JPH02226691A - El display panel and drive method therefor - Google Patents

Abstract

PURPOSE:To reduce the quantity of high voltage resistance ICs and reduce cost by applying the laminated construction of an electroluminescence layer and a photoconducting layer, alternately applying voltage to electrodes classified into a plurality of groups and displaying information via the shift of a luminous point within a display panel. CONSTITUTION:An Al rear electrode 7 is classified into groups (a), (b) and (c). The same group of electrodes is bundled and connected to drive power supplies A, B and C. Also, the rightmost picture element (i) is connected to a power supply I for writing data. In the aforesaid constitution, voltage is alternately applied to the electrode 7 and when one picture element becomes luminous, the photoconducting layer thereof drops in resistance and a picture element adjacent thereto turns to be luminous as well. As a result of the continuous occurrence of the aforesaid operation, a luminous point moves. According to the aforesaid construction, it is possible to display an arbitrary pattern by adding data to the picture element (i). Consequently, the quantity of high voltage resistance ICs can be reduced, thereby ensuring cost reduction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an EL display/mother panel with a simple driving method and low cost.

[Conventional technology]

In recent years, thin film EL elements have been used as display devices such as flat displays because they have advantages such as high brightness and long life. In particular, ZnS:Mn yellow-orange EL panels have high brightness and excellent visibility, so they are becoming popular in many fields.

However, since the driving voltage is as high as about 200 V, expensive high-voltage ICs are required for the number of electrodes, which increases the cost of the thin film EL/# panel. For this reason, their widespread adoption has been delayed compared to low-voltage, low-power consumption, and low-cost liquid crystal displays.

In order to simplify the driving circuit and driving method, research is being conducted on adding memory functions to EL panels. EL a
There are two ways to provide the 4-channel busy memory function. The first conventional method is to increase the Mn concentration in the ZnS:Mn light-emitting layer, and the second conventional method is to stack it with a photoconductive layer of C'ase, amorphous Sl, amorphous SiC, or the like. In addition to the thin film EL, there is also a dispersed EL in which a phosphor is dispersed in an organic binder by a conventional third method.

Note that EL here refers to electroluminescence.

[Problem to be solved by the invention]

However, although the first and second conventional methods simplify the driving method, they still require the same number of high-voltage ICs, so there is a problem in that the price cannot be reduced significantly.

Furthermore, the conventional third method of dispersion type EL elements has low brightness;
Since the luminance-voltage characteristic does not have a sharp switching characteristic, it is used only as a backlight for liquid crystals and 49XY matrix display is not performed.The purpose of the present invention is to replace the conventional simple XY matrix drive. As will be described in detail later, the EL panel has a structure in which an EL layer and a photoconductive layer are laminated, and instead of providing a drive circuit for each electrode, the electrodes are arranged alternately in three groups, and the electrodes in the same group are bundled. Voltage is alternately applied to each of them, and the light emitting point is moved within the panel like a signal charge transfer solid state image sensor (CCD).By stopping, the desired information is displayed on the pEL panel, and the driving Significantly reduces the number of high-voltage ICs,
The objective is to simplify the driving method and significantly reduce costs.

[Means to solve the problem]

In order to solve the above problems, an EL display panel is an EL display panel in which an EL layer and a photoconductive layer are laminated, and a transparent electrode is provided between the EL layer and the photoconductive layer, and this electrode is connected to an adjacent pixel. Furthermore, the back electrode is composed of a plurality of electrode groups divided alternately, and a voltage is applied alternately to these electrodes, and as a predetermined one pixel emits light, the resistance of the photoconductive layer decreases and the corresponding The E
This led to the formation of an L display panel.

[Effect]

Since the EL display i+ channel is formed as described above, the number of high-voltage ICs for driving can be significantly reduced, the driving method can be simplified, and costs can be significantly reduced.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

The origin of the present invention was the idea of an Si signal charge transfer type solid-state image sensor. A signal charge transfer type solid-state image sensor has a large number of XY electrodes, but since the Y electrodes are divided into three groups and connected together, only three driving circuits are required. By alternately applying voltages to these electrodes, space charges generated within the image sensor can be caused to run within the plane of the element. Therefore, the number of driving ICs is small, and driving is simple.

The basic operation of the E L channel of the present invention is the same as that of the St signal charge transfer type solid-state imaging device described above.

That is, in an EL display/main panel in which an EL layer and a photoconductive layer are laminated, a transparent electrode is provided between the EL layer and the photoconductive layer, and this electrode is connected to an adjacent pixel. Furthermore, the back electrode consists of three groups of electrodes separated alternately, and when a voltage is applied alternately to these electrodes and one pixel emits light, the resistance of the photoconductive layer decreases and the adjacent pixels also become emissive. becomes. As this operation occurs continuously, the light emitting point moves.

Preferred embodiments will be described in detail in Examples 1.2.3 below.

Example 1 First, the basic principle of the present invention will be explained. The cross-sectional structure of the simplest thin film EL/gunnel of the present invention is shown in FIG. 1 is a glass substrate, 2 is a transparent electrode, 3 is a CdSe photoconductive layer, 4 is a transparent electrode, 5 is a 5102 insulating layer, 6 is a thin film EL layer, 7 is an AJ back electrode, and the AL back electrodes are a, b, The electrodes in the same group are bundled and driven by power sources A, B, and C.
(8). This EL i! The leftmost pixel of the channel is a data write pixel 1, which is connected to a data write power supply I. Figure 2 shows drive power supply A.
, B, C, and a time chart of the applied voltages of the writing power supply I. FIG. 3 shows the relationship between the voltage applied to the EL layer and the brightness. When a voltage is applied through the adjacent photoconductive layer in a low resistance state, a voltage of V is applied to the EL layer, and the brightness becomes B.

When a voltage is applied through the photoconductive layer which is in its own low resistance state, a voltage ('5io) with the voltage applied to the 8102 layer (vsio) removed is applied, and the brightness becomes B'. When a voltage is applied through the photoconductive layer in its own high resistance state, the voltage becomes v-vsio-vcdse and no light is emitted. Figure 4 shows the shift of the light emitting point from t1 to t4. The voltage and brightness applied to the pixels in FIG. 4 are shown below the pixels.

Transparent electrode 2 is always grounded. When a voltage is applied at tl, pixel i emits light and the resistance of the underlying CdSe layer decreases. At tl, a voltage is applied to the At electrode of pixel (2), and the transparent electrode 4 of pixel (2) is grounded through the CdSe layer of pixel i, so voltage V is applied to the EL layer of pixel (2) and it emits light with a brightness of B.

In the light emitting pixels of group b other than pixel ■, the CdSe layer has high resistance and the insulating layer 5io2 is laminated, so the EL layer has ■
is applied, and no light is emitted. At t2, no voltage is applied to pixel l, so pixel t does not emit light. Further, a voltage V' is applied to the pixel (2) through the 5i02 layer, so that it emits light with a brightness of B'. At t, the pixel (2) continues to emit light, and a voltage V is applied to the EL layer of the pixel (2) through the CdSe of the pixel (2), causing the pixel (2) to emit light at a brightness of B. By repeating the above operations, the light emitting point appears to shift from left to right.

Above we have explained one-dimensional examples, but these can be expressed as
By arranging them, a two-dimensional planar disk gray can be realized. That is, by giving data to the left writing pixel, an arbitrary mother turn can be shifted from left to right, and by fixing the applied voltage, it is also possible to stop the mother turn. In this case, since X rows of leftmost pixels are written, a high voltage IC is required to drive X digits.

However, in order to drive the Y column, three power supplies are required regardless of the number of Y, so the number of high voltage ICs can be reduced to less than half compared to the conventional technology.

Further, in this embodiment, an example in which the photoconductive layer is the underlayer and the EL light-emitting layer is the upper layer has been described, but this embodiment is also effective even when the photoconductive layer is not transparent. For example, when amorphous Sl is used as the underlayer, light does not pass through the amorphous Si layer, so light cannot be extracted from the glass direction. In such a case, amorphous St may be patterned to create a window for taking out light as shown in FIG. 5, or amorphous St may be used as the upper layer as shown in FIG. 6.

Further, although CdSe and amorphous Si were used as the photoconductive layer in this embodiment, the same effect can be obtained using SiC.

In addition, in this embodiment, a thin film type BILL was explained, but
There is no problem even if this is a distributed EL.

Example 2 In Example 1, a flat display was realized by vertically arranging primary elements with writing pixels provided at the left end.

Here, a panel will be described that can display a flat image by providing only one writing pixel at the upper left corner.

FIG. 7 is a schematic diagram of a flat display according to a second embodiment of the present invention. The upper left pixel is a data writing pixel. The cross-sectional structure is the same as in Example 1. FIG. 8 shows how data is written to this panel.

At T1, the writing pixels are made to emit light using the power supply ■ to input data, and then by periodically applying voltages from the power supplies A, B, and C, the light emitting point is shifted as in Example 1, and the entire leftmost X row is Write data to. At T2, one cycle of voltage is applied to the Y column drive power supplies A/, B/, and CI, and the data applied to the X row is shifted to the right. At T3, new data is written to the entire leftmost X row. At T4, these data are shifted to the right.

By repeating the above operations, data can be written from one writing pixel to the entire A channel.

This requires one drive circuit for the write pixel and one for the X and Y pixels.
Only six ICs are required to drive the electrodes, and one high-voltage IC is usually sufficient.

Embodiment 3 In Embodiment 1.2, the human eye can see that the written information shifts from left to right, just like a message card. In contrast, a method will be described in which such intermediate progress cannot be recognized by the human eye and only the final information can be recognized.

In order to prevent the human eye from perceiving the shift of the light emitting point, it is sufficient to increase the speed of the shift, and for this purpose, the pulse width of the applied voltage may be shortened. However, if the arm pulse width is made shorter than the decay time of light emission, all pixels will emit light even after one cycle of shifting is completed, as pixels that should normally stop emitting light will still be in the light emitting state. It turns out. Therefore, the applied voltage and cell width can only be shortened to the same extent as the decay time.

Table 1 shows the decay time of each luminescent layer material and the time required to shift 1000 pixels.
．． Since a time of 0.0.5 seconds is required, the state of the shift can be recognized with the human eye. On the other hand, CaS: m
u, SrS: Since the Ce system can be operated in 0.01 sec, the shift cannot be recognized by the human eye.

By using an alkaline earth luminescent material in this manner, it is possible to display the shift of the luminescent point without making it perceptible.

〔Effect of the invention〕

By laminating the EL layer and the photoconductive layer and configuring it as claimed in claim 1, the number of high voltage ICs for driving can be significantly reduced, the driving method becomes simple, and the cost can be significantly reduced. There is an effect that there is.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional configuration diagram of a thin film gL panel according to Example 1 of the present invention, Fig. 2 is a time chart of applied voltages of drive power supplies A, B, and C and write power supply I, and Fig. 3 is a main A graph showing the relationship between the voltage applied to the EL layer and the brightness of the device according to the embodiment of the invention. FIG. 4 is an explanatory diagram of the shift of the light emitting point from t1 to t4 of the flat display of the embodiment 1. FIG. As the photoconductive layer of the flat display of Example 1, a-S
Fig. 6 is a schematic diagram of a planar display according to Example 1 of the present invention, in which a-Si is used as the photoconductive layer, an EL layer is used as the base layer, and a window is provided as the top layer. A schematic diagram of a structure provided with a photoconductive layer, FIG. 7 is a schematic diagram of a flat display according to a second embodiment of the present invention, in which one writing pixel is provided at the upper left corner, and FIG. 8 is an embodiment of the present invention. 2 flat display T1~
FIG. 3 is an explanatory diagram showing how light shifts at T4. 1...Glass substrate, 2...Transparent electrode, 3...Cd
Se photoconductive layer, 4... Transparent electrode, 5... 5i02 insulating layer, 6... Thin film EL layer, 7... At back electrode, a
, b, c...Divided groups of At back electrodes 7, 8...
Drive power supplies, A, B, C... Drive power supplies in which the same group of power supplies are bundled and connected, l... Data writing pixels, ■.
...Power supply for data writing.

Claims (1)

[Scope of Claims] 1. Formed by transparent electrodes sequentially laminated on a glass substrate, a photoconductive layer, and transparent electrodes arranged in a matrix and provided through a thin film EL layer, a back electrode, and an insulating layer. EL display panel 2 comprising a plurality of groups of pixels, driving means for sequentially driving the pixel groups, and data writing pixels for inputting data.An EL display panel in which an EL layer and a photoconductive layer are laminated. A transparent electrode is provided between the EL layer and the photoconductive layer, and this electrode is connected to an adjacent pixel, and the back electrode is composed of multiple groups of electrodes separated alternately, and a voltage is applied alternately to these electrodes. is applied, and as a predetermined pixel emits light, the resistance of the photoconductive layer decreases, causing pixels adjacent to the predetermined pixel to emit light, and the light emitting operation is caused to occur through continuous propagation. How to drive an EL display panel