JP2006040580A - Fabrication method of organic el device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fabrication method for a top emission type organic EL device, which endows the top emission type organic EL device with high heat dissipation from a substrate, does not cause deterioration of an organic EL layer, can form an ITO layer as a second electrode and continuously a passivation layer on it, and can form an insulator layer on a substrate surface. <P>SOLUTION: The fabrication method for the top emission type organic EL device has: a first step for preparing a metal base made of an alloy containing magnesium, or aluminum, or the two, and forming the insulator layer on a surface of the metal base to make a metal substrate; a second step for forming a plurality of first electrodes; a third step for forming the organic EL layer; a fourth step for forming the second electrode by using a facing targets spattering (FTS) apparatus and indium tin oxide (ITO) as the targets; and a fifth step for continuously forming the passivation layer made of oxidation silicon nitride on the second electrode by replacing the indium tin oxide (ITO) as the targets with silicon and blowing oxygen gas and nitrogen gas mixed at specified partial pressures of each other; in this order. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an organic EL element, and more particularly to a method for manufacturing a top emission type organic EL element using a magnesium material as a substrate.

Organic electroluminescence elements (hereinafter referred to as “organic EL elements” for short) have become possible to form high-purity, high-quality laminated films with a thickness of nm class due to recent advances in thin film formation technology, and have a thickness of about 5V. Low voltage operation is possible.
In this way, organic EL elements are attracting attention as elements for next-generation display systems that have low power consumption, high quality, are thin, and can display curved surfaces.

In an organic EL element, a plurality of films composed of predetermined organic molecular components are stacked one above the other to form an organic EL layer, and an electrode layer is attached to each of the upper and lower sides to form an OLED (organic light emitting diode). A phenomenon in which light is emitted when electrons and holes are recombined by applying a predetermined voltage or current to inject electrons and holes into the organic EL layer is used.
Therefore, in order to guide the emitted light to the outside and perform the display function, at least one of the electrodes provided on the upper and lower sides must be transparent.

  As a transparent electrode, ITO (Indium Tin Oxide) is widely used as a material capable of achieving both electrical conductivity and transparency. In general, however, annealing is required to reduce the electrical resistance of ITO, and ITO Polishing was necessary to increase the surface smoothness (to reduce the roughness).

Since the organic EL layer deteriorates when the ITO is annealed at a high temperature, the organic EL layer conventionally needs to be formed after the ITO.
That is, the stacking order is [substrate-first electrode (ITO) -organic EL layer-second electrode (opaque electrode)], and light is emitted from the substrate side (bottom emission). A glass substrate is used.

  However, the glass substrate has poor thermal conductivity, and the heat dissipation during operation is insufficient to dissipate heat, resulting in a high temperature and easily deteriorating the organic EL layer.

Furthermore, in order to obtain a high-speed and high-definition display system, it is necessary to drive the active matrix (TFT). In that case, since the TFT transistor must be formed between the substrate and the ITO electrode, the presence of the TFT transistor As a result, the aperture ratio decreases, and the external conversion efficiency of light emission decreases.
That is, in order to ensure the required amount of light emission, the power consumption increases, and accordingly, the amount of heat generated in proportion to the power consumption increases, resulting in a higher temperature, and the organic EL layer is more likely to deteriorate.

Therefore, a method of making the second electrode transparent to be [substrate-TFT-first electrode-organic EL layer-second electrode (ITO)] and emitting light from the opposite side of the substrate (top emission) has been studied.
At that time, various measures are taken so that the organic EL layer is not altered by the formation of the second electrode.

  For example, in Patent Document 1, the second electrode (transparent electrode) is made into a multilayer ITO thin film, the transparency is improved while ensuring the same electrical conductivity as before, and the temperature of the substrate during the ITO film formation is kept low. Technology is disclosed.

Further, for example, in Patent Document 2, an organic EL layer substrate (color conversion substrate) created by a bottom emission type and a TFT substrate created separately are bonded together (in this case, an overcoat for gap adjustment and stress relaxation between the two substrates). A technique for switching to a top emission type by providing a layer is disclosed.
However, these technologies do not always have sufficient suppression of temperature rise of the substrate, and there are problems that the number of steps increases and the manufacturing method becomes complicated, and the heat dissipation is sufficient because it relies on a glass substrate. In addition, there is a problem that the organic EL layer is likely to be deteriorated.
JP 2004-139991 A JP 2003-282261 A

  An object of the present invention is to provide an economical manufacturing method of a top emission type organic EL element having high heat dissipation from a substrate.

  In the present invention, the ITO film as the second electrode and the protective film thereon can be continuously formed without causing alteration of the organic EL layer of the top emission type organic EL element, and the ITO film needs to be polished. The object is to provide an economical production method that can be made smoother than possible.

  Another object of the present invention is to provide a method for economically forming an insulating layer on the substrate surface of the top emission type organic EL device.

  In order to achieve the above object, according to the method of manufacturing an organic EL device according to the present invention, a metal base made of magnesium, aluminum, or an alloy containing them is prepared, and an insulating layer is formed on the surface. The target is formed by a first step of forming a metal substrate, a second step of forming a plurality of first electrodes, a third step of forming an organic EL layer, and a counter target sputtering (FTS) apparatus. A fourth step of forming a second electrode as indium tin oxide (ITO) and silicon oxynitride by blowing oxygen gas and nitrogen gas mixed at a predetermined partial pressure instead of silicon as the target And a fifth step of continuously forming a protective film made of the second electrode on the second electrode in this order.

  According to a second aspect of the present invention, in the first step, the insulating layer is formed by oxidizing a surface of a metal matrix.

  According to a third aspect of the present invention, the method further includes a sixth step of forming a TFT transistor at a position corresponding to a lower portion of the organic EL layer between the first step and the second step. And

  According to the manufacturing method of the top emission type organic EL device according to the present invention, the second electrode (ITO) film and the protective film thereon are continuously formed, and the heat dissipation from the substrate is high, so the deterioration of the organic EL layer is prevented. A highly reliable organic EL element can be economically provided without inviting.

  In addition, according to the method of manufacturing a top emission type organic EL element according to the present invention, the organic EL layer is not altered when forming the second electrode (ITO), so that a high-quality organic EL element can be produced with high yield and economy. Can be provided.

  Further, according to the method for producing a top emission type organic EL element according to the present invention, an active matrix type organic EL element in which the aperture ratio is not limited by the TFT transistor can be economically provided.

  Embodiments according to the present invention will be specifically described below with reference to the drawings.

  In the present invention, the ITO transparent electrode film is formed by the facing target sputtering (hereinafter abbreviated as “FTS”) technique, thereby changing the organic EL layer at a lower temperature than in the case of the normal simple sputtering technique. Focus on the fact that ITO with low resistivity, high transparency and good smoothness can be obtained.

The principle of FTS was proposed in 1977 by Professor Naoe et al. At Tokyo Tech.
(Y. Hoshi, M. Naoe and S. Yamanaka, Jpn. J. Appl. Phys., 16 (1977), PP. 1715)
The feature is that the target surface is opposed, the high-density plasma is constrained in the space between the targets, and sputter particles are generated by high vacuum / low voltage discharge. At that time, the sputter particles are deposited to form a substrate The surface is positioned outside the plasma space so that the plasma particles do not directly collide with the substrate surface, and the sputtered particles are deposited on the substrate surface at a low temperature to form a film free from collision damage and grain boundary defects. There is.

Even in simple sputtering, thin film formation by CVD (Chemical Vapor Deposition) method decomposes the source gas uniformly, transports it onto the substrate, and deposits a desired amount of molecules selectively depending on the substrate temperature and substrate bias. A film having no grain boundary defects can be formed.
However, in the CVD method, the substrate temperature may have to be increased, and in that case, it cannot be used for film formation on the organic EL layer.
In addition, toxic gases are often used, and organic substances decomposed by gas adhere to the necessary vacuum vessels and piping systems during the thin film formation process, so a large space and high capital investment considering environmental safety and maintenance are required. Necessary and undesirable.

  1 and 3 are flowcharts showing a method for producing an organic EL element according to the present invention, FIGS. 2 and 4 are schematic cross-sectional views showing a method for producing an organic EL element according to the present invention, and FIGS. In the case of passive matrix driving, FIGS. 3 and 4 are cases of active matrix driving.

As shown in FIGS. 1 and 2, the passive matrix driving type organic EL elements are formed in the following order.
In step 1, first, a metal substrate 100 is prepared. As the material of the metal substrate, it is desirable that the material has high workability and thermal conductivity and is economically available, and magnesium (Mg), aluminum (Al), or an alloy containing them is preferable.

The metal substrate 100 includes a metal base body 102 and an insulating layer 104.
Prior to the formation of the insulating layer, the surface of the metal matrix is polished to obtain a predetermined smoothness. This smoothness greatly affects the optical quality level of the organic EL layer deposited in a later step.
In the case of Mg, it has been reported that excellent smoothness of the order of 0.010 μm can be obtained by using buffing and electropolishing together.

The insulating layer 104 is formed by oxidation of the base metal.
At that time, in the case of Al, anodization, that is, electrical conversion, is required to form alumina, whereas in the case of Mg, for example, it is dipped in a ₂ to 5% solution of magnesium dichloride MgCl _2. Just fire.
The film thickness of the formed Mg oxide is as thin as 50 to 100 nm, but can sufficiently clear the withstand voltage of 15 V required for the organic EL element.

In the case of MgCl ₂ immersion, unevenness and blemishes may occur on the surface, but it has been reported that this problem can be solved by dipping and baking to an appropriate concentration of NaOH + NaCl.
(A. Yamamoto and H. Tsubakino, Materials Trans., 44-4 (2003), pp511-517, Jpn. Inst. Metals)
From the viewpoint of workability as described above, in the following description, the metal substrate is represented by an Mg substrate.

Next, in step 2, a plurality of first electrodes 120 are formed on the insulating layer 104 in parallel with each other.
The material of the first electrode is preferably Mg or Mg—Ag having a low barrier potential and high electrical conductivity.
A space between the first electrodes 120 is filled with a dielectric layer (insulator layer) 122.

Next, in step 3, the organic EL layer 130 is formed on the first electrode 120.
The organic EL layer includes, in order from the bottom, an electron injection layer 132, an electron transport layer 133, a light emitting layer 134, a hole transport layer 135, and a hole injection layer 136, but some layers may be combined.

Next, in step 4, on the hole injection layer 136 of the organic EL layer 130, a plurality of second electrodes 140 made of indium tin oxide ITO are parallel to each other using the FTS device, and the first electrodes And are formed to be orthogonal to each other.
Since the second electrode ITO has a high hole injection efficiency, it is preferable to use a positive electrode. Therefore, the first electrode is preferably a negative electrode.

  When forming the second electrode, the target of the FTS device is set to ITO, the substrate on which the organic EL layer 130 is formed is subjected to predetermined masking, and is then disposed at a predetermined position of the FTS device. It is selectively deposited according to the predetermined mask pattern.

  At that time, since the plasma particles do not collide with the organic EL layer, the organic EL layer is not physically damaged, and is not exposed to a high temperature. Low ITO, high transparency, and smoothness that does not require polishing).

Thus, an organic light emitting diode (OLED) 110 including the first electrode 120, the organic EL layer 130, and the second electrode 140 is formed.
Finally, in step 5, a protective film 150 is formed on the ITO layer 140.
The protective film 150 is silicon oxynitride SiOxNy, and it is desirable that the ratio of oxygen and nitrogen be x / y = 2/3 to 3/1 because both transparency and barrier properties are excellent.
(T. Miyake et al, IDW'03, pp 1299-1292)
For example, it is preferable to take x / y = 8/3.

The protective film 150 is formed continuously after ITO in the FTS apparatus.
That is, after the ITO is formed, the target is changed from ITO to silicon, and oxygen gas and nitrogen gas are mixed as a reactive gas at a predetermined ratio, for example, a partial pressure of 8: 3, outside the plasma region in the FTS apparatus. Blow only on the periphery of the substrate.
At this time, the reactive gas exclusively reacts with the silicon that has fallen from the target to form a protective film on the substrate, and the reactive gas, particularly oxygen molecules do not enter the plasma.

As described above, the organic EL element includes a plurality of organic light emitting diodes (OLEDs) 110 shown in FIG. 2 arranged in a matrix. When a predetermined voltage is applied between the first and second electrodes, A current corresponding to the voltage flows through the OLED and emits a light amount corresponding to the current.
The emitted light passes through the transparent second electrode 140 and the protective film 150 and is emitted to the outside from the upper side of the figure. That is, a top emission type organic EL element is obtained.

  At this time, the power consumption (voltage × current) generated in the OLED at the intersection is the heat energy except for the energy of the light emitted to the outside. In the case of the organic EL element according to the present invention, the heat conduction of the substrate. Since the rate is high, it can be quickly diffused, and the organic EL layer is kept at a low temperature, so that the organic EL layer is not deteriorated.

Referring to FIGS. 3 and 4, the case of active matrix driving is different from that in FIGS. 1 and 2 in that step 6 is interposed between step 1 and step 2.
In this embodiment, the principle of active matrix driving is schematically shown.
In step 6, first, a TFT layer 124 made of polysilicon or amorphous silicon is provided on the insulating layer 104 of the metal substrate 100.

In the TFT layer 124, TFT transistors 126 each having a gate, a source, and a drain are formed, the drain wiring Z is connected to the corresponding first electrode 120, and the gate wiring X and the source wiring Y form a matrix orthogonal to each other.
The first electrodes 120 are formed in an array by the number of intersections of the matrix.
The second electrode 150 may be integrated on the entire surface.

  When a predetermined voltage is applied to the gate X corresponding to a certain row, all the TFTs in that row can be selected, and the voltage applied to the source Y at that time is transferred to and stored in the first electrode 120 of the corresponding OLED. The

  When all the rows are selected and cycled in this way, each OLED can be given a desired voltage with respect to the second electrode, and each OLED is given for one period. As in the case of the first embodiment, a top emission type organic EL element is obtained corresponding to the voltage.

At this time, unlike the case of the bottom emission type, even if the TFT transistor 126 is formed in the region below the organic EL layer 130, the light emission to the outside is not hindered, so that the aperture ratio and thus the final light emission efficiency can be increased. it can.
Conversely, since the same amount of light can be obtained with low power consumption, the temperature of the organic EL layer can be further suppressed and deterioration can be prevented.

It is a flowchart in the case of the passive matrix type of the manufacturing method of the organic EL element by this invention. It is a schematic diagram of a passive matrix type organic EL element. It is a flowchart in the case of an active matrix type of the manufacturing method of the organic EL element by this invention. It is a schematic diagram of an active matrix type organic EL element.

Explanation of symbols

100 Metal Substrate 102 Metal Base 104 Insulating Layer 110 Organic Light-Emitting Diode (OLED)
DESCRIPTION OF SYMBOLS 120 1st electrode 122 Dielectric layer 124 TFT layer 126 TFT transistor 130 Organic EL layer 132 Electron injection layer 133 Electron transport layer 134 Light emitting layer 135 Hole transport layer 136 Hole injection layer 140 2nd electrode (ITO)
150 Protective film

Claims (3)

Preparing a metal base made of magnesium, aluminum, or an alloy containing them, and forming an insulating layer on the surface thereof to form a metal substrate;
A second step of forming a plurality of first electrodes;
A third step of forming an organic EL layer;
A fourth stage in which a second electrode is formed by using an indium tin oxide (ITO) target with a counter target sputtering (FTS) apparatus;
A fifth step of continuously forming a protective film made of silicon oxynitride on the second electrode by changing the target to silicon and blowing oxygen gas and nitrogen gas in a predetermined partial pressure; and
Are included in this order, and the manufacturing method of the organic EL element characterized by the above-mentioned.   2. The method of manufacturing an organic EL element according to claim 1, wherein in the first step, the insulating layer is formed by oxidizing a surface of a metal base.   2. The organic EL according to claim 1, further comprising a sixth step of forming a TFT transistor at a position corresponding to a lower portion of the organic EL layer between the first step and the second step. Element manufacturing method.

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