WO2017130656A1 - 偏光板の製造方法 - Google Patents
偏光板の製造方法 Download PDFInfo
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- WO2017130656A1 WO2017130656A1 PCT/JP2017/000252 JP2017000252W WO2017130656A1 WO 2017130656 A1 WO2017130656 A1 WO 2017130656A1 JP 2017000252 W JP2017000252 W JP 2017000252W WO 2017130656 A1 WO2017130656 A1 WO 2017130656A1
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- film
- polarizing
- resin
- optical film
- polarizing plate
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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
Definitions
- the present invention relates to a method for producing a polarizing plate.
- liquid crystal displays In recent years, low-power consumption, low-voltage, light-weight and thin liquid crystal displays are rapidly spreading as information display devices such as mobile phones, portable information terminals, computer monitors, and televisions. With the development of liquid crystal technology, liquid crystal displays in various modes have been proposed, and problems with liquid crystal displays such as response speed, contrast, and narrow viewing angle are being solved. In addition, with the spread of mobile liquid crystal displays, for example, when used outdoors, the screen of the liquid crystal display may be viewed with polarized sunglasses. Even when viewing the screen through polarized sunglasses, excellent visibility is required.
- Patent Documents 1 to 9 Several means for improving the visibility when viewing the screen through polarized sunglasses have been proposed.
- linearly polarized light emitted from a polarizing plate arranged on the viewing side of an image display element such as a liquid crystal cell is elliptical (or circular).
- a method in which a retardation plate (for example, a ⁇ / 4 wavelength plate) for conversion to polarized light is disposed on the viewing side of the polarizing plate is employed.
- Such a retardation plate is stretched and is often laminated directly on the polarizing film via an adhesive layer. Further, the angle between the absorption axis of the polarizing plate and the slow axis of the retardation plate is often arranged at a predetermined angle (for example, 45 °), and the retardation plate is stretched when it is put into a heat resistance test. As a result, the absorption axis of the polarizing film is locally changed and the degree of polarization is lowered.
- An optical film, a polarizing film, and an adhesive layer are included in this order, and the thickness of the polarizing film is 15 ⁇ m or less, and the angle formed by the absorption axis of the polarizing film and the slow axis of the optical film is approximately 45.
- a method for producing a polarizing plate having an angle of about 135 ° or about 135 ° The manufacturing method of the polarizing plate which has the process of heat-processing the said optical film, before bonding the said optical film to the said polarizing film.
- the optical film includes at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, or a (meth) acrylic resin.
- the manufacturing method of the polarizing plate of description [4] The method for producing a polarizing plate according to any one of [1] to [3], further comprising a protective film between the polarizing film and the pressure-sensitive adhesive layer.
- a method for producing a polarizing plate capable of suppressing a decrease in the degree of polarization due to a shift in the absorption axis of a polarizing film caused by a dimensional change of the optical film during a heat resistance test.
- the layer structure of the polarizing plate 10 obtained by the manufacturing method of the present invention will be described.
- the polarizing plate obtained by the production method of the present invention is preferably configured by laminating the optical film 11, the polarizing film 14, and the pressure-sensitive adhesive layer 16 in this order.
- the angle formed by the absorption axis of the polarizing film 14 and the slow axis of the optical film 11 is approximately 45 ° or approximately 135 °. It is also useful to form the surface treatment layer 20 on the surface of the optical film 11 opposite to the bonding surface with the polarizing film.
- the optical film 11 is preferably a film containing at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth) acrylic resin.
- the polarizing film 14 preferably has a thickness of 15 ⁇ m or less.
- a polarizing plate 10 having a protective film 15 between the polarizing film 14 and the adhesive 16.
- the polarizing film 14 is usually a step of uniaxially stretching a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, and a dichroic dye adsorbed.
- the polyvinyl alcohol-based resin film is produced through a step of crosslinking with a boric acid aqueous solution and a step of washing with water after the crosslinking treatment with the boric acid aqueous solution.
- the polyvinyl alcohol resin can be produced by saponifying a polyvinyl acetate resin.
- the polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate.
- Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.
- the degree of saponification of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more.
- the polyvinyl alcohol resin may be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used.
- the degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.
- a film obtained by forming such a polyvinyl alcohol resin is used as an original film of a polarizing film.
- the method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method.
- the film thickness of the polyvinyl alcohol resin raw film is, for example, about 10 to 100 ⁇ m, preferably about 10 to 50 ⁇ m.
- Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing.
- the uniaxial stretching may be performed before boric acid treatment or during boric acid treatment.
- uniaxial stretching can also be performed in a plurality of stages shown here.
- a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted.
- Uniaxial stretching may be performed by dry stretching in which stretching is performed in the air, or may be performed by wet stretching in which a polyvinyl alcohol-based resin film is stretched using a solvent such as water. The draw ratio is usually about 3 to 8 times.
- the dyeing of the polyvinyl alcohol resin film with the dichroic dye can be performed, for example, by a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye.
- a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye Specifically, iodine or a dichroic organic dye is used as the dichroic dye.
- iodine When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed.
- the content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. It is.
- the temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C.
- the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.
- a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed.
- the content of the dichroic organic dye in this aqueous solution is usually about 1 ⁇ 10 ⁇ 4 to 10 parts by weight, preferably 1 ⁇ 10 ⁇ 3 to 1 part by weight per 100 parts by weight of water.
- This aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant.
- the temperature of the aqueous dichroic organic dye solution used for dyeing is usually about 20 to 80 ° C.
- the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.
- the boric acid treatment after dyeing with the dichroic dye can be performed by a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution.
- the boric acid content in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water.
- the boric acid-containing aqueous solution preferably contains potassium iodide.
- the content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water.
- the immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds.
- the temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.
- the polyvinyl alcohol resin film after the boric acid treatment is usually washed with water.
- the water washing treatment can be performed, for example, by a method of immersing a boric acid-treated polyvinyl alcohol resin film in water.
- the temperature of water in the water washing treatment is usually about 5 to 40 ° C.
- the immersion time is usually about 1 to 120 seconds.
- a drying process is performed to obtain a polarizing film.
- the drying process can be performed using a hot air dryer or a far infrared heater.
- the temperature for the drying treatment is usually about 30 to 100 ° C., preferably 50 to 80 ° C.
- the drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.
- the moisture content in the polarizing film is reduced to a practical level.
- the water content is usually about 5 to 20% by weight, preferably 8 to 15% by weight.
- the moisture content is less than 5% by weight, the polarizing film loses its flexibility, and may be damaged or broken after drying. On the other hand, if the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.
- the polarizing film 14 in which the dichroic dye is adsorbed and oriented on the polyvinyl alcohol-based resin film can be produced.
- the thickness of the polarizing film 14 is 15 ⁇ m or less.
- a polarizing film is used.
- the thickness of the polarizing film 14 is preferably 12 ⁇ m or less.
- the thickness of the polarizing film is usually 3 ⁇ m or more in that good optical properties can be imparted.
- the optical film 11 is preferably composed of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding properties and the like.
- polyolefin resin such as chain polyolefin resin (polypropylene resin, etc.), cyclic polyolefin resin (norbornene resin, etc.); cellulose resin such as cellulose ester resin, such as cellulose triacetate and cellulose diacetate; Polyester resins; polycarbonate resins; (meth) acrylic resins; polystyrene resins; or mixtures and copolymers thereof.
- the optical film 11 has the following formula: (1) 100 nm ⁇ R e (590) ⁇ 180 nm, (2) 0.5 ⁇ R th (590) / R e (590) ⁇ 0.8, (3) 0.85 ⁇ R e (450) / R e (550) ⁇ 1.00, and (4) 1.00 ⁇ R e (630) / R e (550) ⁇ 1.1 It is preferable that the film satisfies the above.
- R e (590), R e (450), R e (550), and R e (630) represent in-plane retardation values at measurement wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, respectively, and R th ( 590) represents a thickness direction retardation value at a measurement wavelength of 590 nm.
- the screen is viewed from various directions (azimuth angle and polar angle) through polarized sunglasses.
- the color change at the time can be effectively suppressed, and the visibility of the liquid crystal display can be improved.
- the color change may be insufficiently suppressed.
- R e (590) in formula (1) is preferably 105 to 170 nm
- R th (590) / R e (590) in formula (2) is 0.6 to 0.75
- R e (450) / R e (550) in the formula (3) is preferably 0.86 to 0.98
- R e in the formula (4) is preferable.
- (630) / R e (550) is preferably 1.01 to 1.06.
- the optical film 11 is a kind of retardation film having a function of converting linearly polarized light emitted from the polarizing film 14 toward the optical film 11 into elliptically polarized light (including a case of circularly polarized light) and emitting the polarized light,
- the angle between the absorption axis of the polarizing film and the slow axis of the optical film is laminated so as to be about 45 ° or about 135 °. If the formed angle is outside this range, the function of converting linearly polarized light into elliptically polarized light and emitting it cannot be obtained, and as a result, the suppression of the color change may be insufficient.
- the angle formed is preferably 35 to 55 ° or 125 to 145 °, more preferably 40 to 50 ° or 130 to 140 °.
- the film 11 preferably includes a cyclic polyolefin-based resin, a polycarbonate-based resin, a cellulose-based resin, a polyester-based resin, a (meth) acrylic resin, or two or more thereof, and the resin component is selected from one or two or more. More preferably, it consists of.
- chain polyolefin resin examples include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.
- Cyclic polyolefin-based resin is a general term for resins that are polymerized using cyclic olefins as polymerization units.
- Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof.
- norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.
- the cellulose ester resin is an ester of cellulose and a fatty acid.
- Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate.
- these copolymers and those in which a part of the hydroxyl group is modified with other substituents can also be used.
- cellulose triacetate triacetyl cellulose: TAC is particularly preferable.
- the polyester-based resin is a resin having an ester bond, and is generally made of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol.
- a polyvalent carboxylic acid or a derivative thereof a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate.
- a divalent diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.
- polyester resin examples include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, and polycyclohexanedimethyl naphthalate.
- Polycarbonate resin is made of a polymer in which monomer units are bonded via a carbonate group.
- the polycarbonate-based resin may be a resin called a modified polycarbonate having a modified polymer skeleton, a copolymer polycarbonate, or the like.
- the (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer.
- Specific examples of the (meth) acrylic resin include, for example, poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylate ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer with the compound (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.).
- a polymer based on a poly (meth) acrylic acid C 1-6 alkyl ester such as poly (meth) acrylic acid methyl is used, and more preferably methyl methacrylate is used as a main component (50 to 100). % Methyl methacrylate-based resin is used.
- the optical film 11 can be produced by stretching a film containing the thermoplastic resin.
- the stretching treatment include uniaxial stretching and biaxial stretching.
- the stretching direction include a machine flow direction (MD) of an unstretched film, a direction perpendicular to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD).
- MD machine flow direction
- MD machine flow direction
- MD direction perpendicular to the machine flow direction
- MD direction oblique to the machine flow direction
- Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.
- the stretching process for example, two or more pairs of nip rolls with increased peripheral speed on the outlet side are used to stretch in the longitudinal direction (machine flow direction: MD), or the both ends of the unstretched film are gripped with a chuck and machine flow is performed. It can be performed by spreading in a direction (TD) orthogonal to the direction.
- the retardation value and the wavelength dispersion can be controlled within the ranges of the above formulas (1) and (2) by adjusting the thickness of the film or adjusting the draw ratio.
- the chromatic dispersion value can be controlled within the range of the above formulas (3) to (4) by adding a chromatic dispersion adjusting agent to the resin.
- the thickness of the optical film 11 is not particularly limited as long as the above formulas (1) to (4) are satisfied, but from the viewpoint of thinning the polarizing plate, it is preferably 90 ⁇ m or less, more preferably 60 ⁇ m or less. From the viewpoint, it is preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more.
- the ratio of the thickness of the stretched optical film 11 to the thickness of the polarizing film 14 is 1.5 or more. Even if it is a case where it is three or more, the fall of a polarization degree can be suppressed effectively. Usually, the ratio of the thickness of the stretched optical film 11 to the thickness of the polarizing film 14 is 10 or less.
- the optical film 11 can contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.
- additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.
- a coating layer (surface treatment layer 20) can be provided on the outer surface of the optical film 11 in order to impart desired surface optical properties or other characteristics.
- Specific examples of the coating layer include a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer.
- the method for forming the coating layer is not particularly limited, and a known method can be used.
- the protective film 15 is preferably made of a material having excellent transparency, mechanical strength, thermal stability, moisture shielding properties, and the like.
- the protective film 15 preferably contains a cellulose resin, a polyolefin resin, or an acrylic resin because the retardation value is easily controlled and easily available.
- the polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin.
- the same materials as those used in the optical film can be used.
- a method for forming a film from the resin as described above a method corresponding to each resin may be appropriately selected.
- the above-described solvent casting method, melt extrusion method, or the like can be employed.
- the melt extrusion method is preferably employed from the viewpoint of productivity.
- a cellulose resin is generally formed into a film by a solvent casting method.
- the transparent protective film When the liquid crystal cell is in an in-plane switching (IPS) mode, the transparent protective film has a retardation value Rth in the thickness direction of ⁇ in order not to impair the wide viewing angle characteristics inherent in the IPS mode liquid crystal cell. It is preferably in the range of 10 to 10 nm.
- Examples of the method for controlling the retardation value Rth in the thickness direction of the transparent protective film within the range of ⁇ 10 to 10 nm include a method for minimizing the distortion remaining in the plane and in the thickness direction as much as possible.
- a method for relaxing residual shrinkage strain in the plane and in the thickness direction generated when the cast resin solution is dried by heat treatment can be employed.
- the melt extrusion method the distance from the die to the cooling drum is reduced as much as possible in order to prevent the resin film from being drawn from the die and cooled, and the extrusion amount and the rotation speed of the cooling drum are reduced.
- a method of controlling the film so that the film is not stretched can be employed.
- the method of relieving the distortion which remains in the obtained film by heat processing similarly to the solvent casting method is also employable.
- the bonding between the polarizing film and the optical film and the bonding between the polarizing film and the protective film can be performed with an adhesive or a pressure-sensitive adhesive.
- the adhesive layer that bonds the polarizing film and the optical film and the adhesive layer that bonds the polarizing film and the protective film can have a thickness of about 0.01 to 30 ⁇ m, preferably 0.01. It is ⁇ 10 ⁇ m, more preferably 0.05 to 5 ⁇ m. If the thickness of the adhesive layer is within this range, the polarizing film and the optical film to be laminated and the protective film and the polarizing film are not floated or peeled off, and an adhesive force having no practical problem can be obtained.
- the pressure-sensitive adhesive layer can have a thickness of about 5 to 50 ⁇ m, preferably 5 to 30 ⁇ m, more preferably 10 to 25 ⁇ m.
- the polarizing film and the optical film are bonded and the polarizing film and the protective film are bonded, it is also useful to perform a saponification treatment, a corona treatment, a plasma treatment or the like on the polarizing film, the optical film, or the protective film in advance.
- an appropriate adhesive can be used as appropriate according to the type and purpose of the adherend, and an anchor coating agent can be used as necessary.
- the adhesive include a solvent-type adhesive, an emulsion-type adhesive, a pressure-sensitive adhesive, a rewet-adhesive, a polycondensation-type adhesive, a solventless-type adhesive, a film-type adhesive, and a hot-melt-type adhesive. Can be mentioned.
- an aqueous adhesive that is, an adhesive component in which the adhesive component is dissolved or dispersed in water.
- adhesive components that can be dissolved in water include polyvinyl alcohol resins.
- An example of an adhesive component that can be dispersed in water is a urethane resin having a hydrophilic group.
- the water-based adhesive can be prepared by mixing such an adhesive component with water together with an additional additive added as necessary.
- examples of commercially available polyvinyl alcohol resins that can be used as water-based adhesives include “KL-318”, which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co., Ltd.
- the water-based adhesive can contain a crosslinking agent as necessary.
- the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, and polyvalent metal salts.
- an aldehyde compound such as glyoxal, a methylol compound such as methylol melamine, a water-soluble epoxy resin, or the like is preferably used as a crosslinking agent.
- the water-soluble epoxy resin is, for example, a polyamide obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a dicarboxylic acid such as adipic acid. It can be an epoxy resin.
- a commercially available water-soluble epoxy resin is “SUMIREZ RESIN (registered trademark) 650 (30)” sold by Taoka Kogyo Co., Ltd.
- a polarizing plate can be obtained by applying a water-based adhesive to the polarizing film and / or the adhesive surface of the optical film or protective film bonded thereto, and bonding them together, followed by drying treatment. Prior to adhesion, it is also effective to subject the protective film to easy adhesion treatment such as saponification treatment, corona discharge treatment, plasma treatment, or primer treatment to enhance wettability.
- the drying temperature can be about 50 to 100 ° C., for example. After drying treatment, curing at a temperature slightly higher than room temperature, for example, at a temperature of about 30 to 50 ° C. for about 1 to 10 days is preferable in order to further increase the adhesive strength.
- Another preferable adhesive is a curable adhesive composition containing an epoxy compound that is cured by irradiation with active energy rays or heating.
- the curable epoxy compound has at least two epoxy groups in the molecule.
- the adhesive between the polarizing film and the protective film is performed by irradiating the applied layer of the adhesive composition with an active energy ray or applying heat to the adhesive composition, and a curable epoxy compound contained in the adhesive. It can carry out by the method of hardening. Curing of the epoxy compound is generally performed by cationic polymerization of the epoxy compound. Further, from the viewpoint of productivity, this curing is preferably performed by irradiation with active energy rays.
- the epoxy compound contained in the curable adhesive composition is preferably one that does not contain an aromatic ring in the molecule.
- epoxy compounds that do not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds.
- the epoxy compound suitably used in such a curable adhesive composition is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-245925, but the outline is also described here.
- the hydrogenated epoxy compound is a glycidyl compound obtained by subjecting an aromatic polyhydroxy compound, which is a raw material of an aromatic epoxy compound, to a nuclear hydrogenated polyhydroxy compound obtained by selectively performing a nuclear hydrogenation reaction in the presence of a catalyst and under pressure. It can be etherified.
- aromatic polyhydroxy compound that is a raw material of the aromatic epoxy compound include bisphenols such as bisphenol A, bisphenol F, and bisphenol S; phenol novolac resin, cresol novolac resin, and hydroxybenzaldehyde phenol novolac resin And novolak type resins; polyhydroxy compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol.
- a glycidyl ether can be obtained by performing a nuclear hydrogenation reaction on such an aromatic polyhydroxy compound and reacting the resulting hydrogenated polyhydroxy compound with epichlorohydrin.
- Suitable hydrogenated epoxy compounds include hydrogenated glycidyl ether of bisphenol A.
- the alicyclic epoxy compound is a compound having at least one epoxy group bonded to the alicyclic ring in the molecule.
- the “epoxy group bonded to the alicyclic ring” means a bridged oxygen atom —O— in the structure represented by the following formula, wherein m is an integer of 2 to 5.
- a compound in which one or a plurality of hydrogen atoms in (CH 2 ) m in this formula are bonded to another chemical structure can be an alicyclic epoxy compound.
- One or more hydrogen atoms in (CH 2 ) m forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group.
- Specific examples of the alicyclic epoxy compound are listed below. Here, the compound names are given first, and then the chemical formulas corresponding to each are shown, and the same reference numerals are given to the compound names and the chemical formulas corresponding thereto.
- the aliphatic epoxy compound can be an aliphatic polyhydric alcohol or a polyglycidyl ether of an alkylene oxide adduct thereof. More specifically, diglycidyl ether of propylene glycol; diglycidyl ether of 1,4-butanediol; diglycidyl ether of 1,6-hexanediol; triglycidyl ether of glycerin; triglycidyl ether of trimethylolpropane; ethylene Polyglycidyl ether of polyether polyol (for example, diglycidyl ether of polyethylene glycol) obtained by adding alkylene oxide (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohol such as glycol, propylene glycol, and glycerin Can be mentioned.
- alkylene oxide ethylene oxide or propylene oxide
- the epoxy compound may be used alone or in combination of two or more.
- the epoxy compound preferably includes an alicyclic epoxy compound having at least one epoxy group bonded to the alicyclic ring in the molecule.
- the epoxy compound used in the curable adhesive composition usually has an epoxy equivalent in the range of 30 to 3,000 g / equivalent, and this epoxy equivalent is preferably in the range of 50 to 1,500 g / equivalent.
- an epoxy compound having an epoxy equivalent of less than 30 g / equivalent is used, there is a possibility that the flexibility of the polarizing plate after curing is lowered or the adhesive strength is lowered.
- compatibility with other components contained in the adhesive composition may be reduced.
- cationic polymerization is preferably used as the curing reaction of the epoxy compound.
- the cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation or heating with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates an epoxy group polymerization reaction.
- active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams
- the cationic polymerization initiator is provided with latency.
- a cationic polymerization initiator that generates a cationic species or Lewis acid by irradiation of active energy rays and initiates a polymerization reaction of an epoxy group is referred to as a “photo cationic polymerization initiator”, and generates a cationic species or a Lewis acid by heat.
- the cationic polymerization initiator that initiates the polymerization reaction of the epoxy group is referred to as “thermal cationic polymerization initiator”.
- the method of curing the adhesive composition by irradiation with active energy rays using a cationic photopolymerization initiator enables curing at normal temperature and humidity, reducing the need to consider the distortion due to heat resistance or expansion of the polarizing film. And it is advantageous in that the protective film and the polarizing film can be satisfactorily bonded.
- the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy compound.
- the photocationic polymerization initiator examples include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes.
- the compounding amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more and preferably 15 parts by weight or less based on 100 parts by weight of the epoxy compound. If the amount of the cationic photopolymerization initiator is less than 0.5 parts by weight based on 100 parts by weight of the epoxy compound, the curing becomes insufficient, and the mechanical strength and adhesive strength of the cured product tend to be reduced.
- the blending amount of the cationic photopolymerization initiator exceeds 20 parts by weight with respect to 100 parts by weight of the epoxy compound, the ionic substance in the cured product increases, resulting in an increase in the hygroscopic property of the cured product and durability performance. May be reduced.
- the curable adhesive composition may further contain a photosensitizer as necessary.
- a photosensitizer By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and adhesive strength of the cured product can be improved.
- the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes.
- the amount is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the curable adhesive composition.
- a sensitizing aid such as a naphthoquinone derivative may be used for improving the curing rate.
- thermal cationic polymerization initiator examples include benzylsulfonium salt, thiophenium salt, thioranium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide.
- the curable adhesive composition containing the epoxy compound is preferably cured by photocationic polymerization as described above, but can be cured by thermal cationic polymerization in the presence of the above-mentioned thermal cationic polymerization initiator. Cationic polymerization and thermal cationic polymerization can be used in combination. When photocationic polymerization and thermal cationic polymerization are used in combination, the curable adhesive composition preferably contains both a photocationic polymerization initiator and a thermal cationic polymerization initiator.
- the curable adhesive composition may further contain a compound that promotes cationic polymerization, such as an oxetane compound or a polyol compound.
- An oxetane compound is a compound having a 4-membered ring ether in the molecule.
- the polyol compound may be alkylene glycol including ethylene glycol, hexamethylene glycol, polyethylene glycol or the like, or an oligomer thereof, polyester polyol, polycaprolactone polyol, polycarbonate polyol and the like.
- the amount is usually 50% by weight or less, preferably 30% by weight or less in the curable adhesive composition.
- the adhesive may be a composition containing a radically polymerizable (meth) acrylic compound.
- the (meth) acrylic compound is a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule; obtained by reacting two or more functional group-containing compounds, and at least two in the molecule.
- (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having (meth) acryloyloxy groups.
- the adhesive preferably contains a radical photopolymerization initiator.
- the photo radical polymerization initiator include acetophenone initiator, benzophenone initiator, benzoin ether initiator, thioxanthone initiator, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone and the like.
- ion trapping agent examples include inorganic compounds including powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed systems thereof.
- antioxidant examples include And hindered phenolic antioxidants.
- the uncured adhesive layer can be cured to bond the polarizing film and the protective film (or optical film).
- an adhesive coating method for example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be adopted.
- This curable adhesive composition can basically be used as a solvent-free adhesive that does not substantially contain a solvent, but each coating system has an optimum viscosity range, so that the viscosity is adjusted.
- a solvent may be contained.
- the solvent is preferably an organic solvent that dissolves each component including an epoxy compound well without degrading the optical performance of the polarizing film.
- hydrocarbons typified by toluene, typified by ethyl acetate, etc. Esters can be used.
- the adhesive composition When the adhesive composition is cured by irradiation with active energy rays, the above-mentioned various types of active energy rays can be used, but since the handling is easy and the amount of irradiation light is easy to control, ultraviolet rays are not emitted. Preferably used. Active energy rays such as ultraviolet irradiation intensity and irradiation dose do not affect various optical performance including polarization degree of polarizing film, and various optical performance including transparency and retardation characteristics of protective film. Therefore, it is determined as appropriate so as to maintain an appropriate productivity.
- active energy rays such as ultraviolet irradiation intensity and irradiation dose do not affect various optical performance including polarization degree of polarizing film, and various optical performance including transparency and retardation characteristics of protective film. Therefore, it is determined as appropriate so as to maintain an appropriate productivity.
- the adhesive composition When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, heating is performed at a temperature higher than the temperature at which the thermal cationic polymerization initiator compounded in the curable adhesive composition generates cationic species and Lewis acid, and the specific heating temperature is, for example, about 50 to 200 ° C. .
- the pressure-sensitive adhesive layer 16 formed on the surface of the protective film 15 opposite to the bonding surface with the polarizing film 14 is a pressure-sensitive adhesive layer for bonding the polarizing plate to the liquid crystal cell, and is optically transparent. It has only to be excellent in adhesive properties including moderate wettability, cohesiveness, adhesiveness, etc., but more preferable in durability and the like.
- a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic resin is preferable.
- the acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin mainly composed of alkyl acrylate such as butyl acrylate, ethyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate.
- This acrylic resin is usually copolymerized with a polar monomer.
- the polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group.
- the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group, and the polar functional group.
- the group can be a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like.
- polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, N-dimethylaminoethyl ( Examples include meth) acrylate and glycidyl (meth) acrylate.
- the acrylic pressure-sensitive adhesive usually contains a crosslinking agent together with the acrylic resin.
- a crosslinking agent is an isocyanate compound having at least two isocyanato groups (—NCO) in the molecule.
- additives may be further added to the adhesive.
- Suitable additives include silane coupling agents and antistatic agents.
- a silane coupling agent is effective in increasing the adhesive strength with glass.
- Antistatic agents are effective in reducing or preventing the generation of static electricity.
- the pressure-sensitive adhesive layer 16 is prepared by preparing a pressure-sensitive adhesive composition in which the above-mentioned pressure-sensitive adhesive component is dissolved in an organic solvent, and directly on either or both of the bonding surfaces (polarizing film or protective film) on which the pressure-sensitive adhesive layer is bonded. Apply the above-mentioned pressure-sensitive adhesive composition to the release treatment surface of the base film made of a resin film that has been subjected to a release treatment by applying and removing the solvent by drying, and remove the solvent to remove the solvent. It can be formed by making it into an agent layer, sticking it to any of the bonding surfaces (polarizing film or protective film), and transferring the pressure-sensitive adhesive layer.
- the pressure-sensitive adhesive layer 16 is formed by the former direct coating method, a resin film (also called a separator) that has been subjected to a release treatment is bonded to the surface, and the pressure-sensitive adhesive layer surface is temporarily protected until use. It is customary.
- the latter transfer method is often employed from the viewpoint of the handleability of the pressure-sensitive adhesive composition that is an organic solvent solution.
- the release-treated base film used for forming the pressure-sensitive adhesive layer first is used. It is also advantageous in that it can be used as a separator after being attached to a polarizing plate.
- the storage elastic modulus of the pressure-sensitive adhesive at 80 ° C. is preferably 5 MPa or less. More preferably, it is 1 MPa or less.
- the protective film 15 and the pressure-sensitive adhesive layer 16 are bonded together, it is also useful to perform corona treatment, plasma treatment or the like on the surface where the protective film 15 and the pressure-sensitive adhesive layer 16 are bonded together.
- the polarizing plate 10 is obtained by bonding together the optical film 11, the polarizing film 14, and the protective film 15 with a roll to roll through an adhesive bond layer. Furthermore, a polarizing plate with an adhesive is obtained by forming the adhesive layer 16 on the protective film 15. The polarizing plate with the pressure-sensitive adhesive can be bonded to the liquid crystal cell via the pressure-sensitive adhesive layer 16.
- the manufacturing method of this invention includes the process of heat-processing the optical film 11 before bonding with the optical film 11 and the polarizing film 14.
- the film may be heated when the stretching process is performed.
- the heating process in the manufacturing method of the present invention is different from the heating in the stretching process. Heat treatment is performed on the completed optical film. That is, the optical film is not substantially stretched in the step of heat treatment in the production method of the present invention.
- the term “not substantially stretched” means that the draw ratio is 1.1 times or less, preferably 1.05 times or less.
- the heat treatment step is preferably performed within 3 days for bonding the optical film 11 and the polarizing film 14, more preferably within 24 hours, and even more preferably within 60 minutes.
- the heat treatment step is preferably performed within 3 days for bonding the optical film 11 and the polarizing film 14, more preferably within 24 hours, and even more preferably within 60 minutes.
- the heat treatment is preferably performed at a temperature of Tg-60 ° C. to Tg ° C. with respect to the glass transition temperature (Tg) of the optical film 11, and is preferably performed at a temperature of Tg-30 ° C. to Tg-5 ° C. More preferred. More preferably, it is Tg-20 ° C to Tg-5 ° C.
- various methods such as a method of performing a heat treatment in an oven in advance or a method of heating in a thermal drum before being bonded to a polarizing film can be selected.
- the polarizing plate thus produced has a dimensional change rate D1 in the direction of 45 ° with respect to the absorption axis of the polarizing film and a dimensional change rate D2 in the direction of 135 ° with respect to the absorption axis of the polarizing film when left for 100 hours in an environment of 85 ° C. Both can also be made 0.25% or less, and the polarization degree fall at the time of a heat test can be suppressed.
- Measurement of thickness Measurement was performed using a digital micrometer “MH-15M” manufactured by Nikon Corporation.
- the polarizing plate is cut into a size of (100 mm in the direction of 45 °) ⁇ (100 mm in the direction of 135 ° C.) with respect to the absorption axis of the polarizing film, and is left still for one day in an environment of temperature 23 ° C. and humidity 55%. Then, the dimension in the 45 ° direction (L0 (45)) with respect to the absorption axis of the polarizing film and the dimension in the 135 ° direction with respect to the absorption axis of the polarizing film (L0 (135)) are measured. Next, the polarizing plate is allowed to stand in an environment of 85 ° C.
- Adhesive A A sheet-like adhesive having a thickness of 25 ⁇ m [“P-3132” manufactured by Lintec Corporation] was prepared.
- Example 1 The optical film A was placed in an oven at 150 ° C. for 3 minutes and subjected to heat treatment. Next, the optical film A subjected to the heat treatment was subjected to a fighting treatment. That is, the heat treatment temperature was Tg-50 ° C.
- Corona treatment was performed on one side of the protective film.
- the corona-treated surface of the protective film and the polarizing film were bonded together with the polarizing film and the optical film A with an aqueous adhesive to obtain a polarizing plate.
- the time from the heat treatment to the optical film A to the bonding to the polarizing film was 30 minutes. Under the present circumstances, it bonded so that the absorption axis of a polarizing plate and the slow axis of the optical film A might be 45 degrees.
- the adhesive A was laminated
- the polarization degree of the polarizing plate was 99.994%.
- the polarizing plate thus prepared was cut into a 40 mm square, and bonded to Corning Eagle XG to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put in an oven at 105 ° C. for 30 minutes.
- the degree of polarization after the heat test was 99.972%.
- the polarizing plate was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put into an oven at 85 ° C. for 500 hours.
- the degree of polarization after the heat test was 99.975%.
- Example 2 The optical film A was put into an oven having an atmospheric temperature of 200 ° C. for 3 minutes and subjected to heat treatment. That is, the heat treatment temperature was equal to Tg. Next, the optical film A subjected to the heat treatment was subjected to a fighting treatment. Others were the same methods as in Example 1 to obtain a polarizing plate with an adhesive having a layer structure of optical film A / polarizing film / protective film / adhesive layer A. The polarization degree of this polarizing plate was 99.995%.
- the polarizing plate thus prepared was cut into a 40 mm square, and bonded to Corning Eagle XG to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put in an oven at 105 ° C. for 30 minutes.
- the degree of polarization after the heat test was 99.980%.
- the polarizing plate was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put into an oven at 85 ° C. for 500 hours.
- the degree of polarization after the heat test was 99.981%.
- Example 3 The optical film B was placed in an oven at 120 ° C. for 3 minutes and subjected to heat treatment. That is, the heat treatment temperature was equal to Tg. Next, the optical film B subjected to the heat treatment was subjected to corona treatment. Except that this optical film B was used in place of the optical film A, a polarizing plate with a pressure-sensitive adhesive comprising the optical film B / polarizing film / protective film / pressure-sensitive adhesive layer A in the same manner as in Example 1. Got. The polarization degree of this polarizing plate was 99.993%.
- the polarizing plate thus prepared was cut into a 40 mm square, and bonded to Corning Eagle XG to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put in an oven at 105 ° C. for 30 minutes.
- the degree of polarization after the heat test was 99.985%.
- the polarizing plate was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put into an oven at 85 ° C. for 500 hours.
- the degree of polarization after the heat test was 99.987%.
- the pressure-sensitive adhesive A was laminated on the protective film B side of the obtained polarizing plate to obtain a polarizing plate with a pressure-sensitive adhesive composed of the optical film A / polarizing film / protective film / pressure-sensitive adhesive layer A.
- the polarization degree of the polarizing plate was 99.995%.
- the polarizing plate thus prepared was cut into a 40 mm square, and bonded to Corning Eagle XG to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put in an oven at 105 ° C. for 30 minutes.
- the degree of polarization after the heat test was 99.954%.
- the polarizing plate was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning to prepare a sample for heat resistance evaluation.
- the sample thus prepared was put into an oven at 85 ° C. for 500 hours.
- the degree of polarization after the heat test was 99.954%.
- the polarizing plates of Examples 1 to 3 where the heat treatment was performed on the optical film had a smaller decrease in the degree of polarization after the heat resistance test than the polarizing plate of Comparative Example 1 where the heat treatment was not performed. It was.
- the present invention is useful because it can provide a method for producing a polarizing plate that can suppress a decrease in the degree of polarization due to the shift of the absorption axis of the polarizing film caused by the dimensional change of the optical film during the heat resistance test.
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Abstract
Description
前記光学フィルムを前記偏光フィルムへ貼合する前に、前記光学フィルムを加熱処理する工程を有する偏光板の製造方法。
[2]前記加熱処理が、前記光学フィルムのガラス転移温度(Tg)に対して、Tg-30℃~Tg-5℃の温度で行われる[1]に記載の偏光板の製造方法。
[3]前記光学フィルムは、環状ポリオレフィン系樹脂、ポリカーボネート系樹脂、セルロース系樹脂、ポリエステル系樹脂又は(メタ)アクリル系樹脂からなる群から選ばれる少なくとも一種を含む、[1]または[2]に記載の偏光板の製造方法。
[4]前記偏光フィルムと前記粘着剤層との間にさらに保護フィルムを有する[1]~[3]のいずれかに記載の偏光板の製造方法。
偏光フィルム14は、通常、ポリビニルアルコール系樹脂フィルムを一軸延伸する工程、ポリビニルアルコール系樹脂フィルムを二色性色素で染色することにより二色性色素を吸着させる工程、二色性色素が吸着されたポリビニルアルコール系樹脂フィルムをホウ酸水溶液で処理して架橋させる工程、及びホウ酸水溶液による架橋処理後に水洗する工程を経て、製造される。
この水溶液におけるヨウ素の含有量は、水100重量部あたり、通常0.01~1重量部程度であり、ヨウ化カリウムの含有量は、水100重量部あたり、通常0.5~20重量部程度である。染色に用いる水溶液の温度は、通常20~40℃程度である。また、この水溶液への浸漬時間(染色時間)は、通常20~1,800秒程度である。
本発明に用いる偏光板において、光学フィルム11としては、特に、透明性、機械的強度、熱安定性、水分遮蔽性などに優れる材料で構成することが好ましい。例えば、鎖状ポリオレフィン系樹脂(ポリプロピレン系樹脂等)、環状ポリオレフィン系樹脂(ノルボルネン系樹脂等)のようなポリオレフィン系樹脂;セルローストリアセテート、セルロースジアセテートのようなセルロースエステル系樹脂等のセルロース系樹脂;ポリエステル系樹脂;ポリカーボネート系樹脂;(メタ)アクリル系樹脂;ポリスチレン系樹脂;又はこれらの混合物、共重合物等を挙げることができる。
(1)100nm≦Re(590)≦180nm、
(2)0.5<Rth(590)/Re(590)≦0.8、
(3)0.85≦Re(450)/Re(550)<1.00、及び
(4)1.00<Re(630)/Re(550)≦1.1
を満たすフィルムであることが好ましい。式中、Re(590)、Re(450)、Re(550)、Re(630)はそれぞれ、測定波長590nm、450nm、550nm、630nmにおける面内位相差値を表し、Rth(590)は測定波長590nmにおける厚み方向位相差値を表す。これらの面内位相差値及び厚み方向位相差値は、温度23℃、相対湿度55%の環境下にて測定される。
Re=(nx-ny)×d
Rth=[{(nx+ny)/2}-nz]×d
で定義される。
保護フィルム15としては、特に、透明性、機械的強度、熱安定性、水分遮蔽性などに優れる材料で構成することが好ましい。保護フィルム15としては、レターデーション値の制御が容易で、入手も容易であることから、セルロース系樹脂、ポリオレフィン系樹脂又はアクリル系樹脂を含むことが好ましい。ここでいうポリオレフィン系樹脂は、鎖状ポリオレフィン系樹脂及び環状ポリオレフィン系樹脂を包含する。
偏光フィルムと光学フィルムとの貼合および偏光フィルムと保護フィルムとの貼合は、接着剤または粘着剤により貼合することができる。
偏光フィルムと光学フィルムとを貼合する接着剤層および偏光フィルムと保護フィルムとを貼合する接着剤層は、その厚さを0.01~30μm程度とすることができ、好ましくは0.01~10μm、さらに好ましくは0.05~5μmである。接着剤層の厚さがこの範囲にあれば、積層される偏光フィルムと光学フィルムおよび保護フィルムと偏光フィルムとの間に浮きや剥がれを生じず、実用上問題のない接着力が得られる。粘着剤層を使用する場合、粘着剤層は、その厚さを5~50μm程度とすることができ、好ましくは5~30μm、さらに好ましくは10~25μmである。
ここで水溶性エポキシ樹脂は、例えば、ジエチレントリアミンやトリエチレンテトラミンのようなポリアルキレンポリアミンとアジピン酸のようなジカルボン酸との反応物であるポリアミドポリアミンに、エピクロロヒドリンを反応させて得られるポリアミドエポキシ樹脂であることができる。水溶性エポキシ樹脂の市販品の例を挙げると、田岡工業株式会社から販売されている“スミレーズレジン(登録商標) 650(30)”などがある。
B:3,4-エポキシ-6-メチルシクロヘキシルメチル 3,4-エポキシ-6-メチルシクロヘキサンカルボキシレート、
C:エチレンビス(3,4-エポキシシクロヘキサンカルボキシレート)、
D:ビス(3,4-エポキシシクロヘキシルメチル) アジペート、
E:ビス(3,4-エポキシ-6-メチルシクロヘキシルメチル) アジペート、
F:ジエチレングリコールビス(3,4-エポキシシクロヘキシルメチルエーテル)、 G:エチレングリコールビス(3,4-エポキシシクロヘキシルメチルエーテル)、
H:2,3,14,15-ジエポキシ-7,11,18,21-テトラオキサトリスピロ[5.2.2.5.2.2]ヘンイコサン、
I:3-(3,4-エポキシシクロヘキシル)-8,9-エポキシ-1,5-ジオキサスピロ[5.5]ウンデカン、
J:4-ビニルシクロヘキセンジオキサイド、
K:リモネンジオキサイド、
L:ビス(2,3-エポキシシクロペンチル)エーテル、
M:ジシクロペンタジエンジオキサイドなど。
光カチオン重合開始剤の配合量が、エポキシ化合物100重量部に対して0.5重量部を下回ると、硬化が不十分になり、硬化物の機械的強度や接着強度が低下する傾向にある。
一方、光カチオン重合開始剤の配合量が、エポキシ化合物100重量部に対して20重量部を超えると、硬化物中のイオン性物質が増加することで硬化物の吸湿性が高くなり、耐久性能が低下する可能性がある。
保護フィルム15における偏光フィルム14との貼合面とは反対側の面に形成される粘着剤層16は、偏光板を液晶セルに貼合するための粘着剤層であり、光学的な透明性に優れ、適度な濡れ性、凝集性、接着性などを包含する粘着特性に優れるものであればよいが、さらに耐久性などに優れるものが好ましい。具体的には、粘着剤層16を形成する粘着剤として、アクリル系樹脂を含有する粘着剤(アクリル系粘着剤)が好ましい。
架橋剤の代表例として、分子内に少なくとも2個のイソシアナト基(-NCO)を有するイソシアネート化合物を挙げることができる。
偏光板を製造する方法としては、特に制限されないが、例えば、光学フィルム11と偏光フィルム14と保護フィルム15とを接着剤層を介してロールツーロールで貼りあわせることで偏光板10が得られる。さらに粘着剤層16を保護フィルム15上に形成することで粘着剤付きの偏光板が得られる。粘着剤付きの偏光板は、粘着剤層16を介して液晶セルに貼合することができる。
株式会社ニコン製のデジタルマイクロメーター“MH-15M”を用いて測定した。
王子計測機器株式会社製の平行ニコル回転法を原理とする位相差計“KOBRA(登録商標)-WPR”を用い、23℃の温度において、所定の波長での面内レターデーション及び厚み方向レターデーションを測定した。
(3)偏光板の偏光度及び単体透過率の測定:
積分球付き分光光度計〔日本分光株式会社製の「V7100」、2度視野;C光源〕を用いて測定した。
85℃の環境下に100hr静置した時の偏光フィルムの吸収軸に対して45°の方向の偏光板の寸法変化率D1および偏光フィルムの吸収軸に対して135°の方向の偏光板の寸法変化率D2を測定する方法は、株式会社ニコン製の二次元測定器“NEXIV VMR-12072”を用いて、次の通り測定した。まず、偏光板を偏光フィルムの吸収軸に対して(45°の方向に100mm)×(135℃の方向に100mm)の大きさに裁断し、温度23℃湿度55%の環境下に1日静置し、偏光フィルムの吸収軸に対して45°方向の寸法(L0(45))および偏光フィルムの吸収軸と135°方向の寸法(L0(135))を測定する。次に偏光板を85℃の環境下に100時間静置し、高温環境下に静置した後の偏光フィルムの吸収軸と45°の方向の寸法(L1(45))および偏光フィルムの吸収軸と135°の方向の寸法(L1(135))を測定する。その結果をもとに式(5)及び(6)から寸法変化率D1(%)、D2(%)を求めた。
寸法変化率D1=
[(L0(45)-L1(45))/L0(45) ]×100 (5)寸法変化率D2=
[(L0(135)-L1(135))/L0(135) ]×100 (6)
厚み20μmのポリビニルアルコールフィルム(平均重合度約2400、ケン化度99.9モル%以上)を、乾式延伸により約4倍に一軸延伸し、さらに緊張状態を保ったまま、40℃の純水に40秒間浸漬した後、ヨウ素/ヨウ化カリウム/水の重量比が0.052/5.7/100の水溶液に28℃で30秒間浸漬して染色処理を行った。その後、ヨウ化カリウム/ホウ酸/水の重量比が11.0/6.2/100の水溶液に70℃で120秒間浸漬した。引き続き、8℃の純水で15秒間洗浄した後、300Nの張力で保持した状態で、60℃で50秒間、次いで75℃で20秒間乾燥して、ポリビニルアルコールフィルムにヨウ素が吸着配向している厚み7μmの吸収型偏光子を得た。
水100重量部に対し、カルボキシル基変性ポリビニルアルコール〔株式会社クラレから入手した商品名「KL-318」〕を3重量部溶解し、その水溶液に水溶性エポキシ樹脂であるポリアミドエポキシ系添加剤〔田岡化学工業株式会社から入手した商品名「スミレーズレジン(登録商標) 650(30)」、固形分濃度30重量%の水溶液〕を1.5重量部添加して、水系接着剤を調製した。
粘着剤A:厚み25μmのシート状粘着剤〔リンテック株式会社製の「P-3132」〕を用意した。
以下の保護フィルムを用意した。
保護フィルム:日本ゼオン株式会社製の環状ポリオレフィン系樹脂フィルム;ZF14-013(厚み13μm、波長590nmでの面内位相差値=0.5nm、波長590nmでの厚み方向位相差=3.3nm)
光学フィルムA:コニカミノルタ株式会社製のトリアセチルセルロースフィルム;KC4UGR-HC(厚み44μm、波長590nmでの面内位相差値=106nm、波長590nmでの厚み方向位相差=75nm、Rth(590)/Re(590)=0.71、Re(450)/Re(550)=0.96、Re(630)/Re(550)=1.02、ガラス転移温度=200℃)を準備した。
光学フィルムB:日本ゼオン株式会社製のシクロオレフィンポリマーフィルム;ZD12-099063-C1330UHD(厚み28μm、波長590nmでの面内位相差値=97nm、波長590nmでの厚み方向位相差=65nm、Rth(590)/Re(590)=0.67、Re(450)/Re(550)=1.01、Re(630)/Re(550)=0.99、ガラス転移温度=120℃)を準備した。
光学フィルムAを150℃のオーブンに3分間投入し、加熱処理を行った。次いで、加熱処理を行った光学フィルムAにケンカ処理を行った。すなわち、加熱処理温度は、Tg-50℃であった。
光学フィルムAに加熱処理をしてから、偏光フィルムに貼合するまでの時間は30分間であった。この際、偏光板の吸収軸と光学フィルムAの遅相軸が45°となるように貼合した。
さらに、得られた偏光板の保護フィルム側に粘着剤Aを積層し、光学フィルムA/偏光フィルム/保護フィルム/粘着剤層Aの層構成からなる粘着剤付き偏光板を得た。
偏光板の偏光度は、99.994%であった。
光学フィルムAを雰囲気温度が200℃のオーブンに3分間投入し、加熱処理を行った。すなわち、加熱処理温度は、Tgに等しかった。次いで、加熱処理を行った光学フィルムAにケンカ処理を行った。その他は実施例1と同様の方法で、光学フィルムA/偏光フィルム/保護フィルム/粘着剤層Aの層構成からなる粘着剤付き偏光板を得た。この偏光板の偏光度は99.995%であった。
光学フィルムBを120℃のオーブンに3分間投入し、加熱処理を行った。すなわち、加熱処理温度は、Tgに等しかった。次いで、加熱処理を行った光学フィルムBにコロナ処理を行った。この光学フィルムBを光学フィルムAの代わりに使用したこと以外は、実施例1と同様の方法により、光学フィルムB/偏光フィルム/保護フィルム/粘着剤層Aの層構成からなる粘着剤付き偏光板を得た。この偏光板の偏光度は99.993%であった。
保護フィルムの一方の面にコロナ処理を、光学フィルムAにケン化処理を行った。保護フィルムのコロナ処理面と偏光フィルムと光学フィルムAとを、この順に水系接着剤で接着し偏光板を得た。偏光フィルムと光学フィルムAとを貼合する前に、光学フィルムAへ加熱処理は行わなかった。得られた偏光板の吸収軸と光学フィルムの遅相軸は45°となるようにした。さらに、得られた偏光板の保護フィルムB側に粘着剤Aを積層し、光学フィルムA/偏光フィルム/保護フィルム/粘着剤層Aの層構成からなる粘着剤付き偏光板を得た。偏光板の偏光度は、99.995%であった。
11 光学フィルム
14 偏光フィルム
15 保護フィルム
16 粘着剤層
20 表面処理層
30 偏光フィルムの吸収軸
31 偏光フィルムの吸収軸に対して45°の方向
32 偏光フィルムの吸収軸に対して135°の方向
33 45°
34 135°
40 寸法変化率測定用の偏光板
Claims (4)
- 光学フィルム、偏光フィルムおよび粘着剤層をこの順に含み、前記偏光フィルムの厚みが15μm以下であって、前記偏光フィルムの吸収軸と前記光学フィルムの遅相軸とのなす角度が略45°又は略135°である偏光板の製造方法であって、
前記光学フィルムを前記偏光フィルムへ貼合する前に、前記光学フィルムを加熱処理する工程を有する偏光板の製造方法。 - 前記加熱処理が、前記光学フィルムのガラス転移温度(Tg)に対して、Tg-30℃~Tg-5℃の温度で行われる請求項1に記載の偏光板の製造方法。
- 前記光学フィルムは、環状ポリオレフィン系樹脂、ポリカーボネート系樹脂、セルロース系樹脂、ポリエステル系樹脂又は(メタ)アクリル系樹脂からなる群から選ばれる少なくとも一種を含む、請求項1または2に記載の偏光板の製造方法。
- 前記偏光フィルムと前記粘着剤層との間にさらに保護フィルムを有する請求項1~3のいずれかに記載の偏光板の製造方法。
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