KR20020090792A - organic electroluminescence display and driving circuit thereof - Google Patents

Abstract

PURPOSE: An organic electroluminescence device and a driving circuit thereof are provided, which can reduce fabrication costs by embedding a source driver of an active matrix organic LED(Light Emitting Diode) in a panel, and can fabricate a high aspect ratio panel by reducing an output line pad pitch of the source driver of the active matrix organic LED. CONSTITUTION: The organic electroluminescence device includes an insulation substrate(110), and a pixel part(120) where a number of pixels(123) are arranged in a matrix on the upper part of the substrate, and a source driver(140) located on the substrate as supplying a data signal to the pixel part, and a gate driver(130) supplying a gate signal to the pixel part. The source driver includes an address shift register controlling red, green and blue video data, and an input register storing the above video data, and a n bit counter counting a signal being output from the input register, and a switching part controlling an external lamp signal by a signal from the n bit counter.

Description

Organic electroluminescent display and driving circuit thereof

The present invention relates to an organic electroluminescent device, and more particularly, to a driving circuit of an active matrix organic electroluminescent device.

Currently, a cathode ray tube (CRT) is used as a main device in a display device such as a television or a monitor, but this has a problem of weight and volume and high driving voltage. Accordingly, there is a need for a flat panel display having excellent characteristics such as thinness, light weight, and low power consumption, and has emerged, such as a liquid crystal display, a plasma display panel, and an electric field emission. Various flat panel display devices such as a field emission display and an electroluminescent display (or electroluminescence display (ELD)) have been researched and developed.

The dual electroluminescent device is a display device using an electroluminescence (EL) phenomenon in which light is generated when a certain electric field is applied to a phosphor, and an inorganic electroluminescent device and an organic electroluminescent device depending on a source causing excitation of carriers. (organic electroluminescence display: OELD or organic ELD).

Among them, the organic electroluminescent device is attracting attention as a natural color display device because it emits light in all regions of visible light including blue, and has high luminance and low operating voltage characteristics. In addition, because of self-luminous, the contrast ratio is high, the ultra-thin display can be realized, and the process is simple, so that environmental pollution is relatively low. On the other hand, the response time is easy to implement a moving picture of a few microseconds, there is no restriction on the viewing angle, stable at low temperatures, and driven at a low voltage of DC 5 to 15V, it is easy to manufacture and design a drive circuit.

The organic electroluminescent device has a structure similar to that of an inorganic electroluminescent device, but the light emitting principle is called organic light emitting diode (OLED) because the light emission is achieved by recombination of electrons and holes. Therefore, hereinafter, referred to as organic LED.

An active matrix type in which a plurality of pixels are arranged in a matrix form and a switching element is connected to each pixel is widely used in a flat panel display device. The active matrix organic LED applied to the organic electroluminescent device is shown in the accompanying drawings. It demonstrates with reference.

FIG. 1 illustrates a typical active matrix organic LED. As shown, an active matrix organic LED includes a pixel portion 11 in which a plurality of pixels (not shown) are arranged in a matrix form on a substrate such as glass to display an image. And a gate driver integrated circuit 12 and a source driver integrated circuit 13 for applying a signal to each pixel of the pixel unit 11. Here, the gate driver integrated circuit 12 and the source driver integrated circuit 13 may be made of single crystal silicon and attached to a substrate on which the pixel portion 11 is formed in the same manner as a tape carrier package.

In order to realize a color image, the image must be represented by using red (R), green (G), and blue (B) as a unit, so that the source driver integrated circuit 13 is more than the gate driver integrated circuit 12. It has a complicated structure.

The structure of such a source driver integrated circuit is shown in FIG. As shown, the source driver integrated circuit includes an address shift register 21, a latch 22, an input register 23, and a digital to analog converter 24.

The n-bit RGB video data signal is passed through the latch 22 to the input register 23, which is controlled by the m-bit address shift register 21 signal and stored in the input register 23.

Subsequently, the signal stored in the input register 23 is transferred to the digital-to-analog converter 24, converted into an analog signal, and then output to the data line. Here, the reference voltage is also applied to the digital-to-analog converter 24.

However, since the source driver integrated circuit is made of single crystal silicon, as described above, the manufacturing cost is high, and the manufacturing process is also complicated because TCP requires a separate attachment process.

On the other hand, in order to attach the source driver integrated circuit to the substrate on which the pixel portion is formed, a separate wiring must be formed, and the minimum pitch, i.e., the minimum pitch between the wiring that can be implemented at present, is about 70 μm. Recently, the size of the pixel is decreasing as a high definition display is required, but at present, a pixel having a width of 70 μm or less cannot be manufactured.

The present invention has been made to solve the above-mentioned conventional problem, and an object of the present invention is to reduce the manufacturing cost by embedding a source driver of an active matrix organic LED in a panel.

Another object of the present invention is to reduce the output wiring pad pitch of the source driver of the active matrix organic LED, thereby making it possible to fabricate a high-definition panel.

1 is a view showing a general organic electroluminescent device.

2 is a diagram illustrating a structure of a source driver integrated circuit of a general organic electroluminescent device.

3 is a view showing an organic electroluminescent device according to the present invention.

4 shows a circuit for one pixel of an organic electroluminescent device according to the invention.

5 is a view showing the structure of a source driver of an organic electroluminescent device according to the present invention.

6 is a diagram illustrating an example of the switching unit of FIG. 5.

7A-7C illustrate output waveforms of a source driver according to the present invention.

In the organic electroluminescent device according to the present invention for achieving the above-described conventional object, a pixel portion in which a plurality of pixels are arranged in a matrix form is formed on an insulating substrate, and a source driver for supplying a data signal to the pixel portion is also provided. A gate driver is formed on the substrate and supplies a gate signal to the pixel portion.

The source driver may include an address shift register for controlling red, green, and blue video data, an input register for storing the red, green, and blue video data, an n-bit counter for counting signals output from the input register, and and a switching unit that adjusts and outputs an external ramp signal by a signal from an n-bit counter.

In this case, the switching unit may include at least one thin film transistor and a capacitor.

The source driver according to the invention can be made of polycrystalline silicon.

The pixel may include a switching thin film transistor operated by the data signal and the gate signal, a driving thin film transistor connected to the switching thin film transistor, a light emitting diode connected to the driving thin film transistor, and the switching thin film transistor; It may also consist of a storage capacitor connected to the driving thin film transistor.

As described above, in the present invention, since the source driver is formed on the substrate on which the pixel portion is formed, a separate attaching process is not required, and the manufacturing cost can be reduced by manufacturing the source driver with polycrystalline silicon.

In general, since active matrix organic LEDs require high current by converting electrical energy into light energy, thin film transistors used as switching elements are formed of polycrystalline silicon having high mobility. Therefore, when the driving circuit is formed on the same substrate as the thin film transistor using the polycrystalline silicon, the process of connecting the thin film transistor and the driving circuit is unnecessary.

Hereinafter, an active matrix organic LED according to the present invention will be described in detail with reference to the accompanying drawings.

3 illustrates an active matrix organic LED according to an embodiment of the present invention, and FIG. 4 illustrates a circuit structure of one pixel of an active matrix organic LED according to the present invention.

As shown in FIG. 3, in the active matrix organic LED according to the present invention, a pixel unit 120 on which an image is represented is formed on a transparent insulating substrate 110 such as glass. A plurality of gate lines 121 are formed in the horizontal direction in the pixel portion 120, and data lines 122 intersecting the gate lines 121 are formed in the vertical direction. The pixel 123 connected to the gate line 121 and the data line 122 is positioned in an area defined by the intersection of the gate line 121 and the data line 122, and the pixel 123 is also connected to the power line 124. It is connected.

As illustrated in FIG. 4, the pixel 123 includes a switching thin film transistor 125, a driving thin film transistor 126, a storage capacitor 127, and a light emitting diode 128. The gate electrode of is connected to the gate line 121, the source electrode is connected to the data line 122. A drain electrode of the switching thin film transistor 125 is connected to a gate electrode of the driving thin film transistor 126, and a source electrode of the driving thin film transistor 126 is connected to an anode of the light emitting diode 128 and a driving thin film transistor ( The drain electrodes of 126 are connected to the power lines 124, respectively. The cathode of the light emitting diode 128 is grounded, one electrode of the storage capacitor 127 is connected to the drain electrode of the switching thin film transistor 125 and the gate electrode of the driving thin film transistor 126, and the capacitor 127 The other electrode of) is connected to the drain electrode of the driving thin film transistor 126 and the power line 124.

Here, the active layers of the switching thin film transistor 125 and the driving thin film transistor 126 are made of polycrystalline silicon.

Next, as shown in FIG. 3, a gate driver integrated circuit 130 connected to the gate line 121 and applied to a signal is disposed on the left side of the pixel unit 120. In this case, the gate driver integrated circuit 130 is a TCP. It may be attached by, and may be formed on the insulating substrate 110.

Next, a source driver 140 connected to the data line 122 is formed at an upper end of the pixel unit 120. The source driver 140 is made of polycrystalline silicon and is positioned on the insulating substrate 110.

Therefore, a separate attaching step is not required and manufacturing cost can be lowered.

Meanwhile, FIG. 5 illustrates a structure of a source driver according to the present invention.

As shown, the source driver includes an address shift register 210, a latch 220, an input register 230, an n-bit counter 240, and a switching. Part 250 is made.

The address shift register 210 is operated by a dot clock (DCLK), and determines whether to shift the signal to the right or the left by the L / R. Here, EIO1 and EIO2 represent a start signal and an end signal.

The output signal of the address shift register 210 is m bits, which are input to the input register 230, and the input register 230 receives n bits of R, G, and B video data through the latch 220. At this time, storing the RGB video data in the input register 230 is controlled by the output signal of the address shift register 210. That is, when the output of the address shift register 210 is high, the RGB video data is stored in the input register 230, and when the output of the address shift register 210 is low, the RGB video data Is not stored in the input register 230. Here, the output of the address shift register 210 is high only at the k th output, and the output of the other address shift register 210 is low, thereby storing RGB video data only at a desired position.

When the RGB video data of one video line is stored, it is stored in the n-bit counter 240 in the next block, and then the data of the next video line is stored in the input register 230.

The n bit counter 240 generates an output signal corresponding to the data stored by the count clock CCLK and transmits the output signal to the switching unit 250. The switching unit 250 outputs the signal of the n bit counter 240 and an external R signal. (Or G or B) Ramp signal is applied to the data line.

An example of such a switching unit 250 is illustrated in FIG. 6, and as shown, the switching unit 250 may include one thin film transistor and one capacitor. Here, the gate electrode of the thin film transistor 251 is connected to the output of the n-bit counter, the source electrode is connected to the external R ramp signal, and the drain electrode is connected to the data line of the pixel portion. Meanwhile, one electrode of the capacitor 252 is connected to the drain electrode of the thin film transistor 251, and the other electrode of the capacitor is grounded.

7A to 7C show waveforms of an external R (or G or B) ramp signal, an n-bit counter output signal, and an output signal of the switching unit in the source driver.

In this case, the output waveform will be described using an example in which the RGB video data is 6 bits. When the RGB video data is 6 bits, the data has a total of 64 output waveforms.

The waveform of the external R (or G or B) lamp signal may be modified to be formed in accordance with the characteristics of the organic LED.

As shown, when an external R (or G or B) ramp signal is periodically applied, the output signal of the switching unit has a different size according to the output signal value of the n-bit counter. Here, the output signal data of FIG. 7B are 000100, 100110, and 111111, respectively.

In this way, the digital signal of the n-bit counter and the analog signal of the external RGB lamp transmitted to the switching unit are converted into an analog signal as shown in FIG. 7C and transferred to the data line.

Therefore, a desired video signal is generated by combining the output waveform of the counter and the external ramp signal, and then stored in the storage capacitor of the pixel, and the structure thereof can be easily manufactured.

As such, the source driver of the present invention is formed on a substrate on which the pixel portion is formed using polycrystalline silicon, and the circuit structure at this time is simpler than that of the source driver integrated circuit including the digital-to-analog converter, thereby reducing manufacturing costs. Can simplify the manufacturing process. In addition, it is not necessary to use TCP for attaching separately, and accordingly, the pitch of the wiring can be reduced, so that a high-definition panel can be manufactured.

In the organic electroluminescent device according to the present invention, since the source driver is formed on the same substrate as the pixel portion in which the image is represented, no separate attachment is required, and thus the manufacturing process can be reduced. In addition, since the source driver according to the present invention is made of polycrystalline silicon and its structure is simple, the manufacturing cost can be reduced, and the pitch of the wiring can be set to 70 µm or less, so that a high-definition panel can be manufactured.

Claims (5)

An insulating substrate; A pixel unit in which a plurality of pixels are arranged in a matrix form on the substrate; A source driver positioned on the substrate and supplying a data signal to the pixel portion; A gate driver supplying a gate signal to the pixel portion Organic electroluminescent device comprising a. The method of claim 1, The source driver may include an address shift register for controlling red, green, and blue video data; An input register storing the red, green, and blue video data; An n bit counter for counting a signal output from the input register; A switching unit for controlling and outputting the external ramp signal by the signal from the n-bit counter Organic electroluminescent device comprising a. The method of claim 2, The switching unit is an organic electroluminescent device consisting of at least one thin film transistor and a capacitor. The method of claim 1, The source driver is an organic electroluminescent device made of polycrystalline silicon. The method of claim 1, The pixel includes a switching thin film transistor operated by the data signal and the gate signal; A driving thin film transistor connected to the switching thin film transistor; A light emitting diode connected to the driving thin film transistor; A storage capacitor connected to the switching thin film transistor and the driving thin film transistor Organic electroluminescent device comprising a.