CN111448246A - Optical film, method for producing same, polarizing plate, and image display device - Google Patents

Optical film, method for producing same, polarizing plate, and image display device Download PDF

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Publication number
CN111448246A
CN111448246A CN201980006223.XA CN201980006223A CN111448246A CN 111448246 A CN111448246 A CN 111448246A CN 201980006223 A CN201980006223 A CN 201980006223A CN 111448246 A CN111448246 A CN 111448246A
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Prior art keywords
layer
optical film
film
slip
fine particles
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CN111448246B (en
Inventor
品川雅
道下空
冈田康彰
徐菁璠
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Nitto Denko Corp
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Nitto Denko Corp
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Priority to CN202110949132.9A priority Critical patent/CN113759455A/en
Priority to CN202110950621.6A priority patent/CN113635632B/en
Priority claimed from PCT/JP2019/028657 external-priority patent/WO2020022269A1/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G02B5/3041—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
    • G02B5/305—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks including organic materials, e.g. polymeric layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/0074—Production of other optical elements not provided for in B29D11/00009- B29D11/0073
    • B29D11/00788—Producing optical films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/00865—Applying coatings; tinting; colouring
    • 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
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
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    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (co)polymers
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    • 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
    • B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
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    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B32B27/325—Layered products comprising a layer of synthetic resin comprising polyolefins comprising polycycloolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
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    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B32B27/365—Layered products comprising a layer of synthetic resin comprising polyesters comprising polycarbonates
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    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
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    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04—Coating
    • C08J7/0427—Coating with only one layer of a composition containing a polymer binder
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J201/00—Adhesives based on unspecified macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • 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
    • G02F1/133528—Polarisers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/50—OLEDs integrated with light modulating elements, e.g. with electrochromic elements, photochromic elements or liquid crystal elements
    • 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
    • B32B2255/00—Coating on the layer surface
    • B32B2255/10—Coating on the layer surface on synthetic resin layer or on natural or synthetic rubber layer
    • 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
    • B32B2255/00—Coating on the layer surface
    • B32B2255/26—Polymeric coating
    • 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
    • B32B2307/42—Polarizing, birefringent, filtering
    • 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
    • B32B2307/70—Other properties
    • B32B2307/726—Permeability to liquids, absorption
    • B32B2307/7265—Non-permeable
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or 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 of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2475/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
    • C08J2475/04—Polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2203/00—Applications of adhesives in processes or use of adhesives in the form of films or foils
    • C09J2203/318—Applications of adhesives in processes or use of adhesives in the form of films or foils for the production of liquid crystal displays
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/30—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/312—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier parameters being the characterizing feature
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
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Abstract

The optical film (1) has an easy-slip layer (15) on the surface of a transparent film substrate (11). The slipping layer (15) contains a binder resin and fine particles. The content of the alkaline component in the slippery layer (15) is 5 to 75 ppm. The composition for forming an easy-slip layer containing a binder resin or a precursor thereof, fine particles, an alkali component and a solvent may be applied to a transparent film substrate and heated to form an easy-slip layer. The optical film can be used as a polarizer protective film.

Description

Optical film, method for producing same, polarizing plate, and image display device
Technical Field
The present invention relates to an optical film having an easily slippery layer on a surface of a transparent film substrate, and a method for producing the same. The present invention also relates to a polarizing plate in which an optical film having an easy-slip layer is bonded to a surface of a polarizer, and an image display device including the polarizing plate.
Background
in the organic E L display device, a circularly polarizing plate (typically, a laminate of a polarizing plate and a 1/4 wavelength plate) is sometimes disposed on the viewing side surface in order to suppress reflection of external light by a metal electrode (cathode) and to be viewed as a mirror surface.
In general, a polarizing plate includes a transparent film (polarizer protective film) for the purpose of protecting a polarizer or the like on one or both surfaces of the polarizer. As a polarizer, a polarizer in which a polyvinyl alcohol (PVA) film is adsorbed with iodine and molecules are oriented by stretching or the like is widely used.
As a polarizer protective film to be bonded to the surface of a polarizer, a polarizing plate to which a low moisture-permeable film made of a resin material such as acrylic, polyester, polycarbonate, or cyclic polyolefin is bonded tends to have excellent durability with little change in optical characteristics even when exposed to a high-humidity environment for a long time. Patent document 1 describes that blocking when the film is wound into a roll shape can be suppressed by providing an easy-slip layer containing fine particles and a binder resin on the surface of an acrylic film. In the examples of patent document 1, a polarizer protective film is disclosed in which a urethane resin layer having an average thickness of 400nm (thickness range of 300 to 500nm) containing 1 to 7% by weight of silica fine particles is provided on the surface of an acrylic film.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 5354733
Disclosure of Invention
Problems to be solved by the invention
In the progress of increasing the size and brightness of an image display device, a polarizing plate constituting the image display device is required to have small changes in optical characteristics even under a severer environment (for example, a condition of higher temperature and higher humidity). The polarizing plate having the polarizer protective film disclosed in patent document 1 newly finds the following problems: when exposed to a high humidity environment for a long time, optical defects such as stripe-like unevenness may occur, and the display characteristics may be degraded.
In view of the above problems, an object of the present invention is to provide an optical film which is less likely to cause blocking and is less likely to cause optical defects even when exposed to a high-temperature and high-humidity environment for a long period of time.
Means for solving the problems
In view of the above-described problems, the present inventors have found that the basic components such as ammonia and amines added to the composition for forming an easily slippery layer for the purpose of improving the dispersibility of fine particles are one cause of the deterioration of durability in a humidified environment, and the above-described problems can be solved by setting the amount of the residual alkali in the easily slippery layer within a predetermined range.
The present invention relates to an optical film having an easily slippery layer on a surface of a transparent film substrate, and a method for producing the same. The slippery layer contains a binder resin and fine particles. The average primary particle diameter of the fine particles is, for example, 10 to 250nm, preferably 10 to 100 nm. The content of the alkaline component in the slippery layer is preferably 5 to 75 ppm. The thickness of the easy-sliding layer is preferably 40-280 nm.
As the transparent film substrate, an acrylic film or the like is used. As the binder resin of the slipping layer, urethane resin or the like is used. The content of the fine particles in the slippery layer is preferably about 3 to 50 wt%, and more preferably 10 to 50 wt%. The particles of the slippery layer may be embedded in the transparent film substrate.
The composition for forming a slip-susceptible layer is applied to the surface of a transparent film substrate and heated to form a slip-susceptible layer. The composition for forming a slip-facilitating layer contains a binder resin or a precursor thereof, fine particles, an alkaline component, and a solvent. When the composition for forming an easily slidable layer contains an alkaline component, the dispersibility of fine particles is improved, and an optical film having excellent sliding properties can be obtained. The basic component may also function as a catalyst for promoting the reaction of the binder resin (precursor). The boiling point of the alkali component is preferably 150 ℃ or lower from the viewpoint of promoting the volatilization of the alkali component by heating. Examples of the basic component include amines and ammonia.
By increasing the heating temperature after the application of the composition for forming a slip-susceptible layer, volatilization of the alkali component is promoted, and a slip-susceptible layer with a small amount of residual alkali component can be formed. For example, the composition for forming a slip-susceptible layer may be heated at a temperature higher by 10 ℃ or more than the glass transition temperature of the transparent film substrate. By raising the heating temperature, the fine particles that easily form the slip-prone layer are embedded in the region of the transparent film base, and the adhesion between the transparent film base and the slip-prone layer tends to be improved.
After the composition for forming an easily slippery layer is applied to the transparent film substrate, the transparent film substrate may be stretched while being heated. In particular, by stretching the transparent film base while heating the composition for forming an easy-slip layer at a temperature higher by 10 ℃ or more than the glass transition temperature of the transparent film base, the adhesion between the transparent film base and the easy-slip layer tends to be improved.
the easy-to-slide layer can contribute to improvement in adhesion to other films, glass substrates, and the like, the optical film can be used as a polarizer protective film, for example, a polarizing plate can be obtained by laminating the optical film on the surface of a polyvinyl alcohol polarizer via an adhesive layer, any one of the easy-to-adhere layer-formed surface and the non-easy-to-adhere layer-formed surface of the optical film can be laminated to a polarizer, and an image display device can be formed by disposing the polarizing plate on the surface of an image display unit such as a liquid crystal display unit or an organic E L unit.
ADVANTAGEOUS EFFECTS OF INVENTION
The optical film of the present invention is excellent in adhesiveness, hardly causes blocking, and hardly causes optical defects even when exposed to a high humidity environment for a long time, and therefore, can be suitably used as a film for display devices such as a polarizer protective film.
Drawings
Fig. 1 is a sectional view showing an example of the structure of an optical film having an easy-slip layer.
Fig. 2A is a cross-sectional view showing an example of the configuration of the polarizing plate.
Fig. 2B is a sectional view showing a configuration example of the polarizing plate.
Fig. 3 is a cross-sectional TEM observation image of an optical film in which an interface layer is formed at the interface between the film base and the slipping layer.
Fig. 4 is a cross-sectional TEM observation image of an optical film in which no interface layer is formed at the interface between the film base and the slipping layer.
Detailed Description
Fig. 1 is a schematic cross-sectional view showing an example of the structure of an optical film according to an embodiment of the present invention. The optical film 1 includes an easy-slip layer 15 on at least one surface of a film base 11. The two surfaces of the film base material can also be provided with the easy-sliding layers. The optical film may be used by bonding to other films, glass substrates, and the like.
Examples of the mode of use of the optical film include a polarizer protective film. Fig. 2A and 2B are cross-sectional views showing examples of the structure of a polarizing plate including the optical film 1 as a polarizer protective film. The polarizing plate 100 shown in fig. 2A and the polarizing plate 101 shown in fig. 2B have an optical film 1 bonded to one surface (first main surface) of a polarizer 5 via an adhesive layer 6. In the polarizing plate 100, the optical film 1 has an easy-slip layer 15 on the surface of the film base 11 that is in contact with the polarizer 5. In the polarizing plate 101 shown in fig. 2B, the polarizer 5 is bonded to the surface of the optical film 1 on which the easy-slip layer 15 is not provided. In the polarizing plate 100 shown in fig. 2A and the polarizing plate 101 shown in fig. 2B, the transparent protective film 2 is bonded to the other surface (second main surface) of the polarizer 5 via the adhesive layer 7.
[ optical film ]
The optical film 1 includes an easy-slip layer 15 on at least one surface of a film base 11.
< film substrate >
As the film substrate 11, a transparent film is preferable. The total light transmittance of the transparent film substrate is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. Examples of the resin material constituting the film base 11 include acrylic resins, polyester resins, polycarbonate resins, polyolefin resins, cyclic polyolefin resins, polystyrene resins, polyamide resins, polyimide resins, and the like. When the optical film is used as an optically isotropic polarizer protective film, an acrylic resin or a cyclic polyolefin resin is preferable, and an acrylic resin is particularly preferable, from the viewpoint of low birefringence, as a resin material of the film base 11.
examples of the cyclic polyolefin resin include polynorbornene, and commercially available products of the cyclic polyolefin resin include ZEONOR and ZEONEX manufactured by Zeon Corporation, ARTON manufactured by JSRCorporation, APE L manufactured by mitsui chemicals, inc., and TOPAS manufactured by TOPAS advanced polymers.
Examples of the acrylic resin include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymers, methyl (meth) acrylate-styrene copolymers (MS resins, etc.), and polymers having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymers, methyl methacrylate- (meth) acrylic acid norbornyl ester copolymers, etc.).
In the present specification, "(meth) acrylic" means acrylic acid and/or methacrylic acid. The acrylic resin includes a resin containing acrylic acid or a derivative thereof as a constituent monomer component and a resin containing methacrylic acid or a derivative thereof as a constituent monomer component.
As the acrylic resin, acrylic resins having a glutaric acid anhydride structure described in japanese patent application laid-open nos. 2006-283013, 2006-335902, and 2006-274118; and/or acrylic resins having a lactone ring structure described in Japanese patent laid-open Nos. 2000-230016, 2001-151814, 2002-120326, 2002-254544, 2005-146084, and the like. Acrylic resins having a glutaric anhydride structure and acrylic resins having a lactone ring structure have high heat resistance, high transparency, and high mechanical strength, and therefore, are suitable for producing a polarizing plate having high polarization degree and excellent durability.
When the film base 11 is an acrylic film, the content of the acrylic resin in the film base is preferably 50% by weight or more, more preferably 60 to 98% by weight, and still more preferably 70 to 97% by weight. The acrylic film may contain a thermoplastic resin other than the acrylic resin. For example, by blending other thermoplastic resins, birefringence of the acrylic resin can be eliminated, and an acrylic film having excellent optical isotropy can be obtained. In addition, a thermoplastic resin other than an acrylic resin may be blended for the purpose of improving the mechanical strength of the film or the like.
Examples of the thermoplastic resin other than the acrylic resin include olefin polymers, halogenated vinyl polymers, polystyrene, copolymers of styrene and acrylic monomers, polyesters, polyamides, polyacetals, polycarbonates, polyphenylene ethers, polyphenylene sulfides, polyether ether ketones, polysulfones, polyether sulfones, polyoxybenzyls (polyoxybenzylenes), polyamide imides, rubber polymers, and the like.
The film base 11 may contain additives such as antioxidants, stabilizers, reinforcing materials, ultraviolet absorbers, flame retardants, antistatic agents, colorants, fillers, plasticizers, lubricants, fillers, and the like. The resin material may be mixed with additives or the like to prepare a thermoplastic resin composition such as pellets in advance and then the mixture may be made into a film.
The film base material 11 has a thickness of about 5 to 200 μm. The film base 11 preferably has a thickness of 10 to 100 μm, more preferably 15 to 60 μm, from the viewpoints of mechanical strength, transparency, handleability, and the like.
The glass transition temperature Tg of the film substrate 11 is preferably 100 ℃ or higher, and more preferably 110 ℃ or higher. When the film substrate 11 is an acrylic film, as described above, the Tg of the acrylic film can be increased and the heat resistance can be improved by using an acrylic resin having a glutaric anhydride structure or an acrylic resin having a lactone ring structure as the acrylic resin. The upper limit of Tg of the film base material 11 is not particularly limited, but is preferably 170 ℃ or lower from the viewpoint of moldability and the like.
Examples of the method for producing the film base material 11 include a solution casting method, a melt extrusion method, a rolling method, a compression molding method, and the like. The film substrate 11 may be an unstretched film or a stretched film. When the film substrate 11 is an acrylic film, the acrylic film is preferably a stretched film stretched in at least 1 direction, and particularly preferably a biaxially stretched film, from the viewpoint of improving mechanical strength. In order to eliminate the birefringence of the acrylic resin, an acrylic film having a small retardation even when stretched and excellent optical isotropy can be obtained by blending another thermoplastic resin.
< slippery layer >
The slip-facilitating layer 15 provided on the surface of the film base 11 contains a binder resin and fine particles. The fine particles contained in the easy-to-slide layer 15 form fine irregularities on the surface of the easy-to-slide layer 15, thereby improving the slidability of the film. This contributes to reducing scratches on the optical film 1 during roll transportation and suppressing blocking when wound into a roll.
(Binder resin)
As the binder resin, a resin (polymer) having a reactive group such as a polyurethane resin, an epoxy resin, an isocyanate resin, a polyester resin, a polymer containing an amino group in a molecule, or an acrylic resin having a crosslinkable functional group such as an oxazoline group can be used in view of excellent adhesion to a film base such as an acrylic film. As the binder resin of the slipping layer 15, a polyurethane resin is particularly preferable. The easy-slip layer 15 containing a urethane resin binder has high adhesion to the film base 11.
Urethane resins are typically the reaction product of a polyol and a polyisocyanate. As the polyol component, a polymer polyol such as a polyacrylic polyol, a polyester polyol, and a polyether polyol is preferably used.
Polyacrylic polyols are typically obtained by polymerization of (meth) acrylates with hydroxyl group-containing monomers. Examples of the (meth) acrylic acid ester include methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cyclohexyl (meth) acrylate. Examples of the hydroxyl group-containing monomer include hydroxyalkyl esters of (meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypentyl (meth) acrylate; (meth) acrylic acid monoesters of polyhydric alcohols such as glycerin and trimethylolpropane; n-methylol (meth) acrylamide and the like.
the acrylic polyol may contain other monomer components than those described above, and examples of the other monomer components include unsaturated monocarboxylic acids such as (meth) acrylic acid, unsaturated dicarboxylic acids such as maleic acid and anhydrides and diesters thereof, (unsaturated nitriles such as (meth) acrylonitrile), (unsaturated amides such as (meth) acrylamide and N-methylol (meth) acrylamide, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers such as methyl vinyl ether, α -olefins such as ethylene and propylene, halogenated α, β -unsaturated aliphatic monomers such as vinyl chloride and vinylidene chloride, and α, β -unsaturated aromatic monomers such as styrene and α -methylstyrene.
Polyester polyols are typically obtained by the reaction of a polybasic acid with a polyhydric alcohol. Examples of the polybasic acid include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, 1, 4-naphthalenedicarboxylic acid, 2, 5-naphthalenedicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetrahydrophthalic acid, and the like; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, tartaric acid, alkylsuccinic acid, linolenic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, and itaconic acid; alicyclic dicarboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, 1, 3-cyclohexanedicarboxylic acid, and 1, 4-cyclohexanedicarboxylic acid; or reactive derivatives thereof such as acid anhydrides, alkyl esters, and acid halides.
Examples of the polyhydric alcohol include ethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, neopentyl glycol, pentanediol, 1, 6-hexanediol, 1, 8-octanediol, 1, 10-decanediol, 1-methyl-1, 3-butanediol, 2-methyl-1, 3-butanediol, 1-methyl-1, 4-pentanediol, 2-methyl-1, 4-pentanediol, 1, 2-dimethyl-neopentyl glycol, 2, 3-dimethyl-neopentyl glycol, 1-methyl-1, 5-pentanediol, 2-methyl-1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 1, 4-butanediol, 1, 3-methyl-1, 5-pentanediol, 1, 4-butanediol, 1, 3-octanediol, 1, 3-methyl-1, 5-pentanediol, 1, 2-dimethylbutylene glycol, 1, 3-dimethylbutylene glycol, 2, 3-dimethylbutylene glycol, 1, 4-dimethylbutylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, 1, 4-cyclohexanedimethanol, 1, 4-cyclohexanediol, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, and the like.
Polyether polyols are typically obtained by ring-opening polymerization of alkylene oxides and addition to polyols. Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and trimethylolpropane. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, and tetrahydrofuran.
examples of the polyisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate, dodecamethylene diisocyanate, 1, 4-butane diisocyanate, hexamethylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate, 2,4, 4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1, 5-diisocyanate and 3-methylpentane-1, 5-diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4 ' -cyclohexylmethane diisocyanate, 1, 4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate and 1, 3-bis (isocyanatomethyl) cyclohexane, alicyclic diisocyanates such as toluene diisocyanate, 2 ' -diphenylmethane diisocyanate, 2,4 ' -diphenylmethane diisocyanate, 4,4 ' -diphenyldimethylmethane diisocyanate, 4,4 ' -dibenzyl diisocyanate, 1, 5-naphthylene diisocyanate, xylylene diisocyanate, 1, 3-phenylene diisocyanate and 1, 4-phenylene diisocyanate, aromatic diisocyanates such as dialkylene diisocyanate, alpha-diphenylmethane diisocyanate, alpha-aliphatic diphenylmethane diisocyanate and alpha-tetramethyldiphenylmethane diisocyanate.
The urethane resin constituting the slipping layer 15 preferably has a carboxyl group. The urethane resin has a carboxyl group, and thus a cross-linked structure can be introduced. The urethane resin having a carboxyl group can be obtained, for example, by reacting a chain extender having a free carboxyl group on the basis of a polyol and a polyisocyanate resin. Examples of the chain extender having a free carboxyl group include dihydroxycarboxylic acid, dihydroxysuccinic acid and the like. Examples of the dihydroxy carboxylic acid include dialkyl alkanoic acids such as dimethylol alkanoic acids (e.g., dimethylol acetic acid, dimethylol butyric acid, dimethylol propionic acid, dimethylol butyric acid, and dimethylol valeric acid).
The method for producing the urethane resin is not particularly limited, and may be any of a one-step method in which monomer components are reacted at once and a multi-step method in which the monomer components are reacted at once. When a chain extender having a free carboxyl group is used to introduce a carboxyl group into a urethane resin, a multistage method is preferable. When producing a urethane resin, a urethane reaction catalyst may be used as needed.
The number average molecular weight of the urethane resin is preferably 5000 to 600000, and more preferably 10000 to 400000. The acid value of the urethane resin is preferably 10 to 50, and more preferably 20 to 45.
The urethane resin may have a cross-linked structure. By introducing a crosslinked structure into the urethane resin, the adhesion between the easy-slip layer 15 and the film base 11 and the hardness of the easy-slip layer 15 tend to be improved. As the crosslinking agent, a crosslinking agent capable of reacting with a crosslinkable functional group of the urethane resin can be used without particular limitation. When the urethane resin has a carboxyl group, a crosslinking agent containing an amino group, an oxazoline group, an epoxy group, a carbodiimide group, or the like can be used. Among these, a crosslinking agent having an oxazoline group is preferable. Since the oxazoline group has low reactivity with a carboxyl group at normal temperature, the pot life when it is mixed with a urethane resin is long, and the lead time (lead time) of the process can be flexibly coped with.
The crosslinking agent may be a low-molecular compound or a polymer. From the viewpoint of high solubility in an aqueous composition and excellent compatibility with a urethane resin, an acrylic polymer is preferable as the crosslinking agent, and an acrylic polymer having an oxazoline group is particularly preferable.
The amount of the crosslinking agent used is preferably 1 to 30 parts by weight, more preferably 3 to 20 parts by weight, based on 100 parts by weight of the urethane resin.
(Fine particles)
By forming fine irregularities on the surface of the slip-facilitating layer by including fine particles in the slip-facilitating layer 15, the slip property of the optical film 1 is improved, and blocking can be suppressed. From the viewpoint of forming irregularities contributing to improvement in sliding properties, the particle diameter (average primary particle diameter) of the fine particles is preferably 10nm or more, more preferably 15nm or more, and still more preferably 20nm or more. The average primary particle diameter of the fine particles is preferably smaller than the thickness of the slippery layer. By making the particle diameter of the fine particles smaller than the thickness of the easy-slippage layer, the falling off of the fine particles from the easy-slippage layer can be suppressed. The particle diameter of the fine particles is preferably 250nm or less, more preferably 200nm or less. Further, by making the average primary particle size of the fine particles smaller than the visible light wavelength, scattering of visible light at the interface between the binder resin and the fine particles can be suppressed. From the viewpoint of improving transparency, the particle diameter of the fine particles is preferably 100nm or less, more preferably 80nm or less, further preferably 60nm or less, and particularly preferably 50nm or less.
The fine particles of the slippery layer 15 may be inorganic fine particles or organic fine particles. From the viewpoint of excellent dispersibility and uniformity of particle size, inorganic fine particles are preferable as the fine particles. Examples of the inorganic fine particles include inorganic oxides such as titanium oxide, aluminum oxide, and zirconium oxide; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, and the like. Among these, inorganic oxides are preferable. Examples of the organic fine particles include silicone resins, fluorine resins, and acrylic resins. In order to suppress light scattering by the fine particles, the difference in refractive index between the binder resin (generally, refractive index of about 1.5) and the fine particles is preferably small. Silica particles are preferable as the fine particles of the easy-slip layer 15 because the difference in refractive index with the binder resin is small and the dispersibility is excellent.
When the slippery layer 15 is formed of an aqueous composition, fine particles having high water dispersibility are preferably used. An aqueous dispersion of fine particles may be blended in the composition. In order to improve the dispersibility of the fine particles, it is preferable to make the composition for forming an easy-slip layer weakly basic by adding a basic component such as amine or ammonia.
As the colloidal silica, can use Hibiscus chemical industry Co Ltd Quarton. P L series, Nippon AEROSI L series, L td. AERODISP series and AEROSI L series, Japanese catalyst type company SEAHOSTAR KE series and other commercial products.
The content of the fine particles in the slipping-easily layer 15 is preferably 3 wt% or more, and more preferably 5 wt% or more, from the viewpoint of improving the slipping property of the optical film 1 by forming irregularities on the surface of the slipping-easily layer 15. Particularly, when the thickness of the easy-slippage layer 15 is small (for example, 280nm or less), it is preferable to increase the content of fine particles to increase the amount (number density) of fine particles per unit area, thereby uniformly forming irregularities in the surface of the easy-slippage layer 15. The content of the fine particles in the slipping layer 15 is preferably 8 wt% or more, more preferably 10 wt% or more, and still more preferably 12 wt% or more. When the content of the fine particles in the slip-susceptible layer 15 is too large, light scattering at the interface between the binder resin and the fine particles increases, and the optical characteristics may be degraded. Further, as the content of the fine particles increases, the relative content of the binder resin decreases, and thus the adhesiveness of the easy-slip layer may decrease. Therefore, the content of the fine particles in the slipping layer 15 is preferably 50 wt% or less, more preferably 40 wt% or less, and still more preferably 30 wt% or less.
(residual alkali amount)
When a basic component such as amine or ammonia is used to improve the dispersibility of the fine particles, the basic component inevitably remains in the slippery layer. When the optical film 1 is used as a polarizer protective film, the residual alkali component in the easily slipping layer 15 may elute into moisture or the like, or the alkali component having passed through the film base 11 may deteriorate the polarizer, resulting in optical defects such as a decrease in the polarization degree of the polarizing plate, and stripe-like unevenness.
The amount of residual alkali in the easy-to-slide layer 15 is preferably 75ppm or less, more preferably 70ppm or less, still more preferably 60ppm or less, and particularly preferably 55ppm or less, from the viewpoint of improving the humidification durability of the polarizing plate. From the viewpoint of improving the humidification durability of the polarizing plate, the smaller the amount of residual alkali in the easy-to-slide layer 15, the more preferable.
On the other hand, when the amount of the residual alkali in the easy-to-slide layer 15 is too small, dispersibility of the fine particles is impaired, and appearance defects such as cloudiness due to aggregation of the fine particles may occur. Further, the fine particles aggregate and fall off from the easy-to-slide layer due to the decrease in dispersibility, and appropriate irregularities are not formed on the surface of the easy-to-slide layer, and the slidability of the optical film tends to decrease. Therefore, the amount of the residual alkali in the slippery layer 15 is preferably 5ppm or more, more preferably 10ppm or more, and still more preferably 20ppm or more.
the amount of the base in the slipping layer can be determined by liquid chromatography, ion chromatography, or the like depending on the type of the base, the amount of the base can be determined by an analytical method (e.g., L C/MS) in which chromatography and Mass Spectrometry (MS) are combined, and when a plurality of base components are contained in the slipping layer, the total amount of each component is defined as the amount of the base component (residual amount) in the slipping layer.
< formation of slip-prone layer >
The method for forming the slipping-easily layer 15 on the surface of the film base material 11 is not particularly limited. The slip-susceptible layer 15 is preferably formed by applying a slip-susceptible layer forming composition (coating solution) containing a binder resin and fine particles on the film base 11 and heating.
(composition for Forming easily slippery layer)
The composition for forming a slip-facilitating layer is preferably an aqueous composition containing water as a solvent (and a dispersion medium for fine particles). The concentration of the solid content (nonvolatile content) in the composition for forming a slip-susceptible layer is preferably 1 to 30% by weight, more preferably 2 to 20% by weight, and still more preferably 3 to 15% by weight.
The aqueous composition for forming an easily slippery layer contains water as a solvent (and a dispersion medium), a binder resin or a precursor thereof, and fine particles. The composition for forming an easily slippery layer preferably further contains an alkaline component. As described above, the alkali component has an action of promoting dispersion of fine particles. Therefore, although fine particles having a small particle diameter tend to aggregate easily, the composition for forming an easily slippery layer contains a basic component such as ammonia or amine, and thus the dispersibility of the fine particles can be improved, and an optical film having excellent appearance and sliding properties can be obtained.
On the other hand, when the base contained in the composition for forming an easy-to-slide layer remains in the easy-to-slide layer, the base causes the moist heat resistance of the polarizing plate to decrease. In particular, a strong alkali such as caustic alkali, even if a small amount of the alkali is used, causes deterioration of the polarizer. Therefore, as the basic component contained in the composition for forming an easy-slip layer, a weakly basic component such as ammonia or amine is preferable. The pH of the composition for forming an easy-slip layer (coating liquid) is preferably about 7.5 to 9 from the viewpoint of contributing to the improvement of the dispersibility of the fine particles and the prevention of the deterioration of the polarizing plate.
From the viewpoint of improving the dispersibility of the fine particles, the amount of the alkali component contained in the composition for forming an easily slippery layer is preferably 300ppm or more, and more preferably 500ppm or more, with respect to the solid content of the composition for forming an easily slippery layer. On the other hand, when the content of the basic component is too large, it may be difficult to reduce the amount of the residual alkali, and therefore the amount of the basic component contained in the composition for forming an easily-slippery layer is preferably 50000ppm or less, more preferably 10000ppm or less, and further preferably 5000ppm or less, relative to the solid content of the composition for forming an easily-slippery layer. As described above, specific examples of the basic components contained in the composition for forming an easily slippery layer include amine and ammonia, and the total content of these basic components is preferably within the above range.
The basic component contained in the composition for forming an easily slippery layer may be a substance having a catalytic action or the like in addition to improving the dispersibility of the fine particles. For example, when the binder resin is a urethane resin, the composition for forming an easily slidable layer may contain a tertiary amine such as triethylamine as a urethane-forming catalyst for a polyurethane precursor (e.g., a polyol or an isocyanate).
By applying the composition for forming a slip-facilitating layer on a film base and heating the composition, the alkali component can be volatilized and removed, and the residual alkali component in the slip-facilitating layer 15 can be reduced. The alkali component contained in the composition for forming a slip-facilitating layer preferably has a boiling point of 150 ℃ or lower from the viewpoint of promoting volatilization of the alkali component by heating. The boiling point of the basic component is more preferably 130 ℃ or lower, still more preferably 120 ℃ or lower, and particularly preferably 110 ℃ or lower. The boiling point of the basic component may be 100 ℃ or lower or 90 ℃ or lower. When a plurality of basic components are contained in the composition for forming an easily slippery layer, the boiling point of at least 1 basic component is preferably in the above range, and the boiling point of 2 or more basic components is preferably in the above range. The boiling point of the alkali component is preferably 50 wt% or more with respect to 100 parts by weight of the total amount of the alkali contained in the slipping layer. It is desirable that the boiling point of all the basic components contained in the composition for forming a slip-facilitating layer is within the above range.
The composition for forming an easily slippery layer may contain a crosslinking agent in addition to the binder resin (or its precursor), the fine particles, and the alkali component. The composition for forming an easy-slip layer may contain a catalyst such as a crosslinking accelerator, an antioxidant, an ultraviolet absorber, a leveling agent, an anti-blocking agent, an antistatic agent, a dispersion stabilizer, an antifoaming agent, a thickener, a dispersant, a surfactant, a lubricant, and the like.
(formation of an easy slip layer on a film substrate)
Before the composition for forming an easily slippery layer is applied to the film base 11, the film base may be subjected to a surface treatment. By performing the surface treatment, the wetting tension of the film base material can be adjusted and the adhesion to the slipping layer 15 can be improved. Examples of the surface treatment include corona treatment, plasma treatment, ozone blowing, ultraviolet irradiation, flame treatment, and chemical treatment. Among these, corona treatment or plasma treatment is preferable.
Examples of the method for applying the composition for forming an easily slidable layer include a bar coating method, a roll coating method, a gravure coating method, a bar coating method, a slot coating method, a curtain coating method, and a jet coating method. The solvent is removed by heating the composition for forming an easy-slip layer after coating, thereby forming the easy-slip layer 15. The precursor material of the binder resin may be cured by reaction with heat. For example, when the composition for forming a slip-susceptible layer contains a crosslinking agent, the crosslinking reaction can be accelerated by heating.
The heating temperature for forming the slippery layer is, for example, about 50 to 200 ℃. The heating temperature is preferably 100 ℃ or higher, more preferably 120 ℃ or higher, further preferably 130 ℃ or higher, and particularly preferably 135 ℃ or higher, from the viewpoint of promoting the curing reaction of the resin component in the composition for forming a slip-resistant layer and effectively volatilizing and removing the alkali component contained in the composition for forming a slip-resistant layer. The heating temperature is preferably higher than the boiling point of the alkali component contained in the composition for forming an easily slippery layer.
The heating temperature at the time of forming the slip-susceptible layer is preferably higher than the glass transition temperature (Tg) of the film base material. By heating at a high temperature, the curing reaction of the resin component in the composition for forming a slip-susceptible layer can be promoted, and the alkali component contained in the composition for forming a slip-susceptible layer can be effectively volatilized and removed. The heating temperature is preferably 10 ℃ or higher than the Tg of the film base.
It is considered that heating at a temperature higher than Tg of the film base improves the efficiency of volatilization and removal of the base in the composition for forming an easily slippery layer, and the composition for forming an easily slippery layer easily penetrates into the surface of the film base, thereby improving the adhesion between the film base 11 and the easily slippery layer 15. The heating temperature is preferably Tg +10 ℃ or higher, more preferably Tg +15 ℃ or higher, and still more preferably Tg +20 ℃ or higher of the film base material, from the viewpoint of improving the adhesion of the slip-resistant layer.
When the film base is heated at a temperature of Tg +10 ℃ or higher, the film base changes from a glass state to a rubber state, and the surface is easily deformed, so that an interface layer in which the resin component of the film base and the constituent component of the slipping layer are mixed is easily formed at the interface between the film base 11 and the slipping layer 15. By forming the interface layer, the adhesion between the film base 11 and the slipping-easily layer 15 tends to be improved.
In particular, as shown in the cross-sectional observation image of fig. 3, when a region in which the fine particles of the slipping layer 15 are embedded is present on the surface of the film base 11, an optical film having high adhesion between the film base 11 and the slipping layer 15 can be obtained. It is considered that when the fine particles are embedded in the film base in a rubber state in which the film base is heated to a temperature higher than Tg and then the film base is returned to a glass state, the fine particles embedded in the surface of the film base and the binder resin present around the fine particles are fixed to the surface of the film base, and therefore the adhesion between the film base 11 and the easy-slip layer 15 is improved.
The slip-facilitating layer may be formed in the process of producing the film base. Further, the slip-susceptible layer may be formed by heating at the time of forming the film base. For example, when the film substrate is a stretched film, the surface of the film before stretching or the film after longitudinal stretching is coated with the composition for forming an easily slippery layer, and the solvent can be dried and the resin can be cured by heating in transverse stretching or simultaneous biaxial stretching in a tenter.
In the case where the film base material is stretched after the composition for forming a slip-susceptible layer is applied, the stretching magnification is preferably 5 times or less, more preferably 4 times or less, further preferably 3 times or less, and particularly preferably 2.5 times or less, from the viewpoint of suppressing the occurrence of defects such as cracking in the slip-susceptible layer. The lower limit of the stretch ratio is not particularly limited, but the stretch ratio is preferably 1.3 times or more, and more preferably 1.5 times or more, from the viewpoint of enhancing the film strength. When the film base material is an acrylic film, it is preferable to stretch the film at the above-described stretch ratios in the Machine Direction (MD) and the width direction (TD), respectively, from the viewpoint of improving the film strength.
In the case of biaxially stretching the film base material, the biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. In addition, oblique stretching may also be performed. In the case of sequential biaxial stretching, the film may be stretched in 1 direction (MD) by roll stretching as described above, and then the composition for forming an easy-slip layer may be applied to the film, and the composition for forming an easy-slip layer may be heated during stretching in a tenter.
The stretching temperature is preferably higher than the Tg of the film base material, as described above as the heating temperature of the slip-facilitating layer, and is preferably Tg +10 ℃ or higher, more preferably Tg +15 ℃ or higher, and still more preferably Tg +20 ℃ or higher. Particularly, it is preferable that the composition for forming an easy-slip layer is applied and then stretched in at least 1 direction at the above temperature. When the film base is stretched in a rubber state at a temperature higher than Tg of the film base, a region where fine particles in the composition for forming an easily slippery layer are embedded in the surface of the film base is easily formed, and adhesion between the film base 11 and the easily slippery layer 15 tends to be improved. The reason why fine particles are easily embedded in the film base material by stretching at a high temperature includes: when the film base material is stretched in a rubber state, the composition for forming an easily slippery layer is likely to be wetted and diffused during deformation of the film base material, and the fine particles are likely to be embedded in the concave portions of the surface irregularities formed during deformation. Further, it is considered that when the film base material is cooled while releasing the stress after stretching, the particles embedded in the surface of the film base material are fixed when the film base material shrinks, and therefore, a region in which fine particles are embedded in the film base material is easily formed.
The thickness of the slipping layer 15 can be adjusted by adjusting the solid content concentration and the coating thickness of the composition for forming a slipping layer. When the film base is stretched after the composition for forming an easy-slip layer is applied, the thickness of the easy-slip layer 15 can be adjusted by the stretch ratio.
The thickness of the slip-facilitating layer 15 is not particularly limited, but is preferably 280nm or less, more preferably 250nm or less, and still more preferably 230nm or less, from the viewpoint of promoting removal of the alkali component by heating. When the optical film 1 is used as a polarizer protective film, the smaller the thickness of the slipping-off facilitating layer 15 is, the higher the humidification durability of the polarizing plate tends to be.
When the composition for forming a slip-prone layer is dried by heating, if the alkali component is excessively removed, the dispersibility of the fine particles in the binder resin is lowered, and aggregation of the fine particles and the accompanying detachment of the fine particles from the surface of the slip-prone layer are likely to occur. When aggregation and detachment of fine particles occur, the sliding property of the optical film is lowered, and scratches during transportation and blocking during winding are likely to occur. Therefore, the thickness of the easy-sliding layer 15 is preferably 40nm or more, more preferably 50nm or more, further preferably 80nm or more, and particularly preferably 100nm or more. The thickness of the slippery layer may be 110nm or more, 120nm or more, 130nm or more, 140nm or more, or 150nm or more.
[ polarizing plate ]
The polarizing plate may have a transparent protective film on only one surface of the polarizer, or may have transparent protective films on both surfaces of the polarizer 5 as shown in fig. 2A and 2B. By bonding the optical film as a polarizer protective film to one surface of a polarizer, a polarizing plate having a transparent protective film only on one surface of the polarizer can be formed. In the polarizing plate having the polarizer protective films on both surfaces of the polarizer, the optical film may be bonded to at least one surface of the polarizer. The polarizing plate may be one in which the optical film is bonded to both surfaces of a polarizer. The polarizer 5 and the optical film 1 are bonded via an adhesive layer 6.
< polarizing plate >
As the polarizer 5, a polyvinyl alcohol (PVA) -based polarizer in which a dichroic material such as iodine or a dichroic dye is adsorbed to a polyvinyl alcohol-based film such as polyvinyl alcohol or partially formalized polyvinyl alcohol and oriented in 1 direction can be used. For example, a PVA-based polarizer can be obtained by subjecting a polyvinyl alcohol-based film to iodine dyeing and stretching.
In the process of producing the polarizer 5, treatments such as washing with water, swelling, and crosslinking may be performed as necessary. The stretching may be performed before or after the iodine dyeing, or may be performed while dyeing. The stretching may be any of stretching in air (dry stretching) or stretching in water or an aqueous solution containing boric acid, potassium iodide, or the like (wet stretching), or a combination thereof may be used. The thickness of the polarizer 5 is not particularly limited, but is generally about 1 to 50 μm.
As the polarizer 5, a thin PVA-based polarizer having a thickness of 10 μm or less may be used. Examples of the thin polarizers include those described in jp-a-51-069644, jp-a-2000-338329, WO2010/100917, japanese patent No. 4691205, and japanese patent No. 4751481. These thin polarizers can be obtained by a manufacturing method including the steps of: a step of stretching the PVA-based resin layer and the stretching resin base material in a laminated state, and a step of iodine dyeing. In this production method, even if the PVA-based resin layer is thin, it can be stretched without causing troubles such as breakage due to stretching because it is supported by the resin base material for stretching.
< adhesive agent >
The material of the adhesive layer 6 for bonding the polarizer 5 and the optical film 1 is not particularly limited as long as it is optically transparent, and examples thereof include epoxy-based resins, silicone-based resins, acrylic-based resins, polyurethanes, polyamides, polyethers, polyvinyl alcohols, and the like. The thickness of the adhesive layer 6 is, for example, about 0.01 to 20 μm, and can be set appropriately according to the kind of adherend, the material of the adhesive, and the like. When a curable adhesive exhibiting adhesiveness by a crosslinking reaction after coating is used, the thickness of the adhesive layer 6 is preferably 0.01 to 5 μm, and more preferably 0.03 to 3 μm.
As the adhesive, various types of adhesives such as aqueous adhesives, solvent adhesives, hot-melt adhesives, and active energy ray-curable adhesives can be used. Among these, an aqueous adhesive or an active energy ray-curable adhesive is preferable because the thickness of the adhesive layer can be reduced.
Examples of the polymer component of the aqueous adhesive include vinyl polymers, gelatin, vinyl latexes, polyurethane, polyester, epoxy, and the like. Among these, vinyl polymers are preferable, and polyvinyl alcohol resins are particularly preferable, from the viewpoint of excellent adhesion to the polarizer. Among the polyvinyl alcohol resins, polyvinyl alcohol containing an acetoacetyl group is preferable.
From the viewpoint of adhesiveness, the polyvinyl alcohol resin preferably has an average polymerization degree of about 100 to 5000, more preferably 1000 to 4000. The average saponification degree of the polyvinyl alcohol resin is preferably 85 mol% or more, and more preferably 90 mol% or more.
The aqueous adhesive composition (solution) may contain a crosslinking agent in addition to a polymer such as a polyvinyl alcohol resin. As the crosslinking agent, a compound having at least two functional groups reactive with the polymer constituting the adhesive in 1 molecule can be used. Examples of the crosslinking agent for the polyvinyl alcohol resin include alkylenediamines; isocyanates; epoxy resin; aldehydes; and amino formaldehydes such as methylol urea and methylol melamine. Among these, amino formaldehyde is preferred. As the amino-formaldehyde resin, a compound having a methylol group is preferable, and methylolmelamine is particularly preferable. The amount of the crosslinking agent to be blended in the adhesive composition is preferably about 10 to 60 parts by weight, more preferably 20 to 50 parts by weight, per 100 parts by weight of the polyvinyl alcohol resin.
The active energy ray-curable adhesive is an adhesive that can undergo radical polymerization, cationic polymerization, or anionic polymerization by irradiation with an active energy ray such as an electron beam or ultraviolet ray. Among them, from the viewpoint of being capable of curing at low energy, a photo radical polymerizable adhesive, a photo cation polymerizable adhesive, or a hybrid adhesive using photo cation polymerization and photo radical polymerization in combination, which starts polymerization by irradiation of ultraviolet rays, is preferable.
Examples of the monomer of the radical polymerizable adhesive include a compound having a (meth) acryloyl group and a compound having a vinyl group. Among them, compounds having a (meth) acryloyl group are preferable. Examples of the compound having a (meth) acryloyl group include (meth) acrylic acid C 1-20Alkyl (meth) acrylates such as chain alkyl esters, alicyclic alkyl (meth) acrylates, and polycyclic alkyl (meth) acrylates; a hydroxyl group-containing (meth) acrylate; epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate, and the like. The radical polymerizable adhesive may contain a nitrogen-containing monomer such as hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, or (meth) acryloylmorpholine. The radical polymerizable adhesive may contain a polyfunctional monomer such as tripropylene glycol diacrylate, 1, 9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate or EO-modified diglycerol tetraacrylate as a crosslinking component.
Examples of the curable component of the cationically polymerizable adhesive include compounds having an epoxy group and an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least 2 epoxy groups in the molecule, and various curable epoxy compounds generally known can be used. Preferable examples of the epoxy compound include a compound having at least 2 epoxy groups and at least 1 aromatic ring in a molecule (aromatic epoxy compound), a compound having at least 2 epoxy groups in a molecule, at least 1 of which is formed between adjacent 2 carbon atoms constituting an alicyclic ring, and the like (alicyclic epoxy compound). The cationic polymerizable adhesive may contain a radical polymerizable compound such as a compound having a (meth) acryloyl group, thereby making it possible to obtain a hybrid adhesive.
The photocurable adhesive preferably contains a photopolymerization initiator. The photopolymerization initiator may be appropriately selected according to the kind of reaction. For example, in the radical polymerizable adhesive, it is preferable to blend a photoradical generator that generates radicals by light irradiation as a photopolymerization initiator. In the cationically polymerizable adhesive, a photo cation polymerization initiator (photo acid generator) that generates a cation species or a lewis acid by light irradiation is preferably blended as a photopolymerization initiator. The hybrid adhesive preferably contains a photo cation polymerization initiator and a photo radical generator.
The content of the polymerization initiator is usually about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the monomer. When a radical polymerizable adhesive is used as the electron beam curing adhesive, a photopolymerization initiator is not necessarily required. In the active energy ray-curable adhesive, a photosensitizer may be added as necessary in order to increase the curing speed and sensitivity. The amount of the photosensitizer used is usually about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, based on 100 parts by weight of the monomer.
The adhesive may contain appropriate additives as needed. Examples of the additives include silane coupling agents, coupling agents such as titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, deterioration inhibitors, dyes, processing aids, ion traps, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat stabilizers, and hydrolysis stabilizers.
[ production of polarizing plate ]
The polarizing plate is manufactured by attaching the optical film 1 to one surface (first main surface) of the polarizer 5 via the adhesive layer 6. The optical film 1 may have the easy-slip layer forming surface bonded to the polarizer 5 via an adhesive layer as shown in fig. 2A, or may have the non-easy-slip layer forming surface bonded to the polarizer 5 via an adhesive layer as shown in fig. 2B.
The easy-slip layer 15 may also function as an easy-adhesive layer. As shown in fig. 2A, when the polarizer 5 is bonded to the surface of the optical film 1 on which the easy-slip layer 15 is formed via the adhesive layer 6, the easy-slip layer 15 can contribute to improvement in adhesion between the polarizer and the polarizer protective film (optical film 1). As shown in fig. 2B, when the non-slip-susceptible layer forming surface is bonded to the polarizer 5 via the adhesive layer, the slip-susceptible layer 15 can contribute to improvement in adhesiveness to other films, adhesive layers, glass substrates, and the like provided on the optical film 1.
In the bonding of the polarizer 5 and the optical film 1, it is preferable that: after the adhesive composition is applied to either or both of the polarizer 5 and the optical film 1, the polarizer 5 and the optical film 1 are bonded to each other by a roll laminator or the like, and the adhesive is cured. Examples of the method of applying the adhesive composition to the polarizer 5 and/or the optical film 1 include a roll method, a spray method, and a dipping method. Before the adhesive composition is applied to the surface of the polarizer 5 and/or the optical film 1, surface treatment such as corona treatment, plasma treatment, saponification treatment, or the like may be performed.
After the polarizing material 5 and the optical film 1 are bonded, the adhesive is cured depending on the type of the adhesive, thereby forming the adhesive layer 6. When an aqueous adhesive is used, the adhesive is cured by heat drying. In the case of using an active energy ray-curable adhesive, the adhesive is cured by irradiation with an active energy ray such as an electron beam or ultraviolet ray. When a photo cation polymerizable adhesive is provided on the slipping layer 15, the photo active species (cation or lewis acid) is easily deactivated by the action of the residual basic component of the slipping layer, and polymerization inhibition may occur. Therefore, when a photo cation polymerizable adhesive or a photo cation/photo radical mixed adhesive is used as the adhesive layer 6, it is preferable to bond the non-slip layer forming surface of the optical film 1 to the polarizer 5 as shown in fig. 2B.
< transparent protective film >
The transparent protective film 2 may be bonded to the second main surface of the polarizer 5 via an adhesive layer 7. As the transparent protective film 2, any suitable transparent film can be used. The thickness of the transparent protective film 2 is about 5 to 200 μm. The thickness of the transparent protective film 2 is preferably 10 to 100 μm, and more preferably 15 to 60 μm from the viewpoint of mechanical strength, transparency, handleability, and the like. The thicknesses of the optical film 1 and the transparent protective film 2 may be the same or different.
Examples of the material for forming the transparent protective film 2 include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); cellulose polymers such as cellulose diacetate and cellulose triacetate; styrene polymers such as polystyrene and acrylonitrile-styrene copolymer; cyclic polyolefins such as polynorbornene; polycarbonates, and the like.
The transparent protective film 2 may be provided with an easy-slip layer (not shown). The transparent protective film 2 may be provided with an easy-slip layer similar to the easy-slip layer 15 of the optical film 1.
As the adhesive layer 7 for bonding the polarizer 5 and the transparent protective film 2, various types of adhesives such as an aqueous adhesive, a solvent adhesive, a hot-melt adhesive, and an active energy ray-curable adhesive can be used. The same adhesive composition can be used for the adhesive layer 6 and the adhesive layer 7.
[ use of polarizing plate ]
the pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer can be selected from those based on acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine-based polymers, rubber-based polymers, and the like.
The polarizing plate may be provided with an adhesive layer in an appropriate manner. Examples thereof include: a method of preparing a pressure-sensitive adhesive solution having a solid content concentration of about 10 to 40 wt% in which a base polymer or the like is dissolved or dispersed in a solvent such as toluene or ethyl acetate, and attaching the pressure-sensitive adhesive solution to a polarizing plate, or a method of transferring a pressure-sensitive adhesive layer formed on an appropriate substrate to a polarizing plate.
Adhesive layers may be provided on both sides of the polarizing plate. When the adhesive layers are provided on both sides of the polarizing plate, the composition and thickness of the adhesive layers on the front and back surfaces may be the same or different. The thickness of the adhesive layer is generally about 5 to 500 μm.
On the surface of the adhesive layer, a separator may be temporarily affixed for the purpose of preventing contamination of the adhesive layer and the like. As the separator, a separator obtained by coating the surface of the plastic film with a release agent such as a silicone release agent, a long-chain alkyl release agent, or a fluorine release agent is preferably used.
The polarizing plate may be a laminated polarizing plate in which other optical layers are laminated. Examples of the optical layer include a retardation plate, a viewing angle compensating film, and a brightness enhancing film.
the organic E L display device is formed by attaching a circular polarizing plate in which the polarizing plate of the present invention and a retardation film (typically, a 1/4 wavelength plate) are combined to the surface of the organic E L cell, whereby re-emission of reflected light of external light due to a metal electrode or the like can be reduced and visibility can be improved.
Examples
The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. The "%" described below refers to% by weight unless otherwise specified.
[ preparation of composition for Forming easily slippery layer ]
an aqueous polyurethane (Super Flex 210R, first industrial pharmaceutical company, Ltd.) having a solid content of 34% and containing polyester urethane and isophorone diisocyanate as resin components, triethylamine as a curing catalyst, and methyl ethyl ketone as a dispersion medium was mixed in an amount of 20.6 parts by weight, an aqueous polymer solution (epicrosws-700, first industrial pharmaceutical company, Ltd.) having a solid content of 25% and containing oxazoline in an amount of 5.2 parts by weight, 1 part by weight of aqueous ammonia in an amount of 2.8 parts by weight, a 20% aqueous dispersion of colloidal silica having an average primary particle diameter of 35nm (quartron. p L-3, manufactured by hibiscus chemical company, Ltd.) in an amount of 7.5 parts by weight, and 63.9 parts by weight of pure water to prepare a composition for forming an easy-sliding layer, the composition being an aqueous solution having a concentration of 9.8% and containing 15.3 parts by weight of silica particles based on 100 parts by weight of the solid content.
[ example 1]
An optical film is produced using a film production apparatus provided with a melt extrusion film-forming apparatus, a gravure coater, a tenter type simultaneous biaxial stretching apparatus, and a winding apparatus. As the acrylic resin, pellets of an imidized MS resin (glass transition temperature: 120 ℃) similar to that used for producing the "transparent protective film 1A" described in example Japanese patent laid-open No. 2017-26939 were used. An acrylic resin was melt-extruded from a T-die to form a film having a thickness of 160 μm, the composition was applied to one surface of the film in a wet thickness of about 9 μm by a gravure coater, and the resultant film was stretched in a heating furnace at a temperature of 140 ℃ by a simultaneous biaxial stretching tenter in the longitudinal direction (MD) and the width direction (TD) by 2 times to obtain an optical film having an easy-slip layer having a thickness of 50nm on one surface of an acrylic film having a thickness of 40 μm.
Examples 2 to 4 and comparative examples 1 and 2
An optical film was obtained in the same manner as in example 1, except that the coating thickness of the composition for forming an easily slippery layer was changed. The thickness of the slip-resistant layer (after stretching) is shown in table 2.
Examples 5 and 6 and comparative examples 3 to 5
The furnace temperature (stretching temperature) during tenter stretching was changed as shown in table 2. An optical film was obtained in the same manner as in example 1, except that the stretching temperature was changed.
[ production of polarizing plate ]
(preparation of polarizing Member)
while a long roll of a polyvinyl alcohol (PVA) resin film (PE 4500, L td.) having a thickness of 45 μm was uniaxially stretched in the longitudinal direction so that the longitudinal direction was 5.9 times, a polarizer having a thickness of 18 μm was produced by transporting the long roll in the order of the swelling bath, the dyeing bath, the crosslinking bath 1, the crosslinking bath 2, and the washing bath shown in table 1 and drying the long roll at 70 ℃ for 5 minutes, and the iodine concentration and the potassium iodide concentration in the dyeing bath were adjusted so that the single-sheet transmittance of the polarizer became 43.4%.
[ Table 1]
Composition of aqueous solution Temperature (. degree.C.) Draw ratio
Swelling bath Pure water 20 2.2
Dyeing bath Iodine and potassium iodide are 1: 7 (weight ratio) 30 1.4
Cross-linking bath 1 5.0% boric acid, 3.0% potassium iodide 40 1.2
Cross-linking bath 2 4.3% boric acid, 5.0% potassium iodide 65 1.6
Cleaning bath 2.6% Potassium iodide 20 -
(preparation of ultraviolet ray-curable adhesive)
An ultraviolet-curable adhesive was prepared, which contained 40 parts by weight of N-hydroxyethyl acrylamide and 60 parts by weight of acryloylmorpholine as curable components, and also contained 3 parts by weight of 2-methyl-1- (4-methylthiophenyl) -2-morpholinyl-1-propanone ("IRGACURE 819", BASFCORPORATION) as a polymerization initiator.
(attachment of polarizer to polarizer protective film)
The optical films of examples and comparative examples were used as the polarizer protective Film on one surface, and a biaxially stretched cyclic polyolefin Film ("ZEONOR Film ZF-14" manufactured by Zeon Corporation) was used as the polarizer protective Film on the other surface. The above ultraviolet-curable adhesive was applied to the surface of the optical Film on which the easy-slip layer was formed and the surface of the ZEONOR Film in a thickness of about 1 μm, and the resultant was laminated to a polarizer by a roll laminator, and then irradiated with a cumulative light amount of 1000/mJ/cm 2The adhesive was cured by ultraviolet rays to obtain a polarizing plate having an acrylic film (optical film) on one surface of the polarizer and a zeonorflm on the other surface.
[ evaluation ]
< amount of alkali remaining in slip-prone layer >
The amounts of triethylamine and ammonia remaining in the slippery layer were quantified. The residual amount of triethylamine was quantified by the following method: the powder obtained by scraping the slipping-off layer from the surface of the optical film was weighed, dissolved in methanol, and quantified by a gas chromatography-mass spectrometry (GC/MS) method of the solution. The residual amount of ammonia was quantified by the following method: the optical film was immersed in pure water at 25 ℃ and then heated and extracted in a drier at 120 ℃ for 60 minutes, and ammonia eluted in water was quantified by ion chromatography. The total of the amount of triethylamine and the amount of ammonia was used as the amount of residual base.
< adhesion of slip-susceptible layer >
An adhesive tape (No. 31B, manufactured by Nindon electric Co., Ltd.) was pressure-bonded to the surface of the optical film on which the easily slipping layer was formed at a linear pressure of 8kg/m and a pressure-bonding speed of 0.3 m/min, and after the tape was stored at 50 ℃ for 48 hours, the tape was held at its tip and subjected to a 180 ℃ peel test at a tensile speed of 30 m/min, and the adhesiveness of the easily slipping layer was judged by the following criteria.
Good: the easily slipping layer is not peeled from the acrylic film, and is peeled at the interface between the adhesive tape and the easily slipping layer
peeling at the interface between the acrylic film and the slip-susceptible layer
< visual evaluation >
The surface of the optical film was visually observed to evaluate the presence or absence of local haze (increase in haze) due to aggregation of silica particles and the presence or absence of scratches on the non-slip layer-forming surface.
Good: no aggregation of silica particles, good in-plane uniformity, no damage
while no turbidity was observed due to aggregation of the silica particles, no damage of 1 μm or less in depth was observed on the non-slip layer-forming surface
confirming turbidity caused by aggregation of silica particles and damage of non-slip layer forming surface
< Presence or absence of interface layer >
The cross section of the optical film was observed with a Transmission Electron Microscope (TEM), and it was confirmed whether or not there was a region (interface layer) in which the particles in the easy-to-slip layer were embedded in the acrylic film at the interface between the acrylic film and the easy-to-slip layer. Fig. 3 shows a TEM observed image of example 3 (with an interface layer), and fig. 4 shows a TEM observed image of comparative example 4 (without an interface layer).
< humidification durability of polarizing plate >
the polarizing plate was cut into a size of 320mm × 240mm, and the surface on the side of the annular polyolefin film was bonded to glass with an acrylic adhesive having a thickness of 20 μm, and the sample was placed in a constant temperature and humidity cell having a temperature of 60 ℃ and a relative humidity of 90% (condition 1) or a constant temperature and humidity cell having a temperature of 85 ℃ and a relative humidity of 85% (condition 2), and held for 500 hours to carry out a heating/humidifying durability test.
Measurement of polarization degree P before durability test 0And a polarization degree P after the durability test, and calculating a change amount Δ P of the polarization degree ═ P-P 0L. Further, another polarizing plate was disposed on the polarizing plate after the durability test with crossed prisms, and the presence or absence of streaky unevenness was visually observed, and evaluated by the following criteria.
excellent-No streaks were observed in any of the samples after the durability tests of conditions 1 and 2
Good: no streaking was observed in the sample after the endurance test of condition 1, and slight streaking was recognized in the sample after the endurance test of condition 2
in both of the samples after the durability tests in conditions 1 and 2, slight streaking was observed
in both of the samples after the endurance tests of the condition 1 and the condition 2, the streaky unevenness was clearly recognized
Table 2 shows the conditions for producing the optical films of examples and comparative examples (stretching temperature and thickness of the easy-to-slip layer after stretching), the evaluation results of the optical films (visual observation, adhesion, presence or absence of an interface layer), and the durability test results of the polarizing plate (presence or absence of stripe unevenness and amount of change Δ P in polarization degree).
[ Table 2]
Figure BDA0002524268620000261
The optical film of comparative example 2 having an easy-slip layer with a thickness of 350nm had good adhesion between the acrylic film and the easy-slip layer, and the appearance of the optical film was also good. However, the polarizing plate using this optical film as a polarizer protective film showed a large decrease in polarization degree after a humidification durability test, and significant streaky unevenness was observed. In comparative examples 3 to 5 in which the stretching temperature (heating temperature at the time of forming the slippery layer) was 120 ℃ or lower, the decrease in polarization degree after the humidification durability test was large, and significant streaky unevenness was observed, as in comparative example 2.
The optical films of examples 1 to 4, in which the slippery layer of 50 to 250nm was formed at a stretching temperature of 140 ℃, showed no clouding due to aggregation of fine particles, and exhibited good appearance. Although fine scratches were observed on the non-slip layer-forming surface of the optical film of example 1, the scratches were of a level that they were buried with a binder, an adhesive, or the like and did not cause optical defects when the film was bonded to another member. In addition, the polarizing plates using the optical films of examples 1 to 4 were superior in humidification durability and suppressed in the occurrence of stripe unevenness, compared to the polarizing plate using the optical film of comparative example 2.
The polarizing plate of the optical film of comparative example 1, in which the slipping layer having a thickness of 30nm was formed, had good humidification durability, but white turbidity due to aggregation of silica fine particles and damage to the surface on which the non-slipping layer was formed were observed, and the appearance was poor. The occurrence of damage is considered to be caused by a decrease in dispersibility, which causes silica fine particles to fall off from the surface of the slip-susceptible layer, thereby decreasing the slip property of the optical film.
As is clear from comparison of examples 1 to 4 with comparative examples 1 and 2, the smaller the thickness of the easy-slip layer is, the less the residual alkali component is, and the more the polarizing plate having excellent humidification durability with suppressed occurrence of stripe unevenness after the humidification durability test can be obtained. On the other hand, it is found that when the thickness of the easy-sliding layer is too small and the residual alkali component is too small, the dispersibility of the fine particles is lowered, which causes poor appearance and a reduction in sliding property.
In examples 5 and 6 in which the easy-slip layer having a thickness of 200nm was formed at a stretching temperature of 160 ℃ or 180 ℃, the optical film was excellent in appearance and the polarizing plate had excellent humidification durability, as in example 3. On the other hand, in comparative examples 3 to 5 in which an easy-slipping layer having a thickness of 200nm was formed at a stretching temperature of 80 to 120 ℃, the amount of residual alkali in the easy-slipping layer was large, and significant streaking was observed after the humidification durability test of the polarizing plate, as in comparative example 2.
From these results, it is understood that an optical film excellent in the humidification durability of a polarizing plate when used as a polarizer protective film can be obtained by reducing the amount of residual alkali in the slipping-prone layer within a range in which the dispersibility of fine particles is not reduced.
In comparative examples 3 to 5 in which stretching was performed at a low temperature, the adhesion between the acrylic film and the slip-susceptible layer was inferior to those of the other examples. In example 3 and the like, an interface layer (see fig. 3) in which particles were embedded in the acrylic film was formed at the interface between the acrylic film and the slip-facilitating layer, whereas in comparative examples 3 to 5, no interface layer was formed (see fig. 4). From these results, it is understood that the increase in the heating temperature after the application of the composition for forming an easily slippery layer can effectively volatilize the alkali component in the composition for forming an easily slippery layer to reduce the amount of residual alkali, and in addition, can improve the adhesion at the interface between the film base and the easily slippery layer.
Description of the reference numerals
1 optical film
11 film base material
15 layer easy to slip
2 transparent film
5 polarizing element
6. 7 adhesive layer
100. 101 polarizing plate

Claims (19)

1. An optical film comprising a transparent film substrate and an easily slidable layer provided on the surface of the substrate,
Wherein the slippery layer contains a binder resin and fine particles,
The content of alkaline components in the slippery layer is 5-75 ppm.
2. An optical film as recited in claim 1, wherein the thickness of the slip-susceptible layer is 40 to 280 nm.
3. An optical film according to claim 1 or 2, wherein a region in which the fine particles are embedded in the transparent film base is present in an interface between the transparent film base and the slip-susceptible layer.
4. An optical film according to any one of claims 1 to 3, wherein the fine particles are inorganic fine particles.
5. An optical film according to any one of claims 1 to 4, wherein the fine particles have an average primary particle diameter of 10 to 250 nm.
6. An optical film according to any one of claims 1 to 5, wherein the content of the fine particles in the slip-susceptible layer is 3 to 50% by weight.
7. An optical film according to any one of claims 1 to 6, wherein the transparent film substrate is an acrylic film.
8. An optical film according to any one of claims 1 to 7, wherein the binder resin of the slipping layer is a urethane resin.
9. A method for producing an optical film according to any one of claims 1 to 8,
Wherein a composition for forming an easily slippery layer containing a binder resin or a precursor thereof, fine particles, an alkali component and a solvent is applied to the surface of a transparent film substrate,
And heating the composition for forming a slip-easily layer at a high temperature higher by 10 ℃ or more than the glass transition temperature of the transparent film substrate to volatilize the solvent and the alkali component.
10. The method of manufacturing an optical film according to claim 9, wherein the alkali component has an action of promoting dispersion of the fine particles.
11. The method for producing an optical film according to claim 9 or 10, wherein the composition for forming an easily-slipping layer contains a polyurethane precursor as a precursor of the binder resin, and contains a tertiary amine as the basic component.
12. The method for producing an optical film according to any one of claims 9 to 11, wherein the composition for forming an easily-slipping layer contains an amine having a boiling point of 150 ℃ or lower as the basic component.
13. The method for producing an optical film according to any one of claims 9 to 12, wherein the transparent film substrate coated with the composition for forming an easily-slippery layer is stretched in at least one direction while heating the composition for forming an easily-slippery layer at a temperature higher by 10 ℃ or more than the glass transition temperature of the transparent film substrate.
14. A polarizing plate comprising: a polyvinyl alcohol-based polarizer having a first main surface and a second main surface, and a transparent film bonded to the first main surface of the polarizer via an adhesive layer,
The transparent film is the optical film according to any one of claims 1 to 8.
15. The polarizing plate of claim 14, wherein the non-slip layer forming surface of the optical film is attached to the first main surface of the polarizer.
16. The polarizing plate according to claim 15, wherein the non-slip layer forming surface of the optical film is bonded to the first main surface of the polarizer with a photo cation polymerizable adhesive or a hybrid adhesive of photo cation polymerization and photo radical polymerization.
17. The polarizing plate of claim 14, wherein the easy-to-slide layer forming surface of the optical film is attached to the first main surface of the polarizer.
18. The polarizing plate according to claim 17, wherein the non-slip layer forming surface of the optical film is bonded to the first main surface of the polarizer with an adhesive having photo radical polymerization property.
19. An image display device comprising an image display unit and the polarizing plate according to any one of claims 14 to 18.
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