JP2009198354A - Inspection device and inspection method of electrooptical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a gap of a liquid crystal panel in a vertical orientation system with high accuracy by a hue system. <P>SOLUTION: An inspection device is equipped with: a light source 21; the first polarizing plate 22 for polarizing light from the light source; the second polarizing plate 25 arranged on an outgoing optical path of the liquid crystal panel, in the vertical orientation system entered by polarized light from the first polarizing plate; at least one phase difference plate 23, 24 arranged on the outgoing optical path of the liquid crystal panel between the liquid crystal panel and the second polarizing plate; a photodetection part 26 for detecting the light transmitted through the second polarizing plate; and a gap detection part 27 for detecting a gap of the liquid crystal panel by the hue of light detected by the detection part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inspection apparatus and an inspection method for an electro-optical device suitable for gap inspection of an electro-optical device.

  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 pair of transparent substrates, injecting liquid crystal therebetween and sealing with a sealing material. Further, for example, in a TN type or STN type liquid crystal panel, polarizing plates serving as a polarizer and an analyzer are arranged on the surfaces of two transparent substrates, respectively.

  In the above manufacturing process, the conditions of the manufacturing process are measured by measuring the gap (cell thickness) of the formed liquid crystal panel (the gap between two substrates or the thickness of the liquid crystal layer injected into this gap). The settings may be modified as appropriate. Variations in the gap of the liquid crystal panel directly affect the display performance of the liquid crystal device, so it must be managed with extreme strictness. Because there is.

  Therefore, a measuring device that measures the gap of the liquid crystal panel is employed. Some measuring devices of this type employ a hue method. In the hue type measuring apparatus, a polarizing plate that serves as a polarizer and a polarizing plate that serves as an analyzer are arranged on both sides of the liquid crystal panel. A light source is disposed in front of one polarizing plate, and a chromaticity meter is disposed in front of the other polarizing plate.

  In such a measuring apparatus, the polarization transmission axes of the two polarizing plates are set so as to be in a predetermined direction with respect to the rubbing direction of the alignment film of the liquid crystal panel. In this state, the light emitted from the light source passes through one polarizing plate to become linearly polarized light, passes through the liquid crystal panel and then passes through the other polarizing plate, and then the hue is detected by the chromaticity meter.

  At this time, the linearly polarized light incident on the liquid crystal panel is modulated by the liquid crystal. The degree of modulation of liquid crystal with respect to linearly polarized light (transmittance of linearly polarized light) is a retardation expressed by Δn · d, where Δn (= ne−no) is the refractive index anisotropy of the liquid crystal and d is the thickness of the liquid crystal layer. It changes according to the value of. Further, the transmittance of the linearly polarized liquid crystal layer has a wavelength dependency, and the relationship between the transmittance and retardation changes for each wavelength component. That is, a hue based on the transmittance of each wavelength component appears for a predetermined retardation value, and another hue appears for other predetermined retardation values. The retardation is proportional to the thickness d of the liquid crystal layer, the hue changes according to the change in the gap of the liquid crystal panel, and a pattern due to the change in the hue is observed. The chromaticity meter detects such a hue. Thereby, the thickness of the liquid crystal layer, that is, the gap of the liquid crystal panel is detected.

For example, using the optical characteristics as described above, a reference hue with respect to a reference gap is obtained in advance, and the reference value of the cell thickness is determined depending on the degree of deviation of the hue detected by the chromaticity meter from the reference hue. The degree of deviation can be determined. Further, the gap unevenness can be determined by the hue change pattern.
JP 2006-171065 A

  However, the above-described cell thickness measurement method can be applied only to a gap inspection of a horizontal alignment type liquid crystal panel. In a vertically aligned liquid crystal panel using negative dielectric anisotropy, the difference in retardation for each wavelength is small. For this reason, it is extremely difficult to observe the difference in gap thickness as a hue.

  An object of the present invention is to provide an inspection apparatus and an inspection method for an electro-optical device that can perform gap inspection on a vertical alignment type liquid crystal device by a hue method.

  An inspection apparatus for an electro-optical device according to the present invention includes: a light source; a first polarizing plate that polarizes light from the light source; and a vertically aligned liquid crystal panel that receives polarized light from the first polarizing plate. A second polarizing plate disposed on the outgoing optical path, at least one retardation plate disposed on the outgoing optical path of the liquid crystal panel between the liquid crystal panel and the second polarizing plate, and the second And a gap detection unit that detects a gap of the liquid crystal panel based on a hue of light detected by the detection unit.

  According to such a configuration, the light transmitted through the second polarizing plate has a hue corresponding to the gap. The retardation of the liquid crystal panel can be strengthened by at least one retardation plate, and the hue change of the transmitted light of the second polarizing plate with respect to the change of the gap of the liquid crystal panel can be increased. Thereby, the gap detection part can obtain | require the gap of a liquid crystal panel with high precision from the detection result of a photon detection part.

  The at least one retardation plate is a λ / 2 retardation plate and a λ / 4 retardation plate.

  According to such a configuration, the retardation of the liquid crystal panel can be sufficiently increased, and the gap of the liquid crystal panel can be obtained with high accuracy.

  An inspection method for an electro-optical device according to the present invention includes a procedure for applying an on-voltage to all pixels of a vertical alignment type liquid crystal panel, a procedure for causing light to enter the liquid crystal panel via a first polarizing plate, A procedure for taking light emitted from the liquid crystal panel through at least one phase difference plate and a second polarizing plate, and a step for obtaining a hue of light from the second polarizing plate and detecting a gap of the liquid crystal panel It was characterized by comprising.

  According to such a configuration, an on-voltage is applied to all the pixels of the liquid crystal panel, and light is incident on the liquid crystal panel via the first polarizing plate. The transmitted light of the liquid crystal panel changes in transmittance for each wavelength due to the influence of retardation, and becomes a hue corresponding to the retardation. At least one retardation plate enhances the retardation of the liquid crystal panel. The hue change of the light from the second polarizing plate with respect to the change of the gap of the liquid crystal panel becomes sufficiently large, and the gap can be obtained with high accuracy based on the hue change.

  The at least one retardation plate is a λ / 2 retardation plate and a λ / 4 retardation plate.

  According to such a configuration, the retardation of the liquid crystal panel can be sufficiently increased, and the gap of the liquid crystal panel can be obtained with high accuracy.

  Further, the at least one retardation plate is installed at an angle that strengthens the retardation of the liquid crystal panel.

  According to such a configuration, the retardation of the liquid crystal panel can be sufficiently increased, and the gap of the liquid crystal panel can be obtained with high accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an inspection apparatus for an electro-optical device according to an embodiment of the present invention.

  The liquid crystal panel 10 is configured by arranging a pair of transparent substrates 11 and 12 to face each other with a liquid crystal layer 15 interposed therebetween. The transparent substrates 11 and 12 are bonded by a sealing material 14 in a state where liquid crystal is sealed. A pixel electrode 11 a and an alignment film 11 b are formed on the surface of the transparent substrate 11, while a common electrode 12 a and an alignment film 12 b are formed on the surface of the transparent substrate 12.

  A polarizing plate 22 that is a polarizer and a polarizing plate 25 that is an analyzer are disposed on both front and back sides of the liquid crystal panel 10, and a light source 21 is disposed outside the polarizing plate 22. An incident light detection unit 26 is disposed outside the polarizing plate 25. The polarizing axes of the polarizing plates 22 and 25 are orthogonal to each other. The liquid crystal panel 10 is a vertical alignment panel, and a liquid crystal material having negative dielectric anisotropy is used for the liquid crystal layer 15.

  In the present embodiment, phase difference plates 23 and 24 are provided between the transparent substrate 12 and the polarizing plate 25. For example, one of the phase difference plates 23 and 24 is a λ / 2 phase difference plate and the other is a λ / 4 phase difference plate. The λ / 2 phase difference plate and the λ / 4 phase difference plate may be interchanged. In the present embodiment, as will be described later, the retardation plates 23 and 24 define the direction of the slow axis with respect to the polarization axis of the polarizing plate 22 so as to increase the retardation of the incident light. .

  Illumination light from the light source 21 passes through the polarizing plate 22, the liquid crystal panel 10, the phase difference plates 23 and 24, and the polarizing plate 25 and enters the incident light detection unit 26. The incident light detection unit 26 is constituted by, for example, a CCD camera or the like.

  In the present embodiment, at the time of gap inspection, all the pixels of the liquid crystal panel 10 are driven with an on-voltage, and the incident light detection unit 26 detects the incident light indicated by the one-dot chain line in FIG. . The incident light detection unit 26 detects incident light passing through the liquid crystal panel 10 and outputs a detection result. For example, the incident light detection unit 26 acquires a color image based on the incident light and outputs an image signal.

  The output of the incident light detection unit 26 is given to the control unit 27. The control unit 27 is configured by a microprocessor unit including, for example, a CPU (Central Processing Unit), ROM, RAM, information storage means (memory) such as a hard disk, an input / output circuit, and the like. The control unit 27 detects a gap (cell thickness) of the liquid crystal panel 10 by arithmetic processing on the input image signal. For example, the control unit 27 converts the input image signal into a HUE value representing a hue, and detects the gap of the liquid crystal panel 10 and the thickness distribution of the gap based on the HUE value.

  The control unit 27 gives the detection result of the gap to the display unit 28 for display. For example, the control unit 27 may display the hue based on the obtained HUE value as it is, or may display the HUE value itself. Furthermore, the control unit 27 may provide the display unit 28 with the output of the incident light detection unit 26 as it is for display.

  In the present embodiment, two retardation plates, that is, retardation plates 23 and 24 that are λ / 2 or λ / 4 retardation plates are arranged between the liquid crystal panel 10 and the polarizing plate 25. Although shown, it is not always necessary to arrange two retardation plates, and only one retardation plate or three or more retardation plates may be arranged.

  In the embodiment configured as described above, an on-voltage is applied to all the pixels of the liquid crystal panel 10 at the time of inspection. Light from the light source 21 is converted into linearly polarized light having a predetermined polarization axis by the polarizing plate 22 and enters the liquid crystal panel 10. The linearly polarized light incident on the liquid crystal layer 15 is described by the combination of the Ne direction component and the No direction component. The relationship between the Ne direction component and the No direction component and the phase difference δ is given by the following equation (1) using retardation (d · Δn).

δ = 2πd · Δn / λ (1)
From this equation (1), it can be seen that when the phase difference δ is π, the plane of polarization of incident light rotates 90 degrees. Since the orthogonal axes of the polarizing plates 22 and 25 are orthogonal, the transmittance is maximum when δ = π, and the retardation (d · Δn) is λ / 2. The relationship between transmittance and retardation changes for each wavelength component of linearly polarized light. If δ is not π, the incident light repeats linearly polarized light and elliptically polarized light.

  The transmitted light from the liquid crystal panel 10 enters the incident light detection unit 26 via the phase difference plates 23 and 24 and the polarizing plate 25. The incident light detection unit 26 detects the incident light and outputs the detection result to the control unit 27. The light incident on the incident light detection unit 26 has a hue based on the transmittance of each wavelength component that has passed through the liquid crystal panel 10, and this hue depends on the retardation value, that is, the thickness d of the liquid crystal layer 15. It will be. The control unit 27 obtains the gap of the liquid crystal panel 10 based on the detection result of the incident light detection unit 26. The control unit 27 gives the obtained gap to the display unit 28 for display.

  In this case, the vertical alignment type liquid crystal panel 10 has a small retardation value, and it is difficult to obtain a hue value corresponding to the change of the gap with high accuracy only from the light emitted from the liquid crystal panel 10.

  Therefore, in the present embodiment, the phase difference plates 23 and 24 are arranged to increase the retardation equivalently, thereby making it possible to obtain the hue value according to the change of the gap with high accuracy.

  Next, the retardation plate disposed between the liquid crystal panel 10 and the polarizing plate 25 will be described.

  FIG. 2 is a graph showing the transmittance of each wavelength component for each retardation, with the horizontal axis representing wavelength and the vertical axis representing transmitted light intensity. FIG. 2 shows the transmittance when an appropriate retardation plate is inserted in place of the retardation plates 23 and 24 in the apparatus of FIG. Waveforms T <b> 1 to T <b> 3 in FIG. 2 indicate characteristics when the liquid crystal panel 10 includes three liquid crystal panels having different gap thicknesses and retardations of 293, 322, and 351, respectively. Waveforms T1-145 to T3-145 in FIG. 2 respectively show the characteristics when the phase difference plate is inserted at an angle of 145 ° with respect to the polarization axis of the polarizing plate 22 in the liquid crystal panel indicated by the waveforms T1 to T3. The retardations are 438, 467, 496, respectively. Waveforms T1-290 to T3-290 show the characteristics when the phase difference plate is inserted at an angle of 290 ° with respect to the polarization axis of the polarizing plate 22 for the liquid crystal panels shown by the waveforms T1 to T3, respectively. The retardation is 583,612,641.

  In this way, different values of retardation can be obtained by inserting the phase difference plate. In FIG. 2, it can be seen that the spectrum of the transmitted light changes by changing the retardation by inserting the retardation plate.

  FIG. 3 is a graph showing the relationship between retardation and hue value, with retardation on the horizontal axis and hue value on the vertical axis. Characteristic A in FIG. 3 shows characteristics when the phase difference plates 23 and 24 are omitted in the apparatus of FIG. 1, and characteristic B is a predetermined phase difference plate arranged in place of the phase difference plates 23 and 24 in the apparatus of FIG. The characteristics are shown.

  Characteristic A in FIG. 3 shows a change in hue when the liquid crystal panel 10 having a retardation of 320 nm is employed and the cell thickness is changed by ± 0.2 μm. When the retardation plates 23 and 24 are omitted, the obtained hue change is about 30 with respect to the cell thickness ± 2 μm. On the other hand, when the retardation plate is arranged so that the retardation is 520 nm, the characteristic when the cell thickness is changed is the characteristic B. In the case of the characteristic B, the obtained hue change is about 70 with respect to the change of the cell thickness ± 2 μm.

  In this way, by arranging the retardation plate so that the retardation is 520 nm, the incident light detection unit 26 detects incident light having a sufficient hue change with respect to a cell thickness change of ± 0.2 μm. You can see that

  Therefore, a suitable retardation plate is disposed between the liquid crystal panel 10 and the polarizing plate 25 so that the change of the hue value with respect to the change of the cell thickness is sufficiently increased by the incident light detected by the incident light detection unit 26. Find the retardation plate.

  Table 1 below shows the relationship between the phase difference plate disposed between the liquid crystal panel 10 and the polarizing plate 25 and the HUE value.

この表１は、既知のセル厚の３つの液晶パネルに対して、位相差板２３，２４に代えて、位相差が０、λ／４、λ／２及び３λ／４の位相差板を配置した場合におけるＨＵＥ値、レンジ及び分解能を夫々求めたものである。なお、分解能は、セル厚と得られたＨＵＥ値との比を示す。 [Table 1]

In Table 1, phase difference plates having phase differences of 0, λ / 4, λ / 2, and 3λ / 4 are arranged in place of the phase difference plates 23 and 24 for three liquid crystal panels having known cell thicknesses. In this case, the HUE value, the range, and the resolution are obtained. The resolution indicates the ratio between the cell thickness and the obtained HUE value.

  As shown in Table 1, when the phase difference is 0, that is, when the phase difference plate is not disposed, when the cell thickness changes ± 0.2 μm around 2.5 μm, the change in the HUE value is ± Only 2 can be obtained. On the other hand, for example, when a phase difference plate having a phase difference of λ / 2 is arranged, the HUE value is +7 to −17 when the change in cell thickness is ± 0.2 μm centered on 2.5 μm. Has also changed. In this case, the resolution is 0.02.

  In this manner, by arranging a retardation plate having a retardation of λ / 2 or 3λ / 4 between the liquid crystal panel 10 and the polarizing plate 25, the retardation is increased, and the hue difference with respect to the change in cell thickness is reduced. It can be seen that the gap can be reliably detected from the hue of the observation image by sufficiently increasing the size.

  By the way, in order to increase the retardation by the liquid crystal panel 10 equivalently by using the retardation plates 23 and 24, the direction of the retardation axis of the retardation plates 23 and 24, and the polarizing plates 22 and 25, so as to increase the retardation. It is necessary to define the relationship between the polarization axis and the major axis direction of the liquid crystal molecules of the liquid crystal layer 15.

  4 is a chart showing the relationship between the arrangement angle of the phase difference plates 23 and 24 with respect to the polarization axis of the polarizing plate 22 and the obtained HUE value in the apparatus of FIG. FIG. 4 shows only the condition of left circularly polarized light (L shift), but the condition of right circularly polarized light (R shift) is obtained by rotating the λ / 2 phase difference plate by 90 degrees. Omitted.

  In the example of FIG. 4, the phase difference plate with a phase difference of λ / 2 is fixed and the phase difference plate with a phase difference of λ / 4 is rotated to obtain the HEU value, but the phase difference is λ / 4. Even when the phase difference plate having the phase difference of λ / 2 is rotated in a state where the phase difference plate is fixed, an appropriate angle can be obtained as the arrangement angle of the phase difference plates 23 and 24.

  In the example of FIG. 4, the retardation plate 23 having a retardation of λ / 2 with respect to the polarization axis of the polarizing plate 22 is set to 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, 90 °, 120 °. The HUE value when the phase difference plate 24 having a phase difference of λ / 4 is rotated while being rotated in the range of 0 to 180 degrees for each λ / 2 phase difference plate is arranged at an angle of 150 °. Show.

  FIG. 4 shows the HUE value and range (difference) when three liquid crystal panels having known cell thicknesses with cell thicknesses of 20 μm, 23 μm, and 27 μm are arranged as the liquid crystal panel 10 of FIG.

  In the example of FIG. 4, for example, when the arrangement angle of the λ / 2 phase difference plate is 0 °, the HUE value is relatively sufficient when the arrangement angle of the λ / 4 phase difference plate is 90 °. You can see that it has a range. Similarly, when the arrangement angle of the λ / 2 phase difference plate is 30 °, the arrangement angle of the λ / 4 phase difference plate is 105 ° and 120 °, and when the arrangement angle of the λ / 2 phase difference plate is 45 °, λ When the arrangement angle of the / 4 retardation plate is 105 °, the arrangement angle of the λ / 2 retardation plate is 75 °, and when the arrangement angle of the λ / 4 retardation plate is 150 °, the λ / 2 retardation plate It is shown that when the arrangement angle is 90 °, good characteristics can be obtained, for example, when the arrangement angle of the λ / 4 retardation plate is 0 °.

  For this reason, in the present embodiment, for left circular polarization, for example, the arrangement angle of the λ / 2 phase difference plate is set to 20 ° with respect to the polarization axis of the polarizing plate 22, and λ / 4 The arrangement angle of the retardation plate is set to 120 ° with respect to the polarization axis of the polarizing plate 22. In the case of right circular polarization, for example, the arrangement angle of the λ / 2 phase difference plate is set to 110 ° with respect to the polarization axis of the polarizing plate 22, and the arrangement angle of the λ / 4 phase difference plate is set to that of the polarizing plate 22. It is set to 120 ° with respect to the polarization axis.

  Thus, the light input to the incident light detection unit 26 has a sufficiently large change in the HUE value with respect to the change in the cell thickness. Thereby, the gap can be detected with high accuracy.

  As described above, in this embodiment, a vertical alignment type liquid crystal panel is energized so that all pixels are turned on, and a 3λ / 4 phase difference plate is interposed between the liquid crystal panel and the polarizing plate. Insert. Thereby, a sufficient hue change can be obtained with respect to the gap change, and the gap and the gap unevenness can be detected easily and accurately by the hue method.

  In the above embodiment, an example in which two retardation plates, a λ / 2 retardation plate and a λ / 4 retardation plate, are described, but only a λ / 2 retardation plate is inserted. Alternatively, only a λ / 4 phase difference plate may be inserted. Even in these cases, a certain degree of effect can be obtained.

1 is a schematic configuration diagram of an inspection apparatus for an electro-optical device according to an embodiment of the present invention. The graph which shows the transmittance | permeability for every retardation of each wavelength component, taking a wavelength on a horizontal axis and taking transmitted light intensity on a vertical axis | shaft. A graph showing the relationship between retardation and hue value, with retardation on the horizontal axis and hue value on the vertical axis. FIG. 2 is a chart showing a relationship between an arrangement angle of the phase difference plates 23 and 24 with respect to a polarization axis of the polarizing plate 22 and an obtained HUE value in the apparatus of FIG.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 10 ... Liquid crystal panel, 15 ... Liquid crystal layer, 22, 25 ... Polarizing plate, 23, 24 ... Phase difference plate, 26 ... Incident light detection part, 27 ... Control part.

Claims (5)

A light source;
A first polarizing plate that polarizes light from the light source;
A second polarizing plate disposed on an outgoing optical path of a vertically aligned liquid crystal panel on which polarized light from the first polarizing plate is incident;
At least one phase difference plate disposed on an outgoing optical path of the liquid crystal panel between the liquid crystal panel and the second polarizing plate;
A light detection unit for detecting light transmitted through the second polarizing plate;
An inspection apparatus for an electro-optical device, comprising: a gap detection unit that detects a gap of the liquid crystal panel based on a hue of light detected by the detection unit. The at least one retardation plate is
The electro-optical device inspection apparatus according to claim 1, wherein the inspection apparatus is a λ / 2 retardation plate and a λ / 4 retardation plate. A procedure for applying an on-voltage to all the pixels of the vertical alignment type liquid crystal panel;
A procedure for making light incident on the liquid crystal panel via a first polarizing plate;
A procedure for capturing the light emitted from the liquid crystal panel via at least one retardation plate and a second polarizing plate;
An inspection method for an electro-optical device, comprising: obtaining a hue of light from the second polarizing plate and detecting a gap of the liquid crystal panel. The at least one retardation plate is
The electro-optical device inspection method according to claim 3, wherein the inspection method is a λ / 2 retardation plate and a λ / 4 retardation plate. The at least one retardation plate is
4. The inspection method for an electro-optical device according to claim 3, wherein the inspection method is installed at an angle that strengthens the retardation of the liquid crystal panel.

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