Polarizing plate after surface processing and method for manufacturing the same

Abstract

The present application provides a polarizing plate having excellent optical properties despite being subjected to curved surface processing, and capable of suppressing the occurrence of cracks, breakage, and yellowing, and a simple manufacturing method thereof. The polarizing plate of the embodiment of the present application includes a polarizer and a protective layer disposed on at least one side of the polarizer, and the polarizing plate is subjected to curved surface processing, and the breakage elongation per unit thickness E of the polarizer is 0.25 (% / μm) or more. The manufacturing method of the polarizing plate of the embodiment of the present application includes: preparing a polarizing plate including a polarizer and a protective layer disposed on at least one side of the polarizer; adhering the polarizing plate to a mold having a given curved surface shape; performing curved surface processing by heating the polarizing plate adhered to the mold; and performing a humidification treatment on the polarizing plate subjected to the curved surface processing in an environment of 40°C to 65°C and 85%RH to 95%RH for 40 minutes or more.

Description

Technical Field

[0001] This invention relates to polarizers that have undergone curved surface processing and their manufacturing methods. Background Technology

[0002] Polarizing films are widely used in image display devices such as liquid crystal displays and organic electroluminescent (EL) displays to achieve image display and / or improve the performance of such image display. For polarizing films, curved surface processing is sometimes required depending on the application. Curved surface processing typically involves shaping the polarizing film into a given shape in a high-temperature environment. However, polarizing films that have undergone curved surface processing suffer from deterioration of optical properties and are prone to cracking, breakage, and / or yellowing.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 8-136731 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The present invention was made to solve the above-mentioned existing problems. Its main purpose is to provide a polarizer with excellent optical properties despite being processed with curved surfaces, and to suppress the occurrence of cracks, fractures and yellowing, as well as a simple manufacturing method thereof.

[0008] Problem Solving Methods

[0009] The polarizer of the present invention comprises a polarizing mirror and a protective layer disposed on at least one side of the polarizing mirror. The polarizer is processed with a curved surface, and the elongation at break E per unit thickness of the polarizing mirror is 0.25 (% / μm) or more.

[0010] In one embodiment, the product of the elongation at break E (% / μm) and the radius of curvature R (mm) of the surface machining, E×R, is 20 or more. In another embodiment, the radius of curvature R is 70 mm or less.

[0011] In one embodiment, the polarizer was subjected to a humidification treatment for more than 40 minutes in an environment of 40°C to 65°C and 85%RH to 95%RH after the surface was processed.

[0012] According to other aspects of the present invention, a method for manufacturing a polarizer is provided, wherein the polarizer is a polarizer that has undergone surface curvature processing. The method includes: preparing a polarizer comprising a polarizing mirror and a protective layer disposed on at least one side of the polarizing mirror; performing surface curvature processing by heating the polarizer together with a mold having a given surface shape; and subjecting the surface-curved polarizer to a humidification treatment at an environment of 40°C to 65°C and 85%RH to 95%RH for at least 40 minutes.

[0013] In one embodiment, the heating temperature in the above-mentioned surface processing is above 100°C.

[0014] The effects of the invention

[0015] According to embodiments of the present invention, for a polarizer that has undergone surface curvature processing, excellent optical properties can be achieved by making the elongation at break per unit thickness of the polarizer 0.25% / μm or higher, and the occurrence of cracks, fractures, and yellowing can be suppressed. A polarizer having such elongation at break (resulting in a polarizer) can be achieved by subjecting the surface-curved polarizer to a given humidification treatment. Attached Figure Description

[0016] Figure 1 This is a three-dimensional schematic diagram of a polarizer according to one embodiment of the present invention.

[0017] Figure 2 yes Figure 1 A cross-sectional schematic diagram of a polarizer.

[0018] Figure 3 (a)~ Figure 3 (c) is a schematic diagram illustrating an example of a method for manufacturing a polarizer after surface processing according to an embodiment of the present invention.

[0019] Symbol Explanation

[0020] 10 polarizing filters

[0021] 20 protective layers

[0022] 30 protective layers

[0023] 100 polarizer Detailed Implementation

[0024] Hereinafter, representative embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. It should be noted that the accompanying drawings are schematic depictions for ease of observation, and their shapes, thicknesses, radii of curvature, etc., differ from the actual figures. In addition, there are also differences between the accompanying drawings.

[0025] A. Polarizing filter

[0026] A-1. Overall Structure of Polarizers

[0027] Figure 1 This is a three-dimensional schematic diagram of a polarizer according to one embodiment of the present invention; Figure 2 yes Figure 1 A cross-sectional schematic diagram of a polarizer is shown. The polarizer 100 in the figure has undergone surface processing. In other words, the polarizer is a polarizer whose properties (representatively optical, chemical, and mechanical properties) have been temporarily degraded due to surface processing (i.e., in a high-temperature environment). According to an embodiment of the invention, by subjecting the temporarily degraded polarizer to the humidification treatment described later, these properties can be restored. As a result, the surface-processed polarizer maintains excellent optical properties and can suppress the occurrence of cracks, fractures, and yellowing. The surface processing temperature can be, for example, 100°C or higher, or for example, 120°C or higher, or for example, 140°C or higher, or for example, 160°C or higher. The upper limit of the surface processing temperature can be, for example, 200°C. The surface processing time can be, for example, 15 seconds to 5 minutes.

[0028] The shape used for surface machining can be any suitable shape that matches the purpose. Specific examples of shapes for surface machining can be given as follows: Figure 1 Such a dome shape or semi-conical shape. Examples of polarizers with this curved surface processing include: polarizers suitable for curved image display devices. Examples of curved image display devices include: virtual reality (VR) goggles, digital signage mounted on curved walls, and pillars. It should be noted that the polarizer in the example figure bulges towards the visible side, but depending on the purpose, the polarizer may also bulge towards the opposite side.

[0029] Polarizer 100 typically includes: a polarizer 10, a protective layer 20 disposed on one side of the polarizer (the visible side in the example), and a protective layer 30 disposed on the other side. Depending on the purpose, either protective layer 20 or protective layer 30 may be omitted. It should be noted that in this specification, protective layer 20 is sometimes referred to as the visible side protective layer, and protective layer 30 as the inner protective layer.

[0030] In embodiments of the present invention, the elongation at break E per unit thickness of the polarizer is 0.25% / μm or more, preferably 0.30% / μm or more, more preferably 0.50% / μm or more, further preferably 0.60% / μm or more, and particularly preferably 0.70% / μm or more. The upper limit of the elongation at break E can be, for example, 5.0% / μm. Such a range of elongation at break E means that the polarizer (resulting in a polarizer plate) hardened due to surface processing is restored and softened by the humidification treatment described later. As a result, polarizer plates containing polarizers with such an elongation at break E exhibit excellent optical properties even after surface processing, and the occurrence of cracks, breakage, and yellowing can be suppressed. It should be noted that the elongation at break E can be obtained by dividing the elongation at break of the polarizer, measured based on JIS K 7161, by the thickness of the polarizer. More specifically, the fracture strength can be determined by making a test sample of a given shape from a polarizer (actually a polarizer) that has been heated at the same temperature as the surface being machined and then further humidified to restore its properties, and by subjecting the test sample to a tensile test.

[0031] In one embodiment, the product of the elongation at break E (% / μm) and the radius of curvature R (mm) of the curved surface, E×R, is preferably 20 or more, more preferably 25 or more, further preferably 30 or more, and particularly preferably 35 or more. The product E×R can, for example, be 50 or more, or even 70 or more, or 80 or more, or 90 or more. The upper limit of the product E×R can, for example, be 1000. When the product E×R is within such a range, even polarizers with small (drastically) curved surfaces exhibit excellent optical properties and can suppress cracking, breakage, and yellowing. The radius of curvature R can, for example, be 70 mm or less, or even 60 mm or less, or even 50 mm or less, or 40 mm or less, or 30 mm or less. The lower limit of the radius of curvature R can, for example, be 10 mm.

[0032] Typically, polarizers undergo humidification treatment (essentially heating / humidification) after surface processing. By subjecting surface-processed polarizers to heating / humidification, the optical properties of the polarizer are restored, and cracking, breakage, and yellowing are suppressed. The effects of such heating / humidification are unexpectedly superior. Details are as follows. Heating / humidification is usually performed in the form of a durability test on the polarizer. The conventional approach of subjecting polarizers to heating / humidification assumes that the optical properties of the polarizer deteriorate (the degree of deterioration is used as an indicator of durability). In other words, it is common knowledge in the art that the optical properties of polarizers deteriorate due to heating / humidification. However, the inventors have discovered that by subjecting a polarizer whose properties have temporarily deteriorated in a high-temperature environment (e.g., after surface processing) to heating / humidification, the deteriorated properties can be restored. That is, the heating / humidification treatment in the embodiments of the present invention is based on a technical concept that contradicts common knowledge in the art, and its effects are unexpectedly superior. The heating temperature in the heating / humidification treatment is preferably 40°C to 65°C, more preferably 55°C to 65°C, further preferably 57°C to 63°C, particularly preferably 58°C to 62°C, and especially preferably about 60°C. Heating temperatures that are too high or too low may prevent the properties from being fully recovered. The humidity in the heating / humidification treatment is preferably 85%RH to 95%RH, more preferably 87%RH to 93%RH, further preferably 88%RH to 92%RH, and especially preferably about 90%RH. Humidity that is too high or too low may prevent the properties from being fully recovered. The treatment time is preferably 40 minutes or more, more preferably 50 minutes or more, further preferably 1 hour or more, and especially preferably 2 hours or more. The upper limit of the treatment time can be, for example, 5 hours. If the treatment time is too short, the properties may not be fully recovered. On the other hand, since even excessively long treatment times do not substantially change the obtained effect, excessively long treatment times are sometimes inefficient.

[0033] The following is a detailed explanation of the polarizer and protective layer.

[0034] A-2. Polarizer

[0035] Typically, a polarizer is formed from a resin film containing a dichroic substance (e.g., iodine, dichroic dye). Any suitable resin film suitable for use as a polarizer can be used as the resin film. Typically, the resin film is a polyvinyl alcohol resin (hereinafter referred to as "PVA-based resin") film. The resin film can be a single layer or a laminate of two or more layers.

[0036] As a specific example of a polarizer composed of a single-layer resin film, a polarizer made by dyeing and stretching a PVA-type resin film with iodine (typically uniaxial stretching) can be cited. The iodine dyeing can be performed, for example, by immersing the PVA-type film in an aqueous iodine solution. The stretching magnification of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after dyeing or during dyeing. Alternatively, dyeing can be performed after stretching. The PVA-type resin film can be subjected to swelling treatment, cross-linking treatment, cleaning treatment, drying treatment, etc., as needed. For example, by immersing the PVA-type resin film in water for washing before dyeing, not only can dirt and anti-blocking agents on the surface of the PVA-type film be washed away, but the PVA-type resin film can also swell to prevent uneven dyeing.

[0037] Specific examples of polarizers obtained using laminates include: polarizers obtained using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or polarizers obtained using a resin substrate and a laminate coated with a PVA-based resin layer formed on the resin substrate. Polarizers obtained using a resin substrate and a laminate coated with a PVA-based resin layer can be manufactured by: for example, coating a PVA-based resin solution onto a resin substrate, allowing it to dry to form a PVA-based resin layer on the resin substrate, obtaining a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to form a polarizer from the PVA-based resin layer. In this embodiment, it is preferable to form a polyvinyl alcohol resin layer comprising a halide and a polyvinyl alcohol resin on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Furthermore, stretching may, as needed, further include stretching the laminate in a gas atmosphere at a high temperature (e.g., above 95°C) before stretching in the aqueous boric acid solution. Furthermore, in this embodiment, it is preferable to subject the laminate to a drying shrinkage treatment, in which it is heated while being transported along its length, causing it to shrink by 2% or more in its width direction. Typically, the manufacturing method of this embodiment includes sequentially subjecting the laminate to assisted stretching in a gas atmosphere, dyeing, stretching in an aqueous solution, and drying shrinkage treatment. By introducing assisted stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, thereby achieving high optical properties. Additionally, by simultaneously improving the orientation of PVA beforehand, problems such as decreased orientation and dissolution of PVA can be prevented when immersed in water during subsequent dyeing and stretching processes, thus achieving high optical properties. Furthermore, when the PVA-type resin layer is immersed in a liquid, compared to when the PVA-type resin layer does not contain halides, the orientation disorder and decrease in orientation of polyvinyl alcohol molecules can be suppressed. Therefore, the optical properties of the polarizer obtained by immersing the laminate in a liquid through dyeing and stretching in an aqueous solution can be improved. Furthermore, by shrinking the laminate in its width direction through the drying shrinkage treatment, optical properties can be improved. The resulting resin substrate / polarizer laminate can be used directly (i.e., the resin substrate can be used as a protective layer for the polarizer), or the resin substrate can be peeled off from the resin substrate / polarizer laminate, and any suitable protective layer conforming to the purpose can be laminated on the peeled surface for use. Detailed descriptions of such a polarizer manufacturing method are provided, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0038] The thickness of the polarizer can be any suitable thickness depending on the purpose. For example, the thickness of the polarizer is 35 μm or less, preferably 20 μm or less, more preferably 15 μm or less, further preferably 12 μm or less, particularly preferably 10 μm or less, even more preferably 8 μm or less, especially preferably 6 μm or less, and most preferably 5 μm or less. The lower limit of the polarizer thickness is preferably 2 μm, more preferably 1 μm.

[0039] The initial degree of polarization of the polarizer (degree of polarization before surface processing) is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more. The initial single-unit transmittance of the polarizer (single-unit transmittance before surface processing) is preferably 40.0% to 46.0%, more preferably 41.0% to 43.5%. The degree of polarization of the polarizer after surface processing is, for example, 0.005% or more less than the initial degree of polarization (a decrease in degree of polarization as an optical characteristic). The degree of polarization of the polarizer after humidification treatment (described later) is, for example, 0.005% or more greater than the degree of polarization after surface processing (a recovery of degree of polarization as an optical characteristic). That is, by humidification treatment, the degree of polarization that has decreased (deteriorated) due to surface processing can be restored to the initial degree of polarization.

[0040] A-3. Protective Layer

[0041] The visible protective layer and the inner protective layer can each be formed from any suitable film that can be used as a protective layer for a polarizing mirror. Specific examples of materials that form the main component of the film include: cellulose resins such as cellulose triacetate (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrene, polynorbornene, polyolefins, (meth)acrylic acids, acetates, and other transparent resins. Additionally, thermosetting resins or UV-curing resins such as (meth)acrylic acids, urethanes, (meth)acrylate urethanes, epoxy resins, and silicone resins can also be used. Furthermore, glassy polymers such as siloxane polymers can also be used. Alternatively, polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As the material for this membrane, resin compositions can be used, for example, thermoplastic resins containing substituted or unsubstituted imide groups on the side chains, and thermoplastic resins containing substituted or unsubstituted phenyl and nitrile groups on the side chains. Examples include resin compositions having alternating copolymers formed from isobutylene and N-methylmaleimide, and acrylonitrile-styrene copolymers. The polymer membrane can be, for example, an extruded product of the above-mentioned resin compositions.

[0042] The inner protective layer is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0 nm to 10 nm, and the phase difference Rth(550) in the thickness direction is -10 nm to +10 nm. Here, "Rth(λ)" is the phase difference in the thickness direction measured at 23°C with light of wavelength λ nm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C with light of wavelength 550 nm. When the thickness of the layer (film) is set as d (nm), Rth(λ) can be obtained by the formula: Rth(λ) = (nx - nz) × d. nz is the refractive index in the thickness direction.

[0043] When the polarizer is positioned on the visible side of an image display device, surface treatments such as hard coating, anti-reflective treatment, anti-adhesion treatment, and anti-glare treatment can be applied to the visible side protective layer as needed. Furthermore / or, treatments can be applied to the visible side protective layer to improve visual recognition when viewed through polarized sunglasses (typically, treatments that impart (elliptical) polarization or ultra-high phase difference).

[0044] The thickness of the protective layer can be any suitable thickness. For example, the thickness of the protective layer is 10 μm to 90 μm, preferably 20 μm to 80 μm, more preferably 20 μm to 60 μm, and even more preferably 20 μm to 40 μm. It should be noted that, in the case of surface treatment, the thickness of the protective layer includes the thickness of the surface treatment layer.

[0045] B. Manufacturing method of polarizer

[0046] The polarizer described in item A above is representative of a polarizer whose properties are restored through a humidification process after surface machining. Therefore, embodiments of the present invention also include a method for manufacturing a polarizer, which includes surface machining and a humidification process. Figure 3 (a)~ Figure 3 (c) is a schematic diagram illustrating an example of a method for manufacturing a polarizer with curved surface processing according to an embodiment of the present invention.

[0047] In the manufacturing method of the embodiments of the present invention, firstly, as Figure 3 As shown in (a), a polarizer 100' comprising a polarizer and a protective layer disposed on at least one side of the polarizer is prepared. Meanwhile, as... Figure 3 As shown in (a), a mold 200 with a given curved surface shape (dome-shaped in the example) is also prepared.

[0048] Next, in one implementation, such as Figure 3As shown in (b), the polarizer 100' is attached to the mold 200. The attachment of the polarizer 100' to the mold 200 can be performed in any suitable manner. In the example shown, the polarizer 100' can be attached to the mold 200, for example, via an adhesive. Next, with the polarizer 100' attached to the mold 200, the polarizer is heated to perform surface processing (forming). In another embodiment not shown, the polarizer 100' is placed in the mold 200 and heated to the surface processing temperature under vacuum. After reaching the surface processing temperature, the system is opened, and surface processing (forming) is performed under air pressure (atmospheric pressure). The surface processing temperature is as described in section A above.

[0049] Next, the polarizer after surface curing undergoes a humidification process. This humidification can be performed directly while the polarizer is bonded or placed in a mold, or it can be done like... Figure 3 (c) This is performed after the polarizer is removed from the mold. The humidification conditions are as described in section A above. In this way, a polarizer 100 with curved surface processing can be obtained.

[0050] Example

[0051] The present invention will now be specifically described through examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. Furthermore, unless otherwise explicitly stated, "parts" and "%" in the examples are based on weight.

[0052] (1) Elastic modulus, breaking strength and elongation at break

[0053] The polarizer before surface machining was heated under the same conditions as surface machining (100°C and 150 seconds). This was used as a polarizer equivalent to a comparative example. The polarizer equivalent to the comparative example was subjected to heating / humidification treatment (65°C, 95% RH, 2 hours) and used as a polarizer equivalent to the embodiment. The polarizer equivalent to the comparative example or the polarizer equivalent to the embodiment was punched to a size of 100mm × 10mm to prepare test samples, which were then subjected to a tensile test using Autograph (manufactured by Shimadzu Corporation). The test environment was 23°C and 50% RH, with a tensile speed of 300mm / min. Tension was performed at this speed until the test sample broke, and the fracture strength (fracture stress) and elongation at break were determined. The fracture strength was automatically measured using Autograph. The elongation at break was calculated using the following formula. It should be noted that the measurement was performed independently three times, and the average value was used as the fracture strength and elongation at break.

[0054] Elongation at break (%) = {Change in sample length up to the break point (mm) / Initial length (100mm)} × 100

[0055] The elastic modulus was calculated using the following formula within the tensile stress range of 10N to 20N.

[0056] Elastic modulus = {(20N - 10N) / sample cross-sectional area (mm²)} 2 )} / {ε(20)-ε(10)}

[0057] In the formula, ε(20) is the strain per unit length (mm / mm: i.e., nominal) when the stress is 20N, and ε(10) is the strain per unit length when the stress is 10N.

[0058] (2) Monomer transmittance and polarization degree

[0059] For the dome-shaped polarizers obtained in the examples and comparative examples after surface processing, the individual transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc were measured using a UV-Vis spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., "LPF-200"), and the Ts, Tp, and Tc used as polarizers were determined. These Ts, Tp, and Tc were measured using a 2-degree field of view (C light source) of JIS Z8701 and the Y values ​​were obtained after visual sensitivity correction.

[0060] The degree of polarization P was calculated based on the obtained Tp and Tc using the following formula.

[0061] Degree of polarization P(%) = {(Tp - Tc) / (Tp + Tc)} 1 / 2 ×100

[0062] The measurements were performed as follows: A region divided into nine grid sections (15mm × 15mm) was defined, excluding the lower end of the dome-shaped polarizer. Measurements were taken from each region, and the average value was used as the unit transmittance and degree of polarization. Furthermore, the dome-shaped polarizer was fixed using a sample holder to ensure accurate positioning and measurement of each region. It should be noted that the Ts and P of the polarizer are essentially governed by the characteristics of the polarizer.

[0063] (3) Appearance

[0064] The appearance of the polarizers obtained in the examples and comparative examples after surface processing was observed with the naked eye and evaluated according to the following criteria. It should be noted that for the polarizers of the comparative examples, their appearance was typically observed with the naked eye after being placed in the environment for 2 hours (the same time as the humidification treatment time of the polarizers of the examples).

[0065] ○: No instances of cracks, fractures, or yellowing were observed.

[0066] △: Any one of the following was observed: cracks, fractures, or yellowing.

[0067] ×: Two or more of the following were observed: cracks, fractures, or yellowing.

[0068] <Example 1>

[0069] 1. Fabrication of a polarizing filter

[0070] As a thermoplastic resin substrate, a strip-shaped amorphous polyethylene terephthalate copolymer film (thickness: 100 μm) with a Tg of approximately 75 °C was used to perform corona treatment on one side of the resin substrate.

[0071] 13 parts by weight of potassium iodide were added to 100 parts by weight of a PVA resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a 9:1 ratio. The resulting mixture was then dissolved in water to prepare a PVA aqueous solution (coating solution).

[0072] The above-mentioned PVA aqueous solution was coated on the corona-treated surface of the resin substrate and dried at 60°C to form a PVA resin layer with a thickness of 13 μm, thus creating a laminate.

[0073] The resulting laminate was unidirectionally stretched to 2.4 times its original length in an oven at 130°C (assisted stretching treatment in a gas atmosphere).

[0074] Next, the laminate is immersed in an insoluble bath at 40°C (an aqueous solution of boric acid prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insoluble treatment).

[0075] Next, the polarizer was immersed for 60 seconds in a staining bath at 30°C (an aqueous solution of iodine and potassium iodide prepared in a 1:7 weight ratio relative to 100 parts by weight of water) while adjusting the concentration to achieve a given value for the monomer transmittance (Ts) of the final polarizer.

[0076] Next, immerse in a crosslinking bath at 40°C (an aqueous solution of boric acid prepared by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (crosslinking treatment).

[0077] Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4 wt% and potassium iodide concentration 5 wt%) at a liquid temperature of 70°C, it was unidirectionally stretched (stretching treatment in aqueous solution) between rollers with different circumferential speeds along the longitudinal direction (length direction) to achieve a total stretch ratio of 5.5 times.

[0078] Then, the laminate was immersed in a cleaning bath at 20°C (an aqueous solution of 100 parts by weight of water and 3 parts by weight of potassium iodide) (cleaning treatment).

[0079] Then, it is dried in an oven at approximately 90°C while being in contact with heated rollers made of SUS at a surface temperature of approximately 75°C (drying shrinkage treatment).

[0080] In this way, a polarizer is formed on a resin substrate, resulting in a laminate having a resin substrate / polarizer configuration.

[0081] 2. Fabrication of Polarizing Films

[0082] An acrylic resin film (40 μm thick) was bonded as a visible-side protective layer to the surface of the polarizer of the aforementioned laminate (the side opposite to the resin substrate) using a UV-curable adhesive. Specifically, the adhesive was applied to achieve a total thickness of approximately 1.0 μm and then bonded using a rolling mill. UV light was then irradiated from the acrylic resin film side to cure the adhesive. Next, the resin substrate was peeled off, resulting in a polarizer having the structure of an acrylic resin film (visible-side protective layer) / polarizer.

[0083] 3. Curved surface machining of polarizers

[0084] The obtained polarizers were punched into single sheets and then surface-processed (shaped) into dome shapes with curvature radii of 48 mm, 70 mm, and 105 mm, respectively. Specifically, the punched polarizers were placed in dome-shaped molds with various curvature radii and heated to 100°C under vacuum. After reaching this temperature, the system was opened and surface-processed (shaped) was performed under air pressure (atmospheric pressure). The actual processing time (pressurization time) was 150 seconds. Next, the surface-processed polarizers were placed in a chamber set at 65°C and 95% RH for 2 hours for heating / humidification treatment. In this way, surface-processed polarizers were obtained. The obtained polarizers were evaluated in (2) and (3) above. The results are shown in Table 1.

[0085] <Example 2>

[0086] Using a 75 μm thick polyvinyl alcohol film (manufactured by Kuraray Co., Ltd.: VF-PS7500), it was immersed in pure water at 30°C for 60 seconds while being stretched to a stretch ratio of 2.5 times. It was then stained in an iodine aqueous solution at 30°C (weight ratio: pure water / iodine (I) / potassium iodide (KI) = 100 / 0.01 / 1) for 45 seconds. After stretching in a 4% boric acid aqueous solution to a total stretch ratio of 5.8 times, it was immersed in pure water for 10 seconds and then dried at 60°C for 3 minutes while maintaining the film tension to obtain a polarizing mirror (thickness 28 μm).

[0087] A triacetate cellulose (TAC) film (47 μm thick) was laminated on one side of the obtained polarizer as a visible protective layer, and an acrylic resin film (30 μm thick) was laminated on the other side as an inner protective layer, thus obtaining a polarizer.

[0088] The following sequence is the same as in Example 1, resulting in a polarizer with a curved surface. The obtained polarizer was evaluated in the same way as in Example 1. The results are shown in Table 1.

[0089] <Examples 3 and 4>

[0090] The polarizer constructed as shown in Table 1 was used, except that a surface-processed polarizer was obtained in the same manner as in Example 1. The obtained polarizer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0091] <Comparative Example 1>

[0092] No heating / humidification treatment was performed; otherwise, a polarizer with a curved surface was obtained in the same manner as in Example 2. The obtained polarizer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0093] <Comparative Examples 2 and 3>

[0094] The polarizer constructed as shown in Table 1 was used, except that a polarizer with a curved surface was obtained in the same manner as in Comparative Example 1. The obtained polarizer was subjected to the same evaluation as in Example 1.

[0095] The results are shown in Table 1.

[0096]

[0097] As can be clearly seen from Table 1, through the embodiments of the present invention, the properties of polarizers deteriorated due to curved surface processing can be restored by heating / humidifying treatment. More specifically, as can be seen by comparing Example 2 with Comparative Example 1, Example 3 with Comparative Example 2, and Example 4 with Comparative Example 3, for the polarizers of the embodiments, the individual transmittance and polarization degree deteriorated due to curved surface processing, as well as the elongation at break E of the polarizer, are significantly restored by heating / humidifying treatment. It is evident that the polarizers of such embodiments suppress the occurrence of cracks, fractures, and yellowing.

[0098] Industrial applicability

[0099] The polarizer of the present invention can be adapted for use in image display devices with curved surfaces (e.g., curved image display devices).

Claims

1. A polarizer comprising: polarizer, and A protective layer disposed on at least one side of the polarizer. The polarizer has a curved shape. The polarizer has an elongation at break (E) of more than 0.25% / μm per unit thickness.

2. The polarizer according to claim 1, wherein, The product of the elongation at break E and the radius of curvature R used for surface processing to form the curved surface shape, E×R, is 20 or more, wherein the unit of the elongation at break E is % / μm, and the unit of the radius of curvature R is mm.

3. The polarizer according to claim 2, wherein, The radius of curvature R is less than 70 mm.

4. A method for manufacturing a polarizer, wherein the polarizer is a polarizer that has undergone curved surface processing. The manufacturing method includes: Prepare a polarizer comprising a polarizer and a protective layer disposed on at least one side of the polarizer; The polarizer, together with a mold having a given curved surface shape, is heated to perform surface machining; and The polarizer that has undergone this curved surface processing is humidified for more than 40 minutes in an environment with a temperature of 40℃~65℃ and a humidity of 85%~95%. The polarizer has a curved shape, and the elongation at break E per unit thickness of the polarizer is 0.25% / μm or more.

5. The manufacturing method according to claim 4, wherein, The heating temperature during the surface machining process is above 100℃.

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