JPH04125683A - El display device - Google Patents

Abstract

PURPOSE:To obtain satisfactory responding speed and angle of visibility, to realize a thin structure and a high luminance by constituting an organic EL system as an EL light emitting layer. CONSTITUTION:The EL display device is equipped with a substrate 1 on which a switching element 2 is installed to be shaped like a matrix, EL element groups subjected to laminate patterning on the substrate 1, an outside circuit which drives the EL element groups through the switching element 2. Then, an EL light emitting part is an electrostatic charge injecting type constitution in which an electrostatic charge transporting layer 7 is laminated on an EL light emitting layer 8 using an organic fluorescent pigments being materials having the high luminance. Thus, an EL display device which has the high luminance, a high speed responsibility, and the wide angle of visibility can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thin display device, and particularly to an EL display device.

(Prior Art) As a thin display device, a so-called TPT LCD is known, in which a TN type liquid crystal is sandwiched between a thin film transistor array and a color filter. However, the TPT
LCDs have the following disadvantages in terms of response speed and viewing angle.

The response speed shows a nematic liquid crystal state at room temperature, and
The size of liquid crystal molecules is roughly determined by the conditions under which the temperature is maintained at temperatures above about 30°F. Furthermore, since molecular species that originally exhibit a liquid crystal state have large intermolecular interactions, there is a limit to how much the viscosity can be reduced. However, T.P.
The response speed of TLCD is considered to be approximately 30m5ec as the limit.

On the other hand, since a so-called mouse is used for computer terminal display, even faster response is required. Furthermore, when displaying a moving image in high definition on both sides, if the response speed is slow, the spatial resolution of the image will be impaired even if the pixel pitch is fine. Therefore, higher speeds are necessary both for information terminals and high-definition displays.

The viewing angle can be said to be a fundamental flaw in this type of device that uses birefringence. However, as the screen size increases, a non-negligible difference occurs in the viewing angle between the center and the periphery of the screen, resulting in differences in image contrast and color tone between the center and periphery of the screen. For a TN type liquid crystal, the viewing angle that is practically acceptable is approximately ±30° in the front, back, left and right directions. Therefore, at a clear viewing distance of 30 cm, a screen with a diagonal size of 14 inches or more will not fit within the viewing angle range. That is,
Enlarging the viewing angle is also necessary for larger screens.

(Problems to be Solved by the Invention) As described above, the conventional TFT LCD type thin display has problems such as a narrow viewing angle and a slow response speed. The following measures have been attempted to address these problems.

First, in order to widen the viewing angle, it is necessary to use a self-luminous type of display, and self-luminous display elements include ■plasma display elements, ■fluorescent display tubes, and ■EL (electroluminescence) displays. .

However, in the case of plasma display elements, the response speed is fast and color printing is possible, so the elements are miniaturized and a large number of elements are fabricated on the substrate using a thick film printing method, and thin display elements are already being produced. We are currently getting the look right. However, there are limits to the improvement of brightness, high definition, etc. from the viewpoints of materials and element structure, and a practically satisfactory product has not yet been obtained.

In addition, in the case of a fluorescent display tube, although it is sufficient in terms of brightness, there are still limits to thinning, color, and high definition due to the element structure.

The present invention was developed in response to the above circumstances, and not only exhibits good response speed and viewing angle, but also allows for a thinner structure, high brightness and color, and high definition. The object of the present invention is to provide an ELL display device that can display images.

[Structure of the Invention] (Means for Solving the Problems) An ELL display device according to the present invention includes a substrate (active matrix) on which switching elements are arranged in a matrix, and It is characterized in that it comprises a group of ELL children and an external circuit that selectively drives the group of ELL children via the switching element, and the EL element is formed by combining an organic EL system with an ELL light layer.

(Function) In the ELL display device according to the present invention, the corresponding ELL child groups are time-divisionally driven and controlled via the respective switching elements arranged in a matrix, and each EL element is selectively activated. A desired display is made by causing the light to emit light.

Since the ELL light layer is made of a high-brightness organic EL material, it exhibits high-brightness light emission, high-speed response, and a wide viewing angle even with a relatively low applied voltage. In other words, ELL has a thin, large screen with good contrast, etc.
It fully demonstrates the functions expected as a display device.

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

As described above, the ELL display device according to the present invention includes a substrate (active matrix) on which switching elements are arranged in a matrix, a group of EL elements deposited and patterned on the substrate, and the switching elements. via E
The configuration includes an external circuit that selectively drives the LL child group. Therefore, the active matrix, E
The LL child group, the counter electrode and the drive external circuit forming a part of the ELL child group are basically constructed as follows.

Active matrix configuration The switching elements that make up the active matrix are:
Either a TPT (thin film transistor) or a nonlinear two-terminal element can be used, but the ability to inject a current of about 10-5 A into the EL element is required. Further, since the EL element is a current-driven element, when using a transistor, the size can be reduced by using a material with high mobility. In this sense, for example, as shown in FIG.
Preferably, the material is made of polycrystalline silicon. Figure 1 (
In a), 1 is a glass substrate, 2 is a polycrystalline silicon TPT having a source region 2a and a drain region 2b,
3 is a gate electrode, 4 is an insulating layer such as 5io2, 5 is a signal electrode bus line connected to the source region 2a of the polycrystalline silicon TPT2, and 6 is the polycrystalline silicon TPT
A pixel electrode made of, for example, ITO is connected to the drain region 2b of No. 2, 7 is a charge transport layer, 8 is an EL light emitting layer, and 9 is a back electrode layer or counter electrode layer made of, for example, Ag or Mg. Note that FIG. 1(b) is different from the above-mentioned FIG. 1(a).
) is a plan view of the configuration example shown in FIG.

Furthermore, by making the active matrix three-dimensional and integrating it, the transistor size can be increased, so amorphous silicon, which is easier to form, is used. Similarly, it is also possible to form a TPT as the switching element 2.

In FIG. 2, the same parts as in FIG. 1(a) are indicated with the same symbols.

Although the above example shows a configuration in which the glass plate 1 is used as a support substrate, as shown in FIG. An active matrix formed of TPT regions can also be used.

Other configurations of the switching element 2 include, for example, CdT.
E, CdS, and InSb can also be used as long as it is possible to form a thin film uniformly over a large area.

On the other hand, in a nonlinear two-terminal element as the switching element 2 constituting the active matrix, the structure of the main part is shown, for example, in cross section in FIG. 4(a) and in perspective in FIG. 4(b). , Ta layer Ta2 05
/ Cr type old H structure may be adopted.

In FIGS. 4(a) and (b), 1 is a glass substrate;
10a is thermally oxidized Ta2 formed on one surface of the glass substrate.
05 layer, 10b is Ta layer, 10c is anodized Ta2
05 layer and 4 are insulating layers such as polyimide resin layers,
6 is the drain region 2b of the polycrystalline silicon TPT 2;
7 is a charge transport layer, 8 is an EL light emitting layer, and 9 is, for example, 8g.

This is a back electrode layer or a counter electrode layer made of Mg or the like.

In each of the above configuration examples, the pixel electrode 6 is made of a transparent material.
In addition to the ITO electrode, a non-transparent metal electrode may be used.

EL Element Configuration In the active matrix of the EL display device according to the present invention, a large number of EL display elements are time-divisionally driven. However, the EL light emitting part is usually 1 mm.
It is patterned according to the size of the angle of respiration. In other words, E.L.
The light emitting section has a charge injection type structure in which a charge transport layer 7 is laminated on an EL light emitting layer 8 using an organic fluorescent dye, which is a material with high brightness. Here, the relationship between the injection current and the luminance of the organic EL element 11 is approximately as shown in FIG. 5.

In addition, if the dimensions of the light emitting pixel (EL element) 11 are 0.3 x O, 3 mg+, then 1000 Cd/IT
In order to obtain a luminance of 7', it is necessary to inject a current of to-5A.

Further, the patterning can be performed, for example, by mask vapor deposition of an organic fluorescent dye, or by patterning a solid vapor-deposited film of an organic fluorescent dye by a lift-off method using a photoresist. Furthermore, it is possible to use a method of slam-printing an organic fluorescent dye solution dissolved in a suitable binder resin onto the substrate by offset printing, screen printing, or the like.

Counter electrode (back electrode) When the light emission of the EL light emitting layer 8 further arranged in a matrix on the active matrix formed on the glass substrate 1 is to be visually observed through the glass substrate 1, the counter electrode (
The back electrode) 9 may be a non-transparent electrode. In order to lower the reflectance, a carbon electrode with a thin gold (Au) layer interposed therein, or a film coated with carbon paste in which metal particles such as gold, platinum, or nickel are dispersed, is used. In addition, in order to increase the reflectance and increase the luminous efficiency,
A vapor deposited film or a sputtered film of gold, platinum, nickel, etc., or a film coated with a paste of these metals is used.

On the other hand, when the light from the EL light-emitting layer 8 is directly viewed without intervening the glass substrate 1, the light-transmitting counter electrode 9 is I
An electrode formed of a low-temperature thin film of TO1 gold, nickel, or platinum, or an electrode of a transparent organic conductive polymer such as polyisocyanapthene is used.

Driving External Circuit Configuration As a driving method, a line sequential driving similar to that of a TFT LCD television can be adopted. In this case, since the driving pulse width of the scanning line is narrow, it is preferable to use the afterimage on the retina in the same way as dot-sequential type CRT type televisions to give a feeling of continuous light emission. Point-sequential driving similar to the above is also possible. The light intensity is insufficient and the screen flickers (
If flicker is observed, the light emission intensity may be supplemented or a means for extending the light emission time may be used in combination.

That is, as shown in FIG. 6 in cross-section of the main structure, for example, a channel plate 12 for light enhancement is provided on one surface of the glass substrate of the EL panel shown in FIG. 1, and the EL light emission is enhanced. . Here, as shown in FIG. 7 in cross section of the main part configuration, the luminescent color of the fluorescent screen of the channel plate 12 is set to white, and the pixels of the channel plate 12 and the EL panel, in other words, the EL element 11 group are positioned. By combining and further superimposing the color filter 13, colorization is also possible.

Further, as another means for sustaining the light emission, for example, in the configuration shown in FIG. A configuration may be adopted in which light emission continues for a certain period of time.

In this case, the selection of the delayed luminescent material depends on the EL material constituting the EL luminescent layer 8, but the delayed luminescent wavelength does not necessarily have to match the EL luminescent wavelength when the selection pulse is applied.

The visual wavelength is determined by the mixing of delayed EL light emission on the retina. Therefore, the visual wavelength can be selected to a predetermined color by setting the wavelength of the delayed EL light emission.

Furthermore, another means for sustaining light emission is to superimpose a delayed light emission panel (photopulse stretcher) on the EL panel, as shown in FIG. In this case, when the photopulse stretcher 14 is irradiated with pulsed light emission from the EL panel, the delayed luminescent material forming the photopulse stretcher 14 is excited to a metastable state. The metastable state undergoes a luminescent transition to the ground state due to thermal excitation, and a delay occurs during the thermal excitation process, resulting in delayed luminescence. For this reason, the delayed light emitting panel 14, which is constructed by patterning two or more types of light emitter layers in a mosaic shape, is used for the pixels (EL elements) of the EL panel.
Colorization is also possible by aligning and superimposing with the first group).

Furthermore, in the case of line sequential driving method, TFT
Since an LCD can be used, the gate driver IC can be used as is. Furthermore, by using an organic EL material, the driving voltage is approximately IOV, and the signal fi source can be the same as the signal line driver used in TFT LCDs, or by adding a current booster.

The EL display device according to the present invention configured as described above includes:
Although it exhibits a wide viewing angle, in order to further improve this, the EL light emitting surface may be made into a diffusing surface or a directional transmission light condensing surface. For example, one surface of the glass substrate of the EL panel may be roughened to diffuse the EL light emission and expand the viewing angle.
Lenticular lens 15 on one side of the glass substrate of the EL panel
The viewing angle can be limited or expanded by providing it by etching or molding with resin and condensing light in a specific viewing direction or uniformly scattering the light.

[Effects of the Invention] As can be seen from the above description, the present invention provides an EL display device with high brightness, high resolution, fast response, and a wide viewing angle without requiring complicated configuration or manufacturing means. becomes possible. In other words, we are developing an EL display device that takes full advantage of its thinner and larger features and has the display functions required for practical use (high brightness, high resolution, high-speed response, etc.) and is also capable of color display. It can be realized.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view showing an example of the configuration of a main part of an EL display device according to the present invention, and FIG. 1(b) shows an example of a structure of main parts of the EL display device illustrated in FIG. 1(a). Plan view, Figure 2, Figure 3
FIG. 4 and FIG. 4(a) are cross-sectional views showing other different configuration examples of essential parts of the EL display device according to the present invention, and FIG.
FIG. 5 is a perspective view showing the configuration of main parts of the EL display device shown in FIG. 5A, and FIG. The curve diagrams, FIGS. 6, 7, 8, and 9 are cross-sectional views showing still other different configuration examples of essential parts of the EL display device according to the present invention. 1...Glass U plate 1'...St wafer 2...Polycrystalline SI TFT 2a...Source region 2b...Drain region 3... ... Gate electrode 4 ... Insulating layer (SiO2, SiN, polyimide, etc.) 5 ... Signal electrode bus bar 6 ... Pixel electrode (ITO, AgMg, etc.) 7.
... Charge transport layer 8 ... EL light emitting layer 9 ... Back (counter) electrode layer 10a ... Thermally oxidized Ta205 layer 10b ... Ta layer 10c ... Anode Oxidized Ta205 layer]...EL element 12...Channel plate 13...Color filter 14...Photopulse stretcher 15...
...Lenticular lens applicant Toshiba Corporation

Claims (1)

[Claims] A substrate (active matrix) on which switching elements are arranged in a matrix, a group of EL elements deposited and patterned on the substrate, and a group of EL elements selectively selected through the switching element. and an external circuit for driving the EL display device, wherein the EL element comprises an organic EL system as an EL light emitting layer.