WO2020217535A1 - 偏光板および液晶表示装置 - Google Patents
偏光板および液晶表示装置 Download PDFInfo
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- WO2020217535A1 WO2020217535A1 PCT/JP2019/018156 JP2019018156W WO2020217535A1 WO 2020217535 A1 WO2020217535 A1 WO 2020217535A1 JP 2019018156 W JP2019018156 W JP 2019018156W WO 2020217535 A1 WO2020217535 A1 WO 2020217535A1
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- protective film
- polarizing plate
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- liquid crystal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- 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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- 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
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
-
- 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
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- 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
- C09J7/20—Adhesives in the form of films or foils characterised by their carriers
- C09J7/29—Laminated material
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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
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- 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
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- 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
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- 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
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2270/00—Resin or rubber layer containing a blend of at least two different polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/40—Properties of the layers or laminate having particular optical properties
- B32B2307/42—Polarizing, birefringent, filtering
Definitions
- the present invention relates to a polarizing plate and a liquid crystal display device.
- a polarizing plate used in a display device such as a liquid crystal display device includes a polarizing element and protective films arranged on both sides thereof.
- a film containing a (meth) acrylic resin such as polymethylmethacrylate as a main component is used because it has excellent transparency, dimensional stability, and low hygroscopicity.
- Such a polarizing plate includes a polarizer and two protective films arranged on both sides thereof, and the two protective films are both (meth) acrylic resins having a structural unit derived from phenylmaleimide.
- a polarizing plate which is a (meth) acrylic resin film containing silica particles is known (for example, Patent Document 1). Then, by applying the polarizing plate to an IPS type liquid crystal display device, it is said that display unevenness when left in a high temperature and high humidity environment for a long time can be suppressed.
- the protective film arranged on the liquid crystal cell side is a protective film containing a (meth) acrylic resin containing a structural unit derived from phenylmaleimide and rubber particles as described above. If there is, there is a problem that the contrast tends to decrease. In particular, there is a problem that the contrast tends to decrease in a liquid crystal display device after high temperature storage or high temperature and high humidity storage.
- the present invention has been made in view of the above circumstances, and is a polarizing plate using a protective film containing a (meth) acrylic resin and rubber particles, even after high-temperature storage or high-temperature and high-humidity storage.
- An object of the present invention is to provide a polarizing plate capable of suppressing a decrease in contrast of a liquid crystal display device and a liquid crystal display device using the same.
- the polarizing plate of the present invention a polarizer, wherein arranged on one surface of the polarizer, the moisture permeability is arranged and 100g / m 2 ⁇ 24hr or less of the protective film A, the other surface of the polarizer A polarizing plate including a protective film B and an adhesive layer arranged on a surface of the protective film B opposite to the polarizer, wherein the protective film B has a weight average molecular weight of 500,000 or more
- the (meth) acrylic resin contains a meta) acrylic resin and rubber particles, and the (meth) acrylic resin is a copolymer containing a structural unit derived from methyl methacrylate and a structural unit derived from phenylmaleimide, and is the rubber.
- the content of the particles is 5 to 25% by mass with respect to the protective film B, and the protective film B further contains an aggregation inhibitor represented by the following formula (1).
- the liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate arranged on one surface of the liquid crystal cell, and a second polarizing plate arranged on the other surface of the liquid crystal cell. At least one of the first polarizing plate and the second polarizing plate is the polarizing plate of the present invention, and the pressure-sensitive adhesive layer of the polarizing plate is adhered to the liquid crystal cell.
- a polarizing plate using a protective film containing a (meth) acrylic resin and rubber particles suppresses a decrease in contrast of a liquid crystal display device even after high-temperature storage or high-temperature and high-humidity storage. It is possible to provide a possible polarizing plate and a liquid crystal display device using the same.
- FIG. 1 is a cross-sectional view showing a polarizing plate according to an embodiment of the present invention.
- FIG. 2 is a cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention.
- the protective film B (F2 or F3 in FIG. 2 described later) arranged on the liquid crystal cell side is made into phenylmaleimide as described above.
- a protective film containing a (meth) acrylic resin containing a derived structural unit and rubber particles is used, the contrast is reduced by a mechanism (particularly in a liquid crystal display device after high-temperature storage or high-temperature and high-humidity storage). The mechanism) is not clear, but it is inferred as follows.
- a protective film containing a (meth) acrylic resin and rubber particles is manufactured by a solution casting method.
- a doping in which a (meth) acrylic resin and rubber particles are added to an organic solvent is cast on a support, and then the solvent is volatilized and removed to obtain a film-like substance. Get a protective film.
- the rubber particles tend to aggregate with each other and the apparent particle size tends to increase.
- the (meth) acrylic resin containing the structural unit derived from phenylmaleimide has a strong interaction between the structural units derived from phenylmaleimide, and thus tends to self-aggregate within or between molecules.
- the rubber particles are less likely to be dispersed in the (meth) acrylic resin, and the rubber particles are also likely to aggregate with each other.
- light scattering of the obtained protective film is likely to occur (internal haze is likely to increase), and contrast is likely to decrease (first phenomenon).
- the base polymer of the pressure-sensitive adhesive composition is likely to be locally precipitated. , It is considered that the contrast tends to decrease (second phenomenon).
- the protective film B may contain a residual monomer such as phenylmaleimide derived from a (meth) acrylic resin. Residual monomers such as phenylmaleimide are likely to diffuse not only in the protective film B but also in the adjacent pressure-sensitive adhesive layer.
- the pressure-sensitive adhesive layer was not a strong three-dimensional crosslink, but a base polymer having a relatively low degree of polymerization (hereinafter, also referred to as “oligomer”) was crosslinked with a relatively low degree of cross-linking in order to adjust to the desired viscoelasticity. , Forming a gel-like network. Therefore, it contains a relatively large amount of uncrosslinked oligomers.
- phenylmaleimide diffuses into such a pressure-sensitive adhesive layer, phenylmaleimide has a relatively high polarity. Therefore, it is considered that an oligomer having a low polarity easily aggregates and precipitates because it exerts a repulsive force on phenylmaleimide.
- Precipitation of the base polymer in the pressure-sensitive adhesive layer is caused by the protective film A (F1 or F4 in FIG. 2 described later) arranged on the side opposite to the liquid crystal cell among the two protective films constituting the polarizing plate in the liquid crystal display device.
- the protective film A F1 or F4 in FIG. 2 described later
- the protective film B F2, F3
- the inside of the polarizing plate becomes a steamed state, and polar components such as moisture and residual monomer phenylmaleimide are likely to remain in the adhesive layer. It is thought that it is easy to spread.
- the present inventors have applied a specific aggregation inhibitor to the protective film B (F2 or F3 in FIG. 2 described later) arranged on the liquid crystal cell side. It has been found that the above-mentioned phenomenon (aggregation of rubber particles in the protective film B and precipitation of oligomers in the pressure-sensitive adhesive layer) can be suppressed by containing the above-mentioned.
- the specific aggregation inhibitor is a compound represented by the following formula (1).
- equation (1) Whether both X 1 and X 2 are t-butyl or t-pentyl groups Alternatively, one of X 1 and X 2 is a t-butyl group or a t-pentyl group, and the other is a hydrogen atom or a methyl group.
- R 1 and R 3 are hydrogen atoms or substituted or unsubstituted alkyl groups, respectively.
- m is an integer from 1 to 4 and R 2 is a substituted or unsubstituted hydrocarbon group having 4 to 25 carbon atoms
- Both the (meth) acrylic resin and the rubber particles are hydrophobic, but the (meth) acrylic resin has a relatively high polarity and the rubber particles have a relatively low polarity, resulting in a polarity difference.
- the aggregation inhibitor has a phenol moiety as represented by the formula (1); the hydroxyl group of the phenol moiety is moderately weakened in polarity by a bulky group (t-butyl group, t-pentyl group, etc.). ing. Furthermore, aggregation inhibitor, as represented by the formula (1), having a specific alkyl group R 2 opposite the hydroxyl group.
- the aggregation inhibitor exhibits a function like a surfactant having the alkyl group as a hydrophobic group and the phenol moiety as an appropriate hydrophilic group, and the (meth) acrylic resin and the rubber particles are well mixed. It is thought that it can be done.
- the phenolic moiety of the aggregation inhibitor easily interacts with the phenylmaleimide moiety of the (meth) acrylic resin. Since the alkyl group of the aggregation inhibitor exhibits hydrophobicity, it tends to be compatible with rubber particles. Therefore, the aggregation inhibitor tends to be oriented so that the phenol structure is on the phenylmaleimide site side of the (meth) acrylic resin and the alkyl group is on the rubber particle side. In this way, by interposing the aggregation inhibitor between the rubber particles and between the (meth) acrylic resin and the rubber particles, it is possible to improve the mixing of the (meth) acrylic resin and the rubber particles.
- the aggregation inhibitor tends to be oriented so that the alkyl group is on the rubber particle side, the hydroxyl group at the phenol moiety repels the hydroxyl group at the phenol moiety of another aggregation inhibitor in the vicinity of the other rubber particles. Therefore, aggregation of rubber particles can be suppressed. It is considered that these can suppress the increase of the internal haze in the protective film B.
- the aggregation inhibitor that interacts with or adheres to the rubber particles supplements phenylmaleimide because its phenolic moiety easily interacts with phenylmaleimide, which is a residual monomer that diffuses in the protective film B, by ⁇ - ⁇ . be able to.
- the residual monomer phenylmaleimide can be suppressed from diffusing into the pressure-sensitive adhesive layer. It is considered that this can suppress the precipitation of the base polymer contained in the pressure-sensitive adhesive layer.
- FIG. 1 is a cross-sectional view showing a polarizing plate 100 according to the present embodiment.
- the polarizing plate 100 has a polarizing element 110 (polarizer), a protective film 120A (protective film A) arranged on one surface thereof, and a protective film 120A on the other surface. Between the arranged protective film 120B (protective film B), the adhesive layer 130A (adhesive layer A) arranged between the protective film 120A and the polarizer 110, and between the protective film 120B and the polarizer 110. It has an arranged adhesive layer 130B (adhesive layer B).
- the polarizing plate 100 further has an adhesive layer 140 arranged on the surface of the protective film 120B opposite to the polarizer 110.
- the pressure-sensitive adhesive layer 140 is a layer for attaching the polarizing plate 100 to a display element (not shown) such as a liquid crystal cell.
- the surface of the pressure-sensitive adhesive layer 140 is usually protected by a release film (not shown).
- Polarizer A polarizing element is an element that allows only light on a plane of polarization in a certain direction to pass through.
- the polarizer can usually be a polyvinyl alcohol-based polarizing film.
- Examples of the polyvinyl alcohol-based polarizing film include a polyvinyl alcohol-based film dyed with iodine and a film dyed with a dichroic dye.
- the polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing it with iodine or a bicolor dye (preferably a film further subjected to a durability treatment with a boron compound); polyvinyl.
- An alcohol-based film may be a film that has been dyed with iodine or a bicolor dye and then uniaxially stretched (preferably a film that has been further subjected to a durability treatment with a boron compound).
- the absorption axis of the polarizer 110 is usually parallel to the maximum stretching direction.
- Examples of the polyvinyl alcohol-based polarizing film include the ethylene unit content of 1 to 4 mol%, the degree of polymerization of 2000 to 4000, and the degree of saponification of 99, which are described in JP-A-2003-248123 and JP-A-2003-342322. 0-99.99 mol% ethylene-modified polyvinyl alcohol is used.
- the thickness of the polarizer is preferably 5 to 30 ⁇ m, and more preferably 5 to 20 ⁇ m from the viewpoint of thinning the polarizing plate.
- the protective film A may be a transparent resin film and is not particularly limited, but is preferably a resin film having a low humidity permeability from the viewpoint of enhancing the moist heat durability.
- the moisture permeability of the protective film A is preferably less 100g / m 2 ⁇ 24hr.
- Moisture permeability of the protective film A is more preferably from the viewpoint, or less 80g / m 2 ⁇ 24hr.
- the moisture permeability of the protective film shall be measured under the conditions of 40 ° C. and 90% RH by the method described in JIS Z 0208, and shall be measured as the value of the moisture permeability for 24 hours per 1 m 2 (g / m 2 ⁇ day). Can be done.
- the resin constituting the protective film A may be any resin having a moisture permeability within the above range, and may be, for example, a (meth) acrylic resin or a polyester resin.
- the (meth) acrylic resin contained in the protective film A may be a homopolymer containing a structural unit derived from methyl methacrylate, or a structural unit derived from methyl methacrylate and a methacryl copolymerizable therewith. It may be a copolymer containing a structural unit derived from a copolymerization monomer other than methyl acid acid.
- the copolymerization monomer is not particularly limited, and the alkyl group other than methyl methacrylate, such as ethyl (meth) acrylate, propyl (meth) acrylate, and six-membered ring lactone (meth) acrylic acid ester, has 1 to 1 to carbon atoms.
- (meth) acrylic acid esters ⁇ , ⁇ -unsaturated acids such as (meth) acrylic acid; unsaturated group-containing divalent carboxylic acids such as maleic anhydride, fumaric acid, itaconic acid; styrene, ⁇ -methylstyrene Aromatic vinyls such as; ⁇ , ⁇ -unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleimides such as maleimide and N-substituted maleimide; maleic anhydride and glutaric anhydride are included.
- One type of copolymerization monomer may be used, or two or more types may be used in combination.
- a homopolymer containing a structural unit derived from methyl methacrylate (polymethyl methacrylate), a structural unit derived from methyl methacrylate, and a glutarimide structure.
- Units eg, structural units derived from (meth) acrylic acid esters reacted with imidizing agents such as amines), structural units derived from glutaric anhydride, or 6-membered ring lactone (meth) acrylic acid It is preferably a copolymer containing a structural unit derived from an ester (lactone ring structural unit), and more preferably a homopolymer containing a structural unit derived from methyl methacrylate (polymethylmethacrylate).
- the content of the structural unit derived from methyl methacrylate is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, based on all the structural units constituting the (meth) acrylic resin. ..
- the type and composition of the (meth) acrylic resin monomer can be specified by 1 1 H-NMR.
- the glass transition temperature (Tg) of the (meth) acrylic resin is preferably 90 ° C. or higher, more preferably 100 to 150 ° C.
- the protective film A in which the Tg of the (meth) acrylic resin is 90 ° C. or higher can have good heat resistance.
- the glass transition temperature (Tg) of the (meth) acrylic resin can be measured using DSC (Differential Scanning Colory) according to JIS K7121-2012 or ASTM D3418-82. ..
- the weight average molecular weight (Mw) of the (meth) acrylic resin is not particularly limited and can be appropriately set according to the film forming method.
- the weight average molecular weight of the (meth) acrylic resin is preferably 100,000 to 300,000.
- the weight average molecular weight of the (meth) acrylic resin is preferably 400,000 to 3 million, preferably 500,000 to 2 million. Is more preferable.
- the weight average molecular weight of the (meth) acrylic resin is in the above range, sufficient mechanical strength (toughness) can be imparted to the film without impairing the film-forming property.
- the weight average molecular weight (Mw) of the (meth) acrylic resin can be measured in terms of polystyrene by gel permeation chromatography (GPC). Specifically, the measurement can be performed using a Tosoh company HLC8220GPC) and a column (Tosoh company TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series). The measurement conditions may be the same as in the examples described later.
- the content of the (meth) acrylic resin is preferably 60% by mass or more, and more preferably 70% by mass or more with respect to the protective film A.
- polyester resin examples include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Of these, polyethylene terephthalate (PET) is preferable.
- the protective film A preferably contains a (meth) acrylic resin.
- the protective film A may further contain other components other than the above, if necessary.
- other ingredients include rubber particles and matting agents.
- the film containing the (meth) acrylic resin since it is brittle, it may further contain rubber particles. Examples of rubber particles include those similar to those that can be used as rubber particles described later.
- the matting agent can be added from the viewpoint of imparting slipperiness to the film.
- examples of the matting agent include inorganic fine particles such as silica particles and organic fine particles having a glass transition temperature of 80 ° C. or higher.
- the protective film A preferably has high transparency.
- the internal haze of the protective film A is preferably 1.0% or less.
- the internal haze of the protective film A can be measured by the following procedure. 1) First, measure the blank haze. Specifically, after dropping one drop (0.05 ml) of glycerin on the washed slide glass, the one on which the cover glass is placed is set in a haze meter (model NDH 2000, manufactured by Nippon Denshoku Co., Ltd.) and blank. Measure haze 1. 2) Next, haze 2 including the protective film is measured. Specifically, glycerin (0.05 ml) is dropped on the washed slide glass, the above-mentioned humidity-controlled protective film A is placed on the slide glass so as not to contain air bubbles, and glycerin (0.05 ml) is placed on the protective film A.
- the cover glass After further dropping, the cover glass is placed.
- the obtained laminate is set in the haze meter described above, and haze 2 is measured.
- the internal haze of the protective film A is calculated by applying the values measured in 1) and 2) to the following formula.
- Internal haze of protective film (haze 2)-(haze 1) In the measurement of haze, the same glass and glycerin as in the examples described later can be used.
- the thickness of the protective film A is not particularly limited, but is preferably thicker than the thickness of the protective film B from the viewpoint of easily reducing the moisture permeability. Specifically, the thickness of the protective film A is preferably 40 to 100 ⁇ m, more preferably 50 to 80 ⁇ m.
- the protective film B When the protective film B is used as a display device, the protective film B is arranged between a polarizing element and a display element such as a liquid crystal cell, and can function as a retardation film for adjusting the phase difference.
- the protective film B contains a (meth) acrylic resin and rubber particles.
- the weight average molecular weight (Mw) of the (meth) acrylic resin contained in the (meth) acrylic resin protective film B is 500,000 or more.
- the weight average molecular weight of the (meth) acrylic resin is 500,000 or more, the viscosity of the dope used for solution casting does not become too low, so that not only the aggregation of rubber particles can be suppressed but also the surface of the protective film B is flat. It can also suppress the deterioration of sex.
- the weight average molecular weight of the (meth) acrylic resin is 500,000 or more, sufficient mechanical strength (toughness) can be imparted to the protective film B.
- the weight average molecular weight of the (meth) acrylic resin is more preferably 500,000 to 3,000,000, and further preferably 600,000 to 2,000,000.
- the weight average molecular weight can be measured by the same method as described above.
- the (meth) acrylic resin is derived from the structural unit (U1) derived from methyl methacrylate and phenylmaleimide from the viewpoint of enhancing the heat resistance of the protective film B and facilitating the acquisition of good display performance even after high-temperature storage. It is preferable to include the structural unit (U2) to be used.
- the content of the structural unit (U1) derived from methyl methacrylate is preferably 50 to 95% by mass, preferably 70 to 90% by mass, based on all the structural units constituting the (meth) acrylic resin. Is more preferable.
- the structural unit (U2) derived from phenylmaleimide has a rigid structure, it is easy to increase the glass transition temperature of the resin and to increase the heat resistance.
- the content of the structural unit (U2) derived from phenylmaleimide is preferably 1 to 25% by mass with respect to all the structural units constituting the (meth) acrylic resin.
- the content of the structural unit (U2) derived from phenylmaleimide is 1% by mass or more, the glass transition temperature of the resin can be easily increased.
- the content of the structural unit (U2) derived from phenylmaleimide is 25% by mass or less, the brittleness of the protective film B is not easily impaired.
- the content of the structural unit (U2) derived from phenylmaleimide is more preferably 7 to 15% by mass.
- the (meth) acrylic resin may further contain structural units derived from other monomers other than the above, if necessary.
- the (meth) acrylic resin may further contain a structural unit (U3) derived from an acrylic acid alkyl ester.
- the structural unit (U3) derived from the acrylic acid alkyl ester has good affinity with the rubber particles containing the structural unit derived from butyl acrylate in the polymer (b) constituting the shell portion, so that the rubber particles are dispersed. Easy to enhance sex.
- the acrylic acid alkyl ester is preferably an acrylic acid alkyl ester having an alkyl portion having 1 to 7 carbon atoms, preferably 1 to 5 carbon atoms.
- alkyl acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate and the like.
- the content of the structural unit (U3) derived from the acrylic acid alkyl ester is preferably 1 to 25% by mass with respect to all the structural units constituting the (meth) acrylic resin.
- the content of the structural unit (U3) derived from the acrylic acid alkyl ester is 1% by mass or more, appropriate flexibility can be imparted to the (meth) acrylic resin, so that the film does not become too brittle and is hard to break. ..
- the content of the structural unit (U3) derived from the acrylic acid alkyl ester is 25% by mass or less, the Tg of the (meth) acrylic resin does not decrease too much, so that the heat resistance of the protective film B is not easily impaired. And the mechanical strength is not easily impaired.
- the content of the structural unit derived from the acrylic acid alkyl ester is more preferably 5 to 15% by mass.
- the ratio of the structural unit (U2) derived from phenylmaleimide to the total amount of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from the acrylic acid alkyl ester shall be 20 to 70% by mass. Is preferable. When the ratio is 20% by mass or more, the heat resistance of the protective film B is likely to be increased, and when it is 70% by mass or less, the protective film B is not too brittle.
- the glass transition temperature (Tg) of the (meth) acrylic resin is preferably 110 ° C. or higher, more preferably 120 to 150 ° C.
- Tg of the (meth) acrylic resin is within the above range, the heat resistance of the protective film B can be easily increased.
- the content of the (meth) acrylic resin is preferably 60% by mass or more, and more preferably 70% by mass or more with respect to the protective film B.
- Rubber particles The rubber particles contained in the protective film B can impart toughness and flexibility to the protective film B.
- Rubber particles are particles containing a rubber-like polymer (crosslinked polymer).
- rubber-like polymers include butadiene-based crosslinked polymers, (meth) acrylic-based crosslinked polymers, and organosiloxane-based crosslinked polymers.
- the (meth) acrylic crosslinked polymer is preferable, and the acrylic crosslinked polymer (acrylic rubber-like polymer) is preferable from the viewpoint that the difference in refractive index from the methacrylic resin is small and the transparency of the protective film B is not easily impaired. Is more preferable.
- the rubber particles are preferably particles containing the acrylic rubber-like polymer (a).
- the acrylic rubber-like polymer (a) is a crosslinked polymer containing an acrylic acid ester as a main component. That is, the acrylic rubber-like polymer (a) has a structural unit derived from an acrylic acid ester, a structural unit derived from a monomer copolymerizable therewith, and two or more radically polymerizable groups (non-conjugated) in one molecule. It is preferably a crosslinked polymer containing a structural unit derived from a polyfunctional monomer having a reactive double bond.
- the acrylic acid ester is preferably an acrylic acid alkyl ester having 1 to 12 carbon atoms of an alkyl group such as methyl acrylate and butyl acrylate.
- the acrylic ester may be one kind or two or more kinds. From the viewpoint of lowering the glass transition temperature of the rubber particles to ⁇ 15 ° C. or lower, the acrylic acid ester preferably contains at least an acrylic acid alkyl ester having 4 to 10 carbon atoms.
- the content of the structural unit derived from the acrylic acid ester is preferably 40 to 80% by mass, preferably 45 to 65% by mass, based on all the structural units constituting the acrylic rubber-like polymer (a). Is more preferable. When the content of the acrylic ester is within the above range, it is easy to impart sufficient toughness to the film.
- the copolymerizable monomer is a monomer copolymerizable with the acrylic acid ester other than the polyfunctional monomer. That is, the copolymerizable monomer does not have two or more radically polymerizable groups.
- copolymerizable monomers include methacrylic acid esters such as methyl methacrylate; styrenes such as styrene and methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile. Above all, the copolymerizable monomer preferably contains styrenes.
- the content of the structural unit derived from styrenes is preferably 5 to 55% by mass, preferably 30 to 50% by mass, based on all the structural units constituting the acrylic rubber-like polymer (a). More preferred.
- polyfunctional monomers examples include allyl (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl malate, divinyl adipate, divinylbenzene, ethylene glycol di (meth) acrylate, and diethylene glycol (meth).
- acrylates triethylene glycol di (meth) acrylates, trimethyl roll propanthry (meth) acrylates, tetromethylol methanetetra (meth) acrylates, dipropylene glycol di (meth) acrylates, and polyethylene glycol di (meth) acrylates.
- the content of the structural unit derived from the polyfunctional monomer is preferably 0.05 to 10% by mass, preferably 0.1 to 5% by mass, based on all the structural units constituting the acrylic rubber-like polymer (a). More preferably, it is by mass%.
- the content of the polyfunctional monomer is 0.05% by mass or more, the degree of cross-linking of the obtained acrylic rubber-like polymer (a) is easily increased, so that the hardness and rigidity of the obtained film are not excessively impaired.
- it is 10% by mass or less the toughness of the film is not easily impaired.
- the monomer composition constituting the acrylic rubber-like polymer (a) can be measured by, for example, the peak area ratio detected by thermal decomposition GC-MS.
- the particles containing the acrylic rubber-like polymer (a) may be particles made of the acrylic rubber-like polymer (a); in the presence of the acrylic rubber-like polymer (a), a methacrylic acid ester.
- the particles may be particles made of an acrylic graft copolymer obtained by polymerizing at least one stage of a monomer mixture such as the above.
- the particles made of the acrylic graft copolymer may be core-shell type particles having a core portion containing the acrylic rubber-like polymer (a) and a shell portion covering the core portion.
- the core portion of the core-shell type particles contains an acrylic rubber-like polymer (a); the shell portion contains a polymer (b) containing a structural unit derived from a methacrylic acid ester.
- the methacrylic acid ester constituting the polymer (b) is preferably an alkyl methacrylate having 1 to 12 carbon atoms of an alkyl group such as methyl methacrylate.
- the methacrylic acid ester may be one kind or two or more kinds.
- the content of the methacrylic acid ester is preferably 50% by mass or more with respect to all the structural units constituting the polymer (b).
- the content of the methacrylic acid ester is 50% by mass or more, it is possible to make it difficult to reduce the hardness and rigidity of the obtained film.
- the content of the methacrylic acid ester is more preferably 70% by mass or more with respect to all the structural units constituting the polymer.
- the polymer (b) may further contain structural units derived from other copolymerizable monomers.
- examples of other monomers are acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate; benzyl (meth) acrylate, dicyclopentanyl (meth) acrylate, phenoxy (meth) acrylate.
- the weight ratio (graft ratio) of the graft component in the rubber particles is preferably 10 to 250%, more preferably 25 to 200%, more preferably 40 to 200%, and 60 to 150%. Is more preferable.
- the mass ratio is 10% or more, the proportion of the shell portion is not too small, so that the hardness and rigidity of the film are not easily impaired.
- the mass ratio is 250% or less, the proportion of the core portion is not too small, so that the toughness and brittleness improving effect of the film are not easily impaired.
- the glass transition temperature (Tg) of the rubber particles is preferably room temperature (25 ° C.) or lower.
- Tg glass transition temperature
- the glass transition temperature (Tg) of the rubber particles may be ⁇ 10 ° C. or lower.
- the glass transition temperature (Tg) of the rubber particles is measured by the same method as described above.
- the glass transition temperature (Tg) of the rubber particles can be adjusted, for example, by adjusting the composition and graft ratio of the polymers constituting the core portion and the shell portion.
- Tg glass transition temperature
- the shape of the rubber particles may be irregular in the cross section along the thickness direction of the film.
- the average major axis of the rubber particles is preferably 100 to 500 nm. When the average major axis of the rubber particles is 100 nm or more, it is easy to impart sufficient toughness or flexibility to the protective film B, and when it is 500 nm or less, it is easy to suppress an increase in haze of the protective film B.
- the average major axis of the rubber particles is more preferably 200 to 400 nm.
- the average major axis of the rubber particles is the average value of the major axis of the rubber particles.
- the average aspect ratio and average major axis of the rubber particles can be calculated by the following methods.
- the observation region may be a region corresponding to the thickness of the protective film B, or a region of 5 ⁇ m ⁇ 5 ⁇ m.
- the number of measurement points may be one.
- the area of 5 ⁇ m ⁇ 5 ⁇ m is used as the observation area, the number of measurement points may be four.
- the average value of the aspect ratios obtained from the plurality of rubber particles is defined as the "average aspect ratio”
- the average value of the major axes obtained from the plurality of rubber particles is defined as the "average major axis”.
- the content of the rubber particles is not particularly limited, but is preferably 5 to 25% by mass, more preferably 5 to 15% by mass, based on the protective film B.
- the aggregation inhibitor is preferably a compound represented by the following formula (1).
- both X 1 and X 2 are t-butyl groups or t-pentyl groups; or one of X 1 and X 2 is a t-butyl group or t-pentyl group, and The other is a hydrogen atom or a methyl group.
- both X 1 and X 2 are t-butyl groups or t-. It is preferably a pentyl group.
- R 1 and R 2 are hydrogen atoms or substituted or unsubstituted alkyl groups, respectively.
- the number of carbon atoms of the substituted or unsubstituted alkyl group is not particularly limited, but may be, for example, 1 to 4.
- M is an integer of 1 to 4, preferably 1.
- R 2 is a substituted or unsubstituted hydrocarbon group having 4 to 25 carbon atoms.
- the number of carbon atoms of the substituted or unsubstituted hydrocarbon group is more preferably 10 to 21.
- the hydrocarbon group constituting R 2 can be, for example, an alkyl group.
- the hydrocarbon group constituting R 2 can be, for example, an alkylene group.
- the hydrocarbon group constituting R 2 can be, for example, a linking group having 3 (or 4) alkylene groups.
- the alkyl group and the alkylene group may be linear or branched, respectively.
- substituents that the hydrocarbon group can have include an alkoxycarbonyl group, an alkylamide group, and the like. Further, the substituent may further contain an alkylene ether chain, an alkylene thioether chain and the like as a partial structure.
- R 2 examples include alkoxycarbonylalkyl groups, alkylamide alkyl groups, alkyleneoxy group-containing carbonylalkyl groups, alkyleneoxy group-containing alkylamide alkyl groups, thioether-containing alkoxycarbonylalkyl groups, and thioether-containing alkylamide alkyl groups. Etc. are included.
- m is preferably 1. That is, the aggregation inhibitor is more preferably a compound represented by the following formula (1').
- X 1, X 2, R 1 ⁇ R 3 of formula (1 ') are respectively synonymous with X 1, X 2, R 1 ⁇ R 3 of formula (1).
- R 2 is a substituted or unsubstituted alkyl group having 4 to 25 carbon atoms, preferably 10 to 21 carbon atoms.
- R 1 and R 3 are preferably hydrogen atoms, and R 2 is preferably a substituted or unsubstituted alkyl group having 4 to 25 carbon atoms; R 1 and R 3 are. , is hydrogen and R 2 is preferably a substituted or unsubstituted alkyl group having a carbon number of 10-21.
- R 1 to R 3 When all of R 1 to R 3 are substituted or unsubstituted alkyl groups, two adjacent substituted or unsubstituted alkyl groups may be bonded to each other to form a ring.
- Examples of the aggregation inhibitor represented by the formula (1) include the following.
- the molecular weight of the aggregation inhibitor is not particularly limited, but is preferably 250 to 2000, for example.
- the molecular weight of the aggregation inhibitor is 250 or more, it is difficult to volatilize in the film forming process of the protective film B, and when it is 2000 or less, the effect of enhancing the dispersibility of the rubber particles in the (meth) acrylic resin is not easily impaired. ..
- the molecular weight of the aggregation inhibitor is more preferably 350 to 1200.
- the molecular weight can be obtained as a formula weight from the chemical structural formula.
- the phenol moiety of the aggregation inhibitor represented by the formula (1) easily interacts with the phenylmaleimide moiety of the (meth) acrylic resin by ⁇ - ⁇ . Further, since the specific alkyl group as R 2 in the formula (1) exhibits hydrophobicity, it easily becomes compatible with rubber particles. Therefore, the aggregation inhibitor tends to be oriented so that the phenol moiety is on the phenylmaleimide portion side of the (meth) acrylic resin and the alkyl group is on the rubber particle side. In this way, by interposing the aggregation inhibitor between the (meth) acrylic resin and the rubber particles, it is possible to improve the mixing between the (meth) acrylic resin and the rubber particles.
- the aggregation inhibitor represented by the formula (1) is oriented so that the alkyl group is on the rubber particle side; the hydroxyl group of the phenol moiety of the aggregation inhibitor is another aggregation in the vicinity of other rubber particles.
- repelling each other with the hydroxyl group of the phenol moiety of the inhibitor aggregation of rubber particles can be suppressed. That is, the aggregation of the rubber particles can be suppressed by interposing the aggregation inhibitor between the rubber particles. It is considered that these can suppress the increase in the internal haze in the protective film B (the first phenomenon described above).
- the aggregation inhibitor represented by the formula (1) can supplement phenylmaleimide because the phenol moiety easily interacts with phenylmaleimide, which is a residual monomer diffusing in the protective film B, by ⁇ - ⁇ . ..
- phenylmaleimide which is a residual monomer
- precipitation of oligomers contained in the pressure-sensitive adhesive layer can be suppressed.
- the content of the aggregation inhibitor is preferably 0.02 to 3.0% by mass with respect to the protective film B.
- the content of the aggregation inhibitor is 0.02% by mass or more, the above action is easily obtained, so that not only the aggregation of the rubber particles is easily suppressed, but also the rubber particles are dispersed in the (meth) acrylic resin. It is easy to improve sex.
- the content of the agglutination inhibitor is 3.0% by mass or less, it is easy to suppress the increase in haze of the protective film B caused by the agglutination inhibitor itself.
- the content of the aggregation inhibitor is more preferably 0.10 to 3.0% by mass with respect to the protective film B.
- the protective film B may further contain components other than the above, if necessary.
- the same component as the other component in the protective film A can be used.
- the internal haze of the protective film B is preferably 1.0% or less, more preferably 0.1% or less, and further preferably 0.05% or less, as described above.
- the internal haze of the protective film B can be measured by the same method as described above.
- the internal haze of the protective film B can be adjusted by the content of the rubber particles, the type and content of the aggregation inhibitor, and the like.
- the content of the rubber particles is preferably reduced, the content of the aggregation inhibitor is preferably appropriately increased, and the aggregation inhibitor of the formula (1) is used.
- substituted or unsubstituted alkyl group and R 2 preferably carbon atoms of 8 or more substituted or unsubstituted alkyl group) preferably in the.
- the in-plane retardation Ro measured in an environment with a measurement wavelength of 550 nm and 23 ° C. and 55% RH is 0 to 10 nm. It is preferably 0 to 5 nm, and more preferably 0 to 5 nm.
- the phase difference Rt in the thickness direction of the protective film B is preferably ⁇ 20 to 20 nm, and more preferably ⁇ 10 to 10 nm.
- the in-plane slow-phase axis of the protective film B can be confirmed by an automatic birefringence meter Axoscan (AxoScan Mueller Matrix Polarimeter: manufactured by Axometrics).
- Ro and Rt can be measured by the following methods. 1) The protective film is humidity-controlled for 24 hours in an environment of 23 ° C. and 55% RH. The average refractive index of this film is measured with an Abbe refractometer, and the thickness d is measured with a commercially available micrometer. 2) The retardation Ro and Rt of the film after humidity control at a measurement wavelength of 550 nm were measured at 23 ° C. and 55% RH using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Matrix Polarimeter), respectively. Measure in the environment.
- the phase difference Ro and Rt of the protective film B can be adjusted by, for example, the monomer composition of the (meth) acrylic resin and the stretching conditions.
- the protective film B Since the protective film B is preferably formed by a casting method, it may further contain a residual solvent.
- the amount of residual solvent is preferably 700 ppm or less, more preferably 30 to 700 ppm, based on the protective film B.
- the content of the residual solvent can be adjusted by the drying conditions of the dope cast on the support in the process of manufacturing the protective film.
- the amount of residual solvent in the protective film B can be measured by headspace gas chromatography.
- a sample is sealed in a container, heated, and the gas in the container is promptly injected into a gas chromatograph with the container filled with volatile components, and mass spectrometry is performed to identify the compound.
- the volatile components are quantified while doing so.
- the thickness of the protective film B is not particularly limited, but is preferably 10 to 60 ⁇ m, and more preferably 10 to 40 ⁇ m.
- Protective films A and B may be manufactured by any method, may be manufactured by a melt casting method (melt), or may be manufactured by a solution casting method (cast method). You may.
- melt melt casting method
- cast method solution casting method
- the protective film A can be manufactured by, for example, a melt casting method (melt).
- the melt-extruded resin composition can be cooled and solidified, and then stretched if necessary to obtain a protective film.
- the draw ratio at the time of producing the protective film A is not particularly limited, but is lower than the draw ratio at the time of producing the protective film B, for example, preferably 10% or less, and more preferably unstretched.
- the protective film B is preferably produced by a solution casting method (cast method) from the viewpoint of using a high molecular weight (meth) acrylic resin. That is, the protective film B has at least 1) a step of obtaining a dope containing the above-mentioned (meth) acrylic resin, rubber particles, and a solvent, and 2) after casting the obtained dope onto a support. It can be produced through a step of obtaining a film-like substance by drying and peeling, and 3) a step of drying the obtained film-like substance while stretching it, if necessary.
- step 1) Acrylic resin and rubber particles are dissolved or dispersed in a solvent to prepare a doping.
- the solvent used for doping includes at least an organic solvent (good solvent) capable of dissolving the (meth) acrylic resin.
- good solvents include chlorine-based organic solvents such as methylene chloride; non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone and tetrahydrofuran. Of these, methylene chloride is preferable.
- the solvent used for doping may further contain a poor solvent.
- poor solvents include straight-chain or branched-chain aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in the doping is high, the film-like substance tends to gel and peels off from the metal support easily.
- linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferable because of its stability of doping, relatively low boiling point, and good drying property.
- the dope obtained in step 2) is cast on the support. Doping can be cast by discharging from a casting die.
- the solvent in the dope cast on the support is evaporated and dried.
- the dried dope is stripped from the support to give a film.
- the residual solvent amount of the doping when peeling from the support is preferably, for example, 25% by mass or more, and more preferably 30 to 37% by mass.
- the amount of residual solvent at the time of peeling is 37% by mass or less, it is easy to prevent the film-like material from being excessively stretched due to peeling.
- the heat treatment for measuring the amount of residual solvent means a heat treatment at 140 ° C. for 30 minutes.
- the amount of residual solvent at the time of peeling can be adjusted by adjusting the drying temperature and drying time of the doping on the support, the temperature of the support, and the like.
- the obtained film-like material is dried. Drying may be performed in one step or in multiple steps. Further, drying may be carried out while stretching, if necessary.
- the drying step of the film-like material includes a step of pre-drying the film-like material (pre-drying step), a step of stretching the film-like material (stretching step), and a step of drying the stretched film-like material (main Drying step) and may be included.
- the pre-drying temperature (drying temperature before stretching) can be higher than the stretching temperature.
- the glass transition temperature of the (meth) acrylic resin is Tg, it is preferably (Tg-50) to (Tg + 50) ° C.
- the pre-drying temperature is (Tg-50) ° C. or higher, the solvent is easily volatilized appropriately, so that the transportability (handleability) is easily improved, and when it is (Tg + 50) ° C. or lower, the solvent does not volatilize too much.
- the stretchability in the subsequent stretching step is not easily impaired.
- the initial drying temperature can be measured as (a) an atmospheric temperature such as the temperature inside the stretching machine or the hot air temperature when the drying is performed by the non-contact heating type while being conveyed by a tenter stretching machine or a roller.
- Stretching may be performed according to the required optical characteristics, and is preferably stretched in at least one direction, and stretches in two directions orthogonal to each other (for example, the width direction (TD direction) of the film-like object and orthogonal to it. Biaxial stretching in the transport direction (MD direction)) may be performed.
- the draw ratio when producing the protective film B is preferably 5 to 100%, more preferably 20 to 100%. In the case of biaxial stretching, it is preferable that the stretching ratio in each direction is within the above range.
- the stretch ratio (%) is defined as (size of the film after stretching in the stretching direction-size of the film before stretching in the stretching direction) / (size of the film before stretching in the stretching direction) ⁇ 100.
- the stretching temperature (drying temperature during stretching) is preferably Tg (° C.) or higher, and is preferably (Tg + 10) to (Tg + 50), when the glass transition temperature of the (meth) acrylic resin is Tg, as described above. More preferably, it is ° C.
- Tg glass transition temperature
- the stretching temperature during production of the protective film B can be, for example, 115 ° C. or higher.
- the stretching temperature it is preferable to measure the ambient temperature such as (a) the temperature inside the stretching machine, as described above.
- the amount of residual solvent in the film-like material at the start of stretching is preferably about the same as the amount of residual solvent in the film-like material at the time of peeling, for example, preferably 20 to 30% by mass, and 25 to 30% by mass. More preferably.
- Stretching of the film-like object in the TD direction can be performed by, for example, fixing both ends of the film-like object with clips or pins and widening the distance between the clips or pins in the traveling direction (tenter method).
- Stretching of the film-like material in the MD direction can be performed by, for example, a method (roll method) in which a plurality of rolls are provided with a peripheral speed difference and the roll peripheral speed difference is used between them.
- the main drying temperature (drying temperature in the case of unstretched) is preferably (Tg-50) to (Tg-30) ° C., where Tg is the glass transition temperature of the (meth) acrylic resin, and (Tg). More preferably, it is ⁇ 40) to (Tg-30) ° C.
- Tg glass transition temperature of the (meth) acrylic resin
- Tg the glass transition temperature of the (meth) acrylic resin
- Tg the post-drying temperature
- the main drying temperature it is preferable to measure the ambient temperature such as (a) hot air temperature as described above.
- Adhesive layers A and B The adhesive layer A is arranged between the protective film A and the polarizer and adheres them. Similarly, the adhesive layer B is placed between the protective film B and the polarizer and adheres them.
- the adhesive layers A and B may be layers obtained from a completely saponified polyvinyl alcohol aqueous solution (water glue), or may be a cured product layer of an active energy ray-curable adhesive. From the viewpoint of having high affinity with the protective films A and B containing the (meth) acrylic resin and facilitating good adhesion, the adhesive layers A and B are cured product layers of the active energy ray-curable adhesive. Is preferable.
- the active energy ray-curable adhesive may be a photoradical polymerizable composition or a photocationic polymerizable composition. Of these, a photocationically polymerizable composition is preferable.
- the photocationic polymerizable composition contains an epoxy compound and a photocationic polymerization initiator.
- the epoxy compound is a compound having one or more, preferably two or more epoxy groups in the molecule.
- epoxy compounds include hydrogenated epoxy compounds obtained by reacting an alicyclic polyol with epichlorohydrin (glycidyl ether of a polyol having an alicyclic ring); an aliphatic polyhydric alcohol or an alkylene thereof.
- Aliphatic epoxy compounds such as polyglycidyl ether as an oxide adduct; include alicyclic epoxy compounds having one or more alicyclic ring-bonded epoxy groups in the molecule. Only one type of epoxy compound may be used, or two or more types may be used in combination.
- the photocationic polymerization initiator may be, for example, an aromatic diazonium salt; an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt; an iron-alene complex or the like.
- the photocationic polymerization initiator may be a cationic polymerization accelerator such as oxetane or polyol, a photosensitizer, an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, or a fluidized agent, if necessary.
- Additives such as modifiers, plasticizers, defoamers, antistatic agents, leveling agents, solvents and the like may be further included.
- the thicknesses of the adhesive layers A and B are not particularly limited, but may be, for example, 0.01 to 10 ⁇ m, preferably about 0.01 to 5 ⁇ m.
- Adhesive layer The adhesive layer is arranged on the surface of the protective film B of the polarizing plate on the side opposite to the polarizer.
- the pressure-sensitive adhesive layer is a layer for bonding the polarizing plate of the present invention to a display element such as a liquid crystal cell.
- the pressure-sensitive adhesive layer is preferably a dry and partially cross-linked pressure-sensitive adhesive composition containing a base polymer, a prepolymer and / or a cross-linking monomer, a cross-linking agent and a solvent. That is, at least a part of the pressure-sensitive adhesive composition may be crosslinked.
- the pressure-sensitive adhesive composition examples include an acrylic pressure-sensitive adhesive composition using a (meth) acrylic polymer as a base polymer, a silicone-based pressure-sensitive adhesive composition using a silicone-based polymer as a base polymer, and a rubber-based pressure-sensitive adhesive composition using a rubber as a base polymer.
- a pressure-sensitive adhesive composition is included.
- an acrylic pressure-sensitive adhesive composition is preferable from the viewpoint of transparency, weather resistance, heat resistance, and processability.
- the (meth) acrylic polymer contained in the acrylic pressure-sensitive adhesive composition can be a copolymer of a (meth) acrylic acid alkyl ester and a cross-linking agent and a cross-linkable functional group-containing monomer.
- the (meth) acrylic acid alkyl ester is preferably an acrylic acid alkyl ester having 2 to 14 carbon atoms in the alkyl group.
- Examples of functional group-containing monomers that can be crosslinked with a cross-linking agent include amide group-containing monomers, carboxyl group-containing monomers (acrylic acid, etc.), and hydroxyl group-containing monomers (hydroxyethyl acrylate, etc.).
- the cross-linking agent and the cross-linkable functional group-containing monomer substantially do not contain the carboxyl group-containing monomer, the polarity of the (meth) acrylic polymer tends to be low.
- highly polar phenylmaleimide which is a residual monomer that can be contained in the protective film B
- aggregation and precipitation of a low-polarity (meth) acrylic polymer are likely to occur.
- Addition of an aggregation inhibitor is particularly effective.
- the content of the carboxyl group-containing monomer is 1% by mass or less, preferably 0.1% by mass, based on all the structural units constituting the (meth) acrylic polymer. % Or less, more preferably 0% by mass.
- cross-linking agent contained in the acrylic pressure-sensitive adhesive composition examples include epoxy-based cross-linking agents, isocyanate-based cross-linking agents, and peroxide-based cross-linking agents.
- the content of the cross-linking agent in the pressure-sensitive adhesive composition can be, for example, 0.01 to 10 parts by mass with respect to 100 parts by mass of the base polymer (solid content).
- the pressure-sensitive adhesive composition can be used as a tackifier, plasticizer, glass fiber, glass beads, metal powder, other fillers, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, silane couplings, as required. Various additives such as agents may be further included.
- the thickness of the pressure-sensitive adhesive layer is usually about 3 to 100 ⁇ m, preferably 5 to 50 ⁇ m.
- the surface of the adhesive layer is protected by a release film that has undergone a mold release treatment.
- the release film include plastic films such as acrylic films, polycarbonate films, polyester films and fluororesin films.
- the polarizing plate of the present invention has a step of 1) laminating and bonding a protective film A on one surface of a polarizing element via an adhesive, and 2) bonding to the other surface of the polarizing element. Obtained through a step of laminating and laminating the protective film B via an agent, and 3) a step of laminating an adhesive layer and a release film on the bonded laminated protective film B to obtain a polarizing plate. Be done.
- an active energy ray-curable adhesive is used as the adhesive will be described.
- step 1) The surface of the protective film A is subjected to surface treatment such as corona treatment as necessary.
- a protective film A is applied to one surface of the polarizing element via a layer of an active energy ray-curable adhesive (in the case of surface treatment, the surface-treated surface of the protective film A is on the polarizer side).
- the active energy ray-curable adhesive is cured by irradiating it with active energy rays.
- the polarizer and the protective film A are bonded to each other via the cured product layer of the active energy ray-curable adhesive.
- the surface of the protective film B is subjected to a surface treatment such as a corona treatment, if necessary.
- a protective film B is applied to the other surface of the polarizer via a layer of an active energy ray-curable adhesive (in the case of surface treatment, the surface-treated surface of the protective film B is on the polarizer side).
- the active energy ray-curable adhesive is cured by irradiating it with active energy rays.
- the polarizer and the protective film B are bonded to each other via the cured product layer of the active energy ray-curable adhesive.
- the steps 1) and 2) may be performed simultaneously or sequentially. From the viewpoint of increasing production efficiency, it is preferable that the steps 1) and 2) are performed at the same time.
- the protective film A, the polarizer, and the protective film B are laminated by a roll-to-roll method. Then, the obtained laminate may be irradiated with active energy rays to cure the active energy ray-curable adhesive.
- the pressure-sensitive adhesive layer and its release film are further attached onto the protective film B of the obtained polarizing plate.
- the pressure-sensitive adhesive layer can be formed by a method such as transferring a release film provided with the pressure-sensitive adhesive layer on the protective film B.
- the liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate arranged on one surface of the liquid crystal cell, and a second polarizing plate arranged on the other surface of the liquid crystal cell. Then, at least one of the first polarizing plate and the second polarizing plate is the polarizing plate of the present invention.
- FIG. 2 is a cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention.
- the liquid crystal display device 200 of the present invention includes a liquid crystal cell 210, a first polarizing plate 220 and a second polarizing plate 230 sandwiching the liquid crystal cell 210, and a backlight 240.
- the display modes of the liquid crystal cell 210 are, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybridaligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment)), It may be PVA (Patterned Vertical Alignment)), IPS (In-Plane-Switching), or the like.
- STN Super-Twisted Nematic
- TN Transmission Nematic
- OCB Optically Compensated Bend
- HAN Hybridaligned Nematic
- VA Very Alignment
- MVA Multi-domain Vertical Alignment
- IPS In-Plane-Switching
- the IPS mode is preferable.
- the first polarizing plate 220 is arranged on the surface of the liquid crystal cell 210 on the visible side via the adhesive layer 224.
- the first polarizing plate 220 is arranged on the surface of the first polarizing element 221 on the viewing side, the protective film 222 (F1), and the surface of the first polarizing element 221 on the liquid crystal cell side.
- Two adhesive layers 225 arranged between the protective film 223 (F2) and the first polarizing element 221 and the protective film 222 (F1) and between the first polarizing element 221 and the protective film 223 (F2). And include.
- the second polarizing plate 230 is arranged on the surface of the liquid crystal cell 210 on the backlight 240 side via the adhesive layer 234.
- the second polarizing plate 230 includes a second polarizing element 231, a protective film 232 (F3) arranged on the surface of the second polarizing element 231 on the liquid crystal cell 210 side, and a surface of the second polarizing element 231 on the backlight 240 side.
- Two adhesives arranged between the protective film 233 (F4) and the second polarizer 231 and the protective film 232 (F3) and between the second polarizing element 231 and the protective film 233 (F4). Includes agent layer 235.
- the absorption axis of the first polarizer 221 and the absorption axis of the second polarizer 231 are orthogonal to each other (cross Nicol).
- the unit composed of the liquid crystal cell 210, the first polarizing plate 220, and the second polarizing plate 230 is also referred to as a liquid crystal display panel 250.
- the protective film 222 (F1) is the protective film A (protective film 120A in FIG. 1)
- the protective film 223 (F2) is the protective film B.
- the adhesive layer 224 is an adhesive layer (adhesive layer 140A in FIG. 1).
- the protective film 233 (F4) is the protective film A (protective film 120A in FIG. 1)
- the protective film 232 (F3) is the protective film.
- B protective film 120B in FIG. 1)
- the adhesive layer 234 is an adhesive layer (adhesive layer 140A in FIG. 1).
- the protective film B (F2 or F3 in FIG. 2 described later) arranged on the liquid crystal cell side contains a specific aggregation inhibitor.
- the aggregation of rubber particles in the protective film B and the precipitation of the base polymer in the pressure-sensitive adhesive layer can be suppressed.
- the glass transition temperature and weight average molecular weight of resins 1 to 5 were measured by the following methods.
- the glass transition temperature (Tg) of the resin was measured using DSC (Differential Scanning Colorimetry) according to JIS K 7121-2012.
- the weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series manufactured by Tosoh Corporation). 20 mg ⁇ 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was injected into a column (temperature 40 ° C.), measured at a detector RI temperature of 40 ° C., and a styrene-converted value was used.
- the internal temperature was adjusted to 80 ° C., and the monomer mixture (a1) was prepared from 27 parts by mass (mixture of methyl methacrylate, butyl acrylate and styrene) and 0.135 parts by mass of allyl methacrylate. 26% by mass of the mixture is added to the polymerization machine in a batch, and then 0.0645 parts by mass of sodium formaldehyde sulfoxylate, 0.0056 parts by mass of -2-sodium ethylenediaminetetraacetate, 0.0014 parts by mass of ferrous sulfate.
- the obtained latex was salted out with magnesium chloride, solidified, washed with water, and dried to obtain a white powdery graft copolymer (rubber particles).
- the graft ratio of the rubber particles was 24.2%, the glass transition temperature (Tg) was 12 ° C., and the average particle diameter was 200 nm.
- the average particle size of the rubber particles was measured by the following method.
- (Average particle size) The dispersed particle size of the rubber particles in the obtained dispersion was measured by a zeta potential / particle size measuring system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).
- protective film 2-1 The pellets of the resin 1 and the rubber particles were dried at 80 ° C. for 4 hours in a dryer, and then supplied to a ⁇ 65 mm single-screw extruder. The molten resin was extruded from the T-die by heating and melting at the extruder outlet so that the resin temperature became 270 ° C. The resin temperature immediately after discharge at the T-die outlet was 270 ° C. The discharged molten resin was sandwiched between a cast roll adjusted to 70 ° C. and a touch roll adjusted to 70 ° C., and cooled and solidified. Then, after continuously slitting both ends of the obtained film, the film was wound while being taken up by a take-up roll to obtain a protective film 101 having a thickness of 60 ⁇ m.
- TAC film triacetyl cellulose film, thickness 60 [mu] m
- Moisture permeability of the protective film was determined as the value of the moisture permeation amount of 1 m 2 per 24 hours (g / m 2 ⁇ 24hr) .
- a dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressurized dissolution tank. Next, the resin 2 was charged into the pressurized dissolution tank with stirring. Then, the rubber particle dispersion liquid prepared above was added, and this was completely dissolved while stirring. This was filtered using SHP150 manufactured by Roki Techno Co., Ltd. to obtain a doping.
- Resin 2 ((meth) acrylic resin): 88.5 parts by mass
- Compound S-1 aggregation inhibitor
- Methylene chloride 200 parts by mass
- Ethanol 40 parts by mass Rubber particle dispersion: 200 parts by mass
- the obtained dope was further stored at 30 ° C. and normal pressure for 48 hours.
- a film was formed using the above-mentioned preserved doping. Specifically, the dope was uniformly spread on the stainless belt support at a temperature of 30 ° C. and a width of 1800 mm using an endless belt casting device. The temperature of the stainless steel belt was controlled to 28 ° C.
- the solvent was evaporated on the stainless belt support until the amount of residual solvent in the cast dope reached 30% by mass. Then, it was peeled from the stainless belt support at a peeling tension of 128 N / m to obtain a film-like material. The amount of residual solvent in the film-like material at the time of peeling was 30% by mass.
- the obtained film-like material was stretched by 20% in the width direction (TD direction) under the condition of 140 ° C. (Tg + 20 ° C.) with a tenter. Then, the film was further dried at 100 ° C. (Tg-20 ° C.) while being conveyed by a roll, and the end portion sandwiched between the tenter clips was slit and wound up to obtain a protective film 201 having a film thickness of 40 ⁇ m.
- Protective films 202 to 203 were obtained in the same manner as the protective film 201 except that the content of the aggregation inhibitor was changed as shown in Table 2.
- Protective films 204 to 208 were obtained in the same manner as the protective film 201 except that the type of the aggregation inhibitor was changed as shown in Table 2.
- a protective film 209 was obtained in the same manner as the protective film 201 except that the type of resin was changed as shown in Table 2 and no aggregation inhibitor was contained.
- Protective films 210 to 211 were obtained in the same manner as the protective film 201 except that the type of resin was changed as shown in Table 2.
- Protective films 212 to 215 were obtained in the same manner as the protective film 201 except that the content of the rubber particles was changed as shown in Table 2. However, since the protective film 213 was rigid and brittle and broke after stretching, it could not proceed to the next step.
- the internal haze of the obtained protective film was measured by the following procedure. 1) First, the blank haze was measured. That is, after dropping one drop (0.05 ml) of glycerin on the washed slide glass, the one on which the cover glass is placed is set in a haze meter (model NDH 2000, manufactured by Nippon Denshoku Co., Ltd.), and the blank haze 1 is set. It was measured. 2) Next, haze 2 including the protective film was measured.
- Table 2 shows the evaluation results of the protective films 201 to 212, 214 and 215.
- a pressure-sensitive adhesive composition 1 (acrylic pressure-sensitive adhesive composition) was obtained.
- the obtained pressure-sensitive adhesive composition 1 was uniformly coated on the surface of a release film made of a polyethylene terephthalate film (PET film, transparent base material) having a thickness of 38 ⁇ m treated with a silicone-based release agent with a fountain coater.
- the adhesive layer 1 having a thickness of 20 ⁇ m was formed by drying in an air circulation type constant temperature oven at 155 ° C. for 2 minutes. As a result, a PET film 1 with an adhesive layer was obtained.
- Adhesive composition 2 Adhesive composition except that a (meth) acrylic polymer having a structural unit derived from an acid component was used instead of a (meth) acrylic polymer having no structural unit derived from an acid component (carboxyl group-containing monomer).
- the pressure-sensitive adhesive composition 2 (acrylic pressure-sensitive adhesive composition) was obtained in the same manner as in 1.
- the pressure-sensitive adhesive layer 2 was formed in the same manner as the method for forming the pressure-sensitive adhesive layer 1 except that the obtained pressure-sensitive adhesive composition was used to obtain a PET film 2 with a pressure-sensitive adhesive layer.
- the protective film 101 is arranged on one surface of the produced polarizing element via the ultraviolet curable adhesive layer, and the protective film 201 is arranged on the other surface via the ultraviolet curable adhesive layer.
- the obtained laminate was irradiated with ultraviolet rays so that the integrated light amount was 750 mJ / cm 2 using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems).
- the UV curable adhesive layer was cured.
- the PET film 1 with the adhesive layer produced above is bonded onto the protective film 201 of the obtained laminate, and the protective film 101 (protective film A) / adhesive layer / polarizer / adhesive layer / protection is attached.
- a polarizing plate 301 having a laminated structure of film 201 (protective film B) / adhesive layer 1 / PET film was obtained.
- Polarizing plates 302 to 309 and 311 to 314 were obtained in the same manner as the polarizing plate 301 except that the protective film B was changed as shown in Table 3.
- the protective film 211 (protective film B) was inferior in film flatness due to the casting of the low-viscosity doping, and it was difficult to produce a good polarizing plate, so further evaluation was not performed. It was.
- polarizing plate 310 was obtained in the same manner as the polarizing plate 301 except that the protective film A was changed to that shown in Table 3.
- a polarizing plate 315 was obtained in the same manner as the polarizing plate 301 except that the PET film 1 with an adhesive layer was changed to the PET film 2 with an adhesive layer.
- the obtained liquid crystal display device was placed in a 50 ° C., dry environment for 24 hours. Then, the backlight was continuously turned on for 24 hours in an environment of 23 ° C. and 55% RH, and then the contrast was measured in the same manner as described above and evaluated according to the same criteria as described above.
- the obtained liquid crystal display device was placed in an environment of 40 ° C. and 95% RH for 300 hours. Then, it was left in a 40 ° C. / dry environment for 2 hours, and then the backlight was continuously turned on for 24 hours in a 23 ° C./55% RH environment, and then the contrast was measured in the same manner as described above. Evaluated in.
- Table 3 shows the configurations and evaluation results of the obtained polarizing plates 301 to 315.
- the liquid crystal display device using the polarizing plate 310 was excluded from the evaluation because the contrast was lowered due to the bend of the liquid crystal display panel after the moist heat durability test.
- the internal haze of the protective film B can be made lower than when only one of them is a t-butyl group. Moreover, it can be seen that the decrease in the constellation after the moist heat durability test can be further reduced (comparison between the polarizing plates 304 and 305).
- the internal haze of the protective film B can be further lowered, and the contrast of the liquid crystal display device can be lowered. It can be seen that the decrease in (particularly after the dry endurance test and also after the wet heat endurance test) can be reduced (contrast with polarizing plates 301, 304 and 306).
- the internal haze of the protective film B can be further lowered, and the contrast of the liquid crystal display device (particularly after the dry durability test and the wet heat durability test). It can be seen that the decrease in the amount of polarizing plates can be reduced (compared with polarizing plates 301 to 303).
- the polarizing plates 307 to 310 and 314 have low contrast of the liquid crystal display device at least after the moist heat durability test. It can be seen that in the polarizing plate 307, the contrast is low because the protective film B does not contain an aggregation inhibitor. It can be seen that the polarizing plate 309 has no problem with the initial contrast, but the contrast is significantly reduced after the wet heat durability test. This is because the (meth) acrylic resin constituting the protective film B does not have a structural unit derived from phenylmaleimide, so that rubber particles are less likely to aggregate, and the initial contrast is less likely to decrease, but it has heat resistance. Therefore, it is considered that the contrast at high temperature or high temperature and high humidity tends to decrease.
- the precipitation of the base polymer in the pressure-sensitive adhesive layer is less than that in the polarizing plate 307, and the contrast immediately after is good.
- the contrast was not evaluated because the ITO conductive layer provided on the surface of the transparent substrate constituting the liquid crystal cell in contact with the adhesive layer was corroded under high temperature or high temperature and high humidity.
- a polarizing plate capable of suppressing a decrease in contrast of a liquid crystal display device even after high temperature storage or high temperature and high humidity storage, and a liquid crystal display device using the same plate.
- Polarizing plate 110 Polarizer 120A, 222, 232 Protective film (protective film A) 120B, 223, 233 Protective film (protective film B) 130A, 130B, 225, 235 Adhesive layer 140, 224, 234 Adhesive layer 200
- Liquid crystal display device 210 Liquid crystal cell 220 First polarizing plate 221 First polarizing plate 230 Second polarizing plate 231 Second polarizing element 240 Backlight 250 Liquid crystal Display panel
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Abstract
Description
X1およびX2の両方がt-ブチル基もしくはt-ペンチル基であるか、
または
X1およびX2の一方がt-ブチル基もしくはt-ペンチル基であり、かつ他方が水素原子もしくはメチル基であり、
R1およびR3は、それぞれ水素原子または置換もしくは無置換のアルキル基であり、
mは、1~4の整数であり、
R2は、炭素原子数4~25の置換もしくは無置換の炭化水素基である)
(メタ)アクリル系樹脂とゴム粒子は、いずれも疎水性ではあるが、(メタ)アクリル系樹脂は極性が相対的に高く、ゴム粒子は極性が相対的に低くなっており、極性差が生じている。凝集抑制剤は、式(1)で表されるようなフェノール部位を有し;当該フェノール部位の水酸基は、嵩高い基(t-ブチル基やt-ペンチル基など)により極性が適度に弱められている。また、凝集抑制剤は、式(1)で表されるように、水酸基とは反対側のR2に特定のアルキル基を有する。すなわち、凝集抑制剤は、当該アルキル基を疎水性基、フェノール部位を適度な親水性基とする界面活性剤のような機能を発現し、(メタ)アクリル系樹脂とゴム粒子との混ざりをよくしうると考えられる。
このように、ゴム粒子と相互作用または付着した凝集抑制剤は、そのフェノール部位が、保護フィルムB中を拡散する残留モノマーであるフェニルマレイミドとπ―π相互作用しやすいため、フェニルマレイミドを補足することができる。それにより、残留モノマーであるフェニルマレイミドが、粘着剤層中に拡散するのを抑制することができる。それにより、粘着剤層に含まれるベースポリマーの析出を抑制できると考えられる。
図1は、本実施の形態に係る偏光板100を示す断面図である。
偏光子は、一定方向の偏波面の光だけを通す素子である。偏光子は、通常、ポリビニルアルコール系偏光フィルムでありうる。ポリビニルアルコール系偏光フィルムの例には、ポリビニルアルコール系フィルムにヨウ素を染色させたものや、二色性染料を染色させたものが含まれる。
保護フィルムAは、透明性を有する樹脂フィルムであればよく、特に制限されないが、湿熱耐久性を高める観点では、透湿度が低い樹脂フィルムであることが好ましい。
保護フィルムAに含まれる(メタ)アクリル系樹脂は、メタクリル酸メチルに由来する構造単位を含む単独重合体であってもよいし、メタクリル酸メチルに由来する構造単位と、それと共重合可能なメタクリル酸メチル以外の共重合モノマーに由来する構造単位とを含む共重合体であってもよい。
ポリエステル樹脂の例には、ポリエチレンテレフタレート、ポリプロピレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレートが含まれる。中でも、ポリエチレンテレフタレート(PET)が好ましい。
保護フィルムAは、必要に応じて上記以外の他の成分をさらに含んでもよい。他の成分の例には、ゴム粒子およびマット剤が含まれる。特に、(メタ)アクリル系樹脂を含むフィルムは脆いため、ゴム粒子をさらに含みうる。ゴム粒子の例には、後述するゴム粒子として使用可能なものと同様のものが含まれる。
保護フィルムAは、透明性が高いことが好ましい。保護フィルムAの内部ヘイズは、1.0%以下であることが好ましい。
1)まず、ブランクヘイズを測定する。具体的には、洗浄したスライドガラス上にグリセリンを一滴(0.05ml)滴下した後、カバーガラスを乗せたものをヘイズメーター(型式NDH 2000、日本電色(株)製)にセットし、ブランクヘイズ1を測定する。
2)次に、保護フィルムを含むヘイズ2を測定する。具体的には、洗浄したスライドガラス上にグリセリン(0.05ml)を滴下し、その上に上記調湿した保護フィルムAを気泡が入らないように乗せ、その上にグリセリン(0.05ml)をさらに滴下した後、カバーガラスを載せる。得られた積層物を、前述のヘイズメーターにセットし、ヘイズ2を測定する。
3)前記1)および2)で測定した値を下記式に当てはめて、保護フィルムAの内部ヘイズを算出する。
保護フィルムの内部ヘイズ=(ヘイズ2)-(ヘイズ1)
なお、ヘイズの測定において、ガラスおよびグリセリンは、後述する実施例と同様のものを使用することができる。
保護フィルムAの厚みは、特に限定されないが、透湿度を低くしやすい観点などから、保護フィルムBの厚みよりも厚いことが好ましい。具体的には、保護フィルムAの厚みは、40~100μmであることが好ましく、50~80μmであることがより好ましい。
保護フィルムBは、表示装置にしたときに、偏光子と、液晶セルなどの表示素子との間に配置され、位相差を調整するための位相差フィルムとして機能しうる。保護フィルムBは、(メタ)アクリル系樹脂と、ゴム粒子とを含む。
保護フィルムBに含まれる(メタ)アクリル系樹脂の重量平均分子量(Mw)は、50万以上である。(メタ)アクリル系樹脂の重量平均分子量が50万以上であると、溶液流延に用いるドープの粘度が低くなりすぎないため、ゴム粒子の凝集を抑制できるだけでなく、保護フィルムBの表面の平坦性が低下することも抑制しうる。さらに、(メタ)アクリル系樹脂の重量平均分子量が50万以上であると、保護フィルムBに十分な機械的強度(靱性)を付与しうる。(メタ)アクリル系樹脂の重量平均分子量は、上記観点から、50万~300万であることがより好ましく、60万~200万であることがさらに好ましい。重量平均分子量は、前述と同様の方法で測定することができる。
保護フィルムBに含まれるゴム粒子は、保護フィルムBに靱性や柔軟性を付与しうる。
アクリル系ゴム状重合体(a)は、アクリル酸エステルを主成分とする架橋重合体である。すなわち、アクリル系ゴム状重合体(a)は、アクリル酸エステルに由来する構造単位と、それと共重合可能なモノマーに由来する構造単位と、1分子中に2以上のラジカル重合性基(非共役な反応性二重結合)を有する多官能性モノマーに由来する構造単位とを含む架橋重合体であることが好ましい。
1)コアシェル型の粒子2gを、メチルエチルケトン50mlに溶解させ、遠心分離機(日立工機(株)製、CP60E)を用い、回転数30000rpm、温度12℃にて1時間遠心し、不溶分と可溶分とに分離する(遠心分離作業を合計3回セット)。
2)得られた不溶分の重量を下記式に当てはめて、グラフト率を算出する。
グラフト率(%)=[{(メチルエチルケトン不溶分の重量)-(アクリル系ゴム状重合体(a)の重量)}/(アクリル系ゴム状重合体(a)の重量)]×100
ゴム粒子のガラス転移温度(Tg)は、室温(25℃)以下であることが好ましい。ゴム粒子のガラス転移温度(Tg)が25℃以下であると、フィルムに適度な靱性を付与しうる。フィルムに十分な靱性を付与しやすくする観点では、ゴム粒子のガラス転移温度(Tg)は、-10℃以下であってもよい。ゴム粒子のガラス転移温度(Tg)は、前述と同様の方法で測定される。
1)保護フィルムBの断面をTEM観察する。観察領域は、保護フィルムBの厚みに相当する領域としてもよいし、5μm×5μmの領域としてもよい。保護フィルムBの厚みに相当する領域を観察領域とする場合、測定箇所は1箇所としうる。5μm×5μmの領域を観察領域とする場合、測定箇所は4箇所としうる。
2)得られたTEM画像における各ゴム粒子の長径、短径を測定し、アスペクト比をそれぞれ算出する。複数のゴム粒子から得られたアスペクト比の平均値を「平均アスペクト比」とし、複数のゴム粒子から得られた長径の平均値を「平均長径」とする。
保護フィルムBは、必要に応じて上記以外の他の成分をさらに含んでもよい。他の成分は、保護フィルムAにおける他の成分と同様のものを使用できる。
(内部ヘイズ)
保護フィルムBの内部ヘイズは、前述と同様に、1.0%以下であることが好ましく、0.1%以下であることがより好ましく、0.05%以下であることがさらに好ましい。保護フィルムBの内部ヘイズは、前述と同様の方法で測定することができる。
保護フィルムBは、例えばIPSモード用の位相差フィルムとして用いる観点では、測定波長550nm、23℃55%RHの環境下で測定される面内方向の位相差Roは、0~10nmであることが好ましく、0~5nmであることがより好ましい。保護フィルムBの厚み方向の位相差Rtは、-20~20nmであることが好ましく、-10~10nmであることがより好ましい。
式(2a):Ro=(nx-ny)×d
式(2b):Rt=((nx+ny)/2-nz)×d
(式中、
nxは、フィルムの面内遅相軸方向(屈折率が最大となる方向)の屈折率を表し、
nyは、フィルムの面内遅相軸に直交する方向の屈折率を表し、
nzは、フィルムの厚み方向の屈折率を表し、
dは、フィルムの厚み(nm)を表す。)
1)保護フィルムを23℃55%RHの環境下で24時間調湿する。このフィルムの平均屈折率をアッベ屈折計で測定し、厚みdを市販のマイクロメーターを用いて測定する。
2)調湿後のフィルムの、測定波長550nmにおけるリターデーションRoおよびRtを、それぞれ自動複屈折率計アクソスキャン(Axo Scan Mueller Matrix Polarimeter:アクソメトリックス社製)を用いて、23℃55%RHの環境下で測定する。
保護フィルムBは、好ましくはキャスト法で製膜されることから、残留溶媒をさらに含みうる。残留溶媒量は、保護フィルムBに対して700ppm以下であることが好ましく、30~700ppmであることがより好ましい。残留溶媒の含有量は、保護フィルムの製造工程における、支持体上に流延させたドープの乾燥条件によって調整されうる。
保護フィルムBの厚みは、特に制限されないが、10~60μmであることが好ましく、10~40μmであることがより好ましい。
保護フィルムAおよびBは、任意の方法で製造されてよく、溶融流延方式(メルト)で製造されてもよいし、溶液流延方式(キャスト法)で製造されてもよい。
(メタ)アクリル系樹脂とゴム粒子とを、溶媒に溶解または分散させて、ドープを調製する。
得られたドープを、支持体上に流延する。ドープの流延は、流延ダイから吐出させて行うことができる。
ドープの残留溶媒量(質量%)=(ドープの加熱処理前質量-ドープの加熱処理後質量)/ドープの加熱処理後質量×100
尚、残留溶媒量を測定する際の加熱処理とは、140℃30分の加熱処理をいう。
得られた膜状物を乾燥させる。乾燥は、一段階で行ってもよいし、多段階で行ってもよい。また、乾燥は、必要に応じて延伸しながら行ってもよい。
予備乾燥温度(延伸前の乾燥温度)は、延伸温度よりも高い温度でありうる。具体的には、(メタ)アクリル系樹脂のガラス転移温度をTgとしたとき(Tg-50)~(Tg+50)℃であることが好ましい。予備乾燥温度が(Tg-50)℃以上であると、溶媒を適度に揮発させやすいため、搬送性(ハンドリング性)を高めやすく、(Tg+50)℃以下であると、溶媒が揮発しすぎないため、この後の延伸工程における延伸性が損なわれにくい。初期乾燥温度は、(a)テンター延伸機やローラーで搬送しながら非接触加熱型で乾燥させる場合は、延伸機内温度または熱風温度などの雰囲気温度として測定されうる。
延伸は、求められる光学特性に応じて行えばよく、少なくとも一方の方向に延伸することが好ましく、互いに直交する二方向に延伸(例えば、膜状物の幅方向(TD方向)と、それと直交する搬送方向(MD方向)の二軸延伸)してもよい。
残留溶媒量をより低減させる観点から、延伸後に得られた膜状物をさらに乾燥させることが好ましい。例えば、延伸後に得られた膜状物を、ロールなどで搬送しながらさらに乾燥させることが好ましい。
接着剤層Aは、保護フィルムAと偏光子との間に配置され、それらを接着させる。同様に、接着剤層Bは、保護フィルムBと偏光子との間に配置され、それらを接着させる。
粘着剤層は、偏光板の保護フィルムBの、偏光子とは反対側の面に配置されている。粘着剤層は、本発明の偏光板を、液晶セルなどの表示素子と貼り合わせるための層である。
本発明の偏光板は、1)偏光子の一方の面に、接着剤を介して保護フィルムAを積層し、貼り合わせる工程と、2)偏光子の他方の面に、接着剤を介して保護フィルムBを積層し、貼り合わせる工程と、3)貼り合わせた積層物の保護フィルムB上に、粘着剤層および剥離フィルムを貼り付けて、偏光板を得る工程とを経て得られる。以下、接着剤として活性エネルギー線硬化性接着剤を用いる例で説明する。
保護フィルムAの表面に、必要に応じてコロナ処理などの表面処理を施す。次いで、偏光子の一方の面に、活性エネルギー線硬化性接着剤の層を介して、保護フィルムAを(表面処理されている場合は、保護フィルムAの表面処理面が偏光子側となるように)積層した後、活性エネルギー線を照射して、活性エネルギー線硬化性接着剤を硬化させる。それにより、偏光子と保護フィルムAとを、活性エネルギー線硬化性接着剤の硬化物層を介して接着させて、貼り合わせる。
同様に、保護フィルムBの表面に、必要に応じてコロナ処理などの表面処理を施す。次いで、偏光子の他方の面に、活性エネルギー線硬化性接着剤の層を介して、保護フィルムBを(表面処理されている場合は、保護フィルムBの表面処理面が偏光子側となるように)積層した後、活性エネルギー線を照射して、活性エネルギー線硬化性接着剤を硬化させる。それにより、偏光子と保護フィルムBとを、活性エネルギー線硬化性接着剤の硬化物層を介して接着させて、貼り合わせる。
次いで、得られた偏光板の保護フィルムB上に、粘着剤層およびその剥離フィルムを、さらに貼り付ける。具体的には、保護フィルムB上に、粘着剤層を設けた剥離フィルムを転写するなどの方法により、粘着剤層を形成することができる。
本発明の液晶表示装置は、液晶セルと、液晶セルの一方の面に配置された第一偏光板と、液晶セルの他方の面に配置された第二偏光板とを含む。そして、第一偏光板と第二偏光板の少なくとも一方は、本発明の偏光板である。
樹脂のガラス転移温度(Tg)は、DSC(Differential Scanning Colorimetry:示差走査熱量法)を用いて、JIS K 7121-2012に準拠して測定した。
樹脂の重量平均分子量(Mw)は、ゲル浸透クロマトグラフィー(東ソー社製 HLC8220GPC)、カラム(東ソー社製 TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL 直列)を用いて測定した。試料20mg±0.5mgをテトラヒドロフラン10mlに溶解し、0.45mmのフィルターで濾過した。この溶液をカラム(温度40℃)に100ml注入し、検出器RI温度40℃で測定し、スチレン換算した値を用いた。
<ゴム粒子の調製>
撹拌機付き8L重合装置に、以下の化合物を仕込んだ。
脱イオン水:175質量部
ポリオキシエチレンラウリルエーテルリン酸:0.104質量部
ホウ酸:0.4725質量部
炭酸ナトリウム:0.04725質量部
次に、水酸化ナトリウム0.0098質量部を2質量%水溶液の形態で、ポリオキシエチレンラウリルエーテルリン酸0.0852質量部をそのまま追加し、上記混合物の残り74質量%を60分かけて連続的に添加した。添加終了30分後に、t-ブチルハイドロパーオキサイド0.069質量部を追加し、さらに30分重合を継続することにより、重合物を得た。
(平均粒子径)
得られた分散液中のゴム粒子の分散粒径を、ゼータ電位・粒径測定システム(大塚電子株式会社製 ELSZ-2000ZS)で測定した。
2-1.保護フィルムA
<保護フィルム101の作製>
樹脂1のペレットとゴム粒子とを、乾燥機にて80℃で4時間乾燥させた後、φ65mm単軸押出機に供給した。押出機出口で樹脂温度が270℃となるように加熱溶融し、Tダイから溶融樹脂を押し出した。Tダイ出口における吐出直後の樹脂温度は270℃であった。吐出された溶融樹脂を、70℃に調整したキャストロールと70℃に調整したタッチロールとで挟み込み、冷却固化した。その後、得られたフィルムの両端を連続的にスリットした後、引き取りロールで引き取りながら巻き取り、厚み60μmの保護フィルム101を得た。
透湿度500g/m2・24hrのTACフィルム(トリアセチルセルロースフィルム、厚み60μm)を用いた。
得られた保護フィルム101および102の透湿度を、以下の方法で測定した。
保護フィルムの透湿度は、JIS Z 0208に記載の方法により、40℃90%RH条件下で測定し、1m2あたり24時間の透湿量の値(g/m2・24hr)として求めた。
<保護フィルム201の作製>
(ゴム粒子分散液の調製)
10質量部のゴム粒子と、190質量部のメチレンクロライドとを、ディゾルバーで50分間撹拌混合した後、マイルダー分散機マイルダー分散機(大平洋機工株式会社製)を用いて1500rpm条件下で分散し、ゴム粒子分散液を得た。
次いで、下記組成のドープを調製した。まず、加圧溶解タンクにメチレンクロライド、およびエタノールを添加した。次いで、加圧溶解タンクに、樹脂2を撹拌しながら投入した。次いで、上記調製したゴム粒子分散液を投入して、これを撹拌しながら、完全に溶解させた。これを、(株)ロキテクノ製のSHP150を使用して濾過し、ドープを得た。
樹脂2((メタ)アクリル系樹脂):88.5質量部
化合物S-1(凝集抑制剤):1.5質量部
メチレンクロライド:200質量部
エタノール:40質量部
ゴム粒子分散液:200質量部
なお、本発明の効果(内部ヘイズの低減、コントラストの向上)を確認しやすくするため、得られたドープを30℃常圧下で48時間さらに保存した。
次いで、上記保存後のドープを用いて製膜を行った。具体的には、無端ベルト流延装置を用い、ドープを温度30℃、1800mm幅でステンレスベルト支持体上に均一に流延した。ステンレスベルトの温度は28℃に制御した。
凝集抑制剤の含有量を、表2に示されるように変更した以外は保護フィルム201と同様にして保護フィルム202~203を得た。
凝集抑制剤の種類を、表2に示されるように変更した以外は保護フィルム201と同様にして保護フィルム204~208を得た。
樹脂の種類を表2に示されるように変更し、かつ凝集抑制剤を含有させなかった以外は保護フィルム201と同様にして保護フィルム209を得た。
樹脂の種類を、表2に示されるように変更した以外は保護フィルム201と同様にして保護フィルム210~211を得た。
ゴム粒子の含有量を、表2に示されるように変更した以外は保護フィルム201と同様にして保護フィルム212~215を得た。ただし、保護フィルム213は、堅脆く、延伸後に破断したため、次の工程に進められなかった。
得られた保護フィルム201~212、214および215の内部ヘイズを、以下の方法で測定した。
得られた保護フィルムの内部ヘイズを、以下の手順で測定した。
1)まず、ブランクヘイズを測定した。すなわち、洗浄したスライドガラス上にグリセリンを一滴(0.05ml)滴下した後、カバーガラスを乗せたものをヘイズメーター(型式NDH 2000、日本電色(株)製)にセットし、ブランクヘイズ1を測定した。
2)次に、保護フィルムを含むヘイズ2を測定した。すなわち、洗浄したスライドガラス上にグリセリン(0.05ml)を滴下し、その上に上記調湿した保護フィルムを気泡が入らないように乗せ、その上にグリセリン(0.05ml)をさらに滴下した後、カバーガラスを載せた。得られた積層物を、前述のヘイズメーターにセットし、ヘイズ2を測定した。
3)前記1)及び2)で測定した値を下記式に当てはめて、保護フィルムの内部ヘイズを算出した。
保護フィルムの内部ヘイズ=(ヘイズ2)-(ヘイズ1)
なお、ヘイズの測定において、ガラスおよびグリセリンは、後述する実施例と同様のものを使用した。
ガラス:MICRO SLIDE GLASS S9213 MATSUNAMI
グリセリン:関東化学製 鹿特級(純度>99.0%) 屈折率1.47
◎:内部ヘイズが0.05%以下
〇:内部ヘイズが0.05%超0.10%以下
△:内部ヘイズが0.10%超1.0%以下
×:内部ヘイズが1.0%超5.0%以下
××:内部ヘイズが5.0%超
△以上が実用上許容されるレベルである。
<粘着剤層付きPETフィルム1の作製>
(粘着剤組成物1の調製)
酸成分(カルボキシル基含有モノマー)に由来する構造単位を有しない(メタ)アクリル系ポリマー溶液の固形分100質量部に対して、イソシアネート系架橋剤(商品名:タケネートD110N、トリメチロールプロパンキシリレンジイソシアネート、三井化学(株)製)0.1質量部、過酸化物系架橋剤のベンゾイルパーオキサイド(商品名:ナイパーBMT、日本油脂(株)製)0.4質量部とを添加し、撹拌して、粘着剤組成物1(アクリル系粘着剤組成物)を得た。
得られた粘着剤組成物1を、シリコーン系剥離剤で処理された厚み38μmのポリエチレンテレフタレートフィルム(PETフィルム、透明基材)からなる離型フィルムの表面に、ファウンテンコータで均一に塗工し、155℃の空気循環式恒温オーブンで2分間乾燥し、厚み20μmの粘着剤層1を形成した。それにより、粘着剤層付きPETフィルム1を得た。
(粘着剤組成物2の調製)
酸成分(カルボキシル基含有モノマー)に由来する構造単位を有しない(メタ)アクリル系ポリマーに代えて、酸成分に由来する構造単位を有する(メタ)アクリル系ポリマーを用いた以外は粘着剤組成物1と同様にして、粘着剤組成物2(アクリル系粘着剤組成物)を得た。
得られた粘着剤組成物を用いた以外は粘着剤層1の形成方法と同様にして粘着剤層2を形成し、粘着剤層付きPETフィルム2を得た。
<偏光板301の作製>
(偏光子の作製)
厚さ25μmのポリビニルアルコール系フィルムを、35℃の水で膨潤させた。得られたフィルムを、ヨウ素0.075g、ヨウ化カリウム5gおよび水100gからなる水溶液に60秒間浸漬し、さらにヨウ化カリウム3g、ホウ酸7.5gおよび水100gからなる45℃の水溶液に浸漬した。得られたフィルムを、延伸温度55℃、延伸倍率5倍の条件で一軸延伸した。この一軸延伸フィルムを、水洗した後、乾燥させて、厚み12μmの偏光子を得た。
下記成分を混合した後、脱泡して、紫外線硬化性接着剤組成物を調製した。
3,4-エポキシシクロヘキシルメチル-3,4-エポキシシクロヘキサンカルボキシレート:45質量部
エポリードGT-301(ダイセル社製の脂環式エポキシ樹脂):40質量部
1,4-ブタンジオールジグリシジルエーテル:15質量部
トリアリールスルホニウムヘキサフルオロホスフェート:2.3質量部(固形分)
9,10-ジブトキシアントラセン:0.1質量部
1,4-ジエトキシナフタレン:2.0質量部
なお、トリアリールスルホニウムヘキサフルオロホスフェートは、50%プロピレンカーボネート溶液として配合した。
上記作製した保護フィルム101の表面に、コロナ出力強度2.0kW、ライン速度18m/分でコロナ放電処理を施した。次いで、保護フィルム101のコロナ放電処理面に、上記調製した紫外線硬化性接着剤組成物を、硬化後の膜厚が約3μmとなるようにバーコーターで塗布して、紫外線硬化性接着剤層を形成した。
同様に、上記作製した保護フィルム201の表面にコロナ放電処理を施した後、上記調製した紫外線硬化性接着剤組成物を、硬化後の膜厚が3μmとなるように塗布して、紫外線硬化性接着剤層を形成した。
保護フィルムBを、表3に示されるように変更した以外は偏光板301と同様にして偏光板302~309、311~314を得た。ただし、保護フィルム211(保護フィルムB)については、低粘度ドープを流延したことによるフィルム平面性に劣っており、良好な偏光板を作成することが困難であったため、以降の評価を行わなかった。
保護フィルムAを、表3に示されるものに変更した以外は偏光板301と同様にして偏光板310を得た。
粘着剤層付きPETフィルム1を、粘着剤層付きPETフィルム2に変更した以外は偏光板301と同様にして偏光板315を得た。
得られた偏光板の寸法安定性、および偏光板を用いた液晶表示装置のコントラストを、以下の方法で測定した。
1)得られた偏光板を、23℃、55%RHの環境下で、24時間調湿した。次いで、同環境下で、偏光板の表面に、フィルムの長手方向と幅手方向とに100mm間隔で2個の十文字の印を付け、その寸法を測定し、その距離をaとした。
2)次いで、100℃で250時間の処理を行った後、再度、23℃、55%RHの環境下で24時間調湿して、2個の印の間の距離を株式会社ミツトヨ製測定顕微鏡MF-A1720で測定し、その値をbとした。
3)上記1)と2)で得られた値を、下記式に当てはめて、偏光板の寸法安定性(寸法変化率)を算出した。
寸法変化率(%)=〔(b-a)/a〕×100
そして、寸法安定性を、以下の基準に基づいて評価した。
○:寸法変化率が0.5%以下
△:寸法変化率が0.5%超1.0%以下
×:寸法変化率が1.0%超3.0%以下
××:寸法変化率が3.0%超
○以上が実用上許容されるレベルである。
(1)タッチパネル部材を有する液晶表示装置の作製
タッチパネル部材を有する液晶表示装置であるSONY社製21.5インチVAIOTap21(SVT21219DJB)から、予め貼り合わされていた2枚の偏光板を剥がして、上記作製した偏光板をそれぞれ貼り合わせて、タッチパネル部材を有する液晶表示装置を得た。
(直後)
得られた液晶表示装置を、23℃55%RHの環境下でバックライトを24時間連続点灯させた後、正面コントラストの測定を行った。正面コントラストの測定は、コニカミノルタセンシング社製の装置「CS-2000」を用い、液晶表示装置の白表示状態、黒表示状態での輝度をそれぞれ液晶表示装置の表示画面の法線方向から測定した。そして、得られた値を下記式に当てはめて、正面コントラスト(CR)を算出した。
正面コントラスト(CR)=(白表示状態での輝度)÷(黒表示状態での輝度)
正面コントラスト(CR)が2000以上であれば実用上許容されるレベルである。
得られた液晶表示装置を、50℃・dry環境下に24時間置いた。その後、23℃・55%RH環境下で、バックライトを24時間連続点灯させた後、前述と同様にしてコントラストを測定し、前述と同様の基準で評価した。
得られた液晶表示装置を、40℃・95%RHの環境下にて300時間置いた。次いで、40℃・dry環境下に2時間置き、その後、バックライトを23℃・55%RH環境下で24時間連続点灯させた後に、前述と同様にしてコントラストを測定し、前述と同様の基準で評価した。
110 偏光子
120A、222、232 保護フィルム(保護フィルムA)
120B、223、233 保護フィルム(保護フィルムB)
130A、130B、225、235 接着剤層
140、224、234 粘着剤層
200 液晶表示装置
210 液晶セル
220 第一偏光板
221 第一偏光子
230 第二偏光板
231 第二偏光子
240 バックライト
250 液晶表示パネル
Claims (9)
- 偏光子と、前記偏光子の一方の面に配置された、透湿度が100g/m2・24hr以下の保護フィルムAと、前記偏光子の他方の面に配置された保護フィルムBと、前記保護フィルムBの前記偏光子とは反対側の面に配置された粘着剤層とを含む偏光板であって、
前記保護フィルムBは、重量平均分子量が50万以上の(メタ)アクリル系樹脂と、ゴム粒子とを含み、
前記(メタ)アクリル系樹脂は、メタクリル酸メチルに由来する構造単位と、フェニルマレイミドに由来する構造単位とを含む共重合体であり、
前記ゴム粒子の含有量は、前記保護フィルムBに対して5~25質量%であり、
前記保護フィルムBは、下記式(1)で表される凝集抑制剤をさらに含む、
偏光板。
X1およびX2の両方がt-ブチル基もしくはt-ペンチル基であるか、
または
X1およびX2の一方がt-ブチル基もしくはt-ペンチル基であり、かつ他方が水素原子もしくはメチル基であり、
R1およびR3は、それぞれ水素原子または置換もしくは無置換のアルキル基であり、
mは、1~4の整数であり、
R2は、炭素原子数4~25の置換もしくは無置換の炭化水素基である) - X1およびX2の両方が、t-ブチル基もしくはt-ペンチル基である、
請求項1に記載の偏光板。 - R2は、炭素原子数10~21の置換または無置換の炭化水素基である、
請求項1または2に記載の偏光板。 - mは、1であり、かつ
R2は、炭素原子数10~21の置換もしくは無置換のアルキル基である、
請求項3に記載の偏光板。 - 前記凝集抑制剤の含有量は、前記保護フィルムBに対して0.10~3.0質量%である、
請求項1~4のいずれか一項に記載の偏光板。 - 前記フェニルマレイミドに由来する構造単位の含有量は、前記(メタ)アクリル系樹脂を構成する全構造単位に対して1~25質量%である、
請求項1~5のいずれか一項に記載の偏光板。 - 前記粘着剤層は、(メタ)アクリル系ポリマーと、架橋剤とを含むアクリル系粘着剤組成物の少なくとも一部が架橋したものであり、
前記(メタ)アクリル系ポリマーは、カルボキシル基含有モノマーに由来する構造単位を実質的に含まない、
請求項1~6のいずれか一項に記載の偏光板。 - 液晶セルと、
前記液晶セルの一方の面に配置された第一偏光板と、
前記液晶セルの他方の面に配置された第二偏光板と、
を有し、
前記第一偏光板と前記第二偏光板の少なくとも一方は、請求項1~7のいずれか一項に記載の偏光板であり、
前記偏光板の前記粘着剤層は、前記液晶セルと接着されている、
液晶表示装置。 - 前記液晶セルは、IPS方式の液晶セルである、
請求項8に記載の液晶表示装置。
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