TW200417965A - Method and apparatus for forming uniform image of active organic light-emitting diode display - Google Patents

Abstract

The method and apparatus for forming uniform image of active organic light-emitting diode (OLED) display are disclosed in the present invention. The display is composed of plural pixel apparatuses, in which each pixel apparatus has a driving unit to drive the OLED to shine. The cathode of OLED is connected to a positive power source, so as to increase the electric potential of OLED through the voltage provided by the positive power source. And, the Vsd (voltage difference between source and drain) when each driving unit is activated is decreased while the Vsg (voltage difference between source and gate) remains unchanged. Therefore, as each driving unit has different threshold voltage due to characteristic variations, each driving unit has smaller output current difference when it is conducted.

Description

200417965

V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a method and device for uniformity of an active organic light-emitting diode display, especially a Vsd by reducing the driving of the thin film electrode (DriWng TFT) (Source, drain voltage difference) and hold (source, gate voltage difference) so that the output current of each driving thin-film transistor (^ iving TFT) does not vary too much. [Prior art]

It is known that the current technology of thin film transistor liquid crystal display (TFT [CD) is divided into two types: amorphous silicon thin film transistor (a-Si TFT) and polycrystalline silicon thin film transistor (Poly-Si TFT). TFT LCD) refers to amorphous silicon thin film transistor (j-Si TFT). At present, the technology is mature and it is the mainstream product of liquid crystal display (LCD). The biggest difference between low-temperature polycrystalline silicon thin-film transistors (LTPS TFT) and amorphous silicon thin-film transistors (a_Si TFT) is that the transistors of low-temperature polycrystalline silicon (LTps) need to be further connected to the process of laser-tempering to convert the amorphous silicon. The thin film of the thin film transistor ("TFT") is transformed into a polycrystalline silicon thin film layer, making low temperature polycrystalline silicon (

) Compared with the amorphous silicon thin film transistor (α_Si TFT) on the Shi Xijing structure, the f-sequence 'can increase the electron conduction rate to 200 cm2 / v-sec. Low temperature polycrystalline stone (LTPS) technology can make the device smaller, reduce the overall TFT element area by more than 50%; and improve the aperture ratio (aperture ratl0) 'Compared with a-Si TFT LCD at the same size can Produces higher resolution with reduced power consumption. In addition, the low-temperature polycrystalline silicon thin film crystal officer (LTPS TFT) still has power saving, high brightness, fine daylight, thin and light and few contacts (less than 200 contacts, which helps to improve the yield. A-Si TFT needs to be larger 200417965 V. Description of the invention (2)-One (3, 8, 4, 2 contacts) and other advantages. However, because of the low-temperature polycrystalline silicon (LTps) manufacturing process, thin film transistors need to undergo a laser tempering process, which often causes the thin film transistor's threshold voltage (Threshold Voltage) and drift rate (Mobility) to vary. 'Make the characteristics of each thin-film transistor (TFT) element different, so' When the drive system uses analog (ana 10g) modulation to represent grayscale, often because thin-film transistor (TFT) is receiving lightning There are different characteristics after the process of shooting and tempering. Even if the same dust signal is written, the organic light-emitting diodes of different pixels generate different currents and emit different brightness. This phenomenon will cause the organic light-emitting diode panel to display a grayscale error image, which will seriously damage the image uniformity. Image thin film display of the organic electroluminescence element of the US patent US5684365. A daylight circuit composed of two thin film transistors and a capacitor f. When this pixel device is scanning image data, the switch unit is turned on. At this time, the image data is entered into the switch by the data line After being scanned by the scanning line, and stored in the storage unit (also the switch unit is turned on to charge the storage unit), the voltage difference of the storage unit will provide Vsg (source and gate voltage difference) as the drive unit, so that The driving unit outputs a current to the organic electro-optical light-emitting element, and the shell degree of the organic electro-light-emitting element is proportional to the magnitude of the current flowing through the element. However, if the characteristics of the driving unit of such a daylight device vary due to process limitations, it will cause uneven emission of organic electroluminescent light elements and destroy the uniformity of the image.

Page 6 200417965 V. Description of the invention (3)

: To improve the display image, the digital drive architecture is displayed, and the gray scale is represented by the I modulation method. Its 4 == ⑴, _. ) (TFT) 邋 ΓΠΜ, the principle of life and death is controlled by the thin film transistor COLED), and the light is not illuminated, * the pattern asks r P τ ·, and the lighting time The ratio of the frame time to the-frame time determines the image gray level.踺 :: 二;: Way to drive organic light-emitting diodes ... There are the following

I time. Electricity = Transistor in the on state (J), each thin film transistor on the display panel can be completely turned off without any output. To avoid the loss of irm " lies in the method and device for solving the above-mentioned traditional lack of t ^ lack of existence of the active image uniformity of the present invention, by: especially a body display unfavorably connected to a positive power source, thereby improving the existence of; d ::; The cathode of the body is connected to τρτ ^ V, which can reduce the difference in the magnitude of the output current of the driving TFT by reducing the Vsd (source and non-polar voltage difference) of the driving TFT. #MtsaMv 通 状 ㈣ In order to achieve the above-mentioned purpose, the method and device for uniforming the image of the display device of the present invention ;: 3 diodes to display the diodes ... ... a driving unit to drive organic light emitting devices. The cathode of the light-emitting diode is connected to a positive electrode. Explanation of the invention (4), by using the positive electrode, the voltage of the organic light-emitting diode is further reduced by driving the positive voltage, and Vsg (,,, / ^, its Vsd (source, drain voltage difference) drive unit due to 4 variability / pole voltage difference), remain unchanged, when each It age), can be etched 夂、 / There are different starting voltages (Threshold V〇 is reduced. ④ The difference in the output current of the mobile unit when it is turned on. [Embodiment] Is it relevant to this day and month? 4 The following are as follows: Technical description, now with drawings [Simplified description of the drawings] Fig. 1 is a schematic diagram of the circuit of the present invention. Fig. 2 is a drive unit. Fig. 3, a drive:: electricity ~-voltage schematic. Wu Zhi electric freezing-voltage diagram (2). 凊 Refer to "Lang Zhang-^ Ge Jie-· Figure 1 ", Is a schematic circuit diagram of the present invention. If the method and the cargo strike type organic light-emitting diode display image are uniformly arranged, the display device is composed of a plurality of pixel devices 10. Once it is set to 10, it has a driving unit 2 to drive the organic light emitting diode 4. The cathode of the two "organic light emitting diode 4 is connected to a positive power source 5, and the positive power source 5 provides a voltage to improve organic light emission. The potential of the diode 4 further reduces the Vsd (source and drain voltage difference) of the driving unit 2 during operation, while Vsg (source and gate voltage difference) remains unchanged. When there is a different initial voltage (Threshold Vtage) due to the variation of the characteristics, the difference between the output currents of the driving units 2 can be reduced when they are turned on.

200417965 V. Description of the invention (5) In order to achieve the above-mentioned method, the present invention includes: a switch unit], a denier (Pixel) device, and an organic light-emitting diode 4; A storage unit 3 and the above-mentioned switching unit 1 are a thin-film electrical unit, and the two input terminals 1 1 and 12 are respectively connected to two (T). This switching unit and-data line 61㈤a 妾 有-know drawing line 6〇 ( Sc-Llne) The driving unit 2 is a thin film transistor (TFT). The driving terminal 21 is connected to a power line 62 (⑽ ... Line), and / a input 钿 2 / is connected to the output terminal of the switching unit 1. 13; The storage unit 3 is composed of a capacitor. One end is connected to a power line 62 (SUpply Line), and the other end is connected to the output terminal 13 of the switch unit 1. The anode of the organic light emitting diode 4 and the drive unit 2 The output terminal 23 is connected, and the cathode thereof is connected to a positive power source 5; 俾 The potential of the cathode and anode of the organic light emitting diode 4 is increased by the voltage provided by the positive power source 5, and the output terminal 23 of the driving unit 2 is also increased Potential, so that the Vsd (source, drain) of the driving unit 2 during operation Voltage difference) decreases, while Vsg (source, gate voltage difference) remains unchanged, so when each drive unit 2 has a different starting voltage (T hre shold Voltage; Vth) due to characteristic variation, The difference between the output currents of the driving units 2 when they are turned on is reduced. In addition, in order to allow the reviewer to fully understand the efficacy achieved in this case, please refer to "shown in Figure 2", which is a schematic diagram of the drive unit's current-voltage. As shown in the figure: When the input voltage Vdd of the power line 62 is 13V and the data line 61

200417965 V. Description of the invention (6) —- When the input voltage signal is 0V, under the conventional pixel device structure, the drive unit 2 has a known load curve 71, so the Vsd operating point of the drive unit is known. Point) is located at the intersection of the conventional load curve 71 and the characteristic curve 72 of the drive unit 2 (when the input voltage (Vdd) of the power line is uv and the input voltage signal (Vdata) of the data line is 0V). Assume that the initial voltage of the TFT element (Thresh〇ld v〇Hage; nh) has a variation of ± L5V due to process limitations. It can be found from the figure that when m has a variation of -1 jV, it will cause the output of the conventional drive unit. The current is 233%. In contrast, when the daylight device 10 of the present invention is used, it is assumed that the cathode potential of the organic light-emitting: pole body (0LED) is increased by the positive power source: = 1 yuan per 2-load curve 73 of the present invention, so Unit ^ 73 (Peratlng Pint) is located at the intersection of the load curve 73 and the characteristic curve of the driving early 2-72 of the present invention (Vthe) is also due to process limitations]. 5V variation 5, The output current of the drive unit 2 of the control unit 1 is only 13.6%. ,, / / / / Refer to "shown in Figure 3", which is the drive unit's electricity: properties *: two pictures (two). As shown in the figure: When the characteristic curve 82 (the input voltage (vdd) of the power line 62 is 8ν, and the data == input: the voltage signal (Vdata) is v), in the traditional daytime device structure The lower Vsg of its traditional drive unit becomes 8v, and the operating point (0perating P0lnt) of the traditional drive unit is located at the intersection of load curve -8 =: characteristic curve of the first drive unit 83 (vsg = 8v). Then the initial voltage m (ΤίΐΓ_〇ιά vQUage) of the TFT

Page 10 200417965 V. Description of the invention (7) Process limitation and i: 1 · 5 V variation will cause 39. 6% variation in the output current of the traditional drive unit. However, when using the driving device of the present invention, since the common cathode potential of the organic light emitting diode (0LED) panel is equal to 5V, the input voltage (Vdd) is 13V, and the input voltage signal (Vdata) of the data line 61 is 0V. The Vsd Operating Point of Unit 2 is located at the intersection of the load curve II 81 and the traditional drive unit characteristic curve II 8 2 (Vsg = 13V). When the initial voltage Vth (Threshold Voltage) of the TFT element has a variation of ± 1 · 5 V due to process limitations, the output current of the drive unit 2 has only a variation of 1 · 3 · 6%. The reason is that “the traditional pixel device becomes smaller when the power supply voltage (Vdd) is small”, although it can reduce the size of the traditional drive unit, it also causes the vSg to decrease. Instead, the output current of each traditional drive unit is affected by the variation of characteristics. It is too large to reduce the vsd of the driving unit 2 and maintain its Vsg at a certain value as in the present invention, so that when the TFT is turned on (0N), the output current is less affected by the characteristics variation of the TFT. The above are merely preferred embodiments of the present invention, and are not intended to limit the scope of implementation of the present invention. That is, all equal changes and modifications made in accordance with the scope of patent application for the present invention are covered by the scope of patent for the present invention.

Page 11 200417965 Schematic description of simple single diagram ί 第 图图图图图图图图明图 明明 发 The present chart is intended to show pressure ^ ¾-- 流 流-^ Ε ϊ ^ 9 Yuanyuankou 6-port 31 J District Μ Ma Department of the Department of Ming & 1 之 # Bid of the evil style strong master [shed input terminal ......... 11, output terminal ... ............. Switch unit ............ Drive unit ............ Storage unit. .............. Organic Light Emitting Diode ............ Positive Power ...... Scan Line ...... Data line ...... t source, line ... ...... Known load curve ............ Characteristic curve .................. The load curve of the present invention ... ...... Load curve two ............ Characteristic curve two ............ Characteristic curve three ............ ....... • · · 10 ^ 21, 22 • 13 > 23 —— · 1 —— · 2 —— · 3 • 4 —— · 5 • · 60 60 · · 61 · · 62 • · 71 · · 72 · · · 73 · · · 81 · · · 82 · · · 83

Page 12

Claims (1)

200417965 6. Scope of patent application [Scope of patent application], this 1 display is dry and one is main: the image uniformity device on the organic light-emitting diode display is composed of a plurality of daylight devices, each-daylight device Included end points ::: U has two input ends and-output #, these two losses and the knife is not connected to the data line and the scan line;-car sister:? ί unit, the upper end of which is connected to the-power line, ⑥ the other-end is connected: the output terminal of the above-mentioned switch unit; and the other I input terminal; there are two input terminals and -output # '其 -input output terminal ; The "original line" and the other input end is connected to an organic light emitting diode of the switching unit, the top and right poles of the basin are connected to the driving unit with a pole and a cathode, the yang source; At the output, the cathode is connected to a positive cathode voltage to increase the organic light-emitting diode, which in turn drives the output potential of the driver unit to 1πΐϊπ. The potential of the output unit of the driver unit is small, and its vsd (source'drain) Voltage difference) minus 2 '. , Gate voltage difference) remain unchanged. Volume display V shadow Λ special: organic light-emitting diode crystal type. The A-ning beta switch can be an active organic light-emitting diode as described in a thin-film electrical display V? Vy? Y. q Ling set, in which the driving unit can be a thin-film electric device. The display of the body display image I wide range, J: the active organic light-emitting diode described above. There are 4 units, and the storage unit is a capacitor unit, which is mainly composed of a plurality of driving organic light-emitting diode display image uniformity driving units to drive a pixel unit, each pixel unit has a cathode俜 is connected to the organic light emitting diode, the organic light emitting diode is highly organic: electricity ^ C ^ ^ ^ ^ ^, ^ ^; Ιΐΐΐ Λ §a, 0 l4. H 叩 V sg (source, gate Voltage difference "Be kept unchanged", then when each drive unit is different due to the straight line, "the difference between the wheel / output current of each drive unit when it is turned on is reduced." Page 14