Background technology
In recent years, OLED, as a kind of emerging technology, has been applied to lighting technical field and display technique field more and more.Owing to adopting the lighting device of OLED, there is the plurality of advantages such as energy consumption is low, complanation, maximization, become the focus that following field of illuminating device people pay close attention to.
Fig. 1 is existing OLED illuminator structure schematic diagram.As shown in Figure 1, existing OLED lighting device comprises substrate 1 and cap 2, wherein, substrate 1 deposits anode 3, and anode 3 is provided with very thin multilayer organic layer 4, and is positioned at the negative electrode 5 on organic layer 4.The anode of existing OLED is monoblock ITO conductive layer, OLED lighting device technique prepared by this mode is relatively simple, but but due to the excessive reason of anode ITO resistance, there are the following problems: 1) uniformity of luminance is poor, and non-uniform light is up to more than 40%; 2) the local thermal value that brightness is high is very large, easy burn-out thus cause whole light source luminescent to lose efficacy; 3) overall brightness is difficult to improve; 4) as long as occur in OLED device that a defect point will cause whole illuminating device luminous inefficacy.
And existing OLED lighting device also needs a special DC constant current power supply, and cost also costly.
In addition, have also appeared a kind of Activematric OLED display panel (AMOLED) in recent years, under it, be coated with thin film transistor (TFT) (TFT) array.AMOLED, because power consumption is low, refresh rate is high, is thus mainly applicable to computer monitor, large screen television and the display field such as electronics billboard or billboard.Fig. 2 shows the electronic line structure schematic diagram of the display that existing AMOLED makes, wherein TFT matrix of pixel cells 6 comprises 1 TFT and two electric capacity, and be connected with gate drivers 7 by sweep trace G1, G2 ... Gn, be connected with data driver 8 by data line D1, D2 ... Dm, gate drivers 7 is connected with timing controller 9 with data driver 8.In actual applications, when making display by AMOLED, in order to make display effect good, usually in TFT pixel cell, also compensating circuit will be adopted, at this moment each TFT pixel cell can comprise several TFT and several electric capacity, and this makes the complex structure of TFT pixel cell, adds existing TFT pixel cell area size little (being generally 70 μm × 210 μm), therefore there is following problem: 1) manufacture craft is more difficult, produce yield low; 2) if the bottom outlet OLED of operation maturation, due to pixel aperture ratio often very low (usually less than 40%), cause its stability of photoluminescence poor.This two problems limits the large-scale production of AMOLED to a certain extent.
Embodiment
By embodiment, the present invention is described in further detail below in conjunction with accompanying drawing, but the present invention is not restricted to this.
In the prior art, active OLED (i.e. AMOLED) is mainly used in display.Because display is in order to control the gray scale variation of each display pixel so must adopt capacitor, circuit relative complex.And lighting device does not need the gray scale variation controlling each pixel, therefore can not make electricity container, and only adopt TFT.Based on this thought, present inventor expects active OLED (i.e. AMOLED) for making lighting device, circuit so not only can be made simple, and due to AMOLED employing TFT, each light emitting pixel unit can be controlled separately, so when defect appears in some light emitting pixel unit, other light emitting pixel unit can not be affected, whole illuminating device luminous inefficacy more can not be caused.
In addition, because grid lead exists resistance, so make voltage in the flow direction to reduce gradually, the electric current I that TFT provides
dsalso can decrease.Because OLED is current d pivability device, I
dsreduction can cause coupled OLED luminosity also can decrease, thus affects the uniformity of luminance of whole lighting device to a certain extent.For this reason, the present invention considers that there is pressure drop region in the flow direction uses the TFT of greater number to reduce the impact of resistance on the luminosity of OLED.
Based on above-mentioned consideration, the invention provides a kind of OLED illumination device, it is by external control Power supply.Particularly, this OLED illumination device comprises plural light emitting pixel unit, and each light emitting pixel unit comprises an Organic Light Emitting Diode and one or more TFT.In each light emitting pixel unit, grid, the drain electrode of TFT are all connected to external control power supply, and the source electrode of TFT is connected to the anode of the Organic Light Emitting Diode in light emitting pixel unit, and the negative electrode of described Organic Light Emitting Diode is connected to external control power supply.Wherein, the quantity of TFT in the light emitting pixel unit of external control power supply is less than the quantity away from the TFT in the light emitting pixel unit of external control power supply, to die down brought impact for stream ability with the TFT alleviated away from external control power supply.
In above-mentioned OLED illumination device of the present invention, in described light emitting pixel unit, the TFT quantity in the light emitting pixel unit of external control power supply is at least than few one of the light emitting pixel unit away from external control power supply.
In addition, in each light emitting pixel unit, described TFT can be arranged on any side of light emitting pixel unit or a few side or corner as requested, and described TFT can be non-crystalline silicon tft or multi-crystal TFT.In addition, in each light emitting pixel unit, grid, the drain potential of described TFT can be different, also can be identical.
In addition, described external control power supply can be DC constant voltage power supply, also can be the power supply containing compensating circuit.Each light emitting pixel cellar area size can be 100 μm × 100 μm and arrive 2cm × 2cm.
On the one hand, the present invention is owing to adopting TFT, so each light emitting pixel unit can be controlled separately, on the other hand, owing to present invention contemplates the resistance of grid lead etc. to the impact of the electric current that TFT provides, use the TFT of greater number in the region away from external control power supply, thus the uniformity of luminance of lighting device of the present invention obtains large increase, at least can reach more than 90%.
In addition, due to TFT be voltage driven and this as controllable current source, so the power supply plan of active OLED lighting device of the present invention is simply cheap, such as, can adopt DC constant voltage Power supply scheme, general notebook adapter such as can be used to be used as power supply.
In addition, the present invention is not owing to making electricity container in light emitting pixel unit, and circuit is simplified, thus makes light emitting pixel unit light-emitting area comparatively large, and aperture opening ratio up to more than 65%, can improve stability of photoluminescence.In addition, lighting device of the present invention is so high unlike display to the uniformity requirements of each TFT, and therefore make yield higher, cost also becomes cheap.
Also have, because the production equipment producing active OLED lighting device and active OLED display can share, so it is produce active OLED lighting device or production displayer that a set of production equipment can switch according to market situation, thus can control preferably in manufacture and equipment cost.
Active mode is applicable to OLED illumination by the present invention, makes to utilize the present invention more easily to make large area lighting device.
Provide several specific embodiments of the lighting device of the active organic LED made by the present invention below.
Embodiment (one)
Fig. 3 shows according to a kind of active OLED lighting device of the present invention.Fig. 4 shows the equivalent circuit diagram corresponding with the active OLED lighting device of the present invention shown in Fig. 3.
As shown in Figure 3 and Figure 4, active OLED lighting device of the present invention comprises 4 light emitting pixel unit, and is powered by external control power supply 13.Wherein, external control power supply 13 is powered from top to the TFT each light emitting pixel unit.TFT in two light emitting pixel unit 1 on top and two light emitting pixel unit 2 102 of bottom all adopts identical non-crystalline silicon tft.
For the area of light emitting pixel unit for 0.5mm × 0.5mm, suppose the electron mobility μ of non-crystalline silicon tft
efffor 0.5cm
2/ vs, unit area gate oxide capacitance C
oxbe 2.44 × 10
-4f/m
2the difference Vgs-Vth of the voltage between the gate-source of light emitting pixel unit 1 and light emitting pixel unit 2 102 non-crystalline silicon tft and threshold voltage is made to be respectively 6V and 5V because lead-in wire exists resistance, light emitting pixel unit 1 is 25 μm/6 μm with the TFT channel width-over-length ratio W/L of light emitting pixel unit 2 102, then can obtain according to following formula 1, light emitting pixel unit 1 is respectively 0.9 μ A and 0.635 μ A with the TFT of light emitting pixel unit 2 102 for flow valuve Ids.
(formula 1)
At this moment, if the aperture opening ratio of the luminescence efficiency of OLED itself, light emitting pixel unit and brightness of illumination are respectively 50cd/A, 68% and 1000cd/m
2, then known by following calculating, needed for each light emitting pixel unit 1, the quantity of non-crystalline silicon tft is at least 8:
Each light emitting pixel unit 1 true brightness is 1000cd/m2 ÷ 68%=1471cd/m
2,
Needed for each light emitting pixel unit 1, current density is 0.001 × 1471cd/m
2÷ 50cd/A=2.94 × 10
-2mA/mm
2,
Needed for each light emitting pixel unit 1, electric current is 2.94 × 10
-2mA/mm
2× 0.5mm × 0.5mm × 1000=7.35 μ A,
Then the quantity of TFT needed for each light emitting pixel unit 1 is 7.35 μ A ÷ 0.9 μ A ≈ 8.
In like manner can obtain, needed for each light emitting pixel unit 1, the quantity of TFT is about 8.
Known by above-mentioned calculating, each light emitting pixel unit 1 comprises at least 8 non-crystalline silicon tfts and an OLED, and each light emitting pixel unit 2 102 comprises at least 11 non-crystalline silicon tfts and an OLED.
As shown in Figure 3 and Figure 4, for light emitting pixel unit 1,8 TFT 11 are connected in parallel and are arranged at the top of each light emitting pixel unit 1, the grid of described 8 TFT 11 and drain electrode are connected to external control power supply 13 respectively by gate control lines 14 with drain control line 15 and current potential is different, the source electrode of described 8 TFT 11 is connected to the anode of OLED 12, and the negative electrode of OLED 12 is by cathodic control line 16 ground connection.For light emitting pixel unit 2 102,11 TFT 11 are connected in parallel and are arranged at the top of each light emitting pixel unit 1, the grid of described 11 TFT 11 and drain electrode are connected to external control power supply 13 respectively by gate control lines 14 with drain control line 15 and current potential is different, the source electrode of described 11 TFT 11 is connected to the anode of OLED 12, and the negative electrode of OLED 12 is by cathodic control line 16 ground connection.Wherein, described gate control lines 14, drain control line 15 and cathodic control line 16 can be plain conductor.Want to be noted that, annexation in a light emitting pixel unit 1 and a light emitting pixel unit 2 102 between each parts and wherein between each parts and external control power supply is only shown in Fig. 3 and Fig. 4 respectively, in other light emitting pixel unit 1 and light emitting pixel unit 2 102 between each parts and wherein also there is identical annexation between each parts with external control power supply, but do not draw one by one.
Embodiment (two)
Fig. 5 gives another embodiment of active OLED lighting device of the present invention, in this embodiment, non-crystalline silicon tft respectively at being arranged on four angles of each light emitting pixel unit 1 and each light emitting pixel unit 2 102, all the other same embodiments (one).Want to be noted that, a light emitting pixel unit 1 and the annexation between a light emitting pixel unit 2 102 and external control power supply are only shown, other light emitting pixel unit 1 and there is identical annexation between light emitting pixel unit 2 102 with external control power supply in Fig. 5.
Embodiment (three)
Fig. 6 gives another embodiment of active OLED lighting device of the present invention, this embodiment and embodiment () unlike, gate control lines 14 and drain control line 15 link together, and then be jointly connected to external control power supply 13, at this moment gate control lines is identical with drain control line current potential.Want to be noted that, a light emitting pixel unit 1 and the annexation between a light emitting pixel unit 2 102 and external control power supply are only shown, other light emitting pixel unit 1 and there is identical annexation between light emitting pixel unit 2 102 with external control power supply in Fig. 6.
Embodiment (four)
In this embodiment, light emitting pixel cellar area is 10mm × 10mm, can obtain according to as calculating similar in embodiment (), each light emitting pixel unit 1 comprises at least 3267 TFT and OLED in parallel, and the source electrode of described at least 3267 TFT is connected with the anode of described OLED by source electrode control line.Light emitting pixel unit 2 102 comprises at least 4630 TFT and OLED in parallel, and the source electrode of described 4630 TFT is connected with the anode of described OLED by source electrode control line, all the other same embodiments (one).
Wherein TFT can be arranged at the top of light emitting pixel unit, side or a few side or corner.
Gate control lines 14 and the drain control line 15 of all TFT can be connected to external control power supply 13, current potential is different from each other, also can link together and then be connected to external control power supply 13, at this moment gate control lines 14 is identical with drain control line 15 current potential.
Above-described embodiment, all for the explanation that non-crystalline silicon tft carries out, in fact also can adopt polysilicon, such as low temperature polycrystalline silicon LTPS.In addition, how several the TFT quantity of number ratio in the light emitting pixel unit of external control power supply away from the TFT in the light emitting pixel unit of external control power supply is can according to circumstances determine, be not limited to 1 described in above-described embodiment, such as also can how 2,3 even more.
Although the present invention is described by specific embodiment, the present invention is not limited to described embodiment.Protection scope of the present invention is only limited by claims.In detail in the claims, term " comprises " and does not get rid of other parts of existence.In addition, although each feature comprises in different claims, these features can combine, and the content comprised in different claims does not mean that the combination of feature is infeasible and/or disadvantageous.In addition, single implication is not got rid of multiple.Therefore, the implication of " " etc. is not got rid of multiple.
More than describing is only the specific embodiment of the present invention; it should be noted that; for the person of ordinary skill of the art; under the premise of without departing from the spirit of the present invention; some improvement, amendment and distortion can be done, these improve, revise and be out of shape all should be considered as dropping in the protection domain of the application.