WO2014083693A1

WO2014083693A1 - Light emitting device

Info

Publication number: WO2014083693A1
Application number: PCT/JP2012/081137
Authority: WO
Inventors: 黒田　和男; 秀雄工藤; 浩大畑; 敏治内田
Original assignee: パイオニア株式会社
Priority date: 2012-11-30
Filing date: 2012-11-30
Publication date: 2014-06-05

Abstract

A light emitting device (100) comprises: a light transmissive substrate (110); a first light transmissive electrode (130) disposed opposite the light emission surface (light extraction surface (110a)) of the light transmissive substrate (110); an organic function layer (140) including at least a light emitting layer; a light reflection layer (160); and a light transmissive interposing layer (120). The interposing layer (120) is disposed between the organic function layer (140) and the light reflection layer (160). The interposing layer (120) is constituted by a first layer (121) and a second layer (122) that have mutually different refractive indexes, and are laminated alternately in three or more layers, the interposing layer (120) having two or more interfaces therein.

Description

Light emitting device

The present invention relates to a light emitting device having an organic light emitting layer.

There is a light emitting device having an organic light emitting layer as one of the light emitting devices. In this light emitting device, it is desired to improve the ratio of light emitted to the outside (light extraction efficiency) of the light generated in the organic light emitting layer.

As a technique for improving the light extraction efficiency, there is one described in Patent Document 1. The organic EL (Electro Luminescence) element described in Patent Document 1 emits light with respect to a light-transmitting front electrode and back electrode, a light-emitting layer disposed between the front electrode and the back electrode, and the back electrode as a reference. A high refractive index light scattering layer disposed on the opposite side of the layer. The high refractive index light scattering layer is constituted by dispersing fine particles such as Y ₂ O ₃ in a resin. Japanese Patent Application Laid-Open No. H10-228707 describes that light traveling from the light emitting layer toward the back side is reflected by the high refractive index light scattering layer and travels toward the front side, so that light can be efficiently extracted from the front side.

JP 2004-14385 A

The inventor considered that the technique described in Patent Document 1 has the following problems.
The high refractive index light scattering layer in the technique of Patent Document 1 scatters light in a random direction. For this reason, the effect of strengthening the intensity of light reflected by the high-refractive-index light scattering layer and reflected toward the front side (reflected light) and the light directed from the light emitting layer toward the front side (direct light) is sufficient. It is difficult to get into. Therefore, the technique of Patent Document 1 has room for improvement regarding light extraction efficiency. Furthermore, a problem peculiar to the scattering layer is that in the case of light in an oblique direction, the probability of scattering increases, and the amount of light toward the extraction surface decreases.

An example of a problem to be solved by the present invention is to improve the light extraction efficiency of the light emitting device.

The invention according to claim 1 is a translucent substrate;
A translucent first electrode disposed on the side opposite to the exit surface of the translucent substrate;
An organic functional layer including at least a light-emitting layer and disposed on the opposite side of the translucent substrate with respect to the first electrode;
A light reflecting layer disposed on the opposite side of the first electrode with respect to the organic functional layer, and reflecting light coming from the organic functional layer side;
A light-transmitting intervening layer disposed between the organic functional layer and the light reflecting layer;
With
The intervening layer is formed by laminating three or more layers having different refractive indexes between adjacent layers, and has two or more interfaces.
In the light emitting device, the refractive indexes of the three or more layers are alternately high and low or alternately low and high from the organic functional layer side toward the light reflecting layer side. is there.

The above-described object and other objects, features, and advantages will be further clarified by a preferred embodiment described below and the following drawings attached thereto.

It is sectional drawing which shows the structure of the light-emitting device which concerns on 1st Embodiment. It is sectional drawing which shows the example of operation | movement of the light-emitting device which concerns on 1st Embodiment. It is a figure which shows the simulation result of the reflectance in the light-emitting device which concerns on 1st Embodiment. It is a figure explaining the interference of the direct light from a light emitting layer and the reflected light reflected in the light reflection layer in the light-emitting device which concerns on the comparative example 1. FIG. It is a figure which shows the relationship between the angle of light in the light-emitting device which concerns on the comparative example 1, and the increase / decrease in the light intensity by interference. It is sectional drawing which shows the 1st example of an organic functional layer. It is sectional drawing which shows the 2nd example of an organic functional layer. FIG. 8A is a plan view showing an example of a more specific configuration of the light emitting device according to the first embodiment, and FIG. 8B is a cross-sectional view taken along line BB in FIG. 8A. FIG. It is sectional drawing which shows the structure of the light-emitting device which concerns on 2nd Embodiment. 1 is a cross-sectional view illustrating a configuration of a light emitting device according to Example 1. FIG. 6 is a cross-sectional view illustrating a configuration of a light emitting device according to Example 2. FIG. 6 is a cross-sectional view illustrating a configuration of a light emitting device according to Example 3. FIG. 6 is a cross-sectional view illustrating a configuration of a light emitting device according to Example 4. FIG.

Hereinafter, embodiments will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

(First embodiment)

FIG. 1 is a cross-sectional view showing a configuration of a light emitting device 100 according to an embodiment. The light emitting device 100 includes an organic EL element. The light emitting device 100 can be used as a light source of, for example, a display, a lighting device, or an optical communication device.

The light emitting device 100 according to the present embodiment includes a light transmissive substrate 110 having an emission surface (light extraction surface 110a), a light transmissive first electrode 130, an organic functional layer 140 including at least a light emitting layer, and light reflection. A layer 160 and a light-transmitting intervening layer 120; The first electrode 130 is disposed on the side opposite to the emission surface of the translucent substrate 110. The organic functional layer 140 is disposed on the opposite side of the translucent substrate 110 with respect to the first electrode 130. The light reflecting layer 160 is disposed on the side opposite to the first electrode 130 with respect to the organic functional layer 140. The light reflecting layer 160 reflects light that arrives at the light reflecting layer 160 from the organic functional layer 140 side. The intervening layer 120 is disposed between the organic functional layer 140 and the light reflecting layer 160. The intervening layer 120 is configured by stacking three or more layers having different refractive indexes between adjacent layers, and has two or more interfaces. The refractive indexes of three or more layers constituting the intervening layer 120 are alternately in the order of high and low from the organic functional layer 140 side to the light reflecting layer 160 side, or alternately low and high. The order is

Hereinafter, in order to simplify the description, description will be made assuming that the positional relationship (vertical relationship, etc.) of each component of the light emitting device 100 is the relationship shown in each drawing. However, the positional relationship in this description is irrelevant to the positional relationship when the light emitting device 100 is used.

As shown in FIG. 1, the translucent substrate 110 is a plate-like member made of a translucent material such as glass or resin. For example, the upper surface of the translucent substrate 110, that is, the surface of the translucent substrate 110 opposite to the organic functional layer 140 side is a flat light extraction surface 110a. The light extraction surface 110a is in contact with air (refractive index 1) filling the light emission space. In addition, the light extraction film is affixed on the upper surface of the translucent board | substrate 110, and the upper surface of this light extraction film may comprise the light extraction surface.

The first electrode 130 may be a transparent electrode made of a metal oxide conductor such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). However, the first electrode 130 may be a metal thin film that is thin enough to transmit light.

The organic functional layer 140 includes a translucent second electrode 150. For example, the second electrode 150 is disposed at the end of the organic functional layer 140 on the intervening layer 120 side. That is, the 2nd electrode 150 comprises the layer of the end by the side of the intervening layer 120 in the organic functional layer 140, for example. Alternatively, the organic functional layer 140 includes an organic layer (such as an electron injection layer) disposed between the second electrode 150 and the intervening layer 120. That is, the second electrode 150 is disposed at an intermediate portion in the thickness direction of the organic functional layer 140. FIG. 1 shows an example in which the second electrode 150 is disposed at the end of the organic functional layer 140 on the intervening layer 120 side. For example, the second electrode 150 can be a metal thin film that is thin enough to transmit light. In this case, the film thickness of the second electrode 150 can be about 10 nm, for example. Examples of the material of the second electrode 150 include silver and aluminum. However, the second electrode 150 may be a transparent electrode made of a metal oxide conductor such as ITO or IZO.

For example, the first electrode 130 constitutes an anode and the second electrode 150 constitutes a cathode. In this case, it is necessary to select a combination of the material of the second electrode 150 and the material of the first electrode 130 so that the work function of the second electrode 150 is smaller than the work function of the first electrode 130.

The portion other than the second electrode 150 in the organic functional layer 140 is made of an organic material such as NPB (N, N-di (naphthalene-1-yl) -N, N-diphenyl-benzidine). The organic functional layer 140 may include, for example, a layer having an electron transport function, a layer having a hole transport function, and the like in addition to the light emitting layer. The refractive index of the organic functional layer 140 is, for example, about 1.6 or more and 2.0 or less.

Each layer constituting the intervening layer 120 is made of, for example, a translucent dielectric. Of the three or more layers constituting the intervening layer 120, adjacent layers are in contact with each other, and an interface is formed between the adjacent layers.
The intervening layer 120 has a laminated structure in which three or more first layers 121 and second layers 122 are alternately laminated. For example, the refractive index of the second layer 122 is smaller than the refractive index of the first layer 121. When the second electrode 150 is positioned at the end of the organic functional layer 140 on the intervening layer 120 side, the refractive index of the first layer 121 is equal to or higher than the refractive index of the organic functional layer 140. For example, the refractive index of the first layer 121 can be about 1.8. For example, the refractive index of the second layer 122 can be about 1.3 to 1.5. The material of the first layer 121 can be the same as the material of the organic functional layer 140, for example. The material of the second layer 122 can be, for example, MgF ₂ (refractive index 1.37) or SiO ₂ (refractive index 1.45). Note that the first layers 121 are not necessarily made of the same material. Similarly, the second layers 122 are not necessarily made of the same material. If the refractive index inside the intervening layer 120 is alternately in the order of high and low from the organic functional layer 140 side to the light reflecting layer 160 side, or alternately in the order of low and high. For example, any refractive index material may be used as the material of the first layer 121 and the second layer 122. If the refractive index inside the intervening layer 120 is alternately in the order of high and low from the organic functional layer 140 side to the light reflecting layer 160 side, or alternately in the order of low and high. For example, the refractive index of any one or more second layers 122 may be larger than the refractive index of any one or more first layers 121.
When the refractive indexes of the first layers 121 are different from each other, the physical film thicknesses of the first layers 121 are different from each other even if the optical path lengths of the film thicknesses of the first layers 121 are the same. Similarly, when the refractive indexes of the second layers 122 are different from each other, even if the optical path lengths of the film thicknesses of the second layers 122 are the same, the physical film thicknesses of the second layers 122 are different from each other.
For example, for the first layer 121 and the second layer 122 close to the organic functional layer 140, a material that does not adversely affect the organic functional layer 140 (for example, porous silica) can be used. In addition, for the first layer 121 and the second layer 122 that are separated from the organic functional layer 140, a material (for example, TiO) that adversely affects the organic functional layer 140 when it is close to the organic functional layer 140 should be selected. Can do. This is because the first layer 121 and the second layer 122 existing between the first layer 121 and the second layer 122 and the organic functional layer 140 serve as a barrier layer.

The uppermost layer (most layer on the organic functional layer 140 side) in the intervening layer 120 may be either the first layer 121 or the second layer 122. However, even if the second electrode 150 is disposed at the end of the organic functional layer 140 on the side of the intervening layer 120 by suppressing the uppermost layer of the intervening layer 120 to the first layer 121 having a high refractive index, the occurrence of plasmon resonance is suppressed. can do. On the other hand, when the uppermost layer in the intervening layer 120 is the second layer 122 having a low refractive index, the interface between the second electrode 150 and the intervening layer 120 has a high refractive index from the light emitting layer side toward the light reflecting layer 160 side. The interface changes from one side to the other, and light can be reflected to the light extraction surface 110a side at this interface. The lowermost layer (the layer closest to the light reflecting layer 160) in the intervening layer 120 may be either the first layer 121 or the second layer 122.

The light reflecting layer 160 is made of, for example, a metal film such as silver or aluminum. That is, the light reflection layer 160 is, for example, conductive. The light reflecting layer 160 reflects light traveling from the organic functional layer 140 toward the light reflecting layer 160 (light coming from the organic functional layer 140 side) toward the translucent substrate 110 side. However, the light reflection layer 160 may be non-conductive (insulating). For this reason, the light reflection layer 160 may not be a metal layer.

When a voltage is applied between the first electrode 130 and the second electrode 150, the light emitting layer of the organic functional layer 140 emits light. The translucent substrate 110, the first electrode 130, the organic functional layer 140, the second electrode 150, and the first layer 121 and the second layer 122 of the intervening layer 120 are all light emitted from the light emitting layer of the organic functional layer 140. Of at least part of it. Part of the light emitted from the light emitting layer is emitted (extracted) from the light extraction surface 110a of the translucent substrate 110 to the outside of the light emitting device 100 (that is, the light emission space).

For example, one surface (the lower surface in FIG. 1) of the translucent substrate 110 and one surface (the upper surface in FIG. 1) of the first electrode 130 are in contact with each other. Further, the other surface (lower surface in FIG. 1) of the first electrode 130 and one surface (upper surface in FIG. 1) of the organic functional layer 140 are in contact with each other. In addition, the second electrode 150 is disposed at the end of the organic functional layer 140 on the intervening layer 120 side. Further, the second electrode 150 and one surface (the upper surface in FIG. 1) of the intervening layer 120 are in contact with each other. More specifically, the surface of the second electrode 150 opposite to the light emitting layer side and one surface (the upper surface in FIG. 1) of the uppermost first layer 121 are in contact with each other. Further, the other surface (lower surface in FIG. 1) of the intervening layer 120 and one surface (upper surface in FIG. 1) of the light reflecting layer 160 are in contact with each other. More specifically, one surface (the lower surface in FIG. 1) of the lowermost first layer 121 and one surface of the light reflecting layer 160 are in contact with each other. However, another layer may exist between the translucent substrate 110 and the first electrode 130. Similarly, another layer may exist between the first electrode 130 and the organic functional layer 140. Similarly, in the organic functional layer 140, another layer may exist between the organic layer (organic material part) such as an electron injection layer and the second electrode 150. Similarly, another layer may exist between the second electrode 150 and the intervening layer 120. Similarly, another layer may exist between the intervening layer 120 and the light reflecting layer 160.

When the maximum peak wavelength of light emitted from the light emitting layer is λ, the thickness of each of the three or more layers constituting the intervening layer 120 is such that the optical path length (optical distance) is λ / 4. Yes. That is, the thickness of each first layer 121 and the thickness of each second layer 122 are such that the optical path length (optical distance) is λ / 4. Here, the maximum peak wavelength λ differs individually depending on the refractive index of each layer. That is, the maximum peak wavelength λ is a value for each layer. Of light of the maximum peak wavelength of the light emitted from the light-emitting layer, ₁ wavelength lambda in the first layer _121, and the wavelength of the second layer 122 and lambda _2, the thickness of the first layer 121 is lambda _1/4 , and the film thickness of the second layer is lambda _2/4. When the maximum peak wavelength when passing through a medium having a refractive index of 1 is λ, the refractive index of the first layer 121 is n ₁ , and the refractive index of the second layer 122 is n ₂ , λ ₁ = λ / n ₁ Thus, λ ₂ = λ / n ₂ .

Further, when the maximum peak wavelength of light emitted from the light emitting layer is λ, the optical path length (optical distance) from the light emitting surface to the interface between the organic functional layer 140 and the intervening layer 120 is a multiple of λ / 2. It has become. Here, the basic unit of light is considered to be one wavelength, and the minimum light emitting region (the lower limit of the size of the region where light emission occurs) is a spherical region having a diameter λ. If the central point of the minimum light emitting region is referred to as the light emitting center point, the light emitting surface is a substantially flat surface composed of a set of light emitting center points. As an example, when the film thickness of the light emitting layer is about 25 nm or more and 35 nm or less, the light emitting surface exists, for example, at a position of about 5 nm from the hole injection layer, depending on conditions. The optical path length from the light emitting surface to the interface between the organic functional layer 140 and the intervening layer 120 in the light emitting layer depends on the refractive index of each layer interposed between the light emitting surface and the interface between the organic functional layer 140 and the interposing layer 120. It becomes length.

Next, the operation will be described. FIG. 1 shows an example in which the uppermost layer and the lowermost layer of the intervening layer 120 are both the first layer 121, and the following operation description is based on this structure.

FIG. 2 is a cross-sectional view showing an example of the operation of the light emitting device 100 according to the first embodiment. Of the light emitted from the light emitting layer, the light traveling toward the translucent substrate 110 (the light of the optical paths L1 and L5) travels toward the translucent substrate 110 through the organic functional layer 140 and the first electrode 130. The refractive index of the first electrode 130 is 1.8, for example, and the refractive index of the translucent substrate 110 is 1.5, for example. The light is totally reflected at the interface with the substrate 110 and the remaining light is transmitted (incident) to the light transmitting substrate 110. Part of the light transmitted (incident) to the translucent substrate 110 is totally reflected at the interface with the light emission space, and the rest is emitted to the light emission space.

On the other hand, part of the light traveling toward the second electrode 150 is reflected by the surface (upper surface) of the second electrode 150, and the rest (light of the optical paths L1, L11, etc.) is transmitted through the second electrode 150 and interposed. Enter layer 120. Here, since the first layer 121 having a high refractive index (refractive index greater than or equal to the organic functional layer 140) is in contact with the second electrode 150, even if the second electrode 150 is made of a metal thin film, Evanescent light and plasmon resonance do not occur at the interface with the first layer 121, and no light loss occurs.

Of the light incident on the intervening layer 120, the light whose angle between the normal to the organic functional layer 140 and the optical axis is within a predetermined angle α is any one of the first layers 121 and the second layer adjacent thereto. The light is reflected at the interface with 122 and synthesized, and acts as if large reflection is occurring at the interface between the organic functional layer 140 and the intervening layer 120.

That is, as described above, the film thickness of each layer constituting the intervening layer 120 (the film thickness of each first layer 121 and the film thickness of each second layer 122) is a film whose optical path length is λ / 4, respectively. By being thick, it is possible to behave such that light within an angle α is reflected at the interface between the organic functional layer 140 and the intervening layer 120. Here, because the film thickness of each first layer 121 and the film thickness of each second layer 122 are λ / 4, respectively, with respect to light having a certain angle or less (light within an angle α), Light reflected at each interface between the first layer 121 and the second layer 122 reinforces each other due to interference. Thereby, the light extraction efficiency can be improved. Note that the effect of strengthening the reflected light in this way increases as the number of layers constituting the intervening layer 120 increases.

In addition, when light is reflected by the light reflection layer 160 that is a metal layer, the phase of the light is shifted by a half wavelength. For this reason, normally, it is necessary to consider the phase of the light reflected by the light reflecting layer 160 and the light from the light emitting surface. However, in the present embodiment, the thickness of each first layer 121 and the thickness of each second layer 122 are λ / 4, and the lowest layer of the intervening layer 120 is the first layer 121. As a result, for light with an angle of a certain degree or less (light within an angle α), more light is reflected at each interface between the first layer 121 and the second layer 122. Therefore, it is not necessary to consider the distance from the light emitting surface to the light reflecting layer 160 as the number of layers constituting the intervening layer 120 increases.

In addition, since the optical path length from the light emitting surface of the light emitting layer to the interface between the organic functional layer 140 and the intervening layer 120 is a multiple of λ / 2, light with a certain angle or less (light within an angle α) With respect to, since the phases of the reflected light at the interface between the organic functional layer 140 and the intervening layer 120 and the light on the light emitting surface coincide with each other, these lights can be intensified.

In addition, when light is reflected on the metal surface (light reflection layer 160), a certain amount of loss occurs, whereas in the reflection using the refractive index between layers, loss is not substantially generated. Accordingly, the light extraction efficiency is improved by the amount of reflected light at the interface between the organic functional layer 140 and the intervening layer 120.

Further, light having an angle between the normal to the organic functional layer 140 and the optical axis that is larger than the angle α and smaller than the angle β (α <β) is transmitted through the intervening layer 120 and reflected by the light reflecting layer 160. To do. In addition, light whose angle between the normal to the organic functional layer 140 and the optical axis is equal to or larger than the angle β is totally reflected at the interface between any one of the first layers 121 and the second layer 122 adjacent thereto.

FIG. 3 is a diagram showing a simulation result of the reflectance in the light emitting device 100 according to the first embodiment. In this simulation, the maximum peak wavelength λ of light emitted from the light emitting layer is 520 nm with respect to the light emitting device 100 including the intervening layer 120 in which six first layers 121 and five second layers 122 are alternately stacked. It was carried out as As shown in FIG. 3, the angle between the normal to the organic functional layer 140 and the optical axis is within about 20 degrees (corresponding to the angle α), and the angle is about 60 degrees (corresponding to β) or more. It can be seen that a remarkably high reflectance (almost 100%) can be obtained with respect to the above light.

FIG. 4 is a diagram illustrating interference between direct light from the light emitting layer and reflected light reflected by the second electrode 150 in the light emitting device according to the comparative example. The light emitting device according to the comparative example is different from the light emitting device 100 shown in FIG. 1 in that the intervening layer 120 and the light reflecting layer 160 are not provided and the second electrode 150 is a reflecting electrode. Then, it shall be comprised similarly to the light-emitting device 100 shown in FIG. That is, in the light emitting device according to Comparative Example 1, the intervening layer 120 does not exist between the light reflecting layer (second electrode 150) and the organic functional layer 140.

A part of the light emitted from the light emitting layer is directed toward the translucent substrate 110 as indicated by an optical path L21 in FIG. Another part of the light emitted from the light emitting layer is directed to the second electrode 150 side as indicated by the optical path L22, reflected at the interface between the organic functional layer 140 and the second electrode 150, and indicated by the optical path 23. In this way, it goes to the translucent substrate 110 side. The light indicated by the optical path L21 (direct light) and the light indicated by the optical path L23 (reflected light) interfere with each other to increase or decrease (increase or decrease) the intensity of the light.

FIG. 5 is a diagram showing the relationship between the light angle and the increase / decrease in light intensity due to interference in the light emitting device according to the comparative example. In FIG. 5, the horizontal axis represents the light angle, and the vertical axis represents the light intensity. The angle of light on the horizontal axis is the angle formed between the normal to the light extraction surface 110a and the optical path. The light intensity on the vertical axis is a simulation result of the light intensity after the interference, and the light intensity before the interference (the light intensity on the optical path L21) is 1. Here, the light intensity shown in FIG. 5 is a simulation result when the distance from the light emitting layer to the second electrode 150 is set so that the light intensity after interference is the strongest when the light angle is 0 degree. is there. In this case, as shown in FIG. 5, as the light angle increases, the light intensity decreases due to the influence of interference.

On the other hand, in this embodiment, the intervening layer 120 exists between the organic functional layer 140 including the light emitting layer and the light reflecting layer (light reflecting layer 160). For light having an angle of a certain degree or more, such as light having an angle of α to β and light having a value of β or more, the reflected light and the reflected light are reflected as the light is reflected at the interface far from the light emitting layer. The influence of interference between the light and the corresponding direct light can be suppressed. This is because the optical axis of the reflected light and the optical axis of the direct light are further away as the light is reflected at the interface far from the light emitting layer. That is, by including the intervening layer 120 having a structure in which the first layer 121 and the second layer 122 are provided in multiple layers as in the present embodiment, the reflected light of the light having a certain angle or more and the direct light interfere with each other. Can suppress mutual weakening. Therefore, the light extraction efficiency is improved as compared with the comparative example.

Next, an example of a process for manufacturing the light emitting device 100 according to this embodiment will be described.

First, a light-transmitting conductive film made of a metal oxide conductor such as ITO or IZO is formed on the lower surface of the light-transmitting substrate 110 by sputtering or the like, and patterned by etching to form the first electrode 130. Form.

Next, the organic functional layer 140 is formed by applying an organic material to the lower surface of the first electrode 130.

Next, a second electrode 150 is formed on the lower surface of the organic functional layer 140 by depositing a metal material such as Al by vapor deposition or the like.

Next, an organic material such as NPB is applied to the lower surface of the second electrode 150 to form the uppermost first layer 121 in the intervening layer 120.

Next, the uppermost layer of the second layer 122 is formed on the lower surface of the uppermost first layer 121 by using MgF ₂ or SiO ₂ .

Hereinafter, similarly, the first layer 121 and the second layer 122 are alternately formed. Then, the first layer 121 is formed as the lowermost layer of the intervening layer 120.

Next, a light reflecting layer 160 is formed by depositing a metal material such as Al on the lower surface of the intervening layer 120 by vapor deposition or the like.

In addition, you may form a bus line and a partition part (refer FIG.8 (b)) at an appropriate timing, respectively as needed. Moreover, you may form a sealing layer in the lower surface of the light reflection layer 160 as needed.

(First example of organic functional layer)
FIG. 6 is a diagram illustrating a first example of the layer structure of the organic functional layer 140. The organic functional layer 140 according to the first example has a structure in which a hole injection layer 141, a hole transport layer 142, a light emitting layer 143, an electron transport layer 144, and an electron injection layer 145 are stacked in this order. That is, the organic functional layer 140 is an organic electroluminescence light emitting layer. Note that instead of the hole injection layer 141 and the hole transport layer 142, one layer having the functions of these two layers may be provided. Similarly, instead of the electron transport layer 144 and the electron injection layer 145, one layer having the function of these two layers may be provided (see FIG. 8B).

In the first example of the organic functional layer 140, the light emitting layer 143 is, for example, a layer that emits red light, a layer that emits blue light, a layer that emits yellow light, or a layer that emits green light. . In this case, in a plan view, a region having a light emitting layer 143 that emits red light, a region having a light emitting layer 143 that emits green light, and a region having a light emitting layer 143 that emits blue light are repeatedly provided. (See FIG. 8B). In this case, when each region emits light simultaneously, the light emitting device 100 emits light in a single light emission color such as white.

Note that the light emitting layer 143 may be configured to emit light in a single light emission color such as white by mixing materials for emitting a plurality of colors.

(Second example of organic functional layer)
FIG. 7 is a diagram illustrating a second example of the layer structure of the organic functional layer 140. FIG. 8 (described later) describes an example in which regions separated from each other by the partition wall portion 180 in the organic functional layer 140 emit red light, green light, and blue light, respectively. On the other hand, in the second example, the light emitting layer 143 of the organic functional layer 140 has a configuration in which the

light emitting layers

143a, 143b, and 143c are stacked in this order. The

light emitting layers

143a, 143b, and 143c emit light of different colors (for example, red, green, and blue). The

light emitting layers

143a, 143b, and 143c emit light at the same time, so that the light emitting device 100 emits light in a single light emission color such as white.

FIG. 8A is a plan view showing an example of a more specific configuration of the light emitting device 100 according to the embodiment, and FIG. 8B is a cross-sectional view taken along line BB in FIG. 8A. is there. 8B and 8A are upside down with respect to FIG.

The first electrode 130 constitutes an anode. The plurality of first electrodes 130 each extend in the Y direction in a strip shape. Adjacent first electrodes 130 are spaced apart from each other at a constant interval in the X direction orthogonal to the Y direction. Each of the first electrodes 130 is made of a metal oxide conductor such as ITO or IZO, for example. The refractive index of the first electrode 130 is approximately the same as that of the first layer 121 (for example, approximately 1.8). A bus line (bus electrode) 170 for supplying a power supply voltage to the first electrode 130 is formed on each surface of the first electrode 130. An insulating film is formed on the translucent substrate 110 and the first electrode 130. In this insulating film, a plurality of stripe-shaped openings each extending in the Y direction are formed. Thereby, a plurality of partition walls 180 made of an insulating film are formed. Each of the openings formed in the insulating film reaches the first electrode 130, and the surface of each first electrode 130 is exposed at the bottom of the opening. An organic functional layer 140 is formed on the first electrode 130 in each opening of the insulating film. The organic material portion of the organic functional layer 140 is configured by laminating a hole injection layer 141, a hole transport layer 142, a light emitting layer 143 (

light emitting layers

143R, 143G, 143B), and an electron transport layer 144 in this order. ing. Materials for the hole injection layer 141 and the hole transport layer 142 include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked by fluorene groups, hydrazones. Derivatives, silazane derivatives, silanamine derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like. The

light emitting layers

143R, 143G, and 143B are made of a fluorescent organometallic compound that emits red light, green light, and blue light, respectively. The

light emitting layers

143R, 143G, and 143B are arranged side by side in a state of being separated from each other by the partition wall portion 180. That is, the organic functional layer 140 is partitioned into a plurality of regions by the partition wall portion 180. An electron transport layer 144 is formed so as to cover the surfaces of the

light emitting layers

143R, 143G, and 143B and the partition wall portion 180. A second electrode 150 is formed so as to cover the surface of the electron transport layer 144. The second electrode 150 constitutes a cathode. The second electrode 150 is formed in a band shape. The second electrode 150 is made of a metal such as Al or an alloy having a low work function and high reflectivity. The refractive index of the organic material portion of the organic functional layer 140 is approximately the same as that of the first electrode 130 and the first layer 121 (for example, a refractive index of approximately 1.8). An intervening layer 120 is formed on the second electrode 150. A light reflecting layer 160 is formed on the intervening layer 120.

As described above, the

light emitting layers

143R, 143G, and 143B that emit red, green, and blue light are repeatedly arranged in a stripe shape, and red, Green and blue light are mixed at an arbitrary ratio to emit light that is recognized as a single emission color (for example, white).

As described above, according to the embodiment, the light emitting device 100 includes the translucent intervening layer 120 disposed between the organic functional layer 140 and the light reflecting layer 160. The intervening layer 120 is formed by laminating three or more layers having different refractive indexes between adjacent layers, and has two or more interfaces. The refractive indexes of three or more layers constituting the intervening layer 120 are alternately in the order of high and low from the organic functional layer 140 side to the light reflecting layer 160 side, or alternately low. , In order of high. Therefore, the optical path length of the light (reflected light) from the organic functional layer 140 toward the light reflecting layer 160 toward the light reflecting layer 160 and then toward the light transmitting substrate 110 is passed through the intervening layer 120. Can earn by. For this reason, since the distance between the optical axis of the direct light and the optical axis of the reflected light can be increased, interference of these lights can be suppressed. Therefore, it is possible to suppress the cancellation of these lights due to interference, so that the light extraction efficiency can be improved. Further, light having an angle of a certain degree or more can be totally reflected at the interface between the first layer 121 and the second layer 122, so that the light can be efficiently directed toward the translucent substrate 110.

When the refractive index of the intervening layer 120 is uniform, the light traveling from the organic functional layer 140 toward the light reflecting layer 160 is reflected by the light reflecting layer 160 that is a metal layer and travels toward the light transmitting substrate 110 side. Head. However, a certain amount of loss occurs in the reflection at the metal layer. On the other hand, in this embodiment, since the refractive index of the second layer 122 is smaller than the refractive index of the first layer 121, a part of the light traveling from the organic functional layer 140 toward the light reflecting layer 160 is Total reflection can be performed at the interface between the first layer 121 and the second layer 122. Thereby, since the loss can be reduced as compared with the case where the refractive index of the intervening layer 120 is uniform, the light extraction efficiency is improved.

For example, the uppermost layer of the intervening layer 120 is the first layer 121 having a high refractive index. In this case, even if the second electrode 150 made of a metal thin film exists at the end of the organic functional layer 140 on the side of the intervening layer 120, the second electrode 150 and the first layer 121 are in contact with each other even if the second electrode 150 and the first layer 121 are in contact with each other. Evanescent light and plasmon resonance do not occur at the interface with the first layer 121. Thereby, the fall of light extraction efficiency can be suppressed.
When the arrangement of the first layer 121 and the second layer 122 is reversed and the uppermost layer of the intervening layer 120 is the second layer 122 having a low refractive index, the second electrode 150 is the intervening layer in the organic functional layer 140. The same effect can be obtained by disposing the second electrode 150 at the intermediate portion in the thickness direction of the organic functional layer 140 instead of disposing it at the end on the 120 side.
In any of these cases, the light is reflected at the interface between the organic functional layer 140 and the intervening layer 120 for light having a certain angle or less. Therefore, the reflected light reflected at the interface between the organic functional layer 140 and the intervening layer 120 and the light on the light emitting surface can be made to interfere with each other. Thereby, the light extraction efficiency can be improved.

Since the thickness of each layer (three or more layers) constituting the intervening layer 120 is such that the optical path length is λ / 4, the light reflected at the interface of each layer constituting the intervening layer 120 Amplify by interfering with each other. Therefore, the intensity of light extracted from the light emitting device 100 can be improved.

Since the optical path length from the light emitting surface in the light emitting layer to the interface between the organic functional layer 140 and the intervening layer 120 is a multiple of λ / 2, the light is reflected at the interface between the organic functional layer 140 and the intervening layer 120. The phases of light and direct light from the light emitting surface of the light emitting layer toward the translucent substrate 110 can be matched, and these light can be amplified by interfering with each other. Therefore, the intensity of light extracted from the light emitting device 100 can be improved.

In the light emitting device 100, since the organic functional layer 140 includes the translucent second electrode 150, it is possible to easily apply a voltage to the light emitting layer in the organic functional layer 140. For example, the second electrode 150 may be drawn out to the peripheral portion of the light emitting device 100 in plan view, and a voltage may be applied to the drawn portion.

(Second Embodiment)
FIG. 9 is a cross-sectional view showing the configuration of the light emitting device 100 according to the second embodiment. The light emitting device 100 according to the second embodiment is different from the light emitting device 100 according to the first embodiment (FIG. 1) in the points described below, and in other points, the light emitting device according to the first embodiment. The configuration is the same as that of the apparatus 100.

The light emitting device 100 according to the second embodiment does not have the second electrode 150 in the organic functional layer 140. For example, the lower surface of the lowermost organic layer (for example, the electron injection layer 145) in the organic functional layer 140 and the upper surface of the intervening layer 120 (the upper surface of the uppermost first layer 121) are in contact with each other. However, another layer may exist between the organic functional layer 140 and the intervening layer 120.

Also in this embodiment, the light reflecting layer 160 is conductive. The light reflecting layer 160 also functions as a cathode. In addition, the organic functional layer 140 includes a hole transport layer disposed on the first electrode 130 side of the light emitting layer. Specifically, for example, the organic functional layer 140 includes a hole injection layer 141 and a hole transport layer 142 similarly to the configuration illustrated in FIG. For example, each first layer 121 and each second layer 122 have an electron transport function. That is, each first layer 121 and each second layer 122 function as an electron transport layer. Each first layer 121 and each second layer 122 may function as an electron transport layer and an electron injection layer. As described above, in the present embodiment, the intervening layer 120 also functions as a part of the organic functional layer 140. Therefore, in the case of this embodiment, the organic functional layer 140 does not need to have an electron carrying layer and an electron injection layer.

In the present embodiment, when a voltage is applied between the first electrode 130 and the light reflecting layer 160, the light emitting layer of the organic functional layer 140 emits light.

In addition, when the 1st electrode 130 is a cathode and the light reflection layer 160 is an anode, the organic functional layer 140 contains the electron carrying layer arrange | positioned at the 1st electrode 130 side of a light emitting layer. Specifically, for example, the organic functional layer 140 includes an electron injection layer and an electron transport layer. Each first layer 121 and each second layer 122 have a hole transport function. Alternatively, each first layer 121 and each second layer 122 may function as a hole transport layer and a hole injection layer. And the organic functional layer 140 does not need to have a positive hole transport layer and a positive hole injection layer.

In the case of the second embodiment, since the second electrode 150 is not present, when the refractive indexes of the layers sandwiching the metal film (the layers on both sides of the metal film) are different from each other (one of the layers sandwiching the metal layer is relatively low). Evanescent light and plasmon resonance generated at the interface between the metal film and the low refractive index layer do not occur in the refractive index layer (when the other is a relatively high refractive index layer).

Further, since the light reflection layer 160 is conductive and each of the first layers 121 and each of the second layers 122 has an electron transport function or a hole transport function, the light emitting device 100 does not have the second electrode 150. Alternatively, the light emitting layer can emit light by applying a voltage to the organic functional layer 140.

According to the second embodiment, other effects similar to those of the first embodiment can be obtained.

(Example 1)
FIG. 10 is a cross-sectional view illustrating a configuration of the light emitting device 100 according to the first embodiment. The light emitting device 100 according to Example 1 is different from the light emitting device 100 according to the first embodiment (FIG. 1) in the points described below, and otherwise the light emitting device 100 according to the first embodiment. It is configured in the same way.

In the case of Example 1, the light scattering layer 210 is provided between the intervening layer 120 and the light reflecting layer 160. For example, the lower surface of the intervening layer 120 and the upper surface of the light scattering layer 210 are in contact with each other, and the lower surface of the light scattering layer 210 and the upper surface of the light reflecting layer 160 are in contact with each other. However, other layers may exist between the intervening layer 120 and the light scattering layer 210 and between the light scattering layer 210 and the light reflecting layer 160, respectively.

The light scattering layer 210 includes, for example, a base material made of a dielectric material and particles disposed in the base material with a refractive index smaller than that of the base material. A plurality of (many) particles are contained in the substrate. Particles, for example, inorganic particles such as SiO _2. The size of the particles is preferably not less than the peak wavelength (maximum peak wavelength) λ of the emission wavelength from the light emitting layer. Here, the particle size means the sphere equivalent diameter of each particle. As an example, the particles may be spherical, where the particle size is the particle diameter. However, the shape of the particles may be any other shape.

In the case of Example 1, a part of the light traveling from the intervening layer 120 toward the light reflecting layer 160 side is scattered in a random direction by the light scattering layer 210. Accordingly, it can be expected that a part of light having an angle that is not emitted from the light emitting device 100 when the light scattering layer 210 is not present can be extracted from the light emitting device 100.

(Example 2)
FIG. 11 is a cross-sectional view illustrating a configuration of the light emitting device 100 according to the second embodiment. The light emitting device 100 according to Example 2 is different from the light emitting device 100 according to the first embodiment (FIG. 1) in the points described below, and otherwise the light emitting device 100 according to the first embodiment. It is configured in the same way.

In the case of Example 2, a first low refractive index layer 147 is disposed between the second electrode 150 and the light emitting layer. The first low refractive index layer 147 is a layer including a first base material and first particles having a refractive index smaller than that of the first base material and disposed in the first base material. A second low refractive index layer 220 is disposed between the second electrode 150 and the intervening layer 120. The second low refractive index layer 220 is a layer including a second base material and second particles having a refractive index smaller than that of the second base material and disposed in the second base material.

The materials of the first base material and the second base material are, for example, the same materials as those of the organic functional layer 140 in the first embodiment. The first particles and the second particles are inorganic particles such as SiO ₂ and nano silica. When the maximum peak wavelength of light emitted from the light emitting layer is λ, the dimensions of the first particles and the second particles may be λ or less. The dimension of the first particle and the second particle can be set to, for example, about 20 nm. Here, the dimension of particle | grains (1st particle | grains and 2nd particle | grains) means the spherical equivalent diameter of each particle | grain in planar view. As an example, the particles may be spherical, where the particle size is the particle diameter. However, the shape of the particles may be any other shape. By including the first particles and the second particles in the first base material and the second base material, respectively, the first low refractive index layer 147 and the second low refractive index layer 220 become the first base material and the first base material. 2 The refractive index is lowered compared to the base material. That is, the pair of layers sandwiching the second electrode 150 has a low refractive index.

The first low refractive index layer 147 functions as, for example, an electron transport layer, or functions as an electron injection layer and an electron transport layer. When the first electrode 130 is a cathode and the second electrode 150 is an anode, the first low refractive index layer 147 functions as, for example, a hole transport layer, or as a hole injection layer and a hole transport layer. Function.

In the case of Example 2, the pair of layers (the first low refractive index layer 147 and the second low refractive index layer 220) sandwiching the second electrode 150 each have a low refractive index. Since the light emitting layer has a high refractive index, light can be totally reflected at the interface between the light emitting layer and the first low refractive index layer 147. Accordingly, light having an angle can be directed to the light extraction surface 110a side without using the intervening layer 120 below the second low refractive index layer 220, so that the light extraction efficiency can be improved.

(Example 3)
FIG. 12 is a cross-sectional view illustrating a configuration of the light emitting device 100 according to the third embodiment. The light emitting device 100 according to Example 3 is different from the light emitting device 100 according to the first embodiment (FIG. 11) in the points described below, and otherwise the light emitting device 100 according to the first embodiment. It is configured in the same way.

In the case of Example 3, the light reflection layer 160 is a conductor. The light emitting device 100 includes a conductor 190 that electrically connects at least one second electrode 150 and the light reflection layer 160 to each other. That is, the light emitting device 100 includes one or a plurality of second electrodes 150, and at least one or more second electrodes 150 are electrically connected to the light reflecting layer 160. The conductor 190 penetrates the intervening layer 120 up and down. The conductor 190 may be a columnar shape (that is, a through hole) or a wall shape.

For example, after forming the second electrode 150, a conductor 190 is formed by vapor-depositing a metal such as Ag using a mask, and then the intervening layer 120 is formed. In addition, the conductor 190 may be arrange | positioned on the partition part 180 (refer FIG. 8), and may be arrange | positioned in another position.

In the case of Example 3, the light reflection layer 160 is conductive, and the second electrode 150 is electrically connected to the light reflection layer 160. As a result, the light reflecting layer 160 can form an electrode together with the second electrode 150, so that a voltage can be more easily applied to the light emitting layer in the organic functional layer 140.

Note that FIG. 12 illustrates an example in which the conductor 190 electrically connects the second electrode 150 and the light reflecting layer 160 through the inside of the intervening layer 120. The second electrode 150 and the light reflecting layer 160 may be electrically connected to each other through the outside. The former is suitable for a light emitting device having a light emitting layer having a relatively large area, and the latter is suitable for a light emitting device having a light emitting layer having a relatively small area.

Note that, instead of providing the conductor 190 in the intervening layer 120, an N-type impurity may be introduced into the intervening layer 120 so that the intervening layer 120 becomes a conductive layer. That is, the intervening layer 120 may be an N-doped layer. Even in this case, the light reflection layer 160 made of a conductor can form an electrode together with the second electrode 150. Note that the second electrode 150 may be an anode and the first electrode 130 may be a cathode. In this case, a P-type impurity can be introduced into the intervening layer 120 to make the intervening layer 120 a P-doped layer.

Example 4
FIG. 13 is a cross-sectional view illustrating a configuration of the light emitting device 100 according to the fourth embodiment. The light emitting device 100 according to the fourth embodiment is different from the light emitting device 100 according to the third embodiment (FIG. 12) in the points described below, and is otherwise configured in the same manner as the light emitting device 100 according to the third embodiment. Has been.

In the case of Example 4, the upper surface of the light reflecting layer 160 is an uneven surface 161 including a plurality of inclined surfaces inclined with respect to the organic functional layer 140. That is, the surface on the intervening layer 120 side of the light reflecting layer 160 is an uneven surface 161. Here, the dimension of each inclined surface (the maximum dimension of each inclined surface in a plane parallel to each inclined surface) is preferably not less than the peak wavelength (maximum peak wavelength) λ of the emission wavelength from the light emitting layer. For example, it is preferable that 50% or more of the surface of the light reflecting layer 160 on the side of the intervening layer 120 be the uneven surface 161. The entire surface on the intervening layer 120 side of the light reflecting layer 160 may be the uneven surface 161, or a part of the surface on the interposing layer 120 side of the light reflecting layer 160 may be a flat surface.

In the case of Example 4, a part of the light traveling from the organic functional layer 140 toward the light reflecting layer 160 is reflected by the light reflecting layer 160. Here, since the upper surface of the light reflecting layer 160 is a concavo-convex surface 161 including a plurality of inclined surfaces inclined with respect to the organic functional layer 140, the light emitting device is formed when the upper surface of the light reflecting layer 160 is a flat surface. It can be expected that a part of the light having an angle that cannot be extracted from 100 can be extracted from the light emitting device 100.

Note that FIG. 13 illustrates an example in which the surface on the intervening layer 120 side of the light reflecting layer 160 is an uneven surface 161 when the light emitting device 100 includes the second electrode 150. In the case where the second electrode 150 is not provided (FIG. 9), the same effect can be obtained even if the surface on the intervening layer 120 side of the light reflecting layer 160 is an uneven surface 161.

As mentioned above, although embodiment and the Example were described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

Claims

A translucent substrate;
A translucent first electrode disposed on the side opposite to the exit surface of the translucent substrate;
An organic functional layer including at least a light-emitting layer and disposed on the opposite side of the translucent substrate with respect to the first electrode;
A light reflecting layer disposed on the opposite side of the first electrode with respect to the organic functional layer, and reflecting light coming from the organic functional layer side;
A light-transmitting intervening layer disposed between the organic functional layer and the light reflecting layer;
With
The intervening layer is formed by laminating three or more layers having different refractive indexes between adjacent layers, and has two or more interfaces.
The refractive indexes of the three or more layers are alternately in the order of high and low from the organic functional layer side toward the light reflecting layer side, or alternately in the order of low and high. Light emitting device.
When the maximum peak wavelength of light emitted from the light emitting layer is λ,
2. The light emitting device according to claim 1, wherein the film thickness of each of the three or more layers is such that the optical path length is λ / 4.
When the maximum peak wavelength of light emitted from the light emitting layer is λ,
3. The light emitting device according to claim 1, wherein an optical path length from a light emitting surface of the light emitting layer to an interface between the organic functional layer and the intervening layer is a multiple of λ / 2.
The light-emitting device according to any one of claims 1 to 3, wherein the organic functional layer includes a translucent second electrode disposed at an end of the organic functional layer on the intermediate layer side.
The light emitting device according to any one of claims 1 to 3, wherein the organic functional layer includes a translucent second electrode, and an organic layer disposed between the second electrode and the intervening layer. apparatus.
Between the second electrode and the light emitting layer, a layer including a first base material and first particles disposed in the first base material is disposed,
The light emission of Claim 4 by which the layer containing the 2nd base material and the 2nd particle | grains arrange | positioned in the said 2nd base material is arrange | positioned between the said 2nd electrode and the said intervening layer. apparatus.