JP5751011B2 - Organic EL lighting device and driving method thereof - Google Patents

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. 3, the reverse bias period (non-light emission period) also occurs with a short cycle (non-light emission frequently occurs). 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.

The present invention is to solve the problems described above, in claim 1, and an anode on a transparent substrate, a light emitting layer, an organic EL panel obtained by laminating a cathode, sequentially, a first current before Symbol anode an anode drive circuit for supplying, in the organic EL lighting device comprising a cathode driving circuit for supplying a second current to the prior SL cathode, and a control unit for controlling said cathode driving circuit and the anode driving circuit, wherein the control unit In the control of the anode driving circuit and the cathode driving circuit, a first current is supplied to the anode via the anode driving circuit for each frame, and the cathode is connected to the ground potential via the cathode driving circuit. A non-emission period, and a non-emission period, and a non-emission period in which the anode is connected to the ground potential via the anode drive circuit and a second current is supplied to the cathode via the cathode drive circuit. It is, of the frame And 0.05% or less with respect to the period, and the are those which are set to at least the time constant is the product of the device capacitance and the wiring resistance of the organic EL panel, by such a configuration, a defective portion of the organic EL device It is possible to provide an organic EL lighting device that reduces flickering and eye fatigue of the viewer while self-healing.

  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.

Further, in claim 3, wherein the control is in the control of the anode driving circuit and the cathode driving circuit, wherein the frequency of the frame is less than or equal to 1 Hz, and the non-emission period in said frame below 0.5msec The organic EL lighting device according to claim 1 is driven at a very low frequency to reduce the frequency of reset (non-light emission) and to self-repair defective portions of the organic EL element. On the other hand, it is possible to provide an organic EL lighting device that further reduces flickering and eye fatigue of the viewer.

Further, in claim 4, wherein the non-light emitting period has been set to the last tail of the frame, the reset period is provided in each frame, it is possible to reliably destroy the defective portion.

  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 invention , there is provided a driving method for an organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate, and a first current is supplied to the anode for each frame. A non-light-emitting period in which the cathode is connected to the ground potential, a non-light-emitting period in which the anode is connected to the ground potential, a second current is supplied to the cathode, and a reverse bias is applied . the ratio of the application time of the reverse bias is not more than 0.05%, further application time of the reverse bias of the organic EL lighting device is constant or when the the product of the device capacitance and the wiring resistance of the organic EL lighting device It is a driving method, and it is possible to provide a driving method of 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 another aspect of the present invention , there is provided a driving method for an organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate, and a first current is supplied to the anode for each frame. A non-emission period in which the cathode is connected to the ground potential, a non-emission period in which the anode is connected to the ground potential, a second current is supplied to the cathode, and a reverse bias is applied. and at 1Hz or less, a further method for driving an organic EL lighting device is constant over time the application time of the reverse bias is a product of the device capacitance and the wiring resistance of less and the organic EL lighting device 0.5 msec, claim 7 is driven at a very low frequency to reduce the frequency of reset (non-light emission), self-repair the defective portion of the organic EL element, Eye The driving method of the organic EL lighting device further reduce the fatigue 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. It is a wave form diagram of a voltage in the organic EL lighting device of the above-mentioned invention, and its drive method. 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 in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate;
Organic comprising an anode drive circuit for supplying a first current to the prior SL anode, a cathode drive circuit for supplying a second current to the prior SL cathode, and a control unit for controlling said anode driving circuit and the cathode driving circuit In an EL lighting device,
In the control of the anode driving circuit and the cathode driving circuit, the control unit supplies a first current to the anode via the anode driving circuit and grounds the cathode via the cathode driving circuit for each frame. A light emission period to be connected to the potential, and a non-light emission period in which the anode is connected to the ground potential via the anode drive circuit and a second current is supplied to the cathode via the cathode drive circuit , and
The non-light emitting period is 0.05% or less with respect to the cycle of the frame , and is set to a time constant that is a product of the element capacitance and the wiring resistance of the organic EL panel. Organic EL lighting device.   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. In the control of the anode driving circuit and the cathode driving circuit , the control unit is configured such that the frequency of the frame is 1 Hz or less and the non-light emission period in the frame is set to 0.5 msec or less. The organic EL lighting device according to claim 1 or 2, characterized in that The non-light emitting period, the organic EL lighting device according to any one of claims 1 to 3, characterized in that, set in the final tail of the 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. A driving method of an organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate , wherein a first current is supplied to the anode for each frame, and the cathode is grounded. a light emitting period to connect to, then connect the anode to the ground potential, the second current is supplied to the cathode, and a non-emission period for applying the reverse bias, the reverse bias application time to the period of the frame The driving of the organic EL lighting device, wherein the ratio is 0.05% or less, and the application time of the reverse bias is a time constant that is a product of the element capacitance and the wiring resistance of the organic EL lighting device Method. A driving method of an organic EL lighting device in which an anode, a light emitting layer, and a cathode are sequentially laminated on a transparent substrate , wherein a first current is supplied to the anode for each frame, and the cathode is grounded. a light emitting period to connect to, then connect the anode to the ground potential, the second current is supplied to the cathode, and a non-emission period for applying a reverse bias, the frequency of the frame is equal to or less than 1 Hz, further wherein the application time of the reverse bias is constant over time is the product of the device capacitance and the wiring resistance of less and the organic EL lighting device 0.5 msec, the driving method of the organic EL lighting device, characterized in that.

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