JPS60262131A - Liquid-crystal display device - Google Patents

Abstract

PURPOSE:To form a bright image even with a small aperture part by providing a couple of lenticular lenses or compound lenses at both sides of a liquid-crystal layer corresponding to positions of picture elements, and making the focal points of the couple of the lenses coincident with each other. CONSTITUTION:Liquid crystal 20 which has picture element electrodes 16 and opaque parts 18 on one surfaceis clamped between substrates 10. Polarizing plates 30 and 30 are laminated outside of them and numbers of lenticular lenses (or compound lens) 40 and 40' having optical axes in parallel are provided further outside. The focal point F1 of the lens 40 and the focal point F2 of the lens 40' are at the same position and parallel input light beams L1 appear at an output side through the picture element electrodes 16. Namely, the parallel incident light L1 is emitted as parallel light beam L1 without being cut off by the opaque parts 18. A light beams which is made incident slantingly is also passed through a picture-element electrode 16 similarly. Consequently, a bright image is formed even with a small aperture part and the visual field is widened, so that this device is used suitably for a large-size projector.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a liquid crystal display device, and particularly to a high-quality display structure of an XY dot matrix type liquid crystal display device with a low aperture ratio. A color liquid crystal television display device will be described below as an example.

<Background of the Invention> A color liquid crystal display panel has been developed as a display device that utilizes the electro-optical effect of liquid crystal for displaying television images. This color liquid crystal display panel consists of a large number of picture element electrodes arranged in a dot matrix, a liquid crystal layer that modulates light according to the voltage applied thereto, and coloring means arranged corresponding to the picture elements. Become. By applying a video signal according to the color corresponding to each picture element electrode 1, color CRT
It is possible to display any dot matrix type image including intermediate colors that are additively mixed using the same principle as that of a cathode ray tube (cathode ray tube).

As is well known, the operating modes of the liquid crystal display panel include twisted nematic (TN) mode, guest host (
There are many modes such as GH) mode, dynamic scattering mode (DSM), and phase transition mode.
Although the present invention is applicable to any of them, particularly TN and GH give preferable results. GH uses black pigment and operates as a so-called black shutter.

Details about liquid crystals are explained in ``Fundamentals and Applications of Liquid Crystal Electronics'' edited by Sasaki, Ohmsha (1979,), etc. One of the following three methods is used:

(1) Simple matrix method Parallel striped electrode groups are arranged on each of two substrates, and the substrates are bonded together so that they are perpendicular to each other, and liquid crystal is injected to form a panel. A row selection signal is sequentially applied to one row electrode. An image signal is applied to the other column electrode in synchronization with the row selection signal. Therefore, the intersection of the row electrode and the column electrode becomes a picture element, and the liquid crystal sandwiched between the two electrodes undergoes optical modulation for each picture element in response to the potential difference between the two electrodes.

Since the liquid crystal has a characteristic of responding to an effective value, the number of scanning lines cannot be set too large in terms of crosstalk and dynamic range.

Therefore, three dog systems have been developed to overcome these limitations.

(2) Multiple matrix This is a method of increasing the number of picture elements in the scanning direction without increasing the number of scanning electrodes by modifying the electrodes of a simple matrix. (Refer to the above document) Multiplexed wires) With +7x, the shape of the electrode becomes complicated and the wiring resistance tends to increase. If the wiring resistance cannot be lowered sufficiently with the transparent conductive film alone, metal wiring is used in combination. When metal wiring is used, the aperture ratio decreases as will be described later.

(3) Addition of non-linear element Varistor, M I M (Metal/I'
n5ulator/Metal), Back-to-Back Diode
This is a method of suppressing crosstalk by adding nonlinear elements such as.

(4) Addition of a switching element In this method, a switching transistor is added to each picture element and driven individually. A drive voltage is applied during the selection period to charge the storage capacitor, which is maintained during the non-selection period. Furthermore, the liquid crystal itself is also a capacitive load.
If the time constant is sufficiently large compared to the repetition period of the drive, the storage capacitor can be omitted. The switching transistor is a thin film transistor or a MOS-FET formed on a silicon wafer.
etc. are used.

The present invention can be applied to any of the above (1) to (4), but the effect is particularly remarkable when metal wiring is used in (1) and in (2) and (3).

Usually, additive primary colors are selected as colors for colored display. As the coloring means, interference filters, filters made of inorganic or organic dyes or pigments, etc. are used. Such a filter or the like may be provided on the outer surface or inner surface of the substrate constituting the liquid crystal panel. In the latter case, it may be provided above or below the picture element electrode or the common electrode.

In color liquid crystal panels, only the spectral region of one of the three primary colors is utilized in the spectrum of incident light, and the remaining components are absorbed by the coloring means. Furthermore, in the case of a liquid crystal operation mode that uses a polarizing plate, the amount of available light is further halved, so that a reflective mode that does not provide illumination means results in a very dark display. For this reason, a light source such as an incandescent lamp, a fluorescent lamp, or an EL panel is provided as an illumination means, or measures are taken to guide ambient light to the back side of the liquid crystal panel. In the case of application to vertical equipment, it is important to improve the luminous efficiency of the light source because power supply capacity is severely constrained.

Furthermore, there is a problem with the aperture ratio that causes the display to become dark.

The aperture ratio is defined as follows.

Aperture ratio = effective area of all pixels / area of display area, that is,
As the portion that does not contribute to display increases, the aperture ratio decreases. Portions that do not contribute to display (opaque portions) include metal wiring of each electrode, added nonlinear elements or switching elements, and gaps around picture element electrodes.

On the other hand, in order to reproduce a high-definition image, the pixel pitch must be reduced. If all of the panel components can be similarly reduced, the aperture ratio will not change, but there are limits to etching accuracy and alignment accuracy, so the width of the metal wiring of the electrodes and the weight and weight of additional elements will be reduced below a certain level. Can not. Therefore, as the pixel pitch decreases, the aperture ratio also decreases.

As described above, the aperture ratio is the controllable proportion of light that enters the liquid crystal display device, and the remaining light is blocked by the opaque portion that does not contribute to display.

Therefore, even when observed under the same lighting conditions, a liquid crystal display panel with a low aperture ratio looks dark. In this way, in the past, the brightness of the display depended on the aperture ratio, and furthermore, the opaque areas between the picture elements formed black borders, resulting in poor image quality.

<Objective of the Invention> The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal display device that is not easily affected by the aperture ratio and can provide a bright and smooth display.

<Configuration of the Invention> In order to achieve the above object, the present invention is configured as follows. The light incident on the liquid crystal layer is focused by a first lenticular lens or a compound eye lens that corresponds in position to each picture element. It is arranged so that its focal point or the image of the light source is near the center of the picture element electrode. The light passing through the liquid crystal layer is modulated according to the video signal voltage applied to the picture element electrode. The light that has passed the focal point is either spread out or converged by a second lenticular lens or a compound eye lens to form an image at the distance of clear vision (25 cm) to infinity.

In order to do this, the focal points of both lenses on the inner and outer sides of each other (the rear focal point F1 of the first lens and the front focal point F2 of the second lens) may be made to match or be placed close to each other. In Figures 1a and 1b, when the rear focal point Fl' and the front focal point F2 are arranged so that they coincide, a case in which a ray A parallel to the optical axis is incident, and a case in which a parallel ray B is incident obliquely. shows.

As shown in FIG. 1a, the light ray A is converged by the first lens 1 to the focal point F,' = F2, forms an image of the light source, and becomes a parallel ray A'' by the second lens 2. In this way, the light ray A is converged and the liquid crystal display device appears bright.Both lenses 1,
Since it does not pass through an opaque part (not shown) in the second lens, there is no loss of light, and as shown in Figure 1b, the light ray B is safely directed by the first lens 1 to a point B far from the optical axis. The light beam converges into a parallel light beam Bll by the second lens 2, and exits in a direction symmetrical to the direction of incidence. If the distance between the first lens 1 and the second lens 2 is made larger than in this case, the light converged on the safe surface of the first lens 1 will converge on its conjugate surface after passing through the second lens 2. and form an image of the light source. If you look at the $2 lens 2 from this position, it will appear the brightest. Therefore,
Depending on the field of application of the liquid crystal display, the distance between the liquid crystal display and the user's eyes is assumed, and the image of the light source is focused at that distance, so that the liquid crystal display appears brightest.

Liquid crystal display devices are generally viewing angle-dependent dog-shaped display elements, but according to the present invention, as can be seen from FIGS. 1a and 1b, the light incident on the liquid crystal display device has a conical shape.
Since the average of these images reaches the user's eyes, viewing angle dependence is alleviated. In a twisted manetic mode liquid crystal display (TN-LCD), the viewing angle with good characteristics is tilted from the direction perpendicular to the display surface, so the method of tilting the central axis of the cone formed by the incident light is shown in Figure 2. The optical axes of the first lens 1 and the second lens 2 may be moved in parallel.

<Operation of the Invention> As described above, according to the configuration of the present invention, the incident light is effectively guided to the pixel electrode, there is almost no loss due to being blocked by the opaque part, and a bright image can be produced even if the aperture ratio is small. can get. Furthermore, according to this configuration, the picture elements appear enlarged and the opaque areas between the picture elements are completely filled, so that a smooth image can be obtained.

In the above explanation, a liquid crystal display element for a color TV was taken as an example, but the application of the present invention is not necessarily limited to a color TV, and the colors are not limited to the three primary colors, but may be monochrome with two colors or four or more colors. Needless to say, the applied form is also applied to graphic display, character display, etc. It is also applicable to a liquid crystal display device in which a large number of liquid crystal display modules are arranged in parallel to obtain a large screen display.

<Example> Figure 3 (A>, (B), and (C) shows an example of the present invention, and shows the liquid crystal display panel used in the TPT success story. FIG. 3 is an explanatory diagram of the main part configuration of the cell substrate.
Figure (A> is a plan view schematically depicting an example of TPT, and Figure 3 (B) is its cross-sectional view. Figure 3 (C)
is an equivalent circuit diagram. TPT has a date electrode 11, a date insulating film 12, and a date electrode 11 on a transparent insulating substrate 10 such as glass.
A semiconductor film 3, a source electrode 14, and a drain electrode 15 are sequentially patterned and laminated. A picture element electrode 16 and a storage capacitor 17 provided as necessary are connected to the drain electrode 15.

Thin film formation methods include vacuum evaporation, sputtering)
A CVD method, a plasma CVD method, a low pressure CVD method, or the like is used, and patterning is performed using a shadow mask or photolithography technique. The substrate on which this TPT is formed constitutes a cell that encapsulates liquid crystal, and further provides a light shield and an alignment film to drive the liquid crystal. Semiconductor film 1
When an n-type semiconductor is used as 3, when a positive voltage is applied to the gate electrode 11, an electron accumulation layer is formed at the interface of the semiconductor film 13 on the gate insulating film 12 side, and the gap between the source electrode 14 and the drain electrode 15 is Resistance is modulated.

A scanning pulse is periodically applied to the gate electrode 11 via the gate line GL, and TPT is turned on. In synchronization with this, an image signal is applied to the source electrode 14 via the source line SL, and is further applied via the TPT to the picture element electrode 16 and a storage capacitor 17 provided as necessary to drive the liquid crystal. When the picture element pitch is several lines per ■,
The aperture ratio is 50 to 80% in a normal design, but if the picture element pitch is made smaller, the aperture ratio decreases to less than this. The storage capacitor 17 is used to maintain the voltage to be applied to the liquid crystal even while the TPT is in the 0FF (off) state. If the time constant of the liquid crystal is sufficiently larger than the scanning period, it is not necessary to provide the storage capacitor 17. Next, a counter-electrode side substrate is prepared, in which a conductive film and a color filter are provided on a transparent substrate such as glass. As the color filter, an interference filter, an inorganic or organic dye or pigment is used. In the color filter, three primary colors are arranged in a stripe or mosaic pattern using a photolithography method or a printing method. A transparent electrode film made of tin-doped indium oxide (ITO) is provided on this by a method such as ion blating, and an alignment layer for aligning the liquid crystal is laminated thereon. A liquid crystal display panel is produced by bonding these two substrates together via a spacer, injecting liquid crystal into the gap between the side substrates, and then sealing the injection port. Incidentally, when the operation mode of the liquid crystal is TN, polarizing plates are provided on both sides of the liquid crystal display panel.

Next, lenticular lenses or compound lenses, which are characteristic components of the present invention, are provided on both sides of the liquid crystal display panel. Note that the arrangement order with respect to the polarizing plate may be reversed.

First, a case where a lenticular lens is used will be explained.

In FIG. 4, 10.10 is a pair of opposing substrates, 1
6 is a pixel electrode provided on the substrate 10, 18 is an opaque portion such as metal wiring provided on the substrate 10, 2° is a liquid crystal provided between the substrates 10 and 10, and 3o is a portion of each substrate 10, 1.0. The polarizing plate provided on the outside, 40.40 is a lenticular lens provided on the outside of the polarizing plate 30.3'O, and P is the pitch of the lenticular lens 40.

1. The ticular lens 40.40 is a large number of semicylindrical lenses arranged at a pitch that is the same as or twice the pixel pitch, and has a convergence effect only in one direction. When the opaque portion 18 is a stripe in only one direction (for example, when metal wiring is provided in a multiple matrix or when a non-linear element is added), it is appropriate to use this lenticular lens 40° 40.

In addition, as shown in FIG.
,..., in the case of a type that adds data electrodes 14゜14,
... and picture element electrodes 16, 16. By arranging lenticular lenses 40, 40 symmetrically in two rows as one set, the pitch of the lenticular lenses 40, 40 can be made twice the pitch of the picture elements. The large pitch of the lenticular lenses 40 is advantageous in terms of processing technology. In this case, if the parallelism of the illumination light is high, a sharp image will be formed in the gap between the two picture element electrodes 16. Just place the image in front or behind.

Next, the case where a compound eye lens is used will be explained based on FIGS. 6 and 7.

The compound eye lens 50.50 has a large number of lenses arranged two-dimensionally so as to match the pixel arrangement.

When the opaque portion 18 is in the form of an XY matrix (
For example, it is appropriate to use the compound eye lens 50 for the GoFT-added type. By carefully arranging the row electrodes, column electrodes, and picture element electrodes 16, the pitch of the compound eye lens 50 in the row direction and/or column direction can be made twice that of the picture element electrodes 16. Figure 7 shows a compound eye lens 5 in both the row and column directions.
This is an example where the pitch P of 0 is twice the pixel pinch.

A large pitch is advantageous in terms of processing technology.

In addition, in FIGS. 6 and 7, the same components as those in FIGS. 4 and 5 are given the same reference numerals, and explanations thereof will be omitted.

When the illumination light is highly parallel, the focal point is moved to the pixel electrode 1.
6 and the liquid crystal layer 20 may be shifted before or after the liquid crystal layer 20 as before.

Although FIG. 4 shows the optical path of parallel light rays, even if the illumination light is diffused light, the lenticular lens 40 or compound eye lens 50 converges the light to some extent and increases the amount of light incident on the picture element electrode 16. A brighter display can be obtained than when this is not used.

In the lenses shown in the above examples, one side is flat and the other side is cylindrical or spherical, and the flat sides face the liquid crystal side, but the orientation is not necessarily limited to this. Further, the focal lengths of a pair of lenses may not be equal.

These lenses can be obtained by injection molding or press molding a transparent resin such as acrylic resin, polycarbonate resin, polystyrene resin, or glass.

Furthermore, the substrate constituting the liquid crystal cell itself can be molded to have a lens effect.

<Effects of the Invention> As is clear from the above description, according to the present invention, even if the aperture ratio is small, a bright and smooth display that is hardly affected by the aperture ratio can be obtained, and the effect is great.

[Brief explanation of the drawing]

Figures 1a, 1b, and 2 are diagrams of the basic principles of the present invention, and Figures 3 (A), 3 (B), and 3 (C) are illustrations of the basic principle of the present invention.
An explanatory diagram of the main part configuration of a cell substrate of a liquid crystal display panel using TPT as an example, FIG. 4 is a perspective view of an example in which a lenticular lens is used, and FIG. 5 is a nonlinear diagram used in the above example. Explanatory diagram of element-added type liquid crystal display substrate, No. 6
The figure is a perspective view of an embodiment of the present invention in which a compound eye lens is used, and FIG. 7 is an explanatory diagram of a TPT substrate used in the above embodiment. DESCRIPTION OF SYMBOLS 10... Substrate, 14... Data electrode, 16... Picture element electrode, 18... Opaque part, 19... Nonlinear element, 20... Liquid crystal, 30... Polarizing plate, 40 ...Runticular lens, 50... Compound lens. Patent Applicant: Sharp Co., Ltd. Agent, Patent Attorney, Above: 2 people, 111o, Figure 2, Figure 4, Figure 5, P, Figure 6, Procedural Amendment (1977). Application No. 1 ] 8707 No. 2 Name of the invention Liquid crystal display device 3 Relationship to the case of the person making the amendment Patent applicant 11 Place 22-22 Nagaike-cho, A13-no-ku, Osaka-shi, Osaka 4 Agent address Higashi, Osaka-shi, Osaka 2-10 Honmachi, Ward Name in Honmachi Building Patent Attorney (62) 4) Aoyama Ao and 2 others 1″ 5
Date of sleeve correction order: Subject of spontaneous 6 amendments: Specification: Detailed description of the invention column. The following points in the statement will be corrected. In the Detailed Description of the Invention column (1), page 6, line 12, the word ``spectral'' should be corrected to ``spectrum.''that's all

Claims (5)

[Claims] (1) In a transmissive liquid crystal display device that has picture elements arranged periodically, there are 1 on both sides of the liquid crystal layer that correspond in position to the arrangement of picture elements.
Equipped with a pair of lenticular or compound lenses,
A liquid crystal display device characterized in that the focal points of the liquid crystal side of the pair of lenses are substantially the same. (2) The liquid crystal display device according to claim 1, wherein the pitch of the lenticular lenses is equal to the row pitch or column pitch of the picture elements. (3) The liquid crystal display device according to claim 1, wherein the pitch of the lenticular lenses is twice the row pitch or column pitch of picture elements. (4) The liquid crystal display device according to claim 1, wherein the pitch of the compound eye lens is equal to the pixel pitch in both rows and columns. (5) In the liquid crystal display device according to claim 1, the pitch in the row direction and/or the column direction of the compound eye lens is 2 times the pixel pitch in the corresponding direction.
A liquid crystal display device characterized by being twice as large.