JP2001324453A - Apparatus, system and method for inspecting defect of film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus, a system and a method for inspecting film defects, whereby an optical defect inspection for the films to be inspected can be carried out simply and easily, and moreover, every optical defect generated during a manufacturing process can be accurately detected without being missed. SOLUTION: There are provided a pair of polarizers arranged parallel to each other to both sides of a film face of the film to be inspected, an illumination light source for shedding light to the film to be inspected via one polarizer, a light-intercepting means for receiving the light which is shed by the illumination light source and passes the other polarizer, and a correction film which has double refraction characteristics nearly equal to double refraction characteristics of a part of the film to be inspected having no optical defects and has an arrangement direction set beforehand, according to the double refraction characteristics of the film to be inspected. The optical defect of the film to be inspected is inspected by obtaining luminance signals of the passing light by the light-receiving means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily and easily performing an optical defect inspection on a film to be inspected, and in particular, performing a defect inspection continuously in a manufacturing process of a viewing angle improving film used for a liquid crystal display device or the like. The present invention belongs to the technical field of a defect inspection apparatus, a defect inspection system, and a defect inspection method for a viewing angle widening film.

[0002]

2. Description of the Related Art Today, TFT liquid crystal display devices and DSTN liquid crystal display devices are widely used as liquid crystal display devices. However, in these liquid crystal display devices, the viewable area has a viewing angle dependency, so that it is difficult to see the display screen if the area deviates from the viewable area. For example, when the viewing angle is tilted in the vertical direction, the color of the display screen becomes lighter as a whole and the contrast is reduced, and the grayscale inversion occurs in the black display portion, making it difficult to view. In addition, since the viewing angle of a large liquid crystal display screen increases with the enlargement of the display screen,
The above-mentioned contrast reduction and gradation inversion tend to occur. Therefore, a liquid crystal display device having a wide visible area is desired.

Under these circumstances, in order to improve the viewing angle of the liquid crystal display device, various methods for dividing the liquid crystal of the liquid crystal display device and a retardation film using an optical compensation film having a negative birefringence are used. Are being considered. For example, Japanese Patent Laying-Open No. 6-214116 disclosed by the present applicant proposes an optically anisotropic element and a method for manufacturing the same. According to this, the liquid crystal molecules of the liquid crystal cell of the liquid crystal display device slightly tilt from the normal direction of the substrate of the liquid crystal display device when a voltage is applied, and the liquid crystal display device shifts the optical axis in a direction slightly tilted from this normal direction. It can be regarded as a positive uniaxial optically anisotropic element having. Therefore, the optical axis of the negative uniaxial optically anisotropic element is slightly tilted in accordance with the tilt, and the phase difference due to the liquid crystal cell is compensated for by the phase difference of the optically anisotropic element, so that a good liquid crystal display device having no viewing angle dependence is provided. Can be obtained. Then, a viewing angle improving film for liquid crystal is commercially available from the present applicant.

By the way, the viewing angle improving film for a liquid crystal, which is composed of a low molecular liquid crystal as an optically anisotropic element, maintains the optimized compensation state of the liquid crystal cell uniformly on the screen.
Although strict homogeneity is required, for example, the viewing angle improving film for liquid crystal is manufactured through various complicated processes of applying liquid crystal on a flexible support, drying the liquid crystal, and further aligning and curing the film. Therefore, foreign substances are mixed during the manufacturing process, the orientation direction of the low-molecular liquid crystal is varied in size due to adhesion, or is randomly changed and disturbed, and the retardation value is changed due to uneven coating or the like, and a desired value is obtained. Various defective portions having no optical characteristics are generated. Such defective portions are accurately detected without omission in the liquid crystal viewing angle improving production line obtained through a complicated manufacturing process, and a liquid crystal viewing angle improving film having such defective portions is marketed. It is desired not to provide.

[0005]

As a defect inspection method in a production line for a viewing angle improving film for a liquid crystal to be conveyed, a deflection transmission optical axis parallel to the conveying direction is provided on one side of the viewing angle improving film for a liquid crystal. On the other side, a pair of polarizers having a deflecting transmission optical axis orthogonal to the transport direction, that is, a pair of polarizers arranged in crossed Nicols, and projecting inspection illumination light from one of the outside, A method of receiving a transmitted light transmitted from the side by a line sensor or the like, obtaining a luminance signal of the transmitted light, and performing a differential process or the like on the luminance signal from a change in the luminance signal to detect a defective portion on the film surface. Has been done.

However, in this method, when a luminance signal photographed by a CCD camera or the like is displayed as an image, although a defective portion forms a bright portion with a normal portion as a background, the transmitted light amount of the normal portion is lower than that of a liquid crystal. The viewing angle improving film itself is non-uniform due to the viewing angle dependence, and the SN ratio of the luminance signal of a bright portion corresponding to the defective portion is low, and the defect detection accuracy is low. In addition, the calculation can be performed by shading correction to remove the uneven background portion of the normal portion, but by performing the calculation,
Since information included in the luminance signal is also processed, it is not possible to detect a defect with high accuracy.

In the above method, defective portions can be relatively detected by arranging a pair of polarizers on both sides of a viewing angle improving film for a liquid crystal with a deflecting and transmitting optical axis parallel to the conveying direction and arranging them in crossed Nicols. Although this facilitates, since the orientation direction of the liquid crystal of the viewing angle improving film for liquid crystal is substantially orthogonal to the deflecting transmission optical axis, the amount of transmitted light on the normal film surface is small, but even in a defective portion forming a bright region. Since the amount of transmitted light is small as a whole, there is also a problem that the SN ratio of the luminance signal at the defective portion is low, and the defect detection accuracy is low.

In the above method, the defect inspection of the transported liquid crystal viewing angle improving film is performed using a line sensor in which the solid-state image sensors are arranged in a line in a direction perpendicular to the transport direction. In parallel with the direction, a defect that occurs continuously or periodically, for example, a step unevenness defect due to uneven coating or the like, cannot be accurately detected from a change in the luminance signal obtained by the line sensor. is there.

For this reason, it is not possible to accurately detect all defects generated during the manufacturing process without leaking.
Such a problem is a problem common to not only the liquid crystal viewing angle improving film but also the entire retardation film using the birefringence.

Therefore, the present invention solves the above problems,
A film defect inspection apparatus, a defect inspection system, and a defect that easily and easily perform an optical defect inspection of a film to be inspected on a production line, and further accurately detect all optical defects generated during a manufacturing process without leaking. Inspection method, in particular, a film defect inspection system that accurately and continuously detects defects caused by mixing of foreign substances, uneven alignment and uneven steps in the manufacturing process of a viewing angle improving film used for a liquid crystal display device or the like without omission. The purpose is to provide.

[0011]

In order to achieve the above object, the present invention provides a pair of polarizers arranged on both sides of a film surface of a film to be inspected for optical defects in parallel with the film to be inspected. An illumination light source disposed outside between the pair of polarizers and projected onto the film to be inspected through one of the pair of polarizers, and the illumination light source outside between the pair of polarizers A light receiving unit that is disposed on the opposite side of the arrangement position and receives transmitted light that is emitted by the illumination light source and transmitted from the other polarizer, and a portion where the birefringence characteristic has no optical defect of the film to be inspected. The film is substantially the same as the birefringence characteristics of the film to be inspected, the arrangement direction is preset according to the birefringence characteristics of the film to be inspected, and the film to be inspected is placed in one gap between the pair of polarizers and the film to be inspected. Correction field A defect of the film for inspecting an optical defect of the film to be inspected by obtaining, by the light receiving means, a luminance signal of transmitted light transmitted through the film to be inspected, the correction film, and the pair of polarizers. An inspection device is provided.

Here, the correction film is obtained by rotating the film to be inspected having no optical defect by 180 degrees in the film plane or by turning the film surface of the film to be inspected having no optical defect upside down. The correction film may be disposed, and the correction film may be bonded to one of the pair of polarizers. Further, it is preferable that an optical system for condensing the transmitted light on the light receiving unit is provided in an optical path of the transmitted light between the light receiving unit and the polarizer disposed on the light receiving unit side of the pair of polarizers. . Preferably, the light receiving means is a solid-state image sensor. Here, when the inspection for the optical defect of the film to be inspected is performed during the transportation of the film to be inspected, the light receiving unit is arranged in a line in a slant with respect to a direction orthogonal to the transport direction of the film to be inspected. It is preferable that the plurality of solid-state imaging devices be a plurality of solid-state imaging devices.

The present invention also relates to a film defect system for inspecting an optical defect of a film to be inspected which is continuously conveyed, wherein the film is inspected for an optical defect on both sides of the film surface in parallel with the film to be inspected. A pair of polarizers, disposed outside the pair of polarizers, via one of the pair of polarizers, an illumination light source that projects light on the film to be inspected, and the pair of polarized light A light-receiving means disposed outside the space between the light sources and opposite to the position where the illumination light source is arranged to receive transmitted light emitted by the illumination light source and transmitted from the other polarizer; The film is substantially the same as the birefringence characteristic of the portion of the inspection film without optical defects, the arrangement direction is preset according to the birefringence characteristics of the film to be inspected, and the pair of polarizer and the film to be inspected One gap between A plurality of film defect inspection devices including a film to be inspected and a correction film arranged in parallel to the film to be inspected are arranged in the transport path of the film to be inspected, and the plurality of film defect inspection devices have a deflection transmission axis of the pair of polarizers. The direction is provided in a crossed Nicol state, and provides a film defect inspection system characterized by being set at different angles with respect to the transport direction of the film to be inspected which is continuously transported. is there.

[0014] Here, three or more film defect inspection devices are arranged, and at least three film defect inspection devices have a deflection transmission axis of the pair of polarizers in a portion of the film to be inspected having no optical defect. It is preferable that the pair of polarizers is arranged so that the crossing angles with respect to the slow axis are in a range of approximately 0 degree, 5 degrees or more and 15 degrees or less, and 35 degrees or more and 45 degrees or less, respectively. It is preferable that at least one of the film defect inspection apparatuses is a solid-state imaging device in which a plurality of the light receiving units are arranged in a row in a slant with respect to a direction orthogonal to a transport direction of the film to be inspected.

Further, according to the present invention, an optical defect of a film to be inspected arranged in parallel between a pair of polarizers is irradiated with illumination light from outside of one of the pair of polarizers and illuminated by the other. When inspecting an optical defect by receiving transmitted light transmitted from a polarizer, a birefringence characteristic is generated in one gap between the pair of polarizers and the film to be inspected. A correction film having substantially the same birefringence characteristics as that of the part without the film is arranged parallel to the film surface of the film to be inspected, and the arrangement direction of the correction film is set in advance according to the birefringence characteristics of the film to be inspected. To provide a method for inspecting a film for defects. Here, it is preferable that the arrangement direction of the deflection transmission optical axes of the pair of polarizers is set according to the type of defect of the film to be inspected.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a film defect inspection apparatus according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings. FIG. 1 shows a schematic configuration of a film defect inspection apparatus 10 for detecting a defect of a viewing angle improving film, which is a preferred embodiment of a film defect inspection apparatus of the present invention.

The film defect inspection apparatus 10 generates a luminance signal for detecting an optically defective portion of a viewing angle improving film (hereinafter, referred to as a film to be inspected) F, that is, a defective portion having a different birefringence characteristic from a normal portion. A device for obtaining
The obtained luminance signal is used as a defect detection device 22 for defect detection.
Sent to The film defect inspection apparatus 10 includes the illumination light source 1
2, a pair of polarizers 14a and 14b sandwiching the film F to be inspected from both sides, a liquid crystal correction film 16, an optical system 18, and a CCD camera 20. You.

The illumination light source 12 is an illumination light source for uniformly projecting parallel light on the film surface of the film F to be inspected via the polarizer 14a. For example, a transmission light is used. The light to be projected is preferably white light, but is not limited as long as it is a light source of projection light having a spectrum in the visible region. The illumination light source 12 may be a surface light source that uniformly projects a certain area on the film surface of the inspection target film F, or a line that uniformly emits light in one direction of the film surface of the inspection target film F. It may be a light source.

The pair of polarizers 14 includes a polarizer 14a and a polarizer 14b. The polarizer 14a is arranged in parallel with the film surface of the film F to be inspected, and linearly deflects or deflects light emitted from the illumination light source 12. , Almost linearly deflected,
This is a part to be incident on the film to be inspected F. Polarizer 14
b indicates the state of crossed Nicols with the polarizer 14a (the polarizer 14a).
(a) with the deflecting transmission optical axis of a and the deflecting transmission optical axis of the polarizer 14b being orthogonal to each other) and being arranged parallel to the film surface of the film F to be inspected and transmitting through the film F to be inspected and a liquid crystal correction film 16 described later. Part of the transmitted light L, ie,
This is a portion that transmits the component of the transmitted light L in the direction of the polarized transmitted light axis of the polarizer 14b. Known polarizers are used as the polarizers 14a and 14b.

The optical system 18 is an optical system lens for condensing transmitted light L, which is parallel light transmitted through the polarizer 14b, to form an image on the light receiving surface of the CCD camera 20, and a known optical system lens is used. Can be In this embodiment, the transmitted light L is condensed from the parallel light by using the optical
The image is formed on the light receiving surface of
This is because the value of the luminance signal obtained by the amount of the transmitted light L when the light is received by the light receiving surface of the D camera 20 has a viewing angle dependency that changes depending on the light receiving position of the light receiving surface of the CCD camera 20. As described above, the optical system 18 is used as a viewing angle correction lens to eliminate the above viewing angle dependency and obtain a luminance signal that does not require shading correction. The optical system 18 is not always indispensable because the luminance signal can be obtained and a luminance signal that does not require shading correction can be obtained. However, it is particularly preferable to use the optical system 18 when detecting a highly defective portion with a smaller viewing angle dependency or when the luminance signal value is small and the SN ratio of the defective portion is small.

The CCD camera 20 includes a polarizer 14a, a film to be inspected F, a liquid crystal correction film 16, and a polarizer 14b.
The light receiving means receives the transmitted light L transmitted through the optical system 18 and collected by the optical system 18 and obtains a luminance signal of the transmitted light L. The solid-state imaging devices on the light receiving surface are linearly arranged in one direction. A line sensor is used. In the present invention, the solid-state imaging device on the light receiving surface may be an area sensor arranged in an area. In the present invention, the present invention is not limited to a CCD camera having a solid-state imaging device on a light receiving surface.
A known solid-state imaging device such as an OS-type imaging device may be used.

The liquid crystal correction film 16 is a feature of the present invention, and takes out a portion of a predetermined range of the film F to be inspected which has been confirmed in advance to be free from optical defects. The film is rotated or turned upside down and arranged in parallel to the film F to be inspected. In this way, the liquid crystal correction film 16 having the same birefringence characteristics as the film F to be inspected is placed in the
The reason why the film is rotated by 80 degrees or the film surface is turned upside down is as follows. That is, since the film to be inspected F is made to have a predetermined birefringence characteristic, if the liquid crystal correction film 16 is not provided, the luminance signal obtained by the CCD camera 20 is
Has a viewing angle dependence that depends on the light receiving position of the light receiving element, so that the luminance signal of the normal film surface does not become a signal of a uniform level. Therefore, the detection that detects a defective portion from the luminance signal of the normal film surface is performed. Accuracy decreases. Therefore, the luminance signal is corrected by using the liquid crystal correction film 16 so that the luminance signal on the normal film surface becomes a constant level regardless of the light receiving position, that is, the luminance signal level becomes uniform.

For example, FIG. 2A shows a normal defect inspection apparatus that does not use the liquid crystal correction film 16,
Here, an example without the optical system 18 is shown. The defect inspection device 30 emits light from the illumination light source 32 and
a, a CCD camera 36 using the transmitted light passing through the film F to be inspected and the polarizer 34b as a light receiving surface of a line sensor.
2B, a luminance signal is obtained, and the luminance signal has a viewing angle dependency in which the level of the luminance signal G of the normal film surface is inclined rightward in the figure as shown in FIG. Therefore, the S / N ratio of the luminance signal N of the defective portion on the normal luminance signal G is low, and the defect detection accuracy is low. On the other hand, a defect inspection apparatus 40 (see FIG. 2C), which is an example of a defect inspection apparatus using the liquid crystal correction film according to the present invention, includes a polarizer 44a, a film F to be inspected, 46 (corresponding to the liquid crystal correction film 16) and the transmitted light passing through the polarizer 44b are received by a CCD camera 48 having a line sensor as a light receiving surface to obtain a luminance signal. As a result, a luminance signal is obtained in which the luminance signal N 'of the defective portion is superimposed on the luminance signal G' of the normal film portion at a uniform level (of course including a noise component) (see FIG. 2D). . As a result, a defective portion can be detected from the luminance signal G without performing shading correction.

As described above, the use of the liquid crystal correction film 16 in the film defect inspection apparatus 10 makes it possible to obtain a luminance signal at a constant level independent of the image pickup position as shown in FIG. In addition to improving the S / N ratio of the luminance signal, the amount of transmitted light received by the CCD camera 20 also increases, and the level of the luminance signal also increases.
The N ratio is improved, and the detection accuracy is also improved.

The liquid crystal correction film 16 has a film F to be inspected having no optical defects within a film plane of 180 degrees.
It is rotated by degrees or arranged with the film surface upside down, but in the present invention, it is not limited to this,
Using a liquid crystal correction film whose birefringence characteristics are substantially the same as the birefringence characteristics of a film to be inspected having no optical defects, as described above, the viewing angle dependency of the luminance signal obtained by the CCD camera 20 is eliminated, and a certain level is obtained. Any correction film may be used as long as the arrangement direction is set in advance in accordance with the predetermined birefringence characteristics of the film F to be inspected so as to obtain the luminance signal. Here, the term “substantially the same birefringence characteristic” depends on the degree of a defect to be detected. For example, the retardation value ((birefringence of slow axis−birefringence of axis orthogonal to slow axis) ± 30n difference in refractive index) x thickness)
m, preferably ± 10 nm or less. In addition, the liquid crystal correction film 16 includes the polarizer 14a or 14
It may be bonded to b. In the film defect inspection apparatus 10, the liquid crystal correction film 16 is disposed between the inspection target film F and the polarizer 14b, but is disposed between the polarizer 14a and the inspection target film F. You may.

The defect detecting device 22 has a predetermined emphasizing circuit, for example, a differentiation processing circuit, a spatial filter circuit, and the like, and a detecting circuit corresponding to the type of defect, for example, a "streak detecting circuit" or a "light stain detecting circuit". Then, the luminance signal subjected to the differential processing and the filter processing is processed in the detection circuit to determine the presence or absence of a defect.

As described above, the CCD camera 20 of the film defect inspection apparatus 10 is constituted by a line sensor in which solid-state image pickup devices are arranged in a line, and the arrangement direction of the solid-state image pickup devices is as shown in FIG. The direction may be a horizontal direction in the plane of the paper, a direction perpendicular to the plane of the paper, or a direction inclined with respect to the plane of the paper. However, when the film F to be inspected is a long object and the film F to be inspected is inspected by the film defect inspecting apparatus 10 during transportation, CC
It is preferable that the solid-state imaging devices of the D camera 20 are arranged to be inclined with respect to a direction orthogonal to the transport direction of the film F to be inspected.

Such an example is shown in FIG. Here, for ease of understanding, the relationship between the CCD camera 20 of the film defect inspection apparatus 10 and the film F to be inspected is shown, and the illumination light source 12, the pair of polarizers 14, the correction film 16, and the optical system 18 are omitted. are doing. Where CCD
The camera 20 is a line sensor in which solid-state imaging devices are arranged in a line, and the CCD camera 20 is arranged so that the CCD camera 20 is inclined at 45 degrees with respect to a direction orthogonal to the transport direction of the film F to be inspected. That is, the solid-state imaging devices of the CCD camera 20 are arranged in a row at an angle of 45 degrees with respect to a direction orthogonal to the transport direction of the film F to be inspected. Such a C
The arrangement of the CD camera 20, a flexible on a support stage unevenness F ₁ to F ₅ caused by coating unevenness in the manufacturing process of the inspection film F for applying the liquid crystal be generated in the direction perpendicular to the transport direction , The luminance signal A sent to the defect detection device 22
(See FIG. 3), the luminance signal value corresponding to the step unevenness F ₂ to F ₅ is changed. The defect detection device 22 differentiates the luminance signal A by a differentiation processing circuit to obtain a change in the luminance signal and obtains a differentially processed luminance signal B. This makes it possible to emphasize the defect and easily detect the defect by comparing the signal value of the differential processing luminance signal B with the threshold. The processing luminance signal A or the differential processing luminance signal B is subjected to image rotation processing so that the transport direction of the film F to be inspected is horizontal or vertical on the screen, and the screen C is displayed on a monitor. You.

On the other hand, as shown in FIG.
If the arrangement direction of the solid-state imaging device 0 'and a direction perpendicular to the conveying direction of the inspected film F, even when imaging a step unevenness F _3, the luminance signal D of the stage unevenness of step unevenness Only the level of the DC component changes as compared to the luminance signal H of the normal part (see FIG. 4). Accordingly, the differentiated luminance signal E obtained by performing the differential processing does not have a large change in the luminance signal value similarly to the differential processed luminance signal I of the normal portion without a defect, and the luminance signal value is compared with the threshold value. No defect can be detected from the data.

As described above, it is preferable that the arrangement direction of the CCD camera 20 is determined by assuming in advance the direction in which a defect such as step unevenness which is likely to occur in one direction is generated in advance. In the example of FIG.
The arrangement direction of the solid-state imaging devices is inclined by 45 degrees with respect to the direction perpendicular to the transport direction of the film F to be inspected, but the inclination angle is not limited in the present invention. However, in consideration of the case where the image is displayed on a monitor screen (not shown) with the transport direction being the horizontal direction or the vertical direction, the inclination angle is preferably set to 45 degrees so that the image can be easily rotated. The film defect inspection device 10 and the defect detection device 22 are configured as described above.

In such a film defect inspection apparatus 10, light uniformly emitted from the illumination light source 12 is applied to the polarizer 1.
Only the component linearly deflected in one direction by 4a is incident on the film F to be inspected. In the test film F, the linearly polarized light is elliptically deflected by the birefringence characteristic of the test film F, and is transmitted from the test film F. Further, the light is subjected to elliptical deflection by the birefringence characteristic of the liquid crystal correction film 16 and is transmitted from the liquid crystal correction film 16. The elliptically-polarized light transmitted from the liquid crystal correction film 16 is transmitted by the polarizer 14a and the polarizer 14b arranged in crossed Nicols so that only the component in the direction of the polarization transmission optical axis of the polarizer 14b is transmitted, and is condensed by the optical system 18. Then, the light is received by the CCD camera 20.

Here, if the film F to be inspected contains a defect, the elliptical deflection component of the light passing through the defective portion is:
It is different from the elliptical polarization component of the light transmitted through the normal portion without any defect. Therefore, even in the luminance signal obtained by receiving light by the CCD camera 20, the luminance signal value of the defective portion greatly changes, for example, the luminance signal value increases. In addition, by the action of the liquid crystal correction film 16, it is obtained by the CCD camera 20.
The luminance signal is a signal of a uniform level having no viewing angle dependency. In the present invention, the elliptical deflection of light due to the birefringence characteristic of the film F to be inspected does not mean that the light is linearly polarized due to the birefringence characteristic of the liquid crystal correction film 16; Is not compensated for using the anisotropy of the birefringence of the liquid crystal correction film 16, but the C
By correcting the visual dependency of the CD camera, that is, the viewing angle dependency in which the value of the luminance signal changes depending on the light receiving position of the light receiving element, using the birefringence characteristic of the liquid crystal correction film 16, the luminance signal can be made uniform. It is what keeps it at the level. Such a luminance signal is sent to the defect detection device 22 and subjected to a differentiation process and a spatial filter process. The luminance signal of the defective portion is identified and detected by distinguishing it from noise components from the luminance signal of a uniform level. Sent to various detection circuits,
Defect detection is performed from the luminance signal.

As described above, the film defect inspection apparatus according to the present invention uses a liquid crystal correction film to obtain a uniform level of luminance signal having no viewing angle dependency. Used in the manufacturing process of the film (liquid crystal viewing angle improving film) F, it is possible to accurately detect all optical defects generated during the manufacturing process of the film F to be inspected without leaking. Hereinafter, a film defect inspection system of the present invention in which the film defect inspection apparatus of the present invention is applied to the manufacturing process of the film to be inspected F will be described.

FIG. 5 shows an example of a defect inspection system according to the present invention, which is a film defect inspection system 50 for inspecting a defect of a viewing angle improving film for liquid crystal (film to be inspected) F.
Is shown. The film defect inspection system 50 includes film defect inspection devices 58, 60, and 62 and a defect detection device 64 having the configuration of the film defect inspection device according to the present invention.
Is provided. Here, the inspection target film F to be inspected is
Is manufactured by applying various steps of applying a liquid crystal on a flexible support, drying the liquid crystal, further aligning the liquid crystal, and curing the film. The film defect inspection system 50 rolls the produced film F to be inspected from the take-up roll 52 to the roller 56a.
In a system in which the film defect inspection devices 58, 60 and 62 are arranged in a transport path for finally and continuously transporting the film to the take-up roll 54 via the control signals 56 to 56j, the luminance signal is output by each of the film defect inspection devices 58, 60 and 62. The luminance signal is sent to the defect detection device 64 to detect a defect.

The defect detection device 64, like the defect detection device 22, has a differential processing circuit and a spatial filter circuit, and a detection circuit corresponding to the type of defect, for example, a "streak detection circuit" or a "light stain detection circuit". Then, the received luminance signals of the film defect inspection devices 58, 60 and 62 are processed by a differentiation processing circuit or a spatial filter circuit, and the presence or absence of a defect is determined by a detection circuit to detect the defect.

The film defect inspection device 58 includes the illumination light source 5
8a, a polarizer 58b, a liquid crystal correction film 58c, a polarizer 58d, an optical system 58e, and a CCD camera 58f. These are the illumination light source 12, the polarizer 14a, the liquid crystal correction film 16, It corresponds to the subunit 14b, the optical system 18, and the CCD camera 20, and the configuration and the operation are the same, so that the description is omitted. Here, the polarizer 58b and the polarizer 58d are arranged such that the deflecting and transmitting optical axes are arranged in crossed Nicols, and one of the deflecting and transmitting optical axes of the polarizer 58b and the polarizer 58d is arranged in parallel with the transport direction. That is, the crossing angle of the polarization transmission axis of the pair of polarizers with respect to the transport direction (the crossing angle of the polarization direction with respect to the transport direction refers to the crossing angle of one of the polarizers with respect to the transport direction of the deflection transmission optical axis. ) Is set to approximately 0 degrees. Here, the term “approximately 0 degrees” is different depending on the birefringence characteristics of the film F to be inspected.
It means within 2-3 degrees.

The film defect inspection device 60 includes the illumination light source 6
0a, a polarizer 60b, a liquid crystal correction film 60c, a polarizer 60d, and a CCD camera 60e. These are the illumination light source 12 and the polarizer 14 of the defect inspection apparatus 10 described above.
a, liquid crystal correction film 16, polarizer 14b and CCD
It corresponds to the camera 20, and these configurations and operations are as follows.
Illumination light source 12, polarizer 14a, liquid crystal correction film 16,
Since they are the same as the polarizer 14b and the CCD camera 20, the description is omitted. In addition, the film defect inspection device 60
Does not include the optical system 18. In addition, the polarizer 60b and the polarizer 60d have a polarization transmission optical axis arranged in crossed Nicols, and one of the polarization transmission optical axes of the polarizer 60b or the polarizer 60d is slightly inclined with respect to the transport direction, for example,
It is arranged to be inclined in a range of 5 degrees or more and 15 degrees or less. That is, the intersection angle of the deflection transmission axis of the pair of polarizers with the transport direction is set to, for example, 5 degrees or more and 15 degrees or less, and preferably, for example, to about 10 degrees.

The film defect inspection device 62 includes the illumination light source 6
2a, a polarizer 62b, a liquid crystal correction film 62c, a polarizer 62d, and a CCD camera 62e. These are the illumination light source 12, the polarizer 14a, the liquid crystal correction film 16, the polarizer 14b, and the CCD of the above-described film defect inspection device 10. Since they correspond to the camera 20 and have the same configuration and operation as those of the illumination light source 12, the polarizer 14a, the liquid crystal correction film 16, the polarizer 14b, and the CCD camera 20, their description will be omitted. The film defect inspection device 62 does not include the optical system 18. The polarizer 62
b and the polarizer 62d are arranged in a crossed Nicols with a deflecting and transmitting optical axis, and one of the deflecting and transmitting optical axes of the polarizer 62b or the polarizer 62d is about 45 degrees with respect to the transport direction, for example, 35 degrees or more and 45 degrees or more. It is arranged at an angle in the range below degrees. That is, the crossing angle of the pair of polarizers with respect to the transport direction of the deflection transmission axis is set to, for example, 35 degrees or more and 45 degrees or less, and preferably, for example, to about 45 degrees.

As described above, the film defect inspection devices 58 and 6
The reason why the crossing angle of the polarization transmission axis of the polarizer in 0 and 62 is changed is to obtain a luminance signal in a state where the SN ratio is the highest according to the type and the degree of the defect of the film F to be inspected. Hereinafter, the operation will be described. FIG. 6 shows that in the film defect inspection apparatus 10, the retardation value of the film F to be inspected ((birefringence of slow axis−birefringence of axis perpendicular to the slow axis) × thickness of film F to be inspected). When the value is 22 nm, the intersection angle between the deflection transmission axis of the pair of polarizers 14 and the slow axis of the film F to be inspected (the intersection angle with the slow axis is one of the pair of polarizers). The ratio of the amount of light transmitted through the other polarizer to the amount of light incident on one polarizer (meaning the angle of intersection between the polarization transmission axis of one polarizer and the slow axis of the film F). (Light amount ratio) changes.

According to FIG. 6, the crossing angle between the slow axis of the film F to be inspected and the deflection transmission axis is 0 degree, that is, the slow axis of the film F to be inspected is parallel to the deflection transmission axis of one polarizer. In some cases, the light incident on the film to be inspected F is a polarizer 14.
a, the polarizer 1 arranged in crossed Nicols to transmit through the film to be inspected F in the state of linear deflection received by
No light is transmitted from the light-receiving portion 4b, so that the transmitted light amount ratio is zero. However, as the intersection angle between the slow axis and the deflecting transmission axis of the film F to be inspected increases, the light linearly deflected by the polarizer 14a becomes affected by the birefringence characteristic of the film F to be inspected, so that the elliptical deflection component is generated. Becomes stronger. Therefore, the polarizer 1
The amount of transmitted light transmitted from 4b gradually increases with the crossing angle, and the transmitted light ratio increases.

Here, a case is considered where a defect exists in the film F to be inspected, that is, the direction of the slow axis of the film F to be inspected is disturbed, and the intersection angle between the slow axis and the deflection transmission axis fluctuates. For example, when the defect of the film F to be inspected is a large alignment defect in which the slow axis is inclined by a predetermined angle or more, for example, 5 degrees or more due to the alignment defect of the liquid crystal, the slow axis and the deflection of the normal part of the film F to be inspected are deflected. Even when the crossing angle of the transmission axis is 0 degree, in the case of a large orientation defect, the direction of the slow axis of the defect portion is largely shifted to form a large crossing angle with the deflection transmission axis. Correspondingly, the amount of transmitted light changes greatly. Therefore, the obtained luminance signal of the defective portion is detected as a large signal change.

On the other hand, when the slow axis of the alignment defect is inclined with respect to the polarization transmission axis of the polarizer 14, but the angle is smaller than a predetermined angle, for example, when the alignment defect is smaller than 5 degrees, the alignment defect is reduced. When the intersection angle between the slow axis and the deflecting transmission axis of the normal portion of the inspection film F is substantially 0 degree, as shown in FIG. Since the transmitted light amount ratio does not change sufficiently, it is difficult to detect a small alignment defect as a luminance signal. Therefore, by setting the crossing angle between the slow axis and the deflection transmission axis of the film F to be inspected to 5 degrees or more and 15 degrees or less, for example, 10 degrees, the change in the transmitted light amount ratio with respect to a slight change in the direction of the slow axis. Can be amplified. That is, in the case of a small alignment defect, the crossing angle between the normal slow axis of the film F to be inspected and the deflection transmission axis of the polarizer 14 is set to 5 degrees or more and 15 or less, thereby changing the transmitted light amount ratio due to the small alignment defects. Can be increased to amplify the change in the luminance signal, the S / N ratio can be improved, and the accuracy of defect detection can be increased.

In this embodiment, by limiting the intersection angle to 5 degrees or more and 15 degrees or less, the luminance signal of a small alignment defect can be reduced while the level of the luminance signal of the normal portion of the film F to be inspected is kept low. Although it can be effectively detected, in the present invention, it is not necessary to limit the crossing angle to 5 degrees or more and 15 degrees or less depending on the birefringence characteristics of the film F to be inspected, and as shown in FIG. The intersection angle may be appropriately set according to the curve of the ratio of the amount of transmitted light to the intersection angle.

In the film F to be inspected, there are no alignment defects, but a phase difference defect whose retardation value fluctuates due to coating unevenness in the manufacturing process, that is, the above-mentioned step unevenness also occurs. When the intersection angle between the slow axis and the polarization transmission axis of the polarizer 14 shown in FIG. 6 is small, the transmitted light amount ratio is originally small, so that the transmitted light amount ratio largely changes in response to the change in the retardation value due to the phase difference defect. do not do. On the other hand, when the crossing angle is large, the transmission light amount itself is large as shown in FIG. 7 showing a change in the transmission light amount ratio with respect to the retardation value when the crossing angle is 45 degrees. The change in the light amount ratio is large. Therefore, in the case of a phase difference defect in which the retardation value changes, the above-mentioned intersection angle is set to a large value, for example, 35 degrees or more and 45 degrees or less, preferably, for example, 45 degrees.
The transmitted light amount ratio with respect to the change in the retardation value can be largely changed, the change in the luminance signal in the phase difference defect portion can be amplified, the SN ratio can be improved, and the detection accuracy of the phase difference defect can be increased. As described above, the preferred mode of the crossing angle is 45 degrees.
4 are arranged in crossed Nicols, the transmission light amount ratio becomes maximum at an intersection angle of 45 degrees, and the change in the transmission light amount ratio with respect to the retardation value at this intersection angle becomes maximum. In the present invention, the film to be inspected F
Depending on the birefringence characteristics of
It is not necessary to limit the angle to the degree or less, and the intersection angle may be appropriately set according to a curve of the transmitted light amount ratio with respect to the intersection angle as shown in FIG.

As described above, by changing the intersection angle between the slow axis of the normal portion of the film F to be inspected and the deflection transmission axis of the polarizer in accordance with the type and the degree of the defect, the defect can be completely leaked. It can be detected with high accuracy.

The film defect inspection system 50 utilizes the fact that the film to be inspected F to be transported is manufactured with the slow axis directed in a direction orthogonal to the transport direction based on the above-described principle. The deflection transmission axes of the polarizers in the inspection devices 58, 60 and 62 are changed in a predetermined direction with respect to the transport direction. That is, in the film defect inspection device 58, the slow axis of the film F to be inspected and the polarizer 5 are detected so that a large alignment defect can be detected with high accuracy.
In order to set the crossing angle of the deflecting transmission optical axis of 8b or 58d to substantially 0 degree, that is, substantially parallel, the polarizer 58b or 58d
Are arranged at substantially 0 degrees, that is, substantially parallel to the transport direction. Accordingly, the defect inspection apparatus 58 can obtain a luminance signal capable of accurately detecting a large alignment defect, and further, a defect due to foreign matter contamination in which the direction of the slow axis varies in various ways and the retardation value varies in various ways. It is also possible to obtain a luminance signal that can be detected with high accuracy.

In the film defect inspection apparatus 60, the intersection angle between the slow axis of the film F to be inspected and the deflecting transmission optical axis of the polarizer 60b or 60d is set to about 10 degrees so that small alignment defects can be detected with high accuracy. Therefore, the polarization transmission optical axis of the polarizer 60b or 60d is arranged at approximately 10 degrees with respect to the transport direction. Thereby, the film defect inspection device 60
In addition to obtaining a luminance signal that can accurately detect small alignment defects, not only large alignment defects, but also the direction of the slow axis varies in various ways and the retardation values vary in various ways. A detectable luminance signal can be obtained.

In the film defect inspection apparatus 62, not the alignment defect in which the direction of the slow axis has changed but the phase difference defect in which the retardation value has changed can be detected with high accuracy so that the slow axis of the film F to be inspected can be detected. The crossing angle of the deflecting transmission optical axis of the polarizer 62b or 62d is set to approximately 45 degrees, and therefore, the deflecting transmission optical axis of the polarizer 62b or 62d is disposed at approximately 45 degrees with respect to the transport direction. As a result, the film defect inspection device 62 can obtain a luminance signal that can accurately detect a phase difference defect.

As described above, the defect inspection system 50 classifies the optical defects of the film F to be inspected into large or small alignment defects depending on the degree of misalignment of the direction of the slow axis. In addition, it is possible to detect a phase difference defect in which the retardation value is deviated, and it is also possible to detect a defect or the like due to foreign matter mixing. In the defect inspection system 50, the deflecting transmission optical axes of the pair of polarizers of the defect inspection apparatus are set to approximately 0 degrees, approximately 10 degrees, and approximately 4 degrees with respect to the transport direction.
Although three defect inspection devices are arranged to intersect at five degrees, the defect inspection system of the present invention does not limit the number of defect inspection devices.
The crossing angle is not limited, and the crossing angle may be variously changed according to the birefringence characteristics such as the direction of the slow axis of the film F to be inspected and the retardation value.

Such a film defect inspection system 50
In the film defect inspection devices 58, 60 and 62, a plurality of CCD cameras are arranged in accordance with the width of the film F to be inspected. For example, in the film defect inspection device 60,
As shown in FIG. 8, the film to be inspected F continuously transported
To fit the width and sends a luminance signal by receiving the light transmitted through the full width by a CCD camera 60e consisting of CCD camera 60e ₁ ~60e ₆ for defect detection device 64.

In the defect inspection system 50, for example, the film F to be inspected continuously conveyed at a speed of 18 m / min.
6 CCD cameras are arranged in the width direction as described above,
The resolution by the camera is set to, for example, 0.125 mm, and the luminance signal obtained by the film defect inspection device 60 is compared with a differentiation circuit, a spatial filter circuit, etc.
For the luminance signal obtained by the film defect inspection apparatus 60 by passing through, a desired defect inspection is performed in-line by passing through a differential processing circuit, a spatial filter circuit, and a "streak detection circuit".

In particular, the above-mentioned coating unevenness during the production of the film to be inspected F causes unevenness in the level generated in the direction perpendicular to the transport direction, resulting in a phase difference defect in which the retardation value changes. When detecting step unevenness using the film defect inspection apparatus 60 having the polarizer 60b or 60d inclined at approximately 45 degrees with respect to the transport direction,
Using the camera 60e ₁ ~60e _6, or a plurality in accordance with the width of the test film F as described above, for example using a six CCD cameras, with respect to a direction perpendicular to the conveying direction of the inspected film F The image may be taken at an angle, for example, at 45 degrees. At this time, it is preferable that the defect detection device 64 performs an image rotation process so as to be in a horizontal or vertical transport direction on the screen. In this manner, the generation cycle of the step unevenness and the strength of the step unevenness can be quantified.

As described above, the film defect inspection apparatus of the present invention
Although the defect inspection system and the defect inspection method have been described in detail, the present invention is not limited to the above embodiment, and various improvements and changes may be made without departing from the spirit of the present invention. is there.

[0054]

As described above in detail, the film to be inspected has substantially the same birefringence characteristics as that of the film to be inspected without optical defects, and the arrangement direction is set in advance according to the birefringence characteristics of the film to be inspected. By using the correction film, the signal level of the luminance signal can be made constant and the amount of transmitted light can be increased, so that the SN ratio of the luminance signal of the defective portion can be increased and the defect detection accuracy can be improved. In addition, an optical defect inspection of a film to be inspected can be easily and easily performed on a production line or the like. Further, by changing the direction of the polarization transmission axis of the pair of polarizers, all optical defects generated during the manufacturing process can be accurately detected without leaking. In particular, in the manufacturing process of a viewing angle improving film used for a liquid crystal display device and the like,
It is possible to continuously detect a defect caused by mixing of a foreign substance, alignment unevenness, step unevenness, and the like without omission, which is effective in in-line total inspection in a manufacturing process. In particular, step unevenness,
Since the detection can be performed based on the luminance signal value of the luminance signal, the occurrence period of the step unevenness and the intensity of the step unevenness can be quantified by using the differential processing and the image processing.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining an outline of an example of a film defect inspection apparatus of the present invention.

2A is an explanatory view illustrating a conventional film inspection apparatus, FIG. 2B is a view illustrating an example of a luminance signal obtained by the inspection apparatus in FIG. 2A, and FIG. It is explanatory drawing explaining the outline of another example of the film defect inspection apparatus of this invention, and (d) is a figure which shows an example of the luminance signal obtained by the inspection apparatus of (c).

FIG. 3 is a diagram illustrating an example of an arrangement of light receiving means of the film defect inspection device according to the present invention.

FIG. 4 is a diagram illustrating an example of an arrangement of light receiving means of a conventional film defect inspection device.

FIG. 5 is a schematic configuration diagram illustrating an outline of an example of a film defect inspection system of the present invention.

FIG. 6 is a diagram showing characteristics of a transmitted light amount ratio obtained by the film defect inspection apparatus of the present invention.

FIG. 7 is a view showing another characteristic of the transmitted light amount ratio obtained by the film defect inspection apparatus of the present invention.

FIG. 8 is a schematic configuration diagram illustrating an outline of an example of a film defect inspection apparatus of the present invention used in the defect inspection system of the present invention.

[Explanation of symbols]

10, 30, 40, 58, 60, 62 Film defect inspection device 12, 32, 42, 58a, 60a, 62a Illumination light source 14 A pair of polarizers 14a, 14b, 34a, 34b, 44a, 44b, 5
8c, 60c, 62c Polarizer 16, 46, 58c, 60c, 62c Liquid crystal correction film 18, 58e Optical system 20, 36, 48, 58f, 60e, 62e CCD camera 22, 64 Defect detection device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G051 AA41 AB02 BA08 BA11 BA20 CA03 CA04 CB02 DA08 DA20 EA08 EA30 FA10 2G086 EE05

Claims (11)

[Claims] 1. A pair of polarizers arranged in parallel with the film to be inspected on both sides of a film surface of the film to be inspected for inspecting an optical defect, and a pair of polarizers arranged outside between the pair of polarizers. An illumination light source for projecting light to the film to be inspected through one of the polarizers; and an outer light source between the pair of polarizers, opposite to the position where the illumination light source is arranged, and light emitted by the illumination light source. A light receiving means for receiving the transmitted light transmitted through the other polarizer; and a film having a birefringence characteristic substantially the same as the birefringence characteristic of a portion of the film to be inspected having no optical defect. The arrangement direction is set in advance according to the birefringence characteristics of the film to be inspected, and a correction film is disposed in parallel with the film to be inspected in one gap between the pair of polarizers and the film to be inspected. Film, correction film And a film defect inspection apparatus for inspecting an optical defect of a film to be inspected by obtaining a luminance signal of transmitted light transmitted through the pair of polarizers by the light receiving unit. 2. The correction film according to claim 1, wherein a portion having no optical defect of the film to be inspected is rotated by 180 degrees in a film surface, or a film surface of a portion having no optical defect of the film to be inspected is turned upside down. The film defect inspection apparatus according to claim 1, wherein the film defect inspection apparatus is arranged in a state where the film is arranged. 3. The film defect inspection apparatus according to claim 1, wherein the correction film is bonded to one of the pair of polarizers. 4. An optical system for condensing transmitted light on said light receiving means in an optical path of transmitted light between said light receiving means and a polarizer arranged on said light receiving means side of said pair of polarizers. The film defect inspection apparatus according to claim 1, wherein: 5. The film defect inspection apparatus according to claim 1, wherein said light receiving means is a solid-state image sensor. 6. When the inspection for the optical defect of the film to be inspected is performed during the transport of the film to be inspected, the light receiving means includes:
The film defect inspection device according to claim 5, wherein the plurality of solid-state imaging devices are arranged in a row in a slant with respect to a direction orthogonal to a transport direction of the film to be inspected. 7. A film defect system for inspecting an optical defect of a film to be inspected which is continuously conveyed, comprising a pair arranged on both sides of a film surface of the film to be inspected for an optical defect in parallel with the film to be inspected. And a light source disposed outside the pair of polarizers, and an illumination light source for projecting the film to be inspected through one of the pair of polarizers, and an outer side between the pair of polarizers. A light receiving means for receiving the transmitted light emitted by the illumination light source and transmitted from the other polarizer, and a birefringence characteristic of an optical element of the film to be inspected. A film that is substantially the same as the birefringence characteristic of the portion having no target defect, the arrangement direction is preset according to the birefringence characteristic of the film to be inspected, and one of the pair of polarizers and the film to be inspected Inspection A plurality of film defect inspection devices comprising a correction film arranged in parallel with the film are arranged in the transport path of the film to be inspected, the direction of the deflection transmission axis of the pair of polarizers of the plurality of film defect inspection devices, A film defect inspection system, wherein the film inspection system is set at different angles with respect to the transport direction of the film to be inspected which is continuously transported in a crossed Nicols state. 8. A film defect inspection device comprising at least three film defect inspection devices, wherein at least three film defect inspection devices have a deflection transmission axis of the pair of polarizers at a position where a portion of the film to be inspected has no optical defect. The pair of polarizers are arranged so that the crossing angles with respect to the phase axis are approximately 0 degree, 5 degrees or more and 15 degrees or less, and 35 degrees or more and 45 degrees or less, respectively. Film defect inspection system. 9. At least one of said film defect inspection devices
9. The solid-state imaging device according to claim 7, wherein the light receiving unit is a plurality of solid-state imaging devices that are arranged in a row in a slant with respect to a direction orthogonal to a transport direction of the film to be inspected.
2. The film defect inspection system according to 1. 10. An optical defect of a film to be inspected arranged in parallel between a pair of polarizers is irradiated with illumination light from outside the one polarizer of the pair of polarizers and transmitted from the other polarizer. When inspecting an optical defect by receiving transmitted light, the gap between one pair of the polarizer and the film to be inspected, the birefringence characteristics of the portion of the film to be inspected without optical defects A correction film having substantially the same birefringence characteristics is arranged in parallel with the film surface of the film to be inspected, and the arrangement direction of the correction film is set in advance according to the birefringence characteristics of the film to be inspected. Defect inspection method. 11. The film defect inspection method according to claim 10, wherein an arrangement direction of the deflection transmission optical axes of the pair of polarizers is set according to a type of a defect of the film to be inspected.