JP6807637B2 - Polarizer inspection method and polarizing plate manufacturing method - Google Patents

Description

The present invention relates to a method for inspecting a polarizer having a non-polarizing portion and a method for manufacturing a polarizing plate.

Some image display devices such as mobile phones and notebook personal computers (PCs) are equipped with internal electronic components such as cameras. Various studies have been made for the purpose of improving the camera performance of such an image display device (for example, Patent Documents 1 to 7). However, with the rapid spread of smartphones and touch panel type information processing devices, further improvement in camera performance and the like is desired. Further, in order to cope with the diversification and high functionality of the shape of the image display device, a polarizing plate having a partial polarization performance is required. In order to realize these demands industrially and commercially, it is desired to manufacture an image display device and / or its parts at an acceptable cost, and various studies are made to establish such a technique. Matters are left.

Japanese Unexamined Patent Publication No. 2011-81315 Japanese Unexamined Patent Publication No. 2007-241314 U.S. Patent Application Publication No. 2004/0212555 Korean Publication No. 10-2012-0118205 Korean Patent No. 10-1293210 Japanese Unexamined Patent Publication No. 2012-137738 U.S. Patent Application Publication No. 2014/0118826

When a non-polarizing portion is provided in the polarizer and the non-polarizing portion corresponds to a camera unit or the like of an image display device, the non-polarizing portion is also designed to be very small with the recent miniaturization of the image display device. Therefore, it is required to efficiently form the non-polarized portion with high accuracy so as to obtain a desired shape and characteristics.

According to the present invention, there is provided a method for inspecting a polarizer having a non-polarizing portion. The inspection method includes an imaging step of irradiating light from one side of a polarizing element having a non-polarizing portion and imaging the light transmitted through the polarizing element from the other side, and the polarizing element based on the obtained image. Including an inspection step of inspecting the non-polarized part of the light.
In one embodiment, the polarizer is elongated and has unpolarized portions arranged at predetermined intervals in the elongated direction and / or the width direction.
In one embodiment, the imaging step is performed while transporting the polarizer in the elongated direction.
In one embodiment, the polarizer is composed of a resin film containing a dichroic substance, and the low concentration portion of the dichroic substance having a relatively low content of the dichroic substance in the resin film is described above. It is a non-polarized part.
In one embodiment, a protective layer is formed on at least one side of the polarizer used in the imaging step.
In one embodiment, the irradiation angle of light on the polarizer in the imaging step is 89 ° to 91 °.
According to another aspect of the present invention, there is provided a method for producing a polarizing plate. The manufacturing method includes forming a non-polarizing portion on the polarizer and inspecting the polarizer having the non-polarizing portion by the above inspection method.
According to yet another aspect of the present invention, an apparatus for inspecting a non-polarized portion of a polarizer is provided. The inspection device includes a light source unit that irradiates one side of a polarizer having a non-polarizing unit, an imaging unit that emits light emitted from the light source unit and transmits light transmitted through the polarizer, and an imaging unit. It is provided with an image processing unit which is connected to the image processing unit and analyzes an image captured by the imaging unit.

In the present invention, light is irradiated from one side of a polarizer having a non-polarizing portion, and the transmitted light is imaged from the other side, and the shape, characteristics, etc. of the non-polarizing portion are determined based on the obtained image. evaluate. According to the inspection method of the present invention, the shape, characteristics, etc. of the non-polarized portion can be efficiently evaluated with excellent accuracy, and as a result, only a polarizer having a non-polarized portion that satisfies the desired characteristics and has excellent shape accuracy can be evaluated. Since it can be mounted on an image display device, an image display device having excellent camera performance can be efficiently obtained.

It is a schematic perspective view of the polarizer which can be suitably used for the inspection method of this invention. It is the schematic explaining one Embodiment of the inspection method of this invention. It is the schematic explaining another embodiment of the inspection method of this invention. It is a schematic perspective view explaining the bonding of a polarizer and a surface protective film having a through hole in the formation of a non-polarized part. It is the schematic sectional drawing of the laminated body which can be subjected to a chemical decolorization treatment. It is the schematic explaining an example of the method of forming a non-polarized part by a chemical decolorization treatment. It is the schematic sectional drawing of the polarizing plate which can be obtained by the manufacturing method of this invention.

[A. Inspection method]
The present invention relates to a method for inspecting a polarizer having a non-polarizing portion. The inspection method of the present invention includes an imaging step of irradiating light from one side of a polarizing element having a non-polarizing portion and imaging the light transmitted through the polarizing element from the other side, and the polarizing element based on the image. Including an inspection step of inspecting the non-polarized part of the light. Hereinafter, the inspection method of the present invention will be described.

A-1. Polarizer with non-polarizing section FIG. 1 is a schematic perspective view of a polarizer that can be suitably used in the inspection method of the present invention. The polarizer 100 has an elongated shape, and is typically wound in a roll shape as shown in FIG. As used herein, the term "long" means an elongated shape having a length sufficiently long with respect to the width, and for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to the width. Including. The polarizer 100 has non-polarizing portions 10 arranged at predetermined intervals (that is, in a predetermined pattern) in the longitudinal direction and / or the width direction. The arrangement pattern of the non-polarizing unit 10 can be appropriately set according to the purpose. Typically, the non-polarizing unit 10 is cut to a predetermined size (for example, cut or punched in the elongated direction and / or the width direction) in order to attach the polarizer 100 to an image display device of a predetermined size. It is arranged at a position corresponding to the camera unit of the image display device. Therefore, when cutting only one size of a polarizer (polarizer piece) from one elongated polarizer 100, the non-polarizing section 10 is used in the elongated direction and the width direction as shown in FIG. In either case, they can be arranged at substantially equal intervals. With such a configuration, it is easy to control the cutting of the polarizer to a predetermined size according to the size of the image display device, and the yield can be improved. Further, it is possible to suppress the variation in the position of the non-polarized portion in the cut single-wafer polarized piece. In addition, "substantially evenly spaced in both the long direction and the width direction" means that the intervals in the long direction are evenly spaced and the intervals in the width direction are evenly spaced. The spacing in the shaku direction and the spacing in the width direction do not have to be equal. For example, when the interval in the long direction is L1 and the interval in the width direction is L2, L1 = L2 or L1 ≠ L2. When cutting a plurality of size polarizers from one elongated polarizer 100, the distance between the non-polarizing portions 10 in the elongated direction and / or the width direction is changed according to the size of the polarizer to be cut. be able to. For example, the non-polarizing portions 10 may be arranged at substantially equal intervals in the elongated direction and at different intervals in the width direction; they may be arranged at different intervals in the elongated direction and in the width direction. They may be arranged at substantially equal intervals. When the non-polarized parts are arranged at different intervals in the longitudinal direction or the width direction, the intervals of the adjacent unpolarized parts may be all different, and only a part (the interval of a specific adjacent unpolarized part) is different. You may be. Further, a plurality of regions may be defined in the elongated direction of the polarizer 100, and the spacing between the non-polarized portions 10 in the elongated direction and / or the width direction may be set for each region. The polarizer piece means a polarizer obtained by cutting a long-shaped polarizer. In the present specification, in the context, a polarizing element obtained by cutting a long-shaped polarizing element may be referred to as a polarizing element piece.

As described above, in FIG. 1, the polarizer 100 has an elongated shape, but unlike the illustrated example, in the inspection method of the present invention, a polarizing element that is not elongated, for example, is cut into a predetermined size. Polarizer pieces can be used in the same manner. Further, the polarizer may have only one non-polarizing portion.

The transmittance of the non-polarized portion (for example, the transmittance measured with light having a wavelength of 550 nm at 23 ° C.) is preferably 50% or more, more preferably 60% or more, still more preferably 75% or more. Particularly preferably, it is 90% or more. With such a transmittance, it is possible to secure the desired transparency as the non-polarized part. As a result, when the polarizer is arranged so that the non-polarizing unit corresponds to the camera unit of the image display device, it is possible to prevent an adverse effect on the shooting performance of the camera.

The non-polarizing unit 10 can be arranged in a predetermined pattern as described above, and can be in any suitable form as long as the desired optical characteristics can be obtained. In one embodiment, the non-polarized portion is a partially decolorized decolorized portion. Specifically, it is a decolorized portion formed by decolorizing a predetermined portion of the polarizer. The decolorized portion can be formed, for example, by laser irradiation or chemical treatment (eg, acid treatment, alkali treatment or a combination thereof). In another embodiment, the non-polarized portion is a through hole (typically a through hole that penetrates the polarizer in the thickness direction). Through holes can be formed, for example, by mechanical punching (eg punching, Thomson blade punching, plotters, water jets) or removal of certain portions of the polarizer (eg laser ablation or chemical dissolution).

As the plan view shape of the non-polarizing unit 10, any suitable shape can be adopted as long as it does not adversely affect the camera performance of the image display device in which the polarizer is used. Specific examples include circles, ovals, squares, rectangles, and rhombuses. By appropriately setting the shape of the through hole of the surface protective film described in the section B described later, a non-polarized portion having a desired plan view shape can be formed.

The polarizer 100 is typically composed 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.

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

The non-polarized part is preferably a decolorized part, more preferably a low concentration part having a relatively low content of the dichroic substance (specifically, the content of the dichroic substance is lower than that of other parts). Low concentration part). According to such a configuration, cracks are generated as compared with the case where the non-polarized portion is formed mechanically (for example, by a method of mechanically punching out using a Thomson blade punch, a plotter, a water jet, etc.). Quality problems such as delamination (delamination) and glue squeeze out are avoided. Further, since the content of the dichroic substance itself is low in the low-concentration part, the transparency of the non-polarized part is higher than that in the case where the dichroic substance is decomposed by laser light or the like to form the non-polarized part. Well maintained.

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

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

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

Any suitable resin can be used as the PVA-based resin that forms the PVA-based resin film. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be mentioned. Polyvinyl alcohol is obtained by saponification of polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. .. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the intended purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.

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

The thickness of the polarizer (resin film) can be set to any suitable value. The thickness is preferably 30 μm or less, more preferably 25 μm or less, still more 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, more preferably 1 μm or more. With such a thickness, a polarizer having excellent durability and optical characteristics can be obtained. The thinner the polarizer (resin film), the better the non-polarized portion can be formed. For example, when the non-polarized portion is formed by decolorization by chemical treatment (details will be described in Section B), the contact time between the decolorizing liquid and the resin film (polarizer) can be shortened. Specifically, it is possible to form a non-polarized portion having a higher transmittance in a shorter time.

The thickness of the portion contacted with the decolorizing solution (for example, a basic solution) may be thinner than that of other portions. This tendency can become stronger as the transmittance of the non-polarized portion obtained by decolorization is increased. By thinning the resin film, it is possible to reduce the step between the non-polarized portion and other portions while achieving a high transmittance (preferably 90% or more) of the non-polarized portion. In this way, it is possible to prevent a problem that may occur due to a step. Other problems include, for example, a protective film or the like in which when a long polarizing element is wound in a roll shape, a step between the non-polarized part and another part is transferred as a winding mark to the overlapped part. It is conceivable that air bubbles are generated due to the step between the non-polarized part and other parts at the time of bonding with the constituent members of the above, and the step is visually recognized in the final product. It is considered that preventing such a defect can also contribute to suppressing variations in the quality of the ultimately used polarizer obtained by cutting the elongated polarizer. It is considered that such an effect can be remarkable, for example, when the transmittance of the non-polarized portion is 90% or more and / or when the content of the dichroic substance is 0.2% by weight or less. The high transmittance of the non-polarized portion of 90% or more can also contribute to suppressing variations in the quality of the polarizer that is finally used. Specifically, when a non-polarized portion is formed by contact with a decolorizing liquid, the transmittance of the obtained non-polarized portion tends to vary if the degree of decolorization is weak, but the transmittance is 90% or more and / or a dichroic substance. By setting the content of the above to 0.2% by weight or less (by increasing the degree of decolorization), the decolorized state can be stably controlled.

In one embodiment, the non-polarized portion is a thin portion thinner than the other portions. For example, a concave portion having a concave surface on one side of the polarizer is formed to form a thin portion. In this case, the step (depth of the recess) between the non-polarized portion and the other portion is, for example, 0.02 μm or more. On the other hand, the step is preferably 2 μm or less, more preferably 1 μm or less. This is the case when a non-polarized portion is formed by decolorization described later (for example, when the transmittance of the non-polarized portion is 90% or more and / or when the content of the dichroic substance is 0.2% by weight or less). However, if the upper limit of the step is within such a range, it is considered that defects due to the step such as winding marks due to roll formation are satisfactorily suppressed. As a result, it is possible to remarkably suppress the variation in the quality of the finally used polarizer obtained by cutting the elongated polarizer. In addition, in this specification, "step (depth of recess)" means the depth of the deepest part of a recess.

The recessed surface on one side is formed, for example, by applying a decolorizing liquid only on one side of the polarizer. By setting the depth of the recess formed after the decolorization treatment within the above range, the treatment after decolorization described later can be uniformly performed. Further, it is considered that since the concave portion can be formed only on one surface side, it is possible to prevent the occurrence of a defect due to a step such as a winding mark due to the roll formation, and to suppress the variation in the quality of the polarizer to be finally used. ..

In the elongated polarizer, the absorption axis may be set in any suitable direction depending on the purpose. The direction of the absorption axis may be, for example, a long direction or a width direction. A polarizer having an absorption axis in the long direction has an advantage of being excellent in manufacturing efficiency. A polarizer having an absorption axis in the width direction has an advantage that it can be laminated with, for example, a retardation film having a slow axis in the long direction by so-called roll-to-roll. In one embodiment, the absorption shaft is substantially parallel in the longitudinal or width direction, and both ends of the polarizer are slitted parallel to the longitudinal direction. With such a configuration, by performing the cutting operation with reference to the end face of the polarizer, it is possible to easily manufacture a plurality of polarizers having a non-polarizing portion and an absorption axis in an appropriate direction. ..

The polarizer used in the imaging step may have a protective layer formed on at least one side thereof. Specifically, any suitable protective layer (resin film) may be laminated on one side or both sides of the polarizer. Specific examples of the resin film include a resin base material and a surface protective film used in the production of the polarizer and the formation of the non-polarizing portion described in Section B; a protective film that protects the polarizer and constitutes a polarizing plate together. , A retardation film, a separator; and the like. In one embodiment, the polarizer used in the imaging step may be a polarizing plate in which a protective film is laminated on at least one side thereof. In the present specification, the term "protective film" simply means a polarizer protective film, which is different from the surface protective film (a film that temporarily protects the polarizer during work) described in Section B.

A-2. Imaging In the imaging step, light is irradiated from one side of the polarizer having the non-polarizing portion (in the case where the resin film is laminated, the laminate of the polarizer and the resin film), and from the other side. The light transmitted through the polarizer is imaged. By imaging the transmitted light, an image of the non-polarized portion can be obtained with a high contrast ratio. In addition, the influence of fine irregularities on the contour of the non-polarized portion can be reduced to obtain a clear image of the non-polarized portion, and as a result, the shape and / or characteristics of the non-polarized portion can be evaluated with high accuracy. It will be possible.

2A and 2B are schematic views illustrating one embodiment of the inspection method of the present invention, respectively. As shown in the figure, the inspection device 400 is connected to a light source unit 410 and an imaging unit 420 arranged so as to face each other with a polarizing element 100 (polarizing plate 300) interposed therebetween, an arbitrary polarizing filter 430, and an imaging unit 420. The image processing unit 440 for analyzing and processing the image captured by the imaging unit 420 is provided. In the illustrated example, the polarizer 100 constitutes a polarizing plate 300 together with a protective film 110 laminated on one side thereof and a protective film 120 laminated on the other side.

The light source unit 410 may be configured using any suitable light source. The light source may be a white light source or a monochromatic light source. The light source can be of any suitable shape and can be, for example, a surface light source, a line light source, a point light source or a ring type light source. Specific examples of the light source include fluorescent lamps, halogen lamps, metal halide lamps, LEDs and the like. The light source unit 410 emits light toward one side (the protective film 120 side in the illustrated example) of the polarizing element 100 (polarizing plate 300). In addition, unlike the illustrated example, when different resin films are laminated on both sides of the polarizer, the light source unit may emit light toward any surface of the polarizer.

The light source unit 410 preferably irradiates light from a direction substantially perpendicular to the polarizer. The irradiation angle of light on the polarizer (illumination angle of light on the main surface of the polarizer) is preferably 89 ° to 91 °, more preferably 89.5 ° to 90.5 °. By setting such an irradiation angle, it is possible to inspect the roughness of the contour of the non-polarized portion in the thickness direction of the polarizer with high accuracy.

The image pickup unit 420 is typically a camera configured by using a lens and an image sensor. As the image sensor, either a CCD type image sensor or a CMOS type image sensor may be used.

The number of pixels of the image sensor is preferably 2000 dpi or more, more preferably 4000 dpi to 6000 dpi. By using an image sensor having such a number of pixels, a high-quality image can be captured, so that the shape and / or characteristics of the non-polarized portion can be inspected with excellent accuracy.

The imaging unit 420 captures light transmitted through the polarizing element 100 (polarizing plate 300) from the other side of the polarizing element 100 (polarizing plate 300) (in the illustrated example, the protective film 110 side). The obtained image is sent to the image processing unit 440 as an electric signal. The image pickup unit is preferably arranged so that its optical axis is substantially perpendicular to the main surface of the polarizer. The angle of the imaging optical axis with respect to the main surface of the polarizer is preferably 89 ° to 91 °, more preferably 89.5 ° to 90.5 °.

In the embodiment shown in FIG. 2A, the polarizing filter 430 is arranged between the image pickup unit 420 and the polarizing element 100 (polarizing plate 300) so that the absorption axis direction thereof is orthogonal to the absorption axis direction of the polarizer 100. There is. According to the embodiment, the light (linearly polarized light) transmitted through a portion other than the non-polarized portion of the polarizer 100 is absorbed by the polarizing filter 430, while a part of the light transmitted through the non-polarized portion is a polarizing filter 430. Can be transmitted, so that the light transmitted through the polarizing filter 430 can be imaged as an image of a substantially unpolarized portion. In addition, in this specification, "orthogonal" also includes the case where it is substantially orthogonal. Here, "substantially orthogonal" includes the case of 90 ° ± 3.0 °, preferably 90 ° ± 1.0 °, and more preferably 90 ° ± 0.5 °.

In the embodiment shown in FIG. 2B, the polarizing filter 430 is arranged between the light source unit 410 and the polarizing element 100 (polarizing plate 300) so that the absorption axis direction thereof is orthogonal to the absorption axis direction of the polarizer 100. .. According to the embodiment, the light (linearly polarized light) emitted from the light source unit 410 and transmitted through the polarizing filter 430 is absorbed by the portion other than the non-polarized portion of the polarizer 100, and is transmitted through the non-polarized portion. Therefore, the light transmitted through the polarizer 100 can be imaged as an image of a substantially unpolarized portion.

The use of the polarizing filter 430 is optional, and the polarizing filter 430 may be omitted if an image capable of inspecting the non-polarized portion can be obtained in the inspection step without using the polarizing filter 430.

In one embodiment, imaging is performed while transporting a long polarizing element in the long direction. In another embodiment, imaging is performed while transporting the cut single-wafer polarizing element pieces on a transport line. By performing imaging while transporting, it is possible to avoid a stoppage of the production line and maintain production efficiency. At this time, the imaging unit may be fixed and the imaging may be performed, or the imaging may be performed while moving in the elongated direction according to the transport speed of the polarizer. It is also possible to perform imaging while moving the imaging unit in the width direction.

When the polarizer is elongated and has unpolarized portions arranged at predetermined intervals in the elongated direction and / or width direction, images of all the unpolarized portions may be obtained, and some non-polarized portions may be obtained. Only the image of the polarized part may be obtained. For example, only images of non-polarized parts selected arbitrarily or according to a specific regularity may be obtained.

A-3. Inspection In the inspection step, the non-polarized part is inspected based on the image obtained in the imaging step. Specifically, the image processing unit 440 is used to analyze the image data sent as an electric signal from the imaging unit 420, and the shape, characteristics, etc. of the non-polarized unit are inspected. Specific examples of the inspection items include the shape accuracy of the non-polarized portion (roundness in the case of a circle), the roughness of the contour, the steepness of the contour, the transmittance and the like. The image processing unit 440 can preferably detect a non-polarized part that does not satisfy a predetermined criterion as a poor formation.

The analysis of the image data can be performed based on, for example, the luminance information. Specifically, in the obtained image data (transmitted light image data), the brightness of the non-polarized portion is relatively high and the brightness of the other portion is low, so that the contrast ratio in the obtained image data is low. A threshold value is provided in the above, and a high-luminance portion having a contrast ratio higher than the threshold value can be specified as a non-polarized portion. Further, the contour of the specified non-polarized portion is 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 in the obtained 180 distance data is the roundness. Can be used as an evaluation standard for. For example, when the obtained value is not more than a predetermined value, the roundness of the non-polarized portion can be evaluated as good. Furthermore, the contour of the non-polarized part is divided into 180 equal parts to obtain a reference approximate ellipse, and the maximum value of the distance from the approximate ellipse to the actual contour in each of the 180 equal parts is used as the evaluation standard for the roughness of the contour. can do. For example, when the obtained maximum value is not more than a predetermined value, the roughness of the contour of the non-polarized portion can be evaluated as good. Furthermore, the average brightness of the non-polarized part and other parts (peripheral part of the non-polarized part) is obtained, the average brightness of the non-polarized part is 0%, the average brightness of the other parts is 100%, and 10% and 20%. The maximum value of the distance from the center of the non-polarized portion to each contour divided into 180 equal parts when binarized into black and white with the brightness of can be used as an evaluation standard for the steepness of the contour. For example, when the obtained maximum value is equal to or less than a predetermined value, the steepness of the contour of the non-polarized portion can be evaluated as good.

For the transmittance of the non-polarized part, for example, the average brightness value, the maximum brightness value, and the minimum brightness value of the non-polarized part are obtained, and the maximum brightness value is divided by the average brightness value or the minimum brightness value is divided by the average brightness value. It can be evaluated based on numerical values. Specifically, when the polarization function remains in the non-polarizing portion and the transmittance is low, the obtained value is also low.

The inspection device 400 (substantially, the image processing unit 440) may be connected to the marking device 500, if necessary. When the inspection device 400 (substantially, the image processing unit 440) detects the formation defect of the non-polarizing portion, the defect detection signal is transmitted to the marking device 500. When inspecting a long-shaped polarizer, the marking device 500 marks a region to be cut as a polarizing element including a poorly formed non-polarized portion based on the signal. The marked area can be easily eliminated as a defective polarizing element after cutting. On the other hand, when inspecting a cut single-wafer polarized piece (single-leaf polarizing plate), the marking device 500 marks the polarized piece including the poorly formed non-polarized portion based on the signal. Examples of the marking include marking using a marker pen and laser marking.

[B. Method for manufacturing polarizing plate]
The method for producing a polarizer having a non-polarizing portion of the present invention includes forming a non-polarizing portion on the polarizing element and inspecting the polarizer having a non-polarizing portion by the above inspection method.

B-1. Step of forming non-polarized part The polarizer is typically a resin film (typically a PVA-based resin film) that is swelled, stretched, dyed with a dichroic substance, crosslinked, and washed. , Obtained by performing various treatments such as drying treatment. When performing various treatments, the resin film may be a resin layer formed on the base material. In this case, for example, the polarizer is a laminate of the resin base material and the PVA-based resin layer by applying a PVA-based resin solution to the resin base material and drying it to form a PVA-based resin layer on the resin base material. It can be produced by: stretching and dyeing the laminate to make a PVA-based resin layer a polarizer; The obtained resin base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protector layer for the polarizer), or the resin substrate / polarizer laminate is protected on the polarizer surface. The films may be bonded and then the resin base material may be peeled off to form a laminate of a polarizer / protective film.

The non-polarizing portion is formed at a predetermined position of the polarizer. When the polarizer is formed from a resin layer formed on a substrate, typically, the laminate of the resin substrate / polarizer or the laminate of the polarizer / protective film is unpolarized. It is used for the formation of the part. When the polarizer is a single resin film, typically the polarizer alone or a protective film / polarizer laminate is used to form the non-polarized portion. Hereinafter, the formation of the non-polarized portion will be specifically described. As a typical example, an example will be described in which a non-polarized portion is formed on the polarizer by decolorization by chemical treatment (hereinafter, also referred to as chemical decolorization treatment) in the laminated body of the protective film / polarizer. It will be apparent to those skilled in the art that similar procedures can be applied to polarizers of other configurations (eg, polarizers that are a single resin film). The formation of the non-polarized portion by the chemical decolorization treatment does not necessarily have to be performed after the production of the polarizer is completed. Specifically, at least the stretching treatment and the dyeing treatment are performed from among various treatments (swelling treatment, stretching treatment, dyeing treatment, cross-linking treatment, washing treatment, drying treatment, etc.) for forming a polarizing element, and the polarizing element is obtained. Chemically use a resin film that is ready for use (for example, a resin film that exhibits absorption dichroism at any wavelength of 380 nm to 780 nm and has the single transmittance and / or polarization degree according to item A). The non-polarized portion may be formed by decolorization by the treatment, and then the remaining treatment may be performed if necessary.

In the chemical decolorization treatment, as shown in FIG. 3, a surface protective film having through holes arranged in a predetermined pattern is attached to the surface of the laminate on the polarizer side by roll-to-roll. As used herein, the term "roll-to-roll" means that roll-shaped films are conveyed and bonded to each other in the same long direction. The surface protective film having through holes is detachably attached to the polarizer via any suitable adhesive. By using a surface protective film having through holes, it is possible to perform decolorization treatment by immersing in a decolorizing liquid, so that a non-polarized portion can be formed with extremely high production efficiency. For convenience, the surface protective film having through holes may be referred to as the first surface protective film.

As described above, the first surface protective film has through holes arranged in a predetermined pattern. The position where the through hole is provided corresponds to the position where the non-polarizing portion of the polarizer is formed. The through hole can have any suitable shape. The shape of the through hole corresponds to the plan view shape of the non-polarized portion to be formed. Through holes can be formed, for example, by mechanical punching (eg punching, Thomson blade punching, plotters, water jets) or removal of certain parts of the film (eg laser ablation or chemical dissolution).

Examples of the material for forming the first surface protective film include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polyethylene and polypropylene, polyamide resins, and polycarbonate resins. Examples thereof include these copolymer resins. An ester resin (particularly, a polyethylene terephthalate resin) is preferable. This is because the elastic modulus is sufficiently high, and for example, even if tension is applied during transportation and / or bonding, deformation of the through hole is unlikely to occur. The thickness of the first surface protective film is typically 20 μm to 250 μm, preferably 30 μm to 150 μm.

Preferably, the second surface protective film is attached to the surface of the laminate on the protective film side by roll-to-roll. The second surface protective film is detachably attached to the protective film via any suitable adhesive. By using the second surface protective film, the laminate (polarizer / protective film) can be appropriately protected in the decolorization treatment by immersion. As the second surface protective film, a film similar to the first surface protective film can be used except that the through holes are not provided.

Next, as shown in FIGS. 4A and 4B, the laminate 200 of the first surface protective film 150 / polarizer 100 / protective film 120 / second surface protective film 160 having the through hole 152 is chemically decolorized. To serve. The chemical decolorization treatment typically involves contacting the laminate 200 with a basic solution as a decolorizing solution. When iodine is used as the dichroic substance, the iodine content of the contact portion can be easily reduced by contacting the basic solution with the desired portion of the resin film.

Contact between the laminate and the basic solution can be done by any suitable means. Typical examples include immersion of the laminate in a basic solution, or application or spraying of the basic solution to the laminate. Immersion is preferred. This is because, as shown in FIG. 4B, the decolorization treatment can be performed while transporting the laminated body 200, so that the production efficiency is remarkably high.

In one embodiment, the basic solution is removed from the polarizer by any suitable means after contact with the polarizer. According to such an embodiment, for example, it is possible to more reliably prevent a decrease in the transmittance of the non-polarized portion due to the use of the polarizer. Specific examples of the method for removing the basic solution include washing, wiping removal with a waste cloth, suction removal, natural drying, heat drying, blast drying, vacuum drying and the like. Preferably, the basic solution is washed. Examples of the cleaning liquid used for cleaning include water (pure water), alcohols such as methanol and ethanol, and mixed solvents thereof. Preferably water is used. The number of washings is not particularly limited and may be performed a plurality of times. When the basic solution is removed by drying, the drying temperature is, for example, 20 ° C to 100 ° C.

Preferably, after the contact with the basic solution, the alkali metal and / or the alkaline earth metal contained in the resin film is reduced at the contact portion with which the basic solution is brought into contact. By reducing the amount of alkali metal and / or alkaline earth metal, a non-polarized portion having excellent dimensional stability can be obtained. Specifically, even in a humidified environment, the shape of the non-polarized portion formed by contact with the basic solution can be maintained as it is.

As the method for reducing the above, preferably, a method of bringing an acidic solution into contact with a contact portion with the basic solution is used. According to such a method, the alkali metal and / or the alkaline earth metal can be efficiently transferred to the acidic solution to reduce the content thereof. The contact with the acidic solution may be performed after the removal of the basic solution, or may be performed without removing the basic solution.

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

Water and alcohol are preferably used as the solvent for the acidic solution. 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. As the contact method for the acidic solution, the same method as the contact method for the basic solution can be adopted. Also, the acidic solution can be removed from the polarizer. As the method for removing the acidic solution, the same method as the method for removing the basic solution can be adopted.

The surface protective film is peeled off and removed at an arbitrary appropriate timing after contact with the basic solution, for example.

Although the chemical decolorization treatment has been described so far, as described above, the non-polarized portion can also be formed by laser irradiation, mechanical punching, or the like.

B-2. Steps for Producing a Polarizing Plate The method for producing a polarizing plate of the present invention typically further comprises producing a polarizing plate having a configuration as a final product using a polarizing element having a non-polarizing portion. As described above, when the polarizer is formed from a resin layer formed on a substrate, the polarizer on which the non-polarizing portion is formed is typically a resin substrate or a protective film on one side thereof. Are laminated. These laminates can be used as they are as a polarizing plate. On the other hand, a polarizing plate having an arbitrary appropriate configuration as a final product is obtained by further subjecting these laminated bodies to this step, peeling off the resin base material, laminating other constituent members such as a protective film, and the like. Can be produced. Similarly, when the polarizing element having a non-polarizing portion is made of a single resin film, the final product can be obtained by sequentially laminating other constituent members such as a protective film on one side or both sides thereof depending on the application or the like. A polarizing plate having any suitable configuration can be obtained.

FIG. 5 is a schematic cross-sectional view of a polarizing plate that can be preferably produced in this step. The polarizing plate can be elongated like the polarizer. The polarizing plate 300 has a polarizing element 100 and protective films 110 and 120 arranged on both sides of the polarizing element 100. In the illustrated example, the protective films are arranged on both sides of the polarizer, but the protective films may be arranged on only one side. Examples of the material for forming the protective film include cellulose-based resins such as diacetyl cellulose and triacetyl cellulose, (meth) acrylic resins, cycloolefin resins, olefin resins such as polypropylene, and ester resins such as polyethylene terephthalate resins. , Polyamide-based resin, polycarbonate-based resin, and copolymer resins thereof. One of the protective films 110 and 120 may be omitted depending on the purpose and the desired configuration.

The thickness of the protective film is typically 10 μm to 100 μm. The protective film is typically laminated on the polarizer via an adhesive layer (specifically, an adhesive layer and an adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an active energy ray-curable adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive. In one embodiment, the thickness of the protective film is 80 μm or less. By using a protective film having such a thickness, it is possible to contribute to thinning the obtained polarizing plate. On the other hand, when a long polarizing plate having a protective film having such a thickness is wound on the other side of a polarizing element having a recess formed on one side, the concave portion is wound in a roll shape. It is considered that defects due to steps such as being transferred to the protective film as winding marks are likely to occur. In such an embodiment, the merit of reducing the step of the recess can be remarkably obtained.

Practically, the polarizing plate 300 has an adhesive layer 130 as the outermost layer. The pressure-sensitive adhesive layer 130 is typically the outermost layer on the image display device side. A separator 132 is temporarily attached to the pressure-sensitive adhesive layer 130 so that it can be peeled off, protecting the pressure-sensitive adhesive layer until actual use and enabling roll formation.

The polarizing plate 300 may further have an arbitrary suitable optical functional layer depending on the purpose. Typical examples of the optical functional layer include a retardation film (optical compensation film) and a surface treatment layer. For example, a retardation film may be placed between the protective film 120 and the pressure-sensitive adhesive layer 130 (not shown). The optical characteristics of the retardation film (for example, refractive index ellipsoid, in-plane retardation, thickness direction retardation) can be appropriately set according to the purpose, the characteristics of the image display device, and the like. The retardation film may also serve as a protective film. In this case, the protective film 120 may be omitted. On the contrary, the protective film 120 may have an optical compensation function (that is, it may have an appropriate refractive index ellipsoid, in-plane retardation, and thickness direction retardation according to the purpose).

The surface treatment layer may be arranged on the outside of the protective film 110 (not shown). Typical examples of the surface treatment layer include a hard coat layer, an antireflection layer, and an antiglare layer. Instead of providing the surface treatment layer, the surface of the protective film 110 may be subjected to the same surface treatment.

Since the polarizer having the non-polarizing portion obtained through the process of forming the non-polarizing portion is typically long, the protective film, the retardation film and the like are laminated by so-called roll-to-roll. Can be

B-3. Cutting Step of Polarizing Plate The method for producing a polarizing plate of the present invention may further include cutting a long polarizing plate into a desired size. Cutting can be done by cutting, punching, etc. The elongated polarizing plate is preferably cut so as to have a size corresponding to the attached image display device and to have a non-polarizing portion at a position corresponding to the camera portion when attached to the image display device. To.

B-4. Polarizer Inspecting Step The step of inspecting a polarizer having a non-polarized portion by the inspection method according to item A can be performed at any appropriate stage after the non-polarized portion is formed. The step of inspecting the polarizer may be performed only once or a plurality of times throughout the entire process of the production method of the present invention.

In one embodiment, the polarizer inspection step can be performed at any suitable step in the polarizing plate fabrication step of item B-2 or after completion of the step. For example, a polarizing plate having a structure as a final product may be produced, and then the polarizer may be inspected. Further, for example, after laminating a retardation film and / or a protective film on the polarizer side of a laminate of protective film / polarizer, the polarizer is inspected, and then a surface treatment layer, an adhesive layer, or the like is laminated. May be good. By inspecting the polarizer at such a stage, the region to be cut as a polarizing element (single-leaf polarizing plate) having a structure as a final product and a non-polarizing portion having poor formation is marked. An identifiable elongated polarizing plate can be obtained. The polarizing plate is cut in a subsequent cutting step, and a polarizing element having a poorly formed non-polarized portion (single-leaf polarizing plate) can be easily removed.

In another embodiment, the polarizer inspection step can be performed after the polarizing plate cutting step according to item B-3. By subjecting the polarizing element piece obtained by cutting to an inspection, the polarizing element piece (single-leaf polarizing plate) having a poorly formed non-polarized part can be easily eliminated.

In yet another embodiment, the polarizer inspection step may be performed at any suitable step in the process of forming the non-polarized portion according to item B-1 or after the step is completed. Explaining a specific example of the case where the non-polarized portion is formed by the chemical decolorization treatment with reference to FIG. 4B, the inspection step includes the stage (a) when the contact treatment with the basic solution is completed, and the basic solution. The stage where the cleaning after the contact is completed (b), the stage where the contact with the treatment solution for reducing the content of the alkali metal and / or the alkali metal salt (acidic solution in FIG. 4B) is completed (c), And / or may be performed at the stage (d) where cleaning after contact with the treatment solution is completed. If the inspection process is performed at such a stage and the proportion of non-polarized parts judged to be defective in shape and / or characteristics exceeds the permissible range, it is suspected that there is a problem in the previous processing. .. Therefore, by checking and adjusting various treatment conditions such as the concentration of the basic solution and the acidic solution and the immersion time, the defect can be detected and eliminated at an early stage. As a result, the process of forming the non-polarizing portion can be suitably controlled, which can contribute to the improvement of the manufacturing efficiency of the polarizer having the non-polarizing portion.

As described in item B-1, when the non-polarized part is formed by a chemical decolorization treatment, the polarizer is typically a surface protective film having a through hole on one side thereof (first surface protective film). The first surface protective film is peeled off after the formation of the non-polarized portion (for example, in the step (d) of FIG. 4B) after the chemical decolorization treatment is performed in the state where the non-polarized part is bonded. Therefore, the polarizer used in the polarizing element inspection step may be in a state in which the first surface protective film 150 is laminated on one side (FIG. 4A), and the first surface protective film 150 may be laminated. May be in a state of being peeled off (not shown). Similarly, for the second surface protective film, the polarizer used in the polarizer inspection step may be in a state in which the second surface protective film 160 is laminated on the other side (FIG. 4A). The second surface protective film 160 may be in a state of being peeled off (not shown).

[C. Use of polarizing plate]
The polarizing plate obtained by the production method according to Item B can be suitably used for an image display device. The image display device includes the above-mentioned polarizing plate cut to a predetermined size. Examples of the image display device include a liquid crystal display device and an organic EL device. Specifically, the liquid crystal display device includes a liquid crystal panel including a liquid crystal cell and the above-mentioned polarizing plate arranged on one side or both sides of the liquid crystal cell. The organic EL device includes an organic EL panel in which the above-mentioned polarizing plate is arranged on the visual side. The polarizing plate is arranged so that the non-polarizing portion of the polarizer corresponds to the camera portion of the image display device.

The inspection method of the present invention is suitably used for manufacturing a polarizer provided in a camera-equipped image display device (liquid crystal display device, organic EL device) such as a mobile phone such as a smartphone, a notebook PC, or a tablet PC. Be done.

10 Non-polarizing unit 100 Polarizing element 300 Polarizing plate 400 Inspection device 410 Light source unit 420 Imaging unit 430 Polarizing filter 440 Image processing unit 500 Marking device

Claims (8)

A method of inspecting a polarizer having a non-polarized portion.
An imaging step of irradiating light from a light source unit arranged on one side of the polarizer and imaging the light transmitted through the polarizer by an imaging unit arranged on the other side.
The non-polarized portion of the polarizer is inspected based on the obtained image, and a non-polarized portion that does not meet a predetermined criterion is poorly formed with respect to at least one selected from shape accuracy, contour roughness and contour steepness. Inspection process to detect as
Including
An inspection method in which a polarizing filter is arranged between the polarizer and the light source unit or between the polarizer and the imaging unit so that the absorption axis direction thereof is orthogonal to the absorption axis direction of the polarizer. .. The inspection method according to claim 1, wherein the polarizer has a long shape and has non-polarizing portions arranged at predetermined intervals in the long direction and / or the width direction. The inspection method according to claim 2, wherein the imaging step is performed while transporting the polarizer in the elongated direction. The polarizer is composed of a resin film containing a dichroic substance.
The inspection method according to any one of claims 1 to 3, wherein the low concentration portion of the dichroic substance having a relatively low content of the dichroic substance in the resin film is the non-polarizing portion. The inspection method according to any one of claims 1 to 4, wherein a protective layer is formed on at least one side of the polarizing element used in the imaging step. The inspection method according to any one of claims 1 to 5, wherein the irradiation angle of light on the polarizer in the imaging step is 89 ° to 91 °. A method for producing a polarizing plate, comprising forming a non-polarizing portion on a polarizing element and inspecting a polarizing element having a non-polarizing portion by the inspection method according to any one of claims 1 to 6. A light source unit that irradiates one side of a polarizer having a non-polarizing unit,
An imaging unit that captures light emitted from the light source unit and transmitted through the polarizer,
It is connected to the imaging unit and analyzes the image captured by the imaging unit to form a non-polarized portion that does not meet a predetermined criterion for at least one selected from shape accuracy, contour roughness and contour steepness. The image processing unit that detects as a defect and
With
A polarizing element in which a polarizing filter is arranged between the polarizer and the light source unit or between the polarizing element and the imaging unit so that the absorption axis direction of the polarizing filter is orthogonal to the absorption axis direction of the polarizer. Inspection device for non-polarized parts.