JP5935266B2 - Scratch defect inspection method and sheet manufacturing method - Google Patents

Description

  The present invention relates to an apparatus for detecting scratch defects in all directions generated on a film, an inspection method for detecting the defects generated on the film, and a film manufacturing method using the inspection method.

  In the process of continuously producing sheets such as films, scratch defects may occur in the sheets, which is a problem.

  As a mechanism for the generation of this scratch defect, when a foreign object adheres to the transport roll and the foreign object is pressed against the film surface, the scratch defect occurs, and the tension applied to the film and the film transport speed are not constant, and the film is transported. There may be a case where a scratch defect is generated by rubbing the roll.

Therefore, as a scratch defect shape, in the former case, it is a dot shape or a shape that is long in the film flow direction, whereas in the latter case, depending on the direction in which the film and the transport roll rub, Scratches with long shapes occur in all directions.
As described above, it is known that scratch defects occur at all angles depending on the film conveyance state.

  Since this scratch defect becomes a problem in the user's processing process, it must be avoided that a film having a scratch defect is shipped as a product.

  Conventionally, when such a defect is inspected, the film being conveyed is irradiated with light by an illuminating device, and when there is a defect on the film, scattered light that is irregularly reflected by the defect is detected. A flaw defect has been detected by capturing an image with a CCD camera or the like and processing the captured image.

As an apparatus for detecting such a scratch defect, there is a method disclosed in Patent Document 1.
The method of Patent Document 1 will be described with reference to FIGS.
The method of Patent Document 1 irradiates light from one surface of a traveling transmissive film 11 with an illuminating device 12, detects the light transmitted through the transmissive film 11 with a line CCD camera 13, and takes an image. The processing device 14 detects image defects of the transmissive film 11 by performing image processing on image data captured and generated by the line CCD camera.

  Moreover, the external view which looked at the test | inspection system of the patent document from the flow direction of the said transparent film 11 is shown in FIG.

  Thus, the illumination device 12 is characterized in that a plurality of optical axes are emitted in parallel with each other, and it is possible to detect a flaw defect generated in the film flow direction with high sensitivity.

  Moreover, there exists a method of patent document 2 as another method.

  The method of Patent Document 2 will be described with reference to FIG.

  In the method of Patent Document 2, light is radiated from a light source 24 controlled by a control unit 23 to sheets 21 continuously conveyed, and light transmitted or reflected by the sheet 21 is transmitted by the control unit 23. Light is received by the controlled light receiving means 22, and the light source 24 is characterized in that the sheet 21 is irradiated with light by a plurality of light emitting sources having different light irradiation angles.

  In this way, by illuminating the sheet 21 with a plurality of light emitting sources with different angles of light irradiation, it is possible to detect a plurality of defects specialized for each light receiving means and light source.

  If this is an optical system specializing in the detection of scratch defects, it is possible to detect the defects with a plurality of shapes with high sensitivity.

JP 2008-216148 A JP 2010-223613 A

  However, the method of Patent Document 1 can detect a defect with high sensitivity for a flaw defect that occurs in a direction perpendicular to the longitudinal direction of the illumination device 12, but the detection sensitivity decreases in other directions. To do.

  That is, as shown in FIG. 5, when the scratch defect 17 having the same intensity occurs, the scattered light 15 when irradiated with light from the illumination device 12 is scattered with the same intensity at any scratch defect angle. Light is generated. However, the scattered light 16 received by the line CCD camera differs depending on the angle of the scratch defect, and decreases as the angle of the scratch defect approaches the same angle as the longitudinal direction of the illumination device 12.

  As described above, the method of Patent Document 1 has a problem that the detection sensitivity differs depending on the angle at which a scratch defect occurs.

  This problem is solved by Patent Document 2. In one optical system, as shown in FIG. 5, a flaw defect with an angle with a poor detection sensitivity always occurs. Therefore, as shown in Patent Document 2, even when a defect with a certain angle is detected by detecting a defect with two or more optical systems, any one optical system can detect it. However, installing a plurality of optical systems in this way has a problem that not only the installation space for the inspection device increases, but also the cost increases significantly.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an inspection apparatus, an inspection method, and a film manufacturing method using the inspection method that can inspect a continuously running sheet surface with low space, low cost, and high accuracy The purpose is to provide.

The present invention is as follows.
(1) Irradiate a line of light from one side of the sheet from the light irradiation means,
The line-shaped light beam reflected by the sheet is received by a light receiving unit disposed on the same side as the light irradiation unit,
In response to the signal received by the light receiving means, the image processing means detects a scratch defect of the sheet,
A scratch defect inspection method for a sheet, wherein the light irradiating means and the light receiving means are simultaneously rotated while maintaining a relative position while being maintained parallel to the sheet.
(2) While maintaining parallel with the sheet, the light irradiation means and the light receiving means are simultaneously
The scratch defect inspection method for a sheet according to (1), wherein the sheet is moved in the width direction of the sheet by a moving unit.
(3) The scratch defect inspection method for a sheet according to (1), wherein a plurality of the light irradiation means, the light receiving means, and the rotation means are arranged in the width direction of the sheet.
(4) The scratch defect inspection method for a sheet according to any one of (1) to (3), wherein the sheet is irradiated with light having a wavelength of 450 nm to 550 nm from the light irradiation unit.
(5) The scratch defect inspection method for a sheet according to any one of (1) to (4), wherein the light receiving means in which light receiving elements of 10 μm × 10 μm or more are arranged in parallel is used.
(6) The scratch in the sheet according to any one of (1) to (5), wherein the sheet is rotated by 90 degrees from −45 degrees to 45 degrees with respect to the width direction of the sheet. Defect inspection method.
(7) A sheet manufacturing method for manufacturing a sheet by inspecting a scratch defect of the sheet by the scratch defect inspection method for a sheet according to any one of (1) to (6).
(8) A light irradiating means for irradiating the sheet with a linear light beam, a light receiving means for arranging a light receiving element for receiving the linear light beam reflected by the sheet, and a signal received by the light receiving means according to the signal A scratch defect inspection apparatus comprising an image processing means for detecting a scratch defect in a sheet, wherein the light irradiation means and the light receiving means are fixed, and the relative positions of the light irradiation means and the light receiving means are maintained. A scratch defect inspection apparatus for a sheet, comprising: a rotating unit that rotates the light irradiation unit and the light receiving unit simultaneously.
(9) The scratch defect inspection apparatus for a sheet according to (8), further including a moving unit that moves the rotating unit that fixes the light irradiation unit and the light receiving unit.
(10) The scratch defect inspection apparatus for a sheet according to (8), wherein a plurality of the rotating means to which the light irradiation means and the light receiving means are fixed are arranged in parallel.
(11) The scratch defect inspection apparatus for a sheet according to any one of (8) to (10), wherein the light emitted from the light irradiation unit has a wavelength of 450 nm to 550 nm.
(12) The scratch defect inspection apparatus for sheets according to any one of (8) to (11), wherein the size of the light receiving elements arranged in parallel with the light receiving means is 10 μm × 10 μm or more.
(13) The rotating angle of the rotating means is 90 degrees from −45 degrees to 45 degrees with respect to the width direction of the sheet. Scratch defect inspection device for the described sheet.

  According to the inspection apparatus and the inspection method of the present invention, it is possible to detect a flaw defect generated on the surface of a continuously traveling sheet with high sensitivity. In particular, the present invention can greatly reduce the cost by making the detection target a scratch defect that periodically occurs.

Schematic showing an example of an embodiment of the present invention Schematic of the invention of Patent Document 1 Schematic view from another angle of the invention of Patent Document 1 Schematic of the invention of Patent Document 2 Diagram showing the amount of light scattered and reflected by the film The figure which shows the positional relationship of the light irradiation means and light receiving means for light reception of a scattered reflected light The top view of one rotation means of the embodiment of the present invention Diagram showing difference in detection sensitivity depending on angle of scratch defect The figure showing the detection sensitivity at the time of rotating the light irradiation means 2 and the light-receiving means 3 Schematic which shows an example of another embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.
(Embodiment 1)
FIG. 1 shows a view of a light-transmitting film inspection apparatus according to the first embodiment of the present invention.

  In FIG. 1, 1 is a film as an object to be inspected, 2 is a light irradiating means, 3 is a light receiving means, 4 is an image processing means, and 5 is the light irradiating means and the light receiving means simultaneously while keeping parallel to the film. It is a rotating means that can rotate. A plurality of the light irradiating means, the light receiving means, and the rotating means are provided so that the film can be inspected without missing the width direction.

  The film 1 is not particularly limited as long as it reflects light, but a colorless and transparent film such as a polyester film such as a polyethylene terephthalate film is preferably used.

  The apparatus of the present invention has a light irradiation means 2. Preferably, the light irradiation means 2 is disposed on one surface side (surface A) of the film 1 and irradiates the surface A of the film 1 with light.

  Moreover, the light irradiation means 2 irradiates the wavelength of visible light region. Further, the wavelength of the light irradiated by the light irradiation means 2 is preferably light having a wavelength shorter than 550 nm in order to increase the scattered light component due to the scratch defect. In addition, due to the spectral sensitivity characteristics of the light receiving means 3, the amount of received light having a wavelength shorter than 450 nm decreases. Therefore, it is more preferable that the wavelength of the light irradiated by the light irradiation means 2 is 450 nm to 550 nm.

  As a light irradiation means for irradiating monochromatic light of a specific wavelength, an LED or fluorescent lamp that irradiates light of a single wavelength, or halogen or metal halide illumination in which a band pass filter is disposed in front of the lamp is irradiated from a transmission rod or an optical fiber. Things can be used. In addition, the light irradiation part of the light irradiation means 2 preferably has a linear shape corresponding to the light receiving range of the light receiving means 3 to be described later. It is preferable to arrange the light irradiation means 3 so that the direction of the light irradiation means 3 is parallel to the longitudinal direction.

  The apparatus of the present invention has light receiving means for receiving light derived from light reflected by the film 1.

The light receiving means 3 is disposed on the same surface A side as the light irradiating means 2 with respect to the film 1, and is disposed so as to receive the light irradiated from the light irradiating means 2 and reflected by the film 1.
The light receiving means 3 is preferably arranged so as to receive the light scattered and reflected by the flaw defect generated in the film 1, and receives the light irradiated from the light irradiation means 2 and regularly reflected by the film 1. It is not preferable to do. Here, in order to receive the light scattered and reflected by the scratch defect generated in the film 1, the positional relationship between the light irradiation means 2 and the light receiving means 3 is important. This positional relationship will be described with reference to FIG. FIG. 6 is a diagram showing the positional relationship between the light irradiating means 2 and the light receiving means 3 for receiving scattered reflected light due to scratch defects. As shown in FIG. 6, it is important that the light receiving means 3 is disposed so as not to receive the light irradiated by the light irradiation means 2 and regularly reflected by the film 1. This can be realized by shifting the angle θ from the optical axis. Here, the angle θ is preferably in the range of 5 ° to 30 °.

  The light receiving means 3 can be a line sensor camera in which light receiving elements are arranged one-dimensionally or an area sensor camera in which light receiving elements are arranged two-dimensionally. It is arrange | positioned so that it may become parallel to a longitudinal direction.

  As the size of the light receiving element of the light receiving means 3 increases, the amount of light entering the light receiving element increases, and minute scattered light due to scratch defects can be received. Therefore, the size of the light receiving element of the light receiving means 3 is preferably 10 μm × 10 μm or more.

  The light receiving means 3 can be a monochrome or color camera. A monochrome camera may be used when capturing the light amount difference of the scattered light due to the scratch defect, and a color camera may be used when capturing the wavelength characteristic of the scattered light due to the scratch defect.

  In addition, it is important that the light received by the light receiving means 3 is light derived from light scattered and reflected by scratch defects generated in the film 1 as described above.

  The apparatus of the present invention has a rotating means 5 for simultaneously rotating the light irradiating means 2 and the light receiving means 3 in parallel with the film 1 surface. Here, the rotating means 5 is a flat table that can rotate in parallel with the film 1 surface, and as shown in FIG. Rotate to axis. That is, the light beam on the surface of the film 1 of the light irradiating means 2 disposed in the rotating means 5 and the visual field width of the light receiving means 3 on the surface of the film 1 are also parallel to the surface of the film 1. 2 and the light receiving means 3 are arranged such that the relative positions are maintained regardless of the rotation angle of the rotating means 5.

  Moreover, although the rotation means 5 can be rotated using a servo motor or a stepping motor, since it is necessary to control a rotation angle with high precision, it is preferable to use a servo motor.

  In addition, the shape of the rotating means is preferably a disk shape in order to make the radius when rotated as small as possible.

  In addition, the rotation means 5 is preferably as the rotation angle region is wider because the defect defect of the detectable angle increases. However, as the angle of the rotating means 5 with respect to the width direction of the film 1 increases, the inspection range for scratch defects by one light receiving means 3 becomes smaller, so the angle φ with respect to the width direction of the film 1 shown in FIG. It is preferably 90 degrees from 45 degrees to 45 degrees.

  Further, the light irradiation means 2, the light receiving means 3, and the rotation means 5 for rotating them can be arranged in the width direction of the film 1 to inspect the entire width of the film.

  The apparatus of the present invention also has an image processing means for inspecting the film surface by detecting a change in the amount of light received by the light receiving means. That is, the output signal of the light receiving means 3 is connected to the image processing means 4.

  An analog or digital signal corresponding to the amount of light received by the light receiving means 3 is output from the light receiving means 3, and when an analog signal is output, it is converted into a digital signal in the image processing means 4. The image processing means 4 detects a digital signal and performs image processing, and detects a scratch defect on the surface of the film 1 based on the image processing result.

  Next, the principle of detecting a flaw in the film 1 according to the present invention will be described.

  In the present invention, the light irradiated by the light irradiation means 2 is irradiated on the film 1 and reflected. Since the light receiving means 3 is disposed at a position where the light regularly reflected by the film 1 is not received, the light receiving means 3 does not receive the light when no flaw defect occurs in the film 1. However, when a flaw defect occurs in the film 1, the flaw defect can be detected by the light receiving means 3 receiving the scattered light due to the flaw defect.

  Furthermore, since the detection sensitivity of the scratch defect differs depending on the angle at which it is generated, it is possible to detect the scratch defect of any angle by rotating the rotating means 5 at regular intervals.

  First, the difference in detection sensitivity depending on the angle of the scratch defect will be described with reference to FIG.

  FIG. 8 is a diagram showing the difference in the amount of scattered light received by the light receiving means 3 when the angle of the scratch defect with respect to the width direction of the film 1 is 90 °, 45 °, and 0 °.

  Scattered light due to a flaw defect generates a lot of scattered light in the direction perpendicular to the longitudinal direction of the flaw defect on the surface of the film 1.

Therefore, when the angle of the scratch defect with respect to the width direction of the film 1 shown in FIG. 8A is 90 °, the scattered light received by the light receiving means 3 is a case where the scattered light due to the scratch defect is a.
a ・ cos 90 ° = 0
Thus, the light receiving means 3 does not receive the light.

When the angle of the scratch defect with respect to the width direction of the film 1 shown in FIG. 8B is 45 °, the scattered light received by the light receiving means 3 is
a · cos 45 ° = a / √2
Thus, as the angle of the scratch defect with respect to the width direction of the film 1 decreases, the scattered light received by the light receiving means 3 increases and the detection sensitivity of the scratch defect increases.
Furthermore, when the angle of the scratch defect with respect to the width direction of the film 1 shown in FIG. 8C is 0 °, the scattered light received by the light receiving means 3 is
a ・ cos0 ° = a
Thus, when the angle of the scratch defect with respect to the width direction of the film 1 is 0 °, the detection sensitivity is the highest.

  Thus, the detection sensitivity differs greatly depending on the angle of the scratch defect with respect to the width direction of the film 1.

Therefore, in this apparatus, as described above, the rotating means 5 that can rotate in a state where the light irradiation means 2 and the light receiving means 3 are kept parallel to the surface of the film 1 is provided. Therefore, as shown in FIG. 9, when the light irradiating means 2 and the light receiving means 3 are rotated by 45 °, the light receiving means 3 receives the light when the flaw defect having an angle of 45 ° with respect to the width direction of the film 1 occurs. Scattered light
a · cos 45 ° = a / √2
Thus, the detection sensitivity is higher than that in FIG.

  Thus, by providing the rotating means 5 that rotates the light irradiating means 2 and the light receiving means 3 in a state where the light irradiating means 2 and the light receiving means 3 are kept parallel to the surface of the film 1, it is possible to improve the detection sensitivity for all flaw defects. In addition, it is preferable to set the rotation angle to 90 degrees from −45 degrees to 45 degrees because the detection sensitivity for scratch defects at all angles can be a / √2 or more.

That is, a flaw defect that cannot be detected at one angle can be detected from another angle, and a flaw defect with a lower detection sensitivity can also be detected.
(Embodiment 2)
When the width of the film 1 is wide, a large number of light irradiating means 2, light receiving means 3, and rotating means 5 for rotating them are required. Further, both when the rotation angle region of the rotating means 5 is increased and when the inspection is performed in the width direction of the film 1, a large number of light irradiating means 2, light receiving means 3 and rotating means 5 for rotating them are required. .

  Thereby, when trying to realize these, the cost may increase significantly.

  Therefore, as shown in FIG. 10, the light irradiation means 2, the light receiving means 3, and the rotating means 5 for rotating them are set as one set, and by providing the moving means 6 for moving them, the cost can be reduced. .

  However, in the embodiment of FIG. 10, since the entire width of the film 1 cannot be inspected at the same time, it is possible to detect a flaw defect that periodically occurs over the entire length of the film 1, but it occurs suddenly. Scratch defects can not be detected. As described above, if only the scratch defect periodically generated over the entire length of the film 1 is detected, the embodiment shown in FIG. 10 can greatly reduce the cost.

  Next, the inspection method of the present invention will be described.

  The inspection method of the present invention is the step 1 of irradiating the surface A of the film 1 with a linear light beam from the light irradiation means 2, and the line light beam reflected by the film 1 on the same surface A side as the light irradiation means 2. Step 2 for receiving light by the arranged light receiving means 3, Step 3 for detecting a scratch defect by the image processing means 4 according to the signal received by the light receiving means 2, and the light irradiation means 2 and the light receiving means 3 at regular intervals. And a step 4 of rotating by the rotating means 5.

  The inspection method of the present invention is an invention in which the steps 1 to 4 are applied in this order to a light reflective film.

  In Step 1, it is preferable to irradiate the film 1 with light having a wavelength of 450 nm to 550 nm in consideration of increasing the spectral sensitivity characteristics of the light receiving means 3 and the scattered light of scratch defects.

  In Step 2, it is preferable that the light irradiated in Step 1 and regularly reflected by the film 1 is not received, and the scattered light due to the scratch defect is received by the light receiving means 3 on the surface A side. Further, it is preferable to use the light receiving means 3 in which light receiving elements having a size of 10 μm × 10 μm or more are arranged in parallel in order to receive minute scattered light due to a flaw defect and improve the detection sensitivity of the flaw defect.

  In step 3, it is important to inspect the surface of the film 1 by detecting a change in the amount of light received in step 2, and for this purpose, there is a method using the above-described detection means.

  In step 4, it is preferable to rotate the light irradiating means 2, the light receiving means 3 and the rotating means 5 for rotating them at regular intervals in parallel with the film 1 surface. Furthermore, it is preferable to rotate 90 degrees from −45 degrees to 45 degrees with respect to the width direction of the film 1 in consideration of the detection sensitivity and inspection width of scratch defects. Furthermore, since the detection sensitivity varies depending on the generation angle of the scratch defect, it is possible to detect a scratch with lower detection sensitivity as the angle of one rotation is smaller. However, since it takes a long time to complete the inspection of scratch defects in all directions, the rotation angle of the rotating means 5 is preferably 10 ° to 30 °.

  In addition, if the inspection time is short, long-period defects cannot be detected. If the inspection time is long, the time until the inspection in all directions is completed becomes long. Therefore, the inspection time for one inspection is 30 seconds to 180 seconds. It is preferable that

  Moreover, the manufacturing method of the film of this invention applies the inspection method of the above-mentioned this invention during the manufacturing process of a film. That is, an example of the film production method of the present invention is to perform the steps 1 to 4 in this order during film formation. Since the film obtained by the production method of the present invention can detect scratch defects with high accuracy in the production process, it is easy to remove the scratch defect from the obtained film, and scratch defects are detected. By stopping the film winding at this point, it is possible to obtain a film roll having no scratch defect.

  In the film production method of the present invention, it is important to have the above-described inspection method in the process, and other film production processes such as an extrusion process, a casting process, a stretching process, and a coating process are known methods. Can be applied.

Example 1
Inspection was performed using an apparatus according to the arrangement of FIG. A PET film having a width of 1000 mm and a thickness of 100 μm was used as the film, and the film was run at 40 m / min. Furthermore, as the light irradiation means, linear LED illumination that irradiates light of 500 nm to 550 nm was used, the angle between the film surface and the LED illumination was 80 °, and the distance between the film surface and the LED illumination was set to 150 mm.

  In addition, a monochrome line sensor camera was used as the light receiving means, and was arranged so as to receive scattered light due to scratch defects generated on the film surface. At this time, the angle between the film surface and the light receiving axis of the monochrome line sensor camera was 75 degrees, and the distance between the film surface and the line sensor camera was set to 200 mm.

  In addition, the LED illumination and the line sensor camera were integrated with a frame, and a rotating surface was arranged in parallel with the film surface, and the frame was fixed to an automatic rotating stage having a rotating surface φ160 mm.

  Further, since the film width inspected by one of the line sensor cameras is 100 mm when the rotation stage is ± 45 °, 10 sets of LED illumination, the line sensor camera, and an automatic rotation stage for rotating these are used.

In addition, by inspecting the rotary stage from -45 ° to 45 ° every 15 ° every minute, it is possible to detect scratch defects in all directions having a depth of 300 nm and a length of 300 μm or more generated on the film surface. did it.
(Example 2)
In the method of Example 1, it is possible to detect flaws in all directions having a depth of 300 nm and a length of 300 μm or more. However, as the film width becomes wider, there are a plurality of LED illuminations, line sensor cameras, and automatic rotation stages. A set is required, which increases costs. Therefore, LED lighting, a line sensor camera, and an automatic rotation stage are set as one set, and these are installed on an automatic movement stage that moves in the film width direction (shown in FIG. 10). .

  The movement method moves every minute in the film width direction. When moving in the film width direction, the angle of the automatic rotation stage is constant, and after moving in the entire film width direction, before moving again Was rotated 15 °.

Thereby, compared with Example 1, cost could be made into about 1/5 and the defect defect of the omnidirectional which generate | occur | produces periodically could be detected.
(Comparative example)
As a method described in Patent Document 1, an apparatus having the same configuration as that in FIG. 2 was used. A PET film having a width of 1000 mm and a thickness of 100 μm was used as the film, and the film was run at 40 m / min. Further, as a light irradiating means, an illumination device in which plastic optical fibers were arranged at an angle of 30 ° with respect to the PET film was disposed at a position 150 mm away from the PET film, and light from a halogen light source was incident on the plastic optical fiber. A monochromatic line sensor camera was used as the light receiving means, and was arranged so as to receive scattered light due to scratch defects generated on the film surface. At this time, the angle between the film surface and the optical axis from the illumination was 75 degrees, and the distance between the film surface and the line sensor camera was 200 mm.

  In the method described in Patent Document 1, it was possible to detect a scratch defect having a depth of 300 nm and a length of 300 μm that occurred in parallel to the flow direction of the PET film, but it occurred in parallel to the width direction of the PET film. The scratch defect with a depth of 300 nm and a length of 300 μm could not be detected.

1: Film 2: Light irradiating means 3: Light receiving means 4: Image processing device 5: Rotating means 6: Moving means 7: Scratch defect 8: Scattered light due to a scratch defect 9: Irradiated from the light irradiating means, and regularly reflected by the film Optical axis 10 of light: Irradiated from light irradiation means and scattered by a scratch defect on the film surface 11: Optical axis of light 11: Transparent film 12: Illuminating device 13: Line CCD camera 14: Image processing device 15: Scratch defect Scattered light 21: Sheet 22: Light receiving means 23: Control means 24: Light source 25: Light source for reflection 26: Light source for transmission

Claims (7)

A scratch defect inspection method for a sheet in which the following steps 1, 2, 3, and 4 are performed during traveling of the sheet.
(Step 1) A line-shaped light beam is irradiated on one surface side of the sheet from the light irradiation means,
(Step 2) The line-shaped light beam reflected by the sheet is received by a light receiving unit disposed on the same surface side as the light irradiation unit,
(Step 3) According to the signal received by the light receiving means, the image processing means detects a scratch defect of the sheet,
(Step 4) While maintaining parallel with the sheet, the light irradiating means and the light receiving means are simultaneously rotated while maintaining a relative position .   2. The scratch defect inspection method for a sheet according to claim 1, wherein the light irradiating means and the light receiving means are simultaneously moved in the width direction of the sheet by the moving means in a state of being maintained parallel to the sheet. .   The scratch defect inspection method for a sheet according to claim 1, wherein a plurality of the light irradiation means, the light receiving means, and the rotating means are arranged in the width direction of the sheet.   The scratch defect inspection method for a sheet according to any one of claims 1 to 3, wherein the sheet is irradiated with light having a wavelength of 450 nm to 550 nm from the light irradiation means.   5. The scratch defect inspection method for a sheet according to claim 1, wherein the light receiving means in which light receiving elements of 10 [mu] m * 10 [mu] m or more are arranged in parallel is used.   The scratch defect inspection method for a sheet according to any one of claims 1 to 5, wherein the sheet is rotated 90 degrees from -45 degrees to 45 degrees with respect to the width direction of the sheet. The manufacturing method of the sheet | seat which test | inspects the flaw defect of a sheet | seat by the flaw defect inspection method in the sheet | seat in any one of Claims 1-6, and manufactures a sheet | seat.

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