JP2009158756A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element having high efficiency and a long lifetime. <P>SOLUTION: This organic electroluminescent element 10 comprises an anode 2, a cathode 6, and a laminate held between the anode 2 and the cathode 6 while containing at least a mixed layer (hole injection layer 3) and an organic luminescent layer 4 in this order, and (A) and (B), or (A) and (C) are contained in the mixed layer. (A) is an alcohol-soluble hole transporting material, and (B) is a copolymer of a siloxane unit and a phosphine-oxide unit. (C) is a mixture composed of a siloxane compound and a phosphin-oxide compound. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element, and more particularly to an organic electroluminescent element used as a component of a display device.

  Since the electroluminescent element is a self-luminous type, it has high visibility, excellent display performance, high-speed response, and can be reduced in thickness. For this reason, electroluminescent elements are attracting attention as display elements such as flat panel displays.

  Among them, an organic electroluminescent device using an organic compound as a light emitter can be driven at a lower voltage than an inorganic electroluminescent device, can be easily enlarged, and can be obtained by selecting an appropriate luminescent material. It has characteristics such as easy emission color. For this reason, organic electroluminescent elements are being actively developed as next-generation displays.

  By the way, there are roughly two methods for producing an organic electroluminescent element using an organic light emitter. That is, a thin film forming a device is formed by using a low molecular weight compound that forms a thin film constituting a device by a dry process such as a vacuum deposition method, and a so-called coating film forming method such as a spin coating method, a casting method, or an ink jet method. Type.

Here, an organic electroluminescent element produced by a coating film forming method (hereinafter referred to as a coated organic electroluminescent element) has the following advantages over an organic electroluminescent element produced by a dry process.
(I) Low cost (ii) Easy large area (iii) Excellent controllability of trace doping

  Hereinafter, a general configuration of the coating type organic electroluminescent element will be described with reference to the drawings. FIG. 10 is a cross-sectional view showing a general configuration of a coating type organic electroluminescent element. In the organic electroluminescent device 110 of FIG. 10, an anode 101, a hole injection layer 102, an organic light emitting layer 103, an electron injection layer 104, and a cathode 105 are provided on a substrate 100 in this order.

  In the organic electroluminescent device 110 of FIG. 10, as a constituent material of the hole injection layer 102, PEDOT: PSS (mixture of polythiophene and polystyrene sulfonic acid) represented by the following formula is generally used.

  When a thin film to be the hole injection layer 102 is actually formed using PEDOT: PSS, the thin film is formed by spin coating or the like in a solution state. Here, PEDOT: PSS is soluble in water and insoluble in nonpolar solvents. For this reason, even if the organic light emitting layer 103 is formed by a coating process using a solution in which a light emitting material or the like is dissolved in a nonpolar solvent, the PEDOT: PSS film is not eluted. Therefore, PEDOT: PSS is a suitable hole injection material for the coating type organic electroluminescence device.

  On the other hand, polyphenylene vinylene, polyfluorene, polyvinyl carbazole, and derivatives thereof are mainly used as a constituent material of the organic light emitting layer 103 formed on the PEDOT: PSS film (hole injection layer 102). When these constituent materials are used, the organic light emitting layer 103 is formed by a spin coat method or the like.

  The electron injection layer 104 formed on the organic light emitting layer 103 uses lithium fluoride and forms a thin film using a vacuum deposition method. After the electron injection layer 104 is formed, a metal electrode to be the cathode 105 is formed by a vacuum evaporation method. An organic electroluminescent element is completed through the above processes.

  As described above, the coating type organic electroluminescent element has an excellent feature that it can be produced by a simple process, and is expected to be applied to various applications. However, there are still problems to be improved such that a sufficiently large emission intensity cannot be obtained and a lifetime is not sufficient.

  Various speculations have been made about the cause of the decrease in the emission intensity, and the deterioration of PEDOT: PSS is considered as one of the main causes. This is thought to be because ionic components such as S and H derived from sulfone groups and Na contained as impurities diffuse into the organic light-emitting layer by energization and have an undesirable effect. Yes.

  In view of these problems, various studies have been conducted on the constituent material of the hole injection layer that replaces PEDOT: PSS. Here, the constituent material of the hole injection layer that replaces PEDOT: PSS is used in the coating process, and it is considered that the organic light emitting layer is formed on the thin film formed by this coating process by the coating process. There must be. For this reason, the hole injection layer itself must be a film insolubilized.

As a means for actually insolubilizing, for example, a method using a difference in solubility in a solvent disclosed in Patent Document 1 is disclosed. In addition, a method of insolubilizing an organic layer serving as a base using a cross-linking agent disclosed in Patent Documents 2 and 3 as a polymer, a hole transport material in a SiO _x matrix disclosed in Patent Documents 4 and 5 A method of dispersing is mentioned.

JP-A-11-251065 Japanese Patent Laid-Open No. 11-87605 JP 2005-340042 A JP 2000-77185 A JP 9-279135 A

However, in the method using the difference in solubility, there is a problem in that the material that can be used from the viewpoint of solubility is limited because the solvent that can be used for lamination is limited. Further, in the method of insolubilization using a crosslinking agent, since the crosslinking agent adversely affects the charge transport of the material, there is a problem that initial characteristics such as light emission efficiency and durability characteristics such as luminance deterioration due to long-time light emission are not sufficient. In the method of dispersing the hole transport material in the siloxane matrix, the siloxane compound has high chemical stability and can improve the stability of the film. However, a siloxane compound is a highly insulating material, and there is a problem in that power efficiency decreases due to an increase in driving voltage when the amount of SiO _x is increased.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an organic electroluminescence device having high efficiency and long life.

The organic electroluminescent element of the present invention comprises an anode, a cathode, a laminate sandwiched between the anode and the cathode and including at least a mixed layer and an organic light emitting layer in this order, and the mixed layer The following (A) and (B), or (A) and (C) are included.
(A) Alcohol-soluble hole transport material (B) Copolymer composed of siloxane unit and phosphine oxide unit (C) Mixture composed of siloxane compound and phosphine oxide compound

  ADVANTAGE OF THE INVENTION According to this invention, a highly efficient and long life organic electroluminescent element can be provided.

  First, the organic electroluminescent element of the present invention will be described. The organic electroluminescent element of the present invention comprises an anode, a cathode, and a laminate that is sandwiched between the anode and the cathode and includes at least a mixed layer and an organic light emitting layer in this order.

  Hereinafter, the organic electroluminescent element of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a first embodiment of the organic electroluminescent element of the present invention. In the organic electroluminescent device 10 of FIG. 1, an anode 2, a hole injection layer 3, an organic light emitting layer 4, an electron injection layer 5, and a cathode 6 are provided on a substrate 1 in this order. In the organic electroluminescent element 10 of FIG. 1, the hole injection layer 3 functions as a mixed layer.

  FIG. 2 is a cross-sectional view showing a second embodiment of the organic electroluminescent element of the present invention. The organic electroluminescent device 20 of FIG. 2 is different from the organic electroluminescent device 10 of FIG. 1 in that the hole transport layer 7 is provided between the hole injection layer 3 and the organic light emitting layer 4, and the organic light emitting layer 4 and the electron injection layer 5 are provided. Are provided with electron transport layers 8 respectively. In the organic electroluminescent element 20 of FIG. 2, the hole injection layer 4 or the hole transport layer 7 functions as a mixed layer.

  FIG. 3 is a cross-sectional view showing a third embodiment of the organic electroluminescent element of the present invention. The organic electroluminescent element 30 of FIG. 3 is provided with an electron blocking layer 9 between the hole injection layer 3 and the organic light emitting layer 4 in the organic electroluminescent element 10 of FIG. In the organic electroluminescent element 30 of FIG. 3, the hole injection layer 3 functions as a mixed layer. Like the organic electroluminescent element 30 in FIG. 3, by interposing the electron blocking layer 9 between the hole injection layer 3 and the organic light emitting layer 4, it becomes possible to prevent leakage of electrons to the mixed layer, It is possible to further increase the efficiency and life of the element.

  By the way, since the mixed layer is a hole transporting layer, it is preferable that the mobility of holes in the mixed layer is high because the driving voltage can be lowered. However, when the band gap of the organic light emitting layer 4 is wider than that of the mixed layer, electrons leak from the organic light emitting layer 4 to the mixed layer, leading to a decrease in light emission efficiency. In addition, there is a concern that the energy of excitons formed in the organic light emitting layer 4 is transferred to the mixed layer, and the light emission efficiency is lowered.

  Therefore, in the organic electroluminescent element of the present invention, an electron blocking layer 9 is provided between the mixed layer and the organic light emitting layer 4. If it carries out like this, it will become possible to prevent the leakage of the electron from the organic light emitting layer 4 to a mixed layer, and the luminous efficiency of an element can be improved.

  Some materials constituting the mixed layer (hole transport material) shorten the life of the material itself by the flow of electrons. However, in the organic electroluminescent element of the present invention, even when a material that shortens the life due to the flow of electrons is used, if the electron blocking layer 9 is provided, the material does not flow, so that material is also used. be able to. When the electron block layer 9 is provided in this way, the range of material selection can be made wider.

  Moreover, in the organic electroluminescent element of this invention, the structure which makes the electron block layer 9 a mixed layer other than the said structure may be sufficient, and the structure which makes the electron block layer 9 and the hole injection layer 3 a mixed layer It may be. In such a case, in any configuration, the band gap of the electron block layer 9 is preferably made wider than the band gap of the hole injection layer 3. The electron blocking layer 9 is preferably made of a material having a hole transporting property in order to further promote the injection of holes into the organic light emitting layer 4.

  However, the organic electroluminescent element of the present invention is not limited to the above embodiment. For example, a hole blocking layer or a charge generation layer that generates holes and electrons inside the element may be provided as the intervening layer. Moreover, the embodiment in which the hole injection layer 3 and the electron injection layer 5 are omitted in the embodiment of FIG.

Moreover, the organic electroluminescent element of this invention is characterized by the following (A) and (B) or (A) and (C) being contained in the layer applicable to a mixed layer.
(A) Alcohol-soluble hole transport material (B) Copolymer composed of siloxane unit and phosphine oxide unit (C) Mixture composed of siloxane compound and phosphine oxide compound

  Thereby, the phosphine oxide can be contained in the layer corresponding to the mixed layer. By containing phosphine oxide in the mixed layer, the mixed layer can be insolubilized even if the amount of siloxane is very small. Therefore, as compared with conventional methods such as Patent Document 4 and Patent Document 5, it is possible to prevent the drive voltage of the organic electroluminescent element from increasing and to further increase the efficiency and life of the element.

  Next, (A) to (C) will be described. First, (A) will be described. The alcohol-soluble hole transport material is not particularly limited as long as it is a hole transport material and an organic compound having an alcohol-soluble portion. By using an alcohol-soluble arylamine compound as the hole transporting material, it is possible to further increase the efficiency and life of the device. As the alcohol-soluble hole transport material, it is particularly preferable to use an arylarylamine compound or a thiophene derivative. By using an alcohol-soluble thiophene derivative as the hole transporting material, it is possible to further increase the efficiency and life of the device.

  In addition, the arylarylamine compound and the thiophene derivative have an ionization potential close to that of ITO or IZO used as a transparent electrode. It is also a material having high hole mobility. Therefore, arylarylamine compounds and thiophene derivatives are frequently used as constituent materials for the hole injection layer 3, the hole transport layer 7, or the electron block layer 9 among the layers constituting the organic electroluminescence element. It is an effective material for achieving higher efficiency and longer life.

  Specific examples of the (A) alcohol-soluble hole transport material are listed below, but the present invention is not limited to this.

  Next, (B) will be described. The copolymer comprising a siloxane unit and a phosphine oxide unit is a polymer compound represented by the following general formula (I) or (II).

  In the formula (I) and the formula (II), R is not particularly limited, but examples thereof include alkyl groups such as hydrogen, hydroxyl group, phenyl group, methyl group, ethyl group, t-butyl group, and octyl group. , Substituted amino groups such as methylamino group, ethylamino group, dimethylamino group, diethylamino group and diphenylamino group, and π-conjugated substituents such as naphthyl group, phenanthryl group, anthryl group, pyrenyl group and fluorenyl group Can be mentioned. R may be different or the same.

  Next, (C) will be described. The siloxane compound is not particularly limited, and has various organic functional groups such as dimethylpolysiloxane, diphenylpolysiloxane, fluoropolysiloxane, styrylpolysiloxane, aminopolysiloxane, mercaptopolysiloxane, and epoxypolysiloxane. The polysiloxane compound which was made is mentioned. Moreover, the polysiloxane to be used may be one type, and may be two or more types.

  On the other hand, examples of the structure of the siloxane compound to be used include those having an organic functional group introduced into the side chain and those having an organic functional group introduced to the terminal, but are not particularly limited. Furthermore, this siloxane compound can be used by curing with various external energies such as heat curing and ultraviolet curing. In the organic electroluminescent device of the present invention, the mixed layer itself is made insoluble in an organic solvent by a method such as curing a thin film to be a mixed layer, so that an organic light emitting layer is formed on the mixed layer by a coating process. Can be stacked.

  The phosphine oxide compound is a compound represented by the following general formula (III).

  In formula (III), R is not particularly limited, and examples thereof include alkyl groups such as hydrogen, hydroxyl group, phenyl group, methyl group, ethyl group, t-butyl group, and octyl group, methylamino group, ethylamino group, and dimethyl group. Examples thereof include substituted amino groups such as amino group, diethylamino group, and diphenylamino group, and further π-conjugated substituents such as naphthyl group, phenanthryl group, anthryl group, pyrenyl group, and fluorenyl group. R may be different or the same.

  Examples of the compound represented by the formula (III) include phosphoric acid, phosphonic acid, phosphinic acid, phosphine oxide, triphenylphosphine, trioctylphosphine oxide, tributylphosphine oxide, piperidylphosphine oxide and the like.

  As described above, a thin film is formed using a combination of a hole transport material corresponding to (A) and a copolymer corresponding to (B), or a material corresponding to (A) and a mixture corresponding to (C). In this way, the amount of the siloxane compound used when forming the insolubilized film can be greatly reduced as compared with the prior art that does not contain phosphine oxide.

  In the coating type organic electroluminescence device, when the organic light emitting layer (or electron block layer) is formed, the mixed layer (hole injection layer or hole transport layer) which is the base layer is a constituent material of the organic light emitting layer. Must be insoluble in the solvent in which it is dissolved.

  On the other hand, since the siloxane compound has a Si—O bond in the molecule, the thin film made of this siloxane compound can be insolubilized in various solvents only by film formation or by performing heat treatment or ultraviolet treatment. Is possible.

  Many siloxane compounds have high chemical stability. For this reason, forming a mixed layer (hole injection layer, hole transport layer, or electron block layer) by insolubilizing a thin film in which a siloxane compound and a hole transport material are mixed is effective from the viewpoint of improving the device lifetime. It is.

  However, since the siloxane compound is a highly insulating material, if the content in the layer is increased, the driving voltage increases, leading to a decrease in power efficiency and a decrease in life.

  On the other hand, the organic electroluminescence device of the present invention can reduce the amount of the siloxane compound to be used when forming a layer (mixed layer) containing the siloxane compound. Can be solved. Therefore, it is possible to further increase the efficiency and the lifetime of the element as compared with the conventional method.

  On the other hand, the hole transport material used as a constituent member of the mixed layer constituting the organic electroluminescent element of the present invention is an alcohol-soluble compound. This is because most of the siloxane compounds and phosphine oxides that are constituent materials of the mixed layer are materials that dissolve in alcohol. Therefore, in the organic electroluminescent device of the present invention, it is possible to uniformly disperse the hole transport material in the matrix siloxane compound by using the alcohol-soluble hole transport material as the constituent material of the mixed layer. It becomes.

  The detailed cause of the phenomenon appearing in the organic electroluminescent device of the present invention is not clearly understood. FIG. 4 is a diagram illustrating an example of a phenomenon that can be manifested in the organic electroluminescent element of the present invention. As illustrated in FIG. 4, an alcohol-soluble hole transport material is obtained by forming a hydrogen bond between an oxygen atom in phosphine oxide (P═O) and an alcohol-soluble portion (such as —OH) of the hole transport material. It can be considered that it is easily dispersed in the matrix and stabilized.

  Next, the structural member of the organic electroluminescent element of this invention is demonstrated.

  The substrate 1 is appropriately selected from glass, ceramic, compound, metal, plastic and the like, but is not particularly limited. Here, when the element configuration of the organic electroluminescent element is a bottom emission type, a transparent substrate such as glass is used. On the other hand, when the element configuration of the organic electroluminescence element is a top emission type, a metal substrate is used to prevent light leakage to the lower part of the substrate, or a thin film of a cathode material such as Ag is formed on a glass substrate or the like. A mirror structure is formed. It is also possible to control the colored light by adding a color filter film, a fluorescent color conversion filter film, a dielectric reflection film, or the like to the substrate. It is also possible to form a thin film transistor on a substrate and connect it to produce an element.

  As a material constituting the anode 2, a material having a work function as large as possible is preferable. For example, simple metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, tungsten, chromium, or alloys thereof combined, tin oxide, zinc oxide, indium oxide, indium tin oxide, indium zinc oxide Further, metal oxides such as CuI and halides such as CuI can be used. In addition, conductive polymers such as polyaniline, polypyrrole, polythiophene, and polyphenylene sulfide can also be used. These electrode materials may be used alone or in combination of two or more. Moreover, the anode may be composed of a single layer or a plurality of layers.

  (A), (B), (C) described above can be used as a constituent material of the layer that is not a mixed layer of the hole injection layer 3 and the hole transport layer 7, but in addition to this, Any material that transports holes can be used. For example, phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, oxazole, oxadiazole, triazole, imidazole, imidazolone, pyrazoline, tetrahydroimidazole, polyarylalkane, butadiene, benzidine type triphenylamine, styrylamine type triphenylamine, diamine type triphenylamine Examples thereof include, but are not limited to, phenylamine and the like and their derivatives, polymer materials such as polyvinyl carbazole, polysilane, and conductive polymer.

  The material constituting the organic light emitting layer 4 may be anything as long as it is an organic compound that performs organic electroluminescence. For example, if it is a low molecular weight system, anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal Illustrative examples include complexes, aminoquinoline metal complexes, benzoquinoline metal complexes, pyran, quinacridone, rubrene and derivatives thereof, and phosphorescent metal complexes represented by iridium-phenylpyridine complexes. Moreover, if it is a high molecular type, a polyvinyl carbazole, polyphenylene vinylene, polyfluorene, and those derivatives can be illustrated.

  The organic light emitting layer 4 may be composed of a single compound, but may be composed of a host and a guest. When the organic light emitting layer 4 is composed of a host and a guest, the combination may be a combination of low molecules, a combination of a polymer and a low molecule, or a combination of polymers. A combination of these may be used.

The constituent material of the electron injection layer 5 may be anything as long as it is a compound having electron conductivity. For example, alkali metal such as LiF, Cs ₂ CO ₃ , and CaO, fluoride of alkaline earth metal, carbonate compound, oxide, and the like can be given. In addition to the above materials, organic compounds having electron conductivity can be used. Examples include quinoline derivatives such as aluminum quinoline complex (Alq), oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, and the like.

  The material constituting the cathode 6 is preferably a material having a small work function. For example, simple metals such as lithium, sodium, potassium, calcium, magnesium, aluminum, indium, ruthenium, titanium, manganese, yttrium, silver, lead, tin, and chromium are used. An alloy in which a plurality of these metals are combined may be used. For example, alloys such as lithium-indium, sodium-potassium, magnesium-silver, aluminum-lithium, aluminum-magnesium, and magnesium-indium can be used. Also, metal oxides such as indium tin oxide can be used. These electrode materials may be used alone or in combination of two or more. Moreover, the cathode 6 may be composed of a single layer or a plurality of layers.

  Moreover, any of the anode 2 and the cathode 6 is desirably transparent or translucent.

  The constituent material of the electron transport layer 8 may be any material that transports electrons. For example, an electron transport material as exemplified in the electron injection layer can be used.

  The constituent material of the electron blocking layer 9 is preferably a hole transport material having a wider band gap than the band gap of the organic light emitting layer 4. For example, insulating materials such as the above-described siloxane compounds, hole transport materials such as polyvinyl carbazole, and the like can be exemplified.

  In the present invention, a protective layer or a sealing layer can be provided for the manufactured element for the purpose of preventing contact with oxygen, moisture, or the like. Examples of the protective layer include an inorganic material film such as diamond thin film, metal oxide, and metal nitride, a polymer film such as fluororesin, polyparaxylene, polyethylene, silicone resin, and polystyrene resin, or a photocurable resin. Further, it is possible to cover glass, a gas-impermeable film, a metal, etc., and to package the element itself with an appropriate sealing resin.

  Next, the manufacturing method of the organic electroluminescent element of this invention is demonstrated.

  As a method for forming the mixed layer, for example, a copolymer corresponding to (B) and a hole transport material corresponding to (A) are dissolved in an alcohol solvent, a thin film is formed by a coating method, and then thermosetting is performed. Or the method of insolubilizing a layer by photocuring can be illustrated. At this time, instead of the copolymer corresponding to (B), the corresponding mixture of (C) may be used.

  In addition to this, a method of forming a mixed layer using a silane compound instead of a siloxane compound can also be exemplified. Specifically, an insolubilized mixed layer is formed using a dehydration condensation reaction of a silane compound by heat treatment or the like. When the dehydration condensation reaction proceeds, the Si—O bond is generated in the silane compound and changes to a siloxane compound.

  The silane compound used at this time is not particularly limited. For example, tetraethoxylane, tetramethoxysilane, methyltrichlorosilane, methyltribromosilane, methyltriisopropoxysilane, ethyltrichlorosilane, ethyltribromo Examples include silane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, phenyltrichlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, and phenyltridiphenyldimethoxysilane. . In addition to these, a partial hydrolyzate of a silane compound, a mixture obtained by combining a plurality of the above-described silane compounds, and the like can also be exemplified.

  In the organic electroluminescent element of the present invention, the content of the hole transport material (corresponding to (A)) contained in the mixed layer is preferably as much as possible as long as the insolubilized film can be maintained. Specifically, it is preferably 50% by weight or more based on the entire material of the mixed layer. More preferably, it is 80% by weight or more.

  The organic light emitting layer 4 is formed by any one of materials, but using any one of a vacuum evaporation method, a spin coating method, an ink jet method and the like. Moreover, the other layer which comprises an organic electroluminescent element is formed by well-known methods, such as a vacuum evaporation method, sputtering, the apply | coating method, etc. according to material.

  A display device such as a display can be configured by appropriately combining the organic electroluminescent elements of the present invention. That is, the display device of the present invention includes a plurality of the organic electroluminescent elements of the present invention and a drive circuit for the organic electroluminescent elements, and is driven by a passive matrix system or an active matrix system. Hereinafter, a display device in which the organic electroluminescent element of the present invention is combined with an active matrix system will be described with reference to the drawings.

  FIG. 5 is a schematic cross-sectional view showing a part of the display device of the present invention. The display device 40 shown in FIG. 5 is adjacent to the organic electroluminescent element unit 42 provided on the substrate 41, the circuit unit 43 disposed outside the organic electroluminescent element unit 42, and the circuit unit 43. The data wiring 44 is provided. Here, the circuit unit 43 is provided with a drive transistor (TFT1) 451, a switching transistor (TFT2) 452, and a storage capacitor (Ch) 46.

  In FIG. 5, only one organic electroluminescent element is shown. However, when actually constructing a display device, a plurality of organic electroluminescent elements are arranged two-dimensionally. A specific example of a display device in which organic electroluminescent elements are arranged two-dimensionally will be described later. In the present embodiment, the organic electroluminescent element section 42 is formed by laminating a lower electrode 47, an organic compound layer 48, and an upper electrode 49 in this order. In the organic electroluminescence element portion 42, the organic compound layer 48 includes at least the mixed layer and the organic light emitting layer.

  FIG. 6 is a diagram showing details of the circuit configuration in the circuit section of the display device of FIG. The circuit unit 50 shown in FIG. 6 has a typical circuit configuration called a current programming method. The circuit that can be employed in the display device of the present invention is not limited to this. The circuit unit 50 shown in FIG. 6 includes a drive transistor (TFT 1) 451, a switching transistor (TFT 2) 452, a storage capacitor (Ch) 46, and an organic electroluminescent element 51. Since the circuit configuration is well known, detailed description of the operation is omitted.

  By the way, the organic electroluminescent element of the present invention can be used as a single light emitting point and used as an exposure light source of a display device such as a display, an illumination device, or an electrophotographic image forming apparatus.

  The case where the organic electroluminescent element of the present invention is used for a display will be described below.

  FIG. 7 is a schematic view showing a display device in which the organic electroluminescence element part and the circuit part shown in FIGS. 5 and 6 are arranged in a matrix with one pixel.

  In the display device 60 of FIG. 7, the pixel 61 is connected to the gate driver 62 and the source driver 63 via a wiring, and enters a light emitting state or a non-light emitting state by a driving pulse supplied from each driver.

  Thus, the area | region where the organic electroluminescent element of this invention is multiply arranged by the in-plane direction in the same surface as a pixel is a display area of the display apparatus of this invention. That is, the organic electroluminescent element of the present invention can be used as a display area of the display device of the present invention.

  The display device of the present invention may be in any embodiment as long as it is a display device for a television or a PC, or a device having a part for displaying an image. For example, a portable display device on which the display device of the present invention is mounted may be used. Alternatively, the display device of the present invention can be used for an electronic imaging device such as a digital camera or a display unit of a mobile phone.

  FIG. 8 is a schematic diagram showing a configuration example in which the display device of FIG. 7 is made into a panel module. The panel module 70 of FIG. 8 is obtained by integrating an interface driver 71, a gate driver 62, and a source driver 63 with a housing 72 in addition to the display device 60 shown in FIG. 7. In the panel module 70 of FIG. 7, although not shown, a component (interface) necessary for connection to an external device such as a connection terminal is built in the housing 72.

  Next, the use of the display device of FIG. 7 will be described with reference to the drawings. FIG. 9 is a diagram illustrating an example of the use of the display device of FIG. The display device 60 of FIG. 7 is a display unit of a portable display device such as the TV monitor 81 and the mobile phone 82 shown in FIG. 9, a display device for PC, an electronic imaging device such as a digital camera, etc. Built in.

  Examples of the present invention will be described below.

  <Synthesis Example 1> Exemplified Compound No. 1 Synthesis of 4

(I) The following reagents and solvents were charged into a 100 ml flask.
Secondary amine compound (compound 1-1): 5.0 g (8.8 mmol)
Iodine (Compound 1-2): 9.3 g (26.4 mmol)
Cu powder: 2.24 g (35.2 mmol)
Potassium carbonate: 3.65 g (26.4 mmol)
15 ml of o-dichlorobenzene

  Next, the reaction solution was stirred for 20 hours while being heated and refluxed in an oil bath at about 200 ° C. After completion of the reaction, the reaction solution was cooled to around 50 ° C., and extracted by adding toluene. Next, the extract was filtered under reduced pressure to separate the organic layer and the inorganic component. Next, the reaction product was obtained by removing the solvent from the organic layer using an evaporator. In order to isolate compound 1-3, which is the target compound, from the obtained reaction product, purification is performed using silica gel column chromatography (developing solvent: toluene) to obtain the diacetyl form (compound 1- 3) was obtained. The obtained diacetyl form was used in the next reaction as it was.

(Ii) Subsequently, after the whole amount of the diacetyl compound (compound 1-3) synthesized in (i) was charged into a 500 ml flask, the following reagents and solvent were further charged.
Methanol: 200ml
Toluene: 100ml
Sodium methylate: 0.3g

  Next, the reaction solution was stirred for 3 hours while refluxing. After completion of the reaction, a dilute aqueous hydrochloric acid solution was added to the reaction solution until the reaction solution became neutral. Next, after separating the reaction solution into an organic layer and an aqueous layer by a liquid separation operation, the organic layer was dried and the solvent was removed using an evaporator to obtain a reaction product.

  From the obtained reaction product, Exemplified Compound No. 1 as the target product was obtained. In order to isolate No. 4, it is purified using silica gel column chromatography (developing solvent: toluene / ethyl acetate mixed solvent) to give the exemplified compound No. 1 as the target compound. 4.5 g of 4 was obtained. The total yield from diacetyl body synthesis was 63.4%.

  <Synthesis Example 2> Exemplified Compound No. 2 Synthesis of 13

  J. et al. Kagan, et al. Org. Chem. , 48 (1983) 4076. The compound 2-1 was synthesized with reference to the synthesis example. Next, by reducing this compound 2-1 with LiAlH 4, exemplary compound No. 13 was obtained. The total yield was 65.3%.

<Example 1>
An organic electroluminescent element having the element configuration shown in FIG. 2 was produced. In this example, the materials shown below were used as constituent members of each layer constituting the organic electroluminescent element.
Substrate 1: Glass substrate Anode 2: Indium tin oxide (ITO)
Hole injection layer 3: Phosphorus-containing silicic acid polymer (Honeywell, P-5S)
Exemplified Compound No. 4

  Organic light emitting layer 4: an oligofluorene compound represented by the following formula as a host

ゲストである下記式に示されるＩｒ（Ｃ₈−ｐｉｑ）₃

Ir (C ₈ -piq) ₃ represented by the following formula as a guest

電子注入層５：Ｃｓ₂ＣＯ₃
陰極６：Ａｌ

Electron injection layer 5: Cs ₂ CO ₃
Cathode 6: Al

  First, an ITO film was formed on a substrate (glass substrate) 1 by sputtering to form an anode 2. At this time, the film thickness of the anode 2 was about 100 nm.

  Next, a phosphorus-containing silicic acid polymer and exemplified compound Nos. 4 was mixed to prepare a 1.0 wt% butanol solution. At this time, the phosphorus-containing silicic acid polymer and Exemplified Compound No. 4 is mixed with a phosphorus-containing silicic acid polymer: Exemplified Compound No. 1 = 10: 90. Next, the prepared butanol solution was dropped on the anode 2 and spin-coated, and then heat treatment was performed at 200 ° C. to form the hole injection layer 3. At this time, the thickness of the hole injection layer 3 was 30 nm.

Next, a host (oligofluorene compound) and a guest (Ir (C ₈ -piq) ₃ ) were mixed in a toluene solvent to prepare a 2.0 wt% toluene solution. At this time, the mixing ratio (weight mixing ratio) of the host and the guest was set to host: guest = 99: 1. Next, the prepared toluene solution was dropped on the third hole injection layer and spin-coated to form the organic light emitting layer 4. At this time, the film thickness of the organic light emitting layer 4 was 90 nm.

Next, Cs ₂ CO ₃ was formed by resistance heating vapor deposition to form the electron injection layer 5. At this time, the thickness of the electron injection layer 5 was 2.4 nm.

  Next, Al was deposited by resistance heating vapor deposition to form the cathode 6. At this time, the film thickness of the cathode 6 was set to 100 nm.

  Finally, a protective glass plate was placed under a nitrogen atmosphere and sealed with an acrylic resin adhesive. An organic electroluminescent element was obtained as described above.

With respect to the obtained device, when a direct current voltage of 8.8 V was applied with the ITO electrode as the positive electrode and the Al electrode as the negative electrode, a current of the device flowed. The current density at this time was about 100 mA / cm ² , and red light emission with a luminance of about 5300 cd / m ² was observed. The chromaticity was NTSC (X, Y) = (0.67, 0.32).

  In this example, the solvent resistance of the hole injection layer was evaluated by the following method. Specifically, after a thin film corresponding to the hole injection layer 3 was formed, toluene was dropped on the thin film, and the film thickness was evaluated after spin coating. Whether the film thickness changed (decreased) was evaluated from the change in the absorbance of the film. Here, the absorbance of the thin film is high when the film thickness is thick, and thus shows a high absorbance. On the other hand, when the film thickness is thin, the absorbance decreases because the medium that absorbs light decreases. For this reason, if the absorbance does not change after toluene dropping, it can be considered that there is no decrease in film thickness. The absorbance was measured using a spectrophotometer (U-2810 manufactured by Hitachi High-Tech Co., Ltd. As a result of the evaluation, no change in the film thickness of the thin film was observed before and after the toluene was dropped. The thin film was found to be an insolubilized film.

<Example 2>
In Example 1, phosphorus-containing silicic acid polymer and Exemplified Compound No. 4 and the phosphorus-containing silicic acid polymer: Exemplified Compound No. An organic electroluminescent element was produced in the same manner as in Example 1 except that 4 = 20: 80. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the hole injection layer was evaluated in the same manner as in Example 1, no change in the film thickness of the thin film was observed before and after the dropwise addition of toluene. The thin film was found to be an insolubilized film.

<Example 3>
In Example 1, phosphorus-containing silicic acid polymer and Exemplified Compound No. 4 and the phosphorus-containing silicic acid polymer: Exemplified Compound No. An organic electroluminescent element was produced in the same manner as in Example 1 except that 4 = 40: 60. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the hole injection layer was evaluated in the same manner as in Example 1, no change in the film thickness of the thin film was observed before and after the dropwise addition of toluene. The thin film was found to be an insolubilized film.

<Example 4>
On the substrate, an organic electroluminescence device was prepared in which an anode, a hole injection layer, a hole transport layer, an organic light emitting layer, an electron injection layer, and a cathode were provided in this order.

  After forming an anode by the same method as in Example 1, PEDOT: PSS was spin-coated on this anode to form a hole injection layer. At this time, the thickness of the hole injection layer was 30 nm. Next, the butanol solution used in Example 1 was spin-coated on the hole injection layer to form a hole transport layer. At this time, the thickness of the hole transport layer was 30 nm. Hereinafter, an organic electroluminescent device was obtained by sequentially forming an organic light emitting layer, an electron transport layer and a cathode by the same method as in Example 1. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the hole transport layer was evaluated in the same manner as in Example 1, no change in the film thickness of the thin film was observed before and after the dropwise addition of toluene. The thin film was found to be an insolubilized film.

<Example 5>
In Example 1, Exemplified Compound No. Instead of Example Compound No. 4 An organic electroluminescent device was produced in the same manner as in Example 1 except that 13 thiophene derivatives were used. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the hole injection layer was evaluated in the same manner as in Example 1, no change in the film thickness of the thin film was observed before and after the dropwise addition of toluene. The thin film was found to be an insolubilized film.

<Example 6>
In Example 4, before forming the organic light emitting layer after forming the hole transport layer, a 0.5 wt% butanol solution in which only the phosphorus-containing silicate polymer is dissolved is dropped onto the hole transport layer and spin-coated. Thus, an electron blocking layer was formed. Except for this, an organic electroluminescent element was produced in the same manner as in Example 4. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the electronic block layer was evaluated in the same manner as in Example 1, no change in the film thickness of the thin film was observed before and after the dropwise addition of toluene. The thin film was found to be an insolubilized film.

<Comparative Example 1>
In Example 1, a siloxane polymer not containing phosphorus (T-11, manufactured by Honeywell) was used in place of the phosphorus-containing silicic acid polymer. 4 was used. Except for this, an organic electroluminescent element was produced in the same manner as in Example 1. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the hole injection layer was evaluated in the same manner as in Example 1, a decrease in the film thickness of the thin film was observed before and after the dropwise addition of toluene. It was found that the thin film was not an insolubilized film.

<Comparative example 2>
In Comparative Example 1, the siloxane polymer and Exemplified Compound No. 4 (weight mixing ratio) with siloxane polymer: Exemplified Compound No. 4 An organic electroluminescent element was produced in the same manner as in Comparative Example 1 except that 4 = 30: 70. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the hole injection layer was evaluated in the same manner as in Example 1, a decrease in the film thickness of the thin film was observed before and after the dropwise addition of toluene. It was found that the thin film was not an insolubilized film.

<Comparative Example 3>
In Comparative Example 1, the siloxane polymer and Exemplified Compound No. 4 (weight mixing ratio) with siloxane polymer: Exemplified Compound No. 4 An organic electroluminescent element was produced in the same manner as in Comparative Example 1 except that 4 = 50: 50. The obtained device was evaluated in the same manner as in Example 1. The results are shown in Table 1. In addition, when the solvent resistance of the thin film corresponding to the hole injection layer was evaluated in the same manner as in Example 1, no change in the film thickness of the thin film was observed before and after the dropwise addition of toluene. The thin film was found to be an insolubilized film.

From Table 1, it was found that by containing phosphine oxide in the SiO _x matrix, an insoluble film can be produced even if it contains a larger amount of hole transport material than when no phosphine oxide is contained.

In addition, from Table 1, it was found that the organic electroluminescent element of each example can be reduced in voltage as compared with the organic electroluminescent element of the comparative example. This is presumably because the content of the hole transport material could be increased by incorporating phosphine oxide into the SiO _x matrix.

  By the way, when Example 5 and Example 6 are compared, it can be seen that Example 5 has higher quantum efficiency. This is presumably because the electron blocking layer was provided in Example 6, and in the device configuration of Example 5, electrons that could flow to the hole injection layer were blocked by the electron blocking layer.

  In Comparative Examples 1 and 2 in which an insolubilized film could not be produced, the characteristics of the elements obtained in each Comparative Example were examined. As a result, the maximum EL light emission efficiency was as low as about 0.1%, and almost no EL light emission could be confirmed.

  From the above, it was found that the organic electroluminescent device of the present invention is a highly efficient and long-life device.

  The organic electroluminescent element of the present invention can be used as a constituent member of a display panel or a display device.

It is sectional drawing which shows 1st embodiment in the organic electroluminescent element of this invention. It is sectional drawing which shows 2nd embodiment in the organic electroluminescent element of this invention. It is sectional drawing which shows 3rd embodiment in the organic electroluminescent element of this invention. It is a figure which shows an example of the phenomenon which can express to the organic electroluminescent element of this invention. It is a cross-sectional schematic diagram which shows a part of display apparatus of this invention. It is a figure which shows the detail of a circuit structure in the circuit part of the display apparatus of FIG. FIG. 7 is a schematic view showing a display device in which the organic light emitting element portion and the circuit portion shown in FIGS. 5 and 6 are arranged in a matrix with one pixel. It is a schematic diagram which shows the structural example which made the display apparatus of FIG. 7 the panel module. It is a schematic diagram which shows an example of the use of the display apparatus of FIG. It is sectional drawing which shows the general structure of a coating type organic electroluminescent element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,41,100 Substrate 2,101 Anode 3,102 Hole injection layer 4,103 Organic light emitting layer 5,104 Electron injection layer 6,105 Cathode 7 Hole transport layer 8 Electron transport layer 9 Electron block layer 10, 20, 30, 51 Organic electroluminescent device 40, 60 Display device 42 Organic light emitting device portion 43, 50 Circuit portion 44 Data wiring 451 Drive transistor (TFT1)
452 Switching transistor (TFT2)
46 Holding capacity (Ch)
47 Lower electrode 48 Organic compound layer 49 Upper electrode 61 Pixel 62 Case driver 63 Source driver 70 Panel module 71 Interface driver 72 Case 81 TV monitor 82 Mobile phone

Claims (6)

An anode and a cathode;
A laminate comprising at least a mixed layer sandwiched between the anode and the cathode and an organic light emitting layer in this order, and
The organic electroluminescent device, wherein the mixed layer contains the following (A) and (B), or (A) and (C).
(A) Alcohol-soluble hole transport material (B) Copolymer composed of siloxane unit and phosphine oxide unit (C) Mixture composed of siloxane compound and phosphine oxide compound   The organic electroluminescent device according to claim 1, wherein the (A) alcohol-soluble hole transport material is an alcohol-soluble arylamine compound or an alcohol-soluble thiophene derivative.   The organic electroluminescent element according to claim 1, wherein an electron blocking layer is further provided between the mixed layer and the organic light emitting layer.   A display device comprising a plurality of the organic electroluminescent elements according to any one of claims 1 to 3 and a drive circuit for the organic electroluminescent elements.   A panel module comprising the display device according to claim 5 and an interface with an external device.   A portable display device comprising the display device according to claim 5.

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