JP2003168565A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element having organic thin films including a light emitting layer between a pair of electrodes properly prevented from generation of leak and short-circuit of current. <P>SOLUTION: For the organic EL element having the organic thin films 40, 50 and 60 including the light emitting layer 50 between a pair of electrodes 20, 80, all organic materials constructing those organic thin films 40, 50 and 60 are made of materials having volatilizing property when forming a film by a vacuum evaporation method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic EL (electroluminescence) device having an organic thin film including a light emitting layer between a pair of electrodes, and is particularly suitable for application to an in-vehicle display exposed to a high temperature environment. Is.

[0002]

2. Description of the Related Art An organic EL element is self-luminous, has excellent visibility, and can be driven at a low voltage of several V to several tens of V. Therefore, it is possible to reduce the weight including a drive circuit. Therefore, it can be expected to be used as a thin film type display, lighting, backlight, and the like. Further, the organic EL element is also characterized in that it has a wide variety of colors.

[0003]

The basic structure of an organic EL device is such that a plurality of organic thin film laminates are formed on electrodes formed on a substrate and then electrodes are formed on the organic thin film laminate. To do. As a material used for the organic thin film, there are mainly a low molecular weight type using a vacuum deposition method and a high molecular weight type applied on a substrate.

Among these, the materials mainly used in the low-molecular system are, in the case of forming a film by a vacuum vapor deposition method, largely a vaporizable material which is vaporized in a liquid state and a sublimable material which is vaporized in a solid state. It can be classified into and.

In general, many of the tertiary amine compounds used in the hole transport layer exhibit an evaporative property, and 8-hydroxyquinoline aluminum complex (hereinafter referred to as Alq3) used in the light emitting layer, the electron transport layer and the injection layer. ) Is a sublimable material. That is, a general organic EL element has a structure in which an evaporative material and a sublimable material are mixed.

The brightness of such an organic EL element is remarkably lowered at high temperatures, and its durability is insufficient as an in-vehicle display which is often used in a high temperature environment as compared with general consumer products.

Therefore, the material manufacturer develops a material having high heat resistance, that is, a material having a high glass transition point, and the device manufacturer has a material having a glass transition temperature (hereinafter, referred to as Tg) higher than the temperature to which the element is exposed. The method of forming a film is generally used. For example, JP-A-11-378
According to Japanese Patent Laid-Open No. 2 (1994), when the ambient temperature exceeds the Tg of the constituent material, crystallization of the constituent material proceeds, and current leakage or short circuit occurs.

However, according to the experiments and studies by the present inventor, even if the organic thin film of the element is made of a material having a Tg higher than the temperature to which the organic EL element is exposed,
We confirmed by experiments that leaks and shorts could not be solved.

In view of the above problems, it is an object of the present invention to appropriately prevent current leakage or short circuit in an organic EL element having an organic thin film including a light emitting layer between a pair of electrodes.

[0010]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the following experimental studies were conducted.

Specifically, after forming an ITO film (transparent electrode) as an anode on a glass substrate and performing a surface treatment with plasma of a mixture of argon and oxygen, CuPc is formed as a hole injection layer with a film thickness of 50 nm. After forming a film in, the hole transporting layer was formed of triphenylamine tetramer, the light emitting layer was Alq3 to which dimethylquinacridone was added, and the electron transporting layer was Alq3.
3. LiF was sequentially formed on the electron injection layer and Al was formed on the cathode, which was sealed with a sealing can to fabricate an organic EL device. Less than,
This is called a prototype.

In the constituent materials of this prototype, the Tg of the triphenylamine tetramer, which is the hole transport layer, is 140 ° C.,
The lowest Tg. When this prototype was operated under various test temperature conditions, it was confirmed that no light was emitted due to a short circuit of the element at 90 ° C or higher. Also, regarding this non-light emission, both the generation time and the number of generations were accelerated by the temperature rise. I understood. That is, Tg of triphenylamine tetramer
It was found that short circuits and leaks occur at temperatures lower than 140 ° C and 50 ° C.

From this, the cause of the short circuit and the leak occurring when exposed to a high temperature environment is not caused by the crystallization of the amorphous material having Tg, that is, an organic thin film mainly made of a sublimable material, that is, Alq3 with dimethylquinacridone added in the prototype
It was experimentally found that it was caused by the morphological change of the light emitting layer composed of.

An experimental study on the cause of this occurrence will be specifically described. In order to carry out the experiment in a short time, the prototype was left for 2 hours at a temperature of 120 ° C. as an acceleration condition. Hereinafter, this leaving test is called accelerated high temperature standing. In the prototype, voltage-luminance characteristics (V-
I characteristic) was investigated.

The results are shown in FIG. In FIG. 10, the horizontal axis represents the applied voltage and the vertical axis represents the current density, and it is shown that before the accelerated high temperature standing is initial and after the accelerated high temperature standing is 120 ° C. for 2 hours.

FIG. 10 shows a normal VI characteristic in which the current density increases with the increase of the applied voltage with the applied voltage of 4 V as the threshold value before the accelerated high temperature standing.
However, after being left at the accelerated high temperature, there was an abnormality such that a leak or a short circuit occurred and a large amount of current would flow at an applied voltage lower than the threshold value.

In order to further pursue this phenomenon, Alq3, which is an organic thin film made of a sublimable material, that is, an electron transport layer, was observed in the prototype. The observation result by the micrograph is shown in FIG. 11 as a schematic sectional view.

In FIG. 11, CuP is formed on the ITO film 20.
c film 30, triphenylamine tetramer film 40, Alq3
The Alq films 50 made of are sequentially laminated. (A) is left at 85 ° C., (b) is left at 100 ° C., and (c) is 12 ° C.
The state after left at 0 ° C. is shown. As shown in FIG. 11, as the standing temperature increased, many voids B were observed on the surface of Alq3, and it was estimated that the formation of these voids B was related to the leak.

The size of the void B is shown as the void depth D shown in FIG. 11, and a graph showing the temperature dependence of the void depth D is shown in FIG. The size of the void B has temperature dependency, and the extrapolated value of the graph determined that the threshold temperature for forming the void B is 70 ° C.

From the above, when the organic EL device is exposed to a high temperature environment of, for example, 70 ° C. or more, voids are generated on the surface of the organic thin film made of a sublimable material in the device, and the organic thin film is accompanied by the generation of voids. It is considered that the occurrence of the unevenness causes a short circuit or a leak between the electrodes.

Since the voids are generated in the Alq3 portion, with respect to the generation of the voids, a film with many gaps, that is, a low density film is formed in the film due to the material characteristics of the sublimable material Alq3. It is presumed that there is a cause for this, and paid attention to the difference in film forming property between the sublimable material and the vaporizable material.

Next, the difference in film forming property between the sublimable material and the vaporizable material will be described based on the data of the experiment conducted by the present inventor.

The surface of the ITO (transparent electrode) formed on the glass substrate was subjected to a surface treatment with plasma of a mixture of argon and oxygen, and then CuPc was formed to a film thickness of 50 nm.
A triphenylamine tetramer as a hole transport layer was formed thereon with a film thickness of 40 nm.

Next, Alq3 having a film thickness of 40 nm was formed as a light emitting layer of a sublimable material on the hole transport layer.
This is called a sublimation element. On the other hand, on the other hand,
On the hole transport layer, an adamantane derivative having the chemical structural formula shown in FIG.
The film was formed in nm. This is called an evaporative element.

Then, the surface of the CuPc film on ITO,
The surface of the light emitting layer in the sublimation element and the evaporation element was observed with a microscope. The result is shown in FIG. Figure 1
4, (a) is the surface of the CuPc film on ITO,
(B) shows the surface of the light emitting layer of the evaporative material in the evaporative element, and (c) shows the surface of the light emitting layer of the sublimable material in the sublimable element. It is a representation.

As shown in FIG. 14, the light emitting layer made of the adamantane derivative of the evaporative material very well reflects the unevenness of the underlying CuPc film, while the light emitting layer made of the sublimable material Alq3. No unevenness of the base was observed at all.

That is, since the evaporative material covers the uneven shape of the base while covering it, the uneven shape remains, whereas the sublimable material does not follow the uneven shape of the base, and therefore it is considered that the shape of the base does not remain. .

The reason for this is estimated as follows. Evaporable materials adhere to the substrate in very small particles because the material is molten and the intermolecular interactions are broken. On the other hand, the sublimable material adheres to the substrate in a relatively large cluster because the intermolecular interaction is not broken. Therefore, in the sublimable material, voids are easily formed in the film and a low density region is easily formed.

When an element having voids or low density regions formed in such a film is heated, densification progresses due to thermal activation energy. As a result, FIG.
The morphological change, that is, void formation, occurs as shown in
The distance between the electrodes becomes short at the void occurrence part in the film,
It is considered that the electric field is concentrated on the uneven portion of the film caused by the void, which leads to a leak or a short circuit.

It is considered that such a phenomenon that the unevenness of the underlayer in the film formation of the sublimable material does not follow occurs not only in the unevenness of the CuPc film but also in the unevenness of the particles or the ITO film. In particular, particles are a problem that always exists in the manufacturing process.

Therefore, in order to prevent leakage or short circuit caused by exposing such an element to a high temperature, the present inventor evaporates in an organic EL element having an organic thin film including a light emitting layer between a pair of electrodes. Using only flexible materials,
We thought that it was necessary to form an organic thin film with a dense film with high coverage. The present invention is based on this idea.

That is, according to the first aspect of the invention, the organic EL device has the organic thin film including the light emitting layer between the pair of electrodes.
In the device, all the organic materials that make up the organic thin film are
It is characterized in that it has an evaporating property during film formation by a vacuum evaporation method.

According to the present invention, since all the organic materials constituting the organic thin film are made of an evaporative material having an evaporative property during the film formation by the vacuum evaporation method, the occurrence of voids in the high temperature environment as described above is prevented. It is possible to prevent the occurrence of current leakage and short circuit.

As a result of further study, in the invention of claim 1, when the accelerated high temperature storage is performed, it is possible to appropriately prevent current leakage and short circuit, but as shown in FIG. The phenomenon that the voltage-current characteristic (VI characteristic) of the device shifts to the high voltage side under a high temperature environment such as high temperature storage has appeared. This is the same as the case where the luminance is reduced when driving with the same voltage. Further, it may occur partially in the element, and in this case, it is recognized as uneven brightness.

The cause of this shift phenomenon was estimated as follows. A film of a sublimable material having a low density region has a buffer property against thermal stress generated during heating,
That is, while the thermal stress is easily absorbed, the film made of the highly dense vaporizable material has a low buffering property and easily propagates the thermal stress.

In other words, it is considered that the film of the sublimable material is relatively soft and hardly deformed by thermal stress, while the film of the evaporable material is relatively hard and easily deformed by thermal stress. Therefore, it is considered that the thermal stress is propagated to the entire element, the constituent films are deformed, and the transport characteristics and injection characteristics of holes and electrons are deteriorated, and the above shift phenomenon occurs.

Further, even when all the organic thin films in the organic EL element are formed of an evaporative material, an amine material or the like which is an evaporative material is used as the hole transport layer on the anode. Since such a hole transport layer generally has a high amorphous property, a chemical bond is not formed between the hole transport layer and the electrode made of the underlying ITO film, so that the mutual adhesion is low.
The interface between the ITO film and the hole transport layer peels off due to the thermal stress. As a result, it is considered that the charges are less likely to be injected and the above-mentioned shift phenomenon occurs.

When such a shift phenomenon occurs after shipping, it is recognized as a defect such as a decrease in brightness and uneven brightness. Therefore, as one means, it is effective to perform a heat treatment before shipping and to shift it in advance. It is target.

The present inventor has examined improving the adhesion at the interface between the ITO film and the hole transport layer as another measure against this shift phenomenon. The invention according to claim 2 is
It is created for the purpose of suppressing the shift phenomenon while achieving the above-mentioned object of the present invention.

That is, according to the second aspect of the invention, the organic EL having the organic thin film including the light emitting layer between the pair of electrodes.
In the element, one of the pair of electrodes is an ITO film made of indium-tin oxide as a transparent electrode.
An organic metal complex film having crystallinity is formed on the TO film, the organic thin film is formed on the organic metal complex film, and all the organic materials forming the organic thin film are vacuum. It is characterized in that it has an evaporating property when a film is formed by a vapor deposition method.

According to this, like the invention of claim 1, since all the organic materials forming the organic thin film are made of the evaporative material, it is possible to appropriately prevent current leakage and short circuit. it can.

Further, an organic metal complex film is formed on the ITO film, and an organic thin film is formed thereon. In this case, IT
The organic thin film on the O film side is a hole transport layer. Therefore, IT
The organic metal complex film is inserted between the O film and the hole transport layer.

Here, when the organometallic complex film is formed on the ITO film, it is formed epitaxially by a vacuum vapor deposition method or the like, so that it has high adhesion to the ITO film. Further, the organometallic complex film has high crystallinity, that is, high molecular polarity, and also has high adhesion with a hole transport material having molecular polarity.

Therefore, inserting the organometallic complex film between the ITO film and the hole transport layer is very effective in improving the adhesion between the ITO film and the hole transport layer. Is. Thereby, peeling between the ITO film and the hole transport layer due to heating can be suppressed, and the charge injection property between the both can be maintained.

From the above, according to the present invention, it is possible to appropriately prevent the occurrence of current leakage and short circuit while suppressing the shift of the VI characteristic of the element to the high voltage side in a high temperature environment. You can

Further, as the above-mentioned organometallic complex film,
It is preferable to reduce the change in crystallinity in a high temperature environment. As a result, the unevenness generated in the organometallic complex film due to the change in crystallinity in a high temperature environment can be reduced, so that the change of the hole injection characteristics from the ITO film to the hole transport layer via the organometallic complex film. Can be suppressed as much as possible.

From this, the change of the hole injection characteristics from the ITO film to the hole transport layer through the organometallic complex film is suppressed as much as possible, and the VI characteristics of the device under the high temperature environment are changed to the high voltage side. In order to suppress the shift to the minimum, an experimental study was conducted to find out what degree of change in crystallinity of the organometallic complex film is preferable.

The invention according to claim 3 is based on the result of the examination for the change in crystallinity of the organometallic complex film, and the value of the diffraction peak of the organometallic complex film is shown by the X-ray diffraction method. The amount of change in the diffraction peak value due to heating within the operating temperature of the organic EL element is within ± 25% of the diffraction peak value before the heating.

As in the present invention, in the value of the diffraction peak of the crystalline organic metal complex film which appears by the X-ray diffraction method, the amount of change in the diffraction peak value due to heating within the operating temperature of the organic EL element is If it is made as small as within ± 25% of the diffraction peak value of, the shift of the VI characteristic of the element to the high voltage side in a high temperature environment is suppressed at a higher level in addition to the effect of the invention of claim 2. be able to.

Here, as in the invention described in claim 4,
Copper phthalocyanine can be used as the organic complex film.

Further, as in the invention described in claim 5, the organic EL element described in each of the above means sufficiently exhibits its effect even when applied to an element exposed to a high temperature environment of 70 ° C. or higher. be able to.

The reference numerals in parentheses of the above means are examples showing the correspondence with the concrete means described in the embodiments described later.

[0053]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 is a diagram showing a schematic sectional configuration of an organic EL element S1 according to the first embodiment of the present invention.

An anode 20 made of indium-tin oxide (hereinafter referred to as ITO) is formed on a substrate 10 made of transparent glass. A hole transport layer 40 made of triphenylamine tetramer is formed on the anode 20.

On the hole transport layer 40, a light emitting layer 50 made of the adamantane derivative to which dimethylquinacridone is added (see FIG. 13) is formed, and on the light emitting layer 50, an electron made of the adamantane derivative is formed. The transport layer 60 is formed. Further, on the electron transport layer 60, L
An electron injection layer 70 made of iF is formed, and on top of that,
A cathode 80 made of Al is formed.

In this organic EL element S1, the anode 2
By applying an electric field between the anode 0 and the cathode 80, holes are injected from the anode 20 and electrons are injected and transported from the cathode 80 to the light emitting layer 50, respectively, and the electrons and holes are recombined in the light emitting layer 50. However, the light emitting layer 50 emits light by the energy at that time. Then, the emitted light is, for example, taken out from the substrate 10 side and visually recognized.

By the way, the organic EL element S1 of the first embodiment is employed, for example, in a vehicle-mounted display or the like, and its operating temperature is about -40 ° C to 120 ° C.

Here, in the organic EL element S1, the organic thin films 40 to 60 formed between the pair of electrodes 20 and 80.
Are all the organic materials that form the organic thin films 40 to 60 that have evaporation properties during film formation by the vacuum evaporation method, that is, evaporation materials.

According to the present organic EL element S1, all the organic materials forming the organic thin film are made of an evaporative material that has an evaporating property during the film formation by the vacuum evaporation method. It is possible to prevent the problem of void generation under a high temperature environment that occurs in the conventional organic EL element using the sublimable material as shown in (3), and it is possible to appropriately prevent current leakage and short circuit.

A method of manufacturing the organic EL element S1 will be described. An ITO film 20 as an anode is formed on the glass substrate 10 by sputtering or the like, and the surface of the ITO film 20 is subjected to a surface treatment with plasma of a mixture of argon and oxygen, and then a triphenylamine tetramer film is formed. Hole transport layer 4
0 is formed into a film having a thickness of 40 nm by a vacuum evaporation method.

Next, a light emitting layer 50 formed by adding 1% of dimethylquinacridone to the adamantane derivative described above.
Is formed into a film having a thickness of 20 nm by a vacuum evaporation method. On top of that, an electron transport layer 60 composed of an adamantane derivative, Li
An electron injection layer 70 made of F is formed by a vacuum deposition method,
The cathode 80 made of Al is formed. In this way, the organic EL element S1 shown in FIG. 1 is completed. The organic EL element S1 is sealed with a sealing can (not shown).

When the thus-formed organic EL element S1 is left at the accelerated high temperature, that is, at a temperature of 120 ° C. for 2 hours, voids can be prevented from being generated in the organic thin films 40 to 60, and leakage of current in the element S1 and It was possible to properly prevent the occurrence of a short circuit.

(Second Embodiment) By the way, when the organic EL element S1 of the first embodiment is examined, as shown in the above-mentioned "Solution Means", as shown in FIG. The voltage of the element S1 is-
The phenomenon that the current characteristic (VI characteristic) shifts to the high voltage side has appeared. In FIG. 2, the voltage is shifted to the high voltage side by about 2V.

As a solution to this shift phenomenon, a schematic sectional structure of an organic EL element S2 according to a second embodiment of the present invention is shown in FIG. FIG. 3 shows a CuPc (copper phthalocyanine) film 30 as an organic metal complex film having crystallinity between the ITO film 20 as an anode and the hole transport layer 40 in the organic EL device S1 shown in FIG. It is inserted. This CuPc film 30 functions as a hole injection layer.

As in the case of the element S1 shown in FIG. 1, the manufacturing method is as follows. After forming the ITO film 20 on the substrate 10 and subjecting the surface of the ITO film 20 to a surface treatment with plasma of a mixture of argon and oxygen, A CuPc film 30 as a hole injection layer is formed to a film thickness of 50 nm by a vacuum evaporation method, and then,
Similarly to the above, the hole transport layer 40, the light emitting layer 50, the electron transport layer 6
0, the electron injection layer 70, and the cathode 80 may be sequentially formed.

The organic EL element S according to the second embodiment
2 was subjected to the accelerated high temperature storage, and as a result, as in the organic EL element S1 shown in FIG.
Voids can be prevented in the device S
There was no current leakage or short circuit in No. 2.
In addition, the organic EL device according to the present embodiment can also be left at an accelerated high temperature.
In the element S2, the shift of the VI characteristic to the high voltage side could be significantly reduced.

[Study of X-Ray Diffraction Peaks of Organometallic Complex Film] Further, in the organic EL element S2 of the second embodiment shown in FIG. 3, as a preferred mode, X of CuPc film 30 which is an organometallic complex film is used. In the value of the diffraction peak that appears by the line diffraction method, the amount of change in the diffraction peak value due to heating within the operating temperature (for example, −40 ° C. to 120 ° C.) of the organic EL element S2 is ± 25% of the diffraction peak value before the heating. It is desirable that it is within the range.

As described above, in the value of the diffraction peak of the CuPc film 20 as the crystalline organic metal complex film, which appears by the X-ray diffraction method, the amount of change in the diffraction peak value due to heating within the operating temperature of the organic EL element S2. Is smaller than ± 25% of the diffraction peak value before heating, in addition to the effect of the present embodiment described above, the shift of the VI characteristic of the element to the high voltage side in a high temperature environment is higher. Can be suppressed.

The grounds for the preferable form of the organic EL element S2 of the second embodiment will be described below.

In this organic EL element S2, the ITO film 20 is formed on the glass substrate 10, the surface of the ITO film 20 is subjected to a surface treatment by plasma of a mixture of argon and oxygen, and then a hole is formed by a vacuum deposition method. CuPc as injection layer
The film 30 is formed with a film thickness of 50 nm.

CuPc formed by such a manufacturing method
The film 30 is left at the accelerated high temperature (120 ° C., 2 h).
r) was performed. C before and after the accelerated high temperature standing
The crystalline state of the uPc film 30 was analyzed by X-ray diffraction. The result is shown in FIG.

As shown in FIG. 4, in the diffraction peak,
The peak occurring at 2θ = 6.68 ° is the CuPc film 3
0 is derived from the crystal structure of the (200) plane parallel to the substrate 10, and this diffraction peak is hereinafter referred to as a CuPc crystallinity peak. In FIG. 4, in this CuPc crystallinity peak, the solid line shows the peak before the accelerated high temperature standing, that is, the initial peak, and the broken line shows the peak after the accelerated high temperature standing, that is, the peak after 120 ° C. for 2 hours. is there.

The larger the integrated value of this CuPc crystallinity peak value, that is, the higher the peak value, the more CuPc
It shows that the crystallinity of the film 30 is high. That is, 12
The peak value (integral value) is changed to 1.5 times as much as that before the accelerated high temperature standing at 0 ° C. and 2 hours.

From this, the present inventor has found that in the organic EL element S2 of the second embodiment, the hole injection layer of Cu is used.
After the hole transport layer 40, the light emitting layer 50, the electron transport layer 60, the electron injection layer 70, the cathode 80 and the like are formed on the Pc film 30,
That is, the change in the crystalline state of the CuPc film 30 in the light emitting element form causes a VI characteristic shift in a high temperature environment, which is a major cause of a decrease in brightness and uneven brightness. I thought there was.

Therefore, it is preferable that the above-mentioned organometallic complex film 30 is originally one having high crystallinity so that the change in crystallinity under a high temperature environment is small. As a result, the unevenness generated in the organometallic complex film 30 in a high temperature environment can be reduced, so that the ITO film 2
Since the change of the hole injection characteristics from 0 to the hole transport layer 40 via the organometallic complex film 30 can be suppressed as much as possible, it was thought that the shift of the VI characteristics can be suppressed to the minimum as a result.

[High crystalline Cu by heat treatment of ITO film]
Realization of Pc film] CuPc film 30 having such high crystallinity
In the organic EL element S2 shown in FIG. 3, the ITO film 20 is formed on the glass substrate 10 and then the ITO film 2 is formed.
It can be realized by irradiating with ultraviolet rays while heating the surface of No. 0 to 300 ° C., and then forming the CuPc film 30 and thereafter. Hereinafter, the treatment for the ITO film 20 will be performed with UV-30.
This is called 0 ° C treatment.

The CuPc film 30 formed on the ITO film 20 subjected to the UV-300 ° C. treatment was subjected to X-ray diffraction before and after the above accelerated high temperature exposure (120 ° C., 2 hr). Analysis was carried out. As a result, 2θ = 6.6
It was confirmed that the CuPc crystallinity peak occurring at 8 ° had a ratio of the value after the standing treatment was 1.02, which was very small compared to the value before the standing treatment. In other words, UV-300
It is shown that the crystallinity of the CuPc film 30 at the time of film formation was extremely high and stable when the temperature treatment was performed.

Further, the organic EL element S2 shown in FIG.
When manufactured by performing V-300 ° C. processing, the element S
About 2 sealed in a sealing can at 120 ° C for 2 hours
As a result of confirming under the above-described accelerated high temperature storage condition, there was almost no shift in the VI characteristic, and no decrease in brightness or uneven brightness was observed. Of course, neither current short circuit nor leakage occurred.

That is, when the organic EL element S2 of the second embodiment shown in FIG. 3 is manufactured by performing the UV-300 ° C. treatment, the above-described preferable form can be realized. That is, at the CuPc crystallinity peak of the CuPc film 30 that is an organometallic complex film, the amount of change in the CuPc crystallinity peak value due to heating within the operating temperature of the organic EL element S2 (for example, −40 ° C. to 120 ° C.) is determined by the heating. It can be within ± 25% of the previous CuPc crystallinity peak value.

Then, the organic EL manufactured thereby
The element S2 can prevent short-circuiting and leakage of current within the operating temperature and realize good luminance characteristics. Such an effect is obtained by the UV-3 in the above manufacturing method.
Although it is due to the treatment at 00 ° C., the mechanism for realizing the effect by the treatment will be described in more detail next.

[Study of Realization Mechanism of Highly Crystalline CuPc Film] In order to efficiently inject holes from the ITO film 20 as an anode into the CuPc film 30 as a hole injection layer, the surface of the ITO film is cleaned. It has long been known that processing is important.

However, it is generally evaluated by the ionization potential (Ip) of the surface of the ITO film after cleaning, and the present inventor considers the hole injection characteristics and the like and immediately after cleaning the ITO film 20. It was judged that there was no problem if the Ip of 20 was 5.5 eV or less.

However, according to the study by the present inventors, Ip is 5.45 eV when the plasma cleaning treatment of argon and oxygen (ratio 1: 1) is performed for 5 minutes, and Ip when only the UV treatment is performed for 20 minutes. 5.5 ev, the above UV-300 ° C. treatment is 2
The Ip at 0 minutes was 5.46 ev, which was not a big difference.

Nevertheless, the result of the element which has been subjected to the UV-300 ° C. treatment is that the VI characteristic shift after being left at a high temperature can be suppressed to the minimum, and the luminance reduction and the luminance unevenness do not occur. Got That is, it is shown that the crystallinity of the organometallic complex film 30 formed on ITO is not determined only by Ip but also exists in other factors.

Therefore, in the UV-300 ° C. treatment, since heat treatment is involved, attention is paid to the water content on the ITO surface, and the thermal desorption method (thermal desorption method) is used.
The amount of water generated at each temperature, that is, the amount of water desorbed from the surface of the ITO film 20 was measured by an n method (hereinafter referred to as TDS method).

FIG. 5 shows that the ITO film 2 is formed on the glass substrate 10.
It is the measurement result by the TDS method immediately after forming 0. This TDS spectrum has a molecular weight, that is, M
The spectrum of H ₂ O in which / z is 18 or OH in which z is 17 is measured.

From the results shown in FIG. 5, it can be seen that there are peaks of water desorption at 70 ° C. and 330 ° C. The former is water that is present as adsorbed water that is physically adsorbed on the surface of the ITO film 20, and the latter is water that is present as bound water that is chemically bonded to ITO on the surface of the ITO film 20. it is conceivable that. Therefore, the bound water on the surface of the ITO film 20 is C
It is considered to be one of the factors that determine the crystallinity during the formation of the uPc film 30.

Actually, the ITO film 2 is formed on the glass substrate 10.
FIG. 6 shows the TDS spectrum when the film of 0 was heat-treated at a temperature of 300 ° C. in a nitrogen atmosphere.
When this heat treatment is not performed, that is, T shown in FIG.
Compared to the DS spectrum, the peak value at 330 ° C is 50
% Has been reduced. Furthermore, FIG. 7 shows a TDS spectrum when this heat treatment at 300 ° C. is performed in vacuum. In this case, the peak at 330 ° C. is hardly recognized.

30 in these nitrogen atmospheres or in vacuum
The sealed element obtained by sealing the organic EL element S2 of the second embodiment, which is created by performing the heat treatment at 0 ° C., with a sealing can is
As a result of confirming under the above accelerated high temperature standing condition of 0 ° C. and 2 hours, there was almost no shift in the VI characteristic, and no decrease in brightness or uneven brightness was observed. In addition, no short circuit or leakage of current occurred.

From the above, the ITO film 2 is formed on the substrate 10.
In the manufacturing method of the method for manufacturing an organic EL element, in which 0 is formed and an organic metal complex film having crystallinity such as the CuPc film 30 is formed on the ITO film 20, the organic metal complex film 30
It is effective to desorb the bound water on the surface of the ITO film 20 before forming the film.

As a result, it is possible to reduce the amount of bound water as well as the amount of adsorbed water on the surface of the ITO film 20 which is the base of the organometallic complex film 30 having crystallinity. Therefore, the crystallinity of the formed organometallic complex film 30 can be made high, current short-circuit and leak can be prevented within the operating temperature, and the VI characteristic shift can be suppressed to reduce the luminance and the luminance unevenness. Can be eliminated.

Here, as shown in FIG. 6, in the TDS spectrum due to water on the surface of the ITO film 20 after the desorption process, the peak value of bound water around 330 ° C.
The peak value of bound water on the surface of the ITO film 20 before the desorption treatment is preferably within 50% of the peak value.

Further, as shown in FIG. 7, the TDS due to water on the surface of the ITO film 20 after the desorption process is performed.
It is even more preferable to eliminate the bound water peak around 330 ° C. in the spectrum.

In order to reduce the bound water existing on the surface of the ITO film 20 to within about 50%, the CuPc film 3
Before forming a crystalline organic material such as 0 on the ITO film 20, the heat treatment temperature of the ITO film 20 is preferably set to 250 ° C. or higher.

[Achievement of Highly Crystalline CuPc Film by Controlling CuPc Film Deposition Temperature] In order to realize the above-described preferable form in the organic EL element S2 of the second embodiment shown in FIG. 3, an ITO film is required. Other than the case of performing the UV-300 ° C. treatment or the heat treatment at 250 ° C. or higher on 20 to manufacture, it can be realized by increasing the material temperature at the time of forming the CuPc film 30.

The grounds for this will be described with a specific example. The ITO film 20 as an anode is formed on the glass substrate 10.
To form a film. In this glass substrate with an ITO film, I
On the TO film 20, a CuPc film 30 serving as a hole injection layer and serving as an organometallic complex film is formed at a material heating temperature of 420 ° C. by a vacuum vapor deposition method. This will be referred to as a 420 ° C. film-formed product.

On the other hand, in the glass substrate with the ITO film,
A CuPc film 30 is formed on the ITO film 20 at a material heating temperature of 520 ° C. by a vacuum vapor deposition method. This is 520 ℃
We will call it a film-formed product.

After that, in each of the 420 ° C. film-formed product and the 520 ° C. film-formed product, the hole transport layer 40, the light emitting layer 50, the electron transport layer 60, the electron injection layer 70, and the cathode are formed on the CuPc film 30 as described above. 80 is sequentially formed into a film to manufacture the organic EL element S2 of the second embodiment.

Here, with respect to the 420 ° C. film-formed product and the 520 ° C. film-formed product, the above accelerated high temperature storage (120
C by X-ray diffraction analysis before and after the treatment at 2 ° C. for 2 hours.
The ratio of the uPc crystal peak values was investigated. Further, the shift of the VI characteristics before and after the above-mentioned accelerated high temperature standing after sealing with a sealing can was examined.

In the case of the 420 ° C. film-formed product, the CuPc crystallinity peak ratio is about 1.5 (see FIG. 4 above), and the shift amount is about 2
On the other hand, in the case of the 520 ° C. film-formed product, the ratio of the CuPc crystallinity peak was about 1.15, and the shift amount was about 1 V, which was favorable.

That is, according to this manufacturing method, CuPc
The crystallinity of the film 30 is very high and stable, and the organic EL element S2 of the second embodiment manufactured by the film 30 can prevent current short circuit and leakage within the operating temperature and shift the VI characteristic. It is possible to suppress the deterioration of brightness and uneven brightness.

[Relationship between CuPc Crystalline Peak Ratio and VI Characteristic Shift Amount] Here, the accelerated high temperature standing (120
The relationship between the ratio of the CuPc crystallinity peak and the VI characteristic shift amount before and after (° C., 2 hr) is summarized. The same relationship is shown as a graph in FIG. 8, and the data that is the basis of FIG. 8 is shown in FIG. In FIGS. 8 and 9, the CuPc crystallinity peak value ratio is described as “X-ray diffraction peak ratio”, and the VI characteristic shift amount is described as “VI shift”.

As described above, the ratio of the CuPc crystallinity peak value is the ratio of the integral value of the CuPc crystallinity peak after the accelerated high temperature standing to the integrated value of the CuPc crystallinity peak before the accelerated high temperature standing. Is larger than 1, the crystallinity of the CuPc film is high by accelerating high temperature standing, and less than 1 is low.

The V-I characteristic shift amount is the V-characteristic after the accelerated high-temperature standing with reference to the VI characteristic before the accelerated high-temperature standing.
It shows how many volts the I characteristic has shifted.
Specifically, in FIG. 4, since the CuPc crystallinity peak ratio was 1.5 and the crystallinity changed significantly, as shown in FIG. 2, the VI characteristic shift amount was as large as about 2V. Was becoming.

In addition, in FIG. 9, "cleaning pretreatment conditions"
Is the ITO film 20 formed on the glass substrate 10
It is a condition for cleaning before forming the Pc film 30, and “plasma” is the plasma cleaning process of the above-mentioned argon and oxygen, “UV”.
“300 ° C.”, “UV250 ° C.”, and “UV150 ° C.” mean the treatment in which the ultraviolet irradiation was performed at each temperature. Further, in FIG. 9, “material heating temperature” is the material temperature at the time of forming the CuPc film 30.

The organic E shown in the graph of FIG. 8 has an X-ray diffraction peak ratio of about 1.22 and a VI shift of 1.6V.
The luminance unevenness was not clearly recognized in the L element.
However, in the organic EL device having the X-ray diffraction peak ratio of about 1.5 and the VI shift of about 2.0 V, the uneven brightness was clearly recognized.

From the above, it can be said that the threshold value of the X-ray diffraction peak ratio is about 1.3 and the threshold value of the VI shift is about 1.6 V in view of the commercial property.

That is, as described above, at the CuPc crystallinity peak, the organic EL of the second embodiment shown in FIG.
By keeping the amount of change in the CuPc crystallinity peak value due to heating within the operating temperature (for example, −40 ° C. to 120 ° C.) of the element S2 within ± 25% of the CuPc crystalline peak before heating, the operating temperature The shift of the VI characteristic can be suppressed to the minimum within the above range, and the decrease in brightness and the uneven brightness can be eliminated.

Further, from FIG. 9, if the heat treatment temperature of the ITO film 20 is not 300 ° C. but is 250 ° C. or higher, the ITO serving as the base of the CuPc film 30 which is the organometallic complex film is formed.
It can be seen that the adsorbed water and the bound water can be effectively reduced on the surface of the film 20, and the organometallic complex film having enhanced crystallinity can be formed.

The change in the CuPc crystallinity peak value due to heating may or may not decrease in the increasing direction. That is, the amount of change may be + 25% or less or −25% or more of the CuPc crystallinity peak before heating, and as shown in FIG. 8, the X-ray diffraction peak ratio is 0.
It may be 75 or more. For example, the X-ray diffraction peak ratio is 0.6
In the case of 8, the VI shift was 2.8 V, and the uneven brightness was recognized.

In the present invention, in the organic EL element having the organic thin film including the light emitting layer between the pair of electrodes, the organic thin film means a hole injection layer, a hole transport layer and a light emitting layer made of an organic material. An electron transport layer, an electron injection layer, an electron block layer, or the like may be used.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a shift phenomenon of voltage-current characteristics of the organic EL element according to the first embodiment under a high temperature environment.

FIG. 3 is an organic E according to a second embodiment of the present invention for solving the voltage-current characteristic shift phenomenon shown in FIG.
It is a schematic sectional drawing of an L element.

FIG. 4 is a diagram showing X-ray diffraction spectra of an organometallic complex film in the organic EL device shown in FIG. 3 before and after being left at a high temperature of 120 ° C. for 2 hours.

FIG. 5: T immediately after forming an ITO film on a glass substrate
It is a figure which shows a DS spectrum.

FIG. 6 is a diagram showing a TDS spectrum of a surface of an ITO film when heat-treated at a temperature of 300 ° C. in a nitrogen atmosphere.

FIG. 7 is a diagram showing a TDS spectrum of the surface of an ITO film when heat-treated at a temperature of 300 ° C. in a vacuum atmosphere.

FIG. 8 is a diagram showing the relationship between the ratio of the CuPc crystallinity peak and the VI characteristic shift amount before and after the high temperature treatment of 120 ° C. and 2 hours.

9 is a chart showing the data that is the basis of FIG. 8. FIG.

FIG. 10: 100 ° C., 12 h in a prototype of the present inventor
It is a figure which shows the VI characteristic before and after leaving to stand at high temperature by r.

FIG. 11: Al as a sublimable material in the prototype
It is a schematic sectional drawing based on the observation result about the organic thin film which consists of q3.

12 is a graph showing the temperature dependence of the depth of the void shown in FIG.

FIG. 13 is a diagram showing a chemical structural formula of an adamantane derivative which is an evaporative material.

FIG. 14 is a diagram showing the surface of a CuPc film on ITO, the surface of a light emitting layer made of a sublimable material, and the surface of a light emitting layer made of an evaporative material based on the result of microscopic observation.

[Explanation of symbols]

10 ... Substrate, 20 ... Anode (ITO film), 30 ... Organometallic complex film (CuPc film), 40 ... Hole transport layer, 50 ... Light emitting layer, 60 ... Electron transport layer, 70 ... Electron injection layer, 80 ... Cathode .

Claims (5)

[Claims] 1. An organic EL device having an organic thin film including a light emitting layer between a pair of electrodes, wherein all the organic materials forming the organic thin film are vaporizable during film formation by a vacuum deposition method. An organic EL device characterized in that 2. An organic EL device having an organic thin film including a light emitting layer between a pair of electrodes, wherein one of the pair of electrodes is made of indium as a transparent electrode.
An ITO film made of tin oxide, an organic metal complex film having crystallinity is formed on the ITO film, and the organic thin film is formed on the organic metal complex film. The organic EL element is characterized in that all the organic materials forming the organic thin film have evaporation properties during film formation by a vacuum evaporation method. 3. In the value of the diffraction peak of the organometallic complex film that appears by the X-ray diffraction method, the amount of change in the diffraction peak value due to heating within the operating temperature of the organic EL element is the diffraction peak value before the heating. It is within ± 25% of the above. 3. The organic EL element according to claim 2, wherein 4. The organic E according to claim 2, wherein the organic complex film is made of copper phthalocyanine.
L element. 5. The organic EL element according to claim 1, which is exposed to an environment of 70 ° C. or higher.