WO2021095526A1 - 偏光膜、偏光板および画像表示装置 - Google Patents

偏光膜、偏光板および画像表示装置 Download PDF

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Publication number
WO2021095526A1
WO2021095526A1 PCT/JP2020/040383 JP2020040383W WO2021095526A1 WO 2021095526 A1 WO2021095526 A1 WO 2021095526A1 JP 2020040383 W JP2020040383 W JP 2020040383W WO 2021095526 A1 WO2021095526 A1 WO 2021095526A1
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polarizing film
stretching
pva
based resin
weight
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PCT/JP2020/040383
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English (en)
French (fr)
Japanese (ja)
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善則 南川
かおる ▲黒▼原
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日東電工株式会社
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Priority to JP2021555994A priority Critical patent/JPWO2021095526A1/ja
Priority to KR1020227012147A priority patent/KR20220098343A/ko
Priority to CN202080078496.8A priority patent/CN114730034A/zh
Publication of WO2021095526A1 publication Critical patent/WO2021095526A1/ja

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/02—Details
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
    • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source

Definitions

  • the present invention relates to a polarizing film, a polarizing plate, and an image display device.
  • a liquid crystal display device which is a typical image display device, has polarizing films arranged on both sides of the liquid crystal cell due to the image forming method.
  • a method for producing a polarizing film for example, a method of stretching a laminate having a resin base material and a polyvinyl alcohol (PVA) -based resin layer and then performing a dyeing treatment to obtain a polarizing film on the resin base material is used. It has been proposed (for example, Patent Document 1). According to such a method, a thin polarizing film can be obtained, which is attracting attention as it can contribute to thinning of display panels such as liquid crystal panels and organic EL panels (as a result, thinning of image display devices). There is. However, a display panel using a thin polarizing film may warp due to a dimensional change (typically, shrinkage) of the polarizing film.
  • shrinkage can be alleviated by lowering the draw ratio when producing the polarizing film, but lowering the draw ratio lowers the optical characteristics, so that dimensional stability and optical characteristics are improved. It is difficult to obtain a compatible polarizing film.
  • the present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide a thin polarizing film in which dimensional changes are suppressed while maintaining optical characteristics.
  • the present invention is composed of a polyvinyl alcohol-based resin film containing iodine, has a simple substance transmittance of 43.0% or more, and is calculated from a degree of polarization: P and an orientation function: F.
  • a polarizing film having an orientation characteristic index: (P-98) / F of 7 or more is provided.
  • the single transmittance of the polarizing film is 44.5% or less.
  • the thickness of the polarizing film is 8 ⁇ m or less.
  • the polarizing film contains alcohol.
  • the alcohol comprises at least one selected from ethanol and glycerin.
  • a polarizing plate including the above-mentioned polarizing film is provided.
  • an image display device including the above-mentioned polarizing plate is provided.
  • the polarizing film according to the embodiment of the present invention is composed of a polyvinyl alcohol (PVA) -based resin film containing iodine, has a single transmittance of 43.0% or more, a degree of polarization: P, and an orientation function: F.
  • Orientation characteristic index calculated from: (P-98) / F is 7 or more.
  • the higher the orientation of the PVA-based resin, the higher the degree of polarization, and the orientation mainly depends on the draw ratio of the PVA-based resin film. Therefore, in the conventional polarizing film, if the orientation is relaxed in order to suppress the dimensional change, the degree of polarization is lowered.
  • the polarizing film according to the embodiment of the present invention can achieve both dimensional stability and optical characteristics when the orientation characteristic index: (P-98) / F is 7 or more.
  • the polarization characteristic index of the polarizing film (P-98) / F (where P is the degree of polarization (%) of the polarizing film and F is the orientation function of the polarizing film) is 7 or more, preferably 7. It is 8 or more, more preferably 9 or more, and even more preferably 10 or more.
  • the upper limit of the orientation characteristic index may be 20, for example.
  • the orientation characteristic index is a value that becomes smaller when the degree of polarization is low and / or when the degree of orientation is high. Therefore, an orientation characteristic index of 7 or more can mean that both a high degree of polarization and an orientation relaxation are compatible.
  • the polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm.
  • the simple substance transmittance of the polarizing film is 43.0% or more, preferably 43.5% or more, and more preferably 43.7% or more. On the other hand, the simple substance transmittance is preferably 44.5% or less, and more preferably less than 44.5%.
  • the degree of polarization of the polarizing film is preferably 99.50% or more, more preferably 99.60% or more, still more preferably 99.70% or more.
  • the simple substance transmittance is typically a Y value measured using an ultraviolet-visible spectrophotometer and corrected for luminosity factor.
  • the single transmittance is a value when the refractive index of one surface of the polarizing plate is converted to 1.50 and the refractive index of the other surface is converted to 1.53.
  • 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.
  • Polarization degree (%) ⁇ (Tp-Tc) / (Tp + Tc) ⁇ 1/2 x 100
  • the orientation function (F) of the polarizing film is, for example, 0.25 or less, preferably 0.23 or less, and more preferably 0.20 or less.
  • the orientation function (F) can be, for example, 0.1 or more, and can be, for example, 0.15 or more. If the orientation function is too small, practically acceptable single transmittance and / or degree of polarization may not be obtained.
  • the orientation function (F) of the polarizing film can be obtained by total reflection attenuation spectroscopy (ATR) measurement using, for example, a Fourier transform infrared spectrophotometer (FT-IR) and polarized light as measurement light. Specifically, the measurement was carried out in a state where the stretching direction of the polarizing film was parallel and perpendicular to the polarization direction of the measurement light, and the intensity of the obtained absorbance spectrum of 2941 cm -1 was used to calculate according to the following formula. Will be done.
  • the intensity I as a reference peak to 3330cm -1, a value of 2941cm -1 / 3330cm -1.
  • the peak of 2941 cm -1 is considered to be absorption caused by the vibration of the main chain (-CH 2-) of PVA in the polarizing film.
  • ⁇ Angle of molecular chain with respect to stretching direction
  • ⁇ Angle of transition dipole moment with respect to molecular chain axis
  • I ⁇ Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing film are perpendicular
  • I // Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing film are parallel
  • the polarizing film preferably contains alcohol.
  • the content ratio of alcohol in the polarizing film can be, for example, 1.0 ⁇ 10 -3 % by weight to 1.0% by weight. Since the polarizing film contains alcohol, the orientation characteristic index can be easily set within the above desired range, and as a result, a thin polarizing film in which dimensional changes are suppressed while maintaining optical characteristics can be preferably obtained. obtain.
  • the mechanism for obtaining such an effect is not limited to the present invention, but can be presumed as follows. That is, the PVA-based resin film constituting the polarizing film is partially crystallized, and in the crystal portion having little involvement in optical characteristics, the orientation of the molecular chain is caused by the interaction of hydroxyl groups (typically, hydrogen bond).
  • the introduction of alcohol into the polarizing film weakens the interaction, which relaxes the orientation around the crystal or improves flexibility, resulting in PVA while maintaining optical properties.
  • the elasticity of the resin film can be reduced, and the dimensional change (shrinkage) of the polarizing film can be suppressed.
  • alcohol having a boiling point of less than 100 ° C. (hereinafter, may be referred to as low boiling point alcohol) may be used, and alcohol having a boiling point of 100 ° C. or higher (hereinafter, may be referred to as high boiling point alcohol) may be used. It may be used, or these may be used in combination.
  • the boiling point of the high boiling alcohol is preferably 150 ° C. or higher, more preferably 180 ° C. or higher, and even more preferably 250 ° C. or higher.
  • the upper limit of the boiling point can be, for example, 310 ° C.
  • a typical example of a low boiling point alcohol is a lower monoalcohol having 1 to 4 carbon atoms. Specific examples include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and tert-butyl alcohol.
  • the low boiling point alcohol may be used alone or in combination of two or more. Preferred are methanol, ethanol, n-propyl alcohol and isopropyl alcohol.
  • the content ratio of the low boiling point alcohol in the polarizing film is, for example, 10 ppm to 300 ppm, preferably 20 ppm to 200 ppm, more preferably 40 ppm to 150 ppm, and further preferably 50 ppm to 120 ppm. If the content ratio is too small, the orientation relaxation effect may not be obtained. If the content ratio is too high, the amount introduced during manufacturing will be large, and the amount volatile to the work environment will be large, which may increase the safety risk.
  • high boiling point alcohols include higher alcohols, alcohols having a ring structure (for example, aromatic alcohols and alicyclic alcohols), and polyhydric alcohols. Specific examples include glycerin, ethylene glycol, butanol, phenol, and pentanol.
  • the high boiling point alcohol may be used alone or in combination of two or more. Preferred are glycerin and ethylene glycol.
  • the content of the high boiling point alcohol in the polarizing film is, for example, 0.1% by weight to 1.0% by weight, preferably 0.1% by weight to 0.9% by weight, and more preferably 0.1% by weight. % To 0.8% by weight, more preferably 0.2% by weight to 0.7% by weight, and particularly preferably 0.2% by weight to 0.6% by weight. If the content ratio is too small, the orientation relaxation effect may not be obtained. If the content ratio is too large, the degree of polarization may decrease significantly in a high temperature and high humidity environment.
  • the thickness of the polarizing film is, for example, 8 ⁇ m or less, preferably 7 ⁇ m or less, more preferably 5 ⁇ m or less, and further preferably 3 ⁇ m or less.
  • the lower limit of the thickness of the polarizing film can be 1 ⁇ m in one embodiment and 2 ⁇ m in another embodiment.
  • the polarizing film has a shrinkage rate in the absorption axis direction after heating at a temperature of 85 ° C. for 120 hours, preferably less than 1.10%, more preferably 1.05% or less, still more preferably 1.00% or less. It is particularly preferably 0.95% or less.
  • the shrinkage rate is a shrinkage rate for a sample having a size of 10 cm in the absorption axis direction and 10 cm in the transmission axis direction.
  • FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention.
  • the polarizing plate 100 has a polarizing film 10, a first protective layer 20 arranged on one side of the polarizing film 10, and a second protective layer 30 arranged on the other side of the polarizing film 10.
  • the polarizing film 10 is the polarizing film of the present invention described in the above section A.
  • One of the first protective layer 20 and the second protective layer 30 may be omitted.
  • One of the first protective layer and the second protective layer may be a resin base material used for producing the above-mentioned polarizing film.
  • the first and second protective layers are formed of any suitable film that can be used as a protective layer for the polarizing film.
  • the material that is the main component of the film include cellulose-based resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like.
  • TAC triacetylcellulose
  • polyester-based polyvinyl alcohol-based
  • polycarbonate-based polyamide-based
  • polyimide-based polyimide-based
  • polyethersulfone-based polysulfone-based
  • thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned.
  • glassy polymers such as siloxane-based polymers can also be mentioned.
  • the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used.
  • a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain.
  • the polymer film can be, for example, an extruded product of the above resin composition.
  • the thickness of the protective layer (outer protective layer) arranged on the side opposite to the display panel is typically 300 ⁇ m or less, preferably 100 ⁇ m or less, more preferably 100 ⁇ m or less. It is 5 ⁇ m to 80 ⁇ m, more preferably 10 ⁇ m to 60 ⁇ m.
  • the thickness of the outer protective layer is the thickness including the thickness of the surface treatment layer.
  • the thickness of the protective layer (inner protective layer) arranged on the display panel side when the polarizing plate 100 is applied to the image display device is preferably 5 ⁇ m to 200 ⁇ m, more preferably 10 ⁇ m to 100 ⁇ m, and further preferably 10 ⁇ m to 60 ⁇ m. is there.
  • the inner protective layer is a retardation layer with any suitable retardation value.
  • the in-plane retardation Re (550) of the retardation layer is, for example, 110 nm to 150 nm.
  • nx is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and “ny” is the in-plane direction orthogonal to the slow-phase axis (that is, phase-advance). It is the refractive index in the axial direction), “nz” is the refractive index in the thickness direction, and “d” is the thickness (nm) of the layer (film).
  • a PVA-based resin solution is applied and dried on one side of a long thermoplastic resin base material to form a PVA-based resin layer. Includes: stretching and dyeing the laminate to form a PVA-based resin layer as a polarizing film; and introducing alcohol into the polarizing film. By introducing alcohol, it is possible to realize a polarizing film in which dimensional changes are suppressed while maintaining excellent optical characteristics.
  • the PVA-based resin solution further comprises a halide.
  • the above-mentioned production method comprises an aerial auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in which the laminate is shrunk by 2% or more in the width direction by heating while being conveyed in the longitudinal direction.
  • the introduction of alcohol can preferably be carried out between the underwater stretching treatment and the drying shrinkage treatment.
  • the PVA-based resin layer is subjected to a dyeing treatment to form a complex with iodine, and the orientation and crystallinity are increased by a stretching treatment, and then alcohol is introduced to form a hydroxyl group around the crystal portion of the PVA-based resin layer. Orientation due to interaction can be selectively relaxed or flexibility can be improved.
  • the content of the halide in the PVA-based resin solution (as a result, the PVA-based resin layer) is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
  • the drying shrinkage treatment is preferably carried out using a heating roll, and the temperature of the heating roll is preferably 60 ° C. to 120 ° C.
  • the shrinkage rate in the width direction of the laminated body by the drying shrinkage treatment is preferably 2% or more. According to such a manufacturing method, the polarizing film described in the above item A can be preferably obtained.
  • a polarizing film having excellent optical characteristics typically, single transmittance and degree of polarization
  • thermoplastic resin base material a thermoplastic resin base material and a PVA-based resin layer
  • any appropriate method can be adopted.
  • a coating liquid containing a halide and a PVA-based resin is applied to the surface of the thermoplastic resin base material and dried to form a PVA-based resin layer on the thermoplastic resin base material.
  • the content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
  • any appropriate method can be adopted as the application method of the coating liquid.
  • 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, a knife coating method (comma coating method, etc.) and the like can be mentioned.
  • 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, 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-adhesion 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.
  • thermoplastic resin base material any suitable thermoplastic resin film can be adopted. Details of the thermoplastic resin base material are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.
  • the coating liquid may contain a halide and a PVA-based resin as described above.
  • the coating liquid is typically a solution in which the halide and the PVA-based resin are dissolved in a solvent.
  • the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Of these, water is preferred.
  • the PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent.
  • 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.
  • Additives may be added to the coating liquid.
  • the additive include a plasticizer, a surfactant and the like.
  • the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin.
  • the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.
  • any suitable resin can be adopted as the PVA-based resin.
  • polyvinyl alcohol and ethylene-vinyl alcohol copolymers can be mentioned.
  • Polyvinyl alcohol is obtained by saponification of polyvinyl acetate.
  • the ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer.
  • the degree of saponification 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%. ..
  • the degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.
  • the average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose.
  • the average degree of polymerization 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.
  • iodide and sodium chloride Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Of these, potassium iodide is preferred.
  • the amount 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, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. It is a department. If the amount of the halide exceeds 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, the halide may bleed out and the finally obtained polarizing film may become cloudy.
  • the stretching of the PVA-based resin layer increases the orientation of the polyvinyl alcohol molecules in the PVA-based resin.
  • the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules become more oriented. The orientation may be disturbed and the orientation may decrease.
  • the laminate of the thermoplastic resin base material and the PVA-based resin layer is stretched in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material.
  • the tendency of the degree of orientation to decrease is remarkable.
  • stretching a PVA film alone in boric acid water is generally performed at 60 ° C.
  • stretching of a laminate of A-PET (thermoplastic resin base material) and a PVA-based resin layer is performed. It is carried out at a high temperature of about 70 ° C., and in this case, the orientation of PVA at the initial stage of stretching may decrease before it is increased by stretching in water.
  • a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin base material is prepared, and the laminate is stretched at a high temperature (auxiliary stretching) in air before being stretched in boric acid water.
  • Crystallization of the PVA-based resin in the PVA-based resin layer of the laminated body after the auxiliary stretching can be promoted.
  • the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide.
  • thermoplastic resin base material can be stretched while suppressing the crystallization of the thermoplastic resin base material, and the thermoplastic resin base material is excessively crystallized in the subsequent stretching in boric acid water. This solves the problem that the stretchability is lowered, and the laminated body can be stretched at a higher magnification.
  • the PVA-based resin when the PVA-based resin is applied on the thermoplastic resin base material, it is compared with the case where the PVA-based resin is applied on a normal metal drum in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material. Therefore, it is necessary to lower the coating temperature, and as a result, the crystallization of the PVA-based resin becomes relatively low, which may cause a problem that sufficient optical characteristics cannot be obtained.
  • the auxiliary stretching it is possible to increase the crystallinity of the PVA-based resin even when the PVA-based resin is applied on the thermoplastic resin base material, and it is possible to achieve high optical characteristics. It will be possible.
  • the stretching method of the 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). Good, but in order to obtain high optical properties, free end stretching can be positively adopted.
  • the aerial stretching treatment includes a heating roll stretching step of stretching the laminated body in the longitudinal direction due to a difference in peripheral speed between the heating rolls.
  • the aerial stretching treatment typically includes a zone stretching step and a heating roll stretching step.
  • the order of the zone stretching step and the heating roll stretching step is not limited, and the zone stretching step may be performed first, or the heating roll stretching step may be performed first.
  • the zone stretching step may be omitted.
  • 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) is set to approach arbitrarily. Preferably, it can be set to be closer to the free end stretch with respect to the stretch ratio in the flow direction.
  • the shrinkage rate in the width direction (1 / stretching ratio) 1/2 .
  • the aerial auxiliary extension may be performed in one step or in multiple steps.
  • the draw ratio is the product of the draw ratios of each stage.
  • the stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.
  • the draw ratio in the aerial auxiliary stretching is preferably 2.0 to 3.5 times.
  • the maximum draw ratio when the aerial auxiliary stretching and the underwater stretching are combined is preferably 5.0 times or more, more preferably 5.5 times or more, and further preferably 6.0 times the original length of the laminated body. That is all.
  • the "maximum draw ratio" means the draw ratio immediately before the laminate breaks, and separately confirms the draw ratio at which the laminate breaks, and means a value 0.2 lower than that value.
  • the stretching temperature of the aerial auxiliary stretching can be set to an arbitrary appropriate value depending on the forming material of the thermoplastic resin base material, the stretching method, and the like.
  • the stretching temperature is preferably the glass transition temperature (Tg) or more of the thermoplastic resin base material, more preferably the glass transition temperature (Tg) of the thermoplastic resin base material (Tg) + 10 ° C. or higher, and particularly preferably Tg + 15 ° C. or higher.
  • the upper limit of the stretching temperature is preferably 170 ° C.
  • an insolubilization treatment is performed after the aerial auxiliary stretching treatment and before the underwater stretching treatment or the dyeing treatment.
  • the insolubilization treatment is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution.
  • the dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine).
  • a cross-linking treatment is performed after the dyeing treatment and before the underwater stretching treatment.
  • the underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment, 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 is crystallized. It is possible to stretch at a high magnification while suppressing the above. As a result, a polarizing film having excellent optical characteristics can be produced.
  • any appropriate method can be adopted as the stretching method of the laminated body. Specifically, it 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 selected.
  • 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 (maximum 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).
  • a 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 produced.
  • 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 particularly preferably 3 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. Is.
  • an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde or the like in a solvent can also be used.
  • iodide is mixed in the above stretching bath (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 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. to 85 ° C., more preferably 60 ° C. to 75 ° C. 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 when the plasticization of the thermoplastic resin base material by water is taken into consideration.
  • 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.
  • alcohol is introduced after the stretching treatment in water (and typically before the drying shrinkage treatment described later).
  • the introduction of alcohol can be done in any suitable manner.
  • the laminate may be immersed in a treatment liquid containing alcohol, or the treatment liquid containing alcohol may be applied to the surface of the polarizing film of the laminate.
  • the introduction of alcohol can be done by immersion. Immersion can be done in any suitable manner.
  • alcohol may be added to the washing bath for the washing treatment to serve as a bath for the treatment liquid, a bath for the treatment liquid may be used instead of the washing bath, or the bath for the treatment liquid may be provided separately from the washing bath. ..
  • alcohol can be added to the cleaning bath (cleaning solution) of the cleaning process.
  • the alcohol concentration of the treatment liquid (cleaning liquid) is preferably 5% by weight to 35% by weight in the case of low boiling point alcohol, and preferably 0.03% by weight to 1.0% by weight in the case of high boiling point alcohol.
  • the immersion time of the laminate in the treatment liquid (cleaning liquid) is preferably 1 second to 20 seconds, more preferably 3 seconds to 10 seconds.
  • the dry shrinkage treatment may be carried out by heating the entire zone by zone heating, or by heating the transport roll (using a so-called heating roll) (heating roll drying method). Preferably, both are used.
  • heating roll heating roll drying method
  • 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 base material can be satisfactorily increased.
  • the rigidity of the thermoplastic resin base material is increased, and the thermoplastic resin base material is in a state where it can withstand the shrinkage of the PVA-based resin layer due to drying, and curling is suppressed.
  • 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 laminated body can be improved in optical characteristics by shrinking in the width direction by a drying shrinkage treatment. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced.
  • the shrinkage ratio in the width direction of the laminate by the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%.
  • FIG. 2 is a schematic view showing an example of the drying shrinkage treatment.
  • 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 resin layer and the surface of the thermoplastic resin base material.
  • one surface of the laminate 200 (for example, thermoplastic) is arranged.
  • the transport rolls R1 to R6 may be arranged so as to continuously heat only the resin base material surface).
  • 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 particularly preferably 70 ° C. to 80 ° C. At such a temperature, the crystallinity of the thermoplastic resin can be satisfactorily increased, curling can be satisfactorily suppressed, and an optical laminate having extremely excellent durability can be produced.
  • 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.
  • 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 a blowing means.
  • a heating furnace provided with a 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.
  • thermoplastic resin base material / polarizing film obtained as described above may be used as it is as a polarizing plate (the thermoplastic resin base material may be used as a protective layer); After the protective layer is attached to the surface of the film, the thermoplastic resin base material may be peeled off and used as a polarizing plate having a protective layer / polarizing film configuration; another protection is provided on the peeled surface of the thermoplastic resin base material.
  • the layers may be bonded together and used as a polarizing plate having a protective layer / polarizing film / protective layer configuration.
  • the polarizing film according to item A and / or the polarizing plate according to item B can be applied to an image display device. Therefore, the present invention includes an image display device using such a polarizing film and / or a polarizing plate.
  • the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device).
  • EL electroluminescence
  • y 4.743E +00 x + 3.105E- 02 ⁇ Glycerin concentration>
  • the polarizing film is freeze-crushed, about 0.02 g is collected in a screw tube, 0.5 ml of methanol is added, and the mixture is permeated and extracted overnight. Then, the extract is filtered through a 0.45 ⁇ m membrane filter, and 1 ⁇ L of the filtrate is prepared.
  • the amount of glycerin contained was calculated from the peak area corresponding to glycerin by injecting into a gas chromatograph (manufactured by Agent Technologies, product name "6890N") using the following calibration curve.
  • y 5.666E- 01 x + 1.833E- 00
  • Single-unit transmittance and polarization degree The single-unit transmittance Ts, measured using an ultraviolet-visible spectrophotometer (LPF-200 manufactured by Otsuka Electronics Co., Ltd.) for the polarizing plates (protective layer / polarizing film) of Examples and Comparative Examples.
  • the parallel transmittance Tp and the orthogonal transmittance Tc were defined as Ts, Tp and Tc of the polarizing film, respectively.
  • Ts, Tp and Tc are Y values measured by the JIS Z8701 2 degree field of view (C light source) and corrected for luminosity factor.
  • the refractive index of the protective layer was 1.50, and the refractive index of the surface of the polarizing film opposite to the protective layer was 1.53.
  • the degree of polarization was determined using the following formula.
  • Polarization degree (%) ⁇ (Tp-Tc) / (Tp + Tc) ⁇ 1/2 x 100 (4) Orientation function
  • the polarizing films obtained in Examples and Comparative Examples were polarized red using a Fourier transformed infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name: "Frontier").
  • FT-IR Fourier transformed infrared spectrophotometer
  • ATR total reflection attenuation spectroscopy
  • Germanium was used as the crystallite to which the polarizing film was brought into close contact, and the incident angle of the measurement light was 45 °.
  • the orientation function was calculated according to the following procedure.
  • the incident polarized infrared light is polarized light (s-polarized light) that vibrates parallel to the surface to which the germanium crystal sample is brought into close contact, and the stretching direction of the polarizing film is perpendicular to the polarization direction of the measurement light (measurement light).
  • the absorbance spectra of each were measured in the state of ⁇ ) and parallel (//).
  • I ⁇ is the relative polarization directions of the measurement light is obtained from the absorbance spectrum obtained when the stretching direction is arranged in a vertical ( ⁇ ) of the polarizing film (2941cm -1 intensity) / (3330cm -1 strength).
  • I // is obtained from the absorbance spectrum obtained when the stretching direction of the polarizing film is arranged parallel (//) with respect to the polarization direction of the measurement light (2941 cm -1 intensity) / (3330 cm -1 intensity). Is.
  • thermoplastic resin base material an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 ⁇ m) having a long shape and a Tg of about 75 ° C. was used. One side of the resin base material was corona-treated.
  • PVA-based resin 100 weight of PVA-based resin in which polyvinyl alcohol (degree of polymerization 4200, degree of saponification 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: 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 ⁇ m to prepare a laminate.
  • the obtained laminate was uniaxially stretched at the free end 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment).
  • the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
  • the finally obtained polarizing film was placed in a dyeing bath having a liquid temperature of 30 ° C.
  • a polarizing film having a thickness of 5.0 ⁇ m was formed on the resin base material.
  • a cycloolefin-based film manufactured by ZEON, product name "G-Film" as a protective layer is attached to the surface of the polarizing film with a UV curable adhesive (thickness 1.0 ⁇ m), and then the resin base material is peeled off.
  • a polarizing plate having a protective layer / polarizing film structure was obtained. The ethanol concentration in the polarizing film of the obtained polarizing plate was 15 ppm.
  • Example 2 A polarizing plate was produced in the same manner as in Example 1. The obtained polarizing plate (or polarizing film) was subjected to the same evaluation as in Example 1. The results are shown in Table 1.
  • Example 3 A polarizing plate was prepared in the same manner as in Example 1 except that 0.2% by weight of glycerin was added to the treatment bath without adding ethanol. The concentration of glycerin in the polarizing film of the obtained polarizing plate was 0.3% by weight. Moreover, the obtained polarizing plate (or polarizing film) was subjected to the same evaluation as in Example 1. The results are shown in Table 1.
  • Example 4 A polarizing plate was produced in the same manner as in Example 1 except that alcohol was not added to the washing bath (washing liquid) and the stretching treatment was performed so that the total stretching ratio was 3.5 times.
  • the obtained polarizing plate (or polarizing film) was subjected to the same evaluation as in Example 1. The results are shown in Table 1.
  • the polarizing plate (polarizing film) of the example having an orientation characteristic index of 7 or more suppresses dimensional changes while maintaining excellent optical characteristics.
  • the polarizing film and the polarizing plate of the present invention are suitably used for image display devices such as liquid crystal display devices and organic EL display devices.
  • Polarizing film 10 Polarizing film 20 First protective layer 30 Second protective layer 100 Polarizing plate

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  • Optics & Photonics (AREA)
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PCT/JP2020/040383 2019-11-11 2020-10-28 偏光膜、偏光板および画像表示装置 WO2021095526A1 (ja)

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