JP2011091093A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode structure for organic EL, with which a large-sized organic EL panel can be easily manufactured. <P>SOLUTION: A top emission-type organic EL element 1,000 includes an anode 12, a light-emitting layer 15 formed over the anode 12, and a cathode 20 formed over the light-emitting layer 15, wherein the anode 12 is made of silver or silver alloy, and a hole injection layer 13 is formed of metal oxide on the anode 12, and a first section 13A of the hole injection hole 13 on a side of the anode 12 is less in oxygen content than a second section 13B on the opposite side from the side of the anode 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic EL element, and more particularly to an anode-side electrode structure used for a top emission type organic EL element including an anode, an organic light emitting layer, and a cathode.

  In recent years, research on organic semiconductor elements has been promoted. As a typical organic semiconductor element, there is an organic electroluminescent element using electroluminescence (hereinafter referred to as “organic EL element”). Organic EL elements are highly visible due to self-emission and are completely solid elements, so they have characteristics such as excellent impact resistance, and their use as light-emitting elements in various display devices has attracted attention. (For example, refer to Patent Document 1).

  The light emitting layer of the organic EL element has been developed in advance of a low molecular type because of the high light emission efficiency of the material and the long life (see, for example, Patent Documents 2 and 3). The low molecular light emitting layer is manufactured using a vacuum process such as vacuum deposition.

JP 2004-171951 A Japanese Patent No. 3369615 Japanese Patent No. 3789991

  It is difficult to manufacture a large-sized organic EL panel of 100 inch class by the low molecular type organic EL manufacturing technology. That is, when the vapor deposition method is used, it is difficult to maintain the mask alignment accuracy for each color (for example, R, G, B) in the mask vapor deposition in the step of forming the light emitting layer. Further, in the process of forming the electrode layer, the enlargement becomes a technical obstacle due to the problem of film thickness uniformity. Therefore, it is extremely difficult to manufacture a 100-inch class organic EL panel at a mass production level.

  The inventor of the present application tried to solve the problems of enlargement of the organic EL panel described above, instead of dealing with the extension of the conventional technique, in a new direction. Specifically, the electrode layer (anode and cathode) and the hole injection layer are formed by sputtering, and the organic layer such as the light emitting layer and the charge injection layer is formed by a wet process such as an ink jet method or a gravure printing method. An attempt was made to facilitate the enlargement of the organic EL panel and the mass production of the large panel using the organic EL technology.

  The present invention has been made in view of the knowledge newly found in such attempts, and the main object thereof is an electrode structure for organic EL capable of easily manufacturing a large organic EL panel. Is to provide.

  The organic EL device according to the present invention is a top emission type organic EL light-emitting device including an anode, an organic light-emitting layer formed above the anode, and a cathode formed above the organic light-emitting layer. The anode is made of silver or a silver alloy, a hole injection layer made of a metal oxide is formed on the anode, and the oxygen content of the first portion located on the anode side of the hole injection layer is The oxygen content of the second part located on the side opposite to the anode side is smaller.

  In a preferred embodiment, the first part and the second part in the hole injection layer are made of tungsten oxide having different oxygen contents.

  In a preferred embodiment, the hole injection layer is a metal oxide layer formed by a sputtering film forming method.

  The organic EL device manufacturing method according to the present invention includes a first step of preparing a substrate, a second step of forming an anode containing silver or a silver alloy on the substrate, and a sputtering process on the anode. Forming a hole injection layer made of a metal oxide by a film method, wherein the third step forms a first portion of the hole injection layer on the anode; and Forming a second portion having an oxygen content larger than that of the first portion on the first portion.

  According to the present invention, in the configuration in which the anode includes silver or a silver alloy, the oxygen content of the first portion located on the anode side in the hole injection layer laminated on the anode is located on the side opposite to the anode side. Since it is smaller than the oxygen content rate of the 2nd site | part to do, the oxidation of the surface of the anode used as a reflective surface can be suppressed. As a result, it is possible to suppress a decrease in reflectance in the top emission type organic semiconductor element.

  The first part in the hole injection layer has a role of suppressing the decrease in reflectivity, the second part has a role of maintaining the hole injection characteristic, and each can be made of the same material (for example, tungsten oxide). it can. Note that it is possible to achieve both the suppression of the decrease in reflectance and the maintenance of the hole injection characteristics by the lamination process of the same material.

  Note that the first part and the second part in the hole injection layer can be made of different materials. In that case, the 1st site | part in a hole injection layer can be comprised from ITO (indium tin oxide).

  Both the anode and the hole injection layer are preferably formed by sputtering. By forming both of them by sputtering, it is possible to easily increase the size and facilitate mass production.

The figure which shows typically the cross-sectional structure of the organic EL element of embodiment. Sectional drawing which shows the structure of the electrode structure of embodiment The figure explaining the manufacturing method of the electrode structure of embodiment (a)-(c). The figure explaining the manufacturing method of the electrode structure of embodiment (a)-(c). The figure explaining the manufacturing method of the electrode structure of embodiment (a)-(c). The figure explaining the manufacturing method of the electrode structure of embodiment (a)-(c). The figure which shows the outline of the substrate structure of the experiment object and the experimental equipment Photo substituted for drawing showing surface condition of substrate structure obtained in experiment Photo substituted for drawing showing surface condition of substrate structure obtained in experiment Photo substituted for drawing showing surface condition of substrate structure obtained in experiment Graph showing the relationship between the film thickness of metal tungsten and the visible light transmittance

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity. In addition, this invention is not limited to the following embodiment.

  An organic semiconductor element according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 schematically shows a cross-sectional configuration of an organic EL element 1000 which is an example of the organic semiconductor element of the present embodiment.

  An organic EL element 1000 shown in FIG. 1 includes a substrate 40, TFTs (thin film transistors) 50 (50A, 50B), which are examples of semiconductor elements formed on the substrate 40, and organic light emitting materials formed thereon. And an EL (electroluminescence) portion 60 including

  The substrate 40 is, for example, a glass substrate. The substrate 40 may be a flexible substrate made of resin. The substrate structure 10 has a function of supporting each layer laminated thereon.

  The TFT 50 includes a source / drain electrode 51, a semiconductor layer 52 formed in contact with the source / drain electrode 51, and a gate insulating film 53 formed on the semiconductor layer 52. A gate electrode 54 is formed on the gate insulating film 53. The TFT 50 </ b> A and the TFT 50 </ b> B in this example are electrically connected to each other by the wiring 55.

  The TFT 50 is disposed for each pixel arranged in a matrix together with a capacitor (not shown), and constitutes a drive circuit for applying a voltage to the EL portion 60 for each pixel. Note that the circuit configuration of the drive circuit is not limited to that having two TFTs 50, and may be, for example, more than that. In this embodiment, the top gate TFT 50 in which the source / drain electrode 51 is located on the substrate side is shown, but the present invention is not limited to this.

  A planarizing film 57 is formed on the substrate 40 so as to cover the TFT 50. The flatness of the upper surface is ensured by the flattening film 57. The substrate 40, the TFT 50, and the planarizing film 57 form the substrate structure 10. The substrate structure 10 may be simply referred to as a substrate 10.

  An EL portion 60 is formed on the substrate 10 including the planarizing film 57. The EL portion 60 includes an anode 12, a hole injection layer 13, a light emitting layer 15 (which may include an intermediate layer (interlayer) 14), an electron injection layer 18, and a cathode 20. The hole injection layer 13 includes a first part 13A located on the anode 12 side and a second part 13B located on the opposite side (the light emitting layer 15 side) from the anode 12 side. The light emitting layer 15 is made of an organic light emitting material, and in this embodiment is made of a polymer material. The cathode 20 is made of a transparent electrode, and a sealing film 22 made of a transparent film or a transparent substrate is formed thereon. A bank layer 16 for forming each layer including the light emitting layer 15 is formed on the substrate 10.

  The organic EL element 1000 shown in FIG. 1 has a top emission structure. When a voltage is applied to the EL portion 60, light is generated in the light emitting layer 15, and the light 70 exits (upward) through the cathode 20 and the sealing film 22 that are transparent electrodes. Further, light emitted from the light emitting layer 15 toward the substrate 10 is reflected by the anode 12, and then the reflected light is emitted as light 70 through the cathode 20 and the sealing film 22 (upward). ) Get out.

  In the top emission structure, the anode 12 on the substrate 10 side is used as a reflection electrode, the cathode 20 and the sealing film 22 facing the anode 12 are made transparent, and light 70 is emitted upward. Therefore, the reflectivity of the anode 12 which is a reflective electrode is an important factor together with the light emission efficiency of the light emitting layer 15.

  To summarize the configuration of the organic EL element 1000 described above, the substrate 10 including the TFT 50, the anode 12, the hole injection layer 13 including the first portion 13A and the second portion 13B, and the intermediate layer (interlayer) 14 are sequentially arranged from the bottom. The light emitting layer 15, the electron injection layer 18, the cathode (transparent electrode) 20, and the sealing film 22 are formed, and has a top emission structure in which light generated in the light emitting layer 15 is extracted from the sealing film 22 side. The organic EL element 1000 is an active type in which the substrate 10 includes the TFT 50.

  The organic EL element 1000 having the top emission structure has an advantage that the light emission area ratio can be increased as compared with the organic EL element having a general bottom emission structure. Since the light emission area ratio is large, the luminance may be low, the voltage may be small, and thus the advantage that the lifetime is extended is also obtained. In the case of the top emission structure, the light emission area ratio can be increased because the substrate 10 including the TFT 50 is provided under the EL portion 60 and the light 70 is extracted in the opposite direction to the substrate 10. This is because even if the space is occupied, the problem of the light emission area ratio can be avoided. In the case of the top emission structure, the substrate 10 does not need to be transparent, and therefore a non-transparent substrate (for example, a silicon substrate) can be used.

  The anode 12 having the top emission structure is required to have light reflectivity in addition to conductivity. The better the light reflectivity, the more the light generated in the light emitting layer 15 can be reflected. Therefore, the light emission efficiency of the organic EL element 1000 can be improved. Examples of the anode material constituting the anode 12 include metals having high reflectivity (Ag or Ag alloy).

Further, the hole injection layer 13 is required to have optical transparency and surface flatness in addition to hole injection. The light transmissivity of the hole injection layer 13 is necessary to transmit light generated in the light emitting layer 15 to the anode 12 and light reflected from the anode 12 to the cathode without loss. Therefore, the luminous efficiency of the organic EL element 1000 can be improved by having good light transmittance. The surface flatness of the hole injection layer 13 ensures that the light emitting layer 15 (intermediate layer 14) formed on the hole injection layer 13 is flatly and uniformly manufactured, and thereby, within the pixel. It is possible to prevent the bias of the electric field between the anode and the cathode due to the variation in the thickness of the light emitting layer 15, the deterioration acceleration due to this, the local light emission in the pixel, and the short circuit. As a material constituting the hole injection layer 13, for example, an oxide of a transition metal such as tungsten oxide (WO _x ) or molybdenum oxide (MoO _x ) can be used. In particular, WO _x has many merits in the present embodiment in terms of manufacturability and price in manufacturing a target.

  When an oxide layer for forming the hole injection layer 13 is formed by a sputtering method, there arises a problem that the anode 12 is oxidized. Therefore, if the hole injection layer 13 is produced by sputtering, the reflectivity and / or surface flatness of the structure in which the anode 12 and the hole injection layer 13 are combined is reduced. As a result, the light emission efficiency of the device is deteriorated and a short circuit failure occurs.

  Therefore, the inventors of the present invention produced an oxide layer by sputtering while suppressing oxygen in order to prevent oxidation of the anode, and the hole injection property of the hole injection layer 13 made of the oxide layer depends on the amount of oxygen. I found out that

  That is, in the case of producing a combined structure of the anode 12 and the hole injection layer 13 by using the sputtering method, there arises a disadvantage that the anode 12 is oxidized when it is produced under normal conditions (in the presence of oxygen), and there is no oxygen. When manufactured under the conditions, there arises a problem that a device having a poor hole injection property occurs.

  On the other hand, if it is necessary to form the hole injection layer 13 using the vapor deposition method used in the low-molecular-type organic EL manufacturing technology, the technology for increasing the size of the organic EL panel is extremely difficult. Therefore, it becomes extremely difficult to manufacture a 100-inch class organic EL panel at a mass production level.

  Under such restrictions, the inventor of the present application has a small oxygen content in the first portion 13A located on the anode 12 side in the configuration of the hole injection layer 13 made of an oxide layer, while on the light emitting layer 15 side. By increasing the oxygen content of the second portion 13B positioned, the hole injection layer 13 was successfully produced while achieving good reflectivity and surface flatness while suppressing deterioration of hole injection properties. The oxygen content was calculated from the composition ratio of W atoms and O atoms on the sample surface using XPS (ESCA).

  Hereinafter, the electrode structure 100 provided with such a hole injection layer 13 will be described. FIG. 2 is a cross-sectional view showing the configuration of the electrode structure 100 according to the embodiment of the present invention.

  The electrode structure 100 shown in FIG. 2 includes an anode 12 and a hole injection layer 13 formed on the anode 12. The hole injection layer 13 of the present embodiment includes a first portion 13A located on the anode 12 side and a second portion 13B located on the opposite side (the light emitting layer 15 side) from the anode 12 side. And in the hole injection layer 13 of this embodiment, it is comprised so that the oxygen content rate of 13 A of 1st site | parts may become lower than the oxygen content rate of the 2nd site | part 13B.

  According to the configuration of this embodiment, even if the hole injection layer 13 is formed on the anode 12 by the sputtering method by reducing the oxygen content of the first portion 13A, the oxidation of the anode 12 is suppressed, Good reflectance and surface flatness can be ensured. In addition, by increasing the oxygen content of the second portion 13B, even if the hole injection layer 13 is formed on the anode 12 by sputtering, it is possible to suppress the deterioration of hole injection properties. As a result, it is possible to realize a structure capable of easily manufacturing a large-sized organic EL panel while preventing deterioration of luminous efficiency and occurrence of short-circuit defects as a device. The sputter deposition method of this embodiment can use a parallel plate type DC sputtering method, an RF sputtering method, a low damage sputtering method, a magnetron sputtering method, or the like.

The first portion 13A and the second portion 13B of the hole injection layer 13 are made of the same material, and in this embodiment, are made of tungsten oxide (WO _x ). By configuring both the first portion 13A and the second portion 13B from the same material, there is an advantage that a decrease in reflectance can be suppressed as compared with the case where different types of multilayer films are used. Note that the first portion 13A and the second portion 13B are not limited to be configured from the same material, but may be configured from different materials. For example, the first portion 13A can be made of ITO (indium tin oxide), and the second portion can be made of tungsten oxide (WO _x ). Further, other components may be added to the tungsten oxide (WO _x ), and for example, tungsten oxide (WO _x ) containing molybdenum (Mo) or molybdenum oxide (MoO _x ) can be used. Note that oxides of transition metals other than WO _x and MoO _x can be used for the hole injection layer, and examples of the transition metals include vanadium (V) and neodymium (Nd).

  The anode 12 is made of a metal having a high light reflectance, and is made of, for example, Ag (silver) or an Ag alloy. The thickness of the anode 12 is, for example, 100 to 300 nm. In the present embodiment, the anode 12 is formed by sputtering. As described above, in the organic EL element 1000, each material (such as the light emitting layer 15) is sandwiched between the anode 12 and the cathode 20, and the anode 12 functions as a hole (hole) in the element. It has the role of injecting into (especially the light emitting layer 15).

  The light reflectance (visible light region) of the laminated film of the anode 12 and the hole injection layer 13 is preferably 80% or more. The laminated film (12, 13) preferably has a surface roughness (Ra) of 2 nm or less.

  A hole injection layer 13 is formed between the anode 12 and the light emitting layer 15. The hole injection layer 13 has effects such as lowering the driving voltage of the organic EL element 1000, stabilizing the hole injection and extending the life of the element, and covering the protrusions of the anode 12 to reduce element defects. Demonstrate.

The first portion 13A located in the lower layer in the hole injection layer 13 is made of a transparent metal oxide. The first portion 13A is made of, for example, ITO (indium-tin-oxide), IZO (indium-zinc-oxide), or WO _x (tungsten oxide). On the first portion 13A, a second portion 13B located in the upper layer in the hole injection layer 13 is formed. The second portion 13B is also made of a transparent metal oxide, and is made of, for example, WO _x (tungsten oxide) or MoO _x (molybdenum oxide). The second portion 13B needs to have a hole injection property.

  The first portion 13A is required to have a thickness that prevents oxidation of the anode 12 when the second portion 13B is formed by sputtering. The thickness of the first portion 13A is, for example, 5 nm or more. On the other hand, as the thickness of the hole injection layer 13 increases, the reflectivity of the hole injection layer 13 decreases. Therefore, the thickness of the hole injection layer 13 is the thickness between the first portion 13A and the second portion 13B. For example, it is preferable to set the thickness to about 10 nm to 100 nm.

  A light emitting layer 15 is formed on the hole injection layer 13. The light emitting layer 15 is a layer that provides a field for transporting electrons and holes and further recombining electrons and holes. In the present embodiment, a polymer material (polymer organic EL material) is used as the light emitting material constituting the light emitting layer 15. Since a polymer having a conjugated system such as an aromatic ring or a condensed ring or a π-conjugated polymer has fluorescence, it can be used as a polymer light emitting material constituting the light emitting layer 15.

  Examples of the polymer light emitting material constituting the light emitting layer 15 include polyphenylene vinylene (PPV) or a derivative thereof (PPV derivative), polyfluorene (PFO) or a derivative thereof (PFO derivative), and a polyspirofluorene derivative. it can. It is also possible to use polythiophene or a derivative thereof. The characteristics of polymer materials are that solvent processes such as inkjet and spin coating can be used for film formation. Furthermore, the device structure is simple and the reliability of the film is essentially excellent. It can also be mentioned that a low-voltage driven device can be constructed.

  The light emitting layer 15 can also include an intermediate layer (interlayer) (intermediate layer 14 in FIG. 1). The intermediate layer 14 is a hole transport layer disposed between the anode 12 and the light emitting layer 15. The intermediate layer 14 has a role of efficiently transporting holes to the light emitting layer 15 and a role of preventing deactivation of excitons at the interface between the light emitting layer 15 and the hole injection layer 13. The intermediate layer 14 also has a role of blocking electrons when the material of the hole injection layer 13 is weak to electrons. The intermediate layer 14 of the present embodiment is made of a hole transporting polymer material, and such materials are, for example, triferamine, ponianiline and the like. The thickness of the intermediate layer 14 is, for example, about 5 to 50 nm.

  An electron injection layer 18 is formed on the light emitting layer 15. The electron injection layer 18 is a layer disposed between the light emitting layer 15 and the cathode 20. The electron injection layer 18 reduces the driving voltage of the organic EL element 1000, stabilizes electron injection and extends the life of the element, enhances the adhesion with the cathode 20 and improves the uniformity of the light emitting surface. Demonstrates the effect of reducing defects. The electron injection layer 18 of this embodiment consists of a BaAl laminated body, a phthalocyanine, and lithium fluoride, for example. The thickness of the electron injection layer 18 is, for example, about 20 to 100 nm.

  A cathode 20 is formed on the electron injection layer 18. The cathode 20 has a function of injecting electrons into the element (in particular, the light emitting layer 15) as a function. The cathode 20 of this embodiment is made of, for example, ITO or IZO. Moreover, the thickness of the cathode 20 is about 5-200 nm, for example.

  Further, a sealing film (a sealing film 22 in FIG. 1) is formed on the cathode 20. The sealing film 22 has a role of protecting the element from moisture. In the organic EL element 1000 which is not sealed, peeling of the electrode and the organic layer proceeds due to moisture, and a dot-like or circular non-light emitting defect called a dark spot (dark defect point) is generated and grows. In order to prevent this, a sealing film 22 is provided. The sealing film 22 of the present embodiment is made of, for example, SiN, SiON, or an organic film. The thickness of the sealing film 22 is, for example, about 20 to 5000 nm.

  A bank layer 16 having an opening for forming the light emitting layer 15 is formed on the substrate 10. The bank layer 16 is made of a resin and is formed by a bank pattern using a photolithography method. The bank layer 16 has a thickness of about 100 to 3000 nm, for example. In the configuration of the present embodiment, the intermediate layer 14 and the light emitting layer 15 are formed in the opening of the bank layer 16 by the ink jet method.

  Next, a method for manufacturing the electrode structure 100 of the present embodiment will be described with reference to FIGS. 3 (a) to 6 (c).

  First, as shown in FIG. 3A, a substrate 10 is prepared. The substrate 10 of the present embodiment is a substrate structure in which a TFT 50 and a planarizing film 57 are formed on a substrate (for example, a glass substrate) 40 as shown in FIG.

Next, as shown in FIG. 3B, the anode 12 is formed on the substrate 10. The anode 12 is obtained by forming a solid layer of Al or Ag (or an alloy thereof) by sputtering. As for the conditions (film formation conditions) of the sputtering method here, for example, an Ag alloy target is placed in a chamber together with a substrate to which a film is attached. Next, after evacuating the chamber, a gas such as argon (Ar) or nitrogen (N ₂ ) is introduced, and a voltage is applied between the target and the substrate. As a result, ions are generated, the ions collide with the Ag alloy target, the target particles are repelled and attached to the substrate, and an Ag alloy film is formed.

Next, as shown in FIG. 3C, a first portion 13A of the hole injection layer 13 is formed on the anode 12 by sputtering. As for the conditions of the sputtering method here, for example, a WO _x target is placed in a chamber together with a substrate on which a film is to be attached. Next, after evacuating the chamber, Ar gas is introduced and a voltage is applied between the target and the substrate. Thereby, Ar ions are generated, the ions collide with the target, the target particles are repelled and attached to the substrate, and a WO _x film is formed.

Next, as shown in FIG. 4A, a second portion 13B is formed on the first portion 13A by sputtering. The sputtering method conditions (film forming conditions) here are, for example, that a WO _x target is placed in a chamber together with a substrate on which a film is to be attached. Next, after the chamber is evacuated, Ar gas and oxygen (O ₂ ) gas are introduced, and a voltage is applied between the target and the substrate. As a result, Ar ions are generated, the ions collide with the target, and the target particles are repelled and attached to the substrate. At this time, by introducing oxygen gas, the target particles are oxidized, and an oxygen-rich WO _x film is formed on the substrate.

  Next, as illustrated in FIG. 4B, a resist mask 81 is formed on the second portion 13 </ b> B of the hole injection layer 13. The resist mask 81 defines the formation region (position / shape) of the anode 12 and the hole injection layer 13. The resist mask 81 is formed by forming a photoresist on the hole injection layer 13 and then patterning it by a photolithography method.

  Next, as shown in FIG. 4C, the anode 12 and the hole injection layer 13 are patterned by wet etching using the resist mask 81 as a mask. As the wet etching conditions here, for example, the substrate is immersed in a fluorine-based etching solution. Thereby, the hole injection layer is etched. Next, the substrate is immersed in a mixed solution of phosphoric acid, nitric acid and acetic acid. Thereby, the anode is etched. The patterning method may be performed by etching each layer in addition to etching the anode 12 and the hole injection layer 13 (13A, 13B) all together.

  Next, the resist mask 81 is removed to obtain the structure shown in FIG. For removing the resist mask 81, for example, the substrate is dissolved in acetone, dimethylformamide, or a commercially available resist stripping solution. Thereby, the resist is removed. After removing the resist, the substrate is washed with isopropyl alcohol (IPA) or pure water. Resist stripping may be performed in this way. Next, the bank layer 16 is formed. First, as shown in FIG. 5B, a resist 82 is formed on the substrate 10 so as to cover the hole injection layer 13. Next, as shown in FIG. 5C, the resist 82 is patterned by photolithography through a mask (not shown) that defines the opening 85 to form the opening 85. In this way, the bank layer 16 is obtained.

  Next, as shown in FIG. 6A, the material constituting the light emitting layer 15 is filled in the opening 85 of the bank layer 16. Here, the light emitting layer 15 is formed in the bank layer 16 using an inkjet method. In addition, the intermediate layer 14 can be formed together with the light-emitting layer 15 by using an inkjet method.

  The ink jet method is a method of forming pixels by ejecting an ink-formed film forming material from a nozzle onto the substrate 10. In order to pattern the polymer material with high accuracy, it is preferable to provide the bank layer 16 in addition to the opening of the pixel as in this embodiment, and furthermore, wettability is controlled by, for example, plasma processing. There is also a technique. After the polymer material is applied by the ink jet method, the light emitting layer 15 is obtained by drying.

  Next, as shown in FIG. 6B, the electron injection layer 18 is formed on the light emitting layer 15. In other words, the electron injection layer 18 is formed on the substrate 10 having the light emitting layer 15 in the bank layer 16. The electron injection layer 18 is formed by a vapor deposition method. The conditions for the vapor deposition method here are, for example, that a Ba raw material is placed in a crucible and placed in a chamber together with a substrate to which a film is to be attached. Next, after the chamber is evacuated, the crucible is heated to evaporate Ba and adhere to the substrate to form a Ba film. The crucible heating method at this time includes a resistance heating type, an electron beam type, and a high frequency induction type.

  Next, as shown in FIG. 6C, when the cathode (transparent electrode) 20 is formed on the electron injection layer 18, the electrode structure 100 of the present embodiment is completed. The cathode 20 is obtained by forming a solid layer on the electron injection layer 18 by vapor deposition or sputtering. As the conditions (deposition conditions) for the vapor deposition method here, for example, an ITO raw material is placed in a crucible and placed in a chamber together with a substrate to which a film is to be attached. Next, after the chamber is evacuated, the crucible is heated with an electron beam to evaporate the ITO and adhere to the substrate to form an ITO film. Thereafter, predetermined patterning is performed as necessary.

  Then, when the sealing film 22 is formed on the cathode 20, the organic EL element 1000 of this embodiment is obtained. The sealing film 22 may be formed by forming a solid layer on the cathode 20 by sputtering. As the conditions (film formation conditions) of the sputtering method here, for example, a SiN target is placed in a chamber together with a substrate to which a film is attached. Next, after the chamber is evacuated, Ar gas is introduced and a voltage is applied between the SiN target and the substrate. Thereby, Ar ions are generated, the ions collide with the target, the target particles are repelled and attached to the substrate, and a SiN film is formed. Thereafter, predetermined patterning is performed as necessary.

  Thus, the electrode structure 100 or the organic EL element 1000 of this embodiment can be manufactured. According to the manufacturing method of this embodiment, the anode 12 and the hole injection layer 13 can be formed by a sputtering method, and the light emitting layer 15 can be formed by a coating or printing method (in this example, an ink jet method). The organic EL panel (for example, 100 inch class) can be easily manufactured, and the large organic EL panel can be manufactured at a mass production level. In the example described above, the light emitting layer 15 made of an organic light emitting material is formed using an inkjet method. However, if the light emitting layer 15 can be formed by coating or printing, other methods such as gravure printing and letterpress printing are used. It is also possible to use a dispenser or the like. Further, depending on the manufacturing method, the light emitting layer 15 can be manufactured without using the bank layer 16.

  Then, according to the manufacturing method of the present embodiment, the hole injection of the hole injection layer 13 can be performed without using the sputtering method in order to avoid the problem of the oxidation of the anode and using the sputtering method without flowing oxygen. The problem of poor performance can also be eliminated or reduced. More specifically, in the manufacturing method of the present embodiment, in the formation of the hole injection layer 13, after the first portion 13A having a low oxygen content is formed, the second portion 13B having a high oxygen content is formed. Further, the oxidation of the surface of the anode 12 serving as the reflection surface can be suppressed. As a result, it is possible to easily manufacture a large organic EL panel while preventing deterioration in light emission efficiency and occurrence of short-circuit defects as an organic EL device.

  Next, effects of the electrode structure 100 of the present embodiment will be described with reference to FIGS.

The inventor of the present application conducted a first experiment in order to investigate the relationship between the film formation conditions of the metal oxide constituting the hole injection layer 13 and the surface state of the metal layer constituting the anode 12. FIG. 7 is a diagram illustrating an outline of a substrate structure 101 to be experimented and an experimental apparatus used for manufacturing the substrate structure 101. In the experimental apparatus shown in FIG. 7, the flow conditions of Ar gas and oxygen (O ₂ ) gas as described below were set by controlling the opening of the valve from the controller.

  The substrate structure 101 is obtained by laminating a metal layer 112 made of an Ag alloy on a silicon substrate 110 and depositing metal oxide layers 113A and 113B on the metal layer 112. The thickness of the metal layer 112 is 150 nm. The experimental results are shown in FIGS. The substrates 500, 600, and 700 shown in FIGS. 8 to 10 are drawing-substituting photographs showing the respective experimental results.

The film forming conditions of the substrate 500 shown in FIG. 8 are as follows. The metal oxide layer 113A is formed by depositing WO _x (tungsten oxide) to a thickness of 80 nm by sputtering under flow conditions of Ar = 16 sccm and O ₂ = 4 sccm. Similarly, the metal oxide layer 113B is formed by depositing WO _x (tungsten oxide) to a thickness of 20 nm by sputtering under flow conditions of Ar = 16 sccm and O ₂ = 4 sccm.

The film forming conditions of the substrate 600 shown in FIG. 9 are as follows. Unlike the conditions shown in FIG. 8, the metal oxide layer 113A is formed by sputtering WO _x (tungsten oxide) to a thickness of 20 nm by sputtering under the flow conditions of Ar = 20 sccm and O ₂ = 0 sccm. It is. Similar to the conditions for FIG. 8, the metal oxide layer 113B was sputtered under the flow conditions of Ar = 16 sccm and O ₂ = 4 sccm to form WO _x (tungsten oxide) to a thickness of 80 nm. Is.

  As shown in the photograph of FIG. 8, in the sputtering under the film formation conditions (comparative example) of the substrate 500, the surface of the metal layer 112 was oxidized, the reflectivity of the substrate 500 was greatly reduced, and the reflectivity was deteriorated. As shown in the photograph of FIG. 9, in the sputtering under the film forming conditions of the substrate 600, the oxidation of the surface of the metal layer 112 was suppressed, and the reflectance of the substrate 600 was good. Therefore, according to the manufacturing method of this embodiment, it was confirmed that the damage of the lower other metal layer (anode) 112 can be reduced, and the anode 12 having good reflectivity can be formed.

For both the substrates 500 and 600, the sputtering apparatus for forming the WO _x film was an RF sputtering apparatus, and the target was WO ₃ (purity 99.9%). The output of the apparatus was 350 W, and the pressure was 0.5 Pa (20 sccm in total). The film formation temperature is room temperature (RT) and TS (target substrate distance) is 12.5 mm.

The substrate 700 shown in FIG. 10 shows the result when the metal oxide layers 113A and 113B are different films. The metal oxide layer 113A is formed by depositing ITO under a small amount of oxygen to a thickness of 20 nm. The metal oxide layer 113B is formed by depositing WO _x (tungsten oxide) to a thickness of 20 nm by sputtering under flow conditions of Ar = 16 sccm and O ₂ = 4 sccm.

  Also in the substrate 700 shown in FIG. 10, as shown in the photograph, the oxidation of the surface of the metal layer 112 was suppressed, and the reflectance of the substrate 700 was good. Therefore, according to the manufacturing method of the present embodiment, even if it is a laminated film of different materials, damage to the lower metal layer (anode) 112 can be reduced, and the anode 12 having good reflectivity is formed. Confirmed that you can.

  Furthermore, the inventor of the present application conducted a second experiment for producing the oxygen content of the metal oxide layer 113A extremely low. By reducing the oxygen content of the metal oxide layer 113A extremely low, reduction of oxidation of the metal layer 112 by oxygen contained in the metal oxide layer 113A is expected. In the second experiment, the substrate structure 101 and the experimental apparatus shown in FIG. 7 were used.

In the second experiment, unlike the conditions used in the first experiment, the metal oxide layer 113A is formed by sputtering using metal tungsten as a target in an atmosphere having a composition of O ₂ : Ar = 3: 97. The film was formed to a thickness of 3 nm. The output of the apparatus was 1.3 kW.

Thus, WO _x having a very low oxygen content is formed as the metal oxide layer 113A by sputtering using metal tungsten as a target in an atmosphere in which the oxygen partial pressure is further reduced as compared with the first experiment. did.

WO _x having an extremely low oxygen content has the property of metallic tungsten, so there is a concern that the light transmittance (visible light region) may deteriorate. Therefore, in order to avoid deterioration of light transmittance (visible light region), the metal oxide layer 113A was thinly formed to a thickness of 3 nm by sputtering for 10 seconds. The basis for 3 nm will be described later.

Subsequently, the metal oxide layer 113B was formed into a thickness of 40 nm by sputtering using metal tungsten as a target in an atmosphere having a composition of O ₂ : Ar = 50: 50. By raising the oxygen partial pressure in the atmosphere as compared with the time of forming the metal oxide layer 113A, the target particles are oxidized, and an oxygen-rich WO _x film is formed on the substrate. Specifically, a WO _x film with x = 2.7 to 2.8 was formed, and good hole injecting properties were exhibited in the metal oxide layer 113B.

In this way, by controlling the composition (oxygen partial pressure) of the sputtering atmosphere, WO _x having a very low oxygen content is formed as the metal oxide layer 113A to reduce damage due to oxidation of the metal layer 112, and As a metal oxide layer 113B, it was possible to form a WO _x film having an oxygen content necessary for obtaining a good hole injection property.

Furthermore, the inventor of the present application forms a film thickness of the metal oxide layer 113A that is acceptable in terms of light transmittance (visible light region) when WO _x having a very low oxygen content is formed as the metal oxide layer 113A. A third experiment was conducted to investigate.

  In the third experiment, a reference sample in which only the metal layer 112 is formed on the silicon substrate 110, and metal tungsten having a thickness of 7.5 nm, 15 nm, 22.5 nm, and 30 nm on the reference sample, respectively. Four types of samples were prepared. These four types of samples were formed by sputtering using metallic tungsten as a target in an atmosphere of 5.0 Pa consisting of only Ar gas and at room temperature. Here, a tungsten metal film was formed on the assumption of the worst condition regarding the light transmittance (visible light region).

  And about the reference sample and four types of samples, the reflection intensity with respect to three types of visible light having wavelengths of 475 nm, 530 nm, and 650 nm is measured, and from the difference between the reflection intensity of the reference sample and the reflection intensity of each sample, The light transmittance (visible light region) of the metal tungsten film was calculated.

FIG. 11 is a graph showing the results. From the graph of FIG. 11, even _if the oxygen content of WO _{x formed} as the metal oxide layer 113A is extremely low and substantially has the properties of metal tungsten, the film thickness is set to 3 nm or less, It can be seen that a light transmittance (visible light region) of 80% or more can be obtained.

Note that in the case where the WO _x formed as the metal oxide layer 113B is formed with x = about 2.7 to 2.8 in order to obtain a good hole injection property, the metal oxide layer 113B becomes visible light. In contrast, it may be considered almost transparent.

  Therefore, by setting the thickness of the metal oxide layer 113A to 3 nm or less, the light reflectance (visible light region) of the stacked film of the metal layer 112, the metal oxide layer 113A, and the metal oxide layer 113B is 80%. This can be done.

  From the result of the third experiment, by using the configuration described in the second experiment, suitable conditions for the light reflectance (visible light region) of the laminated film of the anode 12 and the hole injection layer 13 described in the embodiment are described. It can be seen that an electrode structure 100 satisfying the above can be obtained.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

  Although the configuration is essentially different from that of the embodiment of the present invention, there is one disclosed in Patent Document 1 as a related structure. Patent Document 1 discloses an anode for an organic semiconductor element. However, although Patent Document 1 includes a description in which materials of each layer are listed, a configuration or a technical idea according to an embodiment of the present invention is not described. That is, Patent Document 1 does not describe the configuration that the oxygen content rate of the first portion 13A of the hole injection layer 13 is smaller than the oxygen content rate of the second portion 13B, or the problems and effects of the present invention. .

  ADVANTAGE OF THE INVENTION According to this invention, the electrode structure for organic EL which can manufacture a large sized organic EL panel easily can be provided.

10 Substrate (substrate structure)
DESCRIPTION OF SYMBOLS 12 Anode 13 Hole injection layer 13A 1st site | part 13B 2nd site | part 14 Intermediate layer 15 Light emitting layer 16 Bank layer 18 Electron injection layer 20 Cathode 22 Sealing film 40 Substrate 50, 50A, 50B TFT
51 Source / Drain Electrode 52 Semiconductor Layer 53 Gate Insulating Film 54 Gate Electrode 55 Wiring 57 Flattening Film 60 EL Part 70 Light 81 Resist Mask 82 Resist 85 Opening 100 Electrode Structure 101 Substrate Structure 110 Silicon Substrate 112 Metal Layer 113A, 113B Metal oxide layer 500, 600, 700 Substrate 1000 Organic EL element

Claims (4)

The anode,
An organic light emitting layer formed above the anode;
A cathode formed above the organic light emitting layer;
A top emission type organic EL light emitting device including:
The anode is composed of silver or a silver alloy;
A hole injection layer made of a metal oxide is formed on the anode,
The oxygen content of the first part located on the anode side in the hole injection layer is smaller than the oxygen content of the second part located on the opposite side of the anode side,
Organic EL element. The first part and the second part in the hole injection layer are made of tungsten oxide having different oxygen contents.
The organic EL element according to claim 1. The hole injection layer is a metal oxide layer formed by a sputtering film forming method.
The organic EL element according to any one of claims 1 and 2. A first step of preparing a substrate;
A second step of forming an anode containing silver or a silver alloy on the substrate;
A third step of forming a hole injection layer made of a metal oxide on the anode by a sputtering film forming method, and
The third step includes
Forming a first portion of the hole injection layer on the anode;
Forming a second part having an oxygen content greater than the oxygen content of the first part on the first part.