JP2022535095A - Polarizing Plate Adhesive Unevenness Inspection Apparatus and Polarizing Plate Adhesive Unevenness Inspection Method - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to an adhesive unevenness inspection apparatus for polarizing plates and an inspection method for polarizing plates. The present invention can easily inspect adhesive unevenness occurring in a polarizing plate, and has excellent visibility. [Selection drawing] Fig. 1

Description

The present invention relates to an adhesive unevenness inspecting apparatus for polarizing plates and an adhesive unevenness inspecting method for polarizing plates.

The present invention claims the benefit of priority based on Korean Patent Application No. 10-2019-0067544 filed on Jun. 7, 2019, and all contents disclosed in the Korean Patent Application Document are herein incorporated by reference. It is incorporated as part of the book.

A liquid crystal display (LCD) includes polarizers to control the state of light. Generally, a polarizing plate used in an LCD is manufactured by attaching a polarizer having a polarizing function and protective substrates above and below the polarizer using an adhesive.

Here, the types of adhesives used are roughly divided into two types: thermosetting adhesives and photocurable adhesives. A general water-based adhesive has PVA as a main component and has the same refractive index as the polarizer, so unevenness caused by the thickness deviation of the adhesive does not occur.

However, since the photocurable adhesive has a refractive index different from that of the PVA polarizer, if the thickness is unevenly cured, unevenness is visually recognized.

Such photocurable adhesive unevenness is not highly visible, so it is difficult to confirm by general inspection methods, and it becomes even more difficult to confirm if a protective film and/or release film is attached on the finished polarizing plate. A problem arises. Therefore, there is a demand for an adhesive unevenness inspection apparatus for polarizing plates and an adhesive unevenness inspection method for polarizing plates that can solve the above problems.

An object of the present invention is to provide an apparatus for inspecting adhesive unevenness on a polarizing plate and a method for inspecting adhesive unevenness on a polarizing plate, which can easily inspect adhesive unevenness occurring on a polarizing plate and has excellent visibility. do.

In order to solve the above-mentioned problems, the apparatus for inspecting adhesive unevenness for polarizing plates of the present invention comprises a point light source, a first polarizing member arranged so that light is applied from the point light source, and the first polarizing member. a polarizing plate arranged to receive light transmitted through the polarizing member and reflecting the applied light; and a second polarizing member arranged to receive light reflected from the polarizing plate. , an inspector arranged so that the light transmitted through the second polarizing member is applied, and determining adhesive unevenness of the polarizing plate based on the light transmitted through the second polarizing member; The polarizing plate includes, in order, a polarizer, an adhesive layer containing a photocurable adhesive on the upper portion and the lower portion of the polarizer, and a protective substrate, and the light transmitted through the first polarizing member is Applied to the protective substrate of the polarizer, the point light source applies light at a Brewster angle to the polarizer.

Further, the point light source may emit light that is not polarized toward the first polarizing member.

Further, light emitted from the point light source may have an incident angle of 45° to 75° with respect to the polarizing plate.

Furthermore, the absorption axis of the first polarizing member may be perpendicular to the polarizer of the polarizing plate.

Furthermore, the polarizing plate may be a polarizing plate for a liquid crystal display device.

Furthermore, the light applied to the polarizing plate may be reflected by the adhesive layer.

Furthermore, the photocurable adhesive may contain an adhesive composition containing an acrylic polymer in a cured state.

Furthermore, the adhesive layer may have a refractive index of 1.45 to 1.50.

Furthermore, the polarizer may have a refractive index of greater than 1.5 to 1.6.

Further, the light reflected and emitted from the polarizer may have a reflection angle of 45° to 75° with respect to the polarizer.

Furthermore, the absorption axis of the second polarizing member may be perpendicular to the polarizer of the polarizing plate.

Further, a method for inspecting adhesive unevenness in a polarizing plate of the present invention is a method for inspecting adhesive unevenness in a polarizing plate using the apparatus for inspecting adhesive unevenness in a polarizing plate, wherein light is emitted from a point light source to obtain a first sequentially passing through a polarizing member, a polarizing plate, and a second polarizing member; and determining adhesive unevenness of the polarizing plate based on the light transmitted through the second polarizing member and applied to the inspector. step.

Further, light applied to the polarizer may be reflected.

According to the polarizing plate adhesive unevenness inspection device and the polarizing plate adhesive unevenness inspection method of the present invention, adhesive unevenness occurring in the polarizing plate can be easily inspected, and visibility is improved.

1 is a diagram showing an adhesive unevenness inspection device for a polarizing plate according to an embodiment of the present invention; FIG. FIG. 3 illustrates a polarizing plate according to one embodiment of the present invention; 4 is an image of a second polarizing member photographed with a digital camera to inspect adhesive unevenness of a polarizing plate using the apparatus for inspecting adhesive unevenness of a polarizing plate according to an embodiment of the present invention; 4 is an image of a second polarizing member taken with a digital camera for inspecting adhesive unevenness of a polarizing plate using an adhesive unevenness inspection apparatus for a polarizing plate that is not according to an embodiment of the present invention; FIG. 10 is an image of the second polarizing member photographed with a digital camera for inspecting the adhesive unevenness of the polarizing plate using another adhesive unevenness inspecting apparatus for the polarizing plate that is not according to one embodiment of the present invention; FIG. FIG. 10 is an image of the second polarizing member photographed with a digital camera for inspecting the adhesive unevenness of the polarizing plate using still another polarizing plate adhesive unevenness inspection apparatus that is not according to one embodiment of the present invention; .

Hereinafter, the apparatus for inspecting adhesive unevenness for polarizing plates and the method for inspecting adhesive unevenness for polarizing plates according to the present invention will be described with reference to the accompanying drawings. The accompanying drawings are illustrative only and do not limit the apparatus for inspecting adhesive unevenness for polarizing plates and the method for inspecting polarizing plates of the present invention.

FIG. 1 is a diagram showing an adhesive unevenness inspection apparatus for a polarizing plate according to an embodiment of the present invention. As shown in FIG. 1, the polarizing plate adhesive unevenness inspection apparatus of the present invention includes a point light source 100, a first polarizing member 200, a polarizing plate 300, a second polarizing member 400, and an inspector 500. including. The point light source 100 applies light to the polarizer 300 at the Brewster angle. FIG. 2 illustrates a polarizing plate according to an embodiment of the invention. As shown in FIG. 2, the polarizer 300 includes a polarizer 310, adhesive layers 321 and 322 on and under the polarizer 310, respectively, and protective substrates 331 and 332 in sequence. Also, the adhesive layers 321 and 322 contain a photocurable adhesive. Furthermore, the light transmitted through the first polarizing member 200 is applied to the protective base materials 331 and 332 of the polarizing plate 300 . The apparatus for inspecting adhesive unevenness for polarizing plates of the present invention can easily inspect adhesive unevenness occurring on a polarizing plate, and has excellent visibility.

As used herein, "positioned in series" means that each configuration is positioned parallel in a serial configuration. In addition, the "Brewster angle" in this specification means that when light passes through two media with different refractive indices, only light of a certain polarization component is reflected, and other polarization components are reflected. means the angle of incidence at which all are transmitted without For example, when vertically polarized light (TE, s-polarized light) is incident, almost all of the light is reflected. However, when horizontally polarized light (TM, p-polarized light) is incident, there is almost no reflection, and most of it is transmitted. At this angle, the electric field of the polarized light is parallel to the plane of incidence and is therefore not reflected. That is, there is an incident angle at which the reflection coefficient of horizontally polarized light becomes 0, and this angle is called Brewster's angle. Therefore, when incident near the Brewster angle, the reflected wave has much more vertically polarized components than parallel polarized components. Thus, when light is incident at Brewster's angle, the reflected light is always s-polarized.

The point light source 100 is a light source that emits unpolarized light that oscillates in different directions and emits different white light or different types of light that have a continuous spectrum in the spectral range of the visible light region. A lamp is used. By using non-polarized light as the point light source, the manufacturing cost and maintenance cost of the adhesive unevenness inspection device for the polarizing plate can be reduced. In addition, the point light source is more advantageous than the surface light source in terms of visibility.

The point light source is a light source that virtually has no area and consists of a single geometric point, and is distinguished from a planar surface light source.

As an example, the point light source 100 may emit light that is not polarized to the first polarizing member 200 side. The unpolarized light may be emitted from the point light source 100 and transmitted through the first polarizing member 200 so as to be polarized in a direction parallel to the transmission axis of the first polarizing member 200 .

Also, the point light source 100 may adjust the amount of light. For example, the point light source 100 may improve visibility by adjusting the amount of light to be high.

Also, the incident angle of the light emitted from the point light source 100 may be adjusted. For example, the light emitted from the point light source 100 may have an incident angle of 45° to 75° with respect to the polarizing plate 300 . For example, the incident angle of the light emitted from the point light source 100 with respect to the polarizing plate 300 may be 45°-70°, 50°-70°, or 55°-65°. Here, the incident angle can be determined by the refractive index of the protective base material 332 included on the polarizer 310, and the incident angle in the present invention uses a protective base material with a refractive index of 1.6. This is the angle when If the incident angle of the light emitted from the point light source is within the above range, it is possible to easily inspect adhesive unevenness occurring on the polarizing plate, and the visibility is excellent.

The first polarizing member 200 is a part for polarizing the light emitted from the point light source in a specific direction, and is arranged to receive the light from the point light source.

The term "polarizing member and polarizer" as used herein means a functional layer having a transmission axis formed in one direction and exhibiting anisotropic transmission characteristics with respect to incident light. For example, the polarizing member and the polarizer have a function of transmitting light vibrating in one direction and blocking by reflecting or absorbing light vibrating in other directions among incident light vibrating in various directions. You may Such a polarizer may be, for example, a reflective polarizer or an absorptive polarizer, and the first polarizing member, second polarizing member and polarizer of the present invention may be absorptive polarizers. good.

The term “absorptive polarizer” used herein means that among incident light vibrating in various directions, light having a direction parallel to the transmission axis is transmitted, and light vibrating in other directions is absorbed and blocked. means layer. As an example, an absorptive polarizer may have a transmission axis and an absorption axis that are perpendicular to each other on the plane. For example, the angle between the transmission axis and the absorption axis may range from 85° to 95° or 90°. Here, light oscillating in the direction parallel to the transmission axis may be transmitted, and light oscillating in the direction parallel to the absorption axis may be reflected or absorbed.

When defining an angle in this specification, when terms such as vertical, parallel, orthogonal, and horizontal are used, it means substantially vertical, parallel, orthogonal, or horizontal within a range that does not impair the intended effect. There are, for example, errors in consideration of manufacturing errors, variations, and the like. 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.

As the absorptive polarizer, an ordinary absorptive polarizer known in the art is used. For example, the absorptive polarizer may be a stretched polymer film dyed with iodide or an organic dye, such as a polyvinyl alcohol (PVA) film. Such absorptive polarizers typically have a transmission axis and an absorption axis perpendicular to said transmission axis.

As an example, the first polarizing member 200 may have an absorption axis perpendicular to the polarizer 310 of the polarizing plate 300 . Specifically, when the first polarizing member 200 has an absorption axis in the second direction (indicated by ↑↓), the polarizer 310 of the polarizing plate 300 is The polarizer 310 of the first polarizing member 200 and the polarizing plate 300 may have an absorption axis in a first direction (indicated by ←→) that is perpendicular to each absorption axis (not shown). ). Since the polarizers of the first polarizing member and the polarizing plate have vertical absorption axes, the light linearly polarized in the first direction (indicated by ←→) through the first polarizing member is the polarized light Since it is aligned perpendicular to the transmission axis of the polarizer of the plate, it is reflected by the polarizer of said polarizer. On the other hand, when the absorption axes of the first polarizing member and the polarizer of the polarizing plate are not perpendicular, the light linearly polarized in the first direction (indicated by ←→) through the first polarizing member is , is not aligned perpendicular to the transmission axis of the polarizer of the polarizer, and thus is transmitted through the polarizer of the polarizer. The linearly polarized light passes through the polarizer of the polarizing plate and is reflected by the lower protective substrate. There is a drawback that the unevenness of the agent cannot be visually recognized.

Polarizing plate 300 is a sample to be measured for inspecting adhesive unevenness, and may be included in an inspection unit (not shown). For example, the polarizing plate 300 is arranged above the inspection section.

The polarizing plate 300 is arranged to receive the light transmitted through the first polarizing member 200 and reflects the applied light. Specifically, the light applied to the polarizing plate 300 passes through the adhesive layer 322 formed on the polarizer 310 of the polarizing plate 300 and is reflected by the polarizer 310 of the polarizing plate 300 . Since the light is transmitted through the adhesive layer 322 and reflected by the polarizer 310, the unevenness of the adhesive on the polarizing plate can be inspected.

As an 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 traveling direction of light or adjust the intensity of light. It includes a polarizer to shape the light, but does not require a quarter-wave plate. However, the organic light-emitting display device has a drawback that it is vulnerable to reflection of external light such as sunlight and lighting because the electrodes are exposed. As provided, the polarizer may include a polarizer for forming linearly polarized light and a quarter wave plate for forming circularly polarized light.

The photocurable adhesive may contain an adhesive composition containing an acrylic polymer in a cured state. The term "photocurable adhesive" as used herein means an adhesive that is cured by irradiation with electromagnetic waves. Here, the electromagnetic waves include microwaves, infrared rays (IR), ultraviolet rays (UV), X-rays and gamma rays, alpha-particle beams, proton beams, neutron beams ( particle beams such as neutron beams, electron beams, and the like. The adhesive layers 321 and 322 may be formed by coating one surface of the protective substrates 321 and 322 or the polarizer 310 and then curing by irradiation with electromagnetic waves. The term "curing" refers to a process in which the adhesive composition develops adhesive properties through physical action or chemical reaction. For example, the curing of the adhesive composition is performed by free radical polymerization or cationic reaction by irradiation of electromagnetic waves, and it is preferable that free radical polymerization and cationic reaction are carried out simultaneously or in sequence.

The acrylic polymer may contain a (meth)acrylate monomer. The monomer may be included as a polymerized unit in the polymer. In the present specification, the expression that a monomer is contained in a polymer as a polymerized unit means that the monomer forms a backbone of the polymer, such as a main chain or a side chain, through a polymerization reaction or the like. do. As the (meth)acrylic acid ester monomer, for example, an alkyl (meth)acrylate is used. For example, an alkyl (meth)acrylate having an alkyl group of 1 to 14 carbon atoms is used in consideration of the cohesive force and glass transition temperature of the adhesive. Such monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-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, tetradecyl (meth)acrylate, etc., and the polymer may contain one or a mixture of two or more of the aforementioned monomers.

The protective substrates 331 and 332 are films attached to protect the polarizer 310, and may be attached to the upper and lower portions of the polarizer 310 via adhesive layers 321 and 322, respectively. As the protective base materials 331 and 332, a polarizer protective base material known in the art such as a TAC sheet is used, but the protective base material is not limited to this.

As an example, the adhesive layers 321, 322 may have a refractive index of 1.45-1.50. For example, the refractive index of the adhesive layers 321, 322 may be between 1.46 and 1.49 or between 1.47 and 1.48. If the adhesive layers 321 and 322 have a refractive index within the above range, the refractive index is different from that of the polarizer 310, so that the cured thickness becomes non-uniform, and unevenness of the adhesive is visually recognized.

The refractive index of polarizer 310 may be greater than 1.5 to 1.6. For example, the refractive index of polarizer 310 may be between 1.51 and 1.57 or between 1.52 and 1.54. If the polarizer 310 has a refractive index within the above range, the refractive index is different from that of the adhesive layers 321 and 322, so that the cured thickness becomes non-uniform, and unevenness of the adhesive is visually recognized.

Light reflected and emitted from the polarizer 300 may have a reflection angle of 45° to 75° with respect to the polarizer 300 . For example, the light reflected and emitted from the polarizer 300 may have a reflection angle of 45° to 70°, 50° to 70°, or 55° to 65° with respect to the polarizer 300 . If the reflection angle of the light reflected and emitted from the polarizing plate 300 is within the above range, the light linearly polarized after passing through the first polarizing member 200 cannot pass through the polarizing plate 300, and the protective base material is Except for the light reflected by 332 , the light transmitted through the adhesive layer 322 of the polarizing plate 300 and reflected by the polarizer 310 is absorbed by the second polarizing member 400 . The adhesive unevenness of the adhesive layer 322 can be inspected with excellent visibility.

The second polarizing member 400 is a portion that transmits and/or absorbs the light reflected from the polarizing plate 300 depending on the presence or absence of adhesive unevenness on the polarizing plate 300. The light reflected from the polarizing plate 300 is applied to the second polarizing member 400. are arranged to be Specifically, the light reflected and applied at the portion where the adhesive unevenness exists in the polarizing plate 300 may be transmitted through the second polarizing member 400 . On the contrary, the light that is reflected and applied at the portion where the adhesive unevenness does not exist in the polarizing plate 300 may be absorbed by the second polarizing member 400 . By applying the light reflected from the polarizing plate to the second polarizing member, the adhesive unevenness of the polarizing plate can be inspected.

As an 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 be parallel to that of the first polarizing member 200 . Specifically, when the second polarizing member 400 has an absorption axis in the second direction (indicated by ↑↓), the polarizer 310 of the polarizing plate 300 absorbs in the first direction (indicated by ←→). The second polarizing member 400 and the polarizer 310 of the polarizing plate 300 may have a transmission axis in a direction (not shown) orthogonal to each absorption axis. Since the polarizers of the second polarizing member and the polarizing plate have perpendicular absorption axes, light linearly polarized through the first polarizing member 200 cannot pass through the polarizing plate 300, and the protective substrate Except for the light reflected by 332 , the light transmitted through the adhesive layer 322 of the polarizing plate 300 and reflected by the polarizer 310 is absorbed by the second polarizing member 400 . The adhesive unevenness of the adhesive layer 322 can be inspected with excellent visibility.

The inspector 500 is a part for judging the adhesive unevenness of the polarizing plate 300 based on the light transmitted through the second polarizing member 400. placed in Specifically, the light transmitted through the second polarizing member 400 may exhibit a reddish brown color. Then, it can be determined that the polarizing plate 300 has adhesive unevenness. Also, light that cannot pass through the second polarizing member 400 may exhibit a dark color. Then, it can be determined that there is no adhesive unevenness on the polarizing plate 300 .

As an example, the inspector 500 may directly inspect the adhesive unevenness of the polarizing plate using the naked eye, and as another example, an image obtained by using an imaging device such as a video camera instead of the naked eye. Alternatively, a computer may be used to indirectly inspect the adhesive for unevenness of the polarizing plate.

The present invention also relates to an adhesive unevenness inspection method for a polarizing plate. An exemplary inspection method for adhesive unevenness of a polarizing plate relates to an inspection method using the above-described adhesive unevenness inspection apparatus for a polarizing plate. Therefore, since the contents of the apparatus for inspecting the unevenness of the adhesive for the polarizing plate are similarly applied, the specific matters concerning the method for inspecting the unevenness of the adhesive for the polarizing plate will be omitted.

The adhesive unevenness inspection method for a polarizing plate of the present invention includes a step of transmitting and a step of judging. By using the method for inspecting adhesive unevenness in a polarizing plate of the present invention, adhesive unevenness occurring in a polarizing plate can be easily inspected, and visibility is improved.

The step of transmitting light is a step of transmitting light using the above-described adhesive unevenness inspection device for polarizing plates, and light is emitted from a point light source to pass through the first polarizing member, the polarizing plate, and the second polarizing member. pass through in order. Here, the point light source applies light at a Brewster angle to the polarizer. Since the apparatus for inspecting adhesive unevenness for polarizing plates is the same as that described above, specific details regarding the point light source, the first polarizing member, the polarizing plate, the second polarizing member, and the progress of light are omitted. .

The step of determining is a step for determining adhesive unevenness of the polarizing plate, and based on the light transmitted through the second polarizing member and applied to the inspector, the adhesive of the polarizing plate judge unevenness. That is, when the light reaches the inspector from the point light source and exhibits a reddish brown color, it is determined that there is unevenness in the adhesive on the polarizing plate, and the light does not reach the inspector from the point light source and produces a dark color. If so, it can be determined that there is no adhesive unevenness on the polarizing plate. Further, since the apparatus for inspecting adhesive unevenness of the polarizing plate is the same as that described above, the detailed contents regarding the inspector and the progress of light are omitted.

As an example, light applied to the polarizer may be reflected. Specifically, the light transmitted through the polarizer of the polarizing plate may be reflected by the adhesive layer of the polarizing plate. The unevenness of the adhesive on the polarizing plate can be inspected by reflecting light on the polarizing plate. Since the apparatus for inspecting adhesive unevenness of the polarizing plate is the same as that described above, the specific details regarding the reflection of light are omitted.

A polarizing plate adhesive unevenness inspection device according to one embodiment of the present invention, a polarizing plate adhesive unevenness inspection device not according to one embodiment, another polarizing plate adhesive unevenness inspection device not according to one embodiment, And, it was inspected whether the adhesive unevenness of the polarizing plate was detected using a still another polarizing plate adhesive unevenness inspection device that was not according to the one embodiment.

An apparatus for inspecting adhesive unevenness for a polarizing plate according to an embodiment of the present invention applies a point light source to a first polarizing member having an absorption axis in a second direction (↑↓) at an incident angle of 58° with respect to the polarizing plate. and apply the linearly polarized light to the protective substrate of the polarizer, the adhesive layer containing the photocurable adhesive, and the polarizer having the absorption axis in the first direction (←→). Light applied as described above is then reflected at the polarizer at a reflection angle of 58° with respect to the polarizer. After that, as described above, the reflected light is applied to the adhesive layer of the polarizing plate, the protective substrate, and the second polarizing member having an absorption axis in the second direction (↑↓) to transmit the light, The inspector confirms that the adhesive unevenness of the polarizing plate is detected by the inspected light. FIG. 3 is an image of the second polarizing member photographed with a digital camera for inspecting the adhesive unevenness of the polarizing plate using the adhesive unevenness inspecting apparatus for the polarizing plate according to one embodiment of the present invention. As shown in FIG. 3, it was confirmed that the reddish brown color was clear. That is, it was confirmed that the adhesive unevenness of the polarizing plate can be inspected with excellent visibility when the adhesive unevenness inspection apparatus for the polarizing plate according to the embodiment of the present invention is used to inspect the adhesive unevenness of the polarizing plate.

In addition, the polarizing plate adhesive unevenness inspection apparatus, which is not according to the embodiment of the present invention, is the same as the polarizing plate adhesive unevenness inspection apparatus according to the above-described embodiment, except that the first polarizing member is not included. When the adhesive unevenness of the polarizing plate was similarly inspected, it was confirmed that although the adhesive unevenness of the polarizing plate was detected, the visibility was weak. Therefore, it was confirmed that it was difficult to remove the p-polarized light at an angle other than the correct Brewster's angle when the light was applied to the protective substrate included in the upper part of the polarizer. FIG. 4 is an image of the second polarizing member photographed with a digital camera for inspecting the adhesive unevenness of the polarizing plate using an adhesive unevenness inspection apparatus for the polarizing plate that is not according to one embodiment of the present invention. .

In addition, in another polarizing plate adhesive unevenness inspection apparatus that is not according to one embodiment of the present invention, the above-described method is used except that the absorption axes of the first polarizing member and the second polarizing member are rotated by 90 degrees. When the adhesive unevenness inspection of the polarizing plate was performed in the same manner as the adhesive unevenness inspection apparatus for the polarizing plate according to the above embodiment, it was confirmed that although the adhesive unevenness of the polarizing plate was detected, the visibility was weak. Therefore, from the light that has passed through the first polarizing member 200 and is linearly polarized, the light that cannot pass through the polarizing plate 300 and is reflected by the protective base material 332 is removed, and the light passes through the adhesive layer 322 of the polarizing plate 300. Since the light reflected by the polarizer 310 is absorbed by the second polarizing member 400, the adhesive unevenness of the adhesive layer 322 inside the polarizing plate 300 can be inspected with excellent visibility.

When linearly polarized light transmitted through the first polarizing member is applied to the protective substrate contained on top of the polarizer, Brewster's light between the surface of the protective substrate contained on top of the polarizer and air It has been confirmed that the visibility is reduced due to surface reflection of p-polarized light near the corners. FIG. 5 is an image of the second polarizing member photographed with a digital camera for inspecting the adhesive unevenness of the polarizing plate using another polarizing plate adhesive unevenness inspection device that is not according to one embodiment of the present invention. is.

Furthermore, still another polarizing plate adhesive unevenness inspection device that is not according to one embodiment of the present invention is the same as that of the polarizing plate adhesion according to the above-described embodiment, except that a surface light source is used instead of the point light source. When the adhesive unevenness inspection of the polarizing plate was performed in the same manner as the adhesive unevenness inspection device, it was confirmed that the adhesive unevenness of the polarizing plate was not detected with the surface light source. That is, it was confirmed that the point light source is more advantageous than the surface light source because the unevenness of the adhesive can be well measured at the boundary surface of the light source. FIG. 6 is a photograph of the second polarizing member taken with a digital camera to inspect the adhesive unevenness of the polarizing plate using still another polarizing plate adhesive unevenness inspection device that is not according to one embodiment of the present invention. It is an image.

[Appendix]
[Appendix 1]
a point light source;
a first polarizing member arranged to receive light from the point light source;
a polarizing plate arranged to receive light transmitted through the first polarizing member and reflecting the applied light;
a second polarizing member positioned to receive light reflected from the polarizing plate;
an inspector arranged to apply light transmitted through the second polarizing member and determining adhesive unevenness of the polarizing plate based on the light transmitted through the second polarizing member;
The polarizing plate includes, in order, a polarizer, an adhesive layer containing a photocurable adhesive on the top and bottom of the polarizer, and a protective substrate,
The light transmitted through the first polarizing member is applied to the protective base material of the polarizing plate,
The point light source applies light to the polarizing plate at a Brewster angle.

[Appendix 2]
The apparatus for inspecting adhesive unevenness for a polarizing plate according to Appendix 1, wherein the point light source emits light that is not polarized toward the first polarizing member.

[Appendix 3]
The apparatus for inspecting adhesive unevenness of a polarizing plate according to appendix 2, wherein the light emitted from the point light source has an incident angle with respect to the polarizing plate of 45° to 75°.

[Appendix 4]
The apparatus for inspecting adhesive unevenness for a polarizing plate according to Appendix 1, wherein the absorption axis of the first polarizing member is perpendicular to the polarizer of the polarizing plate.

[Appendix 5]
The apparatus for inspecting adhesive unevenness for a polarizing plate according to Appendix 1, wherein the polarizing plate is a polarizing plate for a liquid crystal display device.

[Appendix 6]
The apparatus for inspecting adhesive unevenness for a polarizing plate according to appendix 1, wherein the light applied to the polarizing plate is reflected by the adhesive layer.

[Appendix 7]
The apparatus for inspecting adhesive unevenness for polarizing plates according to Appendix 1, wherein the photocurable adhesive contains an adhesive composition containing an acrylic polymer in a cured state.

[Appendix 8]
The apparatus for inspecting adhesive unevenness for polarizing plates according to Appendix 1, wherein the adhesive layer has a refractive index of 1.45 to 1.50.

[Appendix 9]
The apparatus for inspecting adhesive unevenness for polarizing plates according to appendix 1, wherein the polarizer has a refractive index of more than 1.5 to 1.6.

[Appendix 10]
The apparatus for inspecting adhesive unevenness for polarizing plates according to appendix 7, wherein the light reflected and emitted from the polarizing plate has a reflection angle of 45° to 75° with respect to the polarizing plate.

[Appendix 11]
The apparatus for inspecting adhesive unevenness for a polarizing plate according to Appendix 1, wherein the absorption axis of the second polarizing member is perpendicular to the polarizer of the polarizing plate.

[Appendix 12]
A method for inspecting adhesive unevenness of a polarizing plate using the apparatus for inspecting adhesive unevenness of a polarizing plate according to Supplementary Note 1,
Emitting light from a point light source to pass through the first polarizing member, the polarizing plate, and the second polarizing member in order;
determining the adhesive unevenness of the polarizing plate based on the light transmitted through the second polarizing member and applied to the inspector.

[Appendix 13]
13. The method for inspecting adhesive unevenness of a polarizing plate according to appendix 12, wherein the light applied to the polarizing plate is reflected.

REFERENCE SIGNS LIST 100 point light source 200 first polarizing member 300 polarizing plate 310 polarizer 321, 322 adhesive layer 331, 332 protective substrate 400 second polarizing member 500 inspector

Claims (13)

a point light source;
a first polarizing member arranged to receive light from the point light source;
a polarizing plate arranged to receive light transmitted through the first polarizing member and reflecting the applied light;
a second polarizing member positioned to receive light reflected from the polarizing plate;
an inspector arranged to apply light transmitted through the second polarizing member and determining adhesive unevenness of the polarizing plate based on the light transmitted through the second polarizing member;
The polarizing plate includes, in order, a polarizer, an adhesive layer containing a photocurable adhesive on the top and bottom of the polarizer, and a protective substrate,
The light transmitted through the first polarizing member is applied to the protective base material of the polarizing plate,
The point light source applies light to the polarizing plate at a Brewster angle. 2. The apparatus for inspecting adhesive unevenness of a polarizing plate according to claim 1, wherein said point light source emits light that is not polarized toward said first polarizing member. 3. The apparatus for inspecting adhesive unevenness of a polarizing plate according to claim 2, wherein the light emitted from said point light source has an incident angle with respect to said polarizing plate of 45° to 75°. 2. The apparatus for inspecting adhesive unevenness of a polarizing plate according to claim 1, wherein said first polarizing member has an absorption axis perpendicular to the polarizer of said polarizing plate. 2. The apparatus for inspecting adhesive unevenness for a polarizing plate according to claim 1, wherein said polarizing plate is a polarizing plate for a liquid crystal display device. 2. The apparatus for inspecting adhesive unevenness of a polarizing plate according to claim 1, wherein the light applied to said polarizing plate is reflected by said adhesive layer. 2. The apparatus for inspecting adhesive unevenness for polarizing plates according to claim 1, wherein said photocurable adhesive contains an adhesive composition containing an acrylic polymer in a cured state. 2. The apparatus for inspecting adhesive unevenness for polarizing plates according to claim 1, wherein said adhesive layer has a refractive index of 1.45 to 1.50. 2. The apparatus for inspecting adhesive unevenness for polarizing plates according to claim 1, wherein said polarizer has a refractive index of more than 1.5 to 1.6. 8. The apparatus of claim 7, wherein the light reflected and emitted from the polarizing plate has a reflection angle of 45° to 75° with respect to the polarizing plate. 2. The apparatus for inspecting adhesive unevenness of a polarizing plate according to claim 1, wherein said second polarizing member has an absorption axis perpendicular to the polarizer of said polarizing plate. A method for inspecting adhesive unevenness for a polarizing plate using the apparatus for inspecting adhesive unevenness for a polarizing plate according to claim 1,
Emitting light from a point light source to pass through the first polarizing member, the polarizing plate, and the second polarizing member in order;
determining the adhesive unevenness of the polarizing plate based on the light transmitted through the second polarizing member and applied to the inspector. 13. The method of claim 12, wherein the light applied to the polarizing plate is reflected.

Images