JPS62229223A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To prevent the degradation in display quality due to a difference of hue on a screen which is caused by the unevenness of cell thickness, by providing a color filter in the cell incorporating a liquid crystal, between a transparent electrode substrate and a polarizing plate, or in the polarizing plate. CONSTITUTION:Substrates 12a and 12b are provided with transparent electrodes 13a and 13b, and oriented films 14a and 14b are provided to face each other. A nematic liquid crystal 18 is charged between oriented films 14a and 14b. Polarizing plates 19a and 19b are provided on the outside of substrates 12a and 12b. A twisting angle 16 of liquid crystal molecules 15 is set to 150-300 deg. to constitute a liquid crystal display element. A color filter 11 which absorbs the light having <=550nm wavelength is provided on the surface of the polarizing plate 19a of the liquid crystal display element. The color filter 11 may be provided in the cell, between the substrate 12a and the polarizing plate 19a, or in the deflecting plate 19a. Since the color filter is provided, the difference of hue on the same picture is reduced though the cell thickness is not uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquid crystal display element used as a large-sized, large-capacity flat display used in image display devices, computer terminals, and the like.

(Summary of the Invention) The present invention relates to a liquid crystal display element used as a large-sized, large-capacity flat display used in image display devices, computer terminals, etc. The twisted helix angle of the lυ structure is 1
In a liquid crystal display element within the range of 50 degrees to 300 degrees, the inside of the cell with the liquid crystal sandwiched, between the electrode substrate and the polarizing plate, inside the polarizing plate, or in contact with the surface of the polarizing plate, in a specific wavelength range. By providing an absorbing color filter, the difference in hue within the screen is reduced and display quality is significantly improved.

(Conventional technology) In recent years, liquid crystal display elements have become larger and larger in capacity.
In particular, the twist lν angle of the nematic liquid crystal is made larger than that of conventional twisted nematic liquid crystal display elements, so that the absorption axis or transmission axis of the polarizing plate and the liquid crystal molecule alignment direction of the adjacent electrode substrate are in the range of 20 degrees to 70 degrees. The birefringence effect (R, A, 5oref a
nd H, J, Rafuse, J, ^pplPhys.
, 43.2029 (1972)), a large-capacity display with a pixel count of 600 x 400 dots or more has been put into practical use. However, these liquid crystal display elements that utilize the birefringence effect have extremely large changes in hue with respect to the uniformity of cell thickness, leading to manufacturing difficulties and a significant deterioration in display quality.

(Problems to be Solved by the Invention) The present invention provides an electric field controlled birefringence effect in which the twist lυ angle of the helical structure of liquid crystal molecules is within the range of 150 degrees to 300 degrees, for large size, large capacity, and large screens. This is intended to prevent deterioration in display quality due to differences in hue within the screen, which occurs in liquid crystal display elements that utilize .

(Means for Solving the Problems) Therefore, as shown in FIG. In a liquid crystal display element that utilizes an electric field-controlled birefringence effect within the range of
Alternatively, by providing a color filter that absorbs in a specific wavelength range in contact with the surface of the polarizing plate, the difference in hue within the screen is reduced and a liquid crystal display element with high display quality is promoted.

(Function) The twist helix angle of the helical structure of liquid crystal molecules is 150DI
A liquid crystal display device that utilizes an electric field-controlled birefringence effect within the range of 300 degrees from As the contrast becomes steeper and the contrast improves, it can now be used as a large-capacity, single-segment display element. Since the birefringence effect is utilized by taking an angle in the range of , the change in hue with respect to the uniformity of cell thickness is extremely large, leading to a deterioration in display quality. Therefore, the present invention focuses on the fact that the difference in hue when no voltage is applied due to a change in cell thickness is caused by a difference in the transmittance of light in a specific wavelength range. By installing a color filter, differences in hue due to non-uniform cell thickness are reduced and display quality is improved.

(Example) Next, embodiments of the present invention will be described in detail using the drawings.

1. First, a cell as shown in Figure 1 was created.

Here, 12a, 12b C/J lath board, 13a
113b is a transparent electrode, 14a and 14b are alignment films, 15 is a liquid crystal molecule, and 17a and 17b are alignment directions. The twist helix angle 16 formed by the helical structure of liquid crystal molecules is 18
It was set to 0 degrees. The sealed liquid crystal 18 is a nematic liquid crystal mixture whose main components are PCH-based, biphenyl-based, 1-transalkyldicyclohexyl 4-n alkoxyphenyl, and 4-n alkoxyphenylcarbonyl trans-n alkylcyclohexyl liquid crystals, and HQr as an optically active substance.
A sample containing S-811 manufactured by Ck Company was used.

In this cell, two polarizing plates 19a and 19b were placed parallel to each other with their transmission axes making an angle of 45 degrees to the alignment direction of liquid crystal molecules.

When the spectral characteristics of the above liquid crystal display element were measured at a certain point when no voltage was applied, they were as shown in FIG. 2. In this case, it can be seen that the element has a yellow-green color. A Canon luminance meter LC-SP model was used for the measurement.

Roughly, the distribution of cell thickness within the same plane of this element was measured at each point, and the cell thickness was 60 mm from the measurement point. When the spectral characteristics were measured at two large points, they were as shown in Fig. 3.

Calculating the color difference between the above two points, ΔEab”=17,5
It was 5.

As described above, in a liquid crystal display element that utilizes the birefringence effect, the hue changes greatly due to a difference in cell thickness, and if there is non-uniformity in the cell thickness within the plane, the display quality will be significantly degraded.

Therefore, a color filter 11 having spectral characteristics as shown in FIG. 4 was installed on the polarizing plate on the viewer's side.

Then, the spectral characteristics of the two points change as shown in the former (Fig. 5) and the latter (Fig. 6), and ΔEab" is 7.
．． It became 68.

From the above results, it can be seen that the present invention suppresses the difference in hue to a small value even in cells with non-uniform cell thickness within the plane, and the quality of the display element is significantly improved.

2. Next, one of the two electrode substrates facing each other,
A color filter was printed on the side of the light plate using Step 7.

The spectral characteristics of the color filter were as shown in Figure 7). Using this electrode substrate, a liquid crystal cell in which the helical structure of the liquid crystal molecules had a twisted helical angle of 21or+x was created. The sealed liquid crystals are POS type, phenyl type, 1-transalkyldicyclohexyl 4-n alkoxyphenyl, and 4-n alkoxyphenylcarboxylic acid 4'-
Hcrck is added as an optically active substance to a nematic liquid crystal mixture containing trans-n alkylcyclohexyl liquid crystal as the main component.
I used the one with company packaging S-811 added. In this cell, 2
A liquid crystal display cell was prepared in which two polarizing plates were installed so that their transmission axes were shifted by 45 degrees in the same direction from the alignment direction of liquid crystal molecules.

Here, as in Example 1, when we measured the spectral characteristics at two points in the same cell with a difference in cell thickness of 0°2m and calculated the color difference, we found that Δ[ab”=8°23. became.

Therefore, it was found that the same effect as in Example 1 can be obtained even if the color filter is installed between the substrate and the polarizing plate.

3. Next, a color filter was created by printing on the transparent electrode of the liquid crystal cell. The spectral characteristics were as shown in (Figure 9). A liquid crystal cell was created in the same manner as in Example 2 using this substrate. The spectral characteristics of the color filter were as shown in FIG. 8.

Regarding the above cell, the spectral characteristics of two points within the same cell with a difference in cell thickness of 0.27 were measured in the same manner as in Example 1 and Examples, and when the hue was calculated, ΔEab'' =
It became 9.72.

Therefore, it was found that the same effects as in Examples 1 and 2 can be obtained even if a color filter is installed inside the cell.

(Effects of the Invention) As explained above, according to the present invention, the difference in hue within the same plane due to non-uniform cell thickness can be reduced, and the field-controlled birefringence of a large, large-capacity single screen with high display quality can be achieved. A liquid crystal display element utilizing this effect can be provided.

[Brief explanation of drawings]

FIG. 1 is a perspective sectional view showing the structure of a liquid crystal display element of the present invention, and FIGS. 2 to 8 are graphs showing the relationship between wavelength and transmittance. 11... Color filters 12a, 12b... Glass substrates 13a, 13b... Transparent electrodes 14a, 14b... Alignment film 15... Liquid crystal molecules 16... Twisted spiral structure 17a, 17b... Direction of alignment of liquid crystal molecules 18...liquid crystal 19a, 19b, 11; + Relatives Figure 1 Figure 3

Claims (2)

[Claims] (1) A nematic liquid crystal is sandwiched between two electrode substrates, forming a spiral structure twisted within a range of 150 degrees to 300 degrees in the thickness direction, and a pair of polarizing plates sandwiching this spiral structure. was installed, and the liquid crystal was sandwiched in a liquid crystal display element in which the absorption axis or transmission axis of the polarizing plate and the liquid crystal molecule alignment direction of the adjacent transparent electrode substrate had an angle within the range of 20 degrees to 70 degrees. A liquid crystal display element comprising a color filter that absorbs in a specific wavelength range inside a cell, between a transparent electrode substrate and a polarizing plate, inside the polarizing plate, or in contact with the surface of the polarizing plate. (2) The liquid crystal display element according to claim 1, wherein the color filter is a filter that absorbs light having a wavelength of about 550 nm or less.