JP2005183203A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element capable of preventing entrance of water into a cathode. <P>SOLUTION: The organic EL element has the cathode containing at least one kind of either oxide or carbonate of alkali metal, or oxide or carbonate of alkali earth metal as an auxiliary component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrode of an organic EL element.

  An organic EL element in which an electron transport material, a light emitting material, a hole transport material, and the like are stacked and sandwiched between conductive materials is widely known as an element that emits light at a low voltage. However, the organic EL element is active with respect to water, and formation of dark spots due to non-light-emitting points or film peeling due to reaction with water is regarded as a problem. As measures against these waters, a method of sealing an element and providing a desiccant inside (for example, see Patent Document 1) has been proposed. FIG. 6 shows a conventional example. In the figure, 101 is a transparent substrate, 102 is an anode electrode, 103 is a hole transport layer, 104 is a light emitting layer, 105 is an electron transport layer, 106 is a cathode electrode, 107 is a desiccant, and 108 is a sealing member. The element is kept in a dry state by providing the desiccant 107 inside the seal.

  In addition, a method of using any one or more of an alkali metal hydride and an alkaline earth metal hydride as a water-absorbing material in the cathode electrode (electron injection electrode) 102 has been proposed (for example, see Patent Document 2). ing.

Patent Document 3 describes an organic electroluminescent device using an electrode containing an alkali metal or an alkaline earth metal as a cathode.
Japanese Patent Laid-Open No. 09-148066 Japanese Patent Laid-Open No. 2000-113990 JP 2002-151257 A

  However, there is a problem that the desiccant provided inside the sealing is not sufficient for the water taken in during the device manufacturing process or the water diffused from the substrate side. Further, in the method of providing an alkali metal hydride or an alkaline earth metal hydride in the electron injection electrode, water at the hole injection side electrode could not be absorbed. In addition, when an oxide conductor such as a transparent electrode is used for the electrode, active oxygen reacts with hydride of alkali metal or hydride of alkaline earth metal, and has sufficient water absorption capability. There was also a problem that it was impossible to obtain.

  First, in an organic light-emitting device having an anode electrode and a cathode electrode, and having at least a layer made of an organic compound sandwiched between the anode electrode and the cathode electrode, at least one of the anode electrode or the cathode electrode is Containing a conductive material as an ingredient, and containing at least one kind of alkali metal oxide or carbonate, or alkaline earth metal oxide or carbonate as an accessory ingredient, suppresses the entry of water into the organic layer. An organic light emitting device characterized by that.

  Second, in an electrode having a conductive material as a main component and containing at least one oxide or carbonate of an alkali metal or alkaline earth metal as a subcomponent, the content ratio of the subcomponent toward the outside of the device is An organic light emitting device having an increasing distribution and preventing electrical connection failure at an interface between an electrode and an organic layer while preventing water from entering the organic layer.

  Third, the organic light-emitting device, wherein the conductive material is a transparent conductive film.

  As described above, it is possible to reduce the intrusion of water from the substrate and the upper surface into the organic layer by forming an oxide or carbonate of an alkali metal, alkaline earth metal on the conductor layer sandwiching the organic layer. It becomes.

  In the anode electrode and the cathode electrode, an organic EL layer containing at least one kind of alkali metal oxide or carbonate or alkaline earth metal oxide or carbonate as a subcomponent in addition to the main component conductive material It is possible to provide a long-life device that prevents water from penetrating and suppresses dark spots.

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of an embodiment of the present invention, and shows a cross-sectional view of an organic EL element. An anode electrode 2 made of a transparent conductive film containing an alkali metal, alkaline earth metal oxide or carbonate is laminated on the surface of the substrate 1, and a hole transport layer 3, a light emitting layer 4, and electron transport are laminated on the anode electrode 2. The layer 5 and the cathode electrode 6 are laminated. By applying a voltage between the anode electrode 2 and the cathode electrode 6, electrons reaching the light emitting layer via the electron transport layer 5 and electrons reaching the light emitting layer via the hole transport layer are converted into the light emitting layer. By recombining at 4, an organic EL element that emits light is formed. Reference numeral 7 denotes a desiccant, 8 denotes a sealing member, and the space is filled with dry nitrogen.

  The substrate 1 can be appropriately selected from materials such as glass and resin. However, in the configuration in which light is extracted from the substrate 1 side, it is necessary to use a transparent material.

  As the main component of the anode electrode 2, it is possible to apply an electrically conductive material such as a metal, an alloy, an oxide conductor, or a mixture thereof. Specific examples of such an electrode material include metals such as silver, gold, chromium, and aluminum, and oxide conductors such as ITO, IZO, SnO2, and ZnO. Moreover, as a subcomponent of the anode electrode 2, water-absorbing materials such as Cs2O, CaO, BaO, Cs2CO3 can be used. The anode electrode 2 can be formed with a structure including a main component and subcomponents using a method such as multi-source sputtering or co-evaporation. In the anode electrode 2, when light is extracted from the substrate 1 side, the main component is a translucent material such as an oxide conductor, and when light is extracted from the opposite side of the substrate 1, the main component is a metal or the like. It is desirable to use a reflective material.

  The hole transport layer 3 is desired to have a high hole injection property from the anode electrode 2, a large hole mobility, a high hole injection property to the light emitting layer 4, and a high electron blocking property. Specific examples of the material include, but are not limited to, α-NPD, TPD, PEDOT, PVCz, and Cz.

  The light emitting layer 4 can be appropriately selected from a single material and a light emitting layer made of a doping material and a host material. For example, examples of the doping material include anthracene, naphthalene, coumarin, metal complex, and examples of the host material include Alq3 and CBP. Various materials can be selected and combined depending on the emission color.

  The hole transport layer 5 is desired to have a high electron injection property from the cathode electrode 2, a large electron mobility, a high electron injection property to the light emitting layer 4, and a high hole blocking property. Specific examples of the material include Alq3, BPhen, and BCP, but are not limited thereto.

  As the cathode electrode 6, the same main component and subcomponent as those of the anode electrode 2 can be applied. In the cathode electrode 6, when the light is extracted from the substrate 1 side, the main component is a reflective material such as a metal, and when the light is extracted from the side opposite to the substrate 1, the main component is a transparent material such as an oxide conductor. It is desirable to use a light material.

  Note that only one of the anode electrode 2 and the cathode electrode 6 may contain a subcomponent water-absorbing material.

  As the desiccant 7, a water-absorbing material such as a reaction material such as CaO, CaCO3, P2O5, Ba, or an adsorbing material such as porous chamber alumina can be used. In addition, it can be formed by various methods such as those obtained by solidifying powder with a binder, those fixed with an adhesive material into a sheet, those directly applied to a sealing member, and those formed by a vacuum film formation method. is there.

  As the sealing member 8, various materials such as glass, resin, and metal can be applied, and the substrate 1 can be sealed using an adhesive material such as an epoxy resin. Note that the inside can be filled in a dry atmosphere by sealing in a dry atmosphere.

  The present invention can be similarly applied to an organic EL device having a structure in which a cathode electrode is provided on a substrate and an electron transport layer, a light emitting layer, a hole transport layer, and an anode electrode are laminated.

(Example)
Next, the present invention will be described in more detail by way of examples.

  FIG. 2 is a view for explaining the first embodiment of the present invention, and is a cross-sectional view of a part of a display panel formed by arranging organic EL elements two-dimensionally. In the figure, 1 is a glass substrate, 2 is an anode electrode, 3 is a hole transport layer, 4 is a light emitting layer, 5 is an electron transport layer, 6 is a cathode electrode, 7 is a desiccant, 8 is a sealing member, and 9 is an element drive. The circuit forming unit 10 is a planarizing film, 11 is an element isolation film, and 12 is a light extraction direction.

  In this embodiment, after the element driving circuit is formed on the glass substrate 1 having a thickness of 0.7 mm, the planarizing film 10 made of a photosensitive acrylic resin is formed, and then the anode electrode 2 is formed in the light emitting region. Cr was patterned to a thickness of 0.2 nm. Further, an element isolation film 11 made of a photosensitive polyimide resin was formed by separating the light emitting region. Next, as the hole transport layer 3, α-NPD was formed to a thickness of 50 nm using a vacuum deposition method. Further, using a mask vapor deposition method, green, red, and blue light emitting materials were formed at desired positions by vapor deposition three times. The thickness of each layer was 30 nm. Furthermore, as the electron transport layer 5, BPhen was formed to a thickness of 40 nm by vapor deposition. In addition, Cs was vapor-deposited with a thickness of 3 nm before forming the cathode electrode 6 for the purpose of enhancing the electron injection property from the cathode electrode 6 to the electron transport layer 5. The cathode electrode 6 was formed to a thickness of 200 nm using a multi-source sputtering apparatus using an ITO target and a CaO target. At this time, the ITO target used was SnO2 of 10 wt%, the Ar: O2 flow ratio was 50: 1, and the input power to the ITO target and CaO target was 300 W and 100 W, respectively.

  In this embodiment, the pixel size is 150 × 230 μm. When a predetermined drive voltage is applied to the organic EL panel formed by this method and a white luminance of 300 cd / cm 2 is obtained in the light extraction direction, and the device is continuously driven for 1000 hours under the conditions, no element is generated with dark spots. Was confirmed. Even in normal television image display, no dark spots were observed after 2000 hours of driving.

  Next, a second embodiment of the present invention will be described. FIG. 3 is a top view of a display panel using the organic EL element of the present invention, and FIG. 4 is a cross-sectional view taken along line A-A 'of FIG.

  3 and 4, 1 is a substrate, 2 is an anode electrode, 31 is an organic layer composed of a hole transport layer, a light emitting layer, and an electron transport layer, 6 is a cathode electrode, 32 is a cathode electrode lead-out portion, 33 is a pad portion, Reference numeral 34 denotes a film cover, and 12 denotes a light extraction direction.

  On the PET substrate 1 coated with the SiON film, an ITO target and a CaO target were used to form a thickness of 200 nm using a multi-source sputtering apparatus. At this time, the ITO target used was SnO2 of 10 wt%, the Ar: O2 flow rate ratio was 80: 1, and the input power to the ITO target and the CaO target was 300 W and 100 W. In addition, it formed in the area | region divided | segmented as shown in FIG. 3 by using a metal mask.

  The formed anode electrode 2 exhibited a sheet resistance of 100Ω / □. Next, as a hole transport layer, α-NPD was formed to a thickness of 50 nm by vacuum deposition. Furthermore, as a light emitting layer, a layer in which 1 vol% of coumarin was doped to Alq3 was formed to a thickness of 40 nm using a co-evaporation method. Furthermore, as an electron transport layer, BPhen was formed to a thickness of 40 nm by vapor deposition to produce an organic layer 31. The cathode electrode 6 was formed to a thickness of 200 nm using a multi-source sputtering apparatus using an Al target and a CaO target. In addition, in order to improve the electron injection property from Al to the electron carrying layer 5, LiF was formed with the thickness of 1 nm using the vapor deposition method before Al vapor deposition. Finally, in a dry nitrogen atmosphere, SiON was coated on both sides, and a 0.3 mm-thick PET film on which CaO was sputtered as a desiccant on the side of the device was bonded with an epoxy resin to produce a device.

  When a driving voltage of 6 V was applied to the organic EL element formed by this method, a luminance of 1000 cd / cm 2 was obtained, and an element with little generation of dark spots could be confirmed even during continuous driving for 500 hours.

  Here, the third embodiment of the present invention will be described.

  The feature of this example is that the concentration of the alkali oxide of the cathode electrode was changed in the film thickness direction using an element having the same configuration as that of Example 1.

  FIG. 5 is an explanatory diagram of the third embodiment of the present invention, and shows how the input power changes with time when the cathode electrode is formed. In the figure, 51 indicates the input power for CaO sputtering, and 52 indicates the input power for ITO sputtering.

  In the formation of the cathode electrode, the input power to CaO is zero until 1 minute after the start of film formation, and is continuously increased to 100 W in 1 minute to 2 minutes. Thereafter, the cathode electrode was formed by co-sputtering with a constant input power so that the ratio of ITO as the main component of the cathode was increased on the electron injection layer side.

  When a predetermined drive voltage was applied to the organic EL panel of this example to obtain a white luminance of 300 cd / cm 2, a lower voltage of 0.2 to 0.4 V was applied for each color as compared with Example 1. The effect was obtained.

  As in Example 1, when 1000 hours of continuous driving was performed, an element without the occurrence of dark spots was confirmed. Even in normal television image display, the generation of dark spots was not recognized in the same manner when driven for 2000 hours.

  As in this example, on the organic EL side of the electrode, by reducing the amount of subcomponents containing at least one alkali metal oxide or carbonate, or alkaline earth metal oxide or carbonate, It is possible to provide a long-life organic EL element that secures water absorption and reduces the occurrence of dark spots without deteriorating injectability.

  In addition, although the present Example showed the example applied to the cathode electrode, it can apply similarly to an anode electrode.

FIG. 1 is a cross-sectional view of an organic EL element according to an embodiment of the present invention. It is explanatory drawing of this invention and 1st Example, and is sectional drawing of a part of organic electroluminescent panel. It is explanatory drawing of this invention and 2nd Example, and is a top view of a display panel using an organic EL element. It is explanatory drawing of this invention and 2nd Example, and is sectional drawing of the display panel using an organic EL element. It is explanatory drawing of this invention and 2nd Example, and is a figure which shows the time change of the input electric power at the time of cathode electrode formation. It is explanatory drawing of the prior art example of an organic EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Anode electrode 3 Hole transport layer 4 Light emitting layer 5 Electron transport layer 6 Cathode electrode 7 Drying material 8 Sealing member 9 Element drive circuit formation part 10 Planarization film 11 Element isolation film 12 Light extraction direction 31 Hole transport Organic layer consisting of layer, light emitting layer, electron transport layer 32 Cathode electrode lead-out part 33 Pad part 34 Film cover 51 Power input to CaO sputtering 52 Power input to ITO sputtering

Claims (3)

  In an organic light emitting device having an anode electrode and a cathode electrode, and having at least a layer made of an organic compound sandwiched between the anode electrode and the cathode electrode, at least one of the anode electrode or the cathode electrode is a conductive material as a main component And an organic light-emitting element containing at least one oxide or carbonate of an alkali metal or oxide or carbonate of an alkaline earth metal as a subcomponent.   In an electrode having a conductive material as a main component of claim 1 and containing at least one oxide or carbonate of an alkali metal or alkaline earth metal as a subcomponent, the content ratio of the subcomponent toward the outside of the device is An organic light emitting device having an increasing distribution. 3. The organic light-emitting element according to claim 1, wherein the conductive material is a transparent conductive film.

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