JP2000106275A - Manufacture of organic electroluminescent display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the planarity of the surface of a lower electrode layer made of a transparent conducting layer and to reduce the resistance of the transparent conducting layer, in order to secure stability of light emission of each organic electroluminescent element. SOLUTION: This method is for manufacture of an organic electroluminescent display device, in which organic electroluminescent elements each having a light-emitting layer formed using at least organic materials between a hole injection electrode and an electron injection electrode are stacked, and the method includes a process of forming a lower electrode layer 2 by forming and patterning an ITO layer over a substrate 1, a process of flattening the surface of the electrode 2, a process of exposing at least a portion of the lower electrode 2 and forming on the substrate an electrically insulating partition wall 5 which projects in a parallel direction, a process of forming an organic light-emitting layer 6 over the lower electrode 2 exposed, and a process of forming an upper electrode layer 7 over the organic light-emitting layer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a display device in which an organic electroluminescence element having at least a light emitting layer using an organic material is formed between a hole injection electrode and an electron injection electrode. The present invention relates to a technique for separating light-emitting regions so that only predetermined light-emitting portions can emit light at random.

[0002]

2. Description of the Related Art In recent years, with the diversification of information equipment and the like, there is an increasing need for a flat display element which consumes less power and has a smaller volume than CRTs generally used conventionally. As one of such surface display elements, an electroluminescence (EL) element has attracted attention.

[0003] Such electroluminescent elements are roughly classified into inorganic electroluminescent elements and organic electroluminescent elements depending on the materials used.

In general, an inorganic electroluminescent element applies a high electric field to a light-emitting portion, accelerates electrons in the high electric field to collide with a light-emitting center, and thereby excites the light-emitting center to emit light.

On the other hand, in an organic electroluminescence device, electrons and holes are recombined at an emission center from an electron injection electrode and a hole injection electrode, respectively, to bring an organic molecule into an excited state. When returning to the fluorescent light is emitted.

[0006] In the case of an inorganic electroluminescence element, a high electric field is required.
While a high voltage of up to 200 V is required, the organic electroluminescence element has an advantage that it can be driven at a low voltage of about 5 to 20 V.

Further, in the case of the above-mentioned organic electroluminescence element, a light-emitting element which emits light of an appropriate color can be obtained by selecting a fluorescent substance which is a light-emitting material, and can be used as a multi-color or full-color display device. It is expected that it can be used, and furthermore, it can be used as a backlight for a liquid crystal display device or the like because it can emit light at low voltage.

[0008] In order to use such an organic electroluminescence element as a display device, it is indispensable to increase the degree of integration and the resolution of the light emitting element. At present, in an organic electroluminescence display device, element separation of a light emitting portion is performed by vapor deposition using a metal mask, and integration has been promoted.

However, in the above-described method using a metal mask, there is a problem that a deposited material is wrapped around due to poor adhesion of the metal mask.
It was necessary to take 4 mm or more, and it was difficult to increase the resolution.

In order to reduce the distance between the light emitting elements and increase the resolution as a display element, Japanese Patent Application Laid-Open No. 8-31598 has been proposed.
As disclosed in Japanese Patent Publication No. 1 (Int. Cl. H05B 33/10), an element isolation technology called “partition (rib) stand” has been introduced.

As shown in FIG. 5, an organic electroluminescence display device formed by using this element isolation technique has a lower electrode layer 2 made of ITO or the like on a glass substrate 1.
Is provided. The lower electrode layers 2 are arranged in a plurality of stripes parallel to each other. A plurality of electrically insulating partitions (ribs) 5 projecting from the substrate 1 are formed across the substrate 1 and the lower electrode layer 2 so as to be orthogonal to the lower electrode layer 2. That is, the partition wall 5 is used to separate the lower electrode layer 2 in the separation part and the direction orthogonal thereto, and is formed on the insulating layer so that the lower electrode layer 2 is not exposed on the surface.

An organic light emitting layer 6 is formed on each of the exposed portions of the lower electrode layer 2. This organic light emitting layer 6
Is formed of an organic material such as a three-layer structure of an organic hole transport layer, an organic light-emitting layer, and an organic electron transport layer, or a two-layer structure of an organic hole transport layer and an organic light-emitting layer. An upper electrode layer 7 is formed on the organic light emitting layer 6 along the extension direction. As described above, the portion of the organic electroluminescence in which the lower and upper electrode layers are intersected with each other corresponds to the light emitting portion.

Next, a method of manufacturing the above-described organic electroluminescent display device will be described with reference to FIGS. 6 is a cross-sectional view taken along line AA of FIG. 5, and FIG. 7 is a cross-sectional view taken along line BB of FIG.

A glass substrate 1 is prepared (see FIGS. 6A and 7A), and a transparent conductor layer 2 made of ITO is formed on the glass substrate 1 by a sputtering method (FIG. 6B).
And FIG. 7 (b)). After that, the transparent conductor layer 2 is patterned to form the lower electrode layer 2 (see FIGS. 6C and 7C).

An insulating layer 13 is formed thereon to reduce a step between the lower electrode layer 2 made of ITO and the insulating portion (FIG. 6).
(D) and FIG. 7 (d)).

Thereafter, a partition (rib) 5 made of an insulating layer having a higher step than the insulating layer 13 is formed on the insulating layer 13.
(See FIGS. 6 (e) and 7 (e)), and further, the organic electroluminescent light emitting layer 6 and the upper electrode layer 7 are formed thereon. Further, a protective film 8 is provided on the upper electrode layer 7 (see FIGS. 6F and 7F).

According to this method, the organic electroluminescent light emitting layer 6 and the organic electroluminescent light emitting layer 6 are formed at the stepped portions of the partition walls 5 formed of an insulating layer having a film thickness sufficiently larger than the film thickness of the organic electroluminescent light emitting layer 6 and the upper electrode 7. "Step disconnection" of the electrode layer 7 occurs, thereby enabling separation between the light emitting elements.

In this process, the surface of the lower electrode layer 2 made of the ITO film in contact with the organic electroluminescent light emitting layer 6 and the electrode layer 7 is laminated with a multilayer film of several hundred angstroms to 2000 angstroms. In order to suppress the occurrence of short circuits and pinholes, it is desirable to be flat and have low resistance in order to maintain the characteristics.

In order to smooth the surface state of the ITO film, a method of forming a film at a low temperature to form an amorphous ITO film is used. However, an amorphous ITO film has a high sheet resistance. Further, when the ITO film is placed at a temperature of, for example, 120 ° C. or more due to a subsequent increase in the process temperature, the ITO film is polycrystallized and has a low resistance. When the upper electrode layer 7 is formed, a short circuit may occur.

[0020]

As described above, the amorphous ITO film formed by sputtering at a low substrate temperature from room temperature to about 70 ° C. has a flat surface, but has a surface of 40 to 50 Ω. It shows a resistance of about / □. After the patterning of the ITO film, if the insulating layer is formed by a sputter of an inorganic material or a cured layer of a resist by a later process, the substrate temperature rises and the surface of the ITO film becomes polycrystalline. When the ITO film is polycrystallized, the sheet resistance of the ITO film decreases, but the surface irregularities increase. In particular, when the substrate temperature after the ITO film formation is increased to 120 ° C. or higher, this tendency becomes remarkable, and the sheet resistance value also decreases to about 20 to several Ω / □, but the surface irregularities increase. When the organic light emitting layer and the upper electrode layer are formed on the uneven surface, there is a problem that a short circuit occurs in the stacked film in the uneven portion, and a non-light emitting point is generated.

The present invention has been made by paying attention to this point. In order to secure the emission stability of the organic electroluminescence element, the flatness of the surface of the ITO substrate is improved and the resistance of the ITO is reduced. It is intended to be.

[0022]

According to the present invention, there is provided an organic electroluminescent display in which an organic electroluminescent element having at least a light emitting layer using an organic material is formed between a hole injection electrode and an electron injection electrode. A method of manufacturing a device, comprising: forming a lower electrode layer by forming and patterning a transparent conductor layer on a substrate; flattening the electrode surface; and exposing at least a portion of the lower electrode; Forming an electrically insulating partition protruding in a direction parallel to the substrate, forming an organic light emitting layer on the exposed lower electrode, and forming an upper electrode layer on the organic light emitting layer; , Is included.

Further, according to the present invention, a transparent conductor layer is formed and patterned on a substrate to form a lower electrode layer, and then an insulating film is formed and the substrate surface is polished to form an insulating film between the electrodes. It is characterized in that it is embedded and the surface of the electrode layer is flattened.

Further, the transparent conductive layer may be composed of a polycrystalline ITO film formed at a high temperature.

Further, it is preferable that the insulating film is formed of an inorganic insulating film.

As described above, according to the present invention, for example, the lower electrode layer is formed by patterning a transparent conductor layer made of a polycrystalline ITO film having a reduced resistance by sputtering at a substrate temperature of 200 ° C. or higher. After forming a lower insulating layer, lapping is performed to flatten the substrate surface, and an electrically insulating partition wall (rib) is formed on the lower insulating layer, thereby lowering the resistance and lowering the flatness. A substrate having an electrode layer is obtained. Therefore, when the organic light emitting layer and the upper electrode layer are formed thereon by vapor deposition, spot defects of the electroluminescent element are suppressed, and the yield is improved. When an organic material is used as the insulating layer, film peeling may occur at the time of lapping, and the process becomes unstable. However, when an inorganic material is used as the insulating layer, film peeling occurs at the time of lapping. Disappears and stabilizes in process.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a method of manufacturing an organic electroluminescence display device according to the present invention for each step. FIG. 1 is a cross-sectional view corresponding to the line AA in FIG. 5 described above, and FIG. BB of 5
It is sectional drawing corresponding to a line part. The same parts as those of the conventional example are denoted by the same reference numerals.

First, the steps of ITO film formation and patterning will be described. As shown in FIGS. 1A and 2A, a glass substrate 1 is prepared. A transparent conductor layer 2 made of an ITO film is formed on the glass substrate 1 by a sputtering method. The thickness of this ITO film is 0.2 μm (see FIGS. 1B and 2B). In the present invention, the transparent conductor layer 2 made of a polycrystalline ITO film having a reduced resistance is formed in advance by sputtering at a substrate temperature of 200 ° C. or higher.

Subsequently, after forming a transparent conductor layer made of an ITO film, a resist is applied, and after prebaking, an exposure phenomenon is performed in a predetermined pattern. Then, after the phenomenon, post-baking is performed, immersed in a ferric chloride solution, and etched to pattern the ITO film, whereby the lower electrode layer 2 made of the ITO film is formed. After the etching, the resist is stripped (see FIGS. 1C and 2C).

Next, the step of forming the first insulating layer 3 will be described. As shown in FIG. 1D and FIG.
After patterning the TO film 2 to form the lower electrode 2, the substrate is washed and the first insulating layer 3 is formed. I
Silicon oxide (SiO ₂ ) was formed by sputtering as an inorganic insulating film on the surface of the glass substrate 1 on which the TO film 2 was patterned. In this embodiment, when the enzyme atmosphere is used, S
By performing Ar sputtering of the i target, SiO ₂
The oxidized film was deposited on the substrate 1. Its film thickness is 0.
The thickness was 5 μm. The film thickness of the insulating layer 3 to be deposited is IT
The thickness of the lower electrode layer 2 made of an O film must be equal to or greater than the thickness of the lower electrode layer 2. Further, in the inorganic insulating layer to be used, in addition to SiO ₂ , Al ₂ O
₃ , oxides such as Si ₃ N ₄ , AlN, BN, and BC, nitrides, and carbides having high insulating properties.
It is desirable to use a material having the same hardness as the film. here,
The reason why the first insulating layer 3 is made of an inorganic material is that in the case of an insulating layer made of an organic material, film peeling may occur during lapping, which will be described later, and the process becomes unstable.

Next, the substrate polishing and flattening step will be described. As shown in FIG. 1E and FIG. 2E, after the first insulating layer 3 is formed, the substrate is polished so that the IT
The surface of the lower electrode layer 2 made of an O film is flattened. By this planarization process, the substrate surface is planarized in a state where the first insulating layer 3 is embedded between the lower electrode layers 2 and 2. In this embodiment, Al ₂ O _{3 is} placed on the polishing pad.
Was applied, and the polishing pad was rotated at a rotation speed of about 50 rpm to flatten the substrate surface.

Next, the steps of forming and patterning the second insulating layer 4 will be described. 1 (f) and 2 (f)
As shown in (1), after the substrate is polished, a resist is applied, and after prebaking, an exposure phenomenon is performed in a predetermined pattern to form the second insulating layer 4. The insulating layer 4 is formed for the purpose of preventing the electrode layer cut off after the deposition of the organic electroluminescent light emitting layer and the upper electrode layer after the formation of the partition walls (rib formation) from coming into contact with the lower electrode layer 2 made of an ITO film. .

In this embodiment, a resist is used for the second insulating layer 4, the film thickness is 1 μm, and after patterning, baking is performed at 200 ° C. for 10 minutes in a nitrogen atmosphere. A rib formation step was performed.

Although the resist after patterning has a shape as shown in FIG. 3A, the pattern edge as shown in FIG. 3B causes shoulder drooping by baking. This is caused by evaporation of the moisture and the solvent in the resist remaining after the resist patterning by baking. This evaporation occurs at a temperature of 130 ° C. or higher. However, in this embodiment, the baking is performed at 200 ° C. in order to sufficiently evaporate the water and the solvent. This shoulder stabilizes the subsequent coverage of the organic electroluminescent layer and the upper electrode layer.

Alternatively, the second insulating layer 4 can be made of the same material as the first insulating layer 3 by using a lift-off method.

Next, the step of partitioning (rib formation) will be described. As shown in FIG. 1 (g) and FIG. 2 (g), after the second insulating layer 4 is formed, a resist is applied, and after pre-baking, an exposure phenomenon is performed in a predetermined pattern to form partition walls (ribs).
5 is formed. Since the partition walls (ribs) 5 need to be cut off after the subsequent deposition of the organic electroluminescent light emitting layer and the electrode layer, the partition walls (ribs) 5 made of a reverse-tapered resist as shown in FIG. 4 are used. Further, a step with respect to the thickness of the deposited film is increased. Examples of the resist include ZPN1 (trade name, manufactured by Zeon Corporation).
A negative type resist such as 100 can be used. In this embodiment, the film thickness of the partition wall (rib) 5 is 4 μm, while the film thickness of the vapor deposition is 0.6 μm.

Next, the steps of depositing the organic electroluminescent light emitting layer and the electrode layer will be described. FIG.
2 (h) and FIG. 2 (h), after forming a partition (rib) 5 on the second insulating layer 4, under predetermined conditions, an organic hole injection layer, an organic hole transport layer, an organic light emitting layer, An organic light emitting layer 6 composed of an organic electron transport layer and an organic electron injection layer is formed,
An upper electrode layer 7 is provided on the organic light emitting layer 6, and a protective film 8 is further formed thereon.

After depositing the protective film 8, in a nitrogen atmosphere,
Sealing is performed using a sealing material. The organic electroluminescence film is likely to contain moisture, and if moisture is contained, the light emission intensity is likely to deteriorate. Therefore, the sealing is performed in a dry nitrogen atmosphere. Thus, the organic electroluminescence display device according to the present invention is obtained. In this organic electroluminescent display device, light emission is emitted from the substrate 1 side.

Although the ITO film is used as the transparent conductor layer in the above embodiment, the same effect can be obtained by using another transparent conductor layer such as SnO ₂ .

[0040]

As described above, according to the method of manufacturing an organic electroluminescent display device according to the present invention, by lowering the flatness of the lower electrode surface, it is possible to reduce the yield due to spot defects of the electroluminescent element. Can be suppressed.

Further, since an ITO film formed at a high temperature can be used, the resistance of the ITO film can be reduced, and the resistance of the driving voltage can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method of manufacturing an organic electroluminescent display device according to the present invention for each process and corresponding to a line AA in FIG.

FIG. 2 is a cross-sectional view illustrating a method of manufacturing an organic electroluminescent display device according to the present invention for each process and corresponding to a line BB in FIG. 5;

FIG. 3 is a cross-sectional view showing a formation state of a second insulating layer used in the organic electroluminescence display device of the present invention.

FIG. 4 is a cross-sectional view of a partition (rib) portion of the organic electroluminescence display device of the present invention.

FIG. 5 is a perspective view showing an organic electroluminescence display device.

FIG. 6 is a cross-sectional view taken along the line AA of FIG. 5, showing a method of manufacturing organic electroluminescence for each process.

FIG. 7 is a cross-sectional view taken along the line BB of FIG. 5, showing a method of manufacturing organic electroluminescence for each step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Lower electrode layer 3 1st insulating layer 4 2nd insulating layer 5 Partition (rib) 6 Organic light emitting layer 7 Upper electrode layer 8 Protective film

Claims (4)

[Claims] 1. A method of manufacturing an organic electroluminescence display device in which an organic electroluminescence element having at least a light emitting layer using an organic material is formed between a hole injection electrode and an electron injection electrode. Forming a lower electrode layer by film-forming and patterning a transparent conductor layer on a substrate, flattening the electrode surface, exposing at least a portion of the lower electrode, and projecting in a direction parallel to the substrate. Forming an electrically insulating partition to be formed, forming an organic light emitting layer on the exposed lower electrode, and forming an upper electrode layer on the organic light emitting layer. A method for manufacturing an organic electroluminescence display device. 2. A method for forming a lower electrode layer by patterning and forming a transparent conductor layer on a substrate, forming an insulating film and polishing the surface of the substrate to fill the insulating film between the electrodes, The method according to claim 1, wherein the surface of the layer is flattened. 3. The method for manufacturing an organic electroluminescent display device according to claim 1, wherein the transparent conductive layer is a polycrystalline ITO film formed at a high temperature. 4. The method for manufacturing an organic electroluminescent display device according to claim 1, wherein the insulating film is an inorganic insulating film.