KR101493223B1 - Organic light emitting display - Google Patents

Abstract

An organic light emitting diode (OLED) display device includes at least two high potential power supply lines, first to third thin film transistors connected to the high potential power supply line, a red organic light emitting diode connected to the first thin film transistor A blue organic light emitting diode connected to the third thin film transistor, and a thin film transistor connected to each of the red, green and blue organic light emitting diodes, And a resistor located between the transistor and the high potential power supply line.

Organic light emitting display, high-potential power line

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED) display, and more particularly, to an organic light emitting diode (OLED) display capable of reducing cost and increasing an aperture ratio by using high power supply lines commonly for each sub-pixel.

Recently, an electro-luminescence display device capable of thinning, such as e-paper, has been attracting attention among a variety of display devices for realizing a variety of information on a screen. An organic electroluminescence display device is a self-luminous device using a thin organic emission layer between electrodes, and is called an organic EL or OLED (Organic Light Emitting Diode) display device. Hereinafter, an OLED display device is used. The OLED display device has advantages such as low power consumption, thinness, and self-luminescence as compared with a liquid crystal display device, but has a short life span.

The OLED display device is developed based on an active matrix type suitable for displaying moving images by independently driving each of three color (R, G, B) sub-pixels constituting one pixel. Each sub-pixel of the active matrix OLED (hereinafter, AMOLED) display device includes an OLED composed of an organic light-emitting layer between an anode and a cathode, and a sub-pixel driver that independently drives the OLED. The sub-pixel driver includes at least two thin film transistors and a storage capacitor, and controls the amount of current supplied to the OLED according to the data signal to control the brightness of the OLED. The OLED includes a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injecting layer stacked with an organic material between an anode and a cathode. When a forward voltage is applied between the anode and the cathode, electrons from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes from the anode move to the light emitting layer through the hole injection layer and the hole transport layer. The light emitting layer emits light when an exciton is formed by recombination of electrons from the electron transporting layer and holes from the hole transporting layer and changes from an excited state to a ground state, And the amount of current flowing between the cathode and the cathode.

The AMOLED display device emits light through the substrate in an encapsulation structure in which a packaging plate is attached to a substrate on which a sub-pixel driver array and an OLED array are formed. A getter that adsorbs moisture and gas is formed on the packaging plate to prevent deterioration of the organic light emitting layer.

1, since the efficiency of red (R), green (G), and blue (B) organic light emitting diodes is different depending on the characteristics of organic materials, red (R), green G), and blue (B) sub-pixels, respectively. Therefore, in order to obtain a uniform luminance, different high voltage (VDD) voltages must be supplied to each of the red (R), green (G) and blue (B) subpixels and accordingly a power generator Since the high power supply line is required for each sub-pixel, there is a problem in that the power IC efficiency is reduced due to a cost increase, a decrease in the aperture ratio, and a static current due to the difference in the voltage level of the high voltage source.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic light emitting display capable of reducing cost and increasing aperture ratio by commonly using a high potential power supply line for each sub-pixel.

According to an aspect of the present invention, there is provided an organic light emitting display including at least two high-potential power supply lines, first through third thin film transistors connected to the high-potential power supply line, A green organic light emitting diode connected to the second thin film transistor; a blue organic light emitting diode connected to the third thin film transistor; and at least two of the red, green and blue organic light emitting diodes And a resistor located between the thin film transistor connected to each of the organic light emitting diodes and the high potential power supply line.

According to another aspect of the present invention, there is provided an organic light emitting display including at least two high-potential power supply lines, first to third thin film transistors connected to the high-potential power supply line, And an organic light emitting diode, wherein at least one of a channel width and a channel length of each thin film transistor is different from each other.

The organic light emitting display according to the present invention has the following effects.

A resistance value according to a voltage difference may be designed for each sub-pixel through a common high potential power supply line so that the same luminance can be exhibited at the same voltage. In addition, by using the high potential power supply line in common, it is possible to improve the aperture ratio of the sub-pixel and to reduce the cost, and there is a static current due to the difference in the voltage level of the high- The problem that the efficiency is reduced can be solved.

FIG. 2A is an equivalent circuit diagram of the organic light emitting diode display according to the first embodiment of the present invention. FIG. 2B is a diagram illustrating an equivalent circuit of the red (R), green (G), and blue (B) And FIG. 2C is a simplified view schematically showing a high-potential power supply line according to the present invention.

2A to 2C, an active matrix OLED (hereinafter referred to as AMOLED) display device for independently driving each of red (R), green (G) and blue (B) An organic light emitting diode (OLED) composed of an organic light emitting layer between the anode and the cathode in each pixel, and a sub-pixel driver for independently driving the organic light emitting diode. The sub-pixel driver includes at least two thin film transistors and a storage capacitor, and controls the amount of current supplied to the OLED according to a data signal to control the brightness of the OLED.

The organic light emitting display includes a common high-potential power supply line 120 for applying power from the power supply unit 200 to the liquid crystal panel 100, a first branched power supply line 120 branched from the common high- A data line DL perpendicularly intersecting the gate line GL and a switching thin film transistor DL connected to the gate line GL and the data line DL are connected to the line 120a and the second branch power source line 120b, A driving thin film transistor T2 connected to the switching thin film transistor T1 and the organic light emitting diode E, a gate electrode of the driving thin film transistor T2, And a storage capacitor C connected between the storage capacitors 120a and 120b.

The switching thin film transistor T1 supplies the data signal of the data line DL to the gate electrode of the driving thin film transistor T2 and the storage capacitor C in response to the scan signal of the gate line GL. In response to the data signal from the switching thin film transistor T1, the driving thin film transistor T2 is connected to the first and second branch power supply lines R, G, And controls the brightness of the organic light emitting diode E by controlling the current supplied from the light emitting diodes 120a and 120b to the organic light emitting diode E.

The storage capacitor C charges the data signal from the switching thin film transistor T1 and supplies the charged voltage to the driving thin film transistor T2 so that even if the switching thin film transistor T1 is turned off, ) Can supply a constant current.

The organic light emitting layer includes a hole injection layer (HIL), a hole transporting layer (HTL), an emission layer (EML), an electron transporting layer (ETL) , And an electron injection layer (EIL). When a forward voltage is applied between the anode and the cathode, electrons from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes from the anode move to the light emitting layer through the hole injection layer and the hole transport layer. The light emitting layer emits light when an exciton is formed by recombination of electrons from the electron transporting layer and holes from the hole transporting layer and changes from an excited state to a ground state, And the amount of current flowing between the cathode and the cathode.

The first high potential voltage is applied to the driving thin film transistor T2 of the blue (B) sub-pixel through the common high potential power supply line 120 and the blue high potential power supply line 120b. The first high potential voltage is applied to the common high potential power supply line 120a through the first resistor R1 located between the first branch high potential power supply line 120a and the source electrode of the driving thin film transistor T2 of the red (R) 120) and applied to the driving thin film transistor T2 of the red (R) sub-pixel. The first high potential voltage is higher than the second high potential voltage through the second resistor R2 located between the first branch power supply line 120a and the source electrode of the driving thin film transistor T2 of the green (G) And is applied to the driving thin film transistor T2 of the green (G) sub-pixel. Accordingly, the blue (B) sub-pixel using the highest high-potential voltage is directly connected to the common high-potential power supply line 120 and the conventional blue (B) sub-pixel is used for the red (R) The resistance value is designed in consideration of the difference between the high-potential voltage applied to the pixel and the high-potential voltage applied to the red (R) and green (G) sub-pixels. For example, when the same luminance of 100 (nit) is used as a reference in FIG. 1, the green (G) sub-pixel is 6.2V, the red (R) sub- The red (R) and green (G) sub-pixels design the resistance value in consideration of the difference from the blue (B) sub-pixel.

1, red (R) sub-pixels and green (G) sub-pixels share a first branch power supply line 120a and are formed to be symmetrical with respect to each other with a first branch power supply line 120a therebetween, ) Sub-pixel and the data line DL of the blue (B) sub-pixel. Also, as shown in FIG. 2, the blue (B) pixel and the red (R) pixel share one branch line and the green (G) pixel and the blue (B) pixel share one branch line.

In this manner, the resistance value according to the voltage difference can be designed for each sub-pixel through the common high potential power supply line, and the same luminance can be exhibited at the same voltage. In addition, by using the high potential power supply line in common, it is possible to improve the aperture ratio of the sub-pixel and to reduce the cost, and there is a static current due to the difference in the voltage level of the high- The problem that the efficiency is reduced can be solved.

FIG. 3A is an equivalent circuit diagram of an organic light emitting display according to a second embodiment of the present invention. FIG. 3B is a diagram illustrating an equivalent circuit of the red (R), green (G), and blue (B) And is a simplified diagram for explaining the relationship.

The organic light emitting display shown in FIGS. 3A and 3B will not be described in detail with reference to FIG. 2A through FIG. 2C.

3A and 3B, the first high potential voltage is applied to the driving thin film transistor T2 of the blue (B) sub-pixel through the common high-potential power supply line 130 and the blue (B) . The first high potential voltage is applied between the common high potential power supply line 130C and the red (R) branch power supply line 130a by a first resistor R1 located at the input terminal of the red (R) branch power supply line 130a (R) sub-pixel to the second high-potential voltage lower than the first high-potential voltage of the common high-potential power supply line 130 and applied to the common high-potential power supply line 130, (G) branch power supply line 130a between the green (G) branch power supply line 130b and the green (G) branch power supply line 130b through a second resistor R2 located at the input of the green And is applied to the driving thin film transistor T2 of the green (G) sub-pixel.

Therefore, the blue (B) sub-pixel using the highest high-potential voltage is directly connected to the common high-potential power supply line 130 through the blue (B) branch power supply line 130c and the red (R) ) Design a resistance value considering the difference between the high potential voltage applied to the conventional blue (B) sub-pixel and the high potential voltage applied to the red (R) and green (G) sub-pixels. For example, when the same luminance of 100 (nit) is used as a reference in FIG. 1, the green (G) sub-pixel is 6.2 V, the red (R) sub- (R) and the green (G) sub-pixel design a resistance value in consideration of a voltage difference between the red (R) and green (G) sub-pixels.

The red (R) branch power supply line 130a is formed to face the data line DL of the green (G) sub-pixel and the green (G) branch power supply line 130b is formed to face the data line DL of the green And are formed so as to face each other adjacent to the data line DL.

In this manner, the resistance value according to the voltage difference can be designed for each sub-pixel through the common high potential power supply line, and the same luminance can be exhibited at the same voltage. In addition, by using the high potential power supply line in common, it is possible to improve the aperture ratio of the sub-pixel and to reduce the cost, and there is a static current due to the difference in the voltage level of the high- The problem that the efficiency is reduced can be solved.

FIG. 4A is a cross-sectional view illustrating a relationship between a gate electrode and a channel length of the driving TFT according to the present invention. FIG. 4B is a cross- , And blue (B) sub-pixels, respectively.

4A, the channel length L of the driving thin film transistor T2 is defined as a region in which the semiconductor layer 108 located under the gate electrode 104 is not doped with an impurity, It depends on the width.

Referring to FIG. 4B, the channel length L is adjusted according to the width of the gate electrode 104 of the driving thin film transistor T2 for each red (R), green (G) and blue (B) Source and drain electrodes 110a and 110b are formed on the upper or lower layer of the semiconductor layer 108 made of silicon and a (gate) insulating film 112 (gate) interposed between the source and drain electrodes 110a and 110b and the semiconductor layer 108 The source and drain electrodes 110a and 110b and the semiconductor layer 108 are connected to each other. Thus, the current and resistance of the driving TFT T2 can be controlled according to Equation 1 or 2 according to the channel length L of the driving TFT T2.

In the equations (1) and (2), I is the current of the driving thin film transistor, R is the self-resistance when the driving thin film transistor is turned on, μ is a constant for the mobility of the driving thin film transistor, Cox is the capacitance of the capacitor, Width is the channel width, Vgs is the gate-source voltage, Vth is the threshold voltage, and Vds is the drain-source voltage.

When the channel length L of the driving thin film transistor T2 is adjusted as shown in Equation 1, the current intensity of the driving thin film transistor T2 is changed, and the luminance proportional to the current intensity is also changed. For example, the channel widths W of the red (R), green (G) and blue (B) sub-pixels are the same, the channel length (L1) When the channel length L 2 of the green (G) sub-pixel is less than 9 μm and less than 11 μm and the channel length L 3 of the blue (B) sub-pixel is less than 5 μm and less than 7 μm, (R), green (G), and blue (B) sub-pixels having a luminance lower than that of the green (G) sub-pixel because the current intensity of the red (G) The red (R), green (G), and blue (B) sub-pixels can exhibit the same luminance while the blue (B) sub-pixel is compensated for brightness in proportion to the current intensity. Here, it is also possible to adjust the channel width (L) as well as the channel width (W), or to adjust the channel length (L) and the channel width (W) Although the channel width W is inversely proportional to the current intensity when the channel width W is adjusted, the channel width W is shortened in the order of green (G), red (R) and blue (B) So that each sub-pixel exhibits the same luminance.

Similarly, when the driving thin film transistor T2 is turned on as shown in Equation 2, the self-resistance is proportional to the channel length L of the driving thin film transistor T2. Therefore, when the common high potential voltage of the blue (B) sub-pixel is taken as a reference, the channel width W of the red (R), green (G), and blue Since the self-resistance is proportional to the channel length L when the length L is long in the order of blue (B), red (R) and green (G) ), And green (G) sub-pixels. Therefore, the blue (B) sub-pixel having the lowest luminance and the red (R) and green (G) sub-pixels can exhibit the same luminance.

Thus, the red (R), green (G) and blue (B) sub-pixels can exhibit the same luminance by adjusting the channel length or channel width of the driving thin film transistor for each sub-pixel through the common high potential power supply line. In addition, by using the high potential power supply line in common, it is possible to improve the aperture ratio of the sub-pixel and to reduce the cost, and there is a static current due to the difference in the voltage level of the high- The problem that the efficiency is reduced can be solved.

The organic light emitting display according to any one of the first to third embodiments may be applied to an organic light emitting display having a plurality of switching transistors.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. It will be clear to those who have knowledge.

1 is a graph illustrating voltage-luminance characteristics of a conventional OLED display.

2A is an equivalent circuit diagram of an OLED display according to a first embodiment of the present invention.

FIG. 2B is a simplified diagram for explaining the relationship between the red (R), green (G) and blue (B) sub-pixels according to the first embodiment and the resistance.

2C is a simplified schematic diagram of a high-potential power supply line according to the present invention.

3A is an equivalent circuit diagram of an OLED display according to a second embodiment of the present invention.

3B is a simplified diagram for explaining the relationship between the red (R), green (G), and blue (B) sub-pixels according to the second embodiment and the resistance.

4A is a cross-sectional view for explaining the relationship between the gate electrode and the channel length of the driving thin film transistor of the present invention.

FIG. 4B is a plan view showing driving thin film transistors of red (R), green (G), and blue (B) sub-pixels of an OLED display according to a third embodiment of the present invention.

Description of the Related Art

120, 130: common high potential power line 120a: red / green high potential power line

120b, 130c: blue high potential power line 130a: red high potential power line

130b: green high potential power line 200: power supply part

Claims (7)

A high-potential power supply line to which the first high-potential voltage is applied Two or more branch power supply lines branched from the high potential power supply line, First to third thin film transistors connected to the high potential power supply line, A red organic light emitting diode connected to the first thin film transistor; A green organic light emitting diode connected to the second thin film transistor, A blue organic light emitting diode connected to the third thin film transistor, The first high-potential voltage is converted into a second high-potential voltage lower than the first high-potential voltage and a third high-potential voltage lower than the second high-voltage, respectively, so that any two of the first through third thin film transistors And a first resistor and a second resistor for respectively supplying the thin film transistors to the thin film transistors. The method according to claim 1, The first resistor A second thin film transistor disposed between the second thin film transistor and the branch power supply line, The second resistor A first thin film transistor and a second thin film transistor, And the third thin film transistor is directly connected to the branch power supply line. delete The method according to claim 1, A red branch power supply line in which the first resistor is disposed at an input terminal and connected to the first thin film transistor; A green branch power supply line in which the second resistor is disposed at an input terminal and is connected to the second thin film transistor, And a blue branch power supply line connected to the third thin film transistor. delete delete delete

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