Device and method for inspecting adhesive stains of polarizing plate

Abstract

The present application relates to a polarizing plate adhesive stain detection device and a polarizing plate adhesive stain detection method. The present application can easily detect adhesive stains formed on a polarizing plate and has excellent visibility.

Description

Technical Field

[0001] The present application relates to a polarizing plate adhesive stain inspection device and a polarizing plate adhesive stain inspection method.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0067544 filed on June 7, 2019, and all contents disclosed in the Korean patent application document are incorporated into this specification as a part. Background Art

[0003] Liquid crystal display (LCD) includes polarizing plates for controlling the state of light. Generally, polarizing plates used in LCD are manufactured by attaching polarizing sheets having a polarization function to the upper and lower parts of the polarizing sheets using an adhesive and a protective substrate.

[0004] As the type of adhesive used at this time, there are two types of adhesives that can be used: thermosetting adhesives and photocurable adhesives. Common water-based adhesives are mainly composed of PVA (Polyvinyl Alcohol) and have the same refractive index as the polarizing plate, so there will be no stains caused by thickness deviation of the adhesive.

[0005] However, when the refractive index of the photocurable adhesive is different from that of the PVA polarizing plate and it is cured with uneven thickness, the problem of visible stains will occur. Such stains of the photocurable adhesive are not easy to see, so the following problems arise: it is difficult to confirm by conventional inspection methods, and it is even more difficult to confirm when a protective film and / or a peeling film is attached to the finished polarizing plate. Therefore, a device for inspecting adhesive stains of polarizing plates and a method for inspecting adhesive stains of polarizing plates are needed to solve this problem. Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] An object of the present application is to provide an adhesive inspection apparatus for a polarizing plate and a method for inspecting an adhesive on a polarizing plate, which can easily inspect an adhesive generated on a polarizing plate and have excellent visibility.

[0008] [Methods of solving the problem]

[0009] In order to solve the above-mentioned problems, the adhesive stain inspection device for the polarizing plate of the present application includes: a point light source; a first polarizing component, configured to receive light from the point light source; a polarizing plate, configured to receive light passing through the first polarizing component, and reflect the received light; a second polarizing component, configured to receive light reflected from the polarizing plate; and an inspection source, configured to receive light passing through the second polarizing component, and judging the adhesive stain of the polarizing plate based on the light passing through the second polarizing component; the polarizing plate sequentially includes a polarizer, an adhesive layer including a photocurable adhesive located at the upper and lower parts of the polarizer respectively, and a protective substrate, the light passing through the first polarizing component is incident on the protective substrate of the polarizing plate, and the point light source is incident on the polarizing plate at a Brewster angle.

[0010] In addition, the point light source can emit non-polarized light toward the first polarizing member side.

[0011] In addition, the incident angle of the light emitted from the point light source with respect to the polarizing plate may be 45° to 75°.

[0012] In addition, the absorption axis of the first polarizing member may be perpendicular to the polarizer of the polarizing plate.

[0013] In addition, the polarizing plate may be a polarizing plate used in a liquid crystal display device.

[0014] In addition, the light incident on the polarizing plate may be reflected by the adhesive layer.

[0015] In addition, the photocurable adhesive includes an adhesive composition having an acrylic polymer in a cured state.

[0016] In addition, the adhesive layer may have a refractive index of 1.45 to 1.50.

[0017] In addition, the refractive index of the polarizer may be greater than 1.5 and range from 1.6.

[0018] In addition, the reflection angle of the light reflected from the polarizing plate relative to the polarizing plate may be 45° to 75°.

[0019] In addition, the absorption axis of the second polarizing member may be perpendicular to the polarizer of the polarizing plate.

[0020] In addition, the method for inspecting adhesive stains on a polarizing plate of the present application is a method for inspecting adhesive stains on a polarizing plate using an adhesive stain inspection device for the polarizing plate, the method comprising: a step of emitting light from a point light source and allowing it to pass through a first polarizing component, a polarizing plate, and a second polarizing component in sequence; and a step of judging the adhesive stains on the polarizing plate based on the light that passes through the second polarizing component and is incident on the inspection source.

[0021] In addition, light incident on the polarizing plate can be reflected.

[0022] [Effects of the Invention]

[0023] According to the polarizing plate adhesive stain inspection device and the polarizing plate adhesive stain inspection method of the present application, adhesive stains formed on the polarizing plate can be easily inspected, and the visibility of the adhesive stains can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure shows an adhesive stain inspection device for polarizing plates according to one embodiment of the present application.

[0025] Figure 2 FIG. 1 is a diagram showing a polarizing plate according to an embodiment of the present application.

[0026] Figure 3 The purpose is to use the polarizing plate adhesive stain inspection device according to one embodiment of the present application to inspect the adhesive stain of the polarizing plate, and to obtain an image of the second polarizing component by photographing it with a digital camera.

[0027] Figure 4 The purpose is to inspect adhesive stains on a polarizing plate using an adhesive stain inspection device for a polarizing plate that is not based on an embodiment of the present application, and to obtain an image of the second polarizing component by photographing it with a digital camera.

[0028] Figure 5 The purpose is to inspect adhesive stains on a polarizing plate using an adhesive stain inspection device for a polarizing plate that is not based on another embodiment of the present application, and to obtain an image of the second polarizing component by photographing it with a digital camera.

[0029] Figure 6 The purpose is to inspect adhesive stains on a polarizing plate using an adhesive stain inspection device for a polarizing plate not according to another embodiment of the present application, and to obtain an image of the second polarizing component by photographing it with a digital camera. DETAILED DESCRIPTION

[0030] Hereinafter, the adhesive stain inspection device and the adhesive stain inspection method for polarizing plates of the present application will be described with reference to the accompanying drawings. The accompanying drawings are merely examples, and the adhesive stain inspection device and the adhesive stain inspection method for polarizing plates of the present application are not limited to the accompanying drawings.

[0031] Figure 1 1 is a diagram showing an adhesive stain inspection device for a polarizing plate according to an embodiment of the present application. Figure 1 As shown, the polarizing plate adhesive stain inspection device of the present application includes a point light source 100, a first polarizing component 200, a polarizing plate 300, a second polarizing component 400 and an inspection source 500. The point light source 100 incidents light on the polarizing plate 300 at a Brewster angle. Figure 2 is a diagram showing a polarizing plate according to an embodiment of the present application. Figure 2 As shown, the polarizing plate 300 includes a polarizer 310, adhesive layers 321 and 322 located at the upper and lower parts of the polarizer 310, and protective substrates 331 and 332. In addition, the adhesive layers 321 and 322 include a photocurable adhesive. In addition, light passing through the first polarizing component 200 is incident on the protective substrates 331 and 332 of the polarizing plate 300. The adhesive stain inspection device for the polarizing plate of the present application can easily inspect the adhesive stain formed on the polarizing plate and has excellent visibility.

[0032] In this specification, the term "positioning in sequence" may refer to the state in which each structure is positioned in parallel according to the series structure. In addition, in this specification, the term "Brewster angle" refers to the following incident angle, that is, when light passes between two media with different refractive indices, only the light of a certain polarization component is reflected, and other polarization components are not reflected and all are transmitted. For example, if vertical polarized light (TE polarization, s polarization) is incident, almost all light will be reflected. However, if horizontal polarized light (TM polarization. p polarization) is incident, almost no reflection occurs and most of the light will be transmitted. At this angle, the electric field of polarized light is parallel to the incident plane and is therefore not reflected. In other words, there is an incident angle at which the reflection coefficient of horizontal polarized light is 0, and at this time, the angle is called the Brewster angle. Therefore, when light is incident at an angle close to the Brewster angle, the vertical polarization component of the reflected wave is far more than the parallel polarization component. Therefore, if light is incident at the Brewster angle, the reflected light is always in the s polarization state.

[0033] The point light source 100, as a light source emitting non-polarized light vibrating in multiple directions, may use various types of lamps emitting various white lights or having a continuous spectrum within the spectral range of the visible light region. By using the point light source emitting non-polarized light, the manufacturing cost and maintenance cost of the polarizing plate adhesive stain inspection device are lower. In addition, compared with a surface light source, the point light source is more advantageous in terms of visibility.

[0034] The point light source is a light source that does not have an imaginary area and is a geometric point, and can be distinguished from a surface light source in a surface form.

[0035] In one example, the point light source 100 may emit unpolarized light to the first polarizing element 200. The point light source 100 emitting the unpolarized light can pass through the first polarizing element 200 and be polarized in a direction parallel to the transmission axis of the first polarizing element 200.

[0036] In addition, the point light source 100 can adjust the light quantity. For example, the point light source 100 can improve visibility by increasing the light quantity.

[0037] In addition, the incident angle of the light emitted from the point light source 100 can be adjusted. In one example, the incident angle of the light emitted from the point light source 100 relative to the polarizing plate 300 can be 45° to 75°. For example, the incident angle of the light emitted from the point light source 100 relative to the polarizing plate 300 can be 45° to 70°, 50° to 70°, or 55° to 65°. At this time, the incident angle can be specified according to the refractive index of the protective substrate 332 included in the upper part of the polarizer 310, and the incident angle in the present application is an angle based on the protective substrate with a refractive index of 1.6. When the incident angle of the light emitted from the point light source satisfies the above range, the adhesive stains formed on the polarizing plate can be easily checked, and the visibility is excellent.

[0038] The first polarizing element 200 is a part for polarizing the light emitted from the point light source in a specific direction, and can be configured to receive light from the point light source.

[0039] In this specification, the term "polarizer and polarizer" may refer to a functional layer having a transmission axis formed in a certain direction and exhibiting anisotropic transmission characteristics to incident light. For example, the polarizer and polarizer may have the following functions: among incident light vibrating in multiple directions, light vibrating in a certain direction is transmitted, and light vibrating in other directions is reflected or absorbed to block it. Such a polarizer may be, for example, a reflective polarizer or an absorptive polarizer, and the first polarizer, the second polarizer and polarizer of the present application may be absorptive polarizers.

[0040] In this specification, the term "absorption-type polarizer" may refer to a layer that transmits light in a direction parallel to the transmission axis among incident light vibrating in multiple directions, and absorbs light vibrating in other directions to block it. In one example, the absorption-type polarizer may have a transmission axis and an absorption axis that are orthogonal to each other in the plane direction. For example, the angle between the transmission axis and the absorption axis may be 85° to 95° or 90°, and light vibrating in a direction parallel to the transmission axis may be transmitted, and light vibrating in a direction parallel to the absorption axis may be reflected or absorbed.

[0041] In this specification, the terms such as vertical, parallel, orthogonal or horizontal used in defining angles refer to substantial vertical, parallel, orthogonal or horizontal within a range that does not impair the target effect, for example, including errors including manufacturing errors or variations, etc. For example, in each of the above cases, an error within about ±15°, an error within about ±10° or an error within about ±5° may be included.

[0042] As the absorption type polarizer, a common absorption type polarizer known in the art can be used. For example, as the absorption type polarizer, a stretched polymer film dyed with an iodine compound or an organic pigment, such as a polyvinyl alcohol (PVA) film, etc. can be used. Such an absorption type polarizer can generally have a transmission axis and an absorption axis orthogonal to the transmission axis.

[0043] In one example, the first polarizing member 200 has an absorption axis that may be perpendicular to the polarizer 310 of the polarizing plate 300. Specifically, when the first polarizing member 200 has an absorption axis along the second direction (shown as), the polarizer 310 of the polarizing plate 300 may have an absorption axis along the first direction (shown as) perpendicular to the absorption axis of the first polarizing member 200, and the first polarizing member 200 and the polarizer 310 of the polarizing plate 300 may respectively have a transmission axis along a direction (not shown) orthogonal to the absorption axis. By making the first polarizing member and the polarizer of the polarizing plate have absorption axes perpendicularly, light linearly polarized along the first direction (shown as) through the first polarizing member is perpendicularly aligned with the transmission axis of the polarizer of the polarizing plate, and can therefore be reflected by the polarizer of the polarizing plate. On the contrary, when the first polarizing member is not perpendicular to the absorption axis of the polarizer of the polarizing plate, the light linearly polarized along the first direction (shown as) via the first polarizing member is not perpendicularly aligned with the transmission axis of the polarizer of the polarizing plate, and thus can pass through the polarizer of the polarizing plate. The linearly polarized light passes through the polarizer of the polarizing plate and is reflected by the protective substrate at the bottom. At this time, there is the following disadvantage: if the plane where the polarizing plate is located, that is, the surface of the inspection unit is not dark, the adhesive stain cannot be visually identified.

[0044] The polarizing plate 300 is a sample to be inspected for adhesive stains and can be included in an inspection unit (not shown). For example, the polarizing plate 300 can be disposed on the inspection unit.

[0045] The polarizing plate 300 is arranged to receive the light transmitted through the first polarizing member 200 and reflect the received light. Specifically, the light is transmitted through the adhesive layer 321 and reflected at the polarizer 310, so that adhesive stains on the polarizing plate can be inspected.

[0046] In one example, the polarizing plate 300 may be a polarizing plate for a liquid crystal display device. Specifically, the liquid crystal display device is a transmissive display device that uses liquid crystal between two polarizing plates to change the direction of light travel or adjust the intensity of light. The polarizing plate includes a polarizer for forming linear polarized light, but does not require a 1 / 4 wavelength plate. However, since the organic light-emitting display device has a disadvantage of being weak in reflecting external light such as sunlight and lighting due to the exposed electrodes, in order to block the surface from reflecting external light when the power is off (OFF) to achieve a dark visual sense, a polarizer for forming linear polarized light and a 1 / 4 wavelength plate for forming circular polarized light may be included in the polarizing plate.

[0047] The photocurable adhesive may include an adhesive composition of an acrylic polymer in a cured state. In this specification, the term "photocurable adhesive" refers to an adhesive that can be cured by irradiating electromagnetic waves. The scope of the electromagnetic wave includes not only microwaves, infrared rays (IR), ultraviolet rays (UV), X-rays and gamma rays, but also particle beams such as alpha-particle beams, proton beams, neutron beams and electron beams. The adhesive layers 321 and 322 can be formed as follows: after being coated on one side of the protective substrate 331, 332 or the polarizer 310, they are cured by irradiating electromagnetic waves. The term "curing" refers to a process in which an adhesive composition exhibits bonding properties through physical action or chemical reaction. In one example, the curing of the adhesive composition can be performed by free radical polymerization or cationic reaction by irradiating electromagnetic waves, preferably by performing free radical polymerization and cationic reaction simultaneously or sequentially.

[0048] As the acrylic polymer, a (meth)acrylate monomer may be included. The monomer may be included in the polymer as a polymerized unit. In this specification, the monomer included in the polymer as a polymerized unit may refer to a state in which the monomer forms the skeleton of the polymer, such as a main chain or a side chain, through a polymerization reaction or the like. As the (meth)acrylate monomer, for example, an alkyl (meth)acrylate may be used. For example, in consideration of the cohesive force or glass transition temperature of the adhesive, an alkyl (meth)acrylate having an alkyl group of 1 to 14 carbon atoms may be used. These monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate and tetradecyl (meth)acrylate, and the like, and a mixture of one or more of the above monomers may be included in the polymer.

[0049] In addition, the protective substrates 331 and 332 are films attached to protect the polarizer 310 and can be attached to the upper and lower parts of the polarizer 310 through adhesive layers 321 and 322, respectively. As the protective substrates 331 and 332, protective substrates for polarizers such as TAC (Triacetyl Cellulose) sheets known in the art can be used, but are not limited thereto.

[0050] In one example, the refractive index of the adhesive layers 321 and 322 may be 1.45 to 1.50. For example, the refractive index of the adhesive layers 321 and 322 may be 1.46 to 1.49 or 1.47 to 1.48. By making the adhesive layers 321 and 322 have the refractive index in the above range, the refractive index will be different from that of the polarizer 310, so that the thickness is uneven during curing, thereby enabling visual identification of adhesive stains.

[0051] The refractive index of the polarizer 310 may be greater than 1.5 and range from 1.6. For example, the refractive index of the polarizer 310 may be 1.51 to 1.57 or 1.52 to 1.54. By making the polarizer 310 have a refractive index in the above range, the refractive index will be different from that of the adhesive layers 321 and 322, so that the thickness is uneven during curing, thereby enabling visual identification of adhesive stains. The light reflected from the polarizing plate 300 may have a reflection angle of 45° to 75° relative to the polarizing plate 300. For example, the light reflected from the polarizing plate 300 may have a reflection angle of 45° to 70°, 50° to 70°, or 55° to 65° relative to the polarizing plate 300. By making the reflection angle of the light reflected from the polarizing plate 300 satisfy the above-mentioned range, among the light that is linearly polarized by passing through the first polarizing component 200, except for the light that fails to pass through the polarizing plate 300 and is reflected by the protective substrate 332, the light that passes through the adhesive layer 322 of the polarizing plate 300 and is reflected by the polarizer 310 can be absorbed by the second polarizing component 400, thereby making it possible to inspect the adhesive stains of the adhesive layer 322 inside the polarizing plate 300 with excellent visibility.

[0052] The second polarizing element 400 is a portion that transmits and / or absorbs light reflected from the polarizing plate 300 according to whether the polarizing plate 300 has adhesive stains, and is configured to receive light reflected from the polarizing plate 300. Specifically, light reflected from a portion of the polarizing plate 300 where adhesive stains are present can be transmitted through the second polarizing element 400. On the contrary, light reflected from a portion of the polarizing plate 300 where no adhesive stains are present can be absorbed by the second polarizing element 400. By allowing the light reflected from the polarizing plate to be incident on the second polarizing element, adhesive stains on the polarizing plate can be inspected.

[0053] In one example, the second polarizing member 400 may have an absorption axis perpendicular to the polarizer 310 of the polarizing plate 300. That is, the transmission axis of the second polarizing member 400 may also be parallel to the first polarizing member 200. Specifically, when the second polarizing member 400 has an absorption axis along the second direction (shown as), the polarizer 310 of the polarizing plate 300 may have an absorption axis along the first direction (shown as), and the second polarizing member 400 and the polarizer 310 of the polarizing plate 300 may respectively have transmission axes along directions (not shown) orthogonal to the absorption axes. By making the second polarizing component have an absorption axis perpendicular to the polarizing element of the polarizing plate, among the light that is linearly polarized by passing through the first polarizing component 200, except for the light that fails to pass through the polarizing plate 300 and is reflected by the protective substrate 332, the light that passes through the adhesive layer 322 of the polarizing plate 300 and is reflected by the polarizing element 310 can be absorbed by the second polarizing component 400, thereby making it possible to inspect the adhesive stains of the adhesive layer 322 inside the polarizing plate 300 with excellent visibility.

[0054] The inspection source 500 is a part for determining the adhesive stain of the polarizing plate 300 based on the light transmitted through the second polarizing member 400, and is arranged to receive the light transmitted through the second polarizing member 400. Specifically, the light transmitted through the second polarizing member 400 may be reddish brown, and in this case, it can be determined that there is adhesive stain on the polarizing plate 300. In addition, the light that fails to transmit the second polarizing member 400 may be dark, and in this case, it can be determined that there is no adhesive stain on the polarizing plate 300.

[0055] In one example, the inspection source 500 can directly inspect the adhesive stains on the polarizing plate with naked eyes. In another example, the inspection source 500 can indirectly inspect the adhesive stains on the polarizing plate with a computer by using a camera or other photographing equipment instead of the image obtained by naked eyes.

[0056] The present application also relates to a method for inspecting adhesive stains on a polarizing plate. An exemplary method for inspecting adhesive stains on a polarizing plate is an inspection method using the device for inspecting adhesive stains on a polarizing plate. Therefore, the specific contents of the method for inspecting adhesive stains on a polarizing plate described below can be identically applied to the contents described in the device for inspecting adhesive stains on a polarizing plate, and are therefore omitted.

[0057] The adhesive stain inspection method of the polarizing plate of the present application includes a transmission step and a judgment step. By using the adhesive stain inspection method of the polarizing plate of the present application, the adhesive stain formed on the polarizing plate can be easily inspected with excellent visibility.

[0058] The transmission step is a step of transmitting light using the adhesive stain inspection device for the polarizing plate, and emits light from a point light source to sequentially transmit the light through the first polarizing component, the polarizing plate, and the second polarizing component. At this time, the point light source incidents the light on the polarizing plate at a Brewster angle. The specific contents of the point light source, the first polarizing component, the polarizing plate, the second polarizing component, and the propagation of light are the same as those described in the adhesive stain inspection device for the polarizing plate, and are therefore omitted.

[0059] The judging step is a step for judging the adhesive stain of the polarizing plate, and judges the adhesive stain of the polarizing plate based on the light that is incident on the inspection source after passing through the second polarizing component. That is, when the light from the point light source reaches the inspection source and is reddish brown, it can be judged that the polarizing plate has adhesive stains, and when the light from the point light source does not reach the inspection source and is dark, it can be judged that the polarizing plate does not have adhesive stains. In addition, the specific content of the inspection source and the propagation of light is the same as that described in the adhesive stain inspection device for the polarizing plate, and is therefore omitted.

[0060] In one example, light incident on the polarizing plate is reflected. Specifically, light transmitted through the polarizer of the polarizing plate is reflected by the adhesive layer of the polarizing plate. By making the light reflected by the polarizing plate, adhesive stains of the polarizing plate can be inspected. The specific content of the light reflection is the same as that described in the adhesive stain inspection device of the polarizing plate, and is therefore omitted.

[0061] Adhesive stains on polarizing plates are inspected using an adhesive stain inspection device for polarizing plates according to one embodiment of the present application, an adhesive stain inspection device for polarizing plates not according to one embodiment, an adhesive stain inspection device for polarizing plates not according to another embodiment, and an adhesive stain inspection device for polarizing plates not according to yet another embodiment.

[0062] According to an adhesive stain inspection device for a polarizing plate of an embodiment of the present application, a point light source is incident on a first polarizing component having an absorption axis along a second direction at an incident angle of 58° relative to the polarizing plate to cause linear polarization, and the linear polarized light is incident on a protective substrate of the polarizing plate, an adhesive layer containing a photocurable adhesive, and a polarizing component having an absorption axis along a first direction. Thereafter, the polarizing component reflects the received light at a reflection angle of 58° relative to the polarizing plate. Thereafter, the reflected light is incident on the adhesive layer of the polarizing plate, the protective substrate, and the second polarizing component having an absorption axis along the second direction to cause it to pass through, thereby detecting adhesive stains on the polarizing plate through the light inspected by the inspection source. Figure 3The purpose is to use the polarizing plate adhesive stain inspection device according to one embodiment of the present application to inspect the adhesive stain of the polarizing plate, and to take an image of the second polarizing component by a digital camera. Figure 3 That is, when the adhesive stain inspection device for polarizing plates according to one embodiment of the present application is used to inspect the adhesive stain of the polarizing plate, the adhesive stain of the polarizing plate can be inspected with excellent visibility.

[0063] In addition, the adhesive stain inspection device for polarizing plates according to one embodiment of the present application is not based on the first polarizing component, and the adhesive stain on the polarizing plate is inspected by the same method as the adhesive stain inspection device for polarizing plates according to the embodiment, but the adhesive stain on the polarizing plate can be detected, but the visibility is poor. The reason is that when light is incident on the protective substrate included in the upper part of the polarizer, it is difficult to remove the p-polarization at an angle other than the accurate Brewster angle. Figure 4 The purpose is to inspect adhesive stains on a polarizing plate using an adhesive stain inspection device for a polarizing plate that is not based on an embodiment of the present application, and to obtain an image of the second polarizing component by photographing it with a digital camera.

[0064] In addition, the adhesive stain inspection device for polarizing plates according to another embodiment of the present application is used to inspect the adhesive stain of the polarizing plate by the same method as the adhesive stain inspection device for polarizing plates according to the embodiment, except that the absorption axes of the first polarizing component and the second polarizing component are rotated 90°. However, although the adhesive stain of the polarizing plate can be detected, the visibility is poor. Among the linearly polarized light passing through the first polarizing component 200, except for the light that fails to pass through the polarizing plate 300 and is reflected by the protective substrate 332, the light that passes through the adhesive layer 322 of the polarizing plate 300 and is reflected by the polarizer 310 can be absorbed by the second polarizing component 400, so the adhesive stain of the adhesive layer 322 can be inspected inside the polarizing plate 300 with excellent visibility.

[0065] When linearly polarized light transmitted through the first polarizing member enters the protective substrate included on the upper portion of the polarizer, surface reflection of p-polarized light occurs near the Brewster angle between the surface of the protective substrate included on the upper portion of the polarizer and the atmosphere, thereby deteriorating visibility. Figure 5 The purpose is to inspect adhesive stains on a polarizing plate using an adhesive stain inspection device for a polarizing plate that is not based on another embodiment of the present application, and to obtain an image of the second polarizing component by photographing it with a digital camera.

[0066] In addition, the adhesive stain inspection device for polarizing plates according to another embodiment of the present application uses a surface light source instead of a point light source to inspect the adhesive stain on the polarizing plate in the same method as the adhesive stain inspection device for polarizing plates of the first embodiment, but the surface light source does not detect the adhesive stain on the polarizing plate. In other words, it is easy to detect the adhesive stain on the boundary surface of the light source, so the point light source is more advantageous than the surface light source. Figure 6 The purpose is to inspect adhesive stains on a polarizing plate using an adhesive stain inspection device for a polarizing plate not according to another embodiment of the present application, and to obtain an image of the second polarizing component by photographing it with a digital camera.

[0067] [Explanation of Symbols]

[0068] 100 light sources

[0069] 200 first polarizing component

[0070] 300 polarizing plate

[0071] 310 polarizer

[0072] 321, 322 adhesive layer

[0073] 331, 332 Protecting the substrate

[0074] 400 second polarizing component

[0075] 500 Check Source

Claims

1. A polarizing plate adhesive stain inspection device, comprising: Point light source; a first polarizing component configured to receive light from the point light source; a polarizing plate configured to receive light transmitted through the first polarizing component and reflect the received light; a second polarizing member configured to receive light reflected from the polarizing plate; as well as an inspection source configured to receive light transmitted through the second polarizing member, and to determine adhesive stains on the polarizing plate based on the light transmitted through the second polarizing member; The polarizing plate includes a polarizer, an adhesive layer including a photocurable adhesive located above and below the polarizer, and a protective substrate. The light passing through the first polarizing component is incident on the protective substrate of the polarizing plate, and the point light source is incident on the polarizing plate at a Brewster angle; The point light source emits non-polarized light toward the first polarizing component; The incident angle of the light emitted from the point light source relative to the polarizing plate is 45° to 75°; the first polarizing component has an absorption axis of the polarizer perpendicular to the polarizing plate; the light incident on the polarizing plate is reflected by the adhesive layer, and the incident angle is specified according to the refractive index of the protective substrate included in the upper part of the polarizing element, and the refractive index of the polarizing element is 1.6; the second polarizing component has an absorption axis of the polarizer perpendicular to the polarizing plate.

2. The device for inspecting adhesive stains on polarizing plates according to claim 1, wherein: The polarizing plate is a polarizing plate used in a liquid crystal display device.

3. The device for inspecting adhesive stains on polarizing plates according to claim 1, wherein: The photocurable adhesive includes an adhesive composition having an acrylic polymer in a cured state.

4. The device for inspecting adhesive stains on polarizing plates according to claim 1, wherein: The adhesive layer has a refractive index of 1.45 to 1.

50.

5. The device for inspecting adhesive stains on polarizing plates according to claim 3, wherein: The light reflected from the polarizing plate has a reflection angle of 45° to 75° relative to the polarizing plate.

6. A method for inspecting adhesive stains on a polarizing plate, the method comprising using the apparatus for inspecting adhesive stains on a polarizing plate according to claim 1, The method comprises: The step of emitting light from a point light source and transmitting the light sequentially through a first polarizing component, a polarizing plate, and a second polarizing component; as well as The step of determining adhesive stains on the polarizing plate based on the light that is incident on the inspection source after passing through the second polarizing member.

7. The method for inspecting adhesive stains on a polarizing plate according to claim 6, wherein: Light incident on the polarizing plate is reflected.

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