JPH07104525B2 - Active matrix liquid crystal device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an active matrix liquid crystal device in which liquid crystals are vertically aligned or hybrid aligned.

[Prior Art] FIGS. 5 and 6 are plan views of a conventional active matrix liquid crystal device. An active element is formed on the substrate and the liquid crystal is horizontally aligned and twisted by 90 °.

In the active matrix liquid crystal device of FIG. 5, one polarizing plate is provided for each of the upper and lower substrates so that the polarization axis directions 56 and 57 intersect each other at right angles. The pixel 51 portion is bright when a voltage is not applied, and the pixel 51 portion is dark when a voltage is applied (hereinafter, this is referred to as a normally white mode). The part 55 between pixels always remains bright.

In the active matrix liquid crystal device of FIG. 6, one polarizing plate is provided for each of the upper and lower substrates so that the polarization axis directions 56 and 57 are parallel to each other.
The pixel 51 portion is dark when no voltage is applied, and the pixel 51 portion is bright when a voltage is applied (hereinafter, this is referred to as a normally black mode). The area 55 between pixels always remains dark.

[Problems to be Solved by the Invention] FIG. 7 shows a contrast curve in the conventional active matrix liquid crystal device as shown in FIGS. 5 and 6. Reference numeral 71 denotes a contrast curve of a normally white mode active matrix liquid crystal device in which the polarization axes of two polarizing plates as shown in FIG. 5 are crossed at right angles, and pixels become darker as a voltage is applied. ing. On the other hand, 72 is a contrast curve of a normally black mode active matrix liquid crystal device in which the polarization axes of the two polarizing plates as shown in FIG. 6 are parallel, and the pixels become brighter as a voltage is applied. Has become.

Comparing the two contrast curves, the contrast curve 72 has a smaller difference between the maximum value and the minimum value of the transmittance, and the normally black mode active matrix liquid crystal device shown in FIG. 6 is shown in FIG. It can be seen that the contrast is not as high as that of the normally white mode active matrix liquid crystal device. Further, the maximum and minimum values of the contrast curve 72 are inferior to the maximum and minimum values of the contrast curve 71, and the normally black mode active matrix liquid crystal device shown in FIG. 6 is shown in FIG. It can be seen that the brightness and darkness are not sufficient compared with the normally white mode active matrix liquid crystal device.

As described above, in the conventional normally black mode active matrix liquid crystal device as shown in FIG. 6, the contrast is not as high as that in the normally white mode active matrix liquid crystal device, and the brightness and darkness are not sufficient. There was a problem.

Further, in a conventional normally white mode active matrix liquid crystal device, light is leaked from a portion 55 between pixels when a voltage is applied, and in this case also, sufficient darkness cannot be obtained and contrast is reduced. There was a problem that it would decrease.

The present invention is intended to solve the above problems, and an object thereof is a normally black mode, which has a higher contrast than a conventional active matrix liquid crystal device,
An object of the present invention is to provide an active matrix liquid crystal device capable of producing sufficient brightness and darkness.

[Means for Solving the Problem] According to the present invention, a liquid crystal having a negative dielectric anisotropy is sandwiched between a first substrate and a second substrate, and the liquid crystal is vertically aligned when no voltage is applied. In an active matrix liquid crystal device that has a hybrid orientation, in which a first polarizing plate is installed on the first substrate and a second polarizing plate is installed on the second substrate, the liquid crystal comprises: When a voltage is applied, they are arranged substantially horizontally with respect to the surface of the substrate and have a 90 ° twist structure, and the first polarizing plate and the second polarizing plate are
The polarization axes of the first polarizing plate are arranged so as to intersect each other at substantially right angles, and the polarization axis of the first polarizing plate is substantially aligned with the alignment direction of the liquid crystal near the surface of the first substrate when a voltage is applied. It is parallel, and the polarization axis direction of the second polarizing plate is substantially parallel to the alignment direction of the liquid crystal near the surface of the second substrate when a voltage is applied.

[Operation] According to the above configuration of the present invention, the state (dark) when a voltage is applied to the conventional normally white mode active matrix liquid crystal device is the same as the state when no voltage is applied in the active matrix liquid crystal device of the present invention. become. The state (bright) of the conventional normally white mode active matrix liquid crystal device when no voltage is applied is the same as the state of the active matrix liquid crystal device of the present invention when voltage is applied. Also,
In the normally black mode, the area between pixels is always dark, and light does not leak from there. Therefore, according to the present invention, even in the normally black mode active matrix liquid crystal device, it is possible to obtain the darkness, brightness and contrast higher than those of the conventional normally white mode active matrix liquid crystal device.

[Embodiment] FIG. 1 is a cross-sectional view showing a first embodiment of an active matrix liquid crystal device of the present invention.

The upper and lower polarizing plates 11 and 12 are installed so that the respective polarization axes 56 and 57 intersect at right angles, and the upper and lower glass substrates 13 and
A liquid crystal 19 having a negative dielectric anisotropy is sandwiched between the fourteen.
On the glass substrates 13 and 14, on the films 15 and 18 (for example, an obliquely vapor-deposited film of an inorganic material, a rubbed organic film, etc.) on which the liquid crystal 19 is aligned horizontally with respect to the substrate surface when a voltage is applied. Vertical alignment films 16 and 17 are formed so as to overlap each other.

FIG. 2 is a sectional view showing a second embodiment of the active matrix liquid crystal device of the present invention.

After the vertical alignment films 16 and 17 are formed on the glass substrates 13 and 14, the films 15 and 18 (for example, an inorganic material obliquely arranged) that have been subjected to a process of aligning the liquid crystal 19 horizontally with respect to the substrate surface when a voltage is applied. Vapor-deposited film, rubbed organic film, etc.) are formed.

In FIGS. 1 and 2, a liquid crystal 19 having a negative dielectric anisotropy 19
Have a vertical orientation when no voltage is applied, are arranged substantially horizontally with respect to the substrate surface when a voltage is applied, and have a 90 ° twist structure.

FIG. 3 is a sectional view showing a third embodiment of the active matrix liquid crystal device of the present invention.

In the third embodiment, on one glass substrate 13,
Only the film 15 that has been subjected to the process of aligning the liquid crystal 19 having a negative dielectric anisotropy horizontally with respect to the substrate surface is formed, and on the other glass substrate 14, the liquid crystal is aligned horizontally with respect to the substrate surface. The vertical alignment film 17 is laminated on the film 18 that has been subjected to the treatment. In this case, on the other glass substrate 14, the above-mentioned second
After the vertical alignment films 16 and 17 are formed, the films 15 and 18 that have been subjected to the process of aligning the liquid crystal 19 horizontally with respect to the substrate surface when voltage is applied may be formed as in the embodiment of FIG. Good.
In this example, the liquid crystal has a hybrid alignment in which one side of the substrate is horizontally aligned and the other side of the substrate is vertically aligned. When a voltage is applied, the liquid crystal layer is arranged almost horizontally with respect to the substrate surface,
And it has a 90 ° twist structure.

FIG. 4 shows a contrast curve 41 of the active matrix liquid crystal device of the present invention. It can be seen that the contrast curve 41 has a lower minimum transmittance and a sufficient darkness as compared with the contrast curve 72 of the conventional normally black mode active matrix liquid crystal device of FIG. In addition, when the pixel is bright, light does not leak from the portion between the pixels,
The brightness is also improved as compared with the conventional normally white mode active matrix liquid crystal device. Therefore, the contrast can be remarkably improved as compared with the conventional active matrix liquid crystal device.

However, since the steepness of the contrast curve is inferior to the conventional one, an active element must be used. Also,
As the active element to be used, a non-linear element having a conductor-insulator-conductor structure is more advantageous in cost than other active elements.

[Effects of the Invention] As described above, according to the above-described configuration of the present invention, it is possible to obtain an active matrix liquid crystal device having a very high contrast in a normally black mode.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of an active matrix liquid crystal device of the present invention. FIG. 2 is a sectional view showing a second embodiment of the active matrix liquid crystal device of the present invention. FIG. 3 is a sectional view showing a third embodiment of the active matrix liquid crystal device of the present invention. FIG. 4 is a diagram showing a contrast curve of the active matrix liquid crystal device of the present invention. FIG. 5 is a plan view showing a state when a voltage is applied to a conventional active matrix liquid crystal device in which an active element is formed on a substrate and two polarizing plates are installed so that their polarization axes intersect each other at right angles. FIG. 6 is a plan view showing a state when a voltage is applied to a conventional active matrix liquid crystal device in which an active element is formed on a substrate and two polarizing plates are installed so that their polarization axes are parallel to each other. FIG. 7 is a diagram showing a contrast curve of a conventional active matrix liquid crystal device. 11 …… Upper polarizing plate 12 …… Lower polarizing plate 13 …… Upper glass substrate 14 …… Lower glass substrate 15 …… Film that has been treated to align liquid crystals horizontally with the substrate surface 16 …… Vertical Alignment film 17 …… Vertical alignment film 18 …… A film that has been processed to align liquid crystals horizontally with respect to the substrate surface 19 …… Liquid crystal with negative dielectric anisotropy 110 …… Upper electrode 111 …… Lower side Electrode 41 …… Contrast curve of active matrix liquid crystal device of the present invention 51 …… Pixel 52 …… Horizontal line electrode 53 …… Vertical line electrode 54 …… Active element 55 …… Between pixels 56 …… Upper polarizing plate Polarization axis direction of 57 ………… Polarization axis direction of lower polarization plate 71 …… Contrast curve of conventional normally white mode active matrix liquid crystal device 72 …… Contrast curve of conventional normally black mode active matrix liquid crystal device

Claims (3)

[Claims] 1. A liquid crystal having a negative dielectric anisotropy is sandwiched between a first substrate and a second substrate, and the first substrate and the second substrate.
An active element is formed on one of the substrates, the liquid crystal has a vertical alignment or a hybrid alignment when no voltage is applied, and a first polarizing plate is installed on the first substrate, In the active matrix liquid crystal device in which the second polarizing plate is installed on the substrate, the liquid crystal is arranged substantially horizontally with respect to the substrate surface when a voltage is applied, and has a 90 ° twist structure. The first polarizing plate and the second polarizing plate are installed so that their polarization axis directions intersect each other at substantially right angles, and the polarization axis direction of the first polarizing plate is It is substantially parallel to the alignment direction of the liquid crystal near the first substrate surface, and the polarization axis direction of the second polarizing plate is substantially parallel to the alignment direction of the liquid crystal near the second substrate surface when a voltage is applied. Characterized by Restorative matrix liquid crystal device. 2. The active matrix liquid crystal device according to claim 1, wherein an element having a conductor-insulator-conductor structure is used as the active element. 3. The active matrix liquid crystal device according to claim 1, wherein a color filter is formed on either one of the first substrate and the second substrate.