Inspection method, inspection device, and method for manufacturing laminate

Abstract

The invention provides a technology capable of easily determining the presence or absence of a defect in a circular polarizing plate, and relates to an inspection method, an inspection device, and a method for manufacturing a laminate. An inspection method according to one embodiment of the present invention inspects the presence or absence of a defect in a first circular polarizing plate of a laminate provided with the first circular polarizing plate having a first linear polarizing plate and a first phase difference film, and a release film formed from a polyethylene terephthalate resin, the inspection method comprising: an irradiation step for irradiating the first circular polarizing plate; irradiating inspection light to the laminate in a state in which the wavelength is changed over time or in a state in which the wavelength is changed over space within an inspection wavelength range including the predetermined wavelength; a detection step for detecting the inspection light output from the release film side of the laminate irradiated with the inspection light; and a determination step for determining the presence or absence of a defect in the first circular polarizing plate on the basis of the detection result, the prescribed wavelength being a wavelength at which the first phase difference or the second phase difference occurs due to the transmission of light of the prescribed wavelength through the release film.

Description

Technical Field

[0001] The present invention relates to an inspection method, an inspection device, and a method for manufacturing a laminated body. Background Art

[0002] The polarizing plate used in liquid crystal display devices, organic EL display devices, etc. is generally formed by sandwiching a polarizer between two protective films. In order to stick the polarizing plate to the display device, an adhesive layer is laminated on a protective film, and a release film is further laminated on the adhesive layer. In addition, a release film (surface protection film) that protects its surface is often also laminated on another protective film. The polarizing plate is circulated and transported in a state laminated with a release film like this, and the release film is peeled off when it is attached to the display device in the manufacturing process of the display device.

[0003] However, when foreign matter is mixed between the polarizer and the protective film during the manufacturing stage of the polarizing plate, or bubbles remain, or the protective film has the function of a phase difference film, there may be an orientation defect (hereinafter, these foreign matter, bubbles and orientation defects are sometimes collectively referred to as "defects"). When the defective polarizing plate is attached to a display device, the defective part may be observed as a bright spot, or the image at the defective part may appear distorted. In particular, defects observed in the form of bright spots are easily observed when the display device is displayed in black.

[0004] Therefore, in the pre-stage of attaching the polarizing plate to the display device (the polarizing plate in the state of having a peeling film), an inspection for detecting defects of the polarizing plate is performed. The inspection of the defects is usually an optical inspection using the polarization axis of the polarizing plate. Specifically, as shown in Patent Document 1, after a polarizing filter is set between the polarizing plate as the object to be inspected and the light source, the polarizing plate or the polarizing filter is rotated in the plane direction, and the directions of their respective polarization axes are set to a specific relationship. In the case where the directions of the polarization axes are orthogonal to each other (i.e., in the case of a configuration that constitutes an orthogonal Nicol prism), the linear polarized light that passes through the polarizing filter does not pass through the polarizing plate. However, if there is a defect in the polarizing plate, the linear polarized light is transmitted at this position, so the presence of the defect is determined by detecting the light. On the other hand, in the case where the polarization axis directions of the polarizing plate and the polarizing filter are parallel, the linear polarized light that passes through the polarizing filter is transmitted through the polarizing plate. However, if there is a defect in the polarizing plate, the linear polarized light is blocked at this position, so the presence of the defect is determined by not detecting the light. The presence or absence of defects in the polarizing plate can be inspected by an inspector visually detecting light transmitted through the polarizing plate, or automatically detecting light by image analysis processing using a combination of a CCD camera and an image processing device.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 9-229817 Summary of the invention

[0008] Problems to be solved by the invention

[0009] When the polarizing plate is a circular polarizing plate, it is conceivable to further arrange a phase difference filter with respect to the circular polarizing plate so as to darken the observation field, and detect a bright spot generated at a defective portion.

[0010] Circular polarizing plates are usually also circulated and transported in a state where a release film is laminated. Therefore, when inspecting a circular polarizing plate, it is inspected in a state where a release film is laminated. The release film is a film that is peeled off when the circular polarizing plate is mounted on a display device, so the phase difference of the release film is not strictly managed. Therefore, sometimes the observation field of view cannot be fully darkened due to the phase difference existing in the release film, and the detection accuracy of defects is reduced.

[0011] Therefore, an object of the present invention is to provide a technology capable of improving the detection accuracy of defects in a circularly polarizing plate.

[0012] Means for solving problems

[0013] [1] An inspection method according to one embodiment inspects whether a film-like laminate having a first circular polarizing plate and a release film has defects, wherein the first circular polarizing plate has a first linear polarizing plate and a first phase difference film laminated on the first linear polarizing plate, and the release film is laminated on the first phase difference film and is formed of a polyethylene terephthalate resin, the inspection method comprising: an irradiation step of irradiating the laminate with inspection light while changing the wavelength with time or with space within an inspection wavelength range including a specified wavelength; a detection step of detecting the inspection light output from the release film side of the laminate irradiated with the inspection light; and a determination step of determining whether the first circular polarizing plate has defects based on the detection result of the detection step, wherein when the specified wavelength is set to λ [nm] and n is set to an integer greater than 1, the specified wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ is generated due to light of the specified wavelength passing through the release film.

[0014] In the inspection method described in [1] above, the inspection light is irradiated onto the above-mentioned laminate while the wavelength is varied over time or in a state where the wavelength is varied over space within the inspection wavelength range including the specified wavelength. Therefore, the detection result of the light of the specified wavelength can be reliably obtained. When the above-mentioned specified wavelength is set to λ [nm] and n is set to an integer greater than 1, the above-mentioned specified wavelength is a wavelength at which the first phase difference of nλ or the second phase difference of (n+1 / 2)λ is generated due to the light of the above-mentioned specified wavelength passing through the above-mentioned release film. As a result, the influence of the release film on the light of the specified wavelength is reduced. Therefore, in the case where there is a defect in the first circularly polarizing plate, the defect can be detected with excellent accuracy.

[0015] [2] In the inspection method described in [1] above, the predetermined wavelength is a wavelength at which the first phase difference is generated when light of the predetermined wavelength passes through the release film, and the inspection wavelength range may be a wavelength of 500 nm to 550 nm.

[0016] When the release film is formed of a PET-based resin, the above-mentioned inspection wavelength range easily includes a predetermined wavelength that generates the first phase difference in light passing through the release film. Therefore, by making the inspection wavelength range the range described in [2] above, when the first circularly polarizing plate has a defect, the defect can be detected with high accuracy.

[0017] [3] In the inspection method described in [2] above, in the irradiation step, the laminate is irradiated with the inspection light from the second linear polarizing plate side through the second circular polarizing plate having the second linear polarizing plate and the second phase difference film, and in the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the peeling film is detected after passing through the third circular polarizing plate having the third linear polarizing plate and the third phase difference film from the third phase difference film side. The second circular polarizing plate and the third circular polarizing plate may be both left-handed or both right-handed circular polarizing plates and may rotate in the opposite direction to the first circular polarizing plate.

[0018] [4] In the inspection method described in [2] above, in the irradiation step, the stacked body is irradiated with the inspection light from the side of the fourth linear polarizing plate through the fourth circular polarizing plate having the fourth linear polarizing plate and the fourth phase difference film from the side of the fourth linear polarizing plate, and in the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the peeling film is detected after passing through the fourth circular polarizing plate from the side of the fourth phase difference film. The fourth circular polarizing plate may be a circular polarizing plate having a rotation direction opposite to that of the first circular polarizing plate.

[0019] [5] In the inspection method described in [2] above, in the irradiation step, the inspection light is irradiated onto the stack from the first circular polarizing plate side, and in the detection step, the inspection light transmitted through the stack in the order of the first circular polarizing plate and the peeling film is detected from the detection phase difference film side through a detection circular polarizing plate having a detection linear polarizing plate and the detection phase difference film. The detection circular polarizing plate may be a circular polarizing plate having a rotation direction opposite to that of the first circular polarizing plate.

[0020] In the inspection methods described in [3], [4] and [5], the detection area (e.g., observation area) of the detection unit is dark. On the other hand, when the first circular polarizing plate has a defect, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0021] [6] In the inspection method described in [1] above, the predetermined wavelength is a wavelength at which the second phase difference is generated when light of the predetermined wavelength passes through the release film, and the inspection wavelength range may be a wavelength of greater than 570 nm and less than 630 nm.

[0022] When the release film is formed of a PET-based resin, the above-mentioned inspection wavelength range easily contains a predetermined wavelength that generates the second phase difference in light passing through the release film. Therefore, by making the inspection wavelength range the range described in [6] above, when there is a defect in the first circularly polarizing plate, the defect can be detected with high accuracy.

[0023] [7] In the inspection method described in [6] above, in the irradiation step, the laminate is irradiated with the inspection light from the second linear polarizing plate side through the second circular polarizing plate having the second linear polarizing plate and the second phase difference film, and in the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the peeling film is detected after passing through the third circular polarizing plate having the third linear polarizing plate and the third phase difference film from the third phase difference film side. The first circular polarizing plate, the second circular polarizing plate and the third circular polarizing plate may be circular polarizing plates having the same rotation direction.

[0024] [8] In the inspection method described in [6] above, in the irradiation step, the stacked body is irradiated with the inspection light from the side of the fourth linear polarizing plate through the fourth circular polarizing plate having the fourth linear polarizing plate and the fourth phase difference film from the side of the fourth linear polarizing plate, and in the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the peeling film is detected after passing through the fourth circular polarizing plate from the side of the fourth phase difference film. The fourth circular polarizing plate may be a circular polarizing plate having a rotation direction opposite to that of the first circular polarizing plate.

[0025] [9] In the inspection method described in [6] above, in the irradiation step, the inspection light is irradiated onto the stack from the first circular polarizing plate side, and in the detection step, the inspection light output from the peeling film side of the stack is passed from the detection phase difference film side through a detection circular polarizing plate having a detection linear polarizing plate and the detection phase difference film for detection, and the detection circular polarizing plate may be a circular polarizing plate having the same rotation direction as the first circular polarizing plate.

[0026] In the inspection methods described in [7], [8] and [9], the detection area (e.g., observation area) of the detection unit is dark. On the other hand, when the first circular polarizing plate has a defect, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0027]

[10] In the inspection method described in any one of [1] to [9] above, in the irradiation step, the stacked body is irradiated with the inspection light obtained by passing light from a light source that outputs light in a wavelength range including the inspection wavelength range through a bandpass filter that selectively passes wavelengths at the upper limit of the inspection wavelength range, the bandpass filter being arranged obliquely with respect to a plane orthogonal to the stacking direction of the first circular polarizing plate and the release film so as to form a wavelength gradient in which the wavelength changes along a prescribed direction within the inspection wavelength range in an irradiation area of ​​the inspection light, and in the detection step, the inspection light output from the release film can be detected while the stacked body is moved along the prescribed direction relative to the irradiation area.

[0028] In the inspection method described in

[10] above, a wavelength gradient in which the wavelength changes within the inspection wavelength range along a prescribed direction is generated. Therefore, in the inspection method, the inspection light is irradiated in a state where the wavelength changes spatially within the inspection wavelength range. In the detection step, the inspection light output from the release film is detected while the stack is moved along the prescribed direction relative to the irradiation area. Therefore, the inspection light of the prescribed wavelength contained in the wavelength gradient can be reliably detected. As a result, defects can be detected with high accuracy.

[0029]

[11] The method for manufacturing a laminate according to another aspect of the present invention comprises a step of inspecting the presence or absence of defects of the first circular polarizing plate of the laminate using the inspection method described in any one of [1] to

[10] . In this case, since the presence or absence of defects of the first circular polarizing plate is inspected using the inspection method described in any one of [1] to

[10] , when the first circular polarizing plate has defects, the defects can be detected with high accuracy. Therefore, quality management of the laminate and the first circular polarizing plate of the laminate can be implemented.

[0030]

[12] Another aspect of the present invention is an inspection device for inspecting whether a film-like laminate having a first circular polarizing plate and a release film has defects, wherein the first circular polarizing plate has a first linear polarizing plate and a first phase difference film stacked on the first linear polarizing plate, and the release film is stacked on the first phase difference film side and is formed of a polyethylene terephthalate resin, the inspection device comprising: a light source unit configured to irradiate the laminate with inspection light while changing the wavelength within an inspection wavelength range including a prescribed wavelength or in a state where the wavelength changes spatially; and a detection unit configured to detect the inspection light output from the release film side of the laminate irradiated with the inspection light, wherein when the prescribed wavelength is set to λ [nm] and n is set to an integer greater than 1, the prescribed wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ is generated due to the light of the prescribed wavelength passing through the release film.

[0031] In the inspection device described in

[12] above, the first circular polarizing plate can be inspected while irradiating the stack with inspection light while changing the wavelength over time within the inspection wavelength range including the specified wavelength or while changing the wavelength over space. In this case, the detection result of the light of the specified wavelength can be reliably obtained. When the above-mentioned specified wavelength is set to λ [nm] and n is set to an integer greater than 1, the above-mentioned specified wavelength is a wavelength at which the first phase difference of nλ or the second phase difference of (n+1 / 2)λ is generated due to the light of the above-mentioned specified wavelength passing through the above-mentioned release film. As a result, the influence of the release film on the light of the specified wavelength is reduced. Therefore, in the case where there is a defect in the first circular polarizing plate, the defect can be detected with excellent accuracy.

[0032]

[13] In the inspection device described in

[12] above, the above-mentioned specified wavelength is a wavelength at which the above-mentioned first phase difference is generated due to the light of the above-mentioned specified wavelength passing through the above-mentioned peeling film, and the above-mentioned inspection wavelength range can be a wavelength greater than 500nm and less than 550nm.

[0033] When the release film is formed of a PET-based resin, the above-mentioned inspection wavelength range easily contains a predetermined wavelength that generates the first phase difference in light passing through the release film. Therefore, by making the inspection wavelength range the range described in

[13] above, when the first circularly polarizing plate has a defect, the defect can be detected with high accuracy.

[0034]

[14] An example of the inspection device described in

[13] above further comprises a second circular polarizing plate having a second linear polarizing plate and a second phase difference film, and a third circular polarizing plate having a third linear polarizing plate and a third phase difference film, the light source unit and the detection unit are arranged on the side of the peeling film, the second circular polarizing plate is arranged between the light source unit and the stacked body in a manner that the second phase difference film faces the peeling film on the optical path of the inspection light, the third circular polarizing plate is arranged between the stacked body and the detection unit in a manner that the third phase difference film faces the peeling film on the optical path of the inspection light reflected by the stacked body, and the second circular polarizing plate and the third circular polarizing plate can be both left-handed or both right-handed circular polarizing plates and can be circular polarizing plates with a rotation direction opposite to that of the first circular polarizing plate.

[0035]

[15] An example of the inspection device described in

[13] above comprises a fourth circular polarizing plate which is arranged on the side of the peeling film relative to the stack and has a fourth linear polarizing plate and a fourth phase difference film, the fourth circular polarizing plate is arranged so that the fourth phase difference film faces the peeling film, the light source unit and the detection unit are arranged opposite to the stack relative to the fourth circular polarizing plate, the fourth circular polarizing plate has a first region located on the optical path of the inspection light between the light source unit and the stack and a second region located on the optical path of the inspection light reflected by the stack, and the fourth circular polarizing plate can be a circular polarizing plate which rotates in the opposite direction to the first circular polarizing plate.

[0036]

[16] An example of the inspection device described in

[13] above further comprises a circular polarizing plate for detection having a linear polarizing plate for detection and a phase difference film for detection, the light source unit is arranged on the side of the first circular polarizing plate, the detection unit is arranged on the side of the peeling film, the circular polarizing plate for detection is arranged between the detection unit and the stacked body in a manner such that the phase difference film for detection faces the peeling film, and the circular polarizing plate for detection can be a circular polarizing plate having a rotation direction opposite to that of the first circular polarizing plate.

[0037] In the inspection methods described in

[14] ,

[15] and

[16] , the detection area (e.g., observation area) of the detection unit is dark. On the other hand, when the first circular polarizing plate has a defect, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0038]

[17] In the inspection device described in

[12] above, the above-mentioned specified wavelength is a wavelength at which the above-mentioned second phase difference is generated due to the light of the above-mentioned specified wavelength passing through the above-mentioned peeling film, and the above-mentioned inspection wavelength range can be greater than 570nm and less than 630nm.

[0039] When the release film is formed of a PET-based resin, the above-mentioned inspection wavelength range is likely to include a predetermined wavelength that generates the first phase difference in light passing through the release film. Therefore, by making the inspection wavelength range the range described in

[17] above, when the first circularly polarizing plate has a defect, the defect can be detected with high accuracy.

[0040]

[18] An example of the inspection device described in

[17] above further comprises: a second circular polarizing plate, which is arranged between the light source unit and the stacked body on the optical path of the inspection light and has a second linear polarizing plate and a second phase difference film; and a third circular polarizing plate, which is arranged between the stacked body and the detection unit on the optical path of the inspection light reflected by the stacked body and has a third linear polarizing plate and a third phase difference film, the light source unit and the detection unit are arranged on the side of the peeling film, the second circular polarizing plate is arranged in a manner such that the second phase difference film faces the peeling film, and the third circular polarizing plate is arranged in a manner such that the third phase difference film faces the peeling film, and the second circular polarizing plate and the third circular polarizing plate can be circular polarizing plates with the same rotation direction as the first circular polarizing plate.

[0041]

[19] An example of the inspection device described in

[17] above comprises a fourth circular polarizing plate which is arranged on the side of the peeling film relative to the stack and has a fourth linear polarizing plate and a fourth phase difference film, the fourth circular polarizing plate is arranged so that the fourth phase difference film faces the peeling film, the light source unit and the detection unit are arranged opposite to the stack relative to the fourth circular polarizing plate, the fourth circular polarizing plate has a first region located on the optical path of the inspection light between the light source unit and the stack and a second region located on the optical path of the inspection light reflected by the stack, and the fourth circular polarizing plate can be a circular polarizing plate having the same rotation direction as the first circular polarizing plate.

[0042]

[20] An example of the inspection device described in

[17] above further comprises a circular polarizing plate for detection having a linear polarizing plate for detection and a phase difference film for detection, the light source unit is arranged on the side of the first circular polarizing plate, the detection unit is arranged on the side of the peeling film, the circular polarizing plate for detection is arranged between the detection unit and the stacked body in a manner such that the phase difference film for detection faces the peeling film, and the circular polarizing plate for detection can be a circular polarizing plate having the same rotation direction as that of the first circular polarizing plate.

[0043] In the inspection devices described in

[18] ,

[19] and

[20] above, the detection area (e.g., observation area) of the detection unit is dark. On the other hand, when the first circular polarizing plate has a defect, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0044]

[21] An example of the inspection device described in any one of

[12] to

[20] above further comprises a moving mechanism for moving the above-mentioned stacked body along a prescribed direction, the above-mentioned light source unit comprises a light source for outputting light of a wavelength range including the above-mentioned inspection wavelength range and a bandpass filter for selectively passing light of a wavelength at an upper limit of the above-mentioned inspection wavelength range among the light output from the above-mentioned light source, and the above-mentioned bandpass filter can be arranged to be inclined relative to a plane orthogonal to the stacking direction of the above-mentioned first circular polarizing plate and the above-mentioned peeling film in a manner that forms a wavelength gradient in which the wavelength changes along a prescribed direction within the above-mentioned inspection wavelength range in an irradiation area of ​​the above-mentioned inspection light.

[0045] In the inspection device described in

[21] above, a wavelength gradient in which the wavelength changes within the inspection wavelength range along a prescribed direction is generated. Therefore, in the inspection method, the inspection light is irradiated in a state in which the wavelength changes spatially within the inspection wavelength range. In the detection step, the inspection light output from the release film is detected while the stack is moved along the prescribed direction relative to the irradiation area. Therefore, the inspection light of the prescribed wavelength contained in the wavelength gradient can be reliably detected. Thus, defects can be detected with high accuracy.

[0046] Effects of the Invention

[0047] According to the present invention, it is possible to provide a technique capable of detecting defects of a circularly polarizing plate with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram for explaining the structure of the laminated body including the first circularly polarizing plate inspected by the inspection apparatus and the inspection method according to the first to fourth embodiments.

[0049] Figure 2 It is a schematic diagram showing a schematic configuration of an inspection device according to the first embodiment.

[0050] Figure 3 It is a schematic diagram for explaining an example of the arrangement relationship among the first circular polarizing plate, the second circular polarizing plate, and the third circular polarizing plate.

[0051] Figure 4 It is a schematic diagram for explaining another example of the arrangement relationship among the first circular polarizing plate, the second circular polarizing plate, and the third circular polarizing plate.

[0052] Figure 5 It is a schematic diagram showing a schematic configuration of an inspection device according to a second embodiment.

[0053] Figure 6 This is a schematic diagram for explaining the gradual change in wavelength in the irradiation area of ​​the inspection light.

[0054] Figure 7Schematic diagram showing an experimental model of an experimental example.

[0055] Figure 8 This is a graph showing the results of Experimental Example 1.

[0056] Fig. 9 This is a graph showing the results of Experimental Example 2.

[0057] Fig.10 This is a schematic diagram for explaining a schematic configuration of an inspection device according to a third embodiment.

[0058] Fig.11 It is a schematic diagram for explaining the schematic configuration of an inspection device according to a fourth embodiment.

[0059] Description of Reference Numerals

[0060] 1 circular polarizing plate (first circular polarizing plate), 2, 2A light source unit, 2a light source, 2b band pass filter, 3 detection unit, 4A circular polarizing plate (second circular polarizing plate), 4B circular polarizing plate (third circular polarizing plate, circular polarizing plate for detection), 4C circular polarizing plate (fourth circular polarizing plate), 5 inspection light, 6 irradiation area, 10 laminate, 11 linear polarizing plate (first linear polarizing plate), 12 phase difference film (first phase difference film), 14a release film, 41a linear polarization Plate (second linear polarizing plate), 41b phase difference film (second phase difference film), 42a linear polarizing plate (third linear polarizing plate, linear polarizing plate for detection), 42b phase difference film (third phase difference film, phase difference film for detection), 43a linear polarizing plate (fourth linear polarizing plate), 43b phase difference film (fourth phase difference film), 44 first area, 45 second area, 100, 100A, 100B, 100C inspection device, D defect, P plane. DETAILED DESCRIPTION

[0061] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are assigned to the same or corresponding parts in each figure, and repeated descriptions are omitted.

[0062] First, a description will be given of a laminated body 10 including a circularly polarizing plate 1 which is inspected by inspection apparatuses and inspection methods according to first to fourth embodiments described below. Figure 1 It is a schematic diagram for explaining the structure of the laminated body 10 including the circular polarizing plate 1 inspected by the inspection apparatus and the inspection method according to the first to fourth embodiments.

[0063] The laminate 10 is a film-like laminate. The laminate 10 includes a circular polarizing plate (first circular polarizing plate) 1 as a main body of the inspection object and a release film 14a laminated on the circular polarizing plate 1. Thus, the laminate 10 is a circular polarizing plate with a release film. The release film 14a is laminated on the circular polarizing plate 1 via an adhesive layer 13. The laminate 10 may also have a surface protection film 14b on the side opposite to the release film 14a as viewed from the circular polarizing plate 1. Hereinafter, the mode in which the laminate 10 has the surface protection film 14b will be described.

[0064] The circular polarizing plate 1 is generally used in a display device, such as a liquid crystal display device or an organic EL display device. When the circular polarizing plate 1 is used, after peeling off the release film 14a of the laminate 10, the circular polarizing plate 1 is attached to the display device via the adhesive layer 13. The circular polarizing plate 1 has a linear polarizing plate (first linear polarizing plate) 11 and a phase difference film (first phase difference film) 12. The phase difference film 12 is laminated on the linear polarizing plate 11.

[0065] The linear polarizing plate 11 has a polarizing plate 11a. The polarizing plate 11a is a film that converts light incident from the surface protection film 14b side into linear polarized light. Examples of the polarizing plate 11a include films obtained by adsorbing and aligning iodine, dichroic pigments, etc. on a polyvinyl alcohol film; and films obtained by adsorbing and aligning a polymer obtained by aligning and polymerizing a polymerizable liquid crystal compound on a dichroic pigment.

[0066] The linear polarizing plate 11 may include protective films 11b and 11c. The protective films 11b and 11c are films for protecting the polarizer 11a. The protective film 11b is provided on one surface of the polarizer 11a, and the protective film 11c is provided on the other surface of the polarizer 11a. The protective films 11b and 11c are bonded to the polarizer 11a via an adhesive.

[0067] The protective films 11b and 11c are used for the purpose of obtaining a polarizing plate with appropriate mechanical strength. As the protective films 11b and 11c, protective films commonly used in the technical field of polarizing plates are used. Typically, cellulose ester films such as triacetylcellulose (TAC) films; cyclic olefin films; polyester films such as polyethylene terephthalate (PET) films; (meth) acrylic films such as polymethyl methacrylate (PMMA) films, etc. can be used as the protective films 11b and 11c. The protective films 11b and 11c may contain additives commonly used in the technical field of polarizing plates.

[0068] Since the protective films 11b and 11c are attached to the display device together with the polarizing plate 11a as components of the circularly polarizing plate 1, strict management of the retardation value is required. As the protective films 11b and 11c, typically, protective films with extremely small retardation values ​​are preferably used.

[0069] The phase difference film 12 is laminated on the protective film 11b via an adhesive layer. The phase difference film 12 is a film that converts light incident from the surface protective film 14b side and converted into linear polarization by the polarizer 11a of the linear polarizing plate 11 into circularly polarized light. If observed from the release film 14a side, the phase difference film 12 is a film that converts circularly polarized light incident from the release film 14a side into linearly polarized light. Therefore, the phase difference film 12 has at least a λ / 4 film. The phase difference film 12 may also be further laminated with a λ / 2 film. In this case, the order of the λ / 2 film and the λ / 4 film can be from the side close to the polarizer 11a.

[0070] The retardation film 12 is formed of, for example, a cured product of a polymerizable liquid crystal compound.

[0071] The polymerizable liquid crystal compound that can form the phase difference film 12 can be cited, for example, as the polymerizable liquid crystal compound disclosed in Japanese Patent Publication No. 2009-173893, Japanese Patent Publication No. 2010-31223, WO2012 / 147904, WO2014 / 10325 and WO2017-43438. The polymerizable liquid crystal compound described in these publications can form a phase difference film with so-called reverse wavelength dispersion that can achieve the same polarized light conversion in a large wavelength range. For example, by applying a solution containing the polymerizable liquid crystal compound (polymerizable liquid crystal compound solution) on a suitable substrate and photopolymerizing it, an extremely thin phase difference film can be formed, so that a circular polarizing plate 1 with an extremely thin thickness can be formed. Such a circular polarizing plate 1 with an extremely thin thickness is advantageous as a circular polarizing plate 1 for a flexible display material that has received attention in recent years.

[0072] As the substrate for coating the polymerizable liquid crystal compound solution, the substrate described in the above-mentioned bulletin can be cited. An orientation film can be provided on the substrate in order to orient the polymerizable liquid crystal compound. The orientation film can be any one of a film that is photo-oriented by irradiation with polarized light and a film that is physically oriented by rubbing treatment. The orientation film is also described in the above-mentioned bulletin.

[0073] The phase difference film 12 can be prepared by coating an alignment film forming composition on a substrate, and then coating a liquid crystal curing film forming composition containing a polymerizable liquid crystal compound thereon. The phase difference film 12 prepared in this way is bonded to the adhesive layer formed on the protective film 11b together with the substrate, and then the substrate is peeled off, thereby transferring the phase difference film 12 to the protective film 11b.

[0074] The release film 14a is laminated on the protective film 11b via the adhesive layer 13. The release film 14a is peeled off from the circularly polarizing plate 1 when the circularly polarizing plate 1 is attached to the display device. Usually, the peeled release film 14a is discarded.

[0075] The surface protection film 14 b is provided on the opposite side of the release film 14 a in the circularly polarizing plate 1 . Figure 1 In the embodiment shown, a surface protection film 14b is bonded to the protection film 11c. The surface protection film 14b is a kind of release film. The surface protection film 14b is also usually peeled off from the circular polarizing plate 1 when bonding to a display device, and unlike the protection films 11b and 11c, strict management of the phase difference value is not required. Figure 1 In the embodiment, the protective film 11c and the surface protective film 14b can be bonded together via a suitable adhesive layer or a pressure-sensitive adhesive layer ( Figure 1 , the adhesive layer or pressure-sensitive adhesive layer is not shown).

[0076] The above-mentioned laminated body 10 is manufactured, for example, as follows. First, a phase difference film 12 is formed on a linear polarizing plate 11 to form a circular polarizing plate 1 (circular polarizing plate forming step). A release film 14a is bonded to the linear polarizing plate 11 of the circular polarizing plate 1 via an adhesive layer 13 (release film bonding step). When manufacturing a laminated body 10 having a surface protective film 14b, the surface protective film 14b is bonded to the protective film 11c of the circular polarizing plate 1 (surface protective film bonding step). When the manufacturing method of the laminated body 10 has a surface protective film bonding step, the order of the release film bonding step and the surface protective film bonding step is not limited.

[0077] An example of a method for forming the phase difference film 12 in the circular polarizing plate forming step is as described above. The circular polarizing plate forming step may include a step of forming the linear polarizing plate 11. The linear polarizing plate 11 may be formed by adsorbing and orienting iodine, a dichroic dye, etc. while stretching a film (e.g., a polyvinyl alcohol film) to be a polarizer 11a.

[0078] The manufacturing method of the laminate 10 further includes a step (inspection step) of inspecting the circular polarizing plate 1 to which the release film 14a is attached. In the inspection step, the presence or absence of defects of the circular polarizing plate 1 is inspected. In the inspection step, if a defect is found, the laminate with the defect is discarded as a defective product. Alternatively, if a defect is found, an adjustment step of adjusting the manufacturing conditions of the laminate 10 may also be implemented. The manufacturing conditions of the laminate 10 adjusted in the above-mentioned adjustment step are, for example, the formation conditions of the phase difference film 12. In the case of having a step of forming the linear polarizing plate 11, the formation conditions of the linear polarizing plate 11, in particular, the formation conditions of the polarizer 11a, etc. are also included in the manufacturing conditions of the laminate 10.

[0079] The circular polarizing plate 1 to be bonded to a display device etc. is manufactured by manufacturing the laminated body 10. Therefore, the manufacturing method of the laminated body 10 described above can also be referred to as a manufacturing method of a circular polarizing plate.

[0080] First to fourth embodiments of the inspection apparatus used in the inspection process and the inspection method using the inspection apparatus will be described. Unless otherwise specified, the laminate 10 will be described as having the surface protection film 14b.

[0081] (First embodiment)

[0082] The inspection device and the inspection method according to the first embodiment will be described. Figure 2 This is a schematic diagram for explaining a schematic configuration of an inspection device according to Embodiment 1. The inspection device 100 is a device for inspecting the surface of the circular polarizing plate 1, between the layers constituting the circular polarizing plate 1, or inside the layers for the presence or absence of defects.

[0083] The inspection apparatus 100 includes an inspection table 20 on which the laminated body 10 is placed. The laminated body 10 is placed on the inspection table 20 in a state where the surface protection film 14b is in contact with the inspection table 20.

[0084] The inspection device 100 includes a light source unit 2 and a detection unit 3 for inspecting the laminated body 10 placed on the inspection table 20. The inspection device 100 may include a circular polarization plate (second circular polarization plate) 4A and a circular polarization plate (third circular polarization plate) 4B. Hereinafter, the inspection device 100 including the circular polarization plate 4A and the circular polarization plate 4B will be described.

[0085] The light source unit 2 is arranged on the side opposite to the inspection table 20 with respect to the laminated body 10. In other words, the light source unit 2 is arranged with respect to the laminated body 10 in such a manner that the inspection light 5 outputted from the light source unit 2 is incident on the laminated body 10 from the release film 14a side. The light source unit 2 outputs the inspection light 5 for inspecting the circular polarizing plate 1. The inspection light 5 is, for example, non-polarized light.

[0086] The light source unit 2 is configured to output the inspection light 5 while changing the wavelength over time or in a spatially varying state within the inspection wavelength range including the predetermined wavelength λ [nm]. An example of the light source unit 2 is a wavelength-variable light source. In this case, the light source unit 2 changes the wavelength over time. The light source unit 2 may also change the wavelength over space. In the first embodiment, for example, a case where a wavelength-variable light source is used as the light source unit 2 and the wavelength is changed over time is described.

[0087] The predetermined wavelength λ is a wavelength that generates a first phase difference of nλ or a second phase difference of (n+1 / 2)λ when light having the predetermined wavelength λ passes through the release film 14a. The above n is an integer greater than or equal to 1.

[0088] In the following, for the sake of convenience of explanation, the specified wavelength λ that produces the above-mentioned first phase difference (nλ) when the light having the specified wavelength λ is transmitted through the stripping film 14a is referred to as the "first specified wavelength λa", and the inspection wavelength range for the first specified wavelength λa is referred to as the "first inspection wavelength range", and the specified wavelength λ that produces the above-mentioned second phase difference ((n+1 / 2)λ) is referred to as the "second specified wavelength λb", and the inspection wavelength range for the second specified wavelength λb is referred to as the "second inspection wavelength range".

[0089] As described above, the release film 14 is a film formed using a polyethylene terephthalate resin (PET resin) (hereinafter sometimes referred to as a "PET resin film"). An example of the first inspection wavelength range for such a release film 14 is 500 nm or more and 550 nm or less. The first inspection wavelength range may also be 530 nm or more and 550 nm or less. An example of the second inspection wavelength range for the release film 14 which is a PET resin film is 570 nm or more and 630 nm or less. The second inspection wavelength range may also be 570 nm or more and 610 nm or less.

[0090] The thickness of the PET-based resin film is 1 μm or more and 500 μm or less, and is preferably 10 μm or more and 200 μm or less, and more preferably 10 μm or more and 100 μm or less from the viewpoint of easy peelability.

[0091] The detection unit 3 is arranged on the same side as the light source unit 2 relative to the inspection table 20. A partition plate may also be present between the light source unit 2 and the detection unit 3. The detection unit 3 detects the inspection light 5 reflected by the stack 10. The inspection light 5 reflected by the stack 10 is sometimes also referred to as reflected light. The detection unit 3 is arranged on the optical path of the reflected light from the stack 10. The detection unit 3 includes a photodetector. In the present embodiment, the photodetector is a camera. As the camera, a CCD camera can be cited.

[0092] The detection unit 3 may include an image processing device for analyzing an image acquired by the photodetector in addition to the photodetector. In this case, defects can be automatically detected by performing image processing analysis on the image data acquired by the photodetector using the image processing device.

[0093] The circular polarizing plate 4A is arranged between the light source unit 2 and the stack 10 on the optical path of the inspection light 5 output from the light source unit 2. The circular polarizing plate 4A has a linear polarizing plate (second linear polarizing plate) 41a and a phase difference film (second phase difference film) 41b stacked on the linear polarizing plate 41a. The linear polarizing plate 41a has a polarizing plate in the same manner as the linear polarizing plate 11 of the circular polarizing plate 1. The linear polarizing plate 41a may also have a protective film corresponding to the protective films 11b and 11c. The phase difference film 41b has the same function as the phase difference film 12 of the circular polarizing plate 1. The phase difference film 41b has a λ / 4 film. In the circular polarizing plate 4A, the linear polarizing plate 41a faces the light source unit 2, and the phase difference film 41b faces the stack 10. In this configuration, the inspection light 5 is irradiated to the stack 10 as right-handed or left-handed circularly polarized light through the circular polarizing plate 4A.

[0094] The circular polarizing plate 4B is arranged between the stack 10 and the detection unit 3 on the optical path of the reflected light from the stack 10. The circular polarizing plate 4B has a linear polarizing plate (the third linear polarizing plate) 42a and a phase difference film (the third phase difference film) 42b stacked on the linear polarizing plate 42a. The linear polarizing plate 42a has a polarizing plate in the same manner as the linear polarizing plate 11 of the circular polarizing plate 1. The linear polarizing plate 42a may also have a protective film corresponding to the protective films 11b and 11c. The phase difference film 42b has the same function as the phase difference film 12 of the circular polarizing plate 1. The phase difference film 42b has a λ / 4 film. In the circular polarizing plate 4B, the linear polarizing plate 42a faces the detection unit 3, and the phase difference film 42b faces the stack 10.

[0095] When the wavelength of the inspection light 5 changes within the first inspection wavelength range, the circular polarization plate 4A and the circular polarization plate 4B satisfy the following condition 1.

[0096] (Condition 1)

[0097] The circular polarizing plate 4A and the circular polarizing plate 4B are left-handed or right-handed circular polarizing plates, and are circular polarizing plates whose rotation direction is opposite to that of the circular polarizing plate 1 .

[0098] Figure 3 It is a schematic diagram for explaining an example of the arrangement relationship among the circular polarizing plate 1 , the circular polarizing plate 4A, and the circular polarizing plate 4B. Figure 3 In FIG. 1 , the peeling film 14 a , the light source unit 2 , and the detection unit 3 are also shown.

[0099] like Figure 3As shown, the circular polarizing plate 4A and the circular polarizing plate 4B are arranged relative to the circular polarizing plate 1 in such a manner that the absorption axes of the linear polarizing plate 11, the absorption axes of the linear polarizing plate 41a, and the absorption axes of the linear polarizing plate 42a are oriented in the same direction, and the slow axes of the phase difference film 12, the slow axes of the phase difference film 41b, and the slow axes of the phase difference film 42b are oriented in the same direction. In this case, the circular polarizing plate 4A and the circular polarizing plate 4B satisfy condition 1.

[0100] When the wavelength of the inspection light 5 changes within the second inspection wavelength range, the circular polarization plate 4A and the circular polarization plate 4B satisfy the following condition 2.

[0101] (Condition 2)

[0102] The circular polarizing plate 1 , the circular polarizing plate 4A, and the circular polarizing plate 4B are circular polarizing plates having the same rotation direction.

[0103] Figure 4 This is a schematic diagram for explaining an example of the arrangement relationship among the circular polarizing plate 1 , the circular polarizing plate 4A, and the circular polarizing plate 4B when the condition 2 is satisfied. Figure 4 In FIG. 1 , the peeling film 14 a , the light source unit 2 , and the detection unit 3 are also shown.

[0104] like Figure 4 As shown, the circular polarizing plate 4A and the circular polarizing plate 4B are arranged relative to the circular polarizing plate 1 in such a manner that the absorption axes of the linear polarizing plate 11, the linear polarizing plate 41a, and the linear polarizing plate 42a are oriented in the same direction, and the slow axes of the phase difference film 41b and the phase difference film 42b are oriented in a direction rotated 90° relative to the direction of the slow axis of the phase difference film 12. In this case, the circular polarizing plate 4A and the circular polarizing plate 4B satisfy condition 2.

[0105] Next, an example of an inspection method of the circular polarization plate 1 using the inspection apparatus 100 will be described. First, a case where the wavelength of the inspection light 5 is changed within the first inspection wavelength range ([Case A]) will be described.

[0106] [Case A] Changing the wavelength of the inspection light 5 within the first inspection wavelength range

[0107] In case A, circular polarization plates 4A and 4B satisfy the above condition 1. For convenience of description, the case where circular polarization plates 4A and 4B are right-handed circular polarization plates and circular polarization plate 1 is a left-handed circular polarization plate is described as an example.

[0108] like Figure 1As shown, the inspection light 5 output from the light source unit 2 is irradiated to the laminate 10 through the circular polarizing plate 4A (irradiation process). In the irradiation process, the inspection light 5 is irradiated to the laminate 10 while changing the wavelength within the first inspection wavelength range. Since the linear polarizing plate 41a and the phase difference film 41b are arranged in the above-mentioned arrangement relationship relative to the light source unit 2 and the laminate 10, the inspection light 5 from the light source unit 2 is incident on the circular polarizing plate 4A from the side of the linear polarizing plate 41a and is output from the phase difference film 41b. Therefore, the inspection light 5 output from the circular polarizing plate 4A has right-handed circular polarization. Thus, the right-handed circularly polarized inspection light 5 is irradiated to the laminate 10. In this irradiation process, the inspection light 5 is irradiated to the laminate 10 from the side of the release film 14a.

[0109] The reflected light from the laminate 10 is detected by the detection unit 3 through the circular polarizing plate 1 (detection step). As described above, in the irradiation step, the inspection light 5 is irradiated to the laminate 10 while changing the wavelength within the first inspection wavelength range. Therefore, in the detection step, the detection result of the reflected light corresponding to the inspection light 5 with a different wavelength is obtained.

[0110] The presence or absence of a defect in the circularly polarizing plate 1 is determined based on the detection result of the detection unit 3 (determination step).

[0111] In the case of case A, since the inspection light 5 is irradiated to the laminate 10 while changing the wavelength within the first inspection wavelength range in the irradiation step, a detection result corresponding to the inspection light 5 of the first predetermined wavelength λa is also obtained. When there is a defect D in the circular polarizing plate 1 (for example, a defect existing at the interface between the retardation film 12 and the polarizing plate 11a, a defect existing in the retardation film 12), the above-mentioned defect D can be detected based on the detection result of the inspection light 5 of the first predetermined wavelength λa. This point will be described in detail.

[0112] A portion of the right-handed circularly polarized inspection light 5 irradiated to the laminate 10 is reflected on the surface of the peeling film 14a. The reflected light on the surface of the peeling film 14a is referred to as reflected light 5a. The reflected light 5a is left-handed circularly polarized light. Since the circular polarizing plate 4B is a right-handed circular polarizing plate and is arranged so that the phase difference film 42b faces the laminate 10, the reflected light 5a from the surface of the peeling film 14a is blocked by the circular polarizing plate 4B. Specifically, the reflected light 5a is absorbed by the linear polarizing plate 42a of the circular polarizing plate 4B.

[0113] Among the circularly polarized inspection light 5 irradiated onto the laminate 10, the inspection light 5 that has passed through the release film 14a is incident on the circular polarization plate 1. When the inspection light 5 passes through the release film 14a, a phase difference is generated in the inspection light 5. Since the inspection light 5 is the inspection light 5 having the first predetermined wavelength λa, the above-mentioned phase difference is the first phase difference, that is, an integer multiple of the first predetermined wavelength λa. In this case, since the polarization state of the inspection light 5 that has passed through the release film 14a does not change, the inspection light 5 that has passed through the release film 14a is right-handed circularly polarized light. As a result, the right-handed circularly polarized inspection light 5 is incident on the circular polarization plate 1. Since the circular polarization plate 1 is a left-handed circular polarization plate, the inspection light 5 that has entered the circular polarization plate 1 is absorbed by the linear polarization plate 11 possessed by the circular polarization plate 1.

[0114] As described above, the reflected light 5a is blocked by the circular polarizing plate 1, and the inspection light 5 having passed through the release film 14a is absorbed by the circular polarizing plate 1. Thus, the observation field of the circular polarizing plate 1 obtained by the detection unit 3 becomes dark.

[0115] When there is a defect D in the circular polarizing plate 1, reflection occurs at the portion of the defect D. The reflected light caused by the defect D is called reflected light 5b. The reflected light 5b is unexpectedly elliptically polarized light because the phase difference deviates from the ideal phase difference due to the defect D. The elliptically polarized reflected light 5b is incident on the circular polarizing plate 4B after passing through the peeling film 14a. When passing through the peeling film 14a, since the phase difference generated in the elliptically polarized reflected light 5b is an integer multiple of the first specified wavelength λa, the polarization state of the reflected light 5b does not change. Therefore, the reflected light 5b is incident on the circular polarizing plate 1 as elliptically polarized. In this case, the reflected light 5b is transmitted without being absorbed by the circular polarizing plate 4B. As a result, in the detection result of the detection unit 3, the portion of the defect D appears as a bright spot, so the defect D of the circular polarizing plate 1 can be detected.

[0116] Although the case where the circular polarizing plates 4A and 4B are right-handed circular polarizing plates and the circular polarizing plate 1 is a left-handed circular polarizing plate has been described, the same applies to the case where the circular polarizing plates 4A and 4B are left-handed circular polarizing plates and the circular polarizing plate 1 is a right-handed circular polarizing plate. Specifically, the description of the case where the circular polarizing plates 4A and 4B are left-handed circular polarizing plates and the circular polarizing plate 1 is a right-handed circular polarizing plate corresponds to the case where "right-handed" is changed to "left-handed" and "left-handed" is changed to "right-handed" in the description of the above-mentioned case A.

[0117] Next, a description will be given of a case where the wavelength of the inspection light 5 is changed within the second inspection wavelength range ([Case B]).

[0118] [Case B] Changing the wavelength of the inspection light 5 within the second inspection wavelength range

[0119] In case B, the circular polarizing plate 4A and the circular polarizing plate 4B satisfy the above condition 2. For convenience of description, the case where the circular polarizing plate 1, the circular polarizing plate 4A, and the circular polarizing plate 4B are right-hand circular polarizing plates will be described as an example.

[0120] The inspection light 5 output from the light source unit 2 is irradiated to the laminate 10 through the circular polarizing plate 1 (irradiation process). In the irradiation process, the inspection light 5 is irradiated to the laminate 10 while changing the wavelength within the second inspection wavelength range. As in the case of the above-mentioned situation A, the circular polarizing plate 1 is a right-handed circular polarizing plate. In addition, the configuration relationship of the circular polarizing plate 1 relative to the light source unit 2 and the laminate 10 is also the same as that of the situation A. Thus, as described in the situation A, the right-handed circularly polarized inspection light 5 is irradiated to the laminate 10 from the peeling film 14a side.

[0121] The reflected light from the stacked body 10 is passed through the circular polarizing plate 4B and detected by the detection unit 3 (detection step). In the irradiation step, since the inspection light 5 is irradiated to the stacked body 10 while changing the wavelength within the second inspection wavelength range, the detection result of the reflected light corresponding to the inspection light 5 with a different wavelength is obtained in the detection step.

[0122] The presence or absence of a defect in the circularly polarizing plate 1 is determined based on the detection result of the detection unit 3 (determination step).

[0123] In the case of case B, since the inspection light 5 is irradiated to the laminated body 10 while changing the wavelength within the second inspection wavelength range in the irradiation step, the detection result of the inspection light 5 with respect to the second predetermined wavelength λb is also obtained. When the circular polarizing plate 1 has the above-mentioned defect D, the above-mentioned defect D can be detected based on the detection result of the inspection light 5 with respect to the second predetermined wavelength λb. This point will be described in detail.

[0124] A part of the right-handed circularly polarized inspection light 5 irradiated to the laminate 10 is reflected on the surface of the release film 14a. In the case B, the reflected light 5a from the surface of the release film 14a is also left-handed circularly polarized light. Therefore, as in the case A, the reflected light 5a is blocked by the circular polarizing plate 4B.

[0125] Among the right-handed circularly polarized inspection light 5 irradiated to the laminate 10, the inspection light 5 that has passed through the release film 14a is incident on the circular polarization plate 1. When the inspection light 5 passes through the release film 14a, a phase difference is generated in the inspection light 5. Since the inspection light 5 is the inspection light 5 having the second specified wavelength λb, the above-mentioned phase difference is the second phase difference, that is, (n+1 / 2) times the second specified wavelength λb. In this case, since the release film 14a is equivalent to a half-wavelength plate, the inspection light 5 that has passed through the release film 14a is left-handed circularly polarized light. As a result, the left-handed circularly polarized inspection light 5 is incident on the circular polarization plate 1. Since the circular polarization plate 1 is a right-handed circular polarization plate, the inspection light 5 incident on the circular polarization plate 1 is absorbed by the linear polarization plate 11 possessed by the circular polarization plate 1.

[0126] As described above, the reflected light 5a is blocked by the circular polarizing plate 4B, and the inspection light 5 having passed through the release film 14a is absorbed by the circular polarizing plate 1. Therefore, in the case B, the observation field of the circular polarizing plate 1 obtained by the detection unit 3 is also dark.

[0127] When there is a defect D in the circular polarizing plate 1, reflection occurs at the portion of the defect D, as in the case of case A. In case B, the reflected light 5b caused by the defect D is also unexpected elliptically polarized light as described in case A. The elliptically polarized reflected light 5b is incident on the circular polarizing plate 4B after passing through the peeling film 14a. When passing through the peeling film 14a, since the phase difference generated in the elliptically polarized reflected light 5b is (n+1 / 2) times the second specified wavelength λb, although the direction of the major axis of the elliptically polarized light rotates, the elliptically polarized light is maintained. Therefore, the elliptically polarized reflected light 5b is incident on the circular polarizing plate 4B. In this case, the reflected light 5b is transmitted without being absorbed by the circular polarizing plate 4B. Therefore, in the detection result of the detection unit 3, since the portion of the defect D appears as a bright spot, the defect D of the circular polarizing plate 1 can be detected.

[0128] Although the case where the circular polarizing plate 1, the circular polarizing plate 4A, and the circular polarizing plate 4B are right-handed circular polarizing plates is exemplified, the case where the circular polarizing plate 1, the circular polarizing plate 4A, and the circular polarizing plate 4B are left-handed circular polarizing plates is also the same. Specifically, the description of the case where the circular polarizing plate 1, the circular polarizing plate 4A, and the circular polarizing plate 4B are left-handed circular polarizing plates corresponds to the description of the case where "right-handed" is changed to "left-handed" in the description of the case where the circular polarizing plate 1, the circular polarizing plate 4A, and the circular polarizing plate 4B are right-handed circular polarizing plates.

[0129] When inspecting the circular polarizing plate 1, the inspection is performed in the state where the laminate 10 is constructed as described above. In this inspection, the inspection light 5 (reflected light 5a, 5b) is transmitted through the peeling film 14a. The peeling film 14a is a film peeled off from the circular polarizing plate 1 when the circular polarizing plate 1 is used, and is a film discarded after being peeled off from the circular polarizing plate 1. Therefore, strict management of the phase difference value is not required for the peeling film 14a.

[0130] In particular, the release film 14a of the present embodiment is formed using a PET resin. The release film (PET resin film) 14a formed using a PET resin is widely used as a release film and has the advantage of being cheap. On the other hand, the cheap PET resin film does not require strict management of the phase difference value as mentioned above. Therefore, for example, there is a case where the phase difference value varies in each product batch. Even if it is the same PET resin film, there is a case where the phase difference value varies within the surface.

[0131] The phase difference value of the release film 14a itself, which is a PET-based resin film, is not managed. However, when light passes through the release film 14a, there is a wavelength that produces the first phase difference (first predetermined wavelength λa) or a wavelength that produces the second phase difference (second predetermined wavelength λb).

[0132] In the inspection device 100 and the inspection method using the inspection device 100, the laminated body 10 (specifically, the circularly polarizing plate 1) can be inspected using the inspection light 5 having the first predetermined wavelength λa or the second predetermined wavelength λb. In this case, since the phase difference generated when the release film 14a is transmitted is the first phase difference or the second phase difference, as described in the case A and the case B, the influence of the release film 14a on the inspection can be substantially eliminated.

[0133] Therefore, in the inspection apparatus 100 and the inspection method using the inspection apparatus 100 , even if the laminated body 10 has the release film 14 a which is a PET-based resin film, the presence or absence of the defect D can be detected with high accuracy.

[0134] For example, the specified wavelength λ can be predetermined for the release film 14a by preliminary experiments or the like. However, since strict management of the phase difference value is not required for the release film 14, as described above, even for the same product, there may be deviations in the phase difference of the release film 14a. Therefore, even if the specified wavelength λ is set for inspection, the actual specified wavelength λ of the release film 14 used in the laminate 10 may deviate from the set specified wavelength λ in the actual inspection.

[0135] In contrast, in the inspection device 100 and the inspection method using the inspection device 100, the inspection of the circular polarizing plate 1 is performed while changing the wavelength of the inspection light 5 within the inspection wavelength range. Therefore, even if a deviation occurs between the predetermined wavelength λ assumed in advance for the release film 14a and the actual predetermined wavelength λ of the release film 14a during the inspection, since any wavelength within the inspection wavelength range coincides with the actual predetermined wavelength λ of the release film 14a provided on the laminated body 10 irradiated with the inspection light 5, the presence or absence of the defect D of the circular polarizing plate 1 can be determined more reliably.

[0136] The phase difference imparted to the light when the light passes through the release film 14a depends on the optical path length when the light passes through the release film 14a. Therefore, it is also possible to adjust the phase difference imparted to the light when the light passes through the release film 14a by, for example, changing the incident angle of the inspection light relative to the laminate 10 to reduce the influence of the above phase difference.

[0137] However, in this case, a rotating mechanism is required to rotate the stack 10 around an axis (hereinafter referred to as the "rotation axis") orthogonal to the stacking direction of the multiple layers constituting the stack 10 during inspection, or an inspector is required to perform inspection while rotating the stack 10 around the above-mentioned axis.

[0138] In contrast, in the inspection device 100 and the inspection method using the inspection device 100, the rotation of the stacked body 10 around the rotation axis is not required. Therefore, the above-mentioned rotation mechanism is not required. As a result, the cost of the inspection device 100 and the manufacturing cost of the stacked body 10 (or the circular polarizing plate 1) can be reduced. In addition, since the inspection operator does not need to operate the stacked body 10, the presence or absence of the defect D can be more objectively determined.

[0139] When a polymerizable liquid crystal compound is used to form the phase difference film 12, the phase difference film 12 can be formed extremely thin. For example, the thickness of the phase difference film 12 is greater than 0.2 μm and less than 10 μm, and preferably the phase difference film 12 is greater than 0.2 μm and less than 5 μm. In addition, the phase difference film 12 can be a single layer or a plurality of layers. In the case of a plurality of layers, the same type of phase difference film 12 can be stacked, or different types of phase difference films 12 can be stacked.

[0140] However, when there are foreign objects on the substrate on which the polymerizable liquid crystal compound solution is applied, or when the substrate itself has scratches, there are cases where defects occur in the coating film itself obtained by applying the polymerizable liquid crystal compound solution. In the case of rubbing the oriented film, the debris of the rubbing cloth remains on the oriented film, which may also cause defects in the coating film of the polymerizable liquid crystal compound solution (liquid crystal curing film forming composition). In this way, although the phase difference film formed by the polymerizable liquid crystal compound can form a phase difference film with an extremely thin thickness, there are factors that cause defects. Once such a defect occurs, it is impossible to convert linearly polarized light into ideal circularly polarized light, but it becomes unexpected elliptically polarized light as described above.

[0141] The inspection apparatus 100 of the present embodiment and the inspection method using the inspection apparatus 100 can inspect with high accuracy the defects D generated in the retardation film 12 formed using the polymerizable liquid crystal compound. As a result, it is easy to manufacture a thin circularly polarizing plate 1.

[0142] In the inspection table 20, when the surface on which the stacked body 10 is placed is subjected to a low-reflection treatment, it is possible to suppress the reflection of the inspection light 5 that accidentally passes through the stacked body 10. As a result, since the observation field is formed darker, it is easy to detect the defect D. From the same point of view, a sheet or the like that suppresses reflection may be arranged between the inspection table 20 and the stacked body 10.

[0143] (Second embodiment)

[0144] Figure 5 1 is a schematic diagram showing a schematic configuration of an inspection device 100A according to a second embodiment. The inspection device 100A is different from the inspection device 100 in that it includes a light source unit 2A instead of the light source unit 2 and an inspection table 20A instead of the inspection table 20. The inspection device 100A will be described with these points as the center. In the second embodiment, the mode in which the inspection device 100A includes the circular polarization plate 4A and the circular polarization plate 4B will also be described in the same manner as in the first embodiment.

[0145] In the description of the second embodiment, the Figure 5 The x-axis, y-axis, and z-axis are shown in FIG. The z-axis direction corresponds to the stacking direction of the plurality of layers of the stacked body 10. The x-axis and y-axis are orthogonal to the z-axis. The x-axis and y-axis are orthogonal to each other.

[0146] The light source unit 2A includes a light source 2a and a bandpass filter 2b.

[0147] The light source 2a is a white light source that outputs non-polarized white light. Various commercially available products can be used as the light source 2a, and it is advantageous if it is linear light such as laser light (including light that is close to linear light).

[0148] The band-pass filter 2 b is a band-pass filter that selectively passes light having a wavelength at the upper limit of the inspection wavelength range.

[0149] "A bandpass filter that selectively passes light of wavelength λi" means a bandpass filter that selectively passes light of wavelength λi when light passes substantially perpendicularly to the surface of the bandpass filter. In other words, the designed center wavelength of the transmission "bandpass filter that selectively passes light of wavelength λi" is wavelength λi.

[0150] The bandpass filter 2b is disposed between the light source 2a and the circular polarization plate 4A. The bandpass filter 2b is inclined at an angle θ (°) relative to the plane P. The plane P is parallel to the stacking direction of the plurality of layers of the stacked body 10 (equivalent to Figure 5 A plane that is orthogonal to the z-axis direction.

[0151] In the inspection apparatus 100A, by tilting the bandpass filter 2b relative to the plane P as described above, Figure 6 As shown, a wavelength gradient is formed in the irradiation area 6 of the inspection light 5 on the stacked body 10 . Figure 6 It is a schematic diagram for explaining the gradual change of the wavelength in the irradiation area 6 of the inspection light 5 . Figure 6 In the figure, changes in wavelength are represented by lightness and darkness. Figure 6 The x-axis and y-axis correspond to Figure 5 The x-axis and y-axis. Figure 6 The direction specified in Figure 6 The x-axis direction is shown.

[0152] Wavelength gradient means that the wavelength changes from wavelength λ1 to wavelength λ2 along a specified direction. That is, in wavelength gradient, the wavelength changes with space. Wavelength λ and wavelength λ2 refer to the center wavelength (peak wavelength). The wavelength λ2, which is the upper limit of the wavelength range for achieving wavelength gradient, is equivalent to the wavelength selectively passed by the bandpass filter 2b. Therefore, the wavelength λ2 is equivalent to the wavelength of the upper limit of the inspection wavelength range.

[0153] An experimental example showing the effect of the tilted band-pass filter 2b will be described. Figure 7 Schematic diagram showing an experimental model of an experimental example.

[0154] (Experimental model)

[0155] like Figure 7As shown, a transparent support platform 32 having an inclined surface 32a is arranged on a backlight 31 that outputs white light. SLT-A4C manufactured by Muto Industries, Ltd. is used as the backlight 31. The inclination angle of the inclined surface 32a relative to the bottom surface 32b of the support platform 32 is called angle α (°). The bottom surface 32b is a surface of the support platform 32 that contacts the light output surface 31a of the backlight 31. A bandpass filter 33 is arranged on the inclined surface 32a. Thus, the bandpass filter 33 is inclined at an angle α relative to the light output surface 31a. A spectroradiometer 34a that detects light output from the backlight 31 and passing through the bandpass filter 33 is arranged above the backlight 31. An objective lens 34b is installed on the spectroradiometer 34a. A 2D spectroradiometer SR-5000HT manufactured by TOPCON TECHNOHOUSE Co., Ltd. is used as the spectroradiometer 34a. The distance L1 between the lower portion of the objective lens 34b and the light output surface 31a of the backlight 31 is 500 mm.

[0156] (Experimental Example 1)

[0157] In Experimental Example 1, a filter that selectively passes a wavelength of 550 nm is used as the bandpass filter 33. The bandpass filter 33 is HMZ0550 manufactured by Asahi Spectroscopy Co., Ltd. The bandpass filter 33 is arranged on a support 32 with an angle α of 10°, and the light 35 output from the backlight 31 and passing through the bandpass filter 33 is detected by a spectroradiometer 34a.

[0158] The support platform 32 with an angle α of 20°, 30°, 40°, and 50° is changed, and the light passing through the bandpass filter 33 is detected by the spectroradiometer in the same manner as the case of using the support platform 32 with an angle α of 10°. Then, instead of using the support platform 32, the bandpass filter 33 is arranged on the light output surface 31a, and the light passing through the bandpass filter 33 is detected by the spectroradiometer 34a in the same manner as the case of using the support platform 32 with an angle α of 10°. The case of not using the support platform 32 but arranging the bandpass filter 33 on the light output surface 31a corresponds to the case of the angle α of 0°. The experimental results of Experimental Example 1 are as follows. Figure 8 shown. Figure 8 The horizontal axis represents wavelength (nm), and the vertical axis represents spectral radiance (W / sr / m 2 / mm).

[0159] (Experimental Example 2)

[0160] In Experimental Example 2, a filter that selectively passes a wavelength of 600 nm is used as the bandpass filter 33. The bandpass filter 33 is HMZ0600 manufactured by Asahi Spectroscopy Corporation. The same experiment as in Experimental Example 1 was conducted except that the bandpass filter 33 that selectively passes a wavelength of 600 nm was used. That is, when the angle α is 0°, 10°, 20°, 30°, 40°, and 50°, the light 35 that has passed through the bandpass filter 33 is detected by the spectroradiometer 34a. The experimental results of Experimental Example 2 are shown in FIG. Fig. 9 shown. Fig. 9 The horizontal axis represents wavelength (nm), and the vertical axis represents spectral radiance (W / sr / m 2 / mm).

[0161] like Figure 8 and Fig. 9 As shown, it can be understood that the central wavelength of the transmission bandpass filter 33 changes with the change of the tilt angle (corresponding to the angle α) of the bandpass filter 33. This is considered to be because the optical path length when passing through the bandpass filter 33 changes due to the tilt of the bandpass filter 33.

[0162] like Figure 5 As shown in FIG. 1 , when the bandpass filter 2b is tilted at an angle θ relative to the plane P, the optical path length of light passing through the bandpass filter 2b varies depending on the position where the light output from the light source 2a is incident on the bandpass filter 2b. Figure 8 and Fig. 9 As shown, the central wavelength that can pass through the bandpass filter 2b varies depending on the incident position of the light. Thus, by tilting the bandpass filter 2b at an angle θ relative to the plane P, a gradual wavelength change occurs in the irradiation area 6. That is, by using the bandpass filter 2b tilted relative to the plane P, the light source unit 2A irradiates the inspection light 5 to the stacked body 10 in a state where the wavelength varies spatially within the inspection wavelength range.

[0163] In the inspection apparatus 100A, the band-pass filter 2 b is arranged so that the wavelength range in which wavelength gradation is achieved is the inspection wavelength range.

[0164] In the inspection device 100A, the angle θ (°) is, for example, greater than 10° and less than 45°. From the viewpoint of reducing the number of inspections, the angle θ is preferably greater than 10° and less than 30°. An example of the angle θ is 21°. As the angle θ increases, the area in which the inspection wavelength range is realized becomes narrower. Therefore, the area that can be inspected in the inspection wavelength range becomes narrower, and there is a case where the operability of the inspection is reduced. On the other hand, as the angle θ decreases, the inspection wavelength range itself becomes narrower. Therefore, in order to inspect within the entire desired inspection wavelength range, it is sometimes necessary to adjust the angle of the bandpass filter 2b again and re-inspect, in which case the efficiency of the inspection is reduced. If the angle θ is within the range exemplified above, it is easy to realize the wavelength gradient in the desired inspection wavelength range for the entire irradiation area 6. As a result, the circular polarizer 1 can be efficiently inspected while ensuring the operability of the inspection.

[0165] An example of the distance L2 between the light source 2a and the bandpass filter 2b is 30 mm or more and 70 mm or less. In the inspection device 100A, since the circular polarizing plate 1 is inspected while the laminate 10 is moved in a predetermined direction, it is preferably 40 mm or more and 60 mm or less from the viewpoint of improving the operability of the inspection. An example of the distance L2 is 55 mm. The distance L2 is the distance in the z-axis direction between the intersection of the optical axis (along the axis of the main light) of the light output from the light source 2a and the bandpass filter 2b and the light output end of the light source 2a.

[0166] The inspection method of the circular polarizing plate 1 using the inspection device 100A is the same as that of the cases A and B, except that in the detection process described in the cases A and B of the first embodiment, the reflected light 5a is detected while the stage main body 21 is moved in a prescribed direction by the driving mechanism 22.

[0167] Therefore, the inspection apparatus 100A and the inspection method using the inspection apparatus 100A have the same operational effects as those of the first embodiment.

[0168] In the inspection device 100A, by tilting the bandpass filter 2b at an angle θ relative to the plane P, a wavelength gradient along a prescribed direction is formed in the irradiation area 6. Therefore, in the inspection device 100A, an irradiation area 6 having an inspection wavelength range in which the wavelength continuously changes can be easily realized. Since the inspection table 20A is provided with a driving mechanism 22, it is possible to inspect the circular polarizing plate 1 while moving the stack 10 in a prescribed direction. By moving the stack 10 in a prescribed direction, the circular polarizing plate 1 is inspected at each wavelength within the inspection wavelength range achieved in the wavelength gradient. Therefore, for example, as described in the first embodiment, even if some deviation occurs in the phase difference of the release film 14a, any wavelength within the above-mentioned inspection wavelength range will function as the first prescribed wavelength λa or the second prescribed wavelength λb relative to the release film 14a attached to the circular polarizing plate 1 to be inspected. As a result, the presence or absence of the defect D can be detected with excellent accuracy.

[0169] (Third embodiment)

[0170] Fig.10 It is a schematic diagram for explaining the schematic configuration of an inspection apparatus 100B according to the third embodiment.

[0171] The inspection device 100B of the third embodiment is different from the inspection device 100 of the first embodiment in that a single circular polarization plate (fourth circular polarization plate) 4C is provided instead of the circular polarization plates 4A and 4B.

[0172] In the inspection apparatus 100B, the light source unit 2 and the detection unit 3 are arranged on the opposite side of the laminate 10 with respect to the circular polarization plate 4C. The light source unit 2 of the inspection apparatus 100B is configured to irradiate the laminate 10 with the inspection light 5 while changing the wavelength within the first inspection wavelength range.

[0173] The circular polarizing plate 4C has a linear polarizing plate (the fourth linear polarizing plate) 43a and a phase difference film (the fourth phase difference film) 43b stacked on the linear polarizing plate 43a. The circular polarizing plate 4C is configured so that the phase difference film 43b faces the stacked body 10. The linear polarizing plate 43a is the same as the linear polarizing plate 41a of the circular polarizing plate 4A or the linear polarizing plate 42a of the circular polarizing plate 4B. The phase difference film 43b is the same as the phase difference film 41b of the linear polarizing plate 41a or the phase difference film 42b of the circular polarizing plate 4B.

[0174] When the wavelength of the inspection light 5 changes within the first inspection wavelength range, the circular polarization plate 4C is arranged to satisfy the following condition 3. When the wavelength of the inspection light 5 changes within the second inspection wavelength range, the circular polarization plate 4C is arranged to satisfy the following condition 4.

[0175] (Condition 3)

[0176] The circular polarizing plate 4C is a circular polarizing plate having a rotation direction opposite to that of the circular polarizing plate 1 .

[0177] (Condition 4)

[0178] The circular polarizing plate 4C has the same rotation direction as that of the circular polarizing plate 1 .

[0179] The circular polarizing plate 4C has a first region 44 located on the optical path of the inspection light 5 output from the light source unit 2 and a second region 45 located on the optical path of the reflected light from the laminate 10. The first region 44 is a region through which the inspection light 5 passes, and the second region 45 is a region into which the reflected light is incident.

[0180] Since the circular polarizing plate 4C has the above-mentioned structure and is arranged so as to satisfy the condition 3, the first region 44 corresponds to the circular polarizing plate 4A, and the second region 45 corresponds to the circular polarizing plate 4B. Figure 1 The circular polarizing plate 4A and the circular polarizing plate 4B shown in the figure in a separated state are integrated into one circular polarizing plate.

[0181] Therefore, the presence or absence of the defect D can be determined using the inspection device 100B in the same manner as in the case A and the case B in the first embodiment.

[0182] Since the circular polarization plate 4C is equivalent to Figure 1 The circular polarization plate 4A and the circular polarization plate 4B shown in the separated state are integrated into a circular polarization plate, so the inspection device 100B and the inspection method using the inspection device 100B have the same effects as the inspection device 100 and the inspection method using the inspection device 100 of the first embodiment.

[0183] (Variant 1)

[0184] The circular polarization plate 4C may be used in place of the circular polarization plate 4A and the circular polarization plate 4B of the second embodiment. In this case, the light source unit 2A is configured to irradiate the inspection light 5 to the laminate 10 in a state where the wavelength varies spatially within the first inspection wavelength range or the second inspection wavelength range. Specifically, the light source unit 2A is configured to make the wavelength range in which the wavelength in the irradiation area 6 changes gradually the first inspection wavelength range.

[0185] (Fourth embodiment)

[0186] The inspection apparatuses 100 , 100A, and 100B described in the first, second, and third embodiments are reflective inspection apparatuses using a reflective optical system, but may be transmissive inspection apparatuses using a transmissive optical system.

[0187] Fig.11 This is a schematic diagram for explaining the schematic configuration of an inspection apparatus 100C according to the fourth embodiment. The inspection apparatus 100C is different in that an inspection table 20B is used instead of the inspection table 20, the light source unit 2 is arranged opposite to the detection unit 3 with respect to the inspection table 20B, and the circular polarization plate 4A is not provided between the light source unit 2 and the stacked body 10.

[0188] The inspection table 20B is a table on which the stacked body 10 is placed similarly to the inspection table 20. The stacked body 10 is placed with respect to the inspection table 20B in the same manner as the case of the inspection table 20. The inspection table 20B has a window portion 20a that allows the inspection light 5 from the light source unit 2 to pass toward the stacked body 10. The window portion 20a may be an opening or a transparent member.

[0189] The light source unit 2 is the same as the light source unit 2 described in the first embodiment, except that the light source unit 2 is arranged opposite to the stacked body 10 when viewed from the inspection stand 20B.

[0190] The detection unit 3 is arranged on the optical path of the inspection light 5 output from the light source unit. The circular polarization plate 4B is arranged between the detection unit 3 and the stacked body 10, and functions as a circular polarization plate for detection in the fourth embodiment. In the fourth embodiment, the linear polarization plate (linear polarization plate for detection) 42a of the circular polarization plate 4B faces the detection unit 3, and the phase difference film (phase difference film for detection) 42b faces the stacked body 10.

[0191] When the wavelength of the inspection light 5 changes within the first inspection wavelength range, the circular polarization plate 4B is arranged to satisfy the following condition 5. When the wavelength of the inspection light 5 changes within the second inspection wavelength range, the circular polarization plate 4B is arranged to satisfy the following condition 6.

[0192] (Condition 5)

[0193] The circular polarizing plate 4B is a circular polarizing plate having a rotation direction opposite to that of the circular polarizing plate 1 .

[0194] (Condition 6)

[0195] The circular polarizing plate 4B has the same rotation direction as that of the circular polarizing plate 1 .

[0196] Next, an example of an inspection method of the circular polarization plate 1 using the inspection apparatus 100C will be described. First, a case where the wavelength of the inspection light 5 is changed within the first inspection wavelength range ([Case A1]) will be described.

[0197] [Case A1] Changing the wavelength of the inspection light 5 within the first inspection wavelength range

[0198] In case A1, the circular polarizing plate 4B satisfies the above condition 5. For convenience of description, the case where the circular polarizing plate 4B is a right-hand circular polarizing plate will be described. Since the circular polarizing plate 4B satisfies the condition 5, the circular polarizing plate 1 is a left-hand circular polarizing plate.

[0199] The inspection light 5 outputted from the light source unit 2 is irradiated toward the stacked body 10 through the window 20a (irradiation step). In the irradiation step, the inspection light 5 is irradiated toward the stacked body 10 while changing the wavelength within the first inspection wavelength range. Fig.10 In the illustrated configuration, the inspection light 5 is irradiated toward the laminated body 10 from the surface protection film 14b side.

[0200] The inspection light 5 (transmitted light) that has passed through the laminate 10 irradiated with the inspection light 5 is passed through the circular polarizing plate 4B and detected by the detection unit 3 (detection step). As described above, in the irradiation step, the inspection light 5 is irradiated to the laminate 10 while changing the wavelength within the first inspection wavelength range, so that in the detection step, a detection result of the transmitted light corresponding to the inspection light 5 with a different wavelength is obtained.

[0201] The presence or absence of a defect in the circularly polarizing plate 1 is determined based on the detection result of the detection unit 3 (determination step).

[0202] In the case of case A1, since the inspection light 5 is irradiated to the laminated body 10 while changing the wavelength within the first inspection wavelength range in the irradiation step, the detection result of the inspection light 5 of the first predetermined wavelength λa is also obtained. When there is a defect D in the circular polarizing plate 1, the defect D can be detected based on the detection result of the inspection light 5 of the first predetermined wavelength λa. This point will be described in detail.

[0203] Inspection light 5 irradiated from the surface protection film 14b side toward the laminate 10 passes through the surface protection film 14b and enters the circular polarization plate 1. Since the circular polarization plate 1 is a left-handed circular polarization plate, the inspection light 5 entering the circular polarization plate 1 is output as left-handed inspection light 5.

[0204] The inspection light 5 output from the circular polarizing plate 1 passes through the release film 14a and is thereby output from the laminate 10. When the inspection light 5 passes through the release film 14a, a phase difference is generated in the inspection light 5. Since the inspection light 5 is the inspection light 5 having the first specified wavelength λa, the above-mentioned phase difference is the first phase difference, that is, an integer multiple of the first specified wavelength λa. In this case, since the polarization state of the inspection light 5 passing through the release film 14a does not change, the inspection light 5 output from the release film 14a is left-handed circularly polarized light. The inspection light 5 output from the laminate 10 after passing through the circular polarizing plate 1 and the release film 14a in this way is called output light 5c. Since the circular polarizing plate 4B is a right-handed circular polarizing plate and is configured in a manner such that the phase difference film 42b faces the laminate 10, the output light 5c is blocked by the circular polarizing plate 4B. Specifically, the output light 5c is absorbed by the linear polarizing plate 42a possessed by the circular polarizing plate 4B.

[0205] Since the output light 5 c as the inspection light 5 that has passed through the laminated body 10 as described above is absorbed by the circular polarization plate 4B, the observation field of the circular polarization plate 1 obtained by the detection unit 3 becomes dark.

[0206] When there is a defect D in the circular polarizing plate 1, scattering occurs at the portion of the defect D. The scattered light based on the defect D has a phase difference deviated from the ideal phase difference due to the defect D, and is unexpected elliptically polarized light. The elliptically polarized scattered light is output from the laminate 10 after passing through the peeling film 14a. The inspection light 5 output from the laminate 10 due to the above-mentioned defect D is called output light 5d. The output light 5d is incident on the circular polarizing plate 4B. When passing through the peeling film 14a, since the phase difference generated in the elliptically polarized scattered light is an integer multiple of the first specified wavelength λa, the polarization state of the scattered light does not change. Therefore, the output light 5d is incident on the circular polarizing plate 1 in the form of elliptically polarized light. In this case, the output light 5d is transmitted without being absorbed by the circular polarizing plate 1. Therefore, in the detection result of the detection unit 3, since the portion of the defect D appears as a bright spot, the defect D of the circular polarizing plate 1 can be detected.

[0207] Although the case where the circular polarizing plate 4B is a right-hand circular polarizing plate and the circular polarizing plate 1 is a left-hand circular polarizing plate has been described, the same applies to the case where the circular polarizing plate 4B is a left-hand circular polarizing plate and the circular polarizing plate 1 is a right-hand circular polarizing plate. Specifically, the description of the case where the circular polarizing plate 4B is a left-hand circular polarizing plate and the circular polarizing plate 1 is a right-hand circular polarizing plate corresponds to the case where "right-hand" is changed to "left-hand" and "left-hand" is changed to "right-hand" in the description of the above-mentioned case A1.

[0208] Next, a description will be given of a case where the wavelength of the inspection light 5 is changed within the second inspection wavelength range ([Case B1]).

[0209] [Case B1] When using the inspection light 5 having the second predetermined wavelength λb

[0210] In case B1, the circular polarizing plate 4B satisfies the above-mentioned condition 6. For the convenience of description, the case where the circular polarizing plate 4B is a right-hand circular polarizing plate will be described. Since the circular polarizing plate 4B satisfies the condition 6, the circular polarizing plate 1 is a right-hand circular polarizing plate.

[0211] The inspection light 5 outputted from the light source unit 2 passes through the window 20a and is irradiated onto the laminate 10 (irradiation step). In the irradiation step, the inspection light 5 is irradiated onto the laminate 10 while changing the wavelength within the second inspection wavelength range. Fig.10 In the illustrated configuration, the inspection light 5 is irradiated toward the laminated body 10 from the surface protection film 14b side.

[0212] The output light from the laminate 10 irradiated with the inspection light 5 is passed through the circular polarizing plate 4B and then detected by the detection unit 3 (detection step). In the irradiation step, the inspection light 5 is irradiated to the laminate 10 while changing the wavelength within the second inspection wavelength range, so that the detection result of the output light corresponding to the inspection light 5 with a different wavelength is obtained in the detection step.

[0213] The presence or absence of a defect in the circularly polarizing plate 1 is determined based on the detection result of the detection unit 3 (determination step).

[0214] In the case of case B1, the inspection light 5 is irradiated to the laminate 10 while changing the wavelength within the second inspection wavelength range in the irradiation step, so the detection result of the inspection light 5 of the second predetermined wavelength λb is also obtained. In the case where the above-mentioned defect D exists in the circular polarizing plate 1, the above-mentioned defect D can be detected based on the detection result of the inspection light 5 of the second predetermined wavelength λb. This point will be described in detail.

[0215] Inspection light 5 irradiated from the surface protection film 14b side toward the laminate 10 passes through the surface protection film 14b and enters the circular polarization plate 1. Since the circular polarization plate 1 is a right-handed circular polarization plate, the inspection light 5 entering the circular polarization plate 1 is output as right-handed inspection light 5.

[0216] The inspection light 5 output from the circular polarizing plate 1 passes through the release film 14a and is thus output from the stack 10. In case B1, the inspection light 5 output in this way is also referred to as output light 5c. When the inspection light 5 passes through the release film 14a, a phase difference is generated in the inspection light 5. Since the inspection light 5 is the inspection light 5 having the second specified wavelength λb, the above-mentioned phase difference is the second phase difference, that is, (n+1 / 2) times the second specified wavelength λb. In this case, the output light 5c as the inspection light 5 that has passed through the release film 14a is left-handed circularly polarized light. That is, the inspection light 5 that has passed through the stack 10 is output light 5c of left-handed circularly polarized light. Since the circular polarizing plate 4B is a right-handed circular polarizing plate and is configured so that the phase difference film 42b faces the stack 10, the output light 5c is blocked by the circular polarizing plate 4B. Specifically, the output light 5c is absorbed by the linear polarizing plate 42a possessed by the circular polarizing plate 4B.

[0217] Since the output light 5 c that has passed through the laminated body 10 as described above is absorbed by the circular polarization plate 4B, the observation field of the circular polarization plate 1 obtained by the detection unit 3 becomes dark.

[0218] When there is a defect D in the circular polarizing plate 1, scattering occurs at the defect D portion. The scattered light based on the defect D has a phase difference deviated from the ideal phase difference due to the defect D, and is unexpected elliptically polarized light. The elliptically polarized scattered light is output from the stack 10 after passing through the release film 14a. In case B1, the inspection light 5 output from the stack 10 due to the defect D is also referred to as output light 5d. The output light 5d is incident on the circular polarizing plate 4B. When passing through the release film 14a, since the phase difference generated in the elliptically polarized scattered light is (n+1 / 2) times the second specified wavelength λb, the direction of the major axis of the elliptically polarized light is rotated but the elliptically polarized light is maintained. Therefore, the output light 5d is incident on the circular polarizing plate 4B in the form of elliptically polarized light. In this case, the output light 5d is transmitted without being absorbed by the circular polarizing plate 4B. Therefore, in the detection result of the detection unit 3, since the defect D portion appears as a bright spot, the defect D of the circular polarizing plate 1 can be detected.

[0219] Although the case where the circular polarizing plate 4B and the circular polarizing plate 1 are right-handed circular polarizing plates has been described, the same applies to the case where the circular polarizing plate 4B and the circular polarizing plate 1 are left-handed circular polarizing plates. Specifically, the description of the case where the circular polarizing plate 4B and the circular polarizing plate 1 are left-handed circular polarizing plates corresponds to the case where "right-handed" is changed to "left-handed" and "left-handed" is changed to "right-handed" in the description of the above-mentioned case B1.

[0220] As described above, in the fourth embodiment, the influence of the phase difference when the light passes through the release film 14a can be substantially eliminated by irradiating the inspection light 5 to the laminate 10 while changing the wavelength within the first inspection wavelength range or the second inspection wavelength range. Therefore, the inspection device 100B of the third embodiment and the inspection method using the inspection device 100B have the same effects as those of the first embodiment.

[0221] (Variant 2)

[0222] In the transmission type inspection apparatus described in the fourth embodiment, as described in the second embodiment, the bandpass filter 2b can be used to form a wavelength gradient in the irradiation area 6. In this modification 2, in the inspection apparatus 100B, it is sufficient to use the inspection table 20A instead of the inspection table 20B, and use the light source unit 2A instead of the light source unit 2. The table body 21 of the inspection table 20A of the modification 2 is formed with the window portion 20a in the same manner as in the case of the inspection table 20B.

[0223] Although various embodiments of the present invention have been described above, the present invention is not limited to these examples, and is intended to include all modifications within the meaning and scope of the claims and equivalents to the claims.

[0224] For example, by Figure 5 The light source 2a) shown in the figure switches a plurality of bandpass filters that selectively pass a plurality of wavelengths in the inspection wavelength range (the first inspection wavelength range or the second inspection wavelength range), thereby changing the wavelength of the inspection light irradiated to the stacked body 10.

[0225] In the second embodiment, the wavelength may be spatially varied by using a prism instead of the bandpass filter 2 b.

[0226] In the second embodiment, the moving mechanism may also be Figure 5 The stage body 21 is moved in the x-axis direction as shown and at the same time in the y-axis direction. For example, Figure 5 The inspection table 20A shown may also be a two-axis stage, thereby making it possible to inspect the entire surface of the stacked body.

[0227] The various embodiments, modifications, and the like described above can be appropriately combined without departing from the gist of the present invention.

Claims

1. An inspection method for inspecting whether a first circular polarizing plate of a film-like laminate having a first circular polarizing plate and a release film has defects, wherein the first circular polarizing plate has a first linear polarizing plate and a first retardation film laminated on the first linear polarizing plate, and the release film is laminated on the first retardation film and is formed of a polyethylene terephthalate resin, the inspection method comprising: an irradiation step of irradiating the stacked body with inspection light while changing the wavelength with time or changing the wavelength with space within an inspection wavelength range including a predetermined wavelength; a detection step of detecting the inspection light output from the release film side of the laminated body irradiated with the inspection light; and a determination step of determining whether the first circularly polarizing plate has a defect based on the detection result of the detection step, When the specified wavelength is set to λ and n is set to an integer greater than 1, the specified wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ is generated due to light of the specified wavelength passing through the release film, and the unit of λ is nm.

2. The inspection method according to claim 1, wherein: The predetermined wavelength is a wavelength at which the first phase difference is generated when light of the predetermined wavelength passes through the release film. The inspection wavelength range is a wavelength of 500 nm or more and 550 nm or less.

3. The inspection method according to claim 2, wherein: In the irradiation step, the inspection light is irradiated from the release film side toward the laminate through the second circular polarizing plate having the second linear polarizing plate and the second retardation film from the second linear polarizing plate side. In the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the release film is detected after passing through a third circular polarizing plate having a third linear polarizing plate and the third retardation film from the third retardation film side. The second circular polarizing plate and the third circular polarizing plate are both left-handed or right-handed circular polarizing plates, and are circular polarizing plates with a rotation direction opposite to that of the first circular polarizing plate.

4. The inspection method according to claim 2, wherein: In the irradiation step, the inspection light is irradiated from the release film side toward the laminate through a fourth circular polarizing plate having the fourth linear polarizing plate and a fourth retardation film from the fourth linear polarizing plate side. In the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the release film is detected after passing through the fourth circular polarizing plate from the fourth retardation film side. The fourth circular polarization plate is a circular polarization plate having a rotation direction opposite to that of the first circular polarization plate.

5. The inspection method according to claim 2, wherein: In the irradiation step, the inspection light is irradiated toward the laminate from the first circularly polarizing plate side. In the detection step, the inspection light output from the release film side of the laminate is detected after passing through a detection circular polarizing plate having a detection linear polarizing plate and the detection retardation film from the detection retardation film side. The detection circular polarization plate is a circular polarization plate having a rotation direction opposite to that of the first circular polarization plate.

6. The inspection method according to claim 1, wherein: The predetermined wavelength is a wavelength at which the second phase difference is generated when light of the predetermined wavelength passes through the release film. The inspection wavelength range is a wavelength of 570 nm or more and 630 nm or less.

7. The inspection method according to claim 6, wherein: In the irradiation step, the inspection light is irradiated from the release film side toward the laminate through the second circular polarizing plate having the second linear polarizing plate and the second retardation film from the second linear polarizing plate side. In the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the release film is detected after passing through a third circular polarizing plate having a third linear polarizing plate and the third retardation film from the third retardation film side. The first circular polarization plate, the second circular polarization plate, and the third circular polarization plate are circular polarization plates having the same rotation direction.

8. The inspection method according to claim 6, wherein: In the irradiation step, the inspection light is irradiated from the release film side toward the laminate through a fourth circular polarizing plate having the fourth linear polarizing plate and a fourth retardation film from the fourth linear polarizing plate side. In the detection step, the inspection light reflected by the first circular polarizing plate and then transmitted through the release film is detected after passing through the fourth circular polarizing plate from the fourth retardation film side. The fourth circular polarization plate is a circular polarization plate having a rotation direction opposite to that of the first circular polarization plate.

9. The inspection method according to claim 6, wherein: In the irradiation step, the inspection light is irradiated toward the laminate from the first circularly polarizing plate side. In the detection step, the inspection light output from the release film side of the laminate is detected after passing through a detection circular polarizing plate having a detection linear polarizing plate and the detection retardation film from the detection retardation film side. The detection circular polarization plate is a circular polarization plate having the same rotation direction as that of the first circular polarization plate.

10. The inspection method according to any one of claims 1 to 9, wherein: In the irradiation step, the stacked body is irradiated with the inspection light, the inspection light being obtained by passing light from a light source that outputs light in a wavelength range including the inspection wavelength range through a bandpass filter that selectively passes an upper wavelength of the inspection wavelength range, The bandpass filter is arranged obliquely with respect to a plane orthogonal to the stacking direction of the first circular polarizing plate and the release film so as to form a wavelength gradient in which the wavelength changes along a predetermined direction within the inspection wavelength range in the irradiation area of ​​the inspection light. In the detection step, the inspection light output from the release film is detected while the stacked body is moved in the predetermined direction relative to the irradiation region. 11 . A method for producing a laminate, the method comprising the step of inspecting whether the first circularly polarizing plate included in the laminate has defects by using the inspection method according to claim 1 .

12. An inspection device for inspecting whether a first circular polarizing plate of a film-like laminate having a first circular polarizing plate and a release film has defects, wherein the first circular polarizing plate has a first linear polarizing plate and a first phase difference film laminated on the first linear polarizing plate, and the release film is laminated on the first phase difference film side and is formed of a polyethylene terephthalate-based resin, the inspection device comprising: a light source unit configured to irradiate inspection light to the stacked body while changing the wavelength within an inspection wavelength range including a predetermined wavelength or while changing the wavelength spatially; and a detection unit that detects the inspection light output from the release film side of the laminated body irradiated with the inspection light, When the specified wavelength is set to λ and n is set to an integer greater than 1, the specified wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ is generated due to light of the specified wavelength passing through the release film, and the unit of λ is nm.

13. The inspection device according to claim 12, wherein: The predetermined wavelength is a wavelength at which the first phase difference is generated when light of the predetermined wavelength passes through the release film. The inspection wavelength range is a wavelength of 500 nm or more and 550 nm or less.

14. The inspection device according to claim 13, further comprising: a second circularly polarizing plate having a second linear polarizing plate and a second retardation film; and a third circularly polarizing plate having a third linear polarizing plate and a third phase difference film, The light source unit and the detection unit are arranged on the peeling film side. The second circular polarizing plate is disposed between the light source unit and the laminate on the optical path of the inspection light so that the second phase difference film faces the release film. The third circular polarizing plate is disposed between the laminate and the detection unit on an optical path of the inspection light reflected by the laminate so that the third phase difference film faces the release film. The second circular polarizing plate and the third circular polarizing plate are both left-handed or right-handed circular polarizing plates, and are circular polarizing plates with a rotation direction opposite to that of the first circular polarizing plate.

15. The inspection device according to claim 13, comprising: a fourth circularly polarizing plate disposed on the release film side relative to the laminate and comprising a fourth linear polarizing plate and a fourth retardation film, The fourth circularly polarizing plate is arranged so that the fourth phase difference film faces the release film. The light source unit and the detection unit are arranged opposite to the stacked body with respect to the fourth circular polarization plate. The fourth circular polarizing plate has a first region located on the optical path of the inspection light between the light source unit and the laminate and a second region located on the optical path of the inspection light reflected by the laminate. The fourth circular polarization plate is a circular polarization plate having a rotation direction opposite to that of the first circular polarization plate.

16. The inspection device according to claim 13, further comprising a circular polarization plate for detection having a linear polarization plate for detection and a phase difference film for detection, The light source unit is arranged on the first circular polarizing plate side, The detection unit is arranged on the peeling film side. The circular polarizing plate for detection is arranged between the detection section and the laminated body so that the phase difference film for detection faces the release film. The detection circular polarization plate is a circular polarization plate having a rotation direction opposite to that of the first circular polarization plate.

17. The inspection device according to claim 12, wherein: The predetermined wavelength is a wavelength at which the second phase difference is generated when light of the predetermined wavelength passes through the release film. The inspection wavelength range is greater than or equal to 570 nm and less than or equal to 630 nm.

18. The inspection device according to claim 17, further comprising: a second circular polarizing plate disposed between the light source unit and the laminated body on an optical path of the inspection light and having a second linear polarizing plate and a second retardation film; and a third circular polarizing plate disposed between the stacked body and the detection unit on an optical path of the inspection light reflected by the stacked body and having a third linear polarizing plate and a third phase difference film, The light source unit and the detection unit are arranged on the peeling film side. The second circularly polarizing plate is arranged so that the second phase difference film faces the release film. The third circularly polarizing plate is arranged so that the third phase difference film faces the release film. The second circular polarization plate and the third circular polarization plate are circular polarization plates having the same rotation direction as that of the first circular polarization plate.

19. The inspection device according to claim 17, comprising: a fourth circularly polarizing plate disposed on the release film side relative to the laminate and comprising a fourth linear polarizing plate and a fourth retardation film, The fourth circularly polarizing plate is arranged so that the fourth phase difference film faces the release film. The light source unit and the detection unit are arranged opposite to the stacked body with respect to the fourth circular polarization plate. The fourth circular polarizing plate has a first region located on the optical path of the inspection light between the light source unit and the laminate and a second region located on the optical path of the inspection light reflected by the laminate. The fourth circular polarization plate is a circular polarization plate having the same rotation direction as that of the first circular polarization plate.

20. The inspection device according to claim 17, further comprising a circular polarization plate for detection having a linear polarization plate for detection and a phase difference film for detection, The light source unit is arranged on the first circular polarizing plate side, The detection unit is arranged on the peeling film side. The circular polarizing plate for detection is arranged between the detection section and the laminated body so that the phase difference film for detection faces the release film. The detection circular polarization plate is a circular polarization plate having the same rotation direction as that of the first circular polarization plate.

21. The inspection device according to any one of claims 12 to 20, further comprising a moving mechanism for moving the stacked body in a predetermined direction. The light source unit comprises: a light source that outputs light in a wavelength range that includes the inspection wavelength range; and a bandpass filter that selectively passes light having a wavelength at an upper limit of the inspection wavelength range among the light output from the light source, The band pass filter is arranged to be inclined with respect to a plane orthogonal to the stacking direction of the first circular polarizing plate and the release film so as to form a wavelength gradient in which the wavelength changes in a predetermined direction within the inspection wavelength range in the irradiation region of the inspection light.

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