JP2008118090A - Organic EL device and method for manufacturing the same - Google Patents

Abstract

In an organic EL device in which an anode is formed on a substrate, a hole injection layer is formed directly thereon, and an organic layer and a cathode including a light emitting layer are formed thereon, a dope material that is stable and can be vacuum-deposited in the atmosphere. Driving voltage is reduced by doping the hole injection layer.
The hole injection layer 30 is doped with a doping material made of a compound having an electron-withdrawing group that does not change even when exposed to the atmosphere, and is formed by vacuum deposition. The hole injection between the anode 20 and the hole injection layer 30 is performed by heating to a temperature higher than the glass transition temperature of the hole injection transport material constituting the hole injection layer 30 as compared with the case where the hole injection layer 30 is not doped with a doping material. Reduced the barrier.
[Selection] Figure 1

Description

  The present invention relates to an organic EL (electroluminescence) element using an organic light-emitting material that emits light when energized, and a method for manufacturing the same, and more particularly to improvement of a hole injection layer located immediately above an anode.

  Conventionally, as a general organic EL element, an anode, a hole injection layer made of a hole injection / transport material directly above the anode, an organic layer including a light emitting layer above the anode, and a cathode on a substrate such as glass It has been proposed to have formed.

  Such an organic EL element is manufactured by forming each layer on a substrate by vacuum deposition or the like. Then, by applying a voltage between the anode and the cathode, holes (holes) from the anode and electrons from the cathode are injected and transported toward the light emitting layer, and these are recombined in the light emitting layer. The light is emitted at.

  In such an organic EL element, ITO (indium tin oxide) is generally used as the anode. One reason for this is that the anode is required to be transparent. However, when ITO is used for the anode, the energy between the work function of ITO (about 5.0 eV), which is the energy level for propagating holes, and the ionization potential (about 5.5 eV) of the hole injection layer immediately above it. Since the barrier, that is, the hole injection barrier is large, it is difficult to reduce the driving voltage.

  In order to solve this problem, a method has been reported in which Lewis acid, which is an electron-accepting compound, is added to the hole injection layer and the hole injection layer is oxidized to reduce the driving voltage (see Non-Patent Document 1). .

  However, since this method uses Lewis acid, which is an unstable metal halide in the atmosphere, it is necessary to react Lewis acid with the material of the hole injection layer in advance under an inert atmosphere to form a stable complex. was there. Furthermore, since the complex formed cannot be formed by vacuum deposition, it is necessary to form a thin film from a solution by spin coating or the like. Therefore, solvent residues and impurities tend to remain in the organic thin film, deteriorating device characteristics. There was a problem of letting.

  In addition, a method of directly vacuum-depositing a metal halide Lewis acid and doping the hole injection layer has been proposed (see, for example, Patent Document 1 and Patent Document 2). However, the Lewis acid used in these conventional methods generally has a high vapor pressure even at room temperature, so it is difficult to control the vapor pressure, and vacuum deposition is performed near room temperature. It was necessary to do.

  Further, in this method, a Lewis acid having a high vapor pressure may be mixed as an impurity in other sample portions, thereby deteriorating the characteristics of the organic EL element. Further, when the vacuum deposition apparatus is opened to the atmosphere, the purity of these Lewis acids that are unstable in the atmosphere is lowered, and there is a problem that the reproducibility of the characteristics of the organic EL element cannot be obtained.

Moreover, in an organic EL element, in order to suppress the short circuit between the upper and lower electrodes induced by the conductive foreign matter, it is required to increase the thickness of the organic layer immediately above the electrodes. Conventionally, it has been reported that the short-circuit between the upper and lower electrodes can be suppressed by setting the film thickness of the hole injection layer on the ITO electrode to 80 nm or more and further heat-treating to cover the conductive foreign matter with the organic layer. (For example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 11-251067 Japanese Patent Laid-Open No. 2001-244079 JP 2005-5149 A Polymer. 1983, vol. 24, June

  As in the organic EL element described in Patent Document 3, increasing the thickness of the organic layer increases the light emission luminance of the organic EL element or suppresses a short circuit between the upper and lower electrodes. Preferably, this method is desired to be applied in the future. In this case, however, there is a problem that the drive voltage increases by increasing the thickness of the hole injection layer.

  Such a high driving voltage of the organic EL element leads to a problem that, for example, the price of the driver IC is increased on the circuit side, and in some cases, the general-purpose driver IC cannot be driven.

  The present invention has been made in view of the above problems, and in an organic EL device in which an anode is formed on a substrate, a hole injection layer is formed immediately above the substrate, and an organic layer and a cathode including a light emitting layer are formed thereon. An object of the present invention is to reduce the driving voltage by doping a hole injection layer with a doping material that is stable and can be vacuum-deposited therein.

  In order to achieve the above object, the present inventor has determined that the driving voltage of the organic EL element varies depending on the energy barrier between the electrode and the organic layer and the energy barrier between the organic layer and the organic layer. We focused on the fact that the driving voltage decreases as the energy barrier decreases. In order to reduce the hole injection barrier between the anode and the hole injection layer immediately above the anode, various doping materials were experimentally studied.

  As a result, as in the present invention, a dope material made of a compound having an electron-withdrawing group that does not change even when exposed to the atmosphere is used. If the film is formed by vacuum deposition and further heated to a temperature higher than the glass transition temperature of the host material, the hole injection barrier between the anode and the hole injection layer can be reduced and the driving voltage can be reduced compared to the case of the host material alone. It was found experimentally that it can be reduced.

  That is, in the present invention, the hole injection layer (30) is doped with a doping material which is a compound having an electron-withdrawing group and which does not change even when exposed to the atmosphere, and is formed by vacuum deposition. Furthermore, by heating to a temperature higher than the glass transition temperature of the hole injecting and transporting material constituting the hole injecting layer (30), the anode (20) and the hole injecting layer (30) are not doped with a doping material. The hole injection barrier between the hole injection layer (30) and the hole injection layer (30) is reduced.

  According to this, as will be described as an experimental result in an embodiment described later, the driving voltage can be reduced by doping the hole injection layer with a doping material that is stable in the atmosphere and can be vacuum-deposited. In this case, it is confirmed by XPS measurement that the bond between carbon and the electron withdrawing group is increased in the hole injection layer (30) (see FIG. 2 described later).

  Further, in the organic EL element having such characteristics, the organic layer (40-60) including the light emitting layer (50) is located between the hole injection layer (30) and the light emitting layer (50) and is injected with holes. When the hole transport layer (40) formed immediately above the layer (30) is provided, the hole transport layer (40) is also doped with a doping material and formed by vacuum deposition. Further, it may be heated above the glass transition temperature of the hole injecting and transporting material constituting the hole transporting layer (40). Thereby, the hole injection barrier between the anode (20) and the hole injection layer (30) is made smaller than when the doping material is not doped into the hole injection layer (30), and only the hole injection layer (30) is provided. The hole injection barrier between the hole injection layer (30) and the hole transport layer (40) may be made smaller than the case where the doping material is doped.

  If the hole transport layer (40) is also doped in this way, as in the relationship between the anode (20) and the hole injection layer (30), the hole transport layer (40) is not doped with a doping material. Since the hole injection barrier between the hole injection layer (30) and the hole transport layer (40) immediately above the hole injection layer (30) can be reduced, it is preferable from the viewpoint of driving voltage reduction. Also in this case, it is confirmed by XPS measurement that the bond between carbon and the electron withdrawing group is increased in the hole injection layer (30).

  Furthermore, in this case, the entire hole transport layer (40) may be doped with a doping material, but the doping material is doped only in the portion of the hole transport layer (40) close to the hole injection layer (30) side. It is preferable to reduce the hole injection barrier at the interface between the hole injection layer (30) and the hole transport layer (40).

  Further, it is preferable to increase the thickness of the hole injection layer (30) to 60 nm or more because it is possible to absorb irregularities due to foreign matters on the surface of the anode (20).

  Moreover, if the dope amount of the dope material is set to 10% by weight or less of the whole hole injection layer (30), association between the dope materials in the hole injection layer (30) can be suppressed, which is preferable.

  Here, examples of the electron-withdrawing group in the dope material include halogen, and more specifically, fluorine. Moreover, what has a phthalocyanine (Pc) frame | skeleton can be employ | adopted as a compound which comprises dope material.

  More specifically, as a compound constituting the dope material, copper 1, 2, 3, 4, 8, 9, 10, 11, 15, 16, 17, 18, 22, 23, 24, 25-hexadeca Fluoro-29H, 31H-phthalocyanine (F-CuPc), zinc 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro -29H, 31H-phthalocyanine (F-ZnPc).

  Moreover, if the host material which comprises the organic layer (40-60) containing a hole injection layer (30) and a light emitting layer (50) is made into the thing whose glass transition temperature is 110 degreeC or more, it will be organic EL for motor vehicles. It is preferable as an element.

  Moreover, as a manufacturing method for manufacturing the organic EL element having the above characteristics, a film is formed by co-evaporating a dope material and a hole injection transporting material constituting the hole injection layer (30) under vacuum, and this film Is heated to a temperature equal to or higher than the glass transition temperature of the hole injecting and transporting material constituting the hole injecting layer (30), whereby the hole injecting layer (30) can be formed. Accordingly, an organic EL element having the above characteristics can be manufactured appropriately.

  In addition, as a manufacturing method for manufacturing an organic EL element when the hole transport layer (40) is doped, a dope material and a hole injection transport material constituting the hole injection layer (30) are co-deposited under vacuum. Then, a first film is formed, and a second film is formed by co-evaporating a doping material and a hole injecting / transporting material constituting the hole transport layer (40) directly on the first film under vacuum. At the same time, the first film and the second film have a higher glass transition between the hole injecting and transporting material constituting the hole injecting layer (30) and the hole injecting and transporting material constituting the hole transporting layer (40). By heating above the temperature, the hole injection layer (30) and the hole transport layer (40) can be formed.

  Accordingly, it is possible to appropriately manufacture an organic EL element obtained by doping the hole injection layer (30) and the hole transport layer (40) with a doping material.

  By the way, each of the above-mentioned means forms a film by doping a hole injection layer with a material that has an electron-withdrawing group and does not change even when exposed to the atmosphere, and heats it above the glass transition temperature of the host material. It was made paying attention to the point.

  Therefore, when further studies were made using such a material, even if such a material was made into a thin film by itself and interposed between the anode and the hole injection layer, the driving was performed in the same manner as described above. It was experimentally found that the voltage can be reduced.

  That is, in the present invention, on the substrate (10), the anode (20), the intervening layer (90) made of a material that has an electron-withdrawing group directly above the anode (20) and does not change even when exposed to the atmosphere, A hole injection layer (30) is formed immediately above the intervening layer (90), an organic layer (30-60) including a light emitting layer (50) is formed on the hole injection layer (30), and a cathode (80). The intervening layer (90) and the hole injection layer (30) may be formed by vacuum deposition, and heated to a temperature higher than the glass transition temperature of the hole injection transport material constituting the hole injection layer (30).

  In this case, the drive voltage can be reduced by reducing the hole injection barrier between the anode (20) and the hole injection layer (30), compared with the case where the intervening layer (90) is not provided. In this case, it is confirmed by XPS measurement that the bond between the carbon and the electron withdrawing group of the intervening layer (90) is increased in the hole injection layer (30).

  In this case, the steepness of the composition change at the interface due to the diffusion of the electron withdrawing group of the intervening layer (90) is reduced at the interface between the hole injection layer (30) and the anode (20), and It is confirmed by SIMS analysis that the electron-withdrawing group is segregated at the interface between the hole injection layer (30) and the hole transport layer (40).

  Also in this case, examples of the electron-withdrawing group of the intervening layer (90) include halogen such as fluorine, and examples of the material constituting the intervening layer (90) include F-CuPc and F-ZnPc described above. Those having a phthalocyanine skeleton can be employed.

  Moreover, as a manufacturing method of the organic EL element which manufactures the organic EL element which has this intervening layer (90), the intervening layer (90) and the hole injection layer (30) are formed into a film by vacuum deposition, and a hole injection layer ( 30) can be heated above the glass transition temperature of the hole injecting and transporting material.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a schematic cross-sectional configuration of an organic EL element 100 according to the first embodiment of the present invention.

  The organic EL device 100 according to this embodiment includes an anode 20, a hole injection layer 30, a hole transport layer 40, a light emitting layer 50, an electron transport layer 60, an electron injection layer 70, and a cathode 80 on a substrate 10. . Here, the hole transport layer 40, the light emitting layer 50, and the electron transport layer 60 constitute the organic layers 40 to 60 including the light emitting layer 50 referred to in the present invention.

  In the organic EL device 100 shown in FIG. 1, the substrate 10 is usually made of glass such as soda glass, barium silicate glass, and aluminosilicate glass, plastic such as polyester, polycarbonate, polysulfone, polymethyl methacrylate, polypropylene, and polyethylene, quartz. General-purpose substrate materials such as ceramics such as ceramics are formed into a plate shape, a sheet shape, or a film shape, and these are appropriately laminated and used as necessary.

  Desirable substrate materials are transparent glass and plastic. When necessary, chromaticity adjusting means such as a filter film, a chromaticity conversion film, and a dielectric reflection film may be provided at an appropriate position on the substrate 10.

  The anode 20 is electrically low in resistivity and has one or more of a metal or a conductive compound having a high light transmittance over the entire visible region, for example, vacuum deposition, sputtering, chemical vapor deposition (CVD), atomic It is made to adhere to one side of substrate 10 by methods, such as layer epitaxy (ALE), application, and immersion.

  Here, the anode 20 has a thickness of 10 to 1000 nm, preferably 50 to 500 nm, so that the resistivity of the anode 20 is 1 kΩ / □ or less, preferably 5 to 50Ω / □. It is formed by forming a film.

  Examples of the conductive material for the anode 20 include metals such as gold, platinum, silver, copper, cobalt, nickel, palladium, vanadium, tungsten, and aluminum, zinc oxide, tin oxide, indium oxide, and tin oxide and indium oxide. Metal oxides such as mixed systems (that is, indium-tin oxide, hereinafter abbreviated as “ITO” in the present embodiment), conductive oligomers having aniline, thiophene, pyrrole and the like as repeating units, and conductivity Polymers.

  Among these, ITO is transparent and can be easily obtained with a low resistivity and can be easily formed by etching with an acid or the like, so that it is preferable to apply to the anode 20.

  A hole injection layer 30 is formed on the anode 20 so as to be in direct contact with the anode 20. That is, the hole injection layer 30 is formed immediately above the anode 20. This hole injecting layer 30 is obtained by using a hole injecting / transporting material as an organic material used in this type of organic EL element as a host material, and doping the host material with a doping material made of a compound having an electron withdrawing group. It is.

  Further, in the hole injection layer 30 of the present embodiment, ultraviolet photoelectron spectroscopy (UPS) is more effective than the case where the hole injection layer 30 is not doped with the above-described doping material, that is, the hole injection layer 30 is made of only a hole injection / transport material. ) The hole injection barrier between the anode 20 and the hole injection layer 30 as measured is reduced.

The hole injecting and transporting material constituting the hole injecting layer 30 of the present embodiment has a small ionization potential and an electric field of 10 ⁴ to 10 ⁶ V / cm, for example, to facilitate hole injection and transport. Below, it is desirable to exhibit a hole mobility of at least 10 ⁻⁶ cm ² / V · sec.

  Specifically, such hole injecting and transporting substances include arylamine derivatives, imidazole derivatives, oxadiazole derivatives, oxazole derivatives, triazole derivatives, chalcone derivatives, styrylanthracene derivatives, stilbene derivatives, tetraarylethene derivatives, tria. Reelamine derivatives, triarylethene derivatives, triarylmethane derivatives, phthalocyanine derivatives, fluorenone derivatives, hydrazone derivatives, N-vinylcarbazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylanthracene derivatives, phenylenediamine derivatives, polyarylalkane derivatives, polysilane derivatives , Polyphenylene vinylene derivatives and the like, and these may be used in appropriate combination as necessary.

  Moreover, as a compound which has an electron withdrawing group used as said dope material, an organic halogen compound is preferable.

  Specifically, copper 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H, 31H-phthalocyanine (F- CuPc), zinc 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H, 31H-phthalocyanine (F-ZnPc) 1,2,3,4,5,6-hexa (4-trifluoromethylphenyl) benzene, 1,4-bis (4-trifluoromethylphenyl) benzene, 1,2,3,4,5,6 -Hexa (4-fluorophenyl) benzene, tetrafluorotetracyanoquinodimethane.

  These compounds having an electron-withdrawing group are stable in the air and do not change in quality when exposed to the air. In other words, the dope material made of these compounds does not decompose or react in the atmosphere and does not deteriorate in purity when exposed to the atmosphere. Thus, an organic EL element having excellent reproducibility and excellent characteristics can be obtained.

  Therefore, in the present embodiment, as a method of doping the hole injection layer 30 with a doping material, a method of co-evaporation by a vacuum evaporation method is adopted, and thereby contamination of impurities can be suppressed.

  Specifically, a film is formed by co-evaporating a dope material and a hole injection / transport material constituting the hole injection layer 30 under vacuum. In this state, the hole injection barrier between the anode 20 and the hole injection layer 30 by ultraviolet photoelectron spectroscopy (UPS) measurement hardly changes from the case where the doping material is not doped. Heat above the glass transition temperature of the hole injecting and transporting material.

  By this heating, the hole injection layer 30 in which the hole injection barrier between the anode 20 and the hole injection layer 30 is reduced is formed. In addition, the heating of the glass transition temperature or higher increases the interaction between the hole injecting and transporting material and the dope material in the hole injecting layer 30, which has been experimentally found by the present inventor. As described in the examples, this is confirmed by the formation of bonds between these materials.

  Here, when the hole injection layer 30 is doped with the above doping material, the doping amount is preferably 30% by weight or less of the whole hole injection layer 30. If it exceeds 30% by weight, the above-mentioned dope material is not preferable because it impedes carrier transmission.

  As shown in FIG. 1, a hole transport layer 40 is formed on the hole injection layer 30 so as to be in direct contact with the hole injection layer 30. That is, the hole transport layer 40 is formed immediately above the hole injection layer 30.

  The hole transport layer 40 is made of a hole injecting and transporting material used for this type of organic EL element. As the hole injecting and transporting material, the compounds mentioned above for the hole injecting layer 30 are employed. can do. The hole injecting / transporting material may be the same or different between the hole injecting layer 30 and the hole transporting layer 40.

  Here, as another configuration in the present embodiment, the hole transport layer 40 also has a hole injecting / transporting material as a host material, and the host material is doped with a doping material made of a compound having an electron attractive group. The hole injection barrier between the hole injection layer 30 and the hole transport layer 40 measured by UPS measurement may be made smaller than when only the hole injection layer 30 is doped with the above doping material.

  In the case of this other configuration, the doping material for doping the hole transport layer 40 can be the doping material in the hole injection layer 30, but the doping material in both layers 30, 40 may be the same or different. Good.

  And also about the hole transport layer 40 in this case, as for dope amount, 30 weight% or less is preferable. In addition, the hole transport layer 40 in this case is similar to the hole injection layer 30 in that the hole injection layer 30 and the hole injection layer 30 are formed more than the case where only the hole injection layer 30 is doped with a film by vacuum deposition and heat treatment. Although the hole injection barrier between the hole transport layers 40 can be made small, specifically, the hole injection layer 30 and the hole transport layer 40 can be formed by the following method.

  That is, the first material is formed by co-evaporation of the dope material constituting the hole injection layer 30 and the hole injection transport material under vacuum, and the dope constituting the hole transport layer 40 is formed directly on the first film. The material and the hole injecting / transporting material are co-evaporated under vacuum to form a second film, and the first film and the second film are formed into the hole injecting / transporting material and the hole constituting the hole injecting layer 30. The hole injection layer 30 and the hole transport layer 40 are formed by heating to a temperature higher than the glass transition temperature of the higher one of the hole injection transport material constituting the transport layer 40.

  Also in this method, the first film to be the hole injection layer 30 and the second film to be the hole transport layer 40 formed by vacuum deposition are heated at the above temperature, so that the doping material is added to the hole injection layer 30. The hole injection barrier 30 between the anode 20 and the hole injection layer 30 is made smaller than when not doped, and the hole injection layer 30 and the hole transport layer 40 are compared with the case where only the hole injection layer 30 is doped with a doping material. The hole injection barrier between them becomes smaller. This has been found by the inventors' experiments.

  This method is further classified according to heating timing. First, each material constituting the hole injection layer 30 is co-evaporated to form a first film, and the first film is subjected to heating at a temperature equal to or higher than the glass transition temperature. Form. Next, each material constituting the hole transport layer 40 is co-evaporated directly on the hole injection layer 30 to form a second film, and the second film is subjected to heating at the glass transition temperature or higher. Then, the hole transport layer 40 is formed.

  Second, the materials constituting the hole injection layer 30 are co-evaporated to form a first film, and the materials constituting the hole transport layer 40 are co-evaporated directly on the first film. A hole injection layer 30 and a hole transport layer 40 are formed by forming a second film and then subjecting the first and second films to heating at the glass transition temperature or higher.

  By these methods, the doped layers 30 and 40 can be appropriately formed. In the first method, when the hole injecting and transporting materials of both layers 30 and 40 are the same, the heating temperature in the method is the same for both the first film and the second film. Good.

  Thus, in the present embodiment, the hole injection layer 30 must be doped with the doping material, and the hole transport layer 40 is also doped with the doping material as necessary.

  By doping the hole transport layer 40 with the above doping material, the hole injection barrier between the hole injection layer 30 and the hole transport layer 40 immediately above the hole transport layer 40 is made smaller than when the hole transport layer 40 is not doped with the doping material. can do.

  Therefore, when the hole transport layer 40 is doped with the above doping material, from the viewpoint of reducing the hole injection barrier at the interface between the hole injection layer 30 and the hole transport layer 40, the hole injection layer 30 side of the hole transport layer 40. The doping material may be doped only in a portion close to the region, and the portion close to the light emitting layer 50 side may not be doped.

  The film thickness of the hole injection layer 30 and the hole transport layer 40 is 10 to 150 nm, preferably 20 to 100 nm. In particular, the thickness of the hole injection layer 30 is preferably 60 nm or more.

  If the unevenness due to foreign matter on the surface of the anode 20 is large, a short circuit between the anode 20 and the cathode 80 due to this is likely to occur. However, if the hole injection layer 30 is made thick to this extent, the unevenness is absorbed. Therefore, it is easy to avoid problems such as the short circuit.

  Moreover, the light emitting layer 50 located on the hole transport layer 40 is obtained by vacuum-depositing a host compound or co-depositing a host compound and a dope material. Further, if necessary, the light emitting layer 50 is formed by separating the light emitting layer 50 into a single layer or multiple layers and forming each of them to a thickness of 10 to 100 nm. In the region of the light emitting layer 50, electron-hole recombination occurs, and as a result, light emission is observed.

  As the host material in the light emitting layer 50, a material having both hole transport properties and electron transport properties is preferable. Such a host material may be formed from a single compound such as tris (8-quinolinolato) aluminum (hereinafter referred to as “Alq3”), or a mixture of a hole injecting and transporting material and an electron transporting material. May be.

  When these are mixed, the hole injection / transport material in the host material may be a substance selected from the hole injection / transport materials used for the hole injection layer 30 and the hole transport layer 40. Further, as the electron transporting substance in the host material, a substance selected from electron transporting substances used for the electron transporting layer 60 described later can be used.

  As a dopant in the light emitting layer 50, the fluorescent pigment material generally used in an organic EL element can be used.

  Examples of such fluorescent dye materials include perylene that emits blue light, styrylamine derivatives, rubrene that emits yellow light, coumarin that emits green light, and dimethylquinacridone. Moreover, the dopant in the light emitting layer 50 can be made into the ratio of 0.05 to 50 weight% with respect to the whole host material, desirably 0.1 to 30 weight%.

  Next, in FIG. 1, the electron transport layer 60 positioned on the light emitting layer 50 is usually in close contact with the light emitting layer 50 to form one or more organic compounds having a high electron affinity to a thickness of 10 to 100 nm. It is formed by filming. When using a plurality of electron transporting substances, the plurality of electron transporting substances may be uniformly mixed to form a single layer, or a plurality of layers adjacent to each electron transporting substance without mixing. You may form in.

  Preferred electron transporting substances include quinolinol metal complexes, anthracene derivatives, cyclic ketones such as benzoquinone, anthraquinone, and fluorenone, derivatives thereof, and silazane derivatives. Of these, quinolinol metal complexes such as tris (8-quinolinolato) aluminum (Alq3) are most preferable.

  The electron injection layer 70 is made of a metal fluoride or a metal oxide. Here, the metal fluoride layer can be selected from alkali fluoride or alkaline earth fluoride. The metal oxide layer can be selected from alkali oxides or alkaline earth oxides.

  This alkali fluoride includes lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, or cesium fluoride. The alkali oxide includes lithium oxide, sodium oxide, potassium oxide, rubidium oxide, or cesium oxide.

  The alkaline earth fluoride includes magnesium fluoride, calcium fluoride, strontium fluoride, or barium fluoride. The alkaline earth oxide includes magnesium oxide, calcium oxide, strontium oxide. Or barium oxide.

  Such an electron injection layer 70 made of a fluoride layer or a metal oxide layer can be formed by a vapor deposition method, and has a thickness in the range of, for example, 0.2 nm to 2.0 nm.

  The cathode 80 has a low work function (usually 5 eV or less). For example, a metal or metal oxide such as lithium, magnesium, calcium, sodium, lithium, silver, copper, aluminum, or indium, or a conductive compound is used alone or in combination. It is formed by vapor deposition. The thickness of the cathode 80 is not particularly limited, and the thickness is usually 10 nm or more so that the resistivity is 1 kΩ / □ or less, taking into consideration the electrical conductivity, the manufacturing cost, the thickness of the entire device, the light transmittance, and the like. Desirably, it is set to 50 nm to 500 nm.

  The specific materials described above are known ones, but are merely examples, and the materials used in the present embodiment should not be limited to these. In the present embodiment, the host material used for the hole injection layer 30, the hole transport layer 40, the light emitting layer 50, and the electron transport layer 60 has a glass transition temperature of 110 ° C. or higher in order to improve durability at high temperatures. It is preferable that

In forming the layers 20 to 80 in the organic EL element 100, in order to minimize the oxidation and decomposition of the organic compound, and the adsorption of oxygen and moisture, etc., under high vacuum, specifically 10 ^{-5 It} is desirable to work consistently below Torr.

  Further, in the hole injection layer 30 and the light emitting layer 50, and in the hole transport layer 40 in the case where the doping is performed, the host material and the doping material are mixed in a predetermined ratio in advance, or in vacuum deposition The mixing ratio of both materials is adjusted by controlling the heating rate of both materials independently of each other.

  In the organic EL element 100 formed in this way, a part or the whole of the element is sealed with, for example, sealing glass or a metal cap in an inert gas atmosphere in order to minimize deterioration in the use environment. Alternatively, it is desirable to cover with a protective layer made of an ultraviolet curable resin or the like.

  A method of using the organic EL element 100 of the present embodiment will be described. The organic EL element 100 applies a relatively high voltage pulsed voltage intermittently or a relatively low voltage depending on the application. A DC voltage (usually 3 to 50 V) is applied continuously to drive.

  The organic EL element 100 emits light only when the potential of the anode 20 is higher than the potential of the cathode 80. Therefore, the voltage applied to the organic EL element 100 may be direct current or alternating current, and the waveform and period of the applied voltage may be appropriate.

  When a direct current is applied, the organic EL element 100 increases in luminance in proportion to the applied direct current value in principle. In the case of the organic EL device 100 shown in FIG. 1, when a voltage is applied between the anode 20 and the cathode 80, holes injected from the anode 20 pass through the hole injection layer 30 and the hole transport layer 40 to the light emitting layer 50, Electrons injected from the cathode 80 reach the light emitting layer 50 through the electron injection layer 70 and the electron transport layer 60, respectively.

  As a result, recombination of holes and electrons occurs in the light emitting layer 50, and light emission of a target color is emitted through the anode 20 and the substrate 10 from the excited dope thus generated.

  By the way, according to the present embodiment, the hole injection layer 30 is doped with a doping material made of a compound having an electron-withdrawing group that is stable in the atmosphere, and a new energy level is formed in the hole injection layer 30. Since the hole injection barrier between 20 and the hole injection layer 30 is reduced, the organic EL element 100 with a reduced driving voltage can be provided. Furthermore, in this embodiment, the organic EL element 100 is provided in which the increase in driving voltage is small even if the hole injection layer 30 is thickened.

  Such an organic EL element 100 that can be driven at a low voltage can be used for light emission with high brightness and development on a large panel, and can be applied to a low-cost driver IC.

  Moreover, when using the organic EL element 100 of this embodiment mounted in a motor vehicle or a vehicle, it is inevitable that it becomes a high temperature environment (for example, about 70 to 80 ° C.). Among the organic layers, an amorphous organic layer is crystallized when the glass transition temperature is reached or higher, and unevenness on the surface of the film increases, and current leakage tends to occur. Therefore, in order to improve the high-temperature heat resistance, when used in a vehicle, as described above, the glass transition temperature of all the host materials of the organic layers 30 to 60 in the organic EL element 100 should be 110 ° C. or higher. Is preferred.

  Next, the first embodiment will be described more specifically with reference to the following examples and comparative examples, although not limited thereto.

[Example 1]
An anode 20 made of ITO having a thickness of 150 nm was formed on the glass substrate 10 by sputtering. After patterning, the ITO surface was polished.

  As a hole injection layer 30 on the anode 20, 4,4 ′, 4 ″ -tris (N, N- (2-naphthyl) phenylamino) triphenylamine (abbreviation: 2-TNATA, glass transition temperature: 110 ° C.) ) And 2-TNATA, 5% by weight of 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H, 31H-phthalocyanine (abbreviation: F-CuPc) was co-evaporated in a vacuum to form a film having a thickness of 200 nm, and this film was heated at 150 ° C. above the glass transition temperature of 2-TNATA for 10 minutes, A hole injection layer 30 was produced.

In addition, when the ultraviolet photoelectron spectroscopy (UPS) measurement of the separately prepared hole injection layer 30 was performed, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30, that is, the hole injection barrier is It was as small as 0.1 eV. Here, the UPS measurement is performed by irradiating the hole injection layer 30 with ultraviolet rays (He I, 21.2 eV) in an ultrahigh vacuum of the order of 10 ⁻¹⁰ Torr and measuring the energy of photoelectrons emitted from the sample surface. did.

  Further, X-ray photoelectron spectroscopy (XPS) measurement was performed on the same hole injection layer 30 as that subjected to UPS measurement. The result is shown in FIG. As shown in FIG. 2, in the hole injection layer 30 of this example, it was confirmed that the bond between carbon and fluorine was increased. From this result, it was suggested that impurities were detached from the inside of the layer by heating, and fluorine atoms were effectively bonded to carbon atoms of the dopant molecules, thereby increasing the doping effect.

Incidentally, FIG. 3 is a diagram showing the result of XPS measurement similarly performed on a film in which 2-TNATA not doped with F-CuPc is heated at 150 ° C. for 10 minutes. In this case, the bond between carbon and fluorine is shown. The increase was hardly observed. Here, the XPS measurement in FIGS. 2 and 3 is performed by irradiating the surface of the sample with X-rays (Mg Kα, 1253.6 eV) in an ultrahigh vacuum of the order of 10 ⁻¹⁰ Torr, and the energy of the photoelectrons emitted from the surface of the sample. We carried out by measuring.

  Further, in this example, N, N′-bis (4-diphenylamino-4′-biphenyl) -N, N′-diphenylbenzidine (abbreviation: DAP-DPB, glass transition temperature: 140 ° C.) as the hole transport layer 40. ) Was formed to a thickness of 50 nm by vacuum deposition.

  And as the light emitting layer 50, Alq3 (glass transition temperature: 167 degreeC) was used for host material, and the layer which added 1% of dimethyl quinacridone as dope material was formed by thickness 60nm by the vacuum evaporation method. Further, Alq3 was formed thereon as an electron transport layer 60 by a vacuum evaporation method to a thickness of 20 nm.

  After these organic layers 30 to 60 were formed, lithium fluoride was formed as an electron transport layer 70 thereon by a thickness of 0.5 nm by vacuum deposition. Furthermore, as a cathode 80 thereon, Al was formed to a thickness of 150 nm by vacuum deposition.

When a DC current of 10 V was applied to the organic EL element thus completed, the current density was 60 mA / cm ² and the luminance was 4000 cd / m ² . In the organic EL device of this example, the half-luminance life at + 25 ° C. at a luminance of 4000 cd / m ² was 200 hours.

[Comparative Example 1]
An organic EL element was produced in the same manner as in Example 1 except that only 2-TNATA was vacuum-deposited as the hole injection layer 30 and formed at a thickness of 200 nm. That is, the organic EL element was manufactured without doping the hole injection layer 30 with the doping material.

  When the UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30 was 0.45 eV, which was compared with Example 1 above. It was quite big.

  FIG. 4 is a diagram showing the result of XPS measurement of the hole injection layer 30 of this example, and the XPS measurement is performed in the same manner as described above without performing the heat treatment above the glass transition temperature for the film made of only 2-TNATA. It is a figure which shows the result. As shown in FIG. 4, in this example, it was hardly observed that the bond between carbon and fluorine was increased.

When a direct current of 10 V was applied to the organic EL element of this example, the current density was 30 mA / cm ² and the luminance was 2000 cd / m ² . In order to obtain a luminance of 4000 cd / m ² , it was necessary to apply a DC current of 12V, and it was necessary to apply a voltage 2V higher than that in Example 1.

In the organic EL device of this example, the half-luminance lifetime at + 25 ° C. at a luminance of 4000 cd / m ² was 100 hours. That is, the organic EL element of the first embodiment represented by the above Example 1 is also effective in extending the luminance life.

[Comparative Example 2]
As the hole injection layer 30, 5% by weight of F-CuPc is co-deposited in vacuum with respect to 2-TNATA, but the same as in Example 1 except that the subsequent heat treatment at 150 ° C. is not performed. An organic EL element was produced. That is, an organic EL element was produced without performing a heat treatment at 150 ° C., which is higher than the glass transition temperature of 2-TNATA of the hole injection layer 30 for 10 minutes.

  When the UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30 was 0.45 eV, which was compared with Example 1 above. It was quite big.

  Moreover, FIG. 5 is a figure which shows the result of the XPS measurement of the hole injection layer 30 of this example, and it does not heat-process about the film | membrane which doped F-CuPc (5%) to 2-TNATA similarly to the above-mentioned XPS measurement. It is a figure which shows the result. As shown in FIG. 5, in this example, it was hardly observed that the bond between carbon and fluorine was increased.

When a direct current of 10 V was applied to the organic EL element of this example, the current density was 32 mA / cm ² and the luminance was 2200 cd / m ² . In order to obtain a luminance of 4000 cd / m ² , it was necessary to apply a DC current of 12V, and it was necessary to apply a voltage 2V higher than that in Example 1. Thus, there was almost no effect if only doping was performed without heating above the glass transition temperature.

  That is, as in this example, in the hole injection layer 30, when the host material is simply doped with the doped material and no bond is formed by the doped material, the hole injection layer 30 is made of only the hole injecting and transporting material. Compared to the case of the configuration, the hole injection barrier between the anode 20 and the hole injection layer 30 is not substantially changed, and the drive voltage is not reduced.

[Example 2]
As the hole injection layer 30, zinc 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexa 5% by weight with respect to 2-TNATA. Organic EL in the same manner as in Example 1 except that decafluoro-29H, 31H-phthalocyanine (abbreviation: F-ZnPc) is co-evaporated in vacuum and the heat treatment is performed to form a 200 nm thick film. An element was produced. That is, the hole injection layer 30 was doped with F-ZnPc instead of F-CuPc to produce an organic EL element.

  When UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the ITO work function of the anode 20 and the HOMO level energy barrier of the hole injection transport layer 30 were 0.1 eV, which was the same as in Example 1 above. It was very small.

  Further, when XPS measurement was performed in the same manner as described above, it was confirmed that the bond between carbon and fluorine was increased as in Example 1. From this result, it was suggested that impurities were detached from the inside of the layer by heating, and fluorine atoms were effectively bonded to carbon atoms of the dopant molecules, thereby increasing the doping effect.

When a direct current of 10 V was applied to the organic EL element of this example, the current density was 59 mA / cm ² and the luminance was 3800 cd / m ² . That is, also in this example, the effect of reducing the driving voltage was remarkable as in the first example.

[Example 3]
As the hole injection layer 30, 8% by weight of 1,2,3,4,5,6-hexa (4-trifluoromethylphenyl) benzene (abbreviation: HFMP-B) with respect to 2-TNATA is co-evaporated in a vacuum. Then, an organic EL element was produced in the same manner as in Example 1 except that the heat treatment was performed to form a 200 nm thick film. That is, the hole injection layer 30 was doped with HFMP-B instead of F-CuPc to produce an organic EL element.

  When the UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30 was 0.15 eV. It was very small.

  Further, when XPS measurement was performed in the same manner as described above, it was confirmed that the bond between carbon and fluorine was increased as in Example 1. From this result, it was suggested that impurities were detached from the inside of the layer by heating, and fluorine atoms were effectively bonded to carbon atoms of the dopant molecules, thereby increasing the doping effect.

When a direct current of 10 V was applied to the organic EL element of this example, the current density was 58 mA / cm ² and the luminance was 3700 cd / m ² . That is, also in this example, the effect of reducing the driving voltage was remarkable as in the first example.

[Example 4]
As the hole injection layer 30, 8% by weight of 1,2,3,4,5,6-hexa (4-fluorophenyl) benzene (abbreviation: HFP-B) with respect to 2-TNATA was co-evaporated in a vacuum, An organic EL element was produced in the same manner as in Example 1 except that the heat treatment was performed to form a 200 nm thick film. That is, the hole injection layer 30 was doped with HFP-B instead of F-CuPc to produce an organic EL element.

  When the UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30 was 0.15 eV. It was very small.

  Further, when XPS measurement was performed in the same manner as described above, it was confirmed that the bond between carbon and fluorine was increased as in Example 1. From this result, it was suggested that impurities were detached from the inside of the layer by heating, and fluorine atoms were effectively bonded to carbon atoms of the dopant molecules, thereby increasing the doping effect.

When a direct current of 10 V was applied to the organic EL element of this example, the current density was 58 mA / cm ² and the luminance was 3700 cd / m ² . That is, also in this example, the effect of reducing the driving voltage was remarkable as in the first example.

[Example 5]
As the hole injection layer 30, 8% by weight of tetrafluorotetracyanoquinodimethane (abbreviation: TFCN-QM) is co-deposited in vacuum with respect to 2-TNATA, and the heat treatment is performed to form a film having a thickness of 200 nm. An organic EL element was produced in the same manner as in Example 1 except that. That is, the hole injection layer 30 was doped with TFCN-QM instead of F-CuPc to produce an organic EL element.

  When UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30 was as very small as 0.13 eV.

  Further, when XPS measurement was performed in the same manner as described above, it was confirmed that the bond between carbon and fluorine was increased as in Example 1. From this result, it was suggested that impurities were detached from the inside of the layer by heating, and fluorine atoms were effectively bonded to carbon atoms of the dopant molecules, thereby increasing the doping effect.

When a direct current of 10 V was applied to the organic EL element of this example, the current density was 58 mA / cm ² and the luminance was 3800 cd / m ² . That is, also in this example, the effect of reducing the driving voltage was remarkable as in the first example.

[Example 6]
Similarly to Example 1 above, 2-TNATA and F-CuPc were co-deposited in vacuum and heated at 150 ° C. for 10 minutes to form the hole injection layer 30. On top of that, DAP-DPB and 5% by weight of F-CuPc were co-evaporated in vacuum to form a 20 nm thick film, which was heated at 150 ° C. for 10 minutes, and only DAP-DPB was further deposited thereon. The hole transport layer 40 was formed by forming a film thickness of 30 nm.

  Here, the hole transport layer 40 is configured by combining the above-described doped 20 nm-thick film and undoped 30 nm-thick film. Other than this, an organic EL device was produced in the same manner as in Example 1.

  That is, in this example, the hole transport layer 40 is also doped with F-CuPc, which is a doped material, to form a bond with the doped material. Further, in this example, the doping material is doped only in the portion near the hole injection layer 30 side in the hole transport layer 40.

  When UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30 was 0.1 eV, which was the same as in Example 1 above. It was very small.

  Further, when the UPS measurement was similarly performed for the hole transport layer 40 of this example, the hole injection barrier between the hole injection layer 30 and the hole transport layer 40 is 0 in the case of the hole transport layer 40 without doping. In the present example in which the hole transport layer 40 was doped, it was as small as 0.2 eV.

  Further, when XPS measurement was performed on the hole injection layer 30 and the hole transport layer 40 of this example in the same manner as described above, in both the layers 30 and 40, as in Example 1, the bond between carbon and fluorine increased. It was confirmed that From this result, it was suggested that impurities were detached from the inside of the layer by heating, and fluorine atoms were effectively bonded to carbon atoms of the dopant molecules, thereby increasing the doping effect.

When a 10 V direct current was applied to the organic EL element of this example, the current density was 65 mA / cm ² and the luminance was 4300 cd / m ² . That is, also in this example, the effect of reducing the driving voltage was remarkable as in the first example.

  In Example 6, after the first film (2-TNATA and F-CuPc) to be the hole injection layer 30 was formed, the hole injection layer 30 was formed by heating the first film. After the second film (DAP-DPB and 5 wt% F-CuPc) to be the hole transport layer 40 is formed, this is heated, and further, only DAP-DPB is formed thereon to transport the hole. Layer 40 is formed.

  Here, as described above, the hole injection layer 30 and the hole transport layer 40 similar to the present example can be formed even if the timing of the heat treatment is changed. For example, a first film (2-TNATA and F-CuPc) to be the hole injection layer 30 is formed, and a second film (DAP-DPB and 5 wt% F--) to be the hole transport layer 40 is formed thereon. After forming CuPc), both layers 30 and 40 may be formed by heating both films at about 150 ° C. and further forming only DAP-DPB thereon.

  Further, after the first film is formed, a film of DAP-DPB and 5 wt% F-CuPc and a film of only DAP-DPB are sequentially formed thereon, and these become the hole transport layer 40. Both layers 30 and 40 may be formed by configuring as the second film and then subjecting the first and second films to the heat treatment.

[Example 7]
As the hole injection layer 30, 25 wt% zinc 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexa with respect to 2-TNATA Organic EL in the same manner as in Example 1 except that decafluoro-29H, 31H-phthalocyanine (abbreviation: F-ZnPc) is co-evaporated in a vacuum and the heat treatment is performed to form a film having a thickness of 200 nm. An element was produced. In other words, the hole injection layer 30 was doped with 25 wt% F—ZnPc instead of 5 wt% F—CuPc to produce an organic EL device.

  When UPS measurement was performed on the hole injection layer 30 in the same manner as described above, the ITO work function of the anode 20 and the HOMO level energy barrier of the hole injection transport layer 30 were 0.1 eV, which was the same as in Example 1 above. It was very small.

  Further, when XPS measurement was performed in the same manner as described above, it was confirmed that the bond between carbon and fluorine was increased as in Example 1. From this result, it was suggested that impurities were detached from the inside of the layer by heating, and fluorine atoms were effectively bonded to carbon atoms of the dopant molecules, thereby increasing the doping effect.

When a direct current of 10 V was applied to the organic EL element of this example, the current density was 57 mA / cm ² and the luminance was 3700 cd / m ² . That is, also in this example, the effect of reducing the driving voltage was remarkable as in the first example.

  As described above, this embodiment uses a doped material that is stable and can be vacuum-deposited in the atmosphere, unlike the conventional case. In addition to doping the doped material into the hole injection layer 30, heating is performed. The hole injection barrier between the anode 20 and the hole injection layer 30 is made smaller than when the doping material is not doped into the hole injection layer 30 by treatment or the like. Thereby, the hole injection layer 30 can be appropriately produced by a normal vacuum deposition method, and the driving voltage of the organic EL element 100 can be reduced.

  Further, as shown in each of the above examples, according to the first embodiment, a relatively low driving voltage can be ensured even when the hole injection layer 30 is made as thick as about 200 nm. An organic EL element in which the increase in driving voltage due to the increase in thickness of 30 is small can be expected. Further, as described above, the driving voltage can be further reduced by adopting a configuration in which the hole transport layer 40 is similarly doped with a doping material.

  The organic EL element 100 shown in FIG. 1 represents an embodiment of the present invention. The organic EL element includes an anode on a substrate, a hole injection layer directly above the anode, An organic layer including a light emitting layer and a cathode may be formed on the upper portion. In some cases, the above-described hole transport layer, electron transport layer, electron injection layer, or the like may be omitted.

(Second Embodiment)
FIG. 6 is a diagram showing a schematic cross-sectional configuration of an organic EL element 101 according to the second embodiment of the present invention.

  The organic EL element 101 of the present embodiment also has an anode 20, a hole injection layer 30, a hole transport layer 40, a light emitting layer 50, an electron transport layer 60, an electron injection layer 70, and a cathode 80 on the substrate 10. The hole transport layer 40, the light emitting layer 50, and the electron transport layer 60 constitute the organic layers 40 to 60 including the light emitting layer 50 in the present invention.

  Here, in the present embodiment, as shown in FIG. 6, an intervening layer as a layer made of a material having an electron-withdrawing group that does not change even when exposed to the atmosphere, between the anode 20 and the hole injection layer 30. 90 is different from the organic EL element of the first embodiment. Hereinafter, this difference will be mainly described.

  The material constituting the intervening layer 90 may be the same as the doped material doped in the hole injection layer 30 in the first embodiment. Specifically, the material of the intervening layer 90 includes organic halogen compounds such as F-CuPc and F-ZnPc as described above. These are materials that do not change even when exposed to the atmosphere, do not decompose or react in the atmosphere, and do not deteriorate in purity when exposed to the atmosphere.

  The intervening layer 90 is a layer obtained by thinning the above material alone immediately above the anode 20, and can be formed by vapor deposition by a vacuum vapor deposition method. The hole injection layer 30 itself is formed by vacuum deposition directly on the intervening layer 90 using a normal hole injection / transport material such as 2-TNATA described above.

  Furthermore, in the present embodiment, the intervening layer 90 and the hole injection layer 30 thus formed on the anode 20 by vacuum deposition are equal to or higher than the glass transition temperature of the hole injection / transport material constituting the hole injection layer 30. It was heated.

  Thereby, in this embodiment, when there is no intervening layer 90 immediately above the anode 20, that is, when a hole injection layer is provided immediately above the anode as in the prior art, the gap between the anode 20 and the hole injection layer 30 is higher. The hole injection barrier is made smaller. This hole injection barrier is based on ultraviolet photoelectron spectroscopy (UPS) measurement, as in the first embodiment.

  Here, the thickness of the intervening layer 90 is preferably 30 nm or less. If it exceeds 30 nm, the intervening layer 90 that does not interact with the hole injection layer 30 is not preferable because it inhibits carrier transmission.

  As described above, in the organic EL element 101 of the present embodiment, the anode 20, the intermediate layer 90 immediately above the anode 20, the hole injection layer 30 immediately above the intermediate layer 90, and the hole injection layer 30 are further formed on the substrate 10. In the upper part, organic layers 30 to 60 including the light emitting layer 50 and a cathode 80 are formed. Here, the organic layers 30 to 60 and the cathode 80 of the present embodiment can be the same as those in the first embodiment.

  Then, according to the present embodiment, the intervening layer 90 and the hole injection layer 30 made of a material that has an electron-withdrawing group and does not change even when exposed to the atmosphere are formed directly on the anode 20 by vacuum deposition. Since a new energy level is formed in the layer 30 and the hole injection barrier between the anode 20 and the hole injection layer 30 is reduced, the organic EL element 101 with a reduced driving voltage can be provided.

  Also in this embodiment, if the host material constituting the organic layers 40 to 60 including the hole injection layer 30 and the light emitting layer 50 is made to have a glass transition temperature of 110 ° C. or higher, the organic EL for automobiles. It is preferable as the element 101.

  In the first embodiment, the hole injecting / transporting material is doped with a compound material that has an electron withdrawing group and does not change even when exposed to the atmosphere to form a hole injecting layer 30, which is above the glass temperature. In the second embodiment, the same material is used as a single layer 90 that is separate from the hole injection layer 30, whereas the hole injection barrier is reduced by subjecting it to heat treatment. The same effect is demonstrated.

  Next, the second embodiment will be described more specifically with reference to the following examples and comparative examples, although not limited thereto.

[Example 8]
An anode 20 made of ITO having a thickness of 150 nm was formed on the glass substrate 10 by sputtering. After patterning, the ITO surface was polished.

  On the anode 20, as the intervening layer 90, F-ZnPc was vacuum-deposited to form a film having a thickness of 10 nm. On top of that, 2-TNATA (glass transition temperature: 110 ° C.) was deposited as a hole injection layer 30 in a vacuum to form a film having a thickness of 100 nm. And these films | membranes were heated for 10 minutes at 150 degreeC above the glass transition temperature of 2-TNATA.

In addition, when UPS measurement of the hole injection layer 30 was carried out with an element manufactured in the same manner, the energy barrier between the ITO work function of the anode 20 and the HOMO level of the hole injection layer 30, that is, the hole injection barrier was 0. It was very small as 07 eV. Here, the UPS measurement is performed by irradiating the hole injection layer 30 with ultraviolet rays (He I, 21.2 eV) in an ultrahigh vacuum of the order of 10 ⁻¹⁰ Torr and measuring the energy of photoelectrons emitted from the sample surface. did.

  Further, when XPS measurement was performed using the same element as that used for the UPS measurement, as in the case of FIG. 2 above, in the hole injection layer 30 of this example, the bond between carbon and fluorine increased. Was confirmed. From this result, it was found that F-ZnPc, which is an intervening layer, permeates into the hole injection layer 30 by heating, and the same effect as when the hole injection layer 30 is doped with F-ZnPc is obtained.

  Further, FIG. 7 shows a case where F-ZnPc as an intervening layer 90 and 2-TNATA as a hole injection layer 30 are formed on the anode 20 in this embodiment and heated at 150 ° C. for 10 minutes. It is a figure which shows the result of having performed secondary ion mass spectrometry (SIMS analysis) from the surface side of the layer 30, FIG. 8 shows the same film formation as FIG. It is a figure which shows the result.

  Here, in the depth (unit: nm) in FIGS. 7 and 8, the surface of the hole injection layer 30, that is, the surface of the hole injection layer 30 on the hole transport layer side is set to a depth of 0. As can be seen from the results of these SIMS analyses, in this example shown in FIG. 7, the composition change is sharper at the interface between the anode 20 and the hole injection layer 30 than in the comparative example shown in FIG. It is confirmed that F-ZnPc existing in a layered form is diffused into the hole injection layer 30 with a gentle gradient composition.

  That is, the steepness of the composition change at the interface is reduced due to the diffusion of F which is an electron-withdrawing group of F—ZnPc as the intervening layer 90 into the interface. From this, it is considered that 2-TNATA is doped with F-ZnPc at a high concentration at the interface between the anode 20 and the 2-TNATA as the hole injection layer 30. As a result, the carrier injection barrier from the anode 20 to 2-TNATA is reduced.

  Further, as can be seen from FIGS. 7 and 8, in this example, fluorine is concentrated in the vicinity of depth 0, that is, on the surface of the hole injection layer 30, as compared with the comparative example, due to heating at the glass transition temperature or higher. Is confirmed.

  This fluorine is known to contain many components obtained by fragmenting the fluorine compound from XPS analysis. When a hole transport layer 40 is further formed on the hole injection layer 30, the hole It is easily envisioned to diffuse into the transport layer 40.

  That is, by performing SIMS analysis in the same manner as that shown in FIG. 7, it was confirmed that fluorine that is an electron-withdrawing group of the intervening layer 90 segregates at the interface between the hole injection layer 30 and the hole transport layer 40. You can say that you can.

  Further, even at the interface between the heated hole injection layer 30 and the hole transport layer 40 newly formed thereon, the hole transport layer 40 is in a state of being highly doped with fluorinated material, and the interface barrier is reduced. it is conceivable that.

  Thereafter, in this example, N, N′-bis (4-diphenylamino-4′-biphenyl) -N, N′-diphenylbenzidine (abbreviation: DAP-DPB, glass transition temperature) is used as the hole transport layer 40. : 140 ° C.) was formed to a thickness of 50 nm by a vacuum deposition method.

  And as the light emitting layer 50, Alq3 (glass transition temperature: 167 degreeC) was used for host material, and the layer which added 1% of dimethyl quinacridone as dope material was formed by thickness 60nm by the vacuum evaporation method. Further, Alq3 was formed thereon as an electron transport layer 60 by a vacuum evaporation method to a thickness of 20 nm.

  After these organic layers 30 to 60 were formed, lithium fluoride was formed as an electron transport layer 70 thereon by a thickness of 0.5 nm by vacuum deposition. Furthermore, as a cathode 80 thereon, Al was formed to a thickness of 150 nm by vacuum deposition.

When a direct current of 10 V was applied to the organic EL element thus completed, the current density was 70 mA / cm ² and the luminance was 4700 cd / m ² . In the organic EL device of this example, the half-luminance lifetime at + 25 ° C. at a luminance of 4700 cd / m ² was 300 hours. That is, in this example, the effect of reducing the drive voltage was significant.

[Example 9]
An organic EL element was produced in the same manner as in Example 8 except that the film thickness of F-ZnPc as the intervening layer 90 was 1 nm.

When a DC current of 10 V was applied to the organic EL element thus completed, the current density was 65 mA / cm ² and the luminance was 4300 cd / m ² . In the organic EL device of this example, the half-luminance life at + 25 ° C. at a luminance of 4300 cd / m ² was 230 hours. That is, also in this example, the effect of reducing the driving voltage was remarkable as in Example 8.

[Example 10]
An organic EL element was produced in the same manner as in Example 8 except that F-CuPc was used as the intervening layer 90 instead of F-ZnPc.

When a DC current of 10 V was applied to the organic EL element thus completed, the current density was 62 mA / cm ² and the luminance was 4100 cd / m ² . Further, in the organic EL device of this example, the half-luminance lifetime at + 25 ° C. at a luminance of 4100 cd / m ² was 200 hours. That is, also in this example, the effect of reducing the driving voltage was remarkable as in Example 8.

  In the second embodiment, the organic EL element 101 shown in FIG. 6 is a specific example of the present embodiment, and the organic EL element of the present embodiment is formed on a substrate. An anode, an intervening layer immediately above the anode, a hole injection layer directly above the anode, an organic layer including a light emitting layer above the cathode, and a cathode may be formed. In some cases, the hole transport layer or electron transport described above may be used. A structure in which layers, electron injection layers, and the like are omitted may be used.

  In addition, as described with reference to each of the above embodiments, the present invention provides the above-described UPS by forming and heating the hole injection layer 30, the hole transport layer 40, and the intervening layer 90 as described above. Of course, it is possible to reduce the hole injection barrier due to XPS, increase the bond between carbon and fluorine by XPS, or as a method of manufacturing an organic EL element that realizes the configuration confirmed by the SIMS.

It is a schematic sectional drawing of the organic EL element which concerns on 1st Embodiment of this invention. It is a figure which shows the XPS measurement result of C1s about the film | membrane which doped 2-TNATA with F-CuPc (5%) and was heated at 150 degreeC for 10 minutes. It is a figure which shows the XPS measurement result of C1s about the film | membrane which heated only 2-TNATA for 10 minutes at 150 degreeC. It is a figure which shows the XPS measurement result of C1s calculated | required without performing heat processing about the film | membrane which consists only of 2-TNATA. It is a figure which shows the XPS measurement result of C1s calculated | required without performing heat processing about the film | membrane which doped 2-TNATA to F-CuPc (5%). It is a schematic sectional drawing of the organic EL element which concerns on 2nd Embodiment of this invention. It is a figure which shows the result of having carried out SIMS analysis of what formed F-ZnPc and 2-TNATA into a film on the anode in 8th Example, and heated at 150 degreeC for 10 minute (s). It is a figure which shows the result of having carried out SIMS analysis of what formed F-ZnPc and 2-TNATA into a film on the anode as a comparative example, and did not heat-process.

Explanation of symbols

10 ... substrate, 20 ... anode, 30 ... hole injection layer, 40 ... hole transport layer,
50 ... light emitting layer, 60 ... electron transport layer, 70 ... electron injection layer, 80 ... cathode,
90: Intervening layer.

Claims (27)

On the substrate (10), an anode (20), a hole injection layer (30) directly above the anode (20), an organic layer (40-60) including a light emitting layer (50) thereon, and a cathode (80 In the organic EL element formed by
The hole injection layer (30) is doped with a doping material which is a compound having an electron-withdrawing group and does not change even when exposed to the atmosphere, and is formed by vacuum deposition, and the hole injection layer ( 30) An organic EL device, wherein the organic EL device is heated to a glass transition temperature or higher of the hole injecting and transporting material. The hole injection layer (30) is doped with a doping material which is a compound having an electron-withdrawing group and does not change even when exposed to the atmosphere, and is formed by vacuum deposition, and the hole injection layer ( 30) by heating above the glass transition temperature of the hole injecting and transporting material constituting
The hole injection barrier between the anode (20) and the hole injection layer (30) is made smaller than when the hole injection layer (30) is not doped with the doping material. The organic EL element of description. The hole injection layer (30) is doped with a doping material which is a compound having an electron-withdrawing group and does not change even when exposed to the atmosphere, and is formed by vacuum deposition, and the hole injection layer ( 30) by heating above the glass transition temperature of the hole injecting and transporting material constituting
3. The organic EL device according to claim 1, wherein an increase in the bond between carbon and the electron-withdrawing group in the hole injection layer is confirmed by XPS measurement. . An anode (20) on the substrate (10), a hole injection layer (30) immediately above the anode (20), a hole transport layer (40) directly above the hole injection layer (30), and a light emitting layer above the hole injection layer (30) In the organic EL element in which the organic layer (50-60) containing (50) and the cathode (80) are formed,
The hole injection layer (30) and the hole transport layer (40) are doped with a doping material which is a compound having an electron-withdrawing group and which does not change even when exposed to the atmosphere, and is formed by vacuum deposition. And an organic material that is heated to a temperature higher than a glass transition temperature of the higher one of the hole injecting and transporting material constituting the hole injecting layer (30) and the hole injecting and transporting material constituting the hole transporting layer (40). EL element. The hole injection layer (30) and the hole transport layer (40) are doped with a doping material which is a compound having an electron-withdrawing group and which does not change even when exposed to the atmosphere, and is formed by vacuum deposition. Then, by heating above the higher glass transition temperature of the hole injecting and transporting material constituting the hole injecting layer (30) and the hole injecting and transporting material constituting the hole transporting layer (40),
The hole injection barrier between the anode (20) and the hole injection layer (30) is made smaller than when the doping material is not doped into the hole injection layer (30), and the hole injection layer (30) 5. The organic EL according to claim 4, wherein a hole injection barrier between the hole injection layer (30) and the hole transport layer (40) is made smaller than when only the doping material is doped. element. The hole injection layer (30) and the hole transport layer (40) are doped with a doping material which is a compound having an electron-withdrawing group and which does not change even when exposed to the atmosphere, and is formed by vacuum deposition. Then, by heating above the higher glass transition temperature of the hole injecting and transporting material constituting the hole injecting layer (30) and the hole injecting and transporting material constituting the hole transporting layer (40),
6. The organic EL device according to claim 4, wherein an increase in the bond between carbon and the electron-withdrawing group is confirmed by XPS measurement in the hole injection layer (30). . The organic EL according to any one of claims 4 to 6, wherein the doped material is doped only in a portion of the hole transport layer (40) close to the hole injection layer (30) side. element. The organic EL element according to claim 1, wherein the hole injection layer has a thickness of 60 nm or more. The organic EL element according to claim 1, wherein the doping amount of the doping material is 30% by weight or less of the whole hole injection layer (30). The organic EL element according to claim 1, wherein the electron-withdrawing group in the dope material is halogen. The organic EL device according to claim 10, wherein the halogen is fluorine. The organic EL device according to claim 1, wherein the compound constituting the dope material has a phthalocyanine (Pc) skeleton. The compound constituting the dope material is copper 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H, 31H- The organic EL device according to claim 12, which is phthalocyanine (F-CuPc). The compound constituting the dope material is zinc 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H, 31H- It is a phthalocyanine (F-ZnPc), The organic EL element of Claim 12 characterized by the above-mentioned. An intervening layer (90) made of a material having an electron withdrawing group immediately above the anode (20) on the substrate (10) and not denatured even when exposed to the atmosphere, the intervening layer (90) A hole injection layer (30) immediately above, an organic layer (30-60) including a light emitting layer (50) above the hole injection layer (30), and a cathode (80);
The intervening layer (90) and the hole injection layer (30) are formed by vacuum deposition, and heated to a temperature equal to or higher than a glass transition temperature of a hole injection / transport material constituting the hole injection layer (30). Organic EL element to be used. The intermediate layer (90) and the hole injection layer (30) are formed by vacuum deposition, and heated to a temperature equal to or higher than the glass transition temperature of the hole injection transport material constituting the hole injection layer (30).
16. The organic EL device according to claim 15, wherein a hole injection barrier between the anode (20) and the hole injection layer (30) is made smaller than when the intervening layer (90) is not provided. . The intermediate layer (90) and the hole injection layer (30) are formed by vacuum deposition, and heated to a temperature equal to or higher than the glass transition temperature of the hole injection transport material constituting the hole injection layer (30).
The XPS measurement confirms that the bonding between carbon and the electron withdrawing group of the intervening layer (90) is increased in the hole injection layer (30). Or the organic EL element of 16. The intermediate layer (90) and the hole injection layer (30) are formed by vacuum deposition, and heated to a temperature equal to or higher than the glass transition temperature of the hole injection transport material constituting the hole injection layer (30).
The steepness of the composition change at the interface is reduced by the diffusion of the electron withdrawing group of the intervening layer (90) at the interface between the hole injection layer (30) and the anode (20). Furthermore, it is confirmed by SIMS analysis that the electron-withdrawing group is segregated at the interface between the hole injection layer (30) and the hole transport layer (40). 16. The organic EL device according to 16. The organic EL device according to any one of claims 15 to 18, wherein the electron-withdrawing group of the intervening layer (90) is halogen. The organic EL device according to claim 19, wherein the halogen is fluorine. 21. The organic EL element according to claim 15, wherein the material constituting the intervening layer (90) has a phthalocyanine (Pc) skeleton. The material constituting the intervening layer (90) is copper 1, 2, 3, 4, 8, 9, 10, 11, 15, 16, 17, 18, 22, 23, 24, 25-hexadecafluoro-29H. The organic EL device according to claim 21, wherein the organic EL device is 31H-phthalocyanine (F—CuPc). The material constituting the intervening layer (90) is zinc 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H. The organic EL device according to claim 21, wherein the organic EL device is 31H-phthalocyanine (F—ZnPc). The host material constituting the organic layer (40-60) including the hole injection layer (30) and the light emitting layer (50) has a glass transition temperature of 110 ° C or higher. The organic EL element as described in any one of -23. It is a manufacturing method of the organic EL element which manufactures the organic EL element as described in any one of Claims 1-3,
Forming the film by co-evaporating the dope material and the hole injection / transport material constituting the hole injection layer (30) under vacuum;
The hole injection layer (30) is formed by heating this film to a temperature equal to or higher than the glass transition temperature of the hole injection / transport material constituting the hole injection layer (30). Production method. It is a manufacturing method of the organic EL element which manufactures the organic EL element as described in any one of Claims 4-6,
The dope material and the hole injecting / transporting material constituting the hole injecting layer (30) are co-evaporated under vacuum to form a first film, and the hole transporting layer ( 40) and forming the second film by co-evaporating the dope material and the hole injecting and transporting material constituting 40) under vacuum,
The first film and the second film are higher in the hole injecting and transporting material constituting the hole injecting layer (30) and the hole injecting and transporting material constituting the hole transporting layer (40). A method for producing an organic EL element, wherein the hole injection layer (30) and the hole transport layer (40) are formed by heating to a glass transition temperature or higher. It is a manufacturing method of the organic EL element which manufactures the organic EL element as described in any one of Claims 15-18,
The intervening layer (90) and the hole injection layer (30) are formed by vacuum deposition, and heated to a temperature equal to or higher than the glass transition temperature of the hole injection / transport material constituting the hole injection layer (30). A method for producing an organic EL element.

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