TWI480539B - Defect inspection apparatus and method for light transmittance material - Google Patents

Description

Device and method for detecting light-transmitting material

The present invention relates to a flaw detection device and a flaw detection method for detecting a light-transmitting material using a polarizing plate.

In order to improve the viewing angle of the liquid crystal display device, an optical compensation film (hereinafter referred to as "phase difference film") in which a liquid crystal layer having optical anisotropy is formed on a transparent film is used. The retardation film is produced by a process of forming an alignment film by a long-length transparent film, and a process of coating a liquid crystal on the alignment film and drying it to form a liquid crystal layer (for example, refer to Japanese Patent Laid-Open No. Hei 9-73081) Bulletin). These manufacturing processes are carried out under strict management, but the molecular alignment unevenness caused by the incorporation or adhesion of foreign matter is completely removed, or the thickness of the transparent film which becomes the support is uneven, and the coating of the liquid crystal layer is uneven. There are difficulties.

In general, in order to detect flaws generated in the manufacturing process of the strip film, the film is inspected on the manufacturing line, that is, the so-called in-line inspection. On-line inspection, first, light is irradiated from the light projector to the film to be inspected, and light transmitted through the film is detected by the light receiver. Moreover, by analyzing the detected light, the position and size of the cymbal are grasped. For example, in the method of detecting a transparent crucible described in Japanese Laid-Open Patent Publication No. H6-1-48095, the first and second polarizing plates are provided on the front surface of the light projector and the light receiver, respectively, so that the mutually polarized directions are orthogonal to each other. The polarizing plates. Thereby, the light passing through the normal portion of the film is shielded by the second polarizing plate, and hardly reaches the photoreceiver, and the light that affects the ridge portion of the polarized light passes through the second polarizing plate. The light is received by light. In the method for detecting pinhole defects described in Japanese Laid-Open Patent Publication No. Hei 6-18445, a polarizing plate is provided on each of the light projector side and the light receiver side of the film to be inspected, so that the polarizing directions of the polarizing plates can be made. Configured in parallel with each other. When the film is not flawed, since the light leaving the polarizing plate on the light projector side is scattered when passing through the film and disordered in the polarizing direction, the intensity of light emitted from the polarizing plate on the light receiver side becomes weak. On the other hand, when there is a pinhole on the film, since the light emitted from the polarizer on the light projector side remains in the original direction of the polarized light and passes through the pinhole, the intensity of light emitted from the polarizer on the light receiver side does not change. By using such a change in the intensity of the light, the detection accuracy of the pinhole flaw can be improved.

However, the conventional method of detecting the use of a polarizing plate has difficulty in detecting minute defects. Therefore, the inventors obtained the following knowledge by reviewing the conventional flaw detection method again. First, an iodine-based polarizing filter has a small transmittance peak in a wavelength region of 400 nm, and light in this wavelength region affects the accuracy of detection of defects. Further, in the iodine-based polarizing filter, light in a wavelength region exceeding 700 nm is hardly polarized. On the other hand, a solid-state imaging device such as a CCD used as a light receiver has sensitivity in a wavelength region of 400 nm or less and 700 nm or more. Therefore, light in a wavelength region of 400 nm or less and 700 nm or more remains in the light-receiving signal for judging 瑕疵, and becomes a noise component, and the accuracy of detection of flaws is lowered.

When the time is small, the light that is detected is also weak. Therefore, in order to improve the detection accuracy of the minute flaws and suppress the noise component entering the light receiver, it is necessary to increase the difference in the amount of light reaching the light receiver in the case where the film is flawed and in the case of no flaw.

An object of the present invention is to provide a flaw detection device and a flaw detection method which can accurately detect flaws of a light-transmitting material using a polarizing plate.

In order to achieve the above object and other objects, the apparatus for detecting light-transmitting material of the present invention includes a light projector, a light receiver, a first polarizing plate, a second polarizing plate, a defect determining unit, and a removal optical system. The light projector is configured to irradiate light to the light transmissive member. The light receiver detects light emitted from the light transmissive member. The first polarizing plate is provided between the light projector and the light transmissive member. The second polarizing plate is disposed between the light transmissive material and the photodetector, and is disposed in a cross Nicol with respect to the first polarizing plate. The 瑕疵 determining unit determines the 瑕疵 of the light transmissive member based on the received light signal of the photodetector. The removal optical system is provided between the light projector and the light receiver, and removes a wavelength region in which the first and second polarizing plates have high orthogonal transmittance.

It is preferable to remove the optical system by removing the wavelength region of 400 nm or less. Further, it is preferable to remove the optical system by removing the wavelength region of 700 nm or more.

In a preferred embodiment of the present invention, the first and second polarizing plates are iodine-based polarizing plates, and the light-receiving device is a solid-state imaging device. Further, the removal optical system is a wavelength region in which 420 nm or less and 700 nm or more are removed. The removal optical system is preferably a dielectric multilayer film filter or a monochromator. Further, it is preferable that the optical removal system is provided between the light projector and the first polarizing plate.

The light projector is equipped with a metal halide lamp This removal optics is preferred. Further, the light transmissive material is preferably a retardation film.

The method for detecting a light-transmitting material according to the present invention includes a step of irradiating light from a light projector through a first polarizing plate to a light-transmitting material, and introducing light having passed through the light-transmitting material into relation to a step of arranging the second polarizing plate in a crossed Nikon style; detecting light passing through the second polarizing plate by the photodetector to detect the light transmissive material; and in the light projector Between the first polarizers, the light is introduced into the optical system to remove a wavelength region in which the first and second polarizers have a high orthogonal transmittance.

According to the invention, the light of the wavelength region having the high orthogonal transmittance of the first and second polarizing plates is removed by removing the optical system. Therefore, the noise is not mixed into the light for detection, and the flaw of the light-transmitting member can be accurately detected.

Detailed description of the preferred embodiment

In the first embodiment, the retardation film producing line 10 includes an alignment film forming device 11, a liquid crystal layer forming device 12, a flaw detecting device 13, and a winding device 14. By the winding of the winding device 14, the transparent resin film 15 and the retardation film 16 travel in the X direction in the drawing.

The alignment film forming apparatus 11 is coated with a coating liquid containing a resin for forming an alignment film on the surface of the long transparent resin film 15 which is sent out from the film roll 18, and dried by heating. Thereby, a resin layer for forming an alignment film is formed on the surface of the transparent resin film 15. Moreover, the alignment film forming device 11, The resin film for forming an alignment film of the transparent resin film 15 is subjected to a rubbing treatment to form an alignment film.

In the liquid crystal layer forming apparatus 12, a coating liquid containing a liquid crystal compound is applied onto an alignment film of the transparent resin film 15, and the solvent is evaporated and then heated to form a liquid crystal layer. Further, crosslinking is carried out by irradiating ultraviolet rays on the liquid crystal layer to obtain a transparent retardation film 16 (hereinafter referred to as "thin film").

The flaw detection device 13 detects flaws occurring on the film 16. The so-called sputum is, for example, a flaw, a thickness unevenness, a coating unevenness, a molecular misalignment, and the like. Further, the object to be inspected is not limited to a retardation film, for example, a reflection preventing film or the like, and may be a member that transmits light transparently or translucently.

The flaw detection device 13 includes guide rollers 20 and 21, a light projector 22, a light amount adjustment unit 23, a light receiver 24, first and second polarizing plates 25 and 26, an optical system 27, and a determination unit 28. The guide rollers 20, 21 are disposed at a predetermined interval on the transport path of the film 16, and are rotated as the film 16 is transported. The film 16, which is hung across the guide rolls 20, 21, is held in a planar shape. Further, an encoder 30 is connected to the guide roller 21. The encoder 30, which is a film 16 that transmits a certain length, generates an encoder pulse signal. The encoder pulse signal is sent to the judging section 28 for specifying the 瑕疵 position in the X direction.

The light projector 22, for example, a metal halide lamp, is disposed below the transport path of the film 16. Further, the light amount adjusting unit 23 is connected to the light projector 22. The light amount adjustment unit 23 controls the light projector 22 based on the light amount detection signal of a sensor (not shown) provided in the vicinity of the light projector 22 to make the light amount constant. Thereby, the light irradiated to the film 16 can be made uniform light Quantity, and often the same sensitivity can be detected. Further, the light projector 22 may be a high-intensity fluorescent lamp, a halogen lamp, a mercury lamp, a laser, or the like as long as the luminance is high.

The photodetector 24 is, for example, a CCD camera, and is disposed above the transport path of the film 16. The light receiver 24 has a plurality of light receiving elements arranged in a line shape in the width direction of the film 16. By this configuration, the full width of the film 16 can be detected to detect defects, and at the same time, the ability to decompose the crucible can be improved. Further, the number of driving frequencies of the photodetector 24 is set so as to sufficiently ensure the decomposition ability even when the film 16 travels at the highest speed. The light receiver 24 picks up a line for each length of the film 16 to be conveyed, and sends the photographing signal to the judging section 28. Further, there may be two or more light receivers 24.

The first and second polarizing plates 25 and 26 are, for example, iodine-based polarizing plates. The first polarizing plate 25 is disposed between the light projector 22 and the film 16, and the second polarizing plate 26 is disposed between the film 16 and the light receiver 24. Further, the first and second polarizing plates 25 and 26 are provided in a crossed Nichol style so as to be orthogonal to each other in the polarization direction. Therefore, in the case where the film 16 is not flawed, the light which is polarized to the specific polarizing surface of the first polarizing plate 25 retains the polarizing surface as it passes through the film 16 and is shielded by the second polarizing plate 26, so that the light hardly passes. Enter the light receiver 24. That is, the light receiver 24 is in a dark field state. On the other hand, when the film 16 has flaws, the light which is polarized to the specific polarizing surface by the first polarizing plate 25 is scattered and diffused in the meandering portion of the film 16, and the polarizing surface is changed. Since the light whose polarizing surface changes passes through the second polarizing plate 26, the photodetector 24 is in a light receiving state. In addition, from the perspective of performance and price Although an iodine-based polarizing plate is used, a dye-based polarizing plate or a polarizing plate formed of a metal film polarizer or calcite may be used.

The optical system 27 is removed by a band pass filter formed of a dielectric multilayer film, and is disposed between the light projector 22 and the first polarizing plate 25. The optical system 27 is removed, and light having a wavelength region of 420 nm or less and 700 nm or more is removed from the light of the light projector 22. Since the first and second polarizing plates 25 and 26 are only incident on light having a wavelength region of more than 420 nm and less than 700 nm, the noise light in the unnecessary wavelength band region is not detected to enter the photoreceiver 24. Therefore, flaws can be detected accurately.

When the iodine-based polarizing plate is disposed in a crossed Nichol style, light may be transmitted through the polarizing plate depending on the wavelength region. As shown in Fig. 2, the transmittance (orthogonal transmittance) when the first and second polarizing plates 25 and 26 which are orthogonal Nikol type are overlapped is increased in the vicinity of 400 nm and in the vicinity of 700 nm. On the other hand, as a CCD camera used as the light receiver 24, light in a wavelength region of 400 nm or less and 700 nm or more is also sensitive. Therefore, if the light in this area is detected as it is, it will become a noise. Therefore, in the present invention, the light of the wavelength region (hatched region) A1 and A2 of 420 nm or less and 700 nm or more is removed by the removal optical system 27 using the band pass filter, and only the wavelength region of more than 420 nm and less than 700 nm is removed. Light is incident on the film 16. Therefore, since the received light signal does not contain noise, the detection accuracy of the flaw can be improved.

The optical system 27 is removed, and may be a monochromator or a wavelength removing filter, a colored glass filter, a diffraction grating, or the like, in addition to a belt passing filter using a dielectric multilayer film. Also, the removal wavelength region generated by the removal of the optical system 27 The domain is not limited to 420 nm or less and 700 nm or more, and can be appropriately determined depending on the type of polarizing plate used. That is, the polarizing plate to be used is arranged in a crossed Nikon style and irradiated from the light projector to remove a wavelength region having a high orthogonal transmittance. Therefore, for example, when the orthogonal transmittance is 400 nm or less and the wavelength region of 700 nm or more is high, light in the wavelength regions is removed by the removal optical system 27.

Further, as the position where the optical system 27 is removed, between the light projector 22 and the first polarizing plate 25, the following six positions can be considered. The first position is the front side of the photodetector 24, the second position is between the photoreceptor 24 and the second polarizing plate 26, and the third position is between the second polarizing plate 26 and the film 16, and the fourth position is Between the film 16 and the first polarizing plate 25, the fifth position is inside the light projector 22, and the sixth position is integral with the light projector 22.

Generally, the polarizing plate is weak for light or heat, so the first to fourth positions are not good. Further, since the light receiver 24 focuses on the film 16, it is preferable to remove the optical system 27 away from the film 16. Therefore, the 3rd and 4th positions are also not good. Further, in the sixth position, each time the light projector 22 is replaced, the detection accuracy of the flaw is changed, which is not preferable. On the other hand, when disposed inside the light projector 22, the optical system 27 is small, and it is inexpensive. Therefore, the fifth position is preferred.

The determination unit 28 applies emphasis processing such as differential processing to the imaging signal from the photodetector 24. Further, the determination unit 28 determines whether or not there is a flaw based on the photographing signal to which the emphasis processing is performed. Further, the judging unit 28 specifies the 瑕疵 position of the film 16 based on the signal corresponding to the 瑕疵 portion among the one-line photographic signals and the encoder pulse signal from the encoder 30. Set on the XY plane coordinates.

Next, the action of the flaw detection device 13 will be described. The film 16 produced by the alignment film forming device 11 and the liquid crystal layer forming device 12 is sent to the flaw detection device 13. At the flaw detection device 13, the light from the light projector 22 is irradiated onto the film 16 that travels at a constant speed. At this time, light in a wavelength region of 420 nm or less and 700 nm or more is removed by the removal optical system 27. On the other hand, light having a wavelength region of more than 420 nm and less than 700 nm is incident on the film 16 after the first polarizing plate 25 is polarized to a specific polarizing surface. Here, in the case where the film 16 is flawless, the light is transmitted through the film 16 as it is, and is shielded by the second polarizing plate 26. On the other hand, the film 16 has a flaw, and since the polarizing surface of the light changes by the flaw, a part of the light passes through the second polarizing plate 26. The light receiver 24 detects the light emitted from the second polarizing plate 26.

In the light receiver 24, the film 16 is photographed by one line for a predetermined length, and the photographing signal is sent to the judging unit 28. The judging unit 28 detects the presence or absence of defects and specifies the position of the crucible. The information about 瑕疵 is displayed on the display (not shown).

The present invention can be variously modified and changed without departing from the spirit of the invention, and even in this case, it should be construed as being included in the scope of the present invention.

10‧‧‧ phase difference film manufacturing line

11‧‧‧Alignment film forming device

12‧‧‧Liquid layer forming device

13‧‧‧瑕疵detection device

14‧‧‧Winding device

15‧‧‧Transparent resin film

16‧‧‧ phase difference film

18‧‧‧ Film Roller

20, 21‧‧‧ Guide rollers

22‧‧‧Light projector

23‧‧‧Light Adjustment Department

24‧‧‧Receiver

25‧‧‧1st polarizer

26‧‧‧2nd polarizer

27‧‧‧Removal of the optical system

28‧‧‧Decision Department

30‧‧‧Encoder

The above objects and advantages are referred to the attached drawings, and by reading the preferred embodiment of the present invention, it will be clear to the practitioner:

Fig. 1 is a view showing the detection of flaws introduced into the light-transmitting member of the present invention. A schematic diagram of a phase difference film manufacturing line of the device.

Fig. 2 is a graph showing the orthogonal transmittance of the polarizing plate.

10‧‧‧ phase difference film manufacturing line

11‧‧‧Alignment film forming device

12‧‧‧Liquid layer forming device

13‧‧‧瑕疵detection device

14‧‧‧Winding device

15‧‧‧Transparent resin film

16‧‧‧ phase difference film

18‧‧‧ Film Roller

20, 21‧‧‧ Guide rollers

22‧‧‧Light projector

23‧‧‧Light Adjustment Department

24‧‧‧Receiver

25‧‧‧1st polarizer

26‧‧‧2nd polarizer

27‧‧‧Removal of the optical system

28‧‧‧Decision Department

30‧‧‧Encoder

Claims (9)

A light-transmitting material detecting device comprising: a light projector that emits light to a light-transmitting material; and a light-receiving device that receives light emitted from the light-transmitting material illuminated by the light projector; the iodine-based first polarized light a plate is disposed between the light projector and the light transmissive material; an iodine-based second polarizing plate is disposed between the light-transmitting material and the light-receiving device; and a 瑕疵 determining portion is received by the light-receiving device Determining the flaw of the light transmissive material by a signal, wherein a noise light removing optical system is disposed between the light projector and the light receiver, and the noise light removing optical system is used to form the first and second polarizing plates When the light transmissive material is sandwiched by a cross Nicol, the noise light of 400 nm or less which hinders the detection of the germanium is removed, and the optical light is removed except for the wavelength region. In addition to light of 400 nm or less, light of 420 nm or less is also removed. The apparatus for detecting a light-transmitting material according to the first aspect of the invention, wherein the noise-removing optical system removes light of 700 nm or more in addition to light having a wavelength region of 400 nm or less. The apparatus for detecting a light-transmitting material according to the first aspect of the invention, wherein the noise-removing optical system removes light of 420 nm or less and 700 nm except for removing light having a wavelength region of 400 nm or less. Above the light. The apparatus for detecting a light-transmitting material according to claim 1, wherein the light-emitting device is a metal halide lamp. A flaw detection device for a light-transmitting material according to the first aspect of the invention, wherein the light-transmitting material is a retardation film. The apparatus for detecting a light-transmitting material according to claim 1, wherein the noise-removing optical system is a dielectric multilayer film filter or a monochromator. The apparatus for detecting a light-transmitting material according to the first aspect of the invention, wherein the noise-removing optical system is provided between the light projector and the first polarizing plate. The apparatus for detecting a light-transmitting material according to the first aspect of the invention, wherein the noise-removing optical system is incorporated in the light projector. A method for detecting a light-transmitting material is: a light projector that emits light to a light-transmitting material; and a light receiver that receives light from the light-transmitting material illuminated by the light projector; the first polarized light of iodine a plate disposed between the light projector and the light transmissive material; an iodine-based second polarizing plate disposed between the light-transmitting material and the light-receiving device; and a 瑕疵 determining portion configured to receive light according to the light-receiving device Determining the flaw of the light transmissive material by a signal, characterized by: being disposed between the light projector and the light receiver When the optical light is removed from the optical system, when the first and second polarizing plates are arranged in a crossed Nikon type and the light transmissive material is sandwiched, the noise light of 400 nm or less which hinders the detection of the flaw is removed. The noise light removal optical system removes light of 420 nm or less in addition to light having a wavelength region of 400 nm or less.