JP2012204261A - Organic el display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL display device capable of improving a light extraction efficiency from the organic EL element and a contrast.SOLUTION: An organic EL display device comprises on a substrate: a drive circuit; a planarization layer having a connection hole; a connection relay layer electrically connected to the drive circuit and formed from the drive circuit to the planarization layer through the connection hole; a convex resin layer formed on the planarization layer and the connection relay layer and covering the connection hole and having a planarized upper surface and a taper in an edge; a first electrode covering the resin layer so as to have a flat part along the upper surface of the resin layer and an inclined surface along the taper, and electrically connected to the connection relay layer on the planarization layer; a barrier wall defining a light emitting region; an organic EL layer provided on the first electrode; and a second electrode provided on the organic EL layer.

Description

  The present invention relates to an organic EL display device in which an organic EL (electroluminescence) element is arranged, and more particularly to an organic EL display device that can improve light extraction efficiency and contrast.

  As a problem of the organic EL element, it is known that the light extraction efficiency is poor. This is because part of the light emitted from the light emitting layer in various directions in the organic EL element is totally reflected at the interface between the organic EL layer and the electrode structure, sealing structure, etc. due to the difference in the refractive index of each layer. This is because it is absorbed and attenuated by the partition wall and the like without being taken out. As a technique for solving this problem, in Patent Document 1, a light reflection layer is formed so as to surround an organic EL element, whereby light guided in a planar direction while totally reflecting in the organic EL element is directed toward the upper surface of the substrate ( A technique of reflecting the light toward the light extraction side) is disclosed.

  In addition, in an organic EL display device that is driven by connecting an upper surface extraction type organic EL element that emits light to the upper surface of a substrate with a TFT (thin film transistor) circuit, it is necessary to connect the TFT circuit and an electrode. Patent Document 2 discloses a technique in which an electrode is provided along the inner wall of a connection hole provided in an insulating film from above the TFT circuit to electrically connect the TFT circuit and the electrode.

JP 2004-119197 A JP 2001-31223 A

  In Patent Document 1, it is shown that a light reflecting layer made of a reflective metal and having a reflective slope toward the upper surface of the substrate is formed by an etching method. However, by etching the metal layer, a uniform tapered shape is obtained in the surface. Hard to get. In addition, since the metal reflecting slope obtained by etching has a rough surface, there is a problem that the light reflectance to the upper surface of the substrate is lowered.

  In Patent Document 2, since the inner wall of the connection hole of the insulating film has an inclined region, the electrode provided along the inner wall of the connection hole has an inclined surface. For this reason, there is a problem that external light reflection occurs on this slope and the contrast deteriorates.

  Accordingly, an object of the present invention is to provide an organic EL display device capable of improving the light extraction efficiency from the organic EL element and improving the contrast.

In order to solve the above problems, the present invention provides a substrate on which
A drive circuit;
A planarization layer provided on the drive circuit and having a connection hole;
A connection relay layer electrically connected to the drive circuit and provided from the drive circuit to the planarization layer through the connection hole;
A convex resin layer provided on the planarizing layer and the connection relay layer so as to cover the connection hole, and having an upper surface planarized and an end tapered.
A first electrode having a flat portion along the upper surface of the resin layer, covering the resin layer so as to have an inclined surface along the taper, and electrically connected to the connection relay layer on the flattening layer When,
A partition wall defining a light emitting area;
An organic EL layer provided on the first electrode;
A second electrode provided on the organic EL layer;
The present invention provides an organic EL display device characterized by comprising:

  According to the present invention, the light extraction efficiency from the organic EL element can be improved, and the contrast can be improved.

It is a figure which shows an example of the pixel of the organic electroluminescent display apparatus of this invention. It is a figure which shows the other example of the pixel of the organic electroluminescent display apparatus of this invention. It is a figure which shows the other example of the pixel of the organic electroluminescent display apparatus of this invention. It is a schematic sectional drawing of the pixel of the conventional organic electroluminescence display. It is a plane schematic diagram of the organic EL display device of the present invention.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. For parts not specifically shown or described in the present specification, well-known or publicly known techniques in the art can be applied.

  FIG. 5 is a schematic plan view of the organic EL display device of the present embodiment. Peripheral circuits including a scanning signal driver 52, an information signal driver 53, and a current supply source 54 are arranged around the display device formed on the substrate 51, and an X direction wiring called a gate line and a Y direction called a data line, respectively. Connected to wiring and power line. The scanning signal driver 52 sequentially selects gate lines, and an image signal is applied from the information signal driver 53 in synchronization therewith. Pixels 55 are arranged in a matrix at the intersections of the gate lines and the data lines.

  FIG. 1 shows an example of a pixel of an organic EL display device according to the present embodiment, in which (a) is an enlarged top view and (b) is a schematic sectional view. FIG. 1 corresponds to one of the pixels 55 of FIG.

Reference numeral 1 denotes a substrate, and Si, glass, a plastic substrate or the like is preferably used. A semiconductor layer 2 is provided on the substrate 1, and a gate electrode 4 is provided thereon via a gate insulating film 3. As the semiconductor layer 2, an amorphous silicon thin film or a polysilicon thin film is generally used. The gate insulating film 3 is an inorganic material such as SiO _2, the gate electrode 4 such as Mo and Mo alloy is preferably used. A source / drain region (not shown) is provided in the semiconductor layer 2, and a source electrode 6 and a drain electrode 7 are formed by contact holes provided in the gate insulating film 3 and the interlayer insulating film 5. The interlayer insulating film 5 is preferably made of SiO, SiN, or the like, and aluminum, aluminum alloy, or the like is preferably used as the wiring material for the source electrode 6 and the drain electrode 7. Thus, on the substrate, a drive circuit is formed which includes the semiconductor layer 2, the gate insulating film 3, the gate electrode 4, the interlayer insulating film 5, the source electrode 6 and the drain electrode 7, and actively drives the organic EL element. ing. A TFT (thin film transistor) is preferably used as the drive circuit. The protective film 8 provided on the drive circuit is for protecting the drive circuit from deterioration factors such as moisture, and SiN or the like is preferably used.

  A planarizing layer 9 is provided on the drive circuit, more precisely on the protective film 8 on the drive circuit. The drive circuit, particularly the source electrode 6 and the drain electrode 7 constituting the wiring layer, generally have a film thickness of about several hundreds nm and have irregularities. Since the unevenness affects the light emission characteristics of the organic EL element, a flattening layer 9 is provided to flatten the unevenness. The protective film 8 and the planarization layer 9 are provided with a connection hole (contact hole) for electrically connecting the drain electrode 7 and the first electrode 12. The planarizing layer 9 is preferably made of an organic material such as a photosensitive resin, and preferably has a film thickness of 0.5 μm or more and 5.0 μm or less in order to exert a planarization effect.

  Reference numeral 10 denotes a connection relay layer, and the drain electrode 7 and the connection relay layer 10 are connected via a connection hole of the protective film 8 and the planarization layer 9. The connection relay layer 10 is electrically connected to the drain electrode 7, and is provided from the drain electrode 7 through the connection hole of the protective film 8 and the planarization layer 9 to the planarization layer. In the present invention, since the resin layer 11 covers the connection hole of the planarizing layer 9, the connection relay layer 10 is provided to ensure electrical connection between the drain electrode 7 and the first electrode 12. A known material can be used for the connection relay layer 10 as long as it is a conductive material.

  Reference numeral 11 denotes a resin layer, which covers the connection hole of the flattening layer 9 on the flattening layer 9 and the connection relay layer 10 and is convex so that the upper surface is flattened and the end has a taper (forward taper structure). A resin layer 11 having a shape is formed. The resin layer 11 is formed by applying a photosensitive resin, exposing and developing by a photolithography process, and can easily make the end taper uniform.

  Reference numeral 12 denotes a first electrode, and the first electrode 12 is formed so as to cover the resin layer 11 so as to have a slope along the taper of the resin layer 11. Thereby, the slope of the first electrode 12 is flattened, and the light guided in the plane direction in the organic EL element is reflected without being scattered by the slope of the first electrode, so that the light reflectance to the upper surface of the substrate is increased. be able to. Further, the first electrode 12 is formed so as to cover the resin layer 11 so as to have a flat portion along the upper surface of the resin layer 11. Thereby, since external light is reflected on the upper surface of the first electrode 12, it is not reflected by the connection hole of the planarizing layer 9. Furthermore, the first electrode 12 is in contact with the exposed region of the connection relay layer 10 on the planarization layer, so that the electrical connection between the drive circuit and the first electrode 12 is reliably realized. The first electrode 12 is preferably made of a reflective metal such as Ag or Al, an alloy thereof, or the like for extracting light to the upper surface of the substrate. In order to improve the carrier injection property to the organic EL layer 14, a form in which an oxide film such as ITO is laminated on the metal layer is also preferably used. As a method of forming the first electrode 12, a sputtering method is preferably used, and a smooth and high light reflectance film can be obtained. One of the first electrode 12 and the second electrode 15 is an anode and the other is a cathode.

  Reference numeral 13 denotes a partition, and the partition 13 is formed so as to define a light emitting region by the partition opening 13a. For example, the partition wall 13 is formed so as to cover at least the flat portion of the first electrode 12 and the slope of the first electrode 12. When formed in this way, it is more preferable in that the tapered portion of the resin layer 11 can be prevented from emitting light and current concentration on the organic EL layer 14 can be avoided in the tapered portion of the resin layer 11.

  An organic EL layer 14 is formed on the first electrode. The organic EL layer 14 is a single layer or a laminated body including a plurality of layers including a light emitting layer. For example, a four-layer structure including a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer, and a three-layer structure including a hole transport layer, a light-emitting layer, and an electron transport layer can be given. As a material constituting the organic EL layer 14 (organic light emitting material, hole transport material, electron transport material, electron injection material, etc.), a known material can be used. In addition, color display is possible by forming a red light emitting material, a green light emitting material, and a blue light emitting material in the light emitting layer.

  A second electrode 15 is formed on the organic EL layer. For the second electrode 15, an electrode material having a light-transmitting property or a semi-transmitting property is preferably selected for extracting light to the upper surface of the substrate.

  Although not shown in FIG. 1, a sealing structure may be provided so that the organic EL display device is not deteriorated by being affected by moisture or oxygen. As the sealing structure, a structure in which a sealing film is formed or a hollow sealing structure in which a separate sealing housing is bonded can be used.

  The structure shown in FIG. 1 exhibits two effects of the present invention. The first effect is an improvement in light extraction efficiency. This effect is that the first electrode 12 is formed on the tapered structure on the pixel opening side of the resin layer 11 formed so as to surround the light emitting region, thereby forming a reflective slope, and one of the organic EL light emission generated in the pixel opening. It appears when the part is taken out toward the upper surface of the substrate without being absorbed and attenuated. The reflective slope formed by the first electrode 12 of the present embodiment is controlled to have a uniform taper shape by the resin layer 11, and since the slope of the first electrode 12 is flattened, a good light reflectance is obtained, and light extraction efficiency is obtained. Will improve. Further, since the taper of the resin layer 11 can be easily made uniform, the slope of the first electrode 12 covering the resin layer 11 can be easily flattened. Therefore, the slope of the first electrode 12 flattened by a highly productive process can be formed. In addition, the resin layer 11 is not limited to the form shown in FIG. 1, It is good also as the arrangement | positioning surrounding an organic EL element, and may change the angle of taper, a shape, etc. FIG.

  The second effect is an improvement in contrast. The contrast of the organic EL display device, particularly in a bright environment, is improved by lowering the level of black display. In general, a technique is used in which a circularly polarizing plate is used to lower the black level, and external light is prevented from coming out again by using a phase change caused by reflection from the display device surface. One factor that increases the black level is reflection of external light from the inclined region of the connection hole of the planarizing layer 9. The reflection of external light generated in the inclined region is an even number of reflections and deviates from a suitable phase change, so that it is extracted outside and leads to an increase in black level. Even when a circularly polarizing plate is not used, light incident on the inclined region from an oblique direction is reflected and travels in the front direction, which causes a reduction in contrast in the front direction. FIG. 4 is a schematic sectional view of a conventional organic EL display device. In the organic EL display device of FIG. 4, since the reflective first electrode 12 is formed in the inclined region of the connection hole of the planarizing layer 9, even-numbered reflection or reflection in the front direction that occurs in this inclined region can be blocked. Therefore, the contrast deteriorates. On the other hand, in the organic EL display device of the present invention, the surface of the connection hole of the flattening layer 9 is filled with the resin layer 11, and the upper part of the connection hole is flattened. A first electrode 12 is formed on the flattened surface. For this reason, the external light is reflected by the first electrode, and the external light reflected by the first electrode 12 is blocked by the circularly polarizing plate. Therefore, the black level is improved and the contrast is improved. Even when a circularly polarizing plate is not used, since the light is reflected by the flat surface of the first electrode 12, light incident in an oblique direction is prevented from being directed obliquely by the regular reflection and coming out in the front direction. Therefore, the contrast in the front direction is improved.

  2 and 3 are other examples of the pixel of the organic EL display device of the present invention, wherein (a) is an enlarged top view and (b) is a schematic cross-sectional view, respectively. FIG. 2 shows a configuration in which the end portion of the resin layer 11 on the connection relay layer 10 is inside the connection relay layer 10. FIG. 3 shows a configuration in which the connection relay layer 10 extends to a region where the pixel opening overlaps with the resin layer 11 around the pixel opening, that is, the entire resin layer 11 is formed on the connection relay layer formed on the planarization layer. It is a configuration. From the viewpoint of efficiently guiding light to the slope of the first electrode 12 and reflecting it to the outside of the element, the configuration of FIG. 3 in which the step of the connection relay layer 10 does not occur between the light emitting region and the resin layer 11 is adopted. Is more preferable.

[Example]
In this example, the organic EL display device of FIG. 1 was manufactured.

  A TFT drive circuit was fabricated on a glass substrate as the substrate 1 using a low-temperature polysilicon forming technique. A planarizing layer 9 made of photosensitive polyimide was formed to planarize a substrate provided with a drive circuit and provided with a protective film connection hole 8a. A connection hole 9a was formed in the planarizing layer 9 by a photolithography process. The thickness of the planarizing layer 9 was 2 μm.

  Next, ITO was patterned as the connection relay layer 10. The connection relay layer 10 was electrically connected to the drain electrode 7, and was formed from the drain electrode 7 through the connection hole of the protective film 8 and the planarization layer 9 to the planarization layer. The film thickness of ITO was 100 nm.

  Subsequently, a resin layer 11 made of photosensitive polyimide was formed, and patterned by a photolithographic process so as to surround the connection hole of the planarization layer 9 and the pixel opening. In this manner, the convex resin layer 11 provided on the planarizing layer and the connection relay layer so as to cover the connection hole of the planarizing layer 9 and having a flat upper surface and a tapered end is formed. The resin layer 11 had a thickness from the upper surface of the planarizing layer 9 of 0.8 μm.

  Next, an Ag alloy (film thickness 100 nm) and ITO (film thickness 10 nm) were continuously sputtered as the first electrode 12 and then patterned by a photolithography process. In this way, the resin layer 11 is covered so as to have a flat portion along the upper surface of the resin layer 11 and an inclined surface along the taper of the resin layer 11, and electrically connected to the connection relay layer 10 on the flattened layer. The 1st electrode 12 connected to was formed.

  Subsequently, a partition wall 13 made of photosensitive polyimide was formed in a pattern so as to cover the flat portion of the first electrode 12 and the slope of the first electrode 12.

  Next, a red EL layer composed of a hole transport layer / red light emitting layer / electron transport layer, and a green composed of hole transport layer / green light emitting layer / electron transport layer as the organic EL layer 14 on the first electrode and the partition. A blue EL layer composed of an EL layer and a hole transport layer / blue light emitting layer / electron transport layer was formed by a vacuum deposition method. The red EL layer, the green EL layer, and the blue EL layer were separately formed for each pixel using a shadow mask.

  Subsequently, an Ag alloy was formed as the second electrode 15 on the organic EL layer by a sputtering method. The film thickness was 15 nm in order to obtain translucency.

  Finally, a glass cap was bonded to obtain an organic EL display device having a hollow sealing structure.

[Comparative example]
In this comparative example, the organic EL display device of FIG. 4 was manufactured. The planarizing layer 9 provided with the connection holes was formed by the same process as in Example 1.

  Next, an Ag alloy (film thickness 100 nm) and ITO (film thickness 10 nm) were continuously sputtered as the first electrode 12 and then patterned by a photolithography process. Subsequently, the barrier ribs 13 made of photosensitive polyimide were patterned. Thereafter, the organic EL layer 14 and the second electrode 15 were formed on the substrate in the same manner as in Example 1, and a glass cap was adhered to obtain an organic EL display device having a hollow sealing structure.

  The organic EL display devices of the above Examples and Comparative Examples were driven using a driving means with a display circularly polarizing plate attached to the display surface side. The front luminance of the example was higher than that of the comparative example, and in the example, it was confirmed that the light extraction efficiency was improved by the reflective slope formed by the resin layer 11 and the first electrode 12. Further, the contrast in the bright environment of the example was improved as compared with the comparative example. In the comparative example, there was external light reflection from the inclined region of the connection hole of the flattening layer 9, and in the example, the effect of flattening the connection hole by the resin layer 11 was confirmed.

  As described above, according to the present invention, in the organic EL display device, an improvement in light extraction efficiency and an improvement in contrast are achieved at the same time.

  1: substrate, 2: semiconductor layer, 3: gate insulating film, 4: gate electrode, 5: interlayer insulating film, 6: source electrode, 7: drain electrode, 8: protective film, 8a: connection hole of protective film, 9 : Planarization layer, 9a: connection hole of flattening layer, 10: connection relay layer, 11: resin layer, 12: first electrode, 13: partition, 13a: partition opening, 14: organic EL layer, 15: first 2 electrodes, 51: substrate, 52: scanning signal driver, 53: information signal driver, 54: current supply source, 55: pixel

Claims (3)

On the board
A drive circuit;
A planarization layer provided on the drive circuit and having a connection hole;
A connection relay layer electrically connected to the drive circuit and provided from the drive circuit to the planarization layer through the connection hole;
A convex resin layer provided on the planarizing layer and the connection relay layer so as to cover the connection hole, and having an upper surface planarized and an end tapered.
A first electrode having a flat portion along the upper surface of the resin layer, covering the resin layer so as to have an inclined surface along the taper, and electrically connected to the connection relay layer on the flattening layer When,
A partition wall defining a light emitting area;
An organic EL layer provided on the first electrode;
A second electrode provided on the organic EL layer;
An organic EL display device comprising:   The organic EL display device according to claim 1, wherein the entire resin layer is formed on the connection relay layer formed on the planarization layer.   The organic EL display device according to claim 1, wherein the partition wall covers at least the flat portion and the slope.

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