JPWO2011148790A1 - Film defect inspection apparatus, defect inspection method, and release film - Google Patents

Abstract

An inspection apparatus for detecting defects in a long film, wherein the illumination means illuminates the film on one side of the film, and a first polarizing plate provided between the illumination means and the film A second polarizing plate provided on the other surface side of the film, and provided on the other surface side of the film and illuminated from the illuminating means, the first polarizing plate, the film and the second polarized light. Light receiving means for receiving transmitted light transmitted through the plate, the angle of the first polarizing plate within the plane of the first polarizing plate, and the angle of the second polarizing plate with the second A defect inspection apparatus for a film, characterized by having an angle adjusting means for adjusting independently in the plane of the polarizing plate.

Description

  The present invention performs simple and easy optical defect inspection of a film to be inspected, and in particular, polarizing plate separation for performing defect inspection continuously before polarizing plate processing of a polarizing plate release film used in a polarizing plate production process. The present invention belongs to the technical field of defect inspection apparatus and defect inspection method for mold film.

  In recent years, the demand for liquid crystal displays (LCDs), which have the advantages of being thinner and lighter, lower power consumption, and higher image quality than the conventional CRT, has been rapidly increasing. LCDs for large-screen TV applications are growing rapidly. In many cases, the LCD has a sufficiently large brightness even on a large screen by increasing the brightness of the backlight or incorporating a functional film for improving the brightness as the LCD becomes larger. In such a high-brightness type LCD, since the brightness is high, small defects existing in the display often become a problem, and in components having optical characteristics such as a polarizing plate and a retardation plate, The disadvantage of the size that did not become a problem has become a problem. Therefore, while preventing the occurrence of defects in the manufacturing process of each optical member, it is also important to improve the inspection property so that even if a defect occurs, the defect can be reliably recognized as a defect.

  The defect inspection of the polarizing plate is generally a visual inspection by the crossed Nicols method, but for polarizing plates used for large screen TVs of 32 inches or more, various inspections by an automatic inspection device using the crossed Nicols method have been studied. Yes.

  The crossed Nicols method is a method in which two polarizing plates are made to have a dark field with their orientation main axes orthogonal, and a measurement object such as a film is sandwiched between them to observe with transmitted light. By arranging in crossed Nicols, if there is no defect, a black image is input from the imaging unit, but if there is a defect, that portion will not become black. In other words, if there is a foreign matter or a defect in the polarizing plate, it appears as a bright spot, so that the defect inspection can be performed. Here, since the oriented polyethylene terephthalate film uniaxially or biaxially stretched through the pressure-sensitive adhesive layer is bonded to the polarizing plate as a release film, when the optical defect of this release film is added, A bright spot is added, which becomes an obstacle to defect inspection. It has been known so far that foreign matters in the release film and scratches on the surface become bright spots during defect inspection.

However, the oriented film is advantageous from the viewpoint of thinning, but also has a birefringence (phase difference) due to orientation due to stretching, so that incident linearly polarized light becomes elliptically polarized light by transmission, In reality, it will not be in a crossed Nicol state. That is, if the two polarizing plates are simply orthogonal, the amount of visible light input to the imaging unit is affected by the birefringence of the film.
In a film manufactured by stretching, as disclosed in Patent Document 1, a phenomenon called bowing occurs due to stretching of the central portion with respect to the stretched end portion. This is because the film in the process is drawn by heating and stretching in a state where the end is gripped, and the central part of the film to be manufactured is pulled and hangs down due to its own weight or thermal shrinkage stress in the direction of gravity or the direction of progress of the manufacturing process. Is a phenomenon caused by the construction of a catenary curve. For this reason, the birefringence of the oriented film differs in the film width direction as in the dichroism in Patent Document 1. As a result, the position in the width direction at the time of manufacture of a film had the problem that the site | part which cannot perform the defect test | inspection which exists in a film with the center part and edge part of a film with a sufficient precision existed.

  As a film defect detection apparatus that solves such a problem, an inspection apparatus disclosed in Patent Document 2 below is known. This defect inspection apparatus has a polarizing plate for inspection between the light source and the optical path of the imaging unit, and in order to cancel the birefringence (phase difference) of the film, the amount of received visible light input to the imaging unit is This is an apparatus for inspecting defects in a film with a polarizing plate in a crossed Nicol state by adjusting the relative angular position of the polarizing plate for inspection so as to be the minimum value.

  However, in Patent Document 2, when inspecting a film having birefringence variation in the width direction, it is necessary to have a plurality of imaging units and polarizing plates in the width direction. According to the knowledge of the present inventors, at this time, even if the polarizing plate angle is adjusted so that the received light amount of visible light input to the imaging unit becomes the minimum value, uniform light reception at every imaging unit position, that is, in the width direction. It is difficult to obtain the amount, and for example, a difference occurs in the light receiving amount level between the film end and the center in the film width direction. Therefore, when inspecting a film having birefringence variation in the width direction, it is impossible to perform defect inspection with high accuracy at the same time.

  Furthermore, according to the knowledge of the present inventors, in the case of a defect that causes only a small light amount change, a polarizing plate is arranged so that the field of view at the time of crossed Nicol inspection is the darkest, regardless of the defect that causes a large light amount change. In such a case, the contrast difference is further reduced, making detection difficult.

Japanese Examined Patent Publication No. 39-029214 Japanese Patent Laid-Open No. 2007-213016

  An object of the present invention is to provide a defect inspection apparatus capable of accurately inspecting defects even in a film having birefringence variations in the film width direction, and increasing the contrast between a defective portion and a normal portion and inspecting with high accuracy. It is to provide.

  In order to achieve the above object, according to the present invention, there is provided an inspection apparatus for detecting a defect of a long film having a certain width, and illumination means for illuminating the film on one side of the film; A first polarizing plate provided between the illumination unit and the film; a second polarizing plate provided on the other side of the film; and the illumination unit provided on the other side of the film. Light receiving means for receiving transmitted light transmitted through the first polarizing plate, the film, and the second polarizing plate, and the angle of the first polarizing plate is set to the angle of the first polarizing plate. The film defect inspection apparatus is characterized by having angle adjusting means for independently adjusting the angle of the second polarizing plate within the plane of the second polarizing plate within the plane of the second polarizing plate.

  According to still another preferable aspect of the present invention, a plurality of the second polarizing plates and the light receiving means are arranged in the width direction of the film, and the second angle adjusting means is the plurality of second polarizing plates. A defect inspection apparatus for a film is provided.

  According to a preferred embodiment of the present invention, the angle adjusting means for adjusting the angle of the first polarizing plate in the first plane includes an axis that functions as a fulcrum when rotating the first polarizing plate. And a linear motion mechanism that pushes and pulls the first polarizing plate in an approximately rotational direction using the end of the first polarizing plate as a power point.

  According to a preferred embodiment of the present invention, the angle of the first and second polarizing plates is adjusted in a range of at least −8 ° to + 8 ° with a rotation accuracy of 1 ° or less. A defect inspection apparatus is provided.

  According to another aspect of the present invention, there is provided a defect inspection method for detecting a defect in a long film having a certain width, wherein the film is illuminated by illumination means provided on one side of the film. The first polarizing plate is provided between the illumination unit and the film, the second polarizing plate is provided on the other surface side of the film, and the first polarizing plate, the film, and the film illuminated by the illumination unit are provided. The transmitted light transmitted through the second polarizing plate is received by a light receiving means provided on the other side of the film, and the angle of the first polarizing plate is set within the plane of the first polarizing plate. A film defect inspection method is provided, wherein the angle of each of the two polarizing plates is independently adjusted within the plane of the second polarizing plate.

  According to a preferred embodiment of the present invention, a plurality of the second polarizing plates and the light receiving means are arranged in the width direction of the film, and the angle of the second polarizing plate is independently adjusted according to the arrangement position. A film defect inspection method is provided.

  According to a preferred embodiment of the present invention, when adjusting the angle of the first polarizing plate in the first plane, the axis serving as a fulcrum when rotating the first polarizing plate; Provided is a film defect inspection method characterized in that a polarizing plate angle is finely adjusted with a rotation accuracy of 1 ° or less by a linear motion mechanism that pushes and pulls in an approximately rotational direction with an end portion of a first polarizing plate as a force point. Is done.

  According to a preferred embodiment of the present invention, in the region to be inspected of the film, the angle of the first and second polarizing plates is such that the amount of light received by the light receiving means is in the range of 10 to 30 with 256 gradations. Thus, a defect inspection method for a film is provided, which is characterized by inspecting at different angles.

  According to a preferred embodiment of the present invention, in the region to be inspected of the film, the angle of the first and second polarizing plates is such that the amount of light received by the light receiving means is in the range of 30 to 50 with 256 gradations. Thus, a defect inspection method for a film is provided, which is characterized by inspecting at different angles.

  According to a preferred embodiment of the present invention, in the region to be inspected of the film, the angle of the first and second polarizing plates is set to 1 to 2 ° from the state where the amount of light received by the light receiving means becomes the minimum value. There is provided a film defect inspection method characterized by inspecting from a state shifted in range.

  Moreover, according to the preferable form of this invention, defect inspection of the film characterized by applying a defect inspection in the state of the release film before bonding another optical film and an optical member in the film to be inspected. A method is provided.

  According to another aspect of the present invention, there is provided an inspection apparatus for detecting a defect of a long film having a certain width, the illumination unit illuminating the film on one side of the film, and the illumination A first polarizing plate provided between the film and the film; a second polarizing plate provided on the other surface side of the film; and provided on the other surface side of the film and illuminated from the illumination device. Light receiving means for receiving transmitted light transmitted through the first polarizing plate, the film, and the second polarizing plate, and the angle of the first polarizing plate is set to the surface of the first polarizing plate. The defect inspection was carried out by the film defect inspection method, characterized in that it has angle adjusting means for independently adjusting the angle of the second polarizing plate within the plane of the second polarizing plate. A release film characterized by .

  Here, the polarizing plate refers to a plate-like or film-like one having a property of transmitting only light vibrating in a specific direction.

  Here, the release film is used for the purpose of being attached to protect the optical properties so as not to lose the optical properties during the manufacture, inspection and shipment of optical members such as polarizing plates and retardation plates, and to be peeled off during use. Film. For this purpose, an adhesive layer necessary for pasting may be provided on the surface, or a release layer may be provided on the surface so that it can be peeled off during use.

  Here, the state of the release film before bonding another optical film or optical member refers to a state in which a substance having polarization characteristics, that is, a substance that changes the incident polarized light and transmits / outputs it is not bonded. Point to.

  According to the present invention, a defect inspection apparatus that can accurately inspect defects even in a film having birefringence variation in the film width direction, and that can inspect with high accuracy by increasing the contrast between the defect portion and the normal portion. It can be carried out.

It is the schematic perspective view which showed one form of the defect detection apparatus of this invention. It is another schematic perspective view which showed one form of the defect detection apparatus of this invention. It is the schematic sectional drawing which showed one form of the defect detection apparatus of this invention. It is the schematic diagram which showed the polarizing plate angle in the film width direction, and the received light quantity distribution in that case. It is another schematic diagram which showed the polarizing plate angle in the film width direction, and the light-receiving amount distribution in that case. It is the schematic diagram which showed light reception amount distribution in each light receiving means of a film width direction. It is another schematic diagram which showed the polarizing plate angle in the film width direction, and the light-receiving amount distribution in that case. It is another schematic diagram which showed received light amount distribution in each light receiving means of a film width direction. Schematic diagram comparing the relationship between the background noise in the defect detection according to the prior art and the received light amount of the defect part (a), and the relationship between the background noise and the received light amount of the defect part in the defect detection according to the present invention (b). It is. It is the schematic diagram which showed one form of arrangement | positioning of the fulcrum and power point at the time of rotating the 1st polarizing plate in the defect detection apparatus of this invention. It is the schematic diagram which showed one form of the linear motion mechanism which pushes and pulls the 1st polarizing plate in a substantially rotational direction in the defect detection apparatus of this invention. It is the schematic diagram which showed one form of arrangement | positioning of the fulcrum and power point at the time of rotating the 2nd polarizing plate in the defect detection apparatus of this invention. The schematic diagram (a) which showed one form of the mechanism which rotates a 2nd polarizing plate in the defect detection apparatus of this invention, and the schematic diagram (b) which showed one form of rotation of the 2nd polarizing plate by it ). An image (a) obtained by imaging a surface defect generated during film processing at room temperature in a range of 10 to 30 in 256 gradations and a range of 30 to 50 in 256 gradations. An image (a ′), an image (b) obtained by imaging the surface defect generated during film production or heating with the light receiving means of the present invention in the range of 10 to 30 in 256 gradations, and 256 gradations It is the image (b ') imaged as the range of 30-50.

  Hereinafter, it explains in detail using a drawing. As shown in FIG. 1, the defect inspection apparatus of the present invention has a first polarizing plate on one side of the film and a second polarizing plate on the other side parallel to the film in the region to be inspected. And the illumination means for illuminating the film from the outside of the polarizing plate with the first polarizing plate interposed therebetween, and the first polarizing plate, the film and the second polarizing plate have been transmitted on the other side of the film Light receiving means for receiving the transmitted light.

  Examples of the film to which the defect inspection apparatus of the present invention is applied include a film used as a release film for an optical member such as a polarizing plate and a retardation plate, specifically, a plastic film such as a polyethylene terephthalate (PET) film.

  In addition, the polarizing plate that can be applied to the first polarizing plate is not particularly limited as long as it can be polarized without leaving the light from the illumination unit that illuminates the film, and a commercially available polarizing plate can be applied. In order to sufficiently polarize the light that illuminates the light, it is necessary to have a size that can sufficiently cover the illumination range of the illumination means, and preferably a polarizing plate having a larger size in a plane parallel to the film than the illumination means It is good to use. More preferably, when a plurality of illuminating means are used side by side in the film width direction, the crossed Nicols optical system can be adjusted with higher accuracy by using the same number of polarizing plates as the number of illuminating means.

  Similarly, the second polarizing plate is not particularly limited as long as it has a size capable of polarizing the illumination light that passes through the film and enters the light receiving means, and a commercially available polarizing plate can be applied. By using the same number of polarizing plates as each device and arranging each polarizing plate in front of the light receiving part of the light receiving device, the angle of the polarizing plate can be adjusted for each light receiving device, so crossing can be performed with higher accuracy. It is preferable that the Nicol optical system can be adjusted.

  The light receiving means is not particularly limited as long as it can receive the scattered / reflected light from the illuminating means through a polarizing plate. However, a commercially available CCD camera or CMOS can be used because of cost and signal processing ease. It is preferable to use a camera. More preferably, it is preferable to use a line sensor camera in which CCDs or CMOSs as light receiving elements are arranged in a straight line from the installation space and the imaging field of view per camera. In consideration of cost, light receiving accuracy, and inspection range, it is also preferable to use a plurality of light receiving means arranged in the width direction as necessary as shown in FIG.

  The illumination means is preferably capable of uniformly illuminating the inspection range of the film, for example, a line-shaped LED illumination in which light-emitting elements are arranged in a line, a rod-shaped fluorescent lamp, a metal haloloid lamp, etc. A method of illuminating by guiding light from a light source to a rod-shaped light guide using an optical fiber can be applied. In particular, since the amount of illumination light is large, a method of illuminating by guiding light from a metal haloloid lamp light source to a rod-shaped light guide using an optical fiber is preferable. In this case, especially when the width of the film is large and the inspection range is wide, the cost of one long light guide increases. Therefore, in consideration of the cost, the inspection range, and the number of light receiving means, a plurality of illumination means are provided. They may be used side by side in the width direction of the film.

  In addition, with respect to the positional relationship between the film and the first polarizing plate, the second polarizing plate, the illumination means, and the light receiving means, it is possible to receive scattered / reflected light from the illumination means due to defects with as strong an intensity as possible. In order to do so, it is preferable to arrange them in a straight line as shown in FIG. More preferably, the surface of the film to be inspected and the straight line are perpendicular to each other from the viewpoint of ease of installation and maintainability.

  Moreover, about the relationship between a 1st polarizing plate and a 2nd polarizing plate, a defect inspection can be performed by the method similar to the said cross Nicol method by arrange | positioning in the state of the cross Nicol in the said cross Nicol method. In that case, if a defect does not exist, a black image is input from the imaging unit. However, if a defect exists, the portion does not become black. That is, if there are foreign matters or defects in the polarizing plate, they appear as bright spots. The signal obtained by the light receiving means is processed by the signal processing means, and processing such as determination of the presence or absence of defects is performed.

  Further, it is preferable that the first and second polarizing plate angles are independently adjusted. This is because, in the case of a film having birefringence variations in the width direction, the angles of the first and second polarizing plates that are crossed Nicols are different in the width direction of the film. Since the birefringence (phase difference) differs between the film and the vicinity of the film edge, if the first polarizing plate angle and the second polarizing plate angle are set to the same angle in the width direction, an optimal cross in the width direction Since the Nicole condition is not satisfied, a difference occurs in the width direction in the amount of received light entering the light receiving means. In FIG. 4, L, C, and R indicate left, center, and right in the film traveling direction.

  Therefore, as shown in FIG. 5, the first polarizing plate angle and the second polarizing plate angle are adjusted to the angle at which each light receiving unit has the smallest amount of received light with respect to the width direction of the film. Is more preferable because a state close to the optically optimal crossed Nicols condition in the width direction can be obtained. Here, adjusting the polarizing plate angle means that both the first and second polarizing plates are rotated in parallel with the film surface and inward or outward with respect to the traveling direction of the film. Further, the direction and size of the angle to be adjusted differ depending on the polarization characteristics in the width direction of the film. For example, when the polarization characteristics in the width direction of the film are U-shaped as shown in FIG. Therefore, the first and second polarizing plates tend to rotate in the opposite direction between the polarizing plate on the left side of the film and the polarizing plate on the right side of the film. The end tends to have an optimum angle.

  More preferably, the angle adjusting means for adjusting the angle of the first polarizing plate in the first plane includes an axis that serves as a fulcrum when rotating the first polarizing plate, and the first polarizing plate. It is preferable to have a linear motion mechanism that pushes and pulls in the direction of rotation in the direction of rotation with the end of the power point as a power point. This is because the first polarizing plate needs to cover the entire width of the film to be inspected, so for an optical film exceeding 2 m such as for a large LCD TV, the first polarizing plate having a width larger than that is used. Due to need. In order to incline such a large first polarizing plate 2 as shown in FIG. 10 with a rotation accuracy of 1 ° or less, the rotation mechanism using a simple stepping motor or servo motor has poor positioning and reproducibility of the rotation angle. 11, by moving the force point 13 as shown in FIG. 10 by the linear motion mechanism 15 as shown in FIG. 11, the end of the first polarizing plate 2 is pushed and pulled in the rotation direction about the fulcrum 14 as the rotational accuracy. From the viewpoint of Furthermore, it is preferable to drive the linear motion mechanism 15 by a servomotor not only in terms of stopping accuracy but also in terms of confirming the completion of the driving operation by feedback and ensuring torque stability even under heavy loads.

  More preferably, by monitoring the amount of light received by the light receiving means, it is preferable to automatically adjust using an operating means such as a motor so that the optimum angle is obtained. At this time, the polarizing plate angle needs to correspond to the variation in the birefringence variation in the width direction of the film, and the higher the adjustment accuracy of the polarizing plate, the closer to the more complete crossed Nicols state, as a result Since high inspection accuracy can be obtained, the first and second polarizing plate angles are preferably adjusted in a range of −8 ° to + 8 ° with a rotation accuracy of 1 ° or less. As shown in FIGS. 12 and 13, the second polarizing plate angle adjusting mechanism is closer to the fulcrum 18 by a lever-shaped mechanism with the end of the second polarizing plate 3 as the fulcrum 18 as an axis. It is preferable to drive at the force point 17. This simply drives the force point 17 closer to the fulcrum 18 than when the end of the second polarizing plate 3 is directly driven by a rotation mechanism such as a stepping motor or servomotor or a linear motion mechanism using them. Therefore, even if the torque of the driving device 19 of the mechanism for rotating the second polarizing plate in FIG. 13 is small due to the principle of the lever, the second polarizing plate is rotated largely with a small force. This is because it becomes possible. In addition, the rod-shaped portion as shown in FIG. 13 is sufficient for adjusting the angle as very small as −8 ° to + 8 ° as shown in FIG. It is possible to obtain an effect.

  More preferably, in the region to be inspected of the film, the angle of the first and second polarizing plates is inspected by shifting the angle so that the amount of light received by the light receiving means is in the range of 10 to 30 in 256 gradations. That is good. As a result, as shown in FIGS. 14A and 14A, surface defects generated during film processing at room temperature can be clearly captured with higher peak intensity.

  More preferably, in the region to be inspected of the film, the angle of the first and second polarizing plates is shifted so that the amount of light received by the light receiving means is in the range of 30 to 50 with 256 gradations. It is good to inspect. As a result, as shown in FIGS. 14B and 14B, surface defects generated during film production and heating can be captured as a wider image having a larger width.

  More preferably, it is preferable to install the polarizing plate by shifting the angle of the polarizing plate within a range of 1 to 2 ° from the crossed Nicol state. This is because the first and second polarizing plate angles are adjusted to the optimum angles by the above-described method, so that even when the cross-Nicol condition is close to the optimum in the width direction, the cross-sections of each light receiving means are crossed. Since the Nicole state is different, for example, when the number of light receiving means is 5, as shown in FIG. 6, the distribution of the received light amount is different between the vicinity of the center of the film and the end of the film. However, since each light receiving means is adjusted to an optimum polarizing plate angle, for example, it is difficult to lower the baseline of the amount of received light near the end of the film and adjust it to the vicinity of the center. Therefore, as shown in FIG. 7, by adjusting the angle of the received light amount in the direction of increasing the baseline of the received light amount by shifting the angle of the second polarizing plate arranged in front of each light receiving means within the range of 1 to 2 °. Even for a film having a curved distribution of birefringence due to bowing, as shown in FIG. 8, it is possible to obtain linearity by uniformizing the amount of light received by each light receiving means in the width direction.

  This makes it possible to make the detection sensitivity constant in the width direction of the film, and there is no defect as shown in FIG. 9B by the technique of the present invention compared to the conventional technique as shown in FIG. 9A. The baseline of the received light amount of the part is adjusted in a brighter direction, and the background noise generated by light scattering by the air layer is covered, so that the noise N can be reduced to N ′ and the S / N ratio is increased. Raised. As a result, it becomes possible to bring the threshold for detecting the defect closer to the baseline of the received light amount in the portion having no defect than in the prior art, and the width h for detecting the received light amount exceeding the threshold due to the defect also becomes h ′. Therefore, it is possible to perform inspection with higher accuracy and fewer false detections.

[Example 1]
“Lumiler” [38R64] manufactured by Toray was prepared as a sample to be inspected.

  In the defect inspection apparatus of the present invention, a 250 W metal halide (BMH-250A manufactured by Mejiro Precision) is used as illumination means, a CCD camera (P3-80-8K-40 manufactured by DALSA) having a resolution of 25 μm and second polarization as light receiving means. A plurality of plates were combined, and an inspection width of 1255 mm was imaged on the sample to be inspected to confirm the amount of received light.

  Evaluation of the amount of received light in the base is a state in which the average value when the angle of both the first polarizing plate and the second polarizing plate is adjusted and the light receiving amount in the entire inspection width is evaluated with 256 gradations is minimized. The difference between the maximum value and the minimum value of the amount of received light was confirmed, and this difference was evaluated as the variation in the amount of received light. It was confirmed that the received light amount variation in the example was 20 or less.

  Furthermore, it was confirmed that by adjusting the angles of both the first polarizing plate and the second polarizing plate, the amount of received light in the base can be adjusted to a range of 10 to 30 and 30 to 50 in 256 gradations. From this, it was confirmed that, under the conditions of Example 1, the inspection accuracy was uniform even in the film having the birefringence variation in the film width direction, and the inspection could be performed with high accuracy.

  FIG. 14 shows a specific image of surface defects taken under the conditions in Example 1. An image (a) obtained by imaging a surface defect generated during processing of a PET film at room temperature in a range of 10 to 30 in 256 gradations, and a range of 30 to 50 in 256 gradations. When the images (a ′) were compared, the peak intensity from the baseline was 40 for (a) and 17 for (a ′). In other words, in detecting defects on the film surface at room temperature in this way, the S / N ratio can be improved by imaging the light receiving amount of the light receiving means of the present invention in the range of 10 to 30 with 256 gradations. Realized.

In addition, an image (b) obtained by imaging the surface defects generated at the time of heat stretching in the PET film production with the light receiving means of the present invention in the range of 10 to 30 in 256 gradations, and the range of 30 to 50 in 256 gradations As a result, the peak intensity from the baseline was 80 in (b) and 70 in (b ′), but the detected width was 760 in (b), (b ′). ) Showed a big difference with 940. In other words, in detecting defects generated on the film surface in the heating process in this way, the amount of light received by the light receiving means of the present invention is imaged in the range of 30 to 50 with 256 gradations, so that the amount of light received exceeding the threshold value can be obtained. Improvement of the detection width h was realized.
[Comparative Example 1]
Using the same apparatus and the same film in Example 1, the angle of the second polarizing plate installed on the camera side is fixed uniformly, and only the angle of the first polarizing plate installed on the light source side is adjusted. Thus, as described in Patent Document 2, images were picked up in the same manner as in Example except that only the relative angle of the polarizing plate was adjusted, and the amount of received light was confirmed.

  Under the conditions of Comparative Example 1, the received light amount variation was larger than 30, and the base received light amount could not be adjusted in the range of 10 to 30 and 30 to 50 in 256 gradations. From this, under the conditions of the comparative example, it was confirmed that the film having birefringence variation in the film width direction does not have uniform inspection accuracy and cannot perform inspection with high accuracy.

  The present invention can be applied not only to a film defect detection apparatus but also to a defect detection apparatus for transparent paper or sheet-like objects, but the application range is not limited thereto.

DESCRIPTION OF SYMBOLS 1 Film to be inspected 2 1st polarizing plate 3 2nd polarizing plate 4 Illumination means 5 Light receiving means 6 Signal processing means 7 Film obtained from the left part at the time of manufacture 8 Film obtained from the center at the time of manufacture 9 Production Sometimes obtained from the right part of the film 10 Received light amount distribution in the film obtained from the left part during production 11 Received light quantity distribution in the film obtained from the central part during production 12 In the film obtained from the right part during production Received light amount distribution 13 Power point when rotating the first polarizing plate 14 Support point when rotating the first polarizing plate 15 Linear motion mechanism that pushes and pulls the first polarizing plate substantially in the direction of rotation 16 Driving the linear motion mechanism Device 17 Power point when rotating the second polarizing plate 18 Support point when rotating the second polarizing plate 19 Driving device of the mechanism for rotating the second polarizing plate

Claims (12)

An inspection apparatus for detecting defects in a long film, wherein the illumination means illuminates the film on one side of the film, and a first polarizing plate provided between the illumination means and the film A second polarizing plate provided on the other surface side of the film, and provided on the other surface side of the film and illuminated from the illuminating means, the first polarizing plate, the film and the second polarized light. Light receiving means for receiving transmitted light transmitted through the plate, the angle of the first polarizing plate within the plane of the first polarizing plate, and the angle of the second polarizing plate with the second A defect inspection apparatus for a film, characterized by having an angle adjusting means for adjusting independently in the plane of the polarizing plate. A plurality of the second polarizing plates and the light receiving means are arranged in the width direction of the film, and the second angle adjusting means is provided in each of the plurality of second polarizing plates. The film defect inspection apparatus according to claim 1. The angle adjusting means for adjusting the angle of the first polarizing plate in the first plane includes an axis that serves as a fulcrum when rotating the first polarizing plate, and an end of the first polarizing plate. The film defect inspection apparatus according to claim 1, further comprising a linear motion mechanism that pushes and pulls in a substantially rotating direction as a force point. The angle of said 1st, 2nd polarizing plate is adjusted in the range of -8 degrees-+8 degrees at least with the rotation precision of 1 degrees or less, The film in any one of Claims 1-3 characterized by the above-mentioned. Defect inspection equipment. A defect inspection method for detecting a defect in a long film, wherein the film is illuminated by illumination means provided on one side of the film, and a first polarizing plate is provided between the illumination means and the film. The second polarizing plate is provided on the other surface side of the film, and the transmitted light that is illuminated from the illumination means and passes through the first polarizing plate, the film, and the second polarizing plate is transmitted to the film. Light is received by a light receiving means provided on the other side, and the angle of the first polarizing plate is in the plane of the first polarizing plate, and the angle of the second polarizing plate is in the plane of the second polarizing plate. Film defect inspection method, characterized in that each is adjusted independently. The said 2nd polarizing plate and the said light-receiving means are multiply arranged by the width direction of the said film, and the angle of the said 2nd polarizing plate is adjusted independently according to an arrangement position, The characterized by the above-mentioned. Film defect inspection method. When the angle of the first polarizing plate is adjusted in the first plane, the axis serving as a fulcrum when rotating the first polarizing plate and the end of the first polarizing plate as a power point The film defect inspection method according to claim 5, wherein the polarizing plate angle is finely adjusted with a rotation accuracy of 1 ° or less by a linear motion mechanism that pushes and pulls in a substantially rotating direction. The angle of said 1st, 2nd polarizing plate is test | inspected by shifting angle so that the light-receiving amount in the said light-receiving means may be in the range of 10-30 in 256 gradations. The film defect inspection method described in 1. The angle of said 1st, 2nd polarizing plate is test | inspected by shifting angle so that the light-receiving amount in the said light-receiving means may be in the range of 30-50 in 256 gradations. The film defect inspection method described in 1. The inspection is performed from a state in which the angles of the first and second polarizing plates are shifted within a range of 1 to 2 ° from a state in which the amount of light received by the light receiving unit is a minimum value. The defect inspection method of the film of crab. The defect inspection method for a film according to any one of claims 5 to 10, wherein the defect inspection is applied in a state of a release film before bonding another optical film or an optical member. A mold release film, wherein the defect inspection is performed by the defect inspection method according to claim 5.