JPS6290619A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the time division characteristics of the titled device by specifying a twisting angle of the liquid crystal molecule to a range of 95-110 deg. in such a way that an angle between polarizing axes or absorption axes of a pair of the polarizing plates is the inside of the twisting angle of the liquid crystal molecule. CONSTITUTION:The titled device provides the liquid crystal cell twist-orientated between two electrode substrates which are facing each other, and the pair of the polarizing plates which are arranged at both sides of the liquid crystal. The rubbing direction 1 of the upper electrode almost accords with the orientation direction of the liquid crystal molecule, while, the rubbing direction 2 of the lower electrode almost accords with the orientation direction of the liquid crystal molecule. The upper electrode and the lower electrode are facing each other in such a way that the twisting direction of the liquid crystal molecule and the twisting angle 5 thereof makes to a range of 95-110 deg.. While, the angle 6 between the polarizing axis 3 of the upper polarizing plate and the polarizing axis 4 of the lower polarizing plate is the inside of the twisting angle of the liquid crystal molecule, the upper polarizing plate is arranged on the outer surface of the upper electrode substrate, and the lower polarizing plate is arranged on the outer surface of the lower electrode substrate respectively. The upper polarizing plate and the lower polarizing plate are disposed in such a way that said angle 6 is in a range of 60-80 deg.. Thus, the product DELTAn.d of the anisotropy DELTAn of the refractive index of the liquid crystal and the thickness of the liquid crystal (d) is a range of 0.5mum-0.8mum.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal display device.

[Conventional technology]

In a conventional twisted nematic (T N ) type liquid crystal display device, polarizing plates are provided above and below a liquid crystal cell with a twist angle of 90 degrees. The directions are almost the same. The TN type liquid crystal display device having such a configuration cannot fully satisfy the demand for improvement in electro-optical characteristics, especially time-division drive characteristics, which has been particularly strong in recent years.

[Purpose of the invention]

However, the conventional technology has a problem in that it is not possible to obtain sufficient contrast. The present invention is intended to solve these problems.The purpose of the present invention is to improve the time-sharing characteristics by improving the twist angle and the arrangement of the polarization axes of the polarizing plate, and also to improve the display hue. An object of the present invention is to provide a liquid crystal display device that exhibits various hues.

[Means for solving problems]

In the liquid crystal display device of the present invention, the twist angle of the liquid crystal molecules is 95
The angle between the polarization axis or the absorption axis of the pair of polarizing plates is located inside the twist angle of the liquid crystal molecules, and the angle is within the range of 60 degrees to 80 degrees, The refractive index anisotropy of the liquid crystal Δoutside and the thickness d of the liquid crystal layer (μ
It is characterized in that the product Δouter·d of m) is within the range from [L5 μm to Q,8 μm.

[Function] According to the present invention, since the liquid crystal display device has a transmitted light intensity that varies depending on the wavelength, the contrast ratio is improved and the display hue of the liquid crystal display device can have a favorable hue.

〔Example〕

FIG. 1 (α) shows the rubbing direction of the present invention and the polarization axis direction of the polarizing plate. In the figure, 1 is the rubbing direction of the upper electrode substrate, 2 is the rubbing direction of the lower electrode substrate, 5 is the polarization axis or absorption axis of the upper polarizing plate, 4 is the polarization axis or absorption axis of the lower polarizing plate, and 5 is the rubbing direction of the lower electrode substrate. The twist direction and angle of the liquid crystal molecules, 6 indicates the angle formed by the polarization axes or absorption axes of the upper and lower polarizing plates.

FIG. 1Cb) shows a model of the structure of a twisted nematic liquid crystal display device, in which a twisted nematic liquid crystal 106 is sandwiched between a pair of upper electrode substrates 102 and lower electrode substrates 105 arranged opposite to each other. is sealed with a sealant 107 and sandwiched between an upper polarizing plate 100 and a lower polarizing plate 1°1 on the outside of the upper and lower electrode substrates. Here, 1
o4 is the upper electrode W71105 is the lower electrode. That is, the rubbing direction 1 of the upper electrode substrate almost matches the liquid crystal molecule orientation, the rubbing direction 2 of the lower electrode substrate almost matches the liquid crystal molecule orientation, and the twist direction and angle 5 of the liquid crystal molecules are from 95 degrees. Upper gM so that the range is up to 110 degrees
The electrode substrate and the lower electrode substrate are arranged to face each other. On the other hand, the angle 6 formed by the polarizing axis 3 of the upper polarizing plate and the polarizing axis 4 of the lower polarizing plate is inside the twist angle 5 of the liquid crystal molecules and ranges from 60 degrees to 80 degrees. A lower polarizing plate is disposed on the outer surface of the lower electrode substrate, and a lower polarizing plate is disposed on the outer surface of the lower electrode substrate. Note that an absorption axis may be used instead of the polarization axis of the polarizing plate. At this time, the twist direction 5 of the liquid crystal molecules can be obtained by adding an optically active substance that induces the twist direction and angle 5 of the liquid crystal molecules to the nematic liquid crystal sandwiched between the upper and lower electrode substrates.

A key representing the time division drive characteristic of the liquid crystal display device having this configuration is defined as β. FIG. 2 shows general voltage-transmittance characteristics of a TN type liquid crystal display device. In the curve shown in FIG. 2, when the voltage at which the transmittance becomes 90% is vth, and the voltage at which the transmittance becomes 10% is VIO, β is defined as β knee curve vth. Further, β indicates a value of 1 or more, and the closer it is to 1, the better the time-division drive characteristics are, and the greater the contrast. Note that the normal direction of the display surface of the liquid crystal display device and the observation direction match.

[Example 1] A cell was used in which the twist angle of the liquid crystal molecules was 100 degrees and the angle formed by the polarization axis of the polarizing plate was 60c'Δn-d=0.7. As a result, the β value is t 191. This has better contrast than the conventional β value of 1,545 when the twist angle of the liquid crystal molecules is 90 degrees. At this time, the voltage vth
and V. The transmittance of each wavelength when .

[Example 2] A filter having light transmission characteristics as shown in Fig. 4 was used in Example 1.
It was placed on the outside of the polarizing plate above the cell. As a result, the light transmittance as shown in Figure 5 is #! The light transmittance becomes as shown in Figure 5, and β
The value becomes 1.180. The hue at this time is yellow.

[Example 3] A filter having light transmission characteristics as shown in Fig. 6 was used in Example 1.
It was placed on the outside of the polarizing plate above the cell. As a result, the light transmittance as shown in Figure 3 becomes the light transmittance as shown in Figure 7, the β value is as good as 1.190, and the hue of the cell is also green, which reduces eye fatigue and gives a favorable impression. It becomes a hue that can last.

〔Effect of the invention〕

As described above, according to the present invention, an extremely excellent effect can be obtained in that a liquid crystal display element with excellent time-division drive characteristics and a pleasing hue can be realized.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the relationship between the rubbing direction of the liquid crystal display element of the present invention and the polarization axis direction of the polarizing plate. In the figure, 1 is the rubbing direction of the upper electrode substrate, 2 is the rubbing direction of the lower electrode substrate, 3 is the polarization axis or absorption axis of the upper polarizing plate, 4 is the polarization axis or absorption axis of the lower polarizing plate,
5 is the twist direction and angle of the liquid crystal molecules, and 6 is the angle formed by the polarization axes or absorption axes of the upper and lower polarizing plates. The second @ is a diagram showing the relationship between general voltage and transmittance characteristics of a TN type liquid crystal display device. Figure 5 is a diagram showing the relationship between wavelength and transmittance characteristics according to Example 1 of the present invention. In the same figure, mark is the applied voltage vth, and ■ is the applied voltage v1°. FIG. 4 is a diagram showing the relationship between wavelength and transmittance characteristics of the filter used in Example 2 of the present invention. FIG. 5 is a diagram showing the relationship between wavelength and transmittance characteristics according to Example 2 of the present invention. In the same figure, mark is the applied voltage vth, and ■ is the applied voltage V. . FIG. 6 is a diagram showing the relationship between wavelength and transmittance characteristics of the filter used in Example 3 of the present invention. The tiz diagram is a diagram showing the relationship between wavelength and transmittance characteristics according to Example 3 of the present invention. In the same figure, mark is the applied voltage vth, and ■ is the applied voltage v1G. that's all

Claims (3)

[Claims] (1) A liquid crystal cell comprising a twisted oriented nematic liquid crystal sandwiched between two electrode substrates disposed facing each other, and a pair of polarizing plates disposed on both sides sandwiching the liquid crystal cell; The liquid crystal has a twist angle in the range of 95 degrees to 110 degrees, an angle between the polarization axes or absorption axes of the pair of polarizing plates in the range of 60 degrees to 80 degrees, and and the product 4n of the refractive index anisotropy Δn of the nematic liquid crystal and the thickness d of the liquid crystal layer is set so that d is within the range of 0.5 μm to 0.8 μm. LCD display device. (2) Transmittance of light in the visible range of 460 nm or less is 50%
2. The liquid crystal display device according to claim 1, wherein at least one of the following filters is disposed in a range from the outside of the upper polarizing plate to the outside of the lower polarizing plate. (3) A filter that has a transmittance of 50% or less for light with a wavelength of 300 nm to 460 nm and a transmittance of 50% or less for light with a wavelength of 580 nm to 700 nm is installed from the outside of the upper polarizing plate to the outside of the lower polarizing plate. 2. The liquid crystal display device according to claim 1, wherein at least one liquid crystal display device is disposed within a range up to an offset.