JP5773465B2 - Organic EL lighting device - Google Patents

Description

  The present invention relates to an organic EL lighting device.

A white organic EL (Electro-Luminescence) panel is conventionally configured by combining an R (red) organic EL panel, a G (green) organic EL panel, and a B (blue) organic EL panel.
The organic EL panel varies in characteristics such as current-voltage characteristics, current-luminance characteristics, and color temperature depending on materials and manufacturing processes. For this reason, the conventional white EL panel has a large variation in brightness, color temperature and the like of each panel, and the product yield is low. In addition, deterioration of individual panels over time is not uniform, and variations in luminance and color temperature between panels increase depending on usage frequency and the like.

  In order to improve such a problem, an organic EL lighting device has been proposed in which light emitting layers of three primary colors of R, G, and B are provided in one panel. As an example of such a panel, Patent Document 1 discloses a configuration in which an anode electrode and a cathode electrode are provided corresponding to each of R, G, and B light emitting layers on the same plane.

JP 2003-163075 A

  The lighting and driving control of the organic EL lighting device having the configuration disclosed in Patent Document 1 requires a large number of scanning driver ICs and data driver ICs, and the driving method is complicated. Further, since the anode electrode and the cathode electrode are patterned in a matrix shape, the aperture ratio is low, the specific resistance is high, a high driving voltage is required, and the power consumption is increased.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a further improved organic EL lighting device.

In order to achieve the above object, an organic EL lighting device according to the present invention includes:
A plurality of light-emitting layers that emit light by recombination of injected charges and have different emission colors;
A first electrode provided in a pair with each of the plurality of light emitting layers;
A second electrode provided facing all of the plurality of light emitting layers in common;
A first transport layer for transporting charges injected from the first electrode to the plurality of light emitting layers;
A second transport layer for transporting charges injected from the second electrode to the plurality of light emitting layers;
A drive circuit for supplying current to the plurality of light emitting layers through the first electrode and the second electrode;
With
Wherein the driving circuit, the first electrode facing the light-emitting layer of the same luminescent color, the same voltage is applied to said second electrode, it applies a set voltage as a reference potential,
It is characterized by that.

  According to the present invention, power saving and high quality can be realized.

It is sectional drawing of the organic electroluminescent illuminating device which concerns on 1st Embodiment. (A)-(c) is a figure which shows arrangement | positioning of the cathode of the organic electroluminescent illuminating device which concerns on 1st Embodiment, a light emitting layer, and an anode. It is a circuit diagram of the organic EL lighting device according to the first embodiment. (A)-(c) is a wave form diagram of the drive voltage applied to the organic electroluminescent illuminating device which concerns on 1st Embodiment. It is a wave form diagram which shows the other example of the drive voltage applied to the organic electroluminescent illuminating device which concerns on 1st Embodiment. (A), (b) is a wave form diagram which shows the further another example of the drive voltage applied to the organic electroluminescent illuminating device which concerns on 1st Embodiment. (A)-(c) is a wave form diagram which shows the example of the drive voltage for PWM drive of the organic electroluminescent illuminating device which concerns on 1st Embodiment. (A)-(c) is a wave form diagram which shows the example of the drive voltage for PAM drive of the organic electroluminescent illuminating device which concerns on 1st Embodiment. It is sectional drawing of the organic electroluminescent illuminating device which concerns on 2nd Embodiment. It is a circuit diagram of the organic electroluminescent illuminating device which concerns on 2nd Embodiment. (A)-(c) is a wave form diagram which shows the example of the drive voltage applied to the organic electroluminescent illuminating device which concerns on 2nd Embodiment. It is a wave form diagram which shows the other example of the drive voltage applied to the organic electroluminescent illuminating device which concerns on 2nd Embodiment. (A), (b) is a wave form diagram which shows the further another example of the drive voltage applied to the organic electroluminescent illuminating device which concerns on 2nd Embodiment. (A)-(c) is a wave form diagram which shows the example of the drive voltage for PWM drive of the organic electroluminescent illuminating device which concerns on 2nd Embodiment. (A)-(c) is a wave form diagram which shows the example of the drive voltage for PAM drive of the organic electroluminescent illuminating device which concerns on 2nd Embodiment. It is sectional drawing of the organic electroluminescent illuminating device of the comparative example 1. FIG. It is sectional drawing of the organic electroluminescent illuminating device of the comparative example 2.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
The organic EL lighting device 1 according to the first embodiment of the present invention is a lighting device capable of emitting multiple colors, and as shown in FIG. 1, a cathode electrode 10, an electron injection layer 20, and an electron transport layer. 30, a hole blocking layer 40, a light emitting layer 50, a hole transport layer 60, a hole injection layer 70, an anode electrode 80, a glass substrate 90, and a diffusion plate 100. Have.

  The cathode electrode 10 is composed of a thin film electrode formed by depositing a metal material having a small electrical resistivity such as aluminum or silver and having a high reflectivity to a uniform thickness. The cathode electrode 10 is composed of a single thin film as shown in FIG. The cathode electrode 10 functions as an electrode for injecting electrons into the light emitting layer 50.

  The electron injection layer 20 is formed on the cathode electrode 10 from an alkali metal such as lithium or cesium or a fluoride or oxide of an alkaline earth metal such as calcium. The electron injection layer 20 can also be formed from an electron-transporting organic compound and a quinolinol-based alkali metal complex such as lithium quinoline as a dopant or an electron-donating metal such as Li. The electron injection layer 20 functions as a layer that increases the efficiency of electron injection from the cathode electrode 10 to the light emitting layer 50.

  The electron transport layer 30 is formed on the electron injection layer 20 from an electron transporting organic compound. Examples of the electron-transporting organic compound include 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (Bu-PBD), 1,3-bis. Oxadiazole derivatives such as (pt-butylphenyl-1,3,4-oxadiazolyl) phenyl (OXD-7), triazole derivatives, quinolinol systems such as tris (8-quinolinol) aluminum complex (Alq3) A metal complex having the above ligand, a zinc complex having 2-hydroxyphenylbenzothiazole, 2-hydroxyphenylbenzoxazole, or the like as a ligand can be used. The electron transport layer 30 transports electrons injected from the cathode electrode 10 through the electron injection layer 20 to the light emitting layer 50.

  The hole blocking layer 40 is formed on the electron transport layer 30 from 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), a triphenyldiamine derivative, a triazole derivative, or the like. The hole blocking layer 40 functions as a layer that blocks holes that pass through the light emitting layer 50 without contributing to light emission, and increases the probability of recombination within the light emitting layer 50.

  As shown in FIGS. 1 and 2B, the light emitting layer 50 includes an R (red) light emitting layer 51R, a G (green) light emitting layer 51G, and a B (blue) light emitting layer 51B that are repeatedly arranged. It is an independent light emitting layer of three primary colors. Electrons are injected from the cathode electrode 10 and holes are injected from the anode electrode 80 into the light emitting layer 50. The holes and electrons injected into the light emitting layer 50 are recombined, and excitons generated along with the recombination transition from the excited state to the ground state, whereby a light emission phenomenon occurs.

The light emitting layer 50 is made of Alq3 (green), bisdiphenylvinylbiphenyl (BDPVBi) (blue), OXD-7 (blue to green), N, N′-bis (2,5-di-t-butylphenyl) perylenetetra. It is formed from carboxylic acid diimide (BPPC) (red) or the like.
The light emitting layer 50 may be composed of a binary system of a host and a dopant. In this case, as the host compound, the above-described light emitting material, a hole transport material described later, and an electron transport material can be used. More specifically, the light-emitting layer 50 is formed by adding 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), 4- (dicyanomethylene) to a quinolinol metal complex such as Alq3. Pyran derivatives such as 2-t-butyl-6- (1,1,7,7-tetramethylurolidyl-9-enyl) -4H-pyran (DCJTB) (the two are red), 2,3 -Doped with quinacridone derivatives such as quinacridone and coumarin derivatives such as 3- (2'-benzothiazole) -7-diethylaminocoumarin (the two are green); bis (2-methyl-8- Hydroxyquinoline) -4-phenylphenol-aluminum complex doped with condensed polycyclic aromatics such as perylene (blue); or 4,4'- as a hole transport material Su (m-tolylphenylamino) biphenyl (TPD) doped with rubrene (yellow); 4,4′-biscarbazolylbiphenyl (CBP), 4,4′-bis (9-carbazolyl) -2 , 2'-dimethylbiphenyl (CDBP) and other carbazole compounds, tris- (2 ferrinylpyridine) iridium (Ir (ppy) 3) (green), bis (4,6-difluorophenyl) -pyridinate- N, C2) iridium (picolinate) (FIr (pic)) (blue), bis (2-2'-benzothienyl) -pyridinate-N, C3 iridium (acetylacetonate) (Btp2Ir (acac)) (red), Tris- (picolinate) iridium (Ir (pic) 3) (red), bis (2-phenylbenzothiozolato-N, C2) iridium (a Cetylacetonate) (Bt2Ir (acac)) (yellow) or the like doped with an iridium complex or platinum complex;

  In the following description, the red light emitting layer 51R, the green light emitting layer 51G, and the blue light emitting layer 51B are collectively referred to as a single color light emitting layer 51. Further, in FIG. 1, six monochromatic light emitting layers 51 are illustrated, but the organic EL lighting device 1 according to the present embodiment is not limited to this, and the number of colors (3 in the present embodiment) × N monochromatic light emission. Layer 51 can be disposed. Furthermore, the color arrangement order of each single color light emitting layer 51 is not limited to this, and the number of color arrangements is not limited to this.

  In this specification, an XYZ orthogonal coordinate system is set as follows. The direction in which the red light emitting layer 51R, the green light emitting layer 51G, and the blue light emitting layer 51B are repeatedly arranged is defined as the X direction, and the direction in which the red light emitting layer 51R, the green light emitting layer 51G, and the blue light emitting layer 51B extends is defined as the Y direction. The direction from the electrode 80 toward the cathode electrode 10 is taken as the Z direction.

  The monochromatic light emitting layer 51 is a non-light emitting portion that does not emit light. Using an inorganic oxide such as SiOx, an inorganic nitride such as SiNx, or an insulating material such as a photoresist, interlayer insulation is formed on the glass substrate 90 in the portion between the monochromatic light emitting layers 51 or between the anode electrodes 80. A film can be formed to separate the light emitting layer 50 into each color. As a result, it is possible to prevent color mixing and short-circuiting due to alignment misalignment of the shadow mask. At this time, the hole transport layer 60 and the hole injection layer 70 are similarly separated.

  The anode electrode 80 is formed on the glass substrate 90 and is made of a light-transmitting conductive material such as metal oxide, for example, ITO (Indium Tin Oxide). As shown in FIGS. 1 and 2C, the anode electrode 80 is formed in a stripe shape so as to face each single-color light emitting layer 51, and a plurality of anode electrodes 80 are arranged. The anode electrode 80 has a function of injecting holes into the light emitting layer 50 and transmitting light emitted from the light emitting layer 50.

  The hole injection layer 70 is formed on the anode electrode 80 and is made of copper phthalocyanine (Cu—Pc) or 4,4 ′, 4 ″ -tris [3-methylphenyl (phenyl) amino] triphenylamine (m-MTDATA). 4,4 ′, 4 ″ -tris [2-naphthyl (phenyl) amino] triphenylamine (2-TNATA), 4,4 ′, 4 ″ -tris (N-carbazolyl) -triphenylamine (TCTA) And arylamine derivatives such as starburst type aromatic amines. The hole injection layer 70 may be composed of a hole-transporting organic compound and an electron-accepting compound that is a dopant. The hole injection layer 70 has a function of increasing the efficiency of hole injection from the anode electrode 80.

  The hole transport layer 60 is formed between the light emitting layer 50 and the hole injection layer 70, and is bis (di (p-tolyl) aminophenyl) -1,1-cyclohexane, N, N′-diphenyl-N—. N-bis (1-naphthyl) -1,1′-biphenyl) -4,4′-diamine (α-NPD), triphenyldiamines such as TPD, starburst aromatic amines, hole transport properties, etc. It is comprised from the organic compound. The hole transport layer 60 transports holes injected from the anode electrode 80 through the hole injection layer 70 to the light emitting layer 50.

  The glass substrate 90 is a translucent substrate made of non-alkali glass. On the glass substrate 90, the cathode electrode 10, the electron injection layer 20, the electron transport layer 30, the hole blocking layer 40, the light emitting layer 50, the hole transport layer 60, the hole injection layer 70, and the anode electrode 80 are stacked. The glass substrate 90 supports these and has a function of emitting light from the light emitting layer 50.

  The diffusing plate 100 is disposed on the light emitting side surface of the glass substrate 90 and is made of polyester such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyethylene, polypropylene, polyamide, fluororesin, polymethyl methacrylate, acrylic or It is composed of a thin transparent resin film such as a polyarylate resin or a glass whose surface is finely processed. The diffuser plate 100 diffuses the light emitted from the light emitting layer 50 and converts it into uniform planar light.

  In the present embodiment, the cathode electrode 10 is arranged as a common electrode facing the all monochromatic light emitting layers 51 as shown in FIGS. 1 and 2A to 2C. On the other hand, the anode electrode 80 is independently arranged so as to be paired with each monochromatic light emitting layer 51.

  When a DC voltage is applied between the cathode electrode 10 and the anode electrode 80, electrons and holes are injected into the light emitting layer 50, and the electrons and holes injected into the respective monochromatic light emitting layers 51 are recombined. Emits light.

  Next, a circuit configuration of the organic EL lighting device 1 having the above configuration will be described with reference to FIG.

  The control unit 110 is connected to the drive circuit 200. The control unit 110 drives the control circuit to specify the current supplied to the red light emitting layer 51R, the green light emitting layer 51G, and the blue light emitting layer 51B so that the light emitting unit 300 emits light of a desired color. Output to 200. The value of the current passed through each monochromatic light-emitting layer 51 is obtained, for example, after manufacturing the organic EL lighting device 1 and by performing tests individually or in units of lots.

  For example, if the emission intensity of the red emission layer 51R, the emission intensity of the green emission layer 51G, and the emission intensity of the blue emission layer 51B are adjusted in a well-balanced manner, white illumination light can be obtained by mixing these colors. For example, if the emission intensity of the red light emitting layer 51R is relatively increased, reddish illumination light can be obtained.

  The rectifying / smoothing circuit 500 is connected to the commercial power source 600, rectifies and smoothes the current supplied from the commercial power source 600, and supplies the smoothed DC voltage to the converter 400.

  The converter 400 is constituted by a DC-DC converter or the like, and is connected to the rectifying / smoothing circuit 500. From the DC voltage supplied from the rectifying / smoothing circuit 500, the converter 400 generates a plurality of DC voltages used for driving the light emitting unit 300. It is generated and supplied to the drive circuit 200.

  The drive circuit 200 uses the DC voltage received from the converter 400 to cause a constant current specified by the control signal received from the control unit 110 to flow through each monochromatic light emitting layer 51 of the light emitting unit 300. Details of the operation of the drive circuit 200 will be described later.

  The light emitting unit 300 includes the cathode electrode 10, the electron injection layer 20,..., And the anode electrode 80, and is connected to the drive circuit 200. The light emitting unit 300 emits light when a predetermined current is supplied from the drive circuit 200.

  Next, the organic EL lighting device 1 having the above configuration will be described.

When the organic EL lighting device 1 is connected to the commercial power source 600 and the power source is turned on, the control unit 110 outputs a control signal indicating a constant current that flows through the monochromatic light emitting layers 50 of red, green, and blue according to the setting. This is supplied to the drive circuit 200.
On the other hand, the rectification / smoothing circuit 500 rectifies and smoothes the AC voltage supplied from the commercial power supply 600 and supplies the rectified and smoothed circuit 500 to the converter 400. The converter 400 generates a voltage used for driving the light emitting unit 300 from the supplied voltage, and supplies the voltage to the drive circuit 200.
The drive circuit 200 drives the light emitting unit 300 using the voltage supplied from the converter 400 in accordance with the control signal supplied from the control unit 110.

The driving operation of the driving circuit 200 will be described with reference to FIGS.
First, the drive circuit 200 applies the reference potential Vcom to the cathode electrode 10. Subsequently, a common potential VO lower than the reference potential Vcom is applied to each anode electrode 80 for a predetermined time Ts. Subsequently, the drive circuit 200 instructs the monochromatic light emitting elements 51R, 51G, and 51B from the control unit 110 to specify the voltage to be applied to each anode electrode 80 while maintaining the reference potential Vcom applied to the cathode electrode 10. Is set to a voltage required to allow the constant current to flow.
In the example of FIG. 4, the drive circuit 200 applies the voltage VpB to the anode electrode 80 corresponding to the red light emitting layer 51R, applies the voltage VpG to the anode electrode 80 corresponding to the green light emitting layer 51G, and emits blue light. A voltage VpB is applied to the anode electrode 80 corresponding to the layer 51 </ b> B, thereby causing a constant current to flow through each monochromatic light emitting layer 51 to cause each monochromatic light emitting layer 51 to emit light.
A part of the light emitted from each monochromatic light emitting layer 51 reaches the diffusion plate 100 via the hole transport layer 60, the hole injection layer 70, the anode electrode 80, and the glass substrate 90. Further, another part of the light emitted from each monochromatic light emitting layer 51 is reflected by the cathode electrode 10 and then passed through the hole transport layer 60, the hole injection layer 70, the anode electrode 80, and the glass substrate 90. The diffusion plate 100 is reached.

The diffusion plate 100 mixes and emits light by diffusing incident red, green, and blue light. Thereby, planar light of a desired color is emitted from the diffusion plate 100.
After that, when the power source of the organic EL lighting device is turned off, the drive circuit 200 stops driving after applying a reverse bias voltage to each monochromatic light emitting layer 51 for a certain period of time.

  In the organic EL lighting device described above, the cathode electrode 10 is common to the plurality of monochromatic light emitting layers 51, and the number of electrodes to be controlled is N + 1 if the number of monochromatic light emitting layers 51 is N. It only takes a piece. Therefore, the configuration and operation of the drive circuit 200, the drive circuit 200, the light emitting layer 300, the wiring, and the like are simple and easy to manufacture.

  In addition, even when the amount of light emitted from the monochromatic light emitting layer 51 deviates from the design value due to manufacturing variations, aging deterioration, etc., the constant current that flows through the monochromatic light emitting layer 51 of each color is adjusted by adjusting the control signal output from the control unit 110. Can be adjusted to obtain a desired amount of emitted light. As a result, the color (temperature color) of the output light of the organic EL light-emitting illuminating device 1 can be appropriately adjusted.

  Further, as shown in FIGS. 4A to 4C, the drive circuit 200 sets the potential VO of the anode electrode 80 to a negative potential with respect to the reference potential Vcom at the time of start-up and power-off. A reverse bias is applied to the light emitting layer 51. The reverse bias voltage is set to be equal to or lower than the dielectric breakdown potential of the organic EL lighting panel, for example, 0 to -5V. Carrier conductivity of organic materials is realized by repeating oxidation and reduction of molecules. For this reason, the continuous application of the one-polarity voltage promotes the deterioration of the material, which causes the luminance deterioration of the organic EL and the voltage increase. The organic EL lighting device 1 according to this embodiment can suppress the deterioration of the material due to the accumulation of electric charges and improve the lifetime by applying a reverse bias.

An organic EL lighting device having the above configuration was manufactured and its characteristics were measured.
First, an ITO thin film was formed on the glass substrate 90 by sputtering. Next, the ITO thin film was patterned into the shape of the color light emitting region by using a photoetching method and a photolithography method, thereby forming an anode electrode 80.
Next, on the anode electrode 80, Cu—Pc was deposited by a vacuum evaporation method to form the hole injection layer. Furthermore, on the hole injection layer 70, α-NPD was deposited to a uniform thickness by a vacuum evaporation method to form the hole transport layer 60.

  Next, a striped CBP film was formed on the hole transport layer 60. Further, Ir (ppy) 3 is diffused in the CBP layer to form the green light emitting layer 51G, Btp2Ir (acac) is diffused in the CBP layer to form the red light emitting layer 51R, and FIr (pic) is further added to the CBP layer. The light emitting layer 50 was formed by diffusing to form the blue light emitting layer 51B. At this time, a shadow mask was formed by a vacuum deposition method or the like, and the light emitting layer 50 was separated into each color.

Next, BCP was deposited on the light emitting layer 50 to form the hole blocking layer 40. Furthermore, Alq3 was deposited on the hole block 40 to form the electron transport layer 30 having a uniform thickness. Further, LiF was deposited on the electron transport layer 30 to form the electron injection layer 20.
Further, the cathode electrode 10 was formed by depositing Al in a uniform thickness.
Thus, an organic EL lighting panel was produced.

In this organic EL lighting panel, a drive current of 27 A / m ² was supplied to the red light emitting part, 25 A / m ^{2 to} the green light emitting part, and 23 A / m ² to the blue light emitting part. At this time, the drive voltage (voltage between the anode electrode 80 and the common cathode electrode 10) is 2.7V, 2.6V, 4.1V, respectively, and the power efficiency of the organic EL lighting panel is 31 lm / W, color The temperature was 2800K. Further, the luminance unevenness in the panel surface of this lighting panel was 6% or less as a difference between the maximum luminance and the minimum luminance.

  An example of the element structure of a lighting panel (hereinafter referred to as Comparative Example 1) of a conventional organic EL lighting device 2 is shown in FIG. The cathode electrode 10 of this comparative example is disposed for each monochromatic light emitting layer 51. In this comparative example, when the same color temperature as described above was set, the driving voltage increased due to an increase in wiring resistance and the like, and the power efficiency became 24 lm / W. The lighting panel of the organic EL lighting device 1 created by the above method Lower than the power efficiency. The difference in power efficiency between the lighting panel of the organic EL lighting device 1 and the comparative example created by the method described above is difficult to accurately separate, but also includes a difference in reflectance due to the cathode area. In Comparative Example 1, 19% in-plane luminance unevenness was observed. In Comparative Example 1, each of the light emitting layers is provided with a cathode electrode, so that the drive circuit becomes complicated, resulting in a 30% increase in cost and cost.

  Furthermore, as shown in FIG. 17, the lighting panel of another organic EL lighting device 3 that is a white element formed by superimposing red, green, and blue light-emitting layers in one organic EL element layer (hereinafter referred to as a comparative example). 2) and the luminance lifetime of the organic EL lighting device 1 were compared. Here, as the luminance life, the time when the luminance is 70% is compared with the initial luminance of 1000 nit. As a result, the luminance life of Comparative Example 2 was 35% shorter than the luminance life of the lighting panel of the organic EL lighting device 1. Further, since the comparative example 2 has different brightness reduction speeds of red, green, and blue, and the comparative example 2 cannot make corrections thereof, the color misalignment / chromaticity difference between the initial stage and the end of the lifetime is different from the organic EL lighting apparatus 1. It was confirmed that Δxy was 5 times or more larger than the lighting panel. In general, when the luminance of blue is faster than other colors and white illumination is used, the color shifts in the direction of lower color temperature along with driving. However, the organic EL lighting device 1 independently adjusts the luminance of each emission color. Since it can be adjusted, the color shift can be minimized by adjusting the luminance of the blue light emitting layer 51B.

  In the above embodiment, a reverse bias is applied to the monochromatic light emitting layer 51 before and after a constant current is passed through the monochromatic light emitting layer 51, but it is not necessary to apply a reverse bias. In this case, for example, as shown in FIG. 5, the drive circuit 200 applies a voltage Vp for supplying a reference voltage Vcom and a constant current to each anode electrode 80.

  Moreover, in the example of FIG. 4, FIG. 5, the example which sends a constant current continuously to each monochromatic light emitting layer 51 from the power-on of the organic EL lighting apparatus 1 to the power-off was shown. The present invention is not limited to this, and a constant current may be intermittently passed through each monochromatic light emitting layer 51. In this case, for example, as shown in FIGS. 6A and 6B, the effective current flowing through each monochromatic light emitting layer 51 is adjusted by intermittently turning on and off the voltage applied to the anode electrode 80. Can do. The effective current is determined by the applied voltage and the duty. The duty may be different for each monochromatic light emitting layer 51 or may be the same.

  Further, the duty may be adjusted. That is, the voltage Vp applied to each anode electrode 80 may be PWM (Pulse Width Modulation, pulse width modulation). In this case, for example, the control unit 110 includes an operation knob for adjusting the brightness. The control unit 110 adjusts the duty of the constant current flowing through each monochromatic light emitting layer 51 according to the operation of the operation knob, and instructs the drive circuit 200 by a control signal. As shown in FIGS. 7A to 7C, the drive circuit 200 adjusts the duty Ton / Tp of the voltage Vp0 applied to each anode electrode 80 according to the instruction of the control signal. The control unit 110 increases the duty Ton / Tp when increasing the light emission amount of the light emitting unit 300, and decreases the duty Ton / Tp when decreasing the light emission amount. It should be noted that the duty of the current passed through each of the red, green, and blue monochromatic light emitting layers 51 may be the same or different.

  FIGS. 7A to 7C show an example in which the voltage applied to the monochromatic light emitting layer 51 and the current to be applied are PWM-controlled. The current to be sent to each monochromatic light emitting layer 51 is represented by PAM (Pulse Amplitude Modulation, pulse amplitude). Modulation) control. In this case, the control unit 110 instructs the drive circuit 200 with a current for obtaining the brightness designated by the operation knob. As illustrated in FIGS. 8A to 8C, the drive circuit 200 applies the voltage VpB, which is applied to each anode electrode 80, so that a constant current instructed by the control signal flows through each monochromatic light emitting layer 51. VpR and VpG are adjusted.

  By driving in this way, the organic EL lighting device 1 can be lit so as to have desired luminance and color temperature. In addition, although the above-mentioned operation | movement is operation | movement in case the organic EL lighting apparatus 1 lights white, it is not restricted to this, The organic EL lighting apparatus 1 can be lighted in multiple colors.

  As described above, according to the organic EL lighting device 1 according to the present embodiment, the cathode electrode 10 is used as a common electrode for each monochromatic light emitting layer 51. Therefore, unlike the case where each light emitting layer is provided with a cathode electrode, the number of drivers for control during lighting and driving can be reduced, and the driving method can be simplified.

  Further, since the cathode electrode 10 including the non-light emitting portion between the monochromatic light emitting layers 51 can be formed with a metal thin film, the wiring resistance can be reduced and the driving voltage is lowered, resulting in power saving. . Moreover, the reflectance of the organic EL light emission of the cathode electrode 10 can be improved by forming into a uniform film. Furthermore, as described above, luminance unevenness can be reduced.

  Further, since each monochromatic light emitting layer 51 is driven independently, the color temperature, luminance, etc. of each monochromatic light emitting layer 51 can be corrected, and even when monochromatic light emitting layers having different luminance degradation rates are combined, The luminance life can be extended.

[Second Embodiment]
In the first embodiment, an organic EL lighting device having a configuration in which cathodes for a plurality of light emitting layers are used as a common electrode has been described. The present invention is not limited to this. It is also possible to use the anode as a common electrode. Hereinafter, an organic EL lighting device 1 ′ having a common anode for a plurality of light emitting layers will be described with reference to FIG.

  In the second embodiment, as shown in FIG. 9, the anode electrode 80 is disposed as a common electrode facing the all-monochromatic light emitting layer 51. On the other hand, the cathode electrode 10 is independently arranged so as to be paired with each monochromatic light emitting layer 51. Other basic configurations of the organic EL lighting device 1 ′ are the same as those of the organic EL lighting device 1 according to the first embodiment.

  The circuit configuration of the organic EL lighting device 1 'is shown in FIG.

  In the circuit of FIG. 10, the drive circuit 200 is based on the control signal received from the control unit 110 so that each single color light emitting layer 51 has a desired luminance and color temperature according to the control signal. A constant current is supplied between the electrodes 80.

  Examples of voltages applied to the cathode voltage 10 and the anode voltage 80 by the drive circuit 200 are shown in FIGS. The drive circuit 200 applies a reference potential Vcom to the anode electrode 80, and applies a common potential VO higher than the reference potential Vcom to each cathode electrode 10 for a predetermined time Ts. Subsequently, the drive circuit 200 maintains the reference potential Vcom applied to the anode electrode 80 while applying a constant current instructed from the control unit 110 to the light-emitting elements 51R, 51G, It is set to a voltage necessary for flowing to 51B. Thus, the drive circuit 200 applies a reverse bias to the potential of the cathode electrode 10 in order to suppress deterioration of the material due to charge accumulation. The positive potential as the reverse bias is set to be equal to or lower than the dielectric breakdown potential of the organic EL lighting panel of 0 to 5 V, for example.

  The drive circuit 200 does not necessarily need to reverse bias the monochromatic light emitting layer 51. An example of the drive waveform in this case is shown in FIG.

  The drive circuit 200 may flow a constant current intermittently. In this case, for example, as shown in FIGS. 13A and 13B, a constant current may be intermittently passed.

  Based on the control signal received from the control unit 110, the drive circuit 200, for example, the effective current supplied to each monochromatic light-emitting layer 51 by PWM control as shown in FIG. 14 or PAM control as shown in FIG. And the amount of emitted light may be controlled.

  By driving in this way, the organic EL lighting device 1 ′ can be lit to have a desired luminance and color temperature. In addition, although the above-mentioned operation | movement is an operation | movement when the organic EL lighting apparatus 1 'lights in white, it is not restricted to this, The organic EL lighting apparatus 1' can be lighted in multiple colors.

An organic EL lighting device 1 ′ having the above-described configuration was manufactured and its characteristics were measured.
First, an ITO thin film was formed to a uniform thickness on a glass substrate by sputtering, and an anode electrode 80 was formed. Furthermore, Cu—Pc was deposited on the anode electrode 80 by a vacuum vapor deposition method to form the hole injection layer 70. Further, α-NPD was deposited on the hole injection layer 70 by a vacuum evaporation method to form the hole transport layer 60.

  Next, a CBP film was formed on the hole transport layer 60. Further, Ir (ppy) 3 is diffused on the stripe in the CBP layer to form a green light emitting layer 51G, and Btp2Ir (acac) is diffused on the stripe in the CBP layer to form a red light emitting layer 51R. Further, the CBP layer The light emitting layer 50 was formed by diffusing FIr (pic) on the stripes to form the blue light emitting layer 51B. At this time, a shadow mask was formed by vacuum deposition or the like, and the light emitting layer 50 was separated into each color.

Next, CP was deposited on the light emitting layer 50 to form the hole blocking layer 40. Furthermore, Alq3 was deposited on the hole block 40 to form the electron transport layer 30 having a uniform thickness. Further, LiF was deposited on the electron transport layer 30 to form the electron injection layer 20.
Further, the cathode electrode 10 was formed by depositing Al in a uniform thickness.
In this way, a lighting panel was produced.

The drive current of 27 A / m ² , 25 A / m ² of green light emission, and 23 A / m ² of blue light emission were passed through the red light emission part of the lighting panel of the organic EL lighting device 1 ′. At this time, the driving voltage was 2.6V, 2.5V, 3.9V, the power efficiency was 32.4 lm / W, and the color temperature was 2800K. In addition, the luminance unevenness in the illumination panel surface was 3.5% or less as a difference between the maximum luminance and the minimum luminance.

Here, the characteristic of the above-mentioned lighting panel and the characteristic of the comparative example 1 used as a comparison object in 1st Embodiment are compared.
Comparative Example 1 is a lighting panel of a conventional organic EL lighting device 2. An example of the element structure is shown in FIG. The anode electrode 80 of the comparative example 1 is disposed for each monochromatic light emitting layer 51.
When the same color temperature as that described above was set as the color temperature of Comparative Example 1, the drive voltage increased due to an increase in wiring resistance and the like, and the power efficiency became 24 lm / W. The organic EL lighting device produced by the above method It was lower than the power efficiency of the 1 'panel. The lighting panel of the organic EL lighting device 1 ′ can reduce the wiring resistance by uniformly forming the anode electrode 80 as compared with the case where the electrode is not uniformly formed. Accordingly, power efficiency is increased. Furthermore, since the sheet resistance of the ITO transparent electrode, which has a high volume resistivity, can be reduced, the effect is great. By reducing the sheet resistance, a decrease in electric field is also suppressed, and the carrier injection efficiency is improved. The in-plane luminance unevenness of Comparative Example 1 is 20%, and the luminance unevenness of the illumination panel of the organic EL lighting device 1 ′ according to this embodiment is lower. Furthermore, since it is not necessary to use an auxiliary electrode such as a metal, the cost can be reduced.

  Further, the driving method can be simplified by reducing the number of control drivers during driving. In the conventional illumination panel, the drive circuit is complicated and the cost is increased by 30% compared to the organic EL illumination device 1 ′ according to the present embodiment.

  Further, as in the first embodiment, since each single color light emitting layer 51 is driven independently, the color temperature, luminance, etc. of each single color light emitting layer 51 can be respectively corrected, and the single color light emitting layers having different luminance degradation rates. Even when these are combined, the luminance life of the organic EL lighting panel can be extended.

  As described above, according to the organic EL lighting device 1 ′ according to the second embodiment, the anode electrode 80 is used as a common electrode for each monochromatic light emitting layer 51. Unlike the case where each light emitting layer is provided with an anode electrode, the number of drivers for control during lighting and driving can be reduced, and the driving method can be simplified. That is, the same effect as the organic EL lighting device 1 according to the first embodiment can be obtained.

[Modification]
The present invention is not limited to the above embodiment, and various modifications and applications are possible. Hereinafter, modifications of the above-described embodiment applicable to the present invention will be described.

  In the above-described embodiment, three colors of red, green, and blue are used for the light emitting layer 50, and white is formed by additive color mixing for illumination. However, the present invention is not limited to this, and white color is formed by mixing two colors for illumination. Also good. For example, blue and yellow may be used for the light emitting layer. The yellow light-emitting layer may be a single light-emitting material such as rubrene dopant shown in the above examples, or a red light-emitting material and a green light-emitting material are doped into the same light-emitting layer and formed by color mixing. May be. By using two colors, the number of non-light emitting portions between the respective light emitting colors can be reduced and the area thereof can be reduced, so that the light emitting portion area (aperture ratio) can be increased. Will improve.

  In the above embodiment, the cathode electrode 10 has been described as an electrode in which, for example, an aluminum metal thin film electrode is formed to have a uniform thickness. However, the present invention is not limited to this, and a metal conductive film and a reflective film with poor light reflectivity are used. It may be a two-layer structure with a metal thin film having excellent properties.

  In the above-described embodiment, the glass substrate 90 has been described as a translucent substrate made of glass, but is not limited thereto, and may be a substrate made of a plastic film. With such a configuration, the organic EL lighting panel can be variously modified.

  Note that a part or all of the embodiment and the drawings may be described as the following supplementary notes, but are not limited to the following. It goes without saying that the embodiments and the drawings can be modified without changing the gist of the present invention.

(Appendix 1)
A plurality of light-emitting layers that emit light by recombination of injected charges and have different emission colors;
A first electrode provided in a pair with each of the plurality of light emitting layers;
A second electrode provided in common to the plurality of light emitting layers;
A first transport layer for transporting charges injected from the first electrode to the plurality of light emitting layers;
A second transport layer for transporting charges injected from the second electrode to the plurality of light emitting layers;
Comprising
An organic EL lighting device.

(Appendix 2)
A drive circuit for supplying current to the plurality of light emitting layers through the first electrode and the second electrode;
The drive circuit uses a potential of either the first electrode or the second electrode as a reference potential, and supplies a constant current to each of the plurality of light emitting layers,
The plurality of light emitting layers emit light based on a constant current supplied from the drive circuit.
The organic EL lighting device according to Supplementary Note 1, wherein:

(Appendix 3)
A drive circuit for supplying current to the plurality of light emitting layers through the first electrode and the second electrode;
The drive circuit uses a potential of either the first electrode or the second electrode as a reference potential, and supplies a constant-current rectangular wave to each of the plurality of light emitting layers,
The plurality of light emitting layers are colored based on a current supplied from the drive circuit,
The organic EL lighting device according to Supplementary Note 1, wherein:

(Appendix 4)
The plurality of light emitting layers are dimmed based on a rectangular wave of a constant current supplied by the drive circuit by pulse width modulation.
The organic EL lighting device according to Supplementary Note 3, wherein

(Appendix 5)
The plurality of light emitting layers are dimmed based on a rectangular wave of a constant current supplied by the drive circuit by pulse amplitude modulation.
The organic EL lighting device according to Supplementary Note 3, wherein

(Appendix 6)
The plurality of light emitting layers are arranged at predetermined intervals, respectively.
The plurality of light emitting layers, a region that does not emit light between the respective light emitting layers, and a metal thin film are formed with a uniform thickness,
The organic EL lighting device according to any one of appendices 1 to 5, characterized in that:

(Appendix 7)
The organic EL lighting device according to appendix 1 or 6, wherein a reverse bias voltage equal to or lower than a dielectric breakdown voltage is applied to the plurality of light emitting layers.

  Various embodiments and modifications can be made to the present invention without departing from the broad spirit and scope of the present invention. Further, the above-described embodiment is for explaining the present invention, and does not limit the scope of the present invention. That is, the scope of the present invention is shown not by the embodiments but by the claims. Various modifications made within the scope of the claims and the equivalent invention are considered to be within the scope of the present invention.

  The present invention is based on Japanese Patent Application No. 2011-210006 filed on Sep. 26, 2011. The specification, claims, and entire drawings of Japanese Patent Application No. 2011-210006 are incorporated herein by reference.

  According to the present invention, power saving and high quality can be realized.

1, 1 ', 2, 3 Organic EL lighting device 10 Cathode electrode 20 Electron injection layer 30 Electron transport layer 40 Hole blocking layer 50 Light emitting layer 51 Monochromatic light emitting layer 51R Red light emitting layer 51G Green light emitting layer 51B Blue light emitting layer 60 Holes Transport layer 70 Hole injection layer 80 Anode electrode 90 Glass substrate 100 Diffusion plate 110 Control unit 200 Drive circuit 300 Light emitting unit 400 Converter 500 Rectification / smoothing circuit 600 Commercial power supply

Claims (6)

A plurality of light-emitting layers that emit light by recombination of injected charges and have different emission colors;
A first electrode provided in a pair with each of the plurality of light emitting layers;
A second electrode provided facing all of the plurality of light emitting layers in common;
A first transport layer for transporting charges injected from the first electrode to the plurality of light emitting layers;
A second transport layer for transporting charges injected from the second electrode to the plurality of light emitting layers;
A drive circuit for supplying current to the plurality of light emitting layers through the first electrode and the second electrode;
Equipped with a,
Wherein the driving circuit, the first electrode facing the light-emitting layer of the same luminescent color, the same voltage is applied to said second electrode, it applies a set voltage as a reference potential,
An organic EL lighting device. A drive circuit for supplying current to the plurality of light emitting layers through the first electrode and the second electrode;
Wherein the drive circuit, the potential of the pre-Symbol second electrodes and a reference potential, and supplies the rectangular wave of a constant current to the plurality of light emitting layers,
The plurality of light emitting layers are colored based on a current supplied from the drive circuit,
The organic EL lighting device according to claim 1. The plurality of light emitting layers are dimmed based on a rectangular wave of a constant current supplied by the drive circuit by pulse width modulation.
The organic EL lighting device according to claim 2 . The plurality of light emitting layers are dimmed based on a rectangular wave of a constant current supplied by the drive circuit by pulse amplitude modulation.
The organic EL lighting device according to claim 2 . The plurality of light emitting layers are arranged at predetermined intervals, respectively.
The second electrode is formed in a uniform thickness with a metal thin film, facing all of the plurality of light emitting layers and a non-light emitting region between the respective light emitting layers.
The organic EL lighting device according to any one of claims 1 to 4, characterized in that. The organic EL lighting device according to any one of claims 1 to 5 , wherein a reverse bias voltage equal to or lower than a dielectric breakdown voltage is applied to the plurality of light emitting layers.

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