JP2010003570A - Plane emission light source using organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element capable of efficiently obtaining plane light emission with uniform intensity distribution for a long period of time. <P>SOLUTION: A plane emission light source, provided with a nearly flat transparent substrate, anodes laminated on the transparent substrate, an organic light-emitting layer laminated so as to cover an outside of the anodes, and a cathode laminated so as to cover an outside of the organic light-emitting layer, uses an organic electroluminescent element having light irradiated toward outside the transparent substrate. The anodes and the cathode are formed of metal or an alloy opaque with light-reflecting properties, and the anodes have a plurality of strip members having tip parts at a side opposed to the cathode formed expanded in nearly a cross-section arc shape laminated so as to be arrayed at a given interval against the transparent substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface-emitting light source using an organic electroluminescent element. More specifically, the present invention relates to a surface emitting light source using an organic electroluminescent element (hereinafter also referred to as “organic EL element”) that emits light by applying a voltage to an organic light emitting layer sandwiched between an anode and a cathode. About.

  Since the organic EL element has an advantage that a surface emitting light source having high luminous efficiency can be manufactured at low cost, in recent years, a light source for an illumination device or a liquid crystal display device using the organic EL element has been actively developed. In an organic EL element, generally, an anode, a single layer or a plurality of layers of an organic light emitting layer including an organic light emitting layer and a cathode are laminated on a flat substrate. In order to take out light emitted from the organic light emitting layer, the anode and At least one of the cathodes is formed of a transparent material.

  Indium tin oxide (hereinafter also referred to as “ITO”) is widely used as a transparent electrode material. However, since the electrical resistance of ITO is much higher than that of a conductive material such as a metal, the emission intensity distribution on the light emitting surface becomes non-uniform due to the problem that the organic EL element deteriorates due to heat generated by energization and the voltage drop. There is also a problem. Such a problem is particularly serious in a surface emitting light source having a large area of ITO, and various improvements have been made so far.

  For example, Patent Literature 1 discloses a lighting device in which an organic EL element is formed on a heat dissipation plate and a heat conductive elastic member. Here, an attempt is made to suppress the deterioration of the element due to heat and to make the light emission intensity distribution uniform by providing a heat radiating plate and a heat conductive elastic member.

Patent Document 2 discloses a transparent electrode formed on a transparent substrate, an organic light emitting layer formed on the transparent electrode, and a metal formed on the transparent electrode at a certain distance from the organic light emitting layer. An organic EL element having an auxiliary electrode and a cathode formed on the organic light emitting layer is disclosed. Here, an attempt is made to reduce the problem of heat generation and voltage drop and to make the emission intensity distribution uniform by forming an auxiliary electrode.
JP 2006-324199 A JP 2003-45674 A

  However, as long as ITO is used as the electrode material, it is difficult to essentially solve the problems of element degradation and uneven emission intensity distribution due to heat generation and voltage drop, which are described in Patent Documents 1 and 2. The technology has room for improvement.

  On the other hand, when a metal having a low electrical resistance is used as the electrode material, the formed electrode is opaque, so that there is a problem that light emitted from the organic light emitting layer cannot be extracted from the electrode surface. In addition, when the said electrode is used as a very thin film and transparency is ensured, since an electrical resistance becomes high, the said problem cannot be solved.

  Accordingly, an object of the present invention is to provide an organic EL device that can efficiently obtain a surface emission having a uniform emission intensity distribution for a long time.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found an organic EL device that can efficiently obtain a surface emission having a uniform light emission intensity distribution for a long time even when an opaque metal or the like is used as an electrode material. The structure has been found and the present invention has been completed.

That is, the present invention relates to the following (1) to (4), for example.
(1) A substantially flat transparent substrate, an anode laminated on the transparent substrate, an organic light emitting layer laminated so as to cover the outside of the anode, and a laminate so as to cover the outside of the organic light emitting layer A surface emitting light source using an organic electroluminescent element that emits light to the outside of the transparent substrate, wherein the anode and the cathode are opaque metals having light reflectivity Alternatively, the anode is formed of an alloy, and the anode has a plurality of strip-shaped members formed with the tip portion facing the cathode bulging in a substantially arc-shaped cross section at predetermined intervals with respect to the transparent substrate. A surface-emitting light source characterized by being stacked in a line.

(2) The surface emitting light source according to (1) above, wherein the shape of the tip of the belt-shaped member is a semicircle, a part of a circle, a cycloid curve, a sine curve, or a Gaussian curve.
(3) The surface emitting light source according to (1) or (2), wherein the organic light emitting layer and the cathode are formed by vacuum deposition, electron beam deposition or sputtering.

  (4) A substantially flat transparent substrate, a cathode laminated on the transparent substrate, an organic light emitting layer laminated so as to cover the outside of the cathode, and a laminate so as to cover the outside of the organic light emitting layer. A surface emitting light source using an organic electroluminescent element that emits light to the outside of the transparent substrate, wherein the anode and the cathode are opaque metals having light reflectivity Alternatively, the cathode is formed of an alloy, and a plurality of strip-shaped members formed with the tip portion facing the anode bulging in a substantially arc-shaped cross section are arranged at predetermined intervals with respect to the transparent substrate. A surface-emitting light source characterized by being stacked in a line.

  According to the surface-emitting light source of the present invention, even if ITO is not used as an electrode material, surface emission having a uniform emission intensity distribution can be obtained efficiently for a long time.

Hereinafter, the present invention will be specifically described.
<Embodiment 1>
FIG. 1 is a perspective view of the surface-emitting light source according to the first embodiment. In the surface-emitting light source of Embodiment 1, the substantially flat transparent substrate 102, the anode 104 stacked on the transparent substrate 102, the organic light-emitting layer 106 stacked so as to cover the outside of the anode 104, and the organic light-emitting layer An organic electroluminescent element that includes a cathode 108 laminated so as to cover the outside of the substrate 106 and emits light to the outside of the transparent substrate 102 is used.

  The anode 104 and the cathode 108 are made of an opaque metal or alloy having light reflectivity. In addition, the anode 104 has a plurality of strip-shaped members formed such that the tip portion facing the cathode 108 bulges in a substantially arc-shaped cross section, that is, a semicircular shape, so that the transparent substrate 102 is arranged at predetermined intervals. Are stacked. The anode 104 and the power source are connected by the surface (connecting portion 110) of the anode 104 where the organic light emitting layer 106 is not formed.

FIG. 2 shows a part of a cross section of the surface-emitting light source according to the first embodiment. Here, referring to FIG. 2, a path through which the light emitted from the organic light emitting layer 106 is extracted to the outside in the surface-emitting light source of Embodiment 1 will be described. A portion that emits light by applying voltage in the organic light emitting layer 106 is a portion sandwiched between the anode 104 and the cathode 108 (portion A surrounded by a dotted line in FIG. 2). Part A
The light emitted from the middle point B travels in all directions, but the anode 104 and the cathode 108 are made of an opaque metal or alloy having light reflectivity, so that reflection is repeated at the anode 104 and the cathode 108. While this reflection is repeated, the light passes through the transparent substrate 102 from the gap between the belt-shaped members constituting the anode 104 (arrow in FIG. 2). That is, the light emitted from the organic light emitting layer 106 is extracted to the outside through the transparent substrate 102 only from the anode 104 side.

  As described above, in the surface-emitting light source according to the first embodiment, the anode 104 is configured by laminating a plurality of band-shaped members so as to be arranged at predetermined intervals. Therefore, even when an opaque metal or alloy is used as the electrode material. Emission can be taken out efficiently. In addition, since a metal or alloy having excellent thermal conductivity and electrical conductivity is used, heat generation and voltage drop can be suppressed unlike using ITO. As a result, the organic EL element hardly deteriorates and the light emission intensity distribution becomes uniform.

  Further, the band-shaped member is formed such that the tip portion on the side facing the cathode 108 bulges in a semicircular shape. When the shape of the end of the belt-shaped member has a corner such as a square or a trapezoid, an electric field concentrates on the corner, and a load may be applied to the organic light emitting layer in the vicinity of the corner to easily cause a short circuit. On the other hand, in Embodiment 1, since the shape of the front-end | tip part of a strip | belt-shaped member is a semicircle without an angle | corner, such a problem does not occur easily. In other words, the possibility of short-circuiting during element driving is suppressed, and surface emission can be extracted for a long time.

  The material of the transparent substrate 102 is not particularly limited as long as it has transparency and electrical insulation, and examples thereof include transparent materials such as glass, PET (polyethylene terephthalate), and polycarbonate.

  The anode 104 is formed on the transparent substrate 102 as shown in FIG. FIG. 3 is a diagram showing a stage in which the anode 104 is formed on the substrate 102 when the surface-emitting light source of Embodiment 1 is manufactured. Specifically, as described above, the anode 104 is composed of a plurality of strip-shaped members, and the strip-shaped members are stacked so as to be arranged at predetermined intervals with respect to the transparent substrate 102. Further, the band-shaped member is formed such that a tip portion on the side facing the cathode 108 bulges out into a substantially circular arc shape (semi-circular shape) in cross section.

  The anode 104 is formed of an opaque metal or alloy having high light reflectivity and excellent electrical conductivity and thermal conductivity. Examples of such an anode material include Al, Cr, In, Sn, Ta, Ti, V, W, Zn, Zr, Hf, Mo, Nb, Cd, Cu, Pb, Ag, Au, Pt, Pd, and Ni. And alloys thereof. Among them, Al, Cr, Ni, Ag, Pd, Pt and alloys of these metals and W are preferable because of high light reflectance and excellent smoothness.

  The width of the belt-shaped member (diameter of the semicircle) at the portion in contact with the substrate is preferably narrow enough not to impair the conductivity of the anode 104, and specifically, it is desirably in the range of 0.1 to 1000 μm. Furthermore, if the said width | variety is this range, light emission of an organic EL element can be visually recognized as a surface light source. The thickness (maximum thickness) of the belt-shaped member is preferably thick enough to exhibit high light reflectance and conductivity, specifically 0.05 to 500 μm, more preferably 0.1 to 100 μm. A range is desirable. The interval between the band-shaped members adjacent to the band-shaped member is preferably within a range in which the light emitted from the organic light emitting layer 106 can be extracted more efficiently and the light emission intensity distribution on the light emitting surface is smaller, specifically, 1 to 10,000 μm, More preferably, it is in the range of 1 to 5000 μm.

In forming the anode, the anode material may be formed after being formed, or the film formation and the forming may be performed simultaneously. Examples of the method for forming the anode material include dry deposition methods such as resistance heating vapor deposition, electron beam vapor deposition, sputtering, and ion plating; and coating methods in which a dispersion containing metal colloid particles is wet-coated. It is done. The film thus formed can be formed into a strip shape by an imprint method or the like. Further, the anode material may be vapor-deposited through the slit, or the shape of a desired strip member may be formed in advance on the surface of the substrate, and the surface may be covered with the anode material.

Further, for the purpose of improving hole injection into the organic light emitting layer 106, the upper surface of the belt-shaped member is made of SiO ₂ ,
It consists of a conductive polymer such as metal oxide such as MoO ₃ , fluorocarbon, polypyrrole,
You may coat | cover with the layer of 0.1-30 nm normally, Preferably it is 0.1-10 nm.

  The organic light emitting layer 106 is laminated so as to cover the outside of the anode 104 as shown in FIG. FIG. 4 is a diagram showing a stage in which the organic light emitting layer 106 is formed on the substrate 102 and the anode 104 when the surface emitting light source of Embodiment 1 is manufactured. Specifically, the organic light emitting layer 106 is uniformly formed on the upper surfaces of all the strip-shaped members and the substrate sandwiched between the strip-shaped members. However, here, the organic light emitting layer 106 is formed on the upper surface of the belt-like member except for the connection portion 110 with the power source.

  Further, the organic light emitting layer 106 is formed with a uniform thickness on the upper surface of the belt-like member and the substrate sandwiched between the belt-like members. By the way, as shown in FIG. 6 to be described later, when the film thickness of the organic light emitting layer is not uniform, the current flows mainly through the thin part of the organic light emitting layer by the application of voltage, and the part emits light. In contrast, when the organic light emitting layer is formed with a uniform thickness as in Embodiment 1, light emission can be efficiently obtained over a wide range of the organic light emitting layer, and stable light emission can be sustained for a long time. .

  The organic light emitting layer 106 is formed of a known material. The organic light emitting layer 106 preferably contains a charge transporting material in addition to the light emitting material, and the charge transporting material preferably contains both a hole transporting material and an electron transporting material. As such a material, for example, a material described in JP-A-2007-12358 can be used.

  In forming the organic light emitting layer 106, a method in which the organic light emitting layer 106 is formed with a uniform thickness is preferably used. Specific examples of such a method include dry deposition methods such as vacuum deposition, electron beam deposition, and sputtering. If the organic light emitting layer 106 can be formed with a uniform thickness, a solution in which a material for forming the organic light emitting layer is dissolved in a solvent may be applied and formed into a film.

  The cathode 108 is laminated so as to cover the outside of the organic light emitting layer 106. Specifically, it is uniformly formed so as to cover the upper surface of the organic light emitting layer 106 as shown in FIG. The cathode 108 is formed of an opaque metal or alloy having high light reflectivity and excellent electrical conductivity and thermal conductivity.

  As a material for forming such a cathode 108, a material having a small work function is preferable in order to efficiently inject electrons into the organic light emitting layer 106. For example, an alkali metal such as Li, Na, K, Cs, Mg, Examples thereof include alkaline earth metals such as Ca and Ba, Al, MgAg alloys, alloys of Al such as AlLi and AlCa, and alkali metals or alkaline earth metals. Alternatively, the cathode 108 may be formed by stacking these metals or alloys.

  The thickness of the cathode 108 is preferably thick enough to exhibit high light reflectivity and conductivity, specifically 0.05 to 1000 μm, more preferably 0.1 to 100 μm. .

As a method for forming the cathode material, vacuum deposition, resistance heating deposition, electron beam deposition,
Examples thereof include dry deposition methods such as sputtering and ion plating; and coating methods in which a dispersion containing metal colloid particles is wet-coated.

  In FIG. 1, the organic light emitting layer 106 is uniformly formed on the upper surface of all the strip members constituting the anode 104 and the substrate sandwiched between the strip members (out of the surface of the anode 104). In the first embodiment, the present invention is not limited to this. For example, you may form uniformly on the upper surface of some strip | belt-shaped members, and the board | substrate pinched | interposed between the strip | belt-shaped members. Further, the thickness of the organic light emitting layer 106 may not be strictly uniform.

  In the first embodiment, the cathode 108 may be formed so as to straddle a plurality of strip-shaped members. In other words, the cathode 108 may be uniformly formed so as to cover a part of the upper surface of the organic light emitting layer 106 as shown in FIG. It may be uniformly formed so as to cover the entire upper surface of the organic light emitting layer 106 so as not to leak from the 108 side. Furthermore, a plurality of cathodes 108 may be formed for one organic light emitting layer 106 as described in, for example, Japanese Patent No. 3918558 for the purpose of dividing the light emitting region into several parts.

<Embodiment 2>
The band-shaped member constituting the anode of Embodiment 1 may be formed so that the tip portion facing the cathode bulges out in a substantially arc shape in cross section, and the shape of the tip portion of the band-shaped member is a part of a circle, It may be a cycloid curve, a sine curve (see FIG. 5) or a Gaussian curve (Embodiment 2).

  Also in this Embodiment 2, it is preferable that the width | variety of the strip | belt-shaped member in the part which contact | connects a board | substrate is narrow so that the electroconductivity of an anode is not impaired, It is preferable that it is the range of 0.1-1000 micrometers. If the width | variety of a strip | belt-shaped member is this range, light emission of an organic EL element can be visually recognized as a surface light source. In addition, the width of the band member at half the height of the maximum film thickness of the band member is preferably 50% or more of the maximum width of the band member in order to maintain high conductivity and light reflectivity. Furthermore, the thickness (maximum thickness) of the belt-like member is preferably thick enough to exhibit high light reflectance and conductivity, specifically 0.05 to 1000 μm, more preferably 0.1 to 0.1 μm. A range of 100 μm is desirable.

  In either case, surface emission having a uniform emission intensity distribution can be obtained efficiently. In addition, when the shape of the front end portion of the belt-like member is a shape having a corner such as a quadrangle or a trapezoid, an electric field concentrates on the corner, and a light emitting layer in the vicinity thereof is loaded and may be easily short-circuited. On the other hand, in the case of the above shape, such a problem is unlikely to occur because the shape of the tip portion of the belt-like member does not have a corner. In other words, the possibility of short-circuiting during element driving is suppressed, and surface emission can be extracted for a long time.

<Other embodiments>
In FIG. 6, a part of cross section is shown about the surface emitting light source of other embodiment. As shown in FIG. 6, in Embodiment 1, the upper surface of the organic light emitting layer 106 may be flat. In other words, the organic light emitting layer 106 is laminated so as to cover the outside of the anode 104 and the upper surface is flat, and the cathode 108 is laminated on the organic light emitting layer 106 in a substantially flat plate shape. Also good. In this case, since the distance between the anode 104 and the cathode 108 is not uniform, a portion where the distance between the anode 104 and the cathode 108 is small (portion A surrounded by a dotted line in FIG. 6) mainly emits light due to voltage application. . However, even in this embodiment, although the intensity is weaker than that in the first embodiment, surface emission having a uniform emission intensity distribution can be obtained for a long time.

FIG. 7 shows a part of the cross section (left end portion) of the surface emitting light source according to another embodiment. As shown in FIG. 7, in Embodiment 1, the side surface of the organic light emitting layer 106 may not be covered with the cathode 108. The same applies to the right end. In this case, although light emission leaks from the outer edge of the organic light emitting layer 106, surface light emission having a uniform light emission intensity distribution can be obtained for a long time.

  FIG. 8 shows a part of a cross section of a surface emitting light source according to another embodiment. As shown in FIG. 8, in Embodiment 1, a through hole 112 is formed in the substrate 102 so as to correspond to at least a part of the anode 104 formed on the transparent substrate 102, and the anode 104 on the substrate 102 is formed. A connecting portion 114 for connecting the anode 104 and the power source may be formed on the surface opposite to the surface on which the is formed. In this case, the anode 104 is connected to the connection portion 114 via the through hole 112.

  FIG. 9 is a perspective view of a surface emitting light source according to another embodiment. In this surface-emitting light source, a substantially flat transparent substrate 102, a cathode 108 laminated on the transparent substrate 102, an organic light-emitting layer 106 laminated so as to cover the outside of the cathode 108, and an outside of the organic light-emitting layer 106 An organic electroluminescent element that includes an anode 104 that is laminated so as to cover the surface and that emits light to the outside of the transparent substrate 102 is used.

  The anode 104 and the cathode 108 are made of an opaque metal or alloy having light reflectivity. In addition, the cathode 108 has a plurality of strip-shaped members formed such that the tip portion on the side facing the anode 104 bulges in a substantially circular cross section, that is, a semicircular shape, and is arranged at predetermined intervals with respect to the transparent substrate 102. Are stacked. The cathode 108 and the power source are connected by the surface (connecting portion 110) of the cathode 108 where the organic light emitting layer 106 is not formed.

  In this embodiment, the light emitted from the organic light emitting layer 106 is repeatedly reflected by the anode 104 and the cathode 108, and then exits to the outside through the transparent substrate 102 from the gap between the strip members. That is, the light emitted from the organic light emitting layer 106 is extracted to the outside through the transparent substrate 102 only from the cathode 108 side. As described above, in this embodiment, as in the first embodiment, the cathode 108 is configured by laminating a plurality of band-shaped members so as to be arranged at predetermined intervals. Therefore, an opaque metal or alloy is used as an electrode material. Even if it is used, light emission can be extracted efficiently. In addition, since a metal or alloy having excellent thermal conductivity and electrical conductivity is used, heat generation and voltage drop can be suppressed unlike using ITO. As a result, the organic EL element hardly deteriorates and the light emission intensity distribution becomes uniform.

  Further, the belt-like member is formed such that the tip on the side facing the anode 104 bulges in a semicircular shape. When the shape of the end of the belt-shaped member has a corner such as a square or a trapezoid, an electric field concentrates on the corner, and a load may be applied to the organic light emitting layer in the vicinity of the corner to easily cause a short circuit. On the other hand, in this embodiment, since the shape of the front-end | tip part of a strip | belt-shaped member is a semicircle without an angle | corner, such a problem does not occur easily. In other words, the possibility of short-circuiting during element driving is suppressed, and surface emission can be extracted for a long time.

  In this embodiment, a through hole is formed in the substrate so as to correspond to at least a part of the cathode formed on the transparent substrate, and the surface opposite to the surface on which the cathode is formed on the substrate. In addition, a connecting portion for connecting the cathode and the power source may be formed. In this case, the cathode is connected to the connection portion through the through hole.

  In the other embodiments described above, the shape of the tip of the belt-shaped member may be a part of a circle, a cycloid curve, a sine curve (see FIG. 5), or a Gaussian curve as in the second embodiment.

In Embodiment 1 and other embodiments, the surface emitting light source may be sealed with a metal oxide film or a sealing material in which a glass plate or a metal plate is attached to a substrate with an adhesive.
In addition, a hole injection layer or a hole transport layer made of an organic compound may be laminated between the anode 104 and the organic light emitting layer 106 in the first embodiment and other embodiments. Between the organic light emitting layer 106 and the cathode 108, a hole blocking layer, an electron transporting layer, an electron injecting layer, a dielectric layer (for example, a layer of an alkali metal or alkaline earth metal halide or oxide). May be laminated.

FIG. 1 is a diagram for explaining a surface-emitting light source according to the first embodiment. FIG. 2 is a diagram for explaining the surface-emitting light source according to the first embodiment. FIG. 3 is a diagram for explaining the surface-emitting light source according to the first embodiment. FIG. 4 is a diagram for explaining the surface-emitting light source according to the first embodiment. FIG. 5 is a diagram for explaining the surface-emitting light source according to the second embodiment. FIG. 6 is a diagram for explaining a surface-emitting light source according to another embodiment. FIG. 7 is a diagram for explaining a surface-emitting light source according to another embodiment. FIG. 8 is a diagram for explaining a surface emitting light source according to another embodiment. FIG. 9 is a diagram for explaining a surface emitting light source according to another embodiment.

Explanation of symbols

102: Transparent substrate 104: Anode 106: Organic light emitting layer 108: Cathode 110: Connection part 112: Through hole 114: Connection part

Claims (4)

A substantially flat transparent substrate, an anode laminated on the transparent substrate, an organic light emitting layer laminated so as to cover the outside of the anode, and a cathode laminated so as to cover the outside of the organic light emitting layer A surface-emitting light source using an organic electroluminescent element that emits light to the outside of the transparent substrate,
The anode and the cathode are made of an opaque metal or alloy having light reflectivity,
The anode is laminated such that a plurality of strip-like members formed with the tip portion facing the cathode bulging in a substantially arc-shaped cross section are arranged at predetermined intervals with respect to the transparent substrate. Surface emitting light source characterized by.   The surface emitting light source according to claim 1, wherein the shape of the tip of the belt-shaped member is a semicircle, a part of a circle, a cycloid curve, a sine curve, or a Gaussian curve.   The surface emitting light source according to claim 1 or 2, wherein the organic light emitting layer and the cathode are formed by vacuum deposition, electron beam deposition or sputtering. A substantially flat transparent substrate, a cathode laminated on the transparent substrate, an organic light emitting layer laminated so as to cover the outside of the cathode, and an anode laminated so as to cover the outside of the organic light emitting layer A surface-emitting light source using an organic electroluminescent element that emits light to the outside of the transparent substrate,
The anode and the cathode are made of an opaque metal or alloy having light reflectivity,
The cathode is laminated such that a plurality of strip-like members formed with the tip portion facing the anode bulging in a substantially arc-shaped cross section are arranged at predetermined intervals with respect to the transparent substrate. Surface emitting light source characterized by.

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