JP2012244078A - Organic el illumination device and driving method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To self-repair a defective part of an organic EL element by applying reverse bias, and reduce visual fatigue or the like of a viewer due to flicker of an organic EL illumination device or a non-light-emission period in which viewing is not allowed.SOLUTION: An organic EL illumination device includes an anode, a light-emitting layer, and a cathode sequentially stacked on a transparent substrate. The proportion X of a reverse bias application time Tr to a frame period F is 0.05% or less. The reverse bias application time Tr is more than or equal to the time constant T, which is the product of element capacitance C and wiring resistance R of the organic EL illumination device 1.

Description

  The present invention relates to an organic EL lighting device using an organic EL panel, and particularly to an organic EL lighting device that reduces flickering and eye fatigue of a viewer while self-repairing a defective portion of a display element, and a driving method thereof.

In recent years, organic EL has been in the spotlight as a self-luminous display device, and has been put on the market as a display application due to advantages such as less viewing angle dependency, higher contrast ratio, and thinner film compared to liquid crystal display devices. In the market, flat-screen TVs using organic EL panels are also on the market.
Furthermore, in recent years, organic EL has been attracting attention as a lighting application because it is not a point light emission like LED lighting but a surface light emission, is a thin and light element, and has no restriction in shape.
When an organic EL panel is used for lighting and has a large-area panel structure, the brightness decreases due to the voltage drop due to the wiring resistance of the anode layer (ITO) at a position away from the anode electrode. Even within the same display element, the intensity of light emission differs between a position close to and far from the anode electrode, resulting in uneven brightness.

  Therefore, in the organic EL lighting device, there is a patented structure in which a plurality of organic EL panels having an area where luminance unevenness does not appear in the panel are used and arranged in a plurality of rows and a plurality of columns to increase the area. It is disclosed as document 1.

  In the manufacturing process of the organic EL element, the anode layer and the cathode layer are short-circuited due to a defect such as a thin portion of the light emitting layer or a portion where the light emitting layer is not present and the anode layer and the cathode layer are in contact with each other. There is a problem that light emission failure occurs, and the thin portions of these light emitting layers have a smaller electrical resistance than the others, and the drive current concentrates on those portions, so that the drive current flowing through other normal light emitting layers is reduced. It decreases and the light emission luminance decreases. Since the effect of the short circuit is exerted on other display pixels on the same cathode line, luminance unevenness occurs.

  When an organic EL panel is used as a lighting application, images are not displayed. Therefore, it is important to emit light with uniform brightness within the panel, and uneven brightness due to the above causes is extremely This is an event that you want to avoid.

Patent Document 2 discloses a method for eliminating these defective portions by applying a reverse bias.
FIG. 6 shows a drive circuit when a reverse bias is applied in an organic EL display device of a passive matrix drive system. Such a passive matrix organic EL display device 1000 includes an organic EL element 100 and a cathode line side drive circuit. 200, an anode line side drive circuit 300, and a display controller 400.

  The cathode line side drive circuit 200 switches all the scanning switches 201 to 20m to the reverse bias Vr side, and the anode line side drive circuit 300 switches all the drive switches 301 to 30n to the ground potential (0 V), A period for applying the reverse bias Vr to the display pixel e (reverse bias period (reset period)) is provided.

Cathode ray For example, when the display pixel e ₃₃ in FIG. 6 is a defective portion, in the reverse bias period, flow concentrates leakage current I ₃₃ due to the reverse bias Vr to the defective portion e ₃₃ is, by the expansion pressure luminous layer is vaporized a bends, and further, the cathode line a breaks and bends. Such a cathode ray portion does not emit light, but does not generate a leakage current, so that it is possible to prevent light emission defects in other normal light emitting layers.

  Thus, destroying a defective portion of the organic EL element 100 and preventing a light emitting failure in another normal light emitting layer is called self-repair.

FIG. 3 is a diagram illustrating the difference in appearance of the organic EL panel due to the relationship between the frame frequency F and the reset period Tr.
Since the organic EL panel does not emit light when reverse bias is applied in order to perform self-repair, when the frame frequency F is 50 Hz or less as in the region P, light emission / non-light emission (bright / dark flicker) is continuously visible. Flicker is generated.

  Therefore, as in the region Q, flicker is prevented by setting the frame frequency F of the organic EL panel to a critical fusion frequency of 50 to 70 Hz or higher at which humans do not feel flicker.

JP 2004-69774 A JP-A-11-305727

  However, when a reverse bias is applied at a high frame frequency of, for example, about 50 Hz to 200 Hz, as in the region Q shown in FIG. Therefore, when used for a long time in applications such as lighting, there was a problem that it was easy to get tired.

  The present invention has been made in view of such problems, and an organic EL lighting device capable of self-repairing a defective portion of an organic EL element by applying a reverse bias and reducing eye fatigue of a viewer, and driving thereof The purpose is to provide a method.

In order to solve the above-described problems, the present invention includes an organic EL panel in which an anode, a light emitting layer, and a cathode are sequentially stacked on a transparent substrate, and an illumination signal from a controller is provided. An organic EL lighting device comprising: an anode driving circuit for supplying a first current to the anode; and a cathode driving circuit for supplying a second current to the cathode based on an illumination signal from the control unit.
The control unit supplies a first current to the anode via the anode driving circuit and connects the cathode to a ground potential via the cathode driving circuit, and the anode via the anode driving circuit. A non-light-emitting period for connecting a ground potential and supplying a second current to the cathode through the cathode driving circuit,
The non-light-emitting period is set to a time constant that is 0.05% or less of the light-emitting period and is a product of the element capacitance and the wiring resistance of the organic EL panel,
With such a configuration, it is possible to provide an organic EL lighting device that reduces flickering and eye fatigue of a viewer while self-repairing a defective portion of the organic EL element.

  According to a second aspect of the present invention, the first current is supplied from a constant current source, and the second current is supplied from a constant voltage source. When the organic EL panel emits light, the constant current is supplied. By driving, the organic EL panel can emit light with stable luminance.

  Moreover, in Claim 3, the illumination signal of the said control part is a frame frequency being 1 Hz or less, and the said non-light-emission period is set to 0.5 msec or less, The organic EL lighting device of Claim 1 On the other hand, by driving at a very low frequency, the frequency of reset (non-light emission) is reduced, and organic EL elements that further reduce flickering and eye fatigue of the viewer while self-repairing defective portions of the organic EL element A lighting device can be provided.

  According to a fourth aspect of the present invention, the non-light emitting period is set at the end of the frame, and a reset period is provided in each frame, so that defective portions can be reliably destroyed.

  According to a fifth aspect of the present invention, a plurality of the organic EL panels are provided, and the organic EL panel can be used as a large-area lighting device while being used in a size that does not cause luminance unevenness.

  According to a sixth aspect of the present invention, the anode driving circuit is connected in parallel to the anodes of the plurality of organic EL panels, and the cathode driving circuit is connected in parallel to the cathodes of the plurality of organic EL panels. Therefore, the drive circuit is not provided for each organic EL panel, and the apparatus can be simplified and the cost can be reduced.

  According to a seventh aspect of the present invention, there is provided an organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate, and the ratio of the reverse bias application time to the frame period is 0.05% or less. Further, the reverse bias application time is a driving method of the organic EL lighting device having a time constant which is a product of the element capacitance and the wiring resistance of the organic EL lighting device, and self-repairs a defective portion of the organic EL element. Thus, it is possible to provide a method for driving an organic EL lighting device that reduces flickering and eye fatigue of a viewer.

According to another aspect of the present invention, there is provided an organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate, the frame frequency is 1 Hz or less, and the reverse bias application time is 0. A driving method of the organic EL lighting device having a time constant of 5 msec or less and a time constant which is a product of the element capacitance and the wiring resistance of the organic EL lighting device, Driving method of the organic EL lighting device that reduces the frequency of reset (non-light emission) by driving at a low frequency, self-repairs the defective portion of the organic EL element, and further reduces flickering and eye fatigue of the viewer Can be provided.

  The present invention provides an organic EL lighting device and a driving method thereof for self-repairing a defective portion of an organic EL element in an organic EL lighting device to reduce flickering and eye fatigue of a viewer.

It is the schematic of the organic electroluminescent illuminating device in one Embodiment of this invention. FIG. 4 is a waveform diagram of voltages in the organic EL lighting device and the driving method thereof according to the invention. It is explanatory drawing about the difference in the appearance of the organic electroluminescent panel by the relationship between the frame frequency of an organic electroluminescent panel, and a reset period. FIG. 4 is a result of subjective evaluation of “ease of viewing” of an organic EL lighting device driven according to an embodiment of the present invention, and is a graph of Table 4. FIG. 3 is a result of subjective evaluation of “hardness to fatigue” of the organic EL lighting device driven by the above embodiment, and is a graph of Table 3. It is a drive circuit diagram in the reset period of the organic EL display device of a passive matrix drive system.

Hereinafter, the driving method of the organic EL lighting device 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram of an organic EL lighting device 1. The organic EL lighting device 1 includes a plurality of organic EL panels 10, an anode line 20, a cathode line 30, an anode drive circuit 41, and a rectangular wave generation drive circuit 40 having a cathode drive circuit 42. Yes.
The organic EL panel 10 includes an anode electrode 10a and a cathode electrode 10b. The organic EL panel 10 is formed with an area where luminance unevenness does not appear in the element, and the organic EL panel 10 is arranged in a plurality of rows and a plurality of columns. The lighting device 1 is increased in area.

  The anode line 20 is a wiring between the anode drive circuit 41 and the anode electrode 10a. When the organic EL panel 10 emits light, the anode drive circuit 41 connects the anode line 20 to a constant current source, and the forward bias Vc is used. One current (constant current 0.3 A) is supplied. When no light is emitted, the anode drive circuit 41 connects the anode line 20 to the ground potential (0 V).

  The cathode line 30 is a wiring between the cathode drive circuit 42 and the cathode electrode 10b. When the organic EL panel 10 emits light, the cathode drive circuit 42 connects the anode line 30 to the ground potential (0 V). Further, when no light is emitted, the cathode drive circuit 42 connects the cathode line 30 to a constant voltage source and supplies a second current with a reverse bias Vr.

From this, the drive method of the organic electroluminescent illuminating device 1 of this invention is demonstrated.
Based on the illumination signal from the control unit 2, the rectangular wave generating drive circuit 40 applies a positive potential to the anode line 20 via the anode drive circuit 41 when turned on (light emission from the organic EL panel 10), and via the cathode drive circuit 42. A ground potential (0 V) is applied to the cathode line 30. When OFF (the organic EL panel 10 is reset), a ground potential (0 V) is applied to the anode wire 20, and a negative potential is applied to the cathode wire 30.
The rectangular wave generating drive circuit 40 sets the frame frequency F to 1 Hz or less (the frame period Tf is 1 sec or more), and sets the reset period Tr for performing the reset control in the frame to 0.5 msec or less (ratio of the reset period Tr to the frame period Tf) 0.05% or less) and a time constant T (450 nF × 9Ω≈4 μsec) obtained from the element capacitance C (450 nF) and the wiring resistance R (9Ω) of the organic EL lighting device 1. The light control of the organic EL lighting device 1 is performed by PWM control or PAM control.

  With such a configuration, as described above, leakage current concentrates on the defective portion of the organic EL lighting device 1 generated in the manufacturing process and the like, and the cathode line is bent due to the expansion pressure evaporated from the light emitting layer. Can be bent and bent, and it is possible to reduce eye fatigue and the like of the viewer while reliably preventing light emission defects in other normal light emitting layers.

In the present invention, since the organic EL panel 10 is used for illumination, static driving is performed instead of dynamic driving.
In the case of the dynamic drive method as shown in FIG. 6, the light emission time per scanning line is a time obtained by dividing the frame period Tf by the number of scanning lines. As the number of scanning lines increases, the light emission period per scanning line becomes shorter and the light emission luminance decreases. In order to obtain a desired light emission luminance in this short light emission period, each display pixel e of the organic EL panel 10 is displayed. Therefore, it is necessary to flow a current several times (several times the number of scanning lines) as compared with the case of the static drive method.
That is, in the dynamic drive method, it is necessary to instantaneously flow a large current to each display pixel e of the organic EL panel 10, which causes power loss and a decrease in the lifetime of the organic EL panel 10. The organic EL lighting device 1 as a lighting application uses a static drive system as an embodiment of the present invention.

From this, among the driving methods of the organic EL lighting device 1, the setting method of the frame frequency F and the reset period Tr will be described using Examples 1 and 2 and Comparative Examples 1 to 6.
In the present invention, the organic EL lighting device 1 applies a constant current waveform of 0.3 A (forward bias Vc) in the forward direction, applies a constant voltage waveform of −5 V in the reverse direction, and emits light at a color temperature of 2000 K at 3000 cd / m 2. An external circuit was created to do this.

The frame frequency F was 1 Hz and the reset period Tr was 0.5 msec (the ratio X of the reset period Tr to the frame period Tf was 0.05%).
Table 1 below summarizes the frame frequency F, the reset period Tr, and the ratio X of the reset period Tr to the frame period Tf in Examples 1 and 2 and Comparative Examples 1 to 6.

<Ease of visibility evaluation>
Ten organic EL lighting devices 1 are turned on in the dark room for each of the driving methods of the examples and comparative examples, and subjectivity is evaluated in five stages (5: easy to see, 1: difficult to see). The evaluation results were organized.

  FIG. 4 is a graph showing the results of Table 2 above. Conventional Example 1 (F = 100 Hz, Tr = 0 sec), Conventional Example 5 (F = 2 Hz, Tr = 0.5 sec), Example 1 (F = 1 Hz, Tr = 0.5 sec) and Example 2 (f = 0.1 Hz, Tr = 0.5 sec) were confirmed to be easy to see.

<Evaluation of fatigue resistance>
The organic EL lighting device 1 is turned on in the dark room by 10 units for each of the driving methods of the examples and comparative examples, and subjectivity is evaluated in five stages (5: less fatigue, 1: easy to fatigue). Table 3 summarizes the evaluation results.

  FIG. 5 is a graph showing the results of Table 3 above. Conventional example 1 (F = 100 Hz, Tr = 0 sec), Example 1 (F = 1 Hz, Tr = 0.5 sec), Example 2 (F = 0.1 Hz, Tr = 0.5 sec), it was confirmed that it was less fatigued.

<Short-circuit evaluation>
The organic EL lighting device 1 was turned on for 450 hours in an environment of 80 ° C., the presence or absence of occurrence of a short circuit was evaluated, and the evaluation results are summarized in Table 4 below. In addition, the average values of the evaluation results of visibility and fatigue resistance were arranged in the same manner.

From Table 4 above, a short circuit was confirmed in Conventional Example 1 (F = 100 Hz, Tr = 0 sec).
The region P (conventional examples 3 to 6) in FIG. 3 is a region where the frame frequency F is lower than the critical fusion frequency and thus flicker occurs, which makes it difficult to see and eye fatigue.
In the region Q (conventional examples 1 and 2), since the frame frequency F is equal to or higher than the critical fusion frequency, flicker does not occur, but reset (non-light emission) occurs in a short period (non-light emission frequently occurs). There are problems such as easy eye fatigue.
In the region R, the time constant T is equal to or less than the time constant T of the organic EL panel 10, and the original purpose of self-repair cannot be achieved.
In the region S1, the reset period ratio X is 0.05% or less, and eye fatigue is suppressed. In the region S2, since the reset period ratio X is sufficiently short as 0.05% or less, flicker is not visually recognized, and furthermore, since the frame frequency F is low, the frequency of non-light emission due to reset is low, and thus eye fatigue is caused. Is suppressed.

  With such an organic EL lighting device and its driving method, a defective portion of the organic EL element can be self-repaired by applying a reverse bias, and eye fatigue of a viewer can be reduced.

DESCRIPTION OF SYMBOLS 1 Organic EL lighting device 2 Control part 10 Organic EL panel 10a Anode electrode 10b Cathode electrode 20 Anode line 30 Cathode line 40 Rectangular wave generation drive circuit 41 Anode drive circuit 42 Cathode drive circuit Vc Forward bias Vr Reset voltage (reverse bias)
Tf Frame period Tr Reset period (reset period)
F Frame frequency X Reset period ratio 1000 Passive matrix organic EL display device 100 Organic EL panel 200 Cathode line scanning circuit 300 Anode line scanning circuit 400 Display controller a Cathode line b Anode line e Display pixel

Claims (8)

An organic EL panel comprising an anode, a light emitting layer, and a cathode laminated on a transparent substrate in sequence, an anode driving circuit for supplying a first current to the anode based on an illumination signal from the control unit; In an organic EL lighting device comprising: a cathode drive circuit that supplies a second current to the cathode based on an illumination signal from a control unit;
The control unit supplies a first current to the anode via the anode driving circuit and connects the cathode to a ground potential via the cathode driving circuit, and the anode via the anode driving circuit. A non-light-emitting period for connecting a ground potential and supplying a second current to the cathode through the cathode driving circuit,
The non-light emitting period is 0.05% or less of the light emitting period, and is set to a time constant that is a product of the element capacitance and the wiring resistance of the organic EL panel or more. apparatus.   The organic EL lighting device according to claim 1, wherein the first current is supplied from a constant current source, and the second current is supplied from a constant voltage source.   3. The organic EL illumination according to claim 1, wherein the illumination signal of the control unit has a frame frequency of 1 Hz or less and the non-light emission period is set to 0.5 msec or less. apparatus.   The organic EL lighting device according to any one of claims 1 to 3, wherein the non-light emitting period is set at a final end of a frame.   The organic EL lighting device according to claim 1, comprising a plurality of the organic EL panels.   The anode drive circuit is connected in parallel to the anodes of the plurality of organic EL panels, and the cathode drive circuit is connected in parallel to the cathodes of the plurality of organic EL panels. Item 6. The organic EL lighting device according to Item 5.   An organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate, and the ratio of the reverse bias application time to the frame period is 0.05% or less. The driving method of an organic EL lighting device, characterized in that time is equal to or more than a time constant that is a product of an element capacitance and a wiring resistance of the organic EL lighting device.   An organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate, the frame frequency is 1 Hz or less, and the reverse bias application time is 0.5 msec or less. A driving method of an organic EL lighting device, wherein the driving time is equal to or more than a time constant that is a product of an element capacity and a wiring resistance of the lighting device.

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