JP2017122886A - Optical film, polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film excellent in antistatic property and transparency with reduced coloring, and a polarizing plate and a liquid crystal display device including the optical film.SOLUTION: The optical film of the present invention essentially comprises a cycloolefin-based resin. The optical film comprises: silica particles having a hydrophobicity degree of 20% or less measured by a methanol wettability method using a first solution containing methanol and pure water by a volume ratio of 3:7, and having a hydrophobicity degree of 80% or more measured by the above method using a second solution containing methanol and pure water by a volume ratio of 6:4; and at least one surfactant selected from an organic nonionic surfactant, an anionic surfactant, a cationic surfactant and an amphoteric surfactant. The optical film has a surface resistance value in a range from 1.0×10to 1.0×10Ω/sq, after the film is subjected to moisture conditioning in an environment at 23°C and 50% RH for 24 hours.SELECTED DRAWING: None

Description

  The present invention relates to an optical film, a polarizing plate, and a liquid crystal display device. More specifically, the present invention relates to an optical film having excellent antistatic properties and transparency and reduced coloring, and a polarizing plate and a liquid crystal display device including the optical film.

  Conventionally, liquid crystal panels with a touch panel used in mobile phones and mobile terminals such as smartphones have various configurations. An external (out-cell type) with a touch panel attached on the liquid crystal panel and a touch sensor inside the liquid crystal panel. There is a built-in type (in-cell type) with at least a part built in. The in-cell type built in the touch panel can make the device thinner and lighter.

  However, in the in-cell type in which a part of the touch sensor is built in the liquid crystal panel, an abnormal image display may occur due to charging inside the panel when the sensor is driven. This is caused by malfunction of liquid crystal molecules due to charging.

  As a countermeasure, it has been proposed to provide an antistatic function to the transparent resin layer arranged on the viewing side rather than the polarizing film provided on the most viewing side in the image display device as in Patent Document 1.

  Further, Patent Document 2 proposes that an antistatic layer is used in at least one of the resin layers composed of two or more layers in order to prevent circuit failure or damage to the display surface caused by static electricity generated during transportation of the liquid crystal display element. ing.

  On the other hand, cellulose ester resins, polycarbonates, cycloolefin resins, and the like have been conventionally known as materials constituting protective films for polarizing plates used in liquid crystal display devices. Among these, cycloolefin resins are attracting attention from the viewpoint of high transparency, heat resistance, and moisture resistance.

  In recent years, optical members used in image display devices have been made thinner, and cycloolefin-based resin films are also used in a thin state. In order to meet the demands for further thinning of devices, we investigated the inclusion of a surfactant in the optical compensation film used for polarizing plates to provide an antistatic function. In the conventional display device, it has become clear that there is a problem of image quality failure that causes image unevenness.

Japanese Patent Laid-Open No. 2015-200698 JP 2007-237555 A

  The present invention has been made in view of the above-described problems and circumstances, and the solution to the problem is an optical film with excellent antistatic properties and transparency and reduced coloring, and a polarizing plate and a liquid crystal display device provided with the optical film. Is to provide.

  In order to solve the above problems, the present inventor has an optical film having a specific surface resistance value, which contains a cycloolefin resin, a surfactant, and specific silica particles in the course of studying the cause of the above problem. Thus, it was found that an optical film excellent in antistatic property and transparency and reduced in coloring can be provided, and the present invention has been achieved.

  That is, the said subject which concerns on this invention is solved by the following means.

1. An optical film comprising a cycloolefin-based resin as a main component, wherein the optical film uses a first solution in which the degree of hydrophobicity measured by a methanol wettability method is 3: 7 by volume of methanol and pure water. Silica particles having a hydrophobization degree of 20% or less when methanol and pure water are used in a second solution having a volume ratio of 6: 4 and a hydrophobization degree of 80% or more, Contains at least one surfactant selected from nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants, and in an environment of 23 ° C. and 50% RH for 24 hours An optical film characterized in that the surface resistance value after conditioning is in the range of 1.0 × 10 ^{7 to} 1.0 × 10 ⁹ Ω / sq.

  2. Item 2. The optical film as described in Item 1, wherein the surfactant is a cationic surfactant.

  3. 3. The optical film according to item 1 or 2, wherein the silica particles are contained within a range of 0.1 to 0.5% by mass with respect to the total mass of the film.

  4). The optical film according to any one of Items 1 to 3, wherein the surfactant is contained within a range of 0.5 to 8% by mass with respect to the total mass of the film.

  5. The optical film according to any one of items 1 to 4, wherein the film thickness is in a range of 5 to 40 μm.

6). The retardation value Ro in the in-plane direction defined by the following formula (i) is in the range of 0 to 10 nm, and the retardation value Rt in the thickness direction defined by the following formula (ii) is −10 to 10. The optical film according to any one of items 1 to 5, which is in a range of 10 nm.
Formula _{(i) Ro = (n x} -n y) × d
Formula (ii) Rt = {(n _x + n _y ) / 2−n _z } × d
(Wherein, n _x is .n _y representing the refractive index in a slow axis direction in the film plane is .n _z representing the fast-axis refractive index in the film plane is in the thickness direction of the film (The refractive index is measured at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH.) D represents the thickness (nm) of the film.)
7). A polarizing plate having a first protective film T1 on the viewing side and a second protective film T2 on the other surface side with a polarizer in between, at least one of the protective film T1 and the protective film T2 being the first A polarizing plate, which is the optical film according to any one of items 6 to 6.

  8). A liquid crystal display device comprising the polarizing plate according to item 7.

  By the above means of the present invention, it is possible to provide an optical film excellent in antistatic property and transparency and reduced in coloring, and a polarizing plate and a liquid crystal display device provided with the optical film.

  The expression mechanism / action mechanism of the effect of the present invention is not clear, but is presumed as follows. As a result of intensive studies by the present inventors, this image unevenness is caused by the change in the external environment of humidity and temperature due to the anti-static and the like, and the optical film mainly composed of a cycloolefin resin containing a surfactant is used. It became clear that the cause was coloring.

  As a result of further investigations, the coloration of the optical film is caused by the resin structure being decomposed by the ionic component of the electrolyte surfactant attacking the polar part of the cycloolefin resin. It was estimated and found to be improved by including silica particles of a specific hydrophobicity in the optical film. This can be improved because the presence of silica particles causes the ionic component of the surfactant to be adsorbed on the silica particles, thereby suppressing attack on the cycloolefin-based resin skeleton. For this reason, it is presumed that decomposition of the resin structure does not easily occur and coloring does not easily occur, and image quality failure is suppressed.

Schematic diagram showing an example of a solution casting film forming apparatus Schematic sectional view showing an example of the configuration of the polarizing plate of the present invention Schematic sectional view showing an example of a liquid crystal display device comprising the polarizing plate of the present invention

The optical film of the present invention is an optical film containing a cycloolefin-based resin as a main component, and the optical film has a hydrophobicity measured by a methanol wettability method, wherein methanol and pure water are in a volume ratio of 3: When the first solution of No. 7 is used, the degree of hydrophobicity is 20% or less, and when the second solution of methanol and pure water is used at a volume ratio of 6: 4, the degree of hydrophobicity is 80% or more. Contains silica particles and at least one surfactant selected from organic nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants, and 23 ° C. and 50% The surface resistance value after conditioning for 24 hours in an RH environment is in the range of 1.0 × 10 ^{7 to} 1.0 × 10 ⁹ Ω / sq. This feature is a technical feature common to or corresponding to the claimed invention.

  As an embodiment of the present invention, the surfactant is preferably a cationic surfactant from the viewpoint of manifesting the effects of the present invention.

  Moreover, it is preferable to contain the said silica particle within the range of 0.1-0.5 mass% with respect to the film total mass since the inhibitory effect with respect to the coloring of a film is acquired.

  Furthermore, in this invention, it is preferable to contain the said surfactant within the range of 0.5-8 mass% with respect to the film total mass. Thereby, the antistatic effect is acquired.

  The film thickness is preferably in the range of 5 to 40 μm from the viewpoints of thinning and downsizing the display and preventing charging.

  The retardation value Ro in the in-plane direction defined by the formula (i) is in the range of 0 to 10 nm, and the retardation value Rt in the thickness direction defined by the formula (ii) is − A range of 10 to 10 nm is preferable from the viewpoint of the visibility of the liquid crystal display device.

  Furthermore, the polarizing plate of the present invention is a polarizing plate having the first protective film T1 on the viewing side and the second protective film T2 on the other surface side with the polarizer in between, and the protective film T1 and It is preferable from the viewpoint of the visibility of the liquid crystal display device that at least one of the protective films T2 is the optical film according to the present invention.

  Moreover, the liquid crystal display device of this invention can comprise suitably the said polarizing plate.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" showing a numerical range is used by the meaning containing the numerical value described before and behind that as a lower limit and an upper limit.

<Outline of optical film>
The optical film of the present invention is an optical film containing a cycloolefin-based resin as a main component, and the optical film has a hydrophobicity measured by a methanol wettability method, wherein methanol and pure water are in a volume ratio of 3: When the first solution of No. 7 is used, the degree of hydrophobicity is 20% or less, and when the second solution of methanol and pure water is used at a volume ratio of 6: 4, the degree of hydrophobicity is 80% or more. Contains silica particles and at least one surfactant selected from organic nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants, and 23 ° C. and 50% The surface resistance value after conditioning for 24 hours in an RH environment is in the range of 1.0 × 10 ^{7 to} 1.0 × 10 ⁹ Ω / sq.

  In addition, the optical film which has cycloolefin resin as a main component means that cycloolefin resin occupies 50 mass% or more of the composition which comprises an optical film.

  Hereinafter, details of each component, characteristic value, manufacturing method and the like of the optical film of the present invention will be described below.

[Cycloolefin resin]
The cycloolefin-based resin contained in the optical film of the present invention is preferably a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and a copolymerizable monomer other than that. .

  The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and is a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2). More preferably.

In General Formula (A-1), R ^{1 to} R ⁴ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p represents an integer of 0 to 2. However, all of R ^{1 to} R ⁴ do not represent hydrogen atoms at the same time, R ¹ and R ² do not represent hydrogen atoms at the same time, and R ³ and R ⁴ do not represent hydrogen atoms at the same time. To do.

In the general formula (A-1), the hydrocarbon group having 1 to 30 carbon atoms represented by R ^{1 to} R ⁴ is preferably, for example, a hydrocarbon group having 1 to 10 carbon atoms, More preferably, it is a hydrocarbon group of 1 to 5. The hydrocarbon group having 1 to 30 carbon atoms may further have, for example, a linking group containing a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom. Examples of such a linking group include divalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

Examples of the polar group represented by R ^{1 to} R ⁴ in the general formula (A-1) include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. Is included. Among these, a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferable, and an alkoxycarbonyl group and an aryloxycarbonyl group are preferable from the viewpoint of ensuring solubility during solution film formation.

  In the general formula (A-1), p preferably represents 1 or 2 from the viewpoint of increasing the heat resistance of the optical film. When p represents 1 or 2, the resulting polymer becomes bulky and the glass transition temperature is likely to be improved.

In General Formula (A-2), R ⁵ represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. R ⁶ represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom or an iodine atom). p represents an integer of 0 to 2.

R ⁵ in the general formula (A-2) preferably represents a hydrocarbon group having 1 to 5 carbon atoms, and more preferably represents a hydrocarbon group having 1 to 3 carbon atoms.

R ⁶ in the general formula (A-2) preferably represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group. From the viewpoint of ensuring solubility during solution film formation, the alkoxycarbonyl group and aryl An oxycarbonyl group is more preferred.

  P in the general formula (A-2) preferably represents 1 or 2 from the viewpoint of enhancing the heat resistance of the optical film. When p represents 1 or 2, the resulting polymer becomes bulky and the glass transition temperature is likely to be improved.

The cycloolefin monomer having the structure represented by the general formula (A-2) is preferable from the viewpoint that other components such as fine particles described later are easily unevenly distributed in the obtained optical film. The reason is not clear, but R ⁵ and R ⁶ in the general formula (A-2) are substituted with only one ring-constituting carbon atom with respect to the symmetry axis of the molecule, so the symmetry of the molecule is low. . This is because the diffusion movement of the cycloolefin resin and other components is promoted during the solvent volatilization during the film formation of the optical film, and the movement of the other components to the film formation film surface is promoted accordingly. it is conceivable that.

  The content ratio of the cycloolefin monomer having the structure represented by the general formula (A-2) in the polymer of the cycloolefin monomer is based on the total of all the cycloolefin monomers constituting the cycloolefin resin. For example, 70 mol% or more, preferably 80 mol% or more, more preferably 100 mol%. When the cycloolefin monomer having a structure represented by the general formula (A-2) is included in a certain amount or more, the orientation of the resin is increased, so that the retardation value is likely to increase.

  Hereinafter, specific examples of the cycloolefin monomer having the structure represented by the general formula (A-1) are shown in the exemplified compounds 1 to 14, and the cycloolefin monomer having the structure represented by the general formula (A-2) is shown. Specific examples of the monomer are shown in Exemplified Compounds 15 to 34.

  Examples of the copolymerizable monomer copolymerizable with the cycloolefin monomer include a copolymerizable monomer capable of ring-opening copolymerization with the cycloolefin monomer, and an addition copolymerization with the cycloolefin monomer. Possible copolymerizable monomers are included.

  Examples of the copolymerizable monomer capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene and dicyclopentadiene.

  Examples of the copolymerizable monomer capable of addition copolymerization include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, and (meth) acrylates. Examples of unsaturated double bond-containing compounds include olefinic compounds having 2 to 12 (preferably 2 to 8) carbon atoms, and examples thereof include ethylene, propylene and butene. Examples of the vinyl-based cyclic hydrocarbon monomer include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of (meth) acrylates include alkyl (meth) acrylates having 1 to 20 carbon atoms such as methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and cyclohexyl (meth) acrylate.

  The content ratio of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer is, for example, 20 to 80 mol% with respect to the total of all monomers constituting the copolymer, Preferably it can be 30-70 mol%.

  As described above, the cycloolefin-based resin is obtained by polymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the general formula (A-1) or (A-2). Examples of the polymer obtained by copolymerization include the following.

(1) Ring-opening polymer of cycloolefin monomer (2) Ring-opening copolymer of cycloolefin monomer and copolymerizable monomer capable of ring-opening copolymerization with it (3) Above (1) (2) Hydrogenated product of ring-opening (co) polymer (4) (4) The ring-opening (co) polymer of (1) or (2) was cyclized by Friedel-Crafts reaction and then hydrogenated ( Co) polymer (5) Saturated copolymer of cycloolefin monomer and unsaturated double bond-containing compound (6) Addition copolymer of cycloolefin monomer with vinyl cyclic hydrocarbon monomer (7) Alternate copolymer of cycloolefin monomer and (meth) acrylate The polymers of (1) to (7) are all known methods, for example, JP-A-2008-107534. Obtained by the method described in Japanese Patent Publication No. 2005-227606. You can. For example, as the catalyst and solvent used in the ring-opening copolymerization (2) above, for example, those described in paragraphs 0019 to 0024 of JP-A-2008-107534 can be used. As the catalyst used for the hydrogenation in the above (3) and (6), for example, those described in paragraphs 0025 to 0028 of JP-A-2008-107534 can be used. As the acidic compound used in the Friedel-Crafts reaction of (4) above, for example, the one described in paragraph 0029 of JP-A-2008-107534 can be used. As the catalyst used in the addition polymerization of the above (5) to (7), for example, those described in paragraphs 0058 to 0063 of JP-A-2005-227606 can be used. The alternating copolymerization reaction (7) can be performed, for example, by the method described in paragraphs 0071 and 0072 of JP-A-2005-227606.

  Among these, the polymers (1) to (3) and (5) are preferable, and the polymers (3) and (5) are more preferable. That is, the cycloolefin-based resin can increase the glass transition temperature of the obtained cycloolefin-based resin and increase the light transmittance, and the structural unit represented by the following general formula (B-1) and It is preferable that at least one of the structural units represented by the following general formula (B-2) is included, and only the structural unit represented by the general formula (B-2) is included or in the general formula (B-1). It is more preferable that both the structural unit represented and the structural unit represented by General Formula (B-2) are included. The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the general formula (A-1), and is represented by the general formula (B-2). The structural unit is a structural unit derived from the cycloolefin monomer represented by the general formula (A-2).

In General Formula (B-1), X represents —CH═CH— or —CH ₂ CH ₂ —. R ¹ to R ⁴ and p are respectively the same as ^R 1 to R ⁴ and p of the general formula (A-1).

In General Formula (B-2), X represents —CH═CH— or —CH ₂ CH ₂ —. R ^{5, R 6} and p are respectively the same as ^R 5, ^{R 6} and p in the general formula (A-2).

  The cycloolefin resin according to the present invention may be a commercial product. Examples of commercially available cycloolefin-based resins include Arton G (for example, G7810), Arton F, Arton R (for example, R4500, R4900, and R5000), and Arton RX (for example, RX4500) manufactured by JSR Corporation. Etc.).

Intrinsic viscosity [η] _inh of the cycloolefin-based resin, at 30 ° C., is preferably 0.2~5cm ³ / g, more preferably 0.3~3cm ³ / g, 0.4~ More preferably, it is 1.5 cm ³ / g.

  The number average molecular weight (Mn) of the cycloolefin resin is preferably 8000 to 100,000, more preferably 10,000 to 80,000, and still more preferably 12,000 to 50,000. The weight average molecular weight (Mw) of the cycloolefin-based resin is preferably 20000 to 300000, more preferably 30000 to 250,000, and still more preferably 40000 to 200000. The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured by gel permeation chromatography (GPC) in terms of polystyrene.

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

  The glass transition temperature (Tg) of the cycloolefin resin is usually 110 ° C. or higher, preferably 110 to 350 ° C., more preferably 120 to 250 ° C., and more preferably 120 to 220 ° C. Further preferred. When Tg is 110 ° C. or higher, it is easy to suppress deformation under high temperature conditions. On the other hand, when Tg is 350 ° C. or lower, the molding process is facilitated, and the deterioration of the resin due to heat during the molding process is easily suppressed.

  The content of the cycloolefin-based resin is preferably 70% by mass or more, and more preferably 80% by mass or more with respect to the optical film.

[Silica particles]
In the optical film of the present invention, the degree of hydrophobicity measured by the methanol wettability method is 20% or less when the first solution in which methanol and pure water have a volume ratio of 3: 7 is used. Further, silica particles having a hydrophobization degree of 80% or more when methanol and pure water are used in a 6: 4 second solution in a volume ratio are contained.

  By including such silica particles, it is possible to reduce the coloration of the optical film mainly composed of a cycloolefin-based resin containing a surfactant with changes in the external environment of humidity and temperature. This is presumably because the presence of silica particles causes the ionic component of the surfactant to be adsorbed on the silica particles, thereby suppressing attack on the cycloolefin resin skeleton.

  Here, the silica particles are particles mainly composed of silicon dioxide. The main component means to contain 50% or more of the components constituting the particles, preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

  Moreover, as addition amount of the said silica particle, it is preferable to contain in the range of 0.1-0.5 mass% with respect to the film total mass. When the addition amount is 0.1% by mass or more, an effect of preventing coloring is obtained, and when it is 0.5% or less, there is no concern that haze deteriorates.

  Since the silica particles according to the present invention improve the poor slipperiness of the film surface, they can also function as a matting agent that gives irregularities to the film surface. If necessary, in order to impart slipperiness, optical and mechanical functions, fine particles of an inorganic compound or fine particles of an organic compound can be added as a matting agent as long as the effects of the present invention are not impaired.

<Methanol wettability method>
The degree of hydrophobicity of the silica particles according to the present invention can be quantified using a solvent containing alcohol or pure water. As a method for quantifying the degree of hydrophobicity, a methanol wettability method (hereinafter referred to as “MW method”) is preferable. In the present invention, the degree of hydrophobicity is represented by a methanol wettability value (hereinafter referred to as “MW value”) determined by this method.

  In the above MW method, in order to quantify the degree of hydrophobicity of the fine particles, a first solution and a second solution in which methanol and pure water are mixed are used. At this time, the mixing ratio of methanol and pure water is a volume ratio of 3: 7 in the first solution, and a volume ratio of 6: 4 in the second solution. Then, the same amount of the fine particles is added to each solution and stirred and mixed, and each mixed solution is centrifuged to determine the volume of the fine particle sediment, and the volume of the fine particle sediment in the first solution is determined. When tmL and the volume of the sediment of fine particles in the second solution are smL, the MW value is MW value in the first solution = (t / A) × 100 [%] and the MW value in the second solution, respectively. = (S / A) × 100 [%] Here, A is the volume (AmL) of the silica particles added first.

[MW method]
(1) The methanol solution C and the pure water D are mixed at a volume ratio of 3: 7 to prepare the first solution A (for example, the pure water D is 40 mL against the methanol solution C). 60mL)
(2) Next, 0.2 g of silica particle powder E and 7 mL of the first solution A are placed in a 10 mL settling tube F.
(3) The settling tube F is covered, and the fine particle powder E is shaken and mixed into the first solution A using a tumbler mixer. At this time, the condition of the tumbler mixer is 90 seconds at 90 rpm.
(4) In order to precipitate the silica particle powder E, a centrifuge is used. The centrifuge conditions are 10 minutes at 3500 rpm.
(5) The sediment amount of the settled fine particle powder E that can be read with the scale of the sedimentation tube is read as a volume, and the value is defined as tmL.
(6) A methanol solution C and pure water D are newly mixed at a volume ratio of 6: 4 to prepare a second solution B (for example, the methanol solution C is pure with respect to 60 mL. 40 mL of water D).
(7) Using the second solution B, prepare the sediment of the silica particle powder E by the same procedures (8) to (11) as the above (2) to (5), and read with the scale of the sedimentation tube The volume of sedimented silica particle powder E that can be read is read as a volume, and the value is taken as smL.
(12) The MW value (%) is obtained by the following formula.

MW value in the first solution = (t / A) × 100 [%]
MW value in the second solution = (s / A) × 100 [%]
Here, A is the volume (AmL) of the silica particles added first.

Silica particles
SiO ₂ → SiO-H → SiO ⁻ + H ⁺
Since the particle surface is in a state having a silanol group and a negative charge as described above, it is considered that the particle surface can interact with the positively charged site of the cationic surfactant.

  The degree of hydrophobicity measured by the methanol wettability method is 20% or less when the first solution having a volume ratio of methanol and pure water of 3: 7 is used, and the volume of methanol and pure water is less than 20%. The silica particles according to the present invention having a hydrophobization degree of 80% or more when the second solution having a ratio of 6: 4 is used have good affinity with the hydrophobic part of the organic surfactant, Since supplementation is easier, an effect of preventing coloring can be obtained.

  The silica particles having the hydrophobicity as described above can be selected from those obtained by subjecting the silica particles to alkylation treatment. Further, when silica particles whose surface is hydrophobized by an alkylation treatment are added, there is an advantage that the dispersibility in a solvent is good and the generation of foreign matters can be suppressed.

  The hydrophobic treatment for the silica particles is preferably an alkylation treatment. The surface of the alkylated fine particles has an alkyl group, and the alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably It is the range of C1-C8.

  The silica particles having an alkyl group having 1 to 20 carbon atoms on the surface can be obtained, for example, by treating the silicon dioxide particles with octylsilane. Moreover, as an example which has an octyl group on the surface, it is marketed by the brand name of Aerosil R805 (made by Nippon Aerosil Co., Ltd.), and is used preferably.

  The average particle diameter of the primary particles of the silica particles is preferably in the range of 5 to 400 nm, and more preferably in the range of 10 to 300 nm.

  The average particle size of the secondary particles of the silica particles is preferably in the range of 100 to 400 nm, and if the average particle size of the primary particles is in the range of 100 to 400 nm, it is included as primary particles without agglomeration. It is also preferable.

<Measuring method of average particle diameter of silica particles>
The particle size of silica particles in an optical film is measured by photographing a cross section of a film cut by a microtome with a scanning electron microscope (SEM) at an appropriate magnification, and 100 particles included in the tomographic cut photograph. The particle diameter is measured and the average value is obtained as the average particle diameter. The particle diameter is the diameter when the cross section of the particle is circular, and is the diameter when the area is calculated and converted into a circle when the cross section is not circular.

SEM: JSM-6060LA (JEOL: JEOL Ltd.)
Microtome: Leica EM UC6
The content of silica particles in the film needs to be 0.1 to 2.5% by mass with respect to the total mass of the film, and is preferably in the range of 0.5 to 2.0% by mass, In particular, it is preferably within the range of 1.0 to 2.0% by mass in order to express the effects of the present invention.

  As the silica particles, commercially available products can be preferably used, and since Aerosil R805, R812, R976S and the like satisfy the degree of hydrophobicity according to the present invention, coloring can be prevented and the haze of the optical film can be kept low. .

  The optical film of the present invention preferably contains silica particles and has a dynamic friction coefficient of at least one surface in the range of 0.2 to 1.0. The dynamic friction coefficient can be measured according to “JIS K7125 Plastic-film and sheet friction coefficient test method”.

  Examples of the method for adding silica particles according to the present invention include the following first to third methods, and any method may be used.

[First addition method]
After stirring and mixing the solvent and the particles, dispersion is performed using a disperser, and this is added to the dope and stirred to obtain a casting dope.

[Second addition method]
After stirring and mixing the solvent and the particles, dispersion is performed using a disperser to prepare a particle dispersion. Next, after adding a small amount of resin to the solvent and stirring and dissolving the particle dispersion, the particle dispersion is added to the raw material dope and mixed well to obtain a casting dope.

[Third addition method]
After a small amount of resin is added to the solvent and dissolved by stirring, the particles are added and dispersed using a disperser. This is added to the dope and mixed thoroughly.

  The silica particles contained in the finished casting dope may be contained in the case where a recycled film is used for the preparation of the dope. The extended dope is preferably according to the present invention.

[Surfactant]
The optical film of the present invention contains an organic surfactant for the purpose of controlling the surface resistance value of the optical film and preventing static charges. The surfactant used in the present invention is at least one surfactant selected from organic nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants.

  In addition, a high-molecular-weight surfactant is preferable to a low-molecular surfactant because it easily exhibits an antistatic effect even at low humidity and has excellent total light transmittance when formed into a film. Furthermore, the expression of the effect of the antistatic agent is generally in the order of cationic> amphoteric> anionic> nonionic, and the cationic surfactant is most preferable. Cationic surfactants are also preferred because of their strong interaction with the silica particles according to the present invention.

  Examples of the anionic surfactant include fatty acid salts, higher alcohol sulfate esters, liquid fatty oil sulfate esters, aliphatic amines and aliphatic amide sulfates, aliphatic alcohol phosphate esters, dibasic fatty acid esters. Sulfonates, aliphatic amide sulfonates, alkylallyl sulfonates, formalin-condensed naphthalene sulfonates, and the like.

  Examples of the cationic surfactant include aliphatic amine salts, quaternary ammonium salts, alkylpyridinium salts, and the like.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, and the like.

  Examples of the zwitterionic surfactant include imidazoline derivatives, betaine-type higher alkylamino derivatives, sulfate ester derivatives, phosphate ester derivatives, and the like.

  Specific compounds are described by Hideo Marumo, “Antistatic Agent, Surface Modification of Polymers”, Koshobo, Augmented “Practical Handbook for Additives for Plastics and Rubbers, p333-p455”, published by Kagaku Kogyosha, JP 11-256143, JP-A-52-32572, JP-A-10-158484 and the like.

  Preferable surfactants include ionic polymer compounds such as anionic surfactants and cationic surfactants. Examples of the ionic polymer compound include anionic polymer compounds such as those described in JP-B-49-23828, JP-A-49-23827, and JP-A-47-28937; JP-B-55-734, JP-A-50-54672 Ionene type polymers having a dissociating group in the main chain, as shown in JP-B Nos. 59-14735, 57-18175, 57-18176, 57-56059 and the like: JP-B 53-13223 No. 57-15376, No. 53-45231, No. 55-145783, No. 55-65950, No. 55-67746, No. 57-11342, No. 57-19735, No. 58-56858. Pendant having a cationic dissociation group in the side chain as seen in JP-A Nos. 61-27853 and 62-9346 Type polymers, mention may be made of graft copolymers such as those found in JP-A-5-230161.

  Preferred polymer type surfactants include polyether ester amic acid type, ethylene oxide-epichlorohydrin type and polyether ester type as nonionic surfactants. Examples of the anionic surfactant include polystyrene sulfonic acid type. Examples of the cationic surfactant include a quaternary ammonium base-containing acrylate polymer type.

  In the present invention, a surfactant that can be preferably used is an ionene conductive polymer described in JP-A-9-203810, a quaternary ammonium cationic conductive polymer having intermolecular crosslinking, or the like.

  The characteristics of the cross-linked cationic conductive polymer are the dispersible granular polymer obtained, and the cationic component in the fine particles can be given a high concentration and high density. The compatibility with the resin is good, and high transparency is selected. Furthermore, no deterioration in conductivity is observed even under a low relative humidity.

  The dispersible granular polymer, which is a crosslinked cationic conductive polymer used for antistatic, is generally in the fine particle size range of about 0.01 to 0.3 μm, preferably in the range of 0.05 to 0.15 μm. Is used.

In the present invention, each of the surfactants described above is preferably contained within a range of 0.5 to 8% by mass with respect to the total mass of the film, and the addition amount of the surfactant is 0.5 to 8% by mass. %, The surface resistance value of the optical film can be adjusted to 10 ⁹ Ω / sq or less, dust and dust adhesion can be effectively suppressed, and the light transmittance of the resin material can be maintained at a desired value. .

<Surface resistance value>
The optical film of the present invention has a surface resistance value in the range of 1.0 × 10 ^{7 to} 1.0 × 10 ⁹ Ω / sq after being conditioned for 24 hours in an environment of 23 ° C. and 50% RH. Preferably, it is in the range of 1.0 × 10 ^{7 to} 5.0 × 10 ⁸ Ω / sq.

When the surface resistance value is less than 1.0 × 10 ⁷ , coloring due to the added surfactant activator is increased, and when applied to a touch panel, the operation sensitivity at the time of touch operation of the display is preferably decreased. Absent.

If it exceeds 1.0 × 10 ⁹ Ω / sq, circuit failure and display surface damage due to static electricity generated during transportation of the liquid crystal display element are likely to occur, and when an optical film is applied to a liquid crystal panel with a touch panel, There is a fear of malfunction, which is not preferable.

  From the viewpoint of preventing malfunction, not only charging characteristics but also discharge characteristics after charging are important. Specifically, after adjusting the humidity for 24 hours in an environment of 23 ° C. and 50% RH, charge the optical film and measure the time until the initial charging voltage drops in half, and measure it as the half-life. Can do. The half-life is preferably within 200 seconds. The half-life varies greatly depending on the thickness of the optical film, and it is preferably thinner. From the viewpoint of shortening the half-life, the thickness of the optical film is preferably within 40 μm.

[Other additives]
Various additives can be applied to the optical film of the present invention as long as the object effects of the present invention are not impaired.

(Polyester plasticizer)
In the optical film of the present invention, it is preferable to apply a polyester plasticizer in that the film elastic modulus, slipperiness, and film film surface hardness are improved, and as a result, high-quality surface quality can be obtained.

  The polyester plasticizer is obtained by subjecting a diol and a dicarboxylic acid to a dehydration condensation reaction, and then converting the hydroxyl group (derived from the diol) at the molecular end of the resulting reaction product to a carboxy group of a hydroxy group-containing monocarboxylic acid having a ring structure. And a compound obtained by a dehydration condensation reaction.

  The polyester plasticizer has a structure represented by the following general formula (1).

General formula (1)
B- (GA) _n -GB
In the general formula (1), B represents a group derived from a hydroxy group-containing monocarboxylic acid having a ring structure. The ring structure refers to a structure having an aliphatic hydrocarbon ring, an aliphatic hetero ring, an aromatic hydrocarbon ring or an aromatic hetero ring, preferably a structure having an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring. . The hydroxy group-containing monocarboxylic acid having a ring structure may be an alicyclic monocarboxylic acid having 5 to 20 carbon atoms, an aromatic monocarboxylic acid having 7 to 20 carbon atoms, and a mixture thereof.

  The alicyclic monocarboxylic acid having 5 to 20 carbon atoms may preferably be an alicyclic monocarboxylic acid having 6 to 15 carbon atoms. Examples of alicyclic monocarboxylic acids include 4-hydroxycyclohexyl acetic acid, 3-hydroxycyclohexyl acetic acid, 2-hydroxycyclohexyl acetic acid, 4-hydroxycyclohexyl propionic acid, 4-hydroxycyclohexyl butyric acid, 4-hydroxycyclohexyl glycolic acid, 4 -Hydroxy-o-methylcyclohexylacetic acid, 4-hydroxy-m-methylcyclohexylacetic acid, 4-hydroxy-p-methylcyclohexylacetic acid, 5-hydroxy-m-methylcyclohexylacetic acid, 6-hydroxy-o-methylcyclohexylacetic acid, 2 , 4-dihydroxycyclohexyl acetic acid, 2,5-dihydroxycyclohexyl acetic acid, 2- (hydroxymethyl) cyclohexyl acetic acid, 3- (hydroxymethyl) cyclohexyl acetic acid, 4- (hydroxymethyl) L) cyclohexylacetic acid, 2- (1-hydroxy-1-methylethyl) cyclohexylacetic acid, 3- (1-hydroxy-1-methylethyl) cyclohexylacetic acid, 4- (1-hydroxy-1-methylethyl) cyclohexylacetic acid, etc. Is included.

  The aromatic monocarboxylic acid having 7 to 20 carbon atoms may preferably be an aromatic monocarboxylic acid having 7 to 15 carbon atoms. Examples of aromatic monocarboxylic acids include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 4-hydroxy-o-toluic acid, 3-hydroxy-p-toluic acid, 5-hydroxy- m-toluic acid, 6-hydroxy-o-toluic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2- (hydroxymethyl) benzoic acid, 3- (hydroxymethyl) benzoic acid, 4- (Hydroxymethyl) benzoic acid, 2- (1-hydroxy-1-methylethyl) benzoic acid, 3- (1-hydroxy-1-methylethyl) benzoic acid, 4- (1-hydroxy-1-methylethyl) benzoic acid Acid etc. are included.

  Among these, hydroxy group-containing monocarboxylic acid containing an aromatic ring (aromatic monocarboxylic acid containing a hydroxy group) is provided because it imparts sufficient hydrophobicity to an optical film and easily suppresses deterioration of the polarizer due to moisture. preferable.

  In the formula, G is a group consisting of an alkylene diol having 2 to 12 carbon atoms, a cycloalkylene diol having 6 to 12 carbon atoms, an oxyalkylene diol having 4 to 12 carbon atoms, and an arylene diol having 6 to 12 carbon atoms. A group derived from at least one selected from the above.

  Examples of alkylene diols having 2 to 12 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propane. Diol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl -1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5- Pentanediol 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol , 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, include 1,12-octadecanediol like.

  Examples of cycloalkylene diols having 6 to 12 carbon atoms include hydrogenated bisphenol A (2,2-bis (4-hydroxycyclohexyl) propane), hydrogenated bisphenol B (2,2-bis (4-hydroxycyclohexyl) Butane and the like are included.

  Examples of the oxyalkylene diol having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like.

  Examples of the arylene diol having 6 to 12 carbon atoms include bisphenol A and bisphenol B.

  The diol is used as one kind or a mixture of two or more kinds. Among these, alkylene glycols having 2 to 12 carbon atoms are preferable in terms of excellent compatibility with cycloolefin resins.

  In the formula, A is at least one selected from the group consisting of alkylene dicarboxylic acids having 4 to 12 carbon atoms, cycloalkylene dicarboxylic acids having 6 to 12 carbon atoms, and arylenedicarboxylic acids having 8 to 16 carbon atoms. Represents a derived group.

  Examples of the alkylene dicarboxylic acid having 4 to 12 carbon atoms include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and the like.

  Examples of the cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid and the like are included.

  Examples of the arylene dicarboxylic acid having 8 to 16 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid and the like.

  The dicarboxylic acid is used as one kind or a mixture of two or more kinds. The dicarboxylic acid is preferably a mixture of alkylene dicarboxylic acid and arylene dicarboxylic acid. The content ratio of the alkylene dicarboxylic acid and the arylenedicarboxylic acid is preferably alkylene dicarboxylic acid: arylene dicarboxylic acid = 40: 60 to 99: 1, and more preferably 50:50 to 90:10.

  In the formula, n represents an integer of 0 or more.

  The number average molecular weight of the polyester plasticizer is preferably 300 to 30000, more preferably 300 to 700, and more preferably 300 to 600. If the number average molecular weight is above a certain level, bleeding out is likely to be suppressed. When the number average molecular weight is not more than a certain value, the compatibility with the cycloolefin-based resin is hardly impaired, and haze increase is easily suppressed.

  The number average molecular weight of the polyester plasticizer can be measured by gel permeation chromatography. Specifically, using a gel permeation chromatography (GPC) measuring device (“HLC-8330” manufactured by Tosoh Corporation), the number average molecular weight (Mn) of the ester compound in terms of standard polystyrene is measured under the following measurement conditions. Can be measured.

(Measurement condition)
Column: “TSK gel SuperHZM-M” × 2 and “TSK gel SuperHZ-2000” × 2 Guard column: “TSK superH-H”
Developing solvent: Tetrahydrofuran Flow rate: 0.35 mL / min The number average molecular weight of the polyester plasticizer can be adjusted by the reaction time of condensation or polycondensation.

  The acid value of the polyester plasticizer is preferably 0.5 mgKOH / g or less, more preferably 0.3 mgKOH / g or less. The hydroxyl value of the polyester plasticizer is preferably 25 mgKOH / g or less, more preferably 15 mgKOH / g or less.

  Polyester plasticizers can be synthesized by a conventional method using a hot melt condensation method by esterification or transesterification of dicarboxylic acid, diol, and end-capping monocarboxylic acid, or dicarboxylic acid and end-capping monocarboxylic acid. It can be performed by any of the interfacial condensation methods of acid chloride and diol. The charging ratio of the diol and the dicarboxylic acid is adjusted so that the molecular terminal is a diol.

  It is preferable that the addition amount with respect to the cycloolefin resin of the polyester plasticizer which has a structure represented by General formula (1) exists in the range of 2-10 mass%. More preferably, it exists in the range of 3-7 mass%. The addition amount is 2% by mass or more, and an effect of increasing the optical film hardness is recognized. When the addition amount is 10% by mass or less, it is preferable from the viewpoint of improving the dimensional stability and the haze stability in a high temperature environment.

(UV absorber)
When a polarizing plate having the first protective film T1 on the viewing side and the second protective film T2 on the other surface side with the polarizer in between, at least one of the protective film T1 and the protective film T2 is the present invention. It is one of the preferred embodiments that the optical film is further configured and that the protective film T1 or the protective film T2 further contains an ultraviolet absorber.

  As an ultraviolet absorber applied to the optical film of the present invention, from the viewpoint of preventing the deterioration of the polarizer and the liquid crystal, it is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of the display property of the liquid crystal, a visible wavelength of 400 nm or more It is preferable to have a characteristic of low light absorption.

  Although the ultraviolet absorber applicable to the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, An inorganic powder etc. are mentioned.

  Examples of ultraviolet absorbers applicable to the present invention include 5-chloro-2- (3,5-di-sec-butyl-2-hydroxyphenyl) -2H-benzotriazole, (2-2H-benzotriazole- 2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, There are tinuvins such as tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, and tinuvin 928, all of which are commercially available products from BASF Japan and can be preferably used.

  More preferably used ultraviolet absorbers are benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, and triazine ultraviolet absorbers, and particularly preferably benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers.

  For example, as the benzotriazole ultraviolet absorber, a compound represented by the following general formula (b) can be used.

In the general formula (b), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different, and are a hydrogen atom, a halogen atom, a nitro group, a hydroxy group, an alkyl group, an alkenyl group, an aryl group. Represents an alkoxy group, an acyloxy group, an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group, an acylamino group or a 5- to 6-membered heterocyclic group, and R ₄ and R ₅ are closed to form a 5- to 6-membered ring The carbocyclic ring may be formed. Moreover, these groups described above may have an arbitrary substituent.

  Although the specific example of a benzotriazole type ultraviolet absorber is given to the following, this invention is not limited to these.

UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole UV-3 : 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-Chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2- (2H-benzotriazol-2-yl) -6 (Linear and side chain dodecyl) -4-methylphenol (TINUVIN171)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- 4-Hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate mixture (TINUVIN 109)
Furthermore, as the benzophenone ultraviolet absorber, a compound represented by the following general formula (c) is preferably used.

In the general formula (c), Y represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, or a phenyl group, and these alkyl group, alkenyl group, and phenyl group may have a substituent. Good. A represents a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group, or a CO (NH) _n-1- D group, and D represents an alkyl group, an alkenyl group, or a substituent. The phenyl group which may have is represented. m and n represent 1 or 2.

  In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxy group represents, for example, an alkoxy group having up to 18 carbon atoms, and the alkenyl group has, for example, carbon number An alkenyl group up to 16 represents an allyl group, a 2-butenyl group, or the like. In addition, as substituents for alkyl groups, alkenyl groups, and phenyl groups, halogen atoms such as chlorine atoms, bromine atoms, fluorine atoms, etc., hydroxy groups, phenyl groups (this phenyl group is substituted with alkyl groups or halogen atoms, etc.) May be used).

  Specific examples of the benzophenone-based ultraviolet absorber represented by the general formula (c) are shown below, but the present invention is not limited thereto.

UV-10: 2,4-dihydroxybenzophenone UV-11: 2,2'-dihydroxy-4-methoxybenzophenone UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13: Bis (2-methoxy -4-hydroxy-5-benzoylphenylmethane)
In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  The optical film which concerns on this invention can also contain 2 or more types of ultraviolet absorbers.

  In the present invention, as the ultraviolet absorber, in particular, “2- (2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1, “3,3-tetramethylbutyl) phenol” is preferably used because it can provide a thin film while achieving both the UV absorption and low retardation of the protective film of the present invention.

  The optical film which concerns on this invention can also contain 2 or more types of ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the ultraviolet absorber is to add the dope after dissolving the ultraviolet absorber in an alcohol such as methanol, ethanol or butanol, a solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof, or You may add directly in dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the use conditions, etc., but when the dry film thickness of the optical film is 10 to 100 μm, it is 0.5 to 10% by mass with respect to the optical film. Is preferable, and the inside of the range of 0.6-4 mass% is still more preferable.

(Antioxidant)
An antioxidant can be applied to the optical film of the present invention.

  Antioxidants have the role of delaying or preventing the optical film from being decomposed by, for example, halogen as a residual solvent in the optical film or phosphoric acid as a phosphoric acid plasticizer. Therefore, the antioxidant is included in the film. Is preferred.

  In this invention, what is generally known can be used as an antioxidant. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, “Irgafos XP40, Irgafos XP60” commercially available from BASF Japan Ltd. can be mentioned.

  Examples of the sulfur compound include “Sumilizer TPL-R” and “Sumilizer TP-D” commercially available from Sumitomo Chemical Co., Ltd.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, “Irganox 1076”, “Irganox 1010” commercially available from BASF Japan Ltd., and ADEKA Corporation are commercially available. "Adeka Stub AO-50" can be mentioned.

  The above double bond compounds are commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”.

  Examples of the hindered amine compound include “Tinvin 144” and “Tinvin 770” commercially available from BASF Japan, and “ADK STAB LA-52” commercially available from ADEKA.

  Examples of the phosphorus compound include “Sumizer GP” commercially available from Sumitomo Chemical Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010” commercially available from ADEKA Corporation. "IRGAFOS P-EPQ" commercially available from BASF Japan, and "GSY-P101" commercially available from Sakai Chemical Industry.

(Impact reinforcement)
In order to improve impact resistance, the optical film of the present invention preferably contains at least one of core / shell type acrylic fine particles, styrene-conjugated diene compound or butyl acrylate compound as an impact reinforcing material.

  In particular, a core / shell type graft copolymer obtained by grafting a (meth) acrylic resin to a copolymer of a (meth) acrylic rubber and an aromatic vinyl compound described in JP-A-2009-84574, or an international It is preferable to contain an impact reinforcing material such as core-shell type acrylic fine particles described in JP 2009/047924 A and styrene-butadiene-based elastic organic fine particles described in JP 2013-83907 A. .

  For example, core / shell type acrylic fine particles are obtained by polymerizing a mixture of 80 to 98.9% by mass of methyl methacrylate, 1 to 20% by mass of alkyl acrylate and 0.01 to 0.3% by mass of a polyfunctional grafting agent. Obtained by polymerizing a mixture of the innermost hard layer and 75 to 98.5% by mass of an alkyl acrylate, 0.01 to 5% by mass of a polyfunctional crosslinking agent and 0.5 to 5% by mass of a polyfunctional grafting agent. It has a soft layer and an outermost hard layer obtained by polymerizing a mixture of 80 to 99% by weight of methyl methacrylate and 1 to 20% by weight of alkyl acrylate.

  The styrene-conjugated diene compound is preferably a styrene-butadiene copolymer. The copolymer may be a rubber-like elastic body or an elastic organic fine particle. Specifically, the elastic organic fine particle is preferably a core-shell type particle.

  A soft polymer contains the structural unit derived from a conjugated diene monomer, and the structural unit derived from another monomer as needed. Examples of the conjugated diene monomer include 1,3-butadiene (hereinafter sometimes simply referred to as “butadiene”), isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, myrcene and the like are included, and butadiene and isoprene are preferable. Examples of other monomers include styrene components such as styrene and α-methylstyrene. The content ratio of the structural unit derived from the conjugated diene monomer in the soft polymer is usually 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

  Examples of other polymers include a copolymer of acrylonitrile and styrene, a polymer mainly composed of a methacrylic ester such as methyl methacrylate, and the like.

  Commercially available products include, for example, Metabrene C-140A, C-215A (above, manufactured by Mitsubishi Rayon Co., Ltd.), Toughprene 126, Asaflex 800, Asaflex 825 (above, manufactured by Asahi Kasei Chemicals Co., Ltd.), TR2000, TR2250. (Above, manufactured by JSR Corporation).

  Examples of other rubber-like elastic bodies include acrylate-based rubber-like polymers, and rubber-like polymers containing acrylate-based polymers containing butyl acrylate as the main component are preferred.

[Optical characteristics of optical film]
In the optical film of the present invention, the retardation value Ro defined by the following formula (i) is in the range of 0 to 10 nm, and the retardation value Rt defined by the following formula (ii) is −10 to 10 nm. It is preferable to be within the range.

Formula (i)
_{Ro = (n x -n y)} × d
Formula (ii)
Rt = {(n _x + n _y ) / 2−n _z } × d
In the above formula (i) and (ii), Ro-plane direction of the retardation value of the film, Rt is the thickness direction of the retardation value of the film, n _x is a refractive index in a slow axis direction in the film plane, _ny is the refractive index in the fast axis direction in the film plane, _nz is the refractive index in the thickness direction of the film (the refractive index is measured at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH), and d is the film Represents thickness (nm).

The retardation value Ro in the in-plane direction and the retardation value Rt in the thickness direction of the film are an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix).
Polarimeter: manufactured by Axometrics) under a 23 ° C./55% RH environment at a wavelength of 590 nm, a three-dimensional refractive index measurement can be performed, and the obtained refractive indexes nx, ny and nz can be calculated. .

  The retardation value Ro defined by the formula (i) defined above is in the range of 0 to 10 nm, and the retardation value Rt represented by the formula (ii) is in the range of −10 to 10 nm means in-plane It means that the retardation value Ro (nm) in the direction and the retardation value Rt (nm) in the thickness direction of the film are almost zero.

  By making the retardation value Ro in the film plane of the optical film and the retardation value Rt in the thickness direction of the film substantially zero, the black in the liquid crystal display device obtained when pasted to the liquid crystal cell on the optical film side Since light leakage during display can be effectively prevented, visibility can be improved. In addition, since the thickness of the optical film can be reduced, the polarizing plate and the liquid crystal display device can be further reduced in thickness and weight, which is preferable.

  Although there is no restriction | limiting in particular as a method of achieving the said conditions, The method of appropriately controlling the extending | stretching conditions at the time of film-forming is suitable.

[Method for producing optical film]
As the method for producing the optical film of the present invention, the usual inflation method, T-die method, calendar method, cutting method, casting method, emulsion method, hot press method and the like can be used. From the viewpoint of suppression of defects and suppression of optical defects such as die lines, a solution casting film forming method and a melt casting film forming method can be selected as a film forming method, and particularly a solution casting film forming method. In addition to the effect of controlling the panel bend by controlling the distribution state of the cycloolefin-based resin, a uniform and smooth surface can be obtained, and this is preferable from the viewpoint of reducing haze and yellow index (YI).

<Solution casting method>
Hereafter, the manufacture example by the solution casting method suitable for manufacture of the optical film of this invention is demonstrated.

  The production of the optical film of the present invention comprises a step of preparing a dope by dissolving a compound such as a cycloolefin resin, a matting agent and, if necessary, a polyester plasticizer in a solvent, and filtering the prepared dope. Or a process of casting on a drum-shaped metal support to form a web, a process of peeling the formed web from the metal support to form a film, a process of stretching and drying the film, and after cooling the dried film It is performed by a step of winding in a roll shape.

  Hereinafter, each step will be described.

(1) Dissolution process In a dissolution vessel, the resin, and optionally other compounds are dissolved in an organic solvent mainly composed of a good solvent for the cycloolefin resin while stirring to form a dope, or the resin solution And the other compound solution is mixed to form a dope which is a main solution.

  When the optical film of the present invention is produced by a solution casting method, an organic solvent useful for forming a dope can be used without limitation as long as it can simultaneously dissolve a cycloolefin resin and other additives. .

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. For example, methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used as the main solvent. Particularly preferably ethyl acetate.

  In addition to the organic solvent, the dope preferably contains a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in the range of 1 to 40% by mass. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the proportion of alcohol is small, cycloolefin-based resins and other compounds in a non-chlorine organic solvent system There is also a role of promoting dissolution of the. In the film formation of the optical film of the present invention, a method of forming a film using a dope having an alcohol concentration in the range of 0.5 to 15.0% by mass is applied in order to improve the flatness of the obtained optical film. can do.

  In particular, a cycloolefin resin and other compounds were dissolved in a total amount of 15 to 45% by mass in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. A dope composition is preferred.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, methanol and ethanol are preferred because of the stability of the dope, the boiling point is relatively low, and the drying property is good.

  For dissolving the cycloolefin-based resin or other compounds, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, Use various dissolution methods such as the method of cooling and dissolving as described in JP-A-9-95557 or JP-A-9-95538, and the method of performing at high pressure described in JP-A-11-21379. However, a method of pressurizing at a pressure higher than the boiling point of the main solvent is particularly preferable.

  It is preferable that the density | concentration of the cycloolefin type resin in dope exists in the range of 10-40 mass%. After the compound is added to the dope during or after dissolution and dissolved and dispersed, it is filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Regarding dope filtration, it is preferable to filter the dope with a filter medium having a 90% collection particle diameter of 10 to 100 times the average particle diameter of fine particles, for example, with a main filter equipped with a leaf disk filter.

  In the present invention, the filter medium used for filtration preferably has a small absolute filtration accuracy, but if the absolute filtration accuracy is too small, the filter medium is likely to be clogged, and the filter medium must be frequently replaced. There is a problem of lowering productivity.

  Therefore, in the present invention, the filter medium used for the dope preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and in the range of 0.003 to 0.006 mm. The filter medium is more preferable.

  There are no particular restrictions on the material of the filter medium, and normal filter media can be used. However, plastic fiber filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel fibers are used to remove fibers. This is preferable.

In the present invention, the flow rate of the dope during filtration, preferably in the range of ^{10~80kg / (h · m 2)} , more preferably ^{20~60kg / (h · m 2)} . Here, if the dope flow rate during filtration is 10 kg / (h · m ² ) or more, efficient productivity is obtained, and the dope flow rate during filtration is 80 kg / (h · m ² ) or less. For example, the pressure applied to the filter medium is appropriate, and the filter medium is preferably not damaged.

  The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

  Next, a specific configuration example for producing the optical film of the present invention by a solution casting method will be described with reference to the drawings. In the following description, the numerals described in parentheses after the components indicate the symbols described in the drawings.

  FIG. 1 is a schematic view showing an example of a solution casting film forming apparatus applicable to the production of the optical film of the present invention.

  Large dough is removed from the dope prepared in the charging kettle (41) by the filter (44), and the dope is fed to the stock kettle (42). Thereafter, various additives are added from the stock kettle (42) to the main dope dissolving kettle (1).

  Thereafter, the main dope is filtered by the main filter (3), and a matting agent dispersion, an ultraviolet absorbent additive, and the like are added in-line through the conduit (16).

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material.

  The return material is, for example, a product obtained by finely pulverizing the optical film of the present invention, which is generated when the optical film is formed, and has exceeded the specified value of the film due to a product obtained by cutting off both side portions of the film or scratches. An optical film stock is used.

  Moreover, as a raw material of cycloolefin resin used for dope preparation, what pelletized resin and other compounds previously can also be used preferably.

(2) Casting step (2-1) Casting of dope An endless metal support that feeds the dope to a pressurizing die (30) through a pump (for example, a pressurized metering gear pump) and transfers it indefinitely. (31) A step of casting a dope from a pressure die slit to a casting position on a metal support such as a stainless steel belt or a rotating metal drum.

  The metal support (31) in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be in the range of 1 to 4 m, preferably in the range of 1.5 to 3 m, and more preferably in the range of 2 to 2.8 m.

  The surface temperature of the metal support (31) in the casting step is set in the range of −50 ° C. to a temperature at which the solvent boils and does not foam, more preferably in the range of −30 to 100 ° C. A higher temperature is preferable because the web drying speed can be increased. However, if the temperature is too high, the web may foam and flatness may deteriorate. As preferable support body temperature, it determines suitably in the range of 0-100 degreeC, and the inside of the range of 5-30 degreeC is still more preferable. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  Although the method in particular of controlling the temperature of a metal support body (31) is not restrict | limited, There exist the method of spraying warm air or cold air, and the method of making warm water contact the back side of a metal support body. It is preferable to use hot water because heat transfer is performed efficiently, so that the time until the temperature of the metal support (31) becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there. In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

  As the die, the pressure die (30) is preferable because the slit shape of the die portion of the die can be adjusted and the film thickness can be easily made uniform. The pressure die (30) includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support (31) is a mirror surface. In order to increase the deposition rate, two or more pressure dies (30) may be provided on the metal support (31), and the dope amount may be divided and laminated.

(3) Solvent evaporation step The web (the dope is cast on the casting support and the formed dope film is referred to as a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method in which air is blown from the web side, a method in which heat is transferred from the back surface of the support by liquid, a method in which heat is transferred from the front and back by radiant heat, and the like. Well preferred. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within a range of 30 to 120 seconds.

(4) Peeling process A peeling process is a process of peeling the web which the solvent evaporated on the metal support body in the peeling position (33). The peeled web is sent to the next process as a film.

  The temperature at the peeling position (33) on the metal support is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

  The amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is preferably within the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, etc. When peeling at a higher residual solvent amount, if the web is too soft, the flatness at the time of peeling is impaired, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

  The amount of residual solvent in the web is defined by the following formula (I).

Formula (I)
Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension when peeling the metal support and the film is usually in the range of 196 to 245 N / m. However, if wrinkles are likely to occur during peeling, the peeling may occur with a tension of 190 N / m or less. preferable.

  In the present invention, the temperature at the peeling position (33) on the metal support (31) is preferably in the range of −50 to 40 ° C., more preferably in the range of 10 to 40 ° C., and 15 to 30. Most preferably, it is within the range of ° C.

(5) Drying and stretching process (Drying process)
The web obtained by peeling from the metal support is dried. The web may be dried while being transported by a large number of rollers arranged above and below, or may be dried while being transported by fixing both ends of the web with clips like a tenter dryer.

  The means for drying the web is not particularly limited, and can be performed with hot air, infrared rays, a heating roller, microwaves, or the like, but it is preferable to perform with hot air in terms of simplicity.

  The drying temperature in the web drying step is preferably equal to or lower than the glass transition temperature (Tg) of the film, and it is effective to perform a heat treatment within a range of 10 to 60 minutes at a temperature of 100 ° C. or higher. Drying is performed at a drying temperature in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

  In addition, a drying process can also be performed by dividing into a preliminary drying process and this drying process.

(Stretching process)
The optical film of the present invention can be oriented to control the orientation of molecules in the film, improve planarity, and obtain toughness.

  The optical film of the present invention is preferably stretched in the longitudinal direction (also referred to as MD direction) and / or in the lateral direction (also referred to as TD direction), and at least 1.01 as a stretching ratio in the longitudinal direction or lateral direction. It is preferable to stretch within a range of 10 times.

  The stretching operation may be performed in multiple stages. Moreover, when performing biaxial stretching, you may perform simultaneous biaxial stretching of MD direction and TD direction, and you may implement in steps. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

  That is, for example, the following stretching steps are possible.

-Stretch in longitudinal direction-> Stretch in width direction-> Stretch in longitudinal direction-> Stretch in longitudinal direction-Stretch in width direction-> Stretch in width direction-> Stretch in longitudinal direction-> Stretch in longitudinal direction--Stretch in width direction-> Stretching in an oblique direction In addition, simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension.

  The amount of residual solvent at the start of stretching is preferably in the range of 2 to 10% by mass.

  If the amount of residual solvent is 2% by mass or more, the film thickness deviation is small, which is preferable from the viewpoint of flatness, and if it is 10% by mass or less, surface unevenness is reduced, and the flatness is improved.

  When the optical film of the present invention has a glass transition temperature of Tg (° C.) in the MD direction and / or TD direction, preferably in the TD direction so that the film thickness after stretching is in a desired range, It is preferable to stretch in a temperature range of (Tg + 15) to (Tg + 50) ° C. If it extends in the said temperature range, since a extending | stretching stress can be reduced, a haze will become low. Moreover, generation | occurrence | production of a fracture | rupture is suppressed and the optical film excellent in planarity is obtained. The stretching temperature is preferably within the range of (Tg + 20) to (Tg + 40) ° C.

  The optical film of the present invention preferably stretches the web at least in the range of 1.01 to 10 times in the MD direction or TD direction, but the range of stretching is 1.1 to 10 times the original width. It is preferably within the range, and more preferably within a range of 1.2 to 8 times. If it is in the said range, a film will become toughness, a film can be thinned, and the planarity of a film can be improved.

  In order to stretch in the MD direction, it is preferable to peel at a peeling tension of 130 N / m or more, and it is particularly preferable to peel within a range of 150 to 170 N / m. Since the web after peeling is in a high residual solvent state, stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the web dries and the residual solvent amount decreases, the stretch ratio in the MD direction decreases.

  In addition, for the stretching in the MD direction, a roller stretching machine using a difference in peripheral speed of rollers can be used, and the stretching ratio can be calculated from the rotation speed of the belt support and the operation speed of the roller stretching machine.

  In order to stretch in the TD direction, for example, the entire drying process or a part of the process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 is performed while holding the width at both ends of the web with clips or pins in the width direction. A drying method (referred to as a tenter method), among them, a tenter method using clips and a pin tenter method using pins are preferably used.

  In stretching in the TD direction, stretching in the width direction of the film at a stretching speed in the range of 250 to 500% / min is preferable from the viewpoint of improving the flatness of the film.

  If the stretching speed is 250% / min or more, the planarity is improved and the film can be processed at a high speed, which is preferable from the viewpoint of production aptitude, and if it is 500% / min or less, the film is broken. Can be processed without any problem.

  A preferable stretching speed is in the range of 300 to 400% / min. The stretching speed is defined by the following formula (II).

Formula (II)
Stretching speed (% / min) = [(d ₁ / d ₂ ) −1] × 100 (%) / t
In the formula (II), d ₁ represents the width in the stretching direction of the resin film after stretching. d ₂ represents the width in the stretching direction of the resin film before stretching. t represents the time (min) required for stretching.

  In the optical film of the present invention, the retardation value (Ro) defined by the formula (i) is in the range of 0 to 10 nm, and the retardation value (Rt) defined by the formula (ii) is −10. It is preferable when it exists in the range of 10 nm as an optical film which does not require retardation especially. The optical film can be stretched while adjusting the stretch ratio in at least the MD direction or the TD direction.

(Knurling)
After a predetermined heat treatment or cooling treatment, it is preferable to provide a slitter and cut off the end portion before winding to obtain a good winding shape. Furthermore, it is preferable to knurling both ends of the width.

  The knurling process can be formed by pressing a heated embossing roller. Fine embossing is formed on the embossing roller, and by pressing the embossing roller, unevenness can be formed on the film and the end can be made bulky.

  The height of the knurling at both ends of the width of the optical film of the present invention is preferably in the range of 4 to 20 μm and in the range of 5 to 20 mm.

  In the present invention, the knurling process is preferably provided after the drying in the film forming step and before the winding.

(6) Winding step The winding step is a step of winding the film as a film after the residual solvent amount in the web is 2% by mass or less. The dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film having good properties can be obtained.

  As a winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

<Melt casting method>
The optical film of the present invention can also be formed by a melt casting method. The melt casting method refers to heating and melting a composition containing the cycloolefin resin and other compounds according to the present invention to a temperature showing fluidity, and then casting the fluid melt.

  In the melt casting method, the melt extrusion method is preferable from the viewpoint of mechanical strength and surface accuracy. A plurality of raw materials used for melt extrusion are usually preferably kneaded and pelletized in advance.

  Pelletization may be performed by a known method, for example, a cycloolefin resin or other compound is fed to an extruder with a feeder and kneaded using a single or twin screw extruder, extruded from a die into a strand, It can be done by water cooling or air cooling and cutting.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders.

  A small amount of additives such as particles and antioxidants are preferably mixed in advance in order to mix uniformly.

  It is preferable to process the extruder at a temperature as low as possible so that the extruder can be pelletized so as to suppress shearing force and prevent the resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. Of course, the raw material powder can be directly supplied to the extruder by a feeder without being pelletized, and a film can be formed as it is.

  Using a single-screw or twin-screw type extruder, the pellets are melted at a temperature of about 200 to 300 ° C., filtered through a leaf disk type filter or the like to remove foreign matters, and then flowed from the T die into a film. Then, the film is nipped with a cooling roller and an elastic touch roller, and solidified on the cooling roller to form an optical film.

  When introducing into the extruder from the supply hopper, it is preferable to prevent oxidative decomposition or the like under vacuum or reduced pressure or in an inert gas atmosphere.

  The extrusion flow rate is preferably adjusted stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. Stainless steel fiber sintered filter is made by compressing the stainless steel fiber body after creating a complex intertwined state, and sintering and integrating the contact points. The density is changed depending on the thickness of the fiber and the compression amount, and filtration is performed. The accuracy can be adjusted.

  Additives such as antioxidants and particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

  The optical film temperature on the touch roller side when the optical film is nipped between the cooling roller and the elastic touch roller is preferably in the temperature range of Tg to (Tg + 110) ° C. of the film. A known roller can be used as the roller having an elastic surface used for such purposes.

  The elastic touch roller is also called a pinching rotator. A commercially available one can be used as the elastic touch roller.

  When peeling the film from the cooling roller, it is preferable to control the tension to prevent deformation of the film.

  Moreover, it is preferable that the film obtained as described above is stretched by a stretching operation after passing through the step of contacting the cooling roller.

  As a stretching method, a known roller stretching machine, a tenter or the like can be preferably used. The stretching temperature is usually preferably in the temperature range of Tg to (Tg + 60) ° C. of the cycloolefin resin constituting the film.

  Before winding, the end may be slit and cut to the width to be the product, and knurling (embossing) may be applied to both ends to prevent sticking and scratching during winding. The knurling method can be processed by heating or pressurizing using a metal ring having an uneven pattern on the side surface. In addition, since the optical film has deform | transformed and cannot use as a product normally, the holding part of the clip of the both ends of a film is cut out and reused.

<Physical properties of optical film>
(Wavelength dispersion)
In the optical film of the present invention, when the values of retardation (Ro) at wavelengths of 450 nm and 550 nm are Ro (450) and Ro (550), respectively, the value calculated by Ro (450) / Ro (550) is Preferably it is less than 1.01.

(Haze)
The optical film of the present invention preferably has a haze value of 1.0% or less, and more preferably 0.5% or less. By setting the haze to 1.0% or less, there is an advantage that the transparency of the film becomes higher and it becomes easier to use as a film for optical applications.

  The haze value is measured with a haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136.

(Yellow Index: YI)
In the optical film of the present invention, YI is preferably 1.0 or less, and more preferably 0.5 or less. By setting YI to 1.0 or less, there is an advantage that the transparency of the film becomes higher and it becomes easier to use as a film for optical applications. In particular, manufacturing the optical film of the present invention by a solution casting method is a preferable manufacturing method from the viewpoint of reducing YI.

  The yellow index (YI) referred to in the present invention can be determined by the method described in JIS K 7105-6.3. As a specific method for measuring the yellow index value, the color tristimulus values X, Y, and Z are obtained using a spectrophotometer U-3200 manufactured by Hitachi, Ltd. and the attached saturation calculation program, etc. The yellow index value is obtained.

Yellow index (%) = 100 (1.28X-1.06Z) / Y
(Total light transmittance)
The total light transmittance of the optical film of the present invention is preferably 80% or more, more preferably 90% or more. More preferably, it is 93% or more. The total light transmittance can be measured according to JIS K 7573 “Plastics—How to determine total light transmittance and total light reflectance”.

(Equilibrium moisture content)
In the optical film of the present invention, the equilibrium water content at 25 ° C. and 55% RH is preferably 3% or less, and more preferably 2% or less. By setting the equilibrium moisture content to 3% or less, it is preferable to easily cope with a change in humidity and to hardly change the optical characteristics and dimensions.

(Film length, width, film thickness)
The optical film of the present invention is preferably long, specifically, preferably has a length of about 100 to 10,000 m, and is wound up in a roll shape. The width of the optical film of the present invention is preferably 1 m or more, more preferably 1.4 m or more, and particularly preferably in the range of 1.4 to 4 m.

  The film thickness of the optical film is preferably in the range of 5 to 40 μm from the viewpoint of thinning the display device and productivity. If the film thickness is 5 μm or more, a certain level of film strength and retardation can be expressed. If the film thickness is 40 μm or less, the film has a desired retardation and can be applied to make the polarizing plate and the display device thinner.

(Moisture permeability)
The moisture permeability at 40 ° C. and 90% RH of the optical film is preferably 300 g / (m ² · day) or less, more preferably 200 g / (m ² · day) or less, and 10 to 100 g / ( m ² · day) is preferable. This is for suppressing a change in the size of the polarizer due to the transmitted water in a high temperature and high humidity environment. The moisture permeability is measured under the conditions of 40 ° C. and 90% RH in accordance with the method described in JIS Z 0208.

"Polarizer"
The polarizing plate of the present invention has a first protective film T1 on the viewing side and a second protective film T2 on the other surface side with at least one of the protective film T1 and the protective film T2 sandwiching the polarizer. The optical film of the present invention described above is characterized by the above. Furthermore, it is a preferable aspect that the protective film T1 or the protective film T2 contains an ultraviolet absorber, and more preferably, the protective film T1 and the protective film T2 are both optical films of the present invention. And it is the aspect which contains the ultraviolet absorber.

  As another specification, as described above, the optical film of the present invention is a polarizing plate protection in which the retardation value Ro (nm) in the in-plane direction and the retardation value Rt (nm) in the thickness direction of the film are almost zero. It is preferably a film, the liquid crystal cell side, that is, the optical film of the present invention is bonded as the second protective film T2, and the conventionally known polarizing plate protective film is bonded to the opposite surface. You can also

  As a conventionally known polarizing plate protective film applicable as one film, a commercially available cellulose ester film (for example, Konica Minoltack KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC4FR, KC4KR, KC4DR, KC4SR, KC8UY, KC6U, KC6UA, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC8UX-RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, and the like, manufactured by Konica Minolta Co., Ltd.

  FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the polarizing plate of the present invention.

  In FIG. 2, the polarizing plate (101A) has a polarizer (104A) in between, a first protective film (T1) on the viewing side, and a second protective film (T2) on the liquid crystal cell side. The structure arranged through the layers (103A and 103B) is representative, and at least one of the first protective film (T1) and the second protective film (T2) is the optical film of the present invention. Is preferably the second protective film (T2) disposed on the liquid crystal cell side, more preferably the first protective film (T1) and the second protective film (T2), It is the structure which is an optical film of invention.

  In the polarizing plate of the present invention, the optical film or the like of the present invention is appropriately surface-treated and bonded using a water-based adhesive or an active energy ray-curable adhesive.

[Polarizer]
A polarizer is an element that passes only light having a plane of polarization in a certain direction, and a typical polarizer known at present is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  As the polarizer, a polarizer obtained by forming a polyvinyl alcohol aqueous solution into a film and dyeing it by uniaxial stretching or dyeing and then uniaxially stretching and then preferably performing a durability treatment with a boron compound may be used.

  The film thickness of the polarizer is in the range of 5.0 to 15.0 μm, and particularly preferably in the range of 5.0 to 10.0 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol within the range is preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature in the range of 66 to 73 ° C. is preferably used. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has little color unevenness, and is particularly preferably used for a large liquid crystal display device.

  Moreover, since it is preferable to make a polarizing plate into a thin film, it is especially preferable that the thickness of a polarizer exists in the range of 2.0-15.0 micrometers from a viewpoint of making the intensity | strength of a polarizing plate, and thin film formation compatible.

  As such a thin film polarizer, a laminated film type polarizer is produced by the method described in JP2011-1000016, JP4691205, JP4751481, JP48080489. Is preferred.

[Production method of polarizing plate]
(1. Production of polarizing plate using aqueous adhesive)
The polarizing plate of the present invention can be produced by a general method. The surface of the polarizer of the optical film of the present invention is subjected to surface treatment such as corona treatment, plasma treatment or excimer light treatment, and is immersed and stretched in an iodine solution. Bonding can be performed using an aqueous alcohol solution (aqueous adhesive).

  In that case, it is preferable that the retardation film and the polarizer are similarly bonded by a completely saponified polyvinyl alcohol aqueous solution (aqueous adhesive). When a cellulose ester film is used as the retardation film, the surface is preferably saponified.

  The direction of bonding with the polarizer is preferably bonded so that the absorption axis of the polarizer and the slow axis of the polarizing plate protective film are orthogonal, for example.

(2. Production of polarizing plate using active energy ray-curable adhesive)
In the polarizing plate of this invention, it is a preferable aspect that the optical film of this invention and at least one surface of a polarizer are bonded by the active energy ray hardening-type adhesive agent. In that case, it is preferable that the said retardation film and polarizer are similarly bonded by the active energy ray hardening-type adhesive agent. Furthermore, it is preferable that it is bonded by the same type of active energy ray-curable adhesive.

  In the present invention, by applying an active energy ray-curable adhesive to the bonding between the optical film of the present invention and a polarizer or the bonding between another polarizing plate protective film and a polarizer, high productivity is achieved. Therefore, it is easy to suppress the deformation of the polarizing plate, and it is possible to obtain characteristics excellent in flatness.

(Composition of active energy ray-curable adhesive)
Examples of the active energy ray-curable adhesive composition applicable to the production of polarizing plates include a photo radical polymerization composition utilizing photo radical polymerization, a photo cation polymerization composition utilizing photo cation polymerization, and photo radical polymerization. In addition, a hybrid composition using both photocationic polymerization and photocationic polymerization is known.

  As a radical photopolymerization type composition, a radical polymerizable compound containing a polar group such as a hydroxy group or a carboxy group described in JP-A-2008-009329 and a radical polymerizable compound not containing a polar group are contained in a specific ratio. Compositions and the like are known. In particular, the radical polymerizable compound is preferably a compound having a radical polymerizable ethylenically unsaturated bond. Preferable examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include an N-substituted (meth) acrylamide compound and a (meth) acrylate compound. (Meth) acrylamide means acrylamide or methacrylamide.

  Moreover, as a photocationic polymerization type composition, as disclosed in JP 2011-08234 A, (α) a cationic polymerizable compound, (β) a photocationic polymerization initiator, and (γ) a wavelength longer than 380 nm. And an active energy ray-curable adhesive composition containing each of the components of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, active energy ray-curable adhesives other than these may be used.

  As the actinic radiation curable adhesive used in the present invention, an ultraviolet curable adhesive as described in the above publication is preferably used.

  Hereinafter, an example of the manufacturing method of the polarizing plate using an active energy ray hardening-type adhesive agent is demonstrated.

As a manufacturing process of the polarizing plate of the present invention, mainly,
1) An adhesive application step of applying an active energy ray-curable adhesive to at least one of the adhesive surfaces of the polarizer and the optical film of the present invention;
2) A bonding step in which a polarizer and a polarizing plate protective film are bonded and bonded together via an adhesive layer;
3) A curing step of curing the adhesive layer in a state where the polarizer and the polarizing plate protective film are bonded via the adhesive layer,
Can be mentioned. Moreover, you may have the pre-process process which carries out an easy adhesion process with respect to the surface which adhere | attaches the polarizer of a polarizing plate protective film.

(Pretreatment process)
In the pretreatment step, an easy adhesion treatment is performed on the surface of the polarizing plate protective film adhered to the polarizer. When the polarizing plate protective film and the retardation film are bonded to both surfaces of the polarizer via an active energy ray curable adhesive, an easy adhesion treatment is applied to each bonding surface of the polarizing plate protective film. .

  In the adhesive application step, which is the next step, the surface subjected to the easy adhesion treatment is treated as a bonding surface with the polarizer, and therefore, the both surfaces of the polarizing plate protective film are bonded to the active energy ray-curable resin layer. An easy adhesion treatment is applied to the surface. Examples of the easy adhesion treatment include corona treatment, plasma treatment, and excimer light treatment.

(Adhesive application process)
In the adhesive application step, the active energy ray-curable adhesive is applied to at least one surface side of the adhesive surfaces of the polarizer and the polarizing plate protective film. When applying an active energy ray hardening-type adhesive directly on the surface of a polarizer or a polarizing plate protective film, there is no special limitation in the coating method. For example, various wet coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting an active energy ray hardening-type adhesive between a polarizer and a polarizing plate protective film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.

(Bonding process)
After apply | coating an active energy ray hardening-type adhesive agent by said method, it processes by a bonding process. In this bonding step, for example, when an active energy ray-curable adhesive is applied to the surface of the polarizer in the previous application step, a polarizing plate protective film is superimposed there. When the active energy ray-curable adhesive is applied to the surface of the polarizing plate protective film in the previous application step, a polarizer is superimposed thereon. Moreover, when an active energy ray hardening-type adhesive agent is cast between a polarizer and a polarizing plate protective film, a polarizer and a polarizing plate protective film are piled up in that state. When a polarizing plate protective film and a retardation film are bonded to both sides of a polarizer, and both surfaces use an active energy ray-curable adhesive, an active energy ray-curable adhesive is applied to both sides of the polarizer. A polarizing plate protective film and a retardation film are superimposed on each other. Usually, in this state, both sides (when a polarizing plate protective film is superimposed on one side of the polarizer, the polarizing plate protective film and the retardation film are provided on both sides of the polarizer and the polarizing plate protective film side. In the case of superimposing, pressure is applied between the polarizing plate protective film and the retardation film side of both surfaces with a roller or the like. As the material of the roller, metal, rubber or the like can be used. The rollers arranged on both sides may be made of the same material or different materials.

(Curing process)
In the curing step, an active energy ray curable adhesive is irradiated with active energy rays, and a cationic polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radical polymerizable compound (for example, an acrylate compound or an acrylamide compound). The active energy ray-curable resin layer containing the compound or the like is cured, and the polarizer and the polarizing plate protective film, or the polarizer and the retardation film are overlapped with each other via the active energy ray-curable adhesive. When bonding a polarizing plate protective film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or a polarizing plate protective film side. In addition, when a polarizing plate protective film and a retardation film are bonded to both sides of the polarizer, the polarizing plate protective film and the retardation film are overlaid on both sides of the polarizer via an active energy ray-curable adhesive, respectively. Therefore, it is advantageous to irradiate active energy rays and simultaneously cure the active energy ray-curable adhesive on both sides.

  Visible light, ultraviolet rays, X-rays, electron beams, etc. can be used as the active energy rays applied for curing, but electron beams and ultraviolet rays are generally preferred because they are easy to handle and have a sufficient curing rate. Used.

  As the ultraviolet light source, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. Further, an ArF excimer laser, a KrF excimer laser, an excimer lamp, synchrotron radiation, or the like can also be used. Among these, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon arc, and a metal halide lamp are preferably used.

  Further, as the electron beam, 50 to 1000 keV emitted from various electron beam accelerators such as a cockroft Walton type, a bandegraph type, a resonance transformation type, an insulation core transformation type, a linear type, a dynamitron type, and a high frequency type, preferably 100 Mention may be made of electron beams having an energy in the range of ˜300 keV.

  Any appropriate condition can be adopted as the electron beam irradiation condition as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably in the range of 5 to 300 kV, more preferably in the range of 10 to 250 kV. If the acceleration voltage is 5 kV or more, the electron beam can reach the adhesive sufficiently to obtain the desired curing conditions, and if the acceleration voltage is 300 kV or less, the penetration force through the bonding unit becomes excessively strong. It can suppress that a transparent polarizing plate protective film and a polarizer are damaged.

  As an irradiation dose, it exists in the range of 5-100 kGy, More preferably, it exists in the range of 10-75 kGy. When the irradiation dose is 5 kGy or more, the active energy ray-curable adhesive is sufficiently cured. When the irradiation dose is 100 kGy or less, the polarizing plate protective film and the polarizer are not damaged, and the mechanical strength is reduced. Changes can be prevented, and predetermined optical characteristics can be obtained.

Any appropriate conditions can be adopted as the irradiation condition of the ultraviolet rays as long as the active energy ray-curable adhesive can be cured. The dose of ultraviolet rays is preferably in accumulated light amount is within the range of 50~1500mJ / cm ^2, and even more preferably in the range of 100 to 500 mJ / cm ^2.

  When performing the said manufacturing method by a continuous line, although a line speed is based on the hardening time of an active energy ray hardening-type adhesive agent, Preferably it exists in the range of 1-500 m / min, More preferably, it is the range of 5-300 m / min. Of these, it is more preferably within a range of 10 to 100 m / min. If the line speed is 1 m / min or more, appropriate productivity can be secured, damage to the transparent polarizing plate protective film can be suppressed, and a polarizing plate that can withstand a durability test can be produced. . Moreover, if the line speed is 500 m / min or less, the resulting adhesive is sufficiently cured, and the desired adhesiveness can be obtained.

  In the polarizing plate obtained as described above, the thickness of the active energy ray-curable adhesive layer is not particularly limited, but is usually in the range of 0.01 to 10 μm, preferably 0.5 to 5 μm. Within range.

<Liquid crystal display device>
By using the polarizing plate on which the optical film of the present invention is bonded to a liquid crystal display device, the liquid crystal display device of the present invention excellent in various visibility can be produced.

  The polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB and the like. Preferably, the IPS liquid crystal display device requires a thin polarizing plate.

  In the liquid crystal display device, usually two polarizing plates, a polarizing plate on the viewing side and a polarizing plate on the backlight side, are used, but it is also preferable to use the polarizing plate of the present invention as both polarizing plates. It is also preferable to use as.

  The direction of bonding of the polarizing plate in the IPS liquid crystal display device can be performed with reference to JP-A-2005-234431.

  The liquid crystal cell used in the present invention includes a liquid crystal layer and a pair of substrates sandwiching the liquid crystal layer, and the pair of substrates is a glass substrate having a thickness in the range of 0.3 to 0.7 mm. From the viewpoint of reducing the thickness and weight of the liquid crystal display device, it is preferable.

  FIG. 3 is a schematic cross-sectional view showing an example of the configuration of the liquid crystal display device (100) in which the polarizing plates (101A) and (101B) of the present invention described above are arranged on both surfaces of the liquid crystal cell (101C).

  In FIG. 3, both surfaces of the liquid crystal layer (107) are sandwiched between glass substrates (108A and 108B) as transparent substrates to form a liquid crystal cell (101C), and the respective surfaces of the respective glass substrates (108A and 108B). In addition, the polarizing plates (101A and 101B) having the configuration shown in FIG. 2 are arranged via the adhesive layer (106) to constitute the liquid crystal display device (100).

  In the polarizing plates (101A and 101B), the optical film of the present invention is preferably bonded at least to the positions of the polarizing plate protective films 102A and 102B or 105A and 105B. The polarizing plate protective film is bonded to the polarizers 104A and 104B by ultraviolet curable adhesives 103A to 10D, respectively.

  For example, when the IPS liquid crystal display device is provided, the polarizing plate protective films 105A (T2) and 105B (T3) are preferably the optical films of the present invention.

  The liquid crystal cell (101C) is configured by arranging an alignment film, a transparent electrode, and glass substrates (108A and 108B) on both sides of a liquid crystal substance.

  By providing the liquid crystal display device with the polarizing plate of the present invention excellent in durability, flatness, etc., it is possible to make it difficult for panel bends to occur even if the glass substrate constituting the liquid crystal cell is thinned. A liquid crystal display device in which thinning is achieved can be obtained.

  Examples of the material constituting the glass substrate (108A and 108B) that can be used for the liquid crystal cell (101C) include soda lime glass and silicate glass, and silicate glass is preferable. Specifically, silica glass or borosilicate glass is more preferable.

  The glass constituting the glass substrate is preferably a non-alkali glass that does not substantially contain an alkali component, specifically, a glass having an alkali component content of 1000 ppm or less. The content of the alkali component in the glass substrate is preferably 500 ppm or less, and more preferably 300 ppm or less. In a glass substrate containing an alkali component, substitution of cations occurs on the film surface, and soda blowing phenomenon tends to occur. Thereby, the density of the film surface layer is likely to decrease, and the glass substrate is easily damaged.

  It is preferable that the thickness of the glass substrate (108A and 108B) of the liquid crystal cell which comprises a liquid crystal display device exists in the range of 0.3-0.7 mm. Such a thickness is preferable in that it can contribute to the thinning of the liquid crystal display device.

  The glass substrate can be formed by a known method such as a float method, a down draw method, an overflow down draw method or the like. Of these, the overflow downdraw method is preferred because the surface of the glass substrate does not come into contact with the molded member during molding and the surface of the resulting glass substrate is hardly damaged.

  Such a glass substrate can also be obtained as a commercial product, for example, non-alkali glass AN100 (thickness 500 μm) manufactured by Asahi Glass Co., Ltd., glass substrate EAGLE XG (r) Slim (thickness manufactured by Corning) 300 μm, 400 μm, etc.), a glass substrate (thickness: 100 to 200 μm) manufactured by Nippon Electric Glass Co., Ltd., and the like.

  Further, the polarizing plates (101A, 101B) as shown in FIG. 3 and the glass base materials (108A, 108B) constituting the liquid crystal cell (101C) are bonded via an adhesive layer (106).

  As the adhesive layer, a double-sided tape, for example, a 25 μm-thick double-sided tape manufactured by Lintec (baseless tape MO-3005C) or the like, or a composition used for forming the actinic ray curable resin layer is applied. Can do.

  In addition to the effects of the present invention, the liquid crystal display device using the polarizing plate of the present invention has advantages such as excellent adhesion between layers, excellent resistance to fading, resistance to egg unevenness of display images, and the like.

  Bonding between the surface of the polarizing plate on the side of the retardation film and at least one surface of the liquid crystal cell is performed by a known method. Depending on the case, it may be bonded through an adhesive layer.

  By using the polarizing plate of the present invention, panel bend is suppressed and a liquid crystal display device excellent in visibility such as display unevenness and front contrast is obtained even in the case of a large-screen liquid crystal display device having a screen size of 30 or more. be able to.

<< Use of polarizing plate protective film >>
The optical film of the present invention can be used as a polarizing plate protective film for various display devices such as liquid crystal display devices and organic electroluminescence display devices. The optical film of the present invention can also serve as a retardation film.

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

Example 1
<< Production of optical film >>
(Preparation of optical film 1)
(Preparation of fine particle dispersion)
Silica particles (Aerosil R812, manufactured by Nippon Aerosil Co., Ltd.) 11% by mass
Dichloromethane 89% by mass
The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed using a Manton Gorin disperser to prepare a fine particle dispersion.

(Preparation of fine particle additive solution 1)
Dichloromethane was placed in the dissolution tank, and the fine particle dispersion prepared above was slowly added to 50% by mass with sufficient stirring of dichloromethane. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

<Preparation of dope (D-1)>
The following composition was put into a mixing tank, heated and stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope (D-1).

Cycloolefin resin: ARTON G7810 (manufactured by JSR) 100 parts by mass Dichloromethane 200 parts by mass Ethanol 10 parts by mass Fine particle additive liquid 5.5 parts by mass Tetramethylammonium chloride 0.4 parts by mass <Web formation>
The dope (D-1) prepared above was cast on a film formation line, dried on a metal support until the dope (D-1) had self-supporting properties, and then peeled off as a web and introduced into a tenter.

<Production of optical film>
Next, the film was stretched and conveyed in the width direction (TD) with a tenter at a stretching ratio of 5% and a temperature in the tenter of 140 ° C. Immediately after leaving the tenter, the roller was conveyed with a tension of 100 N / m, and further dried at 140 ° C., and the film was wound up at a winding length of 4000 m to prepare an optical film 1. The dry film thickness of the optical film 1 was 10 μm. The optical film 1 was provided with a release film. As a peelable release film, a polyethylene terephthalate film with a pressure-sensitive adhesive “MASTACK NBO-0424” (manufactured by Fujimori Kogyo Co., Ltd., thickness: 68 μm) was used.

<Measurement of retardation value>
For the optical film 1 produced above, the retardation value Ro in the film plane and the retardation value Rt in the film thickness direction were measured at a wavelength of 590 nm for three-dimensional refractive index measurement, and the obtained refractive index n _x , n _y, the results calculated from _{n z,} Ro is 2 nm, Rt was 4 nm.

(Preparation of optical films 2 to 30)
In the production of the polarizing plate protective film 1, the type of cycloolefin resin, the type and addition amount of the surfactant, the type and addition amount of silica particles, and the thickness of the optical film were changed as shown in Tables 1 and 2. Except for the above, optical films 2 to 30 were produced in the same manner as optical film 1.

Here, materials used for sample preparation are described below together with abbreviations shown in Tables 1 and 2.
A: Cycloolefin resin ARTON G7810 (manufactured by JSR)
B: Cycloolefin resin ARTON R5000 (manufactured by JSR)
C: cycloolefin resin ARTON RX4500 (manufactured by JSR)
S1: Cationic surfactant Tetramethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.)
S2: Cationic surfactant Lauryltrimethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.)
S3: Cationic surfactant stearyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.)
S4: Anionic surfactant sodium dodecyl sulfate (manufactured by Tokyo Chemical Industry Co., Ltd.)
S5: amphoteric surfactant lauryldimethylaminoacetic acid betaine (manufactured by Tokyo Chemical Industry Co., Ltd.)
S6: Nonionic surfactant sorbitan monolaurate (manufactured by Tokyo Chemical Industry Co., Ltd.)
R812: Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd.)
R200V: Aerosil R200 (manufactured by Nippon Aerosil Co., Ltd.)
R812S: Aerosil R821S (manufactured by Nippon Aerosil Co., Ltd.)
<Measurement of hydrophobicity of silica particles>
The degree of hydrophobicity of the silica particles was represented by the methanol wettability value (hereinafter referred to as MW value) determined by this method using the methanol wettability method (hereinafter referred to as MW method).

  In the above MW method, in order to quantify the degree of hydrophobicity of the fine particles, a first solution and a second solution in which methanol and pure water were mixed were used. At this time, the mixing ratio of methanol and pure water is a volume ratio of 3: 7 in the first solution, and a volume ratio of 6: 4 in the second solution. Then, the same amount of the fine particles is added to each solution and stirred and mixed, and each mixed solution is centrifuged to determine the volume of the fine particle sediment, and the volume of the fine particle sediment in the first solution is determined. When tmL and the volume of the sediment of fine particles in the second solution are smL, the MW value is MW value in the first solution = (t / A) × 100 [%] and the MW value in the second solution, respectively. = (S / A) × 100 [%]. Here, A is the volume (AmL) of the silica particles added first.

[Methanol wettability method]
(1) The methanol solution C and the pure water D are mixed at a volume ratio of 3: 7 to prepare the first solution A (for example, the pure water D is 40 mL against the methanol solution C). 60mL)
(2) Next, 0.2 g of silica particle powder E and 7 mL of the first solution A are placed in a 10 mL settling tube F.
(3) The settling tube F is covered, and the fine particle powder E is shaken and mixed into the first solution A using a tumbler mixer. At this time, the condition of the tumbler mixer is 90 seconds at 90 rpm.
(4) In order to precipitate the silica particle powder E, a centrifuge is used. The centrifuge conditions are 10 minutes at 3500 rpm.
(5) The sediment amount of the settled fine particle powder E that can be read with the scale of the sedimentation tube is read as a volume, and the value is defined as tmL.
(6) A methanol solution C and pure water D are newly mixed at a volume ratio of 6: 4 to prepare a second solution B (for example, the methanol solution C is pure with respect to 60 mL. 40 mL of water D).
(7) Using the second solution B, prepare the sediment of the silica particle powder E by the same procedures (8) to (11) as the above (2) to (5), and read with the scale of the sedimentation tube The volume of sedimented silica particle powder E that can be read is read as a volume, and the value is taken as smL.
(12) The MW value (%) is obtained by the following formula.

MW value in the first solution = (t / A) × 100 [%]
MW value in the second solution = (s / A) × 100 [%]
Here, A is the volume (AmL) of the silica particles added first.

  Tables 1 and 2 show the degree of hydrophobicity obtained by the MW method for the silica particles used.

<< Evaluation of optical film >>
About the produced optical films 1-30, the retardation value, the surface resistance value, the half-life, the increase in haze under high temperature and high humidity, coloring, and the total light transmittance were evaluated, respectively.

<Phase difference value>
About the produced polarizing plate protective film, the retardation value Ro in the film plane and the retardation value Rt in the film thickness direction are measured using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). used, environment of 23 ℃ · 55% RH, at a wavelength of 590 nm, subjected to three-dimensional refractive index measured, resulting refractive indices _{n x,} n y, calculated from _{n z.}

<Surface resistance value>
After conditioning the sample for 24 hours in an environment of 23 ° C. and 50% RH, using a high resistivity meter (Hiresta IP MCP-TESTER HT-260) manufactured by Diainstrument, the applied voltage was 500V The resistance value was defined as the surface specific resistance value. Measured in an environment of 23 ° C. × 50% RH, the unit is Ω / sq.
<Half life>
The sample was conditioned for 24 hours in an environment of 23 ° C. and 50% RH, and then STATIC HONESMETER (half-life) (S-5109 type) manufactured by Shishido Electrostatic Co., Ltd. was used. Under the above conditions, after the gas barrier laminate having antistatic performance was charged for 30 seconds, the time until the initial charging voltage was reduced to half was measured and defined as the half-life. Measured in an environment of 23 ° C. × 50% RH, the unit is second (sec).

  The half-life is preferably 200 seconds or less in order to prevent malfunction due to static electricity.

<Increase of haze under high temperature and high humidity>
A difference ΔHz in haze (%) between the film before and after standing for 300 hours in an environment of 80 ° C. and 90% was measured, and the haze durability in a high temperature and high humidity environment was ranked according to the following evaluation criteria.
In addition, the haze meter measured the haze (%) based on JISK-7136 using the Nippon Denshoku make and product name "NDH 2000".

A: ΔHz is less than 0.1% B: ΔHz is 0.1% or more and less than 0.3 Δ: ΔHz is 0.3% or more <Coloring>
The difference ΔYI between the yellow indexes of the optical films before and after being allowed to stand for 300 hours in an environment of 80 ° C. and 90% was determined, and this was used as the evaluation of coloring.

  The yellow index (YI) is obtained by the method described in JIS K-7105-6.3. As a specific method for measuring the yellow index value, the color tristimulus values X, Y, and Z are obtained using a spectrophotometer U-3200 manufactured by Hitachi High-Technology Co., Ltd. and the attached saturation calculation program. The yellow index value was determined according to the following formula.

Yellow index (YI) = 100 (1.28X-1.06Z) / Y
◎: ΔYI is less than 0.05 ○: ΔYI is 0.05 or more and less than 0.1 Δ: ΔYI is 0.1 or more and less than 0.15 ×: ΔYI is 0.1 or more and 0.15 or more <Total light transmittance>
The total light transmittance was evaluated as an evaluation of transparency. The total light transmittance of each optical film was determined by using a spectrophotometer U-3300 manufactured by Hitachi High-Technologies Corporation in accordance with JIS K-7375 for one sample that was conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH. Then, the transmittance in the visible light region (range of 400 to 700 nm) was measured, the average value was obtained, and evaluated according to the following evaluation criteria.

◎: 90% or more ○: 85% or more and less than 90% △: 80% or more and less than 85% ×: less than 80% << Preparation of Polarizing Plate >>
Polarizing plates 1 to 30 were produced according to the following method.

(Production of polarizer)
A 30 μm thick polyvinyl alcohol film having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% was immersed in warm water at 30 ° C. for 60 seconds to swell. Subsequently, the obtained polyvinyl alcohol film was immersed in an aqueous solution of 0.3% by mass of iodine / potassium iodide (mass ratio = 0.5 / 8) and dyed while being stretched up to 3.5 times. Thereafter, the obtained polyvinyl alcohol film was stretched in a boric acid ester aqueous solution at 65 ° C. so that the total stretching ratio was 6.0 times. Thereafter, the obtained polyvinyl alcohol film was dried in an oven at 40 ° C. for 3 minutes to obtain a polarizer having a thickness of 10 μm.

(Preparation of polarizing plate)
On the surface of the polarizing film, 100 parts of an acrylic resin comprising 90% by mass of n-butyl acrylate, 7% by mass of ethyl acrylate, and 3% by mass of acrylic acid, and trimethylolpropane (3 mol) of tolylene diisocyanate (3 mol) 1 mol) Using the pressure-sensitive adhesive obtained by mixing 2 parts of a cross-linking agent composed of a 75% by mass ethyl acetate solution of the adduct, the above-prepared optical film was positioned at T2 (105A) shown in FIG. Further, a commercially available triacetyl cellulose film (thickness 40 μm, manufactured by Konica Minolta Co., Ltd.) is adhered to one side of the polarizer (104) at the position of T1 (102A) shown in FIG. 2, and a metal halide lamp is 280 to 320 nm. was irradiated from the first protective film side accumulated light quantity at a wavelength of so that 320 mJ / cm ^2, to cure the both surfaces of the adhesive, the Obtain a light plate 30.

<Production of liquid crystal display device>
The polarizing plate of the polarizing plate of the polarizing plate of the polarizing plate of the polarizing plate of Sony Mobile Communications Co., Ltd. made by Sony Mobile Communications Co., Ltd., which is an IPS type liquid crystal display device, is peeled off with the liquid crystal cell sandwiched therebetween. A simple IPS type color liquid crystal display was produced by attaching black tape from the display side so that light was not leaked where it was not sandwiched between the polarizing plates so as to be orthogonal to each other.

<Visibility>
Visibility as a liquid crystal display device was evaluated according to the following criteria and ranked.

○: There is no problem with both contrast and color irregularity △: Slight degradation was observed on one side of contrast and color irregularity ×: Summary of evaluation results that showed clear degradation with either contrast or color irregularity 1 and Table 2.

  As is clear from the results shown in Tables 1 and 2, it can be seen that the optical film of the present invention clearly has less coloring (ΔYI) and is excellent in antistatic property and transparency as compared with the comparative example. .

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber preparation pot 20 Merge pipe 21 Mixer 30 Pressure die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roller dryer 41 Feeding kettle 42 Stock kettle 43 Pump 44 Filter 100 Liquid crystal display 101A, 101B Polarizing plate 101C Liquid crystal cell 102A Polarizing plate protective film T1
102B Polarizing plate protective film T4
103A, 103B, 103C, 103D UV curable adhesive 104A, 104B Polarizer 105A Polarizing plate protective film T2
105B Polarizing plate protective film T3
106 Adhesive layer 107 Liquid crystal layer 108A, 108B Glass substrate BL Backlight

Claims (8)

An optical film comprising a cycloolefin-based resin as a main component, wherein the optical film uses a first solution in which the degree of hydrophobicity measured by a methanol wettability method is 3: 7 by volume of methanol and pure water. Silica particles having a hydrophobization degree of 20% or less when methanol and pure water are used in a second solution having a volume ratio of 6: 4 and a hydrophobization degree of 80% or more, Contains at least one surfactant selected from nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants, and in an environment of 23 ° C. and 50% RH for 24 hours An optical film characterized in that the surface resistance value after conditioning is in the range of 1.0 × 10 ^{7 to} 1.0 × 10 ⁹ Ω / sq.   The optical film according to claim 1, wherein the surfactant is a cationic surfactant.   The optical film according to claim 1, wherein the silica particles are contained within a range of 0.1 to 0.5% by mass with respect to the total mass of the film.   The said surfactant is contained in the range of 0.5-8 mass% with respect to the film total mass, The optical film as described in any one of Claim 1- Claim 3 characterized by the above-mentioned.   A film thickness exists in the range of 5-40 micrometers, The optical film as described in any one of Claim 1- Claim 4 characterized by the above-mentioned. The retardation value Ro in the in-plane direction defined by the following formula (i) is in the range of 0 to 10 nm, and the retardation value Rt in the thickness direction defined by the following formula (ii) is −10 to 10. The optical film according to any one of claims 1 to 5, wherein the optical film is within a range of 10 nm.
Formula _{(i) Ro = (n x} -n y) × d
Formula (ii) Rt = {(n _x + n _y ) / 2−n _z } × d
(Wherein, n _x is .n _y representing the refractive index in a slow axis direction in the film plane is .n _z representing the fast-axis refractive index in the film plane is in the thickness direction of the film (The refractive index is measured at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH.) D represents the thickness (nm) of the film.)   A polarizing plate having a first protective film T1 on the viewing side and a second protective film T2 on the other side, with at least one of the protective film T1 and the protective film T2 across the polarizer. A polarizing plate comprising the optical film according to any one of claims 1 to 6.   A liquid crystal display device comprising the polarizing plate according to claim 7.

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