JP2010040486A - Light-emitting device and light-emitting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce influence from a light-emitting layer to light emission so as to improve light extraction efficiency. <P>SOLUTION: A non-radiative region 303 is disposed outside a light-emitting region 302 in which a light emitting layer emits light when a voltage is applied between a first electrode 103B and a second electrode 104, and a periodic structure 300 is formed on a substrate side 100 with respect to an organic layer 101 having at least the light emitting layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light emitting element and a light emitting device.

  The organic EL light emitting device is a thin film and features self-light emission, and is applied as a new type flat panel display. An organic EL device injects electrons from the cathode and holes (holes) from the anode into the organic layer, generates excitons in the light emitting layer in the organic layer, and emits light when these excitons return to the ground state. The principle is used. The light emitting layer is made of a light emitting material such as a fluorescent organic compound, a phosphorescent organic compound, or a quantum dot.

  One of the development issues of such an organic EL element is to improve luminous efficiency. The configuration of the organic EL element is usually a configuration in which an anode, an organic layer including a light emitting layer, and a cathode are laminated one-dimensionally. At this time, the refractive index of the light emitting layer (about 1.7 to 1.9) is larger than the refractive index of air. For this reason, most of the light emitted from the inside of the light emitting layer is totally reflected at the interface of the laminated film that changes from a high refractive index to a low refractive index, and becomes guided light that propagates in a direction horizontal to the substrate. It will be trapped inside. Of the light generated inside the light emitting layer, the proportion of light that can be extracted and used outside (light extraction efficiency) is usually only about 20%.

Therefore, in order to improve the light emission efficiency of the organic EL element, it is important to improve the light extraction efficiency. In Patent Document 1, for the purpose of preventing total reflection and suppressing light confinement inside the element, a periodic structure (sub-wavelength periodic structure, diffraction grating, etc.) is formed above and below the light emitting layer (on the light extraction side or the opposite side). ) Has been proposed.
Japanese Patent Laid-Open No. 11-283951

  However, in the above-described organic EL element, when the periodic structure is arranged on the top of the light emitting layer, it is necessary to process the periodic structure after forming the light emitting layer, and thus the light emitting layer is damaged by the manufacturing process of the periodic structure. There is a fear.

  In addition, when the periodic structure is arranged under the light emitting layer, there is a problem in the flatness of the light emitting layer and the electrode, the nonuniformity of the film at the time of formation and the decrease in adhesion occur, and the element durability is reduced due to current leakage. There is a possibility that the possibility of non-lighting is increased.

  In view of the above-described problems, an object of the present invention is to provide a light-emitting element that can reduce an influence on light emission from a light-emitting layer and improve light extraction efficiency.

  As a means for solving the above problems, a light emitting device according to the present invention is a light emitting device in which a first electrode, an organic layer having at least a light emitting layer, and a second electrode are stacked on a substrate. A non-light-emitting region that emits light from the light-emitting layer when a voltage is applied between the first electrode and the second electrode, and a non-light-emitting region located outside the light-emitting region. A periodic structure is provided in the region and closer to the substrate than the organic layer.

  According to the present invention, it is possible to reduce the influence on the light emission from the light emitting layer and improve the light extraction efficiency.

  Hereinafter, the principle of the present invention will be described based on structural examples. In the following, an organic EL element is shown and described as an example of a light emitting element, but an inorganic EL element, a QD-LED element, or the like may be used.

  In the present invention, in order to maintain the flatness of the interface between the reflective layer and the electrode and the interface between the electrode and the organic layer in the light emitting region that emits light by voltage application of the organic EL element, and to improve the light extraction efficiency, A periodic structure is formed in the non-light emitting region. A light-emitting region means that by applying a voltage between electrodes, holes are injected from the anode, electrons are injected from the cathode, excitons are generated in the light-emitting layer, and light is emitted when these excitons return to the ground state. In other words, it is a region where the light emitting layer emits light. On the other hand, the non-light emitting region is a region that does not emit light, or a region that emits less light than the light emitting region. The region where light emission is weaker than the light emitting region refers to a region that emits light with a light emission intensity of about 20% or less of the light emission intensity of light generated in the light emission region. The periodic structure is a structure for extracting light guided in the in-plane direction of the light emitting element out of the light emitting element out of the light generated in the light emitting layer in the light emitting region. In addition, the flatness of the interface between the reflective layer and the electrode and the interface between the electrode and the organic layer in the light emitting region 302 preferably has a center line average roughness Ra of 7 nm or less.

  A schematic cross-sectional view schematically showing an organic EL element having a periodic structure formed in a non-light-emitting region located outside the light-emitting region is shown in FIG. 1, and an overhead schematic diagram is shown in FIG. In FIG. 1, 100 is a substrate, 101 is an organic layer having at least a light emitting layer 105, 102 is a reflective layer, 102B is an insulating layer, 103B is a transparent electrode (first electrode), and 104 is a metal translucent electrode (second electrode). 110 are partition walls. Reference numeral 201 denotes a light emitting point, 202 denotes propagating light, 203 denotes guided light, and 204 denotes diffracted light. 1 and 2, reference numeral 300 denotes a periodic structure, 302 denotes a light emitting region, and 303 denotes a non-light emitting region. In FIG. 1, the metal semitransparent electrode 104 side is the light extraction side with respect to the light emitting point 201.

  In the organic EL element (light emitting element) shown in FIG. 1, a reflective layer 102 made of metal is formed on a substrate 100. A photonic crystal (periodic structure 300) formed so as to surround the flat surface of the reflective layer 102 is provided on the surface of the reflective layer 102 opposite to the substrate 100. The reflective layer 102 is covered with an insulating layer 102B, and a transparent electrode 103B is formed as an anode on a part of the insulating layer 102B. In the present embodiment, the transparent electrode 103B is the first electrode provided on the substrate 100 side.

  Further, a partition 110 made of an insulating material is formed so as to cover the periphery of the reflective layer 102 and the insulating layer 102B. The organic layer 101 having at least the light emitting layer 105 is laminated on the exposed portion of the insulating layer 102B exposed from the opening of the partition wall 110 and the transparent electrode 103B, and the metal translucent electrode 104 as a cathode is formed. In the present embodiment, the metal translucent electrode 104 is a light-transmissive second electrode. The light transmissive electrode may be a transparent electrode such as ITO or IZO, a metal translucent electrode made of a metal thin film, or a combination thereof. Further, as the material of the reflective layer 102, a material having high reflectance such as Al or Ag is preferable. Furthermore, as the insulating layer, silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiNxOy), acrylic resin, or the like is preferable. As shown in FIG. 1, a transparent electrode 103B, which is a first electrode, is provided in a region where the flat surface of the reflective layer 102 is formed. That is, this region becomes a light emitting region 302 in which the light emitting layer 105 emits light by applying a voltage between the transparent electrode (first electrode) 103B and the metal translucent electrode (second electrode) 104. On the other hand, as shown in FIG. 1, in a region located outside the light emitting region 302, the transparent electrode 103 </ b> B has a configuration that does not cover the periodic structure 300, and this region becomes a non-light emitting region 303. As shown in FIG. 1, the periodic structure 300 is formed in the non-light emitting region 303 located outside the light emitting region 302 and on the substrate 100 side of the organic layer 101. That is, the periodic structure 300 is not formed in the light emitting region 302, and the periodic structure 300 is formed only in the non-light emitting region 303. However, the non-light emitting region 303 and the region where the periodic structure 300 is formed may be slightly shifted due to contact with the wiring, process accuracy, and the like. In addition, as shown in FIG. 2, the non-light emitting region 303 in which the periodic structure 300 is arranged does not have to be formed on all four sides so as to surround the light emitting region 302, and even one side around the light emitting region 302 can be used. It may be partly formed.

The periodic structure 300 in FIG. 1 indicates a structure in which convex portions are periodically formed in a plane, but is a structure in which concave portions or both concave portions and convex portions are periodically formed in a plane. May be. Further, the concave and convex portions of the periodic structure 300 do not need to have a taper structure having a right apex as shown in FIG. 1, and can have various structures such as a forward taper structure and a reverse taper structure. The periodic structure 300 may be formed of the same material as the reflective layer 102 and may be formed integrally with the reflective layer 102, may be formed of a material different from the reflective layer 102, or may be a metal, a dielectric, or a combination thereof. .
As the material of the periodic structure 300, Al, Ag, Cr can be used for metals, and silicon oxide can be used for dielectrics. Furthermore, the surface of the periodic structure 300 may or may not be planarized with an insulating layer, a light transmissive electrode, or other layers. Furthermore, the periodic structure 300 may be a three-dimensional periodic structure formed by stacking two-dimensional periodic structures.

  As shown in FIG. 3, the organic layer 101 usually has a structure in which a hole transport layer 106, a light emitting layer 105 (R light emitting layer 115, G light emitting layer 125, B light emitting layer 135), and an electron transport layer 107 are laminated. . Here, the R light emitting layer, the G light emitting layer, and the B light emitting layer mean a light emitting layer that emits red (R), a light emitting layer that emits green (G), and a light emitting layer that emits blue (B), respectively. ing. The light emitting layer 105 includes a fluorescent organic compound or a phosphorescent organic compound corresponding to each emission color. Further, if necessary, a charge injection layer may be provided between the charge transport layer and the electrode. Specifically, the hole injection layer 108 may be provided between the anode and the hole transport layer 106, and the electron injection layer 109 may be provided between the cathode and the electron transport layer 107.

  By applying a voltage to these organic EL elements, holes injected from the anode and electrons injected from the cathode are recombined in the light emitting layer 105 in the organic layer 101 to form excitons, thereby emitting light. To do.

  In the configuration example shown in FIG. 1, the interface between the reflective layer 102 and the insulating layer 102 </ b> B becomes the first reflective surface provided on the first electrode side from the light emitting layer 105, and the organic layer 101 and the metal translucent electrode 104. Is the second reflecting surface provided on the second electrode side of the light emitting layer 105. The optical path length between the reflecting surfaces is adjusted between the two reflecting surfaces so that the light emitted from the light emitting layer 105 resonates and strengthens, and the one-dimensional resonator is in the normal direction (vertical direction) of the substrate. The structure is structured. At the same time, the resonator structure functions as a planar optical waveguide 301 in the in-plane direction (horizontal direction) of the substrate. Therefore, in the case of a general organic EL element without the periodic structure 300 as shown in FIG. 4, most (about 80%) of the light emitted from the light emitting point 201 is transmitted in the substrate in-plane direction. The guided light 203 is confined inside the organic EL element. Even when the second reflecting surface is not formed on the light extraction side and the resonator structure is not formed, the total reflection interface exists because the refractive index of the organic layer 101 is larger than the refractive index of air. Therefore, guided light 203 is generated in the in-plane direction between the first reflection surface and the total reflection interface, and similarly, most of the light from the light emitting point 201 is confined inside the organic EL element.

  On the other hand, the organic EL element of the present invention shown in FIG. 1 adopts a configuration in which the periodic structure 300 is provided between the organic layer 101 and the substrate 100 in the non-light emitting region 303. In this case, the guided light 203 generated in the light emitting region 302 is guided to the non-light emitting region 303, and a part of the guided light 203 is converted into the diffracted light 204 by the periodic structure 300. It is taken out from the organic EL element from the (metal translucent electrode 104 side). Therefore, the light extraction efficiency is improved.

  Furthermore, in the present invention, as shown in FIG. 1, it is not necessary to process the periodic structure 300 on the upper or lower portion of the organic layer 101 in the light emitting region 302. Therefore, damage to the organic layer 101 due to the manufacturing process of the periodic structure 300 after the organic layer 101 is formed can be avoided. In addition, since the influence on the light emission from the light emitting region 302 due to the flatness and lowering of adhesion due to the formation of the organic layer 101 on the periodic structure 300 can be suppressed, current leakage, higher drive voltage, lower element durability, Non-lighting can be avoided.

<Antireflection structure>
In general, a display device is required to have high contrast in order to improve visibility. In particular, in a display device that is frequently used outdoors, such as a small display, an external light reflection preventing function is very important for maintaining contrast. As an effective antireflection method for organic EL elements and organic EL display devices, there are a method in which a circular polarizing plate is installed, a resonator interference canceling effect and a color filter are combined. However, since both are effective methods for an organic EL element having a planar structure, if a periodic structure or a diffraction grating is disposed in order to improve the light emission efficiency, the antireflection performance is degraded. Therefore, it is desirable to have a structure that maintains the antireflection function.

  Hereinafter, with reference to FIGS. 5, 6, and 7, a structure example in which the light emitting element of the present invention has an external light reflection preventing function will be described.

  As shown in FIG. 5, in the present invention, a light shielding member 400 is disposed so as to cover the periodic structure 300 on the light extraction side of the light emitting element, and a circularly polarizing plate 401 is disposed thereon. When the display device includes a plurality of light emitting elements, the periodic structure 300 formed outside the light emitting elements is formed between adjacent light emitting elements. The light shielding member 400 is also formed between adjacent light emitting elements.

  The propagating light 202 from the light emitting point 201 is radiated to the outside of the light emitting element from the opening of the light shielding member 400 on the light emitting region 302 on the light extraction side. In addition, the diffraction angle of the diffracted light 204 needs to be larger than 90 ° with respect to the waveguide direction of the guided light 203 so that the diffracted light 204 is emitted to the outside from the opening of the light shielding member 400 at the wavelength desired to be extracted to the outside. There is. It is desirable that the period of the periodic structure 300 is configured to satisfy this demand. Furthermore, it is desirable that the light extracted to the outside through the periodic structure 300 has the maximum intensity or the maximum luminance in a diffraction angle direction larger than 90 ° with respect to the waveguide direction of the guided light 203. As shown in FIG. 5, the diffraction angle is a negative angle with respect to the substrate normal direction. Hereinafter, diffraction in a direction larger than 90 ° with respect to the waveguide direction of the guided light 203 is referred to as “negative diffraction”. The relationship between the negative diffraction and the period of the periodic structure 300 will be described later.

  FIG. 6 shows a schematic diagram when external light is incident on the light emitting element of the present invention at an angle close to vertical. Of the incident light (near vertical) 205, the incident light to the light emitting region 302 is prevented from being reflected by the circularly polarizing plate 401. Also, the incident light above the periodic structure 300 is prevented from being reflected by the light shielding member 400.

  Next, FIG. 7 shows a schematic diagram when external light is incident on the light emitting element of the present invention from an oblique direction. The oblique incident light 208 passes through the circularly polarizing plate 401 and becomes circularly polarized light, and then is reflected by the periodic structure 300 to become obliquely reflected light 209. Although the obliquely reflected light 209 is changed from circularly polarized light to elliptically polarized light by the periodic structure 300, reflection is suppressed because it is absorbed by the light shielding member 400.

  From the above, it is possible to improve the light extraction efficiency by arranging the periodic structure 300, and at the same time, it is possible to reduce the reflected light with respect to the incident external light.

  Similarly, FIGS. 8, 9 and 10 show other configuration examples in which the light emitting element of the present invention has an external light reflection preventing function.

  In FIG. 8, a light-emitting element is a light-emitting element that emits red light (hereinafter referred to as an R element), and has a resonator structure that enhances red. A light shielding member 400 is disposed above the periodic structure 300 on the light extraction side of the R element, and a color filter (R color filter) 410 that transmits red light is disposed in the opening of the light shielding member 400. The light extraction is the same as in FIG.

  FIG. 9 shows a schematic diagram when external light is incident on the R element of the present invention at an angle close to vertical. Of the incident light (near the vertical) 205, incident light to the light emitting region 302 becomes red transmitted light (R transmitted light) 210 by the R color filter 410. In the resonator structure, the condition for strengthening interference in the resonator structure and the condition for canceling interference with the reflected light are substantially the same. Therefore, in the R element having a resonator structure that enhances red, reflected light 211A and 211B from the first reflecting surface and the second reflecting surface interfere with each other and cancel each other with respect to the red transmitted light 210. Further, the light incident on the upper portion of the periodic structure 300 is prevented from being reflected by the light shielding member 400.

  The case where the external light shown in FIG. 9 is incident from an oblique direction is the same as the case of FIG. Although R (red) has been described, the same applies to G (green) and B (blue).

<Negative diffraction conditions>
Hereinafter, the periodic structure 300 for diffracted light to be negative diffraction will be considered.

As shown in FIG. 2, let two basic lattice vectors which define the period of the periodic structure 300 be a ₁ and a ₂ . Also, for these primitive lattice vectors _a 1, _{a 2,} a basic reciprocal lattice that satisfies Equation 1 relationship between _b 1, _{b 2.} In the example of FIG. 2, the periodic structure 300 has a four-fold symmetry so that the same viewing angle characteristics are obtained vertically and horizontally. The n-fold symmetry refers to the property of overlapping with itself when rotated about 2π / n radians around a certain center or axis. That is, a structure having 4-fold symmetry is a structure that coincides with its own structure when a certain structure is rotated by 2π / 4 (= 90 °) radians around the center or axis.

In FIG. 5, when the peak wavelength of the spectrum of light desired to be extracted from the light emitting layer 105 in the organic layer 101 is λ, the wave number k is k = 2π / λ. Further, it is assumed that the refractive index n of the light emitting layer 105 and the refractive index n _ext of the light extraction side medium (usually air) satisfy the condition n> n _ext .

Further, β is a propagation coefficient in the horizontal direction of the substrate 100 with respect to the guided light 203 propagating through the optical waveguide 301, and an effective refractive index n _eff and an effective absorption coefficient κ _eff with respect to the guided light 203 are defined by _Equation 2. The effective refractive index n _eff satisfies the condition n _ext <n _eff <n.

At this time, the diffraction condition is based on the condition of n _ext <n _eff <n, where two integers m ₁ and m ₂ are diffraction orders and the diffraction angle with respect to the substrate normal direction is θ, based on the phase matching condition in the horizontal direction. , Equation 3 is obtained.

In FIG. 5, the condition for the diffracted light 204 to be negatively diffracted is approximately given by Equation 4 from the diffraction condition of Equation 3. However, if the peak wavelength of the spectrum of light to be extracted outside through the periodic structure 300 is λ, the two integers m ₁ and m ₂ are diffraction orders, and the diffraction angle with respect to the substrate normal direction is θ, the condition n _ext <n _eff <N was used.

In the case of a square lattice, assuming that the period is a, the basic lattice vectors a ₁ and a ₂ are expressed by Equation 5, and the basic reciprocal lattice vectors b ₁ and b ₂ are expressed by Equation 6.

  At this time, the diffraction condition of Equation 3 is given by Equation 7. Further, the condition for causing the negative diffraction represented by Equation 4 is Equation 8.

Here, paying attention to one of the one-dimensional directions, m ₂ = 0 (or m ₁ = 0) and | m ₁ | = m> 0 (or | m ₂ | = m> 0). . At this time, the diffraction condition of Equation 7 is simplified to Equation 9. Further, Expression 8 which is a condition for causing negative diffraction is simplified to Expression 10.

In order to control the light emission pattern, efficiency, chromaticity, and the like of the organic EL element, it is desirable to generate only the first-order negative diffracted light. The conditional expression for generating only the first-order negative diffracted light is approximately given by Equation 11. In the organic EL element, normally, the refractive index of the organic layer 101 is about n = 1.5 to 2.0, and the refractive index on the light extraction side is n _ext = 1.0. Therefore, when only the primary negative diffracted light is mainly used, the period a of the periodic structure 300 is preferably about 0.33 to 1.00 times the emission peak wavelength λ. Since the wavelength range of visible light is 380 nm to 780 nm, the period a of the periodic structure 300 is desirably 125 nm or more and 780 nm or less. This period a is determined by the wavelength to be extracted, the refractive index of the organic layer 101, and the like. More specifically, when red light is to be extracted, the period a is determined by the wavelength λ to be extracted from 210 nm to 740 nm and the refractive index n of the organic layer 101 including the R light emitting layer 115. . When it is desired to extract green and blue light, the period a is determined from 165 nm to 565 nm and 150 nm to 485 nm, respectively.

<Resonator>
In the configuration example shown in FIG. 1, the interface between the reflective layer 102 and the insulating layer 102B is the first reflective surface, and the interface between the metal translucent electrode 104 and the organic layer 101 is the second reflective surface, so that the resonator structure is configured. Has been. The optical path length between the first reflecting surface and the second reflecting surface of the resonator structure is set so as to intensify the emission wavelength desired to be extracted outside by interference. Reinforcement conditions by multiple interference of the resonator structure are as follows: the peak wavelength of the spectrum of the light extracted outside is λ, the distance between the reflecting surfaces constituting the resonator structure is d, and the average refractive index between the reflecting surfaces is n Is given by 12. Here, the sum of the phase shift amount of the first reflecting surface and the phase shift amount of the second reflecting surface is φ, and m is an integer. The distance d and the average refractive index n, the thickness d _i of each layer i between the first reflection surface and the second reflecting surface constituting a resonator _structure, the refractive index of each layer as a n _i, respectively, d = Σd _i , n = Σn _i d _i / d.

  Further, in order to reduce the number of modes of the guided light 203 in consideration of the resonance condition of Equation 12, the optical path length between the first reflecting surface and the second reflecting surface is 0.375 of the emission peak wavelength λ. It is desirable that the magnification is about 1.375 times. In the organic EL element, since the refractive index between the first reflecting surface and the second reflecting surface is about n = 1.5 to 2.0, the film thickness between the first reflecting surface and the second reflecting surface. Is preferably from 70 nm to 715 nm. Specifically, when the light to be extracted is red, the film thickness is desirably from 117 nm to 678 nm. Further, when the light to be extracted is green or blue, the film thicknesses are preferably 94 nm to 518 nm and 75 nm to 445 nm.

<Modification>
In FIG. 1, the metal constituting the reflective layer 102 is not limited to a specific one. For example, when the reflective layer 102 is formed of Al, Al alloy, or the like, as shown in FIG. A natural oxide film may be formed on the surface. In this configuration, since it is not necessary to provide the insulating layer 102B on the reflective layer 102, the manufacturing process is reduced. Also in this case, a configuration in which the periodic structure 300 is provided in the non-light-emitting region 303 and closer to the substrate 100 than the organic layer 101 is employed. In addition, since the flat surface is formed on the reflective layer 102, the flatness of the transparent electrode 103B is ensured, and the light emission efficiency from the light emitting region 302 is not reduced.

  In the configuration example shown in FIG. 12, the entire surface of the reflective layer 102 including the portion where the periodic structure 300 is configured is covered with the transparent electrode 103 </ b> B that is an anode. For this reason, the reflective layer 102 and the transparent electrode 103B function as a first electrode. Instead, the electron injection layer 109 (charge injection layer) is formed in a region corresponding to the flat surface of the reflective layer 102 on the surface of the transparent electrode 103 serving as the second electrode on the light emitting layer 105 side. As a result, the electron injection property is good in the flat surface region, so that the light emission region 302 is formed. On the periodic structure 300 provided outside the electron emission property, the electron injection property is not good and the drive voltage is high. The non-light emitting region 303 can be formed. Further, a hole injection layer may be formed instead of the electron injection layer in the transparent electrode 103B in a region corresponding to the flat surface of the reflective layer 102. Further, in this region, a hole injection layer may be formed on the transparent electrode 103B on the reflective layer 102, and an electron injection layer may be formed on the light emitting layer side of the transparent electrode 103 as the second electrode.

  In addition, instead of providing an electron injection layer in the light emitting region 302, by increasing the resistance of the organic layer 101 formed on the periodic structure 300, it becomes difficult for current to flow through this region, so that the non-light emitting region 303 is formed. it can. Specifically, the resistance can be increased by forming at least one of the organic layers 101 in this region thick. The resistance can also be increased by not adding an assist dopant that is added to the light emitting layer or the like in order to enhance charge injection property, charge transport property, and the like.

  In the configuration example shown in FIGS. 13 and 14, the entire surface of the reflective layer 102 including the portion where the periodic structure 300 is configured is covered with the transparent electrode 103B which is the first electrode electrode, as in FIG. ing. Further, a partition 110 made of an insulating material formed so as to surround the light emitting region 302 covers the periodic structure 300. The region of the flat surface of the reflective layer 102 is located at the opening of the partition 110, and the organic layer 101 is laminated on that region, and the metal translucent electrode 104 as a cathode is formed. Thereby, the opening of the partition 110 becomes the light emitting region 302, the region where the partition 110 surrounding the periphery is formed becomes the non-light emitting region 303, the periodic structure 300 is the non-light emitting region 303, and the substrate is more than the organic layer 101. 100 side is provided. In this configuration, since the top emission type is used, the partition wall needs to be made of a transparent material. However, in the case of the bottom emission type as described later, the partition wall does not need to be transparent. Further, in the configuration example of FIG. 14, the partition wall 110 is formed thin so as to cover the periodic structure 300, and by adjusting this film thickness, the optical path length in the substrate normal direction of the light emitting region 302 can be reduced. The optical path lengths in the substrate normal direction of the light emitting region 303 can be made similar.

  In FIG. 1, the distance that the intensity of the guided light 203 is reduced by half due to attenuation (half distance) is about 10 μm. Therefore, the light emitted from the light emitting region 302 is extracted outside the organic EL element by the periodic structure 300, and in order to improve the light emission efficiency, from any position in the light emitting region 302 to the nearest periodic structure 300. The distance is preferably smaller than 10 μm. For this reason, as shown in FIG. 15, the light emitting region 302 may be subdivided so as to increase the proportion of the periodic structure 300 located outside the light emitting region 302 in order to further improve the light emission efficiency.

  In the configuration example shown in FIG. 16, the periodic structure 300 is provided at a position away from the reflective layer 102. Also in this case, the periodic structure 300 is formed in the non-light emitting region 303 and closer to the substrate 100 than the organic layer 101.

  So far, the substrate side has been described as an anode and the light extraction side as a cathode. However, the substrate side is a cathode, the light extraction side is an anode, and a hole transport layer, a light emitting layer, and an electron transport layer are stacked in reverse order. It is possible to implement the present invention even in the configuration. Therefore, the light emitting device according to the present invention is not limited to the configuration in which the substrate side is an anode and the light extraction side is a cathode.

  Further, examples of the organic compound used for the hole transport layer 106, the light emitting layer 105, the electron transport layer 107, the hole injection layer 108 formed as needed, and the electron injection layer 109 include a low molecular material, a polymer material, or It is comprised by both, and it does not specifically limit.

  Furthermore, the periodic structure 300 is not limited to the two-dimensional photonic crystal structure as described above, and may be a combination of a one-dimensional diffraction grating or a three-dimensional photonic crystal structure. In FIG. 1, the reflective layer 102 has a convex photonic crystal structure, but may have a concave photonic crystal structure as shown in FIG.

Furthermore, as shown in FIG. 18, a configuration having any of a plurality of types of periodic structures 300 having different basic lattice vectors may be used. Example of FIG. 18 is a case of combining the primitive lattice vectors _a 1, _{a 2} of the periodic structure 300 and the primitive lattice vector a _'1, a' ₂ of the periodic structure 300. The periodic structure 300 does not have to be completely periodic, and may be a quasicrystalline structure, a fractal structure, a structure having a continuously changing period, a structure having a partially irregular scattering structure, or a combination thereof. Good.

  Furthermore, although FIG. 1 has been described with a configuration in which the light extraction side electrode, that is, the light transmissive second electrode is the metal translucent electrode 104, the light extraction side electrode is a transparent electrode as shown in FIG. 103 may be used. Further, as shown in FIG. 8, a dielectric layer 110B may be formed on the translucent electrode 104 of FIG. 1 or the transparent electrode 103 of FIG. Alternatively, a combination of these multiple layers may be used.

  Further, in the above description, the top emission type configuration in which the opposite side of the substrate 100 is the light extraction side has been described, but the present invention can be implemented in a bottom emission configuration in which the substrate 100 side is the light extraction side. In the organic EL element shown in FIG. 19, a metal semi-transmissive layer 104 </ b> B is formed on a substrate 100. In the light emitting region 302 that generates light by voltage application, the metal semi-transmissive layer 104B is flat and covered with the insulating layer 102B, and the transparent electrode 103B is formed on the insulating layer 102B as an anode. On the other hand, the periodic structure 300 is formed in the metal semi-transmissive layer 104B located in the non-light emitting region 303 and closer to the substrate 100 than the organic layer 101, and the surface of the periodic structure 300 is covered with the insulating layer 102B. Yes. That is, the periodic structure 300 is not formed in the light emitting region 302, and the periodic structure 300 is formed only in the non-light emitting region 303. However, the non-light emitting region 303 and the region where the periodic structure 300 is formed may be slightly shifted due to contact with the wiring, process accuracy, and the like. A bottom emission configuration is shown in which a reflective layer 102 made of an organic layer 101 and a metal and functioning also as a cathode is stacked on an insulating layer 102B. In this case, the substrate 100 needs to be formed of a transparent material. In the configuration example of FIG. 19, the transparent electrode 103B is the first electrode provided on the substrate 100 side, and the reflective layer 102 made of metal is the second electrode. Further, this organic EL element has a resonator structure in which the interface between the metal semi-transmissive layer 104B and the insulating layer 102B is the first reflecting surface, and the interface between the reflecting layer 102 and the organic layer 101 is the second reflecting surface.

Further, in FIG. 1, a surface plasmon that is considered as a kind of guided light is generated by propagating in the horizontal direction of the substrate through the interface (first reflective surface) between the reflective layer 102 made of metal and the dielectric insulating layer 102B. Therefore, the interface between the reflective layer 102 and the insulating layer 102B can be used as an optical waveguide. If the propagation coefficient β _sp of the surface plasmon is the propagation coefficient β of _Equation 2, the diffraction condition is given by Equation 3 as in the case of the ordinary guided light 203. The interface that generates surface plasmons is not limited to the interface between the metal layer and the insulating layer, but may be the interface between the metal layer and the organic layer, or the interface between the metal layer and the transparent electrode.

  The light emitting device of the present invention can be applied to various uses such as a display device, illumination, and a backlight for the display device. Display devices include television receivers, personal computer displays, rear display units of imaging devices, display units of mobile phones, display units of portable music players, display units of portable information terminals, display units of portable game machines, cars It can be applied to a display unit of a navigation system.

  Hereinafter, an organic EL light-emitting device will be described as an example of a light-emitting device configured by arranging a plurality of light-emitting elements of the present invention, but the present invention is not limited in any way by this example.

<Example 1>
A full-color organic EL light-emitting device having the configuration shown in FIG. 20 is manufactured by the following method. That is, the light-emitting device of Example 1 has a plurality of pixels, and each pixel emits red light-emitting elements (R elements), green light-emitting elements (G elements), and blue light-emitting elements (B elements). That is, this is an organic EL light emitting device composed of subpixels of three colors of red, green, and blue. This full-color organic light emitting device is an example that can be preferably applied as a display device.

  First, a TFT driving circuit made of low-temperature polysilicon is formed on a glass substrate as a support, and a planarizing layer made of acrylic resin is formed on the TFT driving circuit. On the substrate 100, an Ag alloy having a thickness of about 150 nm is formed as the reflective layer 102 by sputtering. The reflective layer 102 made of an Ag alloy is a highly reflective electrode having a spectral reflectance of 80% or more in the visible light wavelength range (λ = 380 nm to 780 nm). The reflective layer 102 may use an Al alloy or the like in addition to the Ag alloy. In FIG. 20, the reflective layer 102 is formed independently for each light emitting element, but may be formed commonly for a plurality of light emitting elements.

  First, a positive resist is spin-coated on the reflective layer 102 and prebaked. Thereafter, a periodic structure pattern of a square lattice as shown in FIG. 15 is exposed to the resist, and development and post-baking are performed to form a resist pattern.

  Next, a periodic structure is formed on the reflective layer 102 by lift-off processing. First, an Ag alloy is formed with a film thickness of 40 nm by sputtering. An Ag alloy is formed on the reflective layer 102 in the exposed portion of the positive resist, and an Ag alloy is formed on the resist in a portion other than the exposed portion of the positive resist. Thereafter, the resist is peeled off, and the Ag alloy on the resist is removed to form a convex periodic structure 300 on the upper side.

  In this example, the periodic structure (R periodic structure 310) formed in the R element has a period of 345 nm, a side length of 200 nm, and a height of 40 nm. Further, the periodic structure of the G element (G periodic structure 320) has a period of 250 nm, a side length of 140 nm, and a height of 40 nm, and the B element periodic structure (B periodic structure 330) has a period of 200 nm, a side length of 145 nm, and a high length. It is formed to be 40 nm. This is because the period of the periodic structure formed in the light emitting elements of the respective colors is determined so that the peak wavelength to be extracted meets the negative diffraction condition described above. Thus, the period of the periodic structure formed in the red light emitting element is the longest, and the period of the periodic structure formed in the blue light emitting element is the shortest.

  Next, silicon oxide (SiOx) is formed as the insulating layer 102B with a thickness of 10 nm by sputtering. Further, the transparent conductive material IZO is formed to a thickness of 70 nm by sputtering, and the electrode is patterned in the light emitting region 302 to form the transparent electrode 103B as an anode. The size of the light emitting region 302 is 20 μm for A1 and 20 μm for B1 in FIG. The size of the non-light emitting region 303 is 32 μm for A2 and 95 μm for B2 in FIG.

Further, after a partition 110 of silicon oxynitride (SiN _x O _y ) is formed with a thickness of 320 nm, an opening serving as a light emitting region is etched in each sub-pixel, and an anode substrate in which a photonic crystal is arranged is manufactured.

  This is subjected to ultrasonic cleaning with isopropyl alcohol (IPA) and then dried after boiling and drying. Then, after UV / ozone cleaning, R, G, and B organic layers 111, 121, and 131 are formed by vacuum deposition.

First, compound [I] represented by the following structural formula is applied to each subpixel using a shadow mask, with a film thickness of 150 nm as an R hole transport layer, a film thickness of 90 nm as a G hole transport layer, and 40 nm as a B hole transport layer. The film thickness is formed. The degree of vacuum at this time is 1 × 10 ⁻⁴ Pa, and the deposition rate is 0.2 nm / sec.

Next, as the light emitting layer, the light emitting layers of the R element, the G element, and the B element are formed using a shadow mask. As the R light emitting layer 115 of the R element, 4,4′-Bis (N-carbazole) biphenyl (hereinafter referred to as CBP) and phosphorescent compound Bis [2- (2′-benzothienyl) pyridinato-N , C3] (acetylacetonato) Iridium (hereinafter referred to as Btp2Ir (acac)) is co-evaporated to form the R light emitting layer 115 with a thickness of 30 nm. As the G light emitting layer 125 of the G element, tris- (8-hydroxyquinoline) Aluminum (hereinafter referred to as Alq3) and a luminescent compound 3- (2′-Benzothiazolyl) -7-N, N-diethylaminocoumarin (hereinafter referred to as Alq3) are used. And G) are co-evaporated to form a G light emitting layer 125 with a thickness of 30 nm. As the B light emitting layer 135 of the B element, a compound [II] and a light emitting compound [III] shown below are co-deposited as a host to form the B light emitting layer 135 with a thickness of 30 nm. The degree of vacuum during vapor deposition is 1 × 10 ⁻⁴ Pa, and the film formation rate is 0.2 nm / sec.

Furthermore, as an electron transport layer 107 common to the R element, the G element, and the B element, 1,10-Bathophaneanthroline (hereinafter referred to as BPhen) is collectively formed with a film thickness of 10 nm by a vacuum deposition method. The degree of vacuum during vapor deposition is 1 × 10 ⁻⁴ Pa, and the film formation rate is 0.2 nm / sec. Next, as an electron injection layer common to the R element, G element, and B element, BPhen and Cs ₂ CO ₃ are co-evaporated (weight ratio 90:10) and collectively formed with a film thickness of 30 nm. The degree of vacuum during deposition is 3 × ¹⁰ -4 Pa, deposition rate is 0.2 nm / sec.

  The substrate formed up to the electron injection layer is moved to a sputtering apparatus without breaking the vacuum, and an Ag alloy is formed to a thickness of 20 nm by sputtering as the metal translucent electrode 104.

  Further, as shown in FIG. 8, as the dielectric layer 110B, silicon oxide is formed to a thickness of 290 nm by sputtering.

  Furthermore, an organic EL light emitting device is obtained by disposing a hygroscopic agent in the periphery of the light emitting device and sealing with an etched cap glass.

<Example 2>
FIG. 21 shows a configuration diagram of the organic EL light emitting device of this example. The process up to the formation of the hole transport layer is the same as in Example 1. Next, CBP and Bis [(4,6-difluorophenyl) pyridinato-N, C2] (picolinato) Iridium (hereinafter referred to as FIrpic) (weight ratio 94: as a common three-color laminated white (W) light emitting layer) 6) is formed with a film thickness of 25 nm by co-evaporation. Then, CBP and fac-Tris (2- (2-pyridinyl) phenyl) Iridium (hereinafter referred to as Ir (ppy) ₃ ) (weight ratio 92: 8) are formed to a thickness of 2 nm by co-evaporation. Further, CBP and Btp2Ir (acac) (weight ratio 92: 8) are formed by co-evaporation to a thickness of 2 nm to form a laminated structure. The process from the formation of the electron transport layer to the formation of the Ag alloy is the same as in Example 1.

  Thereafter, a silicon nitride oxide film having a thickness of 5000 nm is formed as a protective film.

  Finally, a color filter substrate in which an R color filter, a G color filter, and a B color filter are patterned on each subpixel and a black matrix (light shielding member) is patterned between the subpixels is formed on a separate substrate. Arranged on top with epoxy resin.

  Thus, an organic EL light emitting device is obtained. In other words, the organic EL light emitting device of this embodiment is configured to have a white organic EL element in which a W organic layer 171 having a resonator structure is formed in each subpixel. At this time, the optical path length of the resonator structure is configured such that the R, G, and B sub-pixels reinforce the emission wavelengths of R, G, and B by multiple interference, respectively. In other words, by combining the interference between the color filter and the resonator and the arrangement of the photonic crystal outside the light emitting region 302, the light emission efficiency is improved and the external light reflection preventing function is maintained.

<Comparative Example 1>
The processes until the formation of the reflective layer 102 are the same as those in the first embodiment. Next, SiOx is formed to a thickness of 10 nm by sputtering. Further, a transparent conductive material IZO is formed to a thickness of 70 nm by sputtering, and an electrode is patterned in the light emitting region 302 (and a contact portion for conduction) to form an anode. After the formation of the hole transport layer, the process is the same as in Example 1. That is, the configuration different from the first embodiment is a configuration that does not have a periodic structure.

  Table 1 shows evaluation values by numerical calculation of the emission intensity (intensity ratio at the peak wavelength of the emission spectrum extracted outside) of each of the R, G, and B light emitting elements in Example 1 and Comparative Example 1. Assuming that the wave height intensity of Comparative Example 1 is 1, the light emission intensity of Example 1 is about 1.2 times in all the R, G, and B light emitting elements, and it can be seen that the light extraction efficiency is improved.

It is a schematic diagram (cross-sectional schematic diagram 1) of the organic EL element which has a periodic structure in a non-light-emission area | region. It is a schematic diagram (overhead schematic diagram 1) of the organic EL element which has a periodic structure in a non-light-emission area | region. It is a schematic diagram (cross-sectional schematic diagram) of an organic layer. It is a schematic diagram (cross-sectional schematic diagram) of the organic EL element which does not have a periodic structure. It is a schematic diagram (cross-sectional schematic diagram 2) of the organic EL element which has a periodic structure in a non-light-emission area | region. It is a schematic diagram (cross-sectional schematic diagram 3) of the organic EL element which has a periodic structure in a non-light-emission area | region. It is a schematic diagram (cross-sectional schematic diagram 4) of the organic EL element which has a periodic structure in a non-light-emission area | region. It is a schematic diagram (cross-sectional schematic diagram 5) of the organic EL element which has a periodic structure in a non-light-emission area | region. It is a schematic diagram (overhead schematic diagram 2) of an organic EL element having a periodic structure in a non-light emitting region. It is a schematic diagram (at the time of light emission) of the organic EL element of a structure which has a periodic structure, a black matrix, and a circularly-polarizing plate. It is a schematic diagram (at the time of perpendicular incidence) of the organic EL element of a structure which has a periodic structure, a black matrix, and a circularly-polarizing plate. It is a schematic diagram (at the time of diagonal incidence) of the organic EL element of a structure which has a periodic structure, a black matrix, and a circularly-polarizing plate. It is a schematic diagram (at the time of light emission) of the organic EL element of a structure which has a periodic structure, a black matrix, and a color filter. It is a schematic diagram (at the time of perpendicular incidence) of the organic EL element of a structure which has a periodic structure, a black matrix, and a color filter. It is a schematic diagram (at the time of diagonal incidence) of the organic EL element of a structure which has a periodic structure, a black matrix, and a color filter. It is a schematic diagram (cross-sectional schematic diagram 6) of the organic EL element which has a periodic structure in the non-light-emitting area | region in the position away from the reflection layer. It is a schematic diagram (cross-sectional schematic diagram 7) of the organic EL element which has a concave periodic structure. It is a schematic diagram (overhead schematic diagram 3) of the organic EL element which has a periodic structure in a non-light-emitting region. It is a schematic diagram (cross-sectional schematic diagram 7) of a bottom emission type organic EL light emitting device having a periodic structure in a non-light emitting region. It is the cross-sectional schematic of the organic electroluminescent display apparatus of the RGB light emitting layer coating composition which has a periodic structure in a non-light-emission area | region. It is a cross-sectional schematic diagram of an organic EL display device having a W light emitting layer common configuration having a periodic structure in a non-light emitting region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Substrate 101 Organic layer 102 Reflective layer 102B Insulating layer 103 Transparent electrode 103B Transparent electrode on reflective layer 104 Metal translucent electrode 105 Light emitting layer 110 Partition 201 Light emitting point 202 Propagating light 203 Waveguide light 204 Diffracted light 300 Periodic structure 301 Optical waveguide 302 Light emitting area 303 Non-light emitting area

Claims (15)

A light emitting device in which a first electrode, an organic layer having at least a light emitting layer, and a second electrode are stacked on a substrate,
A light emitting region in which the light emitting layer emits light by applying a voltage between the first electrode and the second electrode, and a non-light emitting region located outside the light emitting region,
A light-emitting element, wherein a periodic structure is provided in the non-light-emitting region and closer to the substrate than the organic layer.   The light emitting element according to claim 1, wherein the periodic structure is provided between the organic layer and the substrate in the non-light emitting region.   The light emitting element according to claim 1, wherein in the non-light emitting region, a partition formed so as to surround the light emitting region covers the periodic structure.   The light emitting element according to claim 1, wherein an insulating layer is formed between the organic layer and the periodic structure in the non-light emitting region.   5. The light emitting device according to claim 1, wherein the first electrode does not cover the periodic structure. 6.   6. The charge injection layer is formed on the light emitting region side of the first electrode and / or the light emitting layer side of the second electrode in the light emitting region. The light emitting element as described in.   The light emitting device according to any one of claims 1 to 6, wherein the periodic structure has fourfold symmetry.   The light-emitting element according to claim 1, wherein a light-shielding member is disposed so as to cover the periodic structure on a light extraction side of the light-emitting element.   The light emitting device according to claim 8, wherein the light extracted through the periodic structure has a maximum intensity or a maximum luminance in an angle direction larger than 90 ° with respect to a waveguide direction. The basic reciprocal lattice vectors b ₁ and b ₂ of the periodic structure include the refractive index n of the light emitting layer, the refractive index n _ext of the light extraction side medium, and the peak wavelength λ of the spectrum of light extracted outside through the periodic structure. , For integers m ₁ and m ₂ ,

The light-emitting element according to claim 8, wherein:   The light-emitting element according to claim 8, further comprising a color filter that transmits light emitted from the light-emitting element on a light extraction side of the light-emitting element.   The light-emitting element according to claim 8, further comprising a circularly polarizing plate on a light extraction side of the light-emitting element.   Light emitted from the light emitting layer is between a first reflecting surface provided on the first electrode side from the light emitting layer and a second reflecting surface provided on the second electrode side from the light emitting layer. The light emitting device according to claim 1, comprising a resonator structure that resonates.   A light-emitting device, wherein a plurality of the light-emitting elements according to claim 1 are arranged on the substrate.   The light emitting element emitting red light, the light emitting element emitting green light, and the light emitting element emitting blue light, and the period of the periodic structure formed in the light emitting element emitting red light is the longest, The light emitting device according to claim 14, wherein the periodic structure formed in the light emitting element has the shortest period.

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