JP2018097033A - Optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film that has high solvent resistance and transparency and can sufficiently suppress punching failures such as cracks when the film is made thin.SOLUTION: The optical film comprises a cycloolefin-based resin and a copolymer resin having a structural unit derived from a styrene-based monomer and a structural unit derived from a fluorene-based monomer. The cycloolefin-based resin has a polar group; and the structural unit derived from a styrene-based monomer of the copolymer resin has a proton-donating group. The proportion of the copolymer resin relative to the total mass of the cycloolefin-based resin and the copolymer resin is 5 mass% or more and 95 mass% or less.SELECTED DRAWING: None

Description

  The present invention relates to an optical film.

  Liquid crystal displays and organic EL displays are widely used in televisions, notebook computers, smartphones, and the like. As a light-transmitting optical film used for these displays, a cycloolefin resin film having excellent water resistance is used.

  In recent years, optical films are used not only for electrode films such as touch panels and barrier films having gas barrier properties, but also as flexible films. With such expansion of applications, optical films are required to be improved in processability such as solvent resistance and oil resistance.

  In Patent Document 1, a cycloolefin resin is formed by forming a layer having a thickness of 0.1 μm or more and 20 μm or less obtained by applying an aqueous dispersion of non-chlorine polymer particles on the surface of a cycloolefin resin film. It is described that the solvent resistance and oil resistance of the film can be improved. Patent Document 1 describes that a copolymer containing a styrene monomer as a main component can be used as the non-chlorine polymer particles.

  Patent Document 2 describes that a polymer containing a cyclic olefin monomer such as norbornene and a fluorene compound having a polymerizable unsaturated bond as a polymerization component is excellent in heat resistance and the like.

JP 2001-96673 A JP 2012-111942 A

  However, according to the knowledge of the present inventors, a cycloolefin resin film satisfying higher solvent resistance and sebum resistance (oil resistance) required in recent years was not obtained even by the method described in Patent Document 1. .

  Here, it is considered that when a polymer having a rigid structure derived from a fluorene compound described in Patent Document 2 is used, the solvent resistance and oil resistance can be improved.

  In recent years, optical films have been made thinner in order to produce thinner displays. However, the optical film tends to be particularly fragile when it is thinned. For this reason, when trying to reduce the thickness of the optical film, there is a possibility that defective punching such as cracks, cracks, and chippings may occur in the film during stretching or roll conveyance during the production of the optical film.

  On the other hand, the non-chlorine polymer particles described in Patent Document 1 may be a copolymer resin having a structural unit derived from a styrene monomer and a structural unit derived from a fluorene monomer. The solvent resistance of the optical film was not sufficiently increased, but on the other hand, the transparency of the optical film was lowered, and when the film was thinned, the punching failure of the optical film was likely to occur.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical film that has high solvent resistance and transparency and can sufficiently suppress punching defects when thinned.

[1] a cycloolefin resin having a polar group, and a copolymer resin having a structural unit derived from a styrene monomer having a proton-donating group and a structural unit derived from a fluorene monomer, The optical film whose ratio of the said copolymer resin with respect to the total mass of cycloolefin type resin and the said copolymer resin is 5 mass% or more and 95 mass% or less.
[2] The optical film according to [1], wherein the proton donating group is a hydroxyl group.
[3] The ratio of the mass of the copolymer resin to the total mass of the cycloolefin resin and the copolymer resin is 20% by mass or more and 80% by mass or less, according to [1] or [2]. Optical film.
[4] The optical film according to any one of [1] to [3], wherein the cycloolefin-based resin has a structural unit derived from a norbornene-based monomer having a polar group.
[5] The copolymer resin according to any one of [1] to [4], wherein the copolymer resin is a random copolymer of a styrene monomer having the proton donating group and the fluorene monomer. Optical film.
[6] The optical film according to any one of [1] to [5], wherein the film thickness is 10 μm or more and 25 μm or less.
[7] A polarizing plate comprising a polarizer and the optical film according to any one of [1] to [6] disposed on at least one surface thereof.
[8] A display device comprising the polarizing plate according to [7].
[9] A cycloolefin resin having a polar group, a copolymer resin having a structural unit derived from a styrene monomer having a proton donating group and a structural unit derived from a fluorene monomer, and a solvent. An optical film comprising: a step of obtaining a dope including: a step of casting the dope on a support, and drying to obtain a film-like material; and a step of peeling the film-like material from the support. Manufacturing method.

  The present invention can provide an optical film that has high solvent resistance and transparency, and can sufficiently suppress punching defects when thinned.

FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a liquid crystal display.

  The present inventors also refer to a copolymer resin having a structural unit derived from a cycloolefin resin, a structural unit derived from a styrene monomer, and a structural unit derived from a fluorene monomer (hereinafter also simply referred to as “copolymer resin”). ), And the cycloolefin resin has a polar group, and the structural unit derived from the styrene monomer of the copolymer resin has a proton donating group, It has been found that the punching failure when the film is thinned can be sufficiently suppressed while improving the solvent resistance and transparency of the optical film.

  The reason for this is not clear, but is presumed as follows. In other words, it is effective to entangle the copolymer resin obtained by copolymerizing the fluorene compound with the cycloolefin resin in order to sufficiently improve the oil resistance and suppress the punching failure by the fluorene compound. . However, since the cycloolefin resin and the copolymer resin are incompatible with each other, they are not easily mixed when the optical film is produced. Therefore, in the optical film manufactured from these materials, the improvement in solvent resistance due to the structural unit derived from the fluorene-based monomer is not sufficiently exhibited in the entire optical film. In addition, in an optical film manufactured from these materials, breakage tends to occur at the interfaces of the respective resins dispersed with each other, particularly when the film is thinned. Furthermore, in an optical film manufactured from these materials, light is easily refracted at the interfaces of the respective resins dispersed with each other, so that transparency is hardly increased.

  On the other hand, the cycloolefin resin has a polar group, and the structural unit derived from the styrene monomer of the copolymer resin has a proton donating group. The polar group possessed by and the proton donating group possessed by the copolymer resin interact with each other, so that these resins are easily compatible. Thereby, the improvement of solvent resistance by the structural unit derived from the fluorene-based monomer and the suppression of defective punching can be sufficiently exerted on the entire optical film, and the transparency can be enhanced at the same time.

  Furthermore, the fluorene skeleton contained in the copolymer resin can make the retardation of the optical film smaller, but the cycloolefin resin and the copolymer resin are easily compatible with each other, so that the retardation of the optical film is also reduced. It can be made smaller.

1. Optical film The optical film of the present invention is a copolymer having a cycloolefin resin having a polar group, a structural unit derived from a styrene monomer having a proton-donating group, and a structural unit derived from a fluorene monomer. Resin.

  The ratio of the mass of the copolymer resin to the total mass of the cycloolefin resin and the copolymer resin is 5% by mass or more and 95% by mass or less. When the proportion of the mass of the copolymer resin is 5% by mass or more, the effect of improving the oil resistance by the copolymer resin can be more sufficiently exhibited. When the proportion of the mass of the copolymer resin is 95% by mass or less, the characteristics of the cycloolefin are hardly impaired, and the phase difference is hardly exhibited excessively. From the viewpoint of further improving the transparency and sufficiently suppressing punching defects and further reducing the phase difference, the mass ratio of the copolymer resin may be 20% by mass or more and 80% by mass or less. Preferably, the content is 30% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 60% by mass or less.

  The total mass of the cycloolefin resin and the copolymer resin is more preferably 80% by mass or more and 100% by mass or less, and 90% by mass or more and 100% by mass or less with respect to the total mass of the optical film. It is more preferable that

1-1. Cycloolefin-based resin The cycloolefin-based resin contained in the optical film of the present invention is a homopolymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and another copolymerizable monomer. And having a polar group.

  Examples of the polar group include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an allyloxycarbonyl group, a cyano group, an amino group, and an amide group. The polar group may be added to a structural unit derived from a cycloolefin monomer, or may be added to a structural unit derived from a copolymerizable monomer copolymerizable with the cycloolefin monomer. May be.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton having a polar group (norbornene monomer), and is a norbornene monomer represented by the following general formula (A). It is preferable.

R ^{1 to} R ^{4 in} the general formula (A) independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or the polar group. However, at least one of R ^{1 to} R ⁴ is the polar group.

  Examples of the halogen atom include a fluorine atom and a chlorine atom. Examples of the hydrocarbon group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group. The hydrocarbon group having 1 to 5 carbon atoms is a linking group containing a halogen atom, oxygen atom, nitrogen atom, sulfur atom or silicon atom (for example, a carbonyl group, an imino group, an ether bond, a silyl ether bond, a thioether bond, etc. And a divalent linking group).

R ² and R ³ may be bonded to each other to form an aromatic ring or an aliphatic ring.

Moreover, among R ^{1 to} R ⁴ , R ¹ and R ² may be hydrogen atoms at the same time, or R ¹ , R ² and R ³ may be hydrogen atoms at the same time. Since such a norbornene-based monomer has low molecular symmetry, it can promote diffusion movement between the resin and the additive during solvent volatilization in the solution casting film forming step.

  P in the general formula (A) represents an integer of 0 or more and 2 or less. From the viewpoint of increasing the resulting resin bulk to increase the glass transition temperature of the resin and further improving the heat resistance of the optical film, p is preferably 1 or more and 2 or less.

Specific examples of the norbornene-based monomer having a polar group represented by the general formula (A) are shown below.

  The content ratio of the structural unit derived from the norbornene-based monomer having a polar group is, for example, 50 mol% or more with respect to the total of the structural units derived from the cycloolefin monomer constituting the cycloolefin-based resin, preferably It can be 70 mol% or more, more preferably 100 mol%.

  In this case, examples of the copolymerizable monomer copolymerizable with the cycloolefin monomer include a norbornene monomer and a ring-opening copolymerizable monomer, a norbornene monomer, and Copolymerizable monomers capable of addition copolymerization are included.

  Examples of the copolymerizable monomer capable of ring-opening copolymerization with the norbornene-based monomer include cycloolefins including cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

  Examples of the copolymerizable monomer capable of addition copolymerization with the norbornene-based monomer include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, and (meth) acrylates.

  Examples of the unsaturated double bond-containing compound include olefin compounds having 2 to 12 carbon atoms (preferably 2 to 8 carbon atoms), and specifically include ethylene, propylene, and butene. .

  Examples of the vinyl cyclic hydrocarbon monomer include vinylcyclopentene monomers including 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

  Examples of the (meth) acrylate include alkyl (meth) acrylates having 1 to 20 carbon atoms, including methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like.

  The content ratio of the structural unit derived from the norbornene monomer in the copolymer of the norbornene monomer and the other copolymerizable monomer is the sum of the structural units constituting the cycloolefin resin. On the other hand, it can be 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less.

As described above, the cycloolefin resin is a polymer obtained by polymerizing or copolymerizing a cycloolefin monomer, preferably a norbornene monomer represented by the general formula (A). The polymerization or copolymerization may be ring-opening polymerization or ring-opening copolymerization, or may be addition polymerization or addition copolymerization. Examples of polymers include the following:
(1) Ring-opening polymer of norbornene-based monomer (2) Ring-opening copolymer of norbornene-based monomer and copolymerizable monomer capable of ring-opening copolymerization thereof (3) (1) or (2) Hydrogenated product of ring-opening (co) polymer (4) The ring-opening (co) polymer of (1) or (2) above was cyclized by Friedel-Crafts reaction and then hydrogenated (co-polymerized). ) Polymer (5) Addition copolymer of norbornene monomer and unsaturated double bond-containing compound (6) Addition copolymer of norbornene monomer and vinyl cyclic hydrocarbon monomer and its Hydrogenated product (7) Addition copolymer of norbornene monomer and (meth) acrylate

  Any of the polymers (1) to (7) can be obtained by known methods, for example, the methods described in JP-A-2008-107534 and JP-A-2005-227606. For example, as the catalyst and solvent used in the ring-opening copolymerization (2), those described in paragraphs 0019 to 0024 of JP-A-2008-107534 can be used. As the catalyst used for hydrogenation in (3) and (6), those described in paragraphs 0025 to 0028 of JP-A-2008-107534 can be used. As the acidic compound used in the Friedel-Crafts reaction of (4), those described in paragraph 0029 of JP-A-2008-107534 can be used. As the catalyst used for the addition polymerization of (5) to (7), for example, paragraphs 0058 to 0063 of JP-A-2005-227606 can be used. The alternating copolymerization reaction (7) can be performed by the method described in paragraphs 0071 and 0072 of JP-A-2005-227606.

  Among these, (1) to (3) and (5) are preferable, and (1) to (3) are more preferable. That is, the cycloolefin resin is preferably a ring-opening polymer or a ring-opening copolymer of norbornene monomers or a hydrogenated product thereof. Such cycloolefin-based resin can include, for example, a structural unit represented by the following general formula (B). The structural unit represented by the general formula (B) is derived from the ring-opened product of the norbornene monomer represented by the general formula (A).

X in the general formula (B) is —CH═CH— or —CH ₂ CH ₂ —.

^R 1 to R ⁴ and p in the general formula (B) are respectively ^R 1 to R ⁴ and p in the general formula (A) synonymous.

  The cycloolefin-based resin may be a ring-opening polymer, a ring-opening copolymer, an addition copolymer, or a hydrogenated product of a cycloolefin monomer other than the norbornene-based monomer described above. Good.

  The cycloolefin resin may be a commercially available product. Examples of commercially available cycloolefin resins include Arton G (for example, G7810), Arton F, Arton R (for example, R4500, R4900, and R5000), and Arton RX manufactured by JSR Corporation.

The intrinsic viscosity [η] inh of the cycloolefin resin is preferably 0.2 cm ³ / g or more and 5 cm ³ / g or less, more preferably 0.3 cm ³ / g or more and 3 cm ³ / g or less, More preferably, it is 0.4 cm ³ / g or more and 1.5 cm ³ / g or less.

  The number average molecular weight (Mn) of the cycloolefin resin is preferably 8000 or more and 100,000 or less, more preferably 10,000 or more and 80,000 or less, and further preferably 12000 or more and 50000 or less. The weight average molecular weight (Mw) of the cycloolefin resin is preferably 20000 or more and 300000 or more, more preferably 30000 or more and 250,000 or less, and further preferably 40000 or more and 200000 or more. The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured by gel permeation chromatography (GPC) in terms of polystyrene.

  When the intrinsic viscosity [η] inh, the number average molecular weight and the weight average molecular weight are in the above ranges, the heat resistance, water resistance, chemical resistance, mechanical properties of the cycloolefin resin and molding processability as a film are improved. .

  The glass transition temperature (Tg) of the cycloolefin resin is usually 110 ° C. or higher, preferably 110 ° C. or higher and 350 ° C. or lower, more preferably 120 ° C. or higher and 250 ° C. or lower, and 120 ° C. or higher and 220 ° C. or lower. More preferably, it is not higher than ° C. When Tg is 110 ° C. or higher, it is easy to suppress deformation under high temperature conditions. On the other hand, when Tg is 350 ° C. or lower, the molding process is facilitated, and the deterioration of the resin due to the heat during the molding process is easily suppressed.

1-2. Copolymer Resin The copolymer resin contained in the optical film of the present invention is a copolymer resin of a styrene monomer having a proton donating group and a fluorene monomer, and having the above proton donating group. It has a structural unit derived from a monomer and a structural unit derived from the fluorene monomer.

  Examples of the proton donating group include a hydroxy group, a thiol group, and a carboxy group. Among these, from the viewpoint of further improving the compatibility between the cycloolefin resin and the copolymer resin, a hydroxy group that easily interacts with the polar group of the cycloolefin resin is preferable.

  The proton donating group may be added to any of the o-position, m-position and p-position with respect to the vinyl group of styrene. Among these, the influence of the steric hindrance by the structural unit derived from the fluorene monomer is reduced, and the proton donating group and the polar group possessed by the cycloolefin resin are easily interacted with each other. From the viewpoint of making the resin and the copolymer resin more compatible with each other, it is preferably added to the p-position.

  Examples of the styrenic monomer include styrene, α-methylstyrene, β-methylstyrene, pt-butylstyrene, vinyltoluene and the like.

  The fluorene-based monomer is a monomer having a fluorene skeleton and a functional group having a polymerizable unsaturated bond.

  The fluorene skeleton may be a fluorene having no substituent, but is preferably a substituted fluorene having a substituent at the 9-position, more preferably a 9,9-bisarylfluorene skeleton, and a 9,9-bisphenol fluorene skeleton. More preferably.

  The polymerizable unsaturated bond is preferably a carbon-carbon unsaturated bond containing a (meth) acryloyl group and the like. The functional group having a polymerizable unsaturated bond may be directly bonded to the fluorene skeleton, but bonded to a substituent added to the fluorene skeleton (for example, a substituent added to the 9-position of the fluorene skeleton). Preferably it is.

  Examples of the fluorene-based monomer include 9,9-bis ((meth) acryloyloxyaryl) fluorene and 9,9-bis ((meth) acryloyloxy (poly) alkoxyaryl) fluorene.

Specific examples of the 9,9-bis ((meth) acryloyloxyaryl) fluorene include
9,9-bis ((meth) acryloyloxyphenyl) fluorene such as 9,9-bis (4- (meth) acryloyloxyphenyl) fluorene,
9,9-, such as 9,9-bis (4- (meth) acryloyloxy-3-methylphenyl) fluorene and 9,9-bis (4- (meth) acryloyloxy-3,5-dimethylphenyl) fluorene Bis (alkyl- (meth) acryloyloxyphenyl) fluorene,
9,9-bis (aryl (meth) acryloyloxyphenyl) fluorene such as 9,9-bis (4- (meth) acryloyloxy-3-phenylphenyl) fluorene,
9,9-bis [3,4-di ((meth) acryloyloxy) phenyl] fluorene and 9,9-bis [3,4,5-tri ((meth) acryloyloxy) phenyl] fluorene 9-bis (poly (meth) acryloyloxyphenyl) fluorene, and
9,9-, such as 9,9-bis [6- (2- (meth) acryloyloxynaphthyl)] fluorene and 9,9-bis [1- (5- (meth) acryloyloxynaphthyl)] fluorene] Bis ((meth) acryloyloxynaphthyl) fluorene and the like are included.

Specific examples of the 9,9-bis ((meth) acryloyloxy (poly) alkoxyaryl) fluorene include
9,9-bis ((meth) acryloyloxyalkoxyphenyl) fluorene such as 9,9-bis (4- (2- (meth) acryloyloxyethoxy) phenyl) fluorene,
9,9-bis ((meth) acryloyloxydialkoxyphenyl) fluorene such as 9,9-bis {4- [2- (2- (meth) acryloyloxyethoxy) ethoxy] phenyl} fluorene, etc.]
9,9-bis (4- (2- (meth) acryloyloxyethoxy) -3-methylphenyl) fluorene, and 9,9-bis (4- (2- (meth) acryloyloxyethoxy) -3,5- 9,9-bis (alkyl- (meth) acryloyloxyalkoxyphenyl) fluorene such as dimethylphenyl) fluorene,
9,9-bis (aryl- (meth) acryloyloxyalkoxyphenyl) fluorene such as 9,9-bis (4- (2- (meth) acryloyloxyethoxy) -3-phenylphenyl) fluorene,
9,9-bis [3,4-di (2- (meth) acryloyloxyethoxy) phenyl] fluorene, 9,9-bis [3,4,5-tri (2- (meth) acryloyloxyethoxy) phenyl] 9,9-bis [di or tri ((meth) acryloyloxyalkoxy) phenyl] fluorene, such as fluorene, and
9,9-bis ((meth) acryloyloxyalkoxynaphthyl) fluorene and the like such as 9,9-bis ((meth) acryloyloxy C2-4alkoxynaphthyl) fluorene are included.

  The number of moles of the structural unit derived from the styrenic monomer relative to the total number of moles of the structural unit derived from the styrenic monomer and the structural unit derived from the fluorene monomer that the copolymer resin has. The number ratio is preferably 10 mol% or more and 30 mol% or less. When the ratio of the number of moles of structural units derived from the styrenic monomer is 10 mol% or more, the retardation of the optical film can be further reduced. Further, when the ratio of the number of moles of the structural units derived from the styrene monomer is 30 mol% or less, the compatibility with the cycloolefin resin is further improved, and in particular, the transparency of the optical film is increased. be able to.

The molar ratio of the structural unit derived from the styrene monomer and the structural unit derived from the fluorene monomer can be measured by a known method such as ¹ H-NMR and ¹³ C-MNR.

  The copolymer resin has a weight average molecular weight (Mw) of preferably 2000 or more and 1500,000 or less, more preferably 5000 or more and 1000000 or less, and further preferably 12000 or more and 50000 or less. The weight average molecular weight of the copolymer resin can be measured in terms of polystyrene by gel permeation chromatography (GPC).

  The copolymer resin may be any copolymer such as a block copolymer, a random copolymer, and a graft copolymer, but between the polar group of the cycloolefin resin and the proton donating group. A random copolymer is preferable from the viewpoint of causing the interaction in the entire copolymer resin and facilitating the compatibility with the cycloolefin resin.

  The copolymer resin is a component other than the structural unit derived from the styrene monomer and the structural unit derived from the fluorene monomer, as long as the solvent resistance, transparency and brittleness of the optical film are not significantly deteriorated. Other structural units may be included. The ratio of the number of moles of the above other structural units to the copolymer resin is preferably 0 mol% or more and 20 mol% or less, more preferably 0 mol% or more and 10 mol% or less. It is further preferable that other structural units are not substantially contained.

1-3. Other components The optical film may further contain other components as long as the effects of the present invention are not impaired. Examples of the other components include resins other than the cycloolefin resin or copolymer resin, ultraviolet absorbers, antioxidants, and the like.

1-4. Film properties (haze)
The haze of the optical film is preferably 0.01 or more and 2.0 or less. When the haze of the optical film is 2.0 or less, the contrast of the display image on the display can be increased. The haze of the optical film is more preferably from 0.01 to 1.0. The haze of the optical film can be measured with a haze meter (model NDH 2000, manufactured by Nippon Denshoku Co., Ltd.).

  The haze of the optical film can be adjusted mainly by the content of (meth) acrylic resin fine particles and inorganic fine particles. In order to reduce the haze of the optical film, for example, the content of (meth) acrylic resin fine particles and inorganic fine particles is preferably set to a certain value or less.

(Phase difference Ro and Rt)
When the optical film is used as a polarizing plate protective film or a retardation film for a flexible display, it may have retardation values Ro and Rt according to the application.

  For example, when the optical film is used as a zero phase difference film, the phase difference Ro in the in-plane direction measured under an environment of a measurement wavelength of 590 nm and 23 ° C. and 55% RH preferably satisfies 0 nm ≦ Ro ≦ 5 nm. More preferably, 0 nm ≦ Ro ≦ 3 nm. Further, the thickness direction retardation Rt measured in an environment of a measurement wavelength of 590 nm and 23 ° C. and 55% RH preferably satisfies −10 nm ≦ Rt ≦ 10 nm, more preferably −5 nm ≦ Ro ≦ 5 nm.

Ro and Rt of the optical film are respectively defined by the following formulas.
Formula (1a): Ro = (nx−ny) × d
Formula (1b): Rt = ((nx + ny) / 2−nz) × d
(Where
nx represents the refractive index in the in-plane slow axis direction of the optical film (the direction in which the refractive index is maximum),
ny represents the refractive index in the direction orthogonal to the in-plane slow axis of the optical film,
nz represents the refractive index in the thickness direction of the optical film,
d represents the thickness (nm) of the optical film. )

  The in-plane slow axis of the optical film refers to an axis having the maximum refractive index on the film surface. The in-plane slow axis of the optical film can be confirmed by an automatic birefringence meter Axoscan (AxoScan Mueller Matrix Polarimeter: manufactured by Axometrics).

The measurement of Ro and Rt of an optical film can be performed by the following method.
1) Condition the optical film for 24 hours in an environment of 23 ° C. and 55% RH. The average refractive index of this optical film is measured with an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.
2) Retardation Ro and Rt of the optical film after humidity adjustment at a measurement wavelength of 590 nm were each measured at 23 ° C. and 55% RH using an automatic birefringence meter Axoscan (AxoScan Mueller Matrix Polarimeter: manufactured by Axometrics). Measure under the environment.

  The retardations Ro and Rt of the optical film can be adjusted mainly by the draw ratio. In order to increase the retardations Ro and Rt of the optical film, it is preferable to increase the draw ratio.

(Thickness)
The thickness of the optical film is, for example, preferably from 5 μm to 40 μm, and more preferably from 10 μm to 25 μm. The thicker the film thickness, the higher the certain optical film strength can be expressed, and the higher the crack resistance of the optical film and the crack resistance of the polarizing plate using the optical film. The thinner the film thickness, the smaller the retardation of the optical film and the thinner the polarizing plate and the display device.

2. Method for Producing Optical Film The optical film of the present invention can be produced by any method, but is preferably produced by a solution casting method (cast method).

  That is, the optical film of the present invention is obtained by 1) a step of obtaining a dope containing at least the above-mentioned cycloolefin resin, copolymer resin and solvent, and 2) casting the obtained dope on a metal support. It can be manufactured through a step of obtaining a film-like product by drying and peeling, and a step of 3) drying or stretching the obtained film-like product while drying.

Step 1) The dope may be obtained by directly adding and mixing a cycloolefin resin and a copolymer resin to a solvent, or a solution obtained by dissolving a cycloolefin resin in a solvent, and a copolymer resin. It may be obtained by mixing with a solution in which is dissolved in a solvent.

  The solvent used for the dope preferably contains an organic solvent (good solvent) that can dissolve both the cycloolefin-based resin and the copolymer resin. Examples of such good solvents include chlorinated organic solvents including methylene chloride (methylene chloride) and the like, and non-chlorinated organic solvents including methyl acetate, ethyl acetate, acetone, toluene, tetrahydrofuran, and the like. Among these, methylene chloride (methylene chloride) is preferable.

  The solvent used for dope may further contain an organic solvent (poor solvent) that does not dissolve either the cycloolefin-based resin or the copolymer resin. Examples of the poor solvent include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of the alcohol in the dope is increased, the film-like product is easily gelled and is easily peeled off from the metal support. Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferred because the stability of the dope, the boiling point is relatively low, and the drying property is good.

Step 2) The obtained dope is cast on a metal support. The dope can be cast by being discharged from a casting die.

Next, the solvent in the dope cast on the metal support is evaporated and dried. The dried dope is peeled off from the metal support to obtain a film. The residual solvent amount of the dope when peeling from the metal support (residual solvent amount S ₀ when peeling) is 50% by mass or more and 120% by mass from the viewpoint of easily reducing the phase difference Ro or Rt of the obtained optical film. The following is preferable. When the residual solvent amount S ₀ at the time of peeling is more than 50 wt%, the drying or cycloolefin resins and copolymer resins during stretching tends to unoriented easily flow, reducing the Ro and Rt of the optical film obtained Cheap. When the residual solvent amount S ₀ at the time of peeling is 120 wt% or less, since the force is less likely excessively large required upon the release of the dope, it is easy to suppress the breakage of the dope.

The residual solvent amount of the dope is defined by the following formula. The same applies to the following.
Residual amount of dope solvent (mass%) = (mass before heat treatment of dope−mass after heat treatment of dope) / mass after heat treatment of dope × 100
Note that the heat treatment for measuring the residual solvent amount means a heat treatment at 120 ° C. for 60 minutes.

Step 3) The obtained film is dried or stretched while drying. Stretching can be performed in at least one direction. The stretching direction may be any of the longitudinal direction of the film-like material (MD direction), the width direction perpendicular to the longitudinal direction of the film-like material (TD direction), and the oblique direction with respect to the longitudinal direction of the film-like material. Good.

  The draw ratio is set according to the required optical performance, but from the viewpoint of causing the optical film to function as a λ / 4 film or a retardation film for VA, for example, 1.31 times or more and 5.0 times or less. From the viewpoint of functioning as a retardation film for IPS, it can be set to, for example, 1.01 to 1.3 times. The draw ratio is defined as (stretching direction size of the film after stretching) / (stretching direction size of the film before stretching).

  The stretching temperature is preferably (Tg-10) ° C. or more and (Tg + 50) ° C. or less, where Tg is the glass transition temperature of the optical film to be produced, including cycloolefin resin and copolymer resin, (Tg− 5) More preferably, it is not lower than (° C.) and not higher than (Tg + 40) ° C. When the stretching temperature is (Tg-10) ° C. or higher, the tension applied to the film-like material during drying or stretching is not excessively increased, and thus Ro and Rt of the obtained optical film are not excessively increased. When the stretching temperature is (Tg + 50) ° C. or lower, the generation of bubbles due to the vaporization of the solvent in the film-like material is highly suppressed. The stretching temperature can be specifically 120 ° C. or higher and 200 ° C. or lower.

The residual solvent amount S _{1 in} the film-like material at the start of stretching is preferably 5% by mass or more and 20% by mass or less. When the residual solvent amount S ₁ at the start of stretching is 5 mass% or more, by plasticizing effect due to the residual solvent, for substantial Tg of the film-like material at the time of stretching is low, the optical film Ro and Rt is increased Hard to do. When the residual solvent amount S ₁ at the start of stretching is 20 wt% or less, it can be highly suppress the generation of bubbles due to vaporization of the solvent of the membrane-like material. The residual solvent amount S _{1 in} the film-like material at the start of stretching is more preferably 8% by mass or more and 15% by mass or less.

  The film-like material can be stretched in the MD direction by, for example, a method (roll method) in which a difference in peripheral speed is applied to a plurality of rolls, and the difference in peripheral speed between the rolls is utilized. Stretching of the film-like material in the TD direction can be performed by, for example, a method (tenter method) in which both ends of the film-like material are fixed with clips or pins and the distance between the clips or pins is increased in the traveling direction.

3. Applications As described above, the optical film of the present invention has high transparency and is ready to be thinned. Therefore, the optical film of the present invention is a transparent plastic film substrate, an optical film (for example, a polarizing plate protective film, a retardation film, etc.), a touch panel film (electrode film), a display, including a liquid crystal display and an organic EL display. It can use preferably for the protective film etc. which are arrange | positioned at the surface at the side of visual recognition. The optical film of the present invention can also be preferably used for flexible displays and the like. Furthermore, the optical film of the present invention can be preferably used for a sealing substrate of an organic EL device, a sealing film (barrier film) of an organic thin film solar cell, and the like.

(LCD display)
In an example of the use of the optical film of the present invention, the liquid crystal display includes a liquid crystal cell and a pair of polarizing plates that sandwich the liquid crystal cell.

  FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a liquid crystal display. As shown in FIG. 1, the liquid crystal display 10 includes a liquid crystal cell 20, a first polarizing plate 30 and a second polarizing plate 40 that sandwich the liquid crystal cell 20, and a backlight 50.

  The display mode of the liquid crystal cell 20 is not particularly limited, and may be any one of TN (Twisted Nematic), VA (Visual Alignment), IPS (In Plane Switching), and the like.

  The liquid crystal cell 20 includes a pair of transparent plastic film substrates 21 and 23, and a liquid crystal layer 25 disposed between them and containing liquid crystal molecules. The pixel electrode can be disposed on one of the pair of transparent plastic film substrates 21 and 23 (for example, the transparent plastic film substrate 21). The counter electrode may be further disposed on the transparent plastic film substrate 21 on which the pixel electrode is disposed, or may be disposed on the other transparent plastic film substrate 23.

  Then, by applying an electric field between the pixel electrode and the counter electrode, the liquid crystal molecules are aligned in a predetermined direction, thereby changing the transmittance and reflectance of each sub-pixel to display an image.

  The first polarizing plate 30 is disposed on the surface on the viewing side of the liquid crystal cell 20, and the first polarizer 31 and the polarization disposed on the surface opposite to the liquid crystal cell of the first polarizer 31. The plate protective film 33 (F1) and the polarizing plate protective film 35 (F2) disposed on the liquid crystal cell side surface of the first polarizer 31 are included.

  The second polarizing plate 40 is disposed on the surface of the liquid crystal cell 20 on the backlight side, and the second polarizer 41 and the polarizing plate protection disposed on the surface of the second polarizer 41 on the liquid crystal cell side. The film 43 (F3) and the polarizing plate protective film 45 (F4) arrange | positioned at the surface on the opposite side to the liquid crystal cell of the 2nd polarizer 41 are included. The absorption axis of the second polarizer 41 is preferably orthogonal to the absorption axis of the first polarizer 41.

  The optical film of the present invention can be preferably used as the transparent plastic film substrate 21 or 23, or the polarizing plate protective film 33 (F1), 35 (F2), 43 (F3), or 45 (F4). Especially, since the optical film of this invention can function as a zero phase difference film, it is preferable to be used as the protective film 35 (F2) or 43 (F3).

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

1. 1. Material of optical film 1-1. Cycloolefin resin (Cycloolefin resin COP1)
Hydrogenated norbornene resin (manufactured by JSR Corporation, Arton G7810 (“Arton” is a registered trademark of the company)) was used as a cycloolefin-based resin having a polar group. Hereinafter, this cycloolefin resin is referred to as COP1.

(Cycloolefin resin COP2)
As the cycloolefin resin having no polar group, a resin synthesized by the method described in Synthesis Example 1 below was used. Hereinafter, this cycloolefin resin is referred to as COP2.

<Synthesis Example 1>
50 parts by mass of dicyclopentadiene, 35 parts by mass of tetracyclododecene and 15 parts by mass of methanotetrahydrofluorene were mixed, and an amount of 1- Dococene was added to prepare a raw material mixture.

  The glass container was replaced with nitrogen, 7 parts by mass of the above raw material mixture, 1,600 parts by mass of cyclohexane, 1.3 parts by mass of diisopropyl ether, 0.33 parts by mass of isobutyl alcohol, 0.84 parts by mass Of triisobutylaluminum and 30 parts by mass of tungsten hexachloride 0.66% cyclohexane solution were added and stirred for 7 hours while heating to 70 ° C. Thereafter, 693 parts by mass of the above raw material mixture and 72 parts by mass of tungsten hexachloride 0.77% cyclohexane solution were continuously added dropwise over 150 minutes while stirring at 55 ° C., and the mixture was further stirred for 30 minutes. The polymerization reaction was stopped by adding 0.0 part by mass of isopropyl alcohol to obtain a polymer solution.

  Thereafter, 300 parts by mass of the polymer solution was transferred to an autoclave equipped with a stirrer, and 100 parts by mass of cyclohexane and 2.0 parts by mass of a diatomaceous earth-supported nickel catalyst (manufactured by JGC Chemical Co., Ltd., T8400RL, nickel support rate of 58%) were added. Then, after the inside of the autoclave was replaced with hydrogen, a hydrogenation reaction was carried out over 6 hours under a hydrogen pressure of 180 ° C. and 4.5 MPa.

  After completion of the hydrogenation reaction, using diatomaceous earth (Radiolite # 500 manufactured by Showa Chemical Industry Co., Ltd. (“Radiolite” is a registered trademark of the company) ”as a filter bed, using a pressure filter (IHI Co., Ltd., Funda filter) Then, pressure filtration was performed at a pressure of 0.25 MPa to obtain a colorless and transparent solution of cycloolefin resin (norbornene ring-opening copolymer hydride).

  Then, 0.5 parts by mass of Ciba Specialty Chemicals Co., Ltd., Irganox 1010 (“Irganox” is a registered trademark of BASF) with respect to 100 parts by mass of the cycloolefin-based resin. Was added and dissolved, and foreign matters were removed by filtration using a metal fiber filter (manufactured by Nichidai Co., Ltd., pore size 0.4 μm).

  Then, using a cylindrical concentrating dryer (manufactured by Hitachi, Ltd.), at a temperature of 260 ° C. and a pressure of 1 kPa or less, cyclohexane and other volatile components are removed from the filtrate, and a strand is melted from a die directly connected to the concentrator. After extruding into a shape and cooling with water, cutting with a pelletizer (manufactured by Nagata Seisakusho Co., Ltd., OSP-2) was performed to obtain the cycloolefin resin pellets.

  The molecular weight of the cycloolefin resin was 35,000 for Mw and 2.2 for Mw / Mn, the hydrogenation rate was 99.7%, and Tg was 124 ° C.

1-2. Copolymer resin (Copolymer resin 1)
As a copolymer resin having a proton donating group, a copolymer resin synthesized by the method described in Synthesis Example 2 below was used. Hereinafter, this copolymer resin is referred to as copolymer resin 1.

<Synthesis Example 2>
200 mL of dichloromethane was introduced into a glass container for reaction, and 7.79 g of 9,9-bis (4-hydroxyphenyl) fluorene and 0.11 g of hydroquinone were dissolved therein to prepare a raw material solution. 10.45 g of methacryloyl chloride was dropped into the raw material solution from the dropping device while cooling, and after completion of the dropping, the mixture was stirred for 5 hours. Then, the target product extracted in the organic layer was separated by mixing with 200 mL of pure water. The separated target product is concentrated by an evaporator, mixed with hexane, recrystallized, and 9,9-bis (4-methacryloyloxyphenyl) fluorene (hereinafter, copolymer resin) represented by the following general formula (1). The fluorene-based monomer used in the synthesis of (also referred to as “monomer 1”) was isolated.

  A glass container for another reaction was replaced with nitrogen, and under a nitrogen flow, 250 mL of degassed tetrahydrofuran was introduced into the glass container, into which 24.33 g of monomer 1, 0.32 g of p-hydroxystyrene ( Hereinafter, (hereinafter, the styrene monomer used for the synthesis of the copolymer resin is also referred to as “monomer 2”, and the styrene monomer having a proton donating group is also simply referred to as “H-styrene”. If not mentioned, H-styrene means p-hydroxystyrene), and 0.086 g of azobisisobutyronitrile (AIBN) was added and dissolved. After stirring for a period of time, the mixture was allowed to cool at room temperature to prepare a reaction solution, which was then concentrated, dropped into methanol and reprecipitated, and the following general formula (2) The molecular weight Mn of to obtain a copolymer resin 1 represented. Copolymer resin 1 43000, a molecular weight Mw 138000, Mw / Mn was 3.209.

(Copolymer resin 2)
A copolymer resin having a proton-donating group was prepared in the same manner as the synthesis of copolymer resin 1 except that the amount of monomer 1 used for preparing the reaction solution was changed to 24.33 g and the amount of monomer 2 was changed to 1.50 g. A synthesized copolymer resin was used. Hereinafter, this copolymer resin is referred to as copolymer resin 2. The molecular weight Mn of the copolymer resin 2 was 48000, the molecular weight Mw was 136000, and Mw / Mn was 2.833.

(Copolymer resin 3)
A copolymer resin having a proton-donating group was prepared in the same manner as the synthesis of copolymer resin 1 except that the amount of monomer 1 used for preparing the reaction solution was changed to 24.33 g and the amount of monomer 2 was changed to 4.01 g. A synthesized copolymer resin was used. Hereinafter, this copolymer resin is referred to as copolymer resin 3. The molecular weight Mn of the copolymer resin 3 was 45000, the molecular weight Mw was 141000, and Mw / Mn was 3.133.

(Copolymer resin 4)
As another copolymer resin having a proton-donating group, a copolymer resin synthesized by the same method as the synthesis of copolymer resin 1 was used except that monomer 2 was changed to 4-mercaptostyrene. Hereinafter, this copolymer resin is referred to as copolymer resin 4. The molecular weight Mn of the copolymer resin 4 was 55000, the molecular weight Mw was 178000, and Mw / Mn was 3.236.

(Copolymer resin 5)
As a copolymer resin having no proton-donating group, a copolymer resin synthesized by the same method as the synthesis of copolymer resin 1 was used except that monomer 2 was changed to styrene. Hereinafter, this copolymer resin is referred to as copolymer resin 5. The molecular weight Mn of the copolymer resin 5 was 69000, the molecular weight Mw was 198000, and Mw / Mn was 2.870.

1-3. Other resins (fluorene homopolymer)
As a homopolymer obtained by polymerizing a fluorene monomer alone, a homopolymer synthesized by the same method as the synthesis of the copolymer resin 1 except that the monomer 2 was not used was used. Hereinafter, this homopolymer is referred to as a fluorene-based homopolymer. The fluorene homopolymer had a molecular weight Mn of 78000, a molecular weight Mw of 255000, and Mw / Mn of 3.269.

(Styrene homopolymer)
As a homopolymer obtained by polymerizing a styrenic monomer having no proton donating group alone, monomer 1 is not used, and monomer 2 is changed to styrene. The synthesized homopolymer was used. Hereinafter, this homopolymer is referred to as a styrene homopolymer. The styrene homopolymer had a molecular weight Mn of 68,000, a molecular weight Mw of 185000, and Mw / Mn of 2.721.

(H-styrene homopolymer)
As a homopolymer obtained by polymerizing a styrene monomer having a proton donating group alone, a homopolymer synthesized by the same method as the synthesis of the copolymer resin 1 was used except that the monomer 1 was not used. Hereinafter, this homopolymer is referred to as H-styrene homopolymer. The H-styrene homopolymer had a molecular weight Mn of 45000, a molecular weight Mw of 131000, and Mw / Mn of 2.911.

2. Production of Optical Film Optical film 1 to optical film 20 were produced by the following procedure.

(Preparation of optical film 1)
<Preparation of dope>
The following components were put into a sealed container, heated and completely dissolved with stirring. This was designated as Azumi Filter Paper No. 24 was used to obtain a dope.
COP1 (cycloolefin resin): 95 parts by mass Copolymer resin 1: 5 parts by mass Dichloromethane: 200 parts by mass Ethanol: 10 parts by mass

<Film formation>
The obtained dope was kept at 30 ° C. and uniformly cast on a stainless steel belt which is an endless metal support kept at 30 ° C. The cast dope was dried until the residual solvent amount was 50% by mass, and then peeled off from the stainless steel belt to obtain a film-like material.

<Stretching and drying>
The obtained film-like material was dried at 40 ° C. until the residual solvent amount became 10% by mass, and then stretched in the width direction at a stretching ratio of 1.1 times (10%). The obtained film-like material was further dried at 150 ° C. while being conveyed by a large number of rolls to obtain an optical film 1 having a length of 3000 m and a thickness of 20 μm.

(Preparation of optical film 2)
The optical film 2 was changed in the same manner as the optical film 1 except that the amount of COP1 charged into the sealed container was changed to 5 parts by mass and the amount of the copolymer resin 1 charged into the sealed container was changed to 95 parts by mass. Obtained.

(Preparation of optical film 3)
The optical film 3 was changed in the same manner as the optical film 1 except that the amount of COP1 charged into the sealed container was changed to 80 parts by mass and the amount of the copolymer resin 1 charged into the sealed container was changed to 20 parts by mass. Obtained.

(Preparation of optical film 4)
The optical film 4 was changed in the same manner as the optical film 1 except that the amount of COP1 charged into the sealed container was changed to 20 parts by mass and the amount of the copolymer resin 1 charged into the sealed container was changed to 80 parts by mass. Obtained.

(Preparation of optical film 5)
The optical film 5 was changed in the same manner as the optical film 1 except that the amount of COP1 charged into the sealed container was changed to 50 parts by mass and the amount of the copolymer resin 1 charged into the sealed container was changed to 50 parts by mass. Obtained.

(Preparation of optical film 6)
An optical film 6 was obtained in the same manner as the optical film 1 except that the copolymer resin 1 was changed to the copolymer resin 2.

(Preparation of optical film 7)
An optical film 7 was obtained in the same manner as the optical film 1 except that the copolymer resin 1 was changed to the copolymer resin 3.

(Preparation of optical film 8)
An optical film 8 was obtained in the same manner as the optical film 3 except that the copolymer resin 1 was changed to the copolymer resin 4.

(Preparation of optical film 9)
An optical film 9 was obtained in the same manner as the optical film 2 except that the thickness was changed to 5 μm.

(Preparation of optical film 10)
The optical film 10 was obtained in the same manner as the optical film 2 except that the thickness was changed to 10 μm.

(Preparation of optical film 11)
An optical film 11 was obtained in the same manner as the optical film 2 except that the thickness was changed to 40 μm.
(Preparation of optical film 12)
The optical film 12 was changed in the same manner as the optical film 1 except that the amount of COP1 charged into the sealed container was changed to 99 parts by mass and the amount of the copolymer resin 2 charged into the sealed container was changed to 1 part by mass. Obtained.
(Preparation of optical film 13)
The optical film 13 was changed in the same manner as the optical film 1 except that the amount of COP1 charged into the sealed container was changed to 1 part by mass and the amount of the copolymer resin 2 charged into the sealed container was changed to 99 parts by mass. Obtained.

(Preparation of optical film 14)
An optical film 14 was obtained in the same manner as the optical film 1 except that the copolymer resin was not put into the sealed container at the time of preparing the dope.

(Preparation of optical film 15)
The copolymer resin was changed to the fluorene homopolymer, the amount of COP1 charged into the sealed container was changed to 60 parts by mass, and the amount of the fluorene homopolymer charged into the sealed container was changed to 40 parts by mass. An optical film 15 was obtained in the same manner as the optical film 1 except that.

(Preparation of optical film 16)
The copolymer resin was changed to the styrene homopolymer, the amount of COP1 charged into the sealed container was changed to 60 parts by mass, and the amount of the styrene homopolymer charged into the sealed container was changed to 40 parts by mass. Obtained an optical film 16 in the same manner as the optical film 1.

(Preparation of optical film 17)
Optical except that the copolymer resin was changed to copolymer resin 5, the amount of COP1 charged into the sealed container was changed to 60 parts by mass, and the amount of copolymer resin 5 charged into the sealed container was changed to 40 parts by mass. In the same manner as Film 1, an optical film 17 was obtained.

(Preparation of optical film 18)
The copolymer resin 2 was melt kneaded at a resin temperature of 210 ° C. using an extruder, and the obtained strand was cut with a pelletizer to obtain resin pellets containing the copolymer resin 2.

The pellet of COP2 obtained in Synthesis Example 2 containing 60 parts by mass of COP2 and the resin pellet containing 40 parts by mass of copolymer resin 2 were mixed with a blender. Next, these resins were kneaded and extruded under the following kneading conditions with a biaxial kneader (Toshiba Machine Co., Ltd., TEM-35B) to obtain pellets of these resins.
Kneading conditions: screw diameter 37 mm, L / D = 32
Screw rotation speed 250rpm
Resin temperature 250 ℃
Feed rate 15kg / hour

Using a hanger manifold type T-die film melt extrusion molding machine having a resin melt kneader equipped with a screw having a screw diameter of 50 mmφ, a compression ratio of 2.5, and L / D = 30, the obtained pellets were T-die molding was performed under the molding conditions, and adjustment was performed so that the thickness was 20 μm, and the film was taken up with a roll to obtain an optical film 18.
Molding conditions: Die gap 300μm
Molten resin temperature 210 ° C
T die width 300mm
Cooling roll 40 ℃
Cast roll 40 ℃

(Preparation of optical film 19)
An optical film except that the amount of COP1 charged in a sealed container was changed to 60 parts by mass, and the copolymer resin charged in the sealed container was changed to 20 parts by mass of the fluorene homopolymer and 20 parts by mass of the styrene homopolymer. In the same manner as in Example 1, an optical film 19 was obtained.

(Preparation of optical film 20)
The amount of COP1 charged into the sealed container was changed to 60 parts by mass, and the copolymer resin charged into the sealed container was changed to 20 parts by mass of the fluorene-based homopolymer and 20 parts by mass of the H-styrene homopolymer. The optical film 20 was obtained in the same manner as the optical film 1.

  Tables 1 and 2 show the materials used for the production of the optical films 1 to 20 and the ratios thereof.

3. Evaluation of Optical Film The retardation (Ro), retardation (Rt), oil resistance, resin transparency (haze) and brittleness of the obtained optical films 1 to 20 were evaluated by the following methods.

(Phase difference (Ro), Phase difference (Rt))
The optical films 1 to 20 were conditioned for 24 hours in an environment of 23 ° C. and 55% RH. The humidity-controlled optical film was measured at a measurement wavelength of 590 nm and three-dimensional refractive index measurement, and the obtained refractive indexes nx, ny, and nz were respectively measured using an automatic birefringence meter Axoscan (AxoScan Mueller Matrix Polarimeter: manufactured by Axometrics). ) Was measured in an environment of 23 ° C. and 55% RH, and was calculated by applying to the above formulas (1a) and (1b).

(Oil resistance)
After winding optical film 1 to optical film 20 around a 30 mmφ steel tube and fixing with tape, apply beef tallow on the surface of the optical film and leave it at 20 ° C. for 1 hour to see if micro cracks have occurred in the film. It observed visually and evaluated by the following references | standards.
○ No cracks occurred in the optical film △ A small crack occurred in a part of the optical film × A crack occurred in the entire optical film

(Transparency (Haze))
The haze of the optical films 1 to 20 was measured with a haze meter (model NDH 2000, manufactured by Nippon Denshoku Co., Ltd.).

(Brittleness (crack rate))
The outer periphery of the optical film 1 to the optical film 20 that were superposed on each other and the outer peripheral part of a cut piece obtained by punching 100 sheets with a 10 cm square Thomson blade was observed to detect punching defects such as cracks, cracks, and chips. The number of parts (n) was divided by the number of observed outer peripheral parts (m), and the crack generation rate was expressed as a percentage as follows.
Crack generation rate (%) = 100 × (n / m)

  The evaluation results of the optical films 1 to 20 are shown in Table 3 and Table 4.

  A cycloolefin resin having a polar group, a copolymer resin having a structural unit derived from a styrene monomer having a proton-donating group and a structural unit derived from a fluorene monomer, and The ratio of the copolymer resin to the total mass of the olefin resin and the copolymer resin is 5% by mass or more and 95% by mass or less, and the optical film 1 to the optical film 11 have solvent resistance and transparency (compatibility). And punching defects such as cracks were sufficiently suppressed.

  In particular, the optical film 3 to the optical film 5 in which the ratio of the mass of the copolymer resin to the total mass of the cycloolefin resin and the copolymer resin is 20% by mass to 80% by mass is the same cycloolefin. The phase difference is smaller than that of the optical film 1 in which the proportion of the mass of the copolymer resin is lower in the combination of the resin and the copolymer resin, and the solvent resistance is higher than that of the optical film 2 in which the proportion of the mass of the copolymer resin is higher. , The punching defects such as cracks were further suppressed, and the phase difference was further reduced.

  Further, the ratio of the number of moles of the structural unit derived from the styrene monomer to the total number of moles of the structural unit derived from the styrene monomer and the structural unit derived from the fluorene monomer is 10 mol%. The optical film 6 using the copolymer resin of 30 mol% or less has a smaller retardation than the optical film 1 in which the ratio of the number of moles of structural units derived from the styrenic monomer is lower, and the styrenic unit The transparency was higher than that of the optical film 7 in which the ratio of the number of moles of structural units derived from the monomer was larger.

  In addition, the comparison of the optical film 2, the optical film 9, the optical film 10, and the optical film 11 in which the film thickness is changed in the combination of the same cycloolefin-based resin and the copolymer resin indicates that the thicker the film thickness, the more Punching defects are less likely to occur, and the thinner the film thickness, the smaller the phase difference.

  On the other hand, the optical films 12 and 13 in which the ratio of the copolymer resin to the total mass of the cycloolefin resin and the copolymer resin is less than 5 mass% or greater than 95 mass% have a larger retardation. It was.

  Further, the optical film 14 not containing the copolymer resin probably did not have a fluorene skeleton, so that the oil resistance was hardly increased, and the retardation was larger than other optical films containing the fluorene skeleton.

  Also, the optical film 15 using a fluorene homopolymer instead of the copolymer resin was low in transparency because the resins were probably not compatible with each other. Also, since the resins are probably incompatible with each other, the oil resistance due to the fluorene skeleton is not sufficiently improved, and punching defects such as cracks are likely to occur.

  Further, the optical film 16 using a styrene homopolymer instead of the copolymer resin has low transparency because the resins are probably not compatible with each other. In addition, since the fluorene skeleton probably does not exist, the oil resistance of the optical film is hardly increased, and punching defects such as cracks are likely to occur.

  Further, the optical film 17 using a copolymer resin having no proton donating group was low in transparency because the resins were probably not compatible with each other. Also, since the resins are probably incompatible with each other, the oil resistance due to the fluorene skeleton is not sufficiently improved, and punching defects such as cracks are likely to occur.

  Further, the optical film 18 using the cycloolefin-based resin having no polar group probably has low transparency because the resins are not compatible with each other. Also, since the resins are probably incompatible with each other, the oil resistance due to the fluorene skeleton is not sufficiently improved, and punching defects such as cracks are likely to occur.

  In addition, the optical film 19 and the optical film 20 using the fluorene homopolymer and the styrene homopolymer or the H-styrene homopolymer probably had low transparency because the resins were not sufficiently compatible with each other. Also, since the resins are probably not sufficiently compatible with each other, the oil resistance is not sufficiently improved by the fluorene skeleton, and punching defects such as cracks are likely to occur.

  According to the present invention, it is possible to provide an optical film that has high solvent resistance and transparency and can sufficiently suppress punching defects such as cracks when thinned. Such optical films are used as display devices such as liquid crystal displays and organic EL displays widely used in televisions, notebook computers, smartphones, etc., as well as electrode films such as touch panels, barrier films having gas barrier properties, and flexible films. Can also be suitably used.

DESCRIPTION OF SYMBOLS 10 Liquid crystal display 20 Liquid crystal cell 21, 23 Transparent plastic film substrate 25 Liquid crystal layer 30 1st polarizing plate 31 1st polarizer 33 Polarizing plate protective film (F1)
35 Polarizing plate protective film (F2)
40 Second polarizing plate 41 Second polarizer 43 Polarizing plate protective film (F3)
45 Polarizing plate protective film (F4)
50 Backlight

Claims (9)

A cycloolefin resin having a polar group, and a copolymer resin having a structural unit derived from a styrene monomer having a proton donating group and a structural unit derived from a fluorene monomer,
The ratio of the copolymer resin to the total mass of the cycloolefin resin and the copolymer resin is 5% by mass or more and 95% by mass or less.
Optical film.   The optical film according to claim 1, wherein the proton donating group is a hydroxy group.   The optical film according to claim 1 or 2, wherein a ratio of a mass of the copolymer resin to a total mass of the cycloolefin resin and the copolymer resin is 20% by mass or more and 80% by mass or less.   The optical film according to claim 1, wherein the cycloolefin-based resin has a structural unit derived from a norbornene-based monomer having a polar group.   The optical film according to claim 1, wherein the copolymer resin is a random copolymer of a styrene monomer having the proton donating group and the fluorene monomer.   The optical film according to claim 1, wherein the film thickness is 10 μm or more and 25 μm or less.   The polarizing plate containing a polarizer and the optical film of any one of Claims 1-6 arrange | positioned at the at least one surface.   A display device comprising the polarizing plate according to claim 7. A dope containing a cycloolefin resin having a polar group, a copolymer resin having a structural unit derived from a styrene monomer having a proton donating group and a structural unit derived from a fluorene monomer, and a solvent Obtaining a step;
A step of casting the dope on a support and then drying to obtain a film;
Peeling the film from the support; and
A method for producing an optical film, comprising:

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