JP3342268B2 - Method and apparatus for measuring pretilt angle of liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the initial tilt angle of a liquid crystal in a liquid crystal display device in which a liquid crystal is used as an optical member to control the transmittance of each pixel and the transmittance distribution is visually recognized as a display image. About.

[0002]

2. Description of the Related Art As a display device, a liquid crystal display device (LCD: Liquid Crystal D) using a liquid crystal as a light modulation means.
isplay) has the advantages of small size, low profile, low power consumption,
Practical use is progressing in the fields of OA equipment, AV equipment, and the like.
In particular, a matrix type in which transparent electrodes for driving a liquid crystal are arranged in an intersecting manner and a display point is selected in a matrix to apply a voltage, and further, a switch element is connected to each pixel capacitor for driving a liquid crystal, and line-sequentially formed. The active matrix type, which constantly holds the signal voltage electrostatically while selecting the pixel to be rewritten, is capable of displaying moving images with high definition and high contrast ratio, and has been put to practical use in display monitors of personal computers, television, etc. I have.

FIG. 12 is a perspective view showing the structure of an LCD. (1) is a first polarizing plate, (2) is an electrode substrate on which a transparent electrode for driving a liquid crystal is formed, (3) is a liquid crystal, (4) is a transparent counter substrate, and (5) is a second substrate. It is a polarizing plate. TN
In a general configuration of the (Twisted Nematic) mode, the liquid crystal (3) is a nematic phase that tends to align its molecular axes in the same direction. In order to control the alignment of the liquid crystal molecules (3a) on the surfaces of both substrates (2, 4), a polymer film such as polyimide is formed and subjected to a rubbing treatment, whereby At the interface, the orientation of the liquid crystal molecules (3a) is aligned in a certain direction. The rubbing direction is orthogonal to both substrates (2, 4), and the liquid crystal molecules (3a) are twisted by 90 ° between both substrates (2, 4) under the control of both substrates (2, 4). ing. The polarizing plates (1, 5) are also
As indicated by the arrows in the figure, the polarization axes are orthogonal to each other.

In such a system, more specifically, a plurality of strip-shaped transparent electrodes are formed on an electrode substrate (2) and a counter substrate (4), and the two transparent electrodes are arranged so as to cross each other.
There is a simple matrix type that forms pixels at the intersection,
In particular, in the case of a graphic display such as a personal computer monitor, in order to obtain a sharp drive threshold characteristic of the liquid crystal in response to a high duty ratio, the orientation of the liquid crystal is adjusted between the substrates (2, 2).
STN (Super Twisted Ne) twisted 270 ° between 4)
matic) mode or using the electrode substrate (2) as a switching element as a thin film transistor or TFT (Thin Film Tran).
sistor) and a TFT in which unit structures connected to display electrodes that partition pixels are arranged in a matrix.
There is an active matrix type in which a common electrode facing all the display electrodes is formed on the entire surface of the counter substrate (4) and a different voltage is applied to each pixel for each field and held.

Further, as another mode, there is a vertical alignment mode, that is, an initial alignment of liquid crystal molecules is controlled in a direction perpendicular to the substrate. In the TN mode, when no voltage is applied, when light enters from a light source arranged below the figure,
The light is changed to linearly polarized light by the first polarizing plate (1) and transmitted through the electrode substrate (2). The liquid crystal has anisotropy in the refractive index, and the incident linearly polarized light turns along the twist of the orientation of the liquid crystal, passes through the counter substrate (4), and passes through the second polarizing plate (5). At this time, the pixel is a bright point and is recognized as white. Since the liquid crystal also has anisotropy in the dielectric constant, when an electric field is formed between the two substrates (2, 4) at the time of applying a voltage, the liquid crystal molecules (3a ) Is oriented perpendicular to the substrate. For this reason, the incident linearly polarized light that has passed through the first polarizing plate (1) is not rotated by the liquid crystal (3), does not pass through the second polarizing plate (5), and its pixel becomes a dark point and is recognized as black. Is done. Since the amount of transmitted light varies depending on the intensity of the electric field applied to the liquid crystal, especially in the active matrix type, gradation can be displayed by finely adjusting the voltage for each pixel, and the display of a picture can be performed. It becomes possible. In this way, white is displayed when no voltage is applied, and black is obtained by applying a voltage.
This is called white mode.

On the other hand, a type in which the polarization axes of both polarizing plates (1, 5) are arranged parallel to each other is called a normally black mode. In this case, when no voltage is applied, the linearly polarized light that has passed through the first polarizing plate (1) is turned by the liquid crystal (3) and cut off by the second polarizing plate (5), so that the display becomes black. . By applying a voltage, the incident linearly polarized light by the liquid crystal (3) is no longer swirled and passes through the second polarizing plate (5), so that the display becomes white.

As shown in FIG. 13, the liquid crystal molecules (3a)
In the contact interface with the alignment films (2a, 4a) provided on the surfaces of the two electrode substrates (2, 4), the molecular long axes are aligned in a certain direction by the interaction and the rubbing directions (2b, 4b) ), Slightly launched,
It has an initial tilt, ie, pretilt (pt). When a voltage is applied, as shown in FIG. 14, an electric field (6) is formed between the display electrodes formed on both electrode substrates (2, 4) and the common electrode, and has a positive dielectric anisotropy. The liquid crystal molecules (3a) react electrically and turn in the direction along the electric field (6). At this time, the liquid crystal molecules (3a) rise so as to increase the pretilt.

For this reason, as shown in FIG. 15, the liquid crystal molecules (3a) are oriented in a constant direction on average with respect to the rubbing directions (2b, 4b) of the upper and lower substrates. Therefore, in viewing from the left viewing angle direction (L) and the right viewing angle direction (R), the inclination of the liquid crystal molecules (3a) is viewed from the lateral direction, and the transmittance changes depending on the viewing angle. The so-called viewing angle dependency is small. On the other hand, at the vertical viewing angles (U, D), the movement of the liquid crystal molecules (3a) along the molecular axis is seen most, and thus the viewing angle dependence is increased. Normally,
As shown in the figure, when viewed from the lower viewing angle (D) direction, the liquid crystal molecules (3a) are viewed from the back direction, so that a sufficient black level is obtained and the liquid crystal molecules (3a) are obtained.
Even if a) is inclined, the front and back of the molecular axis are reversed, and the inclination of the voltage-transmittance characteristic curve is not reversed, so that the gradation inversion is hardly caused. That is, the lower viewing angle direction (L) is set to be the priority viewing angle direction.

The rising directions of the liquid crystal molecules (3a) upon application of a voltage are uniformly aligned according to the pretilt angle.
As a result, the liquid crystal molecules (3a) partially rise from the opposite side, and the region becomes a reverse tilt domain having different transmittance and viewing angle dependent characteristics, causing a change in transmittance and deteriorating display quality. Was preventing that. Such a reverse tilt domain is less likely to occur as the pretilt angle is larger, but on the other hand, if the reverse tilt domain is larger, it is difficult to obtain sufficient brightness, especially a sufficiently low black level, so that the contrast ratio decreases. Bring. Therefore, the control of the pretilt angle is an important factor for obtaining a good display, and for that purpose,
An accurate measurement of the pretilt angle is essential.

[0010]

As a conventional pretilt angle measuring method, there is a crystal rotation method. That is, the pretilt angle is measured by changing the observation angle and examining the transmission characteristics using a cell dedicated to measurement in which the polarization axes of the upper and lower polarizers are arranged parallel to each other with a predetermined cell gap. Therefore, in this method, it is necessary to make a dedicated cell for measurement suitable for the measuring device, and the cost is high.
In addition, the practical product cell uses the same manufacturing method or the same material of the alignment film as the measurement cell,
Since the pretilt angle was determined to be the same as the pretilt angle measured by the measuring cell, it also took into account variations in the manufacturing process and changes in the interaction effect between the liquid crystal and the alignment film after liquid crystal injection. In addition, it was not possible to measure the pretilt angle of the completed utility cell.

According to the present invention, the pretilt angle can be measured by a simple method for a cell of a practical product, the reliability is improved, and the cause of a decrease in display quality due to a change in the pretilt angle can be determined. It is intended to provide a method and an apparatus thereof.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve this problem. In a method for measuring a pretilt angle of a liquid crystal display device, a pretilt angle and light transmitted through a plurality of predetermined viewing angles are determined in advance. Derive an optical correspondence with an optical value calculated by a predetermined calculation method from the wavelength spectral characteristics of the liquid crystal display device, and measure the pretilt angle of the liquid crystal display device, the wavelength spectral characteristics of the transmitted light in the plurality of predetermined viewing angle directions. The pretilt angle is determined by comparing an optical value calculated by the same calculation method as the predetermined calculation method with the optical correspondence.

A pretilt angle measuring device for a liquid crystal display device, comprising: a support supporting the liquid crystal display device and capable of changing a rotation angle about at least one straight line included in a support plane; A light source for irradiating the device with light,
A spectrometer for measuring the wavelength spectral value of light transmitted from the light source through the liquid crystal display device, a controller for controlling a rotation angle of the support, and a spectrometer and the controller connected to the spectrometer, and An optical correspondence relationship between a pretilt angle and an optical value calculated by a predetermined calculation method from a wavelength spectral value of transmitted light in a plurality of predetermined rotation angle directions is stored, and rotation angle information of the controller and the rotation angle information are stored. An optical value is calculated by the predetermined calculation method by performing an arithmetic process from the wavelength spectral value information of the spectrometer, and the calculated value is compared with the optical correspondence to determine a pretilt angle. And a computer.

As described above, the pretilt angle can be determined only by examining the predetermined wavelength spectrum of the transmitted light by the pretilt angle measuring method utilizing the dependence of the wavelength spectral characteristic of the transmitted light on the pretilt angle. The pretilt angle of the liquid crystal cell can be known, and reliability and cell analysis can be facilitated. In particular, the optical correspondence is the first viewing angle at a wavelength designated by a predetermined method in the wavelength spectral characteristics of transmitted light in each of a first viewing angle direction, a second viewing angle direction, and a third viewing angle direction. And a ratio between a wavelength spectral value in the second viewing angle direction and a wavelength spectral value in the second viewing angle direction, and a difference between the wavelength spectral value in the third viewing angle direction and the wavelength spectral value in the second viewing angle direction.

As described above, the viewing angle direction in which the wavelength spectral characteristic is relatively largely dependent on the pretilt angle is set in the third viewing angle direction, and the first and second viewing angle directions in which the wavelength spectral characteristic is not so dependent on the pretilt angle. By obtaining the functional optical correspondence between the ratio of the spectral value at an appropriate wavelength to the spectral characteristic of the liquid crystal and the pretilt angle at that time, the optical characteristic obtained by the above-described method from the spectral characteristic of the liquid crystal display device to be measured is obtained. By applying the target value to the relational function,
A pretilt angle value is determined. That is, due to the anisotropy of the refractive index of the liquid crystal molecules, the transmitted light characteristic changes greatly due to a change in the viewing angle in a plane mainly including the orientation of the liquid crystal molecules, and the amount of change varies depending on the pretilt angle. are doing. That is, when the pretilt angle changes, the optical characteristics change, but the amount of change differs depending on the viewing angle. In particular, the amount of change in the third viewing angle direction is significantly different from the amount of change in the first and second viewing angle directions. Since they are different, an optical value derived as a ratio of the amount of change in the third viewing angle direction with reference to the amount of change in the first and second viewing angle directions can be a unique value at the pretilt angle. Therefore, those indicating the same amount of change in the optical characteristics are evaluated to have the same pretilt angle.

The wavelengths specified by the predetermined method are the wavelengths that give the minimum value of the wavelength spectral characteristics of the transmitted light in each of the first viewing angle direction, the second viewing angle direction, and the third viewing angle direction. Among them, the wavelength is set to be larger by a certain width than the maximum wavelength. As a result, the wavelength giving the minimum value of the spectral value differs depending on the viewing angle, but is determined at a wavelength at which the spectral value is large in a wavelength region apart from these wavelengths and the difference between these spectral values becomes clear. By determining the wavelength for which an optical value is to be obtained so that the accuracy of collating the power optical value is high, it is possible to measure the pretilt angle with high accuracy.

[0017]

Next, an embodiment of the present invention will be described. FIGS. 1 to 4 show a viewing angle of 0 ° for liquid crystal display devices (A, B, C, D) having different pretilt angles.
That is, the front viewing angle (fr), + 45 °, ie, the upper viewing angle (up),
FIG. 9 is a spectral characteristic diagram showing a relationship between wavelength and transmittance at −45 °, that is, at a lower viewing angle (dn). Devices (A, B,
The liquid crystal used in C and D) was SA-50 manufactured by Chisso Petrochemical Company.
16LB nematic liquid crystal, cell gap 4.6μm
The O-MODE of the polarizing plate on the incident side was set so that the polarization axis was perpendicular to the rubbing direction of the alignment film, and the ordinary ray was linearly polarized.
It is. The rubbing direction is a TN mode orthogonal to each other, as shown in FIG. 15, and is a normally black mode in which the upper and lower polarization axes are parallel. At this time, the viewing angle dependence of the vertical viewing angles (U, D) increases. The alignment films used have different pretilt angles, respectively, and are manufactured by JALS-428,
AL-3506, AL-8534 and RN-1046. The following table shows the nominal values of the pretilt angles of the devices (A, B, C, D).

[0018]

[Table 1]

FIGS. 1 to 4 show that first of all,
The point is that the relationship between the wavelength and the transmittance, that is, the spectral characteristics vary depending on the viewing angle and also vary depending on the pretilt angle. This is because, in the initial state, the alignment state of the liquid crystal is changed by being affected by the pretilt angle, so that the angle formed between the liquid crystal molecules and the incident linearly polarized light changes.

In normally black, the transmittance increases as the liquid crystal stands. For this reason, the liquid crystal molecules (3a) change to a vertical alignment by applying a voltage, or
Change the viewing angle, ie, in this case, the vertical viewing angle (U, D)
When viewed from above, the liquid crystal molecules (3a) appear to stand up, so that the transmittance increases. For this reason, in FIG. 1 having the smallest pretilt angle, especially at the front viewing angle (fr), the optical rotation is effectively performed, so that the light shielding property by the polarizing plate is high and the transmittance is the lowest. On the other hand, in FIG. 2, the liquid crystal rises due to the pretilt, and the twisted alignment structure of the liquid crystal is broken,
The optical rotatory power decreases and light passes between the polarizing plates, so that the transmittance increases. In particular, in the upper viewing angle (up) characteristic, since the liquid crystal molecules are viewed in a dot-like manner as much as the liquid crystal molecules rise due to the pretilt, the optical rotatory power decreases and the transmittance between the polarizing plates increases, so that the transmittance increases. I have. The same can be said for FIGS. 3 and 4.

Further, the following can be seen from the comparison of FIGS. The spectral characteristics at the front viewing angle (fr) are relatively stable without much dependence on the pretilt angle, whereas at the lower viewing angle (dn), the transmittance greatly changes depending on the pretilt angle. In addition, the transmittance decreases as the pretilt angle increases, and the characteristic curve in FIG. 4 is almost close to the front view angle (fr). This is because, at the lower viewing angle (dn), as the pretilt angle increases and the liquid crystal molecules rise, the liquid crystal molecules appear to look like rods, so that the optical rotation increases and the light is well blocked between the polarizing plates. It is. This effect is exactly the opposite of the upper viewing angle (up), but the amount of change is considerably large. This is because, in the normally black mode, it is relatively easy to increase the transmittance, but it is difficult to reduce the transmittance, so that at a viewing angle at which transmitted light obliquely passing through the liquid crystal layer is visually recognized. In particular, it is presumed that the transmittance is greatly reduced at the lower viewing angle (dn) at which the liquid crystal is viewed in a rod shape.

As described above, it is presumed that the transmittance of the liquid crystal display device depends not only on the viewing angle but also on the pretilt angle. That is, when the pretilt angle changes, the orientation of the liquid crystal molecules is affected, and the angle between the optical path and the liquid crystal molecules changes. Based on the above estimation, a simulation was performed to calculate the wavelength spectral characteristics when the pretilt angle was changed. FIGS. 5 to 9 show simulation results using a liquid crystal simulator DIMOS manufactured by Autotronic. In this simulation, Frank's theory of elasticity and a 4 × 4 matrix method are used. 5 shows a pretilt angle of 0 °, FIG. 6 shows 1 °, and FIG.
8, FIG. 8 is 10 °, and FIG. 9 is 20 °, the front viewing angle (0 °) (fr), the upper viewing angle (+ 45 °) (u
p) and the spectral characteristics at the lower viewing angle (−45 °) (dn). The cell conditions in this simulation are the same as those of the liquid crystal display devices (A, B, C, D) shown in FIGS. 5 to 9, as in FIGS. 1 to 4, it can be seen that the transmittance changes not only depending on the viewing angle but also on the pretilt angle, as discussed above. That is,
In the front view angle (fr), the influence of the change in the pretilt angle is not noticeable, but in the upper view angle (up) and the lower view angle (dn),
The longer the distance that passes through the liquid crystal layer, the more affected by pretilt. At the upper viewing angle (up), as the pretilt angle increases, the liquid crystal molecules appear to be point-like, so that the optical rotation decreases and the transmittance increases. However, at the lower viewing angle (dn), as the pretilt angle increases, the pretilt angle increases. Since the liquid crystal molecules look like rods, the optical rotation is enhanced and the transmittance is reduced.

In view of the above, the applicant has focused on the dependence of the transmittance on the pretilt angle, and has invented a method of measuring the transmittance to conversely evaluate the pretilt angle. That is, a functional relationship between a predetermined optical value and a pretilt angle is established in advance, and an optical value to be applied to the functional relationship is obtained from the transmittance characteristic of the liquid crystal display device to be measured. The pretilt angle is determined.

Hereinafter, a method for measuring a pretilt angle of a liquid crystal display device according to an embodiment of the present invention will be described. First, in FIGS. 5 to 9 described above, the front view angle (fr) and the upper view angle (u)
The largest wavelength λmin is read out of the wavelengths giving the minimum values of the spectral characteristic curves of p) and the lower viewing angle (dn). The wavelength λmin is read at the front viewing angle (fr) characteristic in FIGS. 5 to 8 and at the lower viewing angle (dn) in FIG.

Thus, a common condition is given to the optical characteristics at each pretilt angle so that similar comparisons can be made at similar portions. Second, a wavelength λmin of 100
The reference wavelength λo to which nm is added is set. As a result, in the optical characteristics at each pretilt angle, the change amount depending on the wavelength is invalidated, and the mutual comparison based on the change amount depending only on the pretilt angle is enabled.

Third, the upper viewing angle (u) at the reference wavelength
p) The transmittance Tup of the characteristic and the transmittance T of the lower viewing angle (dn) characteristic
(Tup−Tdn) the ratio of the difference between dn and the difference between the transmittance Tup of the upper viewing angle (up) characteristic and the transmittance Tfr of the front viewing angle (fr) characteristic.
/ (Tup-Tfr) is calculated, and this value is set as an optical value at the pretilt angle. Fourth, each optical value when the pretilt angle is changed is calculated to establish a functional relationship between the pretilt angle and the optical value.

FIG. 10 is a graph showing the functional relationship between the pretilt angle thus obtained and the optical value. It can be seen that the optical value corresponds to one value of the pretilt angle on a one-to-one basis. In the present invention, based on such a functional relationship between the pretilt angle and the optical value, the optical value is measured in the same manner as the above-described first to fourth procedures from the spectral characteristics of the liquid crystal display device to be measured. Is calculated, and one pretilt angle is read from the functional relationship shown in FIG. 10 to determine this as the pretilt angle of the liquid crystal display device.

Next, description will be made returning to the embodiment. As an example, the pretilt angle of the liquid crystal display (B) is measured by the method of the present invention. First, a viewing angle direction having a high viewing angle dependency is determined by simple optical observation, and this is determined as a vertical viewing angle direction. Next, the front viewing angle (viewing angle 0 °) (fr), upper viewing angle (up) (viewing angle + 45 °), and lower viewing angle (dn) (viewing angle −
For each viewing angle direction (45 °), the relationship between wavelength and transmittance is examined using, for example, IMAC-7000 manufactured by Otsuka Electronics Co., Ltd., and wavelength spectral characteristics are measured. This result is previously shown in FIG.

Then, the optical value is calculated in the same procedure as when the functional relationship between the pretilt angle and the optical value shown in FIG. 10 is obtained. That is, first, of the wavelengths giving the minimum value of the spectral characteristics at the front viewing angle (fr) or the lower viewing angle (dn), the larger wavelength λmin = 590 nm is read. Next, 100 nm is added to 590 nm, and λo = 690n
m is set to the reference wavelength at this pretilt angle.

The upper viewing angle at 690 nm (u
p) The difference between the transmittance of the characteristic 5.94% and the transmittance of the lower viewing angle (dn) characteristic of 2.64%, and the transmittance of the upper viewing angle (up) characteristic of 5.94% and the transmission of the front viewing angle (fr) characteristic. 0.80%
And the ratio of (5.94-2.64) / (5.94-
2.64) = 0.642, and this value is taken as the optical value at that pretilt angle.

When this optical value 0.642 is applied to the functional relationship in FIG. 10, the pretilt angle is determined to be 4.00 °. Table 1 shows the nominal values by the manufacturer and the values measured by the method of the present invention. It can be seen that fairly accurate values are obtained in all models. As described above, in the present invention, as shown in FIG. 10, by calculating the functional relationship between the pretilt angle and a predetermined optical value, when measuring the actual pretilt angle of the liquid crystal display device, The above optical value is calculated by optical observation, and the pretilt angle can be determined from the above functional relationship.

However, among the above-mentioned embodiments, the data for obtaining the spectral characteristics is not limited to the one using the simulation experiment. For example, the data obtained by the pretilt using a spectrometer such as IMAC7000 is used. Spectral characteristic data for cells whose angles are known can be collected, and the functional relationship between the pretilt angle and the optical value can be determined as shown in FIG. Alternatively, there is room for development of a method of correcting the simulation result by actual measurement.

Regarding the procedure for obtaining the above-described optical value, in the first and second procedures, the reference wavelength λo can be specified by another method depending on the performance of the spectral characteristic measuring device. In the present embodiment, in order to take data on the visible range, the largest wavelength is selected from the wavelengths giving the minimum value of the transmittance, and a reference having a predetermined width larger than that is selected so that the difference in transmittance depending on the viewing angle can be increased. The wavelength λo is specified. For this reason, for example, when a UV measuring device is used as the spectrometer, the reference wavelength must be specified in another wavelength range. Further, the change width for designating the reference wavelength λo is not limited to 100 nm, and by aligning the data, it is possible to check the change width that enables more accurate measurement.

Next, a pretilt angle measuring device for a liquid crystal display device according to an embodiment of the present invention will be described. FIG. 11 is a configuration diagram thereof. (1) is a support for fixedly supporting the liquid crystal display device (2) to be measured. An opening is provided in a portion corresponding to a display portion of the liquid crystal display device (2). Rotation angle around vertical direction (θ)
Is variable. (3) is a light source that irradiates the liquid crystal display device (2) with light, and (4) is a spectrometer that receives light transmitted through the liquid crystal display device (2) and derives wavelength spectral characteristics. The spectrometer (4) includes, for example, the aforementioned IMAC
-7000 is used. (5) a microcomputer, which is connected to the spectrometer (4) and the controller (6) for controlling the rotation angle (θ) of the support (1).

The microcomputer (5) discriminates the front viewing angle, the upper viewing angle and the lower viewing angle from the rotation angle information from the controller (6), and uses the above-described procedure from the spectral characteristic information obtained from the spectrometer (4). Is performed to calculate an optical value in accordance with The microcomputer (5) also stores the functional relationship between the pretilt angle and the optical value as shown in FIG. 10 in advance, and compares the calculated optical value with the functional relationship to obtain the pretilt angle. One value is selected, and this is determined to be the pretilt angle of the liquid crystal display device (2).

In such a pretilt angle measuring apparatus, the distribution of the pretilt angle in one pixel is examined by making the support (1) slightly movable up and down and left and right while the rotation axis is fixed. You can also. This makes it possible to find the reverse tilt domain and to determine the pretilt angle controllability of rubbing a plurality of times in a multi-domain system in which the pretilt is varied by dividing the alignment film and the viewing angle is increased by orienting in multiple directions. Will be useful.

The functional relationship between the pretilt angle and the optical value shown in FIG. 10 is such that the cell gap is determined as described above. Therefore, for different cell gaps, FIG.
By establishing the optical relationship as described above, it becomes possible to obtain the pretilt angle for cells having any cell gap.

[0038]

As is apparent from the above description, the present invention relates to a method for measuring a pretilt angle of a liquid crystal display device, in which a functional relationship between a pretilt angle and a predetermined optical value is established in advance. This is a method of determining the pretilt angle by examining the optical characteristics of the liquid crystal display device to be derived to derive an optical value, and applying this value to the above functional relationship. As a result, the pretilt angle can be measured only by examining the optical characteristics of the liquid crystal display device, which eliminates the need for a measuring cell, thereby reducing the cost and making it possible to measure the pretilt angle reliably with the finished cell. It can be included in one item of the test, and the reliability is improved.

Further, since it is possible to examine the relationship between the pretilt angle and the optical characteristics in the completed cell, it is possible to analyze the reverse tilt domain and to rub and pretilt the alignment film in the multi-domain system by dividing the alignment film. It is also useful for analysis and development of characteristics such as angle and optical characteristics.

[Brief description of the drawings]

FIG. 1 is a spectral characteristic diagram showing measurement results of optical characteristics of a liquid crystal display device.

FIG. 2 is a spectral characteristic diagram showing measurement results of optical characteristics of a liquid crystal display device.

FIG. 3 is a spectral characteristic diagram showing measurement results of optical characteristics of the liquid crystal display device.

FIG. 4 is a spectral characteristic diagram showing measurement results of optical characteristics of the liquid crystal display device.

FIG. 5 is a spectral characteristic diagram showing a simulation result of optical characteristics of the liquid crystal display device.

FIG. 6 is a spectral characteristic diagram showing a simulation result of optical characteristics of the liquid crystal display device.

FIG. 7 is a spectral characteristic diagram showing a simulation result of optical characteristics of the liquid crystal display device.

FIG. 8 is a spectral characteristic diagram showing a simulation result of optical characteristics of the liquid crystal display device.

FIG. 9 is a spectral characteristic diagram showing a simulation result of optical characteristics of the liquid crystal display device.

FIG. 10 is a relationship diagram showing a functional relationship between a pretilt angle and an optical value according to the embodiment of the present invention.

FIG. 11 is a configuration diagram of a pretilt angle measuring device of a liquid crystal display device according to an embodiment of the present invention.

FIG. 12 is a perspective view illustrating a configuration of a liquid crystal display device.

FIG. 13 is a perspective view illustrating the principle of a liquid crystal display device.

FIG. 14 is a perspective view illustrating the principle of a liquid crystal display device.

FIG. 15 is a plan view illustrating a configuration of a liquid crystal display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 support 2 liquid crystal display device 3 light source 4 spectrometer 5 microcomputer 6 controller

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B 11/26 G02F 1/1337

Claims (6)

(57) [Claims] 1. A method for measuring a pretilt angle of a liquid crystal display device, comprising: a method of measuring a pretilt angle in advance and an optical value calculated by a predetermined calculation method from wavelength spectral characteristics of transmitted light in a plurality of predetermined viewing angle directions. The correspondence is derived, and the optical value calculated by the same calculation method as the predetermined calculation method from the wavelength spectral characteristics of the transmitted light in the predetermined plurality of viewing angle directions of the liquid crystal display device for which the pretilt angle is to be measured is calculated as the optical value. The pre-tilt angle is determined by collating with the target correspondence , and the optical correspondence is determined in the first viewing angle direction,
Waves of transmitted light in each of the second viewing angle direction and the third viewing angle direction
In the long spectral characteristics, the wavelength at the specified wavelength
The wavelength spectral value in the first viewing angle direction and the wave in the second viewing angle direction
The difference between the long spectral values, the wavelength spectral value in the third viewing angle direction and the
A method for measuring a pretilt angle of a liquid crystal display device, wherein the ratio is a ratio to a difference between wavelength spectral values in a second viewing angle direction . 2. A method for measuring a pretilt angle of a liquid crystal display device.
In advance, a pretilt angle and a predetermined plurality of viewing angle directions
Calculated from the spectral characteristics of the transmitted light using the prescribed calculation method.
Deriving an optical correspondence relationship with the obtained optical value and measuring the pretilt angle of the liquid crystal display device,
From the wavelength spectral characteristics of transmitted light in a plurality of viewing angle directions,
Optical calculated by the same calculation method as the specified calculation method
By comparing the value to the optical correspondence, the pretil
Angle, and the wavelength spectral characteristic is the predetermined plurality of
The minimum value of the wavelength spectral characteristic of the transmitted light in each case in the viewing angle direction
Waves that are a certain width larger than the maximum wavelength among the given wavelengths
Measurement using a liquid crystal display device.
Retilt angle measurement method . 3. A method for measuring a pretilt angle of a liquid crystal display device.
In advance, a pretilt angle and a predetermined plurality of viewing angle directions
Calculated from the spectral characteristics of the transmitted light using the prescribed calculation method.
Deriving an optical correspondence relationship with the obtained optical value and measuring the pretilt angle of the liquid crystal display device,
From the wavelength spectral characteristics of transmitted light in a plurality of viewing angle directions,
Optical calculated by the same calculation method as the specified calculation method
By comparing the value to the optical correspondence, the pretil
And determining the optical angle, wherein the optical correspondence is a first viewing angle direction,
Waves of transmitted light in each of the second viewing angle direction and the third viewing angle direction
In the long spectral characteristics, the wavelength at the specified wavelength
The wavelength spectral value in the first viewing angle direction and the wave in the second viewing angle direction
The difference between the long spectral values, the wavelength spectral value in the third viewing angle direction and the
It is a ratio with the difference between the wavelength spectral values in the second viewing angle direction, and the wavelength specified by the predetermined method is the transmitted light in each of the first viewing angle direction, the second viewing angle direction, and the third viewing angle direction. A liquid characterized by a wavelength that is a certain width larger than the maximum wavelength among the wavelengths giving the minimum value of the wavelength spectral characteristics.
Method for measuring pretilt angle of crystal display device. 4. A pretilt angle measuring device for a liquid crystal display device, comprising: a support that supports the liquid crystal display device and that can change a rotation angle about at least one straight line included in a support plane as an axis;
A light source that irradiates light to the liquid crystal display device, a spectrometer that measures a wavelength spectral value of light transmitted from the light source through the liquid crystal display device, and a controller that controls a rotation angle of the support, An optical correspondence relationship between a pretilt angle and an optical value calculated by a predetermined calculation method from wavelength spectral values of transmitted light in a plurality of predetermined rotation angle directions, which is connected to the spectrometer and the controller. Is stored, and arithmetic processing is performed from the rotation angle information of the controller and the wavelength spectral value information of the spectrometer to calculate an optical value by the predetermined calculation method, and the calculated value is referred to as the optical correspondence. A microcomputer that determines a pretilt angle by collating with the optical system , wherein the optical value is a straight line included in a support plane of the support.
The first rotation angle direction, the second rotation angle direction, and the third rotation around the axis
In the wavelength spectral characteristics of transmitted light in each case of the turning angle direction
The first rotation angle direction at a wavelength designated by a predetermined method.
Between the wavelength spectral value in the direction of rotation and the wavelength spectral value in the direction of the second rotation angle.
Wavelength spectral value in the third rotation angle direction and the second rotation angle
Liquid, characterized in that it is the ratio to the difference between the wavelength spectral values in the directions.
Pretilt angle measuring device for crystal display device . 5. A pretilt angle measuring device for a liquid crystal display device.
And supporting at least the liquid crystal display device and including at least a support plane.
A support that can change the rotation angle around one straight line,
A light source for irradiating the liquid crystal display device with light;
Of the light transmitted through the liquid crystal display device.
A spectrometer for controlling the rotation angle of the support.
Controller, the spectrometer and the controller
Connected, pre-tilt angle and predetermined multiple front
Predetermined calculation method from wavelength spectral value of transmitted light in the rotation angle direction
The optical correspondence with the optical value calculated by the method is stored.
The rotation angle information of the controller and the spectrometer
The predetermined calculation is performed by performing arithmetic processing from the wavelength spectral value information of
Calculating an optical value by the method, and using the calculated value as the optical value.
Pre-tilt angle is determined by collating the target correspondence
The wavelength spectrometer is provided in each of the plurality of rotation angle directions.
Each wavelength giving the minimum value of the wavelength spectral characteristics of the transmitted light
In other words, use a wavelength that is larger than the maximum wavelength by a certain width.
A pretilt angle measuring device for a liquid crystal display device. 6. A pretilt angle measuring device for a liquid crystal display device.
And supporting at least the liquid crystal display device and including at least a support plane.
A support that can change the rotation angle around one straight line,
A light source for irradiating the liquid crystal display device with light;
Of the light transmitted through the liquid crystal display device.
A spectrometer for controlling the rotation angle of the support.
Controller, the spectrometer and the controller
Connected, pre-tilt angle and predetermined multiple front
Predetermined calculation method from wavelength spectral value of transmitted light in the rotation angle direction
The optical correspondence with the optical value calculated by the method is stored.
The rotation angle information of the controller and the spectrometer
The predetermined calculation is performed by performing arithmetic processing from the wavelength spectral value information of
Calculating an optical value by the method, and using the calculated value as the optical value.
Pre-tilt angle is determined by collating the target correspondence
Microcomputer, wherein the optical value is a straight line included in a support plane of the support.
The first rotation angle direction, the second rotation angle direction, and the third rotation around the axis
In the wavelength spectral characteristics of transmitted light in each case of the turning angle direction
The first rotation angle direction at a wavelength designated by a predetermined method.
Between the wavelength spectral value in the direction of rotation and the wavelength spectral value in the direction of the second rotation angle.
Wavelength spectral value in the third rotation angle direction and the second rotation angle
The wavelength specified by the predetermined method is the wavelength spectral characteristic of the transmitted light in each of the first viewing angle direction, the second viewing angle direction, and the third viewing angle direction. A wavelength that is a certain width larger than the maximum wavelength among the wavelengths giving the minimum value of
Retilt angle measuring device .