JPH10104161A - Method and device for evaluating conversion rate to imide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform a quick and quantitative evaluation the conversion rate to imide of a large area by irradiating light on the surface of a substrate, wherein polyamide is formed, obtaining the absorbance of the substrate at the specified wavelength region from the reflected or transmitted light, comparing the absorbance with the absorbance in a reference region, and obtaining the absorbance difference. SOLUTION: Light 11, which is irradiated on a substrate 1 from a light source 10, is projected on the substrate 1 through a lens 12, a diaphram 13 and a lens 14 as collimated light 15. The reflected light from the substrate 1 is transmitted through narrow-band passing filters 19a, b, c and d by way of lenses 17 and 18. The image of the lights having the respective specified wavelengths transmitted through the narrow-and passing filters 19a, b, c and d are picked up with an infrared camera 22. The image data are stored in the frame memory of an image processor 23. In this constitution, the absorbances at the reference wavelengths in the vicinity of the wavelength of 5.8μm, in the vicinity of the wavelength of 6μm and 5.5μm or less are compared with the absorbances in the vicinity of the wavelength of 5.8μm and in the vicinity of the wavelength of 6μm. Thus, the absorbance caused by polyamide and polyimide is computed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imidation rate evaluation method and an imidation rate evaluation apparatus for quantitatively evaluating, for example, a polyimide constituting an alignment film of a liquid crystal display.

[0002]

2. Description of the Related Art At present, the liquid crystal display market is growing rapidly, and it is important to reduce the cost of the liquid crystal display. One of the factors that hinder the cost reduction is a decrease in yield. One of the causes of the decrease in the yield of the liquid crystal display is poor image quality such as color unevenness and luminance unevenness that become apparent in the lighting inspection in the final process.

It has been found that one of the causes of the color non-uniformity and the luminance non-uniformity is the non-uniformity of the imidization ratio of the alignment film for aligning the liquid crystal molecules. The alignment film of a liquid crystal display is composed of a TFT (Thin Film Transistor) on a glass substrate.
r) The polyimide film is formed by heating and drying the polyamide film applied on the top layer of the multilayer film on which the color filter, transparent electrode film, overcoat transparent resin film, etc. are formed. A rubbing process is performed on the film by physical contact to form a plurality of microgrooves. Polyamide has a lower hardness than polyimide, and if the polyamide remains in the polyimide, grooves are formed unevenly during the rubbing treatment, resulting in color unevenness, luminance unevenness, etc. of the final product. Cause.

[0004] In order to sufficiently convert the polyamide into a polyimide, heating may be performed at a high temperature for a long time. However, when heating is performed at a high temperature for a long time, a TFT having low heat resistance and a transparent electrode film formed below the alignment film are damaged, and the yield is deteriorated. Therefore, from the viewpoint of protecting the structure of the lower layer of the alignment film, it is desired to heat the polyamide at a low temperature in a short time. On the other hand, when the polyimide is formed at a low temperature and for a short time of heating, the imidization ratio of the polyimide film is reduced or non-uniform, which causes color unevenness and brightness unevenness of the liquid crystal display of the final product, and reduces the yield. . Therefore, polyimide must be formed under optimal conditions.

Therefore, an apparatus for evaluating the ratio of polyamide to polyimide, that is, the uniformity of the imidization ratio is desired in order to obtain optimum heating conditions. There is no device to have. However, it is possible to evaluate the imidation rate at the laboratory level. For example, analysis can be performed by using a Fourier analyzer (hereinafter referred to as an IR analyzer) for an infrared light absorption spectrum.

[0006]

However, since the IR analyzer performs a Fourier analysis on the absorption or reflection spectrum of the infrared light at the point to be evaluated, the analysis time per point is long. In addition, the IR analyzer usually has a limitation on the sample size. Therefore, it is difficult to evaluate in a short time the distribution of non-uniformity of the imidization rate of an alignment film applied to a glass substrate (for example, 360 × 460 mm) which has been increasing in size in recent years. It is impossible to use it as a device.

Further, the present inventors have filed Japanese Patent Application No. 8-4 / 1996.
No. 3737 proposes an apparatus for extracting a portion where the imidation ratio is reduced. However, although it is possible to extract a portion having a low imidation rate with this apparatus, it has been difficult to quantitatively evaluate the imidation rate.

An object of the present invention is to provide an imidation rate evaluation method and an imidation rate evaluation apparatus capable of quickly and quantitatively evaluating the imidization rate of a polyimide formed on a large-area sample. It is in.

[0009]

The imidation rate evaluation method and the imidation rate evaluation method of the present invention are configured as follows to solve the above-mentioned problems. (1) The imidation rate evaluation method of the present invention (Claim 1)
Heating the polyamide to irradiate the surface of the substrate on which the polyimide is formed with light, and reflecting or transmitting light from the substrate to one or more reference wavelength ranges of 5.5 μm or less, in the vicinity of 6 μm. The absorbance difference Pa at _a wavelength of 6 μm and the absorbance difference P _i at a wavelength of 5.8 μm are determined by comparing the absorbance of the substrate in the wavelength range of 5.8 μm with the absorbance of the substrate in the wavelength range near 5.8 μm. And a step of calculating an imidization ratio P _i / (P _i + P _a ) from the obtained two absorbance differences P _a and P _i . (2) The imidation rate evaluation device of the present invention (Claim 2)
A light source for projecting light onto the surface of the substrate on which the polyimide is formed by heating the polyamide; and a light range of about 6 μm out of the reflected light or transmitted light from the substrate, 5.8
a plurality of narrow band-pass filters that respectively transmit a wavelength range near μm and one or more types of reference wavelength ranges of 5.5 μm or less; Filter switching means for switching and arranging one of the filters; imaging means for receiving light transmitted through the narrow bandpass filter by a plurality of pixels; and transmitting the plurality of filters from the output of the imaging means. The absorbance difference Pa at _a wavelength of 6 μm and the absorbance difference P _i at _a wavelength of 5.8 μm are compared with the means for determining the absorbance of each pixel of the imaging means in the respective wavelength ranges and the absorbance in the reference wavelength range. And a means for calculating an imidization ratio P _i / (P _i + P _a ) from the determined absorbance differences P _a and P _i. .

[0010] Desirably, the light from the light source is converted into parallel light and irradiated onto the substrate surface. (3) The imidation rate evaluation device of the present invention (claim 3)
Moving means for moving the base on which the polyimide is formed by heating the polyamide in a two-dimensional plane, a light source for projecting light to a plurality of positions on the surface of the base moved by the moving means, and the base A plurality of narrow band pass filters for transmitting at least one of a wavelength range near 6 μm, a wavelength range near 5.8 μm, and at least one reference wavelength range of 5.5 μm or less, among the reflected light or transmitted light from the substrate; Filter switching means for switching and arranging one of the plurality of narrow band-pass filters on the optical path of reflected light or transmitted light from the camera, and an infrared sensor for receiving light transmitted through the narrow band-pass filter Means for determining the absorbance from the output of the infrared sensor for each position irradiated with the light from the light source, and comparing the absorbance in the reference wavelength range with a wavelength of 6 μm. Absorbance difference P _a and the wavelength of 5.8μm
Means for determining the absorbance difference P _i in, the obtained absorbance difference P _a, and means for calculating the imidization ratio _{P i / (P i + P} a) from P _i.

The method for evaluating imidation rate and the method for evaluating imidation rate of the present invention have the following functions and effects by the above constitution. According to experiments by the inventors, polyamide has a wavelength of 6 μm.
It was found that the absorbance was high in the vicinity, and the absorbance of polyimide was high in the vicinity of the wavelength of 5.8 μm. In addition, 5.5 μm
6 μm wavelength based on the absorbance in the following reference wavelength range
And absorbance difference P _a in the vicinity, as calculated the absorbance difference P _i at a wavelength near 5.8 [mu] m, that imidization ratio can be quantitatively evaluated by _{P i / (P i + P} a) × 100 [%] I have confirmed.

For example, the imidation ratio of a stock solution of polyamide is 8% or less, and when sufficiently heated at 200 ° C., the imidization ratio becomes 1%.
It has been confirmed by the imidation ratio evaluation method of the present invention that the imidation ratio is reduced when the heating time is 00% and the heating time is short.

6 μm based on the absorbance in the reference wavelength range
And absorbance difference P _a at by measuring the absorbance difference P _i at 5.8 [mu] m, by calculating the imidization ratio and P _i / (P _i + P _a), is not performed Fourier analysis, the polyimide film having a large area Can be quickly evaluated.

The absorbance in the reference wavelength range is 5.8 μm.
By comparing the absorbances of m and 6 μm and determining the absorbance differences P _a and P _i , it is possible to obtain the absorbance excluding the influence of the fluctuation of the light intensity of the light source and the influence of the non-uniformity of the light amount distribution. The conversion rate can be more accurately evaluated.

In addition, by evaluating the imidation ratio of the alignment film of the liquid crystal display formed on the actual production line, not only the occurrence of color unevenness and luminance unevenness can be prevented, but also the heating temperature and heating time of the polyamide film can be reduced. It is a useful tool for optimizing.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a schematic diagram showing a configuration of an imidation ratio measuring apparatus according to a first embodiment of the present invention. In this embodiment, a measurement target is a substrate (base) 1, which is a glass plate 2 on which a polyimide 3 is formed. A lens 12 and a stop 13 are arranged on the optical path of the light 11 emitted from the light source 10. Note that light having a wavelength of 5 μm or more is emitted. A lens 14 having a focus on the opening 13a is arranged on an optical path emitted from the opening 13a of the stop 13. Light from the lens 14 is applied to the substrate 1 as collimated light 15. Two lenses 17 and 18 are arranged on the optical path of the reflected light 16 from the substrate 1. A narrow band filter 19 (19a, b, c, 19b) for limiting the transmission frequency of the light transmitted through the lenses 17 and 18
d) is arranged. The narrow band pass filter 19 selectively transmits narrow band wavelengths centered on the wavelengths of 5 μm, 5.4 μm, 5.8 μm, and 6 μm, respectively.

The four filters 19 are equally installed on the circumference of the disk holder 20. The center axis of the disc holder 20 is joined to the rotating shaft 21. The rotating shaft is indexed by 90 ° by an indexing device (not shown), and four types of narrow band pass filters 19 are sequentially reflected light. Is arranged on the optical path.

An infrared camera 22 is arranged on the optical path of the reflected light transmitted through the narrow band pass filter 19. An image processing device 23 that processes video data received by the infrared camera 22 is connected to the infrared camera 22. The image processing device 23 calculates the absorbance of the light transmitted through the narrow band pass filter 19 from the luminance level of the imaging area.

Next, the principle and method for evaluating the imidation ratio will be described. FIG. 2 is a characteristic diagram schematically showing typical data obtained by analyzing reflected light of a polyamide film by an IR analyzer. In this characteristic diagram, the horizontal axis represents wavelength, and the vertical axis represents absorbance. 3 and 4 show examples of actual measurement. While the horizontal axis in FIG. 3 has a wave number which is the reciprocal of the wavelength, at 2000 cm ^-1 is 5 [mu] m, at 1724 cm ^-1 is 5.8 [mu] m, 1666 cm ^-1 is 6 [mu] m. In FIGS. 3 and 4, a part of the absorbance shows a negative value, which is generated in the process of Kramers-Kronig transformation. Here, since the difference from the reference (absorbance in the reference wavelength range) is more of a problem than the numerical value, the sign of the numerical value itself has no meaning.

In FIG. 2, there is a peak (point C) of the absorbance due to the polyimide near the wavelength of 5.8 μm, and the wavelength is 6 μm.
There is a peak of absorbance (point D) due to polyamide near m. Further, wavelengths of 5 μm and 5.4 μm are used as reference wavelengths, and a wavelength of 5.8 μm based on an extension L of a straight line connecting absorbances (points A and B) at wavelengths of 5 μm and 5.4 μm.
The absorbance difference at m and 6 μm (points C and D)
_i, and P _a. Then, the imidization rate is calculated as ΔP _i / (P _i
+ P _a )｝ × 100 [%].

Then, the present inventors performed this method for evaluating the imidation ratio based on the experimental results of the present inventors. For example, immediately after spin coating of a stock solution of polyamide on a glass plate, the imidation ratio is 8%, and when heated at a temperature of 200 ° C. for 10 seconds, the imidization ratio reaches 63 to 66%, and 90%. Since the imidation rate increases with heating time, for example, the imidation rate becomes 100% when heated for 2 seconds, it has been confirmed that this imidation rate evaluation method is appropriate.

Next, the operation of evaluating the imidation ratio by the apparatus shown in FIG. 1 by the above-described evaluation method will be described. The light 11 emitted from the light source 10 to the substrate 1
2, collimated light 15 via aperture 13 and lens 14
The light is projected on the substrate 1. The reflected light from the substrate 1 is 2
Narrow bandpass filter 1 via lenses 17 and 18
9a. When the reflected light passes through the narrow band pass filter 19a, a narrow band wavelength centered on 5 μm is selectively transmitted. 5 μm transmitted through the narrow band pass filter 19a
The near-wavelength light is imaged by the infrared camera 22 and the image data is stored as data Da in _a frame memory (not shown) of the image processing device 23. Then, similarly narrow band pass filter 19b, c, sequentially selects d take images in the infrared camera 22, these image data are data D _b, D _c, as D _d, the frame of the image processing apparatus 23 Store in memory.

The pixels of the infrared camera 22 are represented by (i,
j). The imidation rate of each pixel is calculated as follows as a part of the image processing for each pixel unit of the image data.

Here, for the sake of explanation, the symbols LD _k (i, j),
(K = a, b, c, d) is defined. LD _k (i, j) is a pixel (i, j) obtained by normalizing the difference between the luminance level of the (i, j) pixel of the image data D _k (k = a, b, c, d) and the reference luminance level. The absorbance in j). Here, the reference luminance level is, for example, a luminance measured in a state where the polyimide film 3 is not formed. That is, L
D _a (i, j), LD _b (i, j), LD _c (i, j), LD _d (i, j)
j) indicates wavelengths of 5 μm, 5.4 μm, and 5.8 μm, respectively.
The absorbance at the pixel (i, j) in the imaging area at m, 6 μm. Further, the absorbance differences P _i , P _i shown in FIG.
_In order to obtain _a for each pixel (i, j), the following equation may be calculated.

[0025]

(Equation 1)

From the equations (1) and (2), the imidation ratio at the pixel (i, j) is given by P _i (i, j) / (P _i (i, j) + P _a (i, j) ) × 100
It can be evaluated in [%].

That is, the imidation ratio of the substrate can be evaluated for each pixel in the imaging area of the infrared camera.
According to the imidation rate evaluation apparatus of the present embodiment, the imidation rate of polyimide on a large-area sample can be quickly measured.

(Second Embodiment) FIG. 5 is a schematic diagram showing the configuration of an imidation ratio measuring apparatus according to a second embodiment of the present invention. Here, the same parts as those in FIG.
The description is omitted. In the present apparatus, the substrate is placed on an XY stage (not shown), and the imidization ratio can be evaluated at a plurality of positions.

This embodiment is different from the first embodiment in the following points. (1) Light emitted from the light source 10 is focused on the surface of the substrate 1 via the lens 50. The reflected light from the substrate 1 is transmitted through the lens 51 to the narrow bandpass filter 19.
Is collected. (2) The infrared sensor 52 is used instead of the infrared camera. In the present embodiment, the distribution of the imidation ratio of the polyamide film 3 of the substrate 1 is not evaluated at a time at a plurality of points within the imaging range of the infrared camera, but the plurality of points are moved while moving the substrate 1 on the XY stage. The representative point of the evaluation is performed. In practice,
As in the present embodiment, it is sufficient to evaluate the imidation rates at a plurality of representative points on the substrate.

According to the imidation rate evaluation apparatus of the present embodiment, in addition to the effects of the first embodiment, since the configuration is simplified as compared with the apparatus of the first embodiment, the apparatus can be manufactured at low cost. can do.

The present invention is not limited to the above embodiment. For example, the number of reference wavelengths is not limited to two, and may be one or three or more. If there are three or more reference wavelengths,
The straight line L may be obtained by an interpolation method.

In the embodiment, the absorbance is measured from the reflected light, but the absorbance may be measured from the transmitted light. In addition, various modifications can be made without departing from the spirit of the present invention.

[0033]

As described above, according to the method for evaluating imidation ratio of the present invention, the absorbance at a reference wavelength of about 5.8 μm, the wavelength of about 6 μm, and 5.5 μm or less is measured. By comparing the absorbance at a wavelength of about 5.8 μm and the absorbance at a wavelength of about 6 μm, by calculating the absorbance caused by the polyamide and the absorbance caused by the polyimide, the imidization rate of the polyimide film on the large-area substrate can be quickly calculated. And it can be obtained quantitatively.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an imidization rate evaluation device according to a first embodiment.

FIG. 2 is a view for explaining an imidation rate evaluation method.

FIG. 3 is a characteristic diagram (1) showing an example of IR analysis.

FIG. 4 is a characteristic diagram (2) showing an example of IR analysis.

FIG. 5 is a schematic diagram showing a configuration of an imidation rate evaluation device according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 glass plate 3 polyimide film 10 light source 11 light 12 lens 13 aperture 14 lens 15 collimated light 16 reflected light 17 lens 18 lens 19 narrow band pass filter 20 disk holder 21 rotation axis 22 infrared camera 23 image processing device 50 lens 51 Lens 52 infrared sensor

Claims (3)

[Claims] 1. A step of irradiating a surface of a substrate on which a polyimide is formed by heating a polyamide with light, and one or more reference wavelengths of 5.5 μm or less from light reflected or transmitted from the substrate. Range, wavelength range around 6 μm,
A step of determining the absorbance of the substrate in a wavelength range near 5.8 μm and comparing the absorbance in the reference wavelength range with the absorbance difference Pa at _a wavelength of 6 μm and the absorbance difference P at _a wavelength of 5.8 μm;
a step of determining a _i, two absorbance difference P _a obtained, the imidization ratio evaluation method which comprises a step of obtaining a P _i / imidization ratio from _{P i (P i + P a} ). 2. A light source for projecting light onto the surface of a substrate on which a polyimide is formed by heating a polyamide, and a wavelength range of about 6 μm and a wavelength of about 5.8 μm of light reflected or transmitted from the substrate. Wavelength range, 5.5 μm or less 1
A plurality of narrow bandpass filters each transmitting at least one type of reference wavelength band; and one of the plurality of narrowband pass filters is switched and arranged on an optical path of reflected light or transmitted light from the substrate. Filter switching means; imaging means for receiving light transmitted through the narrow band-pass filter by a plurality of pixels; from output of the imaging means, respective pixels of the imaging means in respective wavelength ranges transmitted by the plurality of filters The absorbance difference Pa at _a wavelength of 6 μm and the absorbance difference P at _a wavelength of 5.8 μm are obtained by comparing the means for determining the absorbance of
means for determining the _i for each pixel of said imaging means, the determined absorbance difference P _a, imides, characterized by comprising means for calculating the imidization ratio _{P i / (P i + P} a) from P _i Conversion rate evaluation device. 3. A moving means for moving the base on which the polyimide is formed by heating the polyamide in a two-dimensional plane, and projecting light onto a plurality of positions on the surface of the base moved by the moving means. A light source, and a wavelength range around 6 μm, a wavelength range around 5.8 μm, and a wavelength range of 5.5 μm or less out of reflected light or transmitted light from the substrate.
A plurality of narrow bandpass filters each transmitting at least one type of reference wavelength band; and one of the plurality of narrowband pass filters is switched and arranged on an optical path of reflected light or transmitted light from the substrate. Filter switching means, an infrared sensor for receiving light transmitted through the narrow band-pass filter, means for determining the absorbance from the output of the infrared sensor for each position irradiated with light from the light source, a reference wavelength range The absorbance difference Pa at _a wavelength of 6 μm and the absorbance difference P at _a wavelength of 5.8 μm are compared with the absorbance at
means for determining _i, the obtained absorbance difference P _a, imidization ratio evaluating apparatus characterized by comprising a means for calculating the imidization ratio _{P i / (P i + P} a) from P _i.