JP2007257854A - Organic el element for lighting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element for lighting which can avoid giving a sense of incompatibility by making suitable for the situation of the surrounding. <P>SOLUTION: The organic EL element has an organic luminous layer between a pair of electrodes 5, 11. A light control layer 4 and a first transparent electrode 3 are installed on the opposite side to the organic luminous layer of a second transparent electrode 5 on the side of extracting light out of the electrodes, and a hole injecting layer 6, hole transporting layer 7, light emitting layer 8, electron transporting layer 9, and electron injecting layer 10 are formed in order from the second transparent electrode 5 side, between the second transparent electrode 5 and a metal electrode 11. Thereby, at the time of non-lighting of the lighting device, the external light is absorbed by the light control layer 4 and colored and interference of reflecting light can be eliminated, and a sense of incompatibility with the surrounding can be avoided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL element for illumination, and more particularly to an organic EL element for illumination that eliminates the uncomfortable feeling caused by interference of external light when not lit.

  In general, a self-luminous EL element uses an EL (electroluminescence) phenomenon, and therefore hardly generates heat, and is lightweight and thin. In particular, an organic EL element is more than an inorganic EL element. It has various advantages such as easy color selection, low driving voltage and power saving.

  The organic EL element is composed of a number of thin layers such as a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer in addition to the negative electrode, the organic light emitting layer, and the positive electrode. Therefore, at the time of non-lighting when the light is not emitted, the appearance is impaired due to the light interference effect between the organic film and the electrode film, depending on the viewing direction. In particular, the optical interference effect becomes more prominent as the number of organic EL elements is increased or the area is increased for higher efficiency.

In order to prevent such external light reflection, a light-emitting element in which a layer whose transmittance is changed by voltage application or current injection has been proposed (for example, Patent Document 1). According to the light-emitting element of Patent Document 1, outside light is reflected and looks bright when not turned on without reducing the light utilization efficiency, thereby preventing the contrast from being lowered.
JP 2003-272853 A

  The thing of patent document 1 is a display apparatus, and when it applies to an illuminating device, it will be identified clearly that it exists as a light emitting element also at the time of non-lighting.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an organic EL element for illumination that can be adapted to the surrounding situation so as not to feel uncomfortable.

  In order to achieve the above object, an organic EL element for illumination according to claim 1 is an organic EL element in which an organic light emitting layer is provided between a pair of electrodes. On the opposite side of the transparent electrode layer away from the organic light emitting layer, a light control layer formed by adjacently stacking a light control material layer and an electrolyte layer, and a transparent electrode layer are sequentially formed.

  An organic EL element for illumination according to a second aspect of the present invention is characterized in that the light control material layer of the organic EL element according to the first aspect is formed of a tungsten oxide or Prussian blue thin film.

  The organic EL element for illumination according to the invention described in claim 3 is formed by forming the light control material layer of the organic EL element according to claim 1 from a thin film of rare earth metal such as yttrium or lanthanum or a magnesium-nickel alloy thin film. It is characterized by that.

  The organic EL element for illumination according to the invention of claim 4 is an organic EL element in which an organic light emitting layer is provided between a pair of electrodes, and the organic light emitting layer of the transparent electrode on the light extraction side of the electrodes. Is characterized in that a liquid crystal layer and a transparent electrode layer are sequentially provided on the opposite side.

  According to the first aspect of the present invention, the organic EL element emits light by applying voltage or current to the metal electrode (cathode) and the transparent electrode (anode). Light emitted from the light-emitting layer is incident on the light-modulating material layer through the transparent electrode, but the light-modulating material layer itself has a high light transmittance, and the emitted light is the light-modulating material layer, the electrolyte layer, and the transparent electrode. , And is emitted to the outside through the substrate. On the other hand, at the time of non-lighting, a voltage is applied to the transparent electrodes sandwiching the light control material layer, so that the light control material of the light control material layer is colored. As a result, the light interference effect of the organic EL element can be eliminated, and even if it is used in an indirect lighting device for indoor use, it can be adapted to the surrounding situation when not lit and not feel uncomfortable.

  According to the invention described in claim 2, in addition to the effect of claim 1, it is possible to obtain an organic EL element having a relatively high light transmittance and a luminous efficiency almost equal to that of the organic EL element having no light-modulating material layer. it can.

  According to the third aspect of the present invention, the voltage is applied to the transparent electrode sandwiching the light control material layer when no light is emitted, so that the light control material layer becomes a mirror surface having a high reflectance. Thereby, the illuminating device used as a mirror at the time of non-lighting is obtained.

  According to the fourth aspect of the present invention, when a voltage is applied to the transparent electrode sandwiching the liquid crystal layer when not lit, the liquid crystal layer is activated, and light from the outside is blocked by the liquid crystal layer. The appearance of the lighting device is not impaired.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
FIG. 1 is a cross-sectional view of an organic EL element for illumination according to Embodiment 1 of the present invention. In the organic EL element 1 of the first embodiment, the first transparent electrode 3 is provided on the substrate 2, and the second transparent electrode 5 is formed via the light control layer 4 (light control material layer + electrolyte layer). A hole injection layer 6, a hole transport layer 7, a light emitting layer 8, an electron transport layer 9, and an electron injection layer 10 are sequentially formed, and a metal electrode 11 is formed on the outermost part.

  In the present embodiment, the organic light emitting layer includes a hole injection layer 6, a hole transport layer 7, a light emitting layer 8, an electron transport layer 9, and an electron injection layer 10.

  The substrate 2 may support the light emitting element and be transparent (it may not be transparent if it is not a light transmitting side), such as glass or resin film such as polycarbonate, polymethyl methacrylate, polyethylene terephthalate, etc. Can be used.

  The first transparent electrode 3 is formed downstream of the second transparent electrode 5 in the light emitting direction from the organic light emitting layer (the direction of arrow A in FIG. 1). As the first transparent electrode 3 and the second transparent electrode 5, an oxide transparent electrode such as ITO or tin oxide or a metal thin film of about 5 to several tens of nm is used. And as a formation method of the 1st transparent electrode 3 and the 2nd transparent electrode 5, a sputtering method, a resistance heating vapor deposition method, an electron beam vapor deposition method, an ion plating method etc. are used.

  The light control layer 4 is formed in a thin film on the opposite side of the light emitting layer of the second transparent electrode 5. Examples of the material of the light-modulating material layer of the light-modulating layer 4 include materials that are colored with an improved light absorption rate by applying voltage or current injection, such as electrochromic materials and polymer-dispersed liquid crystals. In this embodiment, an electrochromic material is used. Examples of the material include inorganic compounds such as tungsten oxide, molybdenum oxide, and Prussian blue, and organic compounds such as high molecular weight viologen, polyaniline, polypyrrole, and Lu-diphthalocyanine. can give. Further, when the light-modulating material layer is formed of a thin film of rare earth metal such as yttrium or lanthanum or a magnesium / nickel alloy thin film, the layer can be almost totally reflected. As a result, it is possible to obtain a mirror surface that eliminates optical interference caused by reflection from a large number of layers. And the light control layer 4 formed by laminating | stacking this light control material layer and an electrolyte layer adjacently is formed.

  The hole injection layer 6 is formed to lower the injection barrier between the second transparent electrode 5 and the hole transport layer 7, and is not particularly limited. A material having an appropriate ionization potential is desirable, and a known material is used. it can. Specifically, copper phthalocyanine, starburst amine compound, polyaniline, polythiophene, vanadium oxide, molybdenum oxide, ruthenium oxide, aluminum oxide and the like can be mentioned.

  Since the hole transport layer 7 has a role of transporting holes and injecting them into the light emitting layer, it is desirable that the hole mobility is high, and a known material can be used.

  The light emitting layer 8 is a layer that recombines injected holes and electrons and emits light at a wavelength specific to the material, and the light emission mechanism is that even when the host material forming the light emitting layer 8 emits light itself. The dopant material added in a small amount to the host may emit light. As a material used for the light emitting layer 8, a well-known thing can be used.

  The electron transport layer 9 has a role of transporting electrons and injecting them into the light emitting layer 8. Therefore, it is desirable that the electron mobility is high, and a known material can be used.

  The electron injection layer 10 is used for improving the efficiency of electron injection from the metal electrode 11 to the electron transport layer 9. Specifically, lithium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, magnesium oxide, and aluminum oxide are used as the material for the electron injection layer 10. The material for the electron injection layer 10 is not limited to these, and two or more of these may be used in combination.

  As the metal electrode 11, a conductive film having a small work function for increasing the electron injection efficiency is used. Specific examples include magnesium / silver alloy, aluminum / lithium alloy, aluminum / calcium alloy, aluminum / magnesium alloy, and calcium metal. However, it is not limited to these. In particular, in the present embodiment, since the electron transport layer 9 is provided, a general metal material can be used.

  When the switch 12 of the organic EL element 1 configured as described above is switched from the lighting lighting contact point a to the lighting switching point b, the light control material layer is applied between the first transparent electrode 3 and the second transparent electrode 5. 4 can increase the light absorption rate, absorb light and color, reduce reflection of external light, and eliminate optical interference.

  Needless to say, the present invention is not limited to the above embodiment. For example, in the above, the organic light-emitting layer is composed of five layers of the hole injection layer 6, the hole transport layer 7, the light-emitting layer 8, the electron transport layer 9, and the electron injection layer 10 sequentially from the second transparent electrode 5 side. As explained in the example, a structure in which a hole injection layer and a hole transport layer, a light emitting layer, an electron transport layer and an electron injection layer are combined, and a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are combined. It is good also as a structure.

For example, a multilayer structure of the organic light emitting layer may be configured as shown in FIG.
[Embodiment 2]
FIG. 2 is a sectional view showing the organic EL element 1 for illumination according to the second embodiment. The second embodiment shown in FIG. 2 differs from the above embodiment in that the light emitting direction does not pass through the substrate 2 and that the organic light emitting layer 13 is formed from a multilayer film as a single unit. Therefore, those corresponding to the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 2, the organic light emitting layer 13 is formed as a single unit from a multilayer film. The organic light emitting layer 13 may have a two-layer structure in which a hole transporting layer using TPD or the like and an electron transporting light emitting layer using Alq3 or the like are laminated, or the hole transporting layer, the light emitting layer, and the electron transporting layer may be combined. A three-layer structure formed by stacking may be used. The metal electrode 11 side is an electron transport layer.

In the above-described embodiment, the example in which the electrochromic material is used as the light control material has been described. However, as shown in FIGS.
[Embodiment 3]
FIG. 3 is a sectional view showing an organic EL element for illumination according to Embodiment 3, and FIG. 4 is a plan view thereof. This embodiment 3 is different from the above embodiment only in that liquid crystal is used as the light control material, the number of layers forming the organic light emitting layer 13 and the light emitting direction passing through the substrate 2. Therefore, portions corresponding to the above-described embodiment are denoted by the same reference numerals and detailed description thereof is omitted. The organic light emitting layer 13 and the metal electrode 11 formed of the metal layer are insulated by the insulating layer 14.

  If liquid crystal is used as the light control material as in the present embodiment, the first transparent electrode 3 and the second transparent electrode 3 are switched when the switch 12 of the organic EL element 1 is switched from the lighting on contact a to the lighting off b contact. The liquid crystal layer 41 applied between the electrodes 5 blocks light, reduces reflected light, reduces reflection of external light, and eliminates light interference. As a result, it is possible to avoid a sense of incongruity when the lighting device is not lit.

It is sectional drawing which shows Embodiment 1 of the organic EL element for illumination which concerns on this invention. It is sectional drawing which shows Embodiment 2 of the organic EL element which concerns on this invention. It is sectional drawing which shows Embodiment 3 of the organic EL element which concerns on this invention. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic EL element 2 Board | substrate 3 1st transparent electrode 4 Light control layer 41 Liquid crystal layer 5 2nd transparent electrode 6 Hole injection layer 7 Hole transport layer 8 Light emitting layer 9 Electron transport layer 10 Electron injection layer 11 Metal electrode 12 Switch

Claims (4)

  In the organic EL device in which an organic light emitting layer is provided between a pair of electrodes, a light control material layer and an electrolyte layer are provided on the opposite side of the electrode from which the light is extracted from the transparent electrode layer away from the organic light emitting layer. An organic EL element for illumination, comprising a light control layer formed by stacking adjacent layers and a transparent electrode layer in order.   2. The organic EL element for illumination according to claim 1, wherein the light control material layer is formed of a tungsten oxide or Prussian blue thin film.   2. The organic EL element for illumination according to claim 1, wherein the light control material layer is formed of a thin film of a rare earth metal such as yttrium or lanthanum or a magnesium-nickel alloy thin film.   In the organic EL element in which an organic light emitting layer is provided between a pair of electrodes, a liquid crystal layer and a transparent electrode layer are sequentially provided on the opposite side of the transparent electrode on the light extraction side of the electrode from the organic light emitting layer. An organic EL element for illumination.

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