JP2000321546A - Liquid crystal display device, device and method to measure cell thickness of the device, and phase difference plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device, a measuring device for the cell thickness, a method for the measurement, and a phase difference plate by which the retardation (dLC×Δn) of the liquid crystal layer only in which liquid crystal molecules are present can be obtained and the cell thickness can be obtained. SOLUTION: The measuring device for cell thickness is used to measure the thickness of a liquid crystal cell 5 of a liquid crystal display device equipped with a liquid crystal layer having liquid crystal molecules in the liquid crystal region aligned almost perpendicular when no voltage is applied and a pair of substrates holding the liquid crystal layer between. The liquid crystal cell bas a pair of uniaxial phase difference plates having retardation in the plane attached to both outer faces of the cell with the slow phase axes aligned in the same direction. The measuring device is equipped with a stage 1 to mount the liquid crystal cell, a light source 2, a photodetector 3, and a rotating device 4. The light source 2 has a polarizer 23 and emits polarized light at 44 deg. to 46 deg. azimuth direction to the direction of the slow phase axes of the phase difference plates. The photodetector 3 has an analyzer 31 disposed in a cross-Nicol state with the polarizer for the polarized light and detects the quantity of transmitted light of the polarized light. The rotating device 4 changes the incident angle in the polar angle direction of the polarized light from the direction of the phase difference plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, a cell thickness measuring device and a measuring method thereof, and a retardation plate, and more particularly to a liquid crystal display capable of accurately measuring a gap, a cell thickness measuring method and a liquid crystal display. The present invention relates to a measuring method and a retardation plate.

[0002]

2. Description of the Related Art Various display devices using a liquid crystal material, for example, an active drive type TFT display device, a PALC (plasma addressed liquid crystal) display device, and a duty drive type STN display device are known. In particular, a PALC display device is a display device using a switching element using plasma discharge, and its application to an ultra-large display has received attention. The PALC liquid crystal display device is low in cost because it does not include a semiconductor process such as a TFT, and has attracted attention for its potential as a large liquid crystal display device with low power consumption. The above-described liquid crystal display device has features such as light weight, thin shape, and low power consumption.
As a key device in the coming multimedia society, application development has been made in various OA, AV equipment fields and the like. In this liquid crystal display device, a TN display mode in which nematic liquid crystal molecules are twisted by about 90 degrees near the two electrode substrates or an STN display mode in which liquid crystal molecules are twisted by 180 degrees or more are frequently used. Also, Japanese Patent Application Laid-Open No. 10-18633
No. 0 discloses a liquid crystal display device having a wide viewing angle characteristic and obtaining good display quality. In the above-mentioned liquid crystal display device, the cell thickness is closely related to the display color, the response speed, the stability of the alignment, and the like, and a more accurate measurement method is required. Further, information on the accurate value of the cell thickness is very important in designing and evaluating a liquid crystal display device. Conventionally, in the state of an empty cell in which no liquid crystal material is injected, the retardation of the liquid crystal layer is measured by using the measurement method using the optical interference method, and in the cell into which the liquid crystal is injected, using the crystal rotation method. Thus, many cell thickness measuring devices for determining the cell gap are commercially available.

However, in the measurement of the empty cell thickness by the optical interference method, since the liquid crystal cell has an ITO (transparent electrode), an alignment film, a color filter, and the like, the interference is complicated and the accuracy is lacking. There was a problem that it was difficult to determine the value. Furthermore, when liquid crystal is sealed in the liquid crystal cell, the difference in the refractive index between the liquid crystal layer and the substrate is small, so that interface reflection on the substrate hardly occurs and interference fringes do not appear. There was a problem that could not be done in principle. On the other hand, in the crystal rotation method, the dielectric constant anisotropy of a normally white liquid crystal can be measured only in a positive Np liquid crystal cell, and cannot be used in a negative Nn liquid crystal cell.

Japanese Patent Application Laid-Open No. 3-115804 discloses that the rubbing direction of a lower transparent insulating substrate of a cell thickness measuring device and the rubbing direction of an upper transparent insulating substrate of a measurement symmetric liquid crystal panel are overlapped so as to be orthogonal to each other. Further, it has been proposed to provide a small and lightweight measuring instrument by disposing two polarizing plates whose absorption axis directions are orthogonal to each other on both sides of these panels. Also, in Japanese Patent Application Laid-Open No. 4-80641, by comparing the spectrum transmitted when a liquid crystal cell is arranged between two polarizers by changing the angle of the polarizer by 90 degrees, the optical phase difference of the liquid crystal cell and It is disclosed that the cell thickness and the liquid crystal birefringence can be accurately obtained.
Japanese Patent Application Laid-Open No. 4-184207 proposes that a simple and accurate measurement can be performed by detecting the amount of transmitted light while changing the applied voltage and obtaining a voltage at which the amount of transmitted light is minimized. ing. Japanese Patent Application Laid-Open No. Hei 5-71924 discloses that Np having a positive dielectric anisotropy is positive.
It is disclosed that a liquid crystal cell into which liquid crystal is injected is measured while applying a high voltage of 50 times or more of a threshold voltage or a high magnetic field of 50 times or more of a magnetic field. As described above, various methods have been proposed for measuring the cell thickness.

However, the optical interferometry, which can measure only empty cells, causes a phase difference in the direction parallel to the substrate when polarized light is incident on the substrate of a horizontally aligned Np liquid crystal cell when no voltage is applied. In the crystal rotation method for measuring the incident angle dependence of the transmittance and the other measurement methods described above, a liquid crystal cell with a color filter is vertically aligned when no voltage is applied, and the dielectric anisotropy of the liquid crystal is negative Nn. It has not been possible to easily determine the retardation of a liquid crystal cell by simply measuring the incident angle dependence of the amount of transmitted light without applying an electric or magnetic field to the cell into which the liquid crystal has been injected. That is, in a state where the liquid crystal molecules are vertically aligned with respect to the substrate, there is no optical phase difference in the in-plane direction of the substrate (isotropic), so that the measurement cannot be performed.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and enables a simple and accurate measurement of the cell thickness without applying a voltage to the liquid crystal cell. Since the glass plates, color filters, transparent electrodes, and alignment films that are members are optically isotropic, the retardation (d _LC · Δn) of only the liquid crystal layer where the liquid crystal molecules exist can be obtained, and the cell thickness can be obtained. Liquid crystal display device,
An object of the present invention is to provide a cell thickness measuring device, a measuring method, and a retardation plate.

[0007]

The present invention provides a liquid crystal display comprising a liquid crystal layer in which liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied, and a pair of substrates sandwiching the liquid crystal layer. In a cell thickness measuring device that measures the thickness of the liquid crystal cell of the device, a liquid crystal cell in which a pair of uniaxial retardation plates having in-plane retardation are attached to both outer surfaces with their slow axes aligned. Having a stage and a polarizer, and
Azimuth angle direction 44 degrees to the slow axis direction of the retardation plate
A light source that emits polarized light of 46 degrees to the liquid crystal cell, an analyzer and a light receiver that are disposed in crossed Nicols with respect to the polarized light, and that detects the amount of transmitted polarized light. The present invention is a cell thickness measuring device for a liquid crystal display device, comprising: a photodetector; and a rotating device that changes an incident angle of a polarized light in a polar direction from a direction perpendicular to a slow axis direction of the retardation plate.

The present invention is also a liquid crystal cell thickness measuring device for a liquid crystal display device in which the rotating device rotates a light source and a light receiving device of a photodetector in synchronization to change an incident angle in a polar angle direction.

The present invention is a liquid crystal cell thickness measuring device for a liquid crystal display device in which the rotating device rotates a stage to change an incident angle in a polar angle direction.

Further, the present invention is the cell thickness measuring device for a liquid crystal display device, wherein the light source is a monochromatic laser light source or a light source having an optical coloring filter.

The present invention is also a cell thickness measuring device for a liquid crystal display device, wherein the light source includes a lamp unit having a Y luminosity filter. Regarding the wavelength of the light source, it is preferable to make the wavelength of the light source monochromatic to about 550 nm using a band-pass filter or a monochromatic laser.

Further, the present invention is a cell thickness measuring device of a liquid crystal display device, wherein the stage is provided with a temperature controller and is an XY stage capable of measuring an arbitrary point.

Further, the present invention is a cell thickness measuring device of a liquid crystal display device, wherein the polarizer can be set at an arbitrary angle.

The present invention is also a cell thickness measuring device for a liquid crystal display device, wherein the photodetector has a photodiode and a low noise amplifier.

The present invention is a cell thickness measuring device for a liquid crystal display device in which the photodetector has a display.

Further, the present invention provides a liquid crystal layer having a liquid crystal material having a refractive index difference of Δn, wherein liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied, and the liquid crystal layer is sandwiched. A thickness of a liquid crystal cell of a liquid crystal display device having a pair of substrates to be measured, wherein both outer surfaces of the liquid crystal cell of the liquid crystal display device to be measured have in-plane retardation, and A pair of uniaxial retardation plates having a predetermined thickness are mounted with their slow axes aligned, and then polarized light having an azimuth angle of 44 to 46 degrees with respect to the slow axis direction of the retardation plates. Is incident on the liquid crystal cell while changing the incident angle in the polar angle direction from a direction perpendicular to the slow axis direction of the retardation plate, while being disposed in crossed Nicols with respect to the polarizer of the light source of the polarized light. The amount of transmitted light is detected by a photodetector having a The extinction position angle in the low or extinction state is measured, and the retardation of the liquid crystal cell corresponding to the measured extinction position angle is obtained from the calibration curve of the extinction position angle and the liquid crystal cell retardation at the thickness of the retardation plate. A cell thickness measuring method for a liquid crystal display device in which the cell thickness is calculated using the obtained liquid crystal cell retardation value and the refractive index difference Δn of the liquid crystal material.

The present invention is also a method for measuring the cell thickness of a liquid crystal display device, wherein the calibration curve between the extinction angle and the liquid crystal cell retardation in the thickness of the above retardation plate is obtained by optical calculation.

In the present invention, the calibration curve between the extinction angle and the liquid crystal cell retardation in the thickness of the retardation plate is measured for a liquid crystal display device in which the refractive index difference Δn and the cell thickness are known. This is a method for measuring the cell thickness of the obtained liquid crystal display device.

Further, the present invention relates to a method for measuring a cell thickness of a liquid crystal display device in which a retardation of a mounted uniaxial retardation plate is 10 nm to 50 nm.

The present invention also provides a liquid crystal layer having a liquid crystal material having a negative dielectric anisotropy and in which liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied, and sandwiches the liquid crystal layer. And a pair of substrates having a vertical alignment film, wherein both outer surfaces of the liquid crystal cell have in-plane retardation, and the retardation is 10 nm to 50 nm. This is a liquid crystal display device in which a pair of uniaxial retardation plates are mounted with their slow axis directions aligned.

Further, the present invention relates to a retardation plate used in the cell thickness measuring method of the liquid crystal display device, wherein the retardation plate has in-plane retardation and the retardation is 1%.
The retardation plate has a thickness of 0 nm to 50 nm and is uniaxial.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described. The outline and the like of the liquid crystal display device, the cell thickness measuring device and the measuring method thereof, and the retardation plate of the present invention will be described with reference to FIGS. FIG. 1 is a schematic explanatory view of a cell thickness measuring device of the present invention. FIG. 2 is an explanatory view of a retardation plate used for measuring a cell thickness in the present invention and a polar angle direction. FIG. 3A is an explanatory diagram of the relationship between the extinction position angle and the liquid crystal retardation in the present invention.
(B) is an explanatory view of the relationship between the retardation of the phase difference plate and the cell thickness value error width.

The cell thickness measuring apparatus according to the present invention comprises: a liquid crystal layer in which liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied;
An apparatus for measuring the thickness of a liquid crystal cell of a liquid crystal display device, comprising a pair of substrates sandwiching a liquid crystal layer, wherein a pair of uniaxial retardation plates having in-plane retardation is provided with a slow axis. A stage having a liquid crystal cell mounted on both outer surfaces aligned in the same direction, a polarizer, and a liquid crystal that emits polarized light having an azimuth angle of 44 to 46 degrees with respect to the slow axis direction of the retardation plate. A light source that emits light to the cell, a light detector that has a polarizer and an analyzer and a light receiver that are arranged in crossed Nicols for the polarized light, and that detects a transmitted light amount of the polarized light, and a phase difference plate A rotation device that changes the incident angle of the polarized light in the polar direction from a direction perpendicular to the slow axis direction of the cell thickness measurement device, as shown in FIG. It includes a light detector 3, a rotation device 4, and the like. The stage 1 has a liquid crystal cell 5 to be measured. The light source 2 includes a lamp unit 21, an optical coloring filter 22, a polarizer 23, and the like, and the slow axis of a pair of uniaxial retardation plates 8 attached to both outer surfaces of the liquid crystal cell with their slow axes aligned. Monochromatic polarized light having an azimuthal direction of 44 to 46 degrees with respect to the direction is emitted to the liquid crystal cell 5. The photodetector 3 includes an analyzer 31, a photodetector 32, a photodetector 33, and the like, and detects the amount of transmitted polarized light from the light source 2. The analyzer 31 is disposed in crossed Nicols with the polarizer 21 for polarized light. The rotation device 4 includes a rotation mechanism 4
1. The light source 2 and the light receiver 32 are rotated in synchronization with each other, including a stage unit 42 and an angle operation switch 43. Polarized light is incident from a direction perpendicular to the slow axis direction of the phase difference plate 8 in a polar angle direction. Change the angle. When the incident angle of the polarized light in the polar direction changes from a direction perpendicular to the slow axis direction of the phase difference plate 8, the amount of transmitted light detected by the photodetector 3 decreases and becomes the minimum or extinction state, and the extinction position angle Can be measured. It is also possible to use a rotating device for rotating the stage 1. The light source 2 can be a monochromatic laser light source. In addition, the light source 2 can include a lamp unit having a Y luminosity filter. Stage 1 can be an XY stage that includes a temperature controller and can measure any point. The polarizer 21 can be set at any angle. The light detector 3 can include a photodiode and a low noise amplifier. The light detector 3 can have a display. This cell thickness measuring device has a simple structure and can be used for a liquid crystal cell with a color filter.
It can be measured nondestructively, can be incorporated inline, and can be designed and manufactured at low cost. Since the refractive index difference Δn of the liquid crystal material depends on the temperature, it is preferable to provide a temperature control device (a heater and a cooling unit) for keeping the liquid crystal display device at a constant temperature. The angle of the monochromatic polarized light from the lamp unit is 44 ° with respect to the slow axis direction of the uniaxial retardation plate.
The extinction position is most noticeable at 45 degrees.

According to the cell thickness measuring method of the present invention, the refractive index difference is Δn
A liquid crystal cell of a liquid crystal display device comprising: a liquid crystal layer having a liquid crystal material of the formula (1), and in which liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied, and a pair of substrates sandwiching the liquid crystal layer. A method for measuring the thickness of a liquid crystal cell of a liquid crystal display device to be measured, which has in-plane retardation on both outer surfaces and a pair of uniaxial retardation plates having a predetermined thickness and a retardation thereof. Then, polarized light having an azimuth angle of 44 to 46 degrees with respect to the slow axis direction of the phase difference plate is applied from a direction perpendicular to the slow axis direction of the phase difference plate. The incident light was incident on the liquid crystal cell while changing the angle of incidence in the angular direction, while the amount of transmitted light was measured with a photodetector having an analyzer arranged in a crossed Nicols with respect to the polarizer of the light source of the polarized light. Measure the extinction position angle where the amount of light is minimum or in the extinction state, and The retardation of the liquid crystal cell corresponding to the extinction position angle obtained from the calibration curve of the extinction position angle and the liquid crystal cell retardation at the thickness of the retardation plate, and then the obtained liquid crystal cell retardation value and the refractive index difference of the liquid crystal material. This is a cell thickness measurement method for calculating the cell thickness using Δn. The calibration curve between the extinction angle and the liquid crystal cell retardation at the thickness of the retardation plate can be obtained by optical calculation. Also, it is assumed that the calibration curve of the extinction angle and the liquid crystal cell retardation at the thickness of the retardation plate is obtained by measuring a liquid crystal display device whose refractive index difference Δn and cell thickness are known. be able to. And the retardation of the uniaxial phase difference plate to be attached can be set to 10 nm to 50 nm. As a result, the cell thickness can be inspected in the panel manufacturing process, and the cell thickness control has a large effect on the display characteristics and display quality, which can contribute to the quality control of the liquid crystal display device and the yield factory. .

The liquid crystal display device to be measured in the present invention is:
A liquid crystal layer having a liquid crystal material having a negative dielectric anisotropy and in which liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied, and a liquid crystal layer sandwiching the liquid crystal layer and having a vertical alignment film. And a pair of substrates, wherein both outer surfaces of the liquid crystal cell have in-plane retardation, and the retardation is 10%.
A pair of uniaxial retardation plates having a thickness of 50 nm to 50 nm are mounted with their slow axis directions aligned. Further, the retardation plate used in the measurement in the present invention has in-plane retardation, and the retardation is 10 nm or more.
50 nm and uniaxial. Examples of the uniaxial retardation plate include a plate-like plate and a film-like plate attached to a glass plate.

The liquid crystal display device of the present invention, its cell thickness measuring device, its measuring method, and the retardation plate will be described with respect to the measurement principle and the like. On a liquid crystal panel of a liquid crystal display device to be measured, a uniaxial retardation plate (retardation: 10 nm to 50 nm) having in-plane retardation is arranged on both outer sides with the axial direction aligned. The liquid crystal display device is set on a sample stage, and the monochromatic light emitted from the lamp unit passes through the liquid crystal display device, and the amount of light is detected by the detector and the detector unit.

The analyzer is arranged so as to be crossed with respect to the polarizer. Then, as shown in FIG. 2A, the uniaxial retardation plate 8 has a slow axis direction of 44 to 46 degrees, preferably 45 degrees with respect to the absorption axis directions of the polarizer and the analyzer.
It is attached to both outer surfaces of the liquid crystal cell 5 in such a manner. Therefore, the polarization angle of the monochromatic polarized light from the light source is 44 to 46 degrees with respect to the slow axis direction of the uniaxial retardation plate,
The light is preferably incident at 45 degrees. Further, as shown in FIG. 2A, the monochromatic polarized light from the light source is incident while changing the incident angle in the polar direction from a direction perpendicular to the slow axis direction of the phase difference plate 8. As a result, FIG.
As shown in (b), the uniaxial retardation plates 8 are set on both sides of the liquid crystal cell 5 of the liquid crystal display device, and the change in the light amount according to the change in the polar angle incident angle of the monochromatic polarized light from the lamp unit. Is measured, and the extinction angle at which the obtained light amount or transmittance is minimum or in the extinction state can be detected.

An example of the tilt angle-cell thickness calibration curve used in the present invention will be described. The analysis cell setting parameters were: no voltage applied (0 V), cell thickness (3 μm to 8 μm).
m), liquid crystal physical constants (chiral length: −24 μm, refractive index no: 1.47914, ne: 1.55284, Δn:
0.0737), the initial distribution (pretilt angle: 90 degrees, twist angle: -90 degrees) of the liquid crystal director is set to an equilibrium state, and the energy distribution of Gibbs and Helmholts is solved to determine the orientation distribution of the liquid crystal director. Next, by using the refractive index and thickness of the polarizer and the retardation plate and the orientation distribution of the liquid crystal director as parameters, the transmittance of the transmissive display model is changed to a uniaxial retardation plate (in-plane retardation: An azimuth and an inclination angle of 90 degrees with respect to the slow axis of 10 nm to 50 nm) were calculated using a 2 × 2 determinant of the extended Jones matrix method. The tilt angle of the incident polarized light at the lowest transmittance, that is, the extinction position angle θ (unit: degree) is determined by the retardation d _{LC of the} liquid crystal cell.
-Plotted against Δn to obtain FIG. 3 (a). At this time, the retardation of each uniaxial retardation plate is 10 nm or more.
The following third-order polynomial approximation was performed on the curve for 50 nm, and calibration curves of the following equations (1) to (5) were obtained. _{10nm: d LC · △ n ≒} -0.0279θ 3 + 3.3896θ 2 -137.96θ + 2113.2 (1) 20nm: d LC · △ n ≒ -0.0174θ 3 + 2.4934θ 2 -124 · 48θ + 2434.7 ( 2) 30 nm: d _LC · {n} −0.0064θ ³ + 1.2130θ ² −80.123θ + 216.9 (3) 40 nm: d _LC · {n} −0.0060θ ³ + 1.20556θ ² −84.843θ + 2419. 5 (4) 50 nm: d _LC · {n} −0.0044θ ³ + 0.9870θ ² −76.648θ + 2452.0 (5) Then, each of the above calibration curves is a refractive index difference Δn of the liquid crystal material.
Were the same approximation even if they were different.

The effect of the measurement error of the extinction position angle on the calculated value of the cell thickness will be described. First. Δn is known and measured using a liquid crystal cell of d _LC · Δn = 442.2 nm. For each retardation plate, its extinction position angle θ
Was measured. The light source is 54 using a band-pass filter.
It was made monochromatic at 4 nm. Next, the obtained extinction position angle θ ₀
Assuming that the measurement error is ± 0.1 degrees, each approximation formula (1) to
Based on (5), the extinction position angles θ ₀ and (θ ₀ ± 0.1)
_Is used to calculate d _LC · △ n and the known △ n
The cell thickness and the cell thickness error width were determined from the above. Each phase difference plate and the obtained cell thickness error width are plotted in FIG.
As shown in FIG. 3B, it can be seen that the larger the retardation of the uniaxial retardation plate, the smaller the error width. From FIG. 3B, d _LC · Δn is 300 nm to 550.
In the range of nm, the error width of the required cell thickness is 0.1 μm.
m or less, the preferable range of the retardation of the uniaxial retardation plate is 10 nm to 50 nm.

In particular, d _LC · Δn is 350 nm to 550 n
In the range of m, due to the design of the device for measuring the extinction position, 60
It is preferable that the extinction position be set within a range of degrees, and FIG.
From the calculation results shown in (a), it can be seen that the retardation of the uniaxial retardation plate is preferably 40 nm or less. Further, from the calculation results shown in FIG. 3B, the retardation of the uniaxial retardation plate under the condition that the error width of the cell thickness value is 0.05 μm or less is 20 nm or more. From the above, a more preferable range of the retardation of the uniaxial retardation plate is from 20 nm to 40 nm. In the most preferable range of 30 nm to 40 nm, d _LC · Δn is 400 nm.
The cell thickness can be determined with high accuracy in the range of ５550 nm.

In the above description, the calibration curve of the retardation d _LC · Δn of the liquid crystal cell as a function of the extinction position angle θ is obtained by optical calculation, and the extinction position angle of the liquid crystal cell is measured. The cell thickness _dLC was obtained from the refractive index difference Δn of the material and the calibration curve, but without using optical calculations, a liquid crystal display device in which the Δn of the liquid crystal material and the cell thickness _dLC were known was used. By actually measuring the extinction position angle θ, a calibration curve can be obtained.

Next, embodiments of the liquid crystal display device, the cell thickness measuring device and the measuring method thereof, and the retardation plate of the present invention will be described.
This will be described with reference to FIGS. FIG. 4 is a perspective explanatory view of the cell thickness measuring apparatus according to the first embodiment. FIG. 5 is an explanatory diagram of the liquid crystal display device used for measuring the cell thickness of the first embodiment. FIG.
FIG. 4 is an explanatory diagram of a convex pattern of a liquid crystal display device used for measuring a cell thickness in Example 1. FIG. 7 is an explanatory diagram of an axisymmetric display mode of the liquid crystal display device used for measuring the cell thickness in the first embodiment. FIG. 8 is an explanatory diagram of the relationship between the extinction position angle and the extinction position angle θ when the retardation of the first embodiment is 21 nm. FIG. 9 is an explanatory diagram of the liquid crystal display device used for measuring the cell thickness of the second embodiment.

First, a first embodiment will be described. As shown in FIG. 4, the cell thickness measuring device of this embodiment includes a stage 1, a light source 2, a photodetector 3, a rotating device, a controller 10, and the like. The stage 1 is a sample XY stage, on which a liquid crystal display device to be measured is set, and which can be moved so that any point on the entire surface of the liquid crystal display device can be measured. Light source 2 is a lamp unit, 544 nm
The liquid crystal cell 5 is provided with a filter, a polarizer, and the like for monochromating, and emits polarized light used for cell thickness measurement to the liquid crystal cell 5. The filter is, for example, a Y luminosity filter, which is attached to the lamp unit, and monochromates the light of the lamp unit. The polarizer is mounted at a predetermined angle to polarize monochromatic light from the lamp unit. The photodetector 3 includes an analyzer, a photodetector, a photodetection unit, and the like. The photodetector 3 can use a photodiode and a low-noise amplifier to measure a transmitted light amount with high accuracy by using a display. , Transmittance and rotation angle can be accurately read directly. The analyzer is set at an angle that is crossed with the polarizer. The light receiver receives the transmitted light from the liquid crystal display device 5. The light detection unit determines the minimum or the extinction state of the transmitted light amount received by the light receiver. The rotation device includes a rotation mechanism 41, a stage unit, an angle operation switch 43, and the like. By rotating the light source 2 and the light receiver, the incident angle in the polar direction to the liquid crystal display device 5 can be changed. The angle of the rotation axis of the rotation mechanism 41 can be changed by the angle operation switch 43. Controller 10
Houses a heater, a cooling unit, and the like, and controls the entire cell thickness measuring device.

The measurement by the cell thickness measuring apparatus according to the first embodiment will be described. As shown in FIG. 5, a liquid crystal display device 5 to be measured includes a liquid crystal material 51 and a pair of upper and lower glass substrates 52.
a, 52b, transparent electrodes 53a, 53b, CF (color filter) layer 54, BM (black matrix) 5
5, a liquid crystal layer comprising a first convex portion 56, a column 57, etc., having a liquid crystal material having a negative dielectric anisotropy, and in which liquid crystal molecules in the liquid crystal region are aligned substantially vertically when no voltage is applied. And a pair of vertical alignment films (not shown) for holding the liquid crystal layer and a substrate. An example of a method for manufacturing this liquid crystal display device will be described. A 1 μm grid-like first projection 5 is formed on the glass substrate 52b at a position facing the BM 55 formed in a matrix.
6 was formed by a photolithography process. As the resin material, a photocurable polyimide material or an acrylic photosensitive material was used. Further, a cell thickness control portion having a thickness of 5 μm of the second convex portion was formed on the lattice-shaped convex portion 56 by a photolithography process to form a column 57. First convex portion 56, pillar 5 formed
FIG. 6 shows the pattern of the openings 7 and the openings (picture elements) 58.
A contact step meter was used to measure the thickness of each of the projections 56 and 57. Next, a transparent electrode 53b was formed. Transparent electrode 53b
It is also possible to form the projections 56 and 57 after forming the first. In the manufacturing procedure of the substrate 52a having the CF layer 54, the color filter layer 54 and the BM 55 are formed on the substrate 52a, and a transparent electrode, for example, ITO 53a is formed thereon. A 5.6 type TFT substrate 52a having a CF layer 54 facing the substrate 52b on which the convex portions 56 and 57 are formed,
Lamination was performed using a sealing material. Inject a liquid crystal material (liquid crystal precursor mixture) containing a photocurable resin and a photopolymerization initiator,
Furthermore, a voltage near the threshold value of the liquid crystal material was applied, and the film was exposed to ultraviolet rays to stabilize the axially symmetric alignment. As a result, when a voltage is applied, as shown in FIG.
A stable axially symmetric orientation consisting of Therefore, it was found that an axially symmetric liquid crystal cell was obtained. The liquid crystal display device obtained by the above manufacturing process was measured using the cell thickness measuring device of Example 1 in an atmosphere at room temperature and 25 degrees. The dependency of the transmittance on the polarization light tilt angle was measured, and the tilt angle at the lowest transmittance, that is, the extinction position angle (36.2 degrees ±
0.1 degrees). In addition, on both outer surfaces of the liquid crystal cell 5,
A uniaxial retardation plate 8 having in-plane retardation (21 nm) and a predetermined thickness is attached. Then, the amount of transmitted light with respect to the inclination angle of the monochromatic polarized light from the lamp unit is measured, the extinction position angle at which the obtained amount of light is minimum or in the extinction state is actually measured, and the calibration curve shown in FIG. ) Was used to determine the cell thickness. d _LC · Δn = −0.013θ ³ + 2.0539θ ² −113.07θ + 2460.6 (6) At the same time, the extinction position angle θ and d _LC obtained in advance by the above liquid crystal display device and optical calculation in the measurement form The cell thickness was determined from the Δn calibration curve and Δn = 0.0737, and was found to be 6.00 μm ± 0.02 μm. Since the electro-optical display characteristics as designed for the cell thickness were obtained, it can be said that the numerical values obtained by using the cell thickness measuring device of Example 1 are appropriate.

The cell thickness measuring device of the liquid crystal cell of this embodiment is
Even if it is not the structure of the liquid crystal cell as shown in FIGS. 5 and 6, it can be measured in a liquid crystal display device in which liquid crystal molecules are vertically aligned with the substrate.

Embodiment 2 will be described. In the present embodiment, a liquid crystal display device using a PALC (plasma addressed liquid crystal element) instead of the liquid crystal driving element TFT of the first embodiment is intended. As shown in FIG. 9, a PALC liquid crystal display device used for measurement includes a liquid crystal material 61, a CF substrate 62, an ITO electrode 63 as a transparent electrode, a vertical alignment layer 68, a thin glass 69,
It comprises a plasma partition (rib) 70, an anode electrode A71, a cathode electrode K72, a plasma gas filled channel 73, a plasma support substrate 74, and the like. This liquid crystal display device
On one side (upper side of the figure), a substrate 62 made of transparent glass or the like is sandwiched by a liquid crystal material 61, and on the other side (lower side of the figure), a thin glass 69 as a dielectric sheet and a plasma support substrate 74 are formed. Has a plasma generating substrate disposed in opposition.
A partition 70 is formed in a line between the plasma supporting substrate 74 and the thin glass 69, and a space surrounded by the partition 70, the plasma supporting substrate 74, and the thin glass 69 is
A line-shaped channel 73 in which the plasma gas is sealed is formed. An anode electrode A71 and a cathode electrode K72 for converting plasma gas into plasma are provided in each channel. This plasma address element substrate is manufactured by a known technique.

On the other hand, a color filter (CF) is provided on the liquid crystal layer side of the CF substrate 62, on which a transparent electrode 63 as a data line is formed in a striped and linear plasma channel. For example, the wiring is intersected with the wiring 73 in the vertical direction. The liquid crystal material 61 is sandwiched between a substrate 62 and a thin glass 69, and the cell thickness between the CF substrate 62 and the thin glass 69 is not shown, but is the same as in the first embodiment. It is controlled by the projection. The CF substrate 62 and the thin glass 69
Vertical alignment layers 68, 68 are respectively formed on the surface of the liquid crystal layer. Also, a CF substrate 62, an ITO electrode 63
And the portion made of the liquid crystal material 61 constitutes a liquid crystal cell.
In the liquid crystal display device thus manufactured, since the vertical alignment layer 68 is formed on the surfaces of the thin glass 69 and the CF substrate 62 that are in contact with the liquid crystal layer, the liquid crystal material 61 has a negative dielectric anisotropy. When a liquid crystal material is used, liquid crystal molecules are aligned perpendicular to the substrate 62 when no voltage is applied.

Using this PALC liquid crystal display device as a measurement object, the cell thickness was measured using the same cell thickness measurement device as in Example 1. The result of measuring the cell thickness will be described.
During measurement, the direction in which the polarized light is inclined is
2 and the slow axis of the phase difference plate 8 and the absorption axes of the polarizer and the analyzer were arranged in the relationship shown in FIG. Example 2
For the liquid crystal display device described in the above, the dependency of the transmittance on the polarization light tilt angle was measured by the cell thickness measurement device described with reference to Example 1 and FIG. 4, and the tilt angle at the lowest transmittance, that is, the extinction position angle. (36.2 degrees ± 0.1 degrees). At the same time, the calibration curve for the extinction position angle and d _LC · Δn obtained by optical calculation with the liquid crystal display device to be measured and the phase difference plate (retardation 21 nm) used (see FIG. 6 and the approximate expression (6)). And .DELTA.n = 0.0737, the cell thickness was determined to be 6.00 .mu.m. +-. 0.02 .mu.m. When the cell thickness control unit (the sum of the thicknesses of the first convex portion and the second convex portion) was actually measured by a contact step meter, it was 6.0 μm. These values are reasonable. Therefore, this measurement method
Measurement can also be performed on an LC-type liquid crystal display device.

A comparative example will be described. The liquid crystal display devices measured in Examples 1 and 2 were measured by using a commercially available cell thickness measuring device of the optical interference method, but no appropriate numerical value was obtained.

[0040]

According to the present invention, the cell thickness of a liquid crystal display device can be determined easily and accurately.
In the optical design of liquid crystal panels and inspection processes during manufacturing, etc.
It is possible to obtain a liquid crystal display device, a cell thickness measuring device and a measuring method thereof, and a retardation plate, which are short-time measurement, non-destructive, in-line inspection, and low-cost.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a cell thickness measuring device of the present invention.

FIG. 2 is an explanatory view of a retardation plate used for measuring a cell thickness and a polar angle direction in the present invention.

FIG. 3 is an explanatory diagram of the relationship between the extinction position angle and the liquid crystal retardation and the relationship between the retardation of the retardation plate and the cell thickness value error width in the present invention.

FIG. 4 is an explanatory perspective view of a cell thickness measuring apparatus according to the first embodiment.

FIG. 5 is an explanatory diagram of a liquid crystal display device used for cell thickness measurement in Example 1.

FIG. 6 is an explanatory diagram of a convex pattern of a liquid crystal display device used for measuring a cell thickness in Example 1.

FIG. 7 is an explanatory diagram of an axisymmetric display mode of the liquid crystal display device used for measuring a cell thickness in the first embodiment.

FIG. 8 shows a retardation of the retardation plate of Example 1 of 21 nm.
FIG. 4 is an explanatory diagram of the relationship between the extinction position angle and liquid crystal retardation at the time of FIG.

FIG. 9 is an explanatory diagram of a liquid crystal display device used for cell thickness measurement in Example 2.

[Explanation of symbols]

1 stage 21 lamp unit, 22 filter, 23
Polarizer, 31 analyzer, 32 light receiver, 33 light detection unit, 41 rotation mechanism, 42 stage unit, 43 angle operation switch, 5 liquid crystal display,
51 liquid crystal material, 52a, 52b glass substrate, 53
a, 53b Transparent electrode, 54 CF layer, 55B
M, 56 1st convex part, 57 pillars, 58 opening part (picture element part), 59a black part, 59b white part, 6 PALC
Liquid crystal display device, 61 liquid crystal layer, 62 CF substrate,
63 ITO electrode, 68 vertical alignment layer, 69 thin glass, 70 plasma partition (rib), 71 anode electrode A, 72 cathode electrode K, 73 plasma gas filled channel, 74 plasma support substrate, 8 phase difference plate, 10 controller.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA30 BB02 BB23 CC21 DD04 DD06 EE01 FF49 GG02 GG04 GG22 HH03 HH09 HH13 JJ01 JJ26 KK02 LL33 LL34 LL35 NN05 PP22 TT02 UU07 2G059 AA02 EE01 GG03 HH06 JJ02 JJ19 KK01 MM14 PP04 2H049 BA02 BA06 BB03 BC22 BC23 2H088 FA11 HA15 HA18 KA06 KA07 MA20

Claims (15)

[Claims] 1. The thickness of a liquid crystal cell of a liquid crystal display device comprising a liquid crystal layer in which liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied, and a pair of substrates sandwiching the liquid crystal layer. A cell thickness measuring apparatus comprising: a stage on which a liquid crystal cell in which a pair of uniaxial retardation plates having in-plane retardation are mounted on both outer surfaces with their slow axis directions aligned; and a polarizer. And a light source that emits polarized light having an azimuth angle of 44 to 46 degrees to the liquid crystal cell with respect to the slow axis direction of the retardation plate, and the polarizer and the cross Nicol disposed for the polarized light. A photodetector having an analyzer and a photodetector, and detecting the amount of transmitted polarized light, and polarized light incident from a direction perpendicular to the slow axis direction of the phase difference plate. A rotation device for changing the angle. The thickness measuring device. 2. The liquid crystal cell thickness measuring apparatus according to claim 1, wherein the rotating device rotates the light source and the light receiving device of the photodetector synchronously to change the incident angle in the polar angle direction. 3. The liquid crystal cell thickness measuring apparatus according to claim 1, wherein the rotation device rotates the stage to change the incident angle in the polar angle direction. 4. The apparatus according to claim 1, wherein the light source is a monochromatic laser light source or a light source having an optical coloring filter. 5. The apparatus according to claim 1, wherein the light source includes a lamp unit having a Y luminosity filter. 6. The cell thickness measuring apparatus according to claim 1, wherein the stage is an XY stage having a temperature controller and capable of measuring an arbitrary point. 7. The apparatus according to claim 1, wherein the polarizer can be set at an arbitrary angle. 8. The apparatus according to claim 1, wherein the photodetector has a photodiode and a low noise amplifier. 9. The apparatus according to claim 1, wherein the photodetector has a display. 10. A liquid crystal layer having a liquid crystal material having a refractive index difference of Δn, wherein liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied, and a pair of liquid crystal layers sandwiching the liquid crystal layer. A substrate, and a cell thickness measuring method for measuring the thickness of the liquid crystal cell of the liquid crystal display device comprising: a liquid crystal cell of the liquid crystal display device to be measured having in-plane retardation on both outer surfaces thereof, and a predetermined thickness. A pair of uniaxial phase difference plates are mounted with their slow axis directions aligned.
Azimuth angle direction 44 degrees to 4 with respect to the slow axis direction of the phase difference plate
The polarized light of 6 degrees is incident on the liquid crystal cell while changing the incident angle in the polar direction from the direction perpendicular to the slow axis direction of the retardation plate. The amount of transmitted light is detected by a photodetector having an analyzer arranged in crossed Nicols, the extinction position angle at which the obtained light amount is minimum or in the extinction state is measured, and the liquid crystal corresponding to the measured extinction position angle is measured. The retardation of the cell is obtained from a calibration curve of the extinction position angle at the thickness of the retardation plate and the liquid crystal cell retardation, and then the obtained liquid crystal cell retardation value and the refractive index difference Δn of the liquid crystal material are used to calculate the cell retardation. A method for measuring a cell thickness of a liquid crystal display device, comprising calculating a thickness. 11. The method according to claim 10, wherein the calibration curve between the extinction angle and the liquid crystal cell retardation in the thickness of the retardation plate is obtained by optical calculation. 12. The calibration curve between the extinction angle and the liquid crystal cell retardation at the thickness of the retardation plate is represented by a refractive index difference △.
11. The method for measuring the cell thickness of a liquid crystal display device according to claim 10, wherein the method is obtained by measuring a liquid crystal display device for which n and the cell thickness are known. 13. The method for measuring a cell thickness of a liquid crystal display device according to claim 10, wherein the retardation of the attached uniaxial retardation plate is 10 nm to 50 nm. 14. A liquid crystal material having a negative dielectric anisotropy,
A liquid crystal display device comprising: a liquid crystal layer in which liquid crystal molecules in a liquid crystal region are aligned substantially vertically when no voltage is applied; and a pair of substrates sandwiching the liquid crystal layer and having a vertical alignment film. And a pair of uniaxial retardation plates having a retardation of 10 nm to 50 nm are attached to both outer surfaces of the liquid crystal cell with their slow axes aligned. Liquid crystal display device. 15. A retardation plate used in a method for measuring a cell thickness of a liquid crystal display device according to claim 10, wherein the retardation plate has in-plane retardation, and the retardation is 10 nm to 50 nm. A retardation plate characterized by being uniaxial.