Lubricant-holding base material, method for producing same, lubricating material, and method for producing same

Provided are a lubricating material which is made of a non-fluorine-based compound and thus has a surface that is slippery enough for liquid such as water or oil, a lubricant-holding base material which holds a fluorine-based lubricant and thus can be used as a lubricating material, and methods for producing the same. A slippery film has a holding base and a lubricant. The holding base has pillar structure portions and fluorine-containing portions, and the fluorine-containing portions are provided on outer surfaces of a plurality of pillar portions in the pillar structure portion. The lubricant is a fluorine-based liquid, and the fluorine-containing portion has a C—F bond. The lubricant is loaded into a region surrounded by a plurality of the pillar portions and is held in this region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2015-040586, filed on Mar. 2, 2015. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application.

The following disclosures are submitted under 35 U.S.C section 102(b)(1)(A):

“Fabrication of underwater biomimetic bubble repellent surfaces on the inner surfaces of tubes” made publicity available on Sep. 1, 2014, published in The 75th The Japan Society of Applied Physics (JSAP) Autumn Meeting conference abstract page 12-016, and “Fabrication of omniphobic lubricated surfaces based on self-organized honeycomb and pillared films” made publicity available on Sep. 3, 2014, published in The Society of Polymer Science conference abstract Vol. 63, No. 2, 2014, pp. 6869-6870. Presentation entitled, “Fabrication of biomimetic bubble repellent surfaces on the inner surfaces of tubes” made at The 75th The Japan Society of Applied Physics (JSAP) Autumn Meeting on Sep. 17, 2014 and presentation entitled, “Fabrication of omniphobic lubricated surfaces based on self-organized honeycomb and pillared films” made at the 63th Symposium on Macromolecules on Sep. 24, 2014.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubricant-holding base material, a method for producing the same, a lubricating material, and a method for producing the same.

2. Description of the Related Art

A material holding a fluorine-based lubricant in recess portions of an uneven structure body in which fine protrusions and recesses are formed on the surface has been proposed (Wong, Tak-Sing, et al. “Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity.”, Nature 477. 7365 (2011), p. 443-447). This material is slippery enough to allow liquid droplets to slip on the surface on which the lubricant is exposed through openings in the fine recess portions, and thus the surface is called a slippery liquid-infused porous surface (SLIPS). This material is a non-woven fabric formed of a fiber formed of a compound including fluorine in the structure.

Meanwhile, as the uneven structure body in which fine protrusions and recesses are formed on the surface, there is a honeycomb-structure film or a pillar-structure film. The honeycomb-structure film refers to a film that is provided with a honeycomb structure by arranging a plurality of pores as fine recess portions on a film surface. In addition, the pillar-structure film refers to a film in which protrusion portions are formed in a fine columnar pillar shape.

The honeycomb-structure film can be produced using a dew condensation method (also referred to as a breath figure method) (for example, refer to JP2009-293019A). The dew condensation method is a method in which a solution including a hydrophobic polymer for forming a honeycomb film as a raw material is cast so as to form a cast film, dew is condensed on this cast film so as to form water droplets, and a solvent and water droplets are evaporated, thereby producing a honeycomb-structure film (for example, refer to JP2009-293019A). According to this dew condensation method, the water droplets act as casting molds for pores, and thus it is possible to obtain a honeycomb-structure film in which a plurality of extremely fine and uniform pores are formed in a state of being regularly arranged.

In addition, the pillar-structure film can be produced using the honeycomb-structure film. As a method for producing the pillar-structure film using the honeycomb-structure film, there is a method in which an adhesive film including an adhesive on the surface is attached to one film surface of a honeycomb-structure film on which pores are formed and the adhesive film is drawn, thereby peeling a portion in the above-described film surface side in which pores are formed off from a portion on the other film surface side. In this method, the portion on the other film surface side becomes the pillar-structure film (for example, refer to JP2009-293019A). In addition, a method for producing a pillar-structure film by irradiating a honeycomb-structure film with ultrasonic waves also has been proposed (for example, WO2004/048064A). According to this method, it is possible to easily produce a pillar-structure film using a honeycomb-structure film.

Furthermore, the honeycomb-structure film can also be formed on a curved surface. For example, as a method for forming a honeycomb-structure film on the outer circumferential surface and the inner circumferential surface of a cylinder, there is a method in which the cylinder is immersed in the above-described solution including a hydrophobic polymer as a raw material, a lubricating gas is supplied to the outer circumference and the hollow portion of the cylinder, and then a dried gas is supplied (for example, refer to JP2010-229373A).

SUMMARY OF THE INVENTION

However, since the material of Wong, Tak-Sing, et al. “Bioinspired self-repairing slippery surfaces with pressure-stable ominphobicity.”, Nature 477. 7365 (2011), p. 443-447 is formed of a compound including fluorine in the structure, molding workability is limitative, and the material can be molded only to limited shapes that can be produced using a fiber.

Therefore, an object of the present invention is to provide a lubricating material which is made of a non-fluorine-based compound and thus has a surface that is slippery enough for liquid such as water or oil, a lubricant-holding base material which holds a fluorine-based lubricant and thus can be used as a lubricating material, and a method for producing the lubricating material and the lubricant-holding base material.

In order to solve the above-described problems, the lubricant-holding base material of the present invention includes an uneven structure portion and fluorine-containing portions. The uneven structure portion is formed of a hydrophobic polymer, and, in the uneven structure portion, a plurality of recess portions or a plurality of protrusion portions are regularly arranged, and insides of the recess portions or regions surrounded by a plurality of the protrusion portions adjacent to each other serve as spaces for holding a fluorine-based lubricant. The fluorine-containing portions are provided on inner surfaces of the recess portions or on outer surfaces of the protrusion portions and have a C—F bond.

The uneven structure portion is preferably a pillar structure portion in which a plurality of protrusion portions having a tapering shape and a certain size are formed in an upright shape. A height of the protrusion portion is preferably in a range of 0.1 μm to 20 μm.

The uneven structure portion is preferably a honeycomb structure portion provided with a honeycomb structure by arranging a plurality of the recess portions having a certain size in parallel. A depth of the recess portion is preferably in a range of 0.2 μm to 50 μm, and a diameter of an opening in the recess portion is preferably in a range of 0.2 μm to 50 μm.

The hydrophobic polymer is preferably a polyolefin capable of an ene-thiol reaction with a thiol having a fluorine atom, and the polyolefin is preferably polybutadiene.

The lubricant-holding base material is preferably formed in a film shape.

The lubricating material of the present invention includes the lubricant-holding base material and a fluorine-based lubricant loaded into the insides of the recess portions or the regions surrounded by a plurality of the protrusion portions.

In a method for producing a lubricant-holding base material of the present invention, with respect to an uneven structure body which is formed of a hydrophobic polymer and in which a plurality of recess portions or a plurality of protrusion portions are regularly arranged and insides of the recess portions or regions surrounded by a plurality of the protrusion portions adjacent to each other serve as spaces for holding a fluorine-based liquid lubricant, fluorine-containing portions are formed on inner surfaces of the recess portions or on outer surfaces of the protrusion portions.

The uneven structure body is preferably a pillar structure body in which a plurality of the protrusion portions having a tapering shape and a certain size are formed in an upright shape. The pillar structure body is preferably formed by ultrasonically vibrating a honeycomb structure body provided with a honeycomb structure by arranging a plurality of the recess portions having a certain size in parallel on a surface in liquid so as to peel some portions near the surface off from the honeycomb structure body and leaving a portion of partition walls between the recess portions adjacent to each other in the honeycomb structure body as the protrusion portions.

The uneven structure body is preferably a honeycomb structure body provided with a honeycomb structure by arranging a plurality of the recess portions having a certain size in parallel.

The hydrophobic polymer is preferably a polyolefin capable of an ene-thiol reaction with a thiol having a fluorine atom, and the fluorine-containing portion portions are preferably formed by fluorinating the hydrophobic polymer with the thiol. The polyolefin is preferably polybutadiene.

A method for producing a lubricating material of the present invention includes a fluorine-containing portion-forming step and a loading step. In the fluorine-containing portion-forming step, with respect to an uneven structure body which is formed of a hydrophobic polymer and in which a plurality of recess portions or a plurality of protrusion portions are regularly arranged and insides of the recess portions or regions surrounded by a plurality of the protrusion portions adjacent to each other serve as spaces for holding a fluorine-based liquid lubricant, fluorine-containing portions are formed on inner surfaces of the recess portions or on outer surfaces of the protrusion portions. In the loading step, a fluorine-based lubricant is loaded into the insides of the recess portions or the regions surrounded by a plurality of the protrusion portions.

According to the present invention, a lubricating material which is made of a non-fluorine-based compound and thus has a surface that is slippery enough for liquid such as water or oil and a lubricant-holding base material which holds a fluorine-based lubricant and thus can be used as a lubricating material are obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A slippery film10illustrated inFIG. 1, which is an embodiment of the present invention, is a slippery material formed in a film shape and exhibits a lubricating property (hereinafter, referred to as the slipping property) which, when liquid or gas comes into contact with a surface, suppresses attachment of the liquid or the gas and allows the liquid or the gas to slip. The slippery film10includes a lubricant-holding film base (hereinafter, referred to as the holding base)11and a fluorine-based lubricant (hereinafter, referred to as the lubricant)12. The thickness T10of the slippery film10is set to 10 μm in the present example, but is not limited thereto, and is in a range of 0.2 μm to 100 μm. The slippery film10of the present example has a 5 cm×10 cm rectangular shape when seen in a direction perpendicular to one film surface (hereinafter, referred to as the first film surface)10a, but the size and the shape are not limited thereto. For example, the slippery film can be formed in a round or irregular shape, and, in the case of being produced in a continuous manner as described below, the slippery film can also be formed in a web shape.

The lubricant12is provided to develop a slipping property on a first film surface10aof the slippery film10. The lubricant12is preferably a material which has a structure including a fluorine atom F, maintains a liquid form (a state in which neither a gas phase nor a solid phase appear and a liquid phase is maintained) in a temperature range of −15° C. to 200° C., and is non-volatile and fluid even at a low temperature. In the present example, perfluoroalkylether (Krytox (registered trademark) 103 manufactured by DuPont) is used as the lubricant12, but the lubricant is not limited thereto, and, as another example, Fluorinert FC-70 (manufactured by 3M) may be used or a mixture of two or more thereof may also be used.

The holding base11is provided to hold the lubricant12. The holding base11is made by performing vacuum deposition or an ene-thiol reaction, which will be described below, on a pillar structure film20(refer toFIG. 3) described below and, as illustrated inFIGS. 1 and 2, includes pillar structure portions13and fluorine-containing portions14formed by means of vacuum deposition or an ene-thiol reaction. InFIGS. 1 and 2, the fluorine-containing portion14is illustrated in an exaggerated thickness. In addition, inFIGS. 1 and 2, a boundary between the pillar structure portion13and the fluorine-containing portion14is illustrated, but there is a case in which the boundary is invisible.

A pillar structure portion13is an uneven structure portion including a plurality of columnar pillar portions13aas protrusion portions. A plurality of the pillar portions13ahave almost the same shape and size and are regularly arranged. The respective pillar portions13aface upwards inFIGS. 1 and 2and are provided upright in the thickness direction of the slippery film10. The pillar portion13ahas a so-called tapering shape in which the diameter decreases toward the tip. In this example, the pillar portion13ais formed to be sharp at the tip, but there is another case in which the tip appears to be round depending on the shape of a pillar21(refer toFIG. 3) in the pillar structure film20(refer toFIG. 3) described below which serves as a material. On the other film surface (hereinafter, referred to as the second film surface)10b, a film surface opening portion10cis formed between the pillar portion13aand the pillar portion13a.

The height H13aof the pillar portion13a(hereinafter, referred to as the pillar portion height) is approximately 3 μm in this example, but is not limited thereto, and is in a range of 0.1 μm to 20 μm. Meanwhile, the pillar portion height is represented by a reference signal H13ainFIG. 2. In this example, since the pillar portions13aare formed so as to form the film surface opening portions10c, and the pillar portions13aare formed on the second film surface10b, the pillar portion height H13ais equal to the thickness T10of the slippery film10. The pillar portion height H13acan be changed by changing the pillar height of the pillar structure film20(refer toFIG. 3) described below. In addition, the distance between the pillar portion13aand the pillar portion13awhich are adjacent to each other (hereinafter, referred to as the distance between the pillar portions) is approximately 8 μm in this example, but is not limited thereto, and is almost constant in a range of 0.2 μm to 50 μm. Meanwhile, the distance between the pillar portions refers to the distance between the tips of the pillar portions13aadjacent to each other. The distance between the pillar portions changes depending on the distance between adjacent pillars in the pillar structure film20which is a material.

The pillar structure portion13is formed of a hydrophobic polymer42(refer toFIG. 7). The hydrophobic polymer42is preferably polylactic acid, polycaprolactone, polyglycolic acid, polydioxanone, polyhydroxybutyrate, polybutadiene, polyurethane, polystyrene (PS), poly methyl methacrylate, polycarbonate, a copolymer having a repeating unit thereof, or the like. In the present embodiment, polystyrene is used. As described, it is possible to use a polymer not containing fluorine, that is, a hydrophobic polymer not containing fluorine. The pillar structure portion13may include, in addition to the hydrophobic polymer42, for example, an amphipathic compound, and the amphipathic compound may be any one of a polymer, an oligomer, or a monomer. In a case in which the amphipathic compound is included, the mass of the amphipathic compound is preferably 10 parts by mass or lower with respect to 100 parts by mass of the pillar structure film20.

The fluorine-containing portion14is provided on an outer surface13bof each pillar portion13a. The thickness of the fluorine-containing portion14is 20 nm in the present embodiment, but is not limited thereto, and is in a range of 5 nm to 5 μm. The fluorine-containing portion14is constituted with a material having a C—F bond, examples thereof include polytetrafluoroethylene (PTFE), perfluoroalkoxy alkanes (PFA), perfluorooctanethiol (PFOT), or the like, and, in the present embodiment, perfluorooctanethiol is used. A region surrounded by a plurality of the pillar portions13aincluding the fluorine-containing portion14provided on the outer surface as described above serves as a space for holding the lubricant12. The lubricant12is loaded into the regions surrounded by the pillar portions13a, and only the tips of the pillar portions13aare exposed on the first film surface10a.

When the slippery film10is used, the first film surface10ais disposed on a side on which liquid or gas comes into contact with the slippery film being used. For example, in a case in which the slippery film10is used as an antifouling material, the slippery film10is disposed so that the second film surface10bis attached to an article to be protected from a contaminant (for example, a wall surface) and the first film surface10ais exposed.

The action of the above-described constitution will be described. In the holding base11, since a plurality of the pillar portions13aare regularly arranged, and the outer surface13bof the pillar portion13is formed of a material having a C—F bond, the fluorine-based lubricant12is held in the regions surrounded by a plurality of the pillar portions. The first film surface10ais constituted with the tip surfaces of the pillar portions13aand the lubricant12, and a majority of the region is constituted with the lubricant12, and thus the slippery film exhibits a slipping property with respect to liquid or gas in contact with the slippery film. Even when the static contact angle (also simply referred to as the contact angle) of the first film surface10awith respect to liquid or gas in contact with the slippery film is great, the slipping property with respect to liquid or gas is developed. Therefore, liquid or gas remaining on the first film surface10ais suppressed.

The above-described slipping property can be evaluated by obtaining a sliding angle (also referred to as a dynamic contact angle). The sliding angle refers to an angle at which a liquid droplet begins to slide and drop when a material, which is an evaluation subject, is positioned so that the surface thereof is horizontally placed, the liquid droplet is dropped on the surface, and the material, which is the evaluation subject, is inclined by gradually lifting one end of the material, and is an angle formed between the surface before being inclined and the surface inclined. The sliding angle on the first film surface10aof the slippery film10is 6.8° for a water droplet and 5.2° for a tetradecane liquid droplet. Tetradecane is used as an example of oil.

In the slippery film10, the static contact angle of water on the first film surface10ais in a range of approximately 80° to 130° which is smaller than the contact angle of water on a first film surface20aof the pillar structure film20described below (in a range of approximately 140° to 160°).

In addition, since the fluorine-containing portion14is formed on the outer surface13bof the pillar portion13a, the lubricant12is reliably held for a longer period of time. Therefore, for example, even when the slippery film10is used for a long period of time in an environment in which water is present on or passes through the first film surface10a, a phenomenon in which the lubricant12escapes from the regions surrounded by a plurality of the pillar portions13aand water comes into the regions is suppressed. Therefore, the slipping property is maintained for a long period of time.

Furthermore, the pillar portion height H13ais set to be small in a range of 0.1 μm to 20 μm, and thus the amount of the lubricant12required to be held may be small. Since a force holding the lubricant12is related to the capillary pressure in the region surrounded by a plurality of the pillar portions13aas well as the affinity of the fluorine-containing portion14to fluorine F and the magnitude relationship of specific gravity between liquid or gas in contact with the first film surface10aand the lubricant12, as the amount of the lubricant12required to be held decreases, the lubricant is more reliably held or the holding state is maintained for a longer period of time.

In addition, since the holding base11can be formed of a variety of hydrophobic polymers as described above, the holding base is produced with the size or shape of the pillar portion13a, the pillar portion height H13a, the distance between the pillar portions, and the like set in a various manner. Particularly, since the holding base can be formed of a hydrophobic polymer not containing fluorine, the holding base11has a high degree of freedom which allows the holding base to be formed from a variety of viewpoints such as the pillar portion13aand the pillar portion height H13a, and the holding base can be made at low costs.

The pillar structure film20, which is a material used to make the holding base11, is formed in a film shape as illustrated inFIG. 3. The pillar structure film20is a pillar structure body as an uneven structure body including a plurality of the pillars21, which are columnar protrusion portions, on one surface (hereinafter, referred to as the first film surface)20a. On the other surface (hereinafter, referred to as the second film surface)20b, a film surface opening portion20cis formed between the pillar21and the pillar21.

A plurality of the pillars21are formed in almost the same shape and size and are regularly arranged on the first film surface20a. The pillar21has a tapering columnar shape. The pillar structure film20is produced using a honeycomb structure film25(refer toFIGS. 4 to 6) described below. The tip of the pillar21has a sharp shape in this example, but the shape changes depending on the thickness of a partition wall27(refer toFIGS. 5 and 6) in the honeycomb structure film25. In addition, the size of the pillar21also changes depending on the thickness of the partition wall27. For example, as the thickness of the partition wall27decreases, the shape of the tip of the pillar21becomes sharper, and the pillar21becomes narrower. On the other hand, when the thickness of the partition wall27increases, the shape of the tip of the pillar21becomes rounder, and the pillar21becomes thicker. Meanwhile, inFIG. 3, the pillar21is drawn in a significantly exaggerated thickness with respect to the thickness T20of the pillar structure film20.

The height of the pillar21(hereinafter, referred to as the pillar height) is approximately 3 μm in this example, but is not limited thereto, and is in a range of 0.1 μm to 20 μm. The pillar height can be changed using the thickness T25of the honeycomb structure film25described below, the aspect of the partition wall27, and the conditions of an ultrasonic treatment described below. In addition, the distance between the pillar21and the pillar21which are adjacent to each other (hereinafter, referred to as the inter-pillar distance) is approximately 8 μm in this example, but is not limited thereto, and is almost constant in a range of 0.5 μm to 50 μm. Meanwhile, the inter-pillar distance refers to the distance between the tips of the pillars21adjacent to each other. The inter-pillar distance changes depending on the size of a pore26in the honeycomb structure film25. For example, as the pore26becomes smaller, the inter-pillar distance becomes shorter.

The pillar structure film20is formed of the hydrophobic polymer42(refer toFIG. 7). Examples of the hydrophobic polymer42are as described above, and, in the present embodiment, polystyrene is used. The pillar structure film20may include, in addition to the hydrophobic polymer42, for example, an amphipathic compound, and the amphipathic compound may be any one of a polymer, an oligomer, and a monomer. In a case in which the amphipathic compound is included, the mass of the amphipathic compound is preferably 10 parts by mass or lower with respect to 100 parts by mass of the pillar structure film20.

In the pillar structure film20, the contact angle of water on the first film surface20ais in a range of approximately 140° to 160° which is greater than the contact angle of water on a first film surface25aof the honeycomb structure film25described below (in a range of approximately 100° to 110°). In addition, in the pillar structure film20, the contact angle of air (air bubble) on the first film surface20ais in a range of 150° to 170° in water.

As illustrated inFIGS. 4 to 6, the honeycomb structure film25, which is a material for the pillar structure film20, is a honeycomb structure body as a film-shaped uneven structure body and includes a plurality of the pores26as recess portions open on one surface (hereinafter, referred to as the first film surface)25aand the other surface (hereinafter, referred to as the second film surface)25b. InFIGS. 5 and 6, in the honeycomb structure film25, the thickness of the partition wall27between the pores26adjacent to each other is drawn in an exaggerated manner with respect to the thickness T25of the honeycomb structure film25.

A plurality of the pores26are arranged regularly, more specifically, in a matrix shape, along the first film surface25a. The pore26penetrates the honeycomb structure film25in the thickness direction and is open on both the first film surface25aand the second film surface25band thus form a surface opening portion26a. In addition, as illustrated inFIGS. 5 and 6, the thickness of the partition wall27between the pores26adjacent to each other decreases toward the center in the thickness direction from the first film surface25aand the second film surface25brespectively. In this example, a partition wall opening portion27ais formed in approximately the center of the partition wall27in the thickness direction, and thus the pores26adjacent to each other are connected to each other in the honeycomb structure film25in a direction along the first film surface25a. However, there is another case in which the partition wall opening portion27ais not formed in the partition wall27, and, in such a case, the pores26are independent of each other. The honeycomb structure film25preferably includes the partition wall opening portion27ain the partition wall27rather than not includes the partition wall opening portion27ain the partition wall27from the viewpoint of reliably forming the columnar pillars21. In addition, in a case in which the partition wall opening portion27ais not formed in the partition wall27, the thickness of the partition wall27is preferably small from the viewpoint of reliably forming the columnar pillars21. Each pore26has a constant size and a constant shape, and the size and shape of the surface opening portion26aare also constant. In the above-described honeycomb structure film25, when seen in a direction perpendicular to the first film surface25a, the respective pores26are densely arranged in a state in which six pores26are disposed around an arbitrary pore26at six corners of a hexagon. In such a case, the honeycomb structure film25forms a honeycomb structure having a honeycomb shape.

In the honeycomb structure, the shape of the surface opening portion26aor the shape of a section of the pore26parallel to the first film surface25adoes not need to be a hexagon. In this example, the shape of the surface opening portion26ais round. There is another case in which, depending on the density of the pores26per unit area of the first film surface25a, the distance between the pores26adjacent to each other, or the like, the shape of the surface opening portion26aor the pore26on a section parallel to the first film surface25abecomes, for example, a substantial hexagon, a substantial octagon, or the like having round corners, and this aspect is also included in the scope of the honeycomb structure. In addition, the honeycomb structure may have, in addition to a structure in which the respective pores26are independent of each other, a structure in which the pores26adjacent to each other are connected to each other in the honeycomb structure film25as in this example. Furthermore, the arrangement of the pores26is not limited to the above-described arrangement. Three to five or seven or more pores26may be disposed around an arbitrary pore26, and the pores26may be arranged in a tetragonal manner.

The honeycomb structure film25is formed of the hydrophobic polymer42(refer toFIG. 7) and may include, in addition to the hydrophobic polymer42, for example, an amphipathic compound. The amphipathic compound may be any one of a polymer, an oligomer, and a monomer. Preferred examples of the hydrophobic polymer42and a preferred mass of the amphipathic compound in a case in which the amphipathic compound is included are the same as the examples and the mass for the pillar structure film20.

The thickness T25of the honeycomb structure film25is preferably in a range of 0.5 μm to 100 μm. The thickness T25of the honeycomb structure film25is more preferably set to 0.5 μm or greater since the strength of the honeycomb structure film25becomes higher compared with that of a honeycomb structure having a thickness of smaller than 0.5 μm and is more preferably set to 100 μm or smaller since the honeycomb structure film25can be more easily produced compared with a honeycomb structure film having a thickness of greater than 100 μm.

The open pore diameter of the pore26on the first film surface25a, that is, the diameter ϕ26of the surface opening portion26a, and the interval D26between the pores26may be determined depending on the target distance between protrusions in the pillar structure film20to be produced. In a case in which the distance between protrusions in the pillar structure film20is in a range of 0.5 μm to 50 μm, the diameter ϕ26of the surface opening portion26ais preferably in a range of 0.3 μm to 45 μm, and the interval D26between the pores26is preferably in a range of 0.5 μm to 50 μm.

Meanwhile, in this example, the honeycomb structure film25in which the respective pores26penetrate in the thickness direction is used, but the honeycomb structure film may have a structure in which the respective pores26do not penetrate the honeycomb structure film in the thickness direction. In the structure in which the pores26do not penetrate the honeycomb structure film in the thickness direction, the pores26are open only on the first film surface of the honeycomb structure film, and the second film surface becomes a flat surface including no surface opening portions26a. In a case in which a honeycomb structure film in which the pores26are open only on the first film surface as described above is used, the obtained pillar structure film includes the second film surface on which the film surface opening portions20care not formed, that is, a flat second film surface.

The slippery film10is produced using, for example, a step of producing a slippery film illustrated inFIG. 7. The step of producing a slippery film includes a solution preparation step31, a casting step32, a dew condensation step33, an evaporation step34, an alcohol contact step35, an ultrasonic treatment step36, a fluorine-containing portion formation step37, a loading step38, and a peeling step39.

The solution preparation step31is a step for preparing a solution41for forming the honeycomb structure film25. In this example, the hydrophobic polymer42is dissolved in a solvent43, thereby producing the solution41. The casting step32is a step for forming a cast film44by feeding and spreading the solution41on a supporter68(refer toFIG. 8). It is preferable to adjust the temperature of the supporter68to a desired value in advance and during formation of the cast film44. Meanwhile, in the present embodiment, as the supporter68, a polyethylene terephthalate (PET) sheet is used. However, a material for the supporter68is not limited to PET as long as the material is not dissolved in the solvent43, and the material is for example, glass, aluminum, or the like. As the shape of the supporter68, a variety of shapes such as a sheet shape or a plate shape may be employed. In addition, a long cast film44may be formed by forming the supporter68in a long film shape, moving the long supporter68in the longitudinal direction, and continuously feeding the solution41on the moving supporter68. The supporter can be moved in the longitudinal direction by, for example, disposing a plurality of rollers (not illustrated) along a moving path of the supporter68, supporting the supporter68using the circumferential surfaces of the respective rollers, and rotating the rollers in the circumferential direction.

The dew condensation step33is a step for forming water droplets by condensing dew on a film surface of the cast film44. The water droplets can be formed by, for example, cooling the cast film44through the supporter68so that the temperature of the cast film reaches a temperature lower than the temperature of an ambient atmosphere. However, it is preferable to supply a humidified gas (for example, air) onto the cast film44while adjusting the temperature of the supporter68so that the supporter68is held at a predetermined temperature since, then, a plurality of water droplets are generated at similar points in time or water droplets are formed in a uniform size.

The evaporation step34is a step for evaporating the water droplets formed in the dew condensation step33and the solvent43. In this evaporation step34, the solvent43is evaporated earlier than the water droplets by, for example, supplying a dried gas (for example, air). In such a case, the water droplets are incorporated into the cast film44, and the pores26are formed using the incorporated water droplets as casting molds. Therefore, as the solvent43, a substance having a faster evaporation rate than water is preferably used, and, in the present embodiment, chloroform is used. However, the water droplets do not necessarily need to begin to evaporate after the solvent43is fully evaporated. In addition, as long as the formed pores26are maintained, a portion of the solvent43may remain in the cast film44even after the water droplets are fully evaporated, and, in this case, the remaining solvent43is evaporated after the water droplets are fully evaporated. Meanwhile, there is another case in which the water droplets begin to be incorporated into the cast film44during the dew condensation step33. This evaporation step34produces the honeycomb structure film25on the supporter68. Meanwhile, in this example, the surface of the honeycomb structure film25in contact with the supporter68is the second film surface25b, and the exposed surface serves as the first film surface25a. The dew condensation step33and the evaporation step34are steps of the dew condensation method which is well known as a method for producing the honeycomb structure film25. In addition, in a case in which the cast film44is formed to be long, the dew condensation step33and the evaporation step34can be carried out using a method in which the supporter68on which the cast film44is formed is conveyed in the longitudinal direction and is sequentially passed through a humidifying zone in which a humidified gas is supplied and a drying zone in which a dried gas is supplied, whereby a long film can be obtained as a honeycomb structure body. Meanwhile, in this example, the honeycomb structure film25is produced using the dew condensation method, but the method for producing the honeycomb structure film is not limited to this method, and a honeycomb structure film having a honeycomb structure on a surface may be produced using, for example, a well-known nanoimprint method.

The alcohol contact step35is a step for improving wettability which improves the wettability of the honeycomb structure film25to water. In the ultrasonic treatment step36in the present embodiment, the honeycomb structure film25is ultrasonically vibrated in water, and there is a case in which water is not easily allowed to be incorporated into the pores26since the first film surface25aof the honeycomb structure film25has low wettability to water depending on the kind of the hydrophobic polymer42, the diameter ϕ26of the surface opening portion26a, the interval D26between the pores26, or the like. In the alcohol contact step35, an alcohol is brought into contact with the honeycomb structure film25, thereby improving wettability to water. In such a case, water is more reliably incorporated into the pores26in the ultrasonic treatment step36. As a result, the supporter is more reliably peeled off from the honeycomb structure film25, and furthermore, the supporter is uniformly peeled off from the honeycomb structure film25. In addition, the duration of the ultrasonic treatment is further shortened. The honeycomb structure film25with which an alcohol has been brought into contact is preferably subjected to the ultrasonic treatment step36before the alcohol is fully evaporated, that is, while the alcohol remains, and more preferably while the honeycomb structure film is wetted with the alcohol. Meanwhile, the improvement of the wettability to water means an increase in the contact angle of water.

As described above, an alcohol is brought into contact with the honeycomb structure film in order to improve the wettability of the honeycomb structure film25to water in a case in which water is used in the ultrasonic treatment step36. Therefore, in a case in which, for example, an alcohol is used in place of water in the ultrasonic treatment step36, the alcohol contact step35is included in the ultrasonic treatment step36. In this case, in the alcohol contact step35, the alcohol used for the ultrasonic treatment does two actions of an action of improving the wettability of the honeycomb structure film25and an action of transferring ultrasonic vibrations.

The alcohol used in the alcohol contact step35may be selected depending on the kind of the hydrophobic polymer42and is not particularly limited. However, the alcohol preferably dissolves the hydrophobic polymer42as little as possible and preferably has a solubility of the hydrophobic polymer42of approximately 0.1 g/100 g or lower. The unit of the solubility “g/100 g” means the mass of the hydrophobic polymer42dissolved in 100 g of the alcohol. In addition, the solubility refers to a solubility at the temperature of the alcohol to be brought into contact, and, in the present embodiment, the temperature is room temperature (a temperature in a range of 15° C. to 30° C.). In a case in which the hydrophobic polymer42is polystyrene, the alcohol is preferably ethanol, 1-propanol, 2-propanol, or the like, and the alcohol may be singly used, or a mixture of two or more alcohols may be used. Meanwhile, even in a case in which polylactic acid, polycaprolatone, polyglycolic acid, polydioxanone, polyhydroxybutyrate, polybutadiene, polyurethane, poly methyl methacrylate, polycarbonate, a copolymer having a repeating unit thereof, or the like is used as the hydrophobic polymer42, the alcohol is, similarly, preferably ethanol, 1-propanol, 2-propanol, or the like, and the alcohol may be singly used, or a mixture of two or more alcohols may be used. In the present embodiment, polystyrene is used as the hydrophobic polymer42as described above, and ethanol is used as the alcohol.

In the present embodiment, an alcohol is brought into contact with the honeycomb structure film using a method in which the honeycomb structure film25is immersed in an alcohol stored in a container (not illustrated) in a state of being superimposed on the supporter68, but the method is not limited thereto. For example, a method in which, in place of or in addition to immersion, an alcohol is applied to the first film surface25aof the honeycomb structure film25, a method in which an alcohol is blown in a liquid droplet form or a mist form, or the like may be used. In a case in which the honeycomb structure film25which is a long film is subjected to the alcohol contact step35, an alcohol may be brought into contact with the honeycomb structure film by conveying the supporter68on which the honeycomb structure film25is formed in the longitudinal direction and passing the supporter through the alcohol in the container so as to immerse the honeycomb structure film or applying or blowing the alcohol to the first film surface25aof the honeycomb structure film25being conveyed.

The ultrasonic treatment step36is a step for producing the pillar structure film20by ultrasonically vibrating the honeycomb structure film25. In this ultrasonic treatment step36, for example, an ultrasonic treatment device60described below (refer toFIG. 8) is used, and the detail of the ultrasonic treatment will be described below.

The fluorine-containing portion formation step37is a step for producing the holding base11by forming the fluorine-containing portions14(refer toFIG. 1). In the fluorine-containing portion formation step37, the fluorine-containing portions14are formed on the outer surfaces21a(refer toFIG. 3) of the pillars21in the pillar structure film20. In the present embodiment, perfluoroethylene is supplied by means of vacuum deposition, thereby forming the fluorine-containing portions14. Meanwhile, a method for forming the fluorine-containing portions14is not limited to this method, and other methods will be described in other embodiments.

The loading step38is a step for producing the slippery film10by providing the lubricant12to the holding base11. In the loading step38, the lubricant12is supplied to a surface of the holding base11on which the pillar portions13aare formed, and the lubricant12is loaded in regions surrounded by a plurality of the pillar portions13a. As a method for loading the lubricant12, in the present embodiment, spin coating (the rotation rate is 1000 rotations/minute) is employed, but the loading method is not limited thereto. Examples of another method include die coating or the like. In the case of a continuous method in which the lubricant is continuously loaded into the long holding base11, examples thereof include a method in which the holding base11is conveyed using a plurality of rollers rotating in the circumferential direction in a state in which the side of the holding base opposite to the side on which the pillar portions13aare formed is placed to face downwards, and the lubricant12is continuously applied from above using, for example, a spin coater.

The peeling step39is a step for peeling the slippery film10off from the supporter68. Meanwhile, there is another case in which the peeling step39is not provided depending on an aspect of the storage or use of the slippery film10. For example, in a case in which the slippery film is used as a film-shaped antifouling material, the peeling step39is not provided, and the slippery film10is stored in a state of being superimposed on the supporter68and is provided for use. In addition, in the present embodiment, the peeling step39is provided to peel the slippery film10off from the supporter68, but is not limited thereto. For example, the peeling step may be provided to peel the pillar structure film20off from the supporter68after the ultrasonic treatment step and before the fluorine-containing portion formation step or the peeling step may be provided to peel the holding base11off from the supporter68after the fluorine-containing portion formation step and before the loading step.

The ultrasonic treatment device60is used in the ultrasonic treatment step36and, as illustrated inFIG. 6, includes a device main body61and a holding unit62. The device main body61is made up of a liquid vessel65for containing liquid, an ultrasonic vibrator (not illustrated), an ultrasonic oscillator (not illustrated), and the like. In the present embodiment, as liquid contained in the liquid vessel65, water63is used. In the present embodiment, the ultrasonic vibrator is made up of a plurality of ultrasonic vibrators (not illustrated) provided in a side portion and a bottom portion of the liquid vessel65, but the ultrasonic vibrator is not limited thereto. For example, the ultrasonic vibrator may be a so-called embedded vibrator which is used in a state of being embedded in a liquid vessel or a vibration plate in which a vibrator attached to a hole in the bottom portion of a liquid vessel including the hole open in the bottom portion is disposed on a plate. An ultrasonic vibration element converts high-frequency electric energy generated from the ultrasonic oscillator to mechanical vibration energy, thereby generating sonic waves. As the above-described device main body61, a commercially available ultrasonic washer may be used, and, in the present embodiment, an AU-308CB manufactured by AIWA Medical Industry Co., Ltd. is used.

The holding unit62is made up of a clip66, a moving mechanism67, and the like. The clip66is provided to hold the honeycomb structure film25, and, in the present embodiment, sandwiches the honeycomb structure film25superimposed on the supporter68together with the supporter68. The clip66includes a sandwiching member66afor sandwiching the honeycomb structure film25and the supporter68and a clip main body66bfor controlling sandwiching and releasing by means of the sandwiching member66a. The clip main body66bis connected to the moving mechanism67, and the moving mechanism67moves the clip main body66bin the vertical direction, that is, up and down. Due to the moving mechanism, the honeycomb structure film25sandwiched using the sandwiching member66aand the supporter68is moved in the vertical direction. Meanwhile, a holding member is not limited to the clip66as long as the holding member is capable of holding the honeycomb structure film25, and, for example, a frame-like holding member or the like capable of holding the periphery of the honeycomb structure film25may be used.

The liquid contained in the liquid vessel65is not limited to water, but a liquid that dissolves the hydrophobic polymer42(refer toFIG. 7) as little as possible or a liquid that does not swell the honeycomb structure film25is preferred. A liquid that dissolves the hydrophobic polymer as little as possible is preferably an alcohol having a solubility of the hydrophobic polymer42of approximately 0.1 g/100 g or lower. The unit of the solubility “g/100 g” means the mass of the hydrophobic polymer42dissolved in 100 g of the liquid contained in the liquid vessel65. The solubility refers to a solubility at the temperature during the ultrasonic treatment, and, in the present embodiment, the temperature is room temperature (a temperature in a range of 15° C. to 30° C.). As a preferred example of a liquid other than water, in a case in which the hydrophobic polymer42is polystyrene, the liquid is preferably ethanol, 1-propanol, butanol, or the like, and the liquid may be singly used, or a mixture of two or more liquids may be used. In a case in which the hydrophobic polymer42is polybutadiene, the liquid is preferably ethanol, 1-propanol, acetone, or the like, and the liquid may be singly used, or a mixture of two or more liquids may be used.

The treatment duration during which the honeycomb structure film25is ultrasonically vibrated is set to 10 minutes in the present embodiment. However, the treatment duration may be set in consideration of the thickness of the partition wall27, the presence or absence of the partition wall opening portion27a, the kind of the hydrophobic polymer42, and the like, is not limited to 10 minutes, and is preferably, for example, in a range of 10 seconds to 60 minutes, more preferably in a range of 1 minute to 30 minutes, and still more preferably in a range of 1 minute to 10 minutes. In addition, as the oscillation output increases, the treatment can be carried out within a shorter period of time. In a case in which the oscillation output is small, the treatment duration needs to be set to be long. Meanwhile, as the specific gravity of the liquid contained in the liquid vessel65increases, it becomes more difficult to transfer ultraviolet vibrations, and thus it is necessary to set the treatment duration to be longer and set the oscillation output to be greater.

The action of the ultrasonic treatment device60is as described below. The honeycomb structure film25is sandwiched using the sandwiching member66ain a state of being superimposed on the supporter68. The clip66is moved down using the moving mechanism67in a state in which the honeycomb structure film25and the supporter68are sandwiched using the sandwiching member66a, and thereby moving the honeycomb structure film25to a treatment position below the water surface. Electric energy from the ultrasonic oscillator is converted to mechanical vibration energy using the ultrasonic vibrator, and the vibration energy is imparted to the honeycomb structure film25through water in the liquid vessel65. The honeycomb structure film25is imparted with ultrasonic vibrations in the water63in the above-described manner.

When ultrasonic vibrations are imparted in the water63, a brittle portion in the honeycomb structure film25, that is, a part of the partition wall27approximately in the first film surface25aside from the center thereof in which the partition wall opening portion27ahaving the smallest thickness in the thickness direction of the honeycomb structure film25is formed is broken and peeled off from the honeycomb structure film25. The second film surface25bside of the honeycomb structure film25is in a state in which the entire surface is attached to and supported by the supporter68, and thus the form of the second film surface side is reliably maintained even when ultrasonic vibrations are imparted. In such a case, a part of the partition wall27in the second film surface25bside remains as the pillar21, and the honeycomb structure film25(FIG. 9) turns into the pillar structure film20(FIGS. 10A and 10B). In addition, since the alcohol contact step35improves the wettability of the first film surface25aof the honeycomb structure film25to water, the water63is reliably incorporated into all the pores26, and thus ultrasonic vibrations are more reliably and equally imparted to all the partition walls27. As a result, a uniform pillar structure film20is obtained.

In a case in which a long honeycomb structure film25is subjected to the ultrasonic treatment step36, ultrasonic vibrations may be imparted by conveying the supporter68on which the honeycomb structure film25is formed in the longitudinal direction and passing the supporter through the water in the liquid vessel65so as to immerse the supporter in the water. Meanwhile, in a case in which the liquid vessel65contains an alcohol, the honeycomb structure film is brought into contact with the alcohol and is subjected to the ultrasonic treatment in the liquid vessel65.

In this example, the honeycomb structure film25is imparted with ultrasonic vibrations in a state of being supported by the supporter68; however, in a case in which the second film surface25bside of the honeycomb structure film25is strong enough to withstand the stress of the ultrasonic vibrations, the honeycomb structure film25may be imparted with ultrasonic vibrations in a state of being peeled off from the supporter68.

After the first film surface25aside is peeled off, the clip66is moved up using the moving mechanism67so as to move the pillar structure film20to a shelter position on the water surface. The sandwiching of the pillar structure film20and the supporter68by means of the sandwiching member66ais released, and the pillar structure film20is dried in a state of being supported by the supporter68. The pillar structure film can be dried using a well-known drying method in which, for example, a dried gas (for example, air) is blown. Meanwhile, in this example, the pillar structure film20is dried after the sandwiching by means of the sandwiching member66ais released, but the pillar structure film20may be dried in a state of being sandwiched. In addition, the pillar structure film20may be dried after being peeled off from the supporter68in the peeling step39, but the pillar structure film is more preferably dried in a state of being supported by the supporter68since deformation of the pillar structure film20is suppressed.

In the present embodiment, the supporter68used in the ultrasonic treatment step36is also used in the casting step32, but the supporter is not limited thereto. For example, it is also possible to peel the honeycomb structure film25off from the supporter used in the casting step32after the evaporation step34, attach the honeycomb structure film25to another supporter using an adhesive, adhesive tape, or the like before the alcohol contact step35, and subject the honeycomb structure film25to the alcohol contact step35and the ultrasonic treatment step36in a state of being attached to the new supporter. In this case, as the supporter, a supporter formed of a material that dissolves in the alcohol used in the alcohol contact step35and the liquid used in the ultrasonic treatment step36as little as possible is used.

As another method for producing the pillar structure film20using the honeycomb structure film25, there is peeling by means of adhesive tape, and this method may be used. Specifically, adhesive tape is attached to the first film surface25aof the honeycomb structure film25, and the adhesive tape is drawn so as to be peeled off from the honeycomb structure film25, thereby peeling a part in the first film surface25aside. However, according to the ultrasonic treatment of the present embodiment, the pillar structure film20having a larger size than that produced using the peeling method of the related art by means of adhesive tape is easily produced, which is preferable. In addition, in a case in which the supporter68and the honeycomb structure film25are flexible, for example, the supporter and the honeycomb structure film may be immersed in the water63in the liquid vessel65in a state of being wound in a tubular manner or bent, and, in such a case, the pillar structure film20having a larger area is produced. In addition, even when the first film surface25ais curved like the case of the honeycomb structure film25in a wound state or a bent state, the pillar structure film20is reliably produced. Therefore, for example, when the honeycomb structure film25is formed on an inner wall or an outer wall of a glass tube, and the glass tube on which the honeycomb structure film25is formed is immersed in the water63in the liquid vessel65, the pillar structure film20is formed on the inner wall or the outer wall of the glass tube. Meanwhile, even in this case, the alcohol contact treatment is more preferably carried out before the ultrasonic treatment step since, then, the wettability to water of the first film surface25aof the honeycomb structure film25formed on the inner wall or the outer wall is improved. Regarding the alcohol contact step35, even in a case in which the honeycomb structure film25is formed on an inner wall of an extremely narrow tube having, for example, an outer diameter of 1 mm and an inner diameter of 0.7 mm, wettability to water is reliably improved by immersing the tube in the alcohol, and the pillar structure film20is uniformly and easily formed on the inner wall of the tube. When the fluorine-containing portion formation step and the loading step are carried out on the pillar structure film20formed on the inner wall of the tube, it is possible to form the slippery film10on the inner wall of the tube.

Second Embodiment

Regarding the ultrasonic treatment, as the modulus of elasticity of the honeycomb structure film25decreases, that is, the honeycomb structure film becomes more flexible, the above-described peeling action becomes weaker. In such a case, it is preferable to carry out a hardening treatment in order to further harden the honeycomb structure film25and then subject the honeycomb structure film in a hardened state to the ultrasonic treatment. The modulus of elasticity of the honeycomb structure film20can be measured using Japanese Industrial Standards JIS K 7127 (title: Plastics-Determination of tensile properties—Part 3: Test conditions for films and sheets). The modulus of elasticity of the honeycomb structure film20is preferably set to 1 GPa or higher by means of the hardening treatment. In the present embodiment, as the hardening treatment, a cooling treatment for cooling the honeycomb structure film25is carried out. In a case in which the cooling treatment is carried out, the ultrasonic treatment may be carried out by, for example, putting water and ice into the liquid vessel65and immersing the honeycomb structure film25in the liquid vessel65. Then, the temperature of the honeycomb structure film25decreases, and ultrasonic vibrations are imparted in a state in which the honeycomb structure film becomes harder, that is, the modulus of elasticity becomes higher, and the first film surface25aside is more reliably peeled off. Water and ice put into the liquid vessel65in the cooling treatment are not particularly limited, and, for example, liquid nitrogen or the like may be used.

The cooling treatment is preferably carried out on the honeycomb structure film25under the ultrasonic treatment step36. The cooling treatment is particularly effective in a case in which, for example, polybutadiene, polylactic acid, or the like is used as the hydrophobic polymer42, and, in the present embodiment, polybutadiene, which is a material that is more flexible than polystyrene used in the first embodiment, is used. In a case in which the hydrophobic polymer42used to form the honeycomb structure film25has a glass transition temperature, it is more preferable to cool the honeycomb structure film25to the glass transition temperature or lower in the cooling treatment.

Third Embodiment

Another example of the hardening treatment is a light hardening treatment. The light hardening treatment is effective in a case in which a so-called light polymerizable compound that is polymerized by applying light is used in place of or in addition to the hydrophobic polymer42. The light polymerizable compound may be any one of a polymer, an oligomer, or a mixture of a polymer and an oligomer. In addition, crosslinking can be considered as the polymerization.

As an example of the light hardening treatment, in the present embodiment, the honeycomb structure film25is subjected to a light hardening step71, the alcohol contact step35, and the ultrasonic treatment step36in this order as illustrated inFIG. 11. However, as described above, there is a case in which the alcohol contact step35is not provided, and there is a case in which the alcohol contact step35is included in the ultrasonic treatment step36. As described above, the light hardening step71needs to be provided ahead of the ultrasonic treatment step36. The light hardening step71is a step for carrying out the light hardening treatment, and, in this step, a light polymerizable compound is polymerized by applying light, which polymerizes the light polymerizable compound, to the honeycomb structure film25including the light polymerizable compound, and thus the honeycomb structure film25is further hardened. In the present embodiment, as the hydrophobic polymer42, polybutadiene (manufactured by JSR Corporation, syndioctactic 1,2-polybutadiene, RB820), which is crosslinked by applying ultraviolet rays, is used, and the honeycomb structure film25is made of this hydrophobic polymer42.

In the light hardening treatment in the present embodiment, the honeycomb structure film25is irradiated with ultraviolet rays using a light source (not illustrated) emitting ultraviolet rays. The light source is disposed on the first film surface25aside of the honeycomb structure film25and radiates ultraviolet rays toward the first film surface25a. However, the light source may be disposed on the second film surface25bside in place of or in addition to the first film surface25aside depending on the presence or absence and degree of light transmittance of a material constituting the honeycomb structure film25. The ultraviolet radiation duration is set to 10 minutes in the present embodiment, but is not limited thereto, and is preferably in a range of approximately 1 minute to 60 minutes.

Radiated ultraviolet rays crosslink the hydrophobic polymer42of this example, and the honeycomb structure film25is hardened. The honeycomb structure film25that has undergone this light hardening step71is subjected to the alcohol contact step35and then the ultrasonic treatment step36. Since the honeycomb structure film25has been further hardened in the light hardening step71, compared with a case in which the light hardening treatment is not carried out, the first film surface25aside of the honeycomb structure film25is more reliably peeled off, and a pillar structure film20having a more uniform structure is obtained. Meanwhile, in the present embodiment as well, similar to the first embodiment, the duration of the ultrasonic treatment is set to 10 minutes.

In the second embodiment and the third embodiment, the fluorine-containing portion formation step37is a step in which an ene-thiol reaction is performed and a step for a so-called fluorination treatment. This is because, as the hydrophobic polymer, polybutadiene is used, and thus an ene-thiol reaction with a thiol containing fluorine is possible. Therefore, in a case in which a compound containing fluorine and a polyolefin capable of an ene-thiol reaction are used as the hydrophobic polymer42(refer toFIG. 7) in place of polybutadiene, the above-described method is effective. When an ene-thiol reaction is used, the fluorine-containing portions14are formed in an extremely small thickness, and thus regions surrounded by a plurality of the pillar portions13aare more reliably formed on the holding base11. The thickness of the fluorine-containing portion14in the second embodiment and the third embodiment is much smaller than that in the first embodiment and is a molecule-level thickness.

In the present embodiment, the fluorine-containing portion formation step37in which an ene-thiol reaction is performed is carried out as described below. First, the pillar structure film20is immersed in a solution in which a compound including fluorine (hereinafter, referred to as the fluorine-containing compound) is dissolved. During this immersion, that is, during an ene-thiol reaction, the solution is preferably placed under nitrogen (N2). In addition, during the immersion, the solution is preferably maintained at a temperature in a range of 50° C. to 60° C. and is maintained at 55° C. in the present embodiment. A change in the temperature of the solution is dependent on the cleavage temperature of a radical initiator, and the upper limit thereof is dependent on a thiol chemical (the fluorine-containing compound) and the boiling point of the solution. As a solvent for the fluorine-containing compound, an alcohol is used. As the fluorine-containing compound, 1H,1H,2H,2H-perfluorooctanethiol (PFOT) is used, but the fluorine-containing compound is not limited thereto, and additional examples thereof include 1H, 1H,2H,2H-perfluorodecanethiol (PFDT), 1H,1H,2H,2H-perfluorohexanethiol (PFHT), or the like. The concentration of the fluorine-containing compound in the solution is preferably in a range of 3 g/liter to 300 g/liter and is set to 30 g/liter in the present embodiment.

To the solution, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADV) is added as the radical initiator. The concentration of the radical initiator in the solution is preferably in a range of 0.03 g/liter to 3.0 g/liter and is set to 0.3 g/L in the present embodiment.

The pillar structure film20is left to stand in a state of being immersed in the solution. The duration during which the pillar structure film is left to stand is set to 10 hours in the present embodiment, but is not limited thereto, and is preferably in a range of 5 hours to 25 hours. While the pillar structure film is left to stand in this atmosphere, the ene-thiol reaction progresses, and polybutadiene is fluorinated, thereby forming the fluorine-containing portions14. The fluorine-containing portion14has the following structure.

After being placed under a nitrogen atmosphere, the obtained holding base11is preferably washed. In the present embodiment, the holding base is washed with ethanol, but any substance, for example, 1-propanol or 2-propanol, may be used as long as the substance does not dissolve or swell the holding base11.

Whether or not the fluorine-containing portions14are formed can be confirmed using, for example, a spectrum chart of Fourier transform infrared spectroscopy (FT-IR). In the present embodiment, an FT-IR6100 manufactured by JASCO Corporation is used, a spectrum is obtained using attenuated total reflection (ATR), and formation of the fluorine-containing portions14is confirmed. As illustrated inFIG. 12, a spectrum corresponding to a C—F skeleton vibration is confirmed only after the fluorination treatment at near approximately 1200 cm−1, and thus the fluorine-containing portions14are formed.

In a case in which the fluorine-containing portions14are formed by means of the ene-thiol reaction, and an amphipathic compound is added to the solution41, it is more preferable to remove the amphipathic compound from the surface before the initiation of the ene-thiol reaction. For the removal of the amphipathic compound, there is a method in which the amphipathic compound is washed with an alcohol using a method of immersing the pillar structure film20in the alcohol or of blowing the alcohol to the pillar structure film20, and, in the present embodiment, the pillar structure film is immersed in 1-propanol as the alcohol. As the alcohol, it is possible to use 1-propanol, 2-propanol, ethanol, methanol, or a mixture of two or more thereof. The immersion duration is preferably set to at least 30 seconds and more preferably set in a range of 30 seconds to 24 hours. In such a case, the amphipathic compound on the outer surfaces of the pillars21in the pillar structure film20is removed, and the ene-thiol reaction more rapidly and reliably ends.

In the second embodiment and the third embodiment, the fluorine-containing portions14are formed after the ultrasonic treatment; however, instead, the ultrasonic treatment may be carried out after the fluorine-containing portions14are formed. That is, the holding base11is obtained by being peeled off from the honeycomb structure film25which has undergone the fluorine-containing portion formation step37.

Fourth Embodiment

The slippery film includes the holding base11including the pillar structure portions13and is not limited to the slippery film10obtained using the pillar structure film20. For example, the slippery film can be obtained using the honeycomb structure film25. InFIG. 13, a slippery film80which is an uneven structure body formed in a film shape includes a holding base81and the lubricant12. Meanwhile, inFIG. 13, the same members as inFIG. 1will be given the same reference signs and will not be described.

The holding base81includes honeycomb structure portions83and the fluorine-containing portions14. The honeycomb structure portion83is an uneven structure portion including a plurality of pore portions83aas recess portions. The pore portions83aare regularly arranged. In this example, the pore portions83aare open on one surface (hereinafter, referred to as the first film surface)80aand on the other surface (the second film surface)80b, but there is another case in which the pore portions are open only on the first film surface80a. The fluorine-containing portion14is formed on an inner circumferential surface83bof the pore portion83a. In the present embodiment, the honeycomb structure body83is formed of PB (polybutadiene), but may be formed of a different hydrophobic polymer42. The lubricant12is loaded into the pore portions83a. The thickness T80of the slippery film80is set in a range of 1 μm to 50 μm and is 10 μm in the present embodiment. The depth of the pore portion83ais in a range of 0.2 μm to 50 μm, and the opening diameter ϕ83aof the pore portion83ais in a range of 0.2 μm to 50 μm.

The action of the above-described constitution will be described. In the holding base81, since a plurality of the pore portions83aare regularly arranged, and the inner circumferential surface of the pore portion83ais formed of a material having a C—F bond, the fluorine-based lubricant12is held in the pore portions83a. Since the first film surface80ais constituted with the top surface of the holding base81inFIG. 13and the lubricant12, and a majority of the region is constituted with the lubricant12, the slippery film exhibits a slipping property with respect to liquid or gas in contact with the slippery film. Even when the static contact angle of the first film surface80awith respect to liquid or gas in contact with the slippery film is great, the slipping property with respect to liquid or gas is developed. Therefore, liquid or gas remaining on the first film surface80ais suppressed.

The sliding angle on the first film surface80aof the slippery film80is 3.3° for a water droplet and 5.4° for a tetradecane liquid droplet, and a strong slipping property is exhibited. Therefore, the slippery film does not allow liquid to easily attach thereto and has strong water-repellency and excellent antifouling properties.

In the slippery film80, the static contact angle of water on the first film surface80ais in a range of approximately 105° to 115°.

In addition, since the fluorine-containing portion14is formed on the inner circumferential surface83bof the pore portion83a, the lubricant12is reliably held for a longer period of time. Therefore, for example, even when the slippery film80is used for a long period of time in an environment in which water is present on or passes through the first film surface80a, a phenomenon in which the lubricant12escapes from the regions surrounded by a plurality of the pore portions83aand water comes into the regions is suppressed. Therefore, the slipping property is maintained for a long period of time.

As illustrated inFIG. 14, the slippery film80is produced by subjecting the honeycomb structure film25to the fluorine-containing portion formation step37, the loading step38, and the peeling step39in this order. In the fluorine-containing portion formation step37, the fluorine-containing portions14are formed on the inner surfaces of the pores26in the honeycomb structure film25, thereby producing the holding base81, and, in this example, the fluorine-containing portions14are formed by means of an ene-thiol reaction. In a case in which an amphipathic compound is added to the solution41, it is preferable to remove the amphipathic compound from the honeycomb structure film25before the fluorine-containing portion formation step37.

The slippery material to be produced is not limited to a film-shaped material as described above. For example, the slippery material may be, for example, a block-shaped material having a much larger thickness than the slippery films10and80. When a block-shaped pillar structure body including pillars on the surface or a honeycomb structure including pores is used as the material, a block-shaped slippery material is produced. As an example, a block-shaped honeycomb structure body (not illustrated) including a honeycomb structure, in which water droplets generated on the liquid surface of the solution41are used as casting molds, formed in a part of the surface of the block can be obtained by feeding the solution41into a desired mold and subjecting the solution41in the mold to the dew condensation step33and the evaporation step34. When this honeycomb structure body is subjected to the ultrasonic treatment step36, a block-shaped pillar structure body (not illustrated) is obtained. Even in this case, the above-described alcohol contact treatment and hardening treatment may be carried out.

Fifth Embodiment

A slippery film90is formed in a film shape as illustrated inFIG. 15and includes a first structure portion92and a second structure portion93. Meanwhile, hereinafter, only members different from those in the slippery film10or the slippery film80will be described, and substantially the same members will be given the same reference signs as those inFIGS. 1 and 13and will not be described.

The first structure portion92is constituted in the same manner as in the slippery film10and is formed in an aspect in which a plurality of the pillar portions13aare regularly arranged on a first film surface90aside which is one surface, and the fluorine-containing portion14is formed on the outer surface13b(refer toFIG. 1) of the pillar portion13a. The lubricant12is held in regions surrounded by a plurality of the pillar portions13a. Meanwhile, in order to avoid complication in the drawing, the lubricant12is not illustrated inFIG. 15. The second structure portion93is constituted in the same manner as in the slippery film80and is formed in an aspect in which a plurality of the pore portions83a, which penetrate in the thickness direction from the first film surface90ato a second film surface90bwhich is the other surface, are regularly arranged. The fluorine-containing portion14is formed on the inner surface (refer toFIG. 13) of the pore portion83a, and the lubricant12is held in the pore portions83awhich are not illustrated. In a holding base for the first structure portion92and the second structure portion93, parts excluding the fluorine-containing portions14are constituted with polybutadiene and may include an amphipathic compound.

The first structure portion92is formed in an island shape by being surrounded by the second structure portion93; however, for example, the second structure portion may be formed in an island shape so that the first structure portion surrounds the second structure portion. In addition, in this example, when seen in a direction perpendicular to the first film surface90a, the first structure portion92forms a mirrored image shape of a number “2”, but the shape is not limited thereto. For example, when seen in a direction perpendicular to the first film surface90a, a protrusion structure portion may have a variety of shapes such as a round shape, a rectangular shape, or an irregular shape, and a plurality of protrusion structure portions having equal or different shapes may be isolated and formed in an island shape. The height of the first film surface90ais lower in the first structure portion92than in the second structure portion93.

When the above-described constitution is employed, the degree of a slipping property varies in the first structure portion92and the second structure portion93on the first film surface90a. As described above, when the first structure portion92and the second structure portion93are produced on the same plane, liquid droplets are pinned in the second structure portion93in which the slipping property is weak. Therefore, since the second structure portion93is surrounded by the first structure portions92, it becomes possible to limit the motion of liquid droplets or to control liquid droplets to move only in a patterned direction by patterning the shape of the second structure portion93in a linear shape. When a pattern is formed in a place having different slipping properties, it is possible to form, for example, a micro flow path not including any partition walls.

In a case in which the slippery film90is produced, the light hardening treatment is carried out in a state in which the mask plate94is superimposed on the first film surface25aof the honeycomb structure film25(refer toFIGS. 4 to 6) as illustrated inFIG. 16. In this example, polybutadiene is used as the hydrophobic polymer42(refer toFIG. 7). Therefore, similar to the third embodiment, the honeycomb structure film25on which the mask plate94is superimposed is subjected to the light hardening step71, then, the mask plate94is removed, and the honeycomb structure film is sequentially subjected to the alcohol contact step35and the ultrasonic treatment step36.

The mask plate94is, for example, a plate-like member having a size that is equal to or larger than that of the honeycomb structure film25and includes an opening94ain a part corresponding to the first structure portion92. The mask plate94is made of a metal that does not transmit ultraviolet rays and thus prevent a region in the honeycomb structure film25covered with the mask plate94from being irradiated with ultraviolet rays. A variety of holding bases including a varying number of the first structure portions92having a different size, shape, position, or the like can be formed by changing the size, shape, position, number, or the like of the opening94ain the mask plate94. Meanwhile, from the viewpoint of clarifying the boundary between the first structure portion92and the second structure portion93, the honeycomb structure film25and the mask plate94are preferably superimposed on each other in a state of being attached together.

When the honeycomb structure film25is irradiated with ultraviolet rays in a state in which the mask plate94is superimposed thereon, the hydrophobic polymer42in the honeycomb structure film25which is exposed through the opening94ais crosslinked and hardened, and the hydrophobic polymer42in the region covered with the mask plate94is not crosslinked. In addition, after the light hardening step71, the mask plate94is removed from the honeycomb structure film25, and an alcohol is continuously brought into contact with the honeycomb structure film. Then, the wettability of the first film surface25ato water improves.

Next, the honeycomb structure film25is ultrasonically vibrated, and then the mask plate94is removed. Therefore, in the region exposed through the opening94aduring the irradiation with ultraviolet rays, a part of the partition wall27approximately in the first film surface25aside from the center thereof breaks and peels off from the honeycomb structure film25, thereby forming the pillar structure body13of the first structure portion92. Since the honeycomb structure film is ultrasonically vibrated in a state in which wettability to water is improved by means of contact with an alcohol, the pillar portions13aare formed in a state of a uniform size or shape. In contrast, in the region covered with the mask plate94during the irradiation with ultraviolet rays, the shape of the honeycomb structure film25is maintained, and thus a honeycomb structure portion83of the second structure portion93is formed. The lubricant12is supplied to the obtained holding base, thereby loading the lubricant12to regions surrounded by a plurality of the pillar portions13aand the insides of the pore portions83a. Therefore, the slippery film90is obtained. As described above, in a case in which a light polymerizable compound that is polymerized by means of irradiation with light is used, it is possible to produce a slippery film including the first structure portion and the second structure portion, and the use of the mask plate enables formation of a pattern of the first structure portion and the second structure.