JP6957872B2 - Optical film and its manufacturing method, polarizing plate, liquid crystal display device - Google Patents

Description

The present invention relates to an optical film, a method for producing the same, a polarizing plate, and a liquid crystal display device.

Liquid crystal displays are widely used in televisions, notebook computers, smartphones, and the like. The liquid crystal display device includes a liquid crystal cell and a pair of polarizing plates that sandwich the liquid crystal cell; the polarizing plate includes a polarizing element and a pair of protective films that sandwich the polarizing element.

As the protective film, a film containing a cycloolefin-based polymer as a main component has been studied because it has high water resistance. However, the film containing a cycloolefin polymer as a main component has a problem of insufficient mechanical strength.

On the other hand, it is known that the mechanical strength of the film is improved by adding a compound or a polymer having a fluorene skeleton (see, for example, Patent Documents 1 to 3). Patent Documents 1 and 2 disclose a film obtained from a resin composition containing a cycloolefin-based polymer and a compound having a 9,9-bisarylfluorene skeleton as a strength improver. Patent Document 3 discloses a film obtained from a resin composition containing an aromatic polycarbonate and a fluorene skeleton-containing polyester polymer.

Japanese Unexamined Patent Publication No. 2014-218657 Japanese Unexamined Patent Publication No. 2014-218660 Japanese Patent No. 3023279

By the way, a film containing a cycloolefin polymer as a main component can be produced by various methods, but it is produced by a solution casting method because it is easy to obtain a film having high production efficiency and high film thickness uniformity. Is desired. In the solution casting method, a step of dissolving a cycloolefin polymer in a solvent to obtain a dope; a step of casting the dope on a support and then drying it to obtain a film-like substance; A film containing a cycloolefin-based polymer as a main component can be produced through a step of peeling the film from the support.

However, since the film-like material obtained by drying the above-mentioned dope has low strength in the solvent-containing state, the end portion of the film-like material may be torn when peeling from the support or during transportation, resulting in high production efficiency. There was a problem of lowering.

The films of Patent Documents 1 and 2 are produced by melt-mixing and then press molding, and the films of Patent Document 3 are produced by injection molding, both of which show the above-mentioned problems in the solution casting method. No. When the films of Patent Documents 1 and 2 were produced by the solution casting method, the present inventors had relatively good mechanical strength of the obtained film, but the strength of the film-like material in the solvent-containing state was low. I understand. Further, when the film of Patent Document 3 was produced by a solution casting method, not only the strength of the film-like material in the solvent-containing state was not sufficiently improved, but also a cycloolefin-based polymer and a fluorene skeleton-containing polyester polymer were used. Since the compatibility of fluorene is low, the transparency is easily impaired, and it has been found that the film is not suitable as an optical film.

Further, with the recent reduction in size and weight of display devices, it is required to reduce the thickness of optical films. Since the thinned optical film tends to have low mechanical strength, it is further required to improve the strength in the solvent-containing state.

The present invention has been made in view of the above circumstances, and the film-like material has high strength in a solvent-containing state when it is manufactured by the solution casting method, and is manufactured while suppressing tearing or breaking of the film-like material. It is an object of the present invention to provide an optical film having high transparency and good mechanical strength.

[1] A cycloolefin-based polymer containing a structural unit derived from a cycloolefin monomer having a polar group, a fluorene skeleton-containing polymer containing a structural unit derived from a fluorene skeleton-containing compound, and a proton-donating group or a carbonyl-containing group. Includes a cycloolefin-based oligomer containing a structural unit derived from a cycloolefin-based monomer having (however, the cycloolefin-based oligomer is different from the cycloolefin-based polymer) or an aromatic compound having a proton-donating group. , Optical film.
[2] The fluorene skeleton-containing polymer is a polyester polymer containing a structural unit derived from a fluorene skeleton-containing diol and a structural unit derived from a dicarboxylic acid, a polycarbonate polymer containing a structural unit derived from a fluorene skeleton-containing diol, or a polycarbonate polymer containing a structural unit derived from a fluorene skeleton-containing diol. The optical film according to [1], which is a (meth) acrylate polymer containing a structural unit derived from a fluorene skeleton-containing compound having a polymerizable unsaturated bond and a structural unit derived from a (meth) acrylate monomer.
[3] The optical film according to [1] or [2], wherein the fluorene skeleton-containing polymer has a weight average molecular weight of 5,000 to 1,000,000.
[4] The content of the cycloolefin-based oligomer or the aromatic compound is 1 to 30% by mass with respect to the total mass of the cycloolefin-based polymer and the fluorene skeleton-containing polymer, [1] to [ 3] The optical film according to any one of.
[5] A polarizing plate including a polarizing element and an optical film according to any one of [1] to [4] arranged on at least one surface thereof.
[6] A liquid crystal display device having a first polarizing plate, a liquid crystal cell, a second polarizing plate, and a backlight in this order, wherein the first polarizing plate includes a first polarizing element. It has a protective film F1 arranged on the surface of the first polarizing element on the side opposite to the liquid crystal cell, and a protective film F2 arranged on the surface of the first polarizing element on the surface of the first polarizing element on the liquid crystal cell side. The second polarizing plate includes a second polarizing element, a protective film F3 arranged on a surface of the second polarizing element on a side surface with the liquid crystal cell, and the liquid crystal cell of the second polarizing element. It has a protective film F4 arranged on the opposite surface and has.
A liquid crystal display device in which at least one of the protective films F2 and F3 is the optical film according to any one of [1] to [4].
[7] A cycloolefin-based polymer containing a structural unit derived from a cycloolefin monomer having a polar group, a fluorene skeleton-containing polymer containing a structural unit derived from a fluorene skeleton-containing compound, and a proton-donating group or a carbonyl-containing group. A cycloolefin-based oligomer containing a structural unit derived from a cycloolefin-based monomer having a Optical including a step of obtaining a dope containing the above, a step of casting the dope on a support and then drying it to obtain a film-like substance, and a step of peeling the film-like substance from the support How to make a film.

The present invention is an optical film produced by a solution casting method in which the strength of the film-like material in a solvent-containing state is high and the film-like material is suppressed from tearing or breaking, and has high transparency. And an optical film having good mechanical strength can be provided.

FIG. 1 is a schematic view showing an example of a basic configuration of a liquid crystal display.

As described above, the mechanical strength of the film can be increased by adding the fluorene compound to the cycloolefin polymer. It is considered that this is because the fluorene compound exists in the vicinity of the cycloolefin polymer and interacts with the fluorene compound. However, in the solvent-containing state, since the solvent exists between the cycloolefin-based polymer and the fluorene compound, the interaction between the cycloolefin-based polymer and the fluorene compound cannot be sufficiently obtained, and the fluorene compound is added. However, it is difficult to improve the strength of the film-like substance in the solvent-containing state.

In order to improve the strength of the film-like substance in the solvent-containing state, it is effective to allow the cycloolefin polymer and the fluorene compound to be present in the vicinity even in the solvent-containing state to cause an interaction; for that purpose. It is considered effective to polymerize the fluorene compound so that the molecular chain of the cycloolefin polymer and the molecular chain of the fluorene compound are entangled with each other. On the other hand, when the fluorene compound is polymerized, the molecular weight becomes large, so that the compatibility with the cycloolefin-based polymer is lowered, and the transparency of the obtained film is likely to be impaired. Further, when the compatibility is lowered, the cycloolefin polymer and the fluorene polymer are likely to be aggregated independently, so that the entanglement of the molecular chains is reduced and the interaction may be difficult to occur.

On the other hand, in addition to the cycloolefin-based polymer and the fluorene skeleton-containing polymer, "a cycloolefin-based oligomer having a proton-donating group or a carbonyl group / or an aromatic compound having a proton-donating group" is further added. Therefore, it is possible to easily cause an interaction between the cycloolefin-based polymer and the fluorene skeleton-containing polymer without impairing the compatibility.

That is, since a cycloolefin-based oligomer having a proton-donating group or a carbonyl group has a structure similar to that of a cycloolefin-based polymer, it easily interacts with the cycloolefin-based polymer; Since it has, it is considered that it is easily entangled with the molecular chain of the fluorene skeleton-containing polymer and easily interacts with it. Aromatic compounds having a proton donating group are such that the proton donating group easily interacts with the polar group of the cycloolefin-based polymer; the aromatic ring interacts with the aromatic ring of the fluorene skeleton of the fluorene skeleton-containing polymer. It is considered easy to do.

As described above, the cycloolefin-based oligomer having a proton-donating group or the carbonyl group / or the aromatic compound having a proton-donating group allows the cycloolefin-based polymer and the fluorene skeleton-containing polymer to be mixed without impairing the compatibility. It is possible to facilitate the interaction between them. Therefore, in the film forming process by the solution casting method, the mechanical strength of the film-like material in the solvent-containing state can be increased, so that the film-like material is formed when the film-like material is peeled from the metal support or when the film-like material is transported by roll. It is possible to suppress the occurrence of tears and breaks at the edges of objects. In addition, the transparency of the obtained optical film can be enhanced. The present invention has been made based on such findings.

1. 1. Optical Film The optical film of the present invention contains a cycloolefin-based polymer, a fluorene skeleton-containing polymer, and a cycloolefin-based oligomer having a proton-donating group or a carbonyl-containing group or an aromatic compound having a proton-donating group. ..

1-1. Cycloolefin-based polymer The cycloolefin-based polymer is a polymer of a cycloolefin monomer containing a cycloolefin monomer having a polar group, or a copolymer of the cycloolefin monomer and other monomer. It is a copolymer of.

Examples of a "polar group" in a cycloolefin monomer having a polar group include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an allyloxycarbonyl group, an amino group, an amide group, a cyano group and an aryl group. Is done. The aryl group may be bonded to the cycloolefin ring as a substituent, or may be fused to the cycloolefin ring.

The cycloolefin monomer constituting the cycloolefin-based polymer is preferably a norbornene-based monomer.

The norbornene-based monomer having a polar group is preferably a norbornene-based monomer represented by the following general formula (A).

^{R 1 to} R ⁴ of the general formula (A) represent a hydrogen atom, a halogen atom, and a hydrocarbon group or a polar group having 1 to 5 carbon atoms, respectively.

Examples of halogen atoms include fluorine atoms, chlorine atoms and the like. Examples of the hydrocarbon group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group and the like. The hydrocarbon group having 1 to 5 carbon atoms is a linking group containing a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom; for example, 2 such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. It may further have a valence linking group.

R ² and R ³ may combine with each other to form an aromatic ring or an aliphatic ring.

However, ^{at least one of R 1 to} R ⁴ is a polar group. The polar group is synonymous with the polar group described above.

^Also, if ^{R 1} and ^{R 2} of R 1 to R ⁴ are not hydrogen atoms at the same time, or ^R 1, ^{R 2} and ^{R 3} may be hydrogen atoms at the same time. Since the substituent of such a norbornene-based monomer is substituted with carbon on one side, the molecular symmetry is low, and the diffusion motion between the resin and the additive at the time of solvent volatilization in the film forming process can be promoted.

P in the general formula (A) represents an integer of 0 to 2. From the viewpoint of increasing the heat resistance of the optical film, p is preferably 1 to 2. This is because when p is 1 to 2, the obtained resin becomes bulky and the glass transition temperature tends to improve.

Specific examples of the norbornene-based monomer represented by the general formula (A) are shown below. Among these, examples of norbornene-based monomers having a polar group include the following compounds.

The norbornene-based monomer constituting the cycloolefin-based polymer may further contain not only the norbornene-based monomer having a polar group but also the norbornene-based monomer having no polar group.

In the norbornene-based monomer having no polar group, for example, R ^{1 to} R ⁴ of the general formula (A) are independently hydrogen atoms, halogen atoms, silyl groups, or hydrocarbon groups having 1 to 5 carbon atoms. It can be a monomer.

Examples of norbornene-based monomers having no polar group include the following compounds.

The content ratio of the structural units derived from the norbornene-based monomer having a polar group is, for example, 50 mol% or more, preferably 70 mol% or more, based on the total of the structural units derived from the norbornene-based monomers constituting the cycloolefin polymer. % Or more, more preferably 100 mol%. When the structural unit derived from the norbornene-based monomer having a polar group is contained in a certain amount or more, the polarity of the resin is likely to increase, and the cycloolefin-based polymer can be easily dissolved in the solvent. ) Makes it easier to form a film.

Examples of copolymerizable monomers that can be copolymerized with norbornene-based monomers include copolymerizable monomers that can be ring-opened copolymerized with norbornene-based monomers and addition copolymerizable with norbornene-based monomers. Copolymerizable monomer is included.

Examples of copolymerizable monomers that can be open-ring copolymerized with norbornene-based monomers include cycloolefins other than norbornene-based monomers such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

Examples of copolymerizable monomers that can be additionally copolymerized with norbornene-based monomers include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, and (meth) acrylates. Examples of unsaturated double bond-containing compounds are olefin compounds having 2 to 12 (preferably 2 to 8) carbon atoms, and examples thereof include ethylene, propylene, and butene. Examples of vinyl-based cyclic hydrocarbon monomers include vinyl cyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of the (meth) acrylate include alkyl (meth) acrylates having 1 to 20 carbon atoms such as methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cyclohexyl (meth) acrylate.

The content ratio of the structural units derived from the norbornene-based monomer is 50 to 100 mol%, preferably 60 to 100 mol%, and more preferably 70 to 100 mol% with respect to the total of the structural units constituting the cycloolefin-based polymer. Can be%.

As described above, the cycloolefin-based polymer is a polymer obtained by polymerizing or copolymerizing a norbornene-based monomer containing a norbornene-based monomer having a polar group. The polymerization or copolymerization may be ring-opening polymerization or ring-opening copolymerization, or addition polymerization or addition copolymerization. Examples of polymers include:
(1) Ring-opening polymer of norbornene-based monomer (2) Ring-opening copolymer of norbornene-based monomer and a copolymerizable monomer capable of ring-opening copolymerization (3) The above (1) or Hydrogenation of the ring-opening (co) polymer of (2) (4) The ring-opening (co) polymer of (1) or (2) above was cyclized by the Friedelcrafts reaction and then hydrogenated (co). ) Polymer (5) Addition copolymer of norbornene-based monomer and unsaturated double bond-containing compound (6) Addition copolymer of norbornene-based monomer with vinyl-based cyclic hydrocarbon monomer and its Hydrogenated product (7) Addition polymer of norbornene-based monomer and (meth) acrylate

The polymers (1) to (7) can all 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 for the ring-opening copolymerization of (2), those described in paragraphs 0019 to 0024 of JP-A-2008-107534 can be used. As the catalyst used for hydrogenation of (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 of (7) can be carried out by the method described in paragraphs 0071 and 0072 of JP-A-2005-227606.

Among them, (1) to (3) and (5) are preferable, and (1) to (3) are more preferable. That is, the cycloolefin-based polymer is preferably a ring-opening polymer or a ring-opening copolymer of a norbornene-based monomer, or a hydrogenated product thereof. Such a cycloolefin-based polymer may contain 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-based monomer represented by the general formula (A) described above.

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 polymer may be a commercially available product. Examples of commercially available cycloolefin polymers include Arton G (eg, G7810, etc.), Arton F, Arton R (eg, R4500, R4900, R5000, etc.), and Arton RX, manufactured by JSR Corporation. Is done.

The dipole moment of the cycloolefin polymer is preferably 0.5 to 8.0 debye. When the dipole moment of the cycloolefin polymer is 0.5 debye or more, it has a polarity of a certain level or more, so that it is easily dissolved in a solvent and it is easy to form a film by a solution film forming method (cast method). When the dipole moment of the cycloolefin polymer is 8.0 debye or less, the polarity does not increase too much, so that the compatibility with other components is not easily impaired. The dipole moment of the cycloolefin polymer is more preferably 0.5 to 5.0 debye.

The dipole moment of the cycloolefin polymer can be calculated by the following method.
When the cycloolefin polymer is a homopolymer, 1) optimization of the molecular structure and optimization of the spatial arrangement by the molecular mechanics method (MM3 method) and the semi-empirical molecular orbital method (AM1 method, PM6 method). 2) Calculate the dipole moment using FUJITSU Technical Computing Solution SCIGRESS, which is simulation software manufactured by Fujitsu Limited.

When the cycloolefin-based polymer is a copolymer of two or more monomers, the sum of the product of the content ratio of each monomer in the copolymer and the dipole moment calculated for the homopolymer of each monomer. The dipole moment can be calculated by taking. For example, when the cycloolefin-based polymer is an 80/20 copolymer of monomer 1 and monomer 2, dipole moment = (dipole moment 1 × monomer of the homopolymer of monomer 1). It can be calculated as (content ratio of metric 1) + (dipole moment 2 of homopolymer of monomer 2 × content ratio of monomer 2).

The dipole moment of the cycloolefin-based polymer can be adjusted by the type of polar group and the content ratio of the norbornene-based monomer having a polar group.

The weight average molecular weight (Mw) of the cycloolefin polymer is preferably 20000 to 300000. When the weight average molecular weight is in the above range, the heat resistance, water resistance, chemical resistance, mechanical properties and molding processability of the film of the cycloolefin polymer are improved. The weight average molecular weight (Mw) of the cycloolefin polymer is more preferably 30,000 to 250,000, and even more preferably 40,000 to 200,000. The weight average molecular weight of the cycloolefin polymer can be measured by gel permeation chromatography (GPC) in terms of polystyrene.

The glass transition temperature (Tg) of the cycloolefin polymer is usually 110 ° C. or higher, preferably 110 to 350 ° C., more preferably 120 to 250 ° C., and 120 to 220 ° C. Is even more preferable. When Tg is 110 ° C. or higher, deformation under high temperature conditions can be easily suppressed. On the other hand, when Tg is 350 ° C. or lower, the molding process becomes easy, and the deterioration of the resin due to the heat during the molding process is also easily suppressed.

1-2. Fluorene skeleton-containing polymer The fluorene skeleton-containing polymer may have a function of reducing the phase difference by combining with a cycloolefin-based polymer while increasing the mechanical strength of the film. The fluorene skeleton-containing polymer is a polymer containing a structural unit derived from a fluorene skeleton-containing compound.

The content ratio of the structural unit derived from the fluorene skeleton-containing compound may be 2 mol% or more, preferably 10 mol% or more, based on the total number of moles of the structural unit derived from the monomer constituting the polymer.

Examples of the fluorene skeleton-containing polymer include a fluorene skeleton-containing polyester polymer, a fluorene skeleton-containing polycarbonate polymer, and a fluorene skeleton-containing (meth) acrylate polymer.

(Polyester polymer containing fluorene skeleton)
The fluorene skeleton-containing polyester polymer is a polymer obtained by reacting a diol component containing a fluorene skeleton-containing diol with a dicarboxylic acid component. That is, the fluorene skeleton-containing polyester polymer contains a diol structural unit containing a fluorene skeleton-containing diol structural unit and a dicarboxylic acid structural unit.

The diol structural unit includes a structural unit derived from a fluorene skeleton-containing diol. The fluorene skeleton-containing diol is preferably a compound having a 9,9-bisarylfluorene skeleton, and more preferably a compound represented by the following formula (1).

Z in the formula (1) represents an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is a benzene ring; or a fused polycyclic aromatic hydrocarbon ring such as a naphthalene ring or an anthracene ring, and is preferably a benzene ring.

^{R 1} and R ² of the formula (1) represent alkyl groups having 1 to 4 carbon atoms, respectively. Examples of alkyl groups include methyl, ethyl, propyl and butyl groups. R ³ represents an alkylene group having 1 to 4 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group and a butylene group.

K in the formula (1) is an integer of 0 to 4, preferably 0. m is an integer of 0 or more, preferably 1 or 2. n is an integer of 0 or more, preferably 1. p is an integer of 1 or more, preferably 1.

The compound represented by the formula (1) is more preferably a compound represented by the following formula (1A). ^{R 2} and ^{R 3} of formula (1A) are respectively synonymous with ^{R 2} and ^{R 3} of formula (1).

Examples of the fluorene skeleton-containing diol represented by the formula (1A) include 9,9-bis- (4-hydroxyethoxyphenyl) -fluorene, 9,9-bis- (4-hydroxypropoxyphenyl) -fluorene, 9. , 9-Bis- (4-Hydroxybutoxyphenyl) -fluorene and the like. Of these, 9,9-bis- (4-hydroxyethoxyphenyl) -fluorene is preferable.

The diol structural unit may further contain structural units derived from other diols other than the fluorene skeleton-containing diol. Examples of other diols include aliphatic diols, alicyclic diols, and aromatic diols other than fluorene skeleton-containing diols, preferably aliphatic diols.

The aliphatic diol is preferably an aliphatic diol having 2 to 4 carbon atoms. Examples of aliphatic diols having 2 to 4 carbon atoms include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butane. Contains diol. Of these, ethylene glycol and 1,4-butanediol are preferable, and ethylene glycol is more preferable.

The content ratio of the fluorene skeleton-containing diol structural unit is preferably 5 to 100 mol% with respect to the total number of moles of the diol structural unit. When the content ratio of the fluorene skeleton-containing diol structural unit is 5 mol% or more, not only the interaction with the aromatic compound or the cycloolefin oligomer is likely to occur, but also sufficient mechanical strength is likely to be imparted to the film. In addition, it is easy to sufficiently reduce the phase difference value of the film. The content ratio of the fluorene skeleton-containing diol structural unit is more preferably 15 to 95 mol% with respect to the total number of moles of the diol structural unit.

The dicarboxylic acid structural unit preferably contains a structural unit derived from an aromatic dicarboxylic acid. The aromatic dicarboxylic acid is preferably an aromatic dicarboxylic acid having 8 to 15 carbon atoms, and examples thereof include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and esters thereof. Of these, terephthalic acid or an ester thereof is preferable.

The dicarboxylic acid derivative structural unit may further contain a structural unit derived from an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid, if necessary.

The content ratio of the aromatic dicarboxylic acid structural unit is preferably 50 to 100 mol% with respect to the total number of moles of the dicarboxylic acid structural unit. When the content ratio of the aromatic dicarboxylic acid structural unit is 50 mol% or more, it is easy to impart sufficient mechanical strength to the film. The content ratio of the aromatic dicarboxylic acid structural unit is more preferably 70 to 100 mol% with respect to the total number of moles of the dicarboxylic acid structural unit.

(Fluorene skeleton-containing polycarbonate polymer)
The fluorene skeleton-containing polycarbonate polymer is a polymer obtained by reacting an aromatic diol component containing a fluorene skeleton-containing diol with phosgene or a carbonic acid diester. That is, the fluorene skeleton-containing polycarbonate polymer contains a structural unit derived from an aromatic diol component containing a fluorene skeleton-containing diol.

As the fluorene skeleton-containing diol, the same fluorene skeleton-containing diol as the fluorene skeleton-containing diol constituting the fluorene skeleton-containing polyester polymer can be used.

The aromatic diol component may further contain other aromatic diols other than the fluorene skeleton-containing diol. Other aromatic diols may be those usually used as a diol component of aromatic polycarbonate, and examples thereof include hydroquinone, resorcinol, 4,4'-biphenol, 1,1-bis (4-). Hydroxyphenyl) ethane (bisphenol E), 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 2,2-bis (4-hydroxy-3-methylphenyl) propane (bisphenol C), 2,2 -Bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane (bisphenol Z), 1,1-bis ( 4-Hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxyphenyl) pentane, 4,4'-(p-phenylenediisopropylidene) diphenol, α, α'-bis (4-Hydroxyphenyl) -m-diisopropylbenzene (bisphenol M), 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane and the like are included. Among them, bisphenol is preferable, and bisphenol A is more preferable.

The content ratio of the structural unit derived from the fluorene skeleton-containing diol is preferably 2 to 100 mol% with respect to the total number of moles of the structural unit derived from the aromatic diol component. When the content ratio of the structural unit derived from the fluorene skeleton-containing diol is 5 mol% or more, not only the interaction with the aromatic compound or the cycloolefin oligomer is likely to occur, but also sufficient mechanical strength is imparted to the film. Cheap. The content ratio of the structural unit derived from the fluorene skeleton-containing diol is more preferably 10 to 95 mol% with respect to the total number of moles of the structural unit derived from the aromatic diol component.

(Fluorene skeleton-containing (meth) acrylate polymer)
The fluorene skeleton-containing (meth) acrylate polymer is a polymer obtained by subjecting a fluorene skeleton-containing compound having a polymerizable unsaturated bond and a (meth) acrylate compound to an addition copolymerization reaction. That is, the fluorene skeleton-containing (meth) acrylate polymer contains a structural unit derived from a fluorene skeleton-containing compound having a polymerizable unsaturated bond and a structural unit derived from a (meth) acrylate compound.

The "polymerizable unsaturated bond" in the fluorene skeleton-containing compound having a polymerizable unsaturated bond is preferably a (meth) acryloyl group.

The number of polymerizable unsaturated bonds ((meth) acryloyl groups) may be 1 or more, and may be 2 or more (for example, 2 to 6, preferably 2 to 4, particularly 2). preferable. When such a fluorene skeleton-containing compound is used, a crosslinked structure (three-dimensional structure) can be introduced into a part of the polymer, and the heat resistance and mechanical strength of the obtained film can be easily increased.

The fluorene skeleton-containing compound having a polymerizable unsaturated bond is preferably a compound having a 9,9-bisarylfluorene skeleton, and more preferably a compound represented by the following formula (2).

^Z of formula ^{(2), R 1, R} 2, R 3, k, m, n and p ^{are, R 1, R 2, R} 3, k in Formula (1), m, respectively and n and p interchangeably be. R ⁴ represents a hydrogen atom or a methyl group.

Examples of the compound represented by the formula (2) include 9,9-bis (4- (meth) acryloyloxyphenyl) fluorene and 9,9-bis (4- (meth) acryloyloxy-3-methylphenyl). Fluorene, 9,9-bis (4- (meth) acryloyloxy-3,5-dimethylphenyl) fluorene, 9,9-bis (4- (meth) acryloyloxy-3-phenylphenyl) fluorene, etc. 9,9 -Bis ((meth) acryloyloxyaryl) fluorenes; 9,9-bis ((meth) acryloyloxy (poly)) such as 9,9-bis (4- (2- (meth) acryloyloxyethoxy) phenyl) fluorene. Alkoxyaryl) Fluorenes are included.

The content ratio of the structural unit derived from the fluorene skeleton-containing compound having a polymerizable unsaturated bond is preferably 2 to 50 mol% with respect to the total number of moles of the structural unit derived from the monomer constituting the polymer. When the content ratio is 2 mol% or more, not only is it easy to cause an interaction with an aromatic compound or a cycloolefin oligomer, but also it is easy to impart sufficient mechanical strength to the film. The content ratio is more preferably 2 to 20 mol% with respect to the total number of moles of the structural units constituting the fluorene skeleton-containing (meth) acrylate polymer.

The (meth) acrylate compound is a compound having a (meth) acryloyl group and not having a fluorene skeleton. The (meth) acrylate compound may be a monofunctional (meth) acrylate compound or a bifunctional or higher functional (meth) acrylate compound.

Examples of monofunctional (meth) acrylate compounds include C1-20 alkyl (meth) acrylates (preferably C1-10) such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. Alkyl, more preferably C1-4 alkyl); cycloalkyl (meth) acrylate such as cyclohexyl (meth) acrylate; aryl (meth) acrylate such as phenyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate , 2-Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and other hydroxy C2-10 alkyl (meth) acrylate; diethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate and other (poly) oxy Includes C2-6 alkylene glycol mono (meth) acrylate.

Examples of bifunctional or higher (meth) acrylate compounds include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, and hexanediol di (meth) acrylate. C2-10 alkylene glycol di (meth) acrylate such as neopentyl glycol di (meth) acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth). Includes (poly) oxy C2-6 alkylene glycol di (meth) acrylates such as meta) acrylates.

Among these fluorene skeleton-containing polymers, a fluorene skeleton-containing polyester polymer is preferable because it has good compatibility with cycloolefin-based polymers.

The weight average molecular weight of the fluorene skeleton-containing polymer is preferably 20 to 1.5 million. When the weight average molecular weight of the fluorene skeleton-containing polymer is 2000 or more, the molecular chain has a certain length or more and is likely to be entangled with the molecular chain of the cycloolefin-based polymer. The strength of the state can be further increased, and the phase difference can be further reduced. When the weight average molecular weight of the fluorene skeleton-containing polymer is 1.5 million or less, the compatibility with the cycloolefin-based polymer is not easily impaired, so that the haze of the obtained film can be further lowered. The weight average molecular weight of the fluorene skeleton-containing polymer is more preferably 5000 to 1,000,000. The weight average molecular weight of the fluorene skeleton-containing polymer can be measured in the same manner as the weight average molecular weight of the cycloolefin-based polymer.

The total content of the cycloolefin-based polymer and the fluorene skeleton-containing polymer is preferably 60% by mass or more with respect to the total mass of the optical film. When the total content is 60% by mass or more, the water resistance of the obtained film can be easily increased to a certain level or more, and the phase difference (Ro or Rt) can be easily adjusted to a certain level or less. The total content of the cycloolefin-based polymer and the fluorene skeleton-containing polymer is more preferably 70% by mass or more, and further preferably 80% by mass or more.

The content ratio of the cycloolefin-based polymer to the fluorene skeleton-containing polymer is preferably 99/1 to 40/60 (mass ratio). When the content ratio is within the above range, the balance between the transparency and the mechanical strength of the obtained film is more good, and the phase difference can be easily adjusted to a certain level or less. The content ratio of the cycloolefin-based polymer to the fluorene skeleton-containing polymer is more preferably 95/5 to 50/50 (mass ratio).

1-3. Cycloolefin-based oligomer or aromatic compound The cycloolefin-based oligomer or aromatic compound has a function of facilitating interaction between the cycloolefin-based polymer and the fluorene skeleton-containing polymer, and facilitating compatibility.

(Cycloolefin oligomer)
The cycloolefin-based oligomer is a low molecular weight polymer of a cycloolefin monomer having a proton-donating group or a carbonyl-containing group. That is, the cycloolefin-based oligomer contains a structural unit derived from a cycloolefin monomer having a proton-donating group or a carbonyl-containing group. However, the cycloolefin-based oligomer is different from the above-mentioned cycloolefin-based polymer.

Examples of proton donating groups include -OH, -SH. Examples of carbonyl-containing groups include -COOR (R: alkyl or aryl groups).

The cycloolefin monomer constituting the cycloolefin-based oligomer is more preferably a norbornene-based monomer. Examples of the norbornene-based monomer include those similar to the norbornene-based monomer constituting the cycloolefin-based polymer.

The weight average molecular weight of the cycloolefin-based oligomer is lower than the weight average molecular weight of the cycloolefin-based polymer, and is preferably 1000 to 10000. When the weight average molecular weight of the cycloolefin-based oligomer is 1000 or more, the molecular chain is likely to be entangled with the molecular chain of the fluorene skeleton-containing polymer, so that sufficient interaction with the fluorene skeleton-containing polymer is likely to occur, and the phase is likely to occur. Solubility is also easy to obtain. When the weight average molecular weight of the cycloolefin-based oligomer is 10,000 or less, the compatibility is not easily impaired. The weight average molecular weight of the cycloolefin-based oligomer is more preferably 3000 to 6000. The weight average molecular weight of the cycloolefin-based oligomer can be measured in the same manner as the weight average molecular weight of the cycloolefin-based polymer.

(Aromatic compounds)
An aromatic compound having a proton-donating group is a compound having an aromatic hydrocarbon ring or an aromatic heterocycle and a proton-donating group bonded to these rings. The proton donating group is synonymous with the proton donating group described above.

Examples of aromatic hydrocarbon rings include monocyclic aromatic hydrocarbon rings such as benzene rings; condensed polycyclic aromatic hydrocarbon rings such as naphthalene rings and anthracene rings. Examples of aromatic heterocycles include monocyclic aromatic heterocycles such as pyridine ring, imidazole, pyrazole and oxazole; fused polycyclic aromatic heterocycles such as quinoline and cumene. The aromatic hydrocarbon ring or aromatic heterocycle may be one in which two or more aromatic hydrocarbon rings or aromatic heterocycles are bonded via a single bond. Among them, an aromatic hydrocarbon ring is preferable, and a benzene ring is more preferable.

Examples of aromatic compounds having a proton donating group include
Aromatic compounds with thiol groups such as thiophenols;
Phenol, p-ethylphenol, p-tert-butylphenol, 2,4-di-tert-butylphenol, 3-methoxyphenol, 4-nonylphenol, p-dodecylphenol, catechol, 4-tert-butylpyrocatechol, resorcinol, hydroquinone , Tert-Butylhydroquinone, methylhydroquinone, cresol, xylenol, naphthol, 2,3-dihydroxynaphthalene, 3-hydroxy-2-naphthoic acid, biphenol, 4-phenylphenol, 4-phenoxyphenol, 4,4'-sulfonyldi Aromatic compounds with hydroxy groups such as phenol, bisphenol A, p- (α-cumyl) phenol, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane, 2- (3-hydroxyphenyl) ethanol;
Aromatic heterocyclic compounds having a hydroxy group such as pyridinol;
4- (4-Hydroxyphenyl) -2-butanone, p-hydroxyphenylpyruvate, 3- (4-hydroxyphenyl) propionic acid, methyl 3- (4-hydroxyphenyl) propionate, 4- (4-hydroxyphenyl) ) Cyclohexanone, salicylic acid, ethyl salicylate, thiosalicylic acid, o-hydroxyacetophenone, m-hydroxybenzoic acid, p-hydroxybenzoic acid, methyl p-hydroxybenzoate, salicylaldehyde, 4- (4-hydroxyphenyl) benzoic acid, hydroxy It contains an aromatic compound having a hydroxy group such as phenylacetic acid and 3,4-dihydroxyphenylacetic acid and a carbonyl-containing group.

The aromatic compound having a proton donating group may be a polymer. Such a polymer can be a homopolymer of an aromatic monomer having a polymerizable unsaturated bond and a proton donating group, or a copolymer of a copolymerizable monomer thereof.

The "polymerizable unsaturated bond" in an aromatic monomer having a polymerizable unsaturated bond and a proton donating group can be a vinyl group or a (meth) acryloyl group. Examples of aromatic monomers having a polymerizable unsaturated bond and a proton donating group include paravinylphenol.

Examples of copolymerizable monomers copolymerizable with paravinylphenol include (meth) acrylic acid alkyl ester (alkyl portion having 1 to 18 carbon atoms); (meth) acrylic acid and the like α, β-non. Saturated acid; includes aromatic vinyl compounds such as styrene and α-methylstyrene.

An example of a commercially available product of a homopolymer of an aromatic monomer having a polymerizable unsaturated bond and a proton donating group or a copolymer of a copolymerizable copolymer thereof is Marcalinker M. , S-1 to S-4, CMM, CST (manufactured by Maruzen Petrochemical Co., Ltd.) and the like.

The weight average molecular weight of an aromatic compound having a proton donating group can be 100 to 10,000. When the weight average molecular weight of the aromatic compound having a proton-donating group is within the above range, the cycloolefin-based polymer and the fluorene skeleton-containing polymer can easily interact with each other without impairing the compatibility with other components. ..
When the aromatic compound having a proton donating group is not a polymer, its weight average molecular weight is more preferably 100 to 300; when the aromatic compound having a proton donating group is a polymer, its weight average is The molecular weight is more preferably 1000 to 10000, and even more preferably 1500 to 8000.
The weight average molecular weight of the aromatic compound having a proton donating group can be measured in the same manner as the weight average molecular weight of the cycloolefin polymer.

The content of the cycloolefin-based oligomer or aromatic compound is preferably 0.1 to 50% by mass with respect to the total mass of the cycloolefin-based polymer and the fluorene skeleton-containing polymer. When the content of the cycloolefin-based oligomer or aromatic compound is 0.1% by mass or more, the mechanical strength of the film-like substance in the solvent-containing state can be easily increased, and when it is 50% by mass or less, the cycloolefin-based oligomer is used. Alternatively, the compatibility with other components of the aromatic compound is not easily impaired.

In addition, the addition of a cycloolefin-based oligomer or aromatic compound causes an interaction between the cycloolefin-based polymer and the fluorene skeleton-containing polymer, thereby improving the mechanical strength of the film-like material in the solvent-containing state. However, on the other hand, if the amount of the cycloolefin-based oligomer or aromatic compound is too large with respect to the polymer component containing the cycloolefin-based polymer and the fluorene skeleton-containing polymer, the film-like product in the solvent-containing state It may be difficult to obtain mechanical strength. That is, since the interaction between cycloolefin-based oligomers or aromatic compounds themselves is not so strong, if a large amount of cycloolefin-based oligomers or aromatic compounds is present between the cycloolefin-based polymer and the fluorene skeleton-containing polymer. , The cycloolefin-based polymer molecule and the fluorene skeleton-containing polymer molecule may be difficult to exist in the vicinity, and it may be difficult to obtain sufficient interaction between the polymers. Further, since the cycloolefin-based oligomer or aromatic compound has a relatively low molecular weight, if it is present in a large amount, it is difficult to sufficiently obtain entanglement of the molecular chains of the cycloolefin-based polymer and the fluorene skeleton-containing polymer. There is also. Therefore, the content of the cycloolefin-based oligomer or aromatic compound is more preferably 1 to 30% by mass with respect to the total mass of the cycloolefin-based polymer and the fluorene skeleton-containing polymer.

1-4. Other Components The optical film may further contain other components as long as the effects of the present invention are not impaired. Examples of other components include fine particles (matting agents), ultraviolet absorbers, antioxidants and the like.

The fine particles (matting agent) have a function of increasing the slipperiness of the optical film. Examples of fine particles include silicon dioxide (SiO ₂ ), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Inorganic fine particles such as magnesium silicate and calcium phosphate are included.

Of these, silicon dioxide is preferred in order to reduce the increase in haze of the resulting film. Examples of commercially available silicon dioxide particles include Aerosil R812, R972 (manufactured by Nippon Aerosil Co., Ltd.), NanoTek SiO ₂ (manufactured by CI Kasei Co., Ltd.) and the like.

The shape of the fine particles may be irregular, needle-shaped, flat, or spherical, and is preferably spherical because the transparency of the obtained film is not easily impaired.

The fine particles may be used alone or in combination of two or more. Further, by using particles having different particle sizes and shapes (for example, needle-like and spherical) in combination, transparency and slipperiness may be highly compatible.

The average primary particle size of the fine particles is preferably 5 to 50 nm. When the average primary particle size of the fine particles is 5 nm or more, the surface of the film can be roughened, so that slipperiness can be easily imparted, and when it is 50 nm or less, an increase in haze can be easily suppressed. The average primary particle size of the fine particles is more preferably 5 to 30 nm.

The content of the fine particles may be, for example, 0.1 to 5% by mass with respect to the total mass of the cycloolefin polymer. When the content of the inorganic fine particles is 0.1% by mass or more, the slipperiness of the surface of the optical film is likely to be sufficiently increased, and when the content is 5% by mass or less, the increase in haze of the optical film is likely to be suppressed. The content of the fine particles is more preferably 0.1 to 2.5% by mass and further preferably 0.3 to 2% by mass with respect to the total mass of the cycloolefin polymer.

1-5. Film physical characteristics (haze)
The haze of the optical film is preferably 0.01 to 2.0. 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 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, for example, by adding an aromatic compound having a proton-donating group or a cycloolefin-based oligomer having a proton-donating group or a carbonyl-containing group. In order to reduce the haze of the optical film, for example, it is preferable to add an aromatic compound having a proton-donating group or a cycloolefin-based oligomer having a proton-donating group or a carbonyl-containing group to a certain amount or more.

(Phase difference Ro and Rt)
When the optical film is used as a polarizing plate protective film or a retardation film, it may have retardation values Ro and Rt depending on the application. For example, when an optical film is used as a zero retardation film, the in-plane retardation Ro measured in an environment with a measurement wavelength of 590 nm and 23 ° C. and 55% RH preferably satisfies 0 nm ≦ Ro ≦ 3 nm. The phase difference Rt in the thickness direction preferably satisfies −5 nm ≦ Rt ≦ 5 nm.

Ro and Rt of the optical film are defined by the following formulas, respectively.
Equation (2a): Ro = (nx-ny) × d
Equation (2b): Rt = ((nx + ny) /2-nz) × d
(During the ceremony,
nx represents the refractive index in the in-plane slow-phase axial direction (the direction in which the refractive index is maximized) of the optical film.
ny represents the refractive index in the direction orthogonal to the in-plane slow phase 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-phase axis of the optical film means the axis having the maximum refractive index on the film surface. The in-plane slow-phase axis of the optical film can be confirmed by an automatic birefringence meter Axoscan (AxoScan Mueller Matrix Polarimeter: manufactured by Axometrics).

The Ro and Rt of the optical film can be measured by the following method.
1) The optical film is humidity-controlled 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 with a commercially available micrometer.
2) The retardation Ro and Rt of the optical film after humidity control at the measurement wavelength of 590 nm were measured at 23 ° C. and 55% RH using an automatic birefringence meter Axoscan (AxoScan Mueller Matrix Polarimeter). Measure in the environment.

The phase difference Ro and Rt of the optical film can be adjusted by the content ratio of the cycloolefin-based polymer and the fluorene skeleton-containing polymer, the content of the cycloolefin-based oligomer and the aromatic compound, the stretching ratio, and the like. In order to keep the phase difference Ro and Rt of the optical film below a certain level, the content ratio of the cycloolefin-based polymer and the fluorene skeleton-containing polymer should be within the above range, or the content of the cycloolefin-based oligomer or aromatic compound. It is preferable that the amount is equal to or higher than a certain level or the draw ratio is lowered.

(Thickness)
The thickness of the optical film can be, for example, 5 to 100 μm, preferably 5 to 40 μm, and more preferably 10 to 30 μm.

2. Method for Producing Optical Film The optical film of the present invention can be produced by any method, but the solution film forming method (casting method) is used because the production efficiency is high and a film having high film thickness uniformity can be easily obtained. It is preferably manufactured in.

That is, the optical film of the present invention is a step of obtaining a dope containing the above-mentioned cycloolefin-based polymer, the above-mentioned fluorene skeleton-containing polymer, the above-mentioned cycloolefin-based oligomer or aromatic compound, and a solvent. 2) A step of casting the dope on the support and then drying it to obtain a film-like substance, 3) a step of peeling the obtained film-like substance from the support, and 4) a step of peeling the obtained film-like substance from the support. It can be produced through the steps of drying or stretching while drying.

Step 1) The solvent used for doping preferably contains an organic solvent (good solvent) capable of dissolving the above-mentioned cycloolefin polymer. Examples of such good solvents include chlorine-based organic solvents such as methylene chloride (methylene chloride); non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone and tetrahydrofuran. Of these, methylene chloride (methylene chloride) is preferable.

The solvent used for doping may further contain a poor solvent. Examples of poor solvents include straight-chain or branched-chain aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in the dope is high, the film-like substance tends to gel and peels off from the metal support easily. 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 preferable because it has relatively low dope stability, a relatively low boiling point, and good drying properties.

The dope obtained in step 2) is cast on a metal support. Dope casting can be performed by discharging from a casting die. The solvent in the dope cast on the metal support is then evaporated and dried to give a film.

Step 3) The obtained film-like material is stripped of the dried dope from the metal support. The residual solvent amount of the dope when peeling from the metal support (residual solvent amount S ₀ at the time of peeling) is 30 to 120% by mass in terms of facilitating reduction of the phase difference Ro and Rt of the obtained optical film. Is preferable. When the residual solvent amount S ₀ at the time of peeling is 30% by mass or more, the cycloolefin-based polymer easily flows during drying or stretching and tends to be unoriented, so that Ro and Rt of the obtained optical film can be easily reduced. When the residual solvent amount S ₀ at the time of peeling is 120% by mass or less, the force required for peeling the dope is unlikely to be excessively large, so that it is easy to suppress the breakage of the dope.

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

About step 4) The obtained film-like substance is dried or stretched while being dried. Stretching can be done in at least one direction. The stretching direction may be either the longitudinal direction of the film-like object (MD direction) or the width direction (TD direction) orthogonal to the longitudinal direction of the film-like object.

The draw ratio is set according to the required optical performance, but can be, for example, 1.01 to 1.3 times from the viewpoint of allowing the optical film to function as a zero retardation film. The stretch ratio is defined as (size of the film after stretching in the stretching direction) / (size of the film before stretching in the stretching direction).

The stretching temperature is preferably (Tg-30) ° C. to (Tg + 60) ° C., preferably (Tg-10) ° C. to (Tg + 50) ° C., where Tg is the glass transition temperature of the cycloolefin polymer. Is more preferable. When the stretching temperature is (Tg-30) ° C. or higher, the tension applied to the film-like material during drying or stretching is unlikely to be excessively increased, so that Ro and Rt of the obtained optical film are unlikely to be excessively increased. When the stretching temperature is (Tg + 60) ° C. or lower, it is easy to highly suppress the generation of bubbles due to the vaporization of the solvent in the film-like material. Specifically, the stretching temperature can be 140 to 220 ° C.

_{The amount of residual solvent S 1 in} the film-like material at the start of stretching is preferably 5 to 20% by mass. When the residual solvent amount S ₁ at the start of stretching is 5% by mass or more, the substantial Tg of the film-like substance at the time of stretching is lowered due to the plasticizing effect of the residual solvent, so that Ro and Rt of the optical film are increased. It's hard to do. When the residual solvent amount S ₁ at the start of stretching is 20% by mass or less, the generation of bubbles due to the vaporization of the solvent in the film-like material can be highly suppressed. _{The amount of residual solvent S 1 in} the film-like material at the start of stretching is more preferably 8 to 15% by mass.

Stretching of the film-like material in the MD direction can be performed by, for example, a method (roll method) in which a plurality of rolls are provided with a peripheral speed difference and the roll peripheral speed difference is used between them. Stretching of the film-like object in the TD direction can be performed, for example, by fixing both ends of the film-like object with clips or pins and widening the distance between the clips or pins in the traveling direction (tenter method).

In the present invention, since the film-like product obtained by drying the dope contains the above-mentioned cycloolefin-based oligomer or aromatic compound, the compatibility between the cycloolefin-based polymer and the fluorene skeleton-containing polymer is sufficient. It has been raised. Therefore, since the mechanical strength of the film-like material in the solvent-containing state is increased, when the film-like material is peeled off from the metal support (step (3)) or when the film-like material is roll-transported (step (3)). Step 4)), it is possible to suppress the occurrence of tears and cuts at the edges of the film-like material. Therefore, it is possible to obtain an optical film having high transparency and high mechanical strength.

3. 3. Applications Since the optical film of the present invention has high transparency and good mechanical strength, it has a polarizing plate protective film or a retardation film for a display device, a transparent substrate, a protective film for a display screen, and a film for a touch panel (electrodes). It can be used for films) and the like. Above all, the optical film of the present invention can be preferably used as a polarizing plate protective film or a retardation film because the retardation can be adjusted to a certain level or less.

3-1. Polarizing Plate The polarizing plate of the present invention includes a polarizing element and an optical film of the present invention.

A polarizer is an element that allows only light on a plane of polarization in a certain direction to pass through, and a typical currently known polarizer is a polyvinyl alcohol-based polarizing film. The polyvinyl alcohol-based polarizing film includes a polyvinyl alcohol-based film dyed with iodine and a film obtained by dyeing a dichroic dye.

The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing it with iodine or a bicolor dye (preferably a film further subjected to a durability treatment with a boron compound); polyvinyl. An alcohol-based film may be a film that has been dyed with iodine or a bicolor dye and then uniaxially stretched (preferably a film that has been further subjected to a durability treatment with a boron compound). The absorption axis of the polarizer is usually parallel to the maximum stretching direction.

The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 5 to 20 μm in order to reduce the thickness of the polarizing plate.

When the optical film of the present invention is arranged on only one surface of the polarizer, another optical film may be arranged on the other surface. Examples of other optical films include commercially available cellulose acylate films (eg, Konica Minolta Tuck KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1, KC8UY. -HA, KC8UX-RHA, KC8UE, KC4UE, KC4HR-1, KC4KR-1, KC4UA, KC6UA or more, manufactured by Konica Minolta Opto Co., Ltd. and the like are included.

The polarizing plate of the present invention can be obtained by bonding a polarizing element and an optical film of the present invention via an adhesive. The adhesive may be a fully saponified polyvinyl alcohol aqueous solution (water glue) or an active energy ray-curable adhesive.

3-2. Liquid crystal display device The liquid crystal display device of the present invention includes a liquid crystal cell and a pair of polarizing plates sandwiching the liquid crystal cell.

FIG. 1 is a schematic view showing an example of a basic configuration of a liquid crystal display device. As shown in FIG. 1, the liquid crystal display device 10 of the present invention includes a liquid crystal cell 30, a first polarizing plate 50 and a second polarizing plate 70 sandwiching the liquid crystal cell 30, and a backlight 90.

The display mode of the liquid crystal cell 30 may be any display mode such as TN (Twisted Nematic), VA (Visual Alignment), or IPS (InPlane Switching). For example, the IPS mode is preferable as the liquid crystal cell for mobile devices.

The first polarizing plate 50 is arranged on the surface of the liquid crystal cell 30 on the viewing side, and the first polarizing element 51 and the protective film 53 (F1) arranged on the surface of the first polarizing element 51 on the viewing side. ) And the protective film 55 (F2) arranged on the surface of the first polarizing element 51 on the liquid crystal cell side.

The second polarizing plate 70 is arranged on the surface of the liquid crystal cell 30 on the backlight side, and the second polarizing element 71 and the protective film 73 arranged on the surface of the second polarizing element 71 on the liquid crystal cell side. (F3) and a protective film 75 (F4) arranged on the backlight side surface of the second polarizer 71 are included.

It is preferable that the absorption axis of the first polarizer 51 and the absorption axis of the second polarizer 71 are orthogonal to each other (cross Nicol).

At least one of the protective films 53 (F1), 55 (F2), 73 (F3) and 75 (F4) can be the optical film of the present invention. Above all, since the optical film of the present invention can function as a zero retardation film, it is preferable to use it as a protective film 55 (F2) or 73 (F3).

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

1. 1. Optical film material (1) Cycloolefin-based polymer <Cycloolefin-based polymer 1>
As a cycloolefin monomer (norbornene-based monomer), a reaction vessel in which 100 parts by mass of the following compound, 3.6 parts by mass of 1-hexene as a molecular weight modifier, and 200 parts by mass of toluene are substituted with nitrogen. And heated to 80 ° C. To this, 0.17 parts by mass of a toluene solution of triethylaluminum ((C ₂ H ₅ ) ₃ Al) 1.5 mol / l as a polymerization catalyst and tungsten hexachloride (WCl) modified with t-butanol and methanol were added. _{Add 1.0 part by mass of a WCl6 solution (concentration 0.05 mol / l) containing 6} ) and t-butanol: methanol: tungsten = 0.35: 0.3: 1 (molar ratio) to 80. A polymer solution was obtained by carrying out a ring-opening polymerization reaction by heating and stirring at ° C. for 3 hours. The polymerization conversion rate in this polymerization reaction was 98%.

4000 parts by mass of the obtained polymer solution was placed in an autoclave, _{0.48 parts by mass of RuHCl (CO) [P (C 6} H ₅ ) ₃ ] ₃ was added to the polymer solution, the hydrogen gas pressure was 10 MPa, and the reaction was carried out. The hydrogenation reaction was carried out by heating and stirring for 3 hours under the condition of a temperature of 160 ° C.
After cooling the obtained reaction solution, hydrogen gas was released and the reaction solution was poured into a large amount of methanol to separate and recover the coagulated product. The recovered coagulated product was dried to obtain a cycloolefin polymer 1 (COP1).

When the weight average molecular weight and the dipole moment of the obtained cycloolefin polymer 1 were measured by the following methods, the weight average molecular weight was 140,000 and the dipole moment was 4.79 debye.

(Weight average molecular weight)
The weight average molecular weight of the cycloolefin polymer 1 was measured by gel permeation chromatography (GPC) in terms of polystyrene. The specific measurement conditions are as follows.
(Measurement condition)
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Three made by Showa Denko KK were connected and used)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Science)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 1000000 to 500 A calibration curve of 13 samples was used. 13 samples were used at approximately equal intervals.

(Dipole moment)
The dipole moment of the cycloolefin polymer 1 is optimized by 1) molecular mechanics method (MM3 method) and semi-empirical molecular orbital method (AM1 method, PM6 method) to optimize the molecular structure and spatial arrangement. After that, 2) the dipole moment was calculated using FUJITSU Technical Computing Solution SCIGRESS, which is simulation software manufactured by Fujitsu Limited.

(2) Fluorene skeleton-containing polymer (2-1) Fluorene skeleton-containing polyester polymer <Fluorene skeleton-containing polyester polymer 1>
230 parts by mass of terephthalic acid dimethyl ester, 210 parts by mass of 9,9-bis [4- (2-hydroxyethoxy) phenyl] -fluorene, 130 parts by mass of ethylene glycol are used as raw materials, and 1.5 parts by mass of calcium acetate as a transesterification catalyst. And 0.04 part by mass of manganese acetate was put into a reaction vessel, and the transesterification reaction was carried out by gradually heating from 150 ° C. to 230 ° C. according to a conventional method while stirring. After extracting the predetermined methanol from the system, 0.2 parts by mass of germanium oxide and 0.26 parts by mass of triethyl phosphate phosphate as a coloring and antioxidant are added, and the temperature is gradually increased and decreased. While removing the generated ethylene glycol, the heating temperature was brought to 270 ° C. and the degree of vacuum was brought to 0.5 Torr or less. Maintaining this condition, waiting for the viscosity to increase, and when the torque applied to stirring reaches a predetermined value, the reaction is terminated and extruded into water to extrude the fluorene skeleton-containing polyester polymer 1 (all of the fluorene skeleton-containing diol structural units). Pellets with a content ratio of diol structural unit to the total number of moles = 18.6 mol%) were obtained. The weight average molecular weight of the obtained fluorene skeleton-containing polyester polymer 1 was measured by the above-mentioned method and found to be 110,000.

<Fluorene skeleton-containing polyester polymer 2-7>
In the synthesis of the fluorene skeleton-containing polyester polymer 1, the fluorene skeleton-containing polyester polymers 2 to 7 were obtained in the same manner except that the torque value after the viscosity increase was changed to obtain the weight average molecular weight shown in Table 1. rice field.

<Fluorene skeleton-containing polyester polymer 8>
230 parts by mass of terephthalic acid dimethyl ester, 50 parts by mass of 9,9-bis [4- (2-hydroxyethoxy) phenyl] -fluorene, 130 parts by mass of ethylene glycol are used as raw materials, and 1.5 parts by mass of calcium acetate as a transesterification catalyst. And 0.04 part by mass of manganese acetate was put into a reaction vessel, and the transesterification reaction was carried out by gradually heating from 150 ° C. to 230 ° C. according to a conventional method while stirring. After extracting the predetermined methanol from the system, 0.2 parts by mass of germanium oxide and 0.26 parts by mass of triethyl phosphate phosphate as a coloring and antioxidant are added, and the temperature is gradually increased and decreased. While removing the generated ethylene glycol, the heating temperature was brought to 270 ° C. and the degree of vacuum was brought to 0.5 Torr or less. Maintaining this condition, waiting for the viscosity to increase, and when the torque applied to stirring reaches a predetermined value, the reaction is terminated and extruded into water to extrude the fluorene skeleton-containing polyester polymer 8 (all of the fluorene skeleton-containing diol structural units). Pellets with a content ratio of diol structural unit to the total number of moles = 5.1 mol%) were obtained. The weight average molecular weight of the obtained fluorene skeleton-containing polyester polymer 8 was measured by the above-mentioned method and found to be 110,000.

(2-2) Fluorene skeleton-containing (meth) acrylate polymer <Fluorene skeleton-containing (meth) acrylate polymer 1>
In addition to 520 parts by mass of anhydrous toluene, 30 parts by mass of methyl methacrylate (manufactured by Kanto Chemical Co., Ltd.), 7.5 parts by mass of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene (for the entire polymerization component). 5 mol%), 0.4 parts by mass of α, α'-azobisisobutyronitrile (AIBN) (1 part by mass with respect to 100 parts by mass of the polymerization component) was added and reacted at 50 ° C. for 5 hours. rice field. After the reaction, the precipitate is poured into a hexane to separate the precipitate, washed and dried, and the fluorene skeleton-containing (meth) acrylate polymer 1 (methyl methacrylate / 9,9-bis [4- (2-acryloyloxyethoxy) phenyl) is used. ] Fluorene copolymer) was obtained. The weight average molecular weight of the obtained fluorene skeleton-containing (meth) acrylate polymer 1 was measured by the above-mentioned method and found to be 120,000.

(2-3) Fluorene skeleton-containing polycarbonate polymer <Fluorene skeleton-containing polycarbonate polymer 1>
Put 380 parts by mass of ion-exchanged water and 210 parts by mass of 25% sodium hydroxide aqueous solution into a reactor with a thermometer, agitator, and a reflux cooler, and add 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (hereinafter). 87 parts by mass (sometimes abbreviated as "biscresol fluorene"), 23 parts by mass of 2,2-bis (4-hydroxyphenyl) propane (sometimes abbreviated as "bisphenol A"), and 0 hydrosulfite. After dissolving .22 parts by mass, 360 parts by mass of methylene chloride was added, and then 45 parts by mass of phosgen was blown in at 15 to 25 ° C. under stirring for 60 minutes. After the injection of phosgen was completed, a solution prepared by dissolving 0.4 parts by mass of p-tert-butylphenol in 7 parts by mass of methylene chloride and 26 parts by mass of a 25% aqueous sodium hydroxide solution were added, and after emulsification, triethylamine 0. 08 parts by mass was added and the mixture was stirred at 28 to 33 ° C. for 1 hour to complete the reaction. After completion of the reaction, the product was diluted with methylene chloride and washed with water, acidified with hydrochloric acid and washed with water. When the conductivity of the aqueous phase became almost the same as that of ion-exchanged water, the methylene chloride phase was concentrated and dehydrated. , A solution having a concentration of fluorene skeleton-containing polycarbonate polymer of 20% was obtained. The solvent was removed from this solution to obtain fluorene skeleton-containing polycarbonate polymer 1 (content ratio of fluorene skeleton-containing diol structural unit to the total number of moles of aromatic diol structural unit = 69.5 mol%). The weight average molecular weight of the fluorene skeleton-containing polycarbonate polymer 1 was measured by the above-mentioned method and found to be 80,000.

(3) Specific additive (3-1) Cycloolefin-based oligomer having a proton-donating group or carbonyl group <Synthesis of cycloolefin-based oligomer 1>
As a cycloolefin monomer (norbornene-based monomer), 100 parts by mass of the following compound, 10 parts by mass of 1-hexene as a molecular weight modifier, and 200 parts by mass of toluene were charged in a reaction vessel substituted with nitrogen, and 80 parts by mass was charged. Heated to ° C. To this, 0.17 parts by mass of a 1.5 mol / L toluene solution of triethylaluminum [(C ₂ H ₅ ) _{3 Al] as a polymerization catalyst, and tungsten hexachloride (WCl 6} ) with t-butanol and methanol. Was modified, and 1.0 part by mass of _{a WCl 6} solution (concentration: 0.05 mol / L) having a molar ratio of t-butanol, methanol, and tungsten of 0.35: 0.3: 1 was added, and 3 at 80 ° C. A polymer solution was obtained by carrying out a ring-opening polymerization reaction by heating and stirring for a period of time. The polymerization conversion rate in this polymerization reaction was 98%.

4000 parts by mass of the obtained polymer solution was placed in an autoclave, _{0.48 parts by mass of RuHCl (CO) [P (C 6} H ₅ ) ₃ ] ₃ was added to the polymer solution, and the hydrogen gas pressure was 10 MPa. The hydrogenation reaction was carried out by heating and stirring for 3 hours under the condition of a reaction temperature of 160 ° C.
After cooling the obtained reaction solution, hydrogen gas was released and the reaction solution was poured into a large amount of methanol to separate and recover the coagulated product. The recovered coagulated product was dried to obtain a cycloolefin-based oligomer 1. The weight average molecular weight of the cycloolefin-based oligomer 1 was measured by the above-mentioned method and found to be 5000.

<Synthesis of cycloolefin-based oligomer 2>
As a cycloolefin monomer (norbornene-based monomer), 100 parts by mass of the following compound, 12 parts by mass of 1-hexene as a molecular weight modifier and 200 parts by mass of toluene were charged in a reaction vessel substituted with nitrogen, and the temperature was adjusted to 90 ° C. It was heated. To this, 0.22 parts by mass of a 1.8 mol / L toluene solution of triethylaluminum ((C ₂ H ₅ ) ₃ Al) as a polymerization catalyst, and tungsten hexachloride (WCl) modified with t-butanol and methanol. _{6 ) was modified, and 1.0 part by mass of a WCl 6} solution (concentration: 0.05 mol / L) having a molar ratio of t-butanol to methanol and tungsten of 0.35: 0.3: 1 was added, and 80 parts were added. A ring-opening polymerization reaction was carried out by heating and stirring at ° C. for 5 hours to obtain a polymer solution. The polymerization conversion rate in this polymerization reaction was 97%.

4000 parts by mass of the obtained polymer solution was placed in an autoclave, _{0.48 parts by mass of RuHCl (CO) [P (C 6} H ₅ ) ₃ ] ₃ was added to the polymer solution, and the hydrogen gas pressure was 10 MPa. The hydrogenation reaction was carried out by heating and stirring for 3 hours under the condition of a reaction temperature of 160 ° C.
After cooling the obtained reaction solution, hydrogen gas was released and the reaction solution was poured into a large amount of methanol to separate and recover the coagulated product. The recovered coagulated product was dried to obtain a cycloolefin-based oligomer 2. The weight average molecular weight of the cycloolefin-based oligomer 2 was measured by the method described above and found to be 3500.

芳香族化合物２：ｐ−（α−クミル）フェノール（下記式参照、分子量２１２）

芳香族化合物３：マルカリンカーＭ、Ｓ−１（パラビニルフェノール単独重合体、重量平均分子量１６００〜２４００） (3-2) Aromatic compound having a proton donating group Aromatic compound 1: Methyl p-hydroxybenzoate (see the formula below, molecular weight 152)

Aromatic compound 2: p- (α-cumyl) phenol (see formula below, molecular weight 212)

Aromatic compound 3: Marcalinker M, S-1 (para-vinylphenol homopolymer, weight average molecular weight 1600 to 2400)

(4) Comparative compound polystyrene (weight average molecular weight 220,000)
BPEF: Bisphenoxyethanol fluorene (weight average molecular weight 438.5)

2. Fabrication and evaluation of optical film (Example 1)
<Manufacturing of optical film 1>
(Preparation of matting agent additive liquid)
The following materials were stirred and mixed with a dissolver for 50 minutes, and then dispersed with menton golin. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a matting agent additive solution 1 having a matting agent content of 4.0% by mass.
Matte agent: Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd.): 4 parts by mass Dichloromethane: 48 parts by mass Ethanol: 48 parts by mass

(Preparation of dope)
First, methylene chloride and ethanol were put into a pressurized dissolution tank. Next, the cycloolefin polymer 1 (COP1) was charged into the pressure dissolution tank with stirring. This is Azumi Filter Paper No. made by Azumi Filter Paper Co., Ltd. 244 (Filtration accuracy 0.005 mm) using a filtration flow 300L ^{/ m} 2 · h, and filtered through a filtration pressure 1.0 × ¹⁰ 6 Pa, to prepare a dope.
(Doping composition)
COP1 (cycloolefin polymer): 83.0 parts by mass Fluorene skeleton-containing polyester polymer 1 (fluorene skeleton-containing polymer): 13.0 parts by mass Aromatic compound 1 (specific additive): 2.5 parts by mass Dichloromethane: 300.0 parts by mass Ethanol: 20.0 parts by mass 4% by mass Matting agent additive solution 1: 37.5 parts by mass (Matting agent amount: 1.5 parts by mass)
The solids in the above dope are cycloolefin polymer 1 (83.0% by mass), fluorene skeleton-containing polyester polymer 1 (13.0% by mass), aromatic compound 1 (2.5% by mass), and matting agent. It has a composition of (1.5% by mass).

(Film formation)
The prepared dope was sent from the pressure melting tank to the pressure die by a gear pump and cast on a stainless steel endless support (belt). After evaporating the solvent until the amount of the residual solvent in the cast dope became 40% by mass, the obtained film-like material was peeled off from the stainless steel endless support with a peeling tension of 130 N / m. The peeled film-like material was conveyed to the tenter stretching apparatus while being dried, and was conveyed in the tenter at a stretching ratio of 5% (1.05 times) in the width direction. At this time, the drying conditions from peeling to tenter were adjusted so that the amount of residual solvent during stretching was 11% by mass. The temperature of the tenter stretching apparatus was 160 ° C., and the stretching speed was 200% / min.
Next, the drying was completed while being conveyed in the drying apparatus by a large number of rollers. The drying temperature was 130 ° C., and the transport tension was 100 N / m. Then, after slitting both ends of the obtained optical film, embossing was performed to prepare an optical film 1 having a dry film thickness of 20 μm.

<Preparation of optical films 2-5>
Optical films 2 to 5 were obtained in the same manner as in optical film 1 except that the types of specific additives were changed as shown in Table 1.

<Manufacturing of optical films 6 to 10>
Optical films 6 to 10 were obtained in the same manner as in the optical film 1 except that the contents of the fluorene skeleton-containing polymer and the cycloolefin-based polymer were changed as shown in Table 1.

<Manufacturing of optical films 11 to 16>
Optical films 11 to 16 were obtained in the same manner as in the optical film 1 except that the contents of the specific additive, the cycloolefin polymer, and the fluorene skeleton-containing polymer were changed as shown in Table 1.

<Manufacturing of optical films 17 to 23>
Optical films 17 to 23 were obtained in the same manner as in the optical film 1 except that the weight average molecular weight Mw of the fluorene skeleton-containing polymer was changed as shown in Table 1.

<Manufacturing of optical films 24-29>
Optical films 24-29 were obtained in the same manner as in the optical film 1 except that the combination of the fluorene skeleton-containing polymer and the specific additive was changed as shown in Table 1.

<Manufacturing of optical film 30>
An optical film 30 was obtained in the same manner as in the optical film 1 except that neither the fluorene skeleton-containing polymer nor the specific additive was added.

<Manufacturing of optical films 31 to 32>
The comparative polymer shown in Table 1 was added in place of the fluorene skeleton-containing polymer, and optical films 31 to 32 were obtained in the same manner as in optical film 1 except that no specific additive was added.

<Manufacturing of optical films 33 to 35>
Optical films 33 to 35 were obtained in the same manner as in the optical film 1 except that the fluorene skeleton-containing polymer shown in Table 1 was added and no specific additive was added.

The main compositions of the optical films 1 to 35 are shown in Table 1.

The film strength and compatibility in the solvent-containing state in the step of forming the optical films 1 to 35 were evaluated by the following methods.

(Strength of film-like material in solvent-containing state)
If the strength of the film-like material in the solvent-containing state is not sufficient, tears and cuts will occur from the edge of the film during peeling and transportation of the film-like material. In extreme cases, the film-like material (or film) being transported is completely broken from the tears and cuts, and the productivity is significantly reduced.
Therefore, the strength of the film-like material in the solvent-containing state is such that the dope spread on the support is visually observed at the peeled portion when the dope is peeled from the support, and the end portion is torn during the film formation of 1000 m. The number of times the break was confirmed was counted.
It was judged to be good if the number of times that tears and cuts were confirmed was 5 times or less.

(Compatibility)
The dissolved state of the resin when preparing the dope was visually observed and evaluated according to the following criteria.

Further, the transparency and the phase difference of the obtained optical films 1 to 35 were evaluated by the following methods, respectively.

(transparency)
The haze of the obtained film was measured with a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. in an environment of 23 ° C. and 55% RH in accordance with JIS K-7136.
Haze was judged to be good if it was 2 or less.

(Phase difference)
The obtained film was humidity-controlled for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 55% RH. Then, the three-dimensional refractive index (nx, ny and nz) of the film at a wavelength of 550 nm was measured using Axoscan manufactured by Axometrics. The obtained refractive indexes nx, ny, and nz were applied to the following equations to calculate the phase difference Ro in the in-plane direction and the phase difference Rt in the thickness direction.
Ro = (nx-ny) x d
Rt = ((nx + ny) /2-nz) × d
Ro was 3 nm or less, and Rt was judged to be good if it was in the range of −5 nm to 5 nm.

Table 2 shows the evaluation results of the optical films 1 to 35.

As shown in Table 2, it can be seen that the optical films 1 to 29 of the present invention have a small number of tears and cuts in the film forming process and have high film strength in the solvent-containing state. It can also be seen that the compatibility is also good. Further, it can be seen that the haze (transparency) of the optical film obtained after film formation is low, and the phase difference Ro and Rt are also low.

In particular, it can be seen that by setting the weight average molecular weight of the fluorene skeleton-containing polymer to 5000 or more, the number of tears and breaks generated in the film forming process can be further reduced, and the phase difference can be further reduced (optical films 17 and 18). Comparison with ~ 21). It can be seen that by setting the weight average molecular weight of the fluorene skeleton-containing polymer to 1 million or less, the compatibility of the dope in the film forming process can be further enhanced and the haze of the obtained film can be further lowered (optical films 18 to 21 and 22). Contrast with).

Further, when the content of the cycloolefin-based oligomer or the aromatic compound is within the range of 1 to 45% by mass with respect to the total mass of the cycloolefin-based polymer and the fluorene skeleton-containing polymer, the film in the solvent-containing state. It can be seen that the strength and compatibility are even higher (comparison between optical films 12 to 15 and 12 or 16).

On the other hand, the optical film 30 containing no fluorene skeleton-containing polymer and the optical films 31 and 32 containing a comparative polymer all have many tears and cuts in the film forming process, and are films in a solvent-containing state. It can be seen that the strength is low. Further, even if the fluorene skeleton-containing polymer is contained, the optical films 33 to 35 which do not contain a specific additive are obtained not only with tears and cuts in the film forming process but also with low compatibility. It can be seen that the haze of the film is high.

According to the present invention, the strength of the film-like material in the solvent-containing state when produced by the solution casting method is high, and the optical film is produced while suppressing tearing or breaking of the film-like material, and is high. An optical film having transparency and good mechanical strength can be provided.

10 Liquid crystal display device 30 Liquid crystal cell 50 First polarizing plate 51 First polarizing element 53 Polarizing plate protective film (F1)
55 Polarizing plate protective film (F2)
70 Second polarizing plate 71 Second polarizing plate 73 Polarizing plate protective film (F3)
75 Polarizing plate protective film (F4)
90 backlight

Claims (7)

A cycloolefin-based polymer containing a structural unit derived from a cycloolefin monomer having an alkoxycarbonyl group, and
A fluorene skeleton-containing polymer containing a structural unit derived from a fluorene skeleton-containing compound,
A cycloolefin-based oligomer containing a structural unit derived from a cycloolefin monomer having a proton-donating group or a carbonyl-containing group (however, the cycloolefin-based oligomer is different from the cycloolefin-based polymer) or a proton-donating group. Including aromatic compounds with
Optical film. The fluorene skeleton-containing polymer is
A polyester polymer containing a structural unit derived from a fluorene skeleton-containing diol and a structural unit derived from a dicarboxylic acid.
A (meth) acrylate containing a polycarbonate polymer containing a structural unit derived from a fluorene skeleton-containing diol, or a structural unit derived from a fluorene skeleton-containing compound having a polymerizable unsaturated bond, and a structural unit derived from a (meth) acrylate monomer. It is a polymer,
The optical film according to claim 1. The weight average molecular weight of the fluorene skeleton-containing polymer is 5000 to 1,000,000.
The optical film according to claim 1 or 2. The content of the cycloolefin-based oligomer or the aromatic compound is 1 to 30% by mass with respect to the total mass of the cycloolefin-based polymer and the fluorene skeleton-containing polymer.
The optical film according to any one of claims 1 to 3. The optical film according to any one of claims 1 to 4 , which includes a polarizer and an optical film arranged on at least one surface thereof.
Polarizer. A liquid crystal display device having a first polarizing plate, a liquid crystal cell, a second polarizing plate, and a backlight in this order.
The first polarizing plate includes a first polarizing element, a protective film F1 arranged on a surface of the first polarizing element opposite to the liquid crystal cell, and the liquid crystal cell of the first polarizing element. It has a protective film F2 arranged on the side surface and has.
The second polarizing plate includes a second polarizing element, a protective film F3 arranged on a surface of the second polarizing element on the liquid crystal cell side, and the liquid crystal cell of the second polarizing element. It has a protective film F4 arranged on the opposite surface and has.
At least one of the protective films F2 and F3 is the optical film according to any one of claims 1 to 4.
Liquid crystal display device. It has a cycloolefin-based polymer containing a structural unit derived from a cycloolefin monomer having an alkoxycarbonyl group , a fluorene skeleton-containing polymer containing a structural unit derived from a fluorene skeleton-containing compound, and a proton-donating group or a carbonyl-containing group. A cycloolefin-based oligomer containing a structural unit derived from a cycloolefin monomer (however, the cycloolefin-based oligomer is different from the cycloolefin-based polymer) or an aromatic compound having a proton-donating group, and a solvent. The process of obtaining the containing dope and
A step of casting the dope on a support and then drying it to obtain a film-like substance.
The step of peeling the film-like material from the support and
including,
A method for manufacturing an optical film.

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