JP2008108611A - Forming method and forming apparatus of evaporation layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming films capable of improving controllability in low film forming speed at the time of evaporation, and solving problems occurring in organic materials by not exposing the organic materials to a high temperature. <P>SOLUTION: There is provided a forming method of organic layers for an organic EL device which is provided with an anode electrode and a cathode electrode which are arranged opposite to each other, and at least one organic layer formed between both the electrodes and containing two or more kinds of organic compounds wherein the organic layers for the EL device are formed on a substrate by evaporation in a vacuum film forming chamber by using two or more evaporation sources in which distances from a substrate to each of the evaporation sources, or angles formed of a line connecting the center of the surface of the substrate and the center of the evaporation surface of each of the evaporation sources and the surface of the substrate are different and which have different evaporation rates. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a vapor deposition layer and a manufacturing apparatus, and more particularly to a method for manufacturing an organic layer and a manufacturing apparatus in an organic EL element.

  In recent years, the speed of information communication and the application range have been rapidly increasing. Among these, a high-definition display device capable of high-speed response with low power consumption capable of meeting demands such as portability and displaying moving images has been devised. In particular, for organic electroluminescence (hereinafter referred to as EL) devices, C.E. W. Since Tang announced a highly efficient organic EL device as a device with a two-layer structure (Non-Patent Document 1), various organic EL devices have been developed and are partially put into practical use.

  The organic EL element is composed of a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and the like including a light emitting layer, and these are composed of an organic layer made of an organic material. There are two types of materials for such an organic layer, a low molecular material and a high molecular material. In the case of an organic film using a low molecular material, it is mainly formed by vacuum deposition. A polymer material is dissolved in a solvent and used as a solution, and an organic film is formed mainly by a spin coater method, an ink jet method or the like.

It is well known that a host-guest composite film is used for a light emitting layer as one of high performance organic EL elements. Recently, a technique (doping) for doping a hole injection layer, a hole transport layer, an electron transport layer with an acceptor or an alkali metal has been attracting attention in order to lower the voltage of the device.
C. W. Tang, S.M. A. VanSlyke, Appl. Phys. Lett. 51,913 (1987)

Thus, when forming an organic film on the electrode, co-evaporation technology that simultaneously deposits while controlling the deposition rate of different materials is very important in order to control the doping concentration and film thickness. It becomes.
When forming a composite film containing a host-guest or an alkali metal doped layer on an organic film, the following problems have been pointed out. The amount of the guest material doped into the host material is generally 0.1 to several vol% because of the problem of concentration quenching. In this case, the doping amount can be adjusted by the deposition rate of each material, and the deposition rate of the guest material needs to be controlled to a very small value of 1/100 to 1/1000 of the host material. . For example, when the deposition rate of the host material is 10 Å / s, the guest material is deposited at a rate of 0.1 to 0.01 Å / s. Even in the case of doping with an alkali metal, it is necessary to precisely control 1% to 0.1% in terms of the film forming speed ratio from the relationship between the molecular weight of the organic material and the alkali metal.
On the other hand, it is possible to relatively increase the film formation speed of the guest material by increasing the film formation speed of the host material. However, increasing the film formation speed in an organic material is an It is not preferable from the viewpoint of thermal degradation.
The present invention provides a film-forming method capable of improving the controllability at a low film-forming rate during vapor deposition as described above and solving the problems that occur in organic materials without exposing organic forest materials to high temperatures. It is to provide.

The present invention provides two or more evaporation sources having different evaporation rates, wherein the distance from the substrate to the evaporation source or the angle between the line connecting the center of the substrate surface and the center of the evaporation surface of the evaporation source and the substrate surface is different. The present invention provides a method for manufacturing a vapor deposition layer that forms a vapor deposition layer on a substrate in a vacuum film formation chamber.
In addition, the present invention provides a method for producing an organic layer of an organic EL element, comprising: an opposing anode electrode and cathode electrode; and at least one organic layer containing two or more organic compounds disposed between the two electrodes. The organic layer has a different distance from the substrate to the evaporation source, or an angle between a line connecting the center of the substrate surface and the center of the evaporation surface of the evaporation source and the substrate surface, and different evaporation rates. Provided is a method for producing an organic layer of an organic EL element formed by vapor deposition on a substrate in a vacuum film formation chamber using the above evaporation source.
The present invention relates to an apparatus for producing a vapor deposition layer for forming a vapor deposition layer on a substrate, the substrate holder for supporting the substrate, the distance from the substrate to the evaporation source, or the center of the substrate surface An evaporation source holder for accommodating two or more evaporation sources having different evaporation speeds at different angles formed by the line connecting the evaporation surface center of the evaporation source and the substrate surface; Providing manufacturing equipment.
Moreover, this invention is the manufacturing apparatus of the organic layer of an organic EL element provided with the at least 1 layer of organic layer which is distribute | arranged between the opposing anode electrode and cathode electrode, and both electrodes and contains 2 or more types of organic compounds. In the vacuum film formation chamber for vapor deposition, there is a line connecting the substrate holder for supporting the substrate and the distance from the substrate to the evaporation source, or the center of the substrate surface and the center of the evaporation surface of the evaporation source. Provided is an apparatus for producing an organic layer of an organic EL element, comprising an evaporation source holder for accommodating two or more evaporation sources having different evaporation angles with respect to the substrate surface.

  According to the present invention, an organic EL display having an organic layer formed by a so-called co-evaporation technique can be manufactured with good reproducibility and high yield. For example, the doping control in the small amount doping in the light emitting layer and the doping in the charge transport layer can be greatly improved. By providing a co-evaporation technique with high accuracy and good controllability that can be applied to the light emitting layer and the doping technique, it is possible to improve the performance and yield of the organic EL display and to reduce the cost.

In general, the vapor flow density from the evaporation source (0, 0, 0) is defined by the following equation by Lambert's cos rule from an arbitrary point (x, y, z).
φ (α) = φ ₀・ cosα
(In the above equation, α represents the angle with respect to the normal of the evaporation surface, φ (α) represents the distribution of vapor flow density at angle α, and φ ₀ represents the distribution of vapor flow density at angle α = 0. )
The shorter the distance between the evaporation source and the substrate surface, the higher the vapor flow density on the substrate surface. As the distance between the evaporation source and the substrate surface increases, the vapor flow density on the substrate surface decreases, so when the deposition rate of the organic film deposited on the substrate is fixed, the vapor flow rate from the evaporation source must be increased. I must. For this purpose, it is necessary to increase the temperature of the evaporation source. In this case, the organic film deposited on the substrate is thermally damaged. Therefore, by shortening the distance between the evaporation source and the substrate surface, it is possible to avoid a high temperature of the evaporation source and to suppress thermal damage to the organic film deposited on the substrate. However, when the distance between the evaporation source and the substrate surface is shortened, the angle α in the above equation changes greatly on the substrate surface, so that the vapor flow density distribution characteristic on the substrate is lowered and the film thickness distribution characteristic is lowered. Therefore, by disposing a plurality of evaporation sources, it is possible to form an organic film having a uniform thickness without degrading the film thickness distribution characteristics. The present invention relates to an installation method and arrangement at the time of co-deposition of a host material that is a main component of an organic film and a guest material that functions as a dopant.

  The substrate used in the present invention is preferably a resin such as glass, polyethylene terephthalate, or polymethyl methacrylate. Borosilicate glass or blue plate glass is particularly preferred.

The organic EL layer element has a structure in which at least an organic light emitting layer is held between a pair of electrodes, and a hole injection layer or an electron injection layer is interposed as required. Specifically, for example, those having the following layer structure are adopted.
(A) Anode / organic light emitting layer / cathode (b) anode / hole injection layer / organic light emitting layer / cathode (c) anode / organic light emitting layer / electron injection layer / cathode (d) anode / hole injection layer / organic Light emitting layer / electron injection layer / cathode (e) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron injection layer / cathode In the above layer structure, at least one of the anode and the cathode is an organic light emitter. It is desirable to be transparent in the wavelength range of the emitted light, and light is emitted through the transparent electrode, and the light is preferably incident on the fluorescent color conversion film. In this technique, it is known that it is easy to make the anode transparent, and it is desirable to make the anode transparent also in the present invention.

The anode is preferably made of a material having a large work function in order to efficiently inject holes. In particular, in an ordinary organic EL element, since light is emitted through the anode, the anode is required to be transparent, and a conductive metal oxide such as ITO or IZO is used.
The cathode is preferably a material having a low work function, such as an alkali metal such as lithium or sodium, an alkaline earth metal such as potassium, calcium, magnesium or strontium, or an electron injecting metal such as a fluoride thereof, or the like. Alloys and compounds with these metals are used.

The organic layer includes at least an organic light emitting layer, and has a structure in which a hole injection layer, a hole transport layer, and / or an electron injection layer are interposed as required.
Known materials are used as the material of each layer of the organic layer. For example, in order to obtain blue to blue-green light emission as an organic light emitting layer, for example, a fluorescent brightener such as benzothiazole, benzimidazole, benzoxazole, metal chelated oxonium compound, styrylbenzene compound, aromatic Dimethylidin compounds and the like are preferably used.

An organic EL element is produced as follows, for example.
First, a transparent electrode is formed on the entire surface by sputtering.
Next, the substrate on which the anode is formed is mounted in a resistance heating vapor deposition apparatus, and a hole injection layer, a hole transport layer, an organic light emitting layer, and an electron injection layer are sequentially formed without breaking the vacuum. Specifically, a vacuum deposition apparatus provided with a plurality of vacuum chambers was used. The substrate was transported in a vacuum and deposited in a separate vacuum chamber for each layer. In forming each layer, the internal pressure of the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. Although the thickness of each layer of the organic layer can be appropriately selected according to the characteristics, it is preferably 1 μm or less, more preferably several hundred nm or less.
Thereafter, the cathode was patterned using a mask without breaking the vacuum. When the cathode is a metal material, the cathode is formed by vapor deposition. When the cathode is a transparent electrode, it is formed by sputtering.
The organic EL device thus obtained was sealed with a sealing glass and a UV curable adhesive in a dry nitrogen atmosphere in the glove box (both oxygen and moisture concentrations were 10 ppm or less).
When forming a large number of pixels on a substrate, a transparent electrode is formed on the entire surface by sputtering, then a resist agent is applied on the transparent electrode, and then patterned by a photolithography method to form a stripe pattern. An anode consisting of The organic film is formed by the same procedure as described above.
The cathode is formed by using a mask that can obtain a stripe pattern perpendicular to the anode line without breaking the vacuum.

The organic layer is preferably a film of an organic material doped with an alkali metal or a composite film containing a host-guest.
When the organic layer is an organic material film doped with an alkali metal, an organic material evaporation source and an alkali metal evaporation source are used, and the evaporation rate of the alkali metal is 1/100 to 1/1 of the evaporation rate of the organic material. Those in the range of 1000 are preferred. Specifically, examples of organic materials suitable for the electron transport layer include tris (8-quinolinolato) aluminum (Alq3), tris (4-methyl-8-hydroxyquinolinato) aluminum (Almq3), and derivatives thereof. A metal complex having at least one as a ligand, oxadiazole derivatives such as 2- (4-biphenyl) -5 (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD), 3 -(Biphenyl-4-yl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole (TAZ), 3,5-diphenyl-4-naphth-1-yl-1 2,4-triazole and the like.
Examples of the alkali metal include Li, Na, K, and Cs.

  In the case where the organic layer is a composite film containing a host-guest, the evaporation source of the host material and the evaporation source of the guest material are used, but the evaporation rate of the guest material is in the range of 1/100 to 1/1000 of the host material. Are preferred. Specifically, dimethylidin derivatives such as 4,4′-bis (2,2′-diphenylvinyl) biphenyl (DPVBi), tris (8-quinolinolato) aluminum (Alq3) or a dielectric thereof is coordinated as a host material. Examples thereof include metal complexes having at least one as a child and anthracene compounds such as 2-tert-butyl-9,10-di (2-naphthyl) anthracene (TBADN). Examples of guest materials include distyrylbenzene compounds such as 4,4′-bis [2- {4- (N, N-diphenylamino) phenyl} vinyl] biphenyl (DPAVBi), 3- (2-benzothiazolyl) -7- Examples thereof include coumarin derivatives such as diethylaminocoumarin (coumarin 6), 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), and the like.

  Two or more evaporation sources having a small deposition amount, such as an alkali metal evaporation source or a guest material evaporation source, are preferably provided.

According to the present invention, it is possible to reduce the amount of the guest material flux during vapor deposition by making the distance from the deposition substrate closer.
The present invention will be described with reference to the drawings, taking as an example the case of forming a composite film containing a host-guest as the organic layer, but the same applies to an organic material film doped with an alkali metal.
FIG. 1 shows a vapor deposition apparatus according to an embodiment of the present invention.
In this vacuum deposition apparatus, an evaporation source 6 that accommodates a host material, evaporation sources 5a and 5b that accommodate a guest material, and power sources 16, 15a and 15b for heating each, a substrate (for example, a glass substrate) 1 is provided with a substrate holder 2 that supports 1, a film thickness sensor 3, a deposition preventing plate 4 that prevents the deposition container wall of the deposition material from being contaminated, and a vacuum pump 7. At this time, the inside of the vapor deposition container is kept in vacuum by the vacuum pump 7 during vapor deposition. Each evaporation source has a heating power source outside the vapor deposition container, and can individually control the temperature.

As shown in FIG. 1, the host evaporation source is prepared by charging the material in the lower part of the vapor deposition container.
In the present invention, as the organic compound to be deposited, a sublimable material, a gasified while melting (meltable material), or the like can be used. The guest evaporation source contains an organic material to be deposited in the same manner as the host evaporation source, and is installed at a position near the substrate as shown in FIG. That is, the distance between the substrate of the present invention and the guest evaporation source is shorter than the distance between the substrate and the host evaporation source. The distance between the substrate and each evaporation source is a distance connecting the center of the substrate surface and the center of the evaporation surface of the evaporation source.
The distance between the substrate of the present invention and the guest evaporation source and the distance between the substrate and the host evaporation source can be changed depending on the deposition rate of the material used, that is, the physical properties (boiling point, etc.).

In FIG. 1, the distance from the substrate to the evaporation source is changed, but the angle between the line connecting the center of the substrate surface and the center of the evaporation surface of the evaporation source and the substrate surface may be changed. If the distance from the substrate to the evaporation source is the same and the angle is changed, two or more evaporation sources are arranged on a concentric circle with the center of the substrate surface being the center of the circle. The angle may be changed by changing the distance from the substrate to the evaporation source.
The angle between the substrate and the guest evaporation source of the present invention and the angle between the substrate and the host evaporation source can be changed depending on the deposition rate of the material used, that is, the physical properties (boiling point, etc.).

In order to deposit an organic compound on the substrate 1, first, the vacuum pump 7 is operated to keep the inside of the vacuum chamber 10 in a vacuum, and each evaporation source is heated. When each evaporation source is heated, the internal organic material is heated as heat propagates from the inner wall. When the organic material reaches a certain temperature, the organic compound powder sublimates (vaporizes), and a vapor flow is generated from the upper opening and adheres to the substrate 1 to form a thin film of the organic material. In this case, the host evaporation source and the guest evaporation source can be individually controlled. Since a plurality of guest evaporation sources are installed in the container, the vapor flow generated from each evaporation source is independent. Compared to the case of installing in the, the specified steam flow can be reached with a small amount.
Further, since the distance between the substrate and the evaporation source is short, the temperature of the evaporation source for reaching a prescribed vapor flow can be reduced.

  The evaporation source in the present invention can be arbitrarily changed by arranging two or more evaporation sources. FIG. 2 shows five evaporation sources, evaporation sources 5a to 5d and 6. Needless to say, the arrangement of the evaporation sources is merely an example, and other arrangements are also effective.

According to the present invention, a substrate rotation mechanism that rotates the substrate while facing the evaporation source may be provided.
As an example, FIG. 3 shows a rotating mechanism 17 that rotates a glass substrate in a vacuum vessel.
The rotation mechanism is not particularly limited as long as the rotation mechanism can rotate while facing the evaporation source.

Example 1
An organic material was mounted in each evaporation source according to the present invention to produce an organic EL device.
As the substrate, glass with 50 mm × 50 mm ITO was used in a range of 200 mm × 200 mm. As for the distance between the substrate and the evaporation source in the vacuum vessel provided in this experiment, the distance between the host evaporation source was 400 mm and the distance between the guest evaporation sources was 200 mm. The guest evaporation source was arranged as shown in FIG. The structure of the fabricated device was hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode. The hole transport layer was 40 nm α-NPD, the light-emitting layer (also serving as the electron transport layer) was 30 nm Alq3 doped with 0.1 vol% coumarin 6, and the electron transport layer was Alq3 20 nm. Each film-forming speed was 0.1 nm / sec.
The temperature of the host and guest during co-evaporation was 180 ° C. when Alq3 was 300 ° C. at a film formation rate of 1.0 Å / s, and the film formation rate of each coumarin evaporation source was 0.0025 Å / s. Next, 100 nm of Ag—Mg was stacked as an electron injection layer and a cathode. As a result of evaluating the device thus fabricated, the average current efficiency of the device was 8 cd / A, and the variation was within Δ5%.

Comparative Example 1
As a comparative example, an organic EL device was manufactured using the conventional apparatus shown in FIG. This apparatus includes a substrate 101, a substrate support section 102, a film thickness sensor 103, a deposition plate 104, a guest evaporation source 105 and its heating power source 115, a host evaporation source 106, its heating power source 116 and a vacuum pump 107. It was provided in the vacuum chamber 110. As the substrate, glass with 50 mm × 50 mm ITO was used in a range of 200 mm × 200 mm. The distance between the substrate and the evaporation source in the vacuum container provided in this experiment was 400 mm between the host evaporation source and 400 mm between the guest evaporation sources. The structure of the fabricated device was hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode. The hole transport layer was 40 nm α-NPD, the light-emitting layer (also serving as the electron transport layer) was 30 nm Alq3 doped with 0.1 vol% coumarin 6, and the electron transport layer was Alq3 20 nm. Each film-forming speed was 0.1 nm / sec. The temperature of the host and guest during co-deposition was 300 ° C. at a film formation rate of 1.0 Å / s for Alq3, and 220 ° C. at a film formation rate of each coumarin evaporation source of 0.001 Å / s. Compared with the Examples, the deposition temperature increased by 40 ° C. Next, 100 nm of Ag—Mg was stacked as an electron injection layer and a cathode. As a result of evaluating the device thus fabricated, the average current efficiency of the device was 7 cd / A, and the variation was within Δ15%. The reasons for the decrease in current efficiency and the increase in the variation are considered to be the result of the difficulty in controlling the guest material and the decrease in the uniformity of the film thickness distribution of the guest material.

Example 2
An organic material was mounted in each evaporation source according to the present invention to produce an organic EL device.
As the substrate, glass with 50 mm × 50 mm ITO was used in a range of 200 mm × 200 mm. In the vacuum vessel provided in this experiment, a mechanism for rotating the glass substrate is provided. The distance between the substrate and the evaporation source was 400 mm between the host evaporation source and 100 mm between the guest evaporation sources. The guest evaporation source was arranged as shown in FIG. The structure of the fabricated device was hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode. The hole transport layer was 40 nm α-NPD, the light-emitting layer (also serving as the electron transport layer) was 30 nm Alq3 doped with 0.1 vol% coumarin 6, and the electron transport layer was Alq3 20 nm. Each film-forming speed was 0.1 nm / sec. The substrate rotation was 30 rpm. The temperature of the host and guest during co-deposition was 330 ° C. at a film formation rate of 1.0 Å / s for Alq3, and 200 ° C. with a film formation rate of each coumarin evaporation source of 0.01 Å / s. Next, 100 nm of Ag—Mg was stacked as an electron injection layer and a cathode. As a result of evaluating the device thus fabricated, the average current efficiency of the device was 8 cd / A, and the variation was within Δ5%.

It is an example of the vapor deposition apparatus by this invention. It is an example of the evaporation source arrangement | positioning of this invention. It is an example of the evaporation apparatus provided with the rotation mechanism by this invention. It is an example of the vapor deposition apparatus of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate holder 3 Film thickness sensor 4 Deposition plate 5, 5a, 5b, 5c, 5d Evaporation source for guest 6 Evaporation source for host 7 Vacuum pump 10 Vacuum chamber 15a, 15b Power supply for heating 16 Power supply for heating 17 Rotation mechanism DESCRIPTION OF SYMBOLS 101 Substrate 102 Substrate holder 103 Film thickness sensor 104 Attachment plate 105 Guest evaporation source 106 Host evaporation source 107 Vacuum pump 110 Vacuum chamber 115 Power supply for heating 116 Power supply for heating

Claims (9)

  Using two or more evaporation sources with different evaporation rates, the distance from the substrate to the evaporation source, or the angle between the substrate surface center and the evaporation surface center of the evaporation source is different from the substrate surface, A method for manufacturing a vapor deposition layer, wherein a vapor deposition layer is formed on a substrate in a deposition chamber.   A method for producing an organic layer of an organic EL device comprising: an opposing anode electrode; a cathode electrode; and at least one organic layer containing two or more organic compounds disposed between the two electrodes. Use two or more evaporation sources with different evaporation speeds, where the layer has a different distance from the substrate to the evaporation source, or the angle between the line connecting the center of the substrate surface and the center of the evaporation surface of the evaporation source and the substrate surface A method for producing an organic layer of an organic EL element formed by vapor deposition on a substrate in a vacuum film formation chamber.   The organic layer is a film of an organic material doped with an alkali metal, and the two or more evaporation sources having different evaporation rates are the evaporation source of the organic material and the evaporation source of the alkali metal, and the evaporation of the alkali metal. The method for producing an organic layer of an organic EL element according to claim 2, wherein the speed is in the range of 1/100 to 1/1000 of the evaporation speed of the organic material.   The organic layer is a composite film containing a host-guest, the two or more evaporation sources having different evaporation rates include a host material evaporation source and a guest material evaporation source, and the guest material evaporation rate is The method for producing an organic layer of an organic EL element according to claim 2, wherein the organic material is in the range of 1/100 to 1/1000 of the evaporation rate of the host material.   The method for producing an organic layer of an organic EL element according to claim 3, wherein two or more of the alkali metal evaporation source or the guest material evaporation source are provided.   The method for producing an organic layer of an organic EL element according to claim 2, wherein the organic layer is formed by rotating the substrate while facing the evaporation source.   A vapor deposition layer manufacturing apparatus for forming a vapor deposition layer on a substrate, the substrate holder for supporting the substrate, the distance from the substrate to the evaporation source, or the center of the substrate surface and the evaporation of the evaporation source An apparatus for producing a vapor deposition layer, comprising: an evaporation source holder for housing two or more evaporation sources having different evaporation rates, wherein the angle between a line connecting the center of the surface and the substrate surface is different.   An apparatus for producing an organic layer of an organic EL element, comprising an anode and a cathode facing each other, and an organic EL element comprising at least one organic layer containing two or more organic compounds, The angle between the substrate holder for supporting the substrate and the distance from the substrate to the evaporation source, or the line connecting the center of the substrate surface and the center of the evaporation surface of the evaporation source, with the substrate surface in the vacuum film formation chamber And an evaporation source holder for storing two or more evaporation sources with different evaporation rates.   The apparatus for producing an organic layer of an organic EL element according to claim 8, further comprising a substrate rotating mechanism that rotates the substrate while facing the evaporation source.

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