JP2003257643A - Method of manufacturing organic electro-luminescence element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow boundary surfaces produced between a hole transport layer and a light emitting layer and between the light emitting layer and an electron transport layer to deteriorate an organic EL element when the organic EL element is formed. <P>SOLUTION: The figure shows the secular changes of the brightnesses of the organic EL element formed by a high temperature process for evaporating the materials of the hole transport layer and the light emitting layer at high temperatures and the organic EL element formed by a low temperature process for evaporating the materials thereof at low temperatures. The high temperatures mean that the evaporation temperatures of both NPB and Alq3 are 375°C, and the low temperatures mean that the evaporation temperature of NPB is 330°C and the evaporation temperature of Alq3 is 316°C. A time in which the brightness lowers from an initial brightness of 800 cd/m<SP>2</SP>to a brightness of 400 cd/m<SP>2</SP>in the low temperature process is 1/2 of that in the high temperature process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence display device having a plurality of organic electroluminescence elements.

[0002]

2. Description of the Related Art An organic electroluminescence display device (hereinafter, also simply referred to as "organic EL display device") is expected as a display device to replace a liquid crystal display device which is currently widespread, and is being developed for practical use. There is. In particular, an active matrix type organic EL display device provided with a thin film transistor (TFT) as a switching element is considered to be a main role of a next-generation flat panel display device.

FIG. 1 shows an organic EL device in which each pixel is provided with an organic electroluminescence device (hereinafter, simply referred to as “organic EL device”) which emits red, green and blue light.
The outline of the top view of the above-mentioned pixel region of three colors of a display is shown. Red pixels R including a red light emitting layer in order from the left
Pix, a green pixel Gpix including a green light emitting layer, and a blue pixel Bpix including a blue light emitting layer are provided.

One pixel is formed in a region surrounded by a gate signal line 51 and a drain signal line 52. The first TFT, which is a switching element, is located near the upper left intersection of both signal lines.
130, and a second TFT for driving the organic EL element is formed near the center. Further, the organic EL element is formed in an island shape in the region where the hole injection electrode 12 made of ITO is formed.

Generally, an organic EL device provided in an organic EL display device
The L element injects electrons and holes into the light emitting layer from the electron injecting electrode and the hole injecting electrode, respectively, and recombines them at the interface between the light emitting layer and the hole transporting layer or inside the light emitting layer near the interface to form an organic molecule. Is excited, and when this organic molecule returns from the excited state to the ground state, it emits fluorescence.

Here, an organic EL element which emits an appropriate color can be obtained by selecting the material used for the light emitting layer.
Moreover, a color display device can be realized by appropriately selecting such an organic EL element. 2 shows a red pixel Rpix and a green pixel Gpi of the organic EL display device shown in FIG.
3 shows a general cross-sectional structure of a three-pixel region of x and a blue pixel Bpix. In addition, the organic EL element is generally formed by a vacuum deposition method because it is easily affected by water molecules and oxygen molecules.

[0007]

By the way, the deterioration of an organic EL element due to aging is generally more remarkable than that of an optical element such as a liquid crystal, and the performance of the product may vary. This variation in performance may be due to the manufacturing process of the product. In particular, organic EL display devices are still in the early stages of development for practical use, and various manufacturing processes are currently being proposed.

The present invention has been made in view of such circumstances, and an object thereof is to suppress deterioration of an organic EL element. Another object is to provide a method for manufacturing an organic EL element that is less deteriorated. Another object is to provide a method for manufacturing an organic EL device having good product manufacturing stability.

[0009]

As described above, the organic EL device is generally formed by the vacuum evaporation method. In the process, organic E from the viewpoint of production efficiency
By increasing the vapor deposition temperature of the material of the L element, the vapor deposition rate of the material on the substrate is increased, the manufacturing time is shortened, and the manufacturing cost is often reduced. Although the evaporation temperature was set to be equal to or lower than the thermal decomposition temperature of the vapor deposition material, it was found that the performance of the organic EL element was nevertheless varied.

In such a situation, the present inventor has made the following recognition. That is, conventionally, when vaporizing the vapor deposition material, attention has been paid to the temperature in a steady state in which vapor deposition is actually performed. However, the present inventor recognizes that it is necessary to set the temperature below the thermal decomposition temperature in the whole process of forming the organic EL element, paying attention to the temperature profile from the start of heating the vapor deposition material until the temperature settles to a steady state. did. In order to solve this problem, the present inventors have made the following inventions.

One aspect of the present invention relates to a method for manufacturing an organic EL display. The manufacturing method of this organic EL element is
The vapor deposition material of the organic layer included in the L element is evaporated at a temperature lower than its thermal decomposition temperature, and the material is vapor deposited on a predetermined substrate to form an organic layer.

Another aspect of the present invention also relates to a method for manufacturing an organic EL device. The manufacturing method of this organic EL element is
The method includes a step of evaporating an amine derivative, which is a material of the hole transport layer included in the L element, in a vacuum to deposit it on a predetermined substrate, and in the step, the temperature of the amine derivative is 380 ° C.
Keep below The material for the hole transport layer is N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine (N,
N'-Di (naphthalene-1-yl) -N, N'-diphenyl-benzidin
e: NPB).

[0013]

[Chemical 1]

Yet another aspect of the present invention also relates to a method for manufacturing an organic EL device. This manufacturing method includes a step of evaporating an aluminum quinoline complex, which is a material of an electron transporting layer or a light emitting layer included in an organic electroluminescent element, in a vacuum and depositing the aluminum quinoline complex on a predetermined substrate. Keep below ℃.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In this embodiment, an organic EL element is formed by a vacuum evaporation method. At that time, an upper limit is set for the temperature at which the material is vaporized by the vapor deposition source. When the temperature of the vapor deposition source is increased, the vapor deposition rate of the material on the substrate is increased, and the manufacturing time is shortened and the manufacturing cost is reduced accordingly. Therefore, an appropriate vapor deposition rate that does not reduce the reliability of the formed organic EL element, that is, the upper limit of the evaporation temperature of the material is set.

FIG. 2 schematically shows a typical sectional structure of one pixel of the organic EL display device shown in FIG. The hole injection electrode 12 and the hole transport layer 1 are formed on the glass substrate 10.
6, the light emitting layer 22, the electron transport layer 28, and the electron injection electrode 32 are stacked.

As a material of the hole injecting electrode 12, as a material of the hole injecting electrode 12, indium tin oxide (IT
O), tin oxide (SnO ₂ ), indium oxide (In ₂
O ₃₎ and which may or may not be.

As the material of the hole transport layer 16, N
PB and 4,4 ', 4''-tris (3-methylphenylphenylamino) triphenylamine (4,4', 4 ''-tris (3-meth
ylphenylphenylamino) triphenylamine: MTDATA)
Or N, N'-diphenyl-N, N'-bis (3-methylphenyl)-
1,1'-biphenyl-4,4'-diamine (N, N'-diphenyl-N,
N'-di (3-methylphenyl) -1,1'-biphenyl-4,4'-diam
ine: TPD) and N, N'-diphenyl-N, N'-di (4-methylphenyl) -1,1'-biphenyl-4,4'-diamine (N,
N'-diphenyl-N, N'-di (4-methylphenyl) -1,1'-biph
enyl-4,4'-diamine) and 4,4'-bis (carbazole-9-
Biphenyl (4,4'-Bis (carbazol-9-yl) -bipheny
l: CBP) and N, N, N ', N'-tetrakis (naphtha-2-yl)
-Benzidine (N, N, N ', N'-Tetrakis (naphtha-2-yl) -benzi
dine) and N, N'-bis (phenanthrene-9-yl) -N, N'-
Bis-phenyl-benzidine (N, N'-Bis (phenanthren-9-y
l) -N, N'-bis-phenyl-benzidine) and the like.

[0019]

[Chemical 2]

[0020]

[Chemical 3]

[0021]

[Chemical 4]

Furthermore, two compounds represented by the following chemical formulas in which the two phenyl groups at the center of the structural formula of NPB are changed to three and four can be exemplified.

[0023]

[Chemical 5]

[0024]

[Chemical 6]

Examples of the host of the light emitting layer 22 include aluminum quinoline complex (Alq3) and bis (benzoquinolinolato) beryllium complex (BeBq2).

[0026]

[Chemical 7]

[0027]

[Chemical 8]

Generally, an organic EL element formed by using a chelate metal complex as a material for a light emitting layer has a problem in light emission of a short wavelength color, that is, blue light. Therefore, the blue light emitting layer is disclosed in JP-A-2002-25770. Disclosed in the gazette
tert-butyl substituted dinaphthyl anthracene (TBAD
Acetone and its derivatives such as N) and distilbenzene and its derivatives are often used.

[0029]

[Chemical 9]

Further, the light emitting layer 22 uses the above-mentioned chelate metal complex or condensed polycyclic aromatic compound as a host for Rubren.
Desired emission characteristics can be obtained by doping a dopant such as e). Further, as a material of the electron transport layer 28,
Examples are Alq3 and BeBq2. Further, as a material of the electron injection electrode 32, an aluminum alloy (AlLi) or a magnesium indium alloy (MgI) containing a small amount of Li.
n), magnesium silver alloy (MgAg), etc. can be illustrated. Further, as the electron injection electrode 32, an electrode having a two-layer structure in which a lithium fluoride layer is formed on the side in contact with the organic layer and an aluminum layer is formed thereon can be exemplified.

[0031]

[Chemical 10]

When the organic EL element is formed by the vacuum vapor deposition method, the material of each layer is first held in a container called quartz vapor deposition source made of quartz or the like. An opening having a predetermined size is provided on the upper surface of the container. The upper surface of the container is heated by an electric heater in a vacuum, and the material held in the container is evaporated by the radiant heat and is discharged from the opening. The released material aggregates on the substrate to form a film. Generally, by controlling the temperature of the heater when vaporizing the material, the vaporization temperature of the material is controlled and the vapor deposition rate for forming a film on the substrate is controlled.

FIG. 3 schematically shows the positional relationship between the substrate and the vapor deposition source when vapor-depositing the material of each layer. The vapor deposition source 60 is arranged below the glass substrate 10 at a distance.
The vapor deposition source 60 may be fixed, but the material is evenly vapor-deposited on the glass substrate 10 by moving the vapor deposition source 60 left and right. Further, by appropriately disposing the mask 50 at the time of depositing the material, the material is selectively deposited. Further, a temperature sensor is attached to the upper surface of the vapor deposition source 60 (not shown). Therefore, the evaporation temperature described below means the evaporation source 6
0 means the temperature of the upper surface.

[0034]

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

FIG. 4 shows changes with time in the brightness of the organic EL element by a high temperature process in which the materials of the hole transport layer and the light emitting layer are evaporated at a high temperature, and by the low temperature process in which the material of the hole transport layer and the light emitting layer is evaporated at a low temperature. Here, the high temperature means that the evaporation temperature is 375 ° C. for both NPB which is the hole transport layer and Alq3 which is the light emitting layer. On the other hand, low temperature means NPB
Has an evaporation temperature of 330 ° C, and Alq3 has an evaporation temperature of 3
16 ° C.

FIG. 5A shows a temperature change when NPB is heated, and FIG. 5B shows a temperature change when Alq3 is heated. In both cases, the temperature became stable 200 hours after the start of heating. Therefore, the deposition of NPB and Alq3 started after 200 hours. However, in the high temperature process, the temperature of both NPB and Alq3 rises up to 420 ° C., and the thermal decomposition temperature is assumed to be 380-40
It exceeds the range of 0 ° C. Therefore, NPB and Alq
It can be assumed that in all three, deterioration occurs in the vapor deposition source.

According to FIG. 4, the initial luminance is 800 cd / m ^2.
To 400 cd / m ² in the low temperature process was half that in the high temperature process. That is, it was confirmed that the deterioration of the organic EL element formed by the high temperature process was twice as fast.

As described above, according to this embodiment, the evaporation temperature of the material used for each layer can be appropriately set when the organic EL element is formed by the vacuum evaporation method. Generally, increasing the vapor deposition rate of the material on the substrate can shorten the manufacturing time and realize the cost reduction. On the other hand, if the evaporation temperature is too high, the organic E
Degradation of the L element occurred. Therefore, by setting the evaporation temperature of each material to be equal to or lower than the thermal decomposition temperature of the material in the entire process of vapor-depositing the organic EL element, it is possible to manufacture the organic EL element in which deterioration is suppressed. Further, it has been possible to manufacture an organic EL element in which variations in manufacturing stability are suppressed.

[0039]

According to the present invention, the deterioration of the organic EL element can be suppressed. In addition, from another viewpoint, it is possible to realize a method for manufacturing an organic EL element with little deterioration. Further, from another viewpoint, an organic E having good manufacturing stability while considering the manufacturing cost.
The L display device can be manufactured.

[Brief description of drawings]

FIG. 1 is a plan view of an active matrix organic EL display device, particularly showing a region of three pixels of red, green, and blue.

FIG. 2 is a cross-sectional view schematically showing the structure of an organic EL element of a conventional technique.

FIG. 3 is a diagram schematically showing the arrangement of a substrate and a vapor deposition source when forming an organic EL element by a vacuum vapor deposition method.

FIG. 4 shows an organic EL element formed by a low temperature process,
It is a figure showing the change with time of the brightness of the organic EL element formed by the high temperature process.

FIG. 5 shows the evaporation temperature of a material to be evaporated on a substrate at an evaporation source, (a) is a graph showing changes over time of the evaporation temperature of NPB, and (b) is a graph showing changes over time of Alq3.

[Explanation of symbols]

10 glass substrate, 16 hole transport layer, 22 light emitting layer, 28 electron transport layer, 60 vapor deposition source.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/22 H05B 33/22 D (72) Inventor Shingo Nakano 2-5-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 F term in Sanyo Electric Co., Ltd. (reference) 3K007 AB11 AB12 AB18 DB03 FA01 FA03 4K029 AA09 AA24 BA62 BB02 BC07 CA01 DB06 DB17

Claims (4)

[Claims] 1. An organic electroluminescent device having an organic layer formed, wherein the vapor deposition material of the organic layer is evaporated at a temperature below its thermal decomposition temperature, and the vapor deposition material is vapor deposited on a substrate to form the organic layer. And a method for manufacturing an organic electroluminescence device. 2. An organic electroluminescent device comprising a hole transport layer, comprising a step of evaporating an amine derivative, which is a material of the hole transport layer, in a vacuum and depositing it on a predetermined substrate, wherein the amine derivative is included in the step. Is maintained at 380 ° C. or lower, a method for manufacturing an organic electroluminescence device. 3. The organic electroluminescence device according to claim 2, wherein the material of the hole transport layer is N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine. Device manufacturing method. 4. A step of evaporating an aluminum quinoline complex, which is a material of an electron transport layer or a light emitting layer included in an organic electroluminescence element, in a vacuum and depositing it on a predetermined substrate, wherein the temperature of the aluminum kirin complex is changed. A method for manufacturing an organic electroluminescence device, which is characterized by maintaining the temperature at 350 ° C or lower.