JPH09236807A - Evaluation device for imidization rate of liquid crystal orienting film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an evaluating device for an imidization degree having high productivity and reliability so that the uniformity of imidization degree in orienting films can be evaluated in the production line by evaluating the luminance level and distribution of an output image from a light accepting device which accepts light passed through a specified bad pass filter. SOLUTION: IR rays 3 emitted from an IR light source 2 are made to irradiate the orienting film on the surface of a substrate 1. The device is equipped with a first band pass filter 10, and second and third bad pass filters 16, 19. The first band pass filter corresponds to a first wavelength at which polyimide has low absorptivity and polyamide has high absorptivity in the absorption spectrum of the reflected light 4. The second and third band pass filters 16, 19 correspond to second and third wavelengths shorter and longer than the first wavelength, and both of polyamide and polyimide show low absorptivity. A camera 11 accepts light passed through the first band pass filter 10. In an image processing device, the luminance level and distribution of the output image from light-accepting sensors 17, 20 which accept light from the second and third band pass filters 16, 19, respectively is evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating the imidization ratio of a liquid crystal alignment film, and more particularly, it is a method for drying a polyamide film
The present invention relates to an apparatus for evaluating the imidization ratio (polyamide → polyimide) of an alignment film for liquid crystal display which is baked to form a polyimide film.

[0002]

2. Description of the Related Art Conventionally, an alignment film for a liquid crystal display is formed by printing, drying and baking a polyamide film to form a polyimide film and then rubbing the film. Further, conventionally, there is no apparatus for evaluating the imidization ratio of a polyimide film.

[0003]

By the way, although the liquid crystal display market is a promising market which is rapidly growing, cost reduction of the liquid crystal display is important. One of the factors that hinders the cost reduction is the decrease in yield. One of the major causes of the decrease in the yield of liquid crystal displays is defective image quality such as color unevenness and brightness unevenness, which become apparent in the lighting inspection in the final process.

It has been found that one of the causes of the color unevenness and the brightness unevenness is the nonuniformity of the imide of the alignment film, which will be described below. Polyamide has a lower hardness than polyimide. Therefore, when the polyamide film remains non-uniformly when the polyamide film is dried and fired to form a polyimide film, a problem occurs during the rubbing process. here,
The rubbing treatment is a treatment for forming fine grooves in the polyimide film by physical contact, and the residual polyamide portion has a low hardness and causes non-uniformity of the alignment film.

From the above, an apparatus for evaluating the uniformity of the imidization ratio is desired, but there is no apparatus having a speed applicable to the evaluation at the production site. However, it is possible to evaluate the imidization rate at the laboratory level. For example, a Fourier analysis device for infrared absorption spectrum (hereinafter, IR (Inf
This is possible by using a ra Red) analyzer. However, since the IR analyzer performs Fourier analysis on the absorption or reflection spectrum of infrared light at the point to be evaluated,
The analysis time per point is also long. Further, the IR analyzer is usually limited in sample size.

Therefore, it is difficult to evaluate in a short time the uneven imidization ratio distribution on the surface of a glass substrate having a large-area alignment film, for example, a substrate of 360 × 460 mm, and it is difficult to evaluate the imidization ratio in the production line. It is impossible to use it as an evaluation device.

The present invention has been made in view of the above circumstances, and it is possible to evaluate the uniformity of the imidization ratio of the alignment film on the production line, and to evaluate the imidization ratio of the liquid crystal alignment film with high productivity and reliability. The purpose is to provide a device.

[0008]

The first invention of the present application is a device for projecting infrared light on an alignment film, and an absorption spectrum of reflected light of the infrared light in which absorption coefficient is low for polyimide and absorption for polyamide. A liquid crystal comprising a bandpass filter for a wavelength having a high rate, a light receiver for receiving light passing through the filter, and an image evaluation device for evaluating the brightness level and distribution of an output image of the light receiver. It is an apparatus for evaluating the imidization ratio of an alignment film.

In the first aspect of the invention, the light receiver may be a camera, for example. A second invention of the present application is a device for projecting infrared light onto an alignment film, and a first wavelength for a first wavelength having a low absorptivity of polyimide and a high absorptivity of polyamide in an absorption spectrum of reflected light of the infrared light. Band-pass filter, second and third band-pass filters respectively corresponding to second and third wavelengths having low absorptance for both polyamide and polyimide before and after the first wavelength, and the first band. The 1st which receives the light which passed the passage filter
Optical receiver, a second optical receiver that receives light that has passed through the second band-pass filter, a third optical receiver that receives light that has passed through the third band-pass filter, and the second optical receiver. , An image processing device for evaluating the brightness level and distribution of the output image of the third light receiver, and a device for evaluating the imidization ratio of a liquid crystal alignment film.

In the second invention, examples of the second and third light receivers include a camera and a light receiving sensor, respectively. The operation of the present invention will be described below for each of (1) the uniform film thickness distribution of the alignment film and (2) the non-uniform film thickness distribution of the alignment film.

(1) When the film thickness distribution of the alignment film is uniform In this case, the light intensity of the reflected infrared light depends only on the film quality of the alignment film. Therefore, the polyimide has a low absorptance and the polyamide has a high absorptivity. The reflected infrared light is passed through a band-pass filter for wavelengths, and the passed light is received by a camera having sufficient sensitivity in the wavelength range and the alignment film surface When an image of a constant area is obtained, the brightness level is high in the polyimide part and low in the polyamide part. The brightness level is determined by the ratio of polyimide, that is, the imidization ratio.

(2) When the film thickness distribution of the alignment film is non-uniform In this case, the light intensity of the reflected infrared light is affected not only by the film quality of the alignment film but also by the film thickness. Therefore, the light intensity of the wavelength, which has a low absorptance with polyimide and a high absorptivity with polyamide, is affected by both the film quality and the film thickness. The second and third
The band-pass filter and the second and third photodetectors are intended to eliminate the influence of the nonuniformity of the film thickness.

That is, when the light intensity in the first wavelength region for evaluating the film quality called imidization ratio is evaluated, the polyamide and the polyimide both have low absorptivity and are located before and after the first wavelength region. By using the brightness level in the third wavelength range as a reference, the light intensity in the first wavelength range is calibrated to cancel the influence of the non-uniformity of the film thickness.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described with reference to FIGS. Here, FIG. 1 is an explanatory diagram of an optical head which is one configuration of an imidization ratio evaluation device for a liquid crystal alignment film according to the present invention. FIG. 2 is an explanatory diagram of an image processing and control device which is one configuration of the imidization ratio evaluation device. 2 and 3 are data examples of infrared light absorption spectra of the liquid crystal alignment film, FIG. 2 shows a case where the imidization ratio is high, and FIG. 3 shows a case where the imidization ratio is low. FIG. 4 is an explanatory diagram of the configuration of the image processing and control device.

In FIG. 1, reference numeral 1 is a substrate on which an alignment film having a thickness of about 0.1 μm is formed. The substrate 1 is placed on an XY table (not shown), and is driven and positioned in the X-axis direction of the arrows a and b and in the Y-axis direction perpendicular to the paper surface. The projected light 3 from the infrared light source 2 becomes reflected light 4 on the surface of the alignment film of the substrate 1 and becomes divided lights 6 and 7 by the half prism 5.

Of these, one of the split lights 6 is a lens 6,
A camera 11 as a first light receiver is arranged to pass through a diaphragm 9 and a first band pass filter 10. The other split light 7 is further split by the half prism 12,
It becomes 14. Then, the divided light 13 reaches the light receiving sensor 17, which is a second light receiving device, through the lens 15 and the second band pass filter 16. The other split light 14 is
The light is passed through the lens 18 and the third band pass filter 19 to reach the light receiving sensor 20 which is the third light receiving device.

Next, setting of the pass wavelength bands of the first, second and third band pass filters will be described with reference to FIGS. 3 and 4. 3 and 4, the horizontal axis is wavelength (cm ^-1 )
And the vertical axis represents the reflectance (%). Here, the reflectivity shows how much the amount of reflected light of the film produced is compared with that of the amount of reflected light of the film (blank glass) as 100.

FIG. 3 shows an infrared absorption spectrum of a portion of the alignment film having a low imidization ratio, and an absorption peak is observed in the vicinity of a wavelength of 2950 cm ^-1 , which shows characteristics of polyamide. Further, the size of the peak becomes larger as the imidization ratio is lower, that is, as the polyamide ratio is higher, and the imidization ratio can be evaluated from the size of this peak.

FIG. 4 shows an infrared light absorption spectrum of a portion of the orientation film having a high imidization ratio, and there is almost no absorption peak near the wavelength of 2950 cm ^-1 . The first band-pass filter 10 sets a narrow wavelength band centering on a wavelength of 2950 cm ^-1 as a set pass wavelength band, which is a region c in FIG. The second bandpass filter 16 is shown in FIG.
The narrow wavelength band of the region d is set as the set pass wavelength band. Similarly, the second bandpass filter 19 uses the region e in FIG. 3 as the set pass wavelength region.

Next, the configuration of the image processing and control device shown in FIG. 2 will be described. In FIG. 2, the output image of the camera 11 is triggered by a synchronous clock pulse (not shown) sent from the main control device 21 and transferred to the image processing device 23 via the camera control unit 22 at 33 msec intervals. It has become. The output of the light receiving sensor 17 is transferred to the image processing device 23 via the amplifier 24 and the A / D converter 25, triggered by the synchronous clock pulse. The output of the light receiving sensor 20 is transferred to the image processing device 23 via the amplifier 26 and the A / D converter 27, triggered by the synchronous clock pulse.

In the image processing device 23, the image binarization threshold value is set when extracting a portion having a low luminance level, that is, a portion having a low imidization rate in the image output of the camera 11, by setting This is performed based on the data of the D / D converters 25 and 27, that is, the output levels of the light receiving sensors 17 and 20. It is assumed that the light-receiving sensors 17 and 20 calibrate the alignment film whose film quality has been clarified in advance by analyzing the infrared light absorption spectrum and whose film thickness has been clarified by a thickness analyzer.

In the main controller 21, the coordinate data (X _k , Y _k ) of the XY table obtained every 33 msec by being triggered by the synchronous clock pulse from the NC controller 28 of the XY table (not shown). Is transferred. In the main controller 21, the coordinate data (X _k , Y _k ) and the output of the image processing device 23 are linked to each other, and when the image acquisition of the entire alignment film of the substrate 1 is completed, the imidization of the substrate 1 is completed. The portion having a low rate is output to the monitor TV or the printer 29 as map display data. Further, in the main controller 21,
The quality of the substrate 1 is determined based on the size and number of imidization ratio defective portions.

As described above, the apparatus for evaluating the imidization ratio of the liquid crystal alignment film according to the above-described embodiment includes the infrared light source 2 for projecting infrared light onto the alignment film on the surface of the substrate 1 and the infrared light. Reflected light 4
In the absorption spectrum of 1, the first bandpass filter 10 for the first wavelength has a low absorptance in polyimide and the absorptivity in polyamide has a high absorptivity in polyamide. , Third
Second and third bandpass filters 16 for wavelengths,
19, a camera 11 that receives the light that has passed through the first band-pass filter 16, and the second band-pass filter 16
A light receiving sensor 17 for receiving the light passing through the light receiving sensor 20, a light receiving sensor 20 for receiving the light passing through the third band pass filter 19, the brightness levels of the output images of the second and third light receiving devices 17, 20, and The image processing device 23 for evaluating the distribution is provided.

Therefore, it has the following effects. That is, according to the present apparatus, it is possible to obtain, in a short time, the two-dimensional distribution display data of a portion having an imidization ratio lower than a preset threshold value, that is, a portion having a high ratio of residual polyamide to polyimide. Highly effective imidization rate can be evaluated. In addition, since the influence of the film thickness variation on the evaluation of the imidization ratio of the alignment film is removed, the reliability of the imidization ratio can be evaluated.

Although the rated center wavelength of the first bandpass filter is set to 2950 cm ^-1 in the above embodiment, it is not limited to this wavelength depending on the types of polyimide and polyamide.

In the above embodiment, the case where the light receiving sensor is used as the second and third light receivers has been described.
Not limited to this, a camera may be used. Further, in the above-described embodiment, the case where the light receiving sensor is used as the second and third light receiving devices other than the camera 11 has been described, but when the film thickness distribution is uniform, the light receiving sensor (17, 20) for calibration is used. ), At least one of them is unnecessary, and it is sufficient to evaluate the brightness (luminance level) of the camera 11. That is, if the film thickness distribution becomes stable in the future, the light receiving sensors 17 and 20 will be unnecessary, and the cost of the device can be reduced.

[0027]

As described in detail above, according to the present invention,
It is possible to provide a highly productive and highly reliable liquid crystal alignment film imidization ratio evaluation device capable of evaluating the uniformity of the imidization ratio of the alignment film on the production line.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical head that is a configuration of an imidization ratio evaluation device for a liquid crystal alignment film according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an image processing and control device which is one configuration of an imidization ratio evaluation device for a liquid crystal alignment film according to an embodiment of the present invention.

FIG. 3 is an example of data of an infrared absorption spectrum of a liquid crystal alignment film, which is a characteristic diagram when the imidization ratio is low.

FIG. 4 is an example of data of an infrared absorption spectrum of a liquid crystal alignment film, which is a characteristic diagram when the imidization ratio is high.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Infrared light source, 10 ... 1st bandpass filter, 11 ... Camera, 16 ... 2nd bandpass filter, 17, 20 ... Photosensor, 19 ... 2nd bandpass filter, 23 ... Image processing device.

Claims (2)

[Claims] 1. An apparatus for projecting infrared light onto an alignment film, a band pass filter for a wavelength having a low absorption rate for polyimide and a high absorption rate for polyamide in an absorption spectrum of reflected light of the infrared light, An imidation ratio evaluation device for a liquid crystal alignment film, comprising: a photoreceiver for receiving light that has passed through a filter; and an image evaluation device for evaluating the brightness level and distribution of an output image of the photoreceiver. 2. A device for projecting infrared light on an alignment film, and an absorption spectrum of reflected light of the infrared light, wherein a first band for a first wavelength has a low absorptivity for polyimide and a high absorptivity for polyamide. A pass filter, second and third band pass filters respectively corresponding to second and third wavelengths having a low absorptivity for both polyamide and polyimide before and after the first wavelength, and the first band pass filter A first photoreceiver that receives light that has passed through the second band, a second photoreceiver that receives light that has passed through the second bandpass filter, and a first photoreceiver that receives light that has passed through the third bandpass filter. 3. An imidation ratio evaluation device for a liquid crystal alignment film, comprising: the third photodetector; and an image processing device for evaluating the brightness level and distribution of the output images of the second and third photodetectors.