A process for producing a multilayer film which, even when bent, is less apt to decrease in barrier property or electrical conductivity. The process comprises forming a barrier film and a transparent conductive film on a resin film to produce a multilayer film. The barrier film is formed by a plasma enhanced cvd method which uses electric discharge between rolls. The transparent conductive film is preferably formed by physical vapor deposition. The resin film preferably is a polyester resin film or a polyolefin resin film.
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1. A method comprising:
manufacturing a multilayer film by forming a barrier film containing silicon, oxygen, and carbon and a transparent conductive film on a resin film, wherein said barrier film is formed by a plasma enhanced cvd method which uses electric discharge between two rolls in which two magnets are provided respectively under a pressure of 0.1 pa to 10 pa in a condition where an intermediate frequency is applied between the rolls where a magnetic field is formed, and an organic silicon compound and oxygen are introduced as film formation gas to the rolls where the intermediate frequency is applied to form high-density plasma between the rolls wherein the two rolls each contain therein one of the two magnets.
2. The method of manufacturing a multilayer film according to
3. The method of manufacturing a multilayer film according to
4. The method of manufacturing a multilayer film according to
5. The method of manufacturing a multilayer film according to
6. The method of manufacturing a multilayer film according to
7. The method of manufacturing a multilayer film according to
8. The method of manufacturing a multilayer film according to
9. The method of manufacturing a multilayer film according to
10. The method of manufacturing a multilayer film according to
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This application is a National Stage of International Application No. PCT/JP2010/069394, filed on Oct. 26, 2010, which claims priority from Japanese Patent Application No. 2009-250310, filed on Oct. 30, 2009, the contents of all of which are incorporated herein by reference in their entirety.
The present invention relates to a method of manufacturing a multilayer film by forming a barrier film and a transparent conductive film on a resin film.
In recent years, organic EL devices have drawn attention as self-emitting devices. An organic EL element is an element which has a configuration wherein a light-emitting layer of an organic compound is interposed between electrodes on a substrate, and which emits light when current is supplied between the electrodes. As the light-emitting layer is an organic compound, it is possible to fabricate a flexible organic EL element by using a resin film as the substrate, but as the light-emitting element and the cathode are easily degraded by oxygen and moisture, it is necessary to provide a barrier film on the resin film to block as much as possible the oxygen and moisture that infiltrate via the resin film.
As a member of an organic EL element like the one mentioned above, various studies have been made with respect to a multilayer film which uses a resin film as the substrate, and which has a barrier film, and a transparent conductive film that constitutes one of the electrodes. As a method of forming a barrier film, studies are ongoing with respect to the electron beam method, sputtering method, plasma CVD method, ion plating method and so on; as a method of forming a transparent conductive film, studies are ongoing with respect to physical vapor deposition (PVD) methods such as sputtering and ion plating (see, e.g., JP-A-2008-235165 (paragraph 0002, paragraph 0050)). However, with respect to the aforementioned conventional multilayer film, there is a problem that barrier properties and electrical conductivity tend to decline when bending occurs. Otherwise, it should be noted that CVD is the abbreviation for “chemical vapor deposition.”
The object of the present invention is to offer a method capable of manufacturing a multilayer film which uses a resin film as a substrate and which has a barrier film and a transparent conductive film, and the multilayer film, even when bent, inhibits degradation of barrier properties and electrical conductivity.
As a result of diligent study, the present inventors discovered that it is possible to achieve the aforementioned objectives by adopting a specific plasma CVD method as the method of formation of the barrier film, thereby perfecting the present invention.
That is, the present invention offers a method of manufacturing a multilayer film by forming a barrier film and a transparent conductive film on a resin film, wherein the aforementioned barrier film is formed by a plasma enhanced CVD method which uses electric discharge between rolls.
With respect to the resin film constituting the substrate of the multilayer film, a colorless and transparent film is satisfactory. Examples of the resin composing the resin film include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefin resins such as polyethylene (PE), polypropylene (PP), and cyclic polyolefin; polyamide resin; polycarbonate resin; polystyrene resin; polyvinyl alcohol resin; saponification product of ethylene-acetate vinyl copolymer; polyacrylonitrile resin; acetal resin; polyimide resin; and polyether sulfide (PES). Two or more of these may be combined as necessary. In conjunction with required characteristics such as transparency, heat resistance properties, and linear expansion properties, selection from polyester resins and polyolefin resins is preferable, and PET, PEN, and cyclic polyolefin are more preferable.
The thickness of the resin film may be appropriately set taking into consideration stability and the like at the time of manufacture of the multilayer film, but 5-500 μm is preferable, because conveyance of the resin film even in a vacuum is facilitated. Furthermore, as electric discharge is conducted through the resin film when forming the barrier film by the plasma enhanced CVD method which uses electric discharge between rolls that is adopted by the present invention, the thickness of the resin film is more preferably 50-200 μm, and still more preferably 50-100 μm.
From the viewpoint of adhesion with the barrier film, surface active treatment may be conducted on the resin film in order to clean its surface. Examples of surface active treatment include corona treatment, plasma treatment, and flame treatment.
In the present invention, a plasma enhanced CVD method which uses electric discharge between rolls is employed as the method of forming the barrier film on the resin film. By this means, it is possible to obtain multilayer film which inhibits degradation of barrier properties even when bent. When a conventional multilayer film is bent, cracking tends to occur in the barrier film, and barrier properties tend to deteriorate, but according to the present invention, it is possible to obtain a multilayer film which inhibits cracking of barrier film and degradation of barrier properties even when bent.
Here, the CVD method is one of the methods for forming a thin film on the surface of a substance. The plasma CVD method is one such method, and is a film forming method which radicalizes and/or ionizes a raw material substance, and which deposits the raw material substance on a substrate such as a resin film by conducting plasmafication of gas containing the raw material substance by alternating current. With respect to this plasma CVD method, a low-pressure plasma CVD method is preferable. Here, low pressure is ordinarily 0.1-10 Pa with respect to pressure in the discharge space region where the discharge gas is excited, and pressure in the region where a thin film is formed by contact between the excited discharge gas and the gas that forms the thin film. With the plasma enhanced CVD method that uses electric discharge between rolls, plasma discharge occurs in the space between multiple film forming rolls.
As a typical example of a plasma enhanced CVD method which uses electric discharge between rolls, two water-cooled rotary drums incorporating non-rotating magnets are set up at an interval of 4-5 cm. A magnetic field is formed between these two rolls, and an intermediate frequency is applied between the magnet and the roller. Extremely bright, high-density plasma forms between the two rolls when gas is introduced. Electrons are confined near the center of the gap by the magnetic field and electric field between these rolls, forming high-density plasma (density>1012/cm3).
This plasma source can be actuated with low pressure in the neighborhood of several Pa, and the temperature of neutral particles and ions is low, near room temperature. On the other hand, as the temperature of the electrons is high, radicals and ions are generated in abundance. In addition, the action of the magnetic field prevents high-temperature secondary electrons from flowing into the resin film. Consequently, high electric power can be inputted while keeping the temperature of the resin film low, achieving high-speed film formation. As film deposition occurs for the most part only on the surface of the resin film, and as the electrodes are covered by the resin film and are not easily contaminated, stable film formation can be conducted over long periods.
Here, according to the low-pressure system, the gas phase reaction of the CVD method—i.e., generation of particles—can be prevented. Moreover, as the transparent conductive film formation, which is the next step, is a physical film forming method which also requires a low-pressure environment, there is little pressure difference in film formation environments between the film formation process of the barrier film and the film formation process of the transparent conductive film. That is, compared with the conventional method which forms a barrier film in a high-pressure environment, there is no need for a device to adjust pressure, and equipment costs can be greatly reduced.
The barrier film preferably contains silicon, oxygen, and carbon, and additional inclusion of nitrogen is also preferable. The respective concentrations of the silicon, oxygen, and carbon in the barrier film may be fixed, but it is also acceptable if, for example, the concentrations of carbon and oxygen vary relative to the direction of film thickness. These element concentrations may be measured by an XPS analyzer.
The thickness of the barrier film is appropriately selected, given that optimal conditions will vary according to the type and configuration of the employed material, but 1-5000 nm is preferable. When the barrier film is excessively thin, a uniform film is unobtainable, and it is difficult to obtain a high level of barrier properties relative to gas such as moisture; and when the barrier film is excessively thick, it is difficult to preserve the flexibility of the resin film. Moreover, for configurations where the optical information of electrical devices is transmitted, the barrier film preferably has transparency with little optical loss.
The physical vapor deposition (PVD) method is preferably used as the method of forming the transparent conductive film on the resin film, because it obtains a transparent conductive film of low resistance. Examples thereof include vacuum vapor deposition, electron beam vapor deposition, sputtering, ion plating, and laser abrasion (pulse laser deposition (PLD)). Ion plating and sputtering are preferable from such viewpoints as film formation speed, width of film formation area, uniformity of film formation surface, and etching properties. With respect to ion plating, ion plating which uses a pressure-gradient plasma gun (referred to as an “Uramoto gun”) is preferable, because of inhibition of conductivity degradation even when bending occurs, high film formation speed, and long life due to non-exposure of the cathode to the gas atmosphere, and because it enables continuous conduct of stable film formation over long periods.
It is preferable that the transparent conductive film include at least one element selected from the group consisting of indium (In), tin (Sn), zinc (Zn), and titanium (Ti). In particular, it is preferable to use a film with at least one oxide selected from the group consisting of indium-tin oxide (ITO), zinc-tin oxide (ZTO), indium-zinc oxide (IZO), indium-gallium oxide (IGO), indium-zinc-tin oxide (IZTO), indium-gallium-zinc oxide (IGZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), niobium-doped titanium oxide (NTO), tantalum-doped titanium oxide (TTO), and vanadium-doped titanium oxide (VTO).
With respect to formation of a barrier film and a transparent conductive film on the resin film, the laminar configuration of the obtained multilayer film may be appropriately set according to application and the like: for example, the barrier film may be formed on the surface of one side of the resin film, and then the transparent conductive film may be formed on the barrier film; or the barrier film may be formed on the surface of one side of the resin film, and then the transparent conductive film may be formed on the surface of the other side; or the transparent conductive film may be formed on the surface of one side of the resin film, and then the barrier film may be formed on the surface of the other side; or the barrier film may be formed on both surfaces of the resin film, and then the transparent conductive film may be formed on the barrier film of one side. In particular, the multilayer film manufacturing method of the present invention may be advantageously adopted in the case of manufacture of a multilayer film having a laminar configuration of the transparent conductive film/the barrier film/the resin film, where the barrier film is formed on the surface of one side of the resin film, and then the transparent conductive film is formed on the barrier film.
In the case where the transparent conductive film is formed on barrier film after forming the barrier film on the surface of one side of the resin film, the following modes (1)-(3) can be specifically adopted.
(1) A barrier film is formed while unwinding and continuously conveying roll-shaped resin film, and the obtained film with barrier film is wound into a roll.
Subsequently, this roll-shaped film with the barrier film is unwound, and cut into sheets, and then a transparent conductive film is formed to obtain the multilayer film. This mode conducts formation of barrier film on a roll-to-roll basis, and conducts formation of the transparent conductive film in sheets.
(2) A barrier film is formed while unwinding and continuously conveying a roll-shaped resin film, and the obtained film with the barrier film is wound into a roll. Subsequently, a transparent conductive film is formed while unwinding and continuously conveying this roll-shaped film with barrier film, and the multilayer film is obtained, and wound into a roll. This mode continuously conducts both formation of the barrier film and formation of the transparent conductive film on a roll-to-roll basis.
(3) While unwinding and continuously conveying the resin film from the roll-shaped resin film, a barrier film is formed, and then a transparent conductive film is formed, and the obtained multilayer film is wound into a roll. This mode continuously conducts formation of the barrier film and formation of the transparent conductive film in combination on a roll-to-roll basis.
Prior to formation of the transparent conductive film, other layers may be formed on the barrier film as necessary. For example, as proposed in Patent Document 1, a planarization film may be formed. In the present invention, the transparent conductive film is formed directly without formation of other layers on the transparent conductive film, which is preferable from the viewpoint of reducing equipment costs.
Known rolls can be suitably used as the feed roll 11 and the conveyance rolls 21, 22, 23, 24, and known rolls can also be suitably used as the take-up roll 71. Furthermore, known rolls can be suitably used as the film forming rolls 31 and 32, and the diameter of the film forming rolls 31 and 32 is preferably 5-100 cm. As the gas supply pipe 41, a pipe can be suitably used which enables supply or discharge of raw material gas and the like at a prescribed speed. Furthermore, as the plasma generator 51, a conventional plasma generator can be suitably used. As the magnetic field generators 61 and 62, conventional magnetic field generators can be suitably used. Furthermore, as the resin film 100, a film on which a barrier film has been formed in advance can be used. In this manner, it is possible to thicken the thickness of the barrier film by using the film on which the barrier film has been preformed as the resin film 100.
Using this apparatus, a barrier film can be formed on the resin film 100 by suitably adjusting, for example, the type of raw material gas, the power of the electrode drum of the plasma generator, the pressure within the vacuum chamber, the diameter of the film forming rolls, and the conveyance speed of the film. That is, by generating plasma discharge while supplying film formation gas such as raw material gas to the interior of the vacuum chamber, the aforementioned raw material gas is decomposed by the plasma, forming the barrier film by the plasma CVD method on the surface of the resin film 100. A barrier film is then formed on the surface of the resin film 100 in a roll-to-roll system by having the film forming rolls 31 and 32 respectively convey the resin film 100.
The raw material gas may be appropriately selected for use according to the material of the barrier film to be formed. As the raw material gas, for example, an organic silicon compound containing silicon can be used. Examples of such organic silicon compounds include hexamethyl disiloxane, 1,1,3,3-tetramethyl disiloxane, vinyl trimethyl silane, methyl trimethyl silane, hexamethyl disilane, methyl silane, dimethyl silane, trimethyl silane, diethyl silane, propyl silane, phenyl silane, vinyl triethoxy silane, vinyl trimethoxy silane, tetramethoxy silane, tetraethoxy silane, phenyl trimethoxy silane, methyl triethoxy silane, octamethyl cyclotetrasiloxane, dimethyl disilazane, trimethyl disilazane, tetramethyl disilazane, pentamethyl disilazane, and hexamethyl disilazane. Among these organic silicon compounds, from such viewpoints as handling of the compound and gas barrier properties of the obtained barrier film, hexamethyl disiloxane and 1,1,3,3-tetramethyl disiloxane are preferable. Moreover, these organic silicon compounds may be used alone or in combinations of two or more.
As the aforementioned film formation gas, in addition to the aforementioned raw material gas, reaction gas may also be used. As such reaction gas, gas that reacts with the aforementioned raw material gas to become inorganic compounds such as oxides and nitrides may be appropriately selected for use. As reaction gas that serves to form oxides, for example, oxygen or ozone may be used. As reaction gas that serves to form nitrides, for example, nitrogen or ammonia can be used. These reaction gases may be used alone or in combinations of two or more. In the case where, for example, oxynitrides are formed, reaction gas that serves to form oxides and reaction gas that serves to form nitrides can be used in combination.
As the aforementioned film formation gas, carrier gas may also be used as necessary in order to supply the aforementioned raw material gas to the interior the vacuum chamber. Furthermore, as the aforementioned film formation gas, gas for electric discharge may also be used as necessary in order to generate plasma discharge. As such carrier gas and discharge gas, known gases can be suitably used, e.g., hydrogen and rare gases such as helium, argon, neon, and xenon can be used.
The degree of vacuum within the pertinent vacuum chamber expressed by pressure within the vacuum chamber may be suitably adjusted according to the type of raw material gas and the like, but 0.5-50 Pa is preferable. Moreover, the power of the electrode drum of the plasma generator may be suitably adjusted according to the type of raw material gas, pressure within the vacuum chamber, and the like, but 0.1-10 kW is preferable.
The conveyance speed (line speed) of the resin film 100 can be suitably adjusted according to the type of raw material gas, pressure within the vacuum chamber, and the like, but 0.25-100 m/min is preferable, and 0.5-20 m/min is more preferable. At line speeds below the aforementioned minimums, heat-derived flaws tend to occur in the film, and when, conversely, the aforementioned maximums are exceeded, the thickness of the barrier film that is formed tends to thin.
The multilayer film obtained by the manufacturing method of the present invention described above uses the resin film as the substrate, and can be used as a member in flexible products. In addition, as it has the barrier film and the transparent conductive film, and as it inhibits degradation of barrier properties and conductivity even when bent, it may be suitably used as a member in various types of products that require flexibility as well as barrier properties and conductivity, including organic EL devices.
Examples of the present invention are shown below. The examples shown below are preferred exemplifications that serve to describe the present invention, and the present invention is not limited thereto.
Formation of Barrier Film
Using the manufacturing apparatus shown in
(Film Formation Conditions)
The thickness of the obtained barrier film was 370 nm. With respect to the obtained multilayer film A, water vapor transmittance was 3.1×10−4 g/(m2·day) under conditions where temperature was 40° C., humidity on the low humidity side was 0% RH, and humidity on the high humidity side was 90% RH, and water vapor transmittance was a value below the detection threshold (0.02 g/(m2·day)) under conditions where temperature was 40° C., humidity on the low humidity side was 10% RH, and humidity on the high humidity side was 100% RH. Furthermore, after bending under the condition of a curvature radius of 8 mm, water vapor transmittance was a value below the detection threshold under conditions where temperature was 40° C., humidity on the low humidity side was 10% RH, and humidity on the high humidity side was 100% RH, thereby confirming that reduction of gas barrier properties could be fully inhibited even when the obtained multilayer film A was bent.
With respect to the obtained multilayer film A, XPS depth profile measurement was conducted under the following conditions to investigate composition distribution.
From the composition distribution of XPS depth profile measurement, it could be confirmed that the aforementioned barrier film was film with a composition including silicon, oxygen, and carbon.
Form of Transparent Conductive Film
Using ITO (In:Sn=95:5; high-density product with purity of 99.99% and particle size of 3-5 mm) manufactured by Myojo Kinzoku Co. as the target, transparent conductive film was formed on the barrier film of the aforementioned multilayer film A under the following film formation conditions by an ion plating film formation apparatus with a pressure-gradient plasma gun (manufactured by Chugai Ro Co., Ltd.: SUPLaDUO, CVP-4111) to obtain a multilayer film B.
(Film Formation Conditions)
When obtained by TEM (transmission electron microscope image) using FIB (focused ion beams), the thickness of the transparent conductive film was 150 nm. With respect to the obtained multilayer film B, when total light transmittance and haze were measured using haze meter (manufactured by Shiga Test Equipment Co.: HGM-2DP), total light transmittance was 80.8% and haze was 0.6%. The sheet resistance of the transparent conductive film obtained using a resistivity meter (manufactured by Mitsubishi Chemical Corporation: Loresta-GP, MCP-T610) was 42.7 Ω/sq, and specific resistance was 6.4×10−4 Ωcm. Furthermore, the surface roughness Ra of the transparent conductive film measured using an atomic force microscope AFM (manufactured by SII: SPI3800N) was 2.34 nm.
Using the multilayer film A obtained in Example 1, a transparent conductive film was formed under the following film formation conditions on the barrier film of the multilayer film A by an ion plating film formation apparatus with a pressure-gradient plasma gun (manufactured by Chugai Ro Co., Ltd.: SUPLaDUO, CVP-4111) using ITO (In:Sn=95:5; high-density product with purity of 99.99% and particle size of 3-5 mm) manufactured by Myojo Kinzoku Co. as the target, and a multilayer film C was obtained.
(Film Formation Conditions)
The thickness of the transparent conductive film, the total light transmittance and haze of the multilayer film C, the sheet resistance and specific resistance of the transparent conductive film, and the surface roughness of the transparent conductive film, which were measured in the same manner as Example 1, were respectively 100 nm, 81.2% and 0.6%, 18 Ω/sq and 1.8×10−4 Ωcm, and 2.37 nm.
Using the multilayer film A obtained in Example 1, a transparent conductive film was formed under the following film formation conditions on the barrier film of the multilayer film A by an ion plating film formation apparatus with a pressure-gradient plasma gun (manufactured by Chugai Ro Co., Ltd.: SUPLaDUO, CVP-4111) using ZTO (Zn2SnO4, zinc-tin oxide) as the target, and a multilayer film D was obtained.
As the ZTO target, zinc oxide powder (4N, manufactured by Kojundo Chemical Laboratory Co.) and tin oxide powder (4N, manufactured by Kojundo Chemical Laboratory Co.) were weighed out to obtain zinc:tin=2:1 (mol ratio), mixing and sintering were conducted to obtain a sintered body, and this was pulverized to a particle size of approximately 3-5 mm for use as the target of ion plating.
(Film Formation Conditions)
The thickness of the transparent conductive film, the total light transmittance and haze of the multilayer film D, the sheet resistance and specific resistance of the transparent conductive film, and the surface roughness of the transparent conductive film, which were measured in the same manner as Example 1, were respectively 100 nm, 81.2% and 0.6%, 65 Ω/sq and 6.5×10−3 Ωcm, and 1.93 nm.
Using the multilayer film A obtained in Example 1, a transparent conductive film was formed under the following film formation conditions on the barrier film of the multilayer film A by an ion plating film formation apparatus with a pressure-gradient plasma gun (manufactured by Chugai Ro Co., Ltd.: SUPLaDUO, CVP-4111) using ZTO (Zn2SnO4, zinc-tin oxide) as the target, and a multilayer film E was obtained.
As the ZTO target, zinc oxide powder (4N, manufactured by Kojundo Chemical Laboratory Co.) and tin oxide powder (4N, manufactured by Kojundo Chemical Laboratory Co.) were weighed out to obtain zinc:tin=2:1 (mol ratio), mixing and sintering were conducted to obtain a sintered body, and this was pulverized to a particle size of approximately 3-5 mm for use as the target of ion plating.
(Film Formation Conditions)
The thickness of the transparent conductive film, the total light transmittance and haze of the multilayer film E, the sheet resistance and specific resistance of the transparent conductive film, and the surface roughness of the transparent conductive film, which were measured in the same manner as Example 1, were respectively 100 nm, 82.3% and 0.7%, 40 Ω/sq and 4.0×10−3 Ωcm, and 1.92 nm.
Instead of film formation by the plasma CVD method of Example 1, formation of a silicon oxide film was conducted on the substrate (PEN film) used in Example 1 by the reactive sputtering method using silicon as the target, and a multilayer film F was obtained. When XPS depth profile measurement of the silicon oxide film was conducted in the same manner as Example 1, it was confirmed that the silicon oxide film was film containing silicon and oxygen, but not containing carbon.
The thickness of the obtained silicon oxide film was 100 nm. With respect to the obtained multilayer film F, the barrier properties of the silicon oxide film could not be confirmed, because water vapor transmittance was 1.3 g/(m2·day) under conditions where temperature was 40° C., humidity on the low humidity side was 10% RH, and humidity on the high humidity side was 100% RH, which was identical to the 1.3 g/(m2·day) water vapor transmittance of the PEN substrate.
Using the obtained multilayer film F, a transparent conductive film was formed on the silicon oxide film of the multilayer film F by the sputtering method using ITO, and a multilayer film G was obtained.
The thickness of the transparent conductive film obtained in the same manner as Example 1 was 150 nm, and transmittance of visible light was 79%. The obtained multilayer film G had poor barrier properties, and was unsuitable as a flexible substrate for organic ELs and the like.
According to the present invention, with respect to a multilayer film which uses a resin film as a substrate and which has a barrier film and a transparent conductive film, it is possible to obtain a multilayer film which inhibits degradation of barrier properties and conductivity even when bent.
Hasegawa, Akira, Sanada, Takashi, Kuroda, Toshiya
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