JPH01131532A - Electro-optic element - Google Patents

Abstract

PURPOSE:To remove the coloration of a display part and to improve a display grade by providing an electrode on the inner side of the substrate of a 2nd liquid crystal cell. CONSTITUTION:The 2nd liquid crystal cell 20 is constituted by holding a twist- oriented 2nd nematic liquid crystal 23 between a lower electrode substrate 21 having the electrode 21a on the front face side and an upper electrode substrate 22 having the electrode 22a on the rear face side. The direction of the molecular axis of the liquid crystal molecules of the 2nd liquid crystal cell 20, therefore, changes according to the magnitude of the voltage impressed to the electrode of the 2nd liquid crystal cell 20 when said voltage is impressed to the above-mentioned electrode. The eccentricity and major axis direction of the ellipitically polarized light at the respective wavelengths passing the 2nd liquid crystal cell 20 can then be changed. The prescribed voltages are eventually impressed to the electrodes according to the change in the environmental temp. of use and production errors of the thickness of the liquid crystal layers, etc. and, therefore, the coloration by refractive index anisotropy is removed and the good display is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electro-optical element. More specifically, the present invention relates to an electro-optical element such as a liquid crystal display device using a liquid crystal cell in which a liquid crystal is sandwiched between substrates arranged to face each other.

[Conventional technology]

Conventionally, in the above-mentioned liquid crystal display device, contrast has been improved by interposing a first liquid crystal cell that displays by applying a voltage and a second liquid crystal cell which does not display by applying a voltage between a pair of polarizing plates. Some devices have been proposed that allow high black and white display.

FIG. 18 is a schematic configuration diagram of a liquid crystal display device as a conventional electro-optical element, showing one example thereof. In the figure, 101
102 is a lower polarizing plate; 102 is an upper polarizing plate; 110 is a first liquid crystal cell that performs display by applying a voltage; a lower electrode substrate 111 having an electrode 111a on the upper surface; A liquid crystal 113 is sandwiched between the electronic FiA substrate 112 and the electronic FiA substrate 112. Reference numeral 120 denotes a second liquid crystal cell, in which one liquid crystal cell is placed between the lower substrate 121 and the upper substrate 122.
23 is sandwiched between them.

In the above configuration, the angle between the molecular axis direction of the liquid crystal molecules in contact with the lower electrode substrate 111 of the first liquid crystal cell 110 and the polarization axis (absorption axis) of the lower polarizing plate 101 is usually 20@ ~70°, so when the linearly polarized light that has passed through the lower polarizing plate 101 passes through the first liquid crystal cell 110, the refractive index anisotropy Δn of the liquid crystal molecules, the thickness d of the liquid crystal layer, and the Due to the effect of the twist angle, the light becomes elliptically polarized. The direction of the long axis of this elliptically polarized light differs depending on the wavelength, and the eccentricity also differs. In addition,
The eccentricity e is expressed as follows, where a is the length of the major axis of the elliptically polarized light, and b is the length of the minor axis of the elliptically polarized light.

Therefore, when the elliptically polarized light passes through the second liquid crystal cell 120, the directions of the long axes of the elliptically polarized light are almost the same at each wavelength (visible light range), and the eccentricity e of the elliptically polarized light is approximately the same at each wavelength (visible light range). The size of the twist angle of the liquid crystal molecules in the second liquid crystal cell, the product ΔndCIIm of the refractive index anisotropy Δn of the liquid crystal in the second liquid crystal cell and the thickness d of the liquid crystal layer so that the value approaches 1 in the optical range) ],
and setting the angle between the direction of the molecular axis of the liquid crystal molecule in contact with the lower substrate of the second liquid crystal cell and the direction of the molecular axis of the liquid crystal molecule in contact with the upper electrode substrate of the first liquid crystal cell. There is.

As a result, before passing through the second liquid crystal cell 120, the light is elliptically polarized light, which has a different eccentricity e at each wavelength and a different long axis direction at each wavelength. By passing through the second liquid crystal cell, the light becomes elliptically polarized light with an eccentricity e close to 1 at each wavelength and the directions of the long axes being almost the same.The light that finally passes through the upper polarizing plate becomes white light.

In the above liquid crystal display device, if the conditions of the first liquid crystal cell (the size of the twist angle of the liquid crystal, Δnd) change, the conditions of the second liquid crystal cell (the size of the twist angle of the liquid crystal, Δnd) must also be changed. It won't happen.

As a specific example of a conventional liquid crystal display device, the Δnd of the first liquid crystal cell is approximately 0.9 μm, the twist angle of the liquid crystal molecules of the first liquid crystal cell is approximately 200 degrees to the left (the direction of the twist of the liquid crystal molecules is (expressed in the direction from top to bottom), Δnd of the second liquid crystal cell is approximately 0. 7 μm, the twist angle of the liquid crystal molecules in the second liquid crystal cell is about 150 degrees right-handed, the direction of the polarization axis (absorption axis) of the upper polarizing plate and the molecular axis direction of the liquid crystal molecules in contact with the upper substrate of the second liquid crystal cell. The angle made with the second
The angle between the molecular axis direction of the liquid crystal molecules in contact with the lower substrate of the liquid crystal cell and the molecular axis direction of the liquid crystal molecules in contact with the upper electrode substrate of the first liquid crystal cell is about 90 degrees, and the lower side of the first liquid crystal cell Figure 19 shows the spectra of transmitted light in the ON and OFF states when the angle between the molecular axis direction of the liquid crystal molecules in contact with the electrode substrate and the direction of the polarization axis (absorption axis) of the lower polarizing plate is approximately 50 degrees. , where 1/100 d u t
By applying a selection voltage and a non-selection voltage by multiplex driving of y, a state with high transmittance is turned into an OFF state, and a state with low transmittance is turned into an ON state. No. 19. In the figure, curve I is in the OFF state, and curve ■ is in the ON state. The transmitted light intensity (transmitted light amount) on the vertical axis is expressed in arbitrary units AU (A
Rbitrary Unit).

[Problem that the invention seeks to solve]

As described above, a liquid crystal display device with a black and white display can be obtained with the conventional technology, but when the temperature of the liquid crystal display device changes, the value of the refractive index anisotropy Δn of the first and second liquid crystal cells changes depending on the temperature. Therefore, the external appearance of the liquid crystal display device is not white but colored green, red, etc. (the color varies depending on the conditions of the first liquid crystal cell and the second liquid crystal cell, the characteristics of the liquid crystal used, etc.). Further, even if the thickness d of the liquid crystal layer of each liquid crystal cell is not formed to a predetermined thickness due to manufacturing errors or the like, there is a problem in that the liquid crystal layer is colored in the same manner as described above.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electro-optical element that can provide good display regardless of changes in the operating environment temperature, manufacturing errors in the thickness of the liquid crystal layer, etc. .

[Means for solving problems]

The present invention provides a first liquid crystal cell in which a first liquid crystal layer is sandwiched between electrode substrates arranged to face each other, and a second liquid crystal cell in which a second liquid crystal layer is sandwiched between electrode substrates arranged to face each other. In the electro-optical element having a liquid crystal cell, an electrode is provided inside the substrate of the second liquid crystal cell.

[Effect]

When a voltage is applied to the electrodes of the second liquid crystal cell configured as described above, the direction of the molecular axes of the liquid crystal molecules in the second liquid crystal cell changes depending on the magnitude of the applied voltage, and the second liquid crystal cell The eccentricity and major axis direction of the elliptically polarized light at each wavelength passing through can be changed. Therefore, the coloring can be removed by applying a predetermined voltage to the electrodes according to changes in the operating environment temperature, manufacturing errors in the thickness of the liquid crystal layer, and the like.

〔Example〕

Hereinafter, the present invention will be specifically explained based on embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of a schematic configuration of a liquid crystal display device as an electro-optical element showing one embodiment of the present invention.

In the figure, 1 is a lower polarizing plate, 2 is an upper polarizing plate, 10 is a first liquid crystal cell (hereinafter referred to as the first cell) that performs display by applying a voltage, and a lower electrode substrate having an electrode 11a on the upper surface side. 11 and an upper electrode substrate having an electrode 12a on the lower surface side, a twistedly oriented first nematic liquid crystal 13 is provided.
It makes me hold it. 20 is a second liquid crystal cell (hereinafter referred to as second
A second nematic liquid crystal 23 with twisted orientation is sandwiched between a lower electrode substrate 21 having an electrode 21a on the upper surface side and an upper electrode substrate 22 having an electrode 22a on the lower surface side. .

FIG. 2 is an explanatory diagram showing the relationship between the respective axes of the liquid crystal display device in the example shown in FIG. 1, and the direction of the molecular axis of the liquid crystal molecules in contact with the substrate is shown as the rubbing direction.

In the figure, R11-Rl2 are the first cells 10, respectively.
The rubbing direction of the lower electrode substrate 11 and the upper electrode substrate 12, R21 and R22 are the rubbing directions of the lower electrode substrate 21 and the upper electrode substrate 22 of the second cell 20, respectively, θ
is the rubbing direction R1 of the upper electrode substrate 12 of the first cell 10
2 and the rubbing direction R of the lower electrode substrate 21 of the second cell 20
21, TI is the twist angle size and twist direction of the liquid crystal molecules in the first cell 10, T2 is the twist angle size and twist direction of the liquid crystal molecules in the second cell 20, Pl・P
2 are the directions of the polarization axes (absorption axes) of the lower polarizing plate 1 and the upper polarizing plate 2, respectively, and θl is the direction P1 of the polarizing axis of the lower polarizing plate 1 and the rubbing direction of the lower electrode substrate 11 of the first cell 10. θ2 represents the angle formed between the direction P2 of the polarization axis of the upper polarizing plate 2 and the rubbing direction R22 of the upper electrode substrate 22 of the second cell 20, and the twist direction of the liquid crystal molecules in each cell. is indicated by the twist direction from top to bottom of the cell.

In addition, the state with a large amount of transmitted light can be turned off by applying selection and non-selection voltages using 1/100 duty driving.
A state in which the amount of transmitted light is small is referred to as an ON state. Note that the present invention is not limited to 1/100 duty drive.

In addition, the liquid crystal used in the first cell and the second cell is as follows:
PCI, BCH mixed nematic liquid crystal and R
-O-OR' system etc. are used. Further, the liquid crystals of the first cell and the second cell may be different or the same. Further, in order to obtain twisting of the liquid crystal molecules in the first cell and the second cell, CB-15 (manufactured by BDH) or S-811 (manufactured by Merck & Co., Ltd.) or the like is used as an optically active agent.

Further, although there are no restrictions on the conditions such as the size of the twist angle of the liquid crystal of the first cell and the second cell and the size of Δnd, in order to obtain a good display, it is necessary to It is necessary to change the conditions of the second cell according to the conditions of the first cell so that the second cell restores the differences in the eccentricity and long axis direction of the elliptically polarized light. Below are some examples of conditions for the first cell and the second cell to obtain good display.

b) In FIGS. 1 and 2, for example, the twist angle Tl of the liquid crystal molecules in the first cell 10 is set to about 200 degrees to the left, Δand
Assuming that the angle θ is approximately 0.9 μm, the angle θ is approximately 90 degrees, and the angles θl and θ2 are each in the range of 30 degrees to 60 degrees, the twist angles T2 and Δnd of the liquid crystal of the second cell 20 are the shaded areas in FIG. A good display can be obtained when In particular, it is better to make it more inside than the periphery within the above region.

To explain more specifically, for example: ■ 1st cell 10
The twist angle T1 of the liquid crystal molecules is approximately 200 degrees left twist, Δ
nd is about 0.9 μm 1 angle θ is 90 degrees, angle θ1・θ2
are respectively set to 40 degrees, point A in Figure 3
As shown in FIG. 2, the twist angle T2 of the liquid crystal molecules in the second cell 20 is approximately 140 degrees right-handed, and Δnd is approximately 0.7 μm. The spectrum of the external appearance of the liquid crystal display device at this time is shown in FIG. 4. In the figure, the curve ■ indicates the OFF state, and the curve ■ indicates the ON state.

For example, ■ Twisting angle T1 of liquid crystal molecules in the first cell 10
is twisted to the left by about 200 degrees, Δn'd is about 0°9 μm, angle θ is about 90 degrees, angle θ1 is about 50 degrees, and angle θ2 is about 4
0 degrees, and the twist angle T2 of the liquid crystal molecules in the second cell 2 is approximately 200 degrees.
When the twist angle T1 of the liquid crystal molecules in the first cell 10 is about 200 degrees to the left, and Δnd is about 0.9 μm. The same applies when the angle θ is approximately 90 degrees, the angles θ1 and θ2 are each approximately 40 degrees, the twist angle T2 of the liquid crystal molecules in the second cell 20 is approximately 260 degrees right-handed, and Δnd is approximately 0°8 μm. A good display can be obtained.

) The twist angle TI of the liquid crystal molecules in the first cell 10 is approximately 250.
degree of left-handed twist, Δnd is approximately 0.9 μm, 1 angle θ is approximately 90
degree, and the angles θ1 and θ2 are each in the range from 30 degrees to 60 degrees, the twist angle T2 of the liquid crystal molecules in the second cell 20
When and Δnd are the shaded areas in Figure 5, OFF
A good liquid crystal display device that is almost white in the ON state and almost black in the ON state can be obtained.

More specifically, ■ For example, the twist angle TI of the liquid crystal molecules in the first cell IO is left-handed by about 250 degrees, and Δnd is about 0.
．． 9 μm, the angle θ is about 90 degrees, the angles θ1 and θ2 are each about 40 degrees, the twist angle T2 of the liquid crystal molecules in the second cell 20 is about 160 degrees right-handed, and Δnd is 068 μm. ■ First cell 10 The twist angle T1 of the liquid crystal molecules is approximately 250
Degree of left helix, Δnd is approximately 0.9μm5 angle θ is approximately 90
degree, the angles θ1 and θ2 are each about 40 degrees, and the second cell 20
The twist angle T2 of the liquid crystal molecules is approximately 360 degrees right-handed twist, Δ
When nd is approximately 1.0 μm, the twist angle T1 of the liquid crystal molecules in the first cell 10 is approximately 170 μm.
degree of left-handed twist, Δnd approximately 0.7 μm.

The angle θ is approximately 90 degrees, the angle θ1 is approximately 40 degrees, the angle θ2 is approximately 50 degrees, and the twist angle T2 of the liquid crystal molecules in the second cell 2 is approximately 17 degrees.
For example, the right twist is 0 degrees, and Δnd is 0.7 μm. Furthermore, C) The twist angle Tl of the liquid crystal of the first cell is about 120 degrees left-handed, Δn-d is about 0.9 μm, the angle θ is about 90 degrees, and the angles θ1 and θ2 are each in the range of 30 degrees to 60 degrees. Then, the twist angle T2 and Δnd of the liquid crystal of the second cell are
In the case of the shaded part in the figure 2) The liquid crystal twist angle T1 of the first cell is about 200 degrees left twist, Δnd is about 0.6 μm, the angle θ is about 90 degrees, the angle θ
If l and θ2 are each in the range from 30 degrees to 60 degrees, and the torsion angle T2 and Δnd of the liquid crystal in the second cell are the shaded areas in Fig. 7, then e) the torsion angle TI of the liquid crystal in the first cell. Assuming that T is a left-handed twist of about 200 degrees, Δnd is about 1.5 μm, angle θ is about 90 degrees, and angles θ1 and θ2 are each in the range of 30 degrees to 60 degrees, the twist angle T2 and Δnd of the liquid crystal of the second cell are A good display can be obtained when, for example, the area shown in FIG. 8 is shaded.

However, as mentioned above, when the ambient temperature of the liquid crystal display device changes, the value of the refractive index anisotropy Δn of the first cell and the second cell changes, and the display section becomes colored, making it impossible to obtain a good black and white display. . The same applies when the thickness d of the liquid crystal layer of the first cell and the second cell is not formed to a predetermined thickness.

Therefore, in the present invention, as shown in FIG. 1, the second cell is also provided with electrodes 21a and 22a, and by applying a predetermined voltage to the electrodes, the alignment state of the liquid crystal molecules in the second cell is changed. By adjusting the substantial Δn and matching the Δnd of the first cell and the second cell, the coloring can be removed and the contrast can be enhanced. Furthermore, it is possible to change or control the display section to any color as required.

The number and arrangement of the electrodes 21a and 22a of the second cell 20 are arbitrary, and one electrode may be provided on each substrate 21 and 22, or a plurality of electrodes may be provided on at least one substrate. Furthermore, the overlapping portions of the electrodes 21a and 22a may cover an area equal to or other than the display area of the first cell, or may cover a part of the display area of the first cell. good.

FIGS. 9 to 11 show one example, and represent the arrangement of the electrodes 21a and 22a of the second cell when the liquid crystal display device is viewed from above. 31 to S3 indicate the display area of the first cell.

As shown in FIG. 9, when the second cell has one electrode on both the upper and lower sides, and the area where the two electrodes overlap is wider than the display area S1 of the first cell, the gap between the upper and lower electrodes of the second cell is By applying an appropriate voltage to the display area, coloring can be removed from the entire display area and the contrast can be increased.

As shown in FIG. 10, when the second cell has one electrode on both the upper and lower sides, and the area where the two electrodes overlap is narrower than the display area S2 of the first cell, an appropriate distance is placed between the upper and lower electrodes of the second cell. By applying a voltage, the contrast in the overlapping region can be increased.

As shown in FIG. 11, when there are at least two or more electrodes on either the upper or lower side of the second cell, and the overlapping area of each of the upper and lower electrodes is wider than the display area S3 of the first cell, appropriate upper and lower electrodes are selected. By applying an appropriate voltage between them, the contrast in any part of the overlapping region can be increased.

In addition, in FIGS. 9 to 11 above, if there is a difference in the amount of change due to temperature change in the refractive index anisotropy Δn of the liquid crystal of the first cell and the second cell, the O
The color of the FF state is no longer white. Therefore, by setting the temperature characteristics of the refractive index anisotropy Δn of the liquid crystal of the first cell to an appropriate value, it is possible to apply a voltage between the electrodes of the second cell even if the color changes in the OFF state at low or high temperatures. By doing so, it is possible to obtain a white color.

In FIGS. 9 to 11, the electrode terminals for voltage application that are exposed on the upper and lower substrates of the second cell are made to be exposed on one of the upper and lower substrates using an upper and lower conductive agent. In this case as well, the same effect as above can be obtained.

Furthermore, as shown in FIG. 2, when a third liquid crystal cell (hereinafter referred to as the third cell) 30 configured in the same manner as the second cell is provided in the liquid crystal display device in the example of FIG. 3
Since the voltages applied to the cell and the second cell can be adjusted, the coloring of the display section can also be removed in this case.

In this case, it is preferable that the twist direction of the liquid crystal molecules in at least one of the second cell and the third cell is different from the twist direction of the liquid crystal molecules in the first cell. Furthermore, the vertical positional relationship between the first to third cells may be arbitrary.

Furthermore, three or more liquid crystal cells similar to the second cell may be provided.

In addition, in FIGS. 1 and 12, adjacent substrates of adjacent cells, for example, the upper substrate 12 of the first cell 10 and the lower substrate 21 of the second cell 20 in FIG. It may be composed of a substrate or may be optically bonded. As the bonding means, an embossed polyvinyl butyral film is used and bonded by heating and pressure. Alternatively, thermosetting epoxy and urethane adhesives, acrylic ultraviolet adhesives, and the like may be used. As described above, by making adjacent substrates of adjacent cells to be used in common or by bonding them together, it is possible to reduce reflections at the boundary surfaces of adjacent cells.

Specific examples will be described below.

Example 1 The first cell 10 in the example of FIG. 1 has a phase transition temperature TN at which the nematic phase of the liquid crystal changes to an isotropic liquid by heating.
l is 100''C and Δn at 40°C is o, ioo
and liquid crystals with TNI=60°C and Δn of o and too at 40°C are used in the second cell 20, respectively.
A liquid crystal display device was manufactured in which each axis was configured as described in item (i) of (a) above, and the Δnd of each cell was 0.9 μm at 40°C.

However, in OoC, Δn of the first cell and second cell are 0.110.0.124, respectively, and Δnd is as shown in Table 1 below.
It is now shown in Note that the unit of cell thickness d and Δnd in this example and each example described later is μm, and the units in the table below are omitted.

Table 1 Therefore, good black and white display was obtained at 40°C, but
℃, coloring occurred and good black and white display could not be obtained.

Therefore, by applying an appropriate voltage to the electrodes 21a and 22a of the second cell 20 to reduce the apparent Δnd, a good black and white display could be obtained.

Example 2 TN in the first cell 10, = 60°C, TNI in the second cell 20
= Using a 100'C liquid crystal, each axis is set according to (a) above.
The configuration was as described in Table 2, and the Δnd of each cell was set to the value shown in Table 2 at 0°C, but at 40°C, the values were as shown below.

Table 2 Therefore, a good black and white display could not be obtained at 40°C, but a good black and white display could be obtained by applying an appropriate voltage to the second cell. The black spectrum at this time is shown in FIG. In the figure, l is the spectrum when the temperature is OoC, ■ is the spectrum when the temperature is 40°C, and ■ is the spectrum when the voltage is applied to the second cell at 40°C.

Example 3 T 81-100°C in the first cell 10, T in the second cell 20
Rl - Using a liquid crystal at 60°C, each axis was configured as described in item (a) above, and the Δnd of each cell was set to the value shown in Table 3 at 40°C, but at 0°C it was as follows. Became.

Table 3 Therefore, good black and white display could not be obtained in OoC, but good black and white display could be obtained by applying an appropriate voltage to the second cell.

Example 4 T□-60°C in the first cell 10, T s+ in the second cell 20
= Using a liquid crystal at 100°C, each axis was configured as described in (a) above, and the Δnd of each cell was set to the value shown in Table 4 at 0°C, but at 40°C it was as follows. Became.

Table 4 Therefore, a good black and white display could not be obtained at 40°C, but a good black and white display could be obtained by applying an appropriate voltage to the second cell.

Example 5 Each axis in the liquid crystal display device shown in FIG. 1 and FIG.
If the thickness d of the liquid crystal layer of the cell 20 does not reach the target value (design value) and the actual value of d (actual value) is as shown in Table 5 below, please set an appropriate value for the second cell. Good display was obtained by applying voltage.

FIGS. 14(A) to 14(D) show black spectra in each case of A to D in Table 5 below.

In each figure, ■ indicates the case where the thickness d of the liquid crystal layer of the second cell is the designed value, ■ indicates the case where the actual thickness d is different from the designed value, and ■ indicates the case where the thickness d of the second cell is different from the designed value. This is a spectrum when voltage is applied to two cells.

Example 6 When the same test as in Example 5 was conducted for the case where the thickness d of the liquid crystal layer of the first cell 10 was different from the designed value as shown in Table 6, it was found that by applying a voltage to the second cell Good display was obtained as in the above example.

Note that the actual Δnd in the case of A and B%D in Tables 5 and 6 above falls within the shaded area in FIGS. 3 and 5, but is at a level lower than the optimal condition, and the second cell A better display was obtained by applying a voltage to .

Example 7 When the same test as above was conducted for the case where the thickness d of the liquid crystal layer of the first cell IO and the second cell 20 was different from the designed value as shown in Table 7, it was found that - voltage was applied to the second cell. By doing so, a good display was obtained in the same manner as above.

Example 8 As the liquid crystal of the first cell 10 in the liquid crystal display device shown in FIG. 1, Chisso 5S-4008 and Merck S-81 were used.
1 was mixed with 0.8 wt% of 5S-4008 as the liquid crystal of the second cell 20, and CB-15 manufactured by BDH Co., Ltd.
The liquid crystal N thickness (cell thickness) of the first cell and the second cell was 5.5 wt%, respectively.
8 μm and 6.4 μm, and angles θ1 and θ2 are both 45
'', and the angle θ was 90''. In addition, the twist angle TI of the liquid crystal molecules in the first cell 10 is set to 180" left-handed twist, and the second cell 2
The torsion angle T2 of 0 was set to be a right-handed twist of 180@. The Δnd of the first cell and the second cell are 0°87 μm and 0.9, respectively.
Although the thickness was 6 μm, very good display quality was obtained by applying a voltage of 2°03 V (rectangular wave) to the second cell.

Also, as mentioned above, the value of Δnd of the second cell is changed to Δnd of the first cell.
nd, apply a voltage to the second cell, make Δnd′4i:v;4 nodes of the second cell, and each Δnd
By matching the values of nd, the Δ of the first and second cells
It was possible to eliminate coloring in exactly the same way as in the case where the thickness of each liquid crystal layer was calculated and created so that the values of nd matched.

Figures 15 and 16 show the change in transmitted light intensity with respect to the voltage v1 applied to the first cell.
This is a characteristic in the normal dark mode that is ON when
a is the characteristic of the display device according to the present invention, b is the characteristic of the display device according to the prior art, and C is the characteristic when the voltage applied to the second cell is set to 0 in the present invention. Table 8 shows the conditions for a, b, and c above.

In the case of the present invention, the arrangement of the polarizing plate is exactly the same in both the normal bright mode and the normal dark mode, but the voltage applied to the second cell is different, 2.0-3 V and 1 V, respectively.
．． It is 82V. In the case of the prior art, these two modes are switched by changing the arrangement of the polarizing plates.

In the case of multiplex driving, the voltage applied to the liquid crystal layer is changed between vIl and ■ to select OFF or ON, but the following (1 ) There is a relationship expressed by the formula.

Therefore, for example, when N=200, V, /V, = l.

It becomes 07. Here, if we take as an example a in Fig. 15, Vth = 1.66V, V = 2.05V, so l
Vy V-l < l Vy Vthl,
Can't get enough contrast. In such a case, if the drive is performed as (i), (i), the ON state will be the darkest, and the maximum contrast ratio will be obtained. Therefore, if we compare a and b in FIG. 15, it is clear that the contrast of the present invention is significantly improved.

Next, as can be seen from Figures 15 and 16, in the conventional method, it is not possible to switch between the two modes without changing the arrangement of the polarizing plate, but in the present invention, the voltage applied to the second cell can be changed. Switching is possible by That is, in the present invention, the display mode (negative/positive) can be easily reversed.

Example 9 The arrangement of polarizing plates was the same as in Experimental Example 8, and the thicknesses of the liquid crystal layers of the first cell and the second cell were 6.0 μm and 6.0 μm, respectively.
It was set to 3 μm. In this case as well, the same effects as on the day of the example were obtained.

Example 10 The arrangement of polarizing plates was the same as in Example 8, and the thicknesses of the liquid crystal layers in the first and second cells were 5° and 6 μm, respectively.
It was set to 0 μm. In this case as well, the same effect as in Example 8 was obtained.

Example 11 In all of the above examples, the orientation treatment was performed by rubbing, but in this example, the orientation treatment was performed by obliquely depositing 340. In this case, the pretilt angle of the liquid crystal molecules on each substrate was about 25#. Also, the torsion angles T1 and T2 are both 270", and the angles θ1 and θ
2 are both 450 and the angle θ is 90', the liquid crystal layer thicknesses of the first cell and the second cell are 5.7 μm and 6.2 μm, respectively.
It was set as m. In this example as well, the same effects as in the previous example were obtained.

Example 12 M7195 (Δ
n=0.195) and 1.1 wt% of Merck's 5811.
Add the mixture to the liquid crystal of the second cell 20 and the above M7195 made by Rodinok Co., Ltd. and 1 part CB-15 made by BDH Co., Ltd.
．． A mixture of 2WL% was used, and the first cell had a twist angle T1 of 230'' left-handed twist, and the second cell had a twist angle T2 of 230° right-handed twist. In addition, display devices A to E were created in which the liquid crystal layer thickness d of the first cell was 4.5 μm and the liquid crystal layer thickness d of the second cell were different as shown in Table 9 below, and the other conditions were as described above. A similar test was conducted in the same manner as in Example 8.

Table 9 The contrast ratios in the above table are obtained when driving at a duty of 1/240 with the transmitted light intensity set to 50% when OFF.

Figure 17 (A
) to (E).

The horizontal axis of the figure is the voltage applied to the first cell, and its waveform is a rectangular wave with a frequency of 1 kHz. Also, the vertical axis represents the light intensity of two polarizing plates pasted together with their polarization axes aligned at 100%.
This is the transmitted light intensity when defined as Moreover, the curve shown by the dashed line C in the figure is a voltage transmittance curve when no voltage is applied to the second liquid crystal cell. In this case, not only is there no contrast, but the coloration is also large.On the other hand, the curve a in the figure shows the voltage shown in the table above for the same cell (1kHz,
This is a voltage transmittance curve when a rectangular wave) is applied.

In this case, sufficient contrast was obtained and little coloring was observed.

Note that this example shows how much Δnd of the second cell becomes larger than Δnd of the first cell until it becomes impossible to compensate even if a voltage is applied. Comparing curves a in FIGS. 17(A) to (E), as Δnd of the second cell increases, the amount of transmitted light when the voltage applied to the first cell is 0 increases, making it difficult to obtain contrast. The contrast ratio is shown at the right end of Table 9. If the required contrast ratio is approximately 1:10, the limit of Δnd of the second liquid crystal cell, which can be compensated by applying a voltage, is 4 μm when the value of Δnd of the first liquid crystal cell is 100. It seems that it is the rank.

[Effects of the Invention] As explained above, according to the present invention, since the second cell is also provided with an electrode, when coloring occurs in the display section due to changes in the usage environment temperature or manufacturing errors in the thickness of the liquid crystal layer, By applying a voltage between the electrodes of the second cell, the above coloring can be removed and display quality can be improved. Furthermore, by applying an appropriate voltage to the second cell, it is possible to change the background color and display color, thereby expanding the range of applications for displays and further increasing the design flexibility of electronic devices.

Furthermore, by making the value of Δnd of the second cell larger than Δnd of the first cell, and adjusting the Δnd of the second cell by applying a voltage to the second cell, the values of each Δnd are matched. , 1st. Coloring can be eliminated in exactly the same way as when creating the liquid crystal layer by calculating the thickness of each liquid crystal layer so that the value of Δnd of the second cell matches, so the tolerance range for the difference in the thickness of each liquid crystal layer is widened. As a result, the yield is improved, manufacturing becomes easier, and manufacturing costs can be reduced. In addition, the contrast of the display area has been significantly improved, and by adjusting the voltage applied to the second cell without changing the arrangement of the polarizing plate, the display mode (negative/positive) can be adjusted, including the peripheral areas of the display screen that are not scanned. Since it can be reversed, the display mode can be reversed more easily than other methods, and it has the effect of improving the appearance when the display mode is reversed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a schematic configuration of an embodiment of a liquid crystal display device as an electro-optical element according to the present invention, and FIG. 2 is an explanatory diagram showing the relationship between the orientation direction of liquid crystal molecules and the polarization axis of a polarizing plate. FIG. 3 is an explanatory diagram showing an example of the relationship between the first cell and the second cell suitable for a liquid crystal display device, FIG. 4 is a graph showing characteristics of transmitted light intensity in a suitable liquid crystal display device, and FIG. 6, 7, and 8 are explanatory diagrams showing other examples of the relationship between the first cell and the second cell suitable for a liquid crystal display device, and FIGS. FIG. 12 is a plan view showing an example of a cell arrangement, FIG. 12 is a cross-sectional view of a schematic structure showing an example in which a third liquid crystal cell is provided, and FIGS. 13 and 14 (A) to (D) are specific examples. FIG. 15 is a graph showing the relationship between the voltage applied to the first cell and the transmitted light intensity in the normal bright mode of another example, and FIG. 16 is a graph showing the relationship between the transmitted light intensity in the normal dark mode and Graph showing the relationship between applied voltage to one cell and transmitted light intensity, Figure 17 (A)
-(E) are graphs showing the relationship between the voltage applied to the first cell and the intensity of transmitted light in still other embodiments, and FIG. 18 is a cross section showing the schematic configuration of a liquid level display device as a conventional electro-optical element. 19 are graphs showing characteristics of transmitted light intensity in a conventional liquid crystal display device. 1 is a lower polarizing plate, 2 is an upper polarizing plate, 10 is a first liquid crystal cell (first cell), 11 and 12 are electrode substrates, 11a-12
a is an electrode, 13 is a liquid crystal, 20 is a second liquid crystal cell (second cell), 21 and 22 are electrode substrates, 21a and 22a are electrodes,
23 is a liquid crystal, 30 is a third liquid crystal cell (third cell), 31
- 32 is an electrode substrate, 31a and 32a are electrodes, and 33 is a liquid crystal. Figure 1 Figure 2 zl 2nd Beggar's Lonely Card I! IO entry/death (degree) Fig. 4 J skin length - (7tm) 1st l hLk41 250ft (, um)
Δnxd+cto of the first ask, 9. um second
The Japanese angle of the angle is 0 (cliff). Figure 6: The angle of the angle 2 is the right angle! This (degree) Figure 7 2t! Right angle (degrees) 1st angle (degrees) 1st angle (degrees) 200 degrees (200 degrees) kf fi”tavl (V) Fig. 16 Fig. 17 (A) Fig. 17 (B) Fig. 17 (C) Fig. 17 (D) White r Karo wa Mashi V + (V) tp addition voltage Vl ( V)

Claims (1)

[Claims] 1. A first liquid crystal cell having a first liquid crystal layer sandwiched between electrode substrates arranged to face each other, and a second liquid crystal layer sandwiched between the electrode substrates arranged to face each other. What is claimed is: 1. An electro-optical element comprising a second liquid crystal cell comprising a second liquid crystal cell, characterized in that an electrode is provided inside a substrate of the second liquid crystal cell. 2. The electro-optical element according to claim 1, wherein two or more of the second liquid crystal cells are provided. 3. The electro-optical element according to claim 1 or 2, wherein adjacent substrates of adjacent liquid crystal cells are constituted by a single substrate. 4. The electro-optical element according to claim 1, wherein two or more electrodes are arranged on at least one substrate surface of the opposing substrates of at least one second liquid crystal cell. 5. Claim 1, wherein the birefringence (denoted as Δnd) of the second liquid crystal cell is equal to or larger than Δnd of the first liquid crystal cell in a state where no voltage is applied.
or the electro-optical element according to 2.