JP2014110132A - organic EL display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an organic EL display device by which organic EL layers having different film thicknesses can be deposited at low cost, and an organic EL display device manufactured by the method.SOLUTION: In a method for manufacturing an organic EL display device, a film thickness adjustment layer 20 having a different film thickness for each pixel region is formed on a substrate 10; electrodes 51, 52 and 53 are formed for each pixel region on the film thickness adjustment layer 20, respectively; a pixel separation film 40 for separating the pixel regions on the film thickness adjustment layer 20 is formed so as to expose the electrodes 51, 52 and 53, respectively; organic EL layers 51, 52, 53, 61, 62 and 63 are formed on the electrodes; and an electrode 70 is formed on the organic EL layers.

Description

The present invention relates to a manufacturing method of a display device using an organic EL (Electroluminescence) display element and a display device manufactured by the manufacturing method.

In recent years, organic EL display devices using organic EL elements have been developed. Such an organic EL element is provided with a light emitting layer that emits light for each pixel, and the amount of emitted light can be adjusted by adjusting the amount of current itself supplied to the light emitting layer. Have.

In a display device using such organic EL elements, different organic EL layer structures are realized for each pixel in order to enable emission of multiple colors such as R (red), G (green), and B (blue). The organic EL layer structure is formed of a plurality of films, but the thicknesses of the films are different. Organic EL elements use different materials for each emission color and are strongly affected by optical interference because they are thin films. To obtain the desired characteristics, it is necessary to change the film thickness to be formed for each emission color. Because there is.

In the conventional organic EL element, in order to vary the film thickness of the organic EL layer for each pixel, the film thickness to be formed for each emission color is changed by forming the film using a vacuum vapor deposition method and a shadow mask.

5 and 6 are diagrams showing a process for forming an organic EL layer in the prior art.

As shown in FIG. 5, a planarizing film 21 is formed on the substrate 10, and an anode is formed for each pixel. An anode 31 is formed in the blue pixel region, an anode 32 is formed in the green pixel region, and an anode 33 is formed in the red pixel region. Then, the pixel separation film 40 is formed so as to partition each pixel region. Then, first, a shadow mask is opened only in the blue region (left side in the figure), and an organic EL layer for emitting blue light (here, a layer including a hole transport layer (HTL)) is formed through the opening. Film.

Subsequently, as shown in FIG. 6, a shadow mask is opened only in the green region (the middle side in the figure), and an organic EL layer for green light emission is formed through the opening. The organic EL layer in the green region is formed so as to be thicker than the organic EL layer in the blue region.

Subsequently, as shown in FIG. 7, a shadow mask is opened only in the red region (right side in the drawing), and an organic EL layer for red light emission is formed through the opening. The organic EL layer in the red region is formed so as to be thicker than the organic EL layer in the blue region and the organic EL layer in the green region.

Furthermore, as shown in FIG. 8, by repeating the deposition using a shadow mask a plurality of times, other organic EL layers (emission layer (EML), electron transport layer (ETL), electron injection layer (EIL)) are formed in each pixel region. ) 61, 62 and 63 are formed, and the cathode 70 is formed.

JP 2008-204961 A JP 2000-323277 A

In such a conventional technique, the vacuum deposition method using a shadow mask is repeated many times for the purpose of adjusting the film thickness, and thus, a plurality of expensive vacuum film forming chambers are required, which causes an increase in manufacturing cost. It was.

In addition to the method of repeating the vacuum evaporation method using a shadow mask when forming the organic EL layer, the ink jet method for forming a film for each pixel by changing the submerged amount for each color, and the pixel arrangement in a stripe shape In addition, a nozzle printing method for forming a film by changing the dropping amount for each color is also known, but these methods also cause the manufacturing cost to increase because the film forming process is complicated. It was.

It is an object of the present invention to provide an organic EL display device manufacturing method capable of forming organic EL layers having different film thicknesses at low cost, and an organic EL display device manufactured as such. To do.

In order to solve the above-described problem, a method for manufacturing an organic EL display device according to an embodiment of the present invention forms a film thickness adjustment layer having a different film thickness for each of a plurality of pixel regions on a substrate, thereby adjusting the film thickness. A plurality of first electrodes are formed for each of the plurality of pixel regions on the layer, and a pixel separation film for separating the plurality of pixel regions is formed on the film thickness adjusting layer to expose the plurality of first electrodes, respectively. The organic EL layer is formed on the plurality of first electrodes, and the second electrode is formed on the organic EL layer.

It is desirable that at least some layers of the plurality of films constituting the organic EL layer are collectively formed for the plurality of pixel regions. Moreover, it is desirable that at least a part of the plurality of films constituting the organic EL layer is a hole transport layer. The film thickness adjusting layer is preferably formed by exposing the photosensitive polyimide layer by changing the exposure amount for each of a plurality of pixel regions using a halftone mask.

In order to solve the above problems, an organic EL display device manufactured by the above-described method for manufacturing an organic EL display device is provided.

According to the present invention, organic EL layers having different film thicknesses can be formed at low cost.

It is sectional drawing which showed the manufacturing method of the organic electroluminescence display of this invention. It is sectional drawing which showed the manufacturing method of the organic electroluminescence display of this invention. It is sectional drawing which showed the manufacturing method of the organic electroluminescence display of this invention. It is sectional drawing which showed the manufacturing method of the organic electroluminescence display of this invention. It is sectional drawing which showed the manufacturing method of the conventional organic electroluminescence display. It is sectional drawing which showed the manufacturing method of the conventional organic electroluminescence display. It is sectional drawing which showed the manufacturing method of the conventional organic electroluminescence display. It is sectional drawing which showed the manufacturing method of the conventional organic electroluminescence display.

Hereinafter, the manufacturing method of the organic EL display device of the present invention will be described in detail with reference to FIGS.

First, the substrate 10 is prepared. In this substrate 10, for example, low-temperature polysilicon TFTs and wirings are formed on a glass substrate, and a circuit for selectively supplying a current to the organic EL layer constituting the pixel is formed.

Hereinafter, an example of a method for manufacturing the substrate 10 will be described. First, an active region made of polysilicon is formed in an island-like region where a TFT is formed on a glass substrate. In this polysilicon active region, an amorphous silicon film is formed by plasma enhanced chemical vapor deposition (Plasma Enhanced CVD) or the like, and this is formed into polysilicon by a method such as RTA (rapid thermal annealing) or ELA (excimer laser annealing). And is formed by patterning.

A gate insulating film is formed on one surface of the polysilicon. The gate insulating film is formed from silicon oxide or silicon nitride formed by a CVD method.

A gate electrode is formed in a part of the TFT region on the gate insulating film. This gate electrode is formed by patterning a metal thin film such as Ag, Al, Ti, Mo, Cu, W, or an alloy containing these.

An insulating film is formed on the gate insulating film and the gate electrode. The insulating film is made of silicon oxide or silicon nitride formed by a CVD method, and a contact hole leading to the aforementioned polysilicon is opened. The source / drain wiring is connected through this contact hole. The wiring is also formed by patterning a metal thin film such as Ag, Al, Ti, Mo, Cu, W, or an alloy containing these.

An insulating film is further formed on the insulating film and the wiring to cover them. The insulating film is formed from silicon oxide or silicon nitride formed by a CVD method. The structure so far corresponds to the substrate 10 of FIG. Irregularities exist on the surface of the substrate 10 on which such a circuit is formed.

Next, in order to flatten the unevenness of the surface of the substrate 10 on the substrate 10 and adjust the film thickness of the organic EL layers (especially hole transport layers (HTL) 51, 52, 53) formed thereon. The film thickness adjusting layer 20 is formed. In the substrate 10, areas for forming pixels of different colors such as R (red), G (green), and B (blue) are defined in advance, and the plurality of pixel areas are defined. Each time, the film thickness adjusting layer 20 having a different film thickness is formed.

The film thickness adjusting layer 20 is formed by first slit-coating photosensitive polyimide on the substrate 10 and using a halftone mask having different light transmission characteristics for the pixel area, and for each pixel area, the exposure amount. It is formed by exposing all at once by changing. As a result, the pixel areas having different exposure amounts have different film thicknesses, and steps are formed at the boundaries of the pixel areas. The halftone mask is created by forming chrome thin films having different thicknesses on a quartz mask blank. In the case of using positive photosensitive polyimide, for example, the reaction proceeds more in a portion with a large exposure amount, and as a result, the film thickness adjusting layer 20 is formed thinly after development in a region with a large exposure amount. Instead of the photosensitive polyimide, one or more organic insulating films selected from the group consisting of photosensitive polyamide, acrylic resin, benzocyclobutene, phenol resin, and the like may be used. Further, a negative photosensitive material may be used. In this case, the film thickness of the chrome thin film of the exposure mask is adjusted so that the exposure amount in the region where the film thickness adjusting layer 20 is formed thin is reduced. In addition, an inorganic insulating film made of silicon oxide, silicon nitride, or the like may be used instead of a resin material. In this case, a patterning process is performed multiple times, or a halftone mask is used for patterning a photoresist. Then, the film thickness of the insulating film to be the film thickness adjusting layer 20 is adjusted for each pixel region.

Here, the film thickness adjustment layer 20 has a film thickness for red pixels <for green pixels <for blue pixels. This is because the film thicknesses of the hole transport layers (HTL) 51, 52, and 53 are as follows: for red pixels> for green pixels> for blue pixels, by comparing each region of R (red), G (green), and B (blue). Because there is a need to do.

Subsequently, anodes (electrodes) 31, 32, and 33 electrically connected to the TFT are formed on the film thickness adjusting layer 20 having a different thickness for each pixel region and having a step between the pixel regions. . The anodes 31, 32, and 33 are electrically connected to the TFT formed on the substrate 10 through contact holes formed through the insulating film on the TFT and the film thickness adjusting layer 20. The anodes 31, 32, and 33 are formed of ITO (Indium Tin Oxide), Indium Zinc Oxide, ZnO, MoO ₃ or the like, which is a metal having a relatively large work function. As a result, the blue anode 31 is formed in the blue pixel region where the film thickness adjustment layer 20 is large, and the green anode 32 is formed in the green pixel region where the film thickness adjustment layer 20 is medium. A red anode 33 is formed in each red pixel region where the thickness of the layer 20 is small.

Further, a pixel separation film 40 for separating each pixel region is formed on the film thickness adjusting layer 20 to expose the anodes 31, 32, and 33, respectively. The pixel separation film 40 is one or more organic insulating films selected from the group consisting of polyimide, polyamide, acrylic resin, benzocyclobutene, and phenol resin, and is formed by a method such as slit coating. Further, instead of the organic insulating film, it may be formed of one or more orientation insulating films selected from the group consisting of silicon oxide, silicon nitride, alumina and the like. After forming an insulating film made of these materials, a resist is coated on the surface, the resist is selectively exposed to form a pattern, and each pixel region is separated by etching using the resist as a mask. A pixel isolation film 40 is formed.

Subsequently, an organic EL layer is formed on the anodes 31, 32, and 33 partitioned by the pixel separation film 40. The organic EL layer has a structure in which a hole injection layer (HIL), a hole transport layer (HTL), a light emitting layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL) are formed on the anodes 31, 32, and 33. Each may be formed in order.

First, a hole injection layer (HIL) is formed on the anodes 31, 32, and 33, and then a hole transport layer (HTL) is formed. The hole transport layer (HTL) needs to be for red pixels> green pixels> blue pixels. As shown in FIG. 2, an ink-like hole transport layer material 50 dissolved in a solvent is applied by a slit coating method. Then, the hole transport layer material 50 once completely covers the pixel isolation film 40, but is filled to almost the same height by the flow of the material between the pixels. After coating, the substrate is heated to evaporate the solvent and sinter the hole transport layer material, resulting in the state shown in FIG. Here, when the solvent evaporates, the hole transport layers 51, 52, and 53 for the red pixel, the green pixel, and the blue pixel separated from each other to a height slightly lower than the height of the pixel separation film 40 are respectively provided. It is formed. Since the coating amount of the hole transport layer material 50 inevitably varies depending on the film thickness difference of the film thickness adjusting layer 20, the hole transport layers 51, 52, and 53 having different film thicknesses can be simultaneously formed in each pixel. Become. As the hole transport layer material 50, polyethylene dihydroxythiophene, polyaniline, or the like is used. Further, when the same material is used for all pixels of R (red), G (green), and B (blue), the above HIL or the like may be used instead of HTL.

Subsequently, as shown in FIG. 4, other organic EL layers (light emitting layer (EML), electron transport layer (ETL), electron injection layer (EIL)) 61, 62, and 63 are formed for each pixel. A cathode 70 made of Al, Ni, Mg, an alloy containing these, or the like is formed on the electron injection layer (EIL).

The structure of the organic EL display device described above is a structure in which an anode is disposed on the substrate side and a cathode is disposed on the organic EL layer, but may be a structure in which a cathode is disposed on the substrate side and an anode is disposed on the organic EL layer. In this case, the same effect can be obtained by applying EIL or ETL instead of HTL.

According to the above manufacturing method, the unevenness of the surface on the substrate 10 is flattened for each pixel region of different emission color, and the film thickness adjustment is performed to vary the film thickness of the organic EL layer formed thereon. The layer 20 can be easily formed in one step. Therefore, according to the method for manufacturing an organic EL display device according to an embodiment of the present invention, it is possible to form organic EL layers having different film thicknesses at low cost.

10 Substrate 20 Film thickness adjusting layer 31, 32, 33 Anode 40 Pixel separation film 51, 52, 53 Hole transport layer (part of organic EL layer)
61, 62, 63 Light-emitting layer, etc. (part of the organic EL layer)
70 cathode

Claims (5)

On the substrate, a film thickness adjusting layer having a different film thickness is formed for each of the plurality of pixel regions,
Forming a plurality of first electrodes for each of the plurality of pixel regions on the film thickness adjusting layer;
Forming a pixel separation film that separates the plurality of pixel regions on the film thickness adjustment layer to expose the plurality of first electrodes, respectively;
Forming an organic EL layer on the plurality of first electrodes;
A method of manufacturing an organic EL display device, comprising: forming a second electrode on the organic EL layer. 2. The method of manufacturing an organic EL display device according to claim 1, wherein at least some of the plurality of films constituting the organic EL layer are collectively formed for the plurality of pixel regions. 3. The method of manufacturing an organic EL display device according to claim 2, wherein at least a part of the plurality of films constituting the organic EL layer is a hole transport layer. 4. The film thickness adjusting layer is formed by exposing the photosensitive polyimide layer by changing an exposure amount for each of the plurality of pixel regions using a halftone mask. 5. A method for producing an organic EL display device according to one item. The organic electroluminescence display manufactured by the manufacturing method of the organic electroluminescence display as described in any one of Claims 1 thru | or 4.

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