JP6522766B2 - Light emitting device - Google Patents

Description

  The present invention relates to a light emitting device.

  An organic EL element is one of the light sources of the light emitting device. The organic EL element has a configuration in which an organic layer is disposed between two electrodes. Some organic EL elements have a plurality of organic layers between two electrodes. In recent years, for example, an organic EL element having a plurality of organic layers having different light emission characteristics has also been proposed.

  For example, in Patent Document 1, a first electrode, a first organic layer, a second electrode, a second organic layer, a third electrode, a third organic layer, and a fourth electrode made of ITO are formed on a substrate. It has a configuration of sequentially overlapping. In such a configuration, the first electrode is grounded, the output terminal of the first operational amplifier is connected to the second electrode, and the output terminal of the second operational amplifier is connected to the third electrode. The output terminal of the third operational amplifier is connected to the four electrodes. The noninverting input terminal of the first operational amplifier, the noninverting input terminal of the second operational amplifier, and the noninverting input terminal of the third operational amplifier are connected to different input terminals. The output terminal of the first operational amplifier is also connected to the noninverting input terminal of the second operational amplifier, and the output terminal of the second operational amplifier is also connected to the noninverting input terminal of the third operational amplifier.

  Further, in Patent Document 2, in an organic EL device in which a first electrode, a first light emitting layer, an intermediate electrode layer, a second light emitting layer, and a second electrode are laminated in this order, the second electrode and the third electrode are variable resistance It is described to connect through. Patent Document 2 describes that the luminance can be adjusted in the second light emitting layer by adjusting the resistance of the variable resistor.

Japanese Patent Application Publication No. 2001-511296 JP, 2014-150000, A

  In an organic EL element in which a plurality of light emitting layers having different light emitting colors are stacked, in order to adjust the color of light emitted from the organic EL element, the luminances of the plurality of light emitting layers can be controlled independently of each other It is preferable to do. However, in the method described in Patent Document 1, when the amount of current in the second organic layer is increased by controlling the second operational amplifier, the amount of current flowing from the second organic layer to the first organic layer also increases. It will Therefore, it is difficult to make the ratio of the luminance of the first organic layer to the luminance of the second organic layer equal to or less than a predetermined value.

  Further, in the method described in Patent Document 2, the brightness of the first organic layer is adjusted by reducing the amount of current flowing from the second organic layer to the first organic layer using a variable resistor. For this reason, although the ratio of the luminance of the first organic layer to the luminance of the second organic layer can be lowered, this ratio can not be set to a certain value or more.

  One of the problems to be solved by the present invention is to be able to control the ratio of the luminance of the first organic layer to the luminance of the second organic layer in a wide range.

The invention according to claim 1 comprises a first electrode;
A second electrode overlapping the first electrode;
A third electrode overlapping the second electrode;
A first organic layer located between the first electrode and the second electrode and including a light emitting layer;
A second organic layer located between the second electrode and the third electrode and including a light emitting layer;
A first current source connected to the first electrode;
A switch connecting the second electrode and the third electrode;
A second current source connected to the second electrode;
A control unit that controls the switch and the second current source;
Equipped with
The peak wavelength of the emission spectrum of the first organic layer is a light emitting device different from the peak wavelength of the emission spectrum of the second organic layer.

  The objects described above, and other objects, features and advantages will become more apparent from the preferred embodiments described below and the following drawings associated therewith.

It is a sectional view showing the composition of the light emitting device concerning an embodiment. It is the equivalent circuit schematic of the light-emitting device shown in FIG. It is a figure for demonstrating the control mode of a control part. It is a figure for demonstrating the 1st mode. It is a figure for demonstrating the 1st mode. It is a figure for demonstrating a 2nd mode. It is a figure for demonstrating a 2nd mode. It is a figure for demonstrating a 2nd mode. It is a figure for demonstrating a 2nd mode. It is a figure for demonstrating the 3rd mode. It is a figure for demonstrating the 3rd mode. FIG. 7 is a view showing a configuration of a light emitting device according to a modification example 1; It is a figure for demonstrating the operation | movement of the light-emitting device which concerns on embodiment. FIG. 8 is a diagram for explaining the operation of the light emitting device according to the modification example 1; FIG. 14 is a diagram for describing an operation of a control unit according to a modification 2; FIG. 14 is a diagram for describing an operation of a control unit according to a modification 2;

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

  FIG. 1 is a cross-sectional view showing the configuration of a light emitting device 10 according to the embodiment. FIG. 2 is an equivalent circuit diagram of the light emitting device 10 shown in FIG. The light emitting device 10 according to the embodiment includes a first electrode 110, a first organic layer 120, a second electrode 130, a second organic layer 140, a third electrode 150, a control unit 210, a first current source 220, a switch 230, and A second current source 240 is provided. The second electrode 130 overlaps the first electrode 110, and the third electrode 150 overlaps the second electrode 130. The first organic layer 120 is located between the first electrode 110 and the second electrode 130, and the second organic layer 140 is located between the second electrode 130 and the third electrode 150. The first current source 220 is connected to the first electrode 110, and the second current source 240 is connected to the second electrode 130. The switch 230 also connects the second electrode 130 and the third electrode 150. The peak wavelength of the emission spectrum of the first organic layer 120 is different from the peak wavelength of the emission spectrum of the second organic layer 140. In other words, the luminescent color of the first organic layer 120 is different from the luminescent color of the second organic layer 140. The controller 210 controls the first current source 220, the switch 230, and the second current source 240. The details will be described below.

  The first electrode 110, the first organic layer 120, the second electrode 130, the second organic layer 140, and the third electrode 150 are formed on the first surface of the substrate 100.

The substrate 100 is formed of, for example, a translucent material such as glass or translucent resin. The substrate 100 is, for example, a polygon such as a rectangle. Here, the substrate 100 may have flexibility. When the substrate 100 has flexibility, the thickness of the substrate 100 is, for example, 10 μm or more and 1000 μm or less. In particular, when the substrate 100 is made of a glass material and flexible, the thickness of the substrate 100 is, for example, 200 μm or less. When the substrate 100 is made of a resin material and flexible, for example, PEN (polyethylene naphthalate), PES (polyether sulfone), PET (polyethylene terephthalate), or polyimide is included as a material of the substrate 100. It is formed. When the substrate 100 contains a resin material, an inorganic barrier film such as SiN _x or SiON is formed on at least the light emitting surface (preferably both surfaces) of the substrate 100 in order to prevent moisture from passing through the substrate 100. ing.

  The first electrode 110 and the second electrode 130 are transparent electrodes having light transparency. The transparent conductive material constituting the transparent electrode is a metal-containing material such as metal oxide such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), IWZO (Indium Tungsten Zinc Oxide), ZnO (Zinc Oxide), etc. is there. The thickness of the first electrode 110 and the second electrode 130 is, for example, 10 nm or more and 500 nm or less. The first electrode 110 and the second electrode 130 are formed by using, for example, a sputtering method or a vapor deposition method. The first electrode 110 and the second electrode 130 may be carbon nanotubes, or a conductive organic material such as PEDOT / PSS. Further, in particular, the second electrode 130 has a structure in which a layer containing a material of a third electrode 150 described later is laminated on a layer containing these materials, or a structure in which a material of the third electrode 150 is arranged in a network. It may be. In this case, the layer made of the material of the third electrode 150 is preferably 500 nm or less.

  The third electrode 150 is made of, for example, a metal selected from the first group consisting of Al, Au, Ag, Pt, Mg, Sn, Zn, and In, or an alloy of a metal selected from the first group. Contains a metal layer. In this case, the third electrode 150 has a light shielding property. The thickness of the third electrode 150 is, for example, 10 nm or more and 500 nm or less. However, the third electrode 150 may be formed using the material exemplified as the material of the first electrode 110. The third electrode 150 is formed using, for example, a sputtering method or a vapor deposition method.

  Each of the first organic layer 120 and the second organic layer 140 has a configuration in which a hole injection layer, a light emitting layer, and an electron injection layer are stacked in this order. A hole transport layer may be formed between the hole injection layer and the light emitting layer. In addition, an electron transport layer may be formed between the light emitting layer and the electron injection layer. The first organic layer 120 and the second organic layer 140 may be formed by vapor deposition. In addition, at least one layer of the first organic layer 120, for example, a layer in contact with the first electrode 110 may be formed by an application method such as an inkjet method, a printing method, or a spray method. In addition, at least one layer of the second organic layer 140, for example, a layer in contact with the second electrode 130 may be formed by an application method such as an inkjet method, a printing method, or a spray method. In this case, the remaining layers of the first organic layer 120 and the remaining layers of the second organic layer 140 are formed by vapor deposition. Alternatively, all layers of the first organic layer 120 and all layers of the second organic layer 140 may be formed using a coating method.

  As described above, the peak wavelength of the emission spectrum of the first organic layer 120 is different from the peak wavelength of the emission spectrum of the second organic layer 140. For example, the first organic layer 120 has a peak in a red wavelength range, and the second organic layer 140 has a peak on a shorter wavelength side than red (for example, a blue wavelength range). Therefore, the luminescent color of the light emitting device 10 is a color (for example, white) in which the luminescent color of the first organic layer 120 and the luminescent color of the second organic layer 140 are mixed. The emission color of the light emitting device 10 can be changed by changing the ratio of the luminance of the second organic layer 140 to the luminance of the first organic layer 120. The peak of the first organic layer 120 and the peak of the second organic layer 140 may be reversed.

  The first electrode 110 is an anode of the first organic layer 120, and the output terminal of the first current source 220 is connected. Further, the second electrode 130 is a cathode of the first organic layer 120 and is an anode of the second organic layer 140. The second electrode 130 is further connected to the output terminal of the second current source 240. The third electrode 150 is a cathode of the second organic layer 140, and a ground potential is applied.

  The first current source 220 and the second current source 240 are current sources and are controlled by the controller 210. The first current source 220 and the second current source 240 are, for example, switching regulators. However, the first current source 220 and the second current source 240 may be current sources of other structures.

  In addition, the light emitting device 10 has a switch 230. The switch 230 is, for example, a transistor for power control, and connects the second electrode 130 and the third electrode 150. The controller 210 controls the opening and closing of the switch 230. As described in detail later, the control unit 210 performs PWM (Pulse width modulation) control on the switch 230.

Next, the operation of the control unit 210 will be described. As shown in FIG. 3, the control unit 210 causes the first organic layer 120 and the second organic layer 140 to emit light in three patterns of a first mode, a second mode, and a third mode. In the first mode, the controller 210 turns on the first current source 220 and turns off the switch 230 and the second current source 240. As a result, currents of the same magnitude flow through the first organic layer 120 and the second organic layer 140. In the second mode, the control unit 210 turns on the first current source 220, turns off the second current source 240, and performs PWM control of the switch 230. As a result, the current flowing through the second organic layer 140 is less than or equal to the current flowing through the first organic layer 120. In the third mode, the controller 210 turns on the first current source 220 and the second current source 240 and turns off the switch 230. Accordingly, the current flowing through the second organic layer 140 is larger than the current flowing through the first organic layer 120. The details will be described below. In the following description, as shown in FIG. 2, the current flowed by the first current source 220 is I ₁ , the current flowed by the second current source 240 is I ₂ , the current flowed through the first organic layer 120 is I ₀₁ , the second the current flowing through the organic layer 140 to _{I 02.}

First, the first mode will be described with reference to FIGS. 4 and 5. In the first mode, the controller 210 causes a current to flow from the first current source 220 to the first electrode 110 with the switch 230 open. At this time, the control unit 210 does not operate the second current source 240. That is, I ₂ = 0. Thereby, the current I ₁ flows from the first electrode 110 to the third electrode 150. As a result, the current I ₀₁ flowing through the first organic layer 120 and the current I ₀₂ flowing through the second organic layer 140 both become I ₁ . Therefore, as shown in FIGS. 4 and 5, when the current _{I 1} from the first current source 220 increases, the current _{I 01} and the current _{I 02} in proportion to _{I 1} increases, so that the first organic The intensity (brightness) of the light emitted by the layer 120 and the intensity (brightness) of the light emitted by the second organic layer 140 also increase. On the other hand, when the current _{I 1} from the first current source 220 is reduced, the current _{I 01} and the current _{I 02} in proportion to _{I 1} decreases, the intensity of that light first organic layer 120 emits light (luminance) And the intensity (brightness) of the light emitted by the second organic layer 140 also decreases.

Next, the second mode will be described with reference to FIGS. 6, 7, 8 and 9. In the second mode, the controller 210 causes a current to flow from the first current source 220 to the first electrode 110. In addition, the control unit 210 repeats the opening and closing of the switch 230 to perform PWM control. At this time, the second current source 240 does not operate. That is, I ₂ = 0.

First, as shown in FIG. 6, the current I ₀₁ flowing through the first organic layer 120 is equal to the current I ₁ flowing from the first current source 220 as in the first mode.

Next, the current I ₀₂ flowing through the second organic layer 140 will be described using FIGS. 7 and 8. While the switch 230 is open, the current I ₀₁ (= I ₁ ) flowing through the second organic layer 140 flows to the third electrode 150 via the second electrode 130 and the second organic layer 140. On the other hand, while the switch 230 is closed, the current I ₀₁ flowing through the first organic layer 120 flows directly from the second electrode 130 to the third electrode 150 through the switch 230, so the current flows through the second organic layer 140. Absent. Therefore, assuming that the length of one cycle of opening and closing the switch 230 is T and the length of a period in which the switch 230 is closed (on) in one cycle is H as shown in FIG. The current flowing through the two organic layers 140 is I ₁ × (1−H / T) (duty ratio). Therefore, as shown in FIG. 8, the control unit 210 controls the current I ₀₂ flowing through the second organic layer 140 to a desired value of I ₁ or less by controlling the duty ratio in the PWM control of the switch 230. can do.

  As a result, as shown in FIG. 9, as the duty ratio in the PWM control of the switch 230 increases, the brightness of the second organic layer 140 decreases. Therefore, the luminance of the second organic layer 140 can be reduced while the luminance of the first organic layer 120 is fixed.

Next, the third mode will be described using FIG. 10 and FIG. In the third mode, as described above, the control unit 210 turns on the first current source 220 and the second current source 240 with the switch 230 open. Thus, as shown in FIG. 10, the current I ₀₁ flowing through the first organic layer 120 is equal to the current I ₁ flowing from the first current source 220 as in the first mode. On the other hand, as shown in FIG. 11, the current I ₀₂ flowing through the second organic layer 140 is the current flowing from the second current source 240 to the current I ₀₁ (= I ₁ ) flowing through the first organic layer 120 It will amount plus I _2. Therefore, while the luminance of the first organic layer 120 is fixed, the luminance of the second organic layer 140 can be increased.

According to the above as the present embodiment, the control unit 210 controls the magnitude of the current I ₁ flowing from the first current source 220, it is possible to control the luminance of the first organic layer 120. Further, the control unit 210 can control the brightness of the second organic layer 140 independently of the brightness of the first organic layer 120 by controlling the switch 230 and the second current source 240. At this time, the controller 210 may increase or decrease the luminance of the second current source 240. Therefore, the controller 210 can control the ratio of the brightness of the second organic layer 140 to the brightness of the first organic layer 120 in a wide range. As a result, the changeable range of the light emission color of the light emitting device 10 becomes wide.

(Modification 1)
FIG. 12 is a view showing the configuration of the light emitting device 10 according to the first modification. The light emitting device 10 shown in this figure has the same configuration as the light emitting device 10 according to the embodiment except that a zener diode 250 is provided between the switch 230 and the third electrode 150.

  The zener diode 250 is connected between the switch 230 and the third electrode 150 in the reverse direction. Specifically, the negative electrode of the Zener diode 250 is connected to the switch 230, and the positive electrode of the Zener diode 250 is connected to the third electrode 150. Thereby, the potential of the switch 230 is higher than the ground potential by the Zener potential.

  Next, the operation of the light emitting device 10 according to the present modification will be described using FIGS. 13 and 14. FIG. 13 is a diagram for describing a time lag from when current starts flowing to the second organic layer 140 until the second organic layer 140 glows in the embodiment. In order for the second organic layer 140 to emit light, the potential applied to the second organic layer 140 needs to be equal to or higher than the threshold voltage. On the other hand, since the laminate of the second electrode 130, the second organic layer 140, and the third electrode 150 also functions as a capacitor, the current flows from the second organic layer 140 until the second organic layer 140 emits light (ie, Until the voltage between the second electrode 130 and the third electrode 150 becomes equal to or higher than the reference voltage, a time lag occurs.

  On the other hand, as shown in FIG. 14, in the present modification, a Zener diode 250 is connected in the reverse direction between the switch 230 and the third electrode 150. Therefore, in the second mode, while the switch 230 is closed (that is, before current flows to the second organic layer 140), the voltage of the second electrode 130 is increased by the zener potential of the zener diode 250. Therefore, until the voltage applied to the second organic layer 140 (that is, the voltage between the second electrode 130 and the third electrode 150) becomes equal to or higher than the reference voltage after the switch 230 is opened and current starts to flow to the second organic layer 140. Time will be shortened. Therefore, as compared with the embodiment, the time lag from when current flows to the second organic layer 140 until the second organic layer 140 glows is shortened.

(Modification 2)
FIGS. 15 and 16 are diagrams for explaining the operation of the control unit 210 according to the second modification. As described in the first modified example, until current flows in the second organic layer 140 and the second organic layer 140 emits light (ie, until the voltage between the second electrode 130 and the third electrode 150 becomes equal to or higher than the reference voltage). ) Has a time lag. So, in this modification, as shown in FIG. 15, when the switch 230 is opened and the current I ₀₁ (= I ₁ ) that has flowed through the first organic layer 120 is started to flow through the second organic layer 140 in the second mode. The current I ₂ from the second current source 240 is supplied to the second organic layer 140 for a certain period. As a result, the current flowing through the second organic layer 140 becomes I ₁ + I ₂ , and the rate of charge accumulation in the second organic layer 140 is increased. As a result, the time from when current flows to the second organic layer 140 to when the voltage applied to the second organic layer 140 becomes equal to or higher than the reference voltage becomes short. Therefore, as shown in FIG. 16, compared to the embodiment, the time lag from when current flows to the second organic layer 140 until the second organic layer 140 glows becomes short.

Then, the controller 210 turns off the second current source 240 at the timing when the second organic layer 140 starts to light (or the timing before that). Alternatively, the control unit 210 controls the switch 230 to flow the current I ₂ from the second current source 240 to the second organic layer 140 only for a predetermined fixed period. Thereby, it can suppress that the brightness | luminance of the 2nd organic layer 140 becomes high.

  The control unit 210 performs the above control at each pulse in the PWM control. The control unit 210 may perform the same control as that in FIG. 15 in the first mode.

  Alternatively, the third organic layer and the fourth electrode may be provided on the surface of the third electrode 150 opposite to the second electrode 130, and the third electrode 150 and the fourth electrode may be connected to each other through a switch. . In this case, the first organic layer 120, the second organic layer 140, and the third organic layer may be organic layers having emission peaks at R, G, and B, for example. With such a configuration, the relationship between the control of the switch and the light emission color of the light emission of each organic layer uniquely corresponds, and the control of the light emission color becomes easy. Also, the number of organic layers, electrodes, and switches may be further increased.

  As mentioned above, although an embodiment and an example were described with reference to drawings, these are the illustrations of the present invention and can also adopt various composition except the above.

Claims (5)

A first electrode,
A second electrode overlapping the first electrode;
A third electrode overlapping the second electrode;
A first organic layer located between the first electrode and the second electrode and including a light emitting layer;
A second organic layer located between the second electrode and the third electrode and including a light emitting layer;
A first current source connected to the first electrode;
A switch connecting the second electrode and the third electrode;
A second current source connected to the second electrode;
A control unit that controls the switch and the second current source;
Equipped with
The peak wavelength of the emission spectrum of the first organic layer is different from the peak wavelength of the emission spectrum of the second organic layer. In the light emitting device according to claim 1,
The control unit operates as a control mode:
A first mode for turning off the second current source and the switch;
A second mode in which pulse width modulation is performed by turning off the second current source and repeating on and off of the switch;
A light emitting device having In the light emitting device according to claim 2,
The control unit further includes a third mode in which the switch is turned off and the second current source is turned on as a control mode. In the light emitting device according to claim 2 or 3,
The control unit turns on the second current source when light emission of the second organic layer is started in the second mode, and when or before the second organic layer emits light, 2 Light emitting device to turn off the current source. The light emitting device according to any one of claims 1 to 4.
A light emitting device comprising a Zener diode provided between the switch and the third electrode, wherein a negative electrode is connected to the switch side and a positive electrode is connected to the third electrode side.

Images