JPH03158822A - Two-layer type liquid crystal display device - Google Patents

Abstract

PURPOSE:To increase the total number of scanning lines without reducing contrast and to obtain a colorless black-and-white image with high resolution by sealing two kinds of liquid crystal materials having the same twist angle and respectively reversed revolution into 1st and 2nd liquid crystal cells and alternately arranging the row electrodes of the 1st and 2nd liquid crystal cells so that the row electrode of one cell is arranged between the line electrodes of the other cell. CONSTITUTION:The 1st liquid crystal cell 17 having a liquid crystal layer 11 set up to >=180 deg. twist angle and plural row and column electrodes 8, 13 and the 2nd liquid crystal cell 16a characterized by reversed resolution against the cell 17 and having a liquid crystal layer 4a set up to >=180 deg. twist angle and plural row and column electrodes 8a, 13a are laminated. The product d1.DELTAn1 of the layer thickness of the layer 11 of the cell 17 and its double refractive index DELTAn1 is set up larger than the product d2.DELTAn2 of the layer thickness of the layer 4a of the cell 16a and its double refractive index DELTAn2, the difference between both the products is set up to <=0.1mum and the row electrodes 8 of the cell 17 and the row electrodes 8a of the cell 16a are alternately laminated not to be overlapped.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to, for example, a laptop-type personal computer.

The present invention relates to a two-layer liquid crystal display device suitable for use as a liquid crystal display device for word processors and the like.

[Summary of the invention]

The present invention relates to, for example, a laptop-type personal computer.

Regarding a two-layer liquid crystal display device suitable for use as a liquid crystal display device for word processors, etc., a first liquid crystal cell has a liquid crystal layer set at a twist angle of 180° or more and has a plurality of row electrodes and column electrodes. and a second liquid crystal cell having a liquid crystal layer having a rotational property opposite to that of the first liquid crystal cell and having a twist angle of 180° or more, and having a plurality of row electrodes and column electrodes. The product d, Δn1 between the thickness of the liquid crystal layer and the birefringence of the first liquid crystal cell is the product d2 Δn1 of the thickness of the liquid crystal layer and the birefringence of the second liquid crystal cell.
n2, and the difference is 0.1IIll or less, and the row electrodes of the first liquid crystal cell and the row electrodes of the second liquid crystal cell are arranged alternately so that they do not overlap each other, and scanning is performed without reducing the contrast. The number of electrodes is increased to obtain high-resolution, black-and-white images without color.

[Conventional technology]

Conventionally, in a display device using liquid crystal, a second liquid crystal cell (which has row and column electrodes made of transparent electrodes, and which has no potential in a first liquid crystal cell to which power is supplied to the row and column electrodes) has been used. Compensation cells) are stacked to compensate for colored development.
A two-layer liquid crystal display device is disclosed in Japanese Unexamined Patent Publication No. 57-96315.

The liquid crystal used in the liquid crystal display device disclosed in the above-mentioned publication is a nematic type (hereinafter referred to as T) with a twist angle of 90°.
In this TN type liquid crystal, as shown in Figure 8, when the applied voltage is plotted on the horizontal axis and the transmittance is plotted on the vertical axis, the rise characteristic is gradual as shown by the TN curve. Voltage v ovr and V when the voltage is off and on. The difference in the transmittance of H is small, and there are problems in that the contrast is insufficient and the viewing angle is also narrow. In order to solve such problems, it is known that the contrast and viewing angle are improved using a super twist nematic type (hereinafter referred to as STN type) liquid crystal with a twist angle of 180@ or more.

As shown in the STN curve of FIG. 8, this 03TN type liquid crystal has a twist angle of 180' or more, and the rise characteristic is 2 times steeper than that of the TN curve, providing good contrast and a wide viewing angle.

A two-layer liquid crystal display device using such an STN type liquid crystal is disclosed in Japanese Patent Application Laid-open No. 35420/1983. The conventional configuration disclosed in this publication will be explained below with reference to FIGS. 5 to 7.

FIG. 5 is a side sectional view of a two-layer liquid crystal display device, in which a second liquid crystal cell (17) for compensation is placed on a first liquid crystal cell (16).
are laminated to form a two-layer structure. The second liquid crystal cell (16) for compensation has a first polarizing plate (1) (see polarizing plate (1) in Figure 7) attached to the top surface of the first glass substrate (2), and a second liquid crystal cell (16) for compensation. A peripheral sealing material (
7) to seal the STN type liquid crystal (4).

The first and second liquid crystals (4) sealed between the lower surface of the first glass substrate Fi, (2) and the upper surface of the second glass substrate (6)
The glass substrates (2) and (6) have molecular alignment layers (3) and (5) such that the alignment directions on the lower and upper surfaces are shifted by 180° or more, and the liquid crystal molecules are arranged in the middle part of the liquid crystal (4). is parallel to the surfaces of the first and second glass substrates (2) and (6), and the twist angle is configured to be, for example, 240° with right rotation (as shown in the liquid crystal cell for compensation in Figure 7). 16)
reference).

The lower surface of the first glass substrate (2) and the second glass substrate (
6) The upper and lower planes of the first and second glass substrates (2) and (6) viewed from the side of the STN type liquid crystal (4) sealed between the upper surfaces are the driving electrodes as shown in Figure 6A. is not provided. Such a second liquid crystal cell (16) is placed on a first liquid crystal cell (17), which will be described later, to form a two-layer liquid crystal display device.

Next, a peripheral sealing material (lO) is provided between the lower surface of the third glass substrate (1B) and the upper surface of the fourth glass substrate (14) constituting the first liquid crystal cell (17). The liquid crystal (11) in the mold is sealed. The lower surfaces of the third and fourth glass substrates (18) and (14) of the liquid crystal (11) sealed between the lower surface of the third glass substrate (18) and the upper surface of the fourth glass substrate Ij (14) and The molecular alignment layers (9) and (12) are such that the alignment direction on the upper surface is shifted by 180° or more, and in the middle part of the STN type liquid crystal (11), the liquid crystal molecules are arranged in the third layer.
and parallel to the surfaces of the fourth glass substrates (18) and (14), and the twist angle is left-handed, for example, 24o.

(The first liquid crystal cell (17) in Figure 7)
reference).

The row and column electrodes seen from the third glass substrate (18) side through the STN liquid crystal (11) sealed between the bottom and top surfaces of the third and fourth glass substrates (18) and (14).
As shown in FIG. 6B, the planes of 8) and (13) are patterned with transparent electrodes such as JTO in a matrix pattern to form column electrodes (13) for display and row electrodes (8) for scanning.

A first deflection plate (1
) A second deflection plate (15) (see deflection plate (15) in FIG. 3) is attached so as to be orthogonal to the second deflection plate (15).

In the above configuration, the first liquid crystal cell (17) and the second
Let the film thicknesses of the liquid crystal cell (16) be d and dl, and the birefringence Δn and Δnt, then the relationship between their products d, -Δn, and dz・Δn2 is d+'Δn+>dt・Δn2. By selecting the difference to be less than 0.1μ, the row electrode
Time division drive of 1/200 duty is possible with this,
By controlling d and Δn between the two layers, the birefringence effect is canceled and a high contrast black and white display without coloration can be achieved.

[Problems to be Solved by the Invention] According to the above-mentioned Japanese Patent Application Laid-Open No. 64-35450, a two-layer liquid crystal display device with a wide viewing angle and good color tone uniformity can be obtained. Considering the case of multiplex driving (time division driving) of a liquid crystal display device, this multiplex driving method supplies driving voltage to row electrodes (8) and column electrodes (13) of the transparent electrodes arranged in a matrix. When a predetermined selected point is selected, half-selected points are generated in addition to this selected point. The voltage at this half-selected point varies depending on the number of electrodes and the number of selected points, but the voltage at the half-selected point is approximately 1/2 that of the selected point due to crosstalk. In order to reduce the voltage at such a half-selected point, a driving method using a voltage averaging method has been proposed. This voltage averaging method distributes the voltage applied to half-selected points to non-selected points and averages all voltages other than the selected points. According to this method, the voltage conditions of each electrode are set optimally. When the effective value of the voltage applied to the selected point (display pixel electrode) is V ON
s The effective value of the voltage applied to points other than the selected point (non-display pixel electrode) is ■. , r, and find the ratio, that is, α0, where the ratio α (operating margin) of the effective voltage between the selected point and the non-selected point is the optimal bias condition, αWAX
-V o+i/ V 0FF=1
1) It is expressed as

Here, N is the scanning row electrode (
8).

In this equation (1), the horizontal axis represents the number of row electrodes N, and the vertical axis represents the number of on and off electrodes.
Off voltage ratio■. S/V. If you take FF and make a graph,
The result is as shown in FIG. In FIG. 9, if the number of row electrodes N is increased, ■. N/V. It can be seen that FF approaches l as much as possible. That is, as the number of row electrodes increases, the display contrast decreases, so even if an STN type liquid crystal with a steep rise and good contrast as shown in FIG. /200 duty, that is,
The number of row electrodes is approximately 200, and there is a problem in that if higher duty driving is performed, the contrast will be significantly lowered.

The present invention has been made to solve the above problems, and its purpose is to increase the number of row electrodes without lowering the contrast, and to obtain a high-resolution, black-and-white image with no coloration. type liquid crystal display device.

[Means to solve the problem]

As an example of the two-layer liquid crystal display device of the present invention is shown in FIG. and a first liquid crystal cell (17) having a column electrode (13) and a first liquid crystal cell (17) having opposite rotational properties;
Liquid crystal layer (4a) set to a twist angle of 80' or more
and a plurality of row electrodes (8a) and column electrodes (13
a) and a second liquid crystal cell (16a) having a structure of liquid crystal cell (16a)
The product d of the layer thickness of the liquid crystal layer (4a) and the birefringence, ・Δn2
larger, with a difference of 0.1μ or less, and the row electrodes (8) of the first liquid crystal cell (17) and the row electrodes (4a) of the second liquid crystal cell (16a) are alternated. They are arranged so that they do not overlap each other.

[Effect]

According to the two-layer liquid crystal display device of the present invention, liquid crystals (11) and (4a) having the same twist angle and reverse rotation are sealed in the first and second liquid crystal cells (17) and (16a). The row electrodes (8) and (8a) of these first and second liquid crystal cells are alternately arranged so that one row electrode (8) is connected to the other row electrode (8a).
) (8a) Since the total number of scanning lines can be increased without lowering the contrast, a black and white image with high resolution and no coloration can be obtained.

〔Example〕

An embodiment of the two-layer liquid crystal display device of the present invention will be described below with reference to FIGS. 1 to 3. 5 in Figures 1 to 3.
Components corresponding to those in FIGS. 7 to 7 are designated by the same reference numerals, and redundant explanation will be omitted.

In FIG. 1, the first liquid crystal cell (17) has approximately the same configuration as the first display cell shown in FIG. 5, and the structure shown in FIG. A two-layer liquid crystal display device is constructed by stacking second liquid crystal cells (16a) having different row and column electrodes.

This second liquid crystal cell (16a) is connected to the first glass substrate (2
A first polarizing plate (la) (see polarizing plate (1a) in Figure 3) is pasted on the top surface of a), and a second polarizing plate (la) placed opposite to the bottom surface of the first glass substrate (2a) is attached. A peripheral sealing material (7a) is provided between the upper surface of the glass substrate (6a) and the periphery to seal the STN type liquid crystal (4a). The alignment direction of the liquid crystal (4a) sealed between the lower surface of the first glass substrate (2a) and the upper surface of the second glass substrate (6a) on the lower and upper surfaces of the glass substrates (2a) and (6a) The molecular orientation layers (3a) and (5a) are shifted by 180° or more, and the liquid crystal (4a)
), the liquid crystal molecules intersect between the first and second glass substrates (
2a) and (6a), and the twist angle is right-handed, for example, 240° (the third
(see second liquid crystal cell (16a) in the figure), the first glass substrate (2a) through the STN type liquid crystal (4a) side sealed with the lower surface of the first glass substrate (2a) and the upper surface of the second glass substrate (6a). As shown in Figure 2, the plane viewed from the glass substrate (2a) side is patterned with transparent electrodes such as ITO in a matrix pattern, and row electrodes (8a) are placed on the bottom surface of the first glass substrate (2a) as column electrodes. (13a) is formed on the upper surface of the second glass substrate (6a). The third and fourth glass substrates (18) and (
14) The plane seen from the third glass substrate (1 day) side through the liquid crystal (11) sealed in between is I as shown in Figure 2B.
The row electrodes (8
) and column electrodes (13) are formed. The first one like this
and row electrodes (of the second liquid crystal cells (I7) and (16a))
8) and (8a) Column electrodes (■3) and (13a) on m
Among them, the column electrodes (13) and (13a) are patterned to have the same number so that they overlap each other when they are overlapped.

Furthermore, the row electrodes (3) and (8a) are arranged as shown in Fig. 2A and B when the first and second liquid crystal cells (17) and (16a) are stacked.
The patterning is performed so that one row electrode (8) and the other two row electrodes (8a) are alternately located at the middle part (19a) of (8a). In this way, the number N of row electrodes can be increased compared to the conventional liquid crystal cell (17) shown in FIG. 6 and the first compensating liquid crystal cell (16) having no electrodes, for example. If the number N of row electrodes for scanning up to now is 200, in this example, the first and second
The number of row electrodes of liquid crystal cells (17) and (16a) is 2, respectively.
You can make it in increments of 00.

In this way, with respect to the row electrode (8) of the first liquid crystal cell (17), the product d·Δn of the liquid crystal layer thickness and birefringence is Similarly, the second liquid crystal cell (1
6a) to the row electrode (13a) of the first liquid crystal cell (17).
) is the product d・Δ of the liquid crystal film thickness and birefringence index (19)
Liquid crystals (11) and (11) with the same n and reverse rotational twist angle
Since it operates as a compensation cell by the operation 4a), it has an achromatic effect and can display a black and white image. Furthermore, the first and second
When 200 row electrodes (8) and (8a) of the liquid crystal cells (17) and (16a) are simultaneously scanned, each drive frequency becomes 1/200 duty.

The contrast in this case is the same as the conventional 1/200 duty, but the resolution is doubled. That is, if configured as in this example, it is possible to increase the resolution by increasing the number of row electrodes without lowering the contrast, and to obtain a two-layer liquid crystal display device that can display black and white images without coloration. .

The above-mentioned first and second liquid crystal cells (17) (16a
), the optimal value of d・Δn is d as described in the prior art.

・It is possible to satisfy the condition of Δrll ax・Δn, ≦0.1 um, but when the first and second liquid crystal cells (17) and (16a) cannot be made equally so as to achieve such an optimal value. A method of adjusting d·Δn will be explained with reference to FIG.

FIG. 4 shows an enlarged side sectional view of the first liquid crystal cell (17) shown in FIG.
8) and (14) The middle part (19) between the row electrodes (8) and the column electrodes (13) formed in a matrix on the lower and upper surfaces is made of an inorganic coating material, ITO, etc. The electrode (8) or column electrode (13) and insulated stripes (
20) and (21) are provided, and the thickness of the liquid crystal (!l) layer is adjusted from dl to d, for example.

In this way, the conditions of d,·Δn and d2·Δn can be freely controlled.

Although the present invention has been described with reference to the case where the glass substrates are composed of four glass substrates, it is also possible to construct the composition with three glass substrates in which the second and third glass substrates are common without departing from the gist of the present invention. Obviously, many variations within the range are possible.

(Effects of the Invention) As described above, according to the present invention, the number of row electrodes can be increased compared to the conventional system using a second liquid crystal cell for compensation and a first liquid crystal cell, and high resolution can be achieved. The present invention provides a two-layer liquid crystal display device that can not only display an image, but also obtain a black and white image that compensates for colored development without lowering the contrast.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the two-layer liquid crystal display device of the present invention, and FIG. 2 is a plan view of row and column electrodes showing an embodiment of the two-layer liquid crystal display device of the present invention. FIG. 3 is a schematic diagram for explaining the orientation and angle of the two-layer liquid crystal display device of the present invention, FIG. 4 is a side sectional view for explaining the thickness control method of the two-layer liquid crystal display device of the present invention, and FIG. The figure is a side sectional view of a conventional two-layer liquid crystal display device, FIG. 6 is a plan view of a conventional two-layer liquid crystal display device, and FIG. 7 is for explaining the orientation and angle of a conventional two-layer liquid crystal display device. Schematic diagram of Figure 8 is a transparency characteristic diagram, Figure 9 is a diagram of transparency characteristics.
The figure is a characteristic diagram showing the relationship between the number of row electrodes and the on/off voltage. (1), (5) are deflection plates, (2), (2a),
(6), (6a), (14), (1B) are glass substrates, (3), (3a), (5), (5a
), (9), (12) are molecular orientation layers, (8), (
8a) is a row electrode, (13), (13a) is a column electrode,
(4), (4a), (11) are liquid crystals, (16)
, (16a) is the second liquid crystal cell, and (17) is the first liquid crystal cell.

Claims (1)

[Claims] a first liquid crystal cell having a liquid crystal layer set at a twist angle of 180° or more and a plurality of row electrodes and column electrodes; The layer thickness and birefringence of the liquid crystal layer of the first liquid crystal cell are stacked, and a second liquid crystal cell having a liquid crystal layer set at a twist angle of 100 degrees or more and a plurality of row electrodes and column electrodes is laminated. The product d_1・Δn_1 is the product d_2・Δn_1 of the layer thickness of the liquid crystal layer of the second liquid crystal cell and the birefringence index.
2, and the difference is 0.1 μm or less, and the row electrodes of the first liquid crystal cell and the row electrodes of the second liquid crystal cell are arranged alternately so as not to overlap with each other. A two-layer liquid crystal display device.