JPH09160022A - Liquid crystal electro-optical device - Google Patents

Abstract

(57) An object of the present invention is to widen the viewing angle of a liquid crystal electro-optical device, which is optimum for the OCB mode of normally white mode display and similar modes. When a liquid crystal electro-optical device 1 is combined with a liquid crystal cell 10 in a bend arrangement and an optical anisotropic element 30, an elliptic coefficient Z of a refractive index ellipsoid of the optical anisotropic element 30 is Z = (ndx −ndz ) / (Ndx −ndy), 7 ≦ Z ≦ 10 (the product of the thickness d of the optical anisotropic element 30 and the refractive index n of the optical anisotropic element 30 in the kx, y, z direction components is ndx, ndy, nd).
Let z. ndx and ndy represent components in the in-plane direction of the optically anisotropic element, and ndz represents components in the thickness direction. ) Is provided, which is an optical anisotropic element for compensating the viewing angle characteristics of the liquid crystal layer 13 of the liquid crystal cell 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal electro-optical device, and more particularly to a fast response liquid crystal electro-optical device.

[0002]

2. Description of the Related Art The OCB mode has been attracting attention as a liquid crystal electro-optical device capable of obtaining a high-speed response.

The basic structure of the OCB will be described with reference to FIG.

In the OCB mode, the electrodes 51a, 5 are formed on one main surface.
Two substrates 51, 52 on which 2a is formed are arranged so that their main surfaces face each other, and a liquid crystal cell 50 in which a liquid crystal layer 53 is sandwiched between the two substrates and a liquid crystal cell 50 are sandwiched. The two polarizing plates 60 arranged, the polarizing plate 60 and the liquid crystal cell 50.
It has an optical anisotropic element 70 arranged between them.

As shown in FIG. 2A, the liquid crystal layer 53 is composed of a plurality of liquid crystal molecules 53a which are in contact with one of the two substrates 51 of the liquid crystal molecules of the liquid crystal layer 53.
Liquid crystal layer region A, a second liquid crystal layer region B composed of a plurality of liquid crystal molecules 53b in contact with the other substrate 52 of the two liquid crystal molecules of the liquid crystal layer, and a liquid crystal molecule of the liquid crystal layer 53 A third liquid crystal layer region C composed of a plurality of liquid crystal molecules sandwiched between one liquid crystal layer region A and a second liquid crystal layer region B. By changing the voltage value applied to the electrodes, the liquid crystal molecules in the liquid crystal layer are arranged as shown in FIGS. 2 (a), 2 (b) and 2 (c).

In the OCB mode liquid crystal layer, the orientation directions of the two substrates are the same. When no voltage is applied, the liquid crystal layer is in a splay alignment state as shown in FIG. 2), a part of the liquid crystal molecules 53c1 of the third liquid crystal layer region C is arranged substantially parallel to the normal line direction of the substrate, and when a voltage is further applied, the bend alignment state shown in FIG.
Liquid crystal molecules 53 of the third liquid crystal layer region C as shown in (c)
It is assumed that c2 and 53c3 are arranged substantially parallel to the normal direction of the substrate. The OCB mode is a birefringence effect type display in which display is performed between the respective applied voltages in the states of FIGS. 2B and 2C and the phase difference in the liquid crystal layer is changed by controlling the voltage. According to the literature relating to the OCB mode, it is a liquid crystal display mode, and it is reported that a necessary and sufficient value of several ms can be obtained.

The liquid crystal molecular alignment at the time of display in this display mode is characterized in that the upper half and the lower half of the liquid crystal are always substantially symmetrical. Therefore, in the range of the viewing angle (observation angle) that is parallel to the plane where the liquid crystal molecules are arranged (the direction of the paper surface of FIG. 2), the upper half and the lower half of the liquid crystal have substantially symmetrical shapes, and in this case, the liquid crystal layer The refractive index ellipsoid of is a sphere, and within this range, the viewing angle dependence is almost eliminated and a wide viewing angle can be obtained.

However, for a viewing angle that is not parallel to the plane in which the liquid crystal is lined up, the refractive index ellipsoid of the liquid crystal layer does not become a sphere and the refractive index ellipsoid is deformed depending on the viewing angle, resulting in viewing angle dependence.

As a method for solving such a problem of viewing angle, it has been reported to add an optical anisotropic element having a biaxial optical axis in which the refractive index in the thickness direction is optimized (Miyashita et al. Eurodisplay '93, pp149-152).

In order to obtain a good black display in the OCB mode, a normally white mode display in which black is displayed on the high voltage side is preferable. This is because the voltage is applied and the liquid crystal molecules are
As shown in (c), the liquid crystal molecules 53 in the third liquid crystal layer region C
The state in which c is substantially parallel to the normal line direction of the substrate, that is, the state in which the liquid crystal molecules are almost raised is used for black display. In this state, the phase difference of the liquid crystal layer is a relatively small value, so The uniformity of black obtained by crossing the plates is good.

[0011]

As described above, an OCB mode LCD is mentioned to obtain a wide viewing angle and a high-speed response, and a normally white mode display is preferable to obtain a good black display. In order to compensate the viewing angle, it is important to select an optical anisotropic element that compensates the refractive index ellipsoid of the liquid crystal layer and becomes a sphere.

It is an object of the present invention to provide a liquid crystal electro-optical device having an optical anisotropic element which is optimum for the OCB mode of normally white mode display and its similar modes. The mode similar to the OCB mode means the liquid crystal layer 5
3 has an alignment state in which a part of the liquid crystal molecules 53c1 of the third liquid crystal layer region C are aligned substantially parallel to the normal line direction of the substrate as shown in FIG. 2B, and the liquid crystal in this alignment state. A liquid crystal electro-optical device having a state in which liquid crystal molecules 53c2 and 53c3 in the third liquid crystal layer region C are arranged substantially parallel to the normal direction of the substrate as shown in FIG. Say.
For example, when a liquid crystal having a chiral ability is put in a liquid crystal cell that has been subjected to the same orientation treatment as in the OCB mode, a 180 ° twisted arrangement can be obtained in a uniform arrangement when no voltage is applied. When a large voltage is applied to such an array, the bend array described above can be easily obtained.

[0013]

A liquid crystal electro-optical device according to the present invention is a bend alignment liquid crystal cell including a liquid crystal cell having a twist alignment in the center of the cell, and an optical device for reducing the viewing angle dependence of the bend alignment liquid crystal cell. In a liquid crystal electro-optical device including an anisotropic element, the optical anisotropic element is Z = (ndx
-Ndz) / (ndx-ndy), 7≤Z≤
10 (ndx, ndy, ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the substrate and the optical anisotropic element when the substrate and the optical anisotropic element are arranged substantially parallel to each other) Represents the refractive index component in the x, y, and z directions of the sum of the products of the refractive indices of, where n is the refractive index, and d is the thickness,
The optical anisotropic element may be composed of a plurality of sheets and represents the total sum thereof. dx and ndy represent refractive index components of the optical anisotropic element in the in-plane direction of a plane (xy plane) that is substantially perpendicular to the thickness direction of the optical anisotropic element, and ndx and ndy are perpendicular to each other. ndz represents the refractive index component of the optical anisotropic element in the thickness direction (z direction) of the optical anisotropic element. The present invention provides a liquid crystal electro-optical device characterized in that

That is, the liquid crystal layer of the bend alignment liquid crystal cell of this liquid crystal electro-optical device includes a first liquid crystal layer region composed of a plurality of liquid crystal molecules in contact with one of two substrates out of the liquid crystal molecules of the liquid crystal layer. A second liquid crystal layer comprising a plurality of liquid crystal molecules in contact with the other of the two substrates.
Liquid crystal layer region and a third liquid crystal layer region composed of a plurality of liquid crystal molecules sandwiched between the first liquid crystal layer region and the second liquid crystal layer region among the liquid crystal molecules of the liquid crystal layer. When the first voltage is applied to the electrode, the liquid crystal layer is arranged so that the inclination of some of the liquid crystal molecules in the third liquid crystal layer region is aligned substantially parallel to the normal direction of the substrate, When the second voltage is applied, the liquid crystal layer is arranged such that the tilts of the plurality of liquid crystal molecules in the third liquid crystal layer region are substantially parallel to the normal direction of the substrate.

In the optically anisotropic element, the thickness of the liquid crystal layer sandwiched between the two substrates in the liquid crystal layer when the second voltage is applied in the direction inclined with respect to the normal line direction of the substrates. It is characterized in that the optical anisotropy of the radial component is compensated. That is, in the OCB mode and a mode similar to the OCB mode of the present invention, when the second voltage is applied, the liquid crystal molecules except the liquid crystal molecules near the substrate are substantially parallel to the normal line direction of the substrate. The refractive index anisotropy becomes extremely large in the optical anisotropic component in the normal direction, that is, in the thickness direction of the liquid crystal layer. In the present invention, an optical anisotropic element is arranged to compensate for the optical anisotropy of the liquid crystal layer of such a component in the thickness direction of the liquid crystal layer in the direction inclined with respect to the normal line direction of the substrate.

FIG. 1 shows an example of a liquid crystal electro-optical device in which the liquid crystal layer of the present invention is arranged in a mode similar to the OCB mode.
This will be described with reference to FIG.

As shown in FIG. 1A, the liquid crystal layer 13 is composed of a plurality of liquid crystal molecules, and the liquid crystal layer 13 is in contact with one of the two substrates, that is, the substrate 11 having the electrodes 11a. First liquid crystal layer region A composed of liquid crystal molecules 13a
And the substrate 12 which is the other of the two substrates and has the electrode 12a
A second liquid crystal layer region B made up of a plurality of liquid crystal molecules 13b and a third liquid crystal layer region C made up of a plurality of liquid crystal molecules 13c sandwiched between a first liquid crystal layer region and a second liquid crystal layer region.
Consists of 1A shows the arrangement of liquid crystal molecules when no voltage is applied to the electrodes, FIG. 1B shows the first voltage application state to the electrodes, and FIG. 1C shows the electrode. Shows a second voltage application state to the.

As shown in FIG. 1A, when no voltage is applied to the electrodes 11a and 12a from the voltage driving source 40 connected to the electrodes, a plurality of liquid crystal molecules 13c in the third liquid crystal layer region C are formed.
Are arranged substantially parallel to each other and twisted in the in-plane direction of the substrate from one substrate toward the other substrate.

As shown in FIG. 1 (b), electrodes 11a, 1
When the first voltage is applied to 2a, the tilt of a part of the liquid crystal molecules 13c1 at the center of the plurality of liquid crystal molecules in the third liquid crystal layer region C is arranged substantially parallel to the normal direction of the substrate. . When the first voltage is applied, the liquid crystal molecules are substantially parallel to the normal direction of the substrate at the threshold voltage or more, that is, the phase difference of the liquid crystal cell in which the liquid crystal molecules start to rise is more rapidly changed by the applied voltage. , When the voltage applied to the liquid crystal is increased.

Next, as shown in FIG.
When the second voltage is applied to a and 12a, the tilts of the plurality of liquid crystal molecules 13c2 and 13c3 on the side in contact with the electrodes of the third liquid crystal layer region are arranged substantially parallel to the normal direction of the substrate. When the second voltage is applied, a voltage is further applied than when the first voltage is applied, and at this time, the liquid crystal molecules 13c2 and 13c3 in the third liquid crystal layer region are substantially parallel to the normal direction of the substrate. The liquid crystal is in a state of being aligned, that is, a state in which the liquid crystal is activated.

In the mode similar to the OCB mode and the OCB mode, the liquid crystal layer 13 is sandwiched between the two substrates 11 and 12 in the arrangement state as shown in FIGS. 1B and 1C. In the thickness direction of the liquid crystal layer, the upper half and the lower half of the liquid crystal layer have a substantially symmetrical bend arrangement with the vicinity of the center of the liquid crystal layer as a boundary. Therefore, as shown in FIG. 4, in the range of the viewing angle (observation angle) in which the liquid crystal molecules are substantially parallel to the plane 40 arranged in the thickness direction, the upper half and the lower half of the liquid crystal have a substantially symmetrical shape. In this case, the refractive index ellipsoid representing the optical anisotropy of the liquid crystal layer becomes a sphere, and within this range, the viewing angle dependence is almost eliminated and a wide viewing angle can be obtained. On the other hand, for viewing angles that are not parallel to the plane 40 shown in FIG.
The refractive index ellipsoid of the liquid crystal layer does not become a sphere, and the refractive index ellipsoid is deformed depending on the observation angle, resulting in viewing angle dependence.

The present invention can obtain a wider viewing angle by compensating for the optical anisotropy of the liquid crystal layer.

That is, the liquid crystal electro-optical device of the present invention is
It has an optical anisotropic element having a negative optical anisotropy having a biaxial optical axis having the following refractive index ellipticity coefficient Z value.

Z = (ndx-ndz) / (ndx-nd
y), where 7≤Z≤10, where ndx, ndy, and ndz are the thicknesses of the optical anisotropic element in the normal direction to the substrate when the substrate and the optical anisotropic element are arranged substantially parallel to each other ( (Unit: μm) and the refractive index component in the x, y, z directions of the sum of the products of the refractive indexes of the optical anisotropic element. ndx and ndy represent refractive index components of the optical anisotropic element in an in-plane direction of a plane that is substantially perpendicular to the thickness direction of the optical anisotropic element, and ndx and ndy are perpendicular to each other. ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element.

When the liquid crystal layer of the liquid crystal cell has the orientation shown in FIG. 4, the equivalent index ellipsoid is nzLC>nxLC> nyLC as shown in FIG. 5, and each cross section of the ellipsoid RL in FIG. xz plane, yz plane,
As is clear from the xy plane, for example, a “rugby ball” has a shape compressed in the y direction.

As shown in FIG. 6, the refractive index ellipsoid RC of the optical anisotropic element that compensates for this compresses the "rugby ball" in the major axis direction z more than the other two axes as shown in FIG. The other 2
It is desirable to have a shape in which the y direction of the axis is elongated.

When this refractive index ellipsoid is expressed by a refractive index formula, Z = (nxC-nzC) / (nxC-nyC), where nzC <nxC12 <nyC.

Here, the size of nz is the liquid crystal layer 1 of FIG.
Liquid crystal molecules 13a and 13b in regions A and B contacting the substrate 3
Depending on the pretilt angle.

In order to obtain a uniform display, it is desirable that the pretilt angle and the thickness of the liquid crystal layer are uniform, but it is difficult to manufacture as the pretilt angle that can be made uniform becomes higher, and the maximum is 8 degrees. Therefore, the Z value changes depending on the pretilt angle, and 7 ≦ Z ≦ 10 in the range of the pretilt angle that can be realized.

A liquid crystal electro-optical device having such an optically anisotropic element is suitable for normally white display in OCB mode and similar modes. This makes it possible to compensate for the optical anisotropy of the liquid crystal layer, which is the component in the thickness direction of the liquid crystal layer in the direction inclined with respect to the normal direction of the substrate, and to widen the viewing angle. Within this range, excellent display performance with a wide viewing angle and a very small inversion area can be obtained. When the value of Z is less than 7, the inversion area becomes wide and the range in which the contrast ratio is good becomes narrow. On the other hand, when it becomes larger than 10, the reversal area increases again.

Further, in the present invention, the value of Z is more preferably 8 ≦ Z ≦ 10.

In the present invention, OCB and similar display modes OCB and similar display modes use the optical anisotropic element under the above-mentioned conditions in order to obtain a wider viewing angle. Further, in the present invention, by setting the relationship between the retardation of the optically anisotropic element and the retardation of the liquid crystal cell to a specific condition, the driving voltage is within the practical range,
Moreover, they have found that a bright display can be made.

OCB and similar display modes are
All are in birefringence mode, and the transmittance T of the liquid crystal cell is
It is expressed by the following equation.

T = sin ² (R / πλ)-(1) Equation (1) is a crossed Nicol, and the optical axis represents the transmittance at 45 ° with the transmittance axis. R is the retardation value of the optically anisotropic substance existing between the polarizing plates, and λ is the light source wavelength.

The orientation of the optical axis of the optically anisotropic element is perpendicular to the orientation of the rubbing axis of the liquid crystal cell. In such an arrangement, the total retardation value is the difference between the retardation values RLC of the liquid crystal cell and the retardation Rfxy of the optically anisotropic element, and the parameter R in the formula (1) is R = RLC-Rfxy- -(2)

Therefore, from the equation (2), the transmittance of the liquid crystal cell is determined by the difference between the retardation of the liquid crystal cell and the in-plane retardation of the optically anisotropic element. That is,
The retardation in the in-plane direction of the optically anisotropic element affects the brightness of the display.

The retardation of the liquid crystal cell changes depending on the voltage applied to the liquid crystal layer. When the voltage of the liquid crystal cell changes and the retardation of the liquid crystal cell becomes equal to the retardation of the optically anisotropic element in the in-plane direction, the total retardation becomes zero, and black display is obtained.

That is, the in-plane retardation of the optically anisotropic element affects the voltage value at which black display is obtained. Therefore, M was defined as the ratio of the in-plane retardation of the optically anisotropic element to the in-plane retardation of the optically anisotropic element, that is, the retardation ratio M, and the influence of these was investigated.

M = RLC / Rfxy = ΔnLC × dLC / (ndx −ndy) −− (3) where ΔnLC is the refractive index difference of the liquid crystal and dLC is the thickness of the liquid crystal layer.

FIG. 11 shows the dependence of the retardation ratio M on the electro-optical characteristics. When the value of M is 7.5 or less, the transmittance is lowered, the contrast ratio is lowered, and the display quality is deteriorated. Also, when M is 18 or more,
The transmittance is increased and the display quality is improved, but the black display voltage is 1
It becomes too high as 0 V or more, and it is not practical because a special high breakdown voltage integrated circuit for increasing power consumption and applying a high voltage is required. Therefore, the retardation ratio M that can achieve good brightness and a practical black display voltage is 7.5 <M <18.

In the liquid crystal electro-optical device of the present invention, it is preferable that the optical anisotropic element satisfies 0.022≤ndx-ndy≤0.6670.15 <ndx-ndz <6.7. As a result, ΔnLC · d of the liquid crystal layer
When the LC value is 0.3 μm or more and 5 μm or less, a liquid crystal electro-optical device having an optimal optical anisotropic element can be obtained.

Further, in the liquid crystal electro-optical device of the present invention, one of the two polarizing plates can be used as the reflecting plate.

In this case, since the light passes through the device twice,
The lower limit of (ndx-ndy) is 0.011.

The liquid crystal electro-optical device according to the present invention has the first aspect.
When the display of the liquid crystal electro-optical device is turned on when the voltage is applied to the liquid crystal electro-optical device, when the first voltage is applied, the alignment state of the liquid crystal layer is part of the liquid crystal molecules 9a in the third liquid crystal layer region C.
Since the inclination of is arranged substantially parallel to the normal direction of the substrate,
A fast response display can be obtained.

The liquid crystal electro-optical device according to the present invention has the first aspect.
The display is performed between the time when the voltage is applied and the time when the second voltage is applied. This makes it possible to obtain a fast response display.

In the liquid crystal optical element of the present invention, the two substrates are centered around the liquid crystal molecules arranged substantially parallel to the normal line direction of the substrate in the third liquid crystal layer region when the first voltage is applied. It is characterized in that the inclination of liquid crystal molecules is gradually changed toward each of the two substrates in the thickness direction of the liquid crystal layer sandwiched therebetween.

Further, in the liquid crystal optical element of the present invention, the inclination of the liquid crystal molecules in the central portion of the third liquid crystal layer region in the thickness direction of the liquid crystal layer when the first voltage is applied is substantially parallel to the normal line direction of the substrate. It is characterized by being arranged in.

Further, the liquid crystal electro-optical device of the present invention is characterized in that the two polarizing plates are arranged so that their optical axes are orthogonal to each other. By setting in this way and setting the values of the refractive index elliptic coefficient Z and the retardation ratio M as described above, it is possible to obtain a good black display when the second voltage is applied.

When the two polarizing plates are orthogonal to each other and parallel to each other, both can be displayed, but in order to obtain a good contrast ratio, good black is obtained, that is, the transmittance is low. Since it is necessary, it is more preferable that the polarizing plate is in the orthogonal state. This is because when the polarizing plate is parallel and black, the influence of wavelength dispersion appears. It is considered that the contrast ratio is lowered when the polarizing plates are in the parallel state, but it is easy to increase the transmittance.

The optical axis of the polarizing plate is 45 from the bisector that bisects the angle formed by the orientation processing directions of the two substrates.
The feature is that it is set in a tilted direction. This is 2
By setting in this way, the maximum transmittance can be obtained whether the polarizing plates are arranged orthogonally or in parallel.

Specific arrangement states of the liquid crystal layer in the OCB mode and modes similar to the OCB mode applicable to the above liquid crystal electro-optical device are shown below. The present invention can also be applied to the case where one of the two polarizing plates is a reflecting plate. In this case, since the light incident on the liquid crystal cell passes through a distance twice as large as the thickness of the liquid crystal layer, the thickness of the liquid crystal layer can be reduced to about half that of the transmissive type, and further improvement of the response speed can be expected.

The liquid crystal electro-optical device of the present invention is characterized in that the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates to the other substrate are splay aligned when no voltage is applied. . That is, it can be applied to the OCB mode.

Further, according to one aspect of the liquid crystal electro-optical device of the present invention, the twisting ability of the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates to the other substrate in the in-plane direction in the substrate is provided. θ0 is θ0 = 0 °.

Here, the twisting ability refers to the spontaneous twisting angle of the liquid crystal itself, and generally, the twisting ability can be controlled by the mixing concentration of the cholesteric liquid crystal composition.

Further, in another aspect of the liquid crystal electro-optical device of the present invention, the twisting ability θ0 in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one of the two substrates to the other is in-plane. , Θ0> 0 °. By setting the twisting ability θ 0 to θ 0> 0 ° as described above, the splay alignment state when no voltage is applied changes to the third orientation when the first voltage is applied.
The movement time to the state where the tilts of a part of the liquid crystal molecules in the liquid crystal layer region of are aligned substantially parallel to the normal direction of the substrate is θ0.
It can be made much faster than when = 0 °.

Further, another aspect of the liquid crystal electro-optical device of the present invention is that the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates to the other substrate are twistable in the in-plane direction within the substrate. θ0 is θ0 = 90 ° and the pretilt angle is 2
It is characterized in that the number of substrates is different. When θ 0 = 90 °, it is possible to display by making the pretilt angle different between the two substrates.

Furthermore, another aspect of the liquid crystal electro-optical device of the present invention is that the twisting ability of the liquid crystal molecules of the liquid crystal layer aligned from one substrate of the two substrates to the other substrate in the in-plane direction within the substrate. θ is θ = 180 °. Considering the backflow effect, it is most desirable that the twisting ability is 180 ° and 175 ° to 185 °, which is about 180 °. Here, the backflow effect will be described.
For example, the slightly raised liquid crystal molecules near the center when a voltage is applied are pulled back to the lying liquid crystal molecules near the substrate by turning off the voltage. However, the liquid crystal molecules in the raised portion near the center are prevented from falling into a lying state by the liquid crystal molecules near the center, and the return is delayed. This is called the backflow effect. In the case of the bend arrangement, this backflow effect disappears, but the liquid crystal is 180
This backflow effect occurs when a twisted state occurs except the twisted state.

Further, in the liquid crystal electro-optical device of the present invention, when no voltage is applied to the electrodes, the plurality of liquid crystal molecules in the third liquid crystal layer region are substantially parallel to each other, and the one substrate to the other substrate are It is characterized in that they are twisted and arranged in the in-plane direction of the substrate. That is, it is a mode similar to the OCB mode, and the present invention can be applied even in this case. In this case, high-speed response is possible in the display area as in the OCB mode.

Further, as a mode similar to the OCB mode, in the liquid crystal electro-optical device of the present invention, the surface in the substrate of the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates toward the other substrate. The twist angle θ in the inward direction is about 90 ° or about 270 °, and the pretilt angle of the liquid crystal layer is different between the two substrates. In this case, when the twist angle θ is 90 ° or 270 °, if the pretilt angles of the liquid crystal molecules on the surfaces of the two substrates are equal in the region where the liquid crystal molecules near the center of the liquid crystal layer are upright, The magnitude of the phase difference between the upper half and the lower half is equal, and the directions thereof are substantially 90 degrees.
Therefore, the phase difference of the entire cell has a relationship in which the upper half and the lower half of the cell compensate each other. Therefore, even if the applied voltage is further increased to drive the liquid crystal molecules, the optical response cannot be changed. On the other hand, when the pretilt angle is made different between the two substrates, a phase difference occurs due to the arrangement difference between the upper half and the lower half of the cells, and the saturation of the cells having the same pretilt angle between the two substrates is caused. Bright display is possible even when voltage is applied. Therefore, by further applying a voltage, dark display can be obtained and high-speed display can be performed. When the phase difference of such a cell as a whole is such that the upper half and the lower half of the cell are in a relationship of compensating each other for a twist angle of 90 ° or 270 °, and except for a twist angle of 90 ° in which such a relationship tends to be strong. In the case of 85 ° to 95 ° and 265 ° to 275 ° excluding the twist angle of 270 °, it is effective to change the size of the pretilt angle of the two substrates.

Another aspect of the liquid crystal electro-optical device of the present invention is characterized in that no voltage is applied to the liquid crystal layer when the first voltage is applied. That is, when no voltage is applied, the inclination of the plurality of liquid crystal molecules in a part of the third liquid crystal layer region is arranged substantially parallel to the normal direction of the substrate, which is similar to the OCB mode. Mode, and the present invention can be applied even in this case.

The optical anisotropic element used in the liquid crystal electro-optical device of the present invention is shown below.

The optical anisotropic element is characterized in that it is at least one retardation plate having two optical axes.

Further, one mode of the optical anisotropic element in the case where the range of Z of the present invention cannot be realized by only one sheet is composed of a combination of two or more retardation plates having one optical axis, and at least two. The optical axes of the retardation plates are different.

When the range of Z values cannot be realized by a combination of uniaxial optical anisotropic elements, one mode of the optical anisotropic element is at least one retardation plate composed of a uniaxial optical axis, It is characterized by comprising at least one retardation plate having two optical axes.

Another mode of the optical anisotropic element is at least one retardation plate having a negative optical anisotropy in the normal direction of the substrate when the substrate and the optical anisotropic element are arranged substantially parallel to each other. It consists of and.

Further, in order to better compensate the optical effect of the twist of the liquid crystal cell, another embodiment of the optical anisotropic element is
The twist of the optical axis of the optically anisotropic element is characterized by being twisted in the in-plane direction of the substrate, in the normal direction of the substrate, or in both the in-plane direction and the normal direction of the substrate.

Such an optically anisotropic element compensates for the twist of the liquid crystal layer or compensates for the optical anisotropy of the component in the direction normal to the substrate of the liquid crystal layer.

As described above, according to the present invention, the optical anisotropic element is used as an optical anisotropic element by using a retardation plate having a uniaxial or biaxial optical axis or a negative retardation plate alone or in combination. It suffices to have the optical axis of the axis. For example,
When combining two or more retardation plates having a uniaxial optical axis, at least two retardation plates are arranged so that the optical axes do not coincide with each other, and the biaxial optical axes are used as the optical anisotropic element. You need to have it.

Further, the optical axis of the optical anisotropic element is compensated so as to compensate the twist of the liquid crystal molecules of the liquid crystal layer due to the in-plane direction of the substrate, the normal direction of the substrate, or both the in-plane direction and the normal direction of the substrate. By giving the twist to the optical influence due to the twist of the liquid crystal layer can be compensated. in this case,
In the liquid crystal layer, liquid crystal molecules are twisted in the in-plane direction and / or the normal direction of the substrate continuously or stepwise from one substrate to the other partially or almost entirely. Including the case

Further, the optical axis of the optical anisotropic element is twisted so that the optical characteristic is equivalent to that of the retardation plate having a negative component in the direction normal to the substrate of the liquid crystal layer. It is possible to compensate the optical anisotropy of the component in the direction of the line. In this case, it can be realized by a large optical axis twist angle, for example, an optical axis in which the optical axis of the optical anisotropic element is twisted in the in-plane direction of the substrate.

The material of the retardation plate is polycarbonate, polyarylate, or the like, and a retardation plate such as a cholesteric liquid crystal polymer or a discotic liquid crystal polymer is used as an optical anisotropic element so that the optical axis is twisted. However, the material is not limited to these materials as long as the above characteristics can be obtained.

[0072]

BEST MODE FOR CARRYING OUT THE INVENTION A liquid crystal electro-optical device according to an embodiment of the present invention will be described below in which liquid crystal molecules in a liquid crystal layer are arranged substantially parallel to each other when no voltage is applied. The twist angle θ in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one side to the other side of the substrate is θ = 180 °
The case will be described in detail as an example.

Example 1 As shown in FIGS. 3 and 4,
The liquid crystal electro-optical device 1 of this embodiment includes a liquid crystal cell 10, two polarizing plates 20 sandwiching the liquid crystal cell 10, an optical anisotropic element 30 sandwiched between the liquid crystal cell and one polarizing plate, and a voltage drive source 40. Consists of.

In the liquid crystal cell 10, a first substrate 11 having an electrode 11a formed on one main surface thereof and a second substrate 12 having an electrode 12a formed on one main surface thereof are arranged so that the electrodes face each other.
A liquid crystal layer 13 is sandwiched between the substrates 11 and 12. This device is a normally white display liquid crystal electro-optical device. The optically anisotropic element 30 compensates for the optical anisotropy of the liquid crystal layer 13.

As shown in FIG. 1, the liquid crystal layer 13 is composed of a plurality of liquid crystal molecules, and the liquid crystal layer 13 is composed of a plurality of liquid crystal molecules 13a in contact with one of the two substrates 11.
Liquid crystal layer region A and a second liquid crystal layer region B composed of a plurality of liquid crystal molecules 13b in contact with the other substrate 12 of the two substrates.
And a third liquid crystal layer region C composed of a plurality of liquid crystal molecules 13c sandwiched between the first liquid crystal layer region and the second liquid crystal layer region. 1A shows the arrangement of liquid crystal molecules when no voltage is applied to the electrodes, FIG. 1B shows the first voltage application state to the electrodes, and FIG. 1C shows the electrode. Shows a second voltage application state to the.

As shown in FIG. 1A, the voltage drive source 40
When no voltage is applied to the electrodes 11a and 12a from the electrodes, the plurality of liquid crystal molecules 13c in the third liquid crystal layer region C are substantially parallel to each other and in the in-plane direction of the substrate from one substrate to the other substrate. Twisted and arranged.

As shown in FIG. 1B, when the first voltage is applied to the electrodes, the inclination of some of the liquid crystal molecules 13c1 of the plurality of liquid crystal molecules in the third liquid crystal layer region C is the same as that of the substrate. They are arranged substantially parallel to the line direction. When the first voltage is applied, the liquid crystal molecules are substantially parallel to the normal direction of the substrate at the threshold voltage or more, that is, the phase difference of the liquid crystal cell in which the liquid crystal molecules start to rise is more rapidly changed by the applied voltage. , When the voltage applied to the liquid crystal is further increased.

As shown in FIG. 1C, when the second voltage is applied to the electrodes, the plurality of liquid crystal molecules 1 in the third liquid crystal layer region are
The inclinations of 3c1, 13c2, and 13c3 are arranged substantially parallel to the normal direction of the substrate. When the second voltage is applied, a voltage is further applied than when the first voltage is applied, and at this time, the liquid crystal molecules 13c in the third liquid crystal layer region are arranged substantially parallel to the normal direction of the substrate. The liquid crystal is in a standing state, that is, the state where the liquid crystal is activated.

A liquid crystal cell 10 in which the liquid crystal layer 13 is sandwiched between two substrates is shown in FIG. As shown in the figure, the liquid crystal cell 10 includes an array substrate 12 having electrodes 12a formed on one main surface of a glass substrate and an electrode 1 provided on one main surface of the glass substrate.
Two substrates of the counter substrate 11 on which 1a is formed are arranged so that their main surfaces face each other, and a nematic liquid crystal layer 13 is sandwiched between the two substrates.

As shown in FIG. 3, the array substrate 12 has a plurality of signal lines (not shown) and a plurality of scanning lines (not shown) arranged in a matrix on a glass substrate and corresponds to the intersections of these. Then, the polysilicon TFT 12b and this TFT
The pixel electrode 12a formed by being connected to is formed, and the alignment film 12c is formed thereon. On the other hand, the counter substrate 11 is the array substrate 1 on the glass substrate.
A color filter 11b composed of three primary colors of red, green, and blue corresponding to each pixel electrode 12a of 1 and a black matrix 1 formed so as to partition color filters of each of these colors.
1c is formed, and the ITO electrode 11a and the alignment film 11d are sequentially formed on these.

Next, the manufacturing method and display method will be described.

A polysilicon TFT 3, a gate line which is a scanning line (not shown), a signal line (not shown), and a pixel electrode 12a are formed on a glass substrate. The number of pixels is 480 vertically.
An array substrate 12 having a width of 640 × 3 pixels was formed.

Next, a color filter 11b composed of three primary colors of red, green, and blue corresponding to each pixel electrode of the array substrate 12 on a glass substrate, and a black matrix formed so as to partition the color filters of these colors. 11c, and the ITO electrode 11a is formed thereon to form the counter substrate 11
Was formed. These two array substrates 12 and counter substrate 1
Polyimide (SE-5211, manufactured by Nissan Kagaku Co., Ltd.) as alignment films 12c and 11d, respectively, on the pre-tilt angle of about 5
) Was applied and formed to a thickness of 80 nm. Here, the pixel pitch is 0.33 mm in length and 0.11 mm in width. Then, the alignment film is formed on the two substrates 11 parallel to the scanning line,
The rubbing directions RA of the two substrates were rubbed in directions parallel to each other when the electrodes 11a and 12a on 12 were arranged so as to face each other.

Next, spherical fine particles (Micropearl SP, manufactured by Sekisui Fine Chemical Co., Ltd.) having a diameter of 7.1 μm were formed as spacers (not shown) on the array substrate 12 at 80 / mm ^{2 on} the main surface of one substrate. Sprayed at a density of. An epoxy resin adhesive (XN-21, manufactured by Mitsui Toatsu Chemicals, Inc.) was applied to the peripheral portion of the effective display area of the other counter substrate 11 by screen printing except for the opening for liquid crystal injection. . After that, the array substrate 12 and the counter substrate 11 were overlapped with the alignment films facing each other, and were heated and adhered while being pressed to fabricate a liquid crystal cell 10 having a cell gap of 7.1 μm.

A nematic liquid crystal composition (ZLI-1132, manufactured by E. Merck Co., Ltd.) was used as a liquid crystal composition 13 in this liquid crystal cell.
Δn = 0.14) with chiral agent (S811, manufactured by E. Merck) is injected by the vacuum injection method, and after injection, the liquid crystal injection port is UV curing resin (UV-1000, manufactured by Sony Chemical Co., Ltd.) And sealed. At this time, the concentration of the chiral agent was adjusted so that the helical pitch of the liquid crystal was about 35 μm.
A retardation plate, which is an optically anisotropic element made of polycarbonate, is used as the optically anisotropic element 30 on the side of the counter substrate 11 on which the color filter 11b of the liquid crystal cell is formed, and the direction in which the refractive index of the retardation plate is large is the rubbing direction. It was arranged so as to be orthogonal to.

The elliptic coefficient Z of the optical anisotropic element 30 is set to Z = 9 when Z = (ndx-ndz) / (ndx-ndy).

Here, ndx, ndy and ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the substrate and the optical anisotropic element when the substrate and the optical anisotropic element are arranged substantially parallel to each other, and It represents the sum of the products of the refractive index with the optically anisotropic element. ndx and ndy represent refractive index components of the optical anisotropic element in an in-plane direction of a plane that is substantially perpendicular to the thickness direction of the optical anisotropic element, and ndx and ndy are perpendicular to each other. ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element.

Further, a polarizing plate 20 (G1220DU, manufactured by Nitto Denko Corporation) was attached so that the optical axes thereof were 45 ° with respect to the rubbing direction and the optical axes of the two polarizing plates were orthogonal to each other. In the retardation plate, the film is stretched in the x-axis direction and then stretched in the y-axis direction to be biaxial, and the retardation value in the in-plane direction of the retardation plate is 100 nm (the difference between ndx and ndy is 0). 1) is arranged so as to compensate for the phase difference of the liquid crystal cell when the second voltage is applied, that is, the optical axes of the two polarizing plates are orthogonal to each other, and The plate was arranged so that the direction in which the refractive index was large was orthogonal to the rubbing direction. When the retardation ratio of this optical anisotropic element is M, M = ΔnLC · dLC / (ndx −ndy), and M = 10.

The thickness of the liquid crystal layer is dLC (unit: μm),
The refractive index anisotropy of the liquid crystal layer is ΔnLC.

In the obtained liquid crystal electro-optical device, when no voltage is applied to the electrodes, the plurality of liquid crystal molecules in the third liquid crystal layer region C are substantially parallel to each other and from one substrate to the other substrate. The substrates are arranged twisted by 180 ° in the in-plane direction.

When the first voltage is applied, the inclination of the liquid crystal molecule 13c1 in the central portion of the third liquid crystal layer region C among the plurality of liquid crystal molecules in the third liquid crystal layer region C is substantially parallel to the normal line direction of the substrate. In the thickness direction of the liquid crystal layer 13 sandwiched between the two substrates with the liquid crystal molecules 13c1 arranged in the center.
Like 3c3, the inclination of the liquid crystal molecules is gradually changed toward the two substrates 11 and 12.

When the second voltage is applied, the tilts of the plurality of liquid crystal molecules 13c in the third liquid crystal layer region are arranged substantially parallel to the normal line direction of the substrate.

Display is performed by ON / OFF driving by the voltage driving source 40 between the application of the first voltage and the application of the second voltage. In the case of this example, a voltage at which the effective phase difference of the cell was about 0.26 μm was used as the minimum value of the driving voltage. The display was performed by setting the first voltage application to 2.4V and the second voltage application to 6.5V.

As a result, as shown in FIG. 9, the electro-optical characteristic that the transmittance monotonously decreases with respect to the driving voltage is obtained,
The contrast ratio at the front was 100 or more, and the viewing angle was wide. There was almost no difference in response speed between gradations, which was a high speed of about 5 ms, and good display was obtained without blurring the outline even when a moving image was displayed. In addition,
7 to 10 are diagrams showing equal contrast, showing the contrast according to the observation direction when the center of the circle is the reference direction of the normal line of the substrate, and the hatched portion indicates the inversion region. In FIG. 7 to FIG. 10, as the size of the circle increases concentrically from the center of the circle toward the outside, the angle formed by the direction of the substrate and the observation direction increases, and the center of the circle and a certain angle on the circle. The direction of the line connecting the points (azimuth) represents the observation direction in the in-plane direction of the substrate.

In the figure, the curve (50) indicates the contrast ratio (5
0), the area surrounded by the curve (50) has a contrast ratio of 50 or more, the area surrounded by the curve (10) has a contrast ratio of 50 to 10, and the area surrounded by the curve (1) has a contrast ratio of 1 to 10. Is.

(Embodiment 2) With the value of Z of the retardation plate in Embodiment 1 set to 7, TF was performed under the same members and conditions as in Embodiment 1.
A T-LCD was produced. The result is shown in FIG. The LCD thus obtained provided a good display even when the viewing angle was changed.

(Comparative Example 1) The value of Z of the retardation plate in Example 1 was set to 1 (one uniaxial retardation plate was used), and Example 1 was used.
A TFT-LCD was produced using the same members and conditions as in. The result is shown in FIG. The LCD thus obtained had a very wide reversal region when the viewing angle was swung, and the contrast was significantly deteriorated.

(Comparative Example 2) A TFT-LCD was manufactured under the same members and conditions as in Example 1, except that the Z value of the retardation plate in Example 1 was 12 (one uniaxial retardation plate was used). The result is shown in FIG. The LCD thus obtained had a very wide reversal region when the viewing angle was swung, and the contrast was significantly deteriorated.

As described above, a liquid crystal optical element having a small viewing angle dependency is obtained by using an optical anisotropic element whose Z value is 7 ≦ Z ≦ 10, and more preferably 8 ≦ Z ≦ 10. You can

Further, here, the liquid crystal molecules of the liquid crystal layer are arranged substantially parallel to each other when no voltage is applied.
The case where the twist angle θ in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one substrate to the other of the substrates is θ = 180 ° has been described as an example. Also, the present invention can be applied to the OCB mode in the normally white mode display and similar modes, and similar effects can be obtained.

Further, FIG. 11 shows the relationship between the applied voltage (horizontal axis) and the transmittance (vertical axis) when the value of M was changed with ΔnLC · dLC set to 1.0.

(Embodiment 3) The optical anisotropic element of Embodiment 1 has a retardation value of 400 in the in-plane direction of the retardation plate.
nm uniaxial retardation plate and a uniaxial retardation plate having a retardation value in the in-plane direction of the retardation plate of 500 nm are superposed so that their optical axes are orthogonal, and Z = 9, M = A TFT-LCD was manufactured under the same members and conditions as in Example 1 except that the optical anisotropic element was manufactured so as to have the number 10. The LCD thus obtained had improved viewing angle characteristics.

(Embodiment 4) The optical anisotropic element according to Embodiment 1 has the retardation value of 100 in the in-plane direction of the retardation plate.
nm uniaxial retardation plate and negative retardation plate (ndx, nd
A TFT-LCD was produced under the same members and conditions as in Example 1, except that y> ndz) was combined to produce an optically anisotropic element having a Z value of 9. The LCD thus obtained had improved viewing angle characteristics.

Comparative Example 3 An optical anisotropic element having a Z value of 9 was used as in Example 1 except that the spacer diameter in Example 1 was 5.3 μm and the cell gap was 5.3 μm. TFT-LCD with M = 7.4 using the same materials and conditions
Was prepared. The LCD thus obtained has a low transmittance,
The display quality tended to be impaired.

(Comparative Example 4) T of M = 18.2 under the same members and conditions as in Example 1 except that the diameter of the spacer in Example 1 was 13 μm and the cell gap was 13 μm.
An FT-LCD was produced. The LCD thus obtained could only be applied with a maximum voltage of up to 6V (because the TFT element is destroyed at a voltage higher than this), it could not be made sufficiently black and the display quality tended to be impaired. .

As described above, the optical anisotropic element of the present invention is
Use one or more retardation plates having biaxial optical axes Use two or more retardation plates having uniaxial optical axes and negative retardation with biaxial or uniaxial retardation plates It can be obtained by using a plate together. In addition, the value of M is 7.5 <M <18
By so doing, a liquid crystal optical element with good display quality can be obtained.

(Example 5) One of the polarizing plates in Example 1 was replaced with a reflecting plate, the spacer had a diameter of 3.6 µm, the cell gap was 3.6 µm, and the position of the retardation plate in the in-plane direction was changed. Z = under the same members and conditions as in Example 1 except that a biaxial retardation plate having a phase difference value of 50 nm was used.
A TFT-LCD with 9 and M = 10 was produced. When the LCD thus obtained was driven, good viewing angle characteristics and a bright display were obtained.

Example 6 The optical anisotropic element of Example 1 was produced by combining two twisted phase difference plates. Specifically, a substrate made of a cholesteric liquid crystal polymer has an optical axis twist angle of 10 ° in the in-plane direction and a retardation plate having a phase difference of 100 nm in the in-plane direction, and an optical axis in the in-plane direction of the substrate. Two phase difference plates, each having a twist angle of 650 ° and a phase difference in the in-plane direction of zero, were combined and produced. In this optical anisotropic element, the twist of the optical axis is 660 in the in-plane direction of the substrate as a whole.
° twisted.

Thus, by imparting a twist to the optical axis of the optically anisotropic element, a high contrast can be obtained, and
By using a retardation plate having an optical axis twist angle of 650 °, the same effect as that having a negative retardation plate in terms of optical characteristics was obtained, and the viewing angle characteristics were improved.

Example 7 The optical anisotropic element of Example 1 was produced by combining one twisted phase plate and one negative phase plate. That is, the twist angle of the optical axis is 10 in the direction of the substrate made of cholesteric liquid crystal polymer.
Optical retardation plate with a negative retardation plate having a negative optical anisotropy in the direction normal to the substrate when the substrate and the optical anisotropic element are arranged substantially parallel to each other. Z = for the entire device
An optical anisotropic element was manufactured so as to have No. 9.

As described above, by imparting a twist to the optical axis of the optically anisotropic element, a high contrast was obtained, and since it was a negative retardation plate, the viewing angle characteristics were improved.

Example 8 The optical anisotropic element of Example 1 was produced by combining one biaxially non-twisted retardation plate and one twisted retardation plate. That is, an optical anisotropic element was manufactured by combining one twisted retardation plate made of a cholesteric liquid crystal polymer and a biaxial retardation plate such that Z = 9 in the entire optical anisotropic element. As a result, the viewing angle characteristic was improved.

The liquid crystal electro-optical device of the present invention described in the above embodiments is widely used in liquid crystal display devices used in personal computers, word processors, etc., light valves of video projectors, high-speed liquid crystal shutters used in glasses used in 3D-TV, and the like. It can be applied.

[0114]

In the liquid crystal electro-optical device of the present invention, the optical anisotropic element to be combined with the liquid crystal cell of OCB mode or a similar mode has biaxial and negative optical anisotropy, and the elliptic coefficient Z is 7 or more. Since it is set to 10 or less, it is possible to obtain a liquid crystal electro-optical device having good viewing angle characteristics suitable for normally white display in the above mode.

[Brief description of the drawings]

1A and 1B are views for explaining an embodiment of the present invention, in which FIG. 1A is a cross-sectional view showing an arrangement state of liquid crystal molecules in a liquid crystal cell when no voltage is applied, and FIG. A cross-sectional view showing the alignment state of the liquid crystal molecules at the time, (c) is a cross-sectional view showing the alignment state of the liquid crystal molecules when a second voltage is applied to the liquid crystal cell

2A and 2B are explanatory views of a liquid crystal cell of a conventional OCB-mode liquid crystal electro-optical device, in which FIG. 2A is a sectional view showing an arrangement state of liquid crystal molecules in the liquid crystal cell when no voltage is applied, and FIG. Is a vertical cross-sectional view showing the alignment state of the liquid crystal molecules when the first voltage is not applied, and

FIG. 3 is a sectional view of a liquid crystal electro-optical device that is an embodiment of the present invention,

FIG. 4 is a schematic perspective view illustrating the operation of the embodiment of the present invention.

FIG. 5 is a diagram illustrating a refractive index ellipsoid of a liquid crystal cell used in the present invention,

FIG. 6 is a diagram illustrating an index ellipsoid of an optically anisotropic element used in the present invention,

FIG. 7 is a diagram showing viewing angle characteristics of a liquid crystal electro-optical device of Comparative Example 1,

FIG. 8 is a diagram showing viewing angle characteristics of a liquid crystal electro-optical device according to a second embodiment of the present invention,

FIG. 9 is a diagram showing viewing angle characteristics of the liquid crystal electro-optical device according to Example 1 of the present invention,

FIG. 10 is a diagram showing viewing angle characteristics of a liquid crystal electro-optical device of Comparative Example 2,

FIG. 11 is an applied voltage-transmittance curve diagram in which the value of retardation M is a parameter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal electro-optical device 10 ... Liquid crystal cell 11 ... Substrate 11a ... Electrode 12 ... Substrate 12a ... Electrode 13 ... Liquid crystal layer 13a ... First liquid crystal layer region A liquid crystal molecule 13b ... Second liquid crystal layer region B liquid crystal molecule 13b ... Liquid crystal molecules in third liquid crystal layer region C ... Polarizing plate 30 ... Optical anisotropic element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahito Ishikawa, 8 Shinsita-cho, Isogo-ku, Yokohama, Kanagawa, Yokohama, Ltd. (72) Inventor: Nobuko Fukuoka, Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa Company Toshiba Yokohama Office (72) Inventor Toshihiro Ninomiya 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock Company Incorporated Toshiba Yokohama Office (72) Inventor Tsuyoshi Oyama 8-Shin-Sugita-cho, Isogo-ku, Yokohama, Kanagawa Stock Company Inside the Yokohama office (72) Inventor Norihiro Yoshida 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock Company Toshiba Yokohama Office (72) Inventor Hitoshi Hato 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock company Toshiba Yokohama In-house

Claims (23)

[Claims] 1. A liquid crystal electro-optical device comprising a bend-aligned liquid crystal cell including a liquid crystal layer in which a twisted alignment is present in the center of the cell, and at least one optical anisotropic element for reducing the viewing angle dependence of the bend-aligned liquid crystal cell. In the apparatus, the optical anisotropic element is Z = (ndx-ndz) / (ndx-ndy).
), 7≤Z≤10 (ndx, ndy, ndz
Is the product of the refractive index of the optical anisotropic element and the thickness (unit: μm) of the optical anisotropic element in the normal direction of the substrate when the substrate and the optical anisotropic element are arranged substantially parallel to each other. It represents the refractive index components in the x, y, and z directions of the sum. ndx
, Ndy represent refractive index components of the optical anisotropic element in an in-plane direction of a plane that is substantially perpendicular to the thickness direction of the optical anisotropic element, and ndx and ndy are perpendicular to each other. nd
z represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element. ) A liquid crystal electro-optical device characterized by: 2. Two substrates having electrodes to which a voltage is applied on one main surface are arranged so that the main surfaces face each other.
A liquid crystal cell in which a liquid crystal layer is sandwiched between two substrates, two polarizing plates arranged so as to sandwich the liquid crystal cell, and an optical anisotropic element disposed between the polarizing plate and the liquid crystal cell. ,
A driving unit connected to the electrodes for applying a voltage to the liquid crystal layer, wherein the liquid crystal layer is composed of a plurality of liquid crystal molecules of the liquid crystal layer, the liquid crystal molecules being in contact with one of the two substrates. One liquid crystal layer region; a second liquid crystal layer region composed of a plurality of liquid crystal molecules of the liquid crystal layer that are in contact with the other substrate of the two substrates; and a second liquid crystal molecule of the liquid crystal layer. A third liquid crystal layer region composed of a plurality of liquid crystal molecules sandwiched between one liquid crystal layer region and the second liquid crystal layer region, and when the first voltage is applied to the electrode, the third liquid crystal layer region is formed. Some of the liquid crystal molecules in the liquid crystal layer region are arranged such that their inclinations are substantially parallel to the normal direction of the substrate, and when the second voltage is applied to the electrodes, the third liquid crystal molecules are arranged. The tilts of the plurality of liquid crystal molecules in the layer region are substantially parallel to the normal direction of the substrate. In the liquid crystal electro-optical device of the array of normally white display modes, and when the optical anisotropic element is Z = (ndx-ndz) / (ndx-ndy), 7≤Z≤10 (ndx, ndy and ndz are the refractive index between the optical anisotropic element and the thickness (unit: μm) of the optical anisotropic element in the normal direction of the substrate when the substrate and the optical anisotropic element are arranged substantially parallel to each other. Represents the refractive index components in the x, y, and z directions of the sum of products ndx, nd
y represents the refractive index component of the optical anisotropic element in the in-plane direction of the plane that is substantially perpendicular to the thickness direction of the optical anisotropic element, and ndx and ndy are perpendicular to each other. ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element. ) A liquid crystal electro-optical device characterized by: 3. The liquid crystal electro-optical device according to claim 1, wherein the optically anisotropic element satisfies 8 ≦ Z ≦ 10. 4. The display of the liquid crystal electro-optical device is turned on when the first voltage is applied.
The liquid crystal electro-optical device according to. 5. The liquid crystal electro-optical device according to claim 2, wherein display is performed between when the first voltage is applied and when the second voltage is applied. 6. The third device when the first voltage is applied.
Each of the two substrates in the thickness direction of the liquid crystal layer sandwiched between the two substrates with the liquid crystal molecules arranged in the liquid crystal layer region substantially parallel to the normal direction of the substrates as a center. 3. The liquid crystal electro-optical device according to claim 2, wherein the tilt of the liquid crystal molecules is gradually changed toward. 7. The inclination of the liquid crystal molecules in the central portion of the third liquid crystal layer region in the thickness direction of the liquid crystal layer when the first voltage is applied is arranged substantially parallel to the normal direction of the substrate. The liquid crystal electro-optical device according to claim 2, wherein 8. When the ratio M of the retardation of the liquid crystal cell to the retardation of the optical anisotropic element in the in-plane direction of the optical anisotropic element is M = ΔnLC · dLC / (ndx −ndy), 7.5 <M <18 (the thickness (unit: μm) of the liquid crystal layer is dLC, and the refractive index of the liquid crystal layer is ΔnLC), The liquid crystal electro-optical device according to claim 1 or 2. 9. The liquid crystal electro-optical device according to claim 2, wherein one of the two polarizing plates is a reflection plate. 10. The liquid crystal electro-optical device according to claim 2, wherein the two polarizing plates are arranged such that their optical axes are orthogonal to each other. 11. The optical axis of the polarizing plate is set at a direction inclined by 45 ° from a bisector that divides an angle formed by the alignment treatment directions of the two substrates into two equal parts. The liquid crystal electro-optical device according to claim 2. 12. When no voltage is applied to the electrodes, the plurality of liquid crystal molecules in the third liquid crystal layer region are substantially parallel to each other and are inclined at 3 ° to 8 ° with respect to the electrode surface, and the liquid crystal molecules are Is twisted in the in-plane direction of the substrate from one substrate toward the other substrate and arranged at a twist angle of 180 °, and the twisting ability of the liquid crystal is 10 ° or more and 360 ° or less. The liquid crystal electro-optical device described. 13. The optical anisotropic element comprises a combination of two or more retardation plates each having a uniaxial optical axis, and the at least two retardation plates have different optical axes. 13. The liquid crystal electro-optical device according to claim 2, claim 8, or claim 12. 14. The optical anisotropic element comprises at least one retardation plate having a uniaxial optical axis and at least one retardation plate having a biaxial optical axis. The liquid crystal electro-optical device according to claim 2, claim 8, or claim 12. 15. The at least one retardation plate, wherein the optical anisotropic element has a negative optical anisotropy in a direction normal to the substrate when the substrate and the optical anisotropic element are arranged substantially parallel to each other. 13. The liquid crystal electro-optical device according to claim 2, claim 8, or claim 12. 16. The liquid crystal electro-optical device according to claim 2, wherein the optical axis of the optically anisotropic element is twisted in the in-plane direction of the substrate. . 17. The liquid crystal electro-optical device according to claim 2, wherein the optical axis of the optical anisotropic element is twisted in a direction normal to the substrate. . 18. The optical axis of the optical anisotropic element is twisted in an in-plane direction of the substrate and is also twisted in a normal line direction of the substrate.
The liquid crystal electro-optical device according to any one of 1. 19. The twist of the optical axis of the optical anisotropic element is
3. Compensation of twist of the liquid crystal layer,
The liquid crystal electro-optical device according to claim 8. 20. The twist of the optical axis of the optical anisotropic element is
13. The twist of the liquid crystal layer in the alignment state of the liquid crystal layer, which is taken between the time of applying the first voltage and the time of applying the second voltage, is compensated for. The liquid crystal electro-optical device according to any one of claims. 21. The twist of the optical axis of the optical anisotropic element is
13. The liquid crystal electro-optical device according to claim 2, wherein the twist of the liquid crystal layer in the aligned state of the liquid crystal layer when the first voltage is applied is compensated. 22. The twist of the optical axis of the optical anisotropic element is
The optical anisotropy of a normal direction component of the substrate of the liquid crystal layer is compensated for, and the second, the eighth and the first aspects are characterized.
3. The liquid crystal electro-optical device according to any one of 2. 23. The liquid crystal electro-optical device according to claim 12, wherein the optical anisotropic element is made of any one of polycarbonate, polyarylate, cholesteric liquid crystal polymer, and discotic liquid crystal polymer.