CN106873068B - Polarizing plate and image display device - Google Patents

Polarizing plate and image display device Download PDF

Info

Publication number
CN106873068B
CN106873068B CN201611027254.8A CN201611027254A CN106873068B CN 106873068 B CN106873068 B CN 106873068B CN 201611027254 A CN201611027254 A CN 201611027254A CN 106873068 B CN106873068 B CN 106873068B
Authority
CN
China
Prior art keywords
film
polarizing plate
polarizing
adhesive layer
stretched film
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201611027254.8A
Other languages
Chinese (zh)
Other versions
CN106873068A (en
Inventor
伊藤惠启
松本寿和
小松庆史
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sumitomo Chemical Co Ltd
Original Assignee
Sumitomo Chemical Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sumitomo Chemical Co Ltd filed Critical Sumitomo Chemical Co Ltd
Publication of CN106873068A publication Critical patent/CN106873068A/en
Application granted granted Critical
Publication of CN106873068B publication Critical patent/CN106873068B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • 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
    • 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
    • B32B27/30—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
    • 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
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • 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
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • 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
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B32B27/365—Layered products comprising a layer of synthetic resin comprising polyesters comprising polycarbonates
    • 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
    • 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
    • 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
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • 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
    • 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

Abstract

The invention provides a polarizing plate which can make the visibility of a polarized sunglass good and can restrain the reduction of the polarization degree caused by the deviation of the absorption axis of the polarizing film caused by the dimension change of an optical film in a heat-resisting test. A polarizing plate comprising a stretched film, a polarizing film and a 1 st pressure-sensitive adhesive layer in this order, wherein the angle formed by the absorption axis of the polarizing film and the slow axis of the stretched film is about 45 DEG or about 135 DEG, and the shrinkage force of the stretched film in the stretching direction when heated at 105 ℃ for 30 minutes is 0.2N/2mm or less.

Description

Polarizing plate and image display device
Technical Field
The invention relates to a polarizing plate and an image display device.
Background
In recent years, a lightweight and thin liquid crystal display which consumes low electric power and operates at low voltage has rapidly spread as an information display device such as a mobile phone, a portable information terminal, a monitor for a computer, and a television. With the development of liquid crystal technology, liquid crystal displays of various modes have been proposed, and problems of liquid crystal displays such as response speed, contrast, and narrow viewing angle have been solved. In addition, with the spread of liquid crystal displays for mobile devices, for example, when used outdoors or the like, the screen of the liquid crystal display may be recognized while wearing polarized sunglasses, and in such a case, the liquid crystal display is also required to have excellent visibility even when the screen is viewed through the polarized sunglasses.
As a method for improving visibility when viewing a screen through a polarized sunglass, the following method is employed: in order to convert linearly polarized light emitted from a polarizing plate disposed on the viewing side of an image display device such as a liquid crystal cell into elliptically (or circularly) polarized light, a retardation plate (e.g., a λ/4 wavelength plate) is disposed on the viewing side of the polarizing plate such that the angle formed by the absorption axis of the polarizing film and the slow axis of the retardation plate is 45 ° or 135 ° (patent documents 1 to 9).
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2009-122454
Patent document 2: japanese patent laid-open publication No. 2011-107198
Patent document 3: japanese patent laid-open publication No. 2011-215646
Patent document 4: japanese laid-open patent publication No. 2012-230390
Patent document 5: japanese laid-open patent publication No. H03-174512
Patent document 6: japanese patent laid-open publication No. 2013-231761
Patent document 7: japanese patent laid-open publication No. 2011-113018
Patent document 8: japanese patent laid-open publication No. 2013-182162
Patent document 9: japanese patent laid-open publication No. 2013-200445
Disclosure of Invention
Problems to be solved by the invention
Such a polarizing plate having a polarizing film and a retardation plate laminated thereon has a problem that when the polarizing plate is subjected to a heat resistance test, the absorption axis of the polarizing film is shifted due to a change in the size of the retardation plate, and the degree of polarization is greatly reduced.
Means for solving the problems
[1] A polarizing plate comprising a stretched film, a polarizing film and a 1 st adhesive layer in this order,
the angle formed by the absorption axis of the polarizing film and the slow axis of the stretched film is about 45 DEG or about 135 DEG,
the above stretched film has a shrinkage force in the stretching direction of 0.2N/2mm or less when heated at 105 ℃ for 30 minutes.
[2] The polarizing plate according to [1], wherein the polarizing film and the stretched film are laminated via an adhesive layer, a water-based adhesive layer, or an active energy ray-curable adhesive layer.
[3] The polarizing plate according to [1] or [2], wherein the stretched film contains at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth) acrylic resin.
[4] The polarizing plate according to any one of [1] to [3], wherein the stretched film has a surface-treated layer on a surface opposite to a surface on the polarizer side.
[5] The polarizing plate according to any one of [1] to [4], wherein the stretched film satisfies the following formulae (1) to (4).
(1)100nm≤Re(590)≤180nm、
(2)0.5＜Rth(590)/Re(590)≤0.8、
(3)0.85≤Re(450)/Re(550)＜1.00
(4)1.00＜Re(630)/Re(550)≤1.1
[ formula (1) to formula (4) wherein Re(590)、Re(450)、Re(550)、Re(630) Respectively represents the in-plane phase difference values at wavelengths of 590nm, 450nm, 550nm and 630nm, Rth(590) The thickness direction phase difference value at a wavelength of 590nm is shown.]
[6] The polarizing plate according to any one of [1] to [5], wherein the polarizing plate has a rectangular shape, and a ratio of a length of the long side to a length of the short side is 10: 1 to 1: 1.
[7] An image display device, wherein the polarizing plate according to any one of [1] to [6] is laminated on an image display element with the 1 st adhesive layer interposed therebetween.
Effects of the invention
According to the present invention, it is possible to provide a polarizing plate which can improve visibility through a polarizing sunglass and can suppress a decrease in the degree of polarization due to a shift in the absorption axis of a polarizing film caused by a dimensional change of an optical film during a heat resistance test.
Drawings
Fig. 1 is an example of a schematic cross-sectional view showing a layer structure of a polarizing plate of the present invention.
Detailed Description
The layer structure of the polarizing plate of the present invention will be explained with reference to fig. 1. As shown in fig. 1, a polarizing plate 10 of the present invention has a stretched film 11, a polarizing film 14, and a 1 st adhesive layer 13 in this order.
The stretched film 11 and the polarizing film 14 are preferably laminated, and the stretched film 11 and the polarizing film 14 may be laminated via an adhesive layer, an aqueous adhesive layer, or an active energy ray-curable adhesive layer as described later. In fig. 1, the pressure-sensitive adhesive layer, the water-based pressure-sensitive adhesive layer, and the active energy ray-curable pressure-sensitive adhesive layer are not shown.
The polarizing plate 10 of the present invention preferably has a protective film 12 between the polarizing film 14 and the 1 st adhesive layer 13. By providing the polarizing plate 10 with the protective film 12, the dimensional change of the polarizing film in the heat resistance test can be suppressed, and the reduction of the polarization degree can be further suppressed.
When the polarizing plate 10 of the present invention is mounted on an image display device, the stretched film 11 is often disposed on the viewing side surface of the polarizing plate, and therefore, the stretched film 11 preferably has a surface treatment layer 20 on the surface opposite to the surface bonded to the polarizing film 14.
The following describes in detail the members constituting the image display apparatus of the present invention.
[ polarizing film 14]
The polarizing film 14 is generally manufactured through the following processes: the method for producing the resin film comprises a step of uniaxially stretching a polyvinyl alcohol resin film, a step of dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye, a step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution to crosslink the film, and a step of crosslinking the film with an aqueous boric acid solution and then washing the film with water.
The polyvinyl alcohol resin can be produced by saponifying a polyvinyl acetate resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include: unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.
The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably about 1500 to 5000.
The film made of such a polyvinyl alcohol resin can be used as a raw film for a polarizing film. The method for forming the polyvinyl alcohol resin film is not particularly limited, and the film can be formed by a known method. The thickness of the raw film of the polyvinyl alcohol resin is, for example, about 10 to 100 μm, preferably about 10 to 50 μm.
The uniaxial stretching in the machine direction of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing with the dichroic dye. In the case where the uniaxial longitudinal stretching is performed after dyeing, the uniaxial longitudinal stretching may be performed before or during the boric acid treatment. Of course, the longitudinal uniaxial stretching may also be performed in multiple stages as shown here. For the longitudinal uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be used. The uniaxial stretching in the machine direction may be performed by dry stretching in which stretching is performed in the air, or may be performed by wet stretching in which stretching is performed in a state where the polyvinyl alcohol resin film is swollen with a solvent such as water. The draw ratio is usually about 3 to 8 times.
The dyeing of the polyvinyl alcohol resin film with the dichroic dye can be performed, for example, by a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. The polyvinyl alcohol resin film is preferably subjected to a treatment of immersing in water to swell the film before the dyeing treatment.
When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by immersing the film in an aqueous solution containing iodine and potassium iodide is generally used.
The aqueous solution generally contains about 0.01 to 1 part by weight of iodine per 100 parts by weight of water, and about 0.5 to 20 parts by weight of potassium iodide per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ℃. The immersion time (dyeing time) in the aqueous solution is usually about 20 to 1800 seconds.
On the other hand, the case of using a dichroic organic dye as a dichroic dyeIn general, a method of dyeing a polyvinyl alcohol resin film by immersing the film in an aqueous solution containing a water-soluble dichroic organic dye is used. The content of the dichroic organic dye in the aqueous solution is usually 1X 10 per 100 parts by weight of water-4About 10 parts by weight, preferably 1X 10-3About 1 part by weight. The aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the dichroic organic dye aqueous solution used for dyeing is usually about 20 to 80 ℃. The immersion time (dyeing time) in the aqueous solution is usually about 10 to 1800 seconds.
The boric acid treatment after dyeing with the dichroic dye can be performed by a method of immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. The boric acid content of the aqueous solution containing boric acid is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide. The content of potassium iodide in the aqueous solution containing boric acid is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. The immersion time in the aqueous solution containing boric acid is usually about 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ℃ or higher, preferably 50 to 85 ℃, and more preferably 60 to 80 ℃.
The polyvinyl alcohol resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be performed, for example, by a method of immersing the boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ℃. The dipping time is usually about 1 to 120 seconds.
After washing, the film was dried to obtain a polarizing film. The drying treatment may be performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ℃, preferably 50 to 80 ℃. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. The moisture content in the polarizing film is reduced to a practical level by the drying treatment. The water content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the flexibility of the polarizing film is lost, and damage or breakage may occur after drying. When the water content exceeds 20% by weight, the thermal stability tends to be insufficient.
In this way, the polarizing film 14 in which the dichroic dye is adsorbed and extracted to the polyvinyl alcohol resin film can be produced.
The polarizing film 14 preferably has a shrinkage force in the absorption axis direction of 3N/2mm or less, more preferably 1.5N/2mm or less, when heated at 80 ℃.
The shrinkage force in the transmission axis direction when the polarizing film is heated at 80 ℃ is preferably 3N/2mm or less, more preferably 1.5N/2mm or less. By using such a polarizing film, the shrinkage of the polarizing film in the heat resistance test can be reduced, and the reduction in the degree of polarization can be further reduced.
The shrinkage force of the polarizing film can be measured by the same method as that of a stretched film described later. Note that the "slow axis" is read as "absorption axis" or "transmission axis".
In order to suppress the shrinkage force of the polarizing film 14 to be low, the thickness of the polarizing film 14 is preferably set to 15 μm or less, and more preferably 12 μm or less, for example. The thickness of the polarizing film is usually 3 μm or more from the viewpoint of imparting good optical characteristics. In addition, it is also useful to adjust the conditions of the drying treatment.
The ratio of the thickness of the stretched film 11 to the thickness of the polarizing film 14 is preferably 1 or more, more preferably 2 or more, and still more preferably 3 or more.
The ratio of the thickness of the stretched film 11 to the thickness of the polarizing film 14 is preferably 7 or less. By combining such thickness ratios, the shrinkage of the polarizing film 14 can be suppressed by the stretched film, and the shrinkage of the stretched film can be easily made within the range specified in the present application.
The stretching, dyeing, boric acid treatment, water washing, and drying of the polyvinyl alcohol resin film in the process of producing the polarizing film 14 can be carried out, for example, according to the method described in japanese patent application laid-open No. 2012-159778. As in the method described in this document, a method of forming a polyvinyl alcohol resin layer as a polarizing plate by coating a polyvinyl alcohol resin on a base film is also useful.
[ stretched film 11]
In the polarizing plate used in the present invention, the stretched film 11 is particularly preferably made of a material having excellent transparency, mechanical strength, thermal stability, moisture barrier property, and the like. Examples thereof include: polyolefin resins such as chain polyolefin resins (polypropylene resins and the like) and cyclic polyolefin resins (norbornene resins and the like); cellulose resins such as cellulose ester resins including cellulose triacetate and cellulose diacetate; a polyester resin; a polycarbonate-based resin; (meth) acrylic resins; a polystyrene-based resin; or mixtures, copolymers, etc. thereof.
The stretched film 11 preferably satisfies the following formula.
(1)100nm≤Re(590)≤180nm、
(2)0.5＜Rth(590)/Re(590)≤0.8、
(3)0.85≤Re(450)/Re(550) < 1.00, and
(4)1.00＜Re(630)/Re(550)≤1.1
in the formula, Re(590)、Re(450)、Re(550)、Re(630) Respectively represents the in-plane phase difference values at measurement wavelengths of 590nm, 450nm, 550nm and 630nm, Rth(590) The thickness direction phase difference value at a measurement wavelength of 590nm is shown. These in-plane retardation values and thickness direction retardation values were measured at a temperature of 23 ℃ and a relative humidity of 55%.
The refractive index in the in-plane slow axis direction is nxAnd n represents a refractive index in an in-plane fast axis direction (a direction orthogonal to an in-plane slow axis direction)yN represents a refractive index in a thickness directionzD represents the in-plane retardation value R of the stretched film 11eA phase difference value R in the thickness directionthIs defined by the following formula.
Re＝(nx-ny)×d
Rth＝[{(nx+ny)/2}-nz]×d
In a liquid crystal display in which the stretched film 11 exhibiting the retardation characteristics and the wavelength dispersion characteristics of the above-described formulae (1) to (4) is disposed on the viewing side, it is possible to effectively suppress a change in color tone when the screen is observed from each direction (orientation angle and polar angle) through the polarizing sunglasses, and to improve the visibility of the liquid crystal display. On the other hand, when any one or more of the above expressions (1) to (4) is not satisfied, the suppression of the color tone change may be insufficient.
From the viewpoint of more effectively suppressing the change in hue, R in the formula (1)e(590) Preferably 105 to 170nm, R in the formula (2)th(590)/Re(590) Preferably 0.6 to 0.75, R in the formula (3)e(450)/Re(550) Preferably 0.86 to 0.98, R in the formula (4)e(630)/Re(550) Preferably 1.01 to 1.06.
The stretched film 11 is a phase difference film having a function of converting linearly polarized light emitted from the polarizing film 14 to the stretched film 11 into elliptically polarized light (including the case of circularly polarized light) and emitting the elliptically polarized light, and is laminated so that an angle formed by the absorption axis of the polarizing film and the slow axis of the stretched film is about 45 ° or about 135 ° in order to exhibit the function. When the angle is outside the above range, a function of converting linearly polarized light into elliptically polarized light and emitting the elliptically polarized light cannot be obtained, and as a result, the suppression of the color tone change may be insufficient. In the present invention, about 45 ° or about 135 ° means 25 to 65 ° or 115 to 155 °, preferably 35 to 55 ° or 125 to 145 °, and more preferably 40 to 50 ° or 130 to 140 °.
The stretched optical film preferably contains a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, or a (meth) acrylic resin, or two or more thereof, and more preferably the resin component is composed of one or two or more selected from the above, because the retardation properties and the wavelength dispersion properties of the above formulae (1) to (4) are easily imparted, the moisture permeability is relatively low, and the moisture resistance and the moist heat resistance of the optical laminate can be improved.
Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers of two or more kinds of chain olefins.
The cyclic polyolefin resin is a general term for resins obtained by polymerizing cyclic olefins as polymerization units. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene (typically random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrogenated products of these. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.
The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include: cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate. Further, copolymers thereof and modified products in which a part of the hydroxyl groups is modified with another substituent may also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.
The polyester resin is a resin having an ester bond, and generally contains a polycondensate of a polycarboxylic acid or a derivative thereof and a polyol. As the polycarboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include: terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalate, and the like. As the polyol, a divalent diol can be used, and examples thereof include: ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, cyclohexanedimethanol, and the like.
Specific examples of the polyester-based resin include: polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, polypropylene naphthalate, polycyclohexanedimethylene terephthalate, polycyclohexanedimethylene naphthalate.
The polycarbonate-based resin includes a polymer in which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called modified polycarbonate in which the main chain is modified, a copolymerized polycarbonate, or the like.
The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example: poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymers; methyl methacrylate-acrylate- (meth) acrylic acid copolymer; methyl (meth) acrylate-styrene copolymers (MS resins and the like); a copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group (for example, a methyl methacrylate-cyclohexyl methacrylate copolymer, a methyl methacrylate-norbornyl (meth) acrylate copolymer, etc.). Preferably used is a poly (meth) acrylic acid C such as poly (methyl (meth) acrylate)1-6The polymer containing an alkyl ester as a main component is preferably a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).
The stretched film 11 can be produced by stretching a film containing the thermoplastic resin. Examples of the stretching treatment include: uniaxial stretching, biaxial stretching, and the like. Examples of the stretching direction include: the machine flow direction (MD) of the unstretched film, The Direction (TD) orthogonal to the machine flow direction, the direction oblique to the machine flow direction (MD), and the like. The biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching is performed in the other direction. The stretching treatment may be performed, for example, by stretching in the longitudinal direction (machine flow direction: MD) using two or more pairs of nip rollers having an increased peripheral speed on the exit side, or by spreading in The Direction (TD) orthogonal to the machine flow direction by nipping both side ends of the unstretched film with a jig. In this case, the retardation value and the wavelength dispersion can be controlled within the ranges of the above-described equations (1) to (2) by adjusting the thickness of the film or adjusting the stretch ratio. Further, by adding a wavelength dispersion adjusting agent to the resin, the wavelength dispersion value can be controlled within the ranges of the above-mentioned formulas (3) to (4).
The thickness of the stretched film 11 is not particularly limited as long as the above-described formulas (1) to (4) are satisfied, but is preferably 90 μm or less, more preferably 60 μm or less, and even more preferably 45 μm or less, from the viewpoint of making the polarizing plate thinner, and is preferably 5 μm or more, and more preferably 10 μm or more from the viewpoint of handling.
The tensile modulus of elasticity of the stretched film at 80 ℃ is preferably 2000MPa or more, and more preferably 3500MPa or more. By using such a stretched film having a tensile elastic modulus, the decrease in the degree of polarization can be further reduced.
The stretched film 11 may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. When the stretched film 11 contains an ultraviolet absorber, the transmittance of the stretched film 11 at a wavelength of 380nm is preferably 10% or less.
In addition, in order to impart desired surface optical characteristics or other features, a coating layer (surface treatment layer 20) may be provided on the outer surface of the stretched film 11. Specific examples of the coating layer include a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer. The method for forming the coating layer is not particularly limited, and a known method can be used.
In the present invention, as the stretched film 11, a stretched film having a shrinkage force in the slow axis direction of 0.2N/2mm or less when the stretched film is heated at 105 ℃ is used. From the viewpoint of further reducing the decrease in the degree of polarization, the shrinkage force in the slow axis direction when the stretched film is heated at 105 ℃ is preferably 0.15N/2mm or less. In addition, from the viewpoint of ensuring visibility when the image display device is observed through a polarized sunglass, the shrinkage force in the slow axis direction when the stretched film is heated at 105 ℃ is preferably 0.002N/2mm or more. By using such a stretched film 11, it is possible to suppress the shift of the absorption axis of the polarizing film in the heat resistance test, reduce the decrease in the degree of polarization, and improve the visibility when the image display device is observed through the polarizing sunglasses.
The shrinkage force of the stretched film can be measured in the following manner. And cutting the stretched film into rectangles with the short sides of 2mm and the long sides of 50mm in a mode that the slow axis of the stretched film is consistent with the long sides. The shrinkage force of the cut stretched film can be measured using a commercially available thermomechanical analyzer. The details of the measurement method are described in the examples.
Such a stretched film 11 can be produced by, for example, biaxially stretching a film containing the thermoplastic resin. More specifically, the shrinkage force and the retardation characteristics can be controlled by appropriately adjusting the stretching conditions when biaxial stretching is performed or by annealing the stretched film.
From the viewpoint of easy control of the shrinkage force and the retardation characteristics, the stretched film 11 preferably contains at least one selected from the group consisting of cyclic polyolefin-based resins, polycarbonate-based resins, cellulose-based resins, polyester-based resins, and (meth) acrylic resins.
The stretching method may be simultaneous biaxial stretching or sequential biaxial stretching, but a film produced by simultaneous biaxial stretching is preferable because a film satisfying the above-mentioned shrinkage force can be easily obtained. The method of simultaneous biaxial stretching is not particularly limited, and both ends of the unstretched film may be sandwiched by clamps, and the feed rates of the clamps at both ends may be varied to further expand the unstretched film in The Direction (TD) orthogonal to the machine flow direction. In the simultaneous biaxial stretching, stretching in one direction and contraction by relaxing the tension in the other direction are also included.
In general, since a long polarizing film has an absorption axis in the longitudinal direction, the optical film is preferably a film produced by biaxial stretching and oblique stretching in view of being able to bond a long optical film to a long polarizing film in a roll-to-roll manner.
[ protective film 12]
The protective film 12 is preferably made of a material having excellent transparency, mechanical strength, thermal stability, moisture barrier property, and the like. The protective film 12 preferably contains a cellulose-based resin, a polyolefin-based resin, or an acrylic resin, because the retardation value can be easily controlled and obtained. The polyolefin-based resin referred to herein includes a chain polyolefin-based resin and a cyclic polyolefin-based resin.
As the cellulose-based resin, the cycloolefin-based resin, or the acrylic resin, the same ones as exemplified for the stretched film 11 can be used.
The method of forming a film from the resin as described above may be appropriately selected depending on the respective resins, and for example, the solvent casting method, the melt extrusion method, or the like described above may be employed. Among these, the polyolefin-based resin and the acrylic resin are preferably melt-extruded from the viewpoint of productivity. On the other hand, cellulose-based resins are generally formed into films by a solvent casting method.
In the case where the liquid crystal cell is In-Plane Switching (IPS) mode, the protective film preferably has a retardation value Rth In the thickness direction In the range of-10 to 10nm so as not to impair the wide viewing angle characteristics inherent In the IPS mode liquid crystal cell.
As a method for controlling the retardation value Rth in the thickness direction of the protective film within the range of-10 to 10nm, the following methods can be mentioned: when a film is produced, the deviation remaining in the plane and in the thickness direction is reduced as much as possible. For example, in the solvent casting method, a method of relaxing residual shrinkage strain in the in-plane and thickness directions generated when the casting resin solution is dried by heat treatment or the like can be used. On the other hand, in the above melt extrusion method, in order to prevent the resin film from being stretched during extrusion from the die and cooling, a method of controlling the extrusion amount and the rotation speed of the cooling drum so that the film is not stretched while shortening the distance from the die to the cooling drum as much as possible, or the like may be employed. In addition, as in the solvent casting method, a method of relaxing strain remaining in the obtained film by heat treatment may be employed.
The thickness of the protective film is preferably 90 μm or less, more preferably 60 μm or less, even more preferably 40 μm or less, and particularly preferably 25 μm or less, from the viewpoint of thinning the polarizing plate, and is preferably 5 μm or more, and more preferably 10 μm or more from the viewpoint of handling.
[ lamination of polarizing film 14 and protective film 12]
The polarizing film and the protective film may be attached by an adhesive or a bonding agent.
The thickness of the adhesive layer for bonding the polarizing film and the protective film may be about 0.01 to 30 μm, preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm. When the thickness of the adhesive layer is within the above range, the laminated protective film and the polarizing film are not floated or peeled off, and an adhesive force having no practical problem can be obtained. The thickness of the adhesive layer for bonding the polarizing film and the protective film may be about 5 to 50 μm, preferably 5 to 30 μm, and more preferably 10 to 25 μm.
In the case of bonding the polarizing film and the protective film, it is also useful to preliminarily perform saponification treatment, corona treatment, plasma treatment, or the like on the polarizing film and the protective film.
In the formation of the adhesive layer, a suitable adhesive can be suitably used depending on the kind and purpose of the adherend, and a primer can be used as needed. Examples of the adhesive include: solvent-based adhesives, emulsion-based adhesives, pressure-sensitive adhesives, remoistenable adhesives, condensation-type adhesives, solventless adhesives, film-like adhesives, hot-melt adhesives, and the like.
As one of the preferable adhesives, an aqueous adhesive, that is, an adhesive in which an adhesive component is dissolved or dispersed in water can be cited. There is a polyvinyl alcohol resin as an example of the binder component that can be dissolved in water. Further, there is a polyurethane resin having a hydrophilic group as an example of the adhesive component which can be dispersed in water. The aqueous adhesive can be prepared by mixing such an adhesive component with an additional additive added as needed in water. Examples of commercially available polyvinyl alcohol resins that can form a water-based adhesive include carboxyl-modified polyvinyl alcohol "KL-318" sold by KURARAAY K.K.
The aqueous adhesive may contain a crosslinking agent as needed. Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts, and the like. When a polyvinyl alcohol resin is used as the adhesive component, an aldehyde compound typified by glyoxal, a methylol compound typified by methylolmelamine, a water-soluble epoxy resin, or the like is preferably used as the crosslinking agent.
The water-soluble epoxy resin may be, for example, a polyamide epoxy resin obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a dicarboxylic acid such as adipic acid. Examples of commercially available products of water-soluble epoxy resins include "スミレ - ズレジン (registered trademark) 650 (30)", which is sold by Tianga chemical industries, Ltd.
A polarizing plate is obtained by applying a water-based adhesive to the adhesive surface of a polarizing film and/or a protective film laminated thereto, laminating them, and then drying the laminate. It is also effective to subject the protective film to an easy-adhesion treatment such as saponification treatment, corona discharge treatment, plasma treatment or undercoating treatment to improve the wettability in advance before the adhesion. The drying temperature may be set to about 50 to 100 ℃, for example. In order to further improve the adhesion, it is preferable that the curing is performed at a temperature slightly higher than room temperature (for example, at a temperature of about 30 to 50 ℃) for about 1 to 10 days after the drying treatment.
Another preferable adhesive is an active energy curable adhesive composition containing an epoxy compound that is cured by irradiation with active energy rays or heating. Here, the active energy curable epoxy compound is a compound having at least 2 epoxy groups in a molecule. In this case, the polarizing film and the protective film may be bonded by a method of curing a curable epoxy compound contained in the adhesive by irradiating the coating layer of the adhesive composition with active energy rays or applying heat. Curing of the epoxy compound is generally carried out by cationic polymerization of the epoxy compound. In addition, from the viewpoint of productivity, the curing is preferably performed by irradiation with an active energy ray.
The epoxy compound contained in the active energy curable adhesive composition is preferably an epoxy compound containing no aromatic ring in the molecule from the viewpoints of weather resistance, refractive index, cationic polymerizability, and the like. Examples of the epoxy compound containing no aromatic ring in the molecule include: hydrogenated epoxy compounds, alicyclic epoxy compounds, aliphatic epoxy compounds, and the like. The epoxy compound preferably used in such an active energy curable adhesive composition is described in detail in, for example, Japanese patent application laid-open No. 2004-24925, and the outline thereof will be described here.
The hydrogenated epoxy compound may be a compound as described below: a compound obtained by subjecting an aromatic polyhydroxy compound as a raw material of an aromatic epoxy compound to a nuclear hydrogenation reaction selectively in the presence of a catalyst under pressure, and subjecting the thus-obtained nuclear hydrogenated polyhydroxy compound to glycidyl etherification. Examples of the aromatic polyhydroxy compound to be a raw material of the aromatic epoxy compound include: bisphenols such as bisphenol a, bisphenol F and bisphenol S; novolak resins such as phenol novolak resins, cresol novolak resins and hydroxybenzaldehyde phenol novolak resins; and polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinyl phenol. Glycidyl etherification can be performed by subjecting such an aromatic polyol to a nuclear hydrogenation reaction and reacting epichlorohydrin with the nuclear hydrogenated polyol obtained above. As a preferred hydrogenated epoxy compound, a hydrogenated glycidyl ether of bisphenol A can be cited.
The alicyclic epoxy compound is a compound having at least one epoxy group bonded to an alicyclic ring in a molecule. The "epoxy group bonded to an alicyclic ring" refers to a bridged oxygen atom-O-in the structure represented by the following formula, wherein m is an integer of 2 to 5.
Figure GDA0002495912960000141
Will be (CH) in the formula2)mCompounds in which one or more of the hydrogen atoms are removed and bonded to other chemical structures may form alicyclic epoxy compounds. In addition, forming an alicyclic ring (CH)2)mOne or more hydrogen atoms in (b) may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (a structure in which m is 3 in the above formula) or an oxabicycloheptane ring (a structure in which m is 4 in the above formula) is preferably used in order to exhibit excellent adhesiveness. Specific examples of the alicyclic epoxy compound are shown below. Here, the compound names are listed first, and then the chemical formulae corresponding thereto are shown, respectively, and the compound names and the chemical formulae corresponding thereto are denoted by the same symbols.
A: 3, 4-epoxycyclohexanecarboxylic acid 3, 4-epoxycyclohexylmethyl ester,
B: 3, 4-epoxy-6-methylcyclohexanecarboxylic acid 3, 4-epoxy-6-methylcyclohexylmethyl ester,
C: ethylidene bis (3, 4-epoxycyclohexane formate),
D: bis (3, 4-epoxycyclohexylmethyl) adipate,
E: adipic acid di (3, 4-epoxy-6-methylcyclohexylmethyl) ester,
F: diethylene glycol di (3, 4-epoxycyclohexylmethyl ether),
G: ethylene glycol di (3, 4-epoxy cyclohexyl methyl ether),
H: 2, 3, 14, 15-diepoxy-7, 11, 18, 21-tetraoxatrispiro [5.2.2.5.2.2] heneicosane,
I: 3- (3, 4-epoxycyclohexyl) -8, 9-epoxy-15-dioxaspiro [5.5] undecane,
J: 4-vinylcyclohexene dioxide,
K: a limonene dioxide,
L: di (2, 3-epoxycyclopentyl) ether,
M: dicyclopentadiene dioxide, and the like.
Figure GDA0002495912960000151
The aliphatic epoxy compound may be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, there may be mentioned: a diglycidyl ether of propylene glycol; a diglycidyl ether of 1, 4-butanediol; a diglycidyl ether of 1, 6-hexanediol; triglycidyl ethers of glycerol; triglycidyl ether of trimethylolpropane; polyglycidyl ethers of polyether polyols (for example, diglycidyl ethers of polyethylene glycol) obtained by adding alkylene oxides (ethylene oxide and propylene oxide) to aliphatic polyols such as ethylene glycol, propylene glycol, and glycerin.
In the active ray-curable adhesive composition, only one epoxy compound may be used alone, or two or more epoxy compounds may be used in combination. Among them, the epoxy compound preferably contains an alicyclic epoxy compound having at least one epoxy group bonded to an alicyclic ring in the molecule.
The epoxy compound used in the active ray-curable adhesive composition has an epoxy equivalent generally in the range of 30 to 3000 g/equivalent, and the epoxy equivalent is preferably in the range of 50 to 1500 g/equivalent. When an epoxy compound having an epoxy equivalent of less than 30 g/equivalent is used, the flexibility of the cured polarizing plate may be reduced or the adhesive strength may be reduced. On the other hand, in the case of a compound having an epoxy equivalent of more than 3000 g/equivalent, compatibility with other components contained in the adhesive composition may be lowered.
From the viewpoint of reactivity, cationic polymerization is preferably used as the curing reaction of the epoxy compound. For this reason, it is preferable to add a cationic polymerization initiator to the active ray-curable adhesive composition containing an epoxy compound. The cationic polymerization initiator generates a cationic species or lewis acid by irradiation or heating of active energy rays such as visible light, ultraviolet rays, X-rays, and electron rays, thereby initiating a polymerization reaction of an epoxy group. From the viewpoint of handling properties, it is preferable to impart latency to the cationic polymerization initiator. Hereinafter, a cationic polymerization initiator that generates a cationic species or a lewis acid by irradiation with an active energy ray to initiate a polymerization reaction of an epoxy group is referred to as a "photo cationic polymerization initiator", and a cationic polymerization initiator that generates a cationic species or a lewis acid by heat to initiate a polymerization reaction of an epoxy group is referred to as a "thermal cationic polymerization initiator".
The method of curing the adhesive composition by irradiation with an active energy ray using a photo cation polymerization initiator is advantageous in that the curing can be performed at normal temperature and normal humidity, and the protective film and the polarizing film can be favorably adhered in consideration of the reduction in the necessity of heat resistance of the polarizing film or deformation due to expansion. Further, the photo cation polymerization initiator exhibits a catalytic action by light, and therefore, even when mixed in an epoxy compound, is excellent in storage stability and handling properties.
Examples of the photo cation polymerization initiator include: an aromatic diazonium salt; and onium salts such as aromatic iodonium salts and aromatic sulfonium salts, iron-arene complexes, and the like. The amount of the photo cation polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and more preferably 15 parts by weight or less based on 100 parts by weight of the epoxy compound.
When the compounding amount of the photo cation polymerization initiator is less than 0.5 parts by weight with respect to 100 parts by weight of the epoxy compound, there is a tendency that: the curing becomes insufficient, and the mechanical strength and adhesive strength of the cured product decrease.
On the other hand, when the amount of the photo cation polymerization initiator is more than 20 parts by weight based on 100 parts by weight of the epoxy compound, the increase of ionic substances in the cured product may increase the hygroscopicity of the cured product, thereby deteriorating the durability.
When a photo cation polymerization initiator is used, the active energy curable adhesive composition may further contain a photosensitizer as necessary. By using the photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and adhesive strength of a cured product can be improved. As the photosensitizer, for example: carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, photoreducible pigments, and the like. When the photosensitizer is blended, the amount thereof is preferably set to be in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the active energy curable adhesive composition. In addition, a sensitizing additive such as a naphthoquinone derivative can be used in order to increase the curing speed.
On the other hand, as the thermal cationic polymerization initiator, there can be mentioned: benzylsulfonium salts, thiophenium salts, thialanium (thiolanium) salts, benzylammonium, pyridinium salts, hydrazinium salts, carboxylic acid esters, sulfonic acid esters, and aminimides.
The active energy curable adhesive composition containing an epoxy compound is preferably cured by the photo cationic polymerization as described above, and may be cured by the thermal cationic polymerization in the presence of the thermal cationic polymerization initiator, or may be used in combination of the photo cationic polymerization and the thermal cationic polymerization. When both the photo cation polymerization and the thermal cation polymerization are used, it is preferable that both the photo cation polymerization initiator and the thermal cation polymerization initiator are contained in the active energy curable adhesive composition.
The active energy curable adhesive composition may further contain a compound that promotes cationic polymerization, such as an oxetane compound or a polyol compound. Oxetane compounds are compounds having a quaternary cyclic ether in the molecule. When the oxetane compound is blended, the amount thereof is usually 5 to 95% by weight, preferably 5 to 50% by weight, in the active energy curable adhesive composition. The polyol compound may be an alkylene glycol or its oligomer including ethylene glycol, 1, 6-hexanediol, polyethylene glycol, etc., a polyester polyol, a polycaprolactone polyol, a polycarbonate polyol, etc. When the polyol compound is blended, the amount thereof in the active energy curable adhesive composition is usually 50% by weight or less, preferably 30% by weight or less.
The active energy curable adhesive composition may contain other additives such as an ion trapping agent, an antioxidant, a chain transfer agent, a sensitizer, a thickener, a thermoplastic resin, a filler, a flow control agent, a plasticizer, and an antifoaming agent, as long as the adhesiveness is not impaired. Examples of the ion-capturing agent include powdery inorganic compounds such as bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixtures thereof, and examples of the antioxidant include hindered phenol-based antioxidants.
The active energy curable adhesive composition containing an epoxy compound is applied to the adhesive surface of a polarizing film or a protective film or both of them, and then the surfaces coated with the adhesive are bonded to each other, and the uncured adhesive layer is cured by irradiation with an active energy ray or heating, thereby bonding the polarizing film and the protective film. As a method for applying the adhesive, various application methods such as a doctor blade, a wire bar, a die coater, a comma coater (comma coater), a gravure coater, and the like can be used.
The active energy curable adhesive composition can be used basically as a solventless adhesive containing substantially no solvent, and has an optimum viscosity range for each application method, and therefore, a solvent may be contained for adjusting the viscosity. The solvent is preferably an organic solvent which can dissolve each component represented by an epoxy compound well without degrading the optical performance of the polarizing film, and for example, hydrocarbons represented by toluene, esters represented by ethyl acetate, and the like can be used.
When the adhesive composition is cured by irradiation with an active energy ray, various active energy rays as described above can be used as the active energy ray, but ultraviolet rays are preferably used because handling is easy and control of the amount of irradiation light and the like is easy. The irradiation intensity and the irradiation amount of the active energy ray, for example, ultraviolet ray are appropriately determined within a range not affecting various optical properties represented by the degree of polarization of the polarizing film and various optical properties represented by the transparency and the phase difference characteristics of the protective film so as to maintain appropriate productivity.
When the adhesive composition is cured by heat, heating may be performed by a generally known method. The thermal cationic polymerization initiator to be added to the active energy curable adhesive composition is generally heated at a temperature not lower than the temperature at which the thermal cationic polymerization initiator generates a cationic species or a Lewis acid, and the heating temperature is, for example, about 50 to 200 ℃.
The polarizing film 14 and the protective film may be laminated via an adhesive layer. The pressure-sensitive adhesive layer used for laminating the polarizing film 14 and the protective film may be a pressure-sensitive adhesive having excellent optical transparency and excellent adhesive properties including appropriate wettability, cohesiveness, adhesiveness, and the like, and more preferably a pressure-sensitive adhesive having excellent durability and the like. Specifically, as the adhesive for forming the adhesive layer, an adhesive containing an acrylic resin (acrylic adhesive) is preferable.
The acrylic resin contained in the acrylic adhesive is a resin containing, as a main monomer, an alkyl acrylate such as butyl acrylate, ethyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate. The acrylic resin is usually copolymerized with a polar monomer. The polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group, wherein the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group, and the polar functional group may be a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like. Specific examples of the polar monomer include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.
In addition, a crosslinking agent is generally blended with the acrylic resin in the acrylic adhesive. Typical examples of the crosslinking agent include isocyanate compounds having at least 2 isocyanate groups (-NCO) in the molecule.
Various additives may be further blended in the binder. Preferable additives include silane coupling agents and antistatic agents. The silane coupling agent is effective in improving adhesion to glass. The antistatic agent is effective in reducing or preventing the generation of static electricity.
The pressure-sensitive adhesive layer can be formed by a method of preparing a pressure-sensitive adhesive composition in which the above-mentioned pressure-sensitive adhesive component is dissolved in an organic solvent, applying the composition as it is to either one of the bonding surfaces (polarizing film or protective film), and then drying and removing the solvent, or a method of applying the above-mentioned pressure-sensitive adhesive composition to a release-treated surface of a base film made of a release-treated resin film, then drying and removing the solvent to prepare a pressure-sensitive adhesive layer, bonding the pressure-sensitive adhesive layer to either one of the bonding surfaces (polarizing film or protective film), and then transferring the pressure-sensitive adhesive. In the case of forming an adhesive layer by the former direct coating method, a general example is to temporarily protect the surface of the adhesive layer until use by bonding a resin film (also referred to as a spacer layer) subjected to an anti-sticking treatment to the surface. The latter transfer method is often used from the viewpoint of workability of the adhesive composition as an organic solvent solution, and in this case, the base film subjected to the releasing treatment for forming the adhesive layer is first bonded to the polarizing plate and then the interlayer is formed directly, and the latter transfer method is also preferable.
It is also useful to perform corona treatment, plasma treatment, or the like in advance on the polarizing film surface to be bonded and the optical film surface or adhesive surface after stretching, before laminating the polarizing film and the protective film with an adhesive or an adhesive.
[1 st adhesive layer 13]
The 1 st pressure-sensitive adhesive layer 13 formed on the surface of the protective film 12 opposite to the surface to be bonded to the polarizing film 14 may be a pressure-sensitive adhesive layer having excellent optical transparency and excellent adhesive properties including appropriate wettability, cohesiveness, adhesiveness, and the like, and more preferably a pressure-sensitive adhesive layer having excellent durability and the like. Specifically, as the adhesive for forming the 1 st adhesive layer 13, an adhesive containing an acrylic resin (acrylic adhesive) is preferably used. Specifically, the same adhesive as that which can be used for laminating the polarizing film and the protective film may be used.
The 1 st adhesive layer 13 may contain various additives as in the adhesive layer for laminating the polarizing film and the protective film. Among them, the 1 st adhesive layer 13 preferably contains an antistatic agent. In general, when a polarizing plate is bonded to a liquid crystal cell with an adhesive layer interposed therebetween, a surface protective film (interlayer) that has been once protected by the adhesive layer is peeled off and then bonded to the liquid crystal cell. As a method for reducing or preventing such static electricity generation, it is effective to add an antistatic agent to the adhesive.
In the case of bonding the protective film 12 and the 1 st pressure-sensitive adhesive layer 13, it is also useful to subject the surfaces where the protective film 12 and the 1 st pressure-sensitive adhesive layer 13 are bonded to each other to corona treatment, plasma treatment, or the like.
[ method for producing polarizing plate ]
The method for producing the polarizing plate of the present invention is not particularly limited, and examples thereof include: a method of attaching the polarizing film 14 and the protective film 12 to each other through an adhesive in a roll-to-roll manner, and then attaching the stretched film 11 to the polarizing film 14 through an adhesive in a roll-to-roll manner; a method of simultaneously bonding the stretched film 11, the polarizing film 14, and the protective film 12 with an adhesive interposed therebetween. An adhesive-equipped polarizing plate can be obtained by further forming the 1 st adhesive layer 13 on the protective film 12. The polarizing plate with an adhesive may be bonded to the image display element with the 1 st adhesive layer 13 interposed therebetween.
The polarizing plate is then cut into individual pieces so that a polarizing plate of a desired shape and size can be manufactured. The shape of the polarizing plate is not particularly limited, and is preferably a rectangular shape having long sides and short sides. In the case where the polarizing plate of the present invention has a rectangular shape having long sides and short sides, the ratio of the length of the long sides to the length of the short sides is preferably 10: 1 to 1: 1, and more preferably 2: 1 to 1: 1. The size of the polarizing plate is preferably 50mm or more, more preferably 150mm or more in length of the long side, and preferably 40mm or more, more preferably 80mm or more in length of the short side. Specifically, the size of the polarizing plate of the present invention is, for example, preferably 2.7 type (55mm × 41mm) or more, more preferably 7.0 type (154mm × 87mm) or more, and still more preferably 11.3 type (174mm × 231mm) or more.
Image display element and image display device
The image display device of the present invention includes an image display element and the polarizing plate of the present invention. Examples of the image display element include a liquid crystal cell and an organic Electroluminescence (EL) display element. By laminating the polarizing plate of the present invention on the image display element, an image display device can be manufactured. In the case where the image display device is a liquid crystal display device, the polarizing plate of the present invention is preferably disposed on the viewing side.
Examples
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, parts and% indicating contents or amounts used are on a weight basis. The measurement of each physical property in the following examples was performed by the following method.
(1) Measurement of thickness:
the measurement was carried out using a digital micrometer "MH-15M" manufactured by Nikon K.K.
(2) Determination of in-plane retardation value and wavelength dispersion characteristic
Using a retardation meter "KOBRA-21 ADH" based on the parallel Nichol rotation method manufactured by Oji scientific instruments, in-plane retardation values Re (590), Re (450), Re (550) and Re (630) of the films A to E were measured at 23 ℃ and Re (450)/Re (550) and Re (630)/Re (550) were calculated.
(3) Measurement of degree of polarization and monomer transmittance of polarizing plate:
using a spectrophotometer with an integrating sphere ("V7100" manufactured by japan spectrographic corporation, 2 degree field of view; c illuminant ] was measured.
(4) Measurement of shrinkage force of stretched film
The stretched film was cut into a rectangular shape having a short side of 2mm and a long side of 50mm by a super cutter (manufactured by triarrhena indica co., ltd.) so that the slow axis and the long side of the stretched film were coincident with each other, to prepare a test piece. The shrinkage force of the test piece was measured using a thermomechanical analyzer (model TMA/6100, manufactured by SII Nano Technology Co., Ltd.). The measurement was performed in a constant dimension mode (the distance between the jigs was set to 10mm), and the temperature in the sample chamber was set to be increased from 20 ℃ to 105 ℃ for 10 minutes after the test piece was left in the sample chamber for a sufficient time, and the temperature in the sample chamber was set to be maintained at 105 ℃ after the temperature increase. After the temperature was raised, the test piece was left for further 30 minutes, and then the shrinkage force in the longitudinal direction of the test piece was measured in an environment of 105 ℃. In this measurement, the static load was set to 0mN, and a SUS probe was used as a jig.
Production example 1 polarizing plate with protective film
A polyvinyl alcohol film (average degree of polymerization: 2400, degree of saponification: 99.9 mol% or more) having a thickness of 20 μm was uniaxially stretched by about 5 times by dry stretching, immersed in pure water at 60 ℃ for 1 minute while being kept under tension, and then immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.05/5/100 at 28 ℃ for 60 seconds. Then, the plate was immersed in an aqueous solution of potassium iodide/boric acid/water at a weight ratio of 8.5/8.5/100 at 72 ℃ for 300 seconds. Subsequently, the film was washed with pure water at 26 ℃ for 20 seconds and then dried at 65 ℃ to obtain a polarizing film having a thickness of 7 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.
Then, an epoxy adhesive in which 3 parts of carboxyl-modified polyvinyl alcohol [ trade name "KL-318" obtained from KURARAY corporation, 3 parts of carboxyl-modified polyvinyl alcohol, was dissolved in 100 parts of water, and 1.5 parts of a polyamide epoxy additive [ trade name "スミレ - ズレジン (registered trademark) 650 (30)" obtained from tiangang chemical industries, inc., and an aqueous solution having a solid content concentration of 30%) as a water-soluble epoxy resin was added to the aqueous solution was applied to one side of the polarizing film, and a cyclic olefin resin film [ trade name "ZF-14-013" manufactured by Zeon corporation, japan ] having a thickness of 13 μm was laminated as a protective film, thereby obtaining a polarizing plate with a protective film comprising a protective film/polarizing film.
Production example 2 stretched film
The following stretched film was prepared by adjusting the stretching ratio. Further, an unstretched film was prepared as a reference example.
Stretching the film A: an unstretched triacetyl cellulose (TAC) film was stretched to produce a stretched TAC film having a thickness of 40 μm. The film had a shrinkage force in the slow axis direction of 0.18N/2 mm.
Stretching the film B: the unstretched TAC film was stretched to produce a stretched TAC film having a thickness of 40 μm. The film had a shrinkage force in the slow axis direction of 0.02N/2 mm.
Stretching the film C: the unstretched TAC film was stretched to produce a stretched TAC film having a thickness of 40 μm. The film had a shrinkage force in the slow axis direction of 0.30N/2 mm.
Stretching the film D: an unstretched cycloolefin resin (COP) film was stretched to produce a stretched COP film having a thickness of 25 μm. The film had a shrinkage force in the slow axis direction of 0.002N/2 mm.
Unstretched film E: an unstretched TAC film having a thickness of 40 μm was produced. The contraction force was 0.001N/2mm in either direction.
The optical properties and the like of the film are shown in table 1 below.
[ Table 1]
Figure GDA0002495912960000231
[ example 1]
An epoxy adhesive in which 3 parts of carboxyl-modified polyvinyl alcohol [ trade name "KL-318" obtained from KURARAY co., ltd.) was dissolved in 100 parts of water and 1.5 parts of a polyamide epoxy additive [ trade name "スミレ - ズレジン (registered trademark) 650 (30)" obtained from tiangang chemical industries co., ltd., aqueous solution having a solid content concentration of 30%) as a water-soluble epoxy resin was added to the aqueous solution was applied to a polarizing film of a polarizing plate with a protective film. The stretched film a was attached to the surface coated with the epoxy adhesive to obtain a polarizing plate.
The obtained polarizing plate was cut into a size of 40mm × 40mm, and was pressure-bonded to the alkali-free glass through an adhesive so that the protective film was a bonding surface to the alkali-free glass. The adhesive was cured by leaving the autoclave at 50 ℃ under a load of 5kg for 20 minutes, and then left for 10 hours at 23 ℃/60% RH.
Then, in order to determine the initial degree of polarization of the polarizing plate obtained, the ultraviolet-visible spectrum of the polarizing plate in the transmission axis direction and the absorption axis direction was measured. The degree of polarization (visual acuity correction degree of polarization) was calculated in accordance with JIS-Z8729.
The polarizing plate thus produced was subjected to a heat resistance test in an environment of 105 ℃ for 1 hour using a constant temperature and humidity apparatus manufactured by Espec. The polarization degree was measured by the same method as the measurement of the initial polarization degree within 30 minutes after the polarizing plate was taken out from the thermostat and humidistat. The difference between the initial polarization degree of the polarizing plate and the polarization degree after the heat resistance test (amount of change in polarization degree) was-0.028%.
In order to evaluate visibility through a polarizing sunglass, a polarizing plate was bonded to a liquid crystal cell through an adhesive layer to obtain a liquid crystal display device. The resulting liquid crystal display device was turned on, and the image was observed through a polarized sunglass. The observation was performed from all the orientations of 360 ° with respect to the screen of the liquid crystal display device, and the evaluation was performed according to the following criteria.
< visibility through polarized sunglasses >
O: the image can be recognized from any orientation.
X: there are angles at which the image cannot be recognized.
< coloring of transmitting polarized sunglasses >
Very good: can be recognized from any orientation without changing the color tone.
O: there are angles at which the change in hue occurs but at an allowable level.
Examples 2 to 3, comparative example 1 and reference example 1
Polarizing plates were produced in the same manner as in example 1, except that the stretched film a was changed to the stretched films B to D or the unstretched film E. The polarization plate thus produced was measured for initial polarization degree and polarization degree after heat resistance test, and then visibility and coloration through the polarizing sunglasses were evaluated. The results are shown in table 1.
[ Table 2]
Figure GDA0002495912960000241
Industrial applicability
According to the present invention, it is possible to provide a polarizing plate which is useful because it can improve visibility through a polarizing sunglass and can suppress a decrease in the degree of polarization due to a shift in the absorption axis of a polarizing film caused by a dimensional change of an optical film during a heat resistance test.
Description of the symbols
10 polarizing plate
11 stretch film
12 protective film
13 st adhesive layer
14 polarizing film
15 protective film
20 surface treatment layer

Claims (7)

1. A polarizing plate comprising a stretched film, a polarizing film and a 1 st adhesive layer in this order,
the polarizing film has an absorption axis at an angle of about 45 ° or about 135 ° to the slow axis of the stretched film,
the stretched film has a shrinkage force in the stretching direction of 0.2N/2mm or less when heated at 105 ℃ for 30 minutes.
2. The polarizing plate according to claim 1, wherein the polarizing film and the stretched film are laminated via an adhesive layer, a water-based adhesive layer, or an active energy ray-curable adhesive layer.
3. The polarizing plate according to claim 1 or 2, wherein the stretching film comprises at least one selected from the group consisting of cyclic polyolefin-based resins, polycarbonate-based resins, cellulose-based resins, polyester-based resins, and (meth) acrylic resins.
4. The polarizing plate according to any one of claims 1 to 3, wherein the stretched film has a surface treatment layer on a surface opposite to a surface on the polarizer side.
5. The polarizing plate according to any one of claims 1 to 4, wherein the stretched film satisfies the following formulae (1) to (4),
(1)100nm≤Re(590)≤180nm、
(2)0.5＜Rth(590)/Re(590)≤0.8、
(3)0.85≤Re(450)/Re(550)＜1.00
(4)1.00＜Re(630)/Re(550)≤1.1
in the formulae (1) to (4), Re(590)、Re(450)、Re(550)、Re(630) Respectively represents the in-plane phase difference values at wavelengths of 590nm, 450nm, 550nm and 630nm, Rth(590) The thickness direction phase difference value at a wavelength of 590nm is shown.
6. The polarizing plate according to any one of claims 1 to 5, wherein the polarizing plate has a rectangular shape, and a ratio of a length of the long side to a length of the short side is 10: 1 to 1: 1.
7. An image display device, wherein the polarizing plate according to any one of claims 1 to 6 is laminated on an image display element with the 1 st adhesive layer interposed therebetween.
CN201611027254.8A 2015-11-20 2016-11-18 Polarizing plate and image display device Active CN106873068B (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2015227382A JP2017097087A (en) 2015-11-20 2015-11-20 Polarizing plate and image display device
JP2015-227382 2015-11-20

Publications (2)

Publication Number Publication Date
CN106873068A CN106873068A (en) 2017-06-20
CN106873068B true CN106873068B (en) 2021-06-11

Family

ID=58816667

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201611027254.8A Active CN106873068B (en) 2015-11-20 2016-11-18 Polarizing plate and image display device

Country Status (4)

Country Link
JP (1) JP2017097087A (en)
KR (1) KR20170059407A (en)
CN (1) CN106873068B (en)
TW (1) TWI701469B (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7376494B2 (en) * 2018-09-25 2023-11-08 日東電工株式会社 Polarizing plate, method for manufacturing the same, and image display device including the polarizing plate
CN114072265B (en) * 2019-07-02 2024-04-26 株式会社Lg化学 Injection molded product
JPWO2021117288A1 (en) * 2019-12-11 2021-06-17

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001281452A (en) * 2000-03-31 2001-10-10 Fuji Photo Film Co Ltd Optical film, polarizing plate and liquid crystal display device
JP2010020287A (en) * 2008-06-11 2010-01-28 Sumitomo Chemical Co Ltd Method of manufacturing retardation film
WO2015151466A1 (en) * 2014-03-31 2015-10-08 株式会社クラレ Biaxially stretched film and method for manufacturing same, polarizer protective film, decorative film, and layered film

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4681334B2 (en) * 2005-03-31 2011-05-11 帝人株式会社 Laminated retardation film
CN101414022B (en) * 2007-10-17 2010-10-13 财团法人工业技术研究院 Polarizing optical element, LCD device, polarized light source and method thereof
JP4791434B2 (en) * 2007-11-15 2011-10-12 日東電工株式会社 Liquid crystal display
JP2009282146A (en) * 2008-05-20 2009-12-03 Asahi Kasei E-Materials Corp Optical film excellent in mechanical strength
JP5408923B2 (en) * 2008-08-04 2014-02-05 富士フイルム株式会社 Method for producing thermoplastic film
JP5148431B2 (en) * 2008-09-19 2013-02-20 富士フイルム株式会社 Liquid crystal display
JP2011203641A (en) * 2010-03-26 2011-10-13 Sumitomo Chemical Co Ltd Polarizing plate
JP5985145B2 (en) * 2010-10-07 2016-09-06 住友化学株式会社 Optical laminate and method for producing the same
JP5584672B2 (en) * 2011-11-24 2014-09-03 株式会社ジャパンディスプレイ Liquid crystal display

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001281452A (en) * 2000-03-31 2001-10-10 Fuji Photo Film Co Ltd Optical film, polarizing plate and liquid crystal display device
JP2010020287A (en) * 2008-06-11 2010-01-28 Sumitomo Chemical Co Ltd Method of manufacturing retardation film
WO2015151466A1 (en) * 2014-03-31 2015-10-08 株式会社クラレ Biaxially stretched film and method for manufacturing same, polarizer protective film, decorative film, and layered film

Also Published As

Publication number Publication date
JP2017097087A (en) 2017-06-01
CN106873068A (en) 2017-06-20
TWI701469B (en) 2020-08-11
TW201727286A (en) 2017-08-01
KR20170059407A (en) 2017-05-30

Similar Documents

Publication Publication Date Title
TWI690738B (en) Composite polarizing plate and liquid crystal panel using the same
TWI631376B (en) Polarizing plate set and liquid crystal panel
TW201842363A (en) Polarizing plate and liquid crystal panel
CN106873068B (en) Polarizing plate and image display device
TWI706172B (en) Set of polarizing plates and liquid crystal panel
JP2017083820A (en) Polarizing plate and liquid crystal panel, and manufacturing method of polarizing plate
CN106990471B (en) Polarizing plate and liquid crystal panel
JP2021036328A (en) Polarizing plate set and liquid crystal panel
WO2017130656A1 (en) Production method for polarizing plates
KR20180105193A (en) Method for producing polarizer
KR101748531B1 (en) Polarizing plate set and liquid crystal panel
CN109298479B (en) Polarizing plate group and liquid crystal panel
CN106873069B (en) Polarizing plate and liquid crystal panel
TW201731697A (en) Method for manufacturing single sided protective polarizing plate
JP2020172088A (en) Optical laminate and image display device
TWI681874B (en) Composite polarizing plate and liquid crystal panel using the polarizing plate

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant