JP2003257631A - Method of forming organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an organic EL element capable of easily manufacturing the organic EL element of multi-layer structure formed of a high polymer EL material. <P>SOLUTION: This method of forming the organic EL element comprises the steps of forming a hole carrier layer formed of PVK on a substrate 14 while evaporating organic solvent in vacuum by jetting, in spray shape, solution containing organic solvent (toluene) prepared by dissolving the PVK of the high polymer EL material in the atmosphere of vacuum toward the surface of the substrate 14 and forming a luminescent layer formed of PAT on the substrate 14 having the hole carrier layer formed thereon while evaporating the organic solvent in vacuum by jetting, in spray shape, solution containing organic solvent prepared by dissolving the PAT of high polymer EL material in the atmosphere of vacuum toward the surface of the substrate 14. <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 a method for forming an organic EL element, and more particularly to a method for forming an organic EL element including a layer made of a polymer EL material.

[0002]

2. Description of the Related Art In recent years, with the diversification of information equipment, the development of a display using an organic electroluminescence element (organic EL element) as a flat display element that consumes less power than a CRT which has been generally used conventionally. Is expected. Further, the organic EL element is also expected as a pollution-free (mercury-less) lighting device that replaces a fluorescent lamp or the like.

In the organic EL device, electrons and holes are injected into the light emitting layer from the electron injecting electrode and the hole injecting electrode, respectively, so that the electrons and holes are recombined in the light emitting layer to bring the organic molecules into an excited state. . Then, this organic molecule emits light by fluorescence emitted when returning from the excited state to the ground state. In this organic EL element, the efficiency of light emission can be increased by stacking a material having an electron transporting property, a material having a hole transporting property, and a light emitting material in a multilayer structure. Conventionally, since an organic EL element made of a low molecular weight organic material has a small molecular weight and is light, it is possible to easily form the above-described organic EL element having a multilayer structure by using a vacuum deposition method. On the other hand, conventionally, an organic EL element using a polymer EL material is known. It is known that by stacking this polymer EL material to form an organic EL element, a low voltage operation becomes possible as compared with the case where a low molecular organic material is stacked.

[0004]

However, since the high molecular weight EL material has a large molecular weight and is heavy, it is a low molecular weight EL material.
Unlike the material, there is a disadvantage that it is difficult to form a multilayer film by vacuum vapor deposition. Therefore, when forming the polymer EL material layer, a wet process such as a spin coating method or various printing methods such as an inkjet method is usually used. However, in the wet process, when the solution containing the polymer EL material of the second layer is applied after forming the polymer EL material layer of the first layer, one layer is formed by the organic solvent contained in this solution. The polymer EL material layer of the eye may be dissolved. Therefore, it has been difficult to form an organic EL element having a polymer-based multilayer structure.

In order to solve the above problems, for example, a water-soluble material is used for the first layer polymer EL material, and a material that is soluble in an organic solvent is used for the second layer polymer EL material. It is also possible. As a result, even when the solution containing the polymer EL material of the second layer is applied onto the upper surface of the polymer EL material layer of the first layer, the polymer E of the first layer E
The L material layer is not dissolved by the solvent contained in the solution containing the polymer EL material of the second layer. However, this method has a new problem that the range of material selection for the polymer EL material layer is significantly narrowed. Further, when a water-soluble material is used, there is a problem that water remaining in the organic layer after forming the multilayer film may adversely affect the characteristics and reliability of the organic EL element.

The present invention has been made to solve the above problems, and one object of the present invention is to:
Method of forming organic EL element capable of easily forming multi-layer organic EL element made of polymer EL material without causing a problem such as narrowing of material selection range of polymer EL material layer Is to provide.

Another object of the present invention is to make it possible to separately paint red, blue and green in the above method of forming an organic EL element.

Still another object of the present invention is to improve the adhesiveness of a layer made of a polymeric EL material in the above method of forming an organic EL element.

[0009]

In order to achieve the above object, a method for forming an organic EL element according to one aspect of the present invention is a method of forming a first organic EL material by dissolving a first polymer EL material in a vacuum atmosphere. A step of forming a first polymer EL material layer on the substrate while evaporating the first organic solvent in a vacuum by spraying a solution containing a solvent toward the surface of the substrate; By spraying a solution containing the second organic solvent in which the second polymer EL material is dissolved in a vacuum atmosphere toward the surface of the substrate,
Forming a second polymer EL material layer on the substrate on which the first polymer EL material layer is formed while evaporating the second organic solvent in a vacuum.

In the method of forming an organic EL element according to this aspect, the solution containing the second organic solvent in which the second polymer EL material is dissolved is jetted toward the surface of the substrate to form a second solution. The second polymer EL material layer is formed by forming the second polymer EL material layer on the substrate on which the first polymer EL material layer is formed while evaporating the organic solvent in a vacuum. The second polymer E on the substrate
The second organic solvent is evaporated before the L material arrives.
This can prevent the first polymer EL material layer already formed on the substrate from being dissolved by the second organic solvent. As a result, it is possible to easily form an organic EL element including an organic layer having a multi-layer structure even when a polymer EL material is used. Further, since both the first polymer EL material and the second polymer EL material can be made of a material that is soluble in an organic solvent, the range of material selection for the polymer EL material is not narrowed.

In the method for forming an organic EL device according to the above aspect, preferably, the first polymer EL material has a first electric carrier mobility and the second polymer EL material is a second one. The second polymer EL material layer has a second electric carrier mobility different from the first electric carrier mobility, and is formed over the first polymer EL material layer.
According to this structure, it is possible to easily form the organic EL element having the laminated structure of the first polymer EL material layer and the second polymer EL material layer.

In the method for forming an organic EL element according to the above aspect, it is preferable that a step of providing a mask for separately painting pixels on the front surface of the substrate is further performed prior to the step of forming the first polymer EL material layer. The first polymer EL material has a first emission color, and the second polymer EL material has
A step of forming a first polymer EL material layer having a second light emission color different from the first light emission color and a second polymer EL
The step of forming the material layer is performed when the first polymer EL material layer is formed and when the second polymer EL material layer is formed.
The step of shifting the position of the mask for separately painting pixels is included. According to this structure, in addition to the effect of the method of forming the organic EL element according to the above aspect, for example, red, blue, and green can be separately applied. This makes it possible to form a full-color display organic EL element.

In the above method of forming an organic EL device,
Preferably, in the step of forming the first polymer EL material layer and the step of forming the second polymer EL material layer, the temperature of the substrate is set to the first polymer EL material and the second polymer EL material.
The step of setting the temperature near the glass transition temperature of one of the materials is included. By raising the substrate temperature to near the glass transition point temperature in this way, it is possible to improve the adhesion between the first polymer EL material layer and the second polymer EL material layer. In this case, in the step of setting the temperature of the substrate near the glass transition temperature of one of the first polymer EL material and the second polymer EL material, the temperature of the substrate is set to the first polymer EL material. It is preferable to include a step of setting the temperature near the lower glass transition temperature of the glass transition temperatures of the second polymer EL material. With this configuration, the first
When forming the polymer EL material layer and the second polymer EL material layer, the temperature not lower than the lower glass transition point temperature is not applied, so the first polymer EL material layer having the lower glass transition point temperature. Alternatively, it is possible to prevent the second polymer EL material layer from being deformed.

[0014]

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

First, before describing an embodiment of the method for manufacturing an organic EL element of the present invention, a thin film forming apparatus used in the embodiment will be described. FIG. 1 is a schematic diagram showing the overall configuration of a thin film forming apparatus used in an embodiment of the present invention. As shown in FIG. 1, the thin film forming apparatus 1 used in this embodiment includes a vacuum chamber 2, a heater 3 for heating a substrate, and nozzles 4 and 5. In addition, a high vacuum pump 6 such as a turbo molecular pump is provided in the vacuum chamber 2 via a valve 8.
Are connected. In addition, a low vacuum pump 7 such as a rotary pump is provided in the vacuum chamber 2 via a valve 9.
Are connected. The high vacuum pump 6 and the low vacuum pump 7 connected to the vacuum chamber 2 are provided with valves 8 and 9
Is configured to be automatically switched according to the degree of vacuum of the vacuum chamber 2.

The nozzles 4 and 5 are each formed with a jet port having a diameter of 0.1 mm. Nozzle 4
The polymer material tank 12 is connected via a valve 10, and the nozzle 5 is connected to a polymer material tank 13 via a valve 11. Further, by adjusting (opening / closing) the valves 10 and 11, the amount of the solution containing the polymer EL material ejected in a spray form from the nozzles 4 and 5 can be arbitrarily adjusted. Also, the substrate 1
The nozzle 4 is arranged so as to face the nozzles 4 and 5. The heater 3 is installed on the back surface side of the substrate 14.
In this thin film forming apparatus 1, while the vacuum chamber 2 is kept in a vacuum, a solution containing a polymer EL material is sprayed toward the upper surface of the substrate 14 through a nozzle 4 or 5 to form an organic layer. Form.

Using the thin film forming apparatus 1 described above, organic EL elements according to the following examples and comparative examples were produced.

(Example) FIG. 2 shows an organic EL device according to an example.
FIG. 3 is a structural diagram showing an atomic structure of PVK used as a hole transport layer of an element. FIG. 3 is a structural diagram showing an atomic structure of PAT used as a light emitting layer of the organic EL device according to the example. First, in the embodiment of the present invention, the polymer material tank 12 shown in FIG.
A solution obtained by dissolving (poly vinyl carbazole) in an organic solvent (toluene) at 7 wt% was filled. In addition, the polymer material tank 13 contains PAT (poly 3-alky), which is a polymer EL material emitting red light.
l Thiophene) in an organic solvent (toluene) 5
A solution dissolved at wt% was filled. PVK has the atomic structure shown in FIG. 2, and PAT has the atomic structure shown in FIG.
It has an atomic structure as shown in. PVK is
It is an example of the “first polymer EL material” of the present invention, and PA
T is an example of the "second polymer EL material" of the present invention. Further, toluene is an example of the “first organic solvent” and the “second organic solvent” in the present invention. Then, the substrate 14 on which the transparent electrode made of ITO (indium titanium oxide) was formed was placed horizontally in the thin film forming apparatus 1 shown in FIG. Then, the temperature of the substrate 14 is set to P by the heater 3.
The temperature was raised to near the glass transition temperature of PVK, which is the lower of the glass transition temperature of VK and the glass transition temperature of PAT.

Then, using the high vacuum pump 6, the vacuum chamber 2 was evacuated to a high vacuum level of 133 × 10 −7 Pa. In this state, a solution prepared by dissolving PVK filled in the polymer material tank 12 in an organic solvent (toluene) was sprayed from the nozzle 4 toward the surface of the substrate 14. As a result, while evaporating the organic solvent in a vacuum, a hole transport layer of PVK of 500 n is formed on the transparent electrode on the substrate 14.
It was formed with a thickness of m. In addition, since the organic solvent is actively evaporated during the formation of the hole transport layer, the degree of vacuum is about 133 × 10.
-Decreases to a low vacuum of ³ Pa. As a result, the pump connected to the vacuum chamber 2 is switched from the high vacuum pump 6 to the low vacuum pump 7.

After the hole transport layer made of PVK was formed as described above, the high vacuum pump was used again to evacuate the vacuum chamber 2 to a high vacuum of 133 × 10 −7 Pa. . After this, the polymer material tank 13
A solution prepared by dissolving the PAT filled in the solution in an organic solvent (toluene) was ejected from the nozzle 5 toward the surface of the substrate 14 in a spray form. This allows the PVK on the substrate 14 to evaporate while the organic solvent is being evaporated in a vacuum.
The light emitting layer made of PAT is formed on the hole transport layer made of
It was formed to a thickness of 00 nm.

Finally, after taking out the substrate 14 from the thin film forming apparatus 1, a light emitting layer made of PAT on the substrate 14 is formed.
A Ca cathode was formed to a thickness of 200 nm using a normal vacuum deposition method. In this way, an organic EL device having a polymer type two-layer structure according to the example was produced.

(Comparative Example 1) In Comparative Example 1, a single light-emitting layer made of PAT and having a thickness of 300 nm was formed on the transparent electrode made of ITO on the substrate 14 by spin coating. Thereafter, as in the case of the example, by using a normal vacuum deposition method, a Ca cathode having a thickness of 200 nm is formed on the light emitting layer made of PAT on the substrate 14 to form a polymer-based single layer according to the comparative example 1. Organic E consisting of structure
An L element was produced.

(Comparative Example 2) In Comparative Example 2, a hole transport layer made of PVK was formed to a thickness of 500 nm on the transparent electrode made of ITO on the substrate 14 by a spin coating method, and then this hole transport layer was formed. A light emitting layer made of PAT was further formed on the layer by a spin coating method so as to have a thickness of 300 nm. Then, as in the example, a Ca cathode was formed to a thickness of 200 nm on the light emitting layer made of PAT on the substrate 14 by using a normal vacuum vapor deposition method. In this way, an organic EL element having a two-layer structure of polymer type according to Comparative Example 2 was produced.

(Light-Efficiency Measurement Test) Luminance was measured when a constant current was applied to the organic EL devices produced in the above Examples, Comparative Examples 1 and 2 through the Ca cathode and the transparent electrode. As a result, the luminous efficiency (c
d / A) was measured. The measurement results of the luminous efficiency of the organic EL devices produced in Examples and Comparative Examples 1 and 2 are shown in Table 1 below.
Shown in.

[0025]

[Table 1] It can be seen from Table 1 above that the light emission efficiency of the organic EL elements produced in the examples is higher than the light emission efficiency of the organic EL elements produced in the comparative examples 1 and 2. It is considered that the light emission efficiency of Comparative Example 1 is low because the injection balance of electrons and holes is poor due to the single-layer structure. Further, the light emission efficiency of Comparative Example 2 having a laminated structure is low.
It is considered that this is because the hole transport layer was formed on the hole transport layer by the spin coating method, and thus the hole transport layer was dissolved by the organic solvent at the time of forming the light emitting layer. On the other hand, in the organic EL device according to the example, the substrate 1
By ejecting a solution containing PAT in the form of a spray onto the hole transport layer of No. 4 to form a light emitting layer, the organic solvent contained in the solution is efficiently evaporated. The organic solvent evaporates before the molecular EL material arrives. As a result, it was possible to prevent the underlying hole transport layer from being dissolved,
In the example, it is considered that high luminous efficiency could be obtained.

In the above-mentioned embodiment, PV is used in vacuum.
By forming the hole transport layer made of K and the light emitting layer made of PAT, unlike the case of in air or nitrogen,
It is possible to suppress the scattering of the solution mist of the polymer EL material (PVK and PAT). This allows
A film can be easily formed.

Further, in the above-mentioned embodiment, when the hole transport layer made of PVK and the light emitting layer made of PAT are formed, the temperature of the substrate 14 is set to the glass transition of the polymer EL material PVK used for the hole transport layer. By raising the temperature near the point temperature, the adhesion of the hole transport layer and the light emitting layer can be improved. Further, by setting the temperature of the substrate 14 in the vicinity of the glass transition point temperature of PVK having the lower glass transition point temperature of PVK and PAT, the temperature above the lower glass transition point temperature is not applied, It is possible to prevent the PVK having the lower glass transition temperature from being deformed.

In the above-mentioned embodiment, P having different electric carrier mobilities (Hole mobility and Electron mobility) is used.
By stacking VK and PAT, it is possible to balance the number of electrons injected into the light emitting layer with the application of current and the number of holes injected into the light emitting layer.

Further, in the formation method of the above-mentioned embodiment, since the material which is soluble in the organic solvent can be used for both the hole transport layer and the light emitting layer, the selection range of the material for the hole transport layer and the light emitting layer is narrowed. Nor.

It should be noted that the embodiments disclosed this time are illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

For example, in the above embodiment, the polymer EL
The case where the light emitting layer made of PAT, which is a polymer EL material, is laminated on the hole transport layer made of PVK, which is a material, has been described, but the present invention is not limited to this, and another polymer EL material is laminated. The same effect can be obtained also in the case of doing.

Further, in the above embodiment, the case where PVK and PAT which are polymer EL materials are used is explained, but the present invention is not limited to this, and the polymer EL material is used as a host (main component). It is also applicable to a high molecular weight EL material using a low molecular weight EL material as a guest (dopant).

In the above embodiment, the case where the polymer EL material is laminated in two layers has been described. However, the present invention is not limited to this, and the polymer EL material may be laminated in three or more layers. The same effect can be obtained.

In the above-mentioned embodiment, the monochromatic organic EL element is manufactured in a multi-layer structure, but the present invention is not limited to this. For example, as shown in FIG. By disposing the mask 15 and shifting the position of the mask 15 for separately coloring the pixels, it is possible to separately coat the polymer EL material layers of a plurality of emission colors on the substrate 14. Specifically, after the organic layer having a red emission color is formed in the state where the pixel-selection mask 15 is installed at a predetermined position, the position of the pixel-selection mask 15 is shifted by a predetermined amount. Forming an organic layer having a blue emission color. Further, an organic layer having a green emission color is formed in a state in which the position of the mask 15 for separately painting pixels is shifted by a predetermined amount. This allows the polymer EL material layers having different emission colors of red, blue, and green to be separately coated on the substrate 14. As a result, a full-color display organic EL element can be formed in the process of manufacturing the polymer-type organic EL element having a multilayer structure according to the present embodiment.

[0035]

As described above, according to the present invention, it is possible to easily form a polymer-based multi-layered structure of organic E
A method for forming an L element can be provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing an overall configuration of a thin film forming apparatus used for manufacturing an organic EL element according to an example of the present invention.

FIG. 2 is a structural diagram showing an atomic structure of PVK used as a hole transport layer of an organic EL device according to an example.

FIG. 3 is a structural diagram showing an atomic structure of PAT used as a light emitting layer of an organic EL device according to an example.

FIG. 4 is a schematic diagram showing an overall configuration of a thin film forming apparatus used for manufacturing an organic EL element according to a modified example of this embodiment.

[Explanation of symbols]

14 board Mask for 15-pixel painting

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3K007 AB18 DB03 FA01 FA03                 4D075 AA04 AA53 AA74 AA76 AA84                       AA86 AD08 AD13 AE02 BB23Z                       BB24Z BB56Z BB93Z CA13                       CB08 CB38 DA06 DB13 DC24                       EA07 EB11 EB53

Claims (5)

[Claims] 1. In a vacuum atmosphere, a solution containing a first organic solvent in which a first polymer EL material is dissolved is jetted toward the surface of a substrate in a spray form to remove the first organic solvent in a vacuum. A step of forming a first polymer EL material layer on the substrate while evaporating with, and a solution containing a second organic solvent in which the second polymer EL material is dissolved in the vacuum atmosphere. By ejecting the second organic solvent in a vacuum toward the surface of the substrate, the first polymer system E is evaporated.
And a step of forming a second polymer EL material layer on the substrate on which the L material layer is formed. 2. The first polymer EL material has a first electric carrier mobility, and the second polymer EL material has a first electric carrier mobility different from the first electric carrier mobility. The second polymer EL material layer has an electric carrier mobility of 2.
The method for forming an organic EL device according to claim 1, wherein the organic EL device is formed so as to overlap the material layer. 3. Prior to the step of forming the first polymer EL material layer, the method further comprises the step of installing a mask for separately painting pixels on the front surface of the substrate, wherein the first polymer EL material comprises: Forming a first polymer EL material layer having a first emission color, the second polymer EL material having a second emission color different from the first emission color And the step of forming the second polymer EL material layer, wherein the pixel coating is separately performed when the first polymer EL material layer is formed and when the second polymer EL material layer is formed. The method for forming an organic EL element according to claim 1, further comprising the step of shifting the position of the mask for use. 4. In the step of forming the first polymer EL material layer and the step of forming the second polymer EL material layer, the temperature of the substrate is set to the first polymer EL material and the second polymer EL material layer. The method for forming an organic EL element according to claim 1, comprising a step of setting the temperature near the glass transition point temperature of one of the second polymer EL materials. 5. The temperature of the substrate is set to the first polymer EL
In the step of setting the temperature of the glass transition point of one of the material and the second polymer EL material in the vicinity of the glass transition point temperature, the temperature of the substrate is set to one of the first polymer EL material and the second polymer EL material. The method for forming an organic EL device according to claim 4, comprising a step of setting the temperature near the lower glass transition temperature among the glass transition temperatures.