WO2022107376A1 - Polarizing film and method for producing polarizing film - Google Patents

Polarizing film and method for producing polarizing film Download PDF

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Publication number
WO2022107376A1
WO2022107376A1 PCT/JP2021/023982 JP2021023982W WO2022107376A1 WO 2022107376 A1 WO2022107376 A1 WO 2022107376A1 JP 2021023982 W JP2021023982 W JP 2021023982W WO 2022107376 A1 WO2022107376 A1 WO 2022107376A1
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Prior art keywords
polarizing film
layer
film
resin
water
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PCT/JP2021/023982
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French (fr)
Japanese (ja)
Inventor
理 小島
拓弥 南原
周作 後藤
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日東電工株式会社
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Priority to CN202180078041.0A priority Critical patent/CN116670547A/en
Priority to KR1020237012544A priority patent/KR20230107792A/en
Publication of WO2022107376A1 publication Critical patent/WO2022107376A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/003—Light absorbing elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528—Polarisers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/8793—Arrangements for polarized light emission

Definitions

  • the present invention relates to a polarizing film and a method for manufacturing a polarizing film.
  • a liquid crystal display device which is a typical image display device, has polarizing films arranged on both sides of a liquid crystal cell due to its image forming method.
  • a display (OLED) equipped with an organic electroluminescence (EL) panel and a display (QLED) using a display panel using an inorganic light emitting material such as a quantum dot have been proposed.
  • These panels have a highly reflective metal layer, and are liable to cause problems such as external light reflection and background reflection. Therefore, it is known to prevent these problems by providing a circular polarizing plate having a polarizing film and a ⁇ / 4 plate on the visual recognition side.
  • a method for producing a polarizing film for example, a method has been proposed in which a laminate having a resin base material and a polyvinyl alcohol (PVA) -based resin layer is stretched and then dyed to obtain a polarizing film on the resin base material.
  • PVA polyvinyl alcohol
  • Patent Document 1 Since such a method can obtain a thin polarizing film, it is attracting attention as it can contribute to the thinning of image display devices in recent years. However, the thin polarizing film has a poor appearance and may not have sufficient display characteristics when used in an image display device.
  • the present invention has been made to solve the above problems, and a main object thereof is to provide a polarizing film which is excellent in appearance and can contribute to improvement of display characteristics of an image display device.
  • a polarizing film is provided.
  • This polarizing film is composed of a resin film containing iodine, has a thickness of 7 ⁇ m or less, and has a reflectance Rc of light having a wavelength of 400 nm in the absorption axis direction with respect to a reflectance Rc 680 of light having a wavelength of 680 nm in the absorption axis direction on the surface.
  • the ratio of 400 (Rc 400 / Rc 680 ) is greater than 1.
  • the surface Rc 680 is 5% or less.
  • the surface Rc 400 is 4.8% or higher.
  • the polarizing film has a gradient distribution region at the end on the front surface side, in which the amount of iodine increases from the front surface to the back surface. In one embodiment, in the polarizing film, the amount of iodine on the front surface side is smaller than the amount of iodine on the back surface side. In one embodiment, the polarizing film has a simple substance transmittance of 42.0% or more and a degree of polarization of 99.98% or more. According to another aspect of the present invention, there is provided a method for manufacturing the above-mentioned polarizing film. This production method comprises washing the surface of a resin film containing iodine and having a water content of 15% by weight or less with water.
  • the iodine concentration of the resin film is 5% by weight or more.
  • the resin film is a resin layer formed on a resin substrate.
  • the manufacturing method comprises stretching the resin layer in water at 67 ° C. or lower.
  • the manufacturing method comprises heating the resin layer with a heating roll.
  • a polarizing plate is provided. The polarizing plate has the polarizing film and a protective layer or a retardation layer arranged on at least one side of the polarizing film.
  • a polarizing film having an excellent appearance by controlling the reflection characteristics of the surface. Further, such a polarizing film can contribute to the improvement of the display characteristics of the image display device.
  • Refractive index (nx, ny, nz) "Nx" is the refractive index in the direction in which the refractive index in the plane is maximized (that is, the direction of the slow phase axis), and "ny” is the direction orthogonal to the slow phase axis in the plane (that is, the direction of the phase advance axis). Is the refractive index of, and "nz” is the refractive index in the thickness direction.
  • In-plane phase difference (Re) “Re ( ⁇ )” is an in-plane phase difference measured with light having a wavelength of ⁇ nm at 23 ° C.
  • Re (550) is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C.
  • Phase difference in the thickness direction (Rth) is a phase difference in the thickness direction measured with light having a wavelength of ⁇ nm at 23 ° C.
  • Rth (550) is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C.
  • FIG. 1 is a schematic cross-sectional view of a polarizing film according to one embodiment of the present invention.
  • hatching is omitted in the cross section of the polarizing film in order to make the figure easier to see.
  • the polarizing film 10 has a first main surface (front surface) 10a and a second main surface (back surface) 10b.
  • the polarizing film 10 has an inclined distribution region in which the amount of iodine increases from the front surface 10a toward the back surface 10b at the end portion on the front surface 10a side.
  • the polarizing film 10 is made of a resin film containing iodine.
  • a resin film for example, a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film is used.
  • PVA polyvinyl alcohol
  • the thickness of the polarizing film 10 is 7 ⁇ m or less, preferably 6 ⁇ m or less. A polarizing film having such a thickness tends to have a high iodine concentration. On the other hand, the thickness of the polarizing film is preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more.
  • the polarizing film 10 preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm.
  • the simple substance transmittance (Ts) of the polarizing film 10 is preferably 41.0% or more, more preferably 42.0% or more, and further preferably 42.5% or more. On the other hand, the simple substance transmittance of the polarizing film 10 is, for example, 44.2% or less.
  • the degree of polarization (P) of the polarizing film 10 is preferably 99.95% or more, more preferably 99.98% or more, and further preferably 99.99% or more. On the other hand, the degree of polarization of the polarizing film 10 is, for example, 99.996% or less.
  • the simple substance transmittance is typically a Y value measured by using an ultraviolet-visible spectrophotometer and corrected for luminosity factor.
  • the degree of polarization is typically obtained by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by using an ultraviolet-visible spectrophotometer and corrected for luminosity factor.
  • Degree of polarization (%) ⁇ (Tp-Tc) / (Tp + Tc) ⁇ 1/2 ⁇ 100
  • the ratio (Rc 400 / Rc 680 ) of the reflectance Rc 400 of the light having a wavelength of 400 nm in the absorption axis direction to the reflectance Rc 680 of the light having a wavelength of 680 nm in the absorption axis direction of the surface 10a of the polarizing film 10 exceeds 1. It is preferably 1.3 or more, and more preferably 1.5 or more. By satisfying such a relationship, the reflected hue is well controlled and the appearance can be excellent. Specifically, redness is suppressed and the appearance can be excellent. As a result, for example, an image display device having excellent visibility can be provided.
  • the polarizing film 10 may be arranged so that the surface 10a thereof is on the viewing side of the image display device, or may be arranged so as to be on the side opposite to the viewing side. Get excellent.
  • the surface 10a of the polarizing film 10 so as to be on the visual side of the image display device, the appearance and display characteristics can be extremely excellent.
  • the Rc 400 / Rc 680 of the surface 10a of the polarizing film 10 is, for example, 2 or less.
  • the Rc 400 of the surface 10a of the polarizing film 10 is, for example, 4.8% or more, preferably 4.9% or more, more preferably 5% or more, and further preferably 5.3% or more.
  • the Rc 400 of the surface 10a of the polarizing film 10 is, for example, 6% or less.
  • the Rc 680 of the surface 10a of the polarizing film 10 is, for example, 5% or less, preferably 4.9% or less, more preferably 4.5% or less, and further preferably 4% or less.
  • the Rc 680 of the surface 10a of the polarizing film 10 is, for example, 3% or more.
  • the reflectance Rp 400 of light having a wavelength of 400 nm in the transmission axis direction of the surface 10a of the polarizing film 10 is, for example, 4.5% to 5%.
  • the reflectance Rp 680 of light having a wavelength of 680 nm in the transmission axis direction of the surface 10a of the polarizing film 10 is, for example, 4.3% to 4.8%.
  • Each of the above Rc and Rp is the ratio of the reflected light intensity to the incident light intensity when light is incident on the surface of the polarizing film (resin film) at a predetermined angle and the reflected light in the absorption axis direction and the transmission axis direction is detected. Is.
  • the amount of iodine on the front surface 10a side is smaller than the amount of iodine on the back surface 10b side.
  • the polarizing film 10 has a first region 11 and a second region 12 having different iodine distribution states in this order from the surface side.
  • the first region 11 is a gradient distribution region in which the amount of iodine increases from the front surface 10a to the back surface 10b.
  • Iodine is uniformly distributed in the second region 12.
  • "uniformity" means that, for example, the intensity derived from iodine (for example, iodine ion) detected by analysis is in the range of -20% to + 20% from the average value.
  • the thickness of the first region 11 is preferably 2% or more and 50% or less, and more preferably 10% or more and 40% or less of the thickness of the polarizing film 10.
  • the thickness of the first region 11 may be 20% or more of the thickness of the polarizing film 10.
  • the thickness of the first region 11 is preferably 100 nm or more and 2.7 ⁇ m or less, and more preferably 500 nm or more and 2 ⁇ m or less.
  • the thickness of the first region 11 may be 1 ⁇ m or more. According to such a range, for example, excellent optical characteristics (the above-mentioned simple substance transmittance and degree of polarization) and excellent appearance can be achieved.
  • the polarizing film may have a first region, a second region, and a third region having different iodine distribution states in this order from the surface side.
  • the polarizing film has a first region in which the amount of iodine increases from the front surface to the back surface, a second region in which iodine is uniformly distributed, and a third region in which the amount of iodine decreases from the front surface side to the back surface. It may have an area.
  • the polarizing film is obtained by washing the surface of a resin film containing iodine and having a predetermined water content with water.
  • the water content (before washing with water) of the resin film is 15% by weight or less, preferably 12% by weight or less, more preferably 9% by weight or less, and further preferably 6% by weight or less.
  • the water content of the resin film is, for example, 3% by weight or more.
  • the iodine concentration of the resin film is, for example, 5% by weight or more, 5.5% by weight or more, or 6% by weight or more.
  • the iodine concentration of the resin film is, for example, 8% by weight or less.
  • the thickness of the resin film is, for example, 7 ⁇ m or less, and may be 6 ⁇ m or less.
  • the thickness of the resin film is preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more. It is one of the features of the present invention that an excellent appearance can be achieved in such an iodine concentration and thickness.
  • Resin film For the resin film having the above-mentioned predetermined water content, for example, a resin layer (typically, a polyvinyl alcohol-based resin layer) is formed on a resin base material to prepare a laminated body, and the laminated body (resin layer) is formed. ) Is stretched and stained with iodine (for example, dyed by adsorption of iodine), and then the laminate (resin layer) is dried.
  • iodine for example, dyed by adsorption of iodine
  • a PVA-based resin layer containing a polyvinyl alcohol (PVA) -based resin and a halide is formed on a thermoplastic resin base material (for example, a long shape) to form the laminated body.
  • a coating liquid containing a PVA-based resin and a halide is applied onto a thermoplastic resin base material and dried to prepare a laminate.
  • the thickness of the thermoplastic resin base material is preferably 20 ⁇ m to 300 ⁇ m, and more preferably 50 ⁇ m to 200 ⁇ m. If it is less than 20 ⁇ m, it may be difficult to form a PVA-based resin layer. If it exceeds 300 ⁇ m, for example, in the later-described underwater stretching, it takes time for the thermoplastic resin base material to absorb water, and there is a possibility that an excessive load is required for stretching.
  • the water absorption rate of the thermoplastic resin base material is preferably 0.2% or more, more preferably 0.3% or more.
  • a thermoplastic resin base material absorbs water, and the water can act as a plasticizer to plasticize. As a result, the stretching stress can be significantly reduced and the drawing can be performed at a high magnification.
  • the water absorption rate of the thermoplastic resin base material is preferably 3.0% or less, more preferably 1.0% or less. With such a water absorption rate, it is possible to prevent problems such as deterioration of the quality of the obtained polarizing film due to a significant decrease in the dimensional stability of the thermoplastic resin base material during production.
  • thermoplastic resin base material from breaking or the PVA-based resin layer from peeling off during stretching in water.
  • the water absorption rate of the thermoplastic resin base material can be adjusted, for example, by introducing a modifying group into the constituent material.
  • the water absorption rate is a value obtained according to JIS K 7209.
  • the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 120 ° C. or lower.
  • Tg is more preferably 100 ° C. or lower, still more preferably 90 ° C. or lower.
  • the Tg of the thermoplastic resin base material is preferably 60 ° C. or higher.
  • the thermoplastic resin base material when the coating liquid is applied and dried, the thermoplastic resin base material is prevented from being deformed (for example, unevenness, tarmi, wrinkles, etc.), and the lamination is good. You can make a body. Further, the stretching of the resin layer can be satisfactorily performed at a suitable temperature (for example, about 60 ° C.).
  • the Tg of the thermoplastic resin substrate can be adjusted, for example, by heating with a crystallization material that introduces a modifying group into the constituent material.
  • the glass transition temperature (Tg) is a value obtained according to JIS K7121.
  • thermoplastic resin can be adopted as the constituent material of the thermoplastic resin base material.
  • the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Can be mentioned. Among these, norbornene-based resin and amorphous polyethylene terephthalate-based resin are preferable.
  • an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used.
  • an amorphous (difficult to crystallize) polyethylene terephthalate resin is particularly preferably used.
  • Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid and / or a cyclohexanedicarboxylic acid as a dicarboxylic acid, and a copolymer further containing cyclohexanedimethanol or diethylene glycol as a glycol.
  • a polyethylene terephthalate resin having an isophthalic acid unit is preferably used. This is because the stretchability is extremely excellent and crystallization during stretching can be suppressed. It is considered that this is because the introduction of the isophthalic acid unit gives a large bending to the backbone.
  • the polyethylene terephthalate resin has a terephthalic acid unit and an ethylene glycol unit.
  • the content ratio of the isophthalic acid unit is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, based on the total of all repeating units. This is because a thermoplastic resin base material having extremely excellent stretchability can be obtained.
  • the content ratio of the isophthalic acid unit is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total of all repeating units. This is because the crystallinity can be satisfactorily increased in the drying described later.
  • the thermoplastic resin base material may be stretched in advance (for example, before forming the PVA-based resin layer).
  • the elongated thermoplastic resin substrate is laterally stretched.
  • the lateral direction is preferably a direction orthogonal to the stretching direction of the laminate described later.
  • “orthogonal” includes a case where it is substantially orthogonal.
  • substantially orthogonal includes the case of 90 ° ⁇ 5.0 °, preferably 90 ° ⁇ 3.0 °, and more preferably 90 ° ⁇ 1.0 °.
  • the stretching temperature of the thermoplastic resin base material is preferably Tg-10 ° C. to Tg + 50 ° C. with respect to the glass transition temperature (Tg) of the thermoplastic resin base material.
  • the draw ratio of the thermoplastic resin base material is preferably 1.5 to 3.0 times. Any suitable method can be adopted as the method for stretching the thermoplastic resin base material. Specifically, it may be fixed-end stretching or free-end stretching. The stretching method may be a dry method or a wet method. Stretching may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios in each stage.
  • the coating liquid is typically a solution in which a PVA-based resin and a halide are dissolved in a solvent.
  • the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferable.
  • the content of the PVA-based resin in the coating liquid is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. According to such a range, it is possible to form a uniform coating film in close contact with the thermoplastic resin base material.
  • the content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
  • Examples of the PVA-based resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymers.
  • Polyvinyl alcohol is obtained by saponifying polyvinyl acetate.
  • the ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer.
  • the saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. Is.
  • a PVA-based resin having such a saponification degree a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.
  • the degree of saponification can be determined according to JIS K 6726-1994.
  • the average degree of polymerization of the PVA-based resin is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300.
  • the average degree of polymerization can be determined according to JIS K 6726-1994.
  • any suitable halide can be adopted.
  • iodides such as potassium iodide, sodium iodide and lithium iodide, and chlorides such as sodium chloride.
  • potassium iodide is preferable.
  • a polarizing film having excellent optical characteristics can be obtained. Specifically, the crystallization of the PVA-based resin after the aerial auxiliary stretching described later is promoted, and in the subsequent wet treatment (for example, staining described later, stretching in water), the orientation of the polyvinyl alcohol molecule is disturbed and the orientation is lowered. Is suppressed, and a polarizing film having excellent optical characteristics can be obtained.
  • the halide In the preparation of the coating liquid, it is preferable to add 5 parts by weight to 20 parts by weight of the halide with respect to 100 parts by weight of the PVA-based resin, and more preferably 10 parts by weight to 15 parts by weight.
  • the content of the halide in the obtained PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. Is. If the amount of the halide with respect to the PVA-based resin is large, for example, the halide may bleed out and the obtained polarizing film may become cloudy.
  • Additives may be added to the coating liquid.
  • the additive include a plasticizer and a surfactant.
  • the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin.
  • the surfactant include nonionic surfactants. These are used, for example, for the purpose of improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.
  • Examples of the coating method of the coating liquid include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (comma coating method, etc.). Be done.
  • the coating / drying temperature of the coating liquid is preferably 50 ° C. or higher.
  • the thickness of the PVA-based resin layer is preferably 3 ⁇ m to 40 ⁇ m, and more preferably 3 ⁇ m to 20 ⁇ m.
  • the thermoplastic resin base material Before forming the PVA-based resin layer, the thermoplastic resin base material may be surface-treated (for example, corona treatment or the like), or the easy-adhesive layer may be formed on the thermoplastic resin base material. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.
  • the stretching is preferably performed by stretching the laminate in water after dry stretching (auxiliary stretching in the air).
  • auxiliary stretching it is possible to stretch while suppressing the crystallization of the thermoplastic resin base material, and it solves the problem that the stretchability is lowered due to excessive crystallization of the thermoplastic resin base material in boric acid water stretching.
  • the laminate can be stretched at a higher magnification. Further, when the thermoplastic resin base material is used, since the coating temperature can be set low, there may be a problem that the crystallization of the PVA-based resin is relatively low and sufficient optical characteristics cannot be obtained. On the other hand, by introducing the auxiliary stretching, the crystallinity of the PVA-based resin can be enhanced even when the thermoplastic resin is used.
  • the method of aerial auxiliary stretching may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). ..
  • free-end stretching is adopted.
  • a heating roll stretching method is adopted in which the laminated body is conveyed in the longitudinal direction thereof and is stretched by the difference in peripheral speed between the heating rolls.
  • the aerial auxiliary stretching includes a zone stretching step and a heating roll stretching step in a thermal space (zone).
  • the order of the zone stretching step and the heating roll stretching step is not limited, but for example, the zone stretching step and the heating roll stretching step are performed in this order.
  • the film in the tenter stretching machine, is stretched by grasping the end portion of the film and widening the distance between the tenters in the flow direction (the widening of the distance between the tenters is the stretching ratio).
  • the distance of the tenter in the width direction perpendicular to the flow direction
  • the draw ratio of the aerial auxiliary stretch is preferably 2.0 to 3.5 times.
  • the aerial auxiliary stretching may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios in each stage.
  • the stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching described later.
  • the stretching temperature of the aerial auxiliary stretching is set to an arbitrary appropriate value depending on, for example, the thermoplastic resin base material used, the stretching method, and the like.
  • the stretching temperature is preferably Tg + 10 ° C. or higher, more preferably Tg + 10 ° C. or higher, and even more preferably Tg + 15 ° C. or higher, preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate.
  • the upper limit of the stretching temperature is preferably 170 ° C.
  • the underwater stretching is typically performed by immersing the laminate in a stretching bath.
  • the thermoplastic resin base material or the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically, about 80 ° C.), and the PVA-based resin layer can be crystallized. It can be stretched at a high magnification while suppressing it. As a result, a polarizing film having excellent optical characteristics can be obtained.
  • the method of underwater stretching may be fixed-end stretching or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds).
  • free-end stretching is adopted.
  • the stretching of the laminate may be carried out in one step or in multiple steps. In the case of performing in multiple stages, the draw ratio of the laminated body described later is the product of the draw ratios of each stage.
  • the underwater stretching is preferably carried out by immersing the laminate in a boric acid aqueous solution (boric acid water stretching).
  • boric acid aqueous solution as the stretching bath, it is possible to impart rigidity to withstand the tension applied during stretching and water resistance that does not dissolve in water to the PVA-based resin layer.
  • boric acid can generate a tetrahydroxyboric acid anion in an aqueous solution and crosslink with a PVA-based resin by hydrogen bonding.
  • the PVA-based resin layer can be imparted with rigidity and water resistance, can be stretched satisfactorily, and a polarizing film having excellent optical characteristics can be obtained.
  • the boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent.
  • the boric acid concentration is preferably 1 part by weight to 10 parts by weight, more preferably 2.5 parts by weight to 6 parts by weight, and further preferably 3 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. Is.
  • the boric acid concentration is preferably 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced.
  • an aqueous solution obtained by dissolving a boron compound such as borax, glioxal, glutaraldehyde or the like in a solvent can also be used.
  • iodide is added to the above stretching bath (boric acid aqueous solution).
  • iodide By blending iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed.
  • iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide.
  • the concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, and more preferably 0.5 parts by weight to 8 parts by weight with respect to 100 parts by weight of water.
  • the stretching temperature (liquid temperature of the stretching bath) is preferably 40 ° C. or higher, more preferably 60 ° C. or higher. At such a temperature, the PVA-based resin layer can be stretched at a high magnification while suppressing dissolution.
  • the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40 ° C., it may not be stretched well even in consideration of the plasticization of the thermoplastic resin base material by water.
  • the stretching temperature is, for example, 70 ° C. or lower, preferably 67 ° C. or lower, and more preferably 65 ° C.
  • the immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.
  • the stretching ratio by stretching in water is preferably 1.5 times or more, more preferably 3.0 times or more.
  • the total draw ratio of the laminated body is preferably 5.0 times or more, more preferably 5.5 times or more with respect to the original length of the laminated body. Yes, more preferably 6.0 times or more.
  • Such a high draw ratio can be achieved by adopting an underwater stretching method (boric acid underwater stretching).
  • the above dyeing is typically performed by adsorbing iodine on a PVA-based resin layer.
  • the iodine adsorption method include a method of immersing a PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA-based resin layer, and a method of applying the dyeing solution to the PVA-based resin layer.
  • a method of immersing the laminate in a dyeing solution (staining bath) is preferable. This is because iodine can be adsorbed well.
  • the stain solution is preferably an aqueous iodine solution.
  • the blending amount of iodine is preferably 0.05 part by weight to 0.5 part by weight with respect to 100 parts by weight of water.
  • iodide is added to the aqueous iodine solution.
  • Specific examples of iodide are as described above.
  • potassium iodide is used.
  • the blending amount of the iodide is preferably 0.1 part by weight to 10 parts by weight, and more preferably 0.3 part by weight to 5 parts by weight with respect to 100 parts by weight of water.
  • the liquid temperature at the time of dyeing the dyeing liquid is preferably 20 ° C.
  • the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds in order to secure the transmittance of the PVA-based resin layer.
  • the dyeing conditions are set so that, for example, the single transmittance of the finally obtained polarizing film is 42.0% or more and the degree of polarization is 99.98% or more. can do.
  • a dyeing condition for example, the ratio of the content of iodine and potassium iodide in the iodine aqueous solution which is a dyeing solution is preferably 1: 5 to 1:20, and more preferably 1: 5 to 1. : 10.
  • boric acid When continuous dyeing is performed after a treatment in which the laminate is immersed in a treatment bath containing boric acid (for example, an insolubilization treatment described later), boric acid is mixed in the dyeing bath and the boric acid concentration in the dyeing bath changes. Dyeability may become unstable.
  • the boric acid concentration in the dyeing bath is adjusted to be preferably 4 parts by weight or less, more preferably 2 parts by weight or less with respect to 100 parts by weight of water. Will be done.
  • the boric acid concentration in the dyeing bath is preferably 0.1 part by weight or more, more preferably 0.2 part by weight or more, and further preferably 0.5 part by weight with respect to 100 parts by weight of water. That is all.
  • dyeing is performed using a dyeing bath containing boric acid in advance.
  • the rate of change in boric acid concentration when boric acid is mixed in the dyeing bath can be reduced.
  • the amount of boric acid to be blended in the dyeing bath in advance is preferably 0.1 part by weight to 2 parts by weight, more preferably with respect to 100 parts by weight of water. Is from 0.5 parts by weight to 1.5 parts by weight.
  • insolubilization treatment is performed after the above-mentioned aerial auxiliary stretching and before water stretching and staining.
  • the insolubilization treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution.
  • concentration of the boric acid aqueous solution in the insolubilization treatment is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water.
  • the temperature of the insolubilization treatment liquid temperature of the boric acid aqueous solution
  • the cross-linking treatment is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution.
  • the concentration of the boric acid aqueous solution in the crosslinking treatment is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. It is preferable to add iodide to the boric acid aqueous solution.
  • the elution of iodine adsorbed on the PVA-based resin layer can be suppressed.
  • Specific examples of iodide are as described above.
  • the blending amount of iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water.
  • the temperature of the crosslinking treatment liquid temperature of the boric acid aqueous solution, preferably 20 ° C to 50 ° C.
  • the washing is typically performed by immersing the PVA-based resin layer in an aqueous solution of potassium iodide.
  • the drying can be carried out under any suitable method and conditions as long as a resin film having the above-mentioned predetermined moisture content can be obtained. Specifically, it may be performed by heating the entire zone (zone heating method) or by heating the transport roll (heating roll method). A heating roll method is preferably adopted, and more preferably both are adopted. By using the heating roll, it is possible to efficiently suppress the heating curl of the laminated body and produce a polarizing film having excellent quality. Specifically, by drying the laminated body along the heating roll, the crystallization of the thermoplastic resin base material can be efficiently promoted and the crystallinity can be increased, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be satisfactorily increased.
  • the rigidity of the thermoplastic resin base material is increased, and the PVA-based resin layer is in a state of being able to withstand shrinkage due to drying, and curling is suppressed. Further, by using the heating roll, the laminated body can be dried while being maintained in a flat state, so that not only curling but also wrinkles can be suppressed.
  • the laminate By drying, the laminate can be shrunk in the width direction and the optical characteristics can be improved. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced.
  • the shrinkage rate of the laminate in the width direction due to drying is preferably 1% to 10%, more preferably 2% to 8%, still more preferably 4% to 6%.
  • the heating roll By using the heating roll, the laminated body can be continuously contracted in the width direction while being conveyed, and high productivity can be realized.
  • FIG. 2 is a schematic view showing an example of drying using a heating roll.
  • the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4.
  • the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA-based resin layer and the surface of the thermoplastic resin base material, and for example, one surface of the laminate 200 (for example, The transport rolls R1 to R6 may be arranged so as to continuously heat only the surface of the thermoplastic resin base material).
  • Drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like.
  • the temperature of the heating roll is preferably 60 ° C. to 120 ° C., more preferably 65 ° C. to 100 ° C., and even more preferably 70 ° C. to 80 ° C. According to such a temperature, the crystallinity of the thermoplastic resin can be increased to suppress curling, and the laminated body can be imparted with extremely excellent durability. In addition, the moisture content of the resin film can be satisfactorily achieved.
  • the temperature of the heating roll can be measured with a contact thermometer.
  • the number of transport rolls is usually 2 to 40, preferably 4 to 30.
  • the contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.
  • the heating roll may be provided in a heating furnace (for example, an oven) or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with an air blowing means.
  • a heating furnace provided with an air blowing means.
  • the temperature of hot air drying is preferably 30 ° C to 100 ° C.
  • the hot air drying time is preferably 1 second to 300 seconds.
  • the wind speed of hot air is preferably about 10 m / s to 30 m / s. The wind speed is the wind speed in the heating furnace and can be measured by a mini-vane type digital anemometer.
  • washing with water is performed, for example, by bringing water into contact with the surface of the resin film.
  • washing is performed by immersing the resin film in a water bath.
  • the back surface of the resin film is preferably protected by any suitable protective substrate.
  • the resin base material is used as the protective base material.
  • the resin film is immersed in a water bath without peeling the resin base material from the resin film (in the state of the above-mentioned laminated body).
  • the protective layer described below is used as the protective base material.
  • the resin base material is peeled off from the resin film to prepare a laminate of the protective layer and the resin film, and the laminate is immersed in a water bath.
  • the resin film may be long or single-wafered.
  • the temperature of the water bath is, for example, 20 ° C. or higher, preferably 25 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 35 ° C. or higher, and particularly preferably 40 ° C. or higher. Is. With such a temperature, for example, a polarizing film satisfying the above reflectance can be produced in a short time.
  • the temperature of the water bath is preferably 60 ° C. or lower, more preferably 50 ° C. or lower. According to such a temperature, for example, the obtained polarizing film has excellent surface properties and can maintain excellent optical properties.
  • the immersion time (contact time) in the water bath is set according to, for example, the above temperature, the thickness of the resin film, and the like.
  • the immersion time in the water bath is preferably 15 seconds to 5 minutes, more preferably 30 seconds to 3 minutes.
  • the water bath (water to be contacted) may contain additives such as boric acid.
  • the polarizing film After washing with water, the polarizing film can be subjected to a drying treatment.
  • the drying temperature is, for example, 30 ° C to 60 ° C.
  • the drying time is, for example, 15 seconds to 3 minutes.
  • the polarizing plate according to one embodiment of the present invention has the above-mentioned polarizing film and a protective layer or a retardation layer arranged on at least one side of the polarizing film.
  • FIG. 3 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate according to the first embodiment of the present invention.
  • the polarizing plate (polarizing plate with a retardation layer) 100 has a polarizing film 10, a protective layer 20, a retardation layer 30, and an adhesive layer 40 in this order.
  • the protective layer 20 is arranged only on the back surface 10b side of the polarizing film 10, and the protective layer is not arranged on the front surface 10a side (for example, the visual recognition side), but practically, the polarizing film 10 is arranged.
  • the surface 10a is protected by any suitable protective material (not shown).
  • a protective material is laminated on the polarizing film 10.
  • the retardation layer 30 may be a single layer or may have a laminated structure in which two or more layers are laminated.
  • FIG. 4 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate according to the second embodiment of the present invention.
  • the polarizing plate (polarizing plate with a retardation layer) 110 includes a protective layer 20 arranged on the back surface 10b side of the polarizing film 10, a polarizing film 10, a retardation layer 30 arranged on the front surface 10a side of the polarizing film 10, and an adhesive.
  • the layer 40 is provided in this order from the visual recognition side.
  • the present embodiment differs from the first embodiment in that the retardation layer 30 can function as a protective layer for the polarizing film 10 and the retardation layer 30 is arranged on the surface 10a side of the polarizing film 10.
  • the polarizing plate may further have other functional layers.
  • the types, characteristics, numbers, combinations, arrangements, and the like of the functional layers that the polarizing plate may have can be appropriately set according to the purpose.
  • the polarizing plate may further have a conductive layer or an isotropic substrate with a conductive layer.
  • a polarizing plate having a conductive layer or an isotropic substrate with a conductive layer is applied to, for example, a so-called inner touch panel type input display device in which a touch sensor is incorporated inside an image display panel.
  • the polarizing plate may further have another retardation layer.
  • the optical characteristics for example, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient
  • thickness, arrangement, and the like of the other retardation layers can be appropriately set according to the purpose.
  • another retardation layer typically, a layer that imparts a (elliptical) circular polarization function
  • a super A layer that imparts a high phase difference may be provided on the visual recognition side of the polarizing film 10.
  • Each member constituting the polarizing plate can be laminated via an arbitrary appropriate adhesive layer (not shown).
  • the adhesive layer include an adhesive layer and an adhesive layer.
  • the retardation layer 30 may be attached to the polarizing film 10 or the protective layer 20 via an adhesive layer (preferably using an active energy ray-curable adhesive), or an adhesive. It may be bonded to the polarizing film 10 or the protective layer 20 via the layer.
  • the retardation layer 30 has a laminated structure of two or more layers, the respective retardation layers are bonded together, for example, via an adhesive layer (preferably using an active energy ray-curable adhesive). ..
  • a release film (separator) is practically attached to the surface of the adhesive layer 40.
  • the release film can be tacked temporarily until the polarizing plate is put into use.
  • the release film for example, the pressure-sensitive adhesive layer can be protected and a roll of the polarizing plate can be formed.
  • the polarizing plate may be long or single-lobed.
  • the term "long” refers to an elongated shape having a length sufficiently long with respect to the width, for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to the width.
  • the long polarizing plate can be wound in a roll shape.
  • the protective layer 20 can be formed of any suitable film that can be used as a protective layer for the polarizing film.
  • suitable film include cellulosic resins such as triacetylcellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, and polysulfones.
  • TAC triacetylcellulose
  • the above polarizing plate is typically arranged on the visual side of the image display device. Therefore, even if the protective layer 20 is subjected to surface treatment such as hard coat (HC) treatment, antireflection treatment, anti-sticking treatment, anti-glare treatment, etc., if necessary (for example, in the form shown in FIG. 4). good.
  • surface treatment such as hard coat (HC) treatment, antireflection treatment, anti-sticking treatment, anti-glare treatment, etc.
  • the thickness of the protective layer 20 is preferably 5 ⁇ m to 80 ⁇ m, more preferably 10 ⁇ m to 40 ⁇ m, and even more preferably 10 ⁇ m to 30 ⁇ m. When the surface treatment is applied, the thickness of the protective layer 20 is the thickness including the thickness of the surface treatment layer.
  • the protective layer arranged between the polarizing film 10 and the retardation layer 30 is preferably optically isotropic in one embodiment.
  • optically isotropic means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm.
  • the resin substrate can be used as a protective layer for a polarizing film.
  • the manufacturing process can be reduced by using the resin base material as it is as the protective layer.
  • phase difference layer As the phase difference layer 30, any suitable configuration can be adopted.
  • the alignment solidification layer (liquid crystal alignment solidification layer) of the liquid crystal compound is used as the retardation layer 30.
  • the difference between nx and ny of the obtained retardation layer can be significantly increased as compared with the non-liquid crystal material, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be obtained.
  • the term "aligned solidified layer” refers to a layer in which a liquid crystal compound is oriented in a predetermined direction within the layer and the oriented state is fixed.
  • the "oriented solidified layer” is a concept including an oriented cured layer obtained by curing a liquid crystal monomer as described later.
  • the rod-shaped liquid crystal compounds are typically oriented in a state of being aligned in the slow axis direction of the retardation layer (homogeneous orientation).
  • the thickness of the retardation layer is preferably 8 ⁇ m or less, and more preferably 5 ⁇ m or less, although it depends on the structure (whether it is a single layer or has a laminated structure). On the other hand, the thickness of the retardation layer is, for example, 1 ⁇ m or more.
  • the "thickness of the retardation layer” means the total thickness of each retardation layer. Specifically, the "thickness of the retardation layer” does not include the thickness of the adhesive layer.
  • the surface of a predetermined base material is subjected to an orientation treatment, and a coating liquid containing a liquid crystal compound is applied to the surface to orient the liquid crystal compound in a direction corresponding to the alignment treatment. It can be formed by fixing the orientation state.
  • the orientation treatment any appropriate orientation treatment can be adopted. Specific examples thereof include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of the mechanical orientation treatment include a rubbing treatment and a stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical alignment treatment include an orthorhombic vapor deposition method and a photoalignment treatment.
  • any appropriate conditions may be adopted depending on the purpose.
  • the orientation of the liquid crystal compound is performed by treating at a temperature indicating the liquid crystal phase according to the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound takes a liquid crystal state, and the liquid crystal compound is oriented according to the orientation treatment direction of the surface of the substrate.
  • the orientation state is fixed by cooling the liquid crystal compound oriented as described above.
  • the orientation state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.
  • liquid crystal compound and details of the method for forming the oriented solidified layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this publication is incorporated herein by reference.
  • the retardation layer 30 can function as, for example, a ⁇ / 4 plate.
  • the Re (550) of the retardation layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and further preferably 110 nm to 160 nm.
  • the thickness of the retardation layer can be adjusted to obtain the desired in-plane retardation of the ⁇ / 4 plate.
  • the thickness thereof is, for example, 1.0 ⁇ m to 2.5 ⁇ m.
  • the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and even more preferably 44. ° to 46 °.
  • the retardation layer preferably exhibits a reverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light.
  • the retardation layer 30 has, for example, a two-layer laminated structure in which the H layer and the Q layer are arranged in order from the polarizing film 10 side.
  • the H layer can typically function as a ⁇ / 2 plate
  • the Q layer can typically function as a ⁇ / 4 plate.
  • the Re (550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, still more preferably 230 nm to 280 nm; and the Re (550) of the Q layer is preferably.
  • the thickness of the H layer can be adjusted to obtain the desired in-plane phase difference of the ⁇ / 2 plate.
  • the thickness thereof is, for example, 2.0 ⁇ m to 4.0 ⁇ m.
  • the thickness of the Q layer can be adjusted to obtain the desired in-plane phase difference of the ⁇ / 4 plate.
  • the thickness thereof is, for example, 1.0 ⁇ m to 2.5 ⁇ m.
  • the angle formed by the slow phase axis of the H layer and the absorption axis of the polarizing film is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and even more preferably 12 °.
  • the angle between the slow axis of the Q layer and the absorption axis of the polarizing film is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and even more preferably 72 °. It is ⁇ 76 °.
  • each layer for example, H layer and Q layer
  • the Nz coefficient of the retardation layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3.
  • the retardation layer is preferably a liquid crystal oriented solidifying layer.
  • the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) in which the liquid crystal phase is a nematic phase.
  • a liquid crystal compound for example, a liquid crystal polymer or a liquid crystal monomer can be used.
  • the liquid crystal expression mechanism of the liquid crystal compound may be either lyotropic or thermotropic.
  • the liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.
  • the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or cross-linking (that is, curing) the liquid crystal monomer. After the liquid crystal monomers are oriented, for example, the liquid crystal monomers are polymerized or crosslinked with each other, whereby the oriented state can be fixed.
  • the polymer is formed by polymerization, and the three-dimensional network structure is formed by crosslinking, but these are non-liquid crystal.
  • the formed retardation layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to a liquid crystal compound, for example.
  • the retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.
  • the temperature range in which the liquid crystal monomer exhibits liquid crystal properties differs depending on the type. Specifically, the temperature range is preferably 40 ° C. to 120 ° C., more preferably 50 ° C. to 100 ° C., and most preferably 60 ° C. to 90 ° C.
  • any suitable liquid crystal monomer can be adopted as the liquid crystal monomer.
  • the polymerizable mesogen compounds described in Special Tables 2002-533742 WO00 / 37585
  • EP358208 US5211877
  • EP66137 US43884553
  • WO93 / 22397 EP0261712, DE19504224, DE4408171, and GB2280445
  • Specific examples of such a polymerizable mesogen compound include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767.
  • As the liquid crystal monomer a nematic liquid crystal monomer is preferable.
  • Adhesive Layer As the adhesive layer 40, any suitable configuration can be adopted. Specific examples include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination and blending ratio of the monomers forming the base resin of the pressure-sensitive adhesive, the blending amount of the cross-linking agent, the reaction temperature, the reaction time, etc., the pressure-sensitive adhesive having desired characteristics according to the purpose. Can be prepared.
  • the base resin of the pressure-sensitive adhesive may be used alone or in combination of two or more.
  • the base resin is preferably an acrylic resin (specifically, the pressure-sensitive adhesive layer is preferably composed of an acrylic pressure-sensitive adhesive).
  • the thickness of the pressure-sensitive adhesive layer is, for example, 10 ⁇ m to 20 ⁇ m.
  • Polarizing Plate A polarizing plate can be typically obtained by laminating various layers such as a retardation layer on a polarizing film after washing with water.
  • the resin base material of the laminate of the resin base material and the polarizing film after washing with water is used as it is as the protective layer 20, and the retardation layer 30 and the pressure-sensitive adhesive layer 40 are used on the resin base material.
  • the protective layer 20 is laminated on the resin film side of the laminate of the resin base material and the resin film, and the laminate obtained by peeling the resin base material from the resin film is washed with water to wash the protective layer 20 side. It can be obtained by sequentially laminating the retardation layer 30 and the pressure-sensitive adhesive layer 40.
  • the polarizing plate 100 is obtained by laminating the retardation layer 30 or the retardation layer 30 and the pressure-sensitive adhesive layer 40 on the laminate of the protective layer 20 and the resin film, and then washing with water. May be good.
  • the polarizing plate 110 shown in FIG. 4 is, for example, a laminate obtained by laminating a protective layer 20 on the resin film side of a laminate of the resin base material and the resin film and peeling the resin base material from the resin film. It can be obtained by washing with water and sequentially laminating the retardation layer 30 and the pressure-sensitive adhesive layer 40 on the polarizing film 10 side.
  • the thickness, the iodine concentration of the resin film, and the water content are values measured by the following measuring methods. Unless otherwise specified, "parts" and “%” in Examples and Comparative Examples are based on weight. 1. 1. The thickness of 10 ⁇ m or less was measured using a scanning electron microscope (manufactured by JEOL Ltd., product name “JSM-7100F”). Thicknesses exceeding 10 ⁇ m were measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”). 2. 2. 2.
  • Moisture content of the resin film The amount of water contained in the resin film by drying the resin film alone (the resin film in a state of being peeled off from the resin substrate) at 120 ° C. for 2 hours and measuring the amount of weight change before and after drying. was calculated, and the water content was calculated.
  • thermoplastic resin base material an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 ⁇ m) having a long shape, a water absorption rate of 0.75%, and a Tg of about 75 ° C. was used.
  • One side of the resin substrate was corona-treated.
  • a PVA aqueous solution (coating liquid).
  • the PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 13 ⁇ m, and a laminate was prepared.
  • the obtained laminate was stretched 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching). Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C.
  • boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water
  • a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water
  • the total draw ratio is 5.5 in the vertical direction (longitudinal direction) between rolls having different peripheral speeds.
  • Uniaxial stretching was performed so as to double (stretching in water).
  • the laminate was immersed in a washing bath having a liquid temperature of 20 ° C.
  • the HC-COP film is a film in which an HC layer (thickness 2 ⁇ m) is formed on a cycloolefin resin (COP) film (thickness 25 ⁇ m), and the COP film is attached so as to be on the resin film side.
  • a cycloolefin resin (COP) film thinness 25 ⁇ m
  • the surface of a polyethylene terephthalate (PET) film was rubbed with a rubbing cloth and subjected to an orientation treatment.
  • the direction of the alignment treatment was set to be 15 ° when viewed from the visual recognition side with respect to the direction of the absorption axis of the polarizing film when the polarizing film was attached.
  • the liquid crystal coating liquid was applied to the alignment-treated surface with a bar coater, and the liquid crystal compound was oriented by heating and drying at 90 ° C. for 2 minutes.
  • the liquid crystal layer thus formed is irradiated with light of 1 mJ / cm 2 using a metal halide lamp to cure the liquid crystal layer, whereby a liquid crystal oriented solidified layer A (H layer) is formed on the PET film. did.
  • a liquid crystal oriented solidified layer B (Q layer) was formed.
  • Example 2 A polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the laminate was washed with water by immersing the laminate in a water bath at 40 ° C. for 2 minutes.
  • Example 3 The laminate was immersed in a boric acid aqueous solution having a liquid temperature of 70 ° C. and stretched in water to prepare a resin film having a thickness of 5.4 ⁇ m, an iodine concentration of 6.6%, and a water content of 4.5%.
  • a polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the mixture was washed with water by immersing it in a water bath at 25 ° C. for 5 minutes.
  • the polarizing plate B was not produced due to the surface texture (swelling) of the polarizing film after washing with water.
  • Example 4 The laminate was immersed in a boric acid aqueous solution having a liquid temperature of 67 ° C. and stretched in water to prepare a resin film having a thickness of 4.8 ⁇ m, an iodine concentration of 5.5%, and a water content of 4%.
  • a polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the mixture was washed with water by immersing it in the water bath of 1 for 1 minute.
  • Example 5 The laminate was immersed in a boric acid aqueous solution having a liquid temperature of 67 ° C. and stretched in water to prepare a resin film having a thickness of 4.8 ⁇ m, an iodine concentration of 5.5%, and a water content of 4%.
  • a polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the mixture was washed with water by immersing it in the water bath of No. 1 for 2 minutes.
  • Example 1 A polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the resin film was not washed with water.
  • Example 3 A polarizing film and a polarizing plate were obtained in the same manner as in Example 3 except that the resin film was not washed with water.
  • Reference Example 2 A polarizing film and a polarizing plate were obtained in the same manner as in Reference Example 1 except that the laminate was not washed with water.
  • the incident angle of the light source was set to 5 °, and the measurement wavelength was set to 380 nm to 780 nm. 3. 3.
  • Surface properties The surface properties of the polarizing films of Examples and Comparative Examples (presence or absence of unevenness due to swelling of the resin film) were visually observed. (Evaluation criteria) Good: No unevenness is confirmed Defect: Unevenness is confirmed 4.
  • Polarizer hue (a * and b * ) The polarizing plates (circular polarizing plates) of Examples and Comparative Examples were laminated on an aluminum sheet, and the reflected hue was measured in SCE mode with a spectrophotometer (manufactured by Konica Minolta, cm-2600d).
  • the ionic strength of iodine in the thickness direction was measured for the polarizing films obtained in Example 1, Comparative Example 1 and Reference Example 2.
  • the measurement was performed using a time-of-flight secondary ion mass spectrometer (TOF-SIMS) (manufactured by ION-TOF, product name: TOF-SIMS 5) and Bi 32+ as the primary ion .
  • TOF-SIMS time-of-flight secondary ion mass spectrometer
  • FIG. 5 graph in which the horizontal axis is converted into the thickness of the polarizing film
  • FIG. 5 it was confirmed that the polarizing film of Example 1 had a gradient distribution region in which the amount of iodine increased from the front surface to the back surface at the end portion on the front surface side.
  • the ionic strength of iodine on the vertical axis corresponds to the iodine concentration.
  • the polarizing film according to one embodiment of the present invention is suitably used for an image display device such as a liquid crystal display device, an organic EL display device, or an inorganic EL display device.
  • Polarizing film 10 Polarizing film 20 Protective layer 30 Phase difference layer 40 Adhesive layer 100 Polarizing plate 110 Polarizing plate

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Abstract

The present invention provides a polarizing film which has an excellent appearance and is capable of contributing to the improvement of the display characteristics of an image display device. A polarizing film according to one embodiment of the present invention is composed of a resin film that contains iodine, while having a thickness of 7 μm or less. With respect to the surface of this polarizing film, the ratio of the reflectance Rc400 of the light having a wavelength of 400 nm in the absorption axis direction to the reflectance Rc680 of the light having a wavelength of 680 nm in the absorption axis direction, namely Rc400/Rc680 is more than 1.

Description

偏光膜および偏光膜の製造方法Method for manufacturing a polarizing film and a polarizing film
　本発明は、偏光膜および偏光膜の製造方法に関する。 The present invention relates to a polarizing film and a method for manufacturing a polarizing film.
　代表的な画像表示装置である液晶表示装置には、その画像形成方式に起因して、液晶セルの両側に偏光膜が配置されている。また、薄型ディスプレイの普及と共に、有機エレクトロルミネセンス（ＥＬ）パネルを搭載したディスプレイ（ＯＬＥＤ）や、量子ドットなどの無機発光材料を用いた表示パネルを用いたディスプレイ（ＱＬＥＤ）が提案されている。これらのパネルは反射性の高い金属層を有しており、外光反射や背景の映り込み等の問題を生じやすい。そこで、偏光膜とλ／４板とを有する円偏光板を視認側に設けることにより、これらの問題を防ぐことが知られている。偏光膜の製造方法としては、例えば、樹脂基材とポリビニルアルコール（ＰＶＡ）系樹脂層とを有する積層体を延伸し、次に染色して、樹脂基材上に偏光膜を得る方法が提案されている（例えば、特許文献１）。このような方法によれば、厚みの薄い偏光膜が得られるため、近年の画像表示装置の薄型化に寄与し得るとして注目されている。しかし、厚みの薄い偏光膜は外観が劣り、画像表示装置に用いた場合に十分な表示特性が得られない場合がある。 A liquid crystal display device, which is a typical image display device, has polarizing films arranged on both sides of a liquid crystal cell due to its image forming method. Further, with the spread of thin displays, a display (OLED) equipped with an organic electroluminescence (EL) panel and a display (QLED) using a display panel using an inorganic light emitting material such as a quantum dot have been proposed. These panels have a highly reflective metal layer, and are liable to cause problems such as external light reflection and background reflection. Therefore, it is known to prevent these problems by providing a circular polarizing plate having a polarizing film and a λ / 4 plate on the visual recognition side. As a method for producing a polarizing film, for example, a method has been proposed in which a laminate having a resin base material and a polyvinyl alcohol (PVA) -based resin layer is stretched and then dyed to obtain a polarizing film on the resin base material. (For example, Patent Document 1). Since such a method can obtain a thin polarizing film, it is attracting attention as it can contribute to the thinning of image display devices in recent years. However, the thin polarizing film has a poor appearance and may not have sufficient display characteristics when used in an image display device.
特開２００１－３４３５２１号公報Japanese Unexamined Patent Publication No. 2001-343521
　本発明は上記課題を解決するためになされたものであり、その主たる目的は、外観に優れ、画像表示装置の表示特性の向上に寄与し得る偏光膜を提供することにある。 The present invention has been made to solve the above problems, and a main object thereof is to provide a polarizing film which is excellent in appearance and can contribute to improvement of display characteristics of an image display device.
　本発明の実施形態によれば、偏光膜が提供される。この偏光膜は、ヨウ素を含む樹脂フィルムから構成され、厚みが７μｍ以下であり、表面の、吸収軸方向の波長６８０ｎｍの光の反射率Ｒｃ６８０に対する吸収軸方向の波長４００ｎｍの光の反射率Ｒｃ４００の比（Ｒｃ４００／Ｒｃ６８０）は１を超える。
　１つの実施形態においては、上記表面のＲｃ６８０は５％以下である。
　１つの実施形態においては、上記表面のＲｃ４００は４．８％以上である。
　１つの実施形態においては、上記偏光膜は、上記表面側の端部に、表面から裏面に向かってヨウ素量が多くなる傾斜分布領域を有する。
　１つの実施形態においては、上記偏光膜において、上記表面側のヨウ素量が裏面側のヨウ素量よりも少ない。
　１つの実施形態においては、上記偏光膜は、単体透過率が４２．０％以上であり、偏光度が９９．９８％以上である。
　本発明の別の局面によれば、上記偏光膜の製造方法が提供される。この製造方法は、ヨウ素を含み、水分率が１５重量％以下の樹脂膜の表面を水洗することを含む。
　１つの実施形態においては、上記樹脂膜のヨウ素濃度は５重量％以上である。
　１つの実施形態においては、上記樹脂膜は樹脂基材上に形成された樹脂層である。
　１つの実施形態においては、上記製造方法は、上記樹脂層を６７℃以下で水中延伸することを含む。
　１つの実施形態においては、上記製造方法は、加熱ロールを用いて上記樹脂層を加熱することを含む。
　本発明のさらに別の局面によれば、偏光板が提供される。この偏光板は、上記偏光膜と、上記偏光膜の少なくとも片側に配置される保護層または位相差層とを有する。 According to an embodiment of the present invention, a polarizing film is provided. This polarizing film is composed of a resin film containing iodine, has a thickness of 7 μm or less, and has a reflectance Rc of light having a wavelength of 400 nm in the absorption axis direction with respect to a reflectance Rc 680 of light having a wavelength of 680 nm in the absorption axis direction on the surface. The ratio of 400 (Rc 400 / Rc 680 ) is greater than 1.
In one embodiment, the surface Rc 680 is 5% or less.
In one embodiment, the surface Rc 400 is 4.8% or higher.
In one embodiment, the polarizing film has a gradient distribution region at the end on the front surface side, in which the amount of iodine increases from the front surface to the back surface.
In one embodiment, in the polarizing film, the amount of iodine on the front surface side is smaller than the amount of iodine on the back surface side.
In one embodiment, the polarizing film has a simple substance transmittance of 42.0% or more and a degree of polarization of 99.98% or more.
According to another aspect of the present invention, there is provided a method for manufacturing the above-mentioned polarizing film. This production method comprises washing the surface of a resin film containing iodine and having a water content of 15% by weight or less with water.
In one embodiment, the iodine concentration of the resin film is 5% by weight or more.
In one embodiment, the resin film is a resin layer formed on a resin substrate.
In one embodiment, the manufacturing method comprises stretching the resin layer in water at 67 ° C. or lower.
In one embodiment, the manufacturing method comprises heating the resin layer with a heating roll.
According to yet another aspect of the present invention, a polarizing plate is provided. The polarizing plate has the polarizing film and a protective layer or a retardation layer arranged on at least one side of the polarizing film.
　本発明によれば、表面の反射特性が制御されていることにより、外観に優れた偏光膜を得ることができる。また、このような偏光膜によれば、画像表示装置の表示特性の向上に寄与し得る。 According to the present invention, it is possible to obtain a polarizing film having an excellent appearance by controlling the reflection characteristics of the surface. Further, such a polarizing film can contribute to the improvement of the display characteristics of the image display device.
本発明の１つの実施形態による偏光膜の模式的な断面図である。It is a schematic cross-sectional view of the polarizing film by one Embodiment of this invention. 加熱ロールを用いた乾燥の一例を示す概略図である。It is a schematic diagram which shows an example of drying using a heating roll. 本発明の第一実施形態による偏光板の概略の構成を示す模式的な断面図である。It is a schematic cross-sectional view which shows the schematic structure of the polarizing plate by 1st Embodiment of this invention. 本発明の第二実施形態による偏光板の概略の構成を示す模式的な断面図である。It is a schematic cross-sectional view which shows the schematic structure of the polarizing plate by the 2nd Embodiment of this invention. 実施例１、比較例１および参考例２の偏光膜の厚み方向におけるヨウ素のイオン強度を示すグラフである。It is a graph which shows the ionic strength of iodine in the thickness direction of the polarizing film of Example 1, Comparative Example 1 and Reference Example 2.
　以下、本発明の実施形態について説明するが、本発明はこれらの実施形態には限定されない。 Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.
（用語および記号の定義）
　本明細書における用語および記号の定義は下記の通りである。
（１）屈折率（ｎｘ、ｎｙ、ｎｚ）
　「ｎｘ」は面内の屈折率が最大になる方向（すなわち、遅相軸方向）の屈折率であり、「ｎｙ」は面内で遅相軸と直交する方向（すなわち、進相軸方向）の屈折率であり、「ｎｚ」は厚み方向の屈折率である。
（２）面内位相差（Ｒｅ）
　「Ｒｅ（λ）」は、２３℃における波長λｎｍの光で測定した面内位相差である。例えば、「Ｒｅ（５５０）」は、２３℃における波長５５０ｎｍの光で測定した面内位相差である。Ｒｅ（λ）は、層（フィルム）の厚みをｄ（ｎｍ）としたとき、式：Ｒｅ（λ）＝（ｎｘ－ｎｙ）×ｄによって求められる。
（３）厚み方向の位相差（Ｒｔｈ）
　「Ｒｔｈ（λ）」は、２３℃における波長λｎｍの光で測定した厚み方向の位相差である。例えば、「Ｒｔｈ（５５０）」は、２３℃における波長５５０ｎｍの光で測定した厚み方向の位相差である。Ｒｔｈ（λ）は、層（フィルム）の厚みをｄ（ｎｍ）としたとき、式：Ｒｔｈ（λ）＝（ｎｘ－ｎｚ）×ｄによって求められる。
（４）Ｎｚ係数
　Ｎｚ係数は、Ｎｚ＝Ｒｔｈ／Ｒｅによって求められる。
（５）角度
　本明細書において角度に言及するときは、当該角度は基準方向に対して時計回りおよび反時計回りの両方を包含する。したがって、例えば「４５°」は±４５°を意味する。 (Definition of terms and symbols)
Definitions of terms and symbols herein are as follows.
(1) Refractive index (nx, ny, nz)
"Nx" is the refractive index in the direction in which the refractive index in the plane is maximized (that is, the direction of the slow phase axis), and "ny" is the direction orthogonal to the slow phase axis in the plane (that is, the direction of the phase advance axis). Is the refractive index of, and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
“Re (λ)” is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (550)" is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in the thickness direction (Rth)
“Rth (λ)” is a phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, "Rth (550)" is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is obtained by the formula: Rth (λ) = (nx-nz) × d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re.
(5) Angle When referring to an angle herein, the angle includes both clockwise and counterclockwise with respect to the reference direction. Therefore, for example, "45 °" means ± 45 °.
Ａ．偏光膜
　図１は、本発明の１つの実施形態による偏光膜の模式的な断面図である。なお、図１では、図を見やすくするために偏光膜の断面は、ハッチングを省略している。偏光膜１０は、第一主面（表面）１０ａおよび第二主面（裏面）１０ｂを有する。偏光膜１０は、表面１０ａ側の端部に、表面１０ａから裏面１０ｂに向かってヨウ素量が多くなる傾斜分布領域を有する。 A. Polarizing Film FIG. 1 is a schematic cross-sectional view of a polarizing film according to one embodiment of the present invention. In FIG. 1, hatching is omitted in the cross section of the polarizing film in order to make the figure easier to see. The polarizing film 10 has a first main surface (front surface) 10a and a second main surface (back surface) 10b. The polarizing film 10 has an inclined distribution region in which the amount of iodine increases from the front surface 10a toward the back surface 10b at the end portion on the front surface 10a side.
　偏光膜１０は、ヨウ素を含む樹脂フィルムから構成される。樹脂フィルムとしては、例えば、ポリビニルアルコール（ＰＶＡ）系フィルム、部分ホルマール化ＰＶＡ系フィルム、エチレン・酢酸ビニル共重合体系部分ケン化フィルム等の親水性高分子フィルムが用いられる。 The polarizing film 10 is made of a resin film containing iodine. As the resin film, for example, a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film is used.
　偏光膜１０の厚みは、７μｍ以下であり、好ましくは６μｍ以下である。このような厚みの偏光膜は、ヨウ素濃度が高い傾向にある。一方、偏光膜の厚みは、好ましくは１μｍ以上であり、より好ましくは２μｍ以上である。 The thickness of the polarizing film 10 is 7 μm or less, preferably 6 μm or less. A polarizing film having such a thickness tends to have a high iodine concentration. On the other hand, the thickness of the polarizing film is preferably 1 μm or more, more preferably 2 μm or more.
　偏光膜１０は、好ましくは、波長３８０ｎｍ～７８０ｎｍのいずれかの波長で吸収二色性を示す。偏光膜１０の単体透過率（Ｔｓ）は、好ましくは４１．０％以上であり、より好ましくは４２．０％以上であり、さらに好ましくは４２．５％以上である。一方、偏光膜１０の単体透過率は、例えば４４．２％以下である。偏光膜１０の偏光度（Ｐ）は、好ましくは９９．９５％以上であり、より好ましくは９９．９８％以上であり、さらに好ましくは９９．９９％以上である。一方、偏光膜１０の偏光度は、例えば９９．９９６％以下である。 The polarizing film 10 preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance (Ts) of the polarizing film 10 is preferably 41.0% or more, more preferably 42.0% or more, and further preferably 42.5% or more. On the other hand, the simple substance transmittance of the polarizing film 10 is, for example, 44.2% or less. The degree of polarization (P) of the polarizing film 10 is preferably 99.95% or more, more preferably 99.98% or more, and further preferably 99.99% or more. On the other hand, the degree of polarization of the polarizing film 10 is, for example, 99.996% or less.
　上記単体透過率は、代表的には、紫外可視分光光度計を用いて測定し、視感度補正を行なったＹ値である。上記偏光度は、代表的には、紫外可視分光光度計を用いて測定して視感度補正を行なった平行透過率Ｔｐおよび直交透過率Ｔｃに基づいて、下記式により求められる。
　　　偏光度（％）＝｛（Ｔｐ－Ｔｃ）／（Ｔｐ＋Ｔｃ）｝１／２×１００ The simple substance transmittance is typically a Y value measured by using an ultraviolet-visible spectrophotometer and corrected for luminosity factor. The degree of polarization is typically obtained by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by using an ultraviolet-visible spectrophotometer and corrected for luminosity factor.
Degree of polarization (%) = {(Tp-Tc) / (Tp + Tc)} 1/2 × 100
　偏光膜１０の表面１０ａの、吸収軸方向の波長６８０ｎｍの光の反射率Ｒｃ６８０に対する吸収軸方向の波長４００ｎｍの光の反射率Ｒｃ４００の比（Ｒｃ４００／Ｒｃ６８０）は、１を超え、好ましくは１．３以上であり、より好ましくは１．５以上である。このような関係を満たすことにより、反射色相が良好に制御されて外観に優れ得る。具体的には、赤味が抑制され、外観に優れ得る。その結果、例えば、視認性に優れた画像表示装置を提供し得る。ここで、偏光膜１０を、その表面１０ａが画像表示装置の視認側となるように配置してもよいし視認側とは反対側となるように配置してもよく、いずれの配置においても外観に優れ得る。偏光膜１０の表面１０ａが画像表示装置の視認側となるように配置することにより、外観および表示特性において極めて優れ得る。一方、偏光膜１０の表面１０ａのＲｃ４００／Ｒｃ６８０は、例えば２以下である。 The ratio (Rc 400 / Rc 680 ) of the reflectance Rc 400 of the light having a wavelength of 400 nm in the absorption axis direction to the reflectance Rc 680 of the light having a wavelength of 680 nm in the absorption axis direction of the surface 10a of the polarizing film 10 exceeds 1. It is preferably 1.3 or more, and more preferably 1.5 or more. By satisfying such a relationship, the reflected hue is well controlled and the appearance can be excellent. Specifically, redness is suppressed and the appearance can be excellent. As a result, for example, an image display device having excellent visibility can be provided. Here, the polarizing film 10 may be arranged so that the surface 10a thereof is on the viewing side of the image display device, or may be arranged so as to be on the side opposite to the viewing side. Get excellent. By arranging the surface 10a of the polarizing film 10 so as to be on the visual side of the image display device, the appearance and display characteristics can be extremely excellent. On the other hand, the Rc 400 / Rc 680 of the surface 10a of the polarizing film 10 is, for example, 2 or less.
　偏光膜１０の表面１０ａのＲｃ４００は、例えば４．８％以上であり、好ましくは４．９％以上であり、より好ましくは５％以上であり、さらに好ましくは５．３％以上である。一方、偏光膜１０の表面１０ａのＲｃ４００は、例えば６％以下である。偏光膜１０の表面１０ａのＲｃ６８０は、例えば５％以下であり、好ましくは４．９％以下であり、より好ましくは４．５％以下であり、さらに好ましくは４％以下である。一方、偏光膜１０の表面１０ａのＲｃ６８０は、例えば３％以上である。 The Rc 400 of the surface 10a of the polarizing film 10 is, for example, 4.8% or more, preferably 4.9% or more, more preferably 5% or more, and further preferably 5.3% or more. On the other hand, the Rc 400 of the surface 10a of the polarizing film 10 is, for example, 6% or less. The Rc 680 of the surface 10a of the polarizing film 10 is, for example, 5% or less, preferably 4.9% or less, more preferably 4.5% or less, and further preferably 4% or less. On the other hand, the Rc 680 of the surface 10a of the polarizing film 10 is, for example, 3% or more.
　偏光膜１０の表面１０ａの透過軸方向の波長４００ｎｍの光の反射率Ｒｐ４００は、例えば４．５％～５％である。偏光膜１０の表面１０ａの透過軸方向の波長６８０ｎｍの光の反射率Ｒｐ６８０は、例えば４．３％～４．８％である。 The reflectance Rp 400 of light having a wavelength of 400 nm in the transmission axis direction of the surface 10a of the polarizing film 10 is, for example, 4.5% to 5%. The reflectance Rp 680 of light having a wavelength of 680 nm in the transmission axis direction of the surface 10a of the polarizing film 10 is, for example, 4.3% to 4.8%.
　上記ＲｃおよびＲｐはそれぞれ、偏光膜（樹脂フィルム）の表面に所定の角度で光を入射させて吸収軸方向および透過軸方向の反射光を検出した場合の、入射光強度に対する反射光強度の比率である。 Each of the above Rc and Rp is the ratio of the reflected light intensity to the incident light intensity when light is incident on the surface of the polarizing film (resin film) at a predetermined angle and the reflected light in the absorption axis direction and the transmission axis direction is detected. Is.
　例えば、偏光膜１０は、表面１０ａ側のヨウ素量が裏面１０ｂ側のヨウ素量よりも少ない。具体的には、偏光膜１０は、表面側から、ヨウ素の分布状態が異なる第一領域１１と第二領域１２とをこの順に有する。第一領域１１は、表面１０ａから裏面１０ｂに向かってヨウ素量が多くなる傾斜分布領域である。第二領域１２ではヨウ素は均一に分布している。ここで、均一とは、例えば、分析により検出されるヨウ素に由来する（例えば、ヨウ素イオンの）強度が平均値より－２０％～＋２０％の範囲内であることをいう。第一領域１１の厚みは、偏光膜１０の厚みの２％以上５０％以下であることが好ましく、より好ましくは１０％以上４０％以下である。第一領域１１の厚みは、偏光膜１０の厚みの２０％以上であってもよい。具体的には、第一領域１１の厚みは、１００ｎｍ以上２．７μｍ以下であることが好ましく、より好ましくは５００ｎｍ以上２μｍ以下である。第一領域１１の厚みは、１μｍ以上であってもよい。このような範囲によれば、例えば、優れた光学特性（上記単体透過率および偏光度）と優れた外観とを達成し得る。 For example, in the polarizing film 10, the amount of iodine on the front surface 10a side is smaller than the amount of iodine on the back surface 10b side. Specifically, the polarizing film 10 has a first region 11 and a second region 12 having different iodine distribution states in this order from the surface side. The first region 11 is a gradient distribution region in which the amount of iodine increases from the front surface 10a to the back surface 10b. Iodine is uniformly distributed in the second region 12. Here, "uniformity" means that, for example, the intensity derived from iodine (for example, iodine ion) detected by analysis is in the range of -20% to + 20% from the average value. The thickness of the first region 11 is preferably 2% or more and 50% or less, and more preferably 10% or more and 40% or less of the thickness of the polarizing film 10. The thickness of the first region 11 may be 20% or more of the thickness of the polarizing film 10. Specifically, the thickness of the first region 11 is preferably 100 nm or more and 2.7 μm or less, and more preferably 500 nm or more and 2 μm or less. The thickness of the first region 11 may be 1 μm or more. According to such a range, for example, excellent optical characteristics (the above-mentioned simple substance transmittance and degree of polarization) and excellent appearance can be achieved.
　図示しないが、例えば、偏光膜は、表面側から、ヨウ素の分布状態が異なる第一領域、第二領域および第三領域をこの順に有していてもよい。具体的には、偏光膜は、表面から裏面に向かってヨウ素量が多くなる第一領域、ヨウ素が均一に分布する第二領域、および、表面側から裏面に向かってヨウ素量が少なくなる第三領域を有していてもよい。 Although not shown, for example, the polarizing film may have a first region, a second region, and a third region having different iodine distribution states in this order from the surface side. Specifically, the polarizing film has a first region in which the amount of iodine increases from the front surface to the back surface, a second region in which iodine is uniformly distributed, and a third region in which the amount of iodine decreases from the front surface side to the back surface. It may have an area.
Ｂ．製造方法
　上記偏光膜は、ヨウ素を含み、所定の水分率を有する樹脂膜の表面を水洗することにより得られる。樹脂膜の水分率（水洗前）は、１５重量％以下であり、好ましくは１２重量％以下であり、より好ましくは９重量％以下であり、さらに好ましくは６重量％以下である。一方、樹脂膜の水分率は、例えば３重量％以上である。このような水分率を有する樹脂膜に対し水洗を行うことにより、上記偏光膜を良好に作製し得る。具体的には、優れた光学特性を保持させながら、表面の反射特性（例えば、反射率、色相）を良好に制御することができる。例えば、波長５５０ｎｍ以上の長波長領域の反射率を下げて赤味を抑え、目視にて青味を認識可能にし得る。 B. Manufacturing Method The polarizing film is obtained by washing the surface of a resin film containing iodine and having a predetermined water content with water. The water content (before washing with water) of the resin film is 15% by weight or less, preferably 12% by weight or less, more preferably 9% by weight or less, and further preferably 6% by weight or less. On the other hand, the water content of the resin film is, for example, 3% by weight or more. By washing the resin film having such a water content with water, the above-mentioned polarizing film can be satisfactorily produced. Specifically, it is possible to satisfactorily control the reflection characteristics (for example, reflectance, hue) of the surface while maintaining excellent optical characteristics. For example, the reflectance in a long wavelength region having a wavelength of 550 nm or more can be lowered to suppress redness, and blueness can be visually recognized.
　上記樹脂膜のヨウ素濃度は、例えば５重量％以上であり、５．５重量％以上であってもよく、６重量％以上であってもよい。樹脂膜のヨウ素濃度は、例えば８重量％以下である。上記樹脂膜の厚みは、例えば７μｍ以下であり、６μｍ以下であってもよい。樹脂膜の厚みは、好ましくは１μｍ以上であり、より好ましくは２μｍ以上である。このようなヨウ素濃度、厚みにおいて優れた外観を達成し得ることが、本発明の特徴の一つである。 The iodine concentration of the resin film is, for example, 5% by weight or more, 5.5% by weight or more, or 6% by weight or more. The iodine concentration of the resin film is, for example, 8% by weight or less. The thickness of the resin film is, for example, 7 μm or less, and may be 6 μm or less. The thickness of the resin film is preferably 1 μm or more, more preferably 2 μm or more. It is one of the features of the present invention that an excellent appearance can be achieved in such an iodine concentration and thickness.
Ｂ－１．樹脂膜
　上記所定の水分率を有する樹脂膜は、例えば、樹脂基材上に樹脂層（代表的には、ポリビニルアルコール系樹脂層）を形成して積層体を作製し、この積層体（樹脂層）を延伸およびヨウ素で染色（例えば、ヨウ素の吸着により染色）し、その後、積層体（樹脂層）を乾燥することにより得ることができる。 B-1. Resin film For the resin film having the above-mentioned predetermined water content, for example, a resin layer (typically, a polyvinyl alcohol-based resin layer) is formed on a resin base material to prepare a laminated body, and the laminated body (resin layer) is formed. ) Is stretched and stained with iodine (for example, dyed by adsorption of iodine), and then the laminate (resin layer) is dried.
Ｂ－１－１．積層体
　１つの実施形態においては、熱可塑性樹脂基材（例えば、長尺状の）上に、ポリビニルアルコール（ＰＶＡ）系樹脂とハロゲン化物とを含むＰＶＡ系樹脂層を形成して上記積層体を作製する。具体的には、熱可塑性樹脂基材上に、ＰＶＡ系樹脂とハロゲン化物とを含む塗布液を塗布し、乾燥することにより、積層体を作製する。 B-1-1. Laminated body In one embodiment, a PVA-based resin layer containing a polyvinyl alcohol (PVA) -based resin and a halide is formed on a thermoplastic resin base material (for example, a long shape) to form the laminated body. To make. Specifically, a coating liquid containing a PVA-based resin and a halide is applied onto a thermoplastic resin base material and dried to prepare a laminate.
　上記熱可塑性樹脂基材の厚みは、好ましくは２０μｍ～３００μｍであり、より好ましくは５０μｍ～２００μｍである。２０μｍ未満であると、ＰＶＡ系樹脂層の形成が困難になるおそれがある。３００μｍを超えると、例えば、後述の水中延伸において、熱可塑性樹脂基材が水を吸収するのに時間を要するとともに、延伸に過大な負荷を要するおそれがある。 The thickness of the thermoplastic resin base material is preferably 20 μm to 300 μm, and more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form a PVA-based resin layer. If it exceeds 300 μm, for example, in the later-described underwater stretching, it takes time for the thermoplastic resin base material to absorb water, and there is a possibility that an excessive load is required for stretching.
　熱可塑性樹脂基材の吸水率は、好ましくは０．２％以上であり、さらに好ましくは０．３％以上である。このような熱可塑性樹脂基材は、水を吸収し、水が可塑剤的な働きをして可塑化し得る。その結果、延伸応力を大幅に低下させ、高倍率に延伸し得る。一方、熱可塑性樹脂基材の吸水率は、好ましくは３．０％以下であり、より好ましくは１．０％以下である。このような吸水率によれば、製造時に熱可塑性樹脂基材の寸法安定性が著しく低下して、得られる偏光膜の品質が悪化するなどの不具合を防止することができる。また、水中延伸時に熱可塑性樹脂基材が破断したり、ＰＶＡ系樹脂層が剥離したりするのを防止することができる。熱可塑性樹脂基材の吸水率は、例えば、構成材料に変性基を導入することにより調整することができる。なお、吸水率は、ＪＩＳ　Ｋ　７２０９に準じて求められる値である。 The water absorption rate of the thermoplastic resin base material is preferably 0.2% or more, more preferably 0.3% or more. Such a thermoplastic resin base material absorbs water, and the water can act as a plasticizer to plasticize. As a result, the stretching stress can be significantly reduced and the drawing can be performed at a high magnification. On the other hand, the water absorption rate of the thermoplastic resin base material is preferably 3.0% or less, more preferably 1.0% or less. With such a water absorption rate, it is possible to prevent problems such as deterioration of the quality of the obtained polarizing film due to a significant decrease in the dimensional stability of the thermoplastic resin base material during production. Further, it is possible to prevent the thermoplastic resin base material from breaking or the PVA-based resin layer from peeling off during stretching in water. The water absorption rate of the thermoplastic resin base material can be adjusted, for example, by introducing a modifying group into the constituent material. The water absorption rate is a value obtained according to JIS K 7209.
　熱可塑性樹脂基材のガラス転移温度（Ｔｇ）は、好ましくは１２０℃以下である。このような熱可塑性樹脂基材を用いることにより、ＰＶＡ系樹脂層の結晶化を抑制しながら、積層体の延伸性を十分に確保することができる。さらに、水による熱可塑性樹脂基材の可塑化と、水中延伸を良好に行うことを考慮すると、Ｔｇは、より好ましくは１００℃以下であり、さらに好ましくは９０℃以下である。一方、熱可塑性樹脂基材のＴｇは、好ましくは６０℃以上である。このようなＴｇによれば、上記塗布液を塗布・乾燥する際に、熱可塑性樹脂基材が変形（例えば、凹凸やタルミ、シワ等の発生）するなどの不具合を防止して、良好に積層体を作製することができる。また、上記樹脂層の延伸を、好適な温度（例えば、６０℃程度）にて良好に行うことができる。熱可塑性樹脂基材のＴｇは、例えば、構成材料に変性基を導入する、結晶化材料を用いて加熱することにより調整することができる。なお、ガラス転移温度（Ｔｇ）は、ＪＩＳ　Ｋ　７１２１に準じて求められる値である。 The glass transition temperature (Tg) of the thermoplastic resin base material is preferably 120 ° C. or lower. By using such a thermoplastic resin base material, it is possible to sufficiently secure the stretchability of the laminated body while suppressing the crystallization of the PVA-based resin layer. Further, considering that the thermoplastic resin base material is plasticized with water and well stretched in water, the Tg is more preferably 100 ° C. or lower, still more preferably 90 ° C. or lower. On the other hand, the Tg of the thermoplastic resin base material is preferably 60 ° C. or higher. According to such Tg, when the coating liquid is applied and dried, the thermoplastic resin base material is prevented from being deformed (for example, unevenness, tarmi, wrinkles, etc.), and the lamination is good. You can make a body. Further, the stretching of the resin layer can be satisfactorily performed at a suitable temperature (for example, about 60 ° C.). The Tg of the thermoplastic resin substrate can be adjusted, for example, by heating with a crystallization material that introduces a modifying group into the constituent material. The glass transition temperature (Tg) is a value obtained according to JIS K7121.
　熱可塑性樹脂基材の構成材料としては、任意の適切な熱可塑性樹脂が採用され得る。熱可塑性樹脂としては、例えば、ポリエチレンテレフタレート系樹脂等のエステル系樹脂、ノルボルネン系樹脂等のシクロオレフィン系樹脂、ポリプロピレン等のオレフィン系樹脂、ポリアミド系樹脂、ポリカーボネート系樹脂、これらの共重合体樹脂が挙げられる。これらの中でも、好ましくは、ノルボルネン系樹脂、非晶質のポリエチレンテレフタレート系樹脂である。 Any suitable thermoplastic resin can be adopted as the constituent material of the thermoplastic resin base material. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Can be mentioned. Among these, norbornene-based resin and amorphous polyethylene terephthalate-based resin are preferable.
　１つの実施形態においては、非晶質の（結晶化していない）ポリエチレンテレフタレート系樹脂が好ましく用いられる。中でも、非晶性の（結晶化しにくい）ポリエチレンテレフタレート系樹脂が特に好ましく用いられる。非晶性のポリエチレンテレフタレート系樹脂の具体例としては、ジカルボン酸としてイソフタル酸および／またはシクロヘキサンジカルボン酸をさらに含む共重合体や、グリコールとしてシクロヘキサンジメタノールやジエチレングリコールをさらに含む共重合体が挙げられる。 In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among them, an amorphous (difficult to crystallize) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid and / or a cyclohexanedicarboxylic acid as a dicarboxylic acid, and a copolymer further containing cyclohexanedimethanol or diethylene glycol as a glycol.
　別の実施形態においては、イソフタル酸ユニットを有するポリエチレンテレフタレート系樹脂が好ましく用いられる。延伸性に極めて優れるとともに、延伸時の結晶化が抑制され得るからである。これは、イソフタル酸ユニットを導入することで、主鎖に大きな屈曲を与えることによるものと考えられる。ポリエチレンテレフタレート系樹脂は、テレフタル酸ユニットおよびエチレングリコールユニットを有する。イソフタル酸ユニットの含有割合は、全繰り返し単位の合計に対して、好ましくは０．１モル％以上であり、より好ましくは１．０モル％以上である。延伸性に極めて優れた熱可塑性樹脂基材が得られるからである。一方、イソフタル酸ユニットの含有割合は、全繰り返し単位の合計に対して、好ましくは２０モル％以下であり、より好ましくは１０モル％以下である。後述の乾燥において結晶化度を良好に増加させ得るからである。 In another embodiment, a polyethylene terephthalate resin having an isophthalic acid unit is preferably used. This is because the stretchability is extremely excellent and crystallization during stretching can be suppressed. It is considered that this is because the introduction of the isophthalic acid unit gives a large bending to the backbone. The polyethylene terephthalate resin has a terephthalic acid unit and an ethylene glycol unit. The content ratio of the isophthalic acid unit is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, based on the total of all repeating units. This is because a thermoplastic resin base material having extremely excellent stretchability can be obtained. On the other hand, the content ratio of the isophthalic acid unit is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total of all repeating units. This is because the crystallinity can be satisfactorily increased in the drying described later.
　熱可塑性樹脂基材は、予め（例えば、ＰＶＡ系樹脂層を形成する前に）、延伸されていてもよい。１つの実施形態においては、長尺状の熱可塑性樹脂基材の横方向に延伸されている。横方向は、好ましくは、後述の積層体の延伸方向に直交する方向である。なお、本明細書において、「直交」とは、実質的に直交する場合も包含する。ここで、「実質的に直交」とは、９０°±５．０°である場合を包含し、好ましくは９０°±３．０°、さらに好ましくは９０°±１．０°である。熱可塑性樹脂基材の延伸温度は、熱可塑性樹脂基材のガラス転移温度（Ｔｇ）に対し、好ましくはＴｇ－１０℃～Ｔｇ＋５０℃である。熱可塑性樹脂基材の延伸倍率は、好ましくは１．５倍～３．０倍である。熱可塑性樹脂基材の延伸方法としては、任意の適切な方法が採用され得る。具体的には、固定端延伸でもよいし、自由端延伸でもよい。延伸方式は、乾式でもよいし、湿式でもよい。延伸は、一段階で行ってもよいし、多段階で行ってもよい。多段階で行う場合、上記延伸倍率は、各段階の延伸倍率の積である。 The thermoplastic resin base material may be stretched in advance (for example, before forming the PVA-based resin layer). In one embodiment, the elongated thermoplastic resin substrate is laterally stretched. The lateral direction is preferably a direction orthogonal to the stretching direction of the laminate described later. In addition, in this specification, "orthogonal" includes a case where it is substantially orthogonal. Here, "substantially orthogonal" includes the case of 90 ° ± 5.0 °, preferably 90 ° ± 3.0 °, and more preferably 90 ° ± 1.0 °. The stretching temperature of the thermoplastic resin base material is preferably Tg-10 ° C. to Tg + 50 ° C. with respect to the glass transition temperature (Tg) of the thermoplastic resin base material. The draw ratio of the thermoplastic resin base material is preferably 1.5 to 3.0 times. Any suitable method can be adopted as the method for stretching the thermoplastic resin base material. Specifically, it may be fixed-end stretching or free-end stretching. The stretching method may be a dry method or a wet method. Stretching may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios in each stage.
　上記塗布液は、代表的には、ＰＶＡ系樹脂とハロゲン化物とを溶媒に溶解させた溶液である。溶媒としては、例えば、水、ジメチルスルホキシド、ジメチルホルムアミド、ジメチルアセトアミド、Ｎ－メチルピロリドン、各種グリコール類、トリメチロールプロパン等の多価アルコール類、エチレンジアミン、ジエチレントリアミン等のアミン類が挙げられる。これらは単独で、または、二種以上組み合わせて用いることができる。これらの中でも、好ましくは、水である。塗布液におけるＰＶＡ系樹脂の含有量は、溶媒１００重量部に対して、好ましくは３重量部～２０重量部である。このような範囲によれば、熱可塑性樹脂基材に密着した均一な塗布膜を形成することができる。塗布液におけるハロゲン化物の含有量は、ＰＶＡ系樹脂１００重量部に対して、好ましくは５重量部～２０重量部である。 The coating liquid is typically a solution in which a PVA-based resin and a halide are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferable. The content of the PVA-based resin in the coating liquid is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. According to such a range, it is possible to form a uniform coating film in close contact with the thermoplastic resin base material. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
　上記ＰＶＡ系樹脂としては、例えば、ポリビニルアルコール、エチレン－ビニルアルコール共重合体が挙げられる。ポリビニルアルコールは、ポリ酢酸ビニルをケン化することにより得られる。エチレン－ビニルアルコール共重合体は、エチレン－酢酸ビニル共重合体をケン化することにより得られる。ＰＶＡ系樹脂のケン化度は、通常８５モル％～１００モル％であり、好ましくは９５．０モル％～９９．９５モル％であり、より好ましくは９９．０モル％～９９．９３モル％である。このようなケン化度のＰＶＡ系樹脂を用いることによって、耐久性に優れた偏光膜が得られ得る。ケン化度が高すぎる場合には、ゲル化してしまうおそれがある。なお、ケン化度は、ＪＩＳ　Ｋ　６７２６－１９９４に準じて求めることができる。 Examples of the PVA-based resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. Is. By using a PVA-based resin having such a saponification degree, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur. The degree of saponification can be determined according to JIS K 6726-1994.
　ＰＶＡ系樹脂の平均重合度は、通常１０００～１００００であり、好ましくは１２００～４５００であり、より好ましくは１５００～４３００である。なお、平均重合度は、ＪＩＳ　Ｋ　６７２６－１９９４に準じて求めることができる。 The average degree of polymerization of the PVA-based resin is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.
　上記ハロゲン化物としては、任意の適切なハロゲン化物が採用され得る。例えば、ヨウ化カリウム、ヨウ化ナトリウム、ヨウ化リチウム等のヨウ化物、塩化ナトリウム等の塩化物が挙げられる。これらの中でも、好ましくは、ヨウ化カリウムである。ハロゲン化物を用いることにより、優れた光学特性を有する偏光膜を得ることができる。具体的には、後述の空中補助延伸後のＰＶＡ系樹脂の結晶化が促進され、その後の湿式処理（例えば、後述の染色、水中延伸）において、ポリビニルアルコール分子の配向の乱れおよび配向性の低下が抑制され、優れた光学特性を有する偏光膜を得ることができる。 As the above-mentioned halide, any suitable halide can be adopted. Examples thereof include iodides such as potassium iodide, sodium iodide and lithium iodide, and chlorides such as sodium chloride. Among these, potassium iodide is preferable. By using a halide, a polarizing film having excellent optical characteristics can be obtained. Specifically, the crystallization of the PVA-based resin after the aerial auxiliary stretching described later is promoted, and in the subsequent wet treatment (for example, staining described later, stretching in water), the orientation of the polyvinyl alcohol molecule is disturbed and the orientation is lowered. Is suppressed, and a polarizing film having excellent optical characteristics can be obtained.
　塗布液の調製において、ＰＶＡ系樹脂１００重量部に対して、ハロゲン化物を５重量部～２０重量部配合することが好ましく、より好ましくは１０重量部～１５重量部である。具体的には、得られるＰＶＡ系樹脂層におけるハロゲン化物の含有量は、ＰＶＡ系樹脂１００重量部に対し、好ましくは５重量部～２０重量部であり、より好ましくは１０重量部～１５重量部である。ＰＶＡ系樹脂に対するハロゲン化物の量が多いと、例えば、ハロゲン化物がブリードアウトし、得られる偏光膜が白濁する場合がある。 In the preparation of the coating liquid, it is preferable to add 5 parts by weight to 20 parts by weight of the halide with respect to 100 parts by weight of the PVA-based resin, and more preferably 10 parts by weight to 15 parts by weight. Specifically, the content of the halide in the obtained PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. Is. If the amount of the halide with respect to the PVA-based resin is large, for example, the halide may bleed out and the obtained polarizing film may become cloudy.
　塗布液に、添加剤を配合してもよい。添加剤としては、例えば、可塑剤、界面活性剤が挙げられる。可塑剤としては、例えば、エチレングリコールやグリセリン等の多価アルコールが挙げられる。界面活性剤としては、例えば、非イオン界面活性剤が挙げられる。これらは、例えば、得られるＰＶＡ系樹脂層の均一性や染色性、延伸性を向上させる目的で使用される。 Additives may be added to the coating liquid. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These are used, for example, for the purpose of improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.
　上記塗布液の塗布方法としては、例えば、ロールコート法、スピンコート法、ワイヤーバーコート法、ディップコート法、ダイコート法、カーテンコート法、スプレーコート法、ナイフコート法（コンマコート法等）が挙げられる。塗布液の塗布・乾燥温度は、好ましくは５０℃以上である。 Examples of the coating method of the coating liquid include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (comma coating method, etc.). Be done. The coating / drying temperature of the coating liquid is preferably 50 ° C. or higher.
　上記ＰＶＡ系樹脂層の厚みは、好ましくは３μｍ～４０μｍであり、さらに好ましくは３μｍ～２０μｍである。 The thickness of the PVA-based resin layer is preferably 3 μm to 40 μm, and more preferably 3 μm to 20 μm.
　ＰＶＡ系樹脂層を形成する前に、熱可塑性樹脂基材に表面処理（例えば、コロナ処理等）を施してもよいし、熱可塑性樹脂基材上に易接着層を形成してもよい。このような処理を行うことにより、熱可塑性樹脂基材とＰＶＡ系樹脂層との密着性を向上させることができる。 Before forming the PVA-based resin layer, the thermoplastic resin base material may be surface-treated (for example, corona treatment or the like), or the easy-adhesive layer may be formed on the thermoplastic resin base material. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.
Ｂ－１－２．延伸
　上記延伸は、上記積層体を、乾式延伸（空中補助延伸）した後に、水中延伸することにより行うことが好ましい。補助延伸により、上記熱可塑性樹脂基材の結晶化を抑制しながら延伸することができ、ホウ酸水中延伸において熱可塑性樹脂基材の過度の結晶化により延伸性が低下するという問題を解決し、積層体をより高倍率に延伸することができる。また、熱可塑性樹脂基材を用いる場合、上記塗布温度が低く設定され得ることから、ＰＶＡ系樹脂の結晶化が相対的に低くなって十分な光学特性が得られないという問題が生じ得る。これに対して、補助延伸を導入することにより、熱可塑性樹脂を用いる場合でも、ＰＶＡ系樹脂の結晶性を高め得る。また、ＰＶＡ系樹脂の配向性を事前に高めることで、後の湿式処理時に、ＰＶＡ系樹脂の配向性の低下や溶解などの問題を防止し得る。こうして、優れた光学特性を有する偏光膜が得られ得る。 B-1-2. Stretching The stretching is preferably performed by stretching the laminate in water after dry stretching (auxiliary stretching in the air). By auxiliary stretching, it is possible to stretch while suppressing the crystallization of the thermoplastic resin base material, and it solves the problem that the stretchability is lowered due to excessive crystallization of the thermoplastic resin base material in boric acid water stretching. The laminate can be stretched at a higher magnification. Further, when the thermoplastic resin base material is used, since the coating temperature can be set low, there may be a problem that the crystallization of the PVA-based resin is relatively low and sufficient optical characteristics cannot be obtained. On the other hand, by introducing the auxiliary stretching, the crystallinity of the PVA-based resin can be enhanced even when the thermoplastic resin is used. Further, by increasing the orientation of the PVA-based resin in advance, problems such as deterioration of the orientation of the PVA-based resin and dissolution can be prevented during the subsequent wet treatment. In this way, a polarizing film having excellent optical characteristics can be obtained.
　空中補助延伸の方法は、固定端延伸（例えば、テンター延伸機を用いて延伸する方法）でもよいし、自由端延伸（例えば、周速の異なるロール間に積層体を通して一軸延伸する方法）でもよい。好ましくは、自由端延伸が採用される。例えば、上記積層体をその長手方向に搬送しながら、加熱ロール間の周速差により延伸する加熱ロール延伸が採用される。１つの実施形態においては、空中補助延伸は、熱空間（ゾーン）におけるゾーン延伸工程と加熱ロール延伸工程とを含む。ゾーン延伸工程と加熱ロール延伸工程の順序は限定されないが、例えば、ゾーン延伸工程および加熱ロール延伸工程がこの順に行われる。別の実施形態においては、テンター延伸機において、フィルム端部を把持し、テンター間の距離を流れ方向に広げることで延伸される（テンター間の距離の広がりが延伸倍率となる）。この時、幅方向（流れ方向に対して垂直方向）のテンターの距離は、好ましくは、流れ方向の延伸倍率に対して、自由端延伸により近くなるように設定される。自由端延伸の場合、幅方向の収縮率は、式：幅方向の収縮率＝（１/延伸倍率）１／２で計算される。 The method of aerial auxiliary stretching may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). .. Preferably, free-end stretching is adopted. For example, a heating roll stretching method is adopted in which the laminated body is conveyed in the longitudinal direction thereof and is stretched by the difference in peripheral speed between the heating rolls. In one embodiment, the aerial auxiliary stretching includes a zone stretching step and a heating roll stretching step in a thermal space (zone). The order of the zone stretching step and the heating roll stretching step is not limited, but for example, the zone stretching step and the heating roll stretching step are performed in this order. In another embodiment, in the tenter stretching machine, the film is stretched by grasping the end portion of the film and widening the distance between the tenters in the flow direction (the widening of the distance between the tenters is the stretching ratio). At this time, the distance of the tenter in the width direction (perpendicular to the flow direction) is preferably set so as to be closer to the free end stretching with respect to the stretching ratio in the flow direction. In the case of free-end stretching, the shrinkage in the width direction is calculated by the formula: shrinkage in the width direction = (1 / stretching ratio) 1/2 .
　空中補助延伸の延伸倍率は、好ましくは２．０倍～３．５倍である。空中補助延伸は、一段階で行ってもよいし、多段階で行ってもよい。多段階で行う場合、延伸倍率は、各段階の延伸倍率の積である。空中補助延伸における延伸方向は、好ましくは、後述の水中延伸の延伸方向と略同一である。 The draw ratio of the aerial auxiliary stretch is preferably 2.0 to 3.5 times. The aerial auxiliary stretching may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios in each stage. The stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching described later.
　空中補助延伸の延伸温度は、例えば、用いる熱可塑性樹脂基材、延伸方式等に応じて、任意の適切な値に設定される。延伸温度は、好ましくは熱可塑性樹脂基材のガラス転移温度（Ｔｇ）以上であり、より好ましくはＴｇ＋１０℃以上であり、さらに好ましくはＴｇ＋１５℃以上である。一方、延伸温度の上限は、好ましくは１７０℃である。このような温度で延伸することで、ＰＶＡ系樹脂の結晶化が急速に進むのを抑制して、当該結晶化による不具合（例えば、延伸によるＰＶＡ系樹脂層の配向を妨げる）を抑制することができる。 The stretching temperature of the aerial auxiliary stretching is set to an arbitrary appropriate value depending on, for example, the thermoplastic resin base material used, the stretching method, and the like. The stretching temperature is preferably Tg + 10 ° C. or higher, more preferably Tg + 10 ° C. or higher, and even more preferably Tg + 15 ° C. or higher, preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate. On the other hand, the upper limit of the stretching temperature is preferably 170 ° C. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin and suppress defects due to the crystallization (for example, hindering the orientation of the PVA-based resin layer due to stretching). can.
　上記水中延伸は、代表的には、積層体を延伸浴に浸漬させて行う。水中延伸によれば、上記熱可塑性樹脂基材やＰＶＡ系樹脂層のガラス転移温度（代表的には、８０℃程度）よりも低い温度で延伸し得、ＰＶＡ系樹脂層を、その結晶化を抑えながら、高倍率に延伸することができる。その結果、優れた光学特性を有する偏光膜を得ることができる。 The underwater stretching is typically performed by immersing the laminate in a stretching bath. According to the underwater stretching, the thermoplastic resin base material or the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically, about 80 ° C.), and the PVA-based resin layer can be crystallized. It can be stretched at a high magnification while suppressing it. As a result, a polarizing film having excellent optical characteristics can be obtained.
　水中延伸の方法は、固定端延伸でもよいし、自由端延伸（例えば、周速の異なるロール間に積層体を通して一軸延伸する方法）でもよい。好ましくは、自由端延伸が採用される。積層体の延伸は、一段階で行ってもよいし、多段階で行ってもよい。多段階で行う場合、後述の積層体の延伸倍率は、各段階の延伸倍率の積である。 The method of underwater stretching may be fixed-end stretching or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Preferably, free-end stretching is adopted. The stretching of the laminate may be carried out in one step or in multiple steps. In the case of performing in multiple stages, the draw ratio of the laminated body described later is the product of the draw ratios of each stage.
　水中延伸は、好ましくは、積層体をホウ酸水溶液中に浸漬させて行う（ホウ酸水中延伸）。延伸浴としてホウ酸水溶液を用いることで、ＰＶＡ系樹脂層に、延伸時にかかる張力に耐える剛性と、水に溶解しない耐水性とを付与することができる。具体的には、ホウ酸は、水溶液中でテトラヒドロキシホウ酸アニオンを生成してＰＶＡ系樹脂と水素結合により架橋し得る。その結果、ＰＶＡ系樹脂層に剛性と耐水性とを付与して、良好に延伸することができ、優れた光学特性を有する偏光膜を得ることができる。 The underwater stretching is preferably carried out by immersing the laminate in a boric acid aqueous solution (boric acid water stretching). By using the boric acid aqueous solution as the stretching bath, it is possible to impart rigidity to withstand the tension applied during stretching and water resistance that does not dissolve in water to the PVA-based resin layer. Specifically, boric acid can generate a tetrahydroxyboric acid anion in an aqueous solution and crosslink with a PVA-based resin by hydrogen bonding. As a result, the PVA-based resin layer can be imparted with rigidity and water resistance, can be stretched satisfactorily, and a polarizing film having excellent optical characteristics can be obtained.
　上記ホウ酸水溶液は、好ましくは、溶媒である水にホウ酸および／またはホウ酸塩を溶解させることにより得られる。ホウ酸濃度は、水１００重量部に対して、好ましくは１重量部～１０重量部であり、より好ましくは２．５重量部～６重量部であり、さらに好ましくは３重量部～５重量部である。ホウ酸濃度を１重量部以上とすることにより、ＰＶＡ系樹脂層の溶解を効果的に抑制することができ、より高特性の偏光膜を製造することができる。なお、ホウ酸またはホウ酸塩以外に、ホウ砂等のホウ素化合物、グリオキザール、グルタルアルデヒド等を溶媒に溶解して得られた水溶液も用いることができる。 The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight, more preferably 2.5 parts by weight to 6 parts by weight, and further preferably 3 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. Is. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glioxal, glutaraldehyde or the like in a solvent can also be used.
　好ましくは、上記延伸浴（ホウ酸水溶液）にヨウ化物を配合する。ヨウ化物を配合することにより、ＰＶＡ系樹脂層に吸着させたヨウ素の溶出を抑制することができる。ヨウ化物としては、例えば、ヨウ化カリウム、ヨウ化リチウム、ヨウ化ナトリウム、ヨウ化亜鉛、ヨウ化アルミニウム、ヨウ化鉛、ヨウ化銅、ヨウ化バリウム、ヨウ化カルシウム、ヨウ化錫、ヨウ化チタンが挙げられる。ヨウ化物の濃度は、水１００重量部に対して、好ましくは０．０５重量部～１５重量部であり、より好ましくは０．５重量部～８重量部である。 Preferably, iodide is added to the above stretching bath (boric acid aqueous solution). By blending iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Can be mentioned. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, and more preferably 0.5 parts by weight to 8 parts by weight with respect to 100 parts by weight of water.
　延伸温度（延伸浴の液温）は、好ましくは４０℃以上であり、より好ましくは６０℃以上である。このような温度であれば、ＰＶＡ系樹脂層の溶解を抑制しながら高倍率に延伸することができる。具体的には、上述のように、熱可塑性樹脂基材のガラス転移温度（Ｔｇ）は、ＰＶＡ系樹脂層の形成との関係で、好ましくは６０℃以上である。この場合、延伸温度が４０℃を下回ると、水による熱可塑性樹脂基材の可塑化を考慮しても、良好に延伸できないおそれがある。一方、延伸温度は、例えば７０℃以下であり、好ましくは６７℃以下であり、より好ましくは６５℃以下である。延伸温度が高温になるほど、ＰＶＡ系樹脂層の溶解性が高くなって、優れた光学特性が得られないおそれがある。また、このような延伸温度によれば、後述の水洗においてＰＶＡ系樹脂層が膨潤・溶解するのを抑制し、表面性状に優れた偏光膜を得ることができる。積層体の延伸浴への浸漬時間は、好ましくは１５秒～５分である。 The stretching temperature (liquid temperature of the stretching bath) is preferably 40 ° C. or higher, more preferably 60 ° C. or higher. At such a temperature, the PVA-based resin layer can be stretched at a high magnification while suppressing dissolution. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40 ° C., it may not be stretched well even in consideration of the plasticization of the thermoplastic resin base material by water. On the other hand, the stretching temperature is, for example, 70 ° C. or lower, preferably 67 ° C. or lower, and more preferably 65 ° C. or lower. The higher the stretching temperature, the higher the solubility of the PVA-based resin layer, and there is a possibility that excellent optical properties cannot be obtained. Further, according to such a stretching temperature, it is possible to suppress the swelling and dissolution of the PVA-based resin layer in the washing with water described later, and to obtain a polarizing film having excellent surface properties. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.
　水中延伸による延伸倍率は、好ましくは１．５倍以上であり、より好ましくは３．０倍以上である。積層体の総延伸倍率（空中補助延伸と水中延伸とを組み合わせた延伸倍率）は、積層体の元長に対して、好ましくは５．０倍以上であり、より好ましくは５．５倍以上であり、さらに好ましくは６．０倍以上である。このような高い延伸倍率を達成することにより、光学特性に極めて優れた偏光膜を製造することができる。このような高い延伸倍率は、水中延伸方式（ホウ酸水中延伸）を採用することにより、達成し得る。 The stretching ratio by stretching in water is preferably 1.5 times or more, more preferably 3.0 times or more. The total draw ratio of the laminated body (stretching ratio combining aerial auxiliary stretching and underwater stretching) is preferably 5.0 times or more, more preferably 5.5 times or more with respect to the original length of the laminated body. Yes, more preferably 6.0 times or more. By achieving such a high draw ratio, it is possible to manufacture a polarizing film having extremely excellent optical characteristics. Such a high draw ratio can be achieved by adopting an underwater stretching method (boric acid underwater stretching).
Ｂ－１－３．染色
　上記染色は、代表的には、ＰＶＡ系樹脂層にヨウ素を吸着させることにより行う。ヨウ素の吸着方法としては、例えば、ヨウ素を含む染色液にＰＶＡ系樹脂層（積層体）を浸漬させる方法、ＰＶＡ系樹脂層に当該染色液を塗工する方法、当該染色液をＰＶＡ系樹脂層に噴霧する方法が挙げられる。好ましくは、染色液（染色浴）に積層体を浸漬させる方法である。ヨウ素が良好に吸着され得るからである。 B-1-3. Dyeing The above dyeing is typically performed by adsorbing iodine on a PVA-based resin layer. Examples of the iodine adsorption method include a method of immersing a PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA-based resin layer, and a method of applying the dyeing solution to the PVA-based resin layer. There is a method of spraying on. A method of immersing the laminate in a dyeing solution (staining bath) is preferable. This is because iodine can be adsorbed well.
　上記染色液は、好ましくは、ヨウ素水溶液である。ヨウ素の配合量は、水１００重量部に対して、好ましくは０．０５重量部～０．５重量部である。ヨウ素の水に対する溶解度を高めるため、ヨウ素水溶液にヨウ化物を配合することが好ましい。ヨウ化物の具体例としては、上述のとおりである。好ましくは、ヨウ化カリウムが用いられる。ヨウ化物の配合量は、水１００重量部に対して、好ましくは０．１重量部～１０重量部であり、より好ましくは０．３重量部～５重量部である。染色液の染色時の液温は、ＰＶＡ系樹脂の溶解を抑制するため、好ましくは２０℃～５０℃である。染色液にＰＶＡ系樹脂層を浸漬させる場合、浸漬時間は、ＰＶＡ系樹脂層の透過率を確保するため、好ましくは５秒～５分であり、より好ましくは３０秒～９０秒である。 The stain solution is preferably an aqueous iodine solution. The blending amount of iodine is preferably 0.05 part by weight to 0.5 part by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the aqueous iodine solution. Specific examples of iodide are as described above. Preferably, potassium iodide is used. The blending amount of the iodide is preferably 0.1 part by weight to 10 parts by weight, and more preferably 0.3 part by weight to 5 parts by weight with respect to 100 parts by weight of water. The liquid temperature at the time of dyeing the dyeing liquid is preferably 20 ° C. to 50 ° C. in order to suppress the dissolution of the PVA-based resin. When the PVA-based resin layer is immersed in the dyeing solution, the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds in order to secure the transmittance of the PVA-based resin layer.
　染色条件（濃度、液温、浸漬時間）は、例えば、最終的に得られる偏光膜の単体透過率が４２．０％以上であり、かつ、偏光度が９９．９８％以上となるように設定することができる。このような染色条件としては、例えば、染色液であるヨウ素水溶液において、ヨウ素およびヨウ化カリウムの含有量の比を１：５～１：２０とすることが好ましく、より好ましくは１：５～１：１０である。 The dyeing conditions (concentration, liquid temperature, immersion time) are set so that, for example, the single transmittance of the finally obtained polarizing film is 42.0% or more and the degree of polarization is 99.98% or more. can do. As such a dyeing condition, for example, the ratio of the content of iodine and potassium iodide in the iodine aqueous solution which is a dyeing solution is preferably 1: 5 to 1:20, and more preferably 1: 5 to 1. : 10.
　ホウ酸を含有する処理浴に積層体を浸漬させる処理（例えば、後述の不溶化処理）後に連続して染色を行う場合、ホウ酸が染色浴に混入して染色浴のホウ酸濃度が変化し、染色性が不安定になる場合がある。このような染色性の不安定化を抑制するために、染色浴のホウ酸濃度は、水１００重量部に対して、好ましくは４重量部以下、より好ましくは２重量部以下となるように調整される。一方で、染色浴のホウ酸濃度は、水１００重量部に対して、好ましくは０．１重量部以上であり、より好ましくは０．２重量部以上であり、さらに好ましくは０．５重量部以上である。１つの実施形態においては、予めホウ酸を含む染色浴を用いて染色する。このような形態によれば、ホウ酸が染色浴に混入した場合のホウ酸濃度の変化の割合を低減し得る。予め染色浴に配合するホウ酸の配合量（上記処理浴に由来しないホウ酸の含有量）は、水１００重量部に対して、好ましくは０．１重量部～２重量部であり、より好ましくは０．５重量部～１．５重量部である。 When continuous dyeing is performed after a treatment in which the laminate is immersed in a treatment bath containing boric acid (for example, an insolubilization treatment described later), boric acid is mixed in the dyeing bath and the boric acid concentration in the dyeing bath changes. Dyeability may become unstable. In order to suppress such destabilization of dyeability, the boric acid concentration in the dyeing bath is adjusted to be preferably 4 parts by weight or less, more preferably 2 parts by weight or less with respect to 100 parts by weight of water. Will be done. On the other hand, the boric acid concentration in the dyeing bath is preferably 0.1 part by weight or more, more preferably 0.2 part by weight or more, and further preferably 0.5 part by weight with respect to 100 parts by weight of water. That is all. In one embodiment, dyeing is performed using a dyeing bath containing boric acid in advance. According to such a form, the rate of change in boric acid concentration when boric acid is mixed in the dyeing bath can be reduced. The amount of boric acid to be blended in the dyeing bath in advance (the content of boric acid not derived from the above-mentioned treatment bath) is preferably 0.1 part by weight to 2 parts by weight, more preferably with respect to 100 parts by weight of water. Is from 0.5 parts by weight to 1.5 parts by weight.
Ｂ－１－４．その他の処理
　必要に応じて、上記空中補助延伸の後、水中延伸および染色の前に、不溶化処理を行う。不溶化処理は、代表的には、ホウ酸水溶液にＰＶＡ系樹脂層を浸漬させることにより行う。不溶化処理を施すことにより、ＰＶＡ系樹脂層に耐水性を付与し、水に浸漬した時のＰＶＡの配向低下を防止することができる。不溶化処理におけるホウ酸水溶液の濃度は、水１００重量部に対して、好ましくは１重量部～４重量部である。不溶化処理の温度（ホウ酸水溶液の液温）は、好ましくは２０℃～５０℃である。 B-1-4. Other Treatments If necessary, insolubilization treatment is performed after the above-mentioned aerial auxiliary stretching and before water stretching and staining. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. By performing the insolubilization treatment, it is possible to impart water resistance to the PVA-based resin layer and prevent the orientation of PVA from deteriorating when immersed in water. The concentration of the boric acid aqueous solution in the insolubilization treatment is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. The temperature of the insolubilization treatment (liquid temperature of the boric acid aqueous solution) is preferably 20 ° C to 50 ° C.
　必要に応じて、染色の後、水中延伸の前に、架橋処理を行う。架橋処理は、代表的には、ホウ酸水溶液にＰＶＡ系樹脂層を浸漬させることにより行う。架橋処理を施すことにより、ＰＶＡ系樹脂層に耐水性を付与し、後の水中延伸においてＰＶＡの配向低下を防止することができる。架橋処理におけるホウ酸水溶液の濃度は、水１００重量部に対して、好ましくは１重量部～５重量部である。ホウ酸水溶液にヨウ化物を配合することが好ましい。ヨウ化物を配合することにより、ＰＶＡ系樹脂層に吸着させたヨウ素の溶出を抑制することができる。ヨウ化物の具体例は、上述のとおりである。ヨウ化物の配合量は、水１００重量部に対して、好ましくは１重量部～５重量部である。架橋処理の温度（ホウ酸水溶液の液温）、好ましくは２０℃～５０℃である。 If necessary, perform cross-linking treatment after dyeing and before stretching in water. The cross-linking treatment is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. By performing the cross-linking treatment, the PVA-based resin layer can be imparted with water resistance, and the orientation of PVA can be prevented from being lowered in the subsequent stretching in water. The concentration of the boric acid aqueous solution in the crosslinking treatment is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. It is preferable to add iodide to the boric acid aqueous solution. By blending iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The blending amount of iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. The temperature of the crosslinking treatment (liquid temperature of the boric acid aqueous solution), preferably 20 ° C to 50 ° C.
　好ましくは、水中延伸の後、後述の乾燥の前に、洗浄を行う。洗浄は、代表的には、ヨウ化カリウム水溶液にＰＶＡ系樹脂層を浸漬させることにより行う。 It is preferable to wash after stretching in water and before drying, which will be described later. The washing is typically performed by immersing the PVA-based resin layer in an aqueous solution of potassium iodide.
Ｂ－１－５．乾燥
　上記乾燥は、上記所定の水分率を有する樹脂膜が得られ得る限り、任意の適切な方式および条件において行い得る。具体的には、ゾーン全体を加熱すること（ゾーン加熱方式）により行ってもよいし、搬送ロールを加熱すること（加熱ロール方式）により行ってもよい。好ましくは加熱ロール方式を採用し、より好ましくはその両方を採用する。加熱ロールを用いることにより、効率的に積層体の加熱カールを抑制して、品質に優れた偏光膜を製造することができる。具体的には、加熱ロールに積層体を沿わせた状態で乾燥することにより、上記熱可塑性樹脂基材の結晶化を効率的に促進させて結晶化度を増加させることができ、比較的低い乾燥温度であっても、熱可塑性樹脂基材の結晶化度を良好に増加させることができる。その結果、熱可塑性樹脂基材は、その剛性が増加して、乾燥によるＰＶＡ系樹脂層の収縮に耐え得る状態となり、カールが抑制される。また、加熱ロールを用いることにより、積層体を平らな状態に維持しながら乾燥できるので、カールだけでなくシワの発生も抑制することができる。 B-1-5. Drying The drying can be carried out under any suitable method and conditions as long as a resin film having the above-mentioned predetermined moisture content can be obtained. Specifically, it may be performed by heating the entire zone (zone heating method) or by heating the transport roll (heating roll method). A heating roll method is preferably adopted, and more preferably both are adopted. By using the heating roll, it is possible to efficiently suppress the heating curl of the laminated body and produce a polarizing film having excellent quality. Specifically, by drying the laminated body along the heating roll, the crystallization of the thermoplastic resin base material can be efficiently promoted and the crystallinity can be increased, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material is increased, and the PVA-based resin layer is in a state of being able to withstand shrinkage due to drying, and curling is suppressed. Further, by using the heating roll, the laminated body can be dried while being maintained in a flat state, so that not only curling but also wrinkles can be suppressed.
　乾燥により、積層体を幅方向に収縮させ、光学特性を向上させることができる。ＰＶＡおよびＰＶＡ／ヨウ素錯体の配向性を効果的に高めることができるからである。乾燥による積層体の幅方向の収縮率は、好ましくは１％～１０％であり、より好ましくは２％～８％であり、さらに好ましくは４％～６％である。加熱ロールを用いることにより、積層体を搬送しながら連続的に幅方向に収縮させることができ、高い生産性を実現することができる。 By drying, the laminate can be shrunk in the width direction and the optical characteristics can be improved. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage rate of the laminate in the width direction due to drying is preferably 1% to 10%, more preferably 2% to 8%, still more preferably 4% to 6%. By using the heating roll, the laminated body can be continuously contracted in the width direction while being conveyed, and high productivity can be realized.
　図２は、加熱ロールを用いた乾燥の一例を示す概略図である。図示例では、所定の温度に加熱された搬送ロールＲ１～Ｒ６と、ガイドロールＧ１～Ｇ４とにより、積層体２００を搬送しながら乾燥させる。図示例では、ＰＶＡ系樹脂層の面と熱可塑性樹脂基材の面を交互に連続加熱するように搬送ロールＲ１～Ｒ６が配置されているが、例えば、積層体２００の一方の面（例えば、熱可塑性樹脂基材面）のみを連続的に加熱するように搬送ロールＲ１～Ｒ６を配置してもよい。 FIG. 2 is a schematic view showing an example of drying using a heating roll. In the illustrated example, the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4. In the illustrated example, the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA-based resin layer and the surface of the thermoplastic resin base material, and for example, one surface of the laminate 200 (for example, The transport rolls R1 to R6 may be arranged so as to continuously heat only the surface of the thermoplastic resin base material).
　搬送ロールの加熱温度（加熱ロールの温度）、加熱ロールの数、加熱ロールとの接触時間等を調整することにより、乾燥条件を制御することができる。加熱ロールの温度は、好ましくは６０℃～１２０℃であり、より好ましくは６５℃～１００℃であり、さらに好ましくは７０℃～８０℃である。このような温度によれば、熱可塑性樹脂の結晶化度を増加させてカールを抑制し得るとともに、積層体に極めて優れた耐久性を付与し得る。また、上記樹脂膜の水分率を良好に達成し得る。なお、加熱ロールの温度は、接触式温度計により測定することができる。図示例では、６個の搬送ロールが設けられているが、搬送ロールは複数個であれば特に制限はない。搬送ロールは、通常２個～４０個、好ましくは４個～３０個設けられる。積層体と加熱ロールとの接触時間（総接触時間）は、好ましくは１秒～３００秒であり、より好ましくは１～２０秒であり、さらに好ましくは１～１０秒である。 Drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll is preferably 60 ° C. to 120 ° C., more preferably 65 ° C. to 100 ° C., and even more preferably 70 ° C. to 80 ° C. According to such a temperature, the crystallinity of the thermoplastic resin can be increased to suppress curling, and the laminated body can be imparted with extremely excellent durability. In addition, the moisture content of the resin film can be satisfactorily achieved. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are a plurality of transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.
　加熱ロールは、加熱炉（例えば、オーブン）内に設けてもよいし、通常の製造ライン（室温環境下）に設けてもよい。好ましくは、送風手段を備える加熱炉内に設けられる。加熱ロールによる乾燥と熱風乾燥とを併用することにより、加熱ロール間での急峻な温度変化を抑制することができ、幅方向の収縮を容易に制御することができる。熱風乾燥の温度は、好ましくは３０℃～１００℃である。また、熱風乾燥時間は、好ましくは１秒～３００秒である。熱風の風速は、好ましくは１０ｍ／ｓ～３０ｍ／ｓ程度である。なお、当該風速は加熱炉内における風速であり、ミニベーン型デジタル風速計により測定することができる。 The heating roll may be provided in a heating furnace (for example, an oven) or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with an air blowing means. By using both drying with a heating roll and hot air drying together, a steep temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30 ° C to 100 ° C. The hot air drying time is preferably 1 second to 300 seconds. The wind speed of hot air is preferably about 10 m / s to 30 m / s. The wind speed is the wind speed in the heating furnace and can be measured by a mini-vane type digital anemometer.
Ｂ－２．水洗
　上記水洗は、例えば、上記樹脂膜の表面に水を接触させることにより行う。例えば、樹脂膜を水浴に浸漬させることにより水洗を行う。樹脂膜を水浴に浸漬させる際、樹脂膜の裏面は、任意の適切な保護基材で保護されていることが好ましい。１つの実施形態においては、保護基材として、上記樹脂基材を用いる。具体的には、樹脂膜から樹脂基材を剥離させないで（上記積層体の状態で）、樹脂膜を水浴に浸漬させる。別の実施形態においては、保護基材として、後述の保護層を用いる。例えば、上記積層体の樹脂膜表面に保護層を積層した後、樹脂膜から樹脂基材を剥離して保護層と樹脂膜との積層物を作製し、この積層物を水浴に浸漬させる。水浴に浸漬させる際、樹脂膜は長尺状であってもよいし、枚葉状であってもよい。 B-2. Washing with water The washing with water is performed, for example, by bringing water into contact with the surface of the resin film. For example, washing is performed by immersing the resin film in a water bath. When the resin film is immersed in a water bath, the back surface of the resin film is preferably protected by any suitable protective substrate. In one embodiment, the resin base material is used as the protective base material. Specifically, the resin film is immersed in a water bath without peeling the resin base material from the resin film (in the state of the above-mentioned laminated body). In another embodiment, the protective layer described below is used as the protective base material. For example, after laminating a protective layer on the surface of the resin film of the laminate, the resin base material is peeled off from the resin film to prepare a laminate of the protective layer and the resin film, and the laminate is immersed in a water bath. When immersed in a water bath, the resin film may be long or single-wafered.
　上記水浴（接触させる水）の温度は、例えば２０℃以上であり、好ましくは２５℃以上であり、より好ましくは３０℃以上であり、さらに好ましくは３５℃以上であり、特に好ましくは４０℃以上である。このような温度によれば、例えば、短時間で上記反射率を満足する偏光膜を作製することができる。一方、水浴（接触させる水）の温度は、好ましくは６０℃以下であり、より好ましくは５０℃以下である。このような温度によれば、例えば、得られる偏光膜は表面性状に優れ、優れた光学特性を保持し得る。 The temperature of the water bath (water to be contacted) is, for example, 20 ° C. or higher, preferably 25 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 35 ° C. or higher, and particularly preferably 40 ° C. or higher. Is. With such a temperature, for example, a polarizing film satisfying the above reflectance can be produced in a short time. On the other hand, the temperature of the water bath (water to be brought into contact) is preferably 60 ° C. or lower, more preferably 50 ° C. or lower. According to such a temperature, for example, the obtained polarizing film has excellent surface properties and can maintain excellent optical properties.
　水浴への浸漬時間（接触時間）は、例えば、上記温度、樹脂膜の厚み等に応じて設定される。水浴への浸漬時間は、好ましくは１５秒～５分であり、より好ましくは３０秒～３分である。 The immersion time (contact time) in the water bath is set according to, for example, the above temperature, the thickness of the resin film, and the like. The immersion time in the water bath is preferably 15 seconds to 5 minutes, more preferably 30 seconds to 3 minutes.
　水浴（接触させる水）は、ホウ酸等の添加剤を含んでいてもよい。 The water bath (water to be contacted) may contain additives such as boric acid.
　上記水洗後、偏光膜は乾燥処理に供され得る。乾燥温度は、例えば３０℃～６０℃である。乾燥時間は、例えば１５秒～３分である。 After washing with water, the polarizing film can be subjected to a drying treatment. The drying temperature is, for example, 30 ° C to 60 ° C. The drying time is, for example, 15 seconds to 3 minutes.
Ｃ．偏光板
　本発明の１つの実施形態による偏光板は、上記偏光膜と、この偏光膜の少なくとも片側に配置される保護層または位相差層とを有する。 C. Polarizing Plate The polarizing plate according to one embodiment of the present invention has the above-mentioned polarizing film and a protective layer or a retardation layer arranged on at least one side of the polarizing film.
　図３は、本発明の第一実施形態による偏光板の概略の構成を示す模式的な断面図である。偏光板（位相差層付偏光板）１００は、偏光膜１０、保護層２０、位相差層３０および粘着剤層４０をこの順に有する。偏光板１００において、偏光膜１０の裏面１０ｂ側にのみ保護層２０が配置され、表面１０ａ側（例えば、視認側）には保護層は配置されていないが、実用的には、偏光膜１０の表面１０ａは、任意の適切な保護材（図示せず）で保護される。例えば、偏光板１００の偏光膜１０に対し加工が施された後に、偏光膜１０に保護材が積層される。位相差層３０は、単一層であってもよいし、二層以上が積層された積層構造を有していてもよい。 FIG. 3 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate according to the first embodiment of the present invention. The polarizing plate (polarizing plate with a retardation layer) 100 has a polarizing film 10, a protective layer 20, a retardation layer 30, and an adhesive layer 40 in this order. In the polarizing plate 100, the protective layer 20 is arranged only on the back surface 10b side of the polarizing film 10, and the protective layer is not arranged on the front surface 10a side (for example, the visual recognition side), but practically, the polarizing film 10 is arranged. The surface 10a is protected by any suitable protective material (not shown). For example, after the polarizing film 10 of the polarizing plate 100 is processed, a protective material is laminated on the polarizing film 10. The retardation layer 30 may be a single layer or may have a laminated structure in which two or more layers are laminated.
　図４は、本発明の第二実施形態による偏光板の概略の構成を示す模式的な断面図である。偏光板（位相差層付偏光板）１１０は、偏光膜１０の裏面１０ｂ側に配置された保護層２０、偏光膜１０、偏光膜１０の表面１０ａ側に配置された位相差層３０および粘着剤層４０を視認側からこの順に有する。本実施形態では、位相差層３０が偏光膜１０の保護層として機能し得、位相差層３０が偏光膜１０の表面１０ａ側に配置される点が上記第一実施形態と異なる。 FIG. 4 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate according to the second embodiment of the present invention. The polarizing plate (polarizing plate with a retardation layer) 110 includes a protective layer 20 arranged on the back surface 10b side of the polarizing film 10, a polarizing film 10, a retardation layer 30 arranged on the front surface 10a side of the polarizing film 10, and an adhesive. The layer 40 is provided in this order from the visual recognition side. The present embodiment differs from the first embodiment in that the retardation layer 30 can function as a protective layer for the polarizing film 10 and the retardation layer 30 is arranged on the surface 10a side of the polarizing film 10.
　図示しないが、偏光板は、その他の機能層をさらに有していてもよい。偏光板が有し得る機能層の種類、特性、数、組み合わせ、配置等は、目的に応じて適切に設定され得る。例えば、偏光板は、導電層または導電層付等方性基材をさらに有していてもよい。導電層または導電層付等方性基材を有する偏光板（位相差層付偏光板）は、例えば、画像表示パネル内部にタッチセンサが組み込まれた、いわゆるインナータッチパネル型入力表示装置に適用される。別の例としては、偏光板は、その他の位相差層をさらに有していてもよい。その他の位相差層の光学的特性（例えば、屈折率特性、面内位相差、Ｎｚ係数、光弾性係数）、厚み、配置等は、目的に応じて適切に設定され得る。具体例として、偏光膜１０の視認側には、偏光サングラスを介して視認する場合の視認性を改善するその他の位相差層（代表的には、（楕）円偏光機能を付与する層、超高位相差を付与する層）が設けられていてもよい。このような層を有することにより、偏光サングラス等の偏光レンズを介して表示画面を視認した場合でも、優れた視認性を実現することができる。したがって、得られる偏光板（位相差層付偏光板）は、屋外で用いられ得る画像表示装置にも好適に適用され得る。 Although not shown, the polarizing plate may further have other functional layers. The types, characteristics, numbers, combinations, arrangements, and the like of the functional layers that the polarizing plate may have can be appropriately set according to the purpose. For example, the polarizing plate may further have a conductive layer or an isotropic substrate with a conductive layer. A polarizing plate having a conductive layer or an isotropic substrate with a conductive layer (polarizing plate with a retardation layer) is applied to, for example, a so-called inner touch panel type input display device in which a touch sensor is incorporated inside an image display panel. As another example, the polarizing plate may further have another retardation layer. The optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement, and the like of the other retardation layers can be appropriately set according to the purpose. As a specific example, on the visual recognition side of the polarizing film 10, another retardation layer (typically, a layer that imparts a (elliptical) circular polarization function) that improves visibility when visually recognizing through polarized sunglasses, a super A layer that imparts a high phase difference) may be provided. By having such a layer, excellent visibility can be realized even when the display screen is visually recognized through a polarizing lens such as polarized sunglasses. Therefore, the obtained polarizing plate (polarizing plate with a retardation layer) can be suitably applied to an image display device that can be used outdoors.
　偏光板を構成する各部材は、任意の適切な接着層（図示せず）を介して積層され得る。接着層の具体例としては、接着剤層、粘着剤層が挙げられる。具体的には、位相差層３０は、接着剤層を介して（好ましくは、活性エネルギー線硬化型接着剤を用いて）偏光膜１０または保護層２０に貼り合わせられてもよいし、粘着剤層を介して偏光膜１０または保護層２０に貼り合わせられてもよい。位相差層３０が二層以上の積層構造を有する場合、それぞれの位相差層は、例えば、接着剤層を介して（好ましくは、活性エネルギー線硬化型接着剤を用いて）貼り合わせられている。 Each member constituting the polarizing plate can be laminated via an arbitrary appropriate adhesive layer (not shown). Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. Specifically, the retardation layer 30 may be attached to the polarizing film 10 or the protective layer 20 via an adhesive layer (preferably using an active energy ray-curable adhesive), or an adhesive. It may be bonded to the polarizing film 10 or the protective layer 20 via the layer. When the retardation layer 30 has a laminated structure of two or more layers, the respective retardation layers are bonded together, for example, via an adhesive layer (preferably using an active energy ray-curable adhesive). ..
　図示しないが、粘着剤層４０の表面には、実用的には、剥離フィルム（セパレーター）が貼り合わせられる。剥離フィルムは、偏光板が使用に供されるまで仮着され得る。剥離フィルムを用いることにより、例えば、粘着剤層を保護するとともに、偏光板のロール形成が可能となる。 Although not shown, a release film (separator) is practically attached to the surface of the adhesive layer 40. The release film can be tacked temporarily until the polarizing plate is put into use. By using the release film, for example, the pressure-sensitive adhesive layer can be protected and a roll of the polarizing plate can be formed.
　偏光板は、長尺状であってもよいし、枚葉状であってもよい。本明細書において、「長尺状」とは、幅に対して長さが十分に長い細長形状をいい、例えば、幅に対して長さが１０倍以上、好ましくは２０倍以上の細長形状をいう。長尺状の偏光板は、ロール状に巻回可能である。 The polarizing plate may be long or single-lobed. As used herein, the term "long" refers to an elongated shape having a length sufficiently long with respect to the width, for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to the width. Say. The long polarizing plate can be wound in a roll shape.
Ｃ－１．保護層
　保護層２０は、偏光膜の保護層として使用できる任意の適切なフィルムで形成され得る。当該フィルムの主成分となる材料の具体例としては、トリアセチルセルロース（ＴＡＣ）等のセルロース系樹脂や、ポリエステル系、ポリビニルアルコール系、ポリカーボネート系、ポリアミド系、ポリイミド系、ポリエーテルスルホン系、ポリスルホン系、ポリスチレン系、ポリノルボルネン系等のシクロオレフィン系、ポリオレフィン系、（メタ）アクリル系、アセテート系等の透明樹脂が挙げられる。 C-1. Protective Layer The protective layer 20 can be formed of any suitable film that can be used as a protective layer for the polarizing film. Specific examples of the material that is the main component of the film include cellulosic resins such as triacetylcellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, and polysulfones. , Polyester-based, polynorbornene-based and other cycloolefin-based, polyolefin-based, (meth) acrylic-based, acetate-based and other transparent resins.
　上記偏光板は、代表的には、画像表示装置の視認側に配置される。したがって、保護層２０には、必要に応じて（例えば、図４に示す形態では）、ハードコート（ＨＣ）処理、反射防止処理、スティッキング防止処理、アンチグレア処理等の表面処理が施されていてもよい。 The above polarizing plate is typically arranged on the visual side of the image display device. Therefore, even if the protective layer 20 is subjected to surface treatment such as hard coat (HC) treatment, antireflection treatment, anti-sticking treatment, anti-glare treatment, etc., if necessary (for example, in the form shown in FIG. 4). good.
　保護層２０の厚みは、好ましくは５μｍ～８０μｍ、より好ましくは１０μｍ～４０μｍ、さらに好ましくは１０μｍ～３０μｍである。なお、上記表面処理が施されている場合、保護層２０の厚みは、表面処理層の厚みを含めた厚みである。 The thickness of the protective layer 20 is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 10 μm to 30 μm. When the surface treatment is applied, the thickness of the protective layer 20 is the thickness including the thickness of the surface treatment layer.
　偏光膜１０と位相差層３０との間に配置される保護層は、１つの実施形態においては、光学的に等方性であることが好ましい。本明細書において「光学的に等方性である」とは、面内位相差Ｒｅ（５５０）が０ｎｍ～１０ｎｍであり、厚み方向の位相差Ｒｔｈ（５５０）が－１０ｎｍ～＋１０ｎｍであることをいう。 The protective layer arranged between the polarizing film 10 and the retardation layer 30 is preferably optically isotropic in one embodiment. As used herein, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. Say.
　１つの実施形態においては、上記樹脂基材を偏光膜の保護層として用い得る。例えば、図３に示す形態では、樹脂基材をそのまま保護層として用いることにより、製造工程を少なくすることができる。 In one embodiment, the resin substrate can be used as a protective layer for a polarizing film. For example, in the form shown in FIG. 3, the manufacturing process can be reduced by using the resin base material as it is as the protective layer.
Ｃ－２．位相差層
　位相差層３０としては、任意の適切な構成が採用され得る。１つの実施形態においては、位相差層３０として、液晶化合物の配向固化層（液晶配向固化層）が用いられる。液晶化合物を用いることにより、得られる位相差層のｎｘとｎｙとの差を非液晶材料に比べて格段に大きくすることができるので、所望の面内位相差を得るための位相差層の厚みを格段に小さくすることができる。本明細書において「配向固化層」とは、液晶化合物が層内で所定の方向に配向し、その配向状態が固定されている層をいう。なお、「配向固化層」は、後述のように液晶モノマーを硬化させて得られる配向硬化層を包含する概念である。位相差層においては、代表的には、棒状の液晶化合物が位相差層の遅相軸方向に並んだ状態で配向している（ホモジニアス配向）。 C-2. Phase difference layer As the phase difference layer 30, any suitable configuration can be adopted. In one embodiment, the alignment solidification layer (liquid crystal alignment solidification layer) of the liquid crystal compound is used as the retardation layer 30. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be significantly increased as compared with the non-liquid crystal material, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be obtained. Can be made much smaller. As used herein, the term "aligned solidified layer" refers to a layer in which a liquid crystal compound is oriented in a predetermined direction within the layer and the oriented state is fixed. The "oriented solidified layer" is a concept including an oriented cured layer obtained by curing a liquid crystal monomer as described later. In the retardation layer, the rod-shaped liquid crystal compounds are typically oriented in a state of being aligned in the slow axis direction of the retardation layer (homogeneous orientation).
　上記位相差層の厚みは、その構成（単一層であるか積層構造を有するか）にもよるが、好ましくは８μｍ以下であり、より好ましくは５μｍ以下である。一方、位相差層の厚みは、例えば１μｍ以上である。なお、位相差層が積層構造である場合、「位相差層の厚み」は、各位相差層の厚みの合計を意味する。具体的には、「位相差層の厚み」には接着層の厚みは含まれない。 The thickness of the retardation layer is preferably 8 μm or less, and more preferably 5 μm or less, although it depends on the structure (whether it is a single layer or has a laminated structure). On the other hand, the thickness of the retardation layer is, for example, 1 μm or more. When the retardation layer has a laminated structure, the "thickness of the retardation layer" means the total thickness of each retardation layer. Specifically, the "thickness of the retardation layer" does not include the thickness of the adhesive layer.
　上記液晶配向固化層は、所定の基材の表面に配向処理を施し、当該表面に液晶化合物を含む塗工液を塗工して当該液晶化合物を上記配向処理に対応する方向に配向させ、当該配向状態を固定することにより形成され得る。配向処理としては、任意の適切な配向処理が採用され得る。具体的には、機械的な配向処理、物理的な配向処理、化学的な配向処理が挙げられる。機械的な配向処理の具体例としては、ラビング処理、延伸処理が挙げられる。物理的な配向処理の具体例としては、磁場配向処理、電場配向処理が挙げられる。化学的な配向処理の具体例としては、斜方蒸着法、光配向処理が挙げられる。各種配向処理の処理条件は、目的に応じて任意の適切な条件が採用され得る。 In the liquid crystal alignment solidification layer, the surface of a predetermined base material is subjected to an orientation treatment, and a coating liquid containing a liquid crystal compound is applied to the surface to orient the liquid crystal compound in a direction corresponding to the alignment treatment. It can be formed by fixing the orientation state. As the orientation treatment, any appropriate orientation treatment can be adopted. Specific examples thereof include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of the mechanical orientation treatment include a rubbing treatment and a stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical alignment treatment include an orthorhombic vapor deposition method and a photoalignment treatment. As the treatment conditions for various orientation treatments, any appropriate conditions may be adopted depending on the purpose.
　液晶化合物の配向は、液晶化合物の種類に応じて液晶相を示す温度で処理することにより行われる。このような温度処理を行うことにより、液晶化合物が液晶状態をとり、基材表面の配向処理方向に応じて当該液晶化合物が配向する。 The orientation of the liquid crystal compound is performed by treating at a temperature indicating the liquid crystal phase according to the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound takes a liquid crystal state, and the liquid crystal compound is oriented according to the orientation treatment direction of the surface of the substrate.
　配向状態の固定は、１つの実施形態においては、上記のように配向した液晶化合物を冷却することにより行われる。液晶化合物が重合性モノマーまたは架橋性モノマーである場合には、配向状態の固定は、上記のように配向した液晶化合物に重合処理または架橋処理を施すことにより行われる。 In one embodiment, the orientation state is fixed by cooling the liquid crystal compound oriented as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the orientation state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.
　液晶化合物の具体例および配向固化層の形成方法の詳細は、特開２００６－１６３３４３号公報に記載されている。当該公報の記載は本明細書に参考として援用される。 Specific examples of the liquid crystal compound and details of the method for forming the oriented solidified layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this publication is incorporated herein by reference.
　位相差層３０が単一層である場合、位相差層３０は、例えば、λ／４板として機能し得る。具体的には、位相差層のＲｅ（５５０）は、好ましくは１００ｎｍ～１８０ｎｍであり、より好ましくは１１０ｎｍ～１７０ｎｍであり、さらに好ましくは１１０ｎｍ～１６０ｎｍである。位相差層の厚みは、λ／４板の所望の面内位相差が得られるよう調整され得る。位相差層が上述の液晶配向固化層である場合、その厚みは、例えば１．０μｍ～２．５μｍである。本実施形態においては、位相差層の遅相軸と偏光膜の吸収軸とのなす角度は、好ましくは４０°～５０°であり、より好ましくは４２°～４８°であり、さらに好ましくは４４°～４６°である。本実施形態では、位相差層は、好ましくは、位相差値が測定光の波長に応じて大きくなる逆分散波長特性を示す。なお、この実施形態においては、偏光板は、ｎｚ＞ｎｘ＝ｎｙの屈折率特性を示す層（その他の位相差層、図示せず）をさらに有し得る。 When the retardation layer 30 is a single layer, the retardation layer 30 can function as, for example, a λ / 4 plate. Specifically, the Re (550) of the retardation layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and further preferably 110 nm to 160 nm. The thickness of the retardation layer can be adjusted to obtain the desired in-plane retardation of the λ / 4 plate. When the retardation layer is the liquid crystal alignment solidification layer described above, the thickness thereof is, for example, 1.0 μm to 2.5 μm. In the present embodiment, the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing film is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and even more preferably 44. ° to 46 °. In the present embodiment, the retardation layer preferably exhibits a reverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light. In addition, in this embodiment, the polarizing plate may further have a layer (other retardation layer, not shown) exhibiting a refractive index characteristic of nz> nx = ny.
　位相差層３０が積層構造を有する場合、位相差層３０は、例えば、偏光膜１０側から順にＨ層とＱ層とが配置された、二層の積層構造を有する。Ｈ層は、代表的にはλ／２板として機能し得、Ｑ層は、代表的にはλ／４板として機能し得る。具体的には、Ｈ層のＲｅ（５５０）は好ましくは２００ｎｍ～３００ｎｍであり、より好ましくは２２０ｎｍ～２９０ｎｍであり、さらに好ましくは２３０ｎｍ～２８０ｎｍであり；Ｑ層のＲｅ（５５０）は、好ましくは１００ｎｍ～１８０ｎｍであり、より好ましくは１１０ｎｍ～１７０ｎｍであり、さらに好ましくは１１０ｎｍ～１５０ｎｍである。Ｈ層の厚みは、λ／２板の所望の面内位相差が得られるよう調整され得る。Ｈ層が上述の液晶配向固化層である場合、その厚みは、例えば２．０μｍ～４．０μｍである。Ｑ層の厚みは、λ／４板の所望の面内位相差が得られるよう調整され得る。Ｑ層が上述の液晶配向固化層である場合、その厚みは、例えば１．０μｍ～２．５μｍである。本実施形態においては、Ｈ層の遅相軸と偏光膜の吸収軸とのなす角度は、好ましくは１０°～２０°であり、より好ましくは１２°～１８°であり、さらに好ましくは１２°～１６°であり；Ｑ層の遅相軸と偏光膜の吸収軸とのなす角度は、好ましくは７０°～８０°であり、より好ましくは７２°～７８°であり、さらに好ましくは７２°～７６°である。位相差層３０が積層構造を有する場合、それぞれの層（例えば、Ｈ層およびＱ層）は、位相差値が測定光の波長に応じて大きくなる逆分散波長特性を示してもよく、位相差値が測定光の波長に応じて小さくなる正の波長分散特性を示してもよく、位相差値が測定光の波長によってもほとんど変化しないフラットな波長分散特性を示してもよい。 When the retardation layer 30 has a laminated structure, the retardation layer 30 has, for example, a two-layer laminated structure in which the H layer and the Q layer are arranged in order from the polarizing film 10 side. The H layer can typically function as a λ / 2 plate, and the Q layer can typically function as a λ / 4 plate. Specifically, the Re (550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, still more preferably 230 nm to 280 nm; and the Re (550) of the Q layer is preferably. It is 100 nm to 180 nm, more preferably 110 nm to 170 nm, and even more preferably 110 nm to 150 nm. The thickness of the H layer can be adjusted to obtain the desired in-plane phase difference of the λ / 2 plate. When the H layer is the liquid crystal oriented solidified layer described above, the thickness thereof is, for example, 2.0 μm to 4.0 μm. The thickness of the Q layer can be adjusted to obtain the desired in-plane phase difference of the λ / 4 plate. When the Q layer is the liquid crystal oriented solidified layer described above, the thickness thereof is, for example, 1.0 μm to 2.5 μm. In the present embodiment, the angle formed by the slow phase axis of the H layer and the absorption axis of the polarizing film is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and even more preferably 12 °. The angle between the slow axis of the Q layer and the absorption axis of the polarizing film is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and even more preferably 72 °. It is ~ 76 °. When the retardation layer 30 has a laminated structure, each layer (for example, H layer and Q layer) may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, and the retardation may be exhibited. It may show a positive wavelength dispersion characteristic in which the value becomes smaller according to the wavelength of the measurement light, or may show a flat wavelength dispersion characteristic in which the phase difference value hardly changes depending on the wavelength of the measurement light.
　位相差層３０（積層構造を有する場合にはそれぞれの層）は、代表的には、屈折率特性がｎｘ＞ｎｙ＝ｎｚの関係を示す。なお、「ｎｙ＝ｎｚ」はｎｙとｎｚが完全に等しい場合だけではなく、実質的に等しい場合を包含する。したがって、本発明の効果を損なわない範囲で、ｎｙ＞ｎｚまたはｎｙ＜ｎｚとなる場合があり得る。位相差層のＮｚ係数は、好ましくは０．９～１．５であり、より好ましくは０．９～１．３である。 The retardation layer 30 (each layer in the case of having a laminated structure) typically shows a relationship in which the refractive index characteristics are nx> ny = nz. It should be noted that "ny = nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, ny> nz or ny <nz may occur within a range that does not impair the effect of the present invention. The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3.
　上述のとおり、位相差層は、好ましくは液晶配向固化層である。上記液晶化合物としては、例えば、液晶相がネマチック相である液晶化合物（ネマチック液晶）が挙げられる。このような液晶化合物として、例えば、液晶ポリマーや液晶モノマーが使用可能である。液晶化合物の液晶性の発現機構は、リオトロピックでもサーモトロピックでもどちらでもよい。液晶ポリマーおよび液晶モノマーは、それぞれ単独で用いてもよく、組み合わせてもよい。 As described above, the retardation layer is preferably a liquid crystal oriented solidifying layer. Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) in which the liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal expression mechanism of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.
　液晶化合物が液晶モノマーである場合、当該液晶モノマーは、重合性モノマーおよび架橋性モノマーであることが好ましい。液晶モノマーを重合または架橋（すなわち、硬化）させることにより、液晶モノマーの配向状態を固定できるからである。液晶モノマーを配向させた後に、例えば、液晶モノマー同士を重合または架橋させれば、それによって上記配向状態を固定することができる。ここで、重合によりポリマーが形成され、架橋により３次元網目構造が形成されることとなるが、これらは非液晶性である。したがって、形成された位相差層は、例えば、液晶性化合物に特有の温度変化による液晶相、ガラス相、結晶相への転移が起きることはない。その結果、位相差層は、温度変化に影響されない、極めて安定性に優れた位相差層となる。 When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or cross-linking (that is, curing) the liquid crystal monomer. After the liquid crystal monomers are oriented, for example, the liquid crystal monomers are polymerized or crosslinked with each other, whereby the oriented state can be fixed. Here, the polymer is formed by polymerization, and the three-dimensional network structure is formed by crosslinking, but these are non-liquid crystal. Therefore, the formed retardation layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to a liquid crystal compound, for example. As a result, the retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.
　液晶モノマーが液晶性を示す温度範囲は、その種類に応じて異なる。具体的には、当該温度範囲は、好ましくは４０℃～１２０℃であり、さらに好ましくは５０℃～１００℃であり、最も好ましくは６０℃～９０℃である。 The temperature range in which the liquid crystal monomer exhibits liquid crystal properties differs depending on the type. Specifically, the temperature range is preferably 40 ° C. to 120 ° C., more preferably 50 ° C. to 100 ° C., and most preferably 60 ° C. to 90 ° C.
　上記液晶モノマーとしては、任意の適切な液晶モノマーが採用され得る。例えば、特表２００２－５３３７４２（ＷＯ００／３７５８５）、ＥＰ３５８２０８（ＵＳ５２１１８７７）、ＥＰ６６１３７（ＵＳ４３８８４５３）、ＷＯ９３／２２３９７、ＥＰ０２６１７１２、ＤＥ１９５０４２２４、ＤＥ４４０８１７１、およびＧＢ２２８０４４５等に記載の重合性メソゲン化合物等が使用できる。このような重合性メソゲン化合物の具体例としては、例えば、ＢＡＳＦ社の商品名ＬＣ２４２、Ｍｅｒｃｋ社の商品名Ｅ７、Ｗａｃｋｅｒ－Ｃｈｅｍ社の商品名ＬＣ－Ｓｉｌｌｉｃｏｎ－ＣＣ３７６７が挙げられる。液晶モノマーとしては、ネマチック性液晶モノマーが好ましい。 Any suitable liquid crystal monomer can be adopted as the liquid crystal monomer. For example, the polymerizable mesogen compounds described in Special Tables 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US43884553), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Specific examples of such a polymerizable mesogen compound include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767. As the liquid crystal monomer, a nematic liquid crystal monomer is preferable.
Ｃ－３．粘着剤層
　粘着剤層４０としては、任意の適切な構成が採用され得る。具体例としては、アクリル系粘着剤、ゴム系粘着剤、シリコーン系粘着剤、ポリエステル系粘着剤、ウレタン系粘着剤、エポキシ系粘着剤、およびポリエーテル系粘着剤が挙げられる。粘着剤のベース樹脂を形成するモノマーの種類、数、組み合わせおよび配合比、ならびに、架橋剤の配合量、反応温度、反応時間等を調整することにより、目的に応じた所望の特性を有する粘着剤を調製することができる。粘着剤のベース樹脂は、単独で用いてもよく、二種以上を組み合わせて用いてもよい。ベース樹脂は、好ましくはアクリル樹脂である（具体的には、粘着剤層は、好ましくはアクリル系粘着剤で構成される）。粘着剤層の厚みは、例えば１０μｍ～２０μｍである。 C-3. Adhesive Layer As the adhesive layer 40, any suitable configuration can be adopted. Specific examples include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination and blending ratio of the monomers forming the base resin of the pressure-sensitive adhesive, the blending amount of the cross-linking agent, the reaction temperature, the reaction time, etc., the pressure-sensitive adhesive having desired characteristics according to the purpose. Can be prepared. The base resin of the pressure-sensitive adhesive may be used alone or in combination of two or more. The base resin is preferably an acrylic resin (specifically, the pressure-sensitive adhesive layer is preferably composed of an acrylic pressure-sensitive adhesive). The thickness of the pressure-sensitive adhesive layer is, for example, 10 μm to 20 μm.
Ｃ－４．偏光板の作製
　偏光板は、代表的には、上記水洗後、偏光膜に位相差層等の各種層を積層することにより得ることができる。 C-4. Fabrication of Polarizing Plate A polarizing plate can be typically obtained by laminating various layers such as a retardation layer on a polarizing film after washing with water.
　図３に示す偏光板１００は、例えば、上記水洗後の樹脂基材と偏光膜との積層体の樹脂基材をそのまま保護層２０として用い、樹脂基材に位相差層３０および粘着剤層４０を順次積層することにより得ることができる。また、例えば、上記樹脂基材と樹脂膜との積層体の樹脂膜側に保護層２０を積層し、樹脂膜から樹脂基材を剥離して得られた積層物を水洗し、保護層２０側に位相差層３０および粘着剤層４０を順次積層することにより得ることができる。また、例えば、上記保護層２０と樹脂膜との積層物に、位相差層３０または位相差層３０と粘着剤層４０とを積層した後に、上記水洗を行うことで、偏光板１００を得てもよい。 In the polarizing plate 100 shown in FIG. 3, for example, the resin base material of the laminate of the resin base material and the polarizing film after washing with water is used as it is as the protective layer 20, and the retardation layer 30 and the pressure-sensitive adhesive layer 40 are used on the resin base material. Can be obtained by sequentially laminating. Further, for example, the protective layer 20 is laminated on the resin film side of the laminate of the resin base material and the resin film, and the laminate obtained by peeling the resin base material from the resin film is washed with water to wash the protective layer 20 side. It can be obtained by sequentially laminating the retardation layer 30 and the pressure-sensitive adhesive layer 40. Further, for example, the polarizing plate 100 is obtained by laminating the retardation layer 30 or the retardation layer 30 and the pressure-sensitive adhesive layer 40 on the laminate of the protective layer 20 and the resin film, and then washing with water. May be good.
　図４に示す偏光板１１０は、例えば、上記樹脂基材と樹脂膜との積層体の樹脂膜側に保護層２０を積層し、樹脂膜から樹脂基材を剥離して得られた積層物を水洗し、偏光膜１０側に位相差層３０および粘着剤層４０を順次積層することにより得ることができる。 The polarizing plate 110 shown in FIG. 4 is, for example, a laminate obtained by laminating a protective layer 20 on the resin film side of a laminate of the resin base material and the resin film and peeling the resin base material from the resin film. It can be obtained by washing with water and sequentially laminating the retardation layer 30 and the pressure-sensitive adhesive layer 40 on the polarizing film 10 side.
　以下、実施例によって本発明を具体的に説明するが、本発明はこれら実施例によって限定されるものではない。なお、厚み、樹脂膜のヨウ素濃度および水分率は下記の測定方法により測定した値である。また、特に明記しない限り、実施例および比較例における「部」および「％」は重量基準である。
１．厚み
　１０μｍ以下の厚みは、走査型電子顕微鏡（日本電子社製、製品名「ＪＳＭ－７１００Ｆ」）を用いて測定した。１０μｍを超える厚みは、デジタルマイクロメーター（アンリツ社製、製品名「ＫＣ－３５１Ｃ」）を用いて測定した。
２．樹脂膜のヨウ素濃度
　蛍光Ｘ線分析装置（リガク社製、製品名「ＺＳＸ　Ｐｒｉｍｕｓ　ＩＶ」、測定径：ψ２０ｍｍ）を用いてヨウ素元素の蛍光Ｘ線強度（ｋｃｐｓ）強度を測定し、下記式によりヨウ素濃度（重量％）を算出した。ここで、ヨウ素濃度を算出する際の係数は、検量線を用いて求めた。
　ヨウ素濃度（重量％）＝２０．５×蛍光Ｘ線強度／樹脂膜の厚み（ｋｃｐｓ／μｍ）
３．樹脂膜の水分率
　樹脂膜単体（樹脂基材から剥離した状態の樹脂膜）を１２０℃、２時間の条件で乾燥し、乾燥前後の重量変化量を測定することにより樹脂膜に含まれる水分量を求め、水分率を算出した。 Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The thickness, the iodine concentration of the resin film, and the water content are values measured by the following measuring methods. Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples are based on weight.
1. 1. The thickness of 10 μm or less was measured using a scanning electron microscope (manufactured by JEOL Ltd., product name “JSM-7100F”). Thicknesses exceeding 10 μm were measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
2. 2. Iodine concentration of resin film The fluorescent X-ray intensity (kcps) intensity of the iodine element was measured using a fluorescent X-ray analyzer (manufactured by Rigaku, product name "ZSX Primus IV", measurement diameter: ψ20 mm), and iodine was measured by the following formula. The concentration (% by weight) was calculated. Here, the coefficient for calculating the iodine concentration was obtained using a calibration curve.
Iodine concentration (% by weight) = 20.5 x fluorescent X-ray intensity / resin film thickness (kcps / μm)
3. 3. Moisture content of the resin film The amount of water contained in the resin film by drying the resin film alone (the resin film in a state of being peeled off from the resin substrate) at 120 ° C. for 2 hours and measuring the amount of weight change before and after drying. Was calculated, and the water content was calculated.
［実施例１］
（樹脂膜の作製）
　熱可塑性樹脂基材として、長尺状で、吸水率０．７５％、Ｔｇ約７５℃である、非晶質のイソフタル共重合ポリエチレンテレフタレートフィルム（厚み：１００μｍ）を用いた。樹脂基材の片面に、コロナ処理を施した。
　ポリビニルアルコール（重合度４２００、ケン化度９９．２モル％）およびアセトアセチル変性ＰＶＡ（日本合成化学工業社製、商品名「ゴーセファイマーＺ４１０」）を９：１で混合したＰＶＡ系樹脂１００重量部に、ヨウ化カリウム１３重量部を添加し、ＰＶＡ水溶液（塗布液）を調製した。
　樹脂基材のコロナ処理面に、上記ＰＶＡ水溶液を塗布して６０℃で乾燥することにより、厚み１３μｍのＰＶＡ系樹脂層を形成し、積層体を作製した。
　得られた積層体を、１３０℃のオーブン内で周速の異なるロール間で縦方向（長手方向）に２．４倍に自由端一軸延伸した（空中補助延伸）。
　次いで、積層体を、液温４０℃の不溶化浴（水１００重量部に対して、ホウ酸を４重量部配合して得られたホウ酸水溶液）に３０秒間浸漬させた（不溶化処理）。
　次いで、液温３０℃の染色浴（水１００重量部に対して、ヨウ素とヨウ化カリウムを１：７の重量比で配合して得られたヨウ素水溶液）に、最終的に得られる偏光膜の単体透過率（Ｔｓ）が４３％以上となるように濃度を調整しながら６０秒間浸漬させた（染色）。
　次いで、液温４０℃の架橋浴（水１００重量部に対して、ヨウ化カリウムを３重量部配合し、ホウ酸を５重量部配合して得られたホウ酸水溶液）に３０秒間浸漬させた（架橋処理）。
　その後、積層体を、液温６４℃のホウ酸水溶液（ホウ酸濃度４．０重量％）に浸漬させながら、周速の異なるロール間で縦方向（長手方向）に総延伸倍率が５．５倍となるように一軸延伸を行った（水中延伸）。
　その後、積層体を液温２０℃の洗浄浴（水１００重量部に対して、ヨウ化カリウムを４重量部配合して得られた水溶液）に浸漬させた（洗浄）。
　その後、９０℃に保たれたオーブン中で乾燥しながら、表面温度が７５℃に保たれたＳＵＳ製の加熱ロールに約２秒接触させた（乾燥）。乾燥収縮処理による積層体の幅方向の収縮率は５．２％であった。
　このようにして、樹脂基材上に、厚み５．４μｍ、ヨウ素濃度６．４％、水分率４．４％の樹脂膜を形成した。 [Example 1]
(Preparation of resin film)
As the thermoplastic resin base material, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption rate of 0.75%, and a Tg of about 75 ° C. was used. One side of the resin substrate was corona-treated.
100 weight of PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z410") are mixed at a ratio of 9: 1. 13 parts by weight of potassium iodide was added to the part to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 13 μm, and a laminate was prepared.
The obtained laminate was stretched 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, the final obtained polarizing film was placed in a dyeing bath having a liquid temperature of 30 ° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water). It was immersed for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 43% or more (staining).
Then, it was immersed in a cross-linked bath having a liquid temperature of 40 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight) having a liquid temperature of 64 ° C., the total draw ratio is 5.5 in the vertical direction (longitudinal direction) between rolls having different peripheral speeds. Uniaxial stretching was performed so as to double (stretching in water).
Then, the laminate was immersed in a washing bath having a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (washing).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (drying). The shrinkage rate in the width direction of the laminated body by the dry shrinkage treatment was 5.2%.
In this way, a resin film having a thickness of 5.4 μm, an iodine concentration of 6.4%, and a water content of 4.4% was formed on the resin substrate.
（水洗１）
　次いで、得られた樹脂膜の片面（樹脂基材が配置されていない面）に、紫外線硬化型接着剤を介して、厚み２０μｍのラクトン環構造を有するアクリルフィルムを貼り合わせた後に、樹脂膜から樹脂基材を剥離し、アクリルフィルムと樹脂膜との積層物を４３℃の水浴に２分間浸漬させて、樹脂膜の片面（剥離面）を水洗し、５０℃にて乾燥することにより、アクリルフィルムと偏光膜との積層物を得た。 (Washing 1)
Next, an acrylic film having a lactone ring structure with a thickness of 20 μm is attached to one side of the obtained resin film (the side on which the resin base material is not arranged) via an ultraviolet curable adhesive, and then from the resin film. Acrylic is obtained by peeling off the resin base material, immersing the laminate of the acrylic film and the resin film in a water bath at 43 ° C. for 2 minutes, washing one side (peeled surface) of the resin film with water, and drying at 50 ° C. A laminate of a film and a polarizing film was obtained.
（水洗２）
　次いで、得られた樹脂膜の片面（樹脂基材が配置されていない面）に、紫外線硬化型接着剤を介して、厚み２７μｍのＨＣ－ＣＯＰフィルムを貼り合わせた後に、樹脂膜から樹脂基材を剥離し、ＨＣ－ＣＯＰフィルムと樹脂膜との積層物を４３℃の水浴に２分間浸漬させて、樹脂膜の片面（剥離面）を水洗し、５０℃にて乾燥することにより、ＨＣ－ＣＯＰフィルムと偏光膜との積層物を得た。なお、ＨＣ－ＣＯＰフィルムは、シクロオレフィン系樹脂（ＣＯＰ）フィルム（厚み２５μｍ）にＨＣ層（厚み２μｍ）が形成されたフィルムであり、ＣＯＰフィルムが樹脂膜側となるようにして貼り合わせた。 (Washing 2)
Next, an HC-COP film having a thickness of 27 μm was attached to one side of the obtained resin film (the side on which the resin base material was not arranged) via an ultraviolet curable adhesive, and then the resin base material was applied from the resin film. Is peeled off, the laminate of the HC-COP film and the resin film is immersed in a water bath at 43 ° C. for 2 minutes, one side (peeled surface) of the resin film is washed with water, and dried at 50 ° C. to obtain HC-. A laminate of a COP film and a polarizing film was obtained. The HC-COP film is a film in which an HC layer (thickness 2 μm) is formed on a cycloolefin resin (COP) film (thickness 25 μm), and the COP film is attached so as to be on the resin film side.
（位相差層の作製）
　ネマチック液晶相を示す重合性液晶（ＢＡＳＦ社製：商品名「Ｐａｌｉｏｃｏｌｏｒ　ＬＣ２４２」、下記式で表される）１０ｇと、当該重合性液晶化合物に対する光重合開始剤（ＢＡＳＦ社製：商品名「イルガキュア９０７」）３ｇとを、トルエン４０ｇに溶解して、液晶組成物（塗工液）を調製した。
Figure JPOXMLDOC01-appb-C000001
 (Preparation of retardation layer)
10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name "Pariocolor LC242", represented by the following formula) and a photopolymerization initiator (manufactured by BASF: trade name "Irgacure 907") for the polymerizable liquid crystal compound. ”) 3 g was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).
Figure JPOXMLDOC01-appb-C000001
　ポリエチレンテレフタレート（ＰＥＴ）フィルム（厚み３８μｍ）表面を、ラビング布を用いてラビングし、配向処理を施した。配向処理の方向は、偏光板に貼り合わせる際に偏光膜の吸収軸の方向に対して視認側から見て１５°方向となるようにした。この配向処理表面に、上記液晶塗工液をバーコーターにより塗工し、９０℃で２分間加熱乾燥することによって液晶化合物を配向させた。このようにして形成された液晶層に、メタルハライドランプを用いて１ｍＪ/ｃｍ２の光を照射し、当該液晶層を硬化させることによって、ＰＥＴフィルム上に液晶配向固化層Ａ（Ｈ層）を形成した。液晶配向固化層Ａの厚みは２．５μｍ、面内位相差Ｒｅ（５５０）は２７０ｎｍであった。さらに、液晶配向固化層Ａは、ｎｘ＞ｎｙ＝ｎｚの屈折率特性を示した。 The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth and subjected to an orientation treatment. The direction of the alignment treatment was set to be 15 ° when viewed from the visual recognition side with respect to the direction of the absorption axis of the polarizing film when the polarizing film was attached. The liquid crystal coating liquid was applied to the alignment-treated surface with a bar coater, and the liquid crystal compound was oriented by heating and drying at 90 ° C. for 2 minutes. The liquid crystal layer thus formed is irradiated with light of 1 mJ / cm 2 using a metal halide lamp to cure the liquid crystal layer, whereby a liquid crystal oriented solidified layer A (H layer) is formed on the PET film. did. The thickness of the liquid crystal oriented solidified layer A was 2.5 μm, and the in-plane retardation Re (550) was 270 nm. Further, the liquid crystal oriented solidified layer A showed a refractive index characteristic of nx> ny = nz.
　塗工厚みを変更したこと、および、配向処理方向を偏光膜の吸収軸の方向に対して視認側から見て７５°方向となるようにしたこと以外は上記と同様にして、ＰＥＴフィルム上に液晶配向固化層Ｂ（Ｑ層）を形成した。液晶配向固化層Ｂの厚みは１．５μｍ、面内位相差Ｒｅ（５５０）は１４０ｎｍであった。さらに、液晶配向固化層Ｂは、ｎｘ＞ｎｙ＝ｎｚの屈折率特性を示した。 On the PET film in the same manner as above, except that the coating thickness was changed and the orientation processing direction was set to be 75 ° when viewed from the visual side with respect to the direction of the absorption axis of the polarizing film. A liquid crystal oriented solidified layer B (Q layer) was formed. The thickness of the liquid crystal oriented solidified layer B was 1.5 μm, and the in-plane retardation Re (550) was 140 nm. Further, the liquid crystal oriented solidified layer B exhibited a refractive index characteristic of nx> ny = nz.
（偏光板Ａの作製）
　上記アクリルフィルムと偏光膜との積層物のアクリルフィルム側に、得られた液晶配向固化層Ａ（Ｈ層）および液晶配向固化層Ｂ（Ｑ層）をこの順に転写した。このとき、偏光膜の吸収軸と配向固化層Ａの遅相軸とのなす角度が１５°、偏光膜の吸収軸と配向固化層Ｂの遅相軸とのなす角度が７５°になるようにして転写（貼り合わせ）を行った。それぞれの転写は、紫外線硬化型接着剤（厚み１．０μｍ）を介して行った。その後、液晶配向固化層Ｂ上に厚み１５μｍの粘着剤層を形成して偏光板Ａを得た。 (Preparation of polarizing plate A)
The obtained liquid crystal oriented solidified layer A (H layer) and the liquid crystal oriented solidified layer B (Q layer) were transferred to the acrylic film side of the laminate of the acrylic film and the polarizing film in this order. At this time, the angle between the absorption axis of the polarizing film and the slow axis of the oriented solidification layer A is 15 °, and the angle between the absorption axis of the polarizing film and the slow axis of the oriented solidification layer B is 75 °. Transferred (bonded). Each transfer was carried out via a UV curable adhesive (thickness 1.0 μm). Then, a pressure-sensitive adhesive layer having a thickness of 15 μm was formed on the liquid crystal oriented solidified layer B to obtain a polarizing plate A.
（偏光板Ｂの作製）
　上記ＨＣ－ＣＯＰフィルムと偏光膜との積層物の偏光膜側に、得られた液晶配向固化層Ａ（Ｈ層）および液晶配向固化層Ｂ（Ｑ層）をこの順に転写した。このとき、偏光膜の吸収軸と配向固化層Ａの遅相軸とのなす角度が１５°、偏光膜の吸収軸と配向固化層Ｂの遅相軸とのなす角度が７５°になるようにして転写（貼り合わせ）を行った。それぞれの転写は、紫外線硬化型接着剤（厚み１．０μｍ）を介して行った。その後、液晶配向固化層Ｂ上に厚み１５μｍの粘着剤層を形成して偏光板Ｂを得た。 (Preparation of polarizing plate B)
The obtained liquid crystal oriented solidified layer A (H layer) and liquid crystal oriented solidified layer B (Q layer) were transferred in this order to the polarizing film side of the laminate of the HC-COP film and the polarizing film. At this time, the angle between the absorption axis of the polarizing film and the slow axis of the oriented solidification layer A is 15 °, and the angle between the absorption axis of the polarizing film and the slow axis of the oriented solidification layer B is 75 °. Transferred (bonded). Each transfer was carried out via a UV curable adhesive (thickness 1.0 μm). Then, a pressure-sensitive adhesive layer having a thickness of 15 μm was formed on the liquid crystal oriented solidified layer B to obtain a polarizing plate B.
［実施例２］
　積層体を４０℃の水浴に２分間浸漬させることにより水洗したこと以外は実施例１と同様にして、偏光膜および偏光板を得た。 [Example 2]
A polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the laminate was washed with water by immersing the laminate in a water bath at 40 ° C. for 2 minutes.
［実施例３］
　積層体を液温７０℃のホウ酸水溶液に浸漬させて水中延伸して厚み５．４μｍ、ヨウ素濃度６．６％、水分率４．５％の樹脂膜を作製したこと、および、積層体を２５℃の水浴に５分間浸漬させることにより水洗したこと以外は実施例１と同様にして、偏光膜および偏光板を得た。なお、水洗後の偏光膜の表面性状（膨潤）により偏光板Ｂは作製しなかった。 [Example 3]
The laminate was immersed in a boric acid aqueous solution having a liquid temperature of 70 ° C. and stretched in water to prepare a resin film having a thickness of 5.4 μm, an iodine concentration of 6.6%, and a water content of 4.5%. A polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the mixture was washed with water by immersing it in a water bath at 25 ° C. for 5 minutes. The polarizing plate B was not produced due to the surface texture (swelling) of the polarizing film after washing with water.
［実施例４］
　積層体を液温６７℃のホウ酸水溶液に浸漬させて水中延伸して厚み４．８μｍ、ヨウ素濃度５．５％、水分率４％の樹脂膜を作製したこと、および、積層体を４３℃の水浴に１分間浸漬させることにより水洗したこと以外は実施例１と同様にして、偏光膜および偏光板を得た。 [Example 4]
The laminate was immersed in a boric acid aqueous solution having a liquid temperature of 67 ° C. and stretched in water to prepare a resin film having a thickness of 4.8 μm, an iodine concentration of 5.5%, and a water content of 4%. A polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the mixture was washed with water by immersing it in the water bath of 1 for 1 minute.
［実施例５］
　積層体を液温６７℃のホウ酸水溶液に浸漬させて水中延伸して厚み４．８μｍ、ヨウ素濃度５．５％、水分率４％の樹脂膜を作製したこと、および、積層体を３５℃の水浴に２分間浸漬させることにより水洗したこと以外は実施例１と同様にして、偏光膜および偏光板を得た。 [Example 5]
The laminate was immersed in a boric acid aqueous solution having a liquid temperature of 67 ° C. and stretched in water to prepare a resin film having a thickness of 4.8 μm, an iodine concentration of 5.5%, and a water content of 4%. A polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the mixture was washed with water by immersing it in the water bath of No. 1 for 2 minutes.
［比較例１］
　樹脂膜を水洗しなかったこと以外は実施例１と同様にして、偏光膜および偏光板を得た。 [Comparative Example 1]
A polarizing film and a polarizing plate were obtained in the same manner as in Example 1 except that the resin film was not washed with water.
［比較例２］
　樹脂膜を水洗しなかったこと以外は実施例４と同様にして、偏光膜および偏光板を得た。 [Comparative Example 2]
A polarizing film and a polarizing plate were obtained in the same manner as in Example 4 except that the resin film was not washed with water.
［比較例３］
　樹脂膜を水洗しなかったこと以外は実施例３と同様にして、偏光膜および偏光板を得た。 [Comparative Example 3]
A polarizing film and a polarizing plate were obtained in the same manner as in Example 3 except that the resin film was not washed with water.
［参考例１］
（樹脂膜の作製）
　厚み３０μｍのＰＶＡ系樹脂フィルムの長尺ロールを、ロール延伸機により総延伸倍率が６．５倍になるように、長手方向に６６℃で一軸延伸しながら、同時に膨潤、染色、架橋および洗浄処理を施し、最後に乾燥処理を施すことにより厚み１２μｍ、ヨウ素濃度２．９％、水分率１１％の樹脂膜を作製した。 [Reference Example 1]
(Preparation of resin film)
A long roll of a PVA-based resin film having a thickness of 30 μm is uniaxially stretched at 66 ° C. in the longitudinal direction so that the total draw ratio becomes 6.5 times by a roll stretcher, and at the same time, swelling, dyeing, cross-linking and cleaning treatment are performed. And finally, a drying treatment was carried out to prepare a resin film having a thickness of 12 μm, an iodine concentration of 2.9%, and a water content of 11%.
（水洗１）
　得られた樹脂膜の片面に、紫外線硬化型接着剤を介して、厚み２０μｍのラクトン環構造を有するアクリルフィルムを貼り合わせて積層物を作製し、フィルムと樹脂膜との積層物を４３℃の水浴に２分間浸漬させて、得られた樹脂膜の表面（フィルムが貼り合わせられていない面）を水洗し、５０℃にて乾燥することにより、フィルムと偏光膜との積層物を得た。 (Washing 1)
An acrylic film having a lactone ring structure with a thickness of 20 μm is bonded to one side of the obtained resin film via an ultraviolet curable adhesive to prepare a laminate, and the laminate of the film and the resin film is heated at 43 ° C. The surface of the obtained resin film (the surface to which the film was not bonded) was washed with water by immersing it in a water bath for 2 minutes, and dried at 50 ° C. to obtain a laminate of the film and the polarizing film.
（水洗２）
　得られた樹脂膜の片面に、紫外線硬化型接着剤を介して、厚み２７μｍのＨＣ－ＣＯＰフィルムを貼り合わせて積層物を作製し、フィルムと樹脂膜との積層物を４３℃の水浴に２分間浸漬させて、得られた樹脂膜の表面（フィルムが貼り合わせられていない面）を水洗し、５０℃にて乾燥することにより、フィルムと偏光膜との積層物を得た。 (Washing 2)
An HC-COP film having a thickness of 27 μm is bonded to one side of the obtained resin film via an ultraviolet curable adhesive to prepare a laminate, and the laminate of the film and the resin film is placed in a water bath at 43 ° C. 2 After immersing for a minute, the surface of the obtained resin film (the surface to which the film was not bonded) was washed with water and dried at 50 ° C. to obtain a laminate of the film and the polarizing film.
（偏光板Ａの作製）
　上記アクリルフィルムと偏光膜との積層物のアクリルフィルム側に、得られた液晶配向固化層Ａ（Ｈ層）および液晶配向固化層Ｂ（Ｑ層）をこの順に転写した。このとき、偏光膜の吸収軸と配向固化層Ａの遅相軸とのなす角度が１５°、偏光膜の吸収軸と配向固化層Ｂの遅相軸とのなす角度が７５°になるようにして転写（貼り合わせ）を行った。それぞれの転写は、紫外線硬化型接着剤（厚み１．０μｍ）を介して行った。その後、液晶配向固化層Ｂ上に厚み１５μｍの粘着剤層を形成して偏光板Ａを得た。 (Preparation of polarizing plate A)
The obtained liquid crystal oriented solidified layer A (H layer) and the liquid crystal oriented solidified layer B (Q layer) were transferred to the acrylic film side of the laminate of the acrylic film and the polarizing film in this order. At this time, the angle between the absorption axis of the polarizing film and the slow axis of the oriented solidification layer A is 15 °, and the angle between the absorption axis of the polarizing film and the slow axis of the oriented solidification layer B is 75 °. Transferred (bonded). Each transfer was carried out via a UV curable adhesive (thickness 1.0 μm). Then, a pressure-sensitive adhesive layer having a thickness of 15 μm was formed on the liquid crystal oriented solidified layer B to obtain a polarizing plate A.
（偏光板Ｂの作製）
　上記ＨＣ－ＣＯＰフィルムと偏光膜との積層物の偏光膜側に、得られた液晶配向固化層Ａ（Ｈ層）および液晶配向固化層Ｂ（Ｑ層）をこの順に転写した。このとき、偏光膜の吸収軸と配向固化層Ａの遅相軸とのなす角度が１５°、偏光膜の吸収軸と配向固化層Ｂの遅相軸とのなす角度が７５°になるようにして転写（貼り合わせ）を行った。それぞれの転写は、紫外線硬化型接着剤（厚み１．０μｍ）を介して行った。その後、液晶配向固化層Ｂ上に厚み１５μｍの粘着剤層を形成して偏光板Ｂを得た。 (Preparation of polarizing plate B)
The obtained liquid crystal oriented solidified layer A (H layer) and liquid crystal oriented solidified layer B (Q layer) were transferred in this order to the polarizing film side of the laminate of the HC-COP film and the polarizing film. At this time, the angle between the absorption axis of the polarizing film and the slow axis of the alignment solidification layer A is 15 °, and the angle between the absorption axis of the polarizing film and the slow axis of the alignment solidification layer B is 75 °. Transferred (bonded). Each transfer was carried out via a UV curable adhesive (thickness 1.0 μm). Then, a pressure-sensitive adhesive layer having a thickness of 15 μm was formed on the liquid crystal oriented solidified layer B to obtain a polarizing plate B.
［参考例２］
　積層体を水洗しなかったこと以外は参考例１と同様にして、偏光膜および偏光板を得た。 [Reference Example 2]
A polarizing film and a polarizing plate were obtained in the same manner as in Reference Example 1 except that the laminate was not washed with water.
　実施例および比較例について、下記の評価を行った。評価結果を表１および表２にまとめる。
＜評価＞
１．単体透過率および偏光度
　実施例および比較例の偏光膜（偏光膜／アクリルフィルムまたはＨＣ－ＣＯＰフィルム）について、紫外可視分光光度計（日本分光社製、Ｖ－７１００）を用いて測定した単体透過率Ｔｓ、平行透過率Ｔｐ、直交透過率Ｔｃをそれぞれ、偏光膜のＴｓ、ＴｐおよびＴｃとした。これらのＴｓ、ＴｐおよびＴｃは、ＪＩＳ　Ｚ８７０１の２度視野（Ｃ光源）により測定して視感度補正を行なったＹ値である。
　得られたＴｐおよびＴｃから、下記式により偏光度Ｐを求めた。
　　　偏光度Ｐ（％）＝｛（Ｔｐ－Ｔｃ）／（Ｔｐ＋Ｔｃ）｝１／２×１００
２．反射率（ＲｃおよびＲｐ）
　実施例および比較例の偏光膜の表面（水洗した面）の反射率を、分光光度計（日立ハイテク社製、Ｕ－４１００）により、吸収軸方向の反射率（Ｒｃ）および透過軸方向の反射率（Ｒｐ）を測定した。その際、水洗した面とは反対側の面を黒板に貼り合わせて表面反射のみを測定できるようにした。また、光源（偏光）の入射角度を５°とし、測定波長を３８０ｎｍ～７８０ｎｍとした。
３．表面性状
　実施例および比較例の偏光膜の表面性状（樹脂膜の膨潤による凹凸の発生の有無）を、目視により観察した。
（評価基準）
良好：凹凸は確認されない
不良：凹凸が確認される
４．偏光板の色相（ａ＊およびｂ＊）
　実施例および比較例の偏光板（円偏光板）をアルミシート上に貼り合わせ、分光測色計（コニカミノルタ社製、ｃｍ－２６００ｄ）により、ＳＣＥモードにて反射色相を測定した。 The following evaluations were carried out for Examples and Comparative Examples. The evaluation results are summarized in Table 1 and Table 2.
<Evaluation>
1. 1. Single transmittance and degree of polarization The polarizing film (polarizing film / acrylic film or HC-COP film) of Examples and Comparative Examples was measured with an ultraviolet-visible spectrophotometer (V-7100, manufactured by Nippon Spectroscopy Co., Ltd.). The rate Ts, the parallel transmittance Tp, and the orthogonal transmittance Tc were defined as Ts, Tp, and Tc of the polarizing film, respectively. These Ts, Tp and Tc are Y values measured by the JIS Z8701 two-degree visual field (C light source) and corrected for luminosity factor.
From the obtained Tp and Tc, the degree of polarization P was determined by the following formula.
Degree of polarization P (%) = {(Tp-Tc) / (Tp + Tc)} 1/2 × 100
2. 2. Reflectance (Rc and Rp)
The reflectance of the surface (washed surface) of the polarizing film of Examples and Comparative Examples is measured by a spectrophotometer (Hitachi High-Tech, Ltd., U-4100) in terms of reflectance (Rc) in the absorption axis direction and reflection in the transmission axis direction. The rate (Rp) was measured. At that time, the surface opposite to the washed surface was attached to the blackboard so that only the surface reflection could be measured. Further, the incident angle of the light source (polarization) was set to 5 °, and the measurement wavelength was set to 380 nm to 780 nm.
3. 3. Surface properties The surface properties of the polarizing films of Examples and Comparative Examples (presence or absence of unevenness due to swelling of the resin film) were visually observed.
(Evaluation criteria)
Good: No unevenness is confirmed Defect: Unevenness is confirmed 4. Polarizer hue (a * and b * )
The polarizing plates (circular polarizing plates) of Examples and Comparative Examples were laminated on an aluminum sheet, and the reflected hue was measured in SCE mode with a spectrophotometer (manufactured by Konica Minolta, cm-2600d).
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　実施例、比較例ともに、優れた光学特性（単体透過率および偏光度）が得られる。実施例では、赤味が抑制され、優れた外観が得られる。 Excellent optical characteristics (single transmittance and degree of polarization) can be obtained in both Examples and Comparative Examples. In the examples, redness is suppressed and an excellent appearance is obtained.
　実施例１、比較例１および参考例２で得られた偏光膜について、厚み方向におけるヨウ素のイオン強度を測定した。測定は、飛行時間型二次イオン質量分析計（ＴＯＦ－ＳＩＭＳ）（ＩＯＮ－ＴＯＦ製、製品名：ＴＯＦ－ＳＩＭＳ　５）を用い、一次イオンにはＢｉ３２ ＋を用いて行った。測定結果（横軸を偏光膜の厚みに換算したグラフ）を図５に示す。図５に示すように、実施例１の偏光膜では、表面側の端部に、表面から裏面に向かってヨウ素量が多くなる傾斜分布領域を有することが確認された。なお、縦軸のヨウ素のイオン強度は、ヨウ素濃度に対応する。 The ionic strength of iodine in the thickness direction was measured for the polarizing films obtained in Example 1, Comparative Example 1 and Reference Example 2. The measurement was performed using a time-of-flight secondary ion mass spectrometer (TOF-SIMS) (manufactured by ION-TOF, product name: TOF-SIMS 5) and Bi 32+ as the primary ion . The measurement result (graph in which the horizontal axis is converted into the thickness of the polarizing film) is shown in FIG. As shown in FIG. 5, it was confirmed that the polarizing film of Example 1 had a gradient distribution region in which the amount of iodine increased from the front surface to the back surface at the end portion on the front surface side. The ionic strength of iodine on the vertical axis corresponds to the iodine concentration.
　本発明の１つの実施形態に係る偏光膜は、例えば、液晶表示装置、有機ＥＬ表示装置、無機ＥＬ表示装置等の画像表示装置に好適に用いられる。 The polarizing film according to one embodiment of the present invention is suitably used for an image display device such as a liquid crystal display device, an organic EL display device, or an inorganic EL display device.
　１０　　　偏光膜
　２０　　　保護層
　３０　　　位相差層
　４０　　　粘着剤層
１００　　　偏光板
１１０　　　偏光板 10 Polarizing film 20 Protective layer 30 Phase difference layer 40 Adhesive layer 100 Polarizing plate 110 Polarizing plate

Claims (12)

  1. 　ヨウ素を含む樹脂フィルムから構成され、
    　厚みが７μｍ以下であり、
    　表面の、吸収軸方向の波長６８０ｎｍの光の反射率Ｒｃ６８０に対する吸収軸方向の波長４００ｎｍの光の反射率Ｒｃ４００の比（Ｒｃ４００／Ｒｃ６８０）が１を超える、
    　偏光膜。     Consists of a resin film containing iodine,
    The thickness is 7 μm or less,
    The ratio (Rc 400 / Rc 680 ) of the reflectance Rc 400 of the light having a wavelength of 400 nm in the absorption axis direction to the reflectance Rc 680 of the light having a wavelength of 680 nm in the absorption axis direction on the surface exceeds 1.
    Polarizing film.
  2. 　前記表面のＲｃ６８０が５％以下である、請求項１に記載の偏光膜。 The polarizing film according to claim 1, wherein the Rc 680 of the surface is 5% or less.
  3. 　前記表面のＲｃ４００が４．８％以上である、請求項１または２に記載の偏光膜。 The polarizing film according to claim 1 or 2, wherein the Rc 400 on the surface is 4.8% or more.
  4. 　前記表面側の端部に、表面から裏面に向かってヨウ素量が多くなる傾斜分布領域を有する、請求項１から３のいずれかに記載の偏光膜。 The polarizing film according to any one of claims 1 to 3, which has a gradient distribution region in which the amount of iodine increases from the front surface to the back surface at the end portion on the front surface side.
  5. 　前記表面側のヨウ素量が裏面側のヨウ素量よりも少ない、請求項１から４のいずれかに記載の偏光膜。 The polarizing film according to any one of claims 1 to 4, wherein the amount of iodine on the front surface side is smaller than the amount of iodine on the back surface side.
  6. 　単体透過率が４２．０％以上であり、偏光度が９９．９８％以上である、請求項１から５のいずれかに記載の偏光膜。 The polarizing film according to any one of claims 1 to 5, wherein the simple substance transmittance is 42.0% or more and the degree of polarization is 99.98% or more.
  7. 　ヨウ素を含み、水分率が１５重量％以下の樹脂膜の表面を水洗すること、
    　を含む、請求項１から６のいずれかに記載の偏光膜の製造方法。     Washing the surface of a resin film containing iodine and having a water content of 15% by weight or less with water,
    The method for producing a polarizing film according to any one of claims 1 to 6, which comprises.
  8. 　前記樹脂膜のヨウ素濃度が５重量％以上である、請求項７に記載の製造方法。 The production method according to claim 7, wherein the iodine concentration of the resin film is 5% by weight or more.
  9. 　前記樹脂膜が樹脂基材上に形成された樹脂層である、請求項７または８に記載の製造方法。 The manufacturing method according to claim 7 or 8, wherein the resin film is a resin layer formed on a resin base material.
  10. 　前記樹脂層を６７℃以下で水中延伸することを含む、請求項９に記載の製造方法。 The production method according to claim 9, which comprises stretching the resin layer in water at 67 ° C. or lower.
  11. 　加熱ロールを用いて前記樹脂層を加熱することを含む、請求項９または１０に記載の製造方法。 The production method according to claim 9 or 10, which comprises heating the resin layer using a heating roll.
  12. 　請求項１から６のいずれかに記載の偏光膜と、
    　前記偏光膜の少なくとも片側に配置される保護層または位相差層と
    　を有する、偏光板。     The polarizing film according to any one of claims 1 to 6 and
    A polarizing plate having a protective layer or a retardation layer arranged on at least one side of the polarizing film.
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JP2014170223A (en) * 2013-02-07 2014-09-18 Nitto Denko Corp Optical laminate having polarizing film
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