JPH0613184A - Organic thin film el element and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an organic thin film EL element and a manufacturing method thereof by which patterning becomes possible on an organic thin film composed mainly of photosensitive resin by using light without damaging it and which can cope with full color emission. CONSTITUTION:In an organic thin film EL element constituting an emission part by laminating plural layers (transparent electrode 11, electron hole transporting layer 12, emission layer 13 and back plate 14) on a transparent substrate 10, at least one of the plural layers constituting the emission part is composed mainly of photosensitive resin. At least one layer of the emission part of this EL element is formed of the photosensitive resin, and patterning is made possible by using photosensitive action by means of light, so that the patterning becomes possible on an organic thin film of an EL element on which the patterning by means of a conventional photolithography technology is impossible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic thin film EL device utilizing the electroluminescence (EL) phenomenon.

[0002]

2. Description of the Related Art Recently, thin and lightweight display devices have been established as flat panel displays. The greatest feature of these display devices is that they occupy less volume than CRTs (cathode ray tubes). Among the display elements for this type of display device, there are non-emissive liquid crystal display elements and Light emitting plasma displays, EL devices, and the like are known, and are used properly according to the purpose. Among these display elements, the organic thin film EL element emits light at an extremely low voltage (10 to 20 V) as compared with other self-luminous display elements,
The most distinctive feature is the rich emission color, and many research institutes are developing it for this reason.

Conventionally, as an example of the configuration of this type of EL element, the one shown in FIG. 6 is known. A conventional EL device A shown in FIG. 6 has a structure in which a transparent electrode 2, a hole transport layer 3, a light emitting layer 4, an electron transport layer 5, and a back electrode 6 are sequentially laminated on a transparent substrate 1 made of glass or the like. It is said that this E
A voltage is applied between both electrodes 2 and 6 of the L element A to guide electrons and holes into the light emitting layer 4, and the recombination energy of electron-hole pairs is emitted as fluorescence in the light emitting layer.

Conventionally, as a method for manufacturing an EL element represented by the above structure, a vacuum vapor deposition method for forming a film on a substrate by heating and sublimating an organic material used for an EL element in a vacuum, and an EL element are used. Langmuir-Blodgett method (L
A method B) and a spin coating method in which an organic material used for an EL element is dissolved in a solvent to prepare a solution, and the solution is dropped on a substrate and spin-coated. The EL devices manufactured by the various methods described above have the hole transport layer 3, the light emitting layer 4, and the electron transport layer 5 each having a film thickness of 10 nm to 1 nm.
The thickness is about 1 μm, and the total thickness is about 1 to 2 μm. The light is emitted by applying an AC or DC voltage between the electrodes 2 and 6 as described above. It can be confirmed from the 1st side.

[0005]

The EL device A having the above structure
In this case, no matter how the film is formed by using any of the above-mentioned methods, it cannot be used as a display element unless a pattern such as a dot matrix is formed. Therefore,
As a simple method for use as a display element, if a metal forming an electrode or a transparent electrode material is formed in a pattern by a photolithography technique before forming an organic material, for example, one electrode If the other electrodes are arranged and formed in a matrix so as to be assembled in a grid pattern, a light emitting element corresponding to the pattern can be obtained.

However, considering full-color emission,
Since at least three kinds of light emitting materials need to be independently arranged on the substrate, it is necessary to pattern each organic thin film forming the hole transport layer 3, the light emitting layer 4, and the electron transport layer 5. become. However, at this time, it would be good if the organic thin film material could be simply patterned by the photolithography technique used in the semiconductor process. In the present situation, an effective method for patterning an organic film has not been found, because it is dissolved by a liquid or a stripping solution or is damaged by being altered.

The present invention has been made in view of the above circumstances, and an organic thin film can be formed by using a photosensitive resin as a main component, and the organic thin film can be patterned without damaging the organic thin film, which corresponds to full-color light emission. It is an object of the present invention to provide an organic thin film EL device that can be manufactured and a manufacturing method thereof.

[0008]

In order to solve the above-mentioned problems, an organic thin-film EL device comprising a transparent substrate and a plurality of layers laminated to form a light-emitting portion,
At least one of the plurality of layers forming the light emitting unit is mainly made of a photosensitive resin.

In order to solve the above-mentioned problems, the present invention comprises at least a transparent electrode, an EL light emitting layer and a back electrode on a transparent substrate, and at least one surface side of the EL light emitting layer is provided. In the organic thin film EL device in which the light emitting portion is formed by forming the hole transport layer or the electron transport layer, at least one of the hole transport layer, the electron transport layer, and the EL light emitting layer transports the hole to the photosensitive resin. A material, an electron transporting material, or a light emitting material is added.

In order to solve the above-mentioned problems, the invention according to claim 3 is the organic thin-film EL device according to claim 1 or 2, wherein the light-emitting layer is divided into a plurality of parts, and the plurality of divided light-emitting layers have at least two colors. The light emitting material is mixed in the photosensitive resin of each light emitting layer so that the above emission color can be obtained.

In order to solve the above problems, the invention according to claim 4 is the organic thin film EL element according to claim 1, 2 or 3, wherein the light emitting portion is patterned, and the light emitting portion is made of a photosensitive resin. It is patterned by being selectively removed by a drug due to a property change caused by.

In order to solve the above-mentioned problems, a fifth aspect of the present invention is a method for manufacturing an organic thin film EL device comprising a transparent substrate and a plurality of layers laminated to form a light-emitting portion. At least one of a plurality of constituent layers is formed by mixing a light-emitting material into a photosensitive resin, and after forming this layer, a predetermined portion is irradiated with light, and then a non-exposed portion or a photosensitive portion is removed. To pattern the layer.

[0013]

By forming at least one layer of the light emitting portion of an EL element composed of a plurality of layers from a photosensitive resin, it becomes possible to perform patterning by utilizing the photosensitivity effect by light, and pattern the organic thin film. Will be able to. That is, the resistance to the drug is different between the exposed portion and the non-exposed portion, and it becomes possible to selectively remove the exposed portion or the non-exposed portion in the organic thin film after exposure, whereby the conventional photolithography EL that could not be patterned by technology
The organic thin film for the device can be patterned.
In addition, any of the hole transporting layer, the EL light emitting layer, and the electron transporting layer that constitute the light emitting portion of the EL element is configured by mixing the hole transporting material or the light emitting material or the electron transporting material into the photosensitive resin. This makes it possible to perform patterning on any layer by utilizing the photosensitivity of the photosensitive resin.

Further, by dividing the light emitting portion into a plurality of portions and mixing a light emitting material into the photosensitive resin so that at least two or more emission colors can be obtained for the plurality of divided light emitting portions, two or more colors are obtained. It becomes easy to display the color of. Therefore, for example, by using a light emitting material of three primary colors and alternately using each light emitting material for a plurality of divided light emitting portions, the organic thin film E
Full color display in the L element becomes possible.

On the other hand, according to the method of the present invention, at least one layer of the light emitting portion of the EL element composed of a plurality of layers is formed of a photosensitive resin, and the property of the photosensitive resin is changed by utilizing the photosensitization effect of light. Since it is used and patterned by a chemical agent, it becomes possible to pattern an organic thin film, which was impossible with the conventional lithography technique. That is, the resistance to the drug is different between the exposed portion and the non-exposed portion, and the exposed portion or the non-exposed portion can be selectively removed in the organic thin film after exposure. Therefore, in the conventional photolithography technique, It becomes possible to pattern the organic thin film for the EL element which could not be patterned.

The present invention will be described in more detail below with reference to the drawings. FIG. 1 shows a first embodiment of an organic thin film EL device according to the present invention. An organic thin film EL device B of this example is a transparent substrate 10, a transparent electrode 11, a hole transport layer 12 and EL light emission. The layer 13 and the back electrode 14 are laminated, and by applying an AC voltage or a DC voltage between the electrodes 11 and 14, the EL light emitting layer 13 emits light, and this light emission can be confirmed from the transparent substrate 10 side. It has become. Also,
In the organic thin film EL element B of this example, the transparent electrode 11
The back electrodes 14 and the back electrodes 14 are formed in a stripe shape and arranged in a matrix so as to intersect with each other in a lattice shape. However, in FIG. 1, they are simply stacked for the sake of simplification of the description. The transparent substrate 10 is made of a transparent material such as glass, and the transparent electrode 11 is made of indium tin oxide (I
TO) and the like, and the hole transport layer 12 is made of a photosensitive material to which a hole transport material is added.
The EL light emitting layer 13 is made of a light emitting material described later, the back electrode 14 is made of a conductive metal material such as Al, or
It is composed of the transparent conductive material described above.

In order to manufacture the organic thin film EL element B having the above structure, a film made of a transparent conductive material is formed on the transparent substrate 10, this is processed into a striped electrode shape by the photolithography technique, and the film is formed thereon. Hole transport layer 12 and E
The L light emitting layer 13 and the L light emitting layer 13 are formed by a spin coat method or the like, and finally the back electrode 14 is formed on the EL light emitting layer 13 by a method such as a vapor deposition method or a sputtering method.

Next, an example of forming the hole transport layer 12 will be described. To prepare the hole transport layer 12,
For example, first, the following general formula (I)

[0019]

[Chemical 1]

A hole transporting material such as polyvinylcarbazole represented by is used, and this is dissolved in an organic solvent such as chloroform to prepare a chloroform solution. If the organic hole transport material used here is a polymer represented by the general formula (I), the solution may be spin-coated on the transparent substrate 10 in a nitrogen atmosphere or the like to form a film. Good. If the hole transport material is not a polymer as represented by the general formula (I) but a single molecule, it is mixed with a transparent optical resin and dissolved in an organic solvent. You can spin coat what you did. In this example, polyvinylcarbazole was used as the hole-transporting material, but the hole-transporting material used in the present invention is not limited to this, and other amine-based organic compounds generally known as hole-transporting materials. It can be used as a hole transport material if it has a hole transport property to some extent as compared with an oxadiazole organic compound or a light emitting material.

Next, after the solvent of the liquid film formed by spin coating is volatilized, the solvent is evaporated in a nitrogen atmosphere for 10 times.
Bake at 0-120 ° C. to fully cure the film.
Further, if it is desired to form an arbitrary pattern here, a hole transporting material is mixed with a photosensitive polymer described later, or if it is already a polymer, photosensitivity is added to perform patterning as described later. It is possible.

Next, an example of a method for forming the EL light emitting layer 13 will be described. In this example, first, the following general formula (II)

[0023]

[Chemical 2]

Light emitting material represented by (Al chelate complex)
To use. In addition to such metal chelate complexes, organic fluorescent materials such as aromatic hydrocarbons and laser dyes are suitable as the light emitting material. Next, the following general formula (III)

[0025]

[Chemical 3]

A photosensitive resin represented by (cresol novolac resin + photosensitive material) is prepared. The intermediate of this resin is synthesized by a conventional method. The light-emitting material represented by the general formula (II) is mixed in the organic solvent containing the polymeric photosensitive material at a ratio of about several times the above to prepare a mixed solution, which is spin-coated. At this time, it is preferable to perform the work in safe light so that the photosensitive resin does not cause a photodecomposition reaction carelessly.

Next, an example of a method of patterning using the above-mentioned photosensitive resin and using an exposure machine used in a semiconductor process will be described with reference to FIG. First,
As shown in FIG. 2, the transparent electrode 16 and the hole transport layer 17 are formed on the transparent substrate 15 by the method described above, for example.
Next, a solution containing the light emitting material represented by the general formula (II) is applied onto the hole transport layer 17 and dried to form a polymer mixed layer 18, and the pattern to be transferred is formed on the mixed layer 18. The photomask 20 is arranged corresponding to the above, and light irradiation is performed from above as shown by an arrow to cause photolysis in the mixed layer 18 in a portion other than the lower portion of the photomask 20.

Next, in the developing process, the entire device is immersed in an aqueous solution in which sodium carbonate is dissolved in an amount of 1 to several% to dissolve and remove the exposed portion which causes photodecomposition, and a pattern 21 as shown in FIG. 3 is formed. Create. Next, the entire substrate is baked at 100 to 120 ° C. in a nitrogen atmosphere to completely cure the pattern 21. Then, a back electrode is formed on the pattern 21 by a vacuum evaporation method, and a DC pulse voltage (about 10 to 20 V) is applied between the back electrode and the transparent electrode 16.
Green light emission can be generated by applying.

FIG. 4 shows a second embodiment of the organic thin film EL element according to the present invention. The organic thin-film EL device C of this example has a transparent electrode 11 and a hole transport layer 1 on a transparent substrate 10.
The point that 2 is formed is the same as the configuration of the first embodiment. The organic thin film EL device C of this example is characterized in that, for example, a large number of striped EL light emitting layers 23 are formed on the hole transport layer 12, and the EL light emitting layers 23 ... Are, for example, the left side of FIG. It is characterized in that the red light emitting device, the green light emitting device, and the blue light emitting device are alternately formed in this order. Each of these EL light emitting layers 23 is made of a photosensitive resin mixed with a light emitting material, and a red light emitting material is mixed with a red light emitting material.
A green light emitting material is mixed with a green light emitting material, and a blue light emitting material is mixed with a blue light emitting material.
As the red light emitting material, perylene or the like can be used, as the green light emitting material, an Al chelate complex, a cyanine dye, or the like can be used, and as the blue light emitting material, tetraphenylcyclopentadiene, stillbenzene-based material, or the like can be used. In addition to these, known materials as colored light emitting materials can be appropriately used.

Next, the above-mentioned light emitting materials are mixed in a photosensitive resin to form light emitting layers of three primary colors independently on the plane of the substrate so that light of three colors corresponding to the three primary colors of light can be emitted. Then, an example of a method for manufacturing the organic thin film EL element C having the structure shown in FIG. 4 will be described with reference to FIG. First, FIG.
As shown in (a), a transparent electrode 26 and a hole transport layer 27 are laminated on a transparent substrate 25, and then a photosensitive resin layer 28 mixed with a red light emitting material is formed by spin coating. As shown in FIG. 5 (b), light irradiation is performed through the mask 29, and then, as shown in FIG. 5 (c), the light irradiated portion is developed and removed, and further baked to perform the first light emitting layer 3
Form 0.

Next, as shown in FIG. 5D, a photosensitive resin layer 32 mixed with a green light emitting material is formed on the substrate on which the first light emitting layer 30 has been formed by spin coating, and subsequently, FIG. As shown in (e), the mask 33 is arranged above the first light emitting layer 30 laterally, and then light irradiation is performed.
As shown in (f), the light irradiation portion is developed and removed, and further baked to form the second light emitting layer 34.

Next, as shown in FIG. 5G, a photosensitive resin layer 35 mixed with a blue light emitting material is formed on the substrate on which the first light emitting layer 30 and the second light emitting layer 34 have been formed by spin coating. Then, as shown in FIG. 5 (h), a mask 36 is disposed above the second light emitting layer 34, and light irradiation is performed, and then the light irradiation portion is developed as shown in FIG. 5 (i). And removed, and baking is performed to form the third light emitting layer 37.
To form. Thereafter, the back electrode 24 is formed on the first light emitting layer 30, the second light emitting layer 34, and the third light emitting layer 37, respectively, as shown in FIG.
Can be manufactured. If the manufacturing method as described above is adopted, the light emitting layers 30, 34, and 37 patterned in a matrix having the three primary colors of light can be formed, so that the organic thin film EL capable of full color display.
The device C can be manufactured.

In the above description, the photodegradable resin is used, but even if the photopolymerizable resin is used, the positions where the photomasks 29, 33 and 36 are provided are reversed,
That is, contrary to the case described above, only the portions of the photopolymerizable resin irradiated with light are left, and the remaining portions are used as the first, second, and third light emitting portions, respectively, so that the three primary colors can be displayed as described above. It is possible to manufacture various organic thin film EL devices.

[0034]

[Example] (Example 1) Thickness 1 mm, size 2.5 cm
A transparent electrode made of ITO was formed on a transparent substrate made of glass having a size of 2.5 cm by a sputtering method to form a transparent electrode having a thickness of 0.25 μm. Next, the polyvinylcarbazole represented by the general formula (I) is used,
Use 0 mg to prepare a chloroform solution by dissolving it in 10 ml of chloroform, spin-coat this solution in a nitrogen atmosphere (5000 rpm × 10 seconds), volatilize this solvent, and then perform 1 in a nitrogen atmosphere.
Baking at 00-120 ° C. By the above operation,
It was possible to form a completely cured hole transport layer having a thickness of 0.05 μm.

In order to form a light emitting layer on the hole transport layer, the light emitting material of the Al chelate complex represented by the general formula (II) was used. In addition, the cresol novolac resin represented by the general formula (III) + photosensitive material is about 0.3 to 0.4.
The light emitting material was mixed in an organic solvent containing chloroform at a weight ratio of about 3 times the resin amount to prepare a mixed solution, and the mixed solution was spin-coated on the hole transport layer. (5000 rpm × 10 seconds). At this time, the work was carried out in safe light so that the photosensitive resin would not inadvertently cause a photodecomposition reaction.

The spin-coated mixed solution is heated to 80 ° C. to volatilize the solvent, and then masked with a photomask having a predetermined pattern to irradiate light, and the portion not covered with the photomask Caused photolysis. After this, the whole part including the exposed part is sodium carbonate 1
% Aqueous solution to dissolve and remove only the exposed portion to form a pattern. Further, this substrate was baked at 100 to 120 ° C. in a nitrogen atmosphere to completely cure it. Then, a back electrode made of Al is formed by vacuum evaporation, and a DC pulse voltage (about 1
It was confirmed that green light was emitted by applying 0 to 20 V).

Example 2 The same method as in Example 1 was carried out halfway to form a transparent electrode and a hole transport layer on a transparent substrate, and a light emitting layer was patterned thereon. For this, the exposure machine used in the semiconductor process was used, and the red light emitting layer material (perylene derivative) was added to the photosensitive resin solution used in Example 1 on the hole transport layer in an amount equal to the resin amount. After mixing and spin-coating the mixed solution, the organic solvent is volatilized by heating to about 80 ° C., and then light irradiation is performed through a photomask having a stripe-shaped pattern. The portion irradiated with light was developed and removed with an aqueous solution.
The thus obtained striped red light emitting layer having a thickness of about 0.05 to 0.1 μm was baked at about 100 to 120 ° C. and completely cured. The green light emitting layer is the same as in Example 1.
In the same manner as in (1), solution adjustment, spin coating, and light irradiation through a photomask having a stripe pattern, a striped green light emitting layer having a thickness of about 0.05 to 0.1 μm is formed adjacent to the red light emitting layer. Formed.

For the blue light emitting layer, tetraphenylpentadiene (TPCP) was mixed with the photosensitive resin solution prepared in Example 1 in an amount of about 1 to 2 times the amount of the photosensitive resin, and each step of spin coating, drying, exposing, developing and baking was performed. A striped blue light emitting layer was formed at a position adjacent to the red light emitting layer and the green light emitting layer through the same steps as described above. After that, a back electrode made of Al was formed on each of the upper surfaces of the red light emitting layer, the green light emitting layer, and the blue light emitting layer by vacuum vapor deposition to obtain an organic thin film EL element having the same structure as that shown in FIG. By applying a DC pulse voltage (about 10 to 20 V) to this organic thin film EL element, full color display could be performed.

[0039]

As described above, according to the present invention, E
By forming at least one layer of the light emitting portion of the L element from a photosensitive resin so that the patterning can be performed by utilizing the photosensitizing effect of light, the EL element which cannot be patterned by the conventional photolithography technique. The organic thin film can be patterned. That is, the properties of the photosensitive resin are different between the exposed part and the non-exposed part, and the exposed part or the non-exposed part can be selectively removed in the organic thin film after the exposure, which allows patterning. Like

In any of the hole transporting layer, EL light emitting layer and electron transporting layer constituting the light emitting portion of the EL device, the hole transporting material or the light emitting material or the electron transporting material is mixed in the photosensitive resin. It is possible to configure the structure, which enables patterning in any of the layers by utilizing the photosensitivity of the photosensitive resin.

Further, by dividing the light emitting portion into a plurality of portions and mixing the light emitting material into the photosensitive resin so that at least two or more emission colors can be obtained for the plurality of divided light emitting portions, two or more colors can be obtained. It becomes easy to display the color of. Therefore, for example, by using a light emitting material of three primary colors and alternately using each light emitting material for a plurality of divided light emitting portions, the organic thin film E
Full color display in the L element becomes possible.

On the other hand, according to the method of the present invention, at least one layer of the light emitting portion of the EL element is formed of a photosensitive resin,
Since the patterning is performed by utilizing the property change of the photosensitive resin by utilizing the photosensitization effect of light, it becomes possible to perform the patterning of the organic thin film, which is impossible by the conventional lithography technique. That is, the property of the photosensitive resin is different between the exposed part and the non-exposed part, and the exposed part or the non-exposed part in the organic thin film after exposure can be selectively removed by chemicals or the like. Therefore, it becomes possible to pattern the organic thin film for the EL element which could not be patterned by the conventional photolithography technique.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of an organic thin film EL element according to the present invention.

FIG. 2 is a cross-sectional view for explaining an example of a method of manufacturing an organic thin film EL element according to the present invention.

FIG. 3 is a cross-sectional view for explaining an example of a method for manufacturing an organic thin film EL element according to the present invention.

FIG. 4 is a sectional view showing a second embodiment of the organic thin film EL element according to the present invention.

5 (a) to (i) are organic thin films E according to the present invention.
It is sectional drawing for demonstrating the other example of the manufacturing method of an L element.

FIG. 6 is a sectional view showing an example of a conventional organic thin film EL element.

[Explanation of symbols]

 B, C, organic thin film EL device, 10, 15, 25, transparent substrate, 11, 16, 26, transparent electrode, 12, 17, 27, hole transport layer, 13, 21, 23, light emitting layer, 14, 24 , Back electrode,

Claims (5)

[Claims] 1. An organic thin-film EL device comprising a transparent substrate and a plurality of layers laminated to form a light emitting portion, wherein at least one of the plurality of layers constituting the light emitting portion is mainly made of a photosensitive resin. An organic thin film EL device characterized by the following. 2. At least a transparent electrode and E on a transparent substrate.
An organic thin film EL device comprising an L light emitting layer and a back electrode, wherein a hole transport layer or an electron transport layer is formed on at least one surface side of the EL light emitting layer to form a light emitting portion. At least one of a hole transporting layer, an electron transporting layer, and an EL light emitting layer is formed by adding a hole transporting material, an electron transporting material, or a light emitting material to a photosensitive resin. 3. The organic thin film EL element according to claim 1, wherein the light emitting portion is divided into a plurality of portions, and the plurality of divided light emitting portions are divided so as to obtain at least two or more emission colors. 2. An organic thin film EL element, characterized in that a light emitting material is mixed in a photosensitive resin of the light emitting part. 4. The organic thin film E according to claim 1, 2 or 3.
In the L element, the light emitting portion is patterned, and the light emitting portion is patterned by being selectively removed by a chemical agent due to a property change due to exposure of a photosensitive resin and patterned. 5. A method for manufacturing an organic thin film EL device comprising a light emitting portion by laminating a plurality of layers on a transparent substrate, wherein at least one of the plurality of layers constituting the light emitting portion is exposed. Characterized in that a light-emitting material is mixed with a photosensitive resin, a predetermined portion is irradiated with light after forming this layer, and then the non-exposed portion or the exposed portion is removed to pattern the layer. Method for manufacturing thin film EL device.