TW202016184A - Optical film and manufacturing method thereof, optical stack and liquid crystal display device - Google Patents

Abstract

An optical film, which is an optical film formed by a thermoplastic resin containing a vinylene-based polymer, wherein the glass transition temperature Tg of the thermoplastic resin has a formula (1), which reduces the thermoplastic The birefringence Δn _R exhibited when the free end of the vinyl resin is uniaxially extended to 1.5 times at Tg + 15°C and satisfies the formula (2), and the retardation Rth in the thickness direction of the optical film and the thickness d of the optical film satisfy the formula (3) . (1) Tg≧110℃ (2) Δn _R ≧0.0025 (3) Rth/d≧3.5×10 ^{− 3}

Description

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

The invention relates to an optical film, a method for manufacturing the same, an optical stack, and a liquid crystal display device.

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

"Patent Literature" "Patent Document 1": Japanese Patent Publication No. 2005-043740 "Patent Document 2": Japanese Patent Publication No. 2006-235085 "Patent Document 3": Japanese Patent Publication No. 2006-327112 "Patent Document 4": Japanese Patent Publication No. 2008-114369 "Patent Document 5": Japanese Patent Publication No. 2003-238705

In recent years, an optical film used for an image display device such as a liquid crystal display device is required to have excellent visibility of retardation, and in particular, a film having excellent visibility of retardation Rth in the thickness direction is required. Specifically, the optical film is required to have a large retardation Rth in the thickness direction per unit thickness of the optical film. As a method for obtaining an optical film having a large retardation Rth per unit thickness in the thickness direction using a conventional film made of a thermoplastic resin, it may be considered to stretch at a high stretch magnification. However, the optical film obtained by stretching at a high stretching magnification tends to have lower orientation angle accuracy.

In addition, the image display device is sometimes 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. Accordingly, focusing on the retardation Rth in the thickness direction, it is required to suppress the change in the retardation Rth in the thickness direction even in a high-temperature environment.

The present invention was initiated in view of the foregoing problems, and its object is to provide an "optical film formed of a thermoplastic reduced vinyl resin and having a large retardation Rth in the thickness direction per unit thickness, which has high orientation angle accuracy and can be suppressed at Change of retardation Rth in the thickness direction in a high-temperature environment", an optical film and a method for manufacturing the same, and an optical stack including the aforementioned optical film and a liquid crystal display device.

The inventor has made intensive studies to solve the aforementioned problems. As a result, the present inventors found that by using a glass transition temperature Tg having a specified range and exhibiting a specified birefringence Δn _R when extended under a specified condition as a thermoplastic reduced vinyl resin, the thickness direction per unit thickness can be produced The optical film having a large retardation, high orientation angle accuracy, and excellent heat resistance further completes the present invention.

That is, the present invention includes the following.

[1] An optical film, which is an optical film formed of a thermoplastic reduced vinyl resin containing a reduced vinyl polymer, wherein the glass transition temperature Tg of the thermoplastic reduced vinyl resin satisfies the following formula (1) The birefringence Δn _R exhibited when the free-end uniaxial extension of the thermoplastic reduced vinyl resin at Tg + 15°C for 1 minute to 1.5 times for 1 minute satisfies the following formula (2), the thickness direction of the optical film The retardation Rth and the thickness d of the optical film satisfy the following formula (3). (1) Tg≧110℃ (2) Δn _R ≧0.0025 (3) Rth/d≧3.5×10 ^{− 3}

[2] The optical film as described in [1], wherein the molecular weight distribution of the aforesaid vinylene polymer is 2.4 or less.

[3] The optical film as described in [1] or [2], wherein the aforesaid norbornene-based polymer is selected from a polymer consisting of a monomer containing 25% by weight or more of tetracyclododecene-based monomer and its hydrogenation A group of things, The aforementioned tetracyclododecene monomer is selected from the group consisting of tetracyclododecene and tetracyclododecene derivatives having a substituent bonded to the ring of tetracyclododecene.

[4] The optical film as described in any one of [1] to [3], wherein the photoelastic coefficient of the optical film is 8 or less Brewster.

[5] The optical film according to any one of [1] to [4], wherein the in-plane retardation Re of the optical film is 40 nm or more and 80 nm or less.

[6] A method for manufacturing an optical film, which is the method for manufacturing an optical film as described in any one of [1] to [5], It includes forming the thermoplastic thermoplastic resin by extrusion or solution casting.

[7] An optical stack including the optical film and the polarizing plate as described in any one of [1] to [5].

[8] A liquid crystal display device including the optical stack as described in [7].

According to the present invention, it is possible to provide "an optical film which is formed of thermoplastic resin and has a large retardation Rth in the thickness direction per unit thickness, high orientation angle accuracy, and can suppress the retardation in the thickness direction under a high-temperature environment "Change of Rth" optical film and its manufacturing method, and optical stack and liquid crystal display device including the aforementioned optical film.

The embodiments and examples are disclosed below to explain the present invention in detail. However, the present invention is not limited to the embodiments and examples disclosed below, and can be implemented with any changes without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, the in-plane retardation Re of the film, unless otherwise noted, is the value shown by Re=(nx−ny)×d. In addition, the retardation Rth in the thickness direction of the film, unless otherwise noted, is the value shown by Rth={[(nx+ny)/2]−nz}×d. Here, nx represents the refractive index which is the direction perpendicular to the thickness direction of the film (in-plane direction) and the direction giving the maximum refractive index. ny represents the refractive index which is the aforementioned 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 noted.

In the following description, the so-called "strip-shaped" film refers to a film having a length of 5 times or more relative to the width of the film, preferably 10 times or more, specifically speaking it has A film of a length to be rolled or rolled for storage or handling. The upper limit of the ratio of the length of the film to the width is not particularly limited, but it may be made 100,000 times or less, for example.

In the following description, unless otherwise noted, the so-called "polarizer" includes not only rigid components but also flexible components such as resin films.

[1. Overview of optical film]

An optical film related to an embodiment of the present invention is a film formed of a thermoplastic norbornene-based resin. The aforementioned thermoplastic norbornene-based resin contains a norbornene-based polymer. Furthermore, the optical film related to this embodiment mode satisfies the following first to third requirements.

First, the glass transition temperature Tg of the thermoplastic reduced vinyl resin satisfies the following formula (1). (1) Tg≧110℃

Second, the evaluation birefringence Δn _{R of the} thermoplastic reduced vinyl resin satisfies the following formula (2). Here, the evaluation of birefringence refers to birefringence that appears when a material is uniaxially stretched to 1.5 times the free end at a stretching temperature 15°C higher than the glass transition temperature of the material for 1 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 formula (3). (3) Rth／d≧3.5×10 ^{− 3}

The optical film related to the present embodiment that satisfies the first to third requirements described above has a large retardation Rth in the thickness direction per unit thickness d as shown by equation (3). Moreover, this optical film can suppress the variation of the retardation Rth in the thickness direction under a high-temperature environment. Furthermore, this optical film has a retardation Rth in the thickness direction which is larger than the thickness d as described above, and can achieve high orientation angle accuracy.

[2. Thermoplastic vinylene resin]

Thermoplastic norbornene-based resins are thermoplastic resins containing norbornene-based polymers. The norbornene-based polymer is a polymer having a structure obtained by polymerizing a norbornene-based monomer and further hydrogenating as required. Accordingly, the norbornene-based polymer generally includes one or more structures selected from the group consisting of a repeating structure obtained by polymerizing a norbornene-based monomer and a structure obtained by hydrogenating the aforementioned repeating structure. Such reduced ene-based polymers include, for example: ring-opened polymers of ene-based monomers, ring-opened copolymers of ene-based monomers and any monomers, and these hydrides; ene ene Addition polymers of monomers, addition copolymers of olefin monomers and any monomers, and these hydrides. In addition, the thermoplastic resins included in the thermoplastic norbornene-based resin may be one kind, or two or more kinds.

The norbornene mono-system contains monomers with norbornene structure in the molecule. Examples of the normonene-based monomer include bicyclo[2.2.1]hept-2-ene (common name: normonene], tricyclo[4.3.0.1 ^2,5 ]dec-3,7-diene (common name: dicyclopentadiene), tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] twelve-3-ene: drop 𦯉 (tetracyclododecene common name) and the like aromatic ring structure containing no olefinically Monomer; 5-phenyl-2-northene, 5-(4-methylphenyl)-2-northene, 5-(1-naphthyl)-2-northene, 9-(2 -Normonene-5-yl)carbene and other aromatic monomers with aromatic substituents; 1,4-methyl bridge-1,4,4a,4b,5,8,8a,9a-octahydrogen Fucene, 1,4-methyl bridge -1,4,4a,9a-tetrahydro stilbene (common name: methyl bridge tetrahydro stilbene), 1,4-methyl bridge -1,4,4a,9a-tetrahydrodibenzo Furan, 1,4-methyl bridge-1,4,4a,9a-tetrahydrocarbazole, 1,4-methyl bridge-1,4,4a,9,9a,10-hexahydroanthracene, 1,4-methyl Bridge-1,4,4a,9,10,10a-hexahydrophenanthrene is equal to the reduced monomers in the condensed ring structure that contains both the reduced ring structure and the aromatic ring structure; and derivatives of these compounds (such as Ring has a substituent); etc.

Examples of the substituent include alkyl groups such as methyl, ethyl, propyl, and isopropyl; alkylene groups; alkenyl groups; polar groups; and the like. Examples of polar groups include heteroatoms and atomic groups having heteroatoms. Examples of heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, silicon atoms, halogen atoms, and the like. Specific examples of the polar group include halogen groups such as a fluorine group, a chlorine group, a bromine group, and an iodine group; a carboxyl group; a carbonyloxycarbonyl group; an epoxy group; a hydroxyl group; an oxy group; an alkoxy group; an ester group; a silanol group ; Silicone; Amino; Nitrosyl; Esteryl; Cyano; Acylamino; Acylimino; etc. The number of substituents may be one, or two or more. In addition, 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 saturation water absorption rate and excellent moisture resistance, the amount of the polar monomers is preferably a small amount of polar groups, and preferably has no polar groups.

You can use one kind of norbornene monomers alone or in combination of two or more at any ratio.

The specific types and polymerization ratios of the aforementioned reduced vinyl monomers are selected to meet the expectations in such a way that a thermoplastic reduced vinyl resin having a desired glass transition temperature Tg and evaluation of birefringence Δn _R can be obtained. In general, the glass transition temperature and birefringence visibility of the reduced vinylene polymer depends on the type and polymerization ratio of the reduced vinylene monomer that becomes the raw material of the reduced vinylene polymer. Accordingly, by moderately adjusting the type and polymerization ratio of the vinylene-based monomer, the glass transition temperature and birefringence visibility of the vinylene-based polymer can be adjusted, so the thermoplastics containing the vinylene-based polymer can be adjusted. The glass transition temperature Tg and evaluation birefringence Δn _{R of the} lowered olefin resin are adjusted to satisfy the formula (1) and the formula (2).

In order to increase the glass transition temperature and birefringence visibility of the reduced olefin polymer, it is easy to obtain the glass transition temperature Tg and evaluate the thermoplastic reduced olefin resin with large birefringence Δn _R , in order to use tetracyclododecene It is better to use a monomer as a vinyl monomer. Accordingly, the norbornene-based polymer is preferably selected from the group consisting of a polymer of a monomer including a tetracyclododecene-based monomer and its hydride. Such a reduced-ene polymer usually includes one or more structures selected from the group consisting of a repeating structure obtained by polymerizing a tetracyclododecene-based monomer and a structure obtained by hydrogenating the aforementioned repeating structure (below It is called "tetracyclododecene-based structure" in due time.).

The tetracyclododecene-based monomer means a monomer selected from the group consisting of tetracyclododecene and tetracyclododecene derivatives. The so-called tetracyclododecene derivative is a compound having a structure in which a substituent is bonded to the ring of tetracyclododecene. The number of substituents may be one, or two or more. In addition, the types of two or more substituents may be the same or different. As the good good the tetracyclododecene derivatives include for example: 8-ethylidene-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] twelve-3-ene (common name: ethylene tetracyclododecane Diene), 8-ethyltetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]dodec-3-ene, 8-ethoxycarbonyl tetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ] Dodec-3-ene, 8-methyl-8-methoxycarbonyl tetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]dodec-3-ene, etc. The tetracyclododecene-based monomer may be used alone or in combination of two or more.

The proportion (polymerization ratio) of tetracyclododecene-based monomers contained in the total amount of monomers used as the raw material of the reduced olefin-based polymer is 100% by weight or more, preferably 25% by weight or more, and 27% by weight % Or more is more preferable, 29% by weight or more is more preferable, and 60% by weight or less is more preferable, 55% by weight or less is more preferable, and 50% by weight or less is particularly preferable. When the polymerization ratio of the tetracyclododecene-based monomer is within the aforementioned range, the glass transition temperature and birefringence visibility of the olefin-based polymer can be increased, so that the glass transition of the thermoplastic olefin-based resin can be easily reduced. The temperature Tg and the evaluation birefringence Δn _R fall within the range of formula (1) and formula (2).

Generally, the proportion of the repeating structure (monomer unit) in a certain monomer derived from a monomer is the same as the proportion (polymerization ratio) of this monomer in all monomers. According to this, the ratio of the tetracyclododecene-based structure in the norbornene-based polymer is generally consistent with the polymerization ratio of the tetracyclododecene-based monomer to the total amount of 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 aforementioned tetracyclododecene-based monomer.

Furthermore, from the viewpoint of increasing the glass transition temperature and birefringence visibility of the vinylene-based polymer to easily obtain the glass transition temperature Tg and evaluating the thermoplastic paraffinic resin having a large birefringence Δn _R , the use of dicyclopentane The diene-based monomer is preferred as the reduced-ene monomer. Accordingly, the norbornene-based polymer is preferably selected from the group consisting of a polymer of a monomer including a dicyclopentadiene-based monomer and its hydride. Such a reduced-ene-based polymer usually contains one or more structures selected from the group consisting of a repeating structure obtained by polymerizing a dicyclopentadiene-based monomer and a structure obtained by hydrogenating the aforementioned repeating structure (the following is appropriate) It is called "dicyclopentadiene structure".).

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

The proportion (polymerization ratio) of the dicyclopentadiene-based monomers contained in the total amount of monomers used as the raw material of the reduced olefin-based polymer is 100% by weight or more, preferably 55% by weight or more The above is more preferable, and 60% by weight or more is more preferable, and 80% by weight or less is more preferable, 75% by weight or less is more preferable, and 70% by weight or less is particularly preferable. When the polymerization ratio of the dicyclopentadiene-based monomer is within the aforementioned range, the glass transition temperature and birefringence visibility of the vinyl polymer can be increased, so it is easy to lower the glass transition temperature of the thermoplastic resin. Tg and evaluation birefringence Δn _R fall within the range of formula (1) and formula (2).

Generally, the proportion of dicyclopentadiene-based structure in the norbornene-based polymer is consistent with the polymerization ratio of the dicyclopentadiene-based monomer relative to the total amount of monomers. Therefore, it is preferable that the ratio of the dicyclopentadiene-based structure to 100% by weight of the norbornene-based polymer falls within the same range as the polymerization ratio of the aforementioned dicyclopentadiene-based monomer.

In particular, when a tetracyclododecene-based monomer and a dicyclopentadiene-based monomer are used in combination as a reduced-monene-based monomer, the ratio of these amounts is preferably within a specified range. Specifically, with respect to 100 parts by weight of the tetracyclododecene-based monomer, the amount of the dicyclopentadiene-based monomer is preferably 100 parts by weight or more, preferably 150 parts by weight or more, and 200 parts by weight or more Particularly preferably, it is preferably 500 parts by weight or less, preferably 450 parts by weight or less, and particularly preferably 400 parts by weight or less. Accordingly, in the norbornene-based polymer, the amount of the dicyclopentadiene-based structure is preferably 100 parts by weight or more, and preferably 150 parts by weight or more relative to 100 parts by weight of the tetracyclododecene-based structure. More preferably, it is 200 parts by weight or more, and 500 parts by weight or less, 450 parts by weight or less, and 400 parts by weight or less. In the case where the aforementioned quantity ratio is within the aforementioned range, the glass transition temperature and birefringence visibility of the vinylene-based polymer can be increased, so it is easy to lower the glass transition temperature Tg of the thermoplastic resin and the evaluation of birefringence Δn _R Falls within the scope of formula (1) and formula (2).

In the case of using any monomer copolymerized with the norbornene-based monomer, the type of this arbitrary monomer is within the range of obtaining a thermoplastic butene-based resin having a desired glass transition temperature Tg and evaluating birefringence Δn _R There are no restrictions. Examples of any monomers capable of ring-opening copolymerization with norbornene-based monomers include monocyclic olefins such as cyclohexene, cycloheptene, cyclooctene, and derivatives thereof; cyclohexadiene, cycloheptene Diene and other cyclic conjugated dienes and their derivatives; etc. In addition, examples of the optional monomers capable of addition copolymerization with the norbornene-based monomers include, for example, C 2-20 α-olefins such as ethylene, propylene, and 1-butene, and derivatives thereof; rings Cyclic olefins such as butene, cyclopentene, cyclohexene and their derivatives; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4- Non-conjugated dienes such as hexadiene; etc. Any monomer may be used alone or in combination of two or more.

As the norbornene-based polymer, a hydride containing a structure obtained by polymerizing a norbornene-based monomer and further hydrogenating it. This hydride may be a non-aromatic unsaturated bond in a polymer that has been hydrogenated, a non-aromatic unsaturated bond in a polymer that has been hydrogenated, or a non-aromatic unsaturated bond in a polymer Hydrogenated aromatic aromatic bonds. Among them, it is preferred that the non-aromatic unsaturated bond and the aromatic unsaturated bond in the polymer are hydrogenated to reduce the vinyl polymer. By using such a hydrogenated norbornene-based polymer, the visibility of retardation Rth in the thickness direction can be effectively improved, and the photoelastic coefficient can be reduced. According to this, it becomes possible to balance the large thickness direction retardation Rth and the low photoelastic coefficient. In addition, the mechanical strength, moisture resistance, heat resistance and other characteristics of the optical film are usually effectively improved.

The glass transition temperature of the reduced ene polymer is preferably 110°C or higher, preferably 112°C or higher, and particularly preferably 114°C or higher. By using a drop-type vinyl polymer having such a high glass transition temperature, it is possible to suppress the relaxation of the orientation of the drop-type vinyl polymer in a high-temperature environment. According to this, the variation of the retardation Rth in the thickness direction of the optical film in a high-temperature environment can be suppressed. In addition, a thin film containing a "lower ene monomer and a polymerization ratio adjusted to have a glass transition temperature in the aforementioned range" of the lower ene polymer generally has a large birefringence due to the extension of the visibility 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 reduced olefin polymer is not particularly limited, but it is preferably 180°C or lower, preferably 170°C or lower, and particularly preferably 160°C or lower. In the case where the glass transition temperature of the reduced vinyl polymer is below the aforementioned upper limit, it is easy to increase the retardation Rth in the thickness direction of the optical film.

The glass transition temperature of the lowered olefin polymer can be measured using a differential scanning calorimeter based on JIS K 6911 at a temperature increase rate of 10°C/min.

The glass transition temperature of the reduced vinylene polymer can be adjusted by, for example, the type and polymerization ratio of the reduced vinylene monomer used as the raw material of the reduced vinylene polymer.

It is preferred that the reduced ene polymer has a large birefringence visibility. According to this, the norbornene-based polymer preferably has a large evaluation birefringence. In detail, the evaluation birefringence of the norbornene-based polymer is preferably 0.0025 or more, preferably 0.0026 or more, and particularly preferably 0.0027 or more. By using a reduced-ene polymer having such a large evaluation of birefringence, a large retardation can appear even if the elongation ratio is low. According to this, since the optical film can exhibit a large retardation Rth in the thickness direction with a small stretch magnification, the orientation angle accuracy of the optical film can be effectively improved. The upper limit of birefringence for the evaluation of norbornene-based polymers is not particularly limited, but it is preferably 0.0050 or less, preferably 0.0047 or less, and particularly preferably 0.0045 or less. In the case where the evaluation birefringence of the norbornene-based polymer is below the aforementioned upper limit, the production of the norbornene-based polymer can be easily performed.

The birefringence of the evaluation of norbornene-based polymers can be measured by the following method.

The norbornene-based polymer is shaped to obtain a sheet. This sheet is provided with a free-end uniaxial extension. The so-called free-end uniaxial extension means an extension that extends in one direction and does not exert a binding force on the sheet material outside the extension direction. The elongation temperature of the aforementioned uniaxial extension at the free end is a temperature 15°C higher than the glass transition temperature of the lowered vinyl polymer. In addition, the stretching time was 1 minute, and the stretching magnification of the free end uniaxial stretching was 1.5 times. After the extension, the in-plane retardation at the central portion of the sheet is measured at a measurement wavelength of 550 nm, and this in-plane retardation is divided by the thickness at the central portion of the sheet, thereby obtaining evaluation birefringence.

The birefringence of the evaluation of the norbornene-based polymer can be adjusted by, for example, the type and polymerization ratio of the norbornene-based monomer used as the 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, preferably 15,000 to 80,000, and particularly preferably 20,000 to 60,000. When the weight average molecular weight is in the aforementioned range, the mechanical strength and formability of the optical film can be highly balanced.

The molecular weight distribution Mw/Mn of the norbornene-based polymer is preferably 2.4 or less, preferably 2.35 or less, and particularly preferably 2.3 or less. In the case where the molecular weight distribution Mw/Mn of the norbornene-based polymer is in the aforementioned range, the bonding strength of the optical film can be improved, so the delamination of the optical film can be suppressed. The molecular weight distribution is the ratio of the weight average molecular weight to the number average molecular weight, and is shown by "weight average molecular weight Mw/number average molecular weight Mn". The lower limit of the molecular weight distribution of the reduced ene polymer is usually 1.0 or more.

The weight average molecular weight and number average molecular weight of the reduced polymer can be measured by polyisoprene conversion using gel permeation chromatography using cyclohexane as the eluent. In the case where the norbornene-based polymer is insoluble in cyclohexane, toluene can also be used as the eluent in the aforementioned gel permeation chromatography. When the eluent is toluene, the weight average molecular weight and number average molecular weight can be measured in terms of polystyrene.

The stress birefringence of the reduced polymer is preferably 2350×10 ^{− 12} Pa ^{− 1} or more, preferably 2400×10 ^{− 12} Pa ^{− 1} or more, and more preferably 2550×10 ^{− 12} Pa ^{− 1} or more , And preferably 3000×10 ^{− 12} Pa ^{− 1} or less, 2950×10 ^{− 12} Pa ^{− 1} or less, and 2800×10 ^{− 12} Pa ^{− 1} or less. In the case where the stress birefringence of the reduced polymer is higher than the lower limit of the aforementioned range, the film containing the reduced polymer tends to have a large manifestation of birefringence due to extension, Therefore, it is easy to increase the retardation Rth in the thickness direction of the optical film. In addition, when the stress birefringence of the reduced polymer is below the upper limit of the aforementioned range, it becomes easy to control the retardation Re and Rth of the optical film, and the in-plane variation in retardation can be suppressed.

The stress birefringence of the reduced polymer can be measured by the following method.

The norbornene-based polymer is shaped into a sheet to obtain a sheet. After fixing both ends of this sheet with a jig, fix the weight of the specified weight (for example, 160 g) to the jig on one side. Then, in an oven that has been set to a specified temperature (such as a temperature that is 5°C higher than the glass transition temperature of the ene-based polymer), fix the unfixed weight as the starting point, and hang the sheet for a specified time (for example 1 hour) for extension treatment. The stretched sheet was slowly cooled back to room temperature. For this sheet, the in-plane retardation at the center of the sheet was measured at a measurement wavelength of 650 nm, and this in-plane retardation was divided by the thickness at the center of the sheet to calculate the δn value. Then, the δn value is divided by the stress applied to the sheet (the stress applied when the specified weight is fixed in the above case) to obtain the stress birefringence.

The stress birefringence of the reduced vinylene polymer can be adjusted by the type and polymerization ratio of the reduced vinylene monomer used as the raw material of the reduced vinylene polymer.

The norbornene-based polymer can be produced by, for example, a production method including "polymerizing the norbornene-based monomer and any monomer used as required in the presence of a suitable catalyst." In addition, in the case of producing a hydride as a norbornene-based polymer, the production method of the norbornene-based polymer may be included after the aforementioned polymerization, and the obtained polymer may contain transition metals such as nickel, palladium, ruthenium, etc. It is exposed to hydrogen in the presence of a hydrogenation catalyst to hydrogenate the carbon-carbon unsaturated bond.

The proportion of the vinylene-based polymer contained in the thermoplastic vinylene-based resin is arbitrary as long as the thermoplastic vinylene-based resin satisfying the formula (1) and formula (2) can be obtained. From the viewpoint of making use of the excellent properties of the norbornene-based polymer, the ratio of the norbornene-based polymer contained in the thermoplastic norbornene-based resin is preferably 80% by weight to 100% by weight, and 90% by weight to 100% by weight % By weight is preferred, and 95% to 100% by weight is particularly preferred.

The thermoplastic norbornene-based resin may also contain any component other than the norbornene-based polymer. Examples of the optional components include ultraviolet absorbers, antioxidants, heat stabilizers, light stabilizers, antistatic agents, dispersants, chlorine scavengers, flame retardants, crystal nucleating agents, strengthening agents, and anti-caking agents. , Anti-fogging agent, release agent, pigment, organic or inorganic filler, neutralizing agent, slip agent, decomposition agent, metal deactivator, antifouling agent, antibacterial agent, etc. Any component may be used alone, or two or more types may be combined in any ratio.

The thermoplastic reduced vinyl resin has a glass transition temperature Tg satisfying the aforementioned formula (1). In detail, the glass transition temperature Tg of the thermoplastic reduced vinyl resin is usually 110°C or higher, preferably 112°C or higher, and particularly preferably 114°C or higher. By using a thermoplastic resin having such a high glass transition temperature Tg, it is possible to suppress the relaxation of the orientation of the polymer falling in a high temperature environment. According to this, the variation of the retardation Rth in the thickness direction of the optical film in a high-temperature environment can be suppressed. In addition, a film containing a thermoplastic resin having a "glass transition temperature Tg in the aforementioned range" generally has a tendency to exhibit a large birefringence due to stretching, so it is easy to increase the thickness direction of the optical film The delay Rth. The upper limit of the glass transition temperature Tg of the thermoplastic reduced vinyl resin is not particularly limited, but it is preferably 180°C or lower, preferably 170°C or lower, and particularly preferably 160°C or lower. When the glass transition temperature Tg of the thermoplastic reduced vinyl resin is below the aforementioned upper limit, it is easy to increase the retardation Rth in the thickness direction of the optical film.

The glass transition temperature Tg of the thermoplastic reduced vinyl resin can be measured using a differential scanning calorimeter, based on JIS K 6911, at a temperature increase rate of 10°C/min.

The glass transition temperature Tg of the thermoplastic reduced vinyl resin can be adjusted by, for example, the type and polymerization ratio of the reduced vinyl monomer as the raw material of the reduced vinyl polymer and the content of the reduced vinyl polymer.

The thermoplastic norbornene-based resin has an evaluation birefringence Δn _R that satisfies the aforementioned formula (2). Specifically, the evaluation birefringence Δn _{R of the} thermoplastic reduced vinyl resin is usually 0.0025 or more, and preferably 0.0026 or more, and particularly preferably 0.0027 or more. By using a thermoplastic reduced vinyl resin having such a large evaluation birefringence Δn _R , even if the elongation ratio is low, a large retardation can be manifested. According to this, since the optical film can exhibit a large retardation Rth in the thickness direction with a small stretch magnification, the orientation angle accuracy of the optical film can be effectively improved. The upper limit of the evaluation birefringence Δn _R of the thermoplastic reduced vinyl resin is not particularly limited, but it is preferably 0.0050 or less, preferably 0.0047 or less, and particularly preferably 0.0045 or less. In the case where the evaluation birefringence Δn _R of the thermoplastic norbornene-based resin is equal to or less than the aforementioned upper limit value, the production of the thermoplastic norbornene-based resin can be easily performed.

Evaluation of thermoplastic resins The birefringence Δn _R can be measured by the following method.

The thermoplastic resin is molded to obtain a sheet. This sheet is provided with a free-end uniaxial extension. The elongation temperature of the aforementioned uniaxial extension at the free end is a temperature that is 15°C higher than the glass transition temperature Tg of the thermoplastic reduced vinyl resin (ie, Tg + 15°C). In addition, the stretching time was 1 minute, and the stretching magnification of the free end uniaxial stretching was 1.5 times. After extension, measure the in-plane retardation Re(a) at the center of the sheet at a measurement wavelength of 550 nm, and divide this in-plane retardation Re(a) by the thickness T(a) at the center of the sheet The evaluation birefringence Δn _{R is obtained} .

The evaluation of thermoplastic resins with reduced birefringence Δn _R can be achieved by, for example, the types and polymerization ratio of reduced monomers used as raw materials for reduced vinylene polymers, the molecular weight distribution of reduced vinylene polymers, and Adjust the content of ene polymer.

The stress birefringence C _{R of the} thermoplastic reduced vinyl resin is preferably 2350×10 ^{− 12} Pa ^{− 1} or more, preferably 2400×10 ^{− 12} Pa ^{− 1} or more, and 2550×10 ^{− 12} Pa ^{− 1} or more It is particularly preferred, and 3000×10 ^{− 12} Pa ^{− 1} or less is preferred, 2950×10 ^{− 12} Pa ^{− 1} or less is preferred, and 2800×10 ^{− 12} Pa ^{− 1} or less is particularly preferred. In the case of thermoplastic drop-based resin 𦯉 C _R stress birefringence less than the lower limit of the aforementioned range, comprising this thermoplastic drop 𦯉-based resin film, the birefringence due to the appearance of a large extend This tends to increase the retardation Rth in the thickness direction of the optical film. Further, the thermoplastic resin down 𦯉 stress birefringence alkenyl C _R is the upper limit value of the range, it will become easy to control the retardation Re and Rth of the optical film, the retardation can be suppressed within the staggered plane.

Thermoplastic-based resin drop 𦯉 C _R stress birefringence can be measured by the following methods.

The thermoplastic norbornene-based resin is shaped into a sheet to obtain a sheet. After fixing both ends of this sheet with a jig, fix the weight of the specified weight (for example, 160 g) to the jig on one side. Then, in an oven that has been set to a specified temperature (for example, a temperature 5°C higher than the glass transition temperature Tg of the thermoplastic resin), the fixture without the fixed weight is set as the starting point, and the sheet is hung for a specified time ( E.g. 1 hour) for extension processing. The stretched sheet was slowly cooled back to room temperature. For this sheet, measure the in-plane retardation Re(b) at the center of the sheet at a measurement wavelength of 650 nm, and divide this in-plane retardation Re(b) by the thickness T(b) at the center of the sheet [mm ] To calculate the δn value. Then, this value is divided by the stress applied to δn of the sheet (in the above case based the weight specified fixed applied stress), can be determined stress birefringence C _R.

Thermoplastic-based resin drop 𦯉 C _R stress birefringence can be reduced by as a raw material-based polymer of the type 𦯉 drop 𦯉-based monomer and the copolymerization ratio, also lower holdup 𦯉-based polymer can be adjusted .

[3. Characteristics of optical film]

The optical film related to this embodiment is a film formed by the thermoplastic resin based on the above-mentioned thermoplastic resin, and its thickness direction retardation Rth and thickness d satisfy the foregoing formula (3). Specifically, the ratio Rth / d is generally 3.5 × 10 ^{- 3} or more, and at 3.7 × 10 ^{- 3} or more is preferred, at 4.0 × 10 ^{- 3} or more is preferred. In this way, the optical film related to this embodiment can increase the retardation Rth in the thickness direction per unit thickness d. According to this, while the thickness d is thinned, the retardation Rth in the thickness direction can be increased. The upper limit is not particularly limited ratio Rth / d, but in view of effectively suppressing the delamination of the optical film to 8.0 × 10 ^{- 3} or less is preferable, and 6.0 × 10 ^{- 3} or less is preferred.

The glass transition temperature and birefringence visibility of the reduced vinylene polymer generally depend on the type and polymerization ratio of the reduced vinylene monomer used as the material of the reduced vinylene polymer. Accordingly, the glass transition temperature Tg of the thermoplastic reduced vinyl resin containing this reduced vinyl polymer and the evaluation of the birefringence Δn _R and the type and polymerization of the reduced vinyl monomer as the material of the reduced vinyl polymer Than have relevance. According to this, the glass transition temperature Tg and evaluation birefringence Δn _R of the thermoplastic reduced vinylene resin generally reflect the content of the reduced thermoplastic monomer contained in the thermoplastic reduced vinylene resin as the raw material of the reduced vinylene polymer. Type and polymerization ratio. According to the research of the present inventors, it has been understood that such a thermoplastic reduced vinylene resin containing a reduced vinylene polymer has excellent visibility of the retardation Rth in the thickness direction due to extension. The reduced vinylene polymer uses The type and amount of the reduced monomers selected in such a manner as to have a glass transition temperature Tg of a specified range and to evaluate the birefringence Δn _R. According to this, an optical film having a high Rth/d as described above can be manufactured using a thermoplastic norbornene-based resin contained in the norbornene-based polymer described above as a stretched film.

The photoelastic coefficient of the optical film related to this embodiment is preferably small. The specific photoelastic coefficient of the optical film is preferably 8 cloths or less, preferably 7 cloths or less, and more preferably 6 cloths or less. Here, 1 Brust = 1 × 10 ^{− 13} cm ² /dyn. In the case where the photoelastic coefficient of the optical film is small, even if the optical film is warped, the optical characteristics such as retardation are unlikely to change. According to this, in the case where the optical film is provided in the liquid crystal display device, the occurrence of light leakage due to warpage of the optical film can be suppressed. The so-called light leakage refers to the phenomenon that when the liquid crystal display device is set to the black display state, the light to be shielded leaks from the outside of the screen and the screen becomes bright. The lower limit of the photoelastic coefficient is not particularly limited, but it is preferably 0.5 or higher, preferably 1.0 or higher, and more preferably 1.5 or higher.

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

An optical film having a small photoelasticity coefficient can be realized, for example, by using a thermoplastic norene-based resin "containing hydrogenated norene-based polymers".

The optical film related to this embodiment can achieve high orientation angle accuracy. Specifically, the optical film has a slow axis in an in-plane direction perpendicular to its thickness direction. Moreover, the optical film can suppress the variation in the direction of the slow axis. Therefore, since the variation of the orientation angle θ which is the angle between the slow axis and the reference direction can be suppressed, high orientation angle accuracy can be achieved. When the optical film with high orientation angle accuracy is provided in a liquid crystal display device, the display characteristics such as brightness and contrast of the screen can be uniform within the plane.

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°, 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 between the slow axis of the optical film and a reference direction is measured as the orientation angle θ. This measurement is performed at multiple measurement positions with an interval of 50 mm in the width direction of the optical film and 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.

Generally, the optical film is made of a stretch-reduced vinyl resin as a stretched film. In addition, since the thermoplastic biene-based resin has excellent birefringence visibility, the extension ratio required for the retardation to a large extent satisfying the formula (3) is small. Therefore, when the optical film is manufactured as a stretched film formed of thermoplastic resins, the stretch magnification can be reduced. With such a small stretch magnification, the aforementioned optical film can achieve high orientation angle accuracy.

The optical film according to this embodiment is excellent in heat resistance. Specifically, the optical film can suppress the change in the retardation Rth in the thickness direction under a high-temperature environment. Optical films with excellent heat resistance can be applied to liquid crystal display devices that may be used in high-temperature environments.

The heat resistance of the optical film can be evaluated by the rate of change of the retardation Rth in the thickness direction obtained through a durability test under a high-temperature environment. For example, after measuring the retardation Rth0 in the thickness direction of the optical film, the optical film was subjected to a durability test stored at 85°C for 500 hours. After the endurance test, the retardation Rth1 in the thickness direction of the optical film is measured. Then, the amount of change in retardation in the thickness direction of the optical film Rth0-Rth1 obtained by the endurance test is divided by the delay in thickness direction of the optical film Rth0 before the endurance test to calculate the rate of change. According to the optical film related to this embodiment, it is preferable that the change rate of the retardation Rth in the thickness direction can be made 3% or less.

The thermoplastic resins contained in the optical film have a high glass transition temperature Tg. Accordingly, even in a high-temperature environment, the molecules of the norbornene-based polymer contained in the thermoplastic norbornene-based resin are not likely to undergo directional relaxation. Therefore, the variation of the retardation Rth in the thickness direction under a high-temperature environment can be suppressed as described above.

The optical film related to this embodiment is preferably high in moisture resistance. Accordingly, it is preferable that the optical film can suppress the change of the retardation Rth in the thickness direction under a high humidity environment. The optical film excellent in moisture resistance can be applied to a liquid crystal display device that may be used in a high humidity environment.

The moisture resistance of the optical film can be evaluated by the rate of change of the retardation Rth in the thickness direction obtained through a durability test under a high humidity environment. For example, after measuring the retardation Rth0 in the thickness direction of the optical film, the optical film was subjected to a durability test for 500 hours at 60°C and 90% humidity. After the endurance test, the retardation Rth2 in the thickness direction of the optical film is measured. Then, the amount of change in the retardation in the thickness direction of the optical film Rth0-Rth2 obtained by the endurance test is divided by the delay in the thickness direction of the optical film Rth0 before the endurance test to calculate the rate of change. According to this embodiment, it is preferable that the change rate of the retardation Rth in the thickness direction can be made 3% or less.

The lowering ene polymer is excellent in moisture resistance, so the optical film is easy to suppress the invasion of moisture. According to this, even in a high-humidity environment, the molecules of the vinyl polymer contained in the optical film are less likely to undergo directional relaxation. Therefore, the variation of the retardation Rth in the thickness direction under a high humidity environment can be suppressed as described above.

The optical film related to this embodiment is preferred to have a low water absorption rate. For example, the weight-based water absorption rate of the optical film when immersed in water at 23°C for 24 hours is preferably 0% to 0.15%, preferably 0% to 0.10%, preferably 0% to 0.05 % Is particularly good. With such a low water absorption rate, the optical film may have excellent moisture resistance as described above.

The optical film related to this embodiment is preferably capable of suppressing delamination. Accordingly, 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. In view of the fact that conventional stretched films containing norbornene-based polymers are generally prone to delamination, the optical film related to this embodiment mode can suppress delamination, which is one of the excellent advantages of the optical film.

The in-plane retardation Re of the optical film related to this embodiment is arbitrary depending on the application of the optical film. To reveal the specific range, the in-plane retardation Re of the optical film is preferably 40 nm or more, preferably 45 nm or more, more preferably 50 nm or more, and preferably 80 nm or less and 75 nm or less Preferably, 70 nm or less is particularly preferred. When the in-plane retardation Re of the optical film is equal to or higher than the lower limit of the aforementioned range, it is easy to optimize the visibility of retardation. In addition, when the in-plane retardation Re of the optical film is equal to or lower than the upper limit of the aforementioned range, the in-plane retardation can be suppressed from varying. The in-plane delay Re can be appropriately selected from the above range due to the design of the image display device.

The retardation Rth in the thickness direction of the optical film related to this embodiment is arbitrary depending on the application of the optical film. To reveal the specific range, the retardation Rth in the thickness direction of the optical thin is preferably 100 nm or more, preferably 120 nm or more, more preferably 150 nm or more, and preferably 400 nm or less and 380 nm or less Preferably, 360 nm or less is particularly preferable. When the retardation Rth in the thickness direction of the optical film is equal to or higher than the lower limit of the aforementioned range, the diagonal contrast of the image display device can be improved. In addition, when the retardation Rth in the thickness direction of the optical film is equal to or less than the upper limit value in the aforementioned range, the in-plane variation in the retardation Rth in the thickness direction and the orientation angle can be suppressed. The retardation Rth in the thickness direction may be appropriately selected from the above range according to the design of the image display device.

The optical film related to this embodiment is preferred to have a high total light transmittance. The specific total light transmittance of the optical film is preferably 85% to 100%, preferably 87% to 100%, and particularly preferably 90% to 100%. The total light transmittance must be measured using a commercially available spectrophotometer in the wavelength range from 400 nm to 700 nm.

From the viewpoint of improving the sharpness of the image of a liquid crystal display device incorporating a stacked film, the optical film related to this embodiment is preferably low in haze. The haze of the optical film is preferably 1% or less, preferably 0.8% or less, and particularly preferably 0.5% or less. Haze can be measured in accordance with JIS K7361-1997 using a turbidity meter.

The optical film related to this embodiment is preferably thin. By using the thermoplastic reduced vinyl resin described above, even if the optical film is thin, a large retardation Rth in the thickness direction can be obtained. In addition, when the optical film is thin, the warpage of the optical film can be suppressed, so that changes in optical characteristics such as retardation due to warpage can be reduced. According to this, in the case where the optical film is provided in the liquid crystal display device, the occurrence of light leakage due to warpage of the optical film can be suppressed. 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 from the viewpoint of suppressing delamination, it is preferably 20 μm or more, preferably 30 μm or more, and particularly preferably 40 μm or more.

[4. Manufacturing method of optical film]

The optical film described above can be manufactured by, for example, a manufacturing method including "a process of forming a thermoplastic resin to obtain a resin film" and a "process of extending this resin film". In order to distinguish it from the optical film obtained after stretching, the resin film before stretching is hereinafter referred to as the "pre-stretching film" as appropriate.

In the process of forming the thermoplastic norbornene-based resin to obtain a film before stretching, there is no limitation on the forming method. Examples of molding methods include extrusion molding, solution casting, and inflation molding. Among them, the extrusion forming method and the solution casting method are preferred, and the extrusion forming method is particularly preferred.

After the pre-stretch film is prepared, the process of stretching the pre-stretch film is performed. By this extension, the molecules of the vinylene polymer in the film can be oriented, so that an optical film having the optical characteristics described above can be obtained. The stretching conditions in the step of stretching the film before stretching can be arbitrarily set within a range where a desired optical film can be obtained.

The stretching of the film before stretching may be, for example, uniaxial stretching in one direction or biaxial stretching in two non-parallel directions. In addition, the biaxial extension may be simultaneous biaxial extension while extending in two directions, or successive biaxial extension after extending in one direction and then extending in the other direction. Among these, from the viewpoint of easy production of an optical film with a large retardation Rth in the thickness direction, biaxial stretching is preferred, and sequential biaxial stretching is preferred.

The stretching direction of the film before stretching can be set arbitrarily. For example, when the film before stretching is a long film, the extending direction may be a longitudinal direction, a lateral direction, or an oblique direction. The longitudinal direction refers to the longitudinal direction of the elongated film, the lateral direction refers to the width direction of the elongated film, and the oblique direction refers to a direction that is neither parallel nor perpendicular to the longitudinal direction of the elongated film.

The stretching ratio of the film before stretching is preferably 1.4 or more, preferably 1.5 or more, and preferably 2.2 or less, and preferably 2.1 or less. In the case where the stretching magnification is more than the lower limit of the aforementioned range, an optical film with a large retardation Rth in the thickness direction can be easily obtained. In addition, when the stretching magnification is equal to or lower than the upper limit of the aforementioned range, the orientation angle accuracy of the optical film can be easily improved. In the case of biaxial stretching, it is preferable that the overall stretching magnification shown by the product of the stretching magnification in one direction and the stretching magnification in the other direction falls within the aforementioned range.

The stretching temperature of the film before stretching is preferably Tg°C or higher, preferably Tg+5°C or higher, and preferably Tg+40°C or lower, and preferably Tg+30°C or lower. When the elongation temperature is in the aforementioned range, the thickness of the optical film is easy to be uniform.

In the aforementioned manufacturing method, the optical film can be obtained by stretching the film before stretching as described above, but the aforementioned manufacturing method may further include any steps.

For example, the aforementioned manufacturing method may include a step of trimming the optical film, a step of surface-treating the optical film, and the like.

[5. Optical stack]

An optical stack related to an embodiment of the present invention includes the optical film and polarizing plate described above. Since the optical film can be thinned even if the retardation Rth in the thickness direction is large, the optical stack can be thinned and warpage of the optical stack can be suppressed. Moreover, since the optical film has high orientation angle accuracy, the optical characteristics of the optical stack can be made uniform in the plane. Furthermore, since the optical film has high heat resistance, the optical stack can also have high heat resistance. Such an optical stack can be suitably applied to image display devices such as liquid crystal display devices.

As the polarizing plate, for example, a film provided with a polarizer layer may be used. As the polarizer layer, for example, it is possible to use a suitable vinyl alcohol-based polymer film that is appropriately processed in a suitable order and manner. Examples of such vinyl alcohol-based polymers include polyvinyl alcohol and partially formalized polyvinyl alcohol. Examples of the treatment of the film include dyeing treatment through dichroic substances such as iodine and dichroic dyes, stretching treatment, and cross-linking treatment. The polarizer layer absorbs linear polarized light having a vibration direction parallel to the absorption axis, and particularly preferably has excellent polarization. The thickness of the polarizer layer is generally 5 μm to 80 μm, but it is not limited thereto.

In order to protect the polarizer layer, the polarizer may be provided with a protective film layer on one side or both sides of the polarizer layer. As the protective film layer, any transparent film layer may be used. Among them, a thin film layer of a resin excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, etc. is preferred. Examples of such resins include acetate resins such as cellulose triacetate, polyester resins, polyether resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and thermoplastic resins. Reduced ene resin, (meth) acrylic resin, etc. In terms of low birefringence, acetate resins, thermoplastic resins, and (meth)acrylic resins are preferred. From the viewpoints of transparency, low moisture absorption, dimensional stability, and lightness, etc. In other words, thermoplastic resins are preferred.

For example, the polarizing plate can be manufactured by laminating the polarizer layer and the protective film layer. When bonding, you can also use the cement according to your needs.

The optical stack may further include any component combined with the optical film and the polarizing plate. For example, the optical stack may also include a bonding layer for bonding the optical film and the polarizing plate.

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

[6. LCD device]

A liquid crystal display device according to an embodiment of the present invention is provided in the optical stack described above. As described above, since the optical film included in the optical stack can be thinned, the optical stack is less likely to warp. According to this, the occurrence of light leakage caused by the change in the optical characteristics of the optical film in the warped portion can be suppressed. The aforementioned warpage is generally likely to occur at the corners of the screen of the liquid crystal display device, but in the liquid crystal display device related to this embodiment, such light leakage at the corners can be suppressed. Moreover, since the optical film can have high orientation angle accuracy, the liquid crystal display device related to this embodiment can make the display characteristics such as brightness and contrast of the screen uniform within the plane of the screen. Furthermore, since the optical film has high heat resistance, the liquid crystal display device according to this embodiment mode can suppress the change in display characteristics under a high-temperature environment.

Generally, a liquid crystal display device includes a liquid crystal cell, and an optical stack is provided on at least one side of the liquid crystal cell. Among them, it is preferable that the optical stack is arranged such that the liquid crystal cell, the optical film, and the viewing-side polarizer are arranged in sequence. In such a structure, the optical film can function as a viewing angle compensation film.

The liquid crystal cell may use, for example, in-plane switching (IPS) mode, vertical arrangement (VA) mode, multi-region vertical arrangement (MVA) mode, continuous firework arrangement (CPA) mode, mixed arrangement nematic (HAN) mode, twisted nematic (TN) mode, Super Twisted Nematic (STN) mode, Optical Compensation Bending (OCB) mode and other arbitrary modes of liquid crystal cells.

『Examples』

The following examples are disclosed to specifically illustrate the present invention. However, the present invention is not limited to the following embodiments, and can be arbitrarily changed and implemented without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, the "%" and "parts" indicating the amount are based on weight unless otherwise noted. Unless otherwise noted, the following operations are carried out in normal temperature and pressure atmosphere.

[I. Measurement and calculation methods of physical properties of polymers]

(Measurement method of weight average molecular weight Mw of polymer, number average molecular weight Mn and molecular weight distribution Mw/Mn)

The weight-average molecular weight Mw and the number-average molecular weight Mn of the polymer are measured by gel permeation chromatography (GPC) using cyclohexane as the eluent, and obtained as a standard polyisoprene conversion value.

As the standard polyisoprene, standard polyisoprene (Mw=602, 1390, 3920, 8050, 13800, 22700, 58800, 71300, 109000, 280000) manufactured by Tosoh Corporation was used.

The measurement system used three Tosoh Corporation columns (TSKgelG5000HXL, TSKgelG4000HXL, and TSKgelG2000HXL) 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 is calculated using the measured values of the weight average molecular weight Mw and the number average molecular weight Mn measured by the above method.

(Measurement method of glass transition temperature Tg)

The glass transition temperature Tg was measured using a differential scanning calorimeter ("DSC6220" manufactured by SII NanoTechnology Inc.) in accordance with JIS K 6911 at a temperature increase rate of 10°C/min.

(Measurement method for evaluating birefringence Δn _R )

The resin was formed into a sheet shape of 50 mm long×100 mm wide×100 μm thick to obtain a sample sheet. For this sample sheet, a tensile tester with a thermostat ("Model 5564" manufactured by Instron Japan Company Limited) was used to apply uniaxial extension at the free end. The conditions for this extension are as follows. Extension temperature: Tg＋15℃ Chuck spacing: 65 mm Extension magnification: 1.5 times (extension distance 32.5 mm) Extended time: 1 minute Extension speed: 32.5 mm/min

After the extension process, the extended sample sheet is returned to room temperature to obtain a quantity test sample.

For this amount of test sample, a phase difference meter ("AXOSCAN" manufactured by AXOMETRICS) was used to measure the in-plane retardation Re(a) [nm] at the center of the test sample at a measurement wavelength of 550 nm. Then, the thickness T(a) [mm] of the aforementioned central portion of the quantity test sample is measured. Using these measured values Re(a) and T(a), the evaluation birefringence Δn _{R of the} resin is calculated by the following formula (X1). Δn _R = Re(a)×(1/T(a))×10 ^{− 6} (X1)

(Stress birefringence measuring method of C _R)

The resin was formed into a sheet shape of 35 mm long×10 mm wide×1 mm thick to obtain a sample sheet. After fixing both ends of this sample sheet with a jig, a 160 g weight was fixed to the jig on one side. Subsequently, in an oven where the temperature has been set to the glass transition temperature (Tg) of the resin + 5°C, the jig without the fixed weight is set as the starting point, and the sample sheet is hung for 1 hour for extension treatment. After that, the sample sheet was slowly cooled back to room temperature to obtain a quantity test sample.

For this amount of test sample, use a birefringence meter ("WPA-100" manufactured by Photonic Lattice, Inc.) to measure the in-plane retardation Re(b) at the center of the test sample at a measurement wavelength of 650 nm [ nm]. Then, the thickness T(b) [mm] of the aforementioned central portion of the quantity test sample is measured. Using these measured values Re(b) and T(b), the δn value is calculated by the following formula (X2). δn=Re(b)×(1/T(b))×10 ⁻⁶ (X2)

Using this value and δn stress F applied to the sample, the stress is calculated by the following formula (X3) birefringent C _R. C _R = δn/F (X3)

[II. Evaluation method of characteristics of optical film]

(Measurement method of photoelastic coefficient of optical film)

The photoelastic coefficient of the optical film is measured using an ellipsometer.

(Evaluation method of orientation angle accuracy of optical film)

The absolute value of the angle between the slow axis and the longitudinal direction of the optical film is measured as the orientation angle θ. This measurement is performed using a polarizing microscope (polarizing microscope "BX51" manufactured by Olympus Corporation). In addition, the orientation angle θ was measured at a plurality of measurement positions with an interval of 50 mm in the width direction of the optical film and an interval of 10 m in the longitudinal direction. Calculate the standard deviation θσ of these measurement results as the evaluation index of the orientation angle accuracy. The smaller the standard deviation θσ of the orientation angle θ, the smaller the deviation of the orientation angle θ is.

(Evaluation method of delamination of optical film)

Prepare a non-stretched film ("Zeonor Film" made by Ruion Corporation, thickness 100 μm, resin glass transition temperature 160°C, unstretched) made of resin containing norbornene-based polymer as the adhesive body. The single side of the optical film as the film to be measured and the single side of the unstretched film were subjected to corona treatment. Attach the adhesive (UV adhesive CRB series manufactured by TOYOCHEM CO., LTD.) to both the corona-treated surface of the optical film and the corona-treated surface of the unstretched film. Bond the surfaces to which the bonding agent is attached to each other. Thereafter, using an electrodeless UV irradiation device (manufactured by Heraeus), the bonding agent is irradiated with ultraviolet rays to cure the bonding agent. The aforementioned ultraviolet irradiation was performed using a D bulb as a lamp source under the conditions of a peak illuminance of 100 mW/cm ² and an integrated light amount of 3000 mJ/cm ² . By this, a sample film having a layer structure of unstretched film/adhesive layer/optical film is obtained.

With respect to the obtained sample film, a 90-degree peel test was carried out in the following procedure.

Cut the sample film to a width of 15 mm to obtain a film sheet. Using an adhesive, the surface of the film sheet on the optical film side is attached to the surface of the glass slide. At this time, a double-sided adhesive tape (manufactured by Nitto Denko Corporation, model "CS9621") was used as an adhesive. Clamp the unstretched film contained in the film sheet at the end of a high-performance digital dynamometer ("ZP-5N" manufactured by IMADA), and pull at a speed of 300 mm/min along the normal direction of the surface of the slide For this unstretched film, the strength of the pulling force is measured as the peel strength. The evaluation of the peel strength was performed by the following evaluation criteria. Good: 1.0 N/15 mm or more Bad: less than 1.0 N／15 mm

(Measurement method of retardation Rth, Re and thickness d of optical film, and evaluation method of 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).

The thickness d of the optical film is measured using a caliper ("ID-C112BS" manufactured by Mitutoyo Corporation).

Divide the measured retardation Rth in the thickness direction by the thickness d to calculate Rth/d.

(Evaluation method of the change rate of retardation Rth in the thickness direction of the optical film after 500 hours at 85°C)

Before the durability test described later, the retardation Rth0 in the thickness direction of the optical film was measured. After that, the optical film was subjected to a durability test for 500 hours of storage at 85°C. After the endurance test, the retardation Rth1 in the thickness direction of the optical film is measured. From these measured values Rth0 and Rth1, the change rate of the retardation in the thickness direction of the optical film (Rth change rate) obtained by the endurance test is calculated by the following formula (X4). Rth change rate (%) = [(Rth0-Rth1) / Rth0] × 100　　　 (X4)

The smaller the aforementioned Rth change rate, the better the heat resistance of the optical film. Then, the Rth change rate obtained was evaluated by the following evaluation criteria. Good: Rth change rate is below 3%. Bad: Rth change rate is greater than 3%.

(Evaluation method of the change rate of the retardation Rth in the thickness direction of the optical film at 60°C, 90% humidity, and after 500 hours)

Before the durability test described later, the retardation Rth0 in the thickness direction of the optical film was measured. After that, the optical film was subjected to a durability test for 500 hours of storage at 60°C and 90% humidity. After the endurance test, the retardation Rth2 in the thickness direction of the optical film is measured. From these measured values Rth0 and Rth2, the change rate of the retardation in the thickness direction of the optical film (Rth change rate) obtained by the endurance test is calculated by the following formula (X5). Rth change rate (%) = [(Rth0-Rth2) / Rth0] × 100　　　 (X5)

The smaller the aforementioned Rth change rate, the better the heat resistance and moisture resistance of the optical film. Then, the Rth change rate obtained was evaluated by the following evaluation criteria. Good: Rth change rate is below 3%. Bad: Rth change rate is greater than 3%.

(Measurement method of water absorption of optical film)

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

[III. Evaluation method of characteristics of liquid crystal display device]

(Evaluation of uneven corners)

A durability test of storing the liquid crystal display device under an environment of 85°C for 100 hours was conducted. After that, the screen of the liquid crystal display device is set to a black display state to visually confirm the presence or absence of light leakage (uneven corners) around the screen. Good: There is no light leakage around the screen. Bad: The light leakage around the picture is obvious.

[Example 1]

(1-1) Manufacture of ring-opening polymers:

In a glass reaction vessel in which internal nitrogen has been replaced, 200 parts by weight of dehydrated cyclohexane, 0.75 mol% of 1-hexene, and 0.15 mol of diisopropyl ether with respect to a total of 100 parts by weight of monomers to be described later. % And triisobutylaluminum 0.44 mol%, put into the reactor at room temperature and mix. After that, while maintaining 45°C, 29 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and 3 parts by weight of norbene (NB) were combined with hexachloride Tungsten (0.65 wt% toluene solution) is 0.02 mol%, and it is continuously added to the reactor for polymerization in 2 hours. Subsequently, 0.2 mol% of isopropanol was added to the polymerization solution to passivate the polymerization catalyst to terminate the polymerization reaction. In the foregoing description, the amount indicated by the unit "mol%" is the value which sets the total amount of monomers to 100 mol%. The weight-average molecular weight Mw of the obtained ring-opening polymer of vinylene ring-opening polymer was 2.8×10 ⁴ , and the molecular weight distribution (Mw/Mn) was 2.1. Moreover, the conversion rate from monomer to polymer was 100%.

(1-2) Manufacture of vinyl polymers by hydrogenation:

Subsequently, 300 parts of the reaction solution containing the ring-opening polymer obtained in the previous step (1-1) was transferred to an autoclave equipped with a stirrer, and a nickel catalyst supported by diatomaceous earth ("T8400RL" manufactured by Nisshin Chemical Co., Ltd.) was added. , Nickel bearing rate 57%) 3 parts, hydrogenation reaction under hydrogen pressure 4.5 MPa, 160 ℃ for 4 hours.

After the hydrogenation reaction was completed, the obtained solution was pressure-filtered at a pressure of 0.25 MPa using a RADIOLITE #500 as a filter bed ("FUNDABAC Filter" manufactured by Ishikawashima Harima Heavy Industry Co., Ltd.) to remove the hydrogenation catalyst to obtain a colorless and transparent solution. The obtained solution was poured into a large amount of isopropanol to precipitate the norbornene-based polymer as the hydride of the ring-opening polymer. After filtering out the precipitated ene polymer, for every 100 parts of the ene polymer, add an antioxidant [3-{3,5-di(tertiary butyl)-4-hydroxyl dissolved in it Phenyl]propionic acid}pentaerythritol ester (manufactured by Ciba Specialty Chemicals, product name "Irganox (registered trademark) 1010")] 2.0 parts of 0.1 parts of xylene solution. Subsequently, it was dried with a vacuum dryer (220°C, 1 Torr) for 6 hours to obtain a thermoplastic resin. The weight-average molecular weight of the norbornene-based polymer is 4.0×10 ⁴ and the molecular weight distribution Mw/Mn is 2.3.

The glass transition temperature Tg, evaluation birefringence Δn _R and stress birefringence C _{R of} the obtained thermoplastic reduced vinyl resin were measured by the method described above. Thermoplastic drop 𦯉-based resin glass transition temperature Tg of 110 deg.] C, evaluated 0.0030 birefringence Δn _R, C _R stress birefringence is ^{2600 × 10 - 12 Pa - 1} .

(1-3) Manufacture of film before stretching:

The thermoplastic reduced vinyl resin obtained in the foregoing step (1-2) is put into a biaxial extruder and shaped by hot melt extrusion to form a strand-shaped molded body. This molded body was finely cut using a strand cutter to obtain pellets of thermoplastic resin.

The granules were 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 melted thermoplastic norbornene resin was discharged from the mold onto the cooling drum to obtain a long stretched film with a thickness of 110 μm.

(1-4) Manufacture of optical film:

Prepare to use a longitudinal stretcher with a suspension method between the rolls. Using this longitudinal stretching machine, the aforementioned pre-stretch film was stretched 1.26 times in the longitudinal direction to obtain an intermediate film. The stretching temperature of the aforementioned stretching using the longitudinal stretching machine is 120°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

After that, the aforementioned intermediate film was fed to a transverse stretching machine using a tenter method to adjust the drawing tension and the tension of the tenter chain, while extending 1.43 times in the transverse direction to obtain a long optical film as a biaxially stretched film. The stretching temperature of the aforementioned stretching using a transverse stretching machine is 120°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin. The obtained optical film had an in-plane retardation Re of 60 nm, a thickness direction retardation Rth of 320 nm, and a thickness d of 65 μm.

The obtained optical film was evaluated by the method described above.

(1-5) Manufacture of optical stacks:

Prepare an unstretched polyvinyl alcohol film (Vinylon film, average polymerization degree about 2400, saponification degree 99.9 mol%) with a thickness of 65 μm as a long raw film. The intermediate film is continuously transported along the longitudinal direction of the raw material film, and at the same time, the film is swelled at 30°C for 1 minute in pure water and immersed in the dyeing solution at 32°C (containing iodine at a molar ratio of 1:23 And potassium iodide dye solution, the dye concentration is 1.2 mmol/L) 2 minutes of dyeing treatment, so that the film adsorbs iodine. After that, 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 in an aqueous solution containing 3% boric acid and 5% potassium iodide at 57°C. Thereafter, the film was subjected to a complementary color treatment in an aqueous solution containing 5% potassium iodide and 1.0% boric acid at 35°C. Thereafter, the film was dried at 60°C for 2 minutes to obtain a long polarizer layer with a thickness of 23 μm. The polarization degree of this polarizer layer was measured using an ultraviolet visible light spectrophotometer ("V-7100" manufactured by Japan Spectroscopy Co., Ltd.), and the result was 99.996%.

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

Corona treatment is applied to one side of the obtained protective film layer. After that, an ultraviolet curing adhesive ("ARKLS KRX-7007" manufactured by ADEKA Corporation) was applied to the surface of the protective film layer subjected to corona treatment to form an adhesive layer. Intermediate this bonding layer, and use a pinch roller to bond the polarizer layer and the protective film layer. Immediately thereafter, the bonding layer was irradiated with ultraviolet light at 750 mJ/cm ² using a UV irradiation device to cure the bonding layer. Thereby, a long polarizing plate having a layer structure of polarizer layer/joining layer (thickness 2 μm)/protective film layer was obtained.

Corona treatment is applied to one side of the optical film. After that, an ultraviolet curing adhesive ("ARKLS KRX-7007" manufactured by ADEKA Corporation) was applied to the surface of the optical film that had been subjected to corona treatment to form an adhesive layer. Intermediate this bonding layer, and use a pinch roller to bond the polarizing plate and the optical film. Immediately thereafter, the bonding layer was irradiated with ultraviolet light at 750 mJ/cm ² using a UV irradiation device to cure the bonding layer. The bonding is performed so that the slow axis of the optical film and the absorption axis of the polarizer layer are perpendicular to each other when viewed in the thickness direction. Thus, an elongated optical stack having a layer structure of an optical film/a bonding layer/a polarizer layer/a bonding layer/a protective film layer is obtained.

(1-6) Manufacturing of VA liquid crystal display devices:

VA type liquid crystal display device (type 40 TV "TH-40AX700" manufactured by Panasonic Corporation) is prepared. This liquid crystal display device includes a polarizing plate attached to the viewing side of the glass surface of the liquid crystal cell. Peel off the polarizing plate on the viewing side from the liquid crystal display device. After that, the elongated optical stack manufactured by the aforementioned step (1-5) is cut to a suitable size for the liquid crystal display device, and the surface on the optical film side is bonded to the glass surface of the liquid crystal cell to manufacture VA for test Type liquid crystal display device. The aforementioned lamination is performed in such a manner that the “orientation direction of the absorption axis of the polarizing plate on the viewing side originally provided by the liquid crystal display device” coincides with the “orientation direction of the absorption axis of the polarizer layer newly attached to the optical stack of the liquid crystal cell”.

The obtained liquid crystal display device was evaluated by the method described above.

[Example 2]

Changed the combination of monomers used in the previous step (1-1) to 31 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbene (NB) .

In the aforementioned step (1-4), the longitudinal stretch magnification is changed to 1.28 times, and the lateral stretch magnification is changed to 1.48 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 122.5°C, which is a temperature that is 10°C higher than the glass transition temperature Tg of the thermoplastic reduced vinyl resin (Tg + 10°C).

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Example 3]

The combination of monomers used in the aforementioned step (1-1) was changed to 29 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and ethylenetetracyclododecene ( ETD) 3 parts by weight.

In the aforementioned step (1-4), the longitudinal stretch magnification is changed to 1.27 times, and the lateral stretch magnification is changed to 1.44 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 124°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Example 4]

The combination of monomers used in the aforementioned step (1-1) was changed to 31 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and ethylenetetracyclododecene ( ETD) 1 part by weight.

In the aforementioned step (1-4), the longitudinal stretch magnification is changed to 1.30 times, and the transverse stretch magnification is changed to 1.50 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 125°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Example 5]

The combination of the monomers used in the aforementioned step (1-1) was changed to 30 parts by weight of tetracyclododecene (TCD) and 70 parts by weight of dicyclopentadiene (DCPD).

In the aforementioned step (1-4), the longitudinal stretch magnification is changed to 1.256 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 125.5°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Comparative Example 1]

Changed the combination of monomers used in the previous step (1-1) to 31 parts by weight of tetracyclododecene (TCD), 68 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbene (NB) . Next, the polymerization temperature in the aforementioned step (1-1) was changed to 55°C.

In the aforementioned step (1-4), the longitudinal stretch magnification is changed to 1.25 times, and the transverse stretch magnification is changed to 1.45 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 122°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Comparative Example 2]

The combination of monomers used in the aforementioned step (1-1) was changed to 5 parts by weight of tetracyclododecene (TCD), 80 parts by weight of dicyclopentadiene (DCPD), and ethylene tetracyclododecene ( ETD) 15 parts by weight.

In the aforementioned step (1-4), the longitudinal stretch magnification is changed to 1.35 times, and the lateral stretch magnification is changed to 1.55 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 114°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Comparative Example 3]

Changed the combination of monomers used in the aforementioned step (1-1) to 10 parts by weight of methyl bridge tetrahydrostilbene (MTF), 40 parts by weight of tetracyclododecene (TCD) and 50 parts of dicyclopentadiene (DCPD) Parts by weight.

In the aforementioned step (1-4), the stretch magnification in the longitudinal direction is changed to 1.60 times, and the stretch magnification in the transverse direction is changed to 1.80 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 138°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Comparative Example 4]

Changed the combination of monomers used in the aforementioned step (1-1) to 10 parts by weight of methyl bridge tetrahydrostilbene (MTF), 40 parts by weight of tetracyclododecene (TCD) and 50 parts of dicyclopentadiene (DCPD) Parts by weight.

In the aforementioned step (1-4), the stretch magnification in the longitudinal direction is changed to 1.20 times, and the stretch magnification in the transverse direction is changed to 1.40 times. In addition, in the aforementioned step (1-4), the elongation temperature in the longitudinal and lateral directions is changed to 138°C, which is a temperature 10°C (Tg + 10°C) higher than the glass transition temperature Tg of the thermoplastic resin.

Except for the above matters, by the same operation as in Example 1, the manufacture and evaluation of thermoplastic resins, optical films, and liquid crystal display devices were performed.

[Comparative Example 5]

Except that 50 parts by weight of tetracyclododecene (TCD) and 50 parts by weight of 8-methyltetracyclododecene (MTD) were used as monomers, the same operations as in step (1-1) of Example 1 were performed, A ring-opening polymer is obtained. The weight average molecular weight Mw of the ring-opening polymer is 4.0×10 ⁴ and the molecular weight distribution Mw/Mn is 2.0. The conversion rate from monomer to polymer is 100%.

Transfer 300 parts of the polymerization reaction solution containing the ring-opening polymer thus obtained to an autoclave equipped with a stirrer, and add 3 parts of nickel catalyst supported by diatomaceous earth ("T8400RL" manufactured by Nisshin Chemical Co., Ltd., nickel bearing rate 57%) The hydrogenation reaction was carried out at a hydrogen pressure of 4.5 MPa and 160°C for 4 hours.

After the hydrogenation reaction was completed, the obtained solution was pressure-filtered at a pressure of 0.25 MPa using a RADIOLITE #500 as a filter bed ("FUNDABAC Filter" manufactured by Ishikawashima Harima Heavy Industry Co., Ltd.) to remove the hydrogenation catalyst to obtain a colorless and transparent solution. The obtained solution was poured into a large amount of isopropyl alcohol to precipitate the polymer. After filtering out the precipitated polymer, it was dried with a vacuum dryer (220°C, 1 Torr) for 6 hours to obtain the aforementioned ring-opened polymer hydride. The glass transition temperature Tg of the hydride of the ring-opening polymer was 158°C.

Dissolve 28 parts by weight of the hydride of the ring-opening polymer, 10 parts by weight of maleic anhydride and 3 parts by weight of dicumyl peroxide in 130 parts by weight of tertiary butylbenzene and react at 140°C 6 hours. The obtained reaction product solution was poured into methanol to coagulate the reaction product. The condensate was dried with a vacuum dryer (220°C, 1 Torr) for 6 hours to obtain a hydrogenated ring-opening polymer modified maleic acid. Hereinafter, this maleic acid modified ring-opening polymer hydride is sometimes referred to as "polar COP". The maleic acid content of the polar COP is 25 mol%.

In the aforementioned step (1-3), the aforementioned polar COP is used as the resin of the material before stretching.

In the aforementioned step (1-4), the longitudinal stretch magnification is changed to 1.62 times, and the lateral stretch magnification is changed to 1.82 times. In addition, in the aforementioned step (1-4), the elongation temperature in the vertical and horizontal directions is changed to 180°C, which is 10°C higher than the glass transition temperature Tg of the hydrogenated maleic acid-modified ring-opening polymer. Temperature (Tg + 10°C).

Except for the above matters, the manufacturing and evaluation of the optical film and the liquid crystal display device were performed by the same operation as in Example 1.

[result]

The results of the foregoing examples and comparative examples are disclosed in Tables 1 and 2 below. In Tables 1 and 2 below, the meaning of the abbreviations is as follows. "T" in the monomer column: tetracyclododecene (TCD). "D" in the monomer column: dicyclopentadiene (DCPD). "N" in the single column: NB (NB). "E" in the monomer column: ethylene tetracyclododecene (ETD). "M" in the single column: Metabride Tetrahydrofluorene (MTF). Rth change rate (85°C): The change rate of the retardation in the thickness direction of the optical film obtained through a durability test stored at 85°C for 500 hours. Rth change rate (90% at 60°C): The change rate of the retardation in the thickness direction of the optical film obtained through a durability test stored at 60°C and 90% humidity for 500 hours.

"Table 1" [Table 1. Results of Examples]

"Table 2" [Table 2. Results of Comparative Examples]

[Reference Example 1. Appropriateness of measuring method for peel strength]

Experiments were conducted to evaluate whether it can be said that "the peel strength measurement method used in the above-mentioned examples and comparative examples reflects the evaluator of peel strength when the adherend is a polarizing plate."

The polarizing film and the adhesive were prepared by the same method as described in Example 1 of Japanese Patent Publication No. 2005-70140. In addition, the optical film obtained in Example 1 of the present application is prepared as a measurement target film. A corona treatment is applied to one side of the optical film, and the intermediary bonding agent on the corona treatment surface is attached to one surface of the polarizing film. On the other surface of the polarizing film, an intermediary bonding agent is attached to the cellulose triacetate film. After that, it was dried at 80°C for 7 minutes to cure the bonding agent to obtain a sample film. The obtained sample film was subjected to the same 90-degree peel test as described above (evaluation method of peeling of optical film). As a result, the same value as the peel strength obtained in Example 1 of the present application can be obtained.

From this result, it can be confirmed that the measurement result of the peel strength obtained by the peel strength measurement method used in the above-mentioned examples and comparative examples reflects the case where the adherend is a polarizing plate Evaluator of peel strength.

no.

no.

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Claims (8)

An optical film, which is an optical film formed of a thermoplastic resin containing a vinylene-based polymer, wherein the glass transition temperature Tg of the thermoplastic resin has a formula (1) below. The birefringence Δn _R exhibited when the thermoplastic reduced vinyl resin is uniaxially extended to 1.5 times at Tg + 15°C for 1 minute at a free end for 1 minute satisfies the following formula (2), the retardation Rth in the thickness direction of the optical film and the optical thickness d satisfies the following formula (3): (1) Tg ≧ 110 ℃, (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 aforesaid vinylene polymer is 2.4 or less. The optical film according to claim 1, wherein the aforesaid vinylene-based polymer is selected from the group consisting of a polymer containing a monomer of 25% by weight or more of tetracyclododecene-based monomer and its hydride, The aforementioned tetracyclododecene monomer is selected from the group consisting of tetracyclododecene and tetracyclododecene derivatives having a substituent bonded to the ring of tetracyclododecene. The optical film according to claim 1, wherein the photoelastic coefficient of the optical film is 8 or less Brewster. The optical film according to claim 1, wherein the in-plane retardation Re of the optical film is 40 nm or more and 80 nm or less. A method for manufacturing an optical film, which is the method for manufacturing an optical film according to any one of claims 1 to 5, comprising forming the thermoplastic vinylene resin by extrusion molding or solution casting. An optical stack including the optical film and the polarizing plate according to any one of claims 1 to 5. A liquid crystal display device comprising the optical stack according to claim 7.