Optical Film, Polarizing Plate, and Liquid Crystal Display Device

Abstract

This optical film includes a cycloolefin resin. In the present invention: the ratio As / Ac of an attenuation coefficient As of light having a wavelength of 9.6 μm in at least a surface-layer region Sa and an attenuation coefficient Ac of light having a wavelength of 9.6 μm in an inner-layer region C is 1.1-20, where the surface-layer region Sa is a region from one surface of an optical film to a depth at 30% of the thickness of the optical film, the inner-layer region C is a region between the surface-layer region Sa and a surface-layer region Sb, and the surface-layer region Sb is a region from the other surface of an optical film to a depth at 30% of the thickness of the optical film; and the attenuation coefficient of light having a wavelength of 9.6 μm in the optical film is 1.5×10-5 / μm or greater.

Description

Technical Field

[0001] The present invention relates to an optical film, a polarizing plate, and a liquid crystal display device.

Background Art

[0002] A display device such as a liquid crystal display device includes a polarizing plate. The polarizing plate includes a polarizer and a polarizer protection film. As the polarizer protection film, a cycloolefin resin film may be used because it has excellent transparency and high moisture resistance.

[0003] Such a polarizing plate is usually used after bonding a polarizer and a polarizer protection film with an adhesive or the like and then cutting it into a predetermined size. The cutting of the polarizing plate is performed by, for example, a mechanical cutting method using a knife or a laser cutting method using a laser beam. In the mechanical cutting method, fine scratches are likely to occur and residual stress is also likely to be non-uniform. Therefore, in recent years, the laser cutting method is often adopted.

[0004] Since the cycloolefin resin film generally has a low absorption rate of laser light, it has been difficult to cut it with laser light.

[0005] On the other hand, in order to enable cutting by a laser cutting method, a polarizing plate using a polarizer protection film including a base material containing a laser absorber is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the cuttability of the polarizer protection film containing the cycloolefin resin of Patent Document 1 by laser light was not sufficient. Therefore, in order to cut the polarizer protection film with laser light, irradiation with laser light at high illuminance was required. As a result, there was a problem that the polarizer with a high absorption rate of laser light was likely to be burned and soiled, and the polarizing plate was contaminated. On the other hand, when a large amount of a laser absorber (light absorption material) is added to enhance the cuttability by laser light, the transparency of the optical film is likely to be impaired.

[0008] In contrast, the present inventors have found that by locally increasing the absorption rate of laser light in the surface layer region of the polarizer protection film (optical film), the cuttability by laser light can be enhanced without impairing the transparency of the optical film. On the other hand, if the absorption rate of laser light in the surface layer region is increased too much, there is a new problem that light leakage is likely to occur in the display device.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical film, a polarizing plate, and a liquid crystal display device that can enhance the cuttability by laser light without causing light leakage in the display device.

Means for Solving the Problems

[0010] The present invention relates to the following optical film, polarizing plate, and liquid crystal display device.

[0011] The optical film of the present invention is an optical film containing a cycloolefin resin. When a region from one surface of the optical film to a depth of 30% of the thickness of the optical film is defined as a surface layer region Sa, a region from the other surface of the optical film to a depth of 30% of the thickness of the optical film is defined as a surface layer region Sb, and a region between the surface layer region Sa and the surface layer region Sb is defined as an inner layer region C, at least the ratio As / Ac of the absorption coefficient As of light with a wavelength of 9.6 μm measured by the ATR method in the surface layer region Sa and the absorption coefficient Ac of light with a wavelength of 9.6 μm measured by the ATR method in the inner layer region C is 1.1 to 20, and the absorption coefficient of light with a wavelength of 9.6 μm of the optical film is 1.5×10 -5 / μm or more.

[0012] The polarizing plate of the present invention has a polarizer and the optical film of the present invention disposed on at least one surface of the polarizer.

[0013] The liquid crystal display device of the present invention has a liquid crystal cell and a first polarizing plate and a second polarizing plate sandwiching the liquid crystal cell, and at least one of the first polarizing plate and the second polarizing plate is the polarizing plate of the present invention.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide an optical film, a polarizing plate, and a liquid crystal display device that can enhance the cutability by laser light without causing light leakage in a display device.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] As described above, by locally increasing the absorption rate of the laser light in the surface layer region of the optical film, it is possible to enhance the cutability by the laser light without impairing the transparency of the optical film. However, when used in a display device, light leakage is likely to occur.

[0017] Although the reason for this is not clear, it is presumed as follows. That is, if the absorption rate of the laser light in the surface layer region of the optical film is locally increased too much, the amount of heat generated by the absorption of the laser light in the surface layer region becomes extremely larger than the amount of heat generated in the inner layer region, and a stress difference is likely to occur.

[0018] On the other hand, in the present invention, the absorption rate of the laser light in the surface layer region of the optical film is moderately increased. That is, while the absorption coefficient of the light with a wavelength of 9.6 μm of the entire optical film is set to be a certain value or more, the ratio As / Ac of the absorption coefficient As of the light with a wavelength of 9.6 μm in the surface layer region Sa to the absorption coefficient Ac of the light with a wavelength of 9.6 μm in the inner layer region C is set to 1.1 to 20, preferably 3 to 15. Thereby, while enhancing the cutability by the laser light, it is possible to reduce the stress difference caused by heat generation due to the absorption of the laser light between the surface layer region Sa and the inner layer region C, so that light leakage in the display device can be suppressed. Hereinafter, the configuration of the present invention will be described.

[0019] 1. Optical Film The optical film of the present invention contains a cycloolefin resin. And the absorption rate of the laser light in at least one surface layer region of the optical film is locally high (higher than the inner layer region).

[0020] FIG. 1 is a cross-sectional schematic view showing the surface layer regions Sa, Sb and the inner layer region C of the optical film 10.

[0021] When the regions from one surface 10a and the other surface 10b of the optical film 10 to a depth of 30% of the thickness of the optical film 10 are defined as surface layer regions Sa and Sb respectively, and the region between them as an inner layer region C, the absorption rate of laser light in at least one of the surface layer regions Sa is higher than that in the inner layer region C. Specifically, the ratio As / Ac of the absorption coefficient As of light with a wavelength of 9.6 μm in at least one of the surface layer regions Sa to the absorption coefficient Ac of light with a wavelength of 9.6 μm in the inner layer region C is preferably 1.1 to 20.

[0022] When As / Ac is 1.1 or more, the absorption rate of laser light in the surface layer region Sa can be made relatively high, so it is easy to enhance the cutability by laser light. When As / Ac is 20 or less, the amount of heat generated by laser light absorption in the surface layer region Sa does not become extremely larger than the amount of heat generated by laser light absorption in the inner layer region C, so the stress difference caused thereby can be reduced. Thereby, light leakage in the display device can be suppressed. From the same viewpoint, As / Ac is more preferably 3 to 15.

[0023] As / Ac can be measured by the following method. 1) First, using a microscopic FTIR (Agilent's "UMA600" and "FTS3000") by the ATR method, with an incident light diameter of 100 μm, a prism of Ge (incident angle 45°), a detector of MCT - A, and a resolution of 4.0 cm -1 , the infrared absorption spectrum is measured under the condition of integration: 64 times. From the obtained infrared absorption spectrum, the absorbance of the portion corresponding to a wavelength of 9.6 μm (frequency 1041 cm -1 ) is read, and the absorbance A of the entire optical film 10 is measured. 2) Next, 30% of the thickness is shaved off from one surface 10a of the optical film 10. Then, the absorbance A1 of the shaved surface is measured in the same manner as in 1) above. 3) Also, 30% of the thickness is shaved off from the other surface 10b of the optical film 10. Then, the absorbance A2 of the shaved surface is measured in the same manner as in 1) above. 4) Apply the absorbances A, A1, and A2 obtained in the above 1) to 3) to the following formula to calculate the absorption coefficient As of the surface layer region Sa and the absorption coefficient Ac of the inner layer region C, respectively. Absorption coefficient As of the surface layer region Sa = (A - A1) × loge10 ÷ (0.3T) Absorption coefficient Ac of the inner layer region C = A2 × loge10 ÷ (0.4T) (T: thickness of the optical film 10) A: Absorbance of the optical film 10 A1: Absorbance measured after shaving 30% of the thickness T of the optical film 10 from one surface 10a of the optical film 10 A2: Absorbance measured after shaving 30% of the thickness T of the optical film 10 from the other surface 10b of the optical film 10)

[0024] The absorption coefficient of the laser light in the other surface layer region Sb of the optical film 10 may be higher than or equivalent to the absorption coefficient of the laser light in the inner layer region C. That is, the ratio As / Ac of the absorption coefficient As of the light with a wavelength of 9.6 μm in the surface layer region Sb of the optical film 10 to the absorption coefficient Ac of the light with a wavelength of 9.6 μm in the inner layer region C may be 1 to 20, or may be 1.1 to 20.

[0025] Also, the absorption coefficient of the light with a wavelength of 9.6 μm of the optical film 10 is preferably -5 1.5×10 -5 / μm or more, and more preferably -5 2.0×10

[0026] The As / Ac and the absorption coefficient A of the optical film 10 can be adjusted by the distribution, type, content, etc. of the material (light absorption material) that absorbs the laser light. That is, in order to make As / Ac higher than a certain level, the optical film 10 preferably contains a light absorption material in the surface layer region Sa and the inner layer region C respectively; the content Ms of the light absorption material in the surface layer region Sa is made more than the content Mc of the light absorption material in the inner layer region C (specifically, Ms / Mc is 2.5 to 20, preferably 3.5 to 15). The light absorption material will be described in detail later.

[0027] Such an optical film 10 may be a laminated film having a base material layer and a surface layer, or may be a single-layer film.

[0028] In the following embodiments, an example in which the optical film is a laminated film having a base material layer and a surface layer will be described.

[0029] FIG. 2A is a cross-sectional view showing the configuration of the optical film 10 according to the present embodiment.

[0030] As shown in FIG. 2A, the optical film 10 according to the present embodiment has a base material layer 11 and two surface layers 12 and 13 sandwiching it.

[0031] The base material layer 11 contains a cycloolefin resin and a light absorption material.

[0032] 1-1. Base material layer 1-1-1. Cycloolefin resin The cycloolefin resin is a polymer containing a structural unit derived from a norbornene monomer.

[0033] The norbornene monomer is represented by the following formula (1).

Chemical formula

[0034] R in formula (1) 1 ~R 4 each represents a hydrogen atom, a halogen atom, a hydrocarbon group, or a polar group.

[0035] Examples of the halogen atom include a fluorine atom and a chlorine atom.

[0036] The hydrocarbon group is a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms. Examples of the hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, and butyl group. The hydrocarbon group may further have a divalent linking group containing an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom (for example, a carbonyl group, an imino group, an ether bond, a silyl ether bond, a thioether bond, etc.).

[0037] Examples of the polar group include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an allyloxycarbonyl group, an amino group, an amide group, and a group in which these groups are bonded via a linking group such as a methylene group (-(CH 2 ) n -, where n is an integer of 1 or more). Among them, an alkoxycarbonyl group and an aryloxycarbonyl group are preferable, and an alkoxycarbonyl group is more preferable.

[0038] Among them, at least one of R 1 ~R 4 is preferably a polar group. A cycloolefin resin containing a structural unit derived from a norbornene monomer having a polar group is easily dissolved in a solvent when forming a film by, for example, a solution casting method, and the glass transition temperature of the obtained film is also easily increased. On the other hand, in the melt film forming method, a cycloolefin resin not containing a structural unit derived from a norbornene monomer having a polar group may be used.

[0039] Also, both of R 1 ~R 4 may be hydrogen atoms, where both of R 1 and R 2 (or both of R 3 and R 4 ).

[0040] p in the formula (1) represents an integer of 0 to 2. From the viewpoint of enhancing the heat resistance of the optical film, p is preferably 1 to 2.

[0041] Specific examples of the norbornene monomer represented by formula (1) are shown below. Among these, examples of the norbornene monomer having a polar group include the following.

[0042]

Chemical formula

[0043] Examples of the norbornene monomer having no polar group include the following.

Chemical formula

[0044] The content of the structural unit derived from the norbornene monomer can be 50 to 100 mol% based on all the structural units constituting the cycloolefin resin.

[0045] The cycloolefin resin may further contain a structural unit derived from another monomer copolymerizable with the structural unit derived from the norbornene monomer. Examples of the other copolymerizable monomers include (when the above norbornene monomer has a polar group) a norbornene monomer having no polar group, and cycloolefin monomers having no norbornene skeleton such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0046] As the cycloolefin resin, commercially available products may be used. Examples of commercially available products include ARTON (registered trademark) G, ARTON F, ARTON R, and ARTON RX manufactured by JSR Corporation.

[0047] The weight average molecular weight Mw of the cycloolefin resin is not particularly limited, but is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and even more preferably 40,000 to 200,000. When the weight average molecular weight Mw of the cycloolefin resin is within the above range, the mechanical properties of the optical film can be enhanced without impairing the molding processability.

[0048] The weight average molecular weight Mw of the cycloolefin resin can be measured by gel permeation chromatography (GPC). Specifically, as the measuring device, gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) is used, and as the column, a series of TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoh Corporation is used. Then, 20 ± 0.5 mg of the sample is dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. This solution is injected into the above column (temperature 40°C) at 100 ml, measured with a detector RI at a temperature of 40°C, and the weight average molecular weight is determined in terms of styrene conversion.

[0049] The glass transition temperature Tg of the cycloolefin resin is usually preferably 110°C or higher, more preferably 110 to 350°C, and even more preferably 120 to 250°C. When the Tg of the cycloolefin resin is 110°C or higher, deformation is less likely to occur even under high temperature conditions. When Tg is 350°C or lower, the moldability is less likely to be impaired, and thermal degradation of the cycloolefin resin during molding can be further suppressed.

[0050] The glass transition temperature can be measured by a method conforming to JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

[0051] The content of the cycloolefin resin is not particularly limited, but is preferably 50% by mass or more, and more preferably 70 to 99% by mass, based on the optical film.

[0052] 1-1-2. Light Absorbing Material The light absorbing material can be a light absorbing material having an extinction coefficient of 4.0×10 -3 / μm or more for light with a wavelength of 9.0 to 11.0 μm. Such a light absorbing material is usually a compound having a carbonyl group, preferably an ester compound, or (meth)acrylic polymer particles.

[0053] <Ester compound> The ester compound may be any of a sugar ester compound, a polycondensed ester compound, and a polyhydric alcohol ester compound.

[0054] (Sugar ester compound) The sugar ester compound is a compound in which all or part of the OH groups of a monosaccharide, disaccharide, or trisaccharide are esterified. Such a sugar ester compound is preferably a compound represented by the following formula (FA). [Chemical formula]

[0055] R in formula (FA) 1 ~R 8 represents a substituted or unsubstituted alkylcarbonyl group or a substituted or unsubstituted arylcarbonyl group. R 1 ~R 8 may be the same as or different from each other.

[0056] The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having 2 or more carbon atoms. Examples of the substituted or unsubstituted alkylcarbonyl group include a methylcarbonyl group (acetyl group), an ethylcarbonyl group, and the like. Examples of the substituent of the alkyl group include an aryl group such as a phenyl group.

[0057] The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. Examples of the arylcarbonyl group include a phenylcarbonyl group. Examples of the substituent of the aryl group include an alkyl group such as a methyl group.

[0058] Examples of R in formula (FA) 1 ~R 8 include the following. [Chemical formula]

[0059] The average degree of substitution of the sugar ester compound is preferably 3 to 6. The average degree of substitution of the sugar ester compound indicates the average ratio of the esterified OH groups of the sugar used as the raw material among the total number of OH groups.

[0060] (Polyhydric alcohol ester compound) The polyhydric alcohol ester is an esterified product of a polyhydric aliphatic alcohol having two or more valences (preferably a polyhydric aliphatic alcohol having 2 to 20 valences) and a monocarboxylic acid.

[0061] Examples of the polyhydric alcohol include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, etc., and preferably triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, xylitol.

[0062] The monocarboxylic acid is not particularly limited and may be any of aliphatic monocarboxylic acids such as acetic acid and propionic acid, alicyclic monocarboxylic acids such as cyclopentanecarboxylic acid and cyclohexanecarboxylic acid, and aromatic monocarboxylic acids such as benzoic acid and toluic acid.

[0063] The carboxylic acid used in the polyhydric alcohol ester compound may be one type or a mixture of two or more types. Further, all of the OH groups in the polyhydric alcohol may be esterified or a part may remain as an OH group.

[0064] The molecular weights of the sugar ester compound and the polyhydric alcohol ester compound preferably are moderately low from the viewpoint of easily obtaining good compatibility with the cycloolefin resin, although they also depend on the method for producing the optical film. Specifically, the molecular weight of the sugar ester compound or the ester compound may be, for example, 300 to 1500, preferably 600 to 1200.

[0065] (Polycondensed ester compound) The polycondensed ester compound is a polycondensate (polymer) containing a structural unit obtained by reacting a dicarboxylic acid with a diol.

[0066] The dicarboxylic acid may be any of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an alicyclic dicarboxylic acid, and preferably is an aromatic dicarboxylic acid. The dicarboxylic acid may be of one type or a mixture of two or more types. It is preferable to mix an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid.

[0067] The diol may be any of an aromatic diol, an aliphatic diol, and an alicyclic diol, and preferably is an aliphatic diol, more preferably a diol having 1 to 4 carbon atoms. The diol may be of one type or a mixture of two or more types.

[0068] That is, the polycondensed ester compound preferably contains a structural unit obtained by reacting a dicarboxylic acid containing an aromatic dicarboxylic acid with a diol having 1 to 8 carbon atoms, and more preferably contains a structural unit obtained by reacting a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid with a diol having 1 to 8 carbon atoms. Both ends of the molecule of the polycondensed ester may or may not be blocked.

[0069] Among these ester compounds, the sugar ester compound is particularly preferable in that its molecular weight is moderately low and it has excellent compatibility with the cycloolefin resin.

[0070] ((Meth)acrylic polymer particles) (Meth)acrylic polymer particles are polymer particles containing structural units derived from (meth)acrylates, preferably polymer particles containing structural units derived from methyl methacrylate.

[0071] The polymer containing structural units derived from methyl methacrylate may further contain structural units derived from other copolymerization monomers. Examples of other copolymerization monomers include alkyl (meth)acrylates having 1 to 18 carbon atoms other than methyl methacrylate; α,β-unsaturated acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrenes such as styrene and α-methylstyrene; polyfunctional (meth)acrylic esters having two or more (meth)acrylic groups such as (poly)ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate; and polyfunctional monomers such as allyl alkyl (meth)acrylates such as allyl (meth)acrylate and allyl alkyl (meth)acrylate.

[0072] Among them, it is preferable that the above polymer is a crosslinked polymer, that is, a copolymer containing a structural unit derived from methyl methacrylate and a structural unit derived from a polyfunctional monomer; more preferably, it is a copolymer containing a structural unit derived from methyl methacrylate, a structural unit derived from styrenes, and a structural unit derived from polyfunctional monomers.

[0073] From the viewpoint of increasing the absorption rate of the laser light of the base material layer 11, it is preferable that the content of the structural unit derived from (meth)acrylates containing a carbonyl group is a certain amount or more. From such a viewpoint, the total of the structural units derived from methyl methacrylate is preferably 30 mol% or more, more preferably 50 to 80 mol%, based on all the structural units constituting the polymer.

[0074] The content of the structural unit derived from the polyfunctional monomer is preferably 3 to 50 mol%, more preferably 10 to 35 mol%, based on the total of all the structural units constituting the polymer.

[0075] (Meth)acrylic polymer particles are preferably polymers having a refractive index difference of 0.01 or less from the cycloolefin resin. Such (meth)acrylic polymer particles are less likely to reduce the transparency of the obtained optical film.

[0076] The refractive indices of the cycloolefin resin and the (meth)acrylic polymer particles can each be the refractive index of light with a wavelength of 550 nm. The refractive index of light with a wavelength of 550 nm can be determined, for example, by preparing a sample film containing each component alone and measuring the refractive index of light with a wavelength of 550 nm of the sample film using a Horiba spectroscopic ellipsometer UVSEL.

[0077] The Tg of the (meth)acrylic polymer particles is preferably 80°C or higher. The Tg of the (meth)acrylic polymer particles can be measured in accordance with JIS K 7121-2012 or ASTM D 3418-82 in the same manner as above.

[0078] The average particle diameter of the (meth)acrylic polymer particles is not particularly limited, but is preferably, for example, 50 to 500 nm. When the average particle diameter is within the above range, while increasing the absorption rate of the laser light, it is possible to form irregularities of an appropriate size on the surface of the film, so that slipperiness can be imparted. From the above viewpoints, the average particle diameter of the (meth)acrylic polymer particles is more preferably 0.07 to 0.28 μm.

[0079] The average particle diameter of the (meth)acrylic polymer particles can be measured by the following procedure.

[0080] The average particle diameter of the (meth)acrylic polymer particles in the optical film can be measured by the following method. First, cut the optical film and observe the obtained cut surface by TEM. Then, measure the particle diameter for 100 arbitrary particles. The particle diameter is measured as the equivalent circle diameter of 100 particles obtained by TEM imaging, as described above. Then, the average value of the obtained particle diameters is defined as the "average particle diameter". In the TEM image, a portion with a brightness of 150% or more of the average brightness of the field of view is judged as a particle.

[0081] The content of the light-absorbing material in the base material layer 11 can be set so that Ms / Mc of the optical film 10, and thus As / Ac, satisfy the above ranges, and the absorption coefficient A of the entire optical film 10 satisfies the above range.

[0082] That is, it is preferable that the content Mc' of the light-absorbing material in the base material layer 11 is less than the content Ms' of the light-absorbing material in the surface layer 12 (or 13). Specifically, the content Mc' of the light-absorbing material in the base material layer 11 is preferably 0.1 to 4.5% by mass, more preferably 0.3 to 3.5% by mass, with respect to the base material layer 11. When the content Mc' of the light-absorbing material in the base material layer 11 is within the above range, it is easy to adjust Ms / Mc (or Ms' / Mc'), and thus As / Ac, within the above range while setting the absorption coefficient A of the entire optical film 10 within the above range. Thereby, while enhancing the cutability of the optical film 10 by laser light, the difference in the calorific value of the laser light between the base material layer 11 and the surface layer 12 (or 13) can be reduced, so that light leakage in the display device can be easily suppressed.

[0083] 1-1-3. Other components The base material layer 11 may further contain other components such as inorganic fine particles, if necessary.

[0084] The inorganic fine particles have a function of enhancing the slipperiness of the optical film. Examples of the inorganic material constituting the inorganic fine particles include silicon dioxide (SiO 2) It contains oxides such as titanium dioxide, aluminum oxide, and zirconium oxide. Among them, silicon dioxide is preferable in terms of, for example, being able to reduce the increase in haze of the film.

[0085] Examples of commercially available products of silicon dioxide particles include Aerosil R812, R972 (manufactured by Nippon Aerosil Co., Ltd.), NanoTek SiO2 (manufactured by C.I. Kasei Co., Ltd.), and the like.

[0086] The average primary particle diameter of the inorganic fine particles is preferably 5 to 50 nm. When the average primary particle diameter of the inorganic fine particles is 5 nm or more, the surface of the film can be roughened, so it is easy to impart slipperiness. When it is 50 nm or less, it is easy to suppress the increase in haze. The average primary particle diameter of the inorganic fine particles is more preferably 5 to 30 nm. The average primary particle diameter of the inorganic fine particles in the optical film 10 can be measured by the same method as described above.

[0087] The content of the inorganic fine particles is not particularly limited, but can be 0 to 5% by mass, preferably 0 to 2% by mass, based on the optical film.

[0088] 1-1-4. Physical properties The thickness of the base material layer 11 may be set so that As / Ac and the absorption coefficient of the entire optical film are within the above ranges, and is not particularly limited. For example, it is preferably 30 to 60 μm, and more preferably 35 to 55 μm.

[0089] 1-2. Surface layers 12 and 13 The surface layer 12 is included in the surface layer region Sa from one surface 10a of the optical film 10 to 30% of the thickness; the surface layer 13 is included in the surface layer region Sb from the other surface 10b of the optical film 10 to 30% of the thickness (see FIGS. 1 and 2A). Each of the surface layers 12 and 13 may be composed of a thermoplastic resin composition containing a thermoplastic resin and a light absorption material (Aspect 1), or may be composed of a cured product of a curable composition containing a curable compound having light absorbency (curable compound as the light absorption material) and a curing agent (Aspect 2).

[0090] <Regarding Aspect 1> The surface layers 12 and 13 can each be composed of a resin composition containing a thermoplastic resin and a light absorption material. Note that the thermoplastic resin may also serve as the light absorption material.

[0091] (Thermoplastic resin) The thermoplastic resin contained in the thermoplastic resin composition is not particularly limited as long as it has light transmissibility, and can be a cycloolefin resin, a (meth)acrylic resin, or the like.

[0092] As the cycloolefin resin contained in the surface layer 12 (or 13), the same one as the cycloolefin resin contained in the base material layer 11 can be used.

[0093] The (meth)acrylic resin contained in the surface layer 12 (or 13) can function not only as a thermoplastic resin but also as a light absorption material.

[0094] (Meth)acrylic resin is preferably a polymer containing a structural unit derived from methyl methacrylate. The polymer may further contain a structural unit derived from a monomer copolymerizable with methyl methacrylate. Examples of other monomers copolymerizable with methyl methacrylate include alkyl (meth)acrylates having 1 to 18 carbon atoms other than methyl methacrylate such as 2-ethylhexyl methacrylate; α,β-unsaturated acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrenes such as styrene and α-methylstyrene; maleic anhydride; maleimides such as maleimide and N-phenylmaleimide; and glutaric anhydride.

[0095] The content ratio of the structural unit derived from methyl methacrylate to all the structural units constituting the copolymer is preferably 50% by mass or more, more preferably 70% by mass or more. Further, the weight average molecular weight of the (meth)acrylic resin is more preferably 40,000 to 500,000.

[0096] Among them, from the viewpoint of good interlayer adhesion with the base material layer 11 and being less likely to impair transparency, the thermoplastic resin contained in the surface layer 12 (or 13) is preferably a cycloolefin resin.

[0097] The composition of the cycloolefin resin contained in the surface layer 12 (or 13) may be the same as or different from the composition of the cycloolefin resin contained in the base material layer 11. From the viewpoint of enhancing interlayer adhesion and production efficiency, it is preferable that the composition of the cycloolefin resin contained in the surface layer 12 (or 13) is the same as the composition of the cycloolefin resin contained in the base material layer 11.

[0098] (Light absorption material) As the light absorption material contained in the surface layer 12 (or 13), the same material as the light absorption material contained in the base material layer 11 can be used.

[0099] The type of the light absorption material contained in the surface layer 12 (or 13) may be the same as or different from the type of the light absorption material contained in the base material layer 11. From the viewpoint of enhancing production efficiency, it is preferable that the type of the light absorption material contained in the surface layer 12 (or 13) is the same as the type of the light absorption material contained in the base material layer 11.

[0100] The content of the light absorption material in the surface layer 12 (or 13) is preferably set so that Ms / Mc of the optical film 10, and thus As / Ac, satisfy the above ranges, and the absorption coefficient A of the entire optical film 10 satisfies the above ranges.

[0101] That is, the content Ms' of the light-absorbing material in the surface layer 12 (or 13) is preferably more than the content Mc' of the light-absorbing material in the base material layer 11. Specifically, although it depends on the content Ms' of the light-absorbing material in the surface layer 12 (or 13), Ms' / Mc' is preferably 2.5 to 50, and more preferably 7 to 15. For example, the content Ms' of the light-absorbing material in the surface layer 12 (or 13) is preferably 1 to 30% by mass, and more preferably 3 to 10% by mass with respect to the surface layer 12 (or 13). When the content Ms' of the light-absorbing material in the surface layer 12 (or 13) is within the above range, while making the absorption coefficient A of the entire optical film 10 within the above range, it is easy to adjust Ms / Mc (Ms' / Mc'), and thus As / Ac within the above range. Thereby, while enhancing the cuttability of the optical film 10 by laser light, the difference in the calorific value of the laser light between the base material layer 11 and the surface layer 12 (or 13) can be reduced, so that light leakage in the display device can be easily suppressed. That is, from the viewpoint of suppressing light leakage in the display device, it is preferable that Ms' / Mc' is not too large and Ms' is not too much.

[0102] (Other components) Similar to the base material layer 11, the surface layer 12 (or 13) may further contain other components such as inorganic fine particles.

[0103] <Regarding Embodiment 2> The surface layer 12 (or 13) can be composed of a cured product of a curable composition containing a light-absorbing curable compound and a curing agent.

[0104] The light-absorbing curable compound contained in the curable composition is preferably a urethane compound having a group that reacts with the curing agent.

[0105] (Urethane compound) A urethane compound having a functional group that reacts with a curing agent is obtained by reacting a polyol and a polyisocyanate. The urethane compound may be a monomer or a prepolymer. Such a urethane compound has, for example, functional groups (such as hydroxyl groups, acrylate groups, carboxyl groups, acrylamide groups, etc.) remaining unreacted after the reaction of the polyol and the polyisocyanate as groups that react with the curing agent.

[0106] Examples of polyols include polyester polyols obtained by the reaction of polyol compounds (such as ethylene glycol, propylene glycol, 1,4 - butanediol, neopentyl glycol, glycerin, trimethylolpropane, etc.) and polybasic acids (such as dibasic acids of polyvalent carboxylic acids such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, etc. and polyvalent carboxylic acids containing tricarboxylic acids such as trimellitic acid or their anhydrides, etc.); polyether polyols (such as poly(oxypropylene ether) polyol, poly(oxyethylene - propylene ether) polyol); polycarbonate polyols, etc. Among them, polycarbonate polyurethane is preferred.

[0107] The curing agent is a compound having two or more functional groups in the molecule that react with the (unreacted) functional groups contained in the urethane compound. For example, examples of curing agents for urethane compounds containing a hydroxyl group (as a group that reacts with the curing agent) include epoxy compounds, isocyanate compounds, tertiary amine compounds, carbodiimide compounds; examples of curing agents for urethane compounds having an acrylamide group (as a group that reacts with the curing agent) include active hydrogen compounds such as dicarboxylic acids.

[0108] Incidentally, a urethane compound (urethane acrylate) having an acrylate group (as a group that reacts with a curing agent) may be obtained by reacting a polyol having an acrylate group with a polyisocyanate, or by esterifying unreacted isocyanate groups of the obtained urethane compound with (meth)acrylic acid after reacting a polyol with a polyisocyanate.

[0109] Urethane acrylate may be further used in combination with other (meth)acrylate compounds. Examples of other (meth)acrylate compounds include isocyanuric acid acrylates such as diacrylate isocyanurates and triacrylate isocyanurates.

[0110] The curing agent for urethane acrylate can be a radical curing agent. Examples of radical curing agents include intramolecular cleavage type initiators such as α-hydroxyalkylphenone.

[0111] (Other components) The curable composition may further contain other components such as a curing accelerator, a curing aid, and fine particles, if necessary.

[0112] For example, when an epoxy compound is used as the curing agent, a tertiary amine compound or a boron trifluoride complex compound can be used as the curing accelerator. Examples of fine particles include inorganic fine particles such as silica particles.

[0113] <Common matters of Embodiments 1 and 2> As described above, the surface layer 12 (or 13) may be composed of a thermoplastic resin composition containing a thermoplastic resin and a light absorption material (Embodiment 1), or may be composed of a cured product of a curable composition containing a light-absorbing curable compound and a curing agent (Embodiment 2). Among them, from the viewpoint of good interlayer adhesion with the base material layer 11 and being difficult to peel off, the surface layer 12 (or 13) is preferably composed of a thermoplastic resin composition containing a cycloolefin resin and a light absorption material (Embodiment 1), which is more preferably composed of a thermoplastic resin composition containing a cycloolefin resin and a light absorption material (similar to the base material layer 11).

[0114] 1-1-4. Physical properties The thickness of the surface layer 12 (or 13) may be set so that As / Ac and the absorption coefficient A of the entire optical film are within the above ranges, and is not particularly limited. However, it is preferably 0.3 to 30% with respect to the total thickness of the base material layer 11 and the surface layer 12 (or 13), and more preferably 2 to 10%. Specifically, the total thickness of the base material layer 11 and the surface layer 12 (or surface layer 13) is preferably 20 to 100 μm, and more preferably 35 to 60 μm. Further, the thickness of the base material layer 11 is preferably 15 to 60 μm, and more preferably 30 to 50 μm.

[0115] 1-3. Physical properties of the optical film (Total light transmittance) The total light transmittance of the optical film is not particularly limited as long as it has sufficient light transmittance, but it is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. The total light transmittance of the optical film can be measured in accordance with JIS K7361-1:1997.

[0116] The total light transmittance of the optical film can be adjusted, for example, by the content of the light absorption material. In order to increase the total light transmittance of the optical film, it is preferably, for example, to make the content of the light absorption material below a certain level.

[0117] (Absorption coefficient) As described above, the absorption coefficient A of the optical film, the absorption coefficient A of the light with a wavelength of 9.6 μm is preferably 1.5×10 -5 / μm or more. When the absorption coefficient A of the optical film is 1.5×10 -5 / μm or more, the laser light can be moderately absorbed, so that the cutability by the laser light can be improved. The absorption coefficient A of the optical film is less likely to impair transparency and less likely to cause light leakage in the display device, and is more preferably 2.0×10 -5 ~50×10 -5 / μm, and 5.0×10 -5~20×10 -5 It is more preferably / μm. As described above, the absorption coefficient A of the optical film can be calculated by measuring the absorbance under the above conditions by the ATR method.

[0118] The absorption coefficient A of the optical film can be adjusted by the type and content of the light-absorbing material, etc. From the viewpoint of increasing the absorption coefficient A of the optical film, it is preferable to increase the content of the light-absorbing material.

[0119] (Retardation Ro and Rt) The optical film can have retardation values Ro and Rt according to its use. For example, when the optical film is used as a zero retardation film of a polarizing plate, the in-plane retardation Ro measured under the environment of a measurement wavelength of 590 nm, 23 ° C and 55% RH preferably satisfies 0 nm ≦ Ro ≦ 5 nm, and the retardation Rt in the thickness direction preferably satisfies -5 nm ≦ Rt ≦ 5 nm.

[0120] Ro and Rt of the optical film are respectively defined by the following formulas. Formula (2a): Ro = (nx - ny) × d Formula (2b): Rt = ((nx + ny) / 2 - nz) × d (where nx represents the refractive index in the in-plane slow axis direction (the direction in which the refractive index is maximum) of the optical film, ny represents the refractive index in the direction orthogonal to the in-plane slow axis of the optical film, nz represents the refractive index in the thickness direction of the optical film, d represents the thickness (nm) of the optical film.)

[0121] The in-plane slow axis of the optical film refers to the axis with the maximum refractive index on the film surface. The in-plane slow axis of the optical film can be confirmed by an automatic birefringence meter AxoScan Mueller Matrix Polarimeter (manufactured by Axometrics).

[0122] The measurement of Ro and Rt of the optical film can be performed by the following method. 1) Humidify the optical film for 24 hours in an environment of 23°C and 55% RH. Measure the average refractive index of this optical film with an Abbe refractometer, and measure the thickness d using a commercially available micrometer. 2) Measure the retardations Ro and Rt of the humidified optical film at a measurement wavelength of 590 nm, respectively, using an automatic birefringence meter AxoScan Mueller Matrix Polarimeter (manufactured by Axometrics) in an environment of 23°C and 55% RH.

[0123] The retardations Ro and Rt of the optical film can be mainly adjusted by the draw ratio. To increase the retardations Ro and Rt of the optical film, it is preferable to increase the draw ratio.

[0124] (Thickness) The thickness of the optical film is not particularly limited, but is preferably 20 to 100 μm, and more preferably 35 to 70 μm.

[0125] 1-4. Manufacturing method The optical film of the present invention can be manufactured by any method. For example, the optical film 10 having the surface layer 12 (or 13) may be obtained by co-casting the base material layer 11 and the surface layer 12 (or 13) (co-casting method), or after manufacturing the base material layer 11, the surface layer 12 (or 13) may be applied and cured to obtain it (coating method).

[0126] <Co-casting method> The optical film 10 of the above aspect 1 is preferably manufactured by the co-casting method. The co-casting method may be a solution co-casting method or a melt co-casting method.

[0127] (Melt co-casting method) In melt coextrusion, a hot melt of a thermoplastic resin composition for a base material layer and a hot melt of a thermoplastic resin composition for a surface layer are coextruded and then cooled and solidified to obtain a coextruded film. Specifically, the optical film of the present invention can be obtained through the steps of: A1) preparing a thermoplastic resin composition for a base material layer and a thermoplastic resin composition for a surface layer; A2) coextruding a hot melt of the thermoplastic resin composition for the base material layer and a hot melt of the thermoplastic resin composition for the surface layer and then cooling and solidifying; and, if necessary, A3) stretching the obtained film-like material.

[0128] In the step of A1), after dry blending each component, it is melt-kneaded with a twin-screw extruder or the like to obtain pellets.

[0129] In the step of A2), the prepared pellets of the thermoplastic resin composition for the base material layer and the thermoplastic resin composition for the surface layer are each melt-kneaded with a twin-screw extruder or the like and then coextruded from a coextrusion die. In melt coextrusion, the hot melt temperature can be (Tg + 30) to (Tg + 70)°C when the glass transition temperature of the resin is Tg.

[0130] In the step of A3), stretching may be performed according to the required optical properties, and it is preferably stretched in one or more directions among the width direction (TD direction), the conveyance direction (MD direction), and the diagonal direction.

[0131] The stretching ratio is set according to the required optical performance. For example, from the viewpoint of functioning as a film with low retardation, it can be 1.01 to 1.3 times. The stretching ratio is defined as (the size of the film in the stretching direction after stretching) / (the size of the film in the stretching direction before stretching). The stretching temperature (the drying temperature during stretching) is preferably (Tg - 20) to (Tg + 30)°C.

[0132] (Solution coextrusion method) In solution co-casting, a solution (dope) in which the components for the base material layer are dissolved in a solvent and a solution (dope) in which the components for the surface layer are dissolved in a solvent are co-cast and then dried to obtain a co-cast film. Specifically, the optical film of the present invention can be manufactured through the following steps: B1) preparing a dope containing a cycloolefin resin, a light absorption material, and a solvent; B2) casting the obtained dope onto a support, followed by drying and peeling to obtain a cast film; and, if necessary, B3) stretching the obtained cast film.

[0133] In the step of B1), a dope is prepared by dissolving or dispersing a cycloolefin resin and a light absorption material in a solvent.

[0134] The solvent used contains at least an organic solvent (good solvent) capable of dissolving the cycloolefin resin. Examples of good solvents include chlorinated organic solvents such as methylene chloride; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Preferably, it is methylene chloride.

[0135] The solvent used may further contain a poor solvent. Examples of poor solvents include aliphatic alcohols having 1 to 4 carbon atoms such as methanol and ethanol. Preferably, it is ethanol. Since a dope further containing an aliphatic alcohol is likely to gel, it can be easily peeled from a metal support.

[0136] In the step of B2), the obtained dope is cast onto a support, for example, by discharging it from a casting die. The solvent of the dope cast on the support is evaporated until it can be peeled off by a peeling roll from the support.

[0137] Thereafter, the cast film obtained by evaporating the solvent is peeled off by a peeling roll. The amount of residual solvent of the cast film on the support at the time of peeling depends on drying conditions, the length of the support, etc., but can be, for example, 50 to 120% by mass. The amount of residual solvent is defined by the following formula. Amount of residual solvent (% by mass) = (mass of the cast film before heat treatment - mass of the cast film after heat treatment) / (mass of the cast film after heat treatment) × 100 The heat treatment when measuring the residual solvent amount is a heat treatment at 115°C for 1 hour.

[0138] In the step of B3), the cast film is stretched. The stretching ratio and stretching temperature can be the same as those in the step of A3) above.

[0139] The residual solvent amount in the cast film at the start of stretching is preferably about the same as the residual solvent amount in the cast film at the time of peeling, for example, preferably 20 to 30% by mass, and more preferably 25 to 30% by mass.

[0140] <Coating method> The optical film 10 of the above aspect 2 is preferably manufactured by a coating method. Specifically, the optical film 10 of aspect 2 can be obtained through the steps of C1) manufacturing the base material layer 11, and C2) applying and curing a curable composition containing a light-absorbing curable compound and a curing agent on the obtained base material layer 11 to form the surface layer 12 (or 13).

[0141] In the step of C1), the base material layer 11 may be manufactured by the melt casting method or the solution casting method in the same manner as above.

[0142] In the step of C2), a curable composition containing a light-absorbing curable compound and a curing agent is applied to the surface of the base material layer 11. The application of the curable composition can be performed by any coating method, for example, by roll coating.

[0143] Then, the curable composition is cured to obtain the surface layer 12 (or 13). The curing of the curable composition may be heat curing or light curing, and preferably light curing.

[0144] 1-5. Variation In the above embodiment, an example where the optical film 10 has two surface layers is shown (see Fig. 2A), but it is not limited thereto, and it may have one surface layer (see Fig. 2B).

[0145] FIG. 2B is a diagram showing the configuration of the optical film 10 according to the modification. As shown in FIG. 2B, the optical film 10 may have only one surface layer 12. In particular, when the surface layer 12 (or 13) contains a crosslinked product of the curable composition (the above-described embodiment 2), the optical film 10 preferably has only one surface layer.

[0146] 2. Polarizing plate FIG. 3 is a cross-sectional view showing the configuration of the polarizing plate 100 according to the present embodiment. In the present embodiment, an example in which the optical film 10 of FIG. 2A is used as the optical film 10 is shown.

[0147] As shown in FIG. 3, the polarizing plate 100 according to the present embodiment includes a polarizer 20, the optical film 10 of the present invention disposed on one side thereof, another optical film 30 disposed on the other side, and between the polarizer 20 and the optical film 10, and And a plurality of adhesive layers 40 disposed between the polarizer 20 and the other optical film 30, respectively.

[0148] 2-1. Polarizer 20 The polarizer is an element that passes only light with a polarization plane in a certain direction, and is a polyvinyl alcohol-based polarizing film. The polyvinyl alcohol-based polarizing film includes a polyvinyl alcohol-based film dyed with iodine and a polyvinyl alcohol-based film dyed with a dichroic dye.

[0149] The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing it with iodine or a dichroic dye (preferably a film further subjected to a durability treatment with a boron compound); or a film obtained by dyeing a polyvinyl alcohol-based film with iodine or a dichroic dye and then uniaxially stretching it (preferably a film further subjected to a durability treatment with a boron compound). The absorption axis of the polarizer is parallel to the maximum stretching direction.

[0150] The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 5 to 20 μm for the purpose of thinning the polarizing plate.

[0151] 2-2. Optical Film 10 The optical film of the present invention is disposed on at least one surface of the polarizer (at least the surface facing the liquid crystal cell). Specifically, in the optical film 10 of the present invention, the surface layer 12 or 13 (surface layer 12 in FIG. 3) is disposed so as to be on the side of the polarizer 20.

[0152] 2-3. Other Optical Film 30 As the other optical film, the optical film 10 of the present invention may be used, or other optical films such as a polarizer protection film may be used. Examples of other optical films include polyester films and cellulose ester films (such as TAC films).

[0153] 2-4. Adhesive Layer 40 The adhesive layer is disposed between the optical film 10 (or other optical film 30) and the polarizer 20 to bond them. The adhesive constituting the adhesive layer is not particularly limited and may be a dried product of a fully saponified polyvinyl alcohol aqueous solution (water paste) or a cured product of an active energy ray curable adhesive. The active energy ray curable adhesive may be any of a photoradical polymerization type composition using photoradical polymerization, a photocationic polymerization type composition using photocationic polymerization, or a combination thereof.

[0154] The thickness of the adhesive layer can be, for example, about 0.01 to 10 μm, preferably about 0.03 to 5 μm.

[0155] 2-5. Manufacturing Method FIGS. 4A and B are cross-sectional views showing the manufacturing method of the polarizing plate of FIG. 3.

[0156] As shown in FIGS. 4A and 4B, the polarizing plate 100 according to the present embodiment includes a polarizer 20, the optical film 10 of the present invention disposed (laminated) on one surface thereof, and another optical film 30 disposed (laminated) on the other surface. After obtaining a laminate 200 (see FIG. 4A), the laminate 200 can be obtained by irradiating laser light L from the side of the optical film 10 of the obtained laminate 200 and cutting the laminate 200 into a predetermined size (see FIG. 4B).

[0157] The lamination of the polarizer 20 and the optical film 10 of the present invention is performed such that the surface layer 12 or 13 (surface layer 12 in FIG. 2) having a high absorption coefficient of the optical film 10 of the present invention is on the side of the polarizer 20 from the viewpoint of enhancing the cutability by laser light. After lamination, it is cut to a predetermined size by laser light. Further, the lamination can be performed via an adhesive.

[0158] Cutting by laser light is performed by irradiating laser light from the side of the optical film 10 (the surface layer 13 side of the optical film 10 in FIG. 4A). At this time, since the optical film 10 has high absorbability of laser light in the surface layers 12 and 13, the optical film 10 can be cut with less irradiation energy. Thereby, since the polarizer 20 is not excessively exposed to the laser light, it is possible to suppress the polarizer 20 from being burned and generating soot by excessively absorbing the laser light. Thereby, contamination of the polarizing plate can be suppressed.

[0159] 3. Liquid Crystal Display Device The liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate disposed on one surface of the liquid crystal cell, and a second polarizing plate disposed on the other surface of the liquid crystal cell.

[0160] The display mode of the liquid crystal cell is not particularly limited, and can be, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybridaligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment), PVA (Patterned Vertical Alignment)), IPS (In-Plane-Switching), etc. Among them, the IPS mode is preferred.

[0161] One or both of the first polarizing plate and the second polarizing plate are the polarizing plates of the present invention. The polarizing plate of the present invention is preferably arranged such that the optical film of the present invention faces the liquid crystal cell side.

[0162] As described above, the polarizing plate 100 of the present invention has good cutability by laser light, not only reduces the contamination of the polarizing plate, but also adjusts As / Ac to an appropriate range. Therefore, the amount of heat generated by the absorption of laser light in the surface layer 12 (or 13) of the optical film 10 does not become too large compared to the amount of heat generated by the absorption of laser light in the base material layer 11, so that it is difficult to generate a stress difference due to this. Thereby, light leakage when forming a display device can be suppressed.

Example

[0163] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

[0164] 1. Material of the optical film (1) Cycloolefin resin As the cycloolefin resin, the following COP1 to 6 were prepared.

Table 1

[0165] The structural units A to D derived from the monomers are as follows, respectively. [Chemical formula]

[0166] The Tg and Mw of COP1 to 6 were measured by the following method.

[0167] [Glass transition temperature (Tg)] The glass transition temperature of the resin was measured in accordance with JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

[0168] [Weight average molecular weight (Mw)] The weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation), column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL in series manufactured by Tosoh Corporation). 20 ± 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was injected into the column (temperature 40°C), and the measurement was carried out at a detector RI temperature of 40°C. The weight average molecular weight was determined in terms of styrene conversion.

[0169] (2) Light absorption material <Light absorption material A> [Chemical formula]

[0170] <Light absorption material B> Methyl methacrylate (MMA) / styrene (St) / ethylene glycol dimethacrylate (EGDMA) (70 / 10 / 20 molar ratio) copolymer particles (refractive index 1.51, average particle diameter 0.14 μm)

[0171] <Light absorption material C> Methyl methacrylate (MMA) / styrene (St) / ethylene glycol dimethacrylate (EGDMA) (70 / 10 / 20 molar ratio) copolymer particles (refractive index 1.51, average particle diameter 0.35 μm)

[0172] <Light absorption material D> Pentaerythritol tetrabenzoate (molecular weight 552)

[0173] <Light absorption material E> Methyl methacrylate (MMA) / styrene (St) / ethylene glycol dimethacrylate (EGDMA) (70 / 10 / 20 molar ratio) copolymer particles (refractive index 1.51, average particle diameter 0.3 μm)

[0174] <Light absorption material F> Aqueous urethane resin (Superflex 210 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)

[0175] <Light absorption material G> Urethane acrylate (UA-1100 manufactured by Shin-Nakamura Chemical Co., Ltd.) EO-modified di- and triacrylate of isocyanuric acid

[0176] <Light absorption material H> ((Meth)acrylic resin (MMA / N-phenylmaleimide / 2-ethylhexyl methacrylate polymer, Mw 800000))

[0177] <Light absorption material I> Pentaerythritol tetrabenzoate (molecular weight 552)

[0178] When the extinction coefficients of Light absorption materials A to I for light with a wavelength of 9.0 to 11.0 μm were measured by the ATR method, they were 4.0×10 -3 ~6.0×10 -3 / μm.

[0179] 2. Preparation of optical film <Example 1> (Preparation of base film) The resin of Table 2 and an additive of 2% by mass with respect to the resin were melt-kneaded, and melt extrusion was performed from a coat hanger type T die (width 150 mm) using a single-screw extruder (φ = 20 mm, L / D = 25) to form on a film, and it was stretched while being conveyed to produce a base film (base material layer) with a thickness of 50 μm.

[0180] (Formation of the surface layer) First, Superflex 210 (aqueous urethane resin, light absorption material F) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., adipic acid as a curing agent, and an epoxy resin were dissolved in pure water to obtain a curable composition with a concentration of 10% by mass of Superflex 210.

[0181] Next, the obtained curable composition was applied to the surface of the obtained base film using an extrusion coater, and then dried at 80°C for 5 minutes to form a surface layer with a thickness of 0.2 μm. Thereby, an optical film having a two-layer structure of a base film (base material layer) / surface layer was obtained.

[0182] <Example 2> (Production of the base film) In the same manner as in Example 1, a base film (base material layer) with a thickness of 50 μm was obtained.

[0183] (Formation of the surface layer) First, the following materials were stirred and mixed, and then filtered through a polypropylene filter with a pore size of 0.4 μm to obtain a curable composition. Urethane acrylate (UA-1100 manufactured by Shin-Nakamura Chemical Co., Ltd.): 12% by mass EO-modified di- and triacrylate of isocyanuric acid (M-315 manufactured by Toagosei Co., Ltd.): 8% by mass (above, light absorption material G) Silica fine particle dispersion liquid (V-8804 manufactured by JGC Catalysts & Chemicals Ltd.): 60 parts by mass Irgacure 184 (manufactured by BASF Japan Ltd.): 2.4% by mass KF-351A (polyether-modified silicone oil, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.4% by mass Methanol 18% by mass Propylene glycol monomethyl ether acetate (PGME): 12% by mass

[0184] Next, the above-prepared curable composition was applied to the surface of the base film using an extrusion coater. After drying at 80°C, while purging with nitrogen to create an atmosphere with an oxygen concentration of 1.0% by volume or less, using an ultraviolet lamp, the illuminance of the irradiation part was 100 mW / cm 2 , and the irradiation dose was 0.2 J / cm 2 . Under these conditions, ultraviolet irradiation was performed to cure and form a surface layer with a thickness of 0.5 μm. Thereby, an optical film having a two-layer structure of a base film / surface layer was obtained.

[0185] <Example 3> (Preparation of pellets for the base material layer) COP1 and the light-absorbing material A were mixed using a vacuum Nauta mixer so that the content of the light-absorbing material A was 0.5% by mass. After drying, they were melted using a twin-screw extruder to obtain pellets of the resin mixture.

[0186] (Preparation of pellets for the surface layer) Resin mixture pellets were obtained in the same manner as above, except that the light-absorbing material H ((meth)acrylic resin) was used.

[0187] (Coextrusion) The obtained pellets for the base material layer and the pellets for the surface layer were respectively supplied to two twin-screw extruders under a nitrogen atmosphere, melted, and coextruded. That is, using a coextrusion die, melt coextrusion was performed with the base material layer at the center and the surface layer on both sides thereof. The set temperature of the twin-screw extruders was all 180°C, and the coextrusion die was set at 190°C. The coextrusion die was a coat hanger type three-layer laminated multi-manifold die. Then, the melt-extruded film was sandwiched and formed between a cooling roll and an elastic touch roll, further cooled by the cooling roll, and then peeled off by a peeling roll to obtain an optical film having a two-layer structure of a base material layer / surface layer.

[0188] <Examples 4 to 17 and Comparative Example 1> An optical film having a three-layer structure of surface layer / substrate layer / surface layer was obtained in the same manner as in Example 3, except that the composition and thickness of the substrate layer and the surface layer were changed as shown in Table 2.

[0189] <Example 18> (Preparation of light absorption material addition liquid) 95 parts by mass of methylene chloride was put into a sealed container, and 5 parts by mass of light absorption material B ((meth)acrylic polymer particles) was added while stirring. Then, it was stirred and mixed with a dissolver for 50 minutes. 2000 g of the obtained mixed liquid was passed through a high-pressure dispersion device (trade name: ultra-high pressure homogenizer M110-E / H, manufactured by Microfluidics Corporation) and treated once at 175 MPa to prepare a light absorption material dispersion liquid. This was filtered with Fine Met NF manufactured by Nippon Seisen Co., Ltd. to prepare a light absorption material addition liquid.

[0190] (Preparation of dope for surface layer) A dope having the following composition was prepared. First, methylene chloride and ethanol were added to a pressure dissolution tank. To this, COP6 (cycloolefin resin) and the above light absorption material addition liquid (light absorption material) were added while stirring, heated, and completely dissolved while stirring. This was filtered using Yasuki filter paper No. 244 manufactured by Yasuki Filter Paper Co., Ltd. to prepare a dope. Dichloromethane: 300 parts by mass Ethanol: 19 parts by mass COP6 (cycloolefin resin): 100 parts by mass Light absorption material addition liquid (light absorption material B): 75 parts by mass

[0191] (Preparation of dope for substrate layer) A dope was prepared in the same manner as in the preparation of the above dope, except that the light absorption material addition liquid was not added.

[0192] (Film formation) Next, using an endless belt casting apparatus, the dope for the surface layer and the dope for the base material layer were uniformly co-cast on a stainless steel belt support at a temperature of 33°C and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30°C. After evaporating the solvent until the residual solvent amount in the dope co-cast on the stainless steel belt support reached 30% by mass, it was peeled off from the stainless steel belt support at a peeling tension of 130 N / m. The cast film obtained by peeling was stretched at a stretching ratio of 50% in the width direction (TD direction) under the condition of 160°C (Tg of the resin - 10°C). The residual solvent at the start of stretching was 10% by mass. Next, while conveying the drying zone with a number of rollers, it was dried at 130°C. Thereafter, it was wound up to obtain an optical film having a three-layer structure of surface layer / base material layer / surface layer.

[0193] <Examples 19 to 21> An optical film was obtained in the same manner as in Example 18, except that the compositions of the base material layer and the surface layer were changed as shown in Table 2.

[0194] <Examples 22 to 26, Comparative Example 10> An optical film having a three-layer structure of surface layer / base material layer / surface layer was obtained in the same manner as in Example 4, except that the types and thicknesses of the light absorption materials in the base material layer and the surface layer were changed as shown in Table 3.

[0195] <Comparative Examples 2 to 4> An optical film was obtained in the same manner as in Production Examples 3, 4, and 7 of International Publication No. 2018 / 139638.

[0196] <Comparative Example 5> An optical film was obtained in the same manner as in Example 4 of International Publication No. 2015 / 098956.

[0197] <Comparative Example 6> An optical film (single-layer film) was obtained in the same manner as in Example 12, except that the content of the light absorption material E in the base material layer was changed as shown in Table 3 and the surface layer was not formed.

[0198] <Comparative Example 7> An optical film (single-layer film) was obtained in the same manner as in Comparative Example 6, except that the content of the light absorption material B was changed as shown in Table 3.

[0199] <Comparative Example 8> The thermoplastic resin (J0) used in Production Example 1 of International Publication No. 2018 / 139638 was dried at 100 ° C for 5 hours. The dried thermoplastic resin (J0) was supplied to an extruder and melted in the extruder. The melted thermoplastic resin (J0) was passed through a polymer pipe and a polymer filter, and extruded in a sheet form from a T-die onto a casting drum. The extruded thermoplastic resin (J0) was cooled to obtain a pre-stretching substrate with a thickness of 70 μm. The obtained substrate was stretched 1.4 times to obtain an optical film with a thickness of 50 μm.

[0200] <Comparative Example 9> A curable composition similar to that of Example 2 except that it did not contain a light absorption material was applied onto the optical film of Comparative Example 8, and then dried and cured to form a surface layer, thereby obtaining an optical film.

[0201] <Evaluation> The absorption coefficient and the presence or absence of bleed-out of the obtained optical film were evaluated by the following method. Bleed-out was performed only for some of the examples and comparative examples.

[0202] (1) Ratio of absorption coefficients (As / Ac) 1) First, using a microscopic FTIR (Agilent's "UMA600" and "FTS3000") by the ATR method, the incident light diameter: 100 μm, prism: Ge (incident angle 45°), detector: MCT-A, resolution: 4.0 cm -1 , and integrated 64 times, the infrared absorption spectrum was measured. From the obtained infrared absorption spectrum, the absorbance of the portion corresponding to a wavelength of 9.6 μm (frequency 1041 cm -1 ) was read to obtain the absorbance A of the entire optical film. 2) Next, 30% of the thickness was shaved off from one surface a of the optical film. Then, the absorbance A1 of the obtained shaved surface was measured in the same manner as in 1) above. 3) Also, 30% of the thickness was removed from the other surface b of the optical film. Then, the absorbance A2 of the obtained surface was measured in the same manner as in 1) above. 4) The absorbances A, A1, and A2 obtained in 1) to 3) above were applied to the following formulae to calculate the absorption coefficient As of the surface layer region and the absorption coefficient Ac of the inner layer region, respectively. Surface absorption coefficient As = (A - A1) × loge10 ÷ (0.3T) Internal absorption coefficient Ac = A2 × loge10 ÷ (0.4T) (T: Thickness of the optical film A: Absorbance of the optical film A1: Absorbance measured after removing 30% of the thickness T of the optical film from one surface 10a of the optical film A2: Absorbance measured after removing 30% of the thickness T of the optical film from the other surface 10b of the optical film)

[0203] (2) Bleed - out The obtained film was placed in a high - temperature thermo at 90°C and a damp - heat thermo at 80°C and 90% RH for 3000 hours. It was taken out at any time to observe the presence or absence of surface deposits on the film. The observation was carried out under illumination by a green lamp in a dark room. And the time required until deposits were observed is shown in Tables 2 and 3.

[0204] Also, a polarizing plate and a display device were fabricated using the obtained optical film. Then, the polarizing - plate quality and light leakage were evaluated by the following methods.

[0205] (3) Evaluation of the polarizing plate (polarizing - plate quality) (Production of the polarizer) A PVA resin film with a degree of polymerization of 2400, a saponification degree of 99.7 mol%, and a thickness of 75 μm was prepared. The film was stretched three times in the film conveyance direction while being dyed in an aqueous iodine solution at 30°C, and then stretched in an aqueous solution of 4% by mass boric acid and 5% by mass potassium iodide at 60°C so that the total stretching ratio was six times the original length. Further, the stretched film was washed by immersing it in an aqueous solution of 2% by mass potassium iodide at 30°C for several seconds. The obtained stretched film was dried at 90°C to obtain a polarizer.

[0206] (Production of polarizing plate) A polarizer was bonded to the surface layer (or light absorption layer) of the optical film via an adhesive, and a PET film was bonded to the back surface via an adhesive to produce a polarizing plate.

[0207] (Laser cutability) The obtained polarizing plate was irradiated with a carbon dioxide laser having a wavelength of 9.6 μm to cut the polarizing plate. The cutting conditions were a frequency of 20 kHz, an output of 59 W, and a speed of 60 m / min. The vicinity of the surface over a cutting length of 10 cm was confirmed and evaluated with a microscope. S: No dirt or soot at all A: Slight dirt or soot is slightly visible at the cutting part B: Slight dirt or soot is slightly visible around the cutting part C: Dirt or soot is significant but can be cleaned ×: The dirt is so severe that it cannot be used It was judged to be good if it was C or above.

[0208] (4) Evaluation of display device (light leakage) First, the polarizing plate previously bonded to the Hitachi liquid crystal display device Wooo W32L - H90, which is an IPS - type liquid crystal display device, was carefully peeled off. Then, the laser - cut polarizing plate was attached so as to coincide with the transmission axis of the originally attached polarizing plate to produce a liquid crystal display device. The laser - cut polarizing plate was attached such that the optical film of the present invention was on the liquid crystal cell side.

[0209] Then, the obtained liquid crystal display device was visually observed in a dark room with the entire screen showing black, and the light leakage at the edges was evaluated by 10 people. SS: No light leakage was visible to all 10 people. S: Weak light leakage was visible to 1 out of 10 people. A: Weak light leakage was visible to 2 - 3 out of 10 people. B: Weak light leakage was visible to 4 - 6 out of 10 people. C: Weak light leakage was visible to 7 or more out of 10 people. Practically, there is no problem. ×: Strong light leakage was visible to all 10 people. It was judged to be good if it was C or above.

[0210] The compositions and evaluation results of the optical films of Examples 1 - 21 are shown in Table 2, and the compositions and evaluation results of the optical films of Examples 22 - 26 and Comparative Examples 1 - 10 are shown in Table 3.

Table 2

Table 3

[0211] As shown in Tables 2 and 3, it can be seen that the optical films of Examples 1 - 26 in which the absorption coefficient ratio As / Ac was adjusted to 1.1 - 20 have good laser cutability and excellent polarizer quality (less contamination). Also, it can be seen that the obtained display device has no light leakage.

[0212] On the other hand, it can be seen that the optical films of Comparative Examples 1 - 3 and 6 - 8 in which the absorption coefficient ratio As / Ac is less than 1.1 have poor laser cutability and inferior polarizer quality. Meanwhile, it can be seen that light leakage occurs in the display devices for the optical films of Comparative Examples 4, 5, 9, and 10 in which As / Sc exceeds 20.

[0213] This application claims priority based on Japanese Patent Application No. 2020 - 128426 filed on July 29, 2020. All of the contents described in the specification and drawings of that application are incorporated herein by reference.

Industrial Applicability

[0214] According to the present invention, an optical film, a polarizing plate, and a liquid crystal display device can be provided that can enhance the cutting property by laser light without causing light leakage in the display device.

Explanation of Signs

[0215] 10 Optical film 11 Base material layer 12, 13 Surface layer 20 Polarizer 30 Other optical film 40 Adhesive layer 100 Polarizing plate 200 Laminate Sa, Sb Surface layer region C Inner layer region L Laser light

Claims

1. An optical film containing a cycloolefin resin, wherein when a region from one surface of the optical film to a depth of 30% of the thickness of the optical film is defined as a surface layer region Sa, a region from the other surface of the optical film to a depth of 30% of the thickness of the optical film is defined as a surface layer region Sb, and a region between the surface layer region Sa and the surface layer region Sb is defined as an inner layer region C, the ratio As / Ac of at least the absorption coefficient As of light with a wavelength of 9.6 μm measured by the ATR method in the surface layer region Sa to the absorption coefficient Ac of light with a wavelength of 9.6 μm measured by the ATR method in the inner layer region C is 1.1 to 20, The absorption coefficient of the optical film for light with a wavelength of 9.6 μm is 1.5×10 －５ / μm or more, Optical film.

2. The ratio As / Ac is 3 to 15, The optical film according to Claim 1.

3. The surface region Sa and the inner layer region C each contain a light absorption material having an absorption coefficient of 4.0×10 －３ / μm or more for light with a wavelength of 9.6 μm. The optical film according to Claim 1 or 2.

4. The content Ms of the light absorption material in the surface layer region Sa is higher than the content Mc of the light absorption material in the inner layer region C, The optical film according to Claim 3.

5. Ms / Mc is 2.5 to 20, The optical film according to Claim 4.

6. a base material layer containing a cycloolefin resin and the light absorption material, and a surface layer laminated on at least one surface of the base material layer, the surface layer containing a cycloolefin resin and the light absorption material or containing a (meth)acrylic resin as the light absorption material and having the content Ms' of the light absorption material in the surface layer is higher than the content Mc' of the light absorption material in the base material layer, The optical film according to any one of Claims 3 to 5.

7. Ms' / Mc' is 2.5 to 50, The optical film according to Claim 6.

8. a base material layer containing a cycloolefin resin and the light absorption material, and a surface layer laminated on at least one surface of the base material layer, the surface layer being composed of a cured product of a curable composition containing a curable compound as the light absorption material and a curing agent and having the curable compound is a urethane compound having a group that reacts with the curing agent, The optical film according to any one of Claims 3 to 5.

9. The light absorption material contains an ester compound or (meth)acrylic polymer particles, The optical film according to Claim 8.

10. The light absorption material is a sugar ester compound, The optical film according to Claim 9.

11. a polarizer, and the optical film according to any one of Claims 1 to 10 disposed on at least one surface of the polarizer and having Polarizing plate.

12. The surface included in the surface layer region Sa of the optical film is adhered to the polarizer. The polarizing plate according to claim 11.

13. A liquid crystal cell, A first polarizing plate and a second polarizing plate that sandwich it, having, At least one of the first polarizing plate and the second polarizing plate is the polarizing plate according to claim 11 or 12. Liquid crystal display device.

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