JP5031019B2 - SOLAR CELL COVER, MANUFACTURING METHOD THEREOF - Google Patents

Description

  The present invention relates to a solar cell cover having a thin film made of an oxide photocatalyst that exhibits a photocatalytic action by photoexcitation on the surface, and particularly in a heavy snowy area with a large amount of snow, when installing a solar cell on the roof of a house. The present invention relates to a solar cell cover that can be suitably used.

  Solar cells are installed on the roofs of houses and other buildings, and sunlight is photoelectrically converted and used. However, in heavy snow areas, snow is accumulated on the solar cells. In a snowy state, the light-receiving surface of the solar cell is not exposed to sunlight, and sunlight cannot be used efficiently. Therefore, in order to efficiently use sunlight, it is necessary to periodically perform snow removal work, which hinders the spread of solar cell installation in heavy snowfall areas. The snow-lowering work is performed by an operator climbing on the roof, cutting the snow with a scoop, and dropping the block-shaped snow under the roof.

  In recent years, various proposals have been made to promote the installation of solar cells in heavy snowfall areas. For example, Patent Document 1 proposes a technique of providing a resistance heating wire on the light receiving surface side of a solar cell module.

  In addition, the light receiving surface of the solar cell module is often protected by a protective cover made of a weather-resistant resin film, etc., but this cover becomes dirty with dust during long-term use of the solar cell module and gradually becomes light. The transmittance is lowered, thereby reducing the energy conversion efficiency of the solar cell. On the other hand, since the solar cell cover is installed on the roof or outer wall of a building, it is not easy to clean it regularly or as needed. Thus, for example, Patent Document 2 proposes a solar cell cover in which a surface layer portion containing an oxide photocatalyst is formed on a base film.

JP-A-8-260638 JP-A-10-107303

  By the way, it is considered that the mechanism of the photocatalytic action by the oxide photocatalyst represented by titanium oxide is caused by the generation of electrons in the conduction band and the generation of holes in the valence band by photoexcitation. Organic substances and nitrogen oxides that come into contact with the photocatalyst can be decomposed into water, carbon dioxide gas, etc. due to the strong reducing power of electrons and the strong oxidizing power of holes. Demonstrated. That is, when the oxide photocatalyst is irradiated with light having a wavelength having energy equal to or greater than the band gap (for example, ultraviolet light), the contact angle of water on the oxide photocatalyst surface is reduced, and the oxide photocatalyst is highly hydrophilic. Become. On the other hand, when the ultraviolet light irradiation is stopped, the water contact angle returns to the original state of about 20 to 30 degrees.

  However, once the oxide photocatalyst has been sufficiently hydrophilized, it remains in a highly hydrophilized state for at least several tens of hours without being exposed to ultraviolet light. Therefore, when it is desired to return the surface energy state to the original state, there is a problem that a long time of several tens of hours must be wasted.

  For example, even if the resistance heating element is energized and the snow on the light receiving surface side of the solar cell module is melted by the technique combining Patent Document 1 and Patent Document 2, the surface layer portion on the light receiving surface side is maintained in a hydrophilic state. The following inconveniences occur. The snow that directly contacts the resistance heating element melts, and that portion becomes water, while the snow cover is thick, and it is difficult to dissolve all the snow accumulation in the thickness direction. Therefore, the snow part that did not melt is compressed to the module light-receiving surface side by its own weight, and the surface layer part is in a hydrophilic state, so the snow part that did not melt is held, and eventually, snow removal work separately Must be done.

  The problem to be solved by the invention is to provide a solar cell cover having a photocatalytic thin film as a surface layer capable of quickly eliminating the photocatalytic action developed on the film surface, a manufacturing method thereof, and a snow melting method.

  In order to solve the above-mentioned problems, a solar cell cover according to the present invention is formed by laminating a light-transmitting substrate, a heat generating layer composed of a transparent conductive film, and a photocatalytic thin film in this order, and the photocatalytic thin film Is characterized in that it is formed by performing the following treatment on the surface of the heat generating layer. A sputtering process in which a target made of titanium metal is sputtered in a film forming process region formed inside a vacuum vessel, and a film raw material made of titanium is deposited on the surface of the heat generating layer. A reaction step of generating a first thin film by contacting at least plasma of a reactive gas with the film source material in a reaction process area formed away from the film formation process area; The translucent substrate on which the heat generating layer is formed is moved between the film forming process region and the reaction process region, the sputtering step and the reaction step are repeated a plurality of times, and the first thin film is deposited a plurality of times. A thin film deposition step of forming a second thin film. A plasma post-treatment process in which plasma of a mixed gas obtained by positively mixing the inert gas with the reactive gas at a flow rate at least the same as the flow rate of the reactive gas is brought into contact with the second thin film;

  In the method for manufacturing a solar cell cover according to the present invention, a heat generating layer composed of a transparent conductive film is laminated on the surface of a light-transmitting substrate, and a photocatalytic thin film is laminated on the surface of the heat generating layer. A method of manufacturing a cover, comprising: a first film forming step of forming the heat generating layer on a surface of the translucent substrate; and a second component of forming the photocatalytic thin film on the surface of the heat generating layer. The second film forming step includes sputtering a target made of titanium metal in a film forming process region formed inside the vacuum vessel, and depositing the titanium on the surface of the heat generating layer. The first thin film is formed by bringing at least a reactive gas plasma into contact with the film raw material in a sputtering process for attaching the film raw material to be formed and a reaction process region formed apart from the film forming process region. A reaction step of generating the light-transmitting light Thin film deposition in which a substrate is moved between the film forming process region and the reaction process region, the sputtering step and the reaction step are repeated a plurality of times, and the first thin film is deposited a plurality of times to form a second thin film. And a plasma post-treatment step in which a plasma of a mixed gas in which the inert gas is positively mixed with the reactive gas at a flow rate at least the same as that of the reactive gas is brought into contact with the second thin film. It is characterized by having.

  The snow melting method according to the present invention is a method according to any one of claims 1 to 3, wherein a plurality of solar cells wired in series or in parallel are packaged, and the light receiving surface side of the unitized solar cell module is provided. The solar cell cover is laminated with a light-transmitting substrate, the heat generating layer of the solar cell cover is electrically connected to a power source, and the heat generating layer is heated by supplying electric power, and the photocatalytic thin film It is characterized by melting snow accumulated on the surface of the snow.

  According to the present invention, after the photocatalytic thin film is deposited on the surface of the heat generating layer, the photocatalyst developed on the film surface is obtained by performing a plasma post-treatment in which a plasma of a mixed gas containing a reactive gas and an inert gas is brought into contact. A photocatalytic thin film capable of quickly eliminating the action can be formed on the surface layer.

FIG. 1 is a cross-sectional view showing a configuration example of a solar cell cover according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view showing an example of a film forming apparatus that can manufacture the solar cell cover of FIG. FIG. 3 is a partial longitudinal sectional view taken along line II-II in FIG. FIG. 4 is a plan view showing a configuration example of a solar cell to which the solar cell cover of FIG. 1 can be applied. FIG. 5 is a cross-sectional view of FIG. FIG. 6 is a diagram showing an installation example of the solar cell of FIGS. 4 and 5.

  Hereinafter, preferred embodiments of a solar cell cover according to the present invention will be described in detail with reference to the accompanying drawings.

<Solar cell cover>
As shown in FIG. 1, the solar cell cover 100 according to the present embodiment has a translucent substrate 102. A transparent conductive film 104 as a heat generating layer is laminated on at least a part (preferably all) of the surface of the translucent substrate 102. A photocatalytic thin film 106 is laminated on the transparent conductive film 104.

<Translucent substrate>
As a material for forming the light-transmitting substrate 102, glass and synthetic resin are used. Synthetic resins used for the translucent substrate 102 include, for example, polyethylene resins, polypropylene resins, cyclic polyolefin resins, fluorine resins, polystyrene resins, acrylonitrile-styrene copolymers (AS resins), acrylonitrile-butadienes. -Styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, and polyamides such as various nylons Resin, polyimide resin, polyamideimide resin, polyarylphthalate resin, silicone resin, polyphenylene sulfide resin, polysulfone resin, acetal resin, polyethersulfone resin, polyurethane resin Fat, and cellulosic resins. Among these resins, fluorine resins, cyclic polyolefin resins, polycarbonate resins, poly (meth) acrylic resins, or polyester resins are particularly preferable.

  In the case of the translucent substrate 102 made of synthetic resin, for the purpose of improving and modifying processability, heat resistance, weather resistance, mechanical properties, dimensional stability, etc., for example, a lubricant, a crosslinking agent, an antioxidant, It is also possible to contain various additives such as ultraviolet absorbers, antistatic agents, light stabilizers, fillers, reinforcing fibers, reinforcing agents, flame retardants, flame retardants, foaming agents, fungicides, and pigments.

  The thickness of the translucent substrate 102 is not particularly limited, and is appropriately selected so as to have a required strength and the like according to the material to be used. The thickness of the synthetic resin translucent substrate 102 is preferably 6 to 300 μm. In addition, the thickness of the glass translucent substrate 102 is generally about 3 mm.

<Transparent conductive film>
The transparent conductive film 104 generates heat when a current is conducted, and as a result, has a function as a heating unit that melts snow accumulated on the outer surface of the photocatalytic thin film 106.

  As the transparent conductive film 104, a metal thin film, a single layer or a laminate of a semiconductor thin film, or a laminate of a metal thin film and a transparent thin film can be applied. The layers may be one or more layers. As the metal thin film, metals such as silver, gold, copper, aluminum, nickel, and chromium are used, but silver, gold, and copper are preferable.

  The semiconductor thin film may be any oxide as long as it is an oxide containing indium, tin, zinc, antimony, etc., but preferably indium oxide, tin oxide, ITO (indium tin oxide), IZO ( Examples thereof include thin films such as indium oxide / zinc), ITZO (indium oxide / zinc / tin), AZO (zinc oxide / antimony), and AIZO (indium oxide / zinc / antimony).

  Especially in this embodiment, it is preferable to comprise with the ZnO type | system | group semiconductor thin film which contains a doping component in a predetermined ratio with respect to zinc oxide which is a main component. Such a ZnO-based semiconductor thin film is relatively easy to form, and has a relatively high visible light transmittance at a film thickness for obtaining certain electrical conductivity. The doping component is a component that controls the resistivity of the conductive film 104 and improves durability such as heat resistance, and examples thereof include Al, Pb, Sn, In, and Cd.

The thickness of the transparent conductive film 104 is, for example, 300 to 1000 nm, preferably 300 to 700 nm, the resistivity is 1.0 × 10 ⁻³ (Ω · cm) or less, and the total light transmittance is preferably 80% or more, more preferably. Is 85% or more.

  The transparent conductive film 104 can be formed using various film forming methods such as an ion plating method, a sputtering method, and a vacuum evaporation method, for example, but if the sputtering method is used, a dense film can be formed and wear resistance is increased. This is preferable because of improved properties.

《Photocatalytic thin film》
The photocatalytic thin film 106 can quickly disappear the photocatalytic action once expressed, and is made of titanium oxide in this embodiment.

  In this embodiment, even if the thin film 106 is formed as thin as less than 300 nm, preferably 250 nm or less, more preferably 200 nm or less, the photocatalytic activity necessary and sufficient for the transparent conductive film 104 to function as a buffer layer is exhibited. It is possible. In general, it is considered that the thicker the thin film 106 is, the higher the photocatalytic activity is. However, on the other hand, the substrate 102 is deformed by the film stress or the entire transmittance is lowered. In order to maintain the photocatalytic activity as much as possible at a necessary level as long as such inconvenience does not occur, the transparent conductive film 104 described above is interposed as a buffer layer. Note that the thickness of the thin film 106 needs to be 300 nm or more in order to sufficiently exhibit the photocatalytic activity of the thin film 106 alone without the conductive film 104. Note that the lower limit of the thickness of the thin film 106 is preferably 50 nm, more preferably 100 nm.

  The photocatalytic thin film 106 can be formed using various film forming methods such as an ion plating method, a sputtering method, and a vacuum evaporation method. However, if the sputtering method is used, a dense film can be formed and wear resistance is increased. This is preferable because of improved properties. In particular, when the photocatalytic thin film 106 is formed on the transparent conductive film 104, it is necessary even when the thin film 106 is thin by performing plasma post-treatment after sputtering → plasma treatment, as will be described later. Sufficient photocatalytic activity can be expressed. Although the reason for this is not necessarily clear, the thickness of the thin film 106 is improved by applying a plasma post-treatment to optimize a plurality of factors such as the growth crystal, surface shape, and activity of the photocatalytic thin film 106 to be formed. It is presumed that necessary and sufficient photocatalytic activity can be expressed even if the thickness of the film is thin.

<< Solar Cell Cover Manufacturing Method >>
Next, an example of a preferable method for forming the photocatalytic thin film 106 of the solar cell cover 100 will be described. First, a configuration example of an apparatus that can realize this method will be described.

<Film deposition system>
As shown in FIGS. 2 and 3, the film forming apparatus 1 includes a vacuum container 11 that is a substantially rectangular parallelepiped hollow body. An exhaust pipe 15 a is connected to the vacuum container 11, and a vacuum pump 15 for exhausting the inside of the container 11 is connected to this pipe. The vacuum pump 15 is composed of, for example, a rotary pump or a turbo molecular pump (TMP). A rotating drum 13 is disposed in the vacuum vessel 11. The rotating drum 13 (substrate holding means) is formed of a cylindrical member that can hold the substrate S as a film formation target in the vacuum vessel 11 on the outer peripheral surface thereof. The rotary drum 13 of the present embodiment is disposed in the vacuum container 11 so that the rotation axis Z extending in the cylindrical direction is directed in the vertical direction (Y direction) of the vacuum container 11. The rotating drum 13 rotates about the axis Z by driving the motor 17.

  In the present embodiment, two sputtering sources and one plasma source 80 are disposed around the rotary drum 13 in the vacuum vessel 11.

  Each sputtering source of this embodiment is configured as a dual cathode type including two magnetron sputtering electrodes 21a and 21b (or 41a and 41b). During film formation, targets 29a and 29b (or 49a and 49b) made of a film raw material such as metal are detachably held on one end surface of each electrode 21a and 21b (or 41a and 41b). The The other end of each electrode 21a, 21b (or 41a, 41b) is connected to an AC power source 23 (or 43) as power supply means via a transformer 24 (or 44) as power control means for adjusting the amount of power. Are connected, and an AC voltage of, for example, about 1 k to 100 kHz is applied to each of the electrodes 21a and 21b (or 41a and 41b).

  A sputtering gas supply means is connected to each sputtering source. The sputtering gas supply means of this embodiment includes a reactive gas cylinder 26 (or 46) that stores a reactive gas as an example of a sputtering gas, and a reactive gas supplied from the reactive gas cylinder 26 (or 46). A mass flow controller 25 (or 45) for adjusting the flow rate, an inert gas cylinder 28 (or 48) for storing an inert gas as an example of a sputtering gas, and an inert gas supplied from the inert gas cylinder 28 (or 48). And a mass flow controller 27 (or 47) for adjusting the flow rate of the gas.

  The sputtering gas is introduced into the film forming process region 20 (or 40) through a pipe. The mass flow controllers 25 and 27 (or 45 and 47) are devices for adjusting the flow rate of the sputtering gas. Sputtering gas from the cylinders 26 and 28 (or 46 and 48) is introduced into the film forming process region 20 (or 40) with the flow rate adjusted by the mass flow controllers 25 and 27 (or 45 and 47).

  The plasma source 80 of the present embodiment includes a case body 81 fixed so as to close an opening formed in the wall surface of the vacuum vessel 11, and a dielectric plate 83 fixed to the case body 81. The dielectric plate 83 is fixed to the case body 81 so that an antenna housing chamber is formed in a region surrounded by the case body 81 and the dielectric plate 83. The antenna accommodating chamber communicates with the vacuum pump 15 via the pipe 15a, and by evacuating with the vacuum pump 15, the inside of the antenna accommodating chamber can be exhausted to be in a vacuum state.

  The plasma source 80 includes antennas 85 a and 85 b in addition to the case body 81 and the dielectric plate 83. The antennas 85a and 85b are connected to a high frequency power supply 89 through a matching box 87 that accommodates a matching circuit. The antennas 85 a and 85 b are supplied with electric power from the high frequency power supply 89, generate an induction electric field inside the vacuum vessel 11 (reaction process region 60), and generate plasma in the reaction process region 60. In the present embodiment, an AC voltage having a frequency of 1 to 27 MHz is applied from the high frequency power supply 89 to the antennas 85 a and 85 b to generate a reactive gas plasma in the reaction process region 60. A variable capacitor is provided in the matching box 87 so that the power supplied from the high frequency power supply 89 to the antennas 85a and 85b can be changed.

  A reaction processing gas supply means is connected to the plasma source 80. The reaction processing gas supply means of this embodiment includes a reactive gas cylinder 66 that stores a reactive gas as an example of a reaction processing gas, and a mass flow controller that adjusts the flow rate of the reactive gas supplied from the reactive gas cylinder 66. 65, an inert gas cylinder 68 that stores an inert gas as an example of a reaction processing gas, and a mass flow controller 67 that adjusts the flow rate of the inert gas supplied from the inert gas cylinder 68.

  The reaction processing gas is introduced into the reaction process region 60 through piping. The mass flow controllers 65 and 67 are devices that adjust the flow rate of the reaction processing gas. The reaction processing gas from the cylinders 66 and 68 is introduced into the reaction process region 60 with the flow rate adjusted by the mass flow controllers 65 and 67.

  The reactive gas cylinder 66 and the inert gas cylinder 68 may be the same devices as the reactive gas cylinders 26 and 46 and the inert gas cylinders 28 and 48 in the film forming process regions 20 and 40, or may be used in combination. Further, the mass flow controller 65 and the mass flow controller 67 may be the same apparatus as the mass flow controllers 25 and 27 (or 45 and 47) in the film forming process regions 20 and 40, or may be used in combination.

  Film forming process regions 20 and 40 are formed on the front surface of each sputtering source, respectively. Each region 20, 40 is surrounded on all sides by partition walls 12, 14 projecting from the inner wall surface of the vacuum vessel 11 toward the rotary drum 13, so that each can secure an independent space inside the vacuum vessel 11. It is divided into. Similarly, a reaction process region 60 is formed on the front surface of the plasma source 80. Similarly to the regions 20 and 40, the region 60 is surrounded on all sides by a partition wall 16 that protrudes from the inner wall surface of the vacuum vessel 11 toward the rotary drum 13, so that the region 60 is also inside the vacuum vessel 11. A space independent of the areas 20 and 40 is secured.

<Film formation method>
Next, an example of a film forming method using the film forming apparatus 1 will be described.

  (1) First, preparation before film formation is performed. Specifically, first, targets 29a and 29b (or 49a and 49b) are set on the electrodes 21a and 21b (or 41a and 41b). At the same time, the substrate S is set on the rotary drum 13 outside the vacuum vessel 11 and accommodated in the load lock chamber of the vacuum vessel 11.

  As the substrate S, the translucent substrate 102 of FIG. 1 is used, and a plurality of the light transmitting substrates 102 are intermittently arranged on the outer peripheral surface of the rotating drum 13 along the rotating direction (lateral direction) of the rotating drum 13. A plurality of elements are intermittently arranged along a direction (longitudinal direction, Y direction) parallel to the axis Z.

  The targets 29a and 29b (or 49a and 49b) are obtained by forming a film raw material into a flat plate shape, the longitudinal direction of which is parallel to the rotational axis Z of the rotary drum 13, and the plane in the parallel direction thereof. 13 is held on the surface of each electrode 21a, 21b (or 41a, 41b) so as to oppose the side surface of 13.

  Zinc (Zn) is used as the targets 29a and 29b in the present embodiment. Zn functions as a buffer layer of a titanium oxide thin film (photocatalytic thin film) whose oxide is formed later, and can contribute to ensuring transparency after the film formation. Titanium (Ti) is used as the targets 49a and 49b in the present embodiment. In addition to Ti, other metal materials whose oxides exhibit photocatalytic action by ultraviolet light (except Zn), for example, niobium (Nb), tantalum (Ta), or at least two alloys thereof can be used.

Next, after the rotary drum 13 is moved to the film forming chamber of the vacuum vessel 11, the inside of the vacuum vessel 11 is sealed with the door to the load lock chamber closed, and the vacuum vessel 11 is used by using the vacuum pump 15. The inside is brought to a high vacuum state of about 10 ^{−5 to} 0.1 Pa. At this time, the valve is opened and the antenna accommodating chamber of the plasma source 80 is exhausted at the same time.

  Next, the driving of the motor 17 is started, and the rotary drum 13 is rotated about the axis Z. The rotational speed of the rotating drum 13 is appropriately selected within a range of, for example, 50 rpm or less (excluding 0 rpm; the same applies hereinafter), preferably 10 rpm or less, more preferably 6 rpm or less. Then, the substrate S held on the outer peripheral surface of the rotating drum 13 revolves around the axis Z that is the rotation axis of the rotating drum 13, and faces the film forming process regions 20 and 40 and the reaction process region 60. Move repeatedly between positions. Then, the sputtering process performed in one of the regions 20 and 40 and the plasma process performed in the region 60 are sequentially repeated to generate a final thin film having a predetermined thickness on the surface of the substrate S.

  In this embodiment, an intermediate thin film is formed on the surface of the substrate S by sputtering, and the intermediate thin film is converted into an ultrathin film by subsequent plasma processing. Then, by repeating the sputtering process and the plasma process, the next ultrathin film is deposited on the ultrathin film, and this operation is repeated until the final thin film is obtained.

  In the present embodiment, the “intermediate thin film” is a thin film formed of the metal constituting the targets 29a and 29b (or 49a and 49b) or an incomplete oxide thereof and formed in the region 20 (or 40). is there. “Ultra-thin film” is a term used to prevent confusion with this final “thin film” because an ultra-thin film is deposited multiple times to form a final thin film (thin film with a target thickness). In the sense that it is sufficiently thinner than the final “thin film”.

(2) Hereinafter, after forming a first thin film (transparent conductive film 104 as a heat generating layer) containing ZnO as a main component on the substrate S, a second thin film made of TiO ₂ is formed on the first thin film. A case where a (photocatalytic thin film) is formed will be described.

  (2-1) First, a first thin film is formed on the substrate S. The sputtering process in this case is performed as follows.

  After confirming the stability of the pressure in the vacuum container 11, the pressure in the film forming process region 20 is adjusted to 0.05 to 0.2 Pa, for example, and then the reactive gas is stored via the mass flow controllers 25 and 27. A sputtering gas having a predetermined flow rate is introduced into the film forming process region 20 from the reactive gas cylinder 26 and the inert gas cylinder 28 that stores the inert gas. In this embodiment, an inert gas may be used alone as the sputtering gas, but it may be introduced into the region 20 in a state where a reactive gas is mixed with the inert gas. Then, the surroundings of the targets 29a and 29b become a predetermined gas atmosphere. In this state, an AC voltage is applied from the AC power source 23 to the electrodes 21a and 21b via the transformer 22 so that an alternating electric field is applied to the targets 29a and 29b. In the present embodiment, for example, power (sputtering power) of about 4 kW to 6 kW is supplied. Thereby, at a certain point in time, the target 29a becomes the cathode (negative pole), and at that time, the target 29b always becomes the anode (positive pole). When the direction of the alternating current changes at the next time point, the target 29b becomes the cathode (minus pole) and the target 29a becomes the anode (plus pole). As described above, the pair of targets 29a and 29b alternately become an anode and a cathode, so that a part of the sputtering gas around each target 29a and 29b emits electrons and is ionized. A leakage magnetic field is formed on the surfaces of the targets 29a and 29b by the magnets disposed on the electrodes 21a and 21b, so that the electrons draw a toroidal curve in the magnetic field generated near the surfaces of the targets 29a and 29b. Go around. Strong plasma is generated along the trajectory of the electrons, and ions of the sputtering gas in the plasma are accelerated toward the target in the negative potential state (cathode side) and collide with the targets 29a and 29b. Atoms and particles (Zn atoms and Zn particles) on the surfaces of 29a and 29b are knocked out (sputtering). These atoms and particles are film raw material that is a raw material of the thin film, and adhere to the surface of the substrate S to form an intermediate thin film.

  During sputtering, non-conductive or low-conductivity incomplete oxide may be deposited on the anode. If this anode is converted into a cathode by an alternating electric field, these will be lost. Incomplete oxide or the like is sputtered, and the target surface is in an original clean state. Then, by repeating the pair of targets 29a and 29b alternately becoming an anode and a cathode, a stable anode potential state is always obtained, and a change in the plasma potential (almost equal to the normal anode potential) is prevented, and the substrate An intermediate thin film is stably formed on the surface of S.

  The plasma treatment is performed as follows. Through the mass flow controllers 65 and 67, a reaction gas at a predetermined flow rate is introduced into the reaction process region 60 from the reactive gas cylinder 66 that stores the reactive gas and the inert gas cylinder 68 that stores the inert gas, and the antenna 85a. , 85b is made a predetermined gas atmosphere.

  The pressure in the reaction process region 60 is maintained at 0.07 to 1 Pa, for example. Further, at least during the generation of plasma in the reaction process region 60, the internal pressure of the antenna housing chamber is maintained at 0.001 Pa or less.

  When a reactive gas or inert gas is introduced from the reactive gas cylinder 66 or the inert gas cylinder 68, a voltage of 100 k to 50 MHz (preferably 1 M to 27 MHz) is applied to the antennas 85a and 85b from the high frequency power supply 89. Then, plasma is generated in a region facing the antennas 85a and 85b in the reaction process region 60. When the substrate S is made of a glass material, the power (plasma processing power) supplied from the high-frequency power source 89 is, for example, 3 kW or more, preferably 4 kW or more, more preferably 4.5 kW or more. Is made of a resin material, for example, a small electric power of 1 kW or less, preferably 0.8 kW or less, more preferably 0.5 kW or less.

  A small amount of reactive species of reactive gas is present in the generated plasma, and this active species is guided to the reaction process region 60. When the rotating drum 13 rotates and the substrate S is introduced into the reaction process region 60, the intermediate thin film formed on the surface of the substrate S in the film forming process region 20 is subjected to plasma treatment, and the complete reaction product of the film raw material is obtained. Or convert it into an incomplete reactant to form an ultra-thin film.

  In the plasma processing of the first thin film, a reactive gas may be used alone as a reaction processing gas, but it is introduced into the region 60 in a state where an inert gas is positively mixed with the reactive gas. You can also The meaning of the term “actively mixing” will be described later.

  In the present embodiment, the sputtering process and the plasma process are repeated a plurality of times until the ultrathin film formed on the surface of the substrate S has a predetermined thickness (thin film deposition process). As a result, a final thin film (first thin film) having a target film thickness is generated on the substrate S.

  In both the sputtering process and the plasma process described above, generally, for example, argon and helium are considered as the inert gas, and oxygen gas, nitrogen gas, fluorine gas, ozone gas and the like are considered as the reactive gas. It is done. In this embodiment, argon is used as the inert gas, and oxygen gas is used as the reactive gas.

  (2-2) When the film formation of the first thin film is completed, the operation in the film formation process region 20 (supply of sputtering gas, supply of electric power from the AC power supply 23) is stopped. On the other hand. The operation of the reaction process area 60 is continued as it is.

  (2-3) Next, a second thin film is formed on the first thin film. The sputtering process in this case is performed as follows.

  The pressure in the film forming process region 40 is adjusted to, for example, 0.05 to 0.2 Pa, and then the reactive gas cylinder 46 for storing the reactive gas and the inert gas are stored via the mass flow controllers 45 and 47. A sputtering gas with a predetermined flow rate is introduced from the inert gas cylinder 48 into the film forming process region 40. In this embodiment, an inert gas may be used alone as the sputtering gas, but it may be introduced into the region 40 in a state where a reactive gas is mixed with the inert gas. Then, the surroundings of the targets 49a and 49b become a predetermined gas atmosphere. In this state, an AC voltage is applied from the AC power supply 43 to the electrodes 41a and 41b via the transformer 42 so that an alternating electric field is applied to the targets 49a and 49b. In the present embodiment, for example, power (sputtering power) of about 4 kW to 6 kW is supplied. Thereby, at a certain point in time, the target 49a becomes the cathode (negative pole), and at that time, the target 49b always becomes the anode (positive pole). If the direction of the alternating current changes at the next time point, the target 49b becomes the cathode and the target 49a becomes the anode. In this manner, the pair of targets 49a and 49b alternately become an anode and a cathode, so that a part of the sputtering gas around each target 49a and 49b emits electrons and is ionized. A leakage magnetic field is formed on the surfaces of the targets 49a and 49b by the magnets arranged on the electrodes 41a and 41b, so that the electrons draw a toroidal curve in the magnetic field generated near the surfaces of the targets 49a and 49b. Go around. A strong plasma is generated along the trajectory of the electrons, and ions of the sputtering gas in the plasma are accelerated toward the target in the negative potential state (cathode side) and collide with the targets 49a and 49b. The atoms and particles (Ti atoms and Ti particles) on the surfaces 49a and 49b are knocked out. These atoms and particles are film raw material that is a raw material of the thin film, and adhere to the surface of the first thin film on the substrate S to form an intermediate thin film.

  The plasma treatment can be performed by the same procedure as that for the first thin film. The plasma treatment of the second thin film is preferably introduced into the region 60 in a state where an inert gas is positively mixed with a reactive gas as a reaction treatment gas. The “proactive mixing” is intended to exclude a case where an inert gas is contained as a result, contrary to the intention. For example, an inert gas introduced into the film forming process region 20 (or 40) leaks from the region 20 (or 40) for some reason, and is leaked into the reaction process region 60. As a result, the inert gas is introduced into the reaction process region 60. Is removed when mixed with a reactive gas to form a reaction processing gas.

  The flow rate of the inert gas that is actively mixed into the reaction process region 60 is not particularly limited, and is a small amount that does not hinder the effect of introducing the reactive gas (the amount of the inert gas introduced relative to 100 sccm of the reactive gas is, for example, several ˜several tens sccm), or can be introduced at a flow rate equal to or higher than the flow rate of the reactive gas.

  In the present embodiment, the sputtering process and the plasma process are repeated a plurality of times (thin film deposition process) until the ultrathin film formed on the surface of the first thin film on the substrate S has a predetermined thickness. As a result, a final thin film (second thin film) having a target film thickness is generated on the first thin film.

  (3) In this embodiment, after forming the second thin film, plasma post-treatment is performed on the thin film. Specifically, first, the rotation of the rotary drum 13 is temporarily stopped, and the operation in the film forming process region 40 (supply of sputtering gas, supply of electric power from the AC power supply 43) is stopped. On the other hand, the operation of the reaction process region 60 is continued as it is. That is, in the reaction process region 60, the supply of the reaction processing gas and the supply of electric power from the high frequency power supply 89 are continued to generate plasma. In this state, when the rotating drum 13 is rotated again and the substrate S (including the first thin film and the second thin film) is transported to the reaction process region 60, the second thin film generated on the outermost surface of the substrate S becomes the reaction process region. Plasma processing is performed while passing through 60 (post-processing).

  By performing such plasma post-treatment, it is possible to obtain a titanium oxide thin film as a second thin film capable of quickly eliminating the once-developed photocatalytic action.

  “Photocatalytic” or “photocatalytic action” refers to the property of decomposing organic substances by generating active oxygen species by photoexcitation (decomposition activity) and the property of developing a highly hydrophilic phenomenon (hydrophilization by photoexcitation). Means.

  In the plasma post-treatment of this embodiment, the flow rate of the inert gas that is actively mixed into the reaction process region 60 is preferably at least the same as the flow rate of the reactive gas. However, in order to increase the plasma density of the reaction processing gas in the reaction process region 60 and to smoothly develop the above-described characteristics, the inert gas introduction flow rate may be made larger than the reactive gas introduction flow rate. preferable. More preferably, the introduction flow rate of the inert gas is at least 3 times the introduction flow rate of the reactive gas, more preferably 5 times or more, and most preferably 7 times or more. Specifically, for example, the flow rate of the inert gas introduced into the reactive gas of 100 sccm is preferably 300 sccm or more, more preferably 500 sccm or more, and further preferably 700 sccm or more. By adjusting the introduction ratio of the inert gas to be actively mixed, it is possible to control the time until the disappearance of the photocatalytic action. In addition, when the introduction ratio of the inert gas increases, it tends to take time until the photocatalytic action disappears.

  The plasma post-treatment time is set to an appropriate time within a range of about 1 to 60 minutes depending on the physical and optical characteristics required for the titanium oxide thin film after formation.

  The interface state is formed at the crystal grain boundary of the thin film, and as a result, the photocatalytic action is rapidly disappeared. Therefore, the pressure of the reaction processing gas introduced into the reaction process region 60 (post-processing pressure) is appropriately set. Control. Specifically, it is maintained at, for example, 0.07 to 1 Pa. Further, while the plasma is generated in the reaction process region 60, the internal pressure of the antenna housing chamber is maintained at 0.001 Pa or less.

  The flow rate of the reactive gas can be adjusted by the mass flow controller 65, and the power supplied from the high frequency power supply 89 can be adjusted by the matching box 87, respectively. The flow rate of the inert gas is adjusted by the mass flow controller 67.

  When a reactive gas or inert gas is introduced from the reactive gas cylinder 66 or the inert gas cylinder 68, a voltage of 100 k to 50 MHz (preferably 1 M to 27 MHz) is applied to the antennas 85a and 85b from the high frequency power supply 89. Then, plasma is generated in a region facing the antennas 85a and 85b in the reaction process region 60. When the substrate S is made of a glass material, the power supplied from the high-frequency power source 89 is, for example, 3 kW or more, preferably 4 kW or more, more preferably 4.5 kW or more. When S is composed of a resin material, the power is set to a small power, for example, 1 kW or less, preferably 0.8 kW or less, more preferably 0.5 kW or less.

  When performing the plasma post-treatment, the surface of the targets 29a, 29b (or 49a, 49b) is chemically changed (for example, oxidized) by the reactive gas flowing from the reaction process region 60 into the film forming process region 20 (or 40). In order to prevent this, it is preferable to introduce an inert gas into the film forming process region 20 (or 40). At this time, since power is not supplied from the AC power source 23 (or 43) to the electrodes 21a and 21b (or 41a and 41b), the targets 29a and 29b (or 49a and 49b) are not sputtered.

  In the present embodiment, the plasma treatment (reaction treatment) during the formation of the first thin film and the second thin film and the plasma post-treatment after the formation of the second thin film may be performed under the same conditions or different conditions. You can also.

  (4) When the above steps are completed, the re-rotation of the rotary drum 13 is stopped, the vacuum state inside the vacuum vessel 11 is released, the rotary drum 13 is taken out of the vacuum vessel 11 and the substrate S is recovered. On the surface of the recovered substrate S, a titanium oxide thin film (photocatalytic thin film) as a second thin film capable of appropriately controlling the photocatalytic action is formed.

  The substrate S on which the titanium oxide thin film obtained in this embodiment is formed is used for the solar cell cover 100 shown in FIG.

  When ultraviolet light is irradiated to titanium oxide (titanium oxide photocatalyst) that exhibits a photocatalytic action, it is photoexcited and a valence pair is generated therein. In addition, reactive oxygen species such as hydroxyl radicals and superoxide ions are generated on and near the surface by the valence pairs, and the properties (decomposition activity) of decomposing organic substances by the strong oxidizing power of these active oxygen species. To express. Thus, the excited titanium oxide photocatalyst exhibits high hydrophilicity as well as decomposition activity (hydrophilization phenomenon by photoexcitation). On the other hand, when the excited titanium oxide photocatalyst is left in the dark and a predetermined time elapses, the titanium oxide photocatalyst returns to the ground state.

  However, in the conventional titanium oxide photocatalyst, once the energy state becomes an excited state and the hydrophilization phenomenon appears, even if it is left in the dark, the ground state exhibiting water repellency (for example, the contact angle of water is 20). It takes a long period of several weeks to return to about 30 degrees. For this reason, for example, during daytime (daytime) or when there is no snow, photocatalytic action is developed, and organic components such as dirt adhering to the surface of the titanium oxide photocatalyst are decomposed, while at night or while it is covered with snow The photocatalytic action disappears, and the organic substances attached to the surface of the titanium oxide photocatalyst are lifted up in order to easily decompose the organic substances attached to the surface of the titanium oxide photocatalyst during the next day or when there is no snow. It was difficult to express.

  In order to change the titanium oxide photocatalyst from the ground state to the excited state, it is effective to expose it to sunlight as well as to actively irradiate ultraviolet light. Since sunlight contains an ultraviolet light component, the energy state of the titanium oxide photocatalyst can be changed from the ground state to the excited state by exposing the titanium oxide photocatalyst to sunlight. The same can be said when there is snow in a heavy snow region or when there is no snow.

Therefore, the present inventors have made extensive studies. As a result, I thought as follows.
(1) Titanium oxide photocatalysts that have been excited once and have developed photocatalytic activity continue to develop photocatalytic activity over a long period of time even after being left in the dark. This is because active lifetimes of active electrons (e ⁻ ) and active holes (h ⁺ ) existing on (hereinafter referred to as “film surface”) are long.
(2) If the lifetimes of active electrons and active holes present on the film surface can be shortened, the photocatalytic action expressed on the film surface can be quickly eliminated.

  In order to produce such an action, according to the film forming method using the film forming apparatus 1 shown in FIGS. 2 and 3, the reaction process after converting the incompletely oxidized ultrathin film of titanium into the complete oxide of titanium. In the region 60, an oxygen gas as a reactive gas is actively mixed with an argon gas as an inert gas to generate a plasma of such a mixed gas (reaction treatment gas), and a post-treatment using this plasma. Apply. By performing this post-treatment, it was found that a titanium oxide thin film as a second thin film capable of quickly disappearing the photocatalytic action once expressed can be obtained.

In addition, the mechanism by which such characteristics are manifested by performing specific post-processing is not always clear. In general, it is known from the theory of crystal growth that impurities and defects existing inside the bulk tend to precipitate outside the crystal phase as the crystal phase grows in the bulk. In the present embodiment, if the inert gas is positively included in the reactive gas in the post-processing, the plasma density of the mixed gas in the reaction process region 60 becomes deeper. When plasma with high density contacts the second thin film, defects formed in the titanium oxide are formed outside the columnar structure, that is, at the grain boundary portion in the process of changing the crystal structure of the titanium oxide to the anatase structure. Precipitate. The deposited defect functions as an interface state (defect level) as a recombination center of active electrons (e ⁻ ) and active holes (h ⁺ ) generated on the film surface, which develops photocatalytic action. However, it is considered that the above-described characteristics can be obtained by exhibiting such functions. This interface state draws active electrons and active holes expressed on the film surface into the film and disappears from the film surface. At the same time as the active electrons and active holes that existed on the film surface disappear, the photocatalytic action on the film surface disappears. The “interface level” means an electronic level (electronic state) generated by the presence (or formation) of the interface.

  The solar cell cover 100 shown in FIG. 1 manufactured by a specific method using the film forming apparatus 1 illustrated in FIGS. 2 and 3 is preferably used by being disposed on the light receiving surface side of the solar cell. In addition, you may apply the said laminated body (solar cell cover) to uses other than the cover of a solar cell. For example, building materials, building exteriors, building interiors, window frames, window glass, structural members, plate materials, vehicle exteriors and coatings, machinery and article exteriors, dust covers and coatings, road sign reflectors, various display devices, advertisements Tower, sound insulation wall for road, sound insulation wall for railway, decorative plate for road, light source cover for traffic light, outdoor display board, bridge, guardrail exterior and paint, tunnel interior and paint, tunnel lighting, glass, solar water heater heat collecting cover , Plastic houses, vehicle lamp covers, road mirrors, vehicle mirrors, motorcycle instrument covers and instrument panels, glass lenses, plastic lenses, helmet shields, houses and window glass for automobiles and railway vehicles, showcases, heat insulation Showcases, membrane structures, heat exchange fins, glass surfaces at various locations, blinds, tire wheels, roofing materials, antennas , Power lines, housing equipment, toilets, bathtubs, wash basins, lighting fixtures, lighting covers, kitchenware, tableware, tableware storage, dishwashers, dish dryers, sinks, cooking ranges, kitchen hoods, ventilation fans, antithrombogenic Examples include materials, anti-protein adhesive materials, ship bottoms, and films for attaching to the above articles.

<Solar cell module>
As shown in FIGS. 4 and 5, the solar cell module 200 as an example of the solar cell includes, for example, 6 × 6 rows of solar cells via a filler layer 202 on the back surface 201 </ b> A of the incident surface side light-transmitting substrate 201. As the cells 204 are stacked, a back glass 206 as a back light transmitting base material is stacked on the solar cells 204, and a terminal box 208 connected to each of the solar cells 204 includes the back glass 206. It is configured by being fixed to the back surface 206A.

<< Light entrance base material on the incident surface side >>
The incident surface side light transmissive substrate 201 can be made of the same material as the light transmissive substrate 102 of the solar cell cover 100 shown in FIG. In addition, you may use the translucent base material 102 of the solar cell cover 100 for the said incident surface side light transmissible base material 201. FIG. In this case, the light transmissive substrate 102 of the solar cell cover 100 functions as the light incident surface side light transmissive substrate of the module 200.

<< Filler layer >>
The filler layer 202 is filled around the solar battery cell 204 between the cover 100 and the back glass 206, and protects the adhesiveness between the incident surface side light-transmitting substrate 201 and the back glass 206 and the solar battery cell 204. Scratch resistance, shock absorption, etc. In addition to the above functions, the filler layer 202 laminated on the surface of the solar battery cell 204 has transparency to transmit sunlight.

  Examples of the forming material of the filler layer 202 include polyolefin resins such as fluorine resins, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-acrylic acid or methacrylic acid copolymers, polyethylene resins, polypropylene resins, and polyethylene. Examples include acid-modified polyolene fin-based resins modified with unsaturated carboxylic acids such as acrylic acid, polyvinyl butyral resins, silicone-based resins, epoxy-based resins, (meth) acrylic resins, and the like. Among these synthetic resins, fluorine resins, silicone resins, or ethylene-vinyl acetate resins that are excellent in weather resistance, heat resistance, gas barrier properties, and the like are preferable. The forming material of the filler layer 202 includes various materials such as a crosslinking agent, a thermal antioxidant, a light stabilizer, an ultraviolet absorber, and a photoantioxidant for the purpose of improving weather resistance, heat resistance, gas barrier properties, and the like. Additives can be contained as appropriate. The thickness of the filler layer 202 is not particularly limited, but is preferably 200 to 1000 μm.

<Solar cell>
The solar battery cell 204 is a photovoltaic element that converts light energy into electric energy. Each photovoltaic cell 204 is laid in substantially the same plane and wired in series or in parallel. As the solar cell 204, for example, a crystalline silicon solar electronic element such as a single crystal silicon type solar cell element or a polycrystalline silicon type solar cell element, an amorphous silicon solar cell element such as a single junction type or a tandem structure type, gallium arsenide ( Group 3 to 5 compound semiconductor solar electronic devices such as GaAs) and indium phosphorus (InP), Group 2 to 6 compound semiconductor solar electronic devices such as cadmium tellurium (CdTe) and copper indium selenide (CuInSe ₂ ), etc. These hybrid elements can also be used. In addition, the filler layer 202 is filled between the plurality of solar cells 54 without any gap.

《Back glass》
The back glass 206 functions as a back surface side translucent substrate. Note that instead of the back glass 206, a plate-like glass, a film-like organic material, or an inorganic material may be used.

The thickness of the incident surface side light-transmitting base material 201 and the back glass 206 is such that the strength at the layer portion where the solar cells 204 are disposed or the solar cell module 200 can be maintained so that the required strength of the entire module 200 can be maintained. It can be appropriately set according to the size of the area. For example, when the area of the solar cell 200 is, for example, about 1 m ² , the thickness of the incident surface side light-transmitting substrate 201 is, for example, 4 to 6 mm, and the thickness of the back glass 206 is, for example, float. When glass is used, the thickness is, for example, 4 to 8 mm.

<< Solar Cell Module Manufacturing Method >>
The manufacturing method of the solar cell module 200 is not particularly limited, but generally, first, the incident surface side light-transmitting substrate 201, the filler layer 202, the plurality of solar cells 204, and the back There are a step of laminating the glass 206 in this order, and then a lamination step of integrally forming them by a vacuum heating lamination method or the like in which they are integrated by vacuum suction and thermocompression bonded. In the manufacturing method of the solar cell module 200, for the purpose of adhesiveness between the respective layers, a hot-melt adhesive, a solvent-type adhesive, a photo-curable adhesive, or the like is applied, or each laminated facing surface is applied. Corona discharge treatment, ozone treatment, low temperature plasma treatment, glow discharge treatment, oxidation treatment, primer coat treatment, undercoat treatment, anchor coat treatment, and the like can also be performed.

<Installation of solar cell module>
For example, as shown in FIG. 6, the solar cell module 200 can be installed in a snowy area, in particular, with a slope on the south surface (for example, on the south-facing roof 300). When snow accumulates on the surface of such a module 200, sunlight does not enter the cell 204 in the module 200, and subsequent power generation cannot be performed.

  In the present embodiment, the solar battery cover 100 shown in FIG. 1 is disposed on the light receiving surface side of the module 200, and the transparent conductive film 104 of the solar battery cover 100 is provided with at least one solar battery cell 204 (preferably in the module 200). Is electrically connected to the solar cell module 200. Hereinafter, simply referred to as the solar cell 200), and the transparent conductive film 104 can be heated by supplying power using the solar cell 200 as a power source.

  In order to electrically connect the transparent conductive film 104 to the solar cell 200, for example, an electrode (not shown) is formed so that a current can be conducted to the transparent conductive film 104, and a current is conducted from the solar cell 200 here. It is possible to realize. Note that it is not always necessary to use the power generated by the solar cell 200 for the heat generation of the cover 100, and the power generated by another power source may be used.

  The electrode formed on the transparent conductive film 104 of the solar cell cover 100 may be any electrode as long as it has conductivity, and the material and shape are not particularly limited.

  Examples of the electrode include, for example, a conductive resin; a conductive resin and a metal foil; a metal plating layer on the conductive resin; a metal plating layer; As the conductive resin, a resin such as polypyrrole itself has conductivity, silver paste, silver paste such as copper paste or silver-copper paste, metal powder such as copper, or carbon such as carbon black alone or carbon The thing etc. which were mixed with resin by the mixture are illustrated. The metal foil may be a metal foil, and preferably a metal foil such as a copper foil or a nickel foil. As a metal plating layer, the layer which consists of a metal which can be normally plated, such as nickel and copper, is illustrated. These can be used alone or as a laminated or mixed layer to form an electrode. Needless to say, these may be used in multiple layers.

  The conductive resin layer is installed by a normal printing method, etc. When using metal foil, an adhesive is provided on one side of the metal foil, and the conductive resin layer is adhered to the conductive resin layer. The formation of an electrode provided with a resin is exemplified. The metal plating layer is formed by a method selected from wet processes such as electroplating, electroless plating, or direct plating.

  The thickness of the electrode is not limited as long as the transparent conductive film 104 can flow as much current as it can function as a heat generating surface, but is usually 0.1 μm or more, preferably 0.5 to 100 μm, more preferably 1 to 50 μm. More preferably, it is about 5 to 20 μm.

  By supplying electric power to the transparent conductive film 104 of the solar cell cover 100 to generate heat, when snow accumulates on the surface of the module 200, the transparent conductive film 104 generates heat using the energy stored in the solar cell 200 as a power source. The snow on the cover 100 is melted. At this time, since the surface state of the thin film 106 formed on the outermost surface has returned to the water-repellent state, the entire snow is compressed to the surface of the module 200 by the dead weight of the snow that is piggybacked on the thin film 106 and the module 200. It becomes easy to slide down from the upper part to the lower part (see the arrow in FIG. 6). As a result, snow on the photocatalytic thin film 106 can be effectively removed, and thereafter, sunlight can be made incident on the cell 204 in the module 200, and subsequent power generation can be continued.

  The installation mode of the solar cell module 200 is not limited to such installation on the roof, but may be an embodiment in which the solar cell module 200 is integrated with the roof material, or may be a ground installation type other than the roof. .

<< Other Embodiments >>
The embodiments described above are described for facilitating the understanding of the invention, and are not described for limiting the invention. Therefore, each element disclosed in the above embodiment includes all design changes and equivalents belonging to the technical scope of the above invention.

  In the above-described embodiment, prior to the formation of the first thin film on the substrate S, the surface of the substrate S can be pretreated with plasma. In this case, the pretreatment may be performed under the same conditions as the plasma treatment during the thin film formation and the plasma post treatment after the second thin film formation, or under different conditions.

  In the above-described embodiment, the case where the photocatalytic thin film 106 is formed by sputtering using the film forming apparatus 1 that performs magnetron sputtering, which is an example of sputtering, is illustrated, but the present invention is not limited thereto, and magnetron discharge is used. It is also possible to form a film by another sputtering method using a film forming apparatus that performs other known sputtering such as bipolar sputtering, or by a vacuum evaporation method such as resistance heating evaporation, electron beam evaporation, or ion plating.

  Next, the present invention will be described in more detail with reference to examples that further embody the above-described embodiments.

Example 1
2 and 3 were used. (1) First, a transparent conductive thin film (first thin film) of zinc oxide (ZnO) was formed on the surface of the substrate S. As the substrate S, BK7, which is a glass substrate, was used. Film formation was performed under the following conditions. The film formation rate was 0.45 nm / s.

<< Processing in Deposition Process Area 20 >>
-Substrate temperature: room temperature,
-Targets 29a and 29b: zinc (Zn),
-Power supplied to the target (sputtering power): 3.0 kW,
-Frequency of AC voltage applied to electrodes 21a and 21b: 40 kHz
Argon gas introduction flow rate: 250 sccm.

<< Processing in Reaction Process Area 60 >>
Power supplied from the high frequency power supply 89 to the antennas 85a and 85b (plasma processing power): 2 kW
-Frequency of AC voltage applied to antennas 85a and 85b: 13.56 MHz,
・ Oxygen gas introduction flow rate: 80 sccm,
Argon gas introduction flow rate: 0 sccm.

  Under the film forming conditions described above, the process in the film forming process region 20 and the process in the reaction process region 60 are repeated a plurality of times (thin film deposition step), and a zinc oxide thin film as a first thin film having a thickness of 600 nm is formed on the surface of the substrate S. Formed.

  (2) Next, the rotation of the rotary drum 13 is stopped, the power supply from the AC power source 23 is stopped (the operation of the film forming process region 20 is stopped), and the thin film deposition is finished. Supply of power from the AC power supply 43 in a state where the supply of oxygen gas and argon gas and the supply of power from the high-frequency power source 89 are continued and plasma of a mixed gas of oxygen and argon is generated in the reaction process region 60. Was started (operation of the film forming process region 40 was started), and the rotary drum 13 was rotated again to form the following film on the surface of the first thin film. The film formation rate was 0.3 nm / s.

<< Processing in Film Formation Process Area 40 >>
-Substrate temperature: room temperature,
Target 49a, 49b: Titanium (Ti)
-Power supplied to the target (sputtering power): 5.0 kW,
The frequency of the alternating voltage applied to the electrodes 41a and 41b: 40 kHz
Argon gas introduction flow rate: 500 sccm.

<< Processing in Reaction Process Area 60 >>
Power supplied from the high frequency power supply 89 to the antennas 85a and 85b (plasma processing power): 3 kW
-Frequency of AC voltage applied to antennas 85a and 85b: 13.56 MHz,
・ Oxygen gas introduction flow rate: 200 sccm,
Argon gas introduction flow rate: 500 sccm.

Under the above-described film forming conditions, the process in the film forming process area 40 and the process in the reaction process area 60 are repeated a plurality of times (thin film deposition process), and the second thin film having a thickness of 180 nm on the surface of the zinc oxide thin film on the substrate S. A photocatalytic thin film of titanium oxide (TiO ₂ ) was formed.

  (3) Next, the rotation of the rotating drum 13 is stopped, the power supply from the AC power supply 43 is stopped (the operation of the film forming process region 40 is stopped), and the thin film deposition is finished. In the reaction process region 60, The supply of oxygen gas and argon gas and the supply of power from the high-frequency power source 89 are continued, and the rotating drum 13 is re-rotated in a state where the plasma of the mixed gas of oxygen and argon is generated in the reaction process region 60. Then, the substrate S was transported to the reaction process region 60, and the titanium oxide thin film (second thin film) formed on the outermost surface of the substrate S was subjected to plasma post-treatment while passing through the reaction process region 60. The post-treatment time was 30 minutes.

  Under the above conditions, a titanium oxide thin film having a thickness of 180 nm (total film formation time 45 minutes (film formation 15 minutes + post-treatment 30 minutes)) was formed on the outermost surface of the substrate S.

<< Comparative Example 1 >>
A titanium oxide thin film was formed on the outermost surface of the substrate S in the same manner as in Example 1 except that plasma post-treatment was not performed.

<< Evaluation of thin film >>
The cycle evaluation of the onset and disappearance of the photocatalytic action of the titanium oxide thin films obtained in Example 1 and Comparative Example 1 was performed. This evaluation was performed by examining the change with time of the contact angle of water with respect to the prepared titanium oxide thin film.

Specifically, first, (1) the contact angle of water was measured with respect to the titanium oxide thin film immediately after preparation (contact angle a). Next, (2) the titanium oxide thin film immediately after the production was irradiated with ultraviolet rays at a dose of 10 mW / cm ² for 60 minutes, and the contact angle of water was a predetermined value (contact angle b. In this example, b = 10 It was lowered to below. Next, (3) the titanium oxide thin film in which the contact angle of water has decreased to b, that is, the state in which photocatalysis is exhibited, is left in the dark, and the time until the contact angle of water returns to a described above is obtained. It was.

  In addition, the contact angle with respect to water used the value measured by the method (wetability test) based on JIS-R3257. Specifically, the substrate S is placed on a test stand, distilled water is dropped on the titanium oxide thin film side of the substrate S, and the contact angle of the water droplet is measured with an automatic contact angle meter (DM500, Kyowa Interface Science Co., Ltd.). ) Was used to determine the contact angle with water.

  As a result, in the sample of Example 1, the contact angle of water on the thin film decreased from a little less than 70 ° of the contact angle a to around 10 ° of the contact angle b in about 60 minutes. That is, the photocatalytic action was exhibited by ultraviolet irradiation for about 60 minutes. On the other hand, the contact angle of water rose from around 10 ° of contact angle b to around 70 ° of contact angle a in about 30 minutes after being left in the dark. That is, the photocatalytic action disappeared when left in a dark place for about 30 minutes.

  On the other hand, in the sample of Comparative Example 1, the contact angle of the water of the thin film decreased from a little less than 70 ° of the contact angle a to around 10 ° of the contact angle b after 1 hour of ultraviolet irradiation. That is, the photocatalytic action was expressed by ultraviolet irradiation for 1 hour. On the other hand, the contact angle of water does not change from around 10 ° of the contact angle b even after 1 hour has passed since it is left in a dark place, and the contact angle of water does not contact until this state is continued for another 3 days. The angle a rose to around 70 °. That is, the photocatalytic action finally disappeared after being left in a dark place for a total of 72 hours.

  As can be seen from the above results, it was confirmed that the photocatalytic action developed on the surface of the titanium oxide thin film can be quickly eliminated in the sample of Example 1 as compared with the sample of Comparative Example 1.

<< Examples 2 to 5 >>
The outermost surface of the substrate S was subjected to the same conditions as in Example 1 except that the oxygen gas introduction flow rate was maintained at 200 sccm and the argon gas introduction flow rate into the reaction process region 60 was set to 200 sccm, 400 sccm, 600 sccm, and 800 sccm. Then, a titanium oxide thin film having a thickness of 180 nm (total film formation time 45 minutes (film formation 15 minutes + post-treatment 30 minutes)) was formed.

  When the introduction ratio of argon gas with respect to oxygen gas increases, it tends to take time until the photocatalytic action disappears. However, when compared with the sample of Comparative Example 1, the photocatalytic action that appears significantly on the surface of the titanium oxide thin film. It was confirmed that can be quickly eliminated.

DESCRIPTION OF SYMBOLS 200 ... Solar cell module (solar cell), 100 ... Solar cell cover, 102 ... Translucent substrate, 104 ... Transparent electrically conductive film, 106 ... Photocatalytic thin film, 201 ... Translucent substrate, 202 ... Filler layer, 204 ... Solar cell, 206 ... back glass, 208 ... terminal box, 300 ... roof,
DESCRIPTION OF SYMBOLS 1 ... Film-forming apparatus, 11 ... Vacuum container, 13 ... Rotary drum, S ... Substrate, 12, 14, 16 ... Partition wall,
20, 40 ... deposition process area,
Sputter source (21a, 21b, 41a, 41b ... magnetron sputtering electrode, 23, 43 ... AC power supply, 24, 44 ... transformer, 29a, 29b, 49a, 49b ... target),
Gas supply means for sputtering (26, 46 ... reactive gas cylinder, 28, 48 ... inert gas cylinder, 25, 27, 45, 47 ... mass flow controller),
60 ... Reaction process area,
80 ... Plasma source (81 ... Case body, 83 ... Dielectric plate, 85a, 85b ... Antenna, 87 ... Matching box, 89 ... High frequency power supply), Reaction processing gas supply means (66 ... Reactive gas cylinder, 68 ... Inert Gas cylinder, 65, 67 ... mass flow controller),

Claims (8)

A translucent substrate, a heat generating layer composed of a first thin film made of a ZnO-based transparent conductive film , and a photocatalytic thin film composed of a second thin film having a thickness of 50 nm or more and less than 300 nm are laminated in this order. In the solar cell cover
The solar cell cover, wherein the photocatalytic thin film is formed by performing the following treatments (1) to (4) on the surface of the heat generating layer.
(1) In a film forming process region formed inside a vacuum vessel, a target made of titanium metal is sputtered, and a film raw material material made of titanium is attached to the surface of the heat generating layer to form an intermediate thin film sputtering process you,
(2) A reaction process in which an ultra-thin film is formed by bringing a plasma of oxygen gas , which is a reactive gas , into contact with the intermediate thin film in a reaction process area formed away from the film forming process area,
(3) The translucent substrate on which the heat generating layer is formed is moved between the film forming process region and the reaction process region, the sputtering step and the reaction step are repeated a plurality of times, and the ultrathin film is formed a plurality of times. A thin film deposition step of depositing to form a second thin film;
(4) A plasma post-treatment process in which plasma of a mixed gas obtained by positively mixing an inert gas with the reactive gas at a flow rate at least the same as the flow rate of the reactive gas is brought into contact with the second thin film. The cover according to claim 1, wherein the heating layer, a solar cell cover, wherein the Thickness is 300 to 1000 nm. A heat generating layer composed of a first thin film made of a ZnO-based transparent conductive film is laminated on the surface of the translucent substrate, and the surface of the heat generating layer is composed of a second thin film having a thickness of 50 nm or more and less than 300 nm. A method for producing a solar cell cover in which a photocatalytic thin film is laminated,
A first film forming step of forming the heat generating layer on the surface of the light transmissive substrate, and a second film forming step of forming the photocatalytic thin film on the surface of the heat generating layer,
The second film forming step includes
In the film forming process region formed in the interior of the vacuum vessel, it shall be the titanium metal was sputtered configured target, the intermediate thin layer by depositing a composed film raw material in the titanium on the surface of the heat generating layer sputtered Process,
A reaction step in which an ultra-thin film is formed by bringing a plasma of oxygen gas , which is a reactive gas , into contact with the intermediate thin film in a reaction process region formed away from the film-forming process region;
The translucent substrate is moved between the film formation process region and the reaction process region, the sputtering step and the reaction step are repeated a plurality of times, and the ultrathin film is deposited a plurality of times to form a second thin film. A thin film deposition process;
A plasma post-processing step of bringing a mixed gas plasma in which an inert gas is positively mixed with the reactive gas at a flow rate that is at least the same as that of the reactive gas into contact with the second thin film. A method for producing a solar cell cover. 4. The method for manufacturing a solar cell cover according to claim 3, wherein the heat generating layer is laminated on the surface of the translucent substrate with a thickness of 300 to 1000 nm. 5. The manufacturing method according to claim 3 , wherein in the post-processing step, the inert gas is introduced at a flow rate higher than a flow rate of introduction of the reactive gas, and plasma of the mixed gas is generated. Manufacturing method of solar cell cover. In the manufacturing method according to any one of claims 3 to 5, in the post-processing step, the inert gas is introduced into the reaction process region at a flow rate of at least three times the introduction flow rate of the reactive gas, A method for producing a solar cell cover, comprising generating plasma of the mixed gas. A series or plurality of solar cells wired in parallel packaging, on the light-receiving surface side of the unitized solar cell modules, laminated the light-transmitting substrate according to claim 1 or 2 Symbol placement of the solar cell cover With
The heating layer of the solar cell cover is electrically connected to a power source, and the heating layer is heated by supplying power,
A snow melting method comprising melting snow accumulated on the surface of the photocatalytic thin film.   The snow melting method according to claim 7, wherein the heat generating layer is electrically connected to at least one of the solar cells, and the heat generating layer is heated by supplying electric power. .

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