WO2022044390A1 - Optical laminate inspection method - Google Patents

Abstract

[Problem] Provided is an optical laminate inspection method that suppresses excess detection of defects on the surface of a release film and makes it possible to accurately detect defects between a polarizer and optical film. [Solution] This invention comprises a transmission inspection process S1 for detecting a defect candidate using a transmission image generated from light that has been transmitted by an optical laminate S, a crossed Nicols inspection process S2 for detecting a defect candidate using a crossed Nicols image generated from light that has passed through the optical laminate and polarizing filters 6a, 6b for inspection that are disposed so as to produce a crossed Nicols state along the polarization axis of a polarizer 10, a reflection inspection process S3 for detecting a defect candidate using a reflection image generated from light that has been reflected by the optical laminate, and a computation process S4 for determining that a defect candidate that has been detected in both the transmission inspection process and crossed Nicols inspection process but not in the reflection inspection process is a defect between the polarizer and an optical film 20.

Description

Inspection method of optical laminate

The present invention relates to an inspection method for an optical laminate in which a polarizing element and an optical film are laminated, and a release film is further laminated on at least one of the outermost surfaces in the thickness direction. In particular, the present invention relates to a method for inspecting an optical laminate capable of suppressing over-detection of defects existing on the surface of a release film and accurately detecting defects existing between a polarizing element and an optical film.

Conventionally, an inspection method has been known in which a defect of an optical laminate containing a polarizing element is optically inspected to determine the quality of the optical laminate.
A drawback of the optical laminate is that foreign matter existing between the layers of the optical laminate (specifically, between the polarizing element constituting the optical laminate and the optical film) (in the present specification, appropriately referred to as "bonded foreign matter"). ) And defects (foreign matter, dirt, scratches, etc.) existing on the surface of the optical laminate.

The optical conditions for easily detecting defects differ depending on the type of defects. Therefore, various inspection methods that combine a plurality of optical conditions have been proposed.
For example, Patent Documents 1 and 2 describe the optical film based on the transmitted image of the optical film generated by the light transmitted through the optical film and the reflected image of the optical film generated by the light reflected by the optical film. An inspection method for detecting defects has been proposed (paragraphs 0023 to 0026 of Patent Document 1, claim 2 of Patent Document 2 and the like).
Further, in Patent Document 3, a reflected image of an optical laminate generated by light reflected by an optical laminate containing a polarizing element and an inspection object arranged so as to form a cross Nicol with respect to the polarization axis of the polarizing element. An inspection method for detecting defects in the optical laminate based on a cross Nicol image of the optical laminate generated by light transmitted through the polarizing filter and the optical laminate has been proposed (claim 1 of Patent Document 3 and the like). ).

Here, the inspection target is a laminate of a polarizing element and an optical film (for example, a retardation film), and a release film (for example, a separator or a surface protective film) is further formed on at least one outermost surface side in the thickness direction. In the case of the laminated optical laminate, the defects (foreign matter, dirt, scratches, etc.) existing on the surface of the release film are harmless and do not pose a problem. This is because when the optical laminate is used (for example, the optical laminate is attached to the liquid crystal cell), the release film is peeled off and does not remain.

When the present inventors investigated an inspection method for detecting defects based on a cross Nicol image of an optical laminate containing a polarizing element, it was possible to detect bonded foreign matter existing between the layers of the optical laminate, but it was harmless. It was found that even defects existing on the surface of the film were detected (overdetected). For this reason, an optical laminate having only defects on the surface of the release film (which does not cause a problem because there are no defects between layers) is treated as a defective product, and the product yield of the optical laminate may deteriorate.

In Patent Document 3, in order to suppress the above-mentioned over-detection, the position of the defect candidate detected based on the reflection image of the optical laminate and the position of the defect candidate detected based on the cross Nicol image of the optical laminate are described. When is the same as, it is described that this defect candidate is not treated as a defect (claim 1, paragraph 0083, etc. of Patent Document 3).
However, according to the investigation by the present inventors, as described above, even with the inspection method combining the reflection image and the cross Nicol image, there are cases where the over-detection of harmless defects cannot be sufficiently suppressed. I understood.

The inspection method described in Patent Document 1 has an object of accurately counting the number of defects (paragraph 0007 of Patent Document 1), and is not a method of suppressing over-detection of harmless defects.
Further, the inspection method described in Patent Document 2 has an object of accurately determining the type of defect (paragraph 0018 of Patent Document 2), and is not a method of suppressing over-detection of harmless defects.

Japanese Patent Application Laid-Open No. 2003-329601 Japanese Unexamined Patent Publication No. 2012-167975 Japanese Patent No. 4960161

The present invention has been made to solve the above-mentioned problems of the prior art, and suppresses over-detection of defects existing on the surface of the release film and exists between the polarizing element and the optical film. It is an object of the present invention to provide an inspection method for an optical laminate capable of accurately detecting a defect.

As a result of diligent studies to solve the above problems, the present inventors detected both the transmitted image and the cross Nicol image in each of the transmitted image, the cross Nicol image, and the reflected image, and did not detect them in the reflected image. The present invention has been completed by finding that the defect candidate is likely to be a defect (bonded foreign matter) existing between the polarizing element and the optical film.

That is, in order to solve the above-mentioned problems, the present invention is an inspection method for an optical laminate in which a polarizing element and an optical film are laminated, and a release film is further laminated on at least one outermost surface side in the thickness direction. A transmission inspection step of generating a transmitted image of the optical laminated body by light transmitted through the optical laminated body and detecting defect candidates existing in the optical laminated body based on the transmitted image, and a polarization of the polarizing element. A cross Nicol image of the optical laminate is generated by an inspection polarizing filter arranged so as to form a cross Nicol with respect to the axis and light transmitted through the optical laminate, and the optical laminate is based on the cross Nicol image. A cross Nicol inspection step for detecting defect candidates existing in the optical laminate, a reflected image of the optical laminate is generated by the light reflected by the optical laminate, and defect candidates existing in the optical laminate are generated based on the reflected image. The polarizing element is based on the reflection inspection step to be detected, the defect candidate detected in the transmission inspection step, the defect candidate detected in the cross optics inspection step, and the defect candidate detected in the reflection inspection step. A calculation step for determining defects existing between the optical film and the optical film is included, and is detected in both the transmission inspection step and the cross Nicol inspection step in the calculation step, but is not detected in the reflection inspection step. Provided is a method for inspecting an optical laminate, which determines that a defect candidate is a defect existing between the polarizing element and the optical film.

According to the present invention, in the transmission inspection step, defect candidates existing in the optical laminate are detected based on the transmission image of the optical laminate. For a transmitted image, for example, a light source is arranged on one surface side of the optical laminate, an imaging means is arranged on the other surface side, the light emitted from the light source is emitted, and the light transmitted through the optical laminate is received by the imaging means. It is generated by forming an image (imaging). Defect candidates in a transparent image are detected by applying a known image process such as binarization to extract a pixel region having a different luminance value (pixel value) from another pixel region, for example, to the transparent image. ..
Further, according to the present invention, in the cross Nicol inspection step, defect candidates existing in the optical laminated body are detected based on the cross Nicol image of the optical laminated body. For the cross Nicol image, for example, a light source and a polarizing filter for inspection are arranged on one surface side of the optical laminate, and an imaging means is arranged on the other surface side to emit light from the light source, and the polarizing filter for inspection and the optical laminate are arranged. It is generated by capturing and receiving an image of light transmitted through the body with an imaging means and forming an image (imaging). In this case, the state of the cross Nicol is disrupted by the defect existing between the inspection polarizing filter and the polarizing element of the optical laminate. Therefore, in the cross Nicol image, the defect existing between the inspection polarizing filter and the polarizing element The corresponding pixel area becomes brighter (the brightness value becomes larger). Alternatively, in the cross Nicol image, a light source is arranged on one surface side of the optical laminate, an inspection polarizing filter and an imaging means are arranged on the other surface side, and the light is emitted from the light source to emit the optical laminate and the inspection polarization. It is also generated by receiving light received by an imaging means and forming an image (imaging) of the light transmitted through the filter. In this case as well, the defect existing between the polarizing element of the optical laminate and the polarizing filter for inspection disrupts the state of the cross Nicol, so that the defect existing between the polarizing element and the polarizing filter for inspection in the cross Nicol image is present. The pixel area corresponding to is brighter (the brightness value becomes larger). The defect candidate in the cross Nicol image is, for example, a pixel region having a different brightness value (pixel value) from the other pixel region (specifically, a pixel region having a larger brightness value than the other pixel region) with respect to the cross Nicol image. Is detected by applying known image processing such as binarization.
Further, according to the present invention, in the reflection inspection step, defect candidates existing in the optical laminate are detected based on the reflection image of the optical laminate. For the reflected image, for example, a light source and an image pickup means are arranged on one surface side of the optical laminate, and the light emitted from the light source and reflected by the optical laminate is received by the image pickup means and imaged (imaging). Generated by. Defect candidates in a reflected image are detected by applying known image processing such as binarization to extract a pixel region having a different luminance value (pixel value) from another pixel region, for example, to the reflected image. ..

In the present invention, the "optical film" means an optical film that cannot be peeled off from the polarizing element.
Further, in the present invention, the "inspection polarizing filter arranged so as to form a cross Nicol with respect to the polarization axis of the polarizing element" means that the angle formed by the polarization axis of the polarizing element and the polarization axis of the inspection polarizing filter is the same. It is a concept that includes not only the case where the temperature is completely 90 ° but also the case where the temperature is within the range of 90 ° ± 10 °.
Further, in the present invention, the transmission inspection step, the cross Nicol inspection step, and the reflection inspection step do not necessarily have to be executed in this order, but are executed in any order (when a plurality of inspection steps are partially overlapped). (Including) is possible.

According to the present invention, defect candidates that are detected in both the transmission inspection step and the cross Nicol inspection step and are not detected in the reflection inspection step in the calculation process are present between the polarizing element and the optical film. Judged as (bonded foreign matter).
Whether or not the defect candidate is detected in both the permeation inspection step and the cross Nicol inspection step is determined, for example, at a position equivalent to (same or near) the position of a certain defect candidate detected in the permeation inspection step. It is determined whether or not the defect candidate detected in is present. If there is a defect candidate detected in the cross Nicol inspection step at the same position, it is determined that the defect candidate is detected in both the permeation inspection step and the cross Nicol inspection step. On the other hand, if there is no defect candidate detected in the cross Nicol inspection step at the same position, it is determined that this defect candidate was not detected in both the permeation inspection step and the cross Nicol inspection step.
Whether or not the defect candidate detected in both the permeation inspection step and the cross Nicol inspection step is detected in the reflection inspection step is determined by, for example, the position of a certain defect candidate detected in both the permeation inspection step and the cross Nicol inspection step. It is determined whether or not there is a defect candidate detected in the reflection inspection step at the same (same or near) position. If there is a defect candidate detected in the reflection inspection step at the same position, it is determined that the defect candidate is detected in the reflection inspection step. On the other hand, if there is no defect candidate detected in the reflection inspection step at the same position, it is determined that this defect candidate was not detected in the reflection inspection step.

As described above, according to the findings of the present inventors, the defect candidates detected in both the transmission image and the cross Nicol image but not in the reflection image are the defects existing between the polarizing element and the optical film. There is a high possibility that it is (bonded foreign matter). According to the present invention, in the arithmetic step, it was detected in both the transmission inspection step and the cross Nicol inspection step (that is, it was detected in both the transmission image and the cross Nicol image), and it was not detected in the reflection inspection step (that is,). In order to determine that the defect candidate (which was not detected in the reflected image) is a defect existing between the polarizing element and the optical film, the over-detection of the defect existing on the surface of the release film is suppressed, and the polarizing element is used. It is possible to accurately detect defects existing between the optical film and the optical film.

In the present invention, when the release film is a separator and the optical film is located between the separator and the polarizing element, the inspection polarizing filter is arranged on the separator side in the cross Nicol inspection step. Is preferable.

When the above optical laminate is attached to the liquid crystal cell of the image display device, the separator side is attached to the liquid crystal cell (the separator side is attached after the separator is peeled off). When the separator side of the optical laminate is bonded to the liquid crystal cell, there are drawbacks (specifically, the splitter and the optics located closer to the liquid crystal cell side) that exist between the polarizing element of the optical laminate and the liquid crystal cell. (Defects existing between the film and the film) are displayed as bright spots on the image display device when the liquid crystal cell is driven, which poses a quality problem.
According to the above preferred method, in the cross Nicol inspection step, the inspection polarizing filter is arranged on the same separator side as the liquid crystal cell, which causes a problem when driving the liquid crystal cell (between the liquid crystal cell and the optical film). (Defects existing in) can be detected as defect candidates.

In the present invention, there is a portion of the optical laminate in which the orientation direction of the release film and the direction of the polarization axis of the polarizing element are largely deviated from each other, or the orientation direction of the release film and the direction of the polarization axis of the inspection polarizing filter are present. If there is a part of the optical laminate that is significantly different from the above, even if there is no defect between the polarizing filter for inspection and the polarizing element of the optical laminate, the state of cross Nicol will collapse at the above part. , The detection accuracy of defect candidates in the cross Nicol inspection process is reduced.
Therefore, the present invention is preferably used when the orientation direction of the release film is within ± 6 ° (more preferably within ± 3.5 °) with respect to a predetermined orientation direction. In this way, if the release film has the same orientation direction (within ± 6 ° with respect to the predetermined orientation direction), the predetermined orientation direction of the release film and the direction of the polarization axis of the splitter should match. The release film and the splitter are laminated, or the specified orientation direction of the release film and the direction of the polarization axis of the inspection polarizing filter match (in other words, the specified orientation direction of the release film). It is possible to prevent a decrease in the detection accuracy of defect candidates in the cross Nicol inspection process for an optical laminate in which a release film and a polarizing element are laminated (so that the direction of the polarization axis of the polarizing element is orthogonal to the direction of the polarization axis).

Preferably, the imaging means for generating the transmission image in the transmission inspection step and the imaging means for generating the cross Nicol image in the cross Nicol inspection step are the same, and the transmission inspection step is described. The timing of executing the image pickup by the image pickup means and the timing of executing the image pickup by the image pickup means in the cross Nicol inspection step are switched.

According to the above preferred method, since the imaging means for generating the transparent image and the imaging means for generating the cross Nicol image are the same, the coordinates of the transparent image and the coordinates of the cross Nicol image can be accurately obtained. Can be matched. Therefore, in the calculation process, it is accurately determined whether or not the defect candidate is detected in both the permeation inspection process and the cross Nicol inspection process (for example, at a position equivalent to the position of a certain defect candidate detected in the permeation inspection process). , It is possible to accurately determine whether or not there is a defect candidate detected in the cross Nicol inspection process).

Preferably, the permeation inspection step and / or the cross Nicol inspection step includes a noise reduction procedure for excluding defect candidates having dimensions larger than a predetermined threshold value from the detected defect candidates.

The defects (foreign matter bonded) existing between the polarizing element of the optical laminate and the optical film are often smaller in size than the defects existing on the surface of the release film.
According to the above preferred method, in the permeation inspection step and / or the cross Nicol inspection step, among the defect candidates detected, the defect candidates having a size larger than a predetermined threshold value are excluded from the defect candidates, so that the defect candidates are excluded in the calculation process. , The number of defect candidates for determining whether or not they are detected in both the permeation inspection step and the cross Nicol inspection step can be reduced. Therefore, it has the advantage that the time required for the calculation process can be shortened.

According to the present invention, it is possible to suppress over-detection of defects existing on the surface of the release film and accurately detect defects existing between the polarizing element and the optical film.

It is a figure schematically explaining the schematic structure of the inspection apparatus for carrying out the inspection method of the optical laminated body which concerns on one Embodiment of this invention. It is a flow chart which shows the schematic process of the inspection method of the optical laminated body which concerns on this embodiment. It is a figure schematically explaining an example of defect candidates detected in the permeation inspection step S1 shown in FIG. 2. It is a figure schematically explaining an example of the defect candidate detected in the cross Nicol inspection step S2 shown in FIG. 2. It is a figure schematically explaining the content of the switching control executed by the control calculation means 9 shown in FIG. 1. It is a figure which schematically explains an example of the defect candidate detected in the reflection inspection step S3 shown in FIG. It is a figure which schematically explains the content of the calculation process S4 shown in FIG.

Hereinafter, a method for inspecting an optical laminate according to an embodiment of the present invention will be described with reference to the accompanying drawings as appropriate.
FIG. 1 is a diagram schematically illustrating a schematic configuration of an inspection device for executing an inspection method for an optical laminate according to the present embodiment. FIG. 1A is a side view showing a schematic configuration of an inspection device. FIG. 1B is a cross-sectional view showing a schematic configuration of an optical laminate. In FIG. 1, X indicates a horizontal direction parallel to the transport direction of the optical laminate S, Y indicates a horizontal direction orthogonal to the X direction, and Z indicates a vertical direction.

<Optical laminate S>
First, the configuration of the optical laminate S, which is the inspection target of the inspection device 100 of the present embodiment, will be described.
As shown in FIG. 1 (b), the optical laminate S of the present embodiment is cut into a chip shape according to the intended use, and the polarizing element 10 and the optical films 20 and 30 are laminated and further thickened. The release films 40 and 50 are laminated on the outermost surface side in the direction (Z direction). In the present embodiment, one optical film 20 located below the splitter 10 is a retardation film, and the other optical film 30 located above the splitter 10 is a protective film. Further, in the present embodiment, one release film 40 located below the polarizing element 10 is a separator, and the other release film 50 located above the polarizing element 10 is a surface protective film.
Hereinafter, each component of the optical laminate S will be described.

[Polarizer 10]
The decoder 10 is typically composed of a resin film containing a dichroic substance.
As the resin film, any suitable resin film that can be used as a polarizing element can be adopted. The resin film is typically a polyvinyl alcohol-based resin (hereinafter referred to as “PVA-based resin”) film.

Any suitable resin can be used as the PVA-based resin that forms the PVA-based resin film. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymers can be mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer.

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

Examples of the dichroic substance contained in the resin film include iodine and organic dyes. These can be used alone or in combination of two or more. Preferably iodine is used.

The resin film may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizing element composed of a single-layer resin film include those obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically, a uniaxial stretching treatment). The dyeing treatment with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing or while dyeing. In addition, dyeing may be performed after stretching. If necessary, the PVA-based resin film is subjected to a swelling treatment, a crosslinking treatment, a cleaning treatment, a drying treatment and the like.

Specific examples of the polarizing element composed of the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and this resin base. Examples thereof include a polarizing element composed of a laminate with a PVA-based resin layer coated and formed on a material. A polarizing element composed of a laminate of a resin base material and a PVA-based resin layer coated and formed on the resin base material can be obtained, for example, by applying a PVA-based resin solution to the resin base material and drying it on the resin base material. A PVA-based resin layer is formed on the surface of the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer, and then the laminate is stretched and dyed to use the PVA-based resin layer as a polarizing element. Can be done. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, stretching may optionally include stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in an aqueous boric acid solution. The obtained resin base material / polarizing element laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizing element), or the resin base material may be obtained from the resin base material / polarizing element laminate. It may be peeled off, and an arbitrary appropriate protective layer according to the purpose may be laminated and used on the peeled surface. Details of the method for producing such a polarizing element are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of this publication is incorporated herein by reference.

The thickness of the splitter 10 is preferably 15 μm or less, more preferably 1 μm to 12 μm, further preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

The polarizing element 10 preferably exhibits absorption dichroism at any wavelength in the wavelength range of 380 nm to 780 nm. The simple substance transmittance of the polarizing element 10 is preferably 40.0% to 45.0%, more preferably 41.5% to 43.5%. The degree of polarization of the polarizing element 10 is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

[The retardation film 20]
The retardation film 20 may be, for example, a compensation plate that imparts a wide viewing angle, or may be a retardation plate (circular polarizing plate) that is used together with a polarizing film to generate circularly polarized light. The thickness of the retardation film 20 is, for example, 1 to 200 μm. Instead of the retardation film 20, a protective film as described later or another film such as a reflective polarizing element may be used.

The retardation film 20 is typically formed of any suitable resin capable of achieving the above characteristics. Examples of the resin forming the retardation film 20 include polyarylate, polyamide, polyimide, polyester, polyaryl ether ketone, polyamide-imide, polyesterimide, polyvinyl alcohol, polyfumarate ester, polyether sulfone, polysulfone, and norbornene resin. Examples include polycarbonate resin, cellulose resin and polyurethane. These resins may be used alone or in combination. A cycloolefin-based norbornene resin is preferable.

[Protective film 30]
As the protective film 30, any suitable resin film is used. Examples of the resin film forming material include (meth) acrylic resin, cellulose resin such as diacetyl cellulose and triacetyl cellulose, cycloolefin resin such as norbornene resin, olefin resin such as polypropylene, and polyethylene terephthalate resin. Examples thereof include ester-based resins such as, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. The "(meth) acrylic resin" means an acrylic resin and / or a methacrylic resin.

The thickness of the protective film 30 is typically 10 μm to 100 μm, preferably 20 μm to 40 μm.

The surface of the protective film 30 on the opposite side of the polarizing element 10 may be subjected to surface treatment such as hard coat treatment, antireflection treatment, anti-sticking treatment, and anti-glare treatment, if necessary. Further / or, if necessary, the surface of the protective film 30 opposite to the polarizing element 10 is treated to improve visibility when visually recognizing through polarized sunglasses (typically, (elliptical) circular polarization. Processing for imparting a function, processing for imparting an ultra-high phase difference) may be performed. When the surface treatment is applied to form the surface treatment layer, the thickness of the protective film 30 is the thickness including the surface treatment layer. It was

It should be noted that the retardation film 20 and the protective film 30 are laminated and laminated to the polarizing element 10 via an arbitrary appropriate adhesive layer (not shown). Typical examples of the adhesive constituting the adhesive layer include PVA-based adhesives and activated energy ray-curable adhesives.

[Separator 40]
As the separator 40, any suitable separator can be adopted. Specific examples include a plastic film, a non-woven fabric or paper surface-coated with a release agent. Specific examples of the release agent include a silicone-based release agent, a fluorine-based release agent, and a long-chain alkyl acrylate-based release agent. Specific examples of the plastic film include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. The thickness of the separator can be, for example, 10 μm to 100 μm.

The separator 40 is bonded and laminated to the retardation film 20 via an arbitrary suitable pressure-sensitive adhesive layer (not shown). Specific examples of the adhesives constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. The agent is mentioned. By adjusting the type, number, combination and blending ratio of the monomers forming the base resin of the pressure-sensitive adhesive, the blending amount of the cross-linking agent, the reaction temperature, the reaction time, etc., the pressure-sensitive adhesive having desired characteristics according to the purpose. Can be prepared. The base resin of the pressure-sensitive adhesive may be used alone or in combination of two or more. Acrylic adhesives are preferable from the viewpoint of transparency, processability, durability and the like. Details of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer are described in, for example, Japanese Patent Application Laid-Open No. 2014-115468, and the description of the publication is incorporated herein by reference. The thickness of the pressure-sensitive adhesive layer can be, for example, 10 μm to 100 μm. The storage elastic modulus G'at 25 ° C. of the pressure-sensitive adhesive layer can be, for example, 1.0 × 10 ⁴ [Pa] to 1.0 × 10 ⁶ [Pa]. The storage elastic modulus can be obtained from, for example, dynamic viscoelasticity measurement.

In the present embodiment, the separator 40 whose orientation direction is within ± 6 ° with respect to a predetermined orientation direction is used. For example, if the direction of the polarization axis of the polarizing element 10 of the present embodiment is the X direction, the predetermined orientation direction of the separator 40 is the Y direction, and the orientation direction of any portion of the separator 40 is with respect to the Y direction. The separators 40 are laminated so as to form an angle within ± 6 °.

[Surface protection film 50]
The surface protective film 50 typically has a base material and an adhesive layer. In the present embodiment, the thickness of the surface protective film 50 is, for example, 30 μm or more. The upper limit of the thickness of the surface protective film 50 is, for example, 150 μm. In the present specification, the "thickness of the surface protective film" means the total thickness of the base material and the pressure-sensitive adhesive layer.

The base material can be composed of any suitable resin film. Examples of the resin film forming material include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Can be mentioned. An ester resin (particularly, a polyethylene terephthalate resin) is preferable.

As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, any appropriate pressure-sensitive adhesive can be adopted. Examples of the base resin of the pressure-sensitive adhesive include acrylic resin, styrene resin, silicone resin, urethane resin, and rubber resin.

<Inspection device 100>
Next, the configuration of the inspection device 100 of the present embodiment will be described.
The inspection device 100 of the present embodiment is an device for inspecting the optical laminate S having the configuration described above.
As shown in FIG. 1A, the inspection device 100 of the present embodiment includes a plurality of belt conveyors 1 that convey the optical laminate S in the X direction, and the outermost surface (top surface and bottom surface) of the optical laminate S. It is provided with a clean roller 2 for adsorbing and removing foreign matter adhering to the. Further, the inspection device 100 of the present embodiment includes a light source 3 and an image pickup means 4 for executing the transmission inspection step S1 described later. Further, the inspection device 100 of the present embodiment includes a pair of light sources 5a and 5b and a pair of inspection polarizing filters 6a and 6b for executing the cross Nicol inspection step S2 described later. The image pickup means 4 is also used as an image pickup means for executing the cross Nicol inspection step S2. Further, the inspection device 100 of the present embodiment includes a light source 7 and an image pickup means 8 for executing the reflection inspection step S3 described later. Further, the inspection device 100 of the present embodiment is electrically connected to the light source 3, the image pickup means 4, the light sources 5a and 5b, the light source 7, and the image pickup means 8, and controls their operations while controlling the operation of the light source 3, the image pickup means 4, and the image pickup means 4. A control calculation means 9 for processing an image pickup signal output from No. 8 to determine a defect is provided.
Hereinafter, each component of the inspection device 100 will be described.

[Belt conveyor 1]
The belt conveyor 1 has a configuration in which an annular belt spanned by rollers at both ends moves with the rotation of the rollers to convey the optical laminate S mounted on the belt. After being cut into chips, the optical laminate S is placed on the belt conveyor 1 shown at the left end of FIG. 1 (a), and is placed in the X direction toward the right side of FIG. 1 (a) by each belt conveyor 1. Are sequentially transported to. In the present embodiment, as shown in FIG. 1 (b), the optical laminate S is placed and conveyed on a belt conveyor so that the separator 40 side is facing down. The transport speed V of the optical laminate S by the belt conveyor 1 is set to, for example, 50 mm / sec to 750 mm / sec.

[Clean Roller 2]
The clean roller 2 includes a pair of upper and lower rollers through which the optical laminate S passes through the gaps, and a roll-shaped adhesive tape (not shown) that rotates in contact with each roller. When the pair of upper and lower rollers come into contact with the optical laminate S, foreign matter adhering to the outermost surface (uppermost surface and lowermost surface, that is, the lower surface of the separator 40 and the upper surface of the surface protective film 50) is attached to the rollers. Foreign matter that is adsorbed and adsorbed on this roller is transferred to the adhesive tape and removed.
Disadvantages existing on the surface of the release film (separator 40, surface protective film 50) by removing the foreign matter existing on the outermost surface of the optical laminate S to some extent by the clean roller 2 before executing the transmission inspection step S1 described later. It is possible to further suppress the over-detection of.

[Light source 3]
The light source 3 is a light source for executing the transmission inspection step S1 described later, and is arranged on the lower surface side (separator 40 side) of the optical laminate S in the present embodiment. The optical axis of the light source 3 (shown by a broken line in FIG. 1A) is directed in the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S, and the light source 3 is output from the control calculation means 9. According to the control signal, light is emitted upward in the vertical direction toward the optical laminate S.
The light source 3 is not limited as long as it can emit light having a wavelength that can be transmitted through the optical laminate S, and for example, an LED or a halogen lamp can be used.

[Image pickup means 4]
The image pickup means 4 is an image pickup means for executing the transmission inspection step S1 and the cross Nicol inspection step S2 described later, and is arranged on the upper surface side (surface protection film 50 side) of the optical laminate S in the present embodiment. There is. The optical axis of the image pickup means 4 (shown by a broken line in FIG. 1A) is directed in the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S, and the image pickup means 4 is a control calculation means 9. According to the control signal output from the light source 3, the light emitted from the light source 3 is received and imaged, and the electric signal corresponding to the amount of the light is output to the control calculation means 9 as an image pickup signal. Further, the image pickup means 4 receives and forms an image by receiving light emitted from the light sources 5a and 5b and transmitted through the inspection polarizing filters 6a and 6b and the optical laminate S according to the control signal output from the control calculation means 9. , An electric signal corresponding to the amount of light is output to the control calculation means 9 as an image pickup signal. The focal point of the image pickup means 4 is set on the upper surface of the optical laminate S (the upper surface of the surface protective film 50).

In the present embodiment, as the image pickup means 4, a plurality of imaging elements (CCD or CMOS) are linearly arranged in a direction (Y direction) orthogonal to the transport direction (X direction) of the optical laminate S, and a constant scan is performed. A line sensor that outputs an image pickup signal at a cycle (for example, 7 μsec to 14 μsec) is used. By using the line sensor as the image pickup means 4, the field of view in the X direction of the image pickup means 4 becomes smaller, so that the required irradiation range of the light emitted from the light sources 3, 5a and 5b in the X direction can be narrowed. There is an advantage that the constraint conditions regarding the arrangement of 5a and 5b are relaxed. When the optical laminate S is conveyed in the X direction and the imaging element of the line sensor is scanned in the Y direction, a two-dimensional transmission image is generated in the transmission inspection step S1 described later, and a cross Nicol inspection described later is performed. In step S2, a two-dimensional cross Nicol image will be generated.
However, the image pickup means 4 is not necessarily limited to the line sensor, and for example, a two-dimensional camera with a high-speed shutter can be used as the image pickup means 4.

[ Light source 5a, 5b]
The light sources 5a and 5b are light sources for executing the cross Nicol inspection step S2 described later, and are arranged on the lower surface side (separator 40 side) of the optical laminate S in the present embodiment. The optical axes of the light sources 5a and 5b (shown by the broken line in FIG. 1A) are directed in a direction inclined with respect to the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S. Specifically, the optical axis of the light source 5a is directed in a direction inclined toward the downstream side of the transport direction of the optical laminate S with respect to the vertical direction, and the optical axis of the light source 5b is the optical laminate S with respect to the vertical direction. It is oriented in an inclined direction toward the upstream side in the transport direction. The light sources 5a and 5b emit light upward toward the optical laminate S according to the control signal output from the control calculation means 9.
The light sources 5a and 5b are not limited as long as they can emit light having a wavelength that can be transmitted through the optical laminate S, and for example, an LED or a halogen lamp can be used.
In this embodiment, the image pickup means 4 is used (shared) as an image pickup means for executing both the transmission inspection step S1 and the cross Nicol inspection step S2. That is, since the same imaging means 4 receives the light emitted from the light source 3 and the light sources 5a and 5b, the direction of the optical axis of the light source 5a and 5b is different from the direction of the optical axis of the light source 3. ing. Further, a pair of light sources 5a and 5b are arranged so that a sufficient amount of light emitted from the inclined direction can be secured. However, for example, by adopting a coaxial epi-illumination optical system composed of a half mirror or the like, the direction of the optical axis of the light sources 5a and 5b can be directed in the vertical direction in the same manner as the direction of the optical axis of the light source 3. It is also possible to use a single light source instead of the pair of light sources 5a and 5b.

[Inspection polarizing filters 6a, 6b]
The inspection polarizing filters 6a and 6b are arranged so as to form a cross Nicol with respect to the polarization axis of the polarizing element 10 of the optical laminate S. For example, if the direction of the polarization axis of the polarizing element 10 is the X direction, the direction of the polarization axes of the inspection polarizing filters 6a and 6b is arranged so as to be the Y direction orthogonal to the X direction. However, the angle formed by the polarization axis of the polarizing element 10 and the polarization axes of the inspection polarizing filters 6a and 6b is not limited to 90 °, and may be within the range of 90 ° ± 10 °.
Since the configurations and manufacturing methods of the inspection polarizing filters 6a and 6b are the same as those of the polarizing element 10, detailed description thereof will be omitted here.

The inspection polarizing filters 6a and 6b of the present embodiment are arranged on the lower surface side (separator 40 side) of the optical laminate S. Specifically, the inspection polarizing filters 6a and 6b are arranged between the optical laminate S and the light sources 5a and 5b, respectively, and the light emitted from the light sources 5a and 5b is the inspection polarizing filters 6a and 6b, respectively. Will be transmitted and irradiated to the optical laminated body S. In the case of the present embodiment, the state of the cross Nicol is disrupted due to the defect existing between the inspection polarizing filters 6a and 6b and the polarizing element 10, so that the cloth of the optical laminate S produced in the cross Nicol inspection step S2 described later is used. In the Nicol image, the pixel region corresponding to the defect existing between the inspection polarizing filters 6a and 6b and the polarizing element 10 becomes bright (the brightness value becomes large), and this defect can be detected as a defect candidate.
However, the present invention is not necessarily limited to this, and it is also possible to arrange the inspection polarizing filters 6a and 6b on the upper surface side (surface protection film 50 side) of the optical laminate S. Specifically, one inspection polarizing filter is arranged between the optical laminate S and the image pickup means, and the light emitted from the light sources 5a and 5b and transmitted through the optical laminate S is the inspection polarizing filter. It is also possible to adopt a configuration in which the image is transmitted through and received by the image pickup means 4. In this case, since the state of the cross Nicol is disturbed due to the defect existing between the inspection polarizing filter and the polarizing element 10, the cross Nicol image of the optical laminate S generated in the cross Nicol inspection step S2 described later is used for inspection. The pixel region corresponding to the defect existing between the polarizing filter and the polarizing element 10 becomes bright (the brightness value becomes large), and this defect can be detected as a defect candidate.

[Light source 7]
The light source 7 is a light source for executing the reflection inspection step S3 described later, and is arranged on the lower surface side (separator 40 side) of the optical laminate S in the present embodiment. The optical axis of the light source 7 (shown by a broken line in FIG. 1A) is oriented in a direction inclined with respect to the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S. In the example shown in FIG. 1A, the optical axis of the light source 7 is oriented in a direction inclined toward the upstream side in the transport direction of the optical laminate S with respect to the vertical direction. However, the present invention is not limited to this, and it is also possible to direct the optical axis of the light source 7 in a direction inclined toward the downstream side in the transport direction of the optical laminate S with respect to the vertical direction. Further, for example, by adopting a coaxial epi-illumination optical system composed of a half mirror or the like, it is possible to direct the optical axis of the light source 7 in the vertical direction. The light source 7 emits light upward toward the optical laminate S according to the control signal output from the control calculation means 9.
The light source 7 is not limited as long as it can emit light having a wavelength that can be reflected by the optical laminate S, and for example, an LED or a halogen lamp can be used.

[Imaging means 8]
The image pickup means 8 is an image pickup means for executing the reflection inspection step S3 described later, and is arranged on the lower surface side (separator 40 side) of the optical laminate S in the present embodiment. The optical axis of the image pickup means 8 (shown by a broken line in FIG. 1A) is directed in the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S, and the image pickup means 8 is a control calculation means 9. According to the control signal output from the light source 7, the light emitted from the light source 7 is received and imaged, and the electric signal corresponding to the amount of the light is output to the control calculation means 9 as an image pickup signal. The focal point of the image pickup means 8 is set on the lower surface of the optical laminate S (the lower surface of the separator 40).

In the present embodiment, as the image pickup means 8, a plurality of image pickup elements (CCD or CMOS) are linearly formed in a direction (Y direction) orthogonal to the transport direction (X direction) of the optical laminate S, as in the image pickup means 4. A line sensor is used, which is arranged in a fixed scanning cycle (for example, 7 μsec to 14 μsec) and outputs an image pickup signal. By using the line sensor as the image pickup means 8, the field of view in the X direction of the image pickup means 8 becomes smaller, so that the required irradiation range of the light emitted from the light source 7 in the X direction can be narrowed, and there are restrictions on the arrangement of the light source 7. The advantage is that the conditions are relaxed. The optical laminate S is conveyed in the X direction and the imaging element of the line sensor is scanned in the Y direction, so that a two-dimensional reflection image is generated in the reflection inspection step S3 described later.
However, the image pickup means 8 is not necessarily limited to the line sensor, and for example, a two-dimensional camera with a high-speed shutter can be used as the image pickup means 8.

[Control calculation means 9]
The control calculation means 9 is composed of, for example, a personal computer or a programmable logic controller (PLC) in which a program for executing control processing or calculation processing described later is installed.

<Inspection method according to this embodiment>
Hereinafter, an inspection method for the optical laminate S according to the present embodiment using the inspection apparatus 100 described above will be described.
FIG. 2 is a flow chart showing a schematic process of an inspection method for the optical laminate S according to the present embodiment.
As shown in FIG. 2, the inspection method according to the present embodiment includes a transmission inspection step S1, a cross Nicol inspection step S2, a reflection inspection step S3, and a calculation step 4.
Hereinafter, each process S1 to S4 will be described.

[Penetration inspection step S1]
In the transmission inspection step S1, a transmission image of the optical laminate S is generated by the light transmitted through the optical laminate S, and defect candidates existing in the optical laminate S are detected based on the transmission image (S11 in FIG. 2). ..
Specifically, the light source 3 and the image pickup means 4 are driven by the control signal output from the control calculation means 9 at the timing immediately before the optical laminate S reaches directly under the image pickup means 4. Then, the image pickup means 4 emits light from the light source 3 and receives the light transmitted through the optical laminate S to form an image, and outputs an electric signal corresponding to the amount of the light to the control calculation means 9 as an image pickup signal. The control calculation means 9 generates a two-dimensional transmission image based on the input imaging signal. Then, the control calculation means 9 applies known image processing such as binarization to extract a pixel region having a different luminance value (pixel value) from the other pixel region to the generated transparent image. Detect defect candidates.

FIG. 3 is a diagram schematically illustrating an example of defect candidates detected in the permeation inspection step S1. FIG. 3A is a cross-sectional view schematically illustrating an example of defects existing in the optical laminate S. FIG. 3B is a diagram schematically illustrating an example of defect candidates detected before executing the noise reduction procedure S12 in the transmission inspection step S1. FIG. 3C is a diagram schematically illustrating an example of defect candidates remaining after the noise reduction procedure S12 of the transmission inspection step S1 is executed.
In FIG. 3A, reference numeral F1 indicates a harmless foreign substance adhering to the surface of the separator 40 which is a release film. Reference numeral F2 indicates a harmless scratch existing on the surface of the separator 40. Reference numeral F3 indicates a harmful bonded foreign substance existing between the polarizing element 10 and the retardation film 20. Reference numeral F4 indicates a harmless foreign substance adhering to the surface of the surface protective film 50 which is a release film. 3 (b) and 3 (c) show transmissive images after binarization, and in FIG. 3 (b), three foreign substances F1 (F1a to F1c), two scratches F2 (F2a, F2b), and 1 One bonded foreign substance F3 and two foreign substances F4 (F4a, F4b) are detected as defect candidates, respectively. In FIG. 3C, one foreign matter F1 (F1c), one scratch F2 (F2a), one bonded foreign matter F3, and two foreign matters F4 (F4a, F4b) are detected as defect candidates, respectively.

The transmission inspection step S1 of the present embodiment performs a noise reduction procedure (S12 in FIG. 2) for excluding defect candidates having a dimension (for example, an area) larger than a predetermined threshold value from the detected defect candidates. Includes. Therefore, among the detected defect candidates shown in FIG. 3 (b), foreign substances F1a, F1b, and scratches F2b, which are defect candidates having relatively large dimensions, are excluded, and the state shown in FIG. 3 (c) is obtained. ing.

[Cross Nicol inspection process S2]
In the cross Nicol inspection step S2, a cross Nicol image of the optical laminate S is generated by light transmitted through the inspection polarizing filters 6a and 6b and the optical laminate S, and is present in the optical laminate S based on the cross Nicol image. Detects defect candidates (S2 in FIG. 2).
Specifically, the light sources 5a and 5b and the image pickup means 4 are driven by the control signal output from the control calculation means 9 at the timing immediately before the optical laminate S reaches directly under the image pickup means 4. Then, the image pickup means 4 emits light from the light sources 5a and 5b, receives the light transmitted through the inspection polarizing filters 6a and 6b and the optical laminate S, respectively, and forms an image, and images an electric signal according to the amount of the light. It is output to the control calculation means 9 as a signal. The control calculation means 9 generates a two-dimensional cross Nicol image based on the input imaging signal. Then, the control calculation means 9 is known for binarizing the generated cross Nicol image by extracting a pixel region having a different luminance value (pixel value) from another pixel region (the luminance value becomes larger). By applying image processing, defect candidates are detected.

FIG. 4 is a diagram schematically illustrating an example of defect candidates detected in the cross Nicol inspection step S2. FIG. 4 shows a cross Nicol image after binarization, and three foreign substances F1 (F1a to F1c), three scratches F2 (F2b to F2d), and one bonded foreign substance F3 are detected as defect candidates, respectively. .. Since the foreign matter F4 adhering to the surface of the surface protective film 50 is not located between the polarizing element 10 and the inspection polarizing filters 6a and 6b, it is not detected in the cross Nicol image unlike the transmission image.

In this embodiment, since the image pickup means 4 for generating the transmission image and the image pickup means 4 for generating the cross Nicol image are the same, the control calculation means 9 is the image pickup means in the transmission inspection step S1. Control is performed to switch between the timing of executing the image pickup by the image pickup means 4 and the timing of executing the image pickup by the image pickup means 4 in the cross Nicol inspection step S2.
Specifically, the control calculation means 9 has a timing of emitting light from the light source 3 used for generating a transmission image and a timing of emitting light from the light sources 5a and 5b used for generating a cross image. Is controlled to be switched for each scanning cycle of the image pickup means 4. That is, the control calculation means 9 outputs a control signal for emitting light from the light source 3 in one scanning cycle to the light source 3, and then emits a control signal for emitting light from the light sources 5a and 5b in the next scanning cycle. Output for 5a and 5b. The control calculation means 9 further outputs a control signal for emitting light from the light source 3 to the light source 3 in the next scanning cycle. The control calculation means 9 repeats the above operation until one optical laminate S finishes passing directly under the image pickup means 4.

FIG. 5 is a diagram schematically illustrating the content of the switching control executed by the control calculation means 9. As described above, FIG. 5A shows that the control calculation means 9 switches between the timing of emitting light from the light source 3 and the timing of emitting light from the light sources 5a and 5b for each scanning cycle of the image pickup means 4. As shown, the image pickup means 4 emits light emitted from the light source 3 and transmitted through the optical laminate S (the region shown in white in FIG. 5A) and emitted from the light sources 5a and 5b, and is an inspection polarizing filter. The light transmitted through 6a, 6b and the optical laminate S (the region subjected to the dot-shaped hatching in FIG. 5A) is alternately imaged in the X direction at a pitch corresponding to the scanning period.
The control calculation means 9 extracts only the region shown in white in FIG. 5 (a) and synthesizes it in the X direction according to the scanning cycle of the image pickup means 4, so that the transmitted image as shown in FIG. 5 (b) is synthesized. To generate. Further, the control calculation means 9 extracts only the region in which the dot-shaped hatching is applied in FIG. 5A according to the scanning cycle of the image pickup means 4, and synthesizes them in the X direction, so that FIG. 5C is shown. Generate a cross Nicol image as shown.
As described above, the control calculation means 9 includes the transparent image and the cross Nicol image even if the image pickup means 4 for generating the transparent image and the image pickup means 4 for generating the cross Nicol image are the same. Can be generated separately.

[Reflection inspection step S3]
In the reflection inspection step S3, a reflected image of the optical laminated body S is generated by the light reflected by the optical laminated body S, and defect candidates existing in the optical laminated body S are detected based on the reflected image (S3 in FIG. 2). ..
Specifically, the light source 7 and the image pickup means 8 are driven by the control signal output from the control calculation means 9 at the timing immediately before the optical laminate S reaches directly under the image pickup means 8. Then, the image pickup means 8 emits light from the light source 7, receives the light reflected by the optical laminate S, forms an image, and outputs an electric signal corresponding to the amount of the light to the control calculation means 9 as an image pickup signal. The control calculation means 9 generates a two-dimensional reflected image based on the input imaging signal. Then, the control calculation means 9 applies known image processing such as binarization to extract a pixel region having a different luminance value (pixel value) from the other pixel region to the generated reflected image. Detect defect candidates.

FIG. 6 is a diagram schematically illustrating an example of defect candidates detected in the reflection inspection step S3. FIG. 6 shows a reflected image after binarization, and three foreign substances F1 (F1a to F1c) are detected as defect candidates. Since the reflected image is generated by the light reflected by the optical laminate S, only the foreign matter F1 adhering to the surface of the separator 40 on the side where the light source 7 is arranged is detected. In the example shown in FIG. 6, only the foreign matter F1 is detected, but the scratch F2 existing on the surface of the separator 40 may also be detected.

[Calculation process S4]
In the calculation step S4, the polarizing element 10 and the optics are based on the defect candidates detected in the transmission inspection step S1, the defect candidates detected in the cross Nicol inspection step S2, and the defect candidates detected in the reflection inspection step S3. Defects existing with the film (in the present embodiment, the retardation film 20) are determined (S4 in FIG. 2).
Specifically, in the calculation step S4, the calculation control means 9 first determines whether or not a defect candidate is detected in both the transmission inspection step S1 and the cross Nicol inspection step S2 (S41 in FIG. 2). Whether or not the defect candidate is detected in both the permeation inspection step S1 and the cross Nicol inspection step S2 is checked at the same position (same or near) as the position of a certain defect candidate detected in the permeation inspection step S1. It is determined whether or not the defect candidate detected in the step S2 exists. Specifically, for example, at a position equivalent to the position of the center of gravity of the defect candidate detected in the permeation inspection step S1 (for example, the position of the center of gravity ± 2 mm), the defect candidate detected in the cross Nicol inspection step S2. It is determined by whether or not the center of gravity exists. In order to determine whether or not the defect candidate detected in the cross Nicol inspection step S2 exists at a position equivalent to the position of the defect candidate detected in the transmission inspection step S1, the coordinates of the transmission image and the cross Nicol image are used. The coordinates must match. In the present embodiment, as described above, since the image pickup means 4 for generating the transmission image and the image pickup means 4 for generating the cross Nicol image are the same, the coordinates of the transmission image and the cross Nicole image are used. It almost matches the coordinates, and there is little need to dare to match the coordinates of both images exactly. However, strictly speaking, as can be seen from the contents described with reference to FIG. 5, the coordinates of the transmitted image and the coordinates of the cross Nicol image are deviated in the X direction by the pitch corresponding to the scanning cycle of the imaging means 4. Therefore, it is preferable that the arithmetic control means 9 corrects this deviation and matches the coordinates of both images.

FIG. 7 is a diagram schematically explaining the contents of the calculation step S4.
FIG. 7A is a diagram schematically illustrating an example of defect candidates determined to be detected in both the permeation inspection step S1 and the cross Nicol inspection step S2 in the calculation step S4 (specifically, S41). Is. As shown in FIG. 3C described above, in the permeation inspection step S1, foreign matter F1c, scratch F2a, bonded foreign matter F3, foreign matter F4a, and F4b are detected as defect candidates, and as shown in FIG. In the Nicol inspection step S2, foreign substances F1a to F1c, scratches F2b to F2d, and bonded foreign matter F3 are detected as defect candidates. For example, since the foreign matter F1c detected in the permeation inspection step S1 is also detected in the cross Nicol inspection step S2, the arithmetic control means 9 determines that the foreign matter F1c is detected in both of them (“Yes” in S41 of FIG. 2). "). On the other hand, for example, since the scratch F2a detected in the permeation inspection step S1 is not detected in the cross Nicol inspection step S2, the arithmetic control means 9 determines that the scratch F2a is not detected on both sides (FIG. 2). It becomes "No" in S41), and it is determined that this defect candidate (scratch F2a) is not the bonded foreign matter F3 existing between the polarizing element 10 and the retardation film 20 (S44 in FIG. 2). In the present embodiment, by executing the same calculation for all the defect candidates detected in the permeation inspection step S1, the defect candidates (foreign matter F1c and bonded foreign matter F3) shown in FIG. 7 (a) are subjected to the permeation inspection step S1. And, it is determined that it is a defect candidate detected in both the cross Nicol inspection step S2.

Next, in the calculation step S4, the calculation control means 9 determines whether or not the defect candidate detected in both the transmission inspection step S1 and the cross Nicol inspection step S2 is detected in the reflection inspection step S3 (FIG. 2). S42). Whether or not the defect candidate detected in both the permeation inspection step S1 and the cross Nicol inspection step S2 is detected in the reflection inspection step S3 is a defect candidate detected in both the permeation inspection step S1 and the cross Nicol inspection step S2. It is determined whether or not there is a defect candidate detected in the reflection inspection step S3 at a position equivalent to (same or near) the position of. Specifically, for example, at a position equivalent to the position of the center of gravity of the defect candidate detected in both the transmission inspection step S1 and the cross Nicol inspection step S2 (for example, the position of the center of gravity ± 2 mm), the reflection inspection step S3 It is determined whether or not the center of gravity of the defect candidate detected in is present. To determine whether or not the defect candidate detected in the reflection inspection step S3 exists at a position equivalent to the position of the defect candidate detected in both the transmission inspection step S1 and the cross Nicol inspection step S2, the transmission image is used. And the coordinates of the cross Nicole image and the coordinates of the reflection image must match. The coordinates of the transmitted image and the cross Nicol image and the coordinates of the reflected image are obtained by dividing the separation distance L (see FIG. 1A) between the image pickup means 4 and the image pickup means 8 in the X direction by the transport speed V of the optical laminate S. Since the deviation is in the X direction by the amount of time, it is necessary for the arithmetic control means 9 to correct this deviation and match the coordinates of the transmission image and the cross Nicol image with the coordinates of the reflection image. Further, since the coordinates of the transparent image and the cross Nicol image and the coordinates of the reflected image may be deviated in the Y direction, the arithmetic control means 9 applies a known image processing to the transparent image and the cross. The Y-direction edge (edge of the optical laminate S) in the Nicole image and the Y-direction edge (edge of the optical laminate S) in the reflection image are detected, and the transmission image is arranged so that the positions of these edges match. And it is preferable to match the coordinates of the cross Nicol image with the coordinates of the reflection image.

FIG. 7B is a diagram schematically illustrating an example of defect candidates determined not to be detected in the reflection inspection step S3 in the calculation step S4 (specifically, S42). As shown in FIG. 7A, among the foreign matter F1c and the bonded foreign matter F3 detected in both the permeation inspection step S1 and the cross Nicol inspection step S2, the foreign matter F1c is as shown in FIG. Since it is also detected in the reflection inspection step S3, the arithmetic control means 9 determines that the foreign matter F1c is detected in the reflection inspection step S3 (it becomes “Yes” in S42 of FIG. 2), and this defect candidate (foreign matter F1c). Is not the bonded foreign matter F3 existing between the polarizing element 10 and the retardation film 20 (S44 in FIG. 2). On the other hand, among the foreign matter F1c and the bonded foreign matter F3 detected in both the permeation inspection step S1 and the cross Nicol inspection step S2, the bonded foreign matter F3 is detected in the reflection inspection step S3 as shown in FIG. Therefore, the arithmetic control means 9 determines that the bonded foreign matter F3 is not detected in the reflection inspection step S3 (“No” in S42 of FIG. 2), and the defect candidate (bonded foreign matter F3) is polarized. It is determined that the foreign matter F3 is a bonded foreign substance existing between the child 10 and the retardation film 20 (S43 in FIG. 2).

According to the findings of the present inventors, the defect candidates detected in both the transmission image and the cross Nicol image but not in the reflection image are the defects existing between the polarizing element 10 and the retardation film 20 (paste). There is a high possibility that it is a foreign substance). According to the inspection method according to the present embodiment, as described above, in the calculation step S4, it is detected in both the transmission inspection step S1 and the cross Nicol inspection step S2 (that is, it is detected in both the transmission image and the cross Nicol image). ), The defect candidate not detected in the reflection inspection step S3 (that is, not detected in the reflection image) is determined to be a defect existing between the polarizing element 10 and the retardation film 20. It is possible to suppress over-detection of defects existing on the surface of (separator 40, surface protective film 50) and accurately detect defects existing between the splitter 10 and the retardation film 20.

In the present embodiment, the inspection target is an optical film 20 and 30 (phase difference film 20, protective film 30) laminated on both sides of the polarizing element 10 in the thickness direction, and a release film is formed on both outermost surfaces in the thickness direction. The case where the optical laminate S in which 40 and 50 (separator 40, surface protective film 50) are laminated has been described as an example has been described, but the present invention is not limited to this. As long as it is an optical laminate in which at least one optical film (for example, only the retardation film 20) is laminated on the polarizing element 10, and a release film (for example, only the separator 40) is laminated on at least one outermost surface side. It can be applied to various optical laminates.

Further, in the present embodiment, the case where the inspection target is the optical laminate S cut into a chip shape has been described as an example, but the present invention is not limited to this. Similar to the inspection methods described in Patent Documents 1 to 3, it is also possible to adopt a configuration in which an inspection is performed while transporting a long optical laminate by roll-to-roll.

Further, in the present embodiment, the case where the light sources 3, 5a, 5b, and 7 are arranged on the lower surface side (separator 40 side) of the optical laminate S has been described as an example, but the present invention is limited to this. Instead, the light sources 3, 5a, 5b, and 7 are arranged on the upper surface side (surface protective film 50 side) of the optical laminate S (the inspection polarizing filters 6a, 6b are also arranged on the upper surface side of the optical laminate S). It is also possible to adopt. In this case, the image pickup means 4 is arranged on the lower surface side of the optical laminate S, and the image pickup means 8 is arranged on the upper surface side of the optical laminate S. Then, in this case, in the cross Nicol inspection step S2, the bonded foreign matter existing between the polarizing element 10 and the protective film 30 is detected.

Further, in the present embodiment, the case where the image pickup means 4 for generating a transmission image in the transmission inspection step S1 and the imaging means 4 for generating a cross Nicole image in the cross Nicol inspection step S2 are the same is taken as an example. As described above, the present invention is not limited to this, and it is also possible to separately provide an imaging means for generating a transmission image and an imaging means for generating a cross Nicol image.

Further, in the present embodiment, the transmission inspection step S1, the cross Nicol inspection step S2, and the reflection inspection step S3 are executed in this order (however, the timings of performing the imaging in the transmission inspection step S1 and the cross Nicol inspection step S2 overlap). ) The case has been described as an example, but the present invention is not limited to this, and can be executed in any order. Further, after executing the transmission inspection step S1 and the cross Nicol inspection step S2, only the S41 of the calculation step S4 is executed first, and then the reflection inspection step S3 is executed, and then the S42 of the calculation step S4 is executed. It is also possible to adopt it.

1 ... Belt conveyor 2 ... Clean rollers 3, 5a, 5b, 7 ... Light source 4, 8 ... Imaging means 6a, 6b ... Inspection polarizing filter 10 ... Polarizer 20 ...・ Phase difference film (optical film)
30 ... Protective film (optical film)
40 ... Separator (release film)
50 ... Surface protection film (release film)
100 ... Inspection device S ... Optical laminate S1 ... Transmission inspection process S2 ... Cross Nicol inspection process S3 ... Reflection inspection process S4 ... Calculation process

Claims (5)

1. A method for inspecting an optical laminate in which a polarizing element and an optical film are laminated, and a release film is further laminated on at least one outermost surface side in the thickness direction.
   A transmission inspection step of generating a transmission image of the optical laminate by light transmitted through the optical laminate and detecting defect candidates existing in the optical laminate based on the transmission image.
   A cross Nicol image of the optical laminate is generated by light transmitted through the inspection polarizing filter and the optical laminate arranged so as to form a cross Nicol with respect to the polarization axis of the polarizing element, and based on the cross Nicol image. , A cross Nicol inspection step for detecting defect candidates existing in the optical laminate, and
   A reflection inspection step of generating a reflected image of the optical laminate by the light reflected by the optical laminate and detecting defect candidates existing in the optical laminate based on the reflected image.
   Between the decoder and the optical film based on the defect candidates detected in the transmission inspection step, the defect candidates detected in the cross Nicol inspection step, and the defect candidates detected in the reflection inspection step. Including an arithmetic process for determining the defects present in
   In the calculation step, defect candidates detected in both the transmission inspection step and the cross Nicol inspection step and not detected in the reflection inspection step are defects existing between the polarizing element and the optical film. Judging,
   Inspection method for optical laminates.
2. The release film is a separator,
   The optical film is located between the separator and the polarizing element.
   In the cross Nicol inspection step, the inspection polarizing filter is arranged on the separator side.
   The method for inspecting an optical laminate according to claim 1.
3. The orientation direction of the release film is within ± 6 ° with respect to a predetermined orientation direction.
   The method for inspecting an optical laminate according to claim 1 or 2.
4. The imaging means for generating the transmission image in the transmission inspection step and the imaging means for generating the cross Nicol image in the cross Nicol inspection step are the same.
   Switching between the timing of executing the image pickup by the image pickup means in the transmission inspection step and the timing of executing the image pickup by the image pickup means in the cross Nicol inspection step.
   The method for inspecting an optical laminate according to any one of claims 1 to 3.
5. The permeation inspection step and / or the cross Nicol inspection step includes a noise reduction procedure for excluding defect candidates having a dimension larger than a predetermined threshold value from the detected defect candidates.
   The method for inspecting an optical laminate according to any one of claims 1 to 4.

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