WO2020066899A1

WO2020066899A1 - Optical film, method for manufacturing same, optical layered body, and liquid crystal display device

Info

Publication number: WO2020066899A1
Application number: PCT/JP2019/036994
Authority: WO
Inventors: 寛哉西岡; 和哉須田; 浩成摺出寺
Original assignee: 日本ゼオン株式会社
Priority date: 2018-09-28
Filing date: 2019-09-20
Publication date: 2020-04-02
Also published as: TWI808262B; CN112703435A; KR20210070272A; TW202016184A; JPWO2020066899A1; JP7463965B2; CN112703435B

Abstract

Provided is an optical film, formed from a thermoplastic norbornene-based resin that includes a norbornene-based polymer, wherein the glass transition temperature Tg of the thermoplastic norbornene-based resin satisfies expression (1), the birefringence Δn_R manifested when free-end uniaxial stretching is applied to the thermoplastic norbornene-based resin to a factor of 1.5 at Tg + 15°C satisfies expression (2), and the retardation Rth of the optical film in the thickness direction and the thickness d of the optical film satisfy expression (3). Expression (1): Tg ≥ 110°C Expression (2): Δn_R ≥ 0.0025 Expression (3): Rth / d ≥ 3.5 × 10⁻ ³

Description

Optical film and manufacturing method thereof, optical laminate and liquid crystal display device

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

光学 Conventionally, an optical film formed of a thermoplastic resin is known. For example, Patent Documents 1 to 5 disclose optical films formed of a thermoplastic norbornene-based resin.

JP 2005-043740 A JP 2006-235085 A JP 2006-327112 A JP 2008-114369 A JP 2003-238705 A

In recent years, an optical film for application to an image display device such as a liquid crystal display device has been required to have excellent retardation development, and in particular, a film excellent in thickness direction retardation Rth development is required. Have been. Specifically, there is a demand for an optical film having a large retardation Rth in the thickness direction per the thickness of the optical film. As a method for obtaining an optical film having a large retardation Rth in a thickness direction per thickness by using a conventional film made of a thermoplastic resin, stretching at a high stretching ratio may be considered. However, an optical film obtained by stretching at a high stretching ratio tends to have low orientation angle accuracy.

The image display device may be used in various environments, for example, it may be used in a high-temperature environment. Therefore, high heat resistance is required for the optical film. Therefore, when focusing on the retardation Rth in the thickness direction, it is required that the change in the retardation Rth in the thickness direction can be suppressed even in a high-temperature environment.

The present invention has been made in view of the above problems, and is an optical film formed of a thermoplastic norbornene-based resin and having a large retardation Rth in a thickness direction per thickness, having high orientation angle accuracy, and It is an object of the present invention to provide an optical film capable of suppressing a change in retardation Rth in a thickness direction in a high-temperature environment and a method for manufacturing the same; and an optical laminate and a liquid crystal display device including the optical film.

The present inventor has made intensive studies to solve the above-mentioned problems. As a result, the present inventors, as a thermoplastic norbornene resin has a glass transition temperature Tg of the predetermined range, and, the use of those expressing predetermined birefringence [Delta] n _R when stretched under a predetermined condition As a result, the present inventors have found that an optical film having a large retardation per thickness in the thickness direction, a high orientation angle accuracy, and excellent heat resistance can be produced, and the present invention has been completed.
That is, the present invention includes the following.

[1] An optical film formed of a thermoplastic norbornene-based resin containing a norbornene-based polymer,
The glass transition temperature Tg of the thermoplastic norbornene resin satisfies the following formula (1),
The birefringence Δn _{R which} is expressed when the thermoplastic norbornene-based resin is subjected to free-end uniaxial stretching 1.5 times in 1 minute at Tg + 15 ° C. satisfies the following formula (2):
An optical film, wherein a retardation Rth in a thickness direction of the optical film and a thickness d of the optical film satisfy the following formula (3).
(1) Tg ≧ 110 ° C.
(2) Δn _R ≧ 0.0025
(3) Rth / d ≧ 3.5 × 10 ⁻³
[2] The optical film according to [1], wherein the molecular weight distribution of the norbornene-based polymer is 2.4 or less.
[3] the norbornene-based polymer is selected from the group consisting of a polymer of a monomer containing 25% by weight or more of a tetracyclododecene-based monomer and a hydride thereof;
The tetracyclododecene-based monomer is selected from the group consisting of tetracyclododecene, and a tetracyclododecene derivative in which a substituent is bonded to a ring of tetracyclododecene; [1] or [2]. The optical film of the above.
[4] The optical film according to any one of [1] to [3], wherein the optical film has a photoelastic coefficient of 8 Brewster or less.
[5] The optical film according to any one of [1] to [4], wherein the in-plane retardation Re of the optical film is from 40 nm to 80 nm.
[6] The method for producing an optical film according to any one of [1] to [5],
A method for producing an optical film, comprising molding the thermoplastic norbornene-based resin by an extrusion molding method or a solution casting method.
[7] An optical laminate comprising the optical film according to any one of [1] to [5] and a polarizing plate.
[8] A liquid crystal display device comprising the optical laminate according to [7].

According to the present invention, an optical film formed of a thermoplastic norbornene-based resin and having a large retardation Rth in the thickness direction per thickness, having a high orientation angle accuracy, and having a retardation Rth in the thickness direction in a high-temperature environment. It is possible to provide an optical film capable of suppressing the change and a method for producing the same; and an optical laminate and a liquid crystal display device including the optical film.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and examples, and may be arbitrarily modified and implemented without departing from the scope of the claims and the equivalents thereof.

において In the following description, the in-plane retardation Re of the film is a value represented by Re = (nx−ny) × d unless otherwise specified. The retardation Rth in the thickness direction of the film is a value represented by Rth = [{(nx + ny) / 2} −nz] × d unless otherwise specified. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the film and in a direction giving the maximum refractive index. ny represents a refractive index in the in-plane direction and a direction orthogonal to the direction of nx. nz represents the refractive index in the thickness direction. d represents the thickness of the film. The measurement wavelength is 550 nm unless otherwise specified.

In the following description, a “long” film refers to a film having a length of 5 times or more with respect to the width of the film, preferably having a length of 10 times or more, and specifically, Refers to a film that is long enough to be wound up in a roll and stored or transported. The upper limit of the ratio of the length to the width of the film is not particularly limited, but may be, for example, 100,000 times or less.

In the following description, the term “polarizing plate” includes not only a rigid member but also a flexible member such as a resin film, unless otherwise specified.

[1. Outline of optical film]
The optical film according to one embodiment of the present invention is a film formed of a thermoplastic norbornene-based resin. The thermoplastic norbornene-based resin contains a norbornene-based polymer. The optical film according to the present embodiment satisfies the following first to third requirements.

First, the glass transition temperature Tg of the thermoplastic norbornene resin satisfies the following equation (1).
(1) Tg ≧ 110 ° C.

Second, the evaluation birefringence Δn _R of the thermoplastic norbornene resin satisfies the following expression (2). Here, the evaluation birefringence refers to the birefringence that appears when a certain material is subjected to a free-end uniaxial stretching at a stretching temperature 15 ° C. higher than the glass transition temperature of the material by 1.5 times in one minute.
(2) Δn _R ≧ 0.0025

Third, the retardation Rth in the thickness direction of the optical film and the thickness d of the optical film satisfy the following expression (3).
(3) Rth / d ≧ 3.5 × 10 ⁻³

光学 The optical film according to the present embodiment that satisfies the above first to third requirements has a large retardation Rth in the thickness direction per thickness d as represented by the formula (3). In addition, this optical film can suppress a change in the retardation Rth in the thickness direction in a high-temperature environment. Further, this optical film can achieve high orientation angle accuracy while having a retardation Rth in the thickness direction which is larger than the thickness d as described above.

[2. Thermoplastic norbornene resin]
The thermoplastic norbornene-based resin is a thermoplastic resin containing a norbornene-based polymer. The norbornene-based polymer is a polymer having a structure obtained by polymerizing a norbornene-based monomer and further performing hydrogenation as necessary. Therefore, the norbornene-based polymer usually includes at least one structure selected from the group consisting of a repeating structure obtained by polymerizing a norbornene-based monomer and a structure obtained by hydrogenating the repeating structure. Such norbornene-based polymers include, for example, ring-opened polymers of norbornene-based monomers, ring-opened copolymers of norbornene-based monomers and arbitrary monomers, and hydrides thereof. And an addition copolymer of a norbornene-based monomer and an arbitrary monomer, and a hydride thereof. The number of the norbornene-based polymer contained in the thermoplastic norbornene-based resin may be one, or two or more.

The norbornene-based monomer is a monomer containing a norbornene structure in a molecule. Examples of the norbornene-based monomer include bicyclo [2.2.1] hept-2-ene (common name: norbornene) and tricyclo [4.3.0.1 ^2,5 ] deca-3,7- Diene (common name: dicyclopentadiene), tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodeca-3-ene (common name: tetracyclododecene), norbornene-based monomer having no aromatic ring structure; 5-phenyl-2-norbornene, 5- (4-methylphenyl) Norbornene-based monomers having an aromatic substituent, such as -2-norbornene, 5- (1-naphthyl) -2-norbornene, and 9- (2-norbornen-5-yl) -carbazole; 1,4-methano -1,4,4a, 4b, 5,8,8a, 9a-octahydrofluorene, 1,4-methano-1,4,4a, 9a-tetrahydrofluorene (common name: methanotetrahydrofluorene), 1,4- Methano-1,4,4a, 9a-tetrahydrodibenzofuran, 1,4-methano-1,4,4a, 9a-tetrahydrocarbazole, 1,4-methano-1,4,4a, 9,9 , 10-hexahydroanthracene, 1,4-methano-1,4,4a, 9,10,10a-hexahydrophenanthrene, etc., having a norbornene ring structure and an aromatic ring structure in a condensed polycyclic structure Series monomers; and derivatives of these compounds (for example, those having a substituent on the ring); and the like.

Examples of the substituent include an alkyl group such as a methyl group, an ethyl group, a propyl group, and an isopropyl group; an alkylidene group; an alkenyl group; Examples of the polar group include a hetero atom and an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a halogen group such as a fluoro group, a chloro group, a bromo group, and an iodo group; a carboxyl group; a carbonyloxycarbonyl group; an epoxy group; a hydroxy group; an oxy group; an alkoxy group; an ester group; A silyl group; an amino group; a nitrile group; a sulfone group; a cyano group; an amide group; an imide group; The number of substituents may be one or two or more. The types of two or more substituents may be the same or different. However, from the viewpoint of obtaining an optical film having a low saturated water absorption and excellent moisture resistance, the norbornene-based monomer preferably has a small amount of a polar group, and more preferably has no polar group.

One of the norbornene-based monomers may be used alone, or two or more thereof may be used in combination at an arbitrary ratio.

Specific types and polymerization ratio of the norbornene monomer of above, it is desirable to select such a thermoplastic norbornene resin having a desired glass transition temperature Tg and evaluation birefringence [Delta] n _R is obtained. Usually, the glass transition temperature and birefringence manifestation of the norbornene-based polymer depend on the type and polymerization ratio of the norbornene-based monomer which is a raw material of the norbornene-based polymer. Therefore, by appropriately adjusting the type and polymerization ratio of the norbornene-based monomer, the glass transition temperature and the birefringence manifestation of the norbornene-based polymer can be adjusted, so that the thermoplastic norbornene-based resin containing the norbornene-based polymer can be adjusted. adjust a glass transition temperature Tg and evaluation birefringence [Delta] n _R in to satisfy equation (1) and (2).

By increasing the glass transition temperature and birefringence expression of norbornene polymers, in view of obtaining a glass transition temperature Tg and evaluation birefringence [Delta] n _R is greater thermoplastic norbornene resin easily, as the norbornene-based monomer, tetra It is preferable to use a cyclododecene monomer. Therefore, the norbornene-based polymer is preferably selected from the group consisting of a polymer of a monomer containing a tetracyclododecene-based monomer and a hydride thereof. Such a norbornene-based polymer is usually a repeating structure obtained by polymerizing a tetracyclododecene-based monomer, and one or more members selected from the group consisting of a structure obtained by hydrogenating the repeating structure. (Hereinafter sometimes referred to as “tetracyclododecene-based structure” as appropriate).

The tetracyclododecene-based monomer represents a monomer selected from the group consisting of tetracyclododecene and a tetracyclododecene derivative. A tetracyclododecene derivative is a compound having a structure in which a substituent is bonded to a ring of tetracyclododecene. The number of substituents may be one or two or more. The types of two or more substituents may be the same or different. Preferred tetracyclododecene derivatives include, for example, 8-ethylidene-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -dodec-3-ene (common name: ethylidenetetracyclododecene), 8-ethyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -dodec-3-ene, 8-ethoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 17, ¹⁰ ] -3-dodecene, 8-methyl-8-methoxycarbonyltetracyclo [4.4.0.1 ^2,5 . ^{17, 10} ] -3-dodecene and the like. As the tetracyclododecene-based monomer, one type may be used alone, or two or more types may be used in combination.

The ratio (polymerization ratio) of the tetracyclododecene-based monomer contained in the total amount of the monomer as a raw material of the norbornene-based polymer to 100% by weight is preferably 25% by weight or more, more preferably 27% by weight or more. % By weight, particularly preferably at least 29% by weight, preferably at most 60% by weight, more preferably at most 55% by weight, particularly preferably at most 50% by weight. When the polymerization ratio of the tetracyclododecene-based monomer is within the above range, the glass transition temperature and the birefringence of the norbornene-based polymer can be increased, so that the glass transition temperature Tg of the thermoplastic norbornene-based resin and the evaluation The refraction Δn _R can easily fall within the range of the expressions (1) and (2).

Normally, the ratio of the repeating structure (monomer unit) derived from a certain monomer in the norbornene-based polymer coincides with the ratio (polymerization ratio) of the monomer in all the monomers. Therefore, the ratio of the tetracyclododecene-based structure in the norbornene-based polymer usually coincides with the polymerization ratio of the tetracyclododecene-based monomer to the total amount of the monomers. Therefore, the ratio of the tetracyclododecene-based structure to 100% by weight of the norbornene-based polymer is preferably within the same range as the polymerization ratio of the tetracyclododecene-based monomer.

Furthermore, from the viewpoint of increasing the glass transition temperature and birefringence manifestation of the norbornene-based polymer and easily obtaining a thermoplastic norbornene-based resin having a large glass transition temperature Tg and a large evaluation birefringence Δn _R , the norbornene-based monomer is used as a norbornene-based monomer. It is preferable to use a dicyclopentadiene monomer. Therefore, the norbornene-based polymer is preferably selected from the group consisting of a polymer of a monomer containing a dicyclopentadiene-based monomer and a hydride thereof. Such a norbornene-based polymer usually has a repeating structure obtained by polymerizing a dicyclopentadiene-based monomer, and one or more structures selected from the group consisting of a structure obtained by hydrogenating the repeating structure. (Hereinafter may be referred to as “dicyclopentadiene-based structure” as appropriate).

Dicyclopentadiene-based monomer represents a monomer selected from the group consisting of dicyclopentadiene and dicyclopentadiene derivatives. A dicyclopentadiene derivative is a compound having a structure in which a substituent is bonded to a ring of dicyclopentadiene. The number of substituents may be one or two or more. The types of two or more substituents may be the same or different. One type of dicyclopentadiene-based monomer may be used alone, or two or more types may be used in combination.

The ratio (polymerization ratio) of the dicyclopentadiene-based monomer contained in the total amount of the monomer as a raw material of the norbornene-based polymer to 100% by weight is preferably 50% by weight or more, more preferably 55% by weight. %, Particularly preferably at least 60% by weight, preferably at most 80% by weight, more preferably at most 75% by weight, particularly preferably at most 70% by weight. When the polymerization ratio of the dicyclopentadiene-based monomer is in the above range, the glass transition temperature and the birefringence manifestation of the norbornene-based polymer can be increased, so that the glass transition temperature Tg and the evaluation birefringence of the thermoplastic norbornene-based resin can be increased. Δn _R easily falls within the range of the expressions (1) and (2).

Normally, the ratio of the dicyclopentadiene-based structure in the norbornene-based polymer coincides with the polymerization ratio of the dicyclopentadiene-based monomer to the total amount of the monomers. Accordingly, the ratio of the dicyclopentadiene-based structure to 100% by weight of the norbornene-based polymer preferably falls within the same range as the polymerization ratio of the dicyclopentadiene-based monomer.

In particular, when a tetracyclododecene-based monomer and a dicyclopentadiene-based monomer are used in combination as the norbornene-based monomer, the ratio of the amounts thereof is preferably in a predetermined range. Specifically, the amount of the dicyclopentadiene-based monomer is preferably 100 parts by weight or more, more preferably 150 parts by weight or more, and particularly preferably 200 parts by weight, based on 100 parts by weight of the tetracyclododecene-based monomer. It is at least 500 parts by weight, preferably at most 500 parts by weight, more preferably at most 450 parts by weight, particularly preferably at most 400 parts by weight. Therefore, in the norbornene-based polymer, the amount of the dicyclopentadiene-based structure is preferably 100 parts by weight or more, more preferably 150 parts by weight or more, and particularly preferably 200 parts by weight, based on 100 parts by weight of the tetracyclododecene-based structure. Parts by weight, preferably 500 parts by weight or less, more preferably 450 parts by weight or less, particularly preferably 400 parts by weight or less. When the above ratio is in the above range, the glass transition temperature and birefringence manifestation of the norbornene-based polymer can be increased. Therefore, the glass transition temperature Tg of the thermoplastic norbornene-based resin and the evaluated birefringence Δn _R are calculated by the formula (1). And it is easy to fit in the range of the expression (2).

When an arbitrary monomer to be copolymerized with the norbornene-based monomer is used, a thermoplastic norbornene-based resin having a desired glass transition temperature Tg and an evaluation birefringence Δn _R is obtained as the type of the arbitrary monomer. There is no limit in the range. Examples of the optional monomer capable of ring-opening copolymerization with the norbornene-based monomer include monocyclic olefins such as cyclohexene, cycloheptene and cyclooctene and derivatives thereof; and cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene. And derivatives thereof; Examples of the optional monomer capable of addition copolymerization with the norbornene-based monomer include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene and 1-butene and derivatives thereof; cyclobutene and cyclopentene , Cyclohexene and the like, and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene and 5-methyl-1,4-hexadiene; One kind of the arbitrary monomer may be used alone, or two or more kinds may be used in combination.

As the norbornene-based polymer, a hydride having a structure obtained by polymerizing a norbornene-based monomer and further performing hydrogenation is preferable. This hydride may be one in which the non-aromatic unsaturated bond in the polymer is hydrogenated, one in which the aromatic unsaturated bond in the polymer is hydrogenated, Both the non-aromatic unsaturated bond and the aromatic unsaturated bond may be hydrogenated. Among them, a norbornene-based polymer in which both the non-aromatic unsaturated bond and the aromatic unsaturated bond in the polymer are hydrogenated is preferable. By using such a hydrogenated norbornene-based polymer, the development of retardation Rth in the thickness direction can be effectively increased, and the photoelastic coefficient can be reduced. Therefore, it is possible to achieve both a large thickness direction retardation Rth and a low photoelastic coefficient. Further, usually, properties such as mechanical strength, moisture resistance and heat resistance of the optical film can be effectively improved.

The glass transition temperature of the penorbornene-based polymer is preferably 110 ° C. or higher, more preferably 112 ° C. or higher, and particularly preferably 114 ° C. or higher. By using the norbornene-based polymer having such a high glass transition temperature, relaxation of the orientation of the norbornene-based polymer in a high-temperature environment can be suppressed. Therefore, a change in the retardation Rth in the thickness direction of the optical film in a high-temperature environment can be suppressed. Further, usually, a film containing a norbornene-based polymer in which the type and the polymerization ratio of the norbornene-based monomer are adjusted so as to have a glass transition temperature in the above range, the birefringence due to stretching tends to have a large expression, Therefore, it is easy to increase the retardation Rth in the thickness direction of the optical film. The upper limit of the glass transition temperature of the norbornene-based polymer is not particularly limited, but is preferably 180 ° C or lower, more preferably 170 ° C or lower, and particularly preferably 160 ° C or lower. When the glass transition temperature of the norbornene-based polymer is equal to or lower than the above upper limit, the retardation Rth in the thickness direction of the optical film is easily increased.

The glass transition temperature of the norbornene-based polymer can be measured using a differential scanning calorimeter in accordance with JIS K 6911 at a heating rate of 10 ° C./min.

The glass transition temperature of the norbornene-based polymer can be adjusted by, for example, the type and polymerization ratio of the norbornene-based monomer as a raw material of the norbornene-based polymer.

The norbornene-based polymer preferably has a large birefringence developing property. Therefore, the norbornene-based polymer preferably has a large evaluation birefringence. Specifically, the evaluation birefringence of the norbornene-based polymer is preferably 0.0025 or more, more preferably 0.0026 or more, and particularly preferably 0.0027 or more. By using a norbornene-based polymer having such a large evaluation birefringence, a large retardation can be exhibited even if the stretching ratio is low. Accordingly, a large retardation Rth in the thickness direction can be expressed in the optical film with a small stretching ratio, so that the orientation angle accuracy of the optical film can be effectively improved. The upper limit of the evaluation birefringence of the norbornene-based polymer is not particularly limited, but is preferably 0.0050 or less, more preferably 0.0047 or less, and particularly preferably 0.0045 or less. When the evaluation birefringence of the norbornene-based polymer is equal to or less than the above upper limit, the production of the norbornene-based polymer can be easily performed.

The evaluation birefringence of the norbornene-based polymer can be measured by the following method.
A sheet is obtained by molding a norbornene-based polymer. This sheet is subjected to free-end uniaxial stretching. The free-end uniaxial stretching is stretching in one direction, and means stretching in which a restraining force is not applied to a sheet other than the stretching direction. The stretching temperature of the free-end uniaxial stretching is a temperature 15 ° C. higher than the glass transition temperature of the norbornene-based polymer. The stretching time is 1 minute, and the stretching ratio of the free-end uniaxial stretching is 1.5 times. After the stretching, the in-plane retardation of the central portion of the sheet is measured at a measurement wavelength of 550 nm, and the in-plane retardation is divided by the thickness of the central portion of the sheet to obtain an evaluation birefringence.

評価 Evaluation of norbornene-based polymer The birefringence can be adjusted, for example, by the type and polymerization ratio of the norbornene-based monomer as a raw material of the norbornene-based polymer, and the molecular weight distribution of the norbornene-based polymer.

The weight average molecular weight Mw of the norbornene-based polymer is preferably 10,000 to 100,000, more preferably 15,000 to 80,000, and particularly preferably 20,000 to 60,000. When the weight average molecular weight is in the above range, the mechanical strength and moldability of the optical film are highly balanced.

The molecular weight distribution Mw / Mn of the norbornene-based polymer is preferably 2.4 or less, more preferably 2.35 or less, and particularly preferably 2.3 or less. When the molecular weight distribution Mw / Mn of the norbornene-based polymer is within the above range, the adhesive strength of the optical film can be increased, so that delamination of the optical film can be suppressed. The molecular weight distribution is a ratio between the weight average molecular weight and the number average molecular weight, and is represented by “weight average molecular weight Mw / number average molecular weight Mn”. The lower limit of the molecular weight distribution of the norbornene-based polymer is usually 1.0 or more.

The weight average molecular weight and the number average molecular weight of the norbornene-based polymer can be measured in terms of polyisoprene by gel permeation chromatography using cyclohexane as an eluent. When the norbornene-based polymer does not dissolve in cyclohexane, toluene may be used as an eluent in the gel permeation chromatography. When the eluent is toluene, the weight average molecular weight and the number average molecular weight can be measured in terms of polystyrene.

The stress birefringence of the norbornene-based polymer is preferably at least 2350 × 10 ⁻¹² Pa ⁻¹ , more preferably at least 2400 × 10 ⁻¹² Pa ⁻¹ , particularly preferably at least 2550 × 10 ⁻¹² Pa ⁻¹ , It is preferably at most 3000 × 10 ⁻¹² Pa ⁻¹ , more preferably at most 2950 × 10 ⁻¹² Pa ⁻¹ , particularly preferably at most 2800 × 10 ⁻¹² Pa ⁻¹ . When the stress birefringence of the norbornene-based polymer is equal to or more than the lower limit of the above range, the film containing the norbornene-based polymer tends to have a large birefringence due to stretching, and therefore, in the thickness direction of the optical film. It is easy to increase the retardation Rth. When the stress birefringence of the norbornene-based polymer is equal to or less than the upper limit of the above range, the retardation Re and Rth of the optical film can be easily controlled, and the in-plane variation of the retardation can be suppressed.

The stress birefringence of the norbornene-based polymer can be measured by the following method.
The norbornene-based polymer is formed into a sheet to obtain a sheet. After fixing both ends of the sheet with clips, a weight having a predetermined weight (for example, 160 g) is fixed to one of the clips. Next, a sheet is placed in an oven set at a predetermined temperature (for example, a temperature higher by 5 ° C. than the glass transition temperature of the norbornene-based polymer) for a predetermined time (for example, one hour) starting from the clip with the unfixed weight as a starting point. And a stretching process is performed. The stretched sheet is cooled slowly and returned to room temperature. For this sheet, the in-plane retardation at the center of the sheet is measured at a measurement wavelength of 650 nm, and this in-plane retardation is divided by the thickness at the center of the sheet to calculate a δn value. Then, the δn value is divided by the stress applied to the sheet (in the above case, the stress applied when a predetermined weight is fixed) to obtain the stress birefringence.

応力 The stress birefringence of the norbornene-based polymer can be adjusted by the type and polymerization ratio of the norbornene-based monomer as a raw material of the norbornene-based polymer.

The norbornene-based polymer can be produced, for example, by a production method including polymerizing a norbornene-based monomer and any monomer used as needed in the presence of a suitable catalyst. In the case of producing a hydride as a norbornene-based polymer, the method for producing a norbornene-based polymer includes, after the above-described polymerization, a hydrogen containing a transition metal such as nickel, palladium, and ruthenium with respect to the obtained polymer. Contacting hydrogen in the presence of a hydrogenation catalyst to hydrogenate carbon-carbon unsaturated bonds.

割合 The proportion of the norbornene-based polymer contained in the thermoplastic norbornene-based resin is arbitrary within a range where a thermoplastic norbornene-based resin satisfying the formulas (1) and (2) can be obtained. From the viewpoint of utilizing the excellent properties of the norbornene-based polymer, the proportion of the norbornene-based polymer contained in the thermoplastic norbornene-based resin is preferably 80% by weight to 100% by weight, more preferably 90% by weight to 100% by weight. And particularly preferably from 95% by weight to 100% by weight.

The thermoplastic norbornene-based resin may contain an arbitrary component other than the norbornene-based polymer. As optional components, for example, ultraviolet absorbers, antioxidants, heat stabilizers, light stabilizers, antistatic agents, dispersants, chlorine scavengers, flame retardants, crystallization nucleating agents, reinforcing agents, antiblocking agents, Examples include anti-fogging agents, release agents, pigments, organic or inorganic fillers, neutralizing agents, lubricants, decomposers, metal deactivators, stain inhibitors, antibacterial agents and the like. One type of optional component may be used alone, or two or more types may be used in combination at an arbitrary ratio.

The thermoplastic norbornene-based resin has a glass transition temperature Tg that satisfies the formula (1). Specifically, the glass transition temperature Tg of the thermoplastic norbornene-based resin is usually 110 ° C. or higher, preferably 112 ° C. or higher, and particularly preferably 114 ° C. or higher. By using the thermoplastic norbornene-based resin having such a high glass transition temperature Tg, relaxation of the orientation of the norbornene-based polymer in a high-temperature environment can be suppressed. Therefore, a change in the retardation Rth in the thickness direction of the optical film in a high-temperature environment can be suppressed. Further, usually, a film containing a thermoplastic norbornene-based resin having a glass transition temperature Tg in the above-mentioned range tends to have a large birefringence due to stretching, and therefore, increases the retardation Rth in the thickness direction of the optical film. easy. The upper limit of the glass transition temperature Tg of the thermoplastic norbornene-based resin is not particularly limited, but is preferably 180 ° C or lower, more preferably 170 ° C or lower, and particularly preferably 160 ° C or lower. When the glass transition temperature Tg of the thermoplastic norbornene resin is equal to or lower than the above upper limit, the retardation Rth in the thickness direction of the optical film is easily increased.

ガラス The glass transition temperature Tg of the thermoplastic norbornene-based resin can be measured using a differential scanning calorimeter in accordance with JIS K 6911 at a heating rate of 10 ° C / min.

ガラス The glass transition temperature Tg of the thermoplastic norbornene-based resin can be adjusted by, for example, the type and polymerization ratio of the norbornene-based monomer as a raw material of the norbornene-based polymer, and the content of the norbornene-based polymer.

Thermoplastic norbornene resin has a rating birefringence [Delta] n _R satisfying the equation (2). Specifically, the evaluation birefringence Δn _R of the thermoplastic norbornene-based resin is usually 0.0025 or more, preferably 0.0026 or more, and particularly preferably 0.0027 or more. By using the thermoplastic norbornene resin having such high rating birefringence [Delta] n _R, it can be expressed a large retardation stretch ratio even lower. Accordingly, a large retardation Rth in the thickness direction can be expressed in the optical film with a small stretching ratio, so that the orientation angle accuracy of the optical film can be effectively improved. The upper limit of the evaluation birefringence [Delta] n _R of the thermoplastic norbornene resin is no particular restriction is not, preferably 0.0050 or less, more preferably 0.0047 or less, particularly preferably 0.0045 or less. If the evaluation birefringence [Delta] n _R of the thermoplastic norbornene resin is more than the upper limit of the above, it is possible to easily manufacture the thermoplastic norbornene resin.

Evaluation birefringence [Delta] n _R of the thermoplastic norbornene resin can be measured by the following methods.
A sheet is obtained by molding a thermoplastic norbornene-based resin. This sheet is subjected to free-end uniaxial stretching. The stretching temperature of the free-end uniaxial stretching is a temperature 15 ° C. higher than the glass transition temperature Tg of the thermoplastic norbornene-based resin (that is, Tg + 15 ° C.). The stretching time is 1 minute, and the stretching ratio of the free-end uniaxial stretching is 1.5 times. After stretching, the in-plane retardation Re (a) at the center of the sheet is measured at a measurement wavelength of 550 nm, and the in-plane retardation Re (a) is divided by the thickness T (a) at the center of the sheet to evaluate. A birefringence Δn _R is obtained.

The evaluation birefringence Δn _R of the thermoplastic norbornene-based resin is, for example, the type and polymerization ratio of the norbornene-based monomer as a raw material of the norbornene-based polymer, the molecular weight distribution of the norbornene-based polymer, and the content of the norbornene-based polymer. Can be adjusted by rate.

Stress birefringence _{C R} of the thermoplastic norbornene resin is preferably 2350 × ¹⁰ -12 ^{Pa -1} or higher, more preferably 2400 × ¹⁰ -12 ^{Pa -1} or higher, particularly preferably 2550 × ¹⁰ -12 ^{Pa -1} or higher And preferably at most 3000 × 10 ⁻¹² Pa ⁻¹ , more preferably at most 2950 × 10 ⁻¹² Pa ⁻¹ , particularly preferably at most 2800 × 10 ⁻¹² Pa ⁻¹ . If stress birefringence C _R of the thermoplastic norbornene resin is not less than the lower limit of the range, the film containing the thermoplastic norbornene resin tends expression greater of birefringence by stretching, therefore, the optical film Is easy to increase the retardation Rth in the thickness direction. Also, if the stress birefringence C _R of the thermoplastic norbornene resin is more than the upper limit of the above range, it becomes easy to control the retardation Re and Rth of the optical film, it is possible to suppress the variation in in-plane retardation .

Stress birefringence C _R of the thermoplastic norbornene resin can be measured by the following method.
A sheet is obtained by molding a thermoplastic norbornene-based resin into a sheet. After fixing both ends of the sheet with clips, a weight having a predetermined weight (for example, 160 g) is fixed to one of the clips. Next, in an oven set at a predetermined temperature (for example, a temperature higher by 5 ° C. than the glass transition temperature Tg of the thermoplastic norbornene-based resin), starting from the clip on which the weight is not fixed, for a predetermined time (for example, 1 hour) ) The sheet is suspended and stretched. The stretched sheet is cooled slowly and returned to room temperature. For this sheet, the in-plane retardation Re (b) at the center of the sheet is measured at a measurement wavelength of 650 nm, and this in-plane retardation Re (b) is divided by the thickness T (b) [mm] at the center of the sheet. Thus, the δn value is calculated. Then, the δn value, (in the above case, stress applied when fixing the predetermined weight) stress applied to the seat by dividing, to calculate stress birefringence C _R.

Stress birefringence C _R of the thermoplastic norbornene resin, the kind and the polymerization ratio of norbornene-based monomers as the raw material of the norbornene-based polymer, and can be adjusted by the content of the norbornene-based polymer.

[3. Characteristics of optical film]
The optical film according to the present embodiment is a film formed of the above-described thermoplastic norbornene-based resin, and the retardation Rth and the thickness d in the thickness direction satisfy the above-described formula (3). Specifically, the ratio Rth / d is usually at least 3.5 × 10 ⁻³ , preferably at least 3.7 × 10 ⁻³ , particularly preferably at least 4.0 × 10 ⁻³ . As described above, the optical film according to the present embodiment can increase the retardation Rth in the thickness direction per the thickness d. Therefore, it is possible to increase the retardation Rth in the thickness direction while reducing the thickness d. The upper limit of the ratio Rth / d is not particularly limited, but is preferably 8.0 × 10 ⁻³ or less, and more preferably 6.0 × 10 ⁻³ from the viewpoint of effectively suppressing the delamination of the optical film. It is as follows.

The glass transition temperature and birefringence manifestation of the norbornene-based polymer usually depend on the type and polymerization ratio of the norbornene-based monomer used as the material of the norbornene-based polymer. Therefore, the glass transition temperature Tg and evaluation birefringence [Delta] n _R of the thermoplastic norbornene-based resin containing the norbornene-based polymer has a correlation to the type and polymerization ratio of the norbornene monomer which is a material of the norbornene-based polymer. Therefore, the glass transition temperature Tg and evaluation birefringence [Delta] n _R of a thermoplastic norbornene resin, usually, a norbornene-based monomer type and polymerization ratio of the raw material of the norbornene-based polymer included in the thermoplastic norbornene resin Reflects. According to the studies of the present inventors, thus the glass transition temperature Tg and evaluation birefringence Δn selected type to have _R and amount of norbornene norbornene polymer employing the monomer in a predetermined range It has been found that the thermoplastic norbornene-based resin contained therein has excellent retardation Rth in the thickness direction due to stretching. Therefore, an optical film having a high Rth / d as described above can be manufactured as a stretched film using the above-described thermoplastic norbornene-based resin containing a norbornene-based polymer.

The photoelastic coefficient of the optical film according to the present embodiment is preferably small. The specific photoelastic coefficient of the optical film is preferably 8 Brewster or less, more preferably 7 Brewster or less, and particularly preferably 6 Brewster or less. Here, 1 Brewster = 1 × 10 ⁻¹³ cm ² / dyn. When the photoelastic coefficient of the optical film is small, the optical film hardly causes a change in optical characteristics such as retardation even if warpage occurs. Therefore, when the optical film is provided in the liquid crystal display device, it is possible to suppress the occurrence of light leakage due to the warpage of the optical film. The light leakage refers to a phenomenon in which, when the liquid crystal display device is set to a black display state, light to be shielded leaks from the screen and the screen becomes bright. The lower limit of the photoelastic coefficient is not particularly limited, but is preferably 0.5 Brewster or more, more preferably 1.0 Brewster or more, and particularly preferably 1.5 Brewster or more.

光 The photoelastic coefficient of the optical film can be measured by an ellipsometer.

光学 An optical film having a small photoelastic coefficient can be realized by using, for example, a thermoplastic norbornene-based resin containing a hydrogenated norbornene-based polymer.

光学 The optical film according to the present embodiment can achieve high orientation angle accuracy. Specifically, the optical film has a slow axis in an in-plane direction perpendicular to the thickness direction. The optical film can suppress the variation in the direction of the slow axis. Therefore, since the dispersion of the orientation angle θ as an angle formed by the slow axis with respect to a certain reference direction can be suppressed, high orientation angle accuracy can be achieved. An optical film having a high alignment angle accuracy can make display characteristics such as screen brightness and contrast uniform in a plane when provided in a liquid crystal display device.

配向 The orientation angle accuracy of the optical film can be evaluated by the standard deviation θσ of the orientation angle θ. The smaller the standard deviation θσ of the orientation angle θ of the optical film, the better. Specifically, the standard deviation θσ of the orientation angle θ of the optical film is preferably 0 ° to 0.15 °, more preferably 0 ° to 0.14 °, and particularly preferably 0 ° to 0.13 °. .

The standard deviation θσ of the orientation angle θ of the optical film can be measured by the following method.
The absolute value of the angle formed by the slow axis with respect to a certain reference direction of the optical film is measured as the orientation angle θ. This measurement is performed at a plurality of measurement positions at an interval of 50 mm in the width direction of the optical film and at an interval of 10 m in the length direction. Then, from these measurement results, the standard deviation θσ of the orientation angle θ can be calculated.

Usually, an optical film is manufactured as a stretched film using a thermoplastic norbornene-based resin. In addition, since the thermoplastic norbornene-based resin has excellent birefringence, the stretching ratio required for exhibiting a retardation large enough to satisfy the formula (3) is small. Therefore, when producing an optical film as a stretched film formed of a thermoplastic norbornene-based resin, the draw ratio can be reduced. With such a small stretching ratio, the optical film can achieve high orientation angle accuracy.

光学 The optical film according to the present embodiment is excellent in heat resistance. Specifically, the optical film can suppress a change in the retardation Rth in the thickness direction in a high-temperature environment. An optical film having excellent heat resistance can be applied to a liquid crystal display device that can be used in a high-temperature environment.

耐熱 The heat resistance of the optical film can be evaluated by the rate of change of the retardation Rth in the thickness direction by a durability test in a high temperature environment. For example, after measuring the retardation Rth0 in the thickness direction of the optical film, the optical film is subjected to a durability test in which the optical film is stored at 85 ° C. for 500 hours. After the durability test, the retardation Rth1 in the thickness direction of the optical film is measured. Then, the rate of change can be calculated by dividing the amount of change Rth0−Rth1 of the retardation in the thickness direction of the optical film by the durability test by the retardation Rth0 in the thickness direction of the optical film before the durability test. According to the optical film of this embodiment, the rate of change of the retardation Rth in the thickness direction can be preferably 3% or less.

熱 The thermoplastic norbornene-based resin contained in the optical film has a high glass transition temperature Tg. Therefore, even in a high-temperature environment, the molecules of the norbornene-based polymer contained in the thermoplastic norbornene-based resin are unlikely to cause orientation relaxation. Therefore, as described above, the change in the retardation Rth in the thickness direction in a high-temperature environment can be suppressed.

光学 The optical film according to the present embodiment preferably has high moisture resistance. Therefore, it is preferable that the optical film can suppress the change in the retardation Rth in the thickness direction in a high humidity environment. An optical film having excellent moisture resistance can be applied to a liquid crystal display device that can be used in a high humidity environment.

湿 The moisture resistance of the optical film can be evaluated by the rate of change of the retardation Rth in the thickness direction by a durability test in a high humidity environment. For example, after measuring the retardation Rth0 of the optical film in the thickness direction, the optical film is subjected to a durability test in which the optical film is stored in an environment of 60 ° C. and 90% humidity for 500 hours. After the durability test, the retardation Rth2 in the thickness direction of the optical film is measured. Then, the change rate Rth0−Rth2 of the retardation in the thickness direction of the optical film by the durability test is divided by the retardation Rth0 in the thickness direction of the optical film before the durability test to calculate the rate of change. According to the present embodiment, the rate of change of the retardation Rth in the thickness direction can be made preferably 3% or less.

Since the norbornene-based polymer is preferably excellent in moisture resistance, the optical film easily suppresses the infiltration of moisture. Therefore, even in a high-humidity environment, the molecules of the norbornene-based polymer contained in the optical film hardly cause orientation relaxation. Therefore, as described above, a change in the retardation Rth in the thickness direction in a high humidity environment can be suppressed.

光学 The optical film according to the present embodiment preferably has a low water absorption. For example, when the optical film is immersed in water at 23 ° C. for 24 hours, the water absorption by weight of the optical film is preferably 0% to 0.15%, more preferably 0% to 0.10%, and particularly preferably 0% to 0.1%. 0.05%. When the optical film has such a low water absorption, the optical film can have excellent moisture resistance as described above.

光学 The optical film according to the present embodiment can preferably suppress delamination. Therefore, when the optical film is bonded to a film such as a polarizing plate using an adhesive, the optical film can be hardly peeled off. A conventional stretched film containing a norbornene-based polymer, in view of the fact that generally delamination is likely to occur, that the optical film according to the present embodiment can suppress delamination is one of the excellent advantages of the optical film. is there.

内 The in-plane retardation Re of the optical film according to the present embodiment is optional depending on the use of the optical film. When a specific range is shown, the in-plane retardation Re of the optical film is preferably 40 nm or more, more preferably 45 nm or more, particularly preferably 50 nm or more, preferably 80 nm or less, more preferably 75 nm or less, and particularly preferably. Is 70 nm or less. When the in-plane retardation Re of the optical film is equal to or more than the lower limit of the above range, it is easy to improve the expression of the retardation. When the in-plane retardation Re of the optical film is equal to or less than the upper limit of the above range, the in-plane variation of the retardation can be suppressed. The in-plane retardation Re can be appropriately selected from the above range depending on the design of the image display device.

レター The retardation Rth in the thickness direction of the optical film according to the present embodiment is arbitrary depending on the use of the optical film. When showing a specific range, the retardation Rth in the thickness direction of the optical film is preferably 100 nm or more, more preferably 120 nm or more, particularly preferably 150 nm or more, preferably 400 nm or less, more preferably 380 nm or less, particularly Preferably it is 360 nm or less. When the retardation Rth in the thickness direction of the optical film is equal to or more than the lower limit of the above range, the contrast of the image display device in the oblique direction can be increased. When the retardation Rth in the thickness direction of the optical film is equal to or less than the upper limit of the above range, the in-plane variation of the retardation Rth in the thickness direction and the orientation angle can be suppressed. The retardation Rth in the thickness direction can be appropriately selected from the above range depending on the design of the image display device.

光学 The optical film according to the present embodiment preferably has a high total light transmittance. The specific total light transmittance of the optical film is preferably 85% to 100%, more preferably 87% to 100%, and particularly preferably 90% to 100%. The total light transmittance can be measured using a commercially available spectrophotometer at a wavelength of 400 nm or more and 700 nm or less.

光学 The optical film according to the present embodiment preferably has a small haze from the viewpoint of enhancing the image clarity of the liquid crystal display device incorporating the laminated film. The haze of the optical film is preferably 1% or less, more preferably 0.8% or less, and particularly preferably 0.5% or less. The haze can be measured using a turbidimeter according to JIS K7361-1997.

光学 The optical film according to the present embodiment is preferably thin. By using the above-mentioned thermoplastic norbornene-based resin, a large thickness direction retardation Rth can be obtained even when the optical film is thin. In addition, when the optical film is thin, the warpage of the optical film can be suppressed, so that a change in optical characteristics such as retardation due to the warpage can be reduced. Therefore, when the optical film is provided in the liquid crystal display device, it is possible to suppress the occurrence of light leakage due to the warpage of the optical film. The specific thickness d of the optical film is preferably 120 μm or less, more preferably 100 μm or less, and particularly preferably 80 μm or less. The lower limit of the thickness d is not particularly limited, but is preferably 20 μm or more, more preferably 30 μm or more, and particularly preferably 40 μm or more from the viewpoint of suppressing delamination.

[4. Production method of optical film]
The above-described optical film can be manufactured by, for example, a manufacturing method including a step of forming a thermoplastic norbornene-based resin to obtain a resin film, and a step of stretching the resin film. Hereinafter, in order to distinguish the resin film before being stretched from the optical film obtained after stretching, it may be referred to as “a film before stretching” as appropriate.

工程 In the step of molding the thermoplastic norbornene resin to obtain a film before stretching, there is no limitation on the molding method. Examples of the molding method include an extrusion molding method, a solution casting method, and an inflation molding method. Among them, the extrusion molding method and the solution casting method are preferable, and the extrusion molding method is particularly preferable.

後で After preparing the film before stretching, a step of stretching the film before stretching is performed. By this stretching, the molecules of the norbornene-based polymer in the film can be oriented, so that an optical film having the above-described optical characteristics is obtained. The stretching conditions in the step of stretching the film before stretching can be arbitrarily set as long as a desired optical film can be obtained.

態様 The stretching mode of the film before stretching may be, for example, uniaxial stretching in which stretching is performed in one direction, or biaxial stretching in which stretching is performed in two non-parallel directions. The biaxial stretching may be simultaneous biaxial stretching in which stretching in two directions is performed simultaneously, or sequential biaxial stretching in which stretching is performed in one direction and then stretching in the other direction. You may. Among these, from the viewpoint of easily producing an optical film having a large retardation Rth in the thickness direction, biaxial stretching is preferable, and sequential biaxial stretching is more preferable.

延伸 The stretching direction of the film before stretching can be set arbitrarily. For example, when the film before stretching is a long film, the stretching direction may be a vertical direction, a horizontal direction, or an oblique direction. The longitudinal direction represents the length direction of the long film, the horizontal direction represents the width direction of the long film, and the oblique direction is neither parallel nor perpendicular to the length direction of the long film. Indicates the direction.

延伸 The stretching ratio of the film before stretching is preferably 1.4 or more, more preferably 1.5 or more, preferably 2.2 or less, more preferably 2.1 or less. When the stretching ratio is equal to or more than the lower limit of the above range, an optical film having a large retardation Rth in the thickness direction can be easily obtained. When the stretching ratio is equal to or less than the upper limit of the above range, the orientation angle accuracy of the optical film can be easily increased. When performing biaxial stretching, it is preferable that the entire stretching ratio represented by the product of the stretching ratio of stretching in one direction and the stretching ratio of stretching in the other direction falls within the above range.

延伸 The stretching temperature of the film before stretching is preferably Tg ° C or higher, more preferably Tg + 5 ° C or higher, preferably Tg + 40 ° C or lower, more preferably Tg + 30 ° C or lower. When the stretching temperature is in the above range, it is easy to make the thickness of the optical film uniform.

In the above manufacturing method, as described above, the optical film can be obtained by stretching the film before stretching, but the manufacturing method may further include an optional step.
For example, the above manufacturing method may include a step of trimming the optical film, a step of performing a surface treatment on the optical film, and the like.

[5. Optical laminate]
An optical laminate according to one embodiment of the present invention includes the above-described optical film and a polarizing plate. Since the thickness of the optical film can be reduced even if the retardation Rth in the thickness direction is large, it is possible to reduce the thickness of the optical laminate or to suppress the warpage of the optical laminate. Further, since the optical film has high orientation angle accuracy, the optical characteristics of the optical laminate can be made uniform within the plane. Furthermore, since the optical film has high heat resistance, the optical laminate can also have high heat resistance. Such an optical laminate can be suitably applied to an image display device such as a liquid crystal display device.

フィルム As the polarizing plate, for example, a film having a polarizer layer can be used. As the polarizer layer, for example, a film obtained by performing an appropriate treatment on an appropriate vinyl alcohol-based polymer film in an appropriate order and method can be used. Examples of such a vinyl alcohol-based polymer include polyvinyl alcohol and partially formalized polyvinyl alcohol. Examples of the film treatment include a dyeing treatment with a dichroic substance such as iodine and a dichroic dye, a stretching treatment, and a crosslinking treatment. The polarizer layer is capable of absorbing linearly polarized light having a vibration direction parallel to the absorption axis, and is particularly preferably one having an excellent degree of polarization. The thickness of the polarizer layer is generally 5 μm to 80 μm, but is not limited thereto.

The polarizing plate may include a protective film layer on one or both sides of the polarizer layer to protect the polarizer layer. Any transparent film layer can be used as the protective film layer. Above all, a resin film layer excellent in transparency, mechanical strength, heat stability, moisture shielding property and the like is preferable. Examples of such a resin include an acetate resin such as triacetyl cellulose, a polyester resin, a polyether sulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, a thermoplastic norbornene-based resin, and a (meth) acrylic resin. . Among them, acetate resin, thermoplastic norbornene-based resin, and (meth) acrylic resin are preferred in terms of low birefringence, and thermoplastic norbornene-based resin is particularly preferred from the viewpoints of transparency, low moisture absorption, dimensional stability, and light weight. preferable.

偏光 The polarizing plate can be manufactured by, for example, laminating a polarizer layer and a protective film layer. At the time of bonding, an adhesive may be used as necessary.

The optical laminate may further include an optional member in combination with the optical film and the polarizing plate. For example, the optical laminate may include an adhesive layer for bonding the optical film and the polarizing plate.

厚み The thickness of the optical laminate is not particularly limited, but is preferably 30 µm or more, more preferably 50 µm or more, preferably 150 µm or less, more preferably 130 µm or less.

[6. Liquid crystal display]
A liquid crystal display device according to one embodiment of the present invention includes the above-described optical laminate. As described above, since the optical film included in the optical laminate can be thin, the optical laminate hardly warps. Therefore, it is possible to suppress the occurrence of light leakage due to a change in the optical characteristics of the optical film in the warped portion. The above-described warpage generally tends to occur at a corner of a screen of a liquid crystal display device. However, in the liquid crystal display device according to the present embodiment, light leakage at such a corner can be suppressed. In addition, since the optical film can have high alignment angle accuracy, the liquid crystal display device according to the present embodiment can make the display characteristics such as the brightness and contrast of the screen uniform within the screen. Furthermore, since the optical film has high heat resistance, the liquid crystal display device according to the present embodiment can suppress a change in display characteristics in a high-temperature environment.

Typically, a liquid crystal display device includes a liquid crystal cell, and an optical laminate on at least one side of the liquid crystal cell. Especially, it is preferable that the optical laminated body is provided so that the liquid crystal cell, the optical film, and the viewing side polarizer are arranged in this order. In such a configuration, the optical film can function as a viewing angle compensation film.

The liquid crystal cell includes, for example, an in-plane switching (IPS) mode, a vertical alignment (VA) mode, a multi-domain vertical alignment (MVA) mode, a continuous spin wheel alignment (CPA) mode, a hybrid alignment nematic (HAN) mode, and a twisted nematic. A liquid crystal cell of any mode such as a (TN) mode, a super twisted nematic (STN) mode, and an optically compensated bend (OCB) mode can be used.

Hereinafter, the present invention will be described specifically with reference to examples. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and equivalents thereof.
In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified. The following operations were performed in the normal temperature and normal pressure atmosphere unless otherwise specified.

[I. Method for measuring and calculating physical properties of polymer]
(Method for Measuring Weight Average Molecular Weight Mw, Number Average Molecular Weight Mn, and Molecular Weight Distribution Mw / Mn of Polymer)
The weight average molecular weight Mw and the number average molecular weight Mn of the polymer were measured by gel permeation chromatography (GPC) using cyclohexane as an eluent, and were obtained as standard polyisoprene conversion values.
As standard polyisoprene, standard polyisoprene manufactured by Tosoh Corporation (Mw = 602, 1390, 3920, 8050, 13800, 22700, 58800, 71300, 109000, 280000) was used.
The measurement was carried out using three Tosoh columns (TSKgelG5000HXL, TSKgelG4000HXL and TSKgelG2000HXL) connected in series at a flow rate of 1.0 mL / min, a sample injection volume of 100 μL, and a column temperature of 40 ° C.
The molecular weight distribution Mw / Mn was calculated using the measured values of the weight average molecular weight Mw and the number average molecular weight Mn measured by the above method.

(Method of measuring glass transition temperature Tg)
The glass transition temperature Tg was measured using a differential scanning calorimeter ("DSC6220SII" manufactured by Nanotechnology) based on JIS K 6911 at a heating rate of 10 ° C / min.

(Method of Measuring Evaluation Birefringence Δn _R )
The resin was formed into a sheet having a size of 50 mm long × 100 mm wide × 100 μm thick to obtain a sample sheet. This sample sheet was subjected to free-end uniaxial stretching using a tensile tester equipped with a thermostat (“5564” manufactured by Instron Japan Company Limited). The conditions for this stretching are as follows.
Stretching temperature: Tg + 15 ° C
Chuck distance: 65mm
Stretch ratio: 1.5 times (stretch distance 32.5 mm)
Stretching time: 1 minute Stretching speed: 32.5 mm / min

(4) After the stretching treatment, the stretched sample sheet was returned to room temperature to obtain a measurement sample.

With respect to this measurement sample, the in-plane retardation Re (a) [nm] at the center of the measurement sample was measured at a measurement wavelength of 550 nm using a phase difference meter (“AXOSCAN” manufactured by AXOMETRICS). Further, the thickness T (a) [mm] of the central portion of the measurement sample was measured. Using these measurements Re (a) and T (a), the following equation (X1), and calculates an evaluation birefringence [Delta] n _R of a resin.
Δn _R = Re (a) × (1 / T (a)) × 10 ⁻⁶ (X1)

(Measurement method of stress birefringence _{C R)}
The resin was formed into a sheet having a size of 35 mm long × 10 mm wide × 1 mm thick to obtain a sample sheet. After fixing both ends of the sample sheet with clips, a weight of 160 g was fixed to one of the clips. Next, the sample sheet was hung in an oven in which the temperature was set to the glass transition temperature of the resin Tg + 5 ° C., starting from the clip with the unfixed weight as a starting point, and stretched for 1 hour. Thereafter, the sample sheet was slowly cooled and returned to room temperature to obtain a measurement sample.

For this measurement sample, the in-plane retardation Re (b) [nm] at the center of the measurement sample was measured at a measurement wavelength of 650 nm using a birefringence meter (“WPA-100” manufactured by Photonic Lattice). Further, the thickness T (b) [mm] of the central portion of the measurement sample was measured. Using these measured values Re (b) and T (b), a δn value was calculated by the following equation (X2).
δn = Re (b) × (1 / T (b)) × 10 ⁻⁶ (X2)
Using a stress F which added to the δn value and sample, by the following formula (X3), was calculated stress birefringence C _R.
C _R = δn / F (X3)

[II. Method for evaluating characteristics of optical film]
(Method of measuring photoelastic coefficient of optical film)
The photoelastic coefficient of the optical film was measured by an ellipsometer.

(Evaluation method of orientation angle accuracy of optical film)
The absolute value of the angle formed by the slow axis with respect to the length direction of the optical film was measured as the orientation angle θ. This measurement was performed using a polarizing microscope (a polarizing microscope “BX51” manufactured by Olympus Corporation). The measurement of the orientation angle θ was performed at a plurality of measurement positions at intervals of 50 mm in the width direction of the optical film and at intervals of 10 m in the length direction of the optical film. The standard deviation θσ of those measurement results was calculated as an evaluation index of the orientation angle accuracy. The smaller the standard deviation θσ of the orientation angle θ is, the smaller the dispersion of the orientation angle θ is.

(Evaluation method of delamination of optical film)
As an adherend, an unstretched film formed of a resin containing a norbornene-based polymer (“Zeonor film” manufactured by Zeon Corporation, thickness of 100 μm, glass transition temperature of resin of 160 ° C., not stretched) Prepared. One side of the optical film as a film to be measured and one side of the unstretched film were subjected to corona treatment. An adhesive (UV adhesive CRB series manufactured by Toyochem) was attached to both the corona-treated surface of the optical film and the corona-treated surface of the unstretched film. The surfaces to which the adhesive was attached were stuck together. Thereafter, the adhesive was irradiated with ultraviolet rays using an electrodeless UV irradiation device (manufactured by Heraeus) to cure the adhesive. The ultraviolet irradiation was performed using a D bulb as a lamp under the conditions of a peak illuminance of 100 mW / cm ² and an integrated light amount of 3000 mJ / cm ² . As a result, a sample film having a layer structure of unstretched film / adhesive layer / optical film was obtained.

The obtained sample film was subjected to a 90-degree peel test according to the following procedure.
The sample film was cut into a width of 15 mm to obtain a film piece. The surface of the film piece on the optical film side was bonded to the surface of a slide glass using an adhesive. At this time, a double-sided adhesive tape (manufactured by Nitto Denko Corporation, product number “CS9621”) was used as the adhesive. An unstretched film included in a film piece is sandwiched between the tip of a high-performance digital force gauge (“ZP-5N” manufactured by Imada) and the unstretched film is moved at a speed of 300 mm / min in a direction normal to the surface of the slide glass. And the magnitude of the pulling force was measured as the peel strength. The evaluation of the peel strength was performed according to the following evaluation criteria.
Good: 1.0 N / 15 mm or more.
Poor: less than 1.0 N / 15 mm.

(Method for Measuring Retardation Rth, Re and Thickness d of Optical Film, and Method for Evaluating Rth / d)
The retardation Rth and the in-plane retardation Re in the thickness direction of the optical film were measured at a measurement wavelength of 550 nm using a phase difference meter ("AXOSCAN" manufactured by AXOMETRICS).

厚み The thickness d of the optical film was measured with a snap gauge (“ID-C112BS” manufactured by Mitutoyo Corporation).

ＲRth / d was calculated by dividing the measured retardation Rth in the thickness direction by the thickness d.

(Evaluation method of change rate of retardation Rth in thickness direction of optical film after lapse of 500 hours at 85 ° C.)
Before the durability test described below, the retardation Rth0 in the thickness direction of the optical film was measured. Thereafter, an endurance test of storing the optical film in an environment of 85 ° C. for 500 hours was performed. After the durability test, the retardation Rth1 in the thickness direction of the optical film was measured. From these measured values Rth0 and Rth1, the change rate (Rth change rate) of the retardation in the thickness direction of the optical film by the durability test was calculated by the following equation (X4).
Rth change rate (%) = {(Rth0−Rth1) / Rth0} × 100 (X4)

The smaller the Rth change rate, the better the heat resistance of the optical film. Therefore, the obtained Rth change rate was evaluated according to the following evaluation criteria.
Good: Rth change rate is 3% or less.
Poor: Rth change rate is greater than 3%.

(Evaluation method of the rate of change of the retardation Rth in the thickness direction of the optical film after elapse of 500 hours at 60 ° C. and 90% humidity)
Before the durability test described below, the retardation Rth0 in the thickness direction of the optical film was measured. Thereafter, a durability test was performed in which the optical film was stored in an environment of 60 ° C. and 90% humidity for 500 hours. After the durability test, the retardation Rth2 in the thickness direction of the optical film was measured. From these measured values Rth0 and Rth2, the change rate (Rth change rate) of the retardation in the thickness direction of the optical film by the durability test was calculated by the following equation (X5).
Rth change rate (%) = {(Rth0−Rth2) / Rth0} × 100 (X5)

The smaller the Rth change ratio, the better the heat resistance and moisture resistance of the optical film. Therefore, the obtained Rth change rate was evaluated according to the following evaluation criteria.
Good: Rth change rate is 3% or less.
Poor: Rth change rate is greater than 3%.

(Method of measuring water absorption of optical film)
A part of the optical film was cut to prepare a test piece (size: 100 mm × 100 mm), and the weight w0 of the test piece was measured. Thereafter, the test piece was immersed in water at 23 ° C. for 24 hours. After immersion, the weight w1 of the test piece was measured. Then, the ratio (w1-w0) / w0 of the weight w1-w0 of the test piece increased by immersion to the weight w0 of the test piece before immersion was calculated as the water absorption (%). The smaller the water absorption, the better.

[III. Method for evaluating characteristics of liquid crystal display device]
(Evaluation of corner unevenness)
A durability test was conducted in which the liquid crystal display device was stored in an environment at 85 ° C. for 100 hours. Thereafter, the screen of the liquid crystal display device was set to a black display state, and the presence or absence of light leakage (corner unevenness) around the screen was visually checked.
Good: No light leakage around the screen.
Poor: Light leakage around the screen is remarkable.

[Example 1]
(1-1) Production of ring-opened polymer:
200 parts by weight of dehydrated cyclohexane, 0.75 mol% of 1-hexene, 0.15 mol% of diisopropyl ether, and 0.44 mol% was placed in the reactor at room temperature and mixed. Thereafter, while maintaining at 45 ° C., 29 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), 3 parts by weight of norbornene (NB), and (0.65 wt% toluene solution) and 0.02 mol% were added continuously over 2 hours in parallel to carry out polymerization. Next, 0.2 mol% of isopropyl alcohol was added to the polymerization solution to inactivate the polymerization catalyst, and the polymerization reaction was stopped. In the above description, the amounts represented by the unit “mol%” are values in which the total amount of the monomers is 100 mol%. The weight-average molecular weight Mw of the obtained ring-opened norbornene polymer was 2.8 × 10 ⁴ , and the molecular weight distribution (Mw / Mn) was 2.1. The conversion of the monomer into the polymer was 100%.

(1-2) Production of norbornene-based polymer by hydrogenation:
Next, 300 parts of the reaction solution containing the ring-opening polymer obtained in the above step (1-1) was transferred to an autoclave equipped with a stirrer, and a diatomaceous earth-supported nickel catalyst (“T8400RL” manufactured by JGC Chemical Co., Ltd .; %) And a hydrogenation reaction was carried out at a hydrogen pressure of 4.5 MPa and 160 ° C. for 4 hours.

After the completion of the hydrogenation reaction, the obtained solution was subjected to pressure filtration ("Fundaback filter" manufactured by Ishikawajima-Harima Heavy Industries, Ltd.) at a pressure of 0.25 MPa using Radiolite # 500 as a filtration bed to remove the hydrogenation catalyst. Thus, a colorless and transparent solution was obtained. The obtained solution was poured into a large amount of isopropanol to precipitate a norbornene-based polymer as a hydride of the ring-opening polymer. After the precipitated norbornene-based polymer was collected by filtration, an antioxidant [pentaerythritol-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (100 parts) per 100 parts of the norbornene-based polymer was used. 2.0 parts of a xylene solution in which 0.1 part of a product of "Irganox (registered trademark) 1010" manufactured by Ciba Specialty Chemicals) was dissolved. Next, it was dried in a vacuum dryer (220 ° C., 1 Torr) for 6 hours to obtain a thermoplastic norbornene resin. The weight average molecular weight of the norbornene-based polymer was 4.0 × 10 ⁴ , and the molecular weight distribution Mw / Mn was 2.3.

The glass transition temperature Tg, the evaluation birefringence Δn _R , and the stress birefringence C _R of the obtained thermoplastic norbornene-based resin were measured by the methods described above. The glass transition temperature Tg of the thermoplastic norbornene resin is 110 ° C., evaluation birefringence [Delta] n _R is 0.0030, stress birefringence _{C R} was 2600 × ¹⁰ -12 ^{Pa -1.}

(1-3) Production of film before stretching:
The thermoplastic norbornene-based resin obtained in the above step (1-2) was charged into a twin-screw extruder, and was formed into a strand-like molded body by hot melt extrusion molding. This molded body was cut into pieces using a strand cutter to obtain thermoplastic norbornene-based resin pellets.

The pellet was dried at 100 ° C for 5 hours. Thereafter, the pellets were supplied to an extruder by a conventional method and melted at 250 ° C. Then, the molten thermoplastic norbornene-based resin was discharged from the die onto a cooling drum to obtain a long unstretched film having a thickness of 110 µm.

(1-4) Production of optical film:
A longitudinal stretching machine using a float system between rolls was prepared. Using this longitudinal stretching machine, the above-mentioned film before stretching was stretched 1.26 times in the machine direction to obtain an intermediate film. The stretching temperature in the stretching using a longitudinal stretching machine was 120 ° C., which was a temperature (Tg + 10 ° C.) higher by 10 ° C. than the glass transition temperature Tg of the thermoplastic norbornene-based resin.

Thereafter, the intermediate film is supplied to a transverse stretching machine using a tenter method, and is stretched 1.43 times in a transverse direction while adjusting a take-up tension and a tenter chain tension to obtain a biaxially stretched film. Was obtained. The stretching temperature in the stretching using a transverse stretching machine was 120 ° C., which was 10 ° C. higher than the glass transition temperature Tg of the thermoplastic norbornene-based resin (Tg + 10 ° C.). The obtained optical film had an in-plane retardation Re of 60 nm, a retardation Rth in the thickness direction of 320 nm, and a thickness d of 65 μm.
The obtained optical film was evaluated by the method described above.

(1-5) Production of optical laminate:
An unstretched polyvinyl alcohol film (vinylon film, average degree of polymerization of about 2400, degree of saponification of 99.9 mol%) having a thickness of 65 μm was prepared as a long raw film. While continuously transporting this raw film in the longitudinal direction via a guide roll, the film is swelled by immersing it in pure water at 30 ° C. for 1 minute, and a dyeing solution (molar ratio of iodine and potassium iodide is used). Dyeing treatment was performed by immersing in a dye solution containing 1:23 (dye concentration: 1.2 mmol / L) at 32 ° C. for 2 minutes to adsorb iodine on the film. Thereafter, the film was washed with a 3% aqueous solution of boric acid at 35 ° C. for 30 seconds. Thereafter, the film was stretched 6.0 times at 57 ° C. in an aqueous solution containing 3% of boric acid and 5% of potassium iodide. Thereafter, the film was subjected to a complementary color treatment at 35 ° C. in an aqueous solution containing 5% of potassium iodide and 1.0% of boric acid. Thereafter, the film was dried at 60 ° C. for 2 minutes to obtain a long polarizer layer having a thickness of 23 μm. The degree of polarization of this polarizer layer was measured with an ultraviolet-visible spectrophotometer (“V-7100” manufactured by JASCO Corporation) and found to be 99.996%.

Acrylic resin (“SUMIPEX HT55X” manufactured by Sumitomo Chemical Co., Ltd.) was supplied to a hot melt extruded film forming machine equipped with a T die. The acrylic resin was extruded from the T-die, and the acrylic resin was formed into a film. Thus, a long protective film layer formed of an acrylic resin and having a thickness of 40 μm was obtained.

One surface of the obtained protective film layer was subjected to a corona treatment. Thereafter, an ultraviolet-curing adhesive ("Arcles KRX-7007" manufactured by ADEKA) was applied to the surface of the protective film layer subjected to the corona treatment to form an adhesive layer. The polarizer layer and the protective film layer were bonded via the adhesive layer using a pinch roll. Immediately thereafter, the adhesive layer was irradiated with ultraviolet light at 750 mJ / cm ² by a UV irradiation device to cure the adhesive layer. As a result, a long polarizing plate having a layer structure of polarizer layer / adhesive layer (thickness: 2 μm) / protective film layer was obtained.

One surface of the optical film was subjected to a corona treatment. Thereafter, an ultraviolet-curable adhesive ("Arcles KRX-7007" manufactured by ADEKA) was applied to the surface of the optical film that had been subjected to the corona treatment to form an adhesive layer. The polarizing plate and the optical film were bonded via the adhesive layer using a pinch roll. Immediately thereafter, the adhesive layer was irradiated with ultraviolet light at 750 mJ / cm ² by a UV irradiation device to cure the adhesive layer. Lamination was performed so that the slow axis of the optical film and the absorption axis of the polarizer layer were perpendicular to each other when viewed from the thickness direction. Thus, a long optical laminate having a layer structure of optical film / adhesive layer / polarizer layer / adhesive layer / protective film layer was obtained.

(1-6) Production of VA liquid crystal display device:
A VA-type liquid crystal display device (a 40-inch TV “TH-40AX700” manufactured by Panasonic Corporation) was prepared. This liquid crystal display device had a polarizing plate on the viewing side bonded to a glass surface of a liquid crystal cell. The polarizing plate on the viewing side was peeled off from the liquid crystal display device. Thereafter, the long optical laminate manufactured in the above step (1-5) is cut into an appropriate size for a liquid crystal display device, and the surface on the optical film side is bonded to the glass surface of the liquid crystal cell. A test VA liquid crystal display device was manufactured. In the bonding, the direction of the absorption axis of the polarizing plate on the viewing side originally provided in the liquid crystal display device matches the direction of the absorption axis of the polarizer layer of the optical laminate newly bonded to the liquid crystal cell. I went to do it.
The obtained liquid crystal display device was evaluated by the method described above.

[Example 2]
The combination of monomers used in the above step (1-1) was changed to 31 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbornene (NB).
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.28 times, and the stretching ratio in the transverse direction was changed to 1.48 times. In the step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 122.5 ° C., which was higher than the glass transition temperature Tg of the thermoplastic norbornene resin by 10 ° C. Tg + 10 ° C.).
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Example 3]
The combination of monomers used in the above step (1-1) was combined with 29 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and 3 parts by weight of ethylidenetetracyclododecene (ETD). Changed to
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.27 times, and the stretching ratio in the transverse direction was changed to 1.44 times. In the above step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 124 ° C., which was higher than the glass transition temperature Tg of the thermoplastic norbornene resin by 10 ° C. (Tg + 10 ° C.). )Met.
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Example 4]
The combination of the monomers used in the above step (1-1) was mixed with 31 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of ethylidenetetracyclododecene (ETD). Changed to
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.30 times, and the stretching ratio in the transverse direction was changed to 1.50 times. In the above step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 125 ° C., which was higher by 10 ° C. than the glass transition temperature Tg of the thermoplastic norbornene resin (Tg + 10 ° C.). )Met.
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Example 5]
The combination of monomers used in the above step (1-1) was changed to 30 parts by weight of tetracyclododecene (TCD) and 70 parts by weight of dicyclopentadiene (DCPD).
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.256 times. In the step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 125.5 ° C., which was higher than the glass transition temperature Tg of the thermoplastic norbornene resin by 10 ° C. Tg + 10 ° C.).
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Comparative Example 1]
The combination of monomers used in the above step (1-1) was changed to 31 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbornene (NB). Further, the polymerization temperature in the above step (1-1) was changed to 55 ° C.
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.25 times, and the stretching ratio in the transverse direction was changed to 1.45 times. In the step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 122 ° C., which was higher than the glass transition temperature Tg of the thermoplastic norbornene resin by 10 ° C. (Tg + 10 ° C.). )Met.
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Comparative Example 2]
The combination of monomers used in the above step (1-1) was mixed with 5 parts by weight of tetracyclododecene (TCD), 80 parts by weight of dicyclopentadiene (DCPD), and 15 parts by weight of ethylidenetetracyclododecene (ETD). Changed to
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.35 times, and the stretching ratio in the transverse direction was changed to 1.55 times. In the above step (1-4), the stretching temperature in the longitudinal and transverse directions was changed to 114 ° C., which was higher than the glass transition temperature Tg of the thermoplastic norbornene resin by 10 ° C. (Tg + 10 ° C.). )Met.
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Comparative Example 3]
The combination of monomers used in the step (1-1) was changed to 10 parts by weight of methanotetrahydrofluorene (MTF), 40 parts by weight of tetracyclododecene (TCD), and 50 parts by weight of dicyclopentadiene (DCPD). did.
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.60 times and the stretching ratio in the transverse direction was changed to 1.80 times. In the above step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 138 ° C., which was higher than the glass transition temperature Tg of the thermoplastic norbornene resin by 10 ° C. (Tg + 10 ° C.). )Met.
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Comparative Example 4]
The combination of monomers used in the step (1-1) was changed to 10 parts by weight of methanotetrahydrofluorene (MTF), 40 parts by weight of tetracyclododecene (TCD), and 50 parts by weight of dicyclopentadiene (DCPD). did.
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.20 times, and the stretching ratio in the transverse direction was changed to 1.40 times. In the above step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 138 ° C., which was higher than the glass transition temperature Tg of the thermoplastic norbornene resin by 10 ° C. (Tg + 10 ° C.). )Met.
Except for the above, the production and evaluation of a thermoplastic norbornene-based resin, an optical film and a liquid crystal display were performed by the same operation as in Example 1.

[Comparative Example 5]
The same operation as in step (1-1) of Example 1 was performed, except that 50 parts by weight of tetracyclododecene (TCD) and 50 parts by weight of 8-methyltetracyclododecene (MTD) were used as monomers. Thus, a ring-opened polymer was obtained. The weight average molecular weight Mw of the ring-opened polymer was 4.0 × 10 ⁴ , and the molecular weight distribution Mw / Mn was 2.0. The conversion of the monomer into the polymer was 100%.

300 parts of the polymerization reaction solution containing the ring-opening polymer thus obtained was transferred to an autoclave equipped with a stirrer, and 3 parts of a diatomaceous earth-supported nickel catalyst ("T8400RL" manufactured by JGC Chemicals, nickel support rate 57%) was added, and hydrogen was added. The hydrogenation reaction was performed at a pressure of 4.5 MPa and 160 ° C. for 4 hours.

After the completion of the hydrogenation reaction, the obtained solution was subjected to pressure filtration ("Fundaback filter" manufactured by Ishikawajima-Harima Heavy Industries, Ltd.) at a pressure of 0.25 MPa using Radiolite # 500 as a filtration bed to remove the hydrogenation catalyst. Thus, a colorless and transparent solution was obtained. The resulting solution was poured into a large amount of isopropanol to precipitate the polymer. After the precipitated polymer was collected by filtration, it was dried in a vacuum drier (220 ° C., 1 Torr) for 6 hours to obtain a hydride of the ring-opened polymer. The glass transition temperature Tg of the hydride of the ring-opened polymer was 158 ° C.

２８28 parts by weight of the hydride of this ring-opened polymer, 10 parts by weight of maleic anhydride, and 3 parts by weight of dicumyl peroxide were dissolved in 130 parts by weight of t-butylbenzene and reacted at 140 ° C. for 6 hours. The obtained reaction product solution was poured into methanol to coagulate the reaction product. The coagulated product was dried in a vacuum dryer (220 ° C., 1 Torr) for 6 hours to obtain a hydrogenated maleic acid-modified ring-opened polymer. This hydrogenated maleic acid-modified ring-opening polymer may be hereinafter referred to as “polar COP”. The polar COP had a maleic acid group content of 25 mol%.

In the above step (1-3), the above-mentioned polar COP was used as a resin of the material of the film before stretching.
In the above step (1-4), the stretching ratio in the longitudinal direction was changed to 1.62 times, and the stretching ratio in the transverse direction was changed to 1.82 times. In the step (1-4), the stretching temperature in the machine direction and the transverse direction was changed to 180 ° C., which is higher by 10 ° C. than the glass transition temperature Tg of the hydrogenated maleic acid-modified ring-opening polymer. Temperature (Tg + 10 ° C.).
Except for the above, the same operation as in Example 1 was performed to manufacture and evaluate the optical film and the liquid crystal display device.

[result]
The results of the above examples and comparative examples are shown in Tables 1 and 2 below. In Tables 1 and 2 below, the meanings of the abbreviations are as follows.
"T" in the column of monomer: tetracyclododecene (TCD).
"D" in the column of monomer: dicyclopentadiene (DCPD).
“N” in the column of monomer: norbornene (NB).
"E" in the column of monomer: ethylidenetetracyclododecene (ETD).
“M” in the column of monomer: methanotetrahydrofluorene (MTF).
Rth change rate (85 ° C.): Change rate of retardation in the thickness direction of the optical film by a durability test in which the film is stored at 85 ° C. for 500 hours.
Rth change rate (60 ° C. 90%): Change rate of retardation in the thickness direction of the optical film by an endurance test in which the film is stored in an environment of 60 ° C. and 90% humidity for 500 hours.

[Reference Example 1. The validity of the peel strength measurement method]
An experiment was conducted to evaluate whether or not the peel strength measurement method employed in the above-described Examples and Comparative Examples reflects the evaluation of the peel strength when the adherend is a polarizing plate.

偏光 A polarizing film and an adhesive were prepared by the same method as described in Example 1 of JP-A-2005-70140. Further, the optical film obtained in Example 1 of the present application was prepared as a film to be measured. One surface of the optical film was subjected to a corona treatment, and the corona treated surface was bonded to one surface of the polarizing film via an adhesive. A triacetyl cellulose film was bonded to the other surface of the polarizing film via an adhesive. Thereafter, the adhesive was cured by drying at 80 ° C. for 7 minutes to obtain a sample film. The obtained sample film was subjected to the same 90-degree peel test as described above (the method for evaluating delamination of an optical film). As a result, a peel strength value similar to the value obtained in Example 1 of the present application was obtained.

From this result, it was confirmed that the measurement results of the peel strength by the peel strength measuring method adopted in the above-described Examples and Comparative Examples reflected the evaluation of the peel strength when the adherend was a polarizing plate. Was done.

Claims

An optical film formed of a thermoplastic norbornene-based resin containing a norbornene-based polymer,
The glass transition temperature Tg of the thermoplastic norbornene resin satisfies the following formula (1),
The birefringence Δn R which is expressed when the thermoplastic norbornene-based resin is subjected to free-end uniaxial stretching 1.5 times in 1 minute at Tg + 15 ° C. satisfies the following formula (2):
An optical film, wherein a retardation Rth in a thickness direction of the optical film and a thickness d of the optical film satisfy the following formula (3).
(1) Tg ≧ 110 ° C.
(2) Δn R ≧ 0.0025
(3) Rth / d ≧ 3.5 × 10 −3
The optical film according to claim 1, wherein the molecular weight distribution of the norbornene-based polymer is 2.4 or less.
The norbornene-based polymer is selected from the group consisting of a polymer of a monomer containing at least 25% by weight of a tetracyclododecene-based monomer and a hydride thereof;
3. The method according to claim 1, wherein the tetracyclododecene-based monomer is selected from the group consisting of tetracyclododecene and a tetracyclododecene derivative in which a substituent is bonded to a ring of tetracyclododecene. 4. Optical film.
(4) The optical film according to any one of (1) to (3), wherein the optical film has a photoelastic coefficient of 8 Brewster or less.
The optical film according to any one of claims 1 to 4, wherein the in-plane retardation Re of the optical film is from 40 nm to 80 nm.
A method for producing an optical film according to any one of claims 1 to 5,
A method for producing an optical film, comprising molding the thermoplastic norbornene-based resin by an extrusion molding method or a solution casting method.
光学 An optical laminate comprising the optical film according to any one of claims 1 to 5 and a polarizing plate.
(8) A liquid crystal display device comprising the optical laminate according to claim 7.