KR20000006418A - Method of manufacturing organic electroluminescence display element - Google Patents

Abstract

PURPOSE: A method for making an organic electric-field EL-display device reconnects a hole injected from anode and electron injected from cathode in EL-layer having a light-emitting capacity, uses a light-emitting phenomenon through deactivation step in an excitation state, and performs a light-emitting function. CONSTITUTION: In organic electric-field EL-display element making method, the method forms at least one organic layer on anode layer, forms a oxide layer by depositing oxygen on at least one organic layer, and deposits a cathode material on the oxide layer. The organic layer has a light-emitting layer. The organic layer is deposited between the cathodes and the anodes.

Description

Method of manufacturing organic electroluminescence display element

1. Field of Invention

The present invention provides an organic electric field that emits light by using a phenomenon in which holes injected from an anode and electrons injected from a cathode are recombined in a light emitting layer having a light emitting ability, and light is emitted through a deactivation process in an excited state. A method of manufacturing a light emitting (EL) display device.

2. Description of related technology

An organic electroluminescent display device (hereinafter referred to as an "organic EL device") is a phenomenon in which holes emitted from an anode and electrons injected from a cathode are emitted by a process of decreasing activity when the electrons injected from the cathode are recombined and excited in a light emitting layer having a light emitting ability It is a light emitting device using. As described above, the organic EL element may be widely used as a spontaneous light emitting display device for converting electron energy into light energy, and also used as a thin display device using a feature that the thickness of the organic layer is 1 µm or less. Could be. Therefore, careful research and development on organic EL devices has recently been conducted.

A passive matrix display in which parallel electrodes are arranged orthogonal to each other, and an active matrix display provided in a pixel in which thin film transistors (TFTs) and the like are arranged in parallel are provided with a plurality of organic EL elements having the above characteristics. It is known as a matrix display formed by using as a pixel.

1 is a schematic plan view showing the case where the organic EL elements are arranged in a simple matrix form. As shown in Fig. 1, the anode layer 12 serving as a row electrode and the cathode layer 13 serving as a column electrode are crossed orthogonally to each other such that each intersection forms a pixel, thereby displaying a display panel. It is arranged on the same support substrate to form a. If a control circuit and a drive circuit are also provided in the panel of the above structure, the assembly thus obtained can be used as a display device. Moreover, each intersection can be individually colored in different colors such as red, blue, and green to use the fabricated display as a full color display or as a multi-color display.

The organic EL device utilizes the phenomenon of emitting light through a recombination process of holes injected from the anode and electrons injected from the cathode as described above.

2 is a schematic energy diagram of the luminescence process. The molecular structure is designed so that holes and electrons can be easily injected by applying a voltage of several volts in the hole / electron injection process with a low injection barrier, where holes are injected from the anode 21 into the hole injection layer. Is injected from the cathode 22 into the electrode transport layer 26. On the other hand, when the reverse bias voltage is applied, i.e., the polarity is reversed so that the anode 21 is set to the low potential and the cathode 22 is set to the high potential, the electron injection from the anode 21 and the hole injection from the cathode 22 are As shown in FIG. 2, high barriers are encountered, making it difficult to theoretically inject holes and electrons. For this reason, it is generally considered that organic EL devices have diode characteristics.

In practice, however, a leakage current will be observed when a reverse bias voltage is applied to the organic EL element, and the detailed reason for the leakage current has not been clear so far. Fig. 3 shows the current path when the organic EL elements having diode characteristics are arranged in a matrix. In this case, as shown in FIG. 3, there will be only one path from the column electrode 32 to the row electrode 31 in the forward direction of the diode component, and light can be emitted from only the selected pixel. However, when the organic EL element does not have perfect diode characteristics, there exists a current (reverse leakage current) in which the current path flows in the reverse direction in addition to the original current path in which the current flows in the forward direction. Thus, light is emitted from the periphery around the selected pixel, resulting in a decrease in contrast and pixel defects.

In order to solve the above problem, Japanese Laid-Open Patent Publication No. 9-102395 discloses a method of using a material mainly containing aluminum as the cathode material. However, this method cannot sufficiently improve the rectification rate with high productivity. Moreover, the forward properties of cathodes formed solely of aluminum are worse than conventional magnesium-silver electrodes or aluminum-lithium electrodes and therefore this method is not practical in practice.

Summary of the Invention

The inventors studied closely to solve the commutation rate problem and found a correlation between the commutation rate and the cathode material, especially lithium, sodium and silver having a small atomic radius. In particular, these materials are easier to ionize under application of a bias voltage, and the movement at the interface of the cathode and the electron transport layer affects the commutation characteristics.

It is an object of the present invention to provide a method of manufacturing an organic electroluminescent display device structure which suppresses the movement of materials due to ionization and has excellent rectification characteristics.

According to a first aspect of the invention, forming at least one organic layer on an anode layer, depositing oxygen on the at least one organic layer to form an oxide layer, and depositing a cathode material on the formed oxide An organic electroluminescent display device manufacturing method is provided.

According to a second aspect of the invention, forming at least one organic layer on an anode layer, forming a cathode layer on the at least one organic layer, comprising oxygen to introduce oxygen between the cathode layer and the organic layer An organic electroluminescent display device manufacturing method comprising the step of exposing the cathode layer is provided.

Aluminum or aluminum-lithium alloys are preferably used as the material of the cathode layer. It is preferable that the thickness of the cathode layer is set to 100 nm or less.

In the step of introducing oxygen between the cathode layer and the organic layer, oxygen having a boiling point of 2000 ° C. or less is formed to a thickness of 10 nm or more by a resistance heating method.

The step of inserting an oxygen-containing layer between the cathode layer and the organic layer is to expose the organic layer to an atmosphere containing 10 ppm (volume particles per million) of water and 90% or more oxygen concentration after the organic layer is formed, or 50% or more oxygen concentration. It is preferably carried out by sealing the device under an atmosphere containing.

The layer forming step in the cathode layer forming step is preferably set to a value within the range of 1.5 nm / sec to 3 nm / sec. The cathode material is preferably made as aluminum, in which case the aluminum layer is formed at a rate of 2 nm / sec.

1 is a schematic plan view showing an organic EL element arranged in a matrix form.

2 is an energy diagram schematically showing a light emission process of the organic EL device of FIG. 1;

3 shows a current path when devices each having diode characteristics are arranged in a matrix;

4 is a view showing a state in which the current flowing in the reverse direction in addition to the current path flowing in the forward direction because the device does not have a complete diode characteristics.

Fig. 5 is a longitudinal sectional view showing an organic EL element according to the present invention.

6 is a longitudinal cross-sectional view showing a first example of an organic EL device of the present invention.

7 is a diagram showing a process of manufacturing a seventh example of an organic EL device according to the present invention.

8 is a longitudinal cross-sectional view showing an eleventh example of the organic EL element according to the present invention;

9 is a longitudinal sectional view showing a thirteenth example of organic EL element according to the present invention;

<Explanation of symbols for the main parts of the drawings>

41: support substrate 42: organic layer

43: cathode layer 44: interfacial oxide layer

45: interfacial crystal layer

Detailed description of the preferred embodiment

Preferred embodiments according to the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 5, an embodiment of an organic electroluminescent (EL) display element according to the invention comprises oxygen between an electron transport layer and a cathode layer 43 provided on an anode-supported support substrate 41. It is characterized in that the interfacial oxide layer 44 is interposed.

In order to achieve the electroluminescent display device configured as described above, an interface modification layer 45 made of oxygen is formed at an interface between the organic layer 42 and the cathode layer 43 serving as an electron transporting layer, as shown in FIG. 6. . That is, after the organic layer 42 is formed on the support substrate 41 and exposed to an oxygen atmosphere for at least one hour to form the interfacial crystal layer 45, the cathode layer 3 is shown in Figs. 7A to 7E. As formed. Furthermore, a method may be used in which a cap 46 covering the element is provided and a closed gas filled in the gas filling region 47 of the cap 46 is formed of a gas having an oxygen concentration of 50% or more as shown in FIG. have. The thickness of the cathode layer 43 is preferably set to 100 nm or more as shown in FIG.

In this embodiment, an oxygen material is inserted at the interface between the organic layer and the electron injection electrode. As disclosed in Japanese Patent Laid-Open Nos. 5-251185 and 4-230997, the electron injection electrode of the conventional EL element is made of a material having a low work function such as Li, Ca, or Mg, and Al, In, Ag, and the like. It is made of a mixture or alloy of the same metal.

However, compared with organic materials, these materials have higher boiling points and most of them require temperatures of 500 ° C. or more even in the layer forming process under vacuum. Thus, when the cathode is formed after organic layer formation, the organic layer is exposed to at least both radiant heat from the evaporation source and the energy of the evaporated particles.

In particular, the energy generated when the evaporated particles condense on the substrate can be converted into energy that not only damages the organic layer, but also causes the cathode material to diffuse into the organic layer. Therefore, the band structure as shown in Fig. 2 cannot be achieved. This tendency occurs in common with all these metals, especially with alkali metals. In order to prevent the above diffusion due to deposition and to stabilize the normal characteristics of the device, the inventors found that the oxygen layer is effective in blocking the condensation energy of evaporated particles.

Moreover, the inventors found that the effective thickness of the oxygen layer resulting in the above thermal insulation effect is about 1 nm or more. If the thickness of the oxygen layer is excessively large, the light emission characteristics of the organic EL element itself in the forward direction deteriorate, and therefore, it is preferable to set the thickness to 10 nm or less. In order to control the thickness of the oxygen layer within the above range, the thickness of the oxygen layer may be controlled by a resistance heating method or the like, and considering that the temperature rise of the substrate adversely affects the device, the boiling point of oxygen is preferably 2000 ° C. It is set as follows.

Moreover, when oxidation is performed for about 1 hour under an oxygen atmosphere instead of the process of forming an oxygen layer, the thickness of the formed oxygen layer becomes about 1 nm, and the same effect as the oxygen layer deposition process can be obtained. Alternatively, an oxygen sealed gas may be injected from the side of the device to oxidize the interface. The purity of the oxygen gas is preferably set to 90% or more, more preferably 99% or more. In order to reduce dark spots, the moisture content is preferably set to 10 ppm or more.

When a metal layer such as aluminum is oxidized, oxygen is more easily introduced from the surface of the gold layer as the thickness of the metal layer is reduced. Moreover, the formation of the oxygen layer proceeds with the introduction of oxygen. Therefore, the thickness of the metal layer is preferably as small as possible. In consideration of the breakage of the electrode, the thickness of the metal layer is more preferably set to 50 nm or more. As the rate of formation of the aluminum layer increases, the temperature of the evaporation source rises.

Since aluminum evaporates while taking a small amount of oxygen in the vacuum, an oxygen layer is formed at the interface. The lowest oxygen layer formation rate is about 1.5 nm / sec. However, when the layer formation rate is equal to or more than 3 nm / sec, the layer has an island structure, and the gap is increased to promote foreign material contamination. Therefore, the layer formation rate is preferably set to a range of 1.5nm / sec to 2.5nm / sec.

The following four structures are provided for the organic EL device of the present invention.

(1) anode / light emitting layer / cathode

(2) anode / hole transport layer / light emitting layer / electron transport layer / cathode

(3) anode / light emitting layer / electron transporting layer / cathode

(4) anode / hole transport layer / light emitting layer / cathode

As a result, one or more organic layers laminated between the cathode layer and the anode layer comprise a light emitting layer or a light emitting layer and another layer (hole transporting layer and / or electron transporting layer). The organic layer may be formed of four or more layers.

The hole transport material used in the organic EL device of the present invention is not limited to a specific one, and any compound can be used as long as it can be used as a normal hole transport layer. For example, the hole transport layer material is bis (di (p-tolyl) aminophenyl) -1,1-cyclohexane, N-N'-diphenyl-N, N'-bis (3-methylphenyl) -1 , 1'-biphenyl-4,4'-diamine, N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine, N, N'-diphenyl- NN-bis (1-naphthyl)-(1,1'-biphenyl) -4,4'-diamine, star burst molecules and the like can be used.

Moreover, the electron transporting material used in the organic EL device of the present invention is not limited to a specific one, and any compound can be used as long as it can be used as a normal electron transporting material. Examples of the electron transport layer include 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, bis {2- (4-t-butylphenyl) -1 Oxadiazole derivatives such as, 3,4-oxadiazole} -m-phenylene, auxin metal composites, and the like. Moreover, any kind of compound or a mixture of these compounds may be used as the light emitting material as long as it emits light in the solid state. Examples of the luminescent material include a comarinic compound, a phthaloperinone compound, a benzoxazolyl compound or a benzothiazole compound, a metal chelate oxynoid compound, a stilbene compound, a perylene compound, and the like.

<Example>

An example of introducing an oxygen layer according to the method shown in FIGS. 6 to 9 will be described.

<Example 1>

In this example, the method of FIG. 6 is applied.

ITO (indium-tin oxide) was formed to a thickness of 100 nm on a transparent glass substrate by the sputtering method. At this time, the sheet resistance is 10Ω / It was. Subsequently, ITO was etched in a predetermined pattern to prepare a glass substrate having an ITO pattern. The substrate was washed with pure water, IPA (isopropyl alcohol) and subjected to UV ozone cleaning. As a result, the surface of the substrate was sufficiently cleaned.

Then, tantalum containing 100 mg of α-NPD (N, N'-diphenyl-NN-bis (1-naphthyl)-(1,1'-biphenyl) -4,4'-diamine) as a hole transport material A boat and a tantalum boat containing 100 mg of Alq3 (tri (8-quinolinol) aluminum) as a light emitting material were separately prepared. These tantalum boats were placed as separate evaporation sources in a vacuum deposition apparatus.

After placing the prepared substrate in the same vacuum deposition apparatus, the inside of the apparatus was evacuated to have a vacuum degree of 2 x 10 ^-4 Pa (Pascal), and the boat holding α-NPD was heated when the vacuum degree reached the above value. . After adjusting the temperature until the α-NPD layering rate reached a constant rate (0.3 nm / sec), the layering step was started by opening a shutter installed at the top of the device. The deposition was completed by closing the shutter when the thickness reached 50 nm. Similarly, an Alq3 layer was formed with a thickness of 55 nm and an organic layer was formed at a layer formation rate of 0.3 nm.

Subsequently, the substrate on which the organic layer was formed was transferred to another vacuum apparatus while maintaining the vacuum state, and the vacuum state in the vacuum apparatus in which the layer was formed returned to the standby state. Then, the boat for forming the organic layer was removed, 1 g of aluminum and 1 g of aluminum oxide were placed in a tungsten boat, respectively, and the vacuum was then evacuated again. When the vacuum reached 4 × 10 ⁻⁴ Pa, the boat with aluminum was heated. Heating conditions were set so that the layer formation rate was stabilized at 0.02 nm / sec. When the layer formation conditions were stabilized, the layering process continued until the upper shutter was opened and the layer thickness reached 1 nm.

Next, the boat with aluminum was heated. In this case, the temperature was controlled such that the layer formation rate was 1 nm / sec, and the upper shutter was opened again when the layer formation rate was stabilized. The deposition was completed when the layer thickness was 300 nm, thereby forming a device having an ITO / α-NPD / Alq 3 / Al ₂ O ₃ / Al structure and having a light emitting area of 4 mm ² (FIG. 6).

When a voltage of 15V was applied to the device with ITO as the anode and aluminum as the cathode, 1100 mA of current flowed through the device.

Moreover, when ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 30 nA flowed through the device. When the rectification ratio was calculated with 15V applied, it was calculated as 3.8 x 10 ⁴ .

<Example 2>

The device was formed in the same manner as in Example 1 except that aluminum oxide (Al ₂ O ₃ ) was replaced with Geo. When ITO was used as the anode and aluminum was the cathode, and a voltage of 15 V was applied to the device, a current of 1300 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 20 mA flowed. The rectification ratio was calculated as 3.8 x 10 ⁴ with an application of 15V.

<Example 3>

The device was formed in the same manner as in Example 1 except that aluminum oxide (Al ₂ O ₃ ) was replaced with SiO. When ITO was used as the anode and aluminum was the cathode, and a voltage of 15 V was applied to the device, a current of 1300 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 20 mA flowed. The rectification ratio was calculated as 3.8 x 10 ⁴ with an application of 15V.

<Example 4>

The device was formed in the same manner as in Example 1 except that aluminum oxide (Al ₂ O ₃ ) was replaced with GeO ₂ . When ITO was used as the anode and aluminum was the cathode, and a voltage of 15V was applied to the device, a current of 1600 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 18 nA flowed. The rectification ratio was calculated to be 8.8 x 10 ⁴ with an application of 15V.

Example 5

The device was formed in the same manner as in Example 1 except that aluminum oxide (Al ₂ O ₃ ) was replaced with SrTiO ₃ . When ITO was used as the anode and aluminum was the cathode, and a voltage of 15 V was applied to the device, a current of 1300 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15V was applied to the device, a current of 9nA flowed. The rectification ratio was calculated as 1.4 x 10 ⁵ with an application of 15V.

Example 6

The device was formed in the same manner as in Example 1 except that aluminum was replaced with an aluminum-lithium alloy. When ITO was used as the anode and the aluminum-lithium alloy layer was used as the cathode, a current of 10 m flowed when a voltage of 15 V was applied to the device. When ITO was used as the cathode and the aluminum-lithium alloy layer was the anode, and a voltage of 15 V was applied to the device, a current of 100 pA flowed. The rectification ratio was calculated as 1.0 x 10 ⁸ at 15V application.

Example 7

The device was formed in the same manner as in Example 1, except that aluminum oxide was replaced with a layer in which two components of magnesium and silver were simultaneously deposited. When ITO was used as the anode and the magnesium-silver electrode was used as the cathode, a current of 8 mA flowed when a voltage of 15 V was applied to the device. When ITO was used as the cathode and the magnesium-silver electrode was the anode, and a voltage of 15 V was applied to the device, a current of 130 pA flowed. The rectification ratio was calculated as 6.2 x 10 ⁷ with an application of 15V.

<Example 8>

In this example, the method shown in FIG. 7 was applied.

ITO was formed on a transparent glass substrate by sputtering to have a thickness of 100 nm. At this time, the sheet resistance is 10Ω / It was. Subsequently, ITO was etched in a predetermined pattern to prepare a glass substrate having an ITO pattern. The substrate was washed with pure water, IPA and subjected to UV ozone cleaning. As a result, the surface of the substrate was sufficiently cleaned.

Then, tantalum containing 100 mg of α-NPD (N, N'-diphenyl-NN-bis (1-naphthyl)-(1,1'-biphenyl) -4,4'-diamine) as a hole transport material A boat and a tantalum boat containing Alq3 100mg as a light emitting material were separately prepared. These tantalum boats were placed as separate evaporation sources in a vacuum deposition apparatus.

The substrate prepared in advance was placed in the same vacuum deposition apparatus, and then the inside of the apparatus was evacuated to have a vacuum degree of 2 × 10 ⁻⁴ Pa, and the boat containing α-NPD was heated when the vacuum degree reached the above value. After adjusting the temperature until the α-NPD layering rate reached a constant rate (0.3 nm / sec), the layering step was started by opening a shutter installed at the top of the device. The deposition was completed by closing the shutter when the layer thickness reached 50 nm. Similarly, an Alq3 layer was formed with a thickness of 55 nm and an organic layer was formed at a layer formation rate of 0.3 nm.

Subsequently, the substrate on which the organic layer was formed was transferred to another vacuum apparatus while maintaining the vacuum state, and the vacuum state in the vacuum apparatus in which the layer was formed returned to the standby state. The boat to form the organic layer was then removed, 1 g of aluminum was placed in a tungsten boat and the vacuum was then evacuated again. When the vacuum reached 4 × 10 ⁻⁴ Pa, the boat was heated. Heating conditions were set so that the layer formation rate was stabilized at 0.4 nm / sec. When the layering conditions were stabilized, the layering process continued until the top shutter was opened and the layer thickness reached 5 nm. Next, oxygen was introduced into the vacuum apparatus to return the vacuum state to atmospheric pressure. This state was maintained for about 2 hours to oxidize the aluminum layer.

Then the boat with aluminum was heated when it was evacuated again and the pressure was 2 × 10 ⁻⁴ Pa. The temperature was controlled so that the layer formation rate was 1 nm / sec, and when the layer formation conditions were stabilized, the upper shutter was opened. Further, when the layer thickness reached 300 nm, deposition was terminated to form an element having an ITO /?-NPD / Alq3 / Al oxide structure and a light emitting area of 4 mm ² (FIG. 7).

When ITO was used as the anode and aluminum was the cathode, and a voltage of 15 V was applied to the device, the current flowed at 1000 mA. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 5 nA flowed. The rectification ratio was calculated as 1.1 x 10 ⁵ with 15V applied. The aluminum layer was analyzed by using ESCA. As a result, the thickness of the aluminum oxide layer at the interface between the organic layer and the cathode layer was about 3 nm, and an oxygen layer was formed.

Example 9

The device was formed in the same manner as in Example 8 except that the oxygen exposure time was set to 5 hours. When ITO was used as the anode and aluminum was the cathode, and a voltage of 15 V was applied to the device, the current of 1080 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 8 nA flowed. The rectification ratio was calculated as 1.3 x 10 ⁵ with an application of 15V.

Example 10

The device was formed in the same manner as in Example 8 except that aluminum was replaced with an aluminum-lithium alloy. When ITO was used as the anode and the aluminum-lithium alloy layer was the cathode, and a voltage of 15 V was applied to the device, the current of 20 mA flowed. When ITO was used as the cathode and the aluminum-lithium alloy layer was the anode, and a voltage of 15 V was applied to the device, a current of 60 pA flowed. The rectification ratio was calculated to be 3.3 x 10 ⁸ at 15V.

Example 11

In this example, the method shown in FIG. 8 was applied.

ITO was formed on a transparent glass substrate by sputtering to have a thickness of 100 nm. At this time, the sheet resistance is 10Ω / It was. Subsequently, ITO was etched in a predetermined pattern to prepare a glass substrate having an ITO pattern. The substrate was washed with pure water, IPA and subjected to UV ozone cleaning. As a result, the surface of the substrate was sufficiently cleaned.

Then, tantalum containing 100 mg of α-NPD (N, N'-diphenyl-NN-bis (1-naphthyl)-(1,1'-biphenyl) -4,4'-diamine) as a hole transport material A boat and a tantalum boat containing Alq3 100mg as a light emitting material were separately prepared. These tantalum boats were placed as separate evaporation sources in a vacuum deposition apparatus.

After the substrate prepared in advance was placed in the same vacuum deposition apparatus, the inside of the apparatus was evacuated to have a vacuum degree of 2 × 10 ⁻⁴ Pa, and the boat containing α-NPD was heated when the vacuum degree reached the above value. After adjusting the temperature until the α-NPD layering rate reached a constant rate (0.3 nm / sec), the layering step was started by opening a shutter installed at the top of the device. The deposition was completed by closing the shutter when the layer thickness reached 50 nm. Similarly, an Alq3 layer was formed with a thickness of 55 nm and an organic layer was formed at a layer formation rate of 0.3 nm.

Subsequently, the substrate on which the organic layer was formed was transferred to another vacuum apparatus while maintaining the vacuum state, and the vacuum state in the vacuum apparatus in which the layer was formed returned to the standby state. The boat to form the organic layer was then removed, 1 g of aluminum was placed in a tungsten boat and the vacuum was then evacuated again. When the vacuum reached 4 × 10 ⁻⁴ Pa, the boat was heated. Heating conditions were set so that the layer formation rate was stabilized at 0.5 nm / sec. When the layering conditions were stabilized, the layering process continued until the upper shutter was opened and the layer thickness reached 300 nm, and a device having an ITO / α-NPD / Alq3 / Al structure and a light emitting area of 4 mm ² was manufactured. (FIG. 8).

The device thus produced was transferred to a glove box filled with 99.9% oxygen and sealed with a glass cap to cover the light emitting portion of the device with a glass cap. After sealing, the device was left for about 24 hours. When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, 1140 mA passed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 60 nA flowed. The rectification ratio was calculated as 1.9 x 10 ⁴ with 15V applied.

Example 12

The device was formed in the same manner as in Example 11 except that aluminum was replaced with an aluminum-lithium alloy. When ITO was used as the anode and the aluminum-lithium alloy layer was used as the cathode, a current of 25 mA flowed when a voltage of 15 V was applied to the device. When ITO was used as the cathode and the aluminum-lithium alloy layer was used as the anode, a current of 55 pA flowed when a voltage of 15 V was applied to the device. The rectification ratio was calculated to be 4.5 x 10 ⁸ with an application of 15V.

Example 13

In this example, the method shown in FIG. 9 was applied.

ITO was formed on a transparent glass substrate by sputtering to have a thickness of 100 nm. At this time, the sheet resistance is 10Ω / It was. Subsequently, ITO was etched in a predetermined pattern to prepare a glass substrate having an ITO pattern. The substrate was washed with pure water, IPA and subjected to UV ozone cleaning. As a result, the surface of the substrate was sufficiently cleaned.

Then, tantalum containing 100 mg of α-NPD (N, N'-diphenyl-NN-bis (1-naphthyl)-(1,1'-biphenyl) -4,4'-diamine) as a hole transport material A boat and a tantalum boat containing Alq3 100mg as a light emitting material were separately prepared. These tantalum boats were placed as separate evaporation sources in a vacuum deposition apparatus.

After placing the prepared substrate in the same vacuum deposition apparatus, the inside of the apparatus was evacuated to have a vacuum degree of 2 × 10 ⁻⁴ Pa, and the boat containing α-NPD was heated when the vacuum degree reached the above value. After adjusting the temperature until the α-NPD layering rate reached a constant rate (0.3 nm / sec), the layering step was started by opening a shutter installed at the top of the device. The deposition was completed by closing the shutter when the layer thickness reached 50 nm. Similarly, an Alq3 layer was formed with a thickness of 55 nm and an organic layer was formed at a layer formation rate of 0.3 nm.

Subsequently, the substrate on which the organic layer was formed was transferred to another vacuum apparatus while maintaining the vacuum state, and the vacuum state in the vacuum apparatus in which the layer was formed returned to the standby state. The boat to form the organic layer was then removed, 1 g of aluminum was placed in a tungsten boat and the vacuum was then evacuated again. When the vacuum reached 4 × 10 ⁻⁴ Pa, the boat was heated. Heating conditions were set so that the layer formation rate was stabilized at 0.5 nm / sec. When the layering conditions were stabilized, the layering process continued until the top shutter was opened and the layer thickness reached 60 nm, and a device having an ITO / α-NPD / Alq3 / Al structure and a light emitting area of 4 mm ² was manufactured. (FIG. 9).

It is preferable that the thickness of the cathode layer is set to 100 nm or less. A small amount of oxygen generated inside the vacuum apparatus is absorbed on the surface of the cathode layer, such as the aluminum layer. Part of the oxygen acts as a reducing agent to oxidize the cathode layer. At the same time, unreacted oxygen diffuses into the cathode layer and oxidation proceeds therein. As a result, a layer having a tendency to be gradually oxidized from the surface of the cathode layer is formed so that the interface between the cathode layer and the organic layer is partially oxidized.

When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, 1200 mA of current flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 10 nA flowed. The rectification ratio was calculated as 1.2 x 10 ⁵ with 15V applied. As a result of the analysis of the aluminum layer using ESCA, the thickness of the aluminum oxide layer at the interface between the organic layer and the cathode layer was about 1.5 nm and the formation of the oxygen layer was found.

Example 14

The device was formed in the same manner as in Example 13 except that aluminum was replaced with an aluminum-lithium alloy. When ITO was used as the anode and the aluminum-lithium alloy layer was used as the cathode, a current of 17 mA flowed when a voltage of 15 V was applied to the device. When ITO was used as the cathode and the aluminum-lithium alloy layer was the anode, and a voltage of 15 V was applied to the device, a current of 450 pA flowed. The rectification ratio for 15V is calculated as 3.7 x 10 ⁷ .

Example 15

ITO was formed on a transparent glass substrate by sputtering to have a thickness of 100 nm. At this time, the sheet resistance is 10Ω / It was. Subsequently, ITO was etched in a predetermined pattern to prepare a glass substrate having an ITO pattern. The substrate was washed with pure water, IPA and subjected to UV ozone cleaning. As a result, the surface of the substrate was sufficiently cleaned.

Then, tantalum containing 100 mg of α-NPD (N, N'-diphenyl-NN-bis (1-naphthyl)-(1,1'-biphenyl) -4,4'-diamine) as a hole transport material A boat and a tantalum boat containing Alq3 100mg as a light emitting material were separately prepared. These tantalum boats were placed as separate evaporation sources in a vacuum deposition apparatus.

After placing the prepared substrate in the same vacuum deposition apparatus, the inside of the apparatus was evacuated to have a vacuum degree of 2 × 10 ⁻⁴ Pa, and the boat containing α-NPD was heated when the vacuum degree reached the above value. After adjusting the temperature until the α-NPD layering rate reached a constant rate (0.3 nm / sec), the layering step was started by opening a shutter installed at the top of the device. The deposition was completed by closing the shutter when the layer thickness reached 50 nm. Similarly, an Alq3 layer was formed with a thickness of 55 nm and an organic layer was formed at a layer formation rate of 0.3 nm.

Subsequently, the substrate on which the organic layer was formed was transferred to another vacuum apparatus while maintaining the vacuum state, and the vacuum state in the vacuum apparatus in which the layer was formed returned to the standby state. The boat to form the organic layer was then removed, 1 g of aluminum was placed in a tungsten boat and the vacuum was then evacuated again. When the vacuum reached 4 × 10 ⁻⁴ Pa, the boat was heated. Heating conditions were set so that the layer formation rate was stabilized at 0.3 nm / sec. When the layering conditions were stabilized, the layering process continued until the upper shutter was opened and the layer thickness reached 300 nm, and a device having an ITO / α-NPD / Alq3 / Al structure and a light emitting area of 4 mm ² was manufactured. .

When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, 1400 mA of current flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, a current of 40 nA flowed. The rectification ratio was calculated as 3.5 x 10 ⁴ with 15V applied.

Example 16

The device was formed in the same manner as in Example 15 except that aluminum was replaced with an aluminum-lithium alloy. When ITO was used as the anode and the aluminum-lithium alloy layer was used as the cathode, a current of 20 mA flowed when a voltage of 15 V was applied to the device. When ITO was used as the cathode and the aluminum-lithium alloy layer was the anode, and a voltage of 15 V was applied to the device, a current of 650 pA flowed. The rectification ratio was calculated to be 3.1 x 10 ⁸ with an application of 15V.

Comparative Example 1

The device was formed in the same manner as in Example 1 except that no aluminum oxide was formed. When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, 2080 mA of current flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, an unstable current of 800 nA was observed in the center thereof. The rectification ratio was calculated to be 2.6 x 10 ² with an application of 15V.

<Comparative Example 2>

The device was formed in the same manner as in Example 2 except that aluminum was formed to a thickness of 1 nm and then the aluminum layer was formed without exposing the device to oxygen. When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, a current of 2100 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, an unstable current of 690 nA was observed in the center thereof. The rectification ratio was calculated to be 3.6 x 10 ³ with an application of 15V.

Comparative Example 3

The organic EL device was formed in the same manner as in Example 11, and sealed with a glass cap in a glove box under a nitrogen atmosphere to cover its light emitting part with a glass cap. When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, 2000 mA of current flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, an unstable current of 990 nA was observed in the center thereof. The rectification ratio was calculated as 2.1 x 10 ² with an application of 15V.

Comparative Example 4

The device was formed in the same manner as in Example 13 except that the thickness of the aluminum layer was 200 nm. When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, a current of 2200 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, an unstable current of 900 nA was observed in the center thereof. The rectification ratio was calculated to be 2.4 x 10 ² with an application of 15V.

Comparative Example 5

The device was formed in the same manner as in Example 15 except that the aluminum layer layering rate was 0.5 nm / sec. When a voltage of 15 V was applied to the device with ITO as the anode and aluminum as the cathode, a current of 2200 mA flowed. When ITO was used as the cathode and aluminum was the anode, and a voltage of 15 V was applied to the device, an unstable current of 800 nA was observed in the center thereof. The rectification ratio was calculated to be 2.8 x 10 ² with an application of 15V.

The device having the above method has the first effect that the rectification characteristics are further improved by two forms as compared with the prior art. This is because the cathode material concentrates at the interface without diffusing to the organic layer and thus an ideal Schottky barrier is formed so that leakage current can be suppressed.

The second effect of the present invention is that the formation of an ideal Schottky barrier can suppress the abnormal current appearing under application of a forward voltage of about 3V. With these effects, no unselected pixels are turned on and therefore the contrast can be improved when a simple matrix type display device is manufactured with the EL element.

Claims (10)

In the organic electroluminescent display device manufacturing method, Forming at least one organic layer on the anode layer; Depositing oxygen on the at least one organic layer to form an oxide layer; A method of manufacturing an organic electroluminescent display device comprising depositing a cathode material on the formed oxide layer. The method of claim 1, wherein the at least one organic layer comprises a light emitting layer. The method of claim 1, wherein the one or more organic layers are stacked between a plurality of cathodes constituting a cathode layer and a plurality of anodes constituting the anode layer, and the electrodes are arranged to cross each other. The organic electric field of claim 1, wherein the depositing of oxygen is performed by depositing oxygen having a boiling point of 2000 ° C. or less by using a resistance heating method to form an oxygen layer having a thickness of 10 nm or less. Method of manufacturing a light emitting display device. In the organic electroluminescent display device manufacturing method, Forming at least one organic layer on the anode layer; Forming a cathode layer on the at least one organic layer; And exposing the cathode layer to an atmosphere containing oxygen to introduce oxygen between the cathode layer and the organic layer. The method of claim 5, wherein the at least one organic layer comprises a light emitting layer. The method of claim 5, wherein the one or more organic layers are stacked between a plurality of cathodes constituting a cathode layer and a plurality of anodes constituting the anode layer, and the electrodes are arranged to cross each other. 6. The method of claim 5, wherein exposing the cathode layer to an atmosphere containing oxygen is performed by sealing the device in a cap under an atmosphere containing oxygen. The method of claim 5, wherein the oxygen-containing atmosphere is an atmosphere containing an oxygen concentration of 50% or more. The method of claim 8, wherein the oxygen-containing atmosphere is an atmosphere containing an oxygen concentration of 50% or more.