JPH02118406A - Liquid crystal cell gap measuring device - Google Patents

Abstract

PURPOSE:To eliminate the need of optical subtraction in consideration of the refractive index, etc., of a film which influences the optical interference of a conductive film, etc., and to simplify a calculating operation by calculating the length of the gap of a liquid crystal cell from the phase difference of double refraction of the liquid crystal cell. CONSTITUTION:Monochromatic-meter 4 selects desired monochromatic light K1 out of light beams from a light source 1 and transmits it. A polarizer 6 selects inspecting light K2 whose vibration component is in a constant single direction out of the monochromatic light K1 from the monochromatic-meter 4 and makes it pass. An analyzer 8 which is a 2nd polarizer selects detecting light K3 whose vibration component is in a single direction out of the inspecting light K2 which is transmitted through the liquid crystal cell 7 being an object to be measured and makes it pass. A detector 9 measures the intensity of the detecting light K3. Then, an arithmetic part 10 obtains the phase difference of the double refraction of the liquid crystal cell 7 from the intensity of light measured by the detector 9 and calculates the length of the gap of the liquid crystal cell 7 from the obtained phase difference of the double refraction and the known double refraction index of the liquid crystal cell 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for measuring the gap of a liquid crystal cell, that is, the thickness of a liquid crystal cell.

[Conventional technology]

Although liquid crystal display elements are widely used as display parts of various electronic devices, it is a matter of course that the display ability of this liquid crystal display element is required to be clear and safe.

One of the major causes of deterioration of the display performance of the liquid crystal display element is the liquid crystal cell gap, that is, the non-uniformity of the thickness of the liquid crystal cell. Non-uniformity in the thickness of the liquid crystal cell causes display unevenness and color unevenness in the liquid crystal display element, and deteriorates the quality of the liquid crystal display element.

Therefore, it was necessary to measure the liquid crystal cell gap as one means of checking the display ability of the obtained liquid crystal display element.

In the conventional measurement of the liquid crystal cell gap, the gap length d was calculated and measured by optical interference method from the difference in the reflected optical path of light between the front surface and the back surface of the liquid crystal cell gap.

This conventional formula for calculating the gap length d is as follows: B9 is the refractive index of the cell gap, λ1 is the value of the wavelength showing the maximum or minimum due to interference in the measured spectroscopic spectrum, and the order of interference at wavelength λ7 (integer or half-integer) ) is m, the order of interference m
If the deviation from an integer or half-integer is Δm, then 2n, d=(m+Δm)λ.

becomes.

In this above equation, the deviation Δm is calculated from the refractive index of the glass substrate and the film thickness and refractive index of each layer constituting the liquid crystal cell.

[Problem to be solved by the invention]

As mentioned above, the conventional method for measuring the liquid crystal cell gap length requires optical subtraction in consideration of the refractive index, film thickness, etc. of films that affect optical interference, such as conductive films and alignment films. However, there is a problem in that the operation for calculating the liquid crystal cell gap length is troublesome and complicated.

The present invention was devised to solve the above-mentioned problems in the conventional technology, and eliminates the influence of conductive films, alignment films, etc. in calculating the liquid crystal cell gap length, thereby simplifying the operation of calculating the liquid crystal cell gap length. The purpose is simply to make it achievable.

[Means to solve the problem]

The means of the present invention to achieve the above objects include: having a suitable light source; having a monochromator that selectively transmits desired monochromatic light from among the light rays from the light source; and selecting from the monochromatic light transmitted through the monochromatic meter. It has a polarizer that selectively passes the inspection light, which is a constant unidirectional vibration component, and selectively passes the detection light, which is a unidirectional vibration component, from the test light that has passed through the liquid crystal cell that is the object to be measured. having an analyzer that is a second polarizer, having a detector that measures the light intensity of the detected light obtained by the analyzer, and having a detector that measures the light intensity of the detected light obtained by the detector; The present invention further includes a calculation unit that calculates the birefringence phase difference of the liquid crystal cell from the above and calculates the gap length of the liquid crystal cell from this birefringence phase difference and the known birefringence index of the liquid crystal cell.

Note that the relative angle between the polarization axis direction of the polarizer and the polarization axis direction of the analyzer is 90', and both polarization axis directions are inclined at 45 degrees with respect to the alignment direction of liquid crystal molecules of the liquid crystal cell.

[Effect]

The relative angle between the polarization axis direction of the polarizer and the polarization axis direction of the analyzer is 90°, and the polarization axis directions of both are inclined at 45° with respect to the orientation direction of the liquid crystal molecules in the liquid crystal cell. Since the light that passes through is monochromatic, the liquid crystal cell will be placed under a crossed Nicol situation.

Therefore, the intensity of the monochromatic light that has passed through the liquid crystal cell, which is an optically anisotropic body (birefringent body), that is, the intensity of the detected light Bz measured by the detector, is: B" - A"sin"2θ・sin”πR/λ.
(1) However, Az is the intensity of the polarized light wave incident on the liquid crystal cell, θ is the angle between one of the vibration directions of the liquid crystal cell and the vibration direction of the polarizer, and λ. is the wavelength of the monochromatic light used in the measurement, and R is the retardation Δnd. Further, d in retardation R=Δnd is the thickness of the liquid crystal cell, that is, the liquid crystal cell gap length.

is required.

Separately, the birefringence Δn of a liquid crystal cell whose cell gap length d is measured is given as Δn×nX−ny (2) and is known as a value specific to each liquid crystal cell.

From equation (1), which indicates the intensity B2 of this detected light, and equation (2), which indicates the birefringence Δn of the liquid crystal cell, the retardation R
= Δnd, the cell gap length d is calculated.

[Example] Hereinafter, an example of the apparatus of the present invention will be described with reference to the drawings.

FIG. 1 shows the basics of the optical path configuration of the optical system in the device of the present invention. A first reflecting mirror 3 guides light to a monochromator 4, and a constant wavelength λ is selected from among the incident light from the light source 1. A monochromatic meter 4 that selectively passes only the monochromatic light from the monochromatic meter 4, a second reflecting mirror 5 that guides the monochromatic light from the monochromatic meter 4 to a polarizer 6, and A polarizer 6 that absorbs light in a direction of 45° with respect to the orientation direction of liquid crystal molecules of the liquid crystal self, that is, the direction of the polarization axis is 45° with respect to the orientation direction of liquid crystal molecules, and this polarizer 6 In the inspection light that has passed through the liquid crystal self, it absorbs the light component from 2 in the direction of 45'' on the opposite side to the polarization direction of the polarizer 6 with respect to the alignment direction of the liquid crystal molecules of the liquid crystal self, i.e. An analyzer 8 as a second polarizer whose direction of polarization axis is displaced by 90 degrees with respect to the polarization axis of the polarizer 6, and the detected light obtained by passing through this analyzer 8, A detector 9 that measures the strength B2 and this detector 9
The calculation unit 10 calculates the cell gap length d from the measurement results obtained using the equations (1) and (2).

In the embodiment shown in FIG. 1, when a liquid crystal self having a constant thickness R is observed with white light under crossed Nicols, in equation (1), R/λ,=m (m=o, 1 ,2. ・ ・ ・
)... (3) Since the light intensity Bt is minimum, the minimum wavelength λ in the measured spectrum. The interference order m is determined and the liquid crystal self-adhesion tarpaulsion R is calculated.

That is, in the embodiment shown in FIG. 1, the monochromatic meter 4 provides monochromatic light with a wavelength λ of 1. Then, the minimum value on the shortest wavelength side in the spectrum is selected, and this minimum wavelength λ is determined. The calculation unit 10 determines the interference order m in the retardation R.
The cell gap length d is calculated from the relationship R=Δnd and equation (2).

For example, the sample liquid crystal self-adhesive tarpaulin R is 530
When it is nm, the wavelength λ. 400nm ~800r+
The horizontal axis shows the wavelength λ. , the vertical axis is the detected light B
When 2 is taken and displayed in a graph, it becomes the solid line (a) in FIG. 2(a). Using this graph, the calculation unit 10 calculates the minimum wavelength λ. =530nm is detected, and this interference order m=1
．． By determining 0, retardation R=530 nm is measured from the above equation (3). As a result,
The cell gap length d is calculated from equation (2) from the measured turpitude R and the birefringence Δn of the liquid crystal self, which is a known input.

FIG. 2(b) shows the minimum wavelength λ obtained using a similar method. =
500 nm and interference order m=2.0, retardation R=1000 nm is obtained, and the cell gap length d is determined from this result.

FIG. 3 shows the configuration of a specific example of the device of the present invention, in which, in addition to the basic components shown in FIG. , a trinocular tube 12 for determining the measurement position of the liquid crystal selfie and observing and determining the posture; a focal lens 13 of the trinocular tube 12;
an upper objective lens 14 and a lower objective lens 15 that focus on the liquid crystal self and condense the diffused light in parallel;
Observation light source 16 used for liquid crystal self-alignment operation
and a shank 17 that protects the detector 9 from light from the observation light source 16.

The operating procedure for the measuring device shown in FIG. 3 is to first operate the light source 1 and the monochromatic meter 4 with the liquid crystal display removed, and measure the wavelength λ. The intensity At of the polarized light wave incident on the liquid crystal self, that is, the inspection light in the wavelength range of =400 to 800 nm is stored in the calculation unit 10. However, in this case, the polarization axes of the polarizer 6 and the analyzer 8 are parallel to each other. That is, inspection light KZ=
Set the detection light to 3.

Next, set up the LCD selfie at the specified position, and first press shutter 1.
7 is closed to prevent the light beam from the observation light source 16 from being irradiated onto the detector 9, and the second reflecting mirror 5 is rotationally displaced so that the light beam from the observation light source 16 is irradiated onto the trinocular tube 12. After doing so, the observation light source 16 is turned on. Using the light from this observation light source 16, the upper and lower objective lenses 14
．． 15 to adjust the focus, and at the same time set the location of the liquid crystal self where the cell gap d is to be measured while adjusting the horizontal displacement of the liquid crystal self.

When the installation of the liquid crystal display is completed, the observation light source 16 is turned off, the shutter 17 is opened, and the second reflecting mirror 5 is rotated back to the measurement position to return to the measurement state. Once the return to the measurement state is complete, move the analyzer 8 to 9.
By rotating the optical system by 0" and displacing its polarization axis by 90 degrees with respect to the polarization axis of the polarizer 6, the intensity B2 of the optical system shown in FIG. At this point, the monochromator 4 is operated again to obtain the wavelength λ.=
The intensity B2 of 3 for the detection light in the range of 400 to 800 nm is stored in the calculation unit 10.

Wavelength λ. =Intensity B of detection light in 400 to 800 nm
The arithmetic unit 10 that has stored the wavelength λ is the wavelength λ. =400~8
aj/A at 00n-! Calculate the minimum wavelength λ.

And this minimum wavelength λ. Determine the interference order m at .

The second minimum wavelength λ. If and the interference order m are determined,
Since the retardation R is determined by the formula (3), the birefringence Δn of the liquid crystal self stored in advance in the calculation unit 10
Obtaining the liquid crystal cell gap length d from equation (2) [Effects of the Invention] Since the liquid crystal cell gap measuring device according to the present invention has the above-described configuration, it exhibits the following effects.

Since the liquid crystal cell gap length is calculated from the birefringence phase difference of the liquid crystal cell, there is no need for optical subtraction that takes into account the refractive index, film thickness, etc. of films that affect optical interference, such as conductive films and alignment films. year,
This makes the calculation operation extremely easy and simple.

Since the numerical values set during the measurement operation are all known values, the setting operation is easy and accurate.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the most basic optical system optical path configuration of the apparatus of the present invention. Figure 2 shows the spectral transmission spectrum (solid line) characteristics obtained by installing a birefringent material with a specific retarpsion in the optical system of Figure 1.
a) shows the case where the beam tardage is 530 nm; FIG. 2(b) shows the case where the beam tarp John is 11000 nm. FIG. 3 is a partial layout diagram showing a specific example of the configuration of the device of the present invention configured to actually measure the liquid crystal cell gap. Explanation of symbols 1; light source; 2; condensing lens; 3; first reflecting mirror; 4; monochromator; 5; second reflecting mirror; 6; polarizer; 7; liquid crystal cell;
8: Analyzer, 9: Detector, 10: Arithmetic unit, KI: Monochromatic light, K2: Inspection light, K: Detection light. Applicant O-ri Manufacturing Co., Ltd. 10-Takasaiken (a) (b) Person 0 (nm) 17--Sino [-Noah Kr-(LAL K2-1 stock gorei ni 3--4th Seyo Vλshi

Claims (1)

[Claims] (1) A light source (1) and desired monochromatic light (K1) from among the light rays from the light source (1).
a monochromatic meter (4) that selectively transmits the light, and a polarizer (6) that selectively transmits the inspection light (K2), which is a constant unidirectional vibration component, from the monochromatic light (K1) from the monochromatic meter (4). ), and the inspection light (
The detection light (K3) is a unidirectional vibration component from the light (K2)
), a detector (9) that measures the light intensity (B^2) of the detected light (K3); ) The birefringence retardation (Δnd) of the liquid crystal cell (7) is determined from the light intensity (B^2) measured at
A liquid crystal cell gap measuring device comprising: a calculation unit (10) that calculates the gap length (d) of the liquid crystal cell (7) from the birefringence (Δn=n_x−n_y) of the liquid crystal cell (7);