JP2008298566A - Apparatus and method for inspecting defect of film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect slight thickness irregularities and coating irregularities of optical compensation films and the like. <P>SOLUTION: A light source part 15 is arranged at the lower-side surface of a continuously transferred film to be inspected 7 to irradiate the film to be inspected 7 with light. A light-receiving device 16 for receiving transmitted light from the film to be inspected 7 is arranged in such a way as to look down the film to be inspected 7, and its optical axis P is provided with an angle θ1 of intersection with a reference line (normal) Ln perpendicular to and the film 7 and rotated on the reference line Ln as a center of rotation by an angle θ2 of rotation with respect to a slow axis Lm of a liquid crystal layer. A convex lens 21 is arranged between an imaging lens 16a and the film to be inspected 7 and constitutes a telecentric optical system with the imaging lens 16a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a film defect inspection apparatus and method for irradiating a film to be inspected with light and detecting a film defect based on the transmitted light.

  An optical compensation film (retardation film) that can improve the viewing angle of a liquid crystal display device by forming a liquid crystal layer having optical anisotropy on a transparent film is known. For example, this optical compensation film is manufactured through various processes in which an alignment film is formed on a transparent film, a liquid crystal is applied thereon and dried to form a liquid crystal layer. The manufacturing process is under strict control, but due to various factors, defects such as contamination of foreign matter, uneven molecular orientation due to adhesion, uneven thickness of the transparent film serving as a support, and uneven coating on the liquid crystal layer can occur. It is difficult to eliminate them completely. Therefore, so-called in-line inspection is performed on the production line, and the position on the optical compensation film where the above-described defect occurs is grasped.

A technique for inspecting defects such as the optical compensation film as described above is known from Patent Document 1. In Patent Document 1, an optical compensation film to be inspected is passed between a pair of polarizing plates in a crossed Nicol arrangement, light from a light source is incident on the optical compensation film via one polarizing plate, and transmitted through the optical compensation film. Then, the light emitted from the other polarizing plate is received by the light receiver. In addition, the optical axis of the light receiver intersects with the reference line perpendicular to the film surface in the range of 30 ° to 50 °, and the reference line is the rotation center, and the range of −60 ° to + 60 ° from the film transport direction. By arranging it at the position rotated in step 1, the slight film thickness unevenness and the coating thickness unevenness are detected sharply.
JP-A-2005-250715

  By the way, as a light receiver used for the defect inspection described above, a combination of a line sensor and a photographing lens is used corresponding to the inspection area on the inspection target film being in a line shape. Due to the angular characteristics, that is, the optical anisotropy of the film to be inspected, the amount of light received by the light receiver becomes uneven in the inspection area. Specifically, the received light amount unevenness occurs such that the received light amount is low at one end side of the inspection area and high at the other end side. For this reason, the amount of light received at the other end becomes too large, so that the sensor is saturated and it becomes impossible to detect a defect or a certain S / N ratio cannot be secured in the inspection area. There has been a problem that the defect detection accuracy varies.

  The present invention has been made in view of the above problems, and is a film that can improve the amount of light received by a light receiver and detect defects such as slight thickness unevenness, coating unevenness, and molecular orientation unevenness of a film to be inspected. An object is to provide a defect inspection apparatus and method.

  In achieving the above object, the film defect inspection apparatus according to claim 1 is configured to collect a light source disposed on one surface side of the inspection target film and irradiating the inspection target film with light transmitted through the inspection target film. An optical lens of a photographic lens and an inspection object having a photographic lens that illuminates and a line sensor that receives light collected by the photographic lens and arranged in a line and outputs a light reception signal corresponding to the amount of light received A light receiving device, a light source, and an inspection device provided with a crossing angle θ1 between a reference line perpendicular to the plane of the film and a rotation angle θ2 from the slow axis of the film to be inspected with the reference line as the rotation center A first polarizing plate disposed between the target film and a second polarized light disposed between the light receiver and the inspection target film and having a transmission axis inclined with respect to the transmission axis of the first polarizing plate. Plate, light source and light receiving Receiving light amount correcting means for correcting the light receiving amount of the light transmitted through the inspection target film received by each light receiving element of the line sensor so as to be uniform. .

  In the defect inspection apparatus for a film according to claim 2, the received light amount correction means is a correction optical system disposed between the photographing lens and the film to be inspected, and constitutes a telecentric optical system together with the photographing lens. is there.

  In the film defect inspection apparatus according to the third aspect, the photographing lens is constituted by a telecentric optical system, and the photographing lens is also used as a received light amount correcting means.

  5. The defect inspection apparatus for a film according to claim 4, wherein the received light amount correction means is disposed between the light source and the first polarizing plate so as to be inclined with respect to the inspection object film, and scatters light from the light source. It is a scattering plate that irradiates the film.

  In the film defect inspection apparatus according to claim 5, the light receiving amount correction means is a light control film.

  In the film defect inspection apparatus according to the sixth aspect, the received light amount correcting means is a filter whose transmittance continuously changes along the arrangement direction of the light receiving elements of the line sensor.

  In the film defect inspection apparatus according to claim 7, a filter whose transmittance continuously changes along the arrangement direction of the light receiving elements of the line sensor is arranged between the line sensor and the photographing lens.

  9. The film defect inspection apparatus according to claim 8, wherein the light control film as the light receiving amount correcting means or the filter whose transmittance continuously changes along the arrangement direction of the light receiving elements of the line sensor is used as the light source and the first polarization. It is arranged between the boards.

  In the defect inspection apparatus for a film according to claim 9, the intersection angle θ1 satisfies a condition of “30 ° ≦ θ1 ≦ 50 °”, and the rotation angle θ2 is “−60 ≦ θ2 ≦ −30 °” or “+ 30 ≦ This satisfies the condition of “θ2 ≦ + 60 °”.

  In the film defect inspection apparatus according to claim 10, the first and second polarizing plates are arranged substantially in parallel with the film to be inspected.

  The film defect inspection apparatus according to claim 11 is provided with a conveying means for continuously conveying the inspection object film, and the light receiver receives light every time the inspection object film is conveyed for a certain length. is there.

  In the film defect inspection method according to claim 12, a line sensor is used at a position tilted with respect to a reference line perpendicular to the surface of the inspection target film and rotated from the slow axis of the inspection target film around the reference line. In addition to receiving light, the received light amount of the light transmitted through the inspection target film received by each light receiving element of the line sensor is made uniform by the received light amount correction means arranged at any position between the light source and the light receiver. It is intended to correct to.

  According to the present invention, the amount of light received by the light receiver using the correction optical system, the light control film, the scattering plate, a filter whose density changes continuously, and the like is used to determine the optical anisotropy of the film to be inspected. The film thickness is almost uniform without being influenced by the sensor, so that it is possible to detect the slight film thickness unevenness and the coating thickness unevenness sensitively based on the signal from the light receiver. A very high-precision inspection can be performed on the thickness of the workpiece.

  A defect inspection apparatus according to a first embodiment of the present invention is shown in FIG. The long transparent resin film 3a sent out from the film roll 3 is sent to the alignment film forming apparatus 4 that forms the alignment film. The alignment film forming apparatus 4 applies a coating solution containing an alignment film forming resin to the surface of the transparent resin film 3a and then heat-drys to form an alignment film forming resin layer. Further, the alignment film forming apparatus 4 performs a rubbing process on the alignment film forming resin layer to obtain an alignment film. As is well known, the rubbing treatment is performed by rubbing the alignment layer forming resin layer in a predetermined direction with a cloth or the like.

  The transparent resin film 3a on which the alignment film is formed is sent to the liquid crystal layer forming apparatus 5. The liquid crystal layer forming apparatus 5 applies a coating liquid containing a liquid crystalline compound on the alignment film of the transparent resin film 3a, evaporates the solvent of the coating liquid, and then heats to the liquid crystal phase forming temperature to form a liquid crystal layer. To do. Thereafter, the liquid crystal layer is irradiated with ultraviolet rays to crosslink the liquid crystal layer. In this way, a liquid crystal layer is formed by aligning liquid crystals in a predetermined direction to produce a retardation film having optical anisotropy. This retardation film is used, for example, as a transmission type optical compensation film for improving the viewing angle.

  The defect inspection apparatus 10 uses the retardation film manufactured as described above as a film to be inspected (hereinafter referred to as a film to be inspected) 7, thickness unevenness, coating unevenness of a coating liquid containing a liquid crystalline compound, and molecular orientation unevenness. Inspect and detect various defects such as For example, for thickness unevenness and coating unevenness, a defect having a thickness difference of about 1 nm to 1 μm and a width of about 0.1 mm to 50 mm can be detected.

  The film to be inspected by the defect inspection apparatus of the present invention and the manufacturing method thereof are not limited to those described above, and can be used for various films having optical anisotropy (birefringence).

  The transport mechanism 11 transports the inspection target film 7 in one direction (S direction) at a predetermined speed. An inspection stage is provided in the conveyance path of the inspection object film 7, and two guide rollers 12 and 13 are arranged on the inspection stage at a predetermined interval. The inspection target film 7 is hung between the guide rollers 12 and 13 and held in a flat shape. The guide rollers 12 and 13 are rotatable, and rotate following the conveyance of the inspection object film 7. Note that, on the inspection stage, the inspection object film 7 is conveyed in a posture with the liquid crystal layer down, but the direction is not limited to this.

  The inspection stage is provided with a light source unit 15 and a plurality of light receivers 16. The light source unit 15 is disposed on the lower side of the conveyance path, that is, on the lower surface side (liquid layer side) of the inspection target film 7 and irradiates light toward the inspection target film 7 being conveyed. The light source unit 15 may employ various configurations as long as it illuminates the inspection area 17 inclined with respect to the width direction (M direction) of the inspection target film 7 as described later. In this example, a plurality of tubular lamps 15 a (see FIG. 3) of about 100 to 200 W are arranged in the width direction of the inspection target film 7 in a posture inclined with respect to the width direction of the inspection target film 7.

  The plurality of light receivers 16 are arranged in a line along the width direction of the inspection target film 7 on the upper side of the conveyance path, that is, on the upper surface side of the inspection target film 7. Each light receiver 16 is configured by a linear array camera including a photographing lens 16a and a line sensor 16b (see FIG. 4) including a large number of light receiving elements arranged in a line. As the line sensor 16b, for example, a CCD type or a MOS type can be used.

  Each time the inspection object film 7 is conveyed for a certain length, the light receiver 16 takes an image of the inspection area 17 of the inspection object film 7 and converts it into an electrical light reception signal for output. The inspection area 17 has a long line in one direction corresponding to the light receiving elements of the line sensor 16b being arranged in a line. In addition, although the light source part 15 is arrange | positioned at the liquid crystal layer side, the structure which arrange | positions the light receiver 16 at the liquid crystal layer side and arrange | positions the light source part 15 on the surface side opposite to the liquid crystal layer side may be sufficient.

  As will be described later, each light receiver 16 has a posture rotated by a predetermined angle with respect to the slow axis of the film 7 to be inspected. In this example, since the slow axis of the inspection object film 7 is in a direction substantially coincident with the transport direction, the inspection area 17 is inclined with respect to the width direction of the inspection object film 7. By arranging a plurality of light receivers 16 along the width direction as described above, the inspection areas 17 inclined in the width direction are arranged in the width direction, and the actually used region in the width direction of the inspection target film 7 is inspected. I can do it.

  The distance between the light receiver 16 and the inspection target film 7 and the length of the inspection area 17 can be determined as appropriate. In this example, the distance between the light receiver 16 and the inspection target film 7 is 1500 mm, and the length of the inspection area. The angle at which the inspection target area 17 is desired from the light receiver 16 is 9.5 degrees. Although it is not always necessary because the received light amount unevenness for each point in the inspection area 17 is eliminated by using the received light amount correcting means, which will be described in detail later, it is not always necessary. It is preferable to reduce the desired angle.

  The first polarizing plate 18 is disposed between the light source unit 15 and the inspection target film 7, and the second polarizing plate 19 is disposed between the inspection target film 7 and the light receiver 16 so as to be parallel to the inspection target film 7. It is arranged. Thereby, the light from the light source unit 15 is irradiated onto the film 7 through the first polarizing plate 18, and the light receiver 16 receives the light transmitted through the second polarizing plate 19.

  The first polarizing plate 18 and the second polarizing plate 19 have a crossed Nicols (orthogonal) arrangement in which their respective transmission axes (polarization directions) are orthogonal. In addition, the mutual angle of each transmission axis of this 1st polarizing plate 18 and the 2nd polarizing plate 19 can be suitably set in the range which is not parallel according to the characteristic of the test object film 7, etc. Moreover, the transmission axis direction of each polarizing plate 18 and 19 with respect to the inspection object film 7 can be set as appropriate. Furthermore, in the case of the inspection object film 7 in which the polarizer is integrally formed, the polarizer of the inspection object film 7 can be used as the first polarizing plate 18 or the second polarizing plate 19.

  A convex lens 21 is disposed between each light receiver 16 and the second polarizing plate 18. The convex lens 21 is a correction optical system as a received light amount correcting means for correcting the received light amount uniformly by eliminating unevenness of the received light amount of the line sensor 16b at each position of the inspection area 17. The convex lens 21 and the photographing lens 16a constitute a telecentric optical system. This telecentric optical system is an object-side telecentric optical system or a both-side telecentric optical system, and condenses light, which is parallel to the optical axis P of the photographic lens 16a, from the light emitted from the inspection object film 7 on the line sensor 16b. The received light amount unevenness due to the optical anisotropy of the inspection object film 7 is eliminated.

  As will be described later, when the crossing angle θ1 is large, the defect detection sensitivity is high, but the light reception amount unevenness of the line sensor 16b with respect to each position of the inspection area 17 due to the viewing angle characteristics of the inspection target film 7 is large. Therefore, the received light amount correction means is particularly effective.

  The configuration as the correction optical system is not limited to the convex lens, and various lens configurations can be used. Needless to say, a photographic lens configured as a telecentric optical system can be used.

  The light reception signal from each light receiver 16 is sent to the signal processing device 22. The guide roller 13 is provided with an encoder 23 that generates one encode pulse signal each time the guide roller 13 rotates by a certain angle, that is, every time the film 7 to be inspected is conveyed by a certain length. The encode pulse signal from the encoder 23 is sent to the signal processing device 22 as information for specifying the position of the defect.

  FIG. 2 shows the configuration of the signal processing device 22. A light reception signal from each light receiver 16 is input to the image enhancement circuit 25. The image emphasizing circuit 25 performs an emphasis process for emphasizing a defect signal of the inspection target film 7 on the light reception signal. Examples of enhancement processing include processing for removing low-frequency and high-frequency noise components in the received light signal, and spatial filter processing for enhancing luminance changes. In addition to such processing, shading correction or the like for correcting a decrease in the amount of light at the periphery of the photographing lens 16a may be performed.

  The gain correction circuit 26 performs gain correction on the light reception signal from the image enhancement circuit 25 and automatically adjusts the light reception signal so as to have an appropriate signal level. The gain-corrected light reception signal is sent to the determination processing unit 27. The determination processing unit 27 includes a binarization circuit 27a that binarizes the light reception signal with a predetermined threshold, and determines the presence or absence of a defect based on the binarized light reception signal. When a defect is detected by this determination, the determination processing unit 27 stores the position information of the defect in the inspection target film 7 in the position memory 27b, and also receives the light reception signal for one line including the defect and the photoelectric signals of several lines before and after that. The signal is stored in the image memory 27c. The defect position information can be calculated from the encode pulse signal from the encoder 23 and the signal position corresponding to the defective portion of the light reception signal. The monitor 28 displays an image created based on the position information stored in the position memory 27b and the photoelectric signals for several lines stored in the image memory 27c.

  As shown in FIG. 3, the light receiver 16 has an angle θ1 (hereinafter referred to as an intersection angle) θ1 between the optical axis P and a reference line (normal line) Ln perpendicular to the inspection target film 7 (θ1 ≠). 0), the inspection object film 7 is arranged so as to have an overhead view. By providing the crossing angle θ1, the ratio of the received light signal level when the defect is detected with respect to the received light signal level when the normal formation is detected, that is, the S / N ratio of the received light signal can be increased. . If the intersection angle θ1 is increased in this way, the S / N ratio can be increased. However, if the intersection angle θ1 is increased too much, the S / N ratio is decreased, so that “30 ° ≦ θ1 ≦ 50 °” is satisfied. It is preferable to set to.

  Further, as shown in FIG. 4 as viewed from above, the light receiver 16 rotates between the optical axis P and the slow axis Lm of the inspection object film 7 in a direction rotating around the reference line Ln. An angle (hereinafter referred to as a rotation angle) θ2 is given (θ2 ≠ 0). By providing the rotation angle θ2, the S / N ratio of the received light signal is further increased. If the rotation angle θ2 is excessively increased, the S / N ratio is decreased. Therefore, the rotation angle θ2 is preferably set within an angle range of about 30 ° around the direction rotated 45 ° with respect to the slow axis Lm. . That is, for example, when viewed from one surface side, if the slow axis Lm is the reference (0 °), the clockwise direction is positive and the counterclockwise direction is negative, the rotation angle θ2 is “−60 ≦ θ2 ≦ −30. It is preferable to satisfy the condition of “°” or “+ 30 ≦ θ2 ≦ + 60 °”. In FIG. 4, the polarizing plates 18 and 19 are omitted.

  In this way, by arranging the light receiver 16 at the crossing angle θ1 and the rotation angle θ2 and performing the inspection, it is possible to detect even a very slight thickness unevenness having a depth of about 1 nm. Depending on the direction of the slow axis Lm and the rotation angle θ2, the inspection area 17 may not be inclined in the width direction of the film 7 to be inspected, and the longitudinal direction may coincide with the width direction.

  The operation of the above configuration will be described. The retardation film produced by the alignment film forming device 4 and the liquid crystal layer forming device 5 is sent to the defect inspection device 10 as the inspection object film 7, and further conveyed downstream through the inspection stage. During the conveyance of the inspection stage, the light from the light source unit 15 is irradiated onto the inspection target film 7 through the first polarizing plate 18, and one line for each line is received by each light receiver 16 every time the inspection target film 7 is fed for a certain length. Each of the inspection areas 17 is photographed.

  The light emitted from the light source unit 15 passes through the first polarizing plate 18, and is made only a component of linearly polarized light and enters the inspection object film 7. The linearly polarized light incident on the inspection object film 7 is emitted as elliptically polarized light due to the optical anisotropy of the inspection object film 7, and is incident on the second polarizing plate 19. When the elliptically polarized light enters the second polarizing plate 19, only the linearly polarized light component in the transmission axis direction of the second polarizing plate 19 among the light components is transmitted and enters the convex lens 21.

Light is incident on each position of the inspection area 17 from various directions through the first polarizing plate 18 from the light source unit 15, and light is emitted in various directions from the opposite surface accordingly. Accordingly, the degree of influence of the optical anisotropy of the inspection target film 7 is different, and the light enters the second polarizing plate 19. For this reason, if the traveling direction is different, the size of the linearly polarized light component transmitted through the second polarizing plate changes, which causes unevenness in the amount of received light. However, since the convex lens 21 forms a telecentric optical system together with the photographing lens 16a, the light transmitted through the inspection object film 7 and the second polarizing plate 19 is emitted in a direction parallel to the optical axis P of the photographing lens 16a. Only the light component is received by the line sensor 16b through the photographing lens 16a. For this reason, the light reception by the line sensor 16b does not cause unevenness in the amount of light received due to the optical anisotropy of the inspection object film 7.

  As described above, light reception by each of the light receivers 16 is repeatedly performed, and a light reception signal based on the amount of light reception is sent to the signal processing device 22, and a defect of the inspection target film 7 is determined based on a change in the light reception signal and the like. . For example, when a normal part of the inspection object film 7 is received, the elliptically polarized light component of the light transmitted through the normal part is substantially constant and is transmitted through the second polarizing plate 19 and received by the light receiver 16. The amount of light emitted is also constant. On the other hand, when light passes through the defective portion, the transmitted elliptically polarized light component is different from the normal portion, and the amount of light received by the light receiver 16 is different, and the defective portion is detected by the change. .

  Although defect detection is performed in this manner, since there is no unevenness in the amount of light received due to the optical anisotropy of the inspection object film 7 as described above, the dynamic range of the line sensor 16b is used effectively in the inspection area 17. Defects such as thickness unevenness, coating unevenness, and molecular orientation unevenness can be accurately detected with the same accuracy, and thickness unevenness and coating unevenness with a very slight thickness difference can also be detected.

  FIG. 5 shows an example in which a filter whose transmittance is continuously changed is used as the received light amount correction means. In addition, except being demonstrated below, it is the same as that of 1st embodiment, the same code | symbol is attached | subjected to the substantially same structural member, and the description is abbreviate | omitted.

  A filter unit 31 is disposed between the light source unit 15 and the first polarizing plate 18. As shown in FIG. 6, the filter unit 31 is provided with a filter 32 at a position corresponding to each inspection area 17, and light from the light source unit 15 passes through the filter 32 and the first polarizing plate 18 to be inspected film 7. Is irradiated.

  Each filter 32 has a light transmittance continuously decreasing from one end side to the other end side in the longitudinal direction of the inspection area 17 indicated by an arrow, that is, the density increases. 7 is arranged in such a direction that the density on the side where the amount of received light is large is high due to the optical anisotropy 7 and the density on the side where the amount of received light is small is low. Further, the density change rate of the filter 32 is determined based on the characteristics of the inspection target film 7 to be inspected so that the unevenness of the amount of received light for one line by the light receiver 16 is eliminated and becomes almost uniform. As such a filter 32, for example, a trade name “variable density filter (manufactured by Edmund Optics Japan Ltd.)” can be used.

  According to this embodiment, since the light irradiation amount is reduced by the filter 32 in the portion of the inspection target film 7 where the amount of received light increases due to the optical anisotropy of the inspection target film 7, as a result, the inside of the inspection area 17 is substantially reduced. Light can be received with a uniform amount of received light.

  It is preferable that the filter unit 31 is disposed between the light source unit 15 and the first polarizing plate 18 as in this example, but the filter unit 31 is disposed at any position between the line sensor 16b and the light source unit 15. You can also For example, the filter unit 31 may be disposed between the first polarizing plate 18 and the inspection target film 7, between the second polarizing plate 19 and the inspection target film 7, and between the second polarizing plate 19 and the photographing lens 16a. . Further, as shown in FIG. 7, it is also preferable to provide a filter 33 whose light transmittance continuously changes on the front surface of the line sensor 16b. The filters 32 and 33 may have a characteristic of cutting an unnecessary wavelength region in addition to a type in which the light amount is substantially uniformly reduced for each wavelength of illumination light like a so-called ND filter.

  It is also effective to use a light control film 35 for controlling the direction of transmitted light as shown in FIG. The light control film 35 has a structure in which a large number of opaque louvers 36 arranged in parallel with each other at minute intervals are sandwiched between a pair of transparent films 37, and enters one surface and exits from the other surface. The light irradiation direction is restricted to the direction parallel to the louver 36, that is, the normal direction of the surface of the light control film 35. As such a light control film 35, the thing by Sumitomo 3M Co., Ltd. can be used, for example.

  The light control film 35 is disposed between the light source unit 18 and the first polarizing plate 18, for example, similarly to the filter unit 31. Further, the light control film 35 is disposed in parallel with the inspection target film 7 so that the direction of light emitted from the light control film 35 is the normal direction of the inspection target film 7. According to this, since only light in almost one direction enters the inspection object film 7 and is transmitted therethrough, no change in the amount of light received due to optical anisotropy occurs, and a uniform amount of light received in the inspection area 17 is obtained. be able to. The light control film 35 may be disposed at any position between the light receiver 16 and the light source unit 15 as in the filter unit 31. However, as in this example, the light source unit 18 and the first polarizing plate are disposed. 18 is preferable.

  As shown in FIG. 9, a scattering plate 38 disposed in an inclined posture between the light source unit 15 and the first polarizing plate 18 can also be used as the received light amount correction unit. The scattering plate 38 scatters and emits light incident from one surface. Due to the optical anisotropy of the inspection target film 7, the scattering plate 38 is disposed in an inclined posture so as to approach the inspection target film 7 as the light receiving amount decreases. Thereby, the inspection area 17 is illuminated with a larger amount of light as the light receiving amount becomes smaller due to optical anisotropy, and the light receiving amount of the inspection area 17 by the light receiver 16 is made substantially uniform. In addition, the scattering plate 38 can be disposed in an inclined posture together with the light source unit 15.

  An example of the waveform of the light reception signal from the light receiver 16 when the scattering plate 38 is used as in the example of FIG. 9 is shown in FIG. FIG. 11 shows the waveform of the light reception signal when light is received without using the light receiving amount correction means such as the scattering plate 38. In any case, the photographing distance, that is, the distance between the light receiver 16 and the inspection object film 7 is 1500 mm, the inspection area 17 is 250 mm, and the angle at which the light receiver 16 desires the inspection area 17 is 9.5 °. Is. The intersection angle θ1 is “40 °”, and the rotation angle θ2 is “−45 °”. As the scattering plate, Acrylite (trade name) No. 422 was used and tilted at an angle of 15 °.

  When the scattering plate 38 is not used, the waveform of the light reception signal is inclined, and the amount of light received by the line sensor 16b is excessive in the vicinity of one end of the inspection area 17, whereas the signal change cannot be detected. When the scattering plate 38 is used, it can be seen that a substantially flat light reception signal waveform is obtained, and unevenness in the amount of light received due to optical anisotropy is eliminated. When the scattering plate 38 is not used, the S / N ratio of the inspection area 17 is “1.5” at one end, “2.5” at the center, and “3.5” at the other end. Whereas a difference of “2.0” occurred in the / N ratio, when the diffuser plate was used, the S / N ratio was “3.0” at any point in the inspection area, which was useful for defect detection. Good results were obtained.

It is the schematic which shows the defect inspection apparatus which implemented this invention. It is a block diagram which shows the structure of the signal processing apparatus which determines a defect based on a light received signal. It is explanatory drawing explaining intersection angle (theta) 1 of a light receiver. It is explanatory drawing explaining rotation angle (theta) 2 of a light receiver. It is the schematic which shows the defect inspection apparatus which has arrange | positioned the filter unit. It is explanatory drawing which shows the relationship between the filter of a filter unit, and an inspection area. It is explanatory drawing which shows the example which has distribute | arranged the filter between the line sensor and the imaging lens. It is a fragmentary sectional view which shows the structure of a light control film. It is explanatory drawing which shows the structure of the defect inspection apparatus which has arrange | positioned the scattering plate. It is a graph which shows an example of the waveform of the light reception signal obtained when a scattering plate is used. It is a graph which shows an example of the waveform of the light reception signal obtained when a scattering plate is not used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 7 Inspection object film 10 Defect inspection apparatus 15 Light source part 16 Light receiver 16a Shooting lens 16b Line sensor 18, 19 Polarizing plate 21 Convex lens 32 Filter 35 Light control film 38 Scattering plate

Claims (12)

In the film defect inspection apparatus for detecting defects in the inspection target film based on the light reception signal obtained by receiving the light transmitted through the inspection target film,
A light source disposed on one side of the inspection target film and irradiating the inspection target film with light;
A photographic lens that collects light that has passed through the film to be inspected and a line sensor that includes a plurality of light receiving elements arranged in a line, receives light collected by the photographic lens, and outputs a light reception signal corresponding to the amount of light received A crossing angle θ1 is provided between the optical axis of the photographing lens and a reference line perpendicular to the surface of the inspection target film, and a rotation angle from a slow axis of the inspection target film with the reference line as a rotation center. a receiver disposed at a position of θ2,
A first polarizing plate disposed between the light source and the inspection target film;
A second polarizing plate disposed between the light receiver and the inspection target film, the transmission axis of which is inclined with respect to the transmission axis of the first polarizing plate;
Received light amount correction that is arranged at any position between the light source and the light receiver and corrects the received light amount of the light transmitted through the inspection target film received by each light receiving element of the line sensor to be uniform. A defect inspection apparatus for a film.   2. The film defect inspection according to claim 1, wherein the received light amount correction means is a correction optical system disposed between a photographing lens and a film to be inspected, and constitutes a telecentric optical system together with the photographing lens. apparatus.   2. The film defect inspection apparatus according to claim 1, wherein the photographing lens is constituted by a telecentric optical system, and the photographing lens is the light receiving amount correction means.   The received light amount correcting means is a scattering plate that is disposed between the light source and the first polarizing plate so as to be inclined with respect to the inspection target film, and scatters light from the light source to irradiate the inspection target film. The film defect inspection apparatus according to claim 1.   2. The film defect inspection apparatus according to claim 1, wherein the received light amount correcting means is a light control film.   2. The film defect inspection apparatus according to claim 1, wherein the received light amount correcting means is a filter whose transmittance continuously changes along the arrangement direction of the light receiving elements of the line sensor.   The film defect inspection apparatus according to claim 6, wherein the filter is disposed between the line sensor and the photographing lens.   7. The film defect inspection apparatus according to claim 5, wherein the received light amount correction means is arranged between the light source and the first polarizing plate.   The intersection angle θ1 satisfies the condition “30 ° ≦ θ1 ≦ 50 °”, and the rotation angle θ2 satisfies the condition “−60 ≦ θ2 ≦ −30 °” or “+ 30 ≦ θ2 ≦ + 60 °”. The film defect inspection apparatus according to any one of claims 1 to 8.   10. The film defect inspection apparatus according to claim 1, wherein the first and second polarizing plates are each disposed substantially parallel to the inspection target film. 11.   11. The apparatus according to claim 1, further comprising a conveying unit that continuously conveys the inspection target film, wherein the light receiver receives light each time the inspection target film is conveyed for a predetermined length. Film defect inspection equipment. The light from the light source is irradiated on the inspection target film through the first polarizing plate, and the light transmitted through the inspection target film is transmitted through the second polarizing plate whose transmission axis is inclined with respect to the transmission axis of the first polarizing plate. In the film defect inspection method for detecting defects in the film to be inspected based on the received light signal obtained by the line sensor through the polarizing plate,
Light is received by the line sensor at a position tilted with respect to a reference line perpendicular to the surface of the inspection object film and rotated from the slow axis of the inspection object film around the reference line, and the light source and the light reception The light receiving amount correcting means arranged at any position between the detector and the light receiving element of the line sensor corrects the received light amount of the light transmitted through the inspection target film to be uniform. Defect inspection method for film.

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