WO2020246692A1

WO2020246692A1 - Inspection device for adhesive stains on polarizing plate and inspection method for adhesive stains on polarizing plate

Info

Publication number: WO2020246692A1
Application number: PCT/KR2020/003259
Authority: WO
Inventors: 류재일; 남택근; 최경식
Original assignee: 주식회사 엘지화학
Priority date: 2019-06-07
Filing date: 2020-03-09
Publication date: 2020-12-10
Also published as: CN113906287A; KR20200140639A; JP2022535095A

Abstract

The present application relates to an inspection device for adhesive stains on a polarizing plate, and an inspection method for adhesive stains on a polarizing plate. The present application enables easy inspection of adhesive stains occurring on a polarizing plate, with superior visibility.

Description

Polarizing plate adhesive stain inspection device and polarizing plate adhesive stain inspection method

The present application relates to an apparatus for inspecting adhesive stains on a polarizing plate and a method for inspecting adhesive stains on a polarizing plate.

This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0067544 filed on June 07, 2019, and all contents disclosed in the documents of the Korean patent application are included as part of this specification.

A liquid crystal display (LCD) includes a polarizing plate to control the state of light. In general, a polarizing plate used in an LCD is manufactured by attaching a polarizer having a polarizing function using an adhesive and a protective substrate on the upper and lower portions of the polarizer.

At this time, two types of adhesives are used, a thermosetting adhesive and a photocurable adhesive. A typical water-based adhesive is mainly composed of PVA, and has the same refractive index as that of the polarizer, so that stains due to thickness variation of the adhesive do not occur.

However, when the photocurable adhesive has a different refractive index from that of the PVA polarizer and is cured in a non-uniform thickness, a problem of visible stains occurs.

Such photocurable adhesive stains are not highly visible, and thus it is difficult to check with a general inspection method, and there is a problem that it is more difficult to check when attaching a protective film and/or a release film on a finished polarizing plate. Accordingly, there is a need for an apparatus for inspecting adhesive stains on a polarizing plate and a method for inspecting adhesive stains on a polarizing plate to solve this problem.

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

In order to solve the above problems, the apparatus for inspecting adhesive stains of the polarizing plate of the present application includes a point light source, a first polarizing member disposed to apply light from the point light source, and the light transmitted through the first polarizing member. A polarizing plate reflecting the applied light, a second polarizing member disposed to apply light reflected from the polarizing plate, and a light transmitted through the second polarizing member are applied to the light transmitted through the second polarizing member. And an inspector for determining adhesive stains of the polarizing plate, wherein the polarizing plate sequentially includes a polarizer, an adhesive layer including a photocurable adhesive on top and bottom of the polarizer, and a protective material, and the first polarization The light transmitted through the member is applied to the protective substrate of the polarizing plate, and the point light source applies light at a Brewster angle to the polarizing plate.

In addition, the point light source may emit unpolarized light toward the first polarizing member.

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

In addition, the first polarizing member may have a polarizer and an absorption axis of the polarizing plate perpendicular to each other.

In addition, the polarizing plate may be a polarizing plate for a liquid crystal display.

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

In addition, the photocurable adhesive may include an adhesive composition containing an acrylic polymer in a cured state.

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

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

In addition, the light reflected and emitted from the polarizing plate may have a reflection angle of 45° to 75° with respect to the polarizing plate.

In addition, the second polarizing member may have a polarizer and an absorption axis of the polarizing plate perpendicular to each other.

In addition, the method for inspecting adhesive stains on a polarizing plate according to the present application relates to a method for inspecting adhesive stains on a polarizing plate using an adhesive stain inspection device for the polarizing plate. By emitting light from a point light source, the first polarizing member, the polarizing plate, and the second polarizing member are And sequentially transmitting, and determining an adhesive stain of the polarizing plate based on the light transmitted through the second polarizing member and applied to the inspection source.

In addition, light applied to the polarizing plate may be reflected.

According to the apparatus for inspecting adhesive stains on the polarizing plate and the method for inspecting adhesive stains on the polarizing plate of the present application, adhesive stains generated on the polarizing plate can be easily inspected and excellent visibility.

1 is a view showing an apparatus for inspecting adhesive stains of a polarizing plate according to an exemplary embodiment of the present application.

2 is a view showing a polarizing plate according to an embodiment of the present application.

FIG. 3 is an image photographed by a digital camera of a second polarizing member in order to inspect adhesive stains on a polarizing plate using the apparatus for inspecting adhesive stains on a polarizing plate according to an exemplary embodiment of the present application.

FIG. 4 is an image photographed by a digital camera of a second polarizing member in order to inspect adhesive stains on a polarizing plate using an adhesive stain inspection apparatus for a polarizing plate according to an exemplary embodiment of the present application.

FIG. 5 is an image photographed by a digital camera of a second polarizing member in order to inspect adhesive stains on a polarizing plate using an adhesive stain inspection apparatus for a polarizing plate according to another exemplary embodiment of the present application.

FIG. 6 is an image photographed by a digital camera of a second polarizing member in order to inspect adhesive stains on a polarizing plate using an adhesive stain inspection apparatus for a polarizing plate according to another embodiment of the present application.

Hereinafter, an adhesive stain inspection apparatus for a polarizing plate and an adhesive stain inspection method for a polarizing plate of the present application will be described with reference to the accompanying drawings, and the accompanying drawings are illustrative, and an adhesive stain inspection apparatus and a polarizing plate inspection method of the present application It is not limited to the accompanying drawings.

1 is a view showing an apparatus for inspecting adhesive stains of a polarizing plate according to an exemplary embodiment of the present application. As shown in FIG. 1, the apparatus for inspecting adhesive stains of the polarizing plate of the present application includes a point light source 100, a first polarizing member 200, a polarizing plate 300, a second polarizing member 400, and an inspecting source 500. do. The point light source 100 applies light to the polarizing plate 300 at a Brewster angle. 2 is a view showing a polarizing plate according to an embodiment of the present application. As shown in FIG. 2, the polarizing plate 300 sequentially includes a polarizer 310, an adhesive layer 321, 322, and protective substrates 331, 332 on top and bottom of the polarizer 310, respectively. . In addition, the adhesive layers 321 and 322 include a photocurable adhesive. In addition, the light transmitted through the first polarizing member 200 is applied to the protective substrates 331 and 332 of the polarizing plate 300. The apparatus for inspecting adhesive stains of the polarizing plate of the present application may easily inspect adhesive stains generated on the polarizing plate and may have excellent visibility.

In the present specification, the term "located in sequence" may mean a state in which each component is located in parallel in a series structure. In addition, in the present specification, the term "brewster angle" refers to an incident angle through which only light of a certain polarization component is reflected and all other polarization components are transmitted without reflection when light passes between two media having different refractive indices. For example, when vertically polarized light (TE, s polarized light) is incident, almost all light is reflected. However, when horizontally polarized light (TM. p polarized light) is incident, reflection hardly occurs and most of it is transmitted. At this angle, the electric field of the polarized light is parallel to the incident plane, so it is not reflected. That is, there is an incident angle at which the reflection coefficient of horizontally polarized light becomes 0, and this angle is referred to as Brewster's angle. Therefore, when incident near Brewster's angle, the reflected wave has significantly more vertically polarized components than parallel polarized components. Therefore, 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 vibrating in various directions, and may emit various white light or use various types of lamps having a continuous spectrum in a spectral range of a visible light region. By using unpolarized light as the point light source, the manufacturing cost and maintenance cost of the apparatus for inspecting adhesive stains on the polarizing plate may be inexpensive. In addition, the point light source may be more advantageous in terms of visibility than the surface light source.

The point light source virtually does not have an area and is a geometric one point light source, and can be distinguished from a surface light source in the form of a plane.

In one example, the point light source 100 may emit unpolarized light toward the first polarizing member 200. The point light source 100 from which the unpolarized light is emitted may be polarized in a direction parallel to the transmission axis of the first polarizing member 200 while passing through the first polarizing member 200.

In addition, the point light source 100 may control the amount of light. For example, the point light source 100 may improve visibility by increasing the amount of light.

In addition, the incident angle of light emitted from the point light source 100 may be adjusted. In one example, the light emitted from the point light source 100 may have an incident angle of 45° to 75° to the polarizing plate 300. For example, an incident angle of light emitted from the point light source 100 to the polarizing plate 300 may be 45° to 70°, 50° to 70°, or 55° to 65°. In this case, the angle of incidence may be specified according to the refractive index of the protective substrate 332 included in the upper portion of the polarizer 310, and the incident angle in the present application is an angle based on the protective substrate having a refractive index of 1.6. When the incident angle of light emitted from the point light source satisfies the above-described range, adhesive stains generated on the polarizing plate can be easily inspected, and visibility can be excellent.

The first polarizing member 200 is a portion for polarizing light emitted from the point light source in a specific direction, and may be disposed so that light is applied from the point light source.

In the present specification, the term "polarizing member and polarizer" may mean a functional layer having a transmission axis formed in either direction and exhibiting anisotropic transmission characteristics with respect to incident light. For example, the polarizing member and the polarizer may have a function of transmitting light vibrating in one direction from incident light vibrating in various directions, and reflecting or absorbing light vibrating in the other direction. Such a polarizer may be, for example, a reflective polarizer or an absorption type polarizer, and the first polarizing member, the second polarizing member, and the polarizer of the present application may be absorption type polarizers.

In the present specification, the term “absorption polarizer” may refer to a layer that transmits light having a direction parallel to a transmission axis from incident light vibrating in various directions, and absorbs and blocks light vibrating in the other directions. In one example, the absorption type polarizer may have a transmission axis and an absorption axis orthogonal to each other in a plane direction. For example, the angle between the transmission axis and the absorption axis may form 85° to 95° or 90°, and light vibrating in a direction parallel to the transmission axis may be transmitted, and parallel to the absorption axis. Light vibrating in a direction can be reflected or absorbed.

In the present specification, when the term such as vertical, parallel, orthogonal or horizontal is used while defining an angle, it means substantially vertical, parallel, orthogonal or horizontal within a range that does not impair the desired effect, for example , Manufacturing errors or variations are included. 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 absorption type polarizer, a conventional absorption type polarizer known in the art may be used. For example, as the absorption polarizer, a stretched polymer film dyed with an iodine compound or an organic dye, for example, a polyvinyl alcohol (PVA) film may be used. Such an absorption type polarizer may typically have a transmission axis and an absorption axis orthogonal to the transmission axis.

In one 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 (shown by ↕), the polarizer 310 of the polarizing plate 300 is perpendicular to the absorption axis of the first polarizing member 200 The first polarizing member 200 and the polarizer 310 of the polarizing plate 300 may each have a transmission axis in a direction (not shown) orthogonal to the absorption axis. I can. Since the first polarizing member and the polarizer of the polarizing plate have an absorption axis perpendicular to each other, the light linearly polarized in the first direction (shown as ↔) through the first polarizing member is vertically aligned with the transmission axis of the polarizer of the polarizing plate, It may be reflected by the polarizer of the polarizing plate. On the other hand, when the absorption axis of the polarizer of the first polarizing member and the polarizing plate is not perpendicular, the light linearly polarized in the first direction (shown as ↔) through the first polarizing member is transmitted to the transmission axis of the polarizer of the polarizing plate. Since it is not vertically aligned, the polarizer of the polarizing plate may be transmitted. The linearly polarized light transmits through the polarizer of the polarizing plate and is reflected from the lower protective substrate. At this time, the disadvantage that it is impossible to visually recognize the adhesive stains unless the bottom where the polarizing plate is located, that is, the surface of the inspection unit, shows a dark color. have.

The polarizing plate 300 is a sample to be measured for inspecting adhesive stains and may be included in an inspection unit (not shown). For example, the polarizing plate 300 may be disposed on the inspection unit.

The polarizing plate 300 is disposed so that the light transmitted through the first polarizing member 200 is applied to reflect the caused light. Specifically, the light applied to the polarizing plate 300 may pass through the adhesive layer 322 formed on the polarizer 310 of the polarizing plate 300 and be reflected by the polarizer 310 of the polarizing plate 300. have. By transmitting the adhesive layer 322 and reflecting light from the polarizer 310, it is possible to inspect adhesive stains on the polarizing plate.

In one example, the polarizing plate 300 may be a polarizing plate for a liquid crystal display. Specifically, a liquid crystal display device is a transmission type display device that changes the direction of light or adjusts the intensity of light by using a liquid crystal between two polarizing plates, and includes a polarizer that generates light linearly polarized on the polarizing plate, but a quarter wave plate Do not need. However, the organic light emitting display device has a disadvantage in that it is vulnerable to reflection of external light such as sunlight and lighting due to the exposure of the electrode, so it blocks the reflection of external light from the surface when the power is off, and makes linearly polarized light on the polarizing plate to have a dark sense of view. It may include a polarizer for and a quarter wave plate for making circularly polarized light.

The photocurable adhesive may include an adhesive composition containing an acrylic polymer in a cured state. In the present specification, the term "photocurable adhesive" refers to an adhesive that can be cured by irradiation of electromagnetic waves. In the above, the categories of electromagnetic waves include microwaves, infrared (IR), ultraviolet (UV), X-rays and gamma rays, as well as alpha-particle beams, proton beams, and neutron beams. beam) and a particle beam such as an electron beam. The adhesive layers 321 and 322 may be formed by being applied to one surface of the protective substrate 321 and 322 or the polarizer 310 and then cured by irradiation of electromagnetic waves. In the above, the term curing refers to a process of allowing the adhesive composition to exhibit adhesive properties through a physical action or a chemical reaction. In one example, the curing of the adhesive composition may be performed through free radical polymerization or cationic reaction by irradiation of electromagnetic waves, and preferably, free radical polymerization and cationic reaction may be performed simultaneously or sequentially together.

The acrylic polymer may include a (meth)acrylic acid ester monomer. The monomer may be included in the polymer as a polymerized unit. In the present specification, that a monomer is included in a polymer as a polymerized unit may mean a state in which the monomer forms a skeleton, for example, a main chain or a side chain of the polymer through a polymerization reaction or the like. As the (meth)acrylic acid ester monomer, for example, an alkyl (meth)acrylate may be used. For example, an alkyl (meth)acrylate having an alkyl group having 1 to 14 carbon atoms may be used in consideration of the cohesive strength of the adhesive and the glass transition temperature. These 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, and tetradecyl (meth) acrylate, etc. may be exemplified, and a mixture of one or more types of the aforementioned monomers may be included in the polymer. I can.

In addition, 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 through adhesive layers 321 and 322, respectively. As the protective substrates 331 and 332, a protective substrate for a polarizer known in this field, such as a TAC sheet, may be used, but is not limited thereto.

In one example, the adhesive layers 321 and 322 may have a refractive index of 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. Since the adhesive layers 321 and 322 have a refractive index in the above-described range, the polarizer 310 and the refractive index are different and thus have a non-uniform thickness upon curing, and thus adhesive stains may be visually recognized.

The refractive index of the polarizer 310 may be greater than 1.5 to 1.6. For example, the refractive index of the polarizer 310 may be 1.51 to 1.57 or 1.52 to 1.54. Since the polarizer 310 has a refractive index in the above-described range, the adhesive layers 321 and 322 and the refractive index are different, so that the thickness is non-uniform when cured, so that adhesive stains may be visually recognized.

The light reflected from and emitted from the polarizing plate 300 may have a reflection angle of 45° to 75° with respect to the polarizing plate 300. For example, a reflection angle of light reflected from the polarizing plate 300 and emitted from the polarizing plate 300 may be 45° to 70°, 50° to 70°, or 55° to 65°. Since the reflection angle of the light reflected and emitted from the polarizing plate 300 satisfies the above-described range, the light transmitted through the first polarizing member 200 and linearly polarized, does not pass through the polarizing plate 300 and the protective substrate 332 Except for the light reflected from, the light transmitted through the adhesive layer 322 of the polarizing plate 300 and reflected by the polarizer 310 may be absorbed by the second polarizing member 400, and thus, the polarizing plate (300) It is possible to inspect the adhesive stain of the adhesive layer 322 from the inside with excellent visibility.

The second polarizing member 400 is a part that transmits and/or absorbs light reflected from the polarizing plate 300 according to the presence or absence of adhesive stains on the polarizing plate 300, so that the light reflected from the polarizing plate 300 is applied. Is placed. Specifically, light applied by reflecting a portion of the polarizing plate 300 where adhesive stains exist may pass through the second polarizing member 400. Conversely, light applied by reflecting a portion of the polarizing plate 300 in which adhesive stains do not exist may be absorbed by the second polarizing member 400. As the light reflected from the polarizing plate is applied to the second polarizing member, the adhesive stain of the polarizing plate may be inspected.

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 and the first polarizing member 200 may be parallel. Specifically, when the second polarizing member 400 has an absorption axis in the second direction (shown as ↕), the polarizer 310 of the polarizing plate 300 may have an absorption axis in the first direction (shown as ↔). In addition, the second polarizing member 400 and the polarizer 310 of the polarizing plate 300 may each have a transmission axis in a direction (not shown) orthogonal to an absorption axis. Since the second polarizing member and the polarizer of the polarizing plate have an absorption axis perpendicular to each other, the light transmitted through the first polarizing member 200 and linearly polarized, does not pass through the polarizing plate 300 and is reflected from the protective substrate 332. Excluding light, light transmitted through the adhesive layer 322 of the polarizing plate 300 and reflected by the polarizer 310 may be absorbed by the second polarizing member 400, and thus, the polarizing plate 300 Adhesive stains of the adhesive layer 322 inside can be inspected with excellent visibility.

The inspector 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 the light transmitted through the second polarizing member 400 is applied. It is arranged as much as possible. Specifically, the light transmitted through the second polarizing member 400 may exhibit a reddish brown color, which may be determined as the presence of adhesive stains of the polarizing plate 300. In addition, the light that has not passed through the second polarizing member 400 may exhibit a dark color, which may be determined that there is no adhesive stain on the polarizing plate 300.

In one example, the inspector 500 may directly perform an adhesive stain inspection of the polarizing plate using the naked eye, and in another example, an image obtained by using an imager such as a video camera instead of the naked eye may be converted to a computer. Through this, it is possible to indirectly perform adhesive stain inspection on the polarizing plate.

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 relates to a method for inspecting adhesive stains on a polarizing plate described above. Therefore, specific matters regarding the method for inspecting adhesive stains of a polarizing plate to be described later may be identically applied to the information described in the apparatus for inspecting adhesive stains of the polarizing plate, and thus will be omitted.

The method for inspecting adhesive stains on a polarizing plate of the present application includes transmitting and determining. By using the adhesive stain inspection method of the polarizing plate of the present application, it is possible to easily inspect the adhesive stain generated on the polarizing plate, and excellent visibility.

The transmitting step is a step of transmitting light using the adhesive stain inspection device of the polarizing plate described above, and the first polarizing member, the polarizing plate, and the second polarizing member are sequentially transmitted by emitting light from a point light source. At this time, the point light source applies light to the polarizing plate at a Brewster angle. Details of the point light source, the first polarizing member, the polarizing plate, the second polarizing member, and the progress of light are the same as described above in the apparatus for inspecting adhesive stains of the polarizing plate, and thus will be omitted.

The determining step is a step of determining the adhesive stain of the polarizing plate, and the adhesive stain of the polarizing plate is determined based on the light transmitted through the second polarizing member and applied to the inspection source. That is, when light arrives from the point light source to the inspection source and shows reddish brown color, it is determined that adhesive stains exist on the polarizing plate, and when the light does not reach the inspection source from the point light source and shows a dark color, the polarizing plate It can be determined that there are no adhesive stains. Further, the detailed information on the progress of the inspector and the light is the same as described above in the apparatus for inspecting adhesive stains of the polarizing plate, and thus will be omitted.

In one example, light applied to the polarizing plate may be reflected. Specifically, light transmitted through the polarizer of the polarizing plate may be reflected by the adhesive layer of the polarizing plate. Since light is reflected from the polarizing plate, it is possible to inspect the adhesive stain of the polarizing plate. Details of the reflection of the light are the same as described above in the apparatus for inspecting adhesive stains of the polarizing plate, and thus will be omitted.

An apparatus for inspecting adhesive stains of a polarizing plate according to an exemplary embodiment of the present application, an apparatus for inspecting adhesive stains of a polarizing plate according to an exemplary embodiment, an apparatus for inspecting adhesive stains of a polarizing plate according to another exemplary embodiment, and another exemplary embodiment. Using a non-conforming adhesive stain inspection device on the polarizing plate, an inspection was performed to see if adhesive stains on the polarizing plate were detected.

The apparatus for inspecting adhesive stains of a polarizing plate according to an exemplary embodiment of the present application applies a point light source to a first polarizing member having a second direction (↕) with an absorption axis at an angle of 58° to the polarizing plate to linearly polarize the polarized light, The protective substrate of the polarizing plate, an adhesive layer including a photocurable adhesive, and an absorption axis were applied to a polarizer having a first direction (↔). Thereafter, the applied light was reflected by the polarizer at a reflection angle of 58° to the polarizing plate. Thereafter, by applying the reflected light to the adhesive layer of the polarizing plate, the protective substrate, and the second polarizing member having the absorption axis in the second direction (↕) and transmitting it, adhesive stains of the polarizing plate are detected through the light inspected by the inspector. It was confirmed to be. FIG. 3 is an image photographed by a digital camera of a second polarizing member in order to inspect adhesive stains on a polarizing plate using the apparatus for inspecting adhesive stains on a polarizing plate according to an exemplary embodiment of the present application. As shown in Fig. 3, it was confirmed that reddish brown was clear. That is, when inspecting the adhesive stain of the polarizing plate using the adhesive stain inspection apparatus of the polarizing plate according to an embodiment of the present application, it was confirmed that the adhesive stain of the polarizing plate can be inspected with excellent visibility.

In addition, the adhesive stain inspection apparatus of the polarizing plate according to the embodiment of the present application does not include the first polarizing member, except that the adhesive of the polarizing plate in the same manner as the adhesive stain inspection apparatus of the polarizing plate according to the embodiment. A stain test was performed, but it was confirmed that the adhesive stain of the polarizing plate was detected but the visibility was weak. It was confirmed that this is because it is difficult to remove p-polarized light at an angle other than around the exact Brewster angle when light is applied to the protective substrate included on the upper part of the polarizer. FIG. 4 is an image photographed by a digital camera of a second polarizing member to inspect adhesive stains of a polarizing plate using an adhesive stain inspection apparatus of a polarizing plate according to an exemplary embodiment of the present application.

In addition, the apparatus for inspecting adhesive stains of a polarizing plate, which is not according to another exemplary embodiment of the present application, inspects adhesive stains of the polarizing plate according to the above embodiment, except that the absorption axes of the first and second polarizing members are rotated by 90° The adhesive stain test of the polarizing plate was performed in the same manner as the apparatus, but it was confirmed that the adhesive stain of the polarizing plate was detected but the visibility was weak. This is the adhesive layer 322 of the polarizing plate 300, except for the light reflected from the protective substrate 332 without passing through the polarizing plate 300 in the linearly polarized light transmitted through the first polarizing member 200 Light transmitted through and reflected by the polarizer 310 may be absorbed by the second polarizing member 400, and thus, the adhesive stain of the adhesive layer 322 inside the polarizing plate 300 can be inspected with excellent visibility. I can.

When linearly polarized light through the first polarizing member is applied to the protective substrate included in the upper part of the polarizer, the surface reflection of p-polarized light occurs near the Bourster angle between the surface of the protective substrate included in the upper part of the polarizer and air. Therefore, it was confirmed that the visibility was weakened. FIG. 5 is an image photographed by a digital camera of a second polarizing member in order to inspect adhesive stains on a polarizing plate using an adhesive stain inspection apparatus for a polarizing plate according to another exemplary embodiment of the present application.

In addition, the adhesive stain inspection apparatus of the polarizing plate according to another embodiment of the present application, except that a surface light source instead of a point light source is used, and the adhesive of the polarizing plate is used in the same manner as the adhesive stain inspection apparatus of the polarizing plate according to the above embodiment. Although the stain test was performed, it was confirmed that the adhesive stain of the polarizing plate was not detected in the surface light source. In other words, it was confirmed that the point light source is more advantageous than the surface light source because adhesive stains are well detected on the surface of the light source. FIG. 6 is an image photographed by a digital camera of a second polarizing member in order to inspect adhesive stains on a polarizing plate using an adhesive stain inspection apparatus for a polarizing plate according to another embodiment of the present application.

100: point light source

200: first polarizing member

300: polarizer

310: polarizer

321, 322: adhesive layer

331, 332: protective material

400: second polarizing member

500: inspector

Claims

Point light source;

A first polarizing member disposed to apply light from the point light source;

A polarizing plate disposed so that the light transmitted through the first polarizing member is applied to reflect the applied light;

A second polarizing member disposed to apply light reflected from the polarizing plate; And

Arranged so that the light transmitted through the second polarizing member is applied, and includes an inspector for determining adhesive stains of the polarizing plate based on the light transmitted through the second polarizing member,

The polarizing plate sequentially includes a polarizer, an adhesive layer including a photocurable adhesive on each of the upper and lower portions of the polarizer, and a protective material,

Light transmitted through the first polarizing member is applied as a protective substrate of the polarizing plate,

The point light source is a device for inspecting adhesive stains of a polarizing plate for applying light to the polarizing plate at a Brewster angle.
The apparatus of claim 1, wherein the point light source emits unpolarized light toward the first polarizing member.
The apparatus of claim 2, wherein the light emitted from the point light source has an incident angle of 45° to 75° to the polarizing plate.
The apparatus of claim 1, wherein the first polarizing member has an absorption axis perpendicular to the polarizer of the polarizing plate.
The apparatus of claim 1, wherein the polarizing plate is a polarizing plate for a liquid crystal display device.
The apparatus of claim 1, wherein the light applied to the polarizing plate is reflected by the adhesive layer.
The apparatus of claim 1, wherein the photocurable adhesive comprises an adhesive composition containing an acrylic polymer in a cured state.
The apparatus of claim 1, wherein the adhesive layer has a refractive index of 1.45 to 1.50.
The apparatus of claim 1, wherein the polarizer has a refractive index of greater than 1.5 to 1.6.
The apparatus of claim 7, wherein the light reflected from the polarizing plate has a reflection angle of 45° to 75° with respect to the polarizing plate.
The apparatus of claim 1, wherein the second polarizing member has an absorption axis perpendicular to a polarizer of the polarizing plate.
It relates to a method for inspecting adhesive stains of a polarizing plate using the adhesive stain inspection device of the polarizing plate according to claim 1,

Emitting light from a point light source to sequentially transmit the first polarizing member, the polarizing plate, and the second polarizing member; And

And determining the adhesive stain of the polarizing plate based on the light transmitted through the second polarizing member and applied to the inspection source.
The method of claim 12, wherein the light applied to the polarizing plate is reflected.