JP4087645B2 - ITO film, manufacturing method thereof, and organic EL element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ITO film, a manufacturing method thereof, and an organic EL element.
[0002]
[Prior art]
An ITO (Indium Tin Oxide) film made of a solid solution of tin oxide and indium oxide is widely used as an electrode for various display devices because of its low specific resistance and easy etching.
[0003]
An example of such a display device is an organic EL (Electroluminescence) element.
[0004]
For example, the organic EL element 1a shown in FIG. 1 has a structure in which an anode electrode 6a is formed on a glass substrate 2a, an element body 4a is formed on the anode electrode 6a, and a cathode electrode 7a is formed on the element body 4a. Have. In this case, one or both of the anode electrode 6a and the cathode electrode 7a are formed of a transparent electrode according to the light emission form of the element. And the above-mentioned ITO film | membrane is used suitably as a transparent electrode. Here, the element body 4a is a layer made of an organic substance containing a light emitter such as a phosphor as a light emitting material component, and further includes a hole transport material and an electron transport material when used as a single layer.
[0005]
In the organic EL element 1a, for example, holes are injected from the anode electrode 6a and electrons are injected from the cathode electrode 7a by applying a voltage between the anode electrode 6a and the cathode electrode 7a. In the element body 4a, light and light are emitted by recombination of electrons and holes of the molecules of the light emitting material component. The light emitted from the element body 4a is extracted outside from the glass substrate 2a side in FIG.
[0006]
By the way, EL elements are very sensitive to moisture. In particular, the organic EL element has a significantly shorter lifetime of the light emitting layer than the inorganic EL element, and the deterioration of the light emitting layer is accelerated when it contains moisture. For this reason, it is essential to prevent moisture (water vapor) from entering the light emitting layer of the organic EL element.
[0007]
In the case of the organic EL element 1a, the element body 4a is covered with a sealing metal can 5a and sealed with a desiccant 5b.
[0008]
However, since the organic EL element 1a has the glass substrate 2a and the sealing metal can 5a, downsizing and weight reduction of the element are hindered.
[0009]
Therefore, for example, a thin resin substrate 2b is used like the organic EL element 1b shown in FIG. 2, and in order to prevent moisture from entering the element body 4b through the resin substrate 2b, the resin substrate 2b and the anode electrode are used. A protective film (water vapor permeation preventive film, moisture proof barrier film) 8a for preventing the permeation of moisture is provided between the cathode electrode 7b and a protective film 8b for sealing. As such a prevention film 8a or sealing protective film 8b, a silicon oxide film, an aluminum oxide film or the like is widely used. Further, when the prevention film 8a or the sealing protective film 8b requires transparency, silicon nitride is also used. The organic EL element 1b using the resin substrate 2b also has an advantage as a flexible element.
[0010]
For example, in the case of a top emission type that emits emitted light from the upper surface of the cathode electrode 7c as in the organic EL element 1c shown in FIG. 3, the anode electrode 6c and the element body 4c arranged in pixel units of the display device. A partition wall 9a partitions the cathode electrode 7c from a transparent ITO film, a transparent sealing film 8c is formed on the cathode electrode 7c, and a transparent sealing layer 8d is formed on the sealing film 8c. Has also been formed. In FIG. 3, reference numeral 2c indicates a glass substrate, and reference numeral 9b indicates a drive circuit including TFTs. As for the cathode electrode or the anode electrode, a metal film typified by aluminum is usually used when it is not used as an electrode on the side where emitted light is emitted, that is, an electrode on the side opposite to the light emission.
[0011]
[Problems to be solved by the invention]
However, the various structures for preventing permeation of water vapor do not necessarily provide sufficient water vapor permeation prevention. In addition, if sufficient water vapor permeation preventive properties are to be ensured, various structures for preventing water vapor permeation will be complicated, and miniaturization of the device will be hindered.
[0012]
The present invention has been made in view of the above problems, and an object thereof is to provide an ITO film having good water vapor permeation-preventing property, a method for producing the same, and an organic EL element provided with the ITO film.
[0013]
[Means for Solving the Problems]
As a result of intensive studies on the water vapor permeation prevention structure, the present inventor, for example, can provide a water vapor permeation prevention structure to a transparent electrode made of an ITO film, which is an essential component of an organic EL element. I realized that I could expect it. When the ITO film was examined by focusing on the crystal structure, when the ITO film has a high crystallinity, a small specific resistance can be obtained, but it does not function as a water vapor permeation preventive film. It was found that a film having a good water vapor permeation preventing property can be obtained although the specific resistance is increased when it is lowered. The present invention has been made based on this finding. The level of crystallinity of the ITO film can be compared by the magnitude of the peak on the (222) plane by X-ray diffraction (XRD).
[0014]
The ITO film according to the present invention includes a layer having a high crystallinity structure and a layer having a low crystallinity structure.
[0015]
Further, the ITO film according to the present invention is characterized in that it includes one or two or more sets of laminated structures composed of a layer having a high crystallinity structure and a layer having a low crystallinity structure.
[0016]
In addition, the ITO film according to the present invention is formed by forming a structure with high crystallinity and a structure with low crystallinity at both ends in the thickness direction of the film and continuously changing the structure in the thickness direction. It is characterized by.
[0017]
With the above configuration of the present invention, it is possible to obtain an ITO film having a low specific resistance equivalent to that of a conventional ITO film having a homogeneous structure with high crystallinity and also having a good water vapor permeation preventing property.
[0018]
The ITO film according to the present invention is formed on a resin substrate or a resin sheet and has a two-layer structure of a layer having a high crystallinity structure and a layer having a low crystallinity structure. When the side of the layer having a structure is formed toward the resin substrate or the resin sheet, an ITO film having a higher water vapor permeation prevention property can be obtained.
[0019]
An ITO film manufacturing method according to the present invention is the above-described ITO film manufacturing method, wherein a sputtering method or an ion plating method is used, and the pressure during film formation is changed during the film formation process, or the substrate is applied to the substrate. The bias potential to be applied is changed during the film formation process, or the substrate temperature is changed during the film formation process. Alternatively, the ion plating method is used to load the deposition material and generate the Haas potential to which a voltage is applied. It is characterized by being changed in the film process.
[0020]
With the above configuration of the present invention, an ITO film having the above effects of the present invention can be suitably obtained.
[0021]
In addition, an organic EL element according to the present invention includes the above ITO film as an electrode.
[0022]
With the above configuration of the present invention, the water vapor permeation preventing property of the element can be improved, or the water vapor permeation preventing structure can be simplified.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment (hereinafter referred to as this embodiment) of an ITO film, a method for producing the same, and an organic EL element according to the present invention will be described below with reference to the drawings.
[0024]
First, an organic EL element having an ITO film and an ITO film according to this embodiment will be described with reference to FIGS.
[0025]
As shown in FIG. 4, the organic EL element 10 according to the present embodiment includes a substrate 12, an anode electrode 14 formed on the substrate 12, and an element body 16 formed on the anode electrode 14. And a cathode electrode 18 formed on the element body 16. The element body 16 includes a hole transport layer, an electron transport layer, and a light emitting layer (not shown).
[0026]
The substrate 12 is, for example, a resin substrate or a resin film made of polycarbonate resin. Such a substrate 12 has moisture (water vapor) permeability unlike a glass substrate or the like. For this reason, in order to prevent the deterioration of the element body 16 due to the ingress of moisture, in the prior art, a moisture permeation preventive film is provided on the substrate 12 to provide the moisture permeation preventive property. In the case of a resin film, the substrate 12 is formed to a thickness of about 0.1 to 0.5 mm, for example. Since an element using such a substrate 12 is flexible, it is preferable.
[0027]
The anode electrode 14 is an ITO film according to the present embodiment, which is made of an ITO material and has transparency. As shown in the partially enlarged view of FIG. 5, the anode electrode 14 has a two-layer structure including a first layer 22 formed on the substrate 12 and a second layer 20 formed on the first layer 22. . As shown in the X-ray diffraction diagram (XRD diagram) of FIG. 6, the first layer 22 is a layer having a low crystallinity structure with a small peak on the (222) plane. On the other hand, as shown in the X-ray diffraction diagram of FIG. 7, the second layer 20 is a layer having a high crystallinity structure with a large peak on the (222) plane. 6 and 7, the large peak near the diffraction angle (2θ) of 20 ° is derived from the substrate 12 on which the ITO film is formed. The first layer 22 and the second layer 20 are each formed to a thickness of 50 nm, for example.
[0028]
The element body 16 is a layer made of an organic material containing a light emitter such as a phosphor, and is formed to a thickness of about 100 nm, for example. As described above, the element body 16 has a property that its lifetime is short and deterioration is accelerated by the ingress of moisture.
[0029]
The cathode electrode 18 is an ITO film according to this embodiment having a two-layer structure of a first layer and a second layer similar to the anode electrode 14 (the illustration of the two-layer structure is omitted; see FIG. 5).
[0030]
The organic EL element 10 configured as described above is, for example, a top emission type similar to that shown in FIG. In this case, the anode electrode 14 may be replaced with an ITO material and formed of a metal material that is opaque and has a high reflectance. Further, in the case of a bottom emission type in which light emitted from the organic EL element 10 is emitted from the substrate 12 side, that is, when the lower electrode in FIG. 4 is an anode electrode and the upper electrode is a cathode electrode, the upper electrode is Instead of the ITO material, it may be formed of a metal material that is opaque and has a high reflectance.
[0031]
The manufacturing method of the ITO film as the transparent electrode according to the above embodiment will be described.
[0032]
The ITO film can be manufactured using various film forming methods, but can be preferably manufactured by a sputtering method or an ion plating method. In this embodiment, an ITO film is formed by the latter ion plating method.
[0033]
An outline of the structure and operation of the ion plating apparatus used in this embodiment will be described with reference to FIG.
[0034]
In the ion plating apparatus 24 shown in FIG. 8, a plasma beam PB is irradiated from a pressure gradient type plasma gun 26 into a vacuum container (film formation chamber) 28. A hearth 30 is disposed below the vacuum container (film formation chamber) 28, and a film formation material rod 32 made of an ITO material is inserted into the through hole TH of the hearth 30. The plasma beam PB is incident on the hearth 30. At this time, the plasma beam PB is reliably guided to the hearth 30 by controlling the hearth 30 to an appropriate positive potential. The film forming material rod 32 heated by the plasma beam PB is gradually pushed up by the supply device 34 while the upper end is evaporated.
[0035]
A substrate W transported by the transport mechanism WH is disposed on the upper portion of the vacuum container 28 so as to face the hearth 30. The evaporated film forming material particles are ionized in the plasma beam PB, and the ionized film forming material particles adhere to the surface of the substrate W, whereby the substrate W is formed.
[0036]
In FIG. 8, permanent magnets and coils are arranged around the hearth 30, thereby forming a cusp-like magnetic field and controlling the direction of the plasma beam PB incident on the hearth 30.
[0037]
The conditions for forming the ITO film of the anode electrode 14 or the cathode electrode 18 using the ion plating apparatus 24 will be described.
[0038]
For example, under the conditions that the potential of the hearth 30 is 17.7 eV, the Ar gas flow rate is 120 sccm, the O ₂ gas flow rate is 10 sccm, the deposition pressure is 3.0 mTorr (0.39 Pa), and the substrate temperature is room temperature, An ITO film is formed on the top. Then, when the thickness of the ITO film reaches 50 nm, that is, when the first layer 22 having a thickness of 50 nm is formed, the potential of the hearth 30 is raised to 23.3 eV among the above film formation conditions, Except for lowering the deposition pressure to 1.0 mTorr (0.13 Pa), the deposition was continued with the other conditions kept constant, and when the total thickness of the ITO film reached 100 nm, that is, a second film having a thickness of 50 nm. When the layer 20 is formed, the ITO film formation is completed. In these film formation conditions, the film formation pressure is adjusted to change the plasma density when the potential of the hearth 30 is changed. From the viewpoint of controlling the crystal structure, the film formation pressure is substantially adjusted. Is equivalent to changing only the potential of the hearth 30 and changing only the deposition pressure.
[0039]
The measurement results of the specific resistance and water vapor permeability of the ITO film according to this embodiment described above will be described with reference to the table of FIG. In FIG. 9, Example 1 is an ITO film according to the present embodiment. Reference examples 1 and 2 are ITO films prepared for confirming the effects of the present embodiment. Reference Example 1 is a highly crystalline ITO film prepared with a Haas potential of 23.3 eV and a film formation pressure of 1.0 mTorr (0.13 Pa) to a thickness of 100 nm. Reference Example 2 has a Haas potential of 17.7 eV, This is an ITO film with low crystallinity prepared to a thickness of 100 nm at a deposition pressure of 3.0 mTorr (0.39 Pa). The specific resistance was measured by JIS R1637 (4 probe method), and the water vapor permeability was measured by JIS K7129A (humidity sensitive sensor method). Further, the water vapor permeability is a value in a state including a substrate, including Example 2 described later.
[0040]
From FIG. 9, the ITO film according to this embodiment of Example 1 has a specific resistance smaller than that of Reference Example 2 having a large specific resistance, while the ITO film of Reference Example 1 having a large water vapor permeability. It can be seen that the water vapor permeability is smaller and similar to the ITO film of Reference Example 2.
[0041]
The ITO films (the anode electrode 14 and the cathode electrode 18) according to the present embodiment have a low specific resistance equivalent to that of a conventional ITO film having a high crystallinity and a uniform structure, and also have a good water vapor permeation preventing property. . In addition, the organic EL element 10 according to the present embodiment having the ITO film according to the present embodiment as a transparent electrode can improve the water vapor permeation prevention property or simplify the water vapor permeation prevention structure. Can be achieved.
[0042]
Note that, instead of the ITO film as the transparent electrode according to the present embodiment, tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), or zinc oxide (ZnO) is used as the material of the transparent electrode. A conductive film formed by depositing the above material and forming a structure including a film with high crystallinity and a film with low crystallinity in the same manner as the ITO film according to this embodiment may be used as the transparent electrode.
[0043]
In the film forming method according to this embodiment, the crystallinity of the first layer and the second layer is changed by changing the hearth potential as the film forming condition in the process of forming the ITO film. Changed film quality. That is, by increasing the pressure at the time of film formation, the Haas potential is lowered to reduce the incident energy of the film-forming material particles to the substrate, thereby forming the first layer having low crystallinity. The second layer having high crystallinity was formed by increasing the Hearth potential by decreasing the pressure during film formation. In the same way as this, as a film forming condition, a bias potential when forming a film by applying a bias to the substrate 12 is lowered to form the first layer of the ITO film, and then the bias potential is raised to increase the ITO. A second layer of the film may be formed. Alternatively, in order to obtain the effect of promoting the migration of the film forming material particles when attached to the substrate 12, after forming the first layer of the ITO film by lowering the substrate temperature, the second temperature of the ITO film is increased by raising the substrate temperature. A layer may be formed.
[0044]
In these cases, a plurality of ITO films each composed of a first layer and a second layer are stacked by performing the above-described change of the film formation conditions four times or more in the ITO film formation process. Also, by gradually changing the film formation conditions, the vicinity of the lower surface of the ITO film has a structure with low crystallinity, while the vicinity of the upper surface has a structure with high crystallinity in the thickness direction. It is good also as a structure formed by changing a structure continuously. At this time, it is preferable that the side of the ITO film having low crystallinity is in contact with the substrate.
[0045]
Next, a modified example of the organic EL element 10 using the ITO film according to the present embodiment will be described with reference to FIG.
[0046]
The organic EL element 10a of the modified example is the same as the organic EL element 10 except for the constituent elements other than the anode electrode 14a, and thus the same reference numerals are given and redundant description is omitted.
[0047]
In the organic EL element 10a, the anode electrode 14a has a configuration in which the stacking order of the ITO films of the anode electrode 14 according to this embodiment is reversed. That is, the anode electrode 14a is a layer in which the first layer 36 formed on the substrate 12 has a highly crystalline structure, while the second layer 38 formed on the first layer 36 is crystalline. It is a layer having a low structure.
[0048]
The formation of the ITO film constituting the anode electrode 14a can be performed according to the method for forming the ITO film described above. Each of the first layer and the second layer of the ITO film has a thickness of 50 nm.
[0049]
The film formation quality of the ITO film constituting the anode electrode 14a is also shown in the table of FIG. In FIG. 9, Example 2 is an ITO film constituting the anode electrode 14a.
[0050]
From FIG. 9, the ITO film of Example 2 has a lower specific resistance than the ITO film of Reference Example 2 as well as the ITO film of Reference Example 1, and has a lower water vapor permeability better than the ITO film of Reference Example 1. Have In other words, the ITO film of Example 2 (modified example) is a film having a good balance between specific resistance and water vapor permeation preventing property, and has substantially the same effect as the ITO film of Example 1 (this embodiment). .
[0051]
In addition, although it is not clear why the water vapor permeability of the ITO films of Examples 1 and 2 is different, when the first layer formed on the substrate is a layer having high crystallinity as in Example 2, Since high incident energy is applied to the substrate made of a resin material, the substrate is damaged, and a uniform first layer cannot be obtained due to degassing from the substrate, for example, a hole defect occurs. Therefore, it is considered that the water vapor permeability of the ITO film may not be improved sufficiently.
[0052]
【The invention's effect】
According to the ITO film of the present invention, since it includes a layer with a high crystallinity structure and a layer with a low crystallinity structure, it has a low specific resistance equivalent to that of a conventional ITO film with a high crystallinity and a homogeneous structure. In addition, an ITO film having good water vapor permeation prevention properties can be obtained.
[0053]
Further, the ITO film according to the present invention is formed on a resin substrate or a resin sheet, and has a two-layer structure of a layer having a high crystallinity structure and a layer having a low crystallinity structure. Since the side of the layer having a low structure is formed toward the resin substrate or the resin sheet, an ITO film having a higher water vapor permeation preventing property can be obtained.
[0054]
Further, according to the method for manufacturing an ITO film of the present invention, the sputtering pressure or the ion plating method is used, the pressure during film formation is changed during the film formation process, or the bias potential applied to the substrate is changed during the film formation process. In order to change the substrate temperature in the film formation process, or to change the Haas potential to which the deposition material is loaded and the voltage is applied using the ion plating method in the film formation process. An ITO film exhibiting the above effects can be suitably obtained.
[0055]
In addition, since the organic EL device according to the present invention includes the ITO film as an electrode, it is possible to improve the water vapor permeation prevention property of the device or to simplify the water vapor permeation prevention structure.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an example of a conventional organic EL element.
FIG. 2 is a diagram showing a schematic configuration of another example of a conventional organic EL element.
FIG. 3 is a diagram showing a schematic configuration of still another example of a conventional organic EL element.
FIG. 4 is a diagram showing a schematic configuration of an organic EL element provided with an ITO film according to the present embodiment.
FIG. 5 is an enlarged view of a cathode electrode portion of the organic EL element of FIG.
FIG. 6 is an X-ray diffraction pattern of the first layer of the ITO film according to the present embodiment.
FIG. 7 is an X-ray diffraction pattern of the second layer of the ITO film according to the present embodiment.
FIG. 8 is a diagram showing a schematic configuration of an ion plating apparatus used when an ITO film according to the present embodiment is formed by an ion plating method.
FIG. 9 is a table showing the quality of ITO film formation.
FIG. 10 is a diagram showing a schematic configuration of an organic EL element provided with an ITO film according to a modification.
[Explanation of symbols]
10, 10a Organic EL element 12 Substrate 14, 14a Anode electrode 16 Light emitting layer 18 Cathode electrode 20, 38 Second layer 22, 36 First layer 24 Ion plating device 26 Plasma gun 28 Vacuum vessel 30 Hearth 32 Film forming material rod 34 Supply device

Claims (9)

And a layer of low layer of highly crystalline structure and crystalline structure seen including,
An ITO film characterized in that a structure with high crystallinity and a structure with low crystallinity are formed at both ends in the thickness direction of the film and the structure is continuously changed in the thickness direction. .   It is formed on a resin substrate or a resin sheet and has a two-layer structure of a layer having a highly crystalline structure and a layer having a low crystalline structure, and the side of the layer having the low crystalline structure is the resin substrate or An ITO film, which is formed toward the resin sheet. A method for producing an ITO film comprising a layer having a highly crystalline structure and a layer having a low crystalline structure ,
A method for producing an ITO film, characterized by using a sputtering method or an ion plating method, and changing a film formation pressure during film formation in a vacuum vessel in the sputtering device or ion plating device during the film formation process. Including a layer with a high crystalline structure and a layer with a low crystalline structure
A method for producing an ITO film including one or two or more sets of laminated structures composed of a layer having a high crystallinity structure and a layer having a low crystallinity structure ,
A method for producing an ITO film, characterized by using a sputtering method or an ion plating method, and changing a film formation pressure during film formation in a vacuum vessel in the sputtering device or ion plating device during the film formation process. It is a manufacturing method of the ITO film according to claim 1 or 2 ,
A method for producing an ITO film, characterized by using a sputtering method or an ion plating method, and changing a film formation pressure during film formation in a vacuum vessel in the sputtering device or ion plating device during the film formation process. An ITO film manufacturing method for forming the ITO film according to claim 1 or 2 on a substrate,
A method for producing an ITO film, characterized by using a sputtering method or an ion plating method, and changing a bias potential applied to the substrate during a film formation process. An ITO film manufacturing method for forming the ITO film according to claim 1 or 2 on a substrate,
A method for producing an ITO film, characterized by using a sputtering method or an ion plating method to change the temperature of the substrate during the film formation process. It is a manufacturing method of the ITO film according to claim 1 or 2 ,
A method for producing an ITO film, characterized by using an ion plating method and changing a Haas potential to which a deposition material is loaded and a voltage is applied in a film forming process. The organic EL element characterized in that it comprises an ITO film described as electrodes to claim 1 or 2.

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