JP2007311159A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element equipped with a novel structure capable of making a luminance distribution in a desired state. <P>SOLUTION: The organic EL element 11 is provided with a first electrode 13, an organic layer 14 containing at least a light-emitting layer, and a second electrode 15. The organic layer 14 is fitted between the first electrode 13 and the second electrode 15, so structured that a resistance value per unit length of the former 13 and that of the latter 15 are to be the same. Further, a first power-feeding part 16 is connected with the first electrode 13 at a side of the first electrode 13 opposite to a side where the organic layer 14 is fitted, and a second power-feeding part 17 is connected with the second electrode 15. Moreover, while the first power-feeding part 16 is provided at a position corresponding to a part of light emission area of the element, the second power-feeding part 17 is provided at a position corresponding to an outer periphery part of the light emission area of the element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element.

  An organic electroluminescence element (hereinafter, the electroluminescence element is appropriately referred to as an EL element) is used as a light emitting element in, for example, a display device or a lighting device. A general structure of the organic EL element is, for example, a structure in which a first electrode, an organic light emitting layer, and a second electrode are sequentially laminated on a substrate such as glass.

  In the organic EL element having the above structure, an electric current flows through the organic light emitting layer by connecting an external drive source to the terminal portion of the first electrode and the terminal portion of the second electrode to supply current, and the organic light emitting layer emits light. To do. The light emitted from the organic light emitting layer is generally extracted to the outside through either the first electrode or the second electrode. In this case, at least the light on the side from which the light is extracted is extracted. On the other hand, a transparent electrode having high permeability is used. ITO (indium tin oxide), ZnO (zinc oxide), or the like is used for the transparent electrode. Further, an electrode made of a metal material such as Al (aluminum) or Ag (silver) having high light reflectivity is used as the electrode disposed on the side opposite to the side from which the light emitted from the organic light emitting layer is extracted.

  Here, for example, ITO is used for the first electrode and Al is used for the second electrode to produce an organic EL element having a general structure. In this organic EL element, light emitted from the organic light emitting layer is extracted through the first electrode. When an external drive source is connected to the terminal portion of the first electrode and the terminal portion of the second electrode and current is supplied, current flows through the organic light emitting layer. At this time, the volume resistance of ITO, which is a material for forming the first electrode, Since the rate is higher than the volume resistivity of Al, which is the material for forming the second electrode, the organic light emitting layer between the first electrode and the second electrode increases as the distance from the terminal portion of the first electrode increases. The current density at becomes smaller. In general, the luminance of the organic EL element is affected by the current density in the organic light emitting layer, and the luminance of the organic EL element decreases as the current density in the organic light emitting layer decreases. Therefore, in the light emitting region of the organic EL element, a portion having different luminance depending on the distance from the terminal portion of the first electrode, that is, uneven luminance appears.

One method for adjusting the luminance distribution of the organic EL element is to place a metal electrode having a low volume resistivity on a part of a transparent electrode having a high volume resistivity (see, for example, Patent Document 1). Patent Document 1 discloses that a low-resistance metal electrode 32 is provided on a part of an anode electrode 31 having a high volume resistivity formed on a glass substrate 30 as shown in FIG.
Japanese Patent Laid-Open No. 11-40369 (paragraph [0009] of the specification, FIG. 1)

  However, even when the low-resistance metal electrode 32 is provided on a part of the anode electrode 31 as in Patent Document 1, uneven luminance appears in the light emitting region of the organic EL element. This is because the apparent resistance value of the anode electrode 31 is small at the portion where the low-resistance metal electrode 32 is provided and in the vicinity thereof, so that the organic light-emitting layer 33 in the organic light-emitting layer 33 regardless of the distance from the terminal portion of the anode electrode 31. This is because the current density is substantially equal, but the current density in the organic light emitting layer 33 decreases due to the higher volume resistivity of the anode electrode 31 as the distance from the portion where the low resistance metal electrode 32 is provided. That is, in the light emitting region of the organic EL element, a portion with different luminance appears depending on the distance from the low resistance metal electrode 32 provided on the anode electrode 31.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an organic EL element having a novel structure in which the luminance distribution of the element is set to a desired state. Here, the “desired state” means, for example, a state in which luminance unevenness in the light emitting region of the element is reduced or a state in which a bright part or a dark part is partially generated at an arbitrary position (region) in the light emitting region of the element. means.

  In order to achieve the above object, an invention according to claim 1 is an organic EL element including a first electrode, an organic layer including at least a light emitting layer, and a second electrode, wherein the organic layer is the first. The first electrode and the second electrode are provided between the electrode and the second electrode, and the resistance value per unit length of the first electrode is equal to the resistance value per unit length of the second electrode. The first power feeding part is connected to the first electrode on the side opposite to the side on which the organic layer of the first electrode is provided, and the second power feeding part is connected to the second electrode. The first power feeding portion is provided at a position corresponding to a part of the light emitting region, and the second power feeding portion is provided at a position corresponding to the outer peripheral portion of the light emitting region. Here, the “electrode” refers to a conductor that is in direct contact with the organic layer and supplies electric charges (holes or electrons) to the organic layer. The “power supply unit” is a constituent element of the organic EL element, and indicates a conductor interposed between the electrode and the external drive source. The “resistance value per unit length” means, for example, measuring a resistance value between any two points separated by a distance L with respect to the formed electrode, and dividing the measured resistance value by the measurement distance L. Value. Furthermore, “the resistance value per unit length is equal” is considered not only when the resistance values per unit length of both electrodes are completely equal, but also when the resistance values per unit length of both electrodes are equal. Cases (for example, the difference between the two resistance values is 10% or less of one resistance value). The “light emitting region” refers to a planar region where the organic EL element emits light when the organic EL element is driven.

  In the present invention, since both electrodes are configured so that the resistance value per unit length of the first electrode and the resistance value per unit length of the second electrode are equal, each point on any current path Then, the current density in the organic layer including the light emitting layer is substantially equal, and the luminance of the element is substantially equal. Here, the “current path” indicates a path of a current flowing between the first power supply unit and the second power supply unit of the organic EL element as a virtual line on the light emitting surface that is a light extraction surface of the organic EL element. It is a thing. Specifically, for example, an imaginary line having the shortest distance among imaginary lines passing through an arbitrary point S in the light emitting region of the organic EL element and connecting the first feeding unit and the second feeding unit. A current path of point S is used. As the distance of the current path increases, the resistance value from the first power supply unit to the second power supply unit increases, and thus the luminance at each point on the current path decreases. And since the 1st electric power feeding part is provided in the position corresponding to a part of light emission area | region, and the 2nd electric power feeding part is provided in the position corresponding to the outer peripheral part of a light emission area | region, a 1st electric power feeding part and a 2nd electric power feeding part The distance between each current path in the light emitting region of the organic EL element is controlled by the arrangement position of the EL element, and an EL element in which the luminance distribution is set to a desired state can be provided.

  In addition, “electrode”, “feeding unit”, “resistance value per unit length”, “light emitting region”, and “current path” are defined in the same manner as described above.

  The invention according to claim 2 is the invention according to claim 1, wherein the volume resistivity of the material forming the first electrode is equal to the volume resistivity of the material forming the second electrode, and the first electrode and the first electrode The two electrodes are formed with an equal thickness. In this invention, the resistance value per unit length of the first electrode can be made equal to the resistance value per unit length of the second electrode.

  The invention according to claim 3 is the invention according to claim 1, wherein the volume resistivity of the material forming the first electrode is different from the volume resistivity of the material forming the second electrode, and the volume resistivity is low. The electrode formed of the material is formed thinner than the electrode formed of a material having a high volume resistivity. In this invention, the resistance value per unit length of the first electrode and the resistance value per unit length of the second electrode can be made equal by adjusting the thickness according to the volume resistivity of the electrode forming material. .

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the first power feeding portion is provided at a position corresponding to the central portion of the light emitting region, and the second power feeding is provided. The portion is provided at a position corresponding to the entire outer peripheral portion of the light emitting region. In the present invention, the difference in distance between the current paths in the light emitting region of the organic EL element is reduced. Accordingly, it is possible to provide an organic EL element with reduced luminance unevenness.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, further comprising an insulating layer that exposes a part of the first power feeding part and covers the other part. A first electrode is provided in contact with the exposed portion of the first power feeding unit and the insulating layer. In this invention, since the insulating layer is provided between the first electrode and the portion other than the exposed portion of the first power feeding portion, the exposed portion of the first power feeding portion is placed at an arbitrary position of the first electrode, for example, light emission. It becomes easy to arrange in the position corresponding to the center part of a field.

  The invention according to claim 6 is an organic electroluminescence device comprising a first electrode, an organic layer including at least a light emitting layer, and a second electrode, wherein the organic layer is between the first electrode and the second electrode. The first electrode and the second electrode are configured so that the resistance value per unit length of the first electrode and the resistance value per unit length of the second electrode are equal to each other. The power feeding unit is connected to the first electrode, the second power feeding unit is connected to the second electrode, the first power feeding unit and the second power feeding unit are formed in the same shape, and the light emitting region It is arranged at a point-symmetrical position with respect to the center.

  In the present invention, since the resistance value per unit length of the first electrode is equal to the resistance value per unit length of the second electrode, the light emitting surface of the organic EL element that connects the first power feeding unit and the second power feeding unit At each point on an arbitrary current path, which is the upper virtual line, the luminance of the element is substantially equal. In addition, since the distance of each current path in the light emitting region of the organic EL element is controlled by the arrangement position of the first power supply unit provided in the first electrode and the second power supply unit provided in the second electrode, the luminance distribution is An organic EL element set in a desired state can be provided.

The invention according to claim 7 is the invention according to claim 6, wherein the volume resistivity of the material forming the first electrode is equal to the volume resistivity of the material forming the second electrode, and the first electrode and the first electrode The two electrodes are formed with an equal thickness. In this invention, the resistance value per unit length of the first electrode can be made equal to the resistance value per unit length of the second electrode.
The invention according to claim 8 is the invention according to claim 6, wherein the volume resistivity of the material forming the first electrode is different from the volume resistivity of the material forming the second electrode, and the volume resistivity is low. The electrode formed of the material is formed thinner than the electrode formed of a material having a high volume resistivity. In this invention, the resistance value per unit length of the first electrode and the resistance value per unit length of the second electrode can be made equal by adjusting the thickness according to the volume resistivity of the electrode forming material. .

  The invention according to claim 9 is the invention according to any one of claims 6 to 8, wherein the first electrode, the organic layer, and the second electrode each have a rectangular planar shape. The first power feeding portion is formed over the entire side of the first electrode. In this invention, since the difference in the distance of each current path in the light emitting region of the organic EL element becomes small, it is possible to provide an organic EL element with reduced luminance unevenness.

  An organic EL element in which the luminance distribution of the element is set to a desired state can be provided. Examples of the desired state of the luminance distribution of the element include a state in which the luminance unevenness in the light emitting region of the element is reduced and a state in which a bright part or a dark part is partially generated at an arbitrary position (area) in the light emitting region of the element. Can be mentioned.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in an organic EL element in which luminance unevenness in a light emitting region is reduced will be described with reference to FIGS. 1 (a), 1 (b), and 2. FIG. FIG. 1A is a schematic plan view of an organic EL element, and FIG. 1B is a schematic cross-sectional view taken along the line AA in FIG. FIG. 2 is a partial schematic cross-sectional view of an organic EL element.

  As shown in FIGS. 1A and 1B, the organic EL element 11 includes a first electrode 13 stacked on a substrate 12, an organic layer 14 including at least a light emitting layer, and a second electrode 15. Yes. And the 1st electric power feeding part 16 is connected to the 1st electrode 13 in the surface on the opposite side to the side in which the organic layer 14 of the 1st electrode 13 is provided, and the 2nd electric power feeding part 17 is connected to the 2nd electrode 15. ing. 1A, 1B, and 2 schematically show the configuration of the organic EL element 11, and some dimensions are exaggerated for easy understanding. For this reason, the ratio of dimensions such as the width, length, and thickness of each portion is different from the actual configuration.

  The substrate 12 is a plate-like member for supporting the organic EL element. In the case where the organic EL element is a so-called bottom emission type in which light emitted from the light emitting layer is extracted through the substrate 12, a transparent substrate having a high transmittance with respect to the extracted light is used as the substrate 12. . For example, a glass substrate or an acrylic resin substrate is used. When the organic EL element is a so-called top emission type in which light emitted from the light emitting layer is extracted from the side opposite to the substrate 12, the substrate 12 has a high reflectance in addition to the transparent substrate. An opaque substrate such as a metal substrate or a ceramic substrate can be used. In the first embodiment, the organic EL element 11 constitutes a top emission type element, and light emitted from the light emitting layer is extracted to the outside from the side opposite to the substrate 12.

  As shown in FIG. 1B, the first power feeding unit 16 is formed on one surface of the substrate 12. The first power supply unit 16 includes a portion 16 a disposed at the center of the substrate 12 and a portion 16 b extending from the portion 16 a toward the end of the substrate 12. And the insulating layer 18 which exposes the part 16a of the 1st electric power feeding part 16 and covers another part is provided in the side in which the 1st electric power feeding part 16 of the board | substrate 12 is formed. That is, the portion 16 a of the first power feeding unit 16 is exposed from the insulating layer 18, and the portion 16 b of the first power feeding unit 16 is provided between the substrate 12 and the insulating layer 18.

  The first electrode 13 is formed on the portion 16 a of the first power feeding unit 16 exposed from the insulating layer 18 and the insulating layer 18 surrounding the portion 16 a. The first electrode 13 and the exposed portion 16a of the first power feeding unit 16 are in contact with each other, and the first electrode 13 and the first power feeding unit 16 are electrically connected. In addition, since the insulating layer 18 is provided between the first electrode 13 and the portion 16b of the first power feeding portion 16, the first electrode 13 and the portion 16b of the first power feeding portion 16 are in direct contact. Absent. In the first embodiment, the first electrode 13 is formed in a quadrangular plan shape, and the portion 16 a of the first power feeding portion 16 is in contact with the center portion of the first electrode 13. A second power feeding unit 17 is formed on a part of the insulating layer 18 where the first electrode 13 is not formed. The second power feeding unit 17 surrounds the first electrode 13 and is formed so as not to be in direct contact with the first electrode 13.

  An organic layer 14 including at least a light emitting layer is formed on the surface of the first electrode 13 opposite to the side on which the first power feeding unit 16 is provided. A second electrode 15 is formed on the surface of the organic layer 14 opposite to the side on which the first electrode 13 is provided. That is, the organic layer 14 is provided between the first electrode 13 and the second electrode 15. Further, the second electrode 15 is in contact with the second power feeding portion 17 formed on the insulating layer 18 at the outer peripheral portion thereof, and the second electrode 15 and the second power feeding portion 17 are electrically connected. Note that the organic layer 14 and the second electrode 15 are formed in a quadrangular plan shape.

  In the first embodiment, the first electrode 13, the organic layer 14, and the second electrode 15 are formed so that the centers thereof are arranged at substantially the same position with respect to the substrate 12. The portion 16 a of the first power feeding unit 16 is in contact with the central portion of the first electrode 13. That is, the 1st electric power feeding part 16 is provided in the position corresponding to the center part of the light emission area | region of the organic EL element 11, and the 2nd electric power feeding part 17 is provided in the position corresponding to the whole outer peripheral part of a light emission area | region. .

  Of the first electrode 13 and the second electrode 15, a transparent electrode is used for at least the electrode disposed on the side from which the light from the organic layer 14 is extracted. For the transparent electrode, for example, a known transparent conductive material such as ITO (indium tin oxide), IZO (indium zinc oxide), or ZnO (zinc oxide) is used. Further, even an electrode made of an opaque metal material can be used as a transparent electrode by adjusting the thickness of the electrode and controlling the light transmittance.

  In addition to the transparent conductive material described above, a known metal or alloy having reflectivity with respect to the light emitted from the organic layer 14 is used for the counter electrode disposed on the side facing the electrode disposed on the light extraction side. An opaque electrode material such as can be used. As the opaque electrode material, for example, Al (aluminum), Ag (silver), or the like is used. However, when a transparent conductive material is used for the counter electrode, it is necessary to dispose a member having light reflectivity on the side of the counter electrode opposite to the side where the organic layer 14 is provided.

  In the first embodiment, the organic EL element 11 constitutes a top emission type element that extracts light emitted from the organic layer 14 from the side opposite to the substrate 12, and the light is extracted through the second electrode 15. Therefore, a transparent electrode is used for the second electrode 15. The first electrode 13 that is the electrode facing the second electrode 15 is either a transparent electrode or an opaque electrode such as a metal or an alloy.

  At this time, both electrodes are configured such that the resistance value per unit length of the first electrode 13 and the resistance value per unit length of the second electrode 15 are substantially equal. In general, when electrodes having different thicknesses are formed of materials having the same volume resistivity, the resistance value per unit length decreases as the electrode thickness increases. Accordingly, the electrode material and the electrode thickness are appropriately selected so that the first electrode 13 and the second electrode 15 satisfy the condition that the resistance values per unit length are substantially equal. For example, when the volume resistivity of the material forming the first electrode 13 and the volume resistivity of the material forming the second electrode 15 are equal, both electrodes are formed to have the same thickness. For example, when the volume resistivity of the material forming the first electrode 13 and the volume resistivity of the material forming the second electrode 15 are different, the thickness of the electrode formed of the material having a low volume resistivity is The thicknesses of both electrodes are adjusted so as to be thinner than the thickness of the electrode formed of a material having a high volume resistivity. In the first embodiment, the first electrode 13 and the second electrode 15 are made of the same material, for example, ITO, and the thickness of the first electrode 13 and the thickness of the second electrode 15 are equal. .

The first power supply unit 16 electrically connected to the first electrode 13 and the second power supply unit 17 electrically connected to the second electrode 15 both have a resistance value per unit length. The first electrode 13 and the second electrode 15 are formed to be smaller than the resistance value per unit length. In the first embodiment, the first power supply unit 16 and the second power supply unit 17 are made of a material having a higher electrical conductivity than ITO, which is a material for forming the first electrode 13 and the second electrode 15, for example, a known wiring It is formed thicker than the first electrode 13 and the second electrode 15 using a metal, an alloy, or the like. If the resistance value per unit length of each of the first power feeding unit 16 and the second power feeding unit 17 is sufficiently smaller than the resistance value per unit length of the first electrode 13 and the second electrode 15, the first power feeding. Regardless of which part of the power supply unit 17 and the second power supply unit 17 are connected to the power source, there is almost no difference in the effect relating to the luminance distribution. Therefore, for example, an external drive source can be connected only to the end 17a of the second power feeding unit.
However, when the organic EL element is a bottom emission type element, a transparent conductive material such as ITO or ZnO is used for the first power feeding unit 16.

  In addition, the organic layer 14 including at least the light emitting layer provided between the first electrode 13 and the second electrode 15 may be composed of one light emitting layer, a hole injection layer, a hole transport layer, or the like. , An electron injection layer, an electron transport layer, a hole blocking layer, a buffer layer and the like, and a combination of a light emitting layer and a light emitting layer. A known light emitting material such as Alq3 or TPD is used for the light emitting layer, and the light emitting layer has a structure showing monochromatic light such as red, green, blue, yellow or the like, or a light emitting color by a combination thereof, for example, a structure showing white light emission. A thing etc. are used.

  A known insulating material is used for the insulating layer 18. For example, polyimide resin, SiO2 (silicon oxide), SiN (silicon nitride), or the like is used. However, when the organic EL element is a bottom emission type element, the insulating layer 18 is formed of a transparent insulating material such as SiO 2 or SiN.

  Further, the organic EL element 11 is provided with a protection unit (not shown) for protecting the organic layer 14 from oxygen, moisture, and the like. A protection part is comprised with a well-known passivation film, a sealing can, or those combination. However, in the case where the organic EL element is a top emission type, a material having high transparency to the extracted light is used as a material for forming the protective portion. In the case where the protective portion is formed of a passivation film, a substance that does not allow oxygen or moisture to permeate is used for the passivation film, for example, an inorganic film such as SiO2, SiN, or SiON, a polymer film, or a resin film is used. It is done. This passivation film may be formed of a single layer or may be formed by stacking a plurality of layers. By forming a passivation film on the second electrode 15 and covering the entire organic EL element 11 with the passivation film and the substrate 12, the organic layer 14 is protected from oxygen, moisture, and the like.

  Further, when the protective part is constituted by a sealing can, for example, a sealing can made of metal or glass, or a sealing can made of a polymer or resin that does not permeate oxygen, moisture, or the like is used. The organic layer 14 is protected from oxygen, moisture, and the like by sandwiching the organic EL element 11 between the sealing can and the substrate 12 and bonding the substrate 12 and the end of the sealing can through an adhesive or resin. The An inert gas, a getter agent, or the like can be accommodated inside the sealing can to improve the function as a protective portion. The organic EL element 11 can be covered with a passivation film, and the entire element can be protected with a sealing can.

  Next, a method for manufacturing the organic EL element 11 configured as described above will be described. When the organic EL element 11 is manufactured, first, the first power feeding portion 16 is formed on the substrate 12 by a known thin film forming method such as a sputtering method, a vacuum evaporation method, an ionization evaporation method or the like. The first power feeding unit 16 is patterned into a predetermined shape using a known patterning method such as a mask or etching. Next, the insulating layer 18 is formed on the first power feeding unit 16 by a known thin film forming method as described above. Thereafter, etching is performed so that only the portion 16 a of the first power feeding portion 16 is exposed from the insulating layer 18. A portion 16 b of the first power feeding unit 16 is covered with an insulating layer 18. Next, the first electrode 13 is formed on the portion 16a that is the exposed portion of the first power feeding section 16 and the insulating layer 18 that surrounds the exposed portion by a known thin film forming method. Further, the second power feeding portion 17 is formed on a portion of the insulating layer 18 where the first electrode 13 is not formed by a known thin film forming method using a mask or the like. Then, an organic layer 14 including at least a light emitting layer is formed on the first electrode 13. The organic layer 14 is formed by, for example, a vapor deposition method, and each layer constituting the organic layer 14 is sequentially stacked and formed by vapor deposition. Thereafter, the second electrode 15 is formed on the organic layer 14 by vapor deposition. At this time, the 2nd electrode 15 is connected with the 2nd electric power feeding part 17 in the outer peripheral part. Finally, a protection part is formed. When a ceramic film such as SiN is formed as the protective part, the ceramic film is formed by, for example, a plasma CVD method.

  The operation of the organic EL element 11 configured as described above will be described.

  In the organic EL element 11, the first electrode 13 is an anode and the second electrode 15 is a cathode. An external drive source (not shown) is connected to a portion of the portion 16 b of the first power feeding portion 16 located at the end of the substrate 12 and an end 17 a of the second power feeding portion 17 to supply current. The supplied current flows in order from the first power supply unit 16 to the first electrode 13 that is an anode, the organic layer 14, the second electrode 15 that is a cathode, and the second power supply unit 17. When an electric current flows through the organic layer 14, the organic layer 14 emits light. The light emitted from the organic layer 14 is extracted outside through the second electrode 15. Hereinafter, the state of the current flowing from the first power feeding unit 16 to the second power feeding unit 17 will be described in detail with reference to FIG.

  FIG. 2 is a schematic cross-sectional view in an arbitrary current path of the organic EL element 11. In this specification, the “current path” refers to a path of a current flowing between the first power supply unit 16 and the second power supply unit 17 of the organic EL element 11, a light emitting surface that is a light extraction surface of the organic EL element 11. This is shown as the upper virtual line. The current supplied to the organic EL element 11 flows through the organic EL element 11 through various paths. The current path of the organic EL element 11 is, for example, a virtual line that passes through the point P in the light emitting region and connects the second power feeding unit 17 and the first power feeding unit 16 with the shortest distance in FIG. Current path B in FIG. 1A, which is an imaginary line that passes through the point Q in the light emitting region and connects the second power feeding unit 17 and the first power feeding unit 16 with the shortest distance. Can be mentioned.

  In FIG. 2, the arrows schematically show the state of current flowing inside the organic EL element 11. The current supplied from the first power supply unit 16 to the first electrode 13 flows in the first electrode 13 toward the second power supply unit 17. This current flows through each part of the first electrode 13 and simultaneously flows to the second electrode 15 through the organic layer 14 provided in contact with the first electrode 13, and then to the second power feeding unit 17. It flows. Here, in the 1st electrode 13, the point from which the distance from the 1st electric power feeding part 16 differs is extracted, and it is set as the point D1, the point E1, and the point F1 from the point near the 1st electric power feeding part.

  It flows from the first feeding part 16 to the point D1 of the first electrode 13, flows from this point D1 through the organic layer 14 to the point D2 of the second electrode 15 corresponding to the point D1, and then from the point D2 to the second point 2 A path of a current flowing to the power feeding unit 17 is a path D. Moreover, it flows from the 1st electric power feeding part 16 to the point E1 through the point D1 of the 1st electrode 13, and the point E2 of the 2nd electrode 15 corresponding to the point E1 through the organic layer 14 containing a light emitting layer from this point E1. A path of a current flowing from the point E2 to the second power feeding unit 17 is then defined as a path E. Similarly, the second electrode 15 corresponding to the point F1 flows from the first feeding part 16 to the point F1 through the point D1 and the point E1 of the first electrode 13 and through the organic layer 14 including the light emitting layer from the point F1. A path of a current that flows to the point F2 and then flows from the point F2 to the second power feeding unit 17 is defined as a path F. Since the organic EL element 11 does not easily flow current in the planar direction of the organic layer 14 (left-right direction in FIG. 2), the current supplied from the first electrode 13 to the organic layer 14 is mainly the organic layer 14. And the second electrode 15 flows in the stacking direction (vertical direction in FIG. 2). That is, the distance obtained by adding the distance from the first power feeding unit 16 to the point D1 and the distance from the second power feeding unit 17 to the point D2 is the distance from the first power feeding unit 16 to the point E1 and the distance from the second power feeding unit 17. It becomes equal to the distance which added the distance to the point E2. Similarly, the distance obtained by adding the distance from the first power supply unit 16 to the point D1 and the distance from the second power supply unit 17 to the point D2 is the distance from the first power supply unit 16 to the point F1 and the second power supply. It becomes equal to the distance which added the distance from the part 17 to the point F2.

  Here, considering an equivalent circuit of the paths D, E, and F, the first electrode 13 and the second electrode 15 are configured so that the resistance values per unit length are substantially equal. The combined resistance, the combined resistance of the path E, and the combined resistance of the path F are substantially equal. Therefore, the currents flowing through the paths D, E, and F are substantially equal, and the luminance of the element at the point D1 or D2, the luminance of the element at the point E1 or E2, and the luminance of the element at the point F1 or F2 are substantially equal. . That is, in the organic EL element 11, the current density in the organic layer 14 is substantially equal at each point on an arbitrary current path, which is a virtual line on the light emitting surface connecting the first power supply unit 16 and the second power supply unit 17. The luminance becomes substantially equal.

  Further, when considering the current path of the organic EL element 11, the current path with the longest distance is, for example, the current path B, and the current path with the shortest distance is, for example, the current path C. As the distance of the current path increases, the combined resistance of the path increases, so that the current flowing through the organic layer 14 decreases and the luminance at each point on the current path decreases. That is, if the difference in the distance of each current path in the light emitting region of the organic EL element 11 is reduced, the luminance unevenness in the light emitting region is reduced. In the first embodiment, the first power feeding unit 16 is provided at a position corresponding to the central portion of the light emitting region, and the second power feeding unit 17 is provided at a position corresponding to the entire outer peripheral portion of the light emitting region. . Therefore, the difference in distance between the longest current path B and the shortest current path C can be reduced, and the luminance unevenness in the light emitting region is reduced, so that the luminance distribution becomes substantially uniform.

  The organic EL element 11 with reduced luminance unevenness is used, for example, as a backlight of a liquid crystal display device, a lighting device, a display, or the like.

  This embodiment has the following effects.

    (1) The organic EL element 11 includes a first electrode 13, an organic layer 14 including at least a light emitting layer, and a second electrode 15. The organic layer 14 is provided between the first electrode 13 and the second electrode 15, and the resistance value per unit length of the first electrode 13 is equal to the resistance value per unit length of the second electrode 15. The 1st electrode 13 and the 2nd electrode 15 are comprised so that it may become. The first power feeding unit 16 is connected to the first electrode 13 on the surface of the first electrode 13 opposite to the surface on which the organic layer 14 is provided, and the second power feeding unit 17 is connected to the second electrode 15. Yes. The 1st electric power feeding part 16 is provided in the position corresponding to a part of light emission area | region of an element, and the 2nd electric power feeding part 17 is provided in the position corresponding to the outer peripheral part of the light emission area | region of an element. Therefore, the luminance of the element is substantially equal at each point on an arbitrary current path in the light emitting region of the organic EL element 11, and each current path in the light emitting region depends on the arrangement position of the first power feeding unit 16 and the second power feeding unit 17. Therefore, the EL element in which the luminance distribution of the element is set to a desired state can be provided.

    (2) In the organic EL element 11, the volume resistivity of the material forming the first electrode 13 is equal to the volume resistivity of the material forming the second electrode 15, and the first electrode 13 and the second electrode 15 have the same thickness. Is formed. Therefore, the resistance value per unit length of the first electrode 13 and the resistance value per unit length of the second electrode 15 in the organic EL element 11 can be made equal.

    (3) In the organic EL element 11, the first power supply unit 16 is provided at a position corresponding to the central portion of the light emitting region, and the second power supply unit 17 is provided at a position corresponding to the entire outer peripheral portion of the light emitting region. Yes. Therefore, the difference in the distance of each current path in the light emitting region of the organic EL element 11 is reduced, and an organic EL element in which the luminance unevenness in the light emitting region is reduced can be provided.

    (4) An insulating layer 18 that exposes a part 16a of the first power feeding unit 16 and covers the other part is provided, and the first electrode 13 is in contact with the exposed part 16a of the first power feeding unit 16 and the insulating layer 18. Is provided. Accordingly, since the portion other than the exposed portion 16 a of the first power feeding unit 16 is covered with the insulating layer 18, the first power feeding unit 16 is disposed at an arbitrary position of the first electrode 13, for example, at the center of the first electrode 13. be able to.

    (5) Since the organic EL element 11 is a top emission type element, a known wiring metal or alloy having high electrical conductivity is used for the first power feeding portion 16 disposed in the central portion of the light emitting region. Can do.

    (6) Both the first power supply unit 16 and the second power supply unit 17 have resistance values per unit length that are smaller than the resistance values per unit length of the first electrode 13 and the second electrode 15. Is formed. Therefore, no matter which part on the first power supply unit 16 and the second power supply unit 17 is connected to the power source, there is almost no difference in the effect on the luminance distribution, and an external drive source is connected only to the end 17a of the second power supply unit. Even if connected, the luminance distribution of the element can be set to a desired state, for example, the luminance is substantially uniform.

(Second Embodiment)
Next, a second embodiment in which the present invention is embodied in an organic EL element with reduced luminance unevenness in the light emitting region will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 3 is a schematic plan view of the organic EL element, and FIG. 4 is a schematic cross-sectional view taken along the line GG of the organic EL element of FIG. 3 and 4 schematically show the structure of the organic EL element. For convenience of illustration, some dimensions are exaggerated for easy understanding. The ratio of dimensions such as length and thickness is different from the actual configuration.

  As shown in FIGS. 3 and 4, the organic EL element 20 has a first electrode 13, a first power feeding unit 16, and a second power feeding unit 17 formed on a substrate 12. The first electrode 13 and the first power feeding unit 16 are electrically connected, and an organic layer 14 including at least a light emitting layer is formed on the first electrode 13. A second electrode 15 is formed on the organic layer 14. The second electrode 15 is in contact with the second power feeding unit 17 at the end thereof, and the second electrode 15 and the second power feeding unit 17 are electrically connected. The organic EL element 20 in the second embodiment constitutes a bottom emission type element, and light emitted from the organic layer 14 is extracted to the outside via the first electrode 13 and the substrate 12. Therefore, a transparent substrate is used for the substrate 12, and a transparent electrode is used for the first electrode 13.

  In the second embodiment, the volume resistivity of the material forming the first electrode 13 is higher than the volume resistivity of the material forming the second electrode 15. Then, by adjusting the thicknesses of both electrodes so that the thickness of the first electrode 13 is larger than the thickness of the second electrode 15, the resistance value per unit length of the first electrode 13 and the second The resistance value per unit length of the electrode 15 is equal.

  Further, the organic EL element 20 is provided with a protection unit (not shown) for protecting the organic layer 14 from oxygen, moisture, and the like. The protection part is formed in the same manner as in the first embodiment.

  In the second embodiment, the first electrode 13, the organic layer 14, and the second electrode 15 are each formed with a rectangular planar shape. The first power supply unit 16 is provided over the entire side of the first electrode 13, and the second power supply unit 17 is provided over the entire side of the second electrode 15. Moreover, the 1st electric power feeding part 16 and the 2nd electric power feeding part 17 are formed in the same shape, and are arrange | positioned in the point-symmetrical position with respect to the center of a light emission area | region.

  Further, the resistance values per unit length of the first power feeding unit 16 and the second power feeding unit 17 are formed to be smaller than the resistance values per unit length of the first electrode 13 and the second electrode 15. ing. If the resistance value per unit length of each of the first power supply unit 16 and the second power supply unit 17 is sufficiently smaller than the resistance value per unit length of the first electrode 13 and the second electrode 15, the first power supply unit Even if the external drive source is connected to any part on the part 16 and the second power feeding part 17, there is almost no difference in the effect on the luminance distribution. In the second embodiment, as the material of the first power supply unit 16 and the second power supply unit 17, a metal having high electrical conductivity, for example, copper or aluminum is used, and the thickness of both is sufficiently increased, The resistance values per unit length of both are sufficiently smaller than the resistance values per unit length of the first electrode 13 and the second electrode 15.

  Next, a method for manufacturing the organic EL element 20 having the above configuration will be described. First, the first power feeding unit 16 and the second power feeding unit 17 are formed on the substrate 12 by a known thin film forming method such as a sputtering method, a vacuum deposition method, or an ionization deposition method. The first power supply unit 16 and the second power supply unit 17 are patterned into a predetermined shape using a known patterning method such as a mask or etching. Next, the first electrode 13 is formed by a known thin film forming method so as to be in contact with the first power feeding unit 16 and not in contact with the second power feeding unit 17. Then, an organic layer 14 including a light emitting layer is formed on the first electrode 13. The organic layer 14 including the light emitting layer is formed by, for example, a vapor deposition method, and each layer constituting the organic layer 14 is sequentially stacked and formed by vapor deposition. Thereafter, the second electrode 15 is formed on the organic layer 14 by vapor deposition. At this time, the second electrode 15 is formed so as to be in contact with the second power feeding unit 17 and is electrically connected thereto. Finally, a protection part (not shown) is formed. When a ceramic film such as SiN (silicon nitride) is formed as the protective part, the ceramic film is formed by, for example, a plasma CVD method.

  In the organic EL element 20 having the above configuration, the first electrode 13 is an anode and the second electrode 15 is a cathode. When an external drive source (not shown) is connected to the first power supply unit 16 and the second power supply unit 17 to supply current, the first electrode 13 that is an anode and the light emitting layer are sequentially provided from the first power supply unit 16. Current flows to the organic layer 14 including the second electrode 15 serving as the cathode and the second power feeding unit 17. When current flows through the organic layer 14, the organic layer 14 emits light, and light emitted from the organic layer 14 is extracted to the outside through the first electrode 13 and the substrate 12.

  A first power supply portion 16 provided over the entire side of the first electrode 13 having a rectangular planar shape and a second power supply provided over the entire side of the second electrode 15 having a rectangular planar shape. The part 17 is disposed at a point-symmetrical position with respect to the center of the light emitting region. Therefore, the current path of the organic EL element 20 is, for example, a virtual line that passes through the point R in the light emitting region and connects the second power feeding unit 17 and the first power feeding unit 16 with the shortest distance in FIG. Current path H and a path parallel to the current path H.

  That is, when the current path in the entire light emitting region of the organic EL element 20 is considered, the difference in distance between the current paths is very small. Since both electrodes are configured such that the resistance value per unit length of the first electrode 13 and the resistance value per unit length of the second electrode 15 are equal, each electrode on one current path At the point, the luminance of the element is substantially equal. Therefore, the luminance unevenness in the light emitting region of the organic EL element 20 is sufficiently reduced.

  The second embodiment has the following effects.

    (1) The organic EL element 20 includes a first electrode 13, an organic layer 14 including at least a light emitting layer, and a second electrode 15. The organic layer 14 is provided between the first electrode 13 and the second electrode 15, and the resistance value per unit length of the first electrode 13 is equal to the resistance value per unit length of the second electrode 15. As such, the first electrode and the second electrode are configured. In addition, the first power feeding unit 16 is connected to the first electrode 13, and the second power feeding unit 17 is connected to the second electrode 15. And the 1st electric power feeding part 16 and the 2nd electric power feeding part 17 are formed in the same shape, and are arrange | positioned in the point-symmetrical position with respect to the midpoint of the light emission area | region. Therefore, the luminance of the element is substantially equal at each point on an arbitrary current path in the light emitting region of the organic EL element 20, and depending on the arrangement position of the first power feeding unit 16 and the second power feeding unit 17, Since the current path is adjusted, an EL element in which the luminance distribution of the element is set to a desired state can be provided.

    (2) In the organic EL element 20, the volume resistivity of the material forming the first electrode 13 and the volume resistivity of the material forming the second electrode 15 are different, and the second is formed of a material having a low volume resistivity. The electrode is formed thinner than the first electrode formed of a material having a high volume resistivity. Therefore, since the thickness of the electrode to be formed is adjusted by the volume resistivity of the electrode forming material, the resistance value per unit length of the first electrode 13 and the resistance value per unit length of the second electrode 15 are adjusted. Can be made equal.

    (3) The first electrode 13, the organic layer 14, and the second electrode 15 constituting the organic EL element 20 have a rectangular planar shape, and the first power feeding unit 16 is provided over the entire side of the first electrode 13. It has been. Therefore, the difference in the distance of each current path in the light emitting region of the organic EL element 20 becomes very small, and an organic EL element with sufficiently reduced luminance unevenness can be provided.

    (4) The resistance values per unit length of the first power supply unit 16 and the second power supply unit 17 are sufficiently smaller than the resistance values per unit length of the first electrode 13 and the second electrode 15. Is formed. For this reason, even if the external drive source is connected to any part on the first power supply unit 16 and the second power supply unit 17, there is almost no difference in the effect on the luminance distribution.

  In addition, embodiment is not limited to the above, For example, you may comprise as follows.

  ○ The first power supply unit 16 provided on the first electrode 13 and the second power supply unit 17 provided on the second electrode 15 are only provided over the entire side of the electrode as in the second embodiment. Instead, for example, the organic EL element 21 shown in FIG. 5 may be provided at a position corresponding to a part of each electrode. However, the 1st electric power feeding part 16 and the 2nd electric power feeding part 17 are arrange | positioned in the point-symmetrical position with respect to the center of the light emission area | region.

  As shown in FIG. 5, when the organic EL element 21 has an elongated shape, the difference in distance between the current paths in the light emitting region is reduced, so that unevenness in luminance in the light emitting region of the element can be reduced. .

  The first power supply unit 16 provided on the first electrode 13 of the organic EL element is not limited to being disposed at a position corresponding to the central portion of the light emitting region, and the light emitting region of the light emitting region is selected according to a desired luminance distribution state. You may arrange | position in the position shifted | deviated from the center part. Moreover, the 2nd electric power feeding part 17 provided in the 2nd electrode 15 is not restricted to the case where it arrange | positions in the position corresponding to the whole outer peripheral part of a light emission area, According to the state of desired luminance distribution, the outer peripheral part of a light emission area | region It may be arranged at a position corresponding to a part of

  ○ The organic EL element may not only have a planar outline of a quadrangle or a rectangle, but also may have a circle or an ellipse.

(A) is a schematic top view of the organic EL element in 1st Embodiment, (b) is a schematic cross section in the AA of (a). The schematic cross section of the organic light emitting layer in 1st Embodiment. The schematic plan view of the organic EL element in 2nd Embodiment. The schematic cross section of the organic EL element in the GG line of FIG. The schematic plan view of the organic EL element in another embodiment. The model perspective view of the organic EL element of a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11, 20, 21 ... Organic EL element, 12 ... Board | substrate, 13 ... 1st electrode, 14 ... Organic layer, 15 ... 2nd electrode, 16 ... 1st electric power feeding part, 17 ... 2nd electric power feeding part, 18 ... Insulating layer.

Claims (9)

An organic electroluminescence device comprising a first electrode, an organic layer including at least a light emitting layer, and a second electrode,
The organic layer is provided between the first electrode and the second electrode,
The first electrode and the second electrode are configured such that the resistance value per unit length of the first electrode and the resistance value per unit length of the second electrode are equal.
A first power feeding portion is connected to the first electrode on a surface opposite to the side on which the organic layer of the first electrode is provided;
A second power feeding part is connected to the second electrode;
The first power feeding unit is provided at a position corresponding to a part of the light emitting region,
The said 2nd electric power feeding part is provided in the position corresponding to the outer peripheral part of a light emission area | region. The organic electroluminescent element characterized by the above-mentioned. The volume resistivity of the material forming the first electrode is equal to the volume resistivity of the material forming the second electrode,
The organic electroluminescence element according to claim 1, wherein the first electrode and the second electrode are formed to have an equal thickness. Unlike the volume resistivity of the material forming the first electrode and the volume resistivity of the material forming the second electrode,
The organic electroluminescence device according to claim 1, wherein the electrode formed of a material having a low volume resistivity is formed to be thinner than an electrode formed of a material having a high volume resistivity. The first power feeding unit is provided at a position corresponding to the center of the light emitting region,
The organic electroluminescence element according to any one of claims 1 to 3, wherein the second power feeding unit is provided at a position corresponding to the entire outer peripheral portion of the light emitting region. An insulating layer is provided to expose a part of the first power feeding part and cover the other part;
The organic electroluminescence element according to any one of claims 1 to 4, wherein the first electrode is provided so as to be in contact with an exposed portion of the first power feeding unit and the insulating layer. An organic electroluminescence device comprising a first electrode, an organic layer including at least a light emitting layer, and a second electrode,
The organic layer is provided between the first electrode and the second electrode;
The first electrode and the second electrode are configured such that the resistance value per unit length of the first electrode and the resistance value per unit length of the second electrode are equal.
A first power feeding unit is connected to the first electrode;
A second power feeding part is connected to the second electrode;
The organic electroluminescence element, wherein the first power supply unit and the second power supply unit are formed in an equal shape and are arranged at point-symmetric positions with respect to the center of the light emitting region. The volume resistivity of the material forming the first electrode is equal to the volume resistivity of the material forming the second electrode,
The organic electroluminescence device according to claim 6, wherein the first electrode and the second electrode are formed to have an equal thickness. Unlike the volume resistivity of the material forming the first electrode and the volume resistivity of the material forming the second electrode,
The organic electroluminescent device according to claim 6, wherein the electrode formed of a material having a low volume resistivity is formed to be thinner than an electrode formed of a material having a high volume resistivity. Each of the first electrode, the organic layer, and the second electrode has a planar outline formed in a rectangle,
The organic electroluminescence element according to any one of claims 6 to 8, wherein the first power feeding unit is provided over the entire side of the first electrode.

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