JPH01179912A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To achromatize background and display parts and to display an image in white and black by using a phase plate having a birefringent property to correct the phase with respect to the color determined by the constitution condition of a liquid crystal element. CONSTITUTION:The direction and an angle alpha of twist of liquid crystal molecules are prescribed by the rubbing direction of an arrow 28 of an upper electrode substrate 21, that of an arrow 29 of a lower electrode substrate 22, and the classification and the quantity of an optically active substance added to nematic liquid crystal. The upper limit and the lower limit of the angle alpha of twist are 270 deg. and 180 deg. respectively. An angle beta3 formed between an axis 26 of polarization of an upper polarizing plate 24 and an axis 27 of polarization of a lower polarizing plate 25 is set to 20 deg. in case of the use of the phase plate. The phase plate having the birefringent property is used to correct the phase with respect to the color of the background or display part to achromatize background and display parts, thus displaying an image in white and black.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device, and particularly to a field effect liquid crystal display device that has excellent time division drive characteristics and is capable of black and white display.

[Conventional technology]

Figure 1 shows a perspective view of a twisted nematic type liquid crystal display element, which has excellent time-division drive characteristics and is used in conventional liquid crystal display devices. 'ati substrate 1.2 by nematic liquid crystal 3 with positive dielectric anisotropy from 180 degrees to 27
It has a helical structure twisted in the range of 0 degrees, and both '11
Polarizing plates 4 and 5 were arranged outside the monopolar substrate so that the included angle between their polarization axes (or absorption axes) 6°7 was in the range of 20° to 70°.

For example, f! ! This is done by rubbing the surface of the electrode substrate in contact with the liquid crystal in one direction with a cloth, the so-called rubbing method. The rubbing direction at this time, that is, the rubbing directions 8 and 9, is the alignment direction of the liquid crystal molecules. The two electrode substrates 1 and 2 that have been oriented in this manner are rubbed in the respective rubbing directions 8,
9 are opposed to each other with a gap so that they intersect with each other in the range of approximately 180 degrees to 270 degrees, and the two ff1t & substrates 1.2 are attached with a sealant, and a positive vi is placed in the gap.
When a nematic liquid crystal 3 having dielectric anisotropy is sealed, the liquid crystal molecules are arranged in a spiral structure rotated by approximately 180 degrees to 270 degrees between the electrode substrates. Polarizing plates 4 and 5 are provided above and below the liquid crystal element configured in this way, and their polarizing axes (or absorption axes) 6 and 7 are
Each from the optimal value of contrast? The size is required to be within the range of 0 degrees to 70 degrees clockwise or counterclockwise with reference to the alignment direction of liquid crystal molecules adjacent to the 11-pole substrate.

Although FIG. 1 shows a transmissive mode in which a backlight 10 is arranged, the principle of operation in the reflective mode is essentially the same as that in the transmissive mode.

Figure 2 shows the relationship between the applied voltage and brightness of a display using a liquid crystal element with such a structure.
Two modes, oven mode A and normally closed mode B, are shown, and both have the characteristic that the brightness rises steeply with respect to the applied voltage. This characteristic is a factor that enables high time division driving without reducing contrast.

Here, time-division driving will be briefly explained using a dot matrix display as an example. As shown in FIG. 3, a striped Ylyri pole ((Ft
Place the No. group electrode 12 on the upper side'? An X electrode (scanning electrode) 11 is formed on the r1-pole substrate to display characters, etc.

In the figure, n scanning electrodes are connected to Xx, Xz,
”・XnHxt, Xi+ ... When a certain scanning electrode (Xa in the figure) is selected, which performs time-division driving by reversing Xn and repetitive line sequential scanning, all 'ii!lN on that electrode are selected. Basically, the signal electrodes 12, Yl, y, .
...Y, simultaneously adds selected or non-selected display signals according to the signals to be displayed. In this way, the scan ff1t
Lighting or non-lighting of the intersection is selected by a combination of voltage pulses applied to the signal electrode 12 and the voltage pulse applied to the signal electrode 12. Scanning electrode X in this case
The number corresponds to the number of time divisions.

However, the liquid crystal element with this excellent time-division drive characteristic
Figure 4 shows the background color or display color in blue mode for the twisted nematic type.
E chromaticity coordinates''; however, at least one of the background or the display area was colored and black and white display was not possible.

However, in recent years, demands for improving the image quality of liquid crystal display elements and increasing the amount of displayed information have become stricter, and the required specifications are as follows:
The current situation is that there is a transition from black and white displays to color displays, and we have reached a situation where this required specification cannot be satisfied.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into consideration the fact that the background and the display area are white and black, and there are limitations in terms of display quality. Furthermore, because at least one of the background or the display section is colored, black-and-white display and colorization are not possible with this prior art.

An object of the present invention is to make the background and the display part achromatic to enable black and white display as well as color display.

[Means to solve the problem]

The above purpose is to make the background and display part achromatic by correcting the phase using a phase plate having birefringence for the color determined by the configuration conditions of the liquid crystal element.
A black and white display is achieved.

[Effect]

Twisted nematic type liquid crystal devices, which have excellent time-division drive characteristics, have a color on at least one of the background or display area, or By correcting the phase of the color using a phase plate with birefringence, the background and display section are rendered achromatic. As a result, in a twisted nematic liquid crystal display device having excellent time-division driving characteristics, where at least one of the background and the display part is colored, the background and the display part are no longer colored. Black and white display is possible.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device suitable for carrying out the present invention will be described in detail below with reference to the drawings.

Figure 5 shows the arrangement direction of liquid crystal molecules (for example, rubbing direction), the twist direction of liquid crystal molecules, and the absorption axis (or polarization axis) of the polarizing plate when the liquid crystal display element according to the present invention is viewed from side 1.
It shows the direction. FIG. 6 is a perspective view showing their relationship.

The twist direction and twist angle α of the liquid crystal molecules 23 are determined by the rubbing direction 28 of the -H side electrode substrate 21, the rubbing direction 29 of the lower electrode plate 22, and the type and amount of the optically active substance added to the nematic liquid crystal. Ru. The maximum value of the twist angle α is limited by the lighting state near the threshold value, which scatters light, and the upper limit is 270 degrees.The lower limit is limited by the contrast, and the limit is 180 degrees. be.

In this embodiment, the twist angle α was set to 260 degrees because the purpose was to provide a liquid crystal element capable of self-ff1 display with sufficiently satisfactory contrast even when the number of scanning lines is 200 or more.

The angle β3 formed by the polarization axis (or absorption axis) 26 of the upper polarizing plate 24 and the polarization axis (or absorption axis) 27 of the lower polarizing plate 25 is the brightness of Con1 to Las1-9.

Considering color etc., a range of 0 degrees to 60 degrees is preferable when a phase plate is not used.
DU was used, and β♂ was set to 20 degrees. In addition, the upper polarizing plate 2
4 polarization axis (or absorption axis) 26 and lower electrode substrate 21
The angle βl formed with the rubbing direction 28 and the lower polarizing plate 25
The angle β2 formed between the polarization axis (or absorption axis) 27 and the rubbing direction 29 of the lower electrode substrate 22 is a contrast.

In consideration of brightness, color, etc., a range of 0 degrees to 60 degrees is desirable. In this embodiment, βl is set to 20 degrees, and β2 is set to 40 degrees.

Further, the liquid crystal display element according to this example has a remarkable Δn−d
Indicates n-character, contrast, and brightness.

From the viewpoint of color, when the condition of 0.4 μtn≦Δn-d≦1.0 μm is satisfied, particularly good characteristics are exhibited here.

The value of Δn has wavelength dependence, and tends to be large on the short wavelength side and small on the long wavelength side. The value of Δn used in this specification is He 0, measured at 25°C using
In this example, a nematic liquid crystal containing biphenyl liquid crystal and ester cyclohexane liquid crystal as main components was used, and 0.5% by weight of Merck's 8811 was added as an optically active substance.

In this embodiment, a liquid crystal with Δn = 0,083 was used, and the thickness of the liquid crystal envelope was 6 μm. therefore.

Δ! of the liquid crystal element of this example! 1.d was set to be o,5.

Furthermore, in the configuration of the liquid crystal display element and the polarizing plate as described above, the background color and the display part are colored as described above. A phase plate was placed to make the color achromatic.

In this embodiment, a so-called parallel alignment liquid crystal element with a twist angle α of 0 degrees was used as a phase plate for making the background color and display color achromatic.

The angle β4 between the rubbing direction 34 of the upper substrate 31 of the parallel-aligned liquid crystal element as a phase plate and the polarization axis 26 of the upper polarizing plate 24, and the rubbing direction 35 of the lower substrate 32 and the polarization axis 27 of the lower polarizing plate 25 Considering that the angle βb formed with
A range of 0 degrees to 60 degrees is desirable.

In this example, β4 is 25 degrees, β6 is 45 degrees, or β4
was set at 65 degrees, and βb was set at 45 degrees. Further, Δn-d of the parallel alignment liquid crystal element serving as the phase plate was set to 0.36.

In this embodiment, a cold cathode tube is used as the light source 15, but a hot cathode tube or an electroluminescent tube may be used.

By configuring the liquid crystal element in this manner, the background color and display color can be made achromatic.

In this example, a liquid crystal display element with a twist angle α of 260 degrees was used;
Furthermore, even in a larger range, the background color and display color can be made achromatic.

In this embodiment, a cold cathode tube is used as the light source 15, but a similar achromatic color can be obtained even by using an external light type that uses a reflector without using a light source.

Figure 7 shows the colors of the background and display area in this example.
Shown in E chromaticity coordinates. As shown in the figure, both the background color and the color of the display section are intangible colors near the C light source, indicating that the display is black and white.

Further, the contrast ratio, which is the ratio of the brightness during self-display to the brightness during black display, is 9:1 at this time.

FIG. 8 shows the configuration of a liquid crystal element according to another embodiment suitable for carrying out the present invention. As shown in the same figure, the twist angle α shown in FIG. 0.5, the twist angle α is 260 degrees and Δn・d
A guest-host type liquid crystal display element with a value of 0.5 is used, and the other configurations are the same as those shown in FIG.

Figure 9 shows the colors of the background and display area in this example.
Shown in E chromaticity coordinates. As shown in the figure, both the colors of the background color warping display area are achromatic in the area close to the C light source, indicating that the display is black and white.

Further, the contrast ratio, which is the ratio between the luminance during white display and the luminance during black display, is 15:1.

In this example, Δn-d of the liquid crystal display element was set to 0.5.
However, even if a liquid crystal display element with Δr1·d of 0.96 to 0.97 is used, a similar black and white display can be obtained.

Its configuration is similar to that shown in FIGS. 6 and 8, but the twist angle α of the liquid crystal element used as a phase plate is 180.
Use a degree. At this time, /3zl'j50 degrees,
βz is 30 degrees, β3 is 20 degrees, β4 is 25 degrees, β6 is 4
It is 5 degrees.

Figure 10 shows the displayed colors on the CIE chromaticity coordinates when a liquid crystal display element equipped with an organic color filter is used as the liquid crystal display element in the configuration shown in Figure 8 and driven at l/200 duty. .

As shown in the figure, each color has high color purity and a wide color range. The organic color filter used in this example was one used in liquid crystal color television receivers.

FIG. 11 shows the configuration of a liquid crystal element according to another preferred embodiment of the present invention. In this case, a plastic film having birefringence is used, and the other configurations are the same. The plastic film used as the phase plate here is a polycarbonate film with low crystallization. Figure 12 shows the background color and color of the display area in that configuration on CIE chromaticity coordinates. As shown in the figure, the color of the background and display section is an achromatic color similar to that of the C light source, allowing black and white display.

In addition, the parallel alignment liquid crystal element and the plastic film having birefringence used as the phase plate were arranged so that the twist angle α was 180.
A configuration in which the parallel alignment liquid crystal element used as a phase plate and a plastic film having birefringence are arranged between the liquid crystal display element and the upper polarizing plate with a twist angle α of 180° to 270° has been described. Similarly, for a configuration in which the liquid crystal display element is placed between the liquid crystal display element and the lower polarizing plate in the range of 270 degrees, the background color and the display color can be made intangible colors, and a black and white display can be obtained.

Also, when this plastic film phase plate is used as the lining material for at least one of the upper polarizing plate and the lower polarizing plate, the background color and display color can be made achromatic, and white. Display is obtained.

As described above, by combining a liquid crystal display element and a member having Nd refraction, the background or display part can be made achromatic, making black-and-white display possible.

〔Effect of the invention〕

According to the present invention, since the color of the background and the display section can be made achromatic, there is an effect that black and white display is possible.

[Brief Description of the Drawings] Fig. 1 is a configuration diagram of a conventional twisted nematic type liquid crystal element with excellent time-division driving characteristics, and Fig. 2 shows applied voltages for displays using the conventional and inventive liquid crystal elements. Figure 3 is a configuration diagram of a dot matrix display to explain time-division IW motion, and Figure 4 is a conventional twisted nematic type liquid crystal display with excellent time-division drive characteristics. A diagram showing the background color and display color of a display element on CIE chromaticity coordinates. Figure 5 shows the alignment direction (for example, rubbing direction) of liquid crystal molecules when the liquid crystal display element of the present invention is viewed from above, and the liquid crystal molecules. 6 is a perspective view showing the relationship in FIG. 5, and FIG. 7 is a diagram showing the background and color of the display part of the liquid crystal display element in the present invention. FIG. 8 is a diagram showing the configuration of a liquid crystal display element in another embodiment of the present invention, and FIG. 9 is a diagram showing the configuration of a liquid crystal display element in an embodiment having the configuration shown in FIG. 8. CI for background and display color
Figure 10, which is a diagram shown on the E chromaticity coordinates, shows the displayed color when using a liquid crystal display element equipped with an organic color filter.
A diagram shown on the E chromaticity coordinate, FIG. 11 is a diagram showing the configuration of a liquid crystal display element in another embodiment of the present invention, and FIG. 12 is a background of the liquid crystal display element in the embodiment of the configuration shown in FIG. 11. and a diagram showing the colors of the display section on CIE chromaticity coordinates. 1.21, 41.61... Upper electrode substrate of liquid crystal display element, 2, 22, 42.62... Lower electrode substrate of liquid crystal display element, 3, 23, 33, 43, 53, 63...・Liquid crystal molecules, 4, 24, 44.64... Upper polarizing plate, 5.2
5,45.05...lower polarizing plate, G, 2G. 4G, 66...Polarization axis of upper polarizing plate, 7.27°47
．． 67... Polarization axis of lower polarizing plate, 28,48°68.
...Rubbing direction of upper electrode substrate of liquid crystal display element, 9,
29.49,69...Rubbing direction of lower electrode substrate of liquid crystal display element, 10,30,50°70...Backlight, 11...Scanning ffltM, 12...No. 14 electrode, 31. 51... Upper electrode substrate of the liquid crystal element used as a phase plate, 32.52... Lower electrode substrate of the liquid crystal element used as a phase plate, 34.54... Upper electrode substrate of the liquid crystal element used as a phase plate. Rubbing direction, 35.5
5... Rubbing direction of the lower electrode substrate of a liquid crystal element used as a phase plate, 56... Dichroic dye, 71... Plastic film having birefringence. 1st Chestnut Tea 2 Figure Cf' 60 f, t V (Jr@3) T-3 mouth $4 Country 1,. 51fJ No. 61 1 stem'1 mouth 1a l ¥1

Claims (1)

[Scope of Claims] 1. A nematic liquid crystal having positive dielectric anisotropy and added with an optically active substance is sandwiched between a pair of upper and lower electrode substrates arranged opposite each other, and is oriented 180 degrees in the thickness direction. The polarization axis or absorption axis of a pair of polarizing plates, which form a twisted helical structure within a range of 270 degrees from A liquid crystal display element characterized by shifting. 2. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
The liquid crystal display element according to claim 1, wherein the product Δn·d is in the range of 0.4 μm to 2.5 μm. 3. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
A phase plate is used as a means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d is in the range of 0.4 μm to 2.5 μm, achromatic. A liquid crystal display element according to claim 1. 4. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
As a phase plate used as a means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d is in the range of 0.4 μm to 2.5 μm,
The liquid crystal display element according to claim 1, characterized in that an organic or inorganic member having birefringence is used. 5. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
As a phase plate used as a means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d is in the range of 0.4 μm to 2.5 μm,
A liquid crystal display element according to claim 1, characterized in that one or more liquid crystal elements are used. 6. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
As a phase plate used as a means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d is in the range of 0.4 μm to 2.5 μm,
2. A liquid crystal display element according to claim 1, characterized in that a liquid crystal element with a non-twisted structure, a so-called parallel alignment element, is used. 7. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
As a phase plate used as a means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d is in the range of 0.4 μm to 2.5 μm,
The liquid crystal display element according to claim 1, characterized in that one or more plastic films having birefringence are used. 8. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
The plastic film phase plate used as means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d is in the range of 0.4 μm to 2.5 μm, is at least one of Claim 1 characterized in that it is used as a lining material for one of the polarizing plates.
The liquid crystal display element described in . 9. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δn of liquid crystal
Polycarbonate is used as a plastic film phase plate used as a means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d is in the range of 0.4 μm to 2.5 μm, to an achromatic color. A liquid crystal display element according to claim 1, characterized in that: 10. Thickness d (μm) of liquid crystal layer and refractive index anisotropy Δ of liquid crystal
As a phase plate used as a means for making the color produced in the liquid crystal display element according to claim 1, in which the product Δn·d of n is in the range of 0.4 μm to 2.5 μm, its birefringence Δn・d is 0.05μ
2. The liquid crystal display element according to claim 1, wherein the thickness is in the range of m to 2.0 μm.