WO2017046882A1

WO2017046882A1 - Light-emitting device

Info

Publication number: WO2017046882A1
Application number: PCT/JP2015/076237
Authority: WO
Inventors: 石塚　真一; 吉田　綾子
Original assignee: パイオニア株式会社
Priority date: 2015-09-16
Filing date: 2015-09-16
Publication date: 2017-03-23
Also published as: JPWO2017046882A1; JP6522766B2

Abstract

According to the present invention, a second electrode (130) overlaps a first electrode (110), and a third electrode (150) overlaps the second electrode (130). A first organic layer (120) is located between the first electrode (110) and the second electrode (130), and a second organic layer (140) is located between the second electrode (130) and the third electrode (150). A first current source (220) is connected to the first electrode (110), and a second current source (240) is connected to the second electrode (130). A switch (230) 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).

Description

Light emitting device

The present invention relates to a light emitting device.

An organic EL element is one of the light sources of a 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, organic EL elements having a plurality of types of organic layers having different emission characteristics have been proposed.

For example, Patent Document 1 discloses that a first electrode made of ITO, a first organic layer, a second electrode, a second organic layer, a third electrode, a third organic layer, and a fourth electrode are formed on a substrate. It has the structure which piled up in order. In such a configuration, the first electrode is grounded, the second electrode is connected to the output terminal of the first operational amplifier, the third electrode is connected to the output terminal of the second operational amplifier, The output terminals of the third operational amplifier are connected to the four electrodes. The non-inverting input terminal of the first operational amplifier, the non-inverting input terminal of the second operational amplifier, and the non-inverting input terminal of the third operational amplifier are connected to different input terminals. In addition, the output terminal of the first operational amplifier is connected to the non-inverting input terminal of the second operational amplifier, and the output terminal of the second operational amplifier is also connected to the non-inverting 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 stacked in this order, the second electrode and the third electrode are connected to a variable resistor. It is described that the connection is made through. Patent Document 2 describes that the brightness of the second light emitting layer can be adjusted by adjusting the resistance of the variable resistor.

JP 2001-511296 A JP 2014-150000 A

In an organic EL device in which a plurality of light emitting layers having different light emission colors are stacked, in order to adjust the light emission color emitted from the organic EL device, the luminance of each 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. End up. For this reason, it is difficult to make the ratio of the luminance of the first organic layer to the luminance of the second organic layer below a certain value.

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, even if the ratio of the luminance of the first organic layer to the luminance of the second organic layer can be reduced, this ratio cannot be made a certain value or more.

An example of a problem to be solved by the present invention is that the ratio of the luminance of the first organic layer to the luminance of the second organic layer can be controlled in a wide range.

The invention according to claim 1 is a first electrode;
A second electrode overlapping the first electrode;
A third electrode overlapping the second electrode;
A first organic layer that is located between the first electrode and the second electrode and includes 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 for controlling the switch and the second current source;
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 above-described object and other objects, features, and advantages will be further clarified by a preferred embodiment described below and the following drawings attached thereto.

It is sectional drawing which shows the structure of the light-emitting device which concerns on embodiment. FIG. 2 is an equivalent circuit diagram of the light emitting device shown in FIG. 1. It is a figure for demonstrating the control mode of a control part. It is a figure for demonstrating a 1st mode. It is a figure for demonstrating a 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. It is a figure which shows the structure of the light-emitting device which concerns on the modification 1. FIG. It is a figure for demonstrating operation | movement of the light-emitting device which concerns on embodiment. FIG. 11 is a diagram for explaining the operation of a light emitting device according to Modification Example 1. FIG. 10 is a diagram for explaining an operation of a control unit according to Modification 2. FIG. 10 is a diagram for explaining an operation of a control unit according to Modification 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

FIG. 1 is a cross-sectional view showing a configuration of a light emitting device 10 according to an 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 included. 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 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 emission color of the first organic layer 120 is different from the emission 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. 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 a light-transmitting material such as glass or a light-transmitting resin. The substrate 100 is, for example, a polygon such as a rectangle. Here, the substrate 100 may have flexibility. In the case where the substrate 100 has flexibility, the thickness of the substrate 100 is, for example, not less than 10 μm and not more than 1000 μm. In particular, when the substrate 100 is made of a glass material and has flexibility, the thickness of the substrate 100 is, for example, 200 μm or less. In the case where the substrate 100 is made of a resin material and is flexible, the material of the substrate 100 includes, for example, PEN (polyethylene naphthalate), PES (polyethersulfone), PET (polyethylene terephthalate), or polyimide. Is formed. In the case where the substrate 100 includes 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 suppress moisture from passing through the substrate 100. ing.

The first electrode 110 and the second electrode 130 are transparent electrodes having optical transparency. The transparent conductive material constituting the transparent electrode is a metal-containing material, for example, a metal oxide such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), IWZO (Indium Tungsten Zinc Oxide), ZnO (Zinc Oxide) or the like. is there. The thickness of the first electrode 110 and the second electrode 130 is, for example, not less than 10 nm and not more than 500 nm. The first electrode 110 and the second electrode 130 are formed using, for example, a sputtering method or a vapor deposition method. The first electrode 110 and the second electrode 130 may be a carbon nanotube or a conductive organic material such as PEDOT / PSS. In particular, the second electrode 130 has a structure in which a layer containing the material of the third electrode 150 described later is laminated on a layer containing these materials, or a structure in which the material of the third electrode 150 is arranged in a net shape. There 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, not less than 10 nm and not more than 500 nm. 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 laminated 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 an evaporation method. 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 a coating 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 a coating 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 an evaporation method. Moreover, all the layers of the 1st organic layer 120 and all the layers of the 2nd organic layer 140 may be formed using the apply | 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 the red wavelength region, and the second organic layer 140 has a peak on the shorter wavelength side (for example, the blue wavelength region) than red. For this reason, the light emission color of the light emitting device 10 is a color (for example, white) obtained by mixing the light emission color of the first organic layer 120 and the light emission color of the second organic layer 140. 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. Note that the peak of the first organic layer 120 and the peak of the second organic layer 140 may be reversed.

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

The first current source 220 and the second current source 240 are current sources and are controlled by the control unit 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 having other structures.

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

Next, the operation of the control unit 210 will be described. As illustrated in FIG. 3, the controller 210 causes the first organic layer 120 and the second organic layer 140 to emit light in three patterns of the first mode, the second mode, and the 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, the same current flows through the first organic layer 120 and the second organic layer 140. In the second mode, the controller 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 becomes equal to or less than the current flowing through the first organic layer 120. In the third mode, the control unit 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 greater than the current flowing through the first organic layer 120. Details will be described below. In the following description, as shown in FIG. 2, the current flowing through the first current source 220 is I ₁ , the current flowing through the second current source 240 is I ₂ , the current flowing 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 control unit 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 controller 210 does not operate the second current source 240. That is, I ₂ = 0. As a result, a 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 are both I ₁ . For this reason, 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 increase in proportion to I _1, and as a result, the first organic The intensity (luminance) of light emitted from the layer 120 and the intensity (luminance) of light emitted from the second organic layer 140 are also increased. 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) In addition, the intensity (luminance) of light emitted from the second organic layer 140 is also reduced.

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. The control unit 210 performs PWM control by repeatedly opening and closing the switch 230. 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 with reference to FIGS. 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 through the second electrode 130 and the second organic layer 140. On the other hand, since the current I ₀₁ flowing through the first organic layer 120 flows directly from the second electrode 130 to the third electrode 150 via the switch 230 while the switch 230 is closed, it flows into the second organic layer 140. Absent. For this reason, as shown in FIG. 7, when the length of one cycle of opening / closing of the switch 230 is T and the length of the period during which the switch 230 is closed (on) in one cycle is H, the second current source 240 2 The current flowing through the organic layer 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 equal to or less than I ₁ by controlling the duty ratio in the PWM control of the switch 230. can do.

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

Next, the third mode will be described with reference to FIGS. 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 being opened. Thereby, 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 equal to the current I ₀₁ (= I ₁ ) flowing through the first organic layer 120 and the current flowing from the second current source 240. I ₂ is added. Therefore, the brightness of the second organic layer 140 can be increased while the brightness of the first organic layer 120 is fixed.

As described above, according to the present embodiment, the control unit 210 can control the luminance of the first organic layer 120 by controlling the magnitude of the current I ₁ flowing from the first current source 220. The controller 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 can increase or decrease the luminance of the second current source 240. Therefore, the controller 210 can control the ratio of the luminance of the second organic layer 140 to the luminance of the first organic layer 120 in a wide range. As a result, the changeable range of the emission color of the light emitting device 10 is widened.

(Modification 1)
FIG. 12 is a diagram illustrating a configuration of the light emitting device 10 according to the first modification. The light emitting device 10 shown in the 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 in the reverse direction between the switch 230 and the third electrode 150. 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. As a result, the potential of the switch 230 becomes higher than the ground potential by the Zener potential.

Next, the operation of the light emitting device 10 according to this modification will be described with reference to FIGS. FIG. 13 is a diagram for explaining a time lag from when a current starts to flow through the second organic layer 140 to when the second organic layer 140 shines 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 stacked body of the second electrode 130, the second organic layer 140, and the third electrode 150 also functions as a capacitor, until the second organic layer 140 emits light after the current starts to flow through the second organic layer 140 (that is, A time lag occurs until the voltage between the second electrode 130 and the third electrode 150 becomes equal to or higher than the reference voltage.

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

(Modification 2)
15 and 16 are diagrams for explaining the operation of the control unit 210 according to the second modification. As described in the first modification, until the second organic layer 140 shines after the current starts to flow through the second organic layer 140 (that is, 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. Therefore, in the present modification, as shown in FIG. 15, in the second mode, when the switch 230 is opened and the current I ₀₁ (= I ₁ ) flowing through the first organic layer 120 starts to flow through the second organic layer 140. The current I ₂ from the second current source 240 is passed through the second organic layer 140 for a certain period. Accordingly, the current flowing through the second organic layer 140 becomes I ₁ + I ₂ , and the rate at which charges are accumulated in the second organic layer 140 is increased. As a result, the time from when the current starts to flow through the second organic layer 140 until the voltage applied to the second organic layer 140 becomes equal to or higher than the reference voltage is shortened. Accordingly, as shown in FIG. 16, the time lag from when the current starts to flow through the second organic layer 140 to when the second organic layer 140 shines is shorter than in the embodiment.

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

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

Further, a third organic layer and a 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 via a switch. . In this case, you may make the 1st organic layer 120, the 2nd organic layer 140, and the 3rd organic layer into an organic layer which has an emission peak in each of R, G, B, for example. By adopting such a configuration, the relationship between the control of the switch and the emission color of light emitted from each organic layer uniquely corresponds to the control of the emission color. Further, the organic layers, electrodes, and switches may be further increased.

As mentioned above, although embodiment and the Example were described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

Claims

A first electrode;
A second electrode overlapping the first electrode;
A third electrode overlapping the second electrode;
A first organic layer that is located between the first electrode and the second electrode and includes 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 for controlling the switch and the second current source;
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.
The light-emitting device according to claim 1.
The control unit, as a control mode,
A first mode for turning off the second current source and the switch;
A second mode in which the second current source is turned off and pulse width modulation is performed by repeatedly turning on and off the switch;
A light emitting device.
The light-emitting device according to claim 2.
The control unit is a light emitting device having a third mode as a control mode, further turning off the switch and turning on the second current source.
The light emitting device according to claim 2 or 3,
In the second mode, the control unit turns on the second current source when starting light emission of the second organic layer, and before or before the second organic layer emits light. 2 Light-emitting device that turns 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, a negative electrode connected to the switch side and a positive electrode connected to the third electrode side.