JPS5938591B2 - liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a twisted nematic field effect liquid crystal display device (hereinafter referred to as TN-FEM-LCD), and in particular to a twisted nematic field effect liquid crystal display device (hereinafter referred to as TN-FEM-LCD), in which an aggregate of optical fibers is used to improve the viewing angle direction dependence. This invention relates to display technology for liquid crystal cells used as side substrates.

TN-FEM-LCD has a unique display viewing angle direction range due to the spirally twisted liquid crystal molecular structure, and the viewing angle range changes depending on the applied voltage of the element, especially at low effective value voltages. Produces significant anisotropy when activated. Before explaining the present invention, observation directions θ and φ will first be defined.

In FIG. 1, the display surface of the liquid crystal display device 1 has an orthogonal coordinate X
When the Y-axis is taken, the X-axis direction is set to the long axis direction of the liquid crystal molecules in contact with one of the substrates in the absence of an electric field, and the Z-axis is taken to the normal direction of the display surface, the observation direction vector is )''- -Z
The angle formed with the axis is θ, and the angle formed by the shadow projected onto the XY plane of the observation direction vector with the X axis is φ. In accordance with the above definition, an example of observation direction characteristics in a conventional TN-FEM-LCD is shown in FIG.

In the figure, curves 1, 2, and 3 represent the φ dependence of the display contrast ratio when θ-200 is constant at applied voltages (effective values) of 2.5 volts, 3.0 volts, and 6.0 volts, respectively. There is. That is, the area surrounded by this curve indicates good contrast, and the area outside the curve indicates poor contrast. From this characteristic diagram,
It can be seen that the lower the voltage, the narrower the viewing angle range of φ, and the range with good contrast is limited to a specific direction within the XY plane. In addition, the conditions of the characteristic test shown in Fig. 2 are as follows: MBBA, EBBA, and B as liquid crystal materials.
Using BAB's thick base type mixed liquid crystal, the liquid crystal layer thickness is 6.
μm, the tilt angle of liquid crystal molecules on the substrate in the absence of an electric field is 5
0 or less, the electrode material is SiO2 with a transparent electrode of In2o3 and further wrapped as a TN alignment layer on top of the transparent electrode.
A rectangular AC voltage of 32 Hz was used as the driving voltage.

The φ dependence of the display contrast described above is
This is particularly noticeable when the LCD is multiflex (dynamic) driven.

In order to eliminate this drawback, the applicant has developed a TN-FEML
In a CD, the one on the observer's side of the two substrates sandwiching the liquid crystal layer, that is, the front substrate, is composed of an optical fiber assembly plate whose axis direction is orthogonal to the liquid crystal layer. The inner end surface is substantially parallel to the liquid crystal layer, and a polarizer is provided on the outside of the optical fiber assembly plate.
We advocate N-FEM-LCD. (Special application 52-11
(No. 31368) This liquid crystal display device will be described below.

FIG. 3 shows a schematic cross-sectional view of the same, and as seen from the observer 2 side, the front polarizer 3, the optical fiber plate 4, the front transparent electrode 5, the front liquid crystal molecule alignment layer 6, the liquid crystal layer 7, A seal member 8, a back liquid crystal molecule alignment layer 9, a back transparent electrode 10, a back glass substrate 11, a back polarizer 12, and a reflector 13 are provided, respectively. As shown in the partially enlarged view of FIG. 4, the optical fiber assembly plates 4 are densely arranged with their axial directions perpendicular to the plane formed by the liquid crystal layer 7, and their inner end surfaces 14 are arranged in a direction perpendicular to the plane formed by the liquid crystal layer 7. Cut parallel or nearly parallel to the plane.

Further, the length l of the optical fiber needs to be sufficiently longer than its radius f in order to average the viewing angle direction. Furthermore, the distance m from the inner end surface 14 of the optical fiber to the liquid crystal layer 7, that is, the front transparent electrode 5, the front liquid crystal molecule alignment layer 6,
It is desirable that the thickness occupied by the radius r is 40r or less. Because, when m exceeds 40r,
This is because the area where the light enters the optical fiber increases, making it impossible to form an image. TN-FEM-LCD with the above structure
This is a very effective technique for eliminating viewing angle dependence, but on the other hand, it has the disadvantage that the display becomes dark if the opening area of the core of the optical fiber, which is made up of each single fiber that makes up the fiber plate, is small. It was left behind.

On the other hand, if the core opening area of each single fiber is increased,
This also includes the problem that display active portions and non-active portions of display picture elements coexist within the same aperture area, resulting in deterioration of display contrast.

The present invention has been made in view of the above-mentioned problems, and includes:
It is an object of the present invention to provide a new and useful liquid crystal display device that can obtain a bright display while maintaining good display contrast.

FIG. 5 is an enlarged view of essential parts showing the relationship between the display picture element shown in FIG. 3 and the opening area of each single fiber with a large opening area constituting the fiber flade. What is
This is the part where the optical state can be changed by applying a voltage to the liquid crystal layer.

In other words, in a liquid crystal cell with a sandwich-type electrode, this corresponds to a portion where the electrodes on both substrates overlap. In FIG. 5, an XY matrix electrode is used as the electrode, for example, a front transparent electrode 5 made of In2O3 is formed as the X electrode,
As the Y electrode, a striped back transparent electrode 10 is formed perpendicular to the X electrode.

The area where these two electrodes 5 and 10 intersect is the display picture element 5/
It is. In Fig. 5, 4 is a fiber plate, and the opening area of the core part of each single fiber is shown as 4', and the clad part is shown as 4''.The liquid crystal molecule alignment layers 6 and 9 are wrapped and have a thickness of about 1000λ. The liquid crystal layer 7 is a long-pitch cholesteric liquid crystal or nematic liquid crystal with positive dielectric anisotropy, such as the E-8 type manufactured by BDH or the RO type manufactured by Ruche.
A TN4O3 type or the like is used. If the liquid crystal cell is of a transmission type, a light source is installed in place of the reflection plate 13. The positional relationship between each single picture element of the display picture element q in FIG. 5 and the single fiber opening 4' is shown in FIGS. 6A and 6B.

In this case, the part of the information on the display picture element 5' that is derived through the single fiber opening 4' is limited to the overlapping part of the display picture element 51 and the single fiber opening 4', and the information is effectively transmitted to the observer. As a result, a display with good contrast cannot be obtained. FIGS. 7A and 7B are explanatory diagrams showing each embodiment of the present invention made to eliminate this drawback, and the positional relationship between the display picture element 5' and the single fiber opening 4' in FIG. 5 has been improved. This indicates that the display picture elements 5' and the single fiber openings 4' are substantially arranged in the same position. As a result, the information shown by the display pixels 5' efficiently passes through the single fibers and reaches the observer, making it possible to display with high contrast. In addition,
As shown in FIG. 8, when the core opening area l is relatively large, an optically isotropic and transparent reinforcing layer 14 is provided between the front transparent electrode 5 and the optical fiber assembly plate 4 for reinforcement purposes. It is also possible to intervene.

Further, the polarizer 3 may be bonded and interposed between the optical fiber assembly plate 4 and the reinforcing layer 14. However, in that case, the reinforcing layer 1
The layer thickness in step 4 must be limited to the same level as the aperture diameter or maximum aperture length of the single fiber so as not to blur the display.
The degree of this depends on the core opening area of the single fiber opening 4'. Similarly, isotropic and transparent material such as glass may be bonded to the optical fiber assembly plate 4 between the front polarizer 3 and the optical fiber assembly plate 4 for reinforcement.

Although the above explanation has been made regarding the case of XY matrix electrodes, the present invention can also be applied to the case of so-called segment electrodes.

The arrangement of display picture elements 4' and single fiber openings 5' in that case is shown in FIG. According to the present invention, the front substrate is constructed of an optical fiber assembly board in which the axial direction of each single fiber is perpendicular to the liquid crystal layer, so that the viewing angle characteristics can be favorably improved, and the display can be made brighter. By configuring the core opening shape of each single fiber of the optical fiber assembly plate to substantially match the display pixel shape, display contrast can be made very good.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating observation directions in a TN-FEM-LCD. FIG. 2 is a diagram explaining the characteristics of the TN-FEMLCD. Figure 3 shows TN-FEM- using fiber plate.
FIG. 3 is a schematic cross-sectional view of an LCD. Figures 4 and 5 are the third
It is an enlarged view of the main part of the figure. FIGS. 6A and 6B are layout diagrams showing the positional relationship between conventional display picture elements and fiber plates.
FIGS. 7A and 7B are layout diagrams of display picture elements and fiber plates, respectively, showing embodiments of the present invention. FIG. 8 is a block diagram of the main parts of a TNFEM-LCD showing one embodiment of the present invention. FIG. 9 is a layout diagram of display picture elements and fiber plates showing another embodiment of the present invention. 4... Optical fiber assembly board, 4'... Opening, 5... Front transparent electrode, 5'... Display picture element, 10...・
・Back transparent electrode.

Claims (1)

[Claims] 1 The front substrate of the two substrates that sandwich the liquid crystal layer,
It is composed of an optical fiber assembly plate in which the axial direction of each single fiber is perpendicular to the liquid crystal layer, a polarizing plate is arranged on the outside of the two substrates, and the inner surface of the optical fiber assembly plate is substantially connected to the liquid crystal layer. A twisted nematic field effect type liquid crystal display device, characterized in that the core opening shape of each single fiber of the optical fiber assembly plate substantially matches the shape of a display pixel.