JPS60107083A - Display unit - 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 (a) Technical Field of the Invention The present invention relates to a display device, and particularly to a display device that is devised to perform stable brightness modulation and improve display quality.

(Background of medium wave technology In an EL panel, etc., the number of display elements corresponding to the pixels is required to be sufficient to configure a predetermined screen, and the number of elements is quite large. Since it is necessary to drive them individually, the number of drive circuits required is equal to the number of elements or lines, and the number of drive circuits becomes extremely large.

Therefore, it is desirable that the drive circuit has a simple configuration.

In addition, such a drive circuit is required to be able to modulate the brightness of the display element, and also to have excellent stability of the brightness modulation, and also to be expected to improve display quality. has come to be required.

(c) Prior art and problems As a conventional drive circuit that produces brightness modulation, a one-transistor, one-capacitor configuration (Ql,
There is an active matrix a consisting of C3).

This drive circuit is configured to drive a display element, for example a liquid crystal element. In this drive circuit, a voltage corresponding to luminance information supplied to a data bus C charges a capacitor C3 through a transistor Q1 which is turned on by a scan pulse applied to a scan canvas d, thereby modulating the luminance of the element. It is.

When this drive circuit is applied to drive an AC drive type display element such as a thin film EL, the drive circuit has a two-transistor, one-capacitor configuration (Ql
, Q2. C3), which not only makes it difficult to perform brightness modulation, especially stable halftone modulation, but also lacks a means to improve display quality.

(=) Purpose of the Invention The present invention was devised in view of the drawbacks of conventional circuits such as dual circuits, and its purpose is to provide a display device that can realize stable brightness modulation while also improving display quality. Our goal is to provide the following.

G+) Structure of the Invention In order to achieve this object, the present invention provides a display device in which the drain electrode of a gate control diode of an active matrix circuit is connected to a display element on a semiconductor substrate ε.
In this structure, the gate electrode of the gate control diode is formed into a ring shape.

(F) Embodiments of the Invention The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 3 is a circuit diagram of an embodiment of the present invention, and FIG. 4 is a diagram illustrating the circuit of FIG. 3 contrived to be integrated into an integrated circuit.

In FIG. 3, 1 is an active matrix circuit for EL driving, and 2 is an EL cell (display element). One electrode of the EL nacelle is connected to the drive power supply terminal 3, and the other electrode is connected to the gate control diode (hereinafter referred to as GC).
It is abbreviated as D. ) 4, and the diode 40 substrate SUB is connected to a reference potential, for example ground potential.

The gate of the diode 4 is connected to one electrode of the storage capacitor 5, and is configured to be connected to the data bus 7 via an address transistor. The transistor 6 is, for example, a MOS transistor, and its gate electrode is connected to the scan layer 8. The other electrode of the capacitor 4 is connected to a reference potential, for example ground potential.

In FIG. 4, which shows an integrated circuit with this circuit configuration, the (
, 11) shows a plan view, and (4-2) shows its IV-IV
A vertical cross-sectional view taken along the line arrow is shown. In these figures, the drain electrode and gate electrode G of the atres transistor are connected to a data bus 7 and a scan bus 8, respectively, which are formed in a grid pattern. The source electrode of the l.randistaro is connected to the annular POly Si electrode 10. The outer part of this PolySi electrode 10 has a thickness of 1000 mm.
A storage capacitor 5 is formed by facing the P'' diffusion region across the thermal oxide film (a part of the S102 insulating film 16) 11, and forming the storage capacitor 5 described above. Even at the inner edge, the oxide film under the electrode is a thermal oxide film (S102 insulation film 16
The thermal oxide film 12 at the edge becomes the gate insulating film of the GCD 4 and the Po
1y A portion of the Si electrode 10 acts as a gate electrode of the GCD 4. The inner region (P-type silicon substrate 13) surrounded by the annular PolySi electrode 10 is made of PolyS
Phosphorus is diffused using the i electrode 10 as a mask to form an r region, which serves as the drain electrode of the GCD 4 and the display electrode of the EL nacelle. Note that the display electrode of the EL nacelle may be formed separately and the drain electrode of the GCD 4 may be connected to it.

After forming the drive circuit part by the Si process in this way, a light shield and an electric shield (not shown) are provided as necessary, and thin film forming techniques such as vapor deposition and sputtering are used with only the display electrodes exposed. The EL light emitting layer 14 of the EL nacelle is formed on the entire surface. This light-emitting layer 14 may be only an EL light-emitting layer, or may be made of Y203, Si3N
4. The light emitting layer may include an insulating layer such as Al102. Then, a transparent conductive film (common counter electrode) 15 is formed on the light emitting Jii 14 to complete the EL panel.

The operation of the apparatus of the present invention constructed in this manner will be described below.

The drive voltage VA shown in (5-1) in FIG. 5 is supplied to the power supply terminal 3, while the drive voltage VA shown in (5-1) in FIG.
-2) Scan pulse V with a frame frequency as shown in
Y is supplied to the data bus 7 (5-3) in FIG.
Voltage VX corresponding to luminance information including halftones as shown in
is supplied.

Therefore, when the scan pulse Vy is supplied at the timing shown in (F+-2) in FIG. 5, the address transistor turns on, and the voltage value VG1 at that time is held in the capacitor 5 for one frame. ((5-4 in Figure 5)
), that voltage is applied to the gate of the diode 4.

Diode 4 changes its reverse breakdown voltage according to the relationship shown in FIG. 6 depending on its gate voltage.

This characteristic of the diode 4 is such that the diode 4 has a structure in which the source diffusion region of a MOS transistor is omitted, as shown in FIG. This is obtained because the potential gradient of the PN junction depletion layer under the gate end becomes steeper as the gate voltage becomes lower due to the influence of the potential, causing voltage breakdown at a lower drain voltage.

As mentioned above, since the reverse breakdown voltage of the diode 4 changes, the drain voltage VD of the diode 4 becomes equal to (5) in FIG.
-5), they are clamped to different values. Therefore, the voltage Vc E L L applied across the EL cell 1
As shown in (5-6) in FIG. 5, the positive peak voltage value of =VA-VD changes between Va Vzl and Va Vzo depending on the values of the gate voltages V and G.

In this way, when VcELL changes, the thin film EL element 1 having steep threshold characteristics changes as VCELL changes to Va.
When it is at VzQ, it shines at the saturated brightness BO, and v
When cELL is at VaVz, it shines at the brightness B1 in the dark state (see FIG. 8).

That is, the EL nacelle brightness can be changed by the set values of Va and VD. Therefore, the brightness can be controlled by the gate voltage. This kind of control becomes possible because
If we give the intermediate value ■G2 as the gate voltage,
A middle tone brightness B2 can be obtained.

In the present invention, as shown in FIG.
By increasing the gate length of D4 and reducing its occupied area to expand the light emitting area, stable halftone drive control is possible through low impedance clamping operation, and multifunctional high display quality is achieved. can be realized as a display device.

In the above embodiment, an example was described in which the gate edge of the GCD 4 is formed into a single ring shape, but a plurality of light emitting regions may be formed.

In either of these cases, the light emitting region may be formed outside.

(g) Effects of the invention As described above, according to the present invention, ■Stable halftone drive control is possible, ■ Effects such as improved display quality can be obtained.

[Brief explanation of drawings]

1 and 2 are diagrams showing conventional display element drive circuits, FIG. 3 is a circuit diagram of the display device of the present invention, FIG. 4 is an integrated circuit diagram of the third circuit, and FIG. 5 is a circuit diagram of the present invention. Figure 6 is a diagram showing the characteristics of the gate control diode, Figure 7 is a diagram illustrating the operating principle of the gate control diode, and Figure 8 is a diagram explaining the operation of the EL nacelle. It is a diagram. In the figure, 1 is an active matrix circuit, 2 is an EL nacelle 4 is a gate control diode, 5 is a storage capacitor, 6 is an address transistor, 7 is a data bus, 8 is a scan canvas, 10 is a PolySi electrode, 13
1 is a P-type silicon substrate, 14 is a light emitting layer, and 15 is a transparent conductive film. Patent applicant Fujitsu Ltd. Figure 1 Figure 2 Figure 3 Figure 8 a-vxz Figure 5 Figure 6 Figure 7 LJB

Claims (3)

[Claims] (1) A display device characterized in that when a display device in which a drain electrode of a gate control diode of an active matrix circuit is connected to a display element is formed on a semiconductor substrate, the gate electrode of the gate control diode is formed in an annular shape. (2) Forming an information storage capacitor section on the outer periphery side of the annular gate electrode, forming a drain section of the gate control diode in a region in contact with the inner periphery, and connecting the pixel light emitting region of the display element to the annular gate electrode. 2. The display device according to claim 1, wherein the display device is formed inside the display device. (3) The display device according to claim 1 or 2, wherein the entire inside of the annular gate electrode is used as a drain region, and the drain region is used as a display electrode of the display element.