Inspection method, inspection device and laminate manufacturing method

Abstract

To provide a technique capable of easily determining presence / absence of defects of a circular polarization plate.SOLUTION: An inspection method for inspecting presence / absence of defects of a first circular polarization plate 1 of a laminate 10 including the first circular polarization plate 1 having a first linear polarization plate 11 and a first retardation film 12 and a release film 14a formed of a polyethylene terephthalate-based resin includes an irradiation step of irradiating the laminate with inspection light 5 while a wavelength is temporally changed or in a state in which the wavelength is spatially changed within an inspection wavelength range including a predetermined wavelength, an inspection step of detecting the inspection light 5 output from the release film 14a side of the laminate 10 irradiated with the inspection light 5, and a determination step of determining presence / absence of defects of the first circular polarization plate 1 on the basis of the detection result. The predetermined wavelength is a wavelength generating a first retardation of nλ or a second retardation of (n+1 / 2)λ by transmitting light of a predetermined wavelength through the release film.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an inspection method, an inspection device, and a method for manufacturing a laminate. [Background technology]

[0002] Polarizing plates used in liquid crystal displays, organic EL displays, and the like are generally constructed by sandwiching a polarizer between two protective films. To attach the polarizing plate to a display device, an adhesive layer is laminated on one of the protective films, and a release film is further laminated on the adhesive layer. In many cases, a release film (surface protection film) that protects the surface of the other protective film is also attached. The polarizing plate is transported and distributed in this state with the release film laminated thereon, and the release film is peeled off when the polarizing plate is attached to a display device during the manufacturing process of the display device.

[0003] During the manufacturing process of a polarizing plate, foreign matter may be mixed in between the polarizer and the protective film, air bubbles may remain, or, if the protective film functions as a retardation film, alignment defects may be present (hereinafter, these foreign matter, air bubbles, and alignment defects may be collectively referred to as "defects"). When a polarizing plate having a defect is attached to a display device, the defective area may be visually recognized as a bright spot, or the image may appear distorted at the defective area. In particular, defects that are visually recognized as bright spots are easily visually recognized when the display device displays black.

[0004] Therefore, before the polarizing plate is bonded to the display device (the polarizing plate with the release film), an inspection is performed to detect defects in the polarizing plate. The inspection for this defect is generally an optical inspection using the polarization axis of the polarizing plate. Specifically, as shown in Patent Document 1, a polarizing filter is provided between the polarizing plate to be inspected and a light source, and then the polarizing plate or the polarizing filter is rotated in a planar direction to set the polarization axis directions of these plates in a specific relationship. When the polarization axis directions are perpendicular to each other (i.e., when they are arranged to form a crossed Nicol), the linearly polarized light that has passed through the polarizing filter does not pass through the polarizing plate. However, if there is a defect in the polarizing plate, the linearly polarized light passes through the portion, and the presence of the defect is found by detecting the light. On the other hand, when the polarization axis directions of the polarizing plate and the polarizing filter are parallel to each other, the linearly polarized light that has passed through the polarizing filter passes through the polarizing plate. However, when there is a defect in the polarizing plate, the linearly polarized light is blocked at the portion, and the presence of the defect is found by not detecting the light. The presence or absence of defects in polarizing plates can be detected by an inspector either visually detecting the light that has passed through the polarizing plate, or automatically by image analysis processing values ​​using a combination of a CCD camera and image processing device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-229817 Summary of the Invention [Problem to be solved by the invention]

[0006] When the polarizing plate is a circular polarizing plate, it is possible to further arrange a phase difference filter with respect to the circular polarizing plate so as to darken the observation field, thereby detecting bright spots occurring at defective locations.

[0007] Circular polarizing plates are also usually transported and distributed with a release film laminated thereon. Therefore, when inspecting circular polarizing plates, they are inspected with the release film laminated thereon. Since the release film is a film that is peeled off when the circular polarizing plate is attached to a display device, the phase difference of the release film is not strictly controlled. Therefore, due to the phase difference inherent in the release film, the observation field of view may not be dark enough, which reduces the accuracy of defect detection.

[0008] Therefore, an object of the present invention is to provide a technique capable of improving the accuracy of detecting defects in a circular polarizing plate. [Means for solving the problem]

[0009] [1] An inspection method according to one embodiment is an inspection method for inspecting the presence or absence of defects in a first circular polarizer of a film-like laminate including a first linear polarizer, a first phase difference film laminated on the first linear polarizer, and a release film formed of a polyethylene terephthalate resin and laminated on the first phase difference film, the inspection method including an irradiation step of irradiating the laminate with inspection light while changing the wavelength over time or changing the wavelength over 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 laminate irradiated with the inspection light, and a determination step of determining the presence or absence of defects in the first circular polarizer based on the detection result of the detection step, wherein the predetermined wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ occurs when the light of the predetermined wavelength passes through the release film, where the predetermined wavelength is λ [nm] and n is an integer of 1 or more.

[0010] In the inspection method described in [1] above, the laminate is irradiated with inspection light while changing the wavelength over time or changing the wavelength over space within an inspection wavelength range including a predetermined wavelength. Therefore, it is possible to reliably obtain a detection result for light of a predetermined wavelength. The predetermined wavelength is a wavelength at which, when the predetermined wavelength is λ [nm] and n is an integer of 1 or more, a first phase difference of nλ or a second phase difference of (n+1 / 2)λ occurs when the light of the predetermined wavelength passes through the release film. Therefore, the effect of the release film on the light of the predetermined wavelength is reduced. Therefore, when a defect exists in the first circular polarizing plate, the defect can be detected with high accuracy.

[0011] [2] In the inspection method described in [1] above, the specified wavelength is a wavelength at which the first phase difference occurs when light of the specified wavelength passes through the release film, and the inspection wavelength range may be a wavelength of 500 nm or more and 550 nm or less.

[0012] When the release film is made of a PET resin, the inspection wavelength range is likely to include a predetermined wavelength at which the first phase difference occurs in light transmitted through the release film. Therefore, when a defect exists in the first circular polarizing plate, the defect can be detected with high accuracy by setting the inspection wavelength range to the range described in [2] above.

[0013] [3] In the inspection method described in [2] above, in the irradiation step, the inspection light that has passed through a second circular polarizer having a second linear polarizer and a second phase difference film from the second linear polarizer side is irradiated onto the laminate from the release film side, and in the detection step, the inspection light that has been reflected by the first circular polarizer and then transmitted through the release film is passed through a third circular polarizer having a third linear polarizer and a third phase difference film from the third phase difference film side and detected, and the second circular polarizer and the third circular polarizer may both be left-rotating or right-rotating circular polarizers and may be a circular polarizer that rotates in the opposite direction to the first circular polarizer.

[0014] [4] In the inspection method described in [2] above, in the irradiation step, the inspection light that has passed through a fourth circular polarizer having a fourth linear polarizer and a fourth phase difference film from the fourth linear polarizer side is irradiated onto the laminate from the release film side, and in the detection step, the inspection light that has been reflected by the first circular polarizer and then transmitted through the release film is detected by passing it through the fourth circular polarizer from the fourth phase difference film side, and the fourth circular polarizer may be a circular polarizer that rotates in the opposite direction to the first circular polarizer.

[0015] [5] In the inspection method described in [2] above, in the irradiation step, the inspection light is irradiated onto the laminate from the side of the first circular polarizer, and in the detection step, the inspection light transmitted through the laminate in the order of the first circular polarizer and the release film is passed through a detection circular polarizer having a detection linear polarizer and a detection retardation film from the detection retardation film side and detected, and the detection circular polarizer may be a circular polarizer having an opposite rotation to the first circular polarizer.

[0016] In the inspection methods described in [3], [4], and [5] above, the detection area (e.g., observation area) detected by the detection unit is dark. On the other hand, if there is a defect in the first circular polarizer, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0017] [6] In the inspection method described in [1] above, the specified wavelength is a wavelength at which the second phase difference occurs when light of the specified wavelength passes through the release film, and the inspection wavelength range may be a wavelength of 570 nm or more and 630 nm or less.

[0018] When the release film is made of a PET resin, the inspection wavelength range is likely to include a predetermined wavelength at which the second phase difference occurs in light transmitted through the release film. Therefore, when a defect exists in the first circular polarizing plate, the defect can be detected with high accuracy by setting the inspection wavelength range to the range described in [6] above.

[0019] [7] In the inspection method described in [6] above, in the irradiation step, the inspection light that has passed through a second circular polarizer having a second linear polarizer and a second phase difference film from the second linear polarizer side is irradiated onto the laminate from the release film side, and in the detection step, the inspection light that has been reflected by the first circular polarizer and then transmitted through the release film is passed through a third circular polarizer having a third linear polarizer and a third phase difference film from the third phase difference film side and detected, and the first circular polarizer, the second circular polarizer and the third circular polarizer may be circular polarizers with the same rotation direction.

[0020] [8] In the inspection method described in [6] above, in the irradiation step, the inspection light that has passed through a fourth circular polarizer having a fourth linear polarizer and a fourth phase difference film from the fourth linear polarizer side is irradiated onto the laminate from the release film side, and in the detection step, the inspection light that has been reflected by the first circular polarizer and then transmitted through the release film is detected by passing it through the fourth circular polarizer from the fourth phase difference film side, and the fourth circular polarizer may be a circular polarizer that rotates in the opposite direction to the first circular polarizer.

[0021] [9] In the inspection method described in [6] above, in the irradiation step, the inspection light is irradiated onto the laminate from the first circular polarizer side, and in the detection step, the inspection light output from the peelable film side of the laminate is passed through a third circular polarizer having a detection linear polarizer and a detection retardation film from the detection retardation film side and detected through a detection circular polarizer, which may be a circular polarizer of the same rotation as the first circular polarizer.

[0022] In the inspection methods described in [7], [8], and [9] above, the detection area (e.g., observation area) detected by the detection unit is dark. On the other hand, if there is a defect in the first circular polarizer, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0023]

[10] In the inspection method according to any one of [1] to [9] above, in the irradiation step, the laminate is irradiated with the inspection light obtained by passing light from a light source outputting light in a wavelength range including the inspection wavelength range through a bandpass filter that selectively passes the upper limit wavelength of the inspection wavelength range, and the bandpass filter is arranged at an angle with respect to a plane perpendicular to the lamination direction of the first circular polarizer and the release film so as to form a wavelength gradation in which the wavelength changes within the inspection wavelength range along a predetermined direction in the irradiation area of ​​the inspection light, and in the detection step, the inspection light output from the release film may be detected while moving the laminate along the predetermined direction relative to the irradiation area.

[0024] In the inspection method described in

[10] above, a wavelength gradation occurs in which the wavelength changes within the inspection wavelength range along a predetermined direction. Therefore, in the inspection method, inspection light is irradiated with the wavelength spatially changed within the inspection wavelength range. In the detection process, the inspection light output from the release film is detected while the laminate is moved along the predetermined direction relative to the irradiation area. Therefore, it is possible to reliably detect inspection light of a predetermined wavelength included in the wavelength gradation. Therefore, defects can be detected with high accuracy.

[0025]

[11] A method for producing a laminate according to another aspect of the present invention includes a step of inspecting the first circular polarizer included in the laminate for the presence or absence of defects by the inspection method according to any one of [1] to

[10] above. In this case, since the first circular polarizer is inspected for the presence or absence of defects using the inspection method according to any one of [1] to

[10] above, if a defect exists in the first circular polarizer, the defect can be detected with high accuracy. Therefore, quality control of the laminate and the first circular polarizer included in the laminate can be performed.

[0026]

[12] An inspection device according to another aspect of the present invention is an inspection device for inspecting the presence or absence of defects in a first circular polarizing plate in a film-like laminate including a first linear polarizing plate, a first circular polarizing plate having a first phase difference film laminated on the first linear polarizing plate, and a release film formed of a polyethylene terephthalate resin and laminated on the first phase difference film side, the inspection device comprising: a light source unit configured to irradiate the laminate with inspection light while changing the wavelength or while changing the wavelength spatially within an inspection wavelength range including a predetermined wavelength; and a detection unit that detects the inspection light output from the release film side of the laminate irradiated with the inspection light, wherein the predetermined wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ is generated when the predetermined wavelength is λ [nm] and n is an integer of 1 or more when the light of the predetermined wavelength passes through the release film.

[0027] In the inspection device described in

[12] above, the first circular polarizer can be inspected while irradiating the laminate with inspection light while changing the wavelength over time or changing the wavelength over space within an inspection wavelength range including the predetermined wavelength. In this case, the detection result for the light of the predetermined wavelength can be reliably obtained. The predetermined wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ occurs when the light of the predetermined wavelength passes through the release film, where the predetermined wavelength is λ [nm] and n is an integer of 1 or more. Therefore, the effect of the release film on the light of the predetermined wavelength is reduced. Therefore, if a defect exists in the first circular polarizer, the defect can be detected with high accuracy.

[0028]

[13] In the inspection device described in

[12] above, the predetermined wavelength is a wavelength at which the first phase difference occurs when light of the predetermined wavelength passes through the release film, and the inspection wavelength range may be a wavelength of 500 nm or more and 550 nm or less.

[0029] When the release film is made of a PET resin, the inspection wavelength range is likely to include a predetermined wavelength at which the first phase difference occurs in light transmitted through the release film. Therefore, when a defect exists in the first circular polarizing plate, the defect can be detected with high accuracy by setting the inspection wavelength range to the range described in

[13] above.

[0030]

[14] An example of the inspection device described in

[13] above further includes a second circular polarizer having a second linear polarizer and a second phase difference film, and a third circular polarizer having a third linear polarizer and a third phase difference film, wherein the light source unit and the detection unit are arranged on the release film side, the second circular polarizer is arranged between the light source unit and the laminate on the optical path of the inspection light such that the second phase difference film faces the release film, and the third circular polarizer is arranged between the laminate and the detection unit on the optical path of the inspection light reflected by the laminate such that the third phase difference film faces the release film, and the second circular polarizer and the third circular polarizer are both left-rotating or right-rotating circular polarizers and may be a circular polarizer having an opposite rotation to the first circular polarizer.

[0031]

[15] An example of the inspection device described in

[13] above includes a fourth circular polarizer arranged on the release film side of the laminate, the fourth circular polarizer having a fourth linear polarizer and a fourth phase difference film, the fourth circular polarizer being arranged so that the fourth phase difference film faces the release film, the light source unit and the detection unit being arranged opposite the laminate with respect to the fourth circular polarizer, the fourth circular polarizer having 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, and the fourth circular polarizer may be a circular polarizer having a rotation opposite to that of the first circular polarizer.

[0032]

[16] An example of the inspection device described in

[13] above further includes a detection circular polarizer having a detection linear polarizer and a detection phase difference film, wherein the light source unit is arranged on the first circular polarizer side and the detection unit is arranged on the release film side, and the detection circular polarizer is arranged between the detection unit and the laminate such that the detection phase difference film faces the release film, and the detection circular polarizer may be a circular polarizer having an opposite rotation to the first circular polarizer.

[0033] In the inspection methods described in

[14] ,

[15] and

[16] above, the detection area (e.g., observation area) detected by the detection unit is dark. On the other hand, if there is a defect in the first circular polarizer, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0034]

[17] In the inspection device described in

[12] above, the specified wavelength is a wavelength at which the second phase difference occurs when light of the specified wavelength passes through the release film, and the inspection wavelength range may be 570 nm or more and 630 nm or less.

[0035] When the release film is made of a PET resin, the inspection wavelength range is likely to include a predetermined wavelength at which the first phase difference occurs in light transmitted through the release film. Therefore, when a defect exists in the first circular polarizing plate, the defect can be detected with high accuracy by setting the inspection wavelength range to the range described in

[17] above.

[0036]

[18] An example of the inspection device described in

[17] above further includes a second circular polarizing plate that is arranged on the optical path of the inspection light between the light source unit and the laminate, the second circular polarizing plate having a second linear polarizing plate and a second phase difference film, and a third circular polarizing plate that is arranged on the optical path of the inspection light reflected by the laminate between the laminate and the detection unit, the third circular polarizing plate having a third linear polarizing plate and a third phase difference film, wherein the light source unit and the detection unit are arranged on the release film side, the second circular polarizing plate is arranged so that the second phase difference film faces the release film, and the third circular polarizing plate is arranged so that the third phase difference film faces the release film, and the second circular polarizing plate and the third circular polarizing plate may be circular polarizing plates having the same rotation as the first circular polarizing plate.

[0037]

[19] An example of the inspection device described in

[17] above includes a fourth circular polarizer arranged on the release film side of the laminate, the fourth circular polarizer having a fourth linear polarizer and a fourth phase difference film, the fourth circular polarizer being arranged so that the fourth phase difference film faces the release film, the light source unit and the detection unit being arranged on the opposite side of the laminate with respect to the fourth circular polarizer, the fourth circular polarizer having 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, and the fourth circular polarizer may be a circular polarizer having the same rotation as the first circular polarizer.

[0038]

[20] An example of the inspection device described in

[17] above further includes a detection circular polarizer having a detection linear polarizer and a detection phase difference film, wherein the light source unit is arranged on the first circular polarizer side, the detection unit is arranged on the release film side, and the detection circular polarizer is arranged between the detection unit and the laminate such that the detection phase difference film faces the release film, and the detection circular polarizer may be a circular polarizer with the same rotation as the first circular polarizer.

[0039] In the inspection devices described in

[18] ,

[19] , and

[20] above, the detection area (e.g., observation area) detected by the detection unit is dark. On the other hand, if there is a defect in the first circular polarizer, the defect appears as a bright spot. Therefore, the defect is easy to detect.

[0040]

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

[12] to

[20] above further includes a moving mechanism for moving the laminate along a predetermined direction, wherein the light source unit includes 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 an upper limit wavelength of the inspection wavelength range from the light output from the light source, and the bandpass filter may be arranged at an angle with respect to a plane perpendicular to the lamination direction of the first circular polarizer and the release film so as to form a wavelength gradation in which the wavelength changes within the inspection wavelength range along the predetermined direction in the irradiation area of ​​the inspection light.

[0041] In the inspection device described in

[21] above, a wavelength gradation occurs in which the wavelength changes within the inspection wavelength range along a predetermined direction. Therefore, in the inspection method, inspection light is irradiated with the wavelength spatially changed within the inspection wavelength range. In the detection process, the inspection light output from the release film is detected while the laminate is moved along the predetermined direction relative to the irradiation area. Therefore, it is possible to reliably detect inspection light of a predetermined wavelength included in the wavelength gradation. Therefore, defects can be detected with high accuracy. Effect of the Invention

[0042] According to the present invention, a technique capable of detecting defects in a circular polarizing plate with high accuracy can be provided. [Brief description of the drawings]

[0043] [Figure 1] FIG. 1 is a schematic diagram for explaining the configuration of a laminate including a circular polarizer to be inspected by the inspection apparatus and inspection method according to the first to fourth embodiments. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration of the inspection device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram illustrating an example of the arrangement relationship between the first circular polarizer, the second circular polarizer, and the third circular polarizer. [Figure 4] FIG. 4 is a schematic diagram for explaining another example of the arrangement relationship between the first circular polarizer, the second circular polarizer, and the third circular polarizer. [Diagram 5] FIG. 5 is a schematic diagram showing a schematic configuration of an inspection device according to the second embodiment. [Figure 6] FIG. 6 is a schematic diagram for explaining the wavelength gradation in the irradiation area of ​​the inspection light. [Figure 7] FIG. 7 is a schematic diagram showing an experimental model of an experimental example. [Figure 8] FIG. 8 is a graph showing the results of Experimental Example 1. [Figure 9] FIG. 9 is a graph showing the results of Experimental Example 2. [Figure 10] FIG. 10 is a schematic diagram for explaining a schematic configuration of an inspection device according to the third embodiment. [Figure 11] FIG. 11 is a schematic diagram for explaining a schematic configuration of an inspection device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and duplicated explanations will be omitted.

[0045] First, a laminate 10 including a circular polarizer 1 to be inspected by the inspection device and inspection method according to the first to fourth embodiments will be described. Fig. 1 is a schematic diagram for explaining the configuration of a laminate 10 including a circular polarizer 1 to be inspected by the inspection device and inspection method according to the first to fourth embodiments.

[0046] The laminate 10 is a film-like laminate. The laminate 10 includes a circular polarizer (first circular polarizer) 1, which is the main body to be inspected, and a release film 14a laminated on the circular polarizer 1. Thus, the laminate 10 is a circular polarizer with a release film. The release film 14a is laminated on the circular polarizer 1 via an adhesive layer 13. The laminate 10 may have a surface protective film 14b on the opposite side of the release film 14a from the circular polarizer 1. The following describes an embodiment in which the laminate 10 has the surface protective film 14b.

[0047] The circular polarizer 1 is generally used in display devices, such as liquid crystal display devices and organic EL display devices. When using the circular polarizer 1, the release film 14a of the laminate 10 is peeled off, and then the circular polarizer 1 is attached to a display device via the adhesive layer 13. The circular polarizer 1 has a linear polarizer (first linear polarizer) 11 and a retardation film (first retardation film) 12. The retardation film 12 is laminated on the linear polarizer 11.

[0048] The linear polarizing plate 11 has a polarizer 11a. The polarizer 11a is a film that converts light incident from the surface protective film 14b side into linearly polarized light. Examples of the polarizer 11a include a film in which iodine, a dichroic dye, etc. are adsorbed and oriented on a polyvinyl alcohol film, and a film in which a dichroic dye is adsorbed and oriented on an oriented and polymerized polymerizable liquid crystal compound.

[0049] The linear polarizing plate 11 may have 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 attached to the polarizer 11a via an adhesive.

[0050] The protective films 11b and 11c are used for the purpose of obtaining a polarizing plate having a suitable mechanical strength. The protective films 11b and 11c are generally used in the technical field of polarizing plates. Typically, cellulose ester films such as triacetyl cellulose (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. Additives generally used in the technical field of polarizing plates may be contained in the protective films 11b and 11c.

[0051] The protective films 11b and 11c are required to be adhered to a display device together with the polarizer 11a as components of the circular polarizing plate 1, and therefore require strict management of the retardation value, etc. As the protective films 11b and 11c, those having an extremely small retardation value are typically preferably used.

[0052] The retardation film 12 is laminated on the protective film 11b via an adhesive layer. The retardation film 12 is a film that converts light that is incident from the surface protective film 14b side and linearly polarized by the polarizer 11a of the linear polarizing plate 11 into circularly polarized light. When viewed from the release film 14a side, the retardation film 12 is a film that converts circularly polarized light that is incident from the release film 14a side into linearly polarized light. Therefore, the retardation film 12 includes at least a λ / 4 film. The retardation film 12 may further include a λ / 2 film. In this case, the λ / 2 film and the λ / 4 film may be laminated in this order from the side closer to the polarizer 11a.

[0053] The retardation film 12 is formed, for example, from a cured product of a polymerizable liquid crystal compound.

[0054] Examples of the polymerizable liquid crystal compound capable of forming the retardation film 12 include those disclosed in JP2009-173893A, JP2010-31223A, WO2012 / 147904A, WO2014 / 10325A, and WO2017-43438A. The polymerizable liquid crystal compounds described in these publications can form retardation films having so-called reverse wavelength dispersion, which can perform uniform polarization conversion in a wide wavelength range. For example, a solution containing the polymerizable liquid crystal compound (polymerizable liquid crystal compound solution) can be applied to a suitable substrate and photopolymerized to form an extremely thin retardation film, thereby forming a circular polarizer 1 having an extremely thin thickness. Such a circular polarizer 1 having an extremely thin thickness is advantageous as a circular polarizer 1 for flexible display materials, which have been attracting attention in recent years.

[0055] Examples of the substrate to which the polymerizable liquid crystal compound solution is applied include those described in the above publications. Such a substrate may be provided with an alignment film to align the polymerizable liquid crystal compound. The alignment film may be either one that is optically aligned by irradiation with polarized light or one that is mechanically aligned by rubbing treatment. Such an alignment film is also described in the above publications.

[0056] The retardation film 12 can be produced by applying a composition for forming an alignment film on a substrate, and then applying a composition for forming a liquid crystal cured film containing a polymerizable liquid crystal compound on the composition for forming the alignment film. The retardation film 12 thus produced is attached together with the substrate to an adhesive layer formed on the protective film 11b, and then the substrate is peeled off, so that the retardation film 12 can be transferred onto the protective film 11b.

[0057] Release film 14a is laminated on protective film 11b via adhesive layer 13. Release film 14a is peeled off from circular polarizing plate 1 when attaching to a display device. Usually, peeled release film 14a is discarded.

[0058] The surface protective film 14b is provided on the opposite side of the release film 14a in the circular polarizer 1. In the embodiment shown in FIG. 1, the surface protective film 14b is attached to the protective film 11c. The surface protective film 14b is a type of release film. The surface protective film 14b is also usually peeled off from the circular polarizer 1 when it is attached to a display device, and unlike the protective films 11b and 11c, strict management of the retardation value is not required. In FIG. 1, the protective film 11c and the surface protective film 14b may be attached via a suitable adhesive layer or pressure-sensitive adhesive layer (the adhesive layer or pressure-sensitive adhesive layer is not shown in FIG. 1).

[0059] The laminate 10 is manufactured, for example, as follows. First, a retardation film 12 is formed on a linear polarizer 11 to form a circular polarizer 1 (circular polarizer forming step). A release film 14a is attached to the linear polarizer 11 of the circular polarizer 1 via an adhesive layer 13 (release film attaching step). When manufacturing a laminate 10 having a surface protective film 14b, the surface protective film 14b is attached to a protective film 11c of the circular polarizer 1 (surface protective film attaching step). When the manufacturing method of the laminate 10 includes a surface protective film attaching step, the order of the release film attaching step and the surface protective film attaching step is not limited.

[0060] An example of the method for forming the retardation film 12 in the circular polarizing plate forming step has been described above. The circular polarizing plate forming step may include a step of forming a linear polarizing plate 11. The linear polarizing plate 11 is formed by stretching a film to become the polarizer 11a (e.g., a polyvinyl alcohol film) and by adsorbing and orienting iodine, a dichroic dye, or the like.

[0061] The manufacturing method of the laminate 10 further includes a step (inspection step) of inspecting the circular polarizer 1 to which the release film 14a is attached. In the inspection step, the circular polarizer 1 is inspected for defects. If a defect is found in the inspection step, the laminate in which the defect is found 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 be performed. The manufacturing conditions of the laminate 10 adjusted in the adjustment step are, for example, the formation conditions of the retardation film 12. When the method includes a step of forming the linear polarizer 11, the formation conditions of the linear polarizer 11, particularly the formation conditions of the polarizer 11a, are also included in the manufacturing conditions of the laminate 10.

[0062] By producing the laminate 10, the circular polarizing plate 1 to be attached to a display device or the like is produced. Therefore, the method for producing the laminate 10 can also be called a method for producing a circularly polarized light.

[0063] First to fourth embodiments of the inspection device used in the above inspection process and the inspection method using the inspection device will be described below. Unless otherwise specified, the laminate 10 will be described as having a surface protective film 14b.

[0064] (First embodiment) An inspection device and an inspection method according to the first embodiment will be described. Fig. 2 is a schematic diagram for explaining a schematic configuration of the inspection device according to the first embodiment. The inspection device 100 is a device for inspecting the surface of the circular polarizer 1, between the layers constituting the circular polarizer 1, or inside each layer for the presence or absence of defects.

[0065] The inspection device 100 includes an inspection table 20 on which the laminate 10 is placed. The laminate 10 is placed on the inspection table 20 with the surface protection film 14b in contact with the inspection table 20.

[0066] The inspection device 100 includes a light source unit 2 and a detection unit 3 in order to inspect the laminate 10 placed on an inspection table 20. The inspection device 100 may include a circular polarizer (second circular polarizer) 4A and a circular polarizer (third circular polarizer) 4B. In the following, the inspection device 100 including the circular polarizer 4A and the circular polarizer 4B will be described.

[0067] The light source unit 2 is disposed on the opposite side of the laminate 10 from the inspection table 20. In other words, the light source unit 2 is disposed with respect to the laminate 10 so that the inspection light 5 output from the light source unit 2 enters the laminate 10 from the release film 14a side. The light source unit 2 outputs inspection light 5 for inspecting the circular polarizer 1. The inspection light 5 is, for example, unpolarized light.

[0068] The light source unit 2 is configured to output the inspection light 5 while changing the wavelength over time or changing the wavelength over space within an inspection wavelength range including a predetermined wavelength λ [nm]. An example of the light source unit 2 is a tunable light source. In this case, the light source unit 2 changes the wavelength over time. The light source unit 2 may change the wavelength spatially. In the first embodiment, a case where a tunable light source is used as the light source unit 2 and the wavelength is changed over time will be described.

[0069] The predetermined wavelength λ is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ occurs when light having the predetermined wavelength λ passes through the release film 14a, where n is an integer of 1 or more.

[0070] For ease of explanation, hereinafter, the specified wavelength λ at which the first phase difference (nλ) occurs when light having a specified wavelength λ passes through the peelable film 14a will be referred to as the "first specified wavelength λa," the inspection wavelength range for the first specified wavelength λa will be referred to as the "first inspection wavelength range," the specified wavelength λ at which the second phase difference ((n+1 / 2)λ) occurs will be referred to as the "second specified wavelength λb," and the inspection wavelength range for the second specified wavelength λb will be referred to as the "second inspection wavelength range."

[0071] As described above, the release film 14 is a film formed from a polyethylene terephthalate resin (PET resin) (hereinafter, may be 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 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 be 570 nm or more and 610 nm or less.

[0072] The thickness of the PET resin film is from 1 μm to 500 μm, and from the viewpoint of ease of peeling, is preferably from 10 μm to 200 μm, and more preferably from 10 μm to 100 μm.

[0073] The detection unit 3 is disposed on the same side as the light source unit 2 with respect to the inspection table 20. A partition plate may be provided between the light source unit 2 and the detection unit 3. The detection unit 3 detects the inspection light 5 reflected by the laminate 10. The inspection light 5 reflected by the laminate 10 may also be referred to as reflected light. The detection unit 3 is disposed on the optical path of the reflected light from the laminate 10. The detection unit 3 includes a photodetector. In this embodiment, the photodetector is an imager. An example of the imager is a CCD camera.

[0074] The detection unit 3 may have an image processing device that analyzes the image acquired by the photodetector together with the photodetector. In this case, it is possible to automatically detect defects by processing and analyzing the image data acquired by the photodetector using the image processing device.

[0075] The circular polarizer 4A is disposed between the light source unit 2 and the laminate 10 on the optical path of the inspection light 5 output from the light source unit 2. The circular polarizer 4A has a linear polarizer (second linear polarizer) 41a and a retardation film (second retardation film) 41b laminated on the linear polarizer 41a. The linear polarizer 41a has a polarizer similar to the linear polarizer 11 of the circular polarizer 1. The linear polarizer 41a may have a protective film corresponding to the protective films 11b and 11c. The retardation film 41b has a function similar to that of the retardation film 12 of the circular polarizer 1. The retardation film 41b has a λ / 4 film. In the circular polarizer 4A, the linear polarizer 41a faces the light source unit 2, and the retardation film 41b faces the laminate 10. In this configuration, the inspection light 5 is irradiated to the laminate 10 as right-handed or left-handed circularly polarized light through the circular polarizer 4A.

[0076] The circular polarizer 4B is disposed between the laminate 10 and the detection unit 3 on the optical path of the reflected light from the laminate 10. The circular polarizer 4B has a linear polarizer (third linear polarizer) 42a and a retardation film (third retardation film) 42b laminated on the linear polarizer 42a. The linear polarizer 42a has a polarizer similar to the linear polarizer 11 of the circular polarizer 1. The linear polarizer 42a may have a protective film corresponding to the protective films 11b and 11c. The retardation film 42b has a function similar to that of the retardation film 12 of the circular polarizer 1. The retardation film 42b has a λ / 4 film. In the circular polarizer 4B, the linear polarizer 42a faces the detection unit 3, and the retardation film 42b faces the laminate 10.

[0077] When the wavelength of the inspection light 5 changes within the first inspection wavelength range, the circular polarizers 4A and 4B satisfy the following condition 1. (Condition 1) Circular polarizer 4A and circular polarizer 4B are left-rotating or right-rotating circular polarizers, and are opposite in rotation to circular polarizer 1.

[0078] 3 is a schematic diagram for explaining an example of the positional relationship between the circular polarizer 1, the circular polarizer 4A, and the circular polarizer 4B. In FIG. 3, a release film 14a, a light source unit 2, and a detection unit 3 are also shown.

[0079] 3, the circular polarizer 4A and the circular polarizer 4B are arranged with respect to the circular polarizer 1 so that the absorption axis of the linear polarizer 11, the absorption axis of the linear polarizer 41a, and the absorption axis of the linear polarizer 42a are oriented in the same direction, and the slow axis of the retardation film 12, the slow axis of the retardation film 41b, and the slow axis of the retardation film 42b are oriented in the same direction. In this case, the circular polarizer 4A and the circular polarizer 4B satisfy condition 1.

[0080] When the wavelength of the inspection light 5 changes within the second inspection wavelength range, the circular polarizers 4A and 4B satisfy the following condition 2.

[0081] (Condition 2) The circular polarizer 1, the circular polarizer 4A and the circular polarizer 4B are circular polarizers having the same rotation direction.

[0082] Fig. 4 is a schematic diagram for explaining an example of the positional relationship between the circular polarizer 1, the circular polarizer 4A, and the circular polarizer 4B when the condition 2 is satisfied. In Fig. 4, the release film 14a, the light source unit 2, and the detection unit 3 are also shown.

[0083] 4, the circular polarizers 4A and 4B are disposed with respect to the circular polarizer 1 so that the absorption axes of the linear polarizer 11, the linear polarizer 41a, and the linear polarizer 42a are oriented in the same direction, and the slow axes of the retardation films 41b and 42b are oriented in a direction rotated by 90° with respect to the direction of the slow axis of the retardation film 12. In this case, the circular polarizers 4A and 4B satisfy condition 2.

[0084] Next, a description will be given of an example of a method for inspecting the circular polarizer 1 using the inspection device 100. First, a description will be given of a case in which the wavelength of the inspection light 5 is changed within the first inspection wavelength range ([Case A]).

[0085] [Case A] When the wavelength of the inspection light 5 is changed within the first inspection wavelength range In case A, the circular polarizer 4A and the circular polarizer 4B satisfy the above condition 1. For ease of explanation, a case will be described as an example in which the circular polarizer 4A and the circular polarizer 4B are right-rotating circular polarizers and the circular polarizer 1 is a left-rotating circular polarizer.

[0086] As shown in FIG. 1, the inspection light 5 output from the light source unit 2 is irradiated onto the laminate 10 through the circular polarizer 4A (irradiation process). In the irradiation process, the inspection light 5 is irradiated onto the laminate 10 while changing the wavelength within the first inspection wavelength range. Since the linear polarizer 41a and the retardation film 41b are arranged in the above-mentioned positional relationship with respect 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 polarizer 4A from the linear polarizer 41a side and is output from the retardation film 41b. Therefore, the inspection light 5 output from the circular polarizer 4A has right-handed circular polarization. Therefore, the laminate 10 is irradiated with the inspection light 5 of right-handed circular polarization. In this irradiation process, the inspection light 5 is irradiated onto the laminate 10 from the release film 14a side.

[0087] The reflected light from the laminate 10 is detected by the detection unit 3 through the circular polarizer 1 (detection step). As described above, in the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the first inspection wavelength range, so that in the detection step, detection results of the reflected light corresponding to the inspection light 5 having different wavelengths are obtained.

[0088] Based on the detection result from the detection unit 3, the presence or absence of a defect in the circularly polarizing plate 1 is determined (determination step).

[0089] In case A, in the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the first inspection wavelength range, so that a detection result for the inspection light 5 of the first predetermined wavelength λa is also obtained. If a defect D (for example, a defect present at the interface between the retardation film 12 and the polarizer 11a, or a defect present in the retardation film 12) exists in the circular polarizing plate 1, the defect D can be detected based on the detection result for the inspection light 5 of the first predetermined wavelength λa. This point will be specifically described.

[0090] A portion of the right-handed circularly polarized inspection light 5 irradiated to the laminate 10 is reflected by the surface of the release film 14a. The light reflected by the surface of the release film 14a is referred to as reflected light 5a. The reflected light 5a is left-handed circularly polarized light. Since the circular polarizer 4B is a right-handed circular polarizer and is disposed so that the retardation film 42b faces the laminate 10, the reflected light 5a from the surface of the release film 14a is blocked by the circular polarizer 4B. Specifically, the reflected light 5a is absorbed by the linear polarizer 42a of the circular polarizer 4B.

[0091] Of the circularly polarized inspection light 5 irradiated to the laminate 10, the inspection light 5 transmitted through the release film 14a enters the circular polarizer 1. When the inspection light 5 passes through the release film 14a, a phase difference occurs in the inspection light 5. Since the inspection light 5 has a first predetermined wavelength λa, the phase difference is the first phase difference, that is, an integer multiple of the first predetermined wavelength λa. In this case, the polarization state of the inspection light 5 that has passed through the release film 14a does not change, so the inspection light 5 that has passed through the release film 14a is right-handed circularly polarized light. Therefore, the right-handed circularly polarized inspection light 5 enters the circular polarizer 1. Since the circular polarizer 1 is a left-handed circular polarizer, the inspection light 5 that enters the circular polarizer 1 is absorbed by the linear polarizer 11 that the circular polarizer 1 has.

[0092] As described above, the reflected light 5a is blocked by the circular polarizer 1, and the inspection light 5 that has passed through the release film 14a is absorbed by the circular polarizer 1. Therefore, the observation field of the circular polarizer 1 by the detection unit 3 is dark.

[0093] When a defect D exists in the circular polarizer 1, reflection occurs at the defect D. The reflected light caused by this defect D is called reflected light 5b. The reflected light 5b is unintentionally elliptically polarized light, with a phase difference that is shifted from the ideal due to the defect D. After passing through the peel-off film 14a, this elliptically polarized reflected light 5b is incident on the circular polarizer 4B. When passing through the peel-off film 14a, the phase difference that occurs in the elliptically polarized reflected light 5b is an integer multiple of the first predetermined wavelength λa, so the polarization state of the reflected light 5b does not change. Therefore, it is incident on the circular polarizer 1 as elliptically polarized reflected light 5b. In this case, the reflected light 5b is transmitted without being absorbed by the circular polarizer 1. Therefore, in the detection result of the detection unit 3, the defect D appears as a bright spot, so that the defect D in the circular polarizer 1 can be detected.

[0094] Although the case where circular polarizer 4A and circular polarizer 4B are right-rotating circular polarizers and circular polarizer 1 is a left-rotating circular polarizer has been described, the same applies to the case where circular polarizer 4A and circular polarizer 4B are left-rotating circular polarizers and circular polarizer 1 is a right-rotating circular polarizer. Specifically, the explanation of the case where circular polarizer 4A and circular polarizer 4B are left-rotating circular polarizers and circular polarizer 1 is a right-rotating circular polarizer corresponds to the case where "right rotation" is read as "left rotation" and "left rotation" is read as "right rotation" in the explanation of Case A above.

[0095] Next, a case where the wavelength of the inspection light 5 is changed within the second inspection wavelength range ([Case B]) will be described.

[0096] [Case B] When the wavelength of the inspection light 5 is changed within the second inspection wavelength range In case B, the circular polarizer 4A and the circular polarizer 4B satisfy the above condition 2. For ease of explanation, a case will be described in which the circular polarizer 1, the circular polarizer 4A, and the circular polarizer 4B are right-rotating circular polarizers.

[0097] The inspection light 5 output from the light source unit 2 is passed through the circular polarizer 1 and irradiated onto the laminate 10 (irradiation process). In the irradiation process, the inspection light 5 is irradiated onto the laminate 10 while changing the wavelength within the second inspection wavelength range. As in the above case A, the circular polarizer 1 is a right-rotating circular polarizer. Furthermore, the positional relationship of the circular polarizer 1 with respect to the light source unit 2 and the laminate 10 is also the same as in case A. Therefore, as described in case A, the right-rotating circularly polarized inspection light 5 is irradiated onto the laminate 10 from the release film 14a side.

[0098] The reflected light from the laminate 10 is detected by the detection unit 3 through the circular polarizer 4B (detection step). In the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the second inspection wavelength range, so that in the detection step, detection results of the reflected light corresponding to the inspection light 5 having different wavelengths are obtained.

[0099] Based on the detection result from the detection unit 3, the presence or absence of a defect in the circularly polarizing plate 1 is determined (determination step).

[0100] In case B, in the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the second inspection wavelength range, so that a detection result for the inspection light 5 of the second predetermined wavelength λb is also obtained. If the above-mentioned defect D exists in the circularly polarizing plate 1, the above-mentioned defect D can be detected based on the detection result for the inspection light 5 of the second predetermined wavelength λb. This point will be specifically described.

[0101] A portion of the right-handed circularly polarized inspection light 5 irradiated onto the laminate 10 is reflected by the surface of the release film 14a. In case B, the reflected light 5a from the surface of the release film 14a is also left-handed circularly polarized light. Therefore, as in case A, the reflected light 5a is blocked by the circular polarizer 4B.

[0102] Of 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 enters the circular polarizer 1. When the inspection light 5 passes through the release film 14a, a phase difference occurs in the inspection light 5. Since the inspection light 5 has a second predetermined wavelength λb, the phase difference is the second phase difference, that is, (n+1 / 2) times the second predetermined wavelength λb. In this case, since the release film 14a corresponds to a half-wave plate, the inspection light 5 that has passed through the release film 14a is left-handed circularly polarized light. Therefore, the left-handed circularly polarized inspection light 5 enters the circular polarizer 1. Since the circular polarizer 1 is a right-handed circular polarizer, the inspection light 5 that enters the circular polarizer 1 is absorbed by the linear polarizer 11 of the circular polarizer 1.

[0103] As described above, the reflected light 5a is blocked by the circular polarizer 4B, and the inspection light 5 that has passed through the release film 14a is absorbed by the circular polarizer 1. Therefore, in case B as well, the observation field of the circular polarizer 1 observed by the detection unit 3 is dark.

[0104] When a defect D exists in the circular polarizer 1, reflection occurs at the defect D, as in the case of case A. In case B, the reflected light 5b caused by the defect D is unintentionally elliptically polarized light, as described in case A. This elliptically polarized reflected light 5b passes through the peel-off film 14a and then enters the circular polarizer 4B. When passing through the peel-off film 14a, the phase difference generated in the elliptically polarized reflected light 5b is (n+1 / 2) times the second predetermined wavelength λb, so that the direction of the major axis of the elliptically polarized light rotates but the elliptically polarized light is maintained. Therefore, the elliptically polarized reflected light 5b enters the circular polarizer 4B. In this case, the reflected light 5b is not absorbed by the circular polarizer 1 and is transmitted. Therefore, in the detection result of the detection unit 3, the defect D appears as a bright spot, so that the defect D in the circular polarizer 1 can be detected.

[0105] Although the case where the circular polarizer 1, the circular polarizer 4A, and the circular polarizer 4B are right-rotating circular polarizers has been illustrated, the same applies to the case where the circular polarizer 1, the circular polarizer 4A, and the circular polarizer 4B are left-rotating circular polarizers. Specifically, the explanation of the case where the circular polarizer 1, the circular polarizer 4A, and the circular polarizer 4B are left-rotating circular polarizers corresponds to the explanation of the case where the circular polarizer 1, the circular polarizer 4A, and the circular polarizer 4B are right-rotating circular polarizers, in which "right rotation" is read as "left rotation".

[0106] When inspecting the circular polarizer 1, the laminate 10 is constructed as described above and then inspected. In this inspection, the inspection light 5 (reflected light 5a, 5b) passes through the release film 14a. The release film 14a is peeled off from the circular polarizer 1 when the circular polarizer 1 is used, and is discarded after being peeled off from the circular polarizer 1. Therefore, strict management of the retardation value of the release film 14a is not required.

[0107] In particular, the release film 14a in this embodiment is made of a PET resin. The release film (PET resin film) 14a made of a PET resin has the advantage that it is versatile as a release film and inexpensive. On the other hand, as described above, an inexpensive PET resin film does not require strict management of the retardation value. Therefore, for example, there may be variations in the retardation value for each product lot. Even in the same PET resin film, there may be variations in the retardation value within the plane.

[0108] Although the phase value of the release film 14a itself, which is a PET-based resin film, is not controlled in this manner, there exists a wavelength (first predetermined wavelength λa) at which the first phase difference occurs when light passes through the release film 14a, or a wavelength (second predetermined wavelength λb) at which the second phase difference occurs.

[0109] In the inspection device 100 and the inspection method using the inspection device 100, the laminate 10 (specifically, the circular polarizer 1) can be inspected by the inspection light 5 having the first predetermined wavelength λa or the second predetermined wavelength λb. In this case, the phase difference generated when transmitting through the release film 14a is the first phase difference or the second phase difference, so that, as described in Cases A and B, the influence of the release film 14a on the inspection can be substantially eliminated.

[0110] Therefore, the inspection device 100 and the inspection method using the inspection device 100 can accurately detect the presence or absence of the defect D even if the laminate 10 has the release film 14a that is a PET-based resin film.

[0111] For example, the predetermined wavelength λ for the release film 14a can be determined in advance by a preliminary experiment or the like. However, since strict management of the phase difference value is not required for the release film 14, as described above, the phase difference of the release film 14a may vary even for the same product. Therefore, even if the predetermined wavelength λ is set for inspection, there is a risk that the actual predetermined wavelength λ of the release film 14 used in the laminate 10 in the actual inspection may differ from the set predetermined wavelength λ.

[0112] In contrast, in the inspection device 100 and the inspection method using the inspection device 100, the circular polarizer 1 is inspected while changing the wavelength of the inspection light 5 within the inspection wavelength range. Therefore, even if there is a deviation between the predetermined wavelength λ assumed in advance for the release film 14a and the actual predetermined wavelength λ of the release film 14a at the time of inspection, any wavelength within the inspection wavelength range matches the actual predetermined wavelength λ of the release film 14a included in the laminate 10 to which the inspection light 5 is irradiated, so the presence or absence of the defect D in the circular polarizer 1 can be determined more reliably.

[0113] The phase difference imparted to the light when it passes through the release film 14a depends on the optical path length when the light passes through the release film 14a. Therefore, for example, it is possible to change the incident angle of the inspection light with respect to the laminate 10 to adjust the phase difference imparted to the light when it passes through the release film 14a, thereby reducing the effect of the phase difference.

[0114] However, in this case, a rotation mechanism is required to rotate the stack 10 around an axis (hereinafter referred to as the "rotation axis") perpendicular to the stacking direction of the multiple layers that make up the stack 10 during inspection, or an inspector is required to inspect the stack 10 while rotating it around the above-mentioned axis.

[0115] In contrast, the inspection device 100 and the inspection method using the inspection device 100 do not require rotation of the laminate 10 around the rotation axis. Therefore, the rotation mechanism is not required. As a result, the cost of the inspection device 100 and the manufacturing cost of the laminate 10 (or the circular polarizing plate 1) can be reduced. Furthermore, since there is no need for an inspector to operate the laminate 10, the presence or absence of the defect D can be determined more objectively.

[0116] When the retardation film 12 is formed using a polymerizable liquid crystal compound, the retardation film 12 can be formed very thin. For example, the thickness of the retardation film 12 is 0.2 μm or more and 10 μm or less, and the retardation film 12 is preferably 0.2 μm or more and 5 μm or less. The retardation film 12 may be a single layer or multiple layers. When the retardation film 12 is multiple layers, the same type of retardation film 12 may be laminated, or different types of retardation films 12 may be laminated.

[0117] However, if there are foreign matters or the like on the substrate to which the polymerizable liquid crystal compound solution is applied, or if the substrate itself has scratches or the like, defects may occur in the coating film obtained by applying the polymerizable liquid crystal compound solution. When the alignment film is subjected to a rubbing treatment, scraps of the rubbing cloth remain on the alignment film, which may cause defects in the coating film of the polymerizable liquid crystal compound solution (liquid crystal cured film forming composition). In this way, the retardation film formed from the polymerizable liquid crystal compound can form a retardation film with an extremely thin thickness, but there are factors that cause defects. When such defects occur, linearly polarized light is not completely converted into ideal circularly polarized light, and as described above, it becomes unintended elliptically polarized light.

[0118] The inspection device 100 according to the present embodiment and the inspection method using the same can accurately inspect the defect D occurring in the retardation film 12 formed using the above-mentioned polymerizable liquid crystal compound. As a result, it is easy to manufacture a thin circularly polarizing plate 1.

[0119] When the surface of the inspection table 20 on which the laminate 10 is placed is subjected to low reflection treatment, it is possible to suppress reflection of the inspection light 5 that is unintentionally transmitted through the laminate 10. This makes it possible to make the observation field darker, making it easier to detect defects D. From a similar viewpoint, a sheet or the like that suppresses reflection may be disposed between the inspection table 20 and the laminate 10.

[0120] Second embodiment 5 is a schematic diagram showing a schematic configuration of an inspection device 100A according to the second embodiment. The inspection device 100A differs from the inspection device 100 in that it includes a light source unit 2A instead of the light source unit 2, and in that it includes an inspection table 20A instead of the inspection table 20. The inspection device 100A will be described focusing on these points. In the second embodiment, as in the first embodiment, a form in which the inspection device 100A includes a circular polarizer 4A and a circular polarizer 4B will be described.

[0121] In the description of the second embodiment, the x-axis, y-axis, and z-axis shown in Fig. 5 may be used. The z-axis direction corresponds to the stacking direction of the multiple layers of the laminate 10. The x-axis and y-axis are perpendicular to the z-axis. The x-axis and y-axis are perpendicular to each other.

[0122] The light source section 2A includes a light source 2a and a bandpass filter 2b.

[0123] The light source 2a is a white light source that outputs unpolarized white light. Although various commercially available products can be used as the light source 2a, it is advantageous that the light source 2a is, for example, a linear light such as a laser beam (including light that is approximately linear).

[0124] The bandpass filter 2b is a bandpass filter that selectively passes light having a wavelength at the upper limit of the inspection wavelength range.

[0125] A "bandpass filter that selectively passes light of wavelength λi" refers to a bandpass filter that selectively passes light of wavelength λi when light is passed through the surface of the bandpass filter substantially perpendicularly. In other words, the design center wavelength that passes through a "bandpass filter that selectively passes light of wavelength λi" is wavelength λi.

[0126] The bandpass filter 2b is disposed between the light source 2a and the circular polarizer 4A. The bandpass filter 2b is inclined at an angle θ (°) with respect to a plane P. The plane P is a plane perpendicular to the stacking direction of the layers of the laminate 10 (corresponding to the z-axis direction in FIG. 5).

[0127] In the inspection device 100A, as described above, by tilting the bandpass filter 2b with respect to the plane P, a wavelength gradation is formed in the irradiation area 6 of the laminate 10 with the inspection light 5, as shown in FIG. 6. FIG. 6 is a schematic diagram for explaining the wavelength gradation in the irradiation area 6 with the inspection light 5. In FIG. 6, the change in wavelength is shown by shading. The x-axis and y-axis in FIG. 6 correspond to the x-axis and y-axis in FIG. 5. The predetermined direction in FIG. 6 is the x-axis direction shown in FIG. 6.

[0128] Wavelength gradation means that the wavelength changes from wavelength λ1 to wavelength λ2 along a predetermined direction. In other words, in wavelength gradation, the wavelength changes spatially. Wavelength λ1 and wavelength λ2 mean central wavelengths (peak wavelengths). Wavelength λ2, which is the upper limit of the wavelength range that realizes wavelength gradation, corresponds to the wavelength that bandpass filter 2b selectively passes. Therefore, wavelength λ2 corresponds to the upper limit wavelength of the inspection wavelength range.

[0129] An experimental example showing the effect of tilting the bandpass filter 2b will be described below. Fig. 7 is a schematic diagram showing an experimental model of the experimental example.

[0130] (Experimental model) As shown in FIG. 7, a transparent support base 32 having an inclined surface 32a was placed on a backlight 31 that outputs white light. An SLT-A4C manufactured by Muto Industries Co., Ltd. was used as the backlight 31. The inclination angle of the inclined surface 32a with respect to the bottom surface 32b of the support base 32 is called an angle α (°). The bottom surface 32b was the surface of the support base 32 that was in contact with the light output surface 31a of the backlight 31. A bandpass filter 33 was placed on the inclined surface 32a. As a result, the bandpass filter 33 was inclined at an angle α with respect to the light output surface 31a. A spectroradiometer 34a that detects light output from the backlight 31 and passed through the bandpass filter 33 was placed above the backlight 31. An objective lens 34b was attached to the spectroradiometer 34a. A 2D spectroradiometer SR-5000HT manufactured by Topcon Technohouse Corporation was used as the spectroradiometer 34a. The distance L1 between the bottom of the objective lens 34b and the light output surface 31a of the backlight 31 was 500 mm.

[0131] (Experimental Example 1) In Experimental Example 1, a filter that selectively passes light having a wavelength of 550 nm was used as the bandpass filter 33. The bandpass filter 33 was HMZ0550 manufactured by Asahi Spectroscopy Co., Ltd. The bandpass filter 33 was placed on a support stand 32 with an angle α of 10°, and light 35 output from the backlight 31 and passed through the bandpass filter 33 was detected by a spectroradiometer 34a.

[0132] The light that passed through the bandpass filter 33 was detected by a spectroradiometer in the same manner as when the support stand 32 with an angle α of 10° was used instead of the support stand 32 with angles α of 20°, 30°, 40°, and 50°. Furthermore, the bandpass filter 33 was placed on the light output surface 31a without using the support stand 32, and the light that passed through the bandpass filter 33 was detected by a spectroradiometer 34a in the same manner as when the support stand 32 with an angle α of 10° was used. The case where the bandpass filter 33 was placed on the light output surface 31a without using the support stand 32 corresponds to the case where the angle α is 0°. The experimental results of Experimental Example 1 were as shown in FIG. 8. The horizontal axis of FIG. 8 indicates wavelength (nm), and the vertical axis indicates spectral radiance (W / sr / m 2 / mm).

[0133] (Experimental Example 2) In Experimental Example 2, a filter that selectively passes a wavelength of 600 nm was used as the bandpass filter 33. The bandpass filter 33 was HMZ0600 manufactured by Asahi Spectroscopy Co., Ltd. Except for using the bandpass filter 33 that selectively passes a wavelength of 600 nm, an experiment similar to that of Experimental Example 1 was performed. That is, when the angle α was 0°, 10°, 20°, 30°, 40°, and 50°, the light 35 that passed through the bandpass filter 33 was detected by the spectroradiometer 34a. The experimental results of Experimental Example 2 are as shown in FIG. 9. The horizontal axis of FIG. 9 indicates the wavelength (nm), and the vertical axis indicates the spectral radiance (W / sr / m 2 / mm).

[0134] 8 and 9, it can be seen that the central wavelength transmitted through the bandpass filter 33 changes according to the change in the tilt angle (corresponding to the angle α) of the bandpass filter 33. This is believed to be because the optical path length when passing through the bandpass filter 33 changes when the bandpass filter 33 is tilted.

[0135] As shown in FIG. 5, when the bandpass filter 2b is tilted at an angle θ with respect to the plane P, the optical path length when the light passes through the bandpass filter 2b differs depending on the position where the light output from the light source 2a is incident on the bandpass filter 2b. In this case, as shown in FIG. 8 and FIG. 9, the central wavelength that can pass through the bandpass filter 2b differs depending on the incident position of the light. Therefore, by tilting the bandpass filter 2b at an angle θ with respect to the plane P, a wavelength gradation occurs in the irradiation area 6. That is, by using the bandpass filter 2b tilted with respect to the plane P, the light source unit 2A irradiates the laminate 10 with the inspection light 5 in a state where the wavelength is spatially changed in the inspection wavelength range.

[0136] In the inspection apparatus 100A, the bandpass filter 2b is arranged so that the wavelength range in which the wavelength gradation is realized is the inspection wavelength range.

[0137] In the inspection device 100A, the angle θ (°) is, for example, 10° or more and 45° or less. The angle θ is preferably 10° or more and 30° or less from the viewpoint of reducing the number of inspections. An example of the angle θ is 21°. As the angle θ increases, the region in which the inspection wavelength range is realized becomes narrower. Therefore, the region that can be inspected in the inspection wavelength range becomes narrower, and the handling of the inspection may decrease. On the other hand, as the angle θ decreases, the inspection wavelength range itself becomes narrower. Therefore, in order to inspect the entire desired inspection wavelength range, it may be necessary to adjust the angle of the bandpass filter 2b again and perform the inspection again, in which case the efficiency of the inspection decreases. If the angle θ is in the range exemplified above, it is easy to realize a wavelength gradation in the desired inspection wavelength range for the entire irradiation region 6. As a result, the circular polarizer 1 can be inspected efficiently while ensuring the handling of the inspection.

[0138] 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, the circular polarizer 1 is inspected while moving the laminate 10 in a predetermined direction, so from the viewpoint of improving the handling property of the inspection, the distance is preferably 40 mm or more and 60 mm or less. 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 (axis along the principal ray) of the light output from the light source 2a and the bandpass filter 2b, and the light output end of the light source 2a.

[0139] The inspection method for the circular polarizer 1 using the inspection device 100A is the same as that described for cases A and B in the detection process described in cases A and B in the first embodiment, except that the reflected light 5a is detected while the base body 21 is moved in a predetermined direction by the driving mechanism 22.

[0140] Therefore, the inspection apparatus 100A and the inspection method using the same have the same effects as those in the first embodiment.

[0141] In the inspection device 100A, the bandpass filter 2b is tilted at an angle θ with respect to the plane P to form a wavelength gradation along a predetermined direction in the irradiation area 6. Therefore, in the inspection device 100A, the irradiation area 6 having an inspection wavelength range in which the wavelength changes continuously can be easily realized. Since the inspection table 20A includes a driving mechanism 22, the circular polarizer 1 can be inspected while moving the laminate 10 in a predetermined direction. By moving the laminate 10 in a predetermined direction, the circular polarizer 1 is inspected at each wavelength within the inspection wavelength range realized in the wavelength gradation. Therefore, for example, as described in the first embodiment, even if there is some variation in the phase difference of the release film 14a, any wavelength within the above inspection wavelength range functions as the first predetermined wavelength λa or the second predetermined wavelength λb for the release film 14a attached to the circular polarizer 1 to be inspected. As a result, the presence or absence of a defect D can be detected with high accuracy.

[0142] Third embodiment FIG. 10 is a schematic diagram for explaining a schematic configuration of an inspection apparatus 100B according to the third embodiment.

[0143] The inspection device 100B according to the third embodiment differs from the inspection device 100 according to the first embodiment in that it includes one circular polarizer (fourth circular polarizer) 4C instead of the circular polarizers 4A and 4B.

[0144] In the inspection device 100B, the light source unit 2 and the detection unit 3 are disposed on the opposite side of the circular polarizer 4C from the laminate 10. The light source unit 2 of the inspection device 100B is configured to irradiate the laminate 10 with inspection light 5 while changing the wavelength within a first inspection wavelength range.

[0145] The circular polarizer 4C has a linear polarizer (fourth linear polarizer) 43a and a retardation film (fourth retardation film) 43b laminated on the linear polarizer 43a. The circular polarizer 4C is disposed so that the retardation film 43b faces the laminate 10. The linear polarizer 43a is the same as the linear polarizer 41a included in the circular polarizer 4A or the linear polarizer 42a included in the circular polarizer 4B. The retardation film 43b is the same as the retardation film 41b included in the linear polarizer 41a or the retardation film 42b included in the circular polarizer 4B.

[0146] When the wavelength of the inspection light 5 changes within a first inspection wavelength range, the circular polarizer 4C is disposed so as to satisfy the following condition 3. When the wavelength of the inspection light 5 changes within a second inspection wavelength range, the circular polarizer 4C is disposed so as to satisfy the following condition 4. (Condition 3) Circular polarizer 4C has the opposite rotation to circular polarizer 1. (Condition 4) Circular polarizer 4C has the same rotation as circular polarizer 1.

[0147] The circularly 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.

[0148] Since circular polarizer 4C has the above configuration and is disposed so as to satisfy condition 3, first region 44 corresponds to circular polarizer 4A, and second region 45 corresponds to circular polarizer 4B. In other words, circular polarizer 4C corresponds to a circular polarizer obtained by integrating circular polarizers 4A and 4B, which are shown in a separated state in FIG.

[0149] Therefore, in the same manner as in cases A and B in the first embodiment, the presence or absence of defect D can be determined using inspection apparatus 100B.

[0150] Since circular polarizer 4C corresponds to a circular polarizer formed by integrating circular polarizer 4A and circular polarizer 4B, which are shown in a separated state in FIG. 1, inspection apparatus 100B and an inspection method using inspection apparatus 100B have the same effects as inspection apparatus 100 and an inspection method using inspection apparatus 100 of the first embodiment.

[0151] (Variation 1) The circular polarizer 4C may be used instead of the circular polarizer 4A and the circular polarizer 4B in the second embodiment. In this case, the light source unit 2A is configured to irradiate the laminate 10 with the inspection light 5 in a state in which the wavelength is spatially changed in the first inspection wavelength range or the second inspection wavelength range. Specifically, the light source unit 2A is configured so that the wavelength range of the wavelength gradation in the irradiation region 6 is the first inspection wavelength range.

[0152] (Fourth embodiment) The inspection devices 100, 100A, and 100B described in the first, second, and third embodiments are reflective inspection devices using a reflective optical system. However, they may be transmissive inspection devices using a transmissive optical system.

[0153] 11 is a schematic diagram for explaining a schematic configuration of an inspection device 100C according to a fourth embodiment. The inspection device 100C differs in that an inspection table 20B is used instead of the inspection table 20, the light source unit 2 is disposed opposite the detection unit 3 with respect to the inspection table 20B, and the circular polarizer 4A is not provided between the light source unit 2 and the laminate 10.

[0154] The inspection table 20B is a table on which the laminate 10 is placed, similar to the inspection table 20. The laminate 10 is placed on the inspection table 20B in the same manner as the inspection table 20. The inspection table 20B has a window 20a through which the inspection light 5 from the light source unit 2 passes toward the laminate 10. The window 20a may be an opening or a transparent member.

[0155] The light source section 2 is the same as the light source section 2 described in the first embodiment, except that it is disposed on the opposite side to the laminate 10 when viewed from the inspection table 20B.

[0156] The detection unit 3 is disposed on the optical path of the inspection light 5 output from the light source unit. The circular polarizer 4B is disposed between the detection unit 3 and the laminate 10, and functions as a detection circular polarizer in the fourth embodiment. In the fourth embodiment as well, the linear polarizer (detection linear polarizer) 42a of the circular polarizer 4B faces the detection unit 3, and the retardation film (detection retardation film) 42b faces the laminate 10.

[0157] When the wavelength of the inspection light 5 changes within a first inspection wavelength range, the circular polarizer 4B is disposed so as to satisfy the following condition 5. When the wavelength of the inspection light 5 changes within a second inspection wavelength range, the circular polarizer 4B is disposed so as to satisfy the following condition 6. (Condition 5) Circular polarizer 4B has the opposite rotation to circular polarizer 1. (Condition 6) The circular polarizer 4B has the same rotation as the circular polarizer 1.

[0158] Next, a description will be given of an example of a method for inspecting the circular polarizer 1 using the inspection apparatus 100C. First, a description will be given of a case where the wavelength of the inspection light 5 is changed within the first inspection wavelength range ([Case A1]).

[0159] [Case A1] When the wavelength of the inspection light 5 is changed within the first inspection wavelength range In case A1, the circular polarizer 4B satisfies the above condition 5. For ease of explanation, the case where the circular polarizer 4B is a right-rotating circular polarizer will be described. Since the circular polarizer 4B satisfies the condition 5, the circular polarizer 1 is a left-rotating circular polarizer.

[0160] The inspection light 5 output from the light source unit 2 is irradiated onto the laminate 10 through the window unit 20a (irradiation step). In the irradiation step, the inspection light 5 is irradiated onto the laminate 10 while changing the wavelength within a first inspection wavelength range. Due to the arrangement shown in FIG. 10, the inspection light 5 is irradiated onto the laminate 10 from the surface protection film 14b side.

[0161] The inspection light 5 (transmitted light) that has passed through the laminate 10 irradiated with the inspection light 5 is detected by the detection unit 3 through the circular polarizing plate 4B (detection step). As described above, in the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the first inspection wavelength range, so that in the detection step, detection results of the transmitted light corresponding to the inspection light 5 having different wavelengths are obtained.

[0162] Based on the detection result from the detection unit 3, the presence or absence of a defect in the circularly polarizing plate 1 is determined (determination step).

[0163] In case A1, in the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the first inspection wavelength range, so that a detection result for the inspection light 5 of the first predetermined wavelength λa is also obtained. If a defect D exists in the circularly polarizing plate 1, the defect D can be detected based on the detection result for the inspection light 5 of the first predetermined wavelength λa. This point will be specifically described.

[0164] The inspection light 5 irradiated onto the laminate 10 from the surface protection film 14b side passes through the surface protection film 14b and enters the circular polarizer 1. Since the circular polarizer 1 is a left-rotating circular polarizer, the inspection light 5 entering the circular polarizer 1 is output as left-rotating inspection light 5.

[0165] The inspection light 5 output from the circular polarizer 1 is output from the laminate 10 by passing through the release film 14a. When the inspection light 5 passes through the release film 14a, a phase difference occurs in the inspection light 5. Since the inspection light 5 has a first predetermined wavelength λa, the phase difference is a first phase difference, that is, an integer multiple of the first predetermined wavelength λa. In this case, the polarization state of the inspection light 5 that has passed through the release film 14a does not change, so the inspection light 5 output from the release film 14a is left-handed circularly polarized light. The inspection light 5 that passes through the circular polarizer 1 and the release film 14a and is output from the laminate 10 in this manner is referred to as output light 5c. The circular polarizer 4B is a right-handed circular polarizer and is arranged so that the retardation film 42b faces the laminate 10, so that the output light 5c is blocked by the circular polarizer 4B. Specifically, the output light 5c is absorbed by the linear polarizer 42a of the circular polarizer 4B.

[0166] As described above, the output light 5c, which is the inspection light 5 transmitted through the laminate 10, is absorbed by the circular polarizer 4B, and therefore the observation field of the circular polarizer 1 observed by the detector 3 is dark.

[0167] When a defect D exists in the circular polarizer 1, scattering occurs at the defect D. The scattered light based on this defect D has a phase difference that is different from the ideal due to the defect D, and is unintended elliptically polarized light. This elliptically polarized scattered light passes through the release film 14a and is output from the laminate 10. The inspection light 5 output from the laminate 10 due to the defect D is called output light 5d. The output light 5d is incident on the circular polarizer 4B. When passing through the release film 14a, the phase difference generated in the elliptically polarized scattered light is an integer multiple of the first predetermined wavelength λa, so the polarization state of the scattered light does not change. Therefore, the output light 5d is incident on the circular polarizer 1 as elliptically polarized light. In this case, the output light 5d is transmitted without being absorbed by the circular polarizer 1. Therefore, in the detection result of the detection unit 3, the defect D appears as a bright spot, so that the defect D in the circular polarizer 1 can be detected.

[0168] Although the case where circular polarizer 4B is a right-rotation circular polarizer and circular polarizer 1 is a left-rotation circular polarizer has been described, the same applies to the case where circular polarizer 4B is a left-rotation circular polarizer and circular polarizer 1 is a right-rotation circular polarizer. Specifically, the explanation of the case where circular polarizer 4B is a left-rotation circular polarizer and circular polarizer 1 is a right-rotation circular polarizer corresponds to the case where "right rotation" is replaced with "left rotation" and "left rotation" is replaced with "right rotation" in the explanation of Case A1 above.

[0169] Next, a case where the wavelength of the inspection light 5 is changed within the second inspection wavelength range ([Case B1]) will be described.

[0170] [Case B1] When using inspection light 5 having a second predetermined wavelength λb In case B1, the circular polarizer 4B satisfies the above condition 6. For ease of explanation, a case will be described in which the circular polarizer 4B is a right-rotating circular polarizer. Since the circular polarizer 4B satisfies condition 6, the circular polarizer 1 is a right-rotating circular polarizer.

[0171] The inspection light 5 output from the light source unit 2 is irradiated onto the laminate 10 through the window unit 20a (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. Due to the arrangement shown in Fig. 10, the inspection light 5 is irradiated onto the laminate 10 from the surface protection film 14b side.

[0172] The output light from the laminate 10 irradiated with the inspection light 5 is detected by the detection unit 3 through the circular polarizer 4B (detection step). In the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the second inspection wavelength range, so that in the detection step, detection results of the output light corresponding to the inspection light 5 having different wavelengths are obtained.

[0173] Based on the detection result from the detection unit 3, the presence or absence of a defect in the circularly polarizing plate 1 is determined (determination step).

[0174] In the case of case B1, in the irradiation step, the laminate 10 is irradiated with the inspection light 5 while changing the wavelength within the second inspection wavelength range, so that a detection result for the inspection light 5 of the second predetermined wavelength λb is also obtained. If the above-mentioned defect D exists in the circularly polarizing plate 1, the above-mentioned defect D can be detected based on the detection result for the inspection light 5 of the second predetermined wavelength λb. This point will be specifically described.

[0175] The inspection light 5 irradiated onto the laminate 10 from the surface protection film 14b side passes through the surface protection film 14b and enters the circular polarizer 1. Since the circular polarizer 1 is a right-rotating circular polarizer, the inspection light 5 entering the circular polarizer 1 is output as right-rotating inspection light 5.

[0176] The inspection light 5 output from the circular polarizer 1 is output from the laminate 10 by passing through the release film 14a. The inspection light 5 output in this manner is also referred to as output light 5c in case B1. When the inspection light 5 passes through the release film 14a, a phase difference occurs in the inspection light 5. Since the inspection light 5 has the second predetermined wavelength λb, the phase difference is the second phase difference, that is, (n+1 / 2) times the second predetermined wavelength λb. In this case, the output light 5c, which is 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 laminate 10 is left-handed circularly polarized output light 5c. Since the circular polarizer 4B is a right-handed circular polarizer and is arranged so that the retardation film 42b faces the laminate 10, the output light 5c is blocked by the circular polarizer 4B. Specifically, the output light 5c is absorbed by the linear polarizer 42a of the circular polarizer 4B.

[0177] As described above, output light 5c transmitted through laminate 10 is absorbed by circular polarizer 4B, and therefore the field of view of circular polarizer 1 observed by detector 3 is dark.

[0178] When a defect D exists in the circular polarizer 1, scattering occurs at the defect D. The scattered light based on the defect D has a phase difference that is different from the ideal due to the defect D, and is unintended elliptically polarized light. This elliptically polarized scattered light passes through the release film 14a and is output from the laminate 10. The inspection light 5 output from the laminate 10 due to the defect D is also referred to as output light 5d in case B1. The output light 5d enters the circular polarizer 4B. When passing through the release film 14a, the phase difference that occurs in the elliptically polarized scattered light is (n+1 / 2) times the second predetermined wavelength λb, so that the direction of the major axis of the elliptically polarized light rotates but the elliptically polarized light is maintained. Therefore, the output light 5d enters the circular polarizer 4B as elliptically polarized light. In this case, the output light 5d passes through the circular polarizer 4B without being absorbed. Therefore, in the detection result of the detection unit 3, the defect D appears as a bright spot, so that the defect D in the circular polarizer 1 can be detected.

[0179] Although the case where the circular polarizer 4B and the circular polarizer 1 are right-rotating circular polarizers has been described, the same applies to the case where the circular polarizer 4B and the circular polarizer 1 are left-rotating circular polarizers. Specifically, the explanation of the case where the circular polarizer 4B and the circular polarizer 1 are left-rotating circular polarizers corresponds to the case where "right rotation" is replaced with "left rotation" and "left rotation" is replaced with "right rotation" in the explanation of Case B1 above.

[0180] As described above, in the fourth embodiment as well, it is possible to substantially eliminate the influence of the phase difference when the light passes through the release film 14a by irradiating the laminate 10 with the inspection light 5 while changing the wavelength within the first inspection wavelength range or the second inspection wavelength range. Therefore, the inspection device 100B according to the third embodiment and the inspection method using the same have the same effects as those of the first embodiment.

[0181] (Variation 2) In the transmission type inspection device described in the fourth embodiment, a wavelength gradation may be formed in the irradiation area 6 using the bandpass filter 2b as described in the second embodiment. In this modification 2, in the inspection device 100B, an inspection table 20A is used instead of the inspection table 20B, and a light source unit 2A is used instead of the light source unit 2. A window unit 20a is formed in the table body 21 of the inspection table 20A in modification 2, similarly to the case of the inspection table 20B.

[0182] Although various embodiments of the present invention have been described above, the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0183] For example, the wavelength of the inspection light irradiated to the laminate 10 may be changed by switching between multiple bandpass filters that selectively pass multiple wavelengths within the inspection wavelength range (first inspection wavelength range or second inspection wavelength range) for light from a light source (e.g., light source 2a shown in Figure 5).

[0184] In the second embodiment, the wavelength may be varied spatially by using a prism instead of the bandpass filter 2b.

[0185] In the second embodiment, the movement mechanism may move the table body 21 in the x-axis direction and the y-axis direction shown in Fig. 5. For example, the inspection table 20A shown in Fig. 5 may be a two-axis stage. This allows the entire surface of the laminate to be inspected.

[0186] The various embodiments and modifications exemplified thus far may be combined as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0187] 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, detection circular polarizing plate), 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...Retardation film (first retardation film), 14a...Release film, 41 a...linear polarizing plate (second linear polarizing plate), 41b...phase difference film (second phase difference film), 42a...linear polarizing plate (third linear polarizing plate, detection linear polarizing plate), 42b...phase difference film (third phase difference film, detection phase difference film), 43a...linear polarizing plate (fourth linear polarizing plate), 43b...phase difference film (fourth phase difference film), 44...first region, 45...second region, 100, 100A, 100B, 100C...inspection device, D...defect, P...plane.

Claims

1. A method for inspecting the presence or absence of defects in a first circular polarizing plate of a film-like laminate including a first linear polarizing plate, a first retardation film laminated on the first linear polarizing plate, and a release film laminated on the first retardation film and formed of a polyethylene terephthalate resin, comprising: an irradiation step of irradiating the laminate with an inspection light while changing the wavelength temporally or spatially 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 laminate irradiated with the inspection light; a determination step of determining whether or not the first circular polarizing plate has a defect based on a detection result of the detection step; Equipped with The predetermined wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+1 / 2)λ occurs when the light of the predetermined wavelength passes through the release film, where the predetermined wavelength is λ [nm] and n is an integer of 1 or more. Testing method.

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

3. In the irradiation step, the inspection light having passed through a second circular polarizing plate having a second linear polarizing plate and a second retardation film from the second linear polarizing plate side is irradiated onto the laminate from the release film side, In the detection step, the inspection light reflected by the first circular polarizer and then transmitted through the release film is passed through a third circular polarizer having a third linear polarizer and a third retardation film from the third retardation film side and detected; The second circular polarizer and the third circular polarizer are both left-rotating or right-rotating circular polarizers, and are opposite-rotating circular polarizers to the first circular polarizer. The inspection method according to claim 2.

4. In the irradiation step, the inspection light having passed through a fourth circular polarizing plate having a fourth linear polarizing plate and a fourth retardation film from the fourth linear polarizing plate side is irradiated onto the laminate from the release film side, In the detection step, the inspection light that has been reflected by the first circular polarizer and then transmitted through the release film is passed through the fourth circular polarizer from the fourth retardation film side and detected; The fourth circular polarizer is a circular polarizer having a reverse rotation to the first circular polarizer. The inspection method according to claim 2.

5. In the irradiation step, the laminate is irradiated with the inspection light from the first circular polarizer side, In the detection step, the inspection light output from the release film side of the laminate is passed through a detection circular polarizer having a detection linear polarizer and a detection retardation film from the detection retardation film side to be detected; The detection circular polarizer is a circular polarizer having a rotation opposite to that of the first circular polarizer. The inspection method according to claim 2.

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

7. In the irradiation step, the inspection light having passed through a second circular polarizing plate having a second linear polarizing plate and a second retardation film from the second linear polarizing plate side is irradiated onto the laminate from the release film side, In the detection step, the inspection light reflected by the first circular polarizer and then transmitted through the release film is passed through a third circular polarizer having a third linear polarizer and a third retardation film from the third retardation film side and detected; the first circular polarizer, the second circular polarizer, and the third circular polarizer are circular polarizers having the same rotation direction; The inspection method according to claim 6.

8. In the irradiation step, the inspection light having passed through a fourth circular polarizing plate having a fourth linear polarizing plate and a fourth retardation film from the fourth linear polarizing plate side is irradiated onto the laminate from the release film side, In the detection step, the inspection light that has been reflected by the first circular polarizer and then transmitted through the release film is passed through the fourth circular polarizer from the fourth retardation film side and detected; The fourth circular polarizer is a circular polarizer having a reverse rotation to the first circular polarizer. The inspection method according to claim 6.

9. In the irradiation step, the inspection light is irradiated onto the laminate from the first circular polarizer side, In the detection step, the inspection light output from the release film side of the laminate is passed through a third circular polarizer having a detection linear polarizer and a detection retardation film from the detection retardation film side, and is detected through the detection circular polarizer; The detection circular polarizer is a circular polarizer having the same rotation as the first circular polarizer.

7. The inspection method according to claim 6.

10. In the irradiation step, the laminate 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 an upper limit wavelength of the inspection wavelength range; the bandpass filter is disposed at an angle with respect to a plane perpendicular to a lamination direction of the first circular polarizer and the release film so as to form a wavelength gradation in which the wavelength changes within the inspection wavelength range along a predetermined direction in an irradiation area of ​​the inspection light, In the detection step, the inspection light output from the release film is detected while moving the laminate along the predetermined direction relative to the irradiation area. The inspection method according to any one of claims 1 to 9.

11. A method for manufacturing a laminate, comprising: inspecting the first circular polarizing plate of the laminate for the presence or absence of a defect by the inspection method according to claim 1 .

12. An inspection device for inspecting the presence or absence of defects in a first circular polarizing plate of a film-like laminate including a first linear polarizing plate, a first retardation film laminated on the first linear polarizing plate, and a release film formed of a polyethylene terephthalate resin and laminated on the first retardation film side, comprising: A light source unit configured to irradiate the laminate with inspection light while changing the wavelength or while changing the wavelength spatially within an inspection wavelength range including a predetermined wavelength; a detection unit that detects the inspection light output from the release film side of the laminate irradiated with the inspection light; Equipped with The predetermined wavelength is a wavelength at which a first phase difference of nλ or a second phase difference of (n+½)λ occurs when the light of the predetermined wavelength passes through the release film, where the predetermined wavelength is λ [nm] and n is an integer of 1 or more. Inspection equipment.

13. the predetermined wavelength is a wavelength at which the first phase difference occurs when light of the predetermined wavelength passes through the release film, The inspection wavelength range is 500 nm or more and 550 nm or less.

13. The inspection apparatus according to claim 12.

14. a second circular polarizing plate having a second linear polarizing plate and a second retardation film; a third circular polarizing plate having a third linear polarizing plate and a third retardation film; Furthermore, the light source unit and the detection unit are disposed on the release film side, the second circular polarizing plate is disposed on an optical path of the inspection light between the light source unit and the laminate such that the second retardation film faces the release film, the third circular polarizer is disposed on an optical path of the inspection light reflected by the laminate between the laminate and the detection unit such that the third retardation film faces the release film, The second circular polarizer and the third circular polarizer are both left-rotating or right-rotating circular polarizers, and are opposite-rotating circular polarizers to the first circular polarizer.

14. The inspection apparatus according to claim 13.

15. a fourth circular polarizing plate disposed on the release film side of the laminate and having a fourth linear polarizing plate and a fourth retardation film; Equipped with the fourth circular polarizing plate is disposed so that the fourth retardation film faces the release film, the light source unit and the detection unit are disposed on an opposite side of the laminate with respect to the fourth circular polarizer, the fourth circular polarizer has a first region located on an optical path of the inspection light between the light source unit and the laminate, and a second region located on an optical path of the inspection light reflected by the laminate, The fourth circular polarizer is a circular polarizer having a reverse rotation to the first circular polarizer.

14. The inspection apparatus according to claim 13.

16. Further comprising a detection circular polarizer having a detection linear polarizer and a detection retardation film, the light source unit is disposed on the first circular polarizing plate side, The detection unit is disposed on the release film side, the detection circular polarizer is disposed between the detection unit and the laminate such that the detection retardation film faces the release film, The detection circular polarizer is a circular polarizer having a rotation opposite to that of the first circular polarizer.

14. The inspection apparatus according to claim 13.

17. the predetermined wavelength is a wavelength at which the second phase difference occurs when light of the predetermined wavelength passes through the release film, The inspection wavelength range is 570 nm or more and 630 nm or less.

13. The inspection apparatus according to claim 12.

18. a second circular polarizing plate disposed on an optical path of the inspection light between the light source unit and the laminate, the second circular polarizing plate having a second linear polarizing plate and a second retardation film; a third circular polarizing plate disposed on an optical path of the inspection light reflected by the laminate between the laminate and the detection unit, the third circular polarizing plate having a third linear polarizing plate and a third phase difference film; Further comprising: the light source unit and the detection unit are disposed on the release film side, the second circular polarizing plate is disposed so that the second retardation film faces the release film, the third circular polarizing plate is disposed so that the third retardation film faces the release film, The second circular polarizer and the third circular polarizer are circular polarizers having the same rotation as the first circular polarizer.

18. The inspection apparatus according to claim 17.

19. a fourth circular polarizing plate disposed on the release film side of the laminate and having a fourth linear polarizing plate and a fourth retardation film; Equipped with the fourth circular polarizing plate is disposed so that the fourth retardation film faces the release film, the light source unit and the detection unit are disposed on an opposite side of the laminate with respect to the fourth circular polarizer, the fourth circular polarizer has a first region located on an optical path of the inspection light between the light source unit and the laminate, and a second region located on an optical path of the inspection light reflected by the laminate, The fourth circular polarizer is a circular polarizer having the same rotation as the first circular polarizer.

18. The inspection apparatus according to claim 17.

20. Further comprising a detection circular polarizer having a detection linear polarizer and a detection retardation film, the light source unit is disposed on the first circular polarizing plate side, The detection unit is disposed on the release film side, the detection circular polarizer is disposed between the detection unit and the laminate such that the detection retardation film faces the release film, The detection circular polarizer is a circular polarizer having the same rotation as the first circular polarizer.

18. The inspection apparatus according to claim 17.

21. The stacking device further includes a moving mechanism for moving the stacking body in a predetermined direction, The light source unit includes: a light source that outputs light in a wavelength range that includes the inspection wavelength range; a bandpass filter that selectively passes light having an upper limit wavelength of the inspection wavelength range from the light output from the light source; having The bandpass filter is arranged at an angle with respect to a plane perpendicular to a lamination direction of the first circular polarizer and the release film so as to form a wavelength gradation in which the wavelength changes within the inspection wavelength range along a predetermined direction in the irradiation area of ​​the inspection light. The inspection device according to any one of claims 12 to 20.

Images