JPH0318164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal device, particularly a super twisted nematic type liquid crystal device.

[Conventional technology]

The conventional super twisted nematic type (hereinafter referred to as STN type) liquid crystal device was developed in Japanese Patent Application Laid-open No. 1983-
As in Publication No. 50511, the twist angle of the liquid crystal molecules is 90 degrees or more, and a pair of polarizing plates are provided above and below the liquid crystal cell, and these polarization axes (absorption axes) and the molecules of the liquid crystal molecules adjacent to the electrode substrate are The included angle with the axial direction is 30
It ranged from 60 degrees to 60 degrees. Therefore, due to the coloring caused by birefringence, the external hue of the liquid crystal cell when no voltage is applied is not white, but generally has a hue ranging from green to yellowish red. Further, the external hue when a selection voltage is applied is generally blue instead of black.

FIG. 25 is a schematic diagram of a conventional STN type liquid crystal device. In the figure, 101 is a lower polarizing plate, 102
110 is an upper polarizing plate, 110 is a liquid crystal cell, and a liquid crystal layer 113 is provided between the lower substrate 111 and the upper substrate 112.
It has a configuration in which the Both substrates 111, 11
Transparent electrodes 114 such as ITO electrodes are formed on the opposing surfaces of 2, and an alignment film 115 is formed on each side.
has been applied and rubbed. 116 is a spacer.

FIG. 26 is an explanatory diagram showing the relationship between the liquid crystal cell and the polarization axis (absorption axis) of the polarizing plate in the above liquid crystal device. In the figure, R1 is the rubbing direction of the lower electrode substrate of the liquid crystal cell, and R2 is the liquid crystal The rubbing direction of the upper electrode substrate of the cell, P1 is the direction of the polarization axis (absorption axis) of the lower polarizer, P2 is the direction of the polarization axis (absorption axis) of the upper polarizer, and t is the twist angle of the liquid crystal molecules of the liquid crystal cell. , α1 is the angle between the rubbing direction R1 of the lower electrode substrate and the polarization axis (absorption axis) direction P1 of the lower polarizing plate, α2 is the rubbing direction R2 of the upper electrode substrate and the polarization axis of the upper polarizing plate (absorption axis) and direction P2.

In Fig. 26 above, the angle t is 200 degrees, the angles α1 and α2 are each about 50 degrees, and the product Δn・d of the refractive index anisotropy Δn of the liquid crystal and the thickness d of the liquid crystal layer is
The optical characteristics of the liquid crystal device when the diameter is 0.9μm are as follows.
It is shown in Figure 7.

The figure shows pixels in the positive mode (bright when no voltage is applied) and on-state pixels when the liquid crystal device is driven by the multiplex driving method that is commonly used for driving this type of liquid crystal device. ,
It shows a spectrum of light transmittance of a pixel in an off state.

In this document, the off-state refers to a state in which no electric field is applied or a state in which the molecular orientation of the non-applied state is maintained even when an electric field is applied, and the on-state refers to a state in which the molecular orientation of the liquid crystal changes. is a state in which the phenomenon occurs in a necessary and sufficient manner to cause an optical change.

In FIG. 27, the curve shows the spectrum of the pixel in the off state, and the curve shows the spectrum of the pixel in the on state, and it can be seen that the curve is "bright" and the curve is "dark", that is, it is possible to visually distinguish it from the curve.

[Problem to be solved by the invention]

However, if the spectrum shown in Figure 27 above is plotted on color coordinates, it will look like Figure 28, which shows that in the conventional liquid crystal device, in positive mode, the color is yellow in the off state and blue in the on state. I understand.

As described above, in the conventional technology, when in the positive mode, the external appearance of the liquid crystal device in the off state is colored green, yellow-green, yellow, or yellow-red, and furthermore, in the on state, it becomes blue or dark blue. Also, in negative mode (dark with no voltage applied), the color is dark blue in the off state, and yellow in the on state.

These colors are not colors that are generally preferred as display colors for liquid crystal devices. After all, the display color of a liquid crystal device is a combination of white and black, that is, a combination of a flat spectrum is psychologically and physically suitable, and a liquid crystal device that can display black and white is desired. It is being In particular, when color display is performed in combination with a color filter, whether or not the spectrum is flat has a great effect on the vividness of the color. Aside from green, it becomes difficult to display blue and red at high brightness.

By the way, as a means to eliminate the above-mentioned coloring, in a twisted nematic type (hereinafter referred to as TN type) liquid crystal device, a power supply means is provided in a single layer type twisted nematic field effect type liquid crystal display cell. A liquid crystal device having a two-layer structure in which twisted nematic liquid crystal layers are superimposed is known (see, for example, Japanese Patent Laid-Open No. 57-96315).

However, the liquid crystal device disclosed in the above publication cannot be directly applied to the STN type liquid crystal device described above.

That is, the liquid crystal device described in the above publication is a so-called TN type. That is, the twist angle is 90 degrees, the polarizing plates are arranged parallel or perpendicular to the direction of adjacent liquid crystal molecules, and the operating principle is based on optical rotation. Therefore, the structure is significantly different from that of the STN type, which actively utilizes birefringence as an operating principle, and therefore cannot be simply applied to an STN type liquid crystal device as is.

The present invention was proposed in view of the above-mentioned problems, and can be applied to STN type liquid crystal devices without impairing their characteristics, regardless of the twist angle of the display cell or the value of Δn・d. It is an object of the present invention to provide a liquid crystal device capable of good black and white display without coloring in both the on state and the off state, and furthermore to provide a liquid crystal device suitable for color display.

[Means to solve the problem]

In order to achieve the above object, a liquid crystal device according to the present invention has the following configuration.

That is, a pair of display cells each having a nematic liquid crystal layer twisted and oriented at an angle of 120 degrees or more interposed between a pair of substrates having electrodes formed on their opposing inner surfaces, and at least one liquid crystal layer for compensation. between the polarizing plates, and the polarization axis direction of each polarizing plate is set in a predetermined direction excluding a direction substantially parallel to or substantially perpendicular to the long axis direction of the liquid crystal molecules of the display cell or compensation liquid crystal layer adjacent thereto. At the same time, the light incident on one polarizing plate becomes elliptically polarized light with a different major axis direction for each wavelength between the display cell and the compensation liquid crystal layer, and then enters the other polarizing plate. In this case, the torsion angle of the liquid crystal layer for compensation and the value of Δn·d are adjusted according to the torsion angle of the nematic liquid crystal layer of the display cell and the value of Δn·d so that the long axis direction of the light is elliptically polarized for each wavelength. The present invention is characterized in that d is set to a predetermined value to eliminate coloring of the display in the ON state and OFF state of the display cell.

[Effect]

As described above, the polarization axis direction of each polarizing plate is set to a predetermined direction excluding a direction substantially parallel to or substantially perpendicular to the long axis direction of the liquid crystal molecules of the display cell or compensation liquid crystal layer adjacent thereto, and Light incident on one polarizing plate becomes elliptically polarized light with a different major axis direction for each wavelength between the display cell and the compensation liquid crystal layer, and then when it enters the other polarizing plate, it becomes elliptically polarized light with a different major axis direction for each wavelength. The torsion angle and Δn·d of the compensation liquid crystal layer are set to a predetermined value according to the torsion angle and Δn·d of the nematic liquid crystal layer of the display cell so that the elliptically polarized light is almost aligned in the long axis direction. By setting the display cell to a value of First, it has become possible to obtain a good display without coloring as described above.

〔Example〕

FIG. 1 is a sectional view showing a schematic configuration of a liquid crystal device according to the present invention.

In the figure, 1 is a lower polarizing plate, 2 is an upper polarizing plate,
A display cell 10 performs display by applying a voltage, and has a structure in which a liquid crystal layer 13 is interposed between a pair of upper and lower substrates 21 and 11. Reference numeral 20 denotes a liquid crystal cell for color correction (hereinafter referred to as a compensation cell) having a liquid crystal layer that is an optically anisotropic body, and includes a pair of upper and lower substrates 22, 2.
1, with a liquid crystal layer 23 interposed between them.

The polarizing plate, liquid crystal material, liquid crystal alignment method, liquid crystal element driving method, etc. used in the present invention are conventional TN type,
Alternatively, the same one that is generally known for STN type liquid crystal devices etc. can be applied.
The details will be explained below.

The optical properties are greatly influenced by the polarization properties of the polarizing plate used. In all the specific examples of the present invention, LLC2-82-18 manufactured by Sanritsu Electric Co., Ltd. is used, but it goes without saying that the invention is not limited to this. FIG. 3 shows the wavelength dependence of the light transmittance of the two polarizing plates. In the figure, is the spectrum curve when the pair of polarizing plates are arranged parallel to each other, and is the spectrum curve when the pair is arranged perpendicularly to each other.

The liquid crystal composition used in the present invention is a nematic liquid crystal with positive dielectric anisotropy. An example of a preferable liquid crystal is SS-4008 manufactured by Chitsuso Corporation.
Examples of other preferred liquid crystal compositions include those shown below.

It is preferable to add a chiral dopant to the liquid crystal composition in order to keep the twisted structure of the liquid crystal stable.

As a chiral dopant, for example, CB- manufactured by BDH Co., Ltd. is used to create a right-handed helical structure.
15. Merck S-811 can be used to form a left-handed helical structure.

The display cell 10 used in the present invention can have exactly the same structure as the liquid crystal cell 110 used in the prior art shown in FIG. 25.

the substrate 11 of the display cell 10 and the compensation cell 20;
For example, transparent substrates such as glass and plastic are used as the substrates 12, 21, and 22. Display cell 1
A transparent electrode such as ITO is formed on the substrate 0, and an alignment film layer for determining the alignment of liquid crystal is formed on the transparent electrode. Further, a transparent electrode is provided on the substrate of the compensation cell 20 as required, and an alignment film layer is formed on the electrode or the substrate.

As a preferable example used as an alignment film layer,
Examples include polyimide and polyvinyl alcohol.
Generally, by rubbing these alignment film layers, a certain alignment can be given to the liquid crystal. Further, as another method for aligning liquid crystal, an oblique evaporation method of SiO or the like can also be used.

An example of the method for driving the liquid crystal device of the present invention is shown in FIG. The multiplex driving method shown in the figure is a method that is currently commonly used and has been put into practical use, but in the present invention,
Other driving methods can also be used.

The liquid crystal of the compensation cell used in the present invention is as follows:
Smectic liquid crystal, cholesteric liquid crystal, nematic liquid crystal, etc. can be used. in particular,
It is also desirable to use a nematic liquid crystal, or even the same nematic liquid crystal as the display cell.

Next, the basic role played by the compensation cell 20 will be explained in comparison with the conventional STN type liquid crystal device.

Figure 29 shows the conventional STN shown in Figure 25 above.
FIG. 2 is an explanatory diagram of the optical characteristics of a type liquid crystal device in an off state, and in the diagram, L is incident light. The incident light L
is generally natural light, includes light of all wavelengths in the visible region, and has random polarization directions. When the incident light L passes through the linearly polarizing plate 101, it becomes a set of linearly polarized lights b51, g51, r51, etc. whose polarization directions are aligned. Here, b51, g51, and r51 represent polarized light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively. Naturally, linearly polarized light with other wavelengths is also included, but only these three wavelengths are shown here as representative wavelengths of the three colors of blue, green, and red. These linearly polarized light b51・
g51 and r51 then pass through the liquid crystal cell 110. The liquid crystal layer in the liquid crystal cell has a structure in which nematic liquid crystal exhibiting optically uniaxial refractive index anisotropy is twisted. How the polarization state changes when the linearly polarized lights b51, g51, r51, etc. pass through a liquid crystal layer having such a structure can be predicted by a method described later.
For example, in the case of the conventional liquid crystal device whose spectrum is shown in FIG.
As shown in FIG. 9, the polarization states are b52, g52, and r52, respectively. By passing through the liquid crystal layer in this way, wavelength dispersion occurs in the polarization state.
These polarized lights b52, g52, and r52 finally pass through the linear polarizing plate 102. Of the polarized light of each wavelength, only the component corresponding to the direction of the linear polarizing plate 102 passes through. For example, in the conventional liquid crystal device whose spectrum is shown in FIG. 27, each b5
3, g53, r53. wavelength from this
It can be seen that the amount of light at 550 nm is large, and the amount of light at wavelengths of 450 nm and 650 nm is small. A spectral representation of these results is shown in FIG. 27, and a plot of this on color coordinates is shown in FIG. In this way, conventional STN liquid crystal devices have no choice but to become colored due to wavelength dispersion due to birefringence.

Next, FIG. 5 shows an explanatory diagram of the optical characteristics of the liquid crystal device according to the present invention in the off state. A comparison between FIG. 29 and FIG. 5 shows that FIG. 5 differs from FIG. 29 in that a compensation cell 20 is added as a component in addition to the display cell 10. For convenience of explanation, the conditions of the components except for the compensation cell 20 and the polarizing plate 2 are the same as those of the conventional example shown in FIG. 29, that is, the liquid crystal device whose spectrum is shown in FIG. 27. shall be.

Therefore, in FIG. 5, the polarization state b2, g of each wavelength after passing through the polarizing plate 1 and the display cell 10 is
2, r2 are b52, g52, r52 in Fig. 29
is exactly the same as The difference is that in FIG. 5, each of the polarized lights b2, g2, r2 passes through the compensation cell 20 next. In the present invention, the linearly polarized light b1, g by the polarizing plate 1 is
The compensation cell 20 has the function of canceling the chromatic dispersion caused by the transmission of the wavelength 1, r1 through the display cell 10.

In order to clearly explain this effect, the optical function of the display cell 10 is defined as M. Furthermore b
The polarization state of 1, g1, r1 is P, b2, g2, r
If the polarization state of 2 is P', P' can be obtained from P and M using the following equation.

P'=M*P (1) Here, it is assumed that the optical function of the compensation cell 20 is a function M ^-1 that performs the inverse transformation of M. b3, g3,
Assuming that the polarization state of r3 is P'', P'' is obtained from P' and M ^-1 using the following equation.

P″=M ^-1 *P′...(2) The following equation can be found from equations (1) and (2).

P″＝M ^-1 *M＊P ...(3) Obviously, M ^-1 *M=1 ...(4) Therefore, P″=P ...(5) Equation (5) is b3, g3 , r3 are the same as the polarization states P of b1, g1, and r1, respectively. b1, g1, and r1 are the polarized lights of natural light L immediately after passing through linear polarizer 1. Therefore, all wavelengths are linearly polarized light whose vibration direction corresponds to the orientation of the polarizing plate 1. Therefore, b3, g3,
r3 is also linearly polarized light having a vibration direction in the same direction as b1, g1, and r1. When the polarization axis direction of the linearly polarizing plate 1 matches the vibration direction of the polarized light b3, g3, r3, this linearly polarized light passes through the linearly polarizing plate 2 as it is and becomes b4, g4, r4.

The spectrum of the emitted light at this time matches the spectrum of the polarizing plate shown in FIG. The spectrum of the polarizer is almost flat and colorless. In this manner, the liquid crystal device according to the present invention can eliminate the coloring phenomenon in the off state.

The main points of the present invention are as described above, but the problem is that in FIG.
The question is whether there actually exists a compensation cell that can perform the inverse conversion of the conversion performed by display cell 10 for 1, r1, etc. over all wavelengths. In conclusion, the inventors have found that such conditions for the liquid crystal cell 20 can exist. Moreover, it has been found that such conditions can exist regardless of the conditions of the display cell 10.

To explain this condition, FIG. 2 shows the relationship between each cell and the polarizing plate in the liquid crystal device of the present invention shown in FIG. 1.

In the figure, P1 and P2 are the directions of the polarization axes (absorption axes) of the lower polarizing plate 1 and the upper polarizing plate 2, respectively;
R11 and R12 are the rubbing directions of the lower substrate 11 and upper substrate 12 of the display cell 10, R21 and R22 are the rubbing directions of the lower substrate 21 and the upper substrate 22 of the compensation cell 20, and t1 is the twist angle of the liquid crystal of the display cell 10. and direction, t2 is the twist angle and direction of the liquid crystal of the compensation cell 20, α1 is the direction P1 of the polarization axis of the lower polarizing plate and the rubbing direction R1 of the lower substrate of the display cell.
1, α2 is the direction P2 of the polarization axis of the upper polarizing plate and the rubbing direction R2 of the upper substrate of the compensation cell.
2, and β is the angle formed by the rubbing direction R21 of the lower substrate of the compensation cell and the rubbing direction R12 of the upper substrate of the display cell. Note that the twist direction of the liquid crystal molecules in each cell indicates the previous twist direction from the top to the bottom of the cell. The same applies below.

Here, for example, the conditions of the display cell are exactly the same as those of the conventional positive mode liquid crystal device whose spectrum is shown in FIG. The whitening conditions in μm will be described. Naturally, if there is no compensation cell, the spectrum will be as shown in FIG. 27, resulting in a colored state. However, when using a compensation cell, the twist angle t2 of the liquid crystal layer is negative.
When Δn·d0.9 μm is used at 200 degrees (that is, the twist is opposite to the display cell and the absolute value of the twist angle is equal), the spectrum in the off state becomes almost flat, as shown in FIG. however,
Other conditions at this time are α1 and α2 in Figure 2.
are respectively 45 degrees and β is 90 degrees. Figure 7 shows the spectrum shown in Figure 6 plotted on the color coordinates.
It is a diagram. It can be seen that the color is almost white compared to the conventional method shown in FIG. 27. As shown in the above embodiment, the compensation cell 20 performs inverse conversion of the display cell 10 as shown in FIG. 5 regardless of the wavelength.
The conditions exist. This correspondence relationship is shown as follows. That is, (1) the absolute values of Δn.d of the display cell and Δn·d of the compensation cell are equal.

(2) If the torsion angle t1 of the display cell is θ, the torsion angle t2 of the compensation cell is minus θ (the direction of the twist is opposite).

(3) The angle β between the rubbing direction R12 of the upper substrate of the display cell and the rubbing direction R21 of the lower substrate of the compensation cell is 90 degrees.

When the above three conditions are met, coloring in the off-state of the liquid crystal device can be completely eliminated, that is, whitening can be achieved, regardless of the value of Δn·d or the values of the twist angles t1 and t2.

All of the above explanations were about the mechanism of coloration elimination in the OFF state. In the present invention, coloring in the on state is also eliminated. Although it is not impossible to explain exactly the reason for the elimination of coloring in the on state, it is complicated. In any case, the inventor has experimentally confirmed that there is no or almost no coloration in the on state under various conditions, as shown in many examples in the specific examples described below.

As mentioned above, in order to completely eliminate the coloring in the off state of the positive mode, it is necessary that the above three conditions are satisfied. However, in reality, it is often sufficient for practical purposes even if the compensation cell does not necessarily undergo complete inverse transformation of the transformation of the display cell as shown in FIG. This is conceptually shown in FIG. FIG. 8 corresponds to FIG. 5. The difference from FIG. 5 is that the states b3', g3', r3' of each polarized light after passing through the compensation cell 20' are b3, g3,
It is not completely linearly polarized light like r3, but slightly elliptically polarized light. As a result, the intensity of the polarized lights b4', g4', and r4' after passing through the polarizing plate 2 has a slight wavelength dependence. Despite this, the spectrum of the positive mode appearance is almost white in the off state and almost black in the on state, and there are cases where coloring is almost completely eliminated in terms of color coordinates.

In this way, even under conditions where the above three conditions are not satisfied, there are conditions for a compensation cell that can sufficiently eliminate coloring in practical terms.

Alternatively, for other reasons, it may be more desirable to use a compensation cell other than the above three conditions in a positive sense. One of the reasons for this is that the characteristics of polarizing plates are generally wavelength dependent.
An example is shown in FIG. By appropriately selecting the conditions of the compensation cell for such wavelength characteristics, the coloring of the liquid crystal device can be improved. This applies not only to the off state but also to the on state. Another reason is to change the conditions of the compensation cell in consideration of the wide viewing angle.

The above explanation was about the high transmittance state in the off state, that is, the positive mode. The on-state state with low transmittance, that is, the negative mode, will be explained next. If the orientation of the polarization axis of the polarizing plate 2 shown in FIG.
cannot pass through. Therefore, the spectrum of the transmitted light at this time matches the spectrum of the polarizing plate in the crossed Nicol state shown in FIG. 3 (ignoring light absorption in the liquid crystal cell, compensation cell, etc.). This state is the darkest state that can be obtained using the polarizing plate shown in FIG. As described above, in the present invention, by using a compensation cell, it is possible to obtain the best possible flat spectral characteristics even in the negative mode state. That is, in either case, coloring can be eliminated.

Note that the following explanation will be made regarding the positive mode.

Next, a specific method for calculating the change in the polarization state of light that has passed through the compensation cell will be outlined below.

The light incident on the compensation cell is generally elliptically polarized. The reference plane trace of the elliptically polarized light now traveling in the Z-axis direction is
It can be expressed as a column vector whose elements are xy components as follows.

E = [a _x expi (ωt + φx)] [a _y expi (ωt + φy)]
...(6) Here, a _x and _y are the amplitudes of the xy components, ω is the angular frequency, and φx and φy are the phase angles of the xy components. However, in this case, the absolute phase of the wave does not matter, so
The polarization state was described by the normalized Johns vector of the following equation, which omitted the optical frequency and absolute phase terms in equation (6) and also normalized the amplitude of each component.

Now, the polarized light E in equation (7) passes through the compensation cell, changes its polarization state, and becomes polarized light E'. The compensation cell is represented by a 2x2 Johns matrix that performs this transformation.

For example, when this compensation cell (optically anisotropic) is a uniaxial positive linear retarder like a film-like polymer, the Johns matrix RΔ·θ can be expressed by the following equation.

Here, θ represents the angle that the fast axis of the linear phase shifter makes with the X axis, and Δ represents the retardation. Note that the retardation Δ is defined as Δ≡2πΔn·d/λ using Δn·d of the linear phase shifter and the wavelength λ of the light.

The polarization state of the light that has passed through this film-like polymer can be determined from the left side of the incident light vector E by applying the Johns matrix RΔ·θ of equation (8) as shown in the following equation.

E'=RΔ・θE Furthermore, if the compensation cell is made up of a plurality of film-like polymers stacked together, from the left side of the incident light vector E, sequentially (8 ) can be calculated as the following equation by applying the Johns matrix of the equation.

E′=RΔn・θn RΔn _-1・θn _-1 ……RΔ ₂ θ ₂ RΔ ₁ θ ₁ E The compensation cell is complicated as a retarder because the liquid crystal molecules are twisted and oriented. However, if the liquid crystal layer is divided into a sufficiently large number of layers as shown in FIG. 9a, it can be approximated by stacking liquid crystal layers that are not twisted and oriented as shown in FIG. 9b. Since the liquid crystal layer, which is not twisted and oriented, is a uniaxial linear retardator like the film-like polymer, it can be polarized in the same manner as when multiple film-like polymers are stacked together as described above. You can find the state.

Using the method explained above, the angle t1 in FIG.
is 200 degrees, angle t2 is minus 200 degrees, angle α1 is
45 degrees, angle α2 is 45 degrees, angle β is 90 degrees, and Δn・d of display cell and compensation cell are both 0.9 μm. The transition of the polarization state is shown in FIGS. 10 to 12. Figure 10, Figure 11, Figure 12
The figures show changes in the polarization state of light with wavelengths of 450 nm, 550 nm, and 650 nm, respectively. For example, in the case of Fig. 10, the linearly polarized light b11 incident on the display cell in Fig. 10a passes through five layers, b12, b13,
The polarization state changes to b14, and the elliptically polarized light of b15 is emitted from the cell. This elliptically polarized light b15 continues to enter the compensation cell in b of the same figure, and the polarization state changes to b16, b17, b18 every time it passes through five layers, and the linearly polarized light b19 exits the compensation cell. In each of the above processes, the conversion of the polarization state by the compensation cell in Figure b corresponds to the inverse transformation after the conversion by the display cell in Figure A, and therefore the light incident on the display cell is exactly the same. It exits the compensation cell in a polarized state. This effect is shown in Figures 11 and 12.
As is clear from the figure, since it exists regardless of the wavelength of light, in the liquid crystal device configured according to the present invention, coloring in the off state is completely eliminated, and whitening is possible.

Furthermore, as described above, there are conditions for a liquid crystal layer such as a compensation cell that is an optically anisotropic material that can sufficiently eliminate coloring even if the three conditions described above are not met. The conditions are that the light incident on one polarizing plate becomes elliptically polarized light with a different major axis direction for each wavelength between the display cell and the liquid crystal layer adjacent to the display cell,
After that, the liquid crystal layer may be arranged so that when the light is incident on the other polarizing plate, the light becomes elliptically polarized with substantially the same major axis direction for each wavelength. Specifically, the torsion angle of the liquid crystal layer such as the compensation cell and the value of Δn·d may be appropriately set according to the torsion angle of the display cell and the value of Δn·d. Explain in detail.

[Example 1] In FIGS. 1 and 2, the twist angle t1 of the liquid crystal of the display cell is about 200 degrees to the left, Δn・d is about 0.9 μm, the angle β is about 90 degrees, and the angles α1 and α2 are are in the range from 30 degrees to 60 degrees, and when the torsion angle t2 and Δn・d of the liquid crystal of the compensation cell are the shaded areas in Fig. 13, the color becomes almost white in the OFF state and almost black in the ON state. A liquid crystal device is obtained.

The above conditions can be calculated by using equations (6) to (8) above, and an example of the calculation method will be described below.

In other words, the liquid crystal of a display cell with Δn・d=0.9μm twisted 200° to the left is divided into 200 parts in the thickness direction of the cell.
Calculations are performed using the above formula assuming that each layer has a structure in which a uniaxial retarder with Δn·d=0.0045 μm is twisted to the left by 1°. The wavelength of the light used at this time is in the range of 400 nm to 70 nm. In addition, the polarization state of the light that enters the liquid crystal of the display cell differs depending on the type of polarizing plate used and the direction of the axis.
Here, we use an ideal polarizing plate (transmittance at parallel Nicols: 50
%, transmittance at crossed nicols: 0%). The angle α1 between the rubbing direction of the substrate adjacent to the polarizing plate (the direction of liquid crystal molecules on the surface of the substrate) and the direction of the polarization axis of the polarizing plate is set to 45°. Then, the linearly polarized light that has passed through the polarizing plate is incident on the display cell, and the state of elliptically polarized light of each wavelength that has passed through the display cell is determined.

Next, the state of the elliptically polarized light after it enters and passes through the compensation cell is determined. The elliptically polarized light incident on the compensation cell is determined by the same calculation as above, and the angle β formed by the rubbing direction of the adjacent substrates of the compensation cell and the display cell is 90 degrees. In addition, the liquid crystal of the compensation cell is also divided into 200 parts in the thickness direction of the cell, and the uniaxial retarder is twisted to the right by 0.7 degrees, making the structure twisted 140 degrees to the right as a whole.The Δn of the liquid crystal layer is - If d is set to an appropriate value, the state of the elliptically polarized light that has passed through the compensation cell can be determined from the above calculation formula. Furthermore, here, the angle α2 between the rubbing direction of the substrate adjacent to the polarizing plate and the direction of the polarization axis of the polarizing plate is 45
The spectrum after passing through the polarizing plate is determined as a degree, and the Y value is determined after the visibility correction is performed.

In the above calculation, Δn・ of the liquid crystal of the compensation cell
With the value of d ranging from 0 μm to 1.5 μm, the relationship between Δn·d of the compensation cell and the Y value corrected for visibility is determined.
At this time, when Δn·d of the compensation cell is plotted on the horizontal axis and the Y value is plotted on the vertical axis, as shown in FIG. 14, the Y value has maximum and minimum values and changes periodically. There are 22 directions in which the angle between the polarization axis and the rubbing direction is 45 degrees, so
Two curves are drawn in FIG. 14 above.

Display modes include negative mode (dark when no voltage is applied) and positive mode (bright when no voltage is applied). In negative mode, it is desirable that the state where no voltage is applied is darker, and in positive mode, it is desirable that the state where no voltage is applied is brighter. Therefore, in FIG. 14, the portion where the Y value is maximum is suitable for positive mode, and the portion where Y value is minimum is suitable for negative mode.

The Y value in the conventional negative mode voltage application state is 5%.
It is recognized that the coloring is extremely blue, both visually and on the color coordinates.

On the other hand, the minimum Y value in FIG. 14 is less than half of the negative mode Y value of the conventional STN liquid crystal device. The color at this time is slightly colored on the color coordinates, but because the Y value is small, it is visually recognized as a color that is sufficiently close to black. In addition, it appears white when a voltage is applied. Therefore, in the negative mode, a black and white display is obtained at the portion where the Y value is minimum, so that Δn·d becomes the desired value.

The portion where the Y value is maximum becomes closer to white both visually and on the color coordinates when compared with the color in the conventional positive mode when no voltage is applied. However, the color is close to white even before and after the portion where the Y value is maximum. Therefore, in positive mode, the area where black and white display can be obtained is quite wide, and it is extremely difficult to determine the boundaries. Also, since the angle between the polarization axis and the rubbing direction is 45 degrees, if the direction of the polarization axis in one curve in FIG. 14 is shifted by 90 degrees, it will match the polarization axis in the other curve. Therefore, the maximum and minimum values of Δn·d in FIG. 14 are the same.

From the above, black and white is obtained when the Y value is minimal, Δn·d. In other words, the display cell is twisted to the left.
200 degrees and Δn・d = 0.9 μm, and the angle α1 between the rubbing direction of the display cell substrate adjacent to the polarizing plate and the direction of the polarization axis of the polarizing plate is 45 degrees, and the display cell and compensation cell adjacent substrates are 45 degrees. The angle β formed by each rubbing direction is 90 degrees, and the compensation cell is right-handed.
When the angle α2 between the rubbing direction of the substrate of the compensation cell adjacent to the polarizing plate and the direction of the polarization axis of the polarizing plate is 45 degrees, Δn・d of the compensation cell is
A black-and-white display is obtained when the compensation cell Δn·d is 1.5 μm or less (see FIG. 14).

Next, if the rubbing direction of the substrate of each cell adjacent to the polarizing plate and the direction α1, α2 of the polarization axis of the polarizing plate are other than 45 degrees, or if the rubbing direction of each substrate of the adjacent display cell and compensation cell is The same procedure is used for calculations when the angle is other than 90 degrees. Then, Δn・d of the compensation cell where the Y value is minimum is:
It is found as a range that appears periodically with a certain width (distribution of Δn·d when the twist angle is fixed at 140 degrees to the right in Fig. 13). However, the angle formed by the direction of each axis at this time is within a range where the minimum value of the Y value is 3% or less, or where extreme coloring does not occur.

Also, when the conditions of the display cell remain the same and only the size of the torsion angle of the compensation cell is changed, the range of Δn・d of the compensation cell where the Y value is minimum will appear periodically in the same way as above. . FIG. 13 summarizes the relationship between the magnitude of the torsion angle of the compensation cell obtained in this way and Δn·d.
In other words, from Fig. 13, when the display cell is twisted to the left by 200 degrees and Δn・d is 0.9 μm, the magnitude of the twist angle of the compensation cell that provides black and white display and Δn・d
It can be seen that not only one condition exists, but a fan-shaped range exists periodically.

Furthermore, the magnitude of the torsion angle of the display cell and Δn・
Even when d is changed, the magnitude of the torsion angle and Δn·d of the compensation cell that provides a black-and-white display can be determined by the same procedure as above. In this case as well, the relationship between the torsion angle of the compensation cell and Δn・d is fan-shaped,
Appears periodically.

In this way, for the torsion angle and Δn・d of any display cell, the torsion angle and Δn・d of the compensation cell for black and white display can be found, and the torsion angle and Δn・d of the compensation cell can be calculated. is not the only one, but there are many.

[Example 2] In Example 1, the angle α2 in Fig. 2 was set to about 40
degree, the compensation cell's liquid crystal twist angle t2 is about 140 degrees right-handed, the angle β is about 90 degrees, the display cell's liquid crystal twist angle t1 is about 200 degrees left-handed, and the angle α1 is about 140 degrees right-handed.
40 degrees, Δn・d of the liquid crystal layer of the compensation cell is approximately 0.7 μm,
The Δn·d of the liquid crystal layer of the display cell is approximately 0.9 μm.
The spectrum of the appearance of the liquid crystal device at this time is shown in the 15th
As shown in the figure. In the figure, a curve indicates an off state, and a curve indicates an on state. The external appearance spectrum of the conventional liquid crystal device shown in FIG. 27 is yellow when it is off (curved) and blue when it is on (curved). However, as shown in FIG. 15, in the liquid crystal device of the present invention, the color is almost white in the off state, and the color is almost black in the on state.

[Example 3] In Example 1, the angle α2 in Fig. 2 was changed to about 40
compensation cell's liquid crystal torsion angle t2 of approximately 200 degrees to the right, angle β to approximately 90 degrees, compensation cell's liquid crystal layer torsion angle t1 of approximately 200 degrees to the left, and angle α1 to approximately 50 degrees. Δn・d of the liquid crystal layer of the cell is approximately 0.9μm,
The Δn·d of the liquid crystal layer of the display cell is approximately 0.9 μm.
The spectrum of the appearance of the liquid crystal device at this time is the 16th
As shown in the figure. In the figure, a curve indicates an off state, and a curve indicates an on state. In this case as well, as in Example 2, the color is almost white in the off state and almost black in the on state.

[Example 4] In Example 1, the angle α2 in Fig. 2 was changed to about 40
degree, the compensation cell's liquid crystal twist angle t2 is about 260 degrees to the right, the angle β is about 90 degrees, the display cell's liquid crystal twist t1 is about 200 degrees to the left, and the angle α1 is about 40 degrees.
The Δn·d of the liquid crystal layer of the compensation cell is approximately 0.8 μm, and the Δn·d of the liquid crystal layer of the display cell is approximately 0.9 μm. The spectrum of the appearance of the liquid crystal device at this time is shown in FIG. In the same figure, the curve indicates the off state,
The curve indicates the on state. In this case as well, as in Examples 2 and 3, the color is almost white in the off state and almost black in the on state.

[Example 5] In FIG. 2, the twist angle t of the liquid crystal of the display cell
1 is twisted to the left by about 250 degrees, Δn・d is about 0.9 μm, angle β is about 90 degrees, and angles α1 and α2 are each from 30 degrees.
If the range is up to 60 degrees, and the torsion angle t2 and Δn・d of the liquid crystal in the compensation cell are the shaded areas in Figure 18, we will have a liquid crystal device that is almost white in the OFF state and almost black in the ON state. can get.

[Example 6] In Example 5, the angle α2 in Fig. 2 was changed to about 40
The twist angle t2 of the liquid crystal in the compensation cell is about 160 degrees to the right, the angle β is about 90 degrees, the twist angle t1 of the liquid crystal in the display cell is about 250 degrees to the left, and the angle α1 is about 160 degrees to the right.
40 degrees, Δn・d of the liquid crystal layer of the compensation cell is approximately 0.8 μm,
The Δn·d of the liquid crystal layer of the display cell is approximately 0.9 μm.
The spectrum of the appearance of the liquid crystal device at this time is shown in the 19th
As shown in the figure. In the figure, a curve indicates an off state, and a curve indicates an on state. In this case as well, as in Example 2, the color is almost white in the off state and almost black in the on state.

[Example 7] In FIG. 2, the angle α2 is approximately 40 degrees, the twist angle t2 of the liquid crystal of the compensation cell is approximately 360 degrees right-handed, the angle β is approximately 90 degrees, and the twist angle t1 of the liquid crystal of the display cell is approximately The right twist is 250 degrees, the angle α1 is about 40 degrees, and the liquid crystal layer of the compensation cell has a Δn·d of about 1.0 μm, and the liquid crystal layer of the display cell has a Δn·d of about 0.9 μm. In this case as well, the liquid crystal device becomes white in the off state and blacker in the on state.

[Example 8] In FIG. 2, the angle α2 is about 50 degrees, the twist angle t2 of the liquid crystal in the compensation cell is about 170 degrees right-handed, the angle β is about 90 degrees, and the twist angle t1 of the liquid crystal in the display cell is about 170 degrees. The left twist is 170 degrees, the angle α1 is about 40 degrees, and the liquid crystal layer of the compensation cell has a Δn·d of about 0.7 μm, and the liquid crystal layer of the display cell has a Δn·d of about 0.7 μm. At this time as well, the liquid crystal device becomes white in the off state, and becomes blacker in the on state.

[Example 9] In FIG. 2, the twist angle t of the liquid crystal of the display cell
If 1 is about 120 degrees left-handed twist, Δn・d is about 0.9 μm, angle β is about 90 degrees, and angles α1 and α2 are each in the range of 30 degrees to 60 degrees, then the twist angle of the liquid crystal of the compensation cell is When t2 and Δn·d are defined as the shaded area in FIG. 20, a liquid crystal device is obtained which is substantially white in the off state and substantially black in the on state.

[Example 10] In Fig. 2, the twist angle t of the liquid crystal of the display cell
1 is about 200 degrees left-handed twist, Δn・d is about 0.6 μm, angle β is about 90 degrees, and angles α1 and α2 are each in the range of 30 degrees to 60 degrees, then the twist straightness t2 of the liquid crystal of the compensation cell and When Δn·d is defined as the shaded area in FIG. 21, a liquid crystal device is obtained which is substantially white in the off state and substantially black in the on state.

[Example 11] In Fig. 2, the twist angle t of the liquid crystal of the display cell
1 is twisted to the left by 200 degrees, Δn・d is approximately 1.5 μm, angle β is approximately 90 degrees, and angles α1 and α2 are each from 30 degrees.
If the range is up to 60 degrees, and the torsion angle t2 and Δn.d of the liquid crystal in the compensation cell are the shaded areas in Fig. 22, a liquid crystal device that is almost white in the OFF state and almost black in the ON state can be obtained. It will be done.

[Example 12] In Fig. 2, the twist angle t of the liquid crystal of the display cell
1 is approximately 350 degrees left-handed twist, Δn・d is approximately 0.9 μm, angle β is approximately 90 degrees, and angles α1 and α2 are each in the range of 30 degrees to 60 degrees, then the twist angle t2 of the liquid crystal of the compensation cell and When Δn·d is the shaded area in FIG. 23, a liquid crystal device is obtained which is substantially white in the off state and substantially black in the on state.

[Example 13] In Examples 1 to 12, the same effect can be obtained even if the compensation cell and the display cell are arranged upside down. In addition, the lower substrate 21 of the compensation cell shown in FIG.
and the upper electrode substrate 12 of the display cell.
A similar effect can be obtained even if the structure is replaced with a single substrate.

[Example 14] In FIG. 24, 1 is a lower polarizing plate, 2 is an upper polarizing plate, 10 is a display cell, 20 is an upper compensation cell, 3
0 is the lower compensation cell. In the liquid crystal display device having the structure shown in the figure, the liquid crystal molecules in both the upper compensation cell 20 and the lower compensation cell 30 are right-handed. Furthermore, the liquid crystal molecules of the display cell 10 are left-handed. At this time, the sum of the twist angle of the liquid crystal molecules of the upper compensation cell 20 and the twist angle of the liquid crystal molecules of the lower compensation cell 30 is the torsion angle of the entire compensation cell, and the upper compensation cell 2
Δn・d of the liquid crystal layer of the lower compensation cell 30 and Δn・d of the liquid crystal layer of the lower compensation cell 30 are calculated as Δn・d of the entire compensation cell.
Let it be d. Even when the torsion angle of the entire compensation cell and Δn·d of the entire compensation cell are set to the conditions of the compensation cells of the first to twelfth embodiments, the same effects as those of the first to twelfth embodiments can be obtained. Similar effects can be obtained by arbitrarily changing the arrangement order of the cells 10, 20, and 30. Moreover, three or more layers of compensation cells can be provided under the same conditions as above.

[Example 15] In the structure of Example 14, the lower substrate 21 of the upper compensation cell 20 and the upper electrode substrate 12 of the display cell 10
2 boards are replaced with one board. Further, the two substrates, the lower electrode substrate 11 of the display cell 10 and the upper substrate 32 of the lower compensation cell 30, are replaced with one substrate. In this way, the number of substrates is reduced and the structure is simplified, and the same effect as in the fourteenth embodiment can be obtained.

[Example 16] In Examples 1 to 15, the temperature at the NI point of the liquid crystal of the display cell is T ₁ (°K), and the temperature at the N1 point of the liquid crystal of the compensation cell is T ₂ (°K). At this time, if a liquid crystal satisfying 0.86≦T ₂ /T ₁ ≦1.15 is used, the external color of the liquid crystal device hardly changes even if Δn·d of the liquid crystal layers of the display cell and the compensation cell change due to temperature change.

[Example 17] In Examples 1 to 16, when a liquid crystal with a positive dielectric anisotropy Δε is used as the liquid crystal of the compensation cell, the orientation of the liquid crystal layer of the compensation cell is disturbed due to the influence of external static electricity. , color unevenness may appear on the external appearance of the liquid crystal device. Therefore, if a liquid crystal having a negative dielectric anisotropy Δε is used as the liquid crystal of the compensation cell, a liquid crystal device that does not have color unevenness in appearance even if it is influenced by static electricity from the outside can be obtained.

[Example 18] In Examples 1 to 16, electrodes are provided inside the upper and lower substrates of the compensation cell, and a liquid crystal having a positive Δε is used as the liquid crystal of the compensation cell. By doing so,
Even if the external color of the liquid crystal device changes due to temperature changes, the color change can be canceled out by applying a voltage between the electrodes attached to the upper and lower substrates of the compensation cell.

[Example 19] In Examples 1 to 18, excluding Examples 13 and 15, the compensation cell and the display cell were optically sealed in order to prevent light reflection on the substrate surface where the compensation cell and the display cell were in contact. Glue to. An embossed polyvinyl butyral film is used as an adhesive layer and bonded by heating and pressure. Furthermore, a heat-effect epoxy or urethane adhesive may be used as the adhesive. Furthermore, an acrylic ultraviolet adhesive may be used. By adhering the compensation cell and the display cell as described above, reflection at the interface between the two cells can be reduced.

[Example 20] In Examples 1 to 19, a reflective liquid crystal device with black and white display can be obtained regardless of whether the reflective plate is placed outside of either the upper or lower polarizing plate.

〔Effect of the invention〕

The present invention has solved the coloring phenomenon, which was a major drawback of conventional STN liquid crystal devices. In other words, the present invention enables complete black and white display. Not only that, but the amount of light in the transmitted state has increased, resulting in a brighter display. Furthermore, the amount of entangled light in the non-transmissive state was extremely reduced, and together with the increase in the amount of light in the transparent state, the contrast ratio was greatly improved.

Due to the above effects, the present invention was able to exhibit good color display characteristics when applied to color display. In particular, when the twist angle was 180 degrees or more, the clear vision direction was the front, and the clear vision area was a region close to concentric circles centered on the front. For this reason, as a full-color image display element, compared to a device using a conventional TN type liquid crystal device, it has a wider viewing angle, a direction of the viewing angle (the diagonal direction is the clear viewing direction for TN type devices), and a higher contrast ratio. etc. have been greatly improved. Of course, in the case of color display (8-color display) that does not display gradation,
It is improved compared to the TN type.

In the present invention, the above-mentioned effects can be obtained regardless of the thickness of the liquid crystal layer of the display cell, so a high-speed response liquid crystal device can be easily realized by decreasing the thickness of the liquid crystal layer of the display cell. This is because the response speed is approximately proportional to the square of the thickness of the liquid crystal layer.

Furthermore, since the present invention is effective in improving the contrast ratio as described above, it is also effective in increasing the number of drive lines in multiplex drive.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic configuration of a liquid crystal device in an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the relationship between each axis of the liquid crystal device. FIG. 3 is a diagram showing the wavelength dependence of the light transmittance of two polarizing plates used in a specific example of the present invention. FIG. 4 is a diagram showing an example of a method for driving a liquid crystal device according to the present invention. FIG. 5 is a diagram showing the optical characteristics of the liquid crystal device according to the present invention in an off state.
FIG. 6 is a diagram showing the off-state spectrum of the liquid crystal device according to the present invention. FIG. 7 is an xy chromaticity diagram in which the spectrum shown in FIG. 6 is plotted on color coordinates. 8th
The figure conceptually shows a case where the compensation cell does not undergo a complete inverse transformation of the display cell. FIG. 9a is a schematic diagram of a cross section when the liquid crystal layer is divided into 10 parts. FIG. 9b is a diagram conceptually showing the relationship between the liquid crystal layer thickness and the twist angle in FIG. 9a. Figure 10 shows the transition of the polarization state of light with a wavelength of 450 nm calculated by dividing the liquid crystal layer into 20 parts. Figure 11 is a diagram showing the transition of the polarization state of light with a wavelength of 550 nm calculated by dividing the liquid crystal layer into 20 parts. Figure 12 shows the wavelength calculated by dividing the liquid crystal layer into 20 parts.
A diagram showing the transition of the polarization state of 650 nm light. 13th
The figure is a diagram showing a desirable range of compensation cells relative to display cells in Embodiment 1 of the present invention. FIG. 14 is a diagram showing the relationship of the Y value to Δn·d when the above range is calculated. FIG. 15 is a diagram showing the relationship between wavelength and transmittance characteristics of the external appearance of a liquid crystal device according to Example 2 of the present invention. FIG. 16 is a diagram showing the relationship between wavelength and transmittance characteristics of the external appearance of a liquid crystal device according to Example 3 of the present invention. FIG. 17 is a diagram showing the relationship between wavelength and transmittance characteristics of the external appearance of a liquid crystal device according to Example 4 of the present invention. 1st
FIG. 8 is a diagram showing a desirable range of compensation cells for display cells in Example 5 of the present invention. FIG. 19 is a diagram showing the relationship between wavelength and transmittance characteristics of the external appearance of a liquid crystal device according to Example 6 of the present invention. FIG. 20 is a diagram showing a desirable range of compensation cells for display cells in Example 9 of the present invention. FIG. 21 is the same diagram in Example 10 of the present invention. FIG. 22 is the same diagram in Example 1 of the present invention. FIG. 23 is Embodiment 12 of the present invention
Same figure as above. FIG. 24 is a diagram showing the structure of a liquid crystal display device according to Example 14 of the present invention. FIG. 25 is a schematic diagram of a conventional super twisted nematic type liquid crystal device. FIG. 26 is a diagram showing the relationship between the liquid crystal cell of the liquid crystal device and the polarization axis (absorption axis) of the polarizing plate. Second
FIG. 7 is a diagram showing spectra of light transmittance of pixels in an on state and pixels in an off state during multiplex driving of a conventional liquid crystal device. Figure 28 is an xy chromaticity diagram plotting the spectral curve on color coordinates. Second
FIG. 9 is a diagram showing the optical characteristics of the conventional liquid crystal device in an off state. 1 and 2 are polarizing plates, 10 is a display cell, 20 is a compensation cell as an optically anisotropic liquid crystal layer, t1,
t2 is the twist angle.

Claims (1)

[Scope of Claims] 1. A display cell comprising a pair of substrates having electrodes formed on opposing inner surfaces, and a nematic liquid crystal layer twisted and oriented at an angle of 120° or more interposed;
and a compensation liquid crystal layer between a pair of polarizing plates, and the polarization axis direction of each polarizing plate is approximately parallel to the long axis direction of the liquid crystal molecules of the display cell or the compensation liquid crystal layer adjacent to the polarizing plate. or a predetermined direction other than a substantially orthogonal direction, and the light incident on one polarizing plate is elliptically polarized with a different major axis direction for each wavelength between the display cell and the compensation liquid crystal layer. Then, when the light enters the other polarizing plate, it is compensated according to the torsion angle of the nematic liquid crystal layer of the display cell and the value of Δn・d so that each wavelength becomes elliptically polarized light with almost the same long axis direction. 1. A liquid crystal device characterized in that the twist angle and Δn·d of a liquid crystal layer are set to predetermined values to eliminate display coloring in an on state and an off state of a display cell. 2. Claims characterized in that the angle formed between the polarization axis direction of each of the polarizing plates and the long axis direction of liquid crystal molecules in the display cell or compensation liquid crystal layer adjacent thereto is 30° to 60°. The liquid crystal device according to item 1. 3 Δn・d of the nematic liquid crystal layer of the display cell
2. The liquid crystal device according to claim 1, wherein the thickness is 0.5 to 1.8 μm. 4 The twist angle of the compensation liquid crystal layer is -550°~
Claim 1 characterized in that the angle is 300°.
The liquid crystal device described in Section 1. 5 Δn・d of the liquid crystal layer for compensation is 0.25 to 1.8 μm
A liquid crystal device according to claim 1, characterized in that: 6. The liquid crystal device according to claim 1, wherein the orientation direction of liquid crystal molecules on opposing surfaces of the nematic liquid crystal of the display cell and the compensation liquid crystal layer is approximately 90 degrees. 7. The liquid crystal device according to claim 1, wherein the compensation liquid crystal layer is an aligned nematic liquid crystal or cholesteric liquid crystal. 8. The liquid crystal device according to claim 1, wherein the compensation liquid crystal layer is a twisted nematic liquid crystal. 9. The liquid crystal device according to claim 7, wherein a plurality of oriented compensation liquid crystal layers are arranged. 10. The liquid crystal device according to claim 8, wherein the twist directions of the nematic liquid crystal of the display cell and the nematic liquid crystal of the compensation liquid crystal layer are opposite to each other. 11. The liquid crystal device according to claim 8, wherein the nematic liquid crystal of the display cell and the nematic liquid crystal of the compensation liquid crystal layer have substantially the same twist angle and Δn·d.