EP-4258252-B1 - LIGHT EMITTING DISPLAY DEVICE

EP4258252B1EP 4258252 B1EP4258252 B1EP 4258252B1EP-4258252-B1

Inventors

KIM, KEUN WOO

Dates

Publication Date: 20260506
Application Date: 20230405

Claims (5)

A light emitting display device comprising: a first pixel (PXa) configured to display a first color, wherein the first pixel (PXa) comprises a first light emitting diode (LEDa) and a first pixel circuit portion connected to the first light emitting diode (LEDa); a second pixel (PXb) configured to display a second color, wherein the second pixel (PXb) comprises a second light emitting diode (LEDb) and a second pixel circuit portion connected to the second light emitting diode (LEDb); and a third pixel (PXc) configured to display a third color, wherein the third pixel (PXc) comprises a third light emitting diode (LEDc) and a third pixel circuit portion connected to the third light emitting diode (LEDc); a capacitance (CELa) of the first light emitting diode (LEDa) being greater than a capacitance (CELb) of the second light emitting diode (LEDb), and the capacitance (CELb) of the second light emitting diode (LEDb) being greater than a capacitance (CELc) of the third light emitting diode (LEDc); wherein the first pixel circuit portion comprises an initialization transistor (T7) which is connected to a first electrode of the first light emitting diode (LEDa) and which is configured to transmit an initialization voltage to the first electrode of the first light emitting diode (LEDa), and the initialization transistor (T7) of the first pixel circuit portion comprises a first gate electrode (FG) and a second gate electrode (SG), the first gate electrode (FG) and the second gate electrode (FG) being electrically connected to each other and being disposed above and below a semiconductor layer of the initialization transistor (T7) of the first pixel circuit portion, respectively, wherein the second pixel circuit portion comprises an initialization transistor (T7) which is connected to a first electrode of the second light emitting diode (LEDb) and which is configured to transmit the initialization voltage to the first electrode of the second light emitting diode, and the initialization transistor (T7) of the second pixel circuit portion comprises a first gate electrode (FG) and a second gate electrode (SG), the first gate electrode (FG) and the second gate electrode (FG) being disposed above and below a semiconductor layer of the initialization transistor (T7) of the second pixel circuit portion, respectively, wherein the third pixel circuit portion comprises an initialization transistor (T7) which is connected to a first electrode of the third light emitting diode (LEDc) and which is configured to transmit the initialization voltage to the first electrode of the third light emitting diode, and the initialization transistor (T7) of the third pixel circuit portion comprises a first gate electrode (FG) and a second gate electrode (SG), the first gate electrode (FG) and the second gate electrode (FG) being disposed above and below a semiconductor layer of the initialization transistor (T7) of the third pixel circuit portion, respectively, wherein the initialization transistor (T7) of each of the first to the third pixel circuit portions comprises a first insulation layer (FIL) disposed between the semiconductor layer and the first gate electrode (FG), and a second insulation layer (SIL) disposed between the semiconductor layer and the second gate electrode (SG), wherein the second insulation layer (SIL) is thicker than the first insulation layer (FIL); wherein the light emitting display device is configured to supply the initialization voltage to the first electrode of the first light emitting diode (LEDa) by providing a gate-on voltage to both the first and the second gate electrodes of the initialization transistor of the first pixel circuit portion, to supply the initialization voltage to the first electrode of the second light emitting diode (LEDb) by providing a gate-on voltage only to the first gate electrode, of the first and the second gate electrodes, of the initialization transistor of the second pixel circuit portion, and to supply the initialization voltage to the first electrode of the third light emitting diode (LEDc) by providing a gate-on voltage only to the second gate electrode, of the first and the second gate electrodes, of the initialization transistor of the third pixel circuit portion.
The light emitting display device of claim 1, wherein the first pixel circuit portion further comprises a light emission control transistor configured to transmit a driving current to the first light emitting diode, and the initialization transistor and the light emission control transistor of the first pixel circuit portion are configured to receive a same gate signal as each other.
The light emitting display device of claim 2, wherein the initialization transistor of the first pixel circuit portion is an N-type transistor, and the light emission control transistor is a P-type transistor.
The light emitting display device of claim 1, wherein the first pixel circuit portion further comprises a driving transistor configured to adjust an intensity of a driving current output to the first light emitting diode and a bias transistor configured to apply a bias voltage to the driving transistor, and the initialization transistor and the bias transistor of the first pixel circuit portion are configured to receive a same gate signal as each other.
The light emitting display device of claim 4, wherein the initialization transistor and the bias transistor of the first pixel circuit portion are P-type transistors.

Description

BACKGROUND (a) Field This disclosure relates to a display device, and more particularly, the disclosure relates to a light emitting display device including light emitting diodes. (b) Description of the Related Art A light emitting display device may include light emitting diodes corresponding to pixels, and may display an image by controlling the brightness of each light emitting diode. Unlike a light-receiving display device such as a liquid crystal display (LCD), the light emitting display device does not include a separate light source such as a backlight, and thus thickness and weight thereof may be reduced. In addition, the light emitting display device has other desirable characteristics such as high luminance, high contrast ratio, high color reproduction, and high reaction speed, and therefore it can display high quality images. Due to such desirable characteristics, the light emitting display device is being applied to various electronic devices such as mobile devices, monitors, and televisions, such as smartphones, tablets, and laptop computers, and has been spotlighted as a display device for automobiles. WO 2022/061892 A1 discloses a pixel structure comprising a pixel circuit and a plurality of light emitting devices. EP 3 316 303 A1 discloses a display device comprising a first LED coupled with an input node, and a pixel driver circuitry. US 2021/193049 A1 discloses a display pixel that includes an organic light-emitting diode, one or more emission transistors, a drive transistor, a gate setting transistor, a data loading transistor, and an initialization transistor. US 2021/350740 A1 discloses display device that includes a light emitting diode, a first transistor including a drain electrode, a source electrode, and a gate electrode. US 2018/158406 A1 discloses a display device that includes pixels configured to emit light of various intensity in accordance with driving signals, data lines, scan lines, and a power supply unit configured to supply at least one driving voltage to the pixels. SUMMARY The invention provides a light emitting display device as set out in the accompanying claims. According to embodiments of a light emitting display device, display quality deterioration due to the characteristic difference of pixels may be effectively prevented or substantially reduced. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view of a light emitting display device according to an embodiment.FIG. 2 is a schematic top plan view of pixels arranged in a display area in a light emitting display device according to an embodiment.FIG. 3, FIG. 4, and FIG. 5 each are a circuit diagram of a pixel of a light emitting display device according to an embodiment.FIG. 6 schematically illustrates a cross-sectional structure of a transistor used as a seventh transistor of a pixel in a light emitting display device according to an embodiment.FIG. 7 shows a circuit diagram of the transistor illustrated in FIG. 6.FIG. 8, FIG. 9, and FIG. 10 are schematic views that illustrate operation of the transistor shown in FIG. 6.FIG. 11 is a graph that shows a voltage-current characteristic according to a mode of a seventh transistor in a light emitting display device according to an embodiment.FIG. 12 is a schematic cross-sectional view of the display panel according to an embodiment.FIG. 13, FIG. 14, and FIG. 15 each are a circuit diagram of a pixel of a light emitting display device according to an embodiment.FIG. 16 is a schematic cross-sectional view of a display panel according to an embodiment. DETAILED DESCRIPTION The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present. Throughout the specification, when "connected to" in the entire specification, this does not only mean that two or more constituent elements are directly connected, but also means that two or more constituent elements are indirectly connected, physically connected, and electrically connected through other constituent elements, or being referred to by different names depending on the position or function, while being integral. In the drawings, the signs "x", "y", and "z" are used to indicate the direction, where "x" is a first direction, "y"