Inspection method, method for manufacturing polarizing plate, and inspection device for non-polarizing portion of polarizing plate

Abstract

Provided are an inspection method, a method for manufacturing a polarizing plate, and an inspection device for a non-polarizing portion of a polarizing plate. A non-polarizing portion is efficiently formed in a polarizing plate with high precision so that the non-polarizing portion has a desired shape and characteristics. An inspection method for inspecting a polarizing plate having a non-polarizing portion comprises: an imaging step of irradiating light from one side of the polarizing plate to photograph reflected light from the polarizing plate; and an inspection step of inspecting the non-polarizing portion of the polarizing plate based on the obtained image.

Description

[0001] This application is a divisional application of a Chinese invention patent application filed on September 29, 2016, with application number 201610868030.3 and invention name “Polarizer Inspection Method and Polarizer Manufacturing Method”. Technical Field

[0002] The present invention relates to a method for inspecting a polarizing plate having a non-polarizing portion and a method for manufacturing a polarizing plate. Background Art

[0003] Image display devices such as cellular phones and notebook personal computers (PCs) are sometimes equipped with internal electronic components such as cameras. Various studies have been conducted for the purpose of improving the camera performance of such image display devices (for example, Patent Documents 1 to 7). However, with the rapid popularization of smart phones and touch panel information processing devices, further improvements in camera performance are expected. In addition, in order to support the diversification and high functionality of image display devices, a polarizing plate having polarization performance locally is required. It is expected to manufacture image display devices and / or their components at an acceptable cost to achieve this requirement industrially and commercially, but there are still various matters that need to be studied in order to establish such technology.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2011-81315

[0005] Patent Document 2: Japanese Patent Application Publication No. 2007-241314

[0006] Patent Document 3: U.S. Patent Application Publication No. 2004 / 0212555

[0007] Patent Document 4: Korean Patent Publication No. 10-2012-0118205

[0008] Patent Document 5: Korean Patent No. 10-1293210

[0009] Patent Document 6: Japanese Patent Application Publication No. 2012-137738

[0010] Patent Document 7: U.S. Patent Application Publication No. 2014 / 0118826 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] When a non-polarizing portion is provided in a polarizing plate and the non-polarizing portion corresponds to a camera portion of an image display device, the non-polarizing portion is designed to be very small as the image display device has been miniaturized in recent years. Therefore, it is required to form the non-polarizing portion efficiently with high precision so that the non-polarizing portion has a desired shape and characteristics.

[0013] Solutions for solving problems

[0014] According to the present invention, a method for inspecting a polarizing plate having a non-polarizing portion is provided. The inspection method comprises: an imaging step of irradiating light from one side of the polarizing plate having the non-polarizing portion to photograph reflected light from the polarizing plate; and an inspection step of inspecting the non-polarizing portion of the polarizing plate based on the obtained image.

[0015] In one embodiment, the polarizing plate has a prescribed size for being mounted on an image display device of a prescribed size.

[0016] In one embodiment, the polarizing plate is in a long strip shape and has non-polarizing portions arranged at predetermined intervals in the longitudinal direction and / or the width direction.

[0017] In one embodiment, the polarizing plate is formed of a resin film containing a dichroic substance, and a dichroic substance low concentration portion in the resin film where the content of the dichroic substance is relatively low is provided as the non-polarizing portion.

[0018] In one embodiment, a protective layer is formed on at least one side of the polarizing plate used in the imaging step.

[0019] In one embodiment, in the imaging step, the light irradiation is performed by oblique illumination.

[0020] In one embodiment, in the imaging step, the light irradiation is performed by coaxial epi-illumination.

[0021] In one embodiment, in the imaging step, light irradiation is performed by switching between oblique illumination and coaxial epi-illumination.

[0022] According to another aspect of the present invention, a method for manufacturing a polarizing plate is provided, wherein the method comprises: forming a non-polarizing portion in a polarizing plate; and inspecting the polarizing plate having the non-polarizing portion by the inspection method.

[0023] According to another aspect of the present invention, a device for inspecting a non-polarizing portion of a polarizer is provided. In one embodiment, the device comprises: an oblique illumination unit that irradiates light to one side of the polarizer having the non-polarizing portion; an imaging unit that captures reflected light of the irradiated light from the oblique illumination unit to the polarizer; and an image processing unit that is connected to the imaging unit and analyzes and processes an image captured by the imaging unit.

[0024] In another embodiment, the inspection device comprises: a coaxial incident illumination unit that irradiates light to one side of a polarizing plate having a non-polarizing portion; an imaging unit that captures reflected light of the irradiated light from the coaxial incident illumination unit to the polarizing plate; and an image processing unit that is connected to the imaging unit and analyzes and processes the image captured by the imaging unit.

[0025] In another embodiment, the inspection device comprises: a first lighting unit and a second lighting unit, which irradiate light to one side of a polarizing plate having a non-polarizing portion; an imaging unit, which captures reflected light of the irradiated light from the first lighting unit or the second lighting unit to the polarizing plate; an image processing unit, which is connected to the imaging unit and analyzes and processes the image captured by the imaging unit; and a lighting switching unit, which switches between light irradiation by the first lighting unit and light irradiation by the second lighting unit, wherein the first lighting unit is an oblique illumination unit and the second lighting unit is a coaxial incident illumination unit.

[0026] Provided is an inspection method for inspecting a polarizer having a non-polarizing portion, the method comprising: an imaging step of irradiating light from one side of the polarizer to photograph reflected light from the polarizer; and an inspection step of inspecting the non-polarizing portion of the polarizer based on the obtained image, wherein in the imaging step, the light irradiation is performed by coaxial epi-illumination, or the light irradiation is performed by switching between oblique illumination and coaxial epi-illumination.

[0027] A method for manufacturing a polarizing plate is provided, the method comprising: forming a non-polarizing portion in a polarizing plate; and inspecting the polarizing plate having the non-polarizing portion by the above-mentioned inspection method.

[0028] Provided is a device for inspecting the non-polarizing portion of a polarizing plate, the device comprising: a coaxial incident illumination unit that irradiates light to one side of the polarizing plate having the non-polarizing portion; an imaging unit that captures reflected light emitted from the coaxial incident illumination unit and reflected from the polarizing plate; and an image processing unit that is connected to the imaging unit and analyzes and processes an image captured by the imaging unit.

[0029] Provided is a device for inspecting the non-polarizing portion of a polarizing film, the device comprising: a first lighting unit and a second lighting unit, wherein the first lighting unit and the second lighting unit irradiate light toward one side of the polarizing film having the non-polarizing portion; an imaging unit, which captures reflected light emitted from the first lighting unit or the second lighting unit and reflected from the polarizing film; an image processing unit, which is connected to the imaging unit and analyzes and processes the image captured by the imaging unit; and an illumination switching unit, which switches between light irradiation by the first illumination unit and light irradiation by the second illumination unit, wherein the first illumination unit is an oblique illumination unit and the second illumination unit is a coaxial epi-illumination unit.

[0030] Effects of the Invention

[0031] In the present invention, light is irradiated from one side of a polarizing plate having a non-polarizing portion, reflected light from the polarizing plate is photographed, and the shape, characteristics, etc. of the non-polarizing portion are evaluated based on the obtained image. According to the inspection method of the present invention, the shape, characteristics, etc. of the non-polarizing portion can be efficiently evaluated with excellent accuracy. As a result, only a polarizing plate having a non-polarizing portion that satisfies the desired characteristics and has excellent shape accuracy can be mounted on an image display device, so that an image display device with excellent camera performance can be efficiently obtained. In addition, when coaxial incident illumination is used as a light irradiation method, an effect that it is possible to properly confirm whether there are bubbles around the non-polarizing portion can also be obtained. In the local bleaching treatment (described in detail in item B) of the polarizing plate for the purpose of forming a non-polarizing portion, a fine concave portion is generated at the bleached portion, and then air or the like enters the concave portion when a protective film or the like is laminated, thereby generating bubbles around the non-polarizing portion. This is a problem unique to polarizing plates having non-polarizing portions. In oblique illumination, bubbles are difficult to identify due to the influence of reflected light from portions other than the bubble portion, but bubbles can be detected by using coaxial incident illumination. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic plan view of a polarizing plate that can be suitably used in the inspection method of the present invention.

[0033] Figure 2 It is a schematic diagram for explaining the imaging procedure in the first embodiment of the present invention.

[0034] Figure 3 It is a schematic diagram for explaining the imaging procedure in the second embodiment of the present invention.

[0035] Figure 4 It is a schematic diagram for explaining an imaging procedure in the third embodiment of the present invention.

[0036] Figure 5A This is a schematic diagram showing a state where oblique lighting is performed in the third embodiment.

[0037] Figure 5B This is a schematic diagram showing a state where coaxial epi-illumination is performed in the third embodiment.

[0038] Figure 6 This is a schematic perspective view for explaining bonding between a polarizing plate and a surface protection film having through holes during formation of a non-polarizing portion.

[0039] Fig. 7A This is a schematic cross-sectional view of a laminate that can be subjected to a chemical decolorization treatment.

[0040] Figure 7B This is a schematic diagram for explaining an example of a method for forming a non-polarizing portion by chemical bleaching treatment.

[0041] Figure 8 This is a schematic cross-sectional view of a polarizing plate obtainable by the production method of the present invention.

[0042] Description of Reference Numerals

[0043] 10: non-polarizing part; 100: polarizing film; 300: polarizing plate; 400: inspection device; 410: first lighting part (oblique lighting part); 420: second lighting part (coaxial incident lighting part); 430: imaging part; 440: image processing part; 450: lighting switching part; 460: optical axis control part; 500: marking device. DETAILED DESCRIPTION

[0044] [A. Inspection method]

[0045] The present invention relates to a method for inspecting a polarizing plate having a non-polarizing portion. The inspection method of the present invention comprises: an imaging step of irradiating light from one side of the polarizing plate having the non-polarizing portion and photographing reflected light from the polarizing plate; and an inspection step of inspecting the non-polarizing portion of the polarizing plate based on the obtained image. The inspection method of the present invention is described below.

[0046] A-1. Polarizing plate with non-polarizing portion

[0047] Figure 1It is a schematic top view of a polarizer that can be appropriately used in the inspection method of the present invention. The polarizer 100 can be in the shape of an elongated strip. In this specification, "elongated strip" refers to an elongated shape that is sufficiently long relative to the width, for example, including an elongated shape that is more than 10 times, preferably more than 20 times the width. The elongated polarizer can have a non-polarized portion configured at a specified interval (i.e., in a specified pattern) in the length direction and / or the width direction. The configuration pattern of the non-polarized portion can be appropriately set according to the purpose. Representatively speaking, when the polarizer is cut (for example, cut or punched along the length direction and / or the width direction) to a specified size to be installed in an image display device of a specified size, the non-polarized portion can be configured at a position corresponding to the camera portion of the image display device. In one embodiment, the non-polarized portion is configured at substantially equal intervals in both the length direction and the width direction. In addition, "substantially equal intervals in both the length direction and the width direction" means that the intervals in the length direction are equal intervals and the intervals in the width direction are equal intervals, and the intervals in the length direction and the intervals in the width direction do not need to be equal. In another embodiment, the non-polarizing portions may be arranged substantially at equal intervals in the length direction and at different intervals in the width direction. In the case where the non-polarizing portions are arranged at different intervals in the width direction, the intervals between adjacent non-polarizing portions may be all different or only a part (the intervals between specific adjacent non-polarizing portions) may be different.

[0048] In the inspection method of the present invention, it is also possible to appropriately use a polarizing plate (with Figure 1 The polarizing plate (polarizer) cut to a predetermined size has a non-polarizing portion at a position corresponding to the camera portion of the image display device when installed in the image display device. The number of non-polarizing portions of the polarizing plate may be one or more. In addition, the polarizing plate is a polarizing plate obtained by cutting a long strip of polarizing plate. In this specification, depending on the context, a polarizing plate obtained by cutting a long strip of polarizing plate is sometimes referred to as a polarizing plate.

[0049] The transmittance of the non-polarizing portion (for example, the transmittance measured by light having a wavelength of 550 nm at 23° C.) is preferably 50% or more, more preferably 60% or more, further preferably 75% or more, and particularly preferably 90% or more. With such a transmittance, the desired transparency as the non-polarizing portion can be ensured. As a result, when the polarizing plate is arranged so that the non-polarizing portion corresponds to the camera portion of the image display device, it is possible to prevent adverse effects on the photographic performance of the camera.

[0050] The non-polarizing portion 10 can be configured in a prescribed pattern as described above, and can be in any appropriate manner as long as the above-mentioned desired optical properties can be obtained. In one embodiment, the non-polarizing portion is a decolorized portion obtained by partial decolorization. Specifically, it is a decolorized portion formed by decolorizing a prescribed portion of a polarizer. The decolorized portion can be formed, for example, by laser irradiation or chemical treatment (for example, acid treatment, alkali treatment, or a combination thereof). In another embodiment, the non-polarizing portion is a through hole (representatively, a through hole that penetrates the polarizer in the thickness direction). The through hole can be formed, for example, by mechanical punching (for example, punching, Thomson knife punching, plotter, water jet) or by removing a prescribed portion of the polarizer (for example, laser ablation or chemical dissolution).

[0051] As long as the top view shape of the non-polarizing part 10 does not have a bad influence on the camera performance of the image display device using the polarizer, any appropriate shape can be adopted. As a specific example, a circle, an ellipse, a square, a rectangle, a rhombus can be listed. By appropriately setting the shape of the through hole of the surface protection film described in item B described later, a non-polarizing part with a desired top view shape can be formed.

[0052] Typically, the polarizing plate 100 is formed of a resin film 20 containing a dichroic substance. The resin film 20 is, for example, a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film.

[0053] As the above-mentioned dichroic substance, for example, iodine, organic dyes, etc. can be cited. They can be used alone or in combination of two or more. Preferably, iodine is used. This is because, when the non-polarizing portion is formed by decolorization using a chemical treatment, for example, the iodine complex contained in the resin film (polarizer) is appropriately reduced, so that a non-polarizing portion having characteristics suitable for use in a camera portion can be formed.

[0054] The non-polarized portion is preferably a decolorized portion, and it is more preferred that the non-polarized portion be a low-concentration portion having a relatively low content of dichroic substances (specifically, a low-concentration portion having a low content of dichroic substances compared to other portions). According to this structure, compared with the case where the non-polarized portion is formed mechanically (for example, by mechanically removing the non-polarized portion by using a Thomson knife punching, a plotter, a water jet, etc.), quality problems such as cracks, delamination (interlayer peeling), and glue seepage can be avoided. In addition, the content of the dichroic substance itself in the low-concentration portion is low, so compared with the case where the non-polarized portion is formed by decomposing the dichroic substance using a laser or the like, the transparency of the non-polarized portion can be well maintained.

[0055] The content of the dichroic substance in the above-mentioned low-concentration portion is preferably less than 1.0 weight %, more preferably less than 0.5 weight %, and further preferably less than 0.2 weight %. As long as the content of the dichroic substance in the low-concentration portion is within this range, the desired transparency can be sufficiently imparted to the low-concentration portion. For example, in the case where the low-concentration portion corresponds to the camera portion of an image display device, very excellent photographic performance can be achieved from the viewpoints of both brightness and hue. On the other hand, the lower limit value of the content of the dichroic substance in the low-concentration portion is generally below the detection limit value. In addition, in the case of using iodine as the dichroic substance, for example, the iodine content can be calculated based on the X-ray intensity measured by fluorescent X-ray analysis using a standard curve prepared in advance using a standard sample.

[0056] The difference between the content of the dichroic substance in other parts and the content of the dichroic substance in the low-concentration part is preferably 0.5 wt % or more, more preferably 1 wt % or more. As long as the difference in content is within this range, a low-concentration part having desired transparency can be formed.

[0057] The content of alkali metal and / or alkaline earth metal in the above-mentioned low concentration portion is preferably 3.6% by weight or less, more preferably 2.5% by weight or less, further preferably 1.0% by weight or less, and particularly preferably 0.5% by weight or less. As long as the content of alkali metal and / or alkaline earth metal at the low concentration portion is in this range, the shape of the low concentration portion formed by the contact with the alkaline solution described later can be well maintained (that is, a low concentration portion with excellent dimensional stability can be achieved). For example, a standard curve prepared using a standard sample in advance can be used to obtain the content based on the X-ray intensity measured by fluorescent X-ray analysis. This content can be achieved by reducing the alkali metal and / or alkaline earth metal at the contact portion in the contact with the alkaline solution described later.

[0058] As the PVA resin forming the above-mentioned PVA resin film, any appropriate resin can be used. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be listed. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The saponification degree of PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be obtained according to JIS K 6726-1994. By using a PVA resin with such a saponification degree, a polarizer with excellent durability can be obtained. When the saponification degree is too high, there is a concern about gelation.

[0059] The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 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 determined in accordance with JIS K6726-1994.

[0060] The polarizer (excluding the non-polarized portion) preferably exhibits absorption dichroism at a wavelength between 380 nm and 780 nm. The single transmittance (Ts) of the polarizer (excluding the non-polarized portion) is preferably 39% or more, more preferably 39.5% or more, further preferably 40% or more, and particularly preferably 40.5% or more. In addition, the logical upper limit of the single transmittance is 50%, and the practical upper limit is 46%. In addition, the single transmittance (Ts) is the Y value obtained by measuring the 2-degree field of view (C light source) of JIS Z 8701 and then correcting the visibility, for example, and can be measured using a microscopic spectroscopic system (manufactured by LambdaVision, LVmicro). The polarization degree of the polarizer (excluding the non-polarized portion) is preferably 99.9% or more, more preferably 99.93% or more, and further preferably 99.95% or more.

[0061] The thickness of the polarizer (resin film) can be set to any appropriate value. The thickness is preferably 30 μm or less, more preferably 25 μm or less, further preferably 20 μm or less, and particularly preferably 10 μm or less. On the other hand, the thickness is preferably 0.5 μm or more, and further preferably 1 μm or more. As long as it is this thickness, a polarizer with excellent durability and optical properties can be obtained. The thinner the thickness of the polarizer (resin film), the better the non-polarizing portion can be formed. For example, in the case of forming a non-polarizing portion by decolorizing using a chemical treatment (details are described in item B), the contact time between the decolorizing solution and the resin film (polarizer) can be shortened. Specifically, a non-polarizing portion with a higher transmittance can be formed in a shorter time.

[0062] The thickness of the portion in contact with the above-mentioned decolorizing solution (for example, an alkaline solution) will be thinner than the thickness of other portions. This tendency will become stronger as the transmittance of the non-polarized portion obtained by decolorization becomes higher. By thinning the resin film, it is possible to reduce the thickness difference between the non-polarized portion and other portions while achieving a high transmittance of the non-polarized portion (preferably above 90%). In this way, it is possible to prevent undesirable conditions that may be caused by thickness differences. As undesirable conditions, for example, the following conditions can be thought of: when the long strip of polarizing film is wound into a roll, the thickness difference between the non-polarized portion and other portions is transferred as a winding mark at the overlapping portion; when bonding with other structural members such as a protective film, bubbles are generated due to the thickness difference between the non-polarized portion and other portions; the thickness difference is visually recognized in the final product. It is believed that preventing such undesirable conditions will also help to suppress the deviation in the quality of the final polarizing film obtained by cutting the long strip of polarizing film. It is believed that this effect becomes significant, for example, when the transmittance of the non-polarizing portion is 90% or more and / or the content of the dichroic substance is 0.2% by weight or less. In addition, a transmittance of the non-polarizing portion as high as 90% or more will also help suppress the deviation of the quality of the polarizer used in the end. Specifically, in the case of forming the non-polarizing portion by contact with a decolorizing liquid, when the decolorization degree is weak, the transmittance of the obtained non-polarizing portion is prone to deviation, but by making the transmittance 90% or more and / or making the content of the dichroic substance 0.2% or less (by making the decolorization degree strong), the decolorization state can be stably controlled.

[0063] In one embodiment, the non-polarizing portion is set as a thin-walled portion that is thinner than other parts. For example, a concave portion formed by a surface depression on one side of the polarizer is set as a thin-walled portion. In this case, the thickness difference between the non-polarizing portion and other parts (the depth of the concave portion) is, for example, 0.02 μm or more. On the other hand, the thickness difference is preferably 2 μm or less, and more preferably 1 μm or less. In the case of forming the non-polarizing portion by the bleaching described later (for example, in the case where the transmittance of the non-polarizing portion is 90% or more and / or the content of the dichroic substance is 0.2% by weight or less), such a thickness difference is sometimes formed. It is believed that as long as the upper limit of the thickness difference is within this range, the winding marks caused by the formation of the roll and other undesirable conditions caused by the thickness difference can be well suppressed. As a result, the deviation in the quality of the polarizer finally used by cutting the long strip of polarizer can be significantly suppressed. In addition, in this specification, "thickness difference (depth of concave portion)" refers to the depth of the deepest part of the concave portion.

[0064] The concave portion formed by the surface depression of the above-mentioned one side is formed, for example, by allowing the decolorizing liquid to act only from one side of the polarizer. By making the depth of the concave portion formed after the decolorization treatment within the above-mentioned range, the treatment after decolorization described later can be uniformly implemented. In addition, it is believed that the concave portion can be formed only on one side, thereby preventing the occurrence of undesirable conditions caused by thickness differences such as winding marks generated by forming a roll, thereby suppressing the deviation of the quality of the polarizer finally used.

[0065] In a strip-shaped polarizer, its absorption axis can be set to any appropriate direction according to the purpose. The direction of the absorption axis can be, for example, either the length direction or the width direction. A polarizer having an absorption axis in the length direction has the advantage of excellent manufacturing efficiency. A polarizer having an absorption axis in the width direction has the advantage of being able to be stacked with a phase difference film having a slow axis, for example, in the length direction in a so-called roll-to-roll manner. In one embodiment, the absorption axis is substantially parallel to the length direction or the width direction, and the two ends of the polarizer are slit-processed in a manner parallel to the length direction. If this structure is used, a plurality of polarizers having a non-polarized portion and an absorption axis in an appropriate direction can be easily manufactured by cutting operations based on the end faces of the polarizer.

[0066] The polarizer provided for the imaging step may also have a protective layer formed on at least one side thereof. Specifically, any appropriate protective layer (resin film) may also be laminated on one or both sides of the polarizer. Specific examples of the resin film include: the resin substrate and surface protective film used in the production of the polarizer described in Item B and the formation of the non-polarizing portion; the protective film, phase difference film, and separator that protect the polarizer and together constitute the polarizing plate. In one embodiment, the polarizer provided for the imaging step may also be provided as a polarizing plate by laminating a protective film on at least one side thereof. In addition, in this specification, when it is referred to as a protective film only, it means a polarizer protective film, which is different from the surface protective film described in Item B (a film that temporarily protects the polarizer during operation).

[0067] A-2. Video

[0068] In the photographing step, light is irradiated from one side of the polarizer (a laminate of a polarizer and a resin film in the case of being laminated with a resin film) having the above-mentioned non-polarizing portion, and the reflected light from the polarizer is photographed. In other words, light is irradiated from one side of the polarizer (a laminate of a polarizer and a resin film), and the light irradiation surface of the polarizer (a laminate of a polarizer and a resin film) is photographed. By adopting reflected illumination like this, the photographing unit and the lighting unit can be arranged on one side of the polarizer, so it can help save space in the manufacturing line. In addition, by adopting reflected illumination, the polarizer cut to a specified size can be appropriately photographed on the conveyor line. In addition, in this specification, "reflected light from the polarizer" refers to not only the light reflected on the surface of the polarizer, but also the light reflected on the back side of the polarizer after passing through the polarizer, which can be called "reflected light of the irradiated light irradiated to the polarizer", and the details will be described later.

[0069] Figure 2 1 is a schematic diagram for explaining the imaging step in the first embodiment of the present invention. In the first embodiment, a polarizing plate 100 having a non-polarizing portion (in the example shown in the figure, a polarizing plate 300 consisting of a polarizing plate 100, a protective film 110 laminated on one side thereof, and a protective film 120 laminated on the other side) is input into an inspection device 400a via a conveyor line 600, light is irradiated from an oblique illumination unit 410 to one side of the polarizing plate 100 (polarizing plate 300), and a camera unit 430 captures reflected light from the polarizing plate 100 (polarizing plate 300).

[0070] Oblique illumination unit 410 irradiates light to polaroid 100 from oblique direction. A part of the light irradiated to the polaroid with non-polarized portion is reflected on the polaroid surface. On the other hand, another part of the irradiated light can be reflected through the polaroid, utilizing transmission line 600, diffusion plate 470, etc. on the back side of the polaroid. Therefore, more reflected light than other parts can be obtained in the non-polarized portion. Therefore, by shooting the irradiated surface of the light of the polaroid, the image of the non-polarized portion can be obtained, thereby the shape and / or characteristic (for example, transmittance) of the non-polarized portion can be properly evaluated. In addition, it is also possible to be different from the illustrated example, in the case of different resin films stacked respectively on both sides of the polaroid, irradiate light to any one face of the polaroid.

[0071] The irradiation angle θ of light is preferably 50° to 80°, and more preferably 70° to 80°. By irradiating light at this irradiation angle, the contrast between the non-polarized portion and other portions can be increased.

[0072] Any appropriate light source can be used to form the oblique illumination unit 410. The light source can be a white light source or a monochromatic light source. Specific examples of the light source include a fluorescent lamp, a halogen lamp, a metal halide lamp, and an LED.

[0073] The shape of the oblique illumination unit 410 can be any appropriate shape. For example, it can be planar, linear, annular, etc. Preferably, the oblique illumination unit is annular, because it has the following advantages: it can evenly illuminate the surface of the polarizing plate and it is not easy to cast a shadow. Alternatively, the oblique illumination unit can also be composed of a plurality of planar or linear light sources arranged in different directions (for example, the oblique illumination unit can be composed of four linear light sources arranged at azimuth angles of 0°, 90°, 180°, and 270°).

[0074] Typically, the imaging unit 430 is a camera configured using a lens and an image sensor. Either a CCD image sensor or a CMOS image sensor can be used as the image sensor.

[0075] The number of pixels of the image sensor is preferably 2000 dpi or more, and more preferably 4000 dpi to 6000 dpi. In addition, by using an image sensor having such a number of pixels, a high-quality image can be captured, and thus inspection can be performed with excellent accuracy.

[0076] The imaging unit 430 captures the reflected light from the polarizing plate 100 (polarizing plate 300 ), and the obtained image is sent to the image processing unit 440 connected to the imaging unit 430 as an electric signal.

[0077] A diffusion plate 470 can be arbitrarily provided on the side of the polarizer 100 (polarizer 300) that is not irradiated with light. By providing the diffusion plate 470, the contrast between the non-polarized portion and the other portions can be increased. Different from the example shown in the figure, the diffusion plate 470 can also be provided between the polarizer 100 (polarizer 300) and the conveyor line 600.

[0078] Figure 3 1 is a schematic diagram for explaining the imaging step in the second embodiment of the present invention. In the second embodiment, light is irradiated from the coaxial incident illumination unit 420 to one side of the polarizer 100 (in the example shown, the polarizer 300) input to the inspection device 400b by the conveyor line 600, and the imaging unit 430 captures the reflected light from the polarizer 100 (polarizer 300).

[0079] The coaxial falling illumination unit 420 irradiates light vertically to the polarizer 100 (polarizer 300) in such a way that the optical axis of the camera unit 430 is coaxial or parallel to the optical axis of the irradiated light. By irradiating light to the polarizer 100 (polarizer 300) using coaxial falling illumination, the non-polarized portion generates more regular reflected light than other portions in the same manner as described above. Therefore, by shooting the regular reflected light, a high-contrast image can be obtained. In addition, the image blurring and the reflection of the illumination caused by the mixing of regular reflection and diffuse reflection can be prevented, so a clear image can be obtained. In addition, as described above, due to the thickness difference between the non-polarized portion and other portions, bubbles will be generated between structural members such as the polarizer and the protective film, but by irradiating light to the laminate of the polarizer and other structural members using coaxial falling illumination and shooting its reflected light, the presence or absence of the bubbles can be properly confirmed.

[0080] The coaxial epi-illumination unit 420 can be formed using a light source, a semi-transparent mirror or a beam splitter, an optical lens (telecentric lens), etc. The coaxial epi-illumination unit may also be a pseudo-coaxial epi-illumination unit that uses a semi-transparent mirror or a beam splitter instead of an optical lens to make the optical axis of the irradiation light parallel to the optical axis of the camera lens. The structure of the coaxial epi-illumination unit or the pseudo-coaxial epi-illumination unit is well known to those skilled in the art, so a detailed description thereof is omitted.

[0081] The specific example of the light source, the imaging unit 430, and the configuration of the diffusion plate (not shown) are the same as those described for the inspection device 400a.

[0082] The second embodiment can be performed in the same manner as the first embodiment except that light is irradiated by coaxial epi-illumination.

[0083] Figure 4 : is a schematic diagram for explaining the imaging step in the third embodiment of the present invention. In the third embodiment, an inspection device 400c is used to perform imaging of a polarizing plate having a non-polarizing portion. The inspection device 400c comprises: a first lighting unit 410 and a second lighting unit 420, which are arranged on one side of a polarizing plate 100 (in the example of the figure, a polarizing plate 300) having a non-polarizing portion, and irradiate light to the polarizing plate 100; an imaging unit 430, which captures the reflected light of the light irradiated to the polarizing plate 100 from the first lighting unit 410 or the second lighting unit 420; an image processing unit 440, which is connected to the imaging unit and analyzes and processes the image captured by the imaging unit; an illumination switching unit 450, which switches between the light irradiation by the first lighting unit 410 and the light irradiation by the second lighting unit 420; and an optical axis control unit 460, which controls the angle of the optical axis of the light emitted from the second lighting unit 420 and the reflected light from the polarizing plate 100.

[0084] The first lighting unit 410 is an oblique lighting unit, and can be configured in the same structure as the oblique lighting unit 410 in the above-mentioned inspection device 400a. Figure 5A As shown, the first lighting unit 410 irradiates light to the polarizing plate 100 (polarizing plate 300 ) from an oblique direction, similarly to the oblique lighting unit 410 in the inspection device 400 a .

[0085] The second illumination unit 420 is a coaxial incident illumination unit, and can be the same structure as the coaxial incident illumination unit 420 in the above-mentioned inspection device 400b. Figure 5B As shown, the second illumination unit 420, like the coaxial epi-illumination unit 420 in the inspection device 400b, irradiates light perpendicularly to the polarizer 100 (polarizing plate 300) so that the optical axis of the imaging unit 430 is coaxial or parallel to the optical axis of the irradiated light.

[0086] The first lighting unit 410 and the second lighting unit are connected to the lighting switching unit 450, and are configured to be switchable by the lighting switching unit 450. By switching between oblique illumination and coaxial falling illumination according to the purpose of the inspection, each inspection item can be evaluated with higher accuracy. Specifically, by using oblique illumination and coaxial falling illumination respectively according to the purpose of the inspection, it is possible to appropriately take into account the evaluation of the shape and / or characteristics (for example, transmittance) of the non-polarized portion and the inspection of defects (for example, bubbles) at the peripheral portion of the non-polarized portion. The lighting switching unit 450 is connected to the image processing unit 440, for example, and switches the lighting according to a signal from the image processing unit 440. Alternatively, the lighting is switched according to a predetermined setting.

[0087] The structures of the imaging unit 430 and the diffusion plate (not shown) are the same as those of the inspection device 400a.

[0088] The optical axis control unit 460 controls the angle of the optical axis of the light emitted from the second lighting unit 420 and the reflected light from the polarizing plate 100. By providing the optical axis control unit 460, space can be saved. The optical axis control unit is formed using a reflector, a prism, etc. to form a desired optical path. In the case where there is sufficient space, the optical axis control unit can also be omitted.

[0089] In the illustrated example, the cut single polarizing film is photographed while being transported by a conveyor line, but it is also possible to photograph while transporting a long strip of polarizing film in the length direction, which is different from the illustrated example. In the photographing step, the photographing unit can be fixed to photograph, or the photographing unit can be moved in the length direction in accordance with the transport speed of the polarizing film. In addition, the photographing unit can also be moved in the width direction to photograph.

[0090] When the polarizer is in the shape of an elongated strip and has non-polarizing portions arranged at predetermined intervals in the length direction and / or the width direction, it is possible to obtain an image of all the non-polarizing portions or an image of only a portion of the non-polarizing portions. For example, it is also possible to obtain an image of only the non-polarizing portions selected arbitrarily or according to a specific regularity.

[0091] A-3. Inspection

[0092] In the inspection step, the non-polarization part is inspected based on the image obtained by the imaging step. Specifically, the image processing unit 440 is used to analyze the image data sent from the imaging unit 430 as an electrical signal to inspect the shape, characteristics, etc. of the non-polarization part. As specific examples of inspection items, the shape accuracy (in the case of a circle, roundness, etc.), the thickness of the contour, the steepness of the contour, the transmittance, etc. of the non-polarization part can be listed. The image processing unit 440 is preferably capable of detecting the non-polarization part that does not meet the prescribed benchmark as a defective formation.

[0093] For example, the above-mentioned image data can be analyzed based on brightness information. Specifically, in the image data (reflected light image data) obtained by oblique illumination, the brightness of the non-polarized portion is relatively high, and the brightness of other parts is low, so a threshold value can be set for the contrast in the obtained image data, and a high-brightness portion with a contrast higher than the threshold value is determined as a non-polarized portion. In the image data (reflected light image data) obtained by coaxial falling illumination, the brightness of the non-polarized portion is also relatively high, and the brightness of other parts is low, so a threshold value can be set for the contrast in the obtained image data, and a high-brightness portion with a contrast higher than the threshold value is determined as a non-polarized portion. In addition, the contour of the determined non-polarized portion can be divided into 180 equal parts to obtain the distance from the center to each contour portion, and the value obtained by subtracting the minimum value from the maximum value of the 180 distance data obtained is used as an evaluation benchmark for roundness. For example, when the obtained value is below a specified value, the roundness of the non-polarized portion can be evaluated as good. Furthermore, the contour of the non-polarized portion can be divided into 180 equal parts to obtain an approximate ellipse as a reference, and the maximum value of the distance from the approximate ellipse to the actual contour in each area obtained after the 180-degree division is used as an evaluation standard for the thickness of the contour. For example, when the maximum value obtained is below a specified value, the thickness of the contour of the non-polarized portion can be evaluated as good. Furthermore, the average brightness of the non-polarized portion and other parts (the peripheral part of the non-polarized portion) can be obtained, and the average brightness of the non-polarized portion is set to 100%, and the average brightness of the other parts is set to 0%, and the maximum value of the distance from the center of the non-polarized portion to each contour obtained after the 180-degree division when binarized into black and white at 10% and 20% brightness is used as an evaluation standard for the steepness of the contour. For example, when the maximum value obtained is below a specified value, the steepness of the contour of the non-polarized portion can be evaluated as good.

[0094] Regarding the transmittance of the non-polarizing portion, for example, the average brightness value, the maximum brightness value, and the minimum brightness value of the non-polarizing portion can be obtained, and the transmittance of the non-polarizing portion can be evaluated based on the value obtained by dividing the maximum brightness value by the average brightness value or the value obtained by dividing the minimum brightness value by the average brightness value. Specifically, when the non-polarizing portion has a residual polarization function and the transmittance is low, the obtained value also becomes low.

[0095] The inspection device 400 (substantially, the image processing unit 440) can be connected to the marking device 500 as needed. When the inspection device 400 (substantially, the image processing unit 440) detects that the non-polarizing portion is poorly formed, a poor detection signal is sent to the marking device 500. In the case of inspecting a long strip of polarizing film, the marking device 500 marks the area of ​​the polarizing film that is cut to include the poorly formed non-polarizing portion based on the signal. The marked area can be easily excluded as a poor polarizing film after cutting. On the other hand, in the case of inspecting a single-piece polarizing film (single-piece polarizing plate) after cutting, the marking device 500 marks the polarizing film including the poorly formed non-polarizing portion based on the signal. As markings, marking with a marker pen and laser marking can be listed.

[0096] [B. Method for producing polarizing plate]

[0097] The method for manufacturing a polarizing plate having a non-polarizing portion of the present invention comprises: forming a non-polarizing portion in a polarizing plate; and inspecting the polarizing plate having the non-polarizing portion by the above-mentioned inspection method.

[0098] B-1. Step of forming non-polarizing portion

[0099] Typically, the polarizer is obtained by subjecting the above-mentioned resin film (typically, the PVA-based resin film) to various treatments such as swelling treatment, stretching treatment, dyeing treatment using the above-mentioned dichroic substance, crosslinking treatment, cleaning treatment, and drying treatment. When various treatments are applied, the resin film may also be a resin layer formed on a substrate. In this case, for example, the polarizer can be prepared in the following manner: a PVA-based resin solution is applied to a resin substrate and dried to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of a resin substrate and a PVA-based resin layer; the laminate is stretched and dyed, and the PVA-based resin layer is used as a polarizer. The obtained resin substrate / polarizer laminate can be used directly (that is, the resin substrate can be used as a protective layer of the polarizer), or a protective film can be bonded to the polarizer surface of the resin substrate / polarizer laminate, and then the resin substrate is peeled off to form a polarizer / protective film laminate.

[0100] The non-polarizing portion is formed at a specified position of the polarizer. In the case where the polarizer is formed by a resin layer formed on a substrate, typically, a laminate of a resin substrate / polarizer or a laminate of a polarizer / protective film is provided for the formation of the non-polarizing portion. In the case where the polarizer is a single resin film, typically, a laminate of a protective film / polarizer or a polarizer alone is provided for the formation of the non-polarizing portion. Below, the formation of the non-polarizing portion is specifically described. As a representative example, an example of the following situation is described: in a laminate of a protective film / polarizer, a non-polarizing portion is formed in a polarizer by decolorizing using a chemical treatment (hereinafter also referred to as a chemical decolorization treatment). The same process can also be applied to polarizers of other structures (for example, a polarizer as a single resin film), which is obvious to those skilled in the art. In addition, the formation of the non-polarizing portion by chemical decolorization treatment is not necessarily performed after the production of the polarizer is completed. Specifically, a resin film (for example, a resin film that exhibits absorption dichroism at one wavelength between 380nm and 780nm and has the monomer transmittance and / or polarization degree described in item A) can also be subjected to bleaching by chemical treatment to form a non-polarizing portion, and then the remaining treatment is performed as needed, wherein at least the resin film is subjected to stretching treatment and dyeing treatment from the various treatments used to form a polarizer (swelling treatment, stretching treatment, dyeing treatment, cross-linking treatment, cleaning treatment, drying treatment, etc.) to make the resin film in a state that can be used as a polarizer.

[0101] In chemical decolorization treatment, such as Figure 6 As shown, a surface protection film having through holes arranged in a prescribed pattern is bonded to the surface of the polarizer side of the above-mentioned laminate by a roll-to-roll method. In this specification, "roll-to-roll" refers to bonding while aligning the length directions of each other while conveying a roll-shaped film. The surface protection film having through holes is bonded to the polarizer by any appropriate adhesive in a peelable manner. By using a surface protection film having through holes, a decolorization treatment can be performed by immersing it in a decolorizing solution, so that a non-polarized portion can be formed with a very high manufacturing efficiency. In addition, for convenience, the surface protection film having through holes is sometimes referred to as a first surface protection film.

[0102] As described above, the first surface protection film has through holes arranged in a prescribed pattern. The position of the through hole is corresponding to the position of the non-polarized portion of the polarizer. The through hole can have any appropriate shape. The shape of the through hole corresponds to the top view shape of the non-polarized portion to be formed. For example, the through hole can be formed by mechanical punching (e.g., punching, Thomson knife punching, plotter, water jet) or removing a prescribed portion of the film (e.g., laser ablation or chemical dissolution).

[0103] As the forming material of the above-mentioned first surface protection film, ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polyethylene and polypropylene, polyamide resins, polycarbonate resins, and their copolymer resins can be listed. Ester resins (especially polyethylene terephthalate resins) are preferred. This is because the elastic modulus is high enough, for example, even if tension is applied during transportation and / or bonding, deformation of the through hole is not likely to occur. Typically, the thickness of the first surface protection film is 20μm to 250μm, preferably 30μm to 150μm.

[0104] Preferably, the second surface protection film is bonded to the surface of the protective film side of the above-mentioned laminate by a roll-to-roll method. The second surface protection film is bonded to the protective film in a peelable manner by any appropriate adhesive. By using the second surface protection film, the above-mentioned laminate (polarizer / protective film) can be appropriately protected in the decolorization process using immersion. The second surface protection film can use a film that is the same as the first surface protection film except that no through holes are provided.

[0105] Then, if Fig. 7A and 7B As shown in FIG. 1 , a laminate 200 of a first surface protection film 150 / polarizer 100 / protective film 120 / second surface protection film 160 having a through hole 152 is subjected to a chemical decolorization treatment. Typically, the chemical decolorization treatment includes contacting the laminate 200 with an alkaline solution as a decolorizing solution. When iodine is used as a dichroic substance, the iodine content of the contact portion can be easily reduced by contacting a desired portion of the resin film with the alkaline solution.

[0106] The contact between the laminate and the alkaline solution can be carried out by any appropriate means. As a representative example, the laminate can be immersed in the alkaline solution, or the alkaline solution can be applied or sprayed on the laminate. Immersion is preferred. This is because it can be as Figure 7B As shown, since the decolorization process is performed while the stacked body 200 is conveyed, the production efficiency is significantly high.

[0107] In one embodiment, after the alkaline solution contacts the polarizer, it is removed from the polarizer by any appropriate means. According to this embodiment, for example, it is possible to more reliably prevent the decrease in the transmittance of the non-polarized portion associated with the use of the polarizer. Specific examples of the method for removing the alkaline solution include cleaning, wiping with a rag, etc., suction removal, natural drying, heating drying, air drying, reduced pressure drying, etc. The alkaline solution is preferably cleaned. As the cleaning liquid used in the cleaning, for example, water (pure water), alcohols such as methanol and ethanol, and mixed solvents thereof, etc. can be listed. Water is preferably used. The number of cleaning times is not particularly limited and can be performed multiple times. In the case of removing the alkaline solution by drying, the drying temperature is, for example, 20°C to 100°C.

[0108] Preferably, after contacting with the alkaline solution, the alkali metal and / or alkaline earth metal contained in the resin film is reduced at the contact portion contacting the alkaline solution. By reducing the alkali metal and / or alkaline earth metal, a non-polarizing portion with excellent dimensional stability can be obtained. Specifically, in a humidified environment, the shape of the non-polarizing portion formed by contacting with the alkaline solution can also be maintained as it is.

[0109] As the above-mentioned reduction method, the following method is preferably used: the contact part that contacts the alkaline solution is contacted with an acidic solution. According to this method, the alkali metal and / or alkaline earth metal can be efficiently transferred to the acidic solution to reduce its content. The contact with the acidic solution can be carried out after removing the above-mentioned alkaline solution, and it can also be carried out without removing the alkaline solution.

[0110] Any suitable acidic compound can be used as the acidic compound contained in the above-mentioned acidic solution. As the acidic compound, for example, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid, and organic acids such as formic acid, oxalic acid, citric acid, acetic acid, and benzoic acid can be listed. The acidic compound contained in the acidic solution is preferably an inorganic acid among them, and is more preferably hydrochloric acid, sulfuric acid, and nitric acid. These acidic compounds can be used alone or in combination of two or more.

[0111] As the solvent of the acidic solution, water or ethanol is preferably used. The concentration of the acidic solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, and more preferably 0.1N to 2.5N. The liquid temperature of the acidic solution is, for example, 20°C to 50°C. The contact time of the acidic solution is, for example, 5 seconds to 5 minutes. In addition, the contact method of the acidic solution can be the same as the contact method of the alkaline solution. In addition, the acidic solution can be removed from the polarizer. The removal method of the acidic solution can be the same as the removal method of the alkaline solution.

[0112] In addition, the surface protection film is peeled off and removed at any appropriate timing, for example, after contact with the alkaline solution.

[0113] The chemical decolorization treatment has been described above, but as described above, the non-polarizing portion can also be formed by laser irradiation or mechanical punching.

[0114] B-2. Polarizing Plate Production Steps

[0115] Typically, the method for manufacturing a polarizing plate of the present invention further includes: using a polarizer having a non-polarizing portion to produce a polarizing plate having a structure as a final product. As described above, in the case where the polarizer is formed by a resin layer formed on a substrate, typically, the polarizer having a non-polarizing portion is laminated with a resin substrate or a protective film on one side thereof. These laminates can be used directly as polarizing plates. On the other hand, these laminates can be further supplied to this step to produce a polarizing plate having any appropriate structure as a final product by peeling off other structural components such as the resin substrate and the laminated protective film. Similarly, in the case where the polarizer having a non-polarizing portion is composed of a single resin film, by sequentially laminating other structural components such as a protective film on one side or both sides thereof according to the purpose, a polarizing plate having any appropriate structure as a final product can be obtained.

[0116] Figure 8 This is a schematic cross-sectional view of a polarizing plate that can be preferably produced by this step. The polarizing plate can be in the shape of a long strip, similarly to the polarizer. The polarizing plate 300 has a polarizer 100 and protective films 110 and 120 disposed on both sides of the polarizer 100. In the example shown in the figure, protective films are disposed on both sides of the polarizer, but the protective film can also be disposed only on one side. As materials for forming the protective film, for example, cellulose resins such as diacetate cellulose and triacetate cellulose, (meth) acrylic resins, cycloolefin resins, polypropylene and other olefin resins, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and their copolymer resins can be listed. Depending on the purpose and the desired structure, one of the protective films 110 and 120 can also be omitted.

[0117] Typically, the thickness of the protective film is 10 μm to 100 μm. Typically, the protective film is laminated on the polarizer by means of an adhesive layer (specifically, an adhesive layer, an adhesive layer). Typically, the adhesive layer is formed of a PVA-based adhesive or an active energy ray-curable adhesive. Typically, the adhesive layer is formed of an acrylic adhesive. In one embodiment, the thickness of the protective film is 80 μm or less. By using a protective film of such thickness, it is possible to contribute to the thinning of the obtained polarizing plate. On the other hand, it is believed that when a long strip of polarizing plate obtained by placing a protective film of such thickness on the other side of a polarizer having a concave portion formed on one side is wound into a roll, it is easy to produce the above-mentioned concave portion being transferred to the protective film as a winding mark and other undesirable conditions caused by the thickness difference. In this embodiment, the benefit of reducing the thickness difference of the concave portion can be significantly obtained.

[0118] From a practical point of view, the polarizing plate 300 has an adhesive layer 130 as the outermost layer. Typically, the adhesive layer 130 is the outermost layer on the image display device side. A removable separator 132 is temporarily attached to the adhesive layer 130 to protect the adhesive layer before actual use and to enable the roll to be formed.

[0119] Depending on the purpose, the polarizing plate 300 may also have any appropriate optical functional layer. As representative examples of the optical functional layer, a phase difference film (optical compensation film) and a surface treatment layer can be listed. For example, a phase difference film (not shown) can be arranged between the protective film 120 and the adhesive layer 130. The optical properties of the phase difference film (for example, refractive index ellipsoid, in-plane phase difference, thickness direction phase difference) can be appropriately set according to the purpose, the characteristics of the image display device, etc. The phase difference film can also serve as a protective film. In this case, the protective film 120 can be omitted. Conversely, the protective film 120 may also have an optical compensation function (that is, it may also have an appropriate refractive index ellipsoid, in-plane phase difference and thickness direction phase difference corresponding to the purpose).

[0120] The surface treatment layer can be disposed outside the protective film 110 (not shown). Representative examples of the surface treatment layer include a hard coating layer, an anti-reflection layer, and an anti-glare layer. Instead of providing the surface treatment layer, the surface of the protective film 110 may be subjected to the same surface treatment.

[0121] Typically, the polarizing plate having the non-polarizing portion obtained through the non-polarizing portion forming step is in a long strip shape, and therefore the protective film, retardation film, etc. can be laminated by a so-called roll-to-roll method.

[0122] B-3. ​​Polarizing Plate Cutting Steps

[0123] The method for manufacturing a polarizing plate of the present invention may further include: cutting the long strip of polarizing plate into a desired size. The cutting may be performed by cutting, punching, etc. Preferably, the long strip of polarizing plate is cut into a size corresponding to the image display device to be installed, and has a non-polarizing portion at a position corresponding to the camera portion of the image display device when installed in the image display device.

[0124] B-4. Polarizer Inspection Procedure

[0125] The step of inspecting the polarizer having the non-polarizing portion by the inspection method described in item A can be performed at any appropriate stage after forming the non-polarizing portion. In all the steps of the manufacturing method of the present invention, the step of inspecting the polarizer can be performed only once or multiple times.

[0126] In one embodiment, the inspection step of the polarizer can be performed at any appropriate stage in the production step of the polarizer described in item B-2 or after completing the step. For example, a polarizer having a structure as a final product can also be produced, followed by the inspection of the polarizer. In addition, for example, the polarizer can be inspected after a phase difference film and / or a protective film are stacked on the polarizer side of the laminate of the protective film / polarizer, followed by a stacked surface treatment layer, an adhesive layer, etc. By inspecting the polarizer at this stage, the following long strip of polarizer can be obtained: having a structure as a final product, and being able to be identified by markings, etc. as being cut into a region of a polarizer (a single polarizer) having a poorly formed non-polarized portion and / or bubbles. The polarizer is cut in a subsequent cutting step, and the polarizer (a single polarizer) having a poorly formed non-polarized portion can be easily excluded.

[0127] In another embodiment, the inspection step of the polarizer can be performed after the cutting step of the polarizer described in item B-3. By providing the polarizer obtained by cutting for inspection, it is easy to exclude polarizers with poorly formed non-polarized parts and / or bubbles around the non-polarized parts. In addition, the above inspection method adopts a reflected lighting method for photographing the irradiated surface of the polarizer, so it is particularly useful in the inspection of polarizers (single polarizers) placed on a conveyor line such as a conveyor.

[0128] In another embodiment, the step of inspecting the polarizer can be performed at any appropriate stage in the step of forming the non-polarizing portion described in B-1 or after the step is completed. Figure 7BTo illustrate a specific example of forming a non-polarized portion by chemical decolorization, the inspection step can be performed at the following stages: a stage (a) after the contact treatment with the alkaline solution is completed; a stage (b) after the cleaning is completed after the contact with the alkaline solution; a stage (c) after the contact with the alkaline solution is completed; and a stage (d) after the cleaning is completed after the contact with the alkaline solution. Figure 7B The following are the steps (c) in which contact with the treatment solution (or the acidic solution) is completed; and / or (d) in which cleaning is completed after contact with the treatment solution. When the inspection step is performed at this stage and the proportion of non-polarizing portions whose shapes and / or characteristics are judged to be poor exceeds the allowable range, it is suspected that an adverse condition has occurred in the previous treatment. Therefore, by confirming and adjusting various treatment conditions such as the concentration of alkaline solutions, acidic solutions, etc., immersion time, etc., the adverse condition can be discovered as early as possible and resolved. As a result, the step of forming the non-polarizing portion can be appropriately controlled, thereby helping to improve the manufacturing efficiency of the polarizer with the non-polarizing portion.

[0129] When the non-polarizing portion is formed by chemical decolorization as described in B-1, the polarizing plate is typically subjected to chemical decolorization in a state where a surface protection film having through holes (also referred to as a first surface protection film) is bonded to one side of the polarizing plate, and after the non-polarizing portion is formed (for example, Figure 7B In the stage (d) of the inspection of the polarizing plate, the first surface protection film is peeled off. Therefore, the polarizing plate provided for the inspection step of the polarizing plate can be in a state where the first surface protection film 150 is laminated on one side ( Fig. 7A ), or the first surface protection film 150 may be peeled off and removed (not shown). Similarly, the polarizing film provided for the polarizing film inspection step may be in a state where the second surface protection film 160 is laminated on the other side ( Fig. 7A ), or the second surface protection film 160 may be in a state where it is peeled off and removed (not shown).

[0130] [C. Uses of polarizing plates]

[0131] The polarizing plate obtained by the manufacturing method described in item B can be appropriately used in an image display device. The image display device includes the above-mentioned polarizing plate cut into a specified size. As the image display device, for example, a liquid crystal display device and an organic EL device can be listed. Specifically, the liquid crystal display device includes a liquid crystal cell and a liquid crystal panel including the above-mentioned polarizing plate arranged on one side or both sides of the liquid crystal cell. The organic EL device includes an organic EL panel having the above-mentioned polarizing plate arranged on the visible side. The polarizing plate is arranged so that the non-polarized portion of the polarizer corresponds to the camera portion of the image display device.

[0132] Industrial Applicability

[0133] For example, the inspection method of the present invention can be suitably used when manufacturing polarizing plates included in mobile phones such as smartphones, and image display devices with cameras (liquid crystal display devices, organic EL devices) such as notebook PCs and tablet PCs.

Claims

1. A method for inspecting a polarizer having a non-polarizing portion, the method comprising: an imaging step of irradiating light from one side of the polarizing plate and photographing reflected light from the polarizing plate; as well as an inspection step of inspecting a non-polarizing portion of the polarizing plate based only on an image obtained by photographing reflected light from the polarizing plate, In this imaging step, the light irradiation is performed by coaxial epi-illumination, or the light irradiation is performed by switching between oblique illumination and coaxial epi-illumination.

2. The inspection method according to claim 1, characterized in that: The polarizing plate has a predetermined size for being mounted on an image display device of a predetermined size.

3. The inspection method according to claim 1, characterized in that: The polarizing plate is in a long strip shape and has non-polarizing portions arranged at predetermined intervals in the longitudinal direction and / or the width direction.

4. The inspection method according to any one of claims 1 to 3, characterized in that: The polarizing plate is composed of a resin film containing a dichroic substance. A dichroic material low concentration portion in the resin film, where the content of the dichroic material is relatively low, is provided as the non-polarizing portion.

5. The inspection method according to any one of claims 1 to 3, characterized in that: A protective layer is formed on at least one side of the polarizing plate provided in the imaging step.

6. A method for manufacturing a polarizing plate, comprising: forming a non-polarizing portion in the polarizer; as well as The polarizing plate having a non-polarizing portion is inspected by the inspection method according to any one of claims 1 to 5.

7. An inspection device for a non-polarizing portion of a polarizer, comprising: a coaxial epi-illumination section for irradiating light toward one side of the polarizing plate having the non-polarizing section; An imaging unit that captures reflected light emitted from the coaxial epi-illumination unit and reflected from the polarizing plate; and The image processing unit is connected to the imaging unit and performs analysis processing only on the image obtained by imaging the reflected light from the polarizing plate.

8. An inspection device for a non-polarizing portion of a polarizer, comprising: a first lighting unit and a second lighting unit, wherein the first lighting unit and the second lighting unit irradiate light toward one side of the polarizing plate having the non-polarizing portion; an imaging unit that captures reflected light emitted from the first illumination unit or the second illumination unit and reflected from the polarizing plate; An image processing unit connected to the camera unit and analyzing and processing only the image obtained by the camera unit taking the reflected light from the polarizer; as well as an illumination switching section that switches between light irradiation by the first illumination section and light irradiation by the second illumination section, Wherein, the first lighting unit is an oblique lighting unit, The second illumination unit is a coaxial epi-illumination unit.

Images