JP2007258237A - Structural stabilization method of organic laminated structural materials and its utilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stabilizing an organic laminated structure material by stabilizing an amorphous state of an organic layer constituting the material. <P>SOLUTION: The structure stabilizing method of the organic laminated structure material for stabilizing the amorphous state of the organic layer (24 and/or 28, for example) is provided in the organic laminated structure material having a pair of electrodes 22 and 32, and a carrier transport property solid organic layer in the amorphous state which is arranged between the electrodes. In the method, the organic layer is constituted in such a way that (a) it comprises organic compounds of two types or above which are selected from a group formed of an n-type organic compound and a p-type organic compound, and (b) the organic compounds of two types or above coexist in the amorphous state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for stabilizing an amorphous state of an organic layered structure including an amorphous carrier-transporting solid organic layer.

An organic laminated structure material provided with a solid organic layer is useful as a component of an organic electroluminescent element (organic EL element), an organic thin film transistor, an organic solar cell, or the like. For example, Non-Patent Documents 1 and 2 can be cited as prior art documents related to organic EL.
In such an organic laminated structure material, the morphology of the organic layer contained in the material (for example, a fine structure such as the arrangement and / or regularity of arrangement of components of the organic layer) affects the material properties. Sometimes. For example, in applications where the solid organic layer is required to have carrier transportability, the carrier transport performance may vary depending on the morphology of the organic layer (amorphous state, crystalline state, coexistence of amorphous and crystalline, etc.). Therefore, such a change in morphology is prevented or suppressed from the viewpoint of stabilizing the performance and improving the reliability of an organic laminated structure material having such an organic layer, various elements using the organic layer, or a device including the element. In other words, it is desired to stabilize the structure of the organic layer. For example, in an organic electroluminescent device having a laminated structure having a light emitting layer and at least one carrier (charge) transporting solid organic layer in an amorphous state between a pair of electrodes, the amorphous state of the carrier transporting solid organic layer is more It would be beneficial if it could be stabilized.

Satoshi Miyaguchi, “Development Status of Organic EL Display”, PIONEER R & D, Vol. 13, No. 2, pp. 36-44 Thin Solid Films, 2001, No. 393, p. 109-113

  As a method to increase the stability of the amorphous state of the organic layer, the molecular weight of the organic compound constituting the organic layer is increased to increase the melting point, and a steric hindrance substituent is introduced to inhibit molecular rearrangement. Etc. have been proposed. In Non-Patent Document 2, for an organic film made of a single carrier-transporting organic compound (triphenyldiamine derivative), the film formation conditions and morphological instability (in particular, the amorphous organic film is polycrystallized). The relationship with the phenomenon is being studied. Here, in an organic layer using a single carrier transporting organic compound, the molecular structure of the organic compound itself is improved (for example, an organic compound having a molecular structure that is less likely to be ordered and / or has a higher melting point) If a general-purpose method for stabilizing the amorphous state of the organic layer is provided by an approach different from the study of the preferable manufacturing conditions of the organic layer), the stabilization method and the improvement of the molecular structure and / or Alternatively, a higher stabilization effect can be realized by a synergistic effect with the adoption of preferable production conditions.

An object of the present invention is to provide a highly versatile stabilization method that stabilizes an amorphous state of an organic layer constituting an organic laminated structure material to stabilize the material. Another object of the present invention is to provide an organic electroluminescent device to which such a stabilization method is applied.
In addition, an amorphous state means here the state observed as a substantially uniform non-uniform | heterogenous image in a polarizing microscope (for example, about 5 times-50 times magnification) observation. In other words, the concept of the amorphous state mentioned here can include the case where it is in a completely amorphous state and the case where it contains the presence of nano-order microcrystals that cannot be observed with the polarizing microscope.

According to the present invention, in an organic laminated structure material comprising a pair of electrodes and an amorphous carrier-transporting solid organic layer disposed between the electrodes, the structure of the organic laminated structure material that stabilizes the amorphous state of the organic layer A stabilization method is provided. The stabilization method is carried out by subjecting the organic layer to the following conditions:
(A) containing two or more organic compounds selected from the group consisting of n-type organic compounds and p-type organic compounds; and
(B) Any of these two or more organic compounds are mixed in an amorphous state;
It is characterized by satisfy | filling all.
According to the organic layer constituted in this way, from at least one organic layer among single-component organic layers each composed of individual organic compounds (n-type organic compound or p-type organic compound) contained in the layer. However, a more stable amorphous state (for example, the progress of polycrystallization is prevented or suppressed (delayed)) can be realized. Preferably, a more stable amorphous state can be realized than a single component organic layer composed of any of the individual organic compounds contained in the organic layer. As the organic compound constituting the organic layer in the method disclosed herein, a compound that is easily polycrystallized by itself (for example, in the state of a single component organic layer comprising the compound) is also used. obtain.

  Here, the “n-type organic compound” refers to an organic compound having an electron transporting ability (typically, an electron transporting property is higher than a hole transporting property) or an organic semiconductor using an electron as a carrier (n-type organic semiconductor). Say. Such an n-type organic compound can be understood as an “electron transporting organic compound”. The “p-type organic compound” means an organic compound having a hole transporting ability (typically, a hole transporting ability is higher than an electron transporting ability) or an organic semiconductor (p). Type organic semiconductor). Such p-type organic compounds can be understood as “hole transporting organic compounds”. These n-type organic compound and p-type organic compound can be grasped together as a carrier (charge) transporting organic compound.

In one preferable aspect of the stabilization method disclosed herein, both of the two or more organic compounds constituting the organic layer are low molecular materials. In general, a low molecular material tends to be polycrystallized (in other words, it is difficult to maintain an amorphous state) as compared with a high molecular material. Therefore, the effect (typically, the stabilization effect of the amorphous state) by applying the method of the present invention can be exhibited better.
The “low molecular weight material” here is a concept that is contrasted with a “polymer material” in the field of an organic laminated structure material (organic thin film) (see, for example, Non-Patent Document 1). It is not limited to those having a specific molecular weight or less.

  The stabilization method may be performed, for example, in an embodiment in which at least one of the two or more organic compounds constituting the organic layer is an n-type organic compound. That is, the organic layer is configured such that two or more organic compounds selected from n-type organic compounds are mixed together in an amorphous state, or at least one organic compound selected from n-type organic compounds And at least one organic compound selected from p-type organic compounds may be implemented in such a manner as to be mixed in an amorphous state.

As one preferable application object of the stabilization method of this aspect, an organic laminated structure material constituting the organic electroluminescent element can be exemplified. Accordingly, the technique disclosed herein includes an organic electroluminescent device including an electron injection electrode, a hole injection electrode, and an amorphous carrier (charge) transporting solid organic layer disposed between the electrodes. A method for stabilizing the structure of an organic electroluminescent device for stabilizing an amorphous state of a layer, wherein the organic layer is subjected to the following conditions:
containing two or more organic compounds (carrier (charge) transporting organic compounds) selected from the group consisting of n-type organic compounds (electron transporting compounds) and p-type organic compounds (hole transporting compounds); and
Any of these two or more organic compounds are mixed in an amorphous state;
And a method for stabilizing an organic electroluminescent element (typically, an organic EL element) characterized in that both of the above are satisfied.

  In a preferred embodiment, the organic layer is a layer disposed between a light emitting layer of an organic electroluminescent device and an electron injection electrode (cathode, cathode). The organic layer may be a hole blocking layer (hole blocking layer), an electron transport layer, an electron injection layer, or a layer that functions as one or more of these layers of the organic electroluminescence device. For example, it may be a hole blocking layer and / or an electron transport layer. The organic layer may be a layer disposed between the light emitting layer of the organic electroluminescent element and the hole injection electrode (positive electrode, anode). For example, a hole injection layer, a hole transport layer, or a layer that functions as one or more of these layers may be used.

The two or more organic compounds constituting the organic layer are:
2,9-dimethyl-4,7diphenyl-1,10-phenanthroline (an n-type organic compound, also referred to as Bathocuprine; hereinafter sometimes referred to as “BCP”);
2- (4-biphenyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (an n-type organic compound. Hereinafter, it may be referred to as “PBD”);
N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine (a p-type organic compound. Hereinafter also referred to as “NPD”. And); and
N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-diphenyl-4,4′-diamine (a p-type organic compound; hereinafter referred to as “TPD”) Or an organic compound selected from the group consisting of: For example, a combination of BCP and PBD, a combination of BCP and NPD, and a combination of NPD and TPD are all preferable.

In the stabilization method disclosed herein, the organic layer can be produced (formed) by various conventionally known methods. In a preferred embodiment, the organic layer is formed by a method (solution method) including applying a composition obtained by dissolving the two or more organic compounds in a solvent. The organic layer formed by such a method may exhibit better amorphous state sustainability (for example, the progress of polycrystallization is slow). As a method for applying the composition, for example, a spin coating method can be preferably employed.
In addition, the structure stabilization method of any organic laminated structure material (organic laminated structure) described above can be grasped as the structure stabilization method of the organic layer constituting the structural material.

One organic electroluminescent device (typically, an organic EL device) provided by the present invention includes an electron injection electrode and a hole injection electrode, and a light emitting layer disposed between the electrodes. A solid organic layer disposed between the light emitting layer and the electron injecting electrode and constituting at least a part of an electron supply path from the electron injecting electrode to the light emitting layer; An electron supply layer configured mainly is provided. A solid organic layer disposed between the light emitting layer and the hole injection electrode and constituting at least a part of a hole supply path from the hole injection electrode to the light emitting layer, wherein a p-type organic compound is It has a hole supply layer that is mainly composed. The organic electroluminescent device has the following conditions:
The electron supply layer contains two or more n-type organic compounds or one or more n-type organic compounds and at least one p-type organic compound, and any of these organic compounds is amorphous. Configured to be mixed in state; and
The hole supply layer contains two or more kinds of p-type organic compounds, or contains one or more kinds of p-type organic compounds and at least one kind of n-type organic compound, and any of these organic compounds is amorphous. Configured to mix in state;
Satisfy at least one of the following.
The organic electroluminescence device having such a configuration can have an electron supply layer and / or a hole supply layer stably exhibiting an amorphous state. Therefore, it can be excellent in performance stability (for example, durability) and reliability.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  The stabilization method of the present invention can be applied to various organic laminated structure materials including a solid organic layer (organic film) used in an amorphous state. Such organic laminated structure materials include, for example, organic electroluminescent elements, organic thin film transistors (hereinafter also referred to as “organic TFTs”), organic solar cells (typically organic thin film solar cells), and the like. It can be. The application target of the method disclosed herein is a material (laminated structure) in which at least one carrier-transporting solid organic layer and a non-organic layer mainly composed of an inorganic material or a metal material are laminated. obtain.

  An organic electroluminescent device is exemplified as a particularly preferable application target of the method disclosed herein. The organic electroluminescent element is a charge injection type light emitting element called an organic electroluminescent element (organic EL element) or an organic light emitting diode (OLED). In general, in an organic EL element, an organic layer (light emitting layer) containing a light emitting material is disposed between a hole injection electrode (anode) and an electron injection electrode (cathode), and a DC voltage is applied between both electrodes. The electrons and holes injected from the electron injection electrode and hole injection electrode recombine in the light emitting layer to release energy, and the released energy excites the light emitting material contained in the light emitting layer. To emit light (typically, fluorescence and / or phosphorescence is emitted). Such an organic EL element usually has at least one carrier transport between the electron injection electrode and the light emitting layer and / or between the hole injection electrode and the light emitting layer for the purpose of improving the light emission efficiency and lowering the operating voltage. It is comprised as an organic laminated structure material (organic laminated structure) provided with a conductive solid organic layer. In order to improve the performance of the organic EL device, the carrier transporting organic layer is preferably in an amorphous state. And in order to exhibit the said performance stably (to raise the reliability of an organic EL element), it is important to stabilize the amorphous state.

  One structural example of a typical organic EL element is shown in FIG. This organic EL element 10 has a hole injection electrode (anode) 22, a hole transport layer 24, a light emitting layer 26, a hole blocking layer 28, an electron injection layer 30, and an electron injection electrode (on one side of a transparent substrate (for example, a glass substrate) 20. Cathode) 32 is laminated in this order. Here, the hole blocking layer (hole blocking layer) makes it difficult for holes injected from the hole injection electrode 22 to move from the light emitting layer 26 to the electron injection electrode 32 side. This is a layer having a function of recombining injected electrons and the holes more efficiently in the light emitting layer 26.

The organic EL element to which the stabilization method disclosed herein is applied may be an organic EL element including one or more organic layers used in an amorphous state, and is not limited to the structure shown in FIG. For example, in addition to the configuration shown in FIG. 1 (a configuration in which a hole injection electrode / hole transport layer / light emitting layer / hole blocking layer / electron injection layer / electron injection electrode are stacked in this order):
(A) hole injection electrode / hole transport layer / light emitting layer / electron injection electrode;
(B) hole injection electrode / light emitting layer / electron transport layer / electron injection electrode;
(C) hole injection electrode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection electrode;
(D) hole injection electrode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / electron injection electrode;
(E) hole injection electrode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection electrode;
(F) hole injection electrode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / electron injection electrode;
(G) hole injection electrode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron injection layer / electron injection electrode;
(H) hole injection electrode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / electron injection electrode;
(I) hole injection electrode / hole injection layer / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / electron injection electrode;
It can be an organic EL device having various configurations.

Usually, among the layers included in the organic EL element having such a configuration, the layers (hole injection layer, hole transport layer, electron blocking layer) disposed closer to the hole injection electrode than the light emitting layer are layers having hole transport properties. When the layer is an organic layer (organic layer, inorganic layer, or mixed layer thereof), it is appropriate that the p-type organic compound is a main component. In addition, a layer (hole blocking layer, electron transport layer, electron injection layer) disposed closer to the electron injection electrode than the light emitting layer is a layer having a hole transport property (an organic layer, an inorganic layer, or a mixed layer thereof). In the case where the layer is an organic layer, it is appropriate that the n-type organic compound is a main component.
The stabilization method disclosed herein can be applied to one or more of the organic layers included in any of the above-described configurations. As a preferable application object, one or more selected from a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer and an electron transport layer (more preferably, a hole transport layer, a hole blocking layer and an electron transport layer) An organic layer is illustrated.

  As a constituent material of the hole injection electrode (anode, anode), a material having a large work function is preferable. For example, metals such as carbon, aluminum, cesium, vanadium, iron, cobalt, nickel, copper, zinc, tungsten, silver, gold, platinum, palladium and their alloys; tin oxide, indium oxide, antimony oxide, zinc oxide, oxide Examples thereof include conductive metal compounds such as zirconium and indium tin oxide (ITO); organic conductive resins such as polythiophene and polypyrrole. A material having a work function larger than 4 eV can be preferably employed. The film thickness of the anode is not particularly limited, but is usually suitably in the range of about 10 nm to 5 μm, more preferably in the range of 50 nm to 1 μm, and even more preferably in the range of about 100 nm to 500 nm.

  In addition, the constituent material of the electron injection electrode (cathode, cathode) is preferably a material having a small work function. For example, metals such as magnesium, barium, calcium, cesium, tin, lead, titanium, yttrium, lithium, gadolinium, ytterbium, ruthenium, manganese, and alloys thereof (for example, Mg-Ag alloy) can be used. A material having a work function smaller than 4 eV can be preferably employed. The film thickness of the cathode is not particularly limited, but is usually suitably in the range of about 10 nm to 5 μm, more preferably in the range of about 50 nm to 1 μm, and even more preferably in the range of about 100 nm to 1 μm.

  In order to make the light emission of the organic electroluminescence device recognizable from the outside of the device, it is appropriate to configure at least one of the hole injection electrode and the electron injection electrode (for example, the hole injection electrode) as a transparent electrode. Preferably, such a transparent electrode is formed on a transparent substrate, and various organic layers are laminated thereon. A glass substrate can be preferably used as the transparent substrate. Moreover, you may use the base material which consists of resin material which has transparency, such as polyethylene, a polypropylene, polyether sulfone, polyether ether ketone.

The light emitting layer generally includes a host material and a dopant material. Examples of the light-emitting material or dopant material constituting the light-emitting layer include metal complexes such as 8-hydroxyquinoline aluminum complex (Alq ₃ ), aromatic compounds such as tetraphenylbutadiene, cyclopentadiene derivatives, perinone derivatives, oxadiol derivatives, bis Known materials such as styrylbenzene derivatives, perylene derivatives, coumarin compounds, distyrylpyrazine derivatives, p-phenylene compounds, thiadiazolopyridine derivatives, pyrrolopyridine derivatives, naphthyridine derivatives, rare earth complexes, and the like can be used. More specifically, a compound represented by the following formulas (A1) to (A9) sold as a fluorescent host material from OHJEC CORPORATION, a phosphorescent host material (Phosphorescent Host) Compounds represented by the following formulas (B1) to (B5) sold as Materials), compounds represented by the following formulas (C1) to (C5) sold as green dopant materials (Green Dopant Material), Compounds represented by the following formulas (D1) to (D7), which are sold as blue dopant materials (Blue Dopant Material), and are sold as red dopant materials (Red Dopant Material) Although the following formula (E1) ~ (E5) a compound represented by the like, but is not limited thereto. Note that some of these fluorescent host materials or phosphorescent host materials have an electron transport capability or a hole transport capability.
The film thickness of the light emitting layer is not particularly limited, but it is usually suitably in the range of about 1 nm to 5 μm, more preferably 5 nm to 1 μm, and even more preferably about 10 nm to 500 nm.

The organic layer that is stabilized by applying the method disclosed herein is, for example, a layer (hole injection layer, hole transport layer, etc.) disposed closer to the hole injection electrode than the light emitting layer in the organic electroluminescence device. Thus, the layers constituting at least a part of the hole supply path from the hole injection electrode to the light emitting layer may be referred to as “hole supply layers”, respectively. In this case, the organic layer is
(1) It contains two or more p-type organic compounds, and any of those organic compounds (preferably low molecular weight materials) is mixed in an amorphous state, or
(2) It is configured to contain at least one p-type organic compound and at least one n-type organic compound, and both of these organic compounds (preferably low molecular weight materials) are mixed in an amorphous state. preferable.

  A p-type organic compound constituting such a hole supply layer (for example, a hole transport layer) is known as a material having a hole transport capability or a p-type organic semiconductor in the field of an organic electroluminescence device, an organic TFT, an organic solar cell, and the like. Various materials can be used. For example, phthalocyanine, naphthalocyanine, porphyrin, oxazole, oxadiazole, triazole, imidazole, imidazolone, imidazolethione, pyrazoline, pyrazolone, tetrahydroimidazole, hydrazone, acylhydrazone, polyarylalkane, stilbene, butadiene, benzidine type triphenylamine, It can be appropriately selected from the group consisting of compounds such as styrylamine-type triphenylamine and diamine-type triphenylamine, and derivatives thereof. More specifically, the compounds represented by the following formulas (H1) to (H5) that are sold as hole injection materials from Augec Co., Ltd., sold as hole transport materials from the company. The compounds represented by the following formulas (J1) to (J12) are exemplified, but not limited thereto. For example, a material having a hole transporting ability among the above-described fluorescent host materials or phosphorescent host materials may be used.

The organic layer having the configuration (1) is, for example:
A composition in which two or more compounds selected from hole injection materials (for example, compounds represented by the above formulas (H1) to (H5)) are combined;
A composition in which two or more compounds (for example, (J10) and (J3)) selected from hole transport materials (for example, compounds represented by the above formulas (J1) to (J12)) are combined; or
One or more compounds selected from hole injection materials (for example, compounds represented by the above formulas (H1) to (H5)) and hole transport materials (for example, represented by the above formulas (J1) to (J12)) A combination of one or more compounds selected from (compounds);
It may have.

In the configuration of the above (1), the total amount of other p-type organic compounds is at least 0.1 mol or more (more preferably less than 0.1 mol) per mol of the p-type organic compound having the highest content (typically molar ratio). 5 mol or more) is preferable. For example, in a hole supply layer containing two types of p-type compounds p ₁ and p ₂ , the molar ratio of p ₁ and p ₂ is 1: 0.1 to 1:10 (more preferably 1: 0.5 to 1). : It can be set as the structure contained in the ratio of 2). When the total number of moles of the p-type organic compound constituting the layer is 100% and the number of moles of any one of the p-type organic compounds is more than 90%, the effect of applying the present invention is not sufficiently exhibited. There is a case.

  In addition, the n-type organic compound used together with the p-type organic compound in the configuration of (2) is known as an electron transporting material or an n-type organic semiconductor in the fields of organic electroluminescent elements, organic TFTs, organic solar cells and the like. It can be a variety of materials. For example, from compounds such as fluorenone, anthraquinodimethane, diphenoquinone, thiopyran dioxide, oxazole, oxadiazole, triazole, imidazole, perylenetetracarboxylic acid, fluorenylidenemethane, anthraquinodimethane, anthrone and their derivatives It can select suitably from the group which consists of. More specifically, a compound represented by the following formulas (K1) and (K2) and a compound represented by the above formula (A1) sold as Electron Transport Material from Augec Co., Ltd., the company Examples of the compounds represented by the following formulas (L1) to (L4) sold as hole blocking / electron injection material (Hole Blocking / Electron Injection Material) are not limited thereto.

The organic layer having the configuration (2) is, for example:
One or more compounds selected from hole injection materials (for example, compounds represented by the above formulas (H1) to (H5)) and an electron transport material (for example, the above formulas (K1), (K2), (A1)) And a composition obtained by combining one or two or more compounds selected from hole blocking / electron injection materials (for example, compounds represented by the above formulas (L1) to (L4));
One or more compounds selected from hole transport materials (for example, compounds represented by the above formulas (J1) to (J12)) and electron transport materials (for example, the above formulas (K1), (K2), (A1)) And a composition obtained by combining one or two or more compounds selected from hole blocking / electron injection materials (for example, compounds represented by the above formulas (L1) to (L4));
It may have.

  In a preferred embodiment, the n-type organic compound contained in the organic layer is an n-type organic compound (typically, contained in an organic layer provided on the counter electrode side (electron injection electrode side) with the light emitting layer interposed therebetween (typically, The same n-type organic compound as the main component of the organic layer on the counter electrode side). According to this aspect, the organic layer can be multi-component without increasing the number of components constituting the organic EL element. This is preferable from the viewpoint of, for example, manufacturing costs (raw material costs, apparatus configuration, etc.).

  In the configuration of (2) above, it is appropriate that the total number of moles of the p-type organic compound constituting the layer is 100 and the total number of moles of the n-type organic compound is 20 or less (typically 1 to 20). It is preferably 10 or less (typically 1 to 10), more preferably 3 or less (typically 1 to 3). If the total number of moles of the n-type organic compound is more than the above range, the hole transportability of the layer (and thus the performance of the organic EL device configured to include the layer) may tend to be reduced. In addition, in the case where at least one of the organic compounds after the second type (second component) to be contained in the hole supply layer is an n-type organic compound, compared to a case where the compound is a p-type organic compound, The effect of stabilizing the amorphous state can be appropriately exhibited even with a small content ratio.

The organic layer stabilized by applying the method disclosed herein is also a layer (electron injection layer, electron transport layer, hole blocking layer) disposed on the electron injection electrode side of the light emitting layer in the organic electroluminescence device. In the following, the layers constituting at least part of the electron supply path from the electron injection electrode to the light emitting layer may be referred to as “electron supply layers”, respectively. In this case, the organic layer is
(3) It contains two or more n-type organic compounds and any of those organic compounds (preferably low molecular weight materials) are mixed in an amorphous state, or
(4) Containing at least one type of n-type organic compound and at least one type of p-type organic compound, and any of those organic compounds (preferably low molecular weight materials) mixed in an amorphous state. preferable.

  The n-type organic compound constituting such an electron supply layer (for example, a hole blocking layer) is, for example, the above-described n-type exemplified as a material (typically used together with a p-type organic compound) constituting the hole supply layer. It may be one or more selected from organic compounds.

The organic layer having the configuration (3) is, for example:
A composition in which two or more compounds selected from electron transport materials (for example, compounds represented by the above formulas (K1), (K2), and (A1)) are combined;
A composition comprising a combination of two or more compounds (for example, (L3) and (L2)) selected from hole blocking / electron injection materials (for example, compounds represented by the above formulas (L1) to (L4)); or
One or more compounds selected from electron transport materials (for example, compounds represented by the above formulas (K1), (K2), (A1)) and hole blocking / electron injection materials (for example, the above formulas (L1) to A composition in combination with one or more compounds selected from (compound represented by (L4));
It may have.

  In the configuration of (3) above, the total amount of other n-type organic compounds is at least 0.1 mol per mol of the n-type organic compound having the highest content (typically molar ratio) (more preferably less than 0.1 mol). 5 mol or more) is preferable. For example, in an electron supply layer containing two types of n-type compounds n (A) and n (B), the molar ratio of p (A) and p (B) is 1: 0.1 to 1:10 (more preferably May be contained at a ratio of 1: 0.5 to 1: 2). When the total number of moles of the n-type organic compound constituting the layer is 100% and the number of moles of any one of the n-type organic compounds is more than 90%, the effect of applying the present invention is not sufficiently exhibited. There is a case.

The p-type organic compound used together with the n-type compound in the configuration of (4) is, for example, one or more selected from the above-described p-type organic compounds exemplified as the material constituting the hole supply layer. obtain.
The organic layer having the configuration (4) is, for example:
One or more compounds selected from electron transport materials (for example, compounds represented by the above formulas (K1), (K2), (A1)) and hole injection materials (for example, the above formulas (H1) to (H5)) And a composition comprising a combination of one or two or more compounds selected from hole transport materials (for example, compounds represented by the above formulas (J1) to (J12)); or
Two or more compounds (for example, (L3)) selected from a hole blocking / electron injection material (for example, compounds represented by the above formulas (L1) to (L4)) and a hole injection material (for example, the above formula (H1) A compound represented by (H5)) and a hole transporting material (for example, compounds represented by the above formulas (J1) to (J12)) or one or more compounds (for example, (J10)) Composition;
It may have.

  In one preferred embodiment, the p-type organic compound contained in the organic layer is a p-type organic compound (typically, contained in an organic layer provided on the counter electrode side (hole injection electrode side) with the light emitting layer interposed therebetween (typically, The same p-type organic compound as the main component of the organic layer on the counter electrode side). According to this aspect, the organic layer can be multi-component without increasing the number of components constituting the organic EL element, which is preferable from the viewpoint of manufacturing cost (raw material cost, device configuration, etc.).

  In the configuration of (4) above, the total number of moles of the n-type organic compound constituting the organic layer is 100, and the total number of moles of the p-type organic compound is 20 or less (typically 1 to 20). It is appropriate, and it is preferably 10 or less (typically 1 to 10), more preferably 3 or less (typically 1 to 3). If the total number of moles of the p-type organic compound is more than the above range, the electron transport property of the layer (and thus the performance of the organic EL device configured to include the layer) may tend to be reduced. In addition, in the case where at least one of the organic compounds after the second type (second component) to be contained in the electron supply layer is a p-type organic compound, compared to a case where the compound is an n-type organic compound, The effect of stabilizing the amorphous state can be appropriately exhibited even with a small content ratio.

  The two or more organic compounds constituting the organic layer and their ratio (typically molar ratio) are preferably selected so that these compounds exhibit good compatibility. For example, the molar ratio of BCP to PBD described in the experimental examples described later is a combination of 1: 0.1 to 1:10, the molar ratio of BCP to NPD is 0.1, and the molar ratio of NPD to TPD. Any combination of 1: 1 to 1:10 can exhibit good compatibility.

  In addition, the fine structure (morphology) of the organic layer stabilized by applying the method disclosed herein can be grasped by, for example, observing by a conventional method using a general polarizing microscope. The organic layer may be configured such that at least immediately after manufacture, the p-type and / or n-type organic compounds constituting the organic layer are mixed in an amorphous state. The organic layer in an amorphous state is observed as a substantially uniform image (without unevenness) with a polarizing microscope (for example, about 5 to 50 times magnification).

  The organic layer having such a configuration may be formed so that an organic layer in which two or more kinds of organic compounds described above are mixed together in an amorphous state is formed, and the formation method is not particularly limited. For example, a method in which two or more kinds of solid (preferably powdered) organic compounds are vapor-deposited (typically co-evaporation) under reduced pressure (vacuum) (hereinafter, also referred to as “evaporation method”), these two types A method of applying a liquid composition obtained by dissolving the above organic compound in a suitable solvent (hereinafter also referred to as “solution method”) or the like can be employed. Application of the liquid composition in the solution method can be performed by, for example, a spin coating method, a dipping method, a casting method, a spray method, an ink jet method, a printing method, a bar coating method, a roll coating method, or the like. What is necessary is just to select suitably the solvent which dissolves all the organic compounds to be used as a solvent which comprises the said liquid composition. For example, organic halogen solvents such as dichloroethane, dichloromethane and chloroform; ether solvents such as tetrahydrofuran and 1,4-dioxane; aromatic hydrocarbon solvents such as toluene and xylene; amide solvents such as dimethylformamide and dimethylacetamide; The solvent may be any solvent selected from ester solvents such as ethyl acetate and butyl acetate; or a mixed solvent composed of two or more solvents.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Experimental Example 1: Production and Evaluation of BCP / PBD Alloy Film>
An ITO substrate (manufactured by Geomatic Co., Ltd.) having an ITO film with a thickness of 150 nm formed on the surface of a glass substrate was prepared. 2,9-dimethyl-4,7diphenyl-1,10-phenanthroline (BCP) and 2- (4-biphenyl) -5- (4-tert) as a deposition source using a vacuum deposition apparatus having a general configuration -Butylphenyl) -1,3,4-oxadiazole (PBD) was prepared, and the ITO substrate was set so that the ITO film was on the deposition source side. The distance from the evaporation source to the ITO film was 20 cm. The substrate temperature was not adjusted (forced heating or cooling). The inside of the chamber is depressurized to 2 × 10 ⁻⁶ Torr (about 2.7 × 10 ⁻⁴ Pa) in a dry nitrogen gas atmosphere, and BCP and PBD, which are vapor deposition sources, are each heated to a predetermined temperature to evaporate. An organic film containing PBD and PBD in an amorphous state (hereinafter also referred to as “BCP / PBD alloy film”) was formed (co-evaporated) on the ITO film to a thickness of about 30 nm.

By adjusting the heating temperature of each vapor deposition source in the co-deposition performed in this way, five types of BCP / PBD alloy films having different BCP / PBD content ratios (molar ratios) are formed on the ITO substrate. A sample formed on the membrane was obtained. That is, the content ratio of BCP / PBD is 1 / 0.1 (sample 1), 1 / 0.5 (sample 2), 1/1 (sample 3), 1/2 (sample 4), 1/10 (sample The sample which is 5) was produced.
For comparison, a sample in which a BCP film (single component film) having a thickness of 30 nm is formed on the ITO film in the same manner as Samples 1 to 5 except that only BCP is used as a deposition source ( Sample BCP-d) was obtained. Further, a sample in which a PBD film (single component film) having a thickness of 30 nm is formed on an ITO film (sample PBD-d) in the same manner as in samples 1 to 5 except that only PBD is used as a vapor deposition source. Got.

  These samples were stored in a nitrogen gas atmosphere at 40 ° C. and 70% RH, and the stability of the amorphous state of each organic film (the presence or absence of progress of polycrystallization and the extent thereof) was observed by a polarizing microscope after a predetermined time. ) Was evaluated. A transmission polarizing microscope (Nikon Corporation, trade name “OPTIPHOT-2”) was used for the above-mentioned polarizing microscope observation. The results are shown in Table 1. In the table, the symbol “A” indicating the evaluation result indicates that almost no crystallization was observed, the symbol “B” indicates that the crystallization has progressed a little, and the symbol “C” indicates that the crystallization is not performed. The sign “D” indicates that the polycrystallization was progressing considerably, and the sign “X” indicates that the tendency of polycrystallization was observed throughout the organic film. . That is, the degree of progress of polycrystallization increases in the order of A <B <C <D <X. The sign “−” indicates that the organic film was not observed at that timing. In the observation with a polarizing microscope immediately after the film formation, no crystallization was observed in any of the samples, and it was confirmed that an amorphous film was formed.

  As can be seen from Table 1, the stability of the amorphous state was improved in the BCP / PBD alloy films (Samples 1 to 5) as compared with the PBD single component film. Samples 2-5, in which the molar ratio of BCP to PBD was in the range of 1: 0.1 to 1: 2, showed better stability than either the PBD single component film or the BCP single component film. Particularly good results were obtained with Samples 2 to 4 in which the molar ratio of BCP to PBD was in the range of 1: 0.5 to 1: 2.

<Experimental Example 2: Production and Evaluation of BCP / NPD Alloy Film>
Samples 1-5 except that BCP and N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine (NPD) were used as the evaporation source. In the same manner as above, an organic film containing BCP and NPD in an amorphous state (hereinafter also referred to as “BCP / NPD alloy film”) was formed (co-evaporated) to a thickness of about 30 nm on the ITO film. . This produced Sample 6. The stability of the sample 6 in the amorphous state was evaluated in the same manner as in Experimental Example 1. The evaluation result is shown in Table 2, and a polarizing microscope observation image is shown in FIGS. The meanings of symbols A to D in Table 2 are the same as those in Table 1. In addition, in the observation with a polarizing microscope immediately after the film formation, polycrystallization was not observed, and it was confirmed that an amorphous film was formed.
In Table 2, a part of the result of Experimental Example 1 is shown again in order to prepare a comparison between the sample 6 and other samples. The figure number described next to the evaluation result is the figure number corresponding to the polarization microscope observation image at that timing.

  As can be seen from Table 2, the stability of the amorphous state of the BCP / NPD alloy film was better than that of the BCP single component film. Further, as can be seen from the comparison between sample 6 and sample 1, in the film in which BCP (first component) and NPD (second component) are co-evaporated, the film in which BCP and PBD (second component) are co-evaporated As compared with the above, a higher stabilization effect was realized at the same content ratio (molar ratio) of the second component. In other words, when the first component is BCP, by selecting NPD as the second component, a high stabilizing effect was obtained with a smaller content ratio than when the second component was PBD. .

<Experimental example 3: Production and evaluation of organic EL device provided with BCP / PBD alloy film>
An organic EL element (element sample 1) including a BCP / PBD alloy film as a hole blocking layer was produced. Hereinafter, the configuration of the organic EL element will be described with reference to FIG.
That is, the organic EL element 10 according to this example includes the glass substrate 20 and the hole injection electrode 22 formed on one surface thereof. On the hole injection electrode 22, a hole transport layer 24, a light emitting layer 26 having an electron transport property, a hole blocking layer 28, an electron injection layer 30 and an electron injection electrode 32 are laminated in this order. The hole injection electrode 22 constituting the organic EL element 10 according to this experimental example is an ITO film having a thickness of about 150 nm. The hole transport layer 24 is an NPD film (single component) having a thickness of about 50 nm. The light emitting layer 26 is an Alq ₃ film having a thickness of about 40 nm. The hole blocking layer 28 is a BCP / PBD alloy film (BCP: PBD = 1: 1) having a thickness of about 20 nm. The electron injection layer 30 is a lithium fluoride (LiF) film having a thickness of about 0.5 nm. The electron injection electrode 32 is an aluminum (Al) film having a thickness of about 250 nm. A hole transport layer 24, a light emitting layer 26, a hole blocking layer 28, an electron injection layer 30 and an electron injection electrode 32 are deposited in this order on the ITO film (hole injection electrode 22) of the same ITO substrate used in Experimental Example 1. Thus, the organic EL element 10 was manufactured.
For comparison, an organic EL element (element sample 2) having the same configuration as the element sample 1 except that the hole blocking layer 28 is a 20 nm thick BCP film (single component film) is It produced similarly.

  A step-up voltage (voltage increase rate of 0.5 V / S) was applied to these device samples, and current-voltage (J-V) characteristics were measured. The results are shown in FIG. 7 as a black circle plot for the element sample 1 and a white circle plot for the element sample 2. As can be seen from FIG. 7, in the element sample 1 in which the hole blocking layer is a BCP / PBD alloy film, the current-voltage characteristics are improved as compared with the element sample 2 in which the layer is a BCP single component film. For example, higher current densities were achieved for comparable voltages.

Moreover, the external quantum efficiency of these device samples was measured. The results (η _ext −J characteristics) are plotted in FIG. 8 as black circles for the element sample 1 and white circles for the element sample 2. As can be seen from FIG. 8, the device sample 1 in which the hole blocking layer is a BCP / PBD alloy film has an external quantum efficiency equal to or higher than that of the device sample 2 in which the layer is a BCP single component film. .

<Experimental Example 4: Production (co-evaporation) and stability evaluation of NPD / TPD alloy film>
N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine (NPD) and N, N′-diphenyl-N, N ′ as vapor deposition sources -TPD and NPD were respectively formed on the ITO film in the same manner as in Samples 1 to 5 except that bis (3-methylphenyl) -1,1'-diphenyl-4,4'-diamine (TPD) was used. An organic film containing in an amorphous state (hereinafter sometimes referred to as “NPD / TPD alloy film”) was formed (co-evaporated) with a thickness of about 50 nm. In this manner, samples were obtained in which two types of NPD / TPD alloy films having different content ratios (molar ratios) between NPD and TPD were formed on the ITO film. That is, Sample 7-d having an NPD / TPD content ratio of 1/1 and Sample 8-d having an NPD / TPD content ratio of 1:10 were prepared. For comparison, a sample in which an NPD film (single component film) having a thickness of 50 nm was formed on the ITO film (same as Samples 1 to 5 except that only NPD was used as a deposition source). Sample NPD-d) was obtained. A sample in which a 50 nm thick TPD film (single component film) was formed on an ITO film (sample TPD-d) in the same manner as in samples 1 to 5 except that only TPD was used as the vapor deposition source. Got.

  The stability of these samples in the amorphous state was evaluated in the same manner as in Experimental Example 1. The results are shown in Table 3. The meanings of the symbols in Table 3 are the same as those in Table 1. In addition, in the polarization microscope observation immediately after film formation, no crystallization was observed in any sample, and it was confirmed that an amorphous film was formed.

  As can be seen from Table 3, the stability of the amorphous state was improved in the NPD / TPD alloy films (Samples 7-d and 8-d) as compared with the NPD single component film and the TPD single component film. Sample 7-d with an NPD: TPD molar ratio of 1: 1 gave even better results than Sample 8-d with the same molar ratio of 1:10.

<Experimental Example 5: Creation and Evaluation of Organic EL Device with NPD / TPD Alloy Film>
An organic EL element having the same configuration as that of the element sample 2 provided with an NPD film (single component film) as the hole transport layer except that an NPD / TPD alloy film having a thickness of about 50 nm is provided as the hole transport layer. (Ie, by vapor deposition). In this experimental example, an element sample 3 having an NPD / TPD alloy film having NPD: TPD = 1: 1 and an element sample 4 having an NPD / TPD alloy film having NPD: TPD = 1: 10 are produced. For comparison, device sample 5 in which the hole transport layer is a TPD film (single component) having a thickness of about 50 nm was fabricated.

  Element sample 2 (hole transport layer is NPD film), element sample 3 (hole transport layer is NPD / TPD alloy film with NPD: TPD = 1: 1), element sample 4 (hole transport layer is NPD: TPD = 1: 10 NPD / TPD alloy film) and element sample 5 (the hole transport layer is a TPD film) were evaluated for current-voltage (JV) characteristics in the same manner as in Experimental Example 3. The results are shown in FIG. As can be seen from FIG. 9, the device samples 3 and 4 in which the hole transport layer is an alloy film have the same or better current − than the device samples 2 and 5 in which the layer is a single component film of NPD or TPD. The voltage characteristics are shown.

<Experimental Example 6: Production (spin coating) and stability evaluation of NPD / TPD alloy film>
A composition containing NPD and TPD in a predetermined molar ratio was prepared by dissolving NPD and TPD in a THF-chloroform mixed solvent. By spin coating using this composition, an organic film (NPD / TPD alloy film) containing NPD and TPD in an amorphous state was formed on the ITO film of the same ITO substrate as that used in Experimental Example 1.
By adjusting the molar ratio of NPD and TPD contained in the spin coating composition, two types of NPD / TPD alloy films having different BCP and PBD content ratios (molar ratios) are formed on the ITO film, respectively. Sample was obtained. That is, samples with NPD / TPD content ratios of 1/1 (sample 7-s) and 1:10 (sample 8-s) were produced. For comparison, a composition in which NPD was dissolved in a THF-chloroform mixed solvent and a composition in which TPD was dissolved in the same solvent were prepared, and the ITO of the ITO substrate was prepared by spin coating using these compositions. A sample (sample NPD-s) in which an amorphous NPD film (single component film) was formed on the film and a sample (sample TPD-s) in which a TPD film (single component film) was formed were prepared. The thickness of the organic film provided in each of these samples was about 50 nm.

  The stability of these samples in the amorphous state was evaluated in the same manner as in Experimental Example 1. The evaluation results are shown in Table 4. The meanings of symbols A to D in Table 4 are the same as those in Table 1. In addition, in the polarization microscope observation immediately after film formation, no crystallization was observed in any sample, and it was confirmed that an amorphous film was formed.

  As can be seen from Table 3, the stability of the amorphous state was improved in the NPD / TPD alloy films (Samples 7-d and 8-d) as compared with the NPD single component films.

<Experimental example 7: Creation and evaluation of organic EL element provided with TPD / NPD alloy film>
An organic EL element having the same configuration as that of the element sample 2 including an NPD film (single component) as the hole transport layer is provided as the element sample 2 except that the hole transport layer includes an NPD / TPD alloy film having a thickness of about 50 nm. It was produced in the same manner (that is, by spin coating). In this experimental example, an element sample 3 having an NPD / TPD alloy film having NPD: TPD = 1: 1 and an element sample 4 having an NPD / TPD alloy film having NPD: TPD = 1: 10 are produced. For comparison, device sample 5 in which the hole transport layer is a TPD film (single component) having a thickness of about 50 nm was fabricated.

  Device sample 6 (hole transport layer is NPD film), device sample 7 (hole transport layer is NPD / TPD alloy film having NPD: TPD = 1: 1), device sample 8 (hole transport layer is NPD: TPD = 1) 10 NPD / TPD alloy film) and device sample 9 (the hole transport layer is a TPD film) were evaluated for current-voltage (JV) characteristics in the same manner as in Experimental Example 3. The results are shown in FIG. As can be seen from FIG. 9, the device samples 7 and 8 in which the hole transport layer is an alloy film have the same or better current − than the device samples 6 and 9 in which the layer is a single component film of NPD or TPD. The voltage characteristics are shown.

  In addition, about the sample TPD-d produced by the vapor deposition method in Experimental Example 3 and the sample TPD-s produced by the spin coating method in this Experimental Example, the organic film was obtained with a polarizing microscope 9 days after the production of the organic film. Images obtained by observation are shown in FIGS. The TPD film produced by the spin coating method showed clearly better amorphous state stability than the TPD film produced by the vapor deposition method. This result suggests that better amorphous state stability can be realized by producing various alloy films by spin coating than by alloy films produced by vapor deposition.

It is a schematic diagram which shows one structural example of an organic EL element. It is a polarizing microscope image 3 hours after the deposition of the BCP single component film. It is a polarization microscope image 3 hours after vapor deposition of a BCP / PBD alloy film (BCP / PBD = 1: 1). It is a polarization microscope image 3 hours after the deposition of the BCP / NPD alloy film (BCP: NPD = 1: 0.1). It is a polarization microscope image 3 days after vapor deposition of a BCP / PBD alloy film (BCP / PBD = 1: 1). It is a polarization microscope image 3 days after vapor deposition of a BCP / NPD alloy film (BCP: NPD = 1: 0.1). It is a graph which shows the JV characteristic of the organic EL element which used the BCP / PBD alloy film or the BCP single component film for the hole blocking layer. It is a graph which shows the (eta) _ext- J characteristic of the organic EL element which used the BCP / PBD alloy film or the BCP single component film for the hole blocking layer. It is a graph which shows the JV characteristic of the organic EL element which used the NPD single component film | membrane produced by the vapor deposition method, the TPD single component film, or the NPD / TPD alloy film for the hole transport layer. It is a graph which shows the JV characteristic of the organic EL element which used the NPD single component film | membrane produced by the spin coat method, the TPD single component film, or the NPD / TPD alloy film for the hole transport layer. It is a polarization microscope image of the TPD single film produced by the vapor deposition method. It is a polarization microscope image of the TPD single film produced by the spin coat method.

Explanation of symbols

10: Organic EL element (organic electroluminescent element)
20: Glass substrate 22: Hole injection electrode (anode)
24: Hole transport layer 26: Light emitting layer 28: Hole blocking layer 30: Electron injection layer 32: Electron injection electrode (cathode)

Claims (8)

A method for stabilizing a structure of an organic laminated structure material, comprising stabilizing an amorphous state of the organic layer in an organic laminated structure material comprising a pair of electrodes and an amorphous carrier-transporting solid organic layer disposed between the electrodes. And
The organic layer is subjected to the following conditions:
containing two or more organic compounds selected from the group consisting of n-type organic compounds and p-type organic compounds; and
Any of these two or more organic compounds are mixed in an amorphous state;
A stabilization method, characterized by being configured to satisfy all of the above.   The stabilization method according to claim 1, wherein each of the two or more organic compounds is a low-molecular material.   The stabilization method according to claim 2, wherein at least one of the two or more organic compounds constituting the organic layer is an n-type organic compound.   The said organic laminated structure material is a material which comprises an organic electroluminescent element, The said organic layer is a layer arrange | positioned between the light emitting layer of this organic electroluminescent element, and an electron injection electrode. Stabilization method.   The stabilization method according to claim 4, wherein the organic layer is a hole blocking layer and / or an electron transport layer.   The two or more organic compounds are 2,9-dimethyl-4,7diphenyl-1,10-phenanthroline, 2- (4-biphenyl) -5- (4-tert-butylphenyl) -1,3,4. -Oxadiazole, N, N'-di (1-naphthyl) -N, N'-diphenyl-1,1'-diphenyl-4,4'-diamine, and N, N'-diphenyl-N, N ' The stabilization method according to any one of claims 1 to 5, which is selected from the group consisting of -bis (3-methylphenyl) -1,1'-diphenyl-4,4'-diamine.   The stabilization method according to claim 1, wherein the organic layer is formed by a method including applying a composition obtained by dissolving the two or more organic compounds in a solvent. An electron injection electrode and a hole injection electrode;
A light-emitting layer disposed between the electrodes;
A solid organic layer disposed between the light emitting layer and the electron injection electrode and constituting at least a part of an electron supply path from the electron injection electrode to the light emitting layer, mainly composed of an n-type organic compound A configured electron supply layer;
A solid organic layer disposed between the light emitting layer and the hole injection electrode and constituting at least a part of a hole supply path from the hole injection electrode to the light emitting layer, mainly comprising a p-type organic compound A configured hole supply layer;
An organic electroluminescent device comprising the following conditions:
The electron supply layer contains two or more n-type organic compounds or one or more n-type organic compounds and at least one p-type organic compound, and any of these organic compounds is amorphous. Configured to be mixed in state; and
The hole supply layer contains two or more kinds of p-type organic compounds, or contains one or more kinds of p-type organic compounds and at least one kind of n-type organic compound, and any of these organic compounds is amorphous. Configured to mix in state;
An organic electroluminescent device satisfying at least one of the above.