JP2009245735A - Organic el element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element capable of improving an optical extraction efficiency, and a manufacturing method of the same. <P>SOLUTION: The organic EL element 1 includes an element substrate 2, an anode electrode 3, an organic light-emitting layer 4, a cathode electrode 5, a solid sealing resin layer 6, an encapsulating board 7 and an optical extraction layer 8. The anode electrode 3, the organic light-emitting layer 4 and the cathode electrode 5 are formed in a growth principal plane 2a of the element substrate 2. The optical extracting layer 8 is directly formed on the optical extraction principal plane 2b of the element substrate 2 on an opposite side of the growth principal plane 2a. The optical extraction layer 8 consists of an epoxy resin layer. An optical extraction face 8a, a principal plane outside the optical extraction layer 8, is roughened. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL (electroluminescence) element having a roughened light extraction surface and a method for manufacturing the organic EL element.

  2. Description of the Related Art Conventionally, an organic EL element including an element substrate made of a glass substrate and an anode electrode, an organic light emitting layer, and a cathode electrode formed on the element substrate is known. In such an organic EL element, light emitted from the organic light emitting layer passes through the anode electrode and the element substrate, and is irradiated to the outside from the main surface outside the element substrate (hereinafter referred to as a light extraction surface). However, since there is a difference in refractive index between the element substrate and external air, the emitted light is reflected by the light extraction surface. For this reason, the above-described organic EL device has a problem that the ratio of light extracted outside (hereinafter referred to as light extraction efficiency) to the light emitted from the organic light emitting layer is low.

  Therefore, a technique for improving the light extraction efficiency of the organic EL element is required. Patent Document 1 discloses an organic EL element in which a light extraction surface of an element substrate is roughened. In the organic EL element of Patent Document 1, a part of the light reaching the light extraction surface of the element substrate is transmitted and irradiated to the outside, and the remaining light is reflected and scattered by the light extraction surface. Waveguide through the substrate. Thereafter, the light guided in the element substrate reaches the light extraction surface again. Since the incident angle of the light reaching the light extraction surface changes with the light extraction surface, the amount of light passing through the light extraction surface increases. Thus, the organic EL element of Patent Document 1 improves the light extraction efficiency. However, in the organic EL element of Patent Document 1, since one surface of an element substrate made of a hard glass substrate is roughened, it is difficult to form irregularities, and there are many problems such as breakage of the element substrate. there were.

Therefore, Patent Document 2 discloses an organic EL element including a resin-made diffusion plate attached to an outer surface of an element substrate via optical oil. And in the organic EL element of patent document 2, the unevenness | corrugation is formed in the outer surface of the resin-made diffuser plate. Thus, in the organic EL element of patent document 2, since the unevenness | corrugation is formed in the resin-made diffuser plate softer than a glass substrate, while being able to suppress damage to an element substrate, an unevenness | corrugation can be formed easily. .
JP 2000-231985 JP 2000-323272 A

  However, in the organic EL element of Patent Document 2, since the diffusion plate is attached to the element substrate via optical oil, there are many interfaces between different substances that pass through before the light is extracted to the outside. For this reason, since the light reflected by the said interface increases, there exists a subject that it cannot be said that the light extraction efficiency is fully improving.

  The present invention has been made in order to solve the above-described problems, and an object thereof is to provide an organic EL element and a method for manufacturing the organic EL element that can improve the light extraction efficiency.

  In order to achieve the above object, an invention according to claim 1 includes an element substrate, an organic light emitting layer, a light emitting portion formed on a growth main surface of the element substrate, and a side opposite to the growth main surface. An organic EL device comprising: a light extraction layer formed of a resin layer directly formed on the light extraction main surface of the element substrate, wherein the light extraction surface which is an outer main surface is roughened It is.

  The invention according to claim 2 is the organic EL element according to claim 1, wherein the light extraction layer is formed by applying a resin material to the light extraction main surface. .

  The invention according to claim 3 is characterized in that the light extraction layer is formed only at the center of the light extraction main surface of the element substrate. It is an organic EL element of description.

  According to a fourth aspect of the present invention, there is provided a light emitting portion forming step of forming a light emitting portion including an organic light emitting layer on a growth main surface of an element substrate, and light extraction of the element substrate on the side opposite to the growth main surface. An application step of directly applying a resin material to the main surface, a light extraction layer forming step of curing the resin material to form a light extraction layer, and a light extraction surface which is a main surface outside the light extraction layer An organic EL element manufacturing method comprising a roughening step for roughening.

  The invention according to claim 5 is the method for producing an organic EL element according to claim 4, wherein the roughening step is performed before the resin material is cured.

  According to the present invention, the interface between different substances can be reduced by forming the light extraction layer directly on the light extraction main surface of the element substrate. As a result, it is possible to suppress the light emitted from the organic light emitting layer from being reflected from the interface, thereby improving the light extraction efficiency.

(First embodiment)
Hereinafter, an organic EL device according to a first embodiment of the present invention will be described with reference to the drawings. The organic EL element according to the present invention can be applied to lighting devices and various light sources. FIG. 1 is a cross-sectional view of an organic EL element according to the first embodiment. In the following description, the top and bottom indicated by the arrows in FIG.

  As shown in FIG. 1, the organic EL element 1 according to the first embodiment includes an element substrate 2, an anode electrode 3, an organic light emitting layer 4, a cathode electrode 5, a solid sealing resin layer 6, and a sealing plate. 7 and a light extraction layer 8. In addition, the anode electrode 3, the organic light emitting layer 4, and the cathode electrode 5 correspond to the light emission part of a claim.

  The element substrate 2 is made of a glass substrate having a thickness of about 0.5 mm and capable of transmitting light. The upper surface of the element substrate 2 is a growth main surface 2a on which the layers 3 to 7 are stacked. The lower surface of the element substrate 2 (the surface opposite to the growth main surface 2a) is the light extraction main surface 2b on which the light extraction layer 8 is formed.

  The anode electrode 3 is for injecting holes into the organic light emitting layer 4. The anode electrode 3 is formed on the main growth surface 2 a of the element substrate 2. The anode electrode 3 is made of ITO (indium tin oxide) having a thickness of about 100 nm capable of transmitting light. One end of the anode electrode 3 is connected to an external terminal (not shown).

The organic light emitting layer 4 is for emitting white light. The organic light emitting layer 4 is formed on the anode electrode 3 in an electrically connected state. In the organic light emitting layer 4, a hole transport layer and an electron transport layer are laminated in order from the anode electrode 3 side. The hole transport layer is made of an NPD (diphenylnaphthyldiamine) film having a thickness of about 50 nm. The electron transport layer is made of a quinolinol aluminum complex (Alq ₃ ) film having a thickness of about 50 nm and mixed with a dye. Further, copper phthalocyanine (CuPc) may be laminated between the anode electrode 3 and the organic light emitting layer 4 in order to promote hole injection from the anode electrode 3.

  The cathode electrode 5 is for injecting electrons into the organic light emitting layer 4. The cathode electrode 5 is formed on the organic light emitting layer 4 in an electrically connected state. The cathode electrode 5 is made of an Al film having a thickness of about 100 nm. The cathode electrode 5 is insulated from the anode electrode 3 by an insulating film (not shown). One end of the cathode electrode 5 is connected to an external terminal (not shown).

  The solid sealing resin layer 6 is for sealing the sealing plate 7 on the cathode electrode 5. The solid sealing resin layer 6 is made of an epoxy-based UV curable resin. In addition, you may comprise the solid sealing resin layer 6 with curable resins, such as a thermosetting resin.

  The sealing plate 7 is made of a glass substrate having a thickness of about 0.5 mm. The sealing plate 7 is sealed on the cathode electrode 5 by the solid sealing resin layer 6.

  The light extraction layer 8 is for improving the light extraction efficiency of the light emitted from the organic light emitting layer 4. The light extraction layer 8 is made of an epoxy resin layer. The light extraction layer 8 is formed by applying an epoxy resin material. In addition, the material which forms the light extraction layer 8 is not limited to an epoxy resin, It can change suitably to other resin. The light extraction layer 8 is directly formed on the light extraction main surface 2 b of the element substrate 2. The lower surface (outer main surface) of the light extraction layer 8 is a light extraction surface 8a for extracting light. The light extraction surface 8a is roughened in order to improve the light extraction efficiency.

  Next, the operation of the organic EL element 1 according to the first embodiment described above will be described.

  First, in the organic EL element 1, a voltage is applied between the anode electrode 3 and the cathode electrode 5 by an external power source. As a result, holes are injected from the anode electrode 3 into the organic light emitting layer 4. Electrons are injected from the cathode electrode 5 into the organic light emitting layer 4. The injected holes and electrons recombine in the organic light emitting layer to emit light. The emitted light passes through the anode electrode 3, the element substrate 2, and the light extraction layer 8, and then reaches the light extraction surface 8a. Here, a part of the light passes through the light extraction surface 8a and is irradiated to the outside. The remaining light is reflected and scattered by the roughened light extraction surface 8 a and guided in the light extraction layer 8. Thereafter, the light guided through the light extraction layer 8 changes the incident angle and reaches the light extraction surface 8a again, and a part of the light is transmitted through the light extraction surface 8a and irradiated to the outside.

  Next, a method for manufacturing the organic EL element 1 according to the first embodiment will be described. 2-5 is a figure explaining each manufacturing process of an organic EL element.

  First, as shown in FIG. 2, the patterned anode electrode 3 is formed on the element substrate 2 by sputtering and lift-off. Thereafter, the organic light emitting layer 4 is deposited on the anode electrode 3 through a metal mask (not shown) in which an opening is formed. Further, the patterned cathode electrode 5 is formed on the organic light emitting layer 4 by a sputtering method and a lift-off method (light emitting portion forming step).

  Next, as shown in FIG. 3, a UV curable resin material 6 </ b> A is applied on the cathode electrode 5. Thereafter, the sealing plate 7 is placed on the UV curable resin material 6A. In this state, the UV curable resin material 6 </ b> A is irradiated with ultraviolet rays through the sealing plate 7. Thereby, the UV curable resin material 6 </ b> A is cured to form the solid sealing resin layer 6, and the cathode electrode 5 and the sealing plate 7 are sealed.

  Next, as shown in FIG. 4, a soft epoxy resin material 18 is applied directly to the light extraction main surface 2b of the element substrate 2 on the side opposite to the growth main surface 2a (application step).

  Next, as shown in FIG. 5, before the epoxy resin material 18 is completely cured, the light extraction surface 8a, which is the outer main surface, is roughened (roughened) by a sander (electric sandpaper machine). Process). Thereafter, the epoxy resin material 18 is cured by being left for a predetermined time, and the light extraction layer 8 having the light extraction surface 8a roughened is formed. The epoxy resin material 18 may be cured by a curing agent or the like, or may be cured by ultraviolet irradiation or heat (light extraction layer forming step).

  Then, the organic EL element 1 shown in FIG. 1 is completed by dividing into element units.

  As described above, in the organic EL element 1 according to the first embodiment, the light extraction layer 8 made of an epoxy resin is directly formed on the light extraction main surface 2 b of the element substrate 2. Thereby, it is possible to reduce the interface between different substances through which light passes before being irradiated from the organic light emitting layer 4 to the outside. For this reason, since the light reflected by the interface before reaching the light extraction surface 8a can be reduced, the light extraction efficiency can be improved.

  Moreover, in the organic EL element 1, since the element substrate 2 consisting of a glass substrate is not roughened, damage to the element substrate 2 can be suppressed.

  Moreover, in the organic EL element 1, since the light extraction layer 8 is formed by applying the epoxy resin material 18, the light extraction layer 8 can be formed directly on the light extraction main surface 2b of the element substrate 2. it can. Further, when the light extraction layer is formed by attaching a resin sheet or the like, the shape of the sheet must be changed depending on the shape of the organic EL element, so that the manufacturing process becomes complicated. However, in the organic EL element 1, since the light extraction layer 8 is formed by applying the epoxy resin material 18, it can easily cope with a change in shape.

  Moreover, in the organic EL element 1, a rough surface with large irregularities can be easily realized in a short time by performing the roughening step in a soft state before the epoxy resin material 18 is cured.

(Second Embodiment)
Next, an organic EL element 1A according to a second embodiment in which the first embodiment described above is partially modified will be described. FIG. 6 is a cross-sectional view of an organic EL element according to the second embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 6, in the organic EL element 1 </ b> A according to the second embodiment, the light extraction layer 8 </ b> A is formed only at the center of the light extraction main surface 2 b of the element substrate 2. Here, the ends of the anode electrode 3 and the cathode electrode 5 are connected to an external power source. Accordingly, the voltage applied to the central part of the anode electrode 3 and the cathode electrode 5 is smaller than that of the outer peripheral part. Thereby, the central part of the organic light emitting layer 4 has lower light emission intensity than the outer peripheral part. However, in the organic EL element 1A, the light extraction layer 8A is formed only at the central portion of the light extraction main surface 2b of the element substrate 2, so that the light extraction efficiency at the central portion where the emission intensity is small is changed to the light extraction efficiency at the outer peripheral portion. It is higher than that. Thereby, the brightness of the light at the central portion and the outer peripheral portion of the organic EL element 1A can be reduced in plan view.

(Experiment on light extraction efficiency)
Next, an experiment conducted for examining the characteristics of the organic EL element according to the present invention described above will be described.

  In this experiment, the organic EL element according to the first embodiment (hereinafter referred to as the first example) and the organic EL elements of the first comparative example and the second comparative example for comparison with the first example were manufactured. . The first comparative example is the same as the organic EL element of the first example except that the light extraction main surface of the element substrate made of a glass substrate is roughened without forming a resin light extraction layer on the element substrate. It is the same configuration. The second comparative example has the same configuration as the organic EL element of the first comparative example, except that the light extraction main surface of the element substrate is not roughened.

  First, in this experiment, the degree of roughening was examined. In the first example and the first comparative example, the same sander and the same time roughening were performed. The results are shown in FIGS. FIG. 7 shows the experimental results of the first example. FIG. 8 shows the experimental results of the first comparative example. 7 and 8, the vertical axis indicates the height of the unevenness on the roughened surface. 7 and 8, the horizontal axis indicates the length in the horizontal direction (surface direction) of the surface examined for roughening.

  As shown in FIGS. 7 and 8, the first example in which the light extraction layer made of an epoxy resin is roughened has a larger unevenness than the first comparative example in which the element substrate is roughened. I understand. Thus, it can be seen that the first embodiment can easily form a rough surface with large irregularities on the light extraction surface.

  Next, the light extraction efficiency of the first example, the first comparative example, and the second comparative example was examined. The light extraction efficiency is a ratio of light extracted outside to light emitted from the organic light emitting layer.

  Here, the light extraction efficiency of the second comparative example will be described with reference to FIG. In addition, the same code | symbol is attached to the same structure as 1st Embodiment, and description is abbreviate | omitted. The light emitted from the organic light emitting layer 4 is reflected by the interface between the organic light emitting layer 4 and the anode electrode 3 and the interface between the anode electrode 3 and the element substrate 2, and about 45% is lost inside. Further, the light is reflected at the light extraction main surface 2b of the element substrate 2, that is, at the interface with the outside, and about 35% is lost inside the element substrate 2. Therefore, about 80% of the light emitted from the organic light emitting layer 4 is lost before being emitted to the outside. In other words, the light extraction efficiency of the second comparative example is about 20%. Considering that the refractive index of the glass substrate constituting the element substrate 2 is about 1.52 and the refractive index of the external air is about 1.0, the critical angle α at which total reflection occurs is about 35 °. It is.

  The experimental results of the first example and the first comparative example showed that the light extraction efficiency of the first example was about 34% and the light extraction efficiency of the first comparative example was about 26%. From this, it can be seen that the light extraction efficiency of the first example is about 1.7 times that of the second comparative example in which the surface is not roughened. It can also be seen that the light extraction efficiency of the first example is 1.3 times that of the first comparative example in which the element substrate is roughened. From this, it can be seen that the organic EL device according to the first embodiment of the present invention can improve the light extraction efficiency.

  As mentioned above, although this invention was demonstrated in detail using embodiment, this invention is not limited to embodiment described in this specification. The scope of the present invention is determined by the description of the claims and the scope equivalent to the description of the claims. Hereinafter, modified embodiments in which the above-described embodiment is partially modified will be described.

  The materials, numerical values, shapes, and the like in the above-described embodiments are examples and can be changed as appropriate.

  In the above-described embodiment, the element substrate is configured by a glass substrate, but the element substrate may be configured by a flexible film substrate. Even in the case where the element substrate is constituted by the film substrate that is easily damaged as described above, the element substrate is not roughened in the present invention, so that the element substrate can be prevented from being broken and the protective film is not damaged.

It is sectional drawing of the organic EL element by 1st Embodiment. It is a figure explaining each manufacturing process of an organic EL element. It is a figure explaining each manufacturing process of an organic EL element. It is a figure explaining each manufacturing process of an organic EL element. It is a figure explaining each manufacturing process of an organic EL element. It is sectional drawing of the organic EL element by 2nd Embodiment. It is an experimental result of a grade to the roughening of 1st Example. It is an experimental result of a grade for roughening of the 1st comparative example. It is a figure explaining the light extraction efficiency of a 2nd comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A Organic EL element 2 Element board | substrate 2a Growth main surface 2b Light extraction main surface 3 Anode electrode 4 Organic light emitting layer 5 Cathode electrode 6 Solid sealing resin layer 6A UV curable resin material 7 Sealing plate 8, 8A Light extraction layer 8a Light extraction surface 18 Epoxy resin material α Critical angle

Claims (5)

An element substrate;
A light emitting portion including an organic light emitting layer and formed on a main growth surface of the element substrate;
A light extraction layer formed of a resin layer directly formed on the light extraction main surface of the element substrate opposite to the growth main surface, the light extraction surface being the outer main surface being roughened. An organic EL device characterized by that.   The organic EL element according to claim 1, wherein the light extraction layer is formed by applying a resin material to the light extraction main surface.   3. The organic EL element according to claim 1, wherein the light extraction layer is formed only in a central portion of a light extraction main surface of the element substrate. A light emitting part forming step of forming a light emitting part including an organic light emitting layer on the growth main surface of the element substrate;
An application step of directly applying a resin material to the light extraction main surface of the element substrate opposite to the growth main surface;
A light extraction layer forming step of curing the resin material to form a light extraction layer;
A method for producing an organic EL element, comprising: a roughening step of roughening a light extraction surface which is a main surface outside the light extraction layer.   The method for producing an organic EL element according to claim 4, wherein the roughening step is performed before the resin material is cured.

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