TWI742219B - Optical film and polarizing plate - Google Patents

Abstract

An optical film with an absolute value of retardation in the thickness direction of 3 nm or less, an impact strength of 2×10 ⁻² J or more, and a water vapor transmission rate of 10 g/(m ² ⋅24h) or less.

Description

Optical film and polarizing plate

The present invention relates to an optical film and polarizing plate.

Generally speaking, the polarizing plate includes a polarizer and a polarizer protective film. An optical film made of resin is generally used as a polarizer protective film (refer to Patent Document 1: Japanese Patent Publication No. 2011-013378).

The polarizing plate installed in the liquid crystal display device usually has a polarizing member protective film on both sides of the polarizing member. Among these polarizer protective films, from the viewpoint of achieving good viewing angle characteristics, the inner polarizer protective film disposed on the liquid crystal cell side of the polarizer is desired to have a smaller absolute value of retardation. Here, the applicant has conducted research on an optical film made of a resin whose retardation is difficult to find in order to use it as an inner polarizer protective film.

However, an optical film formed by a resin whose retardation is hard to find is prone to breakage during film transportation, especially during trimming processing. Generally speaking, after the optical film is manufactured as a wide and long film, it is continuously transported along its longitudinal direction and various treatments are applied at the same time. However, when the finishing treatment for processing the optical film into a desired size is performed as the aforementioned treatment, the part where the finishing treatment is applied is likely to be damaged or broken. Therefore, in order to use an optical film made of a resin whose retardation is difficult to detect as an inner polarizer protective film, it is desired to improve its transportability and to be able to transport while suppressing the occurrence of breakage.

In addition, in order to be applicable to various environments, the inner polarizer protective film is preferably one that is difficult to deform in a harsh environment. Especially from the viewpoint of suppressing the deterioration of the image quality caused by the warpage of the polarizing plate or preventing the polarizing plate from falling off the device, the inner polarizer protective film can prevent the inner polarizer protective film from being equipped with the inner polarizer protective film in a high-temperature and high-humidity environment. The degree of warpage of the polarizer that is difficult to deform is desired. However, when the applicant conducted research, although it was difficult to find a resin that delays or can form a film with excellent transportability among the previous resins, it did not find a resin that can better suppress warpage in a high temperature and high humidity environment.

The present invention was conceived in view of the foregoing problems, and aims to provide an optical film with low retardation, excellent transportability, and capable of suppressing warpage in a high-temperature and high-humidity environment; and a polarizing plate provided with the foregoing optical film.

In view of the foregoing problems, the inventors have devoted themselves to the research and found that an optical film with the absolute value of the retardation in the thickness direction, the impact strength and the water vapor transmission rate within the specified range can solve the foregoing problems, and then complete the present invention.

That is, the present invention includes the following contents.

[1] An optical film with an absolute value of retardation in the thickness direction of 3 nm or less, an impact strength of 2×10 ⁻² J or more, and a water vapor transmission rate of 10 g/(m ² ⋅24h) or less.

[2] The optical film according to [1], wherein the optical film includes a core layer formed of resin C, a first surface layer formed on one side of the core layer with resin S1, and a resin S2 formed on the core layer The second surface layer on the other side; the absolute value of the thickness direction retardation of the aforementioned resin C at a thickness of 40 μm is less than 3 nm, and the impact strength of the aforementioned resin S1 at a thickness of 40 μm is 5×10 ⁻² J or more, and the impact strength of the aforementioned resin S2 at a thickness of 40 μm is 5×10 ⁻² J or more.

[3] The optical film according to [2], wherein the resin C contains a hydrogenated product of a block copolymer, and the resin S1 and the resin S2 contain an alicyclic structure-containing polymer.

[4] The optical film as described in [2] or [3], wherein the ratio of the sum of the thickness Ts1 of the first surface layer and the thickness Ts2 of the second surface layer to the thickness Tc of the core layer ((Ts1+Ts2 )/Tc) is 0.05～0.4.

[5] The optical film as described in any one of [1] to [4], which has a thickness of 50 μm or less.

[6] A polarizing plate provided with the optical film and polarizing member as described in any one of [1] to [5].

According to the present invention, it is possible to provide an optical film with low retardation, excellent transportability and capable of suppressing warpage in a high-temperature and high-humidity environment; and a polarizing plate provided with the aforementioned optical film.

Hereinafter, the embodiments and examples of the present invention will be disclosed for detailed description. However, the present invention is not limited to the embodiments and examples disclosed below, and can be arbitrarily changed and implemented without departing from the scope of the present invention's patent application and its equivalent scope.

In the following description, unless otherwise noted, the in-plane retardation Re of the film or layer is the value represented by Re=(nx−ny)×d. In addition, unless otherwise noted, the thickness direction retardation Rth of the film or layer is the value represented by Rth=[(nx+ny)/2−nz]×d. Here, nx represents the refractive index in the direction perpendicular to the thickness direction of the film or layer (in-plane direction) and in the direction that gives the maximum refractive index. ny represents the refractive index of the aforementioned in-plane direction of the film or layer and the direction orthogonal to the direction of nx. nz represents the refractive index in the thickness direction of the film or layer. d represents the thickness of the film or layer. Unless otherwise noted, the measurement wavelength of retardation is 590 nm.

In the following description, unless otherwise noted, the so-called "polarizing plate" is not only a rigid component, but also includes a flexible component such as a resin film.

In the following description, the so-called "long strip" film refers to a film having a length of 5 times or more relative to the width of the film, preferably having a length of 10 times or more. Specifically, it is referred to as having a length that is wound into a roll. Film with the length of storage or transportation. The upper limit of the length of the long film is not particularly limited. For example, it may be 100,000 times or less relative to the width of the film.

In the following description, unless otherwise noted, the so-called inclination direction of a plane means a direction neither parallel nor perpendicular to the plane. Specifically, it means that the polar angle of the aforementioned plane is greater than 0° and less than 90° The direction of the range.

In the following description, unless otherwise noted, the so-called cyclic hydrocarbon group means an aromatic ring, cycloalkane, cycloalkene, and other cyclic structure-containing hydrocarbon groups, and the so-called chain hydrocarbon compound means a hydrocarbon compound that does not contain the cyclic hydrocarbon group.

[1. Overview of optical film]

In the optical film of the present invention, (ii) the absolute value of the retardation in the thickness direction, (iii) the impact strength and (iv) the water vapor transmission rate are within the specified range.

Specifically, the absolute value of the retardation in the thickness direction of the optical film is usually 3 nm or less, preferably 2 nm or less, preferably 1.5 nm or less, and more preferably 1.0 nm or less.

The aforementioned optical film with a small absolute value of retardation in the thickness direction can improve the viewing angle characteristics of a liquid crystal display device equipped with the polarizer when used as a protective film for the inner polarizer of a polarizer. In particular, such an optical film can be used as a protective film for the inner polarizer of the viewing surface of the liquid crystal cell of an In-Plane Switching (IPS) type liquid crystal display device, and it can achieve significant effects. Specifically, when the display surface of the liquid crystal display device is viewed from the oblique direction of the display surface, unintended coloring of the image can be suppressed.

In addition, the optical film of the present invention preferably has an absolute value of (i) in-plane retardation within a specified range. Specifically, the absolute value of the in-plane retardation of the optical film is preferably 6 nm or less, preferably 3 nm or less, more preferably 2 nm or less, among them, it is preferably 1.5 nm or less, especially 1.0 nm or less good. Both the absolute value of the retardation in the thickness direction and the absolute value of the in-plane retardation are such small optical films, which can significantly improve the viewing angle characteristics obtained when used as the protective film for the inner polarizer of the polarizing plate.

The in-plane retardation and thickness direction retardation of the film can be measured at a wavelength of 590 nm using "AxoScan" manufactured by AXOMETRICS as a measuring device. In the case of measuring the retardation in the thickness direction of the film using the aforementioned measuring device, the average refractive index of the film is used. Here, the so-called average refractive index refers to the average value of the refractive index in the two directions perpendicular to each other in the in-plane direction of the film and the refractive index in the thickness direction of the film. In addition, in the case of a multilayer film having multiple films with different average refractive indexes, the average refractive index of the multilayer film may be a weighted average of the average refractive indexes of the layers contained in the multilayer film based on the layer thickness ratio.

The impact strength of the optical film is usually 2×10 ⁻² J or more, preferably 4.0×10 ⁻² J or more, and 6.0×10 ⁻² J or more. Such an optical film with high impact strength is difficult to break due to the impact during film transportation, for example, it is difficult to break and break during the trimming process. Therefore, the optical film with such high impact strength has excellent transportability, and can be transported smoothly while suppressing the occurrence of breakage. Although the impact strength of the optical film is larger, the better, but from the viewpoint of thinning the optical film and the ease of manufacture, 30×10 ⁻² J or less is preferable, and 25×10 ⁻² J or less is preferable ^{, Preferably} less than 20×10 −2 J.

The impact strength can be measured by performing an impact test using a specified striker on the film fixed by the jig. Considering that the thickness of the film is small, it is better not to use a commercially available impact tester, but to measure the impact strength as described in the column of the evaluation item in the embodiment.

The water vapor transmission rate of optical film is usually 10 g/(m ² ⋅24h) or less, preferably 8 g/(m ² ⋅24h) or less, and preferably 6 g/(m ² ⋅24h) or less. For an optical film with such a low water vapor transmission rate in a high-temperature and high-humidity environment, the optical film itself is difficult to deform. Moreover, when this optical film is used as a polarizer protective film, since water can be prevented from penetrating into the polarizer, the generation of stress in the polarizer due to moisture can be suppressed. Therefore, an optical film with a low water vapor transmission rate as described above can be used as an inner polarizer protective film to suppress the warpage of the polarizer provided with the inner polarizer protective film under high temperature and high humidity environments. The lower the water vapor transmission rate of the optical film, the better, and the ideal value is 0 g/(m ² ⋅24h).

The water vapor transmission rate of the optical film must be measured using a water vapor transmission measurement device ("PERMATRAN-W" manufactured by MOCON), which complies with the JIS K 7129 B method, and is measured at a temperature of 40°C and a humidity of 90%RH Measurement.

The aforementioned optical film is usually formed as a resin film. When (ii) the absolute value of the retardation in the thickness direction, (iii) the impact strength and (iv) the water vapor transmission rate fall within the above specified range, the layer structure of the optical film can be arbitrary. The optical film can be realized by, for example, combining a layer formed of a resin with low retardation and a layer formed of a resin with excellent impact strength.

[2. One implementation type of optical film]

The following will explain the specific implementation of the optical film. FIG. 1 is a schematic cross-sectional view of an optical film related to an embodiment of the present invention.

As shown in FIG. 1, an optical film 100 related to an embodiment of the present invention includes a core layer 110 formed of resin C, a first surface layer 120 formed on one side of the core layer 110 with resin S1, and a resin S2 formed on The second surface layer 130 on the other side of the core layer 110. As resin C, a resin whose absolute value of retardation is small is used. In addition, as the resins S1 and S2, resins with excellent impact strength are used. In this way, the above-mentioned optical film can be obtained by providing the core layer 110 formed by the resin C having a small absolute value of the retardation between the first surface layer 120 and the second surface layer 130 formed by the resins S1 and S2 with excellent impact strength.

Although the aforementioned optical film 100 may also include any layer, it is preferred that there is no layer between the core layer 110 and the first surface layer 120 and directly contact, and there is no layer between the core layer 110 and the second surface layer 130. Direct contact with any layer is preferred.

[3. Core layer]

The core layer is a layer formed by resin C whose absolute value of retardation is small. The absolute value of the thickness direction retardation of the resin C at a thickness of 40 μm is usually 3 nm or less, preferably 2 nm or less, preferably 1.5 nm or less, and more preferably 1.0 nm or less. By including the core layer formed by the resin C whose absolute value of the retardation in the thickness direction is so small, the absolute value of the retardation of the optical film itself can be reduced. Furthermore, from the viewpoint of particularly reducing the absolute value of the retardation of the optical film, the absolute value of the in-plane retardation of the resin C at a thickness of 40 μm is preferably 2 nm or less, preferably 1.5 nm or less. 1.0 nm or less is more preferable.

Herein, the in-plane retardation and thickness-direction retardation of resin C at a thickness of 40 μm are referred to as the in-plane retardation and thickness-direction retardation of a film with a thickness of 40 μm formed by this resin C. The in-plane retardation and thickness-direction retardation of resin C at a thickness of 40 μm can be obtained by using resin C to produce a sample film with a thickness of 40 μm and measuring the in-plane retardation and thickness-direction retardation of the sample film.

As the aforementioned resin C, a resin containing a polymer and more optionally containing optional components can be used. Among them, as the aforementioned resin, a resin containing a hydrogenated product of a block copolymer is preferable. In particular, as the hydrogenated product of this block copolymer, a polymer containing block A having a hydride unit (a) of a cyclic hydrocarbon compound and a block B having a hydride unit of a chain hydrocarbon compound (b) is particularly preferred. . Hereinafter, such a polymer may be referred to as "polymer X" as appropriate. By using the resin C containing the polymer X in this way, an optical film having the above-mentioned various characteristics can be easily obtained.

The hydride unit (a) of the cyclic hydrocarbon group-containing compound is a structural unit having the following structure: the cyclic hydrocarbon group-containing compound is polymerized, and the unit obtained by the polymerization is further hydrogenated if the unsaturated bond is present. The obtained structure. However, the hydride unit (a) of the cyclic hydrocarbon group-containing compound includes units obtained by any manufacturing method as long as it has this structure.

The cyclic hydrocarbon group-containing compound hydride unit (a) is preferably an aromatic vinyl compound hydride unit (a) having the following structure: a structure obtained by polymerizing an aromatic vinyl compound and hydrogenating the unsaturated bond. However, the aromatic vinyl compound hydride unit (a) includes units obtained by any manufacturing method as long as it has this structure.

Similar to the foregoing, in this application, for example, styrene is sometimes referred to as a styrene hydride unit with a structural unit obtained by hydrogenating its unsaturated bond. As long as the styrene hydride unit has this structure, it also includes a unit obtained by any manufacturing method.

Examples of the aromatic vinyl compound hydride unit (a) include structural units represented by the following structural formula (1).

（1）【化1】

(1)

In the structural formula (1), R ^C represents an alicyclic hydrocarbon group. For example, R ^C includes: cyclohexyls such as cyclohexyl; decahydronaphthyls and the like.

In the structural formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amide group, an amide group, and silicon Groups or chain hydrocarbon groups substituted with polar groups. Moreover, as a polar group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amido group, an amido group, or a silyl group can be mentioned, for example. Among them, from the viewpoints of heat resistance, low multi-refraction properties, and mechanical strength, hydrogen atoms and a chain hydrocarbon group having 1 to 6 carbon atoms are preferred ^{as R 1} , R ² and R ^3. As the chain hydrocarbon group, a saturated hydrocarbon group is preferred, and an alkyl group is preferred.

As a preferable specific example of the aromatic vinyl compound hydride unit (a), a structural unit represented by the following formula (1-1) can be cited. The structural unit represented by the formula (1-1) is a styrene hydride unit.

（1－1）【化2】

(1-1)

If there are stereoisomers in the exemplified cyclic hydrocarbon group-containing compound hydride unit (a), any of the stereoisomers may also be used. The hydride unit (a) of the cyclic hydrocarbon group-containing compound may be used alone or in combination of two or more in any ratio.

Although the block A preferably includes only the hydride unit (a) of the cyclic hydrocarbon group-containing compound, it may contain any unit other than the hydride unit (a) of the cyclic hydrocarbon group-containing compound. As an example of an arbitrary structural unit, the structural unit based on a vinyl compound other than the hydride unit (a) of a cyclic hydrocarbon group containing compound is mentioned. The content of any structural unit in block A is preferably 10% by weight or less, preferably 5% by weight or less, and more preferably 1% by weight or less.

The chain hydrocarbon compound hydride unit (b) is a structural unit having the following structure: a structure obtained by polymerizing a chain hydrocarbon compound, and if the unit obtained by the polymerization has an unsaturated bond, the unsaturated bond is further hydrogenated. . As long as the hydride unit (b) of the only chain hydrocarbon compound has this structure, it also includes a unit obtained by any manufacturing method.

The chain hydrocarbon compound hydride unit (b) is preferably a diene compound hydride unit (b) having the following structure: the diene compound is polymerized, and if the obtained polymer has an unsaturated bond, the unsaturated bond is hydrogenated Structure obtained by bonding. Only the diene compound hydride unit (b) includes units obtained by any manufacturing method as long as it has this structure.

Same as the foregoing, in the present application, for example, polymerizing isoprene, a structural unit having a structure obtained by hydrogenating its unsaturated bond is sometimes referred to as an isoprene hydride unit. The isoprene hydride unit also includes units obtained by any manufacturing method as long as it has this structure.

The diene compound hydride unit (b) is preferably one that polymerizes a conjugated diene compound such as a linear conjugated diene compound and has a structure obtained by hydrogenating the unsaturated bond. As an example, the structural unit represented by the following structural formula (2), and the structural unit represented by the following structural formula (3) are mentioned.

（2）【化3】

(2)

In the structural formula (2), R ⁴ to R ⁹ each independently represent a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amido group, an imino group, a silyl group or A chain hydrocarbon group substituted with a polar group. Moreover, as a polar group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amido group, an amido group, or a silyl group can be mentioned, for example. Among them, from the viewpoints of heat resistance, low multi-refraction properties, mechanical strength, etc., hydrogen atoms and a chain hydrocarbon group having 1 to 6 carbon atoms are preferably ^{R 4} to R ^9. As the chain hydrocarbon group, a saturated hydrocarbon group is preferred, and an alkyl group is preferred.

（3）【化4】

(3)

In the structural formula (3), R ¹⁰ to R ¹⁵ each independently represent a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amido group, an imino group, a silyl group, or A chain hydrocarbon group substituted with a polar group. Moreover, as a polar group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amido group, an amido group, or a silyl group can be mentioned, for example. Among them, from the viewpoints of heat resistance, low multi-refraction properties, mechanical strength, etc., hydrogen atoms and a chain hydrocarbon group having 1 to 6 carbon atoms are preferably ^{R 10} to R ^15. As the chain hydrocarbon group, a saturated hydrocarbon group is preferred, and an alkyl group is preferred.

Preferred specific examples of the diene compound hydride unit (b) include structural units represented by the following formulas (2-1) to (2-3). The structural units represented by formulas (2-1) to (2-3) are isoprene hydride units.

（2－1）

（2－2）

（2－3）【化5】

(2-1)

(2-2)

(2－3)

If there are stereoisomers in the examples of the chain hydrocarbon compound hydride unit (b), any of the stereoisomers can also be used. The chain hydrocarbon compound hydride unit (b) may be used alone or in combination of two or more in any ratio.

Although the block B is preferably composed only of the chain hydrocarbon compound hydride unit (b), it may contain any unit other than the chain hydrocarbon compound hydride unit (b). As an example of an arbitrary structural unit, the structural unit based on a vinyl compound other than a chain hydrocarbon compound hydride unit (b) is mentioned. The content of any structural unit in block B is preferably 10% by weight or less, preferably 5% by weight or less, and more preferably 1% by weight or less.

The polymer X preferably has a triblock molecular structure of one block B per molecule and two blocks A per molecule connected to its two ends. That is, the polymer X is preferably a triblock copolymer, and the triblock copolymer includes one block B per molecule; it is connected to one end of the block B and has a cyclic hydrocarbon-containing compound hydride unit (a) One block A1 per molecule; and one block A2 per molecule connected to the other end of block B and having a cyclic hydrocarbon-containing compound hydride unit (a). At this time, the block A1 and the block A2 may be the same or different.

In polymer X, the weight ratio (A/B) of block A to block B should fall within the specified range. Specifically, the weight ratio (A/B) is preferably 50/50 or more, preferably 65/35 or more, more preferably 80/20 or more, and preferably 99/1 or less, 95/5 The following is preferable, and 90/10 or less is more preferable. The weight ratio (A/B) of the block A to the block B is in the aforementioned range. The photoelastic coefficient of the polymer X is small, and the retardation discovery is small. Therefore, the core layer with a small absolute value of delay can be easily obtained.

In addition, the water vapor absorptivity of the polymer X is generally low. Therefore, by using polymer X, it is difficult for water vapor to penetrate the core layer, so an optical film with low water vapor transmission rate can be easily obtained.

The manufacturing method of the polymer X is not particularly limited, and any manufacturing method may be adopted. For example, by preparing monomers corresponding to the cyclic hydrocarbon-containing compound hydride unit (a) and the chain hydrocarbon compound hydride unit (b), polymerizing these materials, and hydrogenating the obtained polymer, the polymer X is produced.

As the monomer corresponding to the hydride unit (a) of the cyclic hydrocarbon group-containing compound, an aromatic vinyl compound can be used. As an example, styrene, α-methylstyrene, α-ethylstyrene, α-propylstyrene, α-isopropylstyrene, α-tertiary butylstyrene, 2-methylstyrene Styrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-tertiarybutylstyrene, 5- Styrenes such as tertiary butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene and 4-phenylstyrene; vinylcyclohexane and 3-methylisopropene Cyclohexane and other vinyl cyclohexanes; and 4-vinylcyclohexene, 4-isopropenylcyclohexene, 1-methyl-4-vinylcyclohexene, 1-methyl-4- Vinyl cyclohexenes such as isopropenylcyclohexene, 2-methyl-4-vinylcyclohexene, and 2-methyl-4-isopropenylcyclohexene. These monomers can be used individually by 1 type, and can also be used in combination of 2 or more types in arbitrary ratios.

Examples of the hydride unit (b) corresponding to the chain hydrocarbon compound include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene And 1,3-hexadiene and other linear conjugated dienes. These monomers can be used individually by 1 type, and can also be used in combination of 2 or more types in arbitrary ratios.

As the reaction mode of polymerization, anionic polymerization is usually used. In addition, the polymerization may be performed by any of bulk polymerization, solution polymerization, and the like. Among them, in order to continuously carry out the polymerization reaction and the hydrogenation reaction, solution polymerization is preferred.

Examples of reaction solvents for polymerization include: aliphatic hydrocarbon solvents such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; cyclopentane, cyclohexane, methyl ring Alicyclic hydrocarbon solvents such as pentane, methylcyclohexane and decalin; and aromatic hydrocarbon solvents such as benzene and toluene. Among them, if aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents are used, they can also be used as inactive solvents in the hydrogenation reaction.

The reaction solvent can be used alone or in combination of two or more in any ratio.

The reaction solvent is usually used at a ratio of 200 to 10,000 parts by weight with respect to 100 parts by weight of the total monomers.

During polymerization, a polymerization initiator is usually used. Examples of polymerization initiators include monoorganolithium such as n-butyl lithium, secondary butyl lithium, tertiary butyl lithium, hexyl lithium, and phenyl lithium; and dilithium methane and 1,4-dilithium. Multifunctional organolithium compounds such as butane and 1,4-dilithium-2-ethylcyclohexane. A polymerization initiator may be used individually by 1 type, and may be used combining 2 or more types in arbitrary ratios.

As an example of a production method in the case of producing a triblock copolymer containing block A1, block A2, and block B as polymer X, a production method including the following first to third steps can be cited. Here, the material called "monomer composition" includes not only a mixture of two or more substances, but also a material composed of a single substance.

The first step: the step of polymerizing the monomer composition (a1) containing the aromatic vinyl compound to form the block A.

The second step: at one end of the block A, the monomer composition (b) containing the diene compound is polymerized to form the block B, and then the step of forming the AB diblock polymer.

The third step: a step of polymerizing the monomer composition (a2) containing an aromatic vinyl compound at the end of the block B side of the diblocker polymer to obtain a triblock copolymer. However, the monomer composition (a1) and the monomer composition (a2) may be the same or different.

When each block is polymerized separately, in each block, a polymerization accelerator and a randomizer must be used in order to prevent the chain of a certain component from being too long. For example, in the case of polymerization by anionic polymerization, a Lewis base compound must be used as a random generator. Specific examples of Lewis base compounds include ether compounds such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, diphenyl ether, ethylene glycol diethyl ether, and ethylene glycol methyl phenyl ether. ; Tertiary amine compounds such as tetramethylethylenediamine, trimethylamine, triethylamine and pyridine; alkali metal alkoxide compounds such as potassium tertiary pentanoxide and potassium tertiary butoxide; and phosphines such as triphenylphosphine (Phosphine) compound. These materials can be used alone or in combination of two or more in any ratio.

Although the polymerization temperature is not limited as long as the polymerization can be carried out, it is usually 0°C or higher, preferably 20°C or higher, and usually 200°C or lower, preferably 100°C or lower, and preferably 80°C or lower.

After polymerization, if necessary, the polymer can be recovered from the reaction mixture by any method. Examples of the recovery method include a steam stripping method, a direct solvent removal method, and an alcohol coagulation method. In addition, when the inert solvent used in the hydrogenation reaction is used as the reaction solvent during polymerization, the polymer may not be recovered from the polymerization solution, but may be provided in the hydrogenation step as it is.

The method of hydrogenation of the polymer is not particularly limited, and any method may be adopted. For example, hydrogenation can be carried out using a suitable hydrogenation catalyst. More specifically, in an organic solvent, a hydrogenation catalyst containing at least one metal selected from the group consisting of nickel, cobalt, iron, rhodium, palladium, platinum, ruthenium, and rhenium is used for hydrogenation. The hydrogenation catalyst can be a heterogeneous catalyst or a homogeneous catalyst. The hydrogenation catalyst may be used alone or in combination of two or more in any ratio.

The heterogeneous catalyst can use a metal or a metal compound for this purpose, or it can be carried by a suitable carrier for use. Examples of the carrier include activated carbon, silica, alumina, calcium carbide, titanium dioxide, magnesium oxide, zirconium oxide, diatomaceous earth, and silicon carbide. The loading capacity of the catalyst in the carrier is usually 0.01% by weight or more, preferably 0.05% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less.

Examples of homogeneous catalysts include: catalysts that combine compounds of nickel, cobalt, or iron with organometallic compounds (for example, organoaluminum compounds, organolithium compounds); and organometals such as rhodium, palladium, platinum, ruthenium, and rhenium Complex catalyst. Examples of nickel, cobalt, or iron compounds include acetone acetonates, naphthenates, cyclopentadienyl compounds, and cyclopentadienyl dichloride compounds of these metals. Examples of organoaluminum compounds include: aluminum alkyls such as triethyl aluminum and triisobutyl aluminum; aluminum halides such as diethyl aluminum chloride and ethyl aluminum dichloride; and diisobutyl aluminum hydride. Alkyl aluminum hydride.

Examples of organometallic complex catalysts include, for example, γ-dichloro-π-benzene complexes, dichloroginseng (triphenylphosphine) complexes, and triphenylphosphine complexes of the aforementioned metals. Metal complexes such as objects.

The amount of hydrogenation catalyst used relative to 100 parts by weight of the polymer is usually 0.01 parts by weight or more, preferably 0.05 parts by weight or more, preferably 0.1 parts by weight or more, and usually 100 parts by weight or less, 50 parts by weight The following is preferable, and 30 parts by weight or less is preferable.

The reaction temperature during the hydrogenation reaction is usually 10°C to 250°C, but for the reason that the hydrogenation rate can be increased and the polymer chain scission reaction can be reduced, it is preferably 50°C or higher, and more preferably 80°C or higher. And it is preferably 200°C or less, preferably 180°C or less. In addition, although the pressure during the reaction is usually 0.1 MPa to 30 MPa, from the above-mentioned reasons plus the viewpoint of operability, 1 MPa or more is preferable, 2 MPa or more is more preferable, and 20 MPa or less is preferable Better, preferably 10 MPa or less.

The hydrogenation rate is usually 90% or more, preferably 95% or more, and more preferably 97% or more. By increasing the hydrogenation rate, the low polyrefraction and thermal stability of polymer X can be improved. The hydrogenation rate can be measured by proton nuclear magnetic resonance ( ¹ H-NMR).

The weight average molecular weight Mw of the polymer contained in resin C is preferably 50,000 or more, preferably 55,000 or more, more preferably 60,000 or more, and preferably 80,000 or less, preferably 75,000 or less, preferably 70,000 or less Better. With the weight average molecular weight Mw in the aforementioned range, an optical film with the above-mentioned characteristics can be easily obtained. In particular, by reducing the weight average molecular weight, the delay discovery can be effectively reduced.

The molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the polymer contained in resin C is preferably 2.0 or less, preferably 1.7 or less, particularly preferably 1.5 or less, and 1.0 or more good. With the weight average molecular weight Mw in the aforementioned range, the viscosity of the polymer can be reduced and the moldability can be improved. Moreover, the delay detection can be effectively reduced.

The weight average molecular weight Mw and the number average molecular weight Mn of the polymer are measured as polystyrene conversion values by gel permeation chromatography with tetrahydrofuran as a solvent.

The resin C may contain one type of polymer alone, or two or more types of polymers may be combined in any ratio.

From the viewpoint of easily obtaining the desired optical film, the proportion of the polymer in the resin C is preferably 90% by weight or more, more preferably 95% by weight or more, and particularly preferably 97% by weight or more.

Resin C may contain arbitrary components in combination with the above-mentioned polymer. Examples of optional components include inorganic fine particles; stabilizers such as antioxidants, heat stabilizers, ultraviolet absorbers, and near-infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes or pigments; and Electrostatic agent. As these arbitrary components, 1 type may be used individually, and 2 or more types may be combined and used in arbitrary ratios. However, from the viewpoint of remarkably exerting the effect of the present invention, it is better to make the content ratio of the optional component smaller. For example, the total ratio of the optional components relative to 100 parts by weight of the polymer contained in the resin C is preferably 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 3 parts by weight or less.

The water vapor transmission rate of resin C at a thickness of 40 μm is usually below 100 g/(m ² ⋅24h), preferably below 50 g/(m ² ⋅24h), and 10 g/(m ² ⋅ 24h) The following are preferred. By using resin C with such a low water vapor transmission rate, the water vapor transmission rate of the optical film itself can be reduced.

Herein, the water vapor transmission rate of resin C at a thickness of 40 μm refers to the water vapor transmission rate of a film with a thickness of 40 μm formed by this resin C. The water vapor transmission rate of resin C at a thickness of 40 μm can be obtained by using resin C to make a sample film with a thickness of 40 μm and measuring the water vapor transmission rate of the sample film.

Since the core layer is formed by resin C whose absolute value of retardation is small, the absolute value of retardation of the core layer is usually small. Specifically, the absolute value of the in-plane retardation of the core layer is preferably 2 nm or less, preferably 1.0 nm or less, and more preferably 0.5 nm or less. In addition, the absolute value of the thickness direction retardation of the core layer is preferably 2 nm or less, preferably 1.0 nm or less, and more preferably 0.5 nm or less.

The in-plane retardation and thickness direction retardation of the layer contained in the film can be calculated from the R0 and R40 of the film, the R0 and R40 of the sample film with a part of the layer removed from the film, and the average refractive index of the layer. Here, the so-called R0 represents the retardation measured in the normal direction of the main surface of the film, and represents the in-plane retardation of the film. In addition, the so-called R40 represents the retardation measured in the direction of an angle of 40° with respect to the normal direction of the main surface of the film. These R0 and R40 have to be measured at a wavelength of 590 nm using "AxoScan" manufactured by AXOMETRICS as a measuring device. Furthermore, the average refractive index of the layer contained in the film can be obtained by manufacturing a sample film using the resin contained in the layer and measuring the refractive index of the sample film.

The thickness of the core layer is preferably 20 μm or more, preferably 25 μm or more, more preferably 30 μm or more, and preferably 80 μm or less, preferably 60 μm or less, more preferably 40 μm or less . When the thickness of the core layer is above the lower limit of the aforementioned range, the retardation value can be reduced, and by being below the upper limit of the aforementioned range, the optical film can be thinned.

In addition, the ratio of the sum of the thickness Ts1 of the first surface layer and the thickness Ts2 of the second surface layer to the thickness Tc of the core layer ((Ts1+Ts2)/Tc) should preferably fall within the specified range (refer to FIG. 1). Specifically, the ratio of the aforementioned thickness ((Ts1+Ts2)/Tc) is preferably 0.05 or more, preferably 0.15 or more, more preferably 0.25 or more, and preferably 0.4 or less, preferably 0.38 or less , Preferably 0.35 or less. By the ratio of the aforementioned thickness ((Ts1+Ts2)/Tc) above the lower limit of the aforementioned range, the impact resistance of the optical film can be effectively improved, and by being below the upper limit of the aforementioned range, the optical film can be effectively reduced. The absolute value of the retardation of the film.

[4. The first surface layer]

The first surface layer is a layered body formed on one side of the core layer with resin S1 having excellent impact strength. The impact strength of this resin S1 at a thickness of 40 μm is preferably 5×10 ⁻² J or more, preferably 7×10 ⁻² J or more, and more preferably 9×10 ⁻² J or more. By combining the first surface layer formed by resin S1 with such excellent impact strength and the second surface layer formed by resin S2 having the same excellent impact strength, the impact strength of the optical film itself can be improved. From the viewpoint of ease of manufacturing optical films, the upper limit of the impact strength of resin S1 at a thickness of 40 μm is ^{preferably 30×10 −2} J or less, preferably 25×10 ⁻² J or less. 20×10 ⁻² J or less is better.

Here, the so-called impact strength of resin S1 at a thickness of 40 μm refers to the impact strength of a film with a thickness of 40 μm formed by this resin S1. The impact strength of the resin S1 at a thickness of 40 μm can be obtained by using the resin S1 to make a sample film with a thickness of 40 μm and measuring the impact strength of the sample film.

As the aforementioned resin S1, a resin containing a polymer and more optionally containing any components can be used. Among them, as the aforementioned resin, a resin containing an alicyclic structure-containing polymer is preferred. Hereinafter, the alicyclic structure-containing polymer may be appropriately referred to as the "alicyclic structure-containing polymer". The alicyclic structure polymer has excellent mechanical strength, so it can effectively improve the impact strength of the optical film. In addition, the alicyclic structure-containing polymer has low hygroscopicity, so it can effectively reduce the water vapor transmission rate of the optical film. Furthermore, alicyclic structure-containing polymers generally have excellent transparency, dimensional stability, and light weight.

The alicyclic structure-containing polymer is a polymer with an alicyclic structure in the repeating unit. For example, a polymer obtained by a polymerization reaction using a cycloolefin as a monomer or a hydrogenated product thereof can be cited. Furthermore, as the aforementioned alicyclic structure-containing polymer, it can be used for any of a polymer containing an alicyclic structure in the main chain and a polymer containing an alicyclic structure in the side chain. The alicyclic structure includes, for example, a cycloalkane structure, a cycloalkene structure, etc., but from the viewpoint of thermal stability and the like, a cycloalkane structure is preferred.

The number of carbons contained in an alicyclic structure is preferably 4 or more, preferably 5 or more, more preferably 6 or more, and preferably 30 or less, preferably 20 or less, preferably 15 The following is better. As the number of carbons contained in an alicyclic structure is within the above range, a high balance of mechanical strength, heat resistance and formability can be achieved.

The proportion of repeating units with alicyclic structure in the alicyclic structure-containing polymer is preferably 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, especially 90% by weight or more Better. By increasing the ratio of repeating units having an alicyclic structure, for example, as described above, heat resistance can be improved.

In addition, in the alicyclic structure-containing polymer, the remainder other than the structural unit having the alicyclic structure is not particularly limited, and may be appropriately selected depending on the purpose of use.

As the alicyclic structure-containing polymer, any one of crystalline and non-crystalline can be used, or a combination of the two can be used. Herein, the so-called crystalline polymer is referred to as a polymer having a melting point Mp. In addition, the so-called polymer having a melting point Mp can also be a polymer having a melting point Mp observed by a differential scanning calorimeter (DSC). By using a crystalline polymer containing alicyclic structure, the impact strength of the optical film can be particularly improved. Moreover, by using a non-crystalline polymer containing alicyclic structure, the manufacturing cost of the optical film can be reduced.

Examples of the crystalline alicyclic structure-containing polymer include the following polymers (α) to (δ). Among them, since it is easy to obtain optical films with excellent heat resistance, it is better to use polymer (β) as a crystalline alicyclic structure polymer. Polymer (α): a ring-opening polymer of crystalline cycloolefin monomer. Polymer (β): Hydrogenated product of crystalline polymer (α). Polymer (γ): addition polymer of crystalline cycloolefin monomer. Polymer (δ): Hydrogenated product of crystalline polymer (γ).

Specifically, as a crystalline polymer containing alicyclic structure, it includes crystalline dicyclopentadiene ring-opening polymer and crystalline dicyclopentadiene ring-opening polymer hydride Preferably, the hydrogenated product of a ring-opening polymer of dicyclopentadiene with crystallinity is preferred. Here, the so-called ring-opening polymer of dicyclopentadiene means that the ratio of the structural units derived from dicyclopentadiene relative to the total structural units is usually 50% by weight or more, preferably 70% by weight or more. 90% by weight or more is preferable, and 100% by weight is a more preferable polymer.

Before manufacturing the optical film, the crystalline alicyclic structure-containing polymer can also be uncrystallized. However, after the optical film has been manufactured, the crystalline alicyclic structure-containing polymer contained in the optical film usually has a high degree of crystallinity by crystallization. The specific crystallinity range can be appropriately selected according to the desired performance, but it is preferably 10% or more, and more preferably 15% or more. By setting the crystallinity of the alicyclic structure-containing polymer contained in the optical film to be more than the lower limit of the aforementioned range, it is possible to impart high heat resistance and chemical resistance to the optical film. The degree of crystallinity is measured by X-ray diffraction method.

The melting point Mp of the crystalline alicyclic structure-containing polymer is preferably 200°C or higher, preferably 230°C or higher, and preferably 290°C or lower. By using a crystalline alicyclic structure-containing polymer having such a melting point Mp, an optical film with a more excellent balance between moldability and heat resistance can be obtained.

The crystalline alicyclic structure-containing polymer as described above can be produced by, for example, the method described in International Patent Publication No. 2016/067893.

On the other hand, non-crystalline polymers containing alicyclic structures include, for example: (1) norbornene polymers, (2) monocyclic cycloolefin polymers, (3) cyclic conjugated two Vinyl polymers, (4) vinyl alicyclic hydrocarbon polymers and hydrogenated products of these. Among them, from the viewpoints of transparency and moldability, norene-based polymers and their hydrogenated products are preferred.

Examples of norrene-based polymers include: ring-opening polymers of norrene monomers, ring-opening copolymers formed by norrene monomers and other monomers capable of ring-opening copolymerization, and hydrogenated products of these ; Addition polymers of norene monomers, addition copolymers of norene monomers and other monomers that can be copolymerized, etc. Among them, from the viewpoint of transparency, hydrogenated products of ring-opening polymers of norene monomers are particularly preferred.

The aforementioned alicyclic structure-containing polymer can be selected from, for example, those disclosed in Japanese Patent Publication No. 2002-321302.

As a non-crystalline alicyclic structure-containing polymer, there are various products on the market, so it is necessary to appropriately select those with desired characteristics among them and use them. As an example of this commercially available product, there may be mentioned the trade names "ZEONOR" (manufactured by Zeon Corporation), "ARTON" (manufactured by JSR Co., Ltd.), "APEL" (manufactured by Mitsui Chemicals Co., Ltd.), and " "TOPAS" (manufactured by POLYPLASTICS Co., Ltd.) is a product group.

The glass transition temperature Tg of the polymer contained in the resin S1 is preferably 80°C or higher, preferably 85°C or higher, more preferably 100°C or higher, and preferably 250°C or lower, preferably 170°C or lower . A polymer with a glass transition temperature in this range is unlikely to be deformed and stressed when used at high temperatures, and has excellent durability.

The weight average molecular weight (Mw) of the polymer contained in the resin S1 is preferably 1,000 or more, preferably 2,000 or more, more preferably 10,000 or more, especially 25,000 or more, and preferably 1,000,000 or less, preferably 500,000 The following are preferable, and 100,000 or less is more preferable, among which 80,000 or less is preferable, and 50,000 or less is particularly preferable. A polymer with such a weight average molecular weight has an excellent balance between molding processability and heat resistance.

The molecular weight distribution (Mw/Mn) of the polymer contained in the resin S1 is preferably 1.0 or more, preferably 1.2 or more, more preferably 1.5 or more, and preferably 10 or less, preferably 4.0 or less, 3.5 or less is better. Here, Mn represents the number average molecular weight. A polymer having such a molecular weight distribution has excellent molding processability.

The resin S1 may contain one type of polymer alone, or two or more types of polymers may be combined in any ratio.

From the viewpoint of easily obtaining the desired optical film, the proportion of the polymer in the resin S1 is preferably 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, especially 90% by weight The above is better.

Resin S1 may contain arbitrary components in combination with the above-mentioned polymer. As an example of the optional component, the same example as the optional component contained as the resin C has been exemplified. In addition, the arbitrary component may be used individually by 1 type, and may be used in combination of 2 or more types in arbitrary ratios. However, from the viewpoint of remarkably exerting the effects of the present invention, the content ratio of the optional components is preferably smaller. For example, the total proportion of the arbitrary components relative to 100 parts by weight of the polymer contained in the resin S1 is preferably 50 parts by weight or less, preferably 30 parts by weight or less, more preferably 20 parts by weight or less, especially 10 parts by weight or less is preferable.

The water vapor transmission rate of resin S1 at a thickness of 40 μm is usually below 100 g/(m ² ⋅24h), preferably below 50 g/(m ² ⋅24h), and 10 g/(m ² ⋅ 24h) The following are preferred. By using resin S1 with such a low water vapor transmission rate, the water vapor transmission rate of the optical film itself can be reduced.

Herein, the water vapor transmission rate of the resin S1 at a thickness of 40 μm refers to the water vapor transmission rate of a film with a thickness of 40 μm formed by the resin S1. The water vapor transmission rate of the resin S1 at a thickness of 40 μm can be obtained by manufacturing a sample film with a thickness of 40 μm using the resin S1 and measuring the water vapor transmission rate of the sample film.

From the viewpoint of obtaining an optical film with a small absolute value of retardation, it is better that the absolute value of the retardation of the first surface layer is small. Specifically, the absolute value of the in-plane retardation of the first surface layer is preferably 2 nm or less, preferably 1.5 nm or less, and more preferably 1.0 nm or less. In addition, the absolute value of the retardation in the thickness direction of the first surface layer is preferably 2.0 nm or less, preferably 1.5 nm or less, and more preferably 1.0 nm or less.

The thickness of the first surface layer is preferably 1.0 μm or more, preferably 2.0 μm or more, more preferably 3.0 μm or more, and preferably 9 μm or less, preferably 7 μm or less, more preferably 5 μm or less good. Since the thickness of the first surface layer is above the lower limit of the aforementioned range, the impact strength of the optical film can be effectively increased, and by being below the upper limit of the aforementioned range, the absolute value of the retardation of the optical film can be effectively reduced.

[5. The second surface layer]

The second surface layer is a layer body formed on the other side of the core layer with resin S2 with excellent impact strength. The impact strength of the resin S2 at a thickness of 40 μm is in the same range as the impact strength of the resin S1 at a thickness of 40 μm. However, the impact strength of resin S2 at a thickness of 40 μm can be the same as or different from that of resin S1 at a thickness of 40 μm. By combining the second surface layer formed of resin S2 having such excellent impact strength and the first surface layer formed of resin S1 having such excellent impact strength, the impact strength of the optical film itself can be improved.

Here, the so-called impact strength of resin S2 at a thickness of 40 μm refers to the impact strength of a film with a thickness of 40 μm formed by this resin S2. The impact strength of resin S2 at a thickness of 40 μm can be measured by the same method as the impact strength of resin S1 at a thickness of 40 μm.

As the aforementioned resin S2, it is possible to arbitrarily use what has been described as the range of the resin S1. Thereby, the same effect as that caused by the first surface layer can be obtained from the second surface layer. Although the resin S1 contained in the first surface layer and the resin S2 contained in the second surface layer may be different, the same ones are preferred from the viewpoints of suppressing the manufacturing cost of the optical film and suppressing warpage.

From the viewpoint of obtaining an optical film with a small absolute value of retardation, it is better that the absolute value of the retardation of the second surface layer is small. The absolute value of the specific in-plane retardation of the second surface layer is in the same range as the range of the absolute value of the in-plane retardation of the first surface layer. Moreover, the absolute value of the specific thickness direction retardation of the second surface layer is in the same range as the range of the absolute value of the thickness direction retardation of the first surface layer.

From the same viewpoint as the first surface layer, the thickness of the second surface layer should be in the same range as the thickness of the first surface layer. Thereby, the same effect as the first surface layer can be obtained in the second surface layer. Although the thickness of the first surface layer and the thickness of the second surface layer may be different, from the viewpoint of effectively suppressing the warpage of the optical film, the same one is preferred.

[6. Any layer body]

The optical film may have any combination of layers in the core layer, the first surface layer and the second surface layer as required. Examples of any layer include: hard coat layer to increase the surface hardness of the film, mat layer to optimize the smoothness of the film, and anti-reflection layer. However, from the viewpoint of thinning the optical film, it is preferable that the optical film does not have any layer. Therefore, the optical film is particularly preferably only provided with the first surface layer, the core layer and the second surface layer in this order.

[7. Physical properties and thickness of optical film]

Optical films are usually transparent films that allow visible light to pass through. The specific light transmittance can be appropriately selected depending on the use of the optical film. For example, the light transmittance at a wavelength of 420 nm to 780 nm is preferably 85% or more, preferably 88% or more.

The thickness of the optical film is preferably 5 μm or more, preferably 15 μm or more, more preferably 25 μm or more, and preferably 50 μm or less, preferably 45 μm or less, more preferably 40 μm or less . As the thickness of the optical film is above the lower limit of the aforementioned range, the impact strength of the optical film can be effectively increased, or the water vapor transmission rate can be effectively reduced. Moreover, since the thickness of the optical film is below the upper limit of the aforementioned range, the absolute value of the retardation of the optical film can be effectively reduced.

[8. Manufacturing method of optical film]

The manufacturing method of the optical film is not particularly limited, and any manufacturing method may be adopted. For example, resin C, resin S1, and resin S2 are prepared, and these materials are formed into desired shapes to produce optical films. As a preferable example of the molding method for molding the resin C, the resin S2, and the resin S2, melt extrusion molding by a co-extrusion method can be cited. By performing this melt extrusion forming, an optical film with a desired thickness of each layer can be manufactured efficiently.

The temperature of the resin at the time of melt extrusion molding by the co-extrusion method (hereinafter sometimes referred to as the "extrusion temperature") is not particularly limited, and may be the temperature at which each resin is melted, and may be set appropriately Suitable temperature for forming. Specifically, Tg+80°C or higher is preferred, Tg+100°C or higher is preferred, Tg+180°C or lower is preferred, and Tg+170°C or lower is preferred. Here, "Tg" represents the highest temperature among the glass transition temperatures of resin C, resin S1, and resin S2. By setting the extrusion temperature above the lower limit of the aforementioned range, the fluidity of the resin can be sufficiently improved and the moldability can be optimized, and by setting the extrusion temperature below the upper limit of the aforementioned range, the deterioration of the resin can be suppressed.

By forming the resin C, the resin S1 and the resin S2 as described above into layers, it is possible to obtain a layered body formed of resin S1, a layered body formed of resin C, and a layered body formed of resin C in order along the thickness direction. S2 is a layered multilayer film. This multilayer film is usually obtained as a long film. The multilayer film thus obtained can be used as an optical film as it is. In addition, the aforementioned multilayer film can also be subjected to arbitrary treatments as required, and the obtained one can be used as an optical film.

[9. Use of optical film]

The above-mentioned optical film can be suitably used as a protective film for protecting other layers in display devices such as liquid crystal display devices. Among them, the optical film is suitable as a protective film for polarizers, and is particularly suitable for a protective film for inner polarizers of display devices.

In one embodiment, the polarizer includes a polarizer and the above-mentioned optical film. The optical film functions as a polarizer protective film in the polarizing plate. The polarizing plate can also be further provided with a bonding agent layer between the optical film and the polarizing element for bonding the two.

The polarizer is not particularly limited, and any polarizer may be used. As an example of a polarizer, a polyvinyl alcohol film adsorbs iodine, dichroic dyes, and other materials and then stretches it. Examples of the bonding agent constituting the bonding agent layer include those using various polymers as the base polymer. As an example of this base polymer, for example, acrylic polymer, silicone polymer, polyester, polyurethane, polyether, and synthetic rubber can be cited.

Although the number of polarizers and protective films provided in the polarizer is arbitrary, the polarizer usually has one layer of polarizer and two layers of protective films provided on both sides of the polarizer. In the two-layer protective film, both of them may be the above-mentioned optical film, or only one of them may be the above-mentioned optical film. Especially in a liquid crystal display device equipped with a light source and a liquid crystal cell and having polarizing plates on both the light source side and the display surface side of the liquid crystal cell, an optical film is particularly provided as a protective film used in the position on the light source side. The protective film used for the polarizer that is not on the side of the display surface is better. By having this structure, it is easy to construct a liquid crystal display device with good display quality with oblique viewing angle light leakage and small color unevenness.

As a liquid crystal display device with the aforementioned polarizing plate appropriately arranged, for example, an in-plane switching (In-Plane Switching, IPS) mode, a vertical alignment (Vertical Alignment, VA) mode, and a multi-domain vertical alignment (Multi-domain Vertical Alignment, MVA) can be cited. ) Mode, Continuous Pinwheel Alignment (CPA) mode, Hybrid Alignment Nematic (HAN) mode, Twisted Nematic (TN) mode, Super-Twisted Nematic, STN) mode, optical compensated bend (Optical Compensated Bend, OCB) mode and other driving methods of the liquid crystal display device of the liquid crystal cell, in which the oblique viewing angle caused by the optical film has a significant effect of suppressing light leakage and color unevenness, and it is especially equipped with IPS The liquid crystal display device of the liquid crystal cell of the mode is preferred.

[Example]

Hereinafter, embodiments will be disclosed and the present invention will be specifically described. However, the present invention is not limited to the embodiments disclosed below, and can be implemented with any changes within the scope of the patent application and the equivalent scope of the present invention.

In the following description, unless otherwise noted, the "%" and "parts" of the weight are based on weight. Moreover, unless otherwise noted, the operations described below are performed in an atmosphere of normal temperature and pressure.

[Evaluation method]

[Measuring method of molecular weight]

The weight average molecular weight and number average molecular weight of the polymer are measured at 38°C as a standard polystyrene conversion value determined by gel permeation chromatography with tetrahydrofuran as the eluent. As a measuring device, HLC8020GPC manufactured by TOSOH can be used.

[Measurement method of glass transition temperature and melting point Mp]

The sample heated to 300°C in a nitrogen atmosphere is rapidly cooled with liquid nitrogen, and the glass transition temperature Tg and melting point Mp of the sample heated at 10°C/min are calculated using a differential scanning calorimeter (DSC).

[Measuring method of hydrogenation rate]

The hydrogenation rate of the polymer was ^{measured by 1} H-NMR measurement at 145°C ^{using o-dichlorobenzene-d 4 as a solvent.}

[Method for measuring the proportion of racemic diunits in polymers]

Using o-dichlorobenzene-d ⁴ as the solvent, the inverse-gated decoupling method was applied to carry out the ¹³ C-NMR measurement of the polymer at 200°C. In ^{the result of 13} C-NMR measurement, ^{the 127.5 ppm peak value of o-dichlorobenzene-d 4} was used as the reference offset to determine the 43.35 ppm signal derived from the meso group and the signal derived from the racem group. The signal of 43.43ppm of the unit group. Based on the intensity ratio of these signals, the ratio of the racemic diad of the polymer is obtained.

[Measuring method of layer thickness]

After embedding the optical film in epoxy resin, it was sliced into a thickness of 0.05 μm using a microtome ("RUB-2100" manufactured by Daiwa Koki Kogyo Co., Ltd.). A transmission electron microscope was used to observe the presented cross-section, and to measure the thickness of each layer contained in the optical film.

[Measurement method of impact strength]

Fig. 2 is a perspective view schematically showing an apparatus for measuring the impact strength of optical films used in Examples and Comparative Examples. In addition, FIG. 3 is a cross-sectional view schematically showing a measuring device for the impact strength of optical films used in Examples and Comparative Examples. The impact strength of the optical film was measured using the measuring devices shown in FIGS. 2 to 3.

The film 10a, which is a test piece, is horizontally fixed by a jig provided with an upper clamp ring 201 and a lower clamp ring 202 formed into a hollow cylindrical shape. The inner diameter of the upper clamp ring 201 and the lower clamp ring 202 (indicated by arrow A3) is 4 cm. Make the steel ball 211 (pinball ball, weight 5g, diameter 11 mm) used as a ram to fall freely from various heights in the direction of arrow A1, and fall into the upper surface 10U of the film 10a fixed on the jig. The position on the central axis of the inner is 15P. The aforementioned height h represents the distance between the lowermost horizontal plane H1 of the steel ball 211 and the upper surface 10U of the film 10a. This height is indicated by arrow A2 in Figure 3. Investigate the height h of the boundary between the unbroken condition of the film 10a and the broken condition of the film 10a. Moreover, the position of the steel ball 211 at the height of the aforementioned boundary line is determined as the impact strength.

[Evaluation method of transportability of optical film]

4 is a cross-sectional view schematically showing a cross section of the trimming blades 1 and 2 used in the embodiment and the comparative example cut along a plane perpendicular to the film conveying direction.

In the following Examples and Comparative Examples, the optical film is trimmed while the optical film is transported horizontally. This correction is performed by combining the circular dish-shaped blade 1 arranged above the gravity direction of the optical film 3 and the bowl-shaped blade 2 arranged below the gravity direction of the optical film 3 as shown in FIG. 4. In addition, the combination of the aforementioned dish-shaped blade 1 and the bowl-shaped blade 2 is arranged such that the outer periphery of the bowl-shaped blade 2 is in contact with the optical film 3. Furthermore, the aforementioned combination of the bowl-shaped blade 1 and the bowl-shaped blade 2 is provided at both ends of the optical film 3 in the width direction each in one group, and a total of two groups are provided. In the dressing using the dish-shaped blade 1 and the bowl-shaped blade 2 in this way, the continuous dressing of the optical film 3 is achieved in the part that enters between the dish-shaped blade 1 and the bowl-shaped blade 2.

The optical film 3 is trimmed for 30 minutes while the optical film 3 is transported along its longitudinal direction at a transport speed of 5 m/min. Then, if the optical film 3 is not broken or broken, it is judged as "good", and the optical film 3 is judged as "bad" if it is broken due to the breakage caused by trimming. Herein, the so-called breakage of the optical film 3 refers to a phenomenon in which the optical film 3 is broken in a direction other than the longitudinal direction as its conveying direction.

[Delay measurement method]

Prepare the pellets of the resin contained in each layer of the optical film. The pellets of each resin were melt-extruded to form a sample film. Using a refractive index film thickness measuring device ("Fu Coupler" manufactured by METRICON), the refractive index of the sample film was measured at measurement wavelengths of 405 nm, 532 nm and 633 nm. For these measured values obtained at the measurement wavelengths of 405 nm, 532 nm and 633 nm, the refractive index at the measurement wavelength of 590 nm is calculated by fitting to the Cauchy dispersion formula.

The aforementioned measurement of the refractive index at a wavelength of 590 nm was performed along the extrusion direction of the sample film, the in-plane direction perpendicular to the aforementioned extrusion direction, and the thickness direction. Then, the average refractive index of the sample film at a wavelength of 590 nm was obtained as the average of the refractive index of the aforementioned extrusion direction, the in-plane direction perpendicular to the aforementioned extrusion direction, and the thickness direction, and this was determined as the corresponding sample The average refractive index of the layer of the film.

The average refractive index n _total of the optical film is calculated as the weighted average of the average refractive index of each layer contained in the optical film based on the thickness ratio of the layer. _{Specifically, the average refractive index n total of the} optical film at the measurement wavelength of 590 nm is calculated from the following formula (X). n _total =n _s1 ×[d _s1 /(d _s1 +d _c +d _s2 )]+n _c ×[d _c /(d _s1 +d _c +d _s2 )]+n _s2 ×[d _s2 /(d _s1 +d _c +d _s2 )] (X) (In the aforementioned formula (X), n _s1 represents the average refractive index of the first surface layer at the measurement wavelength of 590 nm, d _s1 represents the thickness of the first surface layer, and n _c represents The average refractive index of the core layer at the measurement wavelength of 590 nm, d _c represents the thickness of the core layer, n _s2 represents the average refractive index of the second surface layer at the measurement wavelength of 590 nm, and d _s2 represents the thickness of the second surface layer.)

Use a measuring device ("AxoScan" manufactured by AXOMETRICS) to measure R0 and R40 of the optical film at a measuring wavelength of 590 nm.

From the R0 and R40 of the aforementioned optical film and the average refractive index n _total of the optical film, the thickness direction retardation of the optical film at a wavelength of 590 nm is calculated.

In addition, sandpaper #100 was used to remove the first surface layer from the optical film, and the surface was polished with sandpaper #2000 to obtain a sample film including a core layer and a second surface layer. Calculate the average refractive index _nave of the sample film as a weighted average of the average refractive index of each layer contained in the sample film based on the layer thickness ratio. _{Specifically, the average refractive index nave of the} sample film at the measurement wavelength of 590 nm was calculated from the following formula (Y). n _ave =n _c ×[d _c /(d _c +d _s2 )]+n _s2 ×[d _s2 /(d _c +d _s2 )] (Y) (In the aforementioned formula (Y), the meaning of the symbol is the same as that of the formula (X) Same.)

Use a measuring device ("AxoScan" manufactured by AXOMETRICS) to measure the R0 and R40 of the sample film at a measuring wavelength of 590 nm.

From the R0 and R40 of the sample film and the average refractive index _nave of the sample film, the in-plane retardation and thickness direction retardation of the sample film with a wavelength of 590 nm are calculated. Furthermore, the in-plane retardation and thickness direction retardation of the optical film including the first surface layer are subtracted from the in-plane retardation and thickness direction retardation of the sample film not including the first surface layer to obtain the in-plane retardation of the first surface layer And the thickness direction is retarded.

Furthermore, the second surface layer was removed from the sample film with sandpaper #100, and the surface was polished with sandpaper #2000 to obtain the core layer. The in-plane retardation and thickness direction retardation of the core layer at a wavelength of 590 nm are calculated from the R0 and R40 of the core layer and the average refractive index n _{c of the core layer.}

And, by subtracting the in-plane retardation and the thickness direction retardation of the core layer from the in-plane retardation and the thickness direction retardation of the sample film including the second surface layer, the in-plane retardation and the thickness direction retardation of the second surface layer are obtained.

[Evaluation method of viewing angle characteristics]

A corona treatment device (manufactured by Kasuga Denki Co., Ltd.) was used for the optical film, and the corona treatment was applied ^{at a discharge rate of 50 W⋅min/m 2.} Use bonding fluid (“GOHSEFIMER Z200” manufactured by Nippon Gosei Chemical Co., Ltd.) to intervene between the optical film on the corona-treated surface and the polarizer made of polyvinyl alcohol (thickness 23 μm) to make the corona-treated optical film and One of the surfaces of the polarizing member is overlapped in a state facing each other, and is laminated using a roll laminator. The multilayer film and the polarizer protective film thus obtained are interposed with a bonding liquid to overlap them, and they are laminated using a roll laminator. The polarizer protective film is subjected to corona under the same conditions as the foregoing. The processed resin contains alicyclic structure polymer (manufactured by Zeon Co., Ltd.; glass transition temperature: 126°C), and the thickness is 40 μm. Thereby, a polarizing plate with a layer structure of (polarizer protective film)/(bonding layer)/(polarizer)/(bonding layer)/(optical film) is obtained.

A commercially available TV is prepared as an IPS-type liquid crystal display device. Take out the polarizing plate on the viewing side of the TV (that is, the polarizing plate closer to the display surface), and install the aforementioned polarizing plate manufactured using the optical film manufactured in the embodiment or the comparative example to replace it. After that, let the TV display a black screen and observe the display surface. The polar angle from the display surface is about 40° and the observation is made in the range of azimuth angle of 0°～180°. As a result of the observation, if the hue of the display surface is slightly bluish, it is judged as "bad", and if the hue cannot be confirmed, it is judged as "good".

[Measurement method of water vapor transmission rate]

Comply with the JIS K 7129 B method, use a water vapor transmission measuring device ("PERMATRAN-W" manufactured by MOCON) to measure the water vapor transmission rate of the optical film at a temperature of 40°C and a humidity of 90%RH.

[Method of evaluating warpage]

Observe the polarizing plate manufactured as described in the aforementioned [Evaluation Method of Viewing Angle Characteristics] with the naked eye. As a result of the observation, unevenness was not confirmed on the surface of the optical film, and the appearance was good.

Cut the aforementioned polarizing plate to obtain a square with a side length of 100 mm. The obtained film sheet was placed in a high temperature and humidity tank with a temperature adjusted to 60° C. and a humidity adjusted to 90% for 100 hours. After that, the film sheet was taken out from the high temperature and humidity tank and placed on the flat glass. At this time, if the end of the film sheet floats by more than 2 mm due to the warpage of the film sheet, it is judged as "bad", and if the amount of float is less than 2 mm, it is judged as "good".

[Production Example 1. Production of Resin I Containing Hydrogenated Block Copolymers]

(The first stage: the elongation of the first block St1 caused by the polymerization reaction)

In a fully dried and nitrogen-replaced stainless steel reactor equipped with a stirring device, 320 parts of dehydrated cyclohexane, 75 parts of styrene, and 0.38 parts of dibutyl ether are charged, and n-butyl lithium is added while stirring at 60°C. 0.41 part of the solution (15% by weight in hexane) was used to initiate the polymerization reaction, and then proceed to the first stage of the polymerization reaction. At 1 hour after the start of the reaction, a sample was taken from the reaction mixture and the sample was analyzed by gas chromatography (GC). As a result, the polymerization conversion rate was 99.5%.

(The second stage: the elongation of the second block Ip caused by the polymerization reaction)

15 parts of isoprene was added to the reaction mixture obtained in the above-mentioned first stage to initiate the subsequent second stage of polymerization reaction. At 1 hour after the start of the second stage of the polymerization reaction, a sample was taken from the reaction mixture and the sample was analyzed by GC. As a result, the polymerization conversion rate was 99.5%.

(The third stage: the elongation of the third block St2 caused by the polymerization reaction)

Add 10 parts of styrene to the reaction mixture obtained in the above second stage to initiate the subsequent third stage polymerization reaction. At 1 hour after the start of the polymerization reaction in the third stage, a sample was sampled from the reaction mixture, and the weight average molecular weight Mw and number average molecular weight Mn of the block copolymer obtained were measured. And at this point of time, the result of GC analysis of the sampled samples showed that the polymerization conversion rate was almost 100%. Immediately afterwards, 0.2 part of isopropanol was added to the reaction mixture to stop the reaction. In this way, a mixture containing a block copolymer is obtained.

The obtained block copolymer can be known as a polymerization of a triblock molecular structure with a weight ratio of the first styrene block St1/isoprene block Ip/the second styrene block St2=75/15/10 Things. The weight average molecular weight (Mw) of this block copolymer is 70,900, and the molecular weight distribution (Mw/Mn) is 1.5.

(The fourth stage: hydrogenation of block copolymer)

Subsequently, the mixture containing the above-mentioned block copolymer was transported to a pressure-resistant reactor equipped with a stirring device, and a diatomaceous earth-supported nickel catalyst ("E22U" manufactured by Nikkei Catalytic Kasei Co., Ltd.) as a hydrogenation catalyst was added and mixed. Nickel carrying capacity 60%) 8.0 parts and dehydrated cyclohexane 100 parts. The inside of the reactor was replaced with hydrogen, the solution was further stirred and hydrogen was supplied at the same time, and the hydrogenation reaction was performed at a temperature of 190° C. and a pressure of 4.5 MPa for 8 hours. The block copolymer is hydrogenated by a hydrogenation reaction to obtain polymer X. The weight average molecular weight (Mw) of the polymer X contained in the obtained reaction solution was 63,300, and the molecular weight distribution (Mw/Mn) was 1.5.

(The fifth stage: remove volatile components)

After the hydrogenation reaction is completed, the reaction solution is filtered to remove the hydrogenation catalyst. After that, add [3-(3,5-di-tertiary butyl-4-hydroxyphenyl) propionic acid] pentaerythrityl tetrakis[3-(3 ,5-di- t -butyl-4-hydroxyphenyl)propionate]) ("Songnox 1010" manufactured by Songyuan Sangyo Co., Ltd.) 0.1 part of xylene solution 2.0 parts, and dissolve it.

Subsequently, a cylindrical concentration dryer (“KONTORO” manufactured by Hitachi, Ltd.) was used to remove cyclohexane, xylene, and other volatile components from the above solution at a temperature of 260°C and a pressure of 0.001 MPa or less. The molten polymer is extruded from a die into a strand shape, and after cooling, a pelletizer is used to produce pellets of the resin I containing the polymer X.

The weight average molecular weight (Mw) of the polymer X contained in the obtained pelletized resin I was 62,200, the molecular weight distribution (Mw/Mn) was 1.5, and the hydrogenation rate was almost 100%.

[Manufacturing Example 2. Manufacturing of resin II containing hydrogenated product of ring-opening polymer of dicyclopentadiene]

(Synthesis of hydride of ring-opening polymer of dicyclopentadiene)

After fully drying the metal pressure-resistant reactor, replace it with nitrogen. Into this metal pressure-resistant reactor, 154.5 parts of cyclohexane and 42.8 parts of cyclohexane solution with 70% concentration of dicyclopentadiene (endoisomer content of 99% or more) (as dicyclopentadiene) The amount of ene is 30 parts) and 1.9 parts of 1-hexene, and heated to 53°C.

Dissolve 0.014 parts of tetrachlorotungsten phenylimide (tetrahydrofuran) complex in 0.70 parts of toluene solution, add 19% diethyl aluminum ethoxide/n-hexane solution 0.061 parts , And stirred for 10 minutes to prepare a catalyst solution.

This catalyst solution is added to the pressure-resistant reactor to initiate the ring-opening polymerization reaction. After that, it was allowed to react for 4 hours while maintaining 53°C to obtain a solution of a ring-opening polymer of dicyclopentadiene.

The number average molecular weight (Mn) and weight average molecular weight (Mw) of the obtained ring-opening polymer of dicyclopentadiene were 8,750 and 28,100, respectively, and the molecular weight distribution (Mw/Mn) obtained from these was 3.21.

0.037 parts of 1,2-ethylene glycol as a stopping agent was added to 200 parts of the obtained solution of the ring-opening polymer of dicyclopentadiene, heated to 60°C, and stirred for 1 hour to stop the polymerization reaction. Here, 1 part of the hydrotalcite-like compound ("KYOWAAD (registered trademark) 2000" manufactured by Kyowa Chemical Industry Co., Ltd.) was added, heated to 60°C, and stirred for 1 hour. After that, 0.4 parts of filter aid ("Radiolite (registered trademark) #1500" made by Showa Chemical Industry Co., Ltd.) was added, and the adsorbent and the solution were separated by filtration using a PP pleated filter element ("TCP-HX" made by ADVANTEC Toyo Co., Ltd.).

Add 200 parts (30 parts of polymer) to the filtered dicyclopentadiene ring-opening polymer solution, add 100 parts of cyclohexane, and add chlorohydridocarbonyl tris(triphenylphosphine) ruthenium) 0.0043 parts, hydrogenation reaction was carried out at a hydrogen pressure of 6 MPa and 180°C for 4 hours. Thereby, a reaction liquid containing the hydrogenated product of the ring-opening polymer of dicyclopentadiene is obtained. The hydride precipitates in this reaction liquid and becomes a slurry solution.

The hydride and the solution contained in the aforementioned reaction liquid were separated by a centrifuge, and dried under reduced pressure at 60° C. for 24 hours to obtain 28.5 parts of the hydride of the ring-opening polymer of dicyclopentadiene with crystallinity. The hydrogenation rate of this hydride is over 99%, the glass transition temperature Tg is 95°C, the crystallization temperature Tc is 180°C, the melting point Mp is 262°C, and the ratio of the racemic diad is 89%.

(Manufacture of pellets)

Antioxidant (4-[methylene-3-(3',5'-di-tertiarybutyl-4'-hydroxyphenyl) propionate] methyl ester; "Irganox (registered trademark) manufactured by BASF Japan 1010") 1.1 parts are mixed with 100 parts of the hydrogenated product of the aforementioned ring-opening polymer of dicyclopentadiene to obtain resin II.

Put this resin II into a biaxial extruder ("TEM-37B" manufactured by Toshiba Machine Co., Ltd.) with 4 mold holes with an inner diameter of 3 mmΦ. Using the aforementioned biaxial extruder, the resin is molded into a strip-shaped molded body by hot melt extrusion. A strand cutter is used to finely cut this shaped body to obtain pellets of resin II containing the hydrogenated product of the ring-opening polymer of dicyclopentadiene. The operating conditions of the aforementioned twin-shaft extruder are as follows. l Barrel setting temperature: 270℃～280℃ l Mold setting temperature: 250℃ l Screw speed: 145 rpm l Feeder speed: 50 rpm

[Example 1]

The resin I manufactured in Manufacturing Example 1 was put into the hopper. Furthermore, the injected resin I is used as the resin C for the core layer, and is supplied to a multi-manifold die.

On the other hand, the resin II manufactured by Manufacturing Example 2 was put into another hopper. Furthermore, the injected resin II is supplied as the resin S1 for the first surface layer and the resin S2 for the second surface layer to the aforementioned manifold mold.

Subsequently, the resin C for the core layer, the resin S1 for the first surface layer, and the resin S2 for the second surface layer are extruded into a film shape from the multi-manifold mold in a molten state. Furthermore, the extruded resin is cast on a cooling roll and cooled to produce a film with a first surface layer/core layer/second surface layer in sequence. The glass transition temperature of the resin C for the core layer is set as TgC, and the temperature of the aforementioned melt extrusion is set in the range of TgC+50°C to TgC+200°C. The obtained film is trimmed to remove the parts at both ends in the width direction of the film to obtain a long optical film with a film width of about 600 mm.

The obtained optical film was evaluated by the above method.

[Example 2]

By adjusting the extrusion amount of resin C, resin S1 and resin S2 in the multi-manifold mold, the thickness of the core layer, the first surface layer and the second surface layer were changed as shown in Table 1. Except for the above matters, the production and evaluation of the optical film were carried out by the same operation as in Example 1.

[Example 3]

Change to resin III containing alicyclic structure polymer without crystallinity (Norene polymer; "ZEONOR" manufactured by Zeon Corporation; glass transition temperature 126°C) instead of the resin manufactured in Manufacturing Example 2 II is used as the resin S1 for the first surface layer and the resin S2 for the second surface layer. In addition, by adjusting the extrusion amounts of resin C, resin S1 and resin S2 in the multi-manifold mold, the thickness of the core layer, the first surface layer and the second surface layer were changed as shown in Table 1. Except for the above matters, the production and evaluation of the optical film were carried out by the same operation as in Example 1.

[Example 4]

Use Resin IV (Norene polymer; "ZEONOR" made by Zeon Co., Ltd.; glass transition temperature 163°C) containing a non-crystalline alicyclic structure polymer instead of Resin III as the first surface layer Resin S1 and resin S2 for the second surface layer. In addition, by adjusting the extrusion amounts of resin C, resin S1 and resin S2 in the multi-manifold mold, the thickness of the first surface layer and the second surface layer were changed as shown in Table 1. Except for the above matters, the production and evaluation of the optical film were performed by the same operation as in Example 3.

[Comparative Example 1]

The resin I manufactured in Manufacturing Example 1 was used as all of the resin C for the core layer, the resin S1 for the first surface layer, and the resin S2 for the second surface layer. Except for the above matters, by the same operations as in Example 1, the production and evaluation of an optical film of a single-layer structure having a layered body formed only of resin I were performed.

[Comparative Example 2]

The resin II manufactured in Manufacturing Example 2 was used as all of the resin C for the core layer, the resin S1 for the first surface layer, and the resin S2 for the second surface layer. Except for the above matters, the rest was performed by the same operation as in Example 1 to manufacture and evaluate an optical film of a single-layer structure having a layered body formed only of resin II.

[Comparative Example 3]

The same resin III as used in Example 3 was used as all of the resin C for the core layer, the resin S1 for the first surface layer, and the resin S2 for the second surface layer. Except for the above matters, by the same operation as in Example 1, the production and evaluation of an optical film of a single-layer structure having a layered body formed only of resin III were performed.

[Comparative Example 4]

By adjusting the extrusion amount of resin C, resin S1 and resin S2 in the multi-manifold mold, the thickness of the core layer, the first surface layer and the second surface layer were changed as shown in Table 1. Except for the above matters, the production and evaluation of the optical film were carried out by the same operation as in Example 1.

[Comparative Example 5]

A triacetyl cellulose film (Fujitack manufactured by FUJIFILM, thickness 40 μm) was prepared as an optical film, and evaluated by the above method.

[result]

The results of the foregoing Examples and Comparative Examples are shown in the following table. In the following table, the meanings of the abbreviations are as follows. I: Resin I containing polymer X which is a hydrogenated product of a block copolymer. II: Resin II containing crystalline alicyclic structure polymer. III: Resin III containing alicyclic structure polymer without crystallinity. IV: Resin IV containing alicyclic structure polymer without crystallinity. TAC: Triacetyl cellulose. Re: In-plane delay. Rth: Retardation in the thickness direction.

[Table 1. Results of Examples]

[Table 2. Results of Comparative Example]

1‧‧‧Dish-shaped blade 2‧‧‧Bowl-shaped blade 3‧‧‧Optical film 10a‧‧‧Film 10U‧‧‧The upper surface of the film 15P‧‧‧Position on the central axis 100‧‧‧Optical film 110‧ ‧‧Core layer 120‧‧‧First surface layer 130‧‧‧Second surface layer 201‧‧‧Upper clamp ring 202‧‧‧Lower clamp ring 211‧‧‧Steel ball

FIG. 1 is a schematic cross-sectional view of an optical film related to an embodiment of the present invention. Fig. 2 is a perspective view schematically showing an apparatus for measuring the impact strength of optical films used in Examples and Comparative Examples. Fig. 3 is a cross-sectional view schematically showing an apparatus for measuring the impact strength of optical films used in Examples and Comparative Examples. Fig. 4 is a cross-sectional view schematically showing a section of the trimming blade used in the embodiment and the comparative example cut along a plane perpendicular to the film conveying direction.

100‧‧‧Optical Film

110‧‧‧Core layer

120‧‧‧First surface

130‧‧‧Second Surface

Tc, Ts1, Ts2‧‧‧Thickness

Claims (4)

An optical film that has an absolute value of retardation in the thickness direction at a measuring wavelength of 590nm of 3nm or less, an impact strength of 2×10 ^-2 J or more, and a water vapor transmission rate of 10g/(m ² ．24h) or less Optical film, the water vapor transmission rate is in accordance with JIS K 7129 B method, measured under the conditions of temperature 40℃ and humidity 90%RH; wherein the impact strength is to make a steel ball weighing 5g and diameter 11mm free When measured when dropped onto the horizontally fixed optical film, the optical film includes a core layer formed of resin C with a thickness of 25 μm or more, a first surface layer formed of resin S1 on one side of the core layer, and resin S2 Formed on the second surface layer on the other side of the core layer, the absolute value of the thickness direction retardation of the resin C at a thickness of 40 μm is 3 nm or less, and the impact strength of the resin S1 at a thickness of 40 μm is 5×10 ^-2 J or more, the impact strength of the resin S2 at a thickness of 40 μm is 5×10 ^-2 J or more, the sum of the thickness Ts1 of the first surface layer and the thickness Ts2 of the second surface layer is relative to the thickness of the core layer The ratio of Tc ((Ts1+Ts2)/Tc) is 0.05 to 0.4. The absolute value of the retardation in the thickness direction of the resin C at a thickness of 40μm represents the measured wavelength of a film with a thickness of 40μm formed by the resin C The absolute value of the retardation in the thickness direction of 590nm. The impact strength of the resin S1 at a thickness of 40μm is to make a steel ball weighing 5g and a diameter of 11 mm fall freely to a film with a thickness of 40μm formed by the resin S1 and fixed horizontally When measured, the impact strength of the resin S2 at a thickness of 40μm was measured by allowing a steel ball weighing 5g and a diameter of 11mm to fall freely to a film formed of the resin S2 and having a thickness of 40μm fixed horizontally. By. The optical film according to claim 1, wherein the resin C contains a hydrogenated product of a block copolymer, and the resin S1 and the resin S2 contain an alicyclic structure-containing polymer. The optical film according to claim 1 or 2, which has a thickness of 50 μm or less. A polarizing plate comprising the optical film and polarizing member according to any one of claims 1 to 3.

Images