JP3831511B2 - Reflective liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reflective liquid crystal display device including an electroluminescence (hereinafter referred to as “EL”) element as a light source.
[0002]
[Prior art]
Conventionally, a so-called reflection type liquid crystal display device has been proposed in which external light such as natural light incident from the observation direction is reflected by a reflection plate to view a display.
However, the reflection type liquid crystal display device has a problem that it is very difficult to see a bright display by taking in and reflecting outside light in a dark place.
[0003]
In order to solve this problem, a reflection type liquid crystal display device having a structure including a white light source and a light source has been proposed.
FIG. 3 is a sectional view of a conventional reflective liquid crystal display device.
As shown in the figure, the conventional reflective liquid crystal display device includes a TFT substrate 100 made of a glass substrate or the like and provided with a thin film transistor (hereinafter referred to as “TFT”), and a TFT made of a glass substrate or the like. A reflective plate 130 having a reflective surface is provided on one side of the liquid crystal display panel 120 composed of the counter substrate 110 facing the substrate 100, and a white light source is provided on the other side in parallel with one side of the liquid crystal display panel 120. 140 and a light guide plate 150 and a light collecting plate 160 for guiding the light from the light source 140 to the entire surface of the liquid crystal display panel 120.
[0004]
Here, when the surroundings of the reflective liquid crystal display device are dark, the white light source 140 is turned on. The light 170 emitted therefrom is transmitted through the light guide plate 150 and the liquid crystal display panel 120, reflected by the reflection plate 130, transmitted through the liquid crystal display panel 120 again, and further transmitted through the light guide plate 150 to the observer's eyes 190. Entering, the observer can observe the display on the display device.
[0005]
Similarly, when viewing the reflection type liquid crystal display device with bright surroundings and taking in external light, the external light passes through the light guide plate 150 and the liquid crystal display panel 120 and is reflected by the reflection plate 130 and is again displayed on the liquid crystal display. The light passes through the panel 120 and further passes through the light guide plate 150 and enters the observer's eyes 190, so that the observer can observe the display on the display device.
[0006]
[Problems to be solved by the invention]
However, when the white light source is turned on with a dark surrounding, a part 180 of the light emitted from the white light source 140 passes through the light guide plate 150 and does not reach the reflection plate 130 on the surface of the liquid crystal display panel 120. Since the light is reflected and again passes through the light guide plate 150 and enters the observer's eyes 190, the white light source 140 itself is reflected together with the light 180 of the white light source 140 and enters the eye 190. Therefore, the observed display is particularly white in the vicinity of the light source 140 provided on one side of the liquid crystal display panel 120, and the display becomes darker as the distance from the white light source 140 increases.
[0007]
Further, when viewing the display by taking in external light, the light guide plate 150 has a characteristic of transmitting external light, but it is difficult to transmit all of the external light to be incorporated into the reflecting plate. That is, since the light to be taken in is attenuated by the light guide plate 150, there is a drawback that the amount of external light contributing to display is reduced.
Accordingly, the present invention has been made in view of the above-described conventional drawbacks, and an object thereof is to provide a reflective liquid crystal display device capable of obtaining a bright and uniform brightness display without being affected by ambient brightness. And
[0008]
[Means for Solving the Problems]
The reflective liquid crystal display device of the present invention includes a first substrate having a TFT connected to a display electrode made of a reflective material and driving a liquid crystal, and a second transparent substrate having an electrode facing the first substrate. The third transparent substrate provided opposite to the second transparent substrate is provided with an EL element in a region other than the display electrode.
[0009]
The EL element is provided at a position corresponding to the light shielding portion.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The reflective liquid crystal display device of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of a reflective liquid crystal display device provided with an EL light source of the present invention.
A gate electrode 2 is formed on an insulating substrate 1 such as glass, and an active layer 4 made of polycrystalline silicon is formed through a gate insulating film 3 provided on the gate electrode 2. The active layer 4 is provided with a channel 5 and a source 5 and a drain 6 formed by implanting impurities by masking the channel 7 with a stopper 8. An interlayer insulating film 9 is formed thereon, and one source 5 is connected to a display electrode (source electrode) 10 made of a reflective material such as Al through a contact hole formed in the interlayer insulating film 9. ing. The other drain 6 is connected to the drain electrode 11 through a contact hole formed in the interlayer insulating film 9. Thus, the insulating substrate 1 on which the TFT is formed, that is, the TFT substrate 1 is completed. The insulating substrate 1 may be transparent or opaque.
[0011]
Next, the transparent substrate as the second substrate, that is, the counter electrode substrate 12 facing the TFT substrate 1, is provided with the counter electrode 13 on the facing surface and the color filter 14 including the light shielding portion 15 thereon. . As shown in FIG. 2, the light shielding portion 15 is formed in a region other than the region where the display electrode 10 is formed (indicated by hatching in the drawing).
The counter electrode substrate 12 thus completed and the TFT substrate 1 are bonded to each other, and the liquid crystal 16 is filled between the substrates 1 and 12 to complete a reflective liquid crystal display panel.
[0012]
Next, the EL element substrate 17 which is a third transparent substrate will be described.
The EL element substrate 17 is made of a transparent insulating substrate such as a glass substrate.
The organic EL element 18 is formed on one surface, that is, the surface not facing the counter electrode substrate 12, and the other surface, that is, the surface facing the counter electrode substrate 12, is the counter electrode substrate. 12 are stuck together.
[0013]
Further, the organic EL element 18 is formed with an anode 20 made of a transparent electrode such as ITO (Indium Thin Oxide) and a MTDATA (4,4′-bis (3-methylphenylphenylamino) biphenyl) at a position where the light shielding portion 15 is formed. 2 hole transport layer, 1st hole transport layer made of TPD (4,4 ', 4 "-tris (3-methylphenylphenylamino) triphenylanine), Bebq2 (10-benzo [h] quinolinol-beryllium complex containing quinacridone derivative) ), A light-emitting element layer 21 made of each organic compound of an electron transport layer made of Bebq2, and a cathode 22 made of magnesium-indium alloy (MgIn) are laminated on the counter electrode substrate 12 in this order. The organic EL element 18 is thus configured by the anode 20, the cathode 22, and the light emitting element layer 21. The organic EL element 18 is formed on the light shielding portion 15. The formation area may be set according to the amount of light required for viewing the display, and the organic EL element 18 may be formed by an external force. In order to prevent the organic EL element 18 from being damaged, it is preferable to cover it with an insulator or the like.
[0014]
In the organic EL element 18, holes injected from the anode 20 and electrons injected from the cathode 22 are recombined inside the light emitting layer, and excitons are generated by exciting organic molecules forming the light emitting layer. Light is emitted from the light emitting layer in the process of radiation deactivation of the excitons, and this light is emitted from the anode 20 toward the reflective liquid crystal display panel (in the direction of the arrow in the figure).
At this time, the light 200 emitted from the organic EL element 18 is emitted toward each display electrode 10, reflected by each display electrode 10 made of the reflective material, and emitted from the transparent EL element substrate 17 to the outside. The eye of the observer 23 is reached. In the case of FIG. 1, since the red (R) color filter 14 is provided, red is observed by the observer 23.
[0015]
As described above, the following effects can be obtained by forming the organic EL element in a region other than the display electrode formation region.
When the surrounding area is dark and external light cannot be taken in, the emitted light of the organic EL element arranged outside the display electrode formation region, that is, around each display electrode travels toward the display electrode and is reflected by the display electrode. Thus, a uniform and bright display can be obtained on the entire surface of the liquid crystal display panel.
[0016]
Even when the surrounding area is bright and external light is taken in, the light guide plate that attenuates the light entering the display panel is not used, so the external light can be used efficiently and a bright display can be obtained. Can do.
In addition, a uniform and bright display can be obtained on the entire surface of the liquid crystal display panel by the EL element provided on the entire surface of the liquid crystal display panel by effectively using the light blocking portion that blocks light.
[0017]
【The invention's effect】
According to the reflective liquid crystal display device of the present invention, a uniform and bright display can be obtained on the entire surface of the liquid crystal display panel without being affected by the brightness of the surroundings.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of one display pixel showing an embodiment of the present invention.
FIG. 2 is a plan view showing a region where an organic EL element of the present invention is formed.
FIG. 3 is a cross-sectional view of a conventional reflective liquid crystal display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 10 Display electrode 12 Counter electrode substrate 13 Counter electrode 14 Color filter 15 Light-shielding part 16 Liquid crystal 17 EL element substrate 18 Organic EL element

Claims (2)

A TFT substrate in which the display electrode made of reflective material including a thin film transistor for driving the liquid crystal are connected, the counter electrode, the light-shielding unit has a counter electrode substrate provided with a color filter, made by filling a liquid crystal between the substrates The EL element substrate that is in close contact with the surface of the counter electrode substrate that does not face the TFT substrate includes an electroluminescence element that emits light toward the TFT substrate in a region corresponding to the periphery of the display electrode. A reflective liquid crystal display device comprising: 2. The reflection type liquid crystal display device according to claim 1 , wherein the electroluminescence element is formed corresponding to the entire surface or a part of a light shielding portion provided on the counter electrode substrate .

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