JP2005307354A - Method and device for producing organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing vapor-deposited films of good quality for organic El elements uniformly and rapidly in high productivity by electromagnetic induction heating of a container to which the raw material is introduced and a device used for the same. <P>SOLUTION: The device for vapor deposition of films for the organic EL elements vaporizes an organic material 5 for the organic EL elements in the container 2 and deposits the material in thin film on the surface of a film-forming substrate 6 and comprises the container 2 constructed of a material capable of generating heat by electromagnetic induction and a means for heating the container for vaporizing the organic material 5 by electromagnetic induction. Also provided is a method for producing the organic EL elements by using the device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for manufacturing an organic electroluminescence element (organic EL element), and more particularly to a method and apparatus for vaporizing an organic EL material in order to form an organic thin film for an organic EL element by a vacuum deposition method.

  As a general structure of an organic EL element, an organic thin film layer such as a hole transport layer, a light emitting layer, and an electron transport layer is formed between an anode and a cathode made of a transparent conductive film. Light emission occurs when holes injected into the light emitting layer through the layer and electrons injected from the cathode through the electron transport layer into the light emitting layer recombine. At this time, if the thickness, composition, etc. of the organic thin film layers such as the hole transport layer, the light emitting layer, and the electron transport layer, which are caused by the instability of the evaporation rate, are not uniform, non-uniformity occurs between the deposition lots, and the device performance This causes problems such as variations in

It is known in Japanese Patent Application Laid-Open No. 2000-68055 and the like that there is a vacuum deposition method as one method for producing an organic thin film for an organic EL element. In the vacuum vapor deposition method, a vapor deposition material vaporized from an evaporation source heated to a vaporization temperature or higher of the vapor deposition material is deposited as a solid on a film formation substrate to form a thin film.
As a method for heating the evaporation source, in addition to the indirect heating method, Appl. Phys. Lett. 68 (16), 15 April 1996 and Japanese Patent Application Laid-Open No. 2000-68055, so-called direct resistance heating that uses resistance heat generation by passing current through a metal container (metal boat) having relatively high electrical resistance. The method is known.
JP 2000-68055 A Appl. Phys. Lett. 68 (16), 15 April 1996

  In the direct resistance heating method, a container in which a metal material such as tungsten, tantalum, or molybdenum having a high melting point is generally processed into a thin plate to increase electric resistance is used, but in order to heat the entire container uniformly, It is necessary that the current distribution be uniform. In a long shape like a boat, a relatively uniform current distribution can be obtained by placing terminals at both ends in the longitudinal direction, but there is still a temperature deviation between the center and the end, and the amount of materials charged is limited. Therefore, it is not suitable for mass production.

  A crucible-like shape is suitable for securing the amount of material charged. However, when resistance heating is performed directly with a terminal in a crucible-like shape, the entire crucible is heated uniformly so that the entire crucible is heated. It is difficult to flow a current uniformly. Therefore, a temperature distribution is formed in the crucible, and the vapor deposition material does not vaporize at a portion where the current density is low and lower than the target temperature. There is a possibility that not only vaporization will occur, but also the organic material used as a raw material will be thermally decomposed and the resulting organic thin film may be altered.

  In general, when a material is charged into a crucible container for mass production, a method of heating the container uniformly by indirect heating from a resistance heating heating element provided separately is used instead of direct resistance heating as described above. . However, such an indirect heating method has poor thermal responsiveness, so that it is difficult to control the evaporation amount. That is, when the temperature is lower than the target temperature, the vaporization amount of the vapor deposition material is not sufficient, and the film thickness becomes thin. On the other hand, when the overshoot exceeds the target temperature, not only the film thickness is too thick but also the thermal decomposition of the organic material. Will occur, resulting in alteration of the organic thin film. In addition, in the indirect heating method, compared with the direct heating method, it takes time from the start of temperature increase until the target temperature is reached and a stable organic thin film layer is obtained. . In any case, until the evaporation rate is stabilized, an operation for preventing vapor deposition on the substrate using a shutter or the like is required, and the above-mentioned loss often occurs.

  The present invention provides a device that can uniformly and quickly heat the vapor deposition raw material and is excellent in thermal response and temperature control, as well as vapor deposition for organic EL elements of good quality with good product yield and productivity. A method of obtaining a membrane is provided.

  The present invention relates to an organic EL thin film vapor deposition method in which an organic material for an organic EL element is vaporized and deposited on a film formation substrate to form a thin film. At least a part of the container in which the organic material is charged is electromagnetic induction. An organic EL element comprising a material that generates heat by heating, and by directly heating the container by electromagnetic induction heating by supplying current to the coil, the charged organic material is sublimated and vaporized It is a manufacturing method. Here, an organic metal complex is illustrated as an organic material for organic EL elements.

  The present invention also relates to a material that at least partially generates heat by electromagnetic induction in organic EL thin film deposition in which an organic material for an organic EL element in a container is vaporized and deposited on a film formation substrate to form a thin film. An organic EL thin film deposition apparatus comprising: the container configured; and means for electromagnetically heating the container by supplying a current to a coil to sublimate and vaporize the organic material. . Here, at least the inner surface of the container is a container made of a material inert to the organic material to be vaporized, or at least the bottom and side parts of the container are made of a material that generates heat by electromagnetic induction. Being a container provides a desirable organic EL thin film deposition apparatus.

Hereinafter, the organic EL thin film deposition apparatus of the present invention and the deposition method using the same will be described in detail.
FIG. 1 is a schematic cross-sectional view showing an example of the apparatus of the present invention, in which 1 is a chamber, 2 is a container, 3 is a coil, 4 is a power supply device, 5 is an organic material, 6 is a substrate, and 7 is a substrate. It is a substrate holder. In this example, the main device is incorporated in the chamber. However, for example, a mode in which the chamber is elongated and the coil is provided outside the chamber is also possible.

  The vacuum vapor deposition apparatus in the above example is disposed in a chamber 1 that can be evacuated, and includes a container 2 in which an organic material 5 is charged, a coil 3 disposed around the container 2, and a power supply apparatus 4 that leads to the coil 3. And a substrate holder 7 for holding the substrate 6 to be deposited. The chamber 1 can be decompressed by a vacuum pump or the like, and has a structure in which an organic material and a substrate inserted therein can be taken in and out.

  The shape of the container 2 can be a normal crucible shape or a simple cylindrical shape, but a so-called crucible shape or a deformed shape thereof is preferable. A shape called a cell, a Knudsen cell, or the like is also a preferable one. Note that when the diameter is large, a structure in which a material that can be heated by induction heating is also provided inside the container. As an example of the latter, it is possible to provide a wall capable of induction heating in the container. Although the shape of the container 2 is not specifically limited, It is preferable that it is a structure which can heat the organic material with which it is charged rapidly and uniformly.

  When the container 2 itself generates heat, it is formed from a heat generating material capable of generating heat by electromagnetic induction, but may be formed together with a material other than the heat generating material. The heat generating material may be either a metal material or a non-metal material, but is preferably a conductive magnetic material. Preferably, a portion including a bottom portion and a side portion of a container with which an organic material to be charged is in contact is formed from a heat generating material capable of generating heat by electromagnetic induction.

  Further, even when the material forming the container is a material that does not generate heat by induction heating, as proposed in JP-A-3-98286 and JP-A-8-264272, it has a structure capable of generating heat by electromagnetic induction heating. The filling body may be disposed in the container, and the heat generated by the filling body may be used as a heating source. In this case, the container is not necessarily made of a material that generates heat by electromagnetic induction. However, if a container that generates heat by electromagnetic induction and is capable of electromagnetic induction heating is disposed, uniform heating can be achieved. This is advantageous. For example, when the container size increases, a temperature gradient is formed between the organic material that is in contact with the inner wall of the container and the organic material that is away from the organic material, which may cause problems in uniform temperature control. In order to avoid such problems, a method of placing a packing body capable of generating heat by electromagnetic induction in the container and heating the packing body directly by electromagnetic induction heating or directly heating together with the container generates a temperature gradient. It is effective to hold down.

  Here, in order for the above-mentioned filling body itself to be heated uniformly by electromagnetic induction heating, the shape, the thickness of the filling body, the interval, the magnetic permeability of the material, the electrical conductivity, the frequency of the supplied alternating current In designing, it is important to optimize various factors. Therefore, it is a laminated body made of a material such as a wire mesh made of electromagnetic induction heatable material, or a large number of small cylindrical objects are made of a material such as a wire mesh or a wire, and organic material powder is present around, inside or in the gap. It is also advantageous. The filler may be in the form of granules, plates, lumps or the like that are not particularly molded.

  For example, when the organic material is a material that forms a light emitting layer, an organometallic complex is often used. However, when the complex metal comes into contact with a different metal at a high temperature, metal exchange occurs at a certain rate. Therefore, the purity of the complex is lowered and sometimes lower than the purity of the raw material. In most cases, metal complexes are decomposed during sublimation purification at high temperatures. The ligand formed by decomposition naturally forms a complex when it comes into contact with a different metal material. When the organic material contains acids, sulfur compounds, halogen compounds, etc., if a metal device is used, these impurities may cause metal corrosion, decomposition due to metal catalysis, contamination due to decomposition products, and the like.

  As described above, the container 2 may be composed of one kind of metal material or may be composed of two or more layers of materials, and the packing disposed in the container 2 even if the container itself does not generate heat by electromagnetic induction. However, if the organic material is contaminated or deteriorated due to the metal material as described above, the inner surface of the container or the surface of the filling is vaporized. It is preferable that the material be inert to the organic material. As a preferable heat generating material, iron-based metals such as iron and iron alloys are generally used. However, from the viewpoint of heat resistance and corrosion resistance, it is also possible to use stainless steel and magnetic ceramics such as graphite and titanium nitride. When the heat-generating material is a metal such as iron, it is often not inert to vaporized substances or trace amounts of residual oxygen gas. In such cases, the inner layer (surface layer in contact with the organic material) Is preferably a layer of an inert material against these organic materials and gases.

  Examples of inert materials include precious metals, alloys and other metals, heat-resistant resins such as fluororesin, polyimide resin, and silicon resin, quartz glass, pyrex (registered trademark), hard glass, glass such as glazing, alumina, and nitriding There are ceramics such as silicon and porcelain. Suitable inert materials include metals, glasses such as soot, fluororesins and ceramics. Of these, materials that do not have strength, are difficult to form, or are expensive can be made into an inner layer by means such as thin film deposition or plating. It is also advantageous to use magnetic ceramics such as titanium nitride, which is a heat generating material and an inert material, as the inner layer. Further, a container made of a material that is a heat generating material such as SiC, graphite, or titanium nitride and that is also an inert material can be used instead of the multilayer structure.

  The coil 3 is for inductively heating the container 2 or the filling body, and is installed around the container 2. The coil installed around the container causes direct heat generation in the container and the filling body by passing an alternating current. The current supplied to the coil 3 is supplied from the power supply device 4. The power supply device 4 is connected to a commercial power source or the like, and generates alternating current with a predetermined frequency. The frequency of the current supplied from the power supply device 4 to the coil 3 may be arbitrarily selected from the range of several tens to 100 kHz in consideration of the thickness of the heating element and the penetration depth of the current. It is desirable that

  Heating is performed by supplying current to the coil 3, and the amount of current supply is controlled so that the vaporization temperature is reached in the shortest possible time. Since reducing the heat capacity of the container is also effective for increasing the vaporization rate, it is advantageous not to make the container larger than necessary or to increase the wall thickness, but any increase in the input current amount Can also accommodate size. The power supply device 4 can have a control mechanism such as a temperature controller that maintains the temperature increase rate and the set temperature within a predetermined range. Therefore, a thermocouple or the like may be disposed in the container. The power supply device 4 is connected to a commercial power source, and preferably converts this into a high-frequency current, outputs it to the induction coil, and allows the supply current to be controlled by a signal from a thermocouple or the like.

  When vaporizing an organic material such as a sublimable substance and depositing it, if the shape of the container is a boat, the center part will evaporate first, and the boat temperature will be raised to evaporate the surrounding materials. However, in the case of the cell, since the raw material near the inner surface of the cell is evaporated and a void is formed there, it is preferable to raise the cell temperature in order to evaporate the raw material in the central part. At this time, it is preferable to monitor the evaporation rate or the actual film thickness, thereby controlling the power supplied from the power supply device 4 to ensure a uniform film thickness.

  The organic EL element has organic thin film layers such as a hole transport layer, a light emitting layer, and an electron transport layer between the anode and the cathode as described above. It is at least 1 type of organic material which forms an organic thin film layer.

  The organic material for organic EL vaporized by electromagnetic induction heating according to the present invention can be applied to any of hole transport materials, light emitting materials, electron transport materials, and the like. Examples of such materials include porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds as hole transport materials, and tris (8-quinolinolato) aluminum complexes and bis (benzoquinolinos) as luminescent materials. Lato) beryllium complex, tri (dibenzoylmethyl) phenanthroline europium complex, etc., and electron transport materials include 1,3,4-oxazole derivatives and 1,2,4-triazole derivatives, but are not limited thereto. Any organic compound for organic EL that can be formed into a thin film by a vapor deposition method can be used. The method of the present invention is also effective for precise deposition amount control such as multi-source deposition of organic materials.

  The substrate holder 7 is provided at a predetermined interval almost directly above the container 2 in the chamber. A substrate 6 constituting an EL element is set on the substrate holder 7, and vaporized organic material is deposited on the surface of the set substrate 6. As the mechanism for holding the substrate 6 by the substrate holder 7, a known means such as a suction method or a holding method can be adopted. If necessary, a cooling mechanism or the like can be provided inside the substrate holder 7. Although the magnitude | size of the board | substrate 6 is not specifically limited, The thing whose maximum length exceeds 500 mm is possible.

  As described above, according to the present invention, a crucible-like container or filling body capable of charging a large amount of vapor deposition raw material can be uniformly and quickly heated by electromagnetic induction heating, and heat Since it is excellent in responsiveness and temperature control, it is possible to obtain a vapor deposition film of good quality, and to improve product yield and productivity. As a result, a high-quality organic EL element can be stably obtained with a high yield.

Next, a method for vapor deposition using the apparatus of the present invention will be described.
The container 2 is charged with a predetermined amount of the organic material 5 to be deposited. In addition, a substrate 6 on which several layers may already be provided by vapor deposition or the like is set on the substrate holder 7 with the surface to be vapor deposited facing the container.
Then, pressure reduction and heating are performed, and vapor deposition starts. The temperature of the evaporation part in the container 2 and its surroundings may be a temperature at which a predetermined vapor pressure of the organic material 5 can be obtained. Usually, this vapor pressure is about several Torr to about 10 ⁻⁸ Torr (about 1 × 10 ² Pa to 1 × 10 ⁻⁶ Pa), but in order to lengthen the mean free path of vaporized molecules, the inside of the chamber is 10 ^{− 6} Torr or less is desirable. In the temperature control of the evaporation unit, the set temperature is maintained by turning on / off the AC power source with a thermometer and a temperature controller, or by controlling the inverter.
The organic material charged in the container is vaporized at a predetermined degree of vacuum and temperature, and passes through a slit disposed in the upper part of the container, for example, and adheres to and deposits on the surface of the substrate as a deposition target to form a deposited thin film. .

  Hereinafter, based on an Example, the specific example of this invention is demonstrated.

Example 1
8-Hydroxyquinoline aluminum (hereinafter referred to as Alq3) was deposited by the deposition apparatus shown in FIG.
The container 2 was a cylindrical crucible in which a molten aluminum plating was applied to the inner surface of a carbon steel pipe having an inner diameter of 15 mmφ and a height of 25 mm. The AC power supply for electromagnetic induction was 200 V, 60 Hz, and the frequency was increased using an inverter in the power supply device 4 equipped with a temperature controller.
The container 2 is charged with 1 g of Alq3, the outer wall temperature of the container 2 is heated at a setting of 360 ° C., the outer periphery of the chamber 1 is kept in contact with room temperature air, and is kept at about room temperature. The pressure was reduced to × 10 ^-7 Torr.
A glass substrate having a size of 100 mm × 100 mm was used as the substrate 6, and the glass substrate was placed about 350 mm directly above the container 2 and rotated. A film thickness monitor was arranged to measure the film thickness rate. The substrate was covered with a shutter until the film thickness rate was stabilized by the film thickness monitor, and when the film thickness rate became constant, the shutter was removed and vapor deposition was started. The power supplied from the power source was adjusted so that the film thickness rate was 0.3 nm / sec. After about 170 seconds, a 50 nm Alq3 film was obtained. The film thickness was ± 5% in the entire area, and ± 1% in the case of 50 mm × 50 mm closer to the center.

Reference example 1
As the container 2, an alumina ceramic crucible having an inner diameter of 15 mmφ and a height of 25 mm was used. Then, after charging a bundle of seven ferritic stainless steel thin tubes (outer diameter 4.8 mmφ, inner diameter 3.0 mm, height 25 mm) that generate heat by electromagnetic induction into the container 2, 0.3 g was charged and vapor deposition was performed under the same conditions as in Example 1. When the film thickness was measured after vapor deposition, the same results as in Example 1 were obtained. FIG. 2 is a perspective view of the filler, and shows the arrangement of the thin tubes 8.

Reference example 2
As the container 2, a stainless-ceramic crucible having an inner diameter of 15 mmφ and a height of 25 mm and having an upper 5 mm material made of ferritic stainless steel and a lower 20 mm material made of alumina ceramics was used. Then, after filling the inside of the container 2 with a 100 mesh wire netting and 9 sheets stacked at intervals (having a diameter in contact with the inner wall of the container 2 and a height of 20 mm) in contact with the bottom, Alq3 0.3 g was charged, and vapor deposition was performed under the same conditions as in Example 1. When the film thickness was measured after vapor deposition, the same results as in Example 1 were obtained. FIG. 3 is a perspective view of the filler, showing a state of lamination of the wire mesh 9.

It is a cross-sectional schematic diagram of the apparatus for organic EL element vapor deposition. It is a perspective view of a filling body. It is a perspective view of another filling body.

Explanation of symbols

  1: chamber, 2: container, 3: coil, 4: power supply device, 5: organic material, 6: substrate, 7: substrate holder

Claims (5)

  In an organic EL thin film vapor deposition method in which an organic material for an organic EL element is vaporized and deposited on a film formation substrate to form a thin film, a material in which at least a part of the container charged with the organic material generates heat by electromagnetic induction A method for producing an organic EL element, wherein the container is directly heated by electromagnetic induction heating by supplying a current to a coil to sublimate and vaporize the charged organic material.   In the organic EL thin film vapor deposition in which an organic material for an organic EL element in a container is vaporized and deposited on a film formation substrate to form a thin film, at least a part of the container is made of a material that generates heat by electromagnetic induction; An organic EL thin film deposition apparatus comprising: means for electromagnetically heating the container by supplying a current to the coil to sublimate and vaporize the organic material.   The organic EL thin film deposition apparatus according to claim 2, wherein at least an inner surface of the container is a container made of a material inert to an organic material to be vaporized.   The organic EL thin film deposition apparatus according to claim 2 or 3, wherein at least the bottom and sides of the container are made of a material that generates heat by electromagnetic induction.   The method for producing an organic EL element according to claim 1, wherein the organic material for the organic EL element is an organometallic complex.

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