JP2011226957A - Defect inspection method and defect inspection device of polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a defect inspection method and a defect inspection device of a polarizing plate which can accurately detect only defects caused by a popularizing plate and an adhesive layer with simple device configuration, without detecting defects which are caused by a separate film and are not problematic, when inspecting defects of a polarizing plate with a separate film.SOLUTION: The defect inspection method of the polarizing plate with the separate film which uses transmission light of a polarizing plate with the use of a light source arranged in one side of the polarizing plate and a camera arranged in the other side thereof adjusts a light-receiving direction of the camera and a position of the light source so as to prevent the transmission light from the light source from directly entering into the camera.

Description

  The present invention relates to a defect inspection method and a defect inspection apparatus for inspecting a defect of a polarizing plate used in a liquid crystal display device or the like.

  In recent years, liquid crystal display devices have come to be used in a wide range of applications as display devices for televisions, computers, mobile phones, car navigation systems, and the like due to their thinness and low power consumption. The polarizing plate is important as one of the optical components constituting such a liquid crystal display device, and is usually bonded to both surfaces of the liquid crystal panel via an adhesive layer.

  As shown in FIG. 1, such a polarizing plate is usually composed of a polarizing element 11 made of a polyvinyl alcohol (hereinafter, PVA) film dyed with iodine or the like and uniaxially stretched, and adhesive layers 12a, It is comprised by the protective films 13a and 13b bonded through 12b. The protective films 13a and 13b are formed of a film made of, for example, triacetyl cellulose (hereinafter referred to as TAC) or norbornene. (Hereinafter, the polarizing plate in which the protective films 13a and 13b are bonded to both surfaces of the polarizing element 11 via the adhesive layers 12a and 12b as shown in FIG. 1 is referred to as a “polarizing plate body”.)

  Furthermore, the polarizing plate used for the liquid crystal display device is formed with an adhesive layer 14 for bonding to the liquid crystal panel on one surface of the polarizing plate body 19 (the surface of the protective film 13a in FIG. 1). A separate film 15 is formed on the pressure-sensitive adhesive layer 14 in order to protect the pressure-sensitive adhesive layer 14 until being bonded to. This separate film 15 is peeled off and discarded at the time of bonding to the liquid crystal panel.

  In order to protect the surface of the other side of the polarizing plate body 19 (the surface of the protective film 13b in FIG. 1), a release film 17 may be further attached via the second pressure-sensitive adhesive layer 16. It is common. The release film 17 is peeled off and discarded when the polarizing plate is bonded to the liquid crystal panel. At that time, the second pressure-sensitive adhesive layer 16 is also peeled in a state where it is adhered to the release film 17 and does not remain on the surface of the polarizing plate body 19. (Hereinafter, a polarizing plate in which a separate film 15 is formed on at least one surface of a polarizing plate body 19 via an adhesive layer 14 as shown in FIG. 1 is referred to as a “polarizing plate with a separate film”. (The polarizing plate 10 with a separate film includes a polarizing plate in which a release film 17 is formed via the second pressure-sensitive adhesive layer 16 described above.)

  Usually, such a polarizing plate is produced almost continuously in a long belt-like sheet state, cut into a shape corresponding to the shape of the liquid crystal panel to be finally bonded, and shipped to the manufacturer of the liquid crystal display device ( Hereinafter, this is referred to as “polarizing plate product”). At that time, it is necessary to cut out the polarizing plate product while avoiding a portion where the polarizing plate has defects such as foreign matter, particles and scratches. Therefore, the process of inspecting the defect of the polarizing film with a separate film 10 before cutting becomes important.

  FIG. 4 is a cross-sectional view of an example of a conventional polarizing plate defect inspection apparatus. In the defect inspection apparatus 40 for the polarizing plate, the polarizing plate 49 to be inspected moves in the horizontal direction from left to right on the paper surface, and the inspection portion is arranged on the first inspection portion 41 and the right side thereof. It consists of a second inspection unit 42. In FIG. 4, the film configuration of the polarizing plate 49 is not shown. The first inspection unit 41 includes a first light source 43 disposed below the polarizing plate 49 in the vertical direction, and a first light source 43 disposed so as to face the first light source 43 above the polarizing plate 49 in the vertical direction. It consists of a camera (imaging unit) 44. Similarly, the second inspection unit 42 has a second light source 45 disposed below the polarizing plate in the vertical direction, and a second light source 45 disposed so as to face the second light source 45 above the polarizing plate in the vertical direction. Camera (imaging part) 46. A polarizing filter 47 is disposed between the second light source 45 and the polarizing plate 49. The polarizing axes of the polarizing plate 49 and the polarizing filter 47 are arranged so as to be crossed Nicols.

Here, the first light source 43 and the first camera 44, the second light source 45 and the second camera 46 are arranged on the vertical line with respect to the polarizing plate 49, respectively, and the first camera 44 and the second camera are arranged. The light receiving direction 46 is directly below, that is, directed to the first light source 43 and the second light source 45, respectively.
In the present invention, the light receiving direction of the camera refers to the direction in which the center of the light receiving lens faces.

  Since the inspection polarizing filter is not arranged in the first inspection unit 41, the defect of the polarizing plate 49 is detected as a dark spot in the transmitted light from the first light source 43, and therefore, a large colored A defect such as a particle is detected as a dark spot by the first camera 44 and detected. In the second inspection unit 42, the polarizing filter 47 for inspection is arranged in crossed Nicols with respect to the polarizing plate 49 to be inspected, so that the normal light is blocked and blackened, but the polarizing plate 49 has a defect. And the transmitted light is detected as a bright spot. Therefore, the second inspection unit 42 can capture and detect the transparent defect that cannot be detected by the first inspection unit 41 and the small defect in the shape of a small mark by the second camera 46.

The images from the first camera 44 and the second camera 46 are each subjected to image processing by a computer system (not shown), determined to be defective with an appropriate threshold, and their positions (coordinates) are stored. Then, after checking the inspection results of the first inspection unit 41 and the second inspection unit 42 by this, a defect is finally determined based on an appropriate determination criterion programmed, and the position (coordinates) is stored. Is done. And the location finally determined as a defect is directly marked by the marking system which is not shown in figure according to the command from a computer system, and the location is made defective. When the polarizing plate product is cut out, the marked defective portion is cut out to obtain a polarizing plate product.
About such a 2nd test | inspection part, it is as having also disclosed by patent document 1 (Unexamined-Japanese-Patent No. 2004-198163), for example.

JP 2004-198163 A

  In such a polarizing plate defect inspection apparatus 40, when the polarizing plate 49 to be inspected is the polarizing plate 10 with a separate film, the second inspection unit 42, that is, the second light source 45 and the polarizing plate 49 to be inspected. In the inspection in which the polarizing filter 47 is arranged between the two and the defect is detected as a bright spot, there is a problem that the defect caused by the separate film 15 is also detected as the bright spot.

  As described above, the separate film 15 is peeled off and discarded at the time of bonding to the liquid crystal panel, so that there is no problem even if there is a defect. However, in the conventional defect inspection apparatus, it was impossible to distinguish whether the defect was caused by the separate film 15 or the defect caused by the polarizing plate body 19 or the pressure-sensitive adhesive layer 14. For this reason, even a defect caused by the separate film 15 is judged to be defective, and there is a problem that the yield is unduly lowered.

  The defects caused by the separate film 15 are usually due to foreign matters or adhering substances in the separate film, and are integrated with the separate film 15 and are colorless and have no significant change in the refractive index. 41, that is, in an inspection in which a defect is detected as a dark spot without arranging a polarizing filter for inspection, the defect is not detected as a dark spot.

  In patent document 1, in order to distinguish the defect resulting from the protective film (equivalent to the separate film 15 of this specification) peeled off from a polarizing plate at the time of bonding to a liquid crystal panel, it is periodic in a dark image. Alternatively, it is disclosed that a bright portion continuously detected is determined as a defect of a protective film (separate film).

  However, the defect of the protective film (separate film) may not always be distinguished in this way. For example, the defect of the protective film (separate film) includes a defect that appears meandering at random. In this case, even a defect in the protective film (separate film) is not regarded as a defect due to the protective film (separate film) by this determination method, and the portion is determined as a defective product. In this way, the defect caused by the protective film (separate film) is determined as a defect of the polarizing plate body, and conversely, the periodic or continuous defect present in the polarizing plate body is a defect of the protective film (separate film). There is a problem that many misjudgments such as

  The present invention has been made in view of such problems, and when inspecting the defects of the polarizing plate with a separate film, the inspection apparatus is complicated and expensive, without causing defects in the separate film. The defect inspection apparatus and defect inspection method of a polarizing plate which can detect only the defect resulting from a polarizing plate main body and an adhesive layer accurately are detected.

As a result of intensive research, the present inventors have used a light source disposed on one side of the polarizing plate and a camera disposed on the other side of the polarizing plate with a separate film that utilizes the transmitted light of the polarizing plate. In the defect inspection method, the present invention has been completed by paying attention to the relationship between the light receiving direction of the camera and the position of the light source.
That is, instead of the conventional defect inspection method / apparatus that uses the transmitted light from the light source in the light receiving direction of the camera, the transmitted light from the light source that is oblique to the light receiving direction of the camera is used. It has become possible to increase the sensitivity of the camera by reducing the amount of received light, to detect foreign matter in a separate film, to detect small marks, and to solve the above-mentioned problems for the first time, and to complete the present invention. The present invention includes the following first to seventh inventions.

  That is, the first invention uses a light source arranged on one side of the polarizing plate and a camera arranged on the other side, and in the defect inspection method for the polarizing plate with a separate film using the transmitted light of the polarizing plate, The present invention relates to a defect inspection method for a polarizing plate, wherein defect inspection is performed based on transmitted light from a light source oblique to a light receiving direction of a camera.

In the second invention, the light receiving direction of the camera is orthogonal to the polarizing plate, and there is a light source at a position shifted from the orthogonal position by 10 mm to 30 mm upstream or downstream in the moving direction of the polarizing plate. 2. The defect inspection method for a polarizing plate according to claim 1, wherein the distance between the polarizing plate and the lower end of the camera is 200 to 260 mm.
With the above arrangement of the light source and the camera, the transmitted light incident on the camera is only from an oblique direction with respect to the light receiving direction of the camera.

In the third invention, the light source and the camera are arranged so as to face each other with the polarizing plate interposed therebetween, and the light receiving direction of the camera is inclined 2 ° to 10 ° upstream or downstream with respect to the moving direction of the polarizing plate. The present invention relates to a polarizing plate defect inspection method according to the first aspect of the present invention.
By installing the camera as described above, the transmitted light incident on the camera is only from an oblique direction with respect to the light receiving direction of the camera by a method different from that of the second invention.

  4th invention is used combining with the defect inspection method of the polarizing plate which carries out defect inspection based on the transmitted light from the light source which faced the light-receiving direction of the camera on both sides of the polarizing plate. The present invention relates to a defect inspection method for a polarizing plate according to any one of the inventions, and enables defect inspection with higher accuracy by combining the present invention and a conventional defect inspection method by transmission inspection.

  According to a fifth aspect of the invention, there is provided the defect inspection method for a polarizing plate according to any one of the first to fourth aspects, wherein the separate film is formed on both surfaces of the polarizing plate body via an adhesive layer. It is about.

  6th invention is a defect inspection apparatus of the polarizing plate with a separate film used for invention of the defect inspection method of the polarizing plate in any one of 1st, 2nd, 4th, 5th, Comprising: A light source, a camera, Is arranged, the light receiving direction of the camera is orthogonal to the polarizing plate, the position of the light source is shifted from the orthogonal position to the upstream side or the downstream side of the moving direction of the polarizing plate by 10 mm to 30 mm, and the distance between the polarizing plate and the upper surface of the light source is 150 to 250 mm, and the distance between the polarizing plate and the lower end of the camera is 200 to 260 mm.

  7th invention is a defect inspection apparatus of the polarizing plate with a separate film used for the invention of the defect inspection method of the polarizing plate in any one of 1st and 3rd-5, Comprising: A light source and a camera pinch | interpose a polarizing plate A polarizing plate defect inspection apparatus, characterized in that the polarizing plate is disposed at a directly facing position, and the light receiving direction of the camera is inclined 2 ° to 10 ° upstream or downstream with respect to the moving direction of the polarizing plate. It is about.

  According to the present invention, when inspecting a defect of a polarizing plate with a separate film, a defect caused by a separate film that does not cause a problem is not detected with a simple apparatus configuration, but is caused by a polarizing plate body and an adhesive layer. Since only the defect can be detected with high accuracy, it is possible to prevent a decrease in yield without degrading the inspection accuracy. Furthermore, the inspection apparatus of the present invention has an effect that a polarizing filter for inspection can be omitted, and it can be configured inexpensively and easily, compared with the conventional inspection apparatus.

Sectional drawing which shows the film | membrane structure of the polarizing plate to be examined. Sectional drawing of the defect inspection apparatus of the polarizing plate by the 1st Embodiment of this invention. Sectional drawing of the defect inspection apparatus of the polarizing plate by the 2nd Embodiment of this invention. Sectional drawing of the defect inspection apparatus of the conventional polarizing plate.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional structure of a polarizing plate with a separate film 10 to be inspected in a defect inspection method and a defect inspection apparatus for a polarizing plate according to the present invention.

  In FIG. 1, 11 is a polarizing element having polarization performance. The polarizing element 11 is made of, for example, a PVA film dyed with iodine and uniaxially stretched, and the film thickness thereof is, for example, 20 μm to 100 μm. Protective films 13a and 13b are formed on the respective surfaces of the polarizing element 11 via adhesive layers 12a and 12b. The adhesive layers 12a and 12b are formed of, for example, a PVA adhesive, an acrylic adhesive, a urethane adhesive, or the like.

  The protective films 13a and 13b are formed of, for example, a film of any one of TAC, norbornene, and polyethylene terephthalate (hereinafter referred to as PET), or a laminated film obtained by laminating these films. The film thickness of each protective film 13a, 13b is, for example, 5 μm to 120 μm. The protective films 13a and 13b may be films of the same material or different materials. Further, either one of the protective films 13a and 13b may be a retardation plate, or a retardation plate may be laminated.

  Moreover, the anti-glare (AG) process may be given to the surface or inner surface of one or both of the protective films 13a and 13b. Thus, the polarizing plate main body 19 is composed of the polarizing element 11 and the protective films 13a and 13b formed on the respective surfaces via the adhesive layers 12a and 12b.

  The polarizing plate 10 with a separate film is composed of a pressure-sensitive adhesive layer 14 formed on one surface of the polarizing plate main body 19 (the protective film 13a side in the example of FIG. 1) and a separate film 15 formed on the upper surface thereof. The Although the adhesive layer 14 is for bonding to a liquid crystal panel, it is previously formed as a part of polarizing plate product.

  The adhesive layer 14 is formed of, for example, an acrylic adhesive, a urethane adhesive, or a silicone adhesive. The separate film 15 is formed on the pressure-sensitive adhesive layer 14 in order to protect the pressure-sensitive adhesive layer 14 until the polarizing plate is bonded to the liquid crystal panel. This separate film 15 is peeled off and discarded at the time of bonding to the liquid crystal panel. The separate film 15 is made of, for example, PET, and the film thickness is, for example, 20 μm to 60 μm.

  In the polarizing plate with a separate film 10, the release film 17 is formed on the other surface of the polarizing plate body 19 (on the protective film 13 b side in the example of FIG. 1) via the second adhesive layer 16. Also good. This release film 17 is a film for protecting the other surface of the polarizing plate body 19 and is peeled off and discarded when the polarizing plate is bonded to the liquid crystal panel. At that time, the second pressure-sensitive adhesive layer 16 is also peeled while sticking to the release film 17 and does not remain on the surface of the polarizing plate body 19. The second adhesive layer 16 is formed of, for example, an acrylic adhesive, a urethane adhesive, or a silicone adhesive. The release film 17 is formed of, for example, PET, and the film thickness is, for example, 20 μm to 60 μm.

Such a polarizing plate 10 with a separate film can be produced using a known production method. An example is briefly described below.
The PVA film is drawn out of the PVA film raw material that is supplied by being fed by a belt-shaped roll, and is swollen in pure water. Subsequently, it is immersed in a potassium iodide solution of iodine, and the PVA film is dyed with iodine. Next, the PVA film dyed with iodine is immersed in an aqueous solution containing boric acid to perform a crosslinking treatment. Next, the PVA film is uniaxially stretched at a predetermined magnification. The draw ratio is, for example, 4 to 7 times. Stretching may be performed in two or more stages, may be performed before or simultaneously with dyeing, or may be performed in a crosslinking treatment step. Thereafter, the PVA film is dried to obtain the polarizing element 11.

  Next, an adhesive layer 12a is formed on one surface of the polarizing element 11 of the PVA film by a coating method using an appropriate solvent, and, for example, a TAC film is bonded to the upper surface as the protective film 13a. Next, the adhesive layer 12b is similarly formed on the other surface by the same coating method, and a TAC film, for example, is bonded to the upper surface as the protective film 13b. In this way, the structure of the polarizing plate body 19 is produced.

  Subsequently, the separate film 15 is bonded to one surface of the polarizing plate body 19 via the pressure-sensitive adhesive layer 14 later, but before that, the release film 17 is bonded to the other surface of the polarizing plate body 19. Is done. The release film 17 has a second adhesive layer 16 formed in advance on one surface thereof, and the surface on which the second adhesive layer 16 is formed is adhered to the other surface of the polarizing plate body 19. It is pasted by. From the process of drawing a PVA film from the PVA film original fabric and swelling it in water, the process of pasting the release film 17 is usually performed continuously.

Thereafter, the pressure-sensitive adhesive layer 14 is formed on one surface of the polarizing plate body 19 by a coating method. The process of applying the pressure-sensitive adhesive layer 14 uses a large amount of an organic solvent. It is often performed in a production room different from the previous process. Therefore, after the process of bonding the release film 17, the band-shaped polarizing plate once produced is wound up in a roll shape. Then, in another production room, the polarizing plate wound up in the form of a roll is pulled out, and the pressure-sensitive adhesive layer 14 is formed by a coating method using an appropriate organic solvent.
After the pressure-sensitive adhesive layer 14 is applied and formed, the separate film 15 is bonded to the upper surface of the pressure-sensitive adhesive layer 14 before it is completely dried, and is appropriately dried. The polarizing plate 10 with a separate film is produced by the above.

  Thereafter, the polarizing plate 10 with a separate film is wound up in a roll shape, and the polarizing plate 10 with a separated film that has been wound up is pulled out again in a cutting step, and the required shape of the liquid crystal panel to be bonded is determined. Cut into a shape and shipped to a liquid crystal display manufacturer as a polarizing plate product. The polarizing plate product may be cut out once in a sheet form and then cut out from the sheet as a polarizing plate product. In some cases, the polarizing plate 10 with a separate film is shipped in the form of a roll to a manufacturer of a liquid crystal display device, and cut at the time of bonding to a liquid crystal panel on the production line of the liquid crystal display device.

  Here, when the polarizing plate product is cut out, defective portions such as foreign matter, particles, and scratches present in the polarizing plate main body 19 and the pressure-sensitive adhesive layer 14 must be avoided and cut out. This is because if the polarizing plate with defects is bonded to the liquid crystal panel, the liquid crystal display device becomes defective. Therefore, the process of inspecting the polarizing plate for defects becomes important.

  The step of inspecting the defect may be performed, for example, after the structure of the polarizing plate main body 19 is manufactured, before the release film 17 is bonded, or after the release film 17 is bonded, in addition to the separation film 15. It is important to inspect after the pasting, that is, in the process completed as the polarizing film 10 with a separate film. Before the pressure-sensitive adhesive layer 14 is formed after the release film 17 is bonded, defects in the pressure-sensitive adhesive layer 14 cannot be detected. Since the adhesive layer 14 remains even after the liquid crystal panel is bonded, it is necessary to detect the defect. In addition, before the pressure-sensitive adhesive layer 14 is formed, there is a possibility that particles or the like may be attached while being wound around a roll and moving through the production chamber, and it is necessary to detect it. In addition, after the pressure-sensitive adhesive layer 14 is formed and before the separation film 15 is bonded, the pressure-sensitive adhesive layer 14 is exposed, and it is not preferable to inspect here. Therefore, it is preferable to inspect after bonding of the separate film 15. The polarizing plate defect inspection method and apparatus according to the present invention are applied to the inspection after the separation of the separate film 15.

  That is, the defect inspection method and apparatus for a polarizing plate according to the present invention inspects defects in the state of a strip-like film of the polarizing plate with a separate film 10 after the separation of the separate film 15 and before winding into a roll. . Moreover, the polarizing plate defect inspection method and apparatus according to the present invention is obtained by laminating the separate film 15 and winding it into a roll, and then pulling out the separate polarizing film 10 with a separate film from the roll and cutting it into a polarizing plate product. Defects may be inspected in the film state.

FIG. 2 is a view showing a polarizing plate defect inspection method and apparatus according to the first embodiment of the present invention. In the defect inspection apparatus 20 for a polarizing plate, the polarizing plate 29 with a separate film is disposed in the horizontal direction and moves from the left to the right on the paper surface. The moving speed is, for example, 10 m / min to 20 m / min.
In FIG. 2, the polarizing film 29 with a separate film has a film configuration of 10 in FIG. Here, it is preferable that the separate film 15 of the polarizing plate 29 with a separate film is on the lower side and the release film 17 is on the upper side.

  The defect inspection apparatus 20 preferably includes a first inspection unit 21 and a second inspection unit 22. The arrangement (inspection order) of the first inspection unit 21 and the second inspection unit 22 is arbitrary, but in the example of FIG. 2, the second inspection unit 22 is on the right side of the first inspection unit 21, that is, a separate. It arrange | positions in the downstream of the moving direction of the polarizing plate 29 with a film.

The first inspection unit 21 is the same as the first inspection unit 41 of the prior art. That is, with respect to the polarizing plate 29 with a separate film, the first light source 23 arranged in the vertical direction, that is, vertically below, and the polarizing plate 29 with a separate film in the same vertical direction, that is, the first light source. 23 and the first camera 24 are composed of a first imaging unit, that is, a first camera 24 arranged so as to face the polarizing plate 29.
Accordingly, the first light source 23 and the first camera 24 have the same vertical (with respect to the polarizing plate 29 with a separate film) so that the light receiving direction of the first camera 24 coincides with the direction of the first light source 23 ( It is arranged on the (vertical) line.

  The first light source 23 is, for example, a fluorescent lamp or an LED, and is disposed throughout the width direction of the polarizing plate 29 with a separate film (perpendicular to the paper surface in the figure). Here, the width of the polarizing plate 29 with a separate film is, for example, 0.6 m to 2.0 m. FIG. 2 shows a case where the first light source 23 is the first fluorescent lamp 23a. Below the first fluorescent lamp 23a, a first reflecting plate 23b is disposed around the lower half surface, and light from the first light source 23 is directed upward. The first reflecting plate 23b may not be provided. The diameter of the tube of the first fluorescent lamp 23a is, for example, 25 mm to 35 mm. The distance between the polarizing plate 29 with a separate film and the upper surface of the first light source 23 is, for example, 150 mm to 250 mm, and more preferably 170 mm to 230 mm.

  The first camera 24 is composed of, for example, a camera equipped with a CCD line sensor or a two-dimensional CCD, and receives light emitted from the first light source 23 and transmitted through the polarizing film 29 with a separate film to be inspected. The first camera 24 has a lens in the lower part, and its light receiving direction is directed immediately below the vertical direction (perpendicular to the polarizing plate 29 with a separate film). That is, the first light source 23 and the first camera 24 are arranged on the same vertical (vertical) line with respect to the polarizing plate 29 with a separate film, and the light receiving direction of the first camera 24 is also vertical (vertical). It looks down on the line. The first camera 24 is also provided with a necessary number arranged in the width direction so as to cover the entire width direction of the polarizing plate 29 with a separate film. The distance between the polarizing plate 29 with a separate film and the lower end of the first camera 24 (the lens of the first camera 24) is, for example, 200 mm to 260 mm, and more preferably 220 mm to 240 mm.

  The second inspection unit 22 includes a second light source 25 disposed below the polarizing plate 29 with a separate film, and a second imaging unit disposed above the polarizing plate 29 with a separate film, that is, a second camera. 26. The configuration of the second light source 25 and the second camera 26 and the distance in the vertical (vertical) direction from the polarizing plate 29 with a separate film are the same as those of the first inspection unit. That is, the 2nd light source 25 is a fluorescent lamp or LED, for example, and is arrange | positioned over the whole width direction of the polarizing plate 29 with a separate film. In FIG. 2, similarly to the first light source 23, the second light source 25 shows an example including a second fluorescent lamp 25a and a second reflector 25b disposed on the lower surface thereof. The light from the light source 25 is directed upward. The second reflecting plate 25b may not be provided. The diameter of the tube of the second fluorescent lamp 25a is, for example, 25 mm to 35 mm. The distance in the vertical direction between the polarizing plate 29 with a separate film and the upper surface of the second light source 25 is, for example, 150 mm to 250 mm, and more preferably 170 mm to 230 mm.

  The second camera 26 is composed of, for example, a camera equipped with a CCD line sensor or a two-dimensional CCD, and receives light emitted from the second light source 25 and transmitted through the polarizing film 29 with a separate film to be inspected. The second camera 26 has a lens in the lower part, and its light receiving direction is directed immediately below the vertical direction (perpendicular to the polarizing plate 29 with a separate film). The second camera 26 is also provided with a necessary number arranged in the width direction so as to cover the entire width direction of the polarizing plate 29 with a separate film. The distance in the vertical (vertical) direction between the polarizing plate 29 with a separate film and the lower end of the second camera 26 (lens portion of the second camera 26) is, for example, 200 mm to 260 mm, and more preferably 220 mm to 240 mm. It is.

The second inspection unit 22 according to the present invention is different from the first inspection unit 21 in that defect inspection by the second camera 26 is performed based on transmitted light from a light source that is oblique to the light receiving direction of the camera. It is a point.
That is, the second light source 25 and the second camera 26 are deviated from the position where they face each other with the polarizing plate 29 interposed therebetween, and the transmitted light enters the camera from an oblique direction with respect to the light receiving direction of the camera. Yes. Specifically, the second light source 25 is arranged at a position shifted from the vertical (vertical) line with respect to the polarizing plate 29 with a separate film of the second camera 26 in the horizontal direction, that is, in the left-right direction on the paper surface in FIG. Is done. Although FIG. 2 shows the case where the second light source 25 is arranged at a position shifted in the left direction, the second light source 25 may be arranged at a position shifted in the right direction. The horizontal shift amount d, that is, the horizontal shift amount d of the second light source from the vertical (vertical) line with respect to the polarizing plate with the separate film of the second camera 26 is, for example, 10 mm to 30 mm. Preferably, it is 15 mm-25 mm.

Here, since the light receiving direction of the second camera 26 is directed to a direction orthogonal to the moving direction of the polarizing plate, that is, directly below the vertical (vertical) direction, the second inspection unit 22 The camera 26 receives light from the second light source 25 from an oblique direction.
Further, in the second inspection unit 22, in the related art, the polarizing filter for inspection is disposed between the polarizing plate to be inspected and the second light source. A polarizing filter is not disposed in the 20 second inspection unit 22.

  Since the second inspection unit 22 of the present invention does not arrange the polarizing filter for inspection in this way, defects caused by the separate film 15 can be captured by the second camera 26 as in the first inspection unit 21. There is no. Or even if it catches, it can restrain to the grade which can be distinguished from another defect with a suitable threshold value. This is because, as described above, defects caused by the separate film 15 are mostly due to foreign matters or adhering substances in the separate film, and these are integrated with the separate film 15 and are colorless and have a large change in refractive index. This is because the second inspection unit 22 of the present invention in which no polarizing filter for inspection is disposed is not detected.

  In addition, by receiving light emitted from the second light source 25 and transmitted through the polarizing film 29 with a separation film to be inspected from an oblique direction, a conventional polarizing filter is used for defects caused by other than the separation film 15. It can be detected at the same level as the defect detected by placement. This is because the second inspection unit 22 according to the present invention does not include a polarizing filter for inspection, and therefore, basically, the defect is detected by detecting a dark spot in the same manner as the first inspection unit 21. However, depending on the type of defect, a bright spot similar to the case where the polarizing filter is disposed is detected. The reason is described below.

  The second inspection unit 22 according to the present invention is basically based on detecting a dark spot. In the conventional defect detection using a conventional dark spot, if the defect is small, it is buried by surrounding light and cannot be detected as a dark spot. However, by making the second camera 26 receive light from an oblique direction as in the present invention, the total amount of light received by the second camera 26 can be kept low, and even a small defect has high sensitivity as a dark spot. Can be detected.

Furthermore, the second inspection unit 22 according to the present invention can apply light to the defect from an oblique direction so as to apply light to the edge of the defect. Since the amount of light is low, it can be regarded as a bright spot. Therefore, it is possible to detect with high sensitivity even defects caused by other than the separate film 15 due to foreign matters having an edge that are colorless and transparent but are not integrated with the film.
As described above, the second inspection unit 22 according to the present invention can be regarded as a dark spot and a bright spot depending on the type of the defect, so that many defects can be detected with high sensitivity. There is also an effect that it is possible to determine the type of defect depending on the point. In addition, no defect due to the separate film 15 is detected.

  The defect inspection method for the polarizing plate of the present invention may be a defect inspection method using only the second inspection unit 22. Moreover, even if the defect inspection apparatus 20 of this invention is comprised only with this 2nd test | inspection part 22 of this invention, it can exhibit an effect. That is, the polarizing plate defect inspection apparatus of the present invention may be configured by only the second inspection unit 22.

  However, as in the embodiment described above, a method that is used in combination with the first inspection unit 21 is more preferable. For example, in the case of a defect made up of relatively large colored particles, in the second inspection unit 22, the size of the dark spot of the defect may be halved due to a bright spot from light from the edge of the defect. In the case of such colored particles, the first inspection unit 21 can detect the size more accurately. Therefore, a polarizing plate defect inspection method / apparatus that uses both the first inspection section and the second inspection section is more desirable.

  Images captured by the first camera 24 and the second camera 26 are each subjected to image processing by a computer system (not shown), determined to be defective with an appropriate threshold, and their positions (coordinates) are stored. Then, after checking the inspection results of the first inspection unit 21 and the second inspection unit 22 by the computer system, it is finally determined whether or not the defect is based on an appropriate determination criterion programmed in the computer system. If it is determined as a defect, the position (coordinates) is stored. Normally, a location determined as a defect in either the first inspection unit 21 or the second inspection unit 22 is determined as a final defect, but the first inspection unit 21 and the second inspection unit It is also possible to program so as to determine a threshold value based on the total of 22 defects and finally determine a defect with an appropriate threshold value.

  And the location finally judged as a defect is directly marked by the marking system which is not shown in figure according to the command from a computer system to the applicable defect location of the polarizing plate 29 with a separate film, and the location is made into a defect. A known means is used as the marking means, and for example, printing by an ink jet method is exemplified. When a polarizing plate product is cut out from the polarizing plate 29 with a separate film, the marked defective portion is cut out to obtain a polarizing plate product.

In the present embodiment, the second inspection unit 22 is arranged on the right side of the first inspection unit 21, that is, on the downstream side in the moving direction of the polarizing plate 29 with a separate film, but the first inspection unit 21 and the second inspection unit 21 are arranged. The arrangement of the part 22 may be reversed in the left-right direction, that is, the second inspection part 22 may be arranged on the upstream side in the moving direction of the polarizing film 29 with a separate film.
In addition, although the separate film 15 side of the polarizing film 29 with the separate film to be inspected is preferably the lower side, that is, the first and second light sources 23 and 25 side, the separate film 15 side is the upper side, that is, the first side. It can also be on the side of the first and second cameras 24, 26.

  Moreover, in this embodiment, although the moving direction of the polarizing plate 29 with a separate film was made into the horizontal direction, the moving direction of the polarizing plate 29 with a separate film was made into the vertical direction or a diagonal direction, and according to it, the 1st test | inspection part The arrangement of the constituent elements of the second inspection unit may be changed according to the spirit of the present invention.

  Moreover, although the polarizing plate 29 with a separate film was made into the state of a strip | belt-shaped film, the polarizing plate product cut out according to the shape of the sheet-like polarizing film with a separated film after being cut out, and the liquid crystal panel to be bonded This can also be applied by providing an appropriate mounting means that supports only both ends of the polarizing plate with a separate film so as to transmit light from the light source and can move in the inspection section. This can be used, for example, for re-inspection before shipment of polarizing plate products or before bonding to a liquid crystal panel.

  Next, a second embodiment of the present invention will be described. FIG. 3 shows a polarizing plate defect inspection method / apparatus according to a second embodiment of the present invention. The defect inspection apparatus 30 for the polarizing plate includes a polarizing plate with a separate film in which the second light source 35 and the second camera 36 as the second imaging unit of the second inspection unit 32 are moving in the horizontal direction. 39, the second camera 36 and the second light source 35 are arranged on the same vertical (vertical) line so as to face each other across the polarizing plate 39.

  However, the light receiving direction of the second camera 36 is directed obliquely, not directly below the vertical (vertical) direction. The tilt direction is preferably a tilt direction in which the tilt angle θ is tilted by 2 ° to 10 ° from the direction directly below the vertical (vertical) direction to the right or left side of the drawing.

  The second light source 35 includes, for example, a second fluorescent lamp 35a and a second reflecting plate 35b arranged around the lower half surface thereof. Other configurations and positional relationships are the same as those in the first embodiment. In addition, the first light source 33 and the first camera 34 including the first fluorescent lamp 33a and the second reflecting plate 33b arranged around the lower half surface of the first inspection unit 31 are also the first. This is the same as the first embodiment. Also with this configuration, the second camera 36 can receive the light emitted from the second light source 35 and transmitted through the polarizing film 39 with the separate film to be inspected from an oblique direction. The same effects as those of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 10 Polarizing plate with separate film 11 Polarizing elements 12a and 12b Adhesive layers 13a and 13b Protective film 14 Adhesive layer 15 Separate film 16 Second adhesive layer 17 Peeling film 19 Polarizing plate body 20, 30, and 40 Defects of polarizing plate Inspection devices 21, 31, 41 First inspection units 22, 32, 42 Second inspection units 23, 33, 43 First light sources 23a, 33a First fluorescent lamps 23b, 33b First reflectors 24, 34 , 44 First camera 25, 35, 45 Second light source 25a, 35a Second fluorescent lamp 25b, 35b Second reflector 26, 36, 46 Second camera 29, 39 Polarizing plate 47 with separate film Polarized light Filter 49 Polarizing plate X Camera light reception direction

Claims (7)

  In a defect inspection method for a polarizing plate with a separate film using a light source disposed on one side of the polarizing plate and a camera disposed on the other side and using the transmitted light of the polarizing plate, the method is oblique with respect to the light receiving direction of the camera. A defect inspection method for a polarizing plate, wherein a defect inspection is performed based on transmitted light from a light source in a direction.   The light receiving direction of the camera is orthogonal to the polarizing plate, and the light source is located 10 mm to 30 mm away from the orthogonal position upstream or downstream of the moving direction of the polarizing plate, and the distance between the polarizing plate and the upper surface of the light source is 150 to 250 mm. The method for inspecting a defect of a polarizing plate according to claim 1, wherein the distance between the polarizing plate and the lower end of the camera is 200 to 260 mm.   The light source and the camera are arranged so as to face each other with a polarizing plate interposed therebetween, and the light receiving direction of the camera is installed so as to be inclined 2 ° to 10 ° upstream or downstream with respect to the moving direction of the polarizing plate. The defect inspection method for a polarizing plate according to claim 1. The polarizing plate is used in combination with a defect inspection method for a polarizing plate for inspecting defects based on light transmitted from a light source facing the light receiving direction of the camera across the polarizing plate. Defect inspection method for polarizing plate.   The defect inspection method for a polarizing plate according to any one of claims 1 to 4, wherein the separate film is formed on both surfaces of the polarizing plate body via an adhesive layer.   6. A defect inspection apparatus for a polarizing plate with a separate film for use in the invention for a defect inspection method for a polarizing plate according to any one of claims 1, 2, 4 and 5, wherein a light source and a camera are arranged across the polarizing plate. The light receiving direction of the camera is orthogonal to the polarizing plate, the position of the light source is shifted 10 mm to 30 mm upstream or downstream of the moving direction of the polarizing plate from the orthogonal position, and the distance between the polarizing plate and the upper surface of the light source is 150 to 250 mm, and the distance between the polarizing plate and the lower end of the camera is 200 to 260 mm.   It is a defect inspection apparatus of the polarizing plate with a separate film used for the defect inspection method invention of the polarizing plate in any one of Claim 1 and Claim 3-5, Comprising: A light source and a camera oppose on both sides of a polarizing plate. A defect inspection apparatus for a polarizing plate, which is disposed at a position and is installed so that a light receiving direction of a camera is inclined 2 ° to 10 ° upstream or downstream with respect to a moving direction of the polarizing plate.