KR20220018599A - Method for detecting non-uniform orientation defects of retardation film and apparatus for detecting non-uniform orientation defects - Google Patents

Abstract

An object of the present invention is to provide a method for detecting a defect in orientation irregularity of a retardation film and a device for detecting a defect in orientation irregularity, which can improve evaluation reproducibility by performing quantitative evaluation of the detection and evaluation of the defect in the orientation irregularity of the retardation film by an optical system. . The method for detecting a defect in orientation non-uniformity of the retardation film of the present invention includes the following steps (1) to (5). (1) It is rotated and arrange|positioned so that the slow axis of the said retardation film may incline by -10 to 10 degrees with respect to the absorption axis of a polarizing plate between two polarizing plates of a cross Nicole arrangement|positioning. (2) Inspection light is irradiated to the said retardation film through one polarizing plate. (3) The retardation film is image|photographed through the other polarizing plate, and a luminance image is obtained. (4) The edge portion is emphasized by differentially processing the photographed luminance image in an oblique direction with respect to the slow axis of the retardation film. (5) An edge-emphasized luminance image is binarized by a predetermined threshold value, a bright pixel or a dark pixel is obtained, and orientation nonuniformity is detected from the said pixel.

Description

Method for detecting non-uniform orientation defects of retardation film and apparatus for detecting non-uniform orientation defects

The present invention relates to a method for detecting a defect in alignment non-uniformity of a retardation film and an apparatus for detecting a defect in alignment non-uniformity. More specifically, by performing the detection and evaluation of the defect in the orientation non-uniformity of the retardation film by quantitative evaluation using an optical system, the burden on the operator can be reduced and the reproducibility of the evaluation result can be improved. And it is related with the orientation nonuniformity defect detection apparatus used for it.

In recent years, from the characteristics of power saving, light weight, thin type, etc., a liquid crystal display device is widely used for the monitor of a television, a PC, etc. A liquid crystal display device has the problem of viewing angle dependence resulting from the refractive index anisotropy of a liquid crystal cell or a polarizing plate with the above-mentioned advantage. As a representative method of improving the viewing angle dependence problem, there is a method of using a retardation film.

In the conventional manufacturing of retardation film, it is difficult to completely prevent the occurrence of defects that impair the surface quality of the film even in a strictly controlled manufacturing process.

Moreover, with thinning of a liquid crystal display device, thin film formation is calculated|required also about the retardation film used there in recent years, and the defect of orientation nonuniformity which originates in a manufacturing process and is expressed with it became remarkable.

In order to prevent the film with such a defect from flowing out to the market, the defect inspection of a film is important, and, as for the quality evaluation of an orientation non-uniformity defect, rank determination was made conventionally by visual observation. However, in such qualitative evaluation by the naked eye, the evaluation result greatly depends on the wetness level of the operator, the reproducibility is low, and the result may vary greatly when the operator changes. In addition, since the number of people who can be trusted and evaluated is limited to habitual workers, the number of workers is biased toward some workers, and problems such as placing a large burden have occurred.

As a defect inspection of an optical film, the defect inspection method and inspection apparatus currently disclosed by patent documents 1 and 2 are known.

In Patent Document 1, a transparent or translucent film sheet is targeted, a light source is provided on one surface of the film sheet to be conveyed, and a first polarizing plate is disposed between the light source and the film, and a linear array camera is provided on the other surface, A second polarizing plate is disposed between the linear array camera and the film, and the deviation angle of the polarization directions of the first and second polarizing plates is within ±20°, and a defect caused by foreign matter in the video signal output from the linear array camera A method for detecting information has been proposed.

In Patent Document 2, for a patterned retardation film used in a 3D television, the first and second polarizing plates are arranged cross-nickel so that the film is interposed therebetween, and the inspection light is irradiated to the film through the first polarizing plate. A light source, the imaging device which image|photographs the transmitted light of a film through a 2nd polarizing plate, and obtains a luminance image, and the defect detection part which detects a defect from the said luminance image are provided.

The 1st and 2nd polarizing plates are made into a state in which either one of the polarization transmission axes is substantially parallel to any one optical axis among a plurality of retardation regions of the patterned retardation film, and the luminance when a defect-free film is photographed. A defect inspection apparatus mainly by foreign matter or the like has been proposed that adjusts one polarization transmission axis so that "each luminance becomes the same level in the vicinity of a quenched state" of an image.

However, in the method proposed in Patent Document 1, the two polarizing plates deviate excessively from the cross nicol state, and in this state, the amount of light from the light source passing through the polarizing plate is large, and the change in the polarization state caused by defects in the film It becomes difficult to grasp|ascertain, and there exists a problem that the information of the orientation nonuniformity which should be acquired cannot be acquired.

Moreover, in the apparatus proposed by patent document 2, since the image|photographed luminance image became the same level in the vicinity of an extinction state, there existed a problem that the minute change of the polarization state for detecting an orientation nonuniformity could not be grasped|ascertained. In addition, from the photographed luminance image, since it is preferred to erase the boundary line of the retardation region in which the patterned retardation film differs by image processing, there is a possibility that even the defective portion to be extracted originally will be erased.

Japanese Patent Laid-Open No. 11-30591 Japanese Laid-Open Patent Publication No. 2013-50393

The present invention has been made in view of the above problems and situations, and the problem to be solved is to reduce the burden on the operator by performing the detection and evaluation of the defect in orientation non-uniformity of the retardation film by quantitative evaluation using an optical system, It is to provide a method for detecting a defect in orientation nonuniformity of a retardation film capable of improving the reproducibility of an evaluation result, and a device for detecting a defect in orientation nonuniformity used therefor.

In the process of examining the cause of the said problem, etc. in order to solve the said subject, this inventor uses the apparatus comprised from 2 sheets of polarizing plate, a light irradiation apparatus, a photographing apparatus, and a defect detection part, The orientation nonuniformity which has a specific step In terms of employing a defect detection method, by performing quantitative evaluation using an optical system to detect and evaluate the defect in the orientation non-uniformity of the retardation film, the burden on the operator can be reduced and the reproducibility of the evaluation result can be improved. It was found that a defect detection method was obtained.

That is, the said subject concerning this invention is solved by the following means.

1. A method for detecting a defect in orientation non-uniformity of a retardation film, the method comprising:

It has following steps (1)-(5), The orientation nonuniformity defect detection method of retardation film characterized by the above-mentioned.

Step (1): when disposing the retardation film between the first polarizing plate and the second polarizing plate arranged cross-nickel, the slow axis of the retardation film is relative to the absorption axis of either the first polarizing plate or the second polarizing plate A step of rotating and disposing any one of the first polarizing plate and the second polarizing plate or the retardation film so as to be within the range of -10 to 10° (however, 0° is excluded).

Step (2): A step of irradiating inspection light to the retardation film via the first polarizing plate.

Step (3): A step of obtaining a luminance image by photographing the phase difference film with a photographing device through the second polarizing plate.

Step (4): Differential (difference) processing of the photographed luminance image in a direction within a range of 35 to 55° or -55 to -35° with respect to the slow axis of the retardation film to obtain a luminance image emphasizing the edge portion step.

Step (5): A step of binarizing the edge-emphasized luminance image at a predetermined threshold value, obtaining bright pixels equal to or greater than the threshold value and dark pixels lower than the threshold value, and detecting alignment unevenness from the bright pixels or dark pixels.

2. In addition, expansion processing is performed on the luminance image binarized in an oblique direction within a range of 70 to 120° with respect to the direction of differential (difference) processing of the retardation film to emphasize the component in the oblique direction It has step (6) which performs image processing, The orientation nonuniformity defect detection method of retardation film of Claim 1 characterized by the above-mentioned.

3. Furthermore, after performing the said expansion|swelling process, it has the step (7) of shrink|contracting processing with respect to the said luminance image in the same direction, The orientation nonuniformity defect detection method of the retardation film of Claim 2 characterized by the above-mentioned.

4. Further, with respect to the luminance image subjected to the shrinkage treatment, a step (8) of extracting, as an orientation non-uniformity defect component in the direction, a filter condition defined by the representative length of each pixel region is extracted. The method for detecting an orientation non-uniformity defect of the retardation film according to claim 3 .

5. The angle of view (θ) of the lens calculated from the distance between the lens tip position of the imaging device and the retardation film, and the size of the inspection area on the retardation film in the longitudinal direction, is 23 with respect to the longitudinal direction of the retardation film It is within °, the defect detection method of non-uniform orientation of the retardation film in any one of Claims 1-4 characterized by the above-mentioned.

6. A device for detecting non-uniform orientation of retardation film used in the method for detecting a defect in orientation non-uniformity of retardation film according to any one of claims 1 to 5,

A first polarizing plate and a second polarizing plate which are arranged to be cross-nickel so that the retardation film is interposed therebetween;

a light source for irradiating inspection light to the retardation film through the first polarizing plate;

a photographing apparatus for photographing the retardation film through the second polarizing plate to obtain a luminance image;

and a defect detection unit for detecting a defect from the luminance image;

The defect detection unit,

When disposing the retardation film between the first polarizing plate and the second polarizing plate arranged cross-nickel, the slow axis of the retardation film is -10 to 10° with respect to the absorption axis of either the first polarizing plate or the second polarizing plate. (However, 0° is excluded) so that the first polarizing plate and the second polarizing plate or any one of the retardation film are rotated and photographed so that the luminance image is rotated with respect to the slow axis of the retardation film. an edge detection circuit for emphasizing an edge portion by performing a differential (differential) process in a direction within a range of 35 to 55° or -55 to -35°;

A binarization circuit that binarizes the edge-detected luminance image at a predetermined threshold, and makes each pixel a bright pixel greater than or equal to the threshold and a dark pixel lower than the threshold.

A device for detecting the orientation non-uniformity of the retardation film, characterized in that it has a.

7. The defect detection unit,

An image processing circuit for emphasizing the component in the oblique direction by performing expansion processing on the binarized luminance image in an oblique direction within a range of 70 to 120° with respect to the direction of differential (difference) processing of the retardation film; It has, the orientation nonuniformity defect detection apparatus of the retardation film of Claim 6 characterized by the above-mentioned.

8. The defect detection unit,

After performing the said expansion process, it has an image processing circuit which performs shrinkage process with respect to the said luminance image in the same direction, The orientation nonuniformity defect detection apparatus of the retardation film of Claim 7 characterized by the above-mentioned.

9. The defect detection unit,

The luminance image that has been subjected to the shrinkage treatment has a filtering circuit that extracts, as an alignment non-uniformity defect component in the direction, a filter condition defined by the representative length of each pixel region as a component of the orientation non-uniformity defect. Film orientation non-uniformity defect detection device.

10. The angle of view (θ) of the lens calculated from the distance between the lens tip position of the imaging device and the retardation film, and the size of the inspection area on the retardation film in the longitudinal direction, is 23° with respect to the longitudinal direction of the retardation film Orientation nonuniformity defect detection apparatus of the retardation film in any one of Claims 6-9 characterized by the above-mentioned.

By the above means of the present invention, the detection and evaluation of defects in the orientation non-uniformity of the retardation film is performed by quantitative evaluation using an optical system, thereby reducing the burden on the operator and improving the reproducibility of the evaluation result. A defect detection method and an orientation nonuniformity defect detection apparatus used therefor can be provided.

Although it is not clear about the expression mechanism thru|or an action mechanism of the effect of this invention, it is guessed as follows.

Two polarizing plates are arranged in a cross nicol so that the slow axis of the retardation film is in the range of -10 to 10° (however, 0° is excluded) with respect to the absorption axis of the polarizing plate, the polarizing plate or any of the retardation films By rotating and disposing, it is estimated that the change of the polarization state accompanying the change of the slow axis is emphasized, and the detection accuracy of the defective part (orientation non-uniformity defect) can be improved.

Differential processing is processing in which edge extraction of an image (extracting a part in which the brightness of the image changes suddenly is called edge extraction) is performed with a differential filter, but in the case of an image, since it is not a continuous value, the difference between pixel values is taken ("Difference" referred to in the present invention.) It is treated as an approximation of the derivative.

In order to emphasize the edge of the said defect part, the direction of the said differentiation process is designated to be inclined in a direction within the range of 35 to 55 degrees or -55 to -35 degrees with respect to the slow axis of the said retardation film. Usually, when manufacturing the retardation film, the slow axis is oriented in one direction by stretching or the like, but minute alignment unevenness due to non-uniformity of the transverse tension applied during stretching or drying is accumulated in other than the one direction. , As a result, it is estimated that the detection precision of orientation nonuniformity can be improved at the point which makes it easy to extract the inclination component of orientation nonuniformity by a differential process.

In addition, the obtained luminance image is binarized in order to roughly distinguish a defective part from a normal area other than that, and the expansion process and the shrinkage process further emphasize the defect part in the said binarized image, so that defect It is presumed that the detection accuracy can be further improved.

With respect to the luminance image subjected to the shrinkage treatment, by extracting as a component of the alignment nonuniformity defect in the direction that satisfies the filter condition defined by the representative length of each pixel region, only the alignment nonuniformity defect can be detected, and the above image processing It is conjectured that it is possible to provide a quantitative method for evaluating orientation non-uniformity defects with good precision.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the outline of the conventional visual evaluation method of an orientation nonuniformity defect.
Fig. 2 is a schematic diagram for explaining the angle of view of a lens attached to a camera used for inspection;
3A is a specific example of an image binarized with a predetermined threshold (original luminance image);
Fig. 3B is a specific example of an image binarized with a predetermined threshold (binarized image);
4 is a flowchart of image processing and a specific example of the processed image;
It is a schematic diagram which shows an example of the orientation nonuniformity defect detection apparatus of the retardation film of this invention.
6 is a schematic diagram illustrating a defect detection unit having an edge detection circuit, a binarization circuit, an image processing circuit, and a filtering circuit;

The method for detecting an orientation non-uniformity defect of the retardation film of the present invention is characterized by having the steps (1) to (5). This feature is a technical feature common to or corresponding to the following embodiments.

In an embodiment of the present invention, from the viewpoint of expression of the effect of the present invention, the luminance image binarized in an oblique direction within a range of 70 to 120° with respect to the direction of differential (difference) processing of the retardation film. Having the step (6) of performing an expansion process on the polarizer and emphasizing the component in the oblique direction is a point of emphasizing a defective portion, from the viewpoint of enabling quantitative alignment nonuniformity defect evaluation with high accuracy. desirable.

Further, having the step (7) of performing the shrinkage treatment in the same direction on the luminance image after performing the expansion treatment is a point of emphasizing a defective portion and reducing noise, and quantitatively evaluating the alignment nonuniformity defect with good accuracy. It is preferable from the viewpoint of enabling

In addition, with respect to the luminance image subjected to the shrinkage treatment, having a step (8) of extracting, as a component of an orientation non-uniformity defect in the direction, a filter condition stipulated by the representative length of each pixel region, is extracted, It is specific, and it is preferable from a viewpoint of enabling quantitative orientation nonuniformity defect evaluation with high precision.

The angle of view (θ) of the lens calculated from the distance between the lens tip position of the imaging device and the retardation film, and the size of the inspection area on the retardation film in the longitudinal direction, is within 23° with respect to the longitudinal direction of the retardation film. It is preferable to be

This means that bringing the angle of view (θ) into the above range, that is, maintaining the distance between the retardation film and the camera to be the angle of view (θ), reduces the dependence on the incident angle of the inspection light, and at the center and corner of the inspection area. This is to make the difference in light and shade of the image of

The apparatus for detecting unevenness of orientation of the retardation film of the present invention includes a first polarizing plate and a second polarizing plate arranged to cross the retardation film so as to be interposed therebetween, and a light source for irradiating inspection light to the retardation film via the first polarizing plate and a photographing apparatus for obtaining a luminance image by photographing the retardation film through the second polarizing plate, and a defect detection unit for detecting a defect from the luminance image, wherein the defect detection unit includes the first With respect to the absorption axis of either the polarizing plate or the second polarizing plate, the first polarizing plate and the second polarizing plate, or The luminance image photographed by rotating any of the retardation films is differentiated (differentially) processed in a direction within the range of 35 to 55° or -55 to -35° with respect to the slow axis of the retardation film to form an edge portion It is characterized in that it has an edge detection circuit for emphasis, and a binarization circuit that binarizes the edge-detected luminance image at a predetermined threshold to make each pixel a bright pixel equal to or greater than the threshold and a dark pixel lower than the threshold.

The defect detection unit performs expansion processing on the binarized luminance image in an oblique direction within a range of 70 to 120° with respect to the direction of differential (difference) processing of the retardation film to emphasize the component in the oblique direction. It is preferable from a viewpoint of enabling quantitative orientation nonuniformity defect evaluation with good precision to have the image processing circuit which says.

In addition, it is preferable from the viewpoint of enabling quantitative alignment non-uniformity defect evaluation with high accuracy that the defect detection unit has an image processing circuit that performs shrinkage processing in the same direction with respect to the luminance image after performing the expansion processing .

In addition, the defect detection unit has a filtering circuit that extracts, with respect to the shrunk-processed luminance image, a filter condition defined by the representative length of each pixel region as an orientation non-uniformity defect component in the direction. It is preferable from a viewpoint of specifying nonuniformity and enabling quantitative orientation nonuniformity defect evaluation with good precision.

The angle of view (θ) of the lens calculated from the distance between the lens tip position of the imaging device and the retardation film, and the size of the inspection area on the retardation film in the longitudinal direction, is within 23° with respect to the longitudinal direction of the retardation film This is preferable from the viewpoint of good working efficiency and enabling quantitative evaluation of the orientation non-uniformity defect.

EMBODIMENT OF THE INVENTION Hereinafter, this invention, its component, and form and aspect for implementing this invention are demonstrated in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

«Summary of the method for detecting a defect in orientation non-uniformity of the retardation film of the present invention»

The method for detecting an orientation non-uniformity defect of the retardation film of the present invention is characterized by having the following steps (1) to (5).

Step (1): when disposing the retardation film between the first polarizing plate and the second polarizing plate arranged cross-nickel, the slow axis of the retardation film is relative to the absorption axis of either the first polarizing plate or the second polarizing plate A step of rotating and disposing any one of the first polarizing plate and the second polarizing plate or the retardation film so as to be within the range of -10 to 10° (however, 0° is excluded).

Step (2): A step of irradiating inspection light to the retardation film via the first polarizing plate.

Step (3): A step of obtaining a luminance image by photographing the phase difference film with a photographing device through the second polarizing plate.

Step (4): Differential (difference) processing of the photographed luminance image in a direction within a range of 35 to 55° or -55 to -35° with respect to the slow axis of the retardation film to obtain a luminance image emphasizing the edge portion step.

Step (5): A step of binarizing the edge-emphasized luminance image at a predetermined threshold value, obtaining bright pixels equal to or greater than the threshold value and dark pixels lower than the threshold value, and detecting alignment unevenness from the bright pixels or dark pixels.

Here, "retardation film" refers to an optical film that improves the problem of viewing angle dependence of a liquid crystal display device, and is, for example, an optical film having birefringence used in a VA (Virtual Alignment) type liquid crystal display device. The said optical film is a transparent resin film which has a specific function based on an optical characteristic. The optical film is formed by stretching or the like, and when it is formed normally, it has uniform optical properties (birefringence or retardation, etc.) in the plane, but in reality, some non-uniformity occurs.

The value of the retardation of the said optical film can be generally defined by the following formula.

That is, retardation Ro of the in-plane direction of an optical film, and retardation Rt of thickness direction are represented by following formula (1) and (2).

Ro = (n _x - n _y ) × d ... (1)

Rt = ｛(n _x + n _y )/2 - n _z ｝×d ... (2)

In the formula, n _x is the refractive index in the slow axis direction in the film plane, n _y is the refractive index in the fast axis direction in the film plane, n _z is the refractive index in the thickness direction of the film, and d is the thickness of the film (nm).

In addition, when light propagates in the film which causes birefringence, a "slow axis" refers to an axis at which the phase is slow and the traveling speed of light becomes the slowest. That is, it refers to the direction in which the refractive index in the plane is maximized. A "fast axis" refers to an axis in which the traveling speed of light becomes the fastest, and refers to a direction in which the in-plane refractive index is minimized.

The in-plane slow axis and fast axis of the retardation film can be confirmed by automatic birefringence meter Axo Scan (Axo Scan Mueller Matr X Polarimeter: manufactured by Axometrics).

The measurement of Ro and Rt of retardation film can be performed with the following method.

1) Humidity control is carried out for retardation film in 23 degreeC and 55 %RH environment for 24 hours. The average refractive index of this retardation film is measured with an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.

2) Retardation Ro and Rt of the retardation film after humidity control at a measurement wavelength of 550 nm were measured at 23°C and 55% using an automatic birefringent meter Axo Scan (Axo Scan Mueller Matr X Polarimeter: manufactured by Axometrics), respectively. Measure under RH environment.

When the retardation film according to the present invention is used, for example, for VA mode, the retardation Ro in the in-plane direction measured under an environment of a measurement wavelength of 550 nm, 23°C, and 55% RH is within the range of 20 to 120 nm It is preferable, and it is more preferable to exist in the range of 30-100 nm. It is preferable to exist in the range of 70-350 nm, and, as for retardation Rt of the thickness direction of an optical film, it is more preferable to exist in the range of 100-320 nm.

In addition, since the retardation is a value that fluctuates depending on the wavelength of light irradiated to the optical film, environmental conditions (temperature and humidity) for measurement, etc., depending on the purpose of optical characteristic evaluation or the type of optical film to be evaluated, the retardation has an arbitrary value It is preferable to set these conditions so that it becomes this.

Here, the "orientation angle" refers to an angle formed by the orientation direction in which molecules forming the retardation film are oriented with respect to a predetermined reference direction, and is usually an angle formed by the in-plane slow axis of the retardation film with respect to the predetermined reference direction. matches with A predetermined reference direction is the width direction of retardation film normally, and means the extending|stretching direction. The "orientation non-uniformity defect" according to the present invention refers to a non-uniformity accompanied by a shift in the direction of the slow axis from the reference direction at each site in which the orientation angle is sampled within the film plane (eg, when multiple samples are taken along the width direction). This means there is a defect.

A "polarizing plate" is one type of a polarizing element, and is comprised with a polarizer and a protective film normally. The polarizer is used to change the vibration direction of the incident linearly polarized light by rotating the direction of its transmission axis with respect to the linearly polarized light having a specific vibration direction extracted from natural light (randomly polarized light). A "polarizer" is a polyvinyl alcohol-type polarizing film as an element which transmits only the light of the polarization plane of a fixed direction. The polyvinyl alcohol-type polarizing film includes a polyvinyl alcohol-type polarizing film in which iodine is dyed and a polyvinyl alcohol-based polarizing film in which dichroic dye is dyed.

The "absorption axis" refers to the direction of the axis in which the polarizer absorbs the vibration of light, and usually refers to an angle coincident with the extending direction of the polarizer.

The "first polarizing plate and the second polarizing plate arranged cross-nickel" means that the "absorption axis" of the polarizer is perpendicular to the 90 degree direction between the first polarizing plate and the second polarizing plate.

EMBODIMENT OF THE INVENTION Hereinafter, this invention, its component, and the form and aspect for implementing this invention are demonstrated. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

[1] Configuration of a method for detecting a defect in the orientation non-uniformity of the retardation film

The method for detecting an orientation non-uniformity defect of a retardation film of the present invention includes the steps (1) to (5), more preferably following the step (5), step (6), step (7) and step (8) ) is preferred.

First, outline is demonstrated about the visual evaluation method of the conventional orientation nonuniformity defect.

1 : is a schematic diagram which shows the outline of the conventional visual evaluation method (10) of an orientation nonuniformity defect.

Evaluation of the orientation non-uniformity defect of the retardation film 1 is the 1st polarizing plate 3, the retardation film 1, and the 2nd polarizing plate 4 for the irradiation light L emitted from the flat LED lighting 2 located below. ), and qualitatively observing the defect of orientation non-uniformity of the retardation film (1) with the naked eye (5). At this time, since the absorption axes of the first polarizing plate 3 and the second polarizing plate 4 are arranged so as to be cross nicol, the irradiated light L does not transmit as it is and becomes a dark part, but the evaluator determines that the retardation film (1) ) is rotated slightly from the absorption axis direction of the polarizing plate (incline in the inclination direction (6) of the arrow in the drawing), so that the irradiated light (L) is polarized and becomes transmitted light according to the direction of the slow axis of the retardation film, If there is an orientation non-uniformity defect in (5), it will be observed as a dark area|region.

Therefore, since the evaluation result is influenced by the evaluation result by rank classification based on the appraiser's familiarity with the handling method of retardation film and the evaluator's experience with respect to an orientation non-uniformity defect, evaluation is a deceptive and qualitative evaluation method.

Since the method for detecting a defect in orientation non-uniformity of the retardation film of the present invention is a method of evaluating the defect by a certain step using an optical evaluation device, the evaluation is not deceptive, and it can provide a quantitative evaluation .

Hereinafter, each step is demonstrated in detail about the orientation nonuniformity defect detection method of the retardation film of this invention.

Step (1): when disposing the retardation film between the first polarizing plate and the second polarizing plate arranged cross-nickel, the slow axis of the retardation film is relative to the absorption axis of either the first polarizing plate or the second polarizing plate A step of rotating and disposing any one of the first polarizing plate and the second polarizing plate or the retardation film so as to be within the range of -10 to 10° (however, 0° is excluded).

When a film is placed between two polarizing plates (first polarizing plate and second polarizing plate) in a cross nicol state, no light is transmitted even if the direction of the slow axis of the film is in the same direction as the absorption axis of the polarizing plate, so nothing can be observed none. If the film is slightly rotated with respect to the absorption axis of the polarizing plate, the polarization state of the light passing through the film changes depending on the slow axis of the retardation film (the direction of polarization changes slightly), so that the light passes through the second polarizing plate and reaches do.

Since the luminance change of the orientation nonuniformity defect which is the inspection object of this time is minute, if a polarizing plate or retardation film is rotated too much, the light reaching the camera which is an imaging device is too strong and cannot be observed. As a result of examination, the first polarizing plate and the second polarizing plate or the retardation film so that the slow axis of the retardation film is in the range of -10 to 10° with respect to the absorption axis of either the first polarizing plate or the second polarizing plate. Since the phase difference nonuniformity was most clearly observed when any one was rotated, it prescribes|regulates in this range.

In actual operation, in the apparatus for detecting an orientation non-uniformity defect of FIG. 5 to be described later, the retardation film is not rotated, but the first polarizing plate and the second polarizing plate are rotated so that the absorption axis of the polarizing plate is set to the slow axis of the retardation film. It is preferable to make it inclined with respect to

Step (2): A step of irradiating inspection light to the retardation film via the first polarizing plate.

As a lighting device for irradiating the inspection light, it is preferable that the first polarizing plate, the retardation film, and the second polarizing plate transmit the inspection light in this order, an area sufficient to photograph the inspection light is required, and the luminance is preferably as uniform as possible. do.

The light source of the lighting device is not particularly limited, but a fiber-type light source using a deuterium lamp, a halogen lamp, or an LED (Light Emitting Diode) lamp as a light source, or a surface light source using a fluorescent lamp, LED, or OLED (Organic Light Emitting Diode) can be used Preferably it is a surface light source (flat surface light source), and it is preferable to use flat LED lighting.

The light amount of the inspection light is managed on the inspection machine control software LabVIEW (manufactured by National Instruments), and the luminance calculation area set on the LabVIEW (for example, a rectangular region of about 80 mm × 60 mm to 400 mm × 300 mm) In order to obtain a sufficient luminance image for evaluation, it is preferable to measure the in-plane average luminance of and to adjust the light amount of the light source so that the luminance value falls within the range of 128±10.

In addition, a phenomenon occurs in that the luminance calculation region becomes darker toward the end of the inspection region under the influence of the incident angle dependence on the inspection region. If it is attempted to adjust the in-plane average luminance to 128 ± 10 including the dark portions of the edges, the central portion becomes excessively bright, and important irregularities cannot be detected. Therefore, the luminance calculation area is narrower than the inspection area It is preferable to set For example, when the inspection area is 400 mm in length x 300 mm in width, it is preferable to set the luminance calculation area to 90 mm in length x 80 mm in width.

Step (3): A step of obtaining a luminance image by photographing the phase difference film with a photographing device through the second polarizing plate.

Although the photographing apparatus is not specifically limited, CCD camera of an area type or a line sensor type can be used. When the inspection area range of the retardation film can be covered by shooting within several times, the area type, and when it is necessary to shoot a wider range, the line sensor type is preferable in terms of shooting time and precision.

The camera which is a photographing apparatus can use the model acA2500-14gm by BASLER, and the lens, the model H6X8-1.0-II by APACECOM, etc. can be used, for example.

The inspection area is determined by the angle of view of the lens mounted on the camera, the size of the polarizing plate and the size of the retardation film, and the distance between the retardation film and the lens mounted on the camera. If the imaging device has a configuration in which the sample can be moved in the width direction, it will be possible to measure any sample of any width if the inspection is conducted multiple times.

For example, as a retardation film, when an inspection area is 400 mm long and 300 mm wide for a sample having a length of 450 mm and a width of 2500 mm, the inspection may be performed by photographing a plurality of times. In addition, the size in the longitudinal direction is fixed by the inspection area of the device. The size of the width is a general maximum width as a retardation film.

In addition, the angle of view (θ) of the lens mounted on the camera is specifically calculated from the distance between the lens tip position of the imaging device and the retardation film, and the size of the inspection area on the retardation film in the longitudinal direction, θ) is preferably within 23° with respect to the longitudinal direction of the retardation film from the viewpoint of good working efficiency and enabling quantitative evaluation of non-uniform orientation defects.

Fig. 2 is a schematic diagram for explaining the angle of view (θ) of a lens attached to a camera used for inspection.

The position of the tip of the lens 56 and the distance WD of the retardation film 51 (abbreviation of Working Distance, which refers to the distance from the tip of the lens to the position where the subject is in focus) is, for example, the orientation according to the present invention As the non-uniformity defect inspection apparatus 50, for example, when WD is 1150 mm, the imaging area of the camera is 450 mm in the longitudinal direction length 51a of the retardation film with respect to the conveyance direction 51c of the retardation film 51; When the width direction length 51b is 375 mm, the angle of view θ of the lens is 22.14°. Moreover, when an inspection area|region is 400 mm in length in a longitudinal direction, and 300 mm in length in a width direction, (theta) becomes 19.73 degrees. In either case, it can be obtained by calculation.

Step (4): Differential (difference) processing of the photographed luminance image in a direction within a range of 35 to 55° or -55 to -35° with respect to the slow axis of the retardation film to obtain a luminance image emphasizing the edge portion step.

The purpose of the general differentiation processing is to emphasize the edge portion of the photographed luminance image. Differential processing is processing in which edge extraction of an image (extracting a part in which the brightness of the image changes suddenly is called edge extraction) is performed with a differential filter, but in the case of an image, since it is not a continuous value, the difference between pixel values is taken ("Difference" in the present invention.) It is treated as an approximation of the derivative. Differentiation processing is a kernel when a matrix called a kernel (also referred to as a matrix) is differentiated in a direction within the range of 35 to 55° in the examination stage, and when differentiating in a direction within the range from -55 to -35°. It is desirable to obtain a kernel and use it.

The edge refers to a portion divided as a region of light and dark in the image. When emphasizing an edge, it is ideal to process it in a direction orthogonal to the direction in which the border of light and dark extends. The orientation non-uniformity defect develops along the direction of about 45° with respect to the longitudinal direction (or the width direction), but there is some deviation in this angle. It is preferable to carry out with a width in the range of 35 to 55 degrees.

Although the software for fine powder processing to be used is not limited, It is preferable to use the analysis software NI vision (made by National Instruments).

Step (5): The edge-emphasized luminance image is binarized by a predetermined binarization software and a threshold value, each pixel is obtained a bright pixel equal to or greater than the threshold value and a dark pixel lower than the threshold value, and alignment unevenness is corrected from the bright pixel or dark pixel. detection step.

In the image|photographed image, the orientation nonuniformity defect is observed as a dark area|region. Therefore, in binarization, in order to leave a darkly reflected element group in the image, a threshold is set and only elements with a luminance lower than the threshold are left.

At this time, the threshold to be set is determined while confirming that the non-uniformity part that can be visually confirmed remains clearly. That is, the threshold value may be determined empirically.

It is preferable to specifically perform binarization by the following method.

[a] The captured luminance image is read into a PC using analysis software NI vision (manufactured by National Instruments). Since the luminance image changes according to adjustment of focus, contrast, and brightness, it is preferable not to do it artificially.

[b] Set the definition of black and white.

In the analysis software NI vision, if you check the Black Backround, the luminance value 0 is displayed in black and the luminance value 255 is displayed in white. If the Black Background is not checked, the luminance value 0 is displayed in white and the luminance value 255 is displayed in black.

[c] Remove noise from images

Shading processing is performed. The shading process removes noise by averaging the luminance in the image.

[d] Apply a band pass filter.

For example, the band-pass filter value is recommended to be 20 to 100. Since this setting value depends on the initial luminance image, it is preferable to set it appropriately and optimally.

[e] Bind the luminance image.

Make it 8 bits in the setting, and set the threshold. It is preferable to adjust the threshold value according to the analysis software NI vision (manufactured by National Instruments).

Since this threshold is changed to the contrast of the image, it is preferable not to be fixed but to be set by the evaluator every time.

When the threshold is determined, a black-and-white image is obtained. By binarizing each pixel to a predetermined threshold value, the dark pixel more than a threshold value and the bright pixel lower than a threshold value are obtained, and orientation nonuniformity is detected from the said bright pixel or a dark pixel.

3 : is a specific example of the image binarized by the predetermined|prescribed threshold value.

3A is a photographed original luminance image, among which dark pixel portions are candidates for orientation non-uniformity defects. Fig. 3B shows that the threshold value is determined so that the candidate of this orientation non-uniformity defect remains clearly, and it is binarized as a dark pixel.

It is preferable that the orientation nonuniformity defect detection method of this invention has the following step (6), step (7), and step (8) further.

Step (6): Expansion processing is performed on the binarized luminance image in an oblique direction within a range of 70 to 120° with respect to the direction of differential (difference) processing of the retardation film to emphasize the component in the oblique direction A step for performing image processing.

Since a lot of noise other than an orientation defect nonuniformity element remains in the image immediately after binarization, in order to emphasize a defect part, it expands and performs expansion processing, and it becomes easy to reduce noise by expansion processing. Here, the "dilation process" is generally performed on a binarized black and white image, and if there is even one white pixel in the vicinity of the pixel of interest, the process of replacing it with white is called dilation. Conversely, in the "shrinkage process" to be described later, if there is a black pixel even for one pixel in the periphery, the process of replacing it with black is called erosion.

In order to remove noise while leaving the said orientation defect nonuniformity, it is effective to process along the direction in which nonuniformity exists. When this is expressed with reference to the direction of the differential processing, processing is performed in a direction orthogonal to the differential processing. This is because it is ideal that the direction of the differential processing is performed in a direction orthogonal to the direction in which the non-uniformity exists. However, since the direction of the non-uniformity also has variations, in order to cope with this variation, it is preferable to provide a width to the angle and perform the expansion treatment in an oblique direction within the range of 70 to 120° with respect to the direction of the differential (difference) treatment. do.

Step (7): A step of performing shrinkage processing on the luminance image in the same direction after performing the expansion processing.

Performing the contraction treatment subsequent to the expansion treatment is also a treatment to remove noise as much as possible, and in the same way, the direction of the differentiation processing is performed in a direction orthogonal to the direction in which the non-uniformity exists. It is preferable to perform the shrinkage treatment in an oblique direction within the range of 70 to 120° with respect to the direction of the differential (differential) treatment.

The said expansion|swelling process and the said shrinkage|contraction process can be performed using the said analysis software NI vision (made by National Instruments).

Step (8): A step of extracting, with respect to the luminance image subjected to the shrinkage treatment, a component that satisfies the filter condition defined by the representative length of each pixel region as a defect component of the orientation non-uniformity in the direction.

This step is also called filter processing or filtering, and "the filter condition defined by the representative length of each pixel region" is a condition calculated|required from experience in the detection of an orientation nonuniformity defect.

From the binarized luminance image, for example, a shape close to a perfect circle is removed (filter processing 1), a short element is removed (filter processing 2), or an area outside a specified range is removed (filter processing 3) ) is performed, and the thing which satisfies the said filter condition prescribed|regulated by the representative length of each pixel area|region is detected as an orientation nonuniformity defect.

Specifically, for example, in the filter processing 1, when the Heywood circular factor H is the quotient obtained by dividing the perimeter of the pixel region by the circumference of the same area, it is preferable to leave only the pixel regions within the range of 1.5 ≤ H ≤ 5 do. Also, the Haywood circular factor H is 1 for gardens.

In addition, as the filter process 2, it is preferable to remove the pixel area|region of a specific length or less in the long side of orientation nonuniformity.

Further, as the filter process 2, when the elongation factor L is the quotient obtained by dividing the maximum Perey diameter of the pixel area by the short side (Perey) of the equivalent rectangle, only the pixel area within the range of 4 ≤ L ≤ 13 is left, and the orientation non-uniformity defect is reduced It is desirable to detect

Although the filter processing software used in the said filter process is not limited, It can perform using the said analysis software NI vision (made by National Instruments).

Fig. 4 shows a flowchart of image processing and a specific example of the processed image.

(P1) to acquire a luminance image by photographing the retardation film;

(P2) shading processing of the luminance image (averaging the luminance within the image to remove noise);

(P3) Emphasizing edge portion by differential (differential) processing of luminance image

(P4) binarization of the luminance image;

(P5) enhancement processing (expansion and contraction processing) of the binarized image;

(P6) Filter processing 1 for a binarized image (removing elements whose shape is close to a perfect circle),

(P7) Filter processing 2 for binarized images (remove short elements);

(P8) Filter processing 3 for binarized images (remove elements whose area is outside the specified range),

(P9) Detecting only orientation non-uniformity defects from a binarized image by filter processing

[2] Defect detection device for non-uniform orientation of retardation film

The apparatus for detecting an orientation irregularity defect of a retardation film used in the method for detecting an orientation irregularity defect of the retardation film of the present invention includes a first polarizing plate and a second polarizing plate that are arranged cross-nickel so that the retardation film is interposed therebetween, and the first polarizing plate A light source for irradiating inspection light to the retardation film therebetween, a photographing device for obtaining a luminance image by photographing the retardation film via the second polarizing plate, and a defect detection unit for detecting a defect from the luminance image; The defect detection unit, with respect to the absorption axis of any one of the first polarizing plate or the second polarizing plate arranged in a cross nicol, the slow axis of the retardation film is in the range of -10 to 10 ° (however, 0 ° is excluded), The first polarizing plate and the second polarizing plate, or the luminance image photographed by rotating and disposing any one of the retardation film, is within the range of 35 to 55° or -55 to -35° with respect to the slow axis of the retardation film. an edge detection circuit for emphasizing an edge portion by performing differential (differential) processing in the direction It is characterized in that it has a binarization circuit.

5 : is a schematic diagram which shows an example of the orientation nonuniformity defect detection apparatus of the retardation film of this invention.

The device for detecting an orientation non-uniformity defect of the retardation film of the present invention 50 is a light-shielding plate 53, a first polarizing plate 54, a retardation film ( 51), the light-shielding plate 53 and the second polarizing plate 55 are transmitted in this order, and the defect of orientation non-uniformity of the said retardation film 51 is image|photographed with the camera 57 with which the lens 56 was attached. At this time, since the absorption axes of the first polarizing plate 53 and the second polarizing plate 54 are arranged so as to be cross nicol, the irradiated light L does not transmit as it is and becomes a dark part, but the retardation film 51 is By slightly rotating (slanting) from the absorption axis direction of the polarizing plate, the irradiated light L is polarized in the direction of the slow axis of the retardation film 51, and the orientation nonuniformity in the photographed image is photographed as a dark area.

In the above-mentioned non-uniformity of orientation defect detection apparatus 50, without rotating the retardation film 51, the first polarizing plate 54 and the second polarizing plate 55 have an absorption axis of the polarizing plate with respect to the slow axis of the retardation film. It is preferable to have a mechanism (not shown) which rotates so that it may become in the range of -10 to 10 degrees.

Moreover, the dimension in particular of each part is although it does not restrict|limit, For example, for the retardation film for evaluation, the strip-shaped sample cut|disconnected by 450 mm in the longitudinal direction and 2000 mm in the width direction is used. The photographing apparatus calculates the angle of view (θ) of the lens calculated from the distance between the lens tip position of the photographing apparatus and the retardation film, and the size of the inspection region on the retardation film in the longitudinal direction, 23 with respect to the longitudinal direction of the retardation film It is preferable to set it within °, for example, in order to test|inspect the area|region of 400 mm in a longitudinal direction and 300 mm in a width direction, it is preferable from a viewpoint of inspection efficiency to assemble the inspection apparatus of the structure shown in FIG.

The light source of the lighting device is not particularly limited, but as described above, a fiber-type light source using a deuterium lamp, a halogen lamp, or an LED lamp as a light source, or a surface light source using a fluorescent lamp, LED, or OLED can be used.

Although the photographing apparatus is not specifically limited, CCD camera of an area type or a line sensor type can be used. When the measurement target range of the retardation film can be covered with less than several shots, the area type, and when it is necessary to shoot a wider range, the line sensor type is preferable in terms of shooting time and precision.

Examples of specifications of the camera and lens are as described above.

Further, with respect to the direction of the differential (difference) processing of the retardation film, the defect detection unit expands the luminance image binarized in the oblique direction within the range of 70 to 120°, and the component in the oblique direction It is desirable to have an image processing circuit that emphasizes.

Moreover, it is preferable that the said defect detection part has an image processing circuit which performs the shrinkage process with respect to the said luminance image in the same direction after performing the said expansion process.

In addition, it is preferable that the defect detection unit has a filtering circuit that extracts, with respect to the shrunken luminance image, a filter condition defined by a representative length of each pixel region as a defect component of non-uniform orientation in the direction. .

6 is a schematic diagram illustrating a defect detection unit having an edge detection circuit, a binarization circuit, an image processing circuit, and a filtering circuit.

[Defect detection unit]

Each structure of the defect detection part 100 is demonstrated.

As shown in FIG. 6 , the defect detection unit 100 includes a control unit 101 , a recording unit 102 , a communication unit 103 , a data processing unit 104 , an operation display unit 105 , and the like, and is connected to the bus 106 . Each part is connected so as to be able to communicate with each other.

The control unit 101 includes a CPU (Central Processing Unit) 101a that collectively controls the operation of the defect detection unit 100, and a work memory for temporarily storing various data when the CPU 101a executes a program. A RAM (Random Access Memory) 101b, and a program read and output by the CPU 101a and a program memory 101c in which fixed data is stored are provided. The program memory 101c is constituted by a ROM or the like.

The recording unit 102 stores and records data of various threshold values used in the image processing circuit and irradiation condition data of the lighting device 52 in addition to the image data that has been photographed and image-processed.

The communication unit 103 is provided with an interface for communication, such as a network I/F, and transmits the measurement condition input from the operation display unit 105 to the shooting adjustment device 120 via a network such as an intranet. In addition, the communication unit 103 receives image data sent from the photographing device 130 .

The data processing unit 104 performs image processing from the luminance image data received by the communication unit 103 and photographed by the photographing apparatus 130 (lens 56 and camera 57 ).

The data processing unit 104 has various processing circuits used in steps (4) to (8) according to the present invention.

The data processing unit 104 performs a differential (differential) process with the shading processing circuit 104a in a direction within a range of 35 to 55° or -55 to -35° with respect to the slow axis of the retardation film to emphasize the edge portion. an edge detection circuit 104b (step (4)), and a binarization circuit 104c that binarizes the edge-detected luminance image at a predetermined threshold, and makes each pixel a bright pixel greater than or equal to the threshold and a dark pixel lower than the threshold. ) (step (5)), an image processing circuit 104d (steps (6) and (7)) for performing expansion or contraction processing on the luminance image, and each pixel for the luminance image that has been contracted It has a filtering circuit 104e (step (8)) which extracts what satisfy|fills the filter condition prescribed|regulated by the representative length of a region as an orientation nonuniformity defect component in the said direction.

The operation display unit 105 may be constituted of, for example, an LCD (Liquid Crystal Display), a touch panel formed to cover the LCD, various switches and buttons, ten keys and operation key groups (not shown). The operation display unit 105 receives an instruction from the user and outputs the operation signal to the control unit 101 . In addition, the operation display unit 105 displays, on the LCD, various setting screens for inputting various operation instructions and setting information, and an operation screen for displaying various processing results, etc. in accordance with the display signal output from the control unit 101 . .

[External output device]

The data processing apparatus 100 may include an external output apparatus 150 connected to the data processing apparatus 100 communicatively. The external output device 150 may be a general personal computer (PC), an image forming device, or the like. Further, the external output device 150 may function as an operation display unit instead of the operation display unit 105 of the data processing apparatus 100 .

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In addition, although the indication of "part" or "%" is used in the Example, unless otherwise indicated, "part by mass" or "mass %" is shown.

[Example 1]

<Preparation of retardation film for evaluation>

According to the following method, the retardation film 101 for evaluation was produced.

(Preparation of fine particle dispersion diluent)

10 parts by mass of Aerosil R812 (manufactured by Nippon Aerosil, primary average particle diameter: 7 nm, apparent specific gravity of 50 g/L) and 90 parts by mass of ethanol were stirred and mixed with a dissolver for 30 minutes, followed by a high-pressure disperser It was dispersed using Manton Gaulin to prepare a fine particle dispersion.

To the obtained dispersion of fine particles, 88 parts by mass of dichloromethane was added while stirring, followed by stirring and mixing with a dissolver for 30 minutes to dilute. The obtained solution was filtered by Advantech Toyo's polypropylene wind cartridge filter TCW-PPS-1N, and the fine particle dispersion dilution liquid was obtained.

(Preparation of in-line additive solution)

To 100 parts by mass of dichloromethane, 36 parts by mass of the prepared fine particle dispersion diluted solution was added while stirring, and after further stirring for 30 minutes, 6 parts by mass of cellulose acetate propionate (CAP: acetyl group substitution degree 2.00, propionate substitution degree) 0.60, weight average molecular weight 270,000) was added while stirring, and the mixture was further stirred for 60 minutes. The obtained solution was filtered with Nippon Seisen Co., Ltd. FineMet NF, and the in-line addition liquid was obtained. As a filter medium, the thing with a nominal filtration precision of 20 micrometers was used.

(Preparation of dope)

The following components were put into a sealed container and completely dissolved while heating and stirring. The obtained solution was filtered at the temperature of 50 degreeC with the filter equipped with the leaf disk filter, and main dope was obtained. As a filter medium, the thing with a nominal filtration precision of 20 micrometers was used.

<Composition of Judoff>

Cellulose acetate propionate (CAP: acetyl group substitution degree 2.00, propionate substitution degree 0.60, weight average molecular weight 270,000) 100 parts by mass

Plasticizers: sugar esters; BzSc (benzyl sucrose: average degree of ester substitution = 5.5) 12 parts by mass

430 parts by mass of dichloromethane

11 parts by mass of methanol

100 mass parts of main dope 1 and 2.5 mass parts of in-line addition liquid were fully mixed with the in-line mixer (Toray static type in-pipe mixer Hi-Mxer, SWJ), and dope was obtained.

(film forming process)

The obtained dope was cast|flow_spreaded uniformly on the stainless steel band support body using the belt casting apparatus on the conditions of 35 degreeC of liquid temperature of dope, and 1950 mm in width conditions, and the conditions used as a final film thickness will be 40 micrometers. On the stainless steel band support body, after evaporating the organic solvent in the obtained dope film until the amount of residual solvent became 100 mass % and forming a web, the web was peeled from the stainless steel band support body. The obtained web was further pre-dried at 110 ° C. for 5 minutes so that the residual solvent amount was 10 mass%, and then the web was stretched 1.4 times with respect to the atomic bomb in the TD direction under the conditions of 160 ° C. with a tenter, and the following predetermined retardation was obtained was given. The stretching rate was 300%/min.

After extending|stretching by a tenter, after relaxation|relaxing at 130 degreeC for 1 minute, drying was complete|finished, conveying a drying zone with many rollers. The drying temperature was 130 degreeC, and the conveyance tension|tensile_strength was 100 N/m. The obtained film was slit to a width of 2000 mm, knurled at both ends of the film with a width of 10 mm and a height of 5 μm, and wound around a core with an inner diameter of 15.24 cm with an initial tension of 220 N/m and a longitudinal tension of 110 N/m, and a length of 4000 m and the retardation film 101 for evaluation with a dry film thickness of 40 micrometers were obtained.

As a result of measuring the retardation of the retardation film 101 by the above-mentioned measuring method, it was Ro:50 nm and Rt:120 nm.

<Evaluation of orientation non-uniformity defect>

By following steps (1)-(8) using the orientation nonuniformity defect evaluation apparatus shown in FIG. 5, the orientation nonuniformity defect of the produced said retardation film was detected and evaluated.

In addition, the retardation film for evaluation was cut|disconnected into the strip sample of 450 mm in the longitudinal direction, and 2000 mm in the width direction. 400 mm in the longitudinal direction by setting the distance between the lens tip position of the imaging device and the retardation film to 1150 mm and the angle of view (θ) of the lens calculated from the lengthwise size of the inspection area on the retardation film to 20° , the imaging was performed a plurality of times in the inspection area of 300 mm in the width direction.

Step (1): When disposing the retardation film between the first polarizing plate and the second polarizing plate arranged in a cross nicol, the slow axis of the retardation film is -7° with respect to the absorption axis of the polarizer of the first polarizing plate, Rotating and disposing the first polarizing plate and the second polarizing plate.

As for the angles shown in Table I, a counterclockwise direction is a negative value, and a clockwise direction is a positive value.

Step (2): A step of irradiating inspection light from flat LED lighting to the retardation film via the first polarizing plate.

Step (3): A step of obtaining a luminance image by photographing the phase difference film with an imaging device (camera) through the second polarizing plate.

Step (4): A step of obtaining a luminance image emphasizing an edge portion by performing differential (difference) processing on the photographed luminance image in a direction of 40° with respect to the slow axis of the retardation film.

Step (5): A step of binarizing the edge-emphasized luminance image at a predetermined threshold value, obtaining bright pixels equal to or greater than the threshold value and dark pixels lower than the threshold value, and detecting alignment unevenness from the bright pixels or dark pixels.

Step (6): With respect to the direction of differential (difference) processing of the retardation film, in a 90° oblique direction, the luminance image binarized is subjected to expansion processing, and image processing for emphasizing the component in the oblique direction steps to do.

Step (7): A step of performing shrinkage processing on the luminance image in the same direction after performing the expansion processing.

Step (8): A step of extracting, with respect to the luminance image subjected to the shrinkage treatment, a component that satisfies a filter condition defined by the representative length of each pixel region as an orientation nonuniformity defect component in the direction.

(Filtering 1)

Heywood circular factor H: When the quotient of the perimeter of the pixel region is divided by the circumference of the same area, only the pixel region within the range of 1.5 ≤ H ≤ 5 is left.

(Filtering 2)

Elongation factor L: When the maximum Perey diameter of the pixel area is taken as the quotient divided by the short side (Perey) of the equivalent rectangle, only the pixel areas within the range of 4 ≤ L ≤ 13 are left.

[Examples 2 to 8]

In the evaluation conditions of Example 1, the apparatus conditions θ, θf, and θp (each represents an angle) described in Table I, and image processing conditions (step (4), step (5), step (6), step ( 7), Step (8)-1: Filtering 1 and (8)-2: Filtering 2) were changed to perform the same evaluation, and Examples 2 to 8 were performed.

Here, θ: the angle of view of the lens mounted on the camera, θf: the angle formed between the retardation film slow axis and the absorption axis of the polarizing plate, and θp: the angle formed by the absorption axis of the two polarizing plates, respectively.

[Comparative Examples 1 to 3]

Using the orientation non-uniformity defect evaluation apparatus of Fig. 1, as an evaluator, 3 of an evaluation experience of 1 year or more (visual evaluation 1), 6 months or more and less than 1 year of evaluation experience (visual evaluation 2), and less than 6 years of evaluation experience (visual evaluation 3) The person evaluated Comparative Examples 1-3.

[Comparative Example 4]

Evaluation was performed based on the Examples described in paragraphs [0113] to [0122] of Japanese Patent Application Laid-Open No. 11-30591.

[Comparative Example 5]

Evaluation based on Example 1 described in Paragraphs [0098] to [0099] of Unexamined-Japanese-Patent No. 2013-50393 was implemented.

≪Evaluation≫

(1) Complexity

Complexity was judged by the time taken to evaluate one sample.

◎: less than 1 minute

○: 1 minute or more, less than 5 minutes

△: 5 minutes or more, less than 10 minutes

×: 10 minutes or more

In the case of (circle) - (double-circle), complexity was low and it was said that it was an excellent evaluation method.

(2) Detection accuracy

After assembling the display device using the tested retardation film, the detection accuracy was ranked according to the degree of agreement between the quality evaluation result (customer evaluation result) and the quality evaluation result in the film state (in-house evaluation result).

(double-circle) : The evaluation result of 9-10 samples agrees

○: The evaluation results of 6 to 8 samples match

△: The evaluation results of 3 to 5 samples coincide

×: The evaluation results of 0 to 2 samples coincide

The detection accuracy is calculated|required more than (triangle|delta), and it is preferable that it is (circle) - (double-circle).

Table I shows the above evaluation methods and evaluation results.

From the evaluation results in Table I, it was found that the complexity and detection accuracy of the evaluation of the alignment non-uniformity defect of the retardation film was improved by using the method and the device for detecting the non-uniform orientation defect of the retardation film of the present invention, compared to the visual evaluation. can

Therefore, according to the present invention, by performing quantitative evaluation of the detection and evaluation of the defect in the orientation non-uniformity of the retardation film by an optical system, the evaluation is not deceptive and the non-uniform orientation defect detection method of the retardation film that can more easily increase the evaluation reproducibility and an alignment non-uniformity defect detection device.

Industrial Applicability

The method and apparatus for detecting non-uniform orientation defects of retardation film of the present invention enable detection and evaluation of defects in orientation non-uniformity of retardation film by quantitative evaluation by an optical system, and the evaluation is not deceptive, more convenient It is used suitably for evaluation of the orientation nonuniformity defect of retardation film.

1: retardation film
2: Flat LED Lights
3: first polarizing plate
4: second polarizing plate
5: naked eye
6: inclined direction
L: irradiated light
θ : angle of view
10: Visual evaluation method of conventional orientation non-uniformity defect
50: alignment non-uniformity defect detection device
51: retardation film
51a: longitudinal length
51b: length in the width direction
52 : flat LED light
53: light shielding plate
54: first polarizing plate
55: second polarizing plate
56: lens
57 : camera
100: defect detection unit
101: control unit
101a: CPU
101b: RAM
101c: program memory
102: register
103: communication department
104: data processing unit
104a: shading processing circuit
104b: edge detection circuit
104c: Binary Circuit
104d: image processing circuit
104e: filtering circuit
105: operation display unit
120: shooting adjustment device
130: shooting device
150: external output device

Claims (10)

As a method for detecting a defect in the orientation non-uniformity of the retardation film,
It has following steps (1)-(5), The orientation nonuniformity defect detection method of retardation film characterized by the above-mentioned.
Step (1): when disposing the retardation film between the first polarizing plate and the second polarizing plate arranged cross-nickel, the slow axis of the retardation film is relative to the absorption axis of either the first polarizing plate or the second polarizing plate A step of rotating and disposing any one of the first polarizing plate and the second polarizing plate or the retardation film so as to be within the range of -10 to 10° (however, 0° is excluded).
Step (2): A step of irradiating inspection light to the retardation film via the first polarizing plate.
Step (3): A step of obtaining a luminance image by photographing the phase difference film with a photographing device through the second polarizing plate.
Step (4): Differential (difference) processing of the photographed luminance image in a direction within a range of 35 to 55° or -55 to -35° with respect to the slow axis of the retardation film to obtain a luminance image emphasizing an edge portion step.
Step (5): A step of binarizing the edge-emphasized luminance image at a predetermined threshold value, obtaining bright pixels equal to or greater than the threshold value and dark pixels lower than the threshold value, and detecting alignment unevenness from the bright pixels or dark pixels. The method of claim 1,
Further, image processing for emphasizing the component in the oblique direction by performing expansion processing on the luminance image binarized in an oblique direction within a range of 70 to 120° with respect to the direction of differential (difference) processing of the retardation film It has the step (6) of performing the orientation nonuniformity defect detection method of retardation film characterized by the above-mentioned. 3. The method of claim 2,
Furthermore, after performing the said expansion process, it has the step (7) of shrink|contracting processing with respect to the said luminance image in the same direction, The orientation nonuniformity defect detection method of retardation film characterized by the above-mentioned. 4. The method of claim 3,
Further, with respect to the luminance image subjected to the shrinkage treatment, a step (8) of extracting, as a component of an orientation non-uniformity defect in the direction, a filter condition defined by the representative length of each pixel region is extracted. A method for detecting a defect in the orientation non-uniformity of the retardation film. 5. The method according to any one of claims 1 to 4,
The angle of view (θ) of the lens calculated from the distance between the lens tip position of the imaging device and the retardation film, and the size of the inspection region on the retardation film in the longitudinal direction, is within 23° with respect to the longitudinal direction of the retardation film A method for detecting a defect in the orientation non-uniformity of the retardation film, characterized in that. An apparatus for detecting an orientation irregularity of a retardation film used for the method for detecting an orientation irregularity defect of the retardation film according to any one of claims 1 to 5,
A first polarizing plate and a second polarizing plate which are arranged to be cross-nickel so that the retardation film is interposed therebetween;
a light source for irradiating inspection light to the retardation film through the first polarizing plate;
a photographing apparatus for photographing the retardation film through the second polarizing plate to obtain a luminance image;
and a defect detection unit for detecting a defect from the luminance image;
The defect detection unit,
When disposing the retardation film between the first polarizing plate and the second polarizing plate arranged cross-nickel, the slow axis of the retardation film is -10 to 10° with respect to the absorption axis of either the first polarizing plate or the second polarizing plate. (However, 0° is excluded) so that the first polarizing plate and the second polarizing plate or any one of the retardation film are rotated and photographed so that the luminance image is rotated with respect to the slow axis of the retardation film. an edge detection circuit for emphasizing an edge portion by performing a differential (differential) process in a direction within a range of 35 to 55° or -55 to -35°;
A binarization circuit which binarizes the edge-detected luminance image at a predetermined threshold value, and makes each pixel a bright pixel equal to or greater than the threshold value and a dark pixel lower than the threshold value.
A device for detecting the orientation non-uniformity of the retardation film, characterized in that it has a. 7. The method of claim 6,
The defect detection unit,
An image processing circuit for emphasizing the component in the oblique direction by performing expansion processing on the binarized luminance image in an oblique direction within a range of 70 to 120° with respect to the direction of differential (difference) processing of the retardation film; It has the orientation nonuniformity defect detection apparatus of retardation film characterized by the above-mentioned. 8. The method of claim 7,
The defect detection unit,
and an image processing circuit for performing a shrinkage treatment in the same direction on the luminance image after performing the expansion treatment. 7. The method of claim 6,
The defect detection unit,
With respect to the luminance image that has been subjected to the shrinkage treatment, it has a filtering circuit that extracts, as a component of the alignment non-uniformity defect in the direction, a filter condition defined by the representative length of each pixel region as a component of the alignment non-uniformity defect in the retardation film. detection device. 10. The method according to any one of claims 6 to 9,
The angle of view (θ) of the lens calculated from the distance between the lens tip position of the imaging device and the retardation film, and the size of the inspection area on the retardation film in the longitudinal direction, is within 23° with respect to the longitudinal direction of the retardation film A defect detection apparatus for non-uniform orientation of the retardation film, characterized in that.

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