Method of manufacturing organic EL element, organic EL element, and organic EL display device Number:6,821,553 from the United States Patent and Trademark Office (PTO) owispatent A method of manufacturing an organic EL element according to the present invention comprises the steps of forming pixel electrodes (801), (802), (803) on a transparent substrate (804) and forming on the pixel electrodes by patterning luminescent layers (806), (807), (808) made of an organic compound by means of an ink-jet method. According to this method, it is possible to carry out a high precise patterning easily and in a short time, thereby enabling to carry out optimization for a film design and luminescent characteristic easily as well as making it easy to adjust a luminous efficiency.<H manufacturing, display, Method, of, manuf, 6821553.html, Patent, pto, 6821553

Title: Method of manufacturing organic EL element, organic EL element, and organic EL display device

Abstract: A method of manufacturing an organic EL element according to the present invention comprises the steps of forming pixel electrodes (801), (802), (803) on a transparent substrate (804) and forming on the pixel electrodes by patterning luminescent layers (806), (807), (808) made of an organic compound by means of an ink-jet method. According to this method, it is possible to carry out a high precise patterning easily and in a short time, thereby enabling to carry out optimization for a film design and luminescent characteristic easily as well as making it easy to adjust a luminous efficiency.

Patent Number: 6,821,553 Issued on 11/23/2004 to Miyashita, et al.

Inventors: Miyashita; Satoru (Suwa, JP); Kiguchi; Hiroshi (Suwa, JP); Shimoda; Tatsuya (Suwa, JP); Kanbe; Sadao (Suwa, JP)
Assignee: Seiko Epson Corporation (Tokyo, JP)

Appl. No.: 166704

Filed: June 12, 2002

Foreign Application Priority Data


Nov 25, 1996 [JP]			8-313828

Current U.S. Class: 427/66 ; 427/68

Field of Search: 427/66,68 428/690

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Primary Examiner: Tarazano; D. Lawrence
Attorney, Agent or Firm: Oliff & Berridge, PLC

Parent Case Text

This is a continuation of application Ser. No. 09/101,083 filed Jul. 8, 1998, which in turn is a U.S. National Stage of PCT/JP97/04283, filed Nov. 25, 1997. The entire disclosure of the prior application(s) is hereby incorporated by reference herein in its entirety.

Claims

What is claimed is:

1. A method of manufacturing an organic EL device, comprising: forming a first electrode on or above a substrate forming at least one luminescent layer on or above said first electrode by discharging a material composition for said at least one luminescent layer toward said substrate and onto said underlying layer from a nozzle in a head provided with a piezoelectric element; and forming a second electrode opposing the first electrode, the material composition serving as luminescence function and carrier transfer function in the formed at least one luminescent layer.

2. The method of manufacturing an organic EL device according to claim 1, at least one compound constituting the composition being a polymer organic compound.

3. The method of manufacturing an organic EL device according to claim 2, the polymer organic compound being a material having functions of hole injection and hole transfer.

4. The method of manufacturing an organic EL device according to claim 2, the polymer organic compound being a polyparaphenylene vinylene, its derivative or a copolymer which contains at least either one of these compounds.

5. The method of manufacturing an organic EL device according to claim 1, said luminescent layer including three types of luminescent layers having different colors and at least two types of luminescent layers in the three types of luminescent layers being formed by discharging the composition for the luminescent layer.

6. The method of manufacturing an organic EL device according to claim 5, said different colors including red, green and blue, and the red luminescent layer and the green luminescent layer being formed by discharging the composition for the luminescent layer.

7. The method of manufacturing an organic EL device according to claim 6, the blue luminescent layer being formed by a vacuum deposition process.

8. The method of manufacturing an organic EL device according to claim 7, the blue luminescent layer being made of a material having functions of electron injection and electron transfer.

9. The method of manufacturing an organic EL device according to claim 1, said underlying layer being a hole injection and transfer layer.

10. The method of manufacturing an organic EL device according to claim 1, further comprising forming a protective film on or above the second electrode.

11. A method of manufacturing an organic EL device, comprising: forming a first electrode on or above a substrate; forming at least one luminescent layer having a certain color and made of an organic compound on or above said electrode; and forming a second electrode opposing the electrode, the formation of said at least one luminescent layer being performed by discharging a material composition for said at least one luminescent layer toward said substrate and onto an underlying layer from a nozzle in a head provided with a piezoelectric element, the material composition serving as luminescence function and carrier transfer function in the formed at least one luminescent layer.

12. A method of manufacturing an organic EL device, comprising: forming first electrodes on or above a substrate; forming at least one luminescent layer having a certain color and made of an organic compound on or above said first electrodes by patterning, said at least one luminescent layer including a plurality of pixel luminescent layers; and forming second electrodes opposing the first electrodes, the formation of said at least one luminescent layer being performed by discharging a material composition for said at least one luminescent layer toward said substrate and onto an underlying layer from a nozzle in a head provided with a piezoelectric element, the material composition serving as luminescence function and carrier transfer function in the formed at least one luminescent layer.

13. A method of manufacturing an organic EL device, comprising: forming a first electrode on or above a substrate forming at least one luminescent layer on or above said first electrode by discharging a material composition for said at least one luminescent layer toward said substrate from a nozzle in a head provided with a piezoelectric element; and forming a second electrode opposing the first electrode, the material composition serving as luminescence function and carrier transfer function in the formed at least one luminescent layer.

14. A method of manufacturing an organic EL device, comprising: forming a first electrode on or above a substrate; forming at least one luminescent layer having a certain color and made of an organic compound on or above said electrode; and forming a second electrode opposing the electrode, the formation of said at least one luminescent layer being performed by discharging a material composition for said at least one luminescent layer toward said substrate from a nozzle in a head provided with a piezoelectric element, the material composition serving as luminescence function and carrier transfer function in the formed at least one luminescent layer.

15. A method of manufacturing an organic EL device, comprising: forming first electrodes on or above a substrate; forming at least one luminescent layer having a certain color and made of an organic compound on or above said first electrodes by patterning, said at least one luminescent layer including a plurality of pixel luminescent layers; and forming second electrodes opposing the first electrodes, the formation of said at least one luminescent layer being performed by discharging a material composition for said at least one luminescent layer toward said substrate from a nozzle in a head provided with a piezoelectric element, the material composition serving as luminescence function and carrier transfer function in the formed at least one luminescent layer.

Description

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing an organic electroluminescent (EL) element, an organic EL element, and an organic EL display device.

BACKGROUND ART

An organic EL element is an element which has a configuration in which a thin film containing a fluorescent organic compound is held between a cathode and an anode. In the organic EL element, electrons and holes are injected from the respective electrodes into the thin film to generate excitons through the recombination of the electrons and holes. The organic EL element produces luminescence by utilizing emission of light (fluorescence or phosphorescence) at the deactivation of the excitons.

The features of the organic EL element is that it is possible to obtain a high intensity surface luminescence on the order of 100 to 100,000 cd/m.sup.2 at a low voltage of less than 10V, and that it is possible to produce luminescence of from blue to red y the selection of the kind of fluorescent material.

The organic EL element is drawing attraction as a device for realizing a large area full color display element at a low cost (see, Institute of Electronics, Information and Communication Engineers (IEICE) Technical Report, Vol. 89, No. 106, 1989, p. 49). According to the report, bright luminescence of blue, green and red were obtained by forming a luminescent layer using an organic luminescent material which emits strong fluorescence. This fact is considered to mean that it is possible to realize a high brightness full color display by using an organic coloring matter which emits strong fluorescence in a thin film state and has less pin hole defects.

In addition, in Japanese Laid-Open Publication No. Hei 5-78655, there is proposed to use an organic luminescent layer containing a luminescent material which is formed of a mixture of an organic charging material and an organic luminescent material, thereby obtaining a high brightness full color element by preventing quenching due to higher concentration as well as expanding the latitude in the selection of the luminescent material.

Further, in App. Phys. Lett. Vol. 64, 1994, p. 815, it is reported that a white luminescence was obtained by using polyvinyl carbazole (PVK) as a luminescent material and doping it with coloring matters corresponding to three primary colors R, G and B. However, in neither of the above references, the configuration or the method of manufacture of an actual full color display panel is not shown.

In the organic thin film EL elements using the organic luminescent materials described above, in order to realize a full color display device, it is necessary to arrange organic luminescent layers which emit any one of the three primary colors for the respective pixels. However, there is a problem in that a polymer or precursor that forms the organic luminescent layer lacks a sufficient resistance to a patterning process such as photolithography, so that it is very difficult to carry out patterning with highly precision.

Further, when several organic layers are to be formed by a vacuum deposition method, it takes a long time. Therefore, such a method cannot be said to be an efficient method of manufacturing the element.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method of manufacturing an organic EL element which makes it possible to carry out patterning easily and precisely, can attain optimization of a film design in a simple manner, and has excellent luminescence characteristics, as well as to provide an organic EL element and an organic EL display device.

In order to achieve the above object, the manufacturing method of an organic EL element according to the present invention comprises the steps of forming pixel electrodes on a transparent substrate, forming on the pixel electrodes by patterning at least one luminescent layer having a certain color and made of an organic compound, and forming a counter electrode opposing the pixel electrodes, wherein the formation of the luminescent layers is performed by means of an ink-jet method.

In the present invention, it is preferable that the organic compound is a polymer organic compound. In this case, it is preferable that the polymer organic compound is a hole injection and transfer type material. Preferably, such a polymer organic compound is a polyparaphenylene vinylene or its derivative or a copolymer which contains at least either one of these compounds.

In this connection, when an organic luminescent material itself is not a hole injection and transfer type material, as is the case in the above-mentioned polymer organic compound, it is possible to add a hole injection and transfer type material to the luminescent layer in addition to the luminescent material.

Further, it is also preferred that the at least one luminescent layer comprises three layers having different colors, in which the at least two colors out of the luminescent layers of three colors are patterned by means of an ink-jet method. The three colors are red, green and blue, and it is preferable that the red luminescent layer and the green luminescent layer are patterned by means of an ink-jet method. In this case, it is more preferable that the blue luminescent layer is formed by a vacuum deposition method. Further, it is preferable that the blue luminescent layer is made of an electron injection and transfer type material, such as an aluminum quinolinol complex.

In the manufacturing method for the organic EL element according to the present invention, it is preferable that at least one luminescent layer is laminated with a hole injection and transfer layer, and it is also preferable that a protective film is formed on the counter electrode.

In the manufacturing method for the organic EL element of the present invention, it is preferable that the transparent substrate is provided with thin film transistors for driving respective pixels.

Further, it is preferable that the pixel electrodes are formed into a transparent pixel electrode.

Furthermore, the organic EL element of the present invention is provided with a transparent substrate, pixel electrodes formed on the transparent substrate, at least one luminescent layers having a certain color and made of an organic compound, the luminescent layer being patterned on the pixel electrodes by an ink-jet method, and a counter electrode formed on the luminescent layer.

It is preferable that the organic compound is a polymer organic compound, and it is more preferable that the polymer organic compound is a hole injection and transfer type material.

Moreover, it is preferable that the polymer organic compound is a polyparaphenylene vinylene or its derivative or a copolymer containing at least one of them.

It is preferred that the at least luminescent layer includes three layers having different three colors, and it is preferable that two layers thereof in the luminescent layers of three colors are patterned by an ink-jet method. The three colors are red, green and blue, and it is more preferable that the red luminescent layer and the green luminescent layer are separately patterned by an ink-jet method. In this case, it is more preferable that the blue luminescent layer is formed by a vacuum deposition method.

It is preferable that the blue luminescent layer is made of an electron injection and transfer material. As for such a blue luminescent layer, a layer containing an aluminum quinolynol complex can be mentioned.

Moreover, it is preferable that at least one luminescent layer is laminated with a hole injection and transfer type layer, and it is more preferable that a protective film is formed on the cathode.

Furthermore, it is preferable that the pixel electrodes are formed into a transparent pixel electrode.

Moreover, the organic EL display device according to the present invention is characterized in that it includes the organic EL element described in the above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view which shows a first embodiment of a manufacturing method for an organic EL element according to the present invention.

FIG. 2 is a sectional view which shows a second embodiment of a manufacturing method for an organic EL element according to the preset invention.

FIG. 3 is a sectional view which shows a third embodiment of a manufacturing method for an organic EL element according to the present invention.

FIG. 4 is a sectional view which shows a fourth embodiment of a manufacturing method for an organic EL element according to the present invention.

FIG. 5 is a sectional view which shows a fifth embodiment of a manufacturing method for an organic EL element according to the preset invention.

FIG. 6 is a sectional view which shows an example of the organic EL element according to the present invention.

FIG. 7 is a sectional view which shows an example of an organic EL display device using the organic EL element according to the present invention.

FIG. 8 is a diagram which shows an example of an active matrix type organic EL display device using the organic EL element according to the present invention.

FIG. 9 is a sectional view which shows an example of a manufacturing method of the active matrix type organic EL display device.

FIG. 10 is a perspective view which shows an example of a configuration of a head for an ink-jet method which is used in the manufacturing method of the organic EL element according to the present invention.

FIG. 11 is a sectional view of the nozzle part of the head for an ink-jet method which is used in the manufacturing method of the organic EL element according to the present invention.

FIG. 12 is a diagram which shows another embodiment of an organic EL display device according to the present invention.

FIG. 13 is a schematic perspective view of an organic EL display device according to the present invention.

FIG. 14 is a diagram which shows an example of the waveform of the driving voltage applied to the electrodes.

FIG. 15 is a partial sectional view which shows another embodiment of an organic EL element according to the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

In the following, the manufacturing method of the organic EL element and the organic EL element according to the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

FIG. 1 shows a first embodiment of the manufacturing method of the organic EL element according to the present invention. This figure shows the manufacturing method of a full color organic EL element with three colors. As shown in the figure, this invention is directed to a method of manufacturing an organic EL element which comprises a step of forming pixel electrodes 101, 102 and 103 on a transparent substrate (transparent support) 104, a step of patterning luminescent layers 106 and 107 which are made of organic compounds on the respective pixel electrodes, and a step of forming a cathode 113, wherein the method is characterized in that the formation of the luminescent layers is carried out by means of an ink-jet method.

The transparent substrate 104 functions not only as a support but also as a surface through which light is taken out. Accordingly, the material for the transparent substrate 104 is selected by taking the light-permeability, thermal stability and the like into consideration. As for examples of the material to be used for the transparent substrate, glass, transparent plastic or the like can be mentioned, and among these materials, a substrate made of glass is particularly preferable in view of its excellent heat resistance.

In more details, the first, pixel electrodes 101, 102 and 103 are formed on the transparent substrate 104. As for examples of methods of forming these pixel electrodes, photolithography, vacuum deposition method, sputtering method and pyrosol method can be mentioned. Among these methods, the photolithography is particularly preferable. As for these pixel electrodes, it is preferred that they are formed into transparent pixel electrodes. As for the materials constituting the transparent pixel electrodes, a tin oxide film, an ITO (indium tin oxide) film and a composite oxide film of indium oxide and zinc oxide can be mentioned.

Next, partitioning walls (banks) 105 are formed to fill the spaces between the pixel electrodes.

In this way, it is possible to improve the contrast, to prevent mixing of colors of the luminescent materials, and to prevent light from leaking between the pixels.

As for the materials constituting the banks 105, no particular limitation is imposed, if they have a resistance to the solvent for the EL material. For example, organic material such as acrylic resin, epoxy resin, photosensitive polyimide and the like; and inorganic material such as liquid glass and the like can be mentioned. In this regard, it is to be noted that the banks 105 may be formed into a black resist which is formed by mixing carbon black and the like into the above-mentioned material.

As for examples of the forming method for the banks 105, photolithography and the like can be mentioned.

Further, organic luminescent layers are formed respectively on the pixel electrodes according to a predetermined pattern. In this case, it is preferable to provide organic luminescent layers with three color types. In this connection, it is preferred that at least one layer among these organic luminescent layers is formed by an ink-jet method.

In the embodiment shown in FIG. 1, a red luminescent layer 106 and a green luminescent layer 107 are formed on the pixel electrodes 101 and 102, respectively, by the ink-jet method.

In the above descriptions, the term "ink-jet method" is used to mean a method of forming a pixel of one of the three primary colors including red, green and blue or a pixel of at least one color which is intermediate between the primary colors by dissolving or dispersing a luminescent material in a solvent to obtain a discharge liquid and then discharging the discharge liquid from a head 110 of an ink-jet device 109.

According to such an ink-jet method, it is possible to carry out fine patterning in a simple manner and in a short time. Further, it is also possible to control easily and freely the luminescent characteristics such as color balance and brightness (luminance) by adjusting the thickness of the layer through adjustment of the discharge amount of the ink or by adjusting the ink concentration.

When the organic luminescent materials are conjugated polymer precursors described later, the luminescent layers are formed by discharging the luminescent materials by the ink-jet method to carry out patterning, and then conjugating (to form a film) the precursor components by heating or irradiation with light or the like.

Next, as shown in FIG. 1, a blue luminescent layer 108 is formed on the red luminescent layer 106, the green luminescent layer 107 and the pixel electrode 103. In this way, it is possible not only to form layers having the three primary colors including red, green and blue, but also to bury the level differences between the banks 105 and each of the red luminescent layer 106 and the green luminescent layer 107 so as to be flattened.

No particular limitation is imposed upon the forming method for the blue luminescent layer 108, and it is possible to form the layer using the general film forming method known as deposition method or wet method, for instance, or using the ink-jet method.

Further, the blue luminescent layer 108 can be formed of an electron injection and transfer material such as aluminum quinolynol complex. In this case, it is possible to promote the injection and transfer of the carriers so as to improve the luminous efficiency. Furthermore, when such a blue luminescent layer 108 is laminated with red and green luminescent layers formed of a hole injection and transfer material described later, it is also possible to inject and transfer the electrons and the holes from the respective electrodes into these laminated luminescent layers with appropriate balance, thereby enabling to improve the luminous efficiency.

Moreover, when such a blue luminescent layer 108 is laminated with the red and green luminescent layers made of a hole injection and transfer type material, the function of hole injection and transfer and the function of electron injection and transfer can be assigned separately to different layers, so that optimum design can be selected for the respective materials. No particular limitation is imposed upon the forming method of such an electron injection and transfer layer, and it is possible to form the layer by using, for example, the general film forming method known as deposition method or wet method or the ink-jet method.

In this connection, as for an organic compound which can form an electron injection and transfer layer, oxadiazole derivative such as PBD, OXD-8 and the like, DSA, aluminum quinolinol complex, Bebq, triazole derivative, azomethine complex, porphine complex, benzoxadiazol and the like can be mentioned. In this case, an electron injection and transfer layer can be formed from just one of these materials, or formed by mixing or laminating one of or two or more of them. In addition, the electron injection and transfer layer may be formed by doping a fluorescence dye described later to the organic compound described. Further, the electron injection and transfer layer itself may have a function of luminescence.

As described above, in this embodiment, organic luminescent layers for two colors are formed by the ink-jet method while the layer for the remaining one color is formed by a different method. Therefore, according to this embodiment, even when a luminescent material which is not so suited for the ink-jet method is used, a full color organic EL element can be formed by using such a material in a combination with other organic luminescent materials that are suited for the ink-jet method, so that the latitude in the design for the EL element will be expanded.

As for examples of the forming method for the luminescent layer other than the ink-jet method, photolithography method, vacuum deposition method, printing method, transfer method, dipping method, spin coating method, casting method, capillary method, roll coating method, bar coating method and the like can be mentioned.

Finally, a cathode (a counter electrode) 113 is formed, thereby the organic EL element of the present invention is completed. In this case, it is preferred that the cathode 113 is formed into a metallic thin film electrode, and as for examples of the metal for forming the cathode, Mg, Ag, Al, Li and the like can be mentioned. In addition, a material having small work function can be used for the material for the cathode 113, and for example, alkali metal, alkali earth metal such as Ca and the like, and alloys containing these metals can be used. Such a cathode 113 may be formed using a deposition method, a sputtering method or the like.

The organic EL element of the present invention is manufactured through the processes described in the above. Namely, as shown in FIG. 1, the pixel electrodes 101 and 102 are provided on the transparent substrate 104, the red luminescent layer 106 and the green luminescent layer 107 which are made of organic compounds are then formed on the pixel electrodes 101 and 102, respectively, by patterning by using the ink-jet method, and then the blue luminescent layer 108 is formed on the luminescent layers 106 and 107 and the pixel electrode 103 by A the vacuum deposition method. Thereafter, the cathode 113 is formed on top of the blue luminescent layer 108, thereby the organic EL element according to the present invention is completed.

Further, as shown in FIG. 6, a protective film 415 may be formed on top of a cathode 413. By forming such a protective film 415, it becomes possible to prevent deterioration, damage, peeling and the like from occurring in the cathode 413 and in the luminescent layers 406, 407 and 408.

As for materials for constructing the protective film 415, epoxy resin, acrylic resin, liquid glass and the like can be mentioned. Further, as for examples of the forming method for the protective film 415, spin coating method, casting method, dipping method, bar coating method, roll coating method, capillary method and the like can be mentioned.

In this embodiment, it is preferable that these luminescent layers are formed of an organic compound, and it is more preferable that these luminescent layers are formed of a polymer organic compound. By providing such luminescent layers that are formed of the organic compound, it is possible to obtain high brightness surface luminescence at low voltages. Further, since luminescent materials can be selected from wide range of field, a rational design for the luminescent element becomes possible.

In particular, polymer organic compounds have an excellent film formation property, and the luminescent layers composed of polymer organic compounds have an extremely good durability. Further, these polymer organic compounds have a band gap in the visible region and a relatively high electrical conductivity. Among such polymer organic compounds, a conjugated polymer can exhibit such properties prominently.

As for materials for the organic luminescent layers, polymer organic compound itself, precursor of conjugated organic polymer compound which is to be conjugated (to form a film) by heating or the like, and other materials are used.

When a precursor prior to conjugation (to form a film) is used as a luminescent material, the viscosity or the like of a discharge liquid used for the ink-jet system can be adjusted easily, so that the patterning is carried out precisely and the luminescence characteristics and the film properties of the luminescent layer can be controlled easily.

It is preferred that the polymer organic compound forming the luminescent layers is a hole injection and transfer material. In this way, it is possible to promote the injection and transfer of the carriers and thereby to improve the lum