JP2007265707A - Organic electroluminescent element, its manufacturing method and mask frame - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of restraining charge-up or sputtering damage caused by the scattering of secondary electrons on an organic thin film, restraining a temperature rise of a target 12 by forcibly cooling by a chiller or the like cooling water flowing at an under part of a backing plate, and restraining mask deformation (flexure) caused by the radiation heat of the target 12, in film-forming a transparent electrode on an organic thin film in the course of the film-forming of the transparent electrode. <P>SOLUTION: By the method of forming a transparent electrode film on an organic thin film without causing charge-up and with sputtering damage restrained, an improvement in characteristics (driving, life or the like) is expected for the transparent organic electroluminescent element and a top-emission organic electroluminescent element with a final film-forming process applied in the sputtering method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a transparent electrode of an organic electroluminescent device, a transparent organic electroluminescent device and a top emission organic electroluminescent device, a polymer organic electroluminescent display device, a flexible organic electroluminescent device, and a mask frame for producing a transparent electrode.

In the organic light emitting device of the upper light extraction type and the double-sided light extraction type, the cathode made of a metal thin film is protected and the wiring resistance is reduced by forming a transparent conductive film (for example, see Patent Document 1).
When the transparent conductive film itself is a cathode, a buffer layer is sandwiched between the light emitting layer and the transparent conductive film for the purpose of protecting the underlying light emitting layer and reducing the electron injection barrier. For the formation of the transparent conductive film, the conventional deposition methods, as well as the plasma and ion beam assisted deposition methods, ion plating methods, ion beam sputtering methods, etc. that have been used in recent years for optical communications are mainly used. In addition, other wet methods such as a sol / gel method and a spray method may be used (for example, Patent Document 2).
On the other hand, there is a sputtering method as a method used in mass production apparatuses in thin film manufacturing processes such as semiconductors, flat panel displays, and electronic components.
The sputtering method is widely used as a method suitable for mass production because the film formation rate and film composition are stable and uniform film formation on a large area substrate is possible. Furthermore, it has become mainstream because of its high uniformity of film thickness, conductivity and transparency, and excellent fine etching characteristics.

The characteristics of the sputtering method include the following.
In general, when the energy of particles incident on the substrate exceeds about 50 eV, the particles enter the substrate, the atoms constituting the substrate are knocked out, or defects are generated in the substrate. Cause problems such as roughness and roughness. Conversely, when forming a film with only thermal energy as in the vapor deposition method, the energy of the incident particles is as low as 0.1 eV, and sufficient migration (migration) cannot be performed on the substrate surface. The film is sparse and the bond strength at the substrate-film interface is small and unstable.
The sputtered particles deposited on the substrate have a much larger particle energy (deposition method: about 0.1 eV ⇒ sputtering method: about 600 eV) compared to the vacuum deposition method, which is the same physical vapor deposition method. There is a concern that the original light emission potential of the organic light emitting material may be lowered by causing the molecular structure of the film to be destroyed by scattering / collision of recoil Ar plasma, γ electrons, target particles, etc., which are high energy particles.

  On the other hand, when an electrode pattern is formed by a metal mask using a sputtering method, the mask is formed by radiant heat on the target surface due to plasma confinement, and secondary electrons (accelerated electrons associated with successive ionization processes) incident on the mask surface due to plasma end loss. There is a concern of thermal expansion and deflection.

上記問題に対してマスク材質に低熱膨張率材料、具体的には表に示すようなオーステナイト系ステンレス鋼やインバー材を用いてたわみを抑制している。
特開２００１−１７６６７０号公報 特許第２８５０９０６号公報

With respect to the above problems, a low thermal expansion coefficient material, specifically austenitic stainless steel or invar material as shown in the table, is used to suppress the deflection.
JP 2001-176670 A Japanese Patent No. 2850906

In the production of a top emission type organic electroluminescence device, it is important to establish a transparent electrode film forming technique that realizes low wiring resistance and high visible light transmittance.
In the present invention, a sputtering mask using a material having a low thermal expansion coefficient and a high electrical insulation (high dielectric constant), specifically, aluminum nitride ceramics (AlN) is used as a mask for forming an electrode pattern in transparent electrode film formation. .

  Another characteristic required for the mask material is that it is excellent in machinability and lightweight because high-definition pattern processing is performed on a thin plate.

  The top emission type organic electroluminescence device forms a transparent electrode, organic thin film, and metal electrode in this order on a glass substrate, whereas a general organic electroluminescence device forms a metal electrode, organic thin film, and transparent on a glass substrate. Film formation is performed in the order of electrodes. By this method, a color filter can be manufactured on the sealing substrate side and bonded to the light-emitting element substrate. In addition, when applying an organic electroluminescence device as an active matrix drive display, the top emission method that extracts light from the upper part of the device on the opposite side of the substrate prevents light from being blocked by the drive circuit on the substrate, and an increase in aperture ratio can be expected. .

  Applications of transparent conductive films are diversifying, such as optical communications, semiconductor lasers, various displays, recording media, consumer devices (digital cameras, projectors, mobile phones, lenses, mirrors, lamps, etc.). In manufacturing technology, stability during mass production, such as yield improvement, and film performance during multilayer film formation have become important requirements.

  ITO is called Indium tin oxide, but its mother crystal is In2O3. ITO (In2O3: Sn) having a composition in which Sn is added in an amount of 5 to 10 wt% in terms of oxide is transparent like an insulator, but has high conductivity (10e + 3 S / cm) and little absorption. Transparency and conductivity are related to each other, but there is no one-to-one correspondence. Transparency means that the structural integrity of the In2O3 crystal is high and the number of electron capture levels in the band gap is very small. This means that the atoms in the crystal are correctly aligned with the coordinate point (lattice position) of the crystal system. It is determined by whether or not it is located without excess or deficiency. The In2O3 reagent is yellowish white, and a transparent conductive film can be obtained by vapor deposition or sputtering in an atmosphere containing a slight amount of oxygen (partial pressure is 10e-1 Pa or less). However, as a compound, it is easy to let go of oxygen, and it is easily reduced by heating in a vacuum or in a reducing atmosphere containing several percent of hydrogen. As the reduction proceeds, the color changes from blue-black to black and further to brown. . Conductivity is manifested by substituting with In atoms or Sn atoms of the mother crystal, or by forming a film under conditions that do not give sufficient and sufficient oxygen atoms.

  The physical meaning of transparency of ITO can be attributed to the fact that the band gap as a semiconductor is near the short wavelength limit of 400 nm in the visible region. However, this is not enough, and in order to ensure high transparency, there are few or negligible levels at which electrons are resident at room temperature in the band gap. Such bandgap levels originate from oxygen vacancies and lattice defects due to In, Sn atoms or atomic groups (clusters) other than Sn atoms substituted at the In position. It must be easy to form a lattice. In2O3 satisfies this requirement unless the film is formed in an atmosphere with extremely weak oxidizing properties. In fact, In2O3 exhibits a well-prepared X-ray diffraction pattern with a narrow half-value width from a thickness of several tens of nanometers, even under atmospheric conditions where oxygen is slightly deficient if the glass substrate temperature is about 300 ° C. Even if Sn is added, this characteristic of being easily crystallized is not lost up to several tens of percent. This is a feature that is greatly different from the SnO 2 film and the ZnO film.

  In the sputtering process, when the electrode material is an insulating material, RF magnetron sputtering is used. In RF magnetron sputtering, when an RF voltage is applied to the cathode (TArget) in a floating state, the positive ion charge-up is canceled, and a DC self-bias voltage is generated on the cathode surface. The cathode material can be sputtered.

  RF magnetron sputtering has a high current density, and ions hit electrons with a high energy of 600 eV, so that the cathode material can be sputtered at high speed. In addition, the average free path of the sputtered particles is long due to the low pressure, and the thin film can be deposited by collecting the sputtered particles on the substrate facing the cathode. However, due to the high-energy process, when depositing on an organic thin film, it must be deposited for a long time with low power, and further, recoiled Ar plasma and γ electrons and further accelerated on the underlying organic thin film. TArget particles collide with each other and cause a large damage.

  In order to achieve the above-mentioned object, the invention according to claim 1 is a method of manufacturing a transparent electrode of an organic electroluminescent device by forming a transparent conductive film on a substrate through a mask facing a target in a sputtering method. A strong magnetic field is formed at a location closer to the target than the mask, and charged particles (Ar ions, secondary electrons) scattered from the target toward the mask are bent in a direction to escape from the mask by the strong magnetic field. This is a method for producing a transparent electrode of an organic electroluminescent element.

  According to a second aspect of the present invention, the target is disposed on a backing plate, and the temperature rise of the target surface is suppressed by cooling the backing plate. It is a manufacturing method of the transparent electrode of an organic electroluminescent element.

  The invention according to claim 3 is characterized in that the cooling of the backing plate is performed by controlling the cooling water flowing through the lower portion of the backing plate to 10 ° C. or less by a refrigerant (chiller) such as liquid nitrogen. It is a manufacturing method of the transparent electrode of the organic electroluminescent element of Claim 2.

  Invention of Claim 4 is the transparent organic electroluminescent element manufactured using the manufacturing method of the transparent electrode of Claim 1, 2, 3, and a top emission type organic electroluminescent element.

  According to a fifth aspect of the present invention, in the organic electroluminescent element according to the fourth aspect, a transparent organic electroluminescent element and a top emission type are characterized in that a polymer organic electroluminescent element forming material is patterned on a substrate. It is an organic electroluminescent element.

  A sixth aspect of the present invention is a polymer organic electroluminescence display device in which R, G, and B color inks are separately applied to the pattern formation according to the fifth aspect using an offset printing method.

  According to a seventh aspect of the present invention, in the organic electroluminescent element and the polymer organic electroluminescent display device according to the fourth, fifth, and sixth aspects, a ternary compound such as a Si3N4 nitride or SiON is formed on the lower electrode of the element. It is a flexible organic electroluminescent element which formed the passivation film using the manufacturing method of Claim 1 after forming a passivation film by CVD method.

  The invention according to claim 8 is the method for producing a transparent electrode of an organic electroluminescent element according to claim 1, wherein the mask is formed of a material having excellent heat dissipation characteristics and a low coefficient of thermal expansion.

  The invention according to claim 9 is a mask frame used in manufacturing a transparent electrode of an organic electroluminescent element by forming a transparent conductive film on a substrate through a mask facing a target in a sputtering method. A direction in which charged particles (Ar ions, secondary electrons) scattered from the target toward the mask at a position of the mask frame closer to the target than a position of the mask frame supporting the mask escape from the mask. A mask frame for producing a transparent electrode of an organic electroluminescent element, comprising a pair of magnets that bend in a straight line.

  A tenth aspect of the present invention is the mask frame for manufacturing a transparent electrode of an organic electroluminescent element according to the ninth aspect, wherein the mask frame is provided in the shape of a cross that forms a lattice.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
As shown in FIGS. 1 and 2, the sputtering mask 2 and the mask frame 16 according to the present invention have a mask frame in which a pair of magnets 5 made of neodymium alloy or the like having different polarities are provided below the mask frame 16. 16, a strong magnetic field is formed in the lower part, and the direction 10 of secondary electrons (acceleration electrons) is bent in the lower part of the mask 2, that is, charged particles (Ar ions, two ions scattered from the target 12 toward the sputtering mask 2. (Secondary electrons) are bent in the direction of escaping from the sputtering mask 2 by the strong magnetic field, thereby making it possible to suppress sputtering damage and substrate charge-up due to electron collision with the organic layer.

  In addition, the sputtering mask 2 and the mask frame 16 according to the present invention are excellent in heat dissipation characteristics and have a low coefficient of thermal expansion when the transparent conductive film is formed by the sputtering method. This can be suppressed by using a material and further providing a grid-like cross 17 at the opening of the mask frame 16 as shown in FIG. By suppressing the mask deformation, it is possible to eliminate the mask pattern blur caused by the target particles wrapping around the gap generated between the mask and the substrate due to the deformation.

  The sputtering apparatus and the sputtering target 12 according to the present invention, when forming a transparent conductive film by a sputtering method, increase the temperature of the surface of the target 12 due to plasma confinement, and use cooling water flowing under the backing plate 13 as a coolant such as liquid nitrogen (chiller). ) By forced cooling to 10 ° C. or lower.

Next, the mask frame 16 and the sputtering apparatus 20 will be described in detail.
As shown in FIGS. 1A and 1B, the mask frame 16 has a rectangular frame shape, and a sputtering mask 2 in which a plurality of mask patterns 1 are formed is disposed inside the opening, and the sputtering mask 2 is formed. The outer peripheral portion is attached to the mask frame 16 with the mask fixing screw 3.
The pair of magnets 5 is provided in parallel with two opposing sides of the mask frame 16, and a magnetic force line 7 is formed along the mask frame 16 between the pair of magnets 5.
Specifically, a pair of magnets 5 is provided at a location closer to the target 12 than the sputtering mask 2, and magnetic lines 7 are formed between the pair of magnets 5.
Sputtered particle incident angle adjusting portions (45 deg) 4 are provided at locations above the pair of magnets 5 where the mask frame 16 faces downward.
As shown in FIG. 2, a glass substrate 6 is superposed on the upper surface of the sputtering mask 2 attached to the mask frame 16.

As shown in FIG. 2, the sputtering apparatus 20 has a mask frame 16 disposed on the upper portion thereof, and a shutter plate 11 and a target so as to face the sputtering mask 2 and the mask frame 16 with a space below the mask frame 16. 12, a backing plate (OFC) 13, a cathode magnet 14 and the like are arranged.
A backing plate 13 is disposed above the cathode magnet 14, and a flow path 15 for flowing the cooling water is formed between the upper portion of the cathode magnet 14 and the lower portion of the backing plate 13.
Ar plasma 8 is generated above the target 12 placed on the backing plate 13, and Ar ions 9 are incident on the target 12 to cause sputtering. The sputtered particles generated from the target 12 are directed upward. A transparent conductive film matching the shape of the mask pattern 1 is formed by moving and depositing on the glass substrate 6 through the mask frame 16.

  In the present invention, a top emission type flexible organic electroluminescence device is produced by forming an electrode pattern of a metal material such as Mg, Al, Cr, etc. on a support substrate by a vacuum deposition method, and then forming a poly (3,4-ethylenediethylene) on the electrode pattern. Water-soluble materials such as oxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) are used as the hole transport layer, and organic solvent-soluble materials such as polyparaphenylene vinylene (PPV) and polyfluorene (PF) are used as the light emitting layer. Form by the method. In this organic layer film formation substrate, the upper transparent electrode is formed by sputtering using the sputtering mask 2 and mask frame 16 and the sputtering apparatus 20 shown in paragraphs 0025, 0026, and 0027.

  In the present invention, the offset printing method used to form a pattern by separately coating a polymer organic electroluminescent material composed of each color of R, G, and B uses ink from the ink supply unit to the entire surface of a blanket made of polydimethylsiloxane or the like. The ink is transferred from the blanket (cylinder) to the convex part of the patterned negative printing plate. Excess ink is transferred to the printing plate, and the necessary ink is transferred directly to the blanket (cylinder). It is a way to leave. This method transfers 100% of the excess ink onto the plate and 100% of the ink from the blanket (cylinder) to the substrate, that is, after the transfer to the printing plate, the blanket (cylinder) has a necessary patterning portion. 100% of the ink remains and it needs to be transferred to 100% of the substrate.

In the CVD method, the vaporized compound (source gas) containing the element to be formed into a film is mixed with a carrier gas such as hydrogen or nitrogen as it is, and sent to the substrate surface heated as high as possible, and decomposed on the substrate surface. In this method, a thin film is formed on a substrate by causing a chemical reaction such as reduction, oxidation, or substitution. As the source gas, a halide, an organic compound, or the like is used. The decomposition, reduction, oxidation, and substitution reactions that occur on the substrate are as follows.
(1) SiH4 → 700-1000 ° C. → Si + 2H2 ... pyrolysis for Si thin film (2) SiCl4 + 2H2 → ˜1200 ° C. → Si + 4HCl ... reduction for Si thin film (3) SiH4 + O2 → ˜ 400 ° C. → SiO 2 + 2H 2... Oxidation for SiO 2 thin film (4) CrCl 2 + Fe → 1000 ° C. → Cr + FeCl 2... Replacement for Cr thin film These reactions are considered to occur through the following steps. Reaction gas diffusion to the substrate surface → Adsorption of the reaction gas to the substrate surface → Chemical reaction on the substrate surface → Desorption / diffusion of by-product gas from the surface (exhaust).
CVD films are characterized by high quality due to high temperature reactions and good coverage (coverability) due to surface reactions.

It is the figure which simulated the mask 2 for sputtering and the mask frame 16 for transparent conductive film formation. FIG. 2 is a diagram simulating the behavior in which charge-up of the mask surface is suppressed by bending the direction of movement of secondary electrons when the sputtering mask 2 and the mask frame 16 shown in FIG. 1 are used. In order to suppress the deflection of the mask surface, it is a diagram simulating the mask frame 16 provided with a grid-like cross 17 (fitting type) at the opening of the mask frame 16.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mask pattern (transparent electrode), 2 ... Sputtering mask, 3 ... Mask fixing screw, 4 ... Sputtering particle incident angle adjustment part, 5 ... Permanent magnet for magnetic field formation, 6 ... Glass substrate, 7 ... Magnetic field line, 8 ... Ar Plasma, 9 ... Ar ion, 10 ... Secondary electron motion direction (bending), 11 ... Shutter plate, 12 ... Target, 13 ... Backing plate (OFC), 14 ... Cathode magnet, 15 ... Channel, 16 ... Mask frame, 17 ... A pier.

Claims (10)

In the sputtering method, when manufacturing a transparent electrode of an organic electroluminescent element by forming a transparent conductive film on a substrate through a mask facing a target,
Forming a strong magnetic field at a location closer to the target than the mask;
The charged particles (Ar ions, secondary electrons) scattered from the target toward the mask are bent in a direction to escape from the mask by the strong magnetic field.
A method for producing a transparent electrode of an organic electroluminescent device, characterized in that:   The transparent electrode of the organic electroluminescent device according to claim 1, wherein the target is disposed on a backing plate, and the temperature rise of the target surface is suppressed by cooling the backing plate. Production method.   3. The organic electroluminescence according to claim 2, wherein the cooling of the backing plate is performed by controlling cooling water flowing under the backing plate to 10 ° C. or less by a refrigerant (chiller) such as liquid nitrogen. A method for producing a transparent electrode of an element.   A transparent organic electroluminescent device and a top emission organic electroluminescent device manufactured using the method for manufacturing a transparent electrode according to claim 1, 2 or 3.   5. The organic electroluminescence device according to claim 4, wherein a polymer organic electroluminescence device forming material is patterned on a substrate, and the organic electroluminescence device and the top emission type organic electroluminescence device.   6. A polymer organic electroluminescence display device in which R, G, and B color inks are separately manufactured by using an offset printing method for pattern formation according to claim 5.   7. The organic electroluminescence device and the polymer organic electroluminescence display device according to claim 4, wherein a passivation film made of a ternary compound such as a nitride of Si3N4 or SiON is formed on the lower electrode of the device by a CVD method. Then, the flexible organic electroluminescent element which performed transparent electrode formation using the manufacturing method of Claim 1.   2. The method for producing a transparent electrode of an organic electroluminescent element according to claim 1, wherein the mask is formed of a material having excellent heat dissipation characteristics and a low coefficient of thermal expansion. In a sputtering method, a mask frame used when manufacturing a transparent electrode of an organic electroluminescent element by forming a transparent conductive film on a substrate through a mask facing a target,
Charged particles (Ar ions, secondary electrons) scattered from the target toward the mask at a position of the mask frame closer to the target than the position of the mask frame supporting the mask in a direction to escape from the mask. A pair of magnets to be bent are provided,
A mask frame for producing a transparent electrode of an organic electroluminescent element, characterized in that: The mask frame for manufacturing a transparent electrode of an organic electroluminescence device according to claim 9, wherein the mask frame is provided in a cross-shape forming a lattice.

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