop a desired retardation. When stretching is performed to develop a retardation for VA using a polymer containing polymer, especially in the case of a thin optical film, it is necessary to develop a retardation by stretching at a higher magnification, so the film breaks during production. The problem was that it was easy.

Conventionally, attempts have been made to improve the retardation by adding a polyester to a polymer containing an alicyclic hydrocarbon monomer (see, for example, Patent Document 1). However, although the retardation expression is certainly improved, it is insufficient to improve haze and rupture during production.

In addition, as liquid crystal display devices are used outdoors (for example, digital signage), there is a strong demand for improvements in heat resistance, light resistance, and mechanical strength of retardation films.

A technique of mixing a resin such as polyurethane with a polymer containing an alicyclic hydrocarbon monomer is known (see, for example, Patent Document 2). A polyurethane containing a diisocyanate and a diol having an alicyclic structure is known (see, for example, Patent Document 3).

However, although the above-mentioned Patent Document 2 describes that as a material for circuit boards, it has excellent stability of dielectric properties over time, excellent solvent resistance, heat resistance, transparency, mechanical properties, etc., optical films, especially There is no description of application to a retardation film to improve haze, film breakage, and the like. In addition, the above-mentioned Patent Document 3 describes improvement of physical properties such as mechanical strength, transparency and light resistance by urethane alone, but by adding it to a polymer containing an alicyclic hydrocarbon monomer and blending it, , there is no disclosure of its application to optical films.

Therefore, an optical film that is a retardation film using a polymer containing an alicyclic hydrocarbon monomer and has improved retardation properties, haze, light resistance, and breakage during film production is expected. It is in a state of waiting.

JP 2018-80211 A JP 2018-123230 A JP-A-2000-178340

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is that a retardation film has a large retardation expression, low haze, excellent light resistance, and no breakage during film production. It is to provide a reduced optical film.

In order to solve the above problems, in the process of studying the causes of the above problems, the present inventors have found that a polymer containing an alicyclic hydrocarbon monomer having a polar group, a urethane polymer having a specific structure, It was found that an optical film having a large retardation expression, low haze, excellent light resistance, and reduced breakage during film production can be obtained as a retardation film.

That is, the above problems related to the present invention are solved by the following means.

1. At least a polymer containing an alicyclic hydrocarbon monomer having a polar group, a diol monomer having an alicyclic structure in the molecule, and an isocyanate monomer having an alicyclic structure in the molecule and a urethane polymer ,
An optical film , wherein one kind of the urethane polymer contains two or more kinds of the diol monomers .

2. 2. The optical film of item 1, wherein the weight average molecular weight of the urethane polymer is in the range of 1,000 to 100,000.

3 . 3. The optical film according to item 1 or item 2 , wherein one kind of the urethane polymer contains two or more kinds of the isocyanate monomers.

4 . The mixing mass ratio (A/B) of the polymer (A) containing the alicyclic hydrocarbon monomer having a polar group and the urethane polymer (B) is in the range of 50/50 to 95/5. The optical film according to any one of items 1 to 3 , characterized in that:

5 . 5. The optical film according to any one of items 1 to 4 , further comprising an organic matting agent.

By the above means of the present invention, it is possible to provide an optical film for a retardation film that exhibits a large retardation, a low haze, an excellent light resistance, and a reduced breakage during film production.

Although the expression mechanism or action mechanism of the effects of the present invention has not been clarified, it is speculated as follows.

The optical film of the present invention has at least a polymer containing an alicyclic hydrocarbon monomer having a polar group, a diol monomer having an alicyclic structure in its molecule, and an alicyclic structure in its molecule. and a urethane polymer containing an isocyanate monomer.

Regarding the retardation property of the optical film, the introduction of the alicyclic structure into the urethane polymer makes it possible to improve the retardation property by arranging the alicyclic structure portions in the film during film stretching. guessed.

If the urethane polymer has a linear or branched fatty chain structure with low electron density, it is difficult to develop a phase difference, and if it is aromatic with a high electron density, it is easy to develop a phase difference. Light resistance is easily deteriorated. Therefore, by introducing an alicyclic structure into the urethane polymer, it is possible to improve the light resistance as well as the retardation.

In addition, by using a polymer containing an alicyclic hydrocarbon monomer and a urethane polymer containing a diol or isocyanate having an alicyclic structure in the molecule, the compatibility between the polymers increases and the compatibility is improved. It is speculated that it can be improved. Originally, polymers containing alicyclic hydrocarbon monomers had a narrow compatibility tolerance, and it was difficult to make polymers with different structures compatible with each other, but having the same type of structure improved compatibility. , it is presumed that the retardation expression was improved and the haze was reduced.

Moreover, when the diol and isocyanate each having an alicyclic structure in the molecule are of one kind, the structure of the urethane polymer becomes regular, so that the urethane bond portions easily overlap between molecules. In this case, the urethane bonds tend to interact with each other, the cohesive force between the urethanes increases, and the compatibility with other components deteriorates slightly. By containing two or more kinds of diols and isocyanates having an alicyclic structure in the molecule, the regularity of the urethane polymer is reduced, and the cohesive force of the urethane itself is reduced. It is thought to be advantageous in reducing haze during stretching and in reducing breakage during transportation.

Regarding breakage during transport, it is speculated that the inclusion of a flexible urethane bond component with good compatibility improves the strength of the film-like material in a solvent-containing state, and stabilizes transportability. contains a matting agent in order to improve the winding and transportability of the film. If the refractive index of the matting agent is different from the refractive index of the polymer containing the alicyclic hydrocarbon monomer, light scattering occurs in the optical film, and haze and transparency are likely to deteriorate.

Therefore, rather than an inorganic matting agent such as silica particles, an organic matting agent adjusted to have a refractive index close to that of a polymer containing an alicyclic hydrocarbon monomer is preferred. preferable.

On the other hand, in the case of a polymer containing an alicyclic hydrocarbon monomer having few polar moieties in the molecule, the organic matting agent is difficult to disperse. In particular, since organic matting agents containing acrylic monomers contain polar groups, they are poorly compatible with polymers containing alicyclic hydrocarbon monomers, and the matting agents are difficult to disperse. Therefore, the matting agent tends to aggregate in the dope, and the dispersion stability tends to be poor.

By adding the urethane polymer, the polar portion of the urethane bond acts with the polar portion of the matting agent to function as a dispersant, thereby improving the dispersibility of the matting agent. Therefore, it is presumed that aggregation of the matting agent in the dope can be suppressed, and the haze and transparency of the optical film can be improved.

A diagram schematically showing an example of a dope preparation step, a casting step and a drying step of a solution casting film forming method preferred for the present invention.

The optical film of the present invention has at least a polymer containing an alicyclic hydrocarbon monomer having a polar group, a diol monomer having an alicyclic structure in its molecule, and an alicyclic structure in its molecule. and a urethane polymer containing an isocyanate monomer , wherein one type of the urethane polymer contains two or more types of the diol monomers . This feature is a technical feature common to or corresponding to the following embodiments.

As an embodiment of the present invention, from the viewpoint of exhibiting the effect of the present invention, the weight-average molecular weight of the urethane polymer is in the range of 1000 to 100000 to maintain the physical properties as an optical film and during transportation. It is preferable from the viewpoint of suppression of breakage.

In addition, the urethane polymer contains two or more diol monomers having an alicyclic structure in the molecule, or two or more isocyanate monomers having an alicyclic structure in the molecule. However, the regularity of the urethane polymer becomes smaller and the cohesive force of the urethane itself is reduced, which improves compatibility with polymers containing alicyclic hydrocarbon monomers and reduces haze during stretching. Also, it works favorably for suppressing breakage during transportation.

Further, the mixing mass ratio (A/B) of the polymer (A) containing the alicyclic hydrocarbon monomer having a polar group and the urethane polymer (B) is from 50/50 to 95/5. Being within the range is a preferable mixing range from the viewpoint of exhibiting the effects of the present invention.

Furthermore, the inclusion of the organic matting agent makes the refractive index of the matting agent close to that of the polymer containing the alicyclic hydrocarbon monomer. and transparency.

DETAILED DESCRIPTION OF THE INVENTION The present invention, its constituent elements, and embodiments and modes for carrying out the present invention will be described in detail below. In the present application, "-" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.

<<Overview of the optical film of the present invention>>
The optical film of the present invention has at least a polymer containing an alicyclic hydrocarbon monomer having a polar group, a diol monomer having an alicyclic structure in its molecule, and an alicyclic structure in its molecule. and a urethane polymer containing an isocyanate monomer.

The mixing mass ratio (A/B) of the polymer (A) containing the alicyclic hydrocarbon monomer having a polar group and the urethane polymer (B) is, in order to exhibit the effect of the present invention, It is preferably in the range of 50/50 to 95/5, more preferably 60/40 to 95/5, still more preferably 80/20 to 95/5.

[1] Polymer containing an alicyclic hydrocarbon monomer The polymer containing an alicyclic hydrocarbon monomer according to the present invention (hereinafter also referred to as polycycloolefin) is a polymer containing a cycloolefin monomer. It is a coalescence or a copolymer of a cycloolefin monomer and other copolymerizable monomers.

The polycycloolefin according to the present invention is characterized by having a polar group, and examples of the polar group include a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. , or a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom).

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton. From the viewpoint of controlling optical properties such as retardation values Ro and Rt (especially Rt), it is preferable to contain a cycloolefin monomer having an asymmetric structure. Examples of cycloolefin monomers having an asymmetric structure include cycloolefin monomers represented by general formula (A-1) below.

R ₁ in general formula (A-1) represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. Among them, a hydrocarbon group having 1 to 5 carbon atoms is preferable, and a hydrocarbon group having 1 to 3 carbon atoms is more preferable.

R ₂ in general formula (A-1) represents a polar group, and as described above, a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amido group, a cyano group, or a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom). Among them, a carboxy group, a hydroxy group, an alkoxycarbonyl group and an aryloxycarbonyl group are preferred, and an alkoxycarbonyl group and an aryloxycarbonyl group are more preferred from the viewpoint of ensuring solubility during solution film formation.

p in the general formula (A-1) represents an integer of 0-2. Preferably, p is 1 or 2.

The cycloolefin monomer represented by general formula (A-1) has an asymmetric structure. That is, since the substituents R ₁ and R ₂ of the cycloolefin monomer represented by general formula (A-1) are substituted only on one ring-constituting carbon atom with respect to the symmetry axis of the molecule, low symmetry. A cycloolefin monomer having such an asymmetric structure promotes the diffusion movement of the resin during solvent volatilization, probably because the symmetry of the molecule is broken, and accordingly promotes uniform orientation of the polyurethane according to the present invention. ,preferable.

The content of the cycloolefin monomer represented by general formula (A-1) is, for example, 50 mol% or more, preferably 50 mol% or more, based on the total amount of all cycloolefin monomers constituting the polycycloolefin according to the present invention. can be 60 mol % or more, more preferably 80 mol % or more. The polycycloolefin according to the present invention containing a certain amount or more of the monomer represented by general formula (A-1) is preferable because it promotes uniform orientation of the polyurethane according to the present invention, as described above.

In addition, the cycloolefin monomer may further contain other cycloolefin monomers other than the cycloolefin monomer represented by general formula (A-1), if necessary. Examples of other cycloolefin monomers include cycloolefin monomers represented by the following general formula (A-2).

R ₃ to R ₆ in general formula (A-2) each independently represent a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. However, R ₃ to R ₆ do not all represent a hydrogen atom at the same time, R ₃ and R ₄ do not represent a hydrogen atom at the same time, and R ₅ and R ₆ do not represent a hydrogen atom at the same time. do. At least one of R ₃ to R ₆ represents a polar group.

The hydrocarbon group having 1 to 30 carbon atoms is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 5 carbon atoms. The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing a halogen atom, oxygen atom, nitrogen atom, sulfur atom or silicon atom. Examples of such linking groups include divalent polar groups such as carbonyl groups, imino groups, ether bonds, silyl ether bonds and thioether bonds. Examples of hydrocarbon groups having 1 to 30 carbon atoms include methyl group, ethyl group, propyl group, butyl group and the like. Examples of the polar group are as described above, and p in general formula (A-2) represents an integer of 0-2. Preferably, p is 1 or 2.

Specific examples of the cycloolefin monomer represented by the general formula (A-1) are shown in Exemplified Compounds 15 to 34, and specific examples of the cycloolefin monomer represented by the general formula (A-2) are illustrated compounds. 1-14.

Examples of other cycloolefin monomers also include dicyclopentadiene, dihydrodicyclopentadiene, and the like.

Examples of copolymerizable monomers copolymerizable with cycloolefin monomers include copolymerizable monomers capable of ring-opening copolymerization with cycloolefin monomers and copolymerizable monomers capable of addition copolymerization with cycloolefin monomers. A copolymerizable monomer is included.

Examples of ring-opening copolymerizable copolymerizable monomers include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclohexene, cyclooctene, cyclopentadiene, cyclohexadiene, cycloheptadiene and cyclooctadiene.

Examples of addition-copolymerizable copolymerizable monomers include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, and (meth)acrylates. Examples of unsaturated double bond-containing compounds are olefinic compounds having 2 to 12 (preferably 2 to 8) carbon atoms, examples of which include ethylene, propylene, butenes. Examples of vinyl-based cyclic hydrocarbon monomers include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of (meth)acrylates include alkyl (meth)acrylates having 1 to 20 carbon atoms such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and cyclohexyl (meth)acrylate.

The content of the cycloolefin monomer in the polycycloolefin according to the present invention can be, for example, 50 to 100 mol%, preferably 60 to 100 mol%, based on the total amount of all monomers constituting the polycycloolefin.

The polycycloolefin according to the present invention is obtained by homopolymerizing or copolymerizing cycloolefin monomers having structures represented by the general formulas (A-1) and (A-2) having a norbornene skeleton, For example, the following (1) to (3) are preferred, and (3) is more preferred.
(1) Ring-opening polymer of cycloolefin monomer (2) Ring-opening copolymer of cycloolefin monomer and copolymerizable monomer (3) Ring-opening of (1) or (2) above ( Hydrogenated (co)polymer of co)polymer (4) A (co)polymer obtained by cyclizing the ring-opening (co)polymer of (1) or (2) above by Friedel-Crafts reaction and then hydrogenating it (5) Saturated polymers of cycloolefin monomers and unsaturated double bond-containing compounds (6) Addition type (co)polymers of cycloolefin monomers and hydrogenated (co)polymers thereof (7) Alternating copolymer of cycloolefin-based monomer and methacrylate or acrylate In this specification, the description of JP-A-2008-107534 can be cited for the method for producing the polycycloolefin according to the present invention. can.

The polycycloolefin according to the present invention preferably has a number average molecular weight Mn of 8,000 to 100,000, more preferably 10,000 to 80,000, even more preferably 12,000 to 50,000. The weight average molecular weight Mw of the polycycloolefin according to the present invention is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, even more preferably 40,000 to 200,000. The number average molecular weight Mn and weight average molecular weight Mw of the polycycloolefin according to the present invention can be measured using gel permeation chromatography (GPC). Measurement conditions are as follows.

(Measurement condition)
Solvent: Dichloromethane Column: Shodex K806, K805, K803G (three columns manufactured by Showa Denko Co., Ltd. were connected and used)
Column temperature: 25°C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Science)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 mL/min
Calibration curve: standard polystyrene STK standard Polystyrene (manufactured by Tosoh Corporation) Mw = 500 to 1,000,000 A calibration curve based on 13 samples was used. 13 samples are used at approximately equal intervals.

Commercially available products can be preferably used as the polycycloolefin according to the present invention. Examples of commercially available products include ARTON (registered trademark) G, ARTON F, ARTON R, and ARTON RX from JSR Corporation. It is sold under the trade name of , and these can be used.

[2] Urethane polymer The urethane polymer according to the present invention comprises a diol monomer having an alicyclic structure in the molecule (also referred to as an alicyclic diol) and an isocyanate monomer having an alicyclic structure in the molecule. (also referred to as alicyclic isocyanate).

[2.1] Diol monomer having an alicyclic structure in the molecule A diol having an alicyclic structure in the molecule refers to a diol having one or more cyclo rings in the structure. . Diols having an alicyclic structure include 1,2-, 1,3- and 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2- and 1,3-cyclopentanediol, and cyclododecanediol. , 2,4-dihydroxy-1,1,3,3-tetramethylcyclobutane, bis(4-hydroxycyclohexyl)-methane, 2,4-bis(4-hydroxycyclohexyl)-2-methylpentane, hydrogenated bisphenol A compounds such as The number of ring structures in one molecule may be any number, but considering the viscosity of the produced polyisocyanate composition, one is preferable. Among them, those having 10 or less carbon atoms are more preferable. These diols having an alicyclic structure may be used alone or in combination.

In order to obtain the polyurethane according to the present invention, it is preferable to use a diol monomer having an alicyclic structure represented by the following general formula (I) or (II).

In general formula (I), X represents a methylene group, isopropylidene group, sulfone group, ketone group, or ether group; in general formulas (I) and (II), R ¹ and R ² each independently It represents an alkylene group having 2 to 4 carbon atoms, and m and n are positive integers satisfying 0≦m+n≦4.

The cyclohexane ring in the general formulas (I) and (II) may further have other substituents such as alkyl groups such as methyl groups and halogen atoms such as chlorine and bromine.

Specific examples of these alicyclic diols, for example, those represented by the general formula (I) include bis(4-hydroxycyclohexyl)methane, 2,2-bis(4'-hydroxycyclohexyl)propane, 4,4'-dihydroxycyclohexyl sulfone, 4,4'-dihydroxycyclohexyl ketone, 4,4'-dihydroxycyclohexyl ether, and their ethylene oxide adducts and propylene oxide adducts. Further, as those represented by the general formula (II), 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, and their Examples include ethylene oxide adducts and propylene oxide adducts. These may be used in combination of two or more. Among them, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4'-hydroxycyclohexyl)propane and 1,4-cyclohexanedimethanol are preferred. 2-bis(4'-hydroxycyclohexyl)propane and 1,4-cyclohexanedimethanol are particularly preferred.

Examples of diols having other structures include bicyclo[5,3,0]decanedimethanol, bicyclo[4,4,0]decanedimethanol, bicyclo[4,3,0]nonanedimethanol, norbornanedimethanol, Tricyclodecanedimethanol, 1,3-adamantanediol (1,3-dihydroxytricyclo[3,3,1,13,7]decane, 3,9-bis(2-hydroxy-1,1-dimethylethyl) -2,4,8,10-Tetraoxaspiro[5,5]undecane and the like are also useful.

[2.2] Isocyanate monomer having an alicyclic structure in the molecule The isocyanate monomer having an alicyclic structure according to the present invention is preferably a diisocyanate having an alicyclic structure, such as cyclohexane diisocyanate, Preferred examples include alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, norbornene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

Among the alicyclic diisocyanates, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate are preferred because they are readily available industrially.

[2.3] Polymer Diol In the urethane polymer according to the present invention, it is also preferable to use a polymer diol in addition to the diol monomer having an alicyclic structure in the molecule and the isocyanate monomer.

Specific examples of polymer diols include polyethylene glycol, polypropylene ether glycol, polytrimethylene ether glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and block or random copolymers of ethylene oxide and propylene oxide. , polyethers such as block or random copolymers of ethylene oxide and tetrahydrofuran, polyesters such as polycaprolactone polyol, polyethylene adipate polyol and polybutylene adipate polyol, and polycarbonates such as 1,6-hexane polycarbonate polyol. Among them, polytetramethylene ether glycol and polycaprolactone polyol are preferred, and polytetramethylene ether glycol is particularly preferred.

The polymeric diol preferably has an average molecular weight of 500-5000, more preferably 800-3000.

The method for producing the urethane polymer of the present invention can be obtained by subjecting an alicyclic diol and an alicyclic diisocyanate to a polyaddition reaction. can be obtained by polyaddition reaction.

For example, in the polyaddition reaction of an alicyclic diol, an alicyclic diisocyanate, and a polymeric diol, the molar ratio of the polymeric diol to the alicyclic diol should be in the range of 1:2 to 1:10. is preferred.

In the polyaddition reaction, for example, the reaction system is heated to about 60 to 100°C by a conventional method, stirred and mixed, and reacted at that temperature for about 1 to 4 hours. It is made by maturing overnight at a temperature of about. These reactions may be carried out by any of a continuous system using an extruder, etc., a batch system using a reaction vessel, etc., and a system in which the monomers are dissolved in a solvent and reacted in the reaction vessel. Organotin-based catalysts such as stannus octoate and dibutyltin dilaurate are used accordingly.

[3] Other Components The optical film of the present invention may further contain components other than those described above, if necessary. Examples of other ingredients include UV absorbers, plasticizers, antioxidants and matting agents.

(Ultraviolet absorber)
A UV absorber may be added for the purpose of improving the light resistance of the optical film. Examples of such UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, salicylate UV absorbers, cyanoacrylate UV absorbers, and triazine UV absorbers.

Examples of benzotriazole-based UV absorbers include 5-chloro-2-(3,5-di-sec-butyl-2-hydroxylphenyl)-2H-benzotriazole, (2-2H-benzotriazol-2-yl )-6-(linear and branched dodecyl)-4-methylphenol. Examples of commercially available benzotriazole-based UV absorbers include TINUVIN series such as TINUVIN109, TINUVIN171, TINUVIN234, TINUVIN326, TINUVIN327, TINUVIN328, and TINUVIN928, all of which are commercially available from BASF.

Examples of benzophenone UV absorbers include 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5- sulfobenzophenone, bis(2-methoxy-4-hydroxy-5-benzoylphenylmethane), and the like.

Examples of salicylate-based ultraviolet absorbers include phenyl salicylate, p-tert-butyl salicylate, and the like.

Examples of cyanoacrylate ultraviolet absorbers include 2'-ethylhexyl-2-cyano-3,3-diphenyl acrylate, ethyl-2-cyano-3-(3',4'-methylenedioxyphenyl)-acrylate and the like. is included.

Examples of triazine-based UV absorbers include 2-(2'-hydroxy-4'-hexyloxyphenyl)-4,6-diphenyltriazine and the like. Commercially available examples of triazine-based UV absorbers include TINUVIN477.

Among these, triazine-based UV absorbers are preferable in that they have good UV absorbability, but they tend to exhibit retardation when stretched. Therefore, benzotriazole-based UV absorbers and benzophenone-based UV absorbers are preferable, and benzotriazole-based UV absorbers are more preferable, in terms of less retardation due to stretching and good UV absorption performance.

The benzotriazole-based UV absorber is slightly inferior to the triazine-based UV absorber in terms of UV absorption performance, so the content of the benzotriazole-based UV absorber in the film must be increased. When the content of the ultraviolet absorber is increased, the wet heat durability tends to decrease.

The content of the ultraviolet absorber is preferably 0.1 to 10% by mass with respect to the total mass of the thermoplastic resin. If the content of the ultraviolet absorber is 0.1% by mass or more with respect to the total mass of the thermoplastic resin, the weather resistance of the optical film can be sufficiently enhanced. If the content of the ultraviolet absorber is 10% by mass or less with respect to the total mass of the thermoplastic resin, the resulting optical film is less likely to lose its transparency. The content of the ultraviolet absorber is more preferably 0.5 to 10% by mass, more preferably 1.5 to 5% by mass, based on the total mass of the polycycloolefin and polyurethane according to the present invention. .

(Plasticizer)
Examples of plasticizers include polyester plasticizers, polyhydric alcohol ester plasticizers, polycarboxylic acid ester plasticizers (including phthalate plasticizers), glycolate plasticizers, ester plasticizers ( (including fatty acid ester plasticizers), sugar ester plasticizers and acrylic plasticizers. The number of plasticizers contained in the optical film may be one, or two or more may be combined. Among these, sugar ester plasticizers are preferable because they are easily compatible with thermoplastic resins and easily obtain good plasticity.

The sugar ester used in the present invention is preferably a sugar ester having at least one pyranose ring or furanose ring and not more than 12 and having all or part of the OH groups in the structure esterified.

The sugar ester used in the present invention is a compound containing at least either a furanose ring or a pyranose ring, and may be a monosaccharide or a polysaccharide in which 2 to 12 sugar structures are linked. The sugar ester is preferably a compound in which at least one OH group of the sugar structure is esterified. In the sugar ester according to the present invention, the average degree of ester substitution is preferably within the range of 4.0 to 8.0, more preferably within the range of 5.0 to 7.5.

The sugar ester used in the present invention is not particularly limited, but sugar esters represented by the following general formula (B) can be mentioned.

General formula (B)
(HO) _m -G-(OC(=O)-R ² ) _n
In the above general formula (B), G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m is a direct bond to the monosaccharide or disaccharide residue. is the total number of hydroxy groups attached, n is the total number of —(O—C(=O)—R ² ) groups attached directly to the monosaccharide or disaccharide residue; 3≦m+n≦8 and n≠0.

A sugar ester having a structure represented by the general formula (B) is ^a single type of It is known that it is difficult to isolate it as a compound, and that it becomes a compound in which several different components of m and n in the formula are mixed. Therefore, the performance as a mixture in which the number (m) of hydroxy groups and the number (n) of —(O—C(=O)—R ² ) groups are each changed is important, and in the case of the cyclic polyolefin film of the present invention, , the average degree of ester substitution is preferably in the range of 5.0 to 7.5.

In the above general formula (B), G represents a monosaccharide or disaccharide residue. Specific examples of monosaccharides include allose, altrose, glucose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose and lyxose.

Specific examples of the compound having a monosaccharide residue of the sugar ester represented by formula (B) are shown below, but the present invention is not limited to these exemplified compounds.

Specific examples of disaccharide residues include trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, isotrehalose and the like.

Specific examples of the compound having a disaccharide residue of the sugar ester represented by formula (B) are shown below, but the present invention is not limited to these exemplified compounds.

In general formula (B), ^R2 represents an aliphatic group or an aromatic group. Here, the aliphatic group and the aromatic group may each independently have a substituent.

Further, in the general formula (B), m is the total number of hydroxy groups directly bonded to the monosaccharide or disaccharide residue, and n is directly bonded to the monosaccharide or disaccharide residue. is the total number of —(O—C(═O)—R ² ) groups present. It is necessary that 3≦m+n≦8, and preferably 4≦m+n≦8. Also, n≠0. When n is 2 or more, the —(O—C(═O)—R ² ) groups may be the same or different.

The aliphatic group in the definition of R ² may be linear, branched, or cyclic, preferably having 1 to 25 carbon atoms, more preferably 1 to 20 carbon atoms, 2 ~15 are particularly preferred. Specific examples of aliphatic groups include methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, tert-butyl, amyl, iso-amyl, tert-amyl, n- Groups such as hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl, and didecyl.

Also, the aromatic group in the definition of R ² may be an aromatic hydrocarbon group or an aromatic heterocyclic group, more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, more preferably 6 to 12 carbon atoms. Specific examples of aromatic hydrocarbon groups include rings of benzene, naphthalene, anthracene, biphenyl, terphenyl, and the like. A benzene ring, a naphthalene ring, and a biphenyl ring are particularly preferred as the aromatic hydrocarbon group. As the aromatic heterocyclic group, a ring containing at least one of an oxygen atom, a nitrogen atom and a sulfur atom is preferred. Specific examples of heterocycles include furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, Rings of isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzthiazole, benzotriazole, tetrazaindene, and the like. As the aromatic heterocyclic group, a pyridine ring, a triazine ring and a quinoline ring are particularly preferred.

Preferred examples of the sugar ester represented by formula (B) are shown below, but the present invention is not limited to these exemplified compounds. The melting point and 1% mass loss temperature Td1 of all of the compounds exemplified below are within the scope of the present invention.

The sugar ester may contain two or more different substituents in one molecule, containing an aromatic substituent and an aliphatic substituent in one molecule, and two or more different aromatic substituents in one molecule. Contained in one molecule, two or more different aliphatic substituents can be contained in one molecule.

Moreover, it is also preferable to mix and contain two or more types of sugar esters. It is also preferred to simultaneously contain a sugar ester containing an aromatic substituent and a sugar ester containing an aliphatic substituent.

<Synthesis Example: Synthesis Example of Sugar Ester Represented by General Formula (B)>
An example of the synthesis of sugar esters suitable for use in the present invention is shown below.

34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride and pyridine were placed in a four-head Kolben equipped with a stirrer, reflux condenser, thermometer and nitrogen gas inlet tube. 379.7 g (4.8 mol) of were charged respectively, and the temperature was raised under stirring while bubbling nitrogen gas through a nitrogen gas introduction tube, and an esterification reaction was carried out at 70° C. for 5 hours. Next, after reducing the pressure in the Kolben to 4 × 10 ² Pa or less and distilling off excess pyridine at 60 ° C., the pressure in the Kolben was reduced to 1.3 × 10 Pa or less, the temperature was raised to 120 ° C., and anhydrous benzoin was added. The acid, most of the benzoic acid formed, was distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass sodium carbonate aqueous solution were added, stirred at 50° C. for 30 minutes, and allowed to stand to separate the toluene layer. Finally, 100 g of water was added to the separated toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer was separated, and toluene was distilled off at 60°C under reduced pressure (4 × 10 ² Pa or less), A mixture of compounds A-1, A-2, A-3, A-4 and A-5 was obtained. The resulting mixture was analyzed by HPLC and LC-MASS, A-1 is 7% by mass, A-2 is 58% by mass, A-3 is 23% by mass, A-4 is 9% by mass, A-5 was 3% by mass, and the average degree of ester substitution of the sugar ester was 6.57. A part of the resulting mixture was purified by silica gel column chromatography to obtain A-1, A-2, A-3, A-4 and A-5 each having a purity of 100%.

The amount of the sugar ester added is preferably in the range of 0.1 to 20% by mass, more preferably in the range of 1 to 15% by mass, based on the cyclic polyolefin resin.

The content of the sugar ester is preferably 1-20% by mass with respect to the total mass of the polycycloolefin and polyurethane according to the present invention. When the content of the plasticizer is within the range of 1 to 20% by mass based on the total mass of the polycycloolefin and polyurethane according to the present invention, bleeding out during plasticization, stretching, and storage can be easily suppressed. More preferably, the content of the sugar ester is 1-15% by mass relative to the total mass of the polycycloolefin and polyurethane according to the present invention.

As one of the effects of the plasticizer, the water content of the polycycloolefin according to the present invention can be lowered to improve water resistance and moisture resistance. Therefore, if the additives other than the plasticizer are highly hydrophobic, the amount of the plasticizer added can be reduced.

(Antioxidant)
The purpose of antioxidants is to suppress the deterioration of the optical film contained in the liquid crystal display device placed under high humidity and high temperature; It can be added for the purpose of delaying or suppressing the decomposition of the resin by acid or the like.

As the antioxidant, a hindered phenol compound is preferably used, examples of which include 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis[3-(3,5-di -t-butyl-4-hydroxyphenyl)propionate], triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3 -(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t -butyl-4-hydroxyphenyl)propionate, N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4 ,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tris-(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate and the like. Among them, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate] is preferred.

The content of the antioxidant is preferably 1 mass ppm to 1.0 mass %, more preferably 10 to 1000 mass ppm, based on the total mass of the polycycloolefin and polyurethane according to the present invention.

(Matting agent and organic matting agent)
A matting agent may be added for the purpose of enhancing the slipperiness of the surface of the optical film. Inorganic fine particles or organic fine particles are used as the fine particles, but an organic matting agent containing organic fine particles described later is preferable from the viewpoint of reducing the difference in refractive index from the polycycloolefin according to the present invention and suppressing haze.

The fine particles preferably form secondary particles having a particle size of 0.1 to 5 μm and are contained in the optical film. It is in the range of 0.6 μm.

Examples of inorganic fine particles include silicon dioxide (silica), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate. and microparticles such as calcium phosphate. Examples of organic fine particles include fine particles of silicone resin, fluororesin, (meth)acrylic resin, and the like.

Examples of fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Seahoster KE-P10, KE-P30, KE-P50, KE-P100 (both manufactured by Nippon Shokubai Co., Ltd.) and the like are included.

The organic fine particles preferable for the present invention are obtained by further polymerizing a (meth)acrylic acid ester as a shell portion to a particulate polymer having an average particle diameter of 0.01 μm or more and 1 μm or less as a core portion and a shell. It is preferable that the organic fine particles have a multi-layered structure consisting of moieties. The organic fine particles have a structure derived from a polyfunctional compound only in the central portion (core), and the portion (shell) surrounding the central portion has high compatibility with the thermoplastic resin constituting the optical film. Having a structure is preferred. As a result, the organic fine particles can be more uniformly dispersed in the thermoplastic resin, and the secondary production of foreign substances caused by aggregation of the organic fine particles can be further suppressed. As a result, the filtering process can be performed in a shorter time during the molding of the optical film.

Organic fine particles having such a core-shell structure can be obtained by using the reactive functional groups (double bonds) remaining unreacted during polymerization of the organic fine particles as graft crossing points, and the above-described (meth)acrylic acid esters. and a hydroxyl group-containing monomer such as α-hydroxymethylstyrene and α-hydroxyethylstyrene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, styrene, vinyltoluene, α-methylstyrene, acrylonitrile, It can be obtained by graft polymerization with at least one monomer selected from methyl vinyl ketone, ethylene, propylene, vinyl acetate and the like.

As the (meth)acrylic acid ester, it is preferable to use one having an alkyl group of 1 to 12 carbon atoms from the viewpoint of polymerizability and cost. For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-acrylate octyl, phenyl acrylate, 2-phenoxyethyl acrylate, and the like.

The average particle size of the core portion is preferably 1 to 500 nm, more preferably 10 to 400 nm, even more preferably 50 to 300 nm, particularly preferably 70 to 300 nm. Here, the particle size is determined, for example, by a dynamic light scattering method using MICROTRAC UPA150 (manufactured by Nikkiso Co., Ltd.), or by a turbidity method that measures the permeability of the polymerization liquid per unit weight using a turbidity meter. can ask.

The mass ratio of the core portion to the shell portion is preferably in the range of 20:80 to 80:20.

The shell portion and core portion of the core-shell structure will be further described below.

<Shell part>
The shell portion is not particularly limited as long as it has a structure that is highly compatible with the thermoplastic resin that constitutes the optical film.

<Core part>
The core portion is not particularly limited as long as it has a structure exhibiting an effect of improving the flexibility of the thermoplastic resin constituting the optical film, and examples thereof include a crosslinked structure. Moreover, the structure having cross-linking is preferably a cross-linked rubber structure.

The above-mentioned crosslinked rubber structure is a rubber whose main chain is a polymer whose glass transition point is in the range of -100 to 25°C, and whose elasticity is imparted by cross-linking between the main chains with a polyfunctional compound. means structure. Examples of the crosslinked rubber structure include structures (repeating structural units) of acrylic rubber, polybutadiene rubber, and olefin rubber. Among these, acrylic rubber is preferable because it is easy to control the average particle size to 300 nm or less, and optical properties such as transparency of the film are good when uniformly dispersed in the resin.

For example, the acrylic acid ester-based rubber-like polymer that is the material of the rubber portion is a rubber-like polymer containing acrylic acid ester as a main component. Specifically, a monomer mixture (100% by mass) consisting of 50 to 100% by mass of acrylic ester and 50 to 0% by mass of another copolymerizable vinyl monomer, and two or more per molecule A polymer obtained by polymerizing a polyfunctional monomer having a non-conjugated reactive double bond is preferred.

As the acrylic acid ester, it is preferable to use an alkyl group having 1 to 12 carbon atoms from the viewpoint of polymerizability and cost. For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-acrylate octyl, phenyl acrylate, 2-phenoxyethyl acrylate, and the like.

As other vinyl-based monomers copolymerizable with acrylic acid esters, methacrylic acid esters are particularly preferred from the viewpoint of weather resistance and transparency. Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylate 2- phenoxyethyl, 2-ethylhexyl methacrylate, phenyl methacrylate, n-octyl methacrylate, and the like.

Also preferred are aromatic vinyls and derivatives thereof, and vinyl cyanides. Examples of these vinyl monomers include styrene, methylstyrene, acrylonitrile, methacrylonitrile and the like. Other examples include unsubstituted and/or substituted maleic anhydrides, (meth)acrylamides, vinyl esters, vinylidene halides, (meth)acrylic acid and its salts, and (hydroxyalkyl)acrylic acid esters.

Examples of polyfunctional monomers to be copolymerized with monofunctional monomers containing acrylic acid ester as a main component include allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, Diallyl maleate, divinyl adipate, divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, dipropylene glycol dimethacrylate, and these acrylates, etc. can do. Two or more of these polyfunctional monomers may be used.

As a method for producing organic fine particles having a core-shell structure in the present invention, any appropriate method capable of producing core-shell type particles can be adopted.

When the organic fine particles having a core-shell structure in the present invention are produced by emulsion polymerization, suspension polymerization, or the like, a known polymerization initiator can be used. Particularly preferred polymerization initiators include potassium persulfate, ammonium persulfate, persulfates such as ammonium persulfate, superphosphates such as sodium perphosphate, organic azo compounds such as azobisisobutyronitrile, and cumene hydroperoxide. , hydroperoxide compounds such as tertiary butyl hydroperoxide, 1,1 dimethyl-2 hydroxyethyl hydroperoxide, peresters such as tertiary butyl isopropyl oxycarbonate, tertiary butyl peroxybutyrate, benzoyl peroxide, Examples include organic peroxide compounds such as dibutyl peroxide and lauryl peroxide. These may be used as thermal decomposition type polymerization initiators, and are used as redox type polymerization initiators in the presence of a catalyst such as ferrous sulfate and a water-soluble reducing agent such as ascorbic acid or sodium formaldehyde sulfoxylate. It may be appropriately selected according to the composition of the monomers to be polymerized, layer structure, polymerization temperature conditions, and the like.

When the organic fine particles having a core-shell structure in the present invention are produced by emulsion polymerization, they can be produced by ordinary emulsion polymerization using a known emulsifier. Known emulsifiers include, for example, anionic sodium alkylsulfonate, sodium alkylbenzenesulfonate, sodium dioctylsulfosuccinate, sodium lauryl sulfate, fatty acid sodium, and phosphate salts such as sodium polyoxyethylene lauryl ether phosphate. Examples include surfactants, nonionic surfactants such as reaction products of alkylphenols, fatty alcohols with propylene oxide and ethylene oxide. These surfactants may be used alone or in combination of two or more. In addition, if desired, cationic surfactants such as alkylamine salts may be used.

The refractive index difference between the organic fine particles having a core-shell structure in the present invention and the polycycloolefin of the present invention is preferably 0.015 or less, more preferably 0.012 or less, and still more preferably. is 0.01 or less. When the refractive index difference is 0.015 or less, an optical film having excellent transparency can be obtained. Methods for satisfying the above refractive index conditions include a method of adjusting the unit composition ratio of each monomer used and/or the composition of the polymer and/or monomers used in each layer of the rubbery-containing particles. A method of adjusting the ratio and the like can be mentioned.

The refractive index can be measured by press-molding organic fine particles and measuring the average refractive index of the molded product with a laser refractometer. Let that value be the refractive index of the organic fine particles.

Similarly, for the polycycloolefin according to the present invention, the material (resin or resin composition) constituting the polycycloolefin is molded, the average refractive index of the molded body is measured with a laser refractometer, and the value is Let it be the refractive index of polycycloolefin.

In addition, the said refractive index means the refractive index with respect to the light of a wavelength of 550 nm in 23 degreeC.

In preparing the organic matting agent-containing dope of the present invention, it is preferable to prepare a dispersion of organic fine particles in advance. The solvent for the dispersion is preferably selected from some or all of the dope solvent species. It is preferable that the organic fine particles are present in a monodisperse state in the dispersion liquid, and therefore, a dispersant or the like is also preferably selected. For the dispersibility of the organic fine particles, anionic, cationic, and nonionic surfactants and polymers for obtaining a steric repulsion effect are preferably added as conventionally known techniques for stabilizing the dispersion of particles.

The organic fine particle content in the dispersion is preferably 1 to 50% by mass. If the content is low, the proportion of the dispersion in the dope in which the amount of organic fine particles to be added increases, and the degree of freedom in dissolving other raw materials decreases. Also, when the content is high, the organic fine particles tend to aggregate in the dispersion, making handling difficult.

As for the state of the organic fine particles in the optical film of the present invention, the most preferable state is that the primary particles are uniformly monodispersed. Conversely, moderate aggregation and uneven distribution may occur within the scope of the present invention.

For example, a form in which the concentration of organic fine particles is high near the surface layer of the film, or conversely a form in which the concentration of organic fine particles is high near the center layer of the film, can be selected depending on the purpose.

The particle shape of individual organic fine particles can be arbitrarily selected from spherical, flat, rod-like, and the like. A flat shape is preferable, and the flat surface is preferably parallel to the film surface because it has little effect on the unevenness of the film surface.

The content of the organic fine particles is preferably 0.05 to 3.0% by mass, more preferably 0.1 to 2.0% by mass, based on the total amount of the polycycloolefin and urethane polymer according to the present invention. is more preferable.

[4] Method for producing the optical film of the present invention The optical film of the present invention is preferably a film produced by a solution casting method.

The optical film of the present invention comprises a step of preparing a dope containing at least the polycycloolefin of the present invention, the polyurethane of the present invention, a matting agent and an organic solvent (dope preparing step), and flowing the dope onto a support. A step of forming a web (also referred to as a casting film) by spreading (casting step), a step of evaporating the solvent from the web on the support (solvent evaporation step), and a step of peeling the web from the support (peeling). step), a step of drying the obtained film (first drying step), a step of stretching the film (stretching step), a step of further drying the film after stretching (second drying step), and drying the obtained optical film. It is preferably manufactured by a winding process (winding process).

The above steps will be described with reference to the drawings.

FIG. 1 is a diagram schematically showing an example of the dope preparation process, the casting process, the drying process and the winding process of the solution casting film forming method preferred for the present invention.

The fine particle dispersion in which the solvent and the matting agent are dispersed by the dispersing machine is passed through the filter 44 from the loading tank 41 and stocked in the stock tank 42 . On the other hand, the polycycloolefin according to the present invention, which is the main dope, is dissolved together with a solvent in the dissolution tank 1, and the matting agent stored in the stock tank 42 is appropriately added and mixed to form the main dope. The obtained main dope is filtered from the filter 3 and the stock pot 4 by the filter 6, added with additives through the confluence tube 20, mixed in the mixer 21, and fed to the pressure die 30.

On the other hand, additives (eg, urethane polymer, ultraviolet absorber, retardation increasing agent, etc.) are dissolved in a solvent, passed through a filter 12 from an additive feeding pot 10 and stocked in a stock pot 13 . After that, it is mixed with the main dope by a confluence tube 20 and a mixer 21 through a filter 15 and a conduit 16 .

The main dope fed to the pressure die 30 is cast on a metal belt-like support 31 to form a web 32, which is dried and peeled at a peeling position 33 to obtain a film. The peeled web 32 is passed through a number of transport rollers in the first drying device 34 and dried to a predetermined amount of residual solvent, and then stretched in the longitudinal direction or the width direction by the stretching device 35 . After stretching, the film is dried while being passed through a conveying roller 37 by a second drying device 36 until a predetermined amount of residual solvent is reached, and then wound into a roll by a winding device 38 .

Each step will be described below.

(1) Dope preparation step In an organic solvent mainly composed of a good solvent for the polycycloolefin according to the present invention, the polycycloolefin and optionally the urethane polymer, matting agent or other compound according to the present invention are dissolved in a dissolution vessel. or mixing the polycycloolefin solution with the urethane polymer, matting agent or other compound solution to prepare the dope, which is the main solution.

When the optical film of the present invention is produced by a solution casting method, the organic solvent useful for forming the dope dissolves the polycycloolefin of the present invention, the urethane polymer of the present invention and other compounds simultaneously. Anything can be used without restriction.

Examples of organic solvents that can be used include chlorine solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, isopropanol, n-butanol, 2-butanol, and the like. alcoholic solvents; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether; One of these solvents may be used alone, or two or more thereof may be used in combination.

The organic solvent used in the present invention is preferably a mixed solvent of a good solvent and a poor solvent, and the good solvent includes, for example, dichloromethane as a chlorinated organic solvent, methyl acetate as a non-chlorinated organic solvent, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro- 1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexa fluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, etc. Among them, dichloromethane is preferred. The good solvent is preferably used in an amount of 55% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more with respect to the total amount of the solvent.

The poor solvent is preferably an alcoholic solvent, and the alcoholic solvent is preferably selected from methanol, ethanol and butanol from the viewpoint of improving the peelability and enabling high-speed casting. Among them, it is preferable to use methanol or ethanol. A high percentage of alcohol in the dope gelled the web, making it easier to peel from the metal substrate, and a low percentage of alcohol reduced the adhesion of polycycloolefins and other compounds in non-chlorinated organic solvent systems. It also plays a role in promoting dissolution. In forming the optical film of the present invention, it is preferable to use a dope having an alcohol concentration in the range of 0.5 to 15.0% by mass in order to improve the flatness of the resulting optical film. .

Dissolution of the polycycloolefin according to the present invention, the urethane polymer according to the present invention, and other compounds may be carried out under normal pressure, below the boiling point of the main solvent, or under pressure above the boiling point of the main solvent. method, JP-A-9-95544, JP-A-9-95557, or a cooling dissolution method as described in JP-A-9-95538, high pressure described in JP-A-11-21379 Various dissolution methods can be used, such as a method of dissolving at a temperature of at least the boiling point of the main solvent.

The concentration of the polycycloolefin according to the invention in the dope is preferably in the range of 10-40% by weight. After the compound is added to the dope during or after dissolution to dissolve and disperse, the dope is filtered with a filter medium, degassed, and sent to the next step by a liquid-sending pump.

Regarding the filtration of the dope, it is preferable to filter the dope with a filter medium having a 90% collection particle size of 10 to 100 times the average particle size of the fine particles, preferably in the main filter 3 having a leaf disk filter.

In the present invention, it is preferable that the filter medium used for filtration has a small absolute filtration accuracy. , there is a problem of lowering productivity.

Therefore, in the present invention, the filter medium used for the polycycloolefin dope preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably 0.001 to 0.008 mm, more preferably 0.003 to 0.008 mm. Filter media in the range of 006 mm are even more preferred.

The material of the filter medium is not particularly limited, and a normal filter medium can be used. It is preferable because there is no

In the present invention, the flow rate of the dope during filtration is preferably 10-80 kg/(h·m ² ), preferably 20-60 kg/(h·m ² ). Here, when the flow rate of the dope during filtration is 10 kg/(h·m ² ) or more, the productivity becomes efficient, and the flow rate of the dope during filtration is within 80 kg/(h·m ² ). If so, the pressure applied to the filter medium becomes appropriate and the filter medium is not damaged, which is preferable.

The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and filtration area.

In many cases, the main dope may contain about 10 to 50% by mass of returned materials.

The returned material is, for example, a finely pulverized product of the optical film of the present invention. The original optical film is used.

Moreover, as a raw material of the resin used for the preparation of the dope, it is also possible to preferably use pellets of the polycycloolefin and other compounds according to the present invention in advance.

(2) Casting process (2-1) Casting of dope The endless metal support 31 that feeds the dope to the pressurized die 30 through a liquid-sending pump (for example, a pressurized metering gear pump) and transfers it endlessly; For example, it is a step of casting the dope from a pressurized die slit onto a casting position on a metal support such as a stainless steel belt or a rotating metal drum.

The metal support used in the casting process preferably has a mirror-finished surface, and a stainless steel belt or a casting drum having a plated surface is preferably used as the metal support. The width of the cast can be in the range 1-4 m, preferably in the range 1.3-3 m, more preferably in the range 1.5-2.8 m. The surface temperature of the metal support in the casting step is set in the range of -50.degree. A higher temperature is preferable because the drying speed of the web (a dope film formed by casting dope on a casting support is called a web) can be increased. Flatness may deteriorate. A preferable support temperature is appropriately determined in the range of 0 to 100°C, more preferably in the range of 5 to 30°C. Alternatively, it is also a preferred method to gel the web by cooling and remove it from the drum in a state containing a large amount of residual solvent. A method for controlling the temperature of the metal support is not particularly limited, but there are a method of blowing hot or cold air and a method of contacting the back side of the metal support with hot water. Heat transfer is more efficient when hot water is used, which is preferable because it takes less time for the temperature of the metal support to become constant. When using hot air, considering the temperature drop of the web due to the latent heat of evaporation of the solvent, hot air above the boiling point of the solvent may be used while preventing foaming and using air with a temperature higher than the target temperature. . In particular, it is preferable to dry efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

The die is preferably a pressurizing die that can adjust the shape of the slit in the mouthpiece portion of the die and can easily make the film thickness uniform. The pressure die includes a coat hanger die, a T die, and the like, both of which are preferably used. The surface of the metal support is a mirror surface. In order to increase the film-forming speed, two or more pressurizing dies may be provided on the metal support, and the doping amount may be divided for lamination.

(2-2) Solvent Evaporation Step This is a step of heating the web on the casting support to evaporate the solvent, and is a step of controlling the residual solvent amount at the time of peeling, which will be described later.

To evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back side of the support with a liquid, and a method of transferring heat from the front and back sides by radiant heat. is good and preferable. Moreover, the method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 30 to 100°C. In order to maintain the atmosphere at 30 to 100° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat it by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and releasability, it is preferable to release the web from the support within 30 to 180 seconds.

(2-3) Peeling Step This is a step of peeling off the web from which the solvent has evaporated on the metal support at the peeling position. The peeled web is sent to the next process as a film.

The temperature at the peeling position on the metal support is preferably in the range of 10-40°C, more preferably in the range of 11-30°C.

In the present invention, the solvent in the web is evaporated in the solvent evaporation step, and the amount of the solvent remaining in the web on the metal support at the time of peeling is preferably in the range of 15 to 100% by mass. The amount of residual solvent is preferably controlled by the drying temperature and drying time in the solvent evaporation step.

When the amount of the residual solvent is 15% by mass or more, the matting agent does not have a distribution in the thickness direction and is uniformly dispersed in the film during the drying process on the support. It is easy to suppress the deformation of the winding shape. In addition, the drying time does not become long, and the productivity is improved.

Further, when the residual solvent amount is within 100% by mass, the film has self-supporting properties, it is possible to avoid peeling failure of the film, and the mechanical strength of the web can be maintained, so that the flatness at the time of peeling is improved. It is possible to suppress the occurrence of creases and vertical streaks due to peeling tension.

The amount of residual solvent in the web or film is defined by the following formula (Z).

Formula (Z):
Residual solvent amount (%) = (weight of web or film before heat treatment - weight of web or film after heat treatment) / (mass of web or film after heat treatment) x 100
Note that the heat treatment for measuring the amount of residual solvent means heat treatment at 115° C. for 1 hour.

The peel tension when peeling the web from the metal support to form a film is usually in the range of 196 to 245 N/m, but if wrinkles are likely to occur during peeling, peel at a tension of 190 N/m or less. preferably.

In the present invention, the temperature at the peeling position on the metal support is preferably in the range of -50 to 40°C, more preferably in the range of 10 to 40°C, and in the range of 15 to 30°C. is most preferred.

(3) Drying and Stretching Process The drying process can be divided into a preliminary drying process (first drying process) and a main drying process (second drying process).

(3-1) Pre-drying step A film obtained by web-peeling from the metal support is pre-dried in the first drying device 34 . In pre-drying the film, the film may be dried while being conveyed by a number of rollers arranged vertically, or may be dried while being conveyed by fixing both ends of the film with clips as in a tenter dryer. good.

The means for drying the web is not particularly limited, and hot air, infrared rays, heating rollers, microwaves, etc. can generally be used, but hot air is preferred from the viewpoint of simplicity.

The drying temperature in the pre-drying step of the web is preferably -5° C. or less of the glass transition point of the film, and it is effective to perform the heat treatment at a temperature of 30° C. or more for 1 minute or more and 30 minutes or less. The drying temperature is in the range of 40 to 150°C, preferably 50 to 100°C.

In the present invention, it is preferable to adjust the residual solvent amount in the film during stretching, which will be described later, in this drying step, but the residual solvent amount may be adjusted in the initial stage of the stretching step. The amount of residual solvent is preferably controlled by the drying temperature and drying time in the preliminary drying step.

(3-2) Stretching step The optical film of the present invention is stretched at a low stretch rate under a specific amount of residual solvent in the stretcher 35, thereby suppressing the generation of minute crazes near the surface of the film. Moreover, uniform distribution of the matting agent can be promoted. Furthermore, target retardation values Ro and Rt can be obtained by controlling the orientation of the molecules in the film.

The method for producing an optical film of the present invention is characterized in that, in the step of stretching the film, the amount of residual solvent at the start of stretching is 1% by mass or more and less than 15% by mass. It is preferably within the range of 2 to 10% by mass.

If the amount of residual solvent at the start of stretching is less than 1% by mass, excessive stress is applied during stretching, and fine crazes tend to occur near the surface of the film, degrading adhesion with UV glue.

On the other hand, when the residual solvent amount is 15% by mass or more, stress is less likely to be applied during stretching, so the fine particles of the matting agent in the film are less likely to move along the orientation of the resin, and the desired uneven structure can be formed on the film surface. However, deformation failure of the winding shape occurs.

The optical film of the present invention is preferably stretched in the longitudinal direction (also referred to as the MD direction or casting direction) and/or the transverse direction (also referred to as the TD direction). It is preferable to manufacture by

The stretching operation may be divided into multiple stages and carried out. Moreover, when performing biaxial stretching, simultaneous biaxial stretching may be performed and you may implement in steps. In this case, stepwise, for example, it is possible to sequentially perform stretching in different stretching directions, or to divide stretching in the same direction into multiple stages and add stretching in different directions to any of the stages. is also possible.

Thus, for example, the following drawing steps are also possible:
・Stretching in the longitudinal direction→stretching in the width direction→stretching in the longitudinal direction→stretching in the longitudinal direction ・Stretching in the width direction→stretching in the width direction→stretching in the longitudinal direction→stretching in the longitudinal direction Simultaneous biaxial stretching Also includes stretching in one direction and shrinking the other by relaxing the tension.

The optical film of the present invention is stretched in the longitudinal direction and/or the width direction, preferably in the width direction, so that the film thickness after stretching is within a desired range, and when the glass transition temperature of the film is Tg, ( Stretching is preferably performed in the temperature range of Tg+5) to (Tg+50)°C. When the film is stretched in the above temperature range, the retardation can be easily adjusted, and the stretching stress can be reduced, so that the haze can be lowered. In addition, it is possible to suppress the occurrence of breakage and obtain an optical film having excellent flatness and colorability of the film itself. The stretching temperature is preferably in the range of (Tg+10) to (Tg+40)°C.

The glass transition temperature Tg referred to here is the midpoint glass transition temperature (Tmg) obtained according to JIS K7121 (1987), measured at a heating rate of 20° C./min using a commercially available differential scanning calorimeter. is. A specific method for measuring the glass transition temperature Tg of the optical film is measured using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. according to JIS K7121 (1987).

The optical film of the present invention is preferably stretched at least in the width direction at a stretching ratio of 5 to 80% with respect to the original width. It is more preferable to draw at a draw ratio within the range of up to 60%. In particular, it is more preferable that the stretching ratio range is 10 to 50% of the original width. If it is within the above range, the occurrence of fine crazes near the film due to high magnification stretching can be suppressed, and especially when a urethane polymer is included, not only the desired retardation value can be obtained, but also the film can be made thinner. The stretch ratio as used in the present invention refers to the ratio (%) of the length or width of the film after stretching to the length or width of the film before stretching.

There is no particular limitation on the method of stretching in the longitudinal direction. For example, there is a method of applying peripheral speed differences to multiple rolls and stretching them in the longitudinal direction using the roll peripheral speed differences between them, fixing both ends of the web with clips and pins, and expanding the intervals between the clips and pins in the direction of travel. and stretching in the longitudinal direction, or stretching in both the longitudinal and transverse directions by spreading the same in the longitudinal and transverse directions at the same time. Of course, these methods may be used in combination.

For stretching in the width direction, for example, the entire drying process or a part of the drying process as shown in Japanese Patent Application Laid-Open No. 46625/1987 is carried out by holding both widthwise ends of the web with clips or pins in the width direction. A method of drying while drying (called a tenter method), among which a tenter method using clips and a pin tenter method using pins are preferably used.

When stretching in the width direction, it is preferable to stretch the film in the width direction at a stretching rate of 250 to 500%/min from the viewpoint of improving the flatness of the film.

If the stretching rate is 250%/min or more, the flatness is improved and the film can be processed at high speed, which is preferable from the viewpoint of production suitability. If it is 500%/min or less, the film breaks. It is preferable because it can be processed without

A preferred drawing speed is in the range of 300 to 400%/min, which is effective when drawing at a low magnification. The stretching speed is defined by Equation 1 below.

Formula 1 Stretching speed (%/min) = [(d ₁ /d ₂ )-1] × 100 (%) / t
(In Formula 1, _d1 is the width dimension in the stretching direction of the optical film of the present invention after stretching, _d2 is the width dimension in the stretching direction of the optical film before stretching, and t is the time required for stretching. (min).)
In the stretching step, holding and relaxation are usually performed after stretching. That is, in this process, it is preferable to carry out, in this order, a stretching step of stretching the film, a holding step of holding the film in the stretched state, and a relaxation step of relaxing the film in the stretched direction. In the holding stage, the stretching at the stretching ratio achieved in the stretching stage is held at the stretching temperature in the stretching stage. In the relaxation stage, the stretching in the stretching stage is held in the holding stage, and then the stretching is relaxed by releasing the tension for stretching. The relaxation stage may be performed at a temperature equal to or lower than the stretching temperature in the stretching stage.

(3-3) Main Drying Step In the main drying step, the second drying device 36 heats and dries the stretched film. When the film is heated with hot air or the like, it is preferable to install a nozzle capable of exhausting used hot air (solvent-containing air or wetting air) to prevent the used hot air from being mixed. The hot air temperature is more preferably in the range of 40 to 350°C. The drying time is preferably about 5 seconds to 60 minutes, more preferably 10 seconds to 30 minutes.

Moreover, the heating and drying means is not limited to hot air, and for example, infrared rays, heating rollers, microwaves, etc. can be used. From the viewpoint of simplicity, it is preferable to dry the film with hot air or the like while transporting the film with transport rollers 37 arranged in a zigzag pattern. The drying temperature is more preferably in the range of 40 to 350° C. in consideration of the amount of residual solvent, the expansion ratio during transportation, and the like.

In the drying step, the film is preferably dried until the amount of residual solvent is 0.5% by mass or less.

(4) Winding Step (4-1) Knurling Processing After a predetermined heat treatment or cooling treatment, it is preferable to provide a slitter and cut off the ends before winding, in order to obtain a good winding shape. Further, it is preferable to perform knurling processing on both widthwise end portions.

The knurling process can be formed by pressing a heated embossing roller against the width edge of the film. The embossing roller has fine unevenness, and by pressing it against the film, unevenness is formed on the film, and the edges can be made bulky.

The knurling height at both lateral ends of the optical film of the present invention is preferably 4 to 20 μm and the width is preferably 5 to 20 mm.

Further, in the present invention, the knurling process is preferably provided after drying and before winding in the film forming process.

(4-2) Winding step This is a step of winding the film after the amount of residual solvent in the film reaches 2% by mass or less. A good film can be obtained.

A winding method generally used may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like.

According to the method for producing an optical film of the present invention, by controlling the amount of residual solvent during stretching within a specific range, it is possible to apply an appropriate stress to the film during stretching. It is possible to form an uneven structure uniformly distributed on the surface, and by ensuring uniform slipperiness, a stable winding shape can be achieved.

[5] Physical properties of optical film (retardation values Ro and Rt)
The optical film of the invention preferably has a function as a retardation film. For example, in order to function as a retardation film, two sheets are arranged above and below the liquid crystal cell of a VA mode liquid crystal display device. is preferably 50 to 80 nm, and the retardation value Rt in the thickness direction is preferably 100 to 200 nm. When functioning as a retardation film arranged on one side of the liquid crystal cell, the retardation value Ro in the in-plane direction is preferably 100 to 200 nm, and the retardation value Rt in the thickness direction is It is preferably 200-400 nm.

Further, when functioning as a retardation film for an IPS mode liquid crystal display device, the retardation value Ro in the in-plane direction measured under an environment of a measurement wavelength of 550 nm and 23° C./55% RH is 0 to It is preferably 8 nm, more preferably 0 to 5 nm. The retardation value Rt in the thickness direction is preferably −10 to 10 nm, more preferably −8 to 8 nm.

In addition, Ro and Rt of the optical film are defined by the following formulas.

Formula (1a): Ro = (n _x -n _y ) x d
Formula (1b): Rt=((n _x +n _y )/2−n _z )×d
(Wherein, n _x is the refractive index in the direction x (in-plane slow axis direction) in which the refractive index is maximized in the in-plane direction of the film, and _ny is the direction x ( is the refractive index in the direction y perpendicular to the in-plane slow axis direction), _nz is the refractive index in the film thickness direction, and d is the film thickness (nm).)
The retardation values Ro and Rt of the optical film can be measured by the following method.

(1) The optical film is conditioned at 23° C. and 55% RH for 24 hours.

(2) Retardation values Ro and Rt at a measurement wavelength of 550 nm of the optical film after humidity conditioning are measured under an environment of 23° C. and 55% RH using an automatic birefringence meter Axoscan manufactured by Axometrics. The specific measurement procedure and measurement conditions are the same as those of the examples described later.

<Haze>
The optical film of the present invention preferably has a haze of less than 1%, more preferably less than 0.5%. By setting the haze to less than 1%, there is an advantage that the transparency of the film becomes higher and it becomes easier to use as an optical film.

The haze value is measured at 10 points at equal intervals in the width direction of the film using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) under an environment of 23° C. and 55% RH, and the average value is calculated. The desired haze is obtained.

<Film length, width, film thickness>
The optical film of the present invention preferably has a long length, and specifically, preferably has a length of about 100 to 10,000 m, and is wound into a roll. The width of the optical film of the present invention is preferably 1 m or more, more preferably 1.3 m or more, and particularly preferably 1.3 to 4 m.

The thickness of the stretched film is preferably in the range of 10 to 50 μm from the viewpoint of thinning of the display device and productivity. If the film thickness is 10 μm or more, film strength and retardation above a certain level can be expressed. If the film thickness is 50 μm or less, a desired retardation can be obtained, and the thickness of the polarizing plate and the display device can be reduced. Preferably, the thickness of the film is in the range of 20-35 μm.
physical properties)
[6] Polarizing plate [6.1] Polarizer A polarizer is an element that transmits only light with a plane of polarization in a certain direction, and examples thereof include polyvinyl alcohol-based polarizing films.

The polyvinyl alcohol-based polarizing film includes a polyvinyl alcohol-based film dyed with iodine and a polyvinyl alcohol-based film dyed with a dichroic dye.

The polarizer can be obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing it, or by dyeing a polyvinyl alcohol film, uniaxially stretching it, and preferably further performing a durability treatment with a boron compound.

The film thickness of the polarizer is preferably in the range of 5 to 30 μm, more preferably in the range of 5 to 15 μm.

As the polyvinyl alcohol film, an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99.0 to 99 are described in JP-A-2003-248123 and JP-A-2003-342322. 0.99 mol % of ethylene-modified polyvinyl alcohol is preferably used. Moreover, it is preferable to manufacture a polarizer by the methods described in JP-A-2011-100161, JP-A-4691205, and JP-A-4804589, and bond the polarizer to the optical system of the present invention to produce a polarizing plate.

[6.2] Adhesive [Water glue]
The polarizing plate of the present invention can be obtained by bonding the optical film of the present invention to a polarizer using a completely saponified polyvinyl alcohol aqueous solution (water glue). It is more preferable that they are bonded with a line-curing adhesive.

As the active energy ray-curable adhesive, it is preferable to use the following UV-curable adhesive.

In the present invention, by applying an ultraviolet curable adhesive to the bonding of the optical film and the polarizer, it is possible to obtain a polarizing plate that is thin but has high strength and excellent flatness.

<Composition of UV curable adhesive>
As the ultraviolet curable adhesive composition for the polarizing plate, a photo-radical polymerization type composition utilizing photo-radical polymerization, a photo-cation polymerization type composition utilizing photo-cation polymerization, and a combination of photo-radical polymerization and photo-cation polymerization. Such hybrid compositions are known.

As the photoradical polymerizable composition, a radically polymerizable compound containing a polar group such as a hydroxy group or a carboxyl group and a radically polymerizable compound containing no polar group described in JP-A-2008-009329 are contained in a specific proportion. composition) and the like are known. In particular, the radically polymerizable compound is preferably a compound having a radically polymerizable ethylenically unsaturated bond. Preferred examples of compounds having a radically polymerizable ethylenically unsaturated bond include compounds having a (meth)acryloyl group. Examples of compounds having a (meth)acryloyl group include N-substituted (meth)acrylamide compounds and (meth)acrylate compounds. (Meth)acrylamide means acrylamide or methacrylamide.

Further, as the photocationically polymerizable composition, as disclosed in JP-A-2011-028234, (α) a cationic polymerizable compound, (β) a photocationic polymerization initiator, (γ) a wavelength longer than 380 nm and (δ) a naphthalene-based photosensitizing aid. However, other ultraviolet curable adhesives may be used.

(1) Pretreatment step The pretreatment step is a step of subjecting the surface of the optical film to be adhered to the polarizer to easy-adhesion treatment. Examples of easy-adhesion treatment include corona treatment and plasma treatment.

(Process of applying UV curable adhesive)
In the step of applying the ultraviolet curable adhesive, the ultraviolet curable adhesive is applied to at least one of the adhesion surfaces of the polarizer and the optical film. When applying the UV-curable adhesive directly to the surface of the polarizer or optical film, there is no particular limitation on the application method. For example, various wet coating methods such as doctor blade, wire bar, die coater, comma coater and gravure coater can be used. Alternatively, a method of casting an ultraviolet curable adhesive between the polarizer and the optical film and then pressing with a roller or the like to spread it uniformly can also be used.

(2) Bonding process After applying the ultraviolet curable adhesive by the above method, it is processed in the bonding process. In this pasting step, for example, when an ultraviolet curable adhesive is applied to the surface of the polarizer in the previous application step, the optical film is superimposed thereon. Also, in the case of a method in which an ultraviolet curable adhesive is first applied to the surface of the optical film, a polarizer is superimposed thereon. Further, when an ultraviolet curable adhesive is cast between the polarizer and the optical film, the polarizer and the optical film are superimposed in that state. Then, in this state, the optical films on both sides are sandwiched and pressurized by pressure rollers or the like. Metal, rubber, or the like can be used as the material of the pressure roller. The pressure rollers arranged on both sides may be made of the same material or may be made of different materials.

(3) Curing step In the curing step, the uncured UV-curable adhesive is irradiated with UV rays to form a cationic polymerizable compound (e.g., epoxy compound or oxetane compound) or a radically polymerizable compound (e.g., acrylate compound, acrylamide). compound, etc.) is cured, and the superimposed polarizer and optical film are adhered via the ultraviolet curable adhesive. When the optical film is laminated on one side of the polarizer, the active energy ray may be applied from either the polarizer side or the optical film side. In addition, when optical films are laminated on both sides of a polarizer, the optical films are superimposed on both sides of the polarizer with an ultraviolet curable adhesive interposed therebetween, and then irradiated with ultraviolet rays. are cured simultaneously.

Any appropriate conditions can be adopted as the irradiation conditions of ultraviolet rays as long as they are conditions under which the ultraviolet curing adhesive applied to the present invention can be cured. The irradiation dose of ultraviolet rays is preferably in the range of 50 to 1500 mJ/cm ² in terms of integrated light quantity, and more preferably in the range of 100 to 500 mJ/cm ² .

When the polarizing plate manufacturing process is carried out on a continuous line, the line speed is preferably in the range of 1 to 500 m/min, more preferably in the range of 5 to 300 m/min, even more preferably in the range of 10 to 300 m/min, although it depends on the curing time of the adhesive. It is in the range of 100m/min. If the line speed is 1 m/min or more, productivity can be ensured, damage to the optical film can be suppressed, and a polarizing plate with excellent durability can be produced. Further, when the line speed is 500 m/min or less, curing of the UV-curable adhesive is sufficient, and an UV-curable adhesive layer having the desired hardness and excellent adhesiveness can be formed.

[6.3]
The film placed on the opposite side of the polarizer to the optical film of the present invention is preferably a film that functions as a protective film for the polarizer.

As such a protective film, the optical film of the present invention may be used. , KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UAKC, 2UAH, KC4UAH, KC6UAH, manufactured by Konica Minolta Co., Ltd., Fujitac T40UZ, Fujitac T60UZ, Fujitac UD, Fujitac T80UZ, 80 TD60UL, FUJITAC TD40UL, FUJITAC R02, FUJITAC R06, all manufactured by Fuji Film Co., Ltd.) can also be preferably used.

Also, for example, resin films such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, etc., alicyclic polyolefins (for example, Nippon Zeon Co., Ltd., Zeonor (registered trademark), polyarylates, polyethersulfones, polysulfones, cycloolefin copolymers, polyimides ( Examples thereof include neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd.), fluorene ring-modified polycarbonate, alicyclic-modified polycarbonate, and resin films of acryloyl compounds (the glass transition temperature Tg is shown in parentheses). Among the materials, films such as polyethylene terephthalate (abbreviation: PET), polybutylene terephthalate, polyethylene naphthalate (abbreviation: PEN), and polycarbonate (abbreviation: PC) are flexible resins in terms of cost and availability. It is preferably used as a base material.

Although the thickness of the protective film is not particularly limited, it can be about 10 to 200 μm, preferably in the range of 10 to 100 μm, more preferably in the range of 10 to 70 μm.

[7] Display Device By using the polarizing plate to which the optical film of the present invention is bonded, various liquid crystal display devices of the present invention having excellent visibility can be produced.

The polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, and OCB. A VA (MVA, PVA) type liquid crystal display device and an IPS type liquid crystal display device are preferable.

Two polarizing plates, a polarizing plate on the viewing side and a polarizing plate on the backlight side, are usually used in a liquid crystal display device. It is also preferable to use as In particular, the polarizing plate of the present invention is preferably used as a polarizing plate on the viewing side that comes into direct contact with the external environment. In that case, when the optical difference film of the present invention is an optical compensation film, it should be placed on the liquid crystal cell side. is preferred.

In addition, a polarizing plate other than the present invention can be used as the polarizing plate on the backlight side. KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC2UAH, KC4UAH, KC6UAH, Konica Minolta T40, Fujitac UZ T60UZ, FUJITAC T80UZ, FUJITAC TD80UL, FUJITAC TD60UL, FUJITAC TD40UL, FUJITAC R02, FUJITAC R06, manufactured by FUJIFILM Corporation, etc.) are preferably used as laminated polarizing plates.

As a polarizing plate on the backlight side, the optical film of the present invention is used on the liquid crystal cell side of the polarizer, and the commercially available protective film, retardation film, polyester film, acrylic film, or polycarbonate film is pasted on the opposite side. A combined polarizer can also be preferably used.

By using the polarizing plate of the present invention, it is possible to obtain a liquid crystal display device having excellent visibility such as display unevenness and front contrast, even if the liquid crystal display device has a large screen of 30 inches or more.

After the optical film of the present invention is formed by a solution casting film forming method, it is obliquely stretched in a direction within a range of 45±10° with respect to the longitudinal direction, and laminated so that the longitudinal direction is aligned with the polarizer. By doing so, a circularly polarizing plate can be produced, and the circularly polarizing plate is useful, for example, as a polarizing plate for an organic electroluminescence display device, as a circularly polarizing plate with antireflection properties and reduced color unevenness.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these. In the examples, "parts" or "%" are used, but "mass parts" or "mass%" are indicated unless otherwise specified.

<Synthesis of polymer (polycycloolefin) containing alicyclic hydrocarbon monomer>
As an alicyclic hydrocarbon monomer (norbornene-based monomer), 100 parts by mass of the following compound (exemplified compound 27), 3.6 parts by mass of 1-hexene as a molecular weight modifier, and 200 parts by mass of toluene A reaction vessel purged with nitrogen was charged with the above mass and heated to 80°C. To this, 0.17 parts by mass of a toluene solution of 1.5 mol/L of triethylaluminum ((C ₂ H ₅ ) ₃ Al) as a polymerization catalyst, t-butanol and methanol-modified tungsten hexachloride (WCl ₆ ), and 1.0 parts by mass of a WCl ₆ solution (concentration 0.05 mol/L) of t-butanol:methanol:tungsten = 0.35:0.3:1 (molar ratio), The mixture was heated and stirred at 80° C. for 3 hours to carry out a ring-opening polymerization reaction to obtain a polymer solution. The polymerization conversion rate in this polymerization reaction was 98%.

4000 parts by mass of the resulting polymer solution was placed in an autoclave, 0.48 parts by mass of RuHCl(CO)[P(C ₆ H ₅ ) ₃ ] ₃ was added to the polymer solution, the hydrogen gas pressure was set to 10 MPa, and the reaction was carried out. A hydrogenation reaction was carried out by heating and stirring for 3 hours at a temperature of 160°C.

After cooling the resulting reaction solution, the pressure of hydrogen gas was released, and the reaction solution was poured into a large amount of methanol to separate and recover the solidified matter. The recovered coagulum was dried to obtain polycycloolefin 1.

The weight average molecular weight of the obtained polycycloolefin 1 was measured by the method described above and found to be 140,000. The refractive index of this polycycloolefin was measured by the method described above and found to be 1.51.

<Synthesis of urethane polymers 1 to 14>
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube was charged with the raw materials shown in Table I below and reacted at 75° C. for 1 hour to obtain a dimethylformamide solution of polyurethane.

After the reaction, the reaction solution was allowed to cool until it returned to room temperature, and the reaction solution was poured into 1500 parts by mass of methanol with vigorous stirring to precipitate a white solid.

A white solid was filtered off by suction filtration and dried at 60° C. overnight. Furthermore, this white solid was again washed with a large amount of methanol and separated by suction filtration. The obtained white solid was dried at 60° C. for 12 hours and then vacuum dried at 90° C. for 6 hours. ~14 was obtained.

The urethane polymers 11 to 14 were adjusted to desired weight average molecular weights by adjusting the reaction time.

The structures of the diol and isocyanate used are as follows.

<Synthesis of polyester plasticizer>
251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst, each equipped with a thermometer, a stirrer and a slow cooling tube. The mixture was placed in a 2 L four-necked flask, and the temperature was gradually raised to 230° C. in a nitrogen stream while stirring. A dehydration condensation reaction was carried out for 15 hours, and after completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200° C. to obtain a polyester plasticizer. As a result of measurement by a conventional method, the acid value was 0.10 mgKOH/g and the number average molecular weight was 450.

<Production of organic matting agent>
(Production of core particles)
A polymerization vessel equipped with a stirrer and a thermometer was charged with 1000 g of deionized water, 200 g of methyl methacrylate and 6 g of t-dodecyl mercaptan were added, and the mixture was heated to 70° C. with stirring and nitrogen replacement. The internal temperature was kept at 70° C., and 20 g of deionized water containing 1 g of potassium persulfate dissolved as a polymerization initiator was added, followed by polymerization for 10 hours. The average particle size of the core particles in the obtained emulsion was 0.44 μm.

(Production of polymer particles)
A polymerization vessel equipped with a stirrer and a thermometer was charged with 800 g of deionized water in which 3 g of ammonium polyoxyethylene tridecyl ether sulfate was dissolved. and 1 g of azobisisobutyronitrile as a polymerization initiator. The mixture is then added to T.I. A dispersion was obtained by stirring with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.).

Further, 60 g of the above emulsion containing core particles was added to the dispersion and stirred at 30° C. for 1 hour to allow the seed particles to absorb the monomer mixture. Next, the absorbed monomer mixture was polymerized by heating at 50° C. for 5 hours under a nitrogen stream, and then cooled to room temperature (about 25° C.) to obtain a slurry containing polymer particles. The average particle diameter of the obtained polymer particles (organic fine particles) was 0.3 μm. The refractive index of the polymer particles was measured by the method described above and found to be 1.51.

This slurry was spray-dried under the following conditions using a spray dryer manufactured by Sakamoto Giken Co., Ltd. (model: atomizer take-up system, model number: TRS-3WK) to obtain polymer particles. This polymer particle was used as an organic matting agent.

Feed rate: 25ml/min
Atomizer rotation speed: 11000rpm
Air volume: 2 m ³ /min
Slurry inlet temperature of spray dryer: 130°C
Polymer particle outlet temperature: 70°C
The average particle size was measured with a zeta potential/particle size measuring system (ELSZ-1000Z manufactured by Otsuka Electronics Co., Ltd.).

<Preparation of matting agent additive liquid 1>
After stirring and mixing the following materials with a dissolver for 50 minutes, they were dispersed with a Manton Gaulin. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare matting agent additive liquid 1 having a matting agent content of 4.0% by mass.

Organic matting agent 4 parts by mass Dichloromethane 96 parts by mass <Preparation of dope>
First, methylene chloride and ethanol were charged into a pressurized dissolution tank. Next, the polymer containing polycycloolefin 1 and the urethane polymer 1 were charged into the pressurized dissolution tank with stirring to prepare a dope having the following composition. Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. 244 (filtration accuracy of 0.005 mm) at a filtration flow rate of 300 L/m ² ·h and a filtration pressure of 1.0×10 ⁶ Pa.

<Composition of dope>
Polycycloolefin 1 90.0 parts by mass Urethane polymer 1 10.0 parts by mass Dichloromethane 300.0 parts by mass Ethanol 20.0 parts by mass It has a composition of Polymer 1 (10.0% by mass).

<Preparation of matting agent-containing dope>
First, methylene chloride and ethanol were charged into a pressurized dissolution tank. Then, the polycycloolefin 1 and the urethane polymer 9 were put into the pressurized dissolution tank while stirring, and a 4% by mass matting agent additive was added to prepare a dope having the following composition. Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. 244 (filtration accuracy of 0.005 mm) at a filtration flow rate of 300 L/m ² ·h and a filtration pressure of 1.0×10 ⁶ Pa.

<Composition of dope>
Polycycloolefin 1 88.0 parts by mass Urethane polymer 9 10.0 parts by mass Dichloromethane 250.0 parts by mass Ethanol 20.0 parts by mass 4% by mass matting agent additive liquid 1 50.0 parts by mass (amount of matting agent: 2.0 parts by mass) 0 parts by mass)
The solid matter in the dope has a composition of polycycloolefin 1 (88.0% by mass), urethane polymer 9 (10.0% by mass), and matting agent (2.0% by mass).

<Preparation of Optical Film by Solution Casting>
The dope prepared above was sent from the pressurized dissolution tank to a pressurized die with a gear pump, and cast onto a stainless steel endless support (belt). After evaporating the solvent until the amount of residual solvent in the cast dope reached 40% by mass, the resulting film-like material was peeled off from the stainless steel endless support with a peel tension of 130 N/m. The peeled film-like material was transported to a tenter stretching device while being dried, and transported through the tenter at a stretching ratio of 50% (1.5 times) in the width direction. At this time, the drying conditions from peeling to tentering were adjusted so that the amount of residual solvent during stretching was 11% by mass. The temperature of the tenter stretching device was set to 160° C., and the stretching speed was set to 200%/min.

Next, the drying was completed while being conveyed in the drying apparatus by a large number of rollers. The drying temperature was 130° C. and the conveying tension was 100 N/m. After that, both ends of the obtained optical film were slit and embossed to prepare optical film 1 having a dry film thickness of 40 μm. bottom. Incidentally, the optical films 23 and 24 used the above-described dope or matting agent-containing dope.

≪Evaluation≫
Using the obtained optical films 1 to 24, the following evaluations were carried out.

(1) Haze The haze of the optical film is based on JIS K-7136, using NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the light source is a 5V9W halogen bulb, and the light receiving part is a silicon photo. A cell (with a relative luminous efficiency filter) was used, and the measurement was performed under the conditions of 23° C. and 55% RH.

For use as an optical film, a haze of more than 1% is not preferable because it is inferior in terms of transparency. It is preferably 0.5% or less, more preferably 0.2% or less.

(2) In-plane retardation value (Ro)
The in-plane retardation value (Ro) of the optical film is measured at a wavelength of 550 nm under an environment of a temperature of 23° C. and a relative humidity of 55%. and measured.

(3) Light resistance An optical film was cut into a size of 100 mm x 100 mm, and an Atlas Weatherometer Ci3000+ (manufactured by Atlas) was used as a xenon weather meter, with an intensity of 60 W/m ² in accordance with ISO 4292-2. was irradiated with light for 100 hours.

The yellow index (YI) of the optical film before and after irradiation was measured, and the difference between before and after was taken as the value of ΔYI.

The yellow index is obtained by the method described in JIS K-7105-6.3. As a specific method for measuring the yellow index value, the tristimulus values X, Y, and Z of the color are obtained using a spectrophotometer U-3200 manufactured by Hitachi High Technology Co., Ltd. and the attached saturation calculation program. , the yellow index value was determined according to the following formula.

Yellow index (YI) = 100 (1.28X-1.06Z)/Y
When the yellow index (YI) is less than 1.2, the transparency is high and can be preferably used for optical films.

If the value of ΔYI after lightfastness is greater than 0.8, the optical film is colored, which is undesirable in terms of durability when used in a liquid crystal display device. Therefore, it is preferred that the value of ΔYI be less than 0.8.

(4) Strength of film If the film does not have sufficient strength in a solvent-containing state, deformation, cracks, and cracks may occur from the tenter clip portion during transportation and stretching of the film, and from the edges during slitting. occurs. In extreme cases, the film-like material (or film) being conveyed may be completely broken from the deformed portion or the tear, resulting in a significant drop in productivity.

Therefore, the strength of the film in the solvent-containing state was determined by visually observing the film from peeling to the end of stretching in the tenter, and the number of times deformations, tears, and eyes were confirmed during film formation of 1000 m. counted.

No deformed parts, tears, or eyes: ◎
Less than 5 deformed parts, tears, and tears: 〇 Deformed parts, tears, and less than 5 to 10 times: △
More than 10 times of deformed parts, tears and eyes: ×
The structure of the optical film and the above evaluation results are shown in Table II.

From Table II, it is clear that the optical film having the structure of the present invention is an optical film having low haze, excellent light resistance, reduced breakage during film production, and excellent retardation expression.

1 dissolution pot 3, 6, 12, 15 filter 4, 13 stock pot 2, 5, 11, 14 liquid feed pump 8, 16 conduit 10 additive preparation pot 20 confluence pipe 21 mixer 30 pressure die 31 metal belt 32 Web 33 Peeling position 34 Stretching device 35 Drying device 36 Conveying roller 37 Winding device 41 Preparation pot 42 Stock pot 43 Pump 44 Filter

Claims (5)

At least a polymer containing an alicyclic hydrocarbon monomer having a polar group, a diol monomer having an alicyclic structure in the molecule, and an isocyanate monomer having an alicyclic structure in the molecule and a urethane polymer ,
An optical film , wherein one kind of the urethane polymer contains two or more kinds of the diol monomers . 2. The optical film according to claim 1, wherein the urethane polymer has a weight average molecular weight in the range of 1,000 to 100,000. 3. The optical film according to claim 1 , wherein one kind of said urethane polymer contains two or more kinds of said isocyanate monomers. The mixing mass ratio (A/B) of the polymer (A) containing the alicyclic hydrocarbon monomer having a polar group and the urethane polymer (B) is in the range of 50/50 to 95/5. The optical film according to any one of claims 1 to 3 , characterized in that: 5. The optical film according to any one of claims 1 to 4 , further comprising an organic matting agent.

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