JPS62176096A - El display panel - 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 1. Industrial Application Field The present invention relates to riL (
The present invention relates to an EL display panel (electroluminescence), and particularly to an EL display panel having an electrode structure for 7-trix display.

[Conventional technology]

Since the discovery of so-called electroluminescence in 1936, in which light is emitted by applying a voltage to a phosphor material, much research and development has been conducted with the aim of applying it to single-sided light sources and display devices. At present, AC-driven thin-film EL elements, in which a thin-film light-emitting layer consisting of a phosphor layer and an insulating layer is sandwiched between two electrodes, at least one of which is transparent, have excellent brightness characteristics and stability, and are in practical use as various displays. has been done.

Figure 6 shows Varnish-I-D7 as a typical EL element.
4. Digest of Technical Papers (S
ID 74 digest or tcct+n1ca
This figure shows a cross-sectional view of a double-insulated thin-film EL device published on page 84 of 1999. In FIG. 6, the structure includes a transparent electrode 10, a first insulator layer 7, a phosphor layer 8, a second insulator layer 9, and a back electrode 11, which are laminated on a substrate 1 made of glass. Drive circuit drives electrodes 10.11
Bright light emission can be obtained by applying an alternating current voltage between the two and inducing a high electric field of 10' V/cm or more in the phosphor layer 8 such as ZnS:Mn. This is because electrons in the light-emitting layer are accelerated at high speed by a high electric field, and the light-emitting centers of Mn and the like are excited by collision.

When 2nS:Mn is used as the phosphor layer 8, the color is yellow-orange, but various colors can be obtained by selecting the luminescent center substance and phosphor material. Further, the insulator layer 7.9 prevents an excessive DC current from flowing through the element, thereby providing stability that prevents the element from being destroyed. Furthermore, the insulator layer 7.9 has the effect of polarization and prevention of diffusion of harmful ions,
This contributes to improving device characteristics and reliability.

This thin-film EL element has high brightness, excellent light-emission response, and has a highly nonlinear light-emitting characteristic with respect to applied voltage. A SOCS-type large display capacity surface emitting display device has been realized.

The structure of such an EL panel for dot matrix display is such that a striped transparent electrode and a back electrode are arranged orthogonally to each other with a light emitting layer sandwiched between them.9 That is, in FIG. 10 is a striped pattern in which the back electrode 11 extends in the direction perpendicular to the plane of the paper, and a light emitting pixel is defined at each intersection. Each electrode 1
0.11 is connected to the data side drive circuit and the scanning side drive circuit to form an EL display device. Back electrode 1 serving as a scanning electrode
256 1s, 64 transparent electrodes 10 that serve as data electrodes
A matrix display EL panel has been manufactured and has already been commercialized as a display device.

[Problem that the invention seeks to solve]

With the development of information equipment, it is desired that the display capacity of flat display devices be further increased. Conventionally, in the case of EL display panels, the light emission phenomenon itself has a sufficiently high-speed response, but
Since it is a large capacitive element, there is a problem in that voltage cannot be applied to the pixel at high speed. In order to prevent the flickering of the luminescent display, it is necessary to display at a rate of about 60 frames per second. Therefore, in order to perform N scans at a frame frequency of 60 Hz, it is necessary to perform line sequential driving by applying voltage to pixels on one scan electrode in an access time of 1/60×N seconds or less.

On the other hand, EL elements have a capacity of about 50 to 100 PF/city, and are used as transparent electrodes.
The sheet resistance of O is quite large, about 100. Therefore, a problem arises in the CR time constant depending on the electrode dimensions. For example, 0.2 am X O, 2+am pixel is 1000X
Assuming an EL panel with 1000 pixels, about 40 microseconds are required from the time constant of CR for voltage to be applied to the farthest pixel from the drive circuit. However, the above-mentioned access time is only 16.7 microseconds for 1000 scans. Therefore, even if a pixel close to the drive circuit displays a light emitting display, a pixel far away may not emit light, or
Or a display H that exhibits significant unevenness in luminance and is used for practical purposes.
It cannot be set to H. This has been the main reason for preventing the increase in display capacity of thin film ELk display panels.

An object of the present invention is to provide an EL display panel that solves the above problems by improving the electrode structure of the EL display panel.

[Means for solving problems]

The EL display panel of the present invention is a thin film EL display panel that performs a 7-trix display, in which a floating electrode made of a transparent conductive film and corresponding to each pixel is formed on one surface of a light emitting layer.
A first electrode and a second electrode for performing matrix driving on the other surface of the light-emitting layer are insulated from each other, but are arranged in a striped pattern in intersecting directions.

1 Effect 1 In order to extract light from the light emitting layer to the outside, at least one of the electrodes sandwiching the light emitting layer needs to be transparent. In the conventional matrix display EL panel shown in FIG. 6, the transparent electrodes serve both as display electrodes that define light-emitting pixels and as wiring electrodes that supply power to each pixel in series. In the EL display panel of the present invention, two dark blue wiring electrodes that are perpendicular to each other are connected to the 1st part of the light emitting layer. ! A transparent electrode is formed on the other side of the light emitting layer as a floating electrode having only the function of a display electrode. Next, the basic aspects of the El-display panel of the present invention will be explained using FIG.

In FIG. 1, floating electrodes 5 made of approximately square transparent conductors are arranged in a matrix on a glass substrate 1, and a light emitting layer 2 made of a phosphor layer and an insulator layer is provided.
is formed. A striped first electrode 3 is formed on this so as to overlap a part of the floating electrode 5. In the figure, the first electrode 3 extends in a direction perpendicular to the plane of the paper. An insulating layer 6 is formed to cover the first electrode 3. The striped second electrode
It is formed in an arrangement perpendicular to the electrode. A portion of the second electrode is in contact with the direct light emission R2 and faces a portion of the floating electrode.

FIG. 2 shows the planar arrangement relationship of the first electrode, the second electrode, and the floating electrode. In Figure 2, the floating electrodes are arranged in matrices vertically and horizontally.
Each first electrode 3 arranged in a sock shape and arranged in the vertical direction
overlaps with a portion of each of the floating electrodes 5 located at the corresponding JiIJ of the matrix of floating electrodes 5. Further, each of the second electrodes 11 arranged laterally overlaps with the floating electrodes 5 located in the corresponding row of the matrix of floating electrodes 5, and a portion of these floating electrodes 5 emit light as shown in FIG. They overlap only through layer 2. The first electrode 3 and the second electrode
The electrode 4 is made of a metal with low resistance, such as metal, and is connected to a drive circuit on the data side or the scanning side, respectively. In an EL display panel having such a basic structure, the first electrode 3
The voltage applied between the first electrode 3 and the second electrode 4 is dividedly applied to the light emitting layer between the first electrode 3 and the floating electrode 5 and between the floating electrode 5 and the second electrode 4.

Therefore, this floating electrode 5 and the first. EL light emission can be obtained from the portion sandwiched between the second electrodes 3.4. In the EL display panel of the present invention having such a basic structure, the transparent electrode, that is, the floating electrode 5 only needs to correspond to one pixel, and there is no problem even if it has a high resistance. The first and second electrodes 3.4, which serve as wiring electrodes, are low-resistance metal electrodes, and can solve the problem caused by the time constant of CR, which has been a problem in conventionally structured EL display panels.

r Example] Next, the present invention will be explained in more detail.

As a first embodiment of the present invention, El of the structure shown in FIG.
-The display panel will be explained in detail.

After sputtering ITO to a thickness of 0.05 microns on the substrate glass 1, it was etched to form a film of 0.3 mm x L3 mm.
The floating electrode 5 was formed by patterning the square shape into a square shape with a pitch of 0.4 mm. The thickness of the TTO, which is the floating electrode 5, is about a fraction of that normally used for EL display panels1, and the sheet resistance is also about 80Ω, which is not very low resistance. On top of this is Ta5i as a first insulator layer.
7. After forming an O amorphous di-amorphous thin film by sputtering, as a phosphor layer. nS: Mn was deposited to a thickness of 0.3 microns and heat treated at 500° C. for 1 hour in vacuum. Then Y21)9 as the second insulator layer
was deposited by sputtering.

After forming the light-emitting layer 2 consisting of the phosphor layer and the insulator layer in this way, a striped first electrode 3 having a width of about 0.degree. As shown in FIGS. 1 and 2, this first electrode 3 was arranged so as to overlap the floating electrode. Next, an insulating layer 6 of polyimide 1 to 6 was formed to cover the first electrode 3. Furthermore, to! The second electrode 4 of the membrane was set to 0.
The stripes were formed in a striped manner perpendicular to the first electrode 3 at a pitch of 4 mm and 0.32 mm. The area of this second electrode 4 sandwiching the direct light emitting layer 2 and facing the floating electrode 5 is 0.13×0.3 Iam2 for one pixel, and
The area corresponding to the floating electrode 5 is also 0.13X0.3 +u
+2. Therefore, one pixel is formed from two rectangular light emitting parts, but there is no problem in visibility because the slit between them is narrow.

The first electrode 3 is connected to the data-side drive circuit, and the second electrode 4 is connected to the scan-side drive circuit, and as a result of light-emitting display, all pixels on the panel surface are connected even when driven at high speed because the wiring resistance is sufficiently low. A voltage was applied to the display, and a uniform luminescent display was achieved.

FIG. 3 is a sectional view of a second embodiment of the invention.

This second embodiment has a structure in which a pixel electrode for the second electrode is provided separately, and the pixel electrode can be formed simultaneously with the first electrode. In FIG. 3, the process up to the formation of the light emitting layer 2 is the same as the first embodiment shown in FIG. 1, but after forming the light emitting layer 2, a striped first electrode 3 and a fine rectangular A two-electrode pixel electrode 12 is simultaneously formed by patterning the e-evaporated film.

Thereafter, an insulating layer 6 with contact holes is formed on the second electrode pixel electrode 12 using polyimide. Next, a striped second electrode 8i! is arranged perpendicular to the first electrode 3! 4 is formed so as to be electrically connected to the pixel electrode 12 through the contact hole.

In this embodiment, the width of the slit-shaped non-light-emitting portion within one pixel can be easily reduced. Furthermore, the overlapping area of the floating electrode 5 and the first and second electrodes 3.4 can be determined more easily and with higher precision than in the first embodiment shown in FIG. EL of the present invention
Since the display panel essentially uses capacitance division of the applied voltage between the floating electrode 5 and the first and second electrodes 3.4,
If the overlapping area between the floating electric current ff15 and the first and second electrodes 3.4 is different, the voltage applied to each part will also be different, resulting in unnecessary light emission or a difference in brightness within one pixel. Floating electricity 8i! 5 and the second electrode 4 was influenced by the patterning of the thick insulating layer 6 in the first embodiment;
In the second embodiment, it is determined only by etching the metal film, etc.
High accuracy can be obtained. .

FIG. 4 is a sectional view of a third embodiment of the invention.

In the first and second embodiments described above, the same light emitting layer is sandwiched between the floating electrode 5 and the first and second electrodes 3.4, but this does not necessarily have to be the case. In the third embodiment of the present invention shown in FIG. 4, the phosphor layer 8 is also formed in the form of stripes or a matrix of rectangles, and a first insulator layer is formed between the floating electrode 5 and the second electrode 4, for example. 7. The phosphor layer 8 and the second insulator layer 9 are sandwiched, but the floating electrode 5 and the first electrode 3
A structure can be provided in which only the insulator layer 7.9 is sandwiched between them.

In the first and second embodiments described above, since the voltage applied between the first and second electrodes 3.4 is divided into two, the external drive voltage is lower than that of the conventional EL display panel structure. However, in this embodiment, by using a high dielectric constant material such as BaTiO3 for the insulator layers 7 and 9, the space between the floating electrode 5 and the first insulator layer 7 is increased. Capacitance can be increased. Therefore, the external drive voltage is effectively applied between the second insulator layer 4 and the floating electrode 5, and an increase in the drive voltage can be reduced.

FIG. 5 is a sectional view of a fourth embodiment of the invention.

In all of the above-mentioned first to third embodiments, the first and second electrodes 3.4 were formed after forming the light emitting layer 2, but as in the fourth embodiment of the present invention shown in FIG. A reverse structure is also possible. After forming the second electrode 4 on the glass substrate 1 , an insulating layer 6 is formed in a striped pattern perpendicular to the second electrode 4 , and the first electrode 3 is formed on the insulating layer 6 . after that,
A light emitting layer 2 is formed, and a floating electric current [!] made of ITO is formed. 5
are formed into a matrix. In the case of this fourth embodiment, when a resin such as polyimide is used for the insulating layer 6, heat treatment at a very high temperature cannot be performed. Therefore, it is preferable to use 5i02 or the like as the insulating layer.

r Effects of the Invention] Since the EL display panel of the present invention is wired using a low-resistance metal film, it has the following advantages: 1. Compared to conventional EL display panels that also use transparent electrodes such as TO for wiring functions, C
This has the effect of greatly reducing problems caused by the time constant of R. That is, even when the EL display panel has a large area and a large display capacity, uniform display luminance can be obtained over the entire surface of the EL display panel.

Further, in conventional EL display panels, a considerable amount of Joule heat is generated in transparent electrodes, but this can also be significantly reduced.

As described above, the present invention has great industrial value.

ff1Y Simple Explanation of the Drawings FIGS. 1 and 2 are a sectional view and a plan view of the first embodiment of the EL display panel of the present invention, respectively, and FIGS. Sectional view of the fourth embodiment, No. 6
The figure is a sectional view of a conventional El-display panel.

DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Light emitting layer, 3... First electrode, 4... Second electrode, 5... Floating electrode, 6... Insulating layer, 7... First Insulator layer, 8... Phosphor layer, 9.
...Second insulator layer, 10...Transparent electrode, 11...Back electrode, 12...Pixel electrode for second electrode.

narrow 2 concave

Claims (1)

[Claims] In a thin film EL display panel that performs matrix display, a floating electrode made of a transparent conductive film and corresponding to each pixel is formed on one surface of a light emitting layer, and a first electrode for matrix driving is formed on the other surface of the light emitting layer. An EL display panel characterized in that an electrode and a second electrode are insulated from each other but are arranged in a striped pattern in intersecting directions.