JP2010146953A - Organic el light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light extraction efficiency in an organic EL light-emitting device utilizing luminescence of an organic light-emitting layer. <P>SOLUTION: The organic EL light-emitting device 1 has a light-transmitting substrate 3 and an organic EL layer 2, and light from the organic EL layer 2 is extracted through the substrate 3. A first reflective layer 4 having a plurality of openings 41 is arranged on a light extracting surface 31 side of the substrate 3, lenses 5 are arranged by corresponding to respective openings 41, and a second reflective layer 6 is arranged on a face of the organic EL layer 2 opposite to the substrate 3. Each lens 5 has an approximately half-ellipse sectioned shape wherein mutually-symmetrical points on a peripheral edge of the opening 41 are respectively set up to be a first focal point 51a and a second focal point 51b, and adjacent lenses 5 are adjoined at a plane-viewed polygonal side 52. Thus, light passing through the opening 41 is incident to the lens 5, and extracted without reflecting on an emitting surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL light emitting device using light emission of organic electroluminescence (hereinafter referred to as organic EL).

  Conventionally, an organic EL element that obtains a surface light source by emitting an organic substance is known. FIG. 10 shows a general configuration of the organic EL element 100. The organic EL element 100 includes a transparent electrode anode 102, a hole transport layer 103, an organic light emitting layer 104, an electron injection layer 105, and a metal electrode cathode 106 on one surface of a transparent substrate 101 in this order. It is formed by stacking. By energizing between the anode 102 and the cathode 106, holes are injected from the anode 102 side, and electrons are injected from the cathode 106 side. The organic light emitting layer 104 emits light by recombination of the injected holes and electrons, and the light is extracted through the anode 102 and the substrate 101.

  Here, the substrate 101 is made of glass or the like, and its refractive index is higher than that of air. For this reason, light that enters the interface 107 with the air from the inside of the substrate 101 at a relatively small incident angle is emitted into the air, but the other light L101 is reflected at the interface 107 and is reflected in the substrate 101. The light is guided in the end direction and disappears, and cannot be taken out from the organic EL element 100. The anode 102 is usually made of ITO (Indium Tin Oxide), and its refractive index is about 1.8, which is higher than that of other layers. For this reason, the guided light L102 that is reflected at the interface with the other layer and guided in the end direction in the anode 102 is generated. Due to the reflection at these interfaces, the light extraction efficiency of the organic EL element 100 is low.

Therefore, an organic EL element is known in which light transmission within the substrate is reduced to reduce reflection at the interface by reducing the translucency of the substrate, thereby improving light extraction efficiency (for example, Patent Documents). 1). In addition, there is known an organic EL element in which a light scattering layer that scatters light between a substrate and an anode is provided to reduce reflection at the interface and improve light extraction efficiency (for example, a patent) Reference 2). However, in the organic EL element as described above, light loss due to light scattering and transmission occurs, so that the effect of improving the light extraction efficiency is not sufficient.
JP 2005-38661 A JP 2005-63704 A

  The present invention solves the above-described problems, and an object of the present invention is to improve light extraction efficiency in an organic EL light emitting device using light emission of an organic light emitting layer.

  In order to achieve the above object, an invention according to claim 1 includes an organic EL layer formed on a transparent substrate and an organic EL layer formed on the substrate, and light from the organic EL layer is extracted through the substrate. An EL light-emitting device, the first reflective layer having a plurality of openings provided on the light extraction surface side of the substrate, and provided on the light extraction surface side of the substrate corresponding to each of the openings And a second reflective layer provided on a side surface opposite to the surface on which the substrate of the organic EL layer is provided, wherein the lens is symmetrical with respect to each peripheral edge of the opening. These lenses have a substantially semi-elliptical cross-sectional shape with the first and second focal points as the first focal point, and adjacent lenses touch each other at sides of the polygon in plan view.

  According to a second aspect of the present invention, in the organic EL light emitting device according to the first aspect, the first reflective layer is disposed on a surface side where the organic EL layer is provided instead of the light extraction surface side of the substrate. It is provided.

  According to a third aspect of the present invention, in the organic EL light-emitting device according to the first aspect, the surface of the substrate on which the organic EL layer is provided is opposed to the periphery of the lenses adjacent to each other and has a substantially semicircular cross section The convex part which protruded in the shape is provided in cyclic | annular form.

  According to a fourth aspect of the present invention, in the second reflective layer, a portion facing the periphery of the adjacent lenses is a scattering reflective layer that scatters and reflects light.

  According to the first aspect of the present invention, light passing from the organic EL layer through the opening of the first reflective layer enters the lens from the light extraction surface of the substrate and is reflected by the exit surface of the lens having a substantially semi-elliptical cross section. Therefore, the light extraction efficiency is improved. Further, since the light reflected by the first reflective layer is reflected by the second reflective layer toward the light extraction surface side, the light extraction efficiency is further improved.

  According to the invention of claim 2, the same effect as that of the invention of claim 1 can be obtained.

  According to the invention of claim 3, since the light from the organic EL layer in the curved region on the convex portion is emitted in the substantially light extraction direction from the edge of the curved region, the incident angle to the substrate is small. The light is extracted through the lens instead of being guided light inside, and the light extraction efficiency of the organic EL light emitting device is improved.

  According to the fourth aspect of the present invention, the light traveling in the organic EL layer is scattered and reflected to the light extraction side and extracted through the lens, so that the light extraction efficiency of the organic EL light emitting device is improved.

(First embodiment)
An organic EL light emitting device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cross-sectional configuration of an organic EL light emitting device 1 (hereinafter referred to as a light emitting device) of the present embodiment. In addition, a figure shows an end surface and cross-sectional hatching is abbreviate | omitting illustration. FIG. 2 shows a configuration of the light emitting device 1 viewed from the light extraction side. In the light emitting device 1, an organic EL layer 2 in which an organic light emitting layer 24 or the like is laminated is formed on a light transmitting substrate 3, and light from the organic EL layer 2 is extracted through the substrate 3. A first reflective layer 4 having a plurality of openings 41 is provided on the light extraction surface 31 side of the substrate 3, and a lens 5 is provided on the light extraction surface 31 side of the substrate 3 corresponding to each of the openings 41. It is done. A second reflective layer 6 is provided on the side of the organic EL layer 2 opposite to the side on which the substrate 3 is provided. The lens 5 has a substantially semi-elliptical cross-sectional shape in which the first focus 51a and the second focus 51b are symmetrical points on the periphery of each of the openings 41, and the adjacent lenses 5 are sides 52 of a polygon in plan view. Contact with.

FIG. 3 shows the configuration of the organic EL layer 2. The organic EL layer 2 includes an anode 22 made of a transparent electrode, a hole transport layer 23, an organic light emitting layer 24, an electron injection layer 25, and a cathode 26, which are laminated in this order. The material of each layer is, for example, an organic layer in which the anode 22 is ITO (Indium Tin Oxide), the hole transport layer 23 is an arylamine, the organic light emitting layer 24 is an aluminum complex (Alq ₃ ), and the electron injection layer 25 is doped with an alkali metal. Alternatively, the lithium complex and the cathode 26 are a metal such as aluminum. Light from the organic light emitting layer 24 is extracted through the transparent anode 22. The cathode 26 made of metal reflects light from the organic light emitting layer 24 to the light extraction side. As long as the organic EL layer 2 is configured so that at least one organic light emitting layer 24 emits light, the type and number of other layers are not limited. For example, a hole injection layer made of copper phthalocyanine or the like may be provided between the anode 22 and the hole transport layer 23, and an electron made of oxadiazoles or the like between the organic light emitting layer 24 and the electron injection layer 25. A transport layer may be provided. These layers of the organic EL layer 2 are sequentially formed from the anode 22 on the one surface 33 side of the substrate 3 by, for example, a vacuum deposition method.

The description will be given with reference to FIGS. 1 and 2 again. The board | substrate 3 consists of resin, such as glass or a polystyrene, for example. The first reflective layer 4 is made of, for example, a metal such as aluminum, and is provided on the light extraction surface 31 side of the substrate 3 by vapor deposition or the like. The first reflective layer 4 has openings 41 at substantially equal intervals. The planar shape of the opening 41 is changed to a shape such as a circle that is point-symmetric with respect to the center by the mask used when forming the first reflective layer 4.

The lens 5 is formed by molding a translucent resin such as polystyrene or acrylic, and is provided on the light extraction surface 31 side of the substrate 3. In order to prevent reflection of light at the interface between the substrate 3 and the lens 5, the refractive index of the lens 5 is desirably substantially the same as the refractive index of the substrate 3, and the refractive index is added by adding molybdenum oxide or the like to the resin. May be adjusted. The lens 5 may be formed by integrally molding a resin with the substrate 3. When the substrate 3 is made of resin, a SiO ₂ thin film may be formed between the substrate 3 and the organic EL layer 2 to improve the protection of the organic EL layer 2. The lens 5 has a convex shape on the light extraction side of the light emitting device 1, and in a cross section including the center 32 </ b> C of the opening 41 and orthogonal to the substrate 3, symmetrical points on the periphery of the opening 41 are respectively set to the first focal points 51 a. The second focal point 51b has a substantially semi-elliptical cross-sectional shape. The optical axis 53 of the lens 5 passes through the center 32 </ b> C of the opening 41 and is in the normal direction of the substrate 3. In plan view, adjacent lenses 5 are in contact with each other at a polygonal side 52. The polygon is, for example, a hexagon, and each lens 5 is in contact with the honeycomb. Further, the polygon may be rectangular and each lens 5 may be in contact with the grid. Although the lens 5 has a substantially semi-elliptical cross-sectional shape, since the distance from the optical axis 53 to the periphery 52 is not constant because the polygonal sides 52 are adjacent to each other, the formed convex shape is an elliptical surface. is not.

  In the second reflective layer 6, the cathode 26 of the organic EL layer 2 is used as the reflective layer 6. The reflective layer 6 may be provided by vapor-depositing a metal such as silver on the side surface of the organic EL layer 2 opposite to the substrate 3.

  FIG. 4 shows a cross-sectional shape of one lens 5. Since the light from the organic EL layer 2 enters the lens 5 through the opening 41, the region of the opening 41 in the light extraction surface 31 of the substrate 3 is regarded as a pseudo light source. The lens 5 has a substantially semi-elliptical cross-sectional shape in which the first focus 51a and the second focus 51b are symmetrical points on the periphery of each of the openings 41. For this reason, the light having the maximum incident angle on the exit surface 54 of the lens 5 is light that enters the center 541 of the exit surface 54 from the first focus 51a and the second focus 51b. By setting the incident angle at this time to an angle α having a predetermined size that is equal to or smaller than the critical angle, the incident angle θ of the arbitrary light incident on the exit surface 54 through the opening 41 becomes equal to or smaller than the angle α. The light is extracted without being reflected by the emission surface 54. The angle α is set by determining the diameters of the opening 41 and the lens 5.

  The optical path of the light emitting device 1 configured as described above will be described with reference to FIG. FIG. 5 shows a cross section of the light emitting device 1. Of the light emitted from the organic EL layer 2, the light L 1 that has passed through the opening 41 enters the lens 5 and is extracted without being reflected by the emission surface 54. Of the light emitted from the organic EL layer 2, the light L 2 incident on the first reflective layer 4 is reflected by the first reflective layer 4 and further reflected by the second reflective layer 6. The light enters the lens 5 and is taken out without being reflected by the exit surface 54. Although the plurality of openings 41 are discretely arranged, light is emitted from the entire emission surface 54 of the lens 5, and the adjacent lenses 5 are arranged in contact with each other at the polygonal side 52 without any gap. In the light emitting device 1, the entire surface on the light extraction side emits light.

  Thus, the light L1 passing through the opening 41 of the first reflective layer 4 from the organic EL layer 2 enters the lens 5 from the light extraction surface 31 of the substrate 3, and the emission surface of the lens 5 having a substantially semi-elliptical cross section. Since the light is extracted without being reflected at 54, the light extraction efficiency is improved. Further, since the light L2 reflected by the first reflective layer 4 is reflected and extracted by the second reflective layer 6 toward the light extraction surface side, the light extraction efficiency is further improved.

(Second Embodiment)
A light emitting device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 6 shows the configuration of the light emitting device 11 of the present embodiment. In the light emitting device 11 of the present embodiment, the first reflective layer 42 is provided on the surface 33 side on which the organic EL layer 2 is provided instead of the light extraction surface 31 side of the substrate 3 in the first embodiment. ing. The first reflective layer 42 is made of a metal such as aluminum, and is provided on the light extraction surface 31 by vapor deposition or the like. The organic EL layer is provided after the first reflective layer 42 is provided. The first reflective layer 42 has openings 421 at substantially equal intervals. The lens 5 has a substantially semi-elliptical cross-sectional shape in which the symmetric points on the periphery of the opening 421 are the first focal point 51a and the second focal point 51b, respectively.

  Of the light emitted from the organic EL layer 2, the light L <b> 3 that has passed through the opening 421 enters the lens 5 and is extracted without being reflected by the emission surface 54. Of the light emitted from the organic EL layer 2, the light L 4 incident on the first reflective layer 42 is reflected by the first reflective layer 42 and further reflected by the second reflective layer 6. The light enters the lens 5 and is taken out without being reflected by the exit surface 54. For this reason, the light emitting device 11 of the present embodiment can obtain the same effects as the light emitting device 1 of the first embodiment.

(Third embodiment)
A light emitting device according to a third embodiment of the present invention will be described with reference to FIGS. 7 and 8 show the configuration of the light emitting device 12 of the present embodiment. In addition to the same configuration as that of the first embodiment, the light emitting device 12 of the present embodiment faces the periphery 52 of the lens 5 on the surface 33 on which the organic EL layer 2 of the substrate 3 is provided. Is provided with an annular projection 7 projecting in a substantially semicircular cross section in the opposite direction. In FIG. 8, the sectional shape of the convex portion 7 is also shown (hatched portion 72). The convex portion 7 is provided around the opening 41 and is formed by molding a resin such as polystyrene or acrylic, for example, and is provided on the surface 33 of the substrate 3 on the organic EL layer 2 side. A metal such as aluminum that reflects light may be deposited on the surface 71 of the convex portion 7. The shape of the convex part 7 does not necessarily have a semicircular cross section, and the cross section may have a semi-ellipse or a parabola, for example. The organic EL layer 2 is formed by vapor deposition or the like after the protrusions 7 are provided. The organic EL layer 2 has a curved region 27 on the convex portion 7.

  According to the light emitting device 12 of the present embodiment, the light L5 from the organic EL layer 2 in the curved region 27 on the convex portion 7 is emitted in the substantially light extraction direction from the edge of the curved region 27, and thus to the substrate 3. Since the incident angle is small, it does not become guided light in the substrate 3 but is extracted through the lens 5 and the light extraction efficiency of the light emitting device 12 is improved. Further, when light is incident on the first reflective layer 4, it is further reflected by the second reflective layer 6 and extracted through the lens 5.

(Fourth embodiment)
A light emitting device according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 shows a configuration of the light emitting device 13 of the present embodiment. The light-emitting device 13 of the present embodiment has the same configuration as that of the second embodiment, and the second reflective layer 6 is a scattering in which light is scattered and reflected at a portion facing the periphery 52 of the lenses 5 adjacent to each other. The reflective layer 61 is used. The portions other than the scattering reflection layer 61 of the second reflection layer 6 are specular reflection layers 62 that do not scatter light. The organic EL layer 2 of the light emitting device 13 is a transparent electrode whose cathode 26 is made of ITO or the like. The scattering reflection layer 61 is formed, for example, by screen printing a white paint containing barium titanate, and the specular reflection layer 62 is formed by vapor deposition of aluminum or silver. Further, in the same configuration as in the first embodiment in which the first reflective layer is provided on the light extraction surface side of the substrate 3, a scattering reflective layer 61 and a specular reflective layer 62 are formed as the second reflective layer 6. Also good.

  According to the light emitting device 13 of the present embodiment, the light L6 traveling in the organic EL layer 2 is scattered and reflected to the light extraction side and extracted through the lens 5, so that the light extraction efficiency of the light emitting device 12 is improved.

  In addition, this invention is not restricted to the structure of said embodiment, A various deformation | transformation is possible in the range which does not change the summary of invention. For example, the planar shape of the opening 41 may be a quadrangle or a hexagon.

1 is an end view of an organic EL light emitting device according to a first embodiment of the present invention. The top view of the apparatus. Sectional drawing of the organic electroluminescent layer in the apparatus. Explanatory drawing of the cross-sectional shape of the lens in the apparatus. The end view which shows the example of an optical path in the apparatus. The end view of the organic electroluminescent light-emitting device which concerns on the 2nd Embodiment of this invention. The end view of the organic electroluminescent light-emitting device which concerns on the 3rd Embodiment of this invention. The partial top view of the apparatus. The end view of the organic electroluminescent light-emitting device which concerns on the 4th Embodiment of this invention. Sectional drawing of a general organic EL element.

Explanation of symbols

1, 11, 12, 13 Organic EL light emitting device 2 Organic EL layer 24 Organic light emitting layer 3 Substrate 4, 42 First reflective layer 41, 421 Opening 5 Lens 51a First focal point 51b Second focal point 52 Side 6 Second Reflective layer 61 Scattered reflective layer 7 Convex part

Claims (4)

An organic EL light-emitting device comprising a light-transmitting substrate and an organic EL layer formed on the substrate, wherein light from the organic EL layer is extracted through the substrate,
A first reflective layer having a plurality of openings provided on the light extraction surface side of the substrate;
A lens provided corresponding to each of the openings on the light extraction surface side of the substrate;
A second reflective layer provided on the side of the organic EL layer opposite to the side on which the substrate is provided,
The lens has a substantially semi-elliptical cross-sectional shape in which the first focus and the second focus are symmetrical points on the periphery of each of the openings, and adjacent lenses are in contact with each other on a side of a polygon in plan view. An organic EL light emitting device characterized.   2. The organic EL light emitting device according to claim 1, wherein the first reflective layer is provided on a surface side on which the organic EL layer is provided instead of the light extraction surface side of the substrate. .   The surface of the substrate on which the organic EL layer is provided is provided with a convex portion projecting in a substantially semicircular cross section so as to face the periphery of the adjacent lenses. Item 2. The organic EL light-emitting device according to Item 1.   3. The organic EL according to claim 1, wherein the second reflective layer is a scattering reflective layer that scatters and reflects light at a portion facing the periphery of the adjacent lenses. 4. Light emitting device.

Images