JP2001291596A - Organic electroluminescent display device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent display device in which the degrees of freedom of wiring pattern are improved. SOLUTION: This organic electroluminescent display device 11 has a pair of anode layer 13 and cathode layer 17 and a luminous layer 16 that is arranged between both electrode layers 13, 17. The cathode layer 17 is equipped with an inner cathode layer 17a formed by vacuum depositing a cathode material having a work function not more than 3.5 eV in light emitting pattern and an outer cathode layer 17b formed by depositing a cathode material having a work function not less than 4 eV on the inner cathode layer 17a in a wiring pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an organic electroluminescence display device used for a display or the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, in a light emitting pattern in an organic electroluminescence display device, a light emitting pattern is formed by adding a patterned insulating film layer or patterning an anode layer or a cathode layer. For these patterning, a method using photolithography or a vapor deposition mask is generally used.

For example, FIGS. 11 and 12 show a main part of an organic electroluminescence display device 1 manufactured by photolithography, in which ITO (indium-tin oxide) is formed on a glass substrate 2 having translucency. , An insulating film layer 4 made of polyimide or the like, a buffer layer 5 (hole transport layer) made of a polymer material, a light emitting layer 6 containing an organic light emitting material, and calcium (Ca). ) And a second cathode layer 8 made of aluminum (Al) or the like to cover and protect the cathode layer 7. The anode layer 3 and the second cathode layer 8 are By applying a voltage from a power source 9 to both layers, light is emitted in a pattern corresponding to the opening 4a formed in the insulating film layer 4.

As a manufacturing method using an evaporation mask, there is a method disclosed in Japanese Patent Application Laid-Open No. H11-135257.

[0005]

However, in the manufacturing method using photolithography, since the substrate 2 is contaminated by the etchant used, the insulating film layer 4 and the like are difficult to adhere to and the hole injection barrier is large. There is a problem that the luminous efficiency deteriorates.

On the other hand, the contamination of the substrate 2 by the etching solution can be improved by sufficiently performing the cleaning of the substrate 2, but the number of steps by cleaning, the cost of the cleaning solvent, and the disposal of the cleaning solvent are increased. There was a risk that new problems such as problems might arise.

If the light emitting pattern is formed by the insulating film layer 4 as described above, the unevenness of the insulating film layer 4 due to the opening 4a tends to cause film unevenness in the upper layer laminated thereon, which causes the light emitting unevenness. There was a possibility that.

On the other hand, the anode layer 3 and the cathode layers 7 and 8 are formed only by a deposition mask without using photolithography.
In this case, there is an advantage that the insulating film layer 4 becomes unnecessary and the other problems as described above can be solved.

However, the anode layer 3 and the cathode layers 7 and 8 not only contribute to the light emitting pattern but also play the role of wiring, and the wiring layer has the anode layer 3 side and the cathode layers 7 and 8 at the wiring portion.
When the sides overlap in the stacking direction, there is a drawback that light is emitted despite portions where light emission is not desired, and it has been necessary to perform respective patterning so that wirings do not overlap each other. Therefore, there has been a problem that the degree of freedom in patterning is reduced when the emission pattern becomes complicated.

[0010] In view of the above problems, the present invention is to provide an organic electroluminescent display device having an improved degree of freedom in wiring patterns and a method of manufacturing the same.

[0011]

The technical means of the display device for solving the above-mentioned problems is to dispose a pair of anode and cathode layers which are at least one of which are transparent, and which are disposed opposite each other. In the organic electroluminescent display device having a light-emitting layer, the cathode layer has a work function of 3.5 eV or less, and an inner cathode layer deposited in a light-emitting pattern by a cathode material having a work function of 3.5 eV or less, and a work function of 4 eV or more. An outer cathode layer formed by forming a wiring pattern on the inner cathode layer with a cathode material and vapor-depositing the wiring pattern.

Further, the inner cathode layer may be formed of a combination of cathode materials having a plurality of work function values.

[0013] Further, the technical means of the manufacturing method for solving the above-mentioned problems includes a pair of an anode layer and a cathode layer which are disposed at least one of which is transparent and are opposed to each other, and a light emitting layer which is arranged between the both electrode layers. In the method for manufacturing an organic electroluminescent display device having the above, an inner cathode layer made of a cathode material having a work function of 3.5 eV or less is formed by vapor deposition through a mask having a passage opening corresponding to a light emitting pattern. Then, a work function of 4 is formed on the inner cathode layer through a mask having a passage opening corresponding to the wiring pattern.
The point is that an outer cathode layer made of a cathode material of eV or more is formed by vapor deposition.

In forming the inner cathode layer, a plurality of cathode materials having different work functions are used, and a plurality of regions having different work function values are formed by changing a mixing ratio of the respective cathode materials at the time of vapor deposition. It may be a method of forming.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section of a main part, particularly an element part, of an organic electroluminescence display device 11 and has translucency. Glass substrate 1 as an example of a substrate
2, an anode layer 13 made of a transparent electrode layer such as ITO (indium-tin oxide), a buffer layer 15 (hole transport layer) made of a polymer material, for example, polyethylene dioxythiophene (PEDT), and an organic light emitting material Light-emitting layer 1 made of, for example, polyfluorene or polyphenylenevinylene
6 and a cathode layer 17 are sequentially laminated.

The cathode layer 17 includes an inner cathode layer 17a deposited on the light emitting layer 16 to form a light emitting pattern;
An outer cathode layer 17b is deposited on the inner cathode layer 17a to form a wiring pattern. The outer cathode layer 17b also has a function of covering and protecting the inner cathode layer 17a. .

The inner cathode layer 17a is made of a cathode material made of a metal or a metal compound having a work function of 3.5 eV or less, for example, calcium (Ca),
It is composed of lithium (Li), lithium fluoride (LiF) or the like. Note that any substance may be used as long as the work function value is equal to or less than 3.5 eV, and is not limited to metals and metal compounds.

The outer cathode layer 17b has a work function of 4
It is made of a cathode material made of a metal or a metal compound having eV or more, and is made of, for example, aluminum (Al), chromium (Cr), titanium (Ti), silver (Ag), or the like. Any substance may be used as long as it has a work function value of 4 eV or more, and is not limited to metals and metal compounds.

Next, a method for manufacturing the organic electroluminescent display device 11 will be described.

First, as shown in FIG.
A transparent anode layer 13 of ITO or the like is formed on 2 by a method such as sputtering. At this time, a desired pattern is formed using a mask if necessary.

Next, as shown in FIGS. 3 and 4, a buffer layer 15 and a light emitting layer 16 are sequentially laminated on the anode layer 13 by a spin coating method, a printing method, a mist method or the like. Note that the film formation method is not limited to these.

Next, as shown in FIG. 5, the light emitting layer 16 and the buffer layer 15 are removed for wiring, the anode layer 13 is partially exposed, and the insulating polymer resin 18 is used as insulating reinforcement.
Is applied to the surrounding edge portion and covered.

Thereafter, as shown in FIG. 6, a metal or a metal compound having a small work function, such as calcium, is vapor-deposited through a mask 19 having an arbitrary shape having a passage opening 19a corresponding to the light-emitting pattern, thereby forming a desired metal. An inner cathode layer 17a corresponding to the shape of the light emitting pattern is formed.

Next, as shown in FIG. 7, a metal or a metal compound having a large work function, such as aluminum, chromium, or silver, is passed through a mask 20 of an arbitrary shape having a passage opening 20a corresponding to the wiring pattern. By vapor deposition, an outer cathode layer 17b corresponding to a desired wiring pattern shape is formed on the inner cathode layer 17a.

Then, as shown in FIG.
When the voltage is applied by connecting the power supply 22 and the outer cathode layer 17b to each other, electrons flow only from the inner cathode layer 17a due to a difference in work function, so that light emission occurs between the outer cathode layer 17b and the anode layer 13. do not do. And the inner cathode layer 1
Light is emitted by energy released when the electrons injected from 7a and the holes injected from the anode layer 13 are combined in the light emitting layer 16 (near the interface with the buffer layer 15).

That is, as shown in FIG. 9, the conduction band order of the inner cathode layer 17a is 2.8 eV, which is slightly higher than the conduction band order of the light emitting layer 16 of 3.2 eV. The conduction band order of the layer 17b is 4.3 eV and 1 e
V or lower. Then, in order for electrons to flow from the outer cathode layer 17b to the light emitting layer 16, the barrier must exceed a barrier (energy gap) of 1 eV, and this barrier is almost equal to a semiconductor such as germanium (Ge) or silicon (Si). The same, at room temperature, a specific resistance of about 200 kΩcm.

Therefore, there is almost no electron injection from the outer cathode layer 17b, and only the pattern of the inner cathode layer 17a can emit light. If a plurality of circuits are provided as shown in FIG. 8, each inner cathode layer 17a can selectively emit light.

As described above, since the wiring pattern of the outer cathode layer 17b does not emit light even if it overlaps with the wiring pattern of the anode layer 13 in the laminating direction, the wiring pattern of the outer cathode layer 17b is independent of the wiring pattern of the anode layer 13. And the degree of freedom of the wiring pattern is improved.

Although an example using aluminum as the outer cathode layer 17b is shown, if gold (4.9 eV) or platinum (5.3 eV) having a larger work function is used for the outer cathode layer 17b, Electron injection from the outer cathode layer 17b can be further reduced. In addition, various other combinations of various materials are possible, and there is no limitation to these combinations.

FIG. 10 shows another manufacturing method, in which an anode layer 13 and a buffer layer 1 are formed on a glass substrate 12 in the same manner as described above.
5, while the light emitting layer 16 is sequentially laminated, the inner cathode layer 1
It is a method of forming the film 7a and the outer cathode layer 17b in the same vapor deposition apparatus.

That is, a plurality of masks 26a and 26b are slidably provided on the pair of guide rails 25, and a substrate holder 27 for holding the glass substrate 12 is provided above the masks 26a and 26b. A shutter 28 that can be freely opened and closed by a moving operation or the like is provided.

Then, the glass substrate 12 is placed on the substrate holder 27.
Is held, for example, calcium is vapor-deposited through one mask 26a to form the inner cathode layer 17a. After that, while the shutter 28 is closed, the masks 26a and 26b are slid and the calcium is exchanged for aluminum. Then, while the shutter 28 is opened, aluminum is vapor-deposited through the mask 26b to form the outer cathode. By forming the layer 17b, the organic electroluminescent display device 11 having a desired light emission pattern can be formed.
Can be manufactured.

At this time, more masks 2 of different shapes
By using 6a and 26b, a more complicated light emitting pattern can be formed.

In the deposition process of the inner cathode layer 17a, a plurality of cathode materials having different work functions are used, and the mixture ratio of the respective cathode materials at the time of deposition is changed, so that the work function value of the inner cathode layer 17a is reduced. A method of forming a plurality of different regions may be used.

For example, when calcium is deposited to form the inner cathode layer 17a, aluminum may be partially deposited at the same time to form a region of a mixture of calcium and aluminum. In this case, the inner cathode layer 17a
Is composed of a combination of cathode materials having multiple work function values.Electron injection efficiency is reduced by mixing aluminum with a large work function into calcium with a small work function, and as a result, the emission luminance of the pattern in that region is reduced. Then, a light emission pattern having a different brightness from the area of the calcium alone portion is obtained.

Here, the organic electroluminescence display device 11 can emit light of different brightness with one or several kinds of power supply potentials.

Although the method of forming regions having different work function values by mixing at the time of vapor deposition as the inner cathode layer 17a is shown, the cathode materials themselves having different work function values are separately vapor-deposited, and the work function values are separately formed. May be a method of forming a different region.

[0038]

As described above, according to the organic electroluminescence display device of the present invention and the method of manufacturing the same,
The cathode layer is formed by depositing a wiring pattern on the inner cathode layer formed of a cathode material having a work function of 3.5 eV or less in a light emitting pattern and a cathode material having a work function of 4 eV or more. Since it has an outer cathode layer, it does not emit light even when the wiring pattern of the outer cathode layer and the wiring pattern of the anode layer overlap, and the wiring pattern of the outer cathode layer can be designed regardless of the wiring pattern of the anode layer. There is an advantage that the degree of freedom of the pattern can be improved.

Further, by forming the inner cathode layer from a combination of cathode materials having a plurality of work function values, there is an advantage that light having different brightness can be obtained in the light emitting pattern region.

[Brief description of the drawings]

FIG. 1 is a sectional view of an organic electroluminescence display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the manufacturing process.

FIG. 3 is an explanatory diagram of the manufacturing process.

FIG. 4 is an explanatory view of the manufacturing process.

FIG. 5 is an explanatory view of the manufacturing process.

FIG. 6 is an explanatory diagram of the manufacturing process.

FIG. 7 is an explanatory view of the manufacturing process.

FIG. 8 is a diagram illustrating light emission of an organic electroluminescence display device.

FIG. 9 is a diagram illustrating the relationship between each layer and a work function.

FIG. 10 is an explanatory diagram of another manufacturing method.

FIG. 11 is a cross-sectional view of an organic electroluminescence display device as a conventional example.

FIG. 12 is a view taken along line XII-XII of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Organic electroluminescent display apparatus 12 Glass substrate 13 Anode layer 15 Buffer layer 16 Light emitting layer 17 Cathode layer 17a Inner cathode layer 17b Outer cathode layer 19 Mask 19a Passing opening 20 Mask 20a Passing opening 26a, 26b Mask 27 Substrate holder 28 Shutter

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuo Tamagawa 1-7-10 Kikuzumi, Minami-ku, Nagoya-shi, Aichi F-term in Harness Research Institute, Inc. (reference) 3K007 AB00 AB11 AB18 CA01 CB01 CC00 DA01 DB03 EB00 FA01 FA02

Claims (4)

[Claims] 1. An organic electroluminescent display device comprising: a pair of an anode layer and a cathode layer, at least one of which is transparent, opposed to each other, and a light emitting layer disposed between the two electrode layers. A cathode material having a work function of 3.5 eV or less in a light-emitting pattern, and an outer cathode formed by forming a wiring pattern on the inner cathode layer with a cathode material having a work function of 4 eV or more. And an organic electroluminescent display device comprising: 2. The organic electroluminescent display device according to claim 1, wherein said inner cathode layer is made of a combination of cathode materials having a plurality of work function values. 3. A method for manufacturing an organic electroluminescent display device, comprising: a pair of an anode layer and a cathode layer, at least one of which is transparent, opposed to each other, and a light emitting layer disposed between the two electrode layers. An inner cathode layer made of a cathode material having a work function of 3.5 eV or less is formed by vapor deposition through a mask having a passage opening corresponding to the light emitting pattern, and the passage opening corresponding to the wiring pattern is formed on the inner cathode layer. A method for manufacturing an organic electroluminescent display device, comprising forming an outer cathode layer made of a cathode material having a work function of 4 eV or more by vapor deposition through a mask having a portion. 4. When forming the inner cathode layer, a plurality of cathode materials having different work functions are used, and a plurality of regions having different work function values are formed by changing a mixing ratio of the respective cathode materials at the time of vapor deposition. The method according to claim 3, wherein the organic electroluminescent display device is formed.