KR20100048907A - Method and apparatus for measuring tilt angle of liquid crystal cell - Google Patents

Abstract

PURPOSE: A method and an apparatus for measuring a tilt angle of a liquid crystal cell are provided to measure a tilt angle of a liquid crystal in a macro spot optical system. CONSTITUTION: A light detector(24) extracts a polarizing component of a direction vertical to a polarizing component in a surface vertical to a progressing direction of light. A detector(26) measures light strength of light transmitted through the light detector. A data processing device(27) calculates a light strength transmittance based on the light strength detected in the detector. The data processing device obtains a tilt angle of the liquid crystal using an normal light refractive index, an abnormal light refracting index, an angle and the thickness of the liquid crystal.

Description

Method and apparatus for measuring tilt angle of liquid crystal cell {METHOD AND APPARATUS FOR MEASURING TILT ANGLE OF LIQUID CRYSTAL CELL}

According to the present invention, a liquid crystal (hereinafter referred to as "VA liquid crystal") in a vertical alignment (VA) mode or a liquid crystal (hereinafter referred to as "IPS liquid crystal") in a horizontal alignment (IPS; In Plain Switching) mode is displayed on a panel. The method and apparatus which measure the tilt angle of the said liquid crystal cell in the sealed state are related.

This invention relates to the method and apparatus which especially measure the tilt angle of the said liquid crystal cell in the VA liquid crystal cell which has a multidomain structure.

The multi-domain structure of VA liquid crystal cell is shown in FIG. In each pixel region of the liquid crystal cell in which the liquid crystal is injected between the opposing glass substrates 11 and 12, a projection-shaped structure 31 is provided on the surface or the bottom of the alignment film on one glass substrate 12. By this structure, the orientation of the liquid crystal molecule a in each area | region (called a domain) in one pixel is inclined in each direction for every domain.

When the voltage is off, each liquid crystal molecule a is slightly inclined in each direction with respect to the substrate surface for each domain because of the structure 31 (this angle is referred to as a "tilt angle", especially when no voltage is applied). Also called `` pretilt angle '' in the sense of tilt angle). When a voltage is applied, the liquid crystal molecules fall largely in the inclined direction in advance. Since this fall-out direction becomes each direction for every domain in a pixel, the outstanding liquid crystal display with a wide viewing angle is obtained.

As a method of measuring the pretilt angle of the conventional VA liquid crystal cell, the light beam which has a single wavelength is irradiated to the liquid crystal cell from the side in which the polarizer was arrange | positioned in the state which arrange | positioned the polarizer and the analyzer on both surfaces of the liquid crystal cell. At this time, the liquid crystal cell is inclined in the specified direction of the liquid crystal cell while maintaining the transmission axes of the polarizer and the analyzer respectively at a predetermined angle (for example, orthogonal or parallel). Thereby, the visual dependence of the transmitted light intensity of the liquid crystal cell detected at the analyzer side at each inclination angle is measured, and the pretilt angle of the liquid crystal molecule is determined based on the angle of the symmetry point (so-called crystal rotation method). For references, see Japanese Patent Application Laid-Open No. 2008-58865 and International Publication No. 01/22029 pamphlet.

By the way, in the conventional method mentioned above, since the transmitted light intensity of a liquid crystal cell is measured multiple times, changing the angle of a liquid crystal cell, measurement takes time.

In addition, in the case of a liquid crystal cell having a multi-domain structure, only the measurement of the average tilt angle over many domains can be performed in the macroscopic optical system of the conventional method described above (that is, the tilt of the individual domains may be canceled out). . Therefore, if the tilt angle was to be measured for each domain, it was necessary to match the measurement spot to the size of the domain using a microscopic optical system. For this reason, a precise brown rice optical system was needed.

It is an object of the present invention to provide a method and apparatus for measuring the tilt angle of a liquid crystal cell that is sufficient to measure the transmitted light intensity of the liquid crystal cell once and that does not require a microscopic optical system.

In the present invention, reference numerals in parentheses denote reference numerals of corresponding components in the following [Specific Contents for Implementation of the Invention], but the scope of the claims is not limited by these reference numerals.

The tilt angle measuring method of the liquid crystal cell of this invention extracts the light of a linearly polarized light component from the light of the light source 21, and transmits the light of this polarized light component to the liquid crystal cell 23, and the optical axis B of the said light is a liquid crystal cell ( 23 and irradiated so as to be at an oblique angle θ, and in a direction perpendicular to the linearly polarized light component of the light transmitted through the liquid crystal cell 23, that is, perpendicular to the propagation direction of light. The light intensity transmittance Tc is obtained based on the light intensity in the polarization component, and the light intensity transmittance Tc, the normal light refractive index no and the abnormal light refractive index ne of the liquid crystal, the angle θ and And the tilt angle β of the liquid crystal using the thickness d of the liquid crystal.

According to this method, the tilt angle β of the liquid crystal can be obtained by only setting the angle θ to a predetermined value and measuring it once.

The process of calculating the tilt angle β of the liquid crystal is performed in this projection surface when the tilt angle β of the liquid crystal and the tilted liquid crystal are projected in a plane perpendicular to the traveling direction of the light in the liquid crystal cell. The first step of obtaining the relationship between the tilt angle β 'of the liquid crystal as a function of the oblique angle θ (called a first function), the tilt angle β of the liquid crystal, and the projection surface It may also include a second step of obtaining a relationship with the tilt angle β 'of the liquid crystal as a function (called a second function) of the light intensity transmittance Tc.

The first function includes a refractive index n of the liquid crystal as a variable, and the second function includes a refractive index difference Δn between the normal light refractive index no and the abnormal light refractive index ne and an optical path length within the liquid crystal. (d ') may be included as a variable, respectively.

If the liquid crystal cell 23 contains a plurality of domains D in one pixel, and the liquid crystal is a liquid crystal cell 23 tilted in a different direction for each domain D, the light intensity transmittance Tc is a liquid crystal. It is preferable to include the ratio of the area of the domain which the tilt angle (beta) faces in the direction not parallel to the optical axis B among the areas of the whole domain of the cell 23 as a coefficient A. As shown in FIG. By considering this coefficient A, the tilt angle β toward each direction can be obtained without canceling each other in the range in which light is irradiated to the liquid crystal cell 23.

The light intensity transmittance Tc is obtained by dividing the light intensity in the polarization component of the light transmitted through the liquid crystal cell 23 directly with the polarization component by the light intensity of the light as it passes through the liquid crystal cell 23. Can be calculated

In addition, the said light intensity transmittance | permeability Tc has the light intensity in the polarization component of the light which permeate | transmitted through the liquid crystal cell 23 directly to a polarization component, and is orthogonal to the polarization component of the light which permeate | transmitted through the liquid crystal cell 23. You may calculate by dividing by the total value of the light intensity in the polarization component of the phosphorus direction, and the light intensity | strength in the polarization component of the direction parallel to a polarization component of the light which permeate | transmitted the liquid crystal cell 23. FIG.

The tilt angle measuring method of the liquid crystal cell of the present invention uses the normal light refractive index (no) and the abnormal light refractive index (ne) of the liquid crystal as a function of the wavelength (λ), and uses the angle (θ) and the thickness (d) of the liquid crystal. By using the tilt angle β of the liquid crystal molecules as a parameter, the relationship [Tc (λ, β)] between the light intensity transmittance Tc and the wavelength lambda is obtained, and the light intensity transmittance (for a plurality of wavelengths lambda) is obtained. The tilt angle β may be obtained by measuring Tc and applying the measured points λ and Tc to this relationship Tc (λ, β). This method measures the light intensity transmittance Tc at a plurality of wavelengths and applies it to the relationship [Tc (λ, β)] between the light intensity transmittance Tc and the wavelength [lambda], thereby more accurately the tilt angle [beta]. Can be obtained.

In the tilt angle measuring device of the present invention, the optical axis B of the polarizer 22 which extracts the linearly polarized light component from the light of the light source 21 and the light of the polarizer 22 to the liquid crystal cell 23 is the liquid crystal cell. The optical axis setting device which can be irradiated by making it become the normal line and oblique angle (theta) of (23), and the direction perpendicular | vertical to the polarization component of the light which permeate | transmitted through the liquid crystal cell 23 (surface perpendicular | vertical to the direction to which light propagates). Analyzer 24 for taking out the polarization component in the direction perpendicular to the inside, detector 26 for measuring the light intensity transmittance Tc of the light transmitted through the analyzer 24, and this light intensity transmittance Tc ), The data processing apparatus 27 for obtaining the tilt angle β of the liquid crystal using the normal light refractive index no and the abnormal light refractive index ne of the liquid crystal, the angle θ, and the thickness d of the liquid crystal. It is to be provided.

The said data processing apparatus has the tilt angle (beta) of the said liquid crystal, and the tilt angle (beta ') of the liquid crystal in this projection surface at the time of projecting the tilted liquid crystal in the surface perpendicular | vertical to the advancing direction of the light in the said liquid crystal cell. Is a first processing device that obtains a relation as a function of the oblique angle θ (called a first function), the tilt angle β of the liquid crystal, and the tilt angle β 'of the liquid crystal in the projection surface. May include a second processing device that obtains the relation as a function of the light intensity transmittance Tc (called a second function).

The first function includes a refractive index n of the liquid crystal as a variable, and the second function includes a refractive index difference Δn between the normal light refractive index no and the abnormal light refractive index ne and an optical path length within the liquid crystal. (d ') may be included as a variable, respectively.

In addition, the tilt angle measuring device of the present invention further includes a spectrometer 25 for spectroscopy of the light transmitted through the analyzer 24, the data processing device 25 is the normal light refractive index (no) and the abnormal light of the liquid crystal The refractive index ne is stored as a function of the wavelength λ, the tilt angle β of the liquid crystal molecules is used as a parameter using the angle θ and the thickness d of the liquid crystal, and the light intensity transmittance Tc. The tilt angle may be obtained by obtaining the relationship [Tc ([lambda], [beta])] between the wavelength and the wavelength [lambda] and applying the measurement point of the light intensity transmittance Tc measured for the plurality of wavelengths [lambda] to this relationship. .

As mentioned above, according to this invention, the outstanding effect which made the tilt angle measurement of a liquid crystal possible also in the optical system of a macro spot does not need a microscopic optical system.

The above-mentioned or another advantage, characteristic, and effect in this invention become clear by description of embodiment described below with reference to an accompanying drawing.

<Device configuration>

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the measuring apparatus which implements the pretilt angle measuring method of this invention.

This measuring device passes through a light source 21 such as a halogen lamp, a polarizer 22 which extracts linearly polarized light from the emitted light of the light source 21, a VA liquid crystal cell 23 and a VA liquid crystal cell 23 provided on the sample mounting table. Detector 24 for extracting linearly polarized light from one light, monochromator 25 for obtaining monochromatic light from light passing through analyzer 24, and detector for detecting the intensity of light emitted from monochromator 25 And a data processing device 27. Instead of the monochromator 25, a polychromator may be disposed. In the case where the monochromator 25 is used, the position of the monochromator 25 may be between the polarizer 22 and the light source 21.

When irradiating the light emitted from the light source 21 to the VA liquid crystal cell 23, the size of the irradiation spot is not limited. It is not necessary to adjust to a narrow spot that contains only one domain.

The polarizer 22 has its polarization direction set such that an electric field of light creates a polarized light (p polarized light) which vibrates in parallel with respect to the incident surface (surface including the traveling direction of the light and the normal line y of the liquid crystal cell). Since the polarizer direction is set in the direction perpendicular to the plane including the traveling direction of light and the normal line y of the liquid crystal cell, the analyzer 24 is placed in the state of the so-called "cross nicol". The passing light can be detected.

The polarizer 22 and the analyzer 24 are fixed to one frame, and the incident angle (theta) to the VA liquid crystal cell 23 can be changed by rotating this frame by a motor. The data of the rotation angle of the motor is input to the data processing apparatus 27 together with the output signal of the detector 26.

In addition, in order to change the incident angle (theta) to VA liquid crystal cell 23, you may employ | adopt the mechanism which fixes a frame and inclines the sample mounting table which mounts VA liquid crystal cell 23. As shown in FIG.

It is a figure which shows the modification of a measuring apparatus. This measuring apparatus differs from the apparatus of FIG. 1 in that the polarizer 22 has a polarization (s) in which an electric field of light vibrates perpendicularly to the incident surface (surface including the traveling direction of the light and the normal line y of the liquid crystal cell). Polarization direction is set to create polarization. Since the polarizer direction is set in the direction perpendicular | vertical to the polarizer 22, the analyzer 24 can detect the light which passed the analyzer 24 in the state of what is called "cross nicol".

Measurement principle

FIG. 3 is a plan view showing the tilt direction in the pixel at the time of voltage-off in the liquid crystal cell of the multi-domain vertical alignment (MVA) mode. FIG.

The rectangular frame represents one pixel P, which is divided into four domains D1 to D4. When the angle is defined here, the upper direction is set to 0 degrees and the clockwise direction is set to 90 degrees, 180 degrees, and 270 degrees. Of the four domains D1 to D4, the upper right domain D1 is 0 to 90 degrees, the lower right domain D2 is 90 to 180 degrees, and the lower left domain D3 is 180 to 270 degrees. It is assumed that the domain D4 in the region, the upper left, is in the region of 270 to 360 degrees (0 degrees).

The liquid crystal molecules a1 pretilted in the direction of the upper right 45 degrees are aligned to the right upper domain D1, and the liquid crystal molecules a2 pretilted in the direction of the lower right 135 degrees are aligned to the right lower domain, and the left side is aligned. The liquid crystal molecules a3 pretilted in the direction of the lower left 225 degrees are aligned in the lower domain, and the liquid crystal molecules a4 pretilted in the direction of the upper left 315 degrees are aligned in the left upper domain. Thus, the orientation of liquid crystal molecules is inclined in four directions for each domain.

In the example of FIG. 3, the liquid crystal is tilted in four directions at intervals of 90 degrees, but the optical axis of the optical system is inclined in one of these directions. This inclined optical axis is called "optical axis B." Specifically, light is irradiated toward the direction of 135 degrees below right from the direction of 315 degrees left upper. Then, the direction of the apparent liquid crystal molecules a1 to a4 as seen from the optical axis B becomes as shown in FIG. 4.

In FIG. 4, liquid crystal molecules are filled between the upper and lower glass substrates 11 and 12 in the liquid crystal cell. The normal direction perpendicular to the surfaces of the glass substrates 11 and 12 is y and the direction perpendicular to the optical axis B and parallel to the surfaces of the glass substrates 11 and 12 is x. Liquid crystal molecules are oriented in the directions corresponding to the four pretilt directions. The liquid crystal molecules a1 appear to be inclined to the left in the x-y plane when viewed from the optical axis B. FIG. The liquid crystal molecules a3 appear to be inclined to the right in the x-y plane when viewed from the optical axis B. FIG. The liquid crystal molecules a2 and a4 look as if they are not inclined when viewed from the optical axis B. FIG.

FIG. 5 is an optical path diagram showing how light propagates through the liquid crystal filled between the glass substrates 11 and 12. The direction perpendicular to the glass substrates 11 and 12 is y, the optical axis B is included, and the direction parallel to the surface of the glass substrate 11 is z, and the light is angled from the y axis in the yz plane. θ) is inclined. When the refractive index of the liquid crystal is n, the optical axis tilt angle θ 'inside the liquid crystal is

Appears. In addition, when the optical path length d 'inside the liquid crystal is a distance (cell gap) between the glass substrates 11 and 12, "d",

Appears.

FIG. 6 is a coordinate diagram illustrating an optical axis B through which light propagates and respective coordinate axes x, y, and z in the liquid crystal. The liquid crystal molecules a3 are inclined in the xy plane with respect to the normal direction y of the glass substrates 11 and 12, and the liquid crystal molecules a1 are inclined in the xy plane with respect to the direction y. －Β) It is inclined. The angle β is

Appears. The optical axis B is inclined at an angle θ 'with respect to the direction y in the y-z plane.

Here, the plane x-y 'perpendicular to the optical axis B is defined. Then, the liquid crystal molecules a3 in the plane x-y are projected onto the plane x-y '. This projected liquid crystal molecule is described as a3 '. It is assumed that the liquid crystal molecules a3 'are inclined at an angle β' on the plane (x-y ') with respect to the y' axis. Angle (beta ') shows the axial shift of the liquid crystal molecule seen from the direction of the optical axis B, and is

Appears.

The relationship between the coordinate y 'on the plane x-y' of the liquid crystal molecule a3 'and the coordinate y on the plane xy is the plane x-y' and the plane xy. Considering that the angle formed by) is 90 degrees -θ ',

to be.

Therefore, the relationship between the angle β 'and the angle β is obtained by using the above formulas [Equation 1] [Equation 4] and [Equation 5].

.

On the other hand, the refractive index n of the liquid crystal is the case where the incident polarization is s polarization (Fig. 2),

When the incident polarization is p polarized light (Fig. 1),

Appears. Here, the term "s-polarized light" means a surface in which an electric field of light includes an incident surface [the traveling direction of light and the normal line y of the liquid crystal cell; y-z plane] refers to the polarized light vibrating perpendicularly, and the term "p-polarized light" refers to the polarized light in which the electric field of light vibrates in parallel with respect to the incident surface described above. The installation of FIG. 1 corresponds to p-polarized light, and the installation of FIG. 2 corresponds to s-polarized light. In addition, no is the normal light refractive index of liquid crystal, ne is the abnormal light refractive index of liquid crystal, and all are constants of a liquid crystal. Incident angle [theta] is a constant inherent to the measurement system.

When the polarization of light is s-polarized light, the relationship between β and β 'can be known using these Equations 6 and 7. In addition, when the polarization of light is p-polarized light, the relationship between β and β 'can be known using these [Equation 6] and [Equation 8].

Since the object of the measuring method of the present invention is to determine β, knowing the other relational expression of β and β ', β can be determined using an equation.

Therefore, hereinafter, the relationship between β 'and β and the light intensity transmittance Tc is obtained.

By calculating the Jones matrix, the expression of the light intensity transmittance (Tc) in the cross nicol state is obtained.

Becomes Here, the refractive index difference Δn is the difference between the refractive index ne of the extra ordinary wave at the time of the oblique incidence and the refractive index no of the normal wave. d 'is the optical path length inside the liquid crystal of the light as described above. λ is the wavelength of light inside the liquid crystal. However, the coefficient A is mentioned later.

When the angle formed between the optical axis B and the liquid crystal molecules a3 is θa (see FIG. 6), between the angle θa and the incident angle θ ′ of light and the tilt angle β of the liquid crystal molecules,

There is a relationship. Using this angle θa, the refractive index difference Δn is expressed by using the normal light refractive index no of the liquid crystal and the abnormal light refractive index ne of the liquid crystal.

Given by This equation can be applied to both p-polarized light (FIG. 1) and s-polarized light (FIG. 2). In this way, the refractive index difference Δn becomes a function of β.

In Equation (9), since Tc is an amount that can be measured by the detector 26, Equation (9) is an expression representing the relationship between β and β '. Therefore, β can be obtained by solving two relational expressions in combination with [Equation 6] and [Equation 7] (or [Equation 6] and [Equation 8]).

The coefficient A described above will be described here, where A is the ratio of the existence of liquid crystal molecules in which the tilt angle β is not parallel to the optical axis B in the liquid crystal cell in the multi-domain vertical alignment (MVA) mode. That is, in each pixel, as shown in FIG. 4, the liquid crystal molecules a2 and a4 in which the tilt angle β is parallel to the optical axis B, and the tilt angle β are not parallel to the optical axis B. Liquid crystal molecules a1 and a3 are present. Liquid crystal molecules a2 and a4 in which the tilt angle β is parallel to the optical axis B have β ′ = 0 in Equation 9, and do not transmit light.

Intuitively, the light incident in the direction of the optical axis B as shown in Fig. 4 passes through the liquid crystal cell as it is without changing the polarization state by the liquid crystal molecules a2 and a4. Since the measuring apparatus of this invention is set to the state of cross nicol, the light which passed the liquid crystal cell as it is is completely interrupted by the analyzer 24. As shown in FIG. Therefore, the liquid crystal molecules a2 and a4 whose tilt angle β is parallel to the optical axis B do not contribute to the transmission of light.

The coefficient A can be called "the ratio of the liquid crystal molecules whose tilt angle (beta) is not parallel to the optical axis B among all the liquid crystal molecules inside a liquid crystal." This "ratio" is assuming that the liquid crystal molecules are evenly distributed in the liquid crystal cell. "In the area of all the domains of the liquid crystal cell, the domain of the liquid crystal molecules in which the tilt angle (beta) is not parallel to the optical axis B exists. Ratio of area ”.

As shown in FIG. 4, when one pixel P is divided into four domains D1 to D4 and liquid crystal molecules are present in the same number in each of the domains D1 to D4, they are directed in different directions by 90 degrees.

Coefficient (A) = [ratio of liquid crystal molecules (a1, a3) in liquid crystal molecules (a1 to a4)] = 0.5

.

<Measurement procedure>

(1) Measurement procedure 1

The measurement procedure by this invention is demonstrated based on a flowchart (FIG. 7).

First, in the measuring apparatus of FIG. 1 or FIG. 2, the liquid crystal cell 23 used as a sample is set, the white light is irradiated with a predetermined range spot from the light source 21, and the incident angle (theta) is set to a certain value. The incidence angle θ is preferably selected from the range of 25 degrees to 80 degrees.

The reason why the "range of 25 degrees to 80 degrees" is preferable is that the extinction ratio is generally about 10 ^-5 even if a polarizing element has a good performance. Accordingly, when a light intensity transmittance (Tc) <10 ^-4, is believed due to the background noise measurement jindago troubled. Therefore, under the conditions of the following Table 1, when the pretilt angle = 1 degree, 25 degrees was set as a lower limit as the incident angle (theta) which becomes light intensity transmittance Tc <10 <^-4> or more.

The reflectance at the cell surface (glass) is about 54% for s-polarized light and about 23% for p-polarized light (assuming the refractive index of glass is 1.5) when θ = 80 degrees, but rapidly increases after 80 °. Therefore, 80 degrees was set as an upper limit as incident angle (theta). If the incidence angle θ is too large than this range, the reflection on the surface of the liquid crystal cell 23 becomes large and the transmittance decreases, so that the S / N of the measurement becomes worse.

For example, the incident angle [theta] is set to 45 degrees.

The wavelength set by the monochromator 25 is preferably selected from the visible wavelength range.

First, a reference measurement is performed with respect to a liquid crystal cell. When the liquid crystal cell is irradiated with light, there are reflections on the surface of the liquid crystal cell 23 and absorption of a color filter substrate in addition to reflection on the surface. Therefore, the calculation process becomes complicated when the absolute light transmittance is to be obtained. Therefore, (a) only the analyzer 24 is removed from the device configuration of FIGS. 1 and 2 to obtain light intensity, or (b) the analyzer 24 is placed in a parallel nicol state in the device configuration of FIGS. The light intensities are measured in the state of and cross nicol respectively, and the total values of the two types of light intensities are referred to as reference (step S0). This reference light intensity is described as R.

Next, the intensity of light in the state of cross nicol is measured (step S1). This measurement value is divided by the light intensity R of the reference, and the quotient thereof is Tc, based on the following calculation.

The cell gap d, the refractive index ne of the extra ordinary wave, and the refractive index no of the ordinary wave of the liquid crystal cell are constants of the liquid crystal cell. Incident angle (theta) is the value set as mentioned above, and coefficient A is also a constant. Β 'is obtained by substituting these values into [Equations 9] to [Equation 11], and the tilt angle [beta] can be obtained using [Equations 6] to [Equation 8] (Step S2, Step S3). In detail, the average value of the tilt angles (beta) can be calculated | required with respect to the liquid crystal molecule which exists in the range of the spot which irradiated the VA liquid crystal cell 23 with the emission light of the light source 21.

(2) Measuring means 2-spectroscopic measurement-

The refractive index ne of the extra ordinary wave of the liquid crystal and the refractive index no of the ordinary wave are a function of the wavelength λ. Incident angle (theta), the cell gap (d), and the coefficient (A) are independent of a wavelength, and are known values. Therefore, these values are substituted in [Equations 9] to [Equation 11], and the relationship between the light intensity transmittance Tc and the wavelength [lambda] (Tc) using the tilt angle β of the liquid crystal molecules as a parameter. Find (λ, β).

For example, as the abnormal light refractive index ne and the normal light refractive index no of the liquid crystal

Using the data in Table 1, the incident angle (θ) = 45 degrees, the cell gap (d) = 3.2 µm, the coefficient (A) = 0.5, and the tilt angle (β) is 1 degree, 2 degrees and 3 degrees. Assuming that the relationship Tc (?,?) Between the wavelength? And the light intensity transmittance Tc was calculated, the graph shown in FIG. 8 was obtained.

Using this graph, the tilt angle β can be accurately determined by measuring the light intensity transmittance Tc for a plurality of wavelengths and plotting the measured points on this graph.

As mentioned above, although embodiment of this invention was described, implementation of this invention is not limited to said form. For example, in the above description, the liquid crystal cell is divided into a plurality of domains within one pixel and tilted in each direction for each domain, but even in the case of a liquid crystal cell which does not have a domain and is tilted in a single direction, By making the optical axis incline in a direction different from the tilt direction, equivalent measurements are possible. In this case, the value of the coefficient A is "1". In addition, various changes can be made within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the measuring apparatus which implements a pretilt angle measuring method.

2 is a configuration diagram of a measuring device according to another embodiment of implementing a pretilt angle measuring method.

FIG. 3 is a plan view showing the tilt direction in the pixel at the time of voltage-off in the liquid crystal cell of the multi-domain vertical alignment (MVA) mode. FIG.

4 is a schematic diagram illustrating the directions of liquid crystal molecules a1 to a4 as seen from the optical axis B. FIG.

Fig. 5 is an optical path diagram showing a state in which light propagates through a liquid crystal filled between glass substrates 11 and 12;

6 is a coordinate diagram illustrating an optical axis B through which light propagates and respective coordinate axes (x, y, z) in a liquid crystal interior.

7 is a flowchart for explaining a measurement procedure of the present invention.

Fig. 8 is a graph showing the relationship Tc (λ, β) between the wavelength λ and the light intensity transmittance Tc using the tilt angle β of the liquid crystal as a parameter.

FIG. 9 is a cross-sectional view showing a multi-domain structure of a liquid crystal cell in which protrusion structures are provided between opposing glass substrates 11 and 12. FIG.

<Explanation of symbols for the main parts of the drawings>

11, 12: glass substrate

21: light source

22: polarizer

23: VA liquid crystal cell

24: analyzer

25: Monochromator

26: detector

27: data processing unit

Claims (12)

The light of the linearly polarized light component is extracted from the light source, The light of this polarization component is irradiated to a liquid crystal cell so that the optical axis of the said light may become an angle to the normal line of the said liquid crystal cell, The light intensity in the polarization component in the direction perpendicular to the polarization component in the plane perpendicular to the traveling direction of light of the light transmitted through the liquid crystal cell is measured to determine the light intensity transmittance, The tilt angle of the liquid crystal cell is obtained using the light intensity transmittance, the normal light refractive index and the abnormal light refractive index of the liquid crystal, the oblique angle, and the thickness of the liquid crystal. The process of claim 1, wherein the step of obtaining the tilt angle of the liquid crystal comprises: A method for obtaining a relationship between the tilt angle of the liquid crystal and the tilt angle of the liquid crystal in the projection surface when the tilted liquid crystal is projected in a plane perpendicular to the advancing direction of the light in the liquid crystal cell as a function of the oblique angle 1 process, The relationship between the tilt angle of the liquid crystal and the tilt angle of the liquid crystal in the projection surface when the tilted liquid crystal is projected in a plane perpendicular to the traveling direction of the light in the liquid crystal cell is obtained as a function of the light intensity transmittance. The tilt angle measurement method of a liquid crystal cell containing a 2nd process. The method of claim 2, wherein the function in the first step includes the refractive index of the liquid crystal as a variable, and the function in the second step includes a difference in refractive index between the normal light refractive index and the abnormal light refractive index and the inside of the liquid crystal. The tilt angle measurement method of a liquid crystal cell containing the optical path length of each as a variable. The liquid crystal cell of claim 1 or 2, wherein the liquid crystal cell includes a plurality of domains in one pixel, The liquid crystal is tilted in different directions for each domain, The said light intensity transmittance | permeability includes the ratio of the area of the domain which the tilt angle of the whole domain of the liquid crystal cell facing in the direction which is not parallel to the said optical axis as a coefficient, The tilt angle measuring method of a liquid crystal cell. The tilt angle of the liquid crystal cell according to claim 1 or 2, wherein an oblique angle formed by the optical axis with the normal line of the liquid crystal cell is in a range of 25 degrees to 80 degrees. The light intensity of the light transmitted through the liquid crystal cell according to claim 1 or 2, wherein the light intensity transmittance is the light intensity in the polarization component in a direction perpendicular to the polarization component of the light transmitted through the liquid crystal cell. The tilt angle measuring method of the liquid crystal cell divided by the intensity. The light intensity of the light emitted through the liquid crystal cell and the light intensity in the polarization component in a direction perpendicular to the polarization component of the light transmitted through the liquid crystal cell and the light emitted through the liquid crystal cell. The tilt angle measurement method of a liquid crystal cell calculated | required using the total value of the light intensity in the polarization component of the direction parallel to the said polarization component. The light intensity according to claim 1 or 2, wherein the tilt angle of the liquid crystal molecules is parameterized using the data of the normal light refractive index and the abnormal light refractive index of the liquid crystal as a function of the wavelength, and the angle and the thickness of the liquid crystal. Find the relationship between transmittance and wavelength, The tilt angle measurement method of a liquid crystal cell which measures the said light intensity transmittance | permeability with respect to a some wavelength, and calculates a tilt angle by applying the measurement point to the said relationship. A polarizer for taking out a linearly polarized light component from a light source, An optical axis setting device capable of irradiating light of this polarizer to the liquid crystal cell so that the optical axis of the light is at an angle to the normal of the liquid crystal cell; An analyzer for extracting a polarized light component in a direction perpendicular to the polarized light component in a plane perpendicular to the traveling direction of light of the light transmitted through the liquid crystal cell; A detector for measuring the light intensity of the light transmitted through the analyzer; Data processing for calculating the light intensity transmittance based on the light intensity detected by the detector, and calculating the tilt angle of the liquid crystal using the normal light refractive index and the abnormal light refractive index of the liquid crystal, the angle, and the thickness of the liquid crystal. The apparatus is provided, The tilt angle measuring apparatus of a liquid crystal cell. The data processing apparatus of claim 9, wherein the data processing apparatus comprises: A method for obtaining a relationship between the tilt angle of the liquid crystal and the tilt angle of the liquid crystal in the projection surface when the tilted liquid crystal is projected in a plane perpendicular to the advancing direction of the light in the liquid crystal cell as a function of the oblique angle With 1 processing unit, The relationship between the tilt angle of the liquid crystal and the tilt angle of the liquid crystal in the projection surface when the tilted liquid crystal is projected in a plane perpendicular to the traveling direction of the light in the liquid crystal cell is obtained as a function of the light intensity transmittance. Tilt angle measuring apparatus of a liquid crystal cell containing a 2nd processing apparatus. 11. The method of claim 10, wherein the function in the first processing device includes the refractive index of the liquid crystal as a variable, and the function in the second processing device includes the difference in refractive index between the normal light refractive index and the abnormal light refractive index, and the liquid crystal inside. A tilt angle measuring apparatus for a liquid crystal cell, each including an optical path length as a variable. The method according to claim 9 or 10, further comprising a spectroscope for spectroscopy of the light transmitted through the analyzer, The data processing apparatus uses the tilt angle of the liquid crystal molecules as a parameter by using the normal light refractive index and the abnormal light refractive index of the liquid crystal as a function of the wavelength [lambda], and the angle and the thickness of the liquid crystal. The tilt angle measuring apparatus for the liquid crystal cell, wherein the tilt angle is determined by obtaining the relationship between the wavelengths and applying the measurement points of the light intensity transmittance measured for the plurality of wavelengths to this relationship.

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