Polarizing plate

Abstract

The present application provides a polarizing plate having a non-polarizing portion that enables multifunctionalization and high-functionalization of electronic devices such as image display devices, and the non-polarizing portion has excellent dimensional stability and appearance. The polarizing plate according to the present application is composed of a resin film containing a dichroic substance, and has a non-polarizing portion at a predetermined position, and the non-polarizing portion is formed as a thin-walled portion having a thickness thinner than other portions of the resin film. In one embodiment of the present application, the non-polarizing portion has a recessed recess on the surface of the one side of the resin film, and the depth of the recess is 2 μm or less.

Description

[0001] This application is a divisional application of application No. 201680037352.1 filed on June 20, 2016 in the name of the present applicant, the title of which is "Polarizing Plate". TECHNICAL FIELD

[0002] The present application relates to a polarizing plate, and more particularly, to a polarizing plate having a non-polarizing portion. BACKGROUND

[0003] Some image display devices such as mobile phones, notebook personal computers (PCs), and the like have internal electronic parts such as cameras mounted thereon. For the purpose of improving the camera performance of, for example, any such image display device, various studies have been made (for example, Patent Literatures 1 to 7). However, with the rapid popularization of use of smartphones, information processing devices of a touch panel type, and the like, further improvement of the camera performance and the like has been desired. In addition, in response to diversification of the shape of image display devices and their high functionalization, a polarizing plate partially having a polarizing performance has been required. In order to industrially and commercially meet these demands, it has been desired to manufacture image display devices and / or their parts at an acceptable cost. However, there are various matters to be researched for establishing such a technology.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2011-81315

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. 2007-241314

[0008] Patent Literature 3: U.S. Patent Application Publication No. 2004 / 0212555

[0009] Patent Literature 4: Korean Patent Laid-Open No. 10-2012-0118205

[0010] Patent Literature 5: Korean Patent No. 10-1293210

[0011] Patent Literature 6: Japanese Patent Application Laid-Open No. 2012-137738

[0012] Patent Literature 7: U.S. Patent Application Publication No. 2014 / 0118826 SUMMARY

[0013] Problems to be Solved by the Invention

[0014] The present application has been made to solve the above problems, and the main object of the present application is to provide a polarizing plate having a non-polarizing portion, which is excellent in dimensional stability and appearance of the non-polarizing portion, and which can realize multifunctionalization and high functionalization of electronic devices such as image display devices.

[0015] Means for Solving the Problems

[0016] The polarizing plate according to the embodiment of the present application includes a resin film containing a dichroic substance, wherein: the polarizing plate has a non-polarizing portion at a predetermined position; and the non-polarizing portion includes a thin-walled portion thinner than other portions of the resin film.

[0017] In one embodiment of the present application, the above non-polarizing portion has a recessed portion recessed on a surface on one side of the resin film, and the depth of the recessed portion is 2 μm or less.

[0018] In one embodiment of the present application, the thickness of the above polarizing plate is 10 μm or less.

[0019] In one embodiment of the present application, the above non-polarizing portion includes a low-concentration portion having a lower content of the above dichroic substance than other portions of the above resin film.

[0020] In one embodiment of the present application, the content of the dichroic substance in the above non-polarizing portion is 1.0% by weight or less.

[0021] In one embodiment of the present application, the content of the dichroic substance in the above non-polarizing portion is 1.0% by weight or less, and the depth of the above recessed portion is 2 μm or less.

[0022] In one embodiment of the present application, the content of alkali metal and / or alkaline earth metal in the above non-polarizing portion is 3.6% by weight or less.

[0023] In one embodiment of the present application, the transmittance of the above non-polarizing portion is 50% or more.

[0024] In one embodiment of the present application, the transmittance of the above non-polarizing portion is 90% or more, and the depth of the above recessed portion is 2 μm or less.

[0025] In one embodiment of the present application, the above resin film includes a polyvinyl alcohol-based resin film containing iodine.

[0026] According to another aspect of the present application, a polarizing plate is provided. The polarizing plate includes: the above polarizing plate; and a protective film disposed on at least one side of the polarizing plate.

[0027] According to another aspect of the present invention, an image display device is provided. The image display device includes the aforementioned polarizer or polarizing plate, wherein the aforementioned non-polarizing portion is disposed at a position corresponding to the camera portion.

[0028] Effects of the Invention

[0029] According to the present invention, in a polarizer having a non-polarized portion that enables multifunctionality and high functionality in electronic devices such as image display devices, the thin-walled portion (step difference) formed in the non-polarized portion is controlled, thereby providing a polarizer with excellent dimensional stability and appearance in the non-polarized portion. More specifically, the non-polarized portion is formed by a predetermined chemical decolorization process (typically, treatment with an alkaline solution and a chemical treatment accompanying the treatment), thereby forming a non-polarized portion with high transmittance, appropriately positioned, for example, corresponding to the camera portion of an image display device, and with excellent dimensional stability and appearance. The inventors of the present invention have discovered that, according to such a chemical decolorization process, especially when the transmittance of the non-polarized portion is set to high, it is unavoidable to generate recesses in the non-polarized portion, and when the depth of the recess is too large, the recess can still be seen even after it has been filled with an adhesive or the like during the formation of the polarizer. Furthermore, the inventors of the present invention have discovered that when the depth of such recesses is controlled (effectively reduced), the visibility of the recesses can be suppressed. Therefore, the inventors have successfully ensured designability while maintaining the excellent characteristics of the non-polarizing portion as described above. As stated above, according to the present invention, a polarizer with excellent dimensional stability and appearance in the non-polarizing portion can be achieved. Attached Figure Description

[0030] FIG. 1 This is an exemplary plan view of a polarizer according to one embodiment of the present invention.

[0031] FIG. 2 for FIG. 1 An exemplary cross-sectional view of a polarizer.

[0032] FIG. 3 This is an exemplary perspective view of a polarizer according to another embodiment of the present invention.

[0033] FIG. 4A This is an exemplary plan view illustrating an example of the configuration pattern of the non-polarizing portion in a strip-shaped polarizer according to an embodiment of the present invention.

[0034] FIG. 4B This is an exemplary plan view illustrating another example of the configuration pattern of the non-polarized portion in a strip-shaped polarizer according to an embodiment of the present invention.

[0035] FIG. 4CThis is an exemplary plan view illustrating yet another example of the configuration pattern of the non-polarizing portion in a strip-shaped polarizer according to an embodiment of the present invention.

[0036] FIG. 5 This is an exemplary cross-sectional view of a polarizing plate according to one embodiment of the present invention.

[0037] FIG. 6 This is an exemplary perspective view illustrating the bonding between a polarizer and a first surface protective film in a method for manufacturing a polarizer according to an embodiment of the present invention.

[0038] FIG. 7 This is an exemplary diagram illustrating the formation of the non-polarizing portion in a method for manufacturing a polarizer according to an embodiment of the present invention.

[0039] FIG. 8 (a) is a graph used to show the evaluation results of surface smoothness in Example 1. FIG. 8 (b) is a graph used to show the evaluation results of surface smoothness in Example 2. Detailed Implementation

[0040] The following describes embodiments of the present invention. However, the present invention is not limited to these embodiments.

[0041] A. Polarizing filter

[0042] A-1. Overall Structure of Polarizers

[0043] FIG. 1 This is an exemplary plan view of a polarizer according to one embodiment of the present invention, and FIG. 2 for FIG. 1 An exemplary cross-sectional view of the polarizer. It should be noted that... FIG. 1 and FIG. 2 They differ from each other in scale and proportion. The polarizer 100 includes a resin film 10 and has a non-polarizing portion 20 at a predetermined position. The resin film 10 contains a dichroic material. In an embodiment of the invention, the non-polarizing portion 20 is a thin-walled portion that is thinner than other parts of the resin film. The non-polarizing portion 20 typically has a recess 22 on one side of the surface of the resin film 10. The depth of the recess 22 is less than 2 μm.

[0044] The polarizer (excluding the polarizing section) preferably exhibits absorption dichroism at any wavelength in the wavelength range of 380 nm to 780 nm. The single-layer transmittance (Ts) of the polarizer (excluding the polarizing section) is preferably 39% or more, more preferably 39.5% or more, even more preferably 40% or more, and particularly preferably 40.5% or more. The theoretical upper limit for single-layer transmittance is 50%, and the practical upper limit is 46%. Furthermore, the single-layer transmittance (Ts) is the Y value measured using a 2-degree field of view (C light source) of JIS Z8701 and corrected for visibility; for example, it can be measured using a microspectral system (manufactured by Lambda Vision Inc., LVmicro). The polarization degree of the polarizer (excluding the polarizing section) is preferably 99.9% or more, more preferably 99.93% or more, and even more preferably 99.95% or more.

[0045] A-2. Resin film

[0046] Any suitable resin film that can be used as a polarizer may be used as resin film 10. Resin film 10 is typically a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film.

[0047] Any suitable resin can be used as the PVA-based resin for forming PVA-based resin films. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers can be obtained by saponifying ethylene-vinyl acetate copolymers. The degree of saponification of PVA-based resins is typically 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined according to JIS K 6726-1994. Using PVA-based resins with such a degree of saponification can provide polarizers with excellent durability. When the saponification is too high, the resin will gel.

[0048] The average degree of polymerization of PVA-based resins can be appropriately selected according to the purpose. The average degree of polymerization is typically 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. The average degree of polymerization can be obtained according to JIS K 6726-1994.

[0049] Examples of dichroic substances in resin films include iodine and organic dyes. These substances can be used alone or in combination. Iodine is preferred. This is because when the non-polarized portion is formed, for example, through decolorization based on chemical treatment, the iodine complex in the resin film (polarizer) is appropriately reduced, thereby forming a non-polarized portion with suitable properties for use, for example, in a camera section.

[0050] The thickness of the resin film (resulting in the polarizer) is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 6 μm or less, and particularly preferably 5 μm or less. Simultaneously, the thickness is preferably 0.5 μm or more, more preferably 1 μm or more. At such thicknesses, polarizers with excellent durability and excellent optical properties can be obtained. Furthermore, as the thickness decreases, the non-polarized portion can be formed more effectively. When the non-polarized portion is formed, for example, by decolorization based on chemical treatment, the contact time between the decolorizing liquid and the resin film (polarizer) can be shortened. Specifically, the non-polarized portion can be formed in a shorter time. Additionally, the thickness of the portion in contact with the decolorizing liquid (e.g., an alkaline solution) becomes thinner than other portions, which can create a step difference in some cases. However, by reducing the thickness of the resin film, such a step difference can be reduced. As a result, the inconvenience of seeing the recess can be suppressed. More specifically, as a result of extensive research, the inventors of the present invention have discovered that when attempting to improve the transmittance of the non-polarized portion by decolorization, a recess with a depth of, for example, approximately 20% of the resin film thickness is formed. Furthermore, the inventors of this invention discovered that it is not the ratio of the recess depth to the resin film thickness, but rather the absolute value of the recess depth that affects the appearance of the polarizer (typically, the visibility of the recess). Therefore, by reducing the thickness of the resin film, the absolute value of the recess depth can be reduced, thereby suppressing the impact on appearance. This effect is exceptionally achieved only after applying techniques involving the formation of non-polarized portions (especially high-transmittance non-polarized portions) through chemically based decolorization to very thin polarizers.

[0051] A-3. Non-polarized part

[0052] As described above, the non-polarized portion 20 is a thin-walled portion that is thinner than other portions. The non-polarized portion 20 typically has a recess 22 on one side of the resin film 10. In this case, the step difference (depth of the recess) between the non-polarized portion and other portions is, for example, 0.02 μm or more. Meanwhile, the step difference is preferably 2 μm or less, more preferably 1 μm or less. Such a step difference is formed when the non-polarized portion is formed by decolorization as described later. However, when the upper limit of the step difference falls within such a range, the impact on the appearance is well suppressed. The term "step difference (depth of the recess)" as used herein refers to the depth of the deepest part of the recess.

[0053] The recessed portion on one side of the surface is formed, for example, by having the decolorizing liquid described later act only on one side of the polarizer (polarizer intermediate). When the depth of the recess formed after the decolorization process is set within the above-mentioned range, the decolorization process described later can be performed uniformly. Furthermore, the recess can be formed only on one side, thereby further suppressing the impact on the appearance.

[0054] The non-polarized portion is preferably a low-concentration portion with a relatively low content of dichroic material. Specifically, this portion is a low-concentration portion with a lower content of dichroic material than any other portion. Based on this structure, compared to forming the non-polarized portion mechanically (e.g., by methods involving mechanically removing this portion using a carving knife, punching machine, plotter, or water jet), problems with quality such as cracking, delamination (interlayer peeling), and adhesive overflow are avoided. Furthermore, the low content of dichroic material in the low-concentration portion itself maintains better transparency of the non-polarized portion compared to the case where the non-polarized portion is formed by decomposing the dichroic material using a laser or the like.

[0055] The low-concentration section is the portion where the content of the dichroic substance is lower than in other sections. The content of the dichroic substance in the low-concentration section is preferably 1.0% by weight or less, more preferably 0.5% by weight or less, and even more preferably 0.2% by weight or less. When the content of the dichroic substance in the low-concentration section falls within such a range, the desired transparency can be sufficiently imparted to the low-concentration section. When the low-concentration section is used, for example, in the camera section of an image display device, excellent photographic performance can be achieved from both brightness and hue perspectives. Simultaneously, the lower limit of the dichroic substance content in the low-concentration section is typically equal to or less than the detection limit. When iodine is used as the dichroic substance, the iodine content can be obtained, for example, from a calibration curve pre-generated using a standard sample and measured by X-ray fluorescence analysis.

[0056] The difference between the content of dichroic substances in other parts and the content of dichroic substances in the low-concentration part is preferably 0.5% by weight or more, more preferably 1% by weight or more. When the content difference falls within such a range, a low-concentration part with the desired transparency can be formed.

[0057] The content of alkali metals and / or alkaline earth metals in the low-concentration portion is 3.6% by weight or less, preferably 2.5% by weight or less, more preferably 1.0% by weight or less, and even more preferably 0.5% by weight or less. When the content of alkali metals and / or alkaline earth metals in the low-concentration portion falls within such a range, the shape of the low-concentration portion formed by contact with the alkaline solution described later can be well maintained (i.e., a low-concentration portion with excellent dimensional stability can be achieved). This content can be obtained, for example, from a calibration curve pre-generated using a standard sample by X-ray fluorescence analysis. Such a content can be achieved by reducing the amount of alkali metals and / or alkaline earth metals in the contact portion that contacts the alkaline solution described later.

[0058] The transmittance of the non-polarized portion (e.g., transmittance measured at 23°C using light with a wavelength of 550 nm) is preferably 50% or more, more preferably 60% or more, even more preferably 75% or more, and particularly preferably 90% or more. At such transmittance, the low-concentration portion exhibits the desired transparency. As a result, when the polarizer is configured to correspond to the camera section of an image display device, adverse effects on the camera's photographic performance can be prevented.

[0059] In the illustrated example, a small circular non-polarizing portion 20 is formed at the center of the upper end of the resin film 10. However, the arrangement, shape, and size of the non-polarizing portion can be appropriately designed. The design is based on, for example, the position, shape, and size of the camera section of an image display device on which a polarizer is mounted. Specifically, the design is carried out in such a way that the non-polarizing portion does not correspond to the display screen of the image display device on which the polarizer is mounted.

[0060] Any suitable shape can be used as the top view shape of the non-polarized section 20, as long as it does not adversely affect the camera performance of the image display device in which a polarizer is used. Specific examples include: circles, ellipses, squares, rectangles, and rhombuses. By appropriately setting the shape of the through-hole of the surface protective film described later in section C, a non-polarized section with the desired top view shape can be formed.

[0061] The above description has illustrated an embodiment in which the polarizer is sheet-shaped; however, in other embodiments, the polarizer of the present invention may be strip-shaped. A sheet-shaped polarizer can be produced by cutting a strip-shaped polarizer to a predetermined size, or by cutting it from a strip-shaped polarizer. The strip-shaped polarizer is described below.

[0062] FIG. 3 This is an exemplary perspective view of a strip-shaped polarizer. The strip-shaped polarizer 101 is typically as follows: FIG. 3 The polarizer is wound into a roll as shown. The term "strip-shaped" as used herein refers to an elongated shape whose length is sufficiently long compared to its width, for example, an elongated shape whose length is more than 10 times, preferably more than 20 times, the width. The polarizer 101 has non-polarizing portions 20 arranged at predetermined intervals (i.e., according to a predetermined pattern) along its length direction and / or its width direction. The arrangement pattern of the non-polarizing portions 20 can be appropriately set according to the purpose. When the polarizer 101 is cut to a predetermined size (e.g., cut or punched along its length and / or width direction) for mounting on an image display device, the non-polarizing portions 20 are typically arranged at positions corresponding to the camera section of the image display device having a predetermined size. Therefore, when a polarizer having only one size is cut from a strip-shaped polarizer 101, as... FIG. 3As shown, the non-polarizing portions 20 can be arranged at substantially equal intervals along both the length and width directions. With this configuration, it is easy to control the cutting of the polarizer to a predetermined size according to the dimensions of the image display device, thereby improving yield. Furthermore, variations in the position of the non-polarizing portions in the sheet-like polarizer cut from the strip-shaped polarizer can be suppressed. Additionally, "at substantially equal intervals along both the length and width directions" means that the intervals in the length direction are substantially equal to each other, and the intervals in the width direction are substantially equal to each other, but the intervals in the length and width directions do not need to be equal to each other. For example, when the intervals in the length direction are each represented by L1, and the intervals in the width direction are each represented by L2, L1 can be equal to L2, or L1 can be not equal to L2. When polarizers of various sizes are cut from a strip-shaped polarizer 101, the interval between the non-polarizing portions 20 in the length and / or width directions can be changed according to the size of the polarizer to be cut from the strip-shaped polarizer. For example, the non-polarizing portions 20 may be arranged at substantially equal intervals along the length direction and at different intervals along the width direction; or they may be arranged at different intervals along the length direction and at substantially equal intervals along the width direction. When the non-polarizing portions are arranged at different intervals along the length or width direction, the intervals between adjacent non-polarizing portions may all be different from each other, or only a portion of the intervals (the intervals between specific adjacent non-polarizing portions) may be different from each other. Furthermore, it is possible to designate multiple regions along the length direction of the polarizer 101 and set the intervals between the non-polarizing portions 20 along the length and / or width directions in each region. Thus, the non-polarizing portions can be formed in the elongated polarizer according to any suitable arrangement pattern.

[0063] FIG. 4A This is an exemplary plan view illustrating an example of the configuration pattern of the non-polarizing portion in a polarizer according to an embodiment of the present invention. FIG. 4B An exemplary plan view for illustrating another example of the configuration pattern of the non-polarized section, and FIG. 4C This is an exemplary plan view illustrating yet another example of the configuration pattern for the non-polarized portion. In one embodiment, as... FIG. 4A As shown, the non-polarizing portion 20 is configured such that the straight lines connecting adjacent non-polarizing portions in the length direction of the polarizer are substantially parallel to the length direction, and the straight lines connecting adjacent non-polarizing portions in its width direction are substantially parallel to the width direction. This embodiment corresponds to FIG. 3 The diagram shows the configuration pattern of the unpolarized portion in a polarizer. In another embodiment, as shown... FIG. 4B As shown, the non-polarized portion 20 is configured such that the straight line connecting adjacent non-polarized portions in the length direction is substantially parallel to the length direction, and the straight line connecting adjacent non-polarized portions in the width direction can have a predetermined angle θ relative to the width direction. W In yet another implementation plan, such asFIG. 4C As shown, the non-polarized portion 20 is configured such that the straight line connecting adjacent non-polarized portions in the length direction can have a predetermined angle θ relative to the length direction. L Furthermore, the straight line connecting adjacent non-polarized portions in the width direction can have a predetermined angle θ relative to the width direction. W θ L and / or θ W Preferably, the angle is greater than 0° and within ±10°. The symbol “±” used herein means both clockwise and counterclockwise directions relative to the reference direction (length or width). FIG. 4B and FIG. 4C Each of the illustrated embodiments has the following advantages. In certain image display devices, in order to improve their display characteristics, in some cases, the absorption axis of the polarizer needs to be configured to deviate from the long or short side of the device by up to approximately 10°. As described later, the absorption axis of the polarizer is manifested in its length direction or its width direction. Therefore, in such a configuration as described above, the absorption axis direction of each sheet-like polarizer 100 cut from the polarizer 101 is precisely controlled at a desired angle, and changes in the absorption axis direction of the polarizer 100 can be significantly suppressed. Furthermore, the configuration pattern of the non-polarized portion is not limited to the illustrated example. For example, the non-polarized portion 20 can be configured such that the straight line connecting adjacent non-polarized portions in the length direction has a predetermined angle θ relative to the length direction. L Furthermore, the straight lines connecting adjacent non-polarized portions in the width direction are substantially parallel to the width direction. Additionally, the following can be performed: multiple regions can be specified along the length direction of the polarizer 101, and θ can be set in each region. L and / or θ W .

[0064] The absorption axis of a strip-shaped polarizer can be set to any suitable direction depending on the purpose. The direction of the absorption axis can be, for example, the length direction or the width direction. Polarizers with an absorption axis along the length direction have advantages in terms of excellent manufacturing efficiency. Polarizers with an absorption axis along the width direction have the advantage that the polarizer can be laminated with a phase difference film having a slow phase axis along the length direction using a so-called roll-to-roll method. In one embodiment, the absorption axis is substantially parallel to the length or width direction, and the two ends of the polarizer undergo slitting parallel to the length direction. With this configuration, when the slitting operation is performed with reference to the end face of the polarizer, multiple polarizers, each having an unpolarized portion and an absorption axis in a suitable direction, can be easily manufactured.

[0065] When the non-polarizing portion has a recess, it is conceivable that inconveniences that can occur in a strip-shaped polarizer may arise. Possible examples of such inconveniences include the possibility that, when the strip-shaped polarizer is wound into a roll, the recess may overlap with other parts of the polarizer as a roll mark; and the possibility that air bubbles may form due to the recess when the polarizer is combined with any other constituent component, such as a protective film. It is conceivable that such inconveniences can be suppressed by reducing the depth of the recess as described above. It is conceivable that, as a result, quality variations between sheet-shaped polarizers produced from the strip-shaped polarizer that would result from such inconveniences can be suppressed.

[0066] B.Polarizing plate

[0067] Polarizer 100 can be practically provided as a polarizing plate. Therefore, the present invention can also provide a polarizing plate. FIG. 5 This is an exemplary cross-sectional view of a polarizing plate according to one embodiment of the present invention. FIG. 5 In the diagram, recess 22 is omitted. The polarizer 300 includes a polarizer 100 and protective films 110 and 120 disposed on both sides of the polarizer 100. In the illustrated example, although the protective films are disposed on both sides of the polarizer, they may be disposed on only one side. Materials used to form the protective films include, for example, cellulose resins such as diacetyl cellulose or triacetyl cellulose, (meth)acrylic resins, cyclic olefin resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymers of these resins. Depending on the purpose and desired structure, one of the protective films 110 and 120 may be omitted. The simple term "protective film" used herein refers to polarizer protective films like those 110 and 120, and is distinct from the surface protective film (a film configured to temporarily protect the polarizer during operation) described in section C. In the illustrated example, a polarizing plate comprising a sheet-like polarizer 100 (i.e., a sheet-like polarizing plate) is described, but the polarizing plate may be sheet-like or strip-like. A strip-like polarizing plate can be manufactured by laminating a strip-like polarizer and a strip-like protective film using, for example, a roll-to-roll method. A sheet-like polarizing plate can be manufactured by laminating a sheet-like protective film on a sheet-like polarizer, or it can be cut from a strip-like polarizing plate to have a predetermined size.

[0068] The thickness of the protective film is typically from 10 μm to 100 μm. The protective film is typically laminated onto the polarizer via an adhesive layer (specifically, an adhesive layer or a pressure-sensitive adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an activating energy radiation-curable adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic-based pressure-sensitive adhesive. In one embodiment, the thickness of the protective film is less than 80 μm. Using a protective film of such thickness can help to achieve a thinner polarizer. In embodiments where the polarizer is elongated, when the elongated polarizer, formed by distributing a protective film of such thickness on the other side of a polarizer having a recess formed on one side, is wound into a roll, problems such as the recess being transferred as a roll mark onto the protective film can easily occur. In such embodiments, the benefit of significantly reducing the depth of the recess can be obtained.

[0069] The polarizing plate 300 practically includes a pressure-sensitive adhesive layer 130 as the outermost layer. The pressure-sensitive adhesive layer 130 is typically used as the outermost layer on the image display device side. A release film 132 is temporarily bonded to the pressure-sensitive adhesive layer 130 in a peelable manner, thereby protecting the pressure-sensitive adhesive layer until actual use and ensuring roll formation.

[0070] The polarizer 300 may further include any suitable optical functional layer depending on the purpose. Typical examples of optical functional layers include a retardation film (optical compensation film) and a surface treatment layer. For example, the retardation film may be disposed between the protective film 120 and the pressure-sensitive adhesive layer 130 (not shown). The optical properties of the retardation film (e.g., refractive index ellipsoid, in-plane phase difference, thickness direction phase difference) may be appropriately set according to, for example, the purpose and characteristics of the image display device. For example, when the image display device is an IPS-mode liquid crystal display device, a retardation film with a refractive index ellipsoid of nx>ny>nz and a retardation film with a refractive index ellipsoid of nz>nx>ny may be configured. The retardation film may also be used as a protective film. In this case, the protective film 120 may be omitted. Instead, the protective film 120 may have optical compensation functions (i.e., the film may have a suitable refractive index ellipsoid, a suitable in-plane phase difference, and a suitable thickness direction phase difference depending on the purpose). The symbol “nx” represents the refractive index in the direction in which the refractive index in the film surface becomes the largest (i.e., the direction of the slow phase axis), the symbol “ny” represents the refractive index in the direction perpendicular to the slow phase axis in the film surface, and the symbol “nz” represents the refractive index in the thickness direction.

[0071] A surface treatment layer may be disposed on the outer side (not shown) of the protective film 110. Typical examples of surface treatment layers include a hard coating, an anti-reflective layer, and an anti-glare layer. For the purpose of improving the humidification durability of the polarizer, the surface treatment layer is preferably a layer with low moisture permeability, for example. A hard coating is provided for the purpose of, for example, preventing damage to the surface of the polarizer. The hard coating can be formed by, for example, applying a cured coating film based on a suitable UV-curable resin such as an acrylic UV-curable resin or a silicone UV-curable resin to the surface, the cured coating film having excellent hardness and sliding properties. The pencil hardness of the hard coating is preferably 2H or higher. The anti-reflective layer is a low-reflection layer provided for the purpose of preventing the reflection of ambient light on the surface of the polarizer. Examples of anti-reflective layers include: a thin-layer type that prevents reflection by utilizing the reflection light elimination effect exhibited by light interference, as disclosed in Japanese Patent Application Publication No. 2005-248173, and a surface structure type that imparts a microstructure to the surface to present a low reflectivity, as disclosed in Japanese Patent Application Publication No. 2011-2759. An anti-glare layer is provided for purposes such as preventing reflection of ambient light on the surface of the polarizer from obstructing the viewing of light emitted through the polarizer. The anti-glare layer is formed by, for example, imparting a finely textured surface with an uneven structure using a suitable system, such as a surface roughening system based on a sandblasting or embossing system, or a system involving the mixing of transparent fine particles. The anti-glare layer can also serve as a diffusion layer for scattering light emitted through the polarizer to magnify the viewing angle (viewing angle magnification function, etc.). The surface of the protective film 110 can undergo a similar surface treatment instead of providing a surface treatment layer.

[0072] C. Manufacturing method of polarizer

[0073] The following describes a method for manufacturing the polarizer of the present invention. For convenience, a method for manufacturing a strip-shaped polarizer will be described. A sheet-shaped polarizer can be obtained by cutting the prepared strip-shaped polarizer into a predetermined size.

[0074] C-1. Manufacturing of Polarizing Films

[0075] The resin film constituting the polarizer (typically a PVA-based resin film) can be a single thin film or a resin layer (typically a PVA-based resin layer) formed on a resin substrate. The PVA-based resin layer can be formed by coating a resin substrate with a coating liquid containing PVA-based resin, or by laminating a PVA-based resin film on a resin substrate. Hereinafter, the case where the polarizer is a PVA-based resin layer formed on a resin substrate will be specifically described. Here, the case where the PVA-based resin layer is formed by coating is described, but the same applies to the case where a PVA-based resin film is laminated. In the case where the polarizer is a single PVA-based resin film, the polarizer can be manufactured by methods known and conventional in the art, and detailed descriptions are omitted.

[0076] C-1-1. Manufacturing of laminates of resin substrate and PVA-based resin layer

[0077] Initially, the laminate of the resin substrate and the PVA-based resin layer is manufactured by coating the resin substrate with a coating liquid containing PVA-based resin and drying the liquid to form the PVA-based resin layer.

[0078] Any suitable thermoplastic resin can be used as a forming material for the resin matrix. Examples of thermoplastic resins include: ester resins such as polyethylene terephthalate resins; cycloolefin resins such as norbornene resins; olefin resins such as polypropylene; polyamide resins; polycarbonate resins; and copolymers of these resins. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred.

[0079] In one embodiment, an amorphous (non-crystalline) polyethylene terephthalate (PET) resin is preferably used. In particular, amorphous (non-crystallizing) PET resins are preferred. Specific examples of amorphous PET resins include copolymers further containing isophthalic acid as a dicarboxylic acid; and copolymers further containing cyclohexanediol as a diol.

[0080] When the underwater stretching mode is used in the stretching process described later, the resin substrate absorbs water, and the water acts like a plasticizer to plasticize the substrate. As a result, the tensile stress can be significantly reduced, allowing the laminate to be stretched at a high ratio. Therefore, superior stretchability compared to air stretching can be achieved. Consequently, polarizers with excellent optical properties can be manufactured. In one embodiment, the water absorption rate of the resin substrate is preferably 0.2% or more, more preferably 0.3% or more. Simultaneously, the water absorption rate of the resin substrate is preferably 3.0% or less, more preferably 1.0% or less. Using such a resin substrate prevents inconveniences such as deterioration of the appearance of the resulting polarizer due to a significant reduction in dimensional stability during manufacturing. Furthermore, this use prevents substrate breakage and peeling of the PVA-based resin layer from the resin substrate during underwater stretching. The water absorption rate of the resin substrate can be adjusted, for example, by introducing modified groups into the forming material. The water absorption rate is a value obtained according to JIS K 7209.

[0081] The glass transition temperature (Tg) of the resin substrate is preferably below 170°C. Using such a resin substrate ensures sufficient stretchability of the laminate while suppressing the crystallization of the PVA-based resin layer. Furthermore, considering the plasticization of the resin substrate by water and good underwater stretching, a glass transition temperature of below 120°C is more preferable. In one embodiment, the glass transition temperature of the resin substrate is preferably above 60°C. Using such a resin substrate prevents inconveniences such as resin substrate deformation (e.g., unevenness, bending, and wrinkling) during coating and drying of the PVA-based resin-containing liquid, thereby ensuring good fabrication of the laminate. Furthermore, this ensures good stretching of the PVA-based resin layer at an appropriate temperature (e.g., approximately 60°C). In another embodiment, the glass transition temperature may be below 60°C, as long as the resin substrate does not deform during coating and drying of the PVA-based resin-containing liquid. The glass transition temperature of the resin substrate can be adjusted, for example, by introducing modified groups into the forming material, or by using a crystalline material as the forming material and heating the material. The glass transition temperature (Tg) is a value obtained according to JIS K 7121.

[0082] The thickness of the resin substrate before stretching is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. When the thickness is less than 20 μm, it becomes difficult to form a PVA-based resin layer. When the thickness exceeds 300 μm, there are risks associated with the need for a long time to allow the resin substrate to absorb water during stretching, for example in water, and the requirement for excessive loads during stretching.

[0083] The PVA-based resin that forms the PVA-based resin layer is as described in section A above.

[0084] The coating solution described above is typically a solution in which a PVA-based resin is dissolved in a solvent. Examples of solvents include: water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These solvents can be used alone or in combination. Water is preferred. The concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. Such a resin concentration ensures the formation of a uniform coating film that adheres tightly to the resin substrate.

[0085] The coating solution may contain additives. Examples of additives include plasticizers and surfactants. Examples of plasticizers include polyols such as ethylene glycol and glycerin. Examples of surfactants include nonionic surfactants. Any such additives may be used to further improve the uniformity, dyeability, and tensile strength of the resulting PVA-based resin layer.

[0086] Any suitable method can be used as a coating method for the coating liquid. Examples include: roller coating, spin coating, wire rod coating, dip coating, die coating, curtain coating, spray coating, and doctor blade coating (e.g., comma coating).

[0087] The preferred temperature for coating and drying the coating solution is above 50°C.

[0088] The thickness of the PVA-based resin layer before stretching is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm.

[0089] Before the PVA-based resin layer is formed, the resin substrate may undergo surface treatment (e.g., corona treatment), or an easy-adhesion layer may be formed on the resin substrate. Performing any of these treatments can improve the adhesion between the resin substrate and the PVA-based resin layer.

[0090] C-1-2. Stretching of laminates

[0091] Any suitable method can be used as a stretching method for the laminate. Specifically, fixed-end stretching or free-end stretching can be used (e.g., a method involving uniaxial stretching of the laminate by passing it between rollers with different circumferential speeds). Free-end stretching is preferred.

[0092] The stretching direction of the laminate can be appropriately set. In one embodiment, the laminate is stretched along its length. As a result, the absorption axis of the resulting polarizer is positioned along its length. In this case, a method typically involves stretching the laminate by passing it between rollers with different circumferential speeds. In another embodiment, the laminate is stretched along its width. As a result, the absorption axis of the resulting polarizer is positioned along its width. In this case, a method typically involves stretching the laminate using a tenter frame to improve its shape.

[0093] The stretching method is not particularly limited and can be either air stretching or underwater stretching. Underwater stretching is preferred. With underwater stretching, stretching can be performed at a temperature lower than the glass transition temperature of the resin substrate or PVA-based resin layer (typically approximately 80°C), thereby allowing the PVA-based resin layer to be stretched at a high magnification while suppressing its crystallization. As a result, polarizers with excellent optical properties can be manufactured.

[0094] The stretching of the laminate can be performed in one stage or in multiple stages. When stretching is performed in multiple stages, for example, the above-described free-end stretching and fixed-end stretching can be combined, or the above-described underwater stretching mode and aerial stretching mode can be combined. Furthermore, when stretching is performed in multiple stages, the stretching ratio (maximum stretching ratio) of the laminate, as described later, is the product of the stretching ratios of each stage.

[0095] The stretching temperature of the laminate can be set to any suitable value depending on, for example, the forming material of the resin substrate and the stretching mode. When using an air stretching mode, the stretching temperature is preferably equal to or greater than the glass transition temperature (Tg) of the resin substrate, more preferably equal to or greater than the glass transition temperature (Tg) of the resin substrate + 10°C, and particularly preferably equal to or greater than Tg + 15°C. Meanwhile, the stretching temperature of the laminate is preferably below 170°C. When stretching is performed at such a temperature, rapid crystallization of the PVA-based resin is suppressed, thereby suppressing the inconvenience caused by such crystallization (e.g., hindering the orientation of the PVA-based resin layer through stretching).

[0096] When using an underwater stretching method, the temperature of the stretching bath is preferably 40°C to 85°C, more preferably 50°C to 85°C. At such temperatures, stretching can be performed at a high magnification while suppressing the dissolution of the PVA-based resin layer. Specifically, as mentioned above, the glass transition temperature (Tg) of the substrate is preferably 60°C or higher, which is related to the formation of the PVA-based resin layer. In this case, when the stretching temperature is below 40°C, even considering the plasticization of the resin substrate by water, there is a risk that stretching cannot be performed well. At the same time, as the temperature of the stretching bath increases, the solubility of the PVA-based resin layer increases, thereby risking that excellent optical properties cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

[0097] When using an underwater stretching method, the laminate is preferably stretched while immersed in an aqueous boric acid solution (boric acid water stretching). Using an aqueous boric acid solution as the stretching bath imparts rigidity to the PVA-based resin layer, ensuring that the layer can withstand the tension applied during stretching, and water resistance, preventing the layer from dissolving in water. Specifically, boric acid can generate tetrahydroxyboronic acid anions in the aqueous solution, thereby crosslinking with the PVA-based resin via hydrogen bonds. As a result, rigidity and water resistance are imparted to the PVA-based resin layer, thereby allowing for good stretching of the layer. Therefore, polarizers with excellent optical properties can be manufactured.

[0098] The aforementioned aqueous boric acid solution is preferably prepared by dissolving boric acid and / or borate in water as a solvent. The concentration of boric acid is preferably 1 to 10 parts by weight relative to 100 parts by weight of water. Setting the concentration of boric acid to 1 part by weight or more effectively suppresses the dissolution of the PVA-based resin layer, thereby ensuring a polarizer with superior properties. In addition to boric acid or borate, aqueous solutions prepared by dissolving, for example, boron compounds such as borax, glyoxal, or glutaraldehyde in a solvent can also be used.

[0099] When the PVA-based resin layer is pre-treated with dyeing (described later) to adsorb dichroic substances (typically iodine), the stretching bath (aqueous boric acid solution) is preferably mixed with an iodide. The presence of an iodide in this bath inhibits the dissolution of iodine already adsorbed by the PVA-based resin layer. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Potassium iodide is preferred. The concentration of the iodide relative to 100 parts by weight of water is preferably from 0.05 parts by weight to 15 parts by weight, more preferably from 0.5 parts by weight to 8 parts by weight.

[0100] The stretch ratio (maximum stretch ratio) of the laminate relative to its original length is preferably 5.0 times or more. Such a high stretch ratio can be achieved, for example, by using an underwater stretching method (boric acid water stretching). As used herein, the term "maximum stretch ratio" refers to the stretch ratio immediately before the laminate fractures, and is a value that is 0.2 lower than the separately measured value of the stretch ratio at the time of laminate fracture.

[0101] In a preferred embodiment, the lamination is stretched in air at a high temperature (e.g., above 95°C) before the stretching in boric acid solution and the staining described later are performed. Such air stretching is hereinafter referred to as "air-assisted stretching" because it can be considered as a preparatory or auxiliary stretching for the stretching in boric acid solution.

[0102] When air-assisted stretching is combined with stretching in boric acid solution, laminates can be stretched at higher magnification in some cases. As a result, polarizers with superior optical properties (e.g., polarization) can be manufactured. For example, when polyethylene terephthalate is used as the resin substrate, in the case of combining air-assisted stretching and stretching in boric acid solution, the laminate can be stretched while suppressing the orientation of the resin substrate to a greater extent compared to stretching solely in boric acid solution. As the orientation of the resin substrate increases, the tensile tension increases, making it difficult to stretch the laminate stably or causing it to break. Therefore, when the laminate is stretched while suppressing the orientation of the resin substrate, it can be stretched at a higher magnification.

[0103] Furthermore, the combination of air-assisted stretching and stretching in boric acid water improves the orientation of PVA-based resins, thereby enhancing their orientation even after stretching in boric acid water. Specifically, it is hypothesized that when the orientation of the PVA-based resin is pre-improved through air-assisted stretching, the PVA-based resin and boric acid readily crosslink during stretching in boric acid water, and the laminate is stretched with boric acid acting as a junction, thus improving the orientation of the PVA-based resin even after stretching in boric acid water. As a result, polarizers with excellent optical properties (e.g., polarization) can be manufactured.

[0104] The stretching ratio of the laminate in the air-assisted stretching is preferably 3.5 times or less. The stretching temperature of the laminate in the air-assisted stretching is preferably equal to or greater than the glass transition temperature of the PVA-based resin. The stretching temperature is preferably 95°C to 150°C. Relative to the original length of the laminate, the maximum stretching ratio of the laminate when combining air-assisted stretching and stretching in boric acid water is preferably 5.0 times or more, more preferably 5.5 times or more, and even more preferably 6.0 times or more.

[0105] C-1-3. Staining

[0106] The above-mentioned staining is typically performed by adsorbing a dichroic substance (preferably iodine) onto a PVA-based resin layer. This adsorption method includes, for example, immersing the PVA-based resin layer (laminated structure) in a staining solution containing iodine, coating the PVA-based resin layer with the staining solution, or spraying the staining solution onto the PVA-based resin layer. The preferred method is the one involving immersing the laminate in the staining solution, because iodine is readily adsorbed onto the laminate.

[0107] The dyeing solution is preferably an aqueous iodine solution. The amount of iodine added is preferably 0.1 to 0.5 parts by weight relative to 100 parts by weight of water. To improve the solubility of iodine in water, the aqueous iodine solution is preferably mixed with an iodide. Specific examples of iodides are described above. The amount of iodide added is preferably 0.02 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, relative to 100 parts by weight of water. The temperature of the dyeing solution during dyeing is preferably 20°C to 50°C to suppress the dissolution of the PVA-based resin. When the PVA-based resin layer is immersed in the dyeing solution, the immersion time is preferably 5 seconds to 5 minutes to ensure the transmittance of the PVA-based resin layer. Furthermore, the dyeing conditions (concentration, temperature, immersion time) can be set so that the polarization or single-layer transmittance of the final polarizer falls within a predetermined range. In one embodiment, the immersion time is set so that the polarization of the resulting polarizer is 99.98% or higher. In another embodiment, the immersion time is set such that the single-layer transmittance of the resulting polarizer is 40% to 44%.

[0108] The dyeing process can be performed at any suitable time. When underwater stretching is performed, the dyeing process is preferably performed before underwater stretching.

[0109] C-1-4. Other treatments

[0110] In addition to stretching and dyeing, the above-described laminate may suitably undergo treatments to transform the PVA-based resin layer into a polarizer (or a polarizer intermediate). Examples of treatments for transforming the layer into a polarizer include: insolubility treatment, crosslinking treatment, washing treatment, and drying treatment. There are no particular limitations on the number of times these treatments are performed or the order in which they are performed.

[0111] The aforementioned insolubility treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. This insolubility treatment imparts water resistance to the PVA-based resin layer. The concentration of this aqueous boric acid solution is preferably 1 to 4 parts by weight relative to 100 parts by weight of water. The temperature of the insolubility bath (aqueous boric acid solution) is preferably 20°C to 50°C. The insolubility treatment is preferably performed before stretching and dyeing in water.

[0112] The crosslinking treatment described above is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. This crosslinking treatment imparts water resistance to the PVA-based resin layer. The concentration of the aqueous boric acid solution is preferably 1 to 5 parts by weight relative to 100 parts by weight of water. Furthermore, when the crosslinking treatment is performed after dyeing, the solution is preferably further mixed with an iodide. The addition of an iodide to the solution inhibits the dissolution of iodine already adsorbed by the PVA-based resin layer. The amount of iodide mixed is preferably 1 to 5 parts by weight relative to 100 parts by weight of water. Specific examples of iodides are described above. The temperature of the crosslinking bath (aqueous boric acid solution) is preferably 20°C to 60°C. The crosslinking treatment is preferably performed before underwater stretching. In a preferred embodiment, dyeing, crosslinking, and underwater stretching are performed sequentially.

[0113] The washing process described above is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution. The drying temperature for the drying process described above is preferably between 30°C and 100°C.

[0114] As described above, a polarizer (polarizer intermediate) is formed on a resin substrate. A protective film is then applied and / or the resin substrate is peeled off as needed. In one embodiment, the protective film is applied to the polarizer surface of the laminate of the resin substrate and the polarizer using a roll-to-roll method, and then the resin substrate is peeled off. Thus, a laminate of the polarizer and the protective film (polarizing plate) is obtained. The protective film in this polarizing plate typically corresponds to... FIG. 5 A protective film (protective film on the image display device side) 120. As described above, this protective film may have optical compensation function. Here, polarizer intermediate means polarizer before the formation of the non-polarized portion, and is intended to be distinguished from the polarizer of the present invention having the non-polarized portion. Therefore, in this document, polarizer intermediate may be simply referred to as "polarizer" in the context. Those skilled in the art will readily understand from the description given herein that the term "polarizer" means polarizer intermediate or means the polarizer of the present invention.

[0115] C-2. Formation of the non-polarized portion

[0116] Next, the polarizer of the present invention is manufactured by forming a non-polarizing portion at a predetermined position in the polarizer intermediate obtained in item C-1 above. When the polarizer (polarizer intermediate) is formed from a PVA-based resin layer coated on a resin substrate, the laminate of the resin substrate and the polarizer or the laminate of the protective film and the polarizer (polarizing plate) typically undergoes the formation of a non-polarizing portion. When the polarizer (polarizer intermediate) is a single resin film, the single polarizer or the laminate of the protective film and the polarizer (polarizing plate) typically undergoes the formation of a non-polarizing portion. Hereinafter, the formation of the non-polarizing portion will be specifically described. As a typical example, the case in which a non-polarizing portion is formed in the polarizer (polarizer intermediate) by chemically treated decolorization (hereinafter sometimes referred to as "chemical decolorization treatment") in the laminate of the protective film and the polarizer (hereinafter simply referred to as "polarizing plate") will be described. Those skilled in the art will understand that the same process is also applicable to polarizer intermediates having any other structure (e.g., polarizer intermediates as a single resin film).

[0117] like FIG. 6 As shown, a surface protective film having through holes arranged according to a predetermined pattern is bonded to the polarizer side surface of a polarizing plate by a roll-to-roll method. The term "roll-to-roll method" as used herein means that the rolled films are bonded together while being transported, with their lengths aligned. The surface protective film with through holes is peelably bonded to the polarizer using any suitable pressure-sensitive adhesive. When using a surface protective film with through holes, a decolorization process based on immersion in a decolorizing solution can be performed, thereby enabling the polarizer of the present invention to be manufactured with very high production efficiency. For convenience, the surface protective film with through holes may be referred to as a "first surface protective film".

[0118] As described above, the first surface protective film has through holes arranged according to a predetermined pattern. The positions of the through holes correspond to the positions where the non-polarizing portion of the polarizer (polarizer intermediate) is formed. FIG. 6 The configuration pattern of the through holes shown is similar to FIG. 4A The configuration pattern of the non-polarized portion is shown. Each through-hole can have any suitable shape. The shape of the through-hole corresponds to the top view shape of the formed non-polarized portion. Each through-hole can be formed by, for example, mechanical punching (e.g., cutting, engraving, plotter, waterjet cutting) or removal (e.g., laser ablation or chemical dissolution) of a predetermined portion of the film.

[0119] The first surface protective film is preferably a film with high hardness (e.g., elastic modulus). This is because it prevents deformation of the through-holes during transport and / or bonding. Materials used to form the first surface protective film include, for example: ester resins such as polyethylene terephthalate resins; cycloolefin resins such as norbornene resins; olefin resins such as polypropylene; polyamide resins; polycarbonate resins; and copolymers of these resins. Ester resins (especially polyethylene terephthalate resins) are preferred. Such materials have a sufficiently high elastic modulus, thus making deformation of the through-holes difficult to occur even when tension is applied during transport and / or bonding.

[0120] The thickness of the first surface protective film is typically 20 μm to 250 μm, preferably 30 μm to 150 μm. Such a thickness has the advantage that deformation of the through-holes is difficult to occur even when tension is applied during transport and / or bonding.

[0121] The elastic modulus of the first surface protective film is preferably 2.2 kN / mm². 2 Up to 4.8 kN / mm 2 When the elastic modulus of the first surface protective film falls within such a range, the following advantages are achieved: even when tension is applied during transport and / or bonding, deformation of the through-holes is difficult to occur. The elastic modulus is measured according to JIS K 7161.

[0122] The tensile elongation of the first surface protective film is preferably between 90% and 170%. When the tensile elongation of the first surface protective film falls within such a range, the following advantage is obtained: the film is less likely to break during transport. The tensile elongation is measured according to JIS K7161.

[0123] Simultaneously, a second surface protective film is bonded to the surface of the protective film side of the polarizing plate using a roll-to-roll method. The second surface protective film is peelably bonded to the protective film via any suitable pressure-sensitive adhesive. Using the second surface protective film allows for proper protection of the polarizing plate (polarizing intermediate / protective film) during immersion-based decolorization processes. A film identical to the first surface protective film, except without through-holes, can be used as the second surface protective film. Furthermore, a soft (e.g., low elastic modulus) film, such as a polyolefin (e.g., polyethylene) film, can also be used as the second surface protective film. The second surface protective film can be bonded simultaneously with the first surface protective film, before bonding the first surface protective film, or after bonding the first surface protective film. Preferably, the second surface protective film is bonded before bonding the first surface protective film. Such a procedure has the advantages of preventing damage to the protective film and preventing through-holes formed in the first surface protective film from being transferred as imprints onto the protective film during winding. When the second surface protective film is bonded before bonding the first surface protective film, for example, the following can be performed. A laminate of a polarizer protective film and a second surface protective film is manufactured and bonded to a resin substrate and a polarizer laminate. Then, the resin substrate is peeled off, and a first surface protective film is bonded to the peeled surface.

[0124] Next, as FIG. 7 As shown, a laminate of a first surface protective film, a polarizer (polarizer intermediate), a protective film, and a second surface protective film undergoes a chemical decolorization treatment. This chemical decolorization treatment involves contacting the laminate with an alkaline solution. In cases where iodine is used as a dichroic substance, the iodine content at the contact point can be easily reduced when the alkaline solution contacts the desired portion of the resin film.

[0125] Contact between the laminate and the alkaline solution can be achieved by any suitable means. Typical examples include: immersing the laminate in an alkaline solution; and coating or spraying the alkaline solution onto the laminate. Immersion is preferred. This is because: FIG. 7As shown, the decolorization process can be performed simultaneously with the transport of the laminate, thereby significantly improving manufacturing efficiency. As described above, immersion is ensured using a first surface protective film (and, if necessary, a second surface protective film). Specifically, when the laminate is immersed in an alkaline solution, only the portion of the polarizer (polarizer intermediate) corresponding to the through-holes of the first surface protective film contacts the alkaline solution. For example, in the case where the polarizer (polarizer intermediate) contains iodine as a dichroic substance, when the polarizer (polarizer intermediate) is brought into contact with the alkaline solution, the iodine concentration in the contact portion of the polarizer (polarizer intermediate) with the alkaline solution is reduced. As a result, the non-polarizing portion can be selectively formed only in this contact portion (which can be set through the through-holes of the first surface protective film). As described above, according to this embodiment, with very high manufacturing efficiency and without any complex operations, the non-polarizing portion can be selectively formed in a predetermined portion of the polarizer (polarizer intermediate). In cases where iodine remains in the prepared polarizer, even when the non-polarized portion is formed by breaking down the iodine complex, there is a risk that the iodine complex will reform with the use of the polarizer, thus preventing the non-polarized portion from exhibiting the desired characteristics. In this embodiment, the iodine itself is removed from the polarizer (essentially the non-polarized portion) by removal with an alkaline solution described later. As a result, changes in the characteristics of the non-polarized portion with the use of the polarizer can be prevented. Furthermore, according to the contact method described above, the recess can be formed only on one side of the resin film. In this case, compared to the case where the recess is formed on both sides of the resin film, controlling the depth of the recess becomes significantly easier. As a result, it becomes easier to suppress the influence on the appearance of the polarizer.

[0126] The formation of the unpolarized portion using an alkaline solution is explained in more detail. After contact with a predetermined portion of the polarizer (polarizer intermediate), the alkaline solution permeates into that predetermined portion. The iodine complex in this predetermined portion is reduced to iodide ions by the alkali in the alkaline solution. The reduction of the iodine complex to iodide ions substantially eliminates the polarizing properties of this portion, thereby resulting in the formation of an unpolarized portion in this portion. Furthermore, the reduction of the iodine complex increases the transmittance of this portion. The iodine that has been converted to iodide ions moves from this portion into the solvent of the alkaline solution. As a result, by removing the alkaline solution as described later, the iodide ions are also removed from this portion along with the alkaline solution. Therefore, the unpolarized portion (low-concentration portion) is selectively formed in the predetermined portion of the polarizer (polarizer intermediate), and this unpolarized portion is a stable portion that does not change over time. By adjusting, for example, the material, thickness, and mechanical properties of the first surface protective film, the concentration of the alkaline solution, and the immersion time of the laminate in the alkaline solution, it is possible to prevent the alkaline solution from penetrating into undesirable portions (resulting in the formation of unpolarized portions in undesirable portions).

[0127] Any suitable basic compound can be used as the basic compound in the above-mentioned alkaline solution. Examples of basic compounds 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; organic alkali metal salts such as sodium acetate; and ammonia. Among these, alkali metal and / or alkaline earth metal hydroxides are preferred, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are more preferred. Using such basic compounds can effectively ionize the iodine complex, thereby making it easier to form the unpolarized portion. These basic compounds can be used alone or in combination.

[0128] Any suitable solvent can be used as the solvent for the above-mentioned alkaline solution. Specific examples include: water; alcohols such as ethanol and methanol; ethers; benzene; chloroform; and mixtures of these solvents. The solvent is preferably water or an alcohol because iodide ions move readily into the solvent, thereby allowing for easy removal of iodide ions during subsequent removal of the alkaline solution.

[0129] The concentration of the alkaline 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 alkaline solution falls within such a range, the iodine concentration in the polarizer (polarizer intermediate) can be effectively reduced, and the ionization of iodine complexes in portions other than the predetermined portion can be prevented. Furthermore, at such a concentration, the depth of the recess that can be formed can be easily controlled.

[0130] The temperature of the alkaline solution is, for example, 20°C to 50°C. The contact time between the laminate (essentially a predetermined portion of the polarizer intermediate) and the alkaline solution can be set according to the thickness of the polarizer intermediate, the type of alkaline compound in the alkaline solution used, and the concentration of the alkaline compound, and is, for example, 5 seconds to 30 minutes. When the contact time falls within such a range, a recess with an appropriate depth can be formed.

[0131] Boric acid can be introduced into polarizers (resin films). Boric acid can be introduced, for example, during stretching or crosslinking processes, by contacting the polarizer with a boric acid solution (e.g., an aqueous boric acid solution). The boric acid content of the polarizer (resin film) is, for example, 10% to 30% by weight. Furthermore, the boric acid content in the contact portion with the alkaline solution is, for example, 5% to 12% by weight.

[0132] After contact with the aforementioned alkaline solution, the amount of alkali metals and / or alkaline earth metals in the resin film decreases in the contact portion that has been in contact with the alkaline solution. Reducing the amount of alkali metals and / or alkaline earth metals provides a low-concentration portion with excellent dimensional stability. Specifically, even in a humidified environment, the shape of the low-concentration portion formed by contact with the alkaline solution can be maintained as is.

[0133] When an alkaline solution is brought into contact with a resin membrane, hydroxides of alkali metals and / or alkaline earth metals may remain in the contact area. Furthermore, when an alkaline solution is brought into contact with a resin membrane, metal salts of alkali metals and / or alkaline earth metals may be formed in the contact area. The hydroxides or metal salts can generate hydroxide ions, and these hydroxide ions act (decompose or reduce) on dichroic substances (e.g., iodine complexes) present around the contact area, thereby expanding the unpolarized region (low concentration region). Therefore, it is hypothesized that reducing the amount of alkali metal and / or alkaline earth metal salts suppresses the expansion of the unpolarized region over time, thereby maintaining the desired shape of the unpolarized region.

[0134] Metal salts that can generate hydroxide ions include, for example, borates. Borates can be generated by neutralization of boric acid in the resin membrane with an alkaline solution (a solution of alkali metal hydroxides and / or alkaline earth metal hydroxides). For example, when the polarizer is placed in a humidified environment, borate (metabort) will hydrolyze to generate hydroxide ions as shown in the following formula.

[0135]

[0136] In the formula, X represents an alkali metal or an alkaline earth metal.

[0137] Preferably, the content of alkali metals and / or alkaline earth metals in the contact portion is reduced such that the content is 3.6% by weight or less, preferably 2.5% by weight or less, more preferably 1.0% by weight or less, and even more preferably 0.5% by weight or less.

[0138] Alkali metals and / or alkaline earth metals can be introduced into the resin film by subjecting it to various treatments for converting the film into a polarizer. For example, potassium can be introduced into the resin film by contacting it with a solution of an iodide, such as potassium iodide. As described above, the alkali metals and / or alkaline earth metals typically introduced into the polarizer do not adversely affect the dimensional stability of the low-concentration sections.

[0139] A method involving contacting the treatment liquid with the contact portion of the alkaline solution is preferably used as the reduction method described above. Such a method allows alkali metals and / or alkaline earth metals to migrate from the resin film into the treatment liquid, thereby reducing their content.

[0140] Any suitable method can be used as a contact method with the treatment liquid. Examples include: methods involving dripping, coating, or spraying the treatment liquid onto the contact portion with the alkaline solution; and methods involving immersing the contact portion with the alkaline solution in the treatment liquid.

[0141] When the resin film is protected by any suitable protective material when in contact with an alkaline solution, the treatment solution preferably contacts the film in its original state (especially when the temperature of the treatment solution is above 50°C). This arrangement prevents a decrease in polarization characteristics due to the treatment solution in areas other than the contact area with the alkaline solution.

[0142] The above-described treatment solution may contain any suitable solvent. Examples of solvents include: water; alcohols such as ethanol and methanol; ethers; benzene; chloroform; and mixtures of these solvents. From the viewpoint of efficiently moving alkali metals and / or alkaline earth metals, water or alcohol is preferred. Any suitable water may be used. Examples include tap water, purified water, and deionized water.

[0143] The temperature of the treatment solution during contact is, for example, 20°C or higher, preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. Such a temperature allows alkali metals and / or alkaline earth metals to effectively migrate into the treatment solution. Specifically, this temperature significantly increases the swelling ratio of the resin film, thereby physically removing alkali metals and / or alkaline earth metals from the resin film. Meanwhile, the temperature of the treatment solution is substantially below 95°C.

[0144] The contact time between the contact portion and the treatment liquid can be appropriately adjusted according to factors such as the contact method, the temperature of the treatment liquid (water), and the thickness of the resin film. For example, when the contact portion is 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.

[0145] In one embodiment, an acidic solution is used as the treatment solution described above. The acidic solution neutralizes hydroxides of alkali metals and / or alkaline earth metals remaining in the resin membrane, thereby chemically removing the alkali metals and / or alkaline earth metals from the resin membrane.

[0146] Any suitable acidic compound can be used as the acidic compound in acidic solutions. Examples of acidic compounds 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. Among these, inorganic acids are preferred as the acidic compounds in acidic solutions, and hydrochloric acid, sulfuric acid, or nitric acid are more preferred. These acidic compounds can be used alone or in combination.

[0147] Preferably, an acidic compound with a stronger acidity than boric acid is used as the aforementioned acidic compound. This is because the compound can also act on metal salts (borates) of alkali metals and / or alkaline earth metals. Specifically, alkali metals and / or alkaline earth metals in the resin membrane can be chemically removed by freeing boric acid from the borates.

[0148] The acidity index mentioned above is, for example, the acid dissociation constant (pKa), and it is preferable to use an acidic compound with a pKa smaller than that of boric acid (9.2). Specifically, the pKa is preferably less than 9.2, more preferably 5 or less. The pKa can be measured using any suitable measuring device and can refer to values ​​described in documents such as "Chemical Handbook Fundamentals, 5th Edition Revision" (edited by The Chemical Society of Japan, Maruzen Publishing Co., Ltd.). Furthermore, in cases where the acidic compound dissociates in multiple stages, the pKa value in each stage can be changed. When using such an acidic compound, a compound whose pKa value in each stage falls within the above-mentioned range is used. The pKa used herein refers to the value in an aqueous solution at 25°C.

[0149] The difference between the pKa of the acidic compound and the pKa of boric acid is, for example, 2.0 or more, preferably 2.5 to 15, more preferably 2.5 to 13. When this difference falls within such a range, alkali metals and / or alkaline earth metals can be effectively moved into the treatment solution, resulting in the achievement of the desired content of alkali metals and / or alkaline earth metals in each low concentration section.

[0150] Examples of acidic compounds that can satisfy the above pKa include: inorganic acids such as hydrochloric acid (pKa: -3.7), sulfuric acid (pK2: 1.96), nitric acid (pKa: -1.8), hydrogen fluoride (pKa: 3.17), and boric acid (pKa: 9.2); and organic acids such as formic acid (pKa: 3.54), oxalic acid (pK1: 1.04, pK2: 3.82), citric acid (pK1: 3.09, pK2: 4.75, pK3: 6.41), acetic acid (pKa: 4.8), and benzoic acid (pKa: 4.0).

[0151] The solvent of the acidic solution (treatment liquid) is as described above, and in this embodiment where the acidic solution is used as the treatment liquid, physical removal of alkali metals and / or alkaline earth metals from the resin membrane can occur.

[0152] 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.

[0153] The temperature of the acidic solution is, for example, 20°C to 50°C. The contact time between the resin membrane and the acidic solution can be set according to the thickness of the resin membrane, the type of acidic compound, and the concentration of the acidic solution, and is, for example, 5 seconds to 30 minutes.

[0154] In addition to the above treatments, the resin membrane may undergo any other suitable treatments. Examples of other treatments include removal from alkaline and / or acidic solutions, and washing.

[0155] The methods for removing alkaline and / or acidic solutions include, for example, wiping with a waste cloth, suction, natural drying, heating drying, air drying, or vacuum drying. The drying temperature is, for example, 20°C to 100°C. The drying time is, for example, 5 seconds to 600 seconds.

[0156] Washing is carried out by any suitable method. Examples of solutions used for washing include: pure water, alcohols such as methanol and ethanol, acidic aqueous solutions, and mixtures of these solutions. FIG. 7 As shown, washing typically occurs simultaneously with the conveying of the laminate. The washing process can be performed at any appropriate stage. The washing process can be repeated multiple times.

[0157] After the non-polarized portion has been formed as described above, the first and second surface protective films can typically be peeled off and removed.

[0158] Therefore, the non-polarizing portion is formed at a predetermined position on the elongated polarizer (polarizer intermediate) according to a predetermined configuration pattern, thereby obtaining the elongated polarizer according to an embodiment of the present invention. As described above, the sheet-like polarizer can be obtained, for example, by cutting the elongated polarizer into a predetermined size.

[0159] D. Image display device

[0160] The image display device of the present invention includes the aforementioned polarizer. The polarizer is cut to fit the dimensions of the image display device. Examples of image display devices include liquid crystal display devices and organic EL devices. Specifically, a liquid crystal display device includes a liquid crystal panel containing liquid crystal cells; and a polarizer disposed on one or both sides of the liquid crystal cells. An organic EL device includes an organic EL panel with the aforementioned polarizer disposed on the viewing side. The polarizer is configured such that the non-polarized portion corresponds to the camera portion of the image display device.

[0161] Embodiments

[0162] The invention will now be specifically described by way of examples. However, the invention is not limited to these examples.

[0163] [Example 1]

[0164] A strip-shaped amorphous polyethylene terephthalate (PET) copolymerized with isophthalic acid (IPA) and containing 0.75% water absorption and a Tg of 75°C (thickness: 100 μm) was used as the resin substrate. One side of the substrate was subjected to corona treatment, and an aqueous solution containing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetyl-modified PVA (degree of polymerization 1200, degree of acetyl-modification 4.6%, degree of saponification ≥ 99.0 mol%, manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z-200") in a 9:1 ratio was coated onto the corona-treated side at 25°C and dried to form a PVA-based resin layer with a thickness of 11 μm. Thus, a laminate was manufactured.

[0165] The resulting laminate is subjected to uniaxial stretching at the free end to 2.0 times its original length (with air-assisted stretching) between rollers with different circumferential speeds in an oven at 120°C.

[0166] Next, the laminate was immersed in an insoluble bath (an aqueous solution of boric acid prepared by mixing 100 parts by weight of water with 4 parts by weight of boric acid) at a liquid temperature of 30°C for 30 seconds (insoluble treatment).

[0167] Next, while adjusting the iodine concentration and immersion time, the laminate was immersed in a dyeing bath at a liquid temperature of 30°C so that the resulting polarizing plate had a predetermined transmittance. In this embodiment, the laminate was immersed in an iodine aqueous solution prepared by mixing 100 parts by weight of water with 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide for 60 seconds (dyeing treatment).

[0168] Next, the laminate was immersed in a crosslinking bath at a liquid temperature of 30°C (an aqueous solution of boric acid prepared by mixing 100 parts by weight of water with 3 parts by weight of potassium iodide and 3 parts by weight of boric acid) for 30 seconds (crosslinking treatment).

[0169] Then, while being immersed in a boric acid aqueous solution at a liquid temperature of 70°C (an aqueous solution prepared by mixing 100 parts by weight of water with 4 parts by weight of boric acid and 5 parts by weight of potassium iodide), the laminate undergoes uniaxial stretching in the longitudinal direction (length direction) between rollers with different circumferential speeds, so that the total stretching ratio becomes 5.5 times (stretching in water).

[0170] Then, the laminate was immersed in a washing bath at a liquid temperature of 30°C (an aqueous solution prepared by mixing 100 parts by weight of water with 4 parts by weight of potassium iodide) (washing treatment).

[0171] Next, an aqueous solution of PVA-based resin (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight) was coated on the surface of the PVA-based resin layer of the laminate, and a protective film (25 μm thick) was attached to it. The resulting material was then heated in an oven at 60°C for 5 minutes. The substrate was then peeled off from the PVA-based resin layer. Thus, a strip-shaped polarizing plate with a width of 1200 mm and a length of 43 m was obtained (polarizer with a thickness of 5 μm (single-layer transmittance 42.3%) / protective film).

[0172] A pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) is applied to one side of an ester resin film (38 μm thick) with a width of 1200 mm and a length of 43 m, resulting in a thickness of 5 μm. Through-holes with a diameter of 2.8 mm are formed in the ester resin film containing this pressure-sensitive adhesive at intervals of 250 mm in the length direction and at intervals of 400 mm in the width direction using a pinnacle blade.

[0173] The ester-based resin film with pressure-sensitive adhesive described above was laminated to the polarizer side of a polarizing plate with a total thickness of 30 μm using a roll-to-roll method. The resulting material was then immersed in a 1 mol / L (1N) sodium hydroxide aqueous solution for 30 seconds. Next, the resulting material was immersed in a 1 mol / L (1N) hydrochloric acid solution for 10 seconds. Finally, the resulting material was dried at 60°C. Thus, a transparent portion was formed in the polarizer.

[0174] [Example 2]

[0175] A 60 μm thick PVA film (made by Kuraray Co., Ltd., PE6000) was immersed in an aqueous solution at 30°C for 30 seconds (swelling step).

[0176] Next, while adjusting the iodine concentration and immersion time, the PVA film was immersed in a dyeing bath at a liquid temperature of 30°C, so that the resulting polarizing plate had a predetermined transmittance. In this embodiment, the PVA film was immersed in an iodine aqueous solution prepared by mixing 100 parts by weight of water with 0.15 parts by weight of iodine and 1.0 parts by weight of potassium iodide for 60 seconds (dyeing treatment).

[0177] Next, the PVA membrane was immersed in a crosslinking bath at a liquid temperature of 30°C (an aqueous solution of boric acid prepared by mixing 100 parts by weight of water with 3 parts by weight of potassium iodide and 3 parts by weight of boric acid) for 30 seconds (crosslinking treatment).

[0178] Then, while immersing the PVA film in a boric acid aqueous solution (prepared by mixing 100 parts by weight of water with 4 parts by weight of boric acid and 5 parts by weight of potassium iodide) at a liquid temperature of 70°C, the PVA film is stretched uniaxially to 5.5 times (stretched in water) between rollers with different circumferential speeds along the longitudinal direction (length direction).

[0179] Then, the PVA membrane is immersed in a washing bath at a liquid temperature of 30°C (an aqueous solution prepared by mixing 100 parts by weight of water with 4 parts by weight of potassium iodide) (washing treatment).

[0180] After washing, an aqueous solution of PVA-based resin (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight) was coated on one side of the PVA film, and a triacetyl cellulose membrane (manufactured by Konica Minolta, Inc., trade name "KC4UY", thickness 40 μm) was laminated onto it. The resulting material was then heated in an oven maintained at 60°C for 5 minutes. Thus, a polarizing plate comprising a polarizer with a thickness of 22 μm (single-layer transmittance 42.5%) was manufactured, the polarizing plate having a width of 1200 mm and a length of 43 m.

[0181] The aforementioned ester-based resin film with through-holes and pressure-sensitive adhesive is bonded to the polarizer surface of the prepared polarizing plate using a roll-to-roll method. The resulting material is then immersed in a 1 mol / L (1N) sodium hydroxide aqueous solution for 180 seconds. Next, the resulting material is immersed in a 1 mol / L (1N) hydrochloric acid solution for 60 seconds. Finally, the resulting material is dried at 60°C. Thus, a transparent portion is formed in the polarizer.

[0182] The following items were evaluated for the transparent portions of the polarizing plates in Examples 1 and 2.

[0183] 1. Transmittance (Ts)

[0184] Measurements were performed using a spectrophotometer (Murakami Color Research Laboratory, product name "DOT-3"). Transmittance (T) is the Y value corrected for visibility using a 2-degree field of view (C light source) according to JIS Z 8701-1982.

[0185] 2. Iodine content

[0186] The iodine content in each transparent portion of the polarizer was determined by X-ray fluorescence analysis. Specifically, the iodine content of the polarizer was obtained from a calibration curve generated in advance using standard samples and X-ray intensities measured under the following conditions.

[0187] Analytical apparatus: X-ray fluorescence (XRF) analyzer manufactured by Rigaku Corporation, product name "ZSX100e"

[0188] For cathode: rhodium

[0189] Spectroscopic crystallization: Lithium fluoride

[0190] Excitation light energy: 40kV-90mA

[0191] Iodine measurement line: I-LA

[0192] Quantitative method: FP method

[0193] 2θ peak: 103.078 deg (iodine)

[0194] Measurement time: 40 seconds

[0195] The transmittance of the transparent portion of the polarizing plates prepared in Examples 1 and 2 was 90.3% (Example 1) and 90.2% (Example 2), respectively, and the iodine content was 0.08% by weight (Example 1) and 0.12% by weight (Example 2), respectively. The iodine content of the portions of each polarizer other than the transparent portion was approximately 5% by weight, thereby forming a transparent portion capable of functioning as a non-polarizing portion in Examples 1 and 2, each of which had a lower content of dichroic material than any other portion.

[0196] 3. Sodium content

[0197] The sodium content in each transparent portion of the polarizer was determined by X-ray fluorescence analysis. Specifically, the sodium content of the polarizer was determined from a pre-generated calibration curve using standard samples measured under the following conditions. The sodium content was measured before and after immersion in hydrochloric acid.

[0198] Analytical apparatus: X-ray fluorescence (XRF) analyzer manufactured by Rigaku Corporation, product name "ZSX100e"

[0199] For cathode: rhodium

[0200] Spectroscopic crystallization: Lithium fluoride

[0201] Excitation light energy: 40kV-90mA

[0202] Sodium measurement line: Na-KA

[0203] Quantitative method: FP method

[0204] Measurement time: 40 seconds

[0205] In the polarizing plate of Example 1, the sodium content of each transparent portion was 4.0% by weight before immersion in hydrochloric acid, and the content was 0.04% by weight after immersion. Furthermore, in the polarizing plate of Example 2, the sodium content of each transparent portion was 4.1% by weight before immersion in hydrochloric acid, and the content was 0.05% by weight after immersion.

[0206] Furthermore, the polarizing plates prepared in Examples 1 and 2 were each placed in an environment of 65°C / 90% RH for 500 hours. As a result, in Examples 1 and 2, no significant change was observed in the size of the transparent portion after the humidification test compared to the size before the test. The same humidification test was performed on each polarizing plate prepared in the same manner as in Examples 1 and 2, except that immersion in hydrochloric acid was not performed. As a result, the size of the transparent portion in each polarizing plate increased by approximately 1.3 times.

[0207] In addition, the surface smoothness near the transparent portions of the polarizing plates of Examples 1 and 2 was measured using an optical measuring instrument, the "ZYGO New View 7300," manufactured by Canon Inc. The evaluation results of the surface smoothness (dimensions of unevenness) of Example 1 are shown in... FIG. 8 In (a), the evaluation results of the surface smoothness of Example 2 are shown in FIG. 8 In (b), in Example 1 where the thickness of the polarizer is 5 μm, the step difference between the transparent portion (recess) and other portions is less than 0.8 μm, which is significantly smaller than that in Example 2 where the thickness of the polarizer is 22 μm, resulting in significantly better surface smoothness.

[0208] 4. Appearance

[0209] Visually observe the appearance of each polarizing plate in Examples 1 and 2. As a result, a recess in the transparent portion is visible in the polarizing plate of Example 2.

[0210] Industrial Applicability

[0211] The polarizer of the present invention can be applied to, for example, image display devices (liquid crystal display devices, organic EL devices) with cameras in mobile phones such as smartphones, notebook PCs or tablet PCs.

[0212] Explanation of Reference Numerals

[0213] 10 Resin film

[0214] 20 Non-polarized part

[0215] 100 polarizer

[0216] 101 Polarizing filter

[0217] 110 Protective Film

[0218] 120 protective film

[0219] 130 Pressure-sensitive adhesive layer

[0220] 132 Separator

[0221] 300 polarizing plate

Claims

1. A polarizer comprising a resin film containing a dichroic substance, wherein... The polarizer has a non-polarizing section at a predetermined position. The transmittance of the non-polarized portion is over 90%. The non-polarized portion includes a thin-walled portion that is thinner than other parts of the resin film. The non-polarized portion has a recessed portion on one side of the resin film, and the depth of the recessed portion is less than 1 μm. The thickness of the polarizer is less than 8 μm.

2. The polarizer according to claim 1, wherein the non-polarized portion comprises a low-concentration portion in which the content of the dichroic substance is lower than that of other portions of the resin film.

3. The polarizer according to claim 2, wherein the content of the dichroic material in the non-polarizing portion is 1.0% by weight or less.

4. The polarizer according to any one of claims 1 to 3, wherein the content of alkali metal and / or alkaline earth metal in the non-polarized portion is 3.6% by weight or less.

5. The polarizer according to any one of claims 1 to 3, wherein the resin film comprises a polyvinyl alcohol-based resin film containing iodine.

6. A polarizing plate, comprising: Polarizer according to any one of claims 1 to 5; and A protective film disposed on at least one side of the polarizer.

7. An image display device, comprising: The polarizer according to any one of claims 1 to 5 or the polarizing plate according to claim 6, wherein the non-polarizing portion is disposed at a position corresponding to the camera portion.

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