CN109416427B - Wide-view angle high-contrast optical compensation film - Google Patents

Wide-view angle high-contrast optical compensation film Download PDF

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CN109416427B
CN109416427B CN201780040736.3A CN201780040736A CN109416427B CN 109416427 B CN109416427 B CN 109416427B CN 201780040736 A CN201780040736 A CN 201780040736A CN 109416427 B CN109416427 B CN 109416427B
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film
formula
rth
less
contrast
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CN109416427A (en
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松本真典
野口哲央
藤掛英夫
石锅隆宏
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Tohoku University NUC
Denka Co Ltd
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Denka Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
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    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F212/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
    • C08F212/02—Monomers containing only one unsaturated aliphatic radical
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/12—Esters of monohydric alcohols or phenols
    • C08F220/16—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms
    • C08F220/18—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms with acrylic or methacrylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F222/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides, or nitriles thereof
    • C08F222/04—Anhydrides, e.g. cyclic anhydrides
    • C08F222/06—Maleic anhydride
    • C08F222/08—Maleic anhydride with vinyl aromatic monomers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L35/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical, and containing at least one other carboxyl radical in the molecule, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • C08L35/06—Copolymers with vinyl aromatic monomers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G—PHYSICS
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    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/418—Refractive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays

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Abstract

Provided is a liquid crystal display device having excellent viewing angle characteristics and a high contrast even in an oblique direction. An optical compensation film comprising a film A satisfying (formula 1) to (formula 3) and a film B satisfying (formula 4) and (formula 5) laminated on each other, wherein the film B is a copolymer comprising an aromatic vinyl monomer unit, an unsaturated dicarboxylic anhydride monomer unit, and a (meth) acrylate monomer unit, Re (450), Re (550), and Re (650) represent in-plane retardation at wavelengths of 450nm, 550nm, and 650nm, Rth (550) represents a thickness direction retardation at wavelength of 550nm, and the refractive index in the slow axis direction of the film is nx, the refractive index in the fast axis direction of the film is ny, the refractive index in the thickness direction of the film is nz, the thickness of the film is d, the in-plane retardation Re is a value defined by (formula 6), and the thickness direction retardation Rth is a value defined by (formula 7). (formula 1) Re (450) < Re (550) < Re (650); (formula 2) Re (550) is more than or equal to 25nm and less than or equal to 280 nm; (formula 3) Rth (550) is not less than 12nm and not more than 95 nm; (formula 4) Re (550) is not less than 0nm and not more than 140 nm; (formula 5) -140 nm-Rth (550) -0 nm; (formula 6) Re ═ nx-ny) × d; (formula 7) Rth { (nx + ny) ÷ 2-nz } × d.

Description

Wide-view angle high-contrast optical compensation film
Technical Field
The present invention relates to an optical compensation film for providing a liquid crystal display device having excellent viewing angle characteristics and a high contrast even in an oblique direction.
Background
Transparent resins are used for various purposes such as parts of home electric appliances, food containers, miscellaneous goods, and the like. In recent years, the liquid crystal display device is widely used as an optical member such as a thin liquid crystal display element or an electroluminescence element instead of a CRT type television display.
As an optical compensation film for a liquid crystal display, a stretched film obtained by uniaxially or biaxially stretching a resin film is widely used. As typical examples of the optical compensation film, there are retardation films, and a λ/2 plate that converts the vibration direction of polarization, or a λ/4 plate that converts circularly polarized light into linearly polarized light and converts linearly polarized light into circularly polarized light are widely used.
The retardation film is required to be optically compensated in a wide viewing field range, and is a very important characteristic that the retardation is not changed even when the film is incident in an oblique direction. In order to meet such required characteristics, patent document 1 discloses a liquid crystal display device including a laminate of a transparent stretched film having negative orientation birefringence and a transparent stretched film having positive orientation birefringence.
Patent document 2 discloses a method of widening the viewing angle of a liquid crystal display device by using an optical compensation film in which a stretched film exhibiting negative oriented birefringence and a stretched film exhibiting positive oriented birefringence are laminated so that the slow axes of the respective stretched films are in parallel, the in-plane retardation (Re) is 60300nm, and the orientation parameter (Nz) is in the range of 0.5 ± 0.1. Further disclosed is: the stretched film exhibiting negative intrinsic birefringence is a resin composition of a copolymer of an alpha-olefin and an N-phenyl-substituted maleimide and an acrylonitrile-styrene copolymer.
Thermoplastic resins exhibiting positive orientation birefringence include polycarbonates, amorphous cyclic polyolefins, and the like, and are excellent in heat resistance, transparency, film strength, and phase difference development, and therefore can be suitably used for optical films. On the other hand, as a thermoplastic resin exhibiting negative orientation birefringence, at least one of heat resistance, transparency, film strength and phase difference developing property is poor, and therefore, the practical examples are extremely few, and a film obtained by laminating a plurality of stretched films exhibiting positive orientation birefringence at an appropriate angle is mainly put into practical use. Therefore, the optical compensation design is complicated and costly, and the optical compensation performance is not sufficient.
In response to these demands, patent documents 3 and 4 propose thermoplastic resin copolymers and stretched films exhibiting negative oriented birefringence, which are excellent in transparency, heat resistance, film formability, film strength, and retardation development, and the retardation films described in patent documents 3 and 4 use cyclic polyolefins as thermoplastic resins exhibiting positive oriented birefringence. Patent document 5 proposes a film having a characteristic that the in-plane phase difference becomes larger as the wavelength becomes longer, so-called reverse wavelength dispersion.
[ Prior art documents ]
[ patent document ]
[ patent document 1] Japanese patent laid-open No. Hei 2-256023
[ patent document 2] Japanese patent laid-open No. 2007-24940
[ patent document 3] WO2014/021265 publication
WO 2015/033877 publication (patent document 4)
[ patent document 5] Japanese patent laid-open No. 2013-164501
Disclosure of Invention
Problems to be solved by the invention
However, the methods described in patent documents 3 and 4 do not have sufficiently high contrast characteristics. Further, in patent document 5, it is expected that high contrast characteristics are exhibited by a film having reverse wavelength dispersion, and although a film having high contrast from the front is obtained, the contrast characteristics from the oblique direction are not sufficient.
The purpose of the present invention is to provide an optical compensation film for providing a liquid crystal display device having excellent viewing angle characteristics and also having a high contrast in an oblique direction.
Means for solving the problems
The present inventors have conducted extensive studies to obtain a high contrast in an oblique direction while achieving excellent viewing angle characteristics, and have found that an optical compensation film for a liquid crystal display device having a high contrast in an oblique direction can be provided by combining a film a having reverse wavelength dispersion characteristics such that the internal phase difference becomes smaller as the wavelength becomes shorter, having positive birefringence of an in-plane phase difference Re and a thickness direction phase difference Rth in a specific range, and a film B having negative birefringence of an in-plane phase difference Re and a thickness direction phase difference Rth in a specific range. The optical compensation film obtained by the method of the present invention can be used for a liquid crystal display device.
The gist of the present invention is as follows.
(1) An optical compensation film comprising a film A satisfying (formula 1) to (formula 3) and a film B satisfying (formula 4) and (formula 5) laminated on each other, wherein the film B is a copolymer comprising an aromatic vinyl monomer unit, an unsaturated dicarboxylic anhydride monomer unit, and a (meth) acrylate monomer unit, Re (450), Re (550), and Re (650) represent in-plane retardation at wavelengths of 450nm, 550nm, and 650nm, Rth (550) represents a thickness direction retardation at wavelength of 550nm, and the refractive index in the slow axis direction of the film is nx, the refractive index in the fast axis direction of the film is ny, the refractive index in the thickness direction of the film is nz, the thickness of the film is d, the in-plane retardation Re is a value defined by (formula 6), and the thickness direction retardation Rth is a value defined by (formula 7).
(formula 1) Re (450) < Re (550) < Re (650)
(formula 2) Re (550) is not less than 25nm and not more than 280nm
(formula 3) Rth (550) of 12nm or less and Rth of 95nm or less
(formula 4) Re (550) is not less than 0nm and not more than 140nm
(formula 5) -140 nm-Rth (550) is less than or equal to 0nm
(formula 6) Re ═ nx-ny) x d
(formula 7) Rth { (nx + ny) ÷ 2-nz } × d
(2) The optically-compensatory film according to (1),
the Nz coefficient of the film a satisfies (equation 8), and is a value defined by (equation 9).
(formula 8) 0.6-Nz 1.2
(formula 9) Nz ═ nx-Nz)/(nx-ny)
(3) The optically-compensatory film according to (1) or (2),
the film B is a positive C plate, and the positive C plate is a film satisfying the formula (10).
(formula 10) nx ═ ny < nz
(4) The optically-compensatory film according to (1) or (2),
the film B is a negative A plate, and the negative A plate is a film satisfying the formula (11).
(formula 11) ny < nz ═ nx
(5) The optically-compensatory film according to (3), wherein,
the film a satisfies (formula 12), (formula 13), and (formula 14), and the film B satisfies (formula 15), and (formula 16).
(formula 12) 0.8. ltoreq. Nz. ltoreq.1.2
(formula 13) Re (550) is not less than 120nm and not more than 170nm
(formula 14) Rth (550) is 55 nm-90 nm
(formula 15) Re (550) is 0
(formula 16) -120 nm-Rth (550) -70nm
(6) The optically-compensatory film according to (3), wherein,
the film A satisfies (formula 17), (formula 18), and (formula 19), and the film B satisfies (formula 20), and (formula 21).
(formula 17) 0.6-Nz 0.8
(formula 18)170 nm-Re (550) -230 nm
(formula 19)15 nm-Rth 550-55 nm
(formula 20) Re (550) is 0
(formula 21) -70 nm-Rth (550) -20nm
(7) The optically-compensatory film according to (4),
the film A satisfies (formula 22) and (formula 23), and the film B satisfies (formula 24) and (formula 25).
(formula 22)70 nm-550 Re-120 nm
(formula 23) Rth (550) of 30nm or less and Rth of 60nm or less
(formula 24)70 nm-Re (550) -120nm
(formula 25) -60 nm-Rth (550) -30nm
(8) A liquid crystal display device comprising the optically compensating film according to any one of (1) to (7).
ADVANTAGEOUS EFFECTS OF INVENTION
The present invention can provide an optical compensation film for a liquid crystal display device having excellent viewing angle characteristics and high contrast even in an oblique direction by a simple method.
Drawings
Fig. 1 is a schematic view of a structure assembled when the thin film B is a positive C plate.
Fig. 2 is a schematic diagram of a combined structure when the film B is made to be a negative a plate.
Detailed Description
< for explanation >
In the present specification, the symbol "a to B" means a value from a to B. Also, the "Nz coefficient" is sometimes expressed as "Nz" in the formula.
The embodiments of the present invention will be described in detail below.
In the present invention, by combining the film a and the film B having specific optical characteristics, an optical compensation film having a high contrast even at an oblique viewing angle can be made possible. That is, by combining the film a having reverse wavelength dispersion characteristics in which the internal phase difference becomes smaller as the wavelength becomes shorter and having positive birefringence of the in-plane phase difference Re and the thickness direction phase difference Rth within a specific range and the film B having negative birefringence of the in-plane phase difference Re and the thickness direction phase difference Rth within a specific range, high contrast can be obtained even at an oblique viewing angle.
The film a used in the optical compensation film of the present invention is characterized by satisfying the following (formula 1) to (formula 3).
(formula 1) Re (450) < Re (550) < Re (650)
(formula 2) Re (550) is not less than 25nm and not more than 280nm
(formula 3) Rth (550) of 12nm or less and Rth of 95nm or less
Here, Re (450), Re (550) and Re (650) represent in-plane retardation at wavelengths of 450nm, 550nm and 650nm, and Rth (550) represents thickness-direction retardation at a wavelength of 550 nm.
When the slow axis of the film, that is, the refractive index in the axial direction when the in-plane refractive index of the film is the maximum, is nx, the fast axis of the film, that is, the refractive index in the axial direction perpendicular to the slow axis is ny, the refractive index in the thickness direction of the film is nz, and the thickness of the film is d, the in-plane phase difference Re is a value defined by (equation 6), and the thickness direction phase difference Rth is a value defined by (equation 7).
(formula 6) Re ═ nx-ny) x d
(formula 7) Rth { (nx + ny) ÷ 2-nz } × d
The film A has a characteristic of Re (450) < Re (550) < Re (650), and when Re (550) < 280nm and Rth (550) < Rth (12 nm) < 95nm are both within a range of 25nm and less, an optical compensation film having a high contrast at an oblique viewing angle can be produced.
In order to produce an optical compensation film having a high contrast at an oblique viewing angle, the Nz coefficient of the film a preferably satisfies the following (formula 8).
(formula 8) 0.6-Nz 1.2
Note that the Nz coefficient is a value defined by (equation 9).
(formula 9) Nz ═ nx-Nz)/(nx-ny)
The thermoplastic resin that can be used for the film A is not particularly limited as long as it satisfies the (formula 1) to (formula 3), and examples thereof include polycarbonate resins such as copolymers with 9, 9-bis [4- (2-hydroxyethoxy) phenyl ] fluorene and isosorbide described in Japanese patent laid-open No. 2012-150477. The resin used for the film a may be used alone in 1 kind, or 2 or more kinds may be used in combination.
The method for producing the film a is not particularly limited, and for example, an unstretched film can be formed by a melt extrusion method, a solution casting method, or the like, and then uniaxially or biaxially stretched by a roll stretching method, a tenter stretching method, or the like to produce an unstretched film.
The film B used for the optical compensation film of the present invention is characterized by satisfying the following (formula 4) to (formula 5).
(formula 4) Re (550) is not less than 0nm and not more than 140nm
(formula 5) -140 nm-Rth (550) is less than or equal to 0nm
When the film B is 0nm or more and Re (550) or more and 140nm or less and-140 nm or more and Rth (550) or more and 0nm or less, an optical compensation film having a high contrast at an oblique viewing angle can be produced.
The thermoplastic resin usable for the film B is a copolymer composed of an aromatic vinyl monomer unit, an unsaturated dicarboxylic anhydride monomer unit, and a (meth) acrylate monomer unit.
Examples of the aromatic vinyl monomer unit include units derived from styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2, 4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α -methylstyrene and α -methyl-p-methylstyrene. Among these, styrene units are preferred. These aromatic vinyl monomer units may be used in 1 kind, or may be used in combination of 2 or more kinds.
Examples of the unsaturated dicarboxylic anhydride monomer unit include units derived from various anhydride monomers such as maleic anhydride, itaconic anhydride, citraconic anhydride, and aconitic anhydride. Among these, maleic anhydride units are preferred. The unsaturated dicarboxylic anhydride monomer unit may be used in 1 kind, or 2 or more kinds may be used in combination.
Examples of the (meth) acrylate monomer unit include units derived from a methacrylate monomer such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, dicyclopentyl methacrylate or isobornyl methacrylate, and an acrylate monomer such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate or decyl acrylate. Among them, methyl methacrylate units are preferred. These (meth) acrylate monomer units may be used in combination of 1 kind or 2 or more kinds.
The copolymer used for the film B may contain -position vinyl monomers other than aromatic vinyl monomer units, (meth) acrylate monomer units and unsaturated dicarboxylic anhydride monomer units, preferably 5% by mass or less, within a range not impairing the effects of the present invention. Examples of the other vinyl monomer at position include the following units of each monomer: vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, vinyl carboxylic acid monomers such as acrylic acid and methacrylic acid, N-alkylmaleimide monomers such as N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide and N-cyclohexylmaleimide, and N-arylmaleimide monomers such as N-phenylmaleimide, N-methylphenylmaleimide and N-chlorophenylmaleimide. The copolymerizable vinyl monomer unit may be used in combination of 2 or more.
The content of the aromatic vinyl monomer unit is preferably 50 to 90% by mass, more preferably 60 to 85% by mass. When the aromatic vinyl monomer unit is 50% by mass or more, the film thickness can be made thin by improving the phase difference development property, and when the film is subjected to film forming processing by melt extrusion, a film suitable for the beauty of the optical compensation film can be obtained, and therefore, it is preferable that the aromatic vinyl monomer unit is 60% by mass or more, the phase difference development property can be further improved, the film thickness can be made thinner, and when the film is subjected to film forming processing by melt extrusion, a more beautiful film suitable for the optical compensation film can be obtained, and therefore, it is particularly preferable. An aromatic vinyl monomer unit of 90% by mass or less is preferable because it improves heat resistance and film strength, and an aromatic vinyl monomer unit of 85% by mass or less is particularly preferable because it further improves heat resistance and film strength.
The content of the unsaturated dicarboxylic anhydride monomer unit is preferably 5 to 25% by mass, more preferably 8 to 20% by mass. When the content of the unsaturated dicarboxylic anhydride monomer unit is 5% by mass or more, the heat resistance is preferably improved, and when the content is 8% by mass or more, the heat resistance is further improved, and thus the unsaturated dicarboxylic anhydride monomer unit is particularly preferably used. When the unsaturated dicarboxylic anhydride monomer unit is 25% by mass or less, the film strength is improved, and when the film is formed by melt extrusion, a film suitable for the aesthetic appearance of the optical compensation film can be obtained, and therefore, it is preferably 20% by mass or less, and when the film is formed by melt extrusion, a more aesthetic film suitable for the optical compensation film can be obtained, and this is particularly preferable.
The preferable content of the (meth) acrylate monomer unit is 5 to 45 mass%, and more preferably 7 to 32 mass%. When the content of the (meth) acrylate monomer unit is 5% by mass or more, the transparency and the film strength are improved, and therefore, it is preferable, and when the content is 7% by mass or more, the transparency and the film strength are further improved, and particularly preferable. When the (meth) acrylate monomer unit is 45 mass% or less, the film thickness can be reduced by improving the phase difference development property, and a more beautiful film suitable for an optical compensation film can be obtained in the film molding process by melt extrusion, and therefore, it is particularly preferable that the (meth) acrylate monomer unit is 32 mass% or less, the phase difference development property can be further improved, the film thickness can be reduced, and a more beautiful film suitable for an optical compensation film can be obtained in the film molding process by melt extrusion, and therefore, it is particularly preferable.
The weight average molecular weight (Mw) of the copolymer for the film B is preferably 12 to 25 ten thousand. A weight average molecular weight (Mw) of 12 ten thousand or more is preferable because the film strength is improved. When the weight average molecular weight (Mw) is 25 ten thousand or less, a film suitable for the aesthetic appearance of an optical compensation film can be obtained when the film is subjected to melt extrusion molding. The weight average molecular weight (Mw) is a value in terms of polystyrene measured by Gel Permeation Chromatography (GPC), and is a measured value under the measurement conditions described below.
Device name: SYSTEM-21Shodex (manufactured by Showa Denko K.K.)
A chromatographic column: connecting 3 PL gel MIXED-B in series
Temperature: 40 deg.C
And (3) detection: differential refractive index
Solvent: tetrahydrofuran (THF)
Concentration: 2% by mass
Standard curve: it was produced using standard Polystyrene (PS) (manufactured by PL corporation).
The method for producing the film B is not particularly limited, and for example, an unstretched film can be formed by a melt extrusion method, a solution casting method, or the like, and then uniaxially or biaxially stretched by a roll stretching method, a tenter stretching method, or the like to produce an unstretched film.
The method for producing the copolymer of the present invention will be explained.
The polymerization mode is not particularly limited, and the polymer can be produced by a known method such as solution polymerization or bulk polymerization, and solution polymerization is more preferable. The solvent used in the solution polymerization is preferably non-polymerizable from the viewpoint of being less likely to generate by-products and being less susceptible to adverse effects. The type of the solvent is not particularly limited, and examples thereof include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; ethers such as tetrahydrofuran and 1, 4-dioxane; aromatic hydrocarbons such as toluene, ethylbenzene, xylene, chlorobenzene, and the like, methyl ethyl ketone and methyl isobutyl ketone are preferable from the viewpoint of solubility of monomers and copolymers and easiness of solvent recovery. The amount of the solvent added is preferably 10100 parts by mass, more preferably 3080 parts by mass, based on 100 parts by mass of the obtained copolymer. When the amount is 10 parts by mass or more, it is preferable to control the reaction rate and the viscosity of the polymerization solution, and when the amount is 100 parts by mass or less, it is preferable to obtain the target weight average molecular weight (Mw).
The polymerization process may be any of a batch polymerization method, a semi-batch polymerization method, and a continuous polymerization method, but is preferably a batch polymerization method in terms of obtaining a desired weight average molecular weight (Mw) and transparency.
The polymerization method is not particularly limited, and a radical polymerization method is preferable from the viewpoint of enabling production with good yield by a simple process. The polymerization initiator is not particularly limited, and examples thereof include well-known organic peroxides such as dibenzoyl peroxide, t-butyl peroxybenzoate, 1-bis (t-butylperoxy) -2-methylcyclohexane, 1-bis (t-butylperoxy) cyclohexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyacetate, dicumyl peroxide, ethyl-3, 3-di- (t-butylperoxy) butyrate, and well-known azo compounds such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile, azobismethylpropionitrile, and azobismethylbutyronitrile. These polymerization initiators may be used in combination of 2 or more. Of these, organic peroxides having a 10-hour half-life temperature of 70110 ℃ are preferably used.
Since the aromatic vinyl monomer and the unsaturated dicarboxylic anhydride monomer have a strong alternating copolymerization property, it is preferable to use a method in which the unsaturated dicarboxylic anhydride monomer is continuously added separately in a manner corresponding to the polymerization rate of the aromatic vinyl monomer and the vinyl cyanide monomer, and the flow rate of the separate addition is also appropriately adjusted depending on the polymerization rate. It is preferable to control the polymerization rate while appropriately adjusting the polymerization temperature, the polymerization time, and the amount of the polymerization initiator to be added, because the composition distribution of the copolymer can be made smaller more precisely.
Further, the method for obtaining a copolymer having a weight average molecular weight (Mw) within a preferred range can be obtained by adjusting the amount of the solvent to be added and the amount of the chain transfer agent to be added, in addition to adjusting the polymerization temperature, the polymerization time, and the amount of the polymerization initiator to be added. The chain transfer agent is not particularly limited, and known chain transfer agents such as n-dodecyl mercaptan, t-dodecyl mercaptan, and 2, 4-diphenyl-4-methyl-1-pentene can be used.
After completion of the polymerization, additives such as heat-resistant stabilizers including hindered phenol compounds, lactone compounds, phosphorus compounds, sulfur compounds, etc., light-resistant stabilizers including hindered amine compounds, benzotriazole compounds, etc., lubricants, plasticizers, colorants, antistatic agents, mineral oils, etc., may be added to the polymerization liquid as needed. The amount added is preferably less than 0.2 part by mass per 100 parts by mass of the whole monomer units. These additives may be used alone, or 2 or more of them may be used in combination.
The method for recovering the copolymer of the present invention from the polymerization solution is not particularly limited, and a known devolatilization technique can be used. Examples thereof include: a method of continuously feeding a polymerization liquid into a twin-screw devolatilization extruder using a gear pump to devolatilize a polymerization solvent, unreacted monomers, and the like. The polymerization solvent may be recovered by condensing the devolatilized components including the polymerization solvent and unreacted monomers using a condenser or the like, and the condensate may be purified by a distillation column and reused.
Since the optical compensation is performed by laminating the film a, the film B used in the optical compensation film of the present invention is preferably a positive C plate or a negative a plate in terms of optical compensation design. The positive C plate is a film satisfying the following (formula 10), and the negative a plate is a film satisfying the following (formula 11).
(formula 10) nx ═ ny < nz
(formula 11) ny < nz ═ nx
The method for stretching the unstretched film is not particularly limited, and may be selected depending on the desired optical compensation, and may be monoaxially or biaxially stretched. In the production of the positive C plate, for example, biaxial stretching is performed, preferably simultaneous biaxial stretching is performed. The stretching magnification can be adjusted according to the objective phase difference value, but is 1.05 to 5 times, more preferably 1.1 to 4 times, and still more preferably 1.5 to 3 times in the longitudinal direction and the lateral direction, respectively. The stretching may be performed in one step or in multiple steps. In the production of the negative a plate, for example, uniaxial stretching, preferably free-end uniaxial stretching, is performed. The elongation ratio can be adjusted according to the objective phase difference value, but is 1.05 to 5 times, more preferably 1.1 to 4 times, and still more preferably 1.5 to 3 times in the longitudinal direction and the lateral direction, respectively. The stretching may be performed in one step or in multiple steps.
When the film B is a positive C-plate, when the film a is disposed adjacent to the film B with the absorption axis of the polarizing plates disposed orthogonal to each other and the absorption axis of one polarizing plate disposed orthogonal to the slow axis, and the film a and the film B are stacked adjacent to each other, an optical compensation film having a high contrast at an oblique viewing angle can be produced. The contrast at an angle of incidence of 60 ° is preferably 100: 1 or more, more preferably 300: 1 or more, more preferably 900: 1 or more, particularly preferably 1000: 1 or more. The contrast ratio represents the difference between the brightness and darkness of the liquid crystal display device, and the higher the contrast ratio is, the sharper the image quality is.
The combined structure when the film B is a positive C plate is shown in fig. 1.
When the film B is a positive C plate type, a high contrast can be obtained by adjusting the balance between the in-plane retardation and the thickness direction retardation of the film a and the film B depending on the Nz coefficient of the film a.
When the film B is a positive C plate and the film a is in the range of the following (formula 12), it is preferable that the film a satisfies (formula 13) and (formula 14) and the film B satisfies (formula 15) and (formula 16) in order to obtain a high contrast.
(formula 12) 0.8. ltoreq. Nz. ltoreq.1.2
(formula 13) Re (550) is not less than 120nm and not more than 170nm
(formula 14) Rth (550) is 55 nm-90 nm
(formula 15) Re (550) is 0
(formula 16) -120 nm-Rth (550) -70nm
In addition, the film B satisfies the following (formula 16') in order to obtain a high contrast.
(formula 16') -110 nm. ltoreq. Rth 550. ltoreq. 90nm
When the film B is a positive C plate and the film a is in the range of (formula 17) below, it is preferable that the film a satisfies (formula 18) and (formula 19) and the film B satisfies (formula 20) and (formula 21) in order to obtain a high contrast.
(formula 17) 0.6-Nz 0.8
(formula 18)170 nm-Re (550) -230 nm
(formula 19)15 nm-Rth 550-55 nm
(formula 20) Re (550) is 0
(formula 21) -70 nm-Rth (550) -20nm
When the film B is a positive C plate, as described above, the Nz coefficient of the film A is preferably 0.6. ltoreq. nz.ltoreq.1.2, more preferably 0.6. ltoreq. nz.ltoreq.0.8. When the Nz coefficient of the film A is 0.6. ltoreq. Nz. ltoreq.0.8, a higher contrast can be obtained because the Nz coefficient is small.
When the film B is a negative a plate, when the film a is disposed adjacent to one of the polarizing plates with the absorption axes thereof being orthogonal to each other, and the film B is stacked adjacent to the film a with the absorption axis thereof being orthogonal to the slow axis thereof, an optical compensation film having a high contrast at an oblique viewing angle can be produced. The contrast at an angle of incidence of 60 ° is preferably 100: 1 or more, more preferably 300: 1 or more.
When the film B is a negative a plate, a high contrast can be obtained by adjusting the balance between the in-plane retardation and the thickness direction retardation of the film a and the film B, depending on the Nz coefficient of the film a.
The combined structure when the film B is a negative a plate is shown in fig. 2.
In the case where the film B is a negative a plate, in order to obtain high contrast, it is preferable that the film a satisfies the following (formula 22) and (formula 23) and the film B satisfies (formula 24) and (formula 25).
(formula 22)70 nm-550 Re-120 nm
(formula 23) Rth (550) of 30nm or less and Rth of 60nm or less
(formula 24)70 nm-Re (550) -120nm
(formula 25) -60 nm-Rth (550) -30nm
When the film B is a negative a plate, the contrast is improved particularly when the difference between the absolute values of the phase differences in the thickness direction of the film a and the film B is small. The absolute value of the retardation in the thickness direction of the film a | RthA | and the absolute value of the retardation in the thickness direction of the film B | RthB |, more preferably satisfy the following (formula 26).
(formula 26) -10nm ≤ RthA | -RthB | < 10nm
The positive C plate and the negative a plate described above are used as the film B, whereby an optical compensation film having a high contrast can be provided. In addition, by combining the positive C plate with the film a, a particularly high contrast can be obtained, and the positive C plate is more preferably used.
The film of the present invention has high contrast at an oblique viewing angle, and can be used as an optical compensation film for a liquid crystal display device.
[ examples ] A method for producing a compound
Hereinafter, examples are given to explain the present invention in more detail. However, the present invention is not limited to these examples and the like.
Production of copolymer for film B
< production example of copolymer (B-1) >
A 20% maleic anhydride solution obtained by dissolving maleic anhydride in methyl isobutyl ketone so that the concentration of maleic anhydride is 20% by mass and a 2% t-butylperoxy-2-ethylhexanoate solution obtained by diluting t-butylperoxy-2-ethylhexanoate in methyl isobutyl ketone so that it is 2% by mass were prepared in advance for polymerization.
A120-liter autoclave equipped with a stirrer was charged with 2.0kg of a 20% maleic anhydride solution, 24kg of styrene, 12kg of methyl methacrylate, 30g of t-dodecyl mercaptan, and 2kg of methyl isobutyl ketone, and the gas phase was replaced with nitrogen gas, and then the temperature was raised to 87 ℃ over 40 minutes while stirring. After the temperature was raised, while maintaining 87 ℃, a 20% maleic anhydride solution was continuously added for 8 hours at a rate of 1.5 kg/hour and a 2% t-butylperoxy-2-ethylhexanoate solution at a rate of 375 g/hour. Then, the addition of each of the 2% t-butylperoxy-2-ethylhexanoate solutions was stopped, and 30g of t-butylperoxyisopropyl monocarbonate was added. The 20% maleic anhydride solution was maintained at a separate addition rate of 1.5 kg/hr and was heated to 120 ℃ over 4 hours at a heating rate of 8.25 ℃ per hour. The respective addition of the 20% maleic anhydride solution was stopped at the point when the respective addition amounts accumulated to 18 kg. After the temperature was raised, the temperature was maintained at 120 ℃ for 1 hour to terminate the polymerization. The polymerization solution was continuously fed into a twin-screw devolatilizing extruder using a gear pump, and methyl isobutyl ketone and a small amount of unreacted monomer were devolatilized, extruded into a linear form and cut to obtain a copolymer (B-1) in a pellet form. The composition of the copolymer (B-1) was analyzed by C-13NMR, and the weight average molecular weight (Mw) was measured by a GPC apparatus. Further, a mirror plate having a vertical length of 90mm, a horizontal length of 55mm and a thickness of 2mm was molded by an injection molding machine (IS-50 EPN manufactured by Toshiba machine Co., Ltd.) under molding conditions of a cylinder temperature of 230 ℃ and a mold temperature of 40 ℃, and the haze of the mirror plate having a thickness of 2mm was measured by a haze meter (NDH-1001 DP manufactured by Nippon Denshoku industries Co., Ltd.) according to ASTM D1003. The composition analysis result showed 59.8 mass% of styrene monomer unit, 29.8 mass% of methyl methacrylate monomer unit, and 10.4 mass% of maleic anhydride monomer unit. Also, the polymerization average molecular weight (Mw) was 18.0 ten thousand g/mol and the haze was 0.4%.
[ example 1]
A film-forming machine using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide was used to form an unstretched film having a thickness of 70 μm using a film-forming machine equipped with a gear pump, a polymer filter "Denafilter, a mesh of 5 μm" (manufactured by Rex industries, Ltd.), a 300mm wide single-layer T die, and a take-up reel "Touch Roll Flexible Type" (manufactured by Research Laboratory of Plastics Technology Co., Ltd.) in a 40mm Φ single-screw extruder. The obtained unstretched film was cut into 100mm squares, and uniaxially stretched at the free end in the longitudinal direction at a temperature of 155 ℃ and a stretching speed of 2mm/S by a biaxial stretching apparatus (X61-S, manufactured by Toyo Seiki Seisaku-Sho Ltd.) to obtain a film (a-1). The birefringence of the film (a-1) was measured using a birefringence measuring apparatus KOBRA-WR,
as a result, Re (450) was 128nm, Re (550) was 146nm, Re (650) was 150nm, Rth (550) was 73nm, the film thickness was 50 μm, and the Nz coefficient was 1.00.
An unstretched film having a thickness of 170 μm was formed from the copolymer (B-1) by using a film forming machine in the same manner as the film (a-1). The obtained unstretched film was cut into 100mm squares, and a film (b-1) which was simultaneously biaxially stretched 2.0 times in the longitudinal direction and 2.0 times in the transverse direction was obtained by a biaxial stretching apparatus (X61-S, manufactured by Toyo Seiki Seisaku-Sho Ltd.) at a temperature of 129 ℃ and an elongation rate of 2 mm/S. The birefringence of the film (b-1) was measured using a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 93nm, and the film thickness was 42 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the film (a-1) and the film (b-1) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring machine (conscope, manufactured by Autronic Melchers), and as a result, the contrast was 945: 1. the results are shown in Table 1.
[ example 2]
A film (B-2) was obtained by stretching the film (B-1) in the same manner as in the case of the film (B-1) except that the thickness of the unstretched film was set to 144 μm using the copolymer (B-1). The birefringence of the film (b-2) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 79nm, and the film thickness was 36 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the film (a-1) and the film (b-1) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 507: 1. the results are shown in Table 1.
[ example 3]
A film (B-3) was obtained by stretching the film (B-1) in the same manner as in the case of the film (B-1) except that the thickness of the unstretched film was changed to 212. mu.m by using the copolymer (B-1). The birefringence of the film (b-3) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 116nm, and the film thickness was 53 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the film (a-1) and the film (b-3) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 335: 1. the results are shown in Table 1.
[ example 4]
A film (B-4) was obtained by stretching the film (B-1) in the same manner as in the case of the film (B-1) except that the thickness of the unstretched film was changed to 108 μm by the copolymer (B-1). The birefringence of the film (b-4) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 60nm, and the film thickness was 27 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the film (a-1) and the film (b-4) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 179: 1. the results are shown in Table 1.
[ example 5]
A film (B-5) was obtained by stretching the film (B-1) in the same manner as in the case of the film (B-1) except that the thickness of the unstretched film was set to 252. mu.m by using the copolymer (B-1). The birefringence of the film (b-5) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) was 0nm, Rth (550) was 139nm, and the film thickness was 63 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the film (a-1) and the film (b-5) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 108: 1. the results are shown in Table 1.
[ example 6]
The film (a-2) was obtained by stretching the film (a-1) in the same manner as in the case of the film (a-1) except that the unstretched film was made 77 μm thick using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. The birefringence of the film (a-2) was measured by a birefringence measuring device KOBRA-WR
The film thickness was 55 μm with a value of Re (450) 141nm, Re (550) 160nm, Re (650) 165nm, Rth (550) 80nm, Nz 1.00.
In the configuration of fig. 1, the film (a-2) and the film (b-1) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 539: 1. the results are shown in Table 1.
[ example 7]
The film (a-3) was obtained by stretching the film (a-1) in the same manner as in the case of the film (a-1) except that the unstretched film thickness was adjusted to 60 μm using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. The birefringence of the film (a-3) was measured with a birefringence measurement device KOBRA-WR, where Re (450) was 109nm, Re (550) was 124nm, Re (650) was 128nm, Rth (550) was 62nm, film thickness 43 μm, and Nz coefficient was 1.00.
In the configuration of fig. 1, the film (a-3) and the film (b-1) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 320: 1. the results are shown in Table 1.
[ example 8]
The film (a-4) was obtained by stretching the film (a-1) in the same manner as in the case of the film (a-1) except that the unstretched film was made 84 μm thick using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. The birefringence of the film (a-4) was measured by a birefringence measuring device KOBRA-WR
The film thickness was 60 μm and the Nz coefficient was 1.00, with the results of 153nm for Re (450), 174nm for Re (550), 179nm for Re (650), 87nm for Rth (550), and 87nm for Re (550).
In the configuration of fig. 1, the film (a-4) and the film (b-1) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and the contrast was 222: 1. the results are shown in Table 1.
[ example 9]
A film (a-5) was obtained by stretching the film (a-1) in the same manner as in the case of the film (a-1) except that the unstretched film was 91 μm thick using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. The birefringence of the film (a-5) was measured by a birefringence measuring device KOBRA-WR
Fruit, Re (450) ═ 165nm, Re (550) ═ 188nm, Re (650) ═ 194nm, Rth (550) ═ 94nm, film thickness 65 μm, and Nz coefficient ═ 1.00.
In the configuration of fig. 1, the film (a-5) and the film (b-1) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 112: 1. the results are shown in Table 1.
[ example 10]
A copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide is dissolved in methylene chloride and directly applied to a shrinkable film (a uniaxially stretched film of PP) with a wire bar to form a coating film. Then, the film was dried at 60 ℃ for 5 minutes to prepare a laminate of a shrinkable film and a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. Subsequently, the laminate was stretched 2.0 times at a stretching speed of 2mm/S in a direction perpendicular to the direction of shrinkage of the laminate while shrinking 0.8 times at 150 ℃ by using a biaxial stretching apparatus (X61-S, manufactured by Toyo Seiki Seisaku-Sho Ltd.). Subsequently, the shrinkable film was peeled off to obtain film (a-6). The birefringence of the film (a-6) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (450) was 153nm, Re (550) was 174nm, Re (650) was 179nm, Rth (550) was 43nm, the film thickness was 60 μm, and the Nz coefficient was 0.75.
A film (B-6) was obtained by stretching the film (B-1) in the same manner as in the case of the film (B-1) except that the thickness of the unstretched film was changed to 120 μm by using the copolymer (B-1). The birefringence of the film (b-6) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 65nm, and the film thickness was 30 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, films (a-6) and (b-6) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, contrast 1020: 1. the results are shown in Table 1.
[ example 11]
A copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide is dissolved in methylene chloride and directly applied to a shrinkable film (a uniaxially stretched film of PP) with a wire bar to form a coating film. Then, the film was dried at 60 ℃ for 5 minutes to prepare a laminate を of a shrinkable film and a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. Subsequently, the laminate was stretched 2.0 times at a stretching speed of 2mm/S in a direction perpendicular to the direction of shrinkage of the laminate while shrinking 0.7 times at 150 ℃ by using a biaxial stretching apparatus (X61-S, manufactured by Toyo Seiki Seisaku-Sho Ltd.). Subsequently, the shrinkable film was peeled off to obtain film (a-7). The birefringence of the film (a-7) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (450) was 183nm, Re (550) was 208nm, Re (650) was 214nm, Rth (550) was 21nm, the film thickness was 72 μm, and the Nz coefficient was 0.60.
A film (B-7) was obtained by stretching the copolymer (B-1) in the same manner as the film (B-1) except that the unstretched film was changed to a film thickness of 76 μm. The birefringence of the film (b-7) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 42nm, and the film thickness was 19 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the films (a-7) and (b-7) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 1135: 1. the results are shown in Table 1.
[ example 12]
A film (B-8) was obtained by stretching the film (B-1) in the same manner as in the case of the film (B-1) except that the thickness of the unstretched film was changed to 20 μm by using the copolymer (B-1). The birefringence of the film (b-8) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 11nm, and the film thickness was 5 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the films (a-7) and (b-8) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 202: 1. the results are shown in Table 1.
[ example 13]
A copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide is dissolved in methylene chloride and directly applied to a shrinkable film (a uniaxially stretched film of PP) with a wire bar to form a coating film. Then, the film was dried at 60 ℃ for 5 minutes to prepare a laminate of a shrinkable film and a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. Subsequently, the laminate was stretched 2.0 times at a stretching speed of 2mm/S in a direction perpendicular to the direction of shrinkage of the laminate while shrinking 0.7 times at 150 ℃ by using a biaxial stretching apparatus (X61-S, manufactured by Toyo Seiki Seisaku-Sho Ltd.). Subsequently, the shrinkable film was peeled off to obtain a film (a-8). The birefringence of the film (a-8) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (450) was 245nm, Re (550) was 278nm, Re (650) was 286nm, Rth (550) was 28nm, the film thickness was 97 μm, and the Nz coefficient was 0.60.
In the configuration of fig. 1, the films (a-8) and (b-7) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 110: 1. the results are shown in Table 1.
[ example 14]
The film (a-9) was obtained by stretching the film (a-1) in the same manner as in the case of the film (a-1) except that the unstretched film was made to have a thickness of 47 μm by using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. The birefringence of the film (a-9) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (450) was 84nm, Re (550) was 96nm, Re (650) was 99nm, Rth (550) was 48nm, the film thickness was 33 μm, and the Nz coefficient was 1.00.
A film (B-9) was obtained by stretching the unstretched film (A-1) in the same manner as in the case of the film (a-1) except that the thickness of the unstretched film was set to 33 μm and the temperature was set to 130 ℃ using the copolymer (B-1). The birefringence of the film (b-9) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 96nm, Rth (550) — 48nm, and the film thickness was 23 μm. And, the refractive index is in the relationship of ny < nz ═ nx, and is a negative A plate.
In the configuration of fig. 2, the films (a-9) and (b-9) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 869: 1. the results are shown in Table 1.
[ example 15]
A film (B-10) was obtained by stretching the unstretched film (A-1) in the same manner as in the case of the film (a-1) except that the thickness of the unstretched film was set to 47 μm and the temperature was set to 130 ℃ by using the copolymer (B-1). The birefringence of the film (b-10) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 136nm, Rth (550) — 68nm, and the film thickness was 32 μm. And, the refractive index is in the relationship of ny < nz ═ nx, and is a negative A plate.
In the configuration of fig. 2, the films (a-9) and (b-10) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 124: 1. the results are shown in Table 1.
[ example 16]
The film (a-10) was obtained by stretching the film (a-1) in the same manner as in the case of the film (a-1) except that the unstretched film was 25 μm thick using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. The birefringence of the film (a-10) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (450) was 46nm, Re (550) was 52nm, Re (650) was 54nm, Rth (550) was 26nm, the film thickness was 18 μm, and the Nz coefficient was 1.00.
In the configuration of fig. 2, the films (a-10) and (b-9) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 102: 1. the results are shown in Table 1.
Comparative example 1
A film (B-11) was obtained by stretching the copolymer (B-1) in the same manner as the film (B-1) except that the thickness of the unstretched film was changed to 312. mu.m. The birefringence of the film (b-11) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 0nm, Rth (550) — 160nm, and the film thickness was 78 μm. And, the refractive index is nx ═ ny < nz, and is a positive C plate.
In the configuration of fig. 1, the film (a-1) and the film (b-11) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 100: 1 or less. The results are shown in Table 1.
Comparative example 2
A film (a-11) was obtained by stretching in the same manner as the film (a-1) except that an unstretched film was formed to a thickness of 105 μm using a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. The birefringence of the film (a-11) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (450) was 192nm, Re (550) was 218nm, Re (650) was 225nm, Rth (550) was 109nm, the film thickness was 75 μm, and the Nz coefficient was 1.00.
In the configuration of fig. 1, the films (a-11) and (b-1) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 100: 1 or less. The results are shown in Table 1.
Comparative example 3
A copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide is dissolved in methylene chloride and directly applied to a shrinkable film (a uniaxially stretched film of PP) with a wire bar to form a coating film. Then, the film was dried at 60 ℃ for 5 minutes to prepare a laminate of a shrinkable film and a copolymer of 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene and isosorbide. Subsequently, the laminate was stretched 2.0 times at a stretching speed of 2mm/S in a direction perpendicular to the direction of shrinkage of the laminate while shrinking 0.7 times at 150 ℃ by using a biaxial stretching apparatus (X61-S, manufactured by Toyo Seiki Seisaku-Sho Ltd.). Subsequently, the shrinkable film was peeled off to obtain a film (a-12). The birefringence of the film (a-12) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (450) was 255nm, Re (550) was 290nm, Re (650) was 299nm, Rth (550) was 29nm, the film thickness was 100 μm, and the Nz coefficient was 0.6.
In the configuration of fig. 1, the films (a-12) and (b-7) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 100: 1 or less. The results are shown in Table 1.
Comparative example 4
A film (B-12) was obtained by stretching the unstretched film (A-1) with the copolymer (B-1) at a temperature of 130 ℃ in the same manner as in the case of the film (a-1). The birefringence of the film (b-12) was measured by a birefringence measurement device KOBRA-WR, and as a result, Re (550) — 154nm, Rth (550) — 77nm, and the film thickness was 37 μm. And, the refractive index is in the relationship of ny < nz ═ nx, and is an A plate.
In the configuration of fig. 2, the films (a-9) and (b-12) were arranged between polarizing plates arranged so that their polarizing axes were orthogonal to each other, and the contrast at an incident angle of 60 degrees was measured by a contrast measuring instrument, and as a result, the contrast was 100: 1 or less. The results are shown in Table 1.
[ TABLE 1]
Figure GDA0002770459130000241
The optical compensation film of the present invention can be used to produce an optical compensation film having improved viewing angle characteristics of a liquid crystal device, that is, having high contrast ratio characteristics at a wide viewing angle.
Industrial applicability
According to the present invention, an optical compensation film for a liquid crystal display device having excellent viewing angle characteristics and high contrast even in an oblique direction can be provided.

Claims (8)

1. An optical compensation film comprising a film A satisfying (formula 1) to (formula 3) and a film B satisfying (formula 4) and (formula 5) laminated on each other, wherein the film B is a copolymer comprising an aromatic vinyl monomer unit, an unsaturated dicarboxylic anhydride monomer unit, and a (meth) acrylate monomer unit,
re (450), Re (550) and Re (650) represent in-plane retardation at wavelengths of 450nm, 550nm and 650nm, Rth (550) represents thickness-direction retardation at wavelength of 550nm,
assuming that the refractive index in the slow axis direction of the film is nx, the refractive index in the fast axis direction of the film is ny, the refractive index in the thickness direction of the film is nz, and the thickness of the film is d, the in-plane retardation Re is a value defined by (equation 6), and the thickness direction retardation Rth is a value defined by (equation 7),
(formula 1) Re (450) < Re (550) < Re (650)
(formula 2) Re (550) is not less than 25nm and not more than 280nm
(formula 3) Rth (550) of 12nm or less and Rth of 95nm or less
(formula 4) Re (550) is not less than 0nm and not more than 140nm
(formula 5) -140 nm-Rth (550) is less than or equal to 0nm
(formula 6) Re ═ nx-ny) x d
(formula 7) Rth { (nx + ny) ÷ 2-nz } × d.
2. The optically-compensatory film according to claim 1,
the Nz coefficient of the film A satisfies (equation 8), the Nz coefficient is a value defined by (equation 9),
(formula 8) 0.6-Nz 1.2
(formula 9) Nz ═ nx-Nz)/(nx-ny).
3. The optical compensation film according to claim 1 or 2,
the film B is a positive C plate, the positive C plate is a film satisfying the formula (10),
(formula 10) nx ═ ny < nz.
4. The optical compensation film according to claim 1 or 2,
the film B is a negative A plate, the negative A plate is a film satisfying the formula (11),
(formula 11) ny < nz ═ nx.
5. The optically-compensatory film according to claim 3,
the film A satisfies (formula 12), (formula 13), and (formula 14), and the film B satisfies (formula 15), and (formula 16),
(formula 12) 0.8. ltoreq. Nz. ltoreq.1.2
(formula 13) Re (550) is not less than 120nm and not more than 170nm
(formula 14) Rth (550) is 55 nm-90 nm
(formula 15) Re (550) is 0
(formula 16) -120nm of Rth (550) is less than or equal to-70 nm.
6. The optically-compensatory film according to claim 3,
the film A satisfies (formula 17), (formula 18), and (formula 19), and the film B satisfies (formula 20), and (formula 21),
(formula 17) 0.6-Nz 0.8
(formula 18)170 nm-Re (550) -230 nm
(formula 19)15 nm-Rth 550-55 nm
(formula 20) Re (550) is 0
(formula 21) -70nm of Rth (550) is less than or equal to-20 nm.
7. The optically-compensatory film according to claim 4,
the film A satisfies (formula 22) and (formula 23), and the film B satisfies (formula 24) and (formula 25),
(formula 22)70 nm-550 Re-120 nm
(formula 23) Rth (550) of 30nm or less and Rth of 60nm or less
(formula 24)70 nm-Re (550) -120nm
(formula 25) -60nm of Rth (550) is less than or equal to-30 nm.
8. A liquid crystal display device comprising the optical compensation film according to any one of claims 1 to 7.
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