JP3711813B2 - Cell thickness measuring method and cell thickness measuring apparatus for liquid crystal panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cell thickness measuring method and a cell thickness measuring apparatus for a liquid crystal panel.
[0002]
[Prior art]
In general, in the manufacturing process of a conventional liquid crystal device, transparent electrodes are formed on the surfaces of two transparent substrates, an alignment film is formed thereon, a predetermined rubbing treatment is performed, and a 2 A liquid crystal panel is formed by laminating a transparent substrate and injecting liquid crystal therebetween to seal a sealing material. Further, for example, in a TN type or STN type liquid crystal panel, polarizing plates to be a polarizer and an analyzer are attached on the surfaces of two transparent substrates.
[0003]
In the manufacturing process described above, the conditions of the manufacturing process are appropriately set by measuring the cell thickness of the formed liquid crystal panel (the gap between the two substrates or the thickness of the liquid crystal layer injected into the gap). May be corrected. The variation in cell thickness of the liquid crystal panel directly affects the display performance of the liquid crystal device, so it must be managed with extreme strictness, but it is slightly distorted by parameters that are difficult to manage such as the gap material distribution density during the manufacturing process. Because there are cases.
[0004]
FIG. 5 shows a schematic configuration of a measuring apparatus for measuring the cell thickness of a conventional liquid crystal panel. In this apparatus, a polarizing plate 22 that serves as a polarizer and a polarizing plate 23 that serves as an analyzer are disposed on both sides of the liquid crystal panel 10. A light source 21 is disposed in front of the polarizing plate 22, and a chromaticity meter 25 is disposed in front of the polarizing plate 23. In the liquid crystal panel 10, transparent electrodes 11a and 12a are respectively formed on the surfaces of the transparent substrates 11 and 12, and alignment films 11b and 12b are further formed thereon. The alignment films 11b and 12b are each rubbed in a predetermined direction. The transparent substrates 11 and 12 are attached via a sealing material 13, and a liquid crystal 14 is sealed inside the sealing material 13.
[0005]
In the measuring apparatus, the polarization transmission axes of the polarizing plates 22 and 23 are set so as to face a predetermined direction based on the rubbing direction of the alignment films 11b and 12b of the liquid crystal panel 10. In this state, the light emitted from the light source 21 passes through the polarizing plate 22 and becomes linearly polarized light. After passing through the liquid crystal panel 10 and further passing through the polarizing plate 23, the color tone is detected by the chromaticity meter 25. .
[0006]
At this time, the linearly polarized light incident on the liquid crystal panel 10 is modulated by the liquid crystal 14. Modulation degree for the linear polarization of the liquid crystal 14, the refractive index anisotropy of the liquid crystal 14 and _{Δn (= n e -n o)} , when the thickness d of the liquid crystal layer, the value of the retardation represented by [Delta] n · d Proportional. Since the degree of modulation of the linearly polarized light by the liquid crystal layer depends on the wavelength, the light detected by the chromaticity meter 25 is colored in a predetermined color tone. Therefore, when the thickness of the liquid crystal layer, that is, the cell thickness of the liquid crystal panel changes, the retardation changes and the color tone detected by the chromaticity meter 25 also changes.
[0007]
Conventionally, a reference color tone with respect to a reference cell thickness is obtained in advance using the optical characteristics as described above, and the cell thickness is determined according to the degree to which the color tone detected by the chromaticity meter 25 deviates from the reference color tone. The degree of deviation from the reference value was determined.
[0008]
[Problems to be solved by the invention]
However, in the above conventional cell thickness measurement method, light is transmitted through the liquid crystal panel 10 in which the polarizer 22 and the analyzer 23 are arranged before and after, and the transmitted light is detected by the chromaticity meter 25. Can be detected in a spot or average manner, and distribution information regarding the cell thickness along the panel surface of the liquid crystal panel 10 cannot be obtained.
[0009]
Further, the color tone detected by the chromaticity meter 25 is an amount determined by at least three independent variables, is complicated, and has a one-to-one correlation with the cell thickness of the liquid crystal panel 10. However, there is a problem in that it is not only possible to determine whether or not the cell thickness is deviated from the reference value only by changing the color tone, and it is impossible to accurately grasp the degree of deviation of the cell thickness from the reference value.
[0010]
Therefore, the present invention solves the above-mentioned problems, and the problem is that a measurement method that can grasp the overall cell thickness distribution of the liquid crystal panel and can easily grasp the amount of deviation (difference) from the reference value of the cell thickness. And providing a measuring device.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, a liquid crystal panel cell thickness measurement method according to the present invention includes a polarizer and an analyzer disposed on both sides of the liquid crystal panel, and the polarization transmission axis of the polarizer and the analyzer is set to the liquid crystal panel. Including a distribution of color tone data along the panel surface of the liquid crystal panel, taking in light sequentially passing through the polarizer, the liquid crystal panel, and the analyzer in a state set to a predetermined orientation according to the liquid crystal alignment state in A color image is acquired, and the color tone data is converted into cell thickness correlation data having linearity with respect to the cell thickness within a predetermined cell thickness range including the cell thickness in the liquid crystal panel, and the panel of the cell thickness correlation data is converted. It is characterized by obtaining a distribution along a plane.
[0012]
According to the present invention, a color image is acquired by taking in light sequentially passing through a polarizer, a liquid crystal panel, and an analyzer, and the color tone data of the color image is converted into cell thickness correlation data. By obtaining the distribution along the panel surface, it is possible to accurately grasp the distribution of the cell thickness along the panel surface, and to easily grasp the magnitude relationship of the actual cell thickness difference with respect to the reference value of the cell thickness. Is possible.
[0013]
In the present invention, the liquid crystal panel is an STN type liquid crystal panel, and the orientation of the transmission polarization axis of the polarizer and the analyzer is set to be in a blue negative mode in combination with the liquid crystal panel, and the color tone is set. It is preferable to obtain an x value of chromaticity coordinates from the data as the cell thickness correlation data.
[0014]
According to the present invention, when the orientations of the polarizer and the analyzer are set so as to be in the blue negative mode in the STN type liquid crystal panel, the cell thickness in a region corresponding to a predetermined cell thickness range (for example, a region around 5 to 6 μm). The linearity of the chromaticity coordinate x with respect to (the property that the chromaticity coordinate x is expressed by a linear expression of the cell thickness) is obtained.
[0015]
Note that the above linearity is not limited to the linearity in a strict sense, and it is sufficient that the linearity is substantially satisfied within the range of measurement error that can be allowed in the cell thickness measurement.
[0016]
In addition, the liquid crystal panel cell thickness measuring apparatus of the present invention includes a polarizer and an analyzer disposed on both front and back sides of the liquid crystal panel placement unit, a light source disposed in front of the polarizer, and a tip of the analyzer. An imaging means for outputting a color image including a distribution of color tone data along a panel surface of the liquid crystal panel with respect to transmitted light emitted from the light source; and the color tone data including a cell thickness in the liquid crystal panel. Data processing means for converting into cell thickness correlation data having linearity with respect to the cell thickness within the cell thickness range.
[0017]
In the present invention, the liquid crystal panel is an STN type liquid crystal panel, and the direction of the transmission polarization axis of the polarizer and the analyzer is set to be in a blue negative mode in combination with the liquid crystal panel, and the data Preferably, the processing means obtains an x value of a color coordinate as the cell thickness correlation data from the color tone data.
[0018]
In the present invention, it is preferable to include output means for outputting a distribution of the cell thickness correlation data along the panel surface.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of a cell thickness measuring method and a cell thickness measuring apparatus for a liquid crystal panel according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing a state of cell thickness measurement in the present embodiment. The liquid crystal panel 10 is the same as that described in the conventional example, and an alignment film 11 b is formed on the surface of the transparent substrate 11, while an alignment film 12 b is formed on the surface of the transparent substrate 12. A polarizing plate 22 as a polarizer and a polarizing plate 23 as an analyzer are arranged on both the front and back sides of the liquid crystal panel 10 as described above, and a light source 21 is arranged outside the polarizing plate 22. In addition, a CCD camera 24 as an imaging unit is disposed outside the polarizing plate 23. The output of the CCD camera 24 is input to a computer device 26 via a predetermined input / output circuit, and a monitor 27 is connected to the computer device 26. As is well known, this computer device 26 is a microprocessor unit having a CPU (Central Processing Unit), information storage means (memory) such as ROM, RAM, and hard disk, a signal and data bus, an input / output circuit and the like. It is.
[0020]
The CCD camera 24 takes in the transmitted light emitted from the polarizing plate 23 to acquire a predetermined color image, and sends this color image data to the computer device 26. The computer device 26 executes a data processing program stored in advance in a ROM, a hard disk or the like, thereby performing arithmetic processing on the color image data output from the CCD camera 24 and converting it into cell thickness correlation data described later. The reconstructed image formed using the cell thickness correlation data can be output to the monitor 27. In addition, the color image data output from the CCD camera 24 can be directly output to the monitor 27.
[0021]
The polarizing plates 22 and 23 are each attached to a support member such as a frame (not shown) so as to be rotatable around the optical axis, and the polarization transmission axis is oriented in a predetermined direction according to the liquid crystal alignment state in the liquid crystal panel 10. To be adjusted.
[0022]
FIG. 2 is an explanatory diagram showing the relationship between the liquid crystal alignment state of the liquid crystal panel 10 and the orientation of the polarization transmission axes of the polarizing plates 22 and 23 in this embodiment. The liquid crystal panel of this embodiment is an STN (super twisted nematic) type liquid crystal panel. The alignment film 11b is rubbed along the rubbing direction 11A, and the alignment film 12b is rubbed along the rubbing direction 12A. The rubbing process is given. By the rubbing directions 11A and 12A, the liquid crystal layer constituted by the liquid crystal 14 is aligned so as to have a twist angle of about 240 to 270 degrees. That is, the major axis of the liquid crystal molecules is aligned in the direction almost equal to the rubbing direction 11A in the vicinity of the transparent substrate 11, and is aligned in the direction almost equal to the rubbing direction 12A in the vicinity of the transparent substrate 12.
[0023]
In the present embodiment, the orientations of the polarization transmission axes 22S and 23S of the polarizing plates 22 and 23 are set so that the liquid crystal panel 10 has a liquid crystal display mode called a so-called blue negative mode. The blue negative mode is a STN type liquid crystal device having polarizing plates on the front and back sides, and is a configuration in which a display mode (white display on a blue background) that is colored blue when no voltage is applied and becomes colorless when a voltage is applied is obtained. Say. Specifically, the polarization transmission axis 22S of the polarizing plate 22 is rotated about 35 to 55 degrees clockwise with respect to the direction of the major axis of the liquid crystal molecules in the vicinity of the transparent substrate 11 (that is, the rubbing direction 11A). And the polarization transmission axis 23S of the polarizing plate 23 is rotated about 35 to 55 degrees counterclockwise with respect to the orientation of the major axis of the liquid crystal molecules in the vicinity of the transparent substrate 12 (that is, the rubbing direction 12A). Set to.
[0024]
In the state described above, the transmitted light formed by the light emitted from the light source 21 passing through the polarizing plate 22, the liquid crystal panel 10, and the polarizing plate 23 is photographed by the CCD camera 24 to form a predetermined color image. The color image at this time is color tone distribution information including color tone data having a predetermined color tone detected for each pixel of the CCD and including distribution information of the color tone data along the panel surface of the liquid crystal panel 10. The color tone of each pixel in this color image can be expressed, for example, in the XYZ color system of CIE (International Lighting Commission). Here, X, Y, and Z are tristimulus values of color. In order to display colors in the XYZ color system, chromaticity coordinates x and y and color stimulus value Y are used. Here, x = X / (X + Y + Z) and y = Y / (X + Y + Z).
[0025]
FIG. 3 is a graph showing the relationship between the chromaticity coordinate x and the cell thickness in the liquid crystal panel 10 of the present embodiment. In this embodiment, the reference cell thickness (cell thickness at the center in the manufacturing process or a desired cell thickness designed in advance) is 5.6 μm, and the reference value of retardation is 0.78. In general, only the chromaticity coordinate x is extracted from the coordinate values x and y representing the chromaticity. As shown in FIG. 3, the chromaticity coordinate x is in the range of 5.4 to 5.8 μm of the liquid crystal panel 10 (that is, It can be seen that the cell thickness is approximately linear with respect to the reference cell thickness (in the range of about plus or minus 5%). That is, the chromaticity coordinate x corresponds to the cell thickness of the liquid crystal panel 10 in a one-to-one relationship within the above range, and changes with a constant inclination with respect to the change in cell thickness. Although the absolute value of the cell thickness range is slightly different depending on the composition of the liquid crystal 14, in general, in an STN type liquid crystal panel, there is a region having linearity with respect to the cell thickness d at the chromaticity coordinate x in the vicinity of the numerical value.
[0026]
In general, the cell thickness correlation data (the chromaticity coordinate x in the case of the present embodiment) having a region having linearity with respect to the cell thickness d suitable for the liquid crystal panel 10 to be measured has the linearity. It is set appropriately considering the range of the area. The range of the cell thickness correlation data and the region having the linearity as described above varies depending on the liquid crystal composition of the liquid crystal 14 of the liquid crystal panel 10, the reference cell thickness of the liquid crystal panel 10, or the designed cell thickness. It is.
[0027]
The color tone data (for example, RGB values by the RGB color system) taken by the CCD camera 24 can be observed on the monitor 27 as a normal color image 30A as shown in FIG. In the present embodiment, the program is converted into the XYZ color system by the program of the computer device 26, and the chromaticity coordinates x are obtained from this. As is well known, the XYZ color system is represented by linear conversion of the three color stimulus values of RGB in the RGB color system, so that a conversion process for obtaining the chromaticity coordinate x is performed by a simple calculation. be able to.
[0028]
Using the chromaticity coordinates x obtained in this way, a reconstructed image 30B showing the data distribution of only the chromaticity coordinates x is formed as shown in FIG. Since the reconstructed image 30B is configured only by the chromaticity coordinates x having linearity with respect to the cell thickness in the present embodiment, the cell thickness of the liquid crystal panel 10 is more accurately shown, and the size of the cell thickness is accurately determined. It can be formed as a reflected display. In the image display of the reconstructed image 30B, the chromaticity coordinates x are usually quantized at a predetermined interval, areas belonging to the same gradation are shown in the same display form, and areas belonging to different gradations are shown in different display forms. It is constructed in this way. As these display modes, a mode in which a plurality of hues, shades (lightness), patterns, and the like can be visually distinguished from each other can be considered. Then, in order to indicate which cell thickness corresponds to the area indicated in each display mode, a display explanation unit 30C indicating a combination of each gray level and the corresponding display mode (for example, gray scale display by hue) When it is performed, a color chart or a color bar) is preferably displayed on the screen of the monitor 27. In this case, it is desirable to clearly indicate the reference cell thickness of the liquid crystal panel 10 in the display explanation part 30C.
[0029]
The reference cell thickness in the manufacturing process is set as a reference value of the chromaticity coordinate x corresponding to the reference value of the retardation Δn · d including the refractive index anisotropy Δn of the liquid crystal 14 commonly used for the liquid crystal panel 10. Is preferred. In the case of actually manufacturing a liquid crystal panel, it is sufficient to grasp the retardation value corresponding to the reference value of the chromaticity coordinate x with reference to the chromaticity coordinate x of the liquid crystal panel showing a preferable display performance. This is because the optical characteristics (display mode) of the liquid crystal panel are determined by the retardation value. Since the liquid crystal 14 is common, if the retardation value can be managed, the cell thickness can be managed. On the other hand, a large measurement error is inevitable for direct measurement of cell thickness and direct measurement of refractive index anisotropy, and an extremely accurate standard for cell thickness measurement as in this embodiment. It is inappropriate and meaningless as a method for obtaining a value.
[0030]
In the above embodiment, in the reconstructed image 30B, the chromaticity coordinates x representing the size of the cell thickness are quantized and displayed, but the chromaticity coordinates x themselves are continuously (analogously) hue. The image may be displayed after being converted into various display modes such as shading. Also in this case, it is preferable to provide an appropriate display explanation unit 30C so that the value of the chromaticity coordinate x can be known to some extent from the displayed chromaticity coordinate x. In any case, since the displayed chromaticity coordinate x corresponds to the cell thickness of the liquid crystal panel 10, it is possible to easily know the size of the cell thickness and the size of the difference with respect to the reference cell thickness.
[0031]
As described above, in the present embodiment, cell thickness correlation data having linearity with respect to the cell thickness of the liquid crystal panel 10 is output as a distribution along the panel surface. The cell thickness distribution can be easily known, and the size of the cell thickness or the difference between the cell thickness and the reference value can be accurately known.
[0032]
Note that the cell thickness measuring method and apparatus of the present invention are not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention.
[0033]
For example, in the above embodiment, the chromaticity coordinate x is used as the cell thickness correlation data, but the cell thickness correlation data is not necessarily limited to the chromaticity coordinate x. The cell thickness correlation data having a one-to-one correlation with the cell thickness and sufficient linearity is the type of liquid crystal used in the liquid crystal panel 10 (for example, the composition, twist angle, refractive index anisotropy value of the liquid crystal). Etc.), depending on the value of the reference cell thickness, the direction of the polarization transmission axis of the polarizer or analyzer, the range of measurement values required for cell thickness measurement, etc. It should be set.
[0034]
Further, in the above embodiment, the cell thickness correlation data is displayed as an image. However, the present invention is not limited to such display, and the cell thickness correlation data is output in a state of being collected in a data table, various statistical values, and the like. You may comprise.
[0035]
【The invention's effect】
As described above, according to the present invention, a color image is obtained by taking in light sequentially passing through a polarizer, a liquid crystal panel, and an analyzer, and color tone data of the color image is converted into cell thickness correlation data. By obtaining the distribution of the cell thickness correlation data along the panel surface, the distribution of the cell thickness along the panel surface can be accurately grasped, and the magnitude relationship of the actual cell thickness difference with respect to the reference value of the cell thickness Can also be easily grasped.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a state of measurement in an embodiment of a cell thickness measuring method and apparatus for a liquid crystal panel according to the present invention.
FIG. 2 is an orientation explanatory diagram showing the orientation of the transmission change axis of the polarizing plate in the same embodiment.
FIG. 3 is a graph showing the relationship (linearity) between chromaticity coordinates x and cell thickness in the same embodiment.
FIG. 4 is an explanatory diagram showing a color image (RGB image) output from an imaging unit and a reconstructed image composed of chromaticity coordinates x in the embodiment.
FIG. 5 is a schematic configuration diagram showing a state of cell thickness measurement of a conventional liquid crystal panel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Liquid crystal panel 11, 12 Transparent substrate 11b, 12b Alignment film | membrane 13 Sealing material 14 Liquid crystal 21 Light source 22 Polarizing plate (polarizer)
23 Polarizing plate (analyzer)
24 CCD camera (imaging means)
26 Computer device (data processing means)
27 Monitor (output means)

Claims (5)

A polarizer and an analyzer are arranged on both the front and back sides of the liquid crystal panel, respectively, and the polarizer and the analyzer are set in a predetermined orientation corresponding to the liquid crystal alignment state of the polarizer and the analyzer, and the polarizer, The light that sequentially passes through the liquid crystal panel and the analyzer is taken in, a color image including a distribution of color tone data along the panel surface of the liquid crystal panel is obtained, and the color tone data includes a cell thickness in the liquid crystal panel. A method for measuring a cell thickness of a liquid crystal panel, wherein the cell thickness correlation data is converted into cell thickness correlation data having linearity with respect to the cell thickness within a predetermined cell thickness range, and a distribution of the cell thickness correlation data along the panel surface is obtained. . 2. The liquid crystal panel according to claim 1, wherein the liquid crystal panel is an STN type liquid crystal panel, and an orientation of the transmission polarization axis of the polarizer and the analyzer is set so as to be in a blue negative mode by a combination with the liquid crystal panel, A method for measuring a cell thickness of a liquid crystal panel, wherein an x value of a color coordinate is obtained from the color tone data as the cell thickness correlation data. Polarizers and analyzers arranged on both front and back sides of the liquid crystal panel arrangement unit, a light source arranged in front of the polarizer, and the liquid crystal arranged in front of the analyzer and for transmitted light emitted from the light source An imaging means for outputting a color image including a distribution of color tone data along a panel surface of the panel, and a cell having linearity with respect to the cell thickness within a predetermined cell thickness range including the cell thickness in the liquid crystal panel. An apparatus for measuring a cell thickness of a liquid crystal panel, comprising: data processing means for converting into thickness correlation data. 4. The liquid crystal panel according to claim 3, wherein the liquid crystal panel is an STN type liquid crystal panel, and an orientation of the transmission polarization axis of the polarizer and the analyzer is set to be in a blue negative mode by a combination with the liquid crystal panel, An apparatus for measuring a cell thickness of a liquid crystal panel, wherein the data processing means obtains an x value of a color coordinate as the cell thickness correlation data from the color tone data. 5. A cell thickness measuring apparatus for a liquid crystal panel according to claim 3, further comprising output means for outputting a distribution of the cell thickness correlation data along the panel surface.

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