JP2021144223A - Polarizing plate, method of manufacturing the same, and image display device having the same - Google Patents

Abstract

To provide a polarizing plate comprising a polarizer with a thin section acting as a non-polarizing section provided in a predetermined part thereof, the thin section containing no air bubbles.SOLUTION: A polarizing plate 100 provided herein comprises a polarizer 10 having a thin section 12 provided on one side thereof and a protective layer 30 bonded to the polarizer on a thin-section side via an adhesive layer 20 composed of an aqueous adhesive. The protective layer and the polarizer are bonded to each other via the adhesive layer. A thickness of the adhesive layer is less than 2.0 μm except for a portion over the thin section.SELECTED DRAWING: Figure 2

Description

The present invention relates to a polarizing plate, a method for producing the same, and an image display device using the polarizing plate.

Some image display devices such as mobile phones and notebook personal computers (PCs) are equipped with internal electronic components such as cameras. In recent years, with the rapid spread of smartphones and touch panel type information processing devices, further improvement of camera performance and the like is desired. Further, in order to cope with the diversification and high functionality of the shape of the image display device, a polarizing plate having a partial polarization performance is required. In order to meet these demands, a polarizer in which a non-polarized portion formed by chemical treatment is formed in a predetermined portion has been proposed (for example, Patent Documents 1 and 2).

Korean Publication No. 10-2015-0086159 JP-A-2015-215609

However, such a polarizer has a dent in a chemically treated portion (that is, a non-polarizing portion), and when a polarizing plate is constructed using the polarizer, bubbles may be present in the dent.

The present invention has been made to solve the above-mentioned newly recognized problem, and its main purpose is to provide a polarizing element having a thin-walled portion as a non-polarized portion in a predetermined portion, and to provide air bubbles in the thin-walled portion. The purpose is to provide a polarizing plate that does not contain the polarizing plate.

The polarizing plate of the present invention has a polarizer having a thin-walled portion on one side; and a protective layer bonded to the thin-walled portion side of the polarizer via an adhesive layer composed of an aqueous adhesive. The protective layer and the polarizing element are bonded to each other via the adhesive layer, and the thickness of the adhesive layer in a portion other than the thin-walled portion is less than 2.0 μm.
According to another aspect of the present invention, there is provided a method for producing a polarizing plate. In this manufacturing method, a predetermined position on one surface of the polarizer is treated with a treatment liquid to form a thin-walled portion at the predetermined position; a viscosity of 35 mPa is formed on the surface of the polarizer on which the thin-walled portion is formed. -Applying a water-based adhesive of S or less and solidifying or curing the water-based adhesive to form an adhesive layer having a thickness of less than 2.0 μm in a portion other than the thin-walled portion; and the adhesion. Includes laminating a protective layer on top of the agent layer.
According to yet another aspect of the present invention, an image display device is provided. This image display device includes the above-mentioned polarizing plate, and the thin-walled portion of the polarizing plate is arranged at a position corresponding to the camera portion.

According to the present invention, in a polarizing plate containing a polarizer having a thin-walled portion as a non-polarizing portion, a polarizing plate containing no bubbles in the thin-walled portion can be realized by using a very thin adhesive layer. Since bubbles are easily recognized by the user in the camera unit of the image display device, there is a problem that the presence of bubbles significantly lowers the commercial value of the image display device rather than the effect on the actual performance. Therefore, according to the present invention, the generation of air bubbles is prevented by the extremely thin adhesive layer, so that the commercial value of the polarizing plate (as a result, the image display device) can be remarkably increased from the viewpoint of thinning.

It is a schematic plan view of the polarizing plate according to one embodiment of the present invention. It is a schematic cross-sectional view of the main part of the polarizing plate of FIG. It is a schematic perspective view of the polarizer in the polarizing plate according to another embodiment of the present invention. It is a schematic perspective view explaining the bonding of the polarizing element and the first surface protective film in the method of manufacturing a polarizing plate according to the embodiment of the present invention. It is the schematic explaining the formation of the non-polarized part in the manufacturing method of the polarizing plate by the embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. For the sake of clarity, the scales and ratios of each figure may not correspond. In addition, the ratio of the thickness of each layer in each figure may differ from the actual one.

A. Overall Configuration of Polarizing Plate FIG. 1 is a schematic plan view of a polarizing plate according to one embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a main part of the polarizing plate of FIG. The polarizing plate 100 has a polarizing element 10 having a thin portion 12 at a predetermined position, and a protective layer 30 bonded to one surface of the polarizing element 10 via an adhesive layer 20. As shown in the illustrated example, the thin-walled portion 12 typically has a recess 14 having a concave surface on one surface side of the polarizer. Typically, as shown in the illustrated example, the protective layer 30 is attached to at least the concave portion 14 side of the polarizer 10. If desired, another protective layer (not shown) may be attached to the other side of the polarizer via any suitable adhesive layer (adhesive layer or adhesive layer). In the embodiment of the present invention, the thin-walled portion 12 (recessed portion 14) substantially does not contain air bubbles. In the present specification, "substantially free of bubbles" means that bubbles are not recognized when the thin portion of the polarizing plate is visually observed against the background of the black portion. The state in which bubbles are not visually recognized may be a state in which bubbles having a diameter of 30 μm or more, more preferably 20 μm or more are not present. In the embodiment of the present invention, in the polarizing plate 100, the protective layer 30 and the polarizing element 10 are interposed via the adhesive layer 20 so that bubbles are not substantially contained between the protective layer 30 and the thin portion 12. It is pasted together. Further, in the embodiment of the present invention, the thickness of the adhesive layer 20 is less than 2.0 μm. According to an embodiment of the present invention, the adhesive layer can be made very thin (thus, it can greatly contribute to the thinning of the polarizing plate and, as a result, the image display device), and the thin portion is substantially thin. It is possible to realize a state in which air bubbles are not contained in the light.

B. Polarizer B-1. Overall Composition of Polarizer The polarizer 10 is typically composed of a resin film containing a dichroic substance. As described above, the polarizer 10 has a thin portion 12 at a predetermined position. As described above, the thin-walled portion 12 typically has a recess 14 having a concave surface on one surface side of the polarizer. The thin portion 12 may be typically a non-polarized portion, and in one embodiment, may be a low concentration portion having a lower content of the dichroic substance than the other portion of the polarizer. Therefore, in the present specification, the thin-walled portion may be referred to as a low-concentration portion or a non-polarized portion depending on the matters to be explained.

The thickness of the polarizer (thickness of the portion other than the thin portion) is typically 8 μm or less, preferably 6 μm or less, more preferably 5 μm or less, and further preferably 4 μm or less. On the other hand, the thickness of the polarizer is preferably 0.5 μm or more, more preferably 1 μm or more. When the thickness of the polarizer is in such a range, it is possible to substantially prevent the generation of air bubbles in the thin portion (recess) by adopting an adhesive layer having a predetermined thickness. Further, with such a thickness, a polarizer having excellent durability and optical characteristics can be obtained. Further, the smaller the thickness, the better the non-polarized portion can be formed. For example, when a non-polarized portion is formed by decolorization by chemical treatment, the contact time between the treatment liquid (typically, a decolorization liquid such as a basic solution: described later) and a polarizer can be shortened. Specifically, the non-polarized portion can be formed in a shorter time. Further, by reducing the thickness of the resin film, the depth of the recess can be reduced, and as a result, the defect that the recess is visually recognized can be suppressed.

The depth of the recess 14 is preferably 0.50 μm or less, more preferably 0.45 μm or less, and further preferably 0.40 μm or less. On the other hand, the depth of the recess 14 is preferably 0.30 μm or more, more preferably 0.35 μm or more. In the present specification, the "depth of the recess" means the depth of the deepest portion of the recess.

The polarizer (excluding the non-polarized portion) preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance (Ts) of the polarizer (excluding the non-polarizing portion) is preferably 39% or more, more preferably 39.5% or more, still more preferably 40% or more, and particularly preferably 40.5% or more. .. The theoretical upper limit of the simple substance transmittance is 50%, and the practical upper limit is 46%. The single transmittance (Ts) is a Y value measured by a JIS Z8701 double-degree field (C light source) and corrected for luminosity factor. For example, a microspectroscopy system (manufactured by Lambdavision, LVmicro) is used. Can be measured. The degree of polarization of the polarizer (excluding the non-polarized portion) is preferably 99.9% or more, more preferably 99.93% or more, still more preferably 99.95% or more.

B-2. Resin film As the resin film, any suitable resin film that can be used as a polarizer can be adopted. The resin film is typically a polyvinyl alcohol-based resin (hereinafter, referred to as “PVA-based resin”) film.

Any suitable resin can be used as the PVA-based resin that forms the PVA-based resin film. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be mentioned. 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%. .. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizer 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 depending on the intended 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.

Examples of the dichroic substance contained in the resin film include iodine and organic dyes. These can be used alone or in combination of two or more. Preferably iodine is used. For example, when a non-polarized part is formed by decolorization by chemical treatment, the iodine complex contained in the resin film (polarizer) is appropriately reduced, so that the non-polarized part has appropriate characteristics when used in a camera part, for example. Because it can form.

B-3. Thin-walled part (or low-concentration part or non-polarized part)
As described above, the thin-walled portion 12 typically has a recess 14 having a concave surface on one surface side of the polarizer. The recess 14 can be formed, for example, by applying a decolorizing liquid only from one surface side of a polarizing element (polarizer intermediate). Since the recess can be formed only on one side, the influence on the appearance can be further suppressed. In the embodiment of the present invention, the recess 14 is substantially free of air bubbles.

In one embodiment, the thin-walled portion (non-polarized portion) 12 is a low-concentration portion having a lower content of the dichroic substance than the other portions of the polarizer. According to such a configuration, cracks are generated as compared with the case where the non-polarized portion is formed mechanically (for example, by a method of mechanically punching out using a punching blade, a plotter, a water jet, etc.). Quality problems such as delamination (delamination) and glue squeeze out are avoided. In addition, since the content of the dichroic substance itself is low in the low-concentration part, the transparency of the non-polarized part is higher than that in the case where the dichroic substance is decomposed by laser light or the like to form the non-polarized part. Well maintained. Such a low concentration portion can be typically formed by decolorization by chemical treatment (for example, decolorization by contact with a basic solution: described later).

The content of the dichroic substance in the low concentration portion is preferably 1.0% by weight or less, more preferably 0.5% by weight or less, still more preferably 0.2% by weight or less. When the content of the dichroic substance in the low-concentration portion is within such a range, the desired transparency can be sufficiently imparted to the low-concentration portion. For example, when a low-density portion is associated with the camera portion of an image display device, extremely excellent shooting performance can be realized from the viewpoints of both brightness and color. On the other hand, the lower limit of the content of the dichroic substance in the low concentration portion is usually not more than the detection limit value. When iodine is used as the bicolor substance, the iodine content can be determined, for example, from the X-ray intensity measured by fluorescent X-ray analysis by a calibration curve prepared in advance using a standard sample.

The difference between the content of the dichroic substance in the other portion and the content of the dichroic substance in the low concentration portion is preferably 0.5% by weight or more, more preferably 1% by weight or more. When the difference in content is within such a range, a low-concentration portion having desired transparency can be formed.

The low concentration portion has an alkali metal and / or alkaline earth metal content of 3.6% by weight or less, preferably 2.5% by weight or less, and more preferably 1.0% by weight or less. , More preferably 0.5% by weight or less. When the content of the alkali metal and / or alkaline earth metal in the low concentration part is within such a range, the shape of the low concentration part formed by contact with the basic solution (bleaching solution) described later is well maintained. (That is, a low concentration portion with excellent dimensional stability can be realized). The content can be determined, for example, from the X-ray intensity measured by fluorescent X-ray analysis by a calibration curve prepared in advance using a standard sample. Such a content can be realized by reducing the alkali metal and / or alkaline earth metal at the contact portion in contact with the basic solution described later.

The transmittance of the non-polarized portion (for example, the transmittance measured with light having a wavelength of 550 nm at 23 ° C.) is preferably 50% or more, more preferably 60% or more, still more preferably 75% or more, and particularly preferably 90% or more. Is. With such a transmittance, the low concentration portion has the desired transparency. As a result, when the polarizing plate is arranged so that the non-polarizing portion corresponds to the camera portion of the image display device, it is possible to prevent an adverse effect on the shooting performance of the camera. Further, the higher the transmittance, the more remarkable the effect of suppressing bubbles by the present invention on the polarizing element having a small thickness. This is because even if the polarizing element has a small thickness, the higher the transmittance, the larger the depth of the recess, and the more easily bubbles are generated.

In the illustrated example, the small circular non-polarizing portion 12 is formed in the central portion of the upper end portion of the polarizer 10, but the arrangement, shape, size, etc. of the non-polarizing portion can be appropriately designed. For example, it is designed according to the position, shape, size, etc. of the camera unit of the mounted image display device. Specifically, it is designed so that the non-polarized portion does not correspond to the display screen of the mounted image display device.

As the plan view shape of the non-polarizing unit 12, any appropriate shape can be adopted as long as it does not adversely affect the camera performance of the image display device in which the polarizing element is used. Specific examples include circles, ovals, squares, rectangles, and rhombuses. By appropriately setting the shape of the through hole of the surface protective film described in the section F-2 described later, a non-polarized portion having a desired plan view shape can be formed.

C. Adhesive layer The adhesive constituting the adhesive layer preferably has a viscosity of 35 mPa · S or less before solidification or curing. The viscosity before solidification or curing is preferably as low as the adhesive layer can be formed. The lower the viscosity before solidification or curing, the better (for example, to the corners) it can flow into the recesses of the polarizer by coating, so even if the adhesive layer is very thin, the generation of bubbles in the recesses should be well prevented. Can be done. As a result, it is possible to both prevent the generation of bubbles and reduce the thickness. Specifically, the viscosity before solidification or curing is preferably 25 mPa · S or less, more preferably 15 mPa · S or less, and further preferably 10 mPa · S or less. The lower limit of the viscosity before solidification or curing is, for example, 5 mPa · S. In addition, since the adhesive has a higher adhesive force than the adhesive, it has an advantage that the obtained polarizing plate has excellent durability.

As the adhesive, any suitable adhesive can be used as long as it has the viscosity before solidification or curing as described above. Specific examples of the form of the adhesive include water-based adhesives, solvent-based adhesives, emulsion-based adhesives, solvent-free adhesives, and active energy ray-curable adhesives (for example, ultraviolet curable adhesives and electron beam-curable adhesives). Adhesives), heat-curable adhesives, etc. A water-based adhesive is preferable. This is because it has a desired solidification or pre-curing viscosity and is excellent in adhesiveness to a polarizer.

As the water-based adhesive, any suitable water-based adhesive can be adopted. Preferably, a water-based adhesive containing a PVA-based resin is used. The average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably about 100 to 5500, more preferably 1000 to 4500, from the viewpoint of adhesiveness. The average saponification degree is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol% from the viewpoint of adhesiveness.

The PVA-based resin contained in the water-based adhesive preferably contains an acetoacetyl group. This is because the adhesion to the polarizer and the protective layer is excellent, and the durability can be excellent. The acetoacetyl group-containing PVA-based resin can be obtained, for example, by reacting the PVA-based resin with diketene by an arbitrary method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 40 mol%, and more preferably 1 mol% to 20 mol. %, Especially preferably 2 mol% to 7 mol%. The degree of acetoacetyl group modification is a value measured by NMR.

The resin concentration of the water-based adhesive is preferably 0.1% by weight to 15% by weight, more preferably 0.5% by weight to 10% by weight.

The amount of water contained in the water-based adhesive per unit area is preferably 0.05 mg / cm ² or more. On the other hand, the water content is preferably 2.0 mg / cm ² or less, more preferably 1.0 mg / cm ² or less. This is because it may take time to dry the adhesive. The amount of water is determined by the amount of water contained in the adhesive and the amount of the adhesive applied to the surface of the polarizer.

The heating temperature for solidifying or curing the aqueous adhesive is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, still more preferably 60 ° C. or higher, and particularly preferably 80 ° C. or higher. The upper limit of the heating temperature is, for example, 100 ° C. If the heating temperature is too low, the adhesive may not solidify or harden sufficiently. If the heating temperature is too high, the edge of the polarizing plate may be broken, which may cause a problem in transportability.

The thickness of the adhesive layer is less than 2.0 μm as described above. As for the thickness of the adhesive layer, the thinner it is, the more preferable it is, as long as the adhesive layer having an adhesive function can be formed. The thickness of the adhesive layer is preferably less than 1.5 μm, more preferably less than 1.0 μm. The lower limit of the thickness of the adhesive layer is, for example, 0.01 μm. In one embodiment, the thickness of the adhesive layer is 0.05 μm to 0.1 μm. In the case of the pressure-sensitive adhesive layer, at a thickness having a practically acceptable adhesive force, the thicker the pressure-sensitive adhesive layer, the more the generation of bubbles in the recesses is suppressed. Can be substantially eliminated. On the other hand, in the case of an adhesive layer (particularly an adhesive layer of a water-based adhesive), although it is not theoretically clear, by optimizing the viscosity before solidification or curing, even if the adhesive layer is very thin. The recesses can be substantially free of air bubbles. Therefore, by adopting an adhesive layer composed of a predetermined adhesive, it is possible to greatly contribute to the thinning of the polarizing plate (as a result, the image display device) while satisfactorily preventing the generation of air bubbles in the recesses. Such an effect is an unexpected finding obtained only by trial and error in order to remove air bubbles in the thin-walled part of the polarizing plate in a polarizing plate using a polarizing element having a thin-walled part (non-polarized part). It is an excellent effect.

D. Protective layer The protective layer 30 is formed of any suitable film that can be used as a protective layer for the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (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. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, a vitreous polymer such as a siloxane-based polymer can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, 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. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

If necessary, the protective layer 30 may be subjected to surface treatment such as hard coating treatment, antireflection treatment, and antiglare treatment. In other words, a surface treatment layer such as a hard coat layer, an antireflection layer, and an antiglare layer may be formed on the surface of the protective layer 30. The surface treatment layer is preferably a layer having low moisture permeability for the purpose of improving the humidification durability of the polarizing plate, for example. The hard coat layer is provided for the purpose of preventing scratches on the surface of the polarizing plate. The hard coat layer can be formed, for example, by a method of adding a cured film having excellent hardness, slipperiness, etc. to the surface by an appropriate ultraviolet curable resin such as an acrylic type or a silicone type. The hard coat layer preferably has a pencil hardness of 2H or more. The antireflection layer is a low reflection layer provided for the purpose of preventing reflection of external light on the surface of the polarizing plate. As the antireflection layer, for example, a thin layer type that prevents reflection by utilizing the effect of canceling reflected light due to the interference action of light as disclosed in JP-A-2005-248173, JP-A-2011-2759. Examples of the surface structure type that develops low reflectance by imparting a fine structure to the surface as disclosed in 1. The anti-glare layer is provided for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the visibility of the light transmitted through the polarizing plate. The anti-glare layer is formed by imparting a fine concavo-convex structure to the surface by an appropriate method such as a sandblasting method, a roughening method by an embossing method, or a blending method of transparent fine particles. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle enlargement function) for diffusing the light transmitted through the polarizing plate to expand the viewing angle and the like.

The thickness of the protective layer 30 is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm. When the surface treatment is applied, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

E. Other Structures of Polarizing Plate Polarizing Plate 100 may further have any suitable optical functional layer depending on the intended purpose. A typical example of the optical functional layer is a retardation film (optical compensation film). For example, a retardation film may be placed on the opposite side of the polarizer 10 from the protective layer 30 (not shown). The optical characteristics of the retardation film (for example, refractive index ellipsoid, in-plane retardation, thickness direction retardation) can be appropriately set according to the purpose, the characteristics of the image display device, and the like. For example, when the image display device is a liquid crystal display device in IPS mode, a retardation film having a refractive index ellipsoid of nx>ny> nz and a retardation film having a refractive index ellipsoid of nz>ny> ny Can be placed. The retardation film may also serve as the other protective layer described above. Note that "nx" is the refractive index in the direction in which the refractive index in the film surface is maximized (that is, the slow-phase axis direction), and "ny" is the refractive index in the direction orthogonal to the slow-phase axis in the film surface. Yes, "nz" is the refractive index in the thickness direction.

Up to this point, an embodiment in which the polarizing plate has a single-wafer shape has been described, but in another embodiment, the polarizing plate of the present invention may have a long shape. The single-wafer-shaped polarizing plate can be obtained by cutting a long-shaped polarizing plate into a predetermined size or shape, or by cutting out from a long-shaped polarizing plate. Hereinafter, the polarizer in the elongated polarizing plate will be briefly described.

FIG. 3 is a schematic perspective view of a long-shaped polarizer. The elongated polarizer 16 can be typically wound in a roll shape as shown in FIG. The polarizer 16 has non-polarizing portions (thin-walled portions) 12 arranged at predetermined intervals (that is, in a predetermined pattern) in the longitudinal direction and / or the width direction. The arrangement pattern of the non-polarizing unit 12 can be appropriately set according to the purpose. Typically, the non-polarizing section 12 is cut to a predetermined size (for example, in the elongated direction and / or the width direction) in order to attach the polarizer 16 (substantially a polarizing plate) to an image display device of a predetermined size. Is arranged at a position corresponding to the camera unit of the image display device when the image is cut or punched. Therefore, when cutting only one size of a polarizing element from one elongated polarizer 16, the non-polarizing section 12 is typically substantially equal in both the elongated direction and the width direction. Can be placed at intervals. With such a configuration, it is easy to control the cutting of the polarizer to a predetermined size according to the size of the image display device, and the yield can be improved. Further, it is possible to suppress the variation in the position of the non-polarized portion in the cut single-wafer-shaped polarizer. In addition, "substantially equal intervals in both the long direction and the width direction" means that the intervals in the long direction are equal intervals and the intervals in the width direction are equal intervals, and the length is long. The spacing in the shaku direction and the spacing in the width direction do not have to be equal. For example, when the interval in the long direction is L1 and the interval in the width direction is L2, L1 = L2 or L1 ≠ L2. When cutting a plurality of size polarizers from one elongated polarizer 16, the distance between the non-polarizing portions 12 in the elongated direction and / or the width direction is changed according to the size of the polarizer to be cut. be able to. For example, the non-polarizing portions 12 may be arranged at substantially equal intervals in the elongated direction and at different intervals in the width direction; they may be arranged at different intervals in the elongated direction and in the width direction. They may be arranged at substantially equal intervals. When the non-polarized parts are arranged at different intervals in the longitudinal direction or the width direction, the intervals of the adjacent unpolarized parts may be all different, and only a part (the interval of a specific adjacent non-polarized part) is different. May be. Further, a plurality of regions may be defined in the elongated direction of the polarizer 16 and the spacing between the non-polarized portions 12 in the elongated direction and / or the width direction may be set for each region. In this way, the non-polarized portion can be formed in an arbitrary appropriate arrangement pattern according to the purpose in the elongated polarizing element. Details of the arrangement pattern of the non-polarizing portion in the polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2016-277392, and the description of the publication is incorporated herein by reference.

Practically, the polarizing plate 100 has an adhesive layer as the outermost layer (not shown). The pressure-sensitive adhesive layer is typically the outermost layer on the image display device side. A separator is temporarily attached to the pressure-sensitive adhesive layer so that it can be peeled off, protecting the pressure-sensitive adhesive layer until actual use and enabling roll formation.

F. Method for manufacturing a polarizing plate Hereinafter, a method for manufacturing a polarizing plate of the present invention will be described. For convenience, a method for manufacturing a long polarizing plate will be described. The single-wafer-shaped polarizing plate can be obtained by cutting the obtained elongated polarizing plate into a predetermined size or shape.

F-1. Fabrication of Polarizer The resin film (typically, PVA-based resin film) constituting the polarizer may be a single film, or a resin layer (typically, representatively) formed on a resin base material. It may be a PVA-based resin layer). The PVA-based resin layer may be formed by applying a coating liquid containing a PVA-based resin on a resin base material, or may be formed by laminating a PVA-based resin film on a resin base material. Hereinafter, the case where the PVA-based resin layer is applied and formed will be briefly described, but the same applies to the case where the PVA-based resin film is laminated. The polarizer obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the resin base material. It is produced by forming a PVA-based resin layer on the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further include, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous solution. The obtained resin substrate / polarizer laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), and the resin substrate is peeled off from the resin substrate / polarizer laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of the method for producing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference. When the polarizer is a single PVA-based resin film, the polarizer can be produced by a method well known and commonly used in the art, and thus detailed description thereof will be omitted.

As described above, a polarizer (polarizer intermediate) is formed on the resin substrate. If necessary, the resin film constituting the protective layer (typically, corresponding to another protective layer (not shown in the above item A) is bonded and / or the resin base material is peeled off. For example, a resin film is attached to the surface of the polarizer of the laminate of the resin substrate / polarizer by roll-to-roll, and then the resin substrate is peeled off. In this way, a laminate of polarizer / protective layer is obtained. Here, the polarizer intermediate means a polarizer before the non-polarizing portion is formed, and is intended to distinguish it from a polarizer having a non-polarizing portion. Therefore, in the present context, the polarizer intermediate may be simply referred to as a polarizer. Those skilled in the art can easily understand whether the "polarizer" means a polarizer intermediate or a polarizer having a non-polarizing portion by looking at the description in the present specification.

F-2. Formation of non-polarized portion Next, a non-polarized portion is formed at a predetermined position of the polarizer intermediate obtained in the above F-1 term. When the polarizer (polarizer intermediate) is formed from a PVA-based resin layer coated on a resin substrate, typically, a resin substrate / a laminate of polarizers or a protective layer / A laminate of polarizers is used to form a non-polarized portion. When the polarizer (polarizer intermediate) is a single resin film, typically, the polarizer alone or a layer of a protective layer / polarizer is used to form a non-polarizing portion. Hereinafter, the formation of the non-polarized portion will be specifically described. As a typical example, a case where a non-polarizing portion is formed on a polarizing element (polarizing element intermediate) in a layered body of a protective layer / polarizing element (hereinafter, simply referred to as a polarizing plate intermediate in this section) will be described. It will be appreciated by those skilled in the art that the same procedure can be applied to a polarizer intermediate having other configurations (for example, a laminate of a resin base material / a polarizer intermediate, a polarizer intermediate which is a single resin film). it is obvious.

The non-polarized portion can be typically formed by decolorization by chemical treatment (hereinafter, also referred to as chemical decolorization treatment). In the chemical decolorization treatment, typically, a predetermined position of a polarizer (polarizer intermediate) is selectively treated with a treatment liquid (typically, a decolorization liquid such as a basic solution: described later). Can be done by. Examples of the method of selectively processing a predetermined portion include a method of using a surface protective film (so-called mask) having through holes arranged in a predetermined pattern, a method of printing a decolorizing liquid at a predetermined position, and a decolorizing liquid. Can be mentioned as a method of injecting the liquid into a predetermined position. Hereinafter, as a typical example, a method of using a surface protective film having through holes arranged in a predetermined pattern will be described.

As shown in FIG. 4, a surface protective film having through holes arranged in a predetermined pattern is attached to the surface of the polarizing plate intermediate on the polarizer side by roll-to-roll. As used herein, the term "roll-to-roll" means that while transporting a roll-shaped film, the films are bonded together in the same long direction. The surface protective film with through holes is detachably attached to the polarizer via any suitable adhesive. By using a surface protective film having through holes, it is possible to perform decolorization treatment by immersing in a decolorizing liquid, so that the polarizing plate of the present invention can be obtained with extremely high production efficiency. For convenience, the surface protective film having through holes may be referred to as the first surface protective film.

The surface protective film has through holes arranged in a predetermined pattern. The position where the through hole is provided corresponds to the position where the non-polarizing portion of the polarizer (polarizer intermediate) is formed. The arrangement pattern of the through holes shown in FIG. 4 corresponds to the arrangement pattern of the non-polarized portion shown in FIG. Through holes can be formed, for example, by mechanical punching (eg punching, engraving blade punching, plotters, water jets) or removal of certain parts of the film (eg laser ablation or chemical dissolution).

The surface protective film is preferably a film having a high hardness (for example, elastic modulus). This is because deformation of the through hole during transportation and / or bonding can be prevented. Materials for forming the surface protective film 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. And so on. The thickness of the surface protective film is typically 20 μm to 250 μm, preferably 30 μm to 150 μm. With such a thickness, there is an advantage that the through hole is less likely to be deformed even when tension is applied during transportation and / or bonding. The elastic modulus of the surface protective film is preferably 2.2 kN / mm ^{2 to} 4.8 kN / mm ² . When the elastic modulus of the surface protective film is within such a range, there is an advantage that the through holes are less likely to be deformed even when tension is applied during transportation and / or bonding. The elastic modulus is measured according to JIS K 6781. The tensile elongation of the surface protective film is preferably 90% to 170%. When the tensile elongation of the first surface protective film is within such a range, it has an advantage that it is unlikely to break during transportation. The tensile elongation is measured according to JIS K 6781.

On the other hand, another surface protective film (also referred to as a second surface protective film) is attached to the surface of the polarizing plate on the protective layer side by roll-to-roll. The second surface protective film is detachably attached to the protective layer via any suitable adhesive. By using the second surface protective film, the polarizing plate intermediate (polarizer intermediate / protective layer) can be appropriately protected in the decolorization treatment by immersion. As the second surface protective film, a film similar to the first surface protective film can be used except that the through holes are not provided. Further, as the second surface protective film, a soft (for example, low elastic modulus) film such as a polyolefin (for example, polyethylene) film can also be used. The second surface protective film may be attached at the same time as the first surface protective film, may be attached before the first surface protective film is attached, or after the first surface protective film is attached. You may stick them together. Preferably, the second surface protective film is attached before the first surface protective film is attached. Such a procedure has the advantages of preventing damage to the protective layer and preventing the through holes formed in the first surface protective film from being transferred to the protective layer as marks during winding. Has. When the second surface protective film is attached before the first surface protective film is attached, for example, a laminate of the protective layer and the second surface protective film is prepared, and the laminate is used as a resin base material. / The resin base material can be peeled off after being bonded to the laminate of the polarizer, and the first surface protective film can be bonded to the peeled surface.

Next, as shown in FIG. 5, the laminate of the first surface protective film / polarizer (polarizer intermediate) / protective layer / second surface protective film is subjected to a chemical decolorization treatment. The chemical decolorization treatment involves contacting the laminate with a treatment liquid (typically a basic solution). When iodine is used as the dichroic substance, the iodine content of the contact portion can be easily reduced by contacting the basic solution with the desired portion of the resin film.

Contact between the laminate and the basic solution can be done by any suitable means. Typical examples include immersion of the laminate in a basic solution, or application or spraying of the basic solution to the laminate. Immersion is preferred. This is because, as shown in FIG. 5, the decolorization treatment can be performed while transporting the laminated body, so that the manufacturing efficiency is remarkably high. As described above, immersion is possible by using the first surface protective film (and, if necessary, the second surface protective film). Specifically, by immersing in a basic solution, only the portion of the polarizer (polarizer intermediate) corresponding to the through hole of the first surface protective film comes into contact with the basic solution. For example, when the polarizer (polarizer intermediate) contains iodine as a dichroic substance, the base of the polarizer (polarizer intermediate) is formed by contacting the polarizer (polarizer intermediate) with a basic solution. The iodine concentration of the contact portion with the sex solution can be reduced, and as a result, the non-polarized portion can be selectively formed only in the contact portion (which can be set by the through hole of the first surface protective film). As described above, according to the present embodiment, the non-polarizing portion can be selectively formed in a predetermined portion of the polarizer (polarizer intermediate) with very high manufacturing efficiency without complicated operations. .. When iodine remains in the obtained polarizer, even if the iodine complex is destroyed to form a non-polarized portion, the iodine complex is formed again with the use of the polarizer, and the non-polarized portion is desired. It may lose its characteristics. In the present embodiment, iodine itself is removed from the polarizer (substantially, the non-polarized portion) by removing the basic solution described later. As a result, it is possible to prevent a change in the characteristics of the non-polarized portion due to the use of the polarizer. In addition, according to the contact method as described above, the recess can be formed only on one surface side of the resin film. In this case, it becomes significantly easier to control the depth of the recesses as compared with the case where the recesses are formed on both sides of the resin film. As a result, it becomes easy to suppress the influence on the appearance.

The formation of the non-polarized portion by the basic solution will be described in more detail. After contact with a predetermined portion of the polarizer (polarizer intermediate), the basic solution permeates into the predetermined portion. The iodine complex contained in the predetermined portion is reduced by the base contained in the basic solution to become an iodine ion. When the iodine complex is reduced to iodine ions, the polarization performance of the portion is substantially lost, and a non-polarized portion is formed in the portion. Further, the reduction of the iodine complex improves the transmittance of the portion. Iodine, which has become an iodide ion, moves from the portion to the solvent of the basic solution. As a result, by removing the basic solution described later, iodine ions as well as the basic solution are removed from the portion. In this way, a non-polarizing portion (low concentration portion) is selectively formed in a predetermined portion of the polarizer (polarizer intermediate), and the non-polarizing portion is stable without change with time. By adjusting the material, thickness and mechanical properties of the first surface protective film, the concentration of the basic solution, the immersion time of the laminate in the basic solution, etc., the basic solution penetrates to an undesired part. (As a result, a non-polarized portion is formed in an undesired portion) can be prevented.

Any suitable basic compound can be used as the basic compound contained in the basic solution. Examples of the basic compound include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, inorganic alkali metal salts such as sodium carbonate, and acetic acid. Examples thereof include organic alkali metal salts such as sodium and aqueous ammonia. Among these, hydroxides of alkali metals and / or alkaline earth metals are preferably used, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are more preferably used. The iodine complex can be efficiently ionized, and the non-polarized portion can be formed more easily. These basic compounds may be used alone or in combination of two or more.

Any suitable solvent can be used as the solvent for the basic solution. Specific examples thereof include water, alcohols such as ethanol and methanol, ether, benzene, chloroform, and a mixed solvent thereof. The solvent is preferably water or alcohol because the iodide ions are satisfactorily transferred to the solvent and the iodide ions can be easily removed in the subsequent removal of the basic solution.

The concentration of the basic solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, and more preferably 0.1N to 2.5N. When the concentration of the basic solution is in such a range, the iodine concentration inside the polarizer (polarizer intermediate) can be efficiently reduced, and the ionization of the iodine complex in a portion other than a predetermined portion is prevented. be able to. Further, with such a concentration, it becomes easy to control the depth of the recesses that can be formed.

The liquid temperature of the basic solution is, for example, 20 ° C to 50 ° C. The contact time between the laminate (substantially a predetermined portion of the polarizer intermediate) and the basic solution is determined by the thickness of the polarizer intermediate, the type of the basic compound contained in the basic solution used, and the base. It can be set according to the concentration of the sex compound, for example, 5 seconds to 30 minutes. If the contact time is within such a range, a recess having an appropriate depth can be formed.

The polarizer may contain boric acid. For example, boric acid may be contained by contacting a boric acid solution (for example, a boric acid aqueous solution) at the time of stretching treatment, cross-linking treatment, etc. for imparting a polarization function. The boric acid content of the polarizer is, for example, 10% by weight to 30% by weight. The boric acid content in the contact portion with the basic solution is, for example, 5% by weight to 12% by weight.

After the contact with the basic solution, the alkali metal and / or the alkaline earth metal contained in the resin film is reduced at the contact portion with which the basic solution is contacted. By reducing alkali metals and / or alkaline earth metals, it is possible to obtain a low-concentration portion having excellent dimensional stability. Specifically, even in a humid environment, the shape of the low-concentration portion formed by contact with the basic solution can be maintained as it is.

By contacting the resin film with the basic solution, hydroxides of alkali metal and / or alkaline earth metal may remain at the contact portion. Further, by bringing the basic solution into contact with the resin film, a metal salt of an alkali metal and / or an alkaline earth metal can be formed at the contact portion. These can generate hydroxide ions, and the generated hydroxide ions act (decompose / reduce) on a dichroic substance (for example, an iodine complex) existing around the contact portion to be in a non-polarized region (low). Concentration range) can be expanded. Therefore, it is considered that by reducing the alkali metal and / or alkaline earth metal salt, it is possible to suppress the expansion of the non-polarized region over time and maintain the desired non-polarized portion shape.

（式中、Ｘはアルカリ金属またはアルカリ土類金属を表す） Examples of the metal salt capable of producing the hydroxide ion include borate. The borate can be produced by neutralizing boric acid contained in the resin film with a basic solution (a solution of an alkali metal hydroxide and / or an alkaline earth metal hydroxide). The borate (metaborate) can be hydrolyzed to generate hydroxide ions as shown in the following formula by, for example, placing a polarizer in a humid environment.

(In the formula, X represents an alkali metal or an alkaline earth metal)

Preferably, the content of the alkali metal and / or alkaline earth metal in the contact portion is 3.6% by weight or less, preferably 2.5% by weight or less, more preferably 1.0% by weight or less, still more preferably 0. The content is reduced to 5% by weight or less.

The resin film may contain an alkali metal and / or an alkaline earth metal in advance by being subjected to various treatments for forming a polarizer. For example, the resin film may contain potassium by contacting it with a solution of iodide such as potassium iodide. As described above, it is generally considered that the alkali metal and / or alkaline earth metal contained in the polarizer does not adversely affect the dimensional stability of the low concentration portion.

As the above-mentioned reduction method, a method of bringing the post-treatment liquid into contact with the contact portion with the basic solution is preferably used. According to such a method, the alkali metal and / or the alkaline earth metal can be transferred from the resin film to the post-treatment liquid to reduce the content thereof.

Any suitable method can be adopted as the contact method of the post-treatment liquid. For example, a method of dropping, coating, and spraying the post-treatment liquid on the contact portion with the basic solution, and a method of immersing the contact portion with the basic solution in the post-treatment liquid can be mentioned.

When the resin film is protected with an arbitrary suitable protective material at the time of contact with the basic solution, it is preferable to contact the post-treatment liquid as it is (particularly when the temperature of the post-treatment liquid is 50 ° C. or higher). According to such a form, it is possible to prevent deterioration of the polarization characteristics due to the post-treatment liquid at a portion other than the contact portion with the basic solution.

The post-treatment liquid may contain any suitable solvent. Examples of the solvent include water, alcohols such as ethanol and methanol, ether, benzene, chloroform, and a mixed solvent thereof. Among these, water and alcohol are preferably used from the viewpoint of efficiently transferring alkali metals and / or alkaline earth metals. As the water, any suitable water can be used. For example, tap water, pure water, deionized water and the like can be mentioned.

The temperature of the post-treatment liquid at the time of contact is, for example, 20 ° C. or higher, preferably 50 ° C. or higher, more preferably 60 ° C. or higher, still more preferably 70 ° C. or higher. At such temperatures, alkali metals and / or alkaline earth metals can be efficiently transferred to the post-treatment liquid. Specifically, the swelling rate of the resin film can be significantly improved, and the alkali metal and / or alkaline earth metal in the resin film can be physically removed. On the other hand, the temperature of water is substantially 95 ° C. or lower.

The contact time can be appropriately adjusted according to the contact method, the temperature of the post-treatment liquid, the thickness of the resin film, and the like. For example, when immersed in warm water, the contact time is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 15 minutes, and even more preferably 60 seconds to 10 minutes.

In one embodiment, an acidic solution is used as the post-treatment liquid. By using an acidic solution, the alkali metal and / or alkaline earth metal hydroxide remaining on the resin film is neutralized, and the alkali metal and / or alkaline earth metal in the resin film is chemically removed. be able to.

As the acidic compound contained in the acidic solution, any suitable acidic compound can be used. Examples of the acidic compound include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrogen fluoride and boric acid, and organic acids such as formic acid, oxalic acid, citric acid, acetic acid and benzoic acid. The acidic compound contained in the acidic solution is preferably an inorganic acid, more preferably hydrochloric acid, sulfuric acid, or nitric acid. These acidic compounds may be used alone or in combination of two or more.

Preferably, as the acidic compound, an acidic compound having a stronger acidity than boric acid is preferably used. This is because it can also act on metal salts (borates) of the above-mentioned alkali metals and / or alkaline earth metals. Specifically, boric acid can be liberated from borate to chemically remove alkali metals and / or alkaline earth metals in the resin film.

Examples of the index of acidity include an acid dissociation constant (pKa), and an acidic compound having a pKa smaller than that of boric acid pKa (9.2) is preferably used. Specifically, pKa is preferably less than 9.2, more preferably 5 or less. pKa may be measured using any suitable measuring device, and the values described in documents such as the Chemical Society of Japan, Revised 5th Edition (edited by the Chemical Society of Japan, Maruzen Publishing) may be referred to. Further, in the case of an acidic compound that dissociates in multiple stages, the value of pKa may change at each stage. When such an acidic compound is used, one in which any of the pKa values at each stage is within the above range is used. In this specification, pKa refers to a value in an aqueous solution at 25 ° C.

The difference between the pKa of the acidic compound and the pKa of the boric acid is, for example, 2.0 or more, preferably 2.5 to 15, and more preferably 2.5 to 13. Within such a range, the alkali metal and / or alkaline earth metal can be efficiently transferred to the post-treatment liquid, and as a result, the desired alkali metal and / or alkaline earth metal is contained in the low concentration portion. The quantity can be realized.

Examples of the acidic compound that can satisfy the above pKa include hydrochloric acid (pKa: -3.7), sulfuric acid (pK ₂ : 1.96), nitrate (pKa: -1.8), and hydrogen fluoride (pKa: 3). .17), inorganic acids such as boric acid (pKa: 9.2), formic acid (pKa: 3.54), oxalic acid (pK ₁ : 1.04, pK ₂ : 3.82), citric acid (pK ₁₎ : 3.09, pK ₂ : 4.75, pK ₃ : 6.41), acetic acid (pKa: 4.8), benzoic acid (pKa: 4.0) and other organic acids.

The solvent of the acidic solution (post-treatment liquid) is as described above, and even in this embodiment in which the acidic solution is used as the post-treatment liquid, the alkali metal and / or alkaline earth metal in the resin film is physically removed. Can happen.

The concentration of the acidic solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, and more preferably 0.1N to 2.5N.

The liquid temperature of the acidic solution is, for example, 20 ° C to 50 ° C. The contact time with the acidic solution can be set according to the thickness of the resin film, the type of the acidic compound, and the concentration of the acidic solution, and is, for example, 5 seconds to 30 minutes.

In addition to the above treatments, the resin film may be further subjected to any other suitable treatment. Other treatments include removal of basic and / or acidic solutions, washing and the like.

Specific examples of the method for removing the basic solution and / or the acidic solution include wiping removal with a waste cloth, suction removal, natural drying, heat drying, blast drying, vacuum drying and the like. The drying temperature is, for example, 20 ° C to 100 ° C. The drying time is, for example, 5 seconds to 600 seconds.

The cleaning process is carried out by any suitable method. Examples of the solution used for the cleaning treatment include pure water, alcohols such as methanol and ethanol, acidic aqueous solutions, and mixed solvents thereof. The cleaning is typically performed while transporting the laminate as shown in FIG. The cleaning process can be performed at any suitable stage. The cleaning treatment may be performed a plurality of times.

As described above, the non-polarizing portion is formed at a predetermined position of the elongated polarizer (polarizer intermediate) in a predetermined arrangement pattern. As described above, the non-polarized part is a thin part. According to the manufacturing method as described above, the thin-walled portion has a recess in which the surface of one surface side (first surface protective film side) of the polarizer is recessed.

F-3. Preparation of Polarizing Plate Next, the first surface protective film is removed (typically peeled off) from the laminate. Further, an adhesive layer is formed on the surface of the laminate from which the first surface protective film has been removed (the surface on which the recesses of the polarizer are formed). Specifically, an adhesive layer can be formed by applying the adhesive according to the above item C to the surface and solidifying or curing the surface. In such a method, since the adhesive can flow into the recesses well at the time of application, the recesses can be filled without gaps by the adhesive after solidification or curing, and the generation of air bubbles can be satisfactorily prevented. As a result, the thin portion of the polarizer can be substantially free of bubbles. Any suitable method can be adopted as the method of applying the adhesive. The solidification or curing method and solidification or curing conditions of the adhesive can be appropriately set depending on the type of adhesive. For example, when a water-based adhesive is used as the adhesive, the adhesive layer can be satisfactorily formed by heating. The heating temperature is, for example, 50 ° C., and the heating time is, for example, 5 minutes. More specifically, the resin film constituting the protective layer is laminated on the adhesive in a state where the adhesive is applied and is not solidified or cured, and the adhesive is applied in a state where the resin film is laminated. Solidify or cure.

As described above, a long polarizing plate having a structure of a protective layer / a polarizer / another protective layer can be obtained. The single-wafer-shaped polarizing plate can be obtained by cutting a long-shaped polarizing plate into, for example, a predetermined size or shape as described above. When producing a polarizing plate having a protective layer / polarizer configuration, a non-polarizing portion is formed on the resin substrate / polarizer laminate in the same manner as described above, and then the resin substrate is removed. A protective layer may be laminated on the removal surface. The second surface protective film can be removed at any suitable time. Specifically, the second surface protective film may be removed from the laminate at the same time as the first surface protective film, may be removed after the elongated polarizing plate is formed, and may be striped. It may be removed after the polarizing plate of the above is formed.

G. Image display device The image display device of the present invention includes the above-mentioned polarizing plate. The polarizing plate is cut according to the size of the image display device. Examples of the image display device include a liquid crystal display device and an organic EL device. Specifically, the liquid crystal display device includes a liquid crystal panel including a liquid crystal cell and the above-mentioned polarizing plate arranged on one side or both sides of the liquid crystal cell. The organic EL device includes an organic EL panel in which the above-mentioned polarizing plate is arranged on the visual side. The polarizing plate is arranged so that the non-polarizing portion corresponds to the camera portion of the image display device.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows.

(1) Thickness Measured using a digital micrometer (manufactured by Anritsu, product name "KC-351C").
(2) Depth of recess The measurement was performed using a scanning electron microscope (manufactured by ZYGO, product name "New View 7300").
(3) Presence or absence of generation of air bubbles 15 non-polarized parts were randomly extracted from the non-polarized parts (thin-walled parts) formed on the polarizing plates obtained in Examples, Comparative Examples and Reference Examples, and the 15 non-polarized parts were randomly extracted. The presence or absence of air bubbles in the polarizing part was confirmed using an FPD scanning microscope (manufactured by OLYMPUS, product name "MX61") at a magnification of 5 times, and evaluated according to the following criteria.
◯: No bubbles are generated in all 15 non-polarized parts ×: Bubbles are found in at least one of the 15 non-polarized parts (4) Number of bubbles Obtained in Examples, Comparative Examples and Reference Examples Fifteen non-polarized parts are randomly extracted from the non-polarized part (thin-walled part) formed on the polarizing plate, and the total number of bubbles generated in the 15 non-polarized parts is measured by an FPD scanning microscope (manufactured by OLYMPUS). The name "MX61") was used to count at a magnification of 5 times.

[Example 1]
As the resin base material, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ° C. was used. One side of the base material is corona-treated, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6) are applied to the corona-treated surface. %, Degree of polymerization of 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z200") in a ratio of 9: 1 is applied and dried at 25 ° C. to a thickness of 13 μm. A PVA-based resin layer was formed 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 120 ° C. (aerial auxiliary stretching).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 30 ° 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).
Next, the polarizing plate was immersed in a dyeing bath having a liquid temperature of 30 ° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was mixed with 100 parts by weight of water, and 1.5 parts by weight of potassium iodide was mixed and immersed in the obtained iodine aqueous solution for 60 seconds (dyeing treatment). ..
Then, it was immersed in a cross-linked bath at a liquid temperature of 30 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, the laminate is immersed in an aqueous solution of boric acid having a liquid temperature of 70 ° C. (an aqueous solution obtained by blending 3 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water). However, uniaxial stretching was performed between rolls having different peripheral speeds so that the total stretching ratio was 5.5 times in the longitudinal direction (longitudinal direction) (underwater stretching).
Then, the laminate was immersed in a washing bath at a liquid temperature of 30 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Subsequently, the adhesive shown below is applied to the surface of the PVA-based resin layer of the laminated body so that the thickness of the adhesive layer after curing is 1.0 μm to form a protective layer (corresponding to another protective layer). A Zeonoa-based resin film (thickness 17 μm) manufactured by Zeon Co., Ltd. was laminated, heated to 50 ° C. from the Zeonoa-based resin film side using an IR heater, and irradiated with the following ultraviolet rays to cure the adhesive. Then, the base material was peeled off from the PVA-based resin layer to obtain a long polarizing plate (polarizer / another protective layer) having a width of about 1300 mm. The thickness of the polarizer was 5 μm, and the single transmittance was 40.8%.
(Adhesive composition)
40 parts by weight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight of acryloyl morpholine (ACMO), and 3 parts by weight of the photoinitiator "IRGACURE 819" (manufactured by BASF) are mixed, and the viscosity before curing is 40 mPa · S. The agent was prepared.
(Ultraviolet rays)
As active energy rays, ultraviolet rays (gallium-filled metal halide lamp, irradiation device: Fusion UV Systems, Light HAMMER10 manufactured by Inc., bulb: V bulb, peak illuminance: 1600 mW / cm ² , cumulative irradiation amount 1000 / mJ / cm ² (wavelength) 380-440 nm)) was used. The illuminance of ultraviolet rays was measured using a Solar-Check system manufactured by Solartell.

A pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) was applied to one surface of an ester-based resin film (thickness 38 μm) having a width of about 1300 mm so as to have a thickness of 5 μm. Through holes having a diameter of 2.8 mm were formed in the ester resin film with an adhesive at intervals of 250 mm in the long direction and at intervals of 400 mm in the width direction using a Pinnacle (registered trademark) blade.

The above-mentioned ester resin film with an adhesive is attached to the polarizer side of the above-mentioned polarizing plate by roll-to-roll, and this is immersed in a 1 mol / L (1N) sodium hydroxide aqueous solution for 30 seconds, and then. It was immersed in 1 mol / L (1N) hydrochloric acid for 10 seconds. Then, it was dried at 60 degreeC, and a non-polarized part was formed in a polarizer. The non-polarized portion was a thin portion having a recess with a depth of 0.5 μm on the ester resin film side.

The ester-based resin film is peeled off from the laminate obtained above, and a water-based adhesive (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name) is provided so that the thickness of the adhesive layer after heating is 0.1 μm on the peeled surface. "Gose Phimmer (registered trademark) Z-200", a PVA-based resin aqueous solution having a resin concentration of 3% by weight and a water content of 97%) is applied, and an acrylic resin film (thickness 40 μm) constituting the protective layer is attached. It was heated for 5 minutes in an oven maintained at 80 ° C. The viscosity of the adhesive before curing was 10 mPa · S.

As described above, a polarizing plate having a structure of a protective layer / a polarizer / another protective layer was produced. The state of bubble generation in the non-polarized portion of the obtained polarizing plate was evaluated according to the criteria (3) and (4) above. The results are shown in Table 1.

[Example 2]
A polarizing plate was produced in the same manner as in Example 1 except that the thickness of the adhesive layer was 0.5 μm. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 3]
A polarizing plate was produced in the same manner as in Example 1 except that the thickness of the adhesive layer was 1.0 μm. The obtained polarizing plate 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 the thickness of the adhesive layer was 1.5 μm. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 5]
A polarizing plate was produced in the same manner as in Example 1 except that the thickness of the adhesive layer was 1.9 μm. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
Example 2 except that the polarizer and the protective layer were bonded together by using the ultraviolet curable adhesive used for bonding the polarizer and another protective layer in place of the water-based adhesive. A polarizing plate was produced in the same manner as in the above. The viscosity of the adhesive before curing was 40 mPa · S, and the thickness of the adhesive layer was 0.5 μm.

[Reference example 1]
A polarizing plate was produced in the same manner as in Comparative Example 1 except that the thickness of the adhesive layer was 2.5 μm. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[evaluation]
As is clear from Table 1, in a polarizing plate containing a polarizer having a thin wall portion, the thickness of the adhesive layer for adhering the polarizer and the protective layer and the viscosity of the adhesive constituting the adhesive layer before curing are adjusted. By doing so, it can be seen that the adhesive layer can be made very thin and the generation of air bubbles in the thin-walled portion can be prevented. As is clear from Comparative Example 1 and Reference Example 1, when an adhesive whose viscosity before curing is outside the range of the present invention is used, it is specified in the adhesive layer in order to prevent the generation of bubbles in the thin-walled portion. It can be seen that a thickness greater than the value is required.

The polarizing plate of the present invention is suitably used for a camera-equipped image display device (liquid crystal display device, organic EL device) such as a mobile phone such as a smartphone, a notebook PC, or a tablet PC.

10 Polarizer 12 Thin-walled part 14 Recessed 20 Adhesive layer 30 Protective layer 100 Polarizing plate

Claims (3)

A polarizer with a thin wall on one side,
It has a protective layer attached to the thin-walled portion side of the polarizer via an adhesive layer composed of a water-based adhesive.
The protective layer and the polarizer are bonded to each other via the adhesive layer.
The thickness of the adhesive layer in the portion other than the thin portion is less than 2.0 μm.
Polarizer. Treating a predetermined position on one surface of the polarizer with a treatment liquid to form a thin portion at the predetermined position,
A water-based adhesive having a viscosity of 35 mPa · S or less is applied to the surface of the polarizer on which the thin-walled portion is formed, and the water-based adhesive is solidified or cured to have a thickness of 2.0 μm in a portion other than the thin-walled portion. A method for producing a polarizing plate, comprising forming an adhesive layer that is less than or equal to, and laminating a protective layer on the adhesive layer. An image display device comprising the polarizing plate according to claim 1, wherein the thin-walled portion of the polarizing plate is arranged at a position corresponding to a camera portion.

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