JP2010205427A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element capable of achieving high efficiency and long life. <P>SOLUTION: Relating to the organic EL element, a positive electrode, a positive hole injection transportation layer, n light-emitting layers (n≥2), an electron injection transportation layer, and a negative electrode are sequentially stacked, with one to (n-1) intermediate layers formed at least at one point between adjoining light-emitting layers. The positive hole injection transportation layer and an electron injection transportation layer contain the same bipolar material. The material constituting the intermediate layer is different from host material of the light-emitting layer adjoining the intermediate layer. The relationship between constituent materials Ip<SB>INL</SB>and Ea<SB>INL</SB>of the intermediate layer and the host materials Ip<SB>EML</SB>and Ea<SB>EML</SB>of the light-emitting layer adjoining the intermediate layer is Ip<SB>INL</SB>≠Ip<SB>EML</SB>, Ea<SB>INL</SB>≠Ea<SB>EML</SB>. The relationship between the constituent material Ea<SB>1</SB>of the positive hole injection transportation layer and the host material Ea<SB>2</SB>of a positive electrode light-emitting layer is Ea<SB>1</SB>≥Ea<SB>2</SB>. The relationship between the constituent material Ip<SB>3</SB>of the electron injection transportation layer and the host material Ip<SB>4</SB>of a negative electrode light-emitting layer is Ip<SB>3</SB>≤Ip<SB>4</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence device having a plurality of light emitting layers.

  Organic electroluminescence (hereinafter, electroluminescence may be abbreviated as EL) elements are attracting attention for use as self-luminous displays, and high brightness, high efficiency, and long life are required.

  As a technique for increasing the brightness of an organic EL element, it is known to use a light emitting layer containing a host material and a light emitting dopant. In this light emitting layer, holes and electrons injected from the anode and the cathode recombine with the host material in the light emitting layer, and the light emitting dopant receives the energy to emit light. In such a light emitting layer, light emission with high luminance and good color purity can be obtained.

  On the other hand, as a technology for improving the efficiency and extending the life of organic EL elements, in addition to a light emitting material, a multilayer in which a plurality of layers are stacked using a material having a hole or electron injection function, a transport function, and a blocking function It is known to have a structure. However, in an organic EL element having a multilayer structure, there is a concern that deterioration occurs at the interface of each layer during driving, resulting in a decrease in light emission efficiency or a decrease in luminance due to deterioration of the element. In particular, in an organic EL element provided with a blocking layer, charges are likely to accumulate at the interface between the light-emitting layer and the blocking layer, and therefore deterioration is likely to occur at the interface.

  Therefore, the present inventors have prescribed the magnitude relationship between the ionization potential and electron affinity of each layer as a method for suppressing the deterioration at the interface of each layer during driving, and developed an organic EL device having no blocking layer. It has been proposed (see Patent Document 1). Furthermore, it is proposed to use the same bipolar material for the hole transport layer and the electron transport layer in order to suppress the deterioration of the hole transport layer and the electron transport layer due to the penetration of charges.

  In recent years, organic EL elements emitting white light have been actively developed because they can be applied to light sources. White light can usually be obtained by light emission of two or three kinds of light emitting materials. However, when the light emitting layer includes a plurality of types of light emitting materials, there is a problem that energy transfer occurs between the light emitting materials and chromaticity changes. Accordingly, it has been proposed to stack a plurality of light emitting layers containing different light emitting materials (see, for example, Patent Documents 2 to 5).

However, in an organic EL device in which a light emitting layer containing a phosphorescent dopant and a light emitting layer containing a fluorescent dopant are stacked, energy transfer occurs from the phosphorescent dopant to the fluorescent dopant, and high efficiency light emission cannot be obtained. There is a problem.
In order to solve this problem, it has been proposed to provide a bipolar layer in which both holes and electrons can move between a light-emitting layer containing a phosphorescent dopant and a light-emitting layer containing a fluorescent light-emitting dopant ( (See Patent Document 6).

  In addition, although it is not a white light emitting organic EL device, it emits light in the light emitting layer in order to suppress light emission from a layer other than the light emitting layer (for example, a hole transport layer or an electron transport layer) and to suppress a decrease in color purity. An organic EL element provided with a region control layer has been proposed (see Patent Document 7).

International Publication No. 2008/102644 Pamphlet JP 2000-68057 A JP 2003-282266 A International Publication No. 2005/91684 Pamphlet JP 2006-269232 A JP 2006-172762 A JP 2003-36980 A

  In an organic EL element in which a plurality of light emitting layers are stacked and a predetermined layer is provided between the light emitting layers, the number of interface between layers increases, so that deterioration may occur at the interface of each layer as described above. There is a concern that the lifetime may be shortened or the light emission efficiency may be reduced. Therefore, when a plurality of light emitting layers are laminated and a predetermined layer is provided between the light emitting layers, there is room for further improvement in order to achieve a long life and high efficiency.

  This invention is made | formed in view of the said situation, and it aims at providing the organic EL element which can implement | achieve high efficiency and a long lifetime.

To achieve the above object, the present invention provides an anode, a hole injecting and transporting layer formed on the anode, and an n layer formed on the hole injecting and transporting layer and containing a host material and a light emitting dopant. (N is an integer greater than or equal to 2) light emitting layer, intermediate layer of 1 layer or more (n-1) layer or less formed in at least any one position between adjacent light emitting layers, and light emission of the n layer Bipolar having an electron injecting and transporting layer formed on the layer and a cathode formed on the electron injecting and transporting layer, wherein the hole injecting and transporting layer and the electron injecting and transporting layer can transport holes and electrons The bipolar material contained in the hole injecting and transporting layer and the electron injecting and transporting layer is the same, and the constituent material of the intermediate layer is different from the host material of the light emitting layer adjacent to the intermediate layer. , Ionization of the constituent material of the intermediate layer When Nsharu the Ip _INL, the ionization potential of the host material of the light emitting layer adjacent to the intermediate layer was set to Ip _EML, an Ip _INL ≠ Ip _EML, the electron affinity of the constituent material of the intermediate layer Ea _INL, the intermediate When the electron affinity of the host material of the light emitting layer adjacent to the layer is Ea _EML , Ea _INL ≠ Ea _EML , the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ , and the hole injection transport layer When the electron affinity of the host material of the light emitting layer adjacent to Ea ₂ is Ea ₂ , Ea ₁ ≧ Ea ₂ and the ionization potential of the constituent material of the electron injection transport layer is Ip ₃ , adjacent to the electron injection transport layer Provided is an organic EL element characterized in that Ip ₃ ≦ Ip ₄ when the ionization potential of the host material of the light emitting layer is Ip ₄ .

According to the present invention, since the electron affinity relationship between the constituent material of the hole injecting and transporting layer and the host material of the light emitting layer adjacent to the hole injecting and transporting layer is Ea ₁ ≧ Ea ₂ , There is no charge accumulation at the interface between the transport layer and the light emitting layer, and deterioration can be suppressed. In addition, since the relationship between the ionization potential of the constituent material of the electron injection transport layer and the host material of the light emitting layer adjacent to the electron injection transport layer is Ip ₃ ≦ Ip ₄ , the interface between the electron injection transport layer and the light emitting layer during driving In this case, there is no charge accumulation in the substrate and deterioration can be suppressed. Furthermore, since the hole injecting and transporting layer and the electron injecting and transporting layer contain the same bipolar material, even if holes penetrate into the electron injecting and transporting layer or electrons penetrate into the hole injecting and transporting layer, driving is in progress. It is possible to effectively suppress deterioration at the interface of each layer. In addition, the constituent material of the intermediate layer is different from the host material of the light emitting layer adjacent to the intermediate layer, and the relationship between the ionization potential and the electron affinity between the constituent material of the intermediate layer and the host material of the light emitting layer adjacent to the intermediate layer is Since Ip _INL ≠ Ip _EML and Ea _INL ≠ Ea _EML , an interface is formed between the intermediate layer and the light emitting layer adjacent to the intermediate layer, and there is a slight energy barrier, so that there is a gap between the intermediate layer and the light emitting layer. It is possible to control the injection of charges in charge transport between them and increase the light emission efficiency. Therefore, a highly efficient and long-life organic EL element can be obtained.

  In the above invention, the intermediate layer is preferably an (n-1) layer, and the intermediate layer is preferably formed between the light emitting layers. This is because the light emission efficiency can be further improved by forming the intermediate layer between the light emitting layers.

  In the present invention, the intermediate layer contains a bipolar material capable of transporting holes and electrons, and the bipolar materials contained in the hole injection transport layer, the electron injection transport layer, and the intermediate layer are the same. Preferably there is. This is because, if the bipolar materials contained in these layers are the same, even if holes penetrate into the electron injecting and transporting layer or electrons penetrate into the hole injecting and transporting layer, these layers are not easily deteriorated. .

  In the present invention, it is preferable that at least one of the n light emitting layers has one or more doped regions containing the light emitting dopant and one or more non-doped regions not containing the light emitting dopant. This is because when at least one of the n light emitting layers has a non-doped region, energy transfer from the light emitting dopant in the doped region to other substances can be suppressed, and the light emission efficiency can be increased.

In the above case, the light emitting layer adjacent to the hole injecting and transporting layer may have the non-doped region on the hole injecting and transporting layer side. For example, when energy transfer can occur from the light emitting dopant contained in the light emitting layer to the constituent material of the hole injecting and transporting layer, the light emitting layer has a non-doped region on the hole injecting and transporting layer side, so that the above energy transfer is unlikely to occur. The luminous efficiency can be improved. In addition, since the light emitting layer has a non-doped region on the hole injecting and transporting layer side, hole injection from the hole injecting and transporting layer to the light emitting layer can be improved. Further, although the electron affinity relationship between the constituent material of the hole injecting and transporting layer and the host material of the light emitting layer is Ea ₁ ≧ Ea ₂ , the light emitting layer has a non-doped region on the hole injecting and transporting layer side. The charge trapped by can balance the charge injected into the light emitting layer.

In the above case, the light emitting layer adjacent to the electron injecting and transporting layer may have the non-doped region on the electron injecting and transporting layer side. For example, when energy transfer can occur from the light emitting dopant contained in the light emitting layer to the constituent material of the electron injecting and transporting layer, the light emitting layer has a non-doped region on the electron injecting and transporting layer side so that the above energy transfer is less likely to occur and light emission Efficiency can be improved. In addition, since the light emitting layer has a non-doped region on the electron injecting and transporting layer side, electron injection from the electron injecting and transporting layer to the light emitting layer can be improved. Furthermore, although the relationship between the ionization potentials of the constituent material of the electron injecting and transporting layer and the host material of the light emitting layer is Ip ₃ ≦ Ip ₄ , the light emitting layer has a non-doped region on the electron injecting and transporting layer side. By this trap, the charge injected into the light emitting layer can be balanced.

  Further, in the above case, the light emitting layer may have the non-doped region on the intermediate layer side. For example, when energy transfer can occur from the light-emitting dopant contained in the light-emitting layer to the constituent material of the intermediate layer, the light-emitting layer has a non-doped region on the intermediate layer side so that the above-described energy transfer is less likely to occur and the light emission efficiency is improved. Because it can.

  In the above case, the light emitting layer may have the two doped regions, and the non-doped region may be disposed between the two doped regions. In this case, the two doped regions are respectively It is preferred to contain different types of luminescent dopants. For example, in the case where energy transfer can occur from a light-emitting dopant contained in one doped region to a light-emitting dopant contained in the other doped region, the non-doped region is disposed between these two doped regions. This is because energy transfer is less likely to occur and the light emission efficiency can be improved.

  In the present invention, it is preferable that at least one of the n light emitting layers contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant. This is because energy transfer is suppressed between the fluorescent light-emitting dopant and the phosphorescent light-emitting dopant, the light emission efficiency is increased, and a desired light emission color can be obtained.

  Furthermore, in the present invention, the n light emitting layers are preferably three light emitting layers, and the three light emitting layers preferably contain light emitting dopants having different emission colors. For example, when three types of light emitting dopants of red, blue, and green corresponding to the three primary colors of light are used, each of the three light emitting layers contains one type of light emitting dopant, and each of the three types of light emitting dopants emits light. This is because white light can be obtained.

  In the present invention, an intermediate layer made of a material different from the host material of the light emitting layer is provided between the plurality of light emitting layers, and the light emitting layer adjacent to the constituent material of the hole injecting and transporting layer and the hole injecting and transporting layer The electron affinity with the host material and the ionization potential of the constituent material of the electron injection / transport layer and the host material of the light emitting layer adjacent to the electron injection / transport layer are the same as those of the hole injection / transport layer and the electron injection / transport layer. By using this bipolar material, there is an effect that it is possible to achieve high efficiency and long life.

It is a schematic sectional drawing which shows an example of the organic EL element of this invention. It is a schematic diagram which shows an example of the band diagram of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention.

Hereinafter, the organic EL device of the present invention will be described in detail.
The organic EL device of the present invention includes an anode, a hole injecting and transporting layer formed on the anode, and an n layer (n is 2) formed on the hole injecting and transporting layer and containing a host material and a light emitting dopant. Formed on at least one (n-1) or less intermediate layer formed in at least any one position between the adjacent light emitting layers and the n light emitting layers. An electron injection transport layer and a cathode formed on the electron injection transport layer, the hole injection transport layer and the electron injection transport layer containing a bipolar material capable of transporting holes and electrons. The bipolar material contained in the hole injecting and transporting layer and the electron injecting and transporting layer is the same, the constituent material of the intermediate layer is different from the host material of the light emitting layer adjacent to the intermediate layer, and the intermediate layer Ionization potential of I p _INL , when the ionization potential of the host material of the light emitting layer adjacent to the intermediate layer is Ip _EML , Ip _INL ≠ Ip _EML , and the electron affinity of the constituent material of the intermediate layer is Ea _INL , When the electron affinity of the host material of the adjacent light emitting layer is Ea _EML , Ea _INL ≠ Ea _EML , and the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ , adjacent to the hole injection transport layer When the electron affinity of the host material of the light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and the ionization potential of the constituent material of the electron injection transport layer is Ip ₃ , and the light emission adjacent to the electron injection transport layer is When the ionization potential of the host material of the layer is Ip ₄ , Ip ₃ ≦ Ip ₄ .

  Of the light emitting layers of n layers (n is an integer of 2 or more), the light emitting layer adjacent to the hole injecting and transporting layer is referred to as the anode side light emitting layer, and the light emitting layer adjacent to the electron injecting and transporting layer is referred to as the cathode side light emitting layer. The light emitting layer other than the anode side light emitting layer and the cathode side light emitting layer may be referred to as a central light emitting layer.

The organic EL element of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the organic EL element of the present invention. As illustrated in FIG. 1, the organic EL element 1 includes three light emitting layers (anode side light emitting layer 5a, central light emitting layer 5b, cathode side light emitting layer 5c) and two intermediate layers (in FIG. A first intermediate layer 6a and a second intermediate layer 6b) on the substrate 2, the anode 3, the hole injection transport layer 4, the anode side light emitting layer 5a, the first intermediate layer 6a and the center. The light emitting layer 5b, the second intermediate layer 6b, the cathode side light emitting layer 5c, the electron injecting and transporting layer 7, and the cathode 8 are sequentially laminated. The hole injection / transport layer 4 and the electron injection / transport layer 7 contain a bipolar material, and the bipolar materials contained in the hole injection / transport layer 4 and the electron injection / transport layer 7 are the same. The constituent material of the first intermediate layer 6a is different from the host material of the anode side light emitting layer 5a and the central light emitting layer 5b adjacent to the first intermediate layer 6a. Similarly, the constituent material of the second intermediate layer 6b is different from the host materials of the central light emitting layer 5b and the cathode side light emitting layer 5c adjacent to the second intermediate layer 6b.

2 to 4 are schematic views each showing an example of a band diagram of the organic EL element of the present invention.
In the organic EL device illustrated in FIG. 1, as shown in FIGS. 2 to 4, the ionization potential of the constituent material of the hole injection transport layer 4 is Ip ₁ , and the ionization potential of the host material of the anode side light emitting layer 5a is Ip _2. The ionization potential of the constituent material of the electron injection transport layer 7 is Ip ₃ , the ionization potential of the host material of the cathode side light emitting layer 5 c is Ip ₄ , the electron affinity of the constituent material of the hole injection transport layer 4 is Ea ₁ , and the anode side the electron affinity of the host material in the light-emitting layer 5a Ea _2, the electron affinity of Ea ₃ of material of the electron injection transport layer 7, the electron affinity of the host material for the cathode-side light-emitting layer 5c and Ea _4.
The relationship between the electron affinity of the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer is Ea ₁ ≧ Ea ₂ . The relationship between the constituent material of the electron injecting and transporting layer and the ionization potential of the host material of the cathode side light emitting layer is Ip ₃ ≦ Ip ₄ .
Further, the hole and electron injecting and transporting layers from that containing the same bipolar material, the relationship of the ionization potential of a constituent material for the hole injecting and transporting layer and the electron injecting and transporting layer is Ip ₁ = Ip _3, The relationship between the electron affinity of the constituent materials of the hole injecting and transporting layer and the electron injecting and transporting layer is Ea ₁ = Ea ₃ .

Further, in the organic EL element illustrated in FIG. 1, as shown in FIGS. 2 to 4, the ionization potential of the host material of the anode side light emitting layer 5a is Ip _EML1 , and the ionization potential of the host material of the central light emitting layer 5b is Ip _EML2. the ionization potential of the host material of the cathode side light emitting layer 5c Ip _EML3, the ionization potential of the constituent material of the first intermediate layer 6a Ip _INL1, the ionization potential of the constituent material of the second intermediate layer 6b and Ip _INL2, anode-side light The electron affinity of the host material of the layer 5a is Ea _EML1 , the electron affinity of the host material of the central light emitting layer 5b is Ea _EML2 , the electron affinity of the host material of the cathode side light emitting layer 5c is Ea _EML3 , and the constituent materials of the first intermediate layer 6a The electron affinity is Ea _INL1 and the electron affinity of the constituent material of the second intermediate layer 6b is Ea _INL2 .
Unlike the constituent material of the first intermediate layer and the host material of the anode side light emitting layer and the central light emitting layer adjacent to the first intermediate layer, the constituent material of the first intermediate layer and the anode side light emission adjacent to the first intermediate layer The relationship of the ionization potential with the host material of the layer and the central light emitting layer is Ip _INL1 ≠ Ip _EML1 and Ip _INL1 ≠ Ip _EML2 , and the constituent material of the first intermediate layer and the anode side light emitting layer adjacent to the first intermediate layer The relationship of the electron affinity with the host material of the central light emitting layer is Ea _INL1 ≠ Ea _EML1 and Ea _INL1 ≠ Ea _EML2 .
Further, unlike the constituent material of the second intermediate layer and the host material of the central light emitting layer and the cathode side light emitting layer adjacent to the second intermediate layer, the constituent material of the second intermediate layer and the center adjacent to the second intermediate layer relation of the ionization potential of the host material of the light emitting layer and a cathode-side layer is a _{Ip INL2 ≠ Ip EML2, Ip INL2} ≠ Ip EML3, a constituent material of the second intermediate layer, a central luminous adjacent to the second intermediate layer relationship in electron affinity between the host material of the layer and the cathode side light emitting layer is _{Ea INL2 ≠ Ea EML2, Ea INL2} ≠ Ea EML3.

Usually, in the organic EL device as illustrated in FIG. 1, the relationship between the electron affinity of the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer is Ea ₁ ≧ Ea _2. When the ionization potential of the material and the host material of the cathode-side light-emitting layer is Ip ₃ ≦ Ip ₄ , it is difficult to efficiently generate charge recombination in the light-emitting layer, generate an excited state, and deactivate radiation. The efficiency deteriorates and the lifetime characteristics deteriorate due to the penetration of holes and electrons into the counter electrode and the injection of electrons into the hole injection / transport layer or the injection of holes into the electron injection / transport layer. It is assumed that

However, in the present invention, since Ea ₁ ≧ Ea ₂ and Ip ₃ ≦ Ip ₄ , holes and electrons penetrate into the counter electrode, but the holes and electrons are transported smoothly. There is no charge accumulation at the interface between the hole injecting and transporting layer and the anode side light emitting layer and at the interface between the electron injecting and transporting layer and the cathode side light emitting layer, and deterioration at the interface between these layers can be suppressed.
In addition, by using the bipolar material for the hole injecting and transporting layer and the electron injecting and transporting layer, the interface between the hole injecting and transporting layer and the anode side light emitting layer and the interface between the electron injecting and transporting layer and the cathode side light emitting layer during driving are used. Can be effectively suppressed.
Further, since the constituent material of the intermediate layer is different from the host material of the light emitting layer adjacent to the intermediate layer, an interface is formed between the intermediate layer and the light emitting layer adjacent to the intermediate layer. Since the relationship between the ionization potential and the electron affinity between the constituent material of the intermediate layer and the host material of the light emitting layer adjacent to this intermediate layer is Ip _INL ≠ Ip _EML and Ea _INL ≠ Ea _EML , the intermediate layer and the light emitting layer There are some energy barriers in charge transport to and from. Thereby, in the charge transport between the intermediate layer and the light emitting layer, the injection of charges can be controlled to increase the light emission efficiency.
Therefore, high efficiency can be achieved and stable life characteristics can be obtained.

  According to the present invention, since the hole injecting and transporting layer and the electron injecting and transporting layer contain the same bipolar material, holes may penetrate into the electron injecting and transporting layer, or electrons may penetrate into the hole injecting and transporting layer. In addition, the hole injection / transport layer and the electron injection / transport layer can be prevented from deteriorating. Further, when the hole injecting and transporting layer and the electron injecting and transporting layer are formed by vacuum deposition or the like, a common deposition source can be used, which is advantageous in the manufacturing process.

  The “constituent material” of each layer refers to the material when each layer is composed of a single material, and the host material when each layer is composed of a host material and a dopant. Say.

  The “ionization potential of the constituent material” of each layer means the ionization potential of the material when each layer is made of a single material, and when each layer is made of a host material and a dopant. Refers to the ionization potential of the host material. Similarly, the “electron affinity of a constituent material” of each layer means the electron affinity of the material when each layer is made of a single material, and each layer is made up of a host material and a dopant. The electron affinity of the host material.

  The ionization potential is a value determined by UPS (ultraviolet photoelectron spectroscopy) (for example, measuring instrument name “AC-2” manufactured by Riken Keiki Co., Ltd.). As a method for measuring electron affinity, first, HOMO energy is obtained by UPS (ultraviolet photoelectron spectroscopy) (for example, “AC-2” manufactured by Riken Keiki Co., Ltd.), and then an energy gap measurement value by light absorption and the above HOMO energy. The method of calculating from is adopted.

  “The material constituting the intermediate layer is different from the host material of the light emitting layer adjacent to the intermediate layer” means that there are two light emitting layers adjacent to the intermediate layer, so the material constituting the intermediate layer and the intermediate layer are adjacent. This means that the host materials of the two light emitting layers are different. For example, in FIG. 1, the anode side light emitting layer 5a and the center light emitting layer 5b are adjacent to the first intermediate layer 6a, and the constituent material of the first intermediate layer 6a and the anode side adjacent to the first intermediate layer 6a The host materials of the light emitting layer 5a and the central light emitting layer 5b are different.

"The relationship between the ionization potential Ip _INL of the constituent material of the intermediate layer and the ionization potential Ip _EML of the host material of the light emitting layer adjacent to the intermediate layer is Ip _INL ≠ Ip _EML " means that the light emitting layer adjacent to the intermediate layer Since there are two layers, the relationship between the ionization potential Ip _INL of the material constituting the intermediate layer and the ionization potential Ip _EML of each host material of the two light emitting layers adjacent to the intermediate layer is Ip _INL ≠ Ip _EML It means that there is. For example, in FIG. 1, the anode side light emitting layer 5a and the central light emitting layer 5b are adjacent to the first intermediate layer 6a. As illustrated in FIG. 2, the ionization potential Ip _INL1 of the constituent material of the first intermediate layer 6a is illustrated. And the ionization potential Ip _EML1 of the host material of the anode side light emitting layer 5a adjacent to the first intermediate layer 6a and the ionization potential Ip _EML2 of the host material of the central light emitting layer 5b adjacent to the first intermediate layer 6a is Ip _INL1 ≠ Ip _EML1 and Ip _INL1 ≠ Ip _EML2 .

"The relationship between the electron affinity Ea _INL of the constituent material of the intermediate layer and the electron affinity Ea _EML of the host material of the light emitting layer adjacent to the intermediate layer is Ea _INL ≠ Ea _EML " means that the light emitting layer adjacent to the intermediate layer Therefore, the relationship between the electron affinity Ea _{INL of the} material constituting the intermediate layer and the electron affinity Ea _EML of each host material of the two light emitting layers adjacent to the intermediate layer is Ea _INL ≠ Ea _EML It means that there is. For example, in FIG. 1, the anode side light emitting layer 5a and the central light emitting layer 5b are adjacent to the first intermediate layer 6a, and as illustrated in FIG. 2, the electron affinity Ea _INL1 of the constituent material of the first intermediate layer 6a. And the electron affinity Ea _EML1 of the host material of the anode side light emitting layer 5a adjacent to the first intermediate layer 6a and the electron affinity Ea _EML2 of the host material of the central light emitting layer 5b adjacent to the first intermediate layer 6a are Ea _INL1 ≠ Ea _EML1 and Ea _INL1 ≠ Ea _EML2 .

A “bipolar material” is a material that can stably transport both holes and electrons, and when a unipolar device for electrons is produced using a material doped with a reducing dopant, It refers to a material that can be stably transported and can transport holes stably when a unipolar device of holes is produced using a material doped with an oxidizing dopant. When producing a unipolar device, specifically, an electron unipolar device is produced using a material doped with Cs or 8-hydroxyquinolinolatolithium (Liq) as a reducing dopant, and is oxidized. A hole unipolar device can be fabricated using a material doped with V ₂ O ₅ or MoO ₃ as a dopant.

  Hereinafter, each structure in the organic EL element of this invention is demonstrated.

1. In the present invention, when the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ , and the electron affinity of the host material of the anode side light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ When the ionization potential of the constituent material of the electron injecting and transporting layer is Ip ₃ , and the ionization potential of the host material of the cathode side light emitting layer is Ip ₄ , Ip ₃ ≦ Ip ₄ is satisfied.
In addition, when the ionization potential of the material constituting the intermediate layer is Ip _INL and the ionization potential of the host material of the light emitting layer adjacent to the intermediate layer is Ip _EML , Ip _INL ≠ Ip _EML , and the electron affinity of the material constituting the intermediate layer the Ea _INL, when the electron affinity of the host material of the light emitting layer adjacent to the intermediate layer was Ea _EML, an Ea _INL ≠ Ea _EML.

The electron affinity of the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer is expressed as follows: Ea _{1 is} the electron affinity of the constituent material of the hole injection transport layer, and When Ea ₂ is satisfied, Ea ₁ ≧ Ea ₂ may be satisfied, but among them, Ea ₁ > Ea ₂ is preferable. This is because if Ea ₁ > Ea ₂ and Ip ₁ <Ip ₂ , the band gap energy of the host material of the anode side light emitting layer can be made relatively large. For example, in order to improve the light emission efficiency, it becomes easy to select the host material and the light emitting dopant so that the ionization potential and the electron affinity of the host material and the light emitting dopant of the anode side light emitting layer satisfy a predetermined relationship.

When Ea ₁ > Ea ₂ , the difference between Ea ₁ and Ea ₂ varies depending on the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer, but specifically 0.1 eV. It is preferable to set it above, and it is more preferable to set it as 0.2 eV or more.

Regarding the relationship between the ionization potential of the hole injection / transport layer material and the anode side emission layer host material, the ionization potential of the hole injection / transport layer component material is Ip ₁ , and the ionization potential of the anode side emission layer host material is when the ip _2, typically are ip ₁ ≦ ip _2. Among these, Ip ₁ <Ip ₂ is preferable. This is because the presence of a certain energy barrier in the hole transport from the hole injection transport layer to the anode side light emitting layer can control the injection of holes and increase the light emission efficiency.

In the case of Ip ₁ <Ip ₂ , the difference between Ip ₁ and Ip ₂ varies depending on the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer, but specifically 0.1 eV It is preferable to set it above, and it is more preferable to set it as 0.2 eV or more. Even when the difference between Ip ₁ and Ip ₂ is relatively large, holes can be transported from the hole injecting and transporting layer to the anode side light emitting layer if the driving voltage is relatively high.

Electron injection as the relationship between the material and the ionization potential of the host material of the cathode side light emitting layer of the transport layer, the ionization potential of the Ip ₃ of material of the electron injecting and transporting layer, the ionization potential of the host material of the cathode side light emitting layer Ip ₄ If Ip ₃ ≦ Ip ₄ , it is preferable that Ip ₃ <Ip ₄ among them. This is because if Ip ₃ <Ip ₄ and Ea ₃ > Ea ₄ , the band gap energy of the host material of the cathode-side light emitting layer can be made relatively large. For example, in order to improve the light emission efficiency, it becomes easy to select the host material and the light emitting dopant so that the ionization potential and the electron affinity of the host material and the light emitting dopant of the cathode side light emitting layer satisfy a predetermined relationship.

In the case of Ip ₃ <Ip ₄ , the difference between Ip ₃ and Ip ₄ varies depending on the constituent material of the electron injection / transport layer and the host material of the cathode side light emitting layer, but specifically 0.1 eV or more And more preferably 0.2 eV or more.

Regarding the relationship between the electron affinity of the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer, the electron affinity of the constituent material of the electron injection transport layer is Ea ₃ , and the electron affinity of the host material of the cathode side light emitting layer is Ea ₄ In general, Ea ₃ ≧ Ea ₄ is set. Among these, it is preferable that Ea ₃ > Ea ₄ . This is because the presence of some energy barrier in the electron transport from the electron injection transport layer to the cathode side light emitting layer makes it possible to control the electron injection and increase the light emission efficiency.

In the case of Ea ₃ > Ea ₄ , the difference between Ea ₃ and Ea ₄ varies depending on the constituent material of the electron injecting and transporting layer and the host material of the cathode side light emitting layer, but specifically 0.1 eV or more It is preferable to set it as 0.2 eV or more and 0.5 eV or less. Even when the difference between Ea ₃ and Ea ₄ is relatively large, electrons can be transported from the electron injecting and transporting layer to the cathode side light emitting layer if the driving voltage is relatively high.

The ionization potential of the material constituting the intermediate layer and the host material of the light emitting layer adjacent to the intermediate layer is expressed by Ip _INL as the ionization potential of the material constituting the intermediate layer and the ionization potential of the host material of the light emitting layer adjacent to the intermediate layer When Ip _EML is set, Ip _INL ≠ Ip _EML may be satisfied, and any of Ip _INL <Ip _EML and Ip _INL > Ip _EML may be used. For example, when the ionization potential of the constituent material of the first intermediate layer 6a is Ip _INL1 and the ionization potential of the host material of the anode side light emitting layer 5a adjacent to the first intermediate layer is Ip _EML1 , Ip _INL1 as shown in FIG. <Ip _EML1 may be used, and as shown in FIG. 3, Ip _INL1 > Ip _EML1 may be used.
When two or more intermediate layers are formed, as shown in FIG. 2, all the intermediate layers (6a, 6b) have Ip _INL < The relationship of Ip _EML may be satisfied, and as shown in FIG. 3, the relationship of Ip _INL > Ip _{EML with} respect to the light emitting layers (5a, 5b, 5c) in which all the intermediate layers (6a, 6b) are respectively adjacent Although not shown, an intermediate layer having a relationship of Ip _INL <Ip _EML with respect to the adjacent light emitting layer and an intermediate layer having a relationship of Ip _INL > Ip _{EML with} respect to the adjacent light emitting layer may be included. May be mixed.

In the case of Ip _INL <Ip _EML or Ip _INL > Ip _EML , the difference between Ip _INL and Ip _EML varies depending on the constituent material of the intermediate layer and the host material of the light emitting layer. 1 eV or more is preferable, and 0.2 eV or more and 0.5 eV or less is more preferable.

The electron affinity of the material constituting the intermediate layer and the host material of the light emitting layer adjacent to the intermediate layer is expressed as follows: Ea _{INL is} the electron affinity of the material constituting the intermediate layer, and the electron affinity of the host material of the light emitting layer adjacent to the intermediate layer is When Ea _EML is set, Ea _INL ≠ Ea _EML may be satisfied, and any of Ea _INL > Ea _EML and Ea _INL <Ea _EML may be used. For example, when the electron affinity of the constituent material of the first intermediate layer 6a is Ea _INL1 and the ionization potential of the host material of the anode side light emitting layer 5a adjacent to the first intermediate layer is Ea _EML1 , Ea _INL1 as shown in FIG. > Ea _{EML1 or} Ea _INL1 <Ea _{EML1 as} shown in FIG.
Further, when two or more intermediate layers are formed, as shown in FIG. 2, all the intermediate layers (6a, 6b) have Ea _INL > The relationship of Ea _EML may be satisfied, and as shown in FIG. 3, all the intermediate layers (6a, 6b) have a relationship of Ea _INL <Ea _{EML with} respect to the adjacent light emitting layers (5a, 5b, 5c). Although not shown, an intermediate layer that has a relationship of Ea _INL > Ea _EML with respect to the adjacent light emitting layer, and an intermediate layer that has a relationship of Ea _INL <Ea _{EML with} respect to the adjacent light emitting layer May be mixed.

When Ea _INL > Ea _EML or Ea _INL <Ea _EML , the difference between Ea _INL and Ea _EML varies depending on the constituent material of the intermediate layer and the host material of the light emitting layer. It is preferably 1 eV or more, more preferably 0.2 eV or more and 0.5 eV or less.

The ionization potential and electron affinity between the constituent material of the intermediate layer and the light-emitting dopant of the light-emitting layer adjacent to the intermediate layer are expressed as Ip _INL and the ionization potential of the light-emitting dopant of the light-emitting layer. When Ip _d is Ip _INL > Ip _d , and when the electron affinity of the constituent material of the intermediate layer is Ea _INL and the electron affinity of the light emitting dopant of the light emitting layer is Ea _d , Ea _INL <Ea _d Preferably there is. This is because when the ionization potential and electron affinity between the constituent material of the intermediate layer and the light-emitting dopant of the light-emitting layer adjacent to the intermediate layer satisfy the above relationship, the light emission efficiency can be increased.

  Here, the ionization potential and the electron affinity of the light-emitting dopant of the light-emitting layer are obtained as follows. The ionization potential is obtained by UPS (ultraviolet photoelectron spectroscopy) (for example, measuring instrument name “AC-2” manufactured by Riken Keiki Co., Ltd.). On the other hand, as a method for measuring electron affinity, first, HOMO energy is obtained by UPS (ultraviolet photoelectron spectroscopy) (for example, “AC-2” manufactured by Riken Keiki Co., Ltd.), and then an energy gap measurement value by light absorption and the above HOMO energy. The method of calculating from is adopted.

Regarding the relationship between the ionization potentials of the constituent materials of the hole injection transport layer and the electron injection transport layer, the ionization potential of the constituent material of the hole injection transport layer is Ip ₁ , and the ionization potential of the constituent material of the electron injection transport layer is Ip ₃ Then, since the hole injecting and transporting layer and the electron injecting and transporting layer contain the same bipolar material, Ip ₁ = Ip ₃ . The electron affinity of the constituent material of the hole injecting and transporting layer and the electron injecting and transporting layer includes Ea _{1 as} the electron affinity of the constituent material of the hole injecting and transporting layer, and Ea _{1 When 3} , the hole injecting and transporting layer and the electron injecting and transporting layer contain the same bipolar material, so Ea ₁ = Ea ₃ .

In the present invention, as illustrated in FIG. 5, a second hole injection transport layer 9 may be formed between the anode 3 and the hole injection transport layer 4.
In this case, the second hole injecting and transporting layer Ea ₅ the electron affinity of the constituent material of the electron affinity of the constituent material for the hole injecting and transporting layer and Ea _1, is preferably Ea ₅ <Ea _1. Even if electrons penetrate to the anode side and electrons are injected into the hole injecting and transporting layer, the second hole injecting and transporting is caused by the existence of an energy barrier between the second hole injecting and transporting layer and the hole injecting and transporting layer. Electron penetration from the layer to the anode side can be prevented. Therefore, deterioration at the interface between the second hole injecting and transporting layer and the anode can be suppressed. Further, the constituent material of the second hole injecting and transporting layer has a wider range of material selection than the constituent material of the hole injecting and transporting layer, and a material suitable for the second hole injecting and transporting layer can be used. . Thereby, it can be set as an advantageous structure in the hole injection from an anode to a 2nd hole injection transport layer.

In the case of Ea ₅ <Ea ₁ , the difference between Ea ₅ and Ea ₁ varies depending on the constituent materials of the second hole injection transport layer and the hole injection transport layer, but specifically 0.1 eV It is preferable to set it as the above, More preferably, it exists in the range of 0.2 eV-2.0 eV.

On the other hand, as the relationship of the electron affinity of the constituent materials of the second hole injection transport layer and the hole injection transport layer, it is also preferable that Ea ₅ ≧ Ea ₁ . This is because there is no charge accumulation at the interface between the second hole injection transport layer and the hole injection transport layer during driving, and deterioration can be suppressed.

In the above case, if the ionization potential of the constituent material of the second hole injecting and transporting layer is Ip ₅ and the ionizing potential of the constituent material of the hole injecting and transporting layer is Ip ₁ , usually Ip ₅ ≦ Ip ₁ . Among these, Ip ₅ <Ip ₁ is preferable. When the energy gap of the anode-side light-emitting layer is relatively large, but the hole to the anode side light emitting layer is not easily transported, first between Ip ₅ <Ip ₁ and comprising as anode and the hole injection transport layer 2 This is because holes can be smoothly transported to the anode side light emitting layer by forming the hole injecting and transporting layer. In addition, the presence of a certain energy barrier in the hole transport from the second hole injecting and transporting layer to the hole injecting and transporting layer makes it possible to control the injection of holes and increase the light emission efficiency.

In the case of Ip ₅ <Ip ₁ , the difference between Ip ₅ and Ip ₁ varies depending on the constituent materials of the second hole injection transport layer and the hole injection transport layer. 0.1 eV or more is preferable, and more preferably in the range of 0.2 eV to 0.5 eV.

In the present invention, as illustrated in FIG. 5, the second electron injection / transport layer 10 may be formed between the electron injection / transport layer 7 and the cathode 8.
In this case, electron injection material constituting the transport layer ionization potential of Ip _3, when the ionization potential of the constituent material of the second electron injecting and transporting layer and Ip _6, it is preferable that Ip ₃ <Ip _6. Even if holes penetrate to the cathode side and holes are injected into the electron injecting and transporting layer, there is an energy barrier between the electron injecting and transporting layer and the second electron injecting and transporting layer. Hole penetration to the cathode side can be prevented. Therefore, it is possible to suppress deterioration at the interface between the second electron injecting and transporting layer and the cathode. In addition, the constituent material of the second electron injecting and transporting layer has a wider range of material selection than the constituent material of the electron injecting and transporting layer, and a material suitable for the second electron injecting and transporting layer can be used. Thereby, it can be set as an advantageous structure in the electron injection from a cathode to the 2nd electron injection transport layer.

In the case of Ip ₃ <Ip ₆ , the difference between Ip ₃ and Ip ₆ varies depending on the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer, but specifically 0.1 eV or more. More preferably, it is in the range of 0.2 eV to 2.0 eV.

On the other hand, the relationship between the ionization potentials of the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer is preferably Ip ₃ ≧ Ip ₆ . This is because there is no charge accumulation at the interface between the second electron injecting and transporting layer and the electron injecting and transporting layer during driving, and deterioration can be suppressed.

In the above case, if the electron affinity of the constituent material of the electron injecting and transporting layer is Ea ₃ , and the electron affinity of the constituent material of the second electron injecting and transporting layer is Ea ₆ , Ea ₃ ≦ Ea ₆ is usually satisfied. Among these, it is preferable that Ea ₃ <Ea ₆ is satisfied. When the energy gap of the cathode side light emitting layer is relatively large, electrons are not easily transported to the cathode side light emitting layer, but the second electron injection is between the cathode and the electron injection transport layer so that Ea ₃ <Ea ₆ This is because by forming the transport layer, electrons can be transported smoothly to the cathode-side light emitting layer. In addition, since there is a slight energy barrier in electron transport from the second electron injection transport layer to the electron injection transport layer, electron injection can be controlled and light emission efficiency can be increased.

In the case of Ea ₃ <Ea ₆ , the difference between Ea ₃ and Ea ₆ varies depending on the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer, but specifically 0.1 eV or more. More preferably, it is in the range of 0.2 eV to 0.5 eV.

In the present invention, as illustrated in FIG. 6, a third hole injection transport layer 11 may be formed between the second hole injection transport layer 9 and the hole injection transport layer 4.
In this case, the electron affinity of the constituent materials of the second hole injecting and transporting layer, the third hole injecting and transporting layer, and the constituent material of the second hole injecting and transporting layer is expressed as Ea _{5. When} the electron affinity of the constituent material of the third hole injecting and transporting layer is Ea ₇ and the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ , Ea ₅ <Ea ₇ , Ea ₇ ≧ Ea ₁ It is preferable. This is because deterioration at the interface between the anode and the second hole injection transport layer and the interface between the third hole injection transport layer and the hole injection transport layer can be suppressed. Further, since Ea ₅ <Ea ₇ , the range of options for the constituent material of the second hole injecting and transporting layer is widened.

In the case of Ea ₅ <Ea ₇ , the difference between Ea ₅ and Ea ₇ varies depending on the constituent materials of the second hole injection transport layer and the third hole injection transport layer, but specifically 0 0.1 eV or more is preferable, and more preferably in the range of 0.2 eV to 2.0 eV.

On the other hand, as the relationship of the electron affinity of the constituent materials of the second hole injection transport layer, the third hole injection transport layer, and the hole injection transport layer, it is also preferable that Ea ₅ ≧ Ea ₇ ≧ Ea ₁ . This is because deterioration at the interface of each layer during driving can be suppressed.

In the above case, the relationship between the ionization potentials of the constituent materials of the second hole injection transport layer, the third hole injection transport layer, and the hole injection transport layer is as follows. Ip ₅ , where the ionization potential of the constituent material of the third hole injection transport layer is Ip ₇ and the ionization potential of the constituent material of the hole injection transport layer is Ip ₁ , usually Ip ₅ ≦ Ip ₇ ≦ Ip ₁ The Among these, Ip ₅ <Ip ₇ <Ip ₁ is preferable. When the difference between Ip ₅ and Ip ₁ is relatively large, holes are hardly transported, but between the second hole injecting and transporting layer so that Ip ₅ <Ip ₇ <Ip ₁ This is because the holes can be transported smoothly by forming the third hole injecting and transporting layer. In addition, the presence of a slight energy barrier can control the injection of holes and increase the light emission efficiency.

In the case of Ip ₅ <Ip ₇ <Ip ₁ , the difference between Ip ₅ and Ip _{7 and} the difference between Ip ₇ and Ip ₁ are the hole injection transport layer, the second hole injection transport layer, and the third hole injection. Although it differs depending on the constituent material of the transport layer, specifically, it is preferably set to 0.1 eV or more, and more preferably in the range of 0.2 eV to 0.5 eV.

In the present invention, as illustrated in FIG. 6, a third electron injection / transport layer 12 may be formed between the electron injection / transport layer 7 and the second electron injection / transport layer 10.
In this case, the electron injecting and transporting layer, the relation of the ionization potential of a constituent material of the third electron injecting and transporting layer and the second electron injecting and transporting layer, the ionization potential of the constituent material for the electron injecting and transporting layer Ip _3, the third electronic injection when the ionization potential of the constituent material of the transport layer Ip _8, the ionization potential of the constituent material of the second electron injection transport layer was _{Ip 6, Ip 3 ≧ Ip 8} , Ip 8 < is preferably Ip _6. This is because deterioration at the interface between the electron injecting and transporting layer and the third electron injecting and transporting layer and at the interface between the second hole injecting and transporting layer and the cathode can be suppressed. Further, since Ip ₈ <Ip ₆ , the range of options for the constituent material of the second electron injecting and transporting layer is widened.

In the case of Ip ₈ <Ip ₆ , the difference between Ip ₈ and Ip ₆ varies depending on the constituent materials of the second electron injection transport layer and the third electron injection transport layer, but specifically 0.1 eV. It is preferable to set it as the above, More preferably, it exists in the range of 0.2 eV-2.0 eV.

On the other hand, as the relationship of ionization potentials of the constituent materials of the electron injection transport layer, the third electron injection transport layer, and the second electron injection transport layer, it is also preferable that Ip ₃ ≧ Ip ₈ ≧ Ip ₆ . This is because deterioration at the interface of each layer during driving can be suppressed.

In the above case, the electron affinity of the constituent materials of the electron injecting and transporting layer, the third electron injecting and transporting layer, and the second electron injecting and transporting layer is expressed as Ea ₃ , When the electron affinity of the constituent material of the injection / transport layer is Ea ₈ and the electron affinity of the constituent material of the second electron injection / transport layer is Ea ₆ , usually, Ea ₃ ≦ Ea ₈ ≦ Ea ₆ . Among these, it is preferable that Ea ₃ <Ea ₈ <Ea ₆ . When the difference between Ea ₃ and Ea ₆ is relatively large, electrons are difficult to be transported, but the _third electron injection transport layer and the second electron injection transport layer are arranged so that Ea ₃ <Ea ₈ <Ea ₆ . This is because electrons can be transported smoothly by forming the electron injecting and transporting layer. In addition, the presence of a slight energy barrier can control the injection of electrons and increase the light emission efficiency.

In the case of Ea ₃ <Ea ₈ <Ea ₆ , the difference between Ea ₃ and Ea _{8 and} the difference between Ea ₈ and Ea ₆ are as follows: Although it differs depending on the constituent material, specifically, it is preferably set to 0.1 eV or more, and more preferably in the range of 0.2 eV to 0.5 eV.

  In addition, the measuring method of the ionization potential and electron affinity of the constituent material of each layer is as having mentioned above.

2. Intermediate layer The intermediate layer in the present invention is formed in at least any one position between adjacent light emitting layers, and is an intermediate layer having one or more (n-1) layers or less with respect to the n light emitting layers. Is formed. The constituent material of the intermediate layer is different from the host material of the light emitting layer adjacent to the intermediate layer.

  Note that “the intermediate layer is formed in at least one place between adjacent light emitting layers” means, for example, that there are three or more light emitting layers and two or more light emitting layers between adjacent light emitting layers. Means that an intermediate layer is formed in at least one place. For example, as shown in FIG. 1 and FIG. 7, when there are three light emitting layers (5a, 5b, 5c), the space between adjacent light emitting layers is between the anode side light emitting layer 5a and the central light emitting layer 5b and the center. There are two places between the light emitting layer 5b and the cathode side light emitting layer 5c. As illustrated in FIG. 1, the intermediate layers 6a and 6b are provided at all places between the adjacent light emitting layers (5a, 5b, 5c). The intermediate layer 6 may be formed only at one place between the adjacent light emitting layers (5a, 5b, 5c) as illustrated in FIG.

  Especially, it is preferable that the intermediate | middle layer is formed between each light emitting layer. For example, as shown in FIG. 1, when the light emitting layers (5a, 5b, 5c) are three layers, the intermediate layers 6a, 6b are provided at all positions between the adjacent light emitting layers (5a, 5b, 5c). Preferably it is formed. An interface is formed between the intermediate layer and the light-emitting layer adjacent to the intermediate layer, and the presence of a slight energy barrier controls the injection of charges in the charge transport between the intermediate layer and the light-emitting layer, thereby improving the luminous efficiency. It is because it can raise further.

  The constituent material of the intermediate layer is not particularly limited as long as it is a material that can transport holes and electrons. Among them, the constituent material of the intermediate layer is preferably a bipolar material. This is because the use of the bipolar material for the intermediate layer can effectively suppress deterioration at the interface of each layer during driving.

  Examples of the bipolar material include a distyrylarene derivative, a polyaromatic compound, an aromatic condensed ring compound, a carbazole derivative, and a heterocyclic compound. Specifically, 4,4′-bis (2,2-diphenyl-ethen-1-yl) diphenyl represented by the following formula (4,4′-bis (2,2-diphenyl-ethen-1-yl) diphenyl (DPVBi), 4,4'-bis (carbazol-9-yl) biphenyl (CBP), 2,2 ', 7,7'-tetrakis ( Carbazol-9-yl) -9,9'-spiro-bifluorene (2,2 ', 7,7'-tetrakis (carbazol-9-yl) -9,9'-spiro-bifluorene; spiro-CBP), 4 , 4 ''-di (N-carbazolyl) -2 ', 3', 5 ', 6'-tetraphenyl-p-terphenyl (4,4' '-di (N-carbazolyl) -2', 3 ' , 5 ', 6'-tetraphenyl-p-terphenyl (CzTT), 1,3-bis (carbazole-9-yl) -benzene (m-CP) 3-tert-butyl-9,10-di (naphtha-2-yl) anthracene (TBADN), and derivatives thereof Can be mentioned.

  Any material that is confirmed to be capable of transporting both hole and electron carriers by the above-described method can be used as the bipolar material in the present invention.

  The number of intermediate layers is appropriately selected according to the number of light emitting layers described later, and may be one or more, but the number of light emitting layers is preferably two or three. Of these, one or two layers are preferred.

  As a method for forming the intermediate layer, for example, a dry method such as a vacuum deposition method or a sputtering method, or a printing method, an inkjet method, a spin coating method, a casting method, a dipping method, a bar coating method, a blade coating method, or a roll coating method. And wet methods such as a gravure coating method, a flexographic printing method, and a spray coating method.

  The thickness of the intermediate layer is not particularly limited as long as a uniform film can be formed. Specifically, it is preferably about 0.1 nm to 30 nm, more preferably 0.5 nm to 20 nm. Within the range, more preferably within the range of 0.8 nm to 15 nm.

3. Light emitting layer The light emitting layer in the present invention is formed of n layers (n is an integer of 2 or more), is formed between the hole injection transport layer and the electron injection transport layer, and contains a host material and a light emitting dopant. is there. This light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

  Examples of the host material for the light emitting layer include a dye material, a metal complex material, and a polymer material.

  Examples of dye-based materials include cyclopentadiene derivatives, tetraphenylbutadiene derivatives, triphenylamine derivatives, oxadiazole derivatives, pyrazoloquinoline derivatives, distyrylbenzene derivatives, distyrylarylene derivatives, silole derivatives, thiophene ring compounds, pyridine Examples thereof include a ring compound, a perinone derivative, a perylene derivative, an oligothiophene derivative, a trifumanylamine derivative, a coumarin derivative, an oxadiazole dimer, and a pyrazoline dimer.

Examples of metal complex materials include aluminum quinolinol complex, benzoquinolinol beryllium complex, benzoxazole zinc complex, benzothiazole zinc complex, azomethyl zinc complex, porphyrin zinc complex, europium complex, iridium metal complex, platinum metal complex, etc. Al, Zn, Be, Ir, Pt, etc., or rare earth metals such as Tb, Eu, Dy, etc., and the ligand has an oxadiazole, thiadiazole, phenylpyridine, phenylbenzimidazole, quinoline structure, etc. A metal complex etc. can be mentioned. Specifically, tris (8-hydroxyquinolinolato) aluminum (Alq ₃ ) can be used.

  Examples of the polymer material include polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyvinylcarbazole, polyfluorenone derivatives, polyfluorene derivatives, polyquinoxaline derivatives, polydialkylfluorene derivatives, and Examples thereof include copolymers thereof. Moreover, what polymerized said pigment-type material and metal complex-type material is also mentioned.

Further, the host material of the light emitting layer may be a bipolar material. This is because the use of the bipolar material for the light emitting layer can effectively suppress deterioration at the interface between the layers during driving.
Since the bipolar material is described in the section of the intermediate layer, description thereof is omitted here.

  When the host material of the anode side light emitting layer is a bipolar material, the bipolar material contained in the anode side light emitting layer and the bipolar material contained in the hole injection transport layer may be the same or different. In particular, as illustrated in FIG. 4, when the bipolar material contained in the anode-side light emitting layer 5 a is the same as the bipolar material contained in the hole-injecting and transporting layer 4, the anode-side light emission from the hole-injecting and transporting layer is performed. The hole injection barrier to the layer is eliminated, and the driving voltage can be lowered.

  When the host material of the cathode side light emitting layer is a bipolar material, the bipolar material contained in the cathode side light emitting layer and the bipolar material contained in the electron injection / transport layer may be the same or different. In particular, as illustrated in FIG. 4, when the bipolar material included in the cathode side light emitting layer 5 c is the same as the bipolar material included in the electron injection transport layer 7, the electron injection transport layer to the cathode side light emitting layer. This eliminates the electron injection barrier and lowers the driving voltage.

  The light emitting dopant of the light emitting layer is not particularly limited as long as it emits fluorescence or phosphorescence. Examples of the luminescent dopant include perylene derivatives, coumarin derivatives, rubrene derivatives, quinacridone derivatives, squalium derivatives, porphyrin derivatives, styryl dyes, tetracene derivatives, pyrazoline derivatives, decacyclene, phenoxazone, quinoxaline derivatives, carbazole derivatives, fluorene derivatives, iridium (Ir ) Compounds, platinum compounds, gold compounds, osmium compounds, ruthenium (Ru) compounds, rhenium (Re) compounds, and the like. More specifically, 2,5,8,11-tetra-tert-butylperylene (2,5,8,11-Tetra-tert-butylperylene) (perylene derivative), 2,3,6,7-tetrahydro- 1,1,7,7, -Tetramethyl-1H, 5H, 11H-10- (2-benzothiazolyl) quinolidino- [9,9a, 1gh] coumarin (C545t) (2,3,6,7-Tetrahydro-1 , 1,7,7, -tetramethyl-1H, 5H, 11H-10- (2-benzothiazolyl) quinolizino- [9,9a, 1gh] coumarin (C545t)) (coumarin derivative), (5,6,11,12 ) -Tetraphenylnaphthacene ((5,6,11,12) -Tetraphenylnaphthacene) (rubrene derivative) and Tris (2-phenylpyridine) iridium (III) (Ir) (ppy) 3), Tris (1-phenylisoquinoline) iridium (III); Ir (piq) 3), bis (3,5-difluoro-2- (2-pyridyl) ) Phenyl- (2-carboxypyridyl) iridium (III) (Bis (3,5-difluoro-2- (2-pyridyl) phenyl- (2-carboxypyridyl) iridium (III); FIrpic)) Compound).

The relationship between the electron affinity and the ionization potential of the host material and the light emitting dopant of the light emitting layer, when the electron affinity of the host material Ea _h, the electron affinity of the light emitting dopant was Ea _d, an Ea _h <Ea _d, and, the ionization potential of the host material Ip _h, when the ionization potential of the light-emitting dopant was Ip _d, it is preferable that Ip _h> Ip _d. This is because, when the electron affinity and ionization potential of the host material and the luminescent dopant satisfy the above relationship, holes and electrons are trapped by the luminescent dopant, so that the luminous efficiency can be improved.

  In the n light emitting layers, the host material contained in each light emitting layer may be the same or different. Especially, it is preferable that at least any two of the n light emitting layers contain different host materials. As will be described later, it is preferable that the light emitting dopants contained in each light emitting layer are different from each other, so that a host material suitable for the light emitting dopant used in the light emitting layer can be selected. For example, when there are a light-emitting layer containing a phosphorescent dopant and a light-emitting layer containing a fluorescent dopant, a host material suitable for the phosphorescent dopant is used for the light-emitting layer containing the phosphorescent dopant, and the fluorescent dopant is used. For the light emitting layer to be contained, a host material suitable for a fluorescent light emitting dopant can be used.

  In the n light emitting layers, the light emitting dopants contained in each light emitting layer are preferably different from each other. This is because energy transfer between the light emitting dopants in the respective light emitting layers can be suppressed, the light emitting dopants in all the light emitting layers can be illuminated, and the light emission efficiency can be increased and a desired light emission color can be obtained. .

  Among these, it is preferable that at least one of the n light emitting layers contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant. When a fluorescent light emitting dopant and a phosphorescent light emitting dopant are contained in a single light emitting layer, or when a light emitting layer containing a fluorescent light emitting dopant and a light emitting layer containing a phosphorescent light emitting dopant are laminated, the fluorescent light emitting dopant In the present invention, since an intermediate layer is formed between each light emitting layer, energy transfer is suppressed between the fluorescent light emitting dopant and the phosphorescent light emitting dopant. This is because both the fluorescent light emitting dopant and the phosphorescent light emitting dopant can be illuminated, so that the light emission efficiency can be improved and a desired light emission color can be obtained.

  When each light emitting layer contains a different kind of light emitting dopant, the light emission color of the light emitting dopant contained in each light emitting layer may be the same or different. Especially, it is preferable that the luminescent color of the luminescent dopant contained in each light emitting layer mutually differs. It is because a desired luminescent color can be obtained by making the luminescent dopant in all the luminescent layers shine.

  In particular, the light emitting layer is preferably three layers, and the three light emitting layers preferably contain light emitting dopants having different emission colors. For example, when three types of light emitting dopants of red, blue, and green corresponding to the three primary colors of light are used, each of the three light emitting layers contains one type of light emitting dopant, and each of the three types of light emitting dopants emits light. This is because white light can be obtained.

  In the light emitting layer, the light emitting dopant concentration may be constant in the thickness direction of the layer, or the light emitting dopant concentration may have a distribution in the layer thickness direction.

  At least one of the n light emitting layers may contain two or more kinds of light emitting dopants. For example, when the light emitting layer has two layers and three kinds of light emitting dopants of red, blue, and green corresponding to the three primary colors of light are used, one of the two light emitting layers contains one kind of light emitting dopant, On the other hand, white light can be obtained by containing two kinds of light emitting dopants and emitting each of the three kinds of light emitting dopants. In addition, for example, when the difference in excitation energy between the host material and the luminescent dopant is relatively large, energy transfer is facilitated by further adding a luminescent dopant having an excitation energy between the excitation energy of the host material and the luminescent dopant. The luminous efficiency can be improved. Further, for example, by containing a light emitting dopant that easily transports holes rather than electrons and a light emitting dopant that easily transports electrons rather than holes, holes injected into the anode side light emitting layer and the cathode side light emitting layer and The balance of electrons can be achieved, and the light emission efficiency can be improved.

When at least one of the n light emitting layers contains two or more kinds of light emitting dopants, each light emitting dopant may emit light or only one kind may emit light. Depending on the magnitude, distribution state, and concentration of the excitation energy of the luminescent dopant, light emission of one or each luminescent dopant can be obtained.
Among them, for example, when the light emitting layer has two layers and white light is obtained using three kinds of light emitting dopants of red, blue, and green corresponding to the three primary colors of light, one of the two light emitting layers is used. It is preferable that one kind of light emitting dopant is contained, and two kinds of light emitting dopants are contained in the other to emit three kinds of light emitting dopants.

When at least one of the n light-emitting layers contains a first light-emitting dopant and a second light-emitting dopant having an excitation energy smaller than the excitation energy of the host material and larger than the excitation energy of the first light-emitting dopant. The first light-emitting dopant and the second light-emitting dopant can be appropriately selected from the above-mentioned light-emitting dopants. For example, when Alq ₃ that emits green light is used as the host material and DCM that emits red light is used as the first light emitting dopant, by using rubrene that emits yellow light as the second light emitting dopant, Alq ₃ (host material) → rubrene (first Energy transfer can be caused smoothly in the order of two light emitting dopants) → DCM (first light emitting dopant).

  When at least one of the n light-emitting layers contains a third light-emitting dopant that easily transports holes rather than electrons and a fourth light-emitting dopant that easily transports electrons rather than holes, the third light-emitting dopant The fourth light emitting dopant can be appropriately selected from the above light emitting dopants according to the combination of the constituent materials of the hole injecting and transporting layer and the electron injecting and transporting layer and the host material of the light emitting layer. For example, when TBADN is used for the hole injecting and transporting layer and the electron injecting and transporting layer, CBP is used as the host material of the light emitting layer, and rubrene is used as the light emitting dopant, rubrene becomes a light emitting dopant that facilitates transporting holes rather than electrons. For example, when TBADN is used for the hole injecting and transporting layer and the electron injecting and transporting layer, CBP is used as the host material of the light emitting layer, and anthracenediamine is used as the light emitting dopant, the anthracene diamine is easier to transport electrons than holes. It becomes.

  Note that whether the light-emitting layer can transport holes more easily than electrons or whether it can transport electrons more easily than holes depends on whether the light-emitting layer contains a host material and a single light-emitting dopant. This can be confirmed by evaluating the angle dependence of the emission pattern of the emission spectrum of the organic EL element. That is, it can be confirmed from the wavelength of the emission spectrum, the refractive index of the material, the optical path length until light is extracted from the light emitting layer by the organic EL element, and the angle dependency of the radiation pattern.

  In the case where at least one of the n light emitting layers contains a third light emitting dopant that easily transports holes rather than electrons and a fourth light emitting dopant that easily transports electrons than holes, The concentrations of the third light-emitting dopant and the fourth light-emitting dopant may be constant in the thickness direction of the layer, or may have a distribution in the thickness direction of the layer. Usually, the concentrations of the third light-emitting dopant and the fourth light-emitting dopant in the light-emitting layer are each made constant in the thickness direction of the layer.

  At least one of the n light emitting layers preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant.

  In the example shown in FIG. 8, the anode-side light emitting layer 5a has a doped region 21a and a non-doped region 22a, the non-doped region 22a is disposed on the hole injection / transport layer 4 side, and the cathode-side light emitting layer 5c has It has a doped region 21b and a non-doped region 22b, and the non-doped region 22b is disposed on the electron injection / transport layer 7 side. For example, when energy transfer can occur from the light emitting dopant in the anode side light emitting layer 5a to the constituent material of the hole injection transport layer 4, the anode side light emitting layer 5a has the non-doped region 22a on the hole injection transport layer 4 side. As a result, the energy transfer is less likely to occur and the luminous efficiency can be improved. For example, when energy transfer can occur from the light emitting dopant in the cathode side light emitting layer 5c to the constituent material of the electron injection transport layer 7, the cathode side light emitting layer 5c has the non-doped region 22b on the electron injection transport layer 7 side. As a result, the energy transfer is less likely to occur and the luminous efficiency can be improved.

  In the example shown in FIG. 8, the central light emitting layer 5b has one doped region 21c and two non-doped regions 22c and 22d, and one non-doped region 22c is disposed on the first intermediate layer 6a side. The other non-doped region 22d is disposed on the second intermediate layer 6b side. For example, in the case where energy transfer can occur from the light emitting dopant in the central light emitting layer 5b to the constituent material of the first intermediate layer 6a, the central light emitting layer 5b has the non-doped region 22c on the first intermediate layer 6a side, so Can be prevented and the luminous efficiency can be improved. For example, when energy transfer can occur from the light emitting dopant in the central light emitting layer 5b to the constituent material of the second intermediate layer 6b, the central light emitting layer 5b has the non-doped region 22d on the second intermediate layer 6b side, thereby Energy transfer is unlikely to occur and the light emission efficiency can be improved.

  In the example shown in FIG. 9, the anode side light emitting layer 5a has two doped regions 21a and 21b and one non-doped region 22, and the non-doped region 22 is disposed between the two doped regions 21a and 21b. Has been. For example, in the case where energy transfer can occur between the light-emitting dopant in the doped region 21a and the light-emitting dopant in the doped region 21b, the non-doped region 22 is disposed between the two doped regions 21a and 21b, so that the above energy is obtained. It is difficult to cause movement and light emission efficiency can be improved. Specifically, when two doped regions contain light emitting dopants having different emission colors, and each light emitting dopant emits light to obtain white light, a non-doped region between the two doped regions. Is preferably arranged. In addition, when one of the two doped regions contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant, and each of the light emitting dopants emits light, the non-doped region is located between the two doped regions. Is preferably arranged.

  As described above, when at least one of the n light emitting layers has a non-doped region, light emission efficiency can be improved.

  Note that the non-doped region that does not contain a light-emitting dopant means a region that does not substantially contain a light-emitting dopant. Specifically, a non-doped region refers to a region formed by closing a shutter of a light emitting dopant deposition source when a host material and a light emitting dopant are co-evaporated to form a light emitting layer. Further, when the thickness of the non-doped region is 10 nm or more, the non-doped region means that the content of the light-emitting dopant is 10% or less, preferably 5 when the content of the light-emitting dopant in the adjacent doped region is 100%. % Or less, more preferably 1% or less.

  The arrangement of the doped region and the non-doped region is not particularly limited as long as at least one of the n light emitting layers has an arrangement of one or more doped regions and one or more non-doped regions. . For example, the anode side light emitting layer may have a non-doped region on the hole injection transport layer side, the anode side light emitting layer may have a non-doped region on the intermediate layer side, and the cathode side light emitting layer has electron injection. The transport layer side may have a non-doped region, and the cathode side light emitting layer may have a non-doped region on the intermediate layer side. Further, the central light emitting layer may have a non-doped region only on one intermediate layer side, or may have a non-doped region on both intermediate layer sides. Furthermore, the light emitting layer may have a non-doped region sandwiched between two doped regions. Although not shown, the light emitting layer may have two doped regions and three non-doped regions, and the doped regions and the non-doped regions may be alternately arranged.

  The arrangement of the doped region and the non-doped region is appropriately selected in consideration of the energy transition of the luminescent dopant. Among them, it is preferable to appropriately select the arrangement of the doped region and the non-doped region so that the injection balance of holes and electrons can be obtained.

In the organic EL device illustrated in FIG. 8, since the anode side light emitting layer 5a has the non-doped region 22a on the hole injection transport layer 4 side, the light emitting dopant is a hole at the interface between the hole injection transport layer and the anode side light emitting layer. It is possible to improve the hole injection from the hole injection transport layer to the anode side light emitting layer without hindering the injection.
Here, in the present invention, the relationship between the electron affinity of the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer is Ea ₁ ≧ Ea ₂ , and the electrons injected into the anode side light emitting layer are directed to the counter electrode. Since there is no blocking layer to prevent penetration, it is difficult to balance the holes and electrons injected into the anode side light emitting layer in the same manner as the organic EL element having a conventional blocking layer. .
On the other hand, in the organic EL device illustrated in FIG. 8, the anode-side light emitting layer has a non-doped region on the hole injecting and transporting layer side, whereby charge trapping by the light emitting dopant can be controlled, and high efficiency. Can be obtained. For example, when the luminescent dopant is more likely to transport electrons than holes, the electron injection tends to be excessive. In this case, since the anode side light emitting layer has a non-doped region on the hole injection transport layer side, the light emission efficiency can be improved. This is because a non-doped region is provided on the hole injection transport layer side (anode side) of the anode side light emitting layer, and a doped region is provided on the intermediate layer side (cathode side) of the anode side light emitting layer. It is thought that this is because electrons injected into the anode are trapped by the light emitting dopant more in the anode side light emitting layer, and are trapped by the light emitting dopant more particularly on the cathode side, thereby preventing penetration into the anode. . That is, when the anode side light emitting layer has a non-doped region on the hole injecting and transporting layer side, it is useful when the electron injection is excessive.

In the organic EL device illustrated in FIG. 8, since the cathode side light emitting layer 5c has the non-doped region 22b on the electron injection transport layer 7 side, the light emitting dopant is electron injected at the interface between the electron injection transport layer and the cathode side light emitting layer. The electron injection from the electron injecting and transporting layer to the cathode side light emitting layer can be made satisfactory.
Here, in the present invention, the relationship between the ionization potential of the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer is Ip ₃ ≦ Ip ₄ , and the holes injected into the cathode side light emitting layer are directed to the counter electrode. Since a blocking layer for preventing penetration is not provided, it is difficult to balance holes and electrons injected into the light emitting layer in the same manner as an organic EL element having a conventional blocking layer.
On the other hand, in the organic EL device illustrated in FIG. 8, the cathode side light emitting layer has a non-doped region on the electron injection and transport layer side, whereby charge trapping by the light emitting dopant can be controlled, and high efficiency. An element can be obtained. For example, when the luminescent dopant is more likely to transport holes than electrons, hole injection tends to be excessive. In this case, since the cathode side light emitting layer has a non-doped region on the electron injection transport layer side, the light emission efficiency can be improved. This is because a non-doped region is provided on the electron-injecting and transporting layer side (cathode side) of the cathode side light emitting layer, and a doped region is provided on the intermediate layer side (anode side) of the cathode side light emitting layer. It is thought that this is because the injected holes are trapped by the light emitting dopant more in the cathode side light emitting layer, and are trapped by the light emitting dopant more particularly on the anode side, thereby preventing penetration into the cathode. . That is, when the cathode side light emitting layer has a non-doped region on the electron injecting and transporting layer side, it is useful when hole injection is excessive.

  The number of non-doped regions may be one or more, but is usually about 1-3. On the other hand, the number of doped regions may be one or more, but is usually about 1-2.

  The doped region may be a region containing a host material and a luminescent dopant. In the doped region, the luminescent dopant concentration may be constant in the layer thickness direction, and the luminescent dopant concentration has a distribution in the layer thickness direction. You may do it. Usually, in the doped region, the luminescent dopant concentration is constant in the thickness direction of the layer.

  As described above, the light emitting layer may contain two or more kinds of light emitting dopants. In this case, for example, one doped region may contain two or more kinds of light emitting dopants, and two places. The doped regions may contain different types of light emitting dopants.

  In the case where one doped region contains two or more kinds of light emitting dopants, for example, when the light emitting layer is two layers and three kinds of light emitting dopants of red, blue and green corresponding to the three primary colors of light are used. Of the two light-emitting layers, one of them contains one kind of light-emitting dopant, the other has a doped region and a non-doped region, and this doped region contains two kinds of light-emitting dopants. By emitting each of the luminescent dopants, white light can be obtained. Further, when one doped region contains two or more kinds of light emitting dopants, for example, when the difference in excitation energy between the host material and the light emitting dopant is relatively large, the excitation energy between the host material and the light emitting dopant is intermediate. By further containing a light-emitting dopant having excitation energy, energy transfer can be caused smoothly, and luminous efficiency can be improved. Furthermore, for example, by including a light emitting dopant that easily transports holes rather than electrons and a light emitting dopant that easily transports electrons rather than holes, the hole and electrons injected into the doped region can be balanced. And luminous efficiency can be improved.

When one dope region contains two or more kinds of light emitting dopants, each light emitting dopant may emit light, or only one kind may emit light. Depending on the magnitude, distribution state, and concentration of the excitation energy of the luminescent dopant, light emission of one or each luminescent dopant can be obtained.
In particular, there are two light emitting layers, and white light is obtained using three kinds of light emitting dopants of red, blue, and green corresponding to the three primary colors of light, and one of the two light emitting layers is 1 In the case where the light-emitting dopant is contained and the other has a doped region and a non-doped region, and the doped region contains two kinds of light-emitting dopants, two kinds of light-emitting dopants in the doped region are used. It is preferable that each emit light.

  When one doped region contains a first luminescent dopant and a second luminescent dopant having an excitation energy smaller than the excitation energy of the host material and larger than the excitation energy of the first luminescent dopant, the first luminescent dopant And as a 2nd light emission dopant, it can select from the above-mentioned light emission dopant suitably, and can use it.

  Moreover, when one doped region contains the 3rd light emission dopant which is easy to transport a hole rather than an electron, and the 4th light emission dopant which is easy to transport an electron rather than a hole, a 3rd light emission dopant and 4th The light emitting dopant can be appropriately selected from the above light emitting dopants according to the combination of the constituent materials of the hole injecting and transporting layer and the electron injecting and transporting layer, and the host material of the light emitting layer.

  When one doped region contains a third light-emitting dopant that easily transports holes rather than electrons and a fourth light-emitting dopant that easily transports electrons rather than holes, the third light-emitting dopant in the doped region The concentration of the fourth light emitting dopant may be constant in the thickness direction of the layer, or may have a distribution in the thickness direction of the layer. Usually, the concentration of the third light-emitting dopant and the fourth light-emitting dopant in the doped region is fixed in the thickness direction of the layer.

  On the other hand, when the two doped regions contain different types of light emitting dopants, for example, as shown in FIG. 9, two light emitting layers (5a, 5c) and one intermediate layer 6 are formed. The three light emitting dopants of red, blue, and green corresponding to the three primary colors of light are used, and one of the two light emitting layers (5a, 5c) is divided into two light emitting layers (5a) in two doped regions 21a, 21b and the non-doped region 22, the two doped regions 21a and 21b each contain one kind of light emitting dopant, and the other light emitting layer (5c) contains one kind of light emitting dopant. In some cases, the non-doped region is disposed between the two doped regions, so that the energy transfer between the light-emitting dopants can be suppressed and the light-emitting dopants can each emit light. Both improving luminous efficiency, white light can be obtained.

  In the present invention, when obtaining white light, it is preferable that the n light emitting layers contain light emitting dopants having different emission colors. For example, a combination of three types of luminescent dopants of red, blue, and green, two types of luminescent dopants of blue and yellow, two types of luminescent dopants of light blue and orange, and two types of luminescent dopants of green and purple can be given. . Among these, it is preferable to use three kinds of light emitting dopants of red, blue, and green.

  In the case of using three types of light emitting dopants of red, blue, and green, as described above, at least one of the n light emitting layers contains a fluorescent light emitting dopant, and the other contains a phosphorescent light emitting dopant. Therefore, for example, when there are two light emitting layers, one side contains a blue fluorescent light emitting dopant and the other contains a red phosphorescent light emitting dopant and a green fluorescent light emitting dopant, or one side contains a red fluorescent light emitting material. It is preferable to contain a dopant and to contain a blue phosphorescent dopant and a green fluorescent dopant on the other side. For example, when the light emitting layer has three layers, one layer contains a blue fluorescent light emitting dopant, one of the other two layers contains a red phosphorescent light emitting dopant, and the other contains a green fluorescent light emitting dopant, or It is preferable to contain a red fluorescent dopant in one layer, a blue phosphorescent dopant in one of the other two layers, and a green fluorescent dopant in the other.

  The number of light-emitting layers may be two or more, and among them, two or three layers are preferable.

  The thickness of each light-emitting layer is not particularly limited as long as it can provide a function of emitting light by providing a recombination field between electrons and holes, and is, for example, about 1 nm to 200 nm. Can be set. Among them, in order to increase the luminous efficiency by improving the injection balance of holes and electrons by increasing the thickness of the light emitting layer, the thickness of each light emitting layer is preferably in the range of 3 nm to 100 nm, More preferably, it is in the range of 5 nm to 80 nm.

  When the light-emitting layer has a doped region and a non-doped region, the thickness of the non-doped region can be formed so that a uniform film can be formed and a function of emitting light by providing a recombination field between electrons and holes is exhibited. The thickness is not particularly limited as long as the region can be secured. Specifically, the thickness of the non-doped region is preferably about 0.1 nm to 30 nm, more preferably in the range of 0.5 nm to 20 nm, and still more preferably in the range of 0.8 nm to 15 nm.

As a method for forming the light emitting layer, a method in which a host material and a light emitting dopant are co-evaporated is preferably used. At this time, a light emitting layer having a doped region and a non-doped region can be formed by opening / closing a shutter of the light emitting dopant vapor deposition source or controlling the vapor deposition rate of the light emitting dopant.
In addition, when a thin film can be formed by application from a solution, a spin coating method, a dip coating method, or the like can be used as a method for forming a light emitting layer. In this case, the host material and the luminescent dopant may be dispersed in an inert polymer.

  In addition, in order to distribute the light emitting dopant concentration in the light emitting layer, for example, a method of changing the deposition rate of the host material and the light emitting dopant continuously or periodically can be used.

4). Hole Injecting and Transporting Layer The hole injecting and transporting layer used in the present invention contains a bipolar material that is formed between the anode and the light emitting layer and can transport holes and electrons. The bipolar material contained in the electron injecting and transporting layer is the same. This hole injecting and transporting layer has a function of stably injecting or transporting holes from the anode to the light emitting layer.

  The hole injection transport layer may be either a hole injection layer having a hole injection function and a hole transport layer having a hole transport function, or may be a hole injection function and a hole transport. It may be a single layer having both functions.

  Since the bipolar material is described in the section of the intermediate layer, description thereof is omitted here.

The hole injecting and transporting layer may have a region where an oxidizing dopant is mixed with a bipolar material at least at the interface with the anode. The hole injection / transport layer has a region in which an oxidizable dopant is mixed with a bipolar material at least at the interface with the anode, thereby reducing the hole injection barrier from the anode to the hole injection / transport layer and driving voltage. It is because it can reduce.
In the organic EL device, the hole injection process from the anode to the organic layer, which is basically an insulator, is oxidation of the organic compound on the anode surface, that is, formation of a radical cation state (Phys. Rev. Lett., 14 , 229 (1965)). By previously doping the hole injection transport layer in contact with the anode with an oxidizing dopant that oxidizes the organic compound, the energy barrier for hole injection from the anode can be lowered. In the hole injecting and transporting layer doped with the oxidizing dopant, an organic compound in a state oxidized by the oxidizing dopant (that is, a state in which electrons are donated) exists, so that the hole injection energy barrier is small, The driving voltage can be lowered compared to the organic EL element.

  The oxidizing dopant is not particularly limited as long as it has a property of oxidizing a bipolar material, but an electron accepting compound is usually used.

As the electron-accepting compound, both inorganic and organic substances can be used. When the electron-accepting compound is an inorganic substance, for example, Lewis such as ferric chloride, aluminum chloride, gallium chloride, indium chloride, antimony pentachloride, molybdenum trioxide (MoO ₃ ), vanadium pentoxide (V ₂ O ₅ ), etc. Examples include acids. Moreover, when an electron-accepting compound is organic substance, a trinitrofluorenone etc. are mentioned, for example.

Among them, as the electron-accepting compound, a metal oxide is _preferable, MoO _3, V 2 _{O 5} is preferably used.

  When the hole injecting and transporting layer has a region in which an oxidizable dopant is mixed with a bipolar material, the hole injecting and transporting layer only needs to have the above region at least at the interface with the anode. The injection transport layer may be uniformly doped with an oxidizing dopant, or may be doped with an oxidizing dopant so that the content of the oxidizing dopant continuously increases from the cathode side to the anode side. The oxidizing dopant may be locally doped only in the interface with the anode of the hole injection transport layer.

  The oxidizing dopant concentration in the hole injecting and transporting layer is not particularly limited, but the molar ratio between the bipolar material and the oxidizing dopant is bipolar material: oxidizing dopant = 1: 0.1 to 1:10. It is preferable to be within the range. This is because if the ratio of the oxidizable dopant is less than the above range, the concentration of the bipolar material oxidized by the oxidizable dopant is too low to obtain a sufficient doping effect. If the ratio of the oxidizing dopant exceeds the above range, the oxidizing dopant concentration in the hole injecting and transporting layer far exceeds the bipolar material concentration, and the concentration of the bipolar material oxidized by the oxidizing dopant is extremely reduced. Therefore, the doping effect may not be sufficiently obtained in the same manner.

  As a film formation method of the hole injection transport layer, for example, a dry method such as a vacuum deposition method or a sputtering method, or a printing method, an ink jet method, a spin coating method, a casting method, a dipping method, a bar coating method, a blade coating method, etc. And wet methods such as a roll coating method, a gravure coating method, a flexographic printing method, and a spray coating method.

  Among these, as a film formation method for the hole injecting and transporting layer doped with the oxidizing dopant, a method of co-evaporating the bipolar material and the oxidizing dopant is preferably used. In this co-evaporation technique, an oxidizing dopant having a relatively low saturation vapor pressure, such as ferric chloride and indium chloride, can be deposited in a crucible by a general resistance heating method. On the other hand, when the vapor pressure is high even at room temperature and the pressure inside the vacuum device cannot be kept below the predetermined vacuum level, the vapor pressure can be controlled by controlling the orifice (opening diameter) like a needle valve or mass flow controller, Alternatively, the vapor pressure may be controlled by cooling the sample holding portion so that the temperature can be controlled independently.

  In addition, as a method of mixing an oxidizable dopant with a bipolar material so that the content of the oxidizable dopant continuously increases from the anode side light emitting layer side to the anode side, for example, the above bipolar material and the oxidizable property can be used. A method of continuously changing the deposition rate with the dopant can be used.

  The thickness of the hole injecting and transporting layer is not particularly limited as long as the thickness of the hole injecting holes from the anode and transporting the holes to the light emitting layer is sufficiently exhibited. It can be set in the range of about 0.5 nm to 1000 nm, and in particular, it is preferably in the range of 5 nm to 500 nm.

  The thickness of the hole injecting and transporting layer doped with the oxidizing dopant is not particularly limited, but is preferably 0.5 nm or more. The hole injecting and transporting layer doped with the oxidizing dopant is not particularly limited in thickness because the bipolar material exists in the state of radical cations even in the absence of an electric field and can act as internal charges. Also, even if the hole injection / transport layer doped with the oxidizing dopant is made thick, the device voltage does not increase, so the distance between the anode and the cathode is set longer than in the case of a normal organic EL device. By doing so, the risk of a short circuit can be greatly reduced.

5). Electron Injecting and Transporting Layer The electron injecting and transporting layer used in the present invention is formed between the cathode and the light emitting layer and contains a bipolar material. The bipolar material contained in the hole injecting and transporting layer and the electron injecting and transporting layer Are the same. This electron injecting and transporting layer has a function of stably injecting or transporting electrons from the cathode to the light emitting layer.

  The electron injection / transport layer may be one of an electron injection layer having an electron injection function and an electron transport layer having an electron transport function, or a single unit having both an electron injection function and an electron transport function. It may be a single layer.

  Since the bipolar material is described in the section of the intermediate layer, description thereof is omitted here.

The electron injecting and transporting layer may have a region where a reducing material is mixed with a bipolar material at least at the interface with the cathode. The electron injection / transport layer has a region in which a reducing dopant is mixed with a bipolar material at least at the interface with the cathode, thereby reducing the electron injection barrier from the cathode to the electron injection / transport layer and lowering the driving voltage. Because it can.
In the organic EL device, the electron injection process from the cathode to the organic layer, which is basically an insulator, is reduction of the organic compound on the cathode surface, that is, formation of a radical anion state (Phys. Rev. Lett., 14, 229 (1965)). By previously doping a reducing dopant that reduces the organic compound into the electron injection transport layer in contact with the cathode, the energy barrier for electron injection from the cathode can be lowered. In the electron injecting and transporting layer, an organic compound in a state reduced by a reducing dopant (that is, a state in which electrons are received and electrons are injected) exists, so that an electron injection energy barrier is small, and a conventional organic EL device As a result, the drive voltage can be reduced. Furthermore, a stable metal such as Al that is generally used as a wiring material can be used for the cathode.

  The reducing dopant is not particularly limited as long as it has a property of reducing the bipolar material, but an electron donating compound is usually used.

As the electron donating compound, a metal (metal simple substance), a metal compound, or an organometallic complex is preferably used. Examples of the metal (metal simple substance), the metal compound, or the organometallic complex include those containing at least one metal selected from the group consisting of alkali metals, alkaline earth metals, and transition metals including rare earth metals. it can. Among them, it is preferable that the material contains at least one metal selected from the group consisting of alkali metals, alkaline earth metals, and transition metals including rare earth metals having a work function of 4.2 eV or less. Examples of such a metal (metal simple substance) include Li, Na, K, Cs, Be, Mg, Ca, Sr, Ba, Y, La, Mg, Sm, Gd, Yb, and W. Examples of the metal compound include metal oxides such as Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, and CaO, LiF, NaF, KF, RbF, CsF, and MgF _2. , CaF ₂ , SrF ₂ , BaF ₂ , LiCl, NaCl, KCl, RbCl, CsCl, MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl _{2 and} other metal salts. Examples of the organometallic complex include organometallic compounds containing W, 8-hydroxyquinolinolatolithium (Liq), and the like. Of these, Cs, Li, and Liq are preferably used. This is because good electron injection characteristics can be obtained by doping these into a bipolar material.

  When the electron injecting and transporting layer has a region in which a reducing dopant is mixed with a bipolar material, the electron injecting and transporting layer only needs to have the above region at least at the interface with the cathode. The reducing dopant may be uniformly doped, and the reducing dopant may be doped so that the content of the reducing dopant continuously increases from the anode side to the cathode side, The reducing dopant may be locally doped only in the interface between the injection transport layer and the cathode.

  The reducing dopant concentration in the electron injecting and transporting layer is not particularly limited, but is preferably about 0.1 to 99% by weight. This is because if the reducing dopant concentration is less than the above range, the concentration of the bipolar material reduced by the reducing dopant may be too low to obtain a sufficient doping effect. If the reducing dopant concentration exceeds the above range, the reducing dopant concentration in the electron injecting and transporting layer far exceeds the bipolar material concentration, and the concentration of the bipolar material reduced by the reducing dopant is extremely reduced. Similarly, the doping effect may not be sufficiently obtained.

  As a method for forming the electron injecting and transporting layer, for example, a dry method such as a vacuum deposition method or a sputtering method, or a printing method, an ink jet method, a spin coating method, a casting method, a dip coating method, a bar coating method, or a blade coating method. And wet methods such as a roll coating method, a gravure coating method, a flexographic printing method, and a spray coating method.

Among these, as a method for forming the electron injecting and transporting layer doped with the reducing dopant, a method of co-evaporating the bipolar material and the reducing dopant is preferably used.
When a thin film can be formed by application from a solution, a spin coating method, a dip coating method, or the like can be used as a method for forming an electron injecting and transporting layer doped with a reducing dopant. In this case, the bipolar material and the reducing dopant may be dispersed in an inert polymer.

  In addition, as a method of mixing the reducing dopant with the bipolar material so that the content of the reducing dopant continuously increases from the anode side to the cathode side, for example, the bipolar material and the reducing dopant may be mixed, for example. A method of continuously changing the deposition rate can be used.

  The thickness of the electron injecting and transporting layer is not particularly limited as long as the thickness of the electron injecting and transporting layer is sufficiently exerted.

  The thickness of the electron injecting and transporting layer doped with the reducing dopant is not particularly limited, but is preferably in the range of 0.1 nm to 300 nm, more preferably in the range of 0.5 nm to 200 nm. Is within. This is because if the thickness is less than the above range, the effect of doping may not be sufficiently obtained because the amount of the bipolar material present near the cathode interface and reduced by the reducing dopant is small. Further, if the thickness exceeds the above range, the film thickness of the entire electron injecting and transporting layer is too thick, which may increase the driving voltage.

6). Second Hole Injection / Transport Layer In the present invention, a second hole injection / transport layer may be formed between the anode and the hole injection / transport layer. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the second hole injection transport layer and the hole injection transport layer satisfy the above-described relationship.

  When the second hole injecting and transporting layer is formed between the anode and the hole injecting and transporting layer, the second hole injecting and transporting layer usually functions as the hole injecting and transporting layer, and the hole injecting and transporting layer is positive. Functions as a hole transport layer.

  The constituent material of the second hole injecting and transporting layer is not particularly limited as long as it can stabilize the injection of holes from the anode, and the compounds exemplified as the host material of the light emitting layer can be used. In addition, arylamines, starburst amines, phthalocyanines, vanadium oxide, molybdenum oxide, ruthenium oxide, aluminum oxide and other oxides, amorphous carbon, polyaniline, polythiophene, polyphenylene vinylene, and other conductive polymers and their derivatives Can be used. Conductive polymers such as polyaniline, polythiophene, polyphenylene vinylene, and derivatives thereof may be doped with an acid. Specifically, N, N′-bis (naphthalen-1-yl) -N, N′-bis (phenyl) -benzidine (α-NPD), 4,4,4-tris (3-methylphenylphenylamino) ) Triphenylamine (MTDATA), poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS), polyvinylcarbazole (PVCz), and the like.

Especially, it is preferable that the constituent material of a 2nd positive hole injection transport layer is a bipolar material. This is because the use of the bipolar material for the second hole injecting and transporting layer can effectively suppress deterioration at the layer interface during driving.
Since the bipolar material is described in the section of the intermediate layer, description thereof is omitted here.

  When the second hole injecting and transporting layer and the second electron injecting and transporting layer described later contain bipolar materials, the bipolar materials contained in these layers may be the same or different.

When the constituent material of the second hole injecting and transporting layer is an organic material (organic compound for hole injecting and transporting layer), the second hole injecting and transporting layer is at least at the interface with the anode for the hole injecting and transporting layer. It is preferable to have a region where an oxidizing dopant is mixed with an organic compound. The second hole injecting and transporting layer has a region in which the oxidizing dopant is mixed with the organic compound for the hole injecting and transporting layer at least at the interface with the anode, so that the anode to the second hole injecting and transporting layer is provided. This is because the hole injection barrier is reduced and the driving voltage can be lowered.
In addition, about the case where the 2nd hole injection transport layer has the area | region where the oxidizing dopant was mixed with the organic compound for hole injection transport layers, the said hole injection transport layer mixed the oxidizing dopant with the bipolar material. Since it is the same as the case where it has an area, explanation here is omitted.

  The film forming method and thickness of the second hole injecting and transporting layer are the same as those of the above-described hole injecting and transporting layer, and thus the description thereof is omitted here.

7). Second Electron Injection / Transport Layer In the present invention, a second electron injection / transport layer may be formed between the electron injection / transport layer and the cathode. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the electron injection / transport layer and the second electron injection / transport layer satisfy the relationship described above.

  When the second electron injecting and transporting layer is formed between the electron injecting and transporting layer and the cathode, normally, the second electron injecting and transporting layer functions as an electron injecting and transporting layer, and the electron injecting and transporting layer functions as an electron transporting layer. .

  The constituent material of the second electron injecting and transporting layer is not particularly limited as long as it is a material that can stabilize the injection of electrons from the cathode. In addition to the compounds exemplified as the host material of the light emitting layer, Ba, Ca, Li, Cs, Mg, Sr and other alkali metals or alkaline earth metals alone, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, lithium fluoride, cesium fluoride and other alkali metals Or alkaline earth metal fluorides, alkali metal alloys such as aluminum lithium alloys, metal oxides such as magnesium oxide, strontium oxide and aluminum oxide, and organic complexes of alkali metals such as sodium polymethyl methacrylate polystyrene sulfonate be able to. Moreover, phenanthroline derivatives such as bathocuproin (BCP) and bathophenanthroline (Bpehn), triazole derivatives, oxadiazole derivatives, and aluminum quinolinol complexes such as tris (8-hydroxyquinolinolato) aluminum (Alq3) can be given.

Among these, the constituent material of the second electron injecting and transporting layer is preferably a bipolar material. By using the bipolar material for the second electron injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed.
Since the bipolar material is described in the section of the intermediate layer, description thereof is omitted here.

When the constituent material of the second electron injecting and transporting layer is an organic compound (organic compound for electron injecting and transporting layer), the second electron injecting and transporting layer is reduced to the organic compound for electron injecting and transporting layer at least at the interface with the cathode. It is preferable to have a region mixed with a conductive dopant. The second electron injecting and transporting layer has a region in which a reducing dopant is mixed with the organic compound for the electron injecting and transporting layer at least at the interface with the cathode, so that an electron injection barrier from the cathode to the second electron injecting and transporting layer is formed. This is because the driving voltage can be reduced.
In the case where the second electron injecting and transporting layer has a region in which the reducing dopant is mixed with the organic compound for the electron injecting and transporting layer, the electron injecting and transporting layer has a region in which the reducing dopant is mixed in the bipolar material. The description here is omitted.

  The film formation method and thickness of the second electron injecting and transporting layer are the same as those of the above-described electron injecting and transporting layer, and thus the description thereof is omitted here.

8). Third hole injection transport layer In the present invention, a third hole injection transport layer may be formed between the second hole injection transport layer and the hole injection transport layer. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the second hole injection transport layer, the third hole injection transport layer, and the hole injection transport layer satisfy the relationship described above.

  When the third hole injection / transport layer is formed between the second hole injection / transport layer and the hole injection / transport layer, the second hole injection / transport layer normally functions as the hole injection layer, The three hole injection transport layer and the hole injection transport layer function as a hole transport layer.

  As a constituent material of the third hole injecting and transporting layer, the same constituent material as that of the second hole injecting and transporting layer can be used.

Among these, the constituent material of the third hole injection transport layer is preferably a bipolar material. By using the bipolar material for the third hole injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed.
Since the bipolar material is described in the section of the intermediate layer, description thereof is omitted here.

  When the third hole injecting and transporting layer and the third electron injecting and transporting layer described later contain a bipolar material, the bipolar materials contained in these layers may be the same or different.

  The film formation method and thickness of the third hole injecting and transporting layer are the same as those of the above-described hole injecting and transporting layer, and thus the description thereof is omitted here.

9. Third Electron Injection / Transport Layer In the present invention, a third electron injection / transport layer may be formed between the electron injection / transport layer and the second electron injection / transport layer. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the electron injection / transport layer, the third electron injection / transport layer, and the second electron injection / transport layer satisfy the relationship described above.

  When the third electron injecting and transporting layer is formed between the electron injecting and transporting layer and the second electron injecting and transporting layer, the second electron injecting and transporting layer normally functions as the electron injecting and transporting layer, and the third electron injecting and transporting layer The electron injecting and transporting layer functions as an electron transporting layer.

  As the constituent material of the third electron injecting and transporting layer, the same material as that of the second electron injecting and transporting layer can be used.

In particular, the constituent material of the third electron injecting and transporting layer is preferably a bipolar material. By using the bipolar material for the third electron injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed.
Since the bipolar material is described in the section of the intermediate layer, description thereof is omitted here.

  Note that the film formation method and thickness of the third electron injecting and transporting layer are the same as those of the above-described electron injecting and transporting layer, and thus the description thereof is omitted here.

10. Anode The anode used in the present invention may be transparent or opaque, but it needs to be a transparent electrode when light is extracted from the anode side.

  For the anode, a conductive material having a large work function is preferably used so that holes can be easily injected. The anode preferably has as low resistance as possible. Generally, a metal material is used, but an organic substance or an inorganic compound may be used. Specific examples include tin oxide, indium tin oxide (ITO), and indium zinc oxide (IZO).

The anode can be formed using a general electrode forming method, and examples thereof include a sputtering method, a vacuum evaporation method, and an ion plating method.
The thickness of the anode is appropriately selected depending on the target resistance value, visible light transmittance, and type of conductive material.

11. Cathode The cathode used in the present invention may be transparent or opaque, but needs to be a transparent electrode when light is extracted from the cathode side.

For the cathode, it is preferable to use a conductive material having a small work function so that electrons can be easily injected. Moreover, it is preferable that the cathode has as low resistance as possible. Generally, a metal material is used, but an organic substance or an inorganic compound may be used. Specifically, Al, Cs, Er, etc. as a simple substance, MgAg, AlLi, AlLi, AlMg, CsTe, etc. as an alloy, Ca / Al, Mg / Al, Li / Al, Cs / Al, Cs ₂ O / Al, LiF / Al, include _ErF 3 / Al or the like.

The cathode can be formed using a general electrode forming method, and examples thereof include a sputtering method, a vacuum deposition method, and an ion plating method.
Further, the thickness of the cathode is appropriately selected depending on the target resistance value, visible light transmittance, and type of conductive material.

12 Substrate The substrate in the present invention supports the above-described anode, hole injection / transport layer, light emitting layer, intermediate layer, electron injection / transport layer, cathode, and the like. When the anode or the cathode has a predetermined strength, the anode or the cathode may serve as the substrate, but the anode or the cathode is usually formed on the substrate having the predetermined strength. In general, when manufacturing an organic EL element, it is possible to produce an organic EL element more stably by laminating from the anode side. A layer, a light emitting layer and an intermediate layer, an electron injection transport layer, and a cathode are laminated in this order.

  The substrate may be transparent or opaque, but needs to be a transparent substrate when light is extracted from the substrate side. Examples of the transparent substrate that can be used include glass substrates such as soda lime glass, alkali glass, lead alkali glass, borosilicate glass, aluminosilicate glass, and silica glass, and resin substrates that can be formed into a film.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Hereinafter, the present invention will be specifically described using examples and comparative examples.
First, the structural formulas of the materials used in the examples, the ionization potential, and the electron affinity are shown below.

[Example 1]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. Its ITO substrate, the total thickness 10nm and TBADN and MoO ₃ represented by the structural formula under the condition of a vacuum degree of 10 ^-5 Pa by volume 67:33, by co-deposition at a deposition rate of 1.0 Å / sec Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TCTA represented by the above structural formula as a host material, using TBPe represented by the above structural formula as a blue light emitting dopant, TCTA and TBPe on the hole transport layer, TBPe concentration is 3 wt. A blue light-emitting layer (first light-emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 sec / sec under a vacuum degree of 10 ⁻⁵ Pa.
Next, TBADN was deposited on the blue light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (first layer) Intermediate layer) was formed.
Next, using TCTA as a host material and C545T represented by the above structural formula as a green light-emitting dopant, TCTA and C545T are placed on the intermediate layer so that the C545T concentration is 3 wt%. ^A green light-emitting layer (second light-emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec under the condition of ⁻⁵ Pa.
Next, TBADN was deposited on the green light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (second layer) Intermediate layer) was formed.
Next, using CBP represented by the above structural formula as a host material and using Ir (piq) ₃ represented by the above structural formula as a red light-emitting dopant, CBP and Ir (piq) _{3 are formed} on the intermediate layer. the, Ir (piq) ₃ to a concentration of 3 wt%, under the condition of a vacuum degree of 10 ^-5 Pa, was formed by vacuum deposition to a thickness of 10nm at a deposition rate of 1 Å / sec, the red light-emitting layer (3 layers The light emitting layer of the eye) was formed.

Next, TBADN was deposited on the red light emitting layer by vacuum deposition under a vacuum degree of 10 ⁻⁵ Pa at a deposition rate of 1 Å / sec to a thickness of 10 nm, and an electron transport layer (first layer) An electron injecting and transporting layer) was formed. Next, a film thickness of TBADN and Liq represented by the above structural formula is co-evaporated at a deposition rate of 1 mm / sec on the electron transport layer under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. The film was formed to 10 nm to form an electron injection layer (second electron injection transport layer).

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Example 2]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TCTA as a host material and TBPe as a blue light-emitting dopant, on the hole transport layer, TCTA and TBPe, conditions of vacuum degree 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TCTA as a host material and C545T as a green light-emitting dopant, TCTA and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec.
Next, the green light emitting layer, TBADN, and under the condition of a vacuum degree of 10 ^-5 Pa, it was formed by vacuum deposition to a thickness of 5nm at a deposition rate of 1.0 Å / sec, to form an intermediate layer.
Next, using CBP as the host material and Ir (piq) ₃ as the red light-emitting dopant, CBP and Ir (piq) ₃ are added onto the intermediate layer so that the Ir (piq) ₃ concentration is 3 wt%. In addition, a red light emitting layer (third light emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, TBADN was deposited on the red light emitting layer by vacuum deposition under a vacuum degree of 10 ⁻⁵ Pa at a deposition rate of 1 Å / sec to a thickness of 10 nm, and an electron transport layer (first layer) An electron injecting and transporting layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Example 3]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TCTA as a host material and TBPe as a blue light-emitting dopant, on the hole transport layer, TCTA and TBPe, conditions of vacuum degree 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, TBADN was deposited on the blue light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa to form an intermediate layer.
Next, using TCTA as a host material and C545T as a green light emitting dopant, on the intermediate layer, TCTA and C545T, under the condition of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%, A green light emitting layer (second light emitting layer) was formed by vacuum deposition at a deposition rate of 1 mm / sec to a thickness of 5 nm.
Next, using CBP as the host material and Ir (piq) ₃ as the red light-emitting dopant, CBP and Ir (piq) ₃ are added onto the intermediate layer so that the Ir (piq) ₃ concentration is 3 wt%. In addition, a red light emitting layer (third light emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, TBADN was deposited on the red light emitting layer by vacuum deposition under a vacuum degree of 10 ⁻⁵ Pa at a deposition rate of 1 Å / sec to a thickness of 10 nm, and an electron transport layer (first layer) An electron injecting and transporting layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Comparative Example 1]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, α-NPD and MoO ₃ represented by the above structural formula were combined at a deposition rate of 1.0 Å / sec by co-evaporation under a vacuum ratio of 10 ^-5 Pa at a volume ratio of 67:33. A film was formed to a thickness of 10 nm to form a hole injection layer. Next, α-NPD and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 under a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. On top of that, α-NPD was vacuum-deposited to a thickness of 10 nm to form a hole transport layer.

Next, using TCTA as a host material and TBPe as a blue light-emitting dopant, on the hole transport layer, TCTA and TBPe, conditions of vacuum degree 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TCTA as a host material and C545T as a green light-emitting dopant, TCTA and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec.
Next, using CBP as the host material and Ir (piq) ₃ as the red light-emitting dopant, CBP and Ir (piq) ₃ are added on the green light-emitting layer with an Ir (piq) ₃ concentration of 3 wt%. As described above, a red light emitting layer (third light emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, on the red light emitting layer, Alq ₃ represented by the above structural formula was deposited by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec under the condition of a vacuum degree of 10 ⁻⁵ Pa, An electron transport layer was formed. Next, on the above electron transport layer, Alq ₃ and Liq were formed to a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-evaporation under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ⁻⁵ Pa, An electron injection layer was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 2 shows the light emission characteristics of the organic EL elements of Examples 1 to 3 and Comparative Example 1 under 10 mA / cm ² .

From the organic EL devices of Examples 1 to 3 and Comparative Example 1, emission peaks derived from TBPe, C545T, and Ir (piq) ₃ were observed. In the organic EL device of Example 1, the luminous efficiency of the front luminance is 8.5 cd / A, and the external quantum efficiency is determined from the number of photons obtained by observing the light emitted to all angles and the number of electrons input. The calculated value was 4.0%. On the other hand, in the organic EL device of Comparative Example 1, the luminous efficiency of the front luminance was 7.3 cd / A, and the external quantum efficiency was 3.4%. Also, the life characteristics, observation of the brightness half-life from the initial luminance 1000 cd / m ² under a constant current density, the organic EL devices of Examples 1 to 3, the time in which the luminance is reduced by half has achieved 250 hours . On the other hand, the brightness of the organic EL device of Comparative Example 1 was reduced by half in 150 hours.

[Example 4]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TCTA as a host material and TBPe as a blue light-emitting dopant, on the hole transport layer, TCTA and TBPe, conditions of vacuum degree 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, TBADN was deposited on the blue light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (first layer) Intermediate layer) was formed.
Next, using CBP as a host material and using Ir (ppy) ₃ represented by the above structural formula as a green light-emitting dopant, CBP and Ir (ppy) ₃ are formed on the intermediate layer, and Ir (ppy) ₃ A green light-emitting layer (second light-emitting layer) is formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ^-5 Pa so that the concentration is 3 wt%. did.
Next, TBADN was deposited on the green light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (second layer) Intermediate layer) was formed.
Next, using CBP as the host material and Ir (piq) ₃ as the red light-emitting dopant, CBP and Ir (piq) ₃ are added onto the intermediate layer so that the Ir (piq) ₃ concentration is 3 wt%. In addition, a red light emitting layer (third light emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Comparative Example 2]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, α-NPD and MoO ₃ were formed by co-evaporation with a volume ratio of 67:33 and a vacuum of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. A hole injection layer was formed. Next, α-NPD and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 under a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. On top of that, α-NPD was vacuum-deposited to a thickness of 10 nm to form a hole transport layer.

Next, using TCTA as a host material and TBPe as a blue light-emitting dopant, on the hole transport layer, TCTA and TBPe, conditions of vacuum degree 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using CBP as the host material and Ir (ppy) ₃ as the green light-emitting dopant, CBP and Ir (ppy) ₃ are added on the intermediate layer so that the Ir (ppy) ₃ concentration is 3 wt%. In addition, a green light emitting layer (second light emitting layer) was formed by vacuum vapor deposition to a thickness of 5 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.
Next, using CBP as the host material and Ir (piq) ₃ as the red light-emitting dopant, CBP and Ir (piq) _{3 are} added onto the intermediate layer so _that the Ir (piq) ₃ concentration is 3 wt%. In addition, a red light emitting layer (third light emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, Alq ₃ was deposited on the light-emitting layer by vacuum deposition under a condition of a vacuum degree of 10 ⁻⁵ Pa at a deposition rate of 1 Å / sec to a thickness of 10 nm to form an electron transport layer. Next, on the electron transport layer, Alq ₃ and Liq represented by the following formula (4) are vapor-deposited at a rate of 1 Å / sec by co-evaporation under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. The film was formed to a thickness of 10 nm to form an electron injection layer.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 3 shows the light emission characteristics of the organic EL elements of Example 4 and Comparative Example ² under 10 mA / cm ² .

From the organic EL devices of Example 4 and Comparative Example 2, emission peaks derived from TBPe, Ir (ppy) ₃ , and Ir (piq) ₃ were observed. In the organic EL device of Example 4, the luminous efficiency of the front luminance is 13.4 cd / A, and the external quantum yield is calculated from the number of photons obtained by observing the luminescence emitted to all angles and the number of injected electrons. Was calculated to be 5.6%. On the other hand, in the organic EL device of Comparative Example 2, the luminous efficiency of front luminance was 9.8 cd / A, and the external quantum yield was 5.0%. As for the lifetime characteristics, the luminance half-life from an initial luminance of 1000 cd / m ² was observed under a constant current density. In the organic EL device of Example 4, the luminance half-life was 300 hours. On the other hand, in the organic EL device of Comparative Example 2, the luminance was reduced by half in 200 hours.

[Example 5]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TCTA as a host material and TBPe as a blue light-emitting dopant, on the hole transport layer, TCTA and TBPe, conditions of vacuum degree 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, TBADN was deposited on the blue light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (first layer) Intermediate layer) was formed.
Next, using TCTA as a host material and C545T as a green light emitting dopant, on the intermediate layer, TCTA and C545T, under the condition of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%, A green light emitting layer (second light emitting layer) was formed by vacuum deposition at a deposition rate of 1 mm / sec to a thickness of 5 nm.
Next, TBADN was deposited on the green light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (second layer) Intermediate layer) was formed.
Next, CBP was deposited on the intermediate layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa to form a non-doped region. Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the non-doped region so that the Ir (piq) ₃ concentration becomes 3 wt%. In addition, a red light emitting region (dope region) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa. As a result, a red light emitting layer (third light emitting layer) having a non-doped region and a doped region was obtained.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Example 6]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TCTA as a host material and TBPe as a blue light-emitting dopant, on the hole transport layer, TCTA and TBPe, conditions of vacuum degree 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, TBADN was deposited on the blue light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (first layer) Intermediate layer) was formed.
Next, using TCTA as a host material and C545T as a green light emitting dopant, on the intermediate layer, TCTA and C545T, under the condition of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%, A green light emitting layer (second light emitting layer) was formed by vacuum deposition at a deposition rate of 1 mm / sec to a thickness of 5 nm.
Next, TBADN was deposited on the green light-emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an intermediate layer (second layer) Intermediate layer) was formed.
Next, CBP was deposited on the intermediate layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa to form a non-doped region. Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the non-doped region so that the Ir (piq) ₃ concentration becomes 3 wt%. In addition, a red light emitting region (dope region) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa. Next, CBP was deposited on the doped region by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa to form a non-doped region. Thus, a red light emitting layer (third light emitting layer) having a non-doped region, a doped region, and a non-doped region was obtained.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 4 shows the light emission characteristics of the organic EL elements of Examples 5 and 6 under 10 mA / cm ² .

From the organic EL devices of Examples 5 and 6, emission peaks derived from TBPe, C545T, and Ir (piq) ₃ were observed. In Examples 5 and 6, it was confirmed that the external quantum efficiency was improved by providing a non-doped region in the light emitting layer. As for the lifetime characteristics, when the luminance half-life from the initial luminance of 1000 cd / m ² was observed under a constant current density, 250 hours were achieved for all the elements.

DESCRIPTION OF SYMBOLS 1 ... Organic EL element 2 ... Substrate 3 ... Anode 4 ... Hole injection transport layer 5a ... Anode side light emitting layer 5b ... Central light emitting layer 5c ... Cathode side light emitting layer 6, 6a, 6b ... Intermediate layer 7 ... Electron injection transport layer 8 ... cathode 9 ... second hole injection transport layer 10 ... second electron injection transport layer 11 ... third hole injection transport layer 12 ... third electron injection transport layer 21, 21, a, 21b, 21c ... doped region 22, 22a, 22b, 22c, 22d ... non-doped region

Claims (10)

The anode,
A hole injecting and transporting layer formed on the anode;
A light emitting layer of n layers (n is an integer of 2 or more) formed on the hole injecting and transporting layer and containing a host material and a light emitting dopant;
An intermediate layer formed of at least one layer between the adjacent light emitting layers and not more than (n-1) layers;
An electron injecting and transporting layer formed on the n light emitting layers;
A cathode formed on the electron injection transport layer,
The hole injection transport layer and the electron injection transport layer contain a bipolar material capable of transporting holes and electrons, and the bipolar material contained in the hole injection transport layer and the electron injection transport layer are the same,
The intermediate layer material and the light emitting layer host material adjacent to the intermediate layer are different, the ionization potential of the intermediate layer component material is Ip _INL , and the light emitting layer host material adjacent to the intermediate layer is ionized When the potential is Ip _EML , Ip _INL ≠ Ip _EML , the electron affinity of the constituent material of the intermediate layer is Ea _INL , and the electron affinity of the host material of the light emitting layer adjacent to the intermediate layer is Ea _EML , Ea _INL ≠ Ea _EML ,
Wherein Ea ₁ electron affinity of the constituent material of the hole injection transport layer, when the electron affinity of the host material of the light emitting layer adjacent to the hole injection transport layer was Ea _2, a Ea ₁ ≧ Ea _2, wherein electron injection material constituting the transport layer ionization potential of Ip _3, when the ionization potential of the host material of the light emitting layer adjacent to the electron injection transport layer was Ip _4, characterized in that it is a Ip ₃ ≦ Ip ₄ Organic electroluminescence device.   The organic electroluminescence device according to claim 1, wherein the intermediate layer is an (n-1) layer, and the intermediate layer is formed between the light emitting layers.   The intermediate layer contains a bipolar material capable of transporting holes and electrons, and the bipolar materials contained in the hole injection transport layer, the electron injection transport layer, and the intermediate layer are the same. The organic electroluminescent element of Claim 1 or Claim 2.   2. At least one of the n light emitting layers has one or more doped regions containing the light emitting dopant and one or more non-doped regions not containing the light emitting dopant. 3. The organic electroluminescence device according to any one of 3 to 3.   The organic electroluminescence device according to claim 4, wherein the light emitting layer adjacent to the hole injection transport layer has the non-doped region on the hole injection transport layer side.   6. The organic electroluminescence device according to claim 4, wherein the light emitting layer adjacent to the electron injection / transport layer has the non-doped region on the electron injection / transport layer side.   The organic electroluminescent element according to claim 4, wherein the light emitting layer has the non-doped region on the intermediate layer side.   The light emitting layer has the two doped regions, the non-doped region is disposed between the two doped regions, and the two doped regions contain different types of light emitting dopants. The organic electroluminescence device according to any one of claims 4 to 7, wherein the organic electroluminescence device is characterized.   The organic electro according to any one of claims 1 to 8, wherein at least one of the n light emitting layers contains a fluorescent light emitting dopant, and the other contains a phosphorescent light emitting dopant. Luminescence element.   The light emitting layer of said n layer is a light emitting layer of 3 layers, The said light emitting layer of 3 layers contains the light emission dopant from which luminescent color differs mutually, The Claim 1-9 characterized by the above-mentioned. Organic electroluminescence element.

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