JPS60165621A - Transmission type display element - Google Patents

Abstract

PURPOSE:To obtain a bright transmission type display element by forming distributed index regions partially in accordance with respective picture elements so as to concentrate the incident light from the rear of a transparent supporting substrate to the picture element regions on the front of the substrate to the rear part of the substrate. CONSTITUTION:Regions 11 having a partial refractive index distribution are formed by an electric field implantation method to the rear part of a transparent supporting substrate 1 for a display element of a photodetection type and transmission type such as a liquid crystal display element. A thin film transistor 2, a drain electrode 3 and a picture element electrode 5 are provided on the liquid crystal 10 side of the substrate and a counter electrode 7 and a color film 8 are provided on the liquid crystal side of a counter transparent substrate 6 in the case of, for example, a liquid crystal display element. The incident light from the substrate 1 side is thus concentrated on the corresponding picture element region 5 by the distributed index region 11. Since the incident lights 20, 21, 22 are concentrated on the display aperture part 12 of the picture element 5 by the region 11 as shown in the figure, the bright display than that in the prior art is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a transmissive type light-receiving display element capable of displaying a bright screen.

(Prior Art) Currently, a CRT (Cathode Ray Tube) is used as a display device for displaying characters, graphics, television images, etc.
, cathode ray tubes) are mainly used, but CRTs have the disadvantage of being large in volume, and various thin display devices have been proposed to replace them, and some have been put into practical use. . These display elements can be classified into light-emitting type and light-receiving type. The light-emitting type includes plasma displays, fluorescent display tubes, electroluminescent displays, light-emitting diode displays, etc., and the light-receiving type includes liquid crystal displays and electroluminescent displays. There are micro displays, electrophoretic displays, electro-optic crystal displays, etc. Each of these thin display elements has its own advantages and disadvantages, but in general, light-emitting display elements provide a brighter display but require a higher driving voltage.
On the other hand, light-receiving display elements generally consume less power, but because they are light-receiving types that do not emit light themselves, they have the disadvantage that the display is difficult to see in dark places. ing. For this reason, light-receiving display elements are designed to incorporate a reflective structure to capture a large amount of ambient light, but even so, the display is hardly visible under weak ambient light. Therefore, in many cases, a light-receiving type display element is provided with a light source for back pressure illumination. However, when a light source for illumination is provided, its power consumption is large, and the advantage of low power consumption of the light-receiving display element is lost. Therefore, in order to reduce power consumption as much as possible and obtain a display brightness comparable to that of a light-emitting display element, K is to use as much of the incident light from the illumination light source as possible for displaying the effective pressure in a transmissive display element. is essential. Conventionally, as a means of achieving this, for example, a fluorescent light is irradiated from the edge of a transparent substrate of a liquid crystal display element, and the incident light from the fluorescent light is repeatedly reflected inside the transparent substrate and effectively illuminates the entire display surface. was taken. (Proceedings of the 3rd Liquid Crystal Symposium, p. 24, 1977) However, even with these efforts, light-receiving display elements still cannot provide sufficiently bright displays with low power consumption. This is the current situation. For example, in the Acte element, which is attracting attention as a thin display element with a large display capacity that can compete with CRT and the possibility of color display, 400
Even if a light source with a brightness of 1.5 nits is used, only 20 nits of brightness can be obtained on the display screen, and a 1.5-inch color C that can achieve 40 nits of brightness with 4W of power consumption.
Even compared to RT, the screen brightness is inferior. However, the present inventor has devised a light-receiving type display element with a novel structure that can effectively utilize ambient light or incident light from an illumination light source, and has achieved the present invention.

(Object of the Invention) An object of the present invention is to provide a light-receiving display element capable of displaying a bright screen.

(Structure of the Invention) A transmissive display element of the present invention uses at least one transparent body as a support substrate for a display substance, and controls incident light from behind the support substrate in each pixel by the display substance. This is a transmissive display element that performs display, and is characterized by a structure in which a refractive index distribution region is partially formed on the back surface of the support substrate to concentrate the incident light on the pixel region.

(Example 1) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing the structure of one support substrate used in an embodiment of the transmission type display element of the present invention. In Fig. 1, 1 is a glass substrate with a thickness of 1.3 mm, and 2 is a TFT (Thin Film) formed of amorphous silicon.
nTransistor, thin film transistor), 3 is M
o drain electrode, 4 is an MO agate electrode, and 5 is an indium oxide pixel electrode (transparent electrode). Although not clearly shown in the figure, the intersection of the drain electrode 30 and the gate electrode 4 is isolated by a silicon nitride insulating film. FIG. 2 is a schematic diagram showing the structure of an embodiment of the transmissive display element of the present invention formed using the support substrate shown in FIG. FIG. In FIG. 2, 1 is the glass substrate of FIG. 1, and 2 and 3.5 are TPT, drain electrode, and pixel electrode formed on the glass substrate 1, respectively.

A partial refractive index distribution region 11 is provided on the back surface of the glass substrate 1.
is formed. This refractive index distribution region was formed by a method known as an electric field transfer method.

Regarding the electric field transfer method, see, for example, Electronics Letters No. 17.
There is a description in the paper starting on page 452 of the volume. 6 is thickness 1
．． It is a 1 mm glass substrate, on which is provided an indium oxide common electrode 7 formed over the entire surface and a dot-shaped color filter 8 formed at a position corresponding to the pixel electrode 5. Note that three types of color filters 8, red, blue, and green, are arranged alternately. Two glass substrates 1 and 6 are adhesively fixed around the periphery with an epoxy adhesive 9, and the gap between them is filled with a liquid crystal material 10 containing a black dichroic dye, forming a so-called guest-host type active matrix. It constitutes a liquid crystal display element with a built-in color filter.

In this embodiment, the liquid crystal material is the display material, and the transparent bodies serving as supporting substrates for the display material are two glass substrates. The liquid crystal material is the gate electrode 4. Drain electrode 3. Depending on the voltage waveform selectively applied to the common electrode 7, it exhibits the known guest-host electro-optic effect. That is, on the "on pixel", the incident light from behind the glass substrate l is On the "off pixel", almost all incident light from behind the glass substrate 1 is absorbed and not transmitted!The transmitted light appears colored by the color filter formed corresponding to each pixel electrode. As a result, a color display using red, blue, green, and a mixture of these colors is realized on a black background.

(Operations and Effects of the Invention) Here, the effects of the partial refractive index distribution region 11 formed on the back surface of the glass substrate 1 will be explained using FIGS. 3 and 4. FIG. 3 is a diagram showing the refractive index distribution in one K of the refractive index distribution regions 11 and the optical path of the incident light. In FIG. It gets bigger towards the center.

Therefore, as shown in FIG. 3, the incident light that has entered the refractive index distribution region travels in a curved manner as shown in the optical path 14. As a result,
As shown in FIG. 4, light incident from behind the glass substrate 1 is concentrated in the pixel area. FIG. 4 is a cross-sectional view of the glass substrate 1 shown in FIG. 2, where 11 is a partially formed refractive index distribution region, and 12 is a so-called "on pixel" in which the liquid crystal material is in a state where it transmits incident light. This shows the area of the opening. That is, as can be seen from FIG. 1, the so-called pixel region where incident light is controlled by the electro-optic effect of the guest-host type liquid crystal material is only the region of the pixel electrode 5 in FIG. 1, and the other regions are It is always in a state of blocking incident light. In this embodiment, the area occupied by the pixel electrode in FIG. 1 is about 60 cm, the length of the opening 12 in FIG. 3 is 180 μm, and the interval between the openings is 70 μm.
It is m. In FIG. 4, out of the incident light from behind the glass substrate 1, the light that takes 20 optical paths travels straight to the opening 1.
2 and contributes effectively to display. Also, 21 or 2
The incident light that takes the second optical path is curved by the refractive index distribution region 11 and also passes through the aperture 12 and effectively contributes to the display. That is, in the transmissive display element of this embodiment, almost all incident light within the plane of FIG. 4 passes through the opening 12 and effectively contributes to display. However, in the conventional structure without the refractive index distribution region 11, as shown by the broken line in FIG.
2, it moves straight and reaches a non-opening area, where the display W no longer contributes. In this example, when an illumination light source with a brightness of 400 nits is installed behind the glass substrate 1, a display brightness of 30 nits is obtained, and a display brightness without a refractive index distribution region is 20 nits. A noticeable improvement was seen, and a brighter screen display was realized. Of course, even when no special illumination light source was installed, the transmissive display element of this example provided a brighter screen display than that of the conventional structure. In the above embodiments, the case of a so-called active matrix type liquid crystal display element with a built-in color filter has been described, but the effects of the present invention can be applied to a color filter built-in type or an active matrix type K [not specified; Furthermore, the operating mode of the liquid crystal material is not limited to the guest-host type. However, in the active matrix method in which a switching element is connected to each pixel to operate a display material such as a liquid crystal material, the effects of the present invention are not particularly effective because the switching element significantly reduces the aperture ratio of the display screen. Ru. Furthermore, even in a liquid crystal display element having a structure in which a color filter array is installed at a position corresponding to each pixel, the effect of the present invention is extremely remarkable because the color filter selects the incident light in terms of wavelength and significantly reduces the amount of transmitted light, that is, the brightness. It is demonstrated.

In addition, in the above-mentioned embodiment, in order to form the refractive index distribution region,
Although electric field transfer techniques have been used, this is by way of example only; other methods, such as ion implantation techniques, have been used.

It may be produced by any method such as thermal diffusion method or ion exchange method.

(Example 2) FIG. 5 shows an example in which an electrocoumic material is used as a display material. In this case, only one support substrate may be used. The figure shows an example, and 41 is a glass substrate, 42 is a TPT made of polysilicon, 43 is a W drain electrode, 45 is a tin oxide pixel electrode, 50 is a tungsten oxide layer as a display material, and 52 is a fluoride film as an ion conductive layer. Magnesium layer,
47 is a tin oxide common electrode, and 51 is a refractive index distribution region provided on the glass substrate 41.

In this example, the same effects as in the first example were obtained.

Regarding the display material, in addition to those used in the above examples, for example, an electro-optic crystal represented by an electromic material or a substance known by the name of PLZT, or a magneto-optic crystal such as garnet may be used. It goes without saying that the present invention is effective.

As described above, according to the present invention, a light-receiving display element capable of displaying a bright screen can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of one supporting substrate in an embodiment of the present invention, in which 1 is a glass substrate, 2 is a thin film transistor, 3 is a drain electrode, 4 is a gate electrode, and 5 is a pixel electrode. FIG. 2 is a cross-sectional view showing the structure of an embodiment of the present invention using the support substrate shown in FIG. 1, in which 1, 2, 3, and 5 are the same as in FIG. A counter electrode, 8 a color filter, 9 an adhesive, 10 a display material, and 11 a partially formed refractive index distribution region. 3 and 4 are diagrams for explaining the effects of the embodiment shown in FIG. 2. FIG. In FIG. 3, 1 is a glass substrate, 13 is a line of equal refractive index at one K of the refractive index distribution regions, and 14 is an optical path of incident light. In FIG. 4, 1 is a glass substrate, 11 is a refractive index distribution region, 12 is a display aperture, 20, 21, 22 is an optical path of incident light, and 31.32 is a refractive index distribution region 11 shown for comparison. This is the optical path of incident light in a conventional structure without Fifth
The figure shows a second embodiment of the invention. ”)=r Figure thousand 3 Figure river'4 Figure thousand 5 figure 7

Claims (1)

[Claims] A support substrate made of at least one or more transparent bodies and a display material supported by the support substrate are provided, and display is performed by controlling incident light from behind the support substrate in each pixel by the display material. 1. A transmissive display element according to the above-mentioned method, characterized in that a refractive index distribution region is partially formed on the back surface of the support substrate to concentrate the incident light on the pixel region.