JP2017102310A - Optical film and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film excellent in flatness and breaking elongation, and to provide a display device having the same.SOLUTION: An optical film is an optical film containing a cycloolefin resin, and contains a compound having a structure represented by general formula (1) or general formula (2).SELECTED DRAWING: None

Description

  The present invention relates to an optical film and a display device, and more particularly to an optical film excellent in flatness and elongation at break and a display device including the same.

  As a base film used for a polarizing plate protective film for a liquid crystal display device, a cellulose acetate film that has been widely used conventionally has a drawback of having hygroscopicity and moisture permeability, while a film using a cycloolefin resin is There are few such defects, water resistance, heat resistance, transparency, optical characteristics, dimensional stability, etc. are good, and it has been attracting attention as an excellent thermoplastic resin optical film.

  In addition, with the recent reduction in weight and thickness of display devices and the expansion of the mobile market, optical films are also required to be made thinner.

  However, when a cycloolefin resin film (also referred to as a cycloolefin-based film in the present application) is thinned, deterioration of various physical properties becomes a problem with the thinning.

  For example, a method for forming a cycloolefin-based film by a solution casting method is a known technique. However, as the film thickness is reduced, surface defects that have not been a problem in the past and mechanical properties of the film are significantly reduced. I came.

  A solution casting method (see Patent Document 1) that controls the flow of residual solvent and air in a drying step after casting is known as a means for improving the deterioration of flatness associated with film thinning. However, this method is a technique for improving deterioration of flatness at the time of drying after casting, and is effective for a relatively thick film of 40 to 65 μm, but is not effective for further thinning. It was enough.

JP 2009-83149 A

  The present invention has been made in view of the above-described problems and situations, and a problem to be solved is to provide an optical film having excellent flatness and elongation at break. Moreover, it is providing the display apparatus provided with it.

  As a result of studying the cause of the above-mentioned problems in order to solve the above-mentioned problems, the present inventors have found that in the solution casting film-forming method of cycloolefin film, when the casting film becomes thin, the casting film is immediately after casting. Until the film is cast on the support, the film strength of the cast film is weak and the stability of the film cannot be maintained, and the flatness deteriorates. As a countermeasure, it is possible to stably cast even a thin film by adding a compound having a structure represented by general formula (1) or general formula (2) and increasing the strength of the cast film. As a result, the present invention has been found.

  That is, the said subject which concerns on this invention is solved by the following means.

  1. An optical film containing a cycloolefin resin, wherein the optical film contains a compound having a structure represented by the following general formula (1) or general formula (2).

(Wherein R _{1 to} R ₄ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms)

(Wherein R _{5 to} R ₇ each independently represents an alkyl group having 1 to 20 carbon atoms.)
2. 2. The optical film according to item 1, wherein the thickness is in the range of 5 to 30 μm.

  3. 2. The optical film according to item 1, wherein the thickness is in the range of 10 to 20 μm.

  4). The optical film according to any one of Items 1 to 3, further comprising an ultraviolet absorber.

  5. The optical film according to any one of Items 1 to 4, further comprising a matting agent.

  6). A display device comprising the optical film according to any one of items 1 to 5.

  By the above means of the present invention, an optical film having excellent flatness and elongation at break can be provided. In addition, a display device including the same can be provided.

  The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

  By adding a compound having a structure represented by the general formula (1) or the general formula (2) that functions as a thickener in the solution casting film forming method of an optical film containing a cycloolefin-based resin. It is estimated that the film strength of the cast film can be increased, and the thin film can be stably cast, so that the flatness is improved. Moreover, the optical film of this invention can improve the mechanical physical property of a thin film optical film by adding the compound which has a structure represented by the said General formula (1) or General formula (2). It is presumed that this is because an interaction such as a hydrogen bond that brings about a thickening action in the dope works even in the film after drying and strengthens the entanglement between the cycloolefin-based resins.

The figure which showed typically an example of the dope preparation process of a solution casting method, a casting process, and a drying process Schematic diagram showing an example of the configuration of a liquid crystal display device

  The optical film of the present invention is an optical film containing a cycloolefin resin, and is characterized by containing a compound having a structure represented by the general formula (1) or the general formula (2). This feature is a technical feature common to the inventions according to claims 1 to 6.

  As an embodiment of the present invention, the thickness is preferably in the range of 5 to 30 μm, and more preferably in the range of 10 to 20 μm, from the viewpoint of manifesting the effects of the present invention.

  Furthermore, in the present invention, it is preferable to contain an ultraviolet absorber from the viewpoint of increasing the elongation at break.

Furthermore, in the present invention, it is preferable to contain a matting agent from the viewpoint of improving the flatness.
The optical film of the present invention can be suitably included in a display device.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<< Outline of Optical Film of the Present Invention >>
The optical film of the present invention is an optical film containing a cycloolefin resin, and is characterized by containing a compound having a structure represented by the general formula (1) or the general formula (2).

  The compound represented by the general formula (1) or the general formula (2) is considered to function as a thickener. By adding this compound to the dope in the solution casting film forming method, the strength of the casting film can be increased, and even a thin film can be stably casted.

  In addition, the addition of this compound can improve the mechanical properties even in thin films because the interaction such as hydrogen bonding that causes thickening action in the solution works even in the film after drying. This is thought to be for strengthening.

  In the embodiment of the present invention, the optical film preferably further contains an ultraviolet absorber or a matting agent. Usually, when an ultraviolet absorber or the like is added, the ultraviolet absorber or the like enters between the cycloolefin resins, and filling the gap increases the density and hardness, but becomes brittle and the elongation at break decreases. However, the elongation at break can be increased by using in combination with the above compound. This is because the compound having the structure represented by the general formula (1) or the general formula (2) and the cycloolefin resin interact to form a network with the cycloolefin resin chain, so an ultraviolet absorber or the like is added. Even in such a case, it is estimated that this is because the structure becomes flexible.

<< Compound having structure represented by general formula (1) or general formula (2) >>
The optical film of the present invention is an optical film containing a cycloolefin resin, and contains a compound having a structure represented by the following general formula (1) or the following general formula (2).

(Wherein R _{1 to} R ₄ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms)
R _{1 to} R ₄ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Of these, a methyl group is preferable.

(Wherein R _{5 to} R ₇ each independently represents an alkyl group having 1 to 20 carbon atoms.)
R _{5 to} R ₇ each independently represents an alkyl group having 1 to 20 carbon atoms. R ₅ and R ₆ are preferably alkyl groups having 1 to 5 carbon atoms. R ₇ is preferably an alkyl group having 4 to 20 carbon atoms. The alkyl group may be linear or branched.

  Although the preferable example of a compound which has a structure represented by General formula (1) or General formula (2) below is given, it is not limited to this.

Ｂ−２
Ｎ−２−エチル−ヘキサノイル−Ｌ−グルタミン酸ジブチルアミド

B-2
N-2-ethyl-hexanoyl-L-glutamic acid dibutylamide

  The content of the compound having the structure represented by the general formula (1) or the general formula (2) in the optical film is in the range of 0.5 to 10% by mass with respect to the cycloolefin resin. preferable.

  The material which comprises the optical film of this invention is described below.

《Cycloolefin resin》
Examples of the cycloolefin resin according to the present invention include a polymer or copolymer of a monomer having the structure shown below.

In the formula, each of R ^{1 to} R ⁴ independently represents a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxy group, a carboxy group, an acyloxy group, an aryloxycarbonyl group, an alkoxycarbonyl group, an alkoxy group, a cyano group, or an amide group. Substituted with an imide group, a silyl group, or a polar group (that is, a halogen atom, a hydroxy group, an acyloxy group, an aryloxycarbonyl group, an alkoxycarbonyl group, an alkoxy group, a cyano group, an amide group, an imide group, or a silyl group) Hydrocarbon group.

However, two or more of R ^{1 to} R ⁴ may be bonded to each other to form an unsaturated bond, a monocycle or a polycycle, and this monocycle or polycycle has a double bond. Alternatively, an aromatic ring may be formed. R ¹ and R ² , or R ³ and R ⁴ may form an alkylidene group. p and m are integers of 0 or more.

In the general formula (3), the hydrocarbon group represented by R ¹ and R ³ is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms.

R ² and R ⁴ are each a hydrogen atom or a monovalent organic group, and at least one of R ² and R ⁴ preferably represents a polar group having a polarity other than a hydrogen atom and a hydrocarbon group, and m is 0 An integer of ˜3, p is an integer of 0 to 3, more preferably m + p = 0 to 4, more preferably 0 to 2, particularly preferably m = 1 and p = 0.

  The specific monomer with m = 1 and p = 0 is preferable in that the resulting cycloolefin resin has a high glass transition temperature and excellent mechanical strength.

  The glass transition temperature here is a value obtained by a method based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

  Examples of the polar group of the specific monomer include a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. These polar groups have a linking group such as a methylene group. It may be bonded via.

  In addition, a hydrocarbon group in which a divalent organic group having a polarity such as a carbonyl group, an ether group, a silyl ether group, a thioether group, or an imino group is bonded as a linking group can also be exemplified.

  Among these, a carboxy group, a hydroxy group, an alkoxycarbonyl group or an aryloxycarbonyl group is preferable, and an alkoxycarbonyl group or an aryloxycarbonyl group is particularly preferable.

Furthermore, a monomer in which at least one of R ² and R ⁴ is a polar group represented by the formula — (CH ₂ ) _n COOR is obtained by using a cycloolefin resin having a high glass transition temperature, a low hygroscopic property, and various materials. It is preferable in that it has excellent adhesion.

  In the formula relating to the specific polar group, R is a hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 4, particularly preferably 1 to 2, and preferably an alkyl group.

  Specific examples of the copolymerizable monomer include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

  The number of carbon atoms of the cycloolefin is preferably 4-20, and more preferably 5-12.

  In this invention, cycloolefin resin can be used individually by 1 type or in combination of 2 or more types.

The preferred molecular weight of the cycloolefin resin according to the present invention is 0.2 to ⁵ cm ³ / g, more preferably 0.3 to ³ cm ³ / g, particularly preferably 0.4 to 1.5 cm in terms of intrinsic viscosity [η] _inh. ³ / g, and the polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 8000 to 100,000, more preferably 10,000 to 80000, and particularly preferably 12,000 to 50,000, and the weight average molecular weight. (Mw) is preferably in the range of 20000 to 300,000, more preferably 30000 to 250,000, particularly preferably 40000 to 200000.

Inherent viscosity [η] _inh , number average molecular weight, and weight average molecular weight are in the above ranges, so heat resistance, water resistance, chemical resistance, mechanical properties of cycloolefin resin and molding processability as an optical film are good. It becomes.

  The glass transition temperature (Tg) of the cycloolefin resin according to the present invention is usually 110 ° C. or higher, preferably 110 to 350 ° C., more preferably 120 to 250 ° C., and particularly preferably 120 to 220 ° C. The case where Tg is 110 ° C. or higher is preferred because deformation hardly occurs due to use under high temperature conditions or secondary processing such as coating or printing.

  On the other hand, when Tg is 350 ° C. or lower, it is possible to avoid the case where the molding process becomes difficult, and it is possible to suppress the possibility that the resin is deteriorated by heat during the molding process.

  For the cycloolefin resin, a specific hydrocarbon resin or a known thermoplastic resin described in, for example, JP-A-9-221577 and JP-A-10-287732, as long as the effects of the present invention are not impaired. Resins, thermoplastic elastomers, rubbery polymers, organic fine particles, inorganic fine particles, etc. may be blended. Specific wavelength dispersants, sugar ester compounds, antioxidants, release accelerators, rubber particles, plasticizers, UV absorption An additive such as an agent may be included.

  In addition, as the cycloolefin resin, a commercially available product can be preferably used, and examples of commercially available products include trade names of ARTON (registered trademark) G, ARTON F, ARTON R, and ARTON RX from JSR Corporation. ZEONOR (registered trademark) ZF14, ZF16, ZEONEX (registered trademark) 250, or ZEONEX 280 are commercially available from ZEON CORPORATION and can be used. .

[Ultraviolet absorber]
The optical film of the present invention preferably contains an ultraviolet absorber in order to shield unnecessary ultraviolet rays irradiated to the polarizing plate and the liquid crystal display device. Moreover, it has the effect of increasing the breaking elongation of an optical film by using together with the compound which has a structure represented by the said General formula (1) or General formula (2) as mentioned above.

  Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like, but less benzotriazole compounds. Compounds are preferred. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used.

  When the optical film of the present invention is used as a protective film for a polarizing plate, the ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and has a liquid crystal display property from the viewpoint of preventing deterioration of a polarizer and liquid crystal. From the viewpoint, it is preferable to have a characteristic that the absorption of visible light having a wavelength of 400 nm or more is small.

  The addition amount of the ultraviolet absorber is preferably in the range of 0.1 to 10.0% by mass, and more preferably in the range of 0.5 to 5.0% by mass with respect to the polymer composition.

  Benzotriazole-based UV absorbers useful in the present invention include, for example, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butyl Phenyl) -5-chlorobenzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2,2 -Methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2'-hydroxy-3) -T-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3 -[3-t-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-t-butyl-4-hydroxy-5- ( A mixture of 5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as a commercial product, “TINUVIN 109”, “TINUVIN 171”, “TINUVIN 326”, “TINUVIN 328” (above, trade name, manufactured by BASF Japan Ltd.) are preferable. Can be used.

(Matting agent)
The optical film of the present invention preferably contains a matting agent in order to impart unevenness to the film surface during film formation, ensure slipperiness, and achieve a stable winding shape.

  In addition, the matting agent can function in order to prevent the produced film from being scratched or having deteriorated transportability when handled. Furthermore, by using together with the compound having the structure represented by the general formula (1) or the general formula (2) as described above, it also has an effect of improving the flatness of the optical film.

  Examples of the matting agent include fine particles of an inorganic compound and fine particles of a resin. Examples of fine particles of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, silicic acid Examples thereof include magnesium and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle size of the fine particles is preferably in the range of 5 to 400 nm, and more preferably in the range of 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size in the range of 0.05 to 0.3 μm. If the particles have an average particle size in the range of 80 to 400 nm, the primary particles are not aggregated. It is also preferable that it is contained.

  The content of these fine particles in the film is preferably in the range of 0.01 to 3.0% by mass, and particularly preferably in the range of 0.01 to 2.0% by mass.

  In the case of a multilayer structure by the co-casting method, it is preferable that the surface contains this amount of fine particles.

  Silicon dioxide fine particles are commercially available under the trade names of, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). .

  Zirconium oxide fine particles are commercially available, for example, under the names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of resin fine particles include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) Are commercially available and can be used.

  Among these, Aerosil 200V, Aerosil R972V, and Aerosil R812 are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the haze of the base film low.

  In the optical film of the present invention, it is preferable that the dynamic friction coefficient of at least one surface is in the range of 0.2 to 1.0.

[Other additives]
In addition to the compound having the structure represented by the general formula (1) or the general formula (2), the ultraviolet absorber, and the additive for the matting agent, the optical film of the present invention further includes a plasticizer, an antioxidant, It may contain additives such as a phase difference increasing agent, a light stabilizer, an antistatic agent, and a release agent. Details of main additives are described below.

(Plasticizer)
In the present invention, a polyester resin can be further used as a plasticizer. The polyester resin is obtained by polymerizing a dicarboxylic acid and a diol, and 70% or more of the dicarboxylic acid structural unit (the structural unit derived from the dicarboxylic acid) is derived from the aromatic dicarboxylic acid, and the diol structural unit (derived from the diol). 70% or more of the structural unit is derived from an aliphatic diol.

  The proportion of the structural unit derived from the aromatic dicarboxylic acid is 70% or more, preferably 80% or more, more preferably 90% or more.

  The proportion of the structural unit derived from the aliphatic diol is 70% or more, preferably 80% or more, and more preferably 90% or more. Two or more polyester resins may be used in combination.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid such as 2,7-naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid. 3,4'-biphenyldicarboxylic acid and the like and ester-forming derivatives thereof.

  As the polyester resin, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid, and monocarboxylic acids such as benzoic acid, propionic acid, and butyric acid can be used without departing from the object of the present invention.

  Examples of the aliphatic diol include ethylene glycol, 1,3-propylene diol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like, and ester-forming derivatives thereof.

  As the polyester resin, monoalcohols such as butyl alcohol, hexyl alcohol, and octyl alcohol, and polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol can be used as long as the object of the present invention is not impaired.

  A known esterification method or transesterification method can be applied to the production of the polyester resin. Examples of the polycondensation catalyst used in the production of the polyester resin include known antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds such as germanium oxide, titanium compounds such as titanium acetate, and aluminum compounds such as aluminum chloride. Although it can, it is not limited to these.

  Preferred polyester resins include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polyethylene-2,6-naphthalene dicarboxylate resin, polyethylene-2, 6-naphthalene dicarboxylate-terephthalate copolymer resin, polyethylene-terephthalate-4,4'-biphenyldicarboxylate resin, poly-1,3-propylene-terephthalate resin, polybutylene terephthalate resin, polybutylene-2,6-naphthalene There are dicarboxylate resins and the like.

  More preferable polyester resins include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polybutylene terephthalate resin, and polyethylene-2,6-naphthalene dicarboxylate. Resin.

The intrinsic viscosity of the polyester resin (phenol / 1,1,2,2-tetrachloroethane = value measured at 25 ° C. in a 60/40 mass ratio mixed solvent) is in the range of 0.7 to 2.0 cm ³ / g. Is more preferable, and it is in the range of 0.8 to 1.5 cm ³ / g. Since the molecular weight of the polyester resin is sufficiently high when the intrinsic viscosity is 0.7 cm ³ / g or more, a molded product comprising the polyester resin composition obtained by using the polyester resin has mechanical properties necessary as a molded product. At the same time, transparency is improved. When the intrinsic viscosity is 2.0 cm ³ / g or less, the moldability is good. As other plasticizers, compounds described in the general formulas (PEI) and (PEII) in paragraphs 0056 to 0080 of JP2013-97279A may be used.

(Antioxidant)
Antioxidant has a role of delaying or preventing the base film from being decomposed by, for example, halogen of a residual solvent in the base film or phosphoric acid of a phosphoric acid plasticizer. It is preferable to make it.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 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-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-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-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 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. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

(Phase difference increasing agent)
The retardation increasing agent as used herein refers to an optical film in which the retardation value Rt (measured at a wavelength of 590 nm) in the thickness direction of an optical film containing 3 parts by mass of the compound with respect to 100 parts by mass of the cycloolefin resin is not added. The compound which has a function which shows a value 1.1 times or more compared with a film.

  The retardation increasing agent that can be used in the present invention is not particularly limited. For example, conventionally known aromatic rings described in paragraphs [0143] to [0179] of JP-A-2006-113239 are used. A discotic compound (1,3,5-triazine compound, etc.), a rod-shaped compound described in JP-A-2006-113239, paragraphs [0106] to [0112], and JP-A-2012-214682, paragraphs [0118] to [0118] [0133] The pyrimidine compounds described in the above can be used.

  The properties required for the retardation increasing agent include excellent compatibility with the cycloolefin resin, excellent retardation development when the film is thinned, excellent precipitation resistance, and moisture content under high humidity. Although it is mentioned that it is excellent in the tolerance of fluctuation | variation of the phase difference value accompanying in / out, it is preferable to select a phase difference raising agent from such a viewpoint.

<< Optical film manufacturing method >>
The optical film of the present invention is preferably a film produced by a solution casting method.

  The optical film of the present invention is a step of preparing a dope containing at least a cycloolefin resin, a compound having a structure represented by the general formula (1) or the general formula (2), and an organic solvent (dope preparation step) And a step of casting the dope on a support to form a web (also referred to as a casting film) (casting step), a step of evaporating the solvent from the web on the support (solvent evaporation step), 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), and a step of further drying the stretched film (second) It is preferable to manufacture by the process (winding process) which winds up the obtained optical film.

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

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

  The fine particle dispersion in which the solvent and the matting agent are dispersed by the disperser passes from the charging tank 41 through the filter 44 and is stocked in the stock tank 42. On the other hand, the cycloolefin resin as the main dope is dissolved in the dissolving pot 1 together with the solvent, and the matting agent stored in the stock pot 42 is added and mixed as appropriate to form the main dope. The obtained main dope is filtered from the filter 3 and the stock kettle 4 by the filter 6, the additive is added by the merge pipe 20, mixed by the mixer 21, and fed to the pressure die 30.

  On the other hand, an additive (for example, a compound having a structure represented by the general formula (1) or the general formula (2), an ultraviolet absorber, etc.) is dissolved in a solvent and passes through the filter 12 from the additive charging vessel 10. Then, it is stocked in the stock pot 13. After that, the main dope is mixed by the merge pipe 20 and the mixer 21 through the conduit 15 through the filter 15.

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

  Hereinafter, each step will be described.

(1) Dope preparation step In an organic solvent mainly composed of a good solvent for cycloolefin resin, the cycloolefin resin, depending on the case, is represented by the general formula (1) or the general formula (2) according to the present invention. A compound having a structure represented by the general formula (1) or the general formula (2) in the step of preparing a dope by dissolving a compound having a structure or other compound while stirring, or the cycloolefin resin solution And other compound solutions are mixed to prepare a dope which is a main solution.

  When the optical film of the present invention is produced by a solution casting method, an organic solvent useful for forming a dope is a cycloolefin resin, a structure represented by the general formula (1) or the general formula (2). Any compound can be used without limitation as long as it simultaneously dissolves the compound having the above and other compounds.

  Examples of the organic solvent used include chlorinated 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. And alcohol solvents such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether, and the like. These solvents may be used alone or in combination of two or more.

  The organic solvent used in the present invention is preferably a mixed solvent of a good solvent and a poor solvent. Examples of the good solvent include dichloromethane as a chlorine-based organic solvent, methyl acetate as a non-chlorine-based 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, - propanol, iso- propanol, n- butanol, sec- butanol, tert- butanol and the like, that among them is dichloromethane 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 based on the total amount of the solvent.

  The poor solvent is preferably an alcohol solvent, and the alcohol solvent is preferably selected from methanol, ethanol and butanol from the viewpoint of improving peelability and enabling high-speed casting. Of these, methanol or ethanol is preferably used. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the proportion of alcohol is small, cycloolefin resins and other compounds in a non-chlorine organic solvent system There is also a role to promote dissolution. In film formation of the optical film of the present invention, it is preferable to form a film using a dope having an alcohol concentration in the range of 0.5 to 15.0% by mass from the viewpoint of improving the flatness of the obtained optical film. .

  For dissolving the cycloolefin resin, the compound having the structure represented by the general formula (1) or the general formula (2), and other compounds, a method performed at normal pressure, a method performed below the boiling point of the main solvent, A method of pressurizing at a boiling point or higher, a method of performing a cooling dissolution method as described in JP-A-9-95544, JP-A-9-95557, or JP-A-9-95538, JP-A-11-21379 Various dissolution methods such as a method performed at a high pressure described in the publication can be used, but a method performed by pressurizing at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

  The concentration of the cycloolefin resin in the dope is preferably in the range of 10 to 40% by mass. After the compound is added to the dope during or after dissolution and dissolved and dispersed, it is filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

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

  In the present invention, the filter medium used for filtration preferably has a small absolute filtration accuracy. However, if the absolute filtration accuracy is too small, the filter medium is likely to be clogged, and the filter medium must be frequently replaced. There is a problem of lowering productivity.

  Therefore, in the present invention, the filter medium used for cycloolefin resin dope preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and 0.003 to 0.006 mm. A filter medium in the range of is more preferable.

  There are no particular restrictions on the material of the filter medium, and normal filter media can be used. However, plastic fiber filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel fibers are used to remove fibers. This is preferable.

In the present invention, the dope flow rate during filtration is preferably 10 to 80 kg / (h · m ² ), more preferably 20 to 60 kg / (h · m ² ). Here, if the flow rate of the dope at the time of filtration is 10 kg / (h · m ² ) or more, it becomes efficient productivity, and the flow rate of the dope at the time of filtration is within 80 kg / (h · m ² ). If so, the pressure applied to the filter medium is 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 the filtration area.

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

  Return material is, for example, a product obtained by finely pulverizing a cycloolefin resin film, which is generated when a cycloolefin resin film is formed. A cycloolefin resin film raw material is used.

  Moreover, as a raw material of resin used for dope preparation, what pelletized cycloolefin resin and another compound previously can be used preferably.

(2) Casting step (2-1) Casting of dope An endless metal support 31 that feeds the dope to the pressurizing die 30 through a feed pump (for example, a pressurization type metering gear pump) and transfers it infinitely, For example, the dope is cast from a pressure die slit at a casting position on a metal support such as a stainless steel belt or a rotating metal drum.

  The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be in the range of 1-4 m, preferably in the range of 1.3-3 m, more preferably in the range of 1.5-2.8 m. The surface temperature of the metal support in the casting step is set in the range of −50 ° C. to a temperature at which the solvent boils and does not foam, more preferably in the range of −30 to 0 ° C. A higher temperature is preferable because the web (the dope is cast on a casting support and the formed dope film is called a web) can be dried at a high speed, but if the temperature is too high, the web foams, The flatness may deteriorate. A preferable support temperature is appropriately determined at 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying 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 pressure die that can adjust the slit shape of the die portion of the die and easily make the film thickness uniform. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and laminated.

(2-2) Solvent evaporation process It is the process of heating a web on the support body for casting, and evaporating a solvent, It is a process of controlling the residual solvent amount at the time of peeling mentioned 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, a method of transferring heat from the front and back by radiant heat, etc. Is preferable. A 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 by means such as infrared rays.

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

(2-3) Peeling Step This is a step of peeling the web where 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 to 40 ° C, more preferably in the range of 11 to 30 ° C.

  In this invention, although the solvent in a web is evaporated in the said solvent evaporation process, it is preferable that the residual solvent amount of the web on the metal support body in the time of peeling shall be in the range of 15-100 mass%. The residual solvent amount is preferably controlled by the drying temperature and drying time in the solvent evaporation step.

  When the residual solvent amount is 15% by mass or more, the matting agent has no distribution in the thickness direction and is uniformly dispersed in the film in the drying process on the support. It is possible to easily suppress the deformation of the winding shape. Also, the drying time is not lengthened and productivity is improved.

  Further, if the amount of the residual solvent is within 100% by mass, the film has self-supporting properties, can avoid poor peeling of the film, and can maintain the mechanical strength of the web, so that the flatness at the time of peeling is improved, Generation of slippage and vertical stripes due to peeling tension can be suppressed.

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

Formula (Z)
Residual solvent amount (%) = (mass before heat treatment of web or film−mass after heat treatment of web or film) / (mass after heat treatment of web or film) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension when peeling the web from the metal support to form a film is usually in the range of 196 to 245 N / m. However, if wrinkles easily occur during peeling, the peeling tension is 190 N / m or less. It is preferable to do.

  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 step The drying step can be divided into a preliminary drying step (first drying step) and a main drying step (second drying step).

(3-1) Pre-drying step The film obtained by peeling the web from the metal support is pre-dried by the first drying device 34. Preliminary drying of the film may be performed while the film is being transported by a number of rollers arranged above and below, or may be dried while being transported by fixing both ends of the film with clips like a tenter dryer. Good.

  The means for drying the web is not particularly limited and can be generally performed with hot air, infrared rays, a heating roller, microwaves, or the like, but it is preferably performed with hot air in terms of simplicity.

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

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

(3-2) Stretching process The optical film of the present invention suppresses the occurrence of microcraze near the film surface by performing a stretching process with a low stretching ratio under a specific residual solvent amount in the stretching apparatus 35, In addition, uniform distribution of the matting agent can be promoted. Furthermore, by controlling the orientation of the molecules in the film, the target retardation value Ro in the in-plane direction and retardation value Rt in the thickness direction can be obtained.

  In the method for producing an optical film of the present invention, in the step of stretching the film, the residual solvent amount at the start of stretching is preferably 1% by mass or more and less than 25% by mass. More preferably, it is in the range of 5 to 20% by mass.

  The optical film of the present invention is preferably stretched in the longitudinal direction (also referred to as MD direction and casting direction) and / or in the lateral direction (also referred to as TD direction), and at least stretched in the lateral direction by a stretching device. It is preferable to manufacture it.

  The stretching operation may be performed in multiple stages. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

Thus, for example, the following stretching steps are possible:
-Stretch in the longitudinal direction-> Stretch in the width direction-> Stretch in the longitudinal direction-> Stretch in the longitudinal direction-Stretch in the width direction-> Stretch in the width direction-> Stretch in the longitudinal direction-> Stretch in the longitudinal direction Includes stretching in one direction and contracting the other while relaxing the tension.

  The optical film of the present invention has a glass transition temperature Tg of the film in the longitudinal direction and / or the width direction, preferably in the width direction so that the film thickness after stretching is in a desired range. It is preferable to stretch in a temperature range of Tg + 5) to (Tg + 50) ° C. When stretched in the above temperature range, the retardation can be easily adjusted, and the stretching stress can be reduced, so that the haze is lowered. Moreover, generation | occurrence | production of a fracture | rupture is suppressed and the optical film excellent in planarity and the coloring property of the film itself is obtained. The stretching temperature is preferably in the range of (Tg + 10) to (Tg + 40) ° C.

  In addition, the glass transition temperature Tg here is measured at a temperature rising rate of 20 ° C./min using a commercially available differential scanning calorimeter, and is determined at an intermediate glass transition temperature (Tmg) determined according to JIS K7121 (1987). It 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).

  In the optical film of the present invention, the film is preferably stretched at least in the width direction at a stretch ratio in the range of 1 to 50% with respect to the original width, and further 2 in the longitudinal direction and the width direction of the film, respectively. More preferably, the film is stretched at a stretch ratio in the range of ˜40%. In particular, the stretching ratio is more preferably 3 to 30% of the original width. If it is within the above range, generation of minute crazing in the vicinity of the film due to stretching at a high magnification is suppressed, and in particular when a retardation increasing agent is included, not only a desired retardation value can be obtained, but also the film can be thinned. . The stretching ratio 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, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the longitudinal direction or a method of stretching in the longitudinal and lateral directions at the same time in the longitudinal and lateral directions. Of course, these methods may be used in combination.

  In order to stretch in the width direction, for example, the entire drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 is held in the width direction by holding the width ends of the web with clips or pins. A method of drying while drying (called a tenter method), among them, a tenter method using a clip and a pin tenter method using a pin are preferably used.

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

  If the stretching speed is 250% / min or more, the planarity is improved and the film can be processed at a high speed, which is preferable from the viewpoint of production aptitude, and if it is within 500% / min, the film is broken. Can be processed without any problem.

  A preferable stretching speed is in a range of 300 to 400% / min, and is effective at the time of stretching at a low magnification. The stretching speed is defined by the following formula 1.

Formula 1 Stretching speed (% / min) = [(d ₁ / d ₂ ) −1] × 100 (%) / t
(In Formula 1, d ₁ is the width dimension in the stretching direction of the optical film of the present invention after stretching, d ₂ is the width dimension in the stretching direction of the optical film before stretching, and t is the time required for stretching. (Min).)
The optical film of the present invention can have a desired retardation value by containing a retardation increasing agent and / or a retardation reducing agent. The retardation value Ro in the in-plane direction and the retardation value Rt in the thickness direction are 23 ° C. and 55% RH using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). Under the environment, a three-dimensional refractive index measurement is performed at a wavelength of 590 nm, and the refractive indexes nx, ny, and nz obtained can be calculated.

  The optical film of the present invention is represented by the following formulas (i) and (ii), the retardation value Ro in the in-plane direction of the optical film is in the range of 40 to 60 nm, and the retardation value Rt in the thickness direction. Is preferably in the range of 110 to 140 nm from the viewpoint of improving the visibility such as viewing angle and contrast when the VA liquid crystal display device is provided. The IPS mode liquid crystal display device has an in-plane retardation value (Ro) in the range of 0 to 10 nm and a thickness direction retardation value (Rt) in the range of -20 to 20 nm. It is preferable as an optical film used for the above. The optical film can be adjusted within the range of the retardation value by stretching while adjusting the stretching ratio at least in the width direction.

Formula _{(i): Ro = (n} x -n y) × d (nm)
Formula (ii): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In [Equation (i) and Formula (ii), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
In the stretching step, usually, after stretching, holding and relaxation are performed. That is, in this step, it is preferable to perform a stretching step for stretching the film, a holding step for holding the film in a stretched state, and a relaxation step for relaxing the film in the stretched direction in this order. In the holding step, the drawing at the drawing rate achieved in the drawing step is held at the drawing temperature in the drawing step. 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 step may be performed at a temperature lower than the stretching temperature in the stretching step.

(3-3) Main drying step In the main drying step, the stretched film is heated and dried by the second drying device 36. When the film is heated with hot air or the like, a means for preventing the mixing of used hot air by installing a nozzle that can exhaust used hot air (air containing solvent or wet air) is also preferably used. 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.

  Further, the heating and drying means is not limited to hot air, and for example, infrared rays, heating rollers, microwaves, and the like can be used. From the viewpoint of simplicity, it is preferable to dry with hot air or the like while transporting the film with the transport rollers 37 arranged in a staggered manner. The drying temperature is more preferably in the range of 40 to 350 ° C. in consideration of the residual solvent amount, the expansion / contraction rate in conveyance, and the like.

  In the drying step, it is preferable to dry the film until the residual solvent amount is 0.5% by mass or less.

(4) Winding step (4-1) Knurling processing It is preferable to provide a slitter after the predetermined heat treatment or cooling treatment and cut off the end portion before winding to obtain a good winding shape. Furthermore, it is preferable to knurling both ends of the width.

  The knurling process can be formed by pressing a heated embossing roller against the film width end. Fine embossing is formed on the embossing roller, and by pressing the embossing roller, unevenness can be formed on the film and the end can be made bulky.

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

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

(4-2) Winding step This is a step of winding the film as a film after the residual solvent amount in the film is 2% by mass or less, and the dimensional stability is preferably set to 0.4% by mass or less. Can be obtained.

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

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

<Physical properties of optical film>
<Elongation at break>
In the present invention, in a measurement based on JIS K 7127 (1999) which is one of the standards of JIS (Japan Industrial Standards Committee), the elongation at break in at least one direction is 10% or more. It is preferable that it is 15% or more. More preferably, it is 20% or more.

<Flatness>
As the planarity of the optical film, unevenness in the longitudinal direction becomes a problem particularly when a thin film is used. This unevenness should be as small as possible, and can be evaluated by placing the optical film on a black base plate and observing the reflected light of the fluorescent lamp.

<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 a film for optical applications.

  The haze value is measured at 10 points at equal intervals in the width direction of the film with a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in an environment of 23 ° C. and 50% RH. The haze is calculated.

<Equilibrium moisture content>
In the optical film of the present invention, the equilibrium water content at 25 ° C. and 60% relative humidity is preferably 4% or less, more preferably 3% or less. By setting the equilibrium moisture content to 4% or less, it is preferable to easily cope with a change in humidity and to hardly change the optical characteristics and dimensions.

  Equilibrium moisture content is determined by leaving the sample film in a room conditioned at 23 ° C. and 20% relative humidity for 4 hours or more and then leaving it in a room conditioned at 23 ° C. and 80% RH for 24 hours. Using a meter (for example, CA-20 model, manufactured by Mitsubishi Chemical Analytech Co., Ltd.), moisture can be dried and vaporized at a temperature of 150 ° C. and then quantified by the Karl Fischer method.

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

  The film thickness of the optical film of the present invention is preferably in the range of 5 to 30 μm from the viewpoint of thinning the display device and productivity. More preferably, it exists in the range of 10-20 micrometers. When the film thickness is 5 μm or more, a certain level of film strength can be provided. If the film thickness is 30 μm or less, the display device can be thinned.

"Polarizer"
A polarizing plate protective film can be arrange | positioned to the polarizing plate on both sides of a polarizer. Moreover, a polarizing plate protective film can be disposed on one side of the polarizer, and a retardation film can be disposed on the other side. The optical film of the present invention can be used for any application, but further on the polarizer surface opposite to the surface on which the polarizing plate protective film is disposed, via an active energy ray-curable adhesive. It is preferable that they are laminated.

(1) Polarizer The polarizer is an element that allows only light having a plane of polarization in a certain direction to pass through, and examples thereof include a polyvinyl alcohol polarizing film.

  The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  The polarizer can be obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing or dyeing the polyvinyl alcohol film, and then uniaxially stretching, and preferably by 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, and more preferably in the range of 5 to 15 μm.

  Examples of the polyvinyl alcohol film include ethylene unit content of 1 to 4 mol%, polymerization degree of 2000 to 4000, and saponification degree of 99.0 to 99 described in JP2003-248123A, JP2003-342322A, and the like. 99 mol% ethylene-modified polyvinyl alcohol is preferably used. In addition, a polarizing plate can be prepared by preparing a polarizer by the method described in JP 2011-1000016 A, JP 4691205 A, and JP 4804589 A, and attaching the polarizer to the optical film of the present invention.

(2) Adhesive The optical film of the present invention can be bonded to the polarizer with water glue or an active energy ray-curable adhesive. The active energy ray curable adhesive is preferably an ultraviolet curable adhesive.

[Water glue]
In the polarizing plate, the optical film is preferably bonded to the polarizer using a completely saponified polyvinyl alcohol aqueous solution (water glue). Another polarizing plate protective film can be bonded to the other surface. When the optical film of the present invention is a liquid crystal display device, it is preferably provided on the liquid crystal cell side of the polarizer. The film outside the polarizer is the optical film of the present invention and the conventional polarizing plate protective film. Either can be used.

  For example, as a conventional polarizing plate protective film, a commercially available cellulose ester film (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC6UA, KC4UY, KC4UE, KC8UE, KC8UE, KC8UE, KC8UE, KC8UE, RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta, Inc.) are preferably used.

[Active energy ray curable adhesive]
In the polarizing plate, the optical film of the present invention and the polarizer are preferably bonded with an active energy ray-curable adhesive. Since the optical film suppresses the occurrence of minute crazing on the film surface due to stretching, the mechanical strength of the part is high, and the peeling from the part is improved after bonding with an active energy ray-curable adhesive. Yes.

  As the active energy ray curable adhesive, the following ultraviolet curable adhesive is preferably used.

  In the present invention, an ultraviolet curable adhesive (hereinafter also referred to as UV glue) is applied to the bonding between the optical film and the polarizer, thereby obtaining a polarizing plate having high strength and excellent flatness even in a thin film. be able to.

<Composition of UV glue>
As UV paste composition for polarizing plate, photo radical polymerization type composition using photo radical polymerization, photo cation polymerization type composition using photo cation polymerization, and hybrid type using photo radical polymerization and photo cation polymerization in combination Compositions are known.

  As a radical photopolymerization type composition, a radical polymerizable compound containing a polar group such as a hydroxy group or a carboxy group described in JP-A-2008-009329 and a radical polymerizable compound not containing a polar group are contained in a specific ratio. Composition) and the like are known. In particular, the radical polymerizable compound is preferably a compound having a radical polymerizable ethylenically unsaturated bond. Preferable examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include an N-substituted (meth) acrylamide compound and a (meth) acrylate compound. (Meth) acrylamide means acrylamide or methacrylamide.

  Moreover, as a photocationic polymerization type composition, as disclosed in JP 2011-08234 A, (α) a cationic polymerizable compound, (β) a photocationic polymerization initiator, and (γ) a wavelength longer than 380 nm. And an ultraviolet curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other UV glues may be used.

(A) Pretreatment process A pretreatment process is a process of performing an easy adhesion process on the adhesive surface of the optical film with the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(UV glue application process)
In the UV glue application step, the UV glue is applied to at least one of the adhesive surfaces of the polarizer and the optical film. When UV glue is applied directly to the surface of the polarizer or the optical film, the application method is not particularly limited. For example, various wet coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting UV glue between a polarizer and an optical film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.

(B) Bonding process After apply | coating UV paste by said method, it processes by a bonding process. In this bonding step, for example, when UV glue is applied to the surface of the polarizer in the previous application step, an optical film is superimposed thereon. In the case of a system in which UV glue is first applied to the surface of the optical film, a polarizer is superimposed thereon. When UV glue is cast between the polarizer and the optical film, the polarizer and the optical film are superposed in that state. In this state, the pressure is usually sandwiched between pressure optical rollers from both sides with a pressure roller. 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 different materials.

(C) Curing step In the curing step, an uncured UV paste is irradiated with ultraviolet rays, and a cationically polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radically polymerizable compound (for example, an acrylate compound, an acrylamide compound, etc.) ) Is cured, and the laminated polarizer and the optical film are bonded via the UV glue. When bonding an optical film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or an optical film side. In addition, when an optical film is bonded to both sides of a polarizer, the UV film on both sides of the polarizer is simultaneously cured by irradiating ultraviolet rays with the optical films superimposed on both sides of the polarizer. It is advantageous.

Any appropriate conditions can be adopted as the irradiation condition of the ultraviolet rays as long as the UV adhesive applied to the present invention can be cured. Preferably the dose of ultraviolet rays in the range of 50~1500mJ / cm ² in accumulated light quantity, and even more preferably in the range of 100 to 500 mJ / cm ^2.

  When performing the manufacturing process of a polarizing plate by a continuous line, although line speed is based on the hardening time of an adhesive agent, Preferably it is the range of 1-500 m / min, More preferably, it is the range of 5-300 m / min, More preferably, it is 10- The range is 100 m / min. When the line speed is 1 m / min or more, productivity can be ensured, or damage to the optical film can be suppressed, and a polarizing plate having excellent durability can be produced. Moreover, if the line speed is 500 m / min or less, the UV glue is sufficiently cured, and a UV glue layer having a desired hardness and excellent adhesiveness can be formed.

(3) Other polarizing plate protective film The film arrange | positioned on the opposite side to the optical film of this invention of a polarizer can also be a film which functions as a protective film of a polarizer, and is a retardation film. You can also.

  In addition, for example, resin films such as polyethylene terephthalate, polyethylene naphthalate, and polycarbonate, alicyclic polyolefins (for example, ZEONOR (registered trademark) manufactured by Nippon Zeon Co., Ltd., polyarylate, polyethersulfone, polysulfone, cycloolefin copolymer, polyimide ( Examples thereof include resin films such as Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd., fluorene ring-modified polycarbonate, alicyclic modified polycarbonate, acryloyl compound, etc. (in parentheses indicate glass transition temperature Tg). Among the materials, in terms of cost and availability, polyethylene terephthalate (abbreviation: PET), polybutylene terephthalate, polyethylene naphthalate (abbreviation: PEN), polycarbonate (abbreviation: PC), etc. Film is preferably used as a protective film.

  Although the thickness of the optical film used for a polarizing plate with the optical film of the said invention is not restrict | limited in particular, It can be set as about 10-200 micrometers, Preferably it exists in the range of 10-100 micrometers, More preferably, it is 10-70 micrometers. Is within the range.

<Liquid crystal display device>
By using the polarizing plate bonded with the optical film of the present invention for a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced.

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

  In the liquid crystal display device, usually two polarizing plates, a polarizing plate on the viewing side and a polarizing plate on the backlight side, are used, but it is also preferable to use the polarizing plate provided with the optical film of the present invention as both polarizing plates. It is also preferable to use it as a polarizing plate on one side. In particular, the polarizing plate provided with the optical film of the present invention is preferably used as a viewing-side polarizing plate that directly touches the external environment. In this case, when the optical film is an optical compensation film, it is disposed on the liquid crystal cell side. It is preferable.

  FIG. 2 is a schematic sectional view showing an example of the configuration of the liquid crystal display device 100 in which the polarizing plates 101A and 101B according to the present invention described above are arranged on both surfaces of the liquid crystal cell 101C.

  In FIG. 2, both surfaces of the liquid crystal layer 107 are sandwiched between glass substrates 108A and 108B as transparent substrates to constitute a liquid crystal cell 101C, and the respective surfaces of the respective glass substrates 108A and 108B are provided with adhesive layers 106 therebetween. The polarizing plates 101 </ b> A and 101 </ b> B having the configuration shown in FIG. 2 are arranged to constitute the liquid crystal display device 100.

  In the polarizing plates 101A and 101B, the optical film of the present invention is preferably bonded at least to the polarizing plate protective film 102 or 105 as a polarizing plate protective film. The polarizing plate protective films are bonded to the polarizer 104 by ultraviolet curable adhesives 103A and 103B, respectively.

  For example, when the IPS liquid crystal display device is provided, the polarizing plate protective film 105 is preferably the optical film of the present invention.

  The liquid crystal cell 101C is configured by arranging an alignment film, a transparent electrode, and glass substrates (108A and 108B) on both sides of a liquid crystal substance.

  By providing the liquid crystal display device with the polarizing plate according to the present invention having excellent durability, flatness, etc., it is possible to make it difficult for panel bends to occur even if the glass substrate constituting the liquid crystal cell is thinned. Thus, a liquid crystal display device in which thinning is achieved can be obtained.

  Examples of the material constituting the glass substrates 108A and 108B that can be used for the liquid crystal cell 101C include soda lime glass and silicate glass, and is preferably silicate glass. Silica glass or borosilicate glass is more preferable.

  The glass constituting the glass substrate is preferably a non-alkali glass that does not substantially contain an alkali component, specifically, a glass having an alkali component content of 1000 ppm or less. The content of the alkali component in the glass substrate is preferably 500 ppm or less, and more preferably 300 ppm or less. In a glass substrate containing an alkali component, substitution of cations occurs on the film surface, and soda blowing phenomenon tends to occur. Thereby, the density of the film surface layer is likely to decrease, and the glass substrate is easily damaged.

  The thicknesses of the glass substrates 108A and 108B of the liquid crystal cell constituting the liquid crystal display device are preferably in the range of 0.3 to 0.7 mm. Such a thickness is preferable in that it can contribute to the thinning of the liquid crystal display device.

  The glass substrate can be formed by a known method such as a float method, a down draw method, an overflow down draw method or the like. Of these, the overflow downdraw method is preferred because the surface of the glass substrate does not come into contact with the molded member during molding and the surface of the resulting glass substrate is hardly damaged.

  Such a glass substrate can also be obtained as a commercial product. For example, non-alkali glass AN100 (thickness 500 μm) manufactured by Asahi Glass Co., Ltd., glass substrate EAGLE XG (r) Slim (thickness manufactured by Corning) 300 μm, 400 μm, etc.), a glass substrate (thickness: 100 to 200 μm) manufactured by Nippon Electric Glass Co., Ltd., and the like.

  Further, the polarizing plates 101A and 101B as shown in FIG. 2 and the glass base materials 108A and 108B constituting the liquid crystal cell 101C are bonded via an adhesive layer 106.

  As the adhesive layer, a double-sided tape, for example, a 25 μm-thick double-sided tape manufactured by Lintec (baseless tape MO-3005C) or the like, or a composition used for forming the actinic ray curable resin layer is applied. Can do.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

Example 1
The cycloolefin resin and other compounds used in the following examples are shown below.
Cycloolefin resin: ARTON G7810 (manufactured by JSR)
Ultraviolet absorber 1 (abbreviated as UV agent 1 in the table): Ti928 (Tinubin 928, manufactured by BASF Japan Ltd.)
Ultraviolet absorber 1 (abbreviated as UV agent 2 in the table): ADK STAB LA-31 (manufactured by ADEKA)
Ultraviolet absorber 1 (abbreviated as UV agent 3 in the table): Ti477 (Tinubin 477, manufactured by BASF Japan Ltd.)
<< Preparation of optical film 1 >>
<Preparation of main dope>
A main dope having the following composition was prepared. First, dichloromethane and ethanol were added to the pressure dissolution tank. Cycloolefin resin exemplary compound A-1 was charged into a pressure dissolution tank containing dichloromethane with stirring. The resin was dissolved while heating and stirring, and the resin was dissolved in Azumi filter paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. The main dope was prepared by filtration using 244.

Cycloolefin resin 100 parts by mass Dichloromethane 200 parts by mass Ethanol 10 parts by mass Exemplified Compound A-1 6 parts by mass Next, using an endless belt casting apparatus, the main dope is uniformly formed on a stainless steel belt support at a temperature of 31 ° C. and a width of 1800 mm. Casted. The temperature of the stainless steel belt was controlled at 28 ° C. The conveyance speed of the stainless steel belt was 20 m / min.

  On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast film was 30.3%. Subsequently, it peeled from the stainless steel belt support body with the peeling tension of 128 N / m. The peeled film was stretched 23% in the longitudinal direction and 58% in the width direction under the condition of 115 ° C. by the stretching apparatus 35. The residual solvent amount at the start of stretching was 10.2% by mass. Next, drying was terminated while the drying zone was conveyed by a number of rollers, and the end was slit with a laser cutter, and then wound up to obtain an optical film 1 having a thickness of 7 μm.

[Preparation of optical films 2 to 24]
<Preparation of fine particle dispersion>
As a matting agent, 11.3 parts by mass of fine particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) and 84 parts by mass of ethanol were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

  5 parts by weight of the fine particle dispersion was slowly added to dichloromethane (100 parts by weight) that was sufficiently stirred in the dissolution tank. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

<Preparation of optical films 2-24>
Table 1 shows the compounds having the structure represented by the general formula (1) or the general formula (2) to be added to the main dope and the addition amount thereof, and the types of the ultraviolet absorber and the matting agent in the production of the optical film 1. Optical films 2 to 24 were prepared in the same manner as the optical film 1 except that the main dope was adjusted as described above.

  The amount of the ultraviolet absorber added to the dope is 3 parts by mass with respect to 100 parts by mass of the cycloolefin resin. The amount of the matting agent added to the dope was 3 parts by mass of the fine particle addition liquid prepared above with respect to 100 parts by mass of the cycloolefin resin.

≪Evaluation≫
With respect to the optical films 1 to 24, the flatness and elongation at break were measured.

[Elongation at break]
In the present invention, in a measurement based on JIS-K 7127 (1999), which is one of the standards of JIS (Japan Industrial Standards Committee), the elongation at break in at least one direction is 10%. Preferably, it is 15% or more. More preferably, it is 20% or more.

◎: 20% or more ○: 15% or more and less than 20% △: 10% or more and less than 15% ×: less than 10% [Flatness]
The flatness of the optical film was evaluated by evaluating a cast horizontal stage failure (longitudinal unevenness). With respect to the optical films 1 to 24, a sample having a length of 3 m (full width) was taken out and left on a flat black plate. On the other hand, an illumination plate in which eight 40 W fluorescent lamps were arranged at intervals of 10 cm was prepared. This lighting plate was placed 1.5 m above the film that was allowed to stand, the flatness of the film was observed, and cast lateral failure (longitudinal unevenness) was evaluated with the following rank. The cast horizontal stage failures (unevenness in the longitudinal direction) of the obtained optical film were evaluated by ranking according to the following criteria, and are shown in Table 1. Preferably, the number of weak unevenness is 10 or less. More preferably, it is within 3 pieces.

◎: No unevenness ○: There are 3 or less weak unevennesses △: There are 4-10 weak unevennesses ×: There are many regular strong irregularities XX: Strong irregularities with regularity are on the entire film surface

Example 2
<< Production of Polarizing Plate and Liquid Crystal Display >>
[Production of polarizer]
A 75 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution of 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 3 times. This uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 25 μm.

<Preparation of UV-curable adhesive liquid 1>
After mixing the following components, defoaming was performed to prepare an ultraviolet curable adhesive liquid 1. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel) 40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Tria Reelsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass [Preparation of polarizing plates 1 to 24]
First, the produced optical film was used as a polarizing plate protective film, and the surface thereof was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the ultraviolet curable adhesive liquid 1 prepared above is applied to the corona discharge treated surface of the polarizing plate protective film with a bar coater so that the film thickness after curing is about 3 μm, and the ultraviolet curable adhesive layer is applied. Formed. The produced polarizer was bonded to the obtained ultraviolet curable adhesive layer.

  Subsequently, KC4UE (manufactured by Konica Minolta Co., Ltd.), which is a commercially available cellulose ester film, was subjected to corona discharge treatment. The conditions of the corona discharge treatment were a corona output intensity of 2.0 kW and a speed of 18 m / min.

  Next, on the corona discharge treated surface of KC4UE, the ultraviolet curable adhesive liquid 1 prepared above was applied with a bar coater so that the film thickness after curing was about 3 μm to form an ultraviolet curable adhesive layer. .

  A polarizer having the polarizing plate protective film bonded to one side is bonded to the ultraviolet curable adhesive layer, and then the polarizing plate protective film / UV curable adhesive layer / polarizer / UV curable adhesive layer. Polarizing plates 1 to 24 having / KC4UE laminated thereon were obtained. In that case, it bonded so that the slow axis of a polarizing plate protective film and KC4UE, and the absorption axis of a polarizer might become mutually orthogonal.

From the cellulose ester film side of this laminate, using a UV irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems Co., Ltd.), the UV light was irradiated so that the accumulated light amount was 750 mJ / cm ^2. Then, the ultraviolet curable adhesive layer was cured to produce polarizing plates 1 to 24.

[Production of liquid crystal display devices 1 to 24]
As a liquid crystal cell, an IPS liquid crystal cell having two glass substrates having a thickness of 0.5 mm and a liquid crystal layer disposed therebetween was prepared. And on both surfaces of the prepared liquid crystal cell, the prepared polarizing plate A1 is attached to the liquid crystal cell side through a 25 μm-thick double-sided tape (baseless tape MO-3005C) manufactured by Lintec. The liquid crystal display device was obtained by bonding. In the bonding, the absorption axis of the polarizer of the polarizing plate A1 on the viewing side and the absorption axis of the polarizer of the polarizing plate A1 on the backlight side were orthogonal to each other.

  The configuration of the liquid crystal display panel was produced as shown in FIG. The polarizing plate protective films 1 to 24 are positions of the polarizing plate protective film 102, respectively.

  It turned out that the liquid crystal display device which used the optical films 1-17 of this invention as a polarizing plate protective film is excellent in visibility, without a display nonuniformity.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock pot 2, 5, 11, 14 Liquid feed pump 8, 16 Conduit 10 Additive charging pot 20 Merge pipe 21 Mixer 30 Pressure die 31 Metal belt 32 Web 33 Peeling position 34 First drying device 35 Stretching device 36 Second drying device 37 Conveying roller 38 Winding device 41 Feeding pot 42 Stock pot 43 Pump 44 Filter 100 Liquid crystal display 101A, 101B Polarizing plate 101C Liquid crystal cell 102 Polarizing plate Protective film 103A, 103B UV curable adhesive 104 Polarizer 105 Polarizing plate protective film 106 Adhesive layer 107 Liquid crystal layer 108A, 108B Glass substrate BL Backlight

Claims (6)

An optical film containing a cycloolefin resin, wherein the optical film contains a compound having a structure represented by the following general formula (1) or general formula (2).

(Wherein R _{1 to} R ₄ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms)

(Wherein R _{5 to} R ₇ each independently represents an alkyl group having 1 to 20 carbon atoms.)   The optical film according to claim 1, wherein the thickness is in the range of 5 to 30 μm.   The optical film according to claim 1, wherein the thickness is in the range of 10 to 20 μm.   The optical film according to any one of claims 1 to 3, further comprising an ultraviolet absorber.   The optical film according to any one of claims 1 to 4, further comprising a matting agent.   A display device comprising the optical film according to any one of claims 1 to 5.

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