JPS61143791A - Color liquid crystal display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color liquid crystal display device, and more particularly to a color liquid crystal display device with little color change depending on the viewing angle.

[Prior Art] In general, since liquid crystal display panels are light-receiving (passive) types, they consume less power than light-emitting (active) displays such as CRTs, operate at low voltage, and are easy to configure into panels. It has the advantage of being easy to use and allowing for a large screen. Among these, those that drive a large number of pixels in a matrix are suitable for TVs and are attracting particular attention for their future potential. This type of liquid crystal display panel is usually TP
Using T (thin transistor), 2 to 10 TPTs for driving are placed on a substrate such as glass or plastic film.
The structure is arranged in a matrix with a density of wood/■.

FIG. 3 is a perspective view showing an example of a staggered structure of a matrix type liquid crystal display panel. In the same figure, T
PT is a gate line formed on the substrate S 1aa, l
It has row electrodes consisting of ab, . . . , and gate electrodes 1a, lb, 1c, 1d, .
After covering these with an insulating layer 5, thin film semiconductor layers 2a, 2b, 2c, 2d, .
, 3b, .

4d... The drain electrode is
These are electrodes that constitute a display unit. Furthermore, the row electrodes and column electrodes are formed of transparent or metal thin film conductive layers.

FIG. 4 is a plan view viewed from the direction of arrow OB in FIG. 3, showing a part of the matrix drive circuit. In FIG. 4, one end of the semiconductors 2a and 2c is a source line 3a.
The ends of the semiconductors 2b and 2d in the same direction are in contact with the source line 3b.
The other end of these semiconductors is in contact with the drain electrode 4a.
, 4c, 4b, and 4d, respectively.

FIG. 5 is a cross-sectional view of a display panel using a substrate having a cross-sectional structure along the line segment A-A shown in FIG. 4, and is an example used in a conventional liquid crystal display device. In Figure 5,
The liquid crystal display panel is formed in a layered structure sandwiched between a substrate S and a substrate 6, and the layered structure includes gate electrodes 1c and 1d.
, insulating layers 5a and 5b, semiconductor layers 2c and 2d, source lines 3a and 3b, drain electrodes 4c and 4d, liquid crystal layer 7
, an insulating layer 8, and a counter electrode 9, and the insulation of the panel is sealed with a sealing member 10. The liquid crystal layer 7 includes dynamic scattering type (DSM) and twisted nematic (TN).
) and other display modes are used, and depending on whether the device is transmissive or reflective, a polarizing plate is used.

It is necessary to appropriately provide optical detection means such as an input/quarter plate and a reflection plate. In particular, in the case of twisted nematic mode, a polarizer 11 and an analyzer 1 are used as optical detection means.
Both of 2 are necessary.

In the above-mentioned liquid crystal display panel, the operating characteristics of the cell itself tend to depend on the thickness of the liquid crystal layer, and the thickness of the liquid crystal layer is made as thin as possible over a predetermined area (for example, 10 cm2) or more. (for example, IL11 or less) and uniformity, otherwise the display characteristics of the entire display panel will deteriorate and neither good gradation nor high-speed response can be obtained. Therefore, in order to maintain the thickness of the liquid crystal layer at a predetermined value, a method of mixing an inert material with a certain particle size into the liquid crystal layer is required.

When a color liquid crystal display device is constructed using such a display panel, it becomes as shown in FIG. 6. That is, a drain electrode 4a which is a display unit forming one image,
At the positions corresponding to 4b, 4c, 4d...
and color filters 14a, 14b.

14c, 14d... are arranged, and the combination of the drain electrode and the color filter forms one color display unit, and one of each color filter is R (red), G ( green) or B (blue), and the colors of adjacent color filters are R and G, respectively.
, H, full color display is possible.

[Problem to be Solved by the Invention 1] In such a color liquid crystal display device, it is technically extremely difficult to make the thickness of the liquid crystal layer thin and uniform. Therefore, the viewing angle as one display characteristic has a very narrow value, and the range in which good gradation can be obtained is further limited.

For this reason, there is a drawback that the contrast decreases and even one displayed color changes depending on the viewer's viewing direction.

In view of the above, it is an object of the present invention to address the problem of viewing angle dependence of a liquid crystal display panel, and to provide a color liquid crystal display device with good contrast and little color change depending on the viewing angle.

[Means for solving the problem] In the present invention, the means taken to solve the above problem is to transmit light to the liquid crystal layer structure sandwiched between the light source side substrate and the display side substrate. In a color liquid crystal display device that displays a color image, a light scattering surface is formed on either or both of the surface of the display side substrate that is in contact with the liquid crystal layer structure and the opposite surface thereof.

In the present invention, the liquid crystal layer structure refers to liquid crystal and T
In the gate electrode, source electrode, drain electrode, counter electrode, insulating layer, semiconductor layer, etc. of PT (fJ membrane transistor),
A thin metal film of Au, Af, Pd, etc. is used for the gate electrode and source electrode, and S is used for the drain electrode and counter electrode.
l2O3, Ln2O3, ITO (Indium-Tin
-Oxide), etc., to Au.

A metal thin film such as Pd or the like is used. The semiconductor layer is amorphous silicon, polysilicon, and CdS.

A thin film semiconductor such as GdSe is used. These layered structures are sandwiched between two substrates, and the light is input from one side, and the light imaged by the liquid crystal is visually observed from the other side. The substrate on the light source side will be referred to as the light source side substrate, and the substrate on the output side will be referred to as the display side substrate. These substrates are usually made of glass or plastic films. The light scattering surfaces formed on these substrates are uneven surfaces, and can be easily formed by chemical etching, mechanical polishing, or the like.

[Function] By providing a light scattering surface on the display side base surface, the output state is expanded and diversified compared to the case where the light is directly emitted convergently from the liquid crystal layer, and the dependence on the viewing angle is reduced. Here, the viewing angle refers to the limit at which the displayed content of the emitted light can be visually confirmed, expressed as a solid angle from the center line of the emitted light.

[Example] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing the structure of an embodiment of a color liquid crystal display channel according to the present invention. In FIG. 1, the color liquid crystal display panel is formed in a layered structure sandwiched between a substrate S and another substrate 15, and the layered structure is formed from the substrate S side.
TPT18 for LCD drive, insulation $17. liquid crystal layer 18,
Alignment film 19. It is composed of a color filter 20 and a transparent electrode 21. The surface of the substrate 15 on the transparent electrode 21 side has a light scattering function according to the present invention, and the substrate surface is provided with an uneven state in order to scatter light. In the case of a glass substrate, a chemical etching method using a hydrofluoric acid solution or a mechanical polishing method is generally used to form irregularities. In this embodiment, a glass substrate that has been frosted by these methods is used. Since the light irradiated from the substrate S side and transmitted through the liquid crystal layer is scattered by this scattering surface, the output state after passing through the substrate 15 is also diversified, and the dependence on the viewing angle is reduced. That is, the viewing angle of the color liquid crystal display device is expanded.

FIG. 2 is a comparison diagram between this embodiment and a conventional example regarding the viewing angle of a color liquid crystal display device. As a result of the measurement, the viewing angle/AOA' of the conventional example was about 20 degrees, while the viewing angle/BOB' of the present example was about 40 degrees.
It has almost doubled. The brightness of the display screen was slightly reduced due to the scattering surface in the optical path, but it was not enough to cause a problem with the naked eye.This is due to the refraction of the material in contact with the glass substrate, which has a refractive index of 1.5. This is because the ratio is 1.8 for transparent electrodes and about 1.55 for liquid crystals, which is not a very large difference. Therefore, the degree of roughness of the scattering surface has a wide allowable range.

In the embodiment shown in FIG. 1, the scattering surface is provided on the liquid crystal side of the substrate 15, but it may also be provided on the outer side of the substrate. In this case, the uneven surface makes the scattering surface smaller. By using a polarizer or by bonding the polarizing plate to the scattering surface using an adhesive with a refractive index close to that of the substrate, it is possible to prevent a decrease in the brightness of the display screen and expand the viewing angle. .

Furthermore, in the embodiment shown in FIG. 1, since the surface area of the substrate is increased by the unevenness, it is possible to obtain the effect of improving adhesion and durability when forming films such as transparent electrodes and color filters on the surface.

Further, the present invention provides a liquid crystal layer as disclosed in US Pat. No. 438,792.
The ferroelectric liquid crystal described in Publication No. 4 can be used.

[Effects of the Invention] As explained above, according to the present invention, by providing a scattering surface on the substrate on the display surface side, the viewing angle is expanded and a color liquid crystal display device with less color change depending on the viewing angle can be provided. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a cross section of the embodiment of the present invention -', Fig. 2 is a comparison of viewing angles between the embodiment and the conventional example, and Figs. 3 and 4 are TPT.
FIG. 5 is a sectional view of the conventional example, and FIG. 6 is a perspective view of the conventional example. S...substrate, l...gate line and gate electrode, 2.
... Semiconductor, 3... Source line, 4... Drain electrode, 5.8.17... Insulating layer, 6
．． 15... Counter substrate, 7.18... Liquid crystal layer, 9
... Counter electrode, lO ... Seal member, 11 ... Polarizer, 12 ... Analyzer, 14.20 ... Color filter, 1B ... TFT, 19 ... Alignment film, 21・
...Transparent electrode.

Claims (1)

[Claims] In a color liquid crystal display device that displays a color image by transmitting light to the liquid crystal layer structure sandwiched between the light source side substrate and the display side substrate, the surface of the display side substrate in contact with the liquid crystal layer structure, or the opposite side. A color liquid crystal display device characterized in that a light scattering surface is formed on one or both of the side surfaces.