JP2010129301A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which has little variations of hue to the variations of voltage to be impressed on an electrode and has a high luminous efficiency, a lighting device using the organic electroluminescent element, a planar light source, and a lighting apparatus. <P>SOLUTION: The organic EL element 11 includes a positive electrode 1 and a negative electrode 6, a plurality of light-emitting units which are provided between the positive electrode 1 and the negative electrode 6 and each of which includes a luminous layer, and a charge generating layer 40 which is arranged interposed between the light-emitting units. At least one of the light-emitting units includes a light-emitting part in which the luminous layers are laminated two layers or more, and each luminous layer to constitute the light-emitting part emits light of mutually different peak wavelength, and the luminous layer having longer peak wavelength of emitting light is arranged nearer the positive electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element (hereinafter sometimes referred to as an organic EL element), a manufacturing method thereof, an illumination device, a planar light source, and a display device.

The organic EL element includes a pair of electrodes and a light emitting layer provided between the electrodes. When a voltage is applied to the organic EL element, holes are injected from the anode and electrons are injected from the cathode, and light is emitted by recombination of these holes and electrons in the light emitting layer.
An organic EL element is used, for example, as a light source for a display device, a lighting device, and the like, and high luminous efficiency is required as its characteristics. The organic EL element is usually configured to include one light emitting layer, but a multiphoton type organic EL element has been proposed in order to improve the light emission efficiency with respect to the injected current. This multiphoton type organic EL element is an organic EL element having a configuration in which a plurality of light emitting units each having a light emitting layer are stacked (for example, see Patent Document 1).

  In addition, organic EL elements that emit white light are often used in display devices, lighting devices, and the like. As one of such organic EL elements, a single white light emitting layer in which a plurality of types of pigments are dispersed is used. An organic EL element including the above is disclosed (for example, see Patent Document 2). In general, a display device, a lighting device, and the like are preferably those whose color does not change even if the brightness changes. Accordingly, the organic EL element used as the light source also has a color with respect to a change in applied voltage. What has little change is required.

JP 2003-272860 A Japanese Patent Application Laid-Open No. 07-220871

  However, in a conventional organic EL device having a white light emitting layer in which a plurality of types of pigments are dispersed, the change in color with respect to the applied voltage is large and the light emission efficiency is low. Therefore, the present inventor has an organic EL element having a configuration in which a plurality of light emitting layers emitting different colors are stacked separately from an organic EL element having a white light emitting layer as an organic EL element that emits white light. Considered.

  The present invention has been made in view of the problems of the prior art, and the problem is that an organic electroluminescence element having a small change in color with respect to a change in voltage applied to an electrode and having a high luminous efficiency, the organic It is providing the illuminating device, surface light source, and illuminating device using an electroluminescent element.

  In order to solve the above-described problems, the present invention provides an organic electroluminescence element adopting the following configuration, and an illumination device, a planar light source, and a display device using the organic electroluminescence element.

[1] An anode, a cathode, a plurality of light emitting units provided between the anode and the cathode and each including a light emitting layer, and a charge generation layer disposed between the light emitting units.
The charge generation layer includes at least one kind of a metal having a work function of 3.0 eV or less and a compound thereof (A) and one or more kinds of a compound (B) having a work function of 4.0 eV or more, and the light emitting unit At least one of the organic electroluminescent elements is characterized by comprising a plurality of light emitting layers disposed closer to the anode as the light emitting layer has a longer peak wavelength of the emitted light.
[2] The charge generation layer includes a first layer containing at least one kind of the metal and its compound (A), and a second layer containing at least one kind of the compound (B), The organic electroluminescence element according to the above [1], wherein the first layer is disposed closer to the anode than the second layer.
[3] The above-mentioned [1], wherein the charge generation layer is a layer formed by mixing one or more of the metal and its compound (A) and one or more of the compound (B). The organic electroluminescent element of description.
[4] The organic electroluminescence device according to any one of [1] to [3], wherein the transmittance of the charge generation layer with respect to a wavelength of 550 nm is 30% or more.
[5] The metal according to any one of [1] to [4], wherein the metal having a work function of 3.0 eV or less is selected from the group consisting of alkali metals and alkaline earth metals. Organic electroluminescence element.
[6] The organic electroluminescence device according to any one of [1] to [5], wherein the compound having a work function of 4.0 eV or more is a transition metal oxide.
[7] The organic electroluminescence element according to any one of [1] to [6], wherein the colors of light emitted from the light emitting units are different from each other.
[8] At least one of the light emitting units has a light emitting layer that emits red light, a light emitting layer that emits green light, and a light emitting layer that emits blue light, and the peak wavelength of the emitted light is The organic electroluminescence device according to any one of [1] to [7], wherein a longer light emitting layer is disposed closer to the anode.
[9] When the voltage applied between the first electrode and the second electrode is changed, the change widths of the coordinate value x and the coordinate value y in the chromaticity coordinates of the light extracted outside are respectively It is 0.05 or less, The organic electroluminescent element as described in any one of said [1] to [8] characterized by the above-mentioned.
[10] An illuminating device comprising the organic electroluminescence element according to any one of [1] to [8].
[11] A planar light source comprising the organic electroluminescent element according to any one of [1] to [8].
[12] A display device comprising the organic electroluminescence element according to any one of [1] to [8].

  The organic EL device according to the present invention constitutes a multi-photon type organic EL device, and changes the voltage applied to the electrodes by arranging the light emitting layers in a predetermined order according to the peak wavelength of the emitted light. On the other hand, it is possible to realize an organic electroluminescence element with little change in color and high luminous efficiency.

  Hereinafter, an organic EL element according to an embodiment of the present invention will be described with reference to the drawings. For ease of understanding, the scale of each member in the drawings may be different from the actual scale. Further, the present invention is not limited by the following description, and can be appropriately changed without departing from the gist of the present invention. In the organic EL device, there are members such as electrode lead wires. However, in the explanation of the present invention, the description is omitted because it is not required directly. For convenience of explanation of the layer structure and the like, in the following example, the explanation will be made together with a diagram in which the substrate is arranged below. It is not used.

  FIG. 1 is a side view showing an organic EL element 11 according to an embodiment of the present invention. The organic EL element 11 of the present embodiment is usually provided on the substrate 10. The organic EL element 11 includes an anode 1, a cathode 6, a plurality of light emitting units each provided between the anode 1 and the cathode 6, each including a light emitting layer, and a charge generation layer 40 disposed between the light emitting units. And at least one of the light emitting units includes a plurality of light emitting layers arranged closer to the anode as the light emitting layer has a longer peak wavelength of emitted light.

The organic EL element of the present embodiment is a multiphoton type organic EL element, and includes two or more light emitting units. The element structure which an organic EL element can take is shown below.
(I) Anode / light emitting unit / charge generating layer / light emitting unit / cathode (ii) Anode / light emitting unit / (charge generating layer / light emitting unit) x / cathode Here, the symbol “/” is a layer sandwiching the symbol “/”. Indicates that they are stacked adjacent to each other. The symbol “x” represents an integer of 2 or more, and “(charge generation layer / light emitting unit) x” represents that x layers of the layered structure including the charge generation layer and the light emitting unit are stacked. Of the multi-photon organic EL elements, the element having the configuration (i) configured by stacking two light emitting units is particularly referred to as a tandem element.

  The organic EL element 11 in the present embodiment includes two light emitting units, a first light emitting unit 20 and a second light emitting unit 60, and a charge generation layer 40 sandwiched between the two light emitting units 20 and 60. Prepare. The organic EL element is usually provided on the substrate in an arrangement in which the anode is closest to the substrate in the configuration (i) or (ii). The organic EL element may be provided on the substrate in the configuration (i) or (ii) so that the cathode is closest to the substrate. The organic EL element 11 of the present embodiment is configured by laminating an anode 1, a first light emitting unit 20, a charge generation layer 40, a second light emitting unit 60, and a cathode 6 in this order on a substrate 10. That is, the organic EL element 11 of the present embodiment is an organic EL element having the configuration (i) and constitutes a so-called tandem organic EL element.

<Board>
The substrate 10 used in the organic EL element of the present embodiment may be any substrate that does not change when the organic EL element is formed. For example, a glass, a plastic, a silicon substrate, a laminate of these, or the like is used. A commercially available substrate can be used as the substrate. Moreover, a board | substrate can also be manufactured by a well-known method. A substrate in which a predetermined electronic circuit is incorporated in advance may be used. For example, a TFT (Thin Film Transistor) substrate may be used.

<Anode>
Since the organic EL element needs to extract light generated from the light emitting unit to the outside, at least one of the anode and the cathode is constituted by an electrode having translucency. In the present embodiment, an organic EL element having a structure in which light is extracted from an anode will be described.
As the anode 1 of the organic EL element of the present embodiment, an electrode having light transmissivity is used, and as such an electrode, a thin film made of metal oxide, metal sulfide, metal or the like having high electrical conductivity is used. Those having a high light transmittance are preferably used. Specifically, from indium oxide, zinc oxide, tin oxide, indium tin oxide (abbreviated as ITO), indium zinc oxide (abbreviated as IZO), gold, platinum, silver, copper, and the like A thin film made of ITO, IZO, or tin oxide is preferably used. Examples of a method for producing the anode include a vacuum deposition method, a sputtering method, an ion plating method, and a plating method. Further, an organic transparent conductive film such as polyaniline or a derivative thereof, polythiophene or a derivative thereof may be used as the anode.
For example, in the case of an organic EL element having a structure that does not extract light from the anode, the anode may be formed using a material that reflects light, such as a metal having a work function of 3.0 eV or more, Metal oxides and metal sulfides are preferred.

  The film thickness of the anode can be appropriately selected in consideration of light transmittance and electrical conductivity, and is, for example, 10 nm to 10 μm, preferably 20 nm to 1 μm, more preferably 50 nm to 500 nm. is there.

<Charge generation layer>
The charge generation layer 40 generates charges (holes and electrons) when a voltage is applied to the anode and the cathode, and injects electrons into the light emitting unit adjacent to the anode side with respect to the charge generation layer. It functions as a layer for injecting holes into the light emitting unit adjacent to the generation layer on the cathode side. In addition to the charges injected from the anode and the cathode, charges generated in the charge generation layer are also injected from the charge generation layer, so that the light emission efficiency (current efficiency) with respect to the injected current is improved.
In the organic EL element 11 of the present embodiment, the charge generation layer 40 is sandwiched between the first light emitting unit 20 and the second light emitting unit 60, and the first light emitting unit 20 and the second light emitting unit 60. (See FIG. 1).

  In the present embodiment, the charge generation layer 40 includes at least one kind of metal having a work function of 3.0 eV or less and its compound (A) and one or more kinds of compound (B) having a work function of 4.0 eV or more. Including. The charge generation layer 40 has one or more types of the compound (B) having a work function of 4.0 eV or more, rather than using one or more types of the metal having a work function of 3.0 eV or less and its compound (A) alone. By using in combination, it is possible to generate charges efficiently.

  The metal compound (A) having a work function of 3.0 eV or less refers to a compound having a metal work function of 3.0 eV or less and a work function of the compound itself of 3.0 eV or less. If the charge generation layer 40 does not contain a material whose work function satisfies the above range, effective charge injection is unlikely to occur, and the effects of the present invention cannot be obtained sufficiently.

  The metal having a work function of 3.0 eV or less constituting the charge generation layer can be selected from the group consisting of alkali metals, alkaline earth metals, and rare earth metals. Of these, alkali metals and alkaline earth metals are preferred. Examples of the alkali metal include lithium (Li) (2.93 eV), sodium (Na) (2.36 eV), potassium (K) (2.28 eV), rubidium (Rb) (2.16 eV), and cesium (Cs). (1.95 eV) is preferable, and as the alkaline earth metal, calcium (Ca) (2.9 eV) and barium (Ba) (2.52 eV) are preferable (the work function is shown in parentheses). Among these, Li is more preferable. Examples of the metal compound (A) having a work function of 3.0 eV or less constituting the charge generation layer include oxides, halides, fluorides, borides, nitrides and carbides of the above metals.

As the compound (B) having a work function of 4.0 eV or more, an inorganic or organic compound having a work function of 4.0 eV or more is selected. As the inorganic compound having a work function of 4.0 eV or more, a transition metal oxide is desirable. Among the transition metal oxides, vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo ), Tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), and the like are preferable, and V ₂ O ₅ is more preferable.

  As an organic compound having a work function of 4.0 eV or more, an electron acceptability that is difficult to dissolve in a coating solution used in a later step and easily receives electrons from a metal having a work function of 3.0 eV or less and its compound (A). The material is preferred. More preferably, it is preferable to form a charge transfer complex with a metal having a work function of 3.0 eV or less and its compound (A). An example of such a material is tetrafluoro-tetracyanoquinodimethane (4F-TCNQ).

The charge generation layer can have the following two structures.
(I) The charge generation layer 40 includes a first layer 4-1 including one or more kinds of the metal and the compound (A), and a second layer 4-2 including one or more kinds of the compound (B). (Laminated structure: see FIG. 1).
(II) The charge generation layer is a layer formed by mixing one or more of the metal and its compound (A) and one or more of the compound (B) (mixed layer).

  In the case of the laminated structure (I), it is preferable that the first layer 4-1 is disposed closer to the anode than the second layer 4-2, as shown in FIG.

  As a method of forming the mixed layer, a method of forming a layer in which two kinds of materials are mixed at a time by a method such as co-evaporation, or a method of forming a material constituting the first layer extremely thinly, A method of forming a mixed layer by forming an island-like discrete structure before forming a film and forming a second layer on this structure can be mentioned.

The thickness of the first layer 4-1 is preferably 10 nm or less, more preferably 6 nm or less, in order to sufficiently obtain the effects of the present invention.
The thickness of the second layer 4-2 is preferably 2 nm to 100 nm, and more preferably 4 nm to 80 nm.

  Further, the charge generation layer of the present embodiment may further include a transparent conductive thin film as the third layer. As the transparent conductive thin film, indium oxide, zinc oxide, tin oxide, indium tin oxide (ITO), or the like can be used.

  As a method for forming the charge generation layer of the present invention, a vacuum deposition method, a sputtering method, a coating method, or the like can be used.

  It is desirable that the light transmittance of the charge generation layer of this embodiment has a high transmittance with respect to light emitted from the light emitting layer. In order to sufficiently extract light and obtain sufficient luminance, the transmittance at a wavelength of 550 nm is preferably 30% or more, and more preferably 50% or more.

<Light emitting unit>
Next, the light emitting unit will be described. The light emitting unit includes at least a light emitting layer. In addition, the light emitting unit may be comprised only by the light emitting layer, and may contain the inorganic layer. The light emitting unit has a configuration similar to that of a portion sandwiched between an anode and a cathode in a normal organic EL element including one light emitting layer that is not a multiphoton type.
The light emitting unit may have a layer other than the light emitting layer as necessary. Among the layers constituting the light emitting unit, examples of the layer provided on the anode side with respect to the light emitting layer include a hole injection layer, a hole transport layer, and an electron block layer. When both the hole injection layer and the hole transport layer are provided, a layer in contact with the charge generation layer or the anode is referred to as a hole injection layer, and a layer excluding this hole injection layer is referred to as a hole transport layer.
The hole injection layer is a layer having a function of improving the efficiency of hole injection from the charge generation layer or the anode. The hole transport layer is a layer having a function of improving hole injection from the anode, the charge generation layer, the hole injection layer, or the hole transport layer closer to the anode. The electron blocking layer is a layer having a function of blocking electron transport. In the case where the hole injection layer and / or the hole transport layer has a function of blocking electron transport, these layers may also serve as an electron blocking layer.
Among the layers constituting the light emitting unit, examples of the layer provided on the cathode side with respect to the light emitting layer include an electron injection layer, an electron transport layer, and a hole blocking layer. When both the electron injection layer and the electron transport layer are provided, a layer in contact with the cathode is referred to as an electron injection layer, and a layer excluding the electron injection layer is referred to as an electron transport layer.
The electron injection layer is a layer having a function of improving electron injection efficiency from the cathode or the charge generation layer. The electron transport layer is a layer having a function of improving electron injection from the cathode, the charge generation layer, the electron injection layer, or the electron transport layer closer to the cathode. The hole blocking layer is a layer having a function of blocking hole transport. In the case where the electron injection layer and / or the electron transport layer have a function of blocking hole transport, these layers may also serve as the hole blocking layer.
The fact that the hole blocking layer has a function of blocking hole transport makes it possible, for example, to produce an element that allows only a hole current to flow, and confirm the blocking effect by reducing the current value.

A specific example of the layer structure that the light emitting unit can take is shown below.
a) Light emitting layer b) Hole injection layer / light emitting layer c) Hole injection layer / light emitting layer / electron injection layer d) Hole injection layer / light emitting layer / electron transport layer e) Hole injection layer / light emitting layer / electron Transport layer / electron injection layer f) hole injection layer / hole transport layer / light emitting layer g) hole injection layer / hole transport layer / light emitting layer / electron injection layer h) hole injection layer / hole transport layer / Light emitting layer / electron transport layer i) hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer j) light emitting layer / electron injection layer k) light emitting layer / electron transport layer / electron injection layer In the configurations of a) to k), the left side is a layer closer to the anode, and the right side is a layer closer to the cathode.

The plurality of light emitting units included in the organic EL element may have the same layer configuration, or may have different layer configurations. The organic EL element of the present embodiment includes a plurality of light emitting units, and at least one light emitting unit includes a plurality of light emitting layers. Hereinafter, a stacked body formed by stacking a plurality of light emitting layers is referred to as a light emitting portion. In the configurations of a) to k), a light emitting unit having only one light emitting layer is shown. However, in the case of a light emitting unit having a plurality of light emitting layers, the “light emitting layer” in the configurations of a) to k) above. "May be replaced with" light emitting part ". The “light emitting portion” may be composed of only a plurality of light emitting layers, and may include a predetermined layer (charge injection layer, charge transport layer, etc.) other than the charge generation layer. The first light emitting unit 20 of the present embodiment shown in FIG. 1 has a configuration in which the “light emitting layer” is replaced with the “light emitting portion” in the configuration of b), that is, the hole injection layer 2 and the first light emitting portion 30. The second light emitting unit 60 is configured by replacing the “light emitting layer” with the “light emitting unit” in the configuration of a), that is, only the second light emitting unit 50. .
Hereinafter, each layer constituting the light emitting unit will be described in more detail.

<Hole injection layer>
As the hole injection material constituting the hole injection layer, oxides such as vanadium oxide, molybdenum oxide, ruthenium oxide, and aluminum oxide, phenylamine type, starburst type amine type, phthalocyanine type, amorphous carbon, polyaniline, And polythiophene derivatives.
Examples of the method for forming the hole injection layer include film formation from a solution containing a hole injection material. The solvent used for film formation from a solution is not particularly limited as long as it dissolves the hole injection material. Chlorine solvents such as chloroform, methylene chloride, dichloroethane, ether solvents such as tetrahydrofuran, toluene, xylene And aromatic hydrocarbon solvents such as acetone, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate, butyl acetate and ethyl cellosolve acetate, and water.
As a film forming method from a solution, a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a dip coating method, a spray coating method, a screen printing method, Examples of the application method include a flexographic printing method, an offset printing method, and an ink jet printing method.
The film thickness of the hole injection layer varies depending on the material used, and is set as appropriate so that the drive voltage and light emission efficiency are appropriate. If it is thick, the driving voltage of the element increases, which is not preferable. Therefore, the film thickness of the hole injection layer is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm.

<Hole transport layer>
Materials constituting the hole transport layer include polyvinyl carbazole or derivatives thereof, polysilane or derivatives thereof, polysiloxane derivatives having aromatic amines in the side chain or main chain, pyrazoline derivatives, arylamine derivatives, stilbene derivatives, triphenyldiamine. Derivatives, polyaniline or derivatives thereof, polythiophene or derivatives thereof, polyarylamine or derivatives thereof, polypyrrole or derivatives thereof, poly (p-phenylene vinylene) or derivatives thereof, or poly (2,5-thienylene vinylene) or derivatives thereof, etc. Is exemplified.

  Among these, as a hole transport material used for the hole transport layer, polyvinyl carbazole or a derivative thereof, polysilane or a derivative thereof, a polysiloxane derivative having an aromatic amine compound group in a side chain or a main chain, polyaniline or a derivative thereof, Polymeric hole transport materials such as polythiophene or derivatives thereof, polyarylamine or derivatives thereof, poly (p-phenylene vinylene) or derivatives thereof, or poly (2,5-thienylene vinylene) or derivatives thereof are preferred, and more preferred Is polyvinyl carbazole or a derivative thereof, polysilane or a derivative thereof, and a polysiloxane derivative having an aromatic amine in a side chain or a main chain. In the case of a low-molecular hole transport material, it is preferably used by being dispersed in a polymer binder.

  Although there is no restriction | limiting in the film-forming method of a positive hole transport layer, In the low molecular hole transport material, the method by the film-forming from a mixed solution with a polymer binder is illustrated. In the case of a polymer hole transport material, a method of film formation from a solution is exemplified.

  The solvent used for film formation from a solution is not particularly limited as long as it can dissolve a hole transport material. Examples of the solvent include chlorine solvents such as chloroform, methylene chloride, and dichloroethane; ether solvents such as tetrahydrofuran; aromatic hydrocarbon solvents such as toluene and xylene; ketone solvents such as acetone and methyl ethyl ketone; ethyl acetate, butyl acetate, An ester solvent such as ethyl cellosolve acetate is exemplified.

  Examples of film formation methods from solution include spin coating from solution, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary Coating methods such as coating methods, spray coating methods, nozzle coating methods, etc., gravure printing methods, screen printing methods, flexographic printing methods, offset printing methods, reverse printing methods, printing methods such as inkjet printing methods, etc. may be used. it can. A printing method such as a gravure printing method, a screen printing method, a flexographic printing method, an offset printing method, a reversal printing method, and an inkjet printing method is preferable in that the pattern formation is easy.

  As the polymer binder to be mixed, those not extremely disturbing charge transport are preferable, and those showing no strong absorption against visible light are suitably used. Examples of the polymer binder include polycarbonate, polyacrylate, polymethyl acrylate, polymethyl methacrylate, polystyrene, polyvinyl chloride, and polysiloxane.

  The film thickness of the hole transport layer differs depending on the material used, and may be selected so that the drive voltage and the light emission efficiency are appropriate. However, at least a thickness that does not cause pinholes is required. If it is too thick, the driving voltage of the element becomes high, which is not preferable. Therefore, the film thickness of the hole transport layer is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm.

<Light emitting part>
In the present invention, at least one of the plurality of light emitting units includes a plurality of light emitting layers arranged closer to the anode as the light emitting layer has a longer peak wavelength of light to be emitted.

FIG. 2 is a diagram more specifically showing an example of the configuration of the light emitting unit in the organic EL element shown in FIG. 1 (note that the substrate 10 is omitted). In the example of the organic EL element 11-1 shown in FIG. 2, the first light emitting unit 30 includes three light emitting layers 3 </ b> R, 3 </ b> G arranged closer to the anode 1 as the light emitting layer having a longer peak wavelength of emitted light. 3B is laminated. Specifically, the first light emitting unit 30 includes, in order from the anode 1 side, a red light emitting layer (hereinafter sometimes referred to as a red light emitting layer) 3R and a green light emitting layer (hereinafter referred to as a green light emitting layer). 3G) (which may be referred to as a layer) and a light emitting layer (hereinafter also referred to as a blue light emitting layer) 3B that emits blue light are stacked in this order.
Further, the second light emitting unit 50 is configured by laminating three light emitting layers 5R, 5G, and 5B disposed closer to the anode 1 as the light emitting layer having a longer peak wavelength of emitted light, and from the anode 1 side. In order, the red light emitting layer 5R, the green light emitting layer 5G, and the blue light emitting layer 5B are stacked in this order.

In the first and second light emitting units 30 and 50, the red light emitting layer 3R (5R) has the longest peak wavelength of emitted light among the three light emitting layers constituting the light emitting layer. Among the three light emitting layers, the green light emitting layer 3G (5G) is disposed in the middle of the three light emitting layers and emits blue light. The layer 3B (5B) is disposed closest to the cathode 6 among the three light emitting layers because the peak wavelength of the emitted light is the shortest among the three light emitting layers.
The peak wavelength emitted from the light emitting layer is a wavelength that gives the strongest light intensity when the emitted light is viewed in the wavelength region.

As the red light emitting layer 3R (5R), one having a peak wavelength of emitted light of, for example, 580 nm to 660 nm, preferably 600 to 640 nm is used. As the green light emitting layer 3G (5G), one having a peak wavelength of emitted light of, for example, 500 nm to 560 nm, preferably 520 nm to 540 nm is used. As the blue light emitting layer 3B (5B), one having a peak wavelength of emitted light of, for example, 400 nm to 500 nm, preferably 420 nm to 480 nm is used.
When light emitted from each of the three light emitting layers that emit light at such peak wavelengths is superimposed, white light is obtained. Therefore, the organic EL element of the present embodiment, in which the light emitting portion is composed of three layers of a red light emitting layer, a green light emitting layer, and a blue light emitting layer, emits white light as a whole.

  In addition, in FIG. 2, although each light emitting unit 20 and 60 shows the tandem-type organic EL element 11-1 provided with the light emitting layer of 3 layers, respectively, it shows, for example in FIGS. There is such a tandem organic EL element.

  An organic EL element 11-2 shown in FIG. 3 is a tandem type element in which the first light emitting unit 30 is configured by two light emitting layers in the organic EL element 11-1 shown in FIG. Specifically, as shown in FIG. 3, the first light emitting unit 30 is configured by stacking two layers of a red light emitting layer 3R and a blue light emitting layer 3B in this order from the anode 1 side. .

In addition, the structure of the 2nd light emission part 50 is the same as that of the organic EL element 11-1 of FIG.
In the organic EL element 11-2 shown in FIG. 3, other laminated structures of the first light emitting unit 30 are: 1) a laminated structure of a green light emitting layer 3 G and a blue light emitting layer 3 B in order from the anode 1 side; ) A red light emitting layer 3R, a green light emitting layer 3G, and a laminated structure can be mentioned in order from the anode 1 side.

An organic EL element 11-3 shown in FIG. 4 is a tandem type element in which the first and second light emitting units 30 and 50 are each composed of two light emitting layers in the organic EL element 11-1 shown in FIG. is there. Specifically, as shown in FIG. 4, the first light emitting unit 30 is configured by stacking two layers of a green light emitting layer 3G and a blue light emitting layer 3B in this order from the anode 1 side.
Further, the second light emitting unit 50 is configured by sequentially stacking a red light emitting layer 5R and a blue light emitting layer 5B in this order from the anode 1 side.

  In the organic EL element shown in FIG. 4, other laminated structures of the first light emitting unit 30 include 1) a laminated structure of a red light emitting layer 3R and a green light emitting layer 3G in order from the anode 1 side, 2) A laminated structure of the green light emitting layer 3G and the blue light emitting layer 3B can be mentioned in order from the anode 1 side. In addition to the above, the other light-emitting portion 50 is laminated in the following order: 1) the red light-emitting layer 5R and green light-emitting layer 5G in order from the anode 1 side; and 2) the anode 1 side in order. There is a laminated configuration of a green light emitting layer 5G and a blue light emitting layer 5B. Therefore, 2 layers × 2 layers (the left side of the symbol “x” represents the number of light emitting layers of the first light emitting unit, and the right side of the symbol “x” represents the number of stacked light emitting layers of the second light emitting unit. The same shall apply hereinafter.) The multi-photon type organic EL device has 9 × 3 × 3 device configurations.

  The organic EL element 11-4 shown in FIG. 5 is a 1 × 2 multiphoton type in which the first light emitting unit has one light emitting layer and the second light emitting unit has two light emitting layers. It is an element. Specifically, the light emitting layer included in the first light unit 20 includes any one of the red light emitting layer 3R, the green light emitting layer 3G, and the blue light emitting layer 3B. In FIG. An example in which 20 includes the green light emitting layer 3G is shown. Further, the second light emitting unit 50 is configured by sequentially stacking a red light emitting layer 5R and a blue light emitting layer 5B in this order from the anode 1 side.

In the multi-photon type organic EL element of 1 layer × 2 layers shown in FIG. 5, the other light emitting part 50 has the following other laminated structure: 1) the red light emitting layer 5R in order from the anode 1 side, There are a laminated structure with the green light emitting layer 5G and 2) a laminated structure with the green light emitting layer 5G and the blue light emitting layer 5B in order from the anode 1 side.
Accordingly, there are nine 3 × 3 element configurations as the multi-photon organic EL element of 1 layer × 2 layers. There are three combinations for white.

In the organic EL element 11-5 shown in FIG. 6, the first light-emitting unit 20 has one light-emitting layer, and the second light-emitting unit 60 has three light-emitting layers. Type element. Specifically, the light emitting layer included in the first light unit is configured by any one of the red light emitting layer 3R, the green light emitting layer 3G, and the blue light emitting layer 3B. In FIG. Shows an example including a green light emitting layer 3G. Further, the second light emitting unit 50 is configured by sequentially stacking a red light emitting layer 5R, a green light emitting layer 5G, and a blue light emitting layer 5B in this order from the anode 1 side.
Therefore, there are 3 × 1 three element configurations as the 1 × 3 multi-photon type organic EL device.

  Each light emitting layer is formed by a coating method in this embodiment. Each light emitting layer formed by coating is insolubilized in the coating solution to be applied before the coating solution of the light emitting layer to be formed next is coated on the surface. Specifically, when the red light emitting layer 3R (5R), the green light emitting layer 3G (5G), and the blue light emitting layer 3B (5B) are formed in this order by the coating method, the green light emitting layer 3G (5G) is formed by the coating method. Before the film formation, the red light emitting layer 3R (5R) is insolubilized, and before the blue light emitting layer 3B (5B) is formed by a coating method, the green light emitting layer 3G (5G) is insolubilized.

  At least a part of the material constituting the light emitting layer to be insolubilized is crosslinked by applying energy. After applying a coating solution containing such a material to form a film, it is possible to insolubilize the film by applying light or heat as energy and crosslinking.

The material mainly constituting the light-emitting layer to be insolubilized may form the light-emitting layer using a material that is cross-linked by applying energy, and among the materials constituting the light-emitting layer to be insolubilized, The light emitting layer may be formed using a material in which at least a part of the remaining material excluding the material mainly constituting the light emitting layer is cross-linked by applying energy.
In the latter case, in addition to the material mainly constituting the light emitting layer, a crosslinking agent that is crosslinked by applying energy is further added to the coating solution.

  In addition, if the material which mainly comprises a light emitting layer is what crosslinks by adding energy, it is not necessary to add a crosslinking agent to a coating liquid.

  The material mainly constituting the light emitting layer is the material having the highest mass concentration in the light emitting layer, and among the materials constituting the light emitting layer, a material that emits fluorescence and / or phosphorescence (hereinafter sometimes referred to as a light emitting material). Equivalent).

In the case of using a material that crosslinks by applying energy as a material mainly constituting the light emitting layer, a polymer compound that includes a group that crosslinks by applying energy (hereinafter referred to as a crosslinkable group) may be used.
Examples of the crosslinking group include a vinyl group. As the material mainly constituting the light emitting layer, specifically, a material using a polymer compound containing a residue obtained by removing at least one hydrogen atom from benzocyclobutane (BCB) in the main chain and / or side chain. Can be mentioned.

  In addition to the material mainly constituting the light emitting layer, the crosslinking agent added to the coating solution includes vinyl group, acetyl group, butenyl group, acrylic group, acrylamide group, methacryl group, methacrylamide group, vinyl ether group, vinyl Examples thereof include compounds having a polymerizable substituent selected from the group consisting of an amino group, a silanol group, a cyclopropyl group, a cyclobutyl group, an epoxy group, an oxetane group, a diketene group, an episulfide group, a lactone group, and a lactam group. . As such a compound for a crosslinking agent, for example, a polyfunctional acrylate is preferable, and dipentaerythritol hexaacrylate (DPHA), trispentaerythritol octaacrylate (TPEA), and the like are more preferable.

  Each light emitting layer includes an organic substance that emits fluorescence and / or phosphorescence, or an organic substance and a dopant. The dopant is added for the purpose of, for example, improving the light emission efficiency or changing the light emission wavelength. Examples of the light emitting material mainly constituting each light emitting layer include the following.

  Examples of dye-based light-emitting materials include cyclopentamine derivatives, tetraphenylbutadiene derivative compounds, triphenylamine derivatives, oxadiazole derivatives, pyrazoloquinoline derivatives, distyrylbenzene derivatives, distyrylarylene derivatives, pyrrole derivatives, thiophenes. Examples of the polymer include ring compounds, pyridine ring compounds, perinone derivatives, perylene derivatives, oligothiophene derivatives, oxadiazole dimers, quinacridone derivatives, coumarin derivatives, and pyrazoline dimers.

  The metal complex-based light emitting material includes Al, Zn, Be or the like as a central metal, or a rare earth metal such as Tb, Eu, or Dy, and oxadiazole, thiadiazole, phenylpyridine, or phenylbenzo as ligands. Examples of the polymer complexes of metal complexes having an imidazole or quinoline structure, such as iridium complexes, platinum complexes, etc., metal complexes that emit light from triplet excited states, aluminum quinolinol complexes, benzoquinolinol beryllium complexes, etc. Benzoxazolyl zinc complex, benzothiazole zinc complex, azomethylzinc complex, porphyrin zinc complex, europium complex and the like.

  Examples of the polymer light-emitting material include polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyfluorene derivatives, and polyvinylcarbazole derivatives.

  As the light emitting material mainly constituting the red light emitting layer 3R (5R), among the above light emitting materials, coumarin derivatives, thiophene ring compounds, and polymers thereof, polyparaphenylene vinylene derivatives, polythiophene derivatives, polyfluorene derivatives, etc. Can be mentioned. Among these, polymer materials such as polyparaphenylene vinylene derivatives, polythiophene derivatives, and polyfluorene derivatives are preferable.

  Examples of materials mainly constituting the green light emitting layer 3G (5G) include quinacridone derivatives, coumarin derivatives, thiophene ring compounds and polymers thereof, polyparaphenylene vinylene derivatives, polyfluorene derivatives, etc. among the above-described light emitting materials. be able to. Of these, polymer materials such as polyparaphenylene vinylene derivatives and polyfluorene derivatives are preferred.

  As a material mainly constituting the blue light emitting layer 3B (5B), among the above light emitting materials, a polymer of a distyrylarylene derivative and / or an oxadiazole derivative, a polyvinylcarbazole derivative, a polyparaphenylene derivative, a polyfluorene Derivatives and the like can be mentioned. Of these, polymer materials such as polyvinyl carbazole derivatives, polyparaphenylene derivatives, and polyfluorene derivatives are preferred.

  As a light emitting material mainly constituting each light emitting layer, in addition to the above light emitting material, for example, a dopant material may be further included for the purpose of improving the light emission efficiency or changing the light emission wavelength. Examples of such dopant materials include perylene derivatives, coumarin derivatives, rubrene derivatives, quinacridone derivatives, squalium derivatives, porphyrin derivatives, styryl dyes, tetracene derivatives, pyrazolone derivatives, decacyclene, phenoxazone, and the like.

  Each light emitting layer can be formed by a method similar to the method of forming the hole injection layer described above. Specifically, the film is formed by applying a coating solution in which the material constituting the light emitting layers 3R, 3G, and 3B is dissolved in the same solvent as the solvent for dissolving the hole injection material by the above-described conventional coating method. can do.

  In the organic EL element 11-1 shown in FIG. 2, first, the red light emitting layer 3 </ b> R is formed on the hole injection layer 2. Specifically, a coating solution in which the material constituting the red light emitting layer 3R described above is dissolved is applied onto the surface of the hole injection layer 2 by a conventional coating method. Next, the coated red light emitting layer 3R is obtained by heating or irradiating the applied film with light. The red light emitting layer 3R thus crosslinked does not elute even when a coating solution is applied to form the green light emitting layer 3G.

  Next, the green light emitting layer 3G is formed. Specifically, a coating solution in which the material constituting the green light emitting layer 3G is dissolved is applied onto the surface of the red light emitting layer 3R by a conventional coating method. Next, the coated green light emitting layer 3G is obtained by heating or irradiating the applied film with light. The green light emitting layer 3G thus cross-linked does not elute even when a coating solution is applied to form the blue light emitting layer 3B.

  Next, a blue light emitting layer 3B is formed. Specifically, the blue light-emitting layer 3B is obtained by applying a coating solution in which the material constituting the blue light-emitting layer 3B described above is dissolved onto the surface of the green light-emitting layer 3G by a conventional coating method and drying.

  As described above, when the light emitting layer to be coated is applied to the surface of the previously formed light emitting layer by insolubilizing the light emitting layer to which the coating liquid is applied in advance. It is possible to prevent the previously formed light emitting layer from being dissolved. Thereby, control of the film thickness of each light emitting layer becomes easy, and the light emitting layer of the intended film thickness can be formed easily.

  After the first light-emitting unit 20 is formed, the charge generation layer 40 is formed, and then the light-emitting layers 5R, 5G, and 5B constituting the second light-emitting unit 60 are formed in the same manner as the first light-emitting unit. To do.

  The layer thickness of each light emitting layer constituting the light emitting layer is preferably as thin as the light emitting layer disposed on the anode 1 side. Specifically, the green light emitting layer 3G (5G) is thicker than the red light emitting layer 3R (5R), and the blue light emitting layer 3B (5B) is thicker than the green light emitting layer 3G (5G). ) Is preferably thicker. More specifically, the layer thickness of the red light emitting layer 3R (5R) is preferably 5 nm to 20 nm, and more preferably 10 nm to 15 nm. Further, the thickness of the green light emitting layer 3G (5G) is preferably 10 nm to 30 nm, and more preferably 15 nm to 25 nm. Further, the layer thickness of the blue light emitting layer 3B (5B) is preferably 40 nm to 70 nm, and more preferably 50 nm to 65 nm. Thus, by setting the layer thickness of each of the light emitting layers 3R (5R), 3G (5G), and 3B (5B), there is little change in color with respect to the change in the voltage applied to the electrodes, and driving An organic EL element that emits light with low voltage and high efficiency can be realized.

  In addition, since each light emitting layer constituting the light emitting unit 30 (50) is arranged closer to the anode 1 as the light emitting layer having a longer peak wavelength of emitted light, the electrode is set by setting the layer thickness of each light emitting layer. It is possible to realize an organic EL element having a small change in color and a low driving voltage with respect to a change in voltage applied to.

  Note that a light emitting layer having a longer peak wavelength of emitted light tends to have a lower highest occupied molecular orbital (abbreviated as HOMO) and lowest unoccupied molecular orbital (abbreviated as LUMO). Therefore, in the organic EL element of the present embodiment in which the light emitting layer having a longer peak wavelength of emitted light is disposed closer to the anode 1, the light emitting layer having lower HOMO and LUMO is disposed closer to the anode 1. Thus, since the HOMO and LUMO are sequentially increased as the light emitting layer is separated from the anode 1, holes and electrons can be efficiently transported between the light emitting layers, resulting in a change in voltage applied to the electrodes. On the other hand, it is presumed that an organic EL element with little change in color and low driving voltage can be realized. Certainly, it is possible to improve the light emission efficiency by constructing a multi-photon type organic EL element, but it does not constitute a multi-photon type organic EL element simply by laminating a plurality of light emitting units. As described above, in consideration of the stacking order of the plurality of light-emitting layers included in each light-emitting unit, the light-emitting layers are stacked in a predetermined stacking order. A multi-photon organic EL element with little change in taste and high luminous efficiency can be realized.

In the organic EL element having such a configuration, when the voltage applied between the anode and the cathode is changed, the range of change in the coordinate value x and the coordinate value y in the chromaticity coordinates of the light extracted outside is as follows. In each case, an organic EL element of 0.05 or less can be realized. Here, the range of the time for changing the voltage to be applied is generally in the range where the luminance is ^{100cd / m 2 ~10000cd / m 2} , a range of at least ^{4000cd / m 2 ~6000cd / m 2} .
Here, the light extracted outside is light obtained by superimposing the light from each of the light emitting layers 3R (5R), 3G (5G), and 3B (5B), and the chromaticity coordinates in the present embodiment. Is CIE1931 established by the International Commission on Illumination (CIE).

  In the embodiment shown in FIG. 2, the first and second light emitting units 30 (50) are configured by stacking three light emitting layers 3R (5R), 3G (5G), and 3B (5B), and are white as a whole. However, each of the light emitting layers 3R (5R), 3G (5G), and 3B (5B) of the present embodiment is provided with a light emitting layer that emits light having a wavelength different from that emitted, for example, white May constitute a light emitting layer that emits light of different wavelengths, and the light emitting section 30 may be composed of four or more light emitting layers. The color of light emitted from each light emitting layer is appropriately selected according to the color of light extracted from each organic EL element.

  In addition, even if the color of the light taken out from the organic EL element is white or a color different from white, and the number of layers of the light emitting part is 3, it is 4 layers or more. However, in each light emitting part, by arranging the light emitting layer having a longer peak wavelength of emitted light closer to the anode 1, there is less change in color with respect to the change in voltage applied to the electrode, and high efficiency. An organic EL element that emits light can be realized.

(Mixed color, white)
Since the organic EL element of the present embodiment includes a plurality of light emitting units that emit light at the same time, the light extracted from the organic EL element by color mixture is made different from each other by changing the colors of the light emitted from each light emitting unit. Can be different from the color of the light emitted from each light emitting unit. For example, the color of the extracted light can be white by combining two colors having a complementary color relationship, mixing three colors such as RGB, or mixing four or more colors. Thus, by making the light emission colors of the respective light emitting units different from each other, the desired light emission color can be taken out, so that the degree of freedom in design is improved.

<Electron transport layer>
As the electron transport layer, known materials can be used, such as oxadiazole derivatives, anthraquinodimethane or derivatives thereof, benzoquinone or derivatives thereof, naphthoquinone or derivatives thereof, anthraquinones or derivatives thereof, tetracyanoanthraquinodimethane or derivatives thereof. , Fluorenone derivatives, diphenyldicyanoethylene or derivatives thereof, diphenoquinone derivatives, or metal complexes of 8-hydroxyquinoline or derivatives thereof, polyquinoline or derivatives thereof, polyquinoxaline or derivatives thereof, polyfluorene or derivatives thereof, and the like.

  Of these, oxadiazole derivatives, benzoquinone or derivatives thereof, anthraquinones or derivatives thereof, or metal complexes of 8-hydroxyquinoline or derivatives thereof, polyquinoline or derivatives thereof, polyquinoxaline or derivatives thereof, polyfluorene or derivatives thereof are preferred, 2- (4-biphenylyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, benzoquinone, anthraquinone, tris (8-quinolinol) aluminum, and polyquinoline are more preferable.

  There are no particular restrictions on the method of forming the electron transport layer, but in the case of a low molecular electron transport material, a vacuum deposition method from powder or a method by film formation from a solution or a molten state is used. Each method is exemplified by film formation from a molten state. When forming a film from a solution or a molten state, a polymer binder may be used in combination. Examples of the method for forming an electron transport layer from a solution include the same film formation method as the method for forming a hole transport layer from a solution described above.

  The film thickness of the electron transport layer varies depending on the material used, and may be selected so that the drive voltage and the light emission efficiency are appropriate. However, at least a thickness that does not cause pinholes is required. If the thickness is too thick, the driving voltage of the element increases, which is not preferable. Therefore, the thickness of the electron transport layer is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, and more preferably 5 nm to 200 nm.

<Electron injection layer>
The electron injection layer is provided between the electron transport layer and the cathode or between the light emitting layer and the cathode. Depending on the type of the light emitting layer, the electron injection layer may be an alkali metal or alkaline earth metal, an alloy containing one or more of the above metals, or an oxide, halide and carbonate of the metal, or a mixture of the above substances. Etc. Examples of alkali metals or oxides, halides and carbonates thereof include lithium, sodium, potassium, rubidium, cesium, lithium oxide, lithium fluoride, sodium oxide, sodium fluoride, potassium oxide, potassium fluoride, rubidium oxide. , Rubidium fluoride, cesium oxide, cesium fluoride, lithium carbonate and the like. Examples of alkaline earth metals or oxides, halides and carbonates thereof include magnesium, calcium, barium, strontium, magnesium oxide, magnesium fluoride, calcium oxide, calcium fluoride, barium oxide, barium fluoride, Examples include strontium oxide, strontium fluoride, and magnesium carbonate. The electron injection layer may be a laminate of two or more layers. Specifically, LiF / Ca etc. are mentioned. The electron injection layer is formed by vapor deposition, sputtering, printing, or the like. The thickness of the electron injection layer is preferably about 1 nm to 1 μm.

<Cathode>
As a material for the cathode used in the organic EL element of this embodiment, a material having a small work function and easy electron injection into the light emitting layer, a high electrical conductivity, and a high visible light reflectance is preferable. As a material for the cathode, an alkali metal, an alkaline earth metal, a transition metal, or a group 13 metal in the periodic table can be used. For example, a metal such as lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, aluminum, scandium, vanadium, zinc, yttrium, indium, cerium, samarium, europium, terbium, ytterbium, or the metal Or an alloy of one or more of them with one or more of gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, tungsten, tin, or a graphite or graphite layer A compound or the like is used. Examples of the alloy include magnesium-silver alloy, magnesium-indium alloy, magnesium-aluminum alloy, indium-silver alloy, lithium-aluminum alloy, lithium-magnesium alloy, lithium-indium alloy, calcium-aluminum alloy, and the like. Moreover, a transparent conductive electrode can be used as a cathode, for example, a conductive metal oxide, a conductive organic substance, etc. can be used. Specifically, indium oxide, zinc oxide, tin oxide, ITO or IZO may be used as the conductive metal oxide, and an organic transparent conductive film such as polyaniline or a derivative thereof, polythiophene or a derivative thereof may be used as the conductive organic substance. Note that the cathode may have a laminated structure of two or more layers. In some cases, the electron injection layer is used as a cathode.

  The thickness of the cathode can be appropriately selected in consideration of electric conductivity and durability, but is, for example, 10 nm to 10 μm, preferably 20 nm to 1 μm, and more preferably 50 nm to 500 nm.

  As a method for producing the cathode, a vacuum deposition method, a sputtering method, a laminating method for bonding a metal thin film, or the like is used.

(Cavity effect)
The order and number of layers to be laminated, and the thickness of each layer can be appropriately used in consideration of the light emission efficiency and the element lifetime, but it is preferable to consider the cavity effect (light interference effect). Specifically, the thickness of the structure sandwiched between the anode and the cathode is an integral multiple of 1/4 of the value obtained by dividing the wavelength of light generated from the light emitting unit by the average refractive index of the structure. Is preferred. This is because the light extraction efficiency is maximized by the light interference effect in the configuration satisfying such a relationship. The effect is maximum when this relationship is strictly established, but the effect is recognized even if there is an error, and the thickness of the structure is generally 1/4 of the value obtained by dividing the emission wavelength by the average refractive index. It may be within ± 20% of an integer multiple of. Further, the distance between the portion that substantially emits light and the reflective electrode (cathode in this embodiment) that reflects light is an integral multiple of 1/4 of the value obtained by dividing the emission wavelength by the average refractive index. In this case, the light interference effect is maximized. When the organic EL element is composed of a plurality of light emitting units having different emission colors, it is preferable to control the film thickness so that the above relationship is established with respect to any one wavelength. Alternatively, the layer thickness may be controlled so that the relationship between the layer thicknesses simultaneously holds for two wavelengths.

  The organic EL device of the present invention is a device on which the organic EL element of the present invention is mounted, specifically a light source device, a display device, and a lighting device.

  In order to obtain planar light emission using the organic EL element of the present embodiment, the planar anode and cathode may be arranged so as to overlap each other. In addition, in order to obtain pattern-like light emission, a method of installing a mask provided with a pattern-like window on the surface of the planar light-emitting element, an organic material layer of a non-light-emitting portion is formed extremely thick and substantially non- There are a method of emitting light and a method of forming either one of the anode or the cathode or both electrodes in a pattern. By forming a pattern by any of these methods and arranging some electrodes so that they can be turned on / off independently, a segment type display element capable of displaying numbers, letters, simple symbols and the like can be obtained. Furthermore, in order to obtain a dot matrix element, both the anode and the cathode may be formed in stripes and arranged so as to be orthogonal to each other. Partial color display and multicolor display are possible by a method of separately coating a plurality of types of light emitting materials having different emission colors or a method using a color filter or a fluorescence conversion filter. The dot matrix element can be driven passively or may be driven actively in combination with TFTs. These display elements can be used as display devices for computers, televisions, mobile terminals, mobile phones, car navigation systems, video camera viewfinders, and the like.

  Furthermore, the planar light-emitting element is a self-luminous thin type, and can be suitably used as a planar light source for a backlight of a liquid crystal display device or a planar illumination light source. If a flexible substrate is used, it can be used as a curved light source or display device.

The organic EL element according to the embodiment of the present invention has a change between the coordinate value x and the coordinate value y in the chromaticity coordinates of the extracted light when the voltage applied between the anode and the cathode is changed. Since each width is 0.05 or less, there is little change in color and it is suitably used for the above-described planar light source, illumination device, and display device.
In particular, as the lighting device, it is preferable that the color does not change when the brightness is adjusted by changing the voltage applied between the anode and the cathode, and the coordinates in the chromaticity coordinates of the light from the lighting device are preferable. Since the change width between the value x and the coordinate value y is preferably 0.05 or less, the organic EL element according to the embodiment of the present invention is suitably used for the lighting device.
Similarly, the backlight of the dot matrix display device and the liquid crystal display device is preferably one that does not change color when the brightness is adjusted, and the coordinate value x in the chromaticity coordinates of the light from the backlight is Since the change width with respect to the coordinate value y is preferably 0.05 or less, the organic EL element according to the embodiment of the present invention is suitably used for the backlight.

Hereinafter, although this invention is demonstrated more concretely based on a manufacture example and a reference example, this invention is not limited to the following illustrations.
In Production Examples 1 and 2 and Reference Examples 1 to 4, organic EL elements having a structure in which two light emitting units were separated by one charge generation layer were produced. In Production Examples 1 and 2, a charge generation layer was formed using V ₂ O ₅ having a work function of 4.0 eV or higher, and the effect was confirmed.

<Production Example 1> (ITO / PEDOT / MEH-PPV / Li / V ₂ O ₅ / MEH-PPV / LiAl)
An example of manufacturing an organic EL element in Preparation Example 1 will be described with reference to FIG. In the organic EL device 11 shown in FIG. 1, an ITO film used as the anode 1 is formed on a glass substrate 10 having a thickness of 150 nm by a sputtering method, and a PEDOT / PSS solution made by BYTRON is made by a spin coating method to a thickness of 40 nm. A hole injection layer 2 was formed by heat treatment at 200 ° C. in a nitrogen atmosphere. Subsequently, 1 wt% toluene of MEH-PPV (poly (2-methoxy-5- (2′-ethyl-hexyloxy) -para-phenylenevinylene) having a weight average molecular weight of about 200,000 manufactured by Aldrich as a light emitting material. A solution was prepared, and this was spin-coated on a substrate on which PEDOT / PSS was formed to form a first light-emitting layer with a thickness of 90 nm, and the hole injection layer 2 and the first light-emitting layer were combined. Thus, the first light emitting unit 20 is obtained.

On top of this, Li (work function: 2.93 eV) and V ₂ O ₅ (work function: 4 eV or more) are sequentially formed with a thickness of 2 nm and 20 nm, respectively, as the charge generation layer 40 by vacuum deposition. The layer 4-1 and the second layer 4-2 were used. Here, the deposition of Li is performed by using an Al-Li alloy (Li content 0.05%) and depositing only Li that flies first for several tens of seconds before Al begins to fly, and immediately after that V ₂ O. Evaporation of ₅ was performed.
Further, a 1% by weight toluene solution of MEH-PPV was spin-coated on the V ₂ O ₅ film to form a second light emitting unit (second light emitting unit) 50 with a film thickness of 90 nm. Further, an Al—Li alloy having a thickness of 100 nm was formed thereon as a cathode 6 by vacuum evaporation. Thus, an organic EL element having a structure in which two light emitting units were separated by one charge generation layer was produced.
When a DC voltage was applied to the obtained device, the light emission starting voltage was 12 V and the maximum luminance was 80 cd / m ² .
The current efficiency was 0.072 cd / A, which was increased 1.95 times compared to the element of Comparative Example 1 (0.037 cd / A) described below.

<Reference Example 1>
For comparison, ITO / PEDOT / having only one light emitting unit as shown in FIG. 7 is the same as the manufacturing example 1 except that the charge generation layer 40 and the second light emitting unit 60 are not provided in the manufacturing example 1. An organic EL element 21 composed of light emitting layer 3 / cathode (Li / Al) was produced. The reference numerals in FIG. 7 are the same as those in FIG.
When a DC voltage was applied to the organic EL element 21 in Reference Example 1, the light emission starting voltage was 5.5 V and the maximum luminance was 52 cd / m ² . The current efficiency was 0.037 cd / A.

<Reference Example 2>
An organic EL element was produced in the same manner as in Production Example 1 except that the charge generation layer was composed of only one layer of V ₂ O _{5 having} a thickness of 30 nm. A voltage of 40 V was applied to the resulting device, but no light was emitted.

<Production Example 2> (Color mixing element composed of a stack of light emitting units of different colors)
Instead of MEH-PPV which is a light emitting layer in Production Example 1, a polymer light emitting layer made of polymer light emitting material 1 (abbreviated as F8-TPA-BT) represented by the following structural formula (1) that emits green light is included. After the first light emitting unit 20 and the charge generation layer 40 are formed, a PEDOT / PSS layer is formed, and then a polymer light emitting material 2 (abbreviated as F8) represented by the following structural formula (2) that emits blue light. -TPA-PDA) After forming the second light emitting unit 60 including the polymer light emitting layer, a cathode is formed in the same manner as in Production Example 1, and the light emitting elements having different emission wavelengths from the two light emitting units are formed. Was made.

Polymer material 1

Polymer material 2

<Reference Examples 3 and 4> (Comparison of Preparation Example 2, single element consisting only of green and blue light-emitting layers)
For comparison with Production Example 2, an element composed of one light emitting unit having a structure of ITO / PEDOT / light emitting layer / cathode (Li / Al) was produced as in Reference Example 2. Here, in Reference Example 3, the green light emitting layer material F8-TPA-BT was used for the light emitting layer, and in Reference Example 4, the blue light emitting material F8-TPA-PDA was used for the light emitting layer.

  The driving voltages in Comparative Examples 3 and 4 were 3.6 V and 5.4 V, respectively, whereas in Manufacturing Example 2, the driving voltage was 8.0 V, which was close to the expected voltage of an element in which two units were stacked. In addition, in the element of Production Example 2, the spectrum was widened and whited green light emission was obtained due to color mixture from the two layers.

<Production Example 3>
In this production example 3, in order to confirm the effect of arranging a plurality of light emitting layers having different peak wavelengths of emitted light in a predetermined order, the organic EL element including one light emitting unit is used. An organic EL device comprising three light emitting layers emitting red, green, and blue, and arranging the light emitting layers from the anode to the cathode and arranging the red light emitting layer, the green light emitting layer, and the blue light emitting layer in this order was manufactured.

As the support substrate, a glass substrate was used, and an ITO film formed on the glass substrate by a sputtering method and patterned into a predetermined shape was used as an anode. An anode having a thickness of 150 nm was used. The substrate on which the anode is formed is washed with an alkaline detergent and ultrapure water and dried, and then a UV-O ₃ apparatus (trade name “Model 312 UV-O ₃ Cleaning System” manufactured by Technovision Co., Ltd.) is used. Then, UV-O ₃ treatment was performed.

  Next, a suspension of poly (3,4) ethylenedioxythiophene / polystyrene sulfonic acid (trade name “BaytronP TP AI4083” manufactured by HC Starck Vitec Co., Ltd.) was filtered through a membrane filter having a pore size of 0.2 μm. . A thin film was formed on the anode by spin coating the liquid obtained by filtration. Next, the hot plate was heated at 200 ° C. for 10 minutes to obtain a hole injection layer having a thickness of 70 nm.

  Next, a red light emitting layer was laminated on the hole injection layer. First, xylene is used as a solvent, a light emitting material (manufactured by Summation, trade name “PR158”) is used as a material mainly constituting a red light emitting layer, and dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, A coating solution was prepared using a trade name “KAYARAD DPHA”). The weight ratio of the light emitting material to the cross-linking agent was 4: 1, and the ratio of the combined material of the light emitting material and the cross-linking agent in the coating solution was 1.0% by mass. The coating solution thus obtained was spin-coated to form a thin film on the hole injection layer. Next, it heated at 200 degreeC for 20 minute (s) in nitrogen atmosphere, and obtained the red light emitting layer with a film thickness of 10 nm. By performing such a heat treatment, the thin film was dried to remove the solvent, and the crosslinking agent was crosslinked to insolubilize the red light emitting layer in the coating solution to be applied next.

  Next, a green light emitting layer was laminated on the red light emitting layer. First, xylene is used as a solvent, a light emitting material (manufactured by Summation, product name “Green 1300”) is used as a material mainly constituting the green light emitting layer, and dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, A coating solution was prepared using a trade name “KAYARAD DPHA”). The weight ratio of the light emitting material to the cross-linking agent was 4: 1, and the ratio of the combined material of the light emitting material and the cross-linking agent in the coating solution was 1.0% by mass. A thin film was formed on the red light emitting layer by spin coating the coating solution thus obtained. Next, it heated at 200 degreeC for 20 minute (s) in nitrogen atmosphere, and obtained the green light emitting layer with a film thickness of 15 nm. By performing such heat treatment, the thin film was dried to remove the solvent, and the cross-linking agent was cross-linked to insolubilize the green light-emitting layer in the coating solution to be applied next.

  Next, a blue light emitting layer was laminated on the green light emitting layer. First, xylene was used as a solvent, and a coating solution was prepared using a light emitting material (manufactured by Summation Co., Ltd., trade name “BP361”) as a material mainly constituting the blue light emitting layer. The ratio of the blue light emitting material in the coating solution was 1.5% by mass. A thin film was formed on the green light emitting layer by spin coating the coating solution thus obtained. Next, it heated at 130 degreeC for 20 minute (s) in nitrogen atmosphere, and obtained the blue light emitting layer with a film thickness of 55 nm. In addition, the shape of the cross section cut by the plane perpendicular to the thickness direction of each light emitting layer was a square of 2 mm × 2 mm.

Next, the substrate on which the blue light emitting layer is formed as described above is introduced into vacuum vapor deposition, and barium is vapor deposited on the blue light emitting layer to form a thin film made of barium having a thickness of about 5 nm. Further, aluminum is vapor-deposited on the thin film made of barium to form a thin film made of aluminum having a thickness of about 80 nm, and a cathode composed of a laminate of the thin film made of barium and the thin film made of aluminum is formed. did. Note that deposition of barium and aluminum was started after the degree of vacuum reached 5 × 10 ⁻⁵ Pa or less.

<Reference Example 5>
As Reference Example 5, an organic EL element including one light emitting layer that emits light in a white wavelength region (hereinafter sometimes referred to as a white light emitting layer) was produced. Since the manufacturing process other than the white light emitting layer is the same as the manufacturing process of the organic EL element of Production Example 3, a redundant description is omitted and only the white light emitting layer manufacturing process will be described.

  First, xylene was used as a solvent, and a coating solution was prepared using a light emitting material (trade name “WP1330”, manufactured by Summation Co., Ltd.) as a material mainly constituting the white light emitting layer. The ratio of the luminescent material in the coating solution was 1.0% by mass. The thin film was formed on the positive hole injection layer by spin-coating the coating liquid obtained in this way on the board | substrate with which the positive hole injection layer was formed. Next, it heated at 130 degreeC for 20 minute (s) in nitrogen atmosphere, and obtained the white light emitting layer with a film thickness of 80 nm.

<Reference Example 6>
As Reference Example 6, an organic EL element different from the organic EL element of Preparation Example 3 was manufactured only in the stacking order of three layers of a red light emitting layer, a green light emitting layer, and a blue light emitting layer. A blue light emitting layer was disposed in the layer closest to the anode, a green light emitting layer was disposed in the middle layer, and a red light emitting layer was disposed in the layer closest to the cathode. Since the manufacturing processes other than the red light emitting layer, the green light emitting layer, and the blue light emitting layer are the same as the manufacturing process of the organic EL element of Preparation Example 2, only the manufacturing process of the red light emitting layer, the green light emitting layer, and the blue light emitting layer will be described. To do.

  First, a blue light emitting layer was laminated on the hole injection layer. Xylene is used as a solvent for the coating solution, a light emitting material (trade name “BP361” manufactured by Summation Co., Ltd.) is used as a material mainly constituting the blue light emitting layer, and dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd.) is used as a crosslinking agent , Trade name “KAYARAD DPHA”). The weight ratio of the light emitting material to the cross-linking agent was 4: 1, and the ratio of the combined material of the light emitting material and the cross-linking agent in the coating solution was 1.0% by mass. The coating solution thus obtained was spin-coated to form a thin film on the hole injection layer. Next, it heated at 130 degreeC for 20 minute (s) in nitrogen atmosphere, and obtained the blue light emitting layer with a film thickness of 55 nm. By performing such heat treatment, the thin film was dried to remove the solvent, and the crosslinking agent was crosslinked to insolubilize the blue light-emitting layer in the coating solution to be applied next.

  Next, a green light emitting layer was laminated on the blue light emitting layer. First, xylene is used as a solvent, a light emitting material (manufactured by Summation, product name “Green 1300”) is used as a material mainly constituting the green light emitting layer, and dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, A coating solution was prepared using a trade name “KAYARAD DPHA”). The weight ratio of the light emitting material to the cross-linking agent was 4: 1, and the ratio of the combined material of the light emitting material and the cross-linking agent in the coating solution was 1.0% by mass. The coating solution thus obtained was spin coated to form a thin film on the blue light emitting layer. Next, it heated at 200 degreeC for 20 minute (s) in nitrogen atmosphere, and obtained the green light emitting layer with a film thickness of 15 nm. By performing such heat treatment, the thin film was dried to remove the solvent, and the cross-linking agent was cross-linked to insolubilize the green light-emitting layer in the coating solution to be applied next.

  Next, a red light emitting layer was laminated on the green light emitting layer. First, xylene was used as a solvent, and a coating solution was prepared using a light emitting material (trade name “PR158”, manufactured by Summation Co., Ltd.) as a material mainly constituting the red light emitting layer. The ratio of the luminescent material in the coating solution was 1.0% by mass. A thin film was formed on the green light emitting layer by spin coating the coating solution thus obtained. Next, it heated at 200 degreeC for 20 minute (s) in nitrogen atmosphere, and obtained the red light emitting layer with a film thickness of 10 nm.

(Evaluation of effect by arrangement of multiple light-emitting layers with different emission wavelengths in a predetermined order)
A voltage was applied to each of the organic EL elements of Production Example 3, Reference Example 5 and Reference Example 6 to measure luminance and chromaticity. In the measurement, the applied voltage was changed stepwise, and the luminance and chromaticity were measured for each applied voltage. The measurement results are shown in (Table 1).

Of changing the voltage applied when changing the luminance to ^{100cd / m 2 ~10000cd / m 2} , Preparation Example 3, Reference Example 5, the coordinate value x in the CIE chromaticity coordinates of the organic EL device of Reference Example 6, Each change width of y is shown in the following (Table 2).

As shown in (Table 1) and (Table 2), the organic EL device of Preparation Example 3, when changing the luminance to 100cd / m ² ~10000cd / m ² by changing the voltage to be applied is taken out The widths of change of the coordinate value x and the coordinate value y in the chromaticity coordinates of light were each 0.016 or less.

As shown in (Table 1), the organic EL element of Preparation Example 3 has a maximum current efficiency as compared with the organic EL element of Reference Example 1 including only one light emitting layer by providing three light emitting layers. Improved.
In addition, the organic EL element of Production Example 3 was improved in the maximum value of current efficiency as compared with the organic EL element of Reference Example 6 by arranging the three light emitting layers in a predetermined arrangement.

  Moreover, as shown in Table 2, the organic EL element of Preparation Example 3 has a voltage higher than that of the organic EL element of Reference Example 5 including only one light emitting layer by providing three light emitting layers. There was little change in color with respect to the change. In addition, the organic EL element of Production Example 3 had less change in color with respect to voltage than the organic EL element of Reference Example 6 by arranging the three light emitting layers in a predetermined arrangement.

It is a side view which shows the organic EL element in this Embodiment. It is a side view which shows the other organic EL element in this Embodiment. It is a side view which shows the other organic EL element in this Embodiment. It is a side view which shows the other organic EL element in this Embodiment. It is a side view which shows the other organic EL element in this Embodiment. It is a side view which shows the other organic EL element in this Embodiment. 5 is a side view showing an organic EL element in Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode 2 Hole injection layer 3 Light emitting layer 20 1st light emission unit 30 1st light emission part 40 Charge generation layer 4-1 1st layer 4-2 2nd layer 50 2nd light emission part 60 2nd Light-emitting unit 6 Cathode 10 Substrate 11, 11-1 to 11-5 Organic EL element

Claims (12)

An anode, a cathode, a plurality of light-emitting units provided between the anode and the cathode and each including a light-emitting layer, and a charge generation layer disposed between the light-emitting units,
The charge generation layer includes one or more kinds of a metal having a work function of 3.0 eV or less and a compound thereof (A), and one or more kinds of a compound (B) having a work function of 4.0 eV or more,
At least one of the light emitting units includes a plurality of light emitting layers arranged closer to the anode as a light emitting layer having a longer peak wavelength of emitted light has an organic electroluminescence element.   The charge generation layer comprises a first layer containing one or more of the metal and its compound (A), and a second layer containing one or more of the compound (B), 2. The organic electroluminescence device according to claim 1, wherein the layer is disposed closer to the anode than the second layer.   2. The organic material according to claim 1, wherein the charge generation layer is a layer formed by mixing one or more of the metal and its compound (A) and one or more of the compound (B). 3. Electroluminescence element.   4. The organic electroluminescence device according to claim 1, wherein a transmittance of the charge generation layer with respect to a wavelength of 550 nm is 30% or more. 5.   The organic electroluminescence according to any one of claims 1 to 4, wherein the metal having a work function of 3.0 eV or less is selected from the group consisting of alkali metals and alkaline earth metals. element.   The organic electroluminescence device according to any one of claims 1 to 5, wherein the compound having a work function of 4.0 eV or more is a transition metal oxide.   The organic electroluminescence element according to any one of claims 1 to 6, wherein colors of light emitted from the light emitting units are different from each other.   At least one of the light emitting units includes a light emitting layer that emits red light, a light emitting layer that emits green light, and a light emitting layer that emits blue light, and a light emitting layer having a long peak wavelength of the emitted light. The organic electroluminescence device according to claim 1, wherein the organic electroluminescence device is disposed closer to the anode.   When the voltage applied between the first electrode and the second electrode is changed, the change width of the coordinate value x and the coordinate value y in the chromaticity coordinates of the light extracted outside is 0.05 respectively. The organic electroluminescence element according to claim 1, wherein the organic electroluminescence element is as follows.   An illuminating device comprising the organic electroluminescence element according to any one of claims 1 to 8.   A planar light source comprising the organic electroluminescence element according to any one of claims 1 to 8.   A display device comprising the organic electroluminescence element according to claim 1.

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